also for #2771 - removal of all MDBX utilities and libmdbx.mir itself

19 files changed, 65415 insertions, 1 deletions

diff --git a/plugins/Dbx_mdbx/src/libmdbx/CMakeLists.txt b/plugins/Dbx_mdbx/src/libmdbx/CMakeLists.txt
new file mode 100644
index 0000000000..46afa66fca
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/CMakeLists.txt
@@ -0,0 +1,866 @@
+##
+##  Copyright 2020-2021 Leonid Yuriev <leo@yuriev.ru>
+##  and other libmdbx authors: please see AUTHORS file.
+##  All rights reserved.
+##
+##  Redistribution and use in source and binary forms, with or without
+##  modification, are permitted only as authorized by the OpenLDAP
+##  Public License.
+##
+##  A copy of this license is available in the file LICENSE in the
+##  top-level directory of the distribution or, alternatively, at
+##  <http://www.OpenLDAP.org/license.html>.
+##
+
+##
+##  libmdbx = { Revised and extended descendant of Symas LMDB. }
+##  Please see README.md at https://github.com/erthink/libmdbx
+##
+##  Libmdbx is superior to LMDB in terms of features and reliability,
+##  not inferior in performance. libmdbx works on Linux, FreeBSD, MacOS X
+##  and other systems compliant with POSIX.1-2008, but also support Windows
+##  as a complementary platform.
+##
+##  The next version is under active non-public development and will be
+##  released as MithrilDB and libmithrildb for libraries & packages.
+##  Admittedly mythical Mithril is resembling silver but being stronger and
+##  lighter than steel. Therefore MithrilDB is rightly relevant name.
+##
+##  MithrilDB will be radically different from libmdbx by the new database
+##  format and API based on C++17, as well as the Apache 2.0 License.
+##  The goal of this revolution is to provide a clearer and robust API,
+##  add more features and new valuable properties of database.
+##
+##  The Future will (be) Positive. Всё будет хорошо.
+##
+
+cmake_minimum_required(VERSION 3.8.2)
+
+cmake_policy(PUSH)
+cmake_policy(VERSION 3.8.2)
+if(NOT CMAKE_VERSION VERSION_LESS 3.15)
+  cmake_policy(SET CMP0091 NEW)
+endif()
+if(NOT CMAKE_VERSION VERSION_LESS 3.13)
+  cmake_policy(SET CMP0077 NEW)
+endif()
+if(NOT CMAKE_VERSION VERSION_LESS 3.12)
+  cmake_policy(SET CMP0075 NEW)
+endif()
+if(NOT CMAKE_VERSION VERSION_LESS 3.9)
+  cmake_policy(SET CMP0069 NEW)
+  include(CheckIPOSupported)
+  check_ipo_supported(RESULT CMAKE_INTERPROCEDURAL_OPTIMIZATION_AVAILABLE)
+else()
+  set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_AVAILABLE FALSE)
+endif()
+
+if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/core.c" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/alloy.c" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/config.h.in" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/version.c.in" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/man1" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/mdbx_chk.c" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/mdbx.c++")
+  set(MDBX_AMALGAMATED_SOURCE FALSE)
+  find_program(GIT git)
+  if(NOT GIT)
+    message(SEND_ERROR "Git command-line tool not found")
+  endif()
+  set(MDBX_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/src")
+elseif(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/VERSION" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/mdbx.c" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/mdbx.c++" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/config.h.in" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/man1" AND
+    EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/mdbx_chk.c")
+  set(MDBX_AMALGAMATED_SOURCE TRUE)
+  set(MDBX_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+else()
+  message(FATAL_ERROR "Please use libmdbx as a git-submodule or the amalgamated source code")
+endif()
+
+if(DEFINED PROJECT_NAME)
+  set(SUBPROJECT ON)
+  set(NOT_SUBPROJECT OFF)
+  if(NOT MDBX_AMALGAMATED_SOURCE AND NOT DEFINED BUILD_TESTING)
+    set(BUILD_TESTING OFF)
+  endif()
+  enable_language(C)
+else()
+  set(SUBPROJECT OFF)
+  set(NOT_SUBPROJECT ON)
+  project(libmdbx C)
+  if(NOT MDBX_AMALGAMATED_SOURCE AND NOT DEFINED BUILD_TESTING)
+    set(BUILD_TESTING ON)
+  endif()
+endif()
+
+if(MDBX_AMALGAMATED_SOURCE AND DEFINED MDBX_ENABLE_TESTS AND MDBX_ENABLE_TESTS)
+  message(WARNING "MDBX_ENABLE_TESTS=${MDBX_ENABLE_TESTS}: But amalgamated source code don't includes tests.")
+  set(MDBX_ENABLE_TESTS OFF)
+endif()
+
+# Try to find a C++ compiler unless sure that this is unnecessary.
+if (NOT CMAKE_CXX_COMPILER_LOADED)
+  include(CheckLanguage)
+  if(NOT DEFINED MDBX_BUILD_CXX OR MDBX_BUILD_CXX
+      OR (NOT MDBX_AMALGAMATED_SOURCE AND (NOT DEFINED MDBX_ENABLE_TESTS OR MDBX_ENABLE_TESTS)))
+    check_language(CXX)
+    if(CMAKE_CXX_COMPILER)
+      enable_language(CXX)
+    endif()
+  endif()
+else()
+  enable_language(CXX)
+endif()
+
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE MinSizeRel CACHE STRING
+    "Choose the type of build, options are: Debug Release RelWithDebInfo MinSizeRel."
+    FORCE)
+endif()
+
+if(NOT_SUBPROJECT AND (CMAKE_CROSSCOMPILING OR IOS))
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+endif()
+
+if(NOT "$ENV{TEAMCITY_PROCESS_FLOW_ID}" STREQUAL "")
+  set(CI TEAMCITY)
+  message(STATUS "TeamCity CI")
+elseif(NOT "$ENV{TRAVIS}" STREQUAL "")
+  set(CI TRAVIS)
+  message(STATUS "Travis CI")
+elseif(NOT "$ENV{CIRCLECI}" STREQUAL "")
+  set(CI CIRCLE)
+  message(STATUS "Circle CI")
+elseif(NOT "$ENV{APPVEYOR}" STREQUAL "")
+  set(CI APPVEYOR)
+  message(STATUS "AppVeyor CI")
+elseif(NOT "$ENV{CI}" STREQUAL "")
+  set(CI "$ENV{CI}")
+  message(STATUS "Other CI (${CI})")
+else()
+  message(STATUS "Assume No any CI environment")
+  unset(CI)
+endif()
+
+# output all mdbx-related targets in single directory
+if(NOT DEFINED MDBX_OUTPUT_DIR)
+  set(MDBX_OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR})
+endif()
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${MDBX_OUTPUT_DIR})
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${MDBX_OUTPUT_DIR})
+set(CMAKE_PDB_OUTPUT_DIRECTORY ${MDBX_OUTPUT_DIR})
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${MDBX_OUTPUT_DIR})
+
+include(CheckFunctionExists)
+include(FindPackageMessage)
+include(GNUInstallDirs)
+
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC" AND MSVC_VERSION LESS 1900)
+  message(SEND_ERROR "MSVC compiler ${MSVC_VERSION} is too old for building MDBX."
+    " At least 'Microsoft Visual Studio 2015' is required.")
+endif()
+
+# Set default build type to Release. This is to ease a User's life.
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE Release CACHE STRING
+    "Choose the type of build, options are: Debug Release RelWithDebInfo MinSizeRel."
+    FORCE)
+endif()
+string(TOUPPER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_UPPERCASE)
+
+set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+set(THREADS_PREFER_PTHREAD_FLAG TRUE)
+find_package(Threads REQUIRED)
+
+include(cmake/utils.cmake)
+include(cmake/compiler.cmake)
+include(cmake/profile.cmake)
+
+# Workaround for `-pthread` toolchain/cmake bug
+if(NOT APPLE AND NOT MSVC
+    AND CMAKE_USE_PTHREADS_INIT AND NOT CMAKE_THREAD_LIBS_INIT
+    AND (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_CLANG))
+  check_compiler_flag("-pthread" CC_HAS_PTHREAD)
+  if(CC_HAS_PTHREAD AND NOT CMAKE_EXE_LINKER_FLAGS MATCHES "-pthread")
+    message(STATUS "Force add -pthread for linker flags to avoid troubles")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -pthread")
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -pthread")
+    set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -pthread")
+  endif()
+endif()
+
+CHECK_FUNCTION_EXISTS(pow NOT_NEED_LIBM)
+if(NOT_NEED_LIBM)
+  set(LIB_MATH "")
+else()
+  set(CMAKE_REQUIRED_LIBRARIES m)
+  CHECK_FUNCTION_EXISTS(pow HAVE_LIBM)
+  if(HAVE_LIBM)
+    set(LIB_MATH m)
+  else()
+    message(FATAL_ERROR "No libm found for math support")
+  endif()
+endif()
+
+if(SUBPROJECT)
+  if(NOT DEFINED BUILD_SHARED_LIBS)
+    option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)" OFF)
+  endif()
+  if(NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
+    option(CMAKE_POSITION_INDEPENDENT_CODE "Generate position independent (PIC)" ON)
+  endif()
+else()
+  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)" ON)
+  option(CMAKE_POSITION_INDEPENDENT_CODE "Generate position independent (PIC)" ON)
+  if (CC_HAS_ARCH_NATIVE)
+    option(BUILD_FOR_NATIVE_CPU "Generate code for the compiling machine CPU" OFF)
+  endif()
+
+  if(CMAKE_CONFIGURATION_TYPES OR NOT CMAKE_BUILD_TYPE_UPPERCASE STREQUAL "DEBUG")
+    set(INTERPROCEDURAL_OPTIMIZATION_DEFAULT ON)
+  else()
+    set(INTERPROCEDURAL_OPTIMIZATION_DEFAULT OFF)
+  endif()
+
+  if(CMAKE_INTERPROCEDURAL_OPTIMIZATION_AVAILABLE
+      OR GCC_LTO_AVAILABLE OR MSVC_LTO_AVAILABLE OR CLANG_LTO_AVAILABLE)
+    option(INTERPROCEDURAL_OPTIMIZATION "Enable interprocedural/LTO optimization" ${INTERPROCEDURAL_OPTIMIZATION_DEFAULT})
+  endif()
+
+  if(INTERPROCEDURAL_OPTIMIZATION)
+    if(GCC_LTO_AVAILABLE)
+      set(LTO_ENABLED TRUE)
+      set(CMAKE_AR ${CMAKE_GCC_AR} CACHE PATH "Path to ar program with LTO-plugin" FORCE)
+      set(CMAKE_NM ${CMAKE_GCC_NM} CACHE PATH "Path to nm program with LTO-plugin" FORCE)
+      set(CMAKE_RANLIB ${CMAKE_GCC_RANLIB} CACHE PATH "Path to ranlib program with LTO-plugin" FORCE)
+      message(STATUS "MDBX indulge Link-Time Optimization by GCC")
+    elseif(CLANG_LTO_AVAILABLE)
+      set(LTO_ENABLED TRUE)
+      set(CMAKE_AR ${CMAKE_CLANG_AR} CACHE PATH "Path to ar program with LTO-plugin" FORCE)
+      set(CMAKE_NM ${CMAKE_CLANG_NM} CACHE PATH "Path to nm program with LTO-plugin" FORCE)
+      set(CMAKE_RANLIB ${CMAKE_CLANG_RANLIB} CACHE PATH "Path to ranlib program with LTO-plugin" FORCE)
+      message(STATUS "MDBX indulge Link-Time Optimization by CLANG")
+    elseif(MSVC_LTO_AVAILABLE)
+      set(LTO_ENABLED TRUE)
+      message(STATUS "MDBX indulge Link-Time Optimization by MSVC")
+    elseif(CMAKE_INTERPROCEDURAL_OPTIMIZATION_AVAILABLE)
+      message(STATUS "MDBX indulge Interprocedural Optimization by CMake")
+      set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+      set(LTO_ENABLED TRUE)
+    else()
+      message(WARNING "Unable to engage interprocedural/LTO optimization.")
+    endif()
+  else()
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION FALSE)
+    set(LTO_ENABLED FALSE)
+  endif()
+
+  if(NOT MDBX_AMALGAMATED_SOURCE)
+    find_program(VALGRIND valgrind)
+    if(VALGRIND)
+      # LY: cmake is ugly and nasty.
+      #      - therefore memcheck-options should be defined before including ctest;
+      #      - otherwise ctest may ignore it.
+      set(MEMORYCHECK_SUPPRESSIONS_FILE
+        "${CMAKE_CURRENT_SOURCE_DIR}/test/valgrind_suppress.txt"
+        CACHE FILEPATH "Suppressions file for Valgrind" FORCE)
+      set(MEMORYCHECK_COMMAND_OPTIONS
+        "--trace-children=yes --leak-check=full --track-origins=yes --error-exitcode=42 --error-markers=@ --errors-for-leak-kinds=definite --fair-sched=yes --suppressions=${MEMORYCHECK_SUPPRESSIONS_FILE}"
+        CACHE STRING "Valgrind options" FORCE)
+      set(VALGRIND_COMMAND_OPTIONS "${MEMORYCHECK_COMMAND_OPTIONS}" CACHE STRING "Valgrind options" FORCE)
+    endif()
+
+    # Enable 'make tags' target.
+    find_program(CTAGS ctags)
+    if(CTAGS)
+      add_custom_target(tags COMMAND ${CTAGS} -R -f tags
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+      add_custom_target(ctags DEPENDS tags)
+    endif(CTAGS)
+
+    if(UNIX)
+      find_program(CLANG_FORMAT
+        NAMES clang-format-12 clang-format-11 clang-format-10 clang-format)
+      if(CLANG_FORMAT)
+        execute_process(COMMAND ${CLANG_FORMAT} "--version" OUTPUT_VARIABLE clang_format_version_info)
+        string(REGEX MATCH "version ([0-9]+)\\.([0-9]+)\\.([0-9]+)(.*)?" clang_format_version_info CLANG_FORMAT_VERSION)
+        if(clang_format_version_info AND NOT CLANG_FORMAT_VERSION VERSION_LESS 10.0)
+          # Enable 'make reformat' target.
+          add_custom_target(reformat
+            VERBATIM
+            COMMAND
+            git ls-files |
+            grep -E \\.\(c|cxx|cc|cpp|h|hxx|hpp\)\(\\.in\)?\$ |
+            xargs ${CLANG_FORMAT} -i --style=file
+            WORKING_DIRECTORY ${CMAKE_SOURCE_DIR})
+        endif()
+      endif()
+    endif()
+
+    if(NOT "${PROJECT_BINARY_DIR}" STREQUAL "${PROJECT_SOURCE_DIR}")
+      add_custom_target(distclean)
+      add_custom_command(TARGET distclean
+        COMMAND ${CMAKE_COMMAND} -E remove_directory "${PROJECT_BINARY_DIR}"
+        COMMENT "Removing the build directory and its content")
+    elseif(IS_DIRECTORY .git AND GIT)
+      add_custom_target(distclean)
+      add_custom_command(TARGET distclean
+        WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+        COMMAND ${GIT} submodule foreach --recursive git clean -f -X -d
+        COMMAND ${GIT} clean -f -X -d
+        COMMENT "Removing all build files from the source directory")
+    endif()
+  endif(NOT MDBX_AMALGAMATED_SOURCE)
+
+  setup_compile_flags()
+endif(SUBPROJECT)
+
+list(FIND CMAKE_C_COMPILE_FEATURES c_std_11 HAS_C11)
+list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_11 HAS_CXX11)
+list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_14 HAS_CXX14)
+list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_17 HAS_CXX17)
+list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_20 HAS_CXX20)
+if(NOT DEFINED MDBX_CXX_STANDARD)
+  if(DEFINED CMAKE_CXX_STANDARD)
+    set(MDBX_CXX_STANDARD ${CMAKE_CXX_STANDARD})
+  elseif(NOT HAS_CXX20 LESS 0)
+    set(MDBX_CXX_STANDARD 20)
+  elseif(NOT HAS_CXX17 LESS 0)
+    set(MDBX_CXX_STANDARD 17)
+  elseif(NOT HAS_CXX14 LESS 0)
+    set(MDBX_CXX_STANDARD 14)
+  elseif(NOT HAS_CXX11 LESS 0)
+    set(MDBX_CXX_STANDARD 11)
+  else()
+    set(MDBX_CXX_STANDARD 98)
+  endif()
+endif()
+if(NOT DEFINED MDBX_C_STANDARD)
+  # MSVC >= 19.28 (Microsoft Visual Studio 16.8) is mad!
+  #               It unable process Windows SDK headers in the C11 mode!
+  if(HAS_C11 LESS 0 OR (MSVC AND MSVC_VERSION GREATER 1927))
+    set(MDBX_C_STANDARD 99)
+  else()
+    set(MDBX_C_STANDARD 11)
+  endif()
+endif()
+
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Windows" AND EXISTS "${MDBX_SOURCE_DIR}/ntdll.def")
+  if(MSVC)
+    if(NOT MSVC_LIB_EXE)
+      # Find lib.exe
+      get_filename_component(CL_NAME ${CMAKE_C_COMPILER} NAME)
+      string(REPLACE cl.exe lib.exe MSVC_LIB_EXE ${CL_NAME})
+      find_program(MSVC_LIB_EXE ${MSVC_LIB_EXE})
+    endif()
+    if(MSVC_LIB_EXE)
+      message(STATUS "Found MSVC's lib tool: ${MSVC_LIB_EXE}")
+      set(MDBX_NTDLL_EXTRA_IMPLIB "${CMAKE_CURRENT_BINARY_DIR}/mdbx_ntdll_extra.lib")
+      add_custom_command(OUTPUT "${MDBX_NTDLL_EXTRA_IMPLIB}"
+        COMMENT "Create extra-import-library for ntdll.dll"
+        MAIN_DEPENDENCY "${MDBX_SOURCE_DIR}/ntdll.def"
+        COMMAND ${MSVC_LIB_EXE} /def:"${MDBX_SOURCE_DIR}/ntdll.def" /out:"${MDBX_NTDLL_EXTRA_IMPLIB}" ${INITIAL_CMAKE_STATIC_LINKER_FLAGS})
+    else()
+      message(WARNING "MSVC's lib tool not found")
+    endif()
+  elseif(MINGW OR MINGW64)
+    if(NOT DLLTOOL)
+      # Find dlltool
+      get_filename_component(GCC_NAME ${CMAKE_C_COMPILER} NAME)
+      string(REPLACE gcc dlltool DLLTOOL_NAME ${GCC_NAME})
+      find_program(DLLTOOL NAMES ${DLLTOOL_NAME})
+    endif()
+    if(DLLTOOL)
+      message(STATUS "Found dlltool: ${DLLTOOL}")
+      set(MDBX_NTDLL_EXTRA_IMPLIB "${CMAKE_CURRENT_BINARY_DIR}/mdbx_ntdll_extra.a")
+      add_custom_command(OUTPUT "${MDBX_NTDLL_EXTRA_IMPLIB}"
+        COMMENT "Create extra-import-library for ntdll.dll"
+        MAIN_DEPENDENCY "${MDBX_SOURCE_DIR}/ntdll.def"
+        COMMAND ${DLLTOOL} -d "${MDBX_SOURCE_DIR}/ntdll.def" -l "${MDBX_NTDLL_EXTRA_IMPLIB}")
+    else()
+      message(WARNING "dlltool not found")
+    endif()
+  endif()
+
+  if(MDBX_NTDLL_EXTRA_IMPLIB)
+    # LY: Sometimes CMake requires a nightmarish magic for simple things.
+    # 1) create a target out of the library compilation result
+    add_custom_target(ntdll_extra_target DEPENDS "${MDBX_NTDLL_EXTRA_IMPLIB}")
+    # 2) create an library target out of the library compilation result
+    add_library(ntdll_extra STATIC IMPORTED GLOBAL)
+    add_dependencies(ntdll_extra ntdll_extra_target)
+    # 3) specify where the library is (and where to find the headers)
+    set_target_properties(ntdll_extra
+      PROPERTIES
+      IMPORTED_LOCATION "${MDBX_NTDLL_EXTRA_IMPLIB}")
+  endif()
+endif()
+
+################################################################################
+################################################################################
+#
+#           ####   #####    #####     #     ####   #    #   ####
+#          #    #  #    #     #       #    #    #  ##   #  #
+#          #    #  #    #     #       #    #    #  # #  #   ####
+#          #    #  #####      #       #    #    #  #  # #       #
+#          #    #  #          #       #    #    #  #   ##  #    #
+#           ####   #          #       #     ####   #    #   ####
+#
+
+set(MDBX_BUILD_OPTIONS ENABLE_ASAN MDBX_USE_VALGRIND ENABLE_GPROF ENABLE_GCOV)
+macro(add_mdbx_option NAME DESCRIPTION DEFAULT)
+  list(APPEND MDBX_BUILD_OPTIONS ${NAME})
+  if(NOT ${DEFAULT} STREQUAL "AUTO")
+    option(${NAME} "${DESCRIPTION}" ${DEFAULT})
+  elseif(NOT DEFINED ${NAME})
+    set(${NAME}_AUTO ON)
+  endif()
+endmacro()
+
+if(IOS)
+  set(MDBX_BUILD_TOOLS_DEFAULT OFF)
+  if(NOT_SUBPROJECT)
+    cmake_policy(SET CMP0006 OLD)
+    set(CMAKE_XCODE_ATTRIBUTE_CODE_SIGNING_ALLOWED "NO")
+  endif()
+else()
+  set(MDBX_BUILD_TOOLS_DEFAULT ON)
+endif()
+
+add_mdbx_option(MDBX_INSTALL_STATIC "Build and install libmdbx for static linking" OFF)
+add_mdbx_option(MDBX_BUILD_SHARED_LIBRARY "Build libmdbx as shared library (DLL)" ${BUILD_SHARED_LIBS})
+add_mdbx_option(MDBX_BUILD_TOOLS "Build MDBX tools (mdbx_chk/stat/dump/load/copy)" ${MDBX_BUILD_TOOLS_DEFAULT})
+CMAKE_DEPENDENT_OPTION(MDBX_INSTALL_MANPAGES "Install man-pages for MDBX tools (mdbx_chk/stat/dump/load/copy)" ON MDBX_BUILD_TOOLS OFF)
+add_mdbx_option(MDBX_TXN_CHECKOWNER "Checking transaction matches the calling thread inside libmdbx's API" ON)
+add_mdbx_option(MDBX_ENV_CHECKPID "Paranoid checking PID inside libmdbx's API" AUTO)
+mark_as_advanced(MDBX_ENV_CHECKPID)
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+  add_mdbx_option(MDBX_DISABLE_GNU_SOURCE "Don't use GNU/Linux libc extensions" OFF)
+  mark_as_advanced(MDBX_DISABLE_GNU_SOURCE)
+endif()
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Darwin" OR IOS)
+  add_mdbx_option(MDBX_OSX_SPEED_INSTEADOF_DURABILITY "Disable use fcntl(F_FULLFSYNC) in favor of speed" OFF)
+  mark_as_advanced(MDBX_OSX_SPEED_INSTEADOF_DURABILITY)
+endif()
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+  if(MDBX_NTDLL_EXTRA_IMPLIB)
+    add_mdbx_option(MDBX_AVOID_CRT "Avoid dependence from MSVC CRT and use ntdll.dll instead" OFF)
+  endif()
+  add_mdbx_option(MDBX_CONFIG_MANUAL_TLS_CALLBACK
+    "Provide mdbx_dll_handler() for manual initialization" OFF)
+  mark_as_advanced(MDBX_CONFIG_MANUAL_TLS_CALLBACK)
+else()
+  add_mdbx_option(MDBX_USE_OFDLOCKS "Use Open file description locks (aka OFD locks, non-POSIX)" AUTO)
+  mark_as_advanced(MDBX_USE_OFDLOCKS)
+endif()
+add_mdbx_option(MDBX_LOCKING "Locking method (Win32=-1, SysV=5, POSIX=1988, POSIX=2001, POSIX=2008, Futexes=1995)" AUTO)
+mark_as_advanced(MDBX_LOCKING)
+add_mdbx_option(MDBX_TRUST_RTC "Does a system have battery-backed Real-Time Clock or just a fake" AUTO)
+mark_as_advanced(MDBX_TRUST_RTC)
+option(MDBX_FORCE_ASSERTIONS "Force enable assertion checking" OFF)
+
+if(NOT MDBX_AMALGAMATED_SOURCE)
+  add_mdbx_option(MDBX_ALLOY_BUILD "Build MDBX library through single/alloyed object file" ON)
+endif()
+
+if((MDBX_BUILD_TOOLS OR MDBX_ENABLE_TESTS) AND MDBX_BUILD_SHARED_LIBRARY)
+  add_mdbx_option(MDBX_LINK_TOOLS_NONSTATIC "Link MDBX tools with non-static libmdbx" OFF)
+else()
+  unset(MDBX_LINK_TOOLS_NONSTATIC CACHE)
+endif()
+
+if(CMAKE_CXX_COMPILER_LOADED AND MDBX_CXX_STANDARD GREATER_EQUAL 11 AND MDBX_CXX_STANDARD LESS 83)
+  if(NOT MDBX_AMALGAMATED_SOURCE)
+    option(MDBX_ENABLE_TESTS "Build MDBX tests" ${BUILD_TESTING})
+  endif()
+  if(NOT MDBX_AVOID_CRT
+      AND NOT (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
+      AND NOT (CMAKE_COMPILER_IS_CLANG AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4)
+      AND NOT (MSVC AND MSVC_VERSION LESS 1900))
+    option(MDBX_BUILD_CXX "Build C++ portion" ON)
+  else()
+    set(MDBX_BUILD_CXX FALSE)
+  endif()
+else()
+  set(MDBX_BUILD_CXX FALSE)
+  set(MDBX_ENABLE_TESTS FALSE)
+endif()
+
+################################################################################
+################################################################################
+
+if(MDBX_BUILD_CXX AND NOT CMAKE_CXX_COMPILER_LOADED)
+  message(FATAL_ERROR "MDBX_BUILD_CXX=${MDBX_BUILD_CXX}: The C++ compiler is required to build the C++API.")
+endif()
+
+# Get version
+fetch_version(MDBX "${CMAKE_CURRENT_SOURCE_DIR}" FALSE)
+message(STATUS "libmdbx version is ${MDBX_VERSION}")
+
+# sources list
+set(LIBMDBX_PUBLIC_HEADERS mdbx.h)
+set(LIBMDBX_SOURCES mdbx.h "${CMAKE_CURRENT_BINARY_DIR}/config.h")
+if(MDBX_AMALGAMATED_SOURCE)
+  list(APPEND LIBMDBX_SOURCES mdbx.c)
+else()
+  # generate version file
+  configure_file("${MDBX_SOURCE_DIR}/version.c.in"
+    "${CMAKE_CURRENT_BINARY_DIR}/version.c" ESCAPE_QUOTES)
+  file(SHA256 "${CMAKE_CURRENT_BINARY_DIR}/version.c" MDBX_SOURCERY_DIGEST)
+  string(MAKE_C_IDENTIFIER "${MDBX_GIT_DESCRIBE}" MDBX_SOURCERY_SUFFIX)
+  set(MDBX_BUILD_SOURCERY "${MDBX_SOURCERY_DIGEST}_${MDBX_SOURCERY_SUFFIX}")
+
+  if(MDBX_ALLOY_BUILD)
+    list(APPEND LIBMDBX_SOURCES "${MDBX_SOURCE_DIR}/alloy.c")
+    include_directories("${MDBX_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}")
+  else()
+    list(APPEND LIBMDBX_SOURCES
+      "${CMAKE_CURRENT_BINARY_DIR}/version.c"
+      "${MDBX_SOURCE_DIR}/options.h" "${MDBX_SOURCE_DIR}/defs.h"
+      "${MDBX_SOURCE_DIR}/internals.h" "${MDBX_SOURCE_DIR}/osal.h"
+      "${MDBX_SOURCE_DIR}/core.c" "${MDBX_SOURCE_DIR}/osal.c"
+      "${MDBX_SOURCE_DIR}/lck-posix.c" "${MDBX_SOURCE_DIR}/lck-windows.c")
+    include_directories("${MDBX_SOURCE_DIR}")
+  endif()
+endif(MDBX_AMALGAMATED_SOURCE)
+if(MDBX_BUILD_CXX)
+  message(STATUS "Use C${MDBX_C_STANDARD} and C++${MDBX_CXX_STANDARD} for libmdbx")
+  list(APPEND LIBMDBX_PUBLIC_HEADERS mdbx.h++)
+  list(APPEND LIBMDBX_SOURCES "${MDBX_SOURCE_DIR}/mdbx.c++" mdbx.h++)
+else()
+  message(STATUS "Use C${MDBX_C_STANDARD} for libmdbx but C++ portion is disabled")
+endif()
+
+macro(target_setup_options TARGET)
+  if(DEFINED INTERPROCEDURAL_OPTIMIZATION)
+    set_target_properties(${TARGET} PROPERTIES
+      INTERPROCEDURAL_OPTIMIZATION $<BOOL:${INTERPROCEDURAL_OPTIMIZATION}>)
+  endif()
+  set_target_properties(${TARGET} PROPERTIES
+    C_STANDARD ${MDBX_C_STANDARD} C_STANDARD_REQUIRED ON)
+  if(MDBX_BUILD_CXX)
+    set_target_properties(${TARGET} PROPERTIES
+      CXX_STANDARD ${MDBX_CXX_STANDARD} CXX_STANDARD_REQUIRED ON)
+  endif()
+  if(CC_HAS_FASTMATH)
+    target_compile_options(${TARGET} PRIVATE "-ffast-math")
+  endif()
+  if(CC_HAS_VISIBILITY)
+    target_compile_options(${TARGET} PRIVATE "-fvisibility=hidden")
+  endif()
+  if(BUILD_FOR_NATIVE_CPU AND CC_HAS_ARCH_NATIVE)
+    target_compile_options(${TARGET} PUBLIC "-march=native")
+  endif()
+endmacro()
+
+macro(libmdbx_setup_libs TARGET MODE)
+  target_link_libraries(${TARGET} ${MODE} Threads::Threads)
+  if(${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+    target_link_libraries(${TARGET} ${MODE} ntdll.lib)
+    if(MDBX_NTDLL_EXTRA_IMPLIB AND MDBX_AVOID_CRT)
+      target_link_libraries(${TARGET} ${MODE} ntdll_extra)
+    endif()
+  elseif(${CMAKE_SYSTEM_NAME} STREQUAL "SunOS" OR ${CMAKE_SYSTEM_NAME} STREQUAL "Solaris")
+    target_link_libraries(${TARGET} ${MODE} kstat)
+  elseif(${CMAKE_SYSTEM_NAME} STREQUAL "Android")
+    target_link_libraries(${TARGET} ${MODE} log)
+  endif()
+  if(LIBCXX_FILESYSTEM AND MDBX_BUILD_CXX)
+    target_link_libraries(${TARGET} ${MODE} ${LIBCXX_FILESYSTEM})
+  endif()
+endmacro()
+
+# build static library
+if(MDBX_INSTALL_STATIC)
+  add_library(mdbx-static STATIC ${LIBMDBX_SOURCES})
+else()
+  add_library(mdbx-static STATIC EXCLUDE_FROM_ALL ${LIBMDBX_SOURCES})
+endif()
+set_target_properties(mdbx-static PROPERTIES PUBLIC_HEADER "${LIBMDBX_PUBLIC_HEADERS}")
+target_compile_definitions(mdbx-static PRIVATE MDBX_BUILD_SHARED_LIBRARY=0)
+target_setup_options(mdbx-static)
+libmdbx_setup_libs(mdbx-static INTERFACE)
+if(MDBX_BUILD_SHARED_LIBRARY)
+  set_target_properties(mdbx-static PROPERTIES OUTPUT_NAME mdbx-static)
+else()
+  set_target_properties(mdbx-static PROPERTIES OUTPUT_NAME mdbx)
+endif()
+
+################################################################################
+
+# build shared library
+if(MDBX_BUILD_SHARED_LIBRARY)
+  add_library(mdbx SHARED ${LIBMDBX_SOURCES})
+  set_target_properties(mdbx PROPERTIES PUBLIC_HEADER "${LIBMDBX_PUBLIC_HEADERS}")
+  target_compile_definitions(mdbx PRIVATE LIBMDBX_EXPORTS MDBX_BUILD_SHARED_LIBRARY=1 INTERFACE LIBMDBX_IMPORTS)
+  target_setup_options(mdbx)
+  libmdbx_setup_libs(mdbx PRIVATE)
+  if(MSVC)
+    if(MDBX_NTDLL_EXTRA_IMPLIB AND MDBX_AVOID_CRT)
+      set_property(TARGET mdbx PROPERTY LINKER_FLAGS "/NODEFAULTLIB")
+    else()
+      set_property(TARGET mdbx PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")
+    endif()
+  endif()
+  if(CC_HAS_VISIBILITY AND (LTO_ENABLED OR INTERPROCEDURAL_OPTIMIZATION))
+    set_target_properties(mdbx PROPERTIES LINK_FLAGS "-fvisibility=hidden")
+  endif()
+  list(APPEND MDBX_BUILD_FLAGS ${CMAKE_SHARED_LINKER_FLAGS})
+endif()
+
+if(MDBX_BUILD_SHARED_LIBRARY AND MDBX_LINK_TOOLS_NONSTATIC)
+  set(TOOL_MDBX_LIB mdbx)
+
+  # use, i.e. don't skip the full RPATH for the build tree
+  set(CMAKE_SKIP_BUILD_RPATH FALSE)
+
+  # when building, don't use the install RPATH already (but later on when installing)
+  set(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
+
+  # add the automatically determined parts of the RPATH
+  # which point to directories outside the build tree to the install RPATH
+  set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+
+  # the RPATH to be used when installing, but only if it's not a system directory
+  list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/lib" isSystemDir)
+  if(isSystemDir EQUAL -1)
+    if(${CMAKE_SYSTEM_NAME} STREQUAL "Darwin")
+      set(CMAKE_INSTALL_RPATH "@executable_path/../lib")
+    else()
+      set(CMAKE_INSTALL_RPATH "\$ORIGIN/../lib")
+    endif()
+  endif()
+else()
+  set(TOOL_MDBX_LIB mdbx-static)
+endif()
+
+# build mdbx-tools
+if(MDBX_BUILD_TOOLS)
+  if(NOT MDBX_AMALGAMATED_SOURCE AND ${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+    set(WINGETOPT_SRC ${MDBX_SOURCE_DIR}/wingetopt.c ${MDBX_SOURCE_DIR}/wingetopt.h)
+  else()
+    set(WINGETOPT_SRC "")
+  endif()
+
+  foreach(TOOL mdbx_chk mdbx_copy mdbx_stat mdbx_dump mdbx_load)
+    add_executable(${TOOL} mdbx.h ${MDBX_SOURCE_DIR}/${TOOL}.c ${WINGETOPT_SRC})
+    if(MDBX_C_STANDARD)
+      set_target_properties(${TOOL} PROPERTIES
+        C_STANDARD ${MDBX_C_STANDARD} C_STANDARD_REQUIRED ON)
+    endif()
+    target_setup_options(${TOOL})
+    target_link_libraries(${TOOL} ${TOOL_MDBX_LIB})
+  endforeach()
+  if(LIB_MATH)
+    target_link_libraries(mdbx_chk ${LIB_MATH})
+    target_link_libraries(mdbx_stat ${LIB_MATH})
+  endif()
+endif()
+
+################################################################################
+
+# mdbx-shared-lib installation
+if(NOT DEFINED MDBX_DLL_INSTALL_DESTINATION)
+  if(WIN32)
+    set(MDBX_DLL_INSTALL_DESTINATION bin)
+  else()
+    set(MDBX_DLL_INSTALL_DESTINATION lib)
+  endif()
+endif()
+if(MDBX_BUILD_SHARED_LIBRARY)
+  if(CMAKE_VERSION VERSION_LESS 3.12)
+    install(TARGETS mdbx EXPORT libmdbx
+      LIBRARY DESTINATION ${MDBX_DLL_INSTALL_DESTINATION} COMPONENT runtime
+      OBJECTS DESTINATION lib COMPONENT devel
+      ARCHIVE DESTINATION lib COMPONENT devel
+      PUBLIC_HEADER DESTINATION include COMPONENT devel
+      INCLUDES DESTINATION include COMPONENT devel)
+  else()
+    install(TARGETS mdbx EXPORT libmdbx
+      LIBRARY DESTINATION ${MDBX_DLL_INSTALL_DESTINATION} COMPONENT runtime
+      NAMELINK_COMPONENT devel
+      OBJECTS DESTINATION lib COMPONENT devel
+      ARCHIVE DESTINATION lib COMPONENT devel
+      PUBLIC_HEADER DESTINATION include COMPONENT devel
+      INCLUDES DESTINATION include COMPONENT devel)
+  endif()
+endif(MDBX_BUILD_SHARED_LIBRARY)
+
+# mdbx-tools installation
+if(MDBX_BUILD_TOOLS)
+  if(NOT DEFINED MDBX_TOOLS_INSTALL_DESTINATION)
+    set(MDBX_TOOLS_INSTALL_DESTINATION bin)
+  endif()
+  install(
+    TARGETS
+    mdbx_chk
+    mdbx_stat
+    mdbx_copy
+    mdbx_dump
+    mdbx_load
+    RUNTIME
+    DESTINATION ${MDBX_TOOLS_INSTALL_DESTINATION}
+    COMPONENT runtime)
+  if(MDBX_INSTALL_MANPAGES)
+    if(NOT DEFINED MDBX_MAN_INSTALL_DESTINATION)
+      set(MDBX_MAN_INSTALL_DESTINATION man/man1)
+    endif()
+    install(
+      FILES
+      "${MDBX_SOURCE_DIR}/man1/mdbx_chk.1"
+      "${MDBX_SOURCE_DIR}/man1/mdbx_stat.1"
+      "${MDBX_SOURCE_DIR}/man1/mdbx_copy.1"
+      "${MDBX_SOURCE_DIR}/man1/mdbx_dump.1"
+      "${MDBX_SOURCE_DIR}/man1/mdbx_load.1"
+      DESTINATION ${MDBX_MAN_INSTALL_DESTINATION}
+      COMPONENT doc)
+  endif()
+endif(MDBX_BUILD_TOOLS)
+
+# mdbx-static-lib installation
+if(MDBX_INSTALL_STATIC)
+  if(CMAKE_VERSION VERSION_LESS 3.12)
+    install(TARGETS mdbx-static EXPORT libmdbx
+      LIBRARY DESTINATION lib COMPONENT devel
+      OBJECTS DESTINATION lib COMPONENT devel
+      ARCHIVE DESTINATION lib COMPONENT devel
+      PUBLIC_HEADER DESTINATION include COMPONENT devel
+      INCLUDES DESTINATION include COMPONENT devel)
+  else()
+    install(TARGETS mdbx-static EXPORT libmdbx
+      LIBRARY DESTINATION lib COMPONENT devel
+      NAMELINK_COMPONENT devel
+      OBJECTS DESTINATION lib COMPONENT devel
+      ARCHIVE DESTINATION lib COMPONENT devel
+      PUBLIC_HEADER DESTINATION include COMPONENT devel
+      INCLUDES DESTINATION include COMPONENT devel)
+  endif()
+endif(MDBX_INSTALL_STATIC)
+
+################################################################################
+
+# collect options & build info
+string(TIMESTAMP MDBX_BUILD_TIMESTAMP UTC)
+set(MDBX_BUILD_FLAGS ${CMAKE_C_FLAGS})
+if(MDBX_BUILD_CXX)
+  set(MDBX_BUILD_FLAGS ${CMAKE_CXX_FLAGS})
+endif()
+
+# append cmake's build-type flags and defines
+if(NOT CMAKE_CONFIGURATION_TYPES)
+  list(APPEND MDBX_BUILD_FLAGS ${CMAKE_C_FLAGS_${CMAKE_BUILD_TYPE_UPPERCASE}})
+  if(MDBX_BUILD_CXX)
+    list(APPEND MDBX_BUILD_FLAGS ${CMAKE_CXX_FLAGS_${CMAKE_BUILD_TYPE_UPPERCASE}})
+  endif()
+endif()
+
+# choice target to fetch definitions and options
+if(MDBX_BUILD_SHARED_LIBRARY)
+  set(target4fetch mdbx)
+else()
+  set(target4fetch mdbx-static)
+endif()
+
+# get definitions
+get_target_property(defs_list ${target4fetch} COMPILE_DEFINITIONS)
+if(defs_list)
+  list(APPEND MDBX_BUILD_FLAGS ${defs_list})
+endif()
+
+# get target compile options
+get_target_property(options_list ${target4fetch} COMPILE_OPTIONS)
+if(options_list)
+  list(APPEND MDBX_BUILD_FLAGS ${options_list})
+endif()
+
+list(REMOVE_DUPLICATES MDBX_BUILD_FLAGS)
+string(REPLACE ";" " " MDBX_BUILD_FLAGS "${MDBX_BUILD_FLAGS}")
+if(CMAKE_CONFIGURATION_TYPES)
+  # add dynamic part via per-configuration define
+  message(STATUS "MDBX Compile Flags: ${MDBX_BUILD_FLAGS} <AND CONFIGURATION DEPENDENT>")
+  add_definitions(-DMDBX_BUILD_FLAGS_CONFIG="$<$<CONFIG:Debug>:${CMAKE_C_FLAGS_DEBUG} ${CMAKE_C_DEFINES_DEBUG}>$<$<CONFIG:Release>:${CMAKE_C_FLAGS_RELEASE} ${CMAKE_C_DEFINES_RELEASE}>$<$<CONFIG:RelWithDebInfo>:${CMAKE_C_FLAGS_RELWITHDEBINFO} ${CMAKE_C_DEFINES_RELWITHDEBINFO}>$<$<CONFIG:MinSizeRel>:${CMAKE_C_FLAGS_MINSIZEREL} ${CMAKE_C_DEFINES_MINSIZEREL}>")
+else()
+  message(STATUS "MDBX Compile Flags: ${MDBX_BUILD_FLAGS}")
+endif()
+
+# get compiler info
+execute_process(COMMAND sh -c "${CMAKE_C_COMPILER} --version | head -1"
+  OUTPUT_VARIABLE MDBX_BUILD_COMPILER
+  OUTPUT_STRIP_TRAILING_WHITESPACE
+  ERROR_QUIET
+  RESULT_VARIABLE rc)
+if(rc OR NOT MDBX_BUILD_COMPILER)
+  string(STRIP "${CMAKE_C_COMPILER_ID}-${CMAKE_C_COMPILER_VERSION}" MDBX_BUILD_COMPILER)
+endif()
+
+# make a build-target triplet
+if(CMAKE_C_COMPILER_TARGET)
+  set(MDBX_BUILD_TARGET "${CMAKE_C_COMPILER_TARGET}")
+elseif(CMAKE_C_PLATFORM_ID AND NOT CMAKE_C_PLATFORM_ID STREQUAL CMAKE_SYSTEM_NAME)
+  string(STRIP "${CMAKE_C_PLATFORM_ID}-${CMAKE_SYSTEM_NAME}" MDBX_BUILD_TARGET)
+elseif(CMAKE_LIBRARY_ARCHITECTURE)
+  string(STRIP "${CMAKE_LIBRARY_ARCHITECTURE}-${CMAKE_SYSTEM_NAME}" MDBX_BUILD_TARGET)
+elseif(CMAKE_GENERATOR_PLATFORM AND NOT CMAKE_C_PLATFORM_ID STREQUAL CMAKE_SYSTEM_NAME)
+  string(STRIP "${CMAKE_GENERATOR_PLATFORM}-${CMAKE_SYSTEM_NAME}" MDBX_BUILD_TARGET)
+elseif(CMAKE_SYSTEM_ARCH)
+  string(STRIP "${CMAKE_SYSTEM_ARCH}-${CMAKE_SYSTEM_NAME}" MDBX_BUILD_TARGET)
+else()
+  string(STRIP "${CMAKE_SYSTEM_PROCESSOR}-${CMAKE_SYSTEM_NAME}" MDBX_BUILD_TARGET)
+endif()
+
+# provide build-type
+if(CMAKE_CONFIGURATION_TYPES)
+  # via per-configuration define
+  add_definitions(-DMDBX_BUILD_TYPE="$<CONFIG>")
+  set(MDBX_BUILD_TYPE "<CONFIGURATION DEPENDENT>")
+else()
+  set(MDBX_BUILD_TYPE ${CMAKE_BUILD_TYPE})
+endif()
+
+# options
+set(options VERSION C_COMPILER CXX_COMPILER MDBX_BUILD_TARGET MDBX_BUILD_TYPE)
+foreach(item IN LISTS options)
+  if(DEFINED ${item})
+    set(value "${${item}}")
+  elseif(DEFINED MDBX_${item})
+    set(item MDBX_${item})
+    set(value "${${item}}")
+  elseif(DEFINED CMAKE_${item})
+    set(item CMAKE_${item})
+    set(value "${${item}}")
+  else()
+    set(value "undefined")
+  endif()
+  message(STATUS "${item}: ${value}")
+endforeach(item)
+
+# provide config.h for library build info
+configure_file("${MDBX_SOURCE_DIR}/config.h.in"
+  "${CMAKE_CURRENT_BINARY_DIR}/config.h" ESCAPE_QUOTES)
+add_definitions(-DMDBX_CONFIG_H="${CMAKE_CURRENT_BINARY_DIR}/config.h")
+
+################################################################################
+
+if(NOT MDBX_AMALGAMATED_SOURCE AND MDBX_ENABLE_TESTS)
+  if(NOT CMAKE_CXX_COMPILER_LOADED)
+    message(FATAL_ERROR "MDBX_ENABLE_TESTS=${MDBX_ENABLE_TESTS}: The C++ compiler is required to build the tests.")
+  endif()
+  add_subdirectory(test)
+endif()
+
+################################################################################
+
+set(PACKAGE "libmdbx")
+set(CPACK_PACKAGE_VERSION_MAJOR ${MDBX_VERSION_MAJOR})
+set(CPACK_PACKAGE_VERSION_MINOR ${MDBX_VERSION_MINOR})
+set(CPACK_PACKAGE_VERSION_PATCH ${MDBX_VERSION_RELEASE})
+set(CPACK_PACKAGE_VERSION_COMMIT ${MDBX_VERSION_REVISION})
+set(PACKAGE_VERSION "${CPACK_PACKAGE_VERSION_MAJOR}.${CPACK_PACKAGE_VERSION_MINOR}.${CPACK_PACKAGE_VERSION_PATCH}.${CPACK_PACKAGE_VERSION_COMMIT}")
+message(STATUS "libmdbx package version is ${PACKAGE_VERSION}")
+
+cmake_policy(POP)
diff --git a/plugins/Dbx_mdbx/src/libmdbx/ChangeLog.md b/plugins/Dbx_mdbx/src/libmdbx/ChangeLog.md
new file mode 100644
index 0000000000..50b911f5a7
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/ChangeLog.md
@@ -0,0 +1,305 @@
+ChangeLog
+---------
+
+## v0.9.3 (in development) scheduled at 2021-02-23
+
+TODO:
+ - Engage new terminology (https://github.com/erthink/libmdbx/issues/137).
+ - Rework/speedup the implementation of the dirty page list (lazy compactification, lazy sorting via merge).
+ - Resolve few TODOs (https://github.com/erthink/libmdbx/issues/124, https://github.com/erthink/libmdbx/issues/127,
+   https://github.com/erthink/libmdbx/issues/132, https://github.com/erthink/libmdbx/issues/115).
+ - Finalize C++ API (few typos and trivia bugs are still likely for now).
+ - Packages for [ROSA Linux](https://www.rosalinux.ru/), [ALT Linux](https://www.altlinux.org/), Fedora/RHEL, Debian/Ubuntu.
+
+Acknowledgements:
+
+ - [Mahlon E. Smith](http://www.martini.nu/) for [FreeBSD port of libmdbx](https://svnweb.freebsd.org/ports/head/databases/mdbx/).
+ - [장세연](http://www.castis.com) for bug fixing and PR.
+ - [Clément Renault](https://github.com/Kerollmops/heed) for [Heed](https://github.com/Kerollmops/heed) fully typed Rust wrapper.
+ - [Alex Sharov](https://github.com/AskAlexSharov) for bug reporting.
+ - [Noel Kuntze](https://github.com/Thermi) for bug reporting.
+
+Removed options and features:
+
+ - Drop `MDBX_HUGE_TRANSACTIONS` build-option (now no longer required).
+
+New features:
+
+ - Package for FreeBSD is available now by Mahlon E. Smith.
+ - New API functions to get/set various options (https://github.com/erthink/libmdbx/issues/128):
+    - the maximum number of named databases for the environment;
+    - the maximum number of threads/reader slots;
+    - threshold (since the last unsteady commit) to force flush the data buffers to disk;
+    - relative period (since the last unsteady commit) to force flush the data buffers to disk;
+    - limit to grow a list of reclaimed/recycled page's numbers for finding a sequence of contiguous pages for large data items;
+    - limit to grow a cache of dirty pages for reuse in the current transaction;
+    - limit of a pre-allocated memory items for dirty pages;
+    - limit of dirty pages for a write transaction;
+    - initial allocation size for dirty pages list of a write transaction;
+    - maximal part of the dirty pages may be spilled when necessary;
+    - minimal part of the dirty pages should be spilled when necessary;
+    - how much of the parent transaction dirty pages will be spilled while start each child transaction;
+ - Unlimited/Dynamic size of retired and dirty page lists (https://github.com/erthink/libmdbx/issues/123).
+ - Added `-p` option (purge subDB before loading) to `mdbx_load` tool.
+ - Reworked spilling of large transaction and committing of nested transactions:
+    - page spilling code reworked to avoid the flaws and bugs inherited from LMDB;
+    - limit for number of dirty pages now is controllable at runtime;
+    - a spilled pages, including overflow/large pages, now can be reused and refunded/compactified in nested transactions;
+    - more effective refunding/compactification especially for the loosed page cache.
+ - Added `MDBX_ENABLE_REFUND` and `MDBX_PNL_ASCENDING` internal/advanced build options.
+ - Added `mdbx_default_pagesize()` function.
+ - Better support architectures with a weak/relaxed memory consistency model (ARM, AARCH64, PPC, MIPS, RISC-V, etc) by means [C11 atomics](https://en.cppreference.com/w/c/atomic).
+
+Fixes:
+
+ - Fixed missing cleanup (null assigned) in the C++ commit/abort (https://github.com/erthink/libmdbx/pull/143).
+ - Fixed `mdbx_realloc()` for case of nullptr and `MDBX_AVOID_CRT=ON` for Windows.
+ - Fixed the possibility to use invalid and renewed (closed & re-opened, dropped & re-created) DBI-handles (https://github.com/erthink/libmdbx/issues/146).
+ - Fixed 4-byte aligned access to 64-bit integers, including access to the `bootid` meta-page's field (https://github.com/erthink/libmdbx/issues/153).
+ - Fixed minor/potential memory leak during page flushing and unspilling.
+ - Fixed handling states of cursors's and subDBs's for nested transactions.
+ - Fixed page leak in extra rare case the list of retired pages changed during update GC on transaction commit.
+ - Fixed assertions to avoid false-positive UB detection by CLANG/LLVM (https://github.com/erthink/libmdbx/issues/153).
+ - Fixed `MDBX_TXN_FULL` and regressive `MDBX_KEYEXIST` during large transaction commit with `MDBX_LIFORECLAIM` (https://github.com/erthink/libmdbx/issues/123).
+ - Fixed auto-recovery (`weak->steady` with the same boot-id) when Database size at last weak checkpoint is large than at last steady checkpoint.
+ - Fixed operation on systems with unusual small/large page size, including PowerPC (https://github.com/erthink/libmdbx/issues/157).
+
+
+## v0.9.2 at 2020-11-27
+
+Acknowledgements:
+
+ - Jens Alfke (Mobile Architect at [Couchbase](https://www.couchbase.com/)) for [NimDBX](https://github.com/snej/nimdbx).
+ - Clément Renault (CTO at [MeiliSearch](https://www.meilisearch.com/)) for [mdbx-rs](https://github.com/Kerollmops/mdbx-rs).
+ - Alex Sharov (Go-Lang Teach Lead at [TurboGeth/Ethereum](https://ethereum.org/)) for an extreme test cases and bug reporting.
+ - George Hazan (CTO at [Miranda NG](https://www.miranda-ng.org/)) for bug reporting.
+ - [Positive Technologies](https://www.ptsecurity.com/) for funding and [The Standoff](https://standoff365.com/).
+
+Added features:
+
+ - Provided package for [buildroot](https://buildroot.org/).
+ - Binding for Nim is [available](https://github.com/snej/nimdbx) now by Jens Alfke.
+ - Added `mdbx_env_delete()` for deletion an environment files in a proper and multiprocess-safe way.
+ - Added `mdbx_txn_commit_ex()` with collecting latency information.
+ - Fast completion pure nested transactions.
+ - Added `LIBMDBX_INLINE_API` macro and inline versions of some API functions.
+ - Added `mdbx_cursor_copy()` function.
+ - Extended tests for checking cursor tracking.
+ - Added `MDBX_SET_LOWERBOUND` operation for `mdbx_cursor_get()`.
+
+Fixes:
+
+ - Fixed missing installation of `mdbx.h++`.
+ - Fixed use of obsolete `__noreturn`.
+ - Fixed use of `yield` instruction on ARM if unsupported.
+ - Added pthread workaround for buggy toolchain/cmake/buildroot.
+ - Fixed use of `pthread_yield()` for non-GLIBC.
+ - Fixed use of `RegGetValueA()` on Windows 2000/XP.
+ - Fixed use of `GetTickCount64()` on Windows 2000/XP.
+ - Fixed opening DB on a network shares (in the exclusive mode).
+ - Fixed copy&paste typos.
+ - Fixed minor false-positive GCC warning.
+ - Added workaround for broken `DEFINE_ENUM_FLAG_OPERATORS` from Windows SDK.
+ - Fixed cursor state after multimap/dupsort repeated deletes (https://github.com/erthink/libmdbx/issues/121).
+ - Added `SIGPIPE` suppression for internal thread during `mdbx_env_copy()`.
+ - Fixed extra-rare `MDBX_KEY_EXIST` error during `mdbx_commit()` (https://github.com/erthink/libmdbx/issues/131).
+ - Fixed spilled pages checking (https://github.com/erthink/libmdbx/issues/126).
+ - Fixed `mdbx_load` for 'plain text' and without `-s name` cases (https://github.com/erthink/libmdbx/issues/136).
+ - Fixed save/restore/commit of cursors for nested transactions.
+ - Fixed cursors state in rare/special cases (move next beyond end-of-data, after deletion and so on).
+ - Added workaround for MSVC 19.28 (Visual Studio 16.8) (but may still hang during compilation).
+ - Fixed paranoidal Clang C++ UB for bitwise operations with flags defined by enums.
+ - Fixed large pages checking (for compatibility and to avoid false-positive errors from `mdbx_chk`).
+ - Added workaround for Wine (https://github.com/miranda-ng/miranda-ng/issues/1209).
+ - Fixed `ERROR_NOT_SUPPORTED` while opening DB by UNC pathnames (https://github.com/miranda-ng/miranda-ng/issues/2627).
+ - Added handling `EXCEPTION_POSSIBLE_DEADLOCK` condition for Windows.
+
+
+## v0.9.1 2020-09-30
+
+Added features:
+
+ - Preliminary C++ API with support for C++17 polymorphic allocators.
+ - [Online C++ API reference](https://erthink.github.io/libmdbx/) by Doxygen.
+ - Quick reference for Insert/Update/Delete operations.
+ - Explicit `MDBX_SYNC_DURABLE` to sync modes for API clarity.
+ - Explicit `MDBX_ALLDUPS` and `MDBX_UPSERT` for API clarity.
+ - Support for read transactions preparation (`MDBX_TXN_RDONLY_PREPARE` flag).
+ - Support for cursor preparation/(pre)allocation and reusing (`mdbx_cursor_create()` and `mdbx_cursor_bind()` functions).
+ - Support for checking database using specified meta-page (see `mdbx_chk -h`).
+ - Support for turn to the specific meta-page after checking (see `mdbx_chk -h`).
+ - Support for explicit reader threads (de)registration.
+ - The `mdbx_txn_break()` function to explicitly mark a transaction as broken.
+ - Improved handling of corrupted databases by `mdbx_chk` utility and `mdbx_walk_tree()` function.
+ - Improved DB corruption detection by checking parent-page-txnid.
+ - Improved opening large DB (> 4Gb) from 32-bit code.
+ - Provided `pure-function` and `const-function` attributes to C API.
+ - Support for user-settable context for transactions & cursors.
+ - Revised API and documentation related to Handle-Slow-Readers callback feature.
+
+Deprecated functions and flags:
+
+ - For clarity and API simplification the `MDBX_MAPASYNC` flag is deprecated.
+   Just use `MDBX_SAFE_NOSYNC` or `MDBX_UTTERLY_NOSYNC` instead of it.
+ - `MDBX_oom_func`, `mdbx_env_set_oomfunc()` and `mdbx_env_get_oomfunc()`
+   replaced with `MDBX_hsr_func`, `mdbx_env_get_hsr` and `mdbx_env_get_hsr()`.
+
+Fixes:
+
+ - Fix `mdbx_strerror()` for `MDBX_BUSY` error (no error description is returned).
+ - Fix update internal meta-geo information in read-only mode (`EACCESS` or `EBADFD` error).
+ - Fix `mdbx_page_get()` null-defer when DB corrupted (crash by `SIGSEGV`).
+ - Fix `mdbx_env_open()` for re-opening after non-fatal errors (`mdbx_chk` unexpected failures).
+ - Workaround for MSVC 19.27 `static_assert()` bug.
+ - Doxygen descriptions and refinement.
+ - Update Valgrind's suppressions.
+ - Workaround to avoid infinite loop of 'nested' testcase on MIPS under QEMU.
+ - Fix a lot of typos & spelling (Thanks to Josh Soref for PR).
+ - Fix `getopt()` messages for Windows (Thanks to Andrey Sporaw for reporting).
+ - Fix MSVC compiler version requirements (Thanks to Andrey Sporaw for reporting).
+ - Workarounds for QEMU's bugs to run tests for cross-builded library under QEMU.
+ - Now C++ compiler optional for building by CMake.
+
+
+## v0.9.0 2020-07-31 (not a release, but API changes)
+
+Added features:
+
+ - [Online C API reference](https://erthink.github.io/libmdbx/) by Doxygen.
+ - Separated enums for environment, sub-databases, transactions, copying and data-update flags.
+
+Deprecated functions and flags:
+
+ - Usage of custom comparators and the `mdbx_dbi_open_ex()` are deprecated, since such databases couldn't be checked by the `mdbx_chk` utility.
+   Please use the value-to-key functions to provide keys that are compatible with the built-in libmdbx comparators.
+
+
+## v0.8.2 2020-07-06
+- Added support multi-opening the same DB in a process with SysV locking (BSD).
+- Fixed warnings & minors for LCC compiler (E2K).
+- Enabled to simultaneously open the same database from processes with and without the `MDBX_WRITEMAP` option.
+- Added key-to-value, `mdbx_get_keycmp()` and `mdbx_get_datacmp()` functions (helpful to avoid using custom comparators).
+- Added `ENABLE_UBSAN` CMake option to enabling the UndefinedBehaviorSanitizer from GCC/CLANG.
+- Workaround for [CLANG bug](https://bugs.llvm.org/show_bug.cgi?id=43275).
+- Returning `MDBX_CORRUPTED` in case all meta-pages are weak and no other error.
+- Refined mode bits while auto-creating LCK-file.
+- Avoids unnecessary database file re-mapping in case geometry changed by another process(es).
+  From the user's point of view, the `MDBX_UNABLE_EXTEND_MAPSIZE` error will now be returned less frequently and only when using the DB in the current process really requires it to be reopened.
+- Remapping on-the-fly and of the database file was implemented.
+  Now remapping with a change of address is performed automatically if there are no dependent readers in the current process.
+
+
+## v0.8.1 2020-06-12
+- Minor change versioning. The last number in the version now means the number of commits since last release/tag.
+- Provide ChangeLog file.
+- Fix for using libmdbx as a C-only sub-project with CMake.
+- Fix `mdbx_env_set_geometry()` for case it is called from an opened environment outside of a write transaction.
+- Add support for huge transactions and `MDBX_HUGE_TRANSACTIONS` build-option (default `OFF`).
+- Refine LTO (link time optimization) for clang.
+- Force enabling exceptions handling for MSVC (`/EHsc` option).
+
+
+## v0.8.0 2020-06-05
+- Support for Android/Bionic.
+- Support for iOS.
+- Auto-handling `MDBX_NOSUBDIR` while opening for any existing database.
+- Engage github-actions to make release-assets.
+- Clarify API description.
+- Extended keygen-cases in stochastic test.
+- Fix fetching of first/lower key from LEAF2-page during page merge.
+- Fix missing comma in array of error messages.
+- Fix div-by-zero while copy-with-compaction for non-resizable environments.
+- Fixes & enhancements for custom-comparators.
+- Fix `MDBX_AVOID_CRT` option and missing `ntdll.def`.
+- Fix `mdbx_env_close()` to work correctly called concurrently from several threads.
+- Fix null-deref in an ASAN-enabled builds while opening the environment with error and/or read-only.
+- Fix AddressSanitizer errors after closing the environment.
+- Fix/workaround to avoid GCC 10.x pedantic warnings.
+- Fix using `ENODATA` for FreeBSD.
+- Avoid invalidation of DBI-handle(s) when it just closes.
+- Avoid using `pwritev()` for single-writes (up to 10% speedup for some kernels & scenarios).
+- Avoiding `MDBX_UTTERLY_NOSYNC` as result of flags merge.
+- Add `mdbx_dbi_dupsort_depthmask()` function.
+- Add `MDBX_CP_FORCE_RESIZEABLE` option.
+- Add deprecated `MDBX_MAP_RESIZED` for compatibility.
+- Add `MDBX_BUILD_TOOLS` option (default `ON`).
+- Refine `mdbx_dbi_open_ex()` to safe concurrently opening the same handle from different threads.
+- Truncate clk-file during environment closing. So a zero-length lck-file indicates that the environment was closed properly.
+- Refine `mdbx_update_gc()` for huge transactions with small sizes of database page.
+- Extends dump/load to support all MDBX attributes.
+- Avoid upsertion the same key-value data, fix related assertions.
+- Rework min/max length checking for keys & values.
+- Checking the order of keys on all pages during checking.
+- Support `CFLAGS_EXTRA` make-option for convenience.
+- Preserve the last txnid while copying with compactification.
+- Auto-reset running transaction in mdbx_txn_renew().
+- Automatically abort errored transaction in mdbx_txn_commit().
+- Auto-choose page size for large databases.
+- Rearrange source files, rework build, options-support by CMake.
+- Crutch for WSL1 (Windows subsystem for Linux).
+- Refine install/uninstall targets.
+- Support for Valgrind 3.14 and later.
+- Add check-analyzer check-ubsan check-asan check-leak targets to Makefile.
+- Minor fix/workaround to avoid UBSAN traps for `memcpy(ptr, NULL, 0)`.
+- Avoid some GCC-analyzer false-positive warnings.
+
+
+## v0.7.0 2020-03-18
+- Workarounds for Wine (Windows compatibility layer for Linux).
+- `MDBX_MAP_RESIZED` renamed to `MDBX_UNABLE_EXTEND_MAPSIZE`.
+- Clarify API description, fix typos.
+- Speedup runtime checks in debug/checked builds.
+- Added checking for read/write transactions overlapping for the same thread, added `MDBX_TXN_OVERLAPPING` error and `MDBX_DBG_LEGACY_OVERLAP` option.
+- Added `mdbx_key_from_jsonInteger()`, `mdbx_key_from_double()`, `mdbx_key_from_float()`, `mdbx_key_from_int64()` and `mdbx_key_from_int32()` functions. See `mdbx.h` for description.
+- Fix compatibility (use zero for invalid DBI).
+- Refine/clarify error messages.
+- Avoids extra error messages "bad txn" from mdbx_chk when DB is corrupted.
+
+
+## v0.6.0 2020-01-21
+- Fix `mdbx_load` utility for custom comparators.
+- Fix checks related to `MDBX_APPEND` flag inside `mdbx_cursor_put()`.
+- Refine/fix dbi_bind() internals.
+- Refine/fix handling `STATUS_CONFLICTING_ADDRESSES`.
+- Rework `MDBX_DBG_DUMP` option to avoid disk I/O performance degradation.
+- Add built-in help to test tool.
+- Fix `mdbx_env_set_geometry()` for large page size.
+- Fix env_set_geometry() for large pagesize.
+- Clarify API description & comments, fix typos.
+
+
+## v0.5.0 2019-12-31
+- Fix returning MDBX_RESULT_TRUE from page_alloc().
+- Fix false-positive ASAN issue.
+- Fix assertion for `MDBX_NOTLS` option.
+- Rework `MADV_DONTNEED` threshold.
+- Fix `mdbx_chk` utility for don't checking some numbers if walking on the B-tree was disabled.
+- Use page's mp_txnid for basic integrity checking.
+- Add `MDBX_FORCE_ASSERTIONS` built-time option.
+- Rework `MDBX_DBG_DUMP` to avoid performance degradation.
+- Rename `MDBX_NOSYNC` to `MDBX_SAFE_NOSYNC` for clarity.
+- Interpret `ERROR_ACCESS_DENIED` from `OpenProcess()` as 'process exists'.
+- Avoid using `FILE_FLAG_NO_BUFFERING` for compatibility with small database pages.
+- Added install section for CMake.
+
+
+## v0.4.0 2019-12-02
+- Support for Mac OSX, FreeBSD, NetBSD, OpenBSD, DragonFly BSD, OpenSolaris, OpenIndiana (AIX and HP-UX pending).
+- Use bootid for decisions of rollback.
+- Counting retired pages and extended transaction info.
+- Add `MDBX_ACCEDE` flag for database opening.
+- Using OFD-locks and tracking for in-process multi-opening.
+- Hot backup into pipe.
+- Support for cmake & amalgamated sources.
+- Fastest internal sort implementation.
+- New internal dirty-list implementation with lazy sorting.
+- Support for lazy-sync-to-disk with polling.
+- Extended key length.
+- Last update transaction number for each sub-database.
+- Automatic read ahead enabling/disabling.
+- More auto-compactification.
+- Using -fsanitize=undefined and -Wpedantic options.
+- Rework page merging.
+- Nested transactions.
+- API description.
+- Checking for non-local filesystems to avoid DB corruption.
diff --git a/plugins/Dbx_mdbx/src/libmdbx/GNUmakefile b/plugins/Dbx_mdbx/src/libmdbx/GNUmakefile
new file mode 100644
index 0000000000..da781606ee
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/GNUmakefile
@@ -0,0 +1,182 @@
+# This makefile is for GNU Make 3.80 or above, and nowadays provided
+# just for compatibility and preservation of traditions.
+#
+# Please use CMake in case of any difficulties or
+# problems with this old-school's magic.
+#
+################################################################################
+#
+# Preprocessor macros (for MDBX_OPTIONS) of interest.
+#
+# Note that the defaults should already be correct for most platforms;
+# you should not need to change any of these. Read their descriptions
+# in README and source code (see src/options.h) if you do.
+# There may be other macros of interest.
+#
+
+SHELL   := env bash
+
+# install sandbox
+DESTDIR ?=
+
+# install prefixes (inside sandbox)
+prefix  ?= /usr/local
+mandir  ?= $(prefix)/man
+
+# lib/bin suffix for multiarch/biarch, e.g. '.x86_64'
+suffix  ?=
+
+CC      ?= gcc
+CFLAGS_EXTRA ?=
+LD      ?= ld
+MDBX_OPTIONS ?= -DNDEBUG=1
+CFLAGS  ?= -O2 -g -Wall -Werror -Wextra -Wpedantic -ffunction-sections -fPIC -fvisibility=hidden -std=gnu11 -pthread -Wno-error=attributes $(CFLAGS_EXTRA)
+# -Wno-tautological-compare
+CXX     ?= g++
+# Choosing C++ standard with deferred simple variable expansion trick
+CXXSTD  ?= $(eval CXXSTD := $$(shell PROBE=$$$$([ -f mdbx.c++ ] && echo mdbx.c++ || echo src/mdbx.c++); for std in gnu++20 c++20 gnu++2a c++2a gnu++17 c++17 gnu++14 c++14 gnu+11 c++11; do $(CXX) -std=$$$${std} -c $$$${PROBE} -o /dev/null 2>/dev/null >/dev/null && echo "-std=$$$${std}" && exit; done))$(CXXSTD)
+CXXFLAGS = $(CXXSTD) $(filter-out -std=gnu11,$(CFLAGS))
+
+# HINT: Try append '--no-as-needed,-lrt' for ability to built with modern glibc, but then run with the old.
+LIBS    ?= $(shell uname | grep -qi SunOS && echo "-lkstat") $(shell uname | grep -qi -e Darwin -e OpenBSD || echo "-lrt") $(shell uname | grep -qi Windows && echo "-lntdll")
+
+LDFLAGS ?= $(shell $(LD) --help 2>/dev/null | grep -q -- --gc-sections && echo '-Wl,--gc-sections,-z,relro,-O1')$(shell $(LD) --help 2>/dev/null | grep -q -- -dead_strip && echo '-Wl,-dead_strip')
+EXE_LDFLAGS ?= -pthread
+
+################################################################################
+
+UNAME      := $(shell uname -s 2>/dev/null || echo Unknown)
+define uname2sosuffix
+  case "$(UNAME)" in
+    Darwin*|Mach*) echo dylib;;
+    CYGWIN*|MINGW*|MSYS*|Windows*) echo dll;;
+    *) echo so;;
+  esac
+endef
+SO_SUFFIX  := $(shell $(uname2sosuffix))
+
+HEADERS    := mdbx.h mdbx.h++
+LIBRARIES  := libmdbx.a libmdbx.$(SO_SUFFIX)
+TOOLS      := mdbx_stat mdbx_copy mdbx_dump mdbx_load mdbx_chk
+MANPAGES   := mdbx_stat.1 mdbx_copy.1 mdbx_dump.1 mdbx_load.1 mdbx_chk.1
+
+.PHONY: mdbx all install clean
+
+all: $(LIBRARIES) $(TOOLS)
+
+mdbx: libmdbx.a libmdbx.$(SO_SUFFIX)
+
+tools: $(TOOLS)
+
+strip: all
+	strip libmdbx.$(SO_SUFFIX) $(TOOLS)
+
+clean:
+	rm -rf $(TOOLS) mdbx_test @* *.[ao] *.[ls]o *.$(SO_SUFFIX) *.dSYM *~ tmp.db/* \
+		*.gcov *.log *.err src/*.o test/*.o mdbx_example dist \
+		config.h src/config.h src/version.c *.tar*
+
+libmdbx.a: mdbx-static.o mdbx++-static.o
+	$(AR) rs $@ $?
+
+libmdbx.$(SO_SUFFIX): mdbx-dylib.o mdbx++-dylib.o
+	$(CXX) $(CXXFLAGS) $^ -pthread -shared $(LDFLAGS) $(LIBS) -o $@
+
+
+################################################################################
+# Amalgamated source code, i.e. distributed after `make dist`
+MAN_SRCDIR := man1/
+
+config.h: mdbx.c $(lastword $(MAKEFILE_LIST))
+	(echo '#define MDBX_BUILD_TIMESTAMP "$(shell date +%Y-%m-%dT%H:%M:%S%z)"' \
+	&& echo '#define MDBX_BUILD_FLAGS "$(CXXSTD) $(CFLAGS) $(LDFLAGS) $(LIBS)"' \
+	&& echo '#define MDBX_BUILD_COMPILER "$(shell (LC_ALL=C $(CC) --version || echo 'Please use GCC or CLANG compatible compiler') | head -1)"' \
+	&& echo '#define MDBX_BUILD_TARGET "$(shell set -o pipefail; (LC_ALL=C $(CC) -v 2>&1 | grep -i '^Target:' | cut -d ' ' -f 2- || (LC_ALL=C $(CC) --version | grep -qi e2k && echo E2K) || echo 'Please use GCC or CLANG compatible compiler') | head -1)"' \
+	) > $@
+
+mdbx-dylib.o: config.h mdbx.c mdbx.h $(lastword $(MAKEFILE_LIST))
+	$(CC) $(CFLAGS) $(MDBX_OPTIONS) '-DMDBX_CONFIG_H="config.h"' -DLIBMDBX_EXPORTS=1 -c mdbx.c -o $@
+
+mdbx-static.o: config.h mdbx.c mdbx.h $(lastword $(MAKEFILE_LIST))
+	$(CC) $(CFLAGS) $(MDBX_OPTIONS) '-DMDBX_CONFIG_H="config.h"' -ULIBMDBX_EXPORTS -c mdbx.c -o $@
+
+mdbx++-dylib.o: config.h mdbx.c++ mdbx.h mdbx.h++ $(lastword $(MAKEFILE_LIST))
+	$(CXX) $(CXXFLAGS) $(MDBX_OPTIONS) '-DMDBX_CONFIG_H="config.h"' -DLIBMDBX_EXPORTS=1 -c mdbx.c++ -o $@
+
+mdbx++-static.o: config.h mdbx.c++ mdbx.h mdbx.h++ $(lastword $(MAKEFILE_LIST))
+	$(CXX) $(CXXFLAGS) $(MDBX_OPTIONS) '-DMDBX_CONFIG_H="config.h"' -ULIBMDBX_EXPORTS -c mdbx.c++ -o $@
+
+mdbx_%:	mdbx_%.c libmdbx.a
+	$(CC) $(CFLAGS) $(MDBX_OPTIONS) '-DMDBX_CONFIG_H="config.h"' $^ $(EXE_LDFLAGS) $(LIBS) -o $@
+
+install: $(LIBRARIES) $(TOOLS) $(HEADERS)
+	install -D -p -s -t $(DESTDIR)$(prefix)/bin$(suffix) $(TOOLS) && \
+	install -D -p -s -t $(DESTDIR)$(prefix)/lib$(suffix) $(filter-out libmdbx.a,$(LIBRARIES)) && \
+	install -D -p -t $(DESTDIR)$(prefix)/lib$(suffix) libmdbx.a && \
+	install -D -p -m 444 -t $(DESTDIR)$(prefix)/include $(HEADERS) && \
+	install -D -p -m 444 -t $(DESTDIR)$(mandir)/man1 $(addprefix $(MAN_SRCDIR), $(MANPAGES))
+
+uninstall:
+	rm -f $(addprefix $(DESTDIR)$(prefix)/bin$(suffix)/,$(TOOLS)) \
+		$(addprefix $(DESTDIR)$(prefix)/lib$(suffix)/,$(LIBRARIES)) \
+		$(addprefix $(DESTDIR)$(prefix)/include/,$(HEADERS)) \
+		$(addprefix $(DESTDIR)$(mandir)/man1/,$(MANPAGES))
+
+################################################################################
+# Benchmarking by ioarena
+
+IOARENA ?= $(shell \
+  (test -x ../ioarena/@BUILD/src/ioarena && echo ../ioarena/@BUILD/src/ioarena) || \
+  (test -x ../../@BUILD/src/ioarena && echo ../../@BUILD/src/ioarena) || \
+  (test -x ../../src/ioarena && echo ../../src/ioarena) || which ioarena)
+NN	?= 25000000
+BENCH_CRUD_MODE ?= nosync
+
+ifneq ($(wildcard $(IOARENA)),)
+
+.PHONY: bench clean-bench re-bench
+
+clean-bench:
+	rm -rf bench-*.txt _ioarena/*
+
+re-bench: clean-bench bench
+
+define bench-rule
+bench-$(1)_$(2).txt: $(3) $(IOARENA) $(lastword $(MAKEFILE_LIST))
+	LD_LIBRARY_PATH="./:$$$${LD_LIBRARY_PATH}" \
+		$(IOARENA) -D $(1) -B crud -m $(BENCH_CRUD_MODE) -n $(2) \
+		| tee $$@ | grep throughput && \
+	LD_LIBRARY_PATH="./:$$$${LD_LIBRARY_PATH}" \
+		$(IOARENA) -D $(1) -B get,iterate -m $(BENCH_CRUD_MODE) -r 4 -n $(2) \
+		| tee -a $$@ | grep throughput \
+	|| mv -f $$@ $$@.error
+
+endef
+
+$(eval $(call bench-rule,mdbx,$(NN),libmdbx.$(SO_SUFFIX)))
+
+$(eval $(call bench-rule,sophia,$(NN)))
+$(eval $(call bench-rule,leveldb,$(NN)))
+$(eval $(call bench-rule,rocksdb,$(NN)))
+$(eval $(call bench-rule,wiredtiger,$(NN)))
+$(eval $(call bench-rule,forestdb,$(NN)))
+$(eval $(call bench-rule,lmdb,$(NN)))
+$(eval $(call bench-rule,nessdb,$(NN)))
+$(eval $(call bench-rule,sqlite3,$(NN)))
+$(eval $(call bench-rule,ejdb,$(NN)))
+$(eval $(call bench-rule,vedisdb,$(NN)))
+$(eval $(call bench-rule,dummy,$(NN)))
+
+$(eval $(call bench-rule,debug,10))
+
+bench: bench-mdbx_$(NN).txt
+
+.PHONY: bench-debug
+
+bench-debug: bench-debug_10.txt
+
+bench-quartet: bench-mdbx_$(NN).txt bench-lmdb_$(NN).txt bench-rocksdb_$(NN).txt bench-wiredtiger_$(NN).txt
+bench-triplet: bench-mdbx_$(NN).txt bench-lmdb_$(NN).txt bench-sqlite3_$(NN).txt
+bench-couple: bench-mdbx_$(NN).txt bench-lmdb_$(NN).txt
+
+endif
diff --git a/plugins/Dbx_mdbx/src/libmdbx/LICENSE b/plugins/Dbx_mdbx/src/libmdbx/LICENSE
new file mode 100644
index 0000000000..05ad7571e4
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/LICENSE
@@ -0,0 +1,47 @@
+The OpenLDAP Public License
+  Version 2.8, 17 August 2003
+
+Redistribution and use of this software and associated documentation
+("Software"), with or without modification, are permitted provided
+that the following conditions are met:
+
+1. Redistributions in source form must retain copyright statements
+   and notices,
+
+2. Redistributions in binary form must reproduce applicable copyright
+   statements and notices, this list of conditions, and the following
+   disclaimer in the documentation and/or other materials provided
+   with the distribution, and
+
+3. Redistributions must contain a verbatim copy of this document.
+
+The OpenLDAP Foundation may revise this license from time to time.
+Each revision is distinguished by a version number.  You may use
+this Software under terms of this license revision or under the
+terms of any subsequent revision of the license.
+
+THIS SOFTWARE IS PROVIDED BY THE OPENLDAP FOUNDATION AND ITS
+CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
+INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT
+SHALL THE OPENLDAP FOUNDATION, ITS CONTRIBUTORS, OR THE AUTHOR(S)
+OR OWNER(S) OF THE SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+The names of the authors and copyright holders must not be used in
+advertising or otherwise to promote the sale, use or other dealing
+in this Software without specific, written prior permission.  Title
+to copyright in this Software shall at all times remain with copyright
+holders.
+
+OpenLDAP is a registered trademark of the OpenLDAP Foundation.
+
+Copyright 1999-2003 The OpenLDAP Foundation, Redwood City,
+California, USA.  All Rights Reserved.  Permission to copy and
+distribute verbatim copies of this document is granted.
diff --git a/plugins/Dbx_mdbx/src/libmdbx/Makefile b/plugins/Dbx_mdbx/src/libmdbx/Makefile
new file mode 100644
index 0000000000..bb4aa0531f
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/Makefile
@@ -0,0 +1,7 @@
+# This is thunk-Makefile for calling GNU Make 3.80 or above
+
+all bench bench-quartet build-test check clean clean-bench cross-gcc cross-qemu dist doxygen gcc-analyzer install mdbx memcheck reformat release-assets strip test test-asan test-fault test-leak test-singleprocess test-ubsan test-valgrind tools:
+	@CC=$(CC) \
+	CXX=`if test -n "$(CXX)" && which "$(CXX)" > /dev/null; then echo "$(CXX)"; elif test -n "$(CCC)" && which "$(CCC)" > /dev/null; then echo "$(CCC)"; else echo "c++"; fi` \
+	`which gmake || which gnumake || echo 'echo "GNU Make 3.80 or above is required"; exit 2;'` \
+		$(MAKEFLAGS) -f GNUmakefile $@
diff --git a/plugins/Dbx_mdbx/src/libmdbx/README.md b/plugins/Dbx_mdbx/src/libmdbx/README.md
new file mode 100644
index 0000000000..66da37c454
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/README.md
@@ -0,0 +1,638 @@
+<!-- Required extensions: pymdownx.betterem, pymdownx.tilde, pymdownx.emoji, pymdownx.tasklist, pymdownx.superfences -->
+
+> Please refer to the online [documentation](https://erthink.github.io/libmdbx/)
+> with [`C` API description](https://erthink.github.io/libmdbx/group__c__api.html)
+> and pay attention to the preliminary [`C++` API](https://github.com/erthink/libmdbx/blob/devel/mdbx.h%2B%2B).
+>
+> Questions, feedback and suggestions are welcome to the [Telegram' group](https://t.me/libmdbx).
+>
+> For NEWS take a look to the [ChangeLog](./ChangeLog.md).
+
+libmdbx
+========
+
+<!-- section-begin overview -->
+_libmdbx_ is an extremely fast, compact, powerful, embedded,
+transactional [key-value database](https://en.wikipedia.org/wiki/Key-value_database),
+with [permissive license](./LICENSE).
+_libmdbx_ has a specific set of properties and capabilities,
+focused on creating unique lightweight solutions.
+
+1. Allows **a swarm of multi-threaded processes to
+[ACID]((https://en.wikipedia.org/wiki/ACID))ly read and update** several
+key-value [maps](https://en.wikipedia.org/wiki/Associative_array) and
+[multimaps](https://en.wikipedia.org/wiki/Multimap) in a locally-shared
+database.
+
+2. Provides **extraordinary performance**, minimal overhead through
+[Memory-Mapping](https://en.wikipedia.org/wiki/Memory-mapped_file) and
+`Olog(N)` operations costs by virtue of [B+
+tree](https://en.wikipedia.org/wiki/B%2B_tree).
+
+3. Requires **no maintenance and no crash recovery** since it doesn't use
+[WAL](https://en.wikipedia.org/wiki/Write-ahead_logging), but that might
+be a caveat for write-intensive workloads with durability requirements.
+
+4. **Compact and friendly for fully embedding**. Only ≈25KLOC of `C11`,
+≈64K x86 binary code of core, no internal threads neither server process(es),
+but implements a simplified variant of the [Berkeley
+DB](https://en.wikipedia.org/wiki/Berkeley_DB) and
+[dbm](https://en.wikipedia.org/wiki/DBM_(computing)) API.
+
+5. Enforces [serializability](https://en.wikipedia.org/wiki/Serializability) for
+writers just by single
+[mutex](https://en.wikipedia.org/wiki/Mutual_exclusion) and affords
+[wait-free](https://en.wikipedia.org/wiki/Non-blocking_algorithm#Wait-freedom)
+for parallel readers without atomic/interlocked operations, while
+**writing and reading transactions do not block each other**.
+
+6. **Guarantee data integrity** after crash unless this was explicitly
+neglected in favour of write performance.
+
+7. Supports Linux, Windows, MacOS, Android, iOS, FreeBSD, DragonFly, Solaris,
+OpenSolaris, OpenIndiana, NetBSD, OpenBSD and other systems compliant with
+**POSIX.1-2008**.
+<!-- section-end -->
+
+Historically, _libmdbx_ is a deeply revised and extended descendant of the amazing
+[Lightning Memory-Mapped Database](https://en.wikipedia.org/wiki/Lightning_Memory-Mapped_Database).
+_libmdbx_ inherits all benefits from _LMDB_, but resolves some issues and adds [a set of improvements](#improvements-beyond-lmdb).
+
+<!-- section-begin mithril -->
+The next version is under active non-public development from scratch and will be
+released as _**MithrilDB**_ and `libmithrildb` for libraries & packages.
+Admittedly mythical [Mithril](https://en.wikipedia.org/wiki/Mithril) is
+resembling silver but being stronger and lighter than steel. Therefore
+_MithrilDB_ is a rightly relevant name.
+  > _MithrilDB_ will be radically different from _libmdbx_ by the new
+  > database format and API based on C++17, as well as the [Apache 2.0
+  > License](https://www.apache.org/licenses/LICENSE-2.0). The goal of this
+  > revolution is to provide a clearer and robust API, add more features and
+  > new valuable properties of the database.
+<!-- section-end -->
+
+[![https://t.me/libmdbx](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/telegram.png)](https://t.me/libmdbx)
+[![GithubCI](https://github.com/erthink/libmdbx/workflows/CI/badge.svg)](https://github.com/erthink/libmdbx/actions?query=workflow%3ACI)
+[![TravisCI](https://travis-ci.org/erthink/libmdbx.svg?branch=master)](https://travis-ci.org/erthink/libmdbx)
+[![AppveyorCI](https://ci.appveyor.com/api/projects/status/ue94mlopn50dqiqg/branch/master?svg=true)](https://ci.appveyor.com/project/leo-yuriev/libmdbx/branch/master)
+[![CircleCI](https://circleci.com/gh/erthink/libmdbx/tree/master.svg?style=svg)](https://circleci.com/gh/erthink/libmdbx/tree/master)
+[![CirrusCI](https://api.cirrus-ci.com/github/erthink/libmdbx.svg)](https://cirrus-ci.com/github/erthink/libmdbx)
+[![Coverity Scan Status](https://scan.coverity.com/projects/12915/badge.svg)](https://scan.coverity.com/projects/reopen-libmdbx)
+
+*The Future will (be) [Positive](https://www.ptsecurity.com). Всё будет хорошо.*
+
+-----
+
+## Table of Contents
+- [Characteristics](#characteristics)
+    - [Features](#features)
+    - [Limitations](#limitations)
+    - [Gotchas](#gotchas)
+    - [Comparison with other databases](#comparison-with-other-databases)
+    - [Improvements beyond LMDB](#improvements-beyond-lmdb)
+    - [History & Acknowledgments](#history)
+- [Usage](#usage)
+    - [Building](#building)
+    - [API description](#api-description)
+    - [Bindings](#bindings)
+- [Performance comparison](#performance-comparison)
+    - [Integral performance](#integral-performance)
+    - [Read scalability](#read-scalability)
+    - [Sync-write mode](#sync-write-mode)
+    - [Lazy-write mode](#lazy-write-mode)
+    - [Async-write mode](#async-write-mode)
+    - [Cost comparison](#cost-comparison)
+
+# Characteristics
+
+<!-- section-begin characteristics -->
+
+## Features
+
+- Key-value data model, keys are always sorted.
+
+- Fully [ACID](https://en.wikipedia.org/wiki/ACID)-compliant, through to
+[MVCC](https://en.wikipedia.org/wiki/Multiversion_concurrency_control)
+and [CoW](https://en.wikipedia.org/wiki/Copy-on-write).
+
+- Multiple key-value sub-databases within a single datafile.
+
+- Range lookups, including range query estimation.
+
+- Efficient support for short fixed length keys, including native 32/64-bit integers.
+
+- Ultra-efficient support for [multimaps](https://en.wikipedia.org/wiki/Multimap). Multi-values sorted, searchable and iterable. Keys stored without duplication.
+
+- Data is [memory-mapped](https://en.wikipedia.org/wiki/Memory-mapped_file) and accessible directly/zero-copy. Traversal of database records is extremely-fast.
+
+- Transactions for readers and writers, ones do not block others.
+
+- Writes are strongly serialized. No transaction conflicts nor deadlocks.
+
+- Readers are [non-blocking](https://en.wikipedia.org/wiki/Non-blocking_algorithm), notwithstanding [snapshot isolation](https://en.wikipedia.org/wiki/Snapshot_isolation).
+
+- Nested write transactions.
+
+- Reads scale linearly across CPUs.
+
+- Continuous zero-overhead database compactification.
+
+- Automatic on-the-fly database size adjustment.
+
+- Customizable database page size.
+
+- `Olog(N)` cost of lookup, insert, update, and delete operations by virtue of [B+ tree characteristics](https://en.wikipedia.org/wiki/B%2B_tree#Characteristics).
+
+- Online hot backup.
+
+- Append operation for efficient bulk insertion of pre-sorted data.
+
+- No [WAL](https://en.wikipedia.org/wiki/Write-ahead_logging) nor any
+transaction journal. No crash recovery needed. No maintenance is required.
+
+- No internal cache and/or memory management, all done by basic OS services.
+
+## Limitations
+
+- **Page size**: a power of 2, maximum `65536` bytes, default `4096` bytes.
+- **Key size**: minimum 0, maximum ≈¼ pagesize (`1300` bytes for default 4K pagesize, `21780` bytes for 64K pagesize).
+- **Value size**: minimum 0, maximum `2146435072` (`0x7FF00000`) bytes for maps, ≈¼ pagesize for multimaps (`1348` bytes for default 4K pagesize, `21828` bytes for 64K pagesize).
+- **Write transaction size**: up to `4194301` (`0x3FFFFD`) pages (16 [GiB](https://en.wikipedia.org/wiki/Gibibyte) for default 4K pagesize, 256 [GiB](https://en.wikipedia.org/wiki/Gibibyte) for 64K pagesize).
+- **Database size**: up to `2147483648` pages (8 [TiB](https://en.wikipedia.org/wiki/Tebibyte) for default 4K pagesize, 128 [TiB](https://en.wikipedia.org/wiki/Tebibyte) for 64K pagesize).
+- **Maximum sub-databases**: `32765`.
+
+## Gotchas
+
+1. There cannot be more than one writer at a time, i.e. no more than one write transaction at a time.
+
+2. _libmdbx_ is based on [B+ tree](https://en.wikipedia.org/wiki/B%2B_tree), so access to database pages is mostly random.
+Thus SSDs provide a significant performance boost over spinning disks for large databases.
+
+3. _libmdbx_ uses [shadow paging](https://en.wikipedia.org/wiki/Shadow_paging) instead of [WAL](https://en.wikipedia.org/wiki/Write-ahead_logging). Thus syncing data to disk might be a bottleneck for write intensive workload.
+
+4. _libmdbx_ uses [copy-on-write](https://en.wikipedia.org/wiki/Copy-on-write) for [snapshot isolation](https://en.wikipedia.org/wiki/Snapshot_isolation) during updates, but read transactions prevents recycling an old retired/freed pages, since it read ones. Thus altering of data during a parallel
+long-lived read operation will increase the process work set, may exhaust entire free database space,
+the database can grow quickly, and result in performance degradation.
+Try to avoid long running read transactions.
+
+5. _libmdbx_ is extraordinarily fast and provides minimal overhead for data access,
+so you should reconsider using brute force techniques and double check your code.
+On the one hand, in the case of _libmdbx_, a simple linear search may be more profitable than complex indexes.
+On the other hand, if you make something suboptimally, you can notice detrimentally only on sufficiently large data.
+
+## Comparison with other databases
+For now please refer to [chapter of "BoltDB comparison with other
+databases"](https://github.com/coreos/bbolt#comparison-with-other-databases)
+which is also (mostly) applicable to _libmdbx_.
+
+<!-- section-end -->
+<!-- section-begin improvements -->
+
+Improvements beyond LMDB
+========================
+
+_libmdbx_ is superior to legendary _[LMDB](https://symas.com/lmdb/)_ in
+terms of features and reliability, not inferior in performance. In
+comparison to _LMDB_, _libmdbx_ make things "just work" perfectly and
+out-of-the-box, not silently and catastrophically break down. The list
+below is pruned down to the improvements most notable and obvious from
+the user's point of view.
+
+## Added Features
+
+1. Keys could be more than 2 times longer than _LMDB_.
+  > For DB with default page size _libmdbx_ support keys up to 1300 bytes
+  > and up to 21780 bytes for 64K page size. _LMDB_ allows key size up to
+  > 511 bytes and may silently loses data with large values.
+
+2. Up to 20% faster than _LMDB_ in [CRUD](https://en.wikipedia.org/wiki/Create,_read,_update_and_delete) benchmarks.
+  > Benchmarks of the in-[tmpfs](https://en.wikipedia.org/wiki/Tmpfs) scenarios,
+  > that tests the speed of the engine itself, showned that _libmdbx_ 10-20% faster than _LMDB_.
+  > These and other results could be easily reproduced with [ioArena](https://github.com/pmwkaa/ioarena) just by `make bench-quartet` command,
+  > including comparisons with [RockDB](https://en.wikipedia.org/wiki/RocksDB)
+  > and [WiredTiger](https://en.wikipedia.org/wiki/WiredTiger).
+
+3. Automatic on-the-fly database size adjustment, both increment and reduction.
+  > _libmdbx_ manages the database size according to parameters specified
+  > by `mdbx_env_set_geometry()` function,
+  > ones include the growth step and the truncation threshold.
+  >
+  > Unfortunately, on-the-fly database size adjustment doesn't work under [Wine](https://en.wikipedia.org/wiki/Wine_(software))
+  > due to its internal limitations and unimplemented functions, i.e. the `MDBX_UNABLE_EXTEND_MAPSIZE` error will be returned.
+
+4. Automatic continuous zero-overhead database compactification.
+  > During each commit _libmdbx_ merges suitable freeing pages into unallocated area
+  > at the end of file, and then truncates unused space when a lot enough of.
+
+5. The same database format for 32- and 64-bit builds.
+  > _libmdbx_ database format depends only on the [endianness](https://en.wikipedia.org/wiki/Endianness) but not on the [bitness](https://en.wiktionary.org/wiki/bitness).
+
+6. LIFO policy for Garbage Collection recycling. This can significantly increase write performance due write-back disk cache up to several times in a best case scenario.
+  > LIFO means that for reuse will be taken the latest becomes unused pages.
+  > Therefore the loop of database pages circulation becomes as short as possible.
+  > In other words, the set of pages, that are (over)written in memory and on disk during a series of write transactions, will be as small as possible.
+  > Thus creates ideal conditions for the battery-backed or flash-backed disk cache efficiency.
+
+7. Fast estimation of range query result volume, i.e. how many items can
+be found between a `KEY1` and a `KEY2`. This is a prerequisite for build
+and/or optimize query execution plans.
+  > _libmdbx_ performs a rough estimate based on common B-tree pages of the paths from root to corresponding keys.
+
+8. `mdbx_chk` utility for database integrity check.
+Since version 0.9.1, the utility supports checking the database using any of the three meta pages and the ability to switch to it.
+
+9. Automated steady sync-to-disk upon several thresholds and/or timeout via cheap polling.
+
+10. Sequence generation and three persistent 64-bit markers.
+
+11. Handle-Slow-Readers callback to resolve a database full/overflow issues due to long-lived read transaction(s).
+
+12. Support for opening databases in the exclusive mode, including on a network share.
+
+## Added Abilities
+
+1. Zero-length for keys and values.
+
+2. Ability to determine whether the particular data is on a dirty page
+or not, that allows to avoid copy-out before updates.
+
+3. Ability to determine whether the cursor is pointed to a key-value
+pair, to the first, to the last, or not set to anything.
+
+4. Extended information of whole-database, sub-databases, transactions, readers enumeration.
+  > _libmdbx_ provides a lot of information, including dirty and leftover pages
+  > for a write transaction, reading lag and holdover space for read transactions.
+
+5. Extended update and delete operations.
+  > _libmdbx_ allows one _at once_ with getting previous value
+  > and addressing the particular item from multi-value with the same key.
+
+## Other fixes and specifics
+
+1. Fixed more than 10 significant errors, in particular: page leaks,
+wrong sub-database statistics, segfault in several conditions,
+nonoptimal page merge strategy, updating an existing record with
+a change in data size (including for multimap), etc.
+
+2. All cursors can be reused and should be closed explicitly,
+regardless ones were opened within a write or read transaction.
+
+3. Opening database handles are spared from race conditions and
+pre-opening is not needed.
+
+4. Returning `MDBX_EMULTIVAL` error in case of ambiguous update or delete.
+
+5. Guarantee of database integrity even in asynchronous unordered write-to-disk mode.
+  > _libmdbx_ propose additional trade-off by `MDBX_SAFE_NOSYNC` with append-like manner for updates,
+  > that avoids database corruption after a system crash contrary to LMDB.
+  > Nevertheless, the `MDBX_UTTERLY_NOSYNC` mode is available to match behaviour of the `MDB_NOSYNC` in LMDB.
+
+6. On **MacOS & iOS** the `fcntl(F_FULLFSYNC)` syscall is used _by
+default_ to synchronize data with the disk, as this is [the only way to
+guarantee data
+durability](https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/fsync.2.html)
+in case of power failure. Unfortunately, in scenarios with high write
+intensity, the use of `F_FULLFSYNC` significantly degrades performance
+compared to LMDB, where the `fsync()` syscall is used. Therefore,
+_libmdbx_ allows you to override this behavior by defining the
+`MDBX_OSX_SPEED_INSTEADOF_DURABILITY=1` option while build the library.
+
+7. On **Windows** the `LockFileEx()` syscall is used for locking, since
+it allows place the database on network drives, and provides protection
+against incompetent user actions (aka
+[poka-yoke](https://en.wikipedia.org/wiki/Poka-yoke)). Therefore
+_libmdbx_ may be a little lag in performance tests from LMDB where the
+named mutexes are used.
+
+<!-- section-end -->
+<!-- section-begin history -->
+
+# History
+
+Historically, _libmdbx_ is a deeply revised and extended descendant of the
+[Lightning Memory-Mapped Database](https://en.wikipedia.org/wiki/Lightning_Memory-Mapped_Database).
+At first the development was carried out within the
+[ReOpenLDAP](https://github.com/erthink/ReOpenLDAP) project. About a
+year later _libmdbx_ was separated into a standalone project, which was
+[presented at Highload++ 2015
+conference](http://www.highload.ru/2015/abstracts/1831.html).
+
+Since 2017 _libmdbx_ is used in [Fast Positive Tables](https://github.com/erthink/libfpta),
+and development is funded by [Positive Technologies](https://www.ptsecurity.com).
+
+## Acknowledgments
+Howard Chu <hyc@openldap.org> is the author of LMDB, from which
+originated the _libmdbx_ in 2015.
+
+Martin Hedenfalk <martin@bzero.se> is the author of `btree.c` code, which
+was used to begin development of LMDB.
+
+<!-- section-end -->
+
+--------------------------------------------------------------------------------
+
+Usage
+=====
+
+<!-- section-begin usage -->
+Currently, libmdbx is only available in a
+[source code](https://en.wikipedia.org/wiki/Source_code) form.
+Packages support for common Linux distributions is planned in the future,
+since release the version 1.0.
+
+## Source code embedding
+
+_libmdbx_ provides two official ways for integration in source code form:
+
+1. Using the amalgamated source code.
+  > The amalgamated source code includes all files required to build and
+  > use _libmdbx_, but not for testing _libmdbx_ itself.
+
+2. Adding the complete original source code as a `git submodule`.
+  > This allows you to build as _libmdbx_ and testing tool.
+  >  On the other hand, this way requires you to pull git tags, and use C++11 compiler for test tool.
+
+_**Please, avoid using any other techniques.**_ Otherwise, at least
+don't ask for support and don't name such chimeras `libmdbx`.
+
+The amalgamated source code could be created from the original clone of git
+repository on Linux by executing `make dist`. As a result, the desired
+set of files will be formed in the `dist` subdirectory.
+
+## Building
+
+Both amalgamated and original source code provides build through the use
+[CMake](https://cmake.org/) or [GNU
+Make](https://www.gnu.org/software/make/) with
+[bash](https://en.wikipedia.org/wiki/Bash_(Unix_shell)). All build ways
+are completely traditional and have minimal prerequirements like
+`build-essential`, i.e. the non-obsolete C/C++ compiler and a
+[SDK](https://en.wikipedia.org/wiki/Software_development_kit) for the
+target platform. Obviously you need building tools itself, i.e. `git`,
+`cmake` or GNU `make` with `bash`.
+
+So just using CMake or GNU Make in your habitual manner and feel free to
+fill an issue or make pull request in the case something will be
+unexpected or broken down.
+
+#### DSO/DLL unloading and destructors of Thread-Local-Storage objects
+When building _libmdbx_ as a shared library or use static _libmdbx_ as a
+part of another dynamic library, it is advisable to make sure that your
+system ensures the correctness of the call destructors of
+Thread-Local-Storage objects when unloading dynamic libraries.
+
+If this is not the case, then unloading a dynamic-link library with
+_libmdbx_ code inside, can result in either a resource leak or a crash
+due to calling destructors from an already unloaded DSO/DLL object. The
+problem can only manifest in a multithreaded application, which makes
+the unloading of shared dynamic libraries with _libmdbx_ code inside,
+after using _libmdbx_. It is known that TLS-destructors are properly
+maintained in the following cases:
+
+- On all modern versions of Windows (Windows 7 and later).
+
+- On systems with the
+[`__cxa_thread_atexit_impl()`](https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables)
+function in the standard C library, including systems with GNU libc
+version 2.18 and later.
+
+- On systems with libpthread/ntpl from GNU libc with bug fixes
+[#21031](https://sourceware.org/bugzilla/show_bug.cgi?id=21031) and
+[#21032](https://sourceware.org/bugzilla/show_bug.cgi?id=21032), or
+where there are no similar bugs in the pthreads implementation.
+
+### Linux and other platforms with GNU Make
+To build the library it is enough to execute `make all` in the directory
+of source code, and `make check` to execute the basic tests.
+
+If the `make` installed on the system is not GNU Make, there will be a
+lot of errors from make when trying to build. In this case, perhaps you
+should use `gmake` instead of `make`, or even `gnu-make`, etc.
+
+### FreeBSD and related platforms
+As a rule, in such systems, the default is to use Berkeley Make. And GNU
+Make is called by the gmake command or may be missing. In addition,
+[bash](https://en.wikipedia.org/wiki/Bash_(Unix_shell)) may be absent.
+
+You need to install the required components: GNU Make, bash, C and C++
+compilers compatible with GCC or CLANG. After that, to build the
+library, it is enough to execute `gmake all` (or `make all`) in the
+directory with source code, and `gmake check` (or `make check`) to run
+the basic tests.
+
+### Windows
+For build _libmdbx_ on Windows the _original_ CMake and [Microsoft Visual
+Studio 2019](https://en.wikipedia.org/wiki/Microsoft_Visual_Studio) are
+recommended. Otherwise do not forget to add `ntdll.lib` to linking.
+
+Building by MinGW, MSYS or Cygwin is potentially possible. However,
+these scripts are not tested and will probably require you to modify the
+CMakeLists.txt or Makefile respectively.
+
+It should be noted that in _libmdbx_ was efforts to resolve
+runtime dependencies from CRT and other libraries Visual Studio.
+For this is enough to define the `MDBX_AVOID_CRT` during build.
+
+An example of running a basic test script can be found in the
+[CI-script](appveyor.yml) for [AppVeyor](https://www.appveyor.com/). To
+run the [long stochastic test scenario](test/long_stochastic.sh),
+[bash](https://en.wikipedia.org/wiki/Bash_(Unix_shell)) is required, and
+such testing is recommended with placing the test data on the
+[RAM-disk](https://en.wikipedia.org/wiki/RAM_drive).
+
+### Windows Subsystem for Linux
+_libmdbx_ could be used in [WSL2](https://en.wikipedia.org/wiki/Windows_Subsystem_for_Linux#WSL_2)
+but NOT in [WSL1](https://en.wikipedia.org/wiki/Windows_Subsystem_for_Linux#WSL_1) environment.
+This is a consequence of the fundamental shortcomings of _WSL1_ and cannot be fixed.
+To avoid data loss, _libmdbx_ returns the `ENOLCK` (37, "No record locks available")
+error when opening the database in a _WSL1_ environment.
+
+### MacOS
+Current [native build tools](https://en.wikipedia.org/wiki/Xcode) for
+MacOS include GNU Make, CLANG and an outdated version of bash.
+Therefore, to build the library, it is enough to run `make all` in the
+directory with source code, and run `make check` to execute the base
+tests. If something goes wrong, it is recommended to install
+[Homebrew](https://brew.sh/) and try again.
+
+To run the [long stochastic test scenario](test/long_stochastic.sh), you
+will need to install the current (not outdated) version of
+[bash](https://en.wikipedia.org/wiki/Bash_(Unix_shell)). To do this, we
+recommend that you install [Homebrew](https://brew.sh/) and then execute
+`brew install bash`.
+
+### Android
+We recommend using CMake to build _libmdbx_ for Android.
+Please refer to the [official guide](https://developer.android.com/studio/projects/add-native-code).
+
+### iOS
+To build _libmdbx_ for iOS, we recommend using CMake with the
+"[toolchain file](https://cmake.org/cmake/help/latest/variable/CMAKE_TOOLCHAIN_FILE.html)"
+from the [ios-cmake](https://github.com/leetal/ios-cmake) project.
+
+<!-- section-end -->
+
+## API description
+
+Please refer to the online [_libmdbx_ API reference](https://erthink.github.io/libmdbx/)
+and/or see the [mdbx.h](mdbx.h) header.
+
+<!-- section-begin bindings -->
+
+Bindings
+========
+
+| Runtime | GitHub | Author |
+| ------- | ------ | ------ |
+| [Nim](https://en.wikipedia.org/wiki/Nim_(programming_language)) | [NimDBX](https://github.com/snej/nimdbx) | [Jens Alfke](https://github.com/snej)
+| Rust    | [heed](https://github.com/Kerollmops/heed), [mdbx-rs](https://github.com/Kerollmops/mdbx-rs)   | [Clément Renault](https://github.com/Kerollmops) |
+| Java    | [mdbxjni](https://github.com/castortech/mdbxjni)   | [Castor Technologies](https://castortech.com/) |
+| .NET    | [mdbx.NET](https://github.com/wangjia184/mdbx.NET) | [Jerry Wang](https://github.com/wangjia184) |
+
+<!-- section-end -->
+
+--------------------------------------------------------------------------------
+
+<!-- section-begin performance -->
+
+Performance comparison
+======================
+
+All benchmarks were done in 2015 by [IOArena](https://github.com/pmwkaa/ioarena)
+and multiple [scripts](https://github.com/pmwkaa/ioarena/tree/HL%2B%2B2015)
+runs on Lenovo Carbon-2 laptop, i7-4600U 2.1 GHz (2 physical cores, 4 HyperThreading cores), 8 Gb RAM,
+SSD SAMSUNG MZNTD512HAGL-000L1 (DXT23L0Q) 512 Gb.
+
+## Integral performance
+
+Here showed sum of performance metrics in 3 benchmarks:
+
+ - Read/Search on the machine with 4 logical CPUs in HyperThreading mode (i.e. actually 2 physical CPU cores);
+
+ - Transactions with [CRUD](https://en.wikipedia.org/wiki/CRUD)
+ operations in sync-write mode (fdatasync is called after each
+ transaction);
+
+ - Transactions with [CRUD](https://en.wikipedia.org/wiki/CRUD)
+ operations in lazy-write mode (moment to sync data to persistent storage
+ is decided by OS).
+
+*Reasons why asynchronous mode isn't benchmarked here:*
+
+  1. It doesn't make sense as it has to be done with DB engines, oriented
+  for keeping data in memory e.g. [Tarantool](https://tarantool.io/),
+  [Redis](https://redis.io/)), etc.
+
+  2. Performance gap is too high to compare in any meaningful way.
+
+![Comparison #1: Integral Performance](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-1.png)
+
+--------------------------------------------------------------------------------
+
+## Read Scalability
+
+Summary performance with concurrent read/search queries in 1-2-4-8
+threads on the machine with 4 logical CPUs in HyperThreading mode (i.e. actually 2 physical CPU cores).
+
+![Comparison #2: Read Scalability](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-2.png)
+
+--------------------------------------------------------------------------------
+
+## Sync-write mode
+
+ - Linear scale on left and dark rectangles mean arithmetic mean
+ transactions per second;
+
+ - Logarithmic scale on right is in seconds and yellow intervals mean
+ execution time of transactions. Each interval shows minimal and maximum
+ execution time, cross marks standard deviation.
+
+**10,000 transactions in sync-write mode**. In case of a crash all data
+is consistent and conforms to the last successful transaction. The
+[fdatasync](https://linux.die.net/man/2/fdatasync) syscall is used after
+each write transaction in this mode.
+
+In the benchmark each transaction contains combined CRUD operations (2
+inserts, 1 read, 1 update, 1 delete). Benchmark starts on an empty database
+and after full run the database contains 10,000 small key-value records.
+
+![Comparison #3: Sync-write mode](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-3.png)
+
+--------------------------------------------------------------------------------
+
+## Lazy-write mode
+
+ - Linear scale on left and dark rectangles mean arithmetic mean of
+ thousands transactions per second;
+
+ - Logarithmic scale on right in seconds and yellow intervals mean
+ execution time of transactions. Each interval shows minimal and maximum
+ execution time, cross marks standard deviation.
+
+**100,000 transactions in lazy-write mode**. In case of a crash all data
+is consistent and conforms to the one of last successful transactions, but
+transactions after it will be lost. Other DB engines use
+[WAL](https://en.wikipedia.org/wiki/Write-ahead_logging) or transaction
+journal for that, which in turn depends on order of operations in the
+journaled filesystem. _libmdbx_ doesn't use WAL and hands I/O operations
+to filesystem and OS kernel (mmap).
+
+In the benchmark each transaction contains combined CRUD operations (2
+inserts, 1 read, 1 update, 1 delete). Benchmark starts on an empty database
+and after full run the database contains 100,000 small key-value
+records.
+
+
+![Comparison #4: Lazy-write mode](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-4.png)
+
+--------------------------------------------------------------------------------
+
+## Async-write mode
+
+ - Linear scale on left and dark rectangles mean arithmetic mean of
+ thousands transactions per second;
+
+ - Logarithmic scale on right in seconds and yellow intervals mean
+ execution time of transactions. Each interval shows minimal and maximum
+ execution time, cross marks standard deviation.
+
+**1,000,000 transactions in async-write mode**. In case of a crash all data is consistent and conforms to the one of last successful transactions, but lost transaction count is much higher than in
+lazy-write mode. All DB engines in this mode do as little writes as
+possible on persistent storage. _libmdbx_ uses
+[msync(MS_ASYNC)](https://linux.die.net/man/2/msync) in this mode.
+
+In the benchmark each transaction contains combined CRUD operations (2
+inserts, 1 read, 1 update, 1 delete). Benchmark starts on an empty database
+and after full run the database contains 10,000 small key-value records.
+
+![Comparison #5: Async-write mode](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-5.png)
+
+--------------------------------------------------------------------------------
+
+## Cost comparison
+
+Summary of used resources during lazy-write mode benchmarks:
+
+ - Read and write IOPs;
+
+ - Sum of user CPU time and sys CPU time;
+
+ - Used space on persistent storage after the test and closed DB, but not
+ waiting for the end of all internal housekeeping operations (LSM
+ compactification, etc).
+
+_ForestDB_ is excluded because benchmark showed it's resource
+consumption for each resource (CPU, IOPs) much higher than other engines
+which prevents to meaningfully compare it with them.
+
+All benchmark data is gathered by
+[getrusage()](http://man7.org/linux/man-pages/man2/getrusage.2.html)
+syscall and by scanning the data directory.
+
+![Comparison #6: Cost comparison](https://raw.githubusercontent.com/wiki/erthink/libmdbx/img/perf-slide-6.png)
+
+<!-- section-end -->
+
+--------------------------------------------------------------------------------
+
+#### This is a mirror of the origin repository that was moved to [abf.io](https://abf.io/erthink/) because of discriminatory restrictions for Russian Crimea.
diff --git a/plugins/Dbx_mdbx/src/libmdbx/VERSION b/plugins/Dbx_mdbx/src/libmdbx/VERSION
new file mode 100644
index 0000000000..ad5a80ff3c
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/VERSION
@@ -0,0 +1 @@
+0.9.2.136
diff --git a/plugins/Dbx_mdbx/src/libmdbx/config.h.in b/plugins/Dbx_mdbx/src/libmdbx/config.h.in
new file mode 100644
index 0000000000..bb3eea07b4
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/config.h.in
@@ -0,0 +1,63 @@
+/* This is CMake-template for libmdbx's config.h
+ ******************************************************************************/
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#cmakedefine LTO_ENABLED
+#cmakedefine MDBX_USE_VALGRIND
+#cmakedefine ENABLE_GPROF
+#cmakedefine ENABLE_GCOV
+#cmakedefine ENABLE_ASAN
+#cmakedefine ENABLE_UBSAN
+#cmakedefine MDBX_FORCE_ASSERTIONS
+
+/* Common */
+#cmakedefine01 MDBX_TXN_CHECKOWNER
+#cmakedefine MDBX_ENV_CHECKPID_AUTO
+#ifndef MDBX_ENV_CHECKPID_AUTO
+#cmakedefine01 MDBX_ENV_CHECKPID
+#endif
+#cmakedefine MDBX_LOCKING_AUTO
+#ifndef MDBX_LOCKING_AUTO
+#cmakedefine MDBX_LOCKING @MDBX_LOCKING@
+#endif
+#cmakedefine MDBX_TRUST_RTC_AUTO
+#ifndef MDBX_TRUST_RTC_AUTO
+#cmakedefine01 MDBX_TRUST_RTC
+#endif
+
+/* Windows */
+#cmakedefine01 MDBX_CONFIG_MANUAL_TLS_CALLBACK
+#cmakedefine01 MDBX_AVOID_CRT
+
+/* MacOS & iOS */
+#cmakedefine01 MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+
+/* POSIX */
+#cmakedefine01 MDBX_DISABLE_GNU_SOURCE
+#cmakedefine MDBX_USE_OFDLOCKS_AUTO
+#ifndef MDBX_USE_OFDLOCKS_AUTO
+#cmakedefine01 MDBX_USE_OFDLOCKS
+#endif
+
+/* Build Info */
+#ifndef MDBX_BUILD_TIMESTAMP
+#cmakedefine MDBX_BUILD_TIMESTAMP "@MDBX_BUILD_TIMESTAMP@"
+#endif
+#ifndef MDBX_BUILD_TARGET
+#cmakedefine MDBX_BUILD_TARGET "@MDBX_BUILD_TARGET@"
+#endif
+#ifndef MDBX_BUILD_TYPE
+#cmakedefine MDBX_BUILD_TYPE "@MDBX_BUILD_TYPE@"
+#endif
+#ifndef MDBX_BUILD_COMPILER
+#cmakedefine MDBX_BUILD_COMPILER "@MDBX_BUILD_COMPILER@"
+#endif
+#ifndef MDBX_BUILD_FLAGS
+#cmakedefine MDBX_BUILD_FLAGS "@MDBX_BUILD_FLAGS@"
+#endif
+#cmakedefine MDBX_BUILD_SOURCERY @MDBX_BUILD_SOURCERY@
+
+/* *INDENT-ON* */
+/* clang-format on */
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx.c
new file mode 100644
index 0000000000..6ceafe5097
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.c
@@ -0,0 +1,28388 @@
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_ALLOY 1
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>.
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * This code is derived from "LMDB engine" written by
+ * Howard Chu (Symas Corporation), which itself derived from btree.c
+ * written by Martin Hedenfalk.
+ *
+ * ---
+ *
+ * Portions Copyright 2011-2015 Howard Chu, Symas Corp. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ *
+ * ---
+ *
+ * Portions Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+
+/*------------------------------------------------------------------------------
+ * Internal inline functions */
+
+MDBX_NOTHROW_CONST_FUNCTION static unsigned log2n(size_t value) {
+  assert(value > 0 && value < INT32_MAX && is_powerof2(value));
+  assert((value & -(int32_t)value) == value);
+#if __GNUC_PREREQ(4, 1) || __has_builtin(__builtin_ctzl)
+  return __builtin_ctzl(value);
+#elif defined(_MSC_VER)
+  unsigned long index;
+  _BitScanForward(&index, (unsigned long)value);
+  return index;
+#else
+  static const uint8_t debruijn_ctz32[32] = {
+      0,  1,  28, 2,  29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4,  8,
+      31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6,  11, 5,  10, 9};
+  return debruijn_ctz32[(uint32_t)(value * 0x077CB531u) >> 27];
+#endif
+}
+
+/*------------------------------------------------------------------------------
+ * Unaligned access */
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __always_inline unsigned
+field_alignment(unsigned alignment_baseline, size_t field_offset) {
+  unsigned merge = alignment_baseline | (unsigned)field_offset;
+  return merge & -(int)merge;
+}
+
+/* read-thunk for UB-sanitizer */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint8_t
+peek_u8(const uint8_t *const __restrict ptr) {
+  return *ptr;
+}
+
+/* write-thunk for UB-sanitizer */
+static __always_inline void poke_u8(uint8_t *const __restrict ptr,
+                                    const uint8_t v) {
+  *ptr = v;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint16_t
+unaligned_peek_u16(const unsigned expected_alignment, const void *const ptr) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(uint16_t)) == 0)
+    return *(const uint16_t *)ptr;
+  else {
+    uint16_t v;
+    memcpy(&v, ptr, sizeof(v));
+    return v;
+  }
+}
+
+static __always_inline void
+unaligned_poke_u16(const unsigned expected_alignment,
+                   void *const __restrict ptr, const uint16_t v) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(v)) == 0)
+    *(uint16_t *)ptr = v;
+  else
+    memcpy(ptr, &v, sizeof(v));
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint32_t unaligned_peek_u32(
+    const unsigned expected_alignment, const void *const __restrict ptr) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(uint32_t)) == 0)
+    return *(const uint32_t *)ptr;
+  else if ((expected_alignment % sizeof(uint16_t)) == 0) {
+    const uint16_t lo =
+        ((const uint16_t *)ptr)[__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__];
+    const uint16_t hi =
+        ((const uint16_t *)ptr)[__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__];
+    return lo | (uint32_t)hi << 16;
+  } else {
+    uint32_t v;
+    memcpy(&v, ptr, sizeof(v));
+    return v;
+  }
+}
+
+static __always_inline void
+unaligned_poke_u32(const unsigned expected_alignment,
+                   void *const __restrict ptr, const uint32_t v) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(v)) == 0)
+    *(uint32_t *)ptr = v;
+  else if ((expected_alignment % sizeof(uint16_t)) == 0) {
+    ((uint16_t *)ptr)[__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__] = (uint16_t)v;
+    ((uint16_t *)ptr)[__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__] =
+        (uint16_t)(v >> 16);
+  } else
+    memcpy(ptr, &v, sizeof(v));
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint64_t unaligned_peek_u64(
+    const unsigned expected_alignment, const void *const __restrict ptr) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(uint64_t)) == 0)
+    return *(const uint64_t *)ptr;
+  else if ((expected_alignment % sizeof(uint32_t)) == 0) {
+    const uint32_t lo =
+        ((const uint32_t *)ptr)[__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__];
+    const uint32_t hi =
+        ((const uint32_t *)ptr)[__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__];
+    return lo | (uint64_t)hi << 32;
+  } else {
+    uint64_t v;
+    memcpy(&v, ptr, sizeof(v));
+    return v;
+  }
+}
+
+static __always_inline void
+unaligned_poke_u64(const unsigned expected_alignment,
+                   void *const __restrict ptr, const uint64_t v) {
+  assert((uintptr_t)ptr % expected_alignment == 0);
+  if (MDBX_UNALIGNED_OK || (expected_alignment % sizeof(v)) == 0)
+    *(uint64_t *)ptr = v;
+  else if ((expected_alignment % sizeof(uint32_t)) == 0) {
+    ((uint32_t *)ptr)[__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__] = (uint32_t)v;
+    ((uint32_t *)ptr)[__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__] =
+        (uint32_t)(v >> 32);
+  } else
+    memcpy(ptr, &v, sizeof(v));
+}
+
+#define UNALIGNED_PEEK_8(ptr, struct, field)                                   \
+  peek_u8((const uint8_t *)(ptr) + offsetof(struct, field))
+#define UNALIGNED_POKE_8(ptr, struct, field, value)                            \
+  poke_u8((uint8_t *)(ptr) + offsetof(struct, field), value)
+
+#define UNALIGNED_PEEK_16(ptr, struct, field)                                  \
+  unaligned_peek_u16(1, (const char *)(ptr) + offsetof(struct, field))
+#define UNALIGNED_POKE_16(ptr, struct, field, value)                           \
+  unaligned_poke_u16(1, (char *)(ptr) + offsetof(struct, field), value)
+
+#define UNALIGNED_PEEK_32(ptr, struct, field)                                  \
+  unaligned_peek_u32(1, (const char *)(ptr) + offsetof(struct, field))
+#define UNALIGNED_POKE_32(ptr, struct, field, value)                           \
+  unaligned_poke_u32(1, (char *)(ptr) + offsetof(struct, field), value)
+
+#define UNALIGNED_PEEK_64(ptr, struct, field)                                  \
+  unaligned_peek_u64(1, (const char *)(ptr) + offsetof(struct, field))
+#define UNALIGNED_POKE_64(ptr, struct, field, value)                           \
+  unaligned_poke_u64(1, (char *)(ptr) + offsetof(struct, field), value)
+
+/* Get the page number pointed to by a branch node */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline pgno_t
+node_pgno(const MDBX_node *const __restrict node) {
+  pgno_t pgno = UNALIGNED_PEEK_32(node, MDBX_node, mn_pgno32);
+  if (sizeof(pgno) > 4)
+    pgno |= ((uint64_t)UNALIGNED_PEEK_8(node, MDBX_node, mn_extra)) << 32;
+  return pgno;
+}
+
+/* Set the page number in a branch node */
+static __always_inline void node_set_pgno(MDBX_node *const __restrict node,
+                                          pgno_t pgno) {
+  assert(pgno >= MIN_PAGENO && pgno <= MAX_PAGENO);
+
+  UNALIGNED_POKE_32(node, MDBX_node, mn_pgno32, (uint32_t)pgno);
+  if (sizeof(pgno) > 4)
+    UNALIGNED_POKE_8(node, MDBX_node, mn_extra,
+                     (uint8_t)((uint64_t)pgno >> 32));
+}
+
+/* Get the size of the data in a leaf node */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+node_ds(const MDBX_node *const __restrict node) {
+  return UNALIGNED_PEEK_32(node, MDBX_node, mn_dsize);
+}
+
+/* Set the size of the data for a leaf node */
+static __always_inline void node_set_ds(MDBX_node *const __restrict node,
+                                        size_t size) {
+  assert(size < INT_MAX);
+  UNALIGNED_POKE_32(node, MDBX_node, mn_dsize, (uint32_t)size);
+}
+
+/* The size of a key in a node */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+node_ks(const MDBX_node *const __restrict node) {
+  return UNALIGNED_PEEK_16(node, MDBX_node, mn_ksize);
+}
+
+/* Set the size of the key for a leaf node */
+static __always_inline void node_set_ks(MDBX_node *const __restrict node,
+                                        size_t size) {
+  assert(size < INT16_MAX);
+  UNALIGNED_POKE_16(node, MDBX_node, mn_ksize, (uint16_t)size);
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint8_t
+node_flags(const MDBX_node *const __restrict node) {
+  return UNALIGNED_PEEK_8(node, MDBX_node, mn_flags);
+}
+
+static __always_inline void node_set_flags(MDBX_node *const __restrict node,
+                                           uint8_t flags) {
+  UNALIGNED_POKE_8(node, MDBX_node, mn_flags, flags);
+}
+
+/* Size of the node header, excluding dynamic data at the end */
+#define NODESIZE offsetof(MDBX_node, mn_data)
+
+/* Address of the key for the node */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline void *
+node_key(const MDBX_node *const __restrict node) {
+  return (char *)node + NODESIZE;
+}
+
+/* Address of the data for a node */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline void *
+node_data(const MDBX_node *const __restrict node) {
+  return (char *)node_key(node) + node_ks(node);
+}
+
+/* Size of a node in a leaf page with a given key and data.
+ * This is node header plus key plus data size. */
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline size_t
+node_size_len(const size_t key_len, const size_t value_len) {
+  return NODESIZE + EVEN(key_len + value_len);
+}
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+node_size(const MDBX_val *key, const MDBX_val *value) {
+  return node_size_len(key ? key->iov_len : 0, value ? value->iov_len : 0);
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline pgno_t
+peek_pgno(const void *const __restrict ptr) {
+  if (sizeof(pgno_t) == sizeof(uint32_t))
+    return (pgno_t)unaligned_peek_u32(1, ptr);
+  else if (sizeof(pgno_t) == sizeof(uint64_t))
+    return (pgno_t)unaligned_peek_u64(1, ptr);
+  else {
+    pgno_t pgno;
+    memcpy(&pgno, ptr, sizeof(pgno));
+    return pgno;
+  }
+}
+
+static __always_inline void poke_pgno(void *const __restrict ptr,
+                                      const pgno_t pgno) {
+  if (sizeof(pgno) == sizeof(uint32_t))
+    unaligned_poke_u32(1, ptr, pgno);
+  else if (sizeof(pgno) == sizeof(uint64_t))
+    unaligned_poke_u64(1, ptr, pgno);
+  else
+    memcpy(ptr, &pgno, sizeof(pgno));
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline pgno_t
+node_largedata_pgno(const MDBX_node *const __restrict node) {
+  assert(node_flags(node) & F_BIGDATA);
+  return peek_pgno(node_data(node));
+}
+
+/*------------------------------------------------------------------------------
+ * Key length limitation factors:
+ *
+ *  - Branch-page must contain at least two (MDBX_MINKEYS) nodes,
+ *    within each a key and a child page number. But we can't split a page if
+ *    it contains less that 4 keys. Therefore, at least 3 branch-node should
+ *    fit in the single branch-page:
+ *      pageroom = pagesize - page_hdr_len;
+ *      branch.maxnode = even_floor(pageroom / 3 - sizeof(indx_t));
+ *      branch.maxkey = branch.maxnode - node_hdr_len;
+ *
+ *  - Leaf-node of non-dupsort database must fit into one leaf-page,
+ *    where a value could be placed on a large/overflow page:
+ *      leaf.maxnode = even_floor(pageroom - sizeof(indx_t));
+ *      leaf.maxkey = leaf.maxnode - node_hdr_len - sizeof(pgno_t);
+ *
+ *  - SubDatabase-node must fit into one leaf-page:
+ *      subdb.maxname = leaf.maxnode - node_hdr_len - sizeof(MDBX_db);
+ *
+ *  - Dupsort values itself are a keys in a dupsort-subdb and couldn't be
+ *    longer than the branch.maxkey. But dupsort node must fit into one
+ *    leaf-page, since dupsort value couldn't be placed on a large/overflow
+ *    page.
+ *
+ * - So, the simplest solution is to use half of branch.maxkey as
+ *   a common maxkey value. Nevertheless, the actual values of maxkey are:
+ *     nondupsort.maxkey = even_floor(pageroom / 3)
+ *                           - sizeof(indx_t) - node_hdr_len;
+ *     dupsort.maxkey(value) = min(nondupsort.maxkey,
+ *                                 leaf.maxnode - even_ceil(length(value)));
+ */
+
+#define PAGEROOM(pagesize) ((pagesize)-PAGEHDRSZ)
+#define EVEN_FLOOR(n) ((n) & ~(size_t)1)
+#define BRANCH_NODEMAX(pagesize)                                               \
+  (EVEN_FLOOR(PAGEROOM(pagesize) / (MDBX_MINKEYS * 2 - 1)) - sizeof(indx_t))
+#define LEAF_NODEMAX(pagesize) (PAGEROOM(pagesize) - sizeof(indx_t))
+#define MAX_GC1OVPAGE(pagesize) (PAGEROOM(pagesize) / sizeof(pgno_t) - 1)
+
+__cold int mdbx_env_get_maxkeysize(const MDBX_env *env) {
+  return mdbx_env_get_maxkeysize_ex(env, MDBX_DUPSORT);
+}
+
+__cold int mdbx_env_get_maxkeysize_ex(const MDBX_env *env,
+                                      MDBX_db_flags_t flags) {
+  if (unlikely(!env || env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return -1;
+
+  return (int)mdbx_limits_keysize_max((intptr_t)env->me_psize, flags);
+}
+
+size_t mdbx_default_pagesize(void) {
+  size_t pagesize = mdbx_syspagesize();
+  mdbx_ensure(nullptr, is_powerof2(pagesize));
+  pagesize = (pagesize >= MIN_PAGESIZE) ? pagesize : MIN_PAGESIZE;
+  pagesize = (pagesize <= MAX_PAGESIZE) ? pagesize : MAX_PAGESIZE;
+  return pagesize;
+}
+
+__cold intptr_t mdbx_limits_keysize_max(intptr_t pagesize,
+                                        MDBX_db_flags_t flags) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_default_pagesize();
+  if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
+               pagesize > (intptr_t)MAX_PAGESIZE ||
+               !is_powerof2((size_t)pagesize)))
+    return -1;
+
+  STATIC_ASSERT(BRANCH_NODEMAX(MIN_PAGESIZE) - NODESIZE - sizeof(pgno_t) >= 8);
+  STATIC_ASSERT(LEAF_NODEMAX(MIN_PAGESIZE) - NODESIZE - sizeof(pgno_t) >= 8);
+  STATIC_ASSERT(LEAF_NODEMAX(MIN_PAGESIZE) - NODESIZE >= sizeof(MDBX_db));
+  if (flags & MDBX_INTEGERKEY)
+    return 8 /* sizeof(uint64_t) */;
+
+  STATIC_ASSERT(BRANCH_NODEMAX(MAX_PAGESIZE) - NODESIZE - sizeof(pgno_t) <
+                LEAF_NODEMAX(MAX_PAGESIZE) - NODESIZE - sizeof(MDBX_db));
+  STATIC_ASSERT(BRANCH_NODEMAX(MIN_PAGESIZE) - NODESIZE - sizeof(pgno_t) <
+                LEAF_NODEMAX(MIN_PAGESIZE) - NODESIZE - sizeof(MDBX_db));
+  if (flags &
+      (MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERDUP | MDBX_REVERSEDUP))
+    return BRANCH_NODEMAX(pagesize) - NODESIZE - sizeof(MDBX_db);
+
+  return BRANCH_NODEMAX(pagesize) - NODESIZE - sizeof(pgno_t);
+}
+
+__cold int mdbx_env_get_maxvalsize_ex(const MDBX_env *env,
+                                      MDBX_db_flags_t flags) {
+  if (unlikely(!env || env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return -1;
+
+  return (int)mdbx_limits_valsize_max((intptr_t)env->me_psize, flags);
+}
+
+__cold intptr_t mdbx_limits_valsize_max(intptr_t pagesize,
+                                        MDBX_db_flags_t flags) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_default_pagesize();
+  if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
+               pagesize > (intptr_t)MAX_PAGESIZE ||
+               !is_powerof2((size_t)pagesize)))
+    return -1;
+
+  if (flags & MDBX_INTEGERDUP)
+    return 8 /* sizeof(uint64_t) */;
+
+  if (flags & (MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_REVERSEDUP))
+    return BRANCH_NODEMAX(pagesize) - NODESIZE;
+
+  const unsigned page_ln2 = log2n(pagesize);
+  const size_t hard = 0x7FF00000ul;
+  const size_t hard_pages = hard >> page_ln2;
+  STATIC_ASSERT(MDBX_PGL_LIMIT <= MAX_PAGENO);
+  const size_t pages_limit = MDBX_PGL_LIMIT / 4;
+  const size_t limit =
+      (hard_pages < pages_limit) ? hard : (pages_limit << page_ln2);
+  return (limit < MAX_MAPSIZE / 2) ? limit : MAX_MAPSIZE / 2;
+}
+
+/* Calculate the size of a leaf node.
+ *
+ * The size depends on the environment's page size; if a data item
+ * is too large it will be put onto an overflow page and the node
+ * size will only include the key and not the data. Sizes are always
+ * rounded up to an even number of bytes, to guarantee 2-byte alignment
+ * of the MDBX_node headers. */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+leaf_size(const MDBX_env *env, const MDBX_val *key, const MDBX_val *data) {
+  size_t node_bytes = node_size(key, data);
+  /* NOTE: The actual limit is LEAF_NODEMAX(env->me_psize), but it reasonable to
+   * use env->me_branch_nodemax (which is 3 times less) as the threshold
+   * because:
+   *  - Large threshold implies that any insertion/update could result split
+   *    a single leaf page to THREE, which requires TWO insertion into parent
+   *    branch page, then could leads to split parent page and so on up to
+   *    the root. Such double-splitting is complex, ie costly (in case simple
+   *    clear implementation) either dangerous (in case high-optimized
+   *    implementation).
+   *  - This does not affect capabilities, i.e. it does not limit the maximum
+   *    key size.
+   *  - At a lower threshold, on average, the density of keys on leaf pages
+   *    increases and the height of the tree decreases. Thus, this lead the
+   *    less number of pages participating in the search, and the search
+   *    speed increases.
+   *  - On the other hand, there is no universal gold ratio here and with a
+   *    smaller threshold, we will create more overflows/large pages,
+   *    i.e. the database size will be larger as will the IOPS volume.
+   *
+   * So, the lower threshold is not a silver bullet, but it allow implementation
+   * to be much simple and robust, without adding a flaws. */
+  if (node_bytes > env->me_branch_nodemax) {
+    /* put on overflow page */
+    node_bytes = node_size(key, nullptr) + sizeof(pgno_t);
+  }
+
+  return node_bytes + sizeof(indx_t);
+}
+
+/* Calculate the size of a branch node.
+ *
+ * The size should depend on the environment's page size but since
+ * we currently don't support spilling large keys onto overflow
+ * pages, it's simply the size of the MDBX_node header plus the
+ * size of the key. Sizes are always rounded up to an even number
+ * of bytes, to guarantee 2-byte alignment of the MDBX_node headers.
+ *
+ * [in] env The environment handle.
+ * [in] key The key for the node.
+ *
+ * Returns The number of bytes needed to store the node. */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+branch_size(const MDBX_env *env, const MDBX_val *key) {
+  /* Size of a node in a branch page with a given key.
+   * This is just the node header plus the key, there is no data. */
+  size_t node_bytes = node_size(key, nullptr);
+  if (unlikely(node_bytes > env->me_branch_nodemax)) {
+    /* put on overflow page */
+    /* not implemented */
+    mdbx_assert_fail(env, "INDXSIZE(key) <= env->me_nodemax", __func__,
+                     __LINE__);
+    node_bytes = node_size(key, nullptr) + sizeof(pgno_t);
+  }
+
+  return node_bytes + sizeof(indx_t);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline uint16_t
+flags_db2sub(uint16_t db_flags) {
+  uint16_t sub_flags = db_flags & MDBX_DUPFIXED;
+
+  /* MDBX_INTEGERDUP => MDBX_INTEGERKEY */
+#define SHIFT_INTEGERDUP_TO_INTEGERKEY 2
+  STATIC_ASSERT((MDBX_INTEGERDUP >> SHIFT_INTEGERDUP_TO_INTEGERKEY) ==
+                MDBX_INTEGERKEY);
+  sub_flags |= (db_flags & MDBX_INTEGERDUP) >> SHIFT_INTEGERDUP_TO_INTEGERKEY;
+
+  /* MDBX_REVERSEDUP => MDBX_REVERSEKEY */
+#define SHIFT_REVERSEDUP_TO_REVERSEKEY 5
+  STATIC_ASSERT((MDBX_REVERSEDUP >> SHIFT_REVERSEDUP_TO_REVERSEKEY) ==
+                MDBX_REVERSEKEY);
+  sub_flags |= (db_flags & MDBX_REVERSEDUP) >> SHIFT_REVERSEDUP_TO_REVERSEKEY;
+
+  return sub_flags;
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline size_t
+pgno2bytes(const MDBX_env *env, pgno_t pgno) {
+  mdbx_assert(env, (1u << env->me_psize2log) == env->me_psize);
+  return ((size_t)pgno) << env->me_psize2log;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline MDBX_page *
+pgno2page(const MDBX_env *env, pgno_t pgno) {
+  return (MDBX_page *)(env->me_map + pgno2bytes(env, pgno));
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline pgno_t
+bytes2pgno(const MDBX_env *env, size_t bytes) {
+  mdbx_assert(env, (env->me_psize >> env->me_psize2log) == 1);
+  return (pgno_t)(bytes >> env->me_psize2log);
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static size_t
+pgno_align2os_bytes(const MDBX_env *env, pgno_t pgno) {
+  return ceil_powerof2(pgno2bytes(env, pgno), env->me_os_psize);
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static pgno_t pgno_align2os_pgno(const MDBX_env *env,
+                                                            pgno_t pgno) {
+  return bytes2pgno(env, pgno_align2os_bytes(env, pgno));
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static size_t
+bytes_align2os_bytes(const MDBX_env *env, size_t bytes) {
+  return ceil_powerof2(ceil_powerof2(bytes, env->me_psize), env->me_os_psize);
+}
+
+/* Address of first usable data byte in a page, after the header */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline void *
+page_data(const MDBX_page *mp) {
+  return (char *)mp + PAGEHDRSZ;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline const MDBX_page *
+data_page(const void *data) {
+  return container_of(data, MDBX_page, mp_ptrs);
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline MDBX_meta *
+page_meta(MDBX_page *mp) {
+  return (MDBX_meta *)page_data(mp);
+}
+
+/* Number of nodes on a page */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline unsigned
+page_numkeys(const MDBX_page *mp) {
+  return mp->mp_lower >> 1;
+}
+
+/* The amount of space remaining in the page */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline unsigned
+page_room(const MDBX_page *mp) {
+  return mp->mp_upper - mp->mp_lower;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline unsigned
+page_space(const MDBX_env *env) {
+  STATIC_ASSERT(PAGEHDRSZ % 2 == 0);
+  return env->me_psize - PAGEHDRSZ;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline unsigned
+page_used(const MDBX_env *env, const MDBX_page *mp) {
+  return page_space(env) - page_room(mp);
+}
+
+/* The percentage of space used in the page, in a percents. */
+MDBX_NOTHROW_PURE_FUNCTION static __maybe_unused __inline double
+page_fill(const MDBX_env *env, const MDBX_page *mp) {
+  return page_used(env, mp) * 100.0 / page_space(env);
+}
+
+/* The number of overflow pages needed to store the given size. */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline pgno_t
+number_of_ovpages(const MDBX_env *env, size_t bytes) {
+  return bytes2pgno(env, PAGEHDRSZ - 1 + bytes) + 1;
+}
+
+__cold static int MDBX_PRINTF_ARGS(2, 3)
+    bad_page(const MDBX_page *mp, const char *fmt, ...) {
+  if (mdbx_log_enabled(MDBX_LOG_ERROR)) {
+    static const MDBX_page *prev;
+    if (prev != mp) {
+      prev = mp;
+      mdbx_debug_log(MDBX_LOG_ERROR, "badpage", 0,
+                     "corrupted page #%u, mod-txnid %" PRIaTXN "\n",
+                     mp->mp_pgno, mp->mp_txnid);
+    }
+
+    va_list args;
+    va_start(args, fmt);
+    mdbx_debug_log_va(MDBX_LOG_ERROR, "badpage", 0, fmt, args);
+    va_end(args);
+  }
+  return MDBX_CORRUPTED;
+}
+
+/* Address of node i in page p */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline MDBX_node *
+page_node(const MDBX_page *mp, unsigned i) {
+  assert((mp->mp_flags & (P_LEAF2 | P_OVERFLOW | P_META)) == 0);
+  assert(page_numkeys(mp) > (unsigned)(i));
+  assert(mp->mp_ptrs[i] % 2 == 0);
+  return (MDBX_node *)((char *)mp + mp->mp_ptrs[i] + PAGEHDRSZ);
+}
+
+/* The address of a key in a LEAF2 page.
+ * LEAF2 pages are used for MDBX_DUPFIXED sorted-duplicate sub-DBs.
+ * There are no node headers, keys are stored contiguously. */
+MDBX_NOTHROW_PURE_FUNCTION static __always_inline void *
+page_leaf2key(const MDBX_page *mp, unsigned i, size_t keysize) {
+  assert((mp->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW | P_META)) ==
+         (P_LEAF | P_LEAF2));
+  assert(mp->mp_leaf2_ksize == keysize);
+  (void)keysize;
+  return (char *)mp + PAGEHDRSZ + (i * mp->mp_leaf2_ksize);
+}
+
+/* Set the node's key into keyptr. */
+static __always_inline void get_key(const MDBX_node *node, MDBX_val *keyptr) {
+  keyptr->iov_len = node_ks(node);
+  keyptr->iov_base = node_key(node);
+}
+
+/* Set the node's key into keyptr, if requested. */
+static __always_inline void
+get_key_optional(const MDBX_node *node, MDBX_val *keyptr /* __may_null */) {
+  if (keyptr)
+    get_key(node, keyptr);
+}
+
+/*------------------------------------------------------------------------------
+ * Workaround for mmaped-lookahead-cross-page-boundary bug
+ * in an obsolete versions of Elbrus's libc and kernels. */
+#if defined(__e2k__) && defined(MDBX_E2K_MLHCPB_WORKAROUND) &&                 \
+    MDBX_E2K_MLHCPB_WORKAROUND
+int __hot mdbx_e2k_memcmp_bug_workaround(const void *s1, const void *s2,
+                                         size_t n) {
+  if (unlikely(n > 42
+               /* LY: align followed access if reasonable possible */
+               && (((uintptr_t)s1) & 7) != 0 &&
+               (((uintptr_t)s1) & 7) == (((uintptr_t)s2) & 7))) {
+    if (((uintptr_t)s1) & 1) {
+      const int diff = *(uint8_t *)s1 - *(uint8_t *)s2;
+      if (diff)
+        return diff;
+      s1 = (char *)s1 + 1;
+      s2 = (char *)s2 + 1;
+      n -= 1;
+    }
+
+    if (((uintptr_t)s1) & 2) {
+      const uint16_t a = *(uint16_t *)s1;
+      const uint16_t b = *(uint16_t *)s2;
+      if (likely(a != b))
+        return (__builtin_bswap16(a) > __builtin_bswap16(b)) ? 1 : -1;
+      s1 = (char *)s1 + 2;
+      s2 = (char *)s2 + 2;
+      n -= 2;
+    }
+
+    if (((uintptr_t)s1) & 4) {
+      const uint32_t a = *(uint32_t *)s1;
+      const uint32_t b = *(uint32_t *)s2;
+      if (likely(a != b))
+        return (__builtin_bswap32(a) > __builtin_bswap32(b)) ? 1 : -1;
+      s1 = (char *)s1 + 4;
+      s2 = (char *)s2 + 4;
+      n -= 4;
+    }
+  }
+
+  while (n >= 8) {
+    const uint64_t a = *(uint64_t *)s1;
+    const uint64_t b = *(uint64_t *)s2;
+    if (likely(a != b))
+      return (__builtin_bswap64(a) > __builtin_bswap64(b)) ? 1 : -1;
+    s1 = (char *)s1 + 8;
+    s2 = (char *)s2 + 8;
+    n -= 8;
+  }
+
+  if (n & 4) {
+    const uint32_t a = *(uint32_t *)s1;
+    const uint32_t b = *(uint32_t *)s2;
+    if (likely(a != b))
+      return (__builtin_bswap32(a) > __builtin_bswap32(b)) ? 1 : -1;
+    s1 = (char *)s1 + 4;
+    s2 = (char *)s2 + 4;
+  }
+
+  if (n & 2) {
+    const uint16_t a = *(uint16_t *)s1;
+    const uint16_t b = *(uint16_t *)s2;
+    if (likely(a != b))
+      return (__builtin_bswap16(a) > __builtin_bswap16(b)) ? 1 : -1;
+    s1 = (char *)s1 + 2;
+    s2 = (char *)s2 + 2;
+  }
+
+  return (n & 1) ? *(uint8_t *)s1 - *(uint8_t *)s2 : 0;
+}
+
+int __hot mdbx_e2k_strcmp_bug_workaround(const char *s1, const char *s2) {
+  while (true) {
+    int diff = *(uint8_t *)s1 - *(uint8_t *)s2;
+    if (likely(diff != 0) || *s1 == '\0')
+      return diff;
+    s1 += 1;
+    s2 += 1;
+  }
+}
+
+int __hot mdbx_e2k_strncmp_bug_workaround(const char *s1, const char *s2,
+                                          size_t n) {
+  while (n > 0) {
+    int diff = *(uint8_t *)s1 - *(uint8_t *)s2;
+    if (likely(diff != 0) || *s1 == '\0')
+      return diff;
+    s1 += 1;
+    s2 += 1;
+    n -= 1;
+  }
+  return 0;
+}
+
+size_t __hot mdbx_e2k_strlen_bug_workaround(const char *s) {
+  size_t n = 0;
+  while (*s) {
+    s += 1;
+    n += 1;
+  }
+  return n;
+}
+
+size_t __hot mdbx_e2k_strnlen_bug_workaround(const char *s, size_t maxlen) {
+  size_t n = 0;
+  while (maxlen > n && *s) {
+    s += 1;
+    n += 1;
+  }
+  return n;
+}
+#endif /* MDBX_E2K_MLHCPB_WORKAROUND */
+
+/*------------------------------------------------------------------------------
+ * safe read/write volatile 64-bit fields on 32-bit architectures. */
+
+enum MDBX_memory_order {
+  mo_Relaxed,
+  mo_AcquireRelease,
+  mo_SequentialConsistency
+};
+
+#ifdef MDBX_HAVE_C11ATOMICS
+
+#if defined(__clang__) && __clang__ < 8
+#define MDBX_WORKAROUND_CLANG_C11ATOMICS_BUG(type, ptr)                        \
+  ((volatile _Atomic(type) *)(ptr))
+#else
+#define MDBX_WORKAROUND_CLANG_C11ATOMICS_BUG(type, ptr) (ptr)
+#endif /* __clang__ < 8.x */
+
+static __always_inline memory_order mo_c11_store(enum MDBX_memory_order fence) {
+  switch (fence) {
+  default:
+    assert(false);
+    __unreachable();
+  case mo_Relaxed:
+    return memory_order_relaxed;
+  case mo_AcquireRelease:
+    return memory_order_release;
+  case mo_SequentialConsistency:
+    return memory_order_seq_cst;
+  }
+}
+
+static __always_inline memory_order mo_c11_load(enum MDBX_memory_order fence) {
+  switch (fence) {
+  default:
+    assert(false);
+    __unreachable();
+  case mo_Relaxed:
+    return memory_order_relaxed;
+  case mo_AcquireRelease:
+    return memory_order_acquire;
+  case mo_SequentialConsistency:
+    return memory_order_seq_cst;
+  }
+}
+#endif /* MDBX_HAVE_C11ATOMICS */
+
+static __maybe_unused __always_inline void mdbx_memory_fence(bool checkpoint,
+                                                             bool write) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(
+      checkpoint ? memory_order_seq_cst
+                 : (write ? memory_order_release : memory_order_acquire));
+#else  /* MDBX_HAVE_C11ATOMICS */
+  mdbx_compiler_barrier();
+  if (checkpoint || (write && MDBX_CPU_WRITEBACK_INCOHERENT))
+    mdbx_memory_barrier();
+#endif /* MDBX_HAVE_C11ATOMICS */
+}
+
+static __maybe_unused __always_inline uint32_t
+atomic_store32(MDBX_atomic_uint32_t *ptr, const uint32_t value,
+               enum MDBX_memory_order order) {
+  STATIC_ASSERT(sizeof(MDBX_atomic_uint32_t) == 4);
+#ifdef MDBX_HAVE_C11ATOMICS
+  assert(atomic_is_lock_free(&ptr->c11a));
+  atomic_store_explicit(&ptr->c11a, value, mo_c11_store(order));
+#else  /* MDBX_HAVE_C11ATOMICS */
+  if (order != mo_Relaxed)
+    mdbx_compiler_barrier();
+  ptr->weak = value;
+  if (order != mo_Relaxed)
+    mdbx_memory_fence(order == mo_SequentialConsistency, true);
+#endif /* MDBX_HAVE_C11ATOMICS */
+  return value;
+}
+
+static __maybe_unused __always_inline uint32_t
+atomic_load32(const MDBX_atomic_uint32_t *ptr, enum MDBX_memory_order order) {
+  STATIC_ASSERT(sizeof(MDBX_atomic_uint32_t) == 4);
+#ifdef MDBX_HAVE_C11ATOMICS
+  assert(atomic_is_lock_free(&ptr->c11a));
+  return atomic_load_explicit(
+      MDBX_WORKAROUND_CLANG_C11ATOMICS_BUG(uint32_t, &ptr->c11a),
+      mo_c11_load(order));
+#else  /* MDBX_HAVE_C11ATOMICS */
+  if (order != mo_Relaxed)
+    mdbx_memory_fence(order == mo_SequentialConsistency, false);
+  const uint32_t value = ptr->weak;
+  if (order != mo_Relaxed)
+    mdbx_compiler_barrier();
+  return value;
+#endif /* MDBX_HAVE_C11ATOMICS */
+}
+
+static __always_inline uint64_t atomic_store64(MDBX_atomic_uint64_t *ptr,
+                                               const uint64_t value,
+                                               enum MDBX_memory_order order) {
+  STATIC_ASSERT(sizeof(MDBX_atomic_uint64_t) == 8);
+#if MDBX_64BIT_ATOMIC
+#ifdef MDBX_HAVE_C11ATOMICS
+  assert(atomic_is_lock_free(&ptr->c11a));
+  atomic_store_explicit(&ptr->c11a, value, mo_c11_store(order));
+#else  /* MDBX_HAVE_C11ATOMICS */
+  if (order != mo_Relaxed)
+    mdbx_compiler_barrier();
+  ptr->weak = value;
+  if (order != mo_Relaxed)
+    mdbx_memory_fence(order == mo_SequentialConsistency, true);
+#endif /* MDBX_HAVE_C11ATOMICS */
+#else  /* !MDBX_64BIT_ATOMIC */
+  atomic_store32(&ptr->low, (uint32_t)value,
+                 (order == mo_Relaxed) ? mo_Relaxed : mo_AcquireRelease);
+  mdbx_jitter4testing(true);
+  atomic_store32(&ptr->high, (uint32_t)(value >> 32), order);
+  mdbx_jitter4testing(true);
+#endif /* !MDBX_64BIT_ATOMIC */
+  return value;
+}
+
+static __always_inline uint64_t atomic_load64(const MDBX_atomic_uint64_t *ptr,
+                                              enum MDBX_memory_order order) {
+  STATIC_ASSERT(sizeof(MDBX_atomic_uint64_t) == 8);
+#if MDBX_64BIT_ATOMIC
+#ifdef MDBX_HAVE_C11ATOMICS
+  assert(atomic_is_lock_free(&ptr->c11a));
+  return atomic_load_explicit(
+      MDBX_WORKAROUND_CLANG_C11ATOMICS_BUG(uint64_t, &ptr->c11a),
+      mo_c11_load(order));
+#else  /* MDBX_HAVE_C11ATOMICS */
+  if (order != mo_Relaxed)
+    mdbx_memory_fence(order == mo_SequentialConsistency, false);
+  const uint64_t value = ptr->weak;
+  if (order != mo_Relaxed)
+    mdbx_compiler_barrier();
+  return value;
+#endif /* MDBX_HAVE_C11ATOMICS */
+#else  /* !MDBX_64BIT_ATOMIC */
+  uint64_t value = (uint64_t)atomic_load32(&ptr->high, order) << 32;
+  mdbx_jitter4testing(true);
+  value |= atomic_load32(&ptr->low, (order == mo_Relaxed) ? mo_Relaxed
+                                                          : mo_AcquireRelease);
+  mdbx_jitter4testing(true);
+  for (;;) {
+    uint64_t again = (uint64_t)atomic_load32(&ptr->high, order) << 32;
+    mdbx_jitter4testing(true);
+    again |= atomic_load32(
+        &ptr->low, (order == mo_Relaxed) ? mo_Relaxed : mo_AcquireRelease);
+    mdbx_jitter4testing(true);
+    if (likely(value == again))
+      return value;
+    value = again;
+  }
+#endif /* !MDBX_64BIT_ATOMIC */
+}
+
+static __always_inline void atomic_yield(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  YieldProcessor();
+#elif defined(__ia32__) || defined(__e2k__)
+  __builtin_ia32_pause();
+#elif defined(__ia64__)
+#if defined(__HP_cc__) || defined(__HP_aCC__)
+  _Asm_hint(_HINT_PAUSE);
+#else
+  __asm__ __volatile__("hint @pause");
+#endif
+#elif defined(__aarch64__) || (defined(__ARM_ARCH) && __ARM_ARCH > 6) ||       \
+    defined(__ARM_ARCH_6K__)
+#ifdef __CC_ARM
+  __yield();
+#else
+  __asm__ __volatile__("yield");
+#endif
+#elif (defined(__mips64) || defined(__mips64__)) && defined(__mips_isa_rev) && \
+    __mips_isa_rev >= 2
+  __asm__ __volatile__("pause");
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+  __asm__ __volatile__(".word 0x00000140");
+#elif defined(__linux__) || defined(__gnu_linux__) || defined(_UNIX03_SOURCE)
+  sched_yield();
+#elif (defined(_GNU_SOURCE) && __GLIBC_PREREQ(2, 1)) || defined(_OPEN_THREADS)
+  pthread_yield();
+#endif
+}
+
+#if MDBX_64BIT_CAS
+static __always_inline bool atomic_cas64(MDBX_atomic_uint64_t *p, uint64_t c,
+                                         uint64_t v) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  STATIC_ASSERT(sizeof(long long) >= sizeof(uint64_t));
+#ifdef ATOMIC_LLONG_LOCK_FREE
+  STATIC_ASSERT(ATOMIC_LLONG_LOCK_FREE > 0);
+#if ATOMIC_LLONG_LOCK_FREE < 2
+  assert(atomic_is_lock_free(&p->c11a));
+#endif /* ATOMIC_LLONG_LOCK_FREE < 2 */
+#else  /* defined(ATOMIC_LLONG_LOCK_FREE) */
+  assert(atomic_is_lock_free(&p->c11a));
+#endif
+  return atomic_compare_exchange_strong(&p->c11a, &c, v);
+#elif defined(__GNUC__) || defined(__clang__)
+  return __sync_bool_compare_and_swap(&p->weak, c, v);
+#elif defined(_MSC_VER)
+  return c == (uint64_t)_InterlockedCompareExchange64(&p->weak, v, c);
+#elif defined(__APPLE__)
+  return OSAtomicCompareAndSwap64Barrier(c, v, &p->weak);
+#else
+#error FIXME: Unsupported compiler
+#endif
+}
+#endif /* MDBX_64BIT_CAS */
+
+static __always_inline bool atomic_cas32(MDBX_atomic_uint32_t *p, uint32_t c,
+                                         uint32_t v) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  STATIC_ASSERT(sizeof(int) >= sizeof(uint32_t));
+#ifdef ATOMIC_INT_LOCK_FREE
+  STATIC_ASSERT(ATOMIC_INT_LOCK_FREE > 0);
+#if ATOMIC_INT_LOCK_FREE < 2
+  assert(atomic_is_lock_free(&p->c11a));
+#endif
+#else
+  assert(atomic_is_lock_free(&p->c11a));
+#endif
+  return atomic_compare_exchange_strong(&p->c11a, &c, v);
+#elif defined(__GNUC__) || defined(__clang__)
+  return __sync_bool_compare_and_swap(&p->weak, c, v);
+#elif defined(_MSC_VER)
+  STATIC_ASSERT(sizeof(volatile long) == sizeof(volatile uint32_t));
+  return c == (uint32_t)_InterlockedCompareExchange(&p->weak, v, c);
+#elif defined(__APPLE__)
+  return OSAtomicCompareAndSwap32Barrier(c, v, &p->weak);
+#else
+#error FIXME: Unsupported compiler
+#endif
+}
+
+static __always_inline uint32_t atomic_add32(MDBX_atomic_uint32_t *p,
+                                             uint32_t v) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  STATIC_ASSERT(sizeof(int) >= sizeof(uint32_t));
+#ifdef ATOMIC_INT_LOCK_FREE
+  STATIC_ASSERT(ATOMIC_INT_LOCK_FREE > 0);
+#if ATOMIC_INT_LOCK_FREE < 2
+  assert(atomic_is_lock_free(&p->c11a));
+#endif
+#else
+  assert(atomic_is_lock_free(&p->c11a));
+#endif
+  return atomic_fetch_add(&p->c11a, v);
+#elif defined(__GNUC__) || defined(__clang__)
+  return __sync_fetch_and_add(&p->weak, v);
+#elif defined(_MSC_VER)
+  STATIC_ASSERT(sizeof(volatile long) == sizeof(volatile uint32_t));
+  return _InterlockedExchangeAdd(&p->weak, v);
+#elif defined(__APPLE__)
+  return OSAtomicAdd32Barrier(v, &p->weak);
+#else
+#error FIXME: Unsupported compiler
+#endif
+}
+
+#define atomic_sub32(p, v) atomic_add32(p, 0 - (v))
+
+static __always_inline uint64_t safe64_txnid_next(uint64_t txnid) {
+  txnid += MDBX_TXNID_STEP;
+#if !MDBX_64BIT_CAS
+  /* avoid overflow of low-part in safe64_reset() */
+  txnid += (UINT32_MAX == (uint32_t)txnid);
+#endif
+  return txnid;
+}
+
+static __always_inline void safe64_reset(MDBX_atomic_uint64_t *ptr,
+                                         bool single_writer) {
+#if !MDBX_64BIT_CAS
+  if (!single_writer) {
+    STATIC_ASSERT(MDBX_TXNID_STEP > 1);
+    /* it is safe to increment low-part to avoid ABA, since MDBX_TXNID_STEP > 1
+     * and overflow was preserved in safe64_txnid_next() */
+    atomic_add32(&ptr->low, 1) /* avoid ABA in safe64_reset_compare() */;
+    atomic_store32(
+        &ptr->high, UINT32_MAX,
+        mo_AcquireRelease) /* atomically make >= SAFE64_INVALID_THRESHOLD */;
+    atomic_add32(&ptr->low, 1) /* avoid ABA in safe64_reset_compare() */;
+  } else
+#elif MDBX_64BIT_ATOMIC
+  /* atomically make value >= SAFE64_INVALID_THRESHOLD by 64-bit operation */
+  atomic_store64(ptr, UINT64_MAX,
+                 single_writer ? mo_AcquireRelease : mo_SequentialConsistency);
+#else
+  /* atomically make value >= SAFE64_INVALID_THRESHOLD by 32-bit operation */
+  atomic_store32(&ptr->high, UINT32_MAX,
+                 single_writer ? mo_AcquireRelease : mo_SequentialConsistency);
+#endif /* MDBX_64BIT_ATOMIC */
+    assert(ptr->weak >= SAFE64_INVALID_THRESHOLD);
+  mdbx_jitter4testing(true);
+}
+
+static __always_inline bool safe64_reset_compare(MDBX_atomic_uint64_t *ptr,
+                                                 txnid_t compare) {
+  /* LY: This function is used to reset `mr_txnid` from hsr-handler in case
+   *     the asynchronously cancellation of read transaction. Therefore,
+   *     there may be a collision between the cleanup performed here and
+   *     asynchronous termination and restarting of the read transaction
+   *     in another proces/thread. In general we MUST NOT reset the `mr_txnid`
+   *     if a new transaction was started (i.e. if `mr_txnid` was changed). */
+#if MDBX_64BIT_CAS
+  bool rc = atomic_cas64(ptr, compare, UINT64_MAX);
+#else
+  /* LY: There is no gold ratio here since shared mutex is too costly,
+   *     in such way we must acquire/release it for every update of mr_txnid,
+   *     i.e. twice for each read transaction). */
+  bool rc = false;
+  if (likely(atomic_load32(&ptr->low, mo_AcquireRelease) == (uint32_t)compare &&
+             atomic_cas32(&ptr->high, (uint32_t)(compare >> 32), UINT32_MAX))) {
+    if (unlikely(atomic_load32(&ptr->low, mo_AcquireRelease) !=
+                 (uint32_t)compare))
+      atomic_cas32(&ptr->high, UINT32_MAX, (uint32_t)(compare >> 32));
+    else
+      rc = true;
+  }
+#endif /* MDBX_64BIT_CAS */
+  mdbx_jitter4testing(true);
+  return rc;
+}
+
+static __always_inline void safe64_write(MDBX_atomic_uint64_t *ptr,
+                                         const uint64_t v) {
+  assert(ptr->weak >= SAFE64_INVALID_THRESHOLD);
+#if MDBX_64BIT_ATOMIC
+  atomic_store64(ptr, v, mo_AcquireRelease);
+#else  /* MDBX_64BIT_ATOMIC */
+  /* update low-part but still value >= SAFE64_INVALID_THRESHOLD */
+  atomic_store32(&ptr->low, (uint32_t)v, mo_AcquireRelease);
+  assert(ptr->weak >= SAFE64_INVALID_THRESHOLD);
+  mdbx_jitter4testing(true);
+  /* update high-part from SAFE64_INVALID_THRESHOLD to actual value */
+  atomic_store32(&ptr->high, (uint32_t)(v >> 32), mo_AcquireRelease);
+#endif /* MDBX_64BIT_ATOMIC */
+  assert(ptr->weak == v);
+  mdbx_jitter4testing(true);
+}
+
+static __always_inline uint64_t safe64_read(const MDBX_atomic_uint64_t *ptr) {
+  mdbx_jitter4testing(true);
+  uint64_t v = atomic_load64(ptr, mo_AcquireRelease);
+  mdbx_jitter4testing(true);
+  return v;
+}
+
+#if 0 /* unused for now */
+ static __maybe_unused __always_inline bool safe64_is_valid(uint64_t v) {
+#if MDBX_WORDBITS >= 64
+  return v < SAFE64_INVALID_THRESHOLD;
+#else
+  return (v >> 32) != UINT32_MAX;
+#endif /* MDBX_WORDBITS */
+}
+
+ static __maybe_unused __always_inline bool
+ safe64_is_valid_ptr(const MDBX_atomic_uint64_t *ptr) {
+#if MDBX_64BIT_ATOMIC
+  return atomic_load64(ptr, mo_AcquireRelease) < SAFE64_INVALID_THRESHOLD;
+#else
+  return atomic_load32(&ptr->high, mo_AcquireRelease) != UINT32_MAX;
+#endif /* MDBX_64BIT_ATOMIC */
+}
+
+static __always_inline void safe64_update(MDBX_atomic_uint64_t *ptr,
+                                          const uint64_t v) {
+#if MDBX_64BIT_ATOMIC
+  safe64_reset(ptr, true);
+#endif /* MDBX_64BIT_ATOMIC */
+  safe64_write(ptr, v);
+}
+#endif /* unused for now */
+
+/*----------------------------------------------------------------------------*/
+/* rthc (tls keys and destructors) */
+
+typedef struct rthc_entry_t {
+  MDBX_reader *begin;
+  MDBX_reader *end;
+  mdbx_thread_key_t thr_tls_key;
+  bool key_valid;
+} rthc_entry_t;
+
+#if MDBX_DEBUG
+#define RTHC_INITIAL_LIMIT 1
+#else
+#define RTHC_INITIAL_LIMIT 16
+#endif
+
+static bin128_t bootid;
+
+#if defined(_WIN32) || defined(_WIN64)
+static CRITICAL_SECTION rthc_critical_section;
+static CRITICAL_SECTION lcklist_critical_section;
+#else
+int __cxa_thread_atexit_impl(void (*dtor)(void *), void *obj, void *dso_symbol)
+    __attribute__((__weak__));
+#ifdef __APPLE__ /* FIXME: Thread-Local Storage destructors & DSO-unloading */
+int __cxa_thread_atexit_impl(void (*dtor)(void *), void *obj,
+                             void *dso_symbol) {
+  (void)dtor;
+  (void)obj;
+  (void)dso_symbol;
+  return -1;
+}
+#endif           /* __APPLE__ */
+
+static pthread_mutex_t lcklist_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t rthc_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t rthc_cond = PTHREAD_COND_INITIALIZER;
+static mdbx_thread_key_t rthc_key;
+static MDBX_atomic_uint32_t rthc_pending;
+
+static void __cold workaround_glibc_bug21031(void) {
+  /* Workaround for https://sourceware.org/bugzilla/show_bug.cgi?id=21031
+   *
+   * Due race between pthread_key_delete() and __nptl_deallocate_tsd()
+   * The destructor(s) of thread-local-storage object(s) may be running
+   * in another thread(s) and be blocked or not finished yet.
+   * In such case we get a SEGFAULT after unload this library DSO.
+   *
+   * So just by yielding a few timeslices we give a chance
+   * to such destructor(s) for completion and avoids segfault. */
+  sched_yield();
+  sched_yield();
+  sched_yield();
+}
+#endif
+
+static unsigned rthc_count, rthc_limit;
+static rthc_entry_t *rthc_table;
+static rthc_entry_t rthc_table_static[RTHC_INITIAL_LIMIT];
+
+static __inline void rthc_lock(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  EnterCriticalSection(&rthc_critical_section);
+#else
+  mdbx_ensure(nullptr, pthread_mutex_lock(&rthc_mutex) == 0);
+#endif
+}
+
+static __inline void rthc_unlock(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  LeaveCriticalSection(&rthc_critical_section);
+#else
+  mdbx_ensure(nullptr, pthread_mutex_unlock(&rthc_mutex) == 0);
+#endif
+}
+
+static __inline int thread_key_create(mdbx_thread_key_t *key) {
+  int rc;
+#if defined(_WIN32) || defined(_WIN64)
+  *key = TlsAlloc();
+  rc = (*key != TLS_OUT_OF_INDEXES) ? MDBX_SUCCESS : GetLastError();
+#else
+  rc = pthread_key_create(key, nullptr);
+#endif
+  mdbx_trace("&key = %p, value %" PRIuPTR ", rc %d",
+             __Wpedantic_format_voidptr(key), (uintptr_t)*key, rc);
+  return rc;
+}
+
+static __inline void thread_key_delete(mdbx_thread_key_t key) {
+  mdbx_trace("key = %" PRIuPTR, (uintptr_t)key);
+#if defined(_WIN32) || defined(_WIN64)
+  mdbx_ensure(nullptr, TlsFree(key));
+#else
+  mdbx_ensure(nullptr, pthread_key_delete(key) == 0);
+  workaround_glibc_bug21031();
+#endif
+}
+
+static __inline void *thread_rthc_get(mdbx_thread_key_t key) {
+#if defined(_WIN32) || defined(_WIN64)
+  return TlsGetValue(key);
+#else
+  return pthread_getspecific(key);
+#endif
+}
+
+static void thread_rthc_set(mdbx_thread_key_t key, const void *value) {
+#if defined(_WIN32) || defined(_WIN64)
+  mdbx_ensure(nullptr, TlsSetValue(key, (void *)value));
+#else
+#define MDBX_THREAD_RTHC_ZERO 0
+#define MDBX_THREAD_RTHC_REGISTERED 1
+#define MDBX_THREAD_RTHC_COUNTED 2
+  static __thread uint32_t thread_registration_state;
+  if (value && unlikely(thread_registration_state == MDBX_THREAD_RTHC_ZERO)) {
+    thread_registration_state = MDBX_THREAD_RTHC_REGISTERED;
+    mdbx_trace("thread registered 0x%" PRIxPTR, mdbx_thread_self());
+    if (&__cxa_thread_atexit_impl == nullptr ||
+        __cxa_thread_atexit_impl(mdbx_rthc_thread_dtor,
+                                 &thread_registration_state,
+                                 (void *)&mdbx_version /* dso_anchor */)) {
+      mdbx_ensure(nullptr, pthread_setspecific(
+                               rthc_key, &thread_registration_state) == 0);
+      thread_registration_state = MDBX_THREAD_RTHC_COUNTED;
+      const unsigned count_before = atomic_add32(&rthc_pending, 1);
+      mdbx_ensure(nullptr, count_before < INT_MAX);
+      mdbx_trace("fallback to pthreads' tsd, key %" PRIuPTR ", count %u",
+                 (uintptr_t)rthc_key, count_before);
+      (void)count_before;
+    }
+  }
+  mdbx_ensure(nullptr, pthread_setspecific(key, value) == 0);
+#endif
+}
+
+__cold void mdbx_rthc_global_init(void) {
+  rthc_limit = RTHC_INITIAL_LIMIT;
+  rthc_table = rthc_table_static;
+#if defined(_WIN32) || defined(_WIN64)
+  InitializeCriticalSection(&rthc_critical_section);
+  InitializeCriticalSection(&lcklist_critical_section);
+#else
+  mdbx_ensure(nullptr,
+              pthread_key_create(&rthc_key, mdbx_rthc_thread_dtor) == 0);
+  mdbx_trace("pid %d, &mdbx_rthc_key = %p, value 0x%x", mdbx_getpid(),
+             __Wpedantic_format_voidptr(&rthc_key), (unsigned)rthc_key);
+#endif
+  /* checking time conversion, this also avoids racing on 32-bit architectures
+   * during writing calculated 64-bit ratio(s) into memory. */
+  uint32_t proba = UINT32_MAX;
+  while (true) {
+    unsigned time_conversion_checkup =
+        mdbx_osal_monotime_to_16dot16(mdbx_osal_16dot16_to_monotime(proba));
+    unsigned one_more = (proba < UINT32_MAX) ? proba + 1 : proba;
+    unsigned one_less = (proba > 0) ? proba - 1 : proba;
+    mdbx_ensure(nullptr, time_conversion_checkup >= one_less &&
+                             time_conversion_checkup <= one_more);
+    if (proba == 0)
+      break;
+    proba >>= 1;
+  }
+
+  bootid = mdbx_osal_bootid();
+}
+
+/* dtor called for thread, i.e. for all mdbx's environment objects */
+__cold void mdbx_rthc_thread_dtor(void *ptr) {
+  rthc_lock();
+  mdbx_trace(">> pid %d, thread 0x%" PRIxPTR ", rthc %p", mdbx_getpid(),
+             mdbx_thread_self(), ptr);
+
+  const uint32_t self_pid = mdbx_getpid();
+  for (unsigned i = 0; i < rthc_count; ++i) {
+    if (!rthc_table[i].key_valid)
+      continue;
+    const mdbx_thread_key_t key = rthc_table[i].thr_tls_key;
+    MDBX_reader *const rthc = thread_rthc_get(key);
+    if (rthc < rthc_table[i].begin || rthc >= rthc_table[i].end)
+      continue;
+#if !defined(_WIN32) && !defined(_WIN64)
+    if (pthread_setspecific(key, nullptr) != 0) {
+      mdbx_trace("== thread 0x%" PRIxPTR
+                 ", rthc %p: ignore race with tsd-key deletion",
+                 mdbx_thread_self(), ptr);
+      continue /* ignore race with tsd-key deletion by mdbx_env_close() */;
+    }
+#endif
+
+    mdbx_trace("== thread 0x%" PRIxPTR
+               ", rthc %p, [%i], %p ... %p (%+i), rtch-pid %i, "
+               "current-pid %i",
+               mdbx_thread_self(), __Wpedantic_format_voidptr(rthc), i,
+               __Wpedantic_format_voidptr(rthc_table[i].begin),
+               __Wpedantic_format_voidptr(rthc_table[i].end),
+               (int)(rthc - rthc_table[i].begin), rthc->mr_pid.weak, self_pid);
+    if (atomic_load32(&rthc->mr_pid, mo_Relaxed) == self_pid) {
+      mdbx_trace("==== thread 0x%" PRIxPTR ", rthc %p, cleanup",
+                 mdbx_thread_self(), __Wpedantic_format_voidptr(rthc));
+      atomic_store32(&rthc->mr_pid, 0, mo_AcquireRelease);
+    }
+  }
+
+#if defined(_WIN32) || defined(_WIN64)
+  mdbx_trace("<< thread 0x%" PRIxPTR ", rthc %p", mdbx_thread_self(), ptr);
+  rthc_unlock();
+#else
+  const char self_registration = *(char *)ptr;
+  *(char *)ptr = MDBX_THREAD_RTHC_ZERO;
+  mdbx_trace("== thread 0x%" PRIxPTR ", rthc %p, pid %d, self-status %d",
+             mdbx_thread_self(), ptr, mdbx_getpid(), self_registration);
+  if (self_registration == MDBX_THREAD_RTHC_COUNTED)
+    mdbx_ensure(nullptr, atomic_sub32(&rthc_pending, 1) > 0);
+
+  if (atomic_load32(&rthc_pending, mo_AcquireRelease) == 0) {
+    mdbx_trace("== thread 0x%" PRIxPTR ", rthc %p, pid %d, wake",
+               mdbx_thread_self(), ptr, mdbx_getpid());
+    mdbx_ensure(nullptr, pthread_cond_broadcast(&rthc_cond) == 0);
+  }
+
+  mdbx_trace("<< thread 0x%" PRIxPTR ", rthc %p", mdbx_thread_self(), ptr);
+  /* Allow tail call optimization, i.e. gcc should generate the jmp instruction
+   * instead of a call for pthread_mutex_unlock() and therefore CPU could not
+   * return to current DSO's code section, which may be unloaded immediately
+   * after the mutex got released. */
+  pthread_mutex_unlock(&rthc_mutex);
+#endif
+}
+
+__cold void mdbx_rthc_global_dtor(void) {
+  mdbx_trace(">> pid %d", mdbx_getpid());
+
+  rthc_lock();
+#if !defined(_WIN32) && !defined(_WIN64)
+  char *rthc = (char *)pthread_getspecific(rthc_key);
+  mdbx_trace("== thread 0x%" PRIxPTR ", rthc %p, pid %d, self-status %d",
+             mdbx_thread_self(), __Wpedantic_format_voidptr(rthc),
+             mdbx_getpid(), rthc ? *rthc : -1);
+  if (rthc) {
+    const char self_registration = *(char *)rthc;
+    *rthc = MDBX_THREAD_RTHC_ZERO;
+    if (self_registration == MDBX_THREAD_RTHC_COUNTED)
+      mdbx_ensure(nullptr, atomic_sub32(&rthc_pending, 1) > 0);
+  }
+
+  struct timespec abstime;
+  mdbx_ensure(nullptr, clock_gettime(CLOCK_REALTIME, &abstime) == 0);
+  abstime.tv_nsec += 1000000000l / 10;
+  if (abstime.tv_nsec >= 1000000000l) {
+    abstime.tv_nsec -= 1000000000l;
+    abstime.tv_sec += 1;
+  }
+#if MDBX_DEBUG > 0
+  abstime.tv_sec += 600;
+#endif
+
+  for (unsigned left;
+       (left = atomic_load32(&rthc_pending, mo_AcquireRelease)) > 0;) {
+    mdbx_trace("pid %d, pending %u, wait for...", mdbx_getpid(), left);
+    const int rc = pthread_cond_timedwait(&rthc_cond, &rthc_mutex, &abstime);
+    if (rc && rc != EINTR)
+      break;
+  }
+  thread_key_delete(rthc_key);
+#endif
+
+  const uint32_t self_pid = mdbx_getpid();
+  for (unsigned i = 0; i < rthc_count; ++i) {
+    if (!rthc_table[i].key_valid)
+      continue;
+    const mdbx_thread_key_t key = rthc_table[i].thr_tls_key;
+    thread_key_delete(key);
+    for (MDBX_reader *rthc = rthc_table[i].begin; rthc < rthc_table[i].end;
+         ++rthc) {
+      mdbx_trace(
+          "== [%i] = key %" PRIuPTR ", %p ... %p, rthc %p (%+i), "
+          "rthc-pid %i, current-pid %i",
+          i, (uintptr_t)key, __Wpedantic_format_voidptr(rthc_table[i].begin),
+          __Wpedantic_format_voidptr(rthc_table[i].end),
+          __Wpedantic_format_voidptr(rthc), (int)(rthc - rthc_table[i].begin),
+          rthc->mr_pid.weak, self_pid);
+      if (atomic_load32(&rthc->mr_pid, mo_Relaxed) == self_pid) {
+        atomic_store32(&rthc->mr_pid, 0, mo_AcquireRelease);
+        mdbx_trace("== cleanup %p", __Wpedantic_format_voidptr(rthc));
+      }
+    }
+  }
+
+  rthc_limit = rthc_count = 0;
+  if (rthc_table != rthc_table_static)
+    mdbx_free(rthc_table);
+  rthc_table = nullptr;
+  rthc_unlock();
+
+#if defined(_WIN32) || defined(_WIN64)
+  DeleteCriticalSection(&lcklist_critical_section);
+  DeleteCriticalSection(&rthc_critical_section);
+#else
+  /* LY: yielding a few timeslices to give a more chance
+   * to racing destructor(s) for completion. */
+  workaround_glibc_bug21031();
+#endif
+
+  mdbx_trace("<< pid %d\n", mdbx_getpid());
+}
+
+__cold int mdbx_rthc_alloc(mdbx_thread_key_t *key, MDBX_reader *begin,
+                           MDBX_reader *end) {
+  int rc;
+  if (key) {
+#ifndef NDEBUG
+    *key = (mdbx_thread_key_t)0xBADBADBAD;
+#endif /* NDEBUG */
+    rc = thread_key_create(key);
+    if (rc != MDBX_SUCCESS)
+      return rc;
+  }
+
+  rthc_lock();
+  const mdbx_thread_key_t new_key = key ? *key : 0;
+  mdbx_trace(">> key %" PRIuPTR ", rthc_count %u, rthc_limit %u",
+             (uintptr_t)new_key, rthc_count, rthc_limit);
+  if (rthc_count == rthc_limit) {
+    rthc_entry_t *new_table =
+        mdbx_realloc((rthc_table == rthc_table_static) ? nullptr : rthc_table,
+                     sizeof(rthc_entry_t) * rthc_limit * 2);
+    if (new_table == nullptr) {
+      rc = MDBX_ENOMEM;
+      goto bailout;
+    }
+    if (rthc_table == rthc_table_static)
+      memcpy(new_table, rthc_table_static, sizeof(rthc_table_static));
+    rthc_table = new_table;
+    rthc_limit *= 2;
+  }
+  mdbx_trace("== [%i] = key %" PRIuPTR ", %p ... %p", rthc_count,
+             (uintptr_t)new_key, __Wpedantic_format_voidptr(begin),
+             __Wpedantic_format_voidptr(end));
+  rthc_table[rthc_count].key_valid = key ? true : false;
+  rthc_table[rthc_count].thr_tls_key = key ? new_key : 0;
+  rthc_table[rthc_count].begin = begin;
+  rthc_table[rthc_count].end = end;
+  ++rthc_count;
+  mdbx_trace("<< key %" PRIuPTR ", rthc_count %u, rthc_limit %u",
+             (uintptr_t)new_key, rthc_count, rthc_limit);
+  rthc_unlock();
+  return MDBX_SUCCESS;
+
+bailout:
+  if (key)
+    thread_key_delete(*key);
+  rthc_unlock();
+  return rc;
+}
+
+__cold void mdbx_rthc_remove(const mdbx_thread_key_t key) {
+  thread_key_delete(key);
+  rthc_lock();
+  mdbx_trace(">> key %zu, rthc_count %u, rthc_limit %u", (size_t)key,
+             rthc_count, rthc_limit);
+
+  for (unsigned i = 0; i < rthc_count; ++i) {
+    if (rthc_table[i].key_valid && key == rthc_table[i].thr_tls_key) {
+      const uint32_t self_pid = mdbx_getpid();
+      mdbx_trace("== [%i], %p ...%p, current-pid %d", i,
+                 __Wpedantic_format_voidptr(rthc_table[i].begin),
+                 __Wpedantic_format_voidptr(rthc_table[i].end), self_pid);
+
+      for (MDBX_reader *rthc = rthc_table[i].begin; rthc < rthc_table[i].end;
+           ++rthc) {
+        if (atomic_load32(&rthc->mr_pid, mo_Relaxed) == self_pid) {
+          atomic_store32(&rthc->mr_pid, 0, mo_AcquireRelease);
+          mdbx_trace("== cleanup %p", __Wpedantic_format_voidptr(rthc));
+        }
+      }
+      if (--rthc_count > 0)
+        rthc_table[i] = rthc_table[rthc_count];
+      else if (rthc_table != rthc_table_static) {
+        mdbx_free(rthc_table);
+        rthc_table = rthc_table_static;
+        rthc_limit = RTHC_INITIAL_LIMIT;
+      }
+      break;
+    }
+  }
+
+  mdbx_trace("<< key %zu, rthc_count %u, rthc_limit %u", (size_t)key,
+             rthc_count, rthc_limit);
+  rthc_unlock();
+}
+
+//------------------------------------------------------------------------------
+
+#define RTHC_ENVLIST_END ((MDBX_env *)((uintptr_t)50459))
+static MDBX_env *inprocess_lcklist_head = RTHC_ENVLIST_END;
+
+static __inline void lcklist_lock(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  EnterCriticalSection(&lcklist_critical_section);
+#else
+  mdbx_ensure(nullptr, pthread_mutex_lock(&lcklist_mutex) == 0);
+#endif
+}
+
+static __inline void lcklist_unlock(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  LeaveCriticalSection(&lcklist_critical_section);
+#else
+  mdbx_ensure(nullptr, pthread_mutex_unlock(&lcklist_mutex) == 0);
+#endif
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static uint64_t rrxmrrxmsx_0(uint64_t v) {
+  /* Pelle Evensen's mixer, https://bit.ly/2HOfynt */
+  v ^= (v << 39 | v >> 25) ^ (v << 14 | v >> 50);
+  v *= UINT64_C(0xA24BAED4963EE407);
+  v ^= (v << 40 | v >> 24) ^ (v << 15 | v >> 49);
+  v *= UINT64_C(0x9FB21C651E98DF25);
+  return v ^ v >> 28;
+}
+
+static int uniq_peek(const mdbx_mmap_t *pending, mdbx_mmap_t *scan) {
+  int rc;
+  uint64_t bait;
+  if (pending->address) {
+    bait = atomic_load64(&pending->lck->mti_bait_uniqueness, mo_AcquireRelease);
+    rc = MDBX_SUCCESS;
+  } else {
+    bait = 0 /* hush MSVC warning */;
+    rc = mdbx_msync(scan, 0, sizeof(MDBX_lockinfo), true);
+    if (rc == MDBX_SUCCESS)
+      rc =
+          mdbx_pread(pending->fd, &bait, sizeof(scan->lck->mti_bait_uniqueness),
+                     offsetof(MDBX_lockinfo, mti_bait_uniqueness));
+  }
+  if (likely(rc == MDBX_SUCCESS) &&
+      bait == atomic_load64(&scan->lck->mti_bait_uniqueness, mo_AcquireRelease))
+    rc = MDBX_RESULT_TRUE;
+
+  mdbx_trace("uniq-peek: %s, bait 0x%016" PRIx64 ",%s rc %d",
+             pending->lck ? "mem" : "file", bait,
+             (rc == MDBX_RESULT_TRUE) ? " found," : (rc ? " FAILED," : ""), rc);
+  return rc;
+}
+
+static int uniq_poke(const mdbx_mmap_t *pending, mdbx_mmap_t *scan,
+                     uint64_t *abra) {
+  if (*abra == 0) {
+    const uintptr_t tid = mdbx_thread_self();
+    uintptr_t uit = 0;
+    memcpy(&uit, &tid, (sizeof(tid) < sizeof(uit)) ? sizeof(tid) : sizeof(uit));
+    *abra =
+        rrxmrrxmsx_0(mdbx_osal_monotime() + UINT64_C(5873865991930747) * uit);
+  }
+  const uint64_t cadabra =
+      rrxmrrxmsx_0(*abra + UINT64_C(7680760450171793) * (unsigned)mdbx_getpid())
+          << 24 |
+      *abra >> 40;
+  atomic_store64(&scan->lck->mti_bait_uniqueness, cadabra,
+                 mo_SequentialConsistency);
+  *abra = *abra * UINT64_C(6364136223846793005) + 1;
+  return uniq_peek(pending, scan);
+}
+
+__cold static int uniq_check(const mdbx_mmap_t *pending, MDBX_env **found) {
+  *found = nullptr;
+  uint64_t salt = 0;
+  for (MDBX_env *scan = inprocess_lcklist_head; scan != RTHC_ENVLIST_END;
+       scan = scan->me_lcklist_next) {
+    int err = atomic_load64(&scan->me_lck_mmap.lck->mti_bait_uniqueness,
+                            mo_AcquireRelease)
+                  ? uniq_peek(pending, &scan->me_lck_mmap)
+                  : uniq_poke(pending, &scan->me_lck_mmap, &salt);
+    if (err == MDBX_ENODATA) {
+      uint64_t length;
+      if (likely(mdbx_filesize(pending->fd, &length) == MDBX_SUCCESS &&
+                 length == 0)) {
+        /* LY: skip checking since LCK-file is empty, i.e. just created. */
+        mdbx_debug("uniq-probe: %s", "unique (new/empty lck)");
+        return MDBX_RESULT_TRUE;
+      }
+    }
+    if (err == MDBX_RESULT_TRUE)
+      err = uniq_poke(pending, &scan->me_lck_mmap, &salt);
+    if (err == MDBX_RESULT_TRUE) {
+      (void)mdbx_msync(&scan->me_lck_mmap, 0, sizeof(MDBX_lockinfo), false);
+      err = uniq_poke(pending, &scan->me_lck_mmap, &salt);
+    }
+    if (err == MDBX_RESULT_TRUE) {
+      err = uniq_poke(pending, &scan->me_lck_mmap, &salt);
+      *found = scan;
+      mdbx_debug("uniq-probe: found %p", __Wpedantic_format_voidptr(*found));
+      return MDBX_RESULT_FALSE;
+    }
+    if (unlikely(err != MDBX_SUCCESS)) {
+      mdbx_debug("uniq-probe: failed rc %d", err);
+      return err;
+    }
+  }
+
+  mdbx_debug("uniq-probe: %s", "unique");
+  return MDBX_RESULT_TRUE;
+}
+
+static int lcklist_detach_locked(MDBX_env *env) {
+  MDBX_env *inprocess_neighbor = nullptr;
+  int rc = MDBX_SUCCESS;
+  if (env->me_lcklist_next != nullptr) {
+    mdbx_ensure(env, env->me_lcklist_next != nullptr);
+    mdbx_ensure(env, inprocess_lcklist_head != RTHC_ENVLIST_END);
+    for (MDBX_env **ptr = &inprocess_lcklist_head; *ptr != RTHC_ENVLIST_END;
+         ptr = &(*ptr)->me_lcklist_next) {
+      if (*ptr == env) {
+        *ptr = env->me_lcklist_next;
+        env->me_lcklist_next = nullptr;
+        break;
+      }
+    }
+    mdbx_ensure(env, env->me_lcklist_next == nullptr);
+  }
+
+  rc = likely(mdbx_getpid() == env->me_pid)
+           ? uniq_check(&env->me_lck_mmap, &inprocess_neighbor)
+           : MDBX_PANIC;
+  if (!inprocess_neighbor && env->me_live_reader)
+    (void)mdbx_rpid_clear(env);
+  if (!MDBX_IS_ERROR(rc))
+    rc = mdbx_lck_destroy(env, inprocess_neighbor);
+  return rc;
+}
+
+/*------------------------------------------------------------------------------
+ * LY: State of the art quicksort-based sorting, with internal stack
+ * and network-sort for small chunks.
+ * Thanks to John M. Gamble for the http://pages.ripco.net/~jgamble/nw.html */
+
+#define SORT_CMP_SWAP(TYPE, CMP, a, b)                                         \
+  do {                                                                         \
+    const TYPE swap_tmp = (a);                                                 \
+    const bool swap_cmp = CMP(swap_tmp, b);                                    \
+    (a) = swap_cmp ? swap_tmp : b;                                             \
+    (b) = swap_cmp ? b : swap_tmp;                                             \
+  } while (0)
+
+//  3 comparators, 3 parallel operations
+//  o-----^--^--o
+//        |  |
+//  o--^--|--v--o
+//     |  |
+//  o--v--v-----o
+//
+//  [[1,2]]
+//  [[0,2]]
+//  [[0,1]]
+#define SORT_NETWORK_3(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+  } while (0)
+
+//  5 comparators, 3 parallel operations
+//  o--^--^--------o
+//     |  |
+//  o--v--|--^--^--o
+//        |  |  |
+//  o--^--v--|--v--o
+//     |     |
+//  o--v-----v-----o
+//
+//  [[0,1],[2,3]]
+//  [[0,2],[1,3]]
+//  [[1,2]]
+#define SORT_NETWORK_4(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+  } while (0)
+
+//  9 comparators, 5 parallel operations
+//  o--^--^-----^-----------o
+//     |  |     |
+//  o--|--|--^--v-----^--^--o
+//     |  |  |        |  |
+//  o--|--v--|--^--^--|--v--o
+//     |     |  |  |  |
+//  o--|-----v--|--v--|--^--o
+//     |        |     |  |
+//  o--v--------v-----v--v--o
+//
+//  [[0,4],[1,3]]
+//  [[0,2]]
+//  [[2,4],[0,1]]
+//  [[2,3],[1,4]]
+//  [[1,2],[3,4]]
+#define SORT_NETWORK_5(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+  } while (0)
+
+//  12 comparators, 6 parallel operations
+//  o-----^--^--^-----------------o
+//        |  |  |
+//  o--^--|--v--|--^--------^-----o
+//     |  |     |  |        |
+//  o--v--v-----|--|--^--^--|--^--o
+//              |  |  |  |  |  |
+//  o-----^--^--v--|--|--|--v--v--o
+//        |  |     |  |  |
+//  o--^--|--v-----v--|--v--------o
+//     |  |           |
+//  o--v--v-----------v-----------o
+//
+//  [[1,2],[4,5]]
+//  [[0,2],[3,5]]
+//  [[0,1],[3,4],[2,5]]
+//  [[0,3],[1,4]]
+//  [[2,4],[1,3]]
+//  [[2,3]]
+#define SORT_NETWORK_6(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+  } while (0)
+
+//  16 comparators, 6 parallel operations
+//  o--^--------^-----^-----------------o
+//     |        |     |
+//  o--|--^-----|--^--v--------^--^-----o
+//     |  |     |  |           |  |
+//  o--|--|--^--v--|--^-----^--|--v-----o
+//     |  |  |     |  |     |  |
+//  o--|--|--|-----v--|--^--v--|--^--^--o
+//     |  |  |        |  |     |  |  |
+//  o--v--|--|--^-----v--|--^--v--|--v--o
+//        |  |  |        |  |     |
+//  o-----v--|--|--------v--v-----|--^--o
+//           |  |                 |  |
+//  o--------v--v-----------------v--v--o
+//
+//  [[0,4],[1,5],[2,6]]
+//  [[0,2],[1,3],[4,6]]
+//  [[2,4],[3,5],[0,1]]
+//  [[2,3],[4,5]]
+//  [[1,4],[3,6]]
+//  [[1,2],[3,4],[5,6]]
+#define SORT_NETWORK_7(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+  } while (0)
+
+//  19 comparators, 6 parallel operations
+//  o--^--------^-----^-----------------o
+//     |        |     |
+//  o--|--^-----|--^--v--------^--^-----o
+//     |  |     |  |           |  |
+//  o--|--|--^--v--|--^-----^--|--v-----o
+//     |  |  |     |  |     |  |
+//  o--|--|--|--^--v--|--^--v--|--^--^--o
+//     |  |  |  |     |  |     |  |  |
+//  o--v--|--|--|--^--v--|--^--v--|--v--o
+//        |  |  |  |     |  |     |
+//  o-----v--|--|--|--^--v--v-----|--^--o
+//           |  |  |  |           |  |
+//  o--------v--|--v--|--^--------v--v--o
+//              |     |  |
+//  o-----------v-----v--v--------------o
+//
+//  [[0,4],[1,5],[2,6],[3,7]]
+//  [[0,2],[1,3],[4,6],[5,7]]
+//  [[2,4],[3,5],[0,1],[6,7]]
+//  [[2,3],[4,5]]
+//  [[1,4],[3,6]]
+//  [[1,2],[3,4],[5,6]]
+#define SORT_NETWORK_8(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+  } while (0)
+
+//  25 comparators, 9 parallel operations
+//  o--^-----^--^-----^-----------------------------------o
+//     |     |  |     |
+//  o--v--^--v--|-----|--^-----^-----------^--------------o
+//        |     |     |  |     |           |
+//  o-----v-----|-----|--|-----|--^-----^--|--^-----^--^--o
+//              |     |  |     |  |     |  |  |     |  |
+//  o--^-----^--v--^--v--|-----|--|-----|--v--|-----|--v--o
+//     |     |     |     |     |  |     |     |     |
+//  o--v--^--v-----|-----v--^--v--|-----|-----|--^--v-----o
+//        |        |        |     |     |     |  |
+//  o-----v--------|--------|-----v--^--v--^--|--|--^-----o
+//                 |        |        |     |  |  |  |
+//  o--^-----^-----v--------|--------|-----|--v--v--v-----o
+//     |     |              |        |     |
+//  o--v--^--v--------------v--------|-----v--------------o
+//        |                          |
+//  o-----v--------------------------v--------------------o
+//
+//  [[0,1],[3,4],[6,7]]
+//  [[1,2],[4,5],[7,8]]
+//  [[0,1],[3,4],[6,7],[2,5]]
+//  [[0,3],[1,4],[5,8]]
+//  [[3,6],[4,7],[2,5]]
+//  [[0,3],[1,4],[5,7],[2,6]]
+//  [[1,3],[4,6]]
+//  [[2,4],[5,6]]
+//  [[2,3]]
+#define SORT_NETWORK_9(TYPE, CMP, begin)                                       \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+  } while (0)
+
+//  29 comparators, 9 parallel operations
+//  o--------------^-----^--^--^-----------------------o
+//                 |     |  |  |
+//  o-----------^--|--^--|--|--v--^--------^-----------o
+//              |  |  |  |  |     |        |
+//  o--------^--|--|--|--|--v--^--v-----^--|--^--------o
+//           |  |  |  |  |     |        |  |  |
+//  o-----^--|--|--|--|--v--^--|-----^--|--v--v--^-----o
+//        |  |  |  |  |     |  |     |  |        |
+//  o--^--|--|--|--|--v-----|--v--^--|--|--^-----v--^--o
+//     |  |  |  |  |        |     |  |  |  |        |
+//  o--|--|--|--|--v--^-----|--^--|--v--v--|-----^--v--o
+//     |  |  |  |     |     |  |  |        |     |
+//  o--|--|--|--v--^--|-----v--|--v--^-----|--^--v-----o
+//     |  |  |     |  |        |     |     |  |
+//  o--|--|--v-----|--|--^-----v--^--|-----v--v--------o
+//     |  |        |  |  |        |  |
+//  o--|--v--------|--v--|--^-----v--v-----------------o
+//     |           |     |  |
+//  o--v-----------v-----v--v--------------------------o
+//
+//  [[4,9],[3,8],[2,7],[1,6],[0,5]]
+//  [[1,4],[6,9],[0,3],[5,8]]
+//  [[0,2],[3,6],[7,9]]
+//  [[0,1],[2,4],[5,7],[8,9]]
+//  [[1,2],[4,6],[7,8],[3,5]]
+//  [[2,5],[6,8],[1,3],[4,7]]
+//  [[2,3],[6,7]]
+//  [[3,4],[5,6]]
+//  [[4,5]]
+#define SORT_NETWORK_10(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+  } while (0)
+
+//  35 comparators, 9 parallel operations
+//  o--^-----^-----------------^--------^--------------------o
+//     |     |                 |        |
+//  o--v--^--|--^--^--------^--|--------|--^-----------------o
+//        |  |  |  |        |  |        |  |
+//  o--^--|--v--v--|-----^--|--|--------|--|-----^--^--------o
+//     |  |        |     |  |  |        |  |     |  |
+//  o--v--v--------|-----|--|--|--^-----|--|--^--v--|--^--^--o
+//                 |     |  |  |  |     |  |  |     |  |  |
+//  o--^-----^-----|-----|--|--v--|--^--v--v--|-----v--|--v--o
+//     |     |     |     |  |     |  |        |        |
+//  o--v--^--|--^--v--^--|--v-----|--|--------|--------v--^--o
+//        |  |  |     |  |        |  |        |           |
+//  o--^--|--v--v--^--|--v--^-----|--|--------|--------^--v--o
+//     |  |        |  |     |     |  |        |        |
+//  o--v--v--------|--|-----|-----v--|--^-----|-----^--|--^--o
+//                 |  |     |        |  |     |     |  |  |
+//  o--^--^--------|--|-----|--------v--|-----v--^--|--v--v--o
+//     |  |        |  |     |           |        |  |
+//  o--v--|--^-----|--v-----|-----------|--------v--v--------o
+//        |  |     |        |           |
+//  o-----v--v-----v--------v-----------v--------------------o
+//
+//  [[0,1],[2,3],[4,5],[6,7],[8,9]]
+//  [[1,3],[5,7],[0,2],[4,6],[8,10]]
+//  [[1,2],[5,6],[9,10],[0,4],[3,7]]
+//  [[1,5],[6,10],[4,8]]
+//  [[5,9],[2,6],[0,4],[3,8]]
+//  [[1,5],[6,10],[2,3],[8,9]]
+//  [[1,4],[7,10],[3,5],[6,8]]
+//  [[2,4],[7,9],[5,6]]
+//  [[3,4],[7,8]]
+#define SORT_NETWORK_11(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+  } while (0)
+
+//  39 comparators, parallel operations
+//  o--^-----^-----------------^--------^--------------------o
+//     |     |                 |        |
+//  o--v--^--|--^--^--------^--|--------|--^-----------------o
+//        |  |  |  |        |  |        |  |
+//  o--^--|--v--v--|-----^--|--|--------|--|-----^--^--------o
+//     |  |        |     |  |  |        |  |     |  |
+//  o--v--v--------|-----|--|--|--^-----|--|--^--v--|--^--^--o
+//                 |     |  |  |  |     |  |  |     |  |  |
+//  o--^-----^-----|-----|--|--v--|--^--v--v--|-----v--|--v--o
+//     |     |     |     |  |     |  |        |        |
+//  o--v--^--|--^--v--^--|--v-----|--|--------|--------v--^--o
+//        |  |  |     |  |        |  |        |           |
+//  o--^--|--v--v--^--|--v--^-----|--|--------|--------^--v--o
+//     |  |        |  |     |     |  |        |        |
+//  o--v--v--------|--|-----|--^--v--|--^--^--|-----^--|--^--o
+//                 |  |     |  |     |  |  |  |     |  |  |
+//  o--^-----^-----|--|-----|--|-----v--|--|--v--^--|--v--v--o
+//     |     |     |  |     |  |        |  |     |  |
+//  o--v--^--|--^--|--v-----|--|--------|--|-----v--v--------o
+//        |  |  |  |        |  |        |  |
+//  o--^--|--v--v--v--------v--|--------|--v-----------------o
+//     |  |                    |        |
+//  o--v--v--------------------v--------v--------------------o
+//
+//  [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11]]
+//  [[1,3],[5,7],[9,11],[0,2],[4,6],[8,10]]
+//  [[1,2],[5,6],[9,10],[0,4],[7,11]]
+//  [[1,5],[6,10],[3,7],[4,8]]
+//  [[5,9],[2,6],[0,4],[7,11],[3,8]]
+//  [[1,5],[6,10],[2,3],[8,9]]
+//  [[1,4],[7,10],[3,5],[6,8]]
+//  [[2,4],[7,9],[5,6]]
+//  [[3,4],[7,8]]
+#define SORT_NETWORK_12(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+  } while (0)
+
+//  45 comparators, 10 parallel operations
+//  o--------^--^-----^-----------------------------^-----------------o
+//           |  |     |                             |
+//  o--^-----|--v-----|-----^--------------^-----^--|-----^-----------o
+//     |     |        |     |              |     |  |     |
+//  o--|-----|--^--^--v-----|--------------|--^--|--|--^--v--^--------o
+//     |     |  |  |        |              |  |  |  |  |     |
+//  o--|--^--|--|--v-----^--|--------^-----|--|--v--|--|--^--v-----^--o
+//     |  |  |  |        |  |        |     |  |     |  |  |        |
+//  o--|--v--|--|--^-----|--v-----^--v-----|--|--^--|--|--|--^--^--v--o
+//     |     |  |  |     |        |        |  |  |  |  |  |  |  |
+//  o--|--^--|--|--|--^--|--------|-----^--|--|--|--v--v--v--|--v--^--o
+//     |  |  |  |  |  |  |        |     |  |  |  |           |     |
+//  o--|--|--|--v--v--|--|--^-----|--^--v--|--v--|--^--------v--^--v--o
+//     |  |  |        |  |  |     |  |     |     |  |           |
+//  o--v--|--|-----^--|--v--|--^--|--|-----v-----v--|--^--------v-----o
+//        |  |     |  |     |  |  |  |              |  |
+//  o-----v--|--^--|--|-----|--v--|--|--^-----^-----v--v--^-----------o
+//           |  |  |  |     |     |  |  |     |           |
+//  o--^-----|--|--|--v-----|-----v--|--v--^--|--^--------v-----------o
+//     |     |  |  |        |        |     |  |  |
+//  o--|-----|--|--|--^-----|--------v--^--|--v--v--------------------o
+//     |     |  |  |  |     |           |  |
+//  o--v-----|--v--|--v-----|--^--------v--v--------------------------o
+//           |     |        |  |
+//  o--------v-----v--------v--v--------------------------------------o
+//
+//  [[1,7],[9,11],[3,4],[5,8],[0,12],[2,6]]
+//  [[0,1],[2,3],[4,6],[8,11],[7,12],[5,9]]
+//  [[0,2],[3,7],[10,11],[1,4],[6,12]]
+//  [[7,8],[11,12],[4,9],[6,10]]
+//  [[3,4],[5,6],[8,9],[10,11],[1,7]]
+//  [[2,6],[9,11],[1,3],[4,7],[8,10],[0,5]]
+//  [[2,5],[6,8],[9,10]]
+//  [[1,2],[3,5],[7,8],[4,6]]
+//  [[2,3],[4,5],[6,7],[8,9]]
+//  [[3,4],[5,6]]
+#define SORT_NETWORK_13(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+  } while (0)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+//  51 comparators, 10 parallel operations
+//  o--^--^-----^-----------^-----------------------------------------------------------o
+//     |  |     |           |
+//  o--v--|--^--|--^--------|--^-----^-----------------------^--------------------------o
+//        |  |  |  |        |  |     |                       |
+//  o--^--v--|--|--|--^-----|--|--^--v-----------------------|--^--^--------------------o
+//     |     |  |  |  |     |  |  |                          |  |  |
+//  o--v-----v--|--|--|--^--|--|--|--^--------------^--------|--|--|--^--^--^-----------o
+//              |  |  |  |  |  |  |  |              |        |  |  |  |  |  |
+//  o--^--^-----v--|--|--|--|--|--|--|--^-----------|-----^--v--|--v--|--|--v-----------o
+//     |  |        |  |  |  |  |  |  |  |           |     |     |     |  |
+//  o--v--|--^-----v--|--|--|--|--|--|--|--^--^-----|-----|-----|--^--|--v-----^--------o
+//        |  |        |  |  |  |  |  |  |  |  |     |     |     |  |  |        |
+//  o--^--v--|--------v--|--|--|--|--|--|--|--|--^--|-----|-----|--v--|-----^--v-----^--o
+//     |     |           |  |  |  |  |  |  |  |  |  |     |     |     |     |        |
+//  o--v-----v-----------v--|--|--|--|--|--|--|--|--|--^--|--^--|-----|--^--|--^--^--v--o
+//                          |  |  |  |  |  |  |  |  |  |  |  |  |     |  |  |  |  |
+//  o--^--^-----^-----------v--|--|--|--|--|--|--|--|--|--v--|--v-----v--|--v--|--v--^--o
+//     |  |     |              |  |  |  |  |  |  |  |  |     |           |     |     |
+//  o--v--|--^--|--^-----------v--|--|--|--|--|--v--|--|-----|--^--------|-----v--^--v--o
+//        |  |  |  |              |  |  |  |  |     |  |     |  |        |        |
+//  o--^--v--|--|--|--------------v--|--|--|--v-----|--|-----|--v--------|--^-----v-----o
+//     |     |  |  |                 |  |  |        |  |     |           |  |
+//  o--v-----v--|--|-----------------v--|--|--------|--v-----|--^--------|--|--^--------o
+//              |  |                    |  |        |        |  |        |  |  |
+//  o--^--------v--|--------------------v--|--------v--------|--|--------v--v--v--------o
+//     |           |                       |                 |  |
+//  o--v-----------v-----------------------v-----------------v--v-----------------------o
+//
+//  [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11],[12,13]]
+//  [[0,2],[4,6],[8,10],[1,3],[5,7],[9,11]]
+//  [[0,4],[8,12],[1,5],[9,13],[2,6],[3,7]]
+//  [[0,8],[1,9],[2,10],[3,11],[4,12],[5,13]]
+//  [[5,10],[6,9],[3,12],[7,11],[1,2],[4,8]]
+//  [[1,4],[7,13],[2,8],[5,6],[9,10]]
+//  [[2,4],[11,13],[3,8],[7,12]]
+//  [[6,8],[10,12],[3,5],[7,9]]
+//  [[3,4],[5,6],[7,8],[9,10],[11,12]]
+//  [[6,7],[8,9]]
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#define SORT_NETWORK_14(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[12], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+  } while (0)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+//  56 comparators, 10 parallel operations
+//  o--^--^-----^-----------^--------------------------------------------------------------o
+//     |  |     |           |
+//  o--v--|--^--|--^--------|--^-----^--------------------------^--------------------------o
+//        |  |  |  |        |  |     |                          |
+//  o--^--v--|--|--|--^-----|--|--^--v--------------------------|--^--^--------------------o
+//     |     |  |  |  |     |  |  |                             |  |  |
+//  o--v-----v--|--|--|--^--|--|--|--^-----------------^--------|--|--|--^--^--^-----------o
+//              |  |  |  |  |  |  |  |                 |        |  |  |  |  |  |
+//  o--^--^-----v--|--|--|--|--|--|--|--^--------------|-----^--v--|--v--|--|--v-----------o
+//     |  |        |  |  |  |  |  |  |  |              |     |     |     |  |
+//  o--v--|--^-----v--|--|--|--|--|--|--|--^-----^-----|-----|-----|--^--|--v-----^--------o
+//        |  |        |  |  |  |  |  |  |  |     |     |     |     |  |  |        |
+//  o--^--v--|--------v--|--|--|--|--|--|--|--^--|--^--|-----|-----|--v--|-----^--v-----^--o
+//     |     |           |  |  |  |  |  |  |  |  |  |  |     |     |     |     |        |
+//  o--v-----v-----------v--|--|--|--|--|--|--|--|--|--|--^--|--^--|-----|--^--|--^--^--v--o
+//                          |  |  |  |  |  |  |  |  |  |  |  |  |  |     |  |  |  |  |
+//  o--^--^-----^-----------v--|--|--|--|--|--|--|--|--|--|--v--|--v-----v--|--v--|--v--^--o
+//     |  |     |              |  |  |  |  |  |  |  |  |  |     |           |     |     |
+//  o--v--|--^--|--^-----------v--|--|--|--|--|--|--v--|--|-----|--^--------|-----v--^--v--o
+//        |  |  |  |              |  |  |  |  |  |     |  |     |  |        |        |
+//  o--^--v--|--|--|--^-----------v--|--|--|--|--v-----|--|-----|--v--------|--^-----v-----o
+//     |     |  |  |  |              |  |  |  |        |  |     |           |  |
+//  o--v-----v--|--|--|--------------v--|--|--|--------|--v-----|--^--^-----|--|--^--------o
+//              |  |  |                 |  |  |        |        |  |  |     |  |  |
+//  o--^--^-----v--|--|-----------------v--|--|--------v--------|--|--|-----v--v--v--------o
+//     |  |        |  |                    |  |                 |  |  |
+//  o--v--|--------v--|--------------------v--|--^--------------v--|--v--------------------o
+//        |           |                       |  |                 |
+//  o-----v-----------v-----------------------v--v-----------------v-----------------------o
+//
+//  [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11],[12,13]]
+//  [[0,2],[4,6],[8,10],[12,14],[1,3],[5,7],[9,11]]
+//  [[0,4],[8,12],[1,5],[9,13],[2,6],[10,14],[3,7]]
+//  [[0,8],[1,9],[2,10],[3,11],[4,12],[5,13],[6,14]]
+//  [[5,10],[6,9],[3,12],[13,14],[7,11],[1,2],[4,8]]
+//  [[1,4],[7,13],[2,8],[11,14],[5,6],[9,10]]
+//  [[2,4],[11,13],[3,8],[7,12]]
+//  [[6,8],[10,12],[3,5],[7,9]]
+//  [[3,4],[5,6],[7,8],[9,10],[11,12]]
+//  [[6,7],[8,9]]
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#define SORT_NETWORK_15(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[12], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[12], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[14]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[13], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+  } while (0)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+//  60 comparators, 10 parallel operations
+//  o--^--^-----^-----------^-----------------------------------------------------------------o
+//     |  |     |           |
+//  o--v--|--^--|--^--------|--^-----^-----------------------------^--------------------------o
+//        |  |  |  |        |  |     |                             |
+//  o--^--v--|--|--|--^-----|--|--^--v-----------------------------|--^--^--------------------o
+//     |     |  |  |  |     |  |  |                                |  |  |
+//  o--v-----v--|--|--|--^--|--|--|--^--------------------^--------|--|--|--^--^--^-----------o
+//              |  |  |  |  |  |  |  |                    |        |  |  |  |  |  |
+//  o--^--^-----v--|--|--|--|--|--|--|--^-----------------|-----^--v--|--v--|--|--v-----------o
+//     |  |        |  |  |  |  |  |  |  |                 |     |     |     |  |
+//  o--v--|--^-----v--|--|--|--|--|--|--|--^--------^-----|-----|-----|--^--|--v-----^--------o
+//        |  |        |  |  |  |  |  |  |  |        |     |     |     |  |  |        |
+//  o--^--v--|--------v--|--|--|--|--|--|--|--^-----|--^--|-----|-----|--v--|-----^--v-----^--o
+//     |     |           |  |  |  |  |  |  |  |     |  |  |     |     |     |     |        |
+//  o--v-----v-----------v--|--|--|--|--|--|--|--^--|--|--|--^--|--^--|-----|--^--|--^--^--v--o
+//                          |  |  |  |  |  |  |  |  |  |  |  |  |  |  |     |  |  |  |  |
+//  o--^--^-----^-----------v--|--|--|--|--|--|--|--|--|--|--|--v--|--v-----v--|--v--|--v--^--o
+//     |  |     |              |  |  |  |  |  |  |  |  |  |  |     |           |     |     |
+//  o--v--|--^--|--^-----------v--|--|--|--|--|--|--|--v--|--|-----|--^--------|-----v--^--v--o
+//        |  |  |  |              |  |  |  |  |  |  |     |  |     |  |        |        |
+//  o--^--v--|--|--|--^-----------v--|--|--|--|--|--v-----|--|-----|--v--------|--^-----v-----o
+//     |     |  |  |  |              |  |  |  |  |        |  |     |           |  |
+//  o--v-----v--|--|--|--^-----------v--|--|--|--|--------|--v-----|--^--^-----|--|--^--------o
+//              |  |  |  |              |  |  |  |        |        |  |  |     |  |  |
+//  o--^--^-----v--|--|--|--------------v--|--|--|--------v--------|--|--|-----v--v--v--------o
+//     |  |        |  |  |                 |  |  |                 |  |  |
+//  o--v--|--^-----v--|--|-----------------v--|--|--^--------------v--|--v--------------------o
+//        |  |        |  |                    |  |  |                 |
+//  o--^--v--|--------v--|--------------------v--|--v-----------------v-----------------------o
+//     |     |           |                       |
+//  o--v-----v-----------v-----------------------v--------------------------------------------o
+//
+//  [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11],[12,13],[14,15]]
+//  [[0,2],[4,6],[8,10],[12,14],[1,3],[5,7],[9,11],[13,15]]
+//  [[0,4],[8,12],[1,5],[9,13],[2,6],[10,14],[3,7],[11,15]]
+//  [[0,8],[1,9],[2,10],[3,11],[4,12],[5,13],[6,14],[7,15]]
+//  [[5,10],[6,9],[3,12],[13,14],[7,11],[1,2],[4,8]]
+//  [[1,4],[7,13],[2,8],[11,14],[5,6],[9,10]]
+//  [[2,4],[11,13],[3,8],[7,12]]
+//  [[6,8],[10,12],[3,5],[7,9]]
+//  [[3,4],[5,6],[7,8],[9,10],[11,12]]
+//  [[6,7],[8,9]]
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#define SORT_NETWORK_16(TYPE, CMP, begin)                                      \
+  do {                                                                         \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[11]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[12], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[14], begin[15]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[12], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[3]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[13], begin[15]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[15]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[14]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[15]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[13], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[11]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[2]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[4], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[1], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[13]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[14]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[2], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[13]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[12]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[10], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[5]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[9]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[3], begin[4]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[5], begin[6]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[7], begin[8]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[9], begin[10]);                             \
+    SORT_CMP_SWAP(TYPE, CMP, begin[11], begin[12]);                            \
+    SORT_CMP_SWAP(TYPE, CMP, begin[6], begin[7]);                              \
+    SORT_CMP_SWAP(TYPE, CMP, begin[8], begin[9]);                              \
+  } while (0)
+
+#define SORT_INNER(TYPE, CMP, begin, end, len)                                 \
+  switch (len) {                                                               \
+  default:                                                                     \
+    __unreachable();                                                           \
+  case 0:                                                                      \
+  case 1:                                                                      \
+    break;                                                                     \
+  case 2:                                                                      \
+    SORT_CMP_SWAP(TYPE, CMP, begin[0], begin[1]);                              \
+    break;                                                                     \
+  case 3:                                                                      \
+    SORT_NETWORK_3(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 4:                                                                      \
+    SORT_NETWORK_4(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 5:                                                                      \
+    SORT_NETWORK_5(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 6:                                                                      \
+    SORT_NETWORK_6(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 7:                                                                      \
+    SORT_NETWORK_7(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 8:                                                                      \
+    SORT_NETWORK_8(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 9:                                                                      \
+    SORT_NETWORK_9(TYPE, CMP, begin);                                          \
+    break;                                                                     \
+  case 10:                                                                     \
+    SORT_NETWORK_10(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 11:                                                                     \
+    SORT_NETWORK_11(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 12:                                                                     \
+    SORT_NETWORK_12(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 13:                                                                     \
+    SORT_NETWORK_13(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 14:                                                                     \
+    SORT_NETWORK_14(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 15:                                                                     \
+    SORT_NETWORK_15(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  case 16:                                                                     \
+    SORT_NETWORK_16(TYPE, CMP, begin);                                         \
+    break;                                                                     \
+  }
+
+#define SORT_SWAP(TYPE, a, b)                                                  \
+  do {                                                                         \
+    const TYPE swap_tmp = (a);                                                 \
+    (a) = (b);                                                                 \
+    (b) = swap_tmp;                                                            \
+  } while (0)
+
+#define SORT_PUSH(low, high)                                                   \
+  do {                                                                         \
+    top->lo = (low);                                                           \
+    top->hi = (high);                                                          \
+    ++top;                                                                     \
+  } while (0)
+
+#define SORT_POP(low, high)                                                    \
+  do {                                                                         \
+    --top;                                                                     \
+    low = top->lo;                                                             \
+    high = top->hi;                                                            \
+  } while (0)
+
+#define SORT_IMPL(NAME, EXPECT_LOW_CARDINALITY_OR_PRESORTED, TYPE, CMP)        \
+                                                                               \
+  static __inline bool NAME##_is_sorted(const TYPE *first, const TYPE *last) { \
+    while (++first <= last)                                                    \
+      if (CMP(first[0], first[-1]))                                            \
+        return false;                                                          \
+    return true;                                                               \
+  }                                                                            \
+                                                                               \
+  typedef struct {                                                             \
+    TYPE *lo, *hi;                                                             \
+  } NAME##_stack;                                                              \
+                                                                               \
+  static __hot void NAME(TYPE *const begin, TYPE *const end) {                 \
+    NAME##_stack stack[sizeof(unsigned) * CHAR_BIT], *top = stack;             \
+                                                                               \
+    TYPE *hi = end - 1;                                                        \
+    TYPE *lo = begin;                                                          \
+    while (true) {                                                             \
+      const ptrdiff_t len = hi - lo;                                           \
+      if (len < 16) {                                                          \
+        SORT_INNER(TYPE, CMP, lo, hi + 1, len + 1);                            \
+        if (unlikely(top == stack))                                            \
+          break;                                                               \
+        SORT_POP(lo, hi);                                                      \
+        continue;                                                              \
+      }                                                                        \
+                                                                               \
+      TYPE *mid = lo + (len >> 1);                                             \
+      SORT_CMP_SWAP(TYPE, CMP, *lo, *mid);                                     \
+      SORT_CMP_SWAP(TYPE, CMP, *mid, *hi);                                     \
+      SORT_CMP_SWAP(TYPE, CMP, *lo, *mid);                                     \
+                                                                               \
+      TYPE *right = hi - 1;                                                    \
+      TYPE *left = lo + 1;                                                     \
+      while (1) {                                                              \
+        while (CMP(*left, *mid))                                               \
+          ++left;                                                              \
+        while (CMP(*mid, *right))                                              \
+          --right;                                                             \
+        if (unlikely(left > right)) {                                          \
+          if (EXPECT_LOW_CARDINALITY_OR_PRESORTED) {                           \
+            if (NAME##_is_sorted(lo, right))                                   \
+              lo = right + 1;                                                  \
+            if (NAME##_is_sorted(left, hi))                                    \
+              hi = left;                                                       \
+          }                                                                    \
+          break;                                                               \
+        }                                                                      \
+        SORT_SWAP(TYPE, *left, *right);                                        \
+        mid = (mid == left) ? right : (mid == right) ? left : mid;             \
+        ++left;                                                                \
+        --right;                                                               \
+      }                                                                        \
+                                                                               \
+      if (right - lo > hi - left) {                                            \
+        SORT_PUSH(lo, right);                                                  \
+        lo = left;                                                             \
+      } else {                                                                 \
+        SORT_PUSH(left, hi);                                                   \
+        hi = right;                                                            \
+      }                                                                        \
+    }                                                                          \
+                                                                               \
+    if (mdbx_audit_enabled()) {                                                \
+      for (TYPE *scan = begin + 1; scan < end; ++scan)                         \
+        assert(CMP(scan[-1], scan[0]));                                        \
+    }                                                                          \
+  }
+
+/*------------------------------------------------------------------------------
+ * LY: Binary search */
+
+#define SEARCH_IMPL(NAME, TYPE_LIST, TYPE_ARG, CMP)                            \
+  static __always_inline const TYPE_LIST *NAME(                                \
+      const TYPE_LIST *first, unsigned length, const TYPE_ARG item) {          \
+    const TYPE_LIST *const begin = first, *const end = begin + length;         \
+                                                                               \
+    while (length > 3) {                                                       \
+      const unsigned whole = length;                                           \
+      length >>= 1;                                                            \
+      const TYPE_LIST *const middle = first + length;                          \
+      if (CMP(*middle, item)) {                                                \
+        first = middle + 1;                                                    \
+        length = whole - length - 1;                                           \
+      }                                                                        \
+    }                                                                          \
+                                                                               \
+    switch (length) {                                                          \
+    case 3:                                                                    \
+      if (!CMP(*first, item))                                                  \
+        break;                                                                 \
+      ++first;                                                                 \
+      __fallthrough /* fall through */;                                        \
+    case 2:                                                                    \
+      if (!CMP(*first, item))                                                  \
+        break;                                                                 \
+      ++first;                                                                 \
+      __fallthrough /* fall through */;                                        \
+    case 1:                                                                    \
+      if (!CMP(*first, item))                                                  \
+        break;                                                                 \
+      ++first;                                                                 \
+      __fallthrough /* fall through */;                                        \
+    case 0:                                                                    \
+      break;                                                                   \
+    default:                                                                   \
+      __unreachable();                                                         \
+    }                                                                          \
+                                                                               \
+    if (mdbx_audit_enabled()) {                                                \
+      for (const TYPE_LIST *scan = begin; scan < first; ++scan)                \
+        assert(CMP(*scan, item));                                              \
+      for (const TYPE_LIST *scan = first; scan < end; ++scan)                  \
+        assert(!CMP(*scan, item));                                             \
+      (void)begin, (void)end;                                                  \
+    }                                                                          \
+                                                                               \
+    return first;                                                              \
+  }
+
+/*----------------------------------------------------------------------------*/
+
+static __always_inline size_t pnl2bytes(const size_t size) {
+  assert(size > 0 && size <= MDBX_PGL_LIMIT);
+  size_t bytes =
+      ceil_powerof2(MDBX_ASSUME_MALLOC_OVERHEAD + sizeof(pgno_t) * (size + 2),
+                    MDBX_PNL_GRANULATE * sizeof(pgno_t)) -
+      MDBX_ASSUME_MALLOC_OVERHEAD;
+  return bytes;
+}
+
+static __always_inline pgno_t bytes2pnl(const size_t bytes) {
+  size_t size = bytes / sizeof(pgno_t);
+  assert(size > 2 && size <= MDBX_PGL_LIMIT);
+  return (pgno_t)size - 2;
+}
+
+static MDBX_PNL mdbx_pnl_alloc(size_t size) {
+  size_t bytes = pnl2bytes(size);
+  MDBX_PNL pl = mdbx_malloc(bytes);
+  if (likely(pl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+    bytes = malloc_usable_size(pl);
+#endif /* malloc_usable_size */
+    pl[0] = bytes2pnl(bytes);
+    assert(pl[0] >= size);
+    pl[1] = 0;
+    pl += 1;
+  }
+  return pl;
+}
+
+static void mdbx_pnl_free(MDBX_PNL pl) {
+  if (likely(pl))
+    mdbx_free(pl - 1);
+}
+
+/* Shrink the PNL to the default size if it has grown larger */
+static void mdbx_pnl_shrink(MDBX_PNL *ppl) {
+  assert(bytes2pnl(pnl2bytes(MDBX_PNL_INITIAL)) == MDBX_PNL_INITIAL);
+  assert(MDBX_PNL_SIZE(*ppl) <= MDBX_PGL_LIMIT &&
+         MDBX_PNL_ALLOCLEN(*ppl) >= MDBX_PNL_SIZE(*ppl));
+  MDBX_PNL_SIZE(*ppl) = 0;
+  if (unlikely(MDBX_PNL_ALLOCLEN(*ppl) >
+               MDBX_PNL_INITIAL * 2 - MDBX_CACHELINE_SIZE / sizeof(pgno_t))) {
+    size_t bytes = pnl2bytes(MDBX_PNL_INITIAL);
+    MDBX_PNL pl = mdbx_realloc(*ppl - 1, bytes);
+    if (likely(pl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+      bytes = malloc_usable_size(pl);
+#endif /* malloc_usable_size */
+      *pl = bytes2pnl(bytes);
+      *ppl = pl + 1;
+    }
+  }
+}
+
+/* Grow the PNL to the size growed to at least given size */
+static int mdbx_pnl_reserve(MDBX_PNL *ppl, const size_t wanna) {
+  const size_t allocated = MDBX_PNL_ALLOCLEN(*ppl);
+  assert(MDBX_PNL_SIZE(*ppl) <= MDBX_PGL_LIMIT &&
+         MDBX_PNL_ALLOCLEN(*ppl) >= MDBX_PNL_SIZE(*ppl));
+  if (likely(allocated >= wanna))
+    return MDBX_SUCCESS;
+
+  if (unlikely(wanna > /* paranoia */ MDBX_PGL_LIMIT)) {
+    mdbx_error("PNL too long (%zu > %zu)", wanna, (size_t)MDBX_PGL_LIMIT);
+    return MDBX_TXN_FULL;
+  }
+
+  const size_t size = (wanna + wanna - allocated < MDBX_PGL_LIMIT)
+                          ? wanna + wanna - allocated
+                          : MDBX_PGL_LIMIT;
+  size_t bytes = pnl2bytes(size);
+  MDBX_PNL pl = mdbx_realloc(*ppl - 1, bytes);
+  if (likely(pl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+    bytes = malloc_usable_size(pl);
+#endif /* malloc_usable_size */
+    *pl = bytes2pnl(bytes);
+    assert(*pl >= wanna);
+    *ppl = pl + 1;
+    return MDBX_SUCCESS;
+  }
+  return MDBX_ENOMEM;
+}
+
+/* Make room for num additional elements in an PNL */
+static __always_inline int __must_check_result mdbx_pnl_need(MDBX_PNL *ppl,
+                                                             size_t num) {
+  assert(MDBX_PNL_SIZE(*ppl) <= MDBX_PGL_LIMIT &&
+         MDBX_PNL_ALLOCLEN(*ppl) >= MDBX_PNL_SIZE(*ppl));
+  assert(num <= MDBX_PGL_LIMIT);
+  const size_t wanna = MDBX_PNL_SIZE(*ppl) + num;
+  return likely(MDBX_PNL_ALLOCLEN(*ppl) >= wanna)
+             ? MDBX_SUCCESS
+             : mdbx_pnl_reserve(ppl, wanna);
+}
+
+static __always_inline void mdbx_pnl_xappend(MDBX_PNL pl, pgno_t pgno) {
+  assert(MDBX_PNL_SIZE(pl) < MDBX_PNL_ALLOCLEN(pl));
+  if (mdbx_audit_enabled()) {
+    for (unsigned i = MDBX_PNL_SIZE(pl); i > 0; --i)
+      assert(pgno != pl[i]);
+  }
+  MDBX_PNL_SIZE(pl) += 1;
+  MDBX_PNL_LAST(pl) = pgno;
+}
+
+/* Append an pgno range onto an unsorted PNL */
+__always_inline static int __must_check_result
+mdbx_pnl_append_range(bool spilled, MDBX_PNL *ppl, pgno_t pgno, unsigned n) {
+  assert(n > 0);
+  int rc = mdbx_pnl_need(ppl, n);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  const MDBX_PNL pnl = *ppl;
+#if MDBX_PNL_ASCENDING
+  unsigned w = MDBX_PNL_SIZE(pnl);
+  do {
+    pnl[++w] = pgno;
+    pgno += spilled ? 2 : 1;
+  } while (--n);
+  MDBX_PNL_SIZE(pnl) = w;
+#else
+  unsigned w = MDBX_PNL_SIZE(pnl) + n;
+  MDBX_PNL_SIZE(pnl) = w;
+  do {
+    pnl[w--] = pgno;
+    pgno += spilled ? 2 : 1;
+  } while (--n);
+#endif
+
+  return MDBX_SUCCESS;
+}
+
+/* Append an pgno range into the sorted PNL */
+static __hot int __must_check_result mdbx_pnl_insert_range(MDBX_PNL *ppl,
+                                                           pgno_t pgno,
+                                                           unsigned n) {
+  assert(n > 0);
+  int rc = mdbx_pnl_need(ppl, n);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  const MDBX_PNL pnl = *ppl;
+  unsigned r = MDBX_PNL_SIZE(pnl), w = r + n;
+  MDBX_PNL_SIZE(pnl) = w;
+  while (r && MDBX_PNL_DISORDERED(pnl[r], pgno))
+    pnl[w--] = pnl[r--];
+
+  for (pgno_t fill = MDBX_PNL_ASCENDING ? pgno + n : pgno; w > r; --w)
+    pnl[w] = MDBX_PNL_ASCENDING ? --fill : fill++;
+
+  return MDBX_SUCCESS;
+}
+
+static bool mdbx_pnl_check(const MDBX_PNL pl, const pgno_t limit) {
+  if (likely(MDBX_PNL_SIZE(pl))) {
+    assert(MDBX_PNL_LEAST(pl) >= MIN_PAGENO);
+    assert(MDBX_PNL_MOST(pl) < limit);
+    assert(MDBX_PNL_SIZE(pl) <= MDBX_PGL_LIMIT);
+    if (unlikely(MDBX_PNL_SIZE(pl) > MDBX_PGL_LIMIT))
+      return false;
+    if (unlikely(MDBX_PNL_LEAST(pl) < MIN_PAGENO))
+      return false;
+    if (unlikely(MDBX_PNL_MOST(pl) >= limit))
+      return false;
+    if (mdbx_audit_enabled()) {
+      for (const pgno_t *scan = &MDBX_PNL_LAST(pl); --scan > pl;) {
+        assert(MDBX_PNL_ORDERED(scan[0], scan[1]));
+        if (unlikely(!MDBX_PNL_ORDERED(scan[0], scan[1])))
+          return false;
+      }
+    }
+  }
+  return true;
+}
+
+static __always_inline bool mdbx_pnl_check4assert(const MDBX_PNL pl,
+                                                  const pgno_t limit) {
+  if (unlikely(pl == nullptr))
+    return true;
+  assert(MDBX_PNL_ALLOCLEN(pl) >= MDBX_PNL_SIZE(pl));
+  if (unlikely(MDBX_PNL_ALLOCLEN(pl) < MDBX_PNL_SIZE(pl)))
+    return false;
+  return mdbx_pnl_check(pl, limit);
+}
+
+/* Merge an PNL onto an PNL. The destination PNL must be big enough */
+static void __hot mdbx_pnl_xmerge(MDBX_PNL dst, const MDBX_PNL src) {
+  assert(mdbx_pnl_check4assert(dst, MAX_PAGENO + 1));
+  assert(mdbx_pnl_check(src, MAX_PAGENO + 1));
+  const size_t total = MDBX_PNL_SIZE(dst) + MDBX_PNL_SIZE(src);
+  assert(MDBX_PNL_ALLOCLEN(dst) >= total);
+  pgno_t *w = dst + total;
+  pgno_t *d = dst + MDBX_PNL_SIZE(dst);
+  const pgno_t *s = src + MDBX_PNL_SIZE(src);
+  dst[0] = /* detent for scan below */ (MDBX_PNL_ASCENDING ? 0 : ~(pgno_t)0);
+  while (s > src) {
+    while (MDBX_PNL_ORDERED(*s, *d))
+      *w-- = *d--;
+    *w-- = *s--;
+  }
+  MDBX_PNL_SIZE(dst) = (pgno_t)total;
+  assert(mdbx_pnl_check4assert(dst, MAX_PAGENO + 1));
+}
+
+static void mdbx_spill_remove(MDBX_txn *txn, unsigned idx, unsigned npages) {
+  mdbx_tassert(txn, idx > 0 && idx <= MDBX_PNL_SIZE(txn->tw.spill_pages) &&
+                        txn->tw.spill_least_removed > 0);
+  txn->tw.spill_least_removed =
+      (idx < txn->tw.spill_least_removed) ? idx : txn->tw.spill_least_removed;
+  txn->tw.spill_pages[idx] |= 1;
+  MDBX_PNL_SIZE(txn->tw.spill_pages) -=
+      (idx == MDBX_PNL_SIZE(txn->tw.spill_pages));
+
+  while (unlikely(npages > 1)) {
+    const pgno_t pgno = (txn->tw.spill_pages[idx] >> 1) + 1;
+    if (MDBX_PNL_ASCENDING) {
+      if (++idx > MDBX_PNL_SIZE(txn->tw.spill_pages) ||
+          (txn->tw.spill_pages[idx] >> 1) != pgno)
+        return;
+    } else {
+      if (--idx < 1 || (txn->tw.spill_pages[idx] >> 1) != pgno)
+        return;
+      txn->tw.spill_least_removed = (idx < txn->tw.spill_least_removed)
+                                        ? idx
+                                        : txn->tw.spill_least_removed;
+    }
+    txn->tw.spill_pages[idx] |= 1;
+    MDBX_PNL_SIZE(txn->tw.spill_pages) -=
+        (idx == MDBX_PNL_SIZE(txn->tw.spill_pages));
+    --npages;
+  }
+}
+
+static MDBX_PNL mdbx_spill_purge(MDBX_txn *txn) {
+  mdbx_tassert(txn, txn->tw.spill_least_removed > 0);
+  const MDBX_PNL sl = txn->tw.spill_pages;
+  if (txn->tw.spill_least_removed != INT_MAX) {
+    unsigned len = MDBX_PNL_SIZE(sl), r, w;
+    for (w = r = txn->tw.spill_least_removed; r <= len; ++r) {
+      sl[w] = sl[r];
+      w += 1 - (sl[r] & 1);
+    }
+    for (size_t i = 1; i < w; ++i)
+      mdbx_tassert(txn, (sl[i] & 1) == 0);
+    MDBX_PNL_SIZE(sl) = w - 1;
+    txn->tw.spill_least_removed = INT_MAX;
+  } else {
+    for (size_t i = 1; i <= MDBX_PNL_SIZE(sl); ++i)
+      mdbx_tassert(txn, (sl[i] & 1) == 0);
+  }
+  return sl;
+}
+
+SORT_IMPL(pgno_sort, false, pgno_t, MDBX_PNL_ORDERED)
+static __hot void mdbx_pnl_sort(MDBX_PNL pnl) {
+  pgno_sort(MDBX_PNL_BEGIN(pnl), MDBX_PNL_END(pnl));
+  assert(mdbx_pnl_check(pnl, MAX_PAGENO + 1));
+}
+
+/* Search for an pgno in an PNL.
+ * Returns The index of the first item greater than or equal to pgno. */
+SEARCH_IMPL(pgno_bsearch, pgno_t, pgno_t, MDBX_PNL_ORDERED)
+
+static __hot unsigned mdbx_pnl_search(const MDBX_PNL pnl, pgno_t pgno) {
+  assert(mdbx_pnl_check4assert(pnl, MAX_PAGENO + 1));
+  const pgno_t *begin = MDBX_PNL_BEGIN(pnl);
+  const pgno_t *it = pgno_bsearch(begin, MDBX_PNL_SIZE(pnl), pgno);
+  const pgno_t *end = begin + MDBX_PNL_SIZE(pnl);
+  assert(it >= begin && it <= end);
+  if (it != begin)
+    assert(MDBX_PNL_ORDERED(it[-1], pgno));
+  if (it != end)
+    assert(!MDBX_PNL_ORDERED(it[0], pgno));
+  return (unsigned)(it - begin + 1);
+}
+
+static __inline unsigned mdbx_pnl_exist(const MDBX_PNL pnl, pgno_t pgno) {
+  unsigned n = mdbx_pnl_search(pnl, pgno);
+  return (n <= MDBX_PNL_SIZE(pnl) && pnl[n] == pgno) ? n : 0;
+}
+
+static __inline unsigned mdbx_pnl_intersect(const MDBX_PNL pnl, pgno_t pgno,
+                                            unsigned npages) {
+  const unsigned len = MDBX_PNL_SIZE(pnl);
+  if (mdbx_log_enabled(MDBX_LOG_EXTRA)) {
+    mdbx_debug_extra("PNL len %u [", len);
+    for (unsigned i = 1; i <= len; ++i)
+      mdbx_debug_extra_print(" %" PRIaPGNO, pnl[i]);
+    mdbx_debug_extra_print("%s\n", "]");
+  }
+  const pgno_t range_last = pgno + npages - 1;
+#if MDBX_PNL_ASCENDING
+  const unsigned n = mdbx_pnl_search(pnl, pgno);
+  assert(n && (n == MDBX_PNL_SIZE(pnl) + 1 || pgno <= pnl[n]));
+  const bool rc = n <= MDBX_PNL_SIZE(pnl) && pnl[n] <= range_last;
+#else
+  const unsigned n = mdbx_pnl_search(pnl, range_last);
+  assert(n && (n == MDBX_PNL_SIZE(pnl) + 1 || range_last >= pnl[n]));
+  const bool rc = n <= MDBX_PNL_SIZE(pnl) && pnl[n] >= pgno;
+#endif
+  if (mdbx_assert_enabled()) {
+    bool check = false;
+    for (unsigned i = 0; i < npages; ++i)
+      check |= mdbx_pnl_exist(pnl, pgno + i) != 0;
+    assert(check == rc);
+  }
+  return rc;
+}
+
+/*----------------------------------------------------------------------------*/
+
+static __always_inline size_t txl2bytes(const size_t size) {
+  assert(size > 0 && size <= MDBX_TXL_MAX * 2);
+  size_t bytes =
+      ceil_powerof2(MDBX_ASSUME_MALLOC_OVERHEAD + sizeof(txnid_t) * (size + 2),
+                    MDBX_TXL_GRANULATE * sizeof(txnid_t)) -
+      MDBX_ASSUME_MALLOC_OVERHEAD;
+  return bytes;
+}
+
+static __always_inline size_t bytes2txl(const size_t bytes) {
+  size_t size = bytes / sizeof(txnid_t);
+  assert(size > 2 && size <= MDBX_TXL_MAX * 2);
+  return size - 2;
+}
+
+static MDBX_TXL mdbx_txl_alloc(void) {
+  size_t bytes = txl2bytes(MDBX_TXL_INITIAL);
+  MDBX_TXL tl = mdbx_malloc(bytes);
+  if (likely(tl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+    bytes = malloc_usable_size(tl);
+#endif /* malloc_usable_size */
+    tl[0] = bytes2txl(bytes);
+    assert(tl[0] >= MDBX_TXL_INITIAL);
+    tl[1] = 0;
+    tl += 1;
+  }
+  return tl;
+}
+
+static void mdbx_txl_free(MDBX_TXL tl) {
+  if (likely(tl))
+    mdbx_free(tl - 1);
+}
+
+static int mdbx_txl_reserve(MDBX_TXL *ptl, const size_t wanna) {
+  const size_t allocated = (size_t)MDBX_PNL_ALLOCLEN(*ptl);
+  assert(MDBX_PNL_SIZE(*ptl) <= MDBX_TXL_MAX &&
+         MDBX_PNL_ALLOCLEN(*ptl) >= MDBX_PNL_SIZE(*ptl));
+  if (likely(allocated >= wanna))
+    return MDBX_SUCCESS;
+
+  if (unlikely(wanna > /* paranoia */ MDBX_TXL_MAX)) {
+    mdbx_error("TXL too long (%zu > %zu)", wanna, (size_t)MDBX_TXL_MAX);
+    return MDBX_TXN_FULL;
+  }
+
+  const size_t size = (wanna + wanna - allocated < MDBX_TXL_MAX)
+                          ? wanna + wanna - allocated
+                          : MDBX_TXL_MAX;
+  size_t bytes = txl2bytes(size);
+  MDBX_TXL tl = mdbx_realloc(*ptl - 1, bytes);
+  if (likely(tl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+    bytes = malloc_usable_size(tl);
+#endif /* malloc_usable_size */
+    *tl = bytes2txl(bytes);
+    assert(*tl >= wanna);
+    *ptl = tl + 1;
+    return MDBX_SUCCESS;
+  }
+  return MDBX_ENOMEM;
+}
+
+static __always_inline int __must_check_result mdbx_txl_need(MDBX_TXL *ptl,
+                                                             size_t num) {
+  assert(MDBX_PNL_SIZE(*ptl) <= MDBX_TXL_MAX &&
+         MDBX_PNL_ALLOCLEN(*ptl) >= MDBX_PNL_SIZE(*ptl));
+  assert(num <= MDBX_PGL_LIMIT);
+  const size_t wanna = (size_t)MDBX_PNL_SIZE(*ptl) + num;
+  return likely(MDBX_PNL_ALLOCLEN(*ptl) >= wanna)
+             ? MDBX_SUCCESS
+             : mdbx_txl_reserve(ptl, wanna);
+}
+
+static __always_inline void mdbx_txl_xappend(MDBX_TXL tl, txnid_t id) {
+  assert(MDBX_PNL_SIZE(tl) < MDBX_PNL_ALLOCLEN(tl));
+  MDBX_PNL_SIZE(tl) += 1;
+  MDBX_PNL_LAST(tl) = id;
+}
+
+#define TXNID_SORT_CMP(first, last) ((first) > (last))
+SORT_IMPL(txnid_sort, false, txnid_t, TXNID_SORT_CMP)
+static void mdbx_txl_sort(MDBX_TXL tl) {
+  txnid_sort(MDBX_PNL_BEGIN(tl), MDBX_PNL_END(tl));
+}
+
+static int __must_check_result mdbx_txl_append(MDBX_TXL *ptl, txnid_t id) {
+  if (unlikely(MDBX_PNL_SIZE(*ptl) == MDBX_PNL_ALLOCLEN(*ptl))) {
+    int rc = mdbx_txl_need(ptl, MDBX_TXL_GRANULATE);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+  mdbx_txl_xappend(*ptl, id);
+  return MDBX_SUCCESS;
+}
+
+/*----------------------------------------------------------------------------*/
+
+static __always_inline size_t dpl2bytes(const ptrdiff_t size) {
+  assert(size > 2 && (size_t)size <= MDBX_PGL_LIMIT);
+  size_t bytes = ceil_powerof2(MDBX_ASSUME_MALLOC_OVERHEAD + sizeof(MDBX_dpl) +
+                                   (size + 2) * sizeof(MDBX_dp),
+                               MDBX_PNL_GRANULATE * sizeof(void *) * 2) -
+                 MDBX_ASSUME_MALLOC_OVERHEAD;
+  return bytes;
+}
+
+static __always_inline unsigned bytes2dpl(const ptrdiff_t bytes) {
+  size_t size = (bytes - sizeof(MDBX_dpl)) / sizeof(MDBX_dp);
+  assert(size > 4 && size <= MDBX_PGL_LIMIT + MDBX_PNL_GRANULATE);
+  return (unsigned)size - 2;
+}
+
+static __always_inline void mdbx_dpl_clear(MDBX_dpl *dl) {
+  dl->sorted = dl->length = 0;
+}
+
+static void mdbx_dpl_free(MDBX_txn *txn) {
+  if (likely(txn->tw.dirtylist)) {
+    mdbx_free(txn->tw.dirtylist);
+    txn->tw.dirtylist = NULL;
+  }
+}
+
+static MDBX_dpl *mdbx_dpl_reserve(MDBX_txn *txn, size_t size) {
+  mdbx_tassert(txn,
+               txn->tw.dirtylist == NULL || txn->tw.dirtylist->length <= size);
+  size_t bytes = dpl2bytes((size < MDBX_PGL_LIMIT) ? size : MDBX_PGL_LIMIT);
+  MDBX_dpl *const dl = mdbx_realloc(txn->tw.dirtylist, bytes);
+  if (likely(dl)) {
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+    bytes = malloc_usable_size(dl);
+#endif /* malloc_usable_size */
+    dl->allocated = bytes2dpl(bytes);
+    dl->items[0].pgno = 0;
+    dl->items[0].ptr = nullptr;
+    mdbx_tassert(txn, txn->tw.dirtylist == NULL || dl->length <= dl->allocated);
+    txn->tw.dirtylist = dl;
+  }
+  return dl;
+}
+
+static int mdbx_dpl_alloc(MDBX_txn *txn) {
+  mdbx_tassert(txn,
+               (txn->mt_flags & MDBX_TXN_RDONLY) == 0 && !txn->tw.dirtylist);
+  MDBX_dpl *const dl =
+      mdbx_dpl_reserve(txn, txn->mt_env->me_options.dp_initial);
+  if (unlikely(!dl))
+    return MDBX_ENOMEM;
+  mdbx_dpl_clear(dl);
+  return MDBX_SUCCESS;
+}
+
+#define DP_SORT_CMP(first, last) ((first).pgno < (last).pgno)
+SORT_IMPL(dp_sort, false, MDBX_dp, DP_SORT_CMP)
+static __always_inline MDBX_dpl *mdbx_dpl_sort(MDBX_dpl *dl) {
+  assert(dl->length <= MDBX_PGL_LIMIT);
+  assert(dl->sorted <= dl->length);
+  if (dl->sorted != dl->length) {
+    dl->sorted = dl->length;
+    dp_sort(dl->items + 1, dl->items + dl->length + 1);
+  }
+  return dl;
+}
+
+/* Returns the index of the first dirty-page whose pgno
+ * member is greater than or equal to id. */
+#define DP_SEARCH_CMP(dp, id) ((dp).pgno < (id))
+SEARCH_IMPL(dp_bsearch, MDBX_dp, pgno_t, DP_SEARCH_CMP)
+
+static unsigned __hot mdbx_dpl_search(MDBX_dpl *dl, pgno_t pgno) {
+  if (mdbx_audit_enabled()) {
+    for (const MDBX_dp *ptr = dl->items + dl->sorted; --ptr > dl->items;) {
+      assert(ptr[0].pgno < ptr[1].pgno);
+      assert(ptr[0].pgno >= NUM_METAS);
+    }
+  }
+
+  switch (dl->length - dl->sorted) {
+  default:
+    /* sort a whole */
+    dl->sorted = dl->length;
+    dp_sort(dl->items + 1, dl->items + dl->length + 1);
+    break;
+  case 0:
+    /* whole sorted cases */
+    break;
+
+#define LINEAR_SEARCH_CASE(N)                                                  \
+  case N:                                                                      \
+    if (dl->items[dl->length - N + 1].pgno == pgno)                            \
+      return dl->length - N + 1;                                               \
+    __fallthrough
+
+    /* try linear search until the threshold */
+    LINEAR_SEARCH_CASE(16); /* fall through */
+    LINEAR_SEARCH_CASE(15); /* fall through */
+    LINEAR_SEARCH_CASE(14); /* fall through */
+    LINEAR_SEARCH_CASE(13); /* fall through */
+    LINEAR_SEARCH_CASE(12); /* fall through */
+    LINEAR_SEARCH_CASE(11); /* fall through */
+    LINEAR_SEARCH_CASE(10); /* fall through */
+    LINEAR_SEARCH_CASE(9);  /* fall through */
+    LINEAR_SEARCH_CASE(8);  /* fall through */
+    LINEAR_SEARCH_CASE(7);  /* fall through */
+    LINEAR_SEARCH_CASE(6);  /* fall through */
+    LINEAR_SEARCH_CASE(5);  /* fall through */
+    LINEAR_SEARCH_CASE(4);  /* fall through */
+    LINEAR_SEARCH_CASE(3);  /* fall through */
+    LINEAR_SEARCH_CASE(2);  /* fall through */
+  case 1:
+    if (dl->items[dl->length].pgno == pgno)
+      return dl->length;
+    /* continue bsearch on the sorted part */
+    break;
+  }
+  return (unsigned)(dp_bsearch(dl->items + 1, dl->sorted, pgno) - dl->items);
+}
+
+static __inline bool mdbx_dpl_intersect(MDBX_dpl *dl, pgno_t pgno,
+                                        unsigned npages) {
+  assert(dl->sorted == dl->length);
+  unsigned const n = mdbx_dpl_search(dl, pgno);
+  assert(n >= 1 && n <= dl->length + 1);
+  assert(n > dl->length || pgno <= dl->items[n].pgno);
+  assert(n == 1 || pgno > dl->items[n - 1].pgno);
+  const MDBX_page *const prev = dl->items[n - 1].ptr;
+  const bool rc =
+      (/* intersection with founded */ n <= dl->length &&
+       pgno + npages > dl->items[n].pgno) ||
+      (/* intersection with prev */ n > 1 && unlikely(IS_OVERFLOW(prev)) &&
+       prev->mp_pgno + prev->mp_pages > pgno);
+  if (mdbx_assert_enabled()) {
+    bool check = false;
+    for (unsigned i = 1; i <= dl->length; ++i) {
+      const MDBX_page *const dp = dl->items[i].ptr;
+      if (!(dp->mp_pgno /* begin */ >= /* end */ pgno + npages ||
+            dp->mp_pgno + (IS_OVERFLOW(dp) ? dp->mp_pages : 1) /* end */ <=
+                /* begin */ pgno))
+        check |= true;
+    }
+    assert(check == rc);
+  }
+  return rc;
+}
+
+static __always_inline unsigned mdbx_dpl_exist(MDBX_dpl *dl, pgno_t pgno) {
+  unsigned i = mdbx_dpl_search(dl, pgno);
+  assert((int)i > 0);
+  return (i <= dl->length && dl->items[i].pgno == pgno) ? i : 0;
+}
+
+static __always_inline MDBX_page *mdbx_dpl_find(MDBX_dpl *dl, pgno_t pgno) {
+  const unsigned i = mdbx_dpl_search(dl, pgno);
+  assert((int)i > 0);
+  return (i <= dl->length && dl->items[i].pgno == pgno) ? dl->items[i].ptr
+                                                        : nullptr;
+}
+
+static __maybe_unused const MDBX_page *debug_dpl_find(const MDBX_dpl *dl,
+                                                      const pgno_t pgno) {
+  for (unsigned i = dl->length; i > dl->sorted; --i)
+    if (dl->items[i].pgno == pgno)
+      return dl->items[i].ptr;
+
+  if (dl->sorted) {
+    const unsigned i =
+        (unsigned)(dp_bsearch(dl->items + 1, dl->sorted, pgno) - dl->items);
+    if (i <= dl->sorted && dl->items[i].pgno == pgno)
+      return dl->items[i].ptr;
+  }
+  return nullptr;
+}
+
+static void mdbx_dpl_remove(MDBX_dpl *dl, unsigned i) {
+  assert((int)i > 0 && i <= dl->length);
+  dl->sorted -= dl->sorted >= i;
+  dl->length -= 1;
+  if (dl->length >= i)
+    memmove(dl->items + i, dl->items + i + 1,
+            (dl->length - i + 1) * sizeof(dl->items[0]));
+}
+
+static __always_inline int __must_check_result
+mdbx_dpl_append(MDBX_txn *txn, pgno_t pgno, MDBX_page *page) {
+  MDBX_dpl *dl = txn->tw.dirtylist;
+  assert(dl->length <= MDBX_PGL_LIMIT + MDBX_PNL_GRANULATE);
+  if (mdbx_audit_enabled()) {
+    for (unsigned i = dl->length; i > 0; --i) {
+      assert(dl->items[i].pgno != pgno);
+      if (unlikely(dl->items[i].pgno == pgno))
+        return MDBX_PROBLEM;
+    }
+  }
+
+  if (unlikely(dl->length == dl->allocated)) {
+    if (unlikely(dl->allocated >= MDBX_PGL_LIMIT)) {
+      mdbx_error("DPL is full (MDBX_PGL_LIMIT %u)", MDBX_PGL_LIMIT);
+      return MDBX_TXN_FULL;
+    }
+    const size_t size = (dl->allocated < MDBX_PNL_INITIAL * 42)
+                            ? dl->allocated + dl->allocated
+                            : dl->allocated + dl->allocated / 2;
+    dl = mdbx_dpl_reserve(txn, size);
+    if (unlikely(!dl))
+      return MDBX_ENOMEM;
+    mdbx_tassert(txn, dl->length < dl->allocated);
+  }
+
+  /* append page */
+  const unsigned n = dl->length + 1;
+  if (n == 1 || (dl->sorted >= dl->length && dl->items[n - 1].pgno < pgno))
+    dl->sorted = n;
+  dl->length = n;
+  dl->items[n].pgno = pgno;
+  dl->items[n].ptr = page;
+  return MDBX_SUCCESS;
+}
+
+/*----------------------------------------------------------------------------*/
+
+uint8_t mdbx_runtime_flags = MDBX_RUNTIME_FLAGS_INIT;
+uint8_t mdbx_loglevel = MDBX_LOG_FATAL;
+MDBX_debug_func *mdbx_debug_logger;
+
+static __must_check_result int mdbx_page_retire(MDBX_cursor *mc, MDBX_page *mp);
+static __must_check_result int mdbx_page_loose(MDBX_txn *txn, MDBX_page *mp);
+static int mdbx_page_alloc(MDBX_cursor *mc, const unsigned num,
+                           MDBX_page **const mp, int flags);
+static txnid_t mdbx_kick_longlived_readers(MDBX_env *env,
+                                           const txnid_t laggard);
+
+static int mdbx_page_new(MDBX_cursor *mc, uint32_t flags, unsigned num,
+                         MDBX_page **mp);
+static int mdbx_page_touch(MDBX_cursor *mc);
+static int mdbx_cursor_touch(MDBX_cursor *mc);
+
+#define MDBX_END_NAMES                                                         \
+  {                                                                            \
+    "committed", "empty-commit", "abort", "reset", "reset-tmp", "fail-begin",  \
+        "fail-beginchild"                                                      \
+  }
+enum {
+  /* mdbx_txn_end operation number, for logging */
+  MDBX_END_COMMITTED,
+  MDBX_END_PURE_COMMIT,
+  MDBX_END_ABORT,
+  MDBX_END_RESET,
+  MDBX_END_RESET_TMP,
+  MDBX_END_FAIL_BEGIN,
+  MDBX_END_FAIL_BEGINCHILD
+};
+#define MDBX_END_OPMASK 0x0F  /* mask for mdbx_txn_end() operation number */
+#define MDBX_END_UPDATE 0x10  /* update env state (DBIs) */
+#define MDBX_END_FREE 0x20    /* free txn unless it is MDBX_env.me_txn0 */
+#define MDBX_END_EOTDONE 0x40 /* txn's cursors already closed */
+#define MDBX_END_SLOT 0x80    /* release any reader slot if MDBX_NOTLS */
+static int mdbx_txn_end(MDBX_txn *txn, const unsigned mode);
+
+static int __must_check_result mdbx_page_get(MDBX_cursor *mc, pgno_t pgno,
+                                             MDBX_page **mp, int *lvl,
+                                             txnid_t pp_txnid);
+static int __must_check_result mdbx_page_search_root(MDBX_cursor *mc,
+                                                     const MDBX_val *key,
+                                                     int flags);
+
+#define MDBX_PS_MODIFY 1
+#define MDBX_PS_ROOTONLY 2
+#define MDBX_PS_FIRST 4
+#define MDBX_PS_LAST 8
+static int __must_check_result mdbx_page_search(MDBX_cursor *mc,
+                                                const MDBX_val *key, int flags);
+static int __must_check_result mdbx_page_merge(MDBX_cursor *csrc,
+                                               MDBX_cursor *cdst);
+static int __must_check_result mdbx_page_flush(MDBX_txn *txn,
+                                               const unsigned keep);
+
+#define MDBX_SPLIT_REPLACE MDBX_APPENDDUP /* newkey is not new */
+static int __must_check_result mdbx_page_split(MDBX_cursor *mc,
+                                               const MDBX_val *newkey,
+                                               MDBX_val *newdata,
+                                               pgno_t newpgno, unsigned nflags);
+
+static int __must_check_result mdbx_read_header(MDBX_env *env, MDBX_meta *meta,
+                                                uint64_t *filesize,
+                                                const int lck_exclusive);
+static int __must_check_result mdbx_sync_locked(MDBX_env *env, unsigned flags,
+                                                MDBX_meta *const pending);
+static int mdbx_env_close0(MDBX_env *env);
+
+static MDBX_node *mdbx_node_search(MDBX_cursor *mc, const MDBX_val *key,
+                                   int *exactp);
+
+static int __must_check_result mdbx_node_add_branch(MDBX_cursor *mc,
+                                                    unsigned indx,
+                                                    const MDBX_val *key,
+                                                    pgno_t pgno);
+static int __must_check_result mdbx_node_add_leaf(MDBX_cursor *mc,
+                                                  unsigned indx,
+                                                  const MDBX_val *key,
+                                                  MDBX_val *data,
+                                                  unsigned flags);
+static int __must_check_result mdbx_node_add_leaf2(MDBX_cursor *mc,
+                                                   unsigned indx,
+                                                   const MDBX_val *key);
+
+static void mdbx_node_del(MDBX_cursor *mc, size_t ksize);
+static void mdbx_node_shrink(MDBX_page *mp, unsigned indx);
+static int __must_check_result mdbx_node_move(MDBX_cursor *csrc,
+                                              MDBX_cursor *cdst, int fromleft);
+static int __must_check_result mdbx_node_read(MDBX_cursor *mc, MDBX_node *leaf,
+                                              MDBX_val *data,
+                                              const txnid_t pp_txnid);
+static int __must_check_result mdbx_rebalance(MDBX_cursor *mc);
+static int __must_check_result mdbx_update_key(MDBX_cursor *mc,
+                                               const MDBX_val *key);
+
+static void mdbx_cursor_pop(MDBX_cursor *mc);
+static int __must_check_result mdbx_cursor_push(MDBX_cursor *mc, MDBX_page *mp);
+
+static int __must_check_result mdbx_audit_ex(MDBX_txn *txn,
+                                             unsigned retired_stored,
+                                             bool dont_filter_gc);
+
+static int __must_check_result mdbx_page_check(MDBX_cursor *const mc,
+                                               const MDBX_page *const mp,
+                                               unsigned options);
+static int __must_check_result mdbx_cursor_check(MDBX_cursor *mc,
+                                                 unsigned options);
+static int __must_check_result mdbx_cursor_del0(MDBX_cursor *mc);
+static int __must_check_result mdbx_del0(MDBX_txn *txn, MDBX_dbi dbi,
+                                         const MDBX_val *key,
+                                         const MDBX_val *data, unsigned flags);
+#define SIBLING_LEFT 0
+#define SIBLING_RIGHT 2
+static int __must_check_result mdbx_cursor_sibling(MDBX_cursor *mc, int dir);
+static int __must_check_result mdbx_cursor_next(MDBX_cursor *mc, MDBX_val *key,
+                                                MDBX_val *data,
+                                                MDBX_cursor_op op);
+static int __must_check_result mdbx_cursor_prev(MDBX_cursor *mc, MDBX_val *key,
+                                                MDBX_val *data,
+                                                MDBX_cursor_op op);
+static int __must_check_result mdbx_cursor_set(MDBX_cursor *mc, MDBX_val *key,
+                                               MDBX_val *data,
+                                               MDBX_cursor_op op, int *exactp);
+static int __must_check_result mdbx_cursor_first(MDBX_cursor *mc, MDBX_val *key,
+                                                 MDBX_val *data);
+static int __must_check_result mdbx_cursor_last(MDBX_cursor *mc, MDBX_val *key,
+                                                MDBX_val *data);
+
+static int __must_check_result mdbx_cursor_init(MDBX_cursor *mc, MDBX_txn *txn,
+                                                MDBX_dbi dbi);
+static int __must_check_result mdbx_xcursor_init0(MDBX_cursor *mc);
+static int __must_check_result mdbx_xcursor_init1(MDBX_cursor *mc,
+                                                  MDBX_node *node,
+                                                  const MDBX_page *mp);
+static int __must_check_result mdbx_xcursor_init2(MDBX_cursor *mc,
+                                                  MDBX_xcursor *src_mx,
+                                                  bool new_dupdata);
+static void cursor_copy_internal(const MDBX_cursor *csrc, MDBX_cursor *cdst);
+
+static int __must_check_result mdbx_drop0(MDBX_cursor *mc, int subs);
+static int __must_check_result mdbx_fetch_sdb(MDBX_txn *txn, MDBX_dbi dbi);
+static int __must_check_result mdbx_setup_dbx(MDBX_dbx *const dbx,
+                                              const MDBX_db *const db,
+                                              const unsigned pagesize);
+
+static MDBX_cmp_func cmp_lexical, cmp_reverse, cmp_int_align4, cmp_int_align2,
+    cmp_int_unaligned, cmp_lenfast;
+
+static __inline MDBX_cmp_func *get_default_keycmp(unsigned flags);
+static __inline MDBX_cmp_func *get_default_datacmp(unsigned flags);
+
+__cold const char *mdbx_liberr2str(int errnum) {
+  /* Table of descriptions for MDBX errors */
+  static const char *const tbl[] = {
+      "MDBX_KEYEXIST: Key/data pair already exists",
+      "MDBX_NOTFOUND: No matching key/data pair found",
+      "MDBX_PAGE_NOTFOUND: Requested page not found",
+      "MDBX_CORRUPTED: Database is corrupted",
+      "MDBX_PANIC: Environment had fatal error",
+      "MDBX_VERSION_MISMATCH: DB version mismatch libmdbx",
+      "MDBX_INVALID: File is not an MDBX file",
+      "MDBX_MAP_FULL: Environment mapsize limit reached",
+      "MDBX_DBS_FULL: Too many DBI-handles (maxdbs reached)",
+      "MDBX_READERS_FULL: Too many readers (maxreaders reached)",
+      NULL /* MDBX_TLS_FULL (-30789): unused in MDBX */,
+      "MDBX_TXN_FULL: Transaction has too many dirty pages,"
+      " i.e transaction is too big",
+      "MDBX_CURSOR_FULL: Cursor stack limit reachedn - this usually indicates"
+      " corruption, i.e branch-pages loop",
+      "MDBX_PAGE_FULL: Internal error - Page has no more space",
+      "MDBX_UNABLE_EXTEND_MAPSIZE: Database engine was unable to extend"
+      " mapping, e.g. since address space is unavailable or busy,"
+      " or Operation system not supported such operations",
+      "MDBX_INCOMPATIBLE: Environment or database is not compatible"
+      " with the requested operation or the specified flags",
+      "MDBX_BAD_RSLOT: Invalid reuse of reader locktable slot,"
+      " e.g. read-transaction already run for current thread",
+      "MDBX_BAD_TXN: Transaction is not valid for requested operation,"
+      " e.g. had errored and be must aborted, has a child, or is invalid",
+      "MDBX_BAD_VALSIZE: Invalid size or alignment of key or data"
+      " for target database, either invalid subDB name",
+      "MDBX_BAD_DBI: The specified DBI-handle is invalid"
+      " or changed by another thread/transaction",
+      "MDBX_PROBLEM: Unexpected internal error, transaction should be aborted",
+      "MDBX_BUSY: Another write transaction is running,"
+      " or environment is already used while opening with MDBX_EXCLUSIVE flag",
+  };
+
+  if (errnum >= MDBX_KEYEXIST && errnum <= MDBX_BUSY) {
+    int i = errnum - MDBX_KEYEXIST;
+    return tbl[i];
+  }
+
+  switch (errnum) {
+  case MDBX_SUCCESS:
+    return "MDBX_SUCCESS: Successful";
+  case MDBX_EMULTIVAL:
+    return "MDBX_EMULTIVAL: The specified key has"
+           " more than one associated value";
+  case MDBX_EBADSIGN:
+    return "MDBX_EBADSIGN: Wrong signature of a runtime object(s),"
+           " e.g. memory corruption or double-free";
+  case MDBX_WANNA_RECOVERY:
+    return "MDBX_WANNA_RECOVERY: Database should be recovered,"
+           " but this could NOT be done automatically for now"
+           " since it opened in read-only mode";
+  case MDBX_EKEYMISMATCH:
+    return "MDBX_EKEYMISMATCH: The given key value is mismatched to the"
+           " current cursor position";
+  case MDBX_TOO_LARGE:
+    return "MDBX_TOO_LARGE: Database is too large for current system,"
+           " e.g. could NOT be mapped into RAM";
+  case MDBX_THREAD_MISMATCH:
+    return "MDBX_THREAD_MISMATCH: A thread has attempted to use a not"
+           " owned object, e.g. a transaction that started by another thread";
+  case MDBX_TXN_OVERLAPPING:
+    return "MDBX_TXN_OVERLAPPING: Overlapping read and write transactions for"
+           " the current thread";
+  default:
+    return NULL;
+  }
+}
+
+const char *__cold mdbx_strerror_r(int errnum, char *buf, size_t buflen) {
+  const char *msg = mdbx_liberr2str(errnum);
+  if (!msg && buflen > 0 && buflen < INT_MAX) {
+#if defined(_WIN32) || defined(_WIN64)
+    const DWORD size = FormatMessageA(
+        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL,
+        errnum, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buf, (DWORD)buflen,
+        NULL);
+    return size ? buf : "FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM) failed";
+#elif defined(_GNU_SOURCE) && defined(__GLIBC__)
+    /* GNU-specific */
+    if (errnum > 0)
+      msg = strerror_r(errnum, buf, buflen);
+#elif (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
+    /* XSI-compliant */
+    if (errnum > 0 && strerror_r(errnum, buf, buflen) == 0)
+      msg = buf;
+#else
+    if (errnum > 0) {
+      msg = strerror(errnum);
+      if (msg) {
+        strncpy(buf, msg, buflen);
+        msg = buf;
+      }
+    }
+#endif
+    if (!msg) {
+      (void)snprintf(buf, buflen, "error %d", errnum);
+      msg = buf;
+    }
+    buf[buflen - 1] = '\0';
+  }
+  return msg;
+}
+
+const char *__cold mdbx_strerror(int errnum) {
+#if defined(_WIN32) || defined(_WIN64)
+  static char buf[1024];
+  return mdbx_strerror_r(errnum, buf, sizeof(buf));
+#else
+  const char *msg = mdbx_liberr2str(errnum);
+  if (!msg) {
+    if (errnum > 0)
+      msg = strerror(errnum);
+    if (!msg) {
+      static char buf[32];
+      (void)snprintf(buf, sizeof(buf) - 1, "error %d", errnum);
+      msg = buf;
+    }
+  }
+  return msg;
+#endif
+}
+
+#if defined(_WIN32) || defined(_WIN64) /* Bit of madness for Windows */
+const char *mdbx_strerror_r_ANSI2OEM(int errnum, char *buf, size_t buflen) {
+  const char *msg = mdbx_liberr2str(errnum);
+  if (!msg && buflen > 0 && buflen < INT_MAX) {
+    const DWORD size = FormatMessageA(
+        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL,
+        errnum, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buf, (DWORD)buflen,
+        NULL);
+    if (!size)
+      msg = "FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM) failed";
+    else if (!CharToOemBuffA(buf, buf, size))
+      msg = "CharToOemBuffA() failed";
+    else
+      msg = buf;
+  }
+  return msg;
+}
+
+const char *mdbx_strerror_ANSI2OEM(int errnum) {
+  static char buf[1024];
+  return mdbx_strerror_r_ANSI2OEM(errnum, buf, sizeof(buf));
+}
+#endif /* Bit of madness for Windows */
+
+void __cold mdbx_debug_log_va(int level, const char *function, int line,
+                              const char *fmt, va_list args) {
+  if (mdbx_debug_logger)
+    mdbx_debug_logger(level, function, line, fmt, args);
+  else {
+#if defined(_WIN32) || defined(_WIN64)
+    if (IsDebuggerPresent()) {
+      int prefix_len = 0;
+      char *prefix = nullptr;
+      if (function && line > 0)
+        prefix_len = mdbx_asprintf(&prefix, "%s:%d ", function, line);
+      else if (function)
+        prefix_len = mdbx_asprintf(&prefix, "%s: ", function);
+      else if (line > 0)
+        prefix_len = mdbx_asprintf(&prefix, "%d: ", line);
+      if (prefix_len > 0 && prefix) {
+        OutputDebugStringA(prefix);
+        mdbx_free(prefix);
+      }
+      char *msg = nullptr;
+      int msg_len = mdbx_vasprintf(&msg, fmt, args);
+      if (msg_len > 0 && msg) {
+        OutputDebugStringA(msg);
+        mdbx_free(msg);
+      }
+    }
+#else
+    if (function && line > 0)
+      fprintf(stderr, "%s:%d ", function, line);
+    else if (function)
+      fprintf(stderr, "%s: ", function);
+    else if (line > 0)
+      fprintf(stderr, "%d: ", line);
+    vfprintf(stderr, fmt, args);
+    fflush(stderr);
+#endif
+  }
+}
+
+void __cold mdbx_debug_log(int level, const char *function, int line,
+                           const char *fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  mdbx_debug_log_va(level, function, line, fmt, args);
+  va_end(args);
+}
+
+/* Dump a key in ascii or hexadecimal. */
+const char *mdbx_dump_val(const MDBX_val *key, char *const buf,
+                          const size_t bufsize) {
+  if (!key)
+    return "<null>";
+  if (!key->iov_len)
+    return "<empty>";
+  if (!buf || bufsize < 4)
+    return nullptr;
+
+  bool is_ascii = true;
+  const uint8_t *const data = key->iov_base;
+  for (unsigned i = 0; i < key->iov_len; i++)
+    if (data[i] < ' ' || data[i] > '~') {
+      is_ascii = false;
+      break;
+    }
+
+  if (is_ascii) {
+    int len =
+        snprintf(buf, bufsize, "%.*s",
+                 (key->iov_len > INT_MAX) ? INT_MAX : (int)key->iov_len, data);
+    assert(len > 0 && (unsigned)len < bufsize);
+    (void)len;
+  } else {
+    char *const detent = buf + bufsize - 2;
+    char *ptr = buf;
+    *ptr++ = '<';
+    for (unsigned i = 0; i < key->iov_len; i++) {
+      const ptrdiff_t left = detent - ptr;
+      assert(left > 0);
+      int len = snprintf(ptr, left, "%02x", data[i]);
+      if (len < 0 || len >= left)
+        break;
+      ptr += len;
+    }
+    if (ptr < detent) {
+      ptr[0] = '>';
+      ptr[1] = '\0';
+    }
+  }
+  return buf;
+}
+
+/*------------------------------------------------------------------------------
+ LY: debug stuff */
+
+static const char *mdbx_leafnode_type(MDBX_node *n) {
+  static const char *const tp[2][2] = {{"", ": DB"},
+                                       {": sub-page", ": sub-DB"}};
+  return F_ISSET(node_flags(n), F_BIGDATA)
+             ? ": overflow page"
+             : tp[F_ISSET(node_flags(n), F_DUPDATA)]
+                 [F_ISSET(node_flags(n), F_SUBDATA)];
+}
+
+/* Display all the keys in the page. */
+static __maybe_unused void mdbx_page_list(MDBX_page *mp) {
+  pgno_t pgno = mp->mp_pgno;
+  const char *type, *state = IS_DIRTY(mp) ? ", dirty" : "";
+  MDBX_node *node;
+  unsigned i, nkeys, nsize, total = 0;
+  MDBX_val key;
+  DKBUF;
+
+  switch (mp->mp_flags &
+          (P_BRANCH | P_LEAF | P_LEAF2 | P_META | P_OVERFLOW | P_SUBP)) {
+  case P_BRANCH:
+    type = "Branch page";
+    break;
+  case P_LEAF:
+    type = "Leaf page";
+    break;
+  case P_LEAF | P_SUBP:
+    type = "Leaf sub-page";
+    break;
+  case P_LEAF | P_LEAF2:
+    type = "Leaf2 page";
+    break;
+  case P_LEAF | P_LEAF2 | P_SUBP:
+    type = "Leaf2 sub-page";
+    break;
+  case P_OVERFLOW:
+    mdbx_verbose("Overflow page %" PRIaPGNO " pages %u%s\n", pgno, mp->mp_pages,
+                 state);
+    return;
+  case P_META:
+    mdbx_verbose("Meta-page %" PRIaPGNO " txnid %" PRIu64 "\n", pgno,
+                 unaligned_peek_u64(4, page_meta(mp)->mm_txnid_a));
+    return;
+  default:
+    mdbx_verbose("Bad page %" PRIaPGNO " flags 0x%X\n", pgno, mp->mp_flags);
+    return;
+  }
+
+  nkeys = page_numkeys(mp);
+  mdbx_verbose("%s %" PRIaPGNO " numkeys %u%s\n", type, pgno, nkeys, state);
+
+  for (i = 0; i < nkeys; i++) {
+    if (IS_LEAF2(mp)) { /* LEAF2 pages have no mp_ptrs[] or node headers */
+      key.iov_len = nsize = mp->mp_leaf2_ksize;
+      key.iov_base = page_leaf2key(mp, i, nsize);
+      total += nsize;
+      mdbx_verbose("key %u: nsize %u, %s\n", i, nsize, DKEY(&key));
+      continue;
+    }
+    node = page_node(mp, i);
+    key.iov_len = node_ks(node);
+    key.iov_base = node->mn_data;
+    nsize = (unsigned)(NODESIZE + key.iov_len);
+    if (IS_BRANCH(mp)) {
+      mdbx_verbose("key %u: page %" PRIaPGNO ", %s\n", i, node_pgno(node),
+                   DKEY(&key));
+      total += nsize;
+    } else {
+      if (F_ISSET(node_flags(node), F_BIGDATA))
+        nsize += sizeof(pgno_t);
+      else
+        nsize += (unsigned)node_ds(node);
+      total += nsize;
+      nsize += sizeof(indx_t);
+      mdbx_verbose("key %u: nsize %u, %s%s\n", i, nsize, DKEY(&key),
+                   mdbx_leafnode_type(node));
+    }
+    total = EVEN(total);
+  }
+  mdbx_verbose("Total: header %u + contents %u + unused %u\n",
+               IS_LEAF2(mp) ? PAGEHDRSZ : PAGEHDRSZ + mp->mp_lower, total,
+               page_room(mp));
+}
+
+/*----------------------------------------------------------------------------*/
+
+/* Check if there is an initialized xcursor, so XCURSOR_REFRESH() is proper */
+#define XCURSOR_INITED(mc)                                                     \
+  ((mc)->mc_xcursor && ((mc)->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
+
+/* Update sub-page pointer, if any, in mc->mc_xcursor.
+ * Needed when the node which contains the sub-page may have moved.
+ * Called with mp = mc->mc_pg[mc->mc_top], ki = mc->mc_ki[mc->mc_top]. */
+#define XCURSOR_REFRESH(mc, mp, ki)                                            \
+  do {                                                                         \
+    MDBX_page *xr_pg = (mp);                                                   \
+    MDBX_node *xr_node = page_node(xr_pg, ki);                                 \
+    if ((node_flags(xr_node) & (F_DUPDATA | F_SUBDATA)) == F_DUPDATA)          \
+      (mc)->mc_xcursor->mx_cursor.mc_pg[0] = node_data(xr_node);               \
+  } while (0)
+
+static __maybe_unused bool cursor_is_tracked(const MDBX_cursor *mc) {
+  for (MDBX_cursor *scan = mc->mc_txn->tw.cursors[mc->mc_dbi]; scan;
+       scan = scan->mc_next)
+    if (mc == ((mc->mc_flags & C_SUB) ? &scan->mc_xcursor->mx_cursor : scan))
+      return true;
+  return false;
+}
+
+/* Perform act while tracking temporary cursor mn */
+#define WITH_CURSOR_TRACKING(mn, act)                                          \
+  do {                                                                         \
+    mdbx_cassert(&(mn),                                                        \
+                 mn.mc_txn->tw.cursors != NULL /* must be not rdonly txt */);  \
+    mdbx_cassert(&(mn), !cursor_is_tracked(&(mn)));                            \
+    MDBX_cursor mc_dummy;                                                      \
+    MDBX_cursor **tracking_head = &(mn).mc_txn->tw.cursors[mn.mc_dbi];         \
+    MDBX_cursor *tracked = &(mn);                                              \
+    if ((mn).mc_flags & C_SUB) {                                               \
+      mc_dummy.mc_flags = C_INITIALIZED;                                       \
+      mc_dummy.mc_top = 0;                                                     \
+      mc_dummy.mc_xcursor = (MDBX_xcursor *)&(mn);                             \
+      tracked = &mc_dummy;                                                     \
+    }                                                                          \
+    tracked->mc_next = *tracking_head;                                         \
+    *tracking_head = tracked;                                                  \
+    { act; }                                                                   \
+    *tracking_head = tracked->mc_next;                                         \
+  } while (0)
+
+int mdbx_cmp(const MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *a,
+             const MDBX_val *b) {
+  mdbx_assert(NULL, txn->mt_signature == MDBX_MT_SIGNATURE);
+  return txn->mt_dbxs[dbi].md_cmp(a, b);
+}
+
+int mdbx_dcmp(const MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *a,
+              const MDBX_val *b) {
+  mdbx_assert(NULL, txn->mt_signature == MDBX_MT_SIGNATURE);
+  return txn->mt_dbxs[dbi].md_dcmp(a, b);
+}
+
+/* Allocate memory for a page.
+ * Re-use old malloc'd pages first for singletons, otherwise just malloc.
+ * Set MDBX_TXN_ERROR on failure. */
+static MDBX_page *mdbx_page_malloc(MDBX_txn *txn, unsigned num) {
+  MDBX_env *env = txn->mt_env;
+  MDBX_page *np = env->me_dp_reserve;
+  size_t size = env->me_psize;
+  if (likely(num == 1 && np)) {
+    mdbx_assert(env, env->me_dp_reserve_len > 0);
+    ASAN_UNPOISON_MEMORY_REGION(np, size);
+    VALGRIND_MEMPOOL_ALLOC(env, np, size);
+    VALGRIND_MAKE_MEM_DEFINED(&np->mp_next, sizeof(np->mp_next));
+    env->me_dp_reserve = np->mp_next;
+    env->me_dp_reserve_len -= 1;
+  } else {
+    size = pgno2bytes(env, num);
+    np = mdbx_malloc(size);
+    if (unlikely(!np)) {
+      txn->mt_flags |= MDBX_TXN_ERROR;
+      return np;
+    }
+    VALGRIND_MEMPOOL_ALLOC(env, np, size);
+  }
+
+  if ((env->me_flags & MDBX_NOMEMINIT) == 0) {
+    /* For a single page alloc, we init everything after the page header.
+     * For multi-page, we init the final page; if the caller needed that
+     * many pages they will be filling in at least up to the last page. */
+    size_t skip = PAGEHDRSZ;
+    if (num > 1)
+      skip += pgno2bytes(env, num - 1);
+    memset((char *)np + skip, 0, size - skip);
+  }
+#if MDBX_DEBUG
+  np->mp_pgno = 0;
+#endif
+  VALGRIND_MAKE_MEM_UNDEFINED(np, size);
+  np->mp_flags = 0;
+  np->mp_pages = num;
+  return np;
+}
+
+/* Free a shadow dirty page */
+static void mdbx_dpage_free(MDBX_env *env, MDBX_page *dp, unsigned npages) {
+  VALGRIND_MAKE_MEM_UNDEFINED(dp, pgno2bytes(env, npages));
+  ASAN_UNPOISON_MEMORY_REGION(dp, pgno2bytes(env, npages));
+  if (MDBX_DEBUG || unlikely(env->me_flags & MDBX_PAGEPERTURB))
+    memset(dp, -1, pgno2bytes(env, npages));
+  if (npages == 1 &&
+      env->me_dp_reserve_len < env->me_options.dp_reserve_limit) {
+    ASAN_POISON_MEMORY_REGION((char *)dp + sizeof(dp->mp_next),
+                              pgno2bytes(env, npages) - sizeof(dp->mp_next));
+    dp->mp_next = env->me_dp_reserve;
+    VALGRIND_MEMPOOL_FREE(env, dp);
+    env->me_dp_reserve = dp;
+    env->me_dp_reserve_len += 1;
+  } else {
+    /* large pages just get freed directly */
+    VALGRIND_MEMPOOL_FREE(env, dp);
+    mdbx_free(dp);
+  }
+}
+
+/* Return all dirty pages to dpage list */
+static void mdbx_dlist_free(MDBX_txn *txn) {
+  MDBX_env *env = txn->mt_env;
+  MDBX_dpl *const dl = txn->tw.dirtylist;
+  const size_t len = dl->length;
+
+  for (size_t i = 1; i <= len; i++) {
+    MDBX_page *dp = dl->items[i].ptr;
+    mdbx_dpage_free(env, dp, IS_OVERFLOW(dp) ? dp->mp_pages : 1);
+  }
+
+  mdbx_dpl_clear(dl);
+}
+
+static __always_inline MDBX_db *mdbx_outer_db(MDBX_cursor *mc) {
+  mdbx_cassert(mc, (mc->mc_flags & C_SUB) != 0);
+  MDBX_xcursor *mx = container_of(mc->mc_db, MDBX_xcursor, mx_db);
+  MDBX_cursor_couple *couple = container_of(mx, MDBX_cursor_couple, inner);
+  mdbx_cassert(mc, mc->mc_db == &couple->outer.mc_xcursor->mx_db);
+  mdbx_cassert(mc, mc->mc_dbx == &couple->outer.mc_xcursor->mx_dbx);
+  return couple->outer.mc_db;
+}
+
+static __cold __maybe_unused bool mdbx_dirtylist_check(MDBX_txn *txn) {
+  if (!mdbx_audit_enabled())
+    return true;
+
+  const MDBX_dpl *const dl = txn->tw.dirtylist;
+  unsigned loose = 0;
+  for (unsigned i = dl->length; i > 0; --i) {
+    const MDBX_page *const dp = dl->items[i].ptr;
+    if (!dp)
+      continue;
+
+    mdbx_tassert(txn, dp->mp_pgno == dl->items[i].pgno);
+    if (unlikely(dp->mp_pgno != dl->items[i].pgno))
+      return false;
+
+    mdbx_tassert(txn, dp->mp_flags & P_DIRTY);
+    if (unlikely((dp->mp_flags & P_DIRTY) == 0))
+      return false;
+    if (dp->mp_flags & P_LOOSE) {
+      mdbx_tassert(txn, dp->mp_flags == (P_LOOSE | P_DIRTY));
+      if (unlikely(dp->mp_flags != (P_LOOSE | P_DIRTY)))
+        return false;
+      loose += 1;
+    }
+
+    const unsigned num = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+    mdbx_tassert(txn, txn->mt_next_pgno >= dp->mp_pgno + num);
+    if (unlikely(txn->mt_next_pgno < dp->mp_pgno + num))
+      return false;
+
+    if (i < dl->sorted) {
+      mdbx_tassert(txn, dl->items[i + 1].pgno >= dp->mp_pgno + num);
+      if (unlikely(dl->items[i + 1].pgno < dp->mp_pgno + num))
+        return false;
+    }
+
+    const unsigned rpa = mdbx_pnl_search(txn->tw.reclaimed_pglist, dp->mp_pgno);
+    mdbx_tassert(txn, rpa > MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) ||
+                          txn->tw.reclaimed_pglist[rpa] != dp->mp_pgno);
+    if (rpa <= MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) &&
+        unlikely(txn->tw.reclaimed_pglist[rpa] == dp->mp_pgno))
+      return false;
+    if (num > 1) {
+      const unsigned rpb =
+          mdbx_pnl_search(txn->tw.reclaimed_pglist, dp->mp_pgno + num - 1);
+      mdbx_tassert(txn, rpa == rpb);
+      if (unlikely(rpa != rpb))
+        return false;
+    }
+  }
+
+  mdbx_tassert(txn, loose == txn->tw.loose_count);
+  if (unlikely(loose != txn->tw.loose_count))
+    return false;
+
+  for (unsigned i = 1; i <= MDBX_PNL_SIZE(txn->tw.retired_pages); ++i) {
+    const MDBX_page *const dp = debug_dpl_find(dl, txn->tw.retired_pages[i]);
+    mdbx_tassert(txn, !dp);
+    if (unlikely(dp))
+      return false;
+  }
+
+  return true;
+}
+
+#if MDBX_ENABLE_REFUND
+static void mdbx_refund_reclaimed(MDBX_txn *txn) {
+  /* Scanning in descend order */
+  pgno_t next_pgno = txn->mt_next_pgno;
+  const MDBX_PNL pnl = txn->tw.reclaimed_pglist;
+  mdbx_tassert(txn, MDBX_PNL_SIZE(pnl) && MDBX_PNL_MOST(pnl) == next_pgno - 1);
+#if MDBX_PNL_ASCENDING
+  unsigned i = MDBX_PNL_SIZE(pnl);
+  mdbx_tassert(txn, pnl[i] == next_pgno - 1);
+  while (--next_pgno, --i > 0 && pnl[i] == next_pgno - 1)
+    ;
+  MDBX_PNL_SIZE(pnl) = i;
+#else
+  unsigned i = 1;
+  mdbx_tassert(txn, pnl[i] == next_pgno - 1);
+  unsigned len = MDBX_PNL_SIZE(pnl);
+  while (--next_pgno, ++i <= len && pnl[i] == next_pgno - 1)
+    ;
+  MDBX_PNL_SIZE(pnl) = len -= i - 1;
+  for (unsigned move = 0; move < len; ++move)
+    pnl[1 + move] = pnl[i + move];
+#endif
+  mdbx_verbose("refunded %" PRIaPGNO " pages: %" PRIaPGNO " -> %" PRIaPGNO,
+               txn->mt_next_pgno - next_pgno, txn->mt_next_pgno, next_pgno);
+  txn->mt_next_pgno = next_pgno;
+  mdbx_tassert(txn, mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                          txn->mt_next_pgno - 1));
+}
+
+static void mdbx_refund_loose(MDBX_txn *txn) {
+  mdbx_tassert(txn, txn->tw.loose_pages != nullptr);
+  mdbx_tassert(txn, txn->tw.loose_count > 0);
+
+  MDBX_dpl *const dl = txn->tw.dirtylist;
+  mdbx_tassert(txn, dl->length >= txn->tw.loose_count);
+
+  pgno_t onstack[MDBX_CACHELINE_SIZE * 8 / sizeof(pgno_t)];
+  MDBX_PNL suitable = onstack;
+
+  if (dl->length - dl->sorted > txn->tw.loose_count) {
+    /* Dirty list is useless since unsorted. */
+    if (bytes2pnl(sizeof(onstack)) < txn->tw.loose_count) {
+      suitable = mdbx_pnl_alloc(txn->tw.loose_count);
+      if (unlikely(!suitable))
+        return /* this is not a reason for transaction fail */;
+    }
+
+    /* Collect loose-pages which may be refunded. */
+    mdbx_tassert(txn, txn->mt_next_pgno >= MIN_PAGENO + txn->tw.loose_count);
+    pgno_t most = MIN_PAGENO;
+    unsigned w = 0;
+    for (const MDBX_page *lp = txn->tw.loose_pages; lp; lp = lp->mp_next) {
+      mdbx_tassert(txn, lp->mp_flags == (P_LOOSE | P_DIRTY));
+      mdbx_tassert(txn, txn->mt_next_pgno > lp->mp_pgno);
+      if (likely(txn->mt_next_pgno - txn->tw.loose_count <= lp->mp_pgno)) {
+        mdbx_tassert(txn,
+                     w < ((suitable == onstack) ? bytes2pnl(sizeof(onstack))
+                                                : MDBX_PNL_ALLOCLEN(suitable)));
+        suitable[++w] = lp->mp_pgno;
+        most = (lp->mp_pgno > most) ? lp->mp_pgno : most;
+      }
+    }
+
+    if (most + 1 == txn->mt_next_pgno) {
+      /* Sort suitable list and refund pages at the tail. */
+      MDBX_PNL_SIZE(suitable) = w;
+      mdbx_pnl_sort(suitable);
+
+      /* Scanning in descend order */
+      const int step = MDBX_PNL_ASCENDING ? -1 : 1;
+      const int begin = MDBX_PNL_ASCENDING ? MDBX_PNL_SIZE(suitable) : 1;
+      const int end = MDBX_PNL_ASCENDING ? 0 : MDBX_PNL_SIZE(suitable) + 1;
+      mdbx_tassert(txn, suitable[begin] >= suitable[end - step]);
+      mdbx_tassert(txn, most == suitable[begin]);
+
+      for (int i = begin + step; i != end; i += step) {
+        if (suitable[i] != most - 1)
+          break;
+        most -= 1;
+      }
+      const unsigned refunded = txn->mt_next_pgno - most;
+      mdbx_debug("refund-suitable %u pages %" PRIaPGNO " -> %" PRIaPGNO,
+                 refunded, most, txn->mt_next_pgno);
+      txn->tw.loose_count -= refunded;
+      txn->tw.dirtyroom += refunded;
+      assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+      txn->mt_next_pgno = most;
+
+      /* Filter-out dirty list */
+      unsigned r = 0;
+      w = 0;
+      if (dl->sorted) {
+        do {
+          if (dl->items[++r].pgno < most) {
+            if (++w != r)
+              dl->items[w] = dl->items[r];
+          }
+        } while (r < dl->sorted);
+        dl->sorted = w;
+      }
+      while (r < dl->length) {
+        if (dl->items[++r].pgno < most) {
+          if (++w != r)
+            dl->items[w] = dl->items[r];
+        }
+      }
+      dl->length = w;
+      mdbx_tassert(txn, txn->mt_parent || txn->tw.dirtyroom + dl->length ==
+                                              txn->mt_env->me_options.dp_limit);
+      goto unlink_loose;
+    }
+  } else {
+    /* Dirtylist is mostly sorted, just refund loose pages at the end. */
+    mdbx_dpl_sort(dl);
+    mdbx_tassert(txn, dl->length < 2 ||
+                          dl->items[1].pgno < dl->items[dl->length].pgno);
+    mdbx_tassert(txn, dl->sorted == dl->length);
+
+    /* Scan dirtylist tail-forward and cutoff suitable pages. */
+    while (dl->length && dl->items[dl->length].pgno == txn->mt_next_pgno - 1 &&
+           dl->items[dl->length].ptr->mp_flags == (P_LOOSE | P_DIRTY)) {
+      MDBX_page *dp = dl->items[dl->length].ptr;
+      mdbx_debug("refund-sorted page %" PRIaPGNO, dp->mp_pgno);
+      mdbx_tassert(txn, dp->mp_pgno == dl->items[dl->length].pgno);
+      txn->mt_next_pgno -= 1;
+      dl->length -= 1;
+    }
+
+    if (dl->sorted != dl->length) {
+      const unsigned refunded = dl->sorted - dl->length;
+      dl->sorted = dl->length;
+      txn->tw.loose_count -= refunded;
+      txn->tw.dirtyroom += refunded;
+      mdbx_tassert(txn, txn->mt_parent || txn->tw.dirtyroom + dl->length ==
+                                              txn->mt_env->me_options.dp_limit);
+      assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+
+      /* Filter-out loose chain & dispose refunded pages. */
+    unlink_loose:
+      for (MDBX_page **link = &txn->tw.loose_pages; *link;) {
+        MDBX_page *dp = *link;
+        mdbx_tassert(txn, dp->mp_flags == (P_LOOSE | P_DIRTY));
+        if (txn->mt_next_pgno > dp->mp_pgno) {
+          link = &dp->mp_next;
+        } else {
+          *link = dp->mp_next;
+          if ((txn->mt_flags & MDBX_WRITEMAP) == 0)
+            mdbx_dpage_free(txn->mt_env, dp, 1);
+        }
+      }
+    }
+  }
+
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  mdbx_tassert(txn, txn->mt_parent || txn->tw.dirtyroom + dl->length ==
+                                          txn->mt_env->me_options.dp_limit);
+  if (suitable != onstack)
+    mdbx_pnl_free(suitable);
+  txn->tw.loose_refund_wl = txn->mt_next_pgno;
+}
+
+static bool mdbx_refund(MDBX_txn *txn) {
+  const pgno_t before = txn->mt_next_pgno;
+
+  if (txn->tw.loose_pages && txn->tw.loose_refund_wl > txn->mt_next_pgno)
+    mdbx_refund_loose(txn);
+
+  while (true) {
+    if (MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) == 0 ||
+        MDBX_PNL_MOST(txn->tw.reclaimed_pglist) != txn->mt_next_pgno - 1)
+      break;
+
+    mdbx_refund_reclaimed(txn);
+    if (!txn->tw.loose_pages || txn->tw.loose_refund_wl <= txn->mt_next_pgno)
+      break;
+
+    const pgno_t memo = txn->mt_next_pgno;
+    mdbx_refund_loose(txn);
+    if (memo == txn->mt_next_pgno)
+      break;
+  }
+
+  if (before == txn->mt_next_pgno)
+    return false;
+
+  if (txn->tw.spill_pages)
+    /* Squash deleted pagenums if we refunded any */
+    mdbx_spill_purge(txn);
+
+  return true;
+}
+#else  /* MDBX_ENABLE_REFUND */
+static __inline bool mdbx_refund(MDBX_txn *txn) {
+  (void)txn;
+  /* No online auto-compactification. */
+  return false;
+}
+#endif /* MDBX_ENABLE_REFUND */
+
+static __cold void mdbx_kill_page(MDBX_env *env, MDBX_page *mp, pgno_t pgno,
+                                  unsigned npages) {
+  mdbx_debug("kill%s %u page %" PRIaPGNO, IS_DIRTY(mp) ? " dirty" : "", npages,
+             pgno);
+  mdbx_assert(env, pgno >= NUM_METAS && npages);
+  if (IS_DIRTY(mp) || (env->me_flags & MDBX_WRITEMAP)) {
+    const size_t bytes = pgno2bytes(env, npages);
+    memset(mp, -1, bytes);
+    mp->mp_pgno = pgno;
+    if ((env->me_flags & MDBX_WRITEMAP) == 0)
+      mdbx_pwrite(env->me_lazy_fd, mp, bytes, pgno2bytes(env, pgno));
+  } else {
+    struct iovec iov[MDBX_COMMIT_PAGES];
+    iov[0].iov_len = env->me_psize;
+    iov[0].iov_base = (char *)env->me_pbuf + env->me_psize;
+    size_t iov_off = pgno2bytes(env, pgno);
+    unsigned n = 1;
+    while (--npages) {
+      iov[n] = iov[0];
+      if (++n == MDBX_COMMIT_PAGES) {
+        mdbx_pwritev(env->me_lazy_fd, iov, MDBX_COMMIT_PAGES, iov_off,
+                     pgno2bytes(env, MDBX_COMMIT_PAGES));
+        iov_off += pgno2bytes(env, MDBX_COMMIT_PAGES);
+        n = 0;
+      }
+    }
+    mdbx_pwritev(env->me_lazy_fd, iov, n, iov_off, pgno2bytes(env, n));
+  }
+}
+
+/* Remove page from dirty list */
+static __inline void mdbx_page_wash(MDBX_txn *txn, const unsigned di,
+                                    MDBX_page *const mp,
+                                    const unsigned npages) {
+  mdbx_tassert(txn, di && di <= txn->tw.dirtylist->length &&
+                        txn->tw.dirtylist->items[di].ptr == mp);
+  mdbx_dpl_remove(txn->tw.dirtylist, di);
+  txn->tw.dirtyroom++;
+  assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+  mdbx_tassert(txn, txn->mt_parent ||
+                        txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                            txn->mt_env->me_options.dp_limit);
+  mp->mp_txnid = INVALID_TXNID;
+  mp->mp_flags = 0xFFFF;
+  VALGRIND_MAKE_MEM_UNDEFINED(mp, PAGEHDRSZ);
+  if (txn->mt_flags & MDBX_WRITEMAP) {
+    VALGRIND_MAKE_MEM_NOACCESS(page_data(mp),
+                               pgno2bytes(txn->mt_env, npages) - PAGEHDRSZ);
+    ASAN_POISON_MEMORY_REGION(page_data(mp),
+                              pgno2bytes(txn->mt_env, npages) - PAGEHDRSZ);
+  } else
+    mdbx_dpage_free(txn->mt_env, mp, npages);
+}
+
+/* Retire, loosen or free a single page.
+ *
+ * Saves single pages to a list for future reuse
+ * in this same txn. It has been pulled from the GC
+ * and already resides on the dirty list, but has been
+ * deleted. Use these pages first before pulling again
+ * from the GC.
+ *
+ * If the page wasn't dirtied in this txn, just add it
+ * to this txn's free list. */
+static int mdbx_page_loose(MDBX_txn *txn, MDBX_page *mp) {
+  const unsigned npages = IS_OVERFLOW(mp) ? mp->mp_pages : 1;
+  const pgno_t pgno = mp->mp_pgno;
+  const bool is_dirty = IS_DIRTY(mp);
+
+  if (is_dirty) {
+    mdbx_tassert(txn, !txn->tw.spill_pages ||
+                          !mdbx_pnl_exist(txn->tw.spill_pages, pgno << 1));
+    mdbx_tassert(txn, debug_dpl_find(txn->tw.dirtylist, pgno) == mp ||
+                          txn->mt_parent);
+  } else {
+    mdbx_tassert(txn, !debug_dpl_find(txn->tw.dirtylist, pgno));
+  }
+
+  const unsigned di = is_dirty ? mdbx_dpl_exist(txn->tw.dirtylist, pgno) : 0;
+  const unsigned si = (!is_dirty && txn->tw.spill_pages)
+                          ? mdbx_pnl_exist(txn->tw.spill_pages, pgno << 1)
+                          : 0;
+
+  if (MDBX_ENABLE_REFUND && unlikely(pgno + npages == txn->mt_next_pgno)) {
+    const char *kind;
+    if (di) {
+      mdbx_tassert(txn, txn->tw.dirtylist->items[di].ptr == mp);
+      if (unlikely(txn->tw.dirtylist->items[di].ptr != mp)) {
+      wrong_dirty:
+        mdbx_error("wrong dirty page 0x%p #%" PRIaPGNO,
+                   __Wpedantic_format_voidptr(mp), pgno);
+        txn->mt_flags |= MDBX_TXN_ERROR;
+        return MDBX_PROBLEM;
+      }
+      /* Страница испачкана в этой транзакции, но до этого могла быть
+       * аллоцирована, испачкана и пролита в одной из родительских транзакций.
+       * Её МОЖНО вытолкнуть в нераспределенный хвост. */
+      kind = "dirty";
+      /* Remove from dirty list */
+      mdbx_page_wash(txn, di, mp, npages);
+    } else if (is_dirty) {
+      /* The page MUST BE from parent transaction. */
+      if (mdbx_audit_enabled()) {
+        const MDBX_page *parent_dp = nullptr;
+        for (MDBX_txn *parent = txn->mt_parent; parent && !parent_dp;
+             parent = parent->mt_parent) {
+          mdbx_tassert(txn,
+                       !parent->tw.spill_pages ||
+                           !mdbx_pnl_exist(parent->tw.spill_pages, pgno << 1));
+          parent_dp = debug_dpl_find(parent->tw.dirtylist, pgno);
+        }
+        mdbx_tassert(txn, parent_dp == mp);
+      }
+      kind = "parent-dirty";
+    } else if (si) {
+      /* Страница пролита в этой транзакции, следовательно она аллоцирована
+       * и запачкана в этой или одной из родительских транзакций.
+       * Её МОЖНО вытолкнуть в нераспределенный хвост. */
+      kind = "spilled";
+      mdbx_spill_remove(txn, si, npages);
+    } else {
+      for (MDBX_txn *parent = txn->mt_parent;
+           parent && (parent->mt_flags & MDBX_TXN_SPILLS);
+           parent = parent->mt_parent)
+        if (parent->tw.spill_pages &&
+            mdbx_pnl_exist(parent->tw.spill_pages, pgno << 1)) {
+          /* Страница аллоцирована, запачкана и пролита в одной из родительских
+           * транзакций. Её МОЖНО вытолкнуть в нераспределенный хвост. */
+          kind = "parent-spilled";
+          goto refund;
+        }
+      /* Страница используется (входит в MVCC-снимки доступные читателям).
+       * Её НЕЛЬЗЯ вытолкнуть в нераспределенных хвост. */
+      goto retire;
+    }
+  refund:
+    mdbx_debug("refunded %u %s page %" PRIaPGNO, npages, kind, pgno);
+    txn->mt_next_pgno = pgno;
+    mdbx_refund(txn);
+    return MDBX_SUCCESS;
+  }
+
+  if (is_dirty) {
+    if (di) {
+      /* Dirty page from this transaction */
+      mdbx_tassert(txn, txn->tw.dirtylist->items[di].ptr == mp);
+      if (unlikely(txn->tw.dirtylist->items[di].ptr != mp))
+        goto wrong_dirty;
+
+      /* If suitable we can reuse it through loose list */
+      if (likely(
+              npages == 1 &&
+              txn->tw.loose_count < txn->mt_env->me_options.dp_loose_limit &&
+              (!MDBX_ENABLE_REFUND ||
+               /* skip pages near to the end in favor of compactification */
+               txn->mt_next_pgno >
+                   pgno + txn->mt_env->me_options.dp_loose_limit ||
+               txn->mt_next_pgno <= txn->mt_env->me_options.dp_loose_limit))) {
+        mdbx_debug("loosen dirty page %" PRIaPGNO, pgno);
+        mp->mp_flags = P_LOOSE | P_DIRTY;
+        mp->mp_next = txn->tw.loose_pages;
+        txn->tw.loose_pages = mp;
+        txn->tw.loose_count++;
+#if MDBX_ENABLE_REFUND
+        txn->tw.loose_refund_wl = (pgno + 2 > txn->tw.loose_refund_wl)
+                                      ? pgno + 2
+                                      : txn->tw.loose_refund_wl;
+#endif /* MDBX_ENABLE_REFUND */
+        if (MDBX_DEBUG || unlikely(txn->mt_env->me_flags & MDBX_PAGEPERTURB))
+          memset(page_data(mp), -1, txn->mt_env->me_psize - PAGEHDRSZ);
+        VALGRIND_MAKE_MEM_NOACCESS(page_data(mp),
+                                   txn->mt_env->me_psize - PAGEHDRSZ);
+        ASAN_POISON_MEMORY_REGION(page_data(mp),
+                                  txn->mt_env->me_psize - PAGEHDRSZ);
+        return MDBX_SUCCESS;
+      }
+
+#if !MDBX_DEBUG && !defined(MDBX_USE_VALGRIND) && !defined(__SANITIZE_ADDRESS__)
+      if (unlikely(txn->mt_env->me_flags & MDBX_PAGEPERTURB))
+#endif
+      {
+        /* Страница могла быть изменена в одной из родительских транзакций,
+         * в том числе, позже выгружена и затем снова загружена и изменена.
+         * В обоих случаях её нельзя затирать на диске и помечать недоступной
+         * в asan и/или valgrind */
+        for (MDBX_txn *parent = txn->mt_parent;
+             parent && (parent->mt_flags & MDBX_TXN_SPILLS);
+             parent = parent->mt_parent) {
+          if (parent->tw.spill_pages &&
+              mdbx_pnl_intersect(parent->tw.spill_pages, pgno << 1,
+                                 npages << 1))
+            goto skip_invalidate;
+          if (mdbx_dpl_intersect(parent->tw.dirtylist, pgno, npages))
+            goto skip_invalidate;
+        }
+
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+        if (MDBX_DEBUG || unlikely(txn->mt_env->me_flags & MDBX_PAGEPERTURB))
+#endif
+          mdbx_kill_page(txn->mt_env, mp, pgno, npages);
+        if (!(txn->mt_flags & MDBX_WRITEMAP)) {
+          VALGRIND_MAKE_MEM_NOACCESS(page_data(pgno2page(txn->mt_env, pgno)),
+                                     pgno2bytes(txn->mt_env, npages) -
+                                         PAGEHDRSZ);
+          ASAN_POISON_MEMORY_REGION(page_data(pgno2page(txn->mt_env, pgno)),
+                                    pgno2bytes(txn->mt_env, npages) -
+                                        PAGEHDRSZ);
+        }
+      }
+    skip_invalidate:
+      /* Remove from dirty list */
+      mdbx_page_wash(txn, di, mp, npages);
+    } else {
+      /* Dirty page MUST BE a clone from (one of) parent transaction(s). */
+      if (mdbx_audit_enabled()) {
+        const MDBX_page *parent_dp = nullptr;
+        /* Check parent(s)'s dirty lists. */
+        for (MDBX_txn *parent = txn->mt_parent; parent && !parent_dp;
+             parent = parent->mt_parent) {
+          mdbx_tassert(txn,
+                       !parent->tw.spill_pages ||
+                           !mdbx_pnl_exist(parent->tw.spill_pages, pgno << 1));
+          parent_dp = debug_dpl_find(parent->tw.dirtylist, pgno);
+        }
+        mdbx_tassert(txn, parent_dp == mp);
+      }
+    }
+
+  reclaim:
+    mdbx_debug("reclaim %u %s page %" PRIaPGNO, npages, "dirty", pgno);
+    int rc = mdbx_pnl_insert_range(&txn->tw.reclaimed_pglist, pgno, npages);
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+    return rc;
+  }
+
+  if (si) {
+    /* Page ws spilled in this txn */
+    mdbx_spill_remove(txn, si, npages);
+    /* Страница могла быть выделена и затем пролита в этой транзакции,
+     * тогда её необходимо поместить в reclaimed-список.
+     * Либо она могла быть выделена в одной из родительских транзакций и затем
+     * пролита в этой транзакции, тогда её необходимо поместить в retired-список
+     * для последующей фильтрации при коммите. */
+    for (MDBX_txn *parent = txn->mt_parent; parent;
+         parent = parent->mt_parent) {
+      if (mdbx_dpl_exist(parent->tw.dirtylist, pgno))
+        goto retire;
+    }
+    /* Страница точно была выделена в этой транзакции
+     * и теперь может быть использована повторно. */
+    goto reclaim;
+  } else {
+    /* Страница может входить в доступный читателям MVCC-снимок, либо же она
+     * могла быть выделена, а затем пролита в одной из родительских транзакций.
+     * Поэтому пока помещаем её в retired-список, который будет фильтроваться
+     * относительно dirty- и spilled-списков родительских транзакций при коммите
+     * дочерних транзакций, либо же будет записан в GC в неизменном виде. */
+  }
+
+retire:
+  mdbx_debug("retire %u page %" PRIaPGNO, npages, pgno);
+  int rc = mdbx_pnl_append_range(false, &txn->tw.retired_pages, pgno, npages);
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  return rc;
+}
+
+static int mdbx_page_retire(MDBX_cursor *mc, MDBX_page *mp) {
+  if (unlikely(mc->mc_flags & C_SUB)) {
+    MDBX_db *outer = mdbx_outer_db(mc);
+    mdbx_cassert(mc, !IS_BRANCH(mp) || outer->md_branch_pages > 0);
+    outer->md_branch_pages -= IS_BRANCH(mp);
+    mdbx_cassert(mc, !IS_LEAF(mp) || outer->md_leaf_pages > 0);
+    outer->md_leaf_pages -= IS_LEAF(mp);
+    mdbx_cassert(mc, !IS_OVERFLOW(mp));
+  }
+  mdbx_cassert(mc, !IS_BRANCH(mp) || mc->mc_db->md_branch_pages > 0);
+  mc->mc_db->md_branch_pages -= IS_BRANCH(mp);
+  mdbx_cassert(mc, !IS_LEAF(mp) || mc->mc_db->md_leaf_pages > 0);
+  mc->mc_db->md_leaf_pages -= IS_LEAF(mp);
+  mdbx_cassert(mc, !IS_OVERFLOW(mp) ||
+                       mc->mc_db->md_overflow_pages >= mp->mp_pages);
+  mc->mc_db->md_overflow_pages -= IS_OVERFLOW(mp) ? mp->mp_pages : 0;
+  return mdbx_page_loose(mc->mc_txn, mp);
+}
+
+static __must_check_result __always_inline int
+mdbx_retire_pgno(MDBX_cursor *mc, const pgno_t pgno) {
+  MDBX_page *mp;
+  int rc;
+  if (mdbx_audit_enabled()) {
+    const unsigned save_flags = mc->mc_flags;
+    mc->mc_flags |= C_RETIRING;
+    rc = mdbx_page_get(mc, pgno, &mp, NULL, mc->mc_txn->mt_txnid);
+    if (likely(rc == MDBX_SUCCESS))
+      rc = mdbx_page_retire(mc, mp);
+    mc->mc_flags = (mc->mc_flags & ~C_RETIRING) | (save_flags & C_RETIRING);
+  } else {
+    rc = mdbx_page_get(mc, pgno, &mp, NULL, mc->mc_txn->mt_txnid);
+    if (likely(rc == MDBX_SUCCESS))
+      rc = mdbx_page_retire(mc, mp);
+  }
+  return rc;
+}
+
+/* Toggle P_KEEP in dirty, non-overflow, non-sub pages watched by txn.
+ *
+ * [in] mc      A cursor handle for the current operation.
+ * [in] pflags  Flags of the pages to update:
+ *                - P_DIRTY to set P_KEEP,
+ *                - P_DIRTY|P_KEEP to clear it. */
+static void mdbx_cursor_xkeep(MDBX_cursor *mc, unsigned pflags) {
+  const unsigned mask = P_SUBP | P_DIRTY | P_LOOSE | P_KEEP;
+  if (mc->mc_flags & C_INITIALIZED) {
+    MDBX_cursor *m3 = mc;
+    for (;;) {
+      MDBX_page *mp = NULL;
+      for (unsigned j = 0; j < m3->mc_snum; j++) {
+        mp = m3->mc_pg[j];
+        if ((mp->mp_flags & mask) == pflags)
+          mp->mp_flags ^= P_KEEP;
+      }
+      if (!(mp && IS_LEAF(mp)))
+        break;
+      /* Proceed to mx if it is at a sub-database */
+      MDBX_xcursor *mx = m3->mc_xcursor;
+      if (!(mx && (mx->mx_cursor.mc_flags & C_INITIALIZED)))
+        break;
+      const unsigned nkeys = page_numkeys(mp);
+      unsigned ki = m3->mc_ki[m3->mc_top];
+      mdbx_cassert(mc, nkeys > 0 &&
+                           (ki < nkeys ||
+                            (ki == nkeys && (mx->mx_cursor.mc_flags & C_EOF))));
+      ki -= ki >= nkeys;
+      if (!(node_flags(page_node(mp, ki)) & F_SUBDATA))
+        break;
+      m3 = &mx->mx_cursor;
+    }
+  }
+}
+
+/* Mark pages seen by cursors: First m0, then tracked cursors
+ * [in] all     No shortcuts. Needed except after a full mdbx_page_flush(). */
+static void mdbx_txn_xkeep(MDBX_txn *txn, MDBX_cursor *m0,
+                           const unsigned pflags, const bool all) {
+  if (m0)
+    mdbx_cursor_xkeep(m0, pflags);
+
+  for (unsigned i = FREE_DBI; i < txn->mt_numdbs; ++i)
+    if (txn->mt_dbistate[i] & DBI_DIRTY)
+      for (MDBX_cursor *mc = txn->tw.cursors[i]; mc; mc = mc->mc_next)
+        if (mc != m0)
+          mdbx_cursor_xkeep(mc, pflags);
+
+  if (all) {
+    /* Mark dirty root pages */
+    const unsigned mask = P_SUBP | P_DIRTY | P_LOOSE | P_KEEP;
+    for (unsigned i = 0; i < txn->mt_numdbs; i++) {
+      if (txn->mt_dbistate[i] & DBI_DIRTY) {
+        pgno_t pgno = txn->mt_dbs[i].md_root;
+        if (pgno == P_INVALID)
+          continue;
+        MDBX_page *dp = mdbx_dpl_find(txn->tw.dirtylist, pgno);
+        if (dp && (dp->mp_flags & mask) == pflags)
+          dp->mp_flags ^= P_KEEP;
+      }
+    }
+  }
+}
+
+/* Spill pages from the dirty list back to disk.
+ * This is intended to prevent running into MDBX_TXN_FULL situations,
+ * but note that they may still occur in a few cases:
+ *
+ * 1) our estimate of the txn size could be too small. Currently this
+ *  seems unlikely, except with a large number of MDBX_MULTIPLE items.
+ *
+ * 2) child txns may run out of space if their parents dirtied a
+ *  lot of pages and never spilled them. TODO: we probably should do
+ *  a preemptive spill during mdbx_txn_begin() of a child txn, if
+ *  the parent's dirtyroom is below a given threshold.
+ *
+ * Otherwise, if not using nested txns, it is expected that apps will
+ * not run into MDBX_TXN_FULL any more. The pages are flushed to disk
+ * the same way as for a txn commit, e.g. their P_DIRTY flag is cleared.
+ * If the txn never references them again, they can be left alone.
+ * If the txn only reads them, they can be used without any fuss.
+ * If the txn writes them again, they can be dirtied immediately without
+ * going thru all of the work of mdbx_page_touch(). Such references are
+ * handled by mdbx_page_unspill().
+ *
+ * Also note, we never spill DB root pages, nor pages of active cursors,
+ * because we'll need these back again soon anyway. And in nested txns,
+ * we can't spill a page in a child txn if it was already spilled in a
+ * parent txn. That would alter the parent txns' data even though
+ * the child hasn't committed yet, and we'd have no way to undo it if
+ * the child aborted. */
+static int mdbx_txn_spill(MDBX_txn *txn, MDBX_cursor *m0, unsigned need) {
+#ifndef MDBX_DEBUG_SPILLING
+  if (likely(txn->tw.dirtyroom > need))
+    return MDBX_SUCCESS;
+  unsigned spill = need - txn->tw.dirtyroom;
+#else
+  /* spill at least one page if defined MDBX_DEBUG_SPILLING */
+  unsigned spill = (need > txn->tw.dirtyroom) ? need - txn->tw.dirtyroom : 1;
+#endif /* MDBX_DEBUG_SPILLING */
+
+  const unsigned dirty = txn->tw.dirtylist->length;
+  const unsigned spill_min =
+      txn->mt_env->me_options.spill_min_denominator
+          ? dirty / txn->mt_env->me_options.spill_min_denominator
+          : 0;
+  const unsigned spill_max =
+      dirty - (txn->mt_env->me_options.spill_max_denominator
+                   ? dirty / txn->mt_env->me_options.spill_max_denominator
+                   : 0);
+  spill = (spill > spill_min) ? spill : spill_min;
+  spill = (spill < spill_max) ? spill : spill_max;
+  if (!spill)
+    return MDBX_SUCCESS;
+
+  mdbx_notice("spilling %u dirty-entries (have %u dirty-room, need %u)", spill,
+              txn->tw.dirtyroom, need);
+  mdbx_tassert(txn, txn->tw.dirtylist->length >= spill);
+
+  int rc;
+  if (!txn->tw.spill_pages) {
+    txn->tw.spill_least_removed = INT_MAX;
+    txn->tw.spill_pages = mdbx_pnl_alloc(spill);
+    if (unlikely(!txn->tw.spill_pages)) {
+      rc = MDBX_ENOMEM;
+      goto bailout;
+    }
+  } else {
+    /* purge deleted slots */
+    mdbx_spill_purge(txn);
+    rc = mdbx_pnl_reserve(&txn->tw.spill_pages, spill);
+    (void)rc /* ignore since the resulting list may be shorter
+     and mdbx_pnl_append() will increase pnl on demand */
+        ;
+  }
+
+  /* Preserve pages which may soon be dirtied again */
+  mdbx_txn_xkeep(txn, m0, P_DIRTY, true);
+
+  MDBX_dpl *const dl = mdbx_dpl_sort(txn->tw.dirtylist);
+  /* Save the page IDs of all the pages we're flushing */
+  /* flush from the tail forward, this saves a lot of shifting later on. */
+  const unsigned dl_len_before = dl->length;
+  unsigned spilled = 0;
+  unsigned keep = dl_len_before;
+  for (; keep && spill; keep--) {
+    const pgno_t pgno = dl->items[keep].pgno;
+    MDBX_page *dp = dl->items[keep].ptr;
+    const unsigned npages = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+    if (dp->mp_flags & (P_LOOSE | P_KEEP)) {
+      mdbx_debug("skip %s %u page %" PRIaPGNO,
+                 (dp->mp_flags & P_LOOSE) ? "loose" : "keep", npages,
+                 dp->mp_pgno);
+    skip:
+      continue;
+    }
+    /* Can't spill twice,
+     * make sure it's not already in a parent's spill list(s). */
+    MDBX_txn *parent = txn->mt_parent;
+    if (parent && (parent->mt_flags & MDBX_TXN_SPILLS)) {
+      do
+        if (parent->tw.spill_pages &&
+            mdbx_pnl_intersect(parent->tw.spill_pages, pgno << 1,
+                               npages << 1)) {
+          mdbx_debug("skip parent-spilled %u page %" PRIaPGNO, npages, pgno);
+          dp->mp_flags |= P_KEEP;
+          goto skip;
+        }
+      while ((parent = parent->mt_parent) != nullptr);
+    }
+    mdbx_debug("spill %u page %" PRIaPGNO, npages, dp->mp_pgno);
+    rc = mdbx_pnl_append_range(true, &txn->tw.spill_pages, pgno << 1, npages);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto bailout;
+    spill--;
+    spilled += 1;
+  }
+  mdbx_pnl_sort(txn->tw.spill_pages);
+
+  /* Flush the spilled part of dirty list */
+  rc = mdbx_page_flush(txn, keep);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout;
+
+  /* Reset any dirty pages we kept that page_flush didn't see */
+  mdbx_tassert(txn, dl_len_before - spilled == dl->length);
+  mdbx_txn_xkeep(txn, m0, P_DIRTY | P_KEEP, keep > 0);
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+
+bailout:
+  txn->mt_flags |= rc ? MDBX_TXN_ERROR : MDBX_TXN_SPILLS;
+  return rc;
+}
+
+static int mdbx_cursor_spill(MDBX_cursor *mc, const MDBX_val *key,
+                             const MDBX_val *data) {
+  if (mc->mc_flags & C_SUB)
+    return MDBX_SUCCESS;
+  MDBX_txn *txn = mc->mc_txn;
+  if (txn->mt_flags & MDBX_WRITEMAP)
+    return MDBX_SUCCESS;
+
+  /* Estimate how much space this operation will take: */
+  /* 1) Max b-tree height, reasonable enough with including dups' sub-tree */
+  unsigned need = CURSOR_STACK + 3;
+  /* 2) GC/FreeDB for any payload */
+  if (mc->mc_dbi > FREE_DBI) {
+    need += txn->mt_dbs[FREE_DBI].md_depth + 3;
+    /* 3) Named DBs also dirty the main DB */
+    if (mc->mc_dbi > MAIN_DBI)
+      need += txn->mt_dbs[MAIN_DBI].md_depth + 3;
+  }
+  /* 4) Factor the key+data which to be put in */
+  need += bytes2pgno(txn->mt_env, node_size(key, data)) + 1;
+  return mdbx_txn_spill(txn, mc, need);
+}
+
+/*----------------------------------------------------------------------------*/
+
+static __always_inline bool meta_bootid_match(const MDBX_meta *meta) {
+  return memcmp(&meta->mm_bootid, &bootid, 16) == 0 &&
+         (bootid.x | bootid.y) != 0;
+}
+
+static bool meta_weak_acceptable(const MDBX_env *env, const MDBX_meta *meta,
+                                 const int lck_exclusive) {
+  return lck_exclusive ? /* exclusive lock */ meta_bootid_match(meta)
+                       : /* db already opened */ env->me_lck &&
+                             (env->me_lck->mti_envmode.weak & MDBX_RDONLY) == 0;
+}
+
+#define METAPAGE(env, n) page_meta(pgno2page(env, n))
+#define METAPAGE_END(env) METAPAGE(env, NUM_METAS)
+
+static __inline txnid_t meta_txnid(const MDBX_env *env, const MDBX_meta *meta,
+                                   const bool allow_volatile) {
+  mdbx_memory_fence(mo_AcquireRelease, false);
+  txnid_t a = unaligned_peek_u64(4, &meta->mm_txnid_a);
+  txnid_t b = unaligned_peek_u64(4, &meta->mm_txnid_b);
+  if (allow_volatile)
+    return (a == b) ? a : 0;
+  mdbx_assert(env, a == b);
+  return a;
+}
+
+static __inline txnid_t mdbx_meta_txnid_stable(const MDBX_env *env,
+                                               const MDBX_meta *meta) {
+  return meta_txnid(env, meta, false);
+}
+
+static __inline txnid_t mdbx_meta_txnid_fluid(const MDBX_env *env,
+                                              const MDBX_meta *meta) {
+  return meta_txnid(env, meta, true);
+}
+
+static __inline void mdbx_meta_update_begin(const MDBX_env *env,
+                                            MDBX_meta *meta, txnid_t txnid) {
+  mdbx_assert(env, meta >= METAPAGE(env, 0) && meta < METAPAGE_END(env));
+  mdbx_assert(env, unaligned_peek_u64(4, meta->mm_txnid_a) < txnid &&
+                       unaligned_peek_u64(4, meta->mm_txnid_b) < txnid);
+  (void)env;
+  unaligned_poke_u64(4, meta->mm_txnid_b, 0);
+  mdbx_memory_fence(mo_AcquireRelease, true);
+  unaligned_poke_u64(4, meta->mm_txnid_a, txnid);
+}
+
+static __inline void mdbx_meta_update_end(const MDBX_env *env, MDBX_meta *meta,
+                                          txnid_t txnid) {
+  mdbx_assert(env, meta >= METAPAGE(env, 0) && meta < METAPAGE_END(env));
+  mdbx_assert(env, unaligned_peek_u64(4, meta->mm_txnid_a) == txnid);
+  mdbx_assert(env, unaligned_peek_u64(4, meta->mm_txnid_b) < txnid);
+  (void)env;
+  mdbx_jitter4testing(true);
+  memcpy(&meta->mm_bootid, &bootid, 16);
+  unaligned_poke_u64(4, meta->mm_txnid_b, txnid);
+  mdbx_memory_fence(mo_AcquireRelease, true);
+}
+
+static __inline void mdbx_meta_set_txnid(const MDBX_env *env, MDBX_meta *meta,
+                                         txnid_t txnid) {
+  mdbx_assert(env, !env->me_map || meta < METAPAGE(env, 0) ||
+                       meta >= METAPAGE_END(env));
+  (void)env;
+  /* update inconsistent since this function used ONLY for filling meta-image
+   * for writing, but not the actual meta-page */
+  memcpy(&meta->mm_bootid, &bootid, 16);
+  unaligned_poke_u64(4, meta->mm_txnid_a, txnid);
+  unaligned_poke_u64(4, meta->mm_txnid_b, txnid);
+}
+
+static __inline uint64_t mdbx_meta_sign(const MDBX_meta *meta) {
+  uint64_t sign = MDBX_DATASIGN_NONE;
+#if 0 /* TODO */
+  sign = hippeus_hash64(...);
+#else
+  (void)meta;
+#endif
+  /* LY: newer returns MDBX_DATASIGN_NONE or MDBX_DATASIGN_WEAK */
+  return (sign > MDBX_DATASIGN_WEAK) ? sign : ~sign;
+}
+
+enum meta_choise_mode { prefer_last, prefer_steady };
+
+static __inline bool mdbx_meta_ot(const enum meta_choise_mode mode,
+                                  const MDBX_env *env, const MDBX_meta *a,
+                                  const MDBX_meta *b) {
+  mdbx_jitter4testing(true);
+  txnid_t txnid_a = mdbx_meta_txnid_fluid(env, a);
+  txnid_t txnid_b = mdbx_meta_txnid_fluid(env, b);
+
+  mdbx_jitter4testing(true);
+  switch (mode) {
+  default:
+    assert(false);
+    __unreachable();
+    /* fall through */
+    __fallthrough;
+  case prefer_steady:
+    if (META_IS_STEADY(a) != META_IS_STEADY(b))
+      return META_IS_STEADY(b);
+    /* fall through */
+    __fallthrough;
+  case prefer_last:
+    mdbx_jitter4testing(true);
+    if (txnid_a == txnid_b)
+      return META_IS_STEADY(b);
+    return txnid_a < txnid_b;
+  }
+}
+
+static __inline bool mdbx_meta_eq(const MDBX_env *env, const MDBX_meta *a,
+                                  const MDBX_meta *b) {
+  mdbx_jitter4testing(true);
+  const txnid_t txnid = mdbx_meta_txnid_fluid(env, a);
+  if (!txnid || txnid != mdbx_meta_txnid_fluid(env, b))
+    return false;
+
+  mdbx_jitter4testing(true);
+  if (META_IS_STEADY(a) != META_IS_STEADY(b))
+    return false;
+
+  mdbx_jitter4testing(true);
+  return true;
+}
+
+static int mdbx_meta_eq_mask(const MDBX_env *env) {
+  MDBX_meta *m0 = METAPAGE(env, 0);
+  MDBX_meta *m1 = METAPAGE(env, 1);
+  MDBX_meta *m2 = METAPAGE(env, 2);
+
+  int rc = mdbx_meta_eq(env, m0, m1) ? 1 : 0;
+  if (mdbx_meta_eq(env, m1, m2))
+    rc += 2;
+  if (mdbx_meta_eq(env, m2, m0))
+    rc += 4;
+  return rc;
+}
+
+static __inline MDBX_meta *mdbx_meta_recent(const enum meta_choise_mode mode,
+                                            const MDBX_env *env, MDBX_meta *a,
+                                            MDBX_meta *b) {
+  const bool a_older_that_b = mdbx_meta_ot(mode, env, a, b);
+  mdbx_assert(env, !mdbx_meta_eq(env, a, b));
+  return a_older_that_b ? b : a;
+}
+
+static __inline MDBX_meta *mdbx_meta_ancient(const enum meta_choise_mode mode,
+                                             const MDBX_env *env, MDBX_meta *a,
+                                             MDBX_meta *b) {
+  const bool a_older_that_b = mdbx_meta_ot(mode, env, a, b);
+  mdbx_assert(env, !mdbx_meta_eq(env, a, b));
+  return a_older_that_b ? a : b;
+}
+
+static __inline MDBX_meta *
+mdbx_meta_mostrecent(const enum meta_choise_mode mode, const MDBX_env *env) {
+  MDBX_meta *m0 = METAPAGE(env, 0);
+  MDBX_meta *m1 = METAPAGE(env, 1);
+  MDBX_meta *m2 = METAPAGE(env, 2);
+
+  MDBX_meta *head = mdbx_meta_recent(mode, env, m0, m1);
+  head = mdbx_meta_recent(mode, env, head, m2);
+  return head;
+}
+
+static MDBX_meta *mdbx_meta_steady(const MDBX_env *env) {
+  return mdbx_meta_mostrecent(prefer_steady, env);
+}
+
+static MDBX_meta *mdbx_meta_head(const MDBX_env *env) {
+  return mdbx_meta_mostrecent(prefer_last, env);
+}
+
+static txnid_t mdbx_recent_committed_txnid(const MDBX_env *env) {
+  while (true) {
+    const MDBX_meta *head = mdbx_meta_head(env);
+    const txnid_t recent = mdbx_meta_txnid_fluid(env, head);
+    mdbx_compiler_barrier();
+    if (likely(head == mdbx_meta_head(env) &&
+               recent == mdbx_meta_txnid_fluid(env, head)))
+      return recent;
+  }
+}
+
+static txnid_t mdbx_recent_steady_txnid(const MDBX_env *env) {
+  while (true) {
+    const MDBX_meta *head = mdbx_meta_steady(env);
+    const txnid_t recent = mdbx_meta_txnid_fluid(env, head);
+    mdbx_compiler_barrier();
+    if (likely(head == mdbx_meta_steady(env) &&
+               recent == mdbx_meta_txnid_fluid(env, head)))
+      return recent;
+  }
+}
+
+static const char *mdbx_durable_str(const MDBX_meta *const meta) {
+  if (META_IS_STEADY(meta))
+    return (unaligned_peek_u64(4, meta->mm_datasync_sign) ==
+            mdbx_meta_sign(meta))
+               ? "Steady"
+               : "Tainted";
+  return "Weak";
+}
+
+/*----------------------------------------------------------------------------*/
+
+/* Find oldest txnid still referenced. */
+static txnid_t mdbx_find_oldest(const MDBX_txn *txn) {
+  mdbx_tassert(txn, (txn->mt_flags & MDBX_TXN_RDONLY) == 0);
+  MDBX_env *env = txn->mt_env;
+  const txnid_t edge = mdbx_recent_steady_txnid(env);
+  mdbx_tassert(txn, edge <= txn->mt_txnid);
+
+  MDBX_lockinfo *const lck = env->me_lck;
+  if (unlikely(lck == NULL /* exclusive mode */))
+    return atomic_store64(&env->me_lckless_stub.oldest, edge,
+                          mo_AcquireRelease);
+
+  const txnid_t last_oldest =
+      atomic_load64(&lck->mti_oldest_reader, mo_AcquireRelease);
+  mdbx_tassert(txn, edge >= last_oldest);
+  if (likely(last_oldest == edge))
+    return edge;
+
+  const uint32_t nothing_changed = MDBX_STRING_TETRAD("None");
+  const uint32_t snap_readers_refresh_flag =
+      atomic_load32(&lck->mti_readers_refresh_flag, mo_AcquireRelease);
+  mdbx_jitter4testing(false);
+  if (snap_readers_refresh_flag == nothing_changed)
+    return last_oldest;
+
+  txnid_t oldest = edge;
+  atomic_store32(&lck->mti_readers_refresh_flag, nothing_changed,
+                 mo_AcquireRelease);
+  const unsigned snap_nreaders =
+      atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+  for (unsigned i = 0; i < snap_nreaders; ++i) {
+    if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease)) {
+      /* mdbx_jitter4testing(true); */
+      const txnid_t snap = safe64_read(&lck->mti_readers[i].mr_txnid);
+      if (oldest > snap && last_oldest <= /* ignore pending updates */ snap) {
+        oldest = snap;
+        if (oldest == last_oldest)
+          return oldest;
+      }
+    }
+  }
+
+  if (oldest != last_oldest) {
+    mdbx_notice("update oldest %" PRIaTXN " -> %" PRIaTXN, last_oldest, oldest);
+    mdbx_tassert(txn, oldest >= lck->mti_oldest_reader.weak);
+    atomic_store64(&lck->mti_oldest_reader, oldest, mo_AcquireRelease);
+  }
+  return oldest;
+}
+
+/* Find largest mvcc-snapshot still referenced. */
+static __cold pgno_t mdbx_find_largest(MDBX_env *env, pgno_t largest) {
+  MDBX_lockinfo *const lck = env->me_lck;
+  if (likely(lck != NULL /* exclusive mode */)) {
+    const unsigned snap_nreaders =
+        atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+    for (unsigned i = 0; i < snap_nreaders; ++i) {
+    retry:
+      if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease)) {
+        /* mdbx_jitter4testing(true); */
+        const pgno_t snap_pages = atomic_load32(
+            &lck->mti_readers[i].mr_snapshot_pages_used, mo_Relaxed);
+        const txnid_t snap_txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
+        if (unlikely(
+                snap_pages !=
+                    atomic_load32(&lck->mti_readers[i].mr_snapshot_pages_used,
+                                  mo_AcquireRelease) ||
+                snap_txnid != safe64_read(&lck->mti_readers[i].mr_txnid)))
+          goto retry;
+        if (largest < snap_pages &&
+            atomic_load64(&lck->mti_oldest_reader, mo_AcquireRelease) <=
+                /* ignore pending updates */ snap_txnid &&
+            snap_txnid <= env->me_txn0->mt_txnid)
+          largest = snap_pages;
+      }
+    }
+  }
+
+  return largest;
+}
+
+/* Add a page to the txn's dirty list */
+static int __must_check_result mdbx_page_dirty(MDBX_txn *txn, MDBX_page *mp) {
+  mp->mp_txnid = INVALID_TXNID;
+  mp->mp_flags |= P_DIRTY;
+  if (unlikely(txn->tw.dirtyroom == 0)) {
+    mdbx_error("Dirtyroom is depleted, DPL length %u",
+               txn->tw.dirtylist->length);
+    return MDBX_TXN_FULL;
+  }
+  const int rc = mdbx_dpl_append(txn, mp->mp_pgno, mp);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    txn->mt_flags |= MDBX_TXN_ERROR;
+    return rc;
+  }
+  txn->tw.dirtyroom--;
+  assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+  mdbx_tassert(txn, txn->mt_parent ||
+                        txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                            txn->mt_env->me_options.dp_limit);
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  return MDBX_SUCCESS;
+}
+
+#if !(defined(_WIN32) || defined(_WIN64))
+static __always_inline __maybe_unused int ignore_enosys(int err) {
+#ifdef ENOSYS
+  if (err == ENOSYS)
+    return MDBX_RESULT_TRUE;
+#endif /* ENOSYS */
+#ifdef ENOIMPL
+  if (err == ENOIMPL)
+    return MDBX_RESULT_TRUE;
+#endif /* ENOIMPL */
+#ifdef ENOTSUP
+  if (err == ENOTSUP)
+    return MDBX_RESULT_TRUE;
+#endif /* ENOTSUP */
+#ifdef ENOSUPP
+  if (err == ENOSUPP)
+    return MDBX_RESULT_TRUE;
+#endif /* ENOSUPP */
+#ifdef EOPNOTSUPP
+  if (err == EOPNOTSUPP)
+    return MDBX_RESULT_TRUE;
+#endif /* EOPNOTSUPP */
+  if (err == EAGAIN)
+    return MDBX_RESULT_TRUE;
+  return err;
+}
+#endif /* defined(_WIN32) || defined(_WIN64) */
+
+/* Turn on/off readahead. It's harmful when the DB is larger than RAM. */
+static __cold int mdbx_set_readahead(MDBX_env *env, const size_t offset,
+                                     const size_t length, const bool enable) {
+  assert(length > 0);
+  mdbx_notice("readahead %s %u..%u", enable ? "ON" : "OFF",
+              bytes2pgno(env, offset), bytes2pgno(env, offset + length));
+
+#if defined(F_RDAHEAD)
+  if (unlikely(fcntl(env->me_lazy_fd, F_RDAHEAD, enable) == -1))
+    return errno;
+#endif /* F_RDAHEAD */
+
+  if (enable) {
+#if defined(F_RDADVISE)
+    struct radvisory hint;
+    hint.ra_offset = offset;
+    hint.ra_count = length;
+    (void)/* Ignore ENOTTY for DB on the ram-disk and so on */ fcntl(
+        env->me_lazy_fd, F_RDADVISE, &hint);
+#endif /* F_RDADVISE */
+#if defined(MADV_WILLNEED)
+    int err = madvise(env->me_map + offset, length, MADV_WILLNEED)
+                  ? ignore_enosys(errno)
+                  : MDBX_SUCCESS;
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(POSIX_MADV_WILLNEED)
+    int err = ignore_enosys(
+        posix_madvise(env->me_map + offset, length, POSIX_MADV_WILLNEED));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(_WIN32) || defined(_WIN64)
+    if (mdbx_PrefetchVirtualMemory) {
+      WIN32_MEMORY_RANGE_ENTRY hint;
+      hint.VirtualAddress = env->me_map + offset;
+      hint.NumberOfBytes = length;
+      (void)mdbx_PrefetchVirtualMemory(GetCurrentProcess(), 1, &hint, 0);
+    }
+#elif defined(POSIX_FADV_WILLNEED)
+    int err = ignore_enosys(
+        posix_fadvise(env->me_lazy_fd, offset, length, POSIX_FADV_WILLNEED));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#endif /* MADV_WILLNEED */
+  } else {
+#if defined(MADV_RANDOM)
+    int err = madvise(env->me_map + offset, length, MADV_RANDOM)
+                  ? ignore_enosys(errno)
+                  : MDBX_SUCCESS;
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(POSIX_MADV_RANDOM)
+    int err = ignore_enosys(
+        posix_madvise(env->me_map + offset, length, POSIX_MADV_RANDOM));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(POSIX_FADV_RANDOM)
+    int err = ignore_enosys(
+        posix_fadvise(env->me_lazy_fd, offset, length, POSIX_FADV_RANDOM));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#endif /* MADV_RANDOM */
+  }
+  return MDBX_SUCCESS;
+}
+
+static __cold int mdbx_mapresize(MDBX_env *env, const pgno_t used_pgno,
+                                 const pgno_t size_pgno,
+                                 const pgno_t limit_pgno, const bool implicit) {
+  if ((env->me_flags & MDBX_WRITEMAP) && env->me_unsynced_pages->weak) {
+    int err = mdbx_msync(&env->me_dxb_mmap, 0,
+                         pgno_align2os_bytes(env, used_pgno), true);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+  }
+
+  const size_t limit_bytes = pgno_align2os_bytes(env, limit_pgno);
+  const size_t size_bytes = pgno_align2os_bytes(env, size_pgno);
+  const size_t prev_size = env->me_dxb_mmap.current;
+  const size_t prev_limit = env->me_dxb_mmap.limit;
+  const void *const prev_addr = env->me_map;
+
+  mdbx_verbose("resize datafile/mapping: "
+               "present %" PRIuPTR " -> %" PRIuPTR ", "
+               "limit %" PRIuPTR " -> %" PRIuPTR,
+               prev_size, size_bytes, prev_limit, limit_bytes);
+
+  mdbx_assert(env, limit_bytes >= size_bytes);
+  mdbx_assert(env, bytes2pgno(env, size_bytes) >= size_pgno);
+  mdbx_assert(env, bytes2pgno(env, limit_bytes) >= limit_pgno);
+
+#if defined(_WIN32) || defined(_WIN64)
+  /* Acquire guard in exclusive mode for:
+   *   - to avoid collision between read and write txns around env->me_dbgeo;
+   *   - to avoid attachment of new reading threads (see mdbx_rdt_lock); */
+  mdbx_srwlock_AcquireExclusive(&env->me_remap_guard);
+  mdbx_handle_array_t *suspended = NULL;
+  mdbx_handle_array_t array_onstack;
+  int rc = MDBX_SUCCESS;
+  if (limit_bytes == env->me_dxb_mmap.limit &&
+      size_bytes == env->me_dxb_mmap.current &&
+      size_bytes == env->me_dxb_mmap.filesize)
+    goto bailout;
+
+  /* 1) Windows allows only extending a read-write section, but not a
+   *    corresponding mapped view. Therefore in other cases we must suspend
+   *    the local threads for safe remap.
+   * 2) At least on Windows 10 1803 the entire mapped section is unavailable
+   *    for short time during NtExtendSection() or VirtualAlloc() execution.
+   * 3) Under Wine runtime environment on Linux a section extending is not
+   *    supported. Therefore thread suspending is always required.
+   *
+   * THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED! */
+  array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
+  array_onstack.count = 0;
+  suspended = &array_onstack;
+  rc = mdbx_suspend_threads_before_remap(env, &suspended);
+  if (rc != MDBX_SUCCESS) {
+    mdbx_error("failed suspend-for-remap: errcode %d", rc);
+    goto bailout;
+  }
+  const bool mapping_can_be_moved = !implicit;
+#else /* Windows */
+  /* Acquire guard to avoid collision between read and write txns
+   * around env->me_dbgeo */
+  bool mapping_can_be_moved = false;
+  int rc = mdbx_fastmutex_acquire(&env->me_remap_guard);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  if (limit_bytes == env->me_dxb_mmap.limit &&
+      size_bytes == env->me_dxb_mmap.current)
+    goto bailout;
+
+  if (limit_bytes != env->me_dxb_mmap.limit && env->me_lck && !implicit) {
+    int err = mdbx_rdt_lock(env) /* lock readers table until remap done */;
+    if (unlikely(MDBX_IS_ERROR(err))) {
+      rc = err;
+      goto bailout;
+    }
+
+    /* looking for readers from this process */
+    MDBX_lockinfo *const lck = env->me_lck;
+    const unsigned snap_nreaders =
+        atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+    mapping_can_be_moved = true;
+    for (unsigned i = 0; i < snap_nreaders; ++i) {
+      if (lck->mti_readers[i].mr_pid.weak == env->me_pid &&
+          lck->mti_readers[i].mr_tid.weak != mdbx_thread_self()) {
+        /* the base address of the mapping can't be changed since
+         * the other reader thread from this process exists. */
+        mdbx_rdt_unlock(env);
+        mapping_can_be_moved = false;
+        break;
+      }
+    }
+  }
+
+#endif /* ! Windows */
+
+  if (size_bytes < prev_size) {
+    mdbx_notice("resize-MADV_%s %u..%u",
+                (env->me_flags & MDBX_WRITEMAP) ? "REMOVE" : "DONTNEED",
+                size_pgno, bytes2pgno(env, prev_size));
+    rc = MDBX_RESULT_TRUE;
+#if defined(MADV_REMOVE)
+    if (env->me_flags & MDBX_WRITEMAP)
+      rc =
+          madvise(env->me_map + size_bytes, prev_size - size_bytes, MADV_REMOVE)
+              ? ignore_enosys(errno)
+              : MDBX_SUCCESS;
+#endif /* MADV_REMOVE */
+#if defined(MADV_DONTNEED)
+    if (rc == MDBX_RESULT_TRUE)
+      rc = madvise(env->me_map + size_bytes, prev_size - size_bytes,
+                   MADV_DONTNEED)
+               ? ignore_enosys(errno)
+               : MDBX_SUCCESS;
+#elif defined(POSIX_MADV_DONTNEED)
+    if (rc == MDBX_RESULT_TRUE)
+      rc = ignore_enosys(posix_madvise(env->me_map + size_bytes,
+                                       prev_size - size_bytes,
+                                       POSIX_MADV_DONTNEED));
+#elif defined(POSIX_FADV_DONTNEED)
+    if (rc == MDBX_RESULT_TRUE)
+      rc = ignore_enosys(posix_fadvise(env->me_lazy_fd, size_bytes,
+                                       prev_size - size_bytes,
+                                       POSIX_FADV_DONTNEED));
+#endif /* MADV_DONTNEED */
+    if (unlikely(MDBX_IS_ERROR(rc)))
+      goto bailout;
+    if (env->me_discarded_tail->weak > size_pgno)
+      env->me_discarded_tail->weak = size_pgno;
+  }
+
+  rc = mdbx_mresize(env->me_flags, &env->me_dxb_mmap, size_bytes, limit_bytes,
+                    mapping_can_be_moved);
+  if (rc == MDBX_SUCCESS && (env->me_flags & MDBX_NORDAHEAD) == 0) {
+    const int readahead =
+        mdbx_is_readahead_reasonable(size_bytes, -(intptr_t)prev_size);
+    if (readahead == MDBX_RESULT_FALSE)
+      rc = mdbx_set_readahead(
+          env, 0, (size_bytes > prev_size) ? size_bytes : prev_size, false);
+    else if (readahead == MDBX_RESULT_TRUE) {
+      const size_t readahead_pivot =
+          (limit_bytes != prev_limit || env->me_dxb_mmap.address != prev_addr
+#if defined(_WIN32) || defined(_WIN64)
+           || prev_size > size_bytes
+#endif /* Windows */
+           )
+              ? 0 /* reassign readahead to the entire map
+                     because it was remapped */
+              : prev_size;
+      if (size_bytes > readahead_pivot) {
+        env->me_discarded_tail->weak = size_pgno;
+        rc = mdbx_set_readahead(env, readahead_pivot,
+                                size_bytes - readahead_pivot, true);
+      }
+    }
+  }
+
+bailout:
+  if (rc == MDBX_SUCCESS) {
+#if defined(_WIN32) || defined(_WIN64)
+    mdbx_assert(env, size_bytes == env->me_dxb_mmap.current);
+    mdbx_assert(env, size_bytes <= env->me_dxb_mmap.filesize);
+    mdbx_assert(env, limit_bytes == env->me_dxb_mmap.limit);
+#endif /* Windows */
+#ifdef MDBX_USE_VALGRIND
+    if (prev_limit != env->me_dxb_mmap.limit || prev_addr != env->me_map) {
+      VALGRIND_DISCARD(env->me_valgrind_handle);
+      env->me_valgrind_handle = 0;
+      if (env->me_dxb_mmap.limit)
+        env->me_valgrind_handle =
+            VALGRIND_CREATE_BLOCK(env->me_map, env->me_dxb_mmap.limit, "mdbx");
+    }
+#endif /* MDBX_USE_VALGRIND */
+  } else {
+    if (rc != MDBX_UNABLE_EXTEND_MAPSIZE) {
+      mdbx_error("failed resize datafile/mapping: "
+                 "present %" PRIuPTR " -> %" PRIuPTR ", "
+                 "limit %" PRIuPTR " -> %" PRIuPTR ", errcode %d",
+                 prev_size, size_bytes, prev_limit, limit_bytes, rc);
+    } else {
+      mdbx_warning("unable resize datafile/mapping: "
+                   "present %" PRIuPTR " -> %" PRIuPTR ", "
+                   "limit %" PRIuPTR " -> %" PRIuPTR ", errcode %d",
+                   prev_size, size_bytes, prev_limit, limit_bytes, rc);
+    }
+    if (!env->me_dxb_mmap.address) {
+      env->me_flags |= MDBX_FATAL_ERROR;
+      if (env->me_txn)
+        env->me_txn->mt_flags |= MDBX_TXN_ERROR;
+      rc = MDBX_PANIC;
+    }
+  }
+
+#if defined(_WIN32) || defined(_WIN64)
+  int err = MDBX_SUCCESS;
+  mdbx_srwlock_ReleaseExclusive(&env->me_remap_guard);
+  if (suspended) {
+    err = mdbx_resume_threads_after_remap(suspended);
+    if (suspended != &array_onstack)
+      mdbx_free(suspended);
+  }
+#else
+  if (env->me_lck && mapping_can_be_moved)
+    mdbx_rdt_unlock(env);
+  int err = mdbx_fastmutex_release(&env->me_remap_guard);
+#endif /* Windows */
+  if (err != MDBX_SUCCESS) {
+    mdbx_fatal("failed resume-after-remap: errcode %d", err);
+    return MDBX_PANIC;
+  }
+  return rc;
+}
+
+static __cold int mdbx_mapresize_implicit(MDBX_env *env, const pgno_t used_pgno,
+                                          const pgno_t size_pgno,
+                                          const pgno_t limit_pgno) {
+  const pgno_t mapped_pgno = bytes2pgno(env, env->me_dxb_mmap.limit);
+  mdbx_assert(env, mapped_pgno >= used_pgno);
+  return mdbx_mapresize(
+      env, used_pgno, size_pgno,
+      (size_pgno > mapped_pgno)
+          ? limit_pgno
+          : /* The actual mapsize may be less since the geo.upper may be changed
+               by other process. So, avoids remapping until it necessary. */
+          mapped_pgno,
+      true);
+}
+
+static int mdbx_meta_unsteady(MDBX_env *env, const txnid_t last_steady,
+                              MDBX_meta *const meta) {
+  const uint64_t wipe = MDBX_DATASIGN_NONE;
+  if (unlikely(META_IS_STEADY(meta)) &&
+      mdbx_meta_txnid_stable(env, meta) <= last_steady) {
+    mdbx_warning("wipe txn #%" PRIaTXN ", meta %" PRIaPGNO, last_steady,
+                 data_page(meta)->mp_pgno);
+    if (env->me_flags & MDBX_WRITEMAP)
+      unaligned_poke_u64(4, meta->mm_datasync_sign, wipe);
+    else
+      return mdbx_pwrite(env->me_lazy_fd, &wipe, sizeof(meta->mm_datasync_sign),
+                         (uint8_t *)&meta->mm_datasync_sign - env->me_map);
+  }
+  return MDBX_SUCCESS;
+}
+
+__cold static int mdbx_wipe_steady(MDBX_env *env, const txnid_t last_steady) {
+  int err = mdbx_meta_unsteady(env, last_steady, METAPAGE(env, 0));
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+  err = mdbx_meta_unsteady(env, last_steady, METAPAGE(env, 1));
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+  err = mdbx_meta_unsteady(env, last_steady, METAPAGE(env, 2));
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+
+  if (env->me_flags & MDBX_WRITEMAP) {
+    mdbx_flush_incoherent_cpu_writeback();
+    err = mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, NUM_METAS),
+                     false);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+  } else {
+#if MDBX_USE_SYNCFILERANGE
+    static bool syncfilerange_unavailable;
+    if (likely(!syncfilerange_unavailable)) {
+      if (likely(!sync_file_range(
+              env->me_lazy_fd, 0, pgno2bytes(env, NUM_METAS),
+              SYNC_FILE_RANGE_WRITE | SYNC_FILE_RANGE_WAIT_AFTER)))
+        goto done_filesync;
+      err = errno;
+      if (ignore_enosys(err) != MDBX_RESULT_TRUE)
+        return err;
+      syncfilerange_unavailable = true;
+    }
+#endif /* MDBX_USE_SYNCFILERANGE */
+    err = mdbx_fsync(env->me_lazy_fd, MDBX_SYNC_DATA);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+#if MDBX_USE_SYNCFILERANGE
+  done_filesync:
+#endif /* MDBX_USE_SYNCFILERANGE */
+    mdbx_flush_incoherent_mmap(env->me_map, pgno2bytes(env, NUM_METAS),
+                               env->me_os_psize);
+  }
+
+  if (likely(env->me_lck))
+    /* force oldest refresh */
+    atomic_store32(&env->me_lck->mti_readers_refresh_flag, true,
+                   mo_AcquireRelease);
+  return MDBX_SUCCESS;
+}
+
+static __inline txnid_t pp_txnid4chk(const MDBX_page *mp, const MDBX_txn *txn) {
+  return IS_DIRTY(mp)
+             ? txn->mt_txnid - 1
+             : (/* maybe zero in legacy DB */ mp->mp_txnid ? mp->mp_txnid
+                                                           : MIN_TXNID);
+}
+
+static __inline txnid_t pp_txnid2chk(const MDBX_txn *txn) {
+#ifdef MDBX_DEBUG_LEGACY
+  if (txn->mt_txnid < 2222)
+    return 0;
+#endif
+  return txn->mt_txnid;
+}
+
+/* Allocate page numbers and memory for writing.  Maintain mt_last_reclaimed,
+ * mt_reclaimed_pglist and mt_next_pgno.  Set MDBX_TXN_ERROR on failure.
+ *
+ * If there are free pages available from older transactions, they
+ * are re-used first. Otherwise allocate a new page at mt_next_pgno.
+ * Do not modify the GC, just merge GC records into mt_reclaimed_pglist
+ * and move mt_last_reclaimed to say which records were consumed.  Only this
+ * function can create mt_reclaimed_pglist and move
+ * mt_last_reclaimed/mt_next_pgno.
+ *
+ * [in] mc    cursor A cursor handle identifying the transaction and
+ *            database for which we are allocating.
+ * [in] num   the number of pages to allocate.
+ * [out] mp   Address of the allocated page(s). Requests for multiple pages
+ *            will always be satisfied by a single contiguous chunk of memory.
+ *
+ * Returns 0 on success, non-zero on failure.*/
+
+#define MDBX_ALLOC_CACHE 1
+#define MDBX_ALLOC_GC 2
+#define MDBX_ALLOC_NEW 4
+#define MDBX_ALLOC_ALL (MDBX_ALLOC_CACHE | MDBX_ALLOC_GC | MDBX_ALLOC_NEW)
+
+__hot static int mdbx_page_alloc(MDBX_cursor *mc, const unsigned num,
+                                 MDBX_page **const mp, int flags) {
+  int rc;
+  MDBX_txn *const txn = mc->mc_txn;
+  MDBX_env *const env = txn->mt_env;
+  MDBX_page *np;
+
+  const unsigned coalesce_threshold =
+      env->me_maxgc_ov1page - env->me_maxgc_ov1page / 4;
+  if (likely(flags & MDBX_ALLOC_GC)) {
+    flags |= env->me_flags & (MDBX_COALESCE | MDBX_LIFORECLAIM);
+    if (MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) > coalesce_threshold)
+      flags &= ~MDBX_COALESCE;
+    if (unlikely(
+            /* If mc is updating the GC, then the retired-list cannot play
+               catch-up with itself by growing while trying to save it. */
+            (mc->mc_flags & C_RECLAIMING) ||
+            /* avoid (recursive) search inside empty tree and while tree is
+               updating, https://github.com/erthink/libmdbx/issues/31 */
+            txn->mt_dbs[FREE_DBI].md_entries == 0 ||
+            /* If our dirty list is already full, we can't touch GC */
+            (txn->tw.dirtyroom < txn->mt_dbs[FREE_DBI].md_depth &&
+             !(txn->mt_dbistate[FREE_DBI] & DBI_DIRTY))))
+      flags &= ~(MDBX_ALLOC_GC | MDBX_COALESCE);
+  }
+
+  if (likely(num == 1 && (flags & MDBX_ALLOC_CACHE) != 0)) {
+    /* If there are any loose pages, just use them */
+    mdbx_assert(env, mp && num);
+    if (likely(txn->tw.loose_pages)) {
+#if MDBX_ENABLE_REFUND
+      if (txn->tw.loose_refund_wl > txn->mt_next_pgno) {
+        mdbx_refund(txn);
+        if (unlikely(!txn->tw.loose_pages))
+          goto no_loose;
+      }
+#endif /* MDBX_ENABLE_REFUND */
+
+      np = txn->tw.loose_pages;
+      txn->tw.loose_pages = np->mp_next;
+      txn->tw.loose_count--;
+      mdbx_debug("db %d use loose page %" PRIaPGNO, DDBI(mc), np->mp_pgno);
+      mdbx_tassert(txn, np->mp_pgno < txn->mt_next_pgno);
+      mdbx_ensure(env, np->mp_pgno >= NUM_METAS);
+      VALGRIND_MAKE_MEM_UNDEFINED(page_data(np), page_space(txn->mt_env));
+      ASAN_UNPOISON_MEMORY_REGION(page_data(np), page_space(txn->mt_env));
+      np->mp_flags = P_DIRTY;
+      np->mp_txnid = INVALID_TXNID;
+      *mp = np;
+      return MDBX_SUCCESS;
+    }
+  }
+#if MDBX_ENABLE_REFUND
+no_loose:
+#endif /* MDBX_ENABLE_REFUND */
+
+  mdbx_tassert(txn,
+               mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+  pgno_t pgno, *re_list = txn->tw.reclaimed_pglist;
+  unsigned range_begin = 0, re_len = MDBX_PNL_SIZE(re_list);
+  txnid_t oldest = 0, last = 0;
+  const unsigned wanna_range = num - 1;
+
+  while (true) { /* hsr-kick retry loop */
+    MDBX_cursor_couple recur;
+    for (MDBX_cursor_op op = MDBX_FIRST;;
+         op = (flags & MDBX_LIFORECLAIM) ? MDBX_PREV : MDBX_NEXT) {
+      MDBX_val key, data;
+
+      /* Seek a big enough contiguous page range.
+       * Prefer pages with lower pgno. */
+      mdbx_tassert(txn, mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                              txn->mt_next_pgno));
+      if ((flags & (MDBX_COALESCE | MDBX_ALLOC_CACHE)) == MDBX_ALLOC_CACHE &&
+          re_len > wanna_range) {
+        mdbx_tassert(txn, MDBX_PNL_LAST(re_list) < txn->mt_next_pgno &&
+                              MDBX_PNL_FIRST(re_list) < txn->mt_next_pgno);
+        range_begin = MDBX_PNL_ASCENDING ? 1 : re_len;
+        pgno = MDBX_PNL_LEAST(re_list);
+        if (likely(wanna_range == 0))
+          goto done;
+#if MDBX_PNL_ASCENDING
+        mdbx_tassert(txn, pgno == re_list[1] && range_begin == 1);
+        while (true) {
+          unsigned range_end = range_begin + wanna_range;
+          if (re_list[range_end] - pgno == wanna_range)
+            goto done;
+          if (range_end == re_len)
+            break;
+          pgno = re_list[++range_begin];
+        }
+#else
+        mdbx_tassert(txn, pgno == re_list[re_len] && range_begin == re_len);
+        while (true) {
+          if (re_list[range_begin - wanna_range] - pgno == wanna_range)
+            goto done;
+          if (range_begin == wanna_range)
+            break;
+          pgno = re_list[--range_begin];
+        }
+#endif /* MDBX_PNL sort-order */
+      }
+
+      if (op == MDBX_FIRST) { /* 1st iteration, setup cursor, etc */
+        if (unlikely(!(flags & MDBX_ALLOC_GC)))
+          break /* reclaiming is prohibited for now */;
+
+        /* Prepare to fetch more and coalesce */
+        oldest = (flags & MDBX_LIFORECLAIM)
+                     ? mdbx_find_oldest(txn)
+                     : atomic_load64(env->me_oldest, mo_AcquireRelease);
+        rc = mdbx_cursor_init(&recur.outer, txn, FREE_DBI);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto fail;
+        if (flags & MDBX_LIFORECLAIM) {
+          /* Begin from oldest reader if any */
+          if (oldest > MIN_TXNID) {
+            last = oldest - 1;
+            op = MDBX_SET_RANGE;
+          }
+        } else if (txn->tw.last_reclaimed) {
+          /* Continue lookup from txn->tw.last_reclaimed to oldest reader */
+          last = txn->tw.last_reclaimed;
+          op = MDBX_SET_RANGE;
+        }
+
+        key.iov_base = &last;
+        key.iov_len = sizeof(last);
+      }
+
+      if (!(flags & MDBX_LIFORECLAIM)) {
+        /* Do not try fetch more if the record will be too recent */
+        if (op != MDBX_FIRST && ++last >= oldest) {
+          oldest = mdbx_find_oldest(txn);
+          if (oldest <= last)
+            break;
+        }
+      }
+
+      rc = mdbx_cursor_get(&recur.outer, &key, NULL, op);
+      if (rc == MDBX_NOTFOUND && (flags & MDBX_LIFORECLAIM)) {
+        if (op == MDBX_SET_RANGE)
+          continue;
+        txnid_t snap = mdbx_find_oldest(txn);
+        if (oldest < snap) {
+          oldest = snap;
+          last = oldest - 1;
+          key.iov_base = &last;
+          key.iov_len = sizeof(last);
+          op = MDBX_SET_RANGE;
+          rc = mdbx_cursor_get(&recur.outer, &key, NULL, op);
+        }
+      }
+      if (unlikely(rc)) {
+        if (rc == MDBX_NOTFOUND)
+          break;
+        goto fail;
+      }
+
+      if (unlikely(key.iov_len != sizeof(txnid_t))) {
+        rc = MDBX_CORRUPTED;
+        goto fail;
+      }
+      last = unaligned_peek_u64(4, key.iov_base);
+      if (unlikely(last < MIN_TXNID || last > MAX_TXNID)) {
+        rc = MDBX_CORRUPTED;
+        goto fail;
+      }
+      if (oldest <= last) {
+        oldest = mdbx_find_oldest(txn);
+        if (oldest <= last) {
+          if (flags & MDBX_LIFORECLAIM)
+            continue;
+          break;
+        }
+      }
+
+      if (flags & MDBX_LIFORECLAIM) {
+        /* skip IDs of records that already reclaimed */
+        if (txn->tw.lifo_reclaimed) {
+          size_t i;
+          for (i = (size_t)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed); i > 0; --i)
+            if (txn->tw.lifo_reclaimed[i] == last)
+              break;
+          if (i)
+            continue;
+        }
+      }
+
+      /* Reading next GC record */
+      np = recur.outer.mc_pg[recur.outer.mc_top];
+      if (unlikely((rc = mdbx_node_read(
+                        &recur.outer,
+                        page_node(np, recur.outer.mc_ki[recur.outer.mc_top]),
+                        &data, pp_txnid4chk(np, txn))) != MDBX_SUCCESS))
+        goto fail;
+
+      if ((flags & MDBX_LIFORECLAIM) && !txn->tw.lifo_reclaimed) {
+        txn->tw.lifo_reclaimed = mdbx_txl_alloc();
+        if (unlikely(!txn->tw.lifo_reclaimed)) {
+          rc = MDBX_ENOMEM;
+          goto fail;
+        }
+      }
+
+      /* Append PNL from GC record to tw.reclaimed_pglist */
+      mdbx_cassert(mc, (mc->mc_flags & C_GCFREEZE) == 0);
+      pgno_t *gc_pnl = (pgno_t *)data.iov_base;
+      mdbx_tassert(txn, data.iov_len >= MDBX_PNL_SIZEOF(gc_pnl));
+      if (unlikely(data.iov_len < MDBX_PNL_SIZEOF(gc_pnl) ||
+                   !mdbx_pnl_check(gc_pnl, txn->mt_next_pgno))) {
+        rc = MDBX_CORRUPTED;
+        goto fail;
+      }
+      const unsigned gc_len = MDBX_PNL_SIZE(gc_pnl);
+      if (unlikely(/* resulting list is tool long */ gc_len +
+                       MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) >
+                   env->me_options.rp_augment_limit) &&
+          (((/* not a slot-request from gc-update */
+             mp || (flags & MDBX_LIFORECLAIM) == 0 ||
+             (txn->tw.lifo_reclaimed &&
+              MDBX_PNL_SIZE(txn->tw.lifo_reclaimed))) &&
+            /* have enough unallocated space */ pgno_add(
+                txn->mt_next_pgno, num) <= txn->mt_geo.upper) ||
+           gc_len + MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) >=
+               MDBX_PGL_LIMIT / 16 * 15)) {
+        /* Stop reclaiming to avoid overflow the page list.
+         * This is a rare case while search for a continuously multi-page region
+         * in a large database. https://github.com/erthink/libmdbx/issues/123 */
+        mdbx_debug("stop reclaiming to avoid PNL overflow: %u (current) + %u "
+                   "(chunk) -> %u",
+                   MDBX_PNL_SIZE(txn->tw.reclaimed_pglist), gc_len,
+                   gc_len + MDBX_PNL_SIZE(txn->tw.reclaimed_pglist));
+        flags &= ~(MDBX_ALLOC_GC | MDBX_COALESCE);
+        break;
+      }
+      rc = mdbx_pnl_need(&txn->tw.reclaimed_pglist, gc_len);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto fail;
+      re_list = txn->tw.reclaimed_pglist;
+
+      /* Remember ID of GC record */
+      if (flags & MDBX_LIFORECLAIM) {
+        rc = mdbx_txl_append(&txn->tw.lifo_reclaimed, last);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto fail;
+      }
+      txn->tw.last_reclaimed = last;
+
+      if (mdbx_log_enabled(MDBX_LOG_EXTRA)) {
+        mdbx_debug_extra("PNL read txn %" PRIaTXN " root %" PRIaPGNO
+                         " num %u, PNL",
+                         last, txn->mt_dbs[FREE_DBI].md_root, gc_len);
+        for (unsigned i = gc_len; i; i--)
+          mdbx_debug_extra_print(" %" PRIaPGNO, gc_pnl[i]);
+        mdbx_debug_extra_print("%s\n", ".");
+      }
+
+      /* Merge in descending sorted order */
+      const unsigned prev_re_len = MDBX_PNL_SIZE(re_list);
+      mdbx_pnl_xmerge(re_list, gc_pnl);
+      /* re-check to avoid duplicates */
+      if (unlikely(!mdbx_pnl_check(re_list, txn->mt_next_pgno))) {
+        rc = MDBX_CORRUPTED;
+        goto fail;
+      }
+      mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+
+      re_len = MDBX_PNL_SIZE(re_list);
+      mdbx_tassert(txn, re_len == 0 || re_list[re_len] < txn->mt_next_pgno);
+      if (MDBX_ENABLE_REFUND && re_len &&
+          unlikely(MDBX_PNL_MOST(re_list) == txn->mt_next_pgno - 1)) {
+        /* Refund suitable pages into "unallocated" space */
+        mdbx_refund(txn);
+        re_list = txn->tw.reclaimed_pglist;
+        re_len = MDBX_PNL_SIZE(re_list);
+      }
+
+      /* Done for a kick-reclaim mode, actually no page needed */
+      if (unlikely((flags & MDBX_ALLOC_CACHE) == 0))
+        return MDBX_SUCCESS;
+
+      /* Don't try to coalesce too much. */
+      if (re_len /* current size */ > coalesce_threshold ||
+          (re_len > prev_re_len && re_len - prev_re_len /* delta from prev */ >=
+                                       coalesce_threshold / 2))
+        flags &= ~MDBX_COALESCE;
+    }
+
+    if (F_ISSET(flags, MDBX_COALESCE | MDBX_ALLOC_CACHE)) {
+      flags -= MDBX_COALESCE;
+      continue;
+    }
+
+    /* There is no suitable pages in the GC and to be able to allocate
+     * we should CHOICE one of:
+     *  - make a new steady checkpoint if reclaiming was stopped by
+     *    the last steady-sync, or wipe it in the MDBX_UTTERLY_NOSYNC mode;
+     *  - kick lagging reader(s) if reclaiming was stopped by ones of it.
+     *  - extend the database file. */
+
+    /* Will use new pages from the map if nothing is suitable in the GC. */
+    range_begin = 0;
+    pgno = txn->mt_next_pgno;
+    const pgno_t next = pgno_add(pgno, num);
+
+    if (flags & MDBX_ALLOC_GC) {
+      const MDBX_meta *const head = mdbx_meta_head(env);
+      MDBX_meta *const steady = mdbx_meta_steady(env);
+      /* does reclaiming stopped at the last steady point? */
+      if (head != steady && META_IS_STEADY(steady) &&
+          oldest == mdbx_meta_txnid_stable(env, steady)) {
+        mdbx_debug("gc-kick-steady: head %" PRIaTXN "-%s, tail %" PRIaTXN
+                   "-%s, oldest %" PRIaTXN,
+                   mdbx_meta_txnid_stable(env, head), mdbx_durable_str(head),
+                   mdbx_meta_txnid_stable(env, steady),
+                   mdbx_durable_str(steady), oldest);
+        rc = MDBX_RESULT_TRUE;
+        const pgno_t autosync_threshold =
+            atomic_load32(env->me_autosync_threshold, mo_Relaxed);
+        const uint64_t autosync_period =
+            atomic_load64(env->me_autosync_period, mo_Relaxed);
+        /* wipe the last steady-point if one of:
+         *  - UTTERLY_NOSYNC mode AND auto-sync threshold is NOT specified
+         *  - UTTERLY_NOSYNC mode AND free space at steady-point is exhausted
+         * otherwise, make a new steady-point if one of:
+         *  - auto-sync threshold is specified and reached;
+         *  - upper limit of database size is reached;
+         *  - database is full (with the current file size)
+         *       AND auto-sync threshold it NOT specified */
+        if (F_ISSET(env->me_flags, MDBX_UTTERLY_NOSYNC) &&
+            ((autosync_threshold | autosync_period) == 0 ||
+             next >= steady->mm_geo.now)) {
+          /* wipe steady checkpoint in MDBX_UTTERLY_NOSYNC mode
+           * without any auto-sync threshold(s). */
+          rc = mdbx_wipe_steady(env, oldest);
+          mdbx_debug("gc-wipe-steady, rc %d", rc);
+          mdbx_assert(env, steady != mdbx_meta_steady(env));
+        } else if ((flags & MDBX_ALLOC_NEW) == 0 ||
+                   (autosync_threshold &&
+                    atomic_load32(env->me_unsynced_pages, mo_Relaxed) >=
+                        autosync_threshold) ||
+                   (autosync_period &&
+                    mdbx_osal_monotime() -
+                            atomic_load64(env->me_sync_timestamp, mo_Relaxed) >=
+                        autosync_period) ||
+                   next >= txn->mt_geo.upper ||
+                   (next >= txn->mt_end_pgno &&
+                    (autosync_threshold | autosync_period) == 0)) {
+          /* make steady checkpoint. */
+          MDBX_meta meta = *head;
+          rc = mdbx_sync_locked(env, env->me_flags & MDBX_WRITEMAP, &meta);
+          mdbx_debug("gc-make-steady, rc %d", rc);
+          mdbx_assert(env, steady != mdbx_meta_steady(env));
+        }
+        if (rc == MDBX_SUCCESS) {
+          if (mdbx_find_oldest(txn) > oldest)
+            continue;
+          /* it is reasonable check/kick lagging reader(s) here,
+           * since we made a new steady point or wipe the last. */
+          if (oldest < txn->mt_txnid - MDBX_TXNID_STEP &&
+              mdbx_kick_longlived_readers(env, oldest) > oldest)
+            continue;
+        } else if (unlikely(rc != MDBX_RESULT_TRUE))
+          goto fail;
+      }
+    }
+
+    /* don't kick lagging reader(s) if is enough unallocated space
+     * at the end of database file. */
+    if ((flags & MDBX_ALLOC_NEW) && next <= txn->mt_end_pgno)
+      goto done;
+    if ((flags & MDBX_ALLOC_GC) && oldest < txn->mt_txnid - MDBX_TXNID_STEP &&
+        mdbx_kick_longlived_readers(env, oldest) > oldest)
+      continue;
+
+    rc = MDBX_NOTFOUND;
+    if (flags & MDBX_ALLOC_NEW) {
+      rc = MDBX_MAP_FULL;
+      if (next <= txn->mt_geo.upper && txn->mt_geo.grow) {
+        mdbx_assert(env, next > txn->mt_end_pgno);
+        pgno_t aligned = pgno_align2os_pgno(
+            env, pgno_add(next, txn->mt_geo.grow - next % txn->mt_geo.grow));
+
+        if (aligned > txn->mt_geo.upper)
+          aligned = txn->mt_geo.upper;
+        mdbx_assert(env, aligned > txn->mt_end_pgno);
+
+        mdbx_verbose("try growth datafile to %" PRIaPGNO " pages (+%" PRIaPGNO
+                     ")",
+                     aligned, aligned - txn->mt_end_pgno);
+        rc = mdbx_mapresize_implicit(env, txn->mt_next_pgno, aligned,
+                                     txn->mt_geo.upper);
+        if (rc == MDBX_SUCCESS) {
+          env->me_txn->mt_end_pgno = aligned;
+          goto done;
+        }
+
+        mdbx_error("unable growth datafile to %" PRIaPGNO " pages (+%" PRIaPGNO
+                   "), errcode %d",
+                   aligned, aligned - txn->mt_end_pgno, rc);
+      } else {
+        mdbx_debug("gc-alloc: next %u > upper %u", next, txn->mt_geo.upper);
+      }
+    }
+
+  fail:
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    if (likely(mp)) {
+      *mp = nullptr;
+      txn->mt_flags |= MDBX_TXN_ERROR;
+    }
+    mdbx_assert(env, rc != MDBX_SUCCESS);
+    return rc;
+  }
+
+done:
+  if (unlikely(mp == nullptr))
+    return MDBX_SUCCESS;
+  if (unlikely(txn->tw.dirtyroom < 1))
+    return MDBX_TXN_FULL;
+  mdbx_ensure(env, pgno >= NUM_METAS);
+  if (env->me_flags & MDBX_WRITEMAP) {
+    np = pgno2page(env, pgno);
+    /* LY: reset no-access flag from mdbx_page_loose() */
+    VALGRIND_MAKE_MEM_UNDEFINED(np, pgno2bytes(env, num));
+    ASAN_UNPOISON_MEMORY_REGION(np, pgno2bytes(env, num));
+  } else {
+    if (unlikely(!(np = mdbx_page_malloc(txn, num)))) {
+      rc = MDBX_ENOMEM;
+      goto fail;
+    }
+  }
+
+  if (range_begin) {
+    mdbx_cassert(mc, (mc->mc_flags & C_GCFREEZE) == 0);
+    mdbx_tassert(txn, pgno < txn->mt_next_pgno);
+    mdbx_tassert(txn, pgno == re_list[range_begin]);
+    /* Cutoff allocated pages from tw.reclaimed_pglist */
+#if MDBX_PNL_ASCENDING
+    for (unsigned i = range_begin + num; i <= re_len;)
+      re_list[range_begin++] = re_list[i++];
+    MDBX_PNL_SIZE(re_list) = re_len = range_begin - 1;
+#else
+    MDBX_PNL_SIZE(re_list) = re_len -= num;
+    for (unsigned i = range_begin - num; i < re_len;)
+      re_list[++i] = re_list[++range_begin];
+#endif
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+  } else {
+    txn->mt_next_pgno = pgno + num;
+    mdbx_assert(env, txn->mt_next_pgno <= txn->mt_end_pgno);
+  }
+
+  if (unlikely(env->me_flags & MDBX_PAGEPERTURB))
+    memset(np, -1, pgno2bytes(env, num));
+  VALGRIND_MAKE_MEM_UNDEFINED(np, pgno2bytes(env, num));
+
+  np->mp_pgno = pgno;
+  np->mp_leaf2_ksize = 0;
+  np->mp_flags = 0;
+  if ((mdbx_assert_enabled() || mdbx_audit_enabled()) && num > 1) {
+    np->mp_pages = num;
+    np->mp_flags = P_OVERFLOW;
+  }
+  rc = mdbx_page_dirty(txn, np);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto fail;
+  *mp = np;
+
+  mdbx_tassert(txn,
+               mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+  return MDBX_SUCCESS;
+}
+
+/* Copy the used portions of a non-overflow page. */
+__hot static void mdbx_page_copy(MDBX_page *dst, MDBX_page *src, size_t psize) {
+  STATIC_ASSERT(UINT16_MAX > MAX_PAGESIZE - PAGEHDRSZ);
+  STATIC_ASSERT(MIN_PAGESIZE > PAGEHDRSZ + NODESIZE * 4);
+  if (!IS_LEAF2(src)) {
+    size_t upper = src->mp_upper, lower = src->mp_lower, unused = upper - lower;
+
+    /* If page isn't full, just copy the used portion. Adjust
+     * alignment so memcpy may copy words instead of bytes. */
+    if (unused >= MDBX_CACHELINE_SIZE * 2) {
+      lower = ceil_powerof2(lower + PAGEHDRSZ, sizeof(void *));
+      upper = floor_powerof2(upper + PAGEHDRSZ, sizeof(void *));
+      memcpy(dst, src, lower);
+      dst = (void *)((char *)dst + upper);
+      src = (void *)((char *)src + upper);
+      psize -= upper;
+    }
+  }
+  memcpy(dst, src, psize);
+}
+
+/* Pull a page off the txn's spill list, if present.
+ *
+ * If a page being referenced was spilled to disk in this txn, bring
+ * it back and make it dirty/writable again.
+ *
+ * [in] txn   the transaction handle.
+ * [in] mp    the page being referenced. It must not be dirty.
+ * [out] ret  the writable page, if any.
+ *            ret is unchanged if mp wasn't spilled. */
+static int __must_check_result mdbx_page_unspill(MDBX_txn *txn, MDBX_page *mp,
+                                                 MDBX_page **ret) {
+  mdbx_tassert(txn, !IS_DIRTY(mp));
+  const pgno_t spilled_pgno = mp->mp_pgno << 1;
+  const MDBX_txn *scan = txn;
+  do {
+    if ((scan->mt_flags & MDBX_TXN_SPILLS) == 0)
+      break;
+    if (!scan->tw.spill_pages)
+      continue;
+    const unsigned si = mdbx_pnl_exist(scan->tw.spill_pages, spilled_pgno);
+    if (!si)
+      continue;
+    const unsigned npages = IS_OVERFLOW(mp) ? mp->mp_pages : 1;
+    MDBX_page *np = mp;
+    if ((txn->mt_flags & MDBX_WRITEMAP) == 0) {
+      np = mdbx_page_malloc(txn, npages);
+      if (unlikely(!np))
+        return MDBX_ENOMEM;
+      if (likely(npages == 1))
+        mdbx_page_copy(np, mp, txn->mt_env->me_psize);
+      else
+        memcpy(np, mp, pgno2bytes(txn->mt_env, npages));
+    }
+    mdbx_debug("unspill page %" PRIaPGNO, mp->mp_pgno);
+    if (scan == txn) {
+      /* If in current txn, this page is no longer spilled.
+       * If it happens to be the last page, truncate the spill list.
+       * Otherwise mark it as deleted by setting the LSB. */
+      mdbx_spill_remove(txn, si, npages);
+    } /* otherwise, if belonging to a parent txn, the
+       * page remains spilled until child commits */
+
+    int rc = mdbx_page_dirty(txn, np);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      if ((txn->mt_flags & MDBX_WRITEMAP) == 0)
+        mdbx_dpage_free(txn->mt_env, np, npages);
+      return rc;
+    }
+    *ret = np;
+    break;
+  } while ((scan = scan->mt_parent) != nullptr);
+  return MDBX_SUCCESS;
+}
+
+/* Touch a page: make it dirty and re-insert into tree with updated pgno.
+ * Set MDBX_TXN_ERROR on failure.
+ *
+ * [in] mc  cursor pointing to the page to be touched
+ *
+ * Returns 0 on success, non-zero on failure. */
+__hot static int mdbx_page_touch(MDBX_cursor *mc) {
+  MDBX_page *const mp = mc->mc_pg[mc->mc_top], *np;
+  MDBX_txn *txn = mc->mc_txn;
+  MDBX_cursor *m2, *m3;
+  pgno_t pgno;
+  int rc;
+
+  if (mdbx_assert_enabled()) {
+    if (mc->mc_dbi >= CORE_DBS) {
+      if (mc->mc_flags & C_SUB) {
+        MDBX_xcursor *mx = container_of(mc->mc_db, MDBX_xcursor, mx_db);
+        MDBX_cursor_couple *couple =
+            container_of(mx, MDBX_cursor_couple, inner);
+        mdbx_cassert(mc, mc->mc_db == &couple->outer.mc_xcursor->mx_db);
+        mdbx_cassert(mc, mc->mc_dbx == &couple->outer.mc_xcursor->mx_dbx);
+        mdbx_cassert(mc, *couple->outer.mc_dbistate & DBI_DIRTY);
+      } else {
+        mdbx_cassert(mc, *mc->mc_dbistate & DBI_DIRTY);
+      }
+      mdbx_cassert(mc, mc->mc_txn->mt_flags & MDBX_TXN_DIRTY);
+    }
+    mdbx_cassert(mc, !IS_OVERFLOW(mp));
+    mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  }
+
+  if (!IS_DIRTY(mp)) {
+    if (txn->mt_flags & MDBX_TXN_SPILLS) {
+      np = NULL;
+      rc = mdbx_page_unspill(txn, mp, &np);
+      if (unlikely(rc))
+        goto fail;
+      if (likely(np))
+        goto done;
+    }
+
+    if (unlikely((rc = mdbx_pnl_need(&txn->tw.retired_pages, 1)) ||
+                 (rc = mdbx_page_alloc(mc, 1, &np, MDBX_ALLOC_ALL))))
+      goto fail;
+
+    pgno = np->mp_pgno;
+    mdbx_debug("touched db %d page %" PRIaPGNO " -> %" PRIaPGNO, DDBI(mc),
+               mp->mp_pgno, pgno);
+    mdbx_cassert(mc, mp->mp_pgno != pgno);
+    mdbx_pnl_xappend(txn->tw.retired_pages, mp->mp_pgno);
+    /* Update the parent page, if any, to point to the new page */
+    if (mc->mc_top) {
+      MDBX_page *parent = mc->mc_pg[mc->mc_top - 1];
+      MDBX_node *node = page_node(parent, mc->mc_ki[mc->mc_top - 1]);
+      node_set_pgno(node, pgno);
+    } else {
+      mc->mc_db->md_root = pgno;
+    }
+  } else if (txn->mt_parent && !IS_SUBP(mp)) {
+    mdbx_tassert(txn, (txn->mt_env->me_flags & MDBX_WRITEMAP) == 0);
+    pgno = mp->mp_pgno;
+    /* If txn has a parent, make sure the page is in our dirty list. */
+    const MDBX_page *const dp = mdbx_dpl_find(txn->tw.dirtylist, pgno);
+    if (dp) {
+      if (unlikely(mp != dp)) { /* bad cursor? */
+        mdbx_error("wrong page 0x%p #%" PRIaPGNO
+                   " in the dirtylist, expecting %p",
+                   __Wpedantic_format_voidptr(dp), pgno,
+                   __Wpedantic_format_voidptr(mp));
+        mc->mc_flags &= ~(C_INITIALIZED | C_EOF);
+        rc = MDBX_PROBLEM;
+        goto fail;
+      }
+      return MDBX_SUCCESS;
+    }
+
+    mdbx_debug("clone db %d page %" PRIaPGNO, DDBI(mc), mp->mp_pgno);
+    mdbx_cassert(mc, txn->tw.dirtylist->length <=
+                         MDBX_PGL_LIMIT + MDBX_PNL_GRANULATE);
+    /* No - copy it */
+    np = mdbx_page_malloc(txn, 1);
+    if (unlikely(!np)) {
+      rc = MDBX_ENOMEM;
+      goto fail;
+    }
+    /* insert a clone of parent's dirty page, so don't touch dirtyroom */
+    rc = mdbx_dpl_append(txn, pgno, np);
+    if (unlikely(rc)) {
+      mdbx_dpage_free(txn->mt_env, np, 1);
+      goto fail;
+    }
+
+    np->mp_pgno = pgno;
+    np->mp_txnid = INVALID_TXNID;
+    np->mp_flags |= P_DIRTY;
+    mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  } else {
+    return MDBX_SUCCESS;
+  }
+
+  mdbx_page_copy(np, mp, txn->mt_env->me_psize);
+  np->mp_pgno = pgno;
+  np->mp_txnid = INVALID_TXNID;
+  np->mp_flags |= P_DIRTY;
+
+done:
+  /* Adjust cursors pointing to mp */
+  mc->mc_pg[mc->mc_top] = np;
+  m2 = txn->tw.cursors[mc->mc_dbi];
+  if (mc->mc_flags & C_SUB) {
+    for (; m2; m2 = m2->mc_next) {
+      m3 = &m2->mc_xcursor->mx_cursor;
+      if (m3->mc_snum < mc->mc_snum)
+        continue;
+      if (m3->mc_pg[mc->mc_top] == mp)
+        m3->mc_pg[mc->mc_top] = np;
+    }
+  } else {
+    for (; m2; m2 = m2->mc_next) {
+      if (m2->mc_snum < mc->mc_snum)
+        continue;
+      if (m2 == mc)
+        continue;
+      if (m2->mc_pg[mc->mc_top] == mp) {
+        m2->mc_pg[mc->mc_top] = np;
+        if (XCURSOR_INITED(m2) && IS_LEAF(np))
+          XCURSOR_REFRESH(m2, np, m2->mc_ki[mc->mc_top]);
+      }
+    }
+  }
+  return MDBX_SUCCESS;
+
+fail:
+  txn->mt_flags |= MDBX_TXN_ERROR;
+  return rc;
+}
+
+__cold static int mdbx_env_sync_internal(MDBX_env *env, bool force,
+                                         bool nonblock) {
+  unsigned flags = env->me_flags & ~MDBX_NOMETASYNC;
+  if (unlikely(flags & (MDBX_RDONLY | MDBX_FATAL_ERROR)))
+    return MDBX_EACCESS;
+
+  if (unlikely(!env->me_map))
+    return MDBX_EPERM;
+
+  int rc = MDBX_RESULT_TRUE /* means "nothing to sync" */;
+  bool need_unlock = false;
+  if (nonblock && atomic_load32(env->me_unsynced_pages, mo_AcquireRelease) == 0)
+    goto fastpath;
+
+  const bool outside_txn = (env->me_txn0->mt_owner != mdbx_thread_self());
+  if (outside_txn) {
+    int err = mdbx_txn_lock(env, nonblock);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+    need_unlock = true;
+  }
+
+  const MDBX_meta *head = mdbx_meta_head(env);
+  pgno_t unsynced_pages = atomic_load32(env->me_unsynced_pages, mo_Relaxed);
+  if (!META_IS_STEADY(head) || unsynced_pages) {
+    const pgno_t autosync_threshold =
+        atomic_load32(env->me_autosync_threshold, mo_Relaxed);
+    const uint64_t autosync_period =
+        atomic_load64(env->me_autosync_period, mo_Relaxed);
+    if (force || (autosync_threshold && unsynced_pages >= autosync_threshold) ||
+        (autosync_period &&
+         mdbx_osal_monotime() -
+                 atomic_load64(env->me_sync_timestamp, mo_Relaxed) >=
+             autosync_period))
+      flags &= MDBX_WRITEMAP /* clear flags for full steady sync */;
+
+    if (outside_txn) {
+      if (unsynced_pages > /* FIXME: define threshold */ 16 &&
+          (flags & MDBX_SAFE_NOSYNC) == 0) {
+        mdbx_assert(env, ((flags ^ env->me_flags) & MDBX_WRITEMAP) == 0);
+        const size_t usedbytes = pgno_align2os_bytes(env, head->mm_geo.next);
+
+        mdbx_txn_unlock(env);
+
+        /* LY: pre-sync without holding lock to reduce latency for writer(s) */
+        int err = (flags & MDBX_WRITEMAP)
+                      ? mdbx_msync(&env->me_dxb_mmap, 0, usedbytes, false)
+                      : mdbx_fsync(env->me_lazy_fd, MDBX_SYNC_DATA);
+        if (unlikely(err != MDBX_SUCCESS))
+          return err;
+
+        err = mdbx_txn_lock(env, nonblock);
+        if (unlikely(err != MDBX_SUCCESS))
+          return err;
+
+        /* LY: head and unsynced_pages may be changed. */
+        head = mdbx_meta_head(env);
+        unsynced_pages = atomic_load32(env->me_unsynced_pages, mo_Relaxed);
+      }
+      env->me_txn0->mt_txnid = meta_txnid(env, head, false);
+      mdbx_find_oldest(env->me_txn0);
+      rc = MDBX_RESULT_FALSE /* means "some data was synced" */;
+    }
+
+    if (!META_IS_STEADY(head) ||
+        ((flags & MDBX_SAFE_NOSYNC) == 0 && unsynced_pages)) {
+      mdbx_debug("meta-head %" PRIaPGNO ", %s, sync_pending %" PRIaPGNO,
+                 data_page(head)->mp_pgno, mdbx_durable_str(head),
+                 unsynced_pages);
+      MDBX_meta meta = *head;
+      int err = mdbx_sync_locked(env, flags | MDBX_SHRINK_ALLOWED, &meta);
+      if (unlikely(err != MDBX_SUCCESS)) {
+        if (need_unlock)
+          mdbx_txn_unlock(env);
+        return err;
+      }
+      rc = MDBX_RESULT_FALSE /* means "some data was synced" */;
+    }
+  }
+
+fastpath:
+  /* LY: sync meta-pages if MDBX_NOMETASYNC enabled
+   *     and someone was not synced above. */
+  if (rc == MDBX_RESULT_TRUE && (env->me_flags & MDBX_NOMETASYNC) != 0) {
+    const txnid_t head_txnid = mdbx_recent_committed_txnid(env);
+    if (atomic_load32(env->me_meta_sync_txnid, mo_Relaxed) !=
+        (uint32_t)head_txnid) {
+      rc = (flags & MDBX_WRITEMAP)
+               ? mdbx_msync(&env->me_dxb_mmap, 0,
+                            pgno_align2os_bytes(env, NUM_METAS), false)
+               : mdbx_fsync(env->me_lazy_fd, MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+      if (likely(rc == MDBX_SUCCESS))
+        atomic_store32(env->me_meta_sync_txnid, (uint32_t)head_txnid,
+                       mo_Relaxed);
+    }
+  }
+  if (need_unlock)
+    mdbx_txn_unlock(env);
+  return rc;
+}
+
+static __inline int check_env(const MDBX_env *env) {
+  if (unlikely(!env))
+    return MDBX_EINVAL;
+
+  if (unlikely(env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+#if MDBX_ENV_CHECKPID
+  if (unlikely(env->me_pid != mdbx_getpid())) {
+    ((MDBX_env *)env)->me_flags |= MDBX_FATAL_ERROR;
+    return MDBX_PANIC;
+  }
+#endif /* MDBX_ENV_CHECKPID */
+
+  if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
+    return MDBX_PANIC;
+
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_env_sync_ex(MDBX_env *env, bool force, bool nonblock) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_env_sync_internal(env, force, nonblock);
+}
+
+__cold int mdbx_env_sync(MDBX_env *env) { return __inline_mdbx_env_sync(env); }
+
+__cold int mdbx_env_sync_poll(MDBX_env *env) {
+  return __inline_mdbx_env_sync_poll(env);
+}
+
+/* Back up parent txn's cursors, then grab the originals for tracking */
+static int mdbx_cursor_shadow(MDBX_txn *parent, MDBX_txn *nested) {
+  for (int i = parent->mt_numdbs; --i >= 0;) {
+    nested->tw.cursors[i] = NULL;
+    MDBX_cursor *mc = parent->tw.cursors[i];
+    if (mc != NULL) {
+      size_t size = mc->mc_xcursor ? sizeof(MDBX_cursor) + sizeof(MDBX_xcursor)
+                                   : sizeof(MDBX_cursor);
+      for (MDBX_cursor *bk; mc; mc = bk->mc_next) {
+        bk = mc;
+        if (mc->mc_signature != MDBX_MC_LIVE)
+          continue;
+        bk = mdbx_malloc(size);
+        if (unlikely(!bk))
+          return MDBX_ENOMEM;
+        *bk = *mc;
+        mc->mc_backup = bk;
+        /* Kill pointers into src to reduce abuse: The
+         * user may not use mc until dst ends. But we need a valid
+         * txn pointer here for cursor fixups to keep working. */
+        mc->mc_txn = nested;
+        mc->mc_db = &nested->mt_dbs[i];
+        mc->mc_dbistate = &nested->mt_dbistate[i];
+        MDBX_xcursor *mx = mc->mc_xcursor;
+        if (mx != NULL) {
+          *(MDBX_xcursor *)(bk + 1) = *mx;
+          mx->mx_cursor.mc_txn = nested;
+        }
+        mc->mc_next = nested->tw.cursors[i];
+        nested->tw.cursors[i] = mc;
+      }
+    }
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Close this write txn's cursors, give parent txn's cursors back to parent.
+ *
+ * [in] txn     the transaction handle.
+ * [in] merge   true to keep changes to parent cursors, false to revert.
+ *
+ * Returns 0 on success, non-zero on failure. */
+static void mdbx_cursors_eot(MDBX_txn *txn, const bool merge) {
+  mdbx_tassert(txn, (txn->mt_flags & MDBX_TXN_RDONLY) == 0);
+  for (int i = txn->mt_numdbs; --i >= 0;) {
+    MDBX_cursor *next, *mc = txn->tw.cursors[i];
+    if (!mc)
+      continue;
+    txn->tw.cursors[i] = NULL;
+    do {
+      const unsigned stage = mc->mc_signature;
+      MDBX_cursor *bk = mc->mc_backup;
+      next = mc->mc_next;
+      mdbx_ensure(txn->mt_env,
+                  stage == MDBX_MC_LIVE || (stage == MDBX_MC_WAIT4EOT && bk));
+      mdbx_cassert(mc, mc->mc_dbi == (unsigned)i);
+      if (bk) {
+        MDBX_xcursor *mx = mc->mc_xcursor;
+        mdbx_cassert(mc, mx == bk->mc_xcursor);
+        mdbx_tassert(txn, txn->mt_parent != NULL);
+        mdbx_ensure(txn->mt_env, bk->mc_signature == MDBX_MC_LIVE);
+        if (stage == MDBX_MC_WAIT4EOT /* Cursor was closed by user */)
+          mc->mc_signature = stage /* Promote closed state to parent txn */;
+        else if (merge) {
+          /* Restore pointers to parent txn */
+          mc->mc_next = bk->mc_next;
+          mc->mc_backup = bk->mc_backup;
+          mc->mc_txn = bk->mc_txn;
+          mc->mc_db = bk->mc_db;
+          mc->mc_dbistate = bk->mc_dbistate;
+          if (mx) {
+            if (mx != bk->mc_xcursor) {
+              *bk->mc_xcursor = *mx;
+              mx = bk->mc_xcursor;
+            }
+            mx->mx_cursor.mc_txn = bk->mc_txn;
+          }
+        } else {
+          /* Restore from backup, i.e. rollback/abort nested txn */
+          *mc = *bk;
+          if (mx)
+            *mx = *(MDBX_xcursor *)(bk + 1);
+        }
+        bk->mc_signature = 0;
+        mdbx_free(bk);
+      } else {
+        mdbx_ensure(txn->mt_env, stage == MDBX_MC_LIVE);
+        mc->mc_signature = MDBX_MC_READY4CLOSE /* Cursor may be reused */;
+        mc->mc_flags = 0 /* reset C_UNTRACK */;
+      }
+    } while ((mc = next) != NULL);
+  }
+}
+
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+/* Find largest mvcc-snapshot still referenced by this process. */
+static pgno_t mdbx_find_largest_this(MDBX_env *env, pgno_t largest) {
+  MDBX_lockinfo *const lck = env->me_lck;
+  if (likely(lck != NULL /* exclusive mode */)) {
+    const unsigned snap_nreaders =
+        atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+    for (unsigned i = 0; i < snap_nreaders; ++i) {
+    retry:
+      if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease) ==
+          env->me_pid) {
+        /* mdbx_jitter4testing(true); */
+        const pgno_t snap_pages = atomic_load32(
+            &lck->mti_readers[i].mr_snapshot_pages_used, mo_Relaxed);
+        const txnid_t snap_txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
+        if (unlikely(
+                snap_pages !=
+                    atomic_load32(&lck->mti_readers[i].mr_snapshot_pages_used,
+                                  mo_AcquireRelease) ||
+                snap_txnid != safe64_read(&lck->mti_readers[i].mr_txnid)))
+          goto retry;
+        if (largest < snap_pages &&
+            atomic_load64(&lck->mti_oldest_reader, mo_AcquireRelease) <=
+                /* ignore pending updates */ snap_txnid &&
+            snap_txnid <= MAX_TXNID)
+          largest = snap_pages;
+      }
+    }
+  }
+  return largest;
+}
+
+static void mdbx_txn_valgrind(MDBX_env *env, MDBX_txn *txn) {
+#if !defined(__SANITIZE_ADDRESS__)
+  if (!RUNNING_ON_VALGRIND)
+    return;
+#endif
+
+  if (txn) { /* transaction start */
+    if (env->me_poison_edge < txn->mt_next_pgno)
+      env->me_poison_edge = txn->mt_next_pgno;
+    VALGRIND_MAKE_MEM_DEFINED(env->me_map, pgno2bytes(env, txn->mt_next_pgno));
+    ASAN_UNPOISON_MEMORY_REGION(env->me_map,
+                                pgno2bytes(env, txn->mt_next_pgno));
+    /* don't touch more, it should be already poisoned */
+  } else { /* transaction end */
+    bool should_unlock = false;
+    pgno_t last = MAX_PAGENO;
+    if (env->me_txn0 && env->me_txn0->mt_owner == mdbx_thread_self()) {
+      /* inside write-txn */
+      MDBX_meta *head = mdbx_meta_head(env);
+      last = head->mm_geo.next;
+    } else if (env->me_flags & MDBX_RDONLY) {
+      /* read-only mode, no write-txn, no wlock mutex */
+      last = NUM_METAS;
+    } else if (mdbx_txn_lock(env, true) == MDBX_SUCCESS) {
+      /* no write-txn */
+      last = NUM_METAS;
+      should_unlock = true;
+    } else {
+      /* write txn is running, therefore shouldn't poison any memory range */
+      return;
+    }
+
+    last = mdbx_find_largest_this(env, last);
+    const pgno_t edge = env->me_poison_edge;
+    if (edge > last) {
+      mdbx_assert(env, last >= NUM_METAS);
+      env->me_poison_edge = last;
+      VALGRIND_MAKE_MEM_NOACCESS(env->me_map + pgno2bytes(env, last),
+                                 pgno2bytes(env, edge - last));
+      ASAN_POISON_MEMORY_REGION(env->me_map + pgno2bytes(env, last),
+                                pgno2bytes(env, edge - last));
+    }
+    if (should_unlock)
+      mdbx_txn_unlock(env);
+  }
+}
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+
+typedef struct {
+  int err;
+  MDBX_reader *rslot;
+} bind_rslot_result;
+
+static bind_rslot_result bind_rslot(MDBX_env *env, const uintptr_t tid) {
+  mdbx_assert(env, env->me_lck);
+  mdbx_assert(env, env->me_lck->mti_magic_and_version == MDBX_LOCK_MAGIC);
+  mdbx_assert(env, env->me_lck->mti_os_and_format == MDBX_LOCK_FORMAT);
+
+  bind_rslot_result result = {mdbx_rdt_lock(env), nullptr};
+  if (unlikely(MDBX_IS_ERROR(result.err)))
+    return result;
+  if (unlikely(env->me_flags & MDBX_FATAL_ERROR)) {
+    mdbx_rdt_unlock(env);
+    result.err = MDBX_PANIC;
+    return result;
+  }
+  if (unlikely(!env->me_map)) {
+    mdbx_rdt_unlock(env);
+    result.err = MDBX_EPERM;
+    return result;
+  }
+
+  if (unlikely(env->me_live_reader != env->me_pid)) {
+    result.err = mdbx_rpid_set(env);
+    if (unlikely(result.err != MDBX_SUCCESS)) {
+      mdbx_rdt_unlock(env);
+      return result;
+    }
+    env->me_live_reader = env->me_pid;
+  }
+
+  result.err = MDBX_SUCCESS;
+  unsigned slot, nreaders;
+  while (1) {
+    nreaders = atomic_load32(&env->me_lck->mti_numreaders, mo_Relaxed);
+    for (slot = 0; slot < nreaders; slot++)
+      if (atomic_load32(&env->me_lck->mti_readers[slot].mr_pid, mo_Relaxed) ==
+          0)
+        break;
+
+    if (likely(slot < env->me_maxreaders))
+      break;
+
+    result.err = mdbx_cleanup_dead_readers(env, true, NULL);
+    if (result.err != MDBX_RESULT_TRUE) {
+      mdbx_rdt_unlock(env);
+      result.err =
+          (result.err == MDBX_SUCCESS) ? MDBX_READERS_FULL : result.err;
+      return result;
+    }
+  }
+
+  result.rslot = &env->me_lck->mti_readers[slot];
+  /* Claim the reader slot, carefully since other code
+   * uses the reader table un-mutexed: First reset the
+   * slot, next publish it in lck->mti_numreaders.  After
+   * that, it is safe for mdbx_env_close() to touch it.
+   * When it will be closed, we can finally claim it. */
+  atomic_store32(&result.rslot->mr_pid, 0, mo_Relaxed);
+  safe64_reset(&result.rslot->mr_txnid, true);
+  if (slot == nreaders)
+    atomic_store32(&env->me_lck->mti_numreaders, ++nreaders, mo_Relaxed);
+  atomic_store64(&result.rslot->mr_tid, (env->me_flags & MDBX_NOTLS) ? 0 : tid,
+                 mo_Relaxed);
+  atomic_store32(&result.rslot->mr_pid, env->me_pid, mo_Relaxed);
+  mdbx_rdt_unlock(env);
+
+  if (likely(env->me_flags & MDBX_ENV_TXKEY)) {
+    mdbx_assert(env, env->me_live_reader == env->me_pid);
+    thread_rthc_set(env->me_txkey, result.rslot);
+  }
+  return result;
+}
+
+__cold int mdbx_thread_register(const MDBX_env *env) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!env->me_lck))
+    return (env->me_flags & MDBX_EXCLUSIVE) ? MDBX_EINVAL : MDBX_EPERM;
+
+  if (unlikely((env->me_flags & MDBX_ENV_TXKEY) == 0)) {
+    mdbx_assert(env, !env->me_lck || (env->me_flags & MDBX_NOTLS));
+    return MDBX_EINVAL /* MDBX_NOTLS mode */;
+  }
+
+  mdbx_assert(env, (env->me_flags & (MDBX_NOTLS | MDBX_ENV_TXKEY |
+                                     MDBX_EXCLUSIVE)) == MDBX_ENV_TXKEY);
+  MDBX_reader *r = thread_rthc_get(env->me_txkey);
+  if (unlikely(r != NULL)) {
+    mdbx_assert(env, r->mr_pid.weak == env->me_pid);
+    mdbx_assert(env, r->mr_tid.weak == mdbx_thread_self());
+    if (unlikely(r->mr_pid.weak != env->me_pid))
+      return MDBX_BAD_RSLOT;
+    return MDBX_RESULT_TRUE /* already registered */;
+  }
+
+  const uintptr_t tid = mdbx_thread_self();
+  if (env->me_txn0 && unlikely(env->me_txn0->mt_owner == tid))
+    return MDBX_TXN_OVERLAPPING;
+  return bind_rslot((MDBX_env *)env, tid).err;
+}
+
+__cold int mdbx_thread_unregister(const MDBX_env *env) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!env->me_lck))
+    return MDBX_RESULT_TRUE;
+
+  if (unlikely((env->me_flags & MDBX_ENV_TXKEY) == 0)) {
+    mdbx_assert(env, !env->me_lck || (env->me_flags & MDBX_NOTLS));
+    return MDBX_RESULT_TRUE /* MDBX_NOTLS mode */;
+  }
+
+  mdbx_assert(env, (env->me_flags & (MDBX_NOTLS | MDBX_ENV_TXKEY |
+                                     MDBX_EXCLUSIVE)) == MDBX_ENV_TXKEY);
+  MDBX_reader *r = thread_rthc_get(env->me_txkey);
+  if (unlikely(r == NULL))
+    return MDBX_RESULT_TRUE /* not registered */;
+
+  mdbx_assert(env, r->mr_pid.weak == env->me_pid);
+  mdbx_assert(env, r->mr_tid.weak == mdbx_thread_self());
+  if (unlikely(r->mr_pid.weak != env->me_pid ||
+               r->mr_tid.weak != mdbx_thread_self()))
+    return MDBX_BAD_RSLOT;
+
+  if (unlikely(r->mr_txnid.weak < SAFE64_INVALID_THRESHOLD))
+    return MDBX_BUSY /* transaction is still active */;
+
+  atomic_store32(&r->mr_pid, 0, mo_AcquireRelease);
+  atomic_store32(&env->me_lck->mti_readers_refresh_flag, true, mo_Relaxed);
+  thread_rthc_set(env->me_txkey, nullptr);
+  return MDBX_SUCCESS;
+}
+
+/* Common code for mdbx_txn_begin() and mdbx_txn_renew(). */
+static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
+  MDBX_env *env = txn->mt_env;
+  int rc;
+
+#if MDBX_ENV_CHECKPID
+  if (unlikely(env->me_pid != mdbx_getpid())) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    return MDBX_PANIC;
+  }
+#endif /* MDBX_ENV_CHECKPID */
+
+  STATIC_ASSERT(sizeof(MDBX_reader) == 32);
+#if MDBX_LOCKING > 0
+  STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_wlock) % MDBX_CACHELINE_SIZE == 0);
+  STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_rlock) % MDBX_CACHELINE_SIZE == 0);
+#else
+  STATIC_ASSERT(
+      offsetof(MDBX_lockinfo, mti_oldest_reader) % MDBX_CACHELINE_SIZE == 0);
+  STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_numreaders) % MDBX_CACHELINE_SIZE ==
+                0);
+#endif /* MDBX_LOCKING */
+  STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_readers) % MDBX_CACHELINE_SIZE ==
+                0);
+
+  const uintptr_t tid = mdbx_thread_self();
+  if (flags & MDBX_TXN_RDONLY) {
+    mdbx_assert(env, (flags & ~(MDBX_TXN_RO_BEGIN_FLAGS | MDBX_WRITEMAP)) == 0);
+    txn->mt_flags =
+        MDBX_TXN_RDONLY | (env->me_flags & (MDBX_NOTLS | MDBX_WRITEMAP));
+    MDBX_reader *r = txn->to.reader;
+    STATIC_ASSERT(sizeof(uintptr_t) <= sizeof(r->mr_tid));
+    if (likely(env->me_flags & MDBX_ENV_TXKEY)) {
+      mdbx_assert(env, !(env->me_flags & MDBX_NOTLS));
+      r = thread_rthc_get(env->me_txkey);
+      if (likely(r)) {
+        if (unlikely(!r->mr_pid.weak) &&
+            (mdbx_runtime_flags & MDBX_DBG_LEGACY_MULTIOPEN)) {
+          thread_rthc_set(env->me_txkey, nullptr);
+          r = nullptr;
+        } else {
+          mdbx_assert(env, r->mr_pid.weak == env->me_pid);
+          mdbx_assert(env, r->mr_tid.weak == mdbx_thread_self());
+        }
+      }
+    } else {
+      mdbx_assert(env, !env->me_lck || (env->me_flags & MDBX_NOTLS));
+    }
+
+    if (likely(r)) {
+      if (unlikely(r->mr_pid.weak != env->me_pid ||
+                   r->mr_txnid.weak < SAFE64_INVALID_THRESHOLD))
+        return MDBX_BAD_RSLOT;
+    } else if (env->me_lck) {
+      bind_rslot_result brs = bind_rslot(env, tid);
+      if (unlikely(brs.err != MDBX_SUCCESS))
+        return brs.err;
+      r = brs.rslot;
+    }
+    txn->to.reader = r;
+    if (flags & (MDBX_TXN_RDONLY_PREPARE - MDBX_TXN_RDONLY)) {
+      mdbx_assert(env, txn->mt_txnid == 0);
+      mdbx_assert(env, txn->mt_owner == 0);
+      mdbx_assert(env, txn->mt_numdbs == 0);
+      if (likely(r)) {
+        mdbx_assert(env, r->mr_snapshot_pages_used.weak == 0);
+        mdbx_assert(env, r->mr_txnid.weak >= SAFE64_INVALID_THRESHOLD);
+        atomic_store32(&r->mr_snapshot_pages_used, 0, mo_Relaxed);
+      }
+      txn->mt_flags = MDBX_TXN_RDONLY | MDBX_TXN_FINISHED;
+      return MDBX_SUCCESS;
+    }
+
+    /* Seek & fetch the last meta */
+    if (likely(/* not recovery mode */ env->me_stuck_meta < 0)) {
+      while (1) {
+        MDBX_meta *const meta = mdbx_meta_head(env);
+        mdbx_jitter4testing(false);
+        const txnid_t snap = mdbx_meta_txnid_fluid(env, meta);
+        mdbx_jitter4testing(false);
+        if (likely(r)) {
+          safe64_reset(&r->mr_txnid, false);
+          atomic_store32(&r->mr_snapshot_pages_used, meta->mm_geo.next,
+                         mo_Relaxed);
+          atomic_store64(&r->mr_snapshot_pages_retired,
+                         unaligned_peek_u64(4, meta->mm_pages_retired),
+                         mo_Relaxed);
+          safe64_write(&r->mr_txnid, snap);
+          mdbx_jitter4testing(false);
+          mdbx_assert(env, r->mr_pid.weak == mdbx_getpid());
+          mdbx_assert(
+              env, r->mr_tid.weak ==
+                       ((env->me_flags & MDBX_NOTLS) ? 0 : mdbx_thread_self()));
+          mdbx_assert(env, r->mr_txnid.weak == snap);
+          atomic_store32(&env->me_lck->mti_readers_refresh_flag, true,
+                         mo_AcquireRelease);
+        }
+        mdbx_jitter4testing(true);
+
+        /* Snap the state from current meta-head */
+        txn->mt_txnid = snap;
+        txn->mt_geo = meta->mm_geo;
+        memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDBX_db));
+        txn->mt_canary = meta->mm_canary;
+
+        /* LY: Retry on a race, ITS#7970. */
+        if (likely(meta == mdbx_meta_head(env) &&
+                   snap == mdbx_meta_txnid_fluid(env, meta) &&
+                   snap >= atomic_load64(env->me_oldest, mo_AcquireRelease))) {
+          mdbx_jitter4testing(false);
+          break;
+        }
+      }
+    } else {
+      /* recovery mode */
+      MDBX_meta *const meta = METAPAGE(env, env->me_stuck_meta);
+      txn->mt_txnid = mdbx_meta_txnid_stable(env, meta);
+      txn->mt_geo = meta->mm_geo;
+      memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDBX_db));
+      txn->mt_canary = meta->mm_canary;
+      if (likely(r)) {
+        atomic_store32(&r->mr_snapshot_pages_used, meta->mm_geo.next,
+                       mo_Relaxed);
+        atomic_store64(&r->mr_snapshot_pages_retired,
+                       unaligned_peek_u64(4, meta->mm_pages_retired),
+                       mo_Relaxed);
+        atomic_store64(&r->mr_txnid, txn->mt_txnid, mo_AcquireRelease);
+        mdbx_jitter4testing(false);
+        mdbx_assert(env, r->mr_pid.weak == mdbx_getpid());
+        mdbx_assert(
+            env, r->mr_tid.weak ==
+                     ((env->me_flags & MDBX_NOTLS) ? 0 : mdbx_thread_self()));
+        mdbx_assert(env, r->mr_txnid.weak == txn->mt_txnid);
+        atomic_store32(&env->me_lck->mti_readers_refresh_flag, true,
+                       mo_AcquireRelease);
+      }
+    }
+
+    if (unlikely(txn->mt_txnid < MIN_TXNID || txn->mt_txnid > MAX_TXNID)) {
+      mdbx_error("%s", "environment corrupted by died writer, must shutdown!");
+      rc = MDBX_CORRUPTED;
+      goto bailout;
+    }
+    mdbx_assert(env, txn->mt_txnid >= env->me_oldest->weak);
+    txn->mt_dbxs = env->me_dbxs; /* mostly static anyway */
+    mdbx_ensure(env,
+                txn->mt_txnid >=
+                    /* paranoia is appropriate here */ env->me_oldest->weak);
+    txn->mt_numdbs = env->me_numdbs;
+  } else {
+    mdbx_assert(env, (flags & ~(MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_SPILLS |
+                                MDBX_WRITEMAP)) == 0);
+    if (unlikely(txn->mt_owner == tid ||
+                 /* not recovery mode */ env->me_stuck_meta >= 0))
+      return MDBX_BUSY;
+    MDBX_lockinfo *const lck = env->me_lck;
+    if (lck && (env->me_flags & MDBX_NOTLS) == 0 &&
+        (mdbx_runtime_flags & MDBX_DBG_LEGACY_OVERLAP) == 0) {
+      const unsigned snap_nreaders =
+          atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+      for (unsigned i = 0; i < snap_nreaders; ++i) {
+        if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_Relaxed) ==
+                env->me_pid &&
+            unlikely(atomic_load64(&lck->mti_readers[i].mr_tid, mo_Relaxed) ==
+                     tid)) {
+          const txnid_t txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
+          if (txnid >= MIN_TXNID && txnid <= MAX_TXNID)
+            return MDBX_TXN_OVERLAPPING;
+        }
+      }
+    }
+
+    /* Not yet touching txn == env->me_txn0, it may be active */
+    mdbx_jitter4testing(false);
+    rc = mdbx_txn_lock(env, F_ISSET(flags, MDBX_TXN_TRY));
+    if (unlikely(rc))
+      return rc;
+    if (unlikely(env->me_flags & MDBX_FATAL_ERROR)) {
+      mdbx_txn_unlock(env);
+      return MDBX_PANIC;
+    }
+#if defined(_WIN32) || defined(_WIN64)
+    if (unlikely(!env->me_map)) {
+      mdbx_txn_unlock(env);
+      return MDBX_EPERM;
+    }
+#endif /* Windows */
+
+    mdbx_jitter4testing(false);
+    MDBX_meta *meta = mdbx_meta_head(env);
+    mdbx_jitter4testing(false);
+    txn->mt_canary = meta->mm_canary;
+    const txnid_t snap = mdbx_meta_txnid_stable(env, meta);
+    txn->mt_txnid = safe64_txnid_next(snap);
+    if (unlikely(txn->mt_txnid > MAX_TXNID)) {
+      rc = MDBX_TXN_FULL;
+      mdbx_error("txnid overflow, raise %d", rc);
+      goto bailout;
+    }
+
+    txn->mt_flags = flags;
+    txn->mt_child = NULL;
+    txn->tw.loose_pages = NULL;
+    txn->tw.loose_count = 0;
+#if MDBX_ENABLE_REFUND
+    txn->tw.loose_refund_wl = 0;
+#endif /* MDBX_ENABLE_REFUND */
+    txn->tw.dirtyroom = txn->mt_env->me_options.dp_limit;
+    mdbx_dpl_clear(txn->tw.dirtylist);
+    MDBX_PNL_SIZE(txn->tw.retired_pages) = 0;
+    txn->tw.spill_pages = NULL;
+    txn->tw.spill_least_removed = 0;
+    txn->tw.last_reclaimed = 0;
+    if (txn->tw.lifo_reclaimed)
+      MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) = 0;
+    env->me_txn = txn;
+    txn->mt_numdbs = env->me_numdbs;
+    memcpy(txn->mt_dbiseqs, env->me_dbiseqs, txn->mt_numdbs * sizeof(unsigned));
+    /* Copy the DB info and flags */
+    memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDBX_db));
+    /* Moved to here to avoid a data race in read TXNs */
+    txn->mt_geo = meta->mm_geo;
+  }
+
+  /* Setup db info */
+  mdbx_compiler_barrier();
+  for (unsigned i = CORE_DBS; i < txn->mt_numdbs; i++) {
+    const unsigned db_flags = env->me_dbflags[i];
+    txn->mt_dbs[i].md_flags = db_flags & DB_PERSISTENT_FLAGS;
+    txn->mt_dbistate[i] =
+        (db_flags & DB_VALID) ? DBI_VALID | DBI_USRVALID | DBI_STALE : 0;
+  }
+  txn->mt_dbistate[MAIN_DBI] = DBI_VALID | DBI_USRVALID;
+  txn->mt_dbistate[FREE_DBI] = DBI_VALID;
+
+  if (unlikely(env->me_flags & MDBX_FATAL_ERROR)) {
+    mdbx_warning("%s", "environment had fatal error, must shutdown!");
+    rc = MDBX_PANIC;
+  } else {
+    const size_t size =
+        pgno2bytes(env, (txn->mt_flags & MDBX_TXN_RDONLY) ? txn->mt_next_pgno
+                                                          : txn->mt_end_pgno);
+    if (unlikely(size > env->me_dxb_mmap.limit)) {
+      if (txn->mt_geo.upper > MAX_PAGENO ||
+          bytes2pgno(env, pgno2bytes(env, txn->mt_geo.upper)) !=
+              txn->mt_geo.upper) {
+        rc = MDBX_UNABLE_EXTEND_MAPSIZE;
+        goto bailout;
+      }
+      rc = mdbx_mapresize(env, txn->mt_next_pgno, txn->mt_end_pgno,
+                          txn->mt_geo.upper,
+                          (txn->mt_flags & MDBX_TXN_RDONLY) ? true : false);
+      if (rc != MDBX_SUCCESS)
+        goto bailout;
+    }
+    if (txn->mt_flags & MDBX_TXN_RDONLY) {
+#if defined(_WIN32) || defined(_WIN64)
+      if ((size > env->me_dbgeo.lower && env->me_dbgeo.shrink) ||
+          (mdbx_RunningUnderWine() &&
+           /* under Wine acquisition of remap_guard is always required,
+            * since Wine don't support section extending,
+            * i.e. in both cases unmap+map are required. */
+           size < env->me_dbgeo.upper && env->me_dbgeo.grow)) {
+        txn->mt_flags |= MDBX_SHRINK_ALLOWED;
+        mdbx_srwlock_AcquireShared(&env->me_remap_guard);
+      }
+#endif /* Windows */
+    } else {
+      env->me_dxb_mmap.current = size;
+#if defined(_WIN32) || defined(_WIN64)
+      env->me_dxb_mmap.filesize =
+          (env->me_dxb_mmap.filesize < size) ? size : env->me_dxb_mmap.filesize;
+#endif /* Windows */
+    }
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+    mdbx_txn_valgrind(env, txn);
+#endif
+    txn->mt_owner = tid;
+    return MDBX_SUCCESS;
+  }
+bailout:
+  mdbx_tassert(txn, rc != MDBX_SUCCESS);
+  mdbx_txn_end(txn, MDBX_END_SLOT | MDBX_END_FAIL_BEGIN);
+  return rc;
+}
+
+static __always_inline int check_txn(const MDBX_txn *txn, int bad_bits) {
+  if (unlikely(!txn))
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_signature != MDBX_MT_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+  if (unlikely(txn->mt_flags & bad_bits))
+    return MDBX_BAD_TXN;
+
+#if MDBX_TXN_CHECKOWNER
+  if ((txn->mt_flags & MDBX_NOTLS) == 0 &&
+      unlikely(txn->mt_owner != mdbx_thread_self()))
+    return txn->mt_owner ? MDBX_THREAD_MISMATCH : MDBX_BAD_TXN;
+#endif /* MDBX_TXN_CHECKOWNER */
+
+  return MDBX_SUCCESS;
+}
+
+static __always_inline int check_txn_rw(const MDBX_txn *txn, int bad_bits) {
+  if (unlikely(!txn))
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_signature != MDBX_MT_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+  if (unlikely(txn->mt_flags & bad_bits))
+    return MDBX_BAD_TXN;
+
+  if (unlikely(F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY)))
+    return MDBX_EACCESS;
+
+#if MDBX_TXN_CHECKOWNER
+  if (unlikely(txn->mt_owner != mdbx_thread_self()))
+    return txn->mt_owner ? MDBX_THREAD_MISMATCH : MDBX_BAD_TXN;
+#endif /* MDBX_TXN_CHECKOWNER */
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_txn_renew(MDBX_txn *txn) {
+  if (unlikely(!txn))
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_signature != MDBX_MT_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+  if (unlikely((txn->mt_flags & MDBX_TXN_RDONLY) == 0))
+    return MDBX_EINVAL;
+
+  int rc;
+  if (unlikely(txn->mt_owner != 0 || !(txn->mt_flags & MDBX_TXN_FINISHED))) {
+    rc = mdbx_txn_reset(txn);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  rc = mdbx_txn_renew0(txn, MDBX_TXN_RDONLY);
+  if (rc == MDBX_SUCCESS) {
+    txn->mt_owner = mdbx_thread_self();
+    mdbx_debug("renew txn %" PRIaTXN "%c %p on env %p, root page %" PRIaPGNO
+               "/%" PRIaPGNO,
+               txn->mt_txnid, (txn->mt_flags & MDBX_TXN_RDONLY) ? 'r' : 'w',
+               (void *)txn, (void *)txn->mt_env, txn->mt_dbs[MAIN_DBI].md_root,
+               txn->mt_dbs[FREE_DBI].md_root);
+  }
+  return rc;
+}
+
+int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, MDBX_txn_flags_t flags,
+                   MDBX_txn **ret) {
+  return __inline_mdbx_txn_begin(env, parent, flags, ret);
+}
+
+int mdbx_txn_set_userctx(MDBX_txn *txn, void *ctx) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED - MDBX_TXN_HAS_CHILD);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  txn->mt_userctx = ctx;
+  return MDBX_SUCCESS;
+}
+
+void *mdbx_txn_get_userctx(const MDBX_txn *txn) {
+  return check_txn(txn, MDBX_TXN_BLOCKED - MDBX_TXN_HAS_CHILD)
+             ? nullptr
+             : txn->mt_userctx;
+}
+
+int mdbx_txn_begin_ex(MDBX_env *env, MDBX_txn *parent, MDBX_txn_flags_t flags,
+                      MDBX_txn **ret, void *context) {
+  MDBX_txn *txn;
+  unsigned size, tsize;
+
+  if (unlikely(!ret))
+    return MDBX_EINVAL;
+  *ret = NULL;
+
+  if (unlikely((flags & ~MDBX_TXN_RW_BEGIN_FLAGS) &&
+               (flags & ~MDBX_TXN_RO_BEGIN_FLAGS)))
+    return MDBX_EINVAL;
+
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(env->me_flags & MDBX_RDONLY &
+               ~flags)) /* write txn in RDONLY env */
+    return MDBX_EACCESS;
+
+  if (unlikely(!env->me_map))
+    return MDBX_EPERM;
+
+  flags |= env->me_flags & MDBX_WRITEMAP;
+
+  if (parent) {
+    /* Nested transactions: Max 1 child, write txns only, no writemap */
+    rc = check_txn_rw(parent,
+                      MDBX_TXN_RDONLY | MDBX_WRITEMAP | MDBX_TXN_BLOCKED);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+
+    if (env->me_options.spill_parent4child_denominator) {
+      /* Spill dirty-pages of parent to provide dirtyroom for child txn */
+      rc = mdbx_txn_spill(parent, nullptr,
+                          parent->tw.dirtylist->length /
+                              env->me_options.spill_parent4child_denominator);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+    }
+    mdbx_tassert(parent, mdbx_audit_ex(parent, 0, false) == 0);
+
+    flags |= parent->mt_flags & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_SPILLS);
+    /* Child txns save MDBX_pgstate and use own copy of cursors */
+    size = env->me_maxdbs * (sizeof(MDBX_db) + sizeof(MDBX_cursor *) + 1);
+    size += tsize = sizeof(MDBX_txn);
+  } else if (flags & MDBX_TXN_RDONLY) {
+    if (env->me_txn0 &&
+        unlikely(env->me_txn0->mt_owner == mdbx_thread_self()) &&
+        (mdbx_runtime_flags & MDBX_DBG_LEGACY_OVERLAP) == 0)
+      return MDBX_TXN_OVERLAPPING;
+    size = env->me_maxdbs * (sizeof(MDBX_db) + 1);
+    size += tsize = sizeof(MDBX_txn);
+  } else {
+    /* Reuse preallocated write txn. However, do not touch it until
+     * mdbx_txn_renew0() succeeds, since it currently may be active. */
+    txn = env->me_txn0;
+    goto renew;
+  }
+  if (unlikely((txn = mdbx_malloc(size)) == NULL)) {
+    mdbx_debug("calloc: %s", "failed");
+    return MDBX_ENOMEM;
+  }
+  memset(txn, 0, tsize);
+  txn->mt_dbxs = env->me_dbxs; /* static */
+  txn->mt_dbs = (MDBX_db *)((char *)txn + tsize);
+  txn->mt_dbistate = (uint8_t *)txn + size - env->me_maxdbs;
+  txn->mt_flags = flags;
+  txn->mt_env = env;
+
+  if (parent) {
+    mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+    txn->tw.cursors = (MDBX_cursor **)(txn->mt_dbs + env->me_maxdbs);
+    txn->mt_dbiseqs = parent->mt_dbiseqs;
+    rc = mdbx_dpl_alloc(txn);
+    if (likely(rc == MDBX_SUCCESS)) {
+      const unsigned len =
+          MDBX_PNL_SIZE(parent->tw.reclaimed_pglist) + parent->tw.loose_count;
+      txn->tw.reclaimed_pglist =
+          mdbx_pnl_alloc((len > MDBX_PNL_INITIAL) ? len : MDBX_PNL_INITIAL);
+      if (unlikely(!txn->tw.reclaimed_pglist))
+        rc = MDBX_ENOMEM;
+    }
+    if (unlikely(rc != MDBX_SUCCESS)) {
+    nested_failed:
+      mdbx_pnl_free(txn->tw.reclaimed_pglist);
+      mdbx_dpl_free(txn);
+      mdbx_free(txn);
+      return rc;
+    }
+    txn->tw.dirtyroom = parent->tw.dirtyroom;
+
+    /* Move loose pages to reclaimed list */
+    if (parent->tw.loose_count) {
+      do {
+        MDBX_page *lp = parent->tw.loose_pages;
+        const unsigned di = mdbx_dpl_exist(parent->tw.dirtylist, lp->mp_pgno);
+        mdbx_tassert(parent, di && parent->tw.dirtylist->items[di].ptr == lp);
+        mdbx_tassert(parent, lp->mp_flags == (P_LOOSE | P_DIRTY));
+        rc =
+            mdbx_pnl_insert_range(&parent->tw.reclaimed_pglist, lp->mp_pgno, 1);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto nested_failed;
+        parent->tw.loose_pages = lp->mp_next;
+        /* Remove from dirty list */
+        mdbx_page_wash(parent, di, lp, 1);
+      } while (parent->tw.loose_pages);
+      parent->tw.loose_count = 0;
+#if MDBX_ENABLE_REFUND
+      parent->tw.loose_refund_wl = 0;
+#endif /* MDBX_ENABLE_REFUND */
+      mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+    }
+
+    mdbx_dpl_sort(parent->tw.dirtylist);
+    if (parent->tw.spill_pages)
+      mdbx_spill_purge(parent);
+
+    mdbx_tassert(txn, MDBX_PNL_ALLOCLEN(txn->tw.reclaimed_pglist) >=
+                          MDBX_PNL_SIZE(parent->tw.reclaimed_pglist));
+    memcpy(txn->tw.reclaimed_pglist, parent->tw.reclaimed_pglist,
+           MDBX_PNL_SIZEOF(parent->tw.reclaimed_pglist));
+    mdbx_assert(env, mdbx_pnl_check4assert(
+                         txn->tw.reclaimed_pglist,
+                         (txn->mt_next_pgno /* LY: intentional assignment here,
+                                                   only for assertion */
+                          = parent->mt_next_pgno) -
+                             MDBX_ENABLE_REFUND));
+
+    txn->tw.last_reclaimed = parent->tw.last_reclaimed;
+    if (parent->tw.lifo_reclaimed) {
+      txn->tw.lifo_reclaimed = parent->tw.lifo_reclaimed;
+      parent->tw.lifo_reclaimed =
+          (void *)(intptr_t)MDBX_PNL_SIZE(parent->tw.lifo_reclaimed);
+    }
+
+    txn->tw.retired_pages = parent->tw.retired_pages;
+    parent->tw.retired_pages =
+        (void *)(intptr_t)MDBX_PNL_SIZE(parent->tw.retired_pages);
+
+    txn->mt_txnid = parent->mt_txnid;
+    txn->mt_geo = parent->mt_geo;
+#if MDBX_ENABLE_REFUND
+    txn->tw.loose_refund_wl = 0;
+#endif /* MDBX_ENABLE_REFUND */
+    txn->mt_canary = parent->mt_canary;
+    parent->mt_flags |= MDBX_TXN_HAS_CHILD;
+    parent->mt_child = txn;
+    txn->mt_parent = parent;
+    txn->mt_numdbs = parent->mt_numdbs;
+    txn->mt_owner = parent->mt_owner;
+    memcpy(txn->mt_dbs, parent->mt_dbs, txn->mt_numdbs * sizeof(MDBX_db));
+    /* Copy parent's mt_dbistate, but clear DB_NEW */
+    for (unsigned i = 0; i < txn->mt_numdbs; i++)
+      txn->mt_dbistate[i] =
+          parent->mt_dbistate[i] & ~(DBI_FRESH | DBI_CREAT | DBI_DIRTY);
+    mdbx_tassert(parent,
+                 parent->mt_parent ||
+                     parent->tw.dirtyroom + parent->tw.dirtylist->length ==
+                         env->me_options.dp_limit);
+    assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+    env->me_txn = txn;
+    rc = mdbx_cursor_shadow(parent, txn);
+    if (unlikely(rc != MDBX_SUCCESS))
+      mdbx_txn_end(txn, MDBX_END_FAIL_BEGINCHILD);
+  } else { /* MDBX_TXN_RDONLY */
+    txn->mt_dbiseqs = env->me_dbiseqs;
+  renew:
+    rc = mdbx_txn_renew0(txn, flags);
+  }
+
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (txn != env->me_txn0)
+      mdbx_free(txn);
+  } else {
+    if (flags & (MDBX_TXN_RDONLY_PREPARE - MDBX_TXN_RDONLY))
+      mdbx_assert(env, txn->mt_flags == (MDBX_TXN_RDONLY | MDBX_TXN_FINISHED));
+    else if (flags & MDBX_TXN_RDONLY)
+      mdbx_assert(env, (txn->mt_flags &
+                        ~(MDBX_NOTLS | MDBX_TXN_RDONLY | MDBX_WRITEMAP |
+                          /* Win32: SRWL flag */ MDBX_SHRINK_ALLOWED)) == 0);
+    else {
+      mdbx_assert(env, (txn->mt_flags & ~(MDBX_WRITEMAP | MDBX_SHRINK_ALLOWED |
+                                          MDBX_NOMETASYNC | MDBX_SAFE_NOSYNC |
+                                          MDBX_TXN_SPILLS)) == 0);
+      assert(!txn->tw.spill_pages && !txn->tw.spill_least_removed);
+    }
+    txn->mt_signature = MDBX_MT_SIGNATURE;
+    txn->mt_userctx = context;
+    *ret = txn;
+    mdbx_debug("begin txn %" PRIaTXN "%c %p on env %p, root page %" PRIaPGNO
+               "/%" PRIaPGNO,
+               txn->mt_txnid, (flags & MDBX_TXN_RDONLY) ? 'r' : 'w',
+               (void *)txn, (void *)env, txn->mt_dbs[MAIN_DBI].md_root,
+               txn->mt_dbs[FREE_DBI].md_root);
+  }
+
+  return rc;
+}
+
+int mdbx_txn_info(const MDBX_txn *txn, MDBX_txn_info *info, bool scan_rlt) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED - MDBX_TXN_HAS_CHILD);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!info))
+    return MDBX_EINVAL;
+
+  MDBX_env *const env = txn->mt_env;
+#if MDBX_ENV_CHECKPID
+  if (unlikely(env->me_pid != mdbx_getpid())) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    return MDBX_PANIC;
+  }
+#endif /* MDBX_ENV_CHECKPID */
+
+  info->txn_id = txn->mt_txnid;
+  info->txn_space_used = pgno2bytes(env, txn->mt_geo.next);
+
+  if (txn->mt_flags & MDBX_TXN_RDONLY) {
+    const MDBX_meta *head_meta;
+    txnid_t head_txnid;
+    uint64_t head_retired;
+    do {
+      /* fetch info from volatile head */
+      head_meta = mdbx_meta_head(env);
+      head_txnid = mdbx_meta_txnid_fluid(env, head_meta);
+      head_retired = unaligned_peek_u64(4, head_meta->mm_pages_retired);
+      info->txn_space_limit_soft = pgno2bytes(env, head_meta->mm_geo.now);
+      info->txn_space_limit_hard = pgno2bytes(env, head_meta->mm_geo.upper);
+      info->txn_space_leftover =
+          pgno2bytes(env, head_meta->mm_geo.now - head_meta->mm_geo.next);
+      mdbx_compiler_barrier();
+    } while (unlikely(head_meta != mdbx_meta_head(env) ||
+                      head_txnid != mdbx_meta_txnid_fluid(env, head_meta)));
+
+    info->txn_reader_lag = head_txnid - info->txn_id;
+    info->txn_space_dirty = info->txn_space_retired = 0;
+    uint64_t reader_snapshot_pages_retired;
+    if (txn->to.reader &&
+        head_retired >
+            (reader_snapshot_pages_retired = atomic_load64(
+                 &txn->to.reader->mr_snapshot_pages_retired, mo_Relaxed))) {
+      info->txn_space_dirty = info->txn_space_retired = pgno2bytes(
+          env, (pgno_t)(head_retired - reader_snapshot_pages_retired));
+
+      size_t retired_next_reader = 0;
+      MDBX_lockinfo *const lck = env->me_lck;
+      if (scan_rlt && info->txn_reader_lag > 1 && lck) {
+        /* find next more recent reader */
+        txnid_t next_reader = head_txnid;
+        const unsigned snap_nreaders =
+            atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+        for (unsigned i = 0; i < snap_nreaders; ++i) {
+        retry:
+          if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease)) {
+            mdbx_jitter4testing(true);
+            const txnid_t snap_txnid =
+                safe64_read(&lck->mti_readers[i].mr_txnid);
+            const uint64_t snap_retired =
+                atomic_load64(&lck->mti_readers[i].mr_snapshot_pages_retired,
+                              mo_AcquireRelease);
+            if (unlikely(snap_retired !=
+                         atomic_load64(
+                             &lck->mti_readers[i].mr_snapshot_pages_retired,
+                             mo_Relaxed)) ||
+                snap_txnid != safe64_read(&lck->mti_readers[i].mr_txnid))
+              goto retry;
+            if (snap_txnid <= txn->mt_txnid) {
+              retired_next_reader = 0;
+              break;
+            }
+            if (snap_txnid < next_reader) {
+              next_reader = snap_txnid;
+              retired_next_reader = pgno2bytes(
+                  env, (pgno_t)(snap_retired -
+                                atomic_load64(
+                                    &txn->to.reader->mr_snapshot_pages_retired,
+                                    mo_Relaxed)));
+            }
+          }
+        }
+      }
+      info->txn_space_dirty = retired_next_reader;
+    }
+  } else {
+    info->txn_space_limit_soft = pgno2bytes(env, txn->mt_geo.now);
+    info->txn_space_limit_hard = pgno2bytes(env, txn->mt_geo.upper);
+    info->txn_space_retired = pgno2bytes(
+        env, txn->mt_child ? (unsigned)(uintptr_t)txn->tw.retired_pages
+                           : MDBX_PNL_SIZE(txn->tw.retired_pages));
+    info->txn_space_leftover = pgno2bytes(env, txn->tw.dirtyroom);
+    info->txn_space_dirty =
+        pgno2bytes(env, txn->mt_env->me_options.dp_limit - txn->tw.dirtyroom);
+    info->txn_reader_lag = INT64_MAX;
+    MDBX_lockinfo *const lck = env->me_lck;
+    if (scan_rlt && lck) {
+      txnid_t oldest_snapshot = txn->mt_txnid;
+      const unsigned snap_nreaders =
+          atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+      if (snap_nreaders) {
+        oldest_snapshot = mdbx_find_oldest(txn);
+        if (oldest_snapshot == txn->mt_txnid - 1) {
+          /* check if there is at least one reader */
+          bool exists = false;
+          for (unsigned i = 0; i < snap_nreaders; ++i) {
+            if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_Relaxed) &&
+                txn->mt_txnid > safe64_read(&lck->mti_readers[i].mr_txnid)) {
+              exists = true;
+              break;
+            }
+          }
+          oldest_snapshot += !exists;
+        }
+      }
+      info->txn_reader_lag = txn->mt_txnid - oldest_snapshot;
+    }
+  }
+
+  return MDBX_SUCCESS;
+}
+
+MDBX_env *mdbx_txn_env(const MDBX_txn *txn) {
+  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE ||
+               txn->mt_env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return NULL;
+  return txn->mt_env;
+}
+
+uint64_t mdbx_txn_id(const MDBX_txn *txn) {
+  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
+    return 0;
+  return txn->mt_txnid;
+}
+
+int mdbx_txn_flags(const MDBX_txn *txn) {
+  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
+    return -1;
+  return txn->mt_flags;
+}
+
+/* Check for misused dbi handles */
+#define TXN_DBI_CHANGED(txn, dbi)                                              \
+  ((txn)->mt_dbiseqs[dbi] != (txn)->mt_env->me_dbiseqs[dbi])
+
+static void dbi_import_locked(MDBX_txn *txn) {
+  MDBX_env *const env = txn->mt_env;
+  const unsigned n = env->me_numdbs;
+  for (unsigned i = CORE_DBS; i < n; ++i) {
+    if (i >= txn->mt_numdbs) {
+      txn->mt_dbistate[i] = 0;
+      if (!(txn->mt_flags & MDBX_TXN_RDONLY))
+        txn->tw.cursors[i] = NULL;
+    }
+    if ((env->me_dbflags[i] & DB_VALID) &&
+        !(txn->mt_dbistate[i] & DBI_USRVALID)) {
+      txn->mt_dbiseqs[i] = env->me_dbiseqs[i];
+      txn->mt_dbs[i].md_flags = env->me_dbflags[i] & DB_PERSISTENT_FLAGS;
+      txn->mt_dbistate[i] = DBI_VALID | DBI_USRVALID | DBI_STALE;
+      mdbx_tassert(txn, txn->mt_dbxs[i].md_cmp != NULL);
+    }
+  }
+  txn->mt_numdbs = n;
+}
+
+/* Import DBI which opened after txn started into context */
+static __cold bool dbi_import(MDBX_txn *txn, MDBX_dbi dbi) {
+  if (dbi < CORE_DBS || dbi >= txn->mt_env->me_numdbs)
+    return false;
+
+  mdbx_ensure(txn->mt_env, mdbx_fastmutex_acquire(&txn->mt_env->me_dbi_lock) ==
+                               MDBX_SUCCESS);
+  dbi_import_locked(txn);
+  mdbx_ensure(txn->mt_env, mdbx_fastmutex_release(&txn->mt_env->me_dbi_lock) ==
+                               MDBX_SUCCESS);
+  return txn->mt_dbistate[dbi] & DBI_USRVALID;
+}
+
+/* Export or close DBI handles opened in this txn. */
+static void dbi_update(MDBX_txn *txn, int keep) {
+  mdbx_tassert(txn, !txn->mt_parent && txn == txn->mt_env->me_txn0);
+  MDBX_dbi n = txn->mt_numdbs;
+  if (n) {
+    bool locked = false;
+    MDBX_env *const env = txn->mt_env;
+
+    for (unsigned i = n; --i >= CORE_DBS;) {
+      if (likely((txn->mt_dbistate[i] & DBI_CREAT) == 0))
+        continue;
+      if (!locked) {
+        mdbx_ensure(env,
+                    mdbx_fastmutex_acquire(&env->me_dbi_lock) == MDBX_SUCCESS);
+        locked = true;
+      }
+      if (env->me_numdbs <= i || txn->mt_dbiseqs[i] != env->me_dbiseqs[i])
+        continue /* dbi explicitly closed and/or then re-opened by other txn */;
+      if (keep) {
+        env->me_dbflags[i] = txn->mt_dbs[i].md_flags | DB_VALID;
+      } else {
+        char *ptr = env->me_dbxs[i].md_name.iov_base;
+        if (ptr) {
+          env->me_dbxs[i].md_name.iov_len = 0;
+          mdbx_memory_fence(false, true);
+          mdbx_assert(env, env->me_dbflags[i] == 0);
+          env->me_dbiseqs[i]++;
+          env->me_dbxs[i].md_name.iov_base = NULL;
+          mdbx_free(ptr);
+        }
+      }
+    }
+
+    n = env->me_numdbs;
+    if (n > CORE_DBS && unlikely(!(env->me_dbflags[n - 1] & DB_VALID))) {
+      if (!locked) {
+        mdbx_ensure(env,
+                    mdbx_fastmutex_acquire(&env->me_dbi_lock) == MDBX_SUCCESS);
+        locked = true;
+      }
+
+      n = env->me_numdbs;
+      while (n > CORE_DBS && !(env->me_dbflags[n - 1] & DB_VALID))
+        --n;
+      env->me_numdbs = n;
+    }
+
+    if (unlikely(locked))
+      mdbx_ensure(env,
+                  mdbx_fastmutex_release(&env->me_dbi_lock) == MDBX_SUCCESS);
+  }
+}
+
+/* Filter-out pgno list from transaction's dirty-page list */
+static void mdbx_dpl_sift(MDBX_txn *const txn, MDBX_PNL pl,
+                          const bool spilled) {
+  if (MDBX_PNL_SIZE(pl) && txn->tw.dirtylist->length) {
+    mdbx_tassert(txn, mdbx_pnl_check4assert(pl, txn->mt_next_pgno << spilled));
+    MDBX_dpl *dl = mdbx_dpl_sort(txn->tw.dirtylist);
+
+    /* Scanning in ascend order */
+    const int step = MDBX_PNL_ASCENDING ? 1 : -1;
+    const int begin = MDBX_PNL_ASCENDING ? 1 : MDBX_PNL_SIZE(pl);
+    const int end = MDBX_PNL_ASCENDING ? MDBX_PNL_SIZE(pl) + 1 : 0;
+    mdbx_tassert(txn, pl[begin] <= pl[end - step]);
+
+    unsigned r = mdbx_dpl_search(dl, pl[begin] >> spilled);
+    mdbx_tassert(txn, dl->sorted == dl->length);
+    for (int i = begin; r <= dl->length;) { /* scan loop */
+      assert(i != end);
+      mdbx_tassert(txn, !spilled || (pl[i] & 1) == 0);
+      pgno_t pl_pgno = pl[i] >> spilled;
+      pgno_t dp_pgno = dl->items[r].pgno;
+      if (likely(dp_pgno != pl_pgno)) {
+        const bool cmp = dp_pgno < pl_pgno;
+        r += cmp;
+        i += cmp ? 0 : step;
+        if (likely(i != end))
+          continue;
+        return;
+      }
+
+      /* update loop */
+      unsigned w = r;
+    remove_dl:
+      if ((txn->mt_env->me_flags & MDBX_WRITEMAP) == 0) {
+        MDBX_page *dp = dl->items[r].ptr;
+        mdbx_dpage_free(txn->mt_env, dp, IS_OVERFLOW(dp) ? dp->mp_pages : 1);
+      }
+      ++r;
+    next_i:
+      i += step;
+      if (unlikely(i == end)) {
+        while (r <= dl->length)
+          dl->items[w++] = dl->items[r++];
+      } else {
+        while (r <= dl->length) {
+          assert(i != end);
+          mdbx_tassert(txn, !spilled || (pl[i] & 1) == 0);
+          pl_pgno = pl[i] >> spilled;
+          dp_pgno = dl->items[r].pgno;
+          if (dp_pgno < pl_pgno)
+            dl->items[w++] = dl->items[r++];
+          else if (dp_pgno > pl_pgno)
+            goto next_i;
+          else
+            goto remove_dl;
+        }
+      }
+      dl->sorted = dl->length = w - 1;
+      txn->tw.dirtyroom += r - w;
+      assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+      return;
+    }
+  }
+}
+
+/* End a transaction, except successful commit of a nested transaction.
+ * May be called twice for readonly txns: First reset it, then abort.
+ * [in] txn   the transaction handle to end
+ * [in] mode  why and how to end the transaction */
+static int mdbx_txn_end(MDBX_txn *txn, const unsigned mode) {
+  MDBX_env *env = txn->mt_env;
+  static const char *const names[] = MDBX_END_NAMES;
+
+#if MDBX_ENV_CHECKPID
+  if (unlikely(txn->mt_env->me_pid != mdbx_getpid())) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    return MDBX_PANIC;
+  }
+#endif /* MDBX_ENV_CHECKPID */
+
+  mdbx_debug("%s txn %" PRIaTXN "%c %p on mdbenv %p, root page %" PRIaPGNO
+             "/%" PRIaPGNO,
+             names[mode & MDBX_END_OPMASK], txn->mt_txnid,
+             (txn->mt_flags & MDBX_TXN_RDONLY) ? 'r' : 'w', (void *)txn,
+             (void *)env, txn->mt_dbs[MAIN_DBI].md_root,
+             txn->mt_dbs[FREE_DBI].md_root);
+
+  mdbx_ensure(env, txn->mt_txnid >=
+                       /* paranoia is appropriate here */ env->me_oldest->weak);
+
+  int rc = MDBX_SUCCESS;
+  if (F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY)) {
+    if (txn->to.reader) {
+      MDBX_reader *slot = txn->to.reader;
+      mdbx_assert(env, slot->mr_pid.weak == env->me_pid);
+      if (likely(!F_ISSET(txn->mt_flags, MDBX_TXN_FINISHED))) {
+        mdbx_assert(env, txn->mt_txnid == slot->mr_txnid.weak &&
+                             slot->mr_txnid.weak >=
+                                 env->me_lck->mti_oldest_reader.weak);
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+        mdbx_txn_valgrind(env, nullptr);
+#endif
+        atomic_store32(&slot->mr_snapshot_pages_used, 0, mo_Relaxed);
+        safe64_reset(&slot->mr_txnid, false);
+        atomic_store32(&env->me_lck->mti_readers_refresh_flag, true,
+                       mo_AcquireRelease);
+      } else {
+        mdbx_assert(env, slot->mr_pid.weak == env->me_pid);
+        mdbx_assert(env, slot->mr_txnid.weak >= SAFE64_INVALID_THRESHOLD);
+      }
+      if (mode & MDBX_END_SLOT) {
+        if ((env->me_flags & MDBX_ENV_TXKEY) == 0)
+          atomic_store32(&slot->mr_pid, 0, mo_AcquireRelease);
+        txn->to.reader = NULL;
+      }
+    }
+#if defined(_WIN32) || defined(_WIN64)
+    if (txn->mt_flags & MDBX_SHRINK_ALLOWED)
+      mdbx_srwlock_ReleaseShared(&env->me_remap_guard);
+#endif
+    txn->mt_numdbs = 0; /* prevent further DBI activity */
+    txn->mt_flags = MDBX_TXN_RDONLY | MDBX_TXN_FINISHED;
+    txn->mt_owner = 0;
+  } else if (!F_ISSET(txn->mt_flags, MDBX_TXN_FINISHED)) {
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+    if (txn == env->me_txn0)
+      mdbx_txn_valgrind(env, nullptr);
+#endif
+    if (!(mode & MDBX_END_EOTDONE)) /* !(already closed cursors) */
+      mdbx_cursors_eot(txn, false);
+
+    txn->mt_flags = MDBX_TXN_FINISHED;
+    txn->mt_owner = 0;
+    env->me_txn = txn->mt_parent;
+    mdbx_pnl_free(txn->tw.spill_pages);
+    txn->tw.spill_pages = nullptr;
+    if (txn == env->me_txn0) {
+      mdbx_assert(env, txn->mt_parent == NULL);
+      /* Export or close DBI handles created in this txn */
+      dbi_update(txn, mode & MDBX_END_UPDATE);
+      mdbx_pnl_shrink(&txn->tw.retired_pages);
+      mdbx_pnl_shrink(&txn->tw.reclaimed_pglist);
+      if (!(env->me_flags & MDBX_WRITEMAP))
+        mdbx_dlist_free(txn);
+      /* The writer mutex was locked in mdbx_txn_begin. */
+      mdbx_txn_unlock(env);
+    } else {
+      mdbx_assert(env, txn->mt_parent != NULL);
+      MDBX_txn *const parent = txn->mt_parent;
+      mdbx_assert(env, parent->mt_signature == MDBX_MT_SIGNATURE);
+      mdbx_assert(env, parent->mt_child == txn &&
+                           (parent->mt_flags & MDBX_TXN_HAS_CHILD) != 0);
+      mdbx_assert(
+          env, mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+
+      if (txn->tw.lifo_reclaimed) {
+        mdbx_assert(env, MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) >=
+                             (unsigned)(uintptr_t)parent->tw.lifo_reclaimed);
+        MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) =
+            (unsigned)(uintptr_t)parent->tw.lifo_reclaimed;
+        parent->tw.lifo_reclaimed = txn->tw.lifo_reclaimed;
+      }
+
+      if (txn->tw.retired_pages) {
+        mdbx_assert(env, MDBX_PNL_SIZE(txn->tw.retired_pages) >=
+                             (unsigned)(uintptr_t)parent->tw.retired_pages);
+        MDBX_PNL_SIZE(txn->tw.retired_pages) =
+            (unsigned)(uintptr_t)parent->tw.retired_pages;
+        parent->tw.retired_pages = txn->tw.retired_pages;
+      }
+
+      parent->mt_child = nullptr;
+      parent->mt_flags &= ~MDBX_TXN_HAS_CHILD;
+      mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+      mdbx_tassert(parent, mdbx_audit_ex(parent, 0, false) == 0);
+      if (!(env->me_flags & MDBX_WRITEMAP))
+        mdbx_dlist_free(txn);
+      mdbx_dpl_free(txn);
+      mdbx_pnl_free(txn->tw.reclaimed_pglist);
+
+      if (parent->mt_geo.upper != txn->mt_geo.upper ||
+          parent->mt_geo.now != txn->mt_geo.now) {
+        /* undo resize performed by child txn */
+        rc = mdbx_mapresize_implicit(env, parent->mt_next_pgno,
+                                     parent->mt_geo.now, parent->mt_geo.upper);
+        if (rc == MDBX_RESULT_TRUE) {
+          /* unable undo resize (it is regular for Windows),
+           * therefore promote size changes from child to the parent txn */
+          mdbx_warning("unable undo resize performed by child txn, promote to "
+                       "the parent (%u->%u, %u->%u)",
+                       txn->mt_geo.now, parent->mt_geo.now, txn->mt_geo.upper,
+                       parent->mt_geo.upper);
+          parent->mt_geo.now = txn->mt_geo.now;
+          parent->mt_geo.upper = txn->mt_geo.upper;
+          rc = MDBX_SUCCESS;
+        } else if (unlikely(rc != MDBX_SUCCESS)) {
+          mdbx_error("error %d while undo resize performed by child txn, fail "
+                     "the parent",
+                     rc);
+          parent->mt_flags |= MDBX_TXN_ERROR;
+          if (!env->me_dxb_mmap.address)
+            env->me_flags |= MDBX_FATAL_ERROR;
+        }
+      }
+    }
+  }
+
+  mdbx_assert(env, txn == env->me_txn0 || txn->mt_owner == 0);
+  if ((mode & MDBX_END_FREE) != 0 && txn != env->me_txn0) {
+    txn->mt_signature = 0;
+    mdbx_free(txn);
+  }
+
+  return rc;
+}
+
+int mdbx_txn_reset(MDBX_txn *txn) {
+  int rc = check_txn(txn, 0);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  /* This call is only valid for read-only txns */
+  if (unlikely((txn->mt_flags & MDBX_TXN_RDONLY) == 0))
+    return MDBX_EINVAL;
+
+  /* LY: don't close DBI-handles */
+  rc = mdbx_txn_end(txn, MDBX_END_RESET | MDBX_END_UPDATE);
+  if (rc == MDBX_SUCCESS) {
+    mdbx_tassert(txn, txn->mt_signature == MDBX_MT_SIGNATURE);
+    mdbx_tassert(txn, txn->mt_owner == 0);
+  }
+  return rc;
+}
+
+int mdbx_txn_break(MDBX_txn *txn) {
+  do {
+    int rc = check_txn(txn, 0);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    txn->mt_flags |= MDBX_TXN_ERROR;
+    if (txn->mt_flags & MDBX_TXN_RDONLY)
+      break;
+    txn = txn->mt_child;
+  } while (txn);
+  return MDBX_SUCCESS;
+}
+
+int mdbx_txn_abort(MDBX_txn *txn) {
+  int rc = check_txn(txn, 0);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY))
+    /* LY: don't close DBI-handles */
+    return mdbx_txn_end(txn, MDBX_END_ABORT | MDBX_END_UPDATE | MDBX_END_SLOT |
+                                 MDBX_END_FREE);
+
+  if (txn->mt_child)
+    mdbx_txn_abort(txn->mt_child);
+
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  return mdbx_txn_end(txn, MDBX_END_ABORT | MDBX_END_SLOT | MDBX_END_FREE);
+}
+
+/* Count all the pages in each DB and in the freelist and make sure
+ * it matches the actual number of pages being used.
+ * All named DBs must be open for a correct count. */
+static __cold int mdbx_audit_ex(MDBX_txn *txn, unsigned retired_stored,
+                                bool dont_filter_gc) {
+  pgno_t pending = 0;
+  if ((txn->mt_flags & MDBX_TXN_RDONLY) == 0) {
+    pending = txn->tw.loose_count + MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) +
+              (MDBX_PNL_SIZE(txn->tw.retired_pages) - retired_stored);
+  }
+
+  MDBX_cursor_couple cx;
+  int rc = mdbx_cursor_init(&cx.outer, txn, FREE_DBI);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  pgno_t freecount = 0;
+  MDBX_val key, data;
+  while ((rc = mdbx_cursor_get(&cx.outer, &key, &data, MDBX_NEXT)) == 0) {
+    if (!dont_filter_gc) {
+      if (unlikely(key.iov_len != sizeof(txnid_t)))
+        return MDBX_CORRUPTED;
+      txnid_t id = unaligned_peek_u64(4, key.iov_base);
+      if (txn->tw.lifo_reclaimed) {
+        for (unsigned i = 1; i <= MDBX_PNL_SIZE(txn->tw.lifo_reclaimed); ++i)
+          if (id == txn->tw.lifo_reclaimed[i])
+            goto skip;
+      } else if (id <= txn->tw.last_reclaimed)
+        goto skip;
+    }
+
+    freecount += *(pgno_t *)data.iov_base;
+  skip:;
+  }
+  mdbx_tassert(txn, rc == MDBX_NOTFOUND);
+
+  for (MDBX_dbi i = FREE_DBI; i < txn->mt_numdbs; i++)
+    txn->mt_dbistate[i] &= ~DBI_AUDITED;
+
+  pgno_t count = 0;
+  for (MDBX_dbi i = FREE_DBI; i <= MAIN_DBI; i++) {
+    if (!(txn->mt_dbistate[i] & DBI_VALID))
+      continue;
+    rc = mdbx_cursor_init(&cx.outer, txn, i);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    txn->mt_dbistate[i] |= DBI_AUDITED;
+    if (txn->mt_dbs[i].md_root == P_INVALID)
+      continue;
+    count += txn->mt_dbs[i].md_branch_pages + txn->mt_dbs[i].md_leaf_pages +
+             txn->mt_dbs[i].md_overflow_pages;
+
+    if (i != MAIN_DBI)
+      continue;
+    rc = mdbx_page_search(&cx.outer, NULL, MDBX_PS_FIRST);
+    while (rc == MDBX_SUCCESS) {
+      MDBX_page *mp = cx.outer.mc_pg[cx.outer.mc_top];
+      for (unsigned j = 0; j < page_numkeys(mp); j++) {
+        MDBX_node *node = page_node(mp, j);
+        if (node_flags(node) == F_SUBDATA) {
+          if (unlikely(node_ds(node) != sizeof(MDBX_db)))
+            return MDBX_CORRUPTED;
+          MDBX_db db_copy, *db;
+          memcpy(db = &db_copy, node_data(node), sizeof(db_copy));
+          if ((txn->mt_flags & MDBX_TXN_RDONLY) == 0) {
+            for (MDBX_dbi k = txn->mt_numdbs; --k > MAIN_DBI;) {
+              if ((txn->mt_dbistate[k] & DBI_VALID) &&
+                  /* txn->mt_dbxs[k].md_name.iov_len > 0 && */
+                  node_ks(node) == txn->mt_dbxs[k].md_name.iov_len &&
+                  memcmp(node_key(node), txn->mt_dbxs[k].md_name.iov_base,
+                         node_ks(node)) == 0) {
+                txn->mt_dbistate[k] |= DBI_AUDITED;
+                if (!(txn->mt_dbistate[k] & MDBX_DBI_STALE))
+                  db = txn->mt_dbs + k;
+                break;
+              }
+            }
+          }
+          count +=
+              db->md_branch_pages + db->md_leaf_pages + db->md_overflow_pages;
+        }
+      }
+      rc = mdbx_cursor_sibling(&cx.outer, SIBLING_RIGHT);
+    }
+    mdbx_tassert(txn, rc == MDBX_NOTFOUND);
+  }
+
+  for (MDBX_dbi i = FREE_DBI; i < txn->mt_numdbs; i++) {
+    if ((txn->mt_dbistate[i] & (DBI_VALID | DBI_AUDITED | DBI_STALE)) !=
+        DBI_VALID)
+      continue;
+    for (MDBX_txn *t = txn; t; t = t->mt_parent)
+      if (F_ISSET(t->mt_dbistate[i], DBI_DIRTY | DBI_CREAT)) {
+        count += t->mt_dbs[i].md_branch_pages + t->mt_dbs[i].md_leaf_pages +
+                 t->mt_dbs[i].md_overflow_pages;
+        txn->mt_dbistate[i] |= DBI_AUDITED;
+        break;
+      }
+    if (!(txn->mt_dbistate[i] & DBI_AUDITED)) {
+      mdbx_warning("audit %s@%" PRIaTXN
+                   ": unable account dbi %d / \"%*s\", state 0x%02x",
+                   txn->mt_parent ? "nested-" : "", txn->mt_txnid, i,
+                   (int)txn->mt_dbxs[i].md_name.iov_len,
+                   (const char *)txn->mt_dbxs[i].md_name.iov_base,
+                   txn->mt_dbistate[i]);
+    }
+  }
+
+  if (pending + freecount + count + NUM_METAS == txn->mt_next_pgno)
+    return MDBX_SUCCESS;
+
+  if ((txn->mt_flags & MDBX_TXN_RDONLY) == 0)
+    mdbx_error("audit @%" PRIaTXN ": %u(pending) = %u(loose-count) + "
+               "%u(reclaimed-list) + %u(retired-pending) - %u(retired-stored)",
+               txn->mt_txnid, pending, txn->tw.loose_count,
+               MDBX_PNL_SIZE(txn->tw.reclaimed_pglist),
+               txn->tw.retired_pages ? MDBX_PNL_SIZE(txn->tw.retired_pages) : 0,
+               retired_stored);
+  mdbx_error("audit @%" PRIaTXN ": %" PRIaPGNO "(pending) + %" PRIaPGNO
+             "(free) + %" PRIaPGNO "(count) = %" PRIaPGNO
+             "(total) <> %" PRIaPGNO "(next-pgno)",
+             txn->mt_txnid, pending, freecount, count + NUM_METAS,
+             pending + freecount + count + NUM_METAS, txn->mt_next_pgno);
+  return MDBX_PROBLEM;
+}
+
+static __always_inline unsigned backlog_size(MDBX_txn *txn) {
+  return MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) + txn->tw.loose_count;
+}
+
+/* LY: Prepare a backlog of pages to modify GC itself,
+ * while reclaiming is prohibited. It should be enough to prevent search
+ * in mdbx_page_alloc() during a deleting, when GC tree is unbalanced. */
+static int mdbx_prep_backlog(MDBX_txn *txn, MDBX_cursor *gc_cursor,
+                             const size_t pnl_bytes) {
+  const unsigned linear4list = number_of_ovpages(txn->mt_env, pnl_bytes);
+  const unsigned backlog4cow = txn->mt_dbs[FREE_DBI].md_depth;
+  const unsigned backlog4rebalance = backlog4cow + 1;
+
+  if (likely(linear4list == 1 &&
+             backlog_size(txn) > (pnl_bytes
+                                      ? backlog4rebalance
+                                      : (backlog4cow + backlog4rebalance))))
+    return MDBX_SUCCESS;
+
+  mdbx_trace(">> pnl_bytes %zu, backlog %u, 4list %u, 4cow %u, 4rebalance %u",
+             pnl_bytes, backlog_size(txn), linear4list, backlog4cow,
+             backlog4rebalance);
+
+  gc_cursor->mc_flags &= ~C_RECLAIMING;
+  int err = mdbx_cursor_touch(gc_cursor);
+  mdbx_trace("== after-touch, backlog %u, err %d", backlog_size(txn), err);
+
+  if (linear4list > 1 && err == MDBX_SUCCESS) {
+    err = mdbx_page_alloc(gc_cursor, linear4list, nullptr,
+                          MDBX_ALLOC_GC | MDBX_ALLOC_CACHE);
+    mdbx_trace("== after-4linear, backlog %u, err %d", backlog_size(txn), err);
+  }
+
+  while (backlog_size(txn) < backlog4cow + linear4list && err == MDBX_SUCCESS)
+    err = mdbx_page_alloc(gc_cursor, 1, NULL, MDBX_ALLOC_GC);
+
+  gc_cursor->mc_flags |= C_RECLAIMING;
+  mdbx_trace("<< backlog %u, err %d", backlog_size(txn), err);
+  return (err != MDBX_NOTFOUND) ? err : MDBX_SUCCESS;
+}
+
+static __inline void clean_reserved_gc_pnl(MDBX_env *env, MDBX_val pnl) {
+  /* PNL is initially empty, zero out at least the length */
+  memset(pnl.iov_base, 0, sizeof(pgno_t));
+  if ((env->me_flags & (MDBX_WRITEMAP | MDBX_NOMEMINIT)) == 0)
+    /* zero out to avoid leaking values from uninitialized malloc'ed memory
+     * to the file in non-writemap mode if length of the saving page-list
+     * was changed during space reservation. */
+    memset(pnl.iov_base, 0, pnl.iov_len);
+}
+
+/* Cleanup reclaimed GC records, than save the retired-list as of this
+ * transaction to GC (aka freeDB). This recursive changes the reclaimed-list
+ * loose-list and retired-list. Keep trying until it stabilizes. */
+static int mdbx_update_gc(MDBX_txn *txn) {
+  /* txn->tw.reclaimed_pglist[] can grow and shrink during this call.
+   * txn->tw.last_reclaimed and txn->tw.retired_pages[] can only grow.
+   * Page numbers cannot disappear from txn->tw.retired_pages[]. */
+  MDBX_env *const env = txn->mt_env;
+  const bool lifo = (env->me_flags & MDBX_LIFORECLAIM) != 0;
+  const char *dbg_prefix_mode = lifo ? "    lifo" : "    fifo";
+  (void)dbg_prefix_mode;
+  mdbx_trace("\n>>> @%" PRIaTXN, txn->mt_txnid);
+
+  unsigned retired_stored = 0, loop = 0;
+  MDBX_cursor_couple couple;
+  int rc = mdbx_cursor_init(&couple.outer, txn, FREE_DBI);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout_notracking;
+
+  couple.outer.mc_flags |= C_RECLAIMING;
+  couple.outer.mc_next = txn->tw.cursors[FREE_DBI];
+  txn->tw.cursors[FREE_DBI] = &couple.outer;
+
+retry:
+  ++loop;
+retry_noaccount:
+  mdbx_trace("%s", " >> restart");
+  mdbx_tassert(txn,
+               mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  mdbx_tassert(txn, txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                        txn->mt_env->me_options.dp_limit);
+  if (unlikely(/* paranoia */ loop > ((MDBX_DEBUG > 0) ? 9 : 99))) {
+    mdbx_error("too more loops %u, bailout", loop);
+    rc = MDBX_PROBLEM;
+    goto bailout;
+  }
+
+  rc = mdbx_prep_backlog(txn, &couple.outer,
+                         MDBX_PNL_SIZEOF(txn->tw.retired_pages));
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout;
+
+  unsigned settled = 0, cleaned_gc_slot = 0, reused_gc_slot = 0,
+           filled_gc_slot = ~0u;
+  txnid_t cleaned_gc_id = 0, gc_rid = txn->tw.last_reclaimed;
+  while (true) {
+    /* Come back here after each Put() in case retired-list changed */
+    MDBX_val key, data;
+    mdbx_trace("%s", " >> continue");
+
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    if (lifo) {
+      if (cleaned_gc_slot < (txn->tw.lifo_reclaimed
+                                 ? MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)
+                                 : 0)) {
+        settled = 0;
+        cleaned_gc_slot = 0;
+        reused_gc_slot = 0;
+        filled_gc_slot = ~0u;
+        /* LY: cleanup reclaimed records. */
+        do {
+          cleaned_gc_id = txn->tw.lifo_reclaimed[++cleaned_gc_slot];
+          mdbx_tassert(txn, cleaned_gc_slot > 0 &&
+                                cleaned_gc_id < env->me_oldest->weak);
+          key.iov_base = &cleaned_gc_id;
+          key.iov_len = sizeof(cleaned_gc_id);
+          rc = mdbx_cursor_get(&couple.outer, &key, NULL, MDBX_SET);
+          if (rc == MDBX_NOTFOUND)
+            continue;
+          if (unlikely(rc != MDBX_SUCCESS))
+            goto bailout;
+          rc = mdbx_prep_backlog(txn, &couple.outer, 0);
+          if (unlikely(rc != MDBX_SUCCESS))
+            goto bailout;
+          mdbx_tassert(txn, cleaned_gc_id < env->me_oldest->weak);
+          mdbx_trace("%s.cleanup-reclaimed-id [%u]%" PRIaTXN, dbg_prefix_mode,
+                     cleaned_gc_slot, cleaned_gc_id);
+          rc = mdbx_cursor_del(&couple.outer, 0);
+          if (unlikely(rc != MDBX_SUCCESS))
+            goto bailout;
+        } while (cleaned_gc_slot < MDBX_PNL_SIZE(txn->tw.lifo_reclaimed));
+        mdbx_txl_sort(txn->tw.lifo_reclaimed);
+      }
+    } else {
+      /* If using records from GC which we have not yet deleted,
+       * now delete them and any we reserved for tw.reclaimed_pglist. */
+      while (cleaned_gc_id <= txn->tw.last_reclaimed) {
+        gc_rid = cleaned_gc_id;
+        settled = 0;
+        rc = mdbx_cursor_first(&couple.outer, &key, NULL);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          if (rc == MDBX_NOTFOUND)
+            break;
+          goto bailout;
+        }
+        if (unlikely(key.iov_len != sizeof(txnid_t))) {
+          rc = MDBX_CORRUPTED;
+          goto bailout;
+        }
+        cleaned_gc_id = unaligned_peek_u64(4, key.iov_base);
+        if (unlikely(cleaned_gc_id < MIN_TXNID || cleaned_gc_id > MAX_TXNID)) {
+          rc = MDBX_CORRUPTED;
+          goto bailout;
+        }
+        if (cleaned_gc_id > txn->tw.last_reclaimed)
+          break;
+        if (cleaned_gc_id < txn->tw.last_reclaimed) {
+          rc = mdbx_prep_backlog(txn, &couple.outer, 0);
+          if (unlikely(rc != MDBX_SUCCESS))
+            goto bailout;
+        }
+        mdbx_tassert(txn, cleaned_gc_id <= txn->tw.last_reclaimed);
+        mdbx_tassert(txn, cleaned_gc_id < env->me_oldest->weak);
+        mdbx_trace("%s.cleanup-reclaimed-id %" PRIaTXN, dbg_prefix_mode,
+                   cleaned_gc_id);
+        rc = mdbx_cursor_del(&couple.outer, 0);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+    }
+
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+    mdbx_tassert(txn, txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                          txn->mt_env->me_options.dp_limit);
+    if (mdbx_audit_enabled()) {
+      rc = mdbx_audit_ex(txn, retired_stored, false);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto bailout;
+    }
+
+    /* return suitable into unallocated space */
+    if (mdbx_refund(txn)) {
+      mdbx_tassert(
+          txn, mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+      if (mdbx_audit_enabled()) {
+        rc = mdbx_audit_ex(txn, retired_stored, false);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+    }
+
+    /* handle loose pages - put ones into the reclaimed- or retired-list */
+    if (txn->tw.loose_pages) {
+      /* Return loose page numbers to tw.reclaimed_pglist,
+       * though usually none are left at this point.
+       * The pages themselves remain in dirtylist. */
+      if (unlikely(!txn->tw.lifo_reclaimed && txn->tw.last_reclaimed < 1)) {
+        if (txn->tw.loose_count > 0) {
+          /* Put loose page numbers in tw.retired_pages,
+           * since unable to return them to tw.reclaimed_pglist. */
+          if (unlikely((rc = mdbx_pnl_need(&txn->tw.retired_pages,
+                                           txn->tw.loose_count)) != 0))
+            goto bailout;
+          for (MDBX_page *mp = txn->tw.loose_pages; mp; mp = mp->mp_next)
+            mdbx_pnl_xappend(txn->tw.retired_pages, mp->mp_pgno);
+          mdbx_trace("%s: append %u loose-pages to retired-pages",
+                     dbg_prefix_mode, txn->tw.loose_count);
+        }
+      } else {
+        /* Room for loose pages + temp PNL with same */
+        rc = mdbx_pnl_need(&txn->tw.reclaimed_pglist,
+                           2 * txn->tw.loose_count + 2);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+        MDBX_PNL loose = txn->tw.reclaimed_pglist +
+                         MDBX_PNL_ALLOCLEN(txn->tw.reclaimed_pglist) -
+                         txn->tw.loose_count - 1;
+        unsigned count = 0;
+        for (MDBX_page *mp = txn->tw.loose_pages; mp; mp = mp->mp_next) {
+          mdbx_tassert(txn, mp->mp_flags == (P_LOOSE | P_DIRTY));
+          loose[++count] = mp->mp_pgno;
+        }
+        mdbx_tassert(txn, count == txn->tw.loose_count);
+        MDBX_PNL_SIZE(loose) = count;
+        mdbx_pnl_sort(loose);
+        mdbx_pnl_xmerge(txn->tw.reclaimed_pglist, loose);
+        mdbx_trace("%s: append %u loose-pages to reclaimed-pages",
+                   dbg_prefix_mode, txn->tw.loose_count);
+      }
+
+      /* filter-out list of dirty-pages from loose-pages */
+      MDBX_dpl *const dl = txn->tw.dirtylist;
+      unsigned w = 0;
+      for (unsigned r = w; ++r <= dl->length;) {
+        MDBX_page *dp = dl->items[r].ptr;
+        mdbx_tassert(txn, (dp->mp_flags & P_DIRTY));
+        mdbx_tassert(txn,
+                     dl->items[r].pgno + (IS_OVERFLOW(dp) ? dp->mp_pages : 1) <=
+                         txn->mt_next_pgno);
+        if ((dp->mp_flags & P_LOOSE) == 0) {
+          if (++w != r)
+            dl->items[w] = dl->items[r];
+        } else {
+          mdbx_tassert(txn, dp->mp_flags == (P_LOOSE | P_DIRTY));
+          if ((env->me_flags & MDBX_WRITEMAP) == 0)
+            mdbx_dpage_free(env, dp, 1);
+        }
+      }
+      mdbx_trace("%s: filtered-out loose-pages from %u -> %u dirty-pages",
+                 dbg_prefix_mode, dl->length, w);
+      mdbx_tassert(txn, txn->tw.loose_count == dl->length - w);
+      dl->length = w;
+      dl->sorted = 0;
+      txn->tw.dirtyroom += txn->tw.loose_count;
+      assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+      txn->tw.loose_pages = NULL;
+      txn->tw.loose_count = 0;
+#if MDBX_ENABLE_REFUND
+      txn->tw.loose_refund_wl = 0;
+#endif /* MDBX_ENABLE_REFUND */
+    }
+
+    const unsigned amount = (unsigned)MDBX_PNL_SIZE(txn->tw.reclaimed_pglist);
+    /* handle retired-list - store ones into single gc-record */
+    if (retired_stored < MDBX_PNL_SIZE(txn->tw.retired_pages)) {
+      if (unlikely(!retired_stored)) {
+        /* Make sure last page of GC is touched and on retired-list */
+        couple.outer.mc_flags &= ~C_RECLAIMING;
+        rc = mdbx_page_search(&couple.outer, NULL,
+                              MDBX_PS_LAST | MDBX_PS_MODIFY);
+        couple.outer.mc_flags |= C_RECLAIMING;
+        if (unlikely(rc != MDBX_SUCCESS) && rc != MDBX_NOTFOUND)
+          goto bailout;
+      }
+      /* Write to last page of GC */
+      key.iov_len = sizeof(txn->mt_txnid);
+      key.iov_base = &txn->mt_txnid;
+      do {
+        data.iov_len = MDBX_PNL_SIZEOF(txn->tw.retired_pages);
+        mdbx_prep_backlog(txn, &couple.outer, data.iov_len);
+        rc = mdbx_cursor_put(&couple.outer, &key, &data, MDBX_RESERVE);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+        /* Retry if tw.retired_pages[] grew during the Put() */
+      } while (data.iov_len < MDBX_PNL_SIZEOF(txn->tw.retired_pages));
+
+      retired_stored = (unsigned)MDBX_PNL_SIZE(txn->tw.retired_pages);
+      mdbx_pnl_sort(txn->tw.retired_pages);
+      mdbx_assert(env, data.iov_len == MDBX_PNL_SIZEOF(txn->tw.retired_pages));
+      memcpy(data.iov_base, txn->tw.retired_pages, data.iov_len);
+
+      mdbx_trace("%s.put-retired #%u @ %" PRIaTXN, dbg_prefix_mode,
+                 retired_stored, txn->mt_txnid);
+
+      if (mdbx_log_enabled(MDBX_LOG_EXTRA)) {
+        unsigned i = retired_stored;
+        mdbx_debug_extra("PNL write txn %" PRIaTXN " root %" PRIaPGNO
+                         " num %u, PNL",
+                         txn->mt_txnid, txn->mt_dbs[FREE_DBI].md_root, i);
+        for (; i; i--)
+          mdbx_debug_extra_print(" %" PRIaPGNO, txn->tw.retired_pages[i]);
+        mdbx_debug_extra_print("%s\n", ".");
+      }
+      if (unlikely(amount != MDBX_PNL_SIZE(txn->tw.reclaimed_pglist))) {
+        mdbx_trace("%s.reclaimed-list changed %u -> %u, retry", dbg_prefix_mode,
+                   amount, (unsigned)MDBX_PNL_SIZE(txn->tw.reclaimed_pglist));
+        goto retry_noaccount /* rare case, but avoids GC fragmentation and one
+                                cycle. */
+            ;
+      }
+      continue;
+    }
+
+    /* handle reclaimed and lost pages - merge and store both into gc */
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    mdbx_tassert(txn, txn->tw.loose_count == 0);
+
+    mdbx_trace("%s", " >> reserving");
+    if (mdbx_audit_enabled()) {
+      rc = mdbx_audit_ex(txn, retired_stored, false);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto bailout;
+    }
+    const unsigned left = amount - settled;
+    mdbx_trace("%s: amount %u, settled %d, left %d, lifo-reclaimed-slots %u, "
+               "reused-gc-slots %u",
+               dbg_prefix_mode, amount, settled, (int)left,
+               txn->tw.lifo_reclaimed
+                   ? (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)
+                   : 0,
+               reused_gc_slot);
+    if (0 >= (int)left)
+      break;
+
+    const unsigned prefer_max_scatter = 257;
+    txnid_t reservation_gc_id;
+    if (lifo) {
+      if (txn->tw.lifo_reclaimed == nullptr) {
+        txn->tw.lifo_reclaimed = mdbx_txl_alloc();
+        if (unlikely(!txn->tw.lifo_reclaimed)) {
+          rc = MDBX_ENOMEM;
+          goto bailout;
+        }
+      }
+      if ((unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) <
+              prefer_max_scatter &&
+          left > ((unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) -
+                  reused_gc_slot) *
+                     env->me_maxgc_ov1page) {
+
+        /* LY: need just a txn-id for save page list. */
+        bool need_cleanup = false;
+        txnid_t snap_oldest;
+      retry_rid:
+        couple.outer.mc_flags &= ~C_RECLAIMING;
+        do {
+          snap_oldest = mdbx_find_oldest(txn);
+          rc = mdbx_page_alloc(&couple.outer, 0, NULL, MDBX_ALLOC_GC);
+          if (likely(rc == MDBX_SUCCESS)) {
+            mdbx_trace("%s: took @%" PRIaTXN " from GC", dbg_prefix_mode,
+                       MDBX_PNL_LAST(txn->tw.lifo_reclaimed));
+            need_cleanup = true;
+          }
+        } while (rc == MDBX_SUCCESS &&
+                 (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) <
+                     prefer_max_scatter &&
+                 left > ((unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) -
+                         reused_gc_slot) *
+                            env->me_maxgc_ov1page);
+        couple.outer.mc_flags |= C_RECLAIMING;
+
+        if (likely(rc == MDBX_SUCCESS)) {
+          mdbx_trace("%s: got enough from GC.", dbg_prefix_mode);
+          continue;
+        } else if (unlikely(rc != MDBX_NOTFOUND))
+          /* LY: some troubles... */
+          goto bailout;
+
+        if (MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)) {
+          if (need_cleanup) {
+            mdbx_txl_sort(txn->tw.lifo_reclaimed);
+            cleaned_gc_slot = 0;
+          }
+          gc_rid = MDBX_PNL_LAST(txn->tw.lifo_reclaimed);
+        } else {
+          mdbx_tassert(txn, txn->tw.last_reclaimed == 0);
+          if (unlikely(mdbx_find_oldest(txn) != snap_oldest))
+            /* should retry mdbx_page_alloc(MDBX_ALLOC_GC)
+             * if the oldest reader changes since the last attempt */
+            goto retry_rid;
+          /* no reclaimable GC entries,
+           * therefore no entries with ID < mdbx_find_oldest(txn) */
+          txn->tw.last_reclaimed = gc_rid = snap_oldest - 1;
+          mdbx_trace("%s: none recycled yet, set rid to @%" PRIaTXN,
+                     dbg_prefix_mode, gc_rid);
+        }
+
+        /* LY: GC is empty, will look any free txn-id in high2low order. */
+        while (MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) < prefer_max_scatter &&
+               left > ((unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) -
+                       reused_gc_slot) *
+                          env->me_maxgc_ov1page) {
+          if (unlikely(gc_rid < 2)) {
+            if (unlikely(MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) <=
+                         reused_gc_slot)) {
+              mdbx_notice("** restart: reserve depleted (reused_gc_slot %u >= "
+                          "lifo_reclaimed %u" PRIaTXN,
+                          reused_gc_slot,
+                          (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed));
+              goto retry;
+            }
+            break;
+          }
+
+          mdbx_tassert(txn, gc_rid >= MIN_TXNID && gc_rid <= MAX_TXNID);
+          --gc_rid;
+          key.iov_base = &gc_rid;
+          key.iov_len = sizeof(gc_rid);
+          rc = mdbx_cursor_get(&couple.outer, &key, &data, MDBX_SET_KEY);
+          if (unlikely(rc == MDBX_SUCCESS)) {
+            mdbx_debug("%s: GC's id %" PRIaTXN
+                       " is used, continue bottom-up search",
+                       dbg_prefix_mode, gc_rid);
+            ++gc_rid;
+            rc = mdbx_cursor_get(&couple.outer, &key, &data, MDBX_FIRST);
+            if (rc == MDBX_NOTFOUND) {
+              mdbx_debug("%s: GC is empty", dbg_prefix_mode);
+              break;
+            }
+            if (unlikely(rc != MDBX_SUCCESS ||
+                         key.iov_len != sizeof(mdbx_tid_t))) {
+              rc = MDBX_CORRUPTED;
+              goto bailout;
+            }
+            txnid_t gc_first = unaligned_peek_u64(4, key.iov_base);
+            if (unlikely(gc_first < MIN_TXNID || gc_first > MAX_TXNID)) {
+              rc = MDBX_CORRUPTED;
+              goto bailout;
+            }
+            if (gc_first < 2) {
+              mdbx_debug("%s: no free GC's id(s) less than %" PRIaTXN,
+                         dbg_prefix_mode, gc_rid);
+              break;
+            }
+            gc_rid = gc_first - 1;
+          }
+
+          rc = mdbx_txl_append(&txn->tw.lifo_reclaimed, gc_rid);
+          if (unlikely(rc != MDBX_SUCCESS))
+            goto bailout;
+
+          if (reused_gc_slot)
+            /* rare case, but it is better to clear and re-create GC entries
+             * with less fragmentation. */
+            need_cleanup = true;
+          else
+            cleaned_gc_slot +=
+                1 /* mark cleanup is not needed for added slot. */;
+
+          mdbx_trace("%s: append @%" PRIaTXN
+                     " to lifo-reclaimed, cleaned-gc-slot = %u",
+                     dbg_prefix_mode, gc_rid, cleaned_gc_slot);
+        }
+
+        if (need_cleanup) {
+          cleaned_gc_slot = 0;
+          mdbx_trace("%s: restart inner-loop to clear and re-create GC entries",
+                     dbg_prefix_mode);
+          continue;
+        }
+      }
+
+      const unsigned i =
+          (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) - reused_gc_slot;
+      mdbx_tassert(txn, i > 0 && i <= MDBX_PNL_SIZE(txn->tw.lifo_reclaimed));
+      reservation_gc_id = txn->tw.lifo_reclaimed[i];
+      mdbx_trace("%s: take @%" PRIaTXN " from lifo-reclaimed[%u]",
+                 dbg_prefix_mode, reservation_gc_id, i);
+    } else {
+      mdbx_tassert(txn, txn->tw.lifo_reclaimed == NULL);
+      if (unlikely(gc_rid == 0)) {
+        gc_rid = mdbx_find_oldest(txn) - 1;
+        rc = mdbx_cursor_get(&couple.outer, &key, NULL, MDBX_FIRST);
+        if (rc == MDBX_SUCCESS) {
+          if (unlikely(key.iov_len != sizeof(txnid_t))) {
+            rc = MDBX_CORRUPTED;
+            goto bailout;
+          }
+          txnid_t gc_first = unaligned_peek_u64(4, key.iov_base);
+          if (unlikely(gc_first < MIN_TXNID || gc_first > MAX_TXNID)) {
+            rc = MDBX_CORRUPTED;
+            goto bailout;
+          }
+          if (gc_rid >= gc_first)
+            gc_rid = gc_first - 1;
+          if (unlikely(gc_rid == 0)) {
+            mdbx_error("%s", "** no GC tail-space to store");
+            goto retry;
+          }
+        } else if (rc != MDBX_NOTFOUND)
+          goto bailout;
+        txn->tw.last_reclaimed = gc_rid;
+      }
+      reservation_gc_id = gc_rid--;
+      mdbx_trace("%s: take @%" PRIaTXN " from head-gc-id", dbg_prefix_mode,
+                 reservation_gc_id);
+    }
+    ++reused_gc_slot;
+
+    unsigned chunk = left;
+    if (unlikely(chunk > env->me_maxgc_ov1page)) {
+      const unsigned avail_gc_slots =
+          txn->tw.lifo_reclaimed
+              ? (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) -
+                    reused_gc_slot + 1
+              : (gc_rid < INT16_MAX) ? (unsigned)gc_rid : INT16_MAX;
+      if (avail_gc_slots > 1) {
+        if (chunk < env->me_maxgc_ov1page * 2)
+          chunk /= 2;
+        else {
+          const unsigned threshold =
+              env->me_maxgc_ov1page * ((avail_gc_slots < prefer_max_scatter)
+                                           ? avail_gc_slots
+                                           : prefer_max_scatter);
+          if (left < threshold)
+            chunk = env->me_maxgc_ov1page;
+          else {
+            const unsigned tail = left - threshold + env->me_maxgc_ov1page + 1;
+            unsigned span = 1;
+            unsigned avail = (unsigned)((pgno2bytes(env, span) - PAGEHDRSZ) /
+                                        sizeof(pgno_t)) /*- 1 + span */;
+            if (tail > avail) {
+              for (unsigned i = amount - span; i > 0; --i) {
+                if (MDBX_PNL_ASCENDING
+                        ? (txn->tw.reclaimed_pglist[i] + span)
+                        : (txn->tw.reclaimed_pglist[i] - span) ==
+                              txn->tw.reclaimed_pglist[i + span]) {
+                  span += 1;
+                  avail = (unsigned)((pgno2bytes(env, span) - PAGEHDRSZ) /
+                                     sizeof(pgno_t)) -
+                          1 + span;
+                  if (avail >= tail)
+                    break;
+                }
+              }
+            }
+
+            chunk = (avail >= tail) ? tail - span
+                                    : (avail_gc_slots > 3 &&
+                                       reused_gc_slot < prefer_max_scatter - 3)
+                                          ? avail - span
+                                          : tail;
+          }
+        }
+      }
+    }
+    mdbx_tassert(txn, chunk > 0);
+
+    mdbx_trace("%s: gc_rid %" PRIaTXN ", reused_gc_slot %u, reservation-id "
+               "%" PRIaTXN,
+               dbg_prefix_mode, gc_rid, reused_gc_slot, reservation_gc_id);
+
+    mdbx_trace("%s: chunk %u, gc-per-ovpage %u", dbg_prefix_mode, chunk,
+               env->me_maxgc_ov1page);
+
+    mdbx_tassert(txn, reservation_gc_id < env->me_oldest->weak);
+    if (unlikely(reservation_gc_id < 1 ||
+                 reservation_gc_id >=
+                     atomic_load64(env->me_oldest, mo_Relaxed))) {
+      mdbx_error("%s", "** internal error (reservation_gc_id)");
+      rc = MDBX_PROBLEM;
+      goto bailout;
+    }
+
+    key.iov_len = sizeof(reservation_gc_id);
+    key.iov_base = &reservation_gc_id;
+    data.iov_len = (chunk + 1) * sizeof(pgno_t);
+    mdbx_trace("%s.reserve: %u [%u...%u] @%" PRIaTXN, dbg_prefix_mode, chunk,
+               settled + 1, settled + chunk + 1, reservation_gc_id);
+    mdbx_prep_backlog(txn, &couple.outer, data.iov_len);
+    rc = mdbx_cursor_put(&couple.outer, &key, &data,
+                         MDBX_RESERVE | MDBX_NOOVERWRITE);
+    mdbx_tassert(txn,
+                 mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                       txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto bailout;
+
+    clean_reserved_gc_pnl(env, data);
+    settled += chunk;
+    mdbx_trace("%s.settled %u (+%u), continue", dbg_prefix_mode, settled,
+               chunk);
+
+    if (txn->tw.lifo_reclaimed &&
+        unlikely(amount < MDBX_PNL_SIZE(txn->tw.reclaimed_pglist))) {
+      mdbx_notice("** restart: reclaimed-list growth %u -> %u", amount,
+                  (unsigned)MDBX_PNL_SIZE(txn->tw.reclaimed_pglist));
+      goto retry_noaccount;
+    }
+
+    continue;
+  }
+
+  mdbx_tassert(
+      txn,
+      cleaned_gc_slot ==
+          (txn->tw.lifo_reclaimed ? MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) : 0));
+
+  mdbx_trace("%s", " >> filling");
+  /* Fill in the reserved records */
+  filled_gc_slot =
+      txn->tw.lifo_reclaimed
+          ? (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed) - reused_gc_slot
+          : reused_gc_slot;
+  rc = MDBX_SUCCESS;
+  mdbx_tassert(txn,
+               mdbx_pnl_check4assert(txn->tw.reclaimed_pglist,
+                                     txn->mt_next_pgno - MDBX_ENABLE_REFUND));
+  mdbx_tassert(txn, mdbx_dirtylist_check(txn));
+  if (MDBX_PNL_SIZE(txn->tw.reclaimed_pglist)) {
+    MDBX_val key, data;
+    key.iov_len = data.iov_len = 0; /* avoid MSVC warning */
+    key.iov_base = data.iov_base = NULL;
+
+    const unsigned amount = MDBX_PNL_SIZE(txn->tw.reclaimed_pglist);
+    unsigned left = amount;
+    if (txn->tw.lifo_reclaimed == nullptr) {
+      mdbx_tassert(txn, lifo == 0);
+      rc = mdbx_cursor_first(&couple.outer, &key, &data);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto bailout;
+    } else {
+      mdbx_tassert(txn, lifo != 0);
+    }
+
+    while (true) {
+      txnid_t fill_gc_id;
+      mdbx_trace("%s: left %u of %u", dbg_prefix_mode, left,
+                 (unsigned)MDBX_PNL_SIZE(txn->tw.reclaimed_pglist));
+      if (txn->tw.lifo_reclaimed == nullptr) {
+        mdbx_tassert(txn, lifo == 0);
+        fill_gc_id = unaligned_peek_u64(4, key.iov_base);
+        if (filled_gc_slot-- == 0 || fill_gc_id > txn->tw.last_reclaimed) {
+          mdbx_notice(
+              "** restart: reserve depleted (filled_slot %u, fill_id %" PRIaTXN
+              " > last_reclaimed %" PRIaTXN,
+              filled_gc_slot, fill_gc_id, txn->tw.last_reclaimed);
+          goto retry;
+        }
+      } else {
+        mdbx_tassert(txn, lifo != 0);
+        if (++filled_gc_slot >
+            (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)) {
+          mdbx_notice("** restart: reserve depleted (filled_gc_slot %u > "
+                      "lifo_reclaimed %u" PRIaTXN,
+                      filled_gc_slot,
+                      (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed));
+          goto retry;
+        }
+        fill_gc_id = txn->tw.lifo_reclaimed[filled_gc_slot];
+        mdbx_trace("%s.seek-reservation @%" PRIaTXN " at lifo_reclaimed[%u]",
+                   dbg_prefix_mode, fill_gc_id, filled_gc_slot);
+        key.iov_base = &fill_gc_id;
+        key.iov_len = sizeof(fill_gc_id);
+        rc = mdbx_cursor_get(&couple.outer, &key, &data, MDBX_SET_KEY);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+      mdbx_tassert(txn, cleaned_gc_slot ==
+                            (txn->tw.lifo_reclaimed
+                                 ? MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)
+                                 : 0));
+      mdbx_tassert(txn, fill_gc_id > 0 && fill_gc_id < env->me_oldest->weak);
+      key.iov_base = &fill_gc_id;
+      key.iov_len = sizeof(fill_gc_id);
+
+      mdbx_tassert(txn, data.iov_len >= sizeof(pgno_t) * 2);
+      couple.outer.mc_flags |= C_GCFREEZE;
+      unsigned chunk = (unsigned)(data.iov_len / sizeof(pgno_t)) - 1;
+      if (unlikely(chunk > left)) {
+        mdbx_trace("%s: chunk %u > left %u, @%" PRIaTXN, dbg_prefix_mode, chunk,
+                   left, fill_gc_id);
+        if ((loop < 5 && chunk - left > loop / 2) ||
+            chunk - left > env->me_maxgc_ov1page) {
+          data.iov_len = (left + 1) * sizeof(pgno_t);
+          if (loop < 7)
+            couple.outer.mc_flags &= ~C_GCFREEZE;
+        }
+        chunk = left;
+      }
+      rc = mdbx_cursor_put(&couple.outer, &key, &data,
+                           MDBX_CURRENT | MDBX_RESERVE);
+      couple.outer.mc_flags &= ~C_GCFREEZE;
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto bailout;
+      clean_reserved_gc_pnl(env, data);
+
+      if (unlikely(txn->tw.loose_count ||
+                   amount != MDBX_PNL_SIZE(txn->tw.reclaimed_pglist))) {
+        mdbx_notice("** restart: reclaimed-list growth (%u -> %u, loose +%u)",
+                    amount, MDBX_PNL_SIZE(txn->tw.reclaimed_pglist),
+                    txn->tw.loose_count);
+        goto retry;
+      }
+      if (unlikely(txn->tw.lifo_reclaimed
+                       ? cleaned_gc_slot < MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)
+                       : cleaned_gc_id < txn->tw.last_reclaimed)) {
+        mdbx_notice("%s", "** restart: reclaimed-slots changed");
+        goto retry;
+      }
+      if (unlikely(retired_stored != MDBX_PNL_SIZE(txn->tw.retired_pages))) {
+        mdbx_tassert(txn,
+                     retired_stored < MDBX_PNL_SIZE(txn->tw.retired_pages));
+        mdbx_notice("** restart: retired-list growth (%u -> %u)",
+                    retired_stored, MDBX_PNL_SIZE(txn->tw.retired_pages));
+        goto retry;
+      }
+
+      pgno_t *dst = data.iov_base;
+      *dst++ = chunk;
+      pgno_t *src = MDBX_PNL_BEGIN(txn->tw.reclaimed_pglist) + left - chunk;
+      memcpy(dst, src, chunk * sizeof(pgno_t));
+      pgno_t *from = src, *to = src + chunk;
+      mdbx_trace("%s.fill: %u [ %u:%" PRIaPGNO "...%u:%" PRIaPGNO
+                 "] @%" PRIaTXN,
+                 dbg_prefix_mode, chunk,
+                 (unsigned)(from - txn->tw.reclaimed_pglist), from[0],
+                 (unsigned)(to - txn->tw.reclaimed_pglist), to[-1], fill_gc_id);
+
+      left -= chunk;
+      if (mdbx_audit_enabled()) {
+        rc = mdbx_audit_ex(txn, retired_stored + amount - left, true);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+      if (left == 0) {
+        rc = MDBX_SUCCESS;
+        break;
+      }
+
+      if (txn->tw.lifo_reclaimed == nullptr) {
+        mdbx_tassert(txn, lifo == 0);
+        rc = mdbx_cursor_next(&couple.outer, &key, &data, MDBX_NEXT);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      } else {
+        mdbx_tassert(txn, lifo != 0);
+      }
+    }
+  }
+
+  mdbx_tassert(txn, rc == MDBX_SUCCESS);
+  if (unlikely(txn->tw.loose_count != 0 ||
+               filled_gc_slot !=
+                   (txn->tw.lifo_reclaimed
+                        ? (unsigned)MDBX_PNL_SIZE(txn->tw.lifo_reclaimed)
+                        : 0))) {
+    mdbx_notice("** restart: reserve excess (filled-slot %u, loose-count %u)",
+                filled_gc_slot, txn->tw.loose_count);
+    goto retry;
+  }
+
+  mdbx_tassert(txn,
+               txn->tw.lifo_reclaimed == NULL ||
+                   cleaned_gc_slot == MDBX_PNL_SIZE(txn->tw.lifo_reclaimed));
+
+bailout:
+  txn->tw.cursors[FREE_DBI] = couple.outer.mc_next;
+
+bailout_notracking:
+  MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) = 0;
+  mdbx_trace("<<< %u loops, rc = %d", loop, rc);
+  return rc;
+}
+
+static int mdbx_flush_iov(MDBX_txn *const txn, struct iovec *iov,
+                          unsigned iov_items, size_t iov_off,
+                          size_t iov_bytes) {
+  MDBX_env *const env = txn->mt_env;
+  mdbx_assert(env, iov_items > 0);
+  int rc;
+  if (likely(iov_items == 1)) {
+    mdbx_assert(env, iov->iov_len == iov_bytes);
+    rc = mdbx_pwrite(env->me_lazy_fd, iov->iov_base, iov_bytes, iov_off);
+  } else {
+    rc = mdbx_pwritev(env->me_lazy_fd, iov, iov_items, iov_off, iov_bytes);
+  }
+
+  if (unlikely(rc != MDBX_SUCCESS))
+    mdbx_error("Write error: %s", mdbx_strerror(rc));
+  else {
+    VALGRIND_MAKE_MEM_DEFINED(txn->mt_env->me_map + iov_off, iov_bytes);
+    ASAN_UNPOISON_MEMORY_REGION(txn->mt_env->me_map + iov_off, iov_bytes);
+  }
+
+  for (unsigned i = 0; i < iov_items; i++)
+    mdbx_dpage_free(env, (MDBX_page *)iov[i].iov_base,
+                    bytes2pgno(env, iov[i].iov_len));
+  return rc;
+}
+
+/* Flush (some) dirty pages to the map, after clearing their dirty flag.
+ * [in] txn   the transaction that's being committed
+ * [in] keep  number of initial pages in dirtylist to keep dirty.
+ * Returns 0 on success, non-zero on failure. */
+__hot static int mdbx_page_flush(MDBX_txn *txn, const unsigned keep) {
+  struct iovec iov[MDBX_COMMIT_PAGES];
+  MDBX_dpl *const dl = mdbx_dpl_sort(txn->tw.dirtylist);
+  MDBX_env *const env = txn->mt_env;
+  pgno_t flush_begin = MAX_PAGENO;
+  pgno_t flush_end = MIN_PAGENO;
+  int rc = MDBX_SUCCESS;
+  unsigned iov_items = 0;
+  size_t iov_bytes = 0;
+  size_t iov_off = 0;
+
+  unsigned r, w;
+  for (r = w = keep; ++r <= dl->length;) {
+    MDBX_page *dp = dl->items[r].ptr;
+    mdbx_tassert(txn,
+                 dp->mp_pgno >= MIN_PAGENO && dp->mp_pgno < txn->mt_next_pgno);
+    mdbx_tassert(txn, dp->mp_flags & P_DIRTY);
+
+    /* Don't flush this page yet */
+    if (dp->mp_flags & P_KEEP) {
+      dp->mp_flags -= P_KEEP;
+      dl->items[++w] = dl->items[r];
+      continue;
+    }
+    if (dp->mp_flags & P_LOOSE) {
+      dl->items[++w] = dl->items[r];
+      continue;
+    }
+
+    const unsigned npages = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+    flush_begin = (flush_begin < dp->mp_pgno) ? flush_begin : dp->mp_pgno;
+    flush_end =
+        (flush_end > dp->mp_pgno + npages) ? flush_end : dp->mp_pgno + npages;
+    env->me_unsynced_pages->weak += npages;
+    dp->mp_flags -= P_DIRTY;
+    dp->mp_txnid = pp_txnid2chk(txn);
+
+    if ((env->me_flags & MDBX_WRITEMAP) == 0) {
+      const size_t size = pgno2bytes(env, npages);
+      if (iov_off + iov_bytes != pgno2bytes(env, dp->mp_pgno) ||
+          iov_items == ARRAY_LENGTH(iov) || iov_bytes + size > MAX_WRITE) {
+        if (iov_items) {
+          rc = mdbx_flush_iov(txn, iov, iov_items, iov_off, iov_bytes);
+#if defined(__linux__) || defined(__gnu_linux__)
+          if (mdbx_linux_kernel_version >= 0x02060b00)
+          /* Linux kernels older than version 2.6.11 ignore the addr and nbytes
+           * arguments, making this function fairly expensive. Therefore, the
+           * whole cache is always flushed. */
+#endif /* Linux */
+            mdbx_flush_incoherent_mmap(env->me_map + iov_off, iov_bytes,
+                                       env->me_os_psize);
+          iov_items = 0;
+          iov_bytes = 0;
+          if (unlikely(rc != MDBX_SUCCESS)) {
+            do
+              dl->items[++w] = dl->items[r];
+            while (++r <= dl->length);
+            break;
+          }
+        }
+        iov_off = pgno2bytes(env, dp->mp_pgno);
+      }
+      iov[iov_items].iov_base = (void *)dp;
+      iov[iov_items].iov_len = size;
+      iov_items += 1;
+      iov_bytes += size;
+    }
+  }
+
+  mdbx_tassert(txn, dl->sorted == dl->length && r == dl->length + 1);
+  txn->tw.dirtyroom += dl->length - w;
+  assert(txn->tw.dirtyroom <= txn->mt_env->me_options.dp_limit);
+  dl->sorted = dl->length = w;
+  mdbx_tassert(txn, txn->mt_parent ||
+                        txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                            txn->mt_env->me_options.dp_limit);
+
+  if (iov_items)
+    rc = mdbx_flush_iov(txn, iov, iov_items, iov_off, iov_bytes);
+
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    txn->mt_flags |= MDBX_TXN_ERROR;
+    return rc;
+  }
+
+#if defined(__linux__) || defined(__gnu_linux__)
+  if ((env->me_flags & MDBX_WRITEMAP) == 0 &&
+      mdbx_linux_kernel_version < 0x02060b00)
+    /* Linux kernels older than version 2.6.11 ignore the addr and nbytes
+     * arguments, making this function fairly expensive. Therefore, the
+     * whole cache is always flushed. */
+    mdbx_flush_incoherent_mmap(env->me_map + pgno2bytes(env, flush_begin),
+                               pgno2bytes(env, flush_end - flush_begin),
+                               env->me_os_psize);
+#endif /* Linux */
+
+  /* TODO: use flush_begin & flush_end for msync() & sync_file_range(). */
+  (void)flush_begin;
+  (void)flush_end;
+  return MDBX_SUCCESS;
+}
+
+/* Check txn and dbi arguments to a function */
+static __always_inline bool mdbx_txn_dbi_exists(MDBX_txn *txn, MDBX_dbi dbi,
+                                                unsigned validity) {
+  if (likely(dbi < txn->mt_numdbs && (txn->mt_dbistate[dbi] & validity)))
+    return true;
+
+  return dbi_import(txn, dbi);
+}
+
+int mdbx_txn_commit(MDBX_txn *txn) { return __inline_mdbx_txn_commit(txn); }
+
+/* Merge child txn into parent */
+static __inline void mdbx_txn_merge(MDBX_txn *const parent, MDBX_txn *const txn,
+                                    const unsigned parent_retired_len) {
+  MDBX_dpl *const src = mdbx_dpl_sort(txn->tw.dirtylist);
+
+  /* Remove refunded pages from parent's dirty list */
+  MDBX_dpl *const dst = mdbx_dpl_sort(parent->tw.dirtylist);
+  while (MDBX_ENABLE_REFUND && dst->length &&
+         dst->items[dst->length].pgno >= parent->mt_next_pgno) {
+    if (!(txn->mt_env->me_flags & MDBX_WRITEMAP)) {
+      MDBX_page *dp = dst->items[dst->length].ptr;
+      mdbx_dpage_free(txn->mt_env, dp, IS_OVERFLOW(dp) ? dp->mp_pages : 1);
+    }
+    dst->length -= 1;
+  }
+  parent->tw.dirtyroom += dst->sorted - dst->length;
+  assert(parent->tw.dirtyroom <= parent->mt_env->me_options.dp_limit);
+  dst->sorted = dst->length;
+  mdbx_tassert(parent,
+               parent->mt_parent ||
+                   parent->tw.dirtyroom + parent->tw.dirtylist->length ==
+                       parent->mt_env->me_options.dp_limit);
+
+  /* Remove reclaimed pages from parent's dirty list */
+  const MDBX_PNL reclaimed_list = parent->tw.reclaimed_pglist;
+  mdbx_dpl_sift(parent, reclaimed_list, false);
+
+  /* Move retired pages from parent's dirty & spilled list to reclaimed */
+  unsigned r, w, d, s, l;
+  for (r = w = parent_retired_len;
+       ++r <= MDBX_PNL_SIZE(parent->tw.retired_pages);) {
+    const pgno_t pgno = parent->tw.retired_pages[r];
+    const unsigned di = mdbx_dpl_exist(parent->tw.dirtylist, pgno);
+    const unsigned si = (!di && unlikely(parent->tw.spill_pages))
+                            ? mdbx_pnl_exist(parent->tw.spill_pages, pgno << 1)
+                            : 0;
+    unsigned npages;
+    const char *kind;
+    if (di) {
+      MDBX_page *dp = parent->tw.dirtylist->items[di].ptr;
+      mdbx_tassert(parent, (dp->mp_flags & ~(P_LEAF | P_LEAF2 | P_BRANCH |
+                                             P_OVERFLOW | P_DIRTY)) == 0);
+      npages = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+      mdbx_page_wash(parent, di, dp, npages);
+      kind = "dirty";
+      l = 1;
+      if (unlikely(npages > l)) {
+        /* OVERFLOW-страница могла быть переиспользована по частям. Тогда
+         * в retired-списке может быть только начало последовательности,
+         * а остаток растащен по dirty, spilled и reclaimed спискам. Поэтому
+         * переносим в reclaimed с проверкой на обрыв последовательности.
+         * В любом случае, все осколки будут учтены и отфильтрованы, т.е. если
+         * страница была разбита на части, то важно удалить dirty-элемент,
+         * а все осколки будут учтены отдельно. */
+
+        /* Список retired страниц не сортирован, но для ускорения сортировки
+         * дополняется в соответствии с MDBX_PNL_ASCENDING */
+#if MDBX_PNL_ASCENDING
+        const unsigned len = MDBX_PNL_SIZE(parent->tw.retired_pages);
+        while (r < len && parent->tw.retired_pages[r + 1] == pgno + l) {
+          ++r;
+          if (++l == npages)
+            break;
+        }
+#else
+        while (w > parent_retired_len &&
+               parent->tw.retired_pages[w - 1] == pgno + l) {
+          --w;
+          if (++l == npages)
+            break;
+        }
+#endif
+      }
+    } else if (unlikely(si)) {
+      l = npages = 1;
+      mdbx_spill_remove(parent, si, 1);
+      kind = "spilled";
+    } else {
+      parent->tw.retired_pages[++w] = pgno;
+      continue;
+    }
+
+    mdbx_debug("reclaim retired parent's %u->%u %s page %" PRIaPGNO, npages, l,
+               kind, pgno);
+    int err = mdbx_pnl_insert_range(&parent->tw.reclaimed_pglist, pgno, l);
+    mdbx_ensure(txn->mt_env, err == MDBX_SUCCESS);
+  }
+  MDBX_PNL_SIZE(parent->tw.retired_pages) = w;
+
+  /* Filter-out parent spill list */
+  if (parent->tw.spill_pages && MDBX_PNL_SIZE(parent->tw.spill_pages) > 0) {
+    const MDBX_PNL sl = mdbx_spill_purge(parent);
+    unsigned len = MDBX_PNL_SIZE(sl);
+    if (len) {
+      /* Remove refunded pages from parent's spill list */
+      if (MDBX_ENABLE_REFUND &&
+          MDBX_PNL_MOST(sl) >= (parent->mt_next_pgno << 1)) {
+#if MDBX_PNL_ASCENDING
+        unsigned i = MDBX_PNL_SIZE(sl);
+        assert(MDBX_PNL_MOST(sl) == MDBX_PNL_LAST(sl));
+        do {
+          if ((sl[i] & 1) == 0)
+            mdbx_debug("refund parent's spilled page %" PRIaPGNO, sl[i] >> 1);
+          i -= 1;
+        } while (i && sl[i] >= (parent->mt_next_pgno << 1));
+        MDBX_PNL_SIZE(sl) = i;
+#else
+        assert(MDBX_PNL_MOST(sl) == MDBX_PNL_FIRST(sl));
+        unsigned i = 0;
+        do {
+          ++i;
+          if ((sl[i] & 1) == 0)
+            mdbx_debug("refund parent's spilled page %" PRIaPGNO, sl[i] >> 1);
+        } while (i < len && sl[i + 1] >= (parent->mt_next_pgno << 1));
+        MDBX_PNL_SIZE(sl) = len -= i;
+        memmove(sl + 1, sl + 1 + i, len * sizeof(sl[0]));
+#endif
+      }
+      mdbx_tassert(txn, mdbx_pnl_check4assert(sl, parent->mt_next_pgno << 1));
+
+      /* Remove reclaimed pages from parent's spill list */
+      s = MDBX_PNL_SIZE(sl), r = MDBX_PNL_SIZE(reclaimed_list);
+      /* Scanning from end to begin */
+      while (s && r) {
+        if (sl[s] & 1) {
+          --s;
+          continue;
+        }
+        const pgno_t spilled_pgno = sl[s] >> 1;
+        const pgno_t reclaimed_pgno = reclaimed_list[r];
+        if (reclaimed_pgno != spilled_pgno) {
+          const bool cmp = MDBX_PNL_ORDERED(spilled_pgno, reclaimed_pgno);
+          s -= !cmp;
+          r -= cmp;
+        } else {
+          mdbx_debug("remove reclaimed parent's spilled page %" PRIaPGNO,
+                     reclaimed_pgno);
+          mdbx_spill_remove(parent, s, 1);
+          --s;
+          --r;
+        }
+      }
+
+      /* Remove anything in our dirty list from parent's spill list */
+      /* Scanning spill list in descend order */
+      const int step = MDBX_PNL_ASCENDING ? -1 : 1;
+      s = MDBX_PNL_ASCENDING ? MDBX_PNL_SIZE(sl) : 1;
+      d = src->length;
+      while (d && (MDBX_PNL_ASCENDING ? s > 0 : s <= MDBX_PNL_SIZE(sl))) {
+        if (sl[s] & 1) {
+          s += step;
+          continue;
+        }
+        const pgno_t spilled_pgno = sl[s] >> 1;
+        const pgno_t dirty_pgno_form = src->items[d].pgno;
+        MDBX_page *dp = src->items[d].ptr;
+        const unsigned npages = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+        const pgno_t dirty_pgno_to = dirty_pgno_form + npages;
+        if (dirty_pgno_form > spilled_pgno) {
+          --d;
+          continue;
+        }
+        if (dirty_pgno_to <= spilled_pgno) {
+          s += step;
+          continue;
+        }
+
+        mdbx_debug("remove dirtied parent's spilled %u page %" PRIaPGNO, npages,
+                   dirty_pgno_form);
+        mdbx_spill_remove(parent, s, 1);
+        s += step;
+      }
+
+      /* Squash deleted pagenums if we deleted any */
+      mdbx_spill_purge(parent);
+    }
+  }
+
+  /* Remove anything in our spill list from parent's dirty list */
+  if (txn->tw.spill_pages) {
+    mdbx_tassert(txn, mdbx_pnl_check4assert(txn->tw.spill_pages,
+                                            parent->mt_next_pgno << 1));
+    mdbx_dpl_sift(parent, txn->tw.spill_pages, true);
+    mdbx_tassert(parent,
+                 parent->mt_parent ||
+                     parent->tw.dirtyroom + parent->tw.dirtylist->length ==
+                         parent->mt_env->me_options.dp_limit);
+  }
+
+  /* Find length of merging our dirty list with parent's and release
+   * filter-out pages */
+  for (l = 0, d = dst->length, s = src->length; d > 0 && s > 0;) {
+    const MDBX_page *sp = src->items[s].ptr;
+    mdbx_tassert(parent,
+                 (sp->mp_flags & ~(P_LEAF | P_LEAF2 | P_BRANCH | P_OVERFLOW |
+                                   P_DIRTY | P_LOOSE)) == 0);
+    const unsigned s_npages = IS_OVERFLOW(sp) ? sp->mp_pages : 1;
+    const pgno_t s_pgno = src->items[s].pgno;
+
+    MDBX_page *dp = dst->items[d].ptr;
+    mdbx_tassert(parent, (dp->mp_flags & ~(P_LEAF | P_LEAF2 | P_BRANCH |
+                                           P_OVERFLOW | P_DIRTY)) == 0);
+    const unsigned d_npages = IS_OVERFLOW(dp) ? dp->mp_pages : 1;
+    const pgno_t d_pgno = dst->items[d].pgno;
+
+    if (d_pgno >= s_pgno + s_npages) {
+      --d;
+      ++l;
+    } else if (d_pgno + d_npages <= s_pgno) {
+      --s;
+      ++l;
+    } else {
+      dst->items[d--].ptr = nullptr;
+      if ((txn->mt_flags & MDBX_WRITEMAP) == 0)
+        mdbx_dpage_free(txn->mt_env, dp, d_npages);
+    }
+  }
+  assert(dst->sorted == dst->length);
+  mdbx_tassert(parent, dst->allocated >= l + d + s);
+  dst->sorted = l + d + s; /* the merged length */
+
+  /* Merge our dirty list into parent's, i.e. merge(dst, src) -> dst */
+  if (dst->sorted >= dst->length) {
+    /* from end to begin with dst extending */
+    for (l = dst->sorted, s = src->length, d = dst->length; s > 0 && d > 0;) {
+      if (unlikely(l <= d)) {
+        /* squash to get a gap of free space for merge */
+        for (r = w = 1; r <= d; ++r)
+          if (dst->items[r].ptr) {
+            if (w != r) {
+              dst->items[w] = dst->items[r];
+              dst->items[r].ptr = nullptr;
+            }
+            ++w;
+          }
+        mdbx_notice("squash to begin for extending-merge %u -> %u", d, w - 1);
+        d = w - 1;
+        continue;
+      }
+      assert(l > d);
+      if (dst->items[d].ptr) {
+        dst->items[l--] = (dst->items[d].pgno > src->items[s].pgno)
+                              ? dst->items[d--]
+                              : src->items[s--];
+      } else
+        --d;
+    }
+    if (s > 0) {
+      assert(l == s);
+      while (d > 0) {
+        assert(dst->items[d].ptr == nullptr);
+        --d;
+      }
+      do {
+        assert(l > 0);
+        dst->items[l--] = src->items[s--];
+      } while (s > 0);
+    } else {
+      assert(l == d);
+      while (l > 0) {
+        assert(dst->items[l].ptr != nullptr);
+        --l;
+      }
+    }
+  } else {
+    /* from begin to end with dst shrinking (a lot of new overflow pages) */
+    for (l = s = d = 1; s <= src->length && d <= dst->length;) {
+      if (unlikely(l >= d)) {
+        /* squash to get a gap of free space for merge */
+        for (r = w = dst->length; r >= d; --r)
+          if (dst->items[r].ptr) {
+            if (w != r) {
+              dst->items[w] = dst->items[r];
+              dst->items[r].ptr = nullptr;
+            }
+            --w;
+          }
+        mdbx_notice("squash to end for shrinking-merge %u -> %u", d, w + 1);
+        d = w + 1;
+        continue;
+      }
+      assert(l < d);
+      if (dst->items[d].ptr) {
+        dst->items[l++] = (dst->items[d].pgno < src->items[s].pgno)
+                              ? dst->items[d++]
+                              : src->items[s++];
+      } else
+        ++d;
+    }
+    if (s <= src->length) {
+      assert(dst->sorted - l == src->length - s);
+      while (d <= dst->length) {
+        assert(dst->items[d].ptr == nullptr);
+        --d;
+      }
+      do {
+        assert(l <= dst->sorted);
+        dst->items[l++] = src->items[s++];
+      } while (s <= src->length);
+    } else {
+      assert(dst->sorted - l == dst->length - d);
+      while (l <= dst->sorted) {
+        assert(l <= d && d <= dst->length && dst->items[d].ptr);
+        dst->items[l++] = dst->items[d++];
+      }
+    }
+  }
+  parent->tw.dirtyroom -= dst->sorted - dst->length;
+  assert(parent->tw.dirtyroom <= parent->mt_env->me_options.dp_limit);
+  dst->length = dst->sorted;
+  mdbx_tassert(parent,
+               parent->mt_parent ||
+                   parent->tw.dirtyroom + parent->tw.dirtylist->length ==
+                       parent->mt_env->me_options.dp_limit);
+  mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+  mdbx_dpl_free(txn);
+
+  if (txn->tw.spill_pages) {
+    if (parent->tw.spill_pages) {
+      /* Must not fail since space was preserved above. */
+      mdbx_pnl_xmerge(parent->tw.spill_pages, txn->tw.spill_pages);
+      mdbx_pnl_free(txn->tw.spill_pages);
+    } else {
+      parent->tw.spill_pages = txn->tw.spill_pages;
+      parent->tw.spill_least_removed = txn->tw.spill_least_removed;
+    }
+    mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+  }
+
+  parent->mt_flags &= ~MDBX_TXN_HAS_CHILD;
+  if (parent->tw.spill_pages) {
+    assert(mdbx_pnl_check4assert(parent->tw.spill_pages,
+                                 parent->mt_next_pgno << 1));
+    if (MDBX_PNL_SIZE(parent->tw.spill_pages))
+      parent->mt_flags |= MDBX_TXN_SPILLS;
+  }
+}
+
+int mdbx_txn_commit_ex(MDBX_txn *txn, MDBX_commit_latency *latency) {
+  STATIC_ASSERT(MDBX_TXN_FINISHED ==
+                MDBX_TXN_BLOCKED - MDBX_TXN_HAS_CHILD - MDBX_TXN_ERROR);
+  const uint64_t ts_0 = latency ? mdbx_osal_monotime() : 0;
+  uint64_t ts_1 = 0, ts_2 = 0, ts_3 = 0, ts_4 = 0;
+  uint32_t audit_duration = 0;
+
+  int rc = check_txn(txn, MDBX_TXN_FINISHED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto provide_latency;
+
+  if (unlikely(txn->mt_flags & MDBX_TXN_ERROR)) {
+    rc = MDBX_RESULT_TRUE;
+    goto fail;
+  }
+
+  MDBX_env *env = txn->mt_env;
+#if MDBX_ENV_CHECKPID
+  if (unlikely(env->me_pid != mdbx_getpid())) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    rc = MDBX_PANIC;
+    goto provide_latency;
+  }
+#endif /* MDBX_ENV_CHECKPID */
+
+  /* mdbx_txn_end() mode for a commit which writes nothing */
+  unsigned end_mode =
+      MDBX_END_PURE_COMMIT | MDBX_END_UPDATE | MDBX_END_SLOT | MDBX_END_FREE;
+  if (unlikely(F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY)))
+    goto done;
+
+  if (txn->mt_child) {
+    rc = mdbx_txn_commit_ex(txn->mt_child, NULL);
+    mdbx_tassert(txn, txn->mt_child == NULL);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto fail;
+  }
+
+  if (unlikely(txn != env->me_txn)) {
+    mdbx_debug("%s", "attempt to commit unknown transaction");
+    rc = MDBX_EINVAL;
+    goto fail;
+  }
+
+  if (txn->mt_parent) {
+    mdbx_tassert(txn, mdbx_audit_ex(txn, 0, false) == 0);
+    mdbx_assert(env, txn != env->me_txn0);
+    MDBX_txn *const parent = txn->mt_parent;
+    mdbx_assert(env, parent->mt_signature == MDBX_MT_SIGNATURE);
+    mdbx_assert(env, parent->mt_child == txn &&
+                         (parent->mt_flags & MDBX_TXN_HAS_CHILD) != 0);
+    mdbx_assert(env, mdbx_dirtylist_check(txn));
+
+    if (txn->tw.dirtylist->length == 0 && !(txn->mt_flags & MDBX_TXN_DIRTY) &&
+        parent->mt_numdbs == txn->mt_numdbs) {
+      for (int i = txn->mt_numdbs; --i >= 0;) {
+        mdbx_tassert(txn, (txn->mt_dbistate[i] & DBI_DIRTY) == 0);
+        if ((txn->mt_dbistate[i] & DBI_STALE) &&
+            !(parent->mt_dbistate[i] & DBI_STALE))
+          mdbx_tassert(txn, memcmp(&parent->mt_dbs[i], &txn->mt_dbs[i],
+                                   sizeof(MDBX_db)) == 0);
+      }
+
+      mdbx_tassert(txn, memcmp(&parent->mt_geo, &txn->mt_geo,
+                               sizeof(parent->mt_geo)) == 0);
+      mdbx_tassert(txn, memcmp(&parent->mt_canary, &txn->mt_canary,
+                               sizeof(parent->mt_canary)) == 0);
+      mdbx_tassert(txn, !txn->tw.spill_pages ||
+                            MDBX_PNL_SIZE(txn->tw.spill_pages) == 0);
+      mdbx_tassert(txn, txn->tw.loose_count == 0);
+
+      /* fast completion of pure nested transaction */
+      end_mode = MDBX_END_PURE_COMMIT | MDBX_END_SLOT | MDBX_END_FREE;
+      goto done;
+    }
+
+    /* Preserve space for spill list to avoid parent's state corruption
+     * if allocation fails. */
+    const unsigned parent_retired_len =
+        (unsigned)(uintptr_t)parent->tw.retired_pages;
+    mdbx_tassert(txn,
+                 parent_retired_len <= MDBX_PNL_SIZE(txn->tw.retired_pages));
+    const unsigned retired_delta =
+        MDBX_PNL_SIZE(txn->tw.retired_pages) - parent_retired_len;
+    if (retired_delta) {
+      rc = mdbx_pnl_need(&txn->tw.reclaimed_pglist, retired_delta);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto fail;
+    }
+
+    if (txn->tw.spill_pages) {
+      if (parent->tw.spill_pages) {
+        rc = mdbx_pnl_need(&parent->tw.spill_pages,
+                           MDBX_PNL_SIZE(txn->tw.spill_pages));
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto fail;
+      }
+      mdbx_spill_purge(txn);
+    }
+
+    if (unlikely(txn->tw.dirtylist->length + parent->tw.dirtylist->length >
+                     parent->tw.dirtylist->allocated &&
+                 !mdbx_dpl_reserve(parent, txn->tw.dirtylist->length +
+                                               parent->tw.dirtylist->length))) {
+      rc = MDBX_ENOMEM;
+      goto fail;
+    }
+
+    //-------------------------------------------------------------------------
+
+    parent->tw.lifo_reclaimed = txn->tw.lifo_reclaimed;
+    txn->tw.lifo_reclaimed = NULL;
+
+    parent->tw.retired_pages = txn->tw.retired_pages;
+    txn->tw.retired_pages = NULL;
+
+    mdbx_pnl_free(parent->tw.reclaimed_pglist);
+    parent->tw.reclaimed_pglist = txn->tw.reclaimed_pglist;
+    txn->tw.reclaimed_pglist = NULL;
+    parent->tw.last_reclaimed = txn->tw.last_reclaimed;
+
+    parent->mt_geo = txn->mt_geo;
+    parent->mt_canary = txn->mt_canary;
+    parent->mt_flags |= txn->mt_flags & MDBX_TXN_DIRTY;
+
+    /* Move loose pages to parent */
+#if MDBX_ENABLE_REFUND
+    parent->tw.loose_refund_wl = txn->tw.loose_refund_wl;
+#endif /* MDBX_ENABLE_REFUND */
+    parent->tw.loose_count = txn->tw.loose_count;
+    parent->tw.loose_pages = txn->tw.loose_pages;
+
+    /* Merge our cursors into parent's and close them */
+    mdbx_cursors_eot(txn, true);
+    end_mode |= MDBX_END_EOTDONE;
+
+    /* Update parent's DBs array */
+    memcpy(parent->mt_dbs, txn->mt_dbs, txn->mt_numdbs * sizeof(MDBX_db));
+    parent->mt_numdbs = txn->mt_numdbs;
+    parent->mt_dbistate[FREE_DBI] = txn->mt_dbistate[FREE_DBI];
+    parent->mt_dbistate[MAIN_DBI] = txn->mt_dbistate[MAIN_DBI];
+    for (unsigned i = CORE_DBS; i < txn->mt_numdbs; i++) {
+      /* preserve parent's status */
+      const uint8_t state =
+          txn->mt_dbistate[i] |
+          (parent->mt_dbistate[i] & (DBI_CREAT | DBI_FRESH | DBI_DIRTY));
+      mdbx_debug("db %u dbi-state %s 0x%02x -> 0x%02x", i,
+                 (parent->mt_dbistate[i] != state) ? "update" : "still",
+                 parent->mt_dbistate[i], state);
+      parent->mt_dbistate[i] = state;
+    }
+
+    ts_1 = latency ? mdbx_osal_monotime() : 0;
+    mdbx_txn_merge(parent, txn, parent_retired_len);
+    ts_2 = latency ? mdbx_osal_monotime() : 0;
+    env->me_txn = parent;
+    parent->mt_child = NULL;
+    mdbx_tassert(parent, mdbx_dirtylist_check(parent));
+
+#if MDBX_ENABLE_REFUND
+    mdbx_refund(parent);
+    if (mdbx_assert_enabled()) {
+      /* Check parent's loose pages not suitable for refund */
+      for (MDBX_page *lp = parent->tw.loose_pages; lp; lp = lp->mp_next)
+        mdbx_tassert(parent, lp->mp_pgno < parent->tw.loose_refund_wl &&
+                                 lp->mp_pgno + 1 < parent->mt_next_pgno);
+      /* Check parent's reclaimed pages not suitable for refund */
+      if (MDBX_PNL_SIZE(parent->tw.reclaimed_pglist))
+        mdbx_tassert(parent, MDBX_PNL_MOST(parent->tw.reclaimed_pglist) + 1 <
+                                 parent->mt_next_pgno);
+    }
+#endif /* MDBX_ENABLE_REFUND */
+
+    ts_4 = ts_3 = latency ? mdbx_osal_monotime() : 0;
+    txn->mt_signature = 0;
+    mdbx_free(txn);
+    mdbx_tassert(parent, mdbx_audit_ex(parent, 0, false) == 0);
+    rc = MDBX_SUCCESS;
+    goto provide_latency;
+  }
+
+  mdbx_tassert(txn, txn->tw.dirtyroom + txn->tw.dirtylist->length ==
+                        txn->mt_env->me_options.dp_limit);
+  mdbx_cursors_eot(txn, false);
+  end_mode |= MDBX_END_EOTDONE;
+
+  if (txn->tw.dirtylist->length == 0 &&
+      (txn->mt_flags & (MDBX_TXN_DIRTY | MDBX_TXN_SPILLS)) == 0) {
+    for (int i = txn->mt_numdbs; --i >= 0;)
+      mdbx_tassert(txn, (txn->mt_dbistate[i] & DBI_DIRTY) == 0);
+    rc = MDBX_SUCCESS;
+    goto done;
+  }
+
+  mdbx_debug("committing txn %" PRIaTXN " %p on mdbenv %p, root page %" PRIaPGNO
+             "/%" PRIaPGNO,
+             txn->mt_txnid, (void *)txn, (void *)env,
+             txn->mt_dbs[MAIN_DBI].md_root, txn->mt_dbs[FREE_DBI].md_root);
+
+  /* Update DB root pointers */
+  if (txn->mt_numdbs > CORE_DBS) {
+    MDBX_cursor_couple couple;
+    MDBX_val data;
+    data.iov_len = sizeof(MDBX_db);
+
+    rc = mdbx_cursor_init(&couple.outer, txn, MAIN_DBI);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto fail;
+    for (MDBX_dbi i = CORE_DBS; i < txn->mt_numdbs; i++) {
+      if (txn->mt_dbistate[i] & DBI_DIRTY) {
+        if (unlikely(TXN_DBI_CHANGED(txn, i))) {
+          rc = MDBX_BAD_DBI;
+          goto fail;
+        }
+        MDBX_db *db = &txn->mt_dbs[i];
+        mdbx_debug("update main's entry for sub-db %u, mod_txnid %" PRIaTXN
+                   " -> %" PRIaTXN,
+                   i, pp_txnid2chk(txn), db->md_mod_txnid);
+        db->md_mod_txnid = pp_txnid2chk(txn);
+        data.iov_base = db;
+        WITH_CURSOR_TRACKING(couple.outer,
+                             rc = mdbx_cursor_put(&couple.outer,
+                                                  &txn->mt_dbxs[i].md_name,
+                                                  &data, F_SUBDATA));
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto fail;
+      }
+    }
+  }
+
+  ts_1 = latency ? mdbx_osal_monotime() : 0;
+  rc = mdbx_update_gc(txn);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto fail;
+
+  ts_2 = latency ? mdbx_osal_monotime() : 0;
+  if (mdbx_audit_enabled()) {
+    rc = mdbx_audit_ex(txn, MDBX_PNL_SIZE(txn->tw.retired_pages), true);
+    const uint64_t audit_end = mdbx_osal_monotime();
+    audit_duration = mdbx_osal_monotime_to_16dot16(audit_end - ts_2);
+    ts_2 = audit_end;
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto fail;
+  }
+
+  rc = mdbx_page_flush(txn, 0);
+  ts_3 = latency ? mdbx_osal_monotime() : 0;
+  if (likely(rc == MDBX_SUCCESS)) {
+    if (txn->mt_dbs[MAIN_DBI].md_flags & DBI_DIRTY)
+      txn->mt_dbs[MAIN_DBI].md_mod_txnid = pp_txnid2chk(txn);
+
+    MDBX_meta meta, *head = mdbx_meta_head(env);
+    memcpy(meta.mm_magic_and_version, head->mm_magic_and_version, 8);
+    meta.mm_extra_flags = head->mm_extra_flags;
+    meta.mm_validator_id = head->mm_validator_id;
+    meta.mm_extra_pagehdr = head->mm_extra_pagehdr;
+    unaligned_poke_u64(4, meta.mm_pages_retired,
+                       unaligned_peek_u64(4, head->mm_pages_retired) +
+                           MDBX_PNL_SIZE(txn->tw.retired_pages));
+
+    meta.mm_geo = txn->mt_geo;
+    meta.mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
+    meta.mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
+    meta.mm_canary = txn->mt_canary;
+    mdbx_meta_set_txnid(env, &meta, txn->mt_txnid);
+
+    rc = mdbx_sync_locked(
+        env, env->me_flags | txn->mt_flags | MDBX_SHRINK_ALLOWED, &meta);
+  }
+  ts_4 = latency ? mdbx_osal_monotime() : 0;
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    goto fail;
+  }
+
+  end_mode = MDBX_END_COMMITTED | MDBX_END_UPDATE | MDBX_END_EOTDONE;
+
+done:
+  rc = mdbx_txn_end(txn, end_mode);
+
+provide_latency:
+  if (latency) {
+    latency->audit = audit_duration;
+    latency->preparation =
+        ts_1 ? mdbx_osal_monotime_to_16dot16(ts_1 - ts_0) : 0;
+    latency->gc =
+        (ts_1 && ts_2) ? mdbx_osal_monotime_to_16dot16(ts_2 - ts_1) : 0;
+    latency->write =
+        (ts_2 && ts_3) ? mdbx_osal_monotime_to_16dot16(ts_3 - ts_2) : 0;
+    latency->sync =
+        (ts_3 && ts_4) ? mdbx_osal_monotime_to_16dot16(ts_4 - ts_3) : 0;
+    const uint64_t ts_5 = mdbx_osal_monotime();
+    latency->ending = ts_4 ? mdbx_osal_monotime_to_16dot16(ts_5 - ts_4) : 0;
+    latency->whole = mdbx_osal_monotime_to_16dot16(ts_5 - ts_0);
+  }
+  return rc;
+
+fail:
+  mdbx_txn_abort(txn);
+  goto provide_latency;
+}
+
+static __cold int
+mdbx_validate_meta(MDBX_env *env, MDBX_meta *const meta, uint64_t *filesize,
+                   const MDBX_page *const page, const unsigned meta_number,
+                   MDBX_meta *dest, const unsigned guess_pagesize) {
+  const uint64_t magic_and_version =
+      unaligned_peek_u64(4, &meta->mm_magic_and_version);
+  if (magic_and_version != MDBX_DATA_MAGIC &&
+      magic_and_version != MDBX_DATA_MAGIC_DEVEL) {
+    mdbx_error("meta[%u] has invalid magic/version %" PRIx64, meta_number,
+               magic_and_version);
+    return ((magic_and_version >> 8) != MDBX_MAGIC) ? MDBX_INVALID
+                                                    : MDBX_VERSION_MISMATCH;
+  }
+
+  if (page->mp_pgno != meta_number) {
+    mdbx_error("meta[%u] has invalid pageno %" PRIaPGNO, meta_number,
+               page->mp_pgno);
+    return MDBX_INVALID;
+  }
+
+  if (page->mp_flags != P_META) {
+    mdbx_error("page #%u not a meta-page", meta_number);
+    return MDBX_INVALID;
+  }
+
+  /* LY: check pagesize */
+  if (!is_powerof2(meta->mm_psize) || meta->mm_psize < MIN_PAGESIZE ||
+      meta->mm_psize > MAX_PAGESIZE) {
+    mdbx_warning("meta[%u] has invalid pagesize (%u), skip it", meta_number,
+                 meta->mm_psize);
+    return is_powerof2(meta->mm_psize) ? MDBX_VERSION_MISMATCH : MDBX_INVALID;
+  }
+
+  if (dest && meta_number == 0 && guess_pagesize != meta->mm_psize) {
+    dest->mm_psize = meta->mm_psize;
+    mdbx_verbose("meta[%u] took pagesize %u", meta_number, meta->mm_psize);
+  }
+
+  if (unaligned_peek_u64(4, &meta->mm_txnid_a) !=
+      unaligned_peek_u64(4, &meta->mm_txnid_b)) {
+    mdbx_warning("meta[%u] not completely updated, skip it", meta_number);
+    return MDBX_RESULT_TRUE;
+  }
+
+  /* LY: check signature as a checksum */
+  if (META_IS_STEADY(meta) &&
+      unaligned_peek_u64(4, &meta->mm_datasync_sign) != mdbx_meta_sign(meta)) {
+    mdbx_warning("meta[%u] has invalid steady-checksum (0x%" PRIx64
+                 " != 0x%" PRIx64 "), skip it",
+                 meta_number, unaligned_peek_u64(4, &meta->mm_datasync_sign),
+                 mdbx_meta_sign(meta));
+    return MDBX_RESULT_TRUE;
+  }
+
+  mdbx_debug("read meta%" PRIaPGNO " = root %" PRIaPGNO "/%" PRIaPGNO
+             ", geo %" PRIaPGNO "/%" PRIaPGNO "-%" PRIaPGNO "/%" PRIaPGNO
+             " +%u -%u, txn_id %" PRIaTXN ", %s",
+             page->mp_pgno, meta->mm_dbs[MAIN_DBI].md_root,
+             meta->mm_dbs[FREE_DBI].md_root, meta->mm_geo.lower,
+             meta->mm_geo.next, meta->mm_geo.now, meta->mm_geo.upper,
+             meta->mm_geo.grow, meta->mm_geo.shrink,
+             unaligned_peek_u64(4, meta->mm_txnid_a), mdbx_durable_str(meta));
+
+  /* LY: check min-pages value */
+  if (meta->mm_geo.lower < MIN_PAGENO || meta->mm_geo.lower > MAX_PAGENO) {
+    mdbx_warning("meta[%u] has invalid min-pages (%" PRIaPGNO "), skip it",
+                 meta_number, meta->mm_geo.lower);
+    return MDBX_INVALID;
+  }
+
+  /* LY: check max-pages value */
+  if (meta->mm_geo.upper < MIN_PAGENO || meta->mm_geo.upper > MAX_PAGENO ||
+      meta->mm_geo.upper < meta->mm_geo.lower) {
+    mdbx_warning("meta[%u] has invalid max-pages (%" PRIaPGNO "), skip it",
+                 meta_number, meta->mm_geo.upper);
+    return MDBX_INVALID;
+  }
+
+  /* LY: check last_pgno */
+  if (meta->mm_geo.next < MIN_PAGENO || meta->mm_geo.next - 1 > MAX_PAGENO) {
+    mdbx_warning("meta[%u] has invalid next-pageno (%" PRIaPGNO "), skip it",
+                 meta_number, meta->mm_geo.next);
+    return MDBX_CORRUPTED;
+  }
+
+  /* LY: check filesize & used_bytes */
+  const uint64_t used_bytes = meta->mm_geo.next * (uint64_t)meta->mm_psize;
+  if (used_bytes > *filesize) {
+    /* Here could be a race with DB-shrinking performed by other process */
+    int err = mdbx_filesize(env->me_lazy_fd, filesize);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+    if (used_bytes > *filesize) {
+      mdbx_warning("meta[%u] used-bytes (%" PRIu64 ") beyond filesize (%" PRIu64
+                   "), skip it",
+                   meta_number, used_bytes, *filesize);
+      return MDBX_CORRUPTED;
+    }
+  }
+  if (meta->mm_geo.next - 1 > MAX_PAGENO || used_bytes > MAX_MAPSIZE) {
+    mdbx_warning("meta[%u] has too large used-space (%" PRIu64 "), skip it",
+                 meta_number, used_bytes);
+    return MDBX_TOO_LARGE;
+  }
+
+  /* LY: check mapsize limits */
+  const uint64_t mapsize_min = meta->mm_geo.lower * (uint64_t)meta->mm_psize;
+  STATIC_ASSERT(MAX_MAPSIZE < PTRDIFF_MAX - MAX_PAGESIZE);
+  STATIC_ASSERT(MIN_MAPSIZE < MAX_MAPSIZE);
+  if (mapsize_min < MIN_MAPSIZE || mapsize_min > MAX_MAPSIZE) {
+    if (MAX_MAPSIZE != MAX_MAPSIZE64 && mapsize_min > MAX_MAPSIZE &&
+        mapsize_min <= MAX_MAPSIZE64) {
+      mdbx_assert(env, meta->mm_geo.next - 1 <= MAX_PAGENO &&
+                           used_bytes <= MAX_MAPSIZE);
+      mdbx_warning("meta[%u] has too large min-mapsize (%" PRIu64 "), "
+                   "but size of used space still acceptable (%" PRIu64 ")",
+                   meta_number, mapsize_min, used_bytes);
+      meta->mm_geo.lower = (pgno_t)(MAX_MAPSIZE / meta->mm_psize);
+    } else {
+      mdbx_warning("meta[%u] has invalid min-mapsize (%" PRIu64 "), skip it",
+                   meta_number, mapsize_min);
+      return MDBX_VERSION_MISMATCH;
+    }
+  }
+
+  const uint64_t mapsize_max = meta->mm_geo.upper * (uint64_t)meta->mm_psize;
+  STATIC_ASSERT(MIN_MAPSIZE < MAX_MAPSIZE);
+  if (mapsize_max > MAX_MAPSIZE ||
+      MAX_PAGENO < ceil_powerof2((size_t)mapsize_max, env->me_os_psize) /
+                       (size_t)meta->mm_psize) {
+    /* allow to open large DB from a 32-bit environment */
+    mdbx_assert(env, meta->mm_geo.next - 1 <= MAX_PAGENO &&
+                         used_bytes <= MAX_MAPSIZE);
+    mdbx_warning("meta[%u] has too large max-mapsize (%" PRIu64 "), "
+                 "but size of used space still acceptable (%" PRIu64 ")",
+                 meta_number, mapsize_max, used_bytes);
+    meta->mm_geo.upper = (pgno_t)(MAX_MAPSIZE / meta->mm_psize);
+  }
+
+  /* LY: check and silently put mm_geo.now into [geo.lower...geo.upper].
+   *
+   * Copy-with-compaction by previous version of libmdbx could produce DB-file
+   * less than meta.geo.lower bound, in case actual filling is low or no data
+   * at all. This is not a problem as there is no damage or loss of data.
+   * Therefore it is better not to consider such situation as an error, but
+   * silently correct it. */
+  if (meta->mm_geo.now < meta->mm_geo.lower)
+    meta->mm_geo.now = meta->mm_geo.lower;
+  if (meta->mm_geo.now > meta->mm_geo.upper &&
+      meta->mm_geo.next <= meta->mm_geo.upper)
+    meta->mm_geo.now = meta->mm_geo.upper;
+
+  if (meta->mm_geo.next > meta->mm_geo.now) {
+    mdbx_warning("meta[%u] next-pageno (%" PRIaPGNO
+                 ") is beyond end-pgno (%" PRIaPGNO "), skip it",
+                 meta_number, meta->mm_geo.next, meta->mm_geo.now);
+    return MDBX_CORRUPTED;
+  }
+
+  /* LY: GC root */
+  if (meta->mm_dbs[FREE_DBI].md_root == P_INVALID) {
+    if (meta->mm_dbs[FREE_DBI].md_branch_pages ||
+        meta->mm_dbs[FREE_DBI].md_depth || meta->mm_dbs[FREE_DBI].md_entries ||
+        meta->mm_dbs[FREE_DBI].md_leaf_pages ||
+        meta->mm_dbs[FREE_DBI].md_overflow_pages) {
+      mdbx_warning("meta[%u] has false-empty GC, skip it", meta_number);
+      return MDBX_CORRUPTED;
+    }
+  } else if (meta->mm_dbs[FREE_DBI].md_root >= meta->mm_geo.next) {
+    mdbx_warning("meta[%u] has invalid GC-root %" PRIaPGNO ", skip it",
+                 meta_number, meta->mm_dbs[FREE_DBI].md_root);
+    return MDBX_CORRUPTED;
+  }
+
+  /* LY: MainDB root */
+  if (meta->mm_dbs[MAIN_DBI].md_root == P_INVALID) {
+    if (meta->mm_dbs[MAIN_DBI].md_branch_pages ||
+        meta->mm_dbs[MAIN_DBI].md_depth || meta->mm_dbs[MAIN_DBI].md_entries ||
+        meta->mm_dbs[MAIN_DBI].md_leaf_pages ||
+        meta->mm_dbs[MAIN_DBI].md_overflow_pages) {
+      mdbx_warning("meta[%u] has false-empty maindb", meta_number);
+      return MDBX_CORRUPTED;
+    }
+  } else if (meta->mm_dbs[MAIN_DBI].md_root >= meta->mm_geo.next) {
+    mdbx_warning("meta[%u] has invalid maindb-root %" PRIaPGNO ", skip it",
+                 meta_number, meta->mm_dbs[MAIN_DBI].md_root);
+    return MDBX_CORRUPTED;
+  }
+
+  if (unaligned_peek_u64(4, &meta->mm_txnid_a) == 0) {
+    mdbx_warning("meta[%u] has zero txnid, skip it", meta_number);
+    return MDBX_RESULT_TRUE;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+/* Read the environment parameters of a DB environment
+ * before mapping it into memory. */
+static __cold int mdbx_read_header(MDBX_env *env, MDBX_meta *dest,
+                                   uint64_t *filesize,
+                                   const int lck_exclusive) {
+  int rc = mdbx_filesize(env->me_lazy_fd, filesize);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  memset(dest, 0, sizeof(MDBX_meta));
+  unaligned_poke_u64(4, dest->mm_datasync_sign, MDBX_DATASIGN_WEAK);
+  rc = MDBX_CORRUPTED;
+
+  /* Read twice all meta pages so we can find the latest one. */
+  unsigned loop_limit = NUM_METAS * 2;
+  for (unsigned loop_count = 0; loop_count < loop_limit; ++loop_count) {
+    /* We don't know the page size on first time.
+     * So, just guess it. */
+    unsigned guess_pagesize = dest->mm_psize;
+    if (guess_pagesize == 0)
+      guess_pagesize =
+          (loop_count > NUM_METAS) ? env->me_psize : env->me_os_psize;
+
+    const unsigned meta_number = loop_count % NUM_METAS;
+    const unsigned offset = guess_pagesize * meta_number;
+
+    char buffer[MIN_PAGESIZE];
+    unsigned retryleft = 42;
+    while (1) {
+      mdbx_trace("reading meta[%d]: offset %u, bytes %u, retry-left %u",
+                 meta_number, offset, MIN_PAGESIZE, retryleft);
+      int err = mdbx_pread(env->me_lazy_fd, buffer, MIN_PAGESIZE, offset);
+      if (err != MDBX_SUCCESS) {
+        if (err == MDBX_ENODATA && offset == 0 && loop_count == 0 &&
+            *filesize == 0 && (env->me_flags & MDBX_RDONLY) == 0)
+          mdbx_warning("read meta: empty file (%d, %s)", err,
+                       mdbx_strerror(err));
+        else
+          mdbx_error("read meta[%u,%u]: %i, %s", offset, MIN_PAGESIZE, err,
+                     mdbx_strerror(err));
+        return err;
+      }
+
+      char again[MIN_PAGESIZE];
+      err = mdbx_pread(env->me_lazy_fd, again, MIN_PAGESIZE, offset);
+      if (err != MDBX_SUCCESS) {
+        mdbx_error("read meta[%u,%u]: %i, %s", offset, MIN_PAGESIZE, err,
+                   mdbx_strerror(err));
+        return err;
+      }
+
+      if (memcmp(buffer, again, MIN_PAGESIZE) == 0 || --retryleft == 0)
+        break;
+
+      mdbx_verbose("meta[%u] was updated, re-read it", meta_number);
+    }
+
+    if (!retryleft) {
+      mdbx_error("meta[%u] is too volatile, skip it", meta_number);
+      continue;
+    }
+
+    MDBX_page *const page = (MDBX_page *)buffer;
+    MDBX_meta *const meta = page_meta(page);
+    rc = mdbx_validate_meta(env, meta, filesize, page, meta_number, dest,
+                            guess_pagesize);
+    if (rc != MDBX_SUCCESS)
+      continue;
+
+    if ((env->me_stuck_meta < 0)
+            ? mdbx_meta_ot(meta_bootid_match(meta) ? prefer_last
+                                                   : prefer_steady,
+                           env, dest, meta)
+            : (meta_number == (unsigned)env->me_stuck_meta)) {
+      *dest = *meta;
+      if (!lck_exclusive && !META_IS_STEADY(dest))
+        loop_limit += 1; /* LY: should re-read to hush race with update */
+      mdbx_verbose("latch meta[%u]", meta_number);
+    }
+  }
+
+  if (dest->mm_psize == 0 ||
+      ((env->me_stuck_meta < 0)
+           ? (!META_IS_STEADY(dest) &&
+              !meta_weak_acceptable(env, dest, lck_exclusive))
+           : false)) {
+    mdbx_error("%s", "no usable meta-pages, database is corrupted");
+    if (rc == MDBX_SUCCESS) {
+      /* TODO: try to restore the database by fully checking b-tree structure
+       * for the each meta page, if the corresponding option was given */
+      return MDBX_CORRUPTED;
+    }
+    return rc;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+static MDBX_page *__cold mdbx_meta_model(const MDBX_env *env, MDBX_page *model,
+                                         unsigned num) {
+
+  mdbx_ensure(env, is_powerof2(env->me_psize));
+  mdbx_ensure(env, env->me_psize >= MIN_PAGESIZE);
+  mdbx_ensure(env, env->me_psize <= MAX_PAGESIZE);
+  mdbx_ensure(env, env->me_dbgeo.lower >= MIN_MAPSIZE);
+  mdbx_ensure(env, env->me_dbgeo.upper <= MAX_MAPSIZE);
+  mdbx_ensure(env, env->me_dbgeo.now >= env->me_dbgeo.lower);
+  mdbx_ensure(env, env->me_dbgeo.now <= env->me_dbgeo.upper);
+
+  memset(model, 0, sizeof(*model));
+  model->mp_pgno = num;
+  model->mp_flags = P_META;
+  MDBX_meta *const model_meta = page_meta(model);
+  unaligned_poke_u64(4, model_meta->mm_magic_and_version, MDBX_DATA_MAGIC);
+
+  model_meta->mm_geo.lower = bytes2pgno(env, env->me_dbgeo.lower);
+  model_meta->mm_geo.upper = bytes2pgno(env, env->me_dbgeo.upper);
+  model_meta->mm_geo.grow = (uint16_t)bytes2pgno(env, env->me_dbgeo.grow);
+  model_meta->mm_geo.shrink = (uint16_t)bytes2pgno(env, env->me_dbgeo.shrink);
+  model_meta->mm_geo.now = bytes2pgno(env, env->me_dbgeo.now);
+  model_meta->mm_geo.next = NUM_METAS;
+
+  mdbx_ensure(env, model_meta->mm_geo.lower >= MIN_PAGENO);
+  mdbx_ensure(env, model_meta->mm_geo.upper <= MAX_PAGENO);
+  mdbx_ensure(env, model_meta->mm_geo.now >= model_meta->mm_geo.lower);
+  mdbx_ensure(env, model_meta->mm_geo.now <= model_meta->mm_geo.upper);
+  mdbx_ensure(env, model_meta->mm_geo.next >= MIN_PAGENO);
+  mdbx_ensure(env, model_meta->mm_geo.next <= model_meta->mm_geo.now);
+  mdbx_ensure(env,
+              model_meta->mm_geo.grow == bytes2pgno(env, env->me_dbgeo.grow));
+  mdbx_ensure(env, model_meta->mm_geo.shrink ==
+                       bytes2pgno(env, env->me_dbgeo.shrink));
+
+  model_meta->mm_psize = env->me_psize;
+  model_meta->mm_flags = (uint16_t)env->me_flags;
+  model_meta->mm_flags |=
+      MDBX_INTEGERKEY; /* this is mm_dbs[FREE_DBI].md_flags */
+  model_meta->mm_dbs[FREE_DBI].md_root = P_INVALID;
+  model_meta->mm_dbs[MAIN_DBI].md_root = P_INVALID;
+  mdbx_meta_set_txnid(env, model_meta, MIN_TXNID + num);
+  unaligned_poke_u64(4, model_meta->mm_datasync_sign,
+                     mdbx_meta_sign(model_meta));
+  return (MDBX_page *)((uint8_t *)model + env->me_psize);
+}
+
+/* Fill in most of the zeroed meta-pages for an empty database environment.
+ * Return pointer to recently (head) meta-page. */
+static MDBX_meta *__cold mdbx_init_metas(const MDBX_env *env, void *buffer) {
+  MDBX_page *page0 = (MDBX_page *)buffer;
+  MDBX_page *page1 = mdbx_meta_model(env, page0, 0);
+  MDBX_page *page2 = mdbx_meta_model(env, page1, 1);
+  mdbx_meta_model(env, page2, 2);
+  mdbx_assert(env, !mdbx_meta_eq(env, page_meta(page0), page_meta(page1)));
+  mdbx_assert(env, !mdbx_meta_eq(env, page_meta(page1), page_meta(page2)));
+  mdbx_assert(env, !mdbx_meta_eq(env, page_meta(page2), page_meta(page0)));
+  return page_meta(page2);
+}
+
+static size_t mdbx_madvise_threshold(const MDBX_env *env,
+                                     const size_t largest_bytes) {
+  /* TODO: use options */
+  const unsigned factor = 9;
+  const size_t threshold = (largest_bytes < (65536ul << factor))
+                               ? 65536 /* minimal threshold */
+                               : (largest_bytes > (MEGABYTE * 4 << factor))
+                                     ? MEGABYTE * 4 /* maximal threshold */
+                                     : largest_bytes >> factor;
+  return bytes_align2os_bytes(env, threshold);
+}
+
+static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
+                            MDBX_meta *const pending) {
+  mdbx_assert(env, ((env->me_flags ^ flags) & MDBX_WRITEMAP) == 0);
+  MDBX_meta *const meta0 = METAPAGE(env, 0);
+  MDBX_meta *const meta1 = METAPAGE(env, 1);
+  MDBX_meta *const meta2 = METAPAGE(env, 2);
+  MDBX_meta *const head = mdbx_meta_head(env);
+  int rc;
+
+  mdbx_assert(env, mdbx_meta_eq_mask(env) == 0);
+  mdbx_assert(env,
+              pending < METAPAGE(env, 0) || pending > METAPAGE(env, NUM_METAS));
+  mdbx_assert(env, (env->me_flags & (MDBX_RDONLY | MDBX_FATAL_ERROR)) == 0);
+  mdbx_assert(env, pending->mm_geo.next <= pending->mm_geo.now);
+
+  if (flags & MDBX_SAFE_NOSYNC) {
+    /* Check auto-sync conditions */
+    const pgno_t autosync_threshold =
+        atomic_load32(env->me_autosync_threshold, mo_Relaxed);
+    const uint64_t autosync_period =
+        atomic_load64(env->me_autosync_period, mo_Relaxed);
+    if ((autosync_threshold &&
+         atomic_load32(env->me_unsynced_pages, mo_Relaxed) >=
+             autosync_threshold) ||
+        (autosync_period &&
+         mdbx_osal_monotime() -
+                 atomic_load64(env->me_sync_timestamp, mo_Relaxed) >=
+             autosync_period))
+      flags &= MDBX_WRITEMAP | MDBX_SHRINK_ALLOWED; /* force steady */
+  }
+
+  pgno_t shrink = 0;
+  if (flags & MDBX_SHRINK_ALLOWED) {
+    /* LY: check conditions to discard unused pages */
+    const pgno_t largest_pgno = mdbx_find_largest(
+        env, (head->mm_geo.next > pending->mm_geo.next) ? head->mm_geo.next
+                                                        : pending->mm_geo.next);
+    mdbx_assert(env, largest_pgno >= NUM_METAS);
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+    const pgno_t edge = env->me_poison_edge;
+    if (edge > largest_pgno) {
+      env->me_poison_edge = largest_pgno;
+      VALGRIND_MAKE_MEM_NOACCESS(env->me_map + pgno2bytes(env, largest_pgno),
+                                 pgno2bytes(env, edge - largest_pgno));
+      ASAN_POISON_MEMORY_REGION(env->me_map + pgno2bytes(env, largest_pgno),
+                                pgno2bytes(env, edge - largest_pgno));
+    }
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+#if defined(MADV_DONTNEED)
+    const size_t largest_bytes = pgno2bytes(env, largest_pgno);
+    /* threshold to avoid unreasonable frequent madvise() calls */
+    const size_t madvise_threshold = mdbx_madvise_threshold(env, largest_bytes);
+    const size_t discard_edge_bytes = bytes_align2os_bytes(
+        env, ((MDBX_RDONLY &
+               (env->me_lck ? env->me_lck->mti_envmode.weak : env->me_flags))
+                  ? largest_bytes
+                  : largest_bytes + madvise_threshold));
+    const pgno_t discard_edge_pgno = bytes2pgno(env, discard_edge_bytes);
+    const pgno_t prev_discarded_pgno =
+        atomic_load32(env->me_discarded_tail, mo_AcquireRelease);
+    if (prev_discarded_pgno >=
+        discard_edge_pgno + bytes2pgno(env, madvise_threshold)) {
+      mdbx_notice("open-MADV_%s %u..%u", "DONTNEED", prev_discarded_pgno,
+                  largest_pgno);
+      atomic_store32(env->me_discarded_tail, discard_edge_pgno,
+                     mo_AcquireRelease);
+      const size_t prev_discarded_bytes =
+          ceil_powerof2(pgno2bytes(env, prev_discarded_pgno), env->me_os_psize);
+      mdbx_ensure(env, prev_discarded_bytes > discard_edge_bytes);
+      int advise = MADV_DONTNEED;
+#if defined(MADV_FREE) &&                                                      \
+    0 /* MADV_FREE works for only anonymous vma at the moment */
+      if ((env->me_flags & MDBX_WRITEMAP) &&
+          mdbx_linux_kernel_version > 0x04050000)
+        advise = MADV_FREE;
+#endif /* MADV_FREE */
+      int err = madvise(env->me_map + discard_edge_bytes,
+                        prev_discarded_bytes - discard_edge_bytes, advise)
+                    ? ignore_enosys(errno)
+                    : MDBX_SUCCESS;
+      if (unlikely(MDBX_IS_ERROR(err)))
+        return err;
+    }
+#endif /* MADV_FREE || MADV_DONTNEED */
+
+    /* LY: check conditions to shrink datafile */
+    const pgno_t backlog_gap = 3 + pending->mm_dbs[FREE_DBI].md_depth * 3;
+    if (pending->mm_geo.shrink && pending->mm_geo.now - pending->mm_geo.next >
+                                      pending->mm_geo.shrink + backlog_gap) {
+      if (pending->mm_geo.now > largest_pgno &&
+          pending->mm_geo.now - largest_pgno >
+              pending->mm_geo.shrink + backlog_gap) {
+        const pgno_t aligner = pending->mm_geo.grow ? pending->mm_geo.grow
+                                                    : pending->mm_geo.shrink;
+        const pgno_t with_backlog_gap = largest_pgno + backlog_gap;
+        const pgno_t aligned = pgno_align2os_pgno(
+            env, with_backlog_gap + aligner - with_backlog_gap % aligner);
+        const pgno_t bottom =
+            (aligned > pending->mm_geo.lower) ? aligned : pending->mm_geo.lower;
+        if (pending->mm_geo.now > bottom) {
+          if (META_IS_STEADY(mdbx_meta_steady(env)))
+            /* force steady, but only if steady-checkpoint is present */
+            flags &= MDBX_WRITEMAP | MDBX_SHRINK_ALLOWED;
+          shrink = pending->mm_geo.now - bottom;
+          pending->mm_geo.now = bottom;
+          if (unlikely(mdbx_meta_txnid_stable(env, head) ==
+                       unaligned_peek_u64(4, pending->mm_txnid_a))) {
+            const txnid_t txnid =
+                safe64_txnid_next(unaligned_peek_u64(4, pending->mm_txnid_a));
+            if (unlikely(txnid > MAX_TXNID)) {
+              rc = MDBX_TXN_FULL;
+              mdbx_error("txnid overflow, raise %d", rc);
+              goto fail;
+            }
+            mdbx_meta_set_txnid(env, pending, txnid);
+          }
+        }
+      }
+    }
+  }
+
+  /* LY: step#1 - sync previously written/updated data-pages */
+  rc = MDBX_RESULT_FALSE /* carry steady */;
+  if (atomic_load32(env->me_unsynced_pages, mo_AcquireRelease)) {
+    mdbx_assert(env, ((flags ^ env->me_flags) & MDBX_WRITEMAP) == 0);
+    enum mdbx_syncmode_bits mode_bits = MDBX_SYNC_NONE;
+    if ((flags & MDBX_SAFE_NOSYNC) == 0) {
+      mode_bits = MDBX_SYNC_DATA;
+      if (pending->mm_geo.next > mdbx_meta_steady(env)->mm_geo.now)
+        mode_bits |= MDBX_SYNC_SIZE;
+      if (flags & MDBX_NOMETASYNC)
+        mode_bits |= MDBX_SYNC_IODQ;
+    }
+    if (flags & MDBX_WRITEMAP)
+      rc =
+          mdbx_msync(&env->me_dxb_mmap, 0,
+                     pgno_align2os_bytes(env, pending->mm_geo.next), mode_bits);
+    else
+      rc = mdbx_fsync(env->me_lazy_fd, mode_bits);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto fail;
+    rc = (flags & MDBX_SAFE_NOSYNC) ? MDBX_RESULT_TRUE /* carry non-steady */
+                                    : MDBX_RESULT_FALSE /* carry steady */;
+  }
+
+  /* Steady or Weak */
+  if (rc == MDBX_RESULT_FALSE /* carry steady */) {
+    atomic_store64(env->me_sync_timestamp, mdbx_osal_monotime(), mo_Relaxed);
+    unaligned_poke_u64(4, pending->mm_datasync_sign, mdbx_meta_sign(pending));
+    atomic_store32(env->me_unsynced_pages, 0, mo_AcquireRelease);
+  } else {
+    assert(rc == MDBX_RESULT_TRUE /* carry non-steady */);
+    unaligned_poke_u64(4, pending->mm_datasync_sign, MDBX_DATASIGN_WEAK);
+  }
+
+  MDBX_meta *target = nullptr;
+  if (mdbx_meta_txnid_stable(env, head) ==
+      unaligned_peek_u64(4, pending->mm_txnid_a)) {
+    mdbx_assert(env, memcmp(&head->mm_dbs, &pending->mm_dbs,
+                            sizeof(head->mm_dbs)) == 0);
+    mdbx_assert(env, memcmp(&head->mm_canary, &pending->mm_canary,
+                            sizeof(head->mm_canary)) == 0);
+    mdbx_assert(env, memcmp(&head->mm_geo, &pending->mm_geo,
+                            sizeof(pending->mm_geo)) == 0);
+    if (!META_IS_STEADY(head) && META_IS_STEADY(pending))
+      target = head;
+    else {
+      mdbx_ensure(env, mdbx_meta_eq(env, head, pending));
+      mdbx_debug("%s", "skip update meta");
+      return MDBX_SUCCESS;
+    }
+  } else if (head == meta0)
+    target = mdbx_meta_ancient(prefer_steady, env, meta1, meta2);
+  else if (head == meta1)
+    target = mdbx_meta_ancient(prefer_steady, env, meta0, meta2);
+  else {
+    mdbx_assert(env, head == meta2);
+    target = mdbx_meta_ancient(prefer_steady, env, meta0, meta1);
+  }
+
+  /* LY: step#2 - update meta-page. */
+  mdbx_debug("writing meta%" PRIaPGNO " = root %" PRIaPGNO "/%" PRIaPGNO
+             ", geo %" PRIaPGNO "/%" PRIaPGNO "-%" PRIaPGNO "/%" PRIaPGNO
+             " +%u -%u, txn_id %" PRIaTXN ", %s",
+             data_page(target)->mp_pgno, pending->mm_dbs[MAIN_DBI].md_root,
+             pending->mm_dbs[FREE_DBI].md_root, pending->mm_geo.lower,
+             pending->mm_geo.next, pending->mm_geo.now, pending->mm_geo.upper,
+             pending->mm_geo.grow, pending->mm_geo.shrink,
+             unaligned_peek_u64(4, pending->mm_txnid_a),
+             mdbx_durable_str(pending));
+
+  mdbx_debug("meta0: %s, %s, txn_id %" PRIaTXN ", root %" PRIaPGNO
+             "/%" PRIaPGNO,
+             (meta0 == head) ? "head" : (meta0 == target) ? "tail" : "stay",
+             mdbx_durable_str(meta0), mdbx_meta_txnid_fluid(env, meta0),
+             meta0->mm_dbs[MAIN_DBI].md_root, meta0->mm_dbs[FREE_DBI].md_root);
+  mdbx_debug("meta1: %s, %s, txn_id %" PRIaTXN ", root %" PRIaPGNO
+             "/%" PRIaPGNO,
+             (meta1 == head) ? "head" : (meta1 == target) ? "tail" : "stay",
+             mdbx_durable_str(meta1), mdbx_meta_txnid_fluid(env, meta1),
+             meta1->mm_dbs[MAIN_DBI].md_root, meta1->mm_dbs[FREE_DBI].md_root);
+  mdbx_debug("meta2: %s, %s, txn_id %" PRIaTXN ", root %" PRIaPGNO
+             "/%" PRIaPGNO,
+             (meta2 == head) ? "head" : (meta2 == target) ? "tail" : "stay",
+             mdbx_durable_str(meta2), mdbx_meta_txnid_fluid(env, meta2),
+             meta2->mm_dbs[MAIN_DBI].md_root, meta2->mm_dbs[FREE_DBI].md_root);
+
+  mdbx_assert(env, !mdbx_meta_eq(env, pending, meta0));
+  mdbx_assert(env, !mdbx_meta_eq(env, pending, meta1));
+  mdbx_assert(env, !mdbx_meta_eq(env, pending, meta2));
+
+  mdbx_assert(env, ((env->me_flags ^ flags) & MDBX_WRITEMAP) == 0);
+  mdbx_ensure(env,
+              target == head || mdbx_meta_txnid_stable(env, target) <
+                                    unaligned_peek_u64(4, pending->mm_txnid_a));
+  if (flags & MDBX_WRITEMAP) {
+    mdbx_jitter4testing(true);
+    if (likely(target != head)) {
+      /* LY: 'invalidate' the meta. */
+      mdbx_meta_update_begin(env, target,
+                             unaligned_peek_u64(4, pending->mm_txnid_a));
+      unaligned_poke_u64(4, target->mm_datasync_sign, MDBX_DATASIGN_WEAK);
+#ifndef NDEBUG
+      /* debug: provoke failure to catch a violators, but don't touch mm_psize
+       * and mm_flags to allow readers catch actual pagesize. */
+      uint8_t *provoke_begin = (uint8_t *)&target->mm_dbs[FREE_DBI].md_root;
+      uint8_t *provoke_end = (uint8_t *)&target->mm_datasync_sign;
+      memset(provoke_begin, 0xCC, provoke_end - provoke_begin);
+      mdbx_jitter4testing(false);
+#endif
+
+      /* LY: update info */
+      target->mm_geo = pending->mm_geo;
+      target->mm_dbs[FREE_DBI] = pending->mm_dbs[FREE_DBI];
+      target->mm_dbs[MAIN_DBI] = pending->mm_dbs[MAIN_DBI];
+      target->mm_canary = pending->mm_canary;
+      memcpy(target->mm_pages_retired, pending->mm_pages_retired, 8);
+      mdbx_jitter4testing(true);
+
+      /* LY: 'commit' the meta */
+      mdbx_meta_update_end(env, target,
+                           unaligned_peek_u64(4, pending->mm_txnid_b));
+      mdbx_jitter4testing(true);
+    } else {
+      /* dangerous case (target == head), only mm_datasync_sign could
+       * me updated, check assertions once again */
+      mdbx_ensure(env, mdbx_meta_txnid_stable(env, head) ==
+                               unaligned_peek_u64(4, pending->mm_txnid_a) &&
+                           !META_IS_STEADY(head) && META_IS_STEADY(pending));
+      mdbx_ensure(env, memcmp(&head->mm_geo, &pending->mm_geo,
+                              sizeof(head->mm_geo)) == 0);
+      mdbx_ensure(env, memcmp(&head->mm_dbs, &pending->mm_dbs,
+                              sizeof(head->mm_dbs)) == 0);
+      mdbx_ensure(env, memcmp(&head->mm_canary, &pending->mm_canary,
+                              sizeof(head->mm_canary)) == 0);
+    }
+    memcpy(target->mm_datasync_sign, pending->mm_datasync_sign, 8);
+    mdbx_flush_incoherent_cpu_writeback();
+    mdbx_jitter4testing(true);
+    /* sync meta-pages */
+    rc =
+        mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, NUM_METAS),
+                   (flags & MDBX_NOMETASYNC) ? MDBX_SYNC_NONE
+                                             : MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto fail;
+  } else {
+    const MDBX_meta undo_meta = *target;
+    const mdbx_filehandle_t fd = (env->me_dsync_fd != INVALID_HANDLE_VALUE)
+                                     ? env->me_dsync_fd
+                                     : env->me_lazy_fd;
+    rc = mdbx_pwrite(fd, pending, sizeof(MDBX_meta),
+                     (uint8_t *)target - env->me_map);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+    undo:
+      mdbx_debug("%s", "write failed, disk error?");
+      /* On a failure, the pagecache still contains the new data.
+       * Try write some old data back, to prevent it from being used. */
+      mdbx_pwrite(fd, &undo_meta, sizeof(MDBX_meta),
+                  (uint8_t *)target - env->me_map);
+      goto fail;
+    }
+    mdbx_flush_incoherent_mmap(target, sizeof(MDBX_meta), env->me_os_psize);
+    /* sync meta-pages */
+    if ((flags & MDBX_NOMETASYNC) == 0 && fd == env->me_lazy_fd) {
+      rc = mdbx_fsync(env->me_lazy_fd, MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+      if (rc != MDBX_SUCCESS)
+        goto undo;
+    }
+  }
+  if (flags & MDBX_NOMETASYNC)
+    env->me_unsynced_pages->weak += 1;
+  else
+    env->me_meta_sync_txnid->weak =
+        (uint32_t)unaligned_peek_u64(4, pending->mm_txnid_a);
+
+  /* LY: shrink datafile if needed */
+  if (unlikely(shrink)) {
+    mdbx_verbose("shrink to %" PRIaPGNO " pages (-%" PRIaPGNO ")",
+                 pending->mm_geo.now, shrink);
+    rc = mdbx_mapresize_implicit(env, pending->mm_geo.next, pending->mm_geo.now,
+                                 pending->mm_geo.upper);
+    if (MDBX_IS_ERROR(rc))
+      goto fail;
+  }
+
+  if (likely(env->me_lck))
+    /* toggle oldest refresh */
+    atomic_store32(&env->me_lck->mti_readers_refresh_flag, false,
+                   mo_AcquireRelease);
+
+  return MDBX_SUCCESS;
+
+fail:
+  env->me_flags |= MDBX_FATAL_ERROR;
+  return rc;
+}
+
+static void __cold mdbx_setup_pagesize(MDBX_env *env, const size_t pagesize) {
+  STATIC_ASSERT(PTRDIFF_MAX > MAX_MAPSIZE);
+  STATIC_ASSERT(MIN_PAGESIZE > sizeof(MDBX_page) + sizeof(MDBX_meta));
+  mdbx_ensure(env, is_powerof2(pagesize));
+  mdbx_ensure(env, pagesize >= MIN_PAGESIZE);
+  mdbx_ensure(env, pagesize <= MAX_PAGESIZE);
+  env->me_psize = (unsigned)pagesize;
+
+  STATIC_ASSERT(MAX_GC1OVPAGE(MIN_PAGESIZE) > 4);
+  STATIC_ASSERT(MAX_GC1OVPAGE(MAX_PAGESIZE) < MDBX_PGL_LIMIT / 4);
+  const intptr_t maxgc_ov1page = (pagesize - PAGEHDRSZ) / sizeof(pgno_t) - 1;
+  mdbx_ensure(env, maxgc_ov1page > 42 &&
+                       maxgc_ov1page < (intptr_t)MDBX_PGL_LIMIT / 4);
+  env->me_maxgc_ov1page = (unsigned)maxgc_ov1page;
+
+  STATIC_ASSERT(LEAF_NODEMAX(MIN_PAGESIZE) > sizeof(MDBX_db) + NODESIZE + 42);
+  STATIC_ASSERT(LEAF_NODEMAX(MAX_PAGESIZE) < UINT16_MAX);
+  STATIC_ASSERT(LEAF_NODEMAX(MIN_PAGESIZE) > BRANCH_NODEMAX(MIN_PAGESIZE));
+  STATIC_ASSERT(BRANCH_NODEMAX(MAX_PAGESIZE) > NODESIZE + 42);
+  STATIC_ASSERT(BRANCH_NODEMAX(MAX_PAGESIZE) < UINT16_MAX);
+  const intptr_t branch_nodemax = BRANCH_NODEMAX(pagesize);
+  mdbx_ensure(env, branch_nodemax > 42 && branch_nodemax < (int)UINT16_MAX &&
+                       branch_nodemax % 2 == 0);
+  env->me_branch_nodemax = (unsigned)branch_nodemax;
+  env->me_psize2log = (uint8_t)log2n(pagesize);
+  mdbx_assert(env, pgno2bytes(env, 1) == pagesize);
+  mdbx_assert(env, bytes2pgno(env, pagesize + pagesize) == 2);
+
+  const pgno_t max_pgno = bytes2pgno(env, MAX_MAPSIZE);
+  if (env->me_options.dp_limit > max_pgno - NUM_METAS)
+    env->me_options.dp_limit = max_pgno - NUM_METAS;
+  if (env->me_options.dp_initial > env->me_options.dp_limit)
+    env->me_options.dp_initial = env->me_options.dp_limit;
+}
+
+__cold int mdbx_env_create(MDBX_env **penv) {
+  MDBX_env *env = mdbx_calloc(1, sizeof(MDBX_env));
+  if (unlikely(!env))
+    return MDBX_ENOMEM;
+
+  env->me_maxreaders = DEFAULT_READERS;
+  env->me_maxdbs = env->me_numdbs = CORE_DBS;
+  env->me_lazy_fd = INVALID_HANDLE_VALUE;
+  env->me_dsync_fd = INVALID_HANDLE_VALUE;
+  env->me_lfd = INVALID_HANDLE_VALUE;
+  env->me_pid = mdbx_getpid();
+  env->me_stuck_meta = -1;
+
+  env->me_options.dp_reserve_limit = 1024;
+  env->me_options.rp_augment_limit = 256 * 1024;
+  env->me_options.dp_limit = 64 * 1024;
+  if (env->me_options.dp_limit > MAX_PAGENO - NUM_METAS)
+    env->me_options.dp_limit = MAX_PAGENO - NUM_METAS;
+  env->me_options.dp_initial = MDBX_PNL_INITIAL;
+  if (env->me_options.dp_initial > env->me_options.dp_limit)
+    env->me_options.dp_initial = env->me_options.dp_limit;
+  env->me_options.spill_max_denominator = 8;
+  env->me_options.spill_min_denominator = 8;
+  env->me_options.spill_parent4child_denominator = 0;
+  env->me_options.dp_loose_limit = 64;
+
+  int rc;
+  const size_t os_psize = mdbx_syspagesize();
+  if (unlikely(!is_powerof2(os_psize) || os_psize < MIN_PAGESIZE)) {
+    mdbx_error("unsuitable system pagesize %" PRIuPTR, os_psize);
+    rc = MDBX_INCOMPATIBLE;
+    goto bailout;
+  }
+  env->me_os_psize = (unsigned)os_psize;
+  mdbx_setup_pagesize(env, (env->me_os_psize < MAX_PAGESIZE) ? env->me_os_psize
+                                                             : MAX_PAGESIZE);
+
+  rc = mdbx_fastmutex_init(&env->me_dbi_lock);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout;
+
+#if defined(_WIN32) || defined(_WIN64)
+  mdbx_srwlock_Init(&env->me_remap_guard);
+  InitializeCriticalSection(&env->me_windowsbug_lock);
+#else
+  rc = mdbx_fastmutex_init(&env->me_remap_guard);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_fastmutex_destroy(&env->me_dbi_lock);
+    goto bailout;
+  }
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV
+  rc = mdbx_ipclock_stub(&env->me_lckless_stub.wlock);
+#endif /* MDBX_LOCKING */
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_fastmutex_destroy(&env->me_remap_guard);
+    mdbx_fastmutex_destroy(&env->me_dbi_lock);
+    goto bailout;
+  }
+#endif /* Windows */
+
+  VALGRIND_CREATE_MEMPOOL(env, 0, 0);
+  env->me_signature.weak = MDBX_ME_SIGNATURE;
+  *penv = env;
+  return MDBX_SUCCESS;
+
+bailout:
+  mdbx_free(env);
+  *penv = nullptr;
+  return rc;
+}
+
+__cold LIBMDBX_API int
+mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower, intptr_t size_now,
+                      intptr_t size_upper, intptr_t growth_step,
+                      intptr_t shrink_threshold, intptr_t pagesize) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  const bool inside_txn =
+      (env->me_txn0 && env->me_txn0->mt_owner == mdbx_thread_self());
+
+#if MDBX_DEBUG
+  if (growth_step < 0)
+    growth_step = 1;
+  if (shrink_threshold < 0)
+    shrink_threshold = 1;
+#endif
+
+  bool need_unlock = false;
+  rc = MDBX_PROBLEM;
+  if (env->me_map) {
+    /* env already mapped */
+    if (unlikely(env->me_flags & MDBX_RDONLY))
+      return MDBX_EACCESS;
+
+    if (!inside_txn) {
+      int err = mdbx_txn_lock(env, false);
+      if (unlikely(err != MDBX_SUCCESS))
+        return err;
+      need_unlock = true;
+    }
+    MDBX_meta *head = mdbx_meta_head(env);
+    if (!inside_txn) {
+      env->me_txn0->mt_txnid = meta_txnid(env, head, false);
+      mdbx_find_oldest(env->me_txn0);
+    }
+
+    /* get untouched params from DB */
+    if (pagesize <= 0 || pagesize >= INT_MAX)
+      pagesize = env->me_psize;
+    if (size_lower < 0)
+      size_lower = pgno2bytes(env, head->mm_geo.lower);
+    if (size_now < 0)
+      size_now = pgno2bytes(env, head->mm_geo.now);
+    if (size_upper < 0)
+      size_upper = pgno2bytes(env, head->mm_geo.upper);
+    if (growth_step < 0)
+      growth_step = pgno2bytes(env, head->mm_geo.grow);
+    if (shrink_threshold < 0)
+      shrink_threshold = pgno2bytes(env, head->mm_geo.shrink);
+
+    if (pagesize != (intptr_t)env->me_psize) {
+      rc = MDBX_EINVAL;
+      goto bailout;
+    }
+    const size_t usedbytes =
+        pgno2bytes(env, mdbx_find_largest(env, head->mm_geo.next));
+    if ((size_t)size_upper < usedbytes) {
+      rc = MDBX_MAP_FULL;
+      goto bailout;
+    }
+    if ((size_t)size_now < usedbytes)
+      size_now = usedbytes;
+  } else {
+    /* env NOT yet mapped */
+    if (unlikely(inside_txn))
+      return MDBX_PANIC;
+
+    /* is requested some auto-value for pagesize ? */
+    if (pagesize >= INT_MAX /* maximal */)
+      pagesize = MAX_PAGESIZE;
+    else if (pagesize <= 0) {
+      if (pagesize < 0 /* default */) {
+        pagesize = env->me_os_psize;
+        if ((uintptr_t)pagesize > MAX_PAGESIZE)
+          pagesize = MAX_PAGESIZE;
+        mdbx_assert(env, (uintptr_t)pagesize >= MIN_PAGESIZE);
+      } else if (pagesize == 0 /* minimal */)
+        pagesize = MIN_PAGESIZE;
+
+      /* choose pagesize */
+      intptr_t max_size = (size_now > size_lower) ? size_now : size_lower;
+      max_size = (size_upper > max_size) ? size_upper : max_size;
+      if (max_size < 0 /* default */)
+        max_size = DEFAULT_MAPSIZE;
+      else if (max_size == 0 /* minimal */)
+        max_size = MIN_MAPSIZE;
+      else if (max_size >= (intptr_t)MAX_MAPSIZE /* maximal */)
+        max_size = MAX_MAPSIZE;
+
+      while (max_size > pagesize * (int64_t)MAX_PAGENO &&
+             pagesize < MAX_PAGESIZE)
+        pagesize <<= 1;
+    }
+  }
+
+  if (pagesize < (intptr_t)MIN_PAGESIZE || pagesize > (intptr_t)MAX_PAGESIZE ||
+      !is_powerof2(pagesize)) {
+    rc = MDBX_EINVAL;
+    goto bailout;
+  }
+
+  if (size_lower <= 0) {
+    size_lower = MIN_MAPSIZE;
+    if (MIN_MAPSIZE / pagesize < MIN_PAGENO)
+      size_lower = MIN_PAGENO * pagesize;
+  }
+  if (size_lower == INTPTR_MAX)
+    size_lower = MAX_MAPSIZE;
+
+  if (size_now <= 0) {
+    size_now = DEFAULT_MAPSIZE;
+    if (size_now < size_lower)
+      size_now = size_lower;
+    if (size_upper >= size_lower && size_now > size_upper)
+      size_now = size_upper;
+  }
+  if (size_now == INTPTR_MAX)
+    size_now = MAX_MAPSIZE;
+
+  if (size_upper <= 0) {
+    if ((size_t)size_now >= MAX_MAPSIZE / 2)
+      size_upper = MAX_MAPSIZE;
+    else if (MAX_MAPSIZE != MAX_MAPSIZE32 &&
+             (size_t)size_now >= MAX_MAPSIZE32 / 2 &&
+             (size_t)size_now <= MAX_MAPSIZE32 / 4 * 3)
+      size_upper = MAX_MAPSIZE32;
+    else {
+      size_upper = size_now + size_now;
+      if ((size_t)size_upper < DEFAULT_MAPSIZE * 2)
+        size_upper = DEFAULT_MAPSIZE * 2;
+    }
+    if ((size_t)size_upper / pagesize > MAX_PAGENO)
+      size_upper = pagesize * MAX_PAGENO;
+  }
+
+  if (unlikely(size_lower < (intptr_t)MIN_MAPSIZE || size_lower > size_upper)) {
+    rc = MDBX_EINVAL;
+    goto bailout;
+  }
+
+  if ((uint64_t)size_lower / pagesize < MIN_PAGENO) {
+    rc = MDBX_EINVAL;
+    goto bailout;
+  }
+
+  if (unlikely((size_t)size_upper > MAX_MAPSIZE ||
+               (uint64_t)size_upper / pagesize > MAX_PAGENO)) {
+    rc = MDBX_TOO_LARGE;
+    goto bailout;
+  }
+
+  const size_t unit = (env->me_os_psize > (size_t)pagesize) ? env->me_os_psize
+                                                            : (size_t)pagesize;
+  size_lower = ceil_powerof2(size_lower, unit);
+  size_upper = ceil_powerof2(size_upper, unit);
+  size_now = ceil_powerof2(size_now, unit);
+
+  /* LY: подбираем значение size_upper:
+   *  - кратное размеру страницы
+   *  - без нарушения MAX_MAPSIZE и MAX_PAGENO */
+  while (unlikely((size_t)size_upper > MAX_MAPSIZE ||
+                  (uint64_t)size_upper / pagesize > MAX_PAGENO)) {
+    if ((size_t)size_upper < unit + MIN_MAPSIZE ||
+        (size_t)size_upper < (size_t)pagesize * (MIN_PAGENO + 1)) {
+      /* паранойа на случай переполнения при невероятных значениях */
+      rc = MDBX_EINVAL;
+      goto bailout;
+    }
+    size_upper -= unit;
+    if ((size_t)size_upper < (size_t)size_lower)
+      size_lower = size_upper;
+  }
+  mdbx_assert(env, (size_upper - size_lower) % env->me_os_psize == 0);
+
+  if (size_now < size_lower)
+    size_now = size_lower;
+  if (size_now > size_upper)
+    size_now = size_upper;
+
+  if (growth_step < 0) {
+    growth_step = ((size_t)(size_upper - size_lower)) / 42;
+    if (growth_step > size_lower)
+      growth_step = size_lower;
+    if (growth_step < 65536)
+      growth_step = 65536;
+    if ((size_t)growth_step > MEGABYTE * 16)
+      growth_step = MEGABYTE * 16;
+  }
+  if (growth_step == 0 && shrink_threshold > 0)
+    growth_step = 1;
+  growth_step = ceil_powerof2(growth_step, unit);
+  if (bytes2pgno(env, growth_step) > UINT16_MAX)
+    growth_step = pgno2bytes(env, UINT16_MAX);
+
+  if (shrink_threshold < 0)
+    shrink_threshold = growth_step + growth_step;
+  shrink_threshold = ceil_powerof2(shrink_threshold, unit);
+  if (bytes2pgno(env, shrink_threshold) > UINT16_MAX)
+    shrink_threshold = pgno2bytes(env, UINT16_MAX);
+
+  /* save user's geo-params for future open/create */
+  env->me_dbgeo.lower = size_lower;
+  env->me_dbgeo.now = size_now;
+  env->me_dbgeo.upper = size_upper;
+  env->me_dbgeo.grow = growth_step;
+  env->me_dbgeo.shrink = shrink_threshold;
+  rc = MDBX_SUCCESS;
+
+  mdbx_ensure(env, pagesize >= MIN_PAGESIZE);
+  mdbx_ensure(env, pagesize <= MAX_PAGESIZE);
+  mdbx_ensure(env, is_powerof2(pagesize));
+  mdbx_ensure(env, is_powerof2(env->me_os_psize));
+
+  mdbx_ensure(env, env->me_dbgeo.lower >= MIN_MAPSIZE);
+  mdbx_ensure(env, env->me_dbgeo.lower / pagesize >= MIN_PAGENO);
+  mdbx_ensure(env, env->me_dbgeo.lower % pagesize == 0);
+  mdbx_ensure(env, env->me_dbgeo.lower % env->me_os_psize == 0);
+
+  mdbx_ensure(env, env->me_dbgeo.upper <= MAX_MAPSIZE);
+  mdbx_ensure(env, env->me_dbgeo.upper / pagesize <= MAX_PAGENO);
+  mdbx_ensure(env, env->me_dbgeo.upper % pagesize == 0);
+  mdbx_ensure(env, env->me_dbgeo.upper % env->me_os_psize == 0);
+
+  mdbx_ensure(env, env->me_dbgeo.now >= env->me_dbgeo.lower);
+  mdbx_ensure(env, env->me_dbgeo.now <= env->me_dbgeo.upper);
+  mdbx_ensure(env, env->me_dbgeo.now % pagesize == 0);
+  mdbx_ensure(env, env->me_dbgeo.now % env->me_os_psize == 0);
+
+  mdbx_ensure(env, env->me_dbgeo.grow % pagesize == 0);
+  mdbx_ensure(env, env->me_dbgeo.grow % env->me_os_psize == 0);
+  mdbx_ensure(env, env->me_dbgeo.shrink % pagesize == 0);
+  mdbx_ensure(env, env->me_dbgeo.shrink % env->me_os_psize == 0);
+
+  if (env->me_map) {
+    /* apply new params to opened environment */
+    mdbx_ensure(env, pagesize == (intptr_t)env->me_psize);
+    MDBX_meta meta;
+    MDBX_meta *head = nullptr;
+    const mdbx_geo_t *current_geo;
+    if (inside_txn) {
+      current_geo = &env->me_txn->mt_geo;
+    } else {
+      head = mdbx_meta_head(env);
+      meta = *head;
+      current_geo = &meta.mm_geo;
+    }
+
+    mdbx_geo_t new_geo;
+    new_geo.lower = bytes2pgno(env, env->me_dbgeo.lower);
+    new_geo.now = bytes2pgno(env, env->me_dbgeo.now);
+    new_geo.upper = bytes2pgno(env, env->me_dbgeo.upper);
+    new_geo.grow = (uint16_t)bytes2pgno(env, env->me_dbgeo.grow);
+    new_geo.shrink = (uint16_t)bytes2pgno(env, env->me_dbgeo.shrink);
+    new_geo.next = current_geo->next;
+
+    mdbx_ensure(env,
+                pgno_align2os_bytes(env, new_geo.lower) == env->me_dbgeo.lower);
+    mdbx_ensure(env,
+                pgno_align2os_bytes(env, new_geo.upper) == env->me_dbgeo.upper);
+    mdbx_ensure(env,
+                pgno_align2os_bytes(env, new_geo.now) == env->me_dbgeo.now);
+    mdbx_ensure(env,
+                pgno_align2os_bytes(env, new_geo.grow) == env->me_dbgeo.grow);
+    mdbx_ensure(env, pgno_align2os_bytes(env, new_geo.shrink) ==
+                         env->me_dbgeo.shrink);
+
+    mdbx_ensure(env, env->me_dbgeo.lower >= MIN_MAPSIZE);
+    mdbx_ensure(env, new_geo.lower >= MIN_PAGENO);
+    mdbx_ensure(env, env->me_dbgeo.upper <= MAX_MAPSIZE);
+    mdbx_ensure(env, new_geo.upper <= MAX_PAGENO);
+    mdbx_ensure(env, new_geo.now >= new_geo.next);
+    mdbx_ensure(env, new_geo.upper >= new_geo.now);
+    mdbx_ensure(env, new_geo.now >= new_geo.lower);
+
+    if (memcmp(current_geo, &new_geo, sizeof(mdbx_geo_t)) != 0) {
+#if defined(_WIN32) || defined(_WIN64)
+      /* Was DB shrinking disabled before and now it will be enabled? */
+      if (new_geo.lower < new_geo.upper && new_geo.shrink &&
+          !(current_geo->lower < current_geo->upper && current_geo->shrink)) {
+        if (!env->me_lck) {
+          rc = MDBX_EPERM;
+          goto bailout;
+        }
+        int err = mdbx_rdt_lock(env);
+        if (unlikely(MDBX_IS_ERROR(err))) {
+          rc = err;
+          goto bailout;
+        }
+
+        /* Check if there are any reading threads that do not use the SRWL */
+        const size_t CurrentTid = GetCurrentThreadId();
+        const MDBX_reader *const begin = env->me_lck->mti_readers;
+        const MDBX_reader *const end =
+            begin +
+            atomic_load32(&env->me_lck->mti_numreaders, mo_AcquireRelease);
+        for (const MDBX_reader *reader = begin; reader < end; ++reader) {
+          if (reader->mr_pid.weak == env->me_pid && reader->mr_tid.weak &&
+              reader->mr_tid.weak != CurrentTid) {
+            /* At least one thread may don't use SRWL */
+            rc = MDBX_EPERM;
+            break;
+          }
+        }
+
+        mdbx_rdt_unlock(env);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+#endif
+
+      if (new_geo.now != current_geo->now ||
+          new_geo.upper != current_geo->upper) {
+        rc = mdbx_mapresize(env, current_geo->next, new_geo.now, new_geo.upper,
+                            false);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+        mdbx_assert(env, (head == nullptr) == inside_txn);
+        if (head)
+          head = /* base address could be changed */ mdbx_meta_head(env);
+      }
+      if (inside_txn) {
+        env->me_txn->mt_geo = new_geo;
+        env->me_txn->mt_flags |= MDBX_TXN_DIRTY;
+      } else {
+        meta.mm_geo = new_geo;
+        const txnid_t txnid =
+            safe64_txnid_next(mdbx_meta_txnid_stable(env, head));
+        if (unlikely(txnid > MAX_TXNID)) {
+          rc = MDBX_TXN_FULL;
+          mdbx_error("txnid overflow, raise %d", rc);
+          goto bailout;
+        }
+        mdbx_meta_set_txnid(env, &meta, txnid);
+        rc = mdbx_sync_locked(env, env->me_flags, &meta);
+      }
+    }
+  } else if (pagesize != (intptr_t)env->me_psize) {
+    mdbx_setup_pagesize(env, pagesize);
+  }
+
+bailout:
+  if (need_unlock)
+    mdbx_txn_unlock(env);
+  return rc;
+}
+
+__cold int mdbx_env_set_mapsize(MDBX_env *env, size_t size) {
+  return __inline_mdbx_env_set_mapsize(env, size);
+}
+
+__cold int mdbx_env_set_maxdbs(MDBX_env *env, MDBX_dbi dbs) {
+  return __inline_mdbx_env_set_maxdbs(env, dbs);
+}
+
+__cold int mdbx_env_get_maxdbs(const MDBX_env *env, MDBX_dbi *dbs) {
+  return __inline_mdbx_env_get_maxdbs(env, dbs);
+}
+
+__cold int mdbx_env_set_maxreaders(MDBX_env *env, unsigned readers) {
+  return __inline_mdbx_env_set_maxreaders(env, readers);
+}
+
+__cold int mdbx_env_get_maxreaders(const MDBX_env *env, unsigned *readers) {
+  return __inline_mdbx_env_get_maxreaders(env, readers);
+}
+
+/* Further setup required for opening an MDBX environment */
+static __cold int mdbx_setup_dxb(MDBX_env *env, const int lck_rc) {
+  uint64_t filesize_before;
+  MDBX_meta meta;
+  int rc = MDBX_RESULT_FALSE;
+  int err = mdbx_read_header(env, &meta, &filesize_before, lck_rc);
+  if (unlikely(err != MDBX_SUCCESS)) {
+    if (lck_rc != /* lck exclusive */ MDBX_RESULT_TRUE || err != MDBX_ENODATA ||
+        (env->me_flags & MDBX_RDONLY) != 0 ||
+        /* recovery mode */ env->me_stuck_meta >= 0)
+      return err;
+
+    mdbx_debug("%s", "create new database");
+    rc = /* new database */ MDBX_RESULT_TRUE;
+
+    if (!env->me_dbgeo.now) {
+      /* set defaults if not configured */
+      err = mdbx_env_set_geometry(env, 0, -1, DEFAULT_MAPSIZE, -1, -1, -1);
+      if (unlikely(err != MDBX_SUCCESS))
+        return err;
+    }
+
+    void *buffer = mdbx_calloc(NUM_METAS, env->me_psize);
+    if (!buffer)
+      return MDBX_ENOMEM;
+
+    meta = *mdbx_init_metas(env, buffer);
+    err = mdbx_pwrite(env->me_lazy_fd, buffer, env->me_psize * NUM_METAS, 0);
+    mdbx_free(buffer);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+
+    err = mdbx_ftruncate(env->me_lazy_fd, filesize_before = env->me_dbgeo.now);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+
+#ifndef NDEBUG /* just for checking */
+    err = mdbx_read_header(env, &meta, &filesize_before, lck_rc);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+#endif
+  }
+
+  mdbx_verbose("header: root %" PRIaPGNO "/%" PRIaPGNO ", geo %" PRIaPGNO
+               "/%" PRIaPGNO "-%" PRIaPGNO "/%" PRIaPGNO
+               " +%u -%u, txn_id %" PRIaTXN ", %s",
+               meta.mm_dbs[MAIN_DBI].md_root, meta.mm_dbs[FREE_DBI].md_root,
+               meta.mm_geo.lower, meta.mm_geo.next, meta.mm_geo.now,
+               meta.mm_geo.upper, meta.mm_geo.grow, meta.mm_geo.shrink,
+               unaligned_peek_u64(4, meta.mm_txnid_a), mdbx_durable_str(&meta));
+
+  mdbx_setup_pagesize(env, meta.mm_psize);
+  const size_t used_bytes = pgno2bytes(env, meta.mm_geo.next);
+  const size_t used_aligned2os_bytes =
+      ceil_powerof2(used_bytes, env->me_os_psize);
+  if ((env->me_flags & MDBX_RDONLY) /* readonly */
+      || lck_rc != MDBX_RESULT_TRUE /* not exclusive */
+      || /* recovery mode */ env->me_stuck_meta >= 0) {
+    /* use present params from db */
+    const size_t pagesize = meta.mm_psize;
+    err = mdbx_env_set_geometry(
+        env, meta.mm_geo.lower * pagesize, meta.mm_geo.now * pagesize,
+        meta.mm_geo.upper * pagesize, meta.mm_geo.grow * pagesize,
+        meta.mm_geo.shrink * pagesize, meta.mm_psize);
+    if (unlikely(err != MDBX_SUCCESS)) {
+      mdbx_error("%s: err %d", "could not apply preconfigured geometry from db",
+                 err);
+      return (err == MDBX_EINVAL) ? MDBX_INCOMPATIBLE : err;
+    }
+  } else if (env->me_dbgeo.now) {
+    /* silently growth to last used page */
+    if (env->me_dbgeo.now < used_aligned2os_bytes)
+      env->me_dbgeo.now = used_aligned2os_bytes;
+    if (env->me_dbgeo.upper < used_aligned2os_bytes)
+      env->me_dbgeo.upper = used_aligned2os_bytes;
+
+    /* apply preconfigured params, but only if substantial changes:
+     *  - upper or lower limit changes
+     *  - shrink threshold or growth step
+     * But ignore change just a 'now/current' size. */
+    if (bytes_align2os_bytes(env, env->me_dbgeo.upper) !=
+            pgno2bytes(env, meta.mm_geo.upper) ||
+        bytes_align2os_bytes(env, env->me_dbgeo.lower) !=
+            pgno2bytes(env, meta.mm_geo.lower) ||
+        bytes_align2os_bytes(env, env->me_dbgeo.shrink) !=
+            pgno2bytes(env, meta.mm_geo.shrink) ||
+        bytes_align2os_bytes(env, env->me_dbgeo.grow) !=
+            pgno2bytes(env, meta.mm_geo.grow)) {
+
+      if (env->me_dbgeo.shrink && env->me_dbgeo.now > used_bytes)
+        /* pre-shrink if enabled */
+        env->me_dbgeo.now = used_bytes + env->me_dbgeo.shrink -
+                            used_bytes % env->me_dbgeo.shrink;
+
+      err = mdbx_env_set_geometry(env, env->me_dbgeo.lower, env->me_dbgeo.now,
+                                  env->me_dbgeo.upper, env->me_dbgeo.grow,
+                                  env->me_dbgeo.shrink, meta.mm_psize);
+      if (unlikely(err != MDBX_SUCCESS)) {
+        mdbx_error("%s: err %d", "could not apply preconfigured db-geometry",
+                   err);
+        return (err == MDBX_EINVAL) ? MDBX_INCOMPATIBLE : err;
+      }
+
+      /* update meta fields */
+      meta.mm_geo.now = bytes2pgno(env, env->me_dbgeo.now);
+      meta.mm_geo.lower = bytes2pgno(env, env->me_dbgeo.lower);
+      meta.mm_geo.upper = bytes2pgno(env, env->me_dbgeo.upper);
+      meta.mm_geo.grow = (uint16_t)bytes2pgno(env, env->me_dbgeo.grow);
+      meta.mm_geo.shrink = (uint16_t)bytes2pgno(env, env->me_dbgeo.shrink);
+
+      mdbx_verbose("amended: root %" PRIaPGNO "/%" PRIaPGNO ", geo %" PRIaPGNO
+                   "/%" PRIaPGNO "-%" PRIaPGNO "/%" PRIaPGNO
+                   " +%u -%u, txn_id %" PRIaTXN ", %s",
+                   meta.mm_dbs[MAIN_DBI].md_root, meta.mm_dbs[FREE_DBI].md_root,
+                   meta.mm_geo.lower, meta.mm_geo.next, meta.mm_geo.now,
+                   meta.mm_geo.upper, meta.mm_geo.grow, meta.mm_geo.shrink,
+                   unaligned_peek_u64(4, meta.mm_txnid_a),
+                   mdbx_durable_str(&meta));
+    } else {
+      /* fetch back 'now/current' size, since it was ignored during comparison
+       * and may differ. */
+      env->me_dbgeo.now = pgno_align2os_bytes(env, meta.mm_geo.now);
+    }
+    mdbx_ensure(env, meta.mm_geo.now >= meta.mm_geo.next);
+  } else {
+    /* geo-params are not pre-configured by user,
+     * get current values from the meta. */
+    env->me_dbgeo.now = pgno2bytes(env, meta.mm_geo.now);
+    env->me_dbgeo.lower = pgno2bytes(env, meta.mm_geo.lower);
+    env->me_dbgeo.upper = pgno2bytes(env, meta.mm_geo.upper);
+    env->me_dbgeo.grow = pgno2bytes(env, meta.mm_geo.grow);
+    env->me_dbgeo.shrink = pgno2bytes(env, meta.mm_geo.shrink);
+  }
+
+  mdbx_ensure(env,
+              pgno_align2os_bytes(env, meta.mm_geo.now) == env->me_dbgeo.now);
+  mdbx_ensure(env, env->me_dbgeo.now >= used_bytes);
+  if (unlikely(filesize_before != env->me_dbgeo.now)) {
+    if (lck_rc != /* lck exclusive */ MDBX_RESULT_TRUE) {
+      mdbx_verbose("filesize mismatch (expect %" PRIuPTR "b/%" PRIaPGNO
+                   "p, have %" PRIu64 "b/%" PRIaPGNO "p), "
+                   "assume other process working",
+                   env->me_dbgeo.now, bytes2pgno(env, env->me_dbgeo.now),
+                   filesize_before, bytes2pgno(env, (size_t)filesize_before));
+    } else {
+      mdbx_warning("filesize mismatch (expect %" PRIuSIZE "b/%" PRIaPGNO
+                   "p, have %" PRIu64 "b/%" PRIaPGNO "p)",
+                   env->me_dbgeo.now, bytes2pgno(env, env->me_dbgeo.now),
+                   filesize_before, bytes2pgno(env, (size_t)filesize_before));
+      if (filesize_before < used_bytes) {
+        mdbx_error("last-page beyond end-of-file (last %" PRIaPGNO
+                   ", have %" PRIaPGNO ")",
+                   meta.mm_geo.next, bytes2pgno(env, (size_t)filesize_before));
+        return MDBX_CORRUPTED;
+      }
+
+      if (env->me_flags & MDBX_RDONLY) {
+        if (filesize_before & (env->me_os_psize - 1)) {
+          mdbx_error("%s", "filesize should be rounded-up to system page");
+          return MDBX_WANNA_RECOVERY;
+        }
+        mdbx_warning("%s", "ignore filesize mismatch in readonly-mode");
+      } else {
+        mdbx_verbose("will resize datafile to %" PRIuSIZE " bytes, %" PRIaPGNO
+                     " pages",
+                     env->me_dbgeo.now, bytes2pgno(env, env->me_dbgeo.now));
+      }
+    }
+  }
+
+  mdbx_verbose("current boot-id %" PRIx64 "-%" PRIx64 " (%savailable)",
+               bootid.x, bootid.y, (bootid.x | bootid.y) ? "" : "not-");
+
+  /* calculate readahead hint before mmap with zero redundant pages */
+  const bool readahead =
+      (env->me_flags & MDBX_NORDAHEAD) == 0 &&
+      mdbx_is_readahead_reasonable(used_bytes, 0) == MDBX_RESULT_TRUE;
+  err = mdbx_mmap(env->me_flags, &env->me_dxb_mmap, env->me_dbgeo.now,
+                  env->me_dbgeo.upper, lck_rc ? MMAP_OPTION_TRUNCATE : 0);
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+
+#if defined(MADV_DONTDUMP)
+  err = madvise(env->me_map, env->me_dxb_mmap.limit, MADV_DONTDUMP)
+            ? ignore_enosys(errno)
+            : MDBX_SUCCESS;
+  if (unlikely(MDBX_IS_ERROR(err)))
+    return err;
+#endif /* MADV_DONTDUMP */
+#if defined(MADV_DODUMP)
+  if (mdbx_runtime_flags & MDBX_DBG_DUMP) {
+    const size_t meta_length_aligned2os = pgno_align2os_bytes(env, NUM_METAS);
+    err = madvise(env->me_map, meta_length_aligned2os, MADV_DODUMP)
+              ? ignore_enosys(errno)
+              : MDBX_SUCCESS;
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+  }
+#endif /* MADV_DODUMP */
+
+#ifdef MDBX_USE_VALGRIND
+  env->me_valgrind_handle =
+      VALGRIND_CREATE_BLOCK(env->me_map, env->me_dxb_mmap.limit, "mdbx");
+#endif /* MDBX_USE_VALGRIND */
+
+  mdbx_assert(env, used_bytes >= pgno2bytes(env, NUM_METAS) &&
+                       used_bytes <= env->me_dxb_mmap.limit);
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  VALGRIND_MAKE_MEM_NOACCESS(env->me_map + used_bytes,
+                             env->me_dxb_mmap.limit - used_bytes);
+  ASAN_POISON_MEMORY_REGION(env->me_map + used_bytes,
+                            env->me_dxb_mmap.limit - used_bytes);
+  env->me_poison_edge = bytes2pgno(env, env->me_dxb_mmap.limit);
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+
+  const unsigned meta_clash_mask = mdbx_meta_eq_mask(env);
+  if (unlikely(meta_clash_mask)) {
+    if (/* not recovery mode */ env->me_stuck_meta < 0) {
+      mdbx_error("meta-pages are clashed: mask 0x%d", meta_clash_mask);
+      return MDBX_CORRUPTED;
+    } else {
+      mdbx_warning("ignore meta-pages clashing (mask 0x%d) in recovery mode",
+                   meta_clash_mask);
+    }
+  }
+
+  while (likely(/* not recovery mode */ env->me_stuck_meta < 0)) {
+    MDBX_meta *const head = mdbx_meta_head(env);
+    const txnid_t head_txnid = mdbx_meta_txnid_fluid(env, head);
+    MDBX_meta *const steady = mdbx_meta_steady(env);
+    const txnid_t steady_txnid = mdbx_meta_txnid_fluid(env, steady);
+    if (head_txnid == steady_txnid)
+      break;
+
+    if (lck_rc == /* lck exclusive */ MDBX_RESULT_TRUE) {
+      mdbx_assert(env, META_IS_STEADY(steady) && !META_IS_STEADY(head));
+      if (meta_bootid_match(head)) {
+        MDBX_meta clone = *head;
+        uint64_t filesize = env->me_dbgeo.now;
+        err = mdbx_validate_meta(
+            env, &clone, &filesize, data_page(head),
+            bytes2pgno(env, (uint8_t *)data_page(head) - env->me_map), nullptr,
+            env->me_psize);
+        if (err == MDBX_SUCCESS) {
+          mdbx_warning(
+              "opening after an unclean shutdown, but boot-id(%016" PRIx64
+              "-%016" PRIx64
+              ") is MATCH: rollback NOT needed, steady-sync NEEDED%s",
+              bootid.x, bootid.y,
+              (env->me_flags & MDBX_RDONLY) ? ", but unable in read-only mode"
+                                            : "");
+          if (env->me_flags & MDBX_RDONLY)
+            return MDBX_WANNA_RECOVERY /* LY: could not recovery/sync */;
+          meta = clone;
+          atomic_store32(env->me_unsynced_pages, meta.mm_geo.next, mo_Relaxed);
+          break;
+        }
+        mdbx_warning("opening after an unclean shutdown, "
+                     "but boot-id(%016" PRIx64 "-%016" PRIx64 ") is MATCH, "
+                     "but last meta not valid, rollback needed",
+                     bootid.x, bootid.y);
+      }
+      if (env->me_flags & MDBX_RDONLY) {
+        mdbx_error("rollback needed: (from head %" PRIaTXN
+                   " to steady %" PRIaTXN "), but unable in read-only mode",
+                   head_txnid, steady_txnid);
+        return MDBX_WANNA_RECOVERY /* LY: could not recovery/rollback */;
+      }
+
+      const MDBX_meta *const meta0 = METAPAGE(env, 0);
+      const MDBX_meta *const meta1 = METAPAGE(env, 1);
+      const MDBX_meta *const meta2 = METAPAGE(env, 2);
+      txnid_t undo_txnid = 0 /* zero means undo is unneeded */;
+      while (
+          (head != meta0 && mdbx_meta_txnid_fluid(env, meta0) == undo_txnid) ||
+          (head != meta1 && mdbx_meta_txnid_fluid(env, meta1) == undo_txnid) ||
+          (head != meta2 && mdbx_meta_txnid_fluid(env, meta2) == undo_txnid))
+        undo_txnid = safe64_txnid_next(undo_txnid);
+      if (unlikely(undo_txnid >= steady_txnid)) {
+        mdbx_fatal("rollback failed: no suitable txnid (0,1,2) < %" PRIaTXN,
+                   steady_txnid);
+        return MDBX_PANIC /* LY: could not recovery/rollback */;
+      }
+
+      /* LY: rollback weak checkpoint */
+      mdbx_notice("rollback: from %" PRIaTXN ", to %" PRIaTXN " as %" PRIaTXN,
+                  head_txnid, steady_txnid, undo_txnid);
+      mdbx_ensure(env, head_txnid == mdbx_meta_txnid_stable(env, head));
+
+      if (env->me_flags & MDBX_WRITEMAP) {
+        /* It is possible to update txnid without safe64_write(),
+         * since DB opened exclusive for now */
+        unaligned_poke_u64(4, head->mm_txnid_a, undo_txnid);
+        unaligned_poke_u64(4, head->mm_datasync_sign, MDBX_DATASIGN_WEAK);
+        unaligned_poke_u64(4, head->mm_txnid_b, undo_txnid);
+        const size_t offset = (uint8_t *)data_page(head) - env->me_dxb_mmap.dxb;
+        const size_t paged_offset = floor_powerof2(offset, env->me_os_psize);
+        const size_t paged_length = ceil_powerof2(
+            env->me_psize + offset - paged_offset, env->me_os_psize);
+        err = mdbx_msync(&env->me_dxb_mmap, paged_offset, paged_length, false);
+      } else {
+        MDBX_meta rollback = *head;
+        mdbx_meta_set_txnid(env, &rollback, undo_txnid);
+        unaligned_poke_u64(4, rollback.mm_datasync_sign, MDBX_DATASIGN_WEAK);
+        err = mdbx_pwrite(env->me_lazy_fd, &rollback, sizeof(MDBX_meta),
+                          (uint8_t *)head - (uint8_t *)env->me_map);
+      }
+      if (err) {
+        mdbx_error("error %d rollback from %" PRIaTXN ", to %" PRIaTXN
+                   " as %" PRIaTXN,
+                   err, head_txnid, steady_txnid, undo_txnid);
+        return err;
+      }
+
+      mdbx_flush_incoherent_mmap(env->me_map, pgno2bytes(env, NUM_METAS),
+                                 env->me_os_psize);
+      mdbx_ensure(env, undo_txnid == mdbx_meta_txnid_fluid(env, head));
+      mdbx_ensure(env, 0 == mdbx_meta_eq_mask(env));
+      continue;
+    }
+
+    if (!env->me_lck) {
+      /* LY: without-lck (read-only) mode, so it is impossible that other
+       * process made weak checkpoint. */
+      mdbx_error("%s", "without-lck, unable recovery/rollback");
+      return MDBX_WANNA_RECOVERY;
+    }
+
+    /* LY: assume just have a collision with other running process,
+     *     or someone make a weak checkpoint */
+    mdbx_verbose("%s", "assume collision or online weak checkpoint");
+    break;
+  }
+
+  const MDBX_meta *head = mdbx_meta_head(env);
+  if (lck_rc == /* lck exclusive */ MDBX_RESULT_TRUE) {
+    /* re-check size after mmap */
+    if ((env->me_dxb_mmap.current & (env->me_os_psize - 1)) != 0 ||
+        env->me_dxb_mmap.current < used_bytes) {
+      mdbx_error("unacceptable/unexpected datafile size %" PRIuPTR,
+                 env->me_dxb_mmap.current);
+      return MDBX_PROBLEM;
+    }
+    if (env->me_dxb_mmap.current != env->me_dbgeo.now) {
+      meta.mm_geo.now = bytes2pgno(env, env->me_dxb_mmap.current);
+      mdbx_notice("need update meta-geo to filesize %" PRIuPTR
+                  " bytes, %" PRIaPGNO " pages",
+                  env->me_dxb_mmap.current, meta.mm_geo.now);
+    }
+
+    if (memcmp(&meta.mm_geo, &head->mm_geo, sizeof(meta.mm_geo))) {
+      if ((env->me_flags & MDBX_RDONLY) != 0 ||
+          /* recovery mode */ env->me_stuck_meta >= 0) {
+        mdbx_warning("skipped update meta.geo in %s mode: from l%" PRIaPGNO
+                     "-n%" PRIaPGNO "-u%" PRIaPGNO "/s%u-g%u, to l%" PRIaPGNO
+                     "-n%" PRIaPGNO "-u%" PRIaPGNO "/s%u-g%u",
+                     (env->me_stuck_meta < 0) ? "read-only" : "recovery",
+                     head->mm_geo.lower, head->mm_geo.now, head->mm_geo.upper,
+                     head->mm_geo.shrink, head->mm_geo.grow, meta.mm_geo.lower,
+                     meta.mm_geo.now, meta.mm_geo.upper, meta.mm_geo.shrink,
+                     meta.mm_geo.grow);
+      } else {
+        const txnid_t txnid = mdbx_meta_txnid_stable(env, head);
+        const txnid_t next_txnid = safe64_txnid_next(txnid);
+        if (unlikely(txnid > MAX_TXNID)) {
+          mdbx_error("txnid overflow, raise %d", MDBX_TXN_FULL);
+          return MDBX_TXN_FULL;
+        }
+        mdbx_notice("updating meta.geo: "
+                    "from l%" PRIaPGNO "-n%" PRIaPGNO "-u%" PRIaPGNO
+                    "/s%u-g%u (txn#%" PRIaTXN "), "
+                    "to l%" PRIaPGNO "-n%" PRIaPGNO "-u%" PRIaPGNO
+                    "/s%u-g%u (txn#%" PRIaTXN ")",
+                    head->mm_geo.lower, head->mm_geo.now, head->mm_geo.upper,
+                    head->mm_geo.shrink, head->mm_geo.grow, txnid,
+                    meta.mm_geo.lower, meta.mm_geo.now, meta.mm_geo.upper,
+                    meta.mm_geo.shrink, meta.mm_geo.grow, next_txnid);
+
+        mdbx_ensure(env, mdbx_meta_eq(env, &meta, head));
+        mdbx_meta_set_txnid(env, &meta, next_txnid);
+        err = mdbx_sync_locked(env, env->me_flags | MDBX_SHRINK_ALLOWED, &meta);
+        if (err) {
+          mdbx_error("error %d, while updating meta.geo: "
+                     "from l%" PRIaPGNO "-n%" PRIaPGNO "-u%" PRIaPGNO
+                     "/s%u-g%u (txn#%" PRIaTXN "), "
+                     "to l%" PRIaPGNO "-n%" PRIaPGNO "-u%" PRIaPGNO
+                     "/s%u-g%u (txn#%" PRIaTXN ")",
+                     err, head->mm_geo.lower, head->mm_geo.now,
+                     head->mm_geo.upper, head->mm_geo.shrink, head->mm_geo.grow,
+                     txnid, meta.mm_geo.lower, meta.mm_geo.now,
+                     meta.mm_geo.upper, meta.mm_geo.shrink, meta.mm_geo.grow,
+                     next_txnid);
+          return err;
+        }
+      }
+    }
+  }
+
+  atomic_store32(env->me_discarded_tail, bytes2pgno(env, used_aligned2os_bytes),
+                 mo_AcquireRelease);
+  if (used_aligned2os_bytes < env->me_dxb_mmap.current) {
+#if defined(MADV_REMOVE)
+    if (lck_rc && (env->me_flags & MDBX_WRITEMAP) != 0 &&
+        /* not recovery mode */ env->me_stuck_meta < 0) {
+      mdbx_notice("open-MADV_%s %u..%u", "REMOVE (deallocate file space)",
+                  env->me_discarded_tail->weak,
+                  bytes2pgno(env, env->me_dxb_mmap.current));
+      err =
+          madvise(env->me_map + used_aligned2os_bytes,
+                  env->me_dxb_mmap.current - used_aligned2os_bytes, MADV_REMOVE)
+              ? ignore_enosys(errno)
+              : MDBX_SUCCESS;
+      if (unlikely(MDBX_IS_ERROR(err)))
+        return err;
+    }
+#endif /* MADV_REMOVE */
+#if defined(MADV_DONTNEED)
+    mdbx_notice("open-MADV_%s %u..%u", "DONTNEED", env->me_discarded_tail->weak,
+                bytes2pgno(env, env->me_dxb_mmap.current));
+    err =
+        madvise(env->me_map + used_aligned2os_bytes,
+                env->me_dxb_mmap.current - used_aligned2os_bytes, MADV_DONTNEED)
+            ? ignore_enosys(errno)
+            : MDBX_SUCCESS;
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(POSIX_MADV_DONTNEED)
+    err = ignore_enosys(posix_madvise(
+        env->me_map + used_aligned2os_bytes,
+        env->me_dxb_mmap.current - used_aligned2os_bytes, POSIX_MADV_DONTNEED));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#elif defined(POSIX_FADV_DONTNEED)
+    err = ignore_enosys(posix_fadvise(
+        env->me_lazy_fd, used_aligned2os_bytes,
+        env->me_dxb_mmap.current - used_aligned2os_bytes, POSIX_FADV_DONTNEED));
+    if (unlikely(MDBX_IS_ERROR(err)))
+      return err;
+#endif /* MADV_DONTNEED */
+  }
+
+  err = mdbx_set_readahead(env, 0, used_bytes, readahead);
+  if (err != MDBX_SUCCESS && lck_rc == /* lck exclusive */ MDBX_RESULT_TRUE)
+    return err;
+
+  return rc;
+}
+
+/******************************************************************************/
+
+/* Open and/or initialize the lock region for the environment. */
+static __cold int mdbx_setup_lck(MDBX_env *env, char *lck_pathname,
+                                 mdbx_mode_t mode) {
+  mdbx_assert(env, env->me_lazy_fd != INVALID_HANDLE_VALUE);
+  mdbx_assert(env, env->me_lfd == INVALID_HANDLE_VALUE);
+
+  int err = mdbx_openfile(MDBX_OPEN_LCK, env, lck_pathname, &env->me_lfd, mode);
+  if (err != MDBX_SUCCESS) {
+    if (!(err == MDBX_ENOFILE && (env->me_flags & MDBX_EXCLUSIVE)) &&
+        !((err == MDBX_EROFS || err == MDBX_EACCESS || err == MDBX_EPERM) &&
+          (env->me_flags & MDBX_RDONLY)))
+      return err;
+
+    /* ensure the file system is read-only */
+    err = mdbx_check_fs_rdonly(env->me_lazy_fd, lck_pathname, err);
+    if (err != MDBX_SUCCESS &&
+        /* ignore ERROR_NOT_SUPPORTED for exclusive mode */
+        !(err == MDBX_ENOSYS && (env->me_flags & MDBX_EXCLUSIVE)))
+      return err;
+
+    /* LY: without-lck mode (e.g. exclusive or on read-only filesystem) */
+    /* beginning of a locked section ---------------------------------------- */
+    lcklist_lock();
+    mdbx_assert(env, env->me_lcklist_next == nullptr);
+    env->me_lfd = INVALID_HANDLE_VALUE;
+    const int rc = mdbx_lck_seize(env);
+    if (MDBX_IS_ERROR(rc)) {
+      /* Calling lcklist_detach_locked() is required to restore POSIX-filelock
+       * and this job will be done by mdbx_env_close0(). */
+      lcklist_unlock();
+      return rc;
+    }
+    /* insert into inprocess lck-list */
+    env->me_lcklist_next = inprocess_lcklist_head;
+    inprocess_lcklist_head = env;
+    lcklist_unlock();
+    /* end of a locked section ---------------------------------------------- */
+
+    env->me_oldest = &env->me_lckless_stub.oldest;
+    env->me_sync_timestamp = &env->me_lckless_stub.sync_timestamp;
+    env->me_autosync_period = &env->me_lckless_stub.autosync_period;
+    env->me_unsynced_pages = &env->me_lckless_stub.autosync_pending;
+    env->me_autosync_threshold = &env->me_lckless_stub.autosync_threshold;
+    env->me_discarded_tail = &env->me_lckless_stub.discarded_tail;
+    env->me_meta_sync_txnid = &env->me_lckless_stub.meta_sync_txnid;
+    env->me_maxreaders = UINT_MAX;
+#if MDBX_LOCKING > 0
+    env->me_wlock = &env->me_lckless_stub.wlock;
+#endif /* MDBX_LOCKING > 0 */
+    mdbx_debug("lck-setup:%s%s%s", " lck-less",
+               (env->me_flags & MDBX_RDONLY) ? " readonly" : "",
+               (rc == MDBX_RESULT_TRUE) ? " exclusive" : " cooperative");
+    return rc;
+  }
+
+  /* beginning of a locked section ------------------------------------------ */
+  lcklist_lock();
+  mdbx_assert(env, env->me_lcklist_next == nullptr);
+
+  /* Try to get exclusive lock. If we succeed, then
+   * nobody is using the lock region and we should initialize it. */
+  err = mdbx_lck_seize(env);
+  if (MDBX_IS_ERROR(err)) {
+  bailout:
+    /* Calling lcklist_detach_locked() is required to restore POSIX-filelock
+     * and this job will be done by mdbx_env_close0(). */
+    lcklist_unlock();
+    return err;
+  }
+
+  MDBX_env *inprocess_neighbor = nullptr;
+  if (err == MDBX_RESULT_TRUE) {
+    err = uniq_check(&env->me_lck_mmap, &inprocess_neighbor);
+    if (MDBX_IS_ERROR(err))
+      goto bailout;
+    if (inprocess_neighbor &&
+        ((mdbx_runtime_flags & MDBX_DBG_LEGACY_MULTIOPEN) == 0 ||
+         (inprocess_neighbor->me_flags & MDBX_EXCLUSIVE) != 0)) {
+      err = MDBX_BUSY;
+      goto bailout;
+    }
+  }
+  const int lck_seize_rc = err;
+
+  mdbx_debug("lck-setup:%s%s%s", " with-lck",
+             (env->me_flags & MDBX_RDONLY) ? " readonly" : "",
+             (lck_seize_rc == MDBX_RESULT_TRUE) ? " exclusive"
+                                                : " cooperative");
+
+  uint64_t size = 0;
+  err = mdbx_filesize(env->me_lfd, &size);
+  if (unlikely(err != MDBX_SUCCESS))
+    goto bailout;
+
+  if (lck_seize_rc == MDBX_RESULT_TRUE) {
+    size = ceil_powerof2(env->me_maxreaders * sizeof(MDBX_reader) +
+                             sizeof(MDBX_lockinfo),
+                         env->me_os_psize);
+    mdbx_jitter4testing(false);
+  } else {
+    if (env->me_flags & MDBX_EXCLUSIVE) {
+      err = MDBX_BUSY;
+      goto bailout;
+    }
+    if (size > INT_MAX || (size & (env->me_os_psize - 1)) != 0 ||
+        size < env->me_os_psize) {
+      mdbx_error("lck-file has invalid size %" PRIu64 " bytes", size);
+      err = MDBX_PROBLEM;
+      goto bailout;
+    }
+  }
+
+  const size_t maxreaders =
+      ((size_t)size - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader);
+  if (maxreaders < 4) {
+    mdbx_error("lck-size too small (up to %" PRIuPTR " readers)", maxreaders);
+    err = MDBX_PROBLEM;
+    goto bailout;
+  }
+  env->me_maxreaders = (maxreaders <= MDBX_READERS_LIMIT)
+                           ? (unsigned)maxreaders
+                           : (unsigned)MDBX_READERS_LIMIT;
+
+  err = mdbx_mmap((env->me_flags & MDBX_EXCLUSIVE) | MDBX_WRITEMAP,
+                  &env->me_lck_mmap, (size_t)size, (size_t)size,
+                  lck_seize_rc ? MMAP_OPTION_TRUNCATE | MMAP_OPTION_SEMAPHORE
+                               : MMAP_OPTION_SEMAPHORE);
+  if (unlikely(err != MDBX_SUCCESS))
+    goto bailout;
+
+#ifdef MADV_DODUMP
+  err = madvise(env->me_lck, size, MADV_DODUMP) ? ignore_enosys(errno)
+                                                : MDBX_SUCCESS;
+  if (unlikely(MDBX_IS_ERROR(err)))
+    goto bailout;
+#endif /* MADV_DODUMP */
+
+#ifdef MADV_WILLNEED
+  err = madvise(env->me_lck, size, MADV_WILLNEED) ? ignore_enosys(errno)
+                                                  : MDBX_SUCCESS;
+  if (unlikely(MDBX_IS_ERROR(err)))
+    goto bailout;
+#endif /* MADV_WILLNEED */
+
+  struct MDBX_lockinfo *const lck = env->me_lck;
+  if (lck_seize_rc == MDBX_RESULT_TRUE) {
+    /* LY: exclusive mode, check and reset lck content */
+    memset(lck, 0, (size_t)size);
+    mdbx_jitter4testing(false);
+    lck->mti_magic_and_version = MDBX_LOCK_MAGIC;
+    lck->mti_os_and_format = MDBX_LOCK_FORMAT;
+    err = mdbx_msync(&env->me_lck_mmap, 0, (size_t)size, false);
+    if (unlikely(err != MDBX_SUCCESS)) {
+      mdbx_error("initial-%s for lck-file failed", "msync");
+      goto bailout;
+    }
+    err = mdbx_fsync(env->me_lck_mmap.fd, MDBX_SYNC_SIZE);
+    if (unlikely(err != MDBX_SUCCESS)) {
+      mdbx_error("initial-%s for lck-file failed", "fsync");
+      goto bailout;
+    }
+  } else {
+    if (lck->mti_magic_and_version != MDBX_LOCK_MAGIC) {
+      mdbx_error("%s", "lock region has invalid magic/version");
+      err = ((lck->mti_magic_and_version >> 8) != MDBX_MAGIC)
+                ? MDBX_INVALID
+                : MDBX_VERSION_MISMATCH;
+      goto bailout;
+    }
+    if (lck->mti_os_and_format != MDBX_LOCK_FORMAT) {
+      mdbx_error("lock region has os/format 0x%" PRIx32 ", expected 0x%" PRIx32,
+                 lck->mti_os_and_format, MDBX_LOCK_FORMAT);
+      err = MDBX_VERSION_MISMATCH;
+      goto bailout;
+    }
+  }
+
+  err = mdbx_lck_init(env, inprocess_neighbor, lck_seize_rc);
+  if (MDBX_IS_ERROR(err))
+    goto bailout;
+
+  mdbx_ensure(env, env->me_lcklist_next == nullptr);
+  /* insert into inprocess lck-list */
+  env->me_lcklist_next = inprocess_lcklist_head;
+  inprocess_lcklist_head = env;
+  lcklist_unlock();
+  /* end of a locked section ------------------------------------------------ */
+
+  mdbx_assert(env, !MDBX_IS_ERROR(lck_seize_rc));
+  env->me_oldest = &lck->mti_oldest_reader;
+  env->me_sync_timestamp = &lck->mti_sync_timestamp;
+  env->me_autosync_period = &lck->mti_autosync_period;
+  env->me_unsynced_pages = &lck->mti_unsynced_pages;
+  env->me_autosync_threshold = &lck->mti_autosync_threshold;
+  env->me_discarded_tail = &lck->mti_discarded_tail;
+  env->me_meta_sync_txnid = &lck->mti_meta_sync_txnid;
+#if MDBX_LOCKING > 0
+  env->me_wlock = &lck->mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+  return lck_seize_rc;
+}
+
+__cold int mdbx_is_readahead_reasonable(size_t volume, intptr_t redundancy) {
+  if (volume <= 1024 * 1024 * 4ul)
+    return MDBX_RESULT_TRUE;
+
+  const intptr_t pagesize = mdbx_syspagesize();
+  if (unlikely(pagesize < MIN_PAGESIZE || !is_powerof2(pagesize)))
+    return MDBX_INCOMPATIBLE;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MEMORYSTATUSEX info;
+  memset(&info, 0, sizeof(info));
+  info.dwLength = sizeof(info);
+  if (!GlobalMemoryStatusEx(&info))
+    return GetLastError();
+#endif
+  const int log2page = log2n(pagesize);
+
+#if defined(_WIN32) || defined(_WIN64)
+  const intptr_t total_ram_pages = (intptr_t)(info.ullTotalPhys >> log2page);
+#elif defined(_SC_PHYS_PAGES)
+  const intptr_t total_ram_pages = sysconf(_SC_PHYS_PAGES);
+  if (total_ram_pages == -1)
+    return errno;
+#elif defined(_SC_AIX_REALMEM)
+  const intptr_t total_ram_Kb = sysconf(_SC_AIX_REALMEM);
+  if (total_ram_Kb == -1)
+    return errno;
+  const intptr_t total_ram_pages = (total_ram_Kb << 10) >> log2page;
+#elif defined(HW_USERMEM) || defined(HW_PHYSMEM64) || defined(HW_MEMSIZE) ||   \
+    defined(HW_PHYSMEM)
+  size_t ram, len = sizeof(ram);
+  static const int mib[] = {
+    CTL_HW,
+#if defined(HW_USERMEM)
+    HW_USERMEM
+#elif defined(HW_PHYSMEM64)
+    HW_PHYSMEM64
+#elif defined(HW_MEMSIZE)
+    HW_MEMSIZE
+#else
+    HW_PHYSMEM
+#endif
+  };
+  if (sysctl(
+#ifdef SYSCTL_LEGACY_NONCONST_MIB
+          (int *)
+#endif
+              mib,
+          ARRAY_LENGTH(mib), &ram, &len, NULL, 0) != 0)
+    return errno;
+  if (len != sizeof(ram))
+    return MDBX_ENOSYS;
+  const intptr_t total_ram_pages = (intptr_t)(ram >> log2page);
+#else
+#error "FIXME: Get User-accessible or physical RAM"
+#endif
+  if (total_ram_pages < 1)
+    return MDBX_ENOSYS;
+
+  const intptr_t volume_pages = (volume + pagesize - 1) >> log2page;
+  const intptr_t redundancy_pages =
+      (redundancy < 0) ? -(intptr_t)((-redundancy + pagesize - 1) >> log2page)
+                       : (intptr_t)(redundancy + pagesize - 1) >> log2page;
+  if (volume_pages >= total_ram_pages ||
+      volume_pages + redundancy_pages >= total_ram_pages)
+    return MDBX_RESULT_FALSE;
+
+#if defined(_WIN32) || defined(_WIN64)
+  const intptr_t avail_ram_pages = (intptr_t)(info.ullAvailPhys >> log2page);
+#elif defined(_SC_AVPHYS_PAGES)
+  const intptr_t avail_ram_pages = sysconf(_SC_AVPHYS_PAGES);
+  if (avail_ram_pages == -1)
+    return errno;
+#elif defined(__MACH__)
+  mach_msg_type_number_t count = HOST_VM_INFO_COUNT;
+  vm_statistics_data_t vmstat;
+  mach_port_t mport = mach_host_self();
+  kern_return_t kerr = host_statistics(mach_host_self(), HOST_VM_INFO,
+                                       (host_info_t)&vmstat, &count);
+  mach_port_deallocate(mach_task_self(), mport);
+  if (unlikely(kerr != KERN_SUCCESS))
+    return MDBX_ENOSYS;
+  const intptr_t avail_ram_pages = vmstat.free_count;
+#elif defined(VM_TOTAL) || defined(VM_METER)
+  struct vmtotal info;
+  size_t len = sizeof(info);
+  static const int mib[] = {
+    CTL_VM,
+#if defined(VM_TOTAL)
+    VM_TOTAL
+#elif defined(VM_METER)
+    VM_METER
+#endif
+  };
+  if (sysctl(
+#ifdef SYSCTL_LEGACY_NONCONST_MIB
+          (int *)
+#endif
+              mib,
+          ARRAY_LENGTH(mib), &info, &len, NULL, 0) != 0)
+    return errno;
+  if (len != sizeof(info))
+    return MDBX_ENOSYS;
+  const intptr_t avail_ram_pages = info.t_free;
+#else
+#error "FIXME: Get Available RAM"
+#endif
+  if (avail_ram_pages < 1)
+    return MDBX_ENOSYS;
+
+  return (volume_pages + redundancy_pages >= avail_ram_pages)
+             ? MDBX_RESULT_FALSE
+             : MDBX_RESULT_TRUE;
+}
+
+/* Merge sync flags */
+static uint32_t merge_sync_flags(const uint32_t a, const uint32_t b) {
+  uint32_t r = a | b;
+
+  /* avoid false MDBX_UTTERLY_NOSYNC */
+  if (F_ISSET(r, MDBX_UTTERLY_NOSYNC) && !F_ISSET(a, MDBX_UTTERLY_NOSYNC) &&
+      !F_ISSET(b, MDBX_UTTERLY_NOSYNC))
+    r = (r - MDBX_UTTERLY_NOSYNC) | MDBX_SAFE_NOSYNC;
+
+  /* convert MDBX_DEPRECATED_MAPASYNC to MDBX_SAFE_NOSYNC */
+  if ((r & (MDBX_WRITEMAP | MDBX_DEPRECATED_MAPASYNC)) ==
+          (MDBX_WRITEMAP | MDBX_DEPRECATED_MAPASYNC) &&
+      !F_ISSET(r, MDBX_UTTERLY_NOSYNC))
+    r = (r - MDBX_DEPRECATED_MAPASYNC) | MDBX_SAFE_NOSYNC;
+
+  /* force MDBX_NOMETASYNC if MDBX_SAFE_NOSYNC enabled */
+  if (r & MDBX_SAFE_NOSYNC)
+    r |= MDBX_NOMETASYNC;
+
+  assert(!(F_ISSET(r, MDBX_UTTERLY_NOSYNC) &&
+           !F_ISSET(a, MDBX_UTTERLY_NOSYNC) &&
+           !F_ISSET(b, MDBX_UTTERLY_NOSYNC)));
+  return r;
+}
+
+__cold int mdbx_env_turn_for_recovery(MDBX_env *env, unsigned target_meta) {
+  if (unlikely(target_meta >= NUM_METAS))
+    return MDBX_EINVAL;
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if ((env->me_flags & (MDBX_EXCLUSIVE | MDBX_RDONLY)) != MDBX_EXCLUSIVE)
+    return MDBX_EPERM;
+
+  MDBX_page *page =
+      (env->me_flags & MDBX_WRITEMAP)
+          ? pgno2page(env, target_meta)
+          : memcpy(env->me_pbuf, pgno2page(env, target_meta), env->me_psize);
+  page->mp_pgno = target_meta;
+  page->mp_flags = P_META;
+
+  MDBX_meta *meta = page_meta(page);
+  unaligned_poke_u64(4, meta->mm_magic_and_version, MDBX_DATA_MAGIC);
+  meta->mm_psize = env->me_psize;
+  txnid_t txnid = mdbx_meta_txnid_stable(env, meta);
+  const txnid_t txnid0 = mdbx_meta_txnid_stable(env, METAPAGE(env, 0));
+  if (target_meta != 0 && txnid <= txnid0)
+    txnid = safe64_txnid_next(txnid0);
+  const txnid_t txnid1 = mdbx_meta_txnid_stable(env, METAPAGE(env, 1));
+  if (target_meta != 1 && txnid <= txnid1)
+    txnid = safe64_txnid_next(txnid1);
+  const txnid_t txnid2 = mdbx_meta_txnid_stable(env, METAPAGE(env, 2));
+  if (target_meta != 2 && txnid <= txnid2)
+    txnid = safe64_txnid_next(txnid2);
+
+  if (!META_IS_STEADY(meta) || mdbx_recent_committed_txnid(env) != txnid) {
+    if (unlikely(txnid > MAX_TXNID)) {
+      mdbx_error("txnid overflow, raise %d", MDBX_TXN_FULL);
+      return MDBX_TXN_FULL;
+    }
+    mdbx_meta_set_txnid(env, meta, txnid);
+    unaligned_poke_u64(4, meta->mm_datasync_sign, mdbx_meta_sign(meta));
+  }
+
+  if (env->me_flags & MDBX_WRITEMAP) {
+    mdbx_flush_incoherent_cpu_writeback();
+    rc = mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, target_meta),
+                    MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+  } else {
+    const mdbx_filehandle_t fd = (env->me_dsync_fd != INVALID_HANDLE_VALUE)
+                                     ? env->me_dsync_fd
+                                     : env->me_lazy_fd;
+    rc = mdbx_pwrite(fd, page, env->me_psize, pgno2bytes(env, target_meta));
+    if (rc == MDBX_SUCCESS && fd == env->me_lazy_fd)
+      rc = mdbx_fsync(env->me_lazy_fd, MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+  }
+
+  return rc;
+}
+
+__cold int mdbx_env_open_for_recovery(MDBX_env *env, const char *pathname,
+                                      unsigned target_meta, bool writeable) {
+  if (unlikely(target_meta >= NUM_METAS))
+    return MDBX_EINVAL;
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  env->me_stuck_meta = (int8_t)target_meta;
+  return mdbx_env_open(
+      env, pathname, writeable ? MDBX_EXCLUSIVE : MDBX_EXCLUSIVE | MDBX_RDONLY,
+      0);
+}
+
+typedef struct {
+  void *buffer_for_free;
+  char *lck, *dxb;
+  size_t ent_len;
+} MDBX_handle_env_pathname;
+
+__cold static int mdbx_handle_env_pathname(MDBX_handle_env_pathname *ctx,
+                                           const char *pathname,
+                                           MDBX_env_flags_t *flags,
+                                           const mdbx_mode_t mode) {
+  int rc;
+  memset(ctx, 0, sizeof(*ctx));
+  if (unlikely(!pathname))
+    return MDBX_EINVAL;
+
+#if defined(_WIN32) || defined(_WIN64)
+  const size_t wlen = mbstowcs(nullptr, pathname, INT_MAX);
+  if (wlen < 1 || wlen > /* MAX_PATH */ INT16_MAX)
+    return ERROR_INVALID_NAME;
+  wchar_t *const pathnameW = _alloca((wlen + 1) * sizeof(wchar_t));
+  if (wlen != mbstowcs(pathnameW, pathname, wlen + 1))
+    return ERROR_INVALID_NAME;
+
+  const DWORD dwAttrib = GetFileAttributesW(pathnameW);
+  if (dwAttrib == INVALID_FILE_ATTRIBUTES) {
+    rc = GetLastError();
+    if (rc != MDBX_ENOFILE)
+      return rc;
+    if (mode == 0 || (*flags & MDBX_RDONLY) != 0)
+      /* can't open existing */
+      return rc;
+
+    /* auto-create directory if requested */
+    if ((*flags & MDBX_NOSUBDIR) == 0 &&
+        !CreateDirectoryW(pathnameW, nullptr)) {
+      rc = GetLastError();
+      if (rc != ERROR_ALREADY_EXISTS)
+        return rc;
+    }
+  } else {
+    /* ignore passed MDBX_NOSUBDIR flag and set it automatically */
+    *flags |= MDBX_NOSUBDIR;
+    if (dwAttrib & FILE_ATTRIBUTE_DIRECTORY)
+      *flags -= MDBX_NOSUBDIR;
+  }
+#else
+  struct stat st;
+  if (stat(pathname, &st)) {
+    rc = errno;
+    if (rc != MDBX_ENOFILE)
+      return rc;
+    if (mode == 0 || (*flags & MDBX_RDONLY) != 0)
+      /* can't open existing */
+      return rc;
+
+    /* auto-create directory if requested */
+    const mdbx_mode_t dir_mode =
+        (/* inherit read/write permissions for group and others */ mode &
+         (S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)) |
+        /* always add read/write/search for owner */ S_IRWXU |
+        ((mode & S_IRGRP) ? /* +search if readable by group */ S_IXGRP : 0) |
+        ((mode & S_IROTH) ? /* +search if readable by others */ S_IXOTH : 0);
+    if ((*flags & MDBX_NOSUBDIR) == 0 && mkdir(pathname, dir_mode)) {
+      rc = errno;
+      if (rc != EEXIST)
+        return rc;
+    }
+  } else {
+    /* ignore passed MDBX_NOSUBDIR flag and set it automatically */
+    *flags |= MDBX_NOSUBDIR;
+    if (S_ISDIR(st.st_mode))
+      *flags -= MDBX_NOSUBDIR;
+  }
+#endif
+
+  static const char dxb_name[] = MDBX_DATANAME;
+  static const size_t dxb_name_len = sizeof(dxb_name) - 1;
+  static const char lck_name[] = MDBX_LOCKNAME;
+  static const char lock_suffix[] = MDBX_LOCK_SUFFIX;
+
+  ctx->ent_len = strlen(pathname);
+  if ((*flags & MDBX_NOSUBDIR) && ctx->ent_len >= dxb_name_len &&
+      !memcmp(dxb_name, pathname + ctx->ent_len - dxb_name_len, dxb_name_len)) {
+    *flags -= MDBX_NOSUBDIR;
+    ctx->ent_len -= dxb_name_len;
+  }
+
+  const size_t bytes_needed =
+      ctx->ent_len * 2 + ((*flags & MDBX_NOSUBDIR)
+                              ? sizeof(lock_suffix) + 1
+                              : sizeof(lck_name) + sizeof(dxb_name));
+  ctx->buffer_for_free = mdbx_malloc(bytes_needed);
+  if (!ctx->buffer_for_free)
+    return MDBX_ENOMEM;
+
+  ctx->lck = ctx->buffer_for_free;
+  if (*flags & MDBX_NOSUBDIR) {
+    ctx->dxb = ctx->lck + ctx->ent_len + sizeof(lock_suffix);
+    sprintf(ctx->lck, "%s%s", pathname, lock_suffix);
+    strcpy(ctx->dxb, pathname);
+  } else {
+    ctx->dxb = ctx->lck + ctx->ent_len + sizeof(lck_name);
+    sprintf(ctx->lck, "%.*s%s", (int)ctx->ent_len, pathname, lck_name);
+    sprintf(ctx->dxb, "%.*s%s", (int)ctx->ent_len, pathname, dxb_name);
+  }
+
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_env_delete(const char *pathname, MDBX_env_delete_mode_t mode) {
+  switch (mode) {
+  default:
+    return MDBX_EINVAL;
+  case MDBX_ENV_JUST_DELETE:
+  case MDBX_ENV_ENSURE_UNUSED:
+  case MDBX_ENV_WAIT_FOR_UNUSED:
+    break;
+  }
+
+  MDBX_env dummy_env;
+  memset(&dummy_env, 0, sizeof(dummy_env));
+  dummy_env.me_flags =
+      (mode == MDBX_ENV_ENSURE_UNUSED) ? MDBX_EXCLUSIVE : MDBX_ENV_DEFAULTS;
+  dummy_env.me_os_psize = (unsigned)mdbx_syspagesize();
+  dummy_env.me_psize = (unsigned)mdbx_default_pagesize();
+  dummy_env.me_pathname = (char *)pathname;
+
+  MDBX_handle_env_pathname env_pathname;
+  STATIC_ASSERT(sizeof(dummy_env.me_flags) == sizeof(MDBX_env_flags_t));
+  int rc = MDBX_RESULT_TRUE,
+      err = mdbx_handle_env_pathname(
+          &env_pathname, pathname, (MDBX_env_flags_t *)&dummy_env.me_flags, 0);
+  if (likely(err == MDBX_SUCCESS)) {
+    mdbx_filehandle_t clk_handle = INVALID_HANDLE_VALUE,
+                      dxb_handle = INVALID_HANDLE_VALUE;
+    if (mode > MDBX_ENV_JUST_DELETE) {
+      err = mdbx_openfile(MDBX_OPEN_DELETE, &dummy_env, env_pathname.dxb,
+                          &dxb_handle, 0);
+      err = (err == MDBX_ENOFILE) ? MDBX_SUCCESS : err;
+      if (err == MDBX_SUCCESS) {
+        err = mdbx_openfile(MDBX_OPEN_DELETE, &dummy_env, env_pathname.lck,
+                            &clk_handle, 0);
+        err = (err == MDBX_ENOFILE) ? MDBX_SUCCESS : err;
+      }
+      if (err == MDBX_SUCCESS && clk_handle != INVALID_HANDLE_VALUE)
+        err = mdbx_lockfile(clk_handle, mode == MDBX_ENV_WAIT_FOR_UNUSED);
+      if (err == MDBX_SUCCESS && dxb_handle != INVALID_HANDLE_VALUE)
+        err = mdbx_lockfile(dxb_handle, mode == MDBX_ENV_WAIT_FOR_UNUSED);
+    }
+
+    if (err == MDBX_SUCCESS) {
+      err = mdbx_removefile(env_pathname.dxb);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (err == MDBX_SUCCESS) {
+      err = mdbx_removefile(env_pathname.lck);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (err == MDBX_SUCCESS && !(dummy_env.me_flags & MDBX_NOSUBDIR)) {
+      err = mdbx_removedirectory(pathname);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (dxb_handle != INVALID_HANDLE_VALUE)
+      mdbx_closefile(dxb_handle);
+    if (clk_handle != INVALID_HANDLE_VALUE)
+      mdbx_closefile(clk_handle);
+  } else if (err == MDBX_ENOFILE)
+    err = MDBX_SUCCESS;
+
+  mdbx_free(env_pathname.buffer_for_free);
+  return (err == MDBX_SUCCESS) ? rc : err;
+}
+
+__cold int mdbx_env_open(MDBX_env *env, const char *pathname,
+                         MDBX_env_flags_t flags, mdbx_mode_t mode) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (flags & ~ENV_USABLE_FLAGS)
+    return MDBX_EINVAL;
+
+  if (env->me_lazy_fd != INVALID_HANDLE_VALUE ||
+      (env->me_flags & MDBX_ENV_ACTIVE) != 0)
+    return MDBX_EPERM;
+
+  /* pickup previously mdbx_env_set_flags(),
+   * but avoid MDBX_UTTERLY_NOSYNC by disjunction */
+  const uint32_t saved_me_flags = env->me_flags;
+  flags = merge_sync_flags(flags, env->me_flags);
+
+  MDBX_handle_env_pathname env_pathname;
+  rc = mdbx_handle_env_pathname(&env_pathname, pathname, &flags, mode);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout;
+
+  if (flags & MDBX_RDONLY) {
+    /* LY: silently ignore irrelevant flags when
+     * we're only getting read access */
+    flags &= ~(MDBX_WRITEMAP | MDBX_DEPRECATED_MAPASYNC | MDBX_SAFE_NOSYNC |
+               MDBX_NOMETASYNC | MDBX_COALESCE | MDBX_LIFORECLAIM |
+               MDBX_NOMEMINIT | MDBX_ACCEDE);
+  } else {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+    /* Temporary `workaround` for OpenBSD kernel's flaw.
+     * See https://github.com/erthink/libmdbx/issues/67 */
+    if ((flags & MDBX_WRITEMAP) == 0) {
+      if (flags & MDBX_ACCEDE)
+        flags |= MDBX_WRITEMAP;
+      else {
+        mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__,
+                       "System (i.e. OpenBSD) requires MDBX_WRITEMAP because "
+                       "of an internal flaw(s) in a file/buffer/page cache.\n");
+        rc = 42 /* ENOPROTOOPT */;
+        goto bailout;
+      }
+    }
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+  }
+
+  env->me_flags = (flags & ~MDBX_FATAL_ERROR) | MDBX_ENV_ACTIVE;
+  env->me_pathname = mdbx_calloc(env_pathname.ent_len + 1, 1);
+  env->me_dbxs = mdbx_calloc(env->me_maxdbs, sizeof(MDBX_dbx));
+  env->me_dbflags = mdbx_calloc(env->me_maxdbs, sizeof(env->me_dbflags[0]));
+  env->me_dbiseqs = mdbx_calloc(env->me_maxdbs, sizeof(env->me_dbiseqs[0]));
+  if (!(env->me_dbxs && env->me_pathname && env->me_dbflags &&
+        env->me_dbiseqs)) {
+    rc = MDBX_ENOMEM;
+    goto bailout;
+  }
+  memcpy(env->me_pathname, env_pathname.dxb, env_pathname.ent_len);
+  env->me_dbxs[FREE_DBI].md_cmp = cmp_int_align4; /* aligned MDBX_INTEGERKEY */
+  env->me_dbxs[FREE_DBI].md_dcmp = cmp_lenfast;
+
+  rc = mdbx_openfile(F_ISSET(flags, MDBX_RDONLY) ? MDBX_OPEN_DXB_READ
+                                                 : MDBX_OPEN_DXB_LAZY,
+                     env, env_pathname.dxb, &env->me_lazy_fd, mode);
+  if (rc != MDBX_SUCCESS)
+    goto bailout;
+
+  mdbx_assert(env, env->me_dsync_fd == INVALID_HANDLE_VALUE);
+  if ((flags & (MDBX_RDONLY | MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC)) == 0) {
+    rc = mdbx_openfile(MDBX_OPEN_DXB_DSYNC, env, env_pathname.dxb,
+                       &env->me_dsync_fd, 0);
+    mdbx_ensure(env, (rc != MDBX_SUCCESS) ==
+                         (env->me_dsync_fd == INVALID_HANDLE_VALUE));
+  }
+
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  env->me_sysv_ipc.key = ftok(env_pathname.dxb, 42);
+  if (env->me_sysv_ipc.key == -1) {
+    rc = errno;
+    goto bailout;
+  }
+#endif /* MDBX_LOCKING */
+
+#if !(defined(_WIN32) || defined(_WIN64))
+  if (mode == 0) {
+    /* pickup mode for lck-file */
+    struct stat st;
+    if (fstat(env->me_lazy_fd, &st)) {
+      rc = errno;
+      goto bailout;
+    }
+    mode = st.st_mode;
+  }
+  mode = (/* inherit read permissions for group and others */ mode &
+          (S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)) |
+         /* always add read/write/search for owner */ S_IRUSR | S_IWUSR |
+         ((mode & S_IRGRP) ? /* +write if readable by group */ S_IWGRP : 0) |
+         ((mode & S_IROTH) ? /* +write if readable by others */ S_IWOTH : 0);
+#endif /* !Windows */
+  const int lck_rc = mdbx_setup_lck(env, env_pathname.lck, mode);
+  if (MDBX_IS_ERROR(lck_rc)) {
+    rc = lck_rc;
+    goto bailout;
+  }
+
+  /* Set the position in files outside of the data to avoid corruption
+   * due to erroneous use of file descriptors in the application code. */
+  mdbx_fseek(env->me_lfd, UINT64_C(1) << 63);
+  mdbx_fseek(env->me_lazy_fd, UINT64_C(1) << 63);
+  if (env->me_dsync_fd != INVALID_HANDLE_VALUE)
+    mdbx_fseek(env->me_dsync_fd, UINT64_C(1) << 63);
+
+  const MDBX_env_flags_t rigorous_flags =
+      MDBX_SAFE_NOSYNC | MDBX_DEPRECATED_MAPASYNC;
+  const MDBX_env_flags_t mode_flags = rigorous_flags | MDBX_NOMETASYNC |
+                                      MDBX_LIFORECLAIM | MDBX_COALESCE |
+                                      MDBX_NORDAHEAD;
+
+  if (env->me_lck && lck_rc != MDBX_RESULT_TRUE &&
+      (env->me_flags & MDBX_RDONLY) == 0) {
+    while (atomic_load32(&env->me_lck->mti_envmode, mo_AcquireRelease) ==
+           MDBX_RDONLY) {
+      if (atomic_cas32(&env->me_lck->mti_envmode, MDBX_RDONLY,
+                       env->me_flags & mode_flags))
+        break;
+      atomic_yield();
+    }
+
+    if (env->me_flags & MDBX_ACCEDE) {
+      /* pickup current mode-flags, including MDBX_LIFORECLAIM |
+       * MDBX_COALESCE | MDBX_NORDAHEAD */
+      const unsigned diff =
+          (env->me_lck->mti_envmode.weak ^ env->me_flags) & mode_flags;
+      mdbx_notice("accede mode-flags: 0x%X, 0x%X -> 0x%X", diff, env->me_flags,
+                  env->me_flags ^ diff);
+      env->me_flags ^= diff;
+    }
+
+    if ((env->me_lck->mti_envmode.weak ^ env->me_flags) & rigorous_flags) {
+      mdbx_error("%s", "current mode/flags incompatible with requested");
+      rc = MDBX_INCOMPATIBLE;
+      goto bailout;
+    }
+  }
+
+  const int dxb_rc = mdbx_setup_dxb(env, lck_rc);
+  if (MDBX_IS_ERROR(dxb_rc)) {
+    rc = dxb_rc;
+    goto bailout;
+  }
+
+  if (unlikely(/* recovery mode */ env->me_stuck_meta >= 0) &&
+      (lck_rc != /* exclusive */ MDBX_RESULT_TRUE ||
+       (flags & MDBX_EXCLUSIVE) == 0)) {
+    mdbx_error("%s", "recovery requires exclusive mode");
+    rc = MDBX_BUSY;
+    goto bailout;
+  }
+
+  mdbx_debug("opened dbenv %p", (void *)env);
+  if (env->me_lck) {
+    if (lck_rc == MDBX_RESULT_TRUE) {
+      env->me_lck->mti_envmode.weak =
+          env->me_flags & (mode_flags | MDBX_RDONLY);
+      rc = mdbx_lck_downgrade(env);
+      mdbx_debug("lck-downgrade-%s: rc %i",
+                 (env->me_flags & MDBX_EXCLUSIVE) ? "partial" : "full", rc);
+      if (rc != MDBX_SUCCESS)
+        goto bailout;
+    } else {
+      rc = mdbx_cleanup_dead_readers(env, false, NULL);
+      if (MDBX_IS_ERROR(rc))
+        goto bailout;
+    }
+
+    if ((env->me_flags & MDBX_NOTLS) == 0) {
+      rc = mdbx_rthc_alloc(&env->me_txkey, &env->me_lck->mti_readers[0],
+                           &env->me_lck->mti_readers[env->me_maxreaders]);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto bailout;
+      env->me_flags |= MDBX_ENV_TXKEY;
+    }
+  }
+
+  if ((flags & MDBX_RDONLY) == 0) {
+    const size_t tsize = sizeof(MDBX_txn),
+                 size = tsize + env->me_maxdbs *
+                                    (sizeof(MDBX_db) + sizeof(MDBX_cursor *) +
+                                     sizeof(unsigned) + 1);
+    rc = mdbx_memalign_alloc(
+        env->me_os_psize,
+        env->me_psize * (1 /* page buffer */ + 1 /* page killer buffer */),
+        &env->me_pbuf);
+    if (rc == MDBX_SUCCESS) {
+      memset(env->me_pbuf, -1, env->me_psize * 2);
+      MDBX_txn *txn = mdbx_calloc(1, size);
+      if (txn) {
+        txn->mt_dbs = (MDBX_db *)((char *)txn + tsize);
+        txn->tw.cursors = (MDBX_cursor **)(txn->mt_dbs + env->me_maxdbs);
+        txn->mt_dbiseqs = (unsigned *)(txn->tw.cursors + env->me_maxdbs);
+        txn->mt_dbistate = (uint8_t *)(txn->mt_dbiseqs + env->me_maxdbs);
+        txn->mt_env = env;
+        txn->mt_dbxs = env->me_dbxs;
+        txn->mt_flags = MDBX_TXN_FINISHED;
+        env->me_txn0 = txn;
+        rc = mdbx_dpl_alloc(txn);
+        if (likely(rc == MDBX_SUCCESS)) {
+          txn->tw.retired_pages = mdbx_pnl_alloc(MDBX_PNL_INITIAL);
+          txn->tw.reclaimed_pglist = mdbx_pnl_alloc(MDBX_PNL_INITIAL);
+          if (unlikely(!txn->tw.retired_pages || !txn->tw.reclaimed_pglist))
+            rc = MDBX_ENOMEM;
+        }
+      } else
+        rc = MDBX_ENOMEM;
+    }
+  }
+
+#if MDBX_DEBUG
+  if (rc == MDBX_SUCCESS) {
+    MDBX_meta *meta = mdbx_meta_head(env);
+    MDBX_db *db = &meta->mm_dbs[MAIN_DBI];
+
+    mdbx_debug("opened database version %u, pagesize %u",
+               (uint8_t)unaligned_peek_u64(4, meta->mm_magic_and_version),
+               env->me_psize);
+    mdbx_debug("using meta page %" PRIaPGNO ", txn %" PRIaTXN,
+               data_page(meta)->mp_pgno, mdbx_meta_txnid_fluid(env, meta));
+    mdbx_debug("depth: %u", db->md_depth);
+    mdbx_debug("entries: %" PRIu64, db->md_entries);
+    mdbx_debug("branch pages: %" PRIaPGNO, db->md_branch_pages);
+    mdbx_debug("leaf pages: %" PRIaPGNO, db->md_leaf_pages);
+    mdbx_debug("overflow pages: %" PRIaPGNO, db->md_overflow_pages);
+    mdbx_debug("root: %" PRIaPGNO, db->md_root);
+    mdbx_debug("schema_altered: %" PRIaTXN, db->md_mod_txnid);
+  }
+#endif
+
+bailout:
+  if (rc != MDBX_SUCCESS) {
+    rc = mdbx_env_close0(env) ? MDBX_PANIC : rc;
+    env->me_flags =
+        saved_me_flags | ((rc != MDBX_PANIC) ? 0 : MDBX_FATAL_ERROR);
+  } else {
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+    mdbx_txn_valgrind(env, nullptr);
+#endif
+  }
+  mdbx_free(env_pathname.buffer_for_free);
+  return rc;
+}
+
+/* Destroy resources from mdbx_env_open(), clear our readers & DBIs */
+static __cold int mdbx_env_close0(MDBX_env *env) {
+  env->me_stuck_meta = -1;
+  if (!(env->me_flags & MDBX_ENV_ACTIVE)) {
+    mdbx_ensure(env, env->me_lcklist_next == nullptr);
+    return MDBX_SUCCESS;
+  }
+
+  env->me_flags &= ~MDBX_ENV_ACTIVE;
+  env->me_oldest = nullptr;
+  env->me_sync_timestamp = nullptr;
+  env->me_autosync_period = nullptr;
+  env->me_unsynced_pages = nullptr;
+  env->me_autosync_threshold = nullptr;
+  env->me_discarded_tail = nullptr;
+  env->me_meta_sync_txnid = nullptr;
+  if (env->me_flags & MDBX_ENV_TXKEY)
+    mdbx_rthc_remove(env->me_txkey);
+
+  lcklist_lock();
+  const int rc = lcklist_detach_locked(env);
+  lcklist_unlock();
+
+  if (env->me_map) {
+    mdbx_munmap(&env->me_dxb_mmap);
+#ifdef MDBX_USE_VALGRIND
+    VALGRIND_DISCARD(env->me_valgrind_handle);
+    env->me_valgrind_handle = -1;
+#endif
+  }
+
+  if (env->me_dsync_fd != INVALID_HANDLE_VALUE) {
+    (void)mdbx_closefile(env->me_dsync_fd);
+    env->me_dsync_fd = INVALID_HANDLE_VALUE;
+  }
+
+  if (env->me_lazy_fd != INVALID_HANDLE_VALUE) {
+    (void)mdbx_closefile(env->me_lazy_fd);
+    env->me_lazy_fd = INVALID_HANDLE_VALUE;
+  }
+
+  if (env->me_lck)
+    mdbx_munmap(&env->me_lck_mmap);
+
+  if (env->me_lfd != INVALID_HANDLE_VALUE) {
+    (void)mdbx_closefile(env->me_lfd);
+    env->me_lfd = INVALID_HANDLE_VALUE;
+  }
+
+  if (env->me_dbxs) {
+    for (unsigned i = env->me_numdbs; --i >= CORE_DBS;)
+      mdbx_free(env->me_dbxs[i].md_name.iov_base);
+    mdbx_free(env->me_dbxs);
+  }
+  mdbx_memalign_free(env->me_pbuf);
+  mdbx_free(env->me_dbiseqs);
+  mdbx_free(env->me_dbflags);
+  mdbx_free(env->me_pathname);
+  if (env->me_txn0) {
+    mdbx_dpl_free(env->me_txn0);
+    mdbx_txl_free(env->me_txn0->tw.lifo_reclaimed);
+    mdbx_pnl_free(env->me_txn0->tw.retired_pages);
+    mdbx_pnl_free(env->me_txn0->tw.spill_pages);
+    mdbx_pnl_free(env->me_txn0->tw.reclaimed_pglist);
+    mdbx_free(env->me_txn0);
+  }
+  env->me_flags = 0;
+  return rc;
+}
+
+__cold int mdbx_env_close_ex(MDBX_env *env, bool dont_sync) {
+  MDBX_page *dp;
+  int rc = MDBX_SUCCESS;
+
+  if (unlikely(!env))
+    return MDBX_EINVAL;
+
+  if (unlikely(env->me_signature.weak != MDBX_ME_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+#if MDBX_ENV_CHECKPID || !(defined(_WIN32) || defined(_WIN64))
+  /* Check the PID even if MDBX_ENV_CHECKPID=0 on non-Windows
+   * platforms (i.e. where fork() is available).
+   * This is required to legitimize a call after fork()
+   * from a child process, that should be allowed to free resources. */
+  if (unlikely(env->me_pid != mdbx_getpid()))
+    env->me_flags |= MDBX_FATAL_ERROR;
+#endif /* MDBX_ENV_CHECKPID */
+
+  if ((env->me_flags & (MDBX_RDONLY | MDBX_FATAL_ERROR)) == 0 && env->me_txn0) {
+    if (env->me_txn0->mt_owner && env->me_txn0->mt_owner != mdbx_thread_self())
+      return MDBX_BUSY;
+  } else
+    dont_sync = true;
+
+  if (!atomic_cas32(&env->me_signature, MDBX_ME_SIGNATURE, 0))
+    return MDBX_EBADSIGN;
+
+  if (!dont_sync) {
+#if defined(_WIN32) || defined(_WIN64)
+    /* On windows, without blocking is impossible to determine whether another
+     * process is running a writing transaction or not.
+     * Because in the "owner died" condition kernel don't release
+     * file lock immediately. */
+    rc = mdbx_env_sync_internal(env, true, false);
+    rc = (rc == MDBX_RESULT_TRUE) ? MDBX_SUCCESS : rc;
+#else
+    struct stat st;
+    if (unlikely(fstat(env->me_lazy_fd, &st)))
+      rc = errno;
+    else if (st.st_nlink > 0 /* don't sync deleted files */) {
+      rc = mdbx_env_sync_internal(env, true, true);
+      rc = (rc == MDBX_BUSY || rc == EAGAIN || rc == EACCES || rc == EBUSY ||
+            rc == EWOULDBLOCK || rc == MDBX_RESULT_TRUE)
+               ? MDBX_SUCCESS
+               : rc;
+    }
+#endif
+  }
+
+  mdbx_assert(env, env->me_signature.weak == 0);
+  rc = mdbx_env_close0(env) ? MDBX_PANIC : rc;
+  mdbx_ensure(env, mdbx_fastmutex_destroy(&env->me_dbi_lock) == MDBX_SUCCESS);
+#if defined(_WIN32) || defined(_WIN64)
+  /* me_remap_guard don't have destructor (Slim Reader/Writer Lock) */
+  DeleteCriticalSection(&env->me_windowsbug_lock);
+#else
+  mdbx_ensure(env,
+              mdbx_fastmutex_destroy(&env->me_remap_guard) == MDBX_SUCCESS);
+#endif /* Windows */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV
+  mdbx_ensure(env, mdbx_ipclock_destroy(&env->me_lckless_stub.wlock) == 0);
+#endif /* MDBX_LOCKING */
+
+  while ((dp = env->me_dp_reserve) != NULL) {
+    ASAN_UNPOISON_MEMORY_REGION(dp, env->me_psize);
+    VALGRIND_MAKE_MEM_DEFINED(&dp->mp_next, sizeof(dp->mp_next));
+    env->me_dp_reserve = dp->mp_next;
+    mdbx_free(dp);
+  }
+  VALGRIND_DESTROY_MEMPOOL(env);
+  mdbx_ensure(env, env->me_lcklist_next == nullptr);
+  env->me_pid = 0;
+  mdbx_free(env);
+
+  return rc;
+}
+
+__cold int mdbx_env_close(MDBX_env *env) {
+  return __inline_mdbx_env_close(env);
+}
+
+/* Compare two items pointing at aligned unsigned int's. */
+static int __hot cmp_int_align4(const MDBX_val *a, const MDBX_val *b) {
+  mdbx_assert(NULL, a->iov_len == b->iov_len);
+  switch (a->iov_len) {
+  case 4:
+    return CMP2INT(unaligned_peek_u32(4, a->iov_base),
+                   unaligned_peek_u32(4, b->iov_base));
+  case 8:
+    return CMP2INT(unaligned_peek_u64(4, a->iov_base),
+                   unaligned_peek_u64(4, b->iov_base));
+  default:
+    mdbx_assert_fail(NULL, "invalid size for INTEGERKEY/INTEGERDUP", __func__,
+                     __LINE__);
+    return 0;
+  }
+}
+
+/* Compare two items pointing at 2-byte aligned unsigned int's. */
+static int __hot cmp_int_align2(const MDBX_val *a, const MDBX_val *b) {
+  mdbx_assert(NULL, a->iov_len == b->iov_len);
+  switch (a->iov_len) {
+  case 4:
+    return CMP2INT(unaligned_peek_u32(2, a->iov_base),
+                   unaligned_peek_u32(2, b->iov_base));
+  case 8:
+    return CMP2INT(unaligned_peek_u64(2, a->iov_base),
+                   unaligned_peek_u64(2, b->iov_base));
+  default:
+    mdbx_assert_fail(NULL, "invalid size for INTEGERKEY/INTEGERDUP", __func__,
+                     __LINE__);
+    return 0;
+  }
+}
+
+/* Compare two items pointing at unsigned values with unknown alignment.
+ *
+ * This is also set as MDBX_INTEGERDUP|MDBX_DUPFIXED's MDBX_dbx.md_dcmp. */
+static int __hot cmp_int_unaligned(const MDBX_val *a, const MDBX_val *b) {
+  mdbx_assert(NULL, a->iov_len == b->iov_len);
+  switch (a->iov_len) {
+  case 4:
+    return CMP2INT(unaligned_peek_u32(1, a->iov_base),
+                   unaligned_peek_u32(1, b->iov_base));
+  case 8:
+    return CMP2INT(unaligned_peek_u64(1, a->iov_base),
+                   unaligned_peek_u64(1, b->iov_base));
+  default:
+    mdbx_assert_fail(NULL, "invalid size for INTEGERKEY/INTEGERDUP", __func__,
+                     __LINE__);
+    return 0;
+  }
+}
+
+/* Compare two items lexically */
+static int __hot cmp_lexical(const MDBX_val *a, const MDBX_val *b) {
+  if (a->iov_len == b->iov_len)
+    return memcmp(a->iov_base, b->iov_base, a->iov_len);
+
+  const int diff_len = (a->iov_len < b->iov_len) ? -1 : 1;
+  const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len;
+  int diff_data = memcmp(a->iov_base, b->iov_base, shortest);
+  return likely(diff_data) ? diff_data : diff_len;
+}
+
+/* Compare two items in reverse byte order */
+static int __hot cmp_reverse(const MDBX_val *a, const MDBX_val *b) {
+  const uint8_t *pa = (const uint8_t *)a->iov_base + a->iov_len;
+  const uint8_t *pb = (const uint8_t *)b->iov_base + b->iov_len;
+  const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len;
+
+  const uint8_t *const end = pa - shortest;
+  while (pa != end) {
+    int diff = *--pa - *--pb;
+    if (likely(diff))
+      return diff;
+  }
+  return CMP2INT(a->iov_len, b->iov_len);
+}
+
+/* Fast non-lexically comparator */
+static int __hot cmp_lenfast(const MDBX_val *a, const MDBX_val *b) {
+  int diff = CMP2INT(a->iov_len, b->iov_len);
+  return likely(diff) ? diff : memcmp(a->iov_base, b->iov_base, a->iov_len);
+}
+
+static bool unsure_equal(MDBX_cmp_func cmp, const MDBX_val *a,
+                         const MDBX_val *b) {
+  return cmp == cmp_lenfast || cmp == cmp_lexical || cmp == cmp_reverse ||
+         cmp == cmp_int_unaligned || cmp_lenfast(a, b) == 0;
+}
+
+/* Search for key within a page, using binary search.
+ * Returns the smallest entry larger or equal to the key.
+ * If exactp is non-null, stores whether the found entry was an exact match
+ * in *exactp (1 or 0).
+ * Updates the cursor index with the index of the found entry.
+ * If no entry larger or equal to the key is found, returns NULL. */
+static MDBX_node *__hot mdbx_node_search(MDBX_cursor *mc, const MDBX_val *key,
+                                         int *exactp) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  const int nkeys = page_numkeys(mp);
+  DKBUF;
+
+  mdbx_debug("searching %u keys in %s %spage %" PRIaPGNO, nkeys,
+             IS_LEAF(mp) ? "leaf" : "branch", IS_SUBP(mp) ? "sub-" : "",
+             mp->mp_pgno);
+
+  int low = IS_LEAF(mp) ? 0 : 1;
+  int high = nkeys - 1;
+  *exactp = 0;
+  if (unlikely(high < low)) {
+    mc->mc_ki[mc->mc_top] = 0;
+    return NULL;
+  }
+
+  int rc = 0, i = 0;
+  MDBX_cmp_func *cmp = mc->mc_dbx->md_cmp;
+  MDBX_val nodekey;
+  if (unlikely(IS_LEAF2(mp))) {
+    mdbx_cassert(mc, mp->mp_leaf2_ksize == mc->mc_db->md_xsize);
+    nodekey.iov_len = mp->mp_leaf2_ksize;
+    do {
+      i = (low + high) >> 1;
+      nodekey.iov_base = page_leaf2key(mp, i, nodekey.iov_len);
+      mdbx_cassert(mc, (char *)mp + mc->mc_txn->mt_env->me_psize >=
+                           (char *)nodekey.iov_base + nodekey.iov_len);
+      rc = cmp(key, &nodekey);
+      mdbx_debug("found leaf index %u [%s], rc = %i", i, DKEY(&nodekey), rc);
+      if (unlikely(rc == 0)) {
+        *exactp = 1;
+        break;
+      }
+      low = (rc < 0) ? low : i + 1;
+      high = (rc < 0) ? i - 1 : high;
+    } while (likely(low <= high));
+
+    /* Found entry is less than the key. */
+    /* Skip to get the smallest entry larger than key. */
+    i += rc > 0;
+
+    /* store the key index */
+    mc->mc_ki[mc->mc_top] = (indx_t)i;
+    return (i < nkeys)
+               ? /* fake for LEAF2 */ (MDBX_node *)(intptr_t)-1
+               : /* There is no entry larger or equal to the key. */ NULL;
+  }
+
+  if (cmp == cmp_int_align2 && IS_BRANCH(mp))
+    /* Branch pages have no data, so if using integer keys,
+     * alignment is guaranteed. Use faster mdbx_cmp_int_align4(). */
+    cmp = cmp_int_align4;
+
+  MDBX_node *node;
+  do {
+    i = (low + high) >> 1;
+
+    node = page_node(mp, i);
+    nodekey.iov_len = node_ks(node);
+    nodekey.iov_base = node_key(node);
+    mdbx_cassert(mc, (char *)mp + mc->mc_txn->mt_env->me_psize >=
+                         (char *)nodekey.iov_base + nodekey.iov_len);
+
+    rc = cmp(key, &nodekey);
+    if (IS_LEAF(mp))
+      mdbx_debug("found leaf index %u [%s], rc = %i", i, DKEY(&nodekey), rc);
+    else
+      mdbx_debug("found branch index %u [%s -> %" PRIaPGNO "], rc = %i", i,
+                 DKEY(&nodekey), node_pgno(node), rc);
+    if (unlikely(rc == 0)) {
+      *exactp = 1;
+      break;
+    }
+    low = (rc < 0) ? low : i + 1;
+    high = (rc < 0) ? i - 1 : high;
+  } while (likely(low <= high));
+
+  /* Found entry is less than the key. */
+  /* Skip to get the smallest entry larger than key. */
+  i += rc > 0;
+
+  /* store the key index */
+  mc->mc_ki[mc->mc_top] = (indx_t)i;
+  return (i < nkeys) ? page_node(mp, i)
+                     : /* There is no entry larger or equal to the key. */ NULL;
+}
+
+#if 0 /* unused for now */
+static void mdbx_cursor_adjust(MDBX_cursor *mc, func) {
+  MDBX_cursor *m2;
+
+  for (m2 = mc->mc_txn->tw.cursors[mc->mc_dbi]; m2; m2 = m2->mc_next) {
+    if (m2->mc_pg[m2->mc_top] == mc->mc_pg[mc->mc_top]) {
+      func(mc, m2);
+    }
+  }
+}
+#endif
+
+/* Pop a page off the top of the cursor's stack. */
+static __inline void mdbx_cursor_pop(MDBX_cursor *mc) {
+  if (mc->mc_snum) {
+    mdbx_debug("popped page %" PRIaPGNO " off db %d cursor %p",
+               mc->mc_pg[mc->mc_top]->mp_pgno, DDBI(mc), (void *)mc);
+    if (--mc->mc_snum) {
+      mc->mc_top--;
+    } else {
+      mc->mc_flags &= ~C_INITIALIZED;
+    }
+  }
+}
+
+/* Push a page onto the top of the cursor's stack.
+ * Set MDBX_TXN_ERROR on failure. */
+static __inline int mdbx_cursor_push(MDBX_cursor *mc, MDBX_page *mp) {
+  mdbx_debug("pushing page %" PRIaPGNO " on db %d cursor %p", mp->mp_pgno,
+             DDBI(mc), (void *)mc);
+
+  if (unlikely(mc->mc_snum >= CURSOR_STACK)) {
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_CURSOR_FULL;
+  }
+
+  mdbx_cassert(mc, mc->mc_snum < UINT16_MAX);
+  mc->mc_top = mc->mc_snum++;
+  mc->mc_pg[mc->mc_top] = mp;
+  mc->mc_ki[mc->mc_top] = 0;
+
+  return MDBX_SUCCESS;
+}
+
+/* Find the address of the page corresponding to a given page number.
+ * Set MDBX_TXN_ERROR on failure.
+ *
+ * [in] mc    the cursor accessing the page.
+ * [in] pgno  the page number for the page to retrieve.
+ * [out] ret  address of a pointer where the page's address will be
+ *            stored.
+ * [out] lvl  dirtylist inheritance level of found page. 1=current txn,
+ *            0=mapped page.
+ *
+ * Returns 0 on success, non-zero on failure. */
+__hot static int mdbx_page_get(MDBX_cursor *mc, pgno_t pgno, MDBX_page **ret,
+                               int *lvl, txnid_t pp_txnid) {
+  MDBX_txn *txn = mc->mc_txn;
+  if (unlikely(pgno >= txn->mt_next_pgno)) {
+    mdbx_error("page #%" PRIaPGNO " beyond next-pgno", pgno);
+  notfound:
+    *ret = nullptr;
+    txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_PAGE_NOTFOUND;
+  }
+
+  MDBX_env *const env = txn->mt_env;
+  MDBX_page *p = nullptr;
+  mdbx_assert(env, ((txn->mt_flags ^ env->me_flags) & MDBX_WRITEMAP) == 0);
+  mdbx_assert(env, pp_txnid >= MIN_TXNID && pp_txnid <= txn->mt_txnid);
+  const uint16_t illegal_bits =
+      (txn->mt_flags & MDBX_TXN_RDONLY)
+          ? ~(P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW)
+          : ~(P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW | P_DIRTY);
+  int level;
+  if (unlikely((txn->mt_flags & (MDBX_TXN_RDONLY | MDBX_WRITEMAP)) == 0)) {
+    level = 1;
+    do {
+      /* Spilled pages were dirtied in this txn and flushed
+       * because the dirty list got full. Bring this page
+       * back in from the map (but don't unspill it here,
+       * leave that unless page_touch happens again). */
+      if (unlikely(txn->mt_flags & MDBX_TXN_SPILLS) && txn->tw.spill_pages &&
+          mdbx_pnl_exist(txn->tw.spill_pages, pgno << 1)) {
+        pp_txnid = txn->mt_txnid;
+        goto spilled;
+      }
+      p = mdbx_dpl_find(txn->tw.dirtylist, pgno);
+      if (p)
+        goto dirty;
+      level++;
+    } while ((txn = txn->mt_parent) != NULL);
+  }
+  level = 0;
+
+spilled:
+  p = pgno2page(env, pgno);
+
+dirty:
+  *(lvl ? lvl : &level) = level;
+  *ret = p;
+
+  if (unlikely(p->mp_pgno != pgno)) {
+    bad_page(
+        p, "mismatch actual pgno (%" PRIaPGNO ") != expected (%" PRIaPGNO ")\n",
+        p->mp_pgno, pgno);
+    goto notfound;
+  }
+
+  if (unlikely(p->mp_flags & illegal_bits)) {
+    bad_page(p, "invalid page's flags (%u)\n", p->mp_flags);
+    goto corrupted;
+  }
+
+  if (unlikely(p->mp_txnid >
+               ((p->mp_flags & P_DIRTY) ? UINT64_MAX : pp_txnid))) {
+    bad_page(p, "page mod-txnid (%" PRIaTXN ") > parent (%" PRIaTXN ")\n",
+             p->mp_txnid, pp_txnid);
+    goto corrupted;
+  }
+
+  if (unlikely((p->mp_upper < p->mp_lower ||
+                ((p->mp_lower | p->mp_upper) & 1) != 0 ||
+                PAGEHDRSZ + p->mp_upper > env->me_psize) &&
+               !IS_OVERFLOW(p))) {
+    bad_page(p, "invalid page lower(%u)/upper(%u) with limit (%u)\n",
+             p->mp_lower, p->mp_upper, page_space(env));
+    goto corrupted;
+  }
+
+  if (mdbx_audit_enabled())
+    return mdbx_page_check(mc, p, C_UPDATING);
+
+  return MDBX_SUCCESS;
+
+corrupted:
+  mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+  return MDBX_CORRUPTED;
+}
+
+/* Finish mdbx_page_search() / mdbx_page_search_lowest().
+ * The cursor is at the root page, set up the rest of it. */
+__hot static int mdbx_page_search_root(MDBX_cursor *mc, const MDBX_val *key,
+                                       int flags) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  int rc;
+  DKBUF;
+
+  while (IS_BRANCH(mp)) {
+    MDBX_node *node;
+    int i;
+
+    mdbx_debug("branch page %" PRIaPGNO " has %u keys", mp->mp_pgno,
+               page_numkeys(mp));
+    /* Don't assert on branch pages in the GC. We can get here
+     * while in the process of rebalancing a GC branch page; we must
+     * let that proceed. ITS#8336 */
+    mdbx_cassert(mc, !mc->mc_dbi || page_numkeys(mp) > 1);
+    mdbx_debug("found index 0 to page %" PRIaPGNO, node_pgno(page_node(mp, 0)));
+
+    if (flags & (MDBX_PS_FIRST | MDBX_PS_LAST)) {
+      i = 0;
+      if (flags & MDBX_PS_LAST) {
+        i = page_numkeys(mp) - 1;
+        /* if already init'd, see if we're already in right place */
+        if (mc->mc_flags & C_INITIALIZED) {
+          if (mc->mc_ki[mc->mc_top] == i) {
+            mc->mc_top = mc->mc_snum++;
+            mp = mc->mc_pg[mc->mc_top];
+            goto ready;
+          }
+        }
+      }
+    } else {
+      int exact;
+      node = mdbx_node_search(mc, key, &exact);
+      if (node == NULL)
+        i = page_numkeys(mp) - 1;
+      else {
+        i = mc->mc_ki[mc->mc_top];
+        if (!exact) {
+          mdbx_cassert(mc, i > 0);
+          i--;
+        }
+      }
+      mdbx_debug("following index %u for key [%s]", i, DKEY(key));
+    }
+
+    mdbx_cassert(mc, i < (int)page_numkeys(mp));
+    node = page_node(mp, i);
+
+    if (unlikely((rc = mdbx_page_get(mc, node_pgno(node), &mp, NULL,
+                                     pp_txnid4chk(mp, mc->mc_txn))) != 0))
+      return rc;
+
+    mc->mc_ki[mc->mc_top] = (indx_t)i;
+    if (unlikely(rc = mdbx_cursor_push(mc, mp)))
+      return rc;
+
+  ready:
+    if (flags & MDBX_PS_MODIFY) {
+      if (unlikely((rc = mdbx_page_touch(mc)) != 0))
+        return rc;
+      mp = mc->mc_pg[mc->mc_top];
+    }
+  }
+
+  if (unlikely(!IS_LEAF(mp))) {
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return bad_page(mp, "index points to a page with 0x%02x flags\n",
+                    mp->mp_flags);
+  }
+
+  mdbx_debug("found leaf page %" PRIaPGNO " for key [%s]", mp->mp_pgno,
+             DKEY(key));
+  mc->mc_flags |= C_INITIALIZED;
+  mc->mc_flags &= ~C_EOF;
+
+  return MDBX_SUCCESS;
+}
+
+static int mdbx_setup_dbx(MDBX_dbx *const dbx, const MDBX_db *const db,
+                          const unsigned pagesize) {
+  if (unlikely(!dbx->md_cmp)) {
+    dbx->md_cmp = get_default_keycmp(db->md_flags);
+    dbx->md_dcmp = get_default_datacmp(db->md_flags);
+  }
+
+  dbx->md_klen_min =
+      (db->md_flags & MDBX_INTEGERKEY) ? 4 /* sizeof(uint32_t) */ : 0;
+  dbx->md_klen_max = mdbx_limits_keysize_max(pagesize, db->md_flags);
+  assert(dbx->md_klen_max != (unsigned)-1);
+
+  dbx->md_vlen_min = (db->md_flags & MDBX_INTEGERDUP)
+                         ? 4 /* sizeof(uint32_t) */
+                         : ((db->md_flags & MDBX_DUPFIXED) ? 1 : 0);
+  dbx->md_vlen_max = mdbx_limits_valsize_max(pagesize, db->md_flags);
+  assert(dbx->md_vlen_max != (unsigned)-1);
+
+  if ((db->md_flags & (MDBX_DUPFIXED | MDBX_INTEGERDUP)) != 0 && db->md_xsize) {
+    if (unlikely(db->md_xsize < dbx->md_vlen_min ||
+                 db->md_xsize > dbx->md_vlen_max)) {
+      mdbx_error("db.md_xsize (%u) <> min/max value-length (%zu/%zu)",
+                 db->md_xsize, dbx->md_vlen_min, dbx->md_vlen_max);
+      return MDBX_CORRUPTED;
+    }
+    dbx->md_vlen_min = dbx->md_vlen_max = db->md_xsize;
+  }
+  return MDBX_SUCCESS;
+}
+
+static int mdbx_fetch_sdb(MDBX_txn *txn, MDBX_dbi dbi) {
+  MDBX_cursor_couple couple;
+  if (unlikely(TXN_DBI_CHANGED(txn, dbi)))
+    return MDBX_BAD_DBI;
+  int rc = mdbx_cursor_init(&couple.outer, txn, MAIN_DBI);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  MDBX_dbx *const dbx = &txn->mt_dbxs[dbi];
+  rc = mdbx_page_search(&couple.outer, &dbx->md_name, 0);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return (rc == MDBX_NOTFOUND) ? MDBX_BAD_DBI : rc;
+
+  MDBX_val data;
+  int exact = 0;
+  MDBX_node *node = mdbx_node_search(&couple.outer, &dbx->md_name, &exact);
+  if (unlikely(!exact))
+    return MDBX_BAD_DBI;
+  if (unlikely((node_flags(node) & (F_DUPDATA | F_SUBDATA)) != F_SUBDATA))
+    return MDBX_INCOMPATIBLE; /* not a named DB */
+
+  const txnid_t pp_txnid =
+      pp_txnid4chk(couple.outer.mc_pg[couple.outer.mc_top], txn);
+  rc = mdbx_node_read(&couple.outer, node, &data, pp_txnid);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(data.iov_len != sizeof(MDBX_db)))
+    return MDBX_INCOMPATIBLE; /* not a named DB */
+
+  uint16_t md_flags = UNALIGNED_PEEK_16(data.iov_base, MDBX_db, md_flags);
+  /* The txn may not know this DBI, or another process may
+   * have dropped and recreated the DB with other flags. */
+  MDBX_db *const db = &txn->mt_dbs[dbi];
+  if (unlikely((db->md_flags & DB_PERSISTENT_FLAGS) != md_flags))
+    return MDBX_INCOMPATIBLE;
+
+  memcpy(db, data.iov_base, sizeof(MDBX_db));
+  mdbx_tassert(txn, txn->mt_txnid >= pp_txnid);
+  if (unlikely(db->md_mod_txnid > pp_txnid)) {
+    mdbx_error("db.md_mod_txnid (%" PRIaTXN ") > page-txnid (%" PRIaTXN ")",
+               db->md_mod_txnid, pp_txnid);
+    return MDBX_CORRUPTED;
+  }
+  rc = mdbx_setup_dbx(dbx, db, txn->mt_env->me_psize);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  txn->mt_dbistate[dbi] &= ~DBI_STALE;
+  return MDBX_SUCCESS;
+}
+
+/* Search for the lowest key under the current branch page.
+ * This just bypasses a numkeys check in the current page
+ * before calling mdbx_page_search_root(), because the callers
+ * are all in situations where the current page is known to
+ * be underfilled. */
+__hot static int mdbx_page_search_lowest(MDBX_cursor *mc) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  mdbx_cassert(mc, IS_BRANCH(mp));
+  MDBX_node *node = page_node(mp, 0);
+  int rc;
+
+  if (unlikely((rc = mdbx_page_get(mc, node_pgno(node), &mp, NULL,
+                                   pp_txnid4chk(mp, mc->mc_txn))) != 0))
+    return rc;
+
+  mc->mc_ki[mc->mc_top] = 0;
+  if (unlikely(rc = mdbx_cursor_push(mc, mp)))
+    return rc;
+  return mdbx_page_search_root(mc, NULL, MDBX_PS_FIRST);
+}
+
+/* Search for the page a given key should be in.
+ * Push it and its parent pages on the cursor stack.
+ *
+ * [in,out] mc  the cursor for this operation.
+ * [in] key     the key to search for, or NULL for first/last page.
+ * [in] flags   If MDBX_PS_MODIFY is set, visited pages in the DB
+ *              are touched (updated with new page numbers).
+ *              If MDBX_PS_FIRST or MDBX_PS_LAST is set, find first or last
+ * leaf.
+ *              This is used by mdbx_cursor_first() and mdbx_cursor_last().
+ *              If MDBX_PS_ROOTONLY set, just fetch root node, no further
+ *              lookups.
+ *
+ * Returns 0 on success, non-zero on failure. */
+__hot static int mdbx_page_search(MDBX_cursor *mc, const MDBX_val *key,
+                                  int flags) {
+  int rc;
+  pgno_t root;
+
+  /* Make sure the txn is still viable, then find the root from
+   * the txn's db table and set it as the root of the cursor's stack. */
+  if (unlikely(mc->mc_txn->mt_flags & MDBX_TXN_BLOCKED)) {
+    mdbx_debug("%s", "transaction has failed, must abort");
+    return MDBX_BAD_TXN;
+  }
+
+  /* Make sure we're using an up-to-date root */
+  if (unlikely(*mc->mc_dbistate & DBI_STALE)) {
+    rc = mdbx_fetch_sdb(mc->mc_txn, mc->mc_dbi);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+  root = mc->mc_db->md_root;
+
+  if (unlikely(root == P_INVALID)) { /* Tree is empty. */
+    mdbx_debug("%s", "tree is empty");
+    return MDBX_NOTFOUND;
+  }
+
+  mdbx_cassert(mc, root >= NUM_METAS);
+  if (!mc->mc_pg[0] || mc->mc_pg[0]->mp_pgno != root) {
+    if (unlikely((rc = mdbx_page_get(
+                      mc, root, &mc->mc_pg[0], NULL,
+                      (/* maybe zero in legacy DB */ mc->mc_db->md_mod_txnid &&
+                       !(*mc->mc_dbistate & DBI_DIRTY))
+                          ? mc->mc_db->md_mod_txnid
+                          : mc->mc_txn->mt_txnid)) != 0))
+      return rc;
+  }
+
+  mc->mc_snum = 1;
+  mc->mc_top = 0;
+
+  mdbx_debug("db %d root page %" PRIaPGNO " has flags 0x%X", DDBI(mc), root,
+             mc->mc_pg[0]->mp_flags);
+
+  if (flags & MDBX_PS_MODIFY) {
+    if (unlikely(rc = mdbx_page_touch(mc)))
+      return rc;
+  }
+
+  if (flags & MDBX_PS_ROOTONLY)
+    return MDBX_SUCCESS;
+
+  return mdbx_page_search_root(mc, key, flags);
+}
+
+/* Return the data associated with a given node.
+ *
+ * [in] mc      The cursor for this operation.
+ * [in] leaf    The node being read.
+ * [out] data   Updated to point to the node's data.
+ *
+ * Returns 0 on success, non-zero on failure. */
+static __always_inline int mdbx_node_read(MDBX_cursor *mc, MDBX_node *node,
+                                          MDBX_val *data,
+                                          const txnid_t pp_txnid) {
+  data->iov_len = node_ds(node);
+  data->iov_base = node_data(node);
+  if (unlikely(F_ISSET(node_flags(node), F_BIGDATA))) {
+    /* Read overflow data. */
+    MDBX_page *omp; /* overflow page */
+    int rc = mdbx_page_get(mc, node_largedata_pgno(node), &omp, NULL, pp_txnid);
+    if (unlikely((rc != MDBX_SUCCESS))) {
+      mdbx_debug("read overflow page %" PRIaPGNO " failed",
+                 node_largedata_pgno(node));
+      return rc;
+    }
+    data->iov_base = page_data(omp);
+  }
+  return MDBX_SUCCESS;
+}
+
+int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key, MDBX_val *data) {
+  DKBUF;
+  mdbx_debug("===> get db %u key [%s]", dbi, DKEY(key));
+
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key || !data))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  int exact = 0;
+  return mdbx_cursor_set(&cx.outer, (MDBX_val *)key, data, MDBX_SET, &exact);
+}
+
+int mdbx_get_equal_or_great(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                            MDBX_val *data) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key || !data))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(txn->mt_flags & MDBX_TXN_BLOCKED))
+    return MDBX_BAD_TXN;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_cursor_get(&cx.outer, key, data, MDBX_SET_LOWERBOUND);
+}
+
+int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data,
+                size_t *values_count) {
+  DKBUF;
+  mdbx_debug("===> get db %u key [%s]", dbi, DKEY(key));
+
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key || !data))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  int exact = 0;
+  rc = mdbx_cursor_set(&cx.outer, key, data, MDBX_SET_KEY, &exact);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc == MDBX_NOTFOUND && values_count)
+      *values_count = 0;
+    return rc;
+  }
+
+  if (values_count) {
+    *values_count = 1;
+    if (cx.outer.mc_xcursor != NULL) {
+      MDBX_node *node = page_node(cx.outer.mc_pg[cx.outer.mc_top],
+                                  cx.outer.mc_ki[cx.outer.mc_top]);
+      if (F_ISSET(node_flags(node), F_DUPDATA)) {
+        mdbx_tassert(txn, cx.outer.mc_xcursor == &cx.inner &&
+                              (cx.inner.mx_cursor.mc_flags & C_INITIALIZED));
+        *values_count =
+            (sizeof(*values_count) >= sizeof(cx.inner.mx_db.md_entries) ||
+             cx.inner.mx_db.md_entries <= PTRDIFF_MAX)
+                ? (size_t)cx.inner.mx_db.md_entries
+                : PTRDIFF_MAX;
+      }
+    }
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Find a sibling for a page.
+ * Replaces the page at the top of the cursor's stack with the specified
+ * sibling, if one exists.
+ *
+ * [in] mc    The cursor for this operation.
+ * [in] dir   SIBLING_LEFT or SIBLING_RIGHT.
+ *
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_cursor_sibling(MDBX_cursor *mc, int dir) {
+  int rc;
+  MDBX_node *node;
+  MDBX_page *mp;
+  assert(dir == SIBLING_LEFT || dir == SIBLING_RIGHT);
+
+  if (unlikely(mc->mc_snum < 2))
+    return MDBX_NOTFOUND; /* root has no siblings */
+
+  mdbx_cursor_pop(mc);
+  mdbx_debug("parent page is page %" PRIaPGNO ", index %u",
+             mc->mc_pg[mc->mc_top]->mp_pgno, mc->mc_ki[mc->mc_top]);
+
+  if ((dir == SIBLING_RIGHT)
+          ? (mc->mc_ki[mc->mc_top] + 1u >= page_numkeys(mc->mc_pg[mc->mc_top]))
+          : (mc->mc_ki[mc->mc_top] == 0)) {
+    mdbx_debug("no more keys aside, moving to next %s sibling",
+               dir ? "right" : "left");
+    if (unlikely((rc = mdbx_cursor_sibling(mc, dir)) != MDBX_SUCCESS)) {
+      /* undo cursor_pop before returning */
+      mc->mc_top++;
+      mc->mc_snum++;
+      return rc;
+    }
+  } else {
+    assert((dir - 1) == -1 || (dir - 1) == 1);
+    mc->mc_ki[mc->mc_top] += (indx_t)(dir - 1);
+    mdbx_debug("just moving to %s index key %u",
+               (dir == SIBLING_RIGHT) ? "right" : "left",
+               mc->mc_ki[mc->mc_top]);
+  }
+  mdbx_cassert(mc, IS_BRANCH(mc->mc_pg[mc->mc_top]));
+
+  node = page_node(mp = mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+  if (unlikely((rc = mdbx_page_get(mc, node_pgno(node), &mp, NULL,
+                                   pp_txnid4chk(mp, mc->mc_txn))) != 0)) {
+    /* mc will be inconsistent if caller does mc_snum++ as above */
+    mc->mc_flags &= ~(C_INITIALIZED | C_EOF);
+    return rc;
+  }
+
+  rc = mdbx_cursor_push(mc, mp);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  mc->mc_ki[mc->mc_top] =
+      (indx_t)((dir == SIBLING_LEFT) ? page_numkeys(mp) - 1 : 0);
+  return MDBX_SUCCESS;
+}
+
+/* Move the cursor to the next data item. */
+static int mdbx_cursor_next(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
+                            MDBX_cursor_op op) {
+  MDBX_page *mp;
+  MDBX_node *node;
+  int rc;
+
+  if ((mc->mc_flags & C_DEL) && op == MDBX_NEXT_DUP)
+    return MDBX_NOTFOUND;
+
+  if (!(mc->mc_flags & C_INITIALIZED))
+    return mdbx_cursor_first(mc, key, data);
+
+  mp = mc->mc_pg[mc->mc_top];
+  if (mc->mc_flags & C_EOF) {
+    if (mc->mc_ki[mc->mc_top] + 1u >= page_numkeys(mp))
+      return MDBX_NOTFOUND;
+    mc->mc_flags ^= C_EOF;
+  }
+
+  if (mc->mc_db->md_flags & MDBX_DUPSORT) {
+    node = page_node(mp, mc->mc_ki[mc->mc_top]);
+    if (F_ISSET(node_flags(node), F_DUPDATA)) {
+      if (op == MDBX_NEXT || op == MDBX_NEXT_DUP) {
+        rc =
+            mdbx_cursor_next(&mc->mc_xcursor->mx_cursor, data, NULL, MDBX_NEXT);
+        if (op != MDBX_NEXT || rc != MDBX_NOTFOUND) {
+          if (likely(rc == MDBX_SUCCESS))
+            get_key_optional(node, key);
+          return rc;
+        }
+      }
+    } else {
+      mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+      if (op == MDBX_NEXT_DUP)
+        return MDBX_NOTFOUND;
+    }
+  }
+
+  mdbx_debug("cursor_next: top page is %" PRIaPGNO " in cursor %p", mp->mp_pgno,
+             (void *)mc);
+  if (mc->mc_flags & C_DEL) {
+    mc->mc_flags ^= C_DEL;
+    goto skip;
+  }
+
+  int ki = mc->mc_ki[mc->mc_top];
+  mc->mc_ki[mc->mc_top] = (indx_t)++ki;
+  const int numkeys = page_numkeys(mp);
+  if (unlikely(ki >= numkeys)) {
+    mdbx_debug("%s", "=====> move to next sibling page");
+    mc->mc_ki[mc->mc_top] = (indx_t)(numkeys - 1);
+    if (unlikely((rc = mdbx_cursor_sibling(mc, SIBLING_RIGHT)) !=
+                 MDBX_SUCCESS)) {
+      mc->mc_flags |= C_EOF;
+      return rc;
+    }
+    mp = mc->mc_pg[mc->mc_top];
+    mdbx_debug("next page is %" PRIaPGNO ", key index %u", mp->mp_pgno,
+               mc->mc_ki[mc->mc_top]);
+  }
+
+skip:
+  mdbx_debug("==> cursor points to page %" PRIaPGNO
+             " with %u keys, key index %u",
+             mp->mp_pgno, page_numkeys(mp), mc->mc_ki[mc->mc_top]);
+
+  if (unlikely(!IS_LEAF(mp)))
+    return MDBX_CORRUPTED;
+
+  if (IS_LEAF2(mp)) {
+    if (likely(key)) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mp, mc->mc_ki[mc->mc_top], key->iov_len);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  node = page_node(mp, mc->mc_ki[mc->mc_top]);
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    rc = mdbx_xcursor_init1(mc, node, mp);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    rc = mdbx_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  } else if (likely(data)) {
+    if (unlikely((rc = mdbx_node_read(mc, node, data,
+                                      pp_txnid4chk(mp, mc->mc_txn))) !=
+                 MDBX_SUCCESS))
+      return rc;
+  }
+
+  get_key_optional(node, key);
+  return MDBX_SUCCESS;
+}
+
+/* Move the cursor to the previous data item. */
+static int mdbx_cursor_prev(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
+                            MDBX_cursor_op op) {
+  MDBX_page *mp;
+  MDBX_node *node;
+  int rc;
+
+  if ((mc->mc_flags & C_DEL) && op == MDBX_PREV_DUP)
+    return MDBX_NOTFOUND;
+
+  if (!(mc->mc_flags & C_INITIALIZED)) {
+    rc = mdbx_cursor_last(mc, key, data);
+    if (unlikely(rc))
+      return rc;
+    mc->mc_ki[mc->mc_top]++;
+  }
+
+  mp = mc->mc_pg[mc->mc_top];
+  if ((mc->mc_db->md_flags & MDBX_DUPSORT) &&
+      mc->mc_ki[mc->mc_top] < page_numkeys(mp)) {
+    node = page_node(mp, mc->mc_ki[mc->mc_top]);
+    if (F_ISSET(node_flags(node), F_DUPDATA)) {
+      if (op == MDBX_PREV || op == MDBX_PREV_DUP) {
+        rc =
+            mdbx_cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDBX_PREV);
+        if (op != MDBX_PREV || rc != MDBX_NOTFOUND) {
+          if (likely(rc == MDBX_SUCCESS)) {
+            get_key_optional(node, key);
+            mc->mc_flags &= ~C_EOF;
+          }
+          return rc;
+        }
+      }
+    } else {
+      mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+      if (op == MDBX_PREV_DUP)
+        return MDBX_NOTFOUND;
+    }
+  }
+
+  mdbx_debug("cursor_prev: top page is %" PRIaPGNO " in cursor %p", mp->mp_pgno,
+             (void *)mc);
+
+  mc->mc_flags &= ~(C_EOF | C_DEL);
+
+  int ki = mc->mc_ki[mc->mc_top];
+  mc->mc_ki[mc->mc_top] = (indx_t)--ki;
+  if (unlikely(ki < 0)) {
+    mc->mc_ki[mc->mc_top] = 0;
+    mdbx_debug("%s", "=====> move to prev sibling page");
+    if ((rc = mdbx_cursor_sibling(mc, SIBLING_LEFT)) != MDBX_SUCCESS)
+      return rc;
+    mp = mc->mc_pg[mc->mc_top];
+    mdbx_debug("prev page is %" PRIaPGNO ", key index %u", mp->mp_pgno,
+               mc->mc_ki[mc->mc_top]);
+  }
+  mdbx_debug("==> cursor points to page %" PRIaPGNO
+             " with %u keys, key index %u",
+             mp->mp_pgno, page_numkeys(mp), mc->mc_ki[mc->mc_top]);
+
+  if (unlikely(!IS_LEAF(mp)))
+    return MDBX_CORRUPTED;
+
+  if (IS_LEAF2(mp)) {
+    if (likely(key)) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mp, mc->mc_ki[mc->mc_top], key->iov_len);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  node = page_node(mp, mc->mc_ki[mc->mc_top]);
+
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    rc = mdbx_xcursor_init1(mc, node, mp);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    rc = mdbx_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  } else if (likely(data)) {
+    if (unlikely((rc = mdbx_node_read(mc, node, data,
+                                      pp_txnid4chk(mp, mc->mc_txn))) !=
+                 MDBX_SUCCESS))
+      return rc;
+  }
+
+  get_key_optional(node, key);
+  return MDBX_SUCCESS;
+}
+
+/* Set the cursor on a specific data item. */
+static int mdbx_cursor_set(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
+                           MDBX_cursor_op op, int *exactp) {
+  int rc;
+  MDBX_page *mp;
+  MDBX_node *node = NULL;
+  int stub_exactp;
+  DKBUF;
+
+  exactp = exactp ? exactp : &stub_exactp;
+
+  if (unlikely(key->iov_len < mc->mc_dbx->md_klen_min ||
+               key->iov_len > mc->mc_dbx->md_klen_max)) {
+    mdbx_cassert(mc, !"Invalid key-size");
+    return MDBX_BAD_VALSIZE;
+  }
+
+  MDBX_val aligned_key = *key;
+  uint64_t aligned_keybytes;
+  if (mc->mc_db->md_flags & MDBX_INTEGERKEY) {
+    switch (aligned_key.iov_len) {
+    default:
+      mdbx_cassert(mc, !"key-size is invalid for MDBX_INTEGERKEY");
+      return MDBX_BAD_VALSIZE;
+    case 4:
+      if (unlikely(3 & (uintptr_t)aligned_key.iov_base))
+        /* copy instead of return error to avoid break compatibility */
+        aligned_key.iov_base =
+            memcpy(&aligned_keybytes, aligned_key.iov_base, 4);
+      break;
+    case 8:
+      if (unlikely(7 & (uintptr_t)aligned_key.iov_base))
+        /* copy instead of return error to avoid break compatibility */
+        aligned_key.iov_base =
+            memcpy(&aligned_keybytes, aligned_key.iov_base, 8);
+      break;
+    }
+  }
+
+  if (mc->mc_xcursor)
+    mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+
+  /* See if we're already on the right page */
+  if (mc->mc_flags & C_INITIALIZED) {
+    MDBX_val nodekey;
+
+    mdbx_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+    mp = mc->mc_pg[mc->mc_top];
+    if (unlikely(!page_numkeys(mp))) {
+      mc->mc_ki[mc->mc_top] = 0;
+      mc->mc_flags |= C_EOF;
+      return MDBX_NOTFOUND;
+    }
+    if (IS_LEAF2(mp)) {
+      nodekey.iov_len = mc->mc_db->md_xsize;
+      nodekey.iov_base = page_leaf2key(mp, 0, nodekey.iov_len);
+    } else {
+      node = page_node(mp, 0);
+      get_key(node, &nodekey);
+    }
+    rc = mc->mc_dbx->md_cmp(&aligned_key, &nodekey);
+    if (unlikely(rc == 0)) {
+      /* Probably happens rarely, but first node on the page
+       * was the one we wanted. */
+      mc->mc_ki[mc->mc_top] = 0;
+      *exactp = 1;
+      mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                               page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                           (mc->mc_flags & C_EOF));
+      goto set1;
+    }
+    if (rc > 0) {
+      const unsigned nkeys = page_numkeys(mp);
+      unsigned i;
+      if (nkeys > 1) {
+        if (IS_LEAF2(mp)) {
+          nodekey.iov_base = page_leaf2key(mp, nkeys - 1, nodekey.iov_len);
+        } else {
+          node = page_node(mp, nkeys - 1);
+          get_key(node, &nodekey);
+        }
+        rc = mc->mc_dbx->md_cmp(&aligned_key, &nodekey);
+        if (rc == 0) {
+          /* last node was the one we wanted */
+          mdbx_cassert(mc, nkeys >= 1 && nkeys <= UINT16_MAX + 1);
+          mc->mc_ki[mc->mc_top] = (indx_t)(nkeys - 1);
+          *exactp = 1;
+          mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                                   page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                               (mc->mc_flags & C_EOF));
+          goto set1;
+        }
+        if (rc < 0) {
+          if (mc->mc_ki[mc->mc_top] < page_numkeys(mp)) {
+            /* This is definitely the right page, skip search_page */
+            if (IS_LEAF2(mp)) {
+              nodekey.iov_base =
+                  page_leaf2key(mp, mc->mc_ki[mc->mc_top], nodekey.iov_len);
+            } else {
+              node = page_node(mp, mc->mc_ki[mc->mc_top]);
+              get_key(node, &nodekey);
+            }
+            rc = mc->mc_dbx->md_cmp(&aligned_key, &nodekey);
+            if (rc == 0) {
+              /* current node was the one we wanted */
+              *exactp = 1;
+              mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                                       page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                                   (mc->mc_flags & C_EOF));
+              goto set1;
+            }
+          }
+          rc = 0;
+          mc->mc_flags &= ~C_EOF;
+          goto set2;
+        }
+      }
+      /* If any parents have right-sibs, search.
+       * Otherwise, there's nothing further. */
+      for (i = 0; i < mc->mc_top; i++)
+        if (mc->mc_ki[i] < page_numkeys(mc->mc_pg[i]) - 1)
+          break;
+      if (i == mc->mc_top) {
+        /* There are no other pages */
+        mdbx_cassert(mc, nkeys <= UINT16_MAX);
+        mc->mc_ki[mc->mc_top] = (uint16_t)nkeys;
+        mc->mc_flags |= C_EOF;
+        return MDBX_NOTFOUND;
+      }
+    }
+    if (!mc->mc_top) {
+      /* There are no other pages */
+      mc->mc_ki[mc->mc_top] = 0;
+      if (op == MDBX_SET_RANGE) {
+        rc = 0;
+        goto set1;
+      } else {
+        mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                                 page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                             (mc->mc_flags & C_EOF));
+        return MDBX_NOTFOUND;
+      }
+    }
+  } else {
+    mc->mc_pg[0] = 0;
+  }
+
+  rc = mdbx_page_search(mc, &aligned_key, 0);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  mp = mc->mc_pg[mc->mc_top];
+  mdbx_cassert(mc, IS_LEAF(mp));
+
+set2:
+  node = mdbx_node_search(mc, &aligned_key, exactp);
+  if (!*exactp && op != MDBX_SET_RANGE) {
+    /* MDBX_SET specified and not an exact match. */
+    if (unlikely(mc->mc_ki[mc->mc_top] >= page_numkeys(mc->mc_pg[mc->mc_top])))
+      mc->mc_flags |= C_EOF;
+    return MDBX_NOTFOUND;
+  }
+
+  if (node == NULL) {
+    mdbx_debug("%s", "===> inexact leaf not found, goto sibling");
+    if (unlikely((rc = mdbx_cursor_sibling(mc, SIBLING_RIGHT)) !=
+                 MDBX_SUCCESS)) {
+      mc->mc_flags |= C_EOF;
+      return rc; /* no entries matched */
+    }
+    mp = mc->mc_pg[mc->mc_top];
+    mdbx_cassert(mc, IS_LEAF(mp));
+    if (!IS_LEAF2(mp))
+      node = page_node(mp, 0);
+  }
+  mdbx_cassert(mc,
+               mc->mc_ki[mc->mc_top] < page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                   (mc->mc_flags & C_EOF));
+
+set1:
+  mc->mc_flags |= C_INITIALIZED;
+  mc->mc_flags &= ~C_EOF;
+
+  if (IS_LEAF2(mp)) {
+    if (op == MDBX_SET_RANGE || op == MDBX_SET_KEY) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mp, mc->mc_ki[mc->mc_top], key->iov_len);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    rc = mdbx_xcursor_init1(mc, node, mp);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    if (op == MDBX_SET || op == MDBX_SET_KEY || op == MDBX_SET_RANGE) {
+      rc = mdbx_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+    } else {
+      rc = mdbx_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL,
+                           MDBX_SET_RANGE, NULL);
+    }
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  } else if (likely(data)) {
+    if (op == MDBX_GET_BOTH || op == MDBX_GET_BOTH_RANGE) {
+      if (unlikely(data->iov_len < mc->mc_dbx->md_vlen_min ||
+                   data->iov_len > mc->mc_dbx->md_vlen_max)) {
+        mdbx_cassert(mc, !"Invalid data-size");
+        return MDBX_BAD_VALSIZE;
+      }
+      MDBX_val aligned_data = *data;
+      uint64_t aligned_databytes;
+      if (mc->mc_db->md_flags & MDBX_INTEGERDUP) {
+        switch (aligned_data.iov_len) {
+        default:
+          mdbx_cassert(mc, !"data-size is invalid for MDBX_INTEGERDUP");
+          return MDBX_BAD_VALSIZE;
+        case 4:
+          if (unlikely(3 & (uintptr_t)aligned_data.iov_base))
+            /* copy instead of return error to avoid break compatibility */
+            aligned_data.iov_base =
+                memcpy(&aligned_databytes, aligned_data.iov_base, 4);
+          break;
+        case 8:
+          if (unlikely(7 & (uintptr_t)aligned_data.iov_base))
+            /* copy instead of return error to avoid break compatibility */
+            aligned_data.iov_base =
+                memcpy(&aligned_databytes, aligned_data.iov_base, 8);
+          break;
+        }
+      }
+      MDBX_val olddata;
+      if (unlikely((rc = mdbx_node_read(
+                        mc, node, &olddata,
+                        pp_txnid4chk(mc->mc_pg[mc->mc_top], mc->mc_txn))) !=
+                   MDBX_SUCCESS))
+        return rc;
+      rc = mc->mc_dbx->md_dcmp(&aligned_data, &olddata);
+      if (rc) {
+        mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                                 page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                             (mc->mc_flags & C_EOF));
+        if (op != MDBX_GET_BOTH_RANGE || rc > 0)
+          return MDBX_NOTFOUND;
+        *exactp = 0;
+        rc = 0;
+      }
+      *data = olddata;
+    } else if (unlikely((rc = mdbx_node_read(mc, node, data,
+                                             pp_txnid4chk(mc->mc_pg[mc->mc_top],
+                                                          mc->mc_txn))) !=
+                        MDBX_SUCCESS))
+      return rc;
+  }
+
+  /* The key already matches in all other cases */
+  if (op == MDBX_SET_RANGE || op == MDBX_SET_KEY)
+    get_key_optional(node, key);
+
+  mdbx_debug("==> cursor placed on key [%s], data [%s]", DKEY(key), DVAL(data));
+  return rc;
+}
+
+/* Move the cursor to the first item in the database. */
+static int mdbx_cursor_first(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data) {
+  int rc;
+
+  if (mc->mc_xcursor)
+    mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+
+  if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+    rc = mdbx_page_search(mc, NULL, MDBX_PS_FIRST);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  if (unlikely(!IS_LEAF(mc->mc_pg[mc->mc_top])))
+    return MDBX_CORRUPTED;
+
+  mc->mc_flags |= C_INITIALIZED;
+  mc->mc_flags &= ~C_EOF;
+  mc->mc_ki[mc->mc_top] = 0;
+
+  if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+    if (likely(key)) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mc->mc_pg[mc->mc_top], 0, key->iov_len);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], 0);
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    rc = mdbx_xcursor_init1(mc, node, mc->mc_pg[mc->mc_top]);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    rc = mdbx_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+    if (unlikely(rc))
+      return rc;
+  } else if (likely(data)) {
+    if (unlikely((rc = mdbx_node_read(
+                      mc, node, data,
+                      pp_txnid4chk(mc->mc_pg[mc->mc_top], mc->mc_txn))) !=
+                 MDBX_SUCCESS))
+      return rc;
+  }
+
+  get_key_optional(node, key);
+  return MDBX_SUCCESS;
+}
+
+/* Move the cursor to the last item in the database. */
+static int mdbx_cursor_last(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data) {
+  int rc;
+
+  if (mc->mc_xcursor)
+    mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+
+  if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+    rc = mdbx_page_search(mc, NULL, MDBX_PS_LAST);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  if (unlikely(!IS_LEAF(mc->mc_pg[mc->mc_top])))
+    return MDBX_CORRUPTED;
+
+  mc->mc_ki[mc->mc_top] = (indx_t)page_numkeys(mc->mc_pg[mc->mc_top]) - 1;
+  mc->mc_flags |= C_INITIALIZED | C_EOF;
+
+  if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+    if (likely(key)) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mc->mc_pg[mc->mc_top],
+                                    mc->mc_ki[mc->mc_top], key->iov_len);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    rc = mdbx_xcursor_init1(mc, node, mc->mc_pg[mc->mc_top]);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    rc = mdbx_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+    if (unlikely(rc))
+      return rc;
+  } else if (likely(data)) {
+    if (unlikely((rc = mdbx_node_read(
+                      mc, node, data,
+                      pp_txnid4chk(mc->mc_pg[mc->mc_top], mc->mc_txn))) !=
+                 MDBX_SUCCESS))
+      return rc;
+  }
+
+  get_key_optional(node, key);
+  return MDBX_SUCCESS;
+}
+
+int mdbx_cursor_get(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
+                    MDBX_cursor_op op) {
+  if (unlikely(mc == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  int rc = check_txn(mc->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  int exact = 0;
+  int (*mfunc)(MDBX_cursor * mc, MDBX_val * key, MDBX_val * data);
+  switch (op) {
+  case MDBX_GET_CURRENT: {
+    if (unlikely(!(mc->mc_flags & C_INITIALIZED)))
+      return MDBX_ENODATA;
+    MDBX_page *mp = mc->mc_pg[mc->mc_top];
+    const unsigned nkeys = page_numkeys(mp);
+    if (mc->mc_ki[mc->mc_top] >= nkeys) {
+      mdbx_cassert(mc, nkeys <= UINT16_MAX);
+      mc->mc_ki[mc->mc_top] = (uint16_t)nkeys;
+      mc->mc_flags |= C_EOF;
+      return MDBX_NOTFOUND;
+    }
+    mdbx_cassert(mc, nkeys > 0);
+
+    rc = MDBX_SUCCESS;
+    if (IS_LEAF2(mp)) {
+      key->iov_len = mc->mc_db->md_xsize;
+      key->iov_base = page_leaf2key(mp, mc->mc_ki[mc->mc_top], key->iov_len);
+    } else {
+      MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
+      get_key_optional(node, key);
+      if (data) {
+        if (F_ISSET(node_flags(node), F_DUPDATA)) {
+          if (unlikely(!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))) {
+            rc = mdbx_xcursor_init1(mc, node, mp);
+            if (unlikely(rc != MDBX_SUCCESS))
+              return rc;
+            rc = mdbx_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+            if (unlikely(rc))
+              return rc;
+          } else {
+            rc = mdbx_cursor_get(&mc->mc_xcursor->mx_cursor, data, NULL,
+                                 MDBX_GET_CURRENT);
+            if (unlikely(rc))
+              return rc;
+          }
+        } else {
+          rc = mdbx_node_read(mc, node, data, pp_txnid4chk(mp, mc->mc_txn));
+          if (unlikely(rc))
+            return rc;
+        }
+      }
+    }
+    break;
+  }
+  case MDBX_GET_BOTH:
+  case MDBX_GET_BOTH_RANGE:
+    if (unlikely(data == NULL))
+      return MDBX_EINVAL;
+    if (unlikely(mc->mc_xcursor == NULL))
+      return MDBX_INCOMPATIBLE;
+    /* fall through */
+    __fallthrough;
+  case MDBX_SET:
+  case MDBX_SET_KEY:
+  case MDBX_SET_RANGE:
+    if (unlikely(key == NULL))
+      return MDBX_EINVAL;
+    rc = mdbx_cursor_set(mc, key, data, op, &exact);
+    if (mc->mc_flags & C_INITIALIZED) {
+      mdbx_cassert(mc, mc->mc_snum > 0 && mc->mc_top < mc->mc_snum);
+      mdbx_cassert(mc, mc->mc_ki[mc->mc_top] <
+                               page_numkeys(mc->mc_pg[mc->mc_top]) ||
+                           (mc->mc_flags & C_EOF));
+    }
+    break;
+  case MDBX_GET_MULTIPLE:
+    if (unlikely(data == NULL || !(mc->mc_flags & C_INITIALIZED)))
+      return MDBX_EINVAL;
+    if (unlikely(!(mc->mc_db->md_flags & MDBX_DUPFIXED)))
+      return MDBX_INCOMPATIBLE;
+    rc = MDBX_SUCCESS;
+    if ((mc->mc_xcursor->mx_cursor.mc_flags & (C_INITIALIZED | C_EOF)) !=
+        C_INITIALIZED)
+      break;
+    goto fetchm;
+  case MDBX_NEXT_MULTIPLE:
+    if (unlikely(data == NULL))
+      return MDBX_EINVAL;
+    if (unlikely(!(mc->mc_db->md_flags & MDBX_DUPFIXED)))
+      return MDBX_INCOMPATIBLE;
+    rc = mdbx_cursor_next(mc, key, data, MDBX_NEXT_DUP);
+    if (rc == MDBX_SUCCESS) {
+      if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+        MDBX_cursor *mx;
+      fetchm:
+        mx = &mc->mc_xcursor->mx_cursor;
+        data->iov_len =
+            page_numkeys(mx->mc_pg[mx->mc_top]) * mx->mc_db->md_xsize;
+        data->iov_base = page_data(mx->mc_pg[mx->mc_top]);
+        mx->mc_ki[mx->mc_top] = (indx_t)page_numkeys(mx->mc_pg[mx->mc_top]) - 1;
+      } else {
+        rc = MDBX_NOTFOUND;
+      }
+    }
+    break;
+  case MDBX_PREV_MULTIPLE:
+    if (data == NULL)
+      return MDBX_EINVAL;
+    if (!(mc->mc_db->md_flags & MDBX_DUPFIXED))
+      return MDBX_INCOMPATIBLE;
+    rc = MDBX_SUCCESS;
+    if (!(mc->mc_flags & C_INITIALIZED))
+      rc = mdbx_cursor_last(mc, key, data);
+    if (rc == MDBX_SUCCESS) {
+      MDBX_cursor *mx = &mc->mc_xcursor->mx_cursor;
+      if (mx->mc_flags & C_INITIALIZED) {
+        rc = mdbx_cursor_sibling(mx, SIBLING_LEFT);
+        if (rc == MDBX_SUCCESS)
+          goto fetchm;
+      } else {
+        rc = MDBX_NOTFOUND;
+      }
+    }
+    break;
+  case MDBX_NEXT:
+  case MDBX_NEXT_DUP:
+  case MDBX_NEXT_NODUP:
+    rc = mdbx_cursor_next(mc, key, data, op);
+    break;
+  case MDBX_PREV:
+  case MDBX_PREV_DUP:
+  case MDBX_PREV_NODUP:
+    rc = mdbx_cursor_prev(mc, key, data, op);
+    break;
+  case MDBX_FIRST:
+    rc = mdbx_cursor_first(mc, key, data);
+    break;
+  case MDBX_FIRST_DUP:
+    mfunc = mdbx_cursor_first;
+  mmove:
+    if (unlikely(data == NULL || !(mc->mc_flags & C_INITIALIZED)))
+      return MDBX_EINVAL;
+    if (unlikely(mc->mc_xcursor == NULL))
+      return MDBX_INCOMPATIBLE;
+    if (mc->mc_ki[mc->mc_top] >= page_numkeys(mc->mc_pg[mc->mc_top])) {
+      mc->mc_ki[mc->mc_top] = (indx_t)page_numkeys(mc->mc_pg[mc->mc_top]);
+      mc->mc_flags |= C_EOF;
+      return MDBX_NOTFOUND;
+    }
+    {
+      MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+      if (!F_ISSET(node_flags(node), F_DUPDATA)) {
+        get_key_optional(node, key);
+        rc = mdbx_node_read(mc, node, data,
+                            pp_txnid4chk(mc->mc_pg[mc->mc_top], mc->mc_txn));
+        break;
+      }
+    }
+    if (unlikely(!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED)))
+      return MDBX_EINVAL;
+    rc = mfunc(&mc->mc_xcursor->mx_cursor, data, NULL);
+    break;
+  case MDBX_LAST:
+    rc = mdbx_cursor_last(mc, key, data);
+    break;
+  case MDBX_LAST_DUP:
+    mfunc = mdbx_cursor_last;
+    goto mmove;
+  case MDBX_SET_LOWERBOUND: {
+    if (unlikely(key == NULL || data == NULL))
+      return MDBX_EINVAL;
+    MDBX_val save_data = *data;
+    rc = mdbx_cursor_set(mc, key, data, MDBX_SET_RANGE, &exact);
+    if (rc == MDBX_SUCCESS && exact && mc->mc_xcursor) {
+      mc->mc_flags &= ~C_DEL;
+      if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+        *data = save_data;
+        exact = 0;
+        rc = mdbx_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL,
+                             MDBX_SET_RANGE, &exact);
+        if (rc == MDBX_NOTFOUND) {
+          mdbx_cassert(mc, !exact);
+          rc = mdbx_cursor_next(mc, key, data, MDBX_NEXT_NODUP);
+        }
+      } else {
+        int cmp = mc->mc_dbx->md_dcmp(&save_data, data);
+        exact = (cmp == 0);
+        if (cmp > 0)
+          rc = mdbx_cursor_next(mc, key, data, MDBX_NEXT_NODUP);
+      }
+    }
+    if (rc == MDBX_SUCCESS && !exact)
+      rc = MDBX_RESULT_TRUE;
+    break;
+  }
+  default:
+    mdbx_debug("unhandled/unimplemented cursor operation %u", op);
+    return MDBX_EINVAL;
+  }
+
+  mc->mc_flags &= ~C_DEL;
+  return rc;
+}
+
+/* Touch all the pages in the cursor stack. Set mc_top.
+ * Makes sure all the pages are writable, before attempting a write operation.
+ * [in] mc The cursor to operate on. */
+static int mdbx_cursor_touch(MDBX_cursor *mc) {
+  int rc = MDBX_SUCCESS;
+
+  if (mc->mc_dbi >= CORE_DBS &&
+      (*mc->mc_dbistate & (DBI_DIRTY | DBI_DUPDATA)) == 0) {
+    mdbx_cassert(mc, (mc->mc_flags & C_RECLAIMING) == 0);
+    /* Touch DB record of named DB */
+    MDBX_cursor_couple cx;
+    if (TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi))
+      return MDBX_BAD_DBI;
+    rc = mdbx_cursor_init(&cx.outer, mc->mc_txn, MAIN_DBI);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    *mc->mc_dbistate |= DBI_DIRTY;
+    mc->mc_txn->mt_flags |= MDBX_TXN_DIRTY;
+    rc = mdbx_page_search(&cx.outer, &mc->mc_dbx->md_name, MDBX_PS_MODIFY);
+    if (unlikely(rc))
+      return rc;
+  }
+  mc->mc_top = 0;
+  if (mc->mc_snum) {
+    do {
+      rc = mdbx_page_touch(mc);
+    } while (!rc && ++(mc->mc_top) < mc->mc_snum);
+    mc->mc_top = mc->mc_snum - 1;
+  }
+  return rc;
+}
+
+int mdbx_cursor_put(MDBX_cursor *mc, const MDBX_val *key, MDBX_val *data,
+                    unsigned flags) {
+  MDBX_env *env;
+  MDBX_page *sub_root = NULL;
+  MDBX_val xdata, *rdata, dkey, olddata;
+  MDBX_db nested_dupdb;
+  int rc2;
+  DKBUF;
+
+  if (unlikely(mc == NULL || key == NULL || data == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  int rc = check_txn_rw(mc->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi)))
+    return MDBX_BAD_DBI;
+
+  mdbx_cassert(mc, cursor_is_tracked(mc));
+  env = mc->mc_txn->mt_env;
+
+  /* Check this first so counter will always be zero on any early failures. */
+  size_t mcount = 0, dcount = 0;
+  if (unlikely(flags & MDBX_MULTIPLE)) {
+    if (unlikely(flags & MDBX_RESERVE))
+      return MDBX_EINVAL;
+    if (unlikely(!F_ISSET(mc->mc_db->md_flags, MDBX_DUPFIXED)))
+      return MDBX_INCOMPATIBLE;
+    dcount = data[1].iov_len;
+    if (unlikely(dcount < 2 || data->iov_len == 0))
+      return MDBX_BAD_VALSIZE;
+    if (unlikely(mc->mc_db->md_xsize != data->iov_len) && mc->mc_db->md_xsize)
+      return MDBX_BAD_VALSIZE;
+    if (unlikely(dcount >
+                 MAX_MAPSIZE / 2 / (BRANCH_NODEMAX(MAX_PAGESIZE) - NODESIZE))) {
+      /* checking for multiplication overflow */
+      if (unlikely(dcount > MAX_MAPSIZE / 2 / data->iov_len))
+        return MDBX_TOO_LARGE;
+    }
+    data[1].iov_len = 0 /* reset done item counter */;
+  }
+
+  if (flags & MDBX_RESERVE) {
+    if (unlikely(mc->mc_db->md_flags & (MDBX_DUPSORT | MDBX_REVERSEDUP |
+                                        MDBX_INTEGERDUP | MDBX_DUPFIXED)))
+      return MDBX_INCOMPATIBLE;
+    data->iov_base = nullptr;
+  }
+
+  const unsigned nospill = flags & MDBX_NOSPILL;
+  flags -= nospill;
+
+  if (unlikely(mc->mc_txn->mt_flags & (MDBX_TXN_RDONLY | MDBX_TXN_BLOCKED)))
+    return (mc->mc_txn->mt_flags & MDBX_TXN_RDONLY) ? MDBX_EACCESS
+                                                    : MDBX_BAD_TXN;
+
+  uint64_t aligned_keybytes, aligned_databytes;
+  MDBX_val aligned_key, aligned_data;
+  if (likely((mc->mc_flags & C_SUB) == 0)) {
+    if (unlikely(key->iov_len < mc->mc_dbx->md_klen_min ||
+                 key->iov_len > mc->mc_dbx->md_klen_max)) {
+      mdbx_cassert(mc, !"Invalid key-size");
+      return MDBX_BAD_VALSIZE;
+    }
+    if (unlikely(data->iov_len < mc->mc_dbx->md_vlen_min ||
+                 data->iov_len > mc->mc_dbx->md_vlen_max)) {
+      mdbx_cassert(mc, !"Invalid data-size");
+      return MDBX_BAD_VALSIZE;
+    }
+
+    if (mc->mc_db->md_flags & MDBX_INTEGERKEY) {
+      switch (key->iov_len) {
+      default:
+        mdbx_cassert(mc, !"key-size is invalid for MDBX_INTEGERKEY");
+        return MDBX_BAD_VALSIZE;
+      case 4:
+        if (unlikely(3 & (uintptr_t)key->iov_base)) {
+          /* copy instead of return error to avoid break compatibility */
+          aligned_key.iov_base =
+              memcpy(&aligned_keybytes, key->iov_base, aligned_key.iov_len = 4);
+          key = &aligned_key;
+        }
+        break;
+      case 8:
+        if (unlikely(7 & (uintptr_t)key->iov_base)) {
+          /* copy instead of return error to avoid break compatibility */
+          aligned_key.iov_base =
+              memcpy(&aligned_keybytes, key->iov_base, aligned_key.iov_len = 8);
+          key = &aligned_key;
+        }
+        break;
+      }
+    }
+    if (mc->mc_db->md_flags & MDBX_INTEGERDUP) {
+      switch (data->iov_len) {
+      default:
+        mdbx_cassert(mc, !"data-size is invalid for MDBX_INTEGERKEY");
+        return MDBX_BAD_VALSIZE;
+      case 4:
+        if (unlikely(3 & (uintptr_t)data->iov_base)) {
+          if (unlikely(flags & MDBX_MULTIPLE))
+            return MDBX_BAD_VALSIZE;
+          /* copy instead of return error to avoid break compatibility */
+          aligned_data.iov_base = memcpy(&aligned_databytes, data->iov_base,
+                                         aligned_data.iov_len = 4);
+          data = &aligned_data;
+        }
+        break;
+      case 8:
+        if (unlikely(7 & (uintptr_t)data->iov_base)) {
+          if (unlikely(flags & MDBX_MULTIPLE))
+            return MDBX_BAD_VALSIZE;
+          /* copy instead of return error to avoid break compatibility */
+          aligned_data.iov_base = memcpy(&aligned_databytes, data->iov_base,
+                                         aligned_data.iov_len = 8);
+          data = &aligned_data;
+        }
+        break;
+      }
+    }
+  }
+
+  mdbx_debug("==> put db %d key [%s], size %" PRIuPTR
+             ", data [%s] size %" PRIuPTR,
+             DDBI(mc), DKEY(key), key->iov_len,
+             DVAL((flags & MDBX_RESERVE) ? nullptr : data), data->iov_len);
+
+  int dupdata_flag = 0;
+  if ((flags & MDBX_CURRENT) != 0 && (mc->mc_flags & C_SUB) == 0) {
+    if (unlikely(flags & (MDBX_APPEND | MDBX_NOOVERWRITE)))
+      return MDBX_EINVAL;
+    /* Опция MDBX_CURRENT означает, что запрошено обновление текущей записи,
+     * на которой сейчас стоит курсор. Проверяем что переданный ключ совпадает
+     * со значением в текущей позиции курсора.
+     * Здесь проще вызвать mdbx_cursor_get(), так как для обслуживания таблиц
+     * с MDBX_DUPSORT также требуется текущий размер данных. */
+    MDBX_val current_key, current_data;
+    rc = mdbx_cursor_get(mc, &current_key, &current_data, MDBX_GET_CURRENT);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    if (mc->mc_dbx->md_cmp(key, &current_key) != 0)
+      return MDBX_EKEYMISMATCH;
+
+    if (unlikely((flags & MDBX_MULTIPLE)))
+      goto drop_current;
+
+    if (F_ISSET(mc->mc_db->md_flags, MDBX_DUPSORT)) {
+      MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+      if (F_ISSET(node_flags(node), F_DUPDATA)) {
+        mdbx_cassert(mc,
+                     mc->mc_xcursor != NULL &&
+                         (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED));
+        /* Если за ключом более одного значения, либо если размер данных
+         * отличается, то вместо обновления требуется удаление и
+         * последующая вставка. */
+        if (mc->mc_xcursor->mx_db.md_entries > 1 ||
+            current_data.iov_len != data->iov_len) {
+        drop_current:
+          rc = mdbx_cursor_del(mc, flags & MDBX_ALLDUPS);
+          if (unlikely(rc != MDBX_SUCCESS))
+            return rc;
+          flags -= MDBX_CURRENT;
+          goto skip_check_samedata;
+        }
+      } else if (unlikely(node_size(key, data) >
+                          /* See note inside leaf_size() */
+                          env->me_branch_nodemax)) {
+        rc = mdbx_cursor_del(mc, 0);
+        if (unlikely(rc != MDBX_SUCCESS))
+          return rc;
+        flags -= MDBX_CURRENT;
+        goto skip_check_samedata;
+      }
+    }
+    if (!(flags & MDBX_RESERVE) &&
+        unlikely(cmp_lenfast(&current_data, data) == 0))
+      return MDBX_SUCCESS /* the same data, nothing to update */;
+  skip_check_samedata:;
+  }
+
+  if (mc->mc_db->md_root == P_INVALID) {
+    /* new database, cursor has nothing to point to */
+    mc->mc_snum = 0;
+    mc->mc_top = 0;
+    mc->mc_flags &= ~C_INITIALIZED;
+    rc = MDBX_NO_ROOT;
+  } else if ((flags & MDBX_CURRENT) == 0) {
+    int exact = false;
+    if ((flags & MDBX_APPEND) && mc->mc_db->md_entries > 0) {
+      rc = mdbx_cursor_last(mc, &dkey, &olddata);
+      if (likely(rc == MDBX_SUCCESS)) {
+        rc = mc->mc_dbx->md_cmp(key, &dkey);
+        if (likely(rc > 0)) {
+          mc->mc_ki[mc->mc_top]++; /* step forward for appending */
+          rc = MDBX_NOTFOUND;
+        } else {
+          if (unlikely(rc != MDBX_SUCCESS || !(flags & MDBX_APPENDDUP)))
+            /* new-key < last-key
+             * or new-key == last-key without MDBX_APPENDDUP */
+            return MDBX_EKEYMISMATCH;
+          exact = true;
+        }
+      }
+    } else {
+      rc = mdbx_cursor_set(mc, (MDBX_val *)key, &olddata, MDBX_SET, &exact);
+    }
+    if (likely(rc == MDBX_SUCCESS)) {
+      if (exact) {
+        if (unlikely(flags & MDBX_NOOVERWRITE)) {
+          mdbx_debug("duplicate key [%s]", DKEY(key));
+          *data = olddata;
+          return MDBX_KEYEXIST;
+        }
+        if (unlikely(mc->mc_flags & C_SUB)) {
+          /* nested subtree of DUPSORT-database with the same key,
+           * nothing to update */
+          mdbx_assert(env, data->iov_len == 0 && olddata.iov_len == 0);
+          return MDBX_SUCCESS;
+        }
+        if (unlikely(flags & MDBX_ALLDUPS) && mc->mc_xcursor &&
+            (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED)) {
+          rc = mdbx_cursor_del(mc, MDBX_ALLDUPS);
+          if (unlikely(rc != MDBX_SUCCESS))
+            return rc;
+          flags -= MDBX_ALLDUPS;
+          rc = MDBX_NOTFOUND;
+          exact = false;
+        } else /* checking for early exit without dirtying pages */
+            if (!(flags & (MDBX_RESERVE | MDBX_MULTIPLE)) &&
+                unlikely(mc->mc_dbx->md_dcmp(data, &olddata) == 0)) {
+          if (!mc->mc_xcursor)
+            /* the same data, nothing to update */
+            return MDBX_SUCCESS;
+          if (flags & MDBX_NODUPDATA)
+            return MDBX_KEYEXIST;
+          if (flags & MDBX_APPENDDUP)
+            return MDBX_EKEYMISMATCH;
+          if (likely(unsure_equal(mc->mc_dbx->md_dcmp, data, &olddata)))
+            /* data is match exactly byte-to-byte, nothing to update */
+            return MDBX_SUCCESS;
+          else {
+            /* The data has differences, but the user-provided comparator
+             * considers them equal. So continue update since called without.
+             * Continue to update since was called without MDBX_NODUPDATA. */
+          }
+        }
+      }
+    } else if (unlikely(rc != MDBX_NOTFOUND))
+      return rc;
+  }
+
+  mc->mc_flags &= ~C_DEL;
+
+  /* Cursor is positioned, check for room in the dirty list */
+  if (!nospill) {
+    if (unlikely(flags & MDBX_MULTIPLE)) {
+      rdata = &xdata;
+      xdata.iov_len = data->iov_len * dcount;
+    } else {
+      rdata = data;
+    }
+    if (unlikely(rc2 = mdbx_cursor_spill(mc, key, rdata)))
+      return rc2;
+  }
+
+  if (unlikely(rc == MDBX_NO_ROOT)) {
+    MDBX_page *np;
+    /* new database, write a root leaf page */
+    mdbx_debug("%s", "allocating new root leaf page");
+    if (unlikely(rc2 = mdbx_page_new(mc, P_LEAF, 1, &np))) {
+      return rc2;
+    }
+    rc2 = mdbx_cursor_push(mc, np);
+    if (unlikely(rc2 != MDBX_SUCCESS))
+      return rc2;
+    mc->mc_db->md_root = np->mp_pgno;
+    mc->mc_db->md_depth++;
+    if (mc->mc_db->md_flags & MDBX_INTEGERKEY) {
+      assert(key->iov_len >= mc->mc_dbx->md_klen_min &&
+             key->iov_len <= mc->mc_dbx->md_klen_max);
+      mc->mc_dbx->md_klen_min = mc->mc_dbx->md_klen_max = key->iov_len;
+    }
+    if (mc->mc_db->md_flags & (MDBX_INTEGERDUP | MDBX_DUPFIXED)) {
+      assert(data->iov_len >= mc->mc_dbx->md_vlen_min &&
+             data->iov_len <= mc->mc_dbx->md_vlen_max);
+      assert(mc->mc_xcursor != NULL);
+      mc->mc_db->md_xsize = mc->mc_xcursor->mx_db.md_xsize =
+          (unsigned)(mc->mc_dbx->md_vlen_min = mc->mc_dbx->md_vlen_max =
+                         mc->mc_xcursor->mx_dbx.md_klen_min =
+                             mc->mc_xcursor->mx_dbx.md_klen_max =
+                                 data->iov_len);
+    }
+    if ((mc->mc_db->md_flags & (MDBX_DUPSORT | MDBX_DUPFIXED)) == MDBX_DUPFIXED)
+      np->mp_flags |= P_LEAF2;
+    mc->mc_flags |= C_INITIALIZED;
+  } else {
+    /* make sure all cursor pages are writable */
+    rc2 = mdbx_cursor_touch(mc);
+    if (unlikely(rc2))
+      return rc2;
+  }
+
+  bool insert_key, insert_data, do_sub = false;
+  insert_key = insert_data = (rc != MDBX_SUCCESS);
+  uint16_t fp_flags = P_LEAF | P_DIRTY;
+  MDBX_page *fp = env->me_pbuf;
+  fp->mp_txnid = pp_txnid2chk(mc->mc_txn);
+  if (insert_key) {
+    /* The key does not exist */
+    mdbx_debug("inserting key at index %i", mc->mc_ki[mc->mc_top]);
+    if ((mc->mc_db->md_flags & MDBX_DUPSORT) &&
+        node_size(key, data) >
+            /* See note inside leaf_size() */ env->me_branch_nodemax) {
+      /* Too big for a node, insert in sub-DB.  Set up an empty
+       * "old sub-page" for prep_subDB to expand to a full page. */
+      fp->mp_leaf2_ksize =
+          (mc->mc_db->md_flags & MDBX_DUPFIXED) ? (uint16_t)data->iov_len : 0;
+      fp->mp_lower = fp->mp_upper = 0;
+      olddata.iov_len = PAGEHDRSZ;
+      goto prep_subDB;
+    }
+  } else {
+    /* there's only a key anyway, so this is a no-op */
+    if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+      char *ptr;
+      unsigned ksize = mc->mc_db->md_xsize;
+      if (unlikely(key->iov_len != ksize))
+        return MDBX_BAD_VALSIZE;
+      ptr = page_leaf2key(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], ksize);
+      memcpy(ptr, key->iov_base, ksize);
+    fix_parent:
+      /* if overwriting slot 0 of leaf, need to
+       * update branch key if there is a parent page */
+      if (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
+        unsigned dtop = 1;
+        mc->mc_top--;
+        /* slot 0 is always an empty key, find real slot */
+        while (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
+          mc->mc_top--;
+          dtop++;
+        }
+        if (mc->mc_ki[mc->mc_top])
+          rc2 = mdbx_update_key(mc, key);
+        else
+          rc2 = MDBX_SUCCESS;
+        mdbx_cassert(mc, mc->mc_top + dtop < UINT16_MAX);
+        mc->mc_top += (uint16_t)dtop;
+        if (rc2)
+          return rc2;
+      }
+
+      if (mdbx_audit_enabled()) {
+        int err = mdbx_cursor_check(mc, 0);
+        if (unlikely(err != MDBX_SUCCESS))
+          return err;
+      }
+      return MDBX_SUCCESS;
+    }
+
+  more:;
+    if (mdbx_audit_enabled()) {
+      int err = mdbx_cursor_check(mc, 0);
+      if (unlikely(err != MDBX_SUCCESS))
+        return err;
+    }
+    MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+
+    /* overflow page overwrites need special handling */
+    if (unlikely(F_ISSET(node_flags(node), F_BIGDATA))) {
+      int level, ovpages,
+          dpages = (node_size(key, data) >
+                    /* See note inside leaf_size() */ env->me_branch_nodemax)
+                       ? number_of_ovpages(env, data->iov_len)
+                       : 0;
+
+      const pgno_t pg = node_largedata_pgno(node);
+      MDBX_page *omp;
+      if (unlikely((rc2 = mdbx_page_get(
+                        mc, pg, &omp, &level,
+                        pp_txnid4chk(mc->mc_pg[mc->mc_top], mc->mc_txn))) != 0))
+        return rc2;
+      ovpages = omp->mp_pages;
+
+      /* Is the ov page large enough? */
+      if (unlikely(mc->mc_flags & C_GCFREEZE)
+              ? ovpages >= dpages
+              : ovpages ==
+                    /* LY: add configurable threshold to keep reserve space */
+                    dpages) {
+        if (!IS_DIRTY(omp) && (level || (env->me_flags & MDBX_WRITEMAP))) {
+          rc2 = mdbx_page_unspill(mc->mc_txn, omp, &omp);
+          if (unlikely(rc2))
+            return rc2;
+          level = 0; /* dirty in this txn or clean */
+        }
+        /* Is it dirty? */
+        if (IS_DIRTY(omp)) {
+          mdbx_cassert(mc, omp->mp_txnid > SAFE64_INVALID_THRESHOLD);
+          /* yes, overwrite it. Note in this case we don't
+           * bother to try shrinking the page if the new data
+           * is smaller than the overflow threshold. */
+          if (unlikely(level > 1)) {
+            /* It is writable only in a parent txn */
+            MDBX_page *np = mdbx_page_malloc(mc->mc_txn, ovpages);
+            if (unlikely(!np))
+              return MDBX_ENOMEM;
+            /* Note - this page is already counted in parent's dirtyroom */
+            rc2 = mdbx_dpl_append(mc->mc_txn, pg, np);
+            if (unlikely(rc2 != MDBX_SUCCESS)) {
+              rc = rc2;
+              mdbx_dpage_free(env, np, ovpages);
+              goto fail;
+            }
+
+            /* Currently we make the page look as with put() in the
+             * parent txn, in case the user peeks at MDBX_RESERVEd
+             * or unused parts. Some users treat ovpages specially. */
+            const size_t whole = pgno2bytes(env, ovpages);
+            /* Skip the part where MDBX will put *data.
+             * Copy end of page, adjusting alignment so
+             * compiler may copy words instead of bytes. */
+            const size_t off =
+                (PAGEHDRSZ + data->iov_len) & -(intptr_t)sizeof(size_t);
+            memcpy((size_t *)((char *)np + off), (size_t *)((char *)omp + off),
+                   whole - off);
+            memcpy(np, omp, PAGEHDRSZ); /* Copy header of page */
+            omp = np;
+            mdbx_cassert(mc, mdbx_dirtylist_check(mc->mc_txn));
+          }
+          node_set_ds(node, data->iov_len);
+          if (F_ISSET(flags, MDBX_RESERVE))
+            data->iov_base = page_data(omp);
+          else
+            memcpy(page_data(omp), data->iov_base, data->iov_len);
+
+          if (mdbx_audit_enabled()) {
+            int err = mdbx_cursor_check(mc, 0);
+            if (unlikely(err != MDBX_SUCCESS))
+              return err;
+          }
+          return MDBX_SUCCESS;
+        }
+      }
+      if ((rc2 = mdbx_page_retire(mc, omp)) != MDBX_SUCCESS)
+        return rc2;
+    } else {
+      olddata.iov_len = node_ds(node);
+      olddata.iov_base = node_data(node);
+      mdbx_cassert(mc, (char *)olddata.iov_base + olddata.iov_len <=
+                           (char *)(mc->mc_pg[mc->mc_top]) + env->me_psize);
+
+      /* DB has dups? */
+      if (F_ISSET(mc->mc_db->md_flags, MDBX_DUPSORT)) {
+        /* Prepare (sub-)page/sub-DB to accept the new item, if needed.
+         * fp: old sub-page or a header faking it.
+         * mp: new (sub-)page.  offset: growth in page size.
+         * xdata: node data with new page or DB. */
+        unsigned i;
+        size_t offset = 0;
+        MDBX_page *mp = fp = xdata.iov_base = env->me_pbuf;
+        mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
+
+        /* Was a single item before, must convert now */
+        if (!F_ISSET(node_flags(node), F_DUPDATA)) {
+
+          /* does data match? */
+          const int cmp = mc->mc_dbx->md_dcmp(data, &olddata);
+          if ((flags & MDBX_APPENDDUP) && unlikely(cmp <= 0))
+            return MDBX_EKEYMISMATCH;
+          if (cmp == 0) {
+            if (flags & MDBX_NODUPDATA)
+              return MDBX_KEYEXIST;
+            if (likely(unsure_equal(mc->mc_dbx->md_dcmp, data, &olddata))) {
+              /* data is match exactly byte-to-byte, nothing to update */
+              if (unlikely(flags & MDBX_MULTIPLE)) {
+                rc = MDBX_SUCCESS;
+                goto continue_multiple;
+              }
+              return MDBX_SUCCESS;
+            } else {
+              /* The data has differences, but the user-provided comparator
+               * considers them equal. So continue update since called without.
+               * Continue to update since was called without MDBX_NODUPDATA. */
+            }
+            mdbx_cassert(
+                mc,
+                node_size(key, data) <=
+                    /* See note inside leaf_size() */ env->me_branch_nodemax);
+            goto current;
+          }
+
+          /* Just overwrite the current item */
+          if (flags & MDBX_CURRENT) {
+            mdbx_cassert(
+                mc,
+                node_size(key, data) <=
+                    /* See note inside leaf_size() */ env->me_branch_nodemax);
+            goto current;
+          }
+
+          /* Back up original data item */
+          memcpy(dkey.iov_base = fp + 1, olddata.iov_base,
+                 dkey.iov_len = olddata.iov_len);
+          dupdata_flag = 1;
+
+          /* Make sub-page header for the dup items, with dummy body */
+          fp->mp_flags = P_LEAF | P_DIRTY | P_SUBP;
+          fp->mp_lower = 0;
+          xdata.iov_len = PAGEHDRSZ + dkey.iov_len + data->iov_len;
+          if (mc->mc_db->md_flags & MDBX_DUPFIXED) {
+            fp->mp_flags |= P_LEAF2;
+            fp->mp_leaf2_ksize = (uint16_t)data->iov_len;
+            xdata.iov_len += 2 * data->iov_len; /* leave space for 2 more */
+            mdbx_cassert(mc, xdata.iov_len <= env->me_psize);
+          } else {
+            xdata.iov_len += 2 * (sizeof(indx_t) + NODESIZE) +
+                             (dkey.iov_len & 1) + (data->iov_len & 1);
+            mdbx_cassert(mc, xdata.iov_len <= env->me_psize);
+          }
+          fp->mp_upper = (uint16_t)(xdata.iov_len - PAGEHDRSZ);
+          olddata.iov_len = xdata.iov_len; /* pretend olddata is fp */
+        } else if (node_flags(node) & F_SUBDATA) {
+          /* Data is on sub-DB, just store it */
+          flags |= F_DUPDATA | F_SUBDATA;
+          goto put_sub;
+        } else {
+          /* Data is on sub-page */
+          fp = olddata.iov_base;
+          switch (flags) {
+          default:
+            if (!(mc->mc_db->md_flags & MDBX_DUPFIXED)) {
+              offset = node_size(data, nullptr) + sizeof(indx_t);
+              break;
+            }
+            offset = fp->mp_leaf2_ksize;
+            if (page_room(fp) < offset) {
+              offset *= 4; /* space for 4 more */
+              break;
+            }
+            /* FALLTHRU: Big enough MDBX_DUPFIXED sub-page */
+            __fallthrough;
+          case MDBX_CURRENT | MDBX_NODUPDATA:
+          case MDBX_CURRENT:
+            fp->mp_flags |= P_DIRTY;
+            fp->mp_txnid = INVALID_TXNID;
+            fp->mp_pgno = mp->mp_pgno;
+            mc->mc_xcursor->mx_cursor.mc_pg[0] = fp;
+            flags |= F_DUPDATA;
+            goto put_sub;
+          }
+          xdata.iov_len = olddata.iov_len + offset;
+        }
+
+        fp_flags = fp->mp_flags;
+        if (NODESIZE + node_ks(node) + xdata.iov_len >
+            /* See note inside leaf_size() */ env->me_branch_nodemax) {
+          /* Too big for a sub-page, convert to sub-DB */
+          fp_flags &= ~P_SUBP;
+        prep_subDB:
+          nested_dupdb.md_xsize = 0;
+          nested_dupdb.md_flags = flags_db2sub(mc->mc_db->md_flags);
+          if (mc->mc_db->md_flags & MDBX_DUPFIXED) {
+            fp_flags |= P_LEAF2;
+            nested_dupdb.md_xsize = fp->mp_leaf2_ksize;
+          }
+          nested_dupdb.md_depth = 1;
+          nested_dupdb.md_branch_pages = 0;
+          nested_dupdb.md_leaf_pages = 1;
+          nested_dupdb.md_overflow_pages = 0;
+          nested_dupdb.md_entries = page_numkeys(fp);
+          xdata.iov_len = sizeof(nested_dupdb);
+          xdata.iov_base = &nested_dupdb;
+          if ((rc2 = mdbx_page_alloc(mc, 1, &mp, MDBX_ALLOC_ALL)))
+            return rc2;
+          mc->mc_db->md_leaf_pages += 1;
+          mdbx_cassert(mc, env->me_psize > olddata.iov_len);
+          offset = env->me_psize - (unsigned)olddata.iov_len;
+          flags |= F_DUPDATA | F_SUBDATA;
+          nested_dupdb.md_root = mp->mp_pgno;
+          nested_dupdb.md_seq = 0;
+          nested_dupdb.md_mod_txnid = pp_txnid2chk(mc->mc_txn);
+          sub_root = mp;
+        }
+        if (mp != fp) {
+          mp->mp_flags = fp_flags | P_DIRTY;
+          mp->mp_txnid = INVALID_TXNID;
+          mp->mp_leaf2_ksize = fp->mp_leaf2_ksize;
+          mp->mp_lower = fp->mp_lower;
+          mdbx_cassert(mc, fp->mp_upper + offset <= UINT16_MAX);
+          mp->mp_upper = (indx_t)(fp->mp_upper + offset);
+          if (unlikely(fp_flags & P_LEAF2)) {
+            memcpy(page_data(mp), page_data(fp),
+                   page_numkeys(fp) * fp->mp_leaf2_ksize);
+          } else {
+            memcpy((char *)mp + mp->mp_upper + PAGEHDRSZ,
+                   (char *)fp + fp->mp_upper + PAGEHDRSZ,
+                   olddata.iov_len - fp->mp_upper - PAGEHDRSZ);
+            memcpy((char *)(&mp->mp_ptrs), (char *)(&fp->mp_ptrs),
+                   page_numkeys(fp) * sizeof(mp->mp_ptrs[0]));
+            for (i = 0; i < page_numkeys(fp); i++) {
+              mdbx_cassert(mc, mp->mp_ptrs[i] + offset <= UINT16_MAX);
+              mp->mp_ptrs[i] += (indx_t)offset;
+            }
+          }
+        }
+
+        rdata = &xdata;
+        flags |= F_DUPDATA;
+        do_sub = true;
+        if (!insert_key)
+          mdbx_node_del(mc, 0);
+        goto new_sub;
+      }
+
+      /* MDBX passes F_SUBDATA in 'flags' to write a DB record */
+      if (unlikely((node_flags(node) ^ flags) & F_SUBDATA))
+        return MDBX_INCOMPATIBLE;
+
+    current:
+      if (data->iov_len == olddata.iov_len) {
+        mdbx_cassert(mc, EVEN(key->iov_len) == EVEN(node_ks(node)));
+        /* same size, just replace it. Note that we could
+         * also reuse this node if the new data is smaller,
+         * but instead we opt to shrink the node in that case. */
+        if (F_ISSET(flags, MDBX_RESERVE))
+          data->iov_base = olddata.iov_base;
+        else if (!(mc->mc_flags & C_SUB))
+          memcpy(olddata.iov_base, data->iov_base, data->iov_len);
+        else {
+          mdbx_cassert(mc, page_numkeys(mc->mc_pg[mc->mc_top]) == 1);
+          mdbx_cassert(mc, PAGETYPE(mc->mc_pg[mc->mc_top]) == P_LEAF);
+          mdbx_cassert(mc, node_ds(node) == 0);
+          mdbx_cassert(mc, node_flags(node) == 0);
+          mdbx_cassert(mc, key->iov_len < UINT16_MAX);
+          node_set_ks(node, key->iov_len);
+          memcpy(node_key(node), key->iov_base, key->iov_len);
+          mdbx_cassert(mc, (char *)node_key(node) + node_ds(node) <
+                               (char *)(mc->mc_pg[mc->mc_top]) + env->me_psize);
+          goto fix_parent;
+        }
+
+        if (mdbx_audit_enabled()) {
+          int err = mdbx_cursor_check(mc, 0);
+          if (unlikely(err != MDBX_SUCCESS))
+            return err;
+        }
+        return MDBX_SUCCESS;
+      }
+    }
+    mdbx_node_del(mc, 0);
+  }
+
+  rdata = data;
+
+new_sub:;
+  unsigned nflags = flags & NODE_ADD_FLAGS;
+  size_t nsize = IS_LEAF2(mc->mc_pg[mc->mc_top]) ? key->iov_len
+                                                 : leaf_size(env, key, rdata);
+  if (page_room(mc->mc_pg[mc->mc_top]) < nsize) {
+    if ((flags & (F_DUPDATA | F_SUBDATA)) == F_DUPDATA)
+      nflags &= ~MDBX_APPEND; /* sub-page may need room to grow */
+    if (!insert_key)
+      nflags |= MDBX_SPLIT_REPLACE;
+    rc = mdbx_page_split(mc, key, rdata, P_INVALID, nflags);
+    if (rc == MDBX_SUCCESS && mdbx_audit_enabled())
+      rc = mdbx_cursor_check(mc, 0);
+  } else {
+    /* There is room already in this leaf page. */
+    if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+      mdbx_cassert(mc, (nflags & (F_BIGDATA | F_SUBDATA | F_DUPDATA)) == 0 &&
+                           rdata->iov_len == 0);
+      rc = mdbx_node_add_leaf2(mc, mc->mc_ki[mc->mc_top], key);
+    } else
+      rc = mdbx_node_add_leaf(mc, mc->mc_ki[mc->mc_top], key, rdata, nflags);
+    if (likely(rc == 0)) {
+      /* Adjust other cursors pointing to mp */
+      const MDBX_dbi dbi = mc->mc_dbi;
+      const unsigned i = mc->mc_top;
+      MDBX_page *const mp = mc->mc_pg[i];
+      for (MDBX_cursor *m2 = mc->mc_txn->tw.cursors[dbi]; m2;
+           m2 = m2->mc_next) {
+        MDBX_cursor *m3 =
+            (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+        if (m3 == mc || m3->mc_snum < mc->mc_snum || m3->mc_pg[i] != mp)
+          continue;
+        if (m3->mc_ki[i] >= mc->mc_ki[i])
+          m3->mc_ki[i] += insert_key;
+        if (XCURSOR_INITED(m3))
+          XCURSOR_REFRESH(m3, mp, m3->mc_ki[i]);
+      }
+    }
+  }
+
+  if (likely(rc == MDBX_SUCCESS)) {
+    /* Now store the actual data in the child DB. Note that we're
+     * storing the user data in the keys field, so there are strict
+     * size limits on dupdata. The actual data fields of the child
+     * DB are all zero size. */
+    if (do_sub) {
+      int xflags;
+      size_t ecount;
+    put_sub:
+      xdata.iov_len = 0;
+      xdata.iov_base = nullptr;
+      MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+#define SHIFT_MDBX_NODUPDATA_TO_MDBX_NOOVERWRITE 1
+      STATIC_ASSERT(
+          (MDBX_NODUPDATA >> SHIFT_MDBX_NODUPDATA_TO_MDBX_NOOVERWRITE) ==
+          MDBX_NOOVERWRITE);
+      xflags = MDBX_CURRENT | MDBX_NOSPILL |
+               ((flags & MDBX_NODUPDATA) >>
+                SHIFT_MDBX_NODUPDATA_TO_MDBX_NOOVERWRITE);
+      if ((flags & MDBX_CURRENT) == 0) {
+        xflags -= MDBX_CURRENT;
+        rc2 = mdbx_xcursor_init1(mc, node, mc->mc_pg[mc->mc_top]);
+        if (unlikely(rc2 != MDBX_SUCCESS))
+          return rc2;
+      }
+      if (sub_root)
+        mc->mc_xcursor->mx_cursor.mc_pg[0] = sub_root;
+      /* converted, write the original data first */
+      if (dupdata_flag) {
+        rc = mdbx_cursor_put(&mc->mc_xcursor->mx_cursor, &dkey, &xdata, xflags);
+        if (unlikely(rc))
+          goto bad_sub;
+        /* we've done our job */
+        dkey.iov_len = 0;
+      }
+      if (!(node_flags(node) & F_SUBDATA) || sub_root) {
+        /* Adjust other cursors pointing to mp */
+        MDBX_cursor *m2;
+        MDBX_xcursor *mx = mc->mc_xcursor;
+        unsigned i = mc->mc_top;
+        MDBX_page *mp = mc->mc_pg[i];
+        const int nkeys = page_numkeys(mp);
+
+        for (m2 = mc->mc_txn->tw.cursors[mc->mc_dbi]; m2; m2 = m2->mc_next) {
+          if (m2 == mc || m2->mc_snum < mc->mc_snum)
+            continue;
+          if (!(m2->mc_flags & C_INITIALIZED))
+            continue;
+          if (m2->mc_pg[i] == mp) {
+            if (m2->mc_ki[i] == mc->mc_ki[i]) {
+              rc2 = mdbx_xcursor_init2(m2, mx, dupdata_flag);
+              if (unlikely(rc2 != MDBX_SUCCESS))
+                return rc2;
+            } else if (!insert_key && m2->mc_ki[i] < nkeys) {
+              XCURSOR_REFRESH(m2, mp, m2->mc_ki[i]);
+            }
+          }
+        }
+      }
+      mdbx_cassert(mc, mc->mc_xcursor->mx_db.md_entries < PTRDIFF_MAX);
+      ecount = (size_t)mc->mc_xcursor->mx_db.md_entries;
+#define SHIFT_MDBX_APPENDDUP_TO_MDBX_APPEND 1
+      STATIC_ASSERT((MDBX_APPENDDUP >> SHIFT_MDBX_APPENDDUP_TO_MDBX_APPEND) ==
+                    MDBX_APPEND);
+      xflags |= (flags & MDBX_APPENDDUP) >> SHIFT_MDBX_APPENDDUP_TO_MDBX_APPEND;
+      rc = mdbx_cursor_put(&mc->mc_xcursor->mx_cursor, data, &xdata, xflags);
+      if (flags & F_SUBDATA) {
+        void *db = node_data(node);
+        mc->mc_xcursor->mx_db.md_mod_txnid = pp_txnid2chk(mc->mc_txn);
+        memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDBX_db));
+      }
+      insert_data = (ecount != (size_t)mc->mc_xcursor->mx_db.md_entries);
+    }
+    /* Increment count unless we just replaced an existing item. */
+    if (insert_data)
+      mc->mc_db->md_entries++;
+    if (insert_key) {
+      /* Invalidate txn if we created an empty sub-DB */
+      if (unlikely(rc))
+        goto bad_sub;
+      /* If we succeeded and the key didn't exist before,
+       * make sure the cursor is marked valid. */
+      mc->mc_flags |= C_INITIALIZED;
+    }
+    if (flags & MDBX_MULTIPLE) {
+      if (!rc) {
+      continue_multiple:
+        mcount++;
+        /* let caller know how many succeeded, if any */
+        data[1].iov_len = mcount;
+        if (mcount < dcount) {
+          data[0].iov_base = (char *)data[0].iov_base + data[0].iov_len;
+          insert_key = insert_data = false;
+          goto more;
+        }
+      }
+    }
+    if (rc == MDBX_SUCCESS && mdbx_audit_enabled())
+      rc = mdbx_cursor_check(mc, 0);
+    return rc;
+  bad_sub:
+    if (unlikely(rc == MDBX_KEYEXIST))
+      mdbx_error("unexpected %s", "MDBX_KEYEXIST");
+    /* should not happen, we deleted that item */
+    rc = MDBX_PROBLEM;
+  }
+fail:
+  mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+  return rc;
+}
+
+int mdbx_cursor_del(MDBX_cursor *mc, MDBX_put_flags_t flags) {
+  if (unlikely(!mc))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  int rc = check_txn_rw(mc->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(!(mc->mc_flags & C_INITIALIZED)))
+    return MDBX_ENODATA;
+
+  if (unlikely(mc->mc_ki[mc->mc_top] >= page_numkeys(mc->mc_pg[mc->mc_top])))
+    return MDBX_NOTFOUND;
+
+  if (unlikely(!(flags & MDBX_NOSPILL) &&
+               (rc = mdbx_cursor_spill(mc, NULL, NULL))))
+    return rc;
+
+  rc = mdbx_cursor_touch(mc);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  if (unlikely(!IS_LEAF(mp)))
+    return MDBX_CORRUPTED;
+  if (IS_LEAF2(mp))
+    goto del_key;
+
+  MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
+  if (F_ISSET(node_flags(node), F_DUPDATA)) {
+    if (flags & (MDBX_ALLDUPS | /* for compatibility */ MDBX_NODUPDATA)) {
+      /* mdbx_cursor_del0() will subtract the final entry */
+      mc->mc_db->md_entries -= mc->mc_xcursor->mx_db.md_entries - 1;
+      mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
+    } else {
+      if (!F_ISSET(node_flags(node), F_SUBDATA))
+        mc->mc_xcursor->mx_cursor.mc_pg[0] = node_data(node);
+      rc = mdbx_cursor_del(&mc->mc_xcursor->mx_cursor, MDBX_NOSPILL);
+      if (unlikely(rc))
+        return rc;
+      /* If sub-DB still has entries, we're done */
+      if (mc->mc_xcursor->mx_db.md_entries) {
+        if (node_flags(node) & F_SUBDATA) {
+          /* update subDB info */
+          void *db = node_data(node);
+          mc->mc_xcursor->mx_db.md_mod_txnid = pp_txnid2chk(mc->mc_txn);
+          memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDBX_db));
+        } else {
+          MDBX_cursor *m2;
+          /* shrink fake page */
+          mdbx_node_shrink(mp, mc->mc_ki[mc->mc_top]);
+          node = page_node(mp, mc->mc_ki[mc->mc_top]);
+          mc->mc_xcursor->mx_cursor.mc_pg[0] = node_data(node);
+          /* fix other sub-DB cursors pointed at fake pages on this page */
+          for (m2 = mc->mc_txn->tw.cursors[mc->mc_dbi]; m2; m2 = m2->mc_next) {
+            if (m2 == mc || m2->mc_snum < mc->mc_snum)
+              continue;
+            if (!(m2->mc_flags & C_INITIALIZED))
+              continue;
+            if (m2->mc_pg[mc->mc_top] == mp) {
+              MDBX_node *inner = node;
+              if (m2->mc_ki[mc->mc_top] >= page_numkeys(mp))
+                continue;
+              if (m2->mc_ki[mc->mc_top] != mc->mc_ki[mc->mc_top]) {
+                inner = page_node(mp, m2->mc_ki[mc->mc_top]);
+                if (node_flags(inner) & F_SUBDATA)
+                  continue;
+              }
+              m2->mc_xcursor->mx_cursor.mc_pg[0] = node_data(inner);
+            }
+          }
+        }
+        mc->mc_db->md_entries--;
+        mdbx_cassert(mc, mc->mc_db->md_entries > 0 && mc->mc_db->md_depth > 0 &&
+                             mc->mc_db->md_root != P_INVALID);
+        return rc;
+      } else {
+        mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
+      }
+      /* otherwise fall thru and delete the sub-DB */
+    }
+
+    if (node_flags(node) & F_SUBDATA) {
+      /* add all the child DB's pages to the free list */
+      rc = mdbx_drop0(&mc->mc_xcursor->mx_cursor, 0);
+      if (unlikely(rc))
+        goto fail;
+    }
+  }
+  /* MDBX passes F_SUBDATA in 'flags' to delete a DB record */
+  else if (unlikely((node_flags(node) ^ flags) & F_SUBDATA))
+    return MDBX_INCOMPATIBLE;
+
+  /* add overflow pages to free list */
+  if (F_ISSET(node_flags(node), F_BIGDATA)) {
+    MDBX_page *omp;
+    if (unlikely((rc = mdbx_page_get(mc, node_largedata_pgno(node), &omp, NULL,
+                                     pp_txnid4chk(mp, mc->mc_txn))) ||
+                 (rc = mdbx_page_retire(mc, omp))))
+      goto fail;
+  }
+
+del_key:
+  return mdbx_cursor_del0(mc);
+
+fail:
+  mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+  return rc;
+}
+
+/* Allocate and initialize new pages for a database.
+ * Set MDBX_TXN_ERROR on failure.
+ *
+ * [in] mc a  cursor on the database being added to.
+ * [in] flags flags defining what type of page is being allocated.
+ * [in] num   the number of pages to allocate. This is usually 1,
+ *            unless allocating overflow pages for a large record.
+ * [out] mp   Address of a page, or NULL on failure.
+ *
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_page_new(MDBX_cursor *mc, unsigned flags, unsigned num,
+                         MDBX_page **mp) {
+  MDBX_page *np;
+  int rc;
+
+  if (unlikely((rc = mdbx_page_alloc(mc, num, &np, MDBX_ALLOC_ALL))))
+    return rc;
+  *mp = np;
+  mdbx_debug("db %u allocated new page %" PRIaPGNO ", num %u", mc->mc_dbi,
+             np->mp_pgno, num);
+  np->mp_flags = (uint16_t)(flags | P_DIRTY);
+  np->mp_txnid = INVALID_TXNID;
+  np->mp_lower = 0;
+  np->mp_upper = (indx_t)(mc->mc_txn->mt_env->me_psize - PAGEHDRSZ);
+
+  *mc->mc_dbistate |= DBI_DIRTY;
+  mc->mc_txn->mt_flags |= MDBX_TXN_DIRTY;
+  mc->mc_db->md_branch_pages += IS_BRANCH(np);
+  mc->mc_db->md_leaf_pages += IS_LEAF(np);
+  if (unlikely(IS_OVERFLOW(np))) {
+    mc->mc_db->md_overflow_pages += num;
+    np->mp_pages = num;
+    mdbx_cassert(mc, !(mc->mc_flags & C_SUB));
+  } else if (unlikely(mc->mc_flags & C_SUB)) {
+    MDBX_db *outer = mdbx_outer_db(mc);
+    outer->md_branch_pages += IS_BRANCH(np);
+    outer->md_leaf_pages += IS_LEAF(np);
+  }
+
+  return MDBX_SUCCESS;
+}
+
+static int __must_check_result mdbx_node_add_leaf2(MDBX_cursor *mc,
+                                                   unsigned indx,
+                                                   const MDBX_val *key) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  DKBUF;
+  mdbx_debug("add to leaf2-%spage %" PRIaPGNO " index %i, "
+             " key size %" PRIuPTR " [%s]",
+             IS_SUBP(mp) ? "sub-" : "", mp->mp_pgno, indx,
+             key ? key->iov_len : 0, DKEY(key));
+
+  mdbx_cassert(mc, key);
+  mdbx_cassert(mc, PAGETYPE(mp) == (P_LEAF | P_LEAF2));
+  const unsigned ksize = mc->mc_db->md_xsize;
+  mdbx_cassert(mc, ksize == key->iov_len);
+  const unsigned nkeys = page_numkeys(mp);
+
+  /* Just using these for counting */
+  const intptr_t lower = mp->mp_lower + sizeof(indx_t);
+  const intptr_t upper = mp->mp_upper - (ksize - sizeof(indx_t));
+  if (unlikely(lower > upper)) {
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_PAGE_FULL;
+  }
+  mp->mp_lower = (indx_t)lower;
+  mp->mp_upper = (indx_t)upper;
+
+  char *const ptr = page_leaf2key(mp, indx, ksize);
+  mdbx_cassert(mc, nkeys >= indx);
+  const unsigned diff = nkeys - indx;
+  if (likely(diff > 0))
+    /* Move higher keys up one slot. */
+    memmove(ptr + ksize, ptr, diff * ksize);
+  /* insert new key */
+  memcpy(ptr, key->iov_base, ksize);
+  return MDBX_SUCCESS;
+}
+
+static int __must_check_result mdbx_node_add_branch(MDBX_cursor *mc,
+                                                    unsigned indx,
+                                                    const MDBX_val *key,
+                                                    pgno_t pgno) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  DKBUF;
+  mdbx_debug("add to branch-%spage %" PRIaPGNO " index %i, node-pgno %" PRIaPGNO
+             " key size %" PRIuPTR " [%s]",
+             IS_SUBP(mp) ? "sub-" : "", mp->mp_pgno, indx, pgno,
+             key ? key->iov_len : 0, DKEY(key));
+
+  mdbx_cassert(mc, PAGETYPE(mp) == P_BRANCH);
+  STATIC_ASSERT(NODESIZE % 2 == 0);
+
+  /* Move higher pointers up one slot. */
+  const unsigned nkeys = page_numkeys(mp);
+  mdbx_cassert(mc, nkeys >= indx);
+  for (unsigned i = nkeys; i > indx; --i)
+    mp->mp_ptrs[i] = mp->mp_ptrs[i - 1];
+
+  /* Adjust free space offsets. */
+  const size_t branch_bytes = branch_size(mc->mc_txn->mt_env, key);
+  const intptr_t lower = mp->mp_lower + sizeof(indx_t);
+  const intptr_t upper = mp->mp_upper - (branch_bytes - sizeof(indx_t));
+  if (unlikely(lower > upper)) {
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_PAGE_FULL;
+  }
+  mp->mp_lower = (indx_t)lower;
+  mp->mp_ptrs[indx] = mp->mp_upper = (indx_t)upper;
+
+  /* Write the node data. */
+  MDBX_node *node = page_node(mp, indx);
+  node_set_pgno(node, pgno);
+  node_set_flags(node, 0);
+  UNALIGNED_POKE_8(node, MDBX_node, mn_extra, 0);
+  node_set_ks(node, 0);
+  if (likely(key != NULL)) {
+    node_set_ks(node, key->iov_len);
+    memcpy(node_key(node), key->iov_base, key->iov_len);
+  }
+  return MDBX_SUCCESS;
+}
+
+static int __must_check_result mdbx_node_add_leaf(MDBX_cursor *mc,
+                                                  unsigned indx,
+                                                  const MDBX_val *key,
+                                                  MDBX_val *data,
+                                                  unsigned flags) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  DKBUF;
+  mdbx_debug("add to leaf-%spage %" PRIaPGNO " index %i, data size %" PRIuPTR
+             " key size %" PRIuPTR " [%s]",
+             IS_SUBP(mp) ? "sub-" : "", mp->mp_pgno, indx,
+             data ? data->iov_len : 0, key ? key->iov_len : 0, DKEY(key));
+  mdbx_cassert(mc, key != NULL && data != NULL);
+  mdbx_cassert(mc, PAGETYPE(mp) == P_LEAF);
+  MDBX_page *largepage = NULL;
+
+  size_t leaf_bytes;
+  if (unlikely(flags & F_BIGDATA)) {
+    /* Data already on overflow page. */
+    STATIC_ASSERT(sizeof(pgno_t) % 2 == 0);
+    leaf_bytes = node_size(key, nullptr) + sizeof(pgno_t) + sizeof(indx_t);
+  } else if (unlikely(node_size(key, data) >
+                      /* See note inside leaf_size() */
+                      mc->mc_txn->mt_env->me_branch_nodemax)) {
+    /* Put data on overflow page. */
+    mdbx_ensure(mc->mc_txn->mt_env,
+                !F_ISSET(mc->mc_db->md_flags, MDBX_DUPSORT));
+    if (unlikely(flags & (F_DUPDATA | F_SUBDATA)))
+      return MDBX_PROBLEM;
+    const pgno_t ovpages = number_of_ovpages(mc->mc_txn->mt_env, data->iov_len);
+    int rc = mdbx_page_new(mc, P_OVERFLOW, ovpages, &largepage);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    mdbx_debug("allocated %u overflow page(s) %" PRIaPGNO "for %" PRIuPTR
+               " data bytes",
+               largepage->mp_pages, largepage->mp_pgno, data->iov_len);
+    flags |= F_BIGDATA;
+    leaf_bytes = node_size(key, nullptr) + sizeof(pgno_t) + sizeof(indx_t);
+  } else {
+    leaf_bytes = node_size(key, data) + sizeof(indx_t);
+  }
+  mdbx_cassert(mc, leaf_bytes == leaf_size(mc->mc_txn->mt_env, key, data));
+
+  /* Move higher pointers up one slot. */
+  const unsigned nkeys = page_numkeys(mp);
+  mdbx_cassert(mc, nkeys >= indx);
+  for (unsigned i = nkeys; i > indx; --i)
+    mp->mp_ptrs[i] = mp->mp_ptrs[i - 1];
+
+  /* Adjust free space offsets. */
+  const intptr_t lower = mp->mp_lower + sizeof(indx_t);
+  const intptr_t upper = mp->mp_upper - (leaf_bytes - sizeof(indx_t));
+  if (unlikely(lower > upper)) {
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_PAGE_FULL;
+  }
+  mp->mp_lower = (indx_t)lower;
+  mp->mp_ptrs[indx] = mp->mp_upper = (indx_t)upper;
+
+  /* Write the node data. */
+  MDBX_node *node = page_node(mp, indx);
+  node_set_ks(node, key->iov_len);
+  node_set_flags(node, (uint8_t)flags);
+  UNALIGNED_POKE_8(node, MDBX_node, mn_extra, 0);
+  node_set_ds(node, data->iov_len);
+  memcpy(node_key(node), key->iov_base, key->iov_len);
+
+  void *nodedata = node_data(node);
+  if (likely(largepage == NULL)) {
+    if (unlikely(flags & F_BIGDATA))
+      memcpy(nodedata, data->iov_base, sizeof(pgno_t));
+    else if (unlikely(flags & MDBX_RESERVE))
+      data->iov_base = nodedata;
+    else if (likely(nodedata != data->iov_base &&
+                    data->iov_len /* to avoid UBSAN traps*/ != 0))
+      memcpy(nodedata, data->iov_base, data->iov_len);
+  } else {
+    poke_pgno(nodedata, largepage->mp_pgno);
+    nodedata = page_data(largepage);
+    if (unlikely(flags & MDBX_RESERVE))
+      data->iov_base = nodedata;
+    else if (likely(nodedata != data->iov_base &&
+                    data->iov_len /* to avoid UBSAN traps*/ != 0))
+      memcpy(nodedata, data->iov_base, data->iov_len);
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Delete the specified node from a page.
+ * [in] mc Cursor pointing to the node to delete.
+ * [in] ksize The size of a node. Only used if the page is
+ * part of a MDBX_DUPFIXED database. */
+static void mdbx_node_del(MDBX_cursor *mc, size_t ksize) {
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  int indx = mc->mc_ki[mc->mc_top];
+  int i, j, nkeys, ptr;
+  MDBX_node *node;
+  char *base;
+
+  mdbx_debug("delete node %u on %s page %" PRIaPGNO, indx,
+             IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno);
+  nkeys = page_numkeys(mp);
+  mdbx_cassert(mc, indx < nkeys);
+
+  if (IS_LEAF2(mp)) {
+    mdbx_cassert(mc, ksize >= sizeof(indx_t));
+    unsigned diff = nkeys - 1 - indx;
+    base = page_leaf2key(mp, indx, ksize);
+    if (diff)
+      memmove(base, base + ksize, diff * ksize);
+    mdbx_cassert(mc, mp->mp_lower >= sizeof(indx_t));
+    mp->mp_lower -= sizeof(indx_t);
+    mdbx_cassert(mc,
+                 (size_t)UINT16_MAX - mp->mp_upper >= ksize - sizeof(indx_t));
+    mp->mp_upper += (indx_t)(ksize - sizeof(indx_t));
+    return;
+  }
+
+  node = page_node(mp, indx);
+  size_t sz = NODESIZE + node_ks(node);
+  if (IS_LEAF(mp)) {
+    if (F_ISSET(node_flags(node), F_BIGDATA))
+      sz += sizeof(pgno_t);
+    else
+      sz += node_ds(node);
+  }
+  sz = EVEN(sz);
+
+  ptr = mp->mp_ptrs[indx];
+  for (i = j = 0; i < nkeys; i++) {
+    if (i != indx) {
+      mp->mp_ptrs[j] = mp->mp_ptrs[i];
+      if (mp->mp_ptrs[i] < ptr) {
+        mdbx_cassert(mc, (size_t)UINT16_MAX - mp->mp_ptrs[j] >= sz);
+        mp->mp_ptrs[j] += (indx_t)sz;
+      }
+      j++;
+    }
+  }
+
+  base = (char *)mp + mp->mp_upper + PAGEHDRSZ;
+  memmove(base + sz, base, ptr - mp->mp_upper);
+
+  mdbx_cassert(mc, mp->mp_lower >= sizeof(indx_t));
+  mp->mp_lower -= sizeof(indx_t);
+  mdbx_cassert(mc, (size_t)UINT16_MAX - mp->mp_upper >= sz);
+  mp->mp_upper += (indx_t)sz;
+
+#if MDBX_DEBUG > 0
+  if (mdbx_audit_enabled()) {
+    int page_check_err = mdbx_page_check(mc, mp, C_UPDATING);
+    mdbx_cassert(mc, page_check_err == MDBX_SUCCESS);
+  }
+#endif
+}
+
+/* Compact the main page after deleting a node on a subpage.
+ * [in] mp The main page to operate on.
+ * [in] indx The index of the subpage on the main page. */
+static void mdbx_node_shrink(MDBX_page *mp, unsigned indx) {
+  MDBX_node *node;
+  MDBX_page *sp, *xp;
+  char *base;
+  size_t nsize, delta, len, ptr;
+  int i;
+
+  node = page_node(mp, indx);
+  sp = (MDBX_page *)node_data(node);
+  delta = page_room(sp);
+  assert(delta > 0);
+
+  /* Prepare to shift upward, set len = length(subpage part to shift) */
+  if (IS_LEAF2(sp)) {
+    delta &= /* do not make the node uneven-sized */ ~(size_t)1;
+    if (unlikely(delta) == 0)
+      return;
+    nsize = node_ds(node) - delta;
+    assert(nsize % 1 == 0);
+    len = nsize;
+  } else {
+    xp = (MDBX_page *)((char *)sp + delta); /* destination subpage */
+    for (i = page_numkeys(sp); --i >= 0;) {
+      assert(sp->mp_ptrs[i] >= delta);
+      xp->mp_ptrs[i] = (indx_t)(sp->mp_ptrs[i] - delta);
+    }
+    nsize = node_ds(node) - delta;
+    len = PAGEHDRSZ;
+  }
+  sp->mp_upper = sp->mp_lower;
+  sp->mp_pgno = mp->mp_pgno;
+  node_set_ds(node, nsize);
+
+  /* Shift <lower nodes...initial part of subpage> upward */
+  base = (char *)mp + mp->mp_upper + PAGEHDRSZ;
+  memmove(base + delta, base, (char *)sp + len - base);
+
+  ptr = mp->mp_ptrs[indx];
+  for (i = page_numkeys(mp); --i >= 0;) {
+    if (mp->mp_ptrs[i] <= ptr) {
+      assert((size_t)UINT16_MAX - mp->mp_ptrs[i] >= delta);
+      mp->mp_ptrs[i] += (indx_t)delta;
+    }
+  }
+  assert((size_t)UINT16_MAX - mp->mp_upper >= delta);
+  mp->mp_upper += (indx_t)delta;
+}
+
+/* Initial setup of a sorted-dups cursor.
+ *
+ * Sorted duplicates are implemented as a sub-database for the given key.
+ * The duplicate data items are actually keys of the sub-database.
+ * Operations on the duplicate data items are performed using a sub-cursor
+ * initialized when the sub-database is first accessed. This function does
+ * the preliminary setup of the sub-cursor, filling in the fields that
+ * depend only on the parent DB.
+ *
+ * [in] mc The main cursor whose sorted-dups cursor is to be initialized. */
+static int mdbx_xcursor_init0(MDBX_cursor *mc) {
+  MDBX_xcursor *mx = mc->mc_xcursor;
+  if (unlikely(mx == nullptr)) {
+    mdbx_error("unexpected dupsort-page for non-dupsort db/cursor (dbi %u)",
+               mc->mc_dbi);
+    return MDBX_CORRUPTED;
+  }
+
+  mx->mx_cursor.mc_xcursor = NULL;
+  mx->mx_cursor.mc_txn = mc->mc_txn;
+  mx->mx_cursor.mc_db = &mx->mx_db;
+  mx->mx_cursor.mc_dbx = &mx->mx_dbx;
+  mx->mx_cursor.mc_dbi = mc->mc_dbi;
+  mx->mx_cursor.mc_dbistate = &mx->mx_dbistate;
+  mx->mx_cursor.mc_snum = 0;
+  mx->mx_cursor.mc_top = 0;
+  mx->mx_cursor.mc_flags = C_SUB | (mc->mc_flags & (C_COPYING | C_SKIPORD));
+  mx->mx_dbx.md_name.iov_len = 0;
+  mx->mx_dbx.md_name.iov_base = NULL;
+  mx->mx_dbx.md_cmp = mc->mc_dbx->md_dcmp;
+  mx->mx_dbx.md_dcmp = NULL;
+  mx->mx_dbx.md_klen_min = INT_MAX;
+  mx->mx_dbx.md_vlen_min = mx->mx_dbx.md_klen_max = mx->mx_dbx.md_vlen_max = 0;
+  return MDBX_SUCCESS;
+}
+
+/* Final setup of a sorted-dups cursor.
+ * Sets up the fields that depend on the data from the main cursor.
+ * [in] mc The main cursor whose sorted-dups cursor is to be initialized.
+ * [in] node The data containing the MDBX_db record for the sorted-dup database.
+ */
+static int mdbx_xcursor_init1(MDBX_cursor *mc, MDBX_node *node,
+                              const MDBX_page *mp) {
+  MDBX_xcursor *mx = mc->mc_xcursor;
+  if (unlikely(mx == nullptr)) {
+    mdbx_error("unexpected dupsort-page for non-dupsort db/cursor (dbi %u)",
+               mc->mc_dbi);
+    return MDBX_CORRUPTED;
+  }
+
+  const uint8_t flags = node_flags(node);
+  switch (flags) {
+  default:
+    mdbx_error("invalid node flags %u", flags);
+    return MDBX_CORRUPTED;
+  case F_DUPDATA | F_SUBDATA:
+    if (unlikely(node_ds(node) != sizeof(MDBX_db))) {
+      mdbx_error("invalid nested-db record size %zu", node_ds(node));
+      return MDBX_CORRUPTED;
+    }
+    memcpy(&mx->mx_db, node_data(node), sizeof(MDBX_db));
+    const txnid_t pp_txnid = IS_DIRTY(mp) ? mc->mc_txn->mt_txnid : mp->mp_txnid;
+    if (unlikely(mx->mx_db.md_mod_txnid > pp_txnid)) {
+      mdbx_error("nested-db.md_mod_txnid (%" PRIaTXN ") > page-txnid (%" PRIaTXN
+                 ")",
+                 mx->mx_db.md_mod_txnid, pp_txnid);
+      return MDBX_CORRUPTED;
+    }
+    mx->mx_cursor.mc_pg[0] = 0;
+    mx->mx_cursor.mc_snum = 0;
+    mx->mx_cursor.mc_top = 0;
+    mx->mx_cursor.mc_flags = C_SUB | (mc->mc_flags & (C_COPYING | C_SKIPORD));
+    break;
+  case F_DUPDATA:
+    if (unlikely(node_ds(node) <= PAGEHDRSZ)) {
+      mdbx_error("invalid nested-page size %zu", node_ds(node));
+      return MDBX_CORRUPTED;
+    }
+    MDBX_page *fp = node_data(node);
+    mx->mx_db.md_depth = 1;
+    mx->mx_db.md_branch_pages = 0;
+    mx->mx_db.md_leaf_pages = 1;
+    mx->mx_db.md_overflow_pages = 0;
+    mx->mx_db.md_entries = page_numkeys(fp);
+    mx->mx_db.md_root = fp->mp_pgno;
+    mx->mx_db.md_mod_txnid = mp->mp_txnid;
+    mx->mx_cursor.mc_snum = 1;
+    mx->mx_cursor.mc_top = 0;
+    mx->mx_cursor.mc_flags =
+        C_INITIALIZED | C_SUB | (mc->mc_flags & (C_COPYING | C_SKIPORD));
+    mx->mx_cursor.mc_pg[0] = fp;
+    mx->mx_cursor.mc_ki[0] = 0;
+    mx->mx_db.md_flags = flags_db2sub(mc->mc_db->md_flags);
+    mx->mx_db.md_xsize =
+        (mc->mc_db->md_flags & MDBX_DUPFIXED) ? fp->mp_leaf2_ksize : 0;
+    break;
+  }
+
+  if (unlikely(mx->mx_db.md_xsize != mc->mc_db->md_xsize)) {
+    if (unlikely(mc->mc_db->md_xsize != 0)) {
+      mdbx_error("cursor mismatched nested-db md_xsize %u",
+                 mc->mc_db->md_xsize);
+      return MDBX_CORRUPTED;
+    }
+    if (unlikely((mc->mc_db->md_flags & MDBX_DUPFIXED) == 0)) {
+      mdbx_error("mismatched nested-db md_flags %u", mc->mc_db->md_flags);
+      return MDBX_CORRUPTED;
+    }
+    if (unlikely(mx->mx_db.md_xsize < mc->mc_dbx->md_vlen_min ||
+                 mx->mx_db.md_xsize > mc->mc_dbx->md_vlen_max)) {
+      mdbx_error("mismatched nested-db.md_xsize (%u) <> min/max value-length "
+                 "(%zu/%zu)",
+                 mx->mx_db.md_xsize, mc->mc_dbx->md_vlen_min,
+                 mc->mc_dbx->md_vlen_max);
+      return MDBX_CORRUPTED;
+    }
+    mc->mc_db->md_xsize = mx->mx_db.md_xsize;
+    mc->mc_dbx->md_vlen_min = mc->mc_dbx->md_vlen_max = mx->mx_db.md_xsize;
+  }
+  mx->mx_dbx.md_klen_min = mc->mc_dbx->md_vlen_min;
+  mx->mx_dbx.md_klen_max = mc->mc_dbx->md_vlen_max;
+
+  mdbx_debug("Sub-db -%u root page %" PRIaPGNO, mx->mx_cursor.mc_dbi,
+             mx->mx_db.md_root);
+  mx->mx_dbistate = DBI_VALID | DBI_USRVALID | DBI_DUPDATA;
+  return MDBX_SUCCESS;
+}
+
+/* Fixup a sorted-dups cursor due to underlying update.
+ * Sets up some fields that depend on the data from the main cursor.
+ * Almost the same as init1, but skips initialization steps if the
+ * xcursor had already been used.
+ * [in] mc The main cursor whose sorted-dups cursor is to be fixed up.
+ * [in] src_mx The xcursor of an up-to-date cursor.
+ * [in] new_dupdata True if converting from a non-F_DUPDATA item. */
+static int mdbx_xcursor_init2(MDBX_cursor *mc, MDBX_xcursor *src_mx,
+                              bool new_dupdata) {
+  MDBX_xcursor *mx = mc->mc_xcursor;
+  if (unlikely(mx == nullptr)) {
+    mdbx_error("unexpected dupsort-page for non-dupsort db/cursor (dbi %u)",
+               mc->mc_dbi);
+    return MDBX_CORRUPTED;
+  }
+
+  if (new_dupdata) {
+    mx->mx_cursor.mc_snum = 1;
+    mx->mx_cursor.mc_top = 0;
+    mx->mx_cursor.mc_flags |= C_INITIALIZED;
+    mx->mx_cursor.mc_ki[0] = 0;
+    mx->mx_dbistate = DBI_VALID | DBI_USRVALID | DBI_DUPDATA;
+  }
+
+  mx->mx_dbx.md_klen_min = src_mx->mx_dbx.md_klen_min;
+  mx->mx_dbx.md_klen_max = src_mx->mx_dbx.md_klen_max;
+  mx->mx_dbx.md_cmp = src_mx->mx_dbx.md_cmp;
+  mx->mx_db = src_mx->mx_db;
+  mx->mx_cursor.mc_pg[0] = src_mx->mx_cursor.mc_pg[0];
+  if (mx->mx_cursor.mc_flags & C_INITIALIZED) {
+    mdbx_debug("Sub-db -%u root page %" PRIaPGNO, mx->mx_cursor.mc_dbi,
+               mx->mx_db.md_root);
+  }
+  return MDBX_SUCCESS;
+}
+
+static __inline int mdbx_couple_init(MDBX_cursor_couple *couple,
+                                     const MDBX_dbi dbi, MDBX_txn *const txn,
+                                     MDBX_db *const db, MDBX_dbx *const dbx,
+                                     uint8_t *const dbstate) {
+  couple->outer.mc_signature = MDBX_MC_LIVE;
+  couple->outer.mc_next = NULL;
+  couple->outer.mc_backup = NULL;
+  couple->outer.mc_dbi = dbi;
+  couple->outer.mc_txn = txn;
+  couple->outer.mc_db = db;
+  couple->outer.mc_dbx = dbx;
+  couple->outer.mc_dbistate = dbstate;
+  couple->outer.mc_snum = 0;
+  couple->outer.mc_top = 0;
+  couple->outer.mc_pg[0] = 0;
+  couple->outer.mc_flags = 0;
+  couple->outer.mc_ki[0] = 0;
+  couple->outer.mc_xcursor = NULL;
+
+  int rc = MDBX_SUCCESS;
+  if (unlikely(*couple->outer.mc_dbistate & DBI_STALE)) {
+    rc = mdbx_page_search(&couple->outer, NULL, MDBX_PS_ROOTONLY);
+    rc = (rc != MDBX_NOTFOUND) ? rc : MDBX_SUCCESS;
+  } else if (unlikely(couple->outer.mc_dbx->md_klen_max == 0)) {
+    rc = mdbx_setup_dbx(couple->outer.mc_dbx, couple->outer.mc_db,
+                        txn->mt_env->me_psize);
+  }
+
+  if (couple->outer.mc_db->md_flags & MDBX_DUPSORT) {
+    couple->inner.mx_cursor.mc_signature = MDBX_MC_LIVE;
+    couple->outer.mc_xcursor = &couple->inner;
+    rc = mdbx_xcursor_init0(&couple->outer);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    couple->inner.mx_dbx.md_klen_min = couple->outer.mc_dbx->md_vlen_min;
+    couple->inner.mx_dbx.md_klen_max = couple->outer.mc_dbx->md_vlen_max;
+  }
+  return rc;
+}
+
+/* Initialize a cursor for a given transaction and database. */
+static int mdbx_cursor_init(MDBX_cursor *mc, MDBX_txn *txn, MDBX_dbi dbi) {
+  STATIC_ASSERT(offsetof(MDBX_cursor_couple, outer) == 0);
+  if (unlikely(TXN_DBI_CHANGED(txn, dbi)))
+    return MDBX_BAD_DBI;
+
+  return mdbx_couple_init(container_of(mc, MDBX_cursor_couple, outer), dbi, txn,
+                          &txn->mt_dbs[dbi], &txn->mt_dbxs[dbi],
+                          &txn->mt_dbistate[dbi]);
+}
+
+MDBX_cursor *mdbx_cursor_create(void *context) {
+  MDBX_cursor_couple *couple = mdbx_calloc(1, sizeof(MDBX_cursor_couple));
+  if (unlikely(!couple))
+    return nullptr;
+
+  couple->outer.mc_signature = MDBX_MC_READY4CLOSE;
+  couple->outer.mc_dbi = UINT_MAX;
+  couple->mc_userctx = context;
+  return &couple->outer;
+}
+
+int mdbx_cursor_set_userctx(MDBX_cursor *mc, void *ctx) {
+  if (unlikely(!mc))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_READY4CLOSE &&
+               mc->mc_signature != MDBX_MC_LIVE))
+    return MDBX_EBADSIGN;
+
+  MDBX_cursor_couple *couple = container_of(mc, MDBX_cursor_couple, outer);
+  couple->mc_userctx = ctx;
+  return MDBX_SUCCESS;
+}
+
+void *mdbx_cursor_get_userctx(const MDBX_cursor *mc) {
+  if (unlikely(!mc))
+    return nullptr;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_READY4CLOSE &&
+               mc->mc_signature != MDBX_MC_LIVE))
+    return nullptr;
+
+  MDBX_cursor_couple *couple = container_of(mc, MDBX_cursor_couple, outer);
+  return couple->mc_userctx;
+}
+
+int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *mc, MDBX_dbi dbi) {
+  if (unlikely(!mc))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_READY4CLOSE &&
+               mc->mc_signature != MDBX_MC_LIVE))
+    return MDBX_EBADSIGN;
+
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_VALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(dbi == FREE_DBI && !F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY)))
+    return MDBX_EACCESS;
+
+  if (unlikely(mc->mc_backup)) /* Cursor from parent transaction */ {
+    mdbx_cassert(mc, mc->mc_signature == MDBX_MC_LIVE);
+    if (unlikely(mc->mc_dbi != dbi ||
+                 /* paranoia */ mc->mc_signature != MDBX_MC_LIVE ||
+                 mc->mc_txn != txn))
+      return MDBX_EINVAL;
+
+    assert(mc->mc_db == &txn->mt_dbs[dbi]);
+    assert(mc->mc_dbx == &txn->mt_dbxs[dbi]);
+    assert(mc->mc_dbi == dbi);
+    assert(mc->mc_dbistate == &txn->mt_dbistate[dbi]);
+    return likely(mc->mc_dbi == dbi &&
+                  /* paranoia */ mc->mc_signature == MDBX_MC_LIVE &&
+                  mc->mc_txn == txn)
+               ? MDBX_SUCCESS
+               : MDBX_EINVAL /* Disallow change DBI in nested transactions */;
+  }
+
+  if (mc->mc_signature == MDBX_MC_LIVE) {
+    if (unlikely(!mc->mc_txn || mc->mc_txn->mt_signature != MDBX_MT_SIGNATURE))
+      return MDBX_PROBLEM;
+    if (mc->mc_flags & C_UNTRACK) {
+      mdbx_cassert(mc, !(mc->mc_txn->mt_flags & MDBX_TXN_RDONLY));
+      MDBX_cursor **prev = &mc->mc_txn->tw.cursors[mc->mc_dbi];
+      while (*prev && *prev != mc)
+        prev = &(*prev)->mc_next;
+      mdbx_cassert(mc, *prev == mc);
+      *prev = mc->mc_next;
+    }
+    mc->mc_signature = MDBX_MC_READY4CLOSE;
+    mc->mc_flags = 0;
+    mc->mc_dbi = UINT_MAX;
+    mc->mc_next = NULL;
+    mc->mc_db = NULL;
+    mc->mc_dbx = NULL;
+    mc->mc_dbistate = NULL;
+  }
+  mdbx_cassert(mc, !(mc->mc_flags & C_UNTRACK));
+
+  rc = mdbx_cursor_init(mc, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (!(txn->mt_flags & MDBX_TXN_RDONLY)) {
+    mc->mc_next = txn->tw.cursors[dbi];
+    txn->tw.cursors[dbi] = mc;
+    mc->mc_flags |= C_UNTRACK;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi, MDBX_cursor **ret) {
+  if (unlikely(!ret))
+    return MDBX_EINVAL;
+  *ret = NULL;
+
+  MDBX_cursor *const mc = mdbx_cursor_create(nullptr);
+  if (unlikely(!mc))
+    return MDBX_ENOMEM;
+
+  int rc = mdbx_cursor_bind(txn, mc, dbi);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_cursor_close(mc);
+    return rc;
+  }
+
+  *ret = mc;
+  return MDBX_SUCCESS;
+}
+
+int mdbx_cursor_renew(MDBX_txn *txn, MDBX_cursor *mc) {
+  return likely(mc) ? mdbx_cursor_bind(txn, mc, mc->mc_dbi) : MDBX_EINVAL;
+}
+
+int mdbx_cursor_copy(const MDBX_cursor *src, MDBX_cursor *dest) {
+  if (unlikely(!src))
+    return MDBX_EINVAL;
+  if (unlikely(src->mc_signature != MDBX_MC_LIVE))
+    return (src->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                      : MDBX_EBADSIGN;
+
+  int rc = mdbx_cursor_bind(src->mc_txn, dest, src->mc_dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  assert(dest->mc_db == src->mc_db);
+  assert(dest->mc_dbi == src->mc_dbi);
+  assert(dest->mc_dbx == src->mc_dbx);
+  assert(dest->mc_dbistate == src->mc_dbistate);
+again:
+  assert(dest->mc_txn == src->mc_txn);
+  dest->mc_flags ^= (dest->mc_flags ^ src->mc_flags) & ~C_UNTRACK;
+  dest->mc_top = src->mc_top;
+  dest->mc_snum = src->mc_snum;
+  for (unsigned i = 0; i < src->mc_snum; ++i) {
+    dest->mc_ki[i] = src->mc_ki[i];
+    dest->mc_pg[i] = src->mc_pg[i];
+  }
+
+  if (src->mc_xcursor) {
+    dest->mc_xcursor->mx_db = src->mc_xcursor->mx_db;
+    dest->mc_xcursor->mx_dbx = src->mc_xcursor->mx_dbx;
+    src = &src->mc_xcursor->mx_cursor;
+    dest = &dest->mc_xcursor->mx_cursor;
+    goto again;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+void mdbx_cursor_close(MDBX_cursor *mc) {
+  if (likely(mc)) {
+    mdbx_ensure(NULL, mc->mc_signature == MDBX_MC_LIVE ||
+                          mc->mc_signature == MDBX_MC_READY4CLOSE);
+    MDBX_txn *const txn = mc->mc_txn;
+    if (!mc->mc_backup) {
+      mc->mc_txn = NULL;
+      /* Remove from txn, if tracked.
+       * A read-only txn (!C_UNTRACK) may have been freed already,
+       * so do not peek inside it.  Only write txns track cursors. */
+      if (mc->mc_flags & C_UNTRACK) {
+        mdbx_ensure(txn->mt_env, check_txn_rw(txn, 0) == MDBX_SUCCESS);
+        MDBX_cursor **prev = &txn->tw.cursors[mc->mc_dbi];
+        while (*prev && *prev != mc)
+          prev = &(*prev)->mc_next;
+        mdbx_tassert(txn, *prev == mc);
+        *prev = mc->mc_next;
+      }
+      mc->mc_signature = 0;
+      mc->mc_next = mc;
+      mdbx_free(mc);
+    } else {
+      /* Cursor closed before nested txn ends */
+      mdbx_tassert(txn, mc->mc_signature == MDBX_MC_LIVE);
+      mdbx_ensure(txn->mt_env, check_txn_rw(txn, 0) == MDBX_SUCCESS);
+      mc->mc_signature = MDBX_MC_WAIT4EOT;
+    }
+  }
+}
+
+MDBX_txn *mdbx_cursor_txn(const MDBX_cursor *mc) {
+  if (unlikely(!mc || mc->mc_signature != MDBX_MC_LIVE))
+    return NULL;
+  MDBX_txn *txn = mc->mc_txn;
+  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
+    return NULL;
+  if (unlikely(txn->mt_flags & MDBX_TXN_FINISHED))
+    return NULL;
+  return txn;
+}
+
+MDBX_dbi mdbx_cursor_dbi(const MDBX_cursor *mc) {
+  if (unlikely(!mc || mc->mc_signature != MDBX_MC_LIVE))
+    return UINT_MAX;
+  return mc->mc_dbi;
+}
+
+/* Return the count of duplicate data items for the current key */
+int mdbx_cursor_count(const MDBX_cursor *mc, size_t *countp) {
+  if (unlikely(mc == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  int rc = check_txn(mc->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(countp == NULL || !(mc->mc_flags & C_INITIALIZED)))
+    return MDBX_EINVAL;
+
+  if (!mc->mc_snum) {
+    *countp = 0;
+    return MDBX_NOTFOUND;
+  }
+
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  if ((mc->mc_flags & C_EOF) && mc->mc_ki[mc->mc_top] >= page_numkeys(mp)) {
+    *countp = 0;
+    return MDBX_NOTFOUND;
+  }
+
+  *countp = 1;
+  if (mc->mc_xcursor != NULL) {
+    MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
+    if (F_ISSET(node_flags(node), F_DUPDATA)) {
+      mdbx_cassert(mc, mc->mc_xcursor && (mc->mc_xcursor->mx_cursor.mc_flags &
+                                          C_INITIALIZED));
+      *countp = unlikely(mc->mc_xcursor->mx_db.md_entries > PTRDIFF_MAX)
+                    ? PTRDIFF_MAX
+                    : (size_t)mc->mc_xcursor->mx_db.md_entries;
+    }
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Replace the key for a branch node with a new key.
+ * Set MDBX_TXN_ERROR on failure.
+ * [in] mc Cursor pointing to the node to operate on.
+ * [in] key The new key to use.
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_update_key(MDBX_cursor *mc, const MDBX_val *key) {
+  MDBX_page *mp;
+  MDBX_node *node;
+  char *base;
+  size_t len;
+  int delta, ksize, oksize;
+  int ptr, i, nkeys, indx;
+  DKBUF;
+
+  mdbx_cassert(mc, cursor_is_tracked(mc));
+  indx = mc->mc_ki[mc->mc_top];
+  mp = mc->mc_pg[mc->mc_top];
+  node = page_node(mp, indx);
+  ptr = mp->mp_ptrs[indx];
+  if (MDBX_DEBUG) {
+    MDBX_val k2;
+    char kbuf2[DKBUF_MAXKEYSIZE * 2 + 1];
+    k2.iov_base = node_key(node);
+    k2.iov_len = node_ks(node);
+    mdbx_debug("update key %u (offset %u) [%s] to [%s] on page %" PRIaPGNO,
+               indx, ptr, mdbx_dump_val(&k2, kbuf2, sizeof(kbuf2)), DKEY(key),
+               mp->mp_pgno);
+  }
+
+  /* Sizes must be 2-byte aligned. */
+  ksize = EVEN(key->iov_len);
+  oksize = EVEN(node_ks(node));
+  delta = ksize - oksize;
+
+  /* Shift node contents if EVEN(key length) changed. */
+  if (delta) {
+    if (delta > (int)page_room(mp)) {
+      /* not enough space left, do a delete and split */
+      mdbx_debug("Not enough room, delta = %d, splitting...", delta);
+      pgno_t pgno = node_pgno(node);
+      mdbx_node_del(mc, 0);
+      int rc = mdbx_page_split(mc, key, NULL, pgno, MDBX_SPLIT_REPLACE);
+      if (rc == MDBX_SUCCESS && mdbx_audit_enabled())
+        rc = mdbx_cursor_check(mc, C_UPDATING);
+      return rc;
+    }
+
+    nkeys = page_numkeys(mp);
+    for (i = 0; i < nkeys; i++) {
+      if (mp->mp_ptrs[i] <= ptr) {
+        mdbx_cassert(mc, mp->mp_ptrs[i] >= delta);
+        mp->mp_ptrs[i] -= (indx_t)delta;
+      }
+    }
+
+    base = (char *)mp + mp->mp_upper + PAGEHDRSZ;
+    len = ptr - mp->mp_upper + NODESIZE;
+    memmove(base - delta, base, len);
+    mdbx_cassert(mc, mp->mp_upper >= delta);
+    mp->mp_upper -= (indx_t)delta;
+
+    node = page_node(mp, indx);
+  }
+
+  /* But even if no shift was needed, update ksize */
+  node_set_ks(node, key->iov_len);
+
+  if (likely(key->iov_len /* to avoid UBSAN traps*/ != 0))
+    memcpy(node_key(node), key->iov_base, key->iov_len);
+  return MDBX_SUCCESS;
+}
+
+/* Move a node from csrc to cdst. */
+static int mdbx_node_move(MDBX_cursor *csrc, MDBX_cursor *cdst, int fromleft) {
+  int rc;
+  DKBUF;
+
+  MDBX_page *psrc = csrc->mc_pg[csrc->mc_top];
+  MDBX_page *pdst = cdst->mc_pg[cdst->mc_top];
+  mdbx_cassert(csrc, PAGETYPE(psrc) == PAGETYPE(pdst));
+  mdbx_cassert(csrc, csrc->mc_dbi == cdst->mc_dbi);
+  mdbx_cassert(csrc, csrc->mc_top == cdst->mc_top);
+  if (unlikely(PAGETYPE(psrc) != PAGETYPE(pdst))) {
+  bailout:
+    csrc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+    return MDBX_PROBLEM;
+  }
+
+  MDBX_val key4move;
+  switch (PAGETYPE(psrc)) {
+  case P_BRANCH: {
+    const MDBX_node *srcnode = page_node(psrc, csrc->mc_ki[csrc->mc_top]);
+    mdbx_cassert(csrc, node_flags(srcnode) == 0);
+    const pgno_t srcpg = node_pgno(srcnode);
+    key4move.iov_len = node_ks(srcnode);
+    key4move.iov_base = node_key(srcnode);
+
+    if (csrc->mc_ki[csrc->mc_top] == 0) {
+      const unsigned snum = csrc->mc_snum;
+      mdbx_cassert(csrc, snum > 0);
+      /* must find the lowest key below src */
+      rc = mdbx_page_search_lowest(csrc);
+      MDBX_page *lowest_page = csrc->mc_pg[csrc->mc_top];
+      if (unlikely(rc))
+        return rc;
+      mdbx_cassert(csrc, IS_LEAF(lowest_page));
+      if (unlikely(!IS_LEAF(lowest_page)))
+        goto bailout;
+      if (IS_LEAF2(lowest_page)) {
+        key4move.iov_len = csrc->mc_db->md_xsize;
+        key4move.iov_base = page_leaf2key(lowest_page, 0, key4move.iov_len);
+      } else {
+        const MDBX_node *lowest_node = page_node(lowest_page, 0);
+        key4move.iov_len = node_ks(lowest_node);
+        key4move.iov_base = node_key(lowest_node);
+      }
+
+      /* restore cursor after mdbx_page_search_lowest() */
+      csrc->mc_snum = snum;
+      csrc->mc_top = snum - 1;
+      csrc->mc_ki[csrc->mc_top] = 0;
+
+      /* paranoia */
+      mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
+      mdbx_cassert(csrc, IS_BRANCH(psrc));
+      if (unlikely(!IS_BRANCH(psrc)))
+        goto bailout;
+    }
+
+    if (cdst->mc_ki[cdst->mc_top] == 0) {
+      const unsigned snum = cdst->mc_snum;
+      mdbx_cassert(csrc, snum > 0);
+      MDBX_cursor mn;
+      cursor_copy_internal(cdst, &mn);
+      mn.mc_xcursor = NULL;
+      /* must find the lowest key below dst */
+      rc = mdbx_page_search_lowest(&mn);
+      if (unlikely(rc))
+        return rc;
+      MDBX_page *const lowest_page = mn.mc_pg[mn.mc_top];
+      mdbx_cassert(cdst, IS_LEAF(lowest_page));
+      if (unlikely(!IS_LEAF(lowest_page)))
+        goto bailout;
+      MDBX_val key;
+      if (IS_LEAF2(lowest_page)) {
+        key.iov_len = mn.mc_db->md_xsize;
+        key.iov_base = page_leaf2key(lowest_page, 0, key.iov_len);
+      } else {
+        MDBX_node *lowest_node = page_node(lowest_page, 0);
+        key.iov_len = node_ks(lowest_node);
+        key.iov_base = node_key(lowest_node);
+      }
+
+      /* restore cursor after mdbx_page_search_lowest() */
+      mn.mc_snum = snum;
+      mn.mc_top = snum - 1;
+      mn.mc_ki[mn.mc_top] = 0;
+
+      const intptr_t delta =
+          EVEN(key.iov_len) - EVEN(node_ks(page_node(mn.mc_pg[mn.mc_top], 0)));
+      const intptr_t needed =
+          branch_size(cdst->mc_txn->mt_env, &key4move) + delta;
+      const intptr_t have = page_room(pdst);
+      if (unlikely(needed > have))
+        return MDBX_RESULT_TRUE;
+
+      if (unlikely((rc = mdbx_page_touch(csrc)) ||
+                   (rc = mdbx_page_touch(cdst))))
+        return rc;
+      psrc = csrc->mc_pg[csrc->mc_top];
+      pdst = cdst->mc_pg[cdst->mc_top];
+
+      WITH_CURSOR_TRACKING(mn, rc = mdbx_update_key(&mn, &key));
+      if (unlikely(rc))
+        return rc;
+    } else {
+      const size_t needed = branch_size(cdst->mc_txn->mt_env, &key4move);
+      const size_t have = page_room(pdst);
+      if (unlikely(needed > have))
+        return MDBX_RESULT_TRUE;
+
+      if (unlikely((rc = mdbx_page_touch(csrc)) ||
+                   (rc = mdbx_page_touch(cdst))))
+        return rc;
+      psrc = csrc->mc_pg[csrc->mc_top];
+      pdst = cdst->mc_pg[cdst->mc_top];
+    }
+
+    mdbx_debug("moving %s-node %u [%s] on page %" PRIaPGNO
+               " to node %u on page %" PRIaPGNO,
+               "branch", csrc->mc_ki[csrc->mc_top], DKEY(&key4move),
+               psrc->mp_pgno, cdst->mc_ki[cdst->mc_top], pdst->mp_pgno);
+    /* Add the node to the destination page. */
+    rc =
+        mdbx_node_add_branch(cdst, cdst->mc_ki[cdst->mc_top], &key4move, srcpg);
+  } break;
+
+  case P_LEAF: {
+    /* Mark src and dst as dirty. */
+    if (unlikely((rc = mdbx_page_touch(csrc)) || (rc = mdbx_page_touch(cdst))))
+      return rc;
+    psrc = csrc->mc_pg[csrc->mc_top];
+    pdst = cdst->mc_pg[cdst->mc_top];
+    const MDBX_node *srcnode = page_node(psrc, csrc->mc_ki[csrc->mc_top]);
+    MDBX_val data;
+    data.iov_len = node_ds(srcnode);
+    data.iov_base = node_data(srcnode);
+    key4move.iov_len = node_ks(srcnode);
+    key4move.iov_base = node_key(srcnode);
+    mdbx_debug("moving %s-node %u [%s] on page %" PRIaPGNO
+               " to node %u on page %" PRIaPGNO,
+               "leaf", csrc->mc_ki[csrc->mc_top], DKEY(&key4move),
+               psrc->mp_pgno, cdst->mc_ki[cdst->mc_top], pdst->mp_pgno);
+    /* Add the node to the destination page. */
+    rc = mdbx_node_add_leaf(cdst, cdst->mc_ki[cdst->mc_top], &key4move, &data,
+                            node_flags(srcnode));
+  } break;
+
+  case P_LEAF | P_LEAF2: {
+    /* Mark src and dst as dirty. */
+    if (unlikely((rc = mdbx_page_touch(csrc)) || (rc = mdbx_page_touch(cdst))))
+      return rc;
+    psrc = csrc->mc_pg[csrc->mc_top];
+    pdst = cdst->mc_pg[cdst->mc_top];
+    key4move.iov_len = csrc->mc_db->md_xsize;
+    key4move.iov_base =
+        page_leaf2key(psrc, csrc->mc_ki[csrc->mc_top], key4move.iov_len);
+    mdbx_debug("moving %s-node %u [%s] on page %" PRIaPGNO
+               " to node %u on page %" PRIaPGNO,
+               "leaf2", csrc->mc_ki[csrc->mc_top], DKEY(&key4move),
+               psrc->mp_pgno, cdst->mc_ki[cdst->mc_top], pdst->mp_pgno);
+    /* Add the node to the destination page. */
+    rc = mdbx_node_add_leaf2(cdst, cdst->mc_ki[cdst->mc_top], &key4move);
+  } break;
+
+  default:
+    goto bailout;
+  }
+
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  /* Delete the node from the source page. */
+  mdbx_node_del(csrc, key4move.iov_len);
+
+  mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
+  mdbx_cassert(cdst, pdst == cdst->mc_pg[cdst->mc_top]);
+  mdbx_cassert(csrc, PAGETYPE(psrc) == PAGETYPE(pdst));
+
+  {
+    /* Adjust other cursors pointing to mp */
+    MDBX_cursor *m2, *m3;
+    const MDBX_dbi dbi = csrc->mc_dbi;
+    mdbx_cassert(csrc, csrc->mc_top == cdst->mc_top);
+    if (fromleft) {
+      /* If we're adding on the left, bump others up */
+      for (m2 = csrc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+        m3 = (csrc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+        if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
+          continue;
+        if (m3 != cdst && m3->mc_pg[csrc->mc_top] == pdst &&
+            m3->mc_ki[csrc->mc_top] >= cdst->mc_ki[csrc->mc_top]) {
+          m3->mc_ki[csrc->mc_top]++;
+        }
+        if (m3 != csrc && m3->mc_pg[csrc->mc_top] == psrc &&
+            m3->mc_ki[csrc->mc_top] == csrc->mc_ki[csrc->mc_top]) {
+          m3->mc_pg[csrc->mc_top] = pdst;
+          m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+          mdbx_cassert(csrc, csrc->mc_top > 0);
+          m3->mc_ki[csrc->mc_top - 1]++;
+        }
+        if (XCURSOR_INITED(m3) && IS_LEAF(psrc))
+          XCURSOR_REFRESH(m3, m3->mc_pg[csrc->mc_top], m3->mc_ki[csrc->mc_top]);
+      }
+    } else {
+      /* Adding on the right, bump others down */
+      for (m2 = csrc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+        m3 = (csrc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+        if (m3 == csrc)
+          continue;
+        if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
+          continue;
+        if (m3->mc_pg[csrc->mc_top] == psrc) {
+          if (!m3->mc_ki[csrc->mc_top]) {
+            m3->mc_pg[csrc->mc_top] = pdst;
+            m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+            mdbx_cassert(csrc, csrc->mc_top > 0);
+            m3->mc_ki[csrc->mc_top - 1]--;
+          } else {
+            m3->mc_ki[csrc->mc_top]--;
+          }
+          if (XCURSOR_INITED(m3) && IS_LEAF(psrc))
+            XCURSOR_REFRESH(m3, m3->mc_pg[csrc->mc_top],
+                            m3->mc_ki[csrc->mc_top]);
+        }
+      }
+    }
+  }
+
+  /* Update the parent separators. */
+  if (csrc->mc_ki[csrc->mc_top] == 0) {
+    mdbx_cassert(csrc, csrc->mc_top > 0);
+    if (csrc->mc_ki[csrc->mc_top - 1] != 0) {
+      MDBX_val key;
+      if (IS_LEAF2(psrc)) {
+        key.iov_len = psrc->mp_leaf2_ksize;
+        key.iov_base = page_leaf2key(psrc, 0, key.iov_len);
+      } else {
+        MDBX_node *srcnode = page_node(psrc, 0);
+        key.iov_len = node_ks(srcnode);
+        key.iov_base = node_key(srcnode);
+      }
+      mdbx_debug("update separator for source page %" PRIaPGNO " to [%s]",
+                 psrc->mp_pgno, DKEY(&key));
+      MDBX_cursor mn;
+      cursor_copy_internal(csrc, &mn);
+      mn.mc_xcursor = NULL;
+      mdbx_cassert(csrc, mn.mc_snum > 0);
+      mn.mc_snum--;
+      mn.mc_top--;
+      /* We want mdbx_rebalance to find mn when doing fixups */
+      WITH_CURSOR_TRACKING(mn, rc = mdbx_update_key(&mn, &key));
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+    }
+    if (IS_BRANCH(psrc)) {
+      const MDBX_val nullkey = {0, 0};
+      const indx_t ix = csrc->mc_ki[csrc->mc_top];
+      csrc->mc_ki[csrc->mc_top] = 0;
+      rc = mdbx_update_key(csrc, &nullkey);
+      csrc->mc_ki[csrc->mc_top] = ix;
+      mdbx_cassert(csrc, rc == MDBX_SUCCESS);
+    }
+  }
+
+  if (cdst->mc_ki[cdst->mc_top] == 0) {
+    mdbx_cassert(cdst, cdst->mc_top > 0);
+    if (cdst->mc_ki[cdst->mc_top - 1] != 0) {
+      MDBX_val key;
+      if (IS_LEAF2(pdst)) {
+        key.iov_len = pdst->mp_leaf2_ksize;
+        key.iov_base = page_leaf2key(pdst, 0, key.iov_len);
+      } else {
+        MDBX_node *srcnode = page_node(pdst, 0);
+        key.iov_len = node_ks(srcnode);
+        key.iov_base = node_key(srcnode);
+      }
+      mdbx_debug("update separator for destination page %" PRIaPGNO " to [%s]",
+                 pdst->mp_pgno, DKEY(&key));
+      MDBX_cursor mn;
+      cursor_copy_internal(cdst, &mn);
+      mn.mc_xcursor = NULL;
+      mdbx_cassert(cdst, mn.mc_snum > 0);
+      mn.mc_snum--;
+      mn.mc_top--;
+      /* We want mdbx_rebalance to find mn when doing fixups */
+      WITH_CURSOR_TRACKING(mn, rc = mdbx_update_key(&mn, &key));
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+    }
+    if (IS_BRANCH(pdst)) {
+      const MDBX_val nullkey = {0, 0};
+      const indx_t ix = cdst->mc_ki[cdst->mc_top];
+      cdst->mc_ki[cdst->mc_top] = 0;
+      rc = mdbx_update_key(cdst, &nullkey);
+      cdst->mc_ki[cdst->mc_top] = ix;
+      mdbx_cassert(cdst, rc == MDBX_SUCCESS);
+    }
+  }
+
+  return MDBX_SUCCESS;
+}
+
+/* Merge one page into another.
+ *
+ * The nodes from the page pointed to by csrc will be copied to the page
+ * pointed to by cdst and then the csrc page will be freed.
+ *
+ * [in] csrc Cursor pointing to the source page.
+ * [in] cdst Cursor pointing to the destination page.
+ *
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
+  MDBX_val key;
+  int rc;
+
+  mdbx_cassert(csrc, csrc != cdst);
+  mdbx_cassert(csrc, cursor_is_tracked(csrc));
+  mdbx_cassert(cdst, cursor_is_tracked(cdst));
+  const MDBX_page *const psrc = csrc->mc_pg[csrc->mc_top];
+  MDBX_page *pdst = cdst->mc_pg[cdst->mc_top];
+  mdbx_debug("merging page %" PRIaPGNO " into %" PRIaPGNO, psrc->mp_pgno,
+             pdst->mp_pgno);
+
+  mdbx_cassert(csrc, PAGETYPE(psrc) == PAGETYPE(pdst));
+  mdbx_cassert(csrc,
+               csrc->mc_dbi == cdst->mc_dbi && csrc->mc_db == cdst->mc_db);
+  mdbx_cassert(csrc, csrc->mc_snum > 1); /* can't merge root page */
+  mdbx_cassert(cdst, cdst->mc_snum > 1);
+  mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                         IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+  mdbx_cassert(csrc, csrc->mc_snum < csrc->mc_db->md_depth ||
+                         IS_LEAF(csrc->mc_pg[csrc->mc_db->md_depth - 1]));
+  mdbx_cassert(cdst, page_room(pdst) >= page_used(cdst->mc_txn->mt_env, psrc));
+  const int pagetype = PAGETYPE(psrc);
+
+  /* Move all nodes from src to dst */
+  const unsigned dst_nkeys = page_numkeys(pdst);
+  const unsigned src_nkeys = page_numkeys(psrc);
+  mdbx_cassert(cdst, dst_nkeys + src_nkeys >=
+                         (unsigned)(IS_LEAF(psrc) ? 1 : MDBX_MINKEYS));
+  if (likely(src_nkeys)) {
+    unsigned j = dst_nkeys;
+    if (unlikely(pagetype & P_LEAF2)) {
+      /* Mark dst as dirty. */
+      if (unlikely(rc = mdbx_page_touch(cdst)))
+        return rc;
+
+      key.iov_len = csrc->mc_db->md_xsize;
+      key.iov_base = page_data(psrc);
+      unsigned i = 0;
+      do {
+        rc = mdbx_node_add_leaf2(cdst, j++, &key);
+        if (unlikely(rc != MDBX_SUCCESS))
+          return rc;
+        key.iov_base = (char *)key.iov_base + key.iov_len;
+      } while (++i != src_nkeys);
+    } else {
+      MDBX_node *srcnode = page_node(psrc, 0);
+      key.iov_len = node_ks(srcnode);
+      key.iov_base = node_key(srcnode);
+      if (pagetype & P_BRANCH) {
+        MDBX_cursor mn;
+        cursor_copy_internal(csrc, &mn);
+        mn.mc_xcursor = NULL;
+        /* must find the lowest key below src */
+        rc = mdbx_page_search_lowest(&mn);
+        if (unlikely(rc))
+          return rc;
+
+        const MDBX_page *mp = mn.mc_pg[mn.mc_top];
+        if (likely(!IS_LEAF2(mp))) {
+          mdbx_cassert(&mn, IS_LEAF(mp));
+          const MDBX_node *lowest = page_node(mp, 0);
+          key.iov_len = node_ks(lowest);
+          key.iov_base = node_key(lowest);
+        } else {
+          mdbx_cassert(&mn, mn.mc_top > csrc->mc_top);
+          key.iov_len = mp->mp_leaf2_ksize;
+          key.iov_base = page_leaf2key(mp, mn.mc_ki[mn.mc_top], key.iov_len);
+        }
+        mdbx_cassert(&mn, key.iov_len >= csrc->mc_dbx->md_klen_min);
+        mdbx_cassert(&mn, key.iov_len <= csrc->mc_dbx->md_klen_max);
+
+        const size_t dst_room = page_room(pdst);
+        const size_t src_used = page_used(cdst->mc_txn->mt_env, psrc);
+        const size_t space_needed = src_used - node_ks(srcnode) + key.iov_len;
+        if (unlikely(space_needed > dst_room))
+          return MDBX_RESULT_TRUE;
+      }
+
+      /* Mark dst as dirty. */
+      if (unlikely(rc = mdbx_page_touch(cdst)))
+        return rc;
+
+      unsigned i = 0;
+      while (true) {
+        if (pagetype & P_LEAF) {
+          MDBX_val data;
+          data.iov_len = node_ds(srcnode);
+          data.iov_base = node_data(srcnode);
+          rc = mdbx_node_add_leaf(cdst, j++, &key, &data, node_flags(srcnode));
+        } else {
+          mdbx_cassert(csrc, node_flags(srcnode) == 0);
+          rc = mdbx_node_add_branch(cdst, j++, &key, node_pgno(srcnode));
+        }
+        if (unlikely(rc != MDBX_SUCCESS))
+          return rc;
+
+        if (++i == src_nkeys)
+          break;
+        srcnode = page_node(psrc, i);
+        key.iov_len = node_ks(srcnode);
+        key.iov_base = node_key(srcnode);
+      }
+    }
+
+    pdst = cdst->mc_pg[cdst->mc_top];
+    mdbx_debug("dst page %" PRIaPGNO " now has %u keys (%.1f%% filled)",
+               pdst->mp_pgno, page_numkeys(pdst),
+               page_fill(cdst->mc_txn->mt_env, pdst));
+
+    mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
+    mdbx_cassert(cdst, pdst == cdst->mc_pg[cdst->mc_top]);
+  }
+
+  /* Unlink the src page from parent and add to free list. */
+  csrc->mc_top--;
+  mdbx_node_del(csrc, 0);
+  if (csrc->mc_ki[csrc->mc_top] == 0) {
+    const MDBX_val nullkey = {0, 0};
+    rc = mdbx_update_key(csrc, &nullkey);
+    if (unlikely(rc)) {
+      csrc->mc_top++;
+      return rc;
+    }
+  }
+  csrc->mc_top++;
+
+  mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
+  mdbx_cassert(cdst, pdst == cdst->mc_pg[cdst->mc_top]);
+
+  {
+    /* Adjust other cursors pointing to mp */
+    MDBX_cursor *m2, *m3;
+    const MDBX_dbi dbi = csrc->mc_dbi;
+    const unsigned top = csrc->mc_top;
+
+    for (m2 = csrc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+      m3 = (csrc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+      if (m3 == csrc || top >= m3->mc_snum)
+        continue;
+      if (m3->mc_pg[top] == psrc) {
+        m3->mc_pg[top] = pdst;
+        mdbx_cassert(m3, dst_nkeys + m3->mc_ki[top] <= UINT16_MAX);
+        m3->mc_ki[top] += (indx_t)dst_nkeys;
+        m3->mc_ki[top - 1] = cdst->mc_ki[top - 1];
+      } else if (m3->mc_pg[top - 1] == csrc->mc_pg[top - 1] &&
+                 m3->mc_ki[top - 1] > csrc->mc_ki[top - 1]) {
+        m3->mc_ki[top - 1]--;
+      }
+      if (XCURSOR_INITED(m3) && IS_LEAF(psrc))
+        XCURSOR_REFRESH(m3, m3->mc_pg[top], m3->mc_ki[top]);
+    }
+  }
+
+  /* If not operating on GC, allow this page to be reused
+   * in this txn. Otherwise just add to free list. */
+  rc = mdbx_page_retire(csrc, (MDBX_page *)psrc);
+  if (unlikely(rc))
+    return rc;
+
+  mdbx_cassert(cdst, cdst->mc_db->md_entries > 0);
+  mdbx_cassert(cdst, cdst->mc_snum <= cdst->mc_db->md_depth);
+  mdbx_cassert(cdst, cdst->mc_top > 0);
+  mdbx_cassert(cdst, cdst->mc_snum == cdst->mc_top + 1);
+  MDBX_page *const top_page = cdst->mc_pg[cdst->mc_top];
+  const indx_t top_indx = cdst->mc_ki[cdst->mc_top];
+  const unsigned save_snum = cdst->mc_snum;
+  const uint16_t save_depth = cdst->mc_db->md_depth;
+  mdbx_cursor_pop(cdst);
+  rc = mdbx_rebalance(cdst);
+  if (unlikely(rc))
+    return rc;
+
+  mdbx_cassert(cdst, cdst->mc_db->md_entries > 0);
+  mdbx_cassert(cdst, cdst->mc_snum <= cdst->mc_db->md_depth);
+  mdbx_cassert(cdst, cdst->mc_snum == cdst->mc_top + 1);
+
+  if (IS_LEAF(cdst->mc_pg[cdst->mc_top])) {
+    /* LY: don't touch cursor if top-page is a LEAF */
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+  mdbx_cassert(cdst, page_numkeys(top_page) == dst_nkeys + src_nkeys);
+
+  if (pagetype != PAGETYPE(top_page)) {
+    /* LY: LEAF-page becomes BRANCH, unable restore cursor's stack */
+    goto bailout;
+  }
+
+  if (top_page == cdst->mc_pg[cdst->mc_top]) {
+    /* LY: don't touch cursor if prev top-page already on the top */
+    mdbx_cassert(cdst, cdst->mc_ki[cdst->mc_top] == top_indx);
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+  const int new_snum = save_snum - save_depth + cdst->mc_db->md_depth;
+  if (unlikely(new_snum < 1 || new_snum > cdst->mc_db->md_depth)) {
+    /* LY: out of range, unable restore cursor's stack */
+    goto bailout;
+  }
+
+  if (top_page == cdst->mc_pg[new_snum - 1]) {
+    mdbx_cassert(cdst, cdst->mc_ki[new_snum - 1] == top_indx);
+    /* LY: restore cursor stack */
+    cdst->mc_snum = (uint16_t)new_snum;
+    cdst->mc_top = (uint16_t)new_snum - 1;
+    mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                           IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+  MDBX_page *const stub_page = (MDBX_page *)(~(uintptr_t)top_page);
+  const indx_t stub_indx = top_indx;
+  if (save_depth > cdst->mc_db->md_depth &&
+      ((cdst->mc_pg[save_snum - 1] == top_page &&
+        cdst->mc_ki[save_snum - 1] == top_indx) ||
+       (cdst->mc_pg[save_snum - 1] == stub_page &&
+        cdst->mc_ki[save_snum - 1] == stub_indx))) {
+    /* LY: restore cursor stack */
+    cdst->mc_pg[new_snum - 1] = top_page;
+    cdst->mc_ki[new_snum - 1] = top_indx;
+    cdst->mc_pg[new_snum] = (MDBX_page *)(~(uintptr_t)cdst->mc_pg[new_snum]);
+    cdst->mc_ki[new_snum] = ~cdst->mc_ki[new_snum];
+    cdst->mc_snum = (uint16_t)new_snum;
+    cdst->mc_top = (uint16_t)new_snum - 1;
+    mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                           IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+bailout:
+  /* LY: unable restore cursor's stack */
+  cdst->mc_flags &= ~C_INITIALIZED;
+  return MDBX_CURSOR_FULL;
+}
+
+/* Copy the contents of a cursor.
+ * [in] csrc The cursor to copy from.
+ * [out] cdst The cursor to copy to. */
+static void cursor_copy_internal(const MDBX_cursor *csrc, MDBX_cursor *cdst) {
+  mdbx_cassert(csrc,
+               csrc->mc_txn->mt_txnid >= csrc->mc_txn->mt_env->me_oldest->weak);
+  cdst->mc_txn = csrc->mc_txn;
+  cdst->mc_dbi = csrc->mc_dbi;
+  cdst->mc_db = csrc->mc_db;
+  cdst->mc_dbx = csrc->mc_dbx;
+  cdst->mc_snum = csrc->mc_snum;
+  cdst->mc_top = csrc->mc_top;
+  cdst->mc_flags = csrc->mc_flags;
+  cdst->mc_dbistate = csrc->mc_dbistate;
+
+  for (unsigned i = 0; i < csrc->mc_snum; i++) {
+    cdst->mc_pg[i] = csrc->mc_pg[i];
+    cdst->mc_ki[i] = csrc->mc_ki[i];
+  }
+}
+
+/* Rebalance the tree after a delete operation.
+ * [in] mc Cursor pointing to the page where rebalancing should begin.
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_rebalance(MDBX_cursor *mc) {
+  mdbx_cassert(mc, cursor_is_tracked(mc));
+  mdbx_cassert(mc, mc->mc_snum > 0);
+  mdbx_cassert(mc, mc->mc_snum < mc->mc_db->md_depth ||
+                       IS_LEAF(mc->mc_pg[mc->mc_db->md_depth - 1]));
+  const int pagetype = PAGETYPE(mc->mc_pg[mc->mc_top]);
+
+  STATIC_ASSERT(P_BRANCH == 1);
+  const unsigned minkeys = (pagetype & P_BRANCH) + 1;
+
+  /* The threshold of minimum page fill factor, in form of a negative binary
+   * exponent, i.e. X = 2 means 1/(2**X) == 1/(2**2) == 1/4 == 25%.
+   * Pages emptier than this are candidates for merging. */
+  const unsigned threshold_fill_exp2 = 2;
+
+  /* The threshold of minimum page fill factor, as a number of free bytes on a
+   * page. Pages emptier than this are candidates for merging. */
+  const unsigned room_threshold =
+      page_space(mc->mc_txn->mt_env) -
+      (page_space(mc->mc_txn->mt_env) >> threshold_fill_exp2);
+
+  const MDBX_page *const tp = mc->mc_pg[mc->mc_top];
+  mdbx_debug("rebalancing %s page %" PRIaPGNO " (has %u keys, %.1f%% full)",
+             (pagetype & P_LEAF) ? "leaf" : "branch", tp->mp_pgno,
+             page_numkeys(tp), page_fill(mc->mc_txn->mt_env, tp));
+
+  if (unlikely(page_numkeys(tp) < minkeys)) {
+    mdbx_debug("page %" PRIaPGNO " must be merged due keys < %u threshold",
+               tp->mp_pgno, minkeys);
+  } else if (unlikely(page_room(tp) > room_threshold)) {
+    mdbx_debug("page %" PRIaPGNO " should be merged due room %u > %u threshold",
+               tp->mp_pgno, page_room(tp), room_threshold);
+  } else {
+    mdbx_debug("no need to rebalance page %" PRIaPGNO
+               ", room %u < %u threshold",
+               tp->mp_pgno, page_room(tp), room_threshold);
+    mdbx_cassert(mc, mc->mc_db->md_entries > 0);
+    return MDBX_SUCCESS;
+  }
+
+  int rc;
+  if (mc->mc_snum < 2) {
+    MDBX_page *const mp = mc->mc_pg[0];
+    const unsigned nkeys = page_numkeys(mp);
+    mdbx_cassert(mc, (mc->mc_db->md_entries == 0) == (nkeys == 0));
+    if (IS_SUBP(mp)) {
+      mdbx_debug("%s", "Can't rebalance a subpage, ignoring");
+      mdbx_cassert(mc, pagetype & P_LEAF);
+      return MDBX_SUCCESS;
+    }
+    if (nkeys == 0) {
+      mdbx_cassert(mc, IS_LEAF(mp));
+      mdbx_debug("%s", "tree is completely empty");
+      mc->mc_db->md_root = P_INVALID;
+      mc->mc_db->md_depth = 0;
+      mdbx_cassert(mc, mc->mc_db->md_branch_pages == 0 &&
+                           mc->mc_db->md_overflow_pages == 0 &&
+                           mc->mc_db->md_leaf_pages == 1);
+      /* Adjust cursors pointing to mp */
+      for (MDBX_cursor *m2 = mc->mc_txn->tw.cursors[mc->mc_dbi]; m2;
+           m2 = m2->mc_next) {
+        MDBX_cursor *m3 =
+            (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+        if (m3 == mc || !(m3->mc_flags & C_INITIALIZED))
+          continue;
+        if (m3->mc_pg[0] == mp) {
+          m3->mc_snum = 0;
+          m3->mc_top = 0;
+          m3->mc_flags &= ~C_INITIALIZED;
+        }
+      }
+      mc->mc_snum = 0;
+      mc->mc_top = 0;
+      mc->mc_flags &= ~C_INITIALIZED;
+
+      rc = mdbx_page_retire(mc, mp);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+    } else if (IS_BRANCH(mp) && nkeys == 1) {
+      mdbx_debug("%s", "collapsing root page!");
+      mc->mc_db->md_root = node_pgno(page_node(mp, 0));
+      rc = mdbx_page_get(mc, mc->mc_db->md_root, &mc->mc_pg[0], NULL,
+                         pp_txnid4chk(mp, mc->mc_txn));
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+      mc->mc_db->md_depth--;
+      mc->mc_ki[0] = mc->mc_ki[1];
+      for (int i = 1; i < mc->mc_db->md_depth; i++) {
+        mc->mc_pg[i] = mc->mc_pg[i + 1];
+        mc->mc_ki[i] = mc->mc_ki[i + 1];
+      }
+
+      /* Adjust other cursors pointing to mp */
+      for (MDBX_cursor *m2 = mc->mc_txn->tw.cursors[mc->mc_dbi]; m2;
+           m2 = m2->mc_next) {
+        MDBX_cursor *m3 =
+            (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+        if (m3 == mc || !(m3->mc_flags & C_INITIALIZED))
+          continue;
+        if (m3->mc_pg[0] == mp) {
+          for (int i = 0; i < mc->mc_db->md_depth; i++) {
+            m3->mc_pg[i] = m3->mc_pg[i + 1];
+            m3->mc_ki[i] = m3->mc_ki[i + 1];
+          }
+          m3->mc_snum--;
+          m3->mc_top--;
+        }
+      }
+      mdbx_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]) ||
+                           PAGETYPE(mc->mc_pg[mc->mc_top]) == pagetype);
+      mdbx_cassert(mc, mc->mc_snum < mc->mc_db->md_depth ||
+                           IS_LEAF(mc->mc_pg[mc->mc_db->md_depth - 1]));
+
+      rc = mdbx_page_retire(mc, mp);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+    } else {
+      mdbx_debug("root page %" PRIaPGNO
+                 " doesn't need rebalancing (flags 0x%x)",
+                 mp->mp_pgno, mp->mp_flags);
+    }
+    return MDBX_SUCCESS;
+  }
+
+  /* The parent (branch page) must have at least 2 pointers,
+   * otherwise the tree is invalid. */
+  const unsigned pre_top = mc->mc_top - 1;
+  mdbx_cassert(mc, IS_BRANCH(mc->mc_pg[pre_top]));
+  mdbx_cassert(mc, !IS_SUBP(mc->mc_pg[0]));
+  mdbx_cassert(mc, page_numkeys(mc->mc_pg[pre_top]) > 1);
+
+  /* Leaf page fill factor is below the threshold.
+   * Try to move keys from left or right neighbor, or
+   * merge with a neighbor page. */
+
+  /* Find neighbors. */
+  MDBX_cursor mn;
+  cursor_copy_internal(mc, &mn);
+  mn.mc_xcursor = NULL;
+
+  MDBX_page *left = nullptr, *right = nullptr;
+  if (mn.mc_ki[pre_top] > 0) {
+    rc = mdbx_page_get(
+        &mn, node_pgno(page_node(mn.mc_pg[pre_top], mn.mc_ki[pre_top] - 1)),
+        &left, NULL, pp_txnid4chk(mn.mc_pg[pre_top], mc->mc_txn));
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    mdbx_cassert(mc, PAGETYPE(left) == PAGETYPE(mc->mc_pg[mc->mc_top]));
+  }
+  if (mn.mc_ki[pre_top] + 1u < page_numkeys(mn.mc_pg[pre_top])) {
+    rc = mdbx_page_get(
+        &mn, node_pgno(page_node(mn.mc_pg[pre_top], mn.mc_ki[pre_top] + 1)),
+        &right, NULL, pp_txnid4chk(mn.mc_pg[pre_top], mc->mc_txn));
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    mdbx_cassert(mc, PAGETYPE(right) == PAGETYPE(mc->mc_pg[mc->mc_top]));
+  }
+
+  const indx_t ki_top = mc->mc_ki[mc->mc_top];
+  const indx_t ki_pre_top = mn.mc_ki[pre_top];
+  const indx_t nkeys = (indx_t)page_numkeys(mn.mc_pg[mn.mc_top]);
+  if (left && page_room(left) > room_threshold &&
+      (!right || page_room(right) < page_room(left))) {
+    /* try merge with left */
+    mdbx_cassert(mc, page_numkeys(left) >= minkeys);
+    mn.mc_pg[mn.mc_top] = left;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top - 1;
+    mn.mc_ki[mn.mc_top] = (indx_t)(page_numkeys(left) - 1);
+    mc->mc_ki[mc->mc_top] = 0;
+    const indx_t new_ki = (indx_t)(ki_top + page_numkeys(left));
+    mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
+    /* We want mdbx_rebalance to find mn when doing fixups */
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_page_merge(mc, &mn));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      cursor_copy_internal(&mn, mc);
+      mc->mc_ki[mc->mc_top] = new_ki;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+  if (right && page_room(right) > room_threshold) {
+    /* try merge with right */
+    mdbx_cassert(mc, page_numkeys(right) >= minkeys);
+    mn.mc_pg[mn.mc_top] = right;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top + 1;
+    mn.mc_ki[mn.mc_top] = 0;
+    mc->mc_ki[mc->mc_top] = nkeys;
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_page_merge(&mn, mc));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      mc->mc_ki[mc->mc_top] = ki_top;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+  if (left && page_numkeys(left) > minkeys &&
+      (!right || page_numkeys(right) <= minkeys ||
+       page_room(right) > page_room(left))) {
+    /* try move from left */
+    mn.mc_pg[mn.mc_top] = left;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top - 1;
+    mn.mc_ki[mn.mc_top] = (indx_t)(page_numkeys(left) - 1);
+    mc->mc_ki[mc->mc_top] = 0;
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_node_move(&mn, mc, true));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      mc->mc_ki[mc->mc_top] = ki_top + 1;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+  if (right && page_numkeys(right) > minkeys) {
+    /* try move from right */
+    mn.mc_pg[mn.mc_top] = right;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top + 1;
+    mn.mc_ki[mn.mc_top] = 0;
+    mc->mc_ki[mc->mc_top] = nkeys;
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_node_move(&mn, mc, false));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      mc->mc_ki[mc->mc_top] = ki_top;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+
+  if (nkeys >= minkeys) {
+#if MDBX_DEBUG > 0
+    if (mdbx_audit_enabled())
+      return mdbx_cursor_check(mc, C_UPDATING);
+#endif
+    return MDBX_SUCCESS;
+  }
+
+  if (left && (!right || page_room(left) > page_room(right))) {
+    /* try merge with left */
+    mdbx_cassert(mc, page_numkeys(left) >= minkeys);
+    mn.mc_pg[mn.mc_top] = left;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top - 1;
+    mn.mc_ki[mn.mc_top] = (indx_t)(page_numkeys(left) - 1);
+    mc->mc_ki[mc->mc_top] = 0;
+    const indx_t new_ki = (indx_t)(ki_top + page_numkeys(left));
+    mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
+    /* We want mdbx_rebalance to find mn when doing fixups */
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_page_merge(mc, &mn));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      cursor_copy_internal(&mn, mc);
+      mc->mc_ki[mc->mc_top] = new_ki;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+  if (likely(right)) {
+    /* try merge with right */
+    mdbx_cassert(mc, page_numkeys(right) >= minkeys);
+    mn.mc_pg[mn.mc_top] = right;
+    mn.mc_ki[mn.mc_top - 1] = ki_pre_top + 1;
+    mn.mc_ki[mn.mc_top] = 0;
+    mc->mc_ki[mc->mc_top] = nkeys;
+    WITH_CURSOR_TRACKING(mn, rc = mdbx_page_merge(&mn, mc));
+    if (likely(rc != MDBX_RESULT_TRUE)) {
+      mc->mc_ki[mc->mc_top] = ki_top;
+      mdbx_cassert(mc, rc || page_numkeys(mc->mc_pg[mc->mc_top]) >= minkeys);
+      return rc;
+    }
+  }
+  return MDBX_PROBLEM;
+}
+
+static __cold int mdbx_page_check(MDBX_cursor *const mc,
+                                  const MDBX_page *const mp, unsigned options) {
+  options |= mc->mc_flags & (C_COPYING | C_UPDATING | C_RETIRING | C_SKIPORD);
+  MDBX_env *const env = mc->mc_txn->mt_env;
+  const unsigned nkeys = page_numkeys(mp);
+  char *const end_of_page = (char *)mp + env->me_psize;
+  if (unlikely(mp->mp_pgno < MIN_PAGENO || mp->mp_pgno > MAX_PAGENO))
+    return bad_page(mp, "invalid pgno (%u)\n", mp->mp_pgno);
+  if (IS_OVERFLOW(mp)) {
+    if (unlikely(mp->mp_pages < 1 && mp->mp_pages >= MAX_PAGENO / 2))
+      return bad_page(mp, "invalid overflow n-pages (%u)\n", mp->mp_pages);
+    if (unlikely(mp->mp_pgno + mp->mp_pages > mc->mc_txn->mt_next_pgno))
+      return bad_page(mp, "overflow page beyond (%u) next-pgno\n",
+                      mp->mp_pgno + mp->mp_pages);
+    return MDBX_SUCCESS;
+  }
+
+  int rc = MDBX_SUCCESS;
+  if ((options & C_UPDATING) == 0 || !IS_DIRTY(mp)) {
+    if (unlikely(nkeys < 2 && IS_BRANCH(mp)))
+      rc = bad_page(mp, "branch-page nkey (%u) < 2\n", nkeys);
+  }
+
+  MDBX_val here, prev = {0, 0};
+  for (unsigned i = 0; i < nkeys; ++i) {
+    if (IS_LEAF2(mp)) {
+      const size_t ksize = mp->mp_leaf2_ksize;
+      char *const key = page_leaf2key(mp, i, ksize);
+      if (unlikely(end_of_page < key + ksize)) {
+        rc = bad_page(mp, "leaf2-key beyond (%zu) page-end\n",
+                      key + ksize - end_of_page);
+        continue;
+      }
+
+      if ((options & C_COPYING) == 0) {
+        if (unlikely(ksize != mc->mc_dbx->md_klen_min)) {
+          if (unlikely(ksize < mc->mc_dbx->md_klen_min ||
+                       ksize > mc->mc_dbx->md_klen_max))
+            rc = bad_page(
+                mp, "leaf2-key size (%zu) <> min/max key-length (%zu/%zu)\n",
+                ksize, mc->mc_dbx->md_klen_min, mc->mc_dbx->md_klen_max);
+          else
+            mc->mc_dbx->md_klen_min = mc->mc_dbx->md_klen_max = ksize;
+        }
+        if ((options & C_SKIPORD) == 0) {
+          here.iov_len = ksize;
+          here.iov_base = key;
+          if (prev.iov_base && unlikely(mc->mc_dbx->md_cmp(&here, &prev) <= 0))
+            rc = bad_page(mp, "leaf2-key #%u wrong order\n", i);
+          prev = here;
+        }
+      }
+    } else {
+      const MDBX_node *const node = page_node(mp, i);
+      const char *node_end = (char *)node + NODESIZE;
+      if (unlikely(node_end > end_of_page)) {
+        rc = bad_page(mp, "node (%zu) beyond page-end\n",
+                      node_end - end_of_page);
+        continue;
+      }
+      if (IS_LEAF(mp) || i > 0) {
+        size_t ksize = node_ks(node);
+        char *key = node_key(node);
+        if (unlikely(end_of_page < key + ksize)) {
+          rc = bad_page(mp, "node-key (%zu) beyond page-end\n",
+                        key + ksize - end_of_page);
+          continue;
+        }
+
+        if ((options & C_COPYING) == 0) {
+          if (unlikely(ksize < mc->mc_dbx->md_klen_min ||
+                       ksize > mc->mc_dbx->md_klen_max))
+            rc = bad_page(
+                mp, "node-key size (%zu) <> min/max key-length (%zu/%zu)\n",
+                ksize, mc->mc_dbx->md_klen_min, mc->mc_dbx->md_klen_max);
+
+          if ((options & C_SKIPORD) == 0) {
+            here.iov_base = key;
+            here.iov_len = ksize;
+            if (prev.iov_base &&
+                unlikely(mc->mc_dbx->md_cmp(&here, &prev) <= 0))
+              rc = bad_page(mp, "node-key #%u wrong order\n", i);
+            prev = here;
+          }
+        }
+      }
+      if (IS_BRANCH(mp)) {
+        if ((options & C_RETIRING) == 0) {
+          const pgno_t ref = node_pgno(node);
+          if (unlikely(ref < MIN_PAGENO || ref >= mc->mc_txn->mt_next_pgno))
+            rc = bad_page(mp, "branch-node wrong pgno (%u)\n", ref);
+        }
+        continue;
+      }
+
+      switch (node_flags(node)) {
+      default:
+        rc = bad_page(mp, "invalid node flags (%u)\n", node_flags(node));
+        break;
+      case F_BIGDATA /* data on large-page */:
+      case 0 /* usual */:
+      case F_SUBDATA /* sub-db */:
+      case F_SUBDATA | F_DUPDATA /* dupsorted sub-tree */:
+      case F_DUPDATA /* short sub-page */:
+        break;
+      }
+
+      if (node_flags(node) & F_BIGDATA) {
+        const size_t dsize = node_ds(node);
+        if ((options & C_COPYING) == 0) {
+          if (unlikely(dsize <= mc->mc_dbx->md_vlen_min ||
+                       dsize > mc->mc_dbx->md_vlen_max))
+            rc = bad_page(
+                mp,
+                "big-node data size (%zu) <> min/max value-length (%zu/%zu)\n",
+                dsize, mc->mc_dbx->md_vlen_min, mc->mc_dbx->md_vlen_max);
+        }
+        if ((options & C_RETIRING) == 0) {
+          MDBX_page *lp;
+          int err = mdbx_page_get(mc, node_largedata_pgno(node), &lp, NULL,
+                                  pp_txnid4chk(mp, mc->mc_txn));
+          if (unlikely(err != MDBX_SUCCESS))
+            return err;
+          if (unlikely(!IS_OVERFLOW(lp))) {
+            rc = bad_page(mp, "big-node refs to non-overflow page (%u)\n",
+                          lp->mp_pgno);
+            continue;
+          }
+          if (unlikely(number_of_ovpages(env, dsize) > lp->mp_pages))
+            rc =
+                bad_page(mp, "big-node size (%zu) mismatch n-pages size (%u)\n",
+                         dsize, lp->mp_pages);
+        }
+        continue;
+      }
+
+      const size_t dsize = node_ds(node);
+      const char *const data = node_data(node);
+      if (unlikely(end_of_page < data + dsize)) {
+        rc = bad_page(mp,
+                      "node-data(%u of %u, %zu bytes) beyond (%zu) page-end\n",
+                      i, nkeys, dsize, data + dsize - end_of_page);
+        continue;
+      }
+
+      switch (node_flags(node)) {
+      default:
+        /* wrong, but already handled */
+        continue;
+      case 0 /* usual */:
+        if ((options & C_COPYING) == 0) {
+          if (unlikely(dsize < mc->mc_dbx->md_vlen_min ||
+                       dsize > mc->mc_dbx->md_vlen_max)) {
+            rc = bad_page(
+                mp, "node-data size (%zu) <> min/max value-length (%zu/%zu)\n",
+                dsize, mc->mc_dbx->md_vlen_min, mc->mc_dbx->md_vlen_max);
+            continue;
+          }
+        }
+        break;
+      case F_SUBDATA /* sub-db */:
+        if (unlikely(dsize != sizeof(MDBX_db))) {
+          rc = bad_page(mp, "invalid sub-db record size (%zu)\n", dsize);
+          continue;
+        }
+        break;
+      case F_SUBDATA | F_DUPDATA /* dupsorted sub-tree */:
+        if (unlikely(dsize != sizeof(MDBX_db))) {
+          rc = bad_page(mp, "invalid nested-db record size (%zu)\n", dsize);
+          continue;
+        }
+        break;
+      case F_DUPDATA /* short sub-page */:
+        if (unlikely(dsize <= PAGEHDRSZ)) {
+          rc = bad_page(mp, "invalid nested-page record size (%zu)\n", dsize);
+          continue;
+        } else {
+          const MDBX_page *const sp = (MDBX_page *)data;
+          const char *const end_of_subpage = data + dsize;
+          const int nsubkeys = page_numkeys(sp);
+          switch (sp->mp_flags & ~P_DIRTY /* ignore for sub-pages */) {
+          case P_LEAF | P_SUBP:
+          case P_LEAF | P_LEAF2 | P_SUBP:
+            break;
+          default:
+            rc = bad_page(mp, "invalid nested-page flags (%u)\n", sp->mp_flags);
+            continue;
+          }
+
+          MDBX_val sub_here, sub_prev = {0, 0};
+          for (int j = 0; j < nsubkeys; j++) {
+            if (IS_LEAF2(sp)) {
+              /* LEAF2 pages have no mp_ptrs[] or node headers */
+              size_t sub_ksize = sp->mp_leaf2_ksize;
+              char *sub_key = page_leaf2key(sp, j, sub_ksize);
+              if (unlikely(end_of_subpage < sub_key + sub_ksize)) {
+                rc = bad_page(mp, "nested-leaf2-key beyond (%zu) nested-page\n",
+                              sub_key + sub_ksize - end_of_subpage);
+                continue;
+              }
+
+              if ((options & C_COPYING) == 0) {
+                if (unlikely(sub_ksize != mc->mc_dbx->md_vlen_min)) {
+                  if (unlikely(sub_ksize < mc->mc_dbx->md_vlen_min ||
+                               sub_ksize > mc->mc_dbx->md_vlen_max)) {
+                    rc = bad_page(mp,
+                                  "nested-leaf2-key size (%zu) <> min/max "
+                                  "value-length (%zu/%zu)\n",
+                                  sub_ksize, mc->mc_dbx->md_vlen_min,
+                                  mc->mc_dbx->md_vlen_max);
+                    continue;
+                  }
+                  mc->mc_dbx->md_vlen_min = mc->mc_dbx->md_vlen_max = sub_ksize;
+                }
+                if ((options & C_SKIPORD) == 0) {
+                  sub_here.iov_len = sub_ksize;
+                  sub_here.iov_base = sub_key;
+                  if (sub_prev.iov_base &&
+                      unlikely(mc->mc_dbx->md_dcmp(&sub_prev, &sub_here) >= 0))
+                    rc = bad_page(mp, "nested-leaf2-key #%u wrong order\n", j);
+                  sub_prev = sub_here;
+                }
+              }
+            } else {
+              const MDBX_node *const sub_node = page_node(sp, j);
+              const char *sub_node_end = (char *)sub_node + NODESIZE;
+              if (unlikely(sub_node_end > end_of_subpage)) {
+                rc = bad_page(mp, "nested-node beyond (%zu) nested-page\n",
+                              end_of_subpage - sub_node_end);
+                continue;
+              }
+              if (unlikely(node_flags(sub_node) != 0))
+                rc = bad_page(mp, "nested-node invalid flags (%u)\n",
+                              node_flags(sub_node));
+
+              size_t sub_ksize = node_ks(sub_node);
+              char *sub_key = node_key(sub_node);
+              size_t sub_dsize = node_ds(sub_node);
+              /* char *sub_data = node_data(sub_node); */
+
+              if ((options & C_COPYING) == 0) {
+                if (unlikely(sub_ksize < mc->mc_dbx->md_vlen_min ||
+                             sub_ksize > mc->mc_dbx->md_vlen_max))
+                  rc = bad_page(mp,
+                                "nested-node-key size (%zu) <> min/max "
+                                "value-length (%zu/%zu)\n",
+                                sub_ksize, mc->mc_dbx->md_vlen_min,
+                                mc->mc_dbx->md_vlen_max);
+
+                if ((options & C_SKIPORD) == 0) {
+                  sub_here.iov_len = sub_ksize;
+                  sub_here.iov_base = sub_key;
+                  if (sub_prev.iov_base &&
+                      unlikely(mc->mc_dbx->md_dcmp(&sub_prev, &sub_here) >= 0))
+                    rc = bad_page(mp, "nested-node-key #%u wrong order\n", j);
+                  sub_prev = sub_here;
+                }
+              }
+              if (unlikely(sub_dsize != 0))
+                rc = bad_page(mp, "nested-node non-empty data size (%zu)\n",
+                              sub_dsize);
+              if (unlikely(end_of_subpage < sub_key + sub_ksize))
+                rc = bad_page(mp, "nested-node-key beyond (%zu) nested-page\n",
+                              sub_key + sub_ksize - end_of_subpage);
+            }
+          }
+        }
+        break;
+      }
+    }
+  }
+  return rc;
+}
+
+static __cold int mdbx_cursor_check(MDBX_cursor *mc, unsigned options) {
+  mdbx_tassert(mc->mc_txn, mc->mc_txn->mt_parent ||
+                               mc->mc_txn->tw.dirtyroom +
+                                       mc->mc_txn->tw.dirtylist->length ==
+                                   mc->mc_txn->mt_env->me_options.dp_limit);
+  mdbx_cassert(mc, mc->mc_top == mc->mc_snum - 1);
+  if (unlikely(mc->mc_top != mc->mc_snum - 1))
+    return MDBX_CURSOR_FULL;
+  mdbx_cassert(mc, (options & C_UPDATING) ? mc->mc_snum <= mc->mc_db->md_depth
+                                          : mc->mc_snum == mc->mc_db->md_depth);
+  if (unlikely((options & C_UPDATING) ? mc->mc_snum > mc->mc_db->md_depth
+                                      : mc->mc_snum != mc->mc_db->md_depth))
+    return MDBX_CURSOR_FULL;
+
+  for (int n = 0; n < (int)mc->mc_snum; ++n) {
+    MDBX_page *mp = mc->mc_pg[n];
+    const unsigned nkeys = page_numkeys(mp);
+    const bool expect_branch = (n < mc->mc_db->md_depth - 1) ? true : false;
+    const bool expect_nested_leaf =
+        (n + 1 == mc->mc_db->md_depth - 1) ? true : false;
+    const bool branch = IS_BRANCH(mp) ? true : false;
+    mdbx_cassert(mc, branch == expect_branch);
+    if (unlikely(branch != expect_branch))
+      return MDBX_CURSOR_FULL;
+    if ((options & C_UPDATING) == 0) {
+      mdbx_cassert(mc,
+                   nkeys > mc->mc_ki[n] || (!branch && nkeys == mc->mc_ki[n] &&
+                                            (mc->mc_flags & C_EOF) != 0));
+      if (unlikely(nkeys <= mc->mc_ki[n] &&
+                   !(!branch && nkeys == mc->mc_ki[n] &&
+                     (mc->mc_flags & C_EOF) != 0)))
+        return MDBX_CURSOR_FULL;
+    } else {
+      mdbx_cassert(mc, nkeys + 1 >= mc->mc_ki[n]);
+      if (unlikely(nkeys + 1 < mc->mc_ki[n]))
+        return MDBX_CURSOR_FULL;
+    }
+
+    int err = mdbx_page_check(mc, mp, options);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+
+    for (unsigned i = 0; i < nkeys; ++i) {
+      if (branch) {
+        MDBX_node *node = page_node(mp, i);
+        mdbx_cassert(mc, node_flags(node) == 0);
+        if (unlikely(node_flags(node) != 0))
+          return MDBX_CURSOR_FULL;
+        pgno_t pgno = node_pgno(node);
+        MDBX_page *np;
+        int rc =
+            mdbx_page_get(mc, pgno, &np, NULL, pp_txnid4chk(mp, mc->mc_txn));
+        mdbx_cassert(mc, rc == MDBX_SUCCESS);
+        if (unlikely(rc != MDBX_SUCCESS))
+          return rc;
+        const bool nested_leaf = IS_LEAF(np) ? true : false;
+        mdbx_cassert(mc, nested_leaf == expect_nested_leaf);
+        if (unlikely(nested_leaf != expect_nested_leaf))
+          return MDBX_CURSOR_FULL;
+        err = mdbx_page_check(mc, np, options);
+        if (unlikely(err != MDBX_SUCCESS))
+          return err;
+      }
+    }
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Complete a delete operation started by mdbx_cursor_del(). */
+static int mdbx_cursor_del0(MDBX_cursor *mc) {
+  int rc;
+  MDBX_page *mp;
+  indx_t ki;
+  unsigned nkeys;
+  MDBX_dbi dbi = mc->mc_dbi;
+
+  mdbx_cassert(mc, cursor_is_tracked(mc));
+  mdbx_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+  ki = mc->mc_ki[mc->mc_top];
+  mp = mc->mc_pg[mc->mc_top];
+  mdbx_node_del(mc, mc->mc_db->md_xsize);
+  mc->mc_db->md_entries--;
+
+  /* Adjust other cursors pointing to mp */
+  for (MDBX_cursor *m2 = mc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+    MDBX_cursor *m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+    if (m3 == mc || !(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+      continue;
+    if (m3->mc_snum < mc->mc_snum)
+      continue;
+    if (m3->mc_pg[mc->mc_top] == mp) {
+      if (m3->mc_ki[mc->mc_top] == ki) {
+        m3->mc_flags |= C_DEL;
+        if (mc->mc_db->md_flags & MDBX_DUPSORT) {
+          /* Sub-cursor referred into dataset which is gone */
+          m3->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
+        }
+        continue;
+      } else if (m3->mc_ki[mc->mc_top] > ki) {
+        m3->mc_ki[mc->mc_top]--;
+      }
+      if (XCURSOR_INITED(m3))
+        XCURSOR_REFRESH(m3, m3->mc_pg[mc->mc_top], m3->mc_ki[mc->mc_top]);
+    }
+  }
+
+  rc = mdbx_rebalance(mc);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto bailout;
+
+  if (unlikely(!mc->mc_snum)) {
+    /* DB is totally empty now, just bail out.
+     * Other cursors adjustments were already done
+     * by mdbx_rebalance and aren't needed here. */
+    mdbx_cassert(mc, mc->mc_db->md_entries == 0 && mc->mc_db->md_depth == 0 &&
+                         mc->mc_db->md_root == P_INVALID);
+    mc->mc_flags |= C_EOF;
+    return MDBX_SUCCESS;
+  }
+
+  ki = mc->mc_ki[mc->mc_top];
+  mp = mc->mc_pg[mc->mc_top];
+  mdbx_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+  nkeys = page_numkeys(mp);
+  mdbx_cassert(mc, (mc->mc_db->md_entries > 0 && nkeys > 0) ||
+                       ((mc->mc_flags & C_SUB) && mc->mc_db->md_entries == 0 &&
+                        nkeys == 0));
+
+  /* Adjust this and other cursors pointing to mp */
+  for (MDBX_cursor *m2 = mc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+    MDBX_cursor *m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+    if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+      continue;
+    if (m3->mc_snum < mc->mc_snum)
+      continue;
+    if (m3->mc_pg[mc->mc_top] == mp) {
+      /* if m3 points past last node in page, find next sibling */
+      if (m3->mc_ki[mc->mc_top] >= nkeys) {
+        rc = mdbx_cursor_sibling(m3, SIBLING_RIGHT);
+        if (rc == MDBX_NOTFOUND) {
+          m3->mc_flags |= C_EOF;
+          rc = MDBX_SUCCESS;
+          continue;
+        }
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+      if (m3->mc_ki[mc->mc_top] >= ki ||
+          /* moved to right sibling */ m3->mc_pg[mc->mc_top] != mp) {
+        if (m3->mc_xcursor && !(m3->mc_flags & C_EOF)) {
+          MDBX_node *node =
+              page_node(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
+          /* If this node has dupdata, it may need to be reinited
+           * because its data has moved.
+           * If the xcursor was not inited it must be reinited.
+           * Else if node points to a subDB, nothing is needed. */
+          if (node_flags(node) & F_DUPDATA) {
+            if (m3->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+              if (!(node_flags(node) & F_SUBDATA))
+                m3->mc_xcursor->mx_cursor.mc_pg[0] = node_data(node);
+            } else {
+              rc = mdbx_xcursor_init1(m3, node, m3->mc_pg[m3->mc_top]);
+              if (unlikely(rc != MDBX_SUCCESS))
+                goto bailout;
+              rc = mdbx_cursor_first(&m3->mc_xcursor->mx_cursor, NULL, NULL);
+              if (unlikely(rc != MDBX_SUCCESS))
+                goto bailout;
+            }
+          }
+          m3->mc_xcursor->mx_cursor.mc_flags |= C_DEL;
+        }
+        m3->mc_flags |= C_DEL;
+      }
+    }
+  }
+
+  mdbx_cassert(mc, rc == MDBX_SUCCESS);
+  if (mdbx_audit_enabled())
+    rc = mdbx_cursor_check(mc, 0);
+  return rc;
+
+bailout:
+  mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+  return rc;
+}
+
+int mdbx_del(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+             const MDBX_val *data) {
+  int rc = check_txn_rw(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(txn->mt_flags & (MDBX_TXN_RDONLY | MDBX_TXN_BLOCKED)))
+    return (txn->mt_flags & MDBX_TXN_RDONLY) ? MDBX_EACCESS : MDBX_BAD_TXN;
+
+  return mdbx_del0(txn, dbi, key, data, 0);
+}
+
+static int mdbx_del0(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                     const MDBX_val *data, unsigned flags) {
+  MDBX_cursor_couple cx;
+  MDBX_cursor_op op;
+  MDBX_val rdata;
+  int rc, exact = 0;
+  DKBUF;
+
+  mdbx_debug("====> delete db %u key [%s], data [%s]", dbi, DKEY(key),
+             DVAL(data));
+
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (data) {
+    op = MDBX_GET_BOTH;
+    rdata = *data;
+    data = &rdata;
+  } else {
+    op = MDBX_SET;
+    flags |= MDBX_ALLDUPS;
+  }
+  rc =
+      mdbx_cursor_set(&cx.outer, (MDBX_val *)key, (MDBX_val *)data, op, &exact);
+  if (likely(rc == MDBX_SUCCESS)) {
+    /* let mdbx_page_split know about this cursor if needed:
+     * delete will trigger a rebalance; if it needs to move
+     * a node from one page to another, it will have to
+     * update the parent's separator key(s). If the new sepkey
+     * is larger than the current one, the parent page may
+     * run out of space, triggering a split. We need this
+     * cursor to be consistent until the end of the rebalance. */
+    cx.outer.mc_next = txn->tw.cursors[dbi];
+    txn->tw.cursors[dbi] = &cx.outer;
+    rc = mdbx_cursor_del(&cx.outer, flags);
+    txn->tw.cursors[dbi] = cx.outer.mc_next;
+  }
+  return rc;
+}
+
+/* Split a page and insert a new node.
+ * Set MDBX_TXN_ERROR on failure.
+ * [in,out] mc Cursor pointing to the page and desired insertion index.
+ * The cursor will be updated to point to the actual page and index where
+ * the node got inserted after the split.
+ * [in] newkey The key for the newly inserted node.
+ * [in] newdata The data for the newly inserted node.
+ * [in] newpgno The page number, if the new node is a branch node.
+ * [in] nflags The NODE_ADD_FLAGS for the new node.
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_page_split(MDBX_cursor *mc, const MDBX_val *newkey,
+                           MDBX_val *newdata, pgno_t newpgno, unsigned nflags) {
+  unsigned flags;
+  int rc = MDBX_SUCCESS, foliage = 0, did_split = 0;
+  pgno_t pgno = 0;
+  unsigned i, ptop;
+  MDBX_env *env = mc->mc_txn->mt_env;
+  MDBX_val sepkey, rkey, xdata;
+  MDBX_page *copy = NULL;
+  MDBX_page *rp, *pp;
+  MDBX_cursor mn;
+  DKBUF;
+
+  MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  unsigned newindx = mc->mc_ki[mc->mc_top];
+  unsigned nkeys = page_numkeys(mp);
+  if (mdbx_audit_enabled()) {
+    rc = mdbx_cursor_check(mc, C_UPDATING);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  mdbx_cassert(mc,
+               nkeys >= (unsigned)(IS_BRANCH(mp) ? MDBX_MINKEYS * 2 - 1 : 1));
+  mdbx_debug("-----> splitting %s page %" PRIaPGNO
+             " and adding [%s] at index %i/%i",
+             IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno, DKEY(newkey),
+             mc->mc_ki[mc->mc_top], nkeys);
+
+  /* Create a right sibling. */
+  if ((rc = mdbx_page_new(mc, mp->mp_flags, 1, &rp)))
+    return rc;
+  rp->mp_leaf2_ksize = mp->mp_leaf2_ksize;
+  mdbx_debug("new right sibling: page %" PRIaPGNO, rp->mp_pgno);
+
+  /* Usually when splitting the root page, the cursor
+   * height is 1. But when called from mdbx_update_key,
+   * the cursor height may be greater because it walks
+   * up the stack while finding the branch slot to update. */
+  if (mc->mc_top < 1) {
+    if ((rc = mdbx_page_new(mc, P_BRANCH, 1, &pp)))
+      goto done;
+    /* shift current top to make room for new parent */
+    mdbx_cassert(mc, mc->mc_snum < 2 && mc->mc_db->md_depth > 0);
+    mc->mc_pg[2] = mc->mc_pg[1];
+    mc->mc_ki[2] = mc->mc_ki[1];
+    mc->mc_pg[1] = mc->mc_pg[0];
+    mc->mc_ki[1] = mc->mc_ki[0];
+    mc->mc_pg[0] = pp;
+    mc->mc_ki[0] = 0;
+    mc->mc_db->md_root = pp->mp_pgno;
+    mdbx_debug("root split! new root = %" PRIaPGNO, pp->mp_pgno);
+    foliage = mc->mc_db->md_depth++;
+
+    /* Add left (implicit) pointer. */
+    if (unlikely((rc = mdbx_node_add_branch(mc, 0, NULL, mp->mp_pgno)) !=
+                 MDBX_SUCCESS)) {
+      /* undo the pre-push */
+      mc->mc_pg[0] = mc->mc_pg[1];
+      mc->mc_ki[0] = mc->mc_ki[1];
+      mc->mc_db->md_root = mp->mp_pgno;
+      mc->mc_db->md_depth--;
+      goto done;
+    }
+    mc->mc_snum++;
+    mc->mc_top++;
+    ptop = 0;
+  } else {
+    ptop = mc->mc_top - 1;
+    mdbx_debug("parent branch page is %" PRIaPGNO, mc->mc_pg[ptop]->mp_pgno);
+  }
+
+  cursor_copy_internal(mc, &mn);
+  mn.mc_xcursor = NULL;
+  mn.mc_pg[mn.mc_top] = rp;
+  mn.mc_ki[mn.mc_top] = 0;
+  mn.mc_ki[ptop] = mc->mc_ki[ptop] + 1;
+
+  unsigned split_indx;
+  if (nflags & MDBX_APPEND) {
+    mn.mc_ki[mn.mc_top] = 0;
+    sepkey = *newkey;
+    split_indx = newindx;
+    nkeys = 0;
+  } else {
+    split_indx = (nkeys + 1) / 2;
+    if (IS_LEAF2(rp)) {
+      char *split, *ins;
+      unsigned lsize, rsize, ksize;
+      /* Move half of the keys to the right sibling */
+      const int x = mc->mc_ki[mc->mc_top] - split_indx;
+      ksize = mc->mc_db->md_xsize;
+      split = page_leaf2key(mp, split_indx, ksize);
+      rsize = (nkeys - split_indx) * ksize;
+      lsize = (nkeys - split_indx) * sizeof(indx_t);
+      mdbx_cassert(mc, mp->mp_lower >= lsize);
+      mp->mp_lower -= (indx_t)lsize;
+      mdbx_cassert(mc, rp->mp_lower + lsize <= UINT16_MAX);
+      rp->mp_lower += (indx_t)lsize;
+      mdbx_cassert(mc, mp->mp_upper + rsize - lsize <= UINT16_MAX);
+      mp->mp_upper += (indx_t)(rsize - lsize);
+      mdbx_cassert(mc, rp->mp_upper >= rsize - lsize);
+      rp->mp_upper -= (indx_t)(rsize - lsize);
+      sepkey.iov_len = ksize;
+      if (newindx == split_indx) {
+        sepkey.iov_base = newkey->iov_base;
+      } else {
+        sepkey.iov_base = split;
+      }
+      if (x < 0) {
+        mdbx_cassert(mc, ksize >= sizeof(indx_t));
+        ins = page_leaf2key(mp, mc->mc_ki[mc->mc_top], ksize);
+        memcpy(rp->mp_ptrs, split, rsize);
+        sepkey.iov_base = rp->mp_ptrs;
+        memmove(ins + ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
+        memcpy(ins, newkey->iov_base, ksize);
+        mdbx_cassert(mc, UINT16_MAX - mp->mp_lower >= (int)sizeof(indx_t));
+        mp->mp_lower += sizeof(indx_t);
+        mdbx_cassert(mc, mp->mp_upper >= ksize - sizeof(indx_t));
+        mp->mp_upper -= (indx_t)(ksize - sizeof(indx_t));
+      } else {
+        memcpy(rp->mp_ptrs, split, x * ksize);
+        ins = page_leaf2key(rp, x, ksize);
+        memcpy(ins, newkey->iov_base, ksize);
+        memcpy(ins + ksize, split + x * ksize, rsize - x * ksize);
+        mdbx_cassert(mc, UINT16_MAX - rp->mp_lower >= (int)sizeof(indx_t));
+        rp->mp_lower += sizeof(indx_t);
+        mdbx_cassert(mc, rp->mp_upper >= ksize - sizeof(indx_t));
+        rp->mp_upper -= (indx_t)(ksize - sizeof(indx_t));
+        mdbx_cassert(mc, x <= (int)UINT16_MAX);
+        mc->mc_ki[mc->mc_top] = (indx_t)x;
+      }
+    } else {
+      /* Maximum free space in an empty page */
+      const unsigned pmax = page_space(env);
+      const size_t nsize = IS_LEAF(mp) ? leaf_size(env, newkey, newdata)
+                                       : branch_size(env, newkey);
+
+      /* grab a page to hold a temporary copy */
+      copy = mdbx_page_malloc(mc->mc_txn, 1);
+      if (unlikely(copy == NULL)) {
+        rc = MDBX_ENOMEM;
+        goto done;
+      }
+      copy->mp_pgno = mp->mp_pgno;
+      copy->mp_flags = mp->mp_flags;
+      copy->mp_txnid = INVALID_TXNID;
+      copy->mp_lower = 0;
+      copy->mp_upper = (indx_t)page_space(env);
+
+      /* prepare to insert */
+      for (unsigned j = i = 0; i < nkeys; i++) {
+        if (i == newindx)
+          copy->mp_ptrs[j++] = 0;
+        copy->mp_ptrs[j++] = mp->mp_ptrs[i];
+      }
+
+      /* When items are relatively large the split point needs
+       * to be checked, because being off-by-one will make the
+       * difference between success or failure in mdbx_node_add.
+       *
+       * It's also relevant if a page happens to be laid out
+       * such that one half of its nodes are all "small" and
+       * the other half of its nodes are "large." If the new
+       * item is also "large" and falls on the half with
+       * "large" nodes, it also may not fit.
+       *
+       * As a final tweak, if the new item goes on the last
+       * spot on the page (and thus, onto the new page), bias
+       * the split so the new page is emptier than the old page.
+       * This yields better packing during sequential inserts. */
+      if (nkeys < 32 || nsize > pmax / 16 || newindx >= nkeys) {
+        /* Find split point */
+        int dir;
+        size_t psize = 0;
+        unsigned k;
+        if (newindx <= split_indx || newindx >= nkeys) {
+          i = 0;
+          dir = 1;
+          k = (newindx >= nkeys) ? nkeys : split_indx + 1 + IS_LEAF(mp);
+          split_indx = k - 1;
+        } else {
+          i = nkeys;
+          dir = -1;
+          k = split_indx - 1;
+          split_indx += 1;
+        }
+        do {
+          if (i == newindx) {
+            psize += nsize;
+          } else {
+            MDBX_node *node =
+                (MDBX_node *)((char *)mp + copy->mp_ptrs[i] + PAGEHDRSZ);
+            psize += NODESIZE + node_ks(node) + sizeof(indx_t);
+            if (IS_LEAF(mp))
+              psize += F_ISSET(node_flags(node), F_BIGDATA) ? sizeof(pgno_t)
+                                                            : node_ds(node);
+            psize = EVEN(psize);
+          }
+          if (psize > pmax) {
+            split_indx = i + (dir < 0);
+            break;
+          }
+          i += dir;
+        } while (i != k);
+      }
+
+      if (split_indx == newindx) {
+        sepkey.iov_len = newkey->iov_len;
+        sepkey.iov_base = newkey->iov_base;
+      } else {
+        MDBX_node *node =
+            (MDBX_node *)((char *)mp + copy->mp_ptrs[split_indx] + PAGEHDRSZ);
+        sepkey.iov_len = node_ks(node);
+        sepkey.iov_base = node_key(node);
+      }
+    }
+  }
+
+  mdbx_debug("separator is %d [%s]", split_indx, DKEY(&sepkey));
+  if (mdbx_audit_enabled()) {
+    rc = mdbx_cursor_check(mc, C_UPDATING);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto done;
+    rc = mdbx_cursor_check(&mn, C_UPDATING);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto done;
+  }
+
+  /* Copy separator key to the parent. */
+  if (page_room(mn.mc_pg[ptop]) < branch_size(env, &sepkey)) {
+    const int snum = mc->mc_snum;
+    const int depth = mc->mc_db->md_depth;
+    mn.mc_snum--;
+    mn.mc_top--;
+    did_split = 1;
+    /* We want other splits to find mn when doing fixups */
+    WITH_CURSOR_TRACKING(
+        mn, rc = mdbx_page_split(&mn, &sepkey, NULL, rp->mp_pgno, 0));
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto done;
+    mdbx_cassert(mc, (int)mc->mc_snum - snum == mc->mc_db->md_depth - depth);
+    if (mdbx_audit_enabled()) {
+      rc = mdbx_cursor_check(mc, C_UPDATING);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto done;
+    }
+
+    /* root split? */
+    ptop += mc->mc_snum - snum;
+
+    /* Right page might now have changed parent.
+     * Check if left page also changed parent. */
+    if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+        mc->mc_ki[ptop] >= page_numkeys(mc->mc_pg[ptop])) {
+      for (i = 0; i < ptop; i++) {
+        mc->mc_pg[i] = mn.mc_pg[i];
+        mc->mc_ki[i] = mn.mc_ki[i];
+      }
+      mc->mc_pg[ptop] = mn.mc_pg[ptop];
+      if (mn.mc_ki[ptop]) {
+        mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
+      } else {
+        /* find right page's left sibling */
+        mc->mc_ki[ptop] = mn.mc_ki[ptop];
+        rc = mdbx_cursor_sibling(mc, SIBLING_LEFT);
+      }
+    }
+  } else {
+    mn.mc_top--;
+    rc = mdbx_node_add_branch(&mn, mn.mc_ki[ptop], &sepkey, rp->mp_pgno);
+    mn.mc_top++;
+  }
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc == MDBX_NOTFOUND) /* improper mdbx_cursor_sibling() result */ {
+      mdbx_error("unexpected %s", "MDBX_NOTFOUND");
+      rc = MDBX_PROBLEM;
+    }
+    goto done;
+  }
+
+  if (nflags & MDBX_APPEND) {
+    mc->mc_pg[mc->mc_top] = rp;
+    mc->mc_ki[mc->mc_top] = 0;
+    switch (PAGETYPE(rp)) {
+    case P_BRANCH: {
+      mdbx_cassert(mc, (nflags & (F_BIGDATA | F_SUBDATA | F_DUPDATA)) == 0);
+      mdbx_cassert(mc, newpgno != 0 && newpgno != P_INVALID);
+      rc = mdbx_node_add_branch(mc, 0, newkey, newpgno);
+    } break;
+    case P_LEAF: {
+      mdbx_cassert(mc, newpgno == 0 || newpgno == P_INVALID);
+      rc = mdbx_node_add_leaf(mc, 0, newkey, newdata, nflags);
+    } break;
+    case P_LEAF | P_LEAF2: {
+      mdbx_cassert(mc, (nflags & (F_BIGDATA | F_SUBDATA | F_DUPDATA)) == 0);
+      mdbx_cassert(mc, newpgno == 0 || newpgno == P_INVALID);
+      rc = mdbx_node_add_leaf2(mc, 0, newkey);
+    } break;
+    default:
+      rc = bad_page(rp, "wrong page-type %u\n", PAGETYPE(rp));
+    }
+    if (rc)
+      goto done;
+    for (i = 0; i < mc->mc_top; i++)
+      mc->mc_ki[i] = mn.mc_ki[i];
+  } else if (!IS_LEAF2(mp)) {
+    /* Move nodes */
+    mc->mc_pg[mc->mc_top] = rp;
+    i = split_indx;
+    indx_t n = 0;
+    do {
+      MDBX_val *rdata = NULL;
+      if (i == newindx) {
+        rkey.iov_base = newkey->iov_base;
+        rkey.iov_len = newkey->iov_len;
+        if (IS_LEAF(mp)) {
+          rdata = newdata;
+        } else
+          pgno = newpgno;
+        flags = nflags;
+        /* Update index for the new key. */
+        mc->mc_ki[mc->mc_top] = n;
+      } else {
+        MDBX_node *node =
+            (MDBX_node *)((char *)mp + copy->mp_ptrs[i] + PAGEHDRSZ);
+        rkey.iov_base = node_key(node);
+        rkey.iov_len = node_ks(node);
+        if (IS_LEAF(mp)) {
+          xdata.iov_base = node_data(node);
+          xdata.iov_len = node_ds(node);
+          rdata = &xdata;
+        } else
+          pgno = node_pgno(node);
+        flags = node_flags(node);
+      }
+
+      switch (PAGETYPE(rp)) {
+      case P_BRANCH: {
+        mdbx_cassert(mc, 0 == (uint16_t)flags);
+        if (n == 0) {
+          /* First branch index doesn't need key data. */
+          rkey.iov_len = 0;
+        }
+        rc = mdbx_node_add_branch(mc, n, &rkey, pgno);
+      } break;
+      case P_LEAF: {
+        mdbx_cassert(mc, pgno == 0);
+        mdbx_cassert(mc, rdata != NULL);
+        rc = mdbx_node_add_leaf(mc, n, &rkey, rdata, flags);
+      } break;
+      /* case P_LEAF | P_LEAF2: {
+        mdbx_cassert(mc, (nflags & (F_BIGDATA | F_SUBDATA | F_DUPDATA)) == 0);
+        mdbx_cassert(mc, gno == 0);
+        rc = mdbx_node_add_leaf2(mc, n, &rkey);
+      } break; */
+      default:
+        rc = bad_page(rp, "wrong page-type %u\n", PAGETYPE(rp));
+      }
+      if (rc)
+        goto done;
+
+      if (i == nkeys) {
+        i = 0;
+        n = 0;
+        mc->mc_pg[mc->mc_top] = copy;
+      } else {
+        i++;
+        n++;
+      }
+    } while (i != split_indx);
+
+    nkeys = page_numkeys(copy);
+    for (i = 0; i < nkeys; i++)
+      mp->mp_ptrs[i] = copy->mp_ptrs[i];
+    mp->mp_lower = copy->mp_lower;
+    mp->mp_upper = copy->mp_upper;
+    memcpy(page_node(mp, nkeys - 1), page_node(copy, nkeys - 1),
+           env->me_psize - copy->mp_upper - PAGEHDRSZ);
+
+    /* reset back to original page */
+    if (newindx < split_indx) {
+      mc->mc_pg[mc->mc_top] = mp;
+    } else {
+      mc->mc_pg[mc->mc_top] = rp;
+      mc->mc_ki[ptop]++;
+      /* Make sure mc_ki is still valid. */
+      if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+          mc->mc_ki[ptop] >= page_numkeys(mc->mc_pg[ptop])) {
+        for (i = 0; i <= ptop; i++) {
+          mc->mc_pg[i] = mn.mc_pg[i];
+          mc->mc_ki[i] = mn.mc_ki[i];
+        }
+      }
+    }
+    if (nflags & MDBX_RESERVE) {
+      MDBX_node *node = page_node(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+      if (!(node_flags(node) & F_BIGDATA))
+        newdata->iov_base = node_data(node);
+    }
+  } else {
+    if (newindx >= split_indx) {
+      mc->mc_pg[mc->mc_top] = rp;
+      mc->mc_ki[ptop]++;
+      /* Make sure mc_ki is still valid. */
+      if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+          mc->mc_ki[ptop] >= page_numkeys(mc->mc_pg[ptop])) {
+        for (i = 0; i <= ptop; i++) {
+          mc->mc_pg[i] = mn.mc_pg[i];
+          mc->mc_ki[i] = mn.mc_ki[i];
+        }
+      }
+    }
+  }
+
+  {
+    /* Adjust other cursors pointing to mp */
+    MDBX_cursor *m2, *m3;
+    MDBX_dbi dbi = mc->mc_dbi;
+    nkeys = page_numkeys(mp);
+
+    for (m2 = mc->mc_txn->tw.cursors[dbi]; m2; m2 = m2->mc_next) {
+      m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+      if (m3 == mc)
+        continue;
+      if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+        continue;
+      if (foliage) {
+        int k;
+        /* sub cursors may be on different DB */
+        if (m3->mc_pg[0] != mp)
+          continue;
+        /* root split */
+        for (k = foliage; k >= 0; k--) {
+          m3->mc_ki[k + 1] = m3->mc_ki[k];
+          m3->mc_pg[k + 1] = m3->mc_pg[k];
+        }
+        m3->mc_ki[0] = (m3->mc_ki[0] >= nkeys) ? 1 : 0;
+        m3->mc_pg[0] = mc->mc_pg[0];
+        m3->mc_snum++;
+        m3->mc_top++;
+      }
+      if (m3->mc_top >= mc->mc_top && m3->mc_pg[mc->mc_top] == mp) {
+        if (m3->mc_ki[mc->mc_top] >= newindx && !(nflags & MDBX_SPLIT_REPLACE))
+          m3->mc_ki[mc->mc_top]++;
+        if (m3->mc_ki[mc->mc_top] >= nkeys) {
+          m3->mc_pg[mc->mc_top] = rp;
+          mdbx_cassert(mc, m3->mc_ki[mc->mc_top] >= nkeys);
+          m3->mc_ki[mc->mc_top] -= (indx_t)nkeys;
+          for (i = 0; i < mc->mc_top; i++) {
+            m3->mc_ki[i] = mn.mc_ki[i];
+            m3->mc_pg[i] = mn.mc_pg[i];
+          }
+        }
+      } else if (!did_split && m3->mc_top >= ptop &&
+                 m3->mc_pg[ptop] == mc->mc_pg[ptop] &&
+                 m3->mc_ki[ptop] >= mc->mc_ki[ptop]) {
+        m3->mc_ki[ptop]++;
+      }
+      if (XCURSOR_INITED(m3) && IS_LEAF(mp))
+        XCURSOR_REFRESH(m3, m3->mc_pg[mc->mc_top], m3->mc_ki[mc->mc_top]);
+    }
+  }
+  mdbx_debug("mp left: %d, rp left: %d", page_room(mp), page_room(rp));
+
+done:
+  if (copy) /* tmp page */
+    mdbx_dpage_free(env, copy, 1);
+  if (unlikely(rc))
+    mc->mc_txn->mt_flags |= MDBX_TXN_ERROR;
+  return rc;
+}
+
+int mdbx_put(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key, MDBX_val *data,
+             unsigned flags) {
+  int rc = check_txn_rw(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key || !data))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(flags & ~(MDBX_NOOVERWRITE | MDBX_NODUPDATA | MDBX_ALLDUPS |
+                         MDBX_ALLDUPS | MDBX_RESERVE | MDBX_APPEND |
+                         MDBX_APPENDDUP | MDBX_CURRENT | MDBX_MULTIPLE)))
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_flags & (MDBX_TXN_RDONLY | MDBX_TXN_BLOCKED)))
+    return (txn->mt_flags & MDBX_TXN_RDONLY) ? MDBX_EACCESS : MDBX_BAD_TXN;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  cx.outer.mc_next = txn->tw.cursors[dbi];
+  txn->tw.cursors[dbi] = &cx.outer;
+
+  /* LY: support for update (explicit overwrite) */
+  if (flags & MDBX_CURRENT) {
+    rc = mdbx_cursor_get(&cx.outer, (MDBX_val *)key, NULL, MDBX_SET);
+    if (likely(rc == MDBX_SUCCESS) &&
+        (txn->mt_dbs[dbi].md_flags & MDBX_DUPSORT) &&
+        (flags & MDBX_ALLDUPS) == 0) {
+      /* LY: allows update (explicit overwrite) only for unique keys */
+      MDBX_node *node = page_node(cx.outer.mc_pg[cx.outer.mc_top],
+                                  cx.outer.mc_ki[cx.outer.mc_top]);
+      if (F_ISSET(node_flags(node), F_DUPDATA)) {
+        mdbx_tassert(txn, XCURSOR_INITED(&cx.outer) &&
+                              cx.outer.mc_xcursor->mx_db.md_entries > 1);
+        rc = MDBX_EMULTIVAL;
+      }
+    }
+  }
+
+  if (likely(rc == MDBX_SUCCESS))
+    rc = mdbx_cursor_put(&cx.outer, key, data, flags);
+  txn->tw.cursors[dbi] = cx.outer.mc_next;
+
+  return rc;
+}
+
+/**** COPYING *****************************************************************/
+
+#ifndef MDBX_WBUF
+#define MDBX_WBUF ((size_t)1024 * 1024)
+#endif
+
+/* State needed for a double-buffering compacting copy. */
+typedef struct mdbx_copy {
+  MDBX_env *mc_env;
+  MDBX_txn *mc_txn;
+  mdbx_condpair_t mc_condpair;
+  uint8_t *mc_wbuf[2];
+  uint8_t *mc_over[2];
+  size_t mc_wlen[2];
+  size_t mc_olen[2];
+  mdbx_filehandle_t mc_fd;
+  /* Error code.  Never cleared if set.  Both threads can set nonzero
+   * to fail the copy.  Not mutex-protected, MDBX expects atomic int. */
+  volatile int mc_error;
+  pgno_t mc_next_pgno;
+  volatile unsigned mc_head;
+  volatile unsigned mc_tail;
+} mdbx_copy;
+
+/* Dedicated writer thread for compacting copy. */
+static THREAD_RESULT __cold THREAD_CALL mdbx_env_copythr(void *arg) {
+  mdbx_copy *my = arg;
+
+#if defined(EPIPE) && !(defined(_WIN32) || defined(_WIN64))
+  sigset_t sigset;
+  sigemptyset(&sigset);
+  sigaddset(&sigset, SIGPIPE);
+  my->mc_error = pthread_sigmask(SIG_BLOCK, &sigset, NULL);
+#endif /* EPIPE */
+
+  mdbx_condpair_lock(&my->mc_condpair);
+  while (!my->mc_error) {
+    while (my->mc_tail == my->mc_head && !my->mc_error) {
+      int err = mdbx_condpair_wait(&my->mc_condpair, true);
+      if (err != MDBX_SUCCESS) {
+        my->mc_error = err;
+        goto bailout;
+      }
+    }
+    const unsigned toggle = my->mc_tail & 1;
+    size_t wsize = my->mc_wlen[toggle];
+    if (wsize == 0) {
+      my->mc_tail += 1;
+      break /* EOF */;
+    }
+    my->mc_wlen[toggle] = 0;
+    uint8_t *ptr = my->mc_wbuf[toggle];
+  again:
+    if (!my->mc_error) {
+      int err = mdbx_write(my->mc_fd, ptr, wsize);
+      if (err != MDBX_SUCCESS) {
+#if defined(EPIPE) && !(defined(_WIN32) || defined(_WIN64))
+        if (err == EPIPE) {
+          /* Collect the pending SIGPIPE,
+           * otherwise at least OS X gives it to the process on thread-exit. */
+          int unused;
+          sigwait(&sigset, &unused);
+        }
+#endif /* EPIPE */
+        my->mc_error = err;
+        goto bailout;
+      }
+    }
+
+    /* If there's an overflow page tail, write it too */
+    wsize = my->mc_olen[toggle];
+    if (wsize) {
+      my->mc_olen[toggle] = 0;
+      ptr = my->mc_over[toggle];
+      goto again;
+    }
+    my->mc_tail += 1;
+    mdbx_condpair_signal(&my->mc_condpair, false);
+  }
+bailout:
+  mdbx_condpair_unlock(&my->mc_condpair);
+  return (THREAD_RESULT)0;
+}
+
+/* Give buffer and/or MDBX_EOF to writer thread, await unused buffer. */
+static __cold int mdbx_env_cthr_toggle(mdbx_copy *my) {
+  mdbx_condpair_lock(&my->mc_condpair);
+  mdbx_assert(my->mc_env, my->mc_head - my->mc_tail < 2 || my->mc_error);
+  my->mc_head += 1;
+  mdbx_condpair_signal(&my->mc_condpair, true);
+  while (!my->mc_error &&
+         my->mc_head - my->mc_tail == 2 /* both buffers in use */) {
+    int err = mdbx_condpair_wait(&my->mc_condpair, false);
+    if (err != MDBX_SUCCESS)
+      my->mc_error = err;
+  }
+  mdbx_condpair_unlock(&my->mc_condpair);
+  return my->mc_error;
+}
+
+/* Depth-first tree traversal for compacting copy.
+ * [in] my control structure.
+ * [in,out] pg database root.
+ * [in] flags includes F_DUPDATA if it is a sorted-duplicate sub-DB. */
+static __cold int mdbx_env_cwalk(mdbx_copy *my, pgno_t *pg, int flags) {
+  MDBX_cursor_couple couple;
+  MDBX_page *mo, *mp, *leaf;
+  char *buf, *ptr;
+  int rc;
+  unsigned i;
+
+  /* Empty DB, nothing to do */
+  if (*pg == P_INVALID)
+    return MDBX_SUCCESS;
+
+  memset(&couple, 0, sizeof(couple));
+  couple.outer.mc_snum = 1;
+  couple.outer.mc_txn = my->mc_txn;
+  couple.outer.mc_flags = couple.inner.mx_cursor.mc_flags =
+      C_COPYING | C_SKIPORD;
+
+  rc = mdbx_page_get(&couple.outer, *pg, &couple.outer.mc_pg[0], NULL,
+                     my->mc_txn->mt_txnid);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  rc = mdbx_page_search_root(&couple.outer, NULL, MDBX_PS_FIRST);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  /* Make cursor pages writable */
+  buf = ptr = mdbx_malloc(pgno2bytes(my->mc_env, couple.outer.mc_snum));
+  if (buf == NULL)
+    return MDBX_ENOMEM;
+
+  for (i = 0; i < couple.outer.mc_top; i++) {
+    mdbx_page_copy((MDBX_page *)ptr, couple.outer.mc_pg[i],
+                   my->mc_env->me_psize);
+    couple.outer.mc_pg[i] = (MDBX_page *)ptr;
+    ptr += my->mc_env->me_psize;
+  }
+
+  /* This is writable space for a leaf page. Usually not needed. */
+  leaf = (MDBX_page *)ptr;
+
+  while (couple.outer.mc_snum > 0) {
+    mp = couple.outer.mc_pg[couple.outer.mc_top];
+    unsigned n = page_numkeys(mp);
+
+    if (IS_LEAF(mp)) {
+      if (!IS_LEAF2(mp) && !(flags & F_DUPDATA)) {
+        for (i = 0; i < n; i++) {
+          MDBX_node *node = page_node(mp, i);
+          if (node_flags(node) & F_BIGDATA) {
+            MDBX_page *omp;
+
+            /* Need writable leaf */
+            if (mp != leaf) {
+              couple.outer.mc_pg[couple.outer.mc_top] = leaf;
+              mdbx_page_copy(leaf, mp, my->mc_env->me_psize);
+              mp = leaf;
+              node = page_node(mp, i);
+            }
+
+            const pgno_t pgno = node_largedata_pgno(node);
+            poke_pgno(node_data(node), my->mc_next_pgno);
+            rc = mdbx_page_get(&couple.outer, pgno, &omp, NULL,
+                               pp_txnid4chk(mp, my->mc_txn));
+            if (unlikely(rc != MDBX_SUCCESS))
+              goto done;
+            unsigned toggle = my->mc_head & 1;
+            if (my->mc_wlen[toggle] + my->mc_env->me_psize > MDBX_WBUF) {
+              rc = mdbx_env_cthr_toggle(my);
+              if (unlikely(rc != MDBX_SUCCESS))
+                goto done;
+              toggle = my->mc_head & 1;
+            }
+            mo = (MDBX_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
+            memcpy(mo, omp, my->mc_env->me_psize);
+            mo->mp_pgno = my->mc_next_pgno;
+            my->mc_next_pgno += omp->mp_pages;
+            my->mc_wlen[toggle] += my->mc_env->me_psize;
+            if (omp->mp_pages > 1) {
+              my->mc_olen[toggle] = pgno2bytes(my->mc_env, omp->mp_pages - 1);
+              my->mc_over[toggle] = (uint8_t *)omp + my->mc_env->me_psize;
+              rc = mdbx_env_cthr_toggle(my);
+              if (unlikely(rc != MDBX_SUCCESS))
+                goto done;
+              toggle = my->mc_head & 1;
+            }
+          } else if (node_flags(node) & F_SUBDATA) {
+            if (node_ds(node) != sizeof(MDBX_db)) {
+              rc = MDBX_CORRUPTED;
+              goto done;
+            }
+
+            /* Need writable leaf */
+            if (mp != leaf) {
+              couple.outer.mc_pg[couple.outer.mc_top] = leaf;
+              mdbx_page_copy(leaf, mp, my->mc_env->me_psize);
+              mp = leaf;
+              node = page_node(mp, i);
+            }
+
+            MDBX_db db;
+            memcpy(&db, node_data(node), sizeof(MDBX_db));
+            rc = mdbx_env_cwalk(my, &db.md_root, node_flags(node) & F_DUPDATA);
+            if (rc)
+              goto done;
+            memcpy(node_data(node), &db, sizeof(MDBX_db));
+          }
+        }
+      }
+    } else {
+      couple.outer.mc_ki[couple.outer.mc_top]++;
+      if (couple.outer.mc_ki[couple.outer.mc_top] < n) {
+      again:
+        rc = mdbx_page_get(
+            &couple.outer,
+            node_pgno(page_node(mp, couple.outer.mc_ki[couple.outer.mc_top])),
+            &mp, NULL, pp_txnid4chk(mp, my->mc_txn));
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto done;
+        couple.outer.mc_top++;
+        couple.outer.mc_snum++;
+        couple.outer.mc_ki[couple.outer.mc_top] = 0;
+        if (IS_BRANCH(mp)) {
+          /* Whenever we advance to a sibling branch page,
+           * we must proceed all the way down to its first leaf. */
+          mdbx_page_copy(couple.outer.mc_pg[couple.outer.mc_top], mp,
+                         my->mc_env->me_psize);
+          goto again;
+        } else
+          couple.outer.mc_pg[couple.outer.mc_top] = mp;
+        continue;
+      }
+    }
+    unsigned toggle = my->mc_head & 1;
+    if (my->mc_wlen[toggle] + my->mc_wlen[toggle] > MDBX_WBUF) {
+      rc = mdbx_env_cthr_toggle(my);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto done;
+      toggle = my->mc_head & 1;
+    }
+    mo = (MDBX_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
+    mdbx_page_copy(mo, mp, my->mc_env->me_psize);
+    mo->mp_pgno = my->mc_next_pgno++;
+    my->mc_wlen[toggle] += my->mc_env->me_psize;
+    if (couple.outer.mc_top) {
+      /* Update parent if there is one */
+      node_set_pgno(page_node(couple.outer.mc_pg[couple.outer.mc_top - 1],
+                              couple.outer.mc_ki[couple.outer.mc_top - 1]),
+                    mo->mp_pgno);
+      mdbx_cursor_pop(&couple.outer);
+    } else {
+      /* Otherwise we're done */
+      *pg = mo->mp_pgno;
+      break;
+    }
+  }
+done:
+  mdbx_free(buf);
+  return rc;
+}
+
+static __cold void compact_fixup_meta(MDBX_env *env, MDBX_meta *meta) {
+  /* Calculate filesize taking in account shrink/growing thresholds */
+  if (meta->mm_geo.next != meta->mm_geo.now) {
+    meta->mm_geo.now = meta->mm_geo.next;
+    const pgno_t aligner =
+        meta->mm_geo.grow ? meta->mm_geo.grow : meta->mm_geo.shrink;
+    if (aligner) {
+      const pgno_t aligned = pgno_align2os_pgno(
+          env, meta->mm_geo.next + aligner - meta->mm_geo.next % aligner);
+      meta->mm_geo.now = aligned;
+    }
+  }
+
+  if (meta->mm_geo.now < meta->mm_geo.lower)
+    meta->mm_geo.now = meta->mm_geo.lower;
+  if (meta->mm_geo.now > meta->mm_geo.upper)
+    meta->mm_geo.now = meta->mm_geo.upper;
+
+  /* Update signature */
+  assert(meta->mm_geo.now >= meta->mm_geo.next);
+  unaligned_poke_u64(4, meta->mm_datasync_sign, mdbx_meta_sign(meta));
+}
+
+/* Make resizeable */
+static __cold void make_sizeable(MDBX_meta *meta) {
+  meta->mm_geo.lower = MIN_PAGENO;
+  if (meta->mm_geo.grow == 0) {
+    const size_t step = 1 + (meta->mm_geo.upper - meta->mm_geo.lower) / 42;
+    meta->mm_geo.grow = (step < UINT16_MAX) ? (uint16_t)step : UINT16_MAX;
+  }
+  if (meta->mm_geo.shrink == 0) {
+    const size_t step = meta->mm_geo.grow + meta->mm_geo.grow;
+    meta->mm_geo.shrink = (step < UINT16_MAX) ? (uint16_t)step : UINT16_MAX;
+  }
+}
+
+/* Copy environment with compaction. */
+static __cold int mdbx_env_compact(MDBX_env *env, MDBX_txn *read_txn,
+                                   mdbx_filehandle_t fd, uint8_t *buffer,
+                                   const bool dest_is_pipe, const int flags) {
+  const size_t meta_bytes = pgno2bytes(env, NUM_METAS);
+  uint8_t *const data_buffer =
+      buffer + ceil_powerof2(meta_bytes, env->me_os_psize);
+  MDBX_meta *const meta = mdbx_init_metas(env, buffer);
+  mdbx_meta_set_txnid(env, meta, read_txn->mt_txnid);
+
+  if (flags & MDBX_CP_FORCE_DYNAMIC_SIZE)
+    make_sizeable(meta);
+
+  /* copy canary sequences if present */
+  if (read_txn->mt_canary.v) {
+    meta->mm_canary = read_txn->mt_canary;
+    meta->mm_canary.v = mdbx_meta_txnid_stable(env, meta);
+  }
+
+  /* Set metapage 1 with current main DB */
+  pgno_t new_root, root = read_txn->mt_dbs[MAIN_DBI].md_root;
+  if ((new_root = root) == P_INVALID) {
+    /* When the DB is empty, handle it specially to
+     * fix any breakage like page leaks from ITS#8174. */
+    meta->mm_dbs[MAIN_DBI].md_flags = read_txn->mt_dbs[MAIN_DBI].md_flags;
+    compact_fixup_meta(env, meta);
+    if (dest_is_pipe) {
+      int rc = mdbx_write(fd, buffer, meta_bytes);
+      if (rc != MDBX_SUCCESS)
+        return rc;
+    }
+  } else {
+    /* Count free pages + GC pages.  Subtract from last_pg
+     * to find the new last_pg, which also becomes the new root. */
+    pgno_t freecount = 0;
+    MDBX_cursor_couple couple;
+    MDBX_val key, data;
+
+    int rc = mdbx_cursor_init(&couple.outer, read_txn, FREE_DBI);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    while ((rc = mdbx_cursor_get(&couple.outer, &key, &data, MDBX_NEXT)) == 0)
+      freecount += *(pgno_t *)data.iov_base;
+    if (unlikely(rc != MDBX_NOTFOUND))
+      return rc;
+
+    freecount += read_txn->mt_dbs[FREE_DBI].md_branch_pages +
+                 read_txn->mt_dbs[FREE_DBI].md_leaf_pages +
+                 read_txn->mt_dbs[FREE_DBI].md_overflow_pages;
+
+    new_root = read_txn->mt_next_pgno - 1 - freecount;
+    meta->mm_geo.next = new_root + 1;
+    meta->mm_dbs[MAIN_DBI] = read_txn->mt_dbs[MAIN_DBI];
+    meta->mm_dbs[MAIN_DBI].md_root = new_root;
+
+    mdbx_copy ctx;
+    memset(&ctx, 0, sizeof(ctx));
+    rc = mdbx_condpair_init(&ctx.mc_condpair);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+
+    memset(data_buffer, 0, MDBX_WBUF * 2);
+    ctx.mc_wbuf[0] = data_buffer;
+    ctx.mc_wbuf[1] = data_buffer + MDBX_WBUF;
+    ctx.mc_next_pgno = NUM_METAS;
+    ctx.mc_env = env;
+    ctx.mc_fd = fd;
+    ctx.mc_txn = read_txn;
+
+    mdbx_thread_t thread;
+    int thread_err = mdbx_thread_create(&thread, mdbx_env_copythr, &ctx);
+    if (likely(thread_err == MDBX_SUCCESS)) {
+      if (dest_is_pipe) {
+        compact_fixup_meta(env, meta);
+        rc = mdbx_write(fd, buffer, meta_bytes);
+      }
+      if (rc == MDBX_SUCCESS)
+        rc = mdbx_env_cwalk(&ctx, &root, 0);
+      mdbx_env_cthr_toggle(&ctx);
+      mdbx_env_cthr_toggle(&ctx);
+      thread_err = mdbx_thread_join(thread);
+      mdbx_assert(env, (ctx.mc_tail == ctx.mc_head &&
+                        ctx.mc_wlen[ctx.mc_head & 1] == 0) ||
+                           ctx.mc_error);
+      mdbx_condpair_destroy(&ctx.mc_condpair);
+    }
+    if (unlikely(thread_err != MDBX_SUCCESS))
+      return thread_err;
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    if (unlikely(ctx.mc_error != MDBX_SUCCESS))
+      return ctx.mc_error;
+
+    if (dest_is_pipe) {
+      if (root != new_root) {
+        mdbx_error("post-compactification root %" PRIaPGNO
+                   " NE expected %" PRIaPGNO
+                   " (source DB corrupted or has a page leak(s))",
+                   root, new_root);
+        return MDBX_CORRUPTED; /* page leak or corrupt DB */
+      }
+    } else {
+      if (root > new_root) {
+        mdbx_error("post-compactification root %" PRIaPGNO
+                   " GT expected %" PRIaPGNO " (source DB corrupted)",
+                   root, new_root);
+        return MDBX_CORRUPTED; /* page leak or corrupt DB */
+      }
+      if (root < new_root) {
+        mdbx_warning("post-compactification root %" PRIaPGNO
+                     " LT expected %" PRIaPGNO " (page leak(s) in source DB)",
+                     root, new_root);
+        /* fixup meta */
+        meta->mm_dbs[MAIN_DBI].md_root = root;
+        meta->mm_geo.next = root + 1;
+      }
+      compact_fixup_meta(env, meta);
+    }
+  }
+
+  /* Extend file if required */
+  if (meta->mm_geo.now != meta->mm_geo.next) {
+    const size_t whole_size = pgno2bytes(env, meta->mm_geo.now);
+    if (!dest_is_pipe)
+      return mdbx_ftruncate(fd, whole_size);
+
+    const size_t used_size = pgno2bytes(env, meta->mm_geo.next);
+    memset(data_buffer, 0, MDBX_WBUF);
+    for (size_t offset = used_size; offset < whole_size;) {
+      const size_t chunk =
+          (MDBX_WBUF < whole_size - offset) ? MDBX_WBUF : whole_size - offset;
+      /* copy to avoid EFAULT in case swapped-out */
+      int rc = mdbx_write(fd, data_buffer, chunk);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return rc;
+      offset += chunk;
+    }
+  }
+  return MDBX_SUCCESS;
+}
+
+/* Copy environment as-is. */
+static __cold int mdbx_env_copy_asis(MDBX_env *env, MDBX_txn *read_txn,
+                                     mdbx_filehandle_t fd, uint8_t *buffer,
+                                     const bool dest_is_pipe, const int flags) {
+  /* We must start the actual read txn after blocking writers */
+  int rc = mdbx_txn_end(read_txn, MDBX_END_RESET_TMP);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  /* Temporarily block writers until we snapshot the meta pages */
+  rc = mdbx_txn_lock(env, false);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  rc = mdbx_txn_renew0(read_txn, MDBX_TXN_RDONLY);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_txn_unlock(env);
+    return rc;
+  }
+
+  mdbx_jitter4testing(false);
+  const size_t meta_bytes = pgno2bytes(env, NUM_METAS);
+  /* Make a snapshot of meta-pages,
+   * but writing ones after the data was flushed */
+  memcpy(buffer, env->me_map, meta_bytes);
+  MDBX_meta *const headcopy = /* LY: get pointer to the snapshot copy */
+      (MDBX_meta *)(buffer + ((uint8_t *)mdbx_meta_head(env) - env->me_map));
+  mdbx_txn_unlock(env);
+
+  if (flags & MDBX_CP_FORCE_DYNAMIC_SIZE)
+    make_sizeable(headcopy);
+  /* Update signature to steady */
+  unaligned_poke_u64(4, headcopy->mm_datasync_sign, mdbx_meta_sign(headcopy));
+
+  /* Copy the data */
+  const size_t whole_size = pgno_align2os_bytes(env, read_txn->mt_end_pgno);
+  const size_t used_size = pgno2bytes(env, read_txn->mt_next_pgno);
+  mdbx_jitter4testing(false);
+
+  if (dest_is_pipe)
+    rc = mdbx_write(fd, buffer, meta_bytes);
+
+  uint8_t *const data_buffer =
+      buffer + ceil_powerof2(meta_bytes, env->me_os_psize);
+  for (size_t offset = meta_bytes; rc == MDBX_SUCCESS && offset < used_size;) {
+#if MDBX_USE_SENDFILE
+    static bool sendfile_unavailable;
+    if (dest_is_pipe && likely(!sendfile_unavailable)) {
+      off_t in_offset = offset;
+      const ssize_t written =
+          sendfile(fd, env->me_lazy_fd, &in_offset, used_size - offset);
+      if (likely(written > 0)) {
+        offset = in_offset;
+        continue;
+      }
+      rc = MDBX_ENODATA;
+      if (written == 0 || ignore_enosys(rc = errno) != MDBX_RESULT_TRUE)
+        break;
+      sendfile_unavailable = true;
+    }
+#endif /* MDBX_USE_SENDFILE */
+
+#if MDBX_USE_COPYFILERANGE
+    static bool copyfilerange_unavailable;
+    if (!dest_is_pipe && likely(!copyfilerange_unavailable)) {
+      off_t in_offset = offset, out_offset = offset;
+      ssize_t bytes_copied = copy_file_range(
+          env->me_lazy_fd, &in_offset, fd, &out_offset, used_size - offset, 0);
+      if (likely(bytes_copied > 0)) {
+        offset = in_offset;
+        continue;
+      }
+      rc = MDBX_ENODATA;
+      if (bytes_copied == 0 || ignore_enosys(rc = errno) != MDBX_RESULT_TRUE)
+        break;
+      copyfilerange_unavailable = true;
+    }
+#endif /* MDBX_USE_COPYFILERANGE */
+
+    /* fallback to portable */
+    const size_t chunk =
+        (MDBX_WBUF < used_size - offset) ? MDBX_WBUF : used_size - offset;
+    /* copy to avoid EFAULT in case swapped-out */
+    memcpy(data_buffer, env->me_map + offset, chunk);
+    rc = mdbx_write(fd, data_buffer, chunk);
+    offset += chunk;
+  }
+
+  /* Extend file if required */
+  if (likely(rc == MDBX_SUCCESS) && whole_size != used_size) {
+    if (!dest_is_pipe)
+      rc = mdbx_ftruncate(fd, whole_size);
+    else {
+      memset(data_buffer, 0, MDBX_WBUF);
+      for (size_t offset = used_size;
+           rc == MDBX_SUCCESS && offset < whole_size;) {
+        const size_t chunk =
+            (MDBX_WBUF < whole_size - offset) ? MDBX_WBUF : whole_size - offset;
+        /* copy to avoid EFAULT in case swapped-out */
+        rc = mdbx_write(fd, data_buffer, chunk);
+        offset += chunk;
+      }
+    }
+  }
+
+  return rc;
+}
+
+__cold int mdbx_env_copy2fd(MDBX_env *env, mdbx_filehandle_t fd,
+                            unsigned flags) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  const int dest_is_pipe = mdbx_is_pipe(fd);
+  if (MDBX_IS_ERROR(dest_is_pipe))
+    return dest_is_pipe;
+
+  if (!dest_is_pipe) {
+    rc = mdbx_fseek(fd, 0);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  const size_t buffer_size =
+      pgno_align2os_bytes(env, NUM_METAS) +
+      ceil_powerof2(((flags & MDBX_CP_COMPACT) ? MDBX_WBUF * 2 : MDBX_WBUF),
+                    env->me_os_psize);
+
+  uint8_t *buffer = NULL;
+  rc = mdbx_memalign_alloc(env->me_os_psize, buffer_size, (void **)&buffer);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  MDBX_txn *read_txn = NULL;
+  /* Do the lock/unlock of the reader mutex before starting the
+   * write txn. Otherwise other read txns could block writers. */
+  rc = mdbx_txn_begin(env, NULL, MDBX_TXN_RDONLY, &read_txn);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_memalign_free(buffer);
+    return rc;
+  }
+
+  if (!dest_is_pipe) {
+    /* Firstly write a stub to meta-pages.
+     * Now we sure to incomplete copy will not be used. */
+    memset(buffer, -1, pgno2bytes(env, NUM_METAS));
+    rc = mdbx_write(fd, buffer, pgno2bytes(env, NUM_METAS));
+  }
+
+  if (likely(rc == MDBX_SUCCESS)) {
+    memset(buffer, 0, pgno2bytes(env, NUM_METAS));
+    rc = ((flags & MDBX_CP_COMPACT) ? mdbx_env_compact : mdbx_env_copy_asis)(
+        env, read_txn, fd, buffer, dest_is_pipe, flags);
+  }
+  mdbx_txn_abort(read_txn);
+
+  if (!dest_is_pipe) {
+    if (likely(rc == MDBX_SUCCESS))
+      rc = mdbx_fsync(fd, MDBX_SYNC_DATA | MDBX_SYNC_SIZE);
+
+    /* Write actual meta */
+    if (likely(rc == MDBX_SUCCESS))
+      rc = mdbx_pwrite(fd, buffer, pgno2bytes(env, NUM_METAS), 0);
+
+    if (likely(rc == MDBX_SUCCESS))
+      rc = mdbx_fsync(fd, MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
+  }
+
+  mdbx_memalign_free(buffer);
+  return rc;
+}
+
+__cold int mdbx_env_copy(MDBX_env *env, const char *dest_path,
+                         MDBX_copy_flags_t flags) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!dest_path))
+    return MDBX_EINVAL;
+
+  /* The destination path must exist, but the destination file must not.
+   * We don't want the OS to cache the writes, since the source data is
+   * already in the OS cache. */
+  mdbx_filehandle_t newfd;
+  rc = mdbx_openfile(MDBX_OPEN_COPY, env, dest_path, &newfd,
+#if defined(_WIN32) || defined(_WIN64)
+                     (mdbx_mode_t)-1
+#else
+                     S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP
+#endif
+  );
+
+  if (rc == MDBX_SUCCESS) {
+#if defined(_WIN32) || defined(_WIN64)
+    OVERLAPPED ov;
+    memset(&ov, 0, sizeof(ov));
+    if (!LockFileEx(newfd, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY,
+                    0, 0, INT32_MAX, &ov))
+      rc = GetLastError();
+#else
+    struct flock lock_op;
+    memset(&lock_op, 0, sizeof(lock_op));
+    lock_op.l_type = F_WRLCK;
+    lock_op.l_whence = SEEK_SET;
+    lock_op.l_start = 0;
+    lock_op.l_len =
+        (sizeof(lock_op.l_len) > 4 ? INT64_MAX : INT32_MAX) & ~(size_t)0xffff;
+    if (fcntl(newfd, F_SETLK, &lock_op)
+#if (defined(__linux__) || defined(__gnu_linux__)) && defined(LOCK_EX) &&      \
+    (!defined(__ANDROID_API__) || __ANDROID_API__ >= 24)
+        || flock(newfd, LOCK_EX | LOCK_NB)
+#endif /* Linux */
+    )
+      rc = errno;
+#endif /* Windows / POSIX */
+  }
+
+  if (rc == MDBX_SUCCESS)
+    rc = mdbx_env_copy2fd(env, newfd, flags);
+
+  if (newfd != INVALID_HANDLE_VALUE) {
+    int err = mdbx_closefile(newfd);
+    if (rc == MDBX_SUCCESS && err != rc)
+      rc = err;
+    if (rc != MDBX_SUCCESS)
+      (void)mdbx_removefile(dest_path);
+  }
+
+  return rc;
+}
+
+/******************************************************************************/
+
+__cold int mdbx_env_set_flags(MDBX_env *env, MDBX_env_flags_t flags,
+                              bool onoff) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(flags & ~ENV_CHANGEABLE_FLAGS))
+    return MDBX_EPERM;
+
+  if (unlikely(env->me_flags & MDBX_RDONLY))
+    return MDBX_EACCESS;
+
+  if (unlikely(env->me_txn0->mt_owner == mdbx_thread_self()))
+    return MDBX_BUSY;
+
+  rc = mdbx_txn_lock(env, false);
+  if (unlikely(rc))
+    return rc;
+
+  if (onoff)
+    env->me_flags = merge_sync_flags(env->me_flags, flags);
+  else
+    env->me_flags &= ~flags;
+
+  mdbx_txn_unlock(env);
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_env_get_flags(const MDBX_env *env, unsigned *arg) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!arg))
+    return MDBX_EINVAL;
+
+  *arg = env->me_flags & ENV_USABLE_FLAGS;
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_env_set_userctx(MDBX_env *env, void *ctx) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  env->me_userctx = ctx;
+  return MDBX_SUCCESS;
+}
+
+void *__cold mdbx_env_get_userctx(const MDBX_env *env) {
+  return env ? env->me_userctx : NULL;
+}
+
+__cold int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+#if MDBX_DEBUG
+  env->me_assert_func = func;
+  return MDBX_SUCCESS;
+#else
+  (void)func;
+  return MDBX_ENOSYS;
+#endif
+}
+
+__cold int mdbx_env_get_path(const MDBX_env *env, const char **arg) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!arg))
+    return MDBX_EINVAL;
+
+  *arg = env->me_pathname;
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_env_get_fd(const MDBX_env *env, mdbx_filehandle_t *arg) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!arg))
+    return MDBX_EINVAL;
+
+  *arg = env->me_lazy_fd;
+  return MDBX_SUCCESS;
+}
+
+/* Common code for mdbx_dbi_stat() and mdbx_env_stat().
+ * [in] env the environment to operate in.
+ * [in] db the MDBX_db record containing the stats to return.
+ * [out] arg the address of an MDBX_stat structure to receive the stats.
+ * Returns 0, this function always succeeds. */
+static void mdbx_stat0(const MDBX_env *env, const MDBX_db *db, MDBX_stat *dest,
+                       size_t bytes) {
+  dest->ms_psize = env->me_psize;
+  dest->ms_depth = db->md_depth;
+  dest->ms_branch_pages = db->md_branch_pages;
+  dest->ms_leaf_pages = db->md_leaf_pages;
+  dest->ms_overflow_pages = db->md_overflow_pages;
+  dest->ms_entries = db->md_entries;
+  if (likely(bytes >=
+             offsetof(MDBX_stat, ms_mod_txnid) + sizeof(dest->ms_mod_txnid)))
+    dest->ms_mod_txnid = db->md_mod_txnid;
+}
+
+__cold int mdbx_env_stat(const MDBX_env *env, MDBX_stat *stat, size_t bytes) {
+  return __inline_mdbx_env_stat(env, stat, bytes);
+}
+
+__cold int mdbx_env_stat_ex(const MDBX_env *env, const MDBX_txn *txn,
+                            MDBX_stat *dest, size_t bytes) {
+  if (unlikely((env == NULL && txn == NULL) || dest == NULL))
+    return MDBX_EINVAL;
+
+  if (txn) {
+    int err = check_txn(txn, MDBX_TXN_BLOCKED);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+  }
+  if (env) {
+    int err = check_env(env);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+    if (txn && unlikely(txn->mt_env != env))
+      return MDBX_EINVAL;
+  }
+
+  const size_t size_before_modtxnid = offsetof(MDBX_stat, ms_mod_txnid);
+  if (unlikely(bytes != sizeof(MDBX_stat)) && bytes != size_before_modtxnid)
+    return MDBX_EINVAL;
+
+  if (txn) {
+    mdbx_stat0(txn->mt_env, &txn->mt_dbs[MAIN_DBI], dest, bytes);
+    return MDBX_SUCCESS;
+  }
+
+  while (1) {
+    const MDBX_meta *const recent_meta = mdbx_meta_head(env);
+    const txnid_t txnid = mdbx_meta_txnid_fluid(env, recent_meta);
+    mdbx_stat0(env, &recent_meta->mm_dbs[MAIN_DBI], dest, bytes);
+    mdbx_compiler_barrier();
+    if (likely(txnid == mdbx_meta_txnid_fluid(env, recent_meta) &&
+               recent_meta == mdbx_meta_head(env)))
+      return MDBX_SUCCESS;
+  }
+}
+
+__cold int mdbx_dbi_dupsort_depthmask(MDBX_txn *txn, MDBX_dbi dbi,
+                                      uint32_t *mask) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mask))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_VALID)))
+    return MDBX_BAD_DBI;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  if ((cx.outer.mc_db->md_flags & MDBX_DUPSORT) == 0)
+    return MDBX_RESULT_TRUE;
+
+  MDBX_val key, data;
+  rc = mdbx_cursor_first(&cx.outer, &key, &data);
+  *mask = 0;
+  while (rc == MDBX_SUCCESS) {
+    const MDBX_node *node = page_node(cx.outer.mc_pg[cx.outer.mc_top],
+                                      cx.outer.mc_ki[cx.outer.mc_top]);
+    const MDBX_db *db = node_data(node);
+    const unsigned flags = node_flags(node);
+    switch (flags) {
+    case F_BIGDATA:
+    case 0:
+      /* single-value entry, deep = 0 */
+      *mask |= 1 << 0;
+      break;
+    case F_DUPDATA:
+      /* single sub-page, deep = 1 */
+      *mask |= 1 << 1;
+      break;
+    case F_DUPDATA | F_SUBDATA:
+      /* sub-tree */
+      *mask |= 1 << unaligned_peek_u16(1, &db->md_depth);
+      break;
+    default:
+      mdbx_error("wrong node-flags %u", flags);
+      return MDBX_CORRUPTED;
+    }
+    rc = mdbx_cursor_next(&cx.outer, &key, &data, MDBX_NEXT_NODUP);
+  }
+
+  return (rc == MDBX_NOTFOUND) ? MDBX_SUCCESS : rc;
+}
+
+__cold int mdbx_env_info(const MDBX_env *env, MDBX_envinfo *info,
+                         size_t bytes) {
+  return __inline_mdbx_env_info(env, info, bytes);
+}
+
+__cold int mdbx_env_info_ex(const MDBX_env *env, const MDBX_txn *txn,
+                            MDBX_envinfo *arg, size_t bytes) {
+  if (unlikely((env == NULL && txn == NULL) || arg == NULL))
+    return MDBX_EINVAL;
+
+  if (txn) {
+    int err = check_txn(txn, MDBX_TXN_BLOCKED);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+  }
+  if (env) {
+    int err = check_env(env);
+    if (unlikely(err != MDBX_SUCCESS))
+      return err;
+    if (txn && unlikely(txn->mt_env != env))
+      return MDBX_EINVAL;
+  } else {
+    env = txn->mt_env;
+  }
+
+  const size_t size_before_bootid = offsetof(MDBX_envinfo, mi_bootid);
+  if (unlikely(bytes != sizeof(MDBX_envinfo)) && bytes != size_before_bootid)
+    return MDBX_EINVAL;
+
+  const MDBX_meta *const meta0 = METAPAGE(env, 0);
+  const MDBX_meta *const meta1 = METAPAGE(env, 1);
+  const MDBX_meta *const meta2 = METAPAGE(env, 2);
+  pgno_t unsynced_pages;
+  while (1) {
+    if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
+      return MDBX_PANIC;
+
+    const MDBX_meta *const recent_meta = mdbx_meta_head(env);
+    arg->mi_recent_txnid = mdbx_meta_txnid_fluid(env, recent_meta);
+    arg->mi_meta0_txnid = mdbx_meta_txnid_fluid(env, meta0);
+    arg->mi_meta0_sign = unaligned_peek_u64(4, meta0->mm_datasync_sign);
+    arg->mi_meta1_txnid = mdbx_meta_txnid_fluid(env, meta1);
+    arg->mi_meta1_sign = unaligned_peek_u64(4, meta1->mm_datasync_sign);
+    arg->mi_meta2_txnid = mdbx_meta_txnid_fluid(env, meta2);
+    arg->mi_meta2_sign = unaligned_peek_u64(4, meta2->mm_datasync_sign);
+    if (likely(bytes > size_before_bootid)) {
+      memcpy(&arg->mi_bootid.meta0, &meta0->mm_bootid, 16);
+      memcpy(&arg->mi_bootid.meta1, &meta1->mm_bootid, 16);
+      memcpy(&arg->mi_bootid.meta2, &meta2->mm_bootid, 16);
+    }
+
+    const MDBX_meta *txn_meta = recent_meta;
+    arg->mi_last_pgno = txn_meta->mm_geo.next - 1;
+    arg->mi_geo.current = pgno2bytes(env, txn_meta->mm_geo.now);
+    if (txn) {
+      arg->mi_last_pgno = txn->mt_next_pgno - 1;
+      arg->mi_geo.current = pgno2bytes(env, txn->mt_end_pgno);
+
+      const txnid_t wanna_meta_txnid = (txn->mt_flags & MDBX_TXN_RDONLY)
+                                           ? txn->mt_txnid
+                                           : txn->mt_txnid - MDBX_TXNID_STEP;
+      txn_meta = (arg->mi_meta0_txnid == wanna_meta_txnid) ? meta0 : txn_meta;
+      txn_meta = (arg->mi_meta1_txnid == wanna_meta_txnid) ? meta1 : txn_meta;
+      txn_meta = (arg->mi_meta2_txnid == wanna_meta_txnid) ? meta2 : txn_meta;
+    }
+    arg->mi_geo.lower = pgno2bytes(env, txn_meta->mm_geo.lower);
+    arg->mi_geo.upper = pgno2bytes(env, txn_meta->mm_geo.upper);
+    arg->mi_geo.shrink = pgno2bytes(env, txn_meta->mm_geo.shrink);
+    arg->mi_geo.grow = pgno2bytes(env, txn_meta->mm_geo.grow);
+    unsynced_pages = atomic_load32(env->me_unsynced_pages, mo_Relaxed) +
+                     (atomic_load32(env->me_meta_sync_txnid, mo_Relaxed) !=
+                      (uint32_t)arg->mi_last_pgno);
+
+    arg->mi_mapsize = env->me_dxb_mmap.limit;
+    mdbx_compiler_barrier();
+    if (likely(arg->mi_meta0_txnid == mdbx_meta_txnid_fluid(env, meta0) &&
+               arg->mi_meta0_sign ==
+                   unaligned_peek_u64(4, meta0->mm_datasync_sign) &&
+               arg->mi_meta1_txnid == mdbx_meta_txnid_fluid(env, meta1) &&
+               arg->mi_meta1_sign ==
+                   unaligned_peek_u64(4, meta1->mm_datasync_sign) &&
+               arg->mi_meta2_txnid == mdbx_meta_txnid_fluid(env, meta2) &&
+               arg->mi_meta2_sign ==
+                   unaligned_peek_u64(4, meta2->mm_datasync_sign) &&
+               recent_meta == mdbx_meta_head(env) &&
+               arg->mi_recent_txnid == mdbx_meta_txnid_fluid(env, recent_meta)))
+      break;
+  }
+
+  arg->mi_maxreaders = env->me_maxreaders;
+  arg->mi_numreaders =
+      env->me_lck ? atomic_load32(&env->me_lck->mti_numreaders, mo_Relaxed)
+                  : INT32_MAX;
+  arg->mi_dxb_pagesize = env->me_psize;
+  arg->mi_sys_pagesize = env->me_os_psize;
+
+  const MDBX_lockinfo *const lck = env->me_lck;
+  if (likely(bytes > size_before_bootid)) {
+    arg->mi_unsync_volume = pgno2bytes(env, unsynced_pages);
+    const uint64_t monotime_now = mdbx_osal_monotime();
+    arg->mi_since_sync_seconds16dot16 = mdbx_osal_monotime_to_16dot16(
+        monotime_now - atomic_load64(env->me_sync_timestamp, mo_Relaxed));
+    arg->mi_since_reader_check_seconds16dot16 =
+        lck ? mdbx_osal_monotime_to_16dot16(
+                  monotime_now -
+                  atomic_load64(&lck->mti_reader_check_timestamp, mo_Relaxed))
+            : 0;
+    arg->mi_autosync_threshold =
+        pgno2bytes(env, atomic_load32(env->me_autosync_threshold, mo_Relaxed));
+    arg->mi_autosync_period_seconds16dot16 = mdbx_osal_monotime_to_16dot16(
+        atomic_load64(env->me_autosync_period, mo_Relaxed));
+    arg->mi_bootid.current.x = bootid.x;
+    arg->mi_bootid.current.y = bootid.y;
+    arg->mi_mode = lck ? lck->mti_envmode.weak : env->me_flags;
+  }
+
+  arg->mi_self_latter_reader_txnid = arg->mi_latter_reader_txnid = 0;
+  if (lck) {
+    arg->mi_self_latter_reader_txnid = arg->mi_latter_reader_txnid =
+        arg->mi_recent_txnid;
+    for (unsigned i = 0; i < arg->mi_numreaders; ++i) {
+      const uint32_t pid =
+          atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease);
+      if (pid) {
+        const txnid_t txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
+        if (arg->mi_latter_reader_txnid > txnid)
+          arg->mi_latter_reader_txnid = txnid;
+        if (pid == env->me_pid && arg->mi_self_latter_reader_txnid > txnid)
+          arg->mi_self_latter_reader_txnid = txnid;
+      }
+    }
+  }
+
+  return MDBX_SUCCESS;
+}
+
+static __inline MDBX_cmp_func *get_default_keycmp(unsigned flags) {
+  return (flags & MDBX_REVERSEKEY)
+             ? cmp_reverse
+             : (flags & MDBX_INTEGERKEY) ? cmp_int_align2 : cmp_lexical;
+}
+
+static __inline MDBX_cmp_func *get_default_datacmp(unsigned flags) {
+  return !(flags & MDBX_DUPSORT)
+             ? cmp_lenfast
+             : ((flags & MDBX_INTEGERDUP)
+                    ? cmp_int_unaligned
+                    : ((flags & MDBX_REVERSEDUP) ? cmp_reverse : cmp_lexical));
+}
+
+static int mdbx_dbi_bind(MDBX_txn *txn, const MDBX_dbi dbi, unsigned user_flags,
+                         MDBX_cmp_func *keycmp, MDBX_cmp_func *datacmp) {
+  /* LY: so, accepting only three cases for the table's flags:
+   * 1) user_flags and both comparators are zero
+   *    = assume that a by-default mode/flags is requested for reading;
+   * 2) user_flags exactly the same
+   *    = assume that the target mode/flags are requested properly;
+   * 3) user_flags differs, but table is empty and MDBX_CREATE is provided
+   *    = assume that a properly create request with custom flags;
+   */
+  if ((user_flags ^ txn->mt_dbs[dbi].md_flags) & DB_PERSISTENT_FLAGS) {
+    /* flags are differs, check other conditions */
+    if ((!user_flags && (!keycmp || keycmp == txn->mt_dbxs[dbi].md_cmp) &&
+         (!datacmp || datacmp == txn->mt_dbxs[dbi].md_dcmp)) ||
+        user_flags == MDBX_ACCEDE) {
+      /* no comparators were provided and flags are zero,
+       * seems that is case #1 above */
+      user_flags = txn->mt_dbs[dbi].md_flags;
+    } else if ((user_flags & MDBX_CREATE) && txn->mt_dbs[dbi].md_entries == 0) {
+      if (txn->mt_flags & MDBX_TXN_RDONLY)
+        return /* FIXME: return extended info */ MDBX_EACCESS;
+      /* make sure flags changes get committed */
+      txn->mt_dbs[dbi].md_flags = user_flags & DB_PERSISTENT_FLAGS;
+      txn->mt_flags |= MDBX_TXN_DIRTY;
+    } else {
+      return /* FIXME: return extended info */ MDBX_INCOMPATIBLE;
+    }
+  }
+
+  if (!keycmp)
+    keycmp = txn->mt_dbxs[dbi].md_cmp ? txn->mt_dbxs[dbi].md_cmp
+                                      : get_default_keycmp(user_flags);
+  if (txn->mt_dbxs[dbi].md_cmp != keycmp) {
+    if (txn->mt_dbxs[dbi].md_cmp)
+      return MDBX_EINVAL;
+    txn->mt_dbxs[dbi].md_cmp = keycmp;
+  }
+
+  if (!datacmp)
+    datacmp = txn->mt_dbxs[dbi].md_dcmp ? txn->mt_dbxs[dbi].md_dcmp
+                                        : get_default_datacmp(user_flags);
+  if (txn->mt_dbxs[dbi].md_dcmp != datacmp) {
+    if (txn->mt_dbxs[dbi].md_dcmp)
+      return MDBX_EINVAL;
+    txn->mt_dbxs[dbi].md_dcmp = datacmp;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+static int dbi_open(MDBX_txn *txn, const char *table_name, unsigned user_flags,
+                    MDBX_dbi *dbi, MDBX_cmp_func *keycmp,
+                    MDBX_cmp_func *datacmp) {
+  int rc = MDBX_EINVAL;
+  if (unlikely(!dbi))
+    return rc;
+
+  if (unlikely((user_flags & ~DB_USABLE_FLAGS) != 0)) {
+  early_bailout:
+    *dbi = 0;
+    return rc;
+  }
+
+  rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto early_bailout;
+
+  switch (user_flags & (MDBX_INTEGERDUP | MDBX_DUPFIXED | MDBX_DUPSORT |
+                        MDBX_REVERSEDUP | MDBX_ACCEDE)) {
+  case MDBX_ACCEDE:
+    if ((user_flags & MDBX_CREATE) == 0)
+      break;
+    __fallthrough /* fall through */;
+  default:
+    rc = MDBX_EINVAL;
+    goto early_bailout;
+
+  case MDBX_DUPSORT:
+  case MDBX_DUPSORT | MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERDUP | MDBX_REVERSEDUP:
+  case 0:
+    break;
+  }
+
+  /* main table? */
+  if (!table_name) {
+    rc = mdbx_dbi_bind(txn, MAIN_DBI, user_flags, keycmp, datacmp);
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto early_bailout;
+    *dbi = MAIN_DBI;
+    return rc;
+  }
+
+  if (txn->mt_dbxs[MAIN_DBI].md_cmp == NULL) {
+    txn->mt_dbxs[MAIN_DBI].md_cmp =
+        get_default_keycmp(txn->mt_dbs[MAIN_DBI].md_flags);
+    txn->mt_dbxs[MAIN_DBI].md_dcmp =
+        get_default_datacmp(txn->mt_dbs[MAIN_DBI].md_flags);
+  }
+
+  /* Is the DB already open? */
+  size_t len = strlen(table_name);
+  MDBX_dbi scan, slot;
+  for (slot = scan = txn->mt_numdbs; --scan >= CORE_DBS;) {
+    if (!txn->mt_dbxs[scan].md_name.iov_len) {
+      /* Remember this free slot */
+      slot = scan;
+      continue;
+    }
+    if (len == txn->mt_dbxs[scan].md_name.iov_len &&
+        !strncmp(table_name, txn->mt_dbxs[scan].md_name.iov_base, len)) {
+      rc = mdbx_dbi_bind(txn, scan, user_flags, keycmp, datacmp);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto early_bailout;
+      *dbi = scan;
+      return rc;
+    }
+  }
+
+  /* Fail, if no free slot and max hit */
+  MDBX_env *env = txn->mt_env;
+  if (unlikely(slot >= env->me_maxdbs)) {
+    rc = MDBX_DBS_FULL;
+    goto early_bailout;
+  }
+
+  /* Cannot mix named table with some main-table flags */
+  if (unlikely(txn->mt_dbs[MAIN_DBI].md_flags &
+               (MDBX_DUPSORT | MDBX_INTEGERKEY))) {
+    rc = (user_flags & MDBX_CREATE) ? MDBX_INCOMPATIBLE : MDBX_NOTFOUND;
+    goto early_bailout;
+  }
+
+  /* Find the DB info */
+  int exact = 0;
+  MDBX_val key, data;
+  key.iov_len = len;
+  key.iov_base = (void *)table_name;
+  MDBX_cursor_couple couple;
+  rc = mdbx_cursor_init(&couple.outer, txn, MAIN_DBI);
+  if (unlikely(rc != MDBX_SUCCESS))
+    goto early_bailout;
+  rc = mdbx_cursor_set(&couple.outer, &key, &data, MDBX_SET, &exact);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc != MDBX_NOTFOUND || !(user_flags & MDBX_CREATE))
+      goto early_bailout;
+  } else {
+    /* make sure this is actually a table */
+    MDBX_node *node = page_node(couple.outer.mc_pg[couple.outer.mc_top],
+                                couple.outer.mc_ki[couple.outer.mc_top]);
+    if (unlikely((node_flags(node) & (F_DUPDATA | F_SUBDATA)) != F_SUBDATA)) {
+      rc = MDBX_INCOMPATIBLE;
+      goto early_bailout;
+    }
+    if (unlikely(data.iov_len != sizeof(MDBX_db))) {
+      rc = MDBX_CORRUPTED;
+      goto early_bailout;
+    }
+  }
+
+  if (rc != MDBX_SUCCESS && unlikely(txn->mt_flags & MDBX_TXN_RDONLY)) {
+    rc = MDBX_EACCESS;
+    goto early_bailout;
+  }
+
+  /* Done here so we cannot fail after creating a new DB */
+  char *namedup = mdbx_strdup(table_name);
+  if (unlikely(!namedup)) {
+    rc = MDBX_ENOMEM;
+    goto early_bailout;
+  }
+
+  int err = mdbx_fastmutex_acquire(&env->me_dbi_lock);
+  if (unlikely(err != MDBX_SUCCESS)) {
+    rc = err;
+    mdbx_free(namedup);
+    goto early_bailout;
+  }
+
+  /* Import handles from env */
+  dbi_import_locked(txn);
+
+  /* Rescan after mutex acquisition & import handles */
+  for (slot = scan = txn->mt_numdbs; --scan >= CORE_DBS;) {
+    if (!txn->mt_dbxs[scan].md_name.iov_len) {
+      /* Remember this free slot */
+      slot = scan;
+      continue;
+    }
+    if (len == txn->mt_dbxs[scan].md_name.iov_len &&
+        !strncmp(table_name, txn->mt_dbxs[scan].md_name.iov_base, len)) {
+      rc = mdbx_dbi_bind(txn, scan, user_flags, keycmp, datacmp);
+      if (unlikely(rc != MDBX_SUCCESS))
+        goto later_bailout;
+      *dbi = scan;
+      goto later_exit;
+    }
+  }
+
+  if (unlikely(slot >= env->me_maxdbs)) {
+    rc = MDBX_DBS_FULL;
+    goto later_bailout;
+  }
+
+  unsigned dbiflags = DBI_FRESH | DBI_VALID | DBI_USRVALID;
+  MDBX_db db_dummy;
+  if (unlikely(rc)) {
+    /* MDBX_NOTFOUND and MDBX_CREATE: Create new DB */
+    mdbx_tassert(txn, rc == MDBX_NOTFOUND);
+    memset(&db_dummy, 0, sizeof(db_dummy));
+    db_dummy.md_root = P_INVALID;
+    db_dummy.md_flags = user_flags & DB_PERSISTENT_FLAGS;
+    data.iov_len = sizeof(db_dummy);
+    data.iov_base = &db_dummy;
+    WITH_CURSOR_TRACKING(couple.outer,
+                         rc = mdbx_cursor_put(&couple.outer, &key, &data,
+                                              F_SUBDATA | MDBX_NOOVERWRITE));
+
+    if (unlikely(rc != MDBX_SUCCESS))
+      goto later_bailout;
+
+    dbiflags |= DBI_DIRTY | DBI_CREAT;
+    txn->mt_flags |= MDBX_TXN_DIRTY;
+  }
+
+  /* Got info, register DBI in this txn */
+  memset(txn->mt_dbxs + slot, 0, sizeof(MDBX_dbx));
+  txn->mt_dbs[slot] = *(MDBX_db *)data.iov_base;
+  env->me_dbflags[slot] = 0;
+  rc = mdbx_dbi_bind(txn, slot, user_flags, keycmp, datacmp);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    mdbx_tassert(txn, (dbiflags & DBI_CREAT) == 0);
+  later_bailout:
+    *dbi = 0;
+  later_exit:
+    mdbx_free(namedup);
+  } else {
+    txn->mt_dbistate[slot] = (uint8_t)dbiflags;
+    txn->mt_dbxs[slot].md_name.iov_base = namedup;
+    txn->mt_dbxs[slot].md_name.iov_len = len;
+    txn->mt_dbiseqs[slot] = ++env->me_dbiseqs[slot];
+    if (!(dbiflags & DBI_CREAT))
+      env->me_dbflags[slot] = txn->mt_dbs[slot].md_flags | DB_VALID;
+    if (txn->mt_numdbs == slot) {
+      mdbx_compiler_barrier();
+      txn->mt_numdbs = env->me_numdbs = slot + 1;
+      if (!(txn->mt_flags & MDBX_TXN_RDONLY))
+        txn->tw.cursors[slot] = NULL;
+    }
+    mdbx_assert(env, env->me_numdbs > slot);
+    *dbi = slot;
+  }
+
+  mdbx_ensure(env, mdbx_fastmutex_release(&env->me_dbi_lock) == MDBX_SUCCESS);
+  return rc;
+}
+
+int mdbx_dbi_open(MDBX_txn *txn, const char *table_name,
+                  MDBX_db_flags_t table_flags, MDBX_dbi *dbi) {
+  return dbi_open(txn, table_name, table_flags, dbi, nullptr, nullptr);
+}
+
+int mdbx_dbi_open_ex(MDBX_txn *txn, const char *table_name,
+                     MDBX_db_flags_t table_flags, MDBX_dbi *dbi,
+                     MDBX_cmp_func *keycmp, MDBX_cmp_func *datacmp) {
+  return dbi_open(txn, table_name, table_flags, dbi, keycmp, datacmp);
+}
+
+__cold int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *dest,
+                         size_t bytes) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!dest))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_VALID)))
+    return MDBX_BAD_DBI;
+
+  const size_t size_before_modtxnid = offsetof(MDBX_stat, ms_mod_txnid);
+  if (unlikely(bytes != sizeof(MDBX_stat)) && bytes != size_before_modtxnid)
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_flags & MDBX_TXN_BLOCKED))
+    return MDBX_BAD_TXN;
+
+  if (unlikely(txn->mt_dbistate[dbi] & DBI_STALE)) {
+    rc = mdbx_fetch_sdb(txn, dbi);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+  mdbx_stat0(txn->mt_env, &txn->mt_dbs[dbi], dest, bytes);
+  return MDBX_SUCCESS;
+}
+
+static int mdbx_dbi_close_locked(MDBX_env *env, MDBX_dbi dbi) {
+  mdbx_assert(env, dbi >= CORE_DBS);
+  if (unlikely(dbi >= env->me_numdbs))
+    return MDBX_BAD_DBI;
+
+  char *ptr = env->me_dbxs[dbi].md_name.iov_base;
+  /* If there was no name, this was already closed */
+  if (unlikely(!ptr))
+    return MDBX_BAD_DBI;
+
+  env->me_dbflags[dbi] = 0;
+  env->me_dbiseqs[dbi]++;
+  env->me_dbxs[dbi].md_name.iov_len = 0;
+  mdbx_memory_fence(false, true);
+  env->me_dbxs[dbi].md_name.iov_base = NULL;
+  mdbx_free(ptr);
+
+  if (env->me_numdbs == dbi + 1)
+    env->me_numdbs = dbi;
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_dbi_close(MDBX_env *env, MDBX_dbi dbi) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(dbi < CORE_DBS || dbi >= env->me_maxdbs))
+    return MDBX_BAD_DBI;
+
+  rc = mdbx_fastmutex_acquire(&env->me_dbi_lock);
+  if (likely(rc == MDBX_SUCCESS)) {
+    rc = (dbi < env->me_maxdbs && (env->me_dbflags[dbi] & DB_VALID))
+             ? mdbx_dbi_close_locked(env, dbi)
+             : MDBX_BAD_DBI;
+    mdbx_ensure(env, mdbx_fastmutex_release(&env->me_dbi_lock) == MDBX_SUCCESS);
+  }
+  return rc;
+}
+
+int mdbx_dbi_flags_ex(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
+                      unsigned *state) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!flags || !state))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_VALID)))
+    return MDBX_BAD_DBI;
+
+  *flags = txn->mt_dbs[dbi].md_flags & DB_PERSISTENT_FLAGS;
+  *state =
+      txn->mt_dbistate[dbi] & (DBI_FRESH | DBI_CREAT | DBI_DIRTY | DBI_STALE);
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_dbi_flags(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags) {
+  return __inline_mdbx_dbi_flags(txn, dbi, flags);
+}
+
+/* Add all the DB's pages to the free list.
+ * [in] mc Cursor on the DB to free.
+ * [in] subs non-Zero to check for sub-DBs in this DB.
+ * Returns 0 on success, non-zero on failure. */
+static int mdbx_drop0(MDBX_cursor *mc, int subs) {
+  int rc = mdbx_page_search(mc, NULL, MDBX_PS_FIRST);
+  if (likely(rc == MDBX_SUCCESS)) {
+    MDBX_txn *txn = mc->mc_txn;
+    MDBX_cursor mx;
+    unsigned i;
+
+    /* DUPSORT sub-DBs have no ovpages/DBs. Omit scanning leaves.
+     * This also avoids any P_LEAF2 pages, which have no nodes.
+     * Also if the DB doesn't have sub-DBs and has no overflow
+     * pages, omit scanning leaves. */
+    if ((mc->mc_flags & C_SUB) || (subs | mc->mc_db->md_overflow_pages) == 0)
+      mdbx_cursor_pop(mc);
+
+    rc = mdbx_pnl_need(&txn->tw.retired_pages,
+                       mc->mc_db->md_branch_pages + mc->mc_db->md_leaf_pages +
+                           mc->mc_db->md_overflow_pages);
+    if (unlikely(rc))
+      goto done;
+
+    cursor_copy_internal(mc, &mx);
+    while (mc->mc_snum > 0) {
+      MDBX_page *mp = mc->mc_pg[mc->mc_top];
+      unsigned n = page_numkeys(mp);
+      if (IS_LEAF(mp)) {
+        for (i = 0; i < n; i++) {
+          MDBX_node *node = page_node(mp, i);
+          if (node_flags(node) & F_BIGDATA) {
+            MDBX_page *omp;
+            rc = mdbx_page_get(mc, node_largedata_pgno(node), &omp, NULL,
+                               pp_txnid4chk(mp, mc->mc_txn));
+            if (unlikely(rc))
+              goto done;
+            mdbx_cassert(mc, IS_OVERFLOW(omp));
+            rc = mdbx_page_retire(mc, omp);
+            if (unlikely(rc))
+              goto done;
+            if (!mc->mc_db->md_overflow_pages && !subs)
+              break;
+          } else if (subs && (node_flags(node) & F_SUBDATA)) {
+            rc = mdbx_xcursor_init1(mc, node, mp);
+            if (unlikely(rc != MDBX_SUCCESS))
+              goto done;
+            rc = mdbx_drop0(&mc->mc_xcursor->mx_cursor, 0);
+            if (unlikely(rc))
+              goto done;
+          }
+        }
+        if (!subs && !mc->mc_db->md_overflow_pages)
+          goto pop;
+      } else {
+        for (i = 0; i < n; i++) {
+          /* free it */
+          rc = mdbx_retire_pgno(mc, node_pgno(page_node(mp, i)));
+          if (unlikely(rc))
+            goto done;
+        }
+      }
+      if (!mc->mc_top)
+        break;
+      mdbx_cassert(mc, i <= UINT16_MAX);
+      mc->mc_ki[mc->mc_top] = (indx_t)i;
+      rc = mdbx_cursor_sibling(mc, SIBLING_RIGHT);
+      if (rc) {
+        if (unlikely(rc != MDBX_NOTFOUND))
+          goto done;
+      /* no more siblings, go back to beginning
+       * of previous level. */
+      pop:
+        mdbx_cursor_pop(mc);
+        mc->mc_ki[0] = 0;
+        for (i = 1; i < mc->mc_snum; i++) {
+          mc->mc_ki[i] = 0;
+          mc->mc_pg[i] = mx.mc_pg[i];
+        }
+      }
+    }
+    /* free it */
+    rc = mdbx_retire_pgno(mc, mc->mc_db->md_root);
+  done:
+    if (unlikely(rc))
+      txn->mt_flags |= MDBX_TXN_ERROR;
+  } else if (rc == MDBX_NOTFOUND) {
+    rc = MDBX_SUCCESS;
+  }
+  mc->mc_flags &= ~C_INITIALIZED;
+  return rc;
+}
+
+int mdbx_drop(MDBX_txn *txn, MDBX_dbi dbi, bool del) {
+  int rc = check_txn_rw(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(TXN_DBI_CHANGED(txn, dbi)))
+    return MDBX_BAD_DBI;
+
+  MDBX_cursor *mc;
+  rc = mdbx_cursor_open(txn, dbi, &mc);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID))) {
+    rc = MDBX_BAD_DBI;
+    goto bailout;
+  }
+
+  if (unlikely(TXN_DBI_CHANGED(txn, dbi))) {
+    rc = MDBX_BAD_DBI;
+    goto bailout;
+  }
+
+  rc = mdbx_drop0(mc, mc->mc_db->md_flags & MDBX_DUPSORT);
+  /* Invalidate the dropped DB's cursors */
+  for (MDBX_cursor *m2 = txn->tw.cursors[dbi]; m2; m2 = m2->mc_next)
+    m2->mc_flags &= ~(C_INITIALIZED | C_EOF);
+  if (unlikely(rc))
+    goto bailout;
+
+  /* Can't delete the main DB */
+  if (del && dbi >= CORE_DBS) {
+    rc = mdbx_del0(txn, MAIN_DBI, &mc->mc_dbx->md_name, NULL, F_SUBDATA);
+    if (likely(rc == MDBX_SUCCESS)) {
+      txn->mt_dbistate[dbi] = DBI_STALE;
+      MDBX_env *env = txn->mt_env;
+      rc = mdbx_fastmutex_acquire(&env->me_dbi_lock);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        txn->mt_flags |= MDBX_TXN_ERROR;
+        goto bailout;
+      }
+      mdbx_dbi_close_locked(env, dbi);
+      mdbx_ensure(env,
+                  mdbx_fastmutex_release(&env->me_dbi_lock) == MDBX_SUCCESS);
+    } else {
+      txn->mt_flags |= MDBX_TXN_ERROR;
+    }
+  } else {
+    /* reset the DB record, mark it dirty */
+    txn->mt_dbistate[dbi] |= DBI_DIRTY;
+    txn->mt_dbs[dbi].md_depth = 0;
+    txn->mt_dbs[dbi].md_branch_pages = 0;
+    txn->mt_dbs[dbi].md_leaf_pages = 0;
+    txn->mt_dbs[dbi].md_overflow_pages = 0;
+    txn->mt_dbs[dbi].md_entries = 0;
+    txn->mt_dbs[dbi].md_root = P_INVALID;
+    txn->mt_dbs[dbi].md_seq = 0;
+    txn->mt_flags |= MDBX_TXN_DIRTY;
+  }
+
+bailout:
+  mdbx_cursor_close(mc);
+  return rc;
+}
+
+int mdbx_set_compare(MDBX_txn *txn, MDBX_dbi dbi, MDBX_cmp_func *cmp) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  txn->mt_dbxs[dbi].md_cmp = cmp;
+  return MDBX_SUCCESS;
+}
+
+int mdbx_set_dupsort(MDBX_txn *txn, MDBX_dbi dbi, MDBX_cmp_func *cmp) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  txn->mt_dbxs[dbi].md_dcmp = cmp;
+  return MDBX_SUCCESS;
+}
+
+__cold int mdbx_reader_list(const MDBX_env *env, MDBX_reader_list_func *func,
+                            void *ctx) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!func))
+    return MDBX_EINVAL;
+
+  rc = MDBX_RESULT_TRUE;
+  int serial = 0;
+  if (likely(env->me_lck)) {
+    const unsigned snap_nreaders =
+        atomic_load32(&env->me_lck->mti_numreaders, mo_AcquireRelease);
+    for (unsigned i = 0; i < snap_nreaders; i++) {
+      const MDBX_reader *r = env->me_lck->mti_readers + i;
+    retry_reader:;
+      const uint32_t pid = atomic_load32(&r->mr_pid, mo_AcquireRelease);
+      if (!pid)
+        continue;
+      txnid_t txnid = safe64_read(&r->mr_txnid);
+      const uint64_t tid = atomic_load64(&r->mr_tid, mo_Relaxed);
+      const pgno_t pages_used =
+          atomic_load32(&r->mr_snapshot_pages_used, mo_Relaxed);
+      const uint64_t reader_pages_retired =
+          atomic_load64(&r->mr_snapshot_pages_retired, mo_Relaxed);
+      if (unlikely(
+              txnid != safe64_read(&r->mr_txnid) ||
+              pid != atomic_load32(&r->mr_pid, mo_AcquireRelease) ||
+              tid != atomic_load64(&r->mr_tid, mo_Relaxed) ||
+              pages_used !=
+                  atomic_load32(&r->mr_snapshot_pages_used, mo_Relaxed) ||
+              reader_pages_retired !=
+                  atomic_load64(&r->mr_snapshot_pages_retired, mo_Relaxed)))
+        goto retry_reader;
+
+      mdbx_assert(env, txnid > 0);
+      if (txnid >= SAFE64_INVALID_THRESHOLD)
+        txnid = 0;
+
+      size_t bytes_used = 0;
+      size_t bytes_retained = 0;
+      uint64_t lag = 0;
+      if (txnid) {
+      retry_header:;
+        const MDBX_meta *const recent_meta = mdbx_meta_head(env);
+        const uint64_t head_pages_retired =
+            unaligned_peek_u64(4, recent_meta->mm_pages_retired);
+        const txnid_t head_txnid = mdbx_meta_txnid_fluid(env, recent_meta);
+        mdbx_compiler_barrier();
+        if (unlikely(
+                recent_meta != mdbx_meta_head(env) ||
+                head_pages_retired !=
+                    unaligned_peek_u64(4, recent_meta->mm_pages_retired)) ||
+            head_txnid != mdbx_meta_txnid_fluid(env, recent_meta))
+          goto retry_header;
+
+        lag = (head_txnid - txnid) / MDBX_TXNID_STEP;
+        bytes_used = pgno2bytes(env, pages_used);
+        bytes_retained = (head_pages_retired > reader_pages_retired)
+                             ? pgno2bytes(env, (pgno_t)(head_pages_retired -
+                                                        reader_pages_retired))
+                             : 0;
+      }
+      rc = func(ctx, ++serial, i, pid, (mdbx_tid_t)tid, txnid, lag, bytes_used,
+                bytes_retained);
+      if (unlikely(rc != MDBX_SUCCESS))
+        break;
+    }
+  }
+
+  return rc;
+}
+
+/* Insert pid into list if not already present.
+ * return -1 if already present. */
+static bool __cold mdbx_pid_insert(uint32_t *ids, uint32_t pid) {
+  /* binary search of pid in list */
+  unsigned base = 0;
+  unsigned cursor = 1;
+  int val = 0;
+  unsigned n = ids[0];
+
+  while (n > 0) {
+    unsigned pivot = n >> 1;
+    cursor = base + pivot + 1;
+    val = pid - ids[cursor];
+
+    if (val < 0) {
+      n = pivot;
+    } else if (val > 0) {
+      base = cursor;
+      n -= pivot + 1;
+    } else {
+      /* found, so it's a duplicate */
+      return false;
+    }
+  }
+
+  if (val > 0)
+    ++cursor;
+
+  ids[0]++;
+  for (n = ids[0]; n > cursor; n--)
+    ids[n] = ids[n - 1];
+  ids[n] = pid;
+  return true;
+}
+
+__cold int mdbx_reader_check(MDBX_env *env, int *dead) {
+  if (dead)
+    *dead = 0;
+  return mdbx_cleanup_dead_readers(env, false, dead);
+}
+
+/* Return:
+ *  MDBX_RESULT_TRUE - done and mutex recovered
+ *  MDBX_SUCCESS     - done
+ *  Otherwise errcode. */
+MDBX_INTERNAL_FUNC __cold int
+mdbx_cleanup_dead_readers(MDBX_env *env, int rdt_locked, int *dead) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  mdbx_assert(env, rdt_locked >= 0);
+  MDBX_lockinfo *const lck = env->me_lck;
+  if (unlikely(lck == NULL)) {
+    /* exclusive mode */
+    if (dead)
+      *dead = 0;
+    return MDBX_SUCCESS;
+  }
+
+  const unsigned snap_nreaders =
+      atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+  uint32_t pidsbuf_onstask[142];
+  uint32_t *const pids =
+      (snap_nreaders < ARRAY_LENGTH(pidsbuf_onstask))
+          ? pidsbuf_onstask
+          : mdbx_malloc((snap_nreaders + 1) * sizeof(uint32_t));
+  if (unlikely(!pids))
+    return MDBX_ENOMEM;
+
+  pids[0] = 0;
+  int count = 0;
+  for (unsigned i = 0; i < snap_nreaders; i++) {
+    const uint32_t pid =
+        atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease);
+    if (pid == 0)
+      continue /* skip empty */;
+    if (pid == env->me_pid)
+      continue /* skip self */;
+    if (!mdbx_pid_insert(pids, pid))
+      continue /* such pid already processed */;
+
+    int err = mdbx_rpid_check(env, pid);
+    if (err == MDBX_RESULT_TRUE)
+      continue /* reader is live */;
+
+    if (err != MDBX_SUCCESS) {
+      rc = err;
+      break /* mdbx_rpid_check() failed */;
+    }
+
+    /* stale reader found */
+    if (!rdt_locked) {
+      err = mdbx_rdt_lock(env);
+      if (MDBX_IS_ERROR(err)) {
+        rc = err;
+        break;
+      }
+
+      rdt_locked = -1;
+      if (err == MDBX_RESULT_TRUE) {
+        /* mutex recovered, the mdbx_ipclock_failed() checked all readers */
+        rc = MDBX_RESULT_TRUE;
+        break;
+      }
+
+      /* a other process may have clean and reused slot, recheck */
+      if (lck->mti_readers[i].mr_pid.weak != pid)
+        continue;
+
+      err = mdbx_rpid_check(env, pid);
+      if (MDBX_IS_ERROR(err)) {
+        rc = err;
+        break;
+      }
+
+      if (err != MDBX_SUCCESS)
+        continue /* the race with other process, slot reused */;
+    }
+
+    /* clean it */
+    for (unsigned j = i; j < snap_nreaders; j++) {
+      if (lck->mti_readers[j].mr_pid.weak == pid) {
+        mdbx_debug("clear stale reader pid %" PRIuPTR " txn %" PRIaTXN,
+                   (size_t)pid, lck->mti_readers[j].mr_txnid.weak);
+        atomic_store32(&lck->mti_readers[j].mr_pid, 0, mo_AcquireRelease);
+        atomic_store32(&lck->mti_readers_refresh_flag, true, mo_AcquireRelease);
+        count++;
+      }
+    }
+  }
+
+  if (likely(!MDBX_IS_ERROR(rc)))
+    atomic_store64(&lck->mti_reader_check_timestamp, mdbx_osal_monotime(),
+                   mo_AcquireRelease);
+
+  if (rdt_locked < 0)
+    mdbx_rdt_unlock(env);
+
+  if (pids != pidsbuf_onstask)
+    mdbx_free(pids);
+
+  if (dead)
+    *dead = count;
+  return rc;
+}
+
+__cold int mdbx_setup_debug(int loglevel, int flags, MDBX_debug_func *logger) {
+  const int rc = mdbx_runtime_flags | (mdbx_loglevel << 16);
+
+  if (loglevel != MDBX_LOG_DONTCHANGE)
+    mdbx_loglevel = (uint8_t)loglevel;
+
+  if (flags != MDBX_DBG_DONTCHANGE) {
+    flags &=
+#if MDBX_DEBUG
+        MDBX_DBG_ASSERT | MDBX_DBG_AUDIT | MDBX_DBG_JITTER |
+#endif
+        MDBX_DBG_DUMP | MDBX_DBG_LEGACY_MULTIOPEN | MDBX_DBG_LEGACY_OVERLAP;
+    mdbx_runtime_flags = (uint8_t)flags;
+  }
+
+  if (logger != MDBX_LOGGER_DONTCHANGE)
+    mdbx_debug_logger = logger;
+  return rc;
+}
+
+static txnid_t __cold mdbx_kick_longlived_readers(MDBX_env *env,
+                                                  const txnid_t laggard) {
+  mdbx_debug("DB size maxed out by reading #%" PRIaTXN, laggard);
+
+  int retry;
+  for (retry = 0; retry < INT_MAX; ++retry) {
+    txnid_t oldest = mdbx_recent_steady_txnid(env);
+    mdbx_assert(env, oldest < env->me_txn0->mt_txnid);
+    mdbx_assert(env, oldest >= laggard);
+    mdbx_assert(env, oldest >= env->me_oldest->weak);
+    if (oldest == laggard || unlikely(!env->me_lck /* without-LCK mode */))
+      return oldest;
+
+    if (MDBX_IS_ERROR(mdbx_cleanup_dead_readers(env, false, NULL)))
+      break;
+
+    MDBX_reader *asleep = nullptr;
+    MDBX_lockinfo *const lck = env->me_lck;
+    uint64_t oldest_retired = UINT64_MAX;
+    const unsigned snap_nreaders =
+        atomic_load32(&lck->mti_numreaders, mo_AcquireRelease);
+    for (unsigned i = 0; i < snap_nreaders; ++i) {
+    retry:
+      if (atomic_load32(&lck->mti_readers[i].mr_pid, mo_AcquireRelease)) {
+        /* mdbx_jitter4testing(true); */
+        const uint64_t snap_retired = atomic_load64(
+            &lck->mti_readers[i].mr_snapshot_pages_retired, mo_Relaxed);
+        const txnid_t snap_txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
+        if (unlikely(snap_retired !=
+                         atomic_load64(
+                             &lck->mti_readers[i].mr_snapshot_pages_retired,
+                             mo_AcquireRelease) ||
+                     snap_txnid != safe64_read(&lck->mti_readers[i].mr_txnid)))
+          goto retry;
+        if (oldest > snap_txnid &&
+            laggard <= /* ignore pending updates */ snap_txnid) {
+          oldest = snap_txnid;
+          oldest_retired = snap_retired;
+          asleep = &lck->mti_readers[i];
+        }
+      }
+    }
+
+    if (laggard < oldest || !asleep) {
+      if (retry && env->me_hsr_callback) {
+        /* LY: notify end of hsr-loop */
+        const txnid_t gap = oldest - laggard;
+        env->me_hsr_callback(env, env->me_txn, 0, 0, laggard,
+                             (gap < UINT_MAX) ? (unsigned)gap : UINT_MAX, 0,
+                             -retry);
+      }
+      mdbx_notice("hsr-kick: update oldest %" PRIaTXN " -> %" PRIaTXN,
+                  env->me_oldest->weak, oldest);
+      mdbx_assert(env, env->me_oldest->weak <= oldest);
+      return atomic_store64(env->me_oldest, oldest, mo_AcquireRelease);
+    }
+
+    if (!env->me_hsr_callback)
+      break;
+
+    uint32_t pid = atomic_load32(&asleep->mr_pid, mo_AcquireRelease);
+    uint64_t tid = asleep->mr_tid.weak;
+    if (safe64_read(&asleep->mr_txnid) != laggard || pid <= 0)
+      continue;
+
+    const MDBX_meta *head_meta = mdbx_meta_head(env);
+    const txnid_t gap =
+        (mdbx_meta_txnid_stable(env, head_meta) - laggard) / MDBX_TXNID_STEP;
+    const uint64_t head_retired =
+        unaligned_peek_u64(4, head_meta->mm_pages_retired);
+    const size_t space =
+        (oldest_retired > head_retired)
+            ? pgno2bytes(env, (pgno_t)(oldest_retired - head_retired))
+            : 0;
+    int rc = env->me_hsr_callback(
+        env, env->me_txn, pid, (mdbx_tid_t)tid, laggard,
+        (gap < UINT_MAX) ? (unsigned)gap : UINT_MAX, space, retry);
+    if (rc < 0)
+      break;
+
+    if (rc > 0) {
+      if (rc == 1) {
+        safe64_reset_compare(&asleep->mr_txnid, laggard);
+      } else {
+        safe64_reset(&asleep->mr_txnid, true);
+        atomic_store64(&asleep->mr_tid, 0, mo_Relaxed);
+        atomic_store32(&asleep->mr_pid, 0, mo_Relaxed);
+      }
+      atomic_store32(&lck->mti_readers_refresh_flag, true, mo_AcquireRelease);
+    }
+  }
+
+  if (retry && env->me_hsr_callback) {
+    /* LY: notify end of hsr-loop */
+    env->me_hsr_callback(env, env->me_txn, 0, 0, laggard, 0, 0, -retry);
+  }
+  return mdbx_find_oldest(env->me_txn);
+}
+
+__cold int mdbx_env_set_syncbytes(MDBX_env *env, size_t threshold) {
+  return __inline_mdbx_env_set_syncbytes(env, threshold);
+}
+
+__cold int mdbx_env_set_syncperiod(MDBX_env *env, unsigned seconds_16dot16) {
+  return __inline_mdbx_env_set_syncperiod(env, seconds_16dot16);
+}
+
+__cold int mdbx_env_set_hsr(MDBX_env *env, MDBX_hsr_func *hsr) {
+  int rc = check_env(env);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  env->me_hsr_callback = hsr;
+  return MDBX_SUCCESS;
+}
+
+MDBX_hsr_func *__cold mdbx_env_get_hsr(const MDBX_env *env) {
+  return likely(env && env->me_signature.weak == MDBX_ME_SIGNATURE)
+             ? env->me_hsr_callback
+             : NULL;
+}
+
+#ifdef __SANITIZE_THREAD__
+/* LY: avoid tsan-trap by me_txn, mm_last_pg and mt_next_pgno */
+__attribute__((__no_sanitize_thread__, __noinline__))
+#endif
+int mdbx_txn_straggler(const MDBX_txn *txn, int *percent)
+{
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return (rc > 0) ? -rc : rc;
+
+  MDBX_env *env = txn->mt_env;
+  if (unlikely((txn->mt_flags & MDBX_TXN_RDONLY) == 0)) {
+    if (percent)
+      *percent =
+          (int)((txn->mt_next_pgno * UINT64_C(100) + txn->mt_end_pgno / 2) /
+                txn->mt_end_pgno);
+    return 0;
+  }
+
+  txnid_t recent;
+  MDBX_meta *meta;
+  do {
+    meta = mdbx_meta_head(env);
+    recent = mdbx_meta_txnid_fluid(env, meta);
+    if (percent) {
+      const pgno_t maxpg = meta->mm_geo.now;
+      *percent = (int)((meta->mm_geo.next * UINT64_C(100) + maxpg / 2) / maxpg);
+    }
+  } while (unlikely(recent != mdbx_meta_txnid_fluid(env, meta)));
+
+  txnid_t lag = (recent - txn->mt_txnid) / MDBX_TXNID_STEP;
+  return (lag > INT_MAX) ? INT_MAX : (int)lag;
+}
+
+typedef struct mdbx_walk_ctx {
+  void *mw_user;
+  MDBX_pgvisitor_func *mw_visitor;
+  MDBX_txn *mw_txn;
+  MDBX_cursor *mw_cursor;
+  bool mw_dont_check_keys_ordering;
+} mdbx_walk_ctx_t;
+
+static __cold int mdbx_walk_sdb(mdbx_walk_ctx_t *ctx, MDBX_db *const db,
+                                const char *name, int deep);
+
+static MDBX_page_type_t walk_page_type(const MDBX_page *mp) {
+  if (mp)
+    switch (mp->mp_flags) {
+    case P_BRANCH:
+      return MDBX_page_branch;
+    case P_LEAF:
+      return MDBX_page_leaf;
+    case P_LEAF | P_LEAF2:
+      return MDBX_page_dupfixed_leaf;
+    case P_OVERFLOW:
+      return MDBX_page_large;
+    case P_META:
+      return MDBX_page_meta;
+    }
+  return MDBX_page_broken;
+}
+
+/* Depth-first tree traversal. */
+static __cold int mdbx_walk_tree(mdbx_walk_ctx_t *ctx, const pgno_t pgno,
+                                 const char *name, int deep,
+                                 txnid_t parent_txnid) {
+  assert(pgno != P_INVALID);
+  MDBX_page *mp = nullptr;
+  int rc, err = mdbx_page_get(ctx->mw_cursor, pgno, &mp, NULL, parent_txnid);
+  if (err == MDBX_SUCCESS)
+    err = mdbx_page_check(ctx->mw_cursor, mp, 0);
+
+  MDBX_page_type_t type = walk_page_type(mp);
+  const int nentries = (mp && !IS_OVERFLOW(mp)) ? page_numkeys(mp) : 1;
+  unsigned npages = (mp && IS_OVERFLOW(mp)) ? mp->mp_pages : 1;
+  size_t pagesize = pgno2bytes(ctx->mw_txn->mt_env, npages);
+  size_t header_size = (mp && !IS_LEAF2(mp) && !IS_OVERFLOW(mp))
+                           ? PAGEHDRSZ + mp->mp_lower
+                           : PAGEHDRSZ;
+  size_t payload_size = 0;
+  size_t unused_size =
+      (mp && !IS_OVERFLOW(mp) ? page_room(mp) : pagesize - header_size) -
+      payload_size;
+  size_t align_bytes = 0;
+
+  if (err == MDBX_SUCCESS) {
+    /* LY: Don't use mask here, e.g bitwise
+     * (P_BRANCH|P_LEAF|P_LEAF2|P_META|P_OVERFLOW|P_SUBP).
+     * Pages should not me marked dirty/loose or otherwise. */
+    switch (mp->mp_flags) {
+    default:
+      err = MDBX_CORRUPTED;
+      break;
+    case P_BRANCH:
+      if (unlikely(nentries < 2))
+        err = MDBX_CORRUPTED;
+    case P_LEAF:
+    case P_LEAF | P_LEAF2:
+      break;
+    }
+  }
+
+  for (int i = 0; err == MDBX_SUCCESS && i < nentries;
+       align_bytes += ((payload_size + align_bytes) & 1), i++) {
+    if (type == MDBX_page_dupfixed_leaf) {
+      /* LEAF2 pages have no mp_ptrs[] or node headers */
+      payload_size += mp->mp_leaf2_ksize;
+      continue;
+    }
+
+    MDBX_node *node = page_node(mp, i);
+    payload_size += NODESIZE + node_ks(node);
+
+    if (type == MDBX_page_branch) {
+      assert(i > 0 || node_ks(node) == 0);
+      continue;
+    }
+
+    assert(type == MDBX_page_leaf);
+    switch (node_flags(node)) {
+    case 0 /* usual node */:
+      payload_size += node_ds(node);
+      break;
+
+    case F_BIGDATA /* long data on the large/overflow page */: {
+      payload_size += sizeof(pgno_t);
+      const pgno_t large_pgno = node_largedata_pgno(node);
+      const size_t over_payload = node_ds(node);
+      const size_t over_header = PAGEHDRSZ;
+      npages = 1;
+
+      MDBX_page *op;
+      err = mdbx_page_get(ctx->mw_cursor, large_pgno, &op, NULL,
+                          pp_txnid4chk(mp, ctx->mw_txn));
+      if (err == MDBX_SUCCESS)
+        err = mdbx_page_check(ctx->mw_cursor, op, 0);
+      if (err == MDBX_SUCCESS) {
+        /* LY: Don't use mask here, e.g bitwise
+         * (P_BRANCH|P_LEAF|P_LEAF2|P_META|P_OVERFLOW|P_SUBP).
+         * Pages should not me marked dirty/loose or otherwise. */
+        if (P_OVERFLOW != op->mp_flags)
+          err = bad_page(mp, "wrong page type %d for large data", op->mp_flags);
+        else
+          npages = op->mp_pages;
+      }
+
+      pagesize = pgno2bytes(ctx->mw_txn->mt_env, npages);
+      const size_t over_unused = pagesize - over_payload - over_header;
+      rc = ctx->mw_visitor(large_pgno, npages, ctx->mw_user, deep, name,
+                           pagesize, MDBX_page_large, err, 1, over_payload,
+                           over_header, over_unused);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return (rc == MDBX_RESULT_TRUE) ? MDBX_SUCCESS : rc;
+    } break;
+
+    case F_SUBDATA /* sub-db */: {
+      const size_t namelen = node_ks(node);
+      payload_size += node_ds(node);
+      if (unlikely(namelen == 0 || node_ds(node) != sizeof(MDBX_db)))
+        err = MDBX_CORRUPTED;
+    } break;
+
+    case F_SUBDATA | F_DUPDATA /* dupsorted sub-tree */:
+      payload_size += sizeof(MDBX_db);
+      if (unlikely(node_ds(node) != sizeof(MDBX_db)))
+        err = MDBX_CORRUPTED;
+      break;
+
+    case F_DUPDATA /* short sub-page */: {
+      if (unlikely(node_ds(node) <= PAGEHDRSZ)) {
+        err = MDBX_CORRUPTED;
+        break;
+      }
+
+      MDBX_page *sp = node_data(node);
+      const int nsubkeys = page_numkeys(sp);
+      size_t subheader_size =
+          IS_LEAF2(sp) ? PAGEHDRSZ : PAGEHDRSZ + sp->mp_lower;
+      size_t subunused_size = page_room(sp);
+      size_t subpayload_size = 0;
+      size_t subalign_bytes = 0;
+      MDBX_page_type_t subtype;
+
+      switch (sp->mp_flags & ~P_DIRTY /* ignore for sub-pages */) {
+      case P_LEAF | P_SUBP:
+        subtype = MDBX_subpage_leaf;
+        break;
+      case P_LEAF | P_LEAF2 | P_SUBP:
+        subtype = MDBX_subpage_dupfixed_leaf;
+        break;
+      default:
+        subtype = MDBX_subpage_broken;
+        err = MDBX_CORRUPTED;
+      }
+
+      for (int j = 0; err == MDBX_SUCCESS && j < nsubkeys;
+           subalign_bytes += ((subpayload_size + subalign_bytes) & 1), j++) {
+
+        if (subtype == MDBX_subpage_dupfixed_leaf) {
+          /* LEAF2 pages have no mp_ptrs[] or node headers */
+          subpayload_size += sp->mp_leaf2_ksize;
+        } else {
+          assert(subtype == MDBX_subpage_leaf);
+          MDBX_node *subnode = page_node(sp, j);
+          subpayload_size += NODESIZE + node_ks(subnode) + node_ds(subnode);
+          if (unlikely(node_flags(subnode) != 0))
+            err = MDBX_CORRUPTED;
+        }
+      }
+
+      rc = ctx->mw_visitor(pgno, 0, ctx->mw_user, deep + 1, name, node_ds(node),
+                           subtype, err, nsubkeys, subpayload_size,
+                           subheader_size, subunused_size + subalign_bytes);
+      if (unlikely(rc != MDBX_SUCCESS))
+        return (rc == MDBX_RESULT_TRUE) ? MDBX_SUCCESS : rc;
+      header_size += subheader_size;
+      unused_size += subunused_size;
+      payload_size += subpayload_size;
+      align_bytes += subalign_bytes;
+    } break;
+
+    default:
+      err = MDBX_CORRUPTED;
+    }
+  }
+
+  rc = ctx->mw_visitor(pgno, 1, ctx->mw_user, deep, name,
+                       ctx->mw_txn->mt_env->me_psize, type, err, nentries,
+                       payload_size, header_size, unused_size + align_bytes);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return (rc == MDBX_RESULT_TRUE) ? MDBX_SUCCESS : rc;
+
+  for (int i = 0; err == MDBX_SUCCESS && i < nentries; i++) {
+    if (type == MDBX_page_dupfixed_leaf)
+      continue;
+
+    MDBX_node *node = page_node(mp, i);
+    if (type == MDBX_page_branch) {
+      err = mdbx_walk_tree(ctx, node_pgno(node), name, deep + 1,
+                           pp_txnid4chk(mp, ctx->mw_txn));
+      if (unlikely(err != MDBX_SUCCESS)) {
+        if (err == MDBX_RESULT_TRUE)
+          break;
+        return err;
+      }
+      continue;
+    }
+
+    assert(type == MDBX_page_leaf);
+    MDBX_db db;
+    switch (node_flags(node)) {
+    default:
+      continue;
+
+    case F_SUBDATA /* sub-db */: {
+      const size_t namelen = node_ks(node);
+      if (unlikely(namelen == 0 || node_ds(node) != sizeof(MDBX_db))) {
+        err = MDBX_CORRUPTED;
+        break;
+      }
+
+      char namebuf_onstask[64];
+      char *const sub_name = (namelen < sizeof(namebuf_onstask))
+                                 ? namebuf_onstask
+                                 : mdbx_malloc(namelen + 1);
+      if (sub_name) {
+        memcpy(sub_name, node_key(node), namelen);
+        sub_name[namelen] = 0;
+        memcpy(&db, node_data(node), sizeof(db));
+        err = mdbx_walk_sdb(ctx, &db, sub_name, deep + 1);
+        if (sub_name != namebuf_onstask)
+          mdbx_free(sub_name);
+      } else {
+        err = MDBX_ENOMEM;
+      }
+    } break;
+
+    case F_SUBDATA | F_DUPDATA /* dupsorted sub-tree */:
+      if (unlikely(node_ds(node) != sizeof(MDBX_db) ||
+                   ctx->mw_cursor->mc_xcursor == NULL))
+        err = MDBX_CORRUPTED;
+      else {
+        memcpy(&db, node_data(node), sizeof(db));
+        assert(ctx->mw_cursor->mc_xcursor ==
+               &container_of(ctx->mw_cursor, MDBX_cursor_couple, outer)->inner);
+        ctx->mw_cursor = &ctx->mw_cursor->mc_xcursor->mx_cursor;
+        err = mdbx_walk_tree(ctx, db.md_root, name, deep + 1,
+                             pp_txnid4chk(mp, ctx->mw_txn));
+        MDBX_xcursor *inner_xcursor =
+            container_of(ctx->mw_cursor, MDBX_xcursor, mx_cursor);
+        MDBX_cursor_couple *couple =
+            container_of(inner_xcursor, MDBX_cursor_couple, inner);
+        ctx->mw_cursor = &couple->outer;
+      }
+      break;
+    }
+  }
+
+  return MDBX_SUCCESS;
+}
+
+static __cold int mdbx_walk_sdb(mdbx_walk_ctx_t *ctx, MDBX_db *const db,
+                                const char *name, int deep) {
+  if (unlikely(db->md_root == P_INVALID))
+    return MDBX_SUCCESS; /* empty db */
+
+  MDBX_cursor_couple couple;
+  MDBX_dbx dbx = {.md_klen_min = INT_MAX};
+  uint8_t dbistate = DBI_VALID | DBI_AUDITED;
+  int rc = mdbx_couple_init(&couple, ~0u, ctx->mw_txn, db, &dbx, &dbistate);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (ctx->mw_dont_check_keys_ordering) {
+    couple.outer.mc_flags |= C_SKIPORD;
+    couple.inner.mx_cursor.mc_flags |= C_SKIPORD;
+  }
+  couple.outer.mc_next = ctx->mw_cursor;
+  ctx->mw_cursor = &couple.outer;
+  rc = mdbx_walk_tree(ctx, db->md_root, name, deep, ctx->mw_txn->mt_txnid);
+  ctx->mw_cursor = couple.outer.mc_next;
+  return rc;
+}
+
+__cold int mdbx_env_pgwalk(MDBX_txn *txn, MDBX_pgvisitor_func *visitor,
+                           void *user, bool dont_check_keys_ordering) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  mdbx_walk_ctx_t ctx;
+  memset(&ctx, 0, sizeof(ctx));
+  ctx.mw_txn = txn;
+  ctx.mw_user = user;
+  ctx.mw_visitor = visitor;
+  ctx.mw_dont_check_keys_ordering = dont_check_keys_ordering;
+
+  rc = visitor(0, NUM_METAS, user, 0, MDBX_PGWALK_META,
+               pgno2bytes(txn->mt_env, NUM_METAS), MDBX_page_meta, MDBX_SUCCESS,
+               NUM_METAS, sizeof(MDBX_meta) * NUM_METAS, PAGEHDRSZ * NUM_METAS,
+               (txn->mt_env->me_psize - sizeof(MDBX_meta) - PAGEHDRSZ) *
+                   NUM_METAS);
+  if (!MDBX_IS_ERROR(rc))
+    rc = mdbx_walk_sdb(&ctx, &txn->mt_dbs[FREE_DBI], MDBX_PGWALK_GC, 0);
+  if (!MDBX_IS_ERROR(rc))
+    rc = mdbx_walk_sdb(&ctx, &txn->mt_dbs[MAIN_DBI], MDBX_PGWALK_MAIN, 0);
+  return rc;
+}
+
+int mdbx_canary_put(MDBX_txn *txn, const MDBX_canary *canary) {
+  int rc = check_txn_rw(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (likely(canary)) {
+    if (txn->mt_canary.x == canary->x && txn->mt_canary.y == canary->y &&
+        txn->mt_canary.z == canary->z)
+      return MDBX_SUCCESS;
+    txn->mt_canary.x = canary->x;
+    txn->mt_canary.y = canary->y;
+    txn->mt_canary.z = canary->z;
+  }
+  txn->mt_canary.v = txn->mt_txnid;
+  txn->mt_flags |= MDBX_TXN_DIRTY;
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_canary_get(const MDBX_txn *txn, MDBX_canary *canary) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(canary == NULL))
+    return MDBX_EINVAL;
+
+  *canary = txn->mt_canary;
+  return MDBX_SUCCESS;
+}
+
+int mdbx_cursor_on_first(const MDBX_cursor *mc) {
+  if (unlikely(mc == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  if (!(mc->mc_flags & C_INITIALIZED))
+    return mc->mc_db->md_entries ? MDBX_RESULT_FALSE : MDBX_RESULT_TRUE;
+
+  for (unsigned i = 0; i < mc->mc_snum; ++i) {
+    if (mc->mc_ki[i])
+      return MDBX_RESULT_FALSE;
+  }
+
+  return MDBX_RESULT_TRUE;
+}
+
+int mdbx_cursor_on_last(const MDBX_cursor *mc) {
+  if (unlikely(mc == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  if (!(mc->mc_flags & C_INITIALIZED))
+    return mc->mc_db->md_entries ? MDBX_RESULT_FALSE : MDBX_RESULT_TRUE;
+
+  for (unsigned i = 0; i < mc->mc_snum; ++i) {
+    unsigned nkeys = page_numkeys(mc->mc_pg[i]);
+    if (mc->mc_ki[i] < nkeys - 1)
+      return MDBX_RESULT_FALSE;
+  }
+
+  return MDBX_RESULT_TRUE;
+}
+
+int mdbx_cursor_eof(const MDBX_cursor *mc) {
+  if (unlikely(mc == NULL))
+    return MDBX_EINVAL;
+
+  if (unlikely(mc->mc_signature != MDBX_MC_LIVE))
+    return (mc->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                     : MDBX_EBADSIGN;
+
+  if ((mc->mc_flags & C_INITIALIZED) == 0)
+    return MDBX_RESULT_TRUE;
+
+  if (mc->mc_snum == 0)
+    return MDBX_RESULT_TRUE;
+
+  if ((mc->mc_flags & C_EOF) &&
+      mc->mc_ki[mc->mc_top] >= page_numkeys(mc->mc_pg[mc->mc_top]))
+    return MDBX_RESULT_TRUE;
+
+  return MDBX_RESULT_FALSE;
+}
+
+//------------------------------------------------------------------------------
+
+struct diff_result {
+  ptrdiff_t diff;
+  unsigned level;
+  int root_nkeys;
+};
+
+/* calculates: r = x - y */
+__hot static int cursor_diff(const MDBX_cursor *const __restrict x,
+                             const MDBX_cursor *const __restrict y,
+                             struct diff_result *const __restrict r) {
+  r->diff = 0;
+  r->level = 0;
+  r->root_nkeys = 0;
+
+  if (unlikely(x->mc_signature != MDBX_MC_LIVE))
+    return (x->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                    : MDBX_EBADSIGN;
+
+  if (unlikely(y->mc_signature != MDBX_MC_LIVE))
+    return (y->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                    : MDBX_EBADSIGN;
+
+  int rc = check_txn(x->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(x->mc_txn != y->mc_txn))
+    return MDBX_BAD_TXN;
+
+  if (unlikely(y->mc_dbi != x->mc_dbi))
+    return MDBX_EINVAL;
+
+  if (unlikely(!(y->mc_flags & x->mc_flags & C_INITIALIZED)))
+    return MDBX_ENODATA;
+
+  while (likely(r->level < y->mc_snum && r->level < x->mc_snum)) {
+    if (unlikely(y->mc_pg[r->level] != x->mc_pg[r->level]))
+      return MDBX_PROBLEM;
+
+    int nkeys = page_numkeys(y->mc_pg[r->level]);
+    assert(nkeys > 0);
+    if (r->level == 0)
+      r->root_nkeys = nkeys;
+
+    const int limit_ki = nkeys - 1;
+    const int x_ki = x->mc_ki[r->level];
+    const int y_ki = y->mc_ki[r->level];
+    r->diff = ((x_ki < limit_ki) ? x_ki : limit_ki) -
+              ((y_ki < limit_ki) ? y_ki : limit_ki);
+    if (r->diff == 0) {
+      r->level += 1;
+      continue;
+    }
+
+    while (unlikely(r->diff == 1) &&
+           likely(r->level + 1 < y->mc_snum && r->level + 1 < x->mc_snum)) {
+      r->level += 1;
+      /*   DB'PAGEs: 0------------------>MAX
+       *
+       *    CURSORs:       y < x
+       *  STACK[i ]:         |
+       *  STACK[+1]:  ...y++N|0++x...
+       */
+      nkeys = page_numkeys(y->mc_pg[r->level]);
+      r->diff = (nkeys - y->mc_ki[r->level]) + x->mc_ki[r->level];
+      assert(r->diff > 0);
+    }
+
+    while (unlikely(r->diff == -1) &&
+           likely(r->level + 1 < y->mc_snum && r->level + 1 < x->mc_snum)) {
+      r->level += 1;
+      /*   DB'PAGEs: 0------------------>MAX
+       *
+       *    CURSORs:       x < y
+       *  STACK[i ]:         |
+       *  STACK[+1]:  ...x--N|0--y...
+       */
+      nkeys = page_numkeys(x->mc_pg[r->level]);
+      r->diff = -(nkeys - x->mc_ki[r->level]) - y->mc_ki[r->level];
+      assert(r->diff < 0);
+    }
+
+    return MDBX_SUCCESS;
+  }
+
+  r->diff = CMP2INT(x->mc_flags & C_EOF, y->mc_flags & C_EOF);
+  return MDBX_SUCCESS;
+}
+
+__hot static ptrdiff_t estimate(const MDBX_db *db,
+                                struct diff_result *const __restrict dr) {
+  /*        root: branch-page    => scale = leaf-factor * branch-factor^(N-1)
+   *     level-1: branch-page(s) => scale = leaf-factor * branch-factor^2
+   *     level-2: branch-page(s) => scale = leaf-factor * branch-factor
+   *     level-N: branch-page(s) => scale = leaf-factor
+   *  leaf-level: leaf-page(s)   => scale = 1
+   */
+  ptrdiff_t btree_power = (ptrdiff_t)db->md_depth - 2 - (ptrdiff_t)dr->level;
+  if (btree_power < 0)
+    return dr->diff;
+
+  ptrdiff_t estimated =
+      (ptrdiff_t)db->md_entries * dr->diff / (ptrdiff_t)db->md_leaf_pages;
+  if (btree_power == 0)
+    return estimated;
+
+  if (db->md_depth < 4) {
+    assert(dr->level == 0 && btree_power == 1);
+    return (ptrdiff_t)db->md_entries * dr->diff / (ptrdiff_t)dr->root_nkeys;
+  }
+
+  /* average_branchpage_fillfactor = total(branch_entries) / branch_pages
+     total(branch_entries) = leaf_pages + branch_pages - 1 (root page) */
+  const size_t log2_fixedpoint = sizeof(size_t) - 1;
+  const size_t half = UINT64_C(1) << (log2_fixedpoint - 1);
+  const size_t factor =
+      ((db->md_leaf_pages + db->md_branch_pages - 1) << log2_fixedpoint) /
+      db->md_branch_pages;
+  while (1) {
+    switch ((size_t)btree_power) {
+    default: {
+      const size_t square = (factor * factor + half) >> log2_fixedpoint;
+      const size_t quad = (square * square + half) >> log2_fixedpoint;
+      do {
+        estimated = estimated * quad + half;
+        estimated >>= log2_fixedpoint;
+        btree_power -= 4;
+      } while (btree_power >= 4);
+      continue;
+    }
+    case 3:
+      estimated = estimated * factor + half;
+      estimated >>= log2_fixedpoint;
+      __fallthrough /* fall through */;
+    case 2:
+      estimated = estimated * factor + half;
+      estimated >>= log2_fixedpoint;
+      __fallthrough /* fall through */;
+    case 1:
+      estimated = estimated * factor + half;
+      estimated >>= log2_fixedpoint;
+      __fallthrough /* fall through */;
+    case 0:
+      if (unlikely(estimated > (ptrdiff_t)db->md_entries))
+        return (ptrdiff_t)db->md_entries;
+      if (unlikely(estimated < -(ptrdiff_t)db->md_entries))
+        return -(ptrdiff_t)db->md_entries;
+      return estimated;
+    }
+  }
+}
+
+int mdbx_estimate_distance(const MDBX_cursor *first, const MDBX_cursor *last,
+                           ptrdiff_t *distance_items) {
+  if (unlikely(first == NULL || last == NULL || distance_items == NULL))
+    return MDBX_EINVAL;
+
+  *distance_items = 0;
+  struct diff_result dr;
+  int rc = cursor_diff(last, first, &dr);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(dr.diff == 0) &&
+      F_ISSET(first->mc_db->md_flags & last->mc_db->md_flags,
+              MDBX_DUPSORT | C_INITIALIZED)) {
+    first = &first->mc_xcursor->mx_cursor;
+    last = &last->mc_xcursor->mx_cursor;
+    rc = cursor_diff(first, last, &dr);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  if (likely(dr.diff != 0))
+    *distance_items = estimate(first->mc_db, &dr);
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_estimate_move(const MDBX_cursor *cursor, MDBX_val *key, MDBX_val *data,
+                       MDBX_cursor_op move_op, ptrdiff_t *distance_items) {
+  if (unlikely(cursor == NULL || distance_items == NULL ||
+               move_op == MDBX_GET_CURRENT || move_op == MDBX_GET_MULTIPLE))
+    return MDBX_EINVAL;
+
+  if (unlikely(cursor->mc_signature != MDBX_MC_LIVE))
+    return (cursor->mc_signature == MDBX_MC_READY4CLOSE) ? MDBX_EINVAL
+                                                         : MDBX_EBADSIGN;
+
+  int rc = check_txn(cursor->mc_txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (!(cursor->mc_flags & C_INITIALIZED))
+    return MDBX_ENODATA;
+
+  MDBX_cursor_couple next;
+  cursor_copy_internal(cursor, &next.outer);
+  next.outer.mc_xcursor = NULL;
+  if (cursor->mc_db->md_flags & MDBX_DUPSORT) {
+    next.outer.mc_xcursor = &next.inner;
+    rc = mdbx_xcursor_init0(&next.outer);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    MDBX_xcursor *mx = &container_of(cursor, MDBX_cursor_couple, outer)->inner;
+    cursor_copy_internal(&mx->mx_cursor, &next.inner.mx_cursor);
+  }
+
+  MDBX_val stub = {0, 0};
+  if (data == NULL) {
+    const unsigned mask =
+        1 << MDBX_GET_BOTH | 1 << MDBX_GET_BOTH_RANGE | 1 << MDBX_SET_KEY;
+    if (unlikely(mask & (1 << move_op)))
+      return MDBX_EINVAL;
+    data = &stub;
+  }
+
+  if (key == NULL) {
+    const unsigned mask = 1 << MDBX_GET_BOTH | 1 << MDBX_GET_BOTH_RANGE |
+                          1 << MDBX_SET_KEY | 1 << MDBX_SET |
+                          1 << MDBX_SET_RANGE;
+    if (unlikely(mask & (1 << move_op)))
+      return MDBX_EINVAL;
+    key = &stub;
+  }
+
+  rc = mdbx_cursor_get(&next.outer, key, data, move_op);
+  if (unlikely(rc != MDBX_SUCCESS &&
+               (rc != MDBX_NOTFOUND || !(next.outer.mc_flags & C_INITIALIZED))))
+    return rc;
+
+  return mdbx_estimate_distance(cursor, &next.outer, distance_items);
+}
+
+int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
+                        MDBX_val *begin_data, MDBX_val *end_key,
+                        MDBX_val *end_data, ptrdiff_t *size_items) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!size_items))
+    return MDBX_EINVAL;
+
+  if (unlikely(begin_data && (begin_key == NULL || begin_key == MDBX_EPSILON)))
+    return MDBX_EINVAL;
+
+  if (unlikely(end_data && (end_key == NULL || end_key == MDBX_EPSILON)))
+    return MDBX_EINVAL;
+
+  if (unlikely(begin_key == MDBX_EPSILON && end_key == MDBX_EPSILON))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  MDBX_cursor_couple begin;
+  /* LY: first, initialize cursor to refresh a DB in case it have DB_STALE */
+  rc = mdbx_cursor_init(&begin.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(begin.outer.mc_db->md_entries == 0)) {
+    *size_items = 0;
+    return MDBX_SUCCESS;
+  }
+
+  if (!begin_key) {
+    if (unlikely(!end_key)) {
+      /* LY: FIRST..LAST case */
+      *size_items = (ptrdiff_t)begin.outer.mc_db->md_entries;
+      return MDBX_SUCCESS;
+    }
+    MDBX_val stub = {0, 0};
+    rc = mdbx_cursor_first(&begin.outer, &stub, &stub);
+    if (unlikely(end_key == MDBX_EPSILON)) {
+      /* LY: FIRST..+epsilon case */
+      return (rc == MDBX_SUCCESS)
+                 ? mdbx_cursor_count(&begin.outer, (size_t *)size_items)
+                 : rc;
+    }
+  } else {
+    if (unlikely(begin_key == MDBX_EPSILON)) {
+      if (end_key == NULL) {
+        /* LY: -epsilon..LAST case */
+        MDBX_val stub = {0, 0};
+        rc = mdbx_cursor_last(&begin.outer, &stub, &stub);
+        return (rc == MDBX_SUCCESS)
+                   ? mdbx_cursor_count(&begin.outer, (size_t *)size_items)
+                   : rc;
+      }
+      /* LY: -epsilon..value case */
+      assert(end_key != MDBX_EPSILON);
+      begin_key = end_key;
+    } else if (unlikely(end_key == MDBX_EPSILON)) {
+      /* LY: value..+epsilon case */
+      assert(begin_key != MDBX_EPSILON);
+      end_key = begin_key;
+    }
+    if (end_key && !begin_data && !end_data &&
+        (begin_key == end_key ||
+         begin.outer.mc_dbx->md_cmp(begin_key, end_key) == 0)) {
+      /* LY: single key case */
+      int exact = 0;
+      rc = mdbx_cursor_set(&begin.outer, begin_key, NULL, MDBX_SET, &exact);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        *size_items = 0;
+        return (rc == MDBX_NOTFOUND) ? MDBX_SUCCESS : rc;
+      }
+      *size_items = 1;
+      if (begin.outer.mc_xcursor != NULL) {
+        MDBX_node *node = page_node(begin.outer.mc_pg[begin.outer.mc_top],
+                                    begin.outer.mc_ki[begin.outer.mc_top]);
+        if (F_ISSET(node_flags(node), F_DUPDATA)) {
+          /* LY: return the number of duplicates for given key */
+          mdbx_tassert(txn,
+                       begin.outer.mc_xcursor == &begin.inner &&
+                           (begin.inner.mx_cursor.mc_flags & C_INITIALIZED));
+          *size_items =
+              (sizeof(*size_items) >= sizeof(begin.inner.mx_db.md_entries) ||
+               begin.inner.mx_db.md_entries <= PTRDIFF_MAX)
+                  ? (size_t)begin.inner.mx_db.md_entries
+                  : PTRDIFF_MAX;
+        }
+      }
+      return MDBX_SUCCESS;
+    } else {
+      rc = mdbx_cursor_set(&begin.outer, begin_key, begin_data,
+                           begin_data ? MDBX_GET_BOTH_RANGE : MDBX_SET_RANGE,
+                           NULL);
+    }
+  }
+
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc != MDBX_NOTFOUND || !(begin.outer.mc_flags & C_INITIALIZED))
+      return rc;
+  }
+
+  MDBX_cursor_couple end;
+  rc = mdbx_cursor_init(&end.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  if (!end_key) {
+    MDBX_val stub = {0, 0};
+    rc = mdbx_cursor_last(&end.outer, &stub, &stub);
+  } else {
+    rc = mdbx_cursor_set(&end.outer, end_key, end_data,
+                         end_data ? MDBX_GET_BOTH_RANGE : MDBX_SET_RANGE, NULL);
+  }
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc != MDBX_NOTFOUND || !(end.outer.mc_flags & C_INITIALIZED))
+      return rc;
+  }
+
+  rc = mdbx_estimate_distance(&begin.outer, &end.outer, size_items);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  assert(*size_items >= -(ptrdiff_t)begin.outer.mc_db->md_entries &&
+         *size_items <= (ptrdiff_t)begin.outer.mc_db->md_entries);
+
+#if 0 /* LY: Was decided to returns as-is (i.e. negative) the estimation       \
+       * results for an inverted ranges. */
+
+  /* Commit 8ddfd1f34ad7cf7a3c4aa75d2e248ca7e639ed63
+     Change-Id: If59eccf7311123ab6384c4b93f9b1fed5a0a10d1 */
+
+  if (*size_items < 0) {
+    /* LY: inverted range case */
+    *size_items += (ptrdiff_t)begin.outer.mc_db->md_entries;
+  } else if (*size_items == 0 && begin_key && end_key) {
+    int cmp = begin.outer.mc_dbx->md_cmp(&origin_begin_key, &origin_end_key);
+    if (cmp == 0 && (begin.inner.mx_cursor.mc_flags & C_INITIALIZED) &&
+        begin_data && end_data)
+      cmp = begin.outer.mc_dbx->md_dcmp(&origin_begin_data, &origin_end_data);
+    if (cmp > 0) {
+      /* LY: inverted range case with empty scope */
+      *size_items = (ptrdiff_t)begin.outer.mc_db->md_entries;
+    }
+  }
+  assert(*size_items >= 0 &&
+         *size_items <= (ptrdiff_t)begin.outer.mc_db->md_entries);
+#endif
+
+  return MDBX_SUCCESS;
+}
+
+//------------------------------------------------------------------------------
+
+/* Позволяет обновить или удалить существующую запись с получением
+ * в old_data предыдущего значения данных. При этом если new_data равен
+ * нулю, то выполняется удаление, иначе обновление/вставка.
+ *
+ * Текущее значение может находиться в уже измененной (грязной) странице.
+ * В этом случае страница будет перезаписана при обновлении, а само старое
+ * значение утрачено. Поэтому исходно в old_data должен быть передан
+ * дополнительный буфер для копирования старого значения.
+ * Если переданный буфер слишком мал, то функция вернет -1, установив
+ * old_data->iov_len в соответствующее значение.
+ *
+ * Для не-уникальных ключей также возможен второй сценарий использования,
+ * когда посредством old_data из записей с одинаковым ключом для
+ * удаления/обновления выбирается конкретная. Для выбора этого сценария
+ * во flags следует одновременно указать MDBX_CURRENT и MDBX_NOOVERWRITE.
+ * Именно эта комбинация выбрана, так как она лишена смысла, и этим позволяет
+ * идентифицировать запрос такого сценария.
+ *
+ * Функция может быть замещена соответствующими операциями с курсорами
+ * после двух доработок (TODO):
+ *  - внешняя аллокация курсоров, в том числе на стеке (без malloc).
+ *  - получения статуса страницы по адресу (знать о P_DIRTY).
+ */
+
+int mdbx_replace_ex(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                    MDBX_val *new_data, MDBX_val *old_data,
+                    MDBX_put_flags_t flags, MDBX_preserve_func preserver,
+                    void *preserver_context) {
+  int rc = check_txn_rw(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!key || !old_data || old_data == new_data))
+    return MDBX_EINVAL;
+
+  if (unlikely(old_data->iov_base == NULL && old_data->iov_len))
+    return MDBX_EINVAL;
+
+  if (unlikely(new_data == NULL &&
+               (flags & (MDBX_CURRENT | MDBX_RESERVE)) != MDBX_CURRENT))
+    return MDBX_EINVAL;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(flags &
+               ~(MDBX_NOOVERWRITE | MDBX_NODUPDATA | MDBX_ALLDUPS |
+                 MDBX_RESERVE | MDBX_APPEND | MDBX_APPENDDUP | MDBX_CURRENT)))
+    return MDBX_EINVAL;
+
+  MDBX_cursor_couple cx;
+  rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  cx.outer.mc_next = txn->tw.cursors[dbi];
+  txn->tw.cursors[dbi] = &cx.outer;
+
+  MDBX_val present_key = *key;
+  if (F_ISSET(flags, MDBX_CURRENT | MDBX_NOOVERWRITE)) {
+    /* в old_data значение для выбора конкретного дубликата */
+    if (unlikely(!(txn->mt_dbs[dbi].md_flags & MDBX_DUPSORT))) {
+      rc = MDBX_EINVAL;
+      goto bailout;
+    }
+
+    /* убираем лишний бит, он был признаком запрошенного режима */
+    flags -= MDBX_NOOVERWRITE;
+
+    rc = mdbx_cursor_get(&cx.outer, &present_key, old_data, MDBX_GET_BOTH);
+    if (rc != MDBX_SUCCESS)
+      goto bailout;
+  } else {
+    /* в old_data буфер для сохранения предыдущего значения */
+    if (unlikely(new_data && old_data->iov_base == new_data->iov_base))
+      return MDBX_EINVAL;
+    MDBX_val present_data;
+    rc = mdbx_cursor_get(&cx.outer, &present_key, &present_data, MDBX_SET_KEY);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      old_data->iov_base = NULL;
+      old_data->iov_len = 0;
+      if (rc != MDBX_NOTFOUND || (flags & MDBX_CURRENT))
+        goto bailout;
+    } else if (flags & MDBX_NOOVERWRITE) {
+      rc = MDBX_KEYEXIST;
+      *old_data = present_data;
+      goto bailout;
+    } else {
+      MDBX_page *page = cx.outer.mc_pg[cx.outer.mc_top];
+      if (txn->mt_dbs[dbi].md_flags & MDBX_DUPSORT) {
+        if (flags & MDBX_CURRENT) {
+          /* disallow update/delete for multi-values */
+          MDBX_node *node = page_node(page, cx.outer.mc_ki[cx.outer.mc_top]);
+          if (F_ISSET(node_flags(node), F_DUPDATA)) {
+            mdbx_tassert(txn, XCURSOR_INITED(&cx.outer) &&
+                                  cx.outer.mc_xcursor->mx_db.md_entries > 1);
+            if (cx.outer.mc_xcursor->mx_db.md_entries > 1) {
+              rc = MDBX_EMULTIVAL;
+              goto bailout;
+            }
+          }
+          /* В оригинальной LMDB флажок MDBX_CURRENT здесь приведет
+           * к замене данных без учета MDBX_DUPSORT сортировки,
+           * но здесь это в любом случае допустимо, так как мы
+           * проверили что для ключа есть только одно значение. */
+        }
+      }
+
+      if (IS_DIRTY(page)) {
+        if (new_data && cmp_lenfast(&present_data, new_data) == 0) {
+          /* если данные совпадают, то ничего делать не надо */
+          *old_data = *new_data;
+          goto bailout;
+        }
+        rc = preserver ? preserver(preserver_context, old_data,
+                                   present_data.iov_base, present_data.iov_len)
+                       : MDBX_SUCCESS;
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      } else {
+        *old_data = present_data;
+      }
+      flags |= MDBX_CURRENT;
+    }
+  }
+
+  if (likely(new_data))
+    rc = mdbx_cursor_put(&cx.outer, key, new_data, flags);
+  else
+    rc = mdbx_cursor_del(&cx.outer, flags & MDBX_ALLDUPS);
+
+bailout:
+  txn->tw.cursors[dbi] = cx.outer.mc_next;
+  return rc;
+}
+
+static int default_value_preserver(void *context, MDBX_val *target,
+                                   const void *src, size_t bytes) {
+  (void)context;
+  if (unlikely(target->iov_len < bytes)) {
+    target->iov_base = nullptr;
+    target->iov_len = bytes;
+    return MDBX_RESULT_TRUE;
+  }
+  memcpy(target->iov_base, src, target->iov_len = bytes);
+  return MDBX_SUCCESS;
+}
+
+int mdbx_replace(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                 MDBX_val *new_data, MDBX_val *old_data,
+                 MDBX_put_flags_t flags) {
+  return mdbx_replace_ex(txn, dbi, key, new_data, old_data, flags,
+                         default_value_preserver, nullptr);
+}
+
+/* Функция сообщает находится ли указанный адрес в "грязной" странице у
+ * заданной пишущей транзакции. В конечном счете это позволяет избавиться от
+ * лишнего копирования данных из НЕ-грязных страниц.
+ *
+ * "Грязные" страницы - это те, которые уже были изменены в ходе пишущей
+ * транзакции. Соответственно, какие-либо дальнейшие изменения могут привести
+ * к перезаписи таких страниц. Поэтому все функции, выполняющие изменения, в
+ * качестве аргументов НЕ должны получать указатели на данные в таких
+ * страницах. В свою очередь "НЕ грязные" страницы перед модификацией будут
+ * скопированы.
+ *
+ * Другими словами, данные из "грязных" страниц должны быть либо скопированы
+ * перед передачей в качестве аргументов для дальнейших модификаций, либо
+ * отвергнуты на стадии проверки корректности аргументов.
+ *
+ * Таким образом, функция позволяет как избавиться от лишнего копирования,
+ * так и выполнить более полную проверку аргументов.
+ *
+ * ВАЖНО: Передаваемый указатель должен указывать на начало данных. Только
+ * так гарантируется что актуальный заголовок страницы будет физически
+ * расположен в той-же странице памяти, в том числе для многостраничных
+ * P_OVERFLOW страниц с длинными данными. */
+int mdbx_is_dirty(const MDBX_txn *txn, const void *ptr) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  const MDBX_env *env = txn->mt_env;
+  const ptrdiff_t offset = (uint8_t *)ptr - env->me_map;
+  if (offset >= 0) {
+    const pgno_t pgno = bytes2pgno(env, offset);
+    if (likely(pgno < txn->mt_next_pgno)) {
+      if (txn->mt_flags & MDBX_TXN_RDONLY)
+        return MDBX_RESULT_FALSE;
+
+      const MDBX_page *page = pgno2page(env, pgno);
+      if (unlikely(page->mp_pgno != pgno)) {
+        /* The ptr pointed into middle of a large page,
+         * not to the beginning of a data. */
+        return MDBX_EINVAL;
+      }
+      if (unlikely(page->mp_flags & (P_DIRTY | P_LOOSE | P_KEEP | P_META)))
+        return MDBX_RESULT_TRUE;
+      if (likely(txn->tw.spill_pages == nullptr))
+        return MDBX_RESULT_FALSE;
+      return mdbx_pnl_exist(txn->tw.spill_pages, pgno << 1) ? MDBX_RESULT_TRUE
+                                                            : MDBX_RESULT_FALSE;
+    }
+    if ((size_t)offset < env->me_dxb_mmap.limit) {
+      /* Указатель адресует что-то в пределах mmap, но за границей
+       * распределенных страниц. Такое может случится если mdbx_is_dirty()
+       * вызывается после операции, в ходе которой грязная страница попала
+       * в loose и затем была возвращена в нераспределенное пространство. */
+      return MDBX_RESULT_TRUE;
+    }
+  }
+
+  /* Страница вне используемого mmap-диапазона, т.е. либо в функцию был
+   * передан некорректный адрес, либо адрес в теневой странице, которая была
+   * выделена посредством malloc().
+   *
+   * Для режима WRITE_MAP режима страница однозначно "не грязная",
+   * а для режимов без WRITE_MAP следует просматривать списки dirty
+   * и spilled страниц у каких-либо транзакций (в том числе дочерних).
+   *
+   * Поэтому для WRITE_MAP возвращаем false, а для остальных режимов
+   * всегда true. Такая логика имеет ряд преимуществ:
+   *  - не тратим время на просмотр списков;
+   *  - результат всегда безопасен (может быть ложно-положительным,
+   *    но не ложно-отрицательным);
+   *  - результат не зависит от вложенности транзакций и от относительного
+   *    положения переданной транзакции в этой рекурсии. */
+  return (env->me_flags & MDBX_WRITEMAP) ? MDBX_RESULT_FALSE : MDBX_RESULT_TRUE;
+}
+
+int mdbx_dbi_sequence(MDBX_txn *txn, MDBX_dbi dbi, uint64_t *result,
+                      uint64_t increment) {
+  int rc = check_txn(txn, MDBX_TXN_BLOCKED);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (unlikely(!mdbx_txn_dbi_exists(txn, dbi, DBI_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(TXN_DBI_CHANGED(txn, dbi)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(txn->mt_dbistate[dbi] & DBI_STALE)) {
+    rc = mdbx_fetch_sdb(txn, dbi);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+  }
+
+  MDBX_db *dbs = &txn->mt_dbs[dbi];
+  if (likely(result))
+    *result = dbs->md_seq;
+
+  if (likely(increment > 0)) {
+    if (unlikely(txn->mt_flags & MDBX_TXN_RDONLY))
+      return MDBX_EACCESS;
+
+    uint64_t new = dbs->md_seq + increment;
+    if (unlikely(new < increment))
+      return MDBX_RESULT_TRUE;
+
+    mdbx_tassert(txn, new > dbs->md_seq);
+    dbs->md_seq = new;
+    txn->mt_flags |= MDBX_TXN_DIRTY;
+    txn->mt_dbistate[dbi] |= DBI_DIRTY;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+/*----------------------------------------------------------------------------*/
+
+__cold MDBX_NOTHROW_CONST_FUNCTION intptr_t mdbx_limits_pgsize_min(void) {
+  return __inline_mdbx_limits_pgsize_min();
+}
+
+__cold MDBX_NOTHROW_CONST_FUNCTION intptr_t mdbx_limits_pgsize_max(void) {
+  return __inline_mdbx_limits_pgsize_max();
+}
+
+__cold intptr_t mdbx_limits_dbsize_min(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_default_pagesize();
+  else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
+                    pagesize > (intptr_t)MAX_PAGESIZE ||
+                    !is_powerof2((size_t)pagesize)))
+    return -1;
+
+  return MIN_PAGENO * pagesize;
+}
+
+__cold intptr_t mdbx_limits_dbsize_max(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_default_pagesize();
+  else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
+                    pagesize > (intptr_t)MAX_PAGESIZE ||
+                    !is_powerof2((size_t)pagesize)))
+    return -1;
+
+  STATIC_ASSERT(MAX_MAPSIZE < INTPTR_MAX);
+  const uint64_t limit = MAX_PAGENO * (uint64_t)pagesize;
+  return (limit < (intptr_t)MAX_MAPSIZE) ? (intptr_t)limit
+                                         : (intptr_t)MAX_MAPSIZE;
+}
+
+__cold intptr_t mdbx_limits_txnsize_max(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_default_pagesize();
+  else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
+                    pagesize > (intptr_t)MAX_PAGESIZE ||
+                    !is_powerof2((size_t)pagesize)))
+    return -1;
+
+  STATIC_ASSERT(MAX_MAPSIZE < INTPTR_MAX);
+  const uint64_t limit = pagesize * (uint64_t)(MDBX_PGL_LIMIT - 1);
+  return (limit < (intptr_t)MAX_MAPSIZE) ? (intptr_t)limit
+                                         : (intptr_t)MAX_MAPSIZE;
+}
+
+/*** Key-making functions to avoid custom comparators *************************/
+
+static __always_inline double key2double(const int64_t key) {
+  union {
+    uint64_t u;
+    double f;
+  } casting;
+
+  casting.u = (key < 0) ? key + UINT64_C(0x8000000000000000)
+                        : UINT64_C(0xffffFFFFffffFFFF) - key;
+  return casting.f;
+}
+
+static __always_inline uint64_t double2key(const double *const ptr) {
+  STATIC_ASSERT(sizeof(double) == sizeof(int64_t));
+  const int64_t i = *(const int64_t *)ptr;
+  const uint64_t u = (i < 0) ? UINT64_C(0xffffFFFFffffFFFF) - i
+                             : i + UINT64_C(0x8000000000000000);
+  if (mdbx_assert_enabled()) {
+    const double f = key2double(u);
+    assert(memcmp(&f, ptr, 8) == 0);
+  }
+  return u;
+}
+
+static __always_inline float key2float(const int32_t key) {
+  union {
+    uint32_t u;
+    float f;
+  } casting;
+
+  casting.u =
+      (key < 0) ? key + UINT32_C(0x80000000) : UINT32_C(0xffffFFFF) - key;
+  return casting.f;
+}
+
+static __always_inline uint32_t float2key(const float *const ptr) {
+  STATIC_ASSERT(sizeof(float) == sizeof(int32_t));
+  const int32_t i = *(const int32_t *)ptr;
+  const uint32_t u =
+      (i < 0) ? UINT32_C(0xffffFFFF) - i : i + UINT32_C(0x80000000);
+  if (mdbx_assert_enabled()) {
+    const float f = key2float(u);
+    assert(memcmp(&f, ptr, 4) == 0);
+  }
+  return u;
+}
+
+uint64_t mdbx_key_from_double(const double ieee754_64bit) {
+  return double2key(&ieee754_64bit);
+}
+
+uint64_t mdbx_key_from_ptrdouble(const double *const ieee754_64bit) {
+  return double2key(ieee754_64bit);
+}
+
+uint32_t mdbx_key_from_float(const float ieee754_32bit) {
+  return float2key(&ieee754_32bit);
+}
+
+uint32_t mdbx_key_from_ptrfloat(const float *const ieee754_32bit) {
+  return float2key(ieee754_32bit);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION uint64_t mdbx_key_from_int64(const int64_t i64) {
+  return __inline_mdbx_key_from_int64(i64);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION uint32_t mdbx_key_from_int32(const int32_t i32) {
+  return __inline_mdbx_key_from_int32(i32);
+}
+
+#define IEEE754_DOUBLE_MANTISSA_SIZE 52
+#define IEEE754_DOUBLE_EXPONENTA_BIAS 0x3FF
+#define IEEE754_DOUBLE_EXPONENTA_MAX 0x7FF
+#define IEEE754_DOUBLE_IMPLICIT_LEAD UINT64_C(0x0010000000000000)
+#define IEEE754_DOUBLE_MANTISSA_MASK UINT64_C(0x000FFFFFFFFFFFFF)
+#define IEEE754_DOUBLE_MANTISSA_AMAX UINT64_C(0x001FFFFFFFFFFFFF)
+
+static __inline int clz64(uint64_t value) {
+#if __GNUC_PREREQ(4, 1) || __has_builtin(__builtin_clzl)
+  if (sizeof(value) == sizeof(int))
+    return __builtin_clz(value);
+  if (sizeof(value) == sizeof(long))
+    return __builtin_clzl(value);
+#if (defined(__SIZEOF_LONG_LONG__) && __SIZEOF_LONG_LONG__ == 8) ||            \
+    __has_builtin(__builtin_clzll)
+  return __builtin_clzll(value);
+#endif /* have(long long) && long long == uint64_t */
+#endif /* GNU C */
+
+#if defined(_MSC_VER)
+  unsigned long index;
+#if defined(_M_AMD64) || defined(_M_ARM64) || defined(_M_X64)
+  _BitScanReverse64(&index, value);
+  return 63 - index;
+#else
+  if (value > UINT32_MAX) {
+    _BitScanReverse(&index, (uint32_t)(value >> 32));
+    return 31 - index;
+  }
+  _BitScanReverse(&index, (uint32_t)value);
+  return 63 - index;
+#endif
+#endif /* MSVC */
+
+  value |= value >> 1;
+  value |= value >> 2;
+  value |= value >> 4;
+  value |= value >> 8;
+  value |= value >> 16;
+  value |= value >> 32;
+  static const uint8_t debruijn_clz64[64] = {
+      63, 16, 62, 7,  15, 36, 61, 3,  6,  14, 22, 26, 35, 47, 60, 2,
+      9,  5,  28, 11, 13, 21, 42, 19, 25, 31, 34, 40, 46, 52, 59, 1,
+      17, 8,  37, 4,  23, 27, 48, 10, 29, 12, 43, 20, 32, 41, 53, 18,
+      38, 24, 49, 30, 44, 33, 54, 39, 50, 45, 55, 51, 56, 57, 58, 0};
+  return debruijn_clz64[value * UINT64_C(0x03F79D71B4CB0A89) >> 58];
+}
+
+static __inline uint64_t round_mantissa(const uint64_t u64, int shift) {
+  assert(shift < 0 && u64 > 0);
+  shift = -shift;
+  const unsigned half = 1 << (shift - 1);
+  const unsigned lsb = 1 & (unsigned)(u64 >> shift);
+  const unsigned tie2even = 1 ^ lsb;
+  return (u64 + half - tie2even) >> shift;
+}
+
+uint64_t mdbx_key_from_jsonInteger(const int64_t json_integer) {
+  const uint64_t bias = UINT64_C(0x8000000000000000);
+  if (json_integer > 0) {
+    const uint64_t u64 = json_integer;
+    int shift = clz64(u64) - (64 - IEEE754_DOUBLE_MANTISSA_SIZE - 1);
+    uint64_t mantissa = u64 << shift;
+    if (unlikely(shift < 0)) {
+      mantissa = round_mantissa(u64, shift);
+      if (mantissa > IEEE754_DOUBLE_MANTISSA_AMAX)
+        mantissa = round_mantissa(u64, --shift);
+    }
+
+    assert(mantissa >= IEEE754_DOUBLE_IMPLICIT_LEAD &&
+           mantissa <= IEEE754_DOUBLE_MANTISSA_AMAX);
+    const uint64_t exponent =
+        IEEE754_DOUBLE_EXPONENTA_BIAS + IEEE754_DOUBLE_MANTISSA_SIZE - shift;
+    assert(exponent > 0 && exponent <= IEEE754_DOUBLE_EXPONENTA_MAX);
+    const uint64_t key = bias + (exponent << IEEE754_DOUBLE_MANTISSA_SIZE) +
+                         (mantissa - IEEE754_DOUBLE_IMPLICIT_LEAD);
+#if !defined(_MSC_VER) ||                                                      \
+    defined(                                                                   \
+        _DEBUG) /* Workaround for MSVC error LNK2019: unresolved external      \
+                   symbol __except1 referenced in function __ftol3_except */
+    assert(key == mdbx_key_from_double((double)json_integer));
+#endif /* Workaround for MSVC */
+    return key;
+  }
+
+  if (json_integer < 0) {
+    const uint64_t u64 = -json_integer;
+    int shift = clz64(u64) - (64 - IEEE754_DOUBLE_MANTISSA_SIZE - 1);
+    uint64_t mantissa = u64 << shift;
+    if (unlikely(shift < 0)) {
+      mantissa = round_mantissa(u64, shift);
+      if (mantissa > IEEE754_DOUBLE_MANTISSA_AMAX)
+        mantissa = round_mantissa(u64, --shift);
+    }
+
+    assert(mantissa >= IEEE754_DOUBLE_IMPLICIT_LEAD &&
+           mantissa <= IEEE754_DOUBLE_MANTISSA_AMAX);
+    const uint64_t exponent =
+        IEEE754_DOUBLE_EXPONENTA_BIAS + IEEE754_DOUBLE_MANTISSA_SIZE - shift;
+    assert(exponent > 0 && exponent <= IEEE754_DOUBLE_EXPONENTA_MAX);
+    const uint64_t key = bias - 1 - (exponent << IEEE754_DOUBLE_MANTISSA_SIZE) -
+                         (mantissa - IEEE754_DOUBLE_IMPLICIT_LEAD);
+#if !defined(_MSC_VER) ||                                                      \
+    defined(                                                                   \
+        _DEBUG) /* Workaround for MSVC error LNK2019: unresolved external      \
+                   symbol __except1 referenced in function __ftol3_except */
+    assert(key == mdbx_key_from_double((double)json_integer));
+#endif /* Workaround for MSVC */
+    return key;
+  }
+
+  return bias;
+}
+
+int64_t mdbx_jsonInteger_from_key(const MDBX_val v) {
+  assert(v.iov_len == 8);
+  const uint64_t key = unaligned_peek_u64(2, v.iov_base);
+  const uint64_t bias = UINT64_C(0x8000000000000000);
+  const uint64_t covalent = (key > bias) ? key - bias : bias - key - 1;
+  const int shift = IEEE754_DOUBLE_EXPONENTA_BIAS + 63 -
+                    (IEEE754_DOUBLE_EXPONENTA_MAX &
+                     (int)(covalent >> IEEE754_DOUBLE_MANTISSA_SIZE));
+  if (unlikely(shift < 1))
+    return (key < bias) ? INT64_MIN : INT64_MAX;
+  if (unlikely(shift > 63))
+    return 0;
+
+  const uint64_t unscaled = ((covalent & IEEE754_DOUBLE_MANTISSA_MASK)
+                             << (63 - IEEE754_DOUBLE_MANTISSA_SIZE)) +
+                            bias;
+  const int64_t absolute = unscaled >> shift;
+  const int64_t value = (key < bias) ? -absolute : absolute;
+  assert(key == mdbx_key_from_jsonInteger(value) ||
+         (mdbx_key_from_jsonInteger(value - 1) < key &&
+          key < mdbx_key_from_jsonInteger(value + 1)));
+  return value;
+}
+
+double mdbx_double_from_key(const MDBX_val v) {
+  assert(v.iov_len == 8);
+  return key2double(unaligned_peek_u64(2, v.iov_base));
+}
+
+float mdbx_float_from_key(const MDBX_val v) {
+  assert(v.iov_len == 4);
+  return key2float(unaligned_peek_u32(2, v.iov_base));
+}
+
+int32_t mdbx_int32_from_key(const MDBX_val v) {
+  assert(v.iov_len == 4);
+  return (int32_t)(unaligned_peek_u32(2, v.iov_base) - UINT32_C(0x80000000));
+}
+
+int64_t mdbx_int64_from_key(const MDBX_val v) {
+  assert(v.iov_len == 8);
+  return (int64_t)(unaligned_peek_u64(2, v.iov_base) -
+                   UINT64_C(0x8000000000000000));
+}
+
+__cold MDBX_cmp_func *mdbx_get_keycmp(unsigned flags) {
+  return get_default_keycmp(flags);
+}
+
+__cold MDBX_cmp_func *mdbx_get_datacmp(unsigned flags) {
+  return get_default_datacmp(flags);
+}
+
+__cold int mdbx_env_set_option(MDBX_env *env, const MDBX_option_t option,
+                               const uint64_t value) {
+  int err = check_env(env);
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+
+  const bool lock_needed = (env->me_map && env->me_txn0 &&
+                            env->me_txn0->mt_owner != mdbx_thread_self());
+  bool should_unlock = false;
+  switch (option) {
+  case MDBX_opt_sync_bytes:
+    if (unlikely(env->me_flags & MDBX_RDONLY))
+      return MDBX_EACCESS;
+    if (unlikely(!env->me_autosync_threshold))
+      return MDBX_EPERM;
+    if (sizeof(value) > sizeof(size_t) && unlikely(value != (size_t)value))
+      return MDBX_TOO_LARGE;
+    if (atomic_store32(env->me_autosync_threshold,
+                       bytes2pgno(env, (size_t)value + env->me_psize - 1),
+                       mo_Relaxed) != 0) {
+      err = mdbx_env_sync_poll(env);
+      if (unlikely(MDBX_IS_ERROR(err)))
+        return err;
+    }
+    break;
+
+  case MDBX_opt_sync_period:
+    if (unlikely(env->me_flags & MDBX_RDONLY))
+      return MDBX_EACCESS;
+    if (unlikely(!env->me_autosync_period))
+      return MDBX_EPERM;
+    if (unlikely(value > UINT32_MAX))
+      return MDBX_TOO_LARGE;
+    if (atomic_store64(env->me_autosync_period,
+                       mdbx_osal_16dot16_to_monotime((uint32_t)value),
+                       mo_Relaxed) != 0) {
+      err = mdbx_env_sync_poll(env);
+      if (unlikely(MDBX_IS_ERROR(err)))
+        return err;
+    }
+    break;
+
+  case MDBX_opt_max_db:
+    if (unlikely(value > MDBX_MAX_DBI))
+      return MDBX_EINVAL;
+    if (unlikely(env->me_map))
+      return MDBX_EPERM;
+    env->me_maxdbs = (unsigned)value + CORE_DBS;
+    break;
+
+  case MDBX_opt_max_readers:
+    if (unlikely(value < 1 || value > MDBX_READERS_LIMIT))
+      return MDBX_EINVAL;
+    if (unlikely(env->me_map))
+      return MDBX_EPERM;
+    env->me_maxreaders = (unsigned)value;
+    break;
+
+  case MDBX_opt_dp_reserve_limit:
+    if (unlikely(value > INT_MAX))
+      return MDBX_EINVAL;
+    if (env->me_options.dp_reserve_limit != (unsigned)value) {
+      if (lock_needed) {
+        err = mdbx_txn_lock(env, false);
+        if (unlikely(err != MDBX_SUCCESS))
+          return err;
+        should_unlock = true;
+      }
+      env->me_options.dp_reserve_limit = (unsigned)value;
+      while (env->me_dp_reserve_len > env->me_options.dp_reserve_limit) {
+        mdbx_assert(env, env->me_dp_reserve != NULL);
+        MDBX_page *dp = env->me_dp_reserve;
+        ASAN_UNPOISON_MEMORY_REGION(dp, env->me_psize);
+        VALGRIND_MAKE_MEM_DEFINED(&dp->mp_next, sizeof(dp->mp_next));
+        env->me_dp_reserve = dp->mp_next;
+        VALGRIND_MEMPOOL_FREE(env, dp);
+        mdbx_free(dp);
+        env->me_dp_reserve_len -= 1;
+      }
+    }
+    break;
+
+  case MDBX_opt_rp_augment_limit:
+    if (unlikely(value > MDBX_PGL_LIMIT))
+      return MDBX_EINVAL;
+    env->me_options.rp_augment_limit = (unsigned)value;
+    break;
+
+  case MDBX_opt_txn_dp_limit:
+  case MDBX_opt_txn_dp_initial:
+    if (unlikely(value > MDBX_PGL_LIMIT || value < CURSOR_STACK * 4 ||
+                 value > bytes2pgno(env, env->me_dbgeo.upper) - NUM_METAS))
+      return MDBX_EINVAL;
+    if (unlikely(env->me_txn0 == NULL))
+      return MDBX_EACCESS;
+    if (lock_needed) {
+      err = mdbx_txn_lock(env, false);
+      if (unlikely(err != MDBX_SUCCESS))
+        return err;
+      should_unlock = true;
+    }
+    if (env->me_txn)
+      err = MDBX_EPERM /* unable change during transaction */;
+    else {
+      mdbx_dpl_clear(env->me_txn0->tw.dirtylist);
+      const unsigned value32 = (unsigned)value;
+      if (option == MDBX_opt_txn_dp_initial &&
+          env->me_options.dp_initial != value32) {
+        if (env->me_options.dp_limit < value32)
+          env->me_options.dp_limit = value32;
+        if (env->me_txn0->tw.dirtylist->allocated < value32 &&
+            !mdbx_dpl_reserve(env->me_txn0, value32))
+          err = MDBX_ENOMEM;
+        else
+          env->me_options.dp_initial = value32;
+      }
+      if (option == MDBX_opt_txn_dp_limit &&
+          env->me_options.dp_limit != value32) {
+        if (env->me_txn0->tw.dirtylist->allocated > value32 &&
+            !mdbx_dpl_reserve(env->me_txn0, value32))
+          err = MDBX_ENOMEM;
+        else {
+          if (env->me_options.dp_initial > value32)
+            env->me_options.dp_initial = value32;
+          env->me_options.dp_limit = value32;
+        }
+      }
+    }
+    break;
+
+  case MDBX_opt_spill_max_denominator:
+    if (unlikely(value > 255))
+      return MDBX_EINVAL;
+    env->me_options.spill_max_denominator = (uint8_t)value;
+    break;
+  case MDBX_opt_spill_min_denominator:
+    if (unlikely(value > 255))
+      return MDBX_EINVAL;
+    env->me_options.spill_min_denominator = (uint8_t)value;
+    break;
+  case MDBX_opt_spill_parent4child_denominator:
+    if (unlikely(value > 255))
+      return MDBX_EINVAL;
+    env->me_options.spill_parent4child_denominator = (uint8_t)value;
+    break;
+
+  case MDBX_opt_loose_limit:
+    if (unlikely(value > 255))
+      return MDBX_EINVAL;
+    env->me_options.dp_loose_limit = (uint8_t)value;
+    break;
+
+  default:
+    return MDBX_EINVAL;
+  }
+
+  if (should_unlock)
+    mdbx_txn_unlock(env);
+  return err;
+}
+
+__cold int mdbx_env_get_option(const MDBX_env *env, const MDBX_option_t option,
+                               uint64_t *value) {
+  int err = check_env(env);
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+  if (unlikely(!value))
+    return MDBX_EINVAL;
+
+  switch (option) {
+  case MDBX_opt_sync_bytes:
+    if (unlikely(!env->me_autosync_threshold))
+      return MDBX_EPERM;
+    *value =
+        pgno2bytes(env, atomic_load32(env->me_autosync_threshold, mo_Relaxed));
+    break;
+
+  case MDBX_opt_sync_period:
+    if (unlikely(!env->me_autosync_period))
+      return MDBX_EPERM;
+    *value = mdbx_osal_monotime_to_16dot16(
+        atomic_load64(env->me_autosync_period, mo_Relaxed));
+    break;
+
+  case MDBX_opt_max_db:
+    *value = env->me_maxdbs - CORE_DBS;
+    break;
+
+  case MDBX_opt_max_readers:
+    *value = env->me_maxreaders;
+    break;
+
+  case MDBX_opt_dp_reserve_limit:
+    *value = env->me_options.dp_reserve_limit;
+    break;
+
+  case MDBX_opt_rp_augment_limit:
+    *value = env->me_options.rp_augment_limit;
+    break;
+
+  case MDBX_opt_txn_dp_limit:
+    *value = env->me_options.dp_limit;
+    break;
+  case MDBX_opt_txn_dp_initial:
+    *value = env->me_options.dp_initial;
+    break;
+
+  case MDBX_opt_spill_max_denominator:
+    *value = env->me_options.spill_max_denominator;
+    break;
+  case MDBX_opt_spill_min_denominator:
+    *value = env->me_options.spill_min_denominator;
+    break;
+  case MDBX_opt_spill_parent4child_denominator:
+    *value = env->me_options.spill_parent4child_denominator;
+    break;
+
+  case MDBX_opt_loose_limit:
+    *value = env->me_options.dp_loose_limit;
+    break;
+
+  default:
+    return MDBX_EINVAL;
+  }
+
+  return MDBX_SUCCESS;
+}
+
+/*** Attribute support functions for Nexenta **********************************/
+#ifdef MDBX_NEXENTA_ATTRS
+
+static __inline int mdbx_attr_peek(MDBX_val *data, mdbx_attr_t *attrptr) {
+  if (unlikely(data->iov_len < sizeof(mdbx_attr_t)))
+    return MDBX_INCOMPATIBLE;
+
+  if (likely(attrptr != NULL))
+    *attrptr = *(mdbx_attr_t *)data->iov_base;
+  data->iov_len -= sizeof(mdbx_attr_t);
+  data->iov_base =
+      likely(data->iov_len > 0) ? ((mdbx_attr_t *)data->iov_base) + 1 : NULL;
+
+  return MDBX_SUCCESS;
+}
+
+static __inline int mdbx_attr_poke(MDBX_val *reserved, MDBX_val *data,
+                                   mdbx_attr_t attr, MDBX_put_flags_t flags) {
+  mdbx_attr_t *space = reserved->iov_base;
+  if (flags & MDBX_RESERVE) {
+    if (likely(data != NULL)) {
+      data->iov_base = data->iov_len ? space + 1 : NULL;
+    }
+  } else {
+    *space = attr;
+    if (likely(data != NULL)) {
+      memcpy(space + 1, data->iov_base, data->iov_len);
+    }
+  }
+
+  return MDBX_SUCCESS;
+}
+
+int mdbx_cursor_get_attr(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
+                         mdbx_attr_t *attrptr, MDBX_cursor_op op) {
+  int rc = mdbx_cursor_get(mc, key, data, op);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_attr_peek(data, attrptr);
+}
+
+int mdbx_get_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data,
+                  uint64_t *attrptr) {
+  int rc = mdbx_get(txn, dbi, key, data);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_attr_peek(data, attrptr);
+}
+
+int mdbx_put_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data,
+                  mdbx_attr_t attr, MDBX_put_flags_t flags) {
+  MDBX_val reserve;
+  reserve.iov_base = NULL;
+  reserve.iov_len = (data ? data->iov_len : 0) + sizeof(mdbx_attr_t);
+
+  int rc = mdbx_put(txn, dbi, key, &reserve, flags | MDBX_RESERVE);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_attr_poke(&reserve, data, attr, flags);
+}
+
+int mdbx_cursor_put_attr(MDBX_cursor *cursor, MDBX_val *key, MDBX_val *data,
+                         mdbx_attr_t attr, MDBX_put_flags_t flags) {
+  MDBX_val reserve;
+  reserve.iov_base = NULL;
+  reserve.iov_len = (data ? data->iov_len : 0) + sizeof(mdbx_attr_t);
+
+  int rc = mdbx_cursor_put(cursor, key, &reserve, flags | MDBX_RESERVE);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  return mdbx_attr_poke(&reserve, data, attr, flags);
+}
+
+int mdbx_set_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data,
+                  mdbx_attr_t attr) {
+  if (unlikely(!key || !txn))
+    return MDBX_EINVAL;
+
+  if (unlikely(txn->mt_signature != MDBX_MT_SIGNATURE))
+    return MDBX_EBADSIGN;
+
+  if (unlikely(!TXN_DBI_EXIST(txn, dbi, DB_USRVALID)))
+    return MDBX_BAD_DBI;
+
+  if (unlikely(txn->mt_flags & (MDBX_TXN_RDONLY | MDBX_TXN_BLOCKED)))
+    return (txn->mt_flags & MDBX_TXN_RDONLY) ? MDBX_EACCESS : MDBX_BAD_TXN;
+
+  MDBX_cursor_couple cx;
+  MDBX_val old_data;
+  int rc = mdbx_cursor_init(&cx.outer, txn, dbi);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+  rc = mdbx_cursor_set(&cx.outer, key, &old_data, MDBX_SET, NULL);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    if (rc == MDBX_NOTFOUND && data) {
+      cx.outer.mc_next = txn->tw.cursors[dbi];
+      txn->tw.cursors[dbi] = &cx.outer;
+      rc = mdbx_cursor_put_attr(&cx.outer, key, data, attr, 0);
+      txn->tw.cursors[dbi] = cx.outer.mc_next;
+    }
+    return rc;
+  }
+
+  mdbx_attr_t old_attr = 0;
+  rc = mdbx_attr_peek(&old_data, &old_attr);
+  if (unlikely(rc != MDBX_SUCCESS))
+    return rc;
+
+  if (old_attr == attr && (!data || (data->iov_len == old_data.iov_len &&
+                                     memcmp(data->iov_base, old_data.iov_base,
+                                            old_data.iov_len) == 0)))
+    return MDBX_SUCCESS;
+
+  cx.outer.mc_next = txn->tw.cursors[dbi];
+  txn->tw.cursors[dbi] = &cx.outer;
+  rc = mdbx_cursor_put_attr(&cx.outer, key, data ? data : &old_data, attr,
+                            MDBX_CURRENT);
+  txn->tw.cursors[dbi] = cx.outer.mc_next;
+  return rc;
+}
+#endif /* MDBX_NEXENTA_ATTRS */
+
+/******************************************************************************/
+/* *INDENT-OFF* */
+/* clang-format off */
+
+__dll_export
+#ifdef __attribute_used__
+    __attribute_used__
+#elif defined(__GNUC__) || __has_attribute(__used__)
+    __attribute__((__used__))
+#endif
+#ifdef __attribute_externally_visible__
+        __attribute_externally_visible__
+#elif (defined(__GNUC__) && !defined(__clang__)) ||                            \
+    __has_attribute(__externally_visible__)
+    __attribute__((__externally_visible__))
+#endif
+    const struct MDBX_build_info mdbx_build = {
+#ifdef MDBX_BUILD_TIMESTAMP
+    MDBX_BUILD_TIMESTAMP
+#else
+    __DATE__ " " __TIME__
+#endif /* MDBX_BUILD_TIMESTAMP */
+
+    ,
+#ifdef MDBX_BUILD_TARGET
+    MDBX_BUILD_TARGET
+#else
+  #if defined(__ANDROID_API__)
+    "Android" STRINGIFY(__ANDROID_API__)
+  #elif defined(__linux__) || defined(__gnu_linux__)
+    "Linux"
+  #elif defined(EMSCRIPTEN) || defined(__EMSCRIPTEN__)
+    "webassembly"
+  #elif defined(__CYGWIN__)
+    "CYGWIN"
+  #elif defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) \
+      || defined(__WINDOWS__)
+    "Windows"
+  #elif defined(__APPLE__)
+    #if (defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE) \
+      || (defined(TARGET_IPHONE_SIMULATOR) && TARGET_IPHONE_SIMULATOR)
+      "iOS"
+    #else
+      "MacOS"
+    #endif
+  #elif defined(__FreeBSD__)
+    "FreeBSD"
+  #elif defined(__DragonFly__)
+    "DragonFlyBSD"
+  #elif defined(__NetBSD__)
+    "NetBSD"
+  #elif defined(__OpenBSD__)
+    "OpenBSD"
+  #elif defined(__bsdi__)
+    "UnixBSDI"
+  #elif defined(__MACH__)
+    "MACH"
+  #elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC))
+    "HPUX"
+  #elif defined(_AIX)
+    "AIX"
+  #elif defined(__sun) && defined(__SVR4)
+    "Solaris"
+  #elif defined(__BSD__) || defined(BSD)
+    "UnixBSD"
+  #elif defined(__unix__) || defined(UNIX) || defined(__unix) \
+      || defined(__UNIX) || defined(__UNIX__)
+    "UNIX"
+  #elif defined(_POSIX_VERSION)
+    "POSIX" STRINGIFY(_POSIX_VERSION)
+  #else
+    "UnknownOS"
+  #endif /* Target OS */
+
+    "-"
+
+  #if defined(__amd64__)
+    "AMD64"
+  #elif defined(__ia32__)
+    "IA32"
+  #elif defined(__e2k__) || defined(__elbrus__)
+    "Elbrus"
+  #elif defined(__alpha__) || defined(__alpha) || defined(_M_ALPHA)
+    "Alpha"
+  #elif defined(__aarch64__) || defined(_M_ARM64)
+    "ARM64"
+  #elif defined(__arm__) || defined(__thumb__) || defined(__TARGET_ARCH_ARM) \
+      || defined(__TARGET_ARCH_THUMB) || defined(_ARM) || defined(_M_ARM) \
+      || defined(_M_ARMT) || defined(__arm)
+    "ARM"
+  #elif defined(__mips64) || defined(__mips64__) || (defined(__mips) && (__mips >= 64))
+    "MIPS64"
+  #elif if defined(__mips__) || defined(__mips) || defined(_R4000) || defined(__MIPS__)
+    "MIPS"
+  #elif defined(__hppa64__) || defined(__HPPA64__) || defined(__hppa64)
+    "PARISC64"
+  #elif defined(__hppa__) || defined(__HPPA__) || defined(__hppa)
+    "PARISC"
+  #elif defined(__ia64__) || defined(__ia64) || defined(_IA64) \
+      || defined(__IA64__) || defined(_M_IA64) || defined(__itanium__)
+    "Itanium"
+  #elif defined(__powerpc64__) || defined(__ppc64__) || defined(__ppc64) \
+      || defined(__powerpc64) || defined(_ARCH_PPC64)
+    "PowerPC64"
+  #elif defined(__powerpc__) || defined(__ppc__) || defined(__powerpc) \
+      || defined(__ppc) || defined(_ARCH_PPC) || defined(__PPC__) || defined(__POWERPC__)
+    "PowerPC"
+  #elif defined(__sparc64__) || defined(__sparc64)
+    "SPARC64"
+  #elif defined(__sparc__) || defined(__sparc)
+    "SPARC"
+  #elif defined(__s390__) || defined(__s390) || defined(__zarch__) || defined(__zarch)
+    "S390"
+  #else
+    "UnknownARCH"
+  #endif
+#endif /* MDBX_BUILD_TARGET */
+
+#ifdef MDBX_BUILD_TYPE
+# if defined(_MSC_VER)
+#   pragma message("Configuration-depended MDBX_BUILD_TYPE: " MDBX_BUILD_TYPE)
+# endif
+    "-" MDBX_BUILD_TYPE
+#endif /* MDBX_BUILD_TYPE */
+    ,
+    "MDBX_DEBUG=" STRINGIFY(MDBX_DEBUG)
+    " MDBX_WORDBITS=" STRINGIFY(MDBX_WORDBITS)
+    " BYTE_ORDER="
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    "LITTLE_ENDIAN"
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    "BIG_ENDIAN"
+#else
+    #error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+    " MDBX_ENV_CHECKPID=" MDBX_ENV_CHECKPID_CONFIG
+    " MDBX_TXN_CHECKOWNER=" MDBX_TXN_CHECKOWNER_CONFIG
+    " MDBX_64BIT_ATOMIC=" MDBX_64BIT_ATOMIC_CONFIG
+    " MDBX_64BIT_CAS=" MDBX_64BIT_CAS_CONFIG
+    " MDBX_TRUST_RTC=" MDBX_TRUST_RTC_CONFIG
+    " MDBX_ENABLE_REFUND=" STRINGIFY(MDBX_ENABLE_REFUND)
+#ifdef __SANITIZE_ADDRESS__
+    " SANITIZE_ADDRESS=YES"
+#endif /* __SANITIZE_ADDRESS__ */
+#ifdef MDBX_USE_VALGRIND
+    " MDBX_USE_VALGRIND=YES"
+#endif /* MDBX_USE_VALGRIND */
+#ifdef MDBX_FORCE_ASSERTIONS
+    " MDBX_FORCE_ASSERTIONS=YES"
+#endif /* MDBX_FORCE_ASSERTIONS */
+#ifdef _GNU_SOURCE
+    " _GNU_SOURCE=YES"
+#else
+    " _GNU_SOURCE=NO"
+#endif /* _GNU_SOURCE */
+#ifdef __APPLE__
+    " MDBX_OSX_SPEED_INSTEADOF_DURABILITY=" STRINGIFY(MDBX_OSX_SPEED_INSTEADOF_DURABILITY)
+#endif /* MacOS */
+#if defined(_WIN32) || defined(_WIN64)
+    " MDBX_AVOID_CRT=" STRINGIFY(MDBX_AVOID_CRT)
+    " MDBX_CONFIG_MANUAL_TLS_CALLBACK=" STRINGIFY(MDBX_CONFIG_MANUAL_TLS_CALLBACK)
+    " MDBX_BUILD_SHARED_LIBRARY=" STRINGIFY(MDBX_BUILD_SHARED_LIBRARY)
+    " WINVER=" STRINGIFY(WINVER)
+#else /* Windows */
+    " MDBX_LOCKING=" MDBX_LOCKING_CONFIG
+    " MDBX_USE_OFDLOCKS=" MDBX_USE_OFDLOCKS_CONFIG
+#endif /* !Windows */
+    " MDBX_CACHELINE_SIZE=" STRINGIFY(MDBX_CACHELINE_SIZE)
+    " MDBX_CPU_WRITEBACK_INCOHERENT=" STRINGIFY(MDBX_CPU_WRITEBACK_INCOHERENT)
+    " MDBX_MMAP_INCOHERENT_CPU_CACHE=" STRINGIFY(MDBX_MMAP_INCOHERENT_CPU_CACHE)
+    " MDBX_MMAP_INCOHERENT_FILE_WRITE=" STRINGIFY(MDBX_MMAP_INCOHERENT_FILE_WRITE)
+    " MDBX_UNALIGNED_OK=" STRINGIFY(MDBX_UNALIGNED_OK)
+    " MDBX_PNL_ASCENDING=" STRINGIFY(MDBX_PNL_ASCENDING)
+    ,
+#ifdef MDBX_BUILD_COMPILER
+    MDBX_BUILD_COMPILER
+#else
+  #ifdef __INTEL_COMPILER
+    "Intel C/C++ " STRINGIFY(__INTEL_COMPILER)
+  #elsif defined(__apple_build_version__)
+    "Apple clang " STRINGIFY(__apple_build_version__)
+  #elif defined(__ibmxl__)
+    "IBM clang C " STRINGIFY(__ibmxl_version__) "." STRINGIFY(__ibmxl_release__)
+    "." STRINGIFY(__ibmxl_modification__) "." STRINGIFY(__ibmxl_ptf_fix_level__)
+  #elif defined(__clang__)
+    "clang " STRINGIFY(__clang_version__)
+  #elif defined(__MINGW64__)
+    "MINGW-64 " STRINGIFY(__MINGW64_MAJOR_VERSION) "." STRINGIFY(__MINGW64_MINOR_VERSION)
+  #elif defined(__MINGW32__)
+    "MINGW-32 " STRINGIFY(__MINGW32_MAJOR_VERSION) "." STRINGIFY(__MINGW32_MINOR_VERSION)
+  #elif defined(__IBMC__)
+    "IBM C " STRINGIFY(__IBMC__)
+  #elif defined(__GNUC__)
+    "GNU C/C++ "
+    #ifdef __VERSION__
+      __VERSION__
+    #else
+      STRINGIFY(__GNUC__) "." STRINGIFY(__GNUC_MINOR__) "." STRINGIFY(__GNUC_PATCHLEVEL__)
+    #endif
+  #elif defined(_MSC_VER)
+    "MSVC " STRINGIFY(_MSC_FULL_VER) "-" STRINGIFY(_MSC_BUILD)
+  #else
+    "Unknown compiler"
+  #endif
+#endif /* MDBX_BUILD_COMPILER */
+    ,
+#ifdef MDBX_BUILD_FLAGS_CONFIG
+    MDBX_BUILD_FLAGS_CONFIG
+#endif /* MDBX_BUILD_FLAGS_CONFIG */
+#ifdef MDBX_BUILD_FLAGS
+    MDBX_BUILD_FLAGS
+#endif /* MDBX_BUILD_FLAGS */
+#if !(defined(MDBX_BUILD_FLAGS_CONFIG) || defined(MDBX_BUILD_FLAGS))
+    "undefined (please use correct build script)"
+#ifdef _MSC_VER
+#pragma message("warning: Build flags undefined. Please use correct build script")
+#else
+#warning "Build flags undefined. Please use correct build script"
+#endif // _MSC_VER
+#endif
+};
+
+#ifdef __SANITIZE_ADDRESS__
+LIBMDBX_API __attribute__((__weak__)) const char *__asan_default_options() {
+  return "symbolize=1:allow_addr2line=1:"
+#ifdef _DEBUG
+         "debug=1:"
+#endif /* _DEBUG */
+         "report_globals=1:"
+         "replace_str=1:replace_intrin=1:"
+         "malloc_context_size=9:"
+         "detect_leaks=1:"
+         "check_printf=1:"
+         "detect_deadlocks=1:"
+#ifndef LTO_ENABLED
+         "check_initialization_order=1:"
+#endif
+         "detect_stack_use_after_return=1:"
+         "intercept_tls_get_addr=1:"
+         "decorate_proc_maps=1:"
+         "abort_on_error=1";
+}
+#endif /* __SANITIZE_ADDRESS__ */
+
+/* *INDENT-ON* */
+/* clang-format on */
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+#if defined(_WIN32) || defined(_WIN64)
+
+#include <winioctl.h>
+
+static int waitstatus2errcode(DWORD result) {
+  switch (result) {
+  case WAIT_OBJECT_0:
+    return MDBX_SUCCESS;
+  case WAIT_FAILED:
+    return GetLastError();
+  case WAIT_ABANDONED:
+    return ERROR_ABANDONED_WAIT_0;
+  case WAIT_IO_COMPLETION:
+    return ERROR_USER_APC;
+  case WAIT_TIMEOUT:
+    return ERROR_TIMEOUT;
+  default:
+    return ERROR_UNHANDLED_ERROR;
+  }
+}
+
+/* Map a result from an NTAPI call to WIN32 error code. */
+static int ntstatus2errcode(NTSTATUS status) {
+  DWORD dummy;
+  OVERLAPPED ov;
+  memset(&ov, 0, sizeof(ov));
+  ov.Internal = status;
+  return GetOverlappedResult(NULL, &ov, &dummy, FALSE) ? MDBX_SUCCESS
+                                                       : GetLastError();
+}
+
+/* We use native NT APIs to setup the memory map, so that we can
+ * let the DB file grow incrementally instead of always preallocating
+ * the full size. These APIs are defined in <wdm.h> and <ntifs.h>
+ * but those headers are meant for driver-level development and
+ * conflict with the regular user-level headers, so we explicitly
+ * declare them here. Using these APIs also means we must link to
+ * ntdll.dll, which is not linked by default in user code. */
+
+extern NTSTATUS NTAPI NtCreateSection(
+    OUT PHANDLE SectionHandle, IN ACCESS_MASK DesiredAccess,
+    IN OPTIONAL POBJECT_ATTRIBUTES ObjectAttributes,
+    IN OPTIONAL PLARGE_INTEGER MaximumSize, IN ULONG SectionPageProtection,
+    IN ULONG AllocationAttributes, IN OPTIONAL HANDLE FileHandle);
+
+typedef struct _SECTION_BASIC_INFORMATION {
+  ULONG Unknown;
+  ULONG SectionAttributes;
+  LARGE_INTEGER SectionSize;
+} SECTION_BASIC_INFORMATION, *PSECTION_BASIC_INFORMATION;
+
+extern NTSTATUS NTAPI NtMapViewOfSection(
+    IN HANDLE SectionHandle, IN HANDLE ProcessHandle, IN OUT PVOID *BaseAddress,
+    IN ULONG_PTR ZeroBits, IN SIZE_T CommitSize,
+    IN OUT OPTIONAL PLARGE_INTEGER SectionOffset, IN OUT PSIZE_T ViewSize,
+    IN SECTION_INHERIT InheritDisposition, IN ULONG AllocationType,
+    IN ULONG Win32Protect);
+
+extern NTSTATUS NTAPI NtUnmapViewOfSection(IN HANDLE ProcessHandle,
+                                           IN OPTIONAL PVOID BaseAddress);
+
+extern NTSTATUS NTAPI NtClose(HANDLE Handle);
+
+extern NTSTATUS NTAPI NtAllocateVirtualMemory(
+    IN HANDLE ProcessHandle, IN OUT PVOID *BaseAddress, IN ULONG_PTR ZeroBits,
+    IN OUT PSIZE_T RegionSize, IN ULONG AllocationType, IN ULONG Protect);
+
+extern NTSTATUS NTAPI NtFreeVirtualMemory(IN HANDLE ProcessHandle,
+                                          IN PVOID *BaseAddress,
+                                          IN OUT PSIZE_T RegionSize,
+                                          IN ULONG FreeType);
+
+#ifndef WOF_CURRENT_VERSION
+typedef struct _WOF_EXTERNAL_INFO {
+  DWORD Version;
+  DWORD Provider;
+} WOF_EXTERNAL_INFO, *PWOF_EXTERNAL_INFO;
+#endif /* WOF_CURRENT_VERSION */
+
+#ifndef WIM_PROVIDER_CURRENT_VERSION
+#define WIM_PROVIDER_HASH_SIZE 20
+
+typedef struct _WIM_PROVIDER_EXTERNAL_INFO {
+  DWORD Version;
+  DWORD Flags;
+  LARGE_INTEGER DataSourceId;
+  BYTE ResourceHash[WIM_PROVIDER_HASH_SIZE];
+} WIM_PROVIDER_EXTERNAL_INFO, *PWIM_PROVIDER_EXTERNAL_INFO;
+#endif /* WIM_PROVIDER_CURRENT_VERSION */
+
+#ifndef FILE_PROVIDER_CURRENT_VERSION
+typedef struct _FILE_PROVIDER_EXTERNAL_INFO_V1 {
+  ULONG Version;
+  ULONG Algorithm;
+  ULONG Flags;
+} FILE_PROVIDER_EXTERNAL_INFO_V1, *PFILE_PROVIDER_EXTERNAL_INFO_V1;
+#endif /* FILE_PROVIDER_CURRENT_VERSION */
+
+#ifndef STATUS_OBJECT_NOT_EXTERNALLY_BACKED
+#define STATUS_OBJECT_NOT_EXTERNALLY_BACKED ((NTSTATUS)0xC000046DL)
+#endif
+#ifndef STATUS_INVALID_DEVICE_REQUEST
+#define STATUS_INVALID_DEVICE_REQUEST ((NTSTATUS)0xC0000010L)
+#endif
+#ifndef STATUS_NOT_SUPPORTED
+#define STATUS_NOT_SUPPORTED ((NTSTATUS)0xC00000BBL)
+#endif
+
+#ifndef FILE_DEVICE_FILE_SYSTEM
+#define FILE_DEVICE_FILE_SYSTEM 0x00000009
+#endif
+
+#ifndef FSCTL_GET_EXTERNAL_BACKING
+#define FSCTL_GET_EXTERNAL_BACKING                                             \
+  CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 196, METHOD_BUFFERED, FILE_ANY_ACCESS)
+#endif
+
+#endif /* _WIN32 || _WIN64 */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(__UCLIBC__)
+__extern_C void __assert(const char *, const char *, unsigned int, const char *)
+#ifdef __THROW
+    __THROW
+#else
+    __nothrow
+#endif /* __THROW */
+    MDBX_NORETURN;
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert(assertion, file, line, function)
+
+#elif _POSIX_C_SOURCE > 200212 &&                                              \
+    /* workaround for avoid musl libc wrong prototype */ (                     \
+        defined(__GLIBC__) || defined(__GNU_LIBRARY__))
+/* Prototype should match libc runtime. ISO POSIX (2003) & LSB 1.x-3.x */
+__extern_C void __assert_fail(const char *assertion, const char *file,
+                              unsigned line, const char *function)
+#ifdef __THROW
+    __THROW
+#else
+    __nothrow
+#endif /* __THROW */
+    MDBX_NORETURN;
+
+#elif defined(__APPLE__) || defined(__MACH__)
+__extern_C void __assert_rtn(const char *function, const char *file, int line,
+                             const char *assertion) /* __nothrow */
+#ifdef __dead2
+    __dead2
+#else
+    MDBX_NORETURN
+#endif /* __dead2 */
+#ifdef __disable_tail_calls
+    __disable_tail_calls
+#endif /* __disable_tail_calls */
+    ;
+
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert_rtn(function, file, line, assertion)
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+__extern_C void __assert_c99(const char *assection, const char *file, int line,
+                             const char *function) MDBX_NORETURN;
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert_c99(assertion, file, line, function)
+#elif defined(__OpenBSD__)
+__extern_C __dead void __assert2(const char *file, int line,
+                                 const char *function,
+                                 const char *assertion) /* __nothrow */;
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert2(file, line, function, assertion)
+#elif defined(__NetBSD__)
+__extern_C __dead void __assert13(const char *file, int line,
+                                  const char *function,
+                                  const char *assertion) /* __nothrow */;
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert13(file, line, function, assertion)
+#elif defined(__FreeBSD__) || defined(__BSD__) || defined(__bsdi__) ||         \
+    defined(__DragonFly__)
+__extern_C void __assert(const char *function, const char *file, int line,
+                         const char *assertion) /* __nothrow */
+#ifdef __dead2
+    __dead2
+#else
+    MDBX_NORETURN
+#endif /* __dead2 */
+#ifdef __disable_tail_calls
+    __disable_tail_calls
+#endif /* __disable_tail_calls */
+    ;
+#define __assert_fail(assertion, file, line, function)                         \
+  __assert(function, file, line, assertion)
+
+#endif /* __assert_fail */
+
+#if !defined(__ANDROID_API__) || MDBX_DEBUG
+
+void __cold mdbx_assert_fail(const MDBX_env *env, const char *msg,
+                             const char *func, int line) {
+#if MDBX_DEBUG
+  if (env && env->me_assert_func) {
+    env->me_assert_func(env, msg, func, line);
+    return;
+  }
+#else
+  (void)env;
+#endif /* MDBX_DEBUG */
+
+  if (mdbx_debug_logger)
+    mdbx_debug_log(MDBX_LOG_FATAL, func, line, "assert: %s\n", msg);
+  else {
+#if defined(_WIN32) || defined(_WIN64)
+    char *message = nullptr;
+    const int num = mdbx_asprintf(&message, "\r\nMDBX-ASSERTION: %s, %s:%u",
+                                  msg, func ? func : "unknown", line);
+    if (num < 1 || !message)
+      message = "<troubles with assertion-message preparation>";
+    OutputDebugStringA(message);
+    if (IsDebuggerPresent())
+      DebugBreak();
+#elif defined(__ANDROID_API__)
+    __android_log_assert(msg, "mdbx", "%s:%u", func, line);
+#else
+    __assert_fail(msg, "mdbx", line, func);
+#endif
+  }
+
+#if defined(_WIN32) || defined(_WIN64)
+  FatalExit(ERROR_UNHANDLED_ERROR);
+#else
+  abort();
+#endif
+}
+
+#endif /* __ANDROID_API__ || MDBX_DEBUG */
+
+__cold void mdbx_panic(const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+
+  char *message = nullptr;
+  const int num = mdbx_vasprintf(&message, fmt, ap);
+  va_end(ap);
+  const char *const const_message =
+      (num < 1 || !message) ? "<troubles with panic-message preparation>"
+                            : message;
+
+#if defined(_WIN32) || defined(_WIN64)
+  OutputDebugStringA("\r\nMDBX-PANIC: ");
+  OutputDebugStringA(const_message);
+  if (IsDebuggerPresent())
+    DebugBreak();
+  FatalExit(ERROR_UNHANDLED_ERROR);
+#else
+#if defined(__ANDROID_API__)
+  __android_log_assert("panic", "mdbx", "%s", const_message);
+#else
+  __assert_fail(const_message, "mdbx", 0, "panic");
+#endif /* __ANDROID_API__ */
+  abort();
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef mdbx_vasprintf
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt,
+                                      va_list ap) {
+  va_list ones;
+  va_copy(ones, ap);
+  int needed = vsnprintf(nullptr, 0, fmt, ap);
+
+  if (unlikely(needed < 0 || needed >= INT_MAX)) {
+    *strp = nullptr;
+    va_end(ones);
+    return needed;
+  }
+
+  *strp = mdbx_malloc(needed + 1);
+  if (unlikely(*strp == nullptr)) {
+    va_end(ones);
+#if defined(_WIN32) || defined(_WIN64)
+    SetLastError(MDBX_ENOMEM);
+#else
+    errno = MDBX_ENOMEM;
+#endif
+    return -1;
+  }
+
+  int actual = vsnprintf(*strp, needed + 1, fmt, ones);
+  va_end(ones);
+
+  assert(actual == needed);
+  if (unlikely(actual < 0)) {
+    mdbx_free(*strp);
+    *strp = nullptr;
+  }
+  return actual;
+}
+#endif /* mdbx_vasprintf */
+
+#ifndef mdbx_asprintf
+MDBX_INTERNAL_FUNC int mdbx_asprintf(char **strp, const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  int rc = mdbx_vasprintf(strp, fmt, ap);
+  va_end(ap);
+  return rc;
+}
+#endif /* mdbx_asprintf */
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result) {
+  assert(is_powerof2(alignment) && alignment >= sizeof(void *));
+#if defined(_WIN32) || defined(_WIN64)
+  (void)alignment;
+  *result = VirtualAlloc(NULL, bytes, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+  return *result ? MDBX_SUCCESS : MDBX_ENOMEM /* ERROR_OUTOFMEMORY */;
+#elif defined(_ISOC11_SOURCE)
+  *result = aligned_alloc(alignment, ceil_powerof2(bytes, alignment));
+  return *result ? MDBX_SUCCESS : errno;
+#elif _POSIX_VERSION >= 200112L &&                                             \
+    (!defined(__ANDROID_API__) || __ANDROID_API__ >= 17)
+  *result = nullptr;
+  return posix_memalign(result, alignment, bytes);
+#elif __GLIBC_PREREQ(2, 16) || __STDC_VERSION__ >= 201112L
+  *result = memalign(alignment, bytes);
+  return *result ? MDBX_SUCCESS : errno;
+#else
+#error FIXME
+#endif
+}
+#endif /* mdbx_memalign_alloc */
+
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr) {
+#if defined(_WIN32) || defined(_WIN64)
+  VirtualFree(ptr, 0, MEM_RELEASE);
+#else
+  mdbx_free(ptr);
+#endif
+}
+#endif /* mdbx_memalign_free */
+
+#ifndef mdbx_strdup
+char *mdbx_strdup(const char *str) {
+  if (!str)
+    return NULL;
+  size_t bytes = strlen(str) + 1;
+  char *dup = mdbx_malloc(bytes);
+  if (dup)
+    memcpy(dup, str, bytes);
+  return dup;
+}
+#endif /* mdbx_strdup */
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair) {
+  int rc;
+  memset(condpair, 0, sizeof(mdbx_condpair_t));
+#if defined(_WIN32) || defined(_WIN64)
+  if ((condpair->mutex = CreateMutexW(NULL, FALSE, NULL)) == NULL) {
+    rc = GetLastError();
+    goto bailout_mutex;
+  }
+  if ((condpair->event[0] = CreateEventW(NULL, FALSE, FALSE, NULL)) == NULL) {
+    rc = GetLastError();
+    goto bailout_event;
+  }
+  if ((condpair->event[1] = CreateEventW(NULL, FALSE, FALSE, NULL)) != NULL)
+    return MDBX_SUCCESS;
+
+  rc = GetLastError();
+  (void)CloseHandle(condpair->event[0]);
+bailout_event:
+  (void)CloseHandle(condpair->mutex);
+#else
+  rc = pthread_mutex_init(&condpair->mutex, NULL);
+  if (unlikely(rc != 0))
+    goto bailout_mutex;
+  rc = pthread_cond_init(&condpair->cond[0], NULL);
+  if (unlikely(rc != 0))
+    goto bailout_cond;
+  rc = pthread_cond_init(&condpair->cond[1], NULL);
+  if (likely(rc == 0))
+    return MDBX_SUCCESS;
+
+  (void)pthread_cond_destroy(&condpair->cond[0]);
+bailout_cond:
+  (void)pthread_mutex_destroy(&condpair->mutex);
+#endif
+bailout_mutex:
+  memset(condpair, 0, sizeof(mdbx_condpair_t));
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair) {
+#if defined(_WIN32) || defined(_WIN64)
+  int rc = CloseHandle(condpair->mutex) ? MDBX_SUCCESS : GetLastError();
+  rc = CloseHandle(condpair->event[0]) ? rc : GetLastError();
+  rc = CloseHandle(condpair->event[1]) ? rc : GetLastError();
+#else
+  int err, rc = pthread_mutex_destroy(&condpair->mutex);
+  rc = (err = pthread_cond_destroy(&condpair->cond[0])) ? err : rc;
+  rc = (err = pthread_cond_destroy(&condpair->cond[1])) ? err : rc;
+#endif
+  memset(condpair, 0, sizeof(mdbx_condpair_t));
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD code = WaitForSingleObject(condpair->mutex, INFINITE);
+  return waitstatus2errcode(code);
+#else
+  return pthread_mutex_lock(&condpair->mutex);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair) {
+#if defined(_WIN32) || defined(_WIN64)
+  return ReleaseMutex(condpair->mutex) ? MDBX_SUCCESS : GetLastError();
+#else
+  return pthread_mutex_unlock(&condpair->mutex);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part) {
+#if defined(_WIN32) || defined(_WIN64)
+  return SetEvent(condpair->event[part]) ? MDBX_SUCCESS : GetLastError();
+#else
+  return pthread_cond_signal(&condpair->cond[part]);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair,
+                                          bool part) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD code = SignalObjectAndWait(condpair->mutex, condpair->event[part],
+                                   INFINITE, FALSE);
+  if (code == WAIT_OBJECT_0) {
+    code = WaitForSingleObject(condpair->mutex, INFINITE);
+    if (code == WAIT_OBJECT_0)
+      return MDBX_SUCCESS;
+  }
+  return waitstatus2errcode(code);
+#else
+  return pthread_cond_wait(&condpair->cond[part], &condpair->mutex);
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex) {
+#if defined(_WIN32) || defined(_WIN64)
+  InitializeCriticalSection(fastmutex);
+  return MDBX_SUCCESS;
+#else
+  return pthread_mutex_init(fastmutex, NULL);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex) {
+#if defined(_WIN32) || defined(_WIN64)
+  DeleteCriticalSection(fastmutex);
+  return MDBX_SUCCESS;
+#else
+  return pthread_mutex_destroy(fastmutex);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex) {
+#if defined(_WIN32) || defined(_WIN64)
+  __try {
+    EnterCriticalSection(fastmutex);
+  } __except (
+      (GetExceptionCode() ==
+       0xC0000194 /* STATUS_POSSIBLE_DEADLOCK / EXCEPTION_POSSIBLE_DEADLOCK */)
+          ? EXCEPTION_EXECUTE_HANDLER
+          : EXCEPTION_CONTINUE_SEARCH) {
+    return ERROR_POSSIBLE_DEADLOCK;
+  }
+  return MDBX_SUCCESS;
+#else
+  return pthread_mutex_lock(fastmutex);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex) {
+#if defined(_WIN32) || defined(_WIN64)
+  LeaveCriticalSection(fastmutex);
+  return MDBX_SUCCESS;
+#else
+  return pthread_mutex_unlock(fastmutex);
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname) {
+#if defined(_WIN32) || defined(_WIN64)
+  const size_t wlen = mbstowcs(nullptr, pathname, INT_MAX);
+  if (wlen < 1 || wlen > /* MAX_PATH */ INT16_MAX)
+    return ERROR_INVALID_NAME;
+  wchar_t *const pathnameW = _alloca((wlen + 1) * sizeof(wchar_t));
+  if (wlen != mbstowcs(pathnameW, pathname, wlen + 1))
+    return ERROR_INVALID_NAME;
+  return DeleteFileW(pathnameW) ? MDBX_SUCCESS : GetLastError();
+#else
+  return unlink(pathname) ? errno : MDBX_SUCCESS;
+#endif
+}
+
+#if !(defined(_WIN32) || defined(_WIN64))
+static bool is_valid_fd(int fd) { return !(isatty(fd) < 0 && errno == EBADF); }
+#endif /*! Windows */
+
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname) {
+#if defined(_WIN32) || defined(_WIN64)
+  const size_t wlen = mbstowcs(nullptr, pathname, INT_MAX);
+  if (wlen < 1 || wlen > /* MAX_PATH */ INT16_MAX)
+    return ERROR_INVALID_NAME;
+  wchar_t *const pathnameW = _alloca((wlen + 1) * sizeof(wchar_t));
+  if (wlen != mbstowcs(pathnameW, pathname, wlen + 1))
+    return ERROR_INVALID_NAME;
+  return RemoveDirectoryW(pathnameW) ? MDBX_SUCCESS : GetLastError();
+#else
+  return rmdir(pathname) ? errno : MDBX_SUCCESS;
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits) {
+  *fd = INVALID_HANDLE_VALUE;
+
+#if defined(_WIN32) || defined(_WIN64)
+  const size_t wlen = mbstowcs(nullptr, pathname, INT_MAX);
+  if (wlen < 1 || wlen > /* MAX_PATH */ INT16_MAX)
+    return ERROR_INVALID_NAME;
+  wchar_t *const pathnameW = _alloca((wlen + 1) * sizeof(wchar_t));
+  if (wlen != mbstowcs(pathnameW, pathname, wlen + 1))
+    return ERROR_INVALID_NAME;
+
+  DWORD CreationDisposition = unix_mode_bits ? OPEN_ALWAYS : OPEN_EXISTING;
+  DWORD FlagsAndAttributes =
+      FILE_FLAG_POSIX_SEMANTICS | FILE_ATTRIBUTE_NOT_CONTENT_INDEXED;
+  DWORD DesiredAccess = FILE_READ_ATTRIBUTES;
+  DWORD ShareMode = (env->me_flags & MDBX_EXCLUSIVE)
+                        ? 0
+                        : (FILE_SHARE_READ | FILE_SHARE_WRITE);
+
+  switch (purpose) {
+  default:
+    return ERROR_INVALID_PARAMETER;
+  case MDBX_OPEN_LCK:
+    CreationDisposition = OPEN_ALWAYS;
+    DesiredAccess |= GENERIC_READ | GENERIC_WRITE;
+    FlagsAndAttributes |= FILE_ATTRIBUTE_HIDDEN | FILE_ATTRIBUTE_TEMPORARY;
+    break;
+  case MDBX_OPEN_DXB_READ:
+    CreationDisposition = OPEN_EXISTING;
+    DesiredAccess |= GENERIC_READ;
+    ShareMode |= FILE_SHARE_READ;
+    break;
+  case MDBX_OPEN_DXB_LAZY:
+    DesiredAccess |= GENERIC_READ | GENERIC_WRITE;
+    break;
+  case MDBX_OPEN_DXB_DSYNC:
+    CreationDisposition = OPEN_EXISTING;
+    DesiredAccess |= GENERIC_WRITE;
+    FlagsAndAttributes |= FILE_FLAG_WRITE_THROUGH;
+    break;
+  case MDBX_OPEN_COPY:
+    CreationDisposition = CREATE_NEW;
+    ShareMode = 0;
+    DesiredAccess |= GENERIC_WRITE;
+    FlagsAndAttributes |=
+        (env->me_psize < env->me_os_psize) ? 0 : FILE_FLAG_NO_BUFFERING;
+    break;
+  case MDBX_OPEN_DELETE:
+    CreationDisposition = OPEN_EXISTING;
+    ShareMode |= FILE_SHARE_DELETE;
+    DesiredAccess =
+        FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES | DELETE | SYNCHRONIZE;
+    break;
+  }
+
+  *fd = CreateFileW(pathnameW, DesiredAccess, ShareMode, NULL,
+                    CreationDisposition, FlagsAndAttributes, NULL);
+  if (*fd == INVALID_HANDLE_VALUE)
+    return GetLastError();
+
+  BY_HANDLE_FILE_INFORMATION info;
+  if (!GetFileInformationByHandle(*fd, &info)) {
+    int err = GetLastError();
+    CloseHandle(*fd);
+    *fd = INVALID_HANDLE_VALUE;
+    return err;
+  }
+  const DWORD AttributesDiff =
+      (info.dwFileAttributes ^ FlagsAndAttributes) &
+      (FILE_ATTRIBUTE_HIDDEN | FILE_ATTRIBUTE_NOT_CONTENT_INDEXED |
+       FILE_ATTRIBUTE_TEMPORARY | FILE_ATTRIBUTE_COMPRESSED);
+  if (AttributesDiff)
+    (void)SetFileAttributesW(pathnameW, info.dwFileAttributes ^ AttributesDiff);
+
+#else
+  int flags = unix_mode_bits ? O_CREAT : 0;
+  switch (purpose) {
+  default:
+    return EINVAL;
+  case MDBX_OPEN_LCK:
+    flags |= O_RDWR;
+    break;
+  case MDBX_OPEN_DXB_READ:
+    flags = O_RDONLY;
+    break;
+  case MDBX_OPEN_DXB_LAZY:
+    flags |= O_RDWR;
+    break;
+  case MDBX_OPEN_COPY:
+    flags = O_CREAT | O_WRONLY | O_EXCL;
+    break;
+  case MDBX_OPEN_DXB_DSYNC:
+    flags |= O_WRONLY;
+#if defined(O_DSYNC)
+    flags |= O_DSYNC;
+#elif defined(O_SYNC)
+    flags |= O_SYNC;
+#elif defined(O_FSYNC)
+    flags |= O_FSYNC;
+#endif
+    break;
+  case MDBX_OPEN_DELETE:
+    flags = O_RDWR;
+    break;
+  }
+
+  const bool direct_nocache_for_copy =
+      env->me_psize >= env->me_os_psize && purpose == MDBX_OPEN_COPY;
+  if (direct_nocache_for_copy) {
+#if defined(O_DIRECT)
+    flags |= O_DIRECT;
+#endif /* O_DIRECT */
+#if defined(O_NOCACHE)
+    flags |= O_NOCACHE;
+#endif /* O_NOCACHE */
+  }
+
+#ifdef O_CLOEXEC
+  flags |= O_CLOEXEC;
+#endif /* O_CLOEXEC */
+
+  /* Safeguard for https://github.com/erthink/libmdbx/issues/144 */
+#if STDIN_FILENO == 0 && STDOUT_FILENO == 1 && STDERR_FILENO == 2
+  int stub_fd0 = -1, stub_fd1 = -1, stub_fd2 = -1;
+  static const char dev_null[] = "/dev/null";
+  if (!is_valid_fd(STDIN_FILENO)) {
+    mdbx_warning("STD%s_FILENO/%d is invalid, open %s for temporary stub", "IN",
+                 STDIN_FILENO, dev_null);
+    stub_fd0 = open(dev_null, O_RDONLY | O_NOCTTY);
+  }
+  if (!is_valid_fd(STDOUT_FILENO)) {
+    mdbx_warning("STD%s_FILENO/%d is invalid, open %s for temporary stub",
+                 "OUT", STDOUT_FILENO, dev_null);
+    stub_fd1 = open(dev_null, O_WRONLY | O_NOCTTY);
+  }
+  if (!is_valid_fd(STDERR_FILENO)) {
+    mdbx_warning("STD%s_FILENO/%d is invalid, open %s for temporary stub",
+                 "ERR", STDERR_FILENO, dev_null);
+    stub_fd2 = open(dev_null, O_WRONLY | O_NOCTTY);
+  }
+#else
+#error "Unexpected or unsupported UNIX or POSIX system"
+#endif /* STDIN_FILENO == 0 && STDERR_FILENO == 2 */
+
+  *fd = open(pathname, flags, unix_mode_bits);
+#if defined(O_DIRECT)
+  if (*fd < 0 && (flags & O_DIRECT) &&
+      (errno == EINVAL || errno == EAFNOSUPPORT)) {
+    flags &= ~(O_DIRECT | O_EXCL);
+    *fd = open(pathname, flags, unix_mode_bits);
+  }
+#endif /* O_DIRECT */
+
+  /* Safeguard for https://github.com/erthink/libmdbx/issues/144 */
+#if STDIN_FILENO == 0 && STDOUT_FILENO == 1 && STDERR_FILENO == 2
+  if (*fd == STDIN_FILENO) {
+    mdbx_warning("Got STD%s_FILENO/%d, avoid using it by dup(fd)", "IN",
+                 STDIN_FILENO);
+    assert(stub_fd0 == -1);
+    *fd = dup(stub_fd0 = *fd);
+  }
+  if (*fd == STDOUT_FILENO) {
+    mdbx_warning("Got STD%s_FILENO/%d, avoid using it by dup(fd)", "OUT",
+                 STDOUT_FILENO);
+    assert(stub_fd1 == -1);
+    *fd = dup(stub_fd1 = *fd);
+  }
+  if (*fd == STDERR_FILENO) {
+    mdbx_warning("Got STD%s_FILENO/%d, avoid using it by dup(fd)", "ERR",
+                 STDERR_FILENO);
+    assert(stub_fd2 == -1);
+    *fd = dup(stub_fd2 = *fd);
+  }
+  if (stub_fd0 != -1)
+    close(stub_fd0);
+  if (stub_fd1 != -1)
+    close(stub_fd1);
+  if (stub_fd2 != -1)
+    close(stub_fd2);
+  if (*fd >= STDIN_FILENO && *fd <= STDERR_FILENO) {
+    mdbx_error(
+        "Rejecting the use of a FD in the range "
+        "STDIN_FILENO/%d..STDERR_FILENO/%d to prevent database corruption",
+        STDIN_FILENO, STDERR_FILENO);
+    close(*fd);
+    return EBADF;
+  }
+#else
+#error "Unexpected or unsupported UNIX or POSIX system"
+#endif /* STDIN_FILENO == 0 && STDERR_FILENO == 2 */
+
+  if (*fd < 0)
+    return errno;
+
+#if defined(FD_CLOEXEC) && !defined(O_CLOEXEC)
+  const int fd_flags = fcntl(*fd, F_GETFD);
+  if (fd_flags != -1)
+    (void)fcntl(*fd, F_SETFD, fd_flags | FD_CLOEXEC);
+#endif /* FD_CLOEXEC && !O_CLOEXEC */
+
+  if (direct_nocache_for_copy) {
+#if defined(F_NOCACHE) && !defined(O_NOCACHE)
+    (void)fcntl(*fd, F_NOCACHE, 1);
+#endif /* F_NOCACHE */
+  }
+
+#endif
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd) {
+#if defined(_WIN32) || defined(_WIN64)
+  return CloseHandle(fd) ? MDBX_SUCCESS : GetLastError();
+#else
+  assert(fd > STDERR_FILENO);
+  return (close(fd) == 0) ? MDBX_SUCCESS : errno;
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t bytes,
+                                  uint64_t offset) {
+  if (bytes > MAX_WRITE)
+    return MDBX_EINVAL;
+#if defined(_WIN32) || defined(_WIN64)
+  OVERLAPPED ov;
+  ov.hEvent = 0;
+  ov.Offset = (DWORD)offset;
+  ov.OffsetHigh = HIGH_DWORD(offset);
+
+  DWORD read = 0;
+  if (unlikely(!ReadFile(fd, buf, (DWORD)bytes, &read, &ov))) {
+    int rc = GetLastError();
+    return (rc == MDBX_SUCCESS) ? /* paranoia */ ERROR_READ_FAULT : rc;
+  }
+#else
+  STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                    "libmdbx requires 64-bit file I/O on 64-bit systems");
+  intptr_t read = pread(fd, buf, bytes, offset);
+  if (read < 0) {
+    int rc = errno;
+    return (rc == MDBX_SUCCESS) ? /* paranoia */ MDBX_EIO : rc;
+  }
+#endif
+  return (bytes == (size_t)read) ? MDBX_SUCCESS : MDBX_ENODATA;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t bytes, uint64_t offset) {
+  while (true) {
+#if defined(_WIN32) || defined(_WIN64)
+    OVERLAPPED ov;
+    ov.hEvent = 0;
+    ov.Offset = (DWORD)offset;
+    ov.OffsetHigh = HIGH_DWORD(offset);
+
+    DWORD written;
+    if (unlikely(!WriteFile(
+            fd, buf, likely(bytes <= MAX_WRITE) ? (DWORD)bytes : MAX_WRITE,
+            &written, &ov)))
+      return GetLastError();
+    if (likely(bytes == written))
+      return MDBX_SUCCESS;
+#else
+    STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                      "libmdbx requires 64-bit file I/O on 64-bit systems");
+    const intptr_t written =
+        pwrite(fd, buf, likely(bytes <= MAX_WRITE) ? bytes : MAX_WRITE, offset);
+    if (likely(bytes == (size_t)written))
+      return MDBX_SUCCESS;
+    if (written < 0) {
+      const int rc = errno;
+      if (rc != EINTR)
+        return rc;
+      continue;
+    }
+#endif
+    bytes -= written;
+    offset += written;
+    buf = (char *)buf + written;
+  }
+}
+
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t bytes) {
+  while (true) {
+#if defined(_WIN32) || defined(_WIN64)
+    DWORD written;
+    if (unlikely(!WriteFile(
+            fd, buf, likely(bytes <= MAX_WRITE) ? (DWORD)bytes : MAX_WRITE,
+            &written, nullptr)))
+      return GetLastError();
+    if (likely(bytes == written))
+      return MDBX_SUCCESS;
+#else
+    STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                      "libmdbx requires 64-bit file I/O on 64-bit systems");
+    const intptr_t written =
+        write(fd, buf, likely(bytes <= MAX_WRITE) ? bytes : MAX_WRITE);
+    if (likely(bytes == (size_t)written))
+      return MDBX_SUCCESS;
+    if (written < 0) {
+      const int rc = errno;
+      if (rc != EINTR)
+        return rc;
+      continue;
+    }
+#endif
+    bytes -= written;
+    buf = (char *)buf + written;
+  }
+}
+
+int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov, int iovcnt,
+                 uint64_t offset, size_t expected_written) {
+#if defined(_WIN32) || defined(_WIN64) || defined(__APPLE__) ||                \
+    (defined(__ANDROID_API__) && __ANDROID_API__ < 24)
+  size_t written = 0;
+  for (int i = 0; i < iovcnt; ++i) {
+    int rc = mdbx_pwrite(fd, iov[i].iov_base, iov[i].iov_len, offset);
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+    written += iov[i].iov_len;
+    offset += iov[i].iov_len;
+  }
+  return (expected_written == written) ? MDBX_SUCCESS
+                                       : MDBX_EIO /* ERROR_WRITE_FAULT */;
+#else
+  int rc;
+  intptr_t written;
+  do {
+    STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                      "libmdbx requires 64-bit file I/O on 64-bit systems");
+    written = pwritev(fd, iov, iovcnt, offset);
+    if (likely(expected_written == (size_t)written))
+      return MDBX_SUCCESS;
+    rc = errno;
+  } while (rc == EINTR);
+  return (written < 0) ? rc : MDBX_EIO /* Use which error code? */;
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  enum mdbx_syncmode_bits mode_bits) {
+#if defined(_WIN32) || defined(_WIN64)
+  if ((mode_bits & (MDBX_SYNC_DATA | MDBX_SYNC_IODQ)) && !FlushFileBuffers(fd))
+    return GetLastError();
+  return MDBX_SUCCESS;
+#else
+
+#if defined(__APPLE__) &&                                                      \
+    MDBX_OSX_SPEED_INSTEADOF_DURABILITY == MDBX_OSX_WANNA_DURABILITY
+  if (mode_bits & MDBX_SYNC_IODQ)
+    return likely(fcntl(fd, F_FULLFSYNC) != -1) ? MDBX_SUCCESS : errno;
+#endif /* MacOS */
+
+  /* LY: This approach is always safe and without appreciable performance
+   * degradation, even on a kernel with fdatasync's bug.
+   *
+   * For more info about of a corresponding fdatasync() bug
+   * see http://www.spinics.net/lists/linux-ext4/msg33714.html */
+  while (1) {
+    switch (mode_bits & (MDBX_SYNC_DATA | MDBX_SYNC_SIZE)) {
+    case MDBX_SYNC_NONE:
+      return MDBX_SUCCESS /* nothing to do */;
+#if defined(_POSIX_SYNCHRONIZED_IO) && _POSIX_SYNCHRONIZED_IO > 0
+    case MDBX_SYNC_DATA:
+      if (fdatasync(fd) == 0)
+        return MDBX_SUCCESS;
+      break /* error */;
+#if defined(__linux__) || defined(__gnu_linux__)
+    case MDBX_SYNC_SIZE:
+      if (mdbx_linux_kernel_version >= 0x03060000)
+        return MDBX_SUCCESS;
+      __fallthrough /* fall through */;
+#endif /* Linux */
+#endif /* _POSIX_SYNCHRONIZED_IO > 0 */
+    default:
+      if (fsync(fd) == 0)
+        return MDBX_SUCCESS;
+    }
+
+    int rc = errno;
+    if (rc != EINTR)
+      return rc;
+  }
+#endif
+}
+
+int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length) {
+#if defined(_WIN32) || defined(_WIN64)
+  BY_HANDLE_FILE_INFORMATION info;
+  if (!GetFileInformationByHandle(fd, &info))
+    return GetLastError();
+  *length = info.nFileSizeLow | (uint64_t)info.nFileSizeHigh << 32;
+#else
+  struct stat st;
+
+  STATIC_ASSERT_MSG(sizeof(off_t) <= sizeof(uint64_t),
+                    "libmdbx requires 64-bit file I/O on 64-bit systems");
+  if (fstat(fd, &st))
+    return errno;
+
+  *length = st.st_size;
+#endif
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd) {
+#if defined(_WIN32) || defined(_WIN64)
+  switch (GetFileType(fd)) {
+  case FILE_TYPE_DISK:
+    return MDBX_RESULT_FALSE;
+  case FILE_TYPE_CHAR:
+  case FILE_TYPE_PIPE:
+    return MDBX_RESULT_TRUE;
+  default:
+    return GetLastError();
+  }
+#else
+  struct stat info;
+  if (fstat(fd, &info))
+    return errno;
+  switch (info.st_mode & S_IFMT) {
+  case S_IFBLK:
+  case S_IFREG:
+    return MDBX_RESULT_FALSE;
+  case S_IFCHR:
+  case S_IFIFO:
+  case S_IFSOCK:
+    return MDBX_RESULT_TRUE;
+  case S_IFDIR:
+  case S_IFLNK:
+  default:
+    return MDBX_INCOMPATIBLE;
+  }
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length) {
+#if defined(_WIN32) || defined(_WIN64)
+  if (mdbx_SetFileInformationByHandle) {
+    FILE_END_OF_FILE_INFO EndOfFileInfo;
+    EndOfFileInfo.EndOfFile.QuadPart = length;
+    return mdbx_SetFileInformationByHandle(fd, FileEndOfFileInfo,
+                                           &EndOfFileInfo,
+                                           sizeof(FILE_END_OF_FILE_INFO))
+               ? MDBX_SUCCESS
+               : GetLastError();
+  } else {
+    LARGE_INTEGER li;
+    li.QuadPart = length;
+    return (SetFilePointerEx(fd, li, NULL, FILE_BEGIN) && SetEndOfFile(fd))
+               ? MDBX_SUCCESS
+               : GetLastError();
+  }
+#else
+  STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                    "libmdbx requires 64-bit file I/O on 64-bit systems");
+  return ftruncate(fd, length) == 0 ? MDBX_SUCCESS : errno;
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos) {
+#if defined(_WIN32) || defined(_WIN64)
+  LARGE_INTEGER li;
+  li.QuadPart = pos;
+  return SetFilePointerEx(fd, li, NULL, FILE_BEGIN) ? MDBX_SUCCESS
+                                                    : GetLastError();
+#else
+  STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t),
+                    "libmdbx requires 64-bit file I/O on 64-bit systems");
+  return (lseek(fd, pos, SEEK_SET) < 0) ? errno : MDBX_SUCCESS;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg) {
+#if defined(_WIN32) || defined(_WIN64)
+  *thread = CreateThread(NULL, 0, start_routine, arg, 0, NULL);
+  return *thread ? MDBX_SUCCESS : GetLastError();
+#else
+  return pthread_create(thread, NULL, start_routine, arg);
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD code = WaitForSingleObject(thread, INFINITE);
+  return waitstatus2errcode(code);
+#else
+  void *unused_retval = &unused_retval;
+  return pthread_join(thread, &unused_retval);
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits) {
+  uint8_t *ptr = (uint8_t *)map->address + offset;
+#if defined(_WIN32) || defined(_WIN64)
+  if (!FlushViewOfFile(ptr, length))
+    return GetLastError();
+#else
+#if defined(__linux__) || defined(__gnu_linux__)
+  if (mode_bits == MDBX_SYNC_NONE && mdbx_linux_kernel_version > 0x02061300)
+    /* Since Linux 2.6.19, MS_ASYNC is in fact a no-op. The kernel properly
+     * tracks dirty pages and flushes them to storage as necessary. */
+    return MDBX_SUCCESS;
+#endif /* Linux */
+  if (msync(ptr, length, (mode_bits & MDBX_SYNC_DATA) ? MS_SYNC : MS_ASYNC))
+    return errno;
+  mode_bits &= ~MDBX_SYNC_DATA;
+#endif
+  return mdbx_fsync(map->fd, mode_bits);
+}
+
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err) {
+#if defined(_WIN32) || defined(_WIN64)
+  (void)pathname;
+  (void)err;
+  if (!mdbx_GetVolumeInformationByHandleW)
+    return MDBX_ENOSYS;
+  DWORD unused, flags;
+  if (!mdbx_GetVolumeInformationByHandleW(handle, nullptr, 0, nullptr, &unused,
+                                          &flags, nullptr, 0))
+    return GetLastError();
+  if ((flags & FILE_READ_ONLY_VOLUME) == 0)
+    return MDBX_EACCESS;
+#else
+  struct statvfs info;
+  if (err != MDBX_ENOFILE) {
+    if (statvfs(pathname, &info))
+      return errno;
+    if ((info.f_flag & ST_RDONLY) == 0)
+      return err;
+  }
+  if (fstatvfs(handle, &info))
+    return errno;
+  if ((info.f_flag & ST_RDONLY) == 0)
+    return (err == MDBX_ENOFILE) ? MDBX_EACCESS : err;
+#endif /* !Windows */
+  return MDBX_SUCCESS;
+}
+
+static int mdbx_check_fs_local(mdbx_filehandle_t handle, int flags) {
+#if defined(_WIN32) || defined(_WIN64)
+  if (mdbx_RunningUnderWine() && !(flags & MDBX_EXCLUSIVE))
+    return ERROR_NOT_CAPABLE /* workaround for Wine */;
+
+  if (GetFileType(handle) != FILE_TYPE_DISK)
+    return ERROR_FILE_OFFLINE;
+
+  if (mdbx_GetFileInformationByHandleEx) {
+    FILE_REMOTE_PROTOCOL_INFO RemoteProtocolInfo;
+    if (mdbx_GetFileInformationByHandleEx(handle, FileRemoteProtocolInfo,
+                                          &RemoteProtocolInfo,
+                                          sizeof(RemoteProtocolInfo))) {
+      if ((RemoteProtocolInfo.Flags & REMOTE_PROTOCOL_INFO_FLAG_OFFLINE) &&
+          !(flags & MDBX_RDONLY))
+        return ERROR_FILE_OFFLINE;
+      if (!(RemoteProtocolInfo.Flags & REMOTE_PROTOCOL_INFO_FLAG_LOOPBACK) &&
+          !(flags & MDBX_EXCLUSIVE))
+        return ERROR_REMOTE_STORAGE_MEDIA_ERROR;
+    }
+  }
+
+  if (mdbx_NtFsControlFile) {
+    NTSTATUS rc;
+    struct {
+      WOF_EXTERNAL_INFO wof_info;
+      union {
+        WIM_PROVIDER_EXTERNAL_INFO wim_info;
+        FILE_PROVIDER_EXTERNAL_INFO_V1 file_info;
+      };
+      size_t reserved_for_microsoft_madness[42];
+    } GetExternalBacking_OutputBuffer;
+    IO_STATUS_BLOCK StatusBlock;
+    rc = mdbx_NtFsControlFile(handle, NULL, NULL, NULL, &StatusBlock,
+                              FSCTL_GET_EXTERNAL_BACKING, NULL, 0,
+                              &GetExternalBacking_OutputBuffer,
+                              sizeof(GetExternalBacking_OutputBuffer));
+    if (NT_SUCCESS(rc)) {
+      if (!(flags & MDBX_EXCLUSIVE))
+        return ERROR_REMOTE_STORAGE_MEDIA_ERROR;
+    } else if (rc != STATUS_OBJECT_NOT_EXTERNALLY_BACKED &&
+               rc != STATUS_INVALID_DEVICE_REQUEST &&
+               rc != STATUS_NOT_SUPPORTED)
+      return ntstatus2errcode(rc);
+  }
+
+  if (mdbx_GetVolumeInformationByHandleW && mdbx_GetFinalPathNameByHandleW) {
+    WCHAR *PathBuffer = mdbx_malloc(sizeof(WCHAR) * INT16_MAX);
+    if (!PathBuffer)
+      return MDBX_ENOMEM;
+
+    int rc = MDBX_SUCCESS;
+    DWORD VolumeSerialNumber, FileSystemFlags;
+    if (!mdbx_GetVolumeInformationByHandleW(handle, PathBuffer, INT16_MAX,
+                                            &VolumeSerialNumber, NULL,
+                                            &FileSystemFlags, NULL, 0)) {
+      rc = GetLastError();
+      goto bailout;
+    }
+
+    if ((flags & MDBX_RDONLY) == 0) {
+      if (FileSystemFlags &
+          (FILE_SEQUENTIAL_WRITE_ONCE | FILE_READ_ONLY_VOLUME |
+           FILE_VOLUME_IS_COMPRESSED)) {
+        rc = ERROR_REMOTE_STORAGE_MEDIA_ERROR;
+        goto bailout;
+      }
+    }
+
+    if (!mdbx_GetFinalPathNameByHandleW(handle, PathBuffer, INT16_MAX,
+                                        FILE_NAME_NORMALIZED |
+                                            VOLUME_NAME_NT)) {
+      rc = GetLastError();
+      goto bailout;
+    }
+
+    if (_wcsnicmp(PathBuffer, L"\\Device\\Mup\\", 12) == 0) {
+      if (!(flags & MDBX_EXCLUSIVE)) {
+        rc = ERROR_REMOTE_STORAGE_MEDIA_ERROR;
+        goto bailout;
+      }
+    } else if (mdbx_GetFinalPathNameByHandleW(handle, PathBuffer, INT16_MAX,
+                                              FILE_NAME_NORMALIZED |
+                                                  VOLUME_NAME_DOS)) {
+      UINT DriveType = GetDriveTypeW(PathBuffer);
+      if (DriveType == DRIVE_NO_ROOT_DIR &&
+          _wcsnicmp(PathBuffer, L"\\\\?\\", 4) == 0 &&
+          _wcsnicmp(PathBuffer + 5, L":\\", 2) == 0) {
+        PathBuffer[7] = 0;
+        DriveType = GetDriveTypeW(PathBuffer + 4);
+      }
+      switch (DriveType) {
+      case DRIVE_CDROM:
+        if (flags & MDBX_RDONLY)
+          break;
+      // fall through
+      case DRIVE_UNKNOWN:
+      case DRIVE_NO_ROOT_DIR:
+      case DRIVE_REMOTE:
+      default:
+        if (!(flags & MDBX_EXCLUSIVE))
+          rc = ERROR_REMOTE_STORAGE_MEDIA_ERROR;
+      // fall through
+      case DRIVE_REMOVABLE:
+      case DRIVE_FIXED:
+      case DRIVE_RAMDISK:
+        break;
+      }
+    }
+  bailout:
+    mdbx_free(PathBuffer);
+    return rc;
+  }
+
+#else
+
+  struct statvfs statvfs_info;
+  if (fstatvfs(handle, &statvfs_info))
+    return errno;
+#if defined(ST_LOCAL) || defined(ST_EXPORTED)
+  const unsigned long st_flags = statvfs_info.f_flag;
+#endif /* ST_LOCAL || ST_EXPORTED */
+
+#if defined(__NetBSD__)
+  const unsigned type = 0;
+  const char *const name = statvfs_info.f_fstypename;
+  const size_t name_len = VFS_NAMELEN;
+#elif defined(_AIX) || defined(__OS400__)
+  const char *const name = statvfs_info.f_basetype;
+  const size_t name_len = sizeof(statvfs_info.f_basetype);
+  struct stat st;
+  if (fstat(handle, &st))
+    return errno;
+  const unsigned type = st.st_vfstype;
+  if ((st.st_flag & FS_REMOTE) != 0 && !(flags & MDBX_EXCLUSIVE))
+    return MDBX_EREMOTE;
+#elif defined(FSTYPSZ) || defined(_FSTYPSZ)
+  const unsigned type = 0;
+  const char *const name = statvfs_info.f_basetype;
+  const size_t name_len = sizeof(statvfs_info.f_basetype);
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+    defined(ST_FSTYPSZ) || defined(_ST_FSTYPSZ)
+  const unsigned type = 0;
+  struct stat st;
+  if (fstat(handle, &st))
+    return errno;
+  const char *const name = st.st_fstype;
+  const size_t name_len = strlen(name);
+#else
+  struct statfs statfs_info;
+  if (fstatfs(handle, &statfs_info))
+    return errno;
+#if defined(__OpenBSD__)
+  const unsigned type = 0;
+#else
+  const unsigned type = statfs_info.f_type;
+#endif
+#if defined(MNT_LOCAL) || defined(MNT_EXPORTED)
+  const unsigned long mnt_flags = statfs_info.f_flags;
+#endif /* MNT_LOCAL || MNT_EXPORTED */
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__) || defined(MFSNAMELEN) ||          \
+    defined(MFSTYPENAMELEN) || defined(VFS_NAMELEN)
+  const char *const name = statfs_info.f_fstypename;
+  const size_t name_len = sizeof(statfs_info.f_fstypename);
+#elif defined(__ANDROID_API__) && __ANDROID_API__ < 21
+  const char *const name = "";
+  const unsigned name_len = 0;
+#else
+
+  const char *name = "";
+  unsigned name_len = 0;
+
+  struct stat st;
+  if (fstat(handle, &st))
+    return errno;
+
+  char pathbuf[PATH_MAX];
+  FILE *mounted = nullptr;
+#if defined(__linux__) || defined(__gnu_linux__)
+  mounted = setmntent("/proc/mounts", "r");
+#endif /* Linux */
+  if (!mounted)
+    mounted = setmntent("/etc/mtab", "r");
+  if (mounted) {
+    const struct mntent *ent;
+#if defined(_BSD_SOURCE) || defined(_SVID_SOURCE) || defined(__BIONIC__) ||    \
+    (defined(_DEFAULT_SOURCE) && __GLIBC_PREREQ(2, 19))
+    struct mntent entbuf;
+    const bool should_copy = false;
+    while (nullptr !=
+           (ent = getmntent_r(mounted, &entbuf, pathbuf, sizeof(pathbuf))))
+#else
+    const bool should_copy = true;
+    while (nullptr != (ent = getmntent(mounted)))
+#endif
+    {
+      struct stat mnt;
+      if (!stat(ent->mnt_dir, &mnt) && mnt.st_dev == st.st_dev) {
+        if (should_copy) {
+          name =
+              strncpy(pathbuf, ent->mnt_fsname, name_len = sizeof(pathbuf) - 1);
+          pathbuf[name_len] = 0;
+        } else {
+          name = ent->mnt_fsname;
+          name_len = strlen(name);
+        }
+        break;
+      }
+    }
+    endmntent(mounted);
+  }
+#endif /* !xBSD && !Android/Bionic */
+#endif
+
+  if (name_len) {
+    if (((name_len > 2 && strncasecmp("nfs", name, 3) == 0) ||
+         strncasecmp("cifs", name, name_len) == 0 ||
+         strncasecmp("ncpfs", name, name_len) == 0 ||
+         strncasecmp("smbfs", name, name_len) == 0 ||
+         ((name_len > 3 && strncasecmp("fuse", name, 4) == 0) &&
+          strncasecmp("fuseblk", name, name_len) != 0)) &&
+        !(flags & MDBX_EXCLUSIVE))
+      return MDBX_EREMOTE;
+    if (strcasecmp("ftp", name) == 0 || strcasecmp("http", name) == 0 ||
+        strcasecmp("sshfs", name) == 0)
+      return MDBX_EREMOTE;
+  }
+
+#ifdef ST_LOCAL
+  if ((st_flags & ST_LOCAL) == 0 && !(flags & MDBX_EXCLUSIVE))
+    return MDBX_EREMOTE;
+#elif defined(MNT_LOCAL)
+  if ((mnt_flags & MNT_LOCAL) == 0 && !(flags & MDBX_EXCLUSIVE))
+    return MDBX_EREMOTE;
+#endif /* ST/MNT_LOCAL */
+
+#ifdef ST_EXPORTED
+  if ((st_flags & ST_EXPORTED) != 0 && !(flags & MDBX_RDONLY))
+    return MDBX_EREMOTE;
+#elif defined(MNT_EXPORTED)
+  if ((mnt_flags & MNT_EXPORTED) != 0 && !(flags & MDBX_RDONLY))
+    return MDBX_EREMOTE;
+#endif /* ST/MNT_EXPORTED */
+
+  switch (type) {
+  case 0xFF534D42 /* CIFS_MAGIC_NUMBER */:
+  case 0x6969 /* NFS_SUPER_MAGIC */:
+  case 0x564c /* NCP_SUPER_MAGIC */:
+  case 0x517B /* SMB_SUPER_MAGIC */:
+#if defined(__digital__) || defined(__osf__) || defined(__osf)
+  case 0x0E /* Tru64 NFS */:
+#endif
+#ifdef ST_FST_NFS
+  case ST_FST_NFS:
+#endif
+    if ((flags & MDBX_EXCLUSIVE) == 0)
+      return MDBX_EREMOTE;
+  case 0:
+  default:
+    break;
+  }
+#endif /* Unix */
+
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t size, const size_t limit,
+                                 const unsigned options) {
+  assert(size <= limit);
+  map->limit = 0;
+  map->current = 0;
+  map->address = nullptr;
+#if defined(_WIN32) || defined(_WIN64)
+  map->section = NULL;
+  map->filesize = 0;
+#endif /* Windows */
+
+  int err = mdbx_check_fs_local(map->fd, flags);
+  if (unlikely(err != MDBX_SUCCESS))
+    return err;
+
+  if ((flags & MDBX_RDONLY) == 0 && (options & MMAP_OPTION_TRUNCATE) != 0) {
+    err = mdbx_ftruncate(map->fd, size);
+    if (err != MDBX_SUCCESS)
+      return err;
+#if defined(_WIN32) || defined(_WIN64)
+    map->filesize = size;
+#else
+    map->current = size;
+#endif
+  } else {
+    uint64_t filesize = 0;
+    err = mdbx_filesize(map->fd, &filesize);
+    if (err != MDBX_SUCCESS)
+      return err;
+#if defined(_WIN32) || defined(_WIN64)
+    map->filesize = filesize;
+#else
+    map->current = (filesize > limit) ? limit : (size_t)filesize;
+#endif
+  }
+
+#if defined(_WIN32) || defined(_WIN64)
+  LARGE_INTEGER SectionSize;
+  SectionSize.QuadPart = size;
+  err = NtCreateSection(
+      &map->section,
+      /* DesiredAccess */
+      (flags & MDBX_WRITEMAP)
+          ? SECTION_QUERY | SECTION_MAP_READ | SECTION_EXTEND_SIZE |
+                SECTION_MAP_WRITE
+          : SECTION_QUERY | SECTION_MAP_READ | SECTION_EXTEND_SIZE,
+      /* ObjectAttributes */ NULL, /* MaximumSize (InitialSize) */ &SectionSize,
+      /* SectionPageProtection */
+      (flags & MDBX_RDONLY) ? PAGE_READONLY : PAGE_READWRITE,
+      /* AllocationAttributes */ SEC_RESERVE, map->fd);
+  if (!NT_SUCCESS(err))
+    return ntstatus2errcode(err);
+
+  SIZE_T ViewSize =
+      (flags & MDBX_RDONLY) ? 0 : mdbx_RunningUnderWine() ? size : limit;
+  err = NtMapViewOfSection(
+      map->section, GetCurrentProcess(), &map->address,
+      /* ZeroBits */ 0,
+      /* CommitSize */ 0,
+      /* SectionOffset */ NULL, &ViewSize,
+      /* InheritDisposition */ ViewUnmap,
+      /* AllocationType */ (flags & MDBX_RDONLY) ? 0 : MEM_RESERVE,
+      /* Win32Protect */
+      (flags & MDBX_WRITEMAP) ? PAGE_READWRITE : PAGE_READONLY);
+  if (!NT_SUCCESS(err)) {
+    NtClose(map->section);
+    map->section = 0;
+    map->address = nullptr;
+    return ntstatus2errcode(err);
+  }
+  assert(map->address != MAP_FAILED);
+
+  map->current = (size_t)SectionSize.QuadPart;
+  map->limit = ViewSize;
+
+#else
+
+#ifndef MAP_TRYFIXED
+#define MAP_TRYFIXED 0
+#endif
+
+#ifndef MAP_HASSEMAPHORE
+#define MAP_HASSEMAPHORE 0
+#endif
+
+#ifndef MAP_CONCEAL
+#define MAP_CONCEAL 0
+#endif
+
+#ifndef MAP_NOSYNC
+#define MAP_NOSYNC 0
+#endif
+
+  map->address = mmap(
+      NULL, limit, (flags & MDBX_WRITEMAP) ? PROT_READ | PROT_WRITE : PROT_READ,
+      MAP_SHARED | MAP_FILE |
+          (F_ISSET(flags, MDBX_UTTERLY_NOSYNC) ? MAP_NOSYNC : 0) |
+          ((options & MMAP_OPTION_SEMAPHORE) ? MAP_HASSEMAPHORE | MAP_NOSYNC
+                                             : MAP_CONCEAL),
+      map->fd, 0);
+
+  if (unlikely(map->address == MAP_FAILED)) {
+    map->limit = 0;
+    map->current = 0;
+    map->address = nullptr;
+    return errno;
+  }
+  map->limit = limit;
+
+#ifdef MADV_DONTFORK
+  if (unlikely(madvise(map->address, map->limit, MADV_DONTFORK) != 0))
+    return errno;
+#endif
+#ifdef MADV_NOHUGEPAGE
+  (void)madvise(map->address, map->limit, MADV_NOHUGEPAGE);
+#endif
+
+#endif
+
+  VALGRIND_MAKE_MEM_DEFINED(map->address, map->current);
+  ASAN_UNPOISON_MEMORY_REGION(map->address, map->current);
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map) {
+  VALGRIND_MAKE_MEM_NOACCESS(map->address, map->current);
+  /* Unpoisoning is required for ASAN to avoid false-positive diagnostic
+   * when this memory will re-used by malloc or another mmapping.
+   * See https://github.com/erthink/libmdbx/pull/93#issuecomment-613687203 */
+  ASAN_UNPOISON_MEMORY_REGION(map->address, map->limit);
+#if defined(_WIN32) || defined(_WIN64)
+  if (map->section)
+    NtClose(map->section);
+  NTSTATUS rc = NtUnmapViewOfSection(GetCurrentProcess(), map->address);
+  if (!NT_SUCCESS(rc))
+    ntstatus2errcode(rc);
+#else
+  if (unlikely(munmap(map->address, map->limit)))
+    return errno;
+#endif
+
+  map->limit = 0;
+  map->current = 0;
+  map->address = nullptr;
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t size,
+                                    size_t limit, const bool may_move) {
+  assert(size <= limit);
+#if defined(_WIN32) || defined(_WIN64)
+  assert(size != map->current || limit != map->limit || size < map->filesize);
+
+  NTSTATUS status;
+  LARGE_INTEGER SectionSize;
+  int err, rc = MDBX_SUCCESS;
+
+  if (!(flags & MDBX_RDONLY) && limit == map->limit && size > map->current &&
+      /* workaround for Wine */ mdbx_NtExtendSection) {
+    /* growth rw-section */
+    SectionSize.QuadPart = size;
+    status = mdbx_NtExtendSection(map->section, &SectionSize);
+    if (!NT_SUCCESS(status))
+      return ntstatus2errcode(status);
+    map->current = size;
+    if (map->filesize < size)
+      map->filesize = size;
+    return MDBX_SUCCESS;
+  }
+
+  if (limit > map->limit) {
+    /* check ability of address space for growth before unmap */
+    PVOID BaseAddress = (PBYTE)map->address + map->limit;
+    SIZE_T RegionSize = limit - map->limit;
+    status = NtAllocateVirtualMemory(GetCurrentProcess(), &BaseAddress, 0,
+                                     &RegionSize, MEM_RESERVE, PAGE_NOACCESS);
+    if (status == /* STATUS_CONFLICTING_ADDRESSES */ 0xC0000018)
+      return MDBX_UNABLE_EXTEND_MAPSIZE;
+    if (!NT_SUCCESS(status))
+      return ntstatus2errcode(status);
+
+    status = NtFreeVirtualMemory(GetCurrentProcess(), &BaseAddress, &RegionSize,
+                                 MEM_RELEASE);
+    if (!NT_SUCCESS(status))
+      return ntstatus2errcode(status);
+  }
+
+  /* Windows unable:
+   *  - shrink a mapped file;
+   *  - change size of mapped view;
+   *  - extend read-only mapping;
+   * Therefore we should unmap/map entire section. */
+  status = NtUnmapViewOfSection(GetCurrentProcess(), map->address);
+  if (!NT_SUCCESS(status))
+    return ntstatus2errcode(status);
+  status = NtClose(map->section);
+  map->section = NULL;
+  PVOID ReservedAddress = NULL;
+  SIZE_T ReservedSize = limit;
+
+  if (!NT_SUCCESS(status)) {
+  bailout_ntstatus:
+    err = ntstatus2errcode(status);
+  bailout:
+    map->address = NULL;
+    map->current = map->limit = 0;
+    if (ReservedAddress) {
+      ReservedSize = 0;
+      status = NtFreeVirtualMemory(GetCurrentProcess(), &ReservedAddress,
+                                   &ReservedSize, MEM_RELEASE);
+      assert(NT_SUCCESS(status));
+      (void)status;
+    }
+    return err;
+  }
+
+retry_file_and_section:
+  /* resizing of the file may take a while,
+   * therefore we reserve address space to avoid occupy it by other threads */
+  ReservedAddress = map->address;
+  status = NtAllocateVirtualMemory(GetCurrentProcess(), &ReservedAddress, 0,
+                                   &ReservedSize, MEM_RESERVE, PAGE_NOACCESS);
+  if (!NT_SUCCESS(status)) {
+    ReservedAddress = NULL;
+    if (status != /* STATUS_CONFLICTING_ADDRESSES */ 0xC0000018)
+      goto bailout_ntstatus /* no way to recovery */;
+
+    if (may_move)
+      /* the base address could be changed */
+      map->address = NULL;
+  }
+
+  err = mdbx_filesize(map->fd, &map->filesize);
+  if (err != MDBX_SUCCESS)
+    goto bailout;
+
+  if ((flags & MDBX_RDONLY) == 0 && map->filesize != size) {
+    err = mdbx_ftruncate(map->fd, size);
+    if (err == MDBX_SUCCESS)
+      map->filesize = size;
+    /* ignore error, because Windows unable shrink file
+     * that already mapped (by another process) */
+  }
+
+  SectionSize.QuadPart = size;
+  status = NtCreateSection(
+      &map->section,
+      /* DesiredAccess */
+      (flags & MDBX_WRITEMAP)
+          ? SECTION_QUERY | SECTION_MAP_READ | SECTION_EXTEND_SIZE |
+                SECTION_MAP_WRITE
+          : SECTION_QUERY | SECTION_MAP_READ | SECTION_EXTEND_SIZE,
+      /* ObjectAttributes */ NULL,
+      /* MaximumSize (InitialSize) */ &SectionSize,
+      /* SectionPageProtection */
+      (flags & MDBX_RDONLY) ? PAGE_READONLY : PAGE_READWRITE,
+      /* AllocationAttributes */ SEC_RESERVE, map->fd);
+
+  if (!NT_SUCCESS(status))
+    goto bailout_ntstatus;
+
+  if (ReservedAddress) {
+    /* release reserved address space */
+    ReservedSize = 0;
+    status = NtFreeVirtualMemory(GetCurrentProcess(), &ReservedAddress,
+                                 &ReservedSize, MEM_RELEASE);
+    ReservedAddress = NULL;
+    if (!NT_SUCCESS(status))
+      goto bailout_ntstatus;
+  }
+
+retry_mapview:;
+  SIZE_T ViewSize = (flags & MDBX_RDONLY) ? size : limit;
+  status = NtMapViewOfSection(
+      map->section, GetCurrentProcess(), &map->address,
+      /* ZeroBits */ 0,
+      /* CommitSize */ 0,
+      /* SectionOffset */ NULL, &ViewSize,
+      /* InheritDisposition */ ViewUnmap,
+      /* AllocationType */ (flags & MDBX_RDONLY) ? 0 : MEM_RESERVE,
+      /* Win32Protect */
+      (flags & MDBX_WRITEMAP) ? PAGE_READWRITE : PAGE_READONLY);
+
+  if (!NT_SUCCESS(status)) {
+    if (status == /* STATUS_CONFLICTING_ADDRESSES */ 0xC0000018 &&
+        map->address && may_move) {
+      /* try remap at another base address */
+      map->address = NULL;
+      goto retry_mapview;
+    }
+    NtClose(map->section);
+    map->section = NULL;
+
+    if (map->address && (size != map->current || limit != map->limit)) {
+      /* try remap with previously size and limit,
+       * but will return MDBX_UNABLE_EXTEND_MAPSIZE on success */
+      rc = MDBX_UNABLE_EXTEND_MAPSIZE;
+      size = map->current;
+      ReservedSize = limit = map->limit;
+      goto retry_file_and_section;
+    }
+
+    /* no way to recovery */
+    goto bailout_ntstatus;
+  }
+  assert(map->address != MAP_FAILED);
+
+  map->current = (size_t)SectionSize.QuadPart;
+  map->limit = ViewSize;
+
+#else
+
+  uint64_t filesize = 0;
+  int rc = mdbx_filesize(map->fd, &filesize);
+  if (rc != MDBX_SUCCESS)
+    return rc;
+
+  if (flags & MDBX_RDONLY) {
+    map->current = (filesize > limit) ? limit : (size_t)filesize;
+    if (map->current != size)
+      rc = MDBX_UNABLE_EXTEND_MAPSIZE;
+  } else if (filesize != size) {
+    rc = mdbx_ftruncate(map->fd, size);
+    if (rc != MDBX_SUCCESS)
+      return rc;
+    map->current = size;
+  }
+
+  if (limit == map->limit)
+    return MDBX_SUCCESS;
+
+  if (limit < map->limit) {
+    /* unmap an excess at end of mapping. */
+    if (unlikely(munmap(map->dxb + limit, map->limit - limit)))
+      return errno;
+    map->limit = limit;
+    return MDBX_SUCCESS;
+  }
+
+  assert(limit > map->limit);
+  uint8_t *ptr = MAP_FAILED;
+
+#if defined(MREMAP_MAYMOVE)
+  ptr = mremap(map->address, map->limit, limit, may_move ? MREMAP_MAYMOVE : 0);
+  if (ptr == MAP_FAILED) {
+    const int err = errno;
+    switch (err) {
+    default:
+      return err;
+    case EAGAIN:
+    case ENOMEM:
+      return MDBX_UNABLE_EXTEND_MAPSIZE;
+    case EFAULT /* MADV_DODUMP / MADV_DONTDUMP are mixed for mmap-range */:
+      break;
+    }
+  }
+#endif /* MREMAP_MAYMOVE */
+
+  const unsigned mmap_flags =
+      MAP_CONCEAL | MAP_SHARED | MAP_FILE |
+      (F_ISSET(flags, MDBX_UTTERLY_NOSYNC) ? MAP_NOSYNC : 0);
+  const unsigned mmap_prot =
+      (flags & MDBX_WRITEMAP) ? PROT_READ | PROT_WRITE : PROT_READ;
+
+  if (ptr == MAP_FAILED) {
+    /* Try to mmap additional space beyond the end of mapping. */
+    ptr = mmap(map->dxb + map->limit, limit - map->limit, mmap_prot,
+               mmap_flags
+#if defined(MAP_FIXED_NOREPLACE)
+                   | MAP_FIXED_NOREPLACE
+#endif /* MAP_FIXED_NOREPLACE */
+               ,
+               map->fd, map->limit);
+    if (ptr == map->dxb + map->limit)
+      ptr = map->dxb;
+    else if (ptr != MAP_FAILED) {
+      /* the desired address is busy, unmap unsuitable one */
+      if (unlikely(munmap(ptr, limit - map->limit)))
+        return errno;
+      ptr = MAP_FAILED;
+    } else {
+      const int err = errno;
+      switch (err) {
+      default:
+        return err;
+      case EAGAIN:
+      case ENOMEM:
+        return MDBX_UNABLE_EXTEND_MAPSIZE;
+      case EEXIST: /* address busy */
+      case EINVAL: /* kernel don't support MAP_FIXED_NOREPLACE */
+        break;
+      }
+    }
+  }
+
+  if (ptr == MAP_FAILED) {
+    /* unmap and map again whole region */
+    if (!may_move) {
+      /* TODO: Perhaps here it is worth to implement suspend/resume threads
+       * and perform unmap/map as like for Windows. */
+      return MDBX_UNABLE_EXTEND_MAPSIZE;
+    }
+
+    if (unlikely(munmap(map->address, map->limit)))
+      return errno;
+
+    ptr = mmap(map->address, limit, mmap_prot, mmap_flags, map->fd, 0);
+    if (unlikely(ptr == MAP_FAILED)) {
+      ptr = mmap(map->address, map->limit, mmap_prot, mmap_flags, map->fd, 0);
+      if (unlikely(ptr == MAP_FAILED)) {
+        VALGRIND_MAKE_MEM_NOACCESS(map->address, map->current);
+        /* Unpoisoning is required for ASAN to avoid false-positive diagnostic
+         * when this memory will re-used by malloc or another mmapping.
+         * See https://github.com/erthink/libmdbx/pull/93#issuecomment-613687203
+         */
+        ASAN_UNPOISON_MEMORY_REGION(map->address, map->limit);
+        map->limit = 0;
+        map->current = 0;
+        map->address = nullptr;
+        return errno;
+      }
+      rc = MDBX_UNABLE_EXTEND_MAPSIZE;
+      limit = map->limit;
+    }
+  }
+
+  assert(ptr && ptr != MAP_FAILED);
+  if (map->address != ptr) {
+    VALGRIND_MAKE_MEM_NOACCESS(map->address, map->current);
+    /* Unpoisoning is required for ASAN to avoid false-positive diagnostic
+     * when this memory will re-used by malloc or another mmapping.
+     * See https://github.com/erthink/libmdbx/pull/93#issuecomment-613687203
+     */
+    ASAN_UNPOISON_MEMORY_REGION(map->address, map->limit);
+
+    VALGRIND_MAKE_MEM_DEFINED(ptr, map->current);
+    ASAN_UNPOISON_MEMORY_REGION(ptr, map->current);
+    map->address = ptr;
+  }
+  map->limit = limit;
+
+#ifdef MADV_DONTFORK
+  if (unlikely(madvise(map->address, map->limit, MADV_DONTFORK) != 0))
+    return errno;
+#endif /* MADV_DONTFORK */
+
+#ifdef MADV_NOHUGEPAGE
+  (void)madvise(map->address, map->limit, MADV_NOHUGEPAGE);
+#endif /* MADV_NOHUGEPAGE */
+
+#endif /* POSIX / Windows */
+
+  return rc;
+}
+
+/*----------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC __cold void mdbx_osal_jitter(bool tiny) {
+  for (;;) {
+#if defined(_M_IX86) || defined(_M_X64) || defined(__i386__) ||                \
+    defined(__x86_64__)
+    const unsigned salt = 277u * (unsigned)__rdtsc();
+#else
+    const unsigned salt = rand();
+#endif
+
+    const unsigned coin = salt % (tiny ? 29u : 43u);
+    if (coin < 43 / 3)
+      break;
+#if defined(_WIN32) || defined(_WIN64)
+    SwitchToThread();
+    if (coin > 43 * 2 / 3)
+      Sleep(1);
+#else
+    sched_yield();
+    if (coin > 43 * 2 / 3)
+      usleep(coin);
+#endif
+  }
+}
+
+#if defined(_WIN32) || defined(_WIN64)
+#elif defined(__APPLE__) || defined(__MACH__)
+#include <mach/mach_time.h>
+#elif defined(__linux__) || defined(__gnu_linux__)
+static __cold clockid_t choice_monoclock(void) {
+  struct timespec probe;
+#if defined(CLOCK_BOOTTIME)
+  if (clock_gettime(CLOCK_BOOTTIME, &probe) == 0)
+    return CLOCK_BOOTTIME;
+#elif defined(CLOCK_MONOTONIC_RAW)
+  if (clock_gettime(CLOCK_MONOTONIC_RAW, &probe) == 0)
+    return CLOCK_MONOTONIC_RAW;
+#elif defined(CLOCK_MONOTONIC_COARSE)
+  if (clock_gettime(CLOCK_MONOTONIC_COARSE, &probe) == 0)
+    return CLOCK_MONOTONIC_COARSE;
+#endif
+  return CLOCK_MONOTONIC;
+}
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_WIN32) || defined(_WIN64)
+static LARGE_INTEGER performance_frequency;
+#elif defined(__APPLE__) || defined(__MACH__)
+static uint64_t ratio_16dot16_to_monotine;
+#endif
+
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16) {
+#if defined(_WIN32) || defined(_WIN64)
+  if (unlikely(performance_frequency.QuadPart == 0))
+    QueryPerformanceFrequency(&performance_frequency);
+  const uint64_t ratio = performance_frequency.QuadPart;
+#elif defined(__APPLE__) || defined(__MACH__)
+  if (unlikely(ratio_16dot16_to_monotine == 0)) {
+    mach_timebase_info_data_t ti;
+    mach_timebase_info(&ti);
+    ratio_16dot16_to_monotine = UINT64_C(1000000000) * ti.denom / ti.numer;
+  }
+  const uint64_t ratio = ratio_16dot16_to_monotine;
+#else
+  const uint64_t ratio = UINT64_C(1000000000);
+#endif
+  return (ratio * seconds_16dot16 + 32768) >> 16;
+}
+
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime) {
+  static uint64_t limit;
+  if (unlikely(monotime > limit)) {
+    if (limit != 0)
+      return UINT32_MAX;
+    limit = mdbx_osal_16dot16_to_monotime(UINT32_MAX - 1);
+    if (monotime > limit)
+      return UINT32_MAX;
+  }
+#if defined(_WIN32) || defined(_WIN64)
+  return (uint32_t)((monotime << 16) / performance_frequency.QuadPart);
+#elif defined(__APPLE__) || defined(__MACH__)
+  return (uint32_t)((monotime << 16) / ratio_16dot16_to_monotine);
+#else
+  return (uint32_t)(monotime * 128 / 1953125);
+#endif
+}
+
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  LARGE_INTEGER counter;
+  counter.QuadPart = 0;
+  QueryPerformanceCounter(&counter);
+  return counter.QuadPart;
+#elif defined(__APPLE__) || defined(__MACH__)
+  return mach_absolute_time();
+#else
+
+#if defined(__linux__) || defined(__gnu_linux__)
+  static clockid_t posix_clockid = -1;
+  if (unlikely(posix_clockid < 0))
+    posix_clockid = choice_monoclock();
+#elif defined(CLOCK_MONOTONIC)
+#define posix_clockid CLOCK_MONOTONIC
+#else
+#define posix_clockid CLOCK_REALTIME
+#endif
+
+  struct timespec ts;
+  if (unlikely(clock_gettime(posix_clockid, &ts) != 0)) {
+    ts.tv_nsec = 0;
+    ts.tv_sec = 0;
+  }
+  return ts.tv_sec * UINT64_C(1000000000) + ts.tv_nsec;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+
+static void bootid_shake(bin128_t *p) {
+  /* Bob Jenkins's PRNG: https://burtleburtle.net/bob/rand/smallprng.html */
+  const uint32_t e = p->a - (p->b << 23 | p->b >> 9);
+  p->a = p->b ^ (p->c << 16 | p->c >> 16);
+  p->b = p->c + (p->d << 11 | p->d >> 21);
+  p->c = p->d + e;
+  p->d = e + p->a;
+}
+
+static void bootid_collect(bin128_t *p, const void *s, size_t n) {
+  p->y += UINT64_C(64526882297375213);
+  bootid_shake(p);
+  for (size_t i = 0; i < n; ++i) {
+    bootid_shake(p);
+    p->y ^= UINT64_C(48797879452804441) * ((const uint8_t *)s)[i];
+    bootid_shake(p);
+    p->y += 14621231;
+  }
+  bootid_shake(p);
+
+  /* minor non-linear tomfoolery */
+  const unsigned z = p->x % 61;
+  p->y = p->y << z | p->y >> (64 - z);
+  bootid_shake(p);
+  bootid_shake(p);
+  const unsigned q = p->x % 59;
+  p->y = p->y << q | p->y >> (64 - q);
+  bootid_shake(p);
+  bootid_shake(p);
+  bootid_shake(p);
+}
+
+#if defined(_WIN32) || defined(_WIN64)
+
+static uint64_t windows_systemtime_ms() {
+  FILETIME ft;
+  GetSystemTimeAsFileTime(&ft);
+  return ((uint64_t)ft.dwHighDateTime << 32 | ft.dwLowDateTime) / 10000ul;
+}
+
+static uint64_t windows_bootime(void) {
+  unsigned confirmed = 0;
+  uint64_t boottime = 0;
+  uint64_t up0 = mdbx_GetTickCount64();
+  uint64_t st0 = windows_systemtime_ms();
+  for (uint64_t fuse = st0; up0 && st0 < fuse + 1000 * 1000u / 42;) {
+    YieldProcessor();
+    const uint64_t up1 = mdbx_GetTickCount64();
+    const uint64_t st1 = windows_systemtime_ms();
+    if (st1 > fuse && st1 == st0 && up1 == up0) {
+      uint64_t diff = st1 - up1;
+      if (boottime == diff) {
+        if (++confirmed > 4)
+          return boottime;
+      } else {
+        confirmed = 0;
+        boottime = diff;
+      }
+      fuse = st1;
+      Sleep(1);
+    }
+    st0 = st1;
+    up0 = up1;
+  }
+  return 0;
+}
+
+static LSTATUS mdbx_RegGetValue(HKEY hKey, LPCSTR lpSubKey, LPCSTR lpValue,
+                                PVOID pvData, LPDWORD pcbData) {
+  LSTATUS rc;
+  if (!mdbx_RegGetValueA) {
+    /* an old Windows 2000/XP */
+    HKEY hSubKey;
+    rc = RegOpenKeyA(hKey, lpSubKey, &hSubKey);
+    if (rc == ERROR_SUCCESS) {
+      rc = RegQueryValueExA(hSubKey, lpValue, NULL, NULL, pvData, pcbData);
+      RegCloseKey(hSubKey);
+    }
+    return rc;
+  }
+
+  rc = mdbx_RegGetValueA(hKey, lpSubKey, lpValue, RRF_RT_ANY, NULL, pvData,
+                         pcbData);
+  if (rc != ERROR_FILE_NOT_FOUND)
+    return rc;
+
+  rc = mdbx_RegGetValueA(hKey, lpSubKey, lpValue,
+                         RRF_RT_ANY | 0x00010000 /* RRF_SUBKEY_WOW6464KEY */,
+                         NULL, pvData, pcbData);
+  if (rc != ERROR_FILE_NOT_FOUND)
+    return rc;
+  return mdbx_RegGetValueA(hKey, lpSubKey, lpValue,
+                           RRF_RT_ANY | 0x00020000 /* RRF_SUBKEY_WOW6432KEY */,
+                           NULL, pvData, pcbData);
+}
+#endif
+
+static __cold __maybe_unused bool bootid_parse_uuid(bin128_t *s, const void *p,
+                                                    const size_t n) {
+  if (n > 31) {
+    unsigned bits = 0;
+    for (unsigned i = 0; i < n; ++i) /* try parse an UUID in text form */ {
+      uint8_t c = ((const uint8_t *)p)[i];
+      if (c >= '0' && c <= '9')
+        c -= '0';
+      else if (c >= 'a' && c <= 'f')
+        c -= 'a' - 10;
+      else if (c >= 'A' && c <= 'F')
+        c -= 'A' - 10;
+      else
+        continue;
+      assert(c <= 15);
+      c ^= s->y >> 60;
+      s->y = s->y << 4 | s->x >> 60;
+      s->x = s->x << 4 | c;
+      bits += 4;
+    }
+    if (bits > 42 * 3)
+      /* UUID parsed successfully */
+      return true;
+  }
+
+  if (n > 15) /* is enough handle it as a binary? */ {
+    if (n == sizeof(bin128_t)) {
+      bin128_t aligned;
+      memcpy(&aligned, p, sizeof(bin128_t));
+      s->x += aligned.x;
+      s->y += aligned.y;
+    } else
+      bootid_collect(s, p, n);
+    return true;
+  }
+
+  if (n)
+    bootid_collect(s, p, n);
+  return false;
+}
+
+__cold MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void) {
+  bin128_t bin = {{0, 0}};
+  bool got_machineid = false, got_boottime = false, got_bootseq = false;
+
+#if defined(__linux__) || defined(__gnu_linux__)
+  {
+    const int fd =
+        open("/proc/sys/kernel/random/boot_id", O_RDONLY | O_NOFOLLOW);
+    if (fd != -1) {
+      struct statfs fs;
+      char buf[42];
+      const ssize_t len =
+          (fstatfs(fd, &fs) == 0 && fs.f_type == /* procfs */ 0x9FA0)
+              ? read(fd, buf, sizeof(buf))
+              : -1;
+      const int err = close(fd);
+      assert(err == 0);
+      (void)err;
+      if (len > 0 && bootid_parse_uuid(&bin, buf, len))
+        return bin;
+    }
+  }
+#endif /* Linux */
+
+#if defined(__APPLE__) || defined(__MACH__)
+  {
+    char buf[42];
+    size_t len = sizeof(buf);
+    if (!sysctlbyname("kern.bootsessionuuid", buf, &len, nullptr, 0) &&
+        bootid_parse_uuid(&bin, buf, len))
+      return bin;
+
+#if defined(__MAC_OS_X_VERSION_MIN_REQUIRED) &&                                \
+    __MAC_OS_X_VERSION_MIN_REQUIRED > 1050
+    uuid_t uuid;
+    struct timespec wait = {0, 1000000000u / 42};
+    if (!gethostuuid(uuid, &wait) &&
+        bootid_parse_uuid(&bin, uuid, sizeof(uuid)))
+      got_machineid = true;
+#endif /* > 10.5 */
+
+    struct timeval boottime;
+    len = sizeof(boottime);
+    if (!sysctlbyname("kern.boottime", &boottime, &len, nullptr, 0) &&
+        len == sizeof(boottime) && boottime.tv_sec)
+      got_boottime = true;
+  }
+#endif /* Apple/Darwin */
+
+#if defined(_WIN32) || defined(_WIN64)
+  {
+    union buf {
+      DWORD BootId;
+      DWORD BaseTime;
+      SYSTEM_TIMEOFDAY_INFORMATION SysTimeOfDayInfo;
+      struct {
+        LARGE_INTEGER BootTime;
+        LARGE_INTEGER CurrentTime;
+        LARGE_INTEGER TimeZoneBias;
+        ULONG TimeZoneId;
+        ULONG Reserved;
+        ULONGLONG BootTimeBias;
+        ULONGLONG SleepTimeBias;
+      } SysTimeOfDayInfoHacked;
+      wchar_t MachineGuid[42];
+      char DigitalProductId[248];
+    } buf;
+
+    static const char HKLM_MicrosoftCryptography[] =
+        "SOFTWARE\\Microsoft\\Cryptography";
+    DWORD len = sizeof(buf);
+    /* Windows is madness and must die */
+    if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_MicrosoftCryptography,
+                         "MachineGuid", &buf.MachineGuid,
+                         &len) == ERROR_SUCCESS &&
+        len > 42 && len < sizeof(buf))
+      got_machineid = bootid_parse_uuid(&bin, &buf.MachineGuid, len);
+
+    if (!got_machineid) {
+      /* again, Windows is madness */
+      static const char HKLM_WindowsNT[] =
+          "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
+      static const char HKLM_WindowsNT_DPK[] =
+          "SOFTWARE\\Microsoft\\Windows "
+          "NT\\CurrentVersion\\DefaultProductKey";
+      static const char HKLM_WindowsNT_DPK2[] =
+          "SOFTWARE\\Microsoft\\Windows "
+          "NT\\CurrentVersion\\DefaultProductKey2";
+
+      len = sizeof(buf);
+      if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_WindowsNT,
+                           "DigitalProductId", &buf.DigitalProductId,
+                           &len) == ERROR_SUCCESS &&
+          len > 42 && len < sizeof(buf)) {
+        bootid_collect(&bin, &buf.DigitalProductId, len);
+        got_machineid = true;
+      }
+      len = sizeof(buf);
+      if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_WindowsNT_DPK,
+                           "DigitalProductId", &buf.DigitalProductId,
+                           &len) == ERROR_SUCCESS &&
+          len > 42 && len < sizeof(buf)) {
+        bootid_collect(&bin, &buf.DigitalProductId, len);
+        got_machineid = true;
+      }
+      len = sizeof(buf);
+      if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_WindowsNT_DPK2,
+                           "DigitalProductId", &buf.DigitalProductId,
+                           &len) == ERROR_SUCCESS &&
+          len > 42 && len < sizeof(buf)) {
+        bootid_collect(&bin, &buf.DigitalProductId, len);
+        got_machineid = true;
+      }
+    }
+
+    static const char HKLM_PrefetcherParams[] =
+        "SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Memory "
+        "Management\\PrefetchParameters";
+    len = sizeof(buf);
+    if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_PrefetcherParams, "BootId",
+                         &buf.BootId, &len) == ERROR_SUCCESS &&
+        len > 1 && len < sizeof(buf)) {
+      bootid_collect(&bin, &buf.BootId, len);
+      got_bootseq = true;
+    }
+
+    len = sizeof(buf);
+    if (mdbx_RegGetValue(HKEY_LOCAL_MACHINE, HKLM_PrefetcherParams, "BaseTime",
+                         &buf.BaseTime, &len) == ERROR_SUCCESS &&
+        len >= sizeof(buf.BaseTime) && buf.BaseTime) {
+      bootid_collect(&bin, &buf.BaseTime, len);
+      got_boottime = true;
+    }
+
+    /* BootTime from SYSTEM_TIMEOFDAY_INFORMATION */
+    NTSTATUS status = NtQuerySystemInformation(
+        0x03 /* SystemTmeOfDayInformation */, &buf.SysTimeOfDayInfo,
+        sizeof(buf.SysTimeOfDayInfo), &len);
+    if (NT_SUCCESS(status) &&
+        len >= offsetof(union buf, SysTimeOfDayInfoHacked.BootTime) +
+                   sizeof(buf.SysTimeOfDayInfoHacked.BootTime) &&
+        buf.SysTimeOfDayInfoHacked.BootTime.QuadPart) {
+      bootid_collect(&bin, &buf.SysTimeOfDayInfoHacked.BootTime,
+                     sizeof(buf.SysTimeOfDayInfoHacked.BootTime));
+      got_boottime = true;
+    }
+
+    if (!got_boottime) {
+      uint64_t boottime = windows_bootime();
+      if (boottime) {
+        bootid_collect(&bin, &boottime, sizeof(boottime));
+        got_boottime = true;
+      }
+    }
+  }
+#endif /* Windows */
+
+#if defined(CTL_HW) && defined(HW_UUID)
+  if (!got_machineid) {
+    static const int mib[] = {CTL_HW, HW_UUID};
+    char buf[42];
+    size_t len = sizeof(buf);
+    if (sysctl(
+#ifdef SYSCTL_LEGACY_NONCONST_MIB
+            (int *)
+#endif
+                mib,
+            ARRAY_LENGTH(mib), &buf, &len, NULL, 0) == 0)
+      got_machineid = bootid_parse_uuid(&bin, buf, len);
+  }
+#endif /* CTL_HW && HW_UUID */
+
+#if defined(CTL_KERN) && defined(KERN_HOSTUUID)
+  if (!got_machineid) {
+    static const int mib[] = {CTL_KERN, KERN_HOSTUUID};
+    char buf[42];
+    size_t len = sizeof(buf);
+    if (sysctl(
+#ifdef SYSCTL_LEGACY_NONCONST_MIB
+            (int *)
+#endif
+                mib,
+            ARRAY_LENGTH(mib), &buf, &len, NULL, 0) == 0)
+      got_machineid = bootid_parse_uuid(&bin, buf, len);
+  }
+#endif /* CTL_KERN && KERN_HOSTUUID */
+
+#if defined(__NetBSD__)
+  if (!got_machineid) {
+    char buf[42];
+    size_t len = sizeof(buf);
+    if (sysctlbyname("machdep.dmi.system-uuid", buf, &len, NULL, 0) == 0)
+      got_machineid = bootid_parse_uuid(&bin, buf, len);
+  }
+#endif /* __NetBSD__ */
+
+#if _XOPEN_SOURCE_EXTENDED
+  if (!got_machineid) {
+    const int hostid = gethostid();
+    if (hostid > 0) {
+      bootid_collect(&bin, &hostid, sizeof(hostid));
+      got_machineid = true;
+    }
+  }
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+  if (!got_machineid) {
+  lack:
+    bin.x = bin.y = 0;
+    return bin;
+  }
+
+  /*--------------------------------------------------------------------------*/
+
+#if defined(CTL_KERN) && defined(KERN_BOOTTIME)
+  if (!got_boottime) {
+    static const int mib[] = {CTL_KERN, KERN_BOOTTIME};
+    struct timeval boottime;
+    size_t len = sizeof(boottime);
+    if (sysctl(
+#ifdef SYSCTL_LEGACY_NONCONST_MIB
+            (int *)
+#endif
+                mib,
+            ARRAY_LENGTH(mib), &boottime, &len, NULL, 0) == 0 &&
+        len == sizeof(boottime) && boottime.tv_sec) {
+      bootid_collect(&bin, &boottime, len);
+      got_boottime = true;
+    }
+  }
+#endif /* CTL_KERN && KERN_BOOTTIME */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+  if (!got_boottime) {
+    kstat_ctl_t *kc = kstat_open();
+    if (kc) {
+      kstat_t *kp = kstat_lookup(kc, "unix", 0, "system_misc");
+      if (kp && kstat_read(kc, kp, 0) != -1) {
+        kstat_named_t *kn = (kstat_named_t *)kstat_data_lookup(kp, "boot_time");
+        if (kn) {
+          switch (kn->data_type) {
+          case KSTAT_DATA_INT32:
+          case KSTAT_DATA_UINT32:
+            bootid_collect(&bin, &kn->value, sizeof(int32_t));
+            got_boottime = true;
+          case KSTAT_DATA_INT64:
+          case KSTAT_DATA_UINT64:
+            bootid_collect(&bin, &kn->value, sizeof(int64_t));
+            got_boottime = true;
+          }
+        }
+      }
+      kstat_close(kc);
+    }
+  }
+#endif /* SunOS / Solaris */
+
+#if _XOPEN_SOURCE_EXTENDED && defined(BOOT_TIME)
+  if (!got_boottime) {
+    setutxent();
+    const struct utmpx id = {.ut_type = BOOT_TIME};
+    const struct utmpx *entry = getutxid(&id);
+    if (entry) {
+      bootid_collect(&bin, entry, sizeof(*entry));
+      got_boottime = true;
+      while (unlikely((entry = getutxid(&id)) != nullptr)) {
+        /* have multiple reboot records, assuming we can distinguish next
+         * bootsession even if RTC is wrong or absent */
+        bootid_collect(&bin, entry, sizeof(*entry));
+        got_bootseq = true;
+      }
+    }
+    endutxent();
+  }
+#endif /* _XOPEN_SOURCE_EXTENDED && BOOT_TIME */
+
+  if (!got_bootseq) {
+    if (!got_boottime || !MDBX_TRUST_RTC)
+      goto lack;
+
+#if defined(_WIN32) || defined(_WIN64)
+    FILETIME now;
+    GetSystemTimeAsFileTime(&now);
+    if (0x1CCCCCC > now.dwHighDateTime)
+#else
+    struct timespec mono, real;
+    if (clock_gettime(CLOCK_MONOTONIC, &mono) ||
+        clock_gettime(CLOCK_REALTIME, &real) ||
+        /* wrong time, RTC is mad or absent */
+        1555555555l > real.tv_sec ||
+        /* seems no adjustment by RTC/NTP, i.e. a fake time */
+        real.tv_sec < mono.tv_sec || 1234567890l > real.tv_sec - mono.tv_sec ||
+        (real.tv_sec - mono.tv_sec) % 900u == 0)
+#endif
+      goto lack;
+  }
+
+  return bin;
+}
+/* This is CMake-template for libmdbx's version.c
+ ******************************************************************************/
+
+
+#if MDBX_VERSION_MAJOR != 0 ||                             \
+    MDBX_VERSION_MINOR != 9
+#error "API version mismatch! Had `git fetch --tags` done?"
+#endif
+
+static const char sourcery[] = STRINGIFY(MDBX_BUILD_SOURCERY);
+
+__dll_export
+#ifdef __attribute_used__
+    __attribute_used__
+#elif defined(__GNUC__) || __has_attribute(__used__)
+    __attribute__((__used__))
+#endif
+#ifdef __attribute_externally_visible__
+        __attribute_externally_visible__
+#elif (defined(__GNUC__) && !defined(__clang__)) ||                            \
+    __has_attribute(__externally_visible__)
+    __attribute__((__externally_visible__))
+#endif
+    const struct MDBX_version_info mdbx_version = {
+        0,
+        9,
+        2,
+        136,
+        {"2021-01-30T02:28:12+03:00", "1ab2fa795a0dee8678b168ffcd961ca5a0fff7c5", "9f0ff865e860435b243d3d1e936e3067097a294f",
+         "v0.9.2-136-g9f0ff86"},
+        sourcery};
+
+__dll_export
+#ifdef __attribute_used__
+    __attribute_used__
+#elif defined(__GNUC__) || __has_attribute(__used__)
+    __attribute__((__used__))
+#endif
+#ifdef __attribute_externally_visible__
+        __attribute_externally_visible__
+#elif (defined(__GNUC__) && !defined(__clang__)) ||                            \
+    __has_attribute(__externally_visible__)
+    __attribute__((__externally_visible__))
+#endif
+    const char *const mdbx_sourcery_anchor = sourcery;
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+#if defined(_WIN32) || defined(_WIN64) /* Windows LCK-implementation */
+
+/* PREAMBLE FOR WINDOWS:
+ *
+ * We are not concerned for performance here.
+ * If you are running Windows a performance could NOT be the goal.
+ * Otherwise please use Linux. */
+
+
+static void mdbx_winnt_import(void);
+
+#if MDBX_BUILD_SHARED_LIBRARY
+#if MDBX_AVOID_CRT && defined(NDEBUG)
+/* DEBUG/CHECKED builds still require MSVC's CRT for runtime checks.
+ *
+ * Define dll's entry point only for Release build when NDEBUG is defined and
+ * MDBX_AVOID_CRT=ON. if the entry point isn't defined then MSVC's will
+ * automatically use DllMainCRTStartup() from CRT library, which also
+ * automatically call DllMain() from our mdbx.dll */
+#pragma comment(linker, "/ENTRY:DllMain")
+#endif /* MDBX_AVOID_CRT */
+
+BOOL APIENTRY DllMain(HANDLE module, DWORD reason, LPVOID reserved)
+#else
+#if !MDBX_CONFIG_MANUAL_TLS_CALLBACK
+static
+#endif /* !MDBX_CONFIG_MANUAL_TLS_CALLBACK */
+    void NTAPI
+    mdbx_dll_handler(PVOID module, DWORD reason, PVOID reserved)
+#endif /* MDBX_BUILD_SHARED_LIBRARY */
+{
+  (void)reserved;
+  switch (reason) {
+  case DLL_PROCESS_ATTACH:
+    mdbx_winnt_import();
+    mdbx_rthc_global_init();
+    break;
+  case DLL_PROCESS_DETACH:
+    mdbx_rthc_global_dtor();
+    break;
+
+  case DLL_THREAD_ATTACH:
+    break;
+  case DLL_THREAD_DETACH:
+    mdbx_rthc_thread_dtor(module);
+    break;
+  }
+#if MDBX_BUILD_SHARED_LIBRARY
+  return TRUE;
+#endif
+}
+
+#if !MDBX_BUILD_SHARED_LIBRARY && !MDBX_CONFIG_MANUAL_TLS_CALLBACK
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(_MSC_VER)
+#  pragma const_seg(push)
+#  pragma data_seg(push)
+
+#  ifdef _WIN64
+     /* kick a linker to create the TLS directory if not already done */
+#    pragma comment(linker, "/INCLUDE:_tls_used")
+     /* Force some symbol references. */
+#    pragma comment(linker, "/INCLUDE:mdbx_tls_anchor")
+     /* specific const-segment for WIN64 */
+#    pragma const_seg(".CRT$XLB")
+     const
+#  else
+     /* kick a linker to create the TLS directory if not already done */
+#    pragma comment(linker, "/INCLUDE:__tls_used")
+     /* Force some symbol references. */
+#    pragma comment(linker, "/INCLUDE:_mdbx_tls_anchor")
+     /* specific data-segment for WIN32 */
+#    pragma data_seg(".CRT$XLB")
+#  endif
+
+   __declspec(allocate(".CRT$XLB")) PIMAGE_TLS_CALLBACK mdbx_tls_anchor = mdbx_dll_handler;
+#  pragma data_seg(pop)
+#  pragma const_seg(pop)
+
+#elif defined(__GNUC__)
+#  ifdef _WIN64
+     const
+#  endif
+   PIMAGE_TLS_CALLBACK mdbx_tls_anchor __attribute__((__section__(".CRT$XLB"), used)) = mdbx_dll_handler;
+#else
+#  error FIXME
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+#endif /* !MDBX_BUILD_SHARED_LIBRARY && !MDBX_CONFIG_MANUAL_TLS_CALLBACK */
+
+/*----------------------------------------------------------------------------*/
+
+#define LCK_SHARED 0
+#define LCK_EXCLUSIVE LOCKFILE_EXCLUSIVE_LOCK
+#define LCK_WAITFOR 0
+#define LCK_DONTWAIT LOCKFILE_FAIL_IMMEDIATELY
+
+static __inline BOOL flock(mdbx_filehandle_t fd, DWORD flags, uint64_t offset,
+                           size_t bytes) {
+  OVERLAPPED ov;
+  ov.hEvent = 0;
+  ov.Offset = (DWORD)offset;
+  ov.OffsetHigh = HIGH_DWORD(offset);
+  return LockFileEx(fd, flags, 0, (DWORD)bytes, HIGH_DWORD(bytes), &ov);
+}
+
+static __inline BOOL funlock(mdbx_filehandle_t fd, uint64_t offset,
+                             size_t bytes) {
+  return UnlockFile(fd, (DWORD)offset, HIGH_DWORD(offset), (DWORD)bytes,
+                    HIGH_DWORD(bytes));
+}
+
+/*----------------------------------------------------------------------------*/
+/* global `write` lock for write-txt processing,
+ * exclusive locking both meta-pages) */
+
+#define LCK_MAXLEN (1u + (size_t)(MAXSSIZE_T))
+#define LCK_META_OFFSET 0
+#define LCK_META_LEN (MAX_PAGESIZE * NUM_METAS)
+#define LCK_BODY_OFFSET LCK_META_LEN
+#define LCK_BODY_LEN (LCK_MAXLEN - LCK_BODY_OFFSET)
+#define LCK_BODY LCK_BODY_OFFSET, LCK_BODY_LEN
+#define LCK_WHOLE 0, LCK_MAXLEN
+
+int mdbx_txn_lock(MDBX_env *env, bool dontwait) {
+  if (dontwait) {
+    if (!TryEnterCriticalSection(&env->me_windowsbug_lock))
+      return MDBX_BUSY;
+  } else {
+    __try {
+      EnterCriticalSection(&env->me_windowsbug_lock);
+    }
+    __except ((GetExceptionCode() ==
+                 0xC0000194 /* STATUS_POSSIBLE_DEADLOCK / EXCEPTION_POSSIBLE_DEADLOCK */)
+                    ? EXCEPTION_EXECUTE_HANDLER
+                    : EXCEPTION_CONTINUE_SEARCH) {
+      return ERROR_POSSIBLE_DEADLOCK;
+    }
+  }
+
+  if ((env->me_flags & MDBX_EXCLUSIVE) ||
+      flock(env->me_lazy_fd,
+            dontwait ? (LCK_EXCLUSIVE | LCK_DONTWAIT)
+                     : (LCK_EXCLUSIVE | LCK_WAITFOR),
+            LCK_BODY))
+    return MDBX_SUCCESS;
+  int rc = GetLastError();
+  LeaveCriticalSection(&env->me_windowsbug_lock);
+  return (!dontwait || rc != ERROR_LOCK_VIOLATION) ? rc : MDBX_BUSY;
+}
+
+void mdbx_txn_unlock(MDBX_env *env) {
+  int rc = (env->me_flags & MDBX_EXCLUSIVE)
+               ? TRUE
+               : funlock(env->me_lazy_fd, LCK_BODY);
+  LeaveCriticalSection(&env->me_windowsbug_lock);
+  if (!rc)
+    mdbx_panic("%s failed: err %u", __func__, GetLastError());
+}
+
+/*----------------------------------------------------------------------------*/
+/* global `read` lock for readers registration,
+ * exclusive locking `mti_numreaders` (second) cacheline */
+
+#define LCK_LO_OFFSET 0
+#define LCK_LO_LEN offsetof(MDBX_lockinfo, mti_numreaders)
+#define LCK_UP_OFFSET LCK_LO_LEN
+#define LCK_UP_LEN (sizeof(MDBX_lockinfo) - LCK_UP_OFFSET)
+#define LCK_LOWER LCK_LO_OFFSET, LCK_LO_LEN
+#define LCK_UPPER LCK_UP_OFFSET, LCK_UP_LEN
+
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env) {
+  mdbx_srwlock_AcquireShared(&env->me_remap_guard);
+  if (env->me_lfd == INVALID_HANDLE_VALUE)
+    return MDBX_SUCCESS; /* readonly database in readonly filesystem */
+
+  /* transition from S-? (used) to S-E (locked),
+   * e.g. exclusive lock upper-part */
+  if ((env->me_flags & MDBX_EXCLUSIVE) ||
+      flock(env->me_lfd, LCK_EXCLUSIVE | LCK_WAITFOR, LCK_UPPER))
+    return MDBX_SUCCESS;
+
+  int rc = GetLastError();
+  mdbx_srwlock_ReleaseShared(&env->me_remap_guard);
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env) {
+  if (env->me_lfd != INVALID_HANDLE_VALUE) {
+    /* transition from S-E (locked) to S-? (used), e.g. unlock upper-part */
+    if ((env->me_flags & MDBX_EXCLUSIVE) == 0 &&
+        !funlock(env->me_lfd, LCK_UPPER))
+      mdbx_panic("%s failed: err %u", __func__, GetLastError());
+  }
+  mdbx_srwlock_ReleaseShared(&env->me_remap_guard);
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait) {
+  return flock(fd,
+               wait ? LCK_EXCLUSIVE | LCK_WAITFOR
+                    : LCK_EXCLUSIVE | LCK_DONTWAIT,
+               0, LCK_MAXLEN)
+             ? MDBX_SUCCESS
+             : GetLastError();
+}
+
+static int suspend_and_append(mdbx_handle_array_t **array,
+                              const DWORD ThreadId) {
+  const unsigned limit = (*array)->limit;
+  if ((*array)->count == limit) {
+    void *ptr = mdbx_realloc(
+        (limit > ARRAY_LENGTH((*array)->handles))
+            ? *array
+            : /* don't free initial array on the stack */ NULL,
+        sizeof(mdbx_handle_array_t) +
+            sizeof(HANDLE) * (limit * 2 - ARRAY_LENGTH((*array)->handles)));
+    if (!ptr)
+      return MDBX_ENOMEM;
+    if (limit == ARRAY_LENGTH((*array)->handles))
+      memcpy(ptr, *array, sizeof(mdbx_handle_array_t));
+    *array = (mdbx_handle_array_t *)ptr;
+    (*array)->limit = limit * 2;
+  }
+
+  HANDLE hThread = OpenThread(THREAD_SUSPEND_RESUME | THREAD_QUERY_INFORMATION,
+                              FALSE, ThreadId);
+  if (hThread == NULL)
+    return GetLastError();
+
+  if (SuspendThread(hThread) == -1) {
+    int err = GetLastError();
+    DWORD ExitCode;
+    if (err == /* workaround for Win10 UCRT bug */ ERROR_ACCESS_DENIED ||
+        !GetExitCodeThread(hThread, &ExitCode) || ExitCode != STILL_ACTIVE)
+      err = MDBX_SUCCESS;
+    CloseHandle(hThread);
+    return err;
+  }
+
+  (*array)->handles[(*array)->count++] = hThread;
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array) {
+  const uintptr_t CurrentTid = GetCurrentThreadId();
+  int rc;
+  if (env->me_lck) {
+    /* Scan LCK for threads of the current process */
+    const MDBX_reader *const begin = env->me_lck->mti_readers;
+    const MDBX_reader *const end =
+        begin + atomic_load32(&env->me_lck->mti_numreaders, mo_AcquireRelease);
+    const uintptr_t WriteTxnOwner = env->me_txn0 ? env->me_txn0->mt_owner : 0;
+    for (const MDBX_reader *reader = begin; reader < end; ++reader) {
+      if (reader->mr_pid.weak != env->me_pid || !reader->mr_tid.weak) {
+      skip_lck:
+        continue;
+      }
+      if (reader->mr_tid.weak == CurrentTid ||
+          reader->mr_tid.weak == WriteTxnOwner)
+        goto skip_lck;
+      if (env->me_flags & MDBX_NOTLS) {
+        /* Skip duplicates in no-tls mode */
+        for (const MDBX_reader *scan = reader; --scan >= begin;)
+          if (scan->mr_tid.weak == reader->mr_tid.weak)
+            goto skip_lck;
+      }
+
+      rc = suspend_and_append(array, (mdbx_tid_t)reader->mr_tid.weak);
+      if (rc != MDBX_SUCCESS) {
+      bailout_lck:
+        (void)mdbx_resume_threads_after_remap(*array);
+        return rc;
+      }
+    }
+    if (WriteTxnOwner && WriteTxnOwner != CurrentTid) {
+      rc = suspend_and_append(array, (mdbx_tid_t)WriteTxnOwner);
+      if (rc != MDBX_SUCCESS)
+        goto bailout_lck;
+    }
+  } else {
+    /* Without LCK (i.e. read-only mode).
+     * Walk through a snapshot of all running threads */
+    mdbx_assert(env,
+                env->me_txn0 == NULL || (env->me_flags & MDBX_EXCLUSIVE) != 0);
+    const HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
+    if (hSnapshot == INVALID_HANDLE_VALUE)
+      return GetLastError();
+
+    THREADENTRY32 entry;
+    entry.dwSize = sizeof(THREADENTRY32);
+
+    if (!Thread32First(hSnapshot, &entry)) {
+      rc = GetLastError();
+    bailout_toolhelp:
+      CloseHandle(hSnapshot);
+      (void)mdbx_resume_threads_after_remap(*array);
+      return rc;
+    }
+
+    do {
+      if (entry.th32OwnerProcessID != env->me_pid ||
+          entry.th32ThreadID == CurrentTid)
+        continue;
+
+      rc = suspend_and_append(array, entry.th32ThreadID);
+      if (rc != MDBX_SUCCESS)
+        goto bailout_toolhelp;
+
+    } while (Thread32Next(hSnapshot, &entry));
+
+    rc = GetLastError();
+    if (rc != ERROR_NO_MORE_FILES)
+      goto bailout_toolhelp;
+    CloseHandle(hSnapshot);
+  }
+
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array) {
+  int rc = MDBX_SUCCESS;
+  for (unsigned i = 0; i < array->count; ++i) {
+    const HANDLE hThread = array->handles[i];
+    if (ResumeThread(hThread) == -1) {
+      const int err = GetLastError();
+      DWORD ExitCode;
+      if (err != /* workaround for Win10 UCRT bug */ ERROR_ACCESS_DENIED &&
+          GetExitCodeThread(hThread, &ExitCode) && ExitCode == STILL_ACTIVE)
+        rc = err;
+    }
+    CloseHandle(hThread);
+  }
+  return rc;
+}
+
+/*----------------------------------------------------------------------------*/
+/* global `initial` lock for lockfile initialization,
+ * exclusive/shared locking first cacheline */
+
+/* Briefly description of locking schema/algorithm:
+ *  - Windows does not support upgrading or downgrading for file locking.
+ *  - Therefore upgrading/downgrading is emulated by shared and exclusive
+ *    locking of upper and lower halves.
+ *  - In other words, we have FSM with possible 9 states,
+ *    i.e. free/shared/exclusive x free/shared/exclusive == 9.
+ *    Only 6 states of FSM are used, which 2 of ones are transitive.
+ *
+ * States:
+ *   ?-?  = free, i.e. unlocked
+ *   S-?  = used, i.e. shared lock
+ *   E-?  = exclusive-read, i.e. operational exclusive
+ *   ?-S
+ *   ?-E  = middle (transitive state)
+ *   S-S
+ *   S-E  = locked (transitive state)
+ *   E-S
+ *   E-E  = exclusive-write, i.e. exclusive due (re)initialization
+ *
+ *  The mdbx_lck_seize() moves the locking-FSM from the initial free/unlocked
+ *  state to the "exclusive write" (and returns MDBX_RESULT_TRUE) if possible,
+ *  or to the "used" (and returns MDBX_RESULT_FALSE).
+ *
+ *  The mdbx_lck_downgrade() moves the locking-FSM from "exclusive write"
+ *  state to the "used" (i.e. shared) state.
+ *
+ *  The mdbx_lck_upgrade() moves the locking-FSM from "used" (i.e. shared)
+ *  state to the "exclusive write" state.
+ */
+
+static void lck_unlock(MDBX_env *env) {
+  int err;
+
+  if (env->me_lfd != INVALID_HANDLE_VALUE) {
+    /* double `unlock` for robustly remove overlapped shared/exclusive locks */
+    while (funlock(env->me_lfd, LCK_LOWER))
+      ;
+    err = GetLastError();
+    assert(err == ERROR_NOT_LOCKED ||
+           (mdbx_RunningUnderWine() && err == ERROR_LOCK_VIOLATION));
+    (void)err;
+    SetLastError(ERROR_SUCCESS);
+
+    while (funlock(env->me_lfd, LCK_UPPER))
+      ;
+    err = GetLastError();
+    assert(err == ERROR_NOT_LOCKED ||
+           (mdbx_RunningUnderWine() && err == ERROR_LOCK_VIOLATION));
+    (void)err;
+    SetLastError(ERROR_SUCCESS);
+  }
+
+  if (env->me_lazy_fd != INVALID_HANDLE_VALUE) {
+    /* explicitly unlock to avoid latency for other processes (windows kernel
+     * releases such locks via deferred queues) */
+    while (funlock(env->me_lazy_fd, LCK_BODY))
+      ;
+    err = GetLastError();
+    assert(err == ERROR_NOT_LOCKED ||
+           (mdbx_RunningUnderWine() && err == ERROR_LOCK_VIOLATION));
+    (void)err;
+    SetLastError(ERROR_SUCCESS);
+
+    while (funlock(env->me_lazy_fd, LCK_WHOLE))
+      ;
+    err = GetLastError();
+    assert(err == ERROR_NOT_LOCKED ||
+           (mdbx_RunningUnderWine() && err == ERROR_LOCK_VIOLATION));
+    (void)err;
+    SetLastError(ERROR_SUCCESS);
+  }
+}
+
+/* Seize state as 'exclusive-write' (E-E and returns MDBX_RESULT_TRUE)
+ * or as 'used' (S-? and returns MDBX_RESULT_FALSE).
+ * Otherwise returns an error. */
+static int internal_seize_lck(HANDLE lfd) {
+  int rc;
+  assert(lfd != INVALID_HANDLE_VALUE);
+
+  /* 1) now on ?-? (free), get ?-E (middle) */
+  mdbx_jitter4testing(false);
+  if (!flock(lfd, LCK_EXCLUSIVE | LCK_WAITFOR, LCK_UPPER)) {
+    rc = GetLastError() /* 2) something went wrong, give up */;
+    mdbx_error("%s, err %u", "?-?(free) >> ?-E(middle)", rc);
+    return rc;
+  }
+
+  /* 3) now on ?-E (middle), try E-E (exclusive-write) */
+  mdbx_jitter4testing(false);
+  if (flock(lfd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_LOWER))
+    return MDBX_RESULT_TRUE /* 4) got E-E (exclusive-write), done */;
+
+  /* 5) still on ?-E (middle) */
+  rc = GetLastError();
+  mdbx_jitter4testing(false);
+  if (rc != ERROR_SHARING_VIOLATION && rc != ERROR_LOCK_VIOLATION) {
+    /* 6) something went wrong, give up */
+    if (!funlock(lfd, LCK_UPPER))
+      mdbx_panic("%s(%s) failed: err %u", __func__, "?-E(middle) >> ?-?(free)",
+                 GetLastError());
+    return rc;
+  }
+
+  /* 7) still on ?-E (middle), try S-E (locked) */
+  mdbx_jitter4testing(false);
+  rc = flock(lfd, LCK_SHARED | LCK_DONTWAIT, LCK_LOWER) ? MDBX_RESULT_FALSE
+                                                        : GetLastError();
+
+  mdbx_jitter4testing(false);
+  if (rc != MDBX_RESULT_FALSE)
+    mdbx_error("%s, err %u", "?-E(middle) >> S-E(locked)", rc);
+
+  /* 8) now on S-E (locked) or still on ?-E (middle),
+   *    transition to S-? (used) or ?-? (free) */
+  if (!funlock(lfd, LCK_UPPER))
+    mdbx_panic("%s(%s) failed: err %u", __func__,
+               "X-E(locked/middle) >> X-?(used/free)", GetLastError());
+
+  /* 9) now on S-? (used, DONE) or ?-? (free, FAILURE) */
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env) {
+  int rc;
+
+  assert(env->me_lazy_fd != INVALID_HANDLE_VALUE);
+  if (env->me_flags & MDBX_EXCLUSIVE)
+    return MDBX_RESULT_TRUE /* nope since files were must be opened
+                               non-shareable */
+        ;
+
+  if (env->me_lfd == INVALID_HANDLE_VALUE) {
+    /* LY: without-lck mode (e.g. on read-only filesystem) */
+    mdbx_jitter4testing(false);
+    if (!flock(env->me_lazy_fd, LCK_SHARED | LCK_DONTWAIT, LCK_WHOLE)) {
+      rc = GetLastError();
+      mdbx_error("%s, err %u", "without-lck", rc);
+      return rc;
+    }
+    return MDBX_RESULT_FALSE;
+  }
+
+  rc = internal_seize_lck(env->me_lfd);
+  mdbx_jitter4testing(false);
+  if (rc == MDBX_RESULT_TRUE && (env->me_flags & MDBX_RDONLY) == 0) {
+    /* Check that another process don't operates in without-lck mode.
+     * Doing such check by exclusive locking the body-part of db. Should be
+     * noted:
+     *  - we need an exclusive lock for do so;
+     *  - we can't lock meta-pages, otherwise other process could get an error
+     *    while opening db in valid (non-conflict) mode. */
+    if (!flock(env->me_lazy_fd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_BODY)) {
+      rc = GetLastError();
+      mdbx_error("%s, err %u", "lock-against-without-lck", rc);
+      mdbx_jitter4testing(false);
+      lck_unlock(env);
+    } else {
+      mdbx_jitter4testing(false);
+      if (!funlock(env->me_lazy_fd, LCK_BODY))
+        mdbx_panic("%s(%s) failed: err %u", __func__,
+                   "unlock-against-without-lck", GetLastError());
+    }
+  }
+
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env) {
+  /* Transite from exclusive-write state (E-E) to used (S-?) */
+  assert(env->me_lazy_fd != INVALID_HANDLE_VALUE);
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+
+  if (env->me_flags & MDBX_EXCLUSIVE)
+    return MDBX_SUCCESS /* nope since files were must be opened non-shareable */
+        ;
+  /* 1) now at E-E (exclusive-write), transition to ?_E (middle) */
+  if (!funlock(env->me_lfd, LCK_LOWER))
+    mdbx_panic("%s(%s) failed: err %u", __func__,
+               "E-E(exclusive-write) >> ?-E(middle)", GetLastError());
+
+  /* 2) now at ?-E (middle), transition to S-E (locked) */
+  if (!flock(env->me_lfd, LCK_SHARED | LCK_DONTWAIT, LCK_LOWER)) {
+    int rc = GetLastError() /* 3) something went wrong, give up */;
+    mdbx_error("%s, err %u", "?-E(middle) >> S-E(locked)", rc);
+    return rc;
+  }
+
+  /* 4) got S-E (locked), continue transition to S-? (used) */
+  if (!funlock(env->me_lfd, LCK_UPPER))
+    mdbx_panic("%s(%s) failed: err %u", __func__, "S-E(locked) >> S-?(used)",
+               GetLastError());
+
+  return MDBX_SUCCESS /* 5) now at S-? (used), done */;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_upgrade(MDBX_env *env) {
+  /* Transite from used state (S-?) to exclusive-write (E-E) */
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+
+  if (env->me_flags & MDBX_EXCLUSIVE)
+    return MDBX_SUCCESS /* nope since files were must be opened non-shareable */
+        ;
+
+  int rc;
+  /* 1) now on S-? (used), try S-E (locked) */
+  mdbx_jitter4testing(false);
+  if (!flock(env->me_lfd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_UPPER)) {
+    rc = GetLastError() /* 2) something went wrong, give up */;
+    mdbx_verbose("%s, err %u", "S-?(used) >> S-E(locked)", rc);
+    return rc;
+  }
+
+  /* 3) now on S-E (locked), transition to ?-E (middle) */
+  if (!funlock(env->me_lfd, LCK_LOWER))
+    mdbx_panic("%s(%s) failed: err %u", __func__, "S-E(locked) >> ?-E(middle)",
+               GetLastError());
+
+  /* 4) now on ?-E (middle), try E-E (exclusive-write) */
+  mdbx_jitter4testing(false);
+  if (!flock(env->me_lfd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_LOWER)) {
+    rc = GetLastError() /* 5) something went wrong, give up */;
+    mdbx_verbose("%s, err %u", "?-E(middle) >> E-E(exclusive-write)", rc);
+    return rc;
+  }
+
+  return MDBX_SUCCESS /* 6) now at E-E (exclusive-write), done */;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag) {
+  (void)env;
+  (void)inprocess_neighbor;
+  (void)global_uniqueness_flag;
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor) {
+  /* LY: should unmap before releasing the locks to avoid race condition and
+   * STATUS_USER_MAPPED_FILE/ERROR_USER_MAPPED_FILE */
+  if (env->me_map)
+    mdbx_munmap(&env->me_dxb_mmap);
+  if (env->me_lck) {
+    const bool synced = env->me_lck_mmap.lck->mti_unsynced_pages.weak == 0;
+    mdbx_munmap(&env->me_lck_mmap);
+    if (synced && !inprocess_neighbor && env->me_lfd != INVALID_HANDLE_VALUE &&
+        mdbx_lck_upgrade(env) == MDBX_SUCCESS)
+      /* this will fail if LCK is used/mmapped by other process(es) */
+      mdbx_ftruncate(env->me_lfd, 0);
+  }
+  lck_unlock(env);
+  return MDBX_SUCCESS;
+}
+
+/*----------------------------------------------------------------------------*/
+/* reader checking (by pid) */
+
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env) {
+  (void)env;
+  return MDBX_SUCCESS;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env) {
+  (void)env;
+  return MDBX_SUCCESS;
+}
+
+/* Checks reader by pid.
+ *
+ * Returns:
+ *   MDBX_RESULT_TRUE, if pid is live (unable to acquire lock)
+ *   MDBX_RESULT_FALSE, if pid is dead (lock acquired)
+ *   or otherwise the errcode. */
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid) {
+  (void)env;
+  HANDLE hProcess = OpenProcess(SYNCHRONIZE, FALSE, pid);
+  int rc;
+  if (likely(hProcess)) {
+    rc = WaitForSingleObject(hProcess, 0);
+    if (unlikely(rc == WAIT_FAILED))
+      rc = GetLastError();
+    CloseHandle(hProcess);
+  } else {
+    rc = GetLastError();
+  }
+
+  switch (rc) {
+  case ERROR_INVALID_PARAMETER:
+    /* pid seems invalid */
+    return MDBX_RESULT_FALSE;
+  case WAIT_OBJECT_0:
+    /* process just exited */
+    return MDBX_RESULT_FALSE;
+  case ERROR_ACCESS_DENIED:
+    /* The ERROR_ACCESS_DENIED would be returned for CSRSS-processes, etc.
+     * assume pid exists */
+    return MDBX_RESULT_TRUE;
+  case WAIT_TIMEOUT:
+    /* pid running */
+    return MDBX_RESULT_TRUE;
+  default:
+    /* failure */
+    return rc;
+  }
+}
+
+//----------------------------------------------------------------------------
+// Stub for slim read-write lock
+// Copyright (C) 1995-2002 Brad Wilson
+
+static void WINAPI stub_srwlock_Init(MDBX_srwlock *srwl) {
+  srwl->readerCount = srwl->writerCount = 0;
+}
+
+static void WINAPI stub_srwlock_AcquireShared(MDBX_srwlock *srwl) {
+  while (true) {
+    assert(srwl->writerCount >= 0 && srwl->readerCount >= 0);
+
+    //  If there's a writer already, spin without unnecessarily
+    //  interlocking the CPUs
+    if (srwl->writerCount != 0) {
+      YieldProcessor();
+      continue;
+    }
+
+    //  Add to the readers list
+    _InterlockedIncrement(&srwl->readerCount);
+
+    // Check for writers again (we may have been preempted). If
+    // there are no writers writing or waiting, then we're done.
+    if (srwl->writerCount == 0)
+      break;
+
+    // Remove from the readers list, spin, try again
+    _InterlockedDecrement(&srwl->readerCount);
+    YieldProcessor();
+  }
+}
+
+static void WINAPI stub_srwlock_ReleaseShared(MDBX_srwlock *srwl) {
+  assert(srwl->readerCount > 0);
+  _InterlockedDecrement(&srwl->readerCount);
+}
+
+static void WINAPI stub_srwlock_AcquireExclusive(MDBX_srwlock *srwl) {
+  while (true) {
+    assert(srwl->writerCount >= 0 && srwl->readerCount >= 0);
+
+    //  If there's a writer already, spin without unnecessarily
+    //  interlocking the CPUs
+    if (srwl->writerCount != 0) {
+      YieldProcessor();
+      continue;
+    }
+
+    // See if we can become the writer (expensive, because it inter-
+    // locks the CPUs, so writing should be an infrequent process)
+    if (_InterlockedExchange(&srwl->writerCount, 1) == 0)
+      break;
+  }
+
+  // Now we're the writer, but there may be outstanding readers.
+  // Spin until there aren't any more; new readers will wait now
+  // that we're the writer.
+  while (srwl->readerCount != 0) {
+    assert(srwl->writerCount >= 0 && srwl->readerCount >= 0);
+    YieldProcessor();
+  }
+}
+
+static void WINAPI stub_srwlock_ReleaseExclusive(MDBX_srwlock *srwl) {
+  assert(srwl->writerCount == 1 && srwl->readerCount >= 0);
+  srwl->writerCount = 0;
+}
+
+MDBX_srwlock_function mdbx_srwlock_Init, mdbx_srwlock_AcquireShared,
+    mdbx_srwlock_ReleaseShared, mdbx_srwlock_AcquireExclusive,
+    mdbx_srwlock_ReleaseExclusive;
+
+/*----------------------------------------------------------------------------*/
+
+#if 0  /* LY: unused for now */
+static DWORD WINAPI stub_DiscardVirtualMemory(PVOID VirtualAddress,
+                                              SIZE_T Size) {
+  return VirtualAlloc(VirtualAddress, Size, MEM_RESET, PAGE_NOACCESS)
+             ? ERROR_SUCCESS
+	  : GetLastError();
+}
+#endif /* unused for now */
+
+static uint64_t WINAPI stub_GetTickCount64(void) {
+  LARGE_INTEGER Counter, Frequency;
+  return (QueryPerformanceFrequency(&Frequency) &&
+          QueryPerformanceCounter(&Counter))
+             ? Counter.QuadPart * 1000ul / Frequency.QuadPart
+             : 0;
+}
+
+/*----------------------------------------------------------------------------*/
+#ifndef MDBX_ALLOY
+MDBX_NtExtendSection mdbx_NtExtendSection;
+MDBX_GetFileInformationByHandleEx mdbx_GetFileInformationByHandleEx;
+MDBX_GetVolumeInformationByHandleW mdbx_GetVolumeInformationByHandleW;
+MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+MDBX_SetFileInformationByHandle mdbx_SetFileInformationByHandle;
+MDBX_NtFsControlFile mdbx_NtFsControlFile;
+MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+MDBX_GetTickCount64 mdbx_GetTickCount64;
+MDBX_RegGetValueA mdbx_RegGetValueA;
+#if 0  /* LY: unused for now */
+MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+#endif /* unused for now */
+#endif /* MDBX_ALLOY */
+
+static void mdbx_winnt_import(void) {
+  const HINSTANCE hNtdll = GetModuleHandleA("ntdll.dll");
+
+#define GET_PROC_ADDR(dll, ENTRY)                                              \
+  mdbx_##ENTRY = (MDBX_##ENTRY)GetProcAddress(dll, #ENTRY)
+
+  if (GetProcAddress(hNtdll, "wine_get_version")) {
+    assert(mdbx_RunningUnderWine());
+  } else {
+    GET_PROC_ADDR(hNtdll, NtFsControlFile);
+    GET_PROC_ADDR(hNtdll, NtExtendSection);
+    assert(!mdbx_RunningUnderWine());
+  }
+
+  const HINSTANCE hKernel32dll = GetModuleHandleA("kernel32.dll");
+  GET_PROC_ADDR(hKernel32dll, GetFileInformationByHandleEx);
+  GET_PROC_ADDR(hKernel32dll, GetTickCount64);
+  if (!mdbx_GetTickCount64)
+    mdbx_GetTickCount64 = stub_GetTickCount64;
+  if (!mdbx_RunningUnderWine()) {
+    GET_PROC_ADDR(hKernel32dll, SetFileInformationByHandle);
+    GET_PROC_ADDR(hKernel32dll, GetVolumeInformationByHandleW);
+    GET_PROC_ADDR(hKernel32dll, GetFinalPathNameByHandleW);
+    GET_PROC_ADDR(hKernel32dll, PrefetchVirtualMemory);
+  }
+
+  const HINSTANCE hAdvapi32dll = GetModuleHandleA("advapi32.dll");
+  GET_PROC_ADDR(hAdvapi32dll, RegGetValueA);
+
+#if 0  /* LY: unused for now */
+  if (!mdbx_RunningUnderWine()) {
+    GET_PROC_ADDR(hKernel32dll, DiscardVirtualMemory);
+    GET_PROC_ADDR(hKernel32dll, OfferVirtualMemory);
+    GET_PROC_ADDR(hKernel32dll, ReclaimVirtualMemory);
+  }
+  if (!mdbx_DiscardVirtualMemory)
+    mdbx_DiscardVirtualMemory = stub_DiscardVirtualMemory;
+  if (!mdbx_OfferVirtualMemory)
+    mdbx_OfferVirtualMemory = stub_OfferVirtualMemory;
+  if (!mdbx_ReclaimVirtualMemory)
+    mdbx_ReclaimVirtualMemory = stub_ReclaimVirtualMemory;
+#endif /* unused for now */
+
+#undef GET_PROC_ADDR
+
+  const MDBX_srwlock_function init =
+      (MDBX_srwlock_function)GetProcAddress(hKernel32dll, "InitializeSRWLock");
+  if (init != NULL) {
+    mdbx_srwlock_Init = init;
+    mdbx_srwlock_AcquireShared = (MDBX_srwlock_function)GetProcAddress(
+        hKernel32dll, "AcquireSRWLockShared");
+    mdbx_srwlock_ReleaseShared = (MDBX_srwlock_function)GetProcAddress(
+        hKernel32dll, "ReleaseSRWLockShared");
+    mdbx_srwlock_AcquireExclusive = (MDBX_srwlock_function)GetProcAddress(
+        hKernel32dll, "AcquireSRWLockExclusive");
+    mdbx_srwlock_ReleaseExclusive = (MDBX_srwlock_function)GetProcAddress(
+        hKernel32dll, "ReleaseSRWLockExclusive");
+  } else {
+    mdbx_srwlock_Init = stub_srwlock_Init;
+    mdbx_srwlock_AcquireShared = stub_srwlock_AcquireShared;
+    mdbx_srwlock_ReleaseShared = stub_srwlock_ReleaseShared;
+    mdbx_srwlock_AcquireExclusive = stub_srwlock_AcquireExclusive;
+    mdbx_srwlock_ReleaseExclusive = stub_srwlock_ReleaseExclusive;
+  }
+}
+
+#endif /* Windows LCK-implementation */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+#if !(defined(_WIN32) || defined(_WIN64)) /* !Windows LCK-implementation */
+
+#include <sys/sem.h>
+
+/*----------------------------------------------------------------------------*/
+/* global constructor/destructor */
+
+#if defined(__linux__) || defined(__gnu_linux__)
+
+#include <sys/utsname.h>
+
+#ifndef MDBX_ALLOY
+uint32_t mdbx_linux_kernel_version;
+bool mdbx_RunningOnWSL1;
+#endif /* MDBX_ALLOY */
+
+static __cold uint8_t probe_for_WSL(const char *tag) {
+  const char *const WSL = strstr(tag, "WSL");
+  if (WSL && WSL[3] >= '2' && WSL[3] <= '9')
+    return WSL[3] - '0';
+  const char *const wsl = strstr(tag, "wsl");
+  if (wsl && wsl[3] >= '2' && wsl[3] <= '9')
+    return wsl[3] - '0';
+  return (WSL || wsl || strcasestr(tag, "Microsoft")) ? 1 : 0;
+}
+
+#endif /* Linux */
+
+static __cold __attribute__((__constructor__)) void
+mdbx_global_constructor(void) {
+#if defined(__linux__) || defined(__gnu_linux__)
+  struct utsname buffer;
+  if (uname(&buffer) == 0) {
+    /* "Official" way of detecting WSL1 but not WSL2
+     * https://github.com/Microsoft/WSL/issues/423#issuecomment-221627364
+     *
+     * WARNING: False negative detection of WSL1 will result in DATA LOSS!
+     * So, the REQUIREMENTS for this code:
+     *  1. MUST detect WSL1 without false-negatives.
+     *  2. DESIRABLE detect WSL2 but without the risk of violating the first. */
+    mdbx_RunningOnWSL1 = probe_for_WSL(buffer.version) == 1 ||
+                         probe_for_WSL(buffer.sysname) == 1 ||
+                         probe_for_WSL(buffer.release) == 1;
+    int i = 0;
+    char *p = buffer.release;
+    while (*p && i < 4) {
+      if (*p >= '0' && *p <= '9') {
+        long number = strtol(p, &p, 10);
+        if (number > 0) {
+          if (number > 255)
+            number = 255;
+          mdbx_linux_kernel_version += number << (24 - i * 8);
+        }
+        ++i;
+      } else {
+        ++p;
+      }
+    }
+  }
+#endif /* Linux */
+
+  mdbx_rthc_global_init();
+}
+
+static __cold __attribute__((__destructor__)) void
+mdbx_global_destructor(void) {
+  mdbx_rthc_global_dtor();
+}
+
+/*----------------------------------------------------------------------------*/
+/* lck */
+
+/* Описание реализации блокировок для POSIX & Linux:
+ *
+ * lck-файл отображается в память, в нём организуется таблица читателей и
+ * размещаются совместно используемые posix-мьютексы (futex). Посредством
+ * этих мьютексов (см struct MDBX_lockinfo) реализуются:
+ *  - Блокировка таблицы читателей для регистрации,
+ *    т.е. функции mdbx_rdt_lock() и mdbx_rdt_unlock().
+ *  - Блокировка БД для пишущих транзакций,
+ *    т.е. функции mdbx_txn_lock() и mdbx_txn_unlock().
+ *
+ * Остальной функционал реализуется отдельно посредством файловых блокировок:
+ *  - Первоначальный захват БД в режиме exclusive/shared и последующий перевод
+ *    в операционный режим, функции mdbx_lck_seize() и mdbx_lck_downgrade().
+ *  - Проверка присутствие процессов-читателей,
+ *    т.е. функции mdbx_rpid_set(), mdbx_rpid_clear() и mdbx_rpid_check().
+ *
+ * Для блокировки файлов используется fcntl(F_SETLK), так как:
+ *  - lockf() оперирует только эксклюзивной блокировкой и требует
+ *    открытия файла в RW-режиме.
+ *  - flock() не гарантирует атомарности при смене блокировок
+ *    и оперирует только всем файлом целиком.
+ *  - Для контроля процессов-читателей используются однобайтовые
+ *    range-блокировки lck-файла посредством fcntl(F_SETLK). При этом
+ *    в качестве позиции используется pid процесса-читателя.
+ *  - Для первоначального захвата и shared/exclusive выполняется блокировка
+ *    основного файла БД и при успехе lck-файла.
+ *
+ * ----------------------------------------------------------------------------
+ * УДЕРЖИВАЕМЫЕ БЛОКИРОВКИ В ЗАВИСИМОСТИ ОТ РЕЖИМА И СОСТОЯНИЯ
+ *
+ * Эксклюзивный режим без lck-файла:
+ *   = заблокирован весь dxb-файл посредством F_RDLCK или F_WRLCK,
+ *     в зависимости от MDBX_RDONLY.
+ *
+ * Не-операционный режим на время пере-инициализации и разрушении lck-файла:
+ *   = F_WRLCK блокировка первого байта lck-файла, другие процессы ждут её
+ *     снятия при получении F_RDLCK через F_SETLKW.
+ *   - блокировки dxb-файла могут меняться до снятие эксклюзивной блокировки
+ *    lck-файла:
+ *       + для НЕ-эксклюзивного режима блокировка pid-байта в dxb-файле
+ *         посредством F_RDLCK или F_WRLCK, в зависимости от MDBX_RDONLY.
+ *       + для ЭКСКЛЮЗИВНОГО режима блокировка pid-байта всего dxb-файла
+ *         посредством F_RDLCK или F_WRLCK, в зависимости от MDBX_RDONLY.
+ *
+ * ОПЕРАЦИОННЫЙ режим с lck-файлом:
+ *   = F_RDLCK блокировка первого байта lck-файла, другие процессы не могут
+ *     получить F_WRLCK и таким образом видят что БД используется.
+ *   + F_WRLCK блокировка pid-байта в clk-файле после первой транзакции чтения.
+ *   + для НЕ-эксклюзивного режима блокировка pid-байта в dxb-файле
+ *     посредством F_RDLCK или F_WRLCK, в зависимости от MDBX_RDONLY.
+ *   + для ЭКСКЛЮЗИВНОГО режима блокировка pid-байта всего dxb-файла
+ *     посредством F_RDLCK или F_WRLCK, в зависимости от MDBX_RDONLY.
+ */
+
+#if MDBX_USE_OFDLOCKS
+static int op_setlk, op_setlkw, op_getlk;
+static void __cold choice_fcntl() {
+  assert(!op_setlk && !op_setlkw && !op_getlk);
+  if ((mdbx_runtime_flags & MDBX_DBG_LEGACY_MULTIOPEN) == 0
+#if defined(__linux__) || defined(__gnu_linux__)
+      && mdbx_linux_kernel_version >
+             0x030f0000 /* OFD locks are available since 3.15, but engages here
+                           only for 3.16 and later kernels (i.e. LTS) because
+                           of reliability reasons */
+#endif                  /* linux */
+  ) {
+    op_setlk = F_OFD_SETLK;
+    op_setlkw = F_OFD_SETLKW;
+    op_getlk = F_OFD_GETLK;
+    return;
+  }
+  op_setlk = F_SETLK;
+  op_setlkw = F_SETLKW;
+  op_getlk = F_GETLK;
+}
+#else
+#define op_setlk F_SETLK
+#define op_setlkw F_SETLKW
+#define op_getlk F_GETLK
+#endif /* MDBX_USE_OFDLOCKS */
+
+#ifndef OFF_T_MAX
+#define OFF_T_MAX                                                              \
+  ((sizeof(off_t) > 4 ? INT64_MAX : INT32_MAX) & ~(size_t)0xffff)
+#endif
+
+static int lck_op(mdbx_filehandle_t fd, int cmd, int lck, off_t offset,
+                  off_t len) {
+  mdbx_jitter4testing(true);
+  for (;;) {
+    struct flock lock_op;
+    memset(&lock_op, 0, sizeof(lock_op));
+    lock_op.l_type = lck;
+    lock_op.l_whence = SEEK_SET;
+    lock_op.l_start = offset;
+    lock_op.l_len = len;
+    int rc = fcntl(fd, cmd, &lock_op);
+    mdbx_jitter4testing(true);
+    if (rc != -1) {
+      if (cmd == op_getlk) {
+        /* Checks reader by pid. Returns:
+         *   MDBX_RESULT_TRUE   - if pid is live (reader holds a lock).
+         *   MDBX_RESULT_FALSE  - if pid is dead (a lock could be placed). */
+        return (lock_op.l_type == F_UNLCK) ? MDBX_RESULT_FALSE
+                                           : MDBX_RESULT_TRUE;
+      }
+      return MDBX_SUCCESS;
+    }
+    rc = errno;
+    if (rc != EINTR || cmd == op_setlkw) {
+      mdbx_assert(nullptr, MDBX_IS_ERROR(rc));
+      return rc;
+    }
+  }
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait) {
+#if MDBX_USE_OFDLOCKS
+  if (unlikely(op_setlk == 0))
+    choice_fcntl();
+#endif /* MDBX_USE_OFDLOCKS */
+  return lck_op(fd, wait ? op_setlkw : op_setlk, F_WRLCK, 0, OFF_T_MAX);
+}
+
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env) {
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+  assert(env->me_pid > 0);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+  return lck_op(env->me_lfd, op_setlk, F_WRLCK, env->me_pid, 1);
+}
+
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env) {
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+  assert(env->me_pid > 0);
+  return lck_op(env->me_lfd, op_setlk, F_UNLCK, env->me_pid, 1);
+}
+
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid) {
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+  assert(pid > 0);
+  return lck_op(env->me_lfd, op_getlk, F_WRLCK, pid, 1);
+}
+
+/*---------------------------------------------------------------------------*/
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc) {
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+  return sem_init(ipc, false, 1) ? errno : 0;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+  return pthread_mutex_init(ipc, nullptr);
+#else
+#error "FIXME"
+#endif
+}
+
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc) {
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+  return sem_destroy(ipc) ? errno : 0;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+  return pthread_mutex_destroy(ipc);
+#else
+#error "FIXME"
+#endif
+}
+#endif /* MDBX_LOCKING > MDBX_LOCKING_SYSV */
+
+static int check_fstat(MDBX_env *env) {
+  struct stat st;
+
+  int rc = MDBX_SUCCESS;
+  if (fstat(env->me_lazy_fd, &st)) {
+    rc = errno;
+    mdbx_error("fstat(%s), err %d", "DXB", rc);
+    return rc;
+  }
+
+  if (!S_ISREG(st.st_mode) || st.st_nlink < 1) {
+#ifdef EBADFD
+    rc = EBADFD;
+#else
+    rc = EPERM;
+#endif
+    mdbx_error("%s %s, err %d", "DXB",
+               (st.st_nlink < 1) ? "file was removed" : "not a regular file",
+               rc);
+    return rc;
+  }
+
+  if (st.st_size < (off_t)(MDBX_MIN_PAGESIZE * NUM_METAS)) {
+    mdbx_verbose("dxb-file is too short (%u), exclusive-lock needed",
+                 (unsigned)st.st_size);
+    rc = MDBX_RESULT_TRUE;
+  }
+
+  //----------------------------------------------------------------------------
+
+  if (fstat(env->me_lfd, &st)) {
+    rc = errno;
+    mdbx_error("fstat(%s), err %d", "LCK", rc);
+    return rc;
+  }
+
+  if (!S_ISREG(st.st_mode) || st.st_nlink < 1) {
+#ifdef EBADFD
+    rc = EBADFD;
+#else
+    rc = EPERM;
+#endif
+    mdbx_error("%s %s, err %d", "LCK",
+               (st.st_nlink < 1) ? "file was removed" : "not a regular file",
+               rc);
+    return rc;
+  }
+
+  /* Checking file size for detect the situation when we got the shared lock
+   * immediately after mdbx_lck_destroy(). */
+  if (st.st_size < (off_t)(sizeof(MDBX_lockinfo) + sizeof(MDBX_reader))) {
+    mdbx_verbose("lck-file is too short (%u), exclusive-lock needed",
+                 (unsigned)st.st_size);
+    rc = MDBX_RESULT_TRUE;
+  }
+
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int __cold mdbx_lck_seize(MDBX_env *env) {
+  assert(env->me_lazy_fd != INVALID_HANDLE_VALUE);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+#if MDBX_USE_OFDLOCKS
+  if (unlikely(op_setlk == 0))
+    choice_fcntl();
+#endif /* MDBX_USE_OFDLOCKS */
+
+  int rc = MDBX_SUCCESS;
+#if defined(__linux__) || defined(__gnu_linux__)
+  if (unlikely(mdbx_RunningOnWSL1)) {
+    rc = ENOLCK /* No record locks available */;
+    mdbx_error("%s, err %u",
+               "WSL1 (Windows Subsystem for Linux) is mad and trouble-full, "
+               "injecting failure to avoid data loss",
+               rc);
+    return rc;
+  }
+#endif /* Linux */
+
+  if (env->me_lfd == INVALID_HANDLE_VALUE) {
+    /* LY: without-lck mode (e.g. exclusive or on read-only filesystem) */
+    rc =
+        lck_op(env->me_lazy_fd, op_setlk,
+               (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0, OFF_T_MAX);
+    if (rc != MDBX_SUCCESS) {
+      mdbx_error("%s, err %u", "without-lck", rc);
+      mdbx_assert(env, MDBX_IS_ERROR(rc));
+      return rc;
+    }
+    return MDBX_RESULT_TRUE /* Done: return with exclusive locking. */;
+  }
+#if defined(_POSIX_PRIORITY_SCHEDULING) && _POSIX_PRIORITY_SCHEDULING > 0
+  sched_yield();
+#endif
+
+retry:
+  if (rc == MDBX_RESULT_TRUE) {
+    rc = lck_op(env->me_lfd, op_setlk, F_UNLCK, 0, 1);
+    if (rc != MDBX_SUCCESS) {
+      mdbx_error("%s, err %u", "unlock-before-retry", rc);
+      mdbx_assert(env, MDBX_IS_ERROR(rc));
+      return rc;
+    }
+  }
+
+  /* Firstly try to get exclusive locking.  */
+  rc = lck_op(env->me_lfd, op_setlk, F_WRLCK, 0, 1);
+  if (rc == MDBX_SUCCESS) {
+    rc = check_fstat(env);
+    if (MDBX_IS_ERROR(rc))
+      return rc;
+
+  continue_dxb_exclusive:
+    rc =
+        lck_op(env->me_lazy_fd, op_setlk,
+               (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0, OFF_T_MAX);
+    if (rc == MDBX_SUCCESS)
+      return MDBX_RESULT_TRUE /* Done: return with exclusive locking. */;
+
+    int err = check_fstat(env);
+    if (MDBX_IS_ERROR(err))
+      return err;
+
+    /* the cause may be a collision with POSIX's file-lock recovery. */
+    if (!(rc == EAGAIN || rc == EACCES || rc == EBUSY || rc == EWOULDBLOCK ||
+          rc == EDEADLK)) {
+      mdbx_error("%s, err %u", "dxb-exclusive", rc);
+      mdbx_assert(env, MDBX_IS_ERROR(rc));
+      return rc;
+    }
+
+    /* Fallback to lck-shared */
+  } else if (!(rc == EAGAIN || rc == EACCES || rc == EBUSY ||
+               rc == EWOULDBLOCK || rc == EDEADLK)) {
+    mdbx_error("%s, err %u", "try-exclusive", rc);
+    mdbx_assert(env, MDBX_IS_ERROR(rc));
+    return rc;
+  }
+
+  /* Here could be one of two:
+   *  - mdbx_lck_destroy() from the another process was hold the lock
+   *    during a destruction.
+   *  - either mdbx_lck_seize() from the another process was got the exclusive
+   *    lock and doing initialization.
+   * For distinguish these cases will use size of the lck-file later. */
+
+  /* Wait for lck-shared now. */
+  /* Here may be await during transient processes, for instance until another
+   * competing process doesn't call lck_downgrade(). */
+  rc = lck_op(env->me_lfd, op_setlkw, F_RDLCK, 0, 1);
+  if (rc != MDBX_SUCCESS) {
+    mdbx_error("%s, err %u", "try-shared", rc);
+    mdbx_assert(env, MDBX_IS_ERROR(rc));
+    return rc;
+  }
+
+  rc = check_fstat(env);
+  if (rc == MDBX_RESULT_TRUE)
+    goto retry;
+  if (rc != MDBX_SUCCESS) {
+    mdbx_error("%s, err %u", "lck_fstat", rc);
+    return rc;
+  }
+
+  /* got shared, retry exclusive */
+  rc = lck_op(env->me_lfd, op_setlk, F_WRLCK, 0, 1);
+  if (rc == MDBX_SUCCESS)
+    goto continue_dxb_exclusive;
+
+  if (!(rc == EAGAIN || rc == EACCES || rc == EBUSY || rc == EWOULDBLOCK ||
+        rc == EDEADLK)) {
+    mdbx_error("%s, err %u", "try-exclusive", rc);
+    mdbx_assert(env, MDBX_IS_ERROR(rc));
+    return rc;
+  }
+
+  /* Lock against another process operating in without-lck or exclusive mode. */
+  rc =
+      lck_op(env->me_lazy_fd, op_setlk,
+             (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, env->me_pid, 1);
+  if (rc != MDBX_SUCCESS) {
+    mdbx_error("%s, err %u", "lock-against-without-lck", rc);
+    mdbx_assert(env, MDBX_IS_ERROR(rc));
+    return rc;
+  }
+
+  /* Done: return with shared locking. */
+  return MDBX_RESULT_FALSE;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env) {
+  assert(env->me_lfd != INVALID_HANDLE_VALUE);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+
+  int rc = MDBX_SUCCESS;
+  if ((env->me_flags & MDBX_EXCLUSIVE) == 0) {
+    rc = lck_op(env->me_lazy_fd, op_setlk, F_UNLCK, 0, env->me_pid);
+    if (rc == MDBX_SUCCESS)
+      rc = lck_op(env->me_lazy_fd, op_setlk, F_UNLCK, env->me_pid + 1,
+                  OFF_T_MAX - env->me_pid - 1);
+  }
+  if (rc == MDBX_SUCCESS)
+    rc = lck_op(env->me_lfd, op_setlk, F_RDLCK, 0, 1);
+  if (unlikely(rc != 0)) {
+    mdbx_error("%s, err %u", "lck", rc);
+    assert(MDBX_IS_ERROR(rc));
+  }
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int __cold mdbx_lck_destroy(MDBX_env *env,
+                                               MDBX_env *inprocess_neighbor) {
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+
+  int rc = MDBX_SUCCESS;
+  struct stat lck_info;
+  if (env->me_lfd != INVALID_HANDLE_VALUE && !inprocess_neighbor &&
+      env->me_lck &&
+      /* try get exclusive access */
+      lck_op(env->me_lfd, op_setlk, F_WRLCK, 0, OFF_T_MAX) == 0 &&
+      /* if LCK was not removed */
+      fstat(env->me_lfd, &lck_info) == 0 && lck_info.st_nlink > 0 &&
+      lck_op(env->me_lazy_fd, op_setlk,
+             (env->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK, 0,
+             OFF_T_MAX) == 0) {
+
+    mdbx_verbose("%p got exclusive, drown locks", (void *)env);
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+    if (env->me_sysv_ipc.semid != -1)
+      rc = semctl(env->me_sysv_ipc.semid, 2, IPC_RMID) ? errno : 0;
+#else
+    rc = mdbx_ipclock_destroy(&env->me_lck->mti_rlock);
+    if (rc == 0)
+      rc = mdbx_ipclock_destroy(&env->me_lck->mti_wlock);
+#endif /* MDBX_LOCKING */
+
+    mdbx_assert(env, rc == 0);
+    if (rc == 0) {
+      const bool synced = env->me_lck_mmap.lck->mti_unsynced_pages.weak == 0;
+      mdbx_munmap(&env->me_lck_mmap);
+      if (synced)
+        rc = ftruncate(env->me_lfd, 0) ? errno : 0;
+    }
+
+    mdbx_jitter4testing(false);
+  }
+
+  /* 1) POSIX's fcntl() locks (i.e. when op_setlk == F_SETLK) should be restored
+   * after file was closed.
+   *
+   * 2) File locks would be released (by kernel) while the file-descriptors will
+   * be closed. But to avoid false-positive EACCESS and EDEADLK from the kernel,
+   * locks should be released here explicitly with properly order. */
+
+  /* close dxb and restore lock */
+  if (env->me_dsync_fd != INVALID_HANDLE_VALUE) {
+    if (unlikely(close(env->me_dsync_fd) != 0) && rc == MDBX_SUCCESS)
+      rc = errno;
+    env->me_dsync_fd = INVALID_HANDLE_VALUE;
+  }
+  if (env->me_lazy_fd != INVALID_HANDLE_VALUE) {
+    if (unlikely(close(env->me_lazy_fd) != 0) && rc == MDBX_SUCCESS)
+      rc = errno;
+    env->me_lazy_fd = INVALID_HANDLE_VALUE;
+    if (op_setlk == F_SETLK && inprocess_neighbor && rc == MDBX_SUCCESS) {
+      /* restore file-lock */
+      rc = lck_op(
+          inprocess_neighbor->me_lazy_fd, F_SETLKW,
+          (inprocess_neighbor->me_flags & MDBX_RDONLY) ? F_RDLCK : F_WRLCK,
+          (inprocess_neighbor->me_flags & MDBX_EXCLUSIVE)
+              ? 0
+              : inprocess_neighbor->me_pid,
+          (inprocess_neighbor->me_flags & MDBX_EXCLUSIVE) ? OFF_T_MAX : 1);
+    }
+  }
+
+  /* close clk and restore locks */
+  if (env->me_lfd != INVALID_HANDLE_VALUE) {
+    if (unlikely(close(env->me_lfd) != 0) && rc == MDBX_SUCCESS)
+      rc = errno;
+    env->me_lfd = INVALID_HANDLE_VALUE;
+    if (op_setlk == F_SETLK && inprocess_neighbor && rc == MDBX_SUCCESS) {
+      /* restore file-locks */
+      rc = lck_op(inprocess_neighbor->me_lfd, F_SETLKW, F_RDLCK, 0, 1);
+      if (rc == MDBX_SUCCESS && inprocess_neighbor->me_live_reader)
+        rc = mdbx_rpid_set(inprocess_neighbor);
+    }
+  }
+
+  if (inprocess_neighbor && rc != MDBX_SUCCESS)
+    inprocess_neighbor->me_flags |= MDBX_FATAL_ERROR;
+  return rc;
+}
+
+/*---------------------------------------------------------------------------*/
+
+MDBX_INTERNAL_FUNC int __cold mdbx_lck_init(MDBX_env *env,
+                                            MDBX_env *inprocess_neighbor,
+                                            int global_uniqueness_flag) {
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  int semid = -1;
+  /* don't initialize semaphores twice */
+  (void)inprocess_neighbor;
+  if (global_uniqueness_flag == MDBX_RESULT_TRUE) {
+    struct stat st;
+    if (fstat(env->me_lazy_fd, &st))
+      return errno;
+  sysv_retry_create:
+    semid = semget(env->me_sysv_ipc.key, 2,
+                   IPC_CREAT | IPC_EXCL |
+                       (st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO)));
+    if (unlikely(semid == -1)) {
+      int err = errno;
+      if (err != EEXIST)
+        return err;
+
+      /* remove and re-create semaphore set */
+      semid = semget(env->me_sysv_ipc.key, 2, 0);
+      if (semid == -1) {
+        err = errno;
+        if (err != ENOENT)
+          return err;
+        goto sysv_retry_create;
+      }
+      if (semctl(semid, 2, IPC_RMID)) {
+        err = errno;
+        if (err != EIDRM)
+          return err;
+      }
+      goto sysv_retry_create;
+    }
+
+    unsigned short val_array[2] = {1, 1};
+    if (semctl(semid, 2, SETALL, val_array))
+      return errno;
+  } else {
+    semid = semget(env->me_sysv_ipc.key, 2, 0);
+    if (semid == -1)
+      return errno;
+
+    /* check read & write access */
+    struct semid_ds data[2];
+    if (semctl(semid, 2, IPC_STAT, data) || semctl(semid, 2, IPC_SET, data))
+      return errno;
+  }
+
+  env->me_sysv_ipc.semid = semid;
+  return MDBX_SUCCESS;
+
+#elif MDBX_LOCKING == MDBX_LOCKING_FUTEX
+  (void)inprocess_neighbor;
+  if (global_uniqueness_flag != MDBX_RESULT_TRUE)
+    return MDBX_SUCCESS;
+#error "FIXME: Not implemented"
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+
+  /* don't initialize semaphores twice */
+  (void)inprocess_neighbor;
+  if (global_uniqueness_flag == MDBX_RESULT_TRUE) {
+    if (sem_init(&env->me_lck->mti_rlock, true, 1))
+      return errno;
+    if (sem_init(&env->me_lck->mti_wlock, true, 1))
+      return errno;
+  }
+  return MDBX_SUCCESS;
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+  if (inprocess_neighbor)
+    return MDBX_SUCCESS /* don't need any initialization for mutexes
+      if LCK already opened/used inside current process */
+        ;
+
+    /* FIXME: Unfortunately, there is no other reliable way but to long testing
+     * on each platform. On the other hand, behavior like FreeBSD is incorrect
+     * and we can expect it to be rare. Moreover, even on FreeBSD without
+     * additional in-process initialization, the probability of an problem
+     * occurring is vanishingly small, and the symptom is a return of EINVAL
+     * while locking a mutex. In other words, in the worst case, the problem
+     * results in an EINVAL error at the start of the transaction, but NOT data
+     * loss, nor database corruption, nor other fatal troubles. Thus, the code
+     * below I am inclined to think the workaround for erroneous platforms (like
+     * FreeBSD), rather than a defect of libmdbx. */
+#if defined(__FreeBSD__)
+  /* seems that shared mutexes on FreeBSD required in-process initialization */
+  (void)global_uniqueness_flag;
+#else
+  /* shared mutexes on many other platforms (including Darwin and Linux's
+   * futexes) doesn't need any addition in-process initialization */
+  if (global_uniqueness_flag != MDBX_RESULT_TRUE)
+    return MDBX_SUCCESS;
+#endif
+
+  pthread_mutexattr_t ma;
+  int rc = pthread_mutexattr_init(&ma);
+  if (rc)
+    return rc;
+
+  rc = pthread_mutexattr_setpshared(&ma, PTHREAD_PROCESS_SHARED);
+  if (rc)
+    goto bailout;
+
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#if defined(PTHREAD_MUTEX_ROBUST) || defined(pthread_mutexattr_setrobust)
+  rc = pthread_mutexattr_setrobust(&ma, PTHREAD_MUTEX_ROBUST);
+#elif defined(PTHREAD_MUTEX_ROBUST_NP) ||                                      \
+    defined(pthread_mutexattr_setrobust_np)
+  rc = pthread_mutexattr_setrobust_np(&ma, PTHREAD_MUTEX_ROBUST_NP);
+#elif _POSIX_THREAD_PROCESS_SHARED < 200809L
+  rc = pthread_mutexattr_setrobust_np(&ma, PTHREAD_MUTEX_ROBUST_NP);
+#else
+  rc = pthread_mutexattr_setrobust(&ma, PTHREAD_MUTEX_ROBUST);
+#endif
+  if (rc)
+    goto bailout;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_POSIX2008 */
+
+#if defined(_POSIX_THREAD_PRIO_INHERIT) && _POSIX_THREAD_PRIO_INHERIT >= 0 &&  \
+    !defined(MDBX_SAFE4QEMU)
+  rc = pthread_mutexattr_setprotocol(&ma, PTHREAD_PRIO_INHERIT);
+  if (rc == ENOTSUP)
+    rc = pthread_mutexattr_setprotocol(&ma, PTHREAD_PRIO_NONE);
+  if (rc && rc != ENOTSUP)
+    goto bailout;
+#endif /* PTHREAD_PRIO_INHERIT */
+
+  rc = pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_ERRORCHECK);
+  if (rc && rc != ENOTSUP)
+    goto bailout;
+
+  rc = pthread_mutex_init(&env->me_lck->mti_rlock, &ma);
+  if (rc)
+    goto bailout;
+  rc = pthread_mutex_init(&env->me_lck->mti_wlock, &ma);
+
+bailout:
+  pthread_mutexattr_destroy(&ma);
+  return rc;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING > 0 */
+}
+
+static int __cold mdbx_ipclock_failed(MDBX_env *env, mdbx_ipclock_t *ipc,
+                                      const int err) {
+  int rc = err;
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX2008 || MDBX_LOCKING == MDBX_LOCKING_SYSV
+  if (err == EOWNERDEAD) {
+    /* We own the mutex. Clean up after dead previous owner. */
+
+    const bool rlocked = (env->me_lck && ipc == &env->me_lck->mti_rlock);
+    rc = MDBX_SUCCESS;
+    if (!rlocked) {
+      if (unlikely(env->me_txn)) {
+        /* env is hosed if the dead thread was ours */
+        env->me_flags |= MDBX_FATAL_ERROR;
+        env->me_txn = NULL;
+        rc = MDBX_PANIC;
+      }
+    }
+    mdbx_warning("%clock owner died, %s", (rlocked ? 'r' : 'w'),
+                 (rc ? "this process' env is hosed" : "recovering"));
+
+    int check_rc = mdbx_cleanup_dead_readers(env, rlocked, NULL);
+    check_rc = (check_rc == MDBX_SUCCESS) ? MDBX_RESULT_TRUE : check_rc;
+
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+    rc = (rc == MDBX_SUCCESS) ? check_rc : rc;
+#else
+#if defined(PTHREAD_MUTEX_ROBUST) || defined(pthread_mutex_consistent)
+    int mreco_rc = pthread_mutex_consistent(ipc);
+#elif defined(PTHREAD_MUTEX_ROBUST_NP) || defined(pthread_mutex_consistent_np)
+    int mreco_rc = pthread_mutex_consistent_np(ipc);
+#elif _POSIX_THREAD_PROCESS_SHARED < 200809L
+    int mreco_rc = pthread_mutex_consistent_np(ipc);
+#else
+    int mreco_rc = pthread_mutex_consistent(ipc);
+#endif
+    check_rc = (mreco_rc == 0) ? check_rc : mreco_rc;
+
+    if (unlikely(mreco_rc))
+      mdbx_error("lock recovery failed, %s", mdbx_strerror(mreco_rc));
+
+    rc = (rc == MDBX_SUCCESS) ? check_rc : rc;
+    if (MDBX_IS_ERROR(rc))
+      pthread_mutex_unlock(ipc);
+#endif /* MDBX_LOCKING == MDBX_LOCKING_POSIX2008 */
+    return rc;
+  }
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001
+  (void)ipc;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+  (void)ipc;
+#elif MDBX_LOCKING == MDBX_LOCKING_FUTEX
+#ifdef _MSC_VER
+#pragma message("warning: TODO")
+#else
+#warning "TODO"
+#endif
+  (void)ipc;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+  mdbx_error("mutex (un)lock failed, %s", mdbx_strerror(err));
+  if (rc != EDEADLK)
+    env->me_flags |= MDBX_FATAL_ERROR;
+  return rc;
+}
+
+static int mdbx_ipclock_lock(MDBX_env *env, mdbx_ipclock_t *ipc,
+                             const bool dont_wait) {
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                  \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+  int rc = dont_wait ? pthread_mutex_trylock(ipc) : pthread_mutex_lock(ipc);
+  rc = (rc == EBUSY && dont_wait) ? MDBX_BUSY : rc;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+  int rc = MDBX_SUCCESS;
+  if (dont_wait) {
+    if (sem_trywait(ipc)) {
+      rc = errno;
+      if (rc == EAGAIN)
+        rc = MDBX_BUSY;
+    }
+  } else if (sem_wait(ipc))
+    rc = errno;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+  struct sembuf op = {.sem_num = (ipc != env->me_wlock),
+                      .sem_op = -1,
+                      .sem_flg = dont_wait ? IPC_NOWAIT | SEM_UNDO : SEM_UNDO};
+  int rc;
+  if (semop(env->me_sysv_ipc.semid, &op, 1)) {
+    rc = errno;
+    if (dont_wait && rc == EAGAIN)
+      rc = MDBX_BUSY;
+  } else {
+    rc = *ipc ? EOWNERDEAD : MDBX_SUCCESS;
+    *ipc = env->me_pid;
+  }
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+  if (unlikely(rc != MDBX_SUCCESS && rc != MDBX_BUSY))
+    rc = mdbx_ipclock_failed(env, ipc, rc);
+  return rc;
+}
+
+static int mdbx_ipclock_unlock(MDBX_env *env, mdbx_ipclock_t *ipc) {
+#if MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                  \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+  int rc = pthread_mutex_unlock(ipc);
+  (void)env;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+  int rc = sem_post(ipc) ? errno : MDBX_SUCCESS;
+  (void)env;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+  if (unlikely(*ipc != (pid_t)env->me_pid))
+    return EPERM;
+  *ipc = 0;
+  struct sembuf op = {
+      .sem_num = (ipc != env->me_wlock), .sem_op = 1, .sem_flg = SEM_UNDO};
+  int rc = semop(env->me_sysv_ipc.semid, &op, 1) ? errno : MDBX_SUCCESS;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env) {
+  mdbx_trace("%s", ">>");
+  mdbx_jitter4testing(true);
+  int rc = mdbx_ipclock_lock(env, &env->me_lck->mti_rlock, false);
+  mdbx_trace("<< rc %d", rc);
+  return rc;
+}
+
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env) {
+  mdbx_trace("%s", ">>");
+  int rc = mdbx_ipclock_unlock(env, &env->me_lck->mti_rlock);
+  mdbx_trace("<< rc %d", rc);
+  if (unlikely(rc != MDBX_SUCCESS))
+    mdbx_panic("%s() failed: err %d\n", __func__, rc);
+  mdbx_jitter4testing(true);
+}
+
+int mdbx_txn_lock(MDBX_env *env, bool dont_wait) {
+  mdbx_trace("%swait %s", dont_wait ? "dont-" : "", ">>");
+  mdbx_jitter4testing(true);
+  int rc = mdbx_ipclock_lock(env, env->me_wlock, dont_wait);
+  mdbx_trace("<< rc %d", rc);
+  return MDBX_IS_ERROR(rc) ? rc : MDBX_SUCCESS;
+}
+
+void mdbx_txn_unlock(MDBX_env *env) {
+  mdbx_trace("%s", ">>");
+  int rc = mdbx_ipclock_unlock(env, env->me_wlock);
+  mdbx_trace("<< rc %d", rc);
+  if (unlikely(rc != MDBX_SUCCESS))
+    mdbx_panic("%s() failed: err %d\n", __func__, rc);
+  mdbx_jitter4testing(true);
+}
+
+#else
+#ifdef _MSC_VER
+#pragma warning(disable : 4206) /* nonstandard extension used: translation     \
+                                   unit is empty */
+#endif                          /* _MSC_VER (warnings) */
+#endif                          /* !Windows LCK-implementation */
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx.c++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.c++
new file mode 100644
index 0000000000..e29b579cef
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.c++
@@ -0,0 +1,4657 @@
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_ALLOY 1
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h++"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+//
+// Copyright (c) 2020-2021, Leonid Yuriev <leo@yuriev.ru>.
+// SPDX-License-Identifier: Apache-2.0
+//
+// Non-inline part of the libmdbx C++ API (preliminary)
+//
+
+#ifdef _MSC_VER
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
+
+
+#include <atomic>
+#include <cctype> // for isxdigit(), etc
+#include <system_error>
+
+namespace {
+
+#if 0 /* Unused for now */
+
+class trouble_location {
+
+#ifndef TROUBLE_PROVIDE_LINENO
+#define TROUBLE_PROVIDE_LINENO 1
+#endif
+
+#ifndef TROUBLE_PROVIDE_CONDITION
+#define TROUBLE_PROVIDE_CONDITION 1
+#endif
+
+#ifndef TROUBLE_PROVIDE_FUNCTION
+#define TROUBLE_PROVIDE_FUNCTION 1
+#endif
+
+#ifndef TROUBLE_PROVIDE_FILENAME
+#define TROUBLE_PROVIDE_FILENAME 1
+#endif
+
+#if TROUBLE_PROVIDE_LINENO
+  const unsigned line_;
+#endif
+#if TROUBLE_PROVIDE_CONDITION
+  const char *const condition_;
+#endif
+#if TROUBLE_PROVIDE_FUNCTION
+  const char *const function_;
+#endif
+#if TROUBLE_PROVIDE_FILENAME
+  const char *const filename_;
+#endif
+
+public:
+  MDBX_CXX11_CONSTEXPR trouble_location(unsigned line, const char *condition,
+                                   const char *function, const char *filename)
+      :
+#if TROUBLE_PROVIDE_LINENO
+        line_(line)
+#endif
+#if TROUBLE_PROVIDE_CONDITION
+        ,
+        condition_(condition)
+#endif
+#if TROUBLE_PROVIDE_FUNCTION
+        ,
+        function_(function)
+#endif
+#if TROUBLE_PROVIDE_FILENAME
+        ,
+        filename_(filename)
+#endif
+  {
+#if !TROUBLE_PROVIDE_LINENO
+    (void)line;
+#endif
+#if !TROUBLE_PROVIDE_CONDITION
+    (void)condition;
+#endif
+#if !TROUBLE_PROVIDE_FUNCTION
+    (void)function;
+#endif
+#if !TROUBLE_PROVIDE_FILENAME
+    (void)filename;
+#endif
+  }
+
+  trouble_location(const trouble_location &&) = delete;
+
+  unsigned line() const {
+#if TROUBLE_PROVIDE_LINENO
+    return line_;
+#else
+    return 0;
+#endif
+  }
+
+  const char *condition() const {
+#if TROUBLE_PROVIDE_CONDITION
+    return condition_;
+#else
+    return "";
+#endif
+  }
+
+  const char *function() const {
+#if TROUBLE_PROVIDE_FUNCTION
+    return function_;
+#else
+    return "";
+#endif
+  }
+
+  const char *filename() const {
+#if TROUBLE_PROVIDE_FILENAME
+    return filename_;
+#else
+    return "";
+#endif
+  }
+};
+
+//------------------------------------------------------------------------------
+
+__cold std::string format_va(const char *fmt, va_list ap) {
+  va_list ones;
+  va_copy(ones, ap);
+#ifdef _MSC_VER
+  int needed = _vscprintf(fmt, ap);
+#else
+  int needed = vsnprintf(nullptr, 0, fmt, ap);
+#endif
+  assert(needed >= 0);
+  std::string result;
+  result.reserve(size_t(needed + 1));
+  result.resize(size_t(needed), '\0');
+  assert(int(result.capacity()) > needed);
+  int actual = vsnprintf(const_cast<char *>(result.data()), result.capacity(),
+                         fmt, ones);
+  assert(actual == needed);
+  (void)actual;
+  va_end(ones);
+  return result;
+}
+
+__cold std::string format(const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  std::string result = format_va(fmt, ap);
+  va_end(ap);
+  return result;
+}
+
+class bug : public std::runtime_error {
+  const trouble_location &location_;
+
+public:
+  bug(const trouble_location &) noexcept;
+  /* temporary workaround for "private field 'FOO' is not used" from CLANG
+   * and for "function 'BAR' was declared but never referenced" from LCC. */
+#ifndef __LCC__
+  const trouble_location &location() const noexcept { return location_; }
+#endif
+  virtual ~bug() noexcept;
+};
+
+__cold bug::bug(const trouble_location &location) noexcept
+    : std::runtime_error(format("mdbx.bug: %s.%s at %s:%u", location.function(),
+                                location.condition(), location.filename(),
+                                location.line())),
+      location_(location) {}
+
+__cold bug::~bug() noexcept {}
+
+[[noreturn]] __cold void raise_bug(const trouble_location &what_and_where) {
+  throw bug(what_and_where);
+}
+
+#define RAISE_BUG(line, condition, function, file)                             \
+  do {                                                                         \
+    static MDBX_CXX11_CONSTEXPR_VAR trouble_location bug(line, condition,      \
+                                                         function, file);      \
+    raise_bug(bug);                                                            \
+  } while (0)
+
+#define ENSURE(condition)                                                      \
+  do                                                                           \
+    if (MDBX_UNLIKELY(!(condition)))                                           \
+      RAISE_BUG(__LINE__, #condition, __func__, __FILE__);                     \
+  while (0)
+
+#define NOT_IMPLEMENTED()                                                      \
+  RAISE_BUG(__LINE__, "not_implemented", __func__, __FILE__);
+
+#endif /* Unused*/
+
+//------------------------------------------------------------------------------
+
+template <typename PATH> struct path_to_pchar {
+  const std::string str;
+  path_to_pchar(const PATH &path) : str(path.generic_string()) {}
+  operator const char *() const { return str.c_str(); }
+};
+
+template <typename PATH> PATH pchar_to_path(const char *c_str) {
+  return PATH(c_str);
+}
+
+template <> struct path_to_pchar<std::string> {
+  const char *const ptr;
+  path_to_pchar(const std::string &path) : ptr(path.c_str()) {}
+  operator const char *() const { return ptr; }
+};
+
+#if defined(_WIN32) || defined(_WIN64)
+
+template <> struct path_to_pchar<std::wstring> {
+  std::string str;
+  path_to_pchar(const std::wstring &path) {
+    if (!path.empty()) {
+      const int chars =
+          WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, path.data(),
+                              int(path.size()), nullptr, 0, nullptr, nullptr);
+      if (chars == 0)
+        mdbx::error::throw_exception(GetLastError());
+      str.append(chars, '\0');
+      WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, path.data(),
+                          int(path.size()), const_cast<char *>(str.data()),
+                          chars, nullptr, nullptr);
+    }
+  }
+  operator const char *() const { return str.c_str(); }
+};
+
+template <> std::wstring pchar_to_path<std::wstring>(const char *c_str) {
+  std::wstring wstr;
+  if (c_str && *c_str) {
+    const int chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, c_str,
+                                          int(strlen(c_str)), nullptr, 0);
+    if (chars == 0)
+      mdbx::error::throw_exception(GetLastError());
+    wstr.append(chars, '\0');
+    MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, c_str,
+                        int(strlen(c_str)), const_cast<wchar_t *>(wstr.data()),
+                        chars);
+  }
+  return wstr;
+}
+
+#endif /* Windows */
+
+} // namespace
+
+//------------------------------------------------------------------------------
+
+namespace mdbx {
+
+[[noreturn]] __cold void throw_max_length_exceeded() {
+  throw std::length_error(
+      "mdbx:: exceeded the maximal length of data/slice/buffer");
+}
+
+[[noreturn]] __cold void throw_too_small_target_buffer() {
+  throw std::length_error("mdbx:: the target buffer is too small");
+}
+
+[[noreturn]] __cold void throw_out_range() {
+  throw std::out_of_range("mdbx:: slice or buffer method was called with "
+                          "an argument that exceeds the length");
+}
+
+__cold exception::exception(const ::mdbx::error &error) noexcept
+    : base(error.what()), error_(error) {}
+
+__cold exception::~exception() noexcept {}
+
+static std::atomic_int fatal_countdown;
+
+__cold fatal::fatal(const ::mdbx::error &error) noexcept : base(error) {
+  ++fatal_countdown;
+}
+
+__cold fatal::~fatal() noexcept {
+  if (--fatal_countdown == 0)
+    std::terminate();
+}
+
+#define DEFINE_EXCEPTION(NAME)                                                 \
+  __cold NAME::NAME(const ::mdbx::error &rc) : exception(rc) {}                \
+  __cold NAME::~NAME() noexcept {}
+
+DEFINE_EXCEPTION(bad_map_id)
+DEFINE_EXCEPTION(bad_transaction)
+DEFINE_EXCEPTION(bad_value_size)
+DEFINE_EXCEPTION(db_corrupted)
+DEFINE_EXCEPTION(db_full)
+DEFINE_EXCEPTION(db_invalid)
+DEFINE_EXCEPTION(db_too_large)
+DEFINE_EXCEPTION(db_unable_extend)
+DEFINE_EXCEPTION(db_version_mismatch)
+DEFINE_EXCEPTION(db_wanna_write_for_recovery)
+DEFINE_EXCEPTION(incompatible_operation)
+DEFINE_EXCEPTION(internal_page_full)
+DEFINE_EXCEPTION(internal_problem)
+DEFINE_EXCEPTION(key_exists)
+DEFINE_EXCEPTION(key_mismatch)
+DEFINE_EXCEPTION(max_maps_reached)
+DEFINE_EXCEPTION(max_readers_reached)
+DEFINE_EXCEPTION(multivalue)
+DEFINE_EXCEPTION(no_data)
+DEFINE_EXCEPTION(not_found)
+DEFINE_EXCEPTION(operation_not_permitted)
+DEFINE_EXCEPTION(permission_denied_or_not_writeable)
+DEFINE_EXCEPTION(reader_slot_busy)
+DEFINE_EXCEPTION(remote_media)
+DEFINE_EXCEPTION(something_busy)
+DEFINE_EXCEPTION(thread_mismatch)
+DEFINE_EXCEPTION(transaction_full)
+DEFINE_EXCEPTION(transaction_overlapping)
+
+#undef DEFINE_EXCEPTION
+
+__cold const char *error::what() const noexcept {
+  if (is_mdbx_error())
+    return mdbx_liberr2str(code());
+
+  switch (code()) {
+#define ERROR_CASE(CODE)                                                       \
+  case CODE:                                                                   \
+    return STRINGIFY(CODE)
+    ERROR_CASE(MDBX_ENODATA);
+    ERROR_CASE(MDBX_EINVAL);
+    ERROR_CASE(MDBX_EACCESS);
+    ERROR_CASE(MDBX_ENOMEM);
+    ERROR_CASE(MDBX_EROFS);
+    ERROR_CASE(MDBX_ENOSYS);
+    ERROR_CASE(MDBX_EIO);
+    ERROR_CASE(MDBX_EPERM);
+    ERROR_CASE(MDBX_EINTR);
+    ERROR_CASE(MDBX_ENOFILE);
+    ERROR_CASE(MDBX_EREMOTE);
+#undef ERROR_CASE
+  default:
+    return "SYSTEM";
+  }
+}
+
+__cold std::string error::message() const {
+  char buf[1024];
+  const char *msg = ::mdbx_strerror_r(code(), buf, sizeof(buf));
+  return std::string(msg ? msg : "unknown");
+}
+
+[[noreturn]] __cold void error::panic(const char *context,
+                                      const char *func) const noexcept {
+  assert(code() != MDBX_SUCCESS);
+  ::mdbx_panic("mdbx::%s.%s(): \"%s\" (%d)", context, func, what(), code());
+  std::terminate();
+}
+
+__cold void error::throw_exception() const {
+  switch (code()) {
+  case MDBX_EINVAL:
+    throw std::invalid_argument("mdbx");
+  case MDBX_ENOMEM:
+    throw std::bad_alloc();
+  case MDBX_SUCCESS:
+    static_assert(MDBX_SUCCESS == MDBX_RESULT_FALSE, "WTF?");
+    throw std::logic_error("MDBX_SUCCESS (MDBX_RESULT_FALSE)");
+  case MDBX_RESULT_TRUE:
+    throw std::logic_error("MDBX_RESULT_TRUE");
+#define CASE_EXCEPTION(NAME, CODE)                                             \
+  case CODE:                                                                   \
+    throw NAME(code())
+    CASE_EXCEPTION(bad_map_id, MDBX_BAD_DBI);
+    CASE_EXCEPTION(bad_transaction, MDBX_BAD_TXN);
+    CASE_EXCEPTION(bad_value_size, MDBX_BAD_VALSIZE);
+    CASE_EXCEPTION(db_corrupted, MDBX_CORRUPTED);
+    CASE_EXCEPTION(db_corrupted, MDBX_CURSOR_FULL); /* branch-pages loop */
+    CASE_EXCEPTION(db_corrupted, MDBX_PAGE_NOTFOUND);
+    CASE_EXCEPTION(db_full, MDBX_MAP_FULL);
+    CASE_EXCEPTION(db_invalid, MDBX_INVALID);
+    CASE_EXCEPTION(db_too_large, MDBX_TOO_LARGE);
+    CASE_EXCEPTION(db_unable_extend, MDBX_UNABLE_EXTEND_MAPSIZE);
+    CASE_EXCEPTION(db_version_mismatch, MDBX_VERSION_MISMATCH);
+    CASE_EXCEPTION(db_wanna_write_for_recovery, MDBX_WANNA_RECOVERY);
+    CASE_EXCEPTION(fatal, MDBX_EBADSIGN);
+    CASE_EXCEPTION(fatal, MDBX_PANIC);
+    CASE_EXCEPTION(incompatible_operation, MDBX_INCOMPATIBLE);
+    CASE_EXCEPTION(internal_page_full, MDBX_PAGE_FULL);
+    CASE_EXCEPTION(internal_problem, MDBX_PROBLEM);
+    CASE_EXCEPTION(key_mismatch, MDBX_EKEYMISMATCH);
+    CASE_EXCEPTION(max_maps_reached, MDBX_DBS_FULL);
+    CASE_EXCEPTION(max_readers_reached, MDBX_READERS_FULL);
+    CASE_EXCEPTION(multivalue, MDBX_EMULTIVAL);
+    CASE_EXCEPTION(no_data, MDBX_ENODATA);
+    CASE_EXCEPTION(not_found, MDBX_NOTFOUND);
+    CASE_EXCEPTION(operation_not_permitted, MDBX_EPERM);
+    CASE_EXCEPTION(permission_denied_or_not_writeable, MDBX_EACCESS);
+    CASE_EXCEPTION(reader_slot_busy, MDBX_BAD_RSLOT);
+    CASE_EXCEPTION(remote_media, MDBX_EREMOTE);
+    CASE_EXCEPTION(something_busy, MDBX_BUSY);
+    CASE_EXCEPTION(thread_mismatch, MDBX_THREAD_MISMATCH);
+    CASE_EXCEPTION(transaction_full, MDBX_TXN_FULL);
+    CASE_EXCEPTION(transaction_overlapping, MDBX_TXN_OVERLAPPING);
+#undef CASE_EXCEPTION
+  default:
+    if (is_mdbx_error())
+      throw exception(*this);
+    throw std::system_error(std::error_code(code(), std::system_category()));
+  }
+}
+
+//------------------------------------------------------------------------------
+
+bool slice::is_printable(bool disable_utf8) const noexcept {
+  enum : byte {
+    LS = 4,                     // shift for UTF8 sequence length
+    P_ = 1 << LS,               // printable ASCII flag
+    N_ = 0,                     // non-printable ASCII
+    second_range_mask = P_ - 1, // mask for range flag
+    r80_BF = 0,                 // flag for UTF8 2nd byte range
+    rA0_BF = 1,                 // flag for UTF8 2nd byte range
+    r80_9F = 2,                 // flag for UTF8 2nd byte range
+    r90_BF = 3,                 // flag for UTF8 2nd byte range
+    r80_8F = 4,                 // flag for UTF8 2nd byte range
+
+    // valid utf-8 byte sequences
+    // http://www.unicode.org/versions/Unicode6.0.0/ch03.pdf - page 94
+    //                        Code               | Bytes  |        |        |
+    //                        Points             | 1st    | 2nd    | 3rd    |4th
+    //                       --------------------|--------|--------|--------|---
+    C2 = 2 << LS | r80_BF, // U+000080..U+0007FF | C2..DF | 80..BF |        |
+    E0 = 3 << LS | rA0_BF, // U+000800..U+000FFF | E0     | A0..BF | 80..BF |
+    E1 = 3 << LS | r80_BF, // U+001000..U+00CFFF | E1..EC | 80..BF | 80..BF |
+    ED = 3 << LS | r80_9F, // U+00D000..U+00D7FF | ED     | 80..9F | 80..BF |
+    EE = 3 << LS | r80_BF, // U+00E000..U+00FFFF | EE..EF | 80..BF | 80..BF |
+    F0 = 4 << LS | r90_BF, // U+010000..U+03FFFF | F0     | 90..BF | 80..BF |...
+    F1 = 4 << LS | r80_BF, // U+040000..U+0FFFFF | F1..F3 | 80..BF | 80..BF |...
+    F4 = 4 << LS | r80_BF, // U+100000..U+10FFFF | F4     | 80..8F | 80..BF |...
+  };
+
+  static const byte range_from[] = {0x80, 0xA0, 0x80, 0x90, 0x80};
+  static const byte range_to[] = {0xBF, 0xBF, 0x9F, 0xBF, 0x8F};
+
+  static const byte map[256] = {
+      //  1   2   3   4   5   6   7   8   9   a   b   c   d   e   f
+      N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, // 00
+      N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, N_, // 10
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // 20
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // 30
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // 40
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // 50
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // 60
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, N_, // 70
+      N_, N_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, N_, P_, N_, // 80
+      N_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, N_, P_, P_, // 90
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // a0
+      P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, // b0
+      P_, P_, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, // c0
+      C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, C2, // df
+      E0, E1, E1, E1, E1, E1, E1, E1, E1, E1, E1, E1, E1, ED, EE, EE, // e0
+      F0, F1, F1, F1, F4, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_, P_  // f0
+  };
+
+  if (length() < 1)
+    return false;
+
+  auto src = byte_ptr();
+  const auto end = src + length();
+  if (MDBX_UNLIKELY(disable_utf8)) {
+    do
+      if (MDBX_UNLIKELY((P_ & map[*src]) == 0))
+        return false;
+    while (++src < end);
+    return true;
+  }
+
+  do {
+    const auto bits = map[*src];
+    const auto second_from = range_from[bits & second_range_mask];
+    const auto second_to = range_to[bits & second_range_mask];
+    switch (bits >> LS) {
+    default:
+      return false;
+    case 1:
+      src += 1;
+      continue;
+    case 2:
+      if (unlikely(src + 1 >= end))
+        return false;
+      if (unlikely(src[1] < second_from || src[1] > second_to))
+        return false;
+      src += 2;
+      continue;
+    case 3:
+      if (unlikely(src + 3 >= end))
+        return false;
+      if (unlikely(src[1] < second_from || src[1] > second_to))
+        return false;
+      if (unlikely(src[2] < 0x80 || src[2] > 0xBF))
+        return false;
+      src += 3;
+      continue;
+    case 4:
+      if (unlikely(src + 4 >= end))
+        return false;
+      if (unlikely(src[1] < second_from || src[1] > second_to))
+        return false;
+      if (unlikely(src[2] < 0x80 || src[2] > 0xBF))
+        return false;
+      if (unlikely(src[3] < 0x80 || src[3] > 0xBF))
+        return false;
+      src += 4;
+      continue;
+    }
+  } while (src < end);
+
+  return true;
+}
+
+//------------------------------------------------------------------------------
+
+char *slice::to_hex(char *__restrict dest, size_t dest_size, bool uppercase,
+                    unsigned wrap_width) const {
+  if (MDBX_UNLIKELY(to_hex_bytes(wrap_width) > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  const char alphabase = (uppercase ? 'A' : 'a') - 10;
+  auto line = dest;
+  for (const auto end = src + length(); src != end; ++src) {
+    const int8_t hi = *src >> 4;
+    const int8_t lo = *src & 15;
+    dest[0] = char(alphabase + hi + (((hi - 10) >> 7) & -7));
+    dest[1] = char(alphabase + lo + (((lo - 10) >> 7) & -7));
+    dest += 2;
+    if (wrap_width && size_t(dest - line) >= wrap_width) {
+      *dest = '\n';
+      line = ++dest;
+    }
+  }
+  return dest;
+}
+
+byte *slice::from_hex(byte *__restrict dest, size_t dest_size,
+                      bool ignore_spaces) const {
+  if (MDBX_UNLIKELY(length() % 2 && !ignore_spaces))
+    throw std::domain_error(
+        "mdbx::from_hex:: odd length of hexadecimal string");
+  if (MDBX_UNLIKELY(from_hex_bytes() > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(*src <= ' ') &&
+        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_UNLIKELY(left < 1 || !isxdigit(src[0]) || !isxdigit(src[1])))
+      throw std::domain_error("mdbx::from_hex:: invalid hexadecimal string");
+
+    int8_t hi = src[0];
+    hi = (hi | 0x20) - 'a';
+    hi += 10 + ((hi >> 7) & 7);
+
+    int8_t lo = src[1];
+    lo = (lo | 0x20) - 'a';
+    lo += 10 + ((lo >> 7) & 7);
+
+    *dest++ = hi << 4 | lo;
+    src += 2;
+    left -= 2;
+  }
+  return dest;
+}
+
+bool slice::is_hex(bool ignore_spaces) const noexcept {
+  if (MDBX_UNLIKELY(length() % 2 && !ignore_spaces))
+    return false;
+
+  bool got = false;
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(*src <= ' ') &&
+        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_UNLIKELY(left < 1 || !isxdigit(src[0]) || !isxdigit(src[1])))
+      return false;
+
+    got = true;
+    src += 2;
+    left -= 2;
+  }
+  return got;
+}
+
+//------------------------------------------------------------------------------
+
+enum : signed char {
+  OO /* ASCII NUL */ = -8,
+  EQ /* BASE64 '=' pad */ = -4,
+  SP /* SPACE */ = -2,
+  IL /* invalid */ = -1
+};
+
+static const byte b58_alphabet[58] = {
+    '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
+    'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
+    'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm',
+    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
+
+#ifndef bswap64
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+static inline uint64_t bswap64(uint64_t v) noexcept {
+#if __GNUC_PREREQ(4, 4) || __CLANG_PREREQ(4, 0) ||                             \
+    __has_builtin(__builtin_bswap64)
+  return __builtin_bswap64(v);
+#elif defined(_MSC_VER) && !defined(__clang__)
+  return _byteswap_uint64(v);
+#elif defined(__bswap_64)
+  return __bswap_64(v);
+#elif defined(bswap_64)
+  return bswap_64(v);
+#else
+  return v << 56 | v >> 56 | ((v << 40) & UINT64_C(0x00ff000000000000)) |
+         ((v << 24) & UINT64_C(0x0000ff0000000000)) |
+         ((v << 8) & UINT64_C(0x000000ff00000000)) |
+         ((v >> 8) & UINT64_C(0x00000000ff000000)) |
+         ((v >> 24) & UINT64_C(0x0000000000ff0000)) |
+         ((v >> 40) & UINT64_C(0x000000000000ff00));
+#endif
+}
+#endif /* __BYTE_ORDER__ */
+#endif /* ifdef bswap64 */
+
+static inline char b58_8to11(uint64_t &v) noexcept {
+  const unsigned i = unsigned(v % 58);
+  v /= 58;
+  return b58_alphabet[i];
+}
+
+char *slice::to_base58(char *__restrict dest, size_t dest_size,
+                       unsigned wrap_width) const {
+  if (MDBX_UNLIKELY(to_base58_bytes(wrap_width) > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  size_t left = length();
+  auto line = dest;
+  while (MDBX_LIKELY(left > 7)) {
+    left -= 8;
+    uint64_t v;
+    std::memcpy(&v, src, 8);
+    src += 8;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    v = bswap64(v);
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+    dest[10] = b58_8to11(v);
+    dest[9] = b58_8to11(v);
+    dest[8] = b58_8to11(v);
+    dest[7] = b58_8to11(v);
+    dest[6] = b58_8to11(v);
+    dest[5] = b58_8to11(v);
+    dest[4] = b58_8to11(v);
+    dest[3] = b58_8to11(v);
+    dest[2] = b58_8to11(v);
+    dest[1] = b58_8to11(v);
+    dest[0] = b58_8to11(v);
+    assert(v == 0);
+    dest += 11;
+    if (wrap_width && size_t(dest - line) >= wrap_width) {
+      *dest = '\n';
+      line = ++dest;
+    }
+  }
+
+  if (left) {
+    uint64_t v = 0;
+    unsigned parrots = 31;
+    do {
+      v = (v << 8) + *src++;
+      parrots += 43;
+    } while (--left);
+
+    auto ptr = dest += parrots >> 5;
+    do {
+      *--ptr = b58_8to11(v);
+      parrots -= 32;
+    } while (parrots > 31);
+    assert(v == 0);
+  }
+
+  return dest;
+}
+
+const signed char b58_map[256] = {
+    //   1   2   3   4   5   6   7   8   9   a   b   c   d   e   f
+    OO, IL, IL, IL, IL, IL, IL, IL, IL, SP, SP, SP, SP, SP, IL, IL, // 00
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 10
+    SP, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 20
+    IL, 0,  1,  2,  3,  4,  5,  6,  7,  8,  IL, IL, IL, IL, IL, IL, // 30
+    IL, 9,  10, 11, 12, 13, 14, 15, 16, IL, 17, 18, 19, 20, 21, IL, // 40
+    22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, IL, IL, IL, IL, IL, // 50
+    IL, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, IL, 44, 45, 46, // 60
+    47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, IL, IL, IL, IL, IL, // 70
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 80
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 90
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // a0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // b0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // c0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // d0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // e0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL  // f0
+};
+
+static inline signed char b58_11to8(uint64_t &v, const byte c) noexcept {
+  const signed char m = b58_map[c];
+  v = v * 58 + m;
+  return m;
+}
+
+byte *slice::from_base58(byte *__restrict dest, size_t dest_size,
+                         bool ignore_spaces) const {
+  if (MDBX_UNLIKELY(from_base58_bytes() > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(isspace(*src)) && ignore_spaces) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_LIKELY(left > 10)) {
+      uint64_t v = 0;
+      if (MDBX_UNLIKELY((b58_11to8(v, src[0]) | b58_11to8(v, src[1]) |
+                         b58_11to8(v, src[2]) | b58_11to8(v, src[3]) |
+                         b58_11to8(v, src[4]) | b58_11to8(v, src[5]) |
+                         b58_11to8(v, src[6]) | b58_11to8(v, src[7]) |
+                         b58_11to8(v, src[8]) | b58_11to8(v, src[9]) |
+                         b58_11to8(v, src[10])) < 0))
+        goto bailout;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+      v = bswap64(v);
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+      std::memcpy(dest, &v, 8);
+      dest += 8;
+      src += 11;
+      left -= 11;
+      continue;
+    }
+
+    constexpr unsigned invalid_length_mask = 1 << 1 | 1 << 4 | 1 << 8;
+    if (invalid_length_mask & (1 << left))
+      goto bailout;
+
+    uint64_t v = 1;
+    unsigned parrots = 0;
+    do {
+      if (MDBX_UNLIKELY(b58_11to8(v, *src++) < 0))
+        goto bailout;
+      parrots += 32;
+    } while (--left);
+
+    auto ptr = dest += parrots / 43;
+    do {
+      *--ptr = byte(v);
+      v >>= 8;
+    } while (v > 255);
+    break;
+  }
+  return dest;
+
+bailout:
+  throw std::domain_error("mdbx::from_base58:: invalid base58 string");
+}
+
+bool slice::is_base58(bool ignore_spaces) const noexcept {
+  bool got = false;
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(*src <= ' ') &&
+        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_LIKELY(left > 10)) {
+      if (MDBX_UNLIKELY((b58_map[src[0]] | b58_map[src[1]] | b58_map[src[2]] |
+                         b58_map[src[3]] | b58_map[src[4]] | b58_map[src[5]] |
+                         b58_map[src[6]] | b58_map[src[7]] | b58_map[src[8]] |
+                         b58_map[src[9]] | b58_map[src[10]]) < 0))
+        return false;
+      src += 11;
+      left -= 11;
+      got = true;
+      continue;
+    }
+
+    constexpr unsigned invalid_length_mask = 1 << 1 | 1 << 4 | 1 << 8;
+    if (invalid_length_mask & (1 << left))
+      return false;
+
+    do
+      if (MDBX_UNLIKELY(b58_map[*src++] < 0))
+        return false;
+    while (--left);
+    got = true;
+    break;
+  }
+  return got;
+}
+
+//------------------------------------------------------------------------------
+
+static inline void b64_3to4(const byte x, const byte y, const byte z,
+                            char *__restrict dest) noexcept {
+  static const byte alphabet[64] = {
+      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+      'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+      'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
+      'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
+  dest[0] = alphabet[(x & 0xfc) >> 2];
+  dest[1] = alphabet[((x & 0x03) << 4) + ((y & 0xf0) >> 4)];
+  dest[2] = alphabet[((y & 0x0f) << 2) + ((z & 0xc0) >> 6)];
+  dest[3] = alphabet[z & 0x3f];
+}
+
+char *slice::to_base64(char *__restrict dest, size_t dest_size,
+                       unsigned wrap_width) const {
+  if (MDBX_UNLIKELY(to_base64_bytes(wrap_width) > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  size_t left = length();
+  auto line = dest;
+  while (true) {
+    switch (left) {
+    default:
+      MDBX_CXX20_LIKELY left -= 3;
+      b64_3to4(src[0], src[1], src[2], dest);
+      dest += 4;
+      src += 3;
+      if (wrap_width && size_t(dest - line) >= wrap_width) {
+        *dest = '\n';
+        line = ++dest;
+      }
+      continue;
+    case 2:
+      b64_3to4(src[0], 0, 0, dest);
+      dest[2] = dest[3] = '=';
+      return dest + 4;
+    case 1:
+      b64_3to4(src[0], src[1], 0, dest);
+      dest[3] = '=';
+      return dest + 4;
+    case 0:
+      return dest;
+    }
+  }
+}
+
+static const signed char b64_map[256] = {
+    //   1   2   3   4   5   6   7   8   9   a   b   c   d   e   f
+    OO, IL, IL, IL, IL, IL, IL, IL, IL, SP, SP, SP, SP, SP, IL, IL, // 00
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 10
+    SP, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, 62, IL, IL, IL, 63, // 20
+    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, IL, IL, IL, EQ, IL, IL, // 30
+    IL, 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10, 11, 12, 13, 14, // 40
+    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, IL, IL, IL, IL, IL, // 50
+    IL, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, // 60
+    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, IL, IL, IL, IL, IL, // 70
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 80
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // 90
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // a0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // b0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // c0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // d0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, // e0
+    IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL  // f0
+};
+
+static inline signed char b64_4to3(signed char a, signed char b, signed char c,
+                                   signed char d,
+                                   byte *__restrict dest) noexcept {
+  dest[0] = byte((a << 2) + ((b & 0x30) >> 4));
+  dest[1] = byte(((b & 0xf) << 4) + ((c & 0x3c) >> 2));
+  dest[2] = byte(((c & 0x3) << 6) + d);
+  return a | b | c | d;
+}
+
+byte *slice::from_base64(byte *__restrict dest, size_t dest_size,
+                         bool ignore_spaces) const {
+  if (MDBX_UNLIKELY(length() % 4 && !ignore_spaces))
+    throw std::domain_error("mdbx::from_base64:: odd length of base64 string");
+  if (MDBX_UNLIKELY(from_base64_bytes() > dest_size))
+    throw_too_small_target_buffer();
+
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(*src <= ' ') &&
+        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_UNLIKELY(left < 3)) {
+    bailout:
+      throw std::domain_error("mdbx::from_base64:: invalid base64 string");
+    }
+    const signed char a = b64_map[src[0]], b = b64_map[src[1]],
+                      c = b64_map[src[2]], d = b64_map[src[3]];
+    if (MDBX_UNLIKELY(b64_4to3(a, b, c, d, dest) < 0)) {
+      if (left == 4 && (a | b) >= 0 && d == EQ) {
+        if (c >= 0)
+          return dest + 2;
+        if (c == d)
+          return dest + 1;
+      }
+      goto bailout;
+    }
+    src += 4;
+    left -= 4;
+  }
+  return dest;
+}
+
+bool slice::is_base64(bool ignore_spaces) const noexcept {
+  if (MDBX_UNLIKELY(length() % 4 && !ignore_spaces))
+    return false;
+
+  bool got = false;
+  auto src = byte_ptr();
+  for (auto left = length(); left > 0;) {
+    if (MDBX_UNLIKELY(*src <= ' ') &&
+        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
+      ++src;
+      --left;
+      continue;
+    }
+
+    if (MDBX_UNLIKELY(left < 3))
+      return false;
+    const signed char a = b64_map[src[0]], b = b64_map[src[1]],
+                      c = b64_map[src[2]], d = b64_map[src[3]];
+    if (MDBX_UNLIKELY((a | b | c | d) < 0)) {
+      if (left == 4 && (a | b) >= 0 && d == EQ && (c >= 0 || c == d))
+        return true;
+      return false;
+    }
+    got = true;
+    src += 4;
+    left -= 4;
+  }
+  return got;
+}
+
+//------------------------------------------------------------------------------
+
+template class LIBMDBX_API_TYPE buffer<legacy_allocator>;
+
+#if defined(__cpp_lib_memory_resource) && __cpp_lib_memory_resource >= 201603L
+template class LIBMDBX_API_TYPE buffer<polymorphic_allocator>;
+#endif /* __cpp_lib_memory_resource >= 201603L */
+
+//------------------------------------------------------------------------------
+
+static inline MDBX_env_flags_t mode2flags(env::mode mode) {
+  switch (mode) {
+  default:
+    MDBX_CXX20_UNLIKELY throw std::invalid_argument("db::mode is invalid");
+  case env::mode::readonly:
+    return MDBX_RDONLY;
+  case env::mode::write_file_io:
+    return MDBX_ENV_DEFAULTS;
+  case env::mode::write_mapped_io:
+    return MDBX_WRITEMAP;
+  }
+}
+
+__cold MDBX_env_flags_t
+env::operate_parameters::make_flags(bool accede, bool use_subdirectory) const {
+  MDBX_env_flags_t flags = mode2flags(mode);
+  if (accede)
+    flags |= MDBX_ACCEDE;
+  if (!use_subdirectory)
+    flags |= MDBX_NOSUBDIR;
+  if (options.exclusive)
+    flags |= MDBX_EXCLUSIVE;
+  if (options.orphan_read_transactions)
+    flags |= MDBX_NOTLS;
+  if (options.disable_readahead)
+    flags |= MDBX_NORDAHEAD;
+  if (options.disable_clear_memory)
+    flags |= MDBX_NOMEMINIT;
+
+  if (mode != readonly) {
+    if (options.nested_write_transactions)
+      flags &= ~MDBX_WRITEMAP;
+    if (reclaiming.coalesce)
+      flags |= MDBX_COALESCE;
+    if (reclaiming.lifo)
+      flags |= MDBX_LIFORECLAIM;
+    switch (durability) {
+    default:
+      MDBX_CXX20_UNLIKELY throw std::invalid_argument(
+          "db::durability is invalid");
+    case env::durability::robust_synchronous:
+      break;
+    case env::durability::half_synchronous_weak_last:
+      flags |= MDBX_NOMETASYNC;
+      break;
+    case env::durability::lazy_weak_tail:
+      static_assert(MDBX_MAPASYNC == MDBX_SAFE_NOSYNC, "WTF? Obsolete C API?");
+      flags |= MDBX_SAFE_NOSYNC;
+      break;
+    case env::durability::whole_fragile:
+      flags |= MDBX_UTTERLY_NOSYNC;
+      break;
+    }
+  }
+  return flags;
+}
+
+env::mode
+env::operate_parameters::mode_from_flags(MDBX_env_flags_t flags) noexcept {
+  if (flags & MDBX_RDONLY)
+    return env::mode::readonly;
+  return (flags & MDBX_WRITEMAP) ? env::mode::write_mapped_io
+                                 : env::mode::write_file_io;
+}
+
+env::durability env::operate_parameters::durability_from_flags(
+    MDBX_env_flags_t flags) noexcept {
+  if ((flags & MDBX_UTTERLY_NOSYNC) == MDBX_UTTERLY_NOSYNC)
+    return env::durability::whole_fragile;
+  if (flags & MDBX_SAFE_NOSYNC)
+    return env::durability::lazy_weak_tail;
+  if (flags & MDBX_NOMETASYNC)
+    return env::durability::half_synchronous_weak_last;
+  return env::durability::robust_synchronous;
+}
+
+env::reclaiming_options::reclaiming_options(MDBX_env_flags_t flags) noexcept
+    : lifo((flags & MDBX_LIFORECLAIM) ? true : false),
+      coalesce((flags & MDBX_COALESCE) ? true : false) {}
+
+env::operate_options::operate_options(MDBX_env_flags_t flags) noexcept
+    : orphan_read_transactions(
+          ((flags & (MDBX_NOTLS | MDBX_EXCLUSIVE)) == MDBX_NOTLS) ? true
+                                                                  : false),
+      nested_write_transactions((flags & (MDBX_WRITEMAP | MDBX_RDONLY)) ? false
+                                                                        : true),
+      exclusive((flags & MDBX_EXCLUSIVE) ? true : false),
+      disable_readahead((flags & MDBX_NORDAHEAD) ? true : false),
+      disable_clear_memory((flags & MDBX_NOMEMINIT) ? true : false) {}
+
+env::operate_parameters::operate_parameters(const env &env)
+    : max_maps(env.max_maps()), max_readers(env.max_readers()) {
+  const auto flags = env.get_flags();
+  mode = mode_from_flags(flags);
+  durability = durability_from_flags(flags);
+  reclaiming = reclaiming_from_flags(flags);
+  options = options_from_flags(flags);
+}
+
+bool env::is_pristine() const {
+  return get_stat().ms_mod_txnid == 0 &&
+         get_info().mi_recent_txnid == INITIAL_TXNID;
+}
+
+bool env::is_empty() const { return get_stat().ms_branch_pages == 0; }
+
+#ifdef MDBX_STD_FILESYSTEM_PATH
+env &env::copy(const ::std::filesystem::path &destination, bool compactify,
+               bool force_dynamic_size) {
+  const path_to_pchar<::std::filesystem::path> utf8(destination);
+  error::success_or_throw(
+      ::mdbx_env_copy(handle_, utf8,
+                      (compactify ? MDBX_CP_COMPACT : MDBX_CP_DEFAULTS) |
+                          (force_dynamic_size ? MDBX_CP_FORCE_DYNAMIC_SIZE
+                                              : MDBX_CP_DEFAULTS)));
+  return *this;
+}
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+
+#if defined(_WIN32) || defined(_WIN64)
+env &env::copy(const ::std::wstring &destination, bool compactify,
+               bool force_dynamic_size) {
+  const path_to_pchar<::std::wstring> utf8(destination);
+  error::success_or_throw(
+      ::mdbx_env_copy(handle_, utf8,
+                      (compactify ? MDBX_CP_COMPACT : MDBX_CP_DEFAULTS) |
+                          (force_dynamic_size ? MDBX_CP_FORCE_DYNAMIC_SIZE
+                                              : MDBX_CP_DEFAULTS)));
+  return *this;
+}
+#endif /* Windows */
+
+env &env::copy(const ::std::string &destination, bool compactify,
+               bool force_dynamic_size) {
+  const path_to_pchar<::std::string> utf8(destination);
+  error::success_or_throw(
+      ::mdbx_env_copy(handle_, utf8,
+                      (compactify ? MDBX_CP_COMPACT : MDBX_CP_DEFAULTS) |
+                          (force_dynamic_size ? MDBX_CP_FORCE_DYNAMIC_SIZE
+                                              : MDBX_CP_DEFAULTS)));
+  return *this;
+}
+
+env &env::copy(filehandle fd, bool compactify, bool force_dynamic_size) {
+  error::success_or_throw(
+      ::mdbx_env_copy2fd(handle_, fd,
+                         (compactify ? MDBX_CP_COMPACT : MDBX_CP_DEFAULTS) |
+                             (force_dynamic_size ? MDBX_CP_FORCE_DYNAMIC_SIZE
+                                                 : MDBX_CP_DEFAULTS)));
+  return *this;
+}
+
+path env::get_path() const {
+  const char *c_str;
+  error::success_or_throw(::mdbx_env_get_path(handle_, &c_str));
+  return pchar_to_path<path>(c_str);
+}
+
+#ifdef MDBX_STD_FILESYSTEM_PATH
+bool env::remove(const ::std::filesystem::path &pathname,
+                 const remove_mode mode) {
+  const path_to_pchar<::std::filesystem::path> utf8(pathname);
+  return error::boolean_or_throw(
+      ::mdbx_env_delete(utf8, MDBX_env_delete_mode_t(mode)));
+}
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+
+#if defined(_WIN32) || defined(_WIN64)
+bool env::remove(const ::std::wstring &pathname, const remove_mode mode) {
+  const path_to_pchar<::std::wstring> utf8(pathname);
+  return error::boolean_or_throw(
+      ::mdbx_env_delete(utf8, MDBX_env_delete_mode_t(mode)));
+}
+#endif /* Windows */
+
+bool env::remove(const ::std::string &pathname, const remove_mode mode) {
+  const path_to_pchar<::std::string> utf8(pathname);
+  return error::boolean_or_throw(
+      ::mdbx_env_delete(utf8, MDBX_env_delete_mode_t(mode)));
+}
+
+//------------------------------------------------------------------------------
+
+static inline MDBX_env *create_env() {
+  MDBX_env *ptr;
+  error::success_or_throw(::mdbx_env_create(&ptr));
+  assert(ptr != nullptr);
+  return ptr;
+}
+
+env_managed::~env_managed() noexcept {
+  if (handle_)
+    error::success_or_panic(::mdbx_env_close(handle_), "mdbx::~env()",
+                            "mdbx_env_close");
+}
+
+void env_managed::close(bool dont_sync) {
+  const error rc =
+      static_cast<MDBX_error_t>(::mdbx_env_close_ex(handle_, dont_sync));
+  switch (rc.code()) {
+  case MDBX_EBADSIGN:
+    handle_ = nullptr;
+    __fallthrough /* fall through */;
+  default:
+    rc.throw_exception();
+  case MDBX_SUCCESS:
+    handle_ = nullptr;
+  }
+}
+
+__cold void env_managed::setup(unsigned max_maps, unsigned max_readers) {
+  if (max_readers > 0)
+    error::success_or_throw(::mdbx_env_set_maxreaders(handle_, max_readers));
+  if (max_maps > 0)
+    error::success_or_throw(::mdbx_env_set_maxdbs(handle_, max_maps));
+}
+
+#ifdef MDBX_STD_FILESYSTEM_PATH
+__cold env_managed::env_managed(const ::std::filesystem::path &pathname,
+                                const operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::filesystem::path> utf8(pathname);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede), 0));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+
+__cold env_managed::env_managed(const ::std::filesystem::path &pathname,
+                                const env_managed::create_parameters &cp,
+                                const env::operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::filesystem::path> utf8(pathname);
+  set_geometry(cp.geometry);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede, cp.use_subdirectory),
+                      cp.file_mode_bits));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+
+#if defined(_WIN32) || defined(_WIN64)
+__cold env_managed::env_managed(const ::std::wstring &pathname,
+                                const operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::wstring> utf8(pathname);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede), 0));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+
+__cold env_managed::env_managed(const ::std::wstring &pathname,
+                                const env_managed::create_parameters &cp,
+                                const env::operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::wstring> utf8(pathname);
+  set_geometry(cp.geometry);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede, cp.use_subdirectory),
+                      cp.file_mode_bits));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+#endif /* Windows */
+
+__cold env_managed::env_managed(const ::std::string &pathname,
+                                const operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::string> utf8(pathname);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede), 0));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+
+__cold env_managed::env_managed(const ::std::string &pathname,
+                                const env_managed::create_parameters &cp,
+                                const env::operate_parameters &op, bool accede)
+    : env_managed(create_env()) {
+  setup(op.max_maps, op.max_readers);
+  const path_to_pchar<::std::string> utf8(pathname);
+  set_geometry(cp.geometry);
+  error::success_or_throw(
+      ::mdbx_env_open(handle_, utf8, op.make_flags(accede, cp.use_subdirectory),
+                      cp.file_mode_bits));
+
+  if (op.options.nested_write_transactions &&
+      !get_options().nested_write_transactions)
+    error::throw_exception(MDBX_INCOMPATIBLE);
+}
+
+//------------------------------------------------------------------------------
+
+txn_managed txn::start_nested() {
+  MDBX_txn *nested;
+  error::throw_on_nullptr(handle_, MDBX_BAD_TXN);
+  error::success_or_throw(::mdbx_txn_begin(mdbx_txn_env(handle_), handle_,
+                                           MDBX_TXN_READWRITE, &nested));
+  assert(nested != nullptr);
+  return txn_managed(nested);
+}
+
+txn_managed::~txn_managed() noexcept {
+  if (handle_)
+    error::success_or_panic(::mdbx_txn_abort(handle_), "mdbx::~txn",
+                            "mdbx_txn_abort");
+}
+
+void txn_managed::abort() {
+  const error err = static_cast<MDBX_error_t>(::mdbx_txn_abort(handle_));
+  if (MDBX_LIKELY(err.code() != MDBX_THREAD_MISMATCH))
+    handle_ = nullptr;
+  if (MDBX_UNLIKELY(err.code() != MDBX_SUCCESS))
+    err.throw_exception();
+}
+
+void txn_managed::commit() {
+  const error err = static_cast<MDBX_error_t>(::mdbx_txn_commit(handle_));
+  if (MDBX_LIKELY(err.code() != MDBX_THREAD_MISMATCH))
+    handle_ = nullptr;
+  if (MDBX_UNLIKELY(err.code() != MDBX_SUCCESS))
+    err.throw_exception();
+}
+
+//------------------------------------------------------------------------------
+
+bool txn::drop_map(const char *name, bool throw_if_absent) {
+  map_handle map;
+  const int err = ::mdbx_dbi_open(handle_, name, MDBX_DB_ACCEDE, &map.dbi);
+  switch (err) {
+  case MDBX_SUCCESS:
+    drop_map(map);
+    return true;
+  case MDBX_NOTFOUND:
+  case MDBX_BAD_DBI:
+    if (!throw_if_absent)
+      return false;
+    MDBX_CXX17_FALLTHROUGH /* fallthrough */;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+bool txn::clear_map(const char *name, bool throw_if_absent) {
+  map_handle map;
+  const int err = ::mdbx_dbi_open(handle_, name, MDBX_DB_ACCEDE, &map.dbi);
+  switch (err) {
+  case MDBX_SUCCESS:
+    clear_map(map);
+    return true;
+  case MDBX_NOTFOUND:
+  case MDBX_BAD_DBI:
+    if (!throw_if_absent)
+      return false;
+    MDBX_CXX17_FALLTHROUGH /* fallthrough */;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+//------------------------------------------------------------------------------
+
+void cursor_managed::close() {
+  if (MDBX_UNLIKELY(!handle_))
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  ::mdbx_cursor_close(handle_);
+  handle_ = nullptr;
+}
+
+//------------------------------------------------------------------------------
+
+__cold ::std::ostream &operator<<(::std::ostream &out, const slice &it) {
+  out << "{";
+  if (!it.is_valid())
+    out << "INVALID." << it.length();
+  else if (it.is_null())
+    out << "NULL";
+  else if (it.empty())
+    out << "EMPTY->" << it.data();
+  else {
+    const slice root(it.head(std::min(it.length(), size_t(64))));
+    out << it.length() << ".";
+    if (root.is_printable())
+      (out << "\"").write(root.char_ptr(), root.length()) << "\"";
+    else
+      out << root.base58_encode();
+    if (root.length() < it.length())
+      out << "...";
+  }
+  return out << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out, const pair &it) {
+  return out << "{" << it.key << " => " << it.value << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out, const pair_result &it) {
+  return out << "{" << (it.done ? "done: " : "non-done: ") << it.key << " => "
+             << it.value << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const ::mdbx::env::geometry::size &it) {
+  switch (it.bytes) {
+  case ::mdbx::env::geometry::default_value:
+    return out << "default";
+  case ::mdbx::env::geometry::minimal_value:
+    return out << "minimal";
+  case ::mdbx::env::geometry::maximal_value:
+    return out << "maximal";
+  }
+
+  const auto bytes = (it.bytes < 0) ? out << "-",
+             size_t(-it.bytes) : size_t(it.bytes);
+  struct {
+    size_t one;
+    const char *suffix;
+  } static const scales[] = {
+#if MDBX_WORDBITS > 32
+    {env_managed::geometry::EiB, "EiB"},
+    {env_managed::geometry::EB, "EB"},
+    {env_managed::geometry::PiB, "PiB"},
+    {env_managed::geometry::PB, "PB"},
+    {env_managed::geometry::TiB, "TiB"},
+    {env_managed::geometry::TB, "TB"},
+#endif
+    {env_managed::geometry::GiB, "GiB"},
+    {env_managed::geometry::GB, "GB"},
+    {env_managed::geometry::MiB, "MiB"},
+    {env_managed::geometry::MB, "MB"},
+    {env_managed::geometry::KiB, "KiB"},
+    {env_managed::geometry::kB, "kB"},
+    {1, " bytes"}
+  };
+
+  for (const auto i : scales)
+    if (bytes % i.one == 0)
+      return out << bytes / i.one << i.suffix;
+
+  assert(false);
+  __unreachable();
+  return out;
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env::geometry &it) {
+  return                                                                //
+      out << "\tlower " << env::geometry::size(it.size_lower)           //
+          << ",\n\tnow " << env::geometry::size(it.size_now)            //
+          << ",\n\tupper " << env::geometry::size(it.size_upper)        //
+          << ",\n\tgrowth " << env::geometry::size(it.growth_step)      //
+          << ",\n\tshrink " << env::geometry::size(it.shrink_threshold) //
+          << ",\n\tpagesize " << env::geometry::size(it.pagesize) << "\n";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env::operate_parameters &it) {
+  return out << "{\n"                                 //
+             << "\tmax_maps " << it.max_maps          //
+             << ",\n\tmax_readers " << it.max_readers //
+             << ",\n\tmode " << it.mode               //
+             << ",\n\tdurability " << it.durability   //
+             << ",\n\treclaiming " << it.reclaiming   //
+             << ",\n\toptions " << it.options         //
+             << "\n}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out, const env::mode &it) {
+  switch (it) {
+  case env::mode::readonly:
+    return out << "readonly";
+  case env::mode::write_file_io:
+    return out << "write_file_io";
+  case env::mode::write_mapped_io:
+    return out << "write_mapped_io";
+  default:
+    return out << "mdbx::env::mode::invalid";
+  }
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env::durability &it) {
+  switch (it) {
+  case env::durability::robust_synchronous:
+    return out << "robust_synchronous";
+  case env::durability::half_synchronous_weak_last:
+    return out << "half_synchronous_weak_last";
+  case env::durability::lazy_weak_tail:
+    return out << "lazy_weak_tail";
+  case env::durability::whole_fragile:
+    return out << "whole_fragile";
+  default:
+    return out << "mdbx::env::durability::invalid";
+  }
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env::reclaiming_options &it) {
+  return out << "{"                                            //
+             << "lifo: " << (it.lifo ? "yes" : "no")           //
+             << ", coalesce: " << (it.coalesce ? "yes" : "no") //
+             << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env::operate_options &it) {
+  static const char comma[] = ", ";
+  const char *delimiter = "";
+  out << "{";
+  if (it.orphan_read_transactions) {
+    out << delimiter << "orphan_read_transactions";
+    delimiter = comma;
+  }
+  if (it.nested_write_transactions) {
+    out << delimiter << "nested_write_transactions";
+    delimiter = comma;
+  }
+  if (it.exclusive) {
+    out << delimiter << "exclusive";
+    delimiter = comma;
+  }
+  if (it.disable_readahead) {
+    out << delimiter << "disable_readahead";
+    delimiter = comma;
+  }
+  if (it.disable_clear_memory) {
+    out << delimiter << "disable_clear_memory";
+    delimiter = comma;
+  }
+  if (delimiter != comma)
+    out << "default";
+  return out << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const env_managed::create_parameters &it) {
+  return out << "{\n"                                                        //
+             << "\tfile_mode " << std::oct << it.file_mode_bits << std::dec  //
+             << ",\n\tsubdirectory " << (it.use_subdirectory ? "yes" : "no") //
+             << ",\n"
+             << it.geometry << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const MDBX_log_level_t &it) {
+  switch (it) {
+  case MDBX_LOG_FATAL:
+    return out << "LOG_FATAL";
+  case MDBX_LOG_ERROR:
+    return out << "LOG_ERROR";
+  case MDBX_LOG_WARN:
+    return out << "LOG_WARN";
+  case MDBX_LOG_NOTICE:
+    return out << "LOG_NOTICE";
+  case MDBX_LOG_VERBOSE:
+    return out << "LOG_VERBOSE";
+  case MDBX_LOG_DEBUG:
+    return out << "LOG_DEBUG";
+  case MDBX_LOG_TRACE:
+    return out << "LOG_TRACE";
+  case MDBX_LOG_EXTRA:
+    return out << "LOG_EXTRA";
+  case MDBX_LOG_DONTCHANGE:
+    return out << "LOG_DONTCHANGE";
+  default:
+    return out << "mdbx::log_level::invalid";
+  }
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const MDBX_debug_flags_t &it) {
+  if (it == MDBX_DBG_DONTCHANGE)
+    return out << "DBG_DONTCHANGE";
+
+  static const char comma[] = "|";
+  const char *delimiter = "";
+  out << "{";
+  if (it & MDBX_DBG_ASSERT) {
+    out << delimiter << "DBG_ASSERT";
+    delimiter = comma;
+  }
+  if (it & MDBX_DBG_AUDIT) {
+    out << delimiter << "DBG_AUDIT";
+    delimiter = comma;
+  }
+  if (it & MDBX_DBG_JITTER) {
+    out << delimiter << "DBG_JITTER";
+    delimiter = comma;
+  }
+  if (it & MDBX_DBG_DUMP) {
+    out << delimiter << "DBG_DUMP";
+    delimiter = comma;
+  }
+  if (it & MDBX_DBG_LEGACY_MULTIOPEN) {
+    out << delimiter << "DBG_LEGACY_MULTIOPEN";
+    delimiter = comma;
+  }
+  if (it & MDBX_DBG_LEGACY_OVERLAP) {
+    out << delimiter << "DBG_LEGACY_OVERLAP";
+    delimiter = comma;
+  }
+  if (delimiter != comma)
+    out << "DBG_NONE";
+  return out << "}";
+}
+
+__cold ::std::ostream &operator<<(::std::ostream &out,
+                                  const ::mdbx::error &err) {
+  return out << err.what() << " (" << long(err.code()) << ")";
+}
+
+} // namespace mdbx
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx.h b/plugins/Dbx_mdbx/src/libmdbx/mdbx.h
new file mode 100644
index 0000000000..9d7dba99e9
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.h
@@ -0,0 +1,5017 @@
+/**
+
+_libmdbx_ is an extremely fast, compact, powerful, embedded,
+transactional [key-value
+store](https://en.wikipedia.org/wiki/Key-value_database) database, with
+[permissive license](./LICENSE). _MDBX_ has a specific set of properties and
+capabilities, focused on creating unique lightweight solutions with
+extraordinary performance.
+
+_libmdbx_ is superior to [LMDB](https://bit.ly/26ts7tL) in terms of features
+and reliability, not inferior in performance. In comparison to LMDB, _libmdbx_
+makes many things just work perfectly, not silently and catastrophically
+break down. _libmdbx_ supports Linux, Windows, MacOS, OSX, iOS, Android,
+FreeBSD, DragonFly, Solaris, OpenSolaris, OpenIndiana, NetBSD, OpenBSD and other
+systems compliant with POSIX.1-2008.
+
+_The Future will (be) [Positive](https://www.ptsecurity.com). Всё будет хорошо._
+
+
+\section copyright LICENSE & COPYRIGHT
+
+\authors Copyright (c) 2015-2021, Leonid Yuriev <leo@yuriev.ru>
+and other _libmdbx_ authors: please see [AUTHORS](./AUTHORS) file.
+
+\copyright Redistribution and use in source and binary forms, with or without
+modification, are permitted only as authorized by the OpenLDAP Public License.
+
+A copy of this license is available in the file LICENSE in the
+top-level directory of the distribution or, alternatively, at
+<http://www.OpenLDAP.org/license.html>.
+
+ ---
+
+This code is derived from "LMDB engine" written by
+Howard Chu (Symas Corporation), which itself derived from btree.c
+written by Martin Hedenfalk.
+
+ ---
+
+Portions Copyright 2011-2015 Howard Chu, Symas Corp. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted only as authorized by the OpenLDAP
+Public License.
+
+A copy of this license is available in the file LICENSE in the
+top-level directory of the distribution or, alternatively, at
+<http://www.OpenLDAP.org/license.html>.
+
+ ---
+
+Portions Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+*******************************************************************************/
+
+#pragma once
+#ifndef LIBMDBX_H
+#define LIBMDBX_H
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/**
+ \file mdbx.h
+ \brief The libmdbx C API header file
+
+ \defgroup c_api C API
+ @{
+ \defgroup c_err Error handling
+ \defgroup c_opening Opening & Closing
+ \defgroup c_transactions Transactions
+ \defgroup c_dbi Databases
+ \defgroup c_crud Create/Read/Update/Delete (see Quick Reference in details)
+
+ \details
+ \anchor c_crud_hints
+# Quick Reference for Insert/Update/Delete operations
+
+Historically, libmdbx inherits the API basis from LMDB, where it is often
+difficult to select flags/options and functions for the desired operation.
+So it is recommend using this hints.
+
+## Databases with UNIQUE keys
+
+In databases created without the \ref MDBX_DUPSORT option, keys are always
+unique. Thus always a single value corresponds to the each key, and so there
+are only a few cases of changing data.
+
+| Case                                        | Flags to use        | Result                 |
+|---------------------------------------------|---------------------|------------------------|
+| _INSERTING_|||
+|Key is absent → Insertion                    |\ref MDBX_NOOVERWRITE|Insertion               |
+|Key exist → Error since key present          |\ref MDBX_NOOVERWRITE|Error \ref MDBX_KEYEXIST and return Present value|
+| _UPSERTING_|||
+|Key is absent → Insertion                    |\ref MDBX_UPSERT     |Insertion               |
+|Key exist → Update                           |\ref MDBX_UPSERT     |Update                  |
+|  _UPDATING_|||
+|Key is absent → Error since no such key      |\ref MDBX_CURRENT    |Error \ref MDBX_NOTFOUND|
+|Key exist → Update                           |\ref MDBX_CURRENT    |Update value            |
+| _DELETING_|||
+|Key is absent → Error since no such key      |\ref mdbx_del() or \ref mdbx_replace()|Error \ref MDBX_NOTFOUND|
+|Key exist → Delete by key                    |\ref mdbx_del() with the parameter `data = NULL`|Deletion|
+|Key exist → Delete by key with with data matching check|\ref mdbx_del() with the parameter `data` filled with the value which should be match for deletion|Deletion or \ref MDBX_NOTFOUND if the value does not match|
+|Delete at the current cursor position        |\ref mdbx_cursor_del() with \ref MDBX_CURRENT flag|Deletion|
+|Extract (read & delete) value by the key     |\ref mdbx_replace() with zero flag and parameter `new_data = NULL`|Returning a deleted value|
+
+
+## Databases with NON-UNIQUE keys
+
+In databases created with the \ref MDBX_DUPSORT (Sorted Duplicates) option, keys
+may be non unique. Such non-unique keys in a key-value database may be treated
+as a duplicates or as like a multiple values corresponds to keys.
+
+
+| Case                                        | Flags to use        | Result                 |
+|---------------------------------------------|---------------------|------------------------|
+| _INSERTING_|||
+|Key is absent → Insertion                    |\ref MDBX_NOOVERWRITE|Insertion|
+|Key exist → Needn't to add new values        |\ref MDBX_NOOVERWRITE|Error \ref MDBX_KEYEXIST with returning the first value from those already present|
+| _UPSERTING_|||
+|Key is absent → Insertion                    |\ref MDBX_UPSERT     |Insertion|
+|Key exist → Wanna to add new values          |\ref MDBX_UPSERT     |Add one more value to the key|
+|Key exist → Replace all values with a new one|\ref MDBX_UPSERT + \ref MDBX_ALLDUPS|Overwrite by single new value|
+|  _UPDATING_|||
+|Key is absent → Error since no such key      |\ref MDBX_CURRENT    |Error \ref MDBX_NOTFOUND|
+|Key exist, Single value → Update             |\ref MDBX_CURRENT    |Update single value    |
+|Key exist, Multiple values → Replace all values with a new one|\ref MDBX_CURRENT + \ref MDBX_ALLDUPS|Overwrite by single new value|
+|Key exist, Multiple values → Error since it is unclear which of the values should be updated|\ref mdbx_put() with \ref MDBX_CURRENT|Error \ref MDBX_EMULTIVAL|
+|Key exist, Multiple values → Update particular entry of multi-value|\ref mdbx_replace() with \ref MDBX_CURRENT + \ref MDBX_NOOVERWRITE and the parameter `old_value` filled with the value that wanna to update|Update one multi-value entry|
+|Key exist, Multiple values → Update the current entry of multi-value|\ref mdbx_cursor_put() with \ref MDBX_CURRENT|Update one multi-value entry|
+| _DELETING_|||
+|Key is absent → Error since no such key      |\ref mdbx_del() or \ref mdbx_replace()|Error \ref MDBX_NOTFOUND|
+|Key exist → Delete all values corresponds given key|\ref mdbx_del() with the parameter `data = NULL`|Deletion|
+|Key exist → Delete particular value corresponds given key|\ref mdbx_del() with the parameter `data` filled with the value that wanna to delete, or \ref mdbx_replace() with \ref MDBX_CURRENT + \ref MDBX_NOOVERWRITE and the `old_value` parameter filled with the value that wanna to delete and `new_data = NULL`| Deletion or \ref MDBX_NOTFOUND if no such key-value pair|
+|Delete one value at the current cursor position|\ref mdbx_cursor_del() with \ref MDBX_CURRENT flag|Deletion only the current entry|
+|Delete all values of key at the current cursor position|\ref mdbx_cursor_del() with with \ref MDBX_ALLDUPS flag|Deletion all duplicates of key (all multi-values) at the current cursor position|
+
+ \defgroup c_cursors Cursors
+ \defgroup c_statinfo Statistics & Information
+ \defgroup c_settings Settings
+ \defgroup c_debug Logging and runtime debug
+ \defgroup c_rqest Range query estimation
+ \defgroup c_extra Extra operations
+*/
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(_WIN32) || defined(_WIN64)
+#include <windows.h>
+#include <winnt.h>
+#ifndef __mode_t_defined
+typedef unsigned short mdbx_mode_t;
+#else
+typedef mode_t mdbx_mode_t;
+#endif /* __mode_t_defined */
+typedef HANDLE mdbx_filehandle_t;
+typedef DWORD mdbx_pid_t;
+typedef DWORD mdbx_tid_t;
+#else                  /* Windows */
+#include <errno.h>     /* for error codes */
+#include <pthread.h>   /* for pthread_t */
+#include <sys/types.h> /* for pid_t */
+#include <sys/uio.h>   /* for struct iovec */
+#define HAVE_STRUCT_IOVEC 1
+typedef int mdbx_filehandle_t;
+typedef pid_t mdbx_pid_t;
+typedef pthread_t mdbx_tid_t;
+typedef mode_t mdbx_mode_t;
+#endif /* !Windows */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+/** @} close c_api
+ * \defgroup api_macros Common Macros
+ * @{ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __has_attribute
+#define __has_attribute(x) (0)
+#endif /* __has_attribute */
+
+#ifndef __has_cpp_attribute
+#define __has_cpp_attribute(x) 0
+#endif /* __has_cpp_attribute */
+
+#ifndef __has_feature
+#define __has_feature(x) (0)
+#endif /* __has_feature */
+
+#ifndef __has_extension
+#define __has_extension(x) (0)
+#endif /* __has_extension */
+
+#ifndef __has_builtin
+#define __has_builtin(x) (0)
+#endif /* __has_builtin */
+
+/** Many functions have no effects except the return value and their
+ * return value depends only on the parameters and/or global variables.
+ * Such a function can be subject to common subexpression elimination
+ * and loop optimization just as an arithmetic operator would be.
+ * These functions should be declared with the attribute pure. */
+#if (defined(__GNUC__) || __has_attribute(__pure__)) &&                        \
+    (!defined(__clang__) /* https://bugs.llvm.org/show_bug.cgi?id=43275 */     \
+     || !defined(__cplusplus) || !__has_feature(cxx_exceptions))
+#define MDBX_PURE_FUNCTION __attribute__((__pure__))
+#elif defined(_MSC_VER) && !defined(__clang__) && _MSC_VER >= 1920
+#define MDBX_PURE_FUNCTION
+#elif defined(__cplusplus) && __has_cpp_attribute(gnu::pure) &&                \
+    (!defined(__clang__) || !__has_feature(cxx_exceptions))
+#define MDBX_PURE_FUNCTION [[gnu::pure]]
+#else
+#define MDBX_PURE_FUNCTION
+#endif /* MDBX_PURE_FUNCTION */
+
+/** Like \ref MDBX_PURE_FUNCTION with addition `noexcept` restriction
+ * that is compatible to CLANG and proposed [[pure]]. */
+#if defined(__GNUC__) ||                                                       \
+    (__has_attribute(__pure__) && __has_attribute(__nothrow__))
+#define MDBX_NOTHROW_PURE_FUNCTION __attribute__((__pure__, __nothrow__))
+#elif defined(_MSC_VER) && !defined(__clang__) && _MSC_VER >= 1920
+#if __has_cpp_attribute(pure)
+#define MDBX_NOTHROW_PURE_FUNCTION [[pure]]
+#else
+#define MDBX_NOTHROW_PURE_FUNCTION
+#endif
+#elif defined(__cplusplus) && __has_cpp_attribute(gnu::pure)
+#if __has_cpp_attribute(gnu::nothrow)
+#define MDBX_NOTHROW_PURE_FUNCTION [[gnu::pure, gnu::nothrow]]
+#else
+#define MDBX_NOTHROW_PURE_FUNCTION [[gnu::pure]]
+#endif
+#elif defined(__cplusplus) && __has_cpp_attribute(pure)
+#define MDBX_NOTHROW_PURE_FUNCTION [[pure]]
+#else
+#define MDBX_NOTHROW_PURE_FUNCTION
+#endif /* MDBX_NOTHROW_PURE_FUNCTION */
+
+/** Many functions do not examine any values except their arguments,
+ * and have no effects except the return value. Basically this is just
+ * slightly more strict class than the PURE attribute, since function
+ * is not allowed to read global memory.
+ *
+ * Note that a function that has pointer arguments and examines the
+ * data pointed to must not be declared const. Likewise, a function
+ * that calls a non-const function usually must not be const.
+ * It does not make sense for a const function to return void. */
+#if (defined(__GNUC__) || __has_attribute(__pure__)) &&                        \
+    (!defined(__clang__) /* https://bugs.llvm.org/show_bug.cgi?id=43275 */     \
+     || !defined(__cplusplus) || !__has_feature(cxx_exceptions))
+#define MDBX_CONST_FUNCTION __attribute__((__const__))
+#elif defined(_MSC_VER) && !defined(__clang__) && _MSC_VER >= 1920
+#define MDBX_CONST_FUNCTION MDBX_PURE_FUNCTION
+#elif defined(__cplusplus) && __has_cpp_attribute(gnu::const) &&               \
+    (!defined(__clang__) || !__has_feature(cxx_exceptions))
+#define MDBX_CONST_FUNCTION [[gnu::const]]
+#else
+#define MDBX_CONST_FUNCTION MDBX_PURE_FUNCTION
+#endif /* MDBX_CONST_FUNCTION */
+
+/** Like \ref MDBX_CONST_FUNCTION with addition `noexcept` restriction
+ * that is compatible to CLANG and future [[const]]. */
+#if defined(__GNUC__) ||                                                       \
+    (__has_attribute(__const__) && __has_attribute(__nothrow__))
+#define MDBX_NOTHROW_CONST_FUNCTION __attribute__((__const__, __nothrow__))
+#elif defined(_MSC_VER) && !defined(__clang__) && _MSC_VER >= 1920
+#define MDBX_NOTHROW_CONST_FUNCTION MDBX_NOTHROW_PURE_FUNCTION
+#elif defined(__cplusplus) && __has_cpp_attribute(gnu::const)
+#if __has_cpp_attribute(gnu::nothrow)
+#define MDBX_NOTHROW_PURE_FUNCTION [[gnu::const, gnu::nothrow]]
+#else
+#define MDBX_NOTHROW_PURE_FUNCTION [[gnu::const]]
+#endif
+#elif defined(__cplusplus) && __has_cpp_attribute(const)
+#define MDBX_NOTHROW_CONST_FUNCTION [[const]]
+#else
+#define MDBX_NOTHROW_CONST_FUNCTION MDBX_NOTHROW_PURE_FUNCTION
+#endif /* MDBX_NOTHROW_CONST_FUNCTION */
+
+#ifndef MDBX_DEPRECATED /* may be predefined to avoid warnings "deprecated" */
+#ifdef __deprecated
+#define MDBX_DEPRECATED __deprecated
+#elif defined(__GNUC__) || __has_attribute(__deprecated__)
+#define MDBX_DEPRECATED __attribute__((__deprecated__))
+#elif defined(_MSC_VER)
+#define MDBX_DEPRECATED __declspec(deprecated)
+#else
+#define MDBX_DEPRECATED
+#endif
+#endif /* MDBX_DEPRECATED */
+
+#ifndef __dll_export
+#if defined(_WIN32) || defined(__CYGWIN__)
+#if defined(__GNUC__) || __has_attribute(__dllexport__)
+#define __dll_export __attribute__((__dllexport__))
+#elif defined(_MSC_VER)
+#define __dll_export __declspec(dllexport)
+#else
+#define __dll_export
+#endif
+#elif defined(__GNUC__) || __has_attribute(__visibility__)
+#define __dll_export __attribute__((__visibility__("default")))
+#else
+#define __dll_export
+#endif
+#endif /* __dll_export */
+
+#ifndef __dll_import
+#if defined(_WIN32) || defined(__CYGWIN__)
+#if defined(__GNUC__) || __has_attribute(__dllimport__)
+#define __dll_import __attribute__((__dllimport__))
+#elif defined(_MSC_VER)
+#define __dll_import __declspec(dllimport)
+#else
+#define __dll_import
+#endif
+#else
+#define __dll_import
+#endif
+#endif /* __dll_import */
+
+/** \brief Auxiliary macro for robustly define the both inline version of API
+ * function and non-inline fallback dll-exported version for applications linked
+ * with old version of libmdbx, with a strictly ODR-common implementation. */
+#if !defined(LIBMDBX_INTERNALS)
+#define LIBMDBX_INLINE_API(TYPE, NAME, ARGS) static __inline TYPE NAME ARGS
+#else
+#define LIBMDBX_INLINE_API(TYPE, NAME, ARGS)                                   \
+  /* proto of exported which uses common impl */ LIBMDBX_API TYPE NAME ARGS;   \
+  /* definition of common impl */ static __inline TYPE __inline_##NAME ARGS
+#endif /* LIBMDBX_INLINE_API */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __cplusplus
+#ifndef bool
+#define bool _Bool
+#endif
+#ifndef true
+#define true (1)
+#endif
+#ifndef false
+#define false (0)
+#endif
+#endif /* bool without __cplusplus */
+
+#if !defined(DOXYGEN) && (!defined(__cpp_noexcept_function_type) ||            \
+                          __cpp_noexcept_function_type < 201510L)
+#define MDBX_CXX17_NOEXCEPT
+#else
+#define MDBX_CXX17_NOEXCEPT noexcept
+#endif /* MDBX_CXX17_NOEXCEPT */
+
+/* Workaround for old compilers without properly support for constexpr. */
+#if !defined(__cplusplus)
+#define MDBX_CXX01_CONSTEXPR __inline
+#define MDBX_CXX01_CONSTEXPR_VAR const
+#elif !defined(DOXYGEN) &&                                                     \
+    (!defined(__cpp_constexpr) || __cpp_constexpr < 200704L ||                 \
+     (defined(__LCC__) && __LCC__ < 124) ||                                    \
+     (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 407) &&          \
+      !defined(__clang__) && !defined(__LCC__)) ||                             \
+     (defined(_MSC_VER) && _MSC_VER < 1910) ||                                 \
+     (defined(__clang__) && __clang_major__ < 4))
+#define MDBX_CXX01_CONSTEXPR inline
+#define MDBX_CXX01_CONSTEXPR_VAR const
+#else
+#define MDBX_CXX01_CONSTEXPR constexpr
+#define MDBX_CXX01_CONSTEXPR_VAR constexpr
+#endif /* MDBX_CXX01_CONSTEXPR */
+
+#if !defined(__cplusplus)
+#define MDBX_CXX11_CONSTEXPR __inline
+#define MDBX_CXX11_CONSTEXPR_VAR const
+#elif !defined(DOXYGEN) &&                                                     \
+    (!defined(__cpp_constexpr) || __cpp_constexpr < 201304 ||                  \
+     (defined(__LCC__) && __LCC__ < 124) ||                                    \
+     (defined(__GNUC__) && __GNUC__ < 6 && !defined(__clang__) &&              \
+      !defined(__LCC__)) ||                                                    \
+     (defined(_MSC_VER) && _MSC_VER < 1910) ||                                 \
+     (defined(__clang__) && __clang_major__ < 5))
+#define MDBX_CXX11_CONSTEXPR inline
+#define MDBX_CXX11_CONSTEXPR_VAR const
+#else
+#define MDBX_CXX11_CONSTEXPR constexpr
+#define MDBX_CXX11_CONSTEXPR_VAR constexpr
+#endif /* MDBX_CXX11_CONSTEXPR */
+
+#if !defined(__cplusplus)
+#define MDBX_CXX14_CONSTEXPR __inline
+#define MDBX_CXX14_CONSTEXPR_VAR const
+#elif defined(DOXYGEN) ||                                                      \
+    defined(__cpp_constexpr) && __cpp_constexpr >= 201304L &&                  \
+        ((defined(_MSC_VER) && _MSC_VER >= 1910) ||                            \
+         (defined(__clang__) && __clang_major__ > 4) ||                        \
+         (defined(__GNUC__) && __GNUC__ > 6) ||                                \
+         (!defined(__GNUC__) && !defined(__clang__) && !defined(_MSC_VER)))
+#define MDBX_CXX14_CONSTEXPR constexpr
+#define MDBX_CXX14_CONSTEXPR_VAR constexpr
+#else
+#define MDBX_CXX14_CONSTEXPR inline
+#define MDBX_CXX14_CONSTEXPR_VAR const
+#endif /* MDBX_CXX14_CONSTEXPR */
+
+#if defined(__noreturn)
+#define MDBX_NORETURN __noreturn
+#elif defined(_Noreturn)
+#define MDBX_NORETURN _Noreturn
+#elif defined(__GNUC__) || __has_attribute(__noreturn__)
+#define MDBX_NORETURN __attribute__((__noreturn__))
+#elif defined(_MSC_VER) && !defined(__clang__)
+#define MDBX_NORETURN __declspec(noreturn)
+#else
+#define MDBX_NORETURN
+#endif /* MDBX_NORETURN */
+
+#ifndef MDBX_PRINTF_ARGS
+#if defined(__GNUC__) || __has_attribute(__format__)
+#define MDBX_PRINTF_ARGS(format_index, first_arg)                              \
+  __attribute__((__format__(__printf__, format_index, first_arg)))
+#else
+#define MDBX_PRINTF_ARGS(format_index, first_arg)
+#endif
+#endif /* MDBX_PRINTF_ARGS */
+
+/* Oh, below are some songs and dances since:
+ *  - C++ requires explicit definition of the necessary operators.
+ *  - the proper implementation of DEFINE_ENUM_FLAG_OPERATORS for C++ required
+ *    the constexpr feature which is broken in most old compilers;
+ *  - DEFINE_ENUM_FLAG_OPERATORS may be defined broken as in the Windows SDK. */
+#ifndef DEFINE_ENUM_FLAG_OPERATORS
+
+#ifdef __cplusplus
+#if !defined(__cpp_constexpr) || __cpp_constexpr < 200704L ||                  \
+    (defined(__LCC__) && __LCC__ < 124) ||                                     \
+    (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 407) &&           \
+     !defined(__clang__) && !defined(__LCC__)) ||                              \
+    (defined(_MSC_VER) && _MSC_VER < 1910) ||                                  \
+    (defined(__clang__) && __clang_major__ < 4)
+/* The constexpr feature is not available or (may be) broken */
+#define CONSTEXPR_ENUM_FLAGS_OPERATIONS 0
+#else
+/* C always allows these operators for enums */
+#define CONSTEXPR_ENUM_FLAGS_OPERATIONS 1
+#endif /* __cpp_constexpr */
+
+/// Define operator overloads to enable bit operations on enum values that are
+/// used to define flags (based on Microsoft's DEFINE_ENUM_FLAG_OPERATORS).
+#define DEFINE_ENUM_FLAG_OPERATORS(ENUM)                                       \
+  extern "C++" {                                                               \
+  MDBX_CXX01_CONSTEXPR ENUM operator|(ENUM a, ENUM b) {                        \
+    return ENUM(unsigned(a) | unsigned(b));                                    \
+  }                                                                            \
+  MDBX_CXX14_CONSTEXPR ENUM &operator|=(ENUM &a, ENUM b) { return a = a | b; } \
+  MDBX_CXX01_CONSTEXPR ENUM operator&(ENUM a, ENUM b) {                        \
+    return ENUM(unsigned(a) & unsigned(b));                                    \
+  }                                                                            \
+  MDBX_CXX01_CONSTEXPR ENUM operator&(ENUM a, unsigned b) {                    \
+    return ENUM(unsigned(a) & b);                                              \
+  }                                                                            \
+  MDBX_CXX01_CONSTEXPR ENUM operator&(unsigned a, ENUM b) {                    \
+    return ENUM(a & unsigned(b));                                              \
+  }                                                                            \
+  MDBX_CXX14_CONSTEXPR ENUM &operator&=(ENUM &a, ENUM b) { return a = a & b; } \
+  MDBX_CXX14_CONSTEXPR ENUM &operator&=(ENUM &a, unsigned b) {                 \
+    return a = a & b;                                                          \
+  }                                                                            \
+  MDBX_CXX01_CONSTEXPR unsigned operator~(ENUM a) { return ~unsigned(a); }     \
+  MDBX_CXX01_CONSTEXPR ENUM operator^(ENUM a, ENUM b) {                        \
+    return ENUM(unsigned(a) ^ unsigned(b));                                    \
+  }                                                                            \
+  MDBX_CXX14_CONSTEXPR ENUM &operator^=(ENUM &a, ENUM b) { return a = a ^ b; } \
+  }
+#else /* __cplusplus */
+/* nope for C since it always allows these operators for enums */
+#define DEFINE_ENUM_FLAG_OPERATORS(ENUM)
+#define CONSTEXPR_ENUM_FLAGS_OPERATIONS 1
+#endif /* !__cplusplus */
+
+#elif !defined(CONSTEXPR_ENUM_FLAGS_OPERATIONS)
+
+#ifdef __cplusplus
+/* DEFINE_ENUM_FLAG_OPERATORS may be defined broken as in the Windows SDK */
+#define CONSTEXPR_ENUM_FLAGS_OPERATIONS 0
+#else
+/* C always allows these operators for enums */
+#define CONSTEXPR_ENUM_FLAGS_OPERATIONS 1
+#endif
+
+#endif /* DEFINE_ENUM_FLAG_OPERATORS */
+
+/** @} end of Common Macros */
+
+/*----------------------------------------------------------------------------*/
+
+/** \addtogroup c_api
+ * @{ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* MDBX version 0.9.x */
+#define MDBX_VERSION_MAJOR 0
+#define MDBX_VERSION_MINOR 9
+
+#ifndef LIBMDBX_API
+#if defined(LIBMDBX_EXPORTS)
+#define LIBMDBX_API __dll_export
+#elif defined(LIBMDBX_IMPORTS)
+#define LIBMDBX_API __dll_import
+#else
+#define LIBMDBX_API
+#endif
+#endif /* LIBMDBX_API */
+
+#ifdef __cplusplus
+#if defined(__clang__) || __has_attribute(type_visibility)
+#define LIBMDBX_API_TYPE LIBMDBX_API __attribute__((type_visibility("default")))
+#else
+#define LIBMDBX_API_TYPE LIBMDBX_API
+#endif
+#else
+#define LIBMDBX_API_TYPE
+#endif /* LIBMDBX_API_TYPE */
+
+#if defined(LIBMDBX_IMPORTS)
+#define LIBMDBX_VERINFO_API __dll_import
+#else
+#define LIBMDBX_VERINFO_API __dll_export
+#endif /* LIBMDBX_VERINFO_API */
+
+/** \brief libmdbx version information */
+extern LIBMDBX_VERINFO_API const struct MDBX_version_info {
+  uint8_t major;     /**< Major version number */
+  uint8_t minor;     /**< Minor version number */
+  uint16_t release;  /**< Release number of Major.Minor */
+  uint32_t revision; /**< Revision number of Release */
+  struct {
+    const char *datetime; /**< committer date, strict ISO-8601 format */
+    const char *tree;     /**< commit hash (hexadecimal digits) */
+    const char *commit;   /**< tree hash, i.e. digest of the source code */
+    const char *describe; /**< git-describe string */
+  } git;                  /**< source information from git */
+  const char *sourcery;   /**< sourcery anchor for pinning */
+} /** \brief libmdbx version information */ mdbx_version;
+
+/** \brief libmdbx build information
+ * \attention Some strings could be NULL in case no corresponding information
+ *            was provided at build time (i.e. flags). */
+extern LIBMDBX_VERINFO_API const struct MDBX_build_info {
+  const char *datetime; /**< build timestamp (ISO-8601 or __DATE__ __TIME__) */
+  const char *target;   /**< cpu/arch-system-config triplet */
+  const char *options;  /**< mdbx-related options */
+  const char *compiler; /**< compiler */
+  const char *flags;    /**< CFLAGS and CXXFLAGS */
+} /** \brief libmdbx build information */ mdbx_build;
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !MDBX_BUILD_SHARED_LIBRARY
+
+/* MDBX internally uses global and thread local storage destructors to
+ * automatically (de)initialization, releasing reader lock table slots
+ * and so on.
+ *
+ * If MDBX builded as a DLL this is done out-of-the-box by DllEntry() function,
+ * which called automatically by Windows core with passing corresponding reason
+ * argument.
+ *
+ * Otherwise, if MDBX was builded not as a DLL, some black magic
+ * may be required depending of Windows version:
+ *  - Modern Windows versions, including Windows Vista and later, provides
+ *    support for "TLS Directory" (e.g .CRT$XL[A-Z] sections in executable
+ *    or dll file). In this case, MDBX capable of doing all automatically,
+ *    and you do not need to call mdbx_dll_handler().
+ *  - Obsolete versions of Windows, prior to Windows Vista, REQUIRES calling
+ *    mdbx_dll_handler() manually from corresponding DllMain() or WinMain()
+ *    of your DLL or application.
+ *  - This behavior is under control of the MODX_CONFIG_MANUAL_TLS_CALLBACK
+ *    option, which is determined by default according to the target version
+ *    of Windows at build time.
+ *    But you may override MODX_CONFIG_MANUAL_TLS_CALLBACK in special cases.
+ *
+ * Therefore, building MDBX as a DLL is recommended for all version of Windows.
+ * So, if you doubt, just build MDBX as the separate DLL and don't worry. */
+
+#ifndef MDBX_CONFIG_MANUAL_TLS_CALLBACK
+#if defined(_WIN32_WINNT_VISTA) && WINVER >= _WIN32_WINNT_VISTA
+/* As described above mdbx_dll_handler() is NOT needed forWindows Vista
+ * and later. */
+#define MDBX_CONFIG_MANUAL_TLS_CALLBACK 0
+#else
+/* As described above mdbx_dll_handler() IS REQUIRED for Windows versions
+ * prior to Windows Vista. */
+#define MDBX_CONFIG_MANUAL_TLS_CALLBACK 1
+#endif
+#endif /* MDBX_CONFIG_MANUAL_TLS_CALLBACK */
+
+#if MDBX_CONFIG_MANUAL_TLS_CALLBACK
+void LIBMDBX_API NTAPI mdbx_dll_handler(PVOID module, DWORD reason,
+                                        PVOID reserved);
+#endif /* MDBX_CONFIG_MANUAL_TLS_CALLBACK */
+#endif /* !MDBX_BUILD_SHARED_LIBRARY */
+#endif /* Windows */
+
+/* OPACITY STRUCTURES *********************************************************/
+
+/** \brief Opaque structure for a database environment.
+ * \details An environment supports multiple key-value sub-databases (aka
+ * key-value spaces or tables), all residing in the same shared-memory map.
+ * \see mdbx_env_create() \see mdbx_env_close() */
+#ifndef __cplusplus
+typedef struct MDBX_env MDBX_env;
+#else
+struct MDBX_env;
+#endif
+
+/** \brief Opaque structure for a transaction handle.
+ * \ingroup c_transactions
+ * \details All database operations require a transaction handle. Transactions
+ * may be read-only or read-write.
+ * \see mdbx_txn_begin() \see mdbx_txn_commit() \see mdbx_txn_abort() */
+#ifndef __cplusplus
+typedef struct MDBX_txn MDBX_txn;
+#else
+struct MDBX_txn;
+#endif
+
+/** \brief A handle for an individual database (key-value spaces) in the
+ * environment. \ingroup c_dbi \details Zero handle is used internally (hidden
+ * Garbage Collection DB). So, any valid DBI-handle great than 0 and less than
+ * or equal \ref MDBX_MAX_DBI. \see mdbx_dbi_open() \see mdbx_dbi_close() */
+typedef uint32_t MDBX_dbi;
+
+/** \brief Opaque structure for navigating through a database
+ * \ingroup c_cursors
+ * \see mdbx_cursor_create() \see mdbx_cursor_bind() \see mdbx_cursor_close()
+ */
+#ifndef __cplusplus
+typedef struct MDBX_cursor MDBX_cursor;
+#else
+struct MDBX_cursor;
+#endif
+
+/** \brief Generic structure used for passing keys and data in and out of the
+ * database.
+ * \anchor MDBX_val \see mdbx::slice \see mdbx::buffer
+ *
+ * \details Values returned from the database are valid only until a subsequent
+ * update operation, or the end of the transaction. Do not modify or
+ * free them, they commonly point into the database itself.
+ *
+ * Key sizes must be between 0 and \ref mdbx_env_get_maxkeysize() inclusive.
+ * The same applies to data sizes in databases with the \ref MDBX_DUPSORT flag.
+ * Other data items can in theory be from 0 to \ref MDBX_MAXDATASIZE bytes long.
+ *
+ * \note The notable difference between MDBX and LMDB is that MDBX support zero
+ * length keys. */
+#ifndef HAVE_STRUCT_IOVEC
+struct iovec {
+  void *iov_base; /**< pointer to some data */
+  size_t iov_len; /**< the length of data in bytes */
+};
+#define HAVE_STRUCT_IOVEC
+#endif /* HAVE_STRUCT_IOVEC */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+/* The `iov_len` is signed on Sun/Solaris.
+ * So define custom MDBX_val to avoid a lot of warnings. */
+struct MDBX_val {
+  void *iov_base; /**< pointer to some data */
+  size_t iov_len; /**< the length of data in bytes */
+};
+#ifndef __cplusplus
+typedef struct MDBX_val MDBX_val;
+#endif
+#else  /* SunOS */
+typedef struct iovec MDBX_val;
+#endif /* ! SunOS */
+
+enum MDBX_constants {
+  /** The hard limit for DBI handles */
+  MDBX_MAX_DBI = UINT32_C(32765),
+
+  /** The maximum size of a data item. */
+  MDBX_MAXDATASIZE = UINT32_C(0x7fff0000),
+
+  /** The minimal database page size in bytes. */
+  MDBX_MIN_PAGESIZE = 256,
+
+  /** The maximal database page size in bytes. */
+  MDBX_MAX_PAGESIZE = 65536,
+};
+
+/* THE FILES *******************************************************************
+ * At the file system level, the environment corresponds to a pair of files. */
+
+/** \brief The name of the lock file in the environment */
+#define MDBX_LOCKNAME "/mdbx.lck"
+/** \brief The name of the data file in the environment */
+#define MDBX_DATANAME "/mdbx.dat"
+
+/** \brief The suffix of the lock file when \ref MDBX_NOSUBDIR is used */
+#define MDBX_LOCK_SUFFIX "-lck"
+
+/* DEBUG & LOGGING ************************************************************/
+
+/** \addtogroup c_debug
+ * \note Most of debug feature enabled only when libmdbx builded with
+ * \ref MDBX_DEBUG build option. @{ */
+
+/** Log level (requires build libmdbx with \ref MDBX_DEBUG option) */
+enum MDBX_log_level_t {
+  /** Critical conditions, i.e. assertion failures */
+  MDBX_LOG_FATAL = 0,
+
+  /** Enables logging for error conditions and \ref MDBX_LOG_FATAL */
+  MDBX_LOG_ERROR = 1,
+
+  /** Enables logging for warning conditions and \ref MDBX_LOG_ERROR ...
+      \ref MDBX_LOG_FATAL */
+  MDBX_LOG_WARN = 2,
+
+  /** Enables logging for normal but significant condition and
+      \ref MDBX_LOG_WARN ... \ref MDBX_LOG_FATAL */
+  MDBX_LOG_NOTICE = 3,
+
+  /** Enables logging for verbose informational and \ref MDBX_LOG_NOTICE ...
+      \ref MDBX_LOG_FATAL */
+  MDBX_LOG_VERBOSE = 4,
+
+  /** Enables logging for debug-level messages and \ref MDBX_LOG_VERBOSE ...
+      \ref MDBX_LOG_FATAL */
+  MDBX_LOG_DEBUG = 5,
+
+  /** Enables logging for trace debug-level messages and \ref MDBX_LOG_DEBUG ...
+      \ref MDBX_LOG_FATAL */
+  MDBX_LOG_TRACE = 6,
+
+  /** Enables extra debug-level messages (dump pgno lists)
+      and all other log-messages */
+  MDBX_LOG_EXTRA = 7,
+
+  /** for \ref mdbx_setup_debug() only: Don't change current settings */
+  MDBX_LOG_DONTCHANGE = -1
+};
+#ifndef __cplusplus
+typedef enum MDBX_log_level_t MDBX_log_level_t;
+#endif
+
+/** \brief Runtime debug flags
+ *
+ * \details `MDBX_DBG_DUMP` and `MDBX_DBG_LEGACY_MULTIOPEN` always have an
+ * effect, but `MDBX_DBG_ASSERT`, `MDBX_DBG_AUDIT` and `MDBX_DBG_JITTER` only if
+ * libmdbx builded with \ref MDBX_DEBUG. */
+enum MDBX_debug_flags_t {
+  /** Enable assertion checks.
+   * Requires build with \ref MDBX_DEBUG > 0 */
+  MDBX_DBG_ASSERT = 1,
+
+  /** Enable pages usage audit at commit transactions.
+   * Requires build with \ref MDBX_DEBUG > 0 */
+  MDBX_DBG_AUDIT = 2,
+
+  /** Enable small random delays in critical points.
+   * Requires build with \ref MDBX_DEBUG > 0 */
+  MDBX_DBG_JITTER = 4,
+
+  /** Include or not meta-pages in coredump files.
+   * May affect performance in \ref MDBX_WRITEMAP mode */
+  MDBX_DBG_DUMP = 8,
+
+  /** Allow multi-opening environment(s) */
+  MDBX_DBG_LEGACY_MULTIOPEN = 16,
+
+  /** Allow read and write transactions overlapping for the same thread */
+  MDBX_DBG_LEGACY_OVERLAP = 32,
+
+  /** for mdbx_setup_debug() only: Don't change current settings */
+  MDBX_DBG_DONTCHANGE = -1
+};
+#ifndef __cplusplus
+typedef enum MDBX_debug_flags_t MDBX_debug_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_debug_flags_t)
+#endif
+
+/** \brief A debug-logger callback function,
+ * called before printing the message and aborting.
+ * \see mdbx_setup_debug()
+ *
+ * \param [in] env  An environment handle returned by \ref mdbx_env_create().
+ * \param [in] msg  The assertion message, not including newline. */
+typedef void MDBX_debug_func(MDBX_log_level_t loglevel, const char *function,
+                             int line, const char *fmt,
+                             va_list args) MDBX_CXX17_NOEXCEPT;
+
+/** \brief The "don't change `logger`" value for mdbx_setup_debug() */
+#define MDBX_LOGGER_DONTCHANGE ((MDBX_debug_func *)(intptr_t)-1)
+
+/** \brief Setup global log-level, debug options and debug logger.
+ * \returns The previously `debug_flags` in the 0-15 bits
+ *          and `log_level` in the 16-31 bits. */
+LIBMDBX_API int mdbx_setup_debug(MDBX_log_level_t log_level,
+                                 MDBX_debug_flags_t debug_flags,
+                                 MDBX_debug_func *logger);
+
+/** \brief A callback function for most MDBX assert() failures,
+ * called before printing the message and aborting.
+ * \see mdbx_env_set_assert()
+ *
+ * \param [in] env  An environment handle returned by mdbx_env_create().
+ * \param [in] msg  The assertion message, not including newline. */
+typedef void MDBX_assert_func(const MDBX_env *env, const char *msg,
+                              const char *function,
+                              unsigned line) MDBX_CXX17_NOEXCEPT;
+
+/** \brief Set or reset the assert() callback of the environment.
+ *
+ * Does nothing if libmdbx was built with MDBX_DEBUG=0 or with NDEBUG,
+ * and will return `MDBX_ENOSYS` in such case.
+ *
+ * \param [in] env   An environment handle returned by mdbx_env_create().
+ * \param [in] func  An MDBX_assert_func function, or 0.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func);
+
+/** \brief Dump given MDBX_val to the buffer
+ *
+ * Dumps it as string if value is printable (all bytes in the range 0x20..0x7E),
+ * otherwise made hexadecimal dump. Requires at least 4 byte length buffer.
+ *
+ * \returns One of:
+ *  - NULL if given buffer size less than 4 bytes;
+ *  - pointer to constant string if given value NULL or empty;
+ *  - otherwise pointer to given buffer. */
+LIBMDBX_API const char *mdbx_dump_val(const MDBX_val *key, char *const buf,
+                                      const size_t bufsize);
+
+/** \brief Panics with message and causes abnormal process termination. */
+LIBMDBX_API void mdbx_panic(const char *fmt, ...) MDBX_PRINTF_ARGS(1, 2);
+
+/** @} end of logging & debug */
+
+/** \brief Environment flags
+ * \ingroup c_opening
+ * \anchor env_flags
+ * \see mdbx_env_open() \see mdbx_env_set_flags() */
+enum MDBX_env_flags_t {
+  MDBX_ENV_DEFAULTS = 0,
+
+  /** No environment directory.
+   *
+   * By default, MDBX creates its environment in a directory whose pathname is
+   * given in path, and creates its data and lock files under that directory.
+   * With this option, path is used as-is for the database main data file.
+   * The database lock file is the path with "-lck" appended.
+   *
+   * - with `MDBX_NOSUBDIR` = in a filesystem we have the pair of MDBX-files
+   *   which names derived from given pathname by appending predefined suffixes.
+   *
+   * - without `MDBX_NOSUBDIR` = in a filesystem we have the MDBX-directory with
+   *   given pathname, within that a pair of MDBX-files with predefined names.
+   *
+   * This flag affects only at new environment creating by \ref mdbx_env_open(),
+   * otherwise at opening an existing environment libmdbx will choice this
+   * automatically. */
+  MDBX_NOSUBDIR = UINT32_C(0x4000),
+
+  /** Read only mode.
+   *
+   * Open the environment in read-only mode. No write operations will be
+   * allowed. MDBX will still modify the lock file - except on read-only
+   * filesystems, where MDBX does not use locks.
+   *
+   * - with `MDBX_RDONLY` = open environment in read-only mode.
+   *   MDBX supports pure read-only mode (i.e. without opening LCK-file) only
+   *   when environment directory and/or both files are not writable (and the
+   *   LCK-file may be missing). In such case allowing file(s) to be placed
+   *   on a network read-only share.
+   *
+   * - without `MDBX_RDONLY` = open environment in read-write mode.
+   *
+   * This flag affects only at environment opening but can't be changed after.
+   */
+  MDBX_RDONLY = UINT32_C(0x20000),
+
+  /** Open environment in exclusive/monopolistic mode.
+   *
+   * `MDBX_EXCLUSIVE` flag can be used as a replacement for `MDB_NOLOCK`,
+   * which don't supported by MDBX.
+   * In this way, you can get the minimal overhead, but with the correct
+   * multi-process and multi-thread locking.
+   *
+   * - with `MDBX_EXCLUSIVE` = open environment in exclusive/monopolistic mode
+   *   or return \ref MDBX_BUSY if environment already used by other process.
+   *   The main feature of the exclusive mode is the ability to open the
+   *   environment placed on a network share.
+   *
+   * - without `MDBX_EXCLUSIVE` = open environment in cooperative mode,
+   *   i.e. for multi-process access/interaction/cooperation.
+   *   The main requirements of the cooperative mode are:
+   *
+   *   1. data files MUST be placed in the LOCAL file system,
+   *      but NOT on a network share.
+   *   2. environment MUST be opened only by LOCAL processes,
+   *      but NOT over a network.
+   *   3. OS kernel (i.e. file system and memory mapping implementation) and
+   *      all processes that open the given environment MUST be running
+   *      in the physically single RAM with cache-coherency. The only
+   *      exception for cache-consistency requirement is Linux on MIPS
+   *      architecture, but this case has not been tested for a long time).
+   *
+   * This flag affects only at environment opening but can't be changed after.
+   */
+  MDBX_EXCLUSIVE = UINT32_C(0x400000),
+
+  /** Using database/environment which already opened by another process(es).
+   *
+   * The `MDBX_ACCEDE` flag is useful to avoid \ref MDBX_INCOMPATIBLE error
+   * while opening the database/environment which is already used by another
+   * process(es) with unknown mode/flags. In such cases, if there is a
+   * difference in the specified flags (\ref MDBX_NOMETASYNC,
+   * \ref MDBX_SAFE_NOSYNC, \ref MDBX_UTTERLY_NOSYNC, \ref MDBX_LIFORECLAIM,
+   * \ref MDBX_COALESCE and \ref MDBX_NORDAHEAD), instead of returning an error,
+   * the database will be opened in a compatibility with the already used mode.
+   *
+   * `MDBX_ACCEDE` has no effect if the current process is the only one either
+   * opening the DB in read-only mode or other process(es) uses the DB in
+   * read-only mode. */
+  MDBX_ACCEDE = UINT32_C(0x40000000),
+
+  /** Map data into memory with write permission.
+   *
+   * Use a writeable memory map unless \ref MDBX_RDONLY is set. This uses fewer
+   * mallocs and requires much less work for tracking database pages, but
+   * loses protection from application bugs like wild pointer writes and other
+   * bad updates into the database. This may be slightly faster for DBs that
+   * fit entirely in RAM, but is slower for DBs larger than RAM. Also adds the
+   * possibility for stray application writes thru pointers to silently
+   * corrupt the database.
+   *
+   * - with `MDBX_WRITEMAP` = all data will be mapped into memory in the
+   *   read-write mode. This offers a significant performance benefit, since the
+   *   data will be modified directly in mapped memory and then flushed to disk
+   *   by single system call, without any memory management nor copying.
+   *
+   * - without `MDBX_WRITEMAP` = data will be mapped into memory in the
+   *   read-only mode. This requires stocking all modified database pages in
+   *   memory and then writing them to disk through file operations.
+   *
+   * \warning On the other hand, `MDBX_WRITEMAP` adds the possibility for stray
+   * application writes thru pointers to silently corrupt the database.
+   *
+   * \note The `MDBX_WRITEMAP` mode is incompatible with nested transactions,
+   * since this is unreasonable. I.e. nested transactions requires mallocation
+   * of database pages and more work for tracking ones, which neuters a
+   * performance boost caused by the `MDBX_WRITEMAP` mode.
+   *
+   * This flag affects only at environment opening but can't be changed after.
+   */
+  MDBX_WRITEMAP = UINT32_C(0x80000),
+
+  /** Tie reader locktable slots to read-only transactions
+   * instead of to threads.
+   *
+   * Don't use Thread-Local Storage, instead tie reader locktable slots to
+   * \ref MDBX_txn objects instead of to threads. So, \ref mdbx_txn_reset()
+   * keeps the slot reserved for the \ref MDBX_txn object. A thread may use
+   * parallel read-only transactions. And a read-only transaction may span
+   * threads if you synchronizes its use.
+   *
+   * Applications that multiplex many user threads over individual OS threads
+   * need this option. Such an application must also serialize the write
+   * transactions in an OS thread, since MDBX's write locking is unaware of
+   * the user threads.
+   *
+   * \note Regardless to `MDBX_NOTLS` flag a write transaction entirely should
+   * always be used in one thread from start to finish. MDBX checks this in a
+   * reasonable manner and return the \ref MDBX_THREAD_MISMATCH error in rules
+   * violation.
+   *
+   * This flag affects only at environment opening but can't be changed after.
+   */
+  MDBX_NOTLS = UINT32_C(0x200000),
+
+  /** Don't do readahead.
+   *
+   * Turn off readahead. Most operating systems perform readahead on read
+   * requests by default. This option turns it off if the OS supports it.
+   * Turning it off may help random read performance when the DB is larger
+   * than RAM and system RAM is full.
+   *
+   * By default libmdbx dynamically enables/disables readahead depending on
+   * the actual database size and currently available memory. On the other
+   * hand, such automation has some limitation, i.e. could be performed only
+   * when DB size changing but can't tracks and reacts changing a free RAM
+   * availability, since it changes independently and asynchronously.
+   *
+   * \note The mdbx_is_readahead_reasonable() function allows to quickly find
+   * out whether to use readahead or not based on the size of the data and the
+   * amount of available memory.
+   *
+   * This flag affects only at environment opening and can't be changed after.
+   */
+  MDBX_NORDAHEAD = UINT32_C(0x800000),
+
+  /** Don't initialize malloc'd memory before writing to datafile.
+   *
+   * Don't initialize malloc'd memory before writing to unused spaces in the
+   * data file. By default, memory for pages written to the data file is
+   * obtained using malloc. While these pages may be reused in subsequent
+   * transactions, freshly malloc'd pages will be initialized to zeroes before
+   * use. This avoids persisting leftover data from other code (that used the
+   * heap and subsequently freed the memory) into the data file.
+   *
+   * Note that many other system libraries may allocate and free memory from
+   * the heap for arbitrary uses. E.g., stdio may use the heap for file I/O
+   * buffers. This initialization step has a modest performance cost so some
+   * applications may want to disable it using this flag. This option can be a
+   * problem for applications which handle sensitive data like passwords, and
+   * it makes memory checkers like Valgrind noisy. This flag is not needed
+   * with \ref MDBX_WRITEMAP, which writes directly to the mmap instead of using
+   * malloc for pages. The initialization is also skipped if \ref MDBX_RESERVE
+   * is used; the caller is expected to overwrite all of the memory that was
+   * reserved in that case.
+   *
+   * This flag may be changed at any time using `mdbx_env_set_flags()`. */
+  MDBX_NOMEMINIT = UINT32_C(0x1000000),
+
+  /** Aims to coalesce a Garbage Collection items.
+   *
+   * With `MDBX_COALESCE` flag MDBX will aims to coalesce items while recycling
+   * a Garbage Collection. Technically, when possible short lists of pages
+   * will be combined into longer ones, but to fit on one database page. As a
+   * result, there will be fewer items in Garbage Collection and a page lists
+   * are longer, which slightly increases the likelihood of returning pages to
+   * Unallocated space and reducing the database file.
+   *
+   * This flag may be changed at any time using mdbx_env_set_flags(). */
+  MDBX_COALESCE = UINT32_C(0x2000000),
+
+  /** LIFO policy for recycling a Garbage Collection items.
+   *
+   * `MDBX_LIFORECLAIM` flag turns on LIFO policy for recycling a Garbage
+   * Collection items, instead of FIFO by default. On systems with a disk
+   * write-back cache, this can significantly increase write performance, up
+   * to several times in a best case scenario.
+   *
+   * LIFO recycling policy means that for reuse pages will be taken which became
+   * unused the lastest (i.e. just now or most recently). Therefore the loop of
+   * database pages circulation becomes as short as possible. In other words,
+   * the number of pages, that are overwritten in memory and on disk during a
+   * series of write transactions, will be as small as possible. Thus creates
+   * ideal conditions for the efficient operation of the disk write-back cache.
+   *
+   * \ref MDBX_LIFORECLAIM is compatible with all no-sync flags, but gives NO
+   * noticeable impact in combination with \ref MDBX_SAFE_NOSYNC or
+   * \ref MDBX_UTTERLY_NOSYNC. Because MDBX will reused pages only before the
+   * last "steady" MVCC-snapshot, i.e. the loop length of database pages
+   * circulation will be mostly defined by frequency of calling
+   * \ref mdbx_env_sync() rather than LIFO and FIFO difference.
+   *
+   * This flag may be changed at any time using mdbx_env_set_flags(). */
+  MDBX_LIFORECLAIM = UINT32_C(0x4000000),
+
+  /** Debugging option, fill/perturb released pages. */
+  MDBX_PAGEPERTURB = UINT32_C(0x8000000),
+
+  /* SYNC MODES****************************************************************/
+  /** \defgroup sync_modes SYNC MODES
+   *
+   * \attention Using any combination of \ref MDBX_SAFE_NOSYNC, \ref
+   * MDBX_NOMETASYNC and especially \ref MDBX_UTTERLY_NOSYNC is always a deal to
+   * reduce durability for gain write performance. You must know exactly what
+   * you are doing and what risks you are taking!
+   *
+   * \note for LMDB users: \ref MDBX_SAFE_NOSYNC is NOT similar to LMDB_NOSYNC,
+   * but \ref MDBX_UTTERLY_NOSYNC is exactly match LMDB_NOSYNC. See details
+   * below.
+   *
+   * THE SCENE:
+   * - The DAT-file contains several MVCC-snapshots of B-tree at same time,
+   *   each of those B-tree has its own root page.
+   * - Each of meta pages at the beginning of the DAT file contains a
+   *   pointer to the root page of B-tree which is the result of the particular
+   *   transaction, and a number of this transaction.
+   * - For data durability, MDBX must first write all MVCC-snapshot data
+   *   pages and ensure that are written to the disk, then update a meta page
+   *   with the new transaction number and a pointer to the corresponding new
+   *   root page, and flush any buffers yet again.
+   * - Thus during commit a I/O buffers should be flushed to the disk twice;
+   *   i.e. fdatasync(), FlushFileBuffers() or similar syscall should be
+   *   called twice for each commit. This is very expensive for performance,
+   *   but guaranteed durability even on unexpected system failure or power
+   *   outage. Of course, provided that the operating system and the
+   *   underlying hardware (e.g. disk) work correctly.
+   *
+   * TRADE-OFF:
+   * By skipping some stages described above, you can significantly benefit in
+   * speed, while partially or completely losing in the guarantee of data
+   * durability and/or consistency in the event of system or power failure.
+   * Moreover, if for any reason disk write order is not preserved, then at
+   * moment of a system crash, a meta-page with a pointer to the new B-tree may
+   * be written to disk, while the itself B-tree not yet. In that case, the
+   * database will be corrupted!
+   *
+   * \see MDBX_SYNC_DURABLE \see MDBX_NOMETASYNC \see MDBX_SAFE_NOSYNC
+   * \see MDBX_UTTERLY_NOSYNC
+   *
+   * @{ */
+
+  /** Default robust and durable sync mode.
+   *
+   * Metadata is written and flushed to disk after a data is written and
+   * flushed, which guarantees the integrity of the database in the event
+   * of a crash at any time.
+   *
+   * \attention Please do not use other modes until you have studied all the
+   * details and are sure. Otherwise, you may lose your users' data, as happens
+   * in [Miranda NG](https://www.miranda-ng.org/) messenger. */
+  MDBX_SYNC_DURABLE = 0,
+
+  /** Don't sync the meta-page after commit.
+   *
+   * Flush system buffers to disk only once per transaction commit, omit the
+   * metadata flush. Defer that until the system flushes files to disk,
+   * or next non-\ref MDBX_RDONLY commit or \ref mdbx_env_sync(). Depending on
+   * the platform and hardware, with \ref MDBX_NOMETASYNC you may get a doubling
+   * of write performance.
+   *
+   * This trade-off maintains database integrity, but a system crash may
+   * undo the last committed transaction. I.e. it preserves the ACI
+   * (atomicity, consistency, isolation) but not D (durability) database
+   * property.
+   *
+   * `MDBX_NOMETASYNC` flag may be changed at any time using
+   * \ref mdbx_env_set_flags() or by passing to \ref mdbx_txn_begin() for
+   * particular write transaction. \see sync_modes */
+  MDBX_NOMETASYNC = UINT32_C(0x40000),
+
+  /** Don't sync anything but keep previous steady commits.
+   *
+   * Like \ref MDBX_UTTERLY_NOSYNC the `MDBX_SAFE_NOSYNC` flag disable similarly
+   * flush system buffers to disk when committing a transaction. But there is a
+   * huge difference in how are recycled the MVCC snapshots corresponding to
+   * previous "steady" transactions (see below).
+   *
+   * With \ref MDBX_WRITEMAP the `MDBX_SAFE_NOSYNC` instructs MDBX to use
+   * asynchronous mmap-flushes to disk. Asynchronous mmap-flushes means that
+   * actually all writes will scheduled and performed by operation system on it
+   * own manner, i.e. unordered. MDBX itself just notify operating system that
+   * it would be nice to write data to disk, but no more.
+   *
+   * Depending on the platform and hardware, with `MDBX_SAFE_NOSYNC` you may get
+   * a multiple increase of write performance, even 10 times or more.
+   *
+   * In contrast to \ref MDBX_UTTERLY_NOSYNC mode, with `MDBX_SAFE_NOSYNC` flag
+   * MDBX will keeps untouched pages within B-tree of the last transaction
+   * "steady" which was synced to disk completely. This has big implications for
+   * both data durability and (unfortunately) performance:
+   *  - a system crash can't corrupt the database, but you will lose the last
+   *    transactions; because MDBX will rollback to last steady commit since it
+   *    kept explicitly.
+   *  - the last steady transaction makes an effect similar to "long-lived" read
+   *    transaction (see above in the \ref restrictions section) since prevents
+   *    reuse of pages freed by newer write transactions, thus the any data
+   *    changes will be placed in newly allocated pages.
+   *  - to avoid rapid database growth, the system will sync data and issue
+   *    a steady commit-point to resume reuse pages, each time there is
+   *    insufficient space and before increasing the size of the file on disk.
+   *
+   * In other words, with `MDBX_SAFE_NOSYNC` flag MDBX insures you from the
+   * whole database corruption, at the cost increasing database size and/or
+   * number of disk IOPs. So, `MDBX_SAFE_NOSYNC` flag could be used with
+   * \ref mdbx_env_sync() as alternatively for batch committing or nested
+   * transaction (in some cases). As well, auto-sync feature exposed by
+   * \ref mdbx_env_set_syncbytes() and \ref mdbx_env_set_syncperiod() functions
+   * could be very useful with `MDBX_SAFE_NOSYNC` flag.
+   *
+   * The number and volume of of disk IOPs with MDBX_SAFE_NOSYNC flag will
+   * exactly the as without any no-sync flags. However, you should expect a
+   * larger process's [work set](https://bit.ly/2kA2tFX) and significantly worse
+   * a [locality of reference](https://bit.ly/2mbYq2J), due to the more
+   * intensive allocation of previously unused pages and increase the size of
+   * the database.
+   *
+   * `MDBX_SAFE_NOSYNC` flag may be changed at any time using
+   * \ref mdbx_env_set_flags() or by passing to \ref mdbx_txn_begin() for
+   * particular write transaction. */
+  MDBX_SAFE_NOSYNC = UINT32_C(0x10000),
+
+  /** \deprecated Please use \ref MDBX_SAFE_NOSYNC instead of `MDBX_MAPASYNC`.
+   *
+   * Since version 0.9.x the `MDBX_MAPASYNC` is deprecated and has the same
+   * effect as \ref MDBX_SAFE_NOSYNC with \ref MDBX_WRITEMAP. This just API
+   * simplification is for convenience and clarity. */
+  MDBX_MAPASYNC = MDBX_SAFE_NOSYNC,
+
+  /** Don't sync anything and wipe previous steady commits.
+   *
+   * Don't flush system buffers to disk when committing a transaction. This
+   * optimization means a system crash can corrupt the database, if buffers are
+   * not yet flushed to disk. Depending on the platform and hardware, with
+   * `MDBX_UTTERLY_NOSYNC` you may get a multiple increase of write performance,
+   * even 100 times or more.
+   *
+   * If the filesystem preserves write order (which is rare and never provided
+   * unless explicitly noted) and the \ref MDBX_WRITEMAP and \ref
+   * MDBX_LIFORECLAIM flags are not used, then a system crash can't corrupt the
+   * database, but you can lose the last transactions, if at least one buffer is
+   * not yet flushed to disk. The risk is governed by how often the system
+   * flushes dirty buffers to disk and how often \ref mdbx_env_sync() is called.
+   * So, transactions exhibit ACI (atomicity, consistency, isolation) properties
+   * and only lose `D` (durability). I.e. database integrity is maintained, but
+   * a system crash may undo the final transactions.
+   *
+   * Otherwise, if the filesystem not preserves write order (which is
+   * typically) or \ref MDBX_WRITEMAP or \ref MDBX_LIFORECLAIM flags are used,
+   * you should expect the corrupted database after a system crash.
+   *
+   * So, most important thing about `MDBX_UTTERLY_NOSYNC`:
+   *  - a system crash immediately after commit the write transaction
+   *    high likely lead to database corruption.
+   *  - successful completion of mdbx_env_sync(force = true) after one or
+   *    more committed transactions guarantees consistency and durability.
+   *  - BUT by committing two or more transactions you back database into
+   *    a weak state, in which a system crash may lead to database corruption!
+   *    In case single transaction after mdbx_env_sync, you may lose transaction
+   *    itself, but not a whole database.
+   *
+   * Nevertheless, `MDBX_UTTERLY_NOSYNC` provides "weak" durability in case
+   * of an application crash (but no durability on system failure), and
+   * therefore may be very useful in scenarios where data durability is
+   * not required over a system failure (e.g for short-lived data), or if you
+   * can take such risk.
+   *
+   * `MDBX_UTTERLY_NOSYNC` flag may be changed at any time using
+   * \ref mdbx_env_set_flags(), but don't has effect if passed to
+   * \ref mdbx_txn_begin() for particular write transaction. \see sync_modes */
+  MDBX_UTTERLY_NOSYNC = MDBX_SAFE_NOSYNC | UINT32_C(0x100000),
+
+  /** @} end of SYNC MODES */
+};
+#ifndef __cplusplus
+/** \ingroup c_opening */
+typedef enum MDBX_env_flags_t MDBX_env_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_env_flags_t)
+#endif
+
+/** Transaction flags
+ * \ingroup c_transactions
+ * \anchor txn_flags
+ * \see mdbx_txn_begin() \see mdbx_txn_flags() */
+enum MDBX_txn_flags_t {
+  /** Start read-write transaction.
+   *
+   * Only one write transaction may be active at a time. Writes are fully
+   * serialized, which guarantees that writers can never deadlock. */
+  MDBX_TXN_READWRITE = 0,
+
+  /** Start read-only transaction.
+   *
+   * There can be multiple read-only transactions simultaneously that do not
+   * block each other and a write transactions. */
+  MDBX_TXN_RDONLY = MDBX_RDONLY,
+
+/** Prepare but not start read-only transaction.
+ *
+ * Transaction will not be started immediately, but created transaction handle
+ * will be ready for use with \ref mdbx_txn_renew(). This flag allows to
+ * preallocate memory and assign a reader slot, thus avoiding these operations
+ * at the next start of the transaction. */
+#if CONSTEXPR_ENUM_FLAGS_OPERATIONS || defined(DOXYGEN)
+  MDBX_TXN_RDONLY_PREPARE = MDBX_RDONLY | MDBX_NOMEMINIT,
+#else
+  MDBX_TXN_RDONLY_PREPARE = uint32_t(MDBX_RDONLY) | uint32_t(MDBX_NOMEMINIT),
+#endif
+
+  /** Do not block when starting a write transaction. */
+  MDBX_TXN_TRY = UINT32_C(0x10000000),
+
+  /** Exactly the same as \ref MDBX_NOMETASYNC,
+   * but for this transaction only */
+  MDBX_TXN_NOMETASYNC = MDBX_NOMETASYNC,
+
+  /** Exactly the same as \ref MDBX_SAFE_NOSYNC,
+   * but for this transaction only */
+  MDBX_TXN_NOSYNC = MDBX_SAFE_NOSYNC
+};
+#ifndef __cplusplus
+typedef enum MDBX_txn_flags_t MDBX_txn_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_txn_flags_t)
+#endif
+
+/** \brief Database flags
+ * \ingroup c_dbi
+ * \anchor db_flags
+ * \see mdbx_dbi_open() */
+enum MDBX_db_flags_t {
+  MDBX_DB_DEFAULTS = 0,
+
+  /** Use reverse string keys */
+  MDBX_REVERSEKEY = UINT32_C(0x02),
+
+  /** Use sorted duplicates, i.e. allow multi-values */
+  MDBX_DUPSORT = UINT32_C(0x04),
+
+  /** Numeric keys in native byte order either uint32_t or uint64_t. The keys
+   * must all be of the same size and must be aligned while passing as
+   * arguments. */
+  MDBX_INTEGERKEY = UINT32_C(0x08),
+
+  /** With \ref MDBX_DUPSORT; sorted dup items have fixed size */
+  MDBX_DUPFIXED = UINT32_C(0x10),
+
+  /** With \ref MDBX_DUPSORT and with \ref MDBX_DUPFIXED; dups are fixed size
+   * \ref MDBX_INTEGERKEY -style integers. The data values must all be of the
+   * same size and must be aligned while passing as arguments. */
+  MDBX_INTEGERDUP = UINT32_C(0x20),
+
+  /** With \ref MDBX_DUPSORT; use reverse string comparison */
+  MDBX_REVERSEDUP = UINT32_C(0x40),
+
+  /** Create DB if not already existing */
+  MDBX_CREATE = UINT32_C(0x40000),
+
+  /** Opens an existing sub-database created with unknown flags.
+   *
+   * The `MDBX_DB_ACCEDE` flag is intend to open a existing sub-database which
+   * was created with unknown flags (\ref MDBX_REVERSEKEY, \ref MDBX_DUPSORT,
+   * \ref MDBX_INTEGERKEY, \ref MDBX_DUPFIXED, \ref MDBX_INTEGERDUP and
+   * \ref MDBX_REVERSEDUP).
+   *
+   * In such cases, instead of returning the \ref MDBX_INCOMPATIBLE error, the
+   * sub-database will be opened with flags which it was created, and then an
+   * application could determine the actual flags by \ref mdbx_dbi_flags(). */
+  MDBX_DB_ACCEDE = MDBX_ACCEDE
+};
+#ifndef __cplusplus
+/** \ingroup c_dbi */
+typedef enum MDBX_db_flags_t MDBX_db_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_db_flags_t)
+#endif
+
+/** \brief Data changing flags
+ * \ingroup c_crud
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ * \see mdbx_put() \see mdbx_cursor_put() \see mdbx_replace() */
+enum MDBX_put_flags_t {
+  /** Upsertion by default (without any other flags) */
+  MDBX_UPSERT = 0,
+
+  /** For insertion: Don't write if the key already exists. */
+  MDBX_NOOVERWRITE = UINT32_C(0x10),
+
+  /** Has effect only for \ref MDBX_DUPSORT databases.
+   * For upsertion: don't write if the key-value pair already exist.
+   * For deletion: remove all values for key. */
+  MDBX_NODUPDATA = UINT32_C(0x20),
+
+  /** For upsertion: overwrite the current key/data pair.
+   * MDBX allows this flag for \ref mdbx_put() for explicit overwrite/update
+   * without insertion.
+   * For deletion: remove only single entry at the current cursor position. */
+  MDBX_CURRENT = UINT32_C(0x40),
+
+  /** Has effect only for \ref MDBX_DUPSORT databases.
+   * For deletion: remove all multi-values (aka duplicates) for given key.
+   * For upsertion: replace all multi-values for given key with a new one. */
+  MDBX_ALLDUPS = UINT32_C(0x80),
+
+  /** For upsertion: Just reserve space for data, don't copy it.
+   * Return a pointer to the reserved space. */
+  MDBX_RESERVE = UINT32_C(0x10000),
+
+  /** Data is being appended.
+   * Don't split full pages, continue on a new instead. */
+  MDBX_APPEND = UINT32_C(0x20000),
+
+  /** Has effect only for \ref MDBX_DUPSORT databases.
+   * Duplicate data is being appended.
+   * Don't split full pages, continue on a new instead. */
+  MDBX_APPENDDUP = UINT32_C(0x40000),
+
+  /** Only for \ref MDBX_DUPFIXED.
+   * Store multiple data items in one call. */
+  MDBX_MULTIPLE = UINT32_C(0x80000)
+};
+#ifndef __cplusplus
+/** \ingroup c_crud */
+typedef enum MDBX_put_flags_t MDBX_put_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_put_flags_t)
+#endif
+
+/** \brief Environment copy flags
+ * \ingroup c_extra
+ * \see mdbx_env_copy() \see mdbx_env_copy2fd() */
+enum MDBX_copy_flags_t {
+  MDBX_CP_DEFAULTS = 0,
+
+  /** Copy with compactification: Omit free space from copy and renumber all
+   * pages sequentially */
+  MDBX_CP_COMPACT = 1u,
+
+  /** Force to make resizeable copy, i.e. dynamic size instead of fixed */
+  MDBX_CP_FORCE_DYNAMIC_SIZE = 2u
+};
+#ifndef __cplusplus
+/** \ingroup c_extra */
+typedef enum MDBX_copy_flags_t MDBX_copy_flags_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_copy_flags_t)
+#endif
+
+/** \brief Cursor operations
+ * \ingroup c_cursors
+ * This is the set of all operations for retrieving data using a cursor.
+ * \see mdbx_cursor_set() */
+enum MDBX_cursor_op {
+  /** Position at first key/data item */
+  MDBX_FIRST,
+
+  /** \ref MDBX_DUPSORT -only: Position at first data item of current key. */
+  MDBX_FIRST_DUP,
+
+  /** \ref MDBX_DUPSORT -only: Position at key/data pair. */
+  MDBX_GET_BOTH,
+
+  /** \ref MDBX_DUPSORT -only: Position at given key and at first data greater
+   * than or equal to specified data. */
+  MDBX_GET_BOTH_RANGE,
+
+  /** Return key/data at current cursor position */
+  MDBX_GET_CURRENT,
+
+  /** \ref MDBX_DUPFIXED -only: Return up to a page of duplicate data items
+   * from current cursor position. Move cursor to prepare
+   * for \ref MDBX_NEXT_MULTIPLE. */
+  MDBX_GET_MULTIPLE,
+
+  /** Position at last key/data item */
+  MDBX_LAST,
+
+  /** \ref MDBX_DUPSORT -only: Position at last data item of current key. */
+  MDBX_LAST_DUP,
+
+  /** Position at next data item */
+  MDBX_NEXT,
+
+  /** \ref MDBX_DUPSORT -only: Position at next data item of current key. */
+  MDBX_NEXT_DUP,
+
+  /** \ref MDBX_DUPFIXED -only: Return up to a page of duplicate data items
+   * from next cursor position. Move cursor to prepare
+   * for `MDBX_NEXT_MULTIPLE`. */
+  MDBX_NEXT_MULTIPLE,
+
+  /** Position at first data item of next key */
+  MDBX_NEXT_NODUP,
+
+  /** Position at previous data item */
+  MDBX_PREV,
+
+  /** \ref MDBX_DUPSORT -only: Position at previous data item of current key. */
+  MDBX_PREV_DUP,
+
+  /** Position at last data item of previous key */
+  MDBX_PREV_NODUP,
+
+  /** Position at specified key */
+  MDBX_SET,
+
+  /** Position at specified key, return both key and data */
+  MDBX_SET_KEY,
+
+  /** Position at first key greater than or equal to specified key. */
+  MDBX_SET_RANGE,
+
+  /** \ref MDBX_DUPFIXED -only: Position at previous page and return up to
+   * a page of duplicate data items. */
+  MDBX_PREV_MULTIPLE,
+
+  /** Position at first key-value pair greater than or equal to specified,
+   * return both key and data, and the return code depends on a exact match.
+   *
+   * For non DUPSORT-ed collections this work the same to \ref MDBX_SET_RANGE,
+   * but returns \ref MDBX_SUCCESS if key found exactly and
+   * \ref MDBX_RESULT_TRUE if greater key was found.
+   *
+   * For DUPSORT-ed a data value is taken into account for duplicates,
+   * i.e. for a pairs/tuples of a key and an each data value of duplicates.
+   * Returns \ref MDBX_SUCCESS if key-value pair found exactly and
+   * \ref MDBX_RESULT_TRUE if the next pair was returned. */
+  MDBX_SET_LOWERBOUND
+};
+#ifndef __cplusplus
+/** \ingroup c_cursors */
+typedef enum MDBX_cursor_op MDBX_cursor_op;
+#endif
+
+/** \brief Errors and return codes
+ * \ingroup c_err
+ *
+ * BerkeleyDB uses -30800 to -30999, we'll go under them
+ * \see mdbx_strerror() \see mdbx_strerror_r() \see mdbx_liberr2str() */
+enum MDBX_error_t {
+  /** Successful result */
+  MDBX_SUCCESS = 0,
+
+  /** Alias for \ref MDBX_SUCCESS */
+  MDBX_RESULT_FALSE = MDBX_SUCCESS,
+
+  /** Successful result with special meaning or a flag */
+  MDBX_RESULT_TRUE = -1,
+
+  /** key/data pair already exists */
+  MDBX_KEYEXIST = -30799,
+
+  /** The first LMDB-compatible defined error code */
+  MDBX_FIRST_LMDB_ERRCODE = MDBX_KEYEXIST,
+
+  /** key/data pair not found (EOF) */
+  MDBX_NOTFOUND = -30798,
+
+  /** Requested page not found - this usually indicates corruption */
+  MDBX_PAGE_NOTFOUND = -30797,
+
+  /** Database is corrupted (page was wrong type and so on) */
+  MDBX_CORRUPTED = -30796,
+
+  /** Environment had fatal error,
+   * i.e. update of meta page failed and so on. */
+  MDBX_PANIC = -30795,
+
+  /** DB file version mismatch with libmdbx */
+  MDBX_VERSION_MISMATCH = -30794,
+
+  /** File is not a valid MDBX file */
+  MDBX_INVALID = -30793,
+
+  /** Environment mapsize reached */
+  MDBX_MAP_FULL = -30792,
+
+  /** Environment maxdbs reached */
+  MDBX_DBS_FULL = -30791,
+
+  /** Environment maxreaders reached */
+  MDBX_READERS_FULL = -30790,
+
+  /** Transaction has too many dirty pages, i.e transaction too big */
+  MDBX_TXN_FULL = -30788,
+
+  /** Cursor stack too deep - this usually indicates corruption,
+   * i.e branch-pages loop */
+  MDBX_CURSOR_FULL = -30787,
+
+  /** Page has not enough space - internal error */
+  MDBX_PAGE_FULL = -30786,
+
+  /** Database engine was unable to extend mapping, e.g. since address space
+   * is unavailable or busy. This can mean:
+   *  - Database size extended by other process beyond to environment mapsize
+   *    and engine was unable to extend mapping while starting read
+   *    transaction. Environment should be reopened to continue.
+   *  - Engine was unable to extend mapping during write transaction
+   *    or explicit call of \ref mdbx_env_set_geometry(). */
+  MDBX_UNABLE_EXTEND_MAPSIZE = -30785,
+
+  /** Environment or database is not compatible with the requested operation
+   * or the specified flags. This can mean:
+   *  - The operation expects an \ref MDBX_DUPSORT / \ref MDBX_DUPFIXED
+   *    database.
+   *  - Opening a named DB when the unnamed DB has \ref MDBX_DUPSORT /
+   *    \ref MDBX_INTEGERKEY.
+   *  - Accessing a data record as a database, or vice versa.
+   *  - The database was dropped and recreated with different flags. */
+  MDBX_INCOMPATIBLE = -30784,
+
+  /** Invalid reuse of reader locktable slot,
+   * e.g. read-transaction already run for current thread */
+  MDBX_BAD_RSLOT = -30783,
+
+  /** Transaction is not valid for requested operation,
+   * e.g. had errored and be must aborted, has a child, or is invalid */
+  MDBX_BAD_TXN = -30782,
+
+  /** Invalid size or alignment of key or data for target database,
+   * either invalid subDB name */
+  MDBX_BAD_VALSIZE = -30781,
+
+  /** The specified DBI-handle is invalid
+   * or changed by another thread/transaction */
+  MDBX_BAD_DBI = -30780,
+
+  /** Unexpected internal error, transaction should be aborted */
+  MDBX_PROBLEM = -30779,
+
+  /** The last LMDB-compatible defined error code */
+  MDBX_LAST_LMDB_ERRCODE = MDBX_PROBLEM,
+
+  /** Another write transaction is running or environment is already used while
+   * opening with \ref MDBX_EXCLUSIVE flag */
+  MDBX_BUSY = -30778,
+
+  /** The first of MDBX-added error codes */
+  MDBX_FIRST_ADDED_ERRCODE = MDBX_BUSY,
+
+  /** The specified key has more than one associated value */
+  MDBX_EMULTIVAL = -30421,
+
+  /** Bad signature of a runtime object(s), this can mean:
+   *  - memory corruption or double-free;
+   *  - ABI version mismatch (rare case); */
+  MDBX_EBADSIGN = -30420,
+
+  /** Database should be recovered, but this could NOT be done for now
+   * since it opened in read-only mode */
+  MDBX_WANNA_RECOVERY = -30419,
+
+  /** The given key value is mismatched to the current cursor position */
+  MDBX_EKEYMISMATCH = -30418,
+
+  /** Database is too large for current system,
+   * e.g. could NOT be mapped into RAM. */
+  MDBX_TOO_LARGE = -30417,
+
+  /** A thread has attempted to use a not owned object,
+   * e.g. a transaction that started by another thread. */
+  MDBX_THREAD_MISMATCH = -30416,
+
+  /** Overlapping read and write transactions for the current thread */
+  MDBX_TXN_OVERLAPPING = -30415,
+
+  /* The last of MDBX-added error codes */
+  MDBX_LAST_ADDED_ERRCODE = MDBX_TXN_OVERLAPPING,
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_ENODATA = ERROR_HANDLE_EOF,
+  MDBX_EINVAL = ERROR_INVALID_PARAMETER,
+  MDBX_EACCESS = ERROR_ACCESS_DENIED,
+  MDBX_ENOMEM = ERROR_OUTOFMEMORY,
+  MDBX_EROFS = ERROR_FILE_READ_ONLY,
+  MDBX_ENOSYS = ERROR_NOT_SUPPORTED,
+  MDBX_EIO = ERROR_WRITE_FAULT,
+  MDBX_EPERM = ERROR_INVALID_FUNCTION,
+  MDBX_EINTR = ERROR_CANCELLED,
+  MDBX_ENOFILE = ERROR_FILE_NOT_FOUND,
+  MDBX_EREMOTE = ERROR_REMOTE_STORAGE_MEDIA_ERROR
+#else /* Windows */
+#ifdef ENODATA
+  MDBX_ENODATA = ENODATA,
+#else
+  MDBX_ENODATA = -1,
+#endif /* ENODATA */
+  MDBX_EINVAL = EINVAL,
+  MDBX_EACCESS = EACCES,
+  MDBX_ENOMEM = ENOMEM,
+  MDBX_EROFS = EROFS,
+  MDBX_ENOSYS = ENOSYS,
+  MDBX_EIO = EIO,
+  MDBX_EPERM = EPERM,
+  MDBX_EINTR = EINTR,
+  MDBX_ENOFILE = ENOENT,
+  MDBX_EREMOTE = ENOTBLK
+#endif /* !Windows */
+};
+#ifndef __cplusplus
+/** \ingroup c_err */
+typedef enum MDBX_error_t MDBX_error_t;
+#endif
+
+/** MDBX_MAP_RESIZED
+ * \ingroup c_err
+ * \deprecated Please review your code to use MDBX_UNABLE_EXTEND_MAPSIZE
+ * instead. */
+MDBX_DEPRECATED static __inline int MDBX_MAP_RESIZED_is_deprecated() {
+  return MDBX_UNABLE_EXTEND_MAPSIZE;
+}
+#define MDBX_MAP_RESIZED MDBX_MAP_RESIZED_is_deprecated()
+
+/** \brief Return a string describing a given error code.
+ * \ingroup c_err
+ *
+ * This function is a superset of the ANSI C X3.159-1989 (ANSI C) `strerror()`
+ * function. If the error code is greater than or equal to 0, then the string
+ * returned by the system function `strerror()` is returned. If the error code
+ * is less than 0, an error string corresponding to the MDBX library error is
+ * returned. See errors for a list of MDBX-specific error codes.
+ *
+ * `mdbx_strerror()` is NOT thread-safe because may share common internal buffer
+ * for system messages. The returned string must NOT be modified by the
+ * application, but MAY be modified by a subsequent call to
+ * \ref mdbx_strerror(), `strerror()` and other related functions.
+ * \see mdbx_strerror_r()
+ *
+ * \param [in] errnum  The error code.
+ *
+ * \returns "error message" The description of the error. */
+LIBMDBX_API const char *mdbx_strerror(int errnum);
+
+/** \brief Return a string describing a given error code.
+ * \ingroup c_err
+ *
+ * This function is a superset of the ANSI C X3.159-1989 (ANSI C) `strerror()`
+ * function. If the error code is greater than or equal to 0, then the string
+ * returned by the system function `strerror()` is returned. If the error code
+ * is less than 0, an error string corresponding to the MDBX library error is
+ * returned. See errors for a list of MDBX-specific error codes.
+ *
+ * `mdbx_strerror_r()` is thread-safe since uses user-supplied buffer where
+ * appropriate. The returned string must NOT be modified by the application,
+ * since it may be pointer to internal constant string. However, there is no
+ * restriction if the returned string points to the supplied buffer.
+ * \see mdbx_strerror()
+ *
+ * mdbx_liberr2str() returns string describing only MDBX error numbers but NULL
+ * for non-MDBX error codes. This function is thread-safe since return pointer
+ * to constant non-localized strings.
+ *
+ * \param [in] errnum  The error code.
+ * \param [in,out] buf Buffer to store the error message.
+ * \param [in] buflen The size of buffer to store the message.
+ *
+ * \returns "error message" The description of the error. */
+LIBMDBX_API const char *mdbx_strerror_r(int errnum, char *buf, size_t buflen);
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API const char *mdbx_liberr2str(int errnum);
+
+#if defined(_WIN32) || defined(_WIN64) || defined(DOXYGEN)
+/** Bit of Windows' madness. The similar to \ref mdbx_strerror() but returns
+ * Windows error-messages in the OEM-encoding for console utilities.
+ * \ingroup c_err
+ * \see mdbx_strerror_r_ANSI2OEM() */
+LIBMDBX_API const char *mdbx_strerror_ANSI2OEM(int errnum);
+
+/** Bit of Windows' madness. The similar to \ref mdbx_strerror_r() but returns
+ * Windows error-messages in the OEM-encoding for console utilities.
+ * \ingroup c_err
+ * \see mdbx_strerror_ANSI2OEM() */
+LIBMDBX_API const char *mdbx_strerror_r_ANSI2OEM(int errnum, char *buf,
+                                                 size_t buflen);
+#endif /* Bit of Windows' madness */
+
+/** \brief Create an MDBX environment instance.
+ * \ingroup c_opening
+ *
+ * This function allocates memory for a \ref MDBX_env structure. To release
+ * the allocated memory and discard the handle, call \ref mdbx_env_close().
+ * Before the handle may be used, it must be opened using \ref mdbx_env_open().
+ *
+ * Various other options may also need to be set before opening the handle,
+ * e.g. \ref mdbx_env_set_geometry(), \ref mdbx_env_set_maxreaders(),
+ * \ref mdbx_env_set_maxdbs(), depending on usage requirements.
+ *
+ * \param [out] penv  The address where the new handle will be stored.
+ *
+ * \returns a non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_create(MDBX_env **penv);
+
+/** \brief MDBX environment options. */
+enum MDBX_option_t {
+  /** \brief Controls the maximum number of named databases for the environment.
+   *
+   * \details By default only unnamed key-value database could used and
+   * appropriate value should set by `MDBX_opt_max_db` to using any more named
+   * subDB(s). To reduce overhead, use the minimum sufficient value. This option
+   * may only set after \ref mdbx_env_create() and before \ref mdbx_env_open().
+   *
+   * \see mdbx_env_set_maxdbs() \see mdbx_env_get_maxdbs() */
+  MDBX_opt_max_db,
+
+  /** \brief Defines the maximum number of threads/reader slots
+   * for all processes interacting with the database.
+   *
+   * \details This defines the number of slots in the lock table that is used to
+   * track readers in the the environment. The default is about 100 for 4K
+   * system page size. Starting a read-only transaction normally ties a lock
+   * table slot to the current thread until the environment closes or the thread
+   * exits. If \ref MDBX_NOTLS is in use, \ref mdbx_txn_begin() instead ties the
+   * slot to the \ref MDBX_txn object until it or the \ref MDBX_env object is
+   * destroyed. This option may only set after \ref mdbx_env_create() and before
+   * \ref mdbx_env_open(), and has an effect only when the database is opened by
+   * the first process interacts with the database.
+   *
+   * \see mdbx_env_set_maxreaders() \see mdbx_env_get_maxreaders() */
+  MDBX_opt_max_readers,
+
+  /** \brief Controls interprocess/shared threshold to force flush the data
+   * buffers to disk, if \ref MDBX_SAFE_NOSYNC is used.
+   *
+   * \see mdbx_env_set_syncbytes() \see mdbx_env_get_syncbytes() */
+  MDBX_opt_sync_bytes,
+
+  /** \brief Controls interprocess/shared relative period since the last
+   * unsteady commit to force flush the data buffers to disk,
+   * if \ref MDBX_SAFE_NOSYNC is used.
+   * \see mdbx_env_set_syncperiod() \see mdbx_env_get_syncperiod() */
+  MDBX_opt_sync_period,
+
+  /** \brief Controls the in-process limit to grow a list of reclaimed/recycled
+   * page's numbers for finding a sequence of contiguous pages for large data
+   * items.
+   *
+   * \details A long values requires allocation of contiguous database pages.
+   * To find such sequences, it may be necessary to accumulate very large lists,
+   * especially when placing very long values (more than a megabyte) in a large
+   * databases (several tens of gigabytes), which is much expensive in extreme
+   * cases. This threshold allows you to avoid such costs by allocating new
+   * pages at the end of the database (with its possible growth on disk),
+   * instead of further accumulating/reclaiming Garbage Collection records.
+   *
+   * On the other hand, too small threshold will lead to unreasonable database
+   * growth, or/and to the inability of put long values.
+   *
+   * The `MDBX_opt_rp_augment_limit` controls described limit for the current
+   * process. Default is 262144, it is usually enough for most cases. */
+  MDBX_opt_rp_augment_limit,
+
+  /** \brief Controls the in-process limit to grow a cache of dirty
+   * pages for reuse in the current transaction.
+   *
+   * \details A 'dirty page' refers to a page that has been updated in memory
+   * only, the changes to a dirty page are not yet stored on disk.
+   * To reduce overhead, it is reasonable to release not all such pages
+   * immediately, but to leave some ones in cache for reuse in the current
+   * transaction.
+   *
+   * The `MDBX_opt_loose_limit` allows you to set a limit for such cache inside
+   * the current process. Should be in the range 0..255, default is 64. */
+  MDBX_opt_loose_limit,
+
+  /** \brief Controls the in-process limit of a pre-allocated memory items
+   * for dirty pages.
+   *
+   * \details A 'dirty page' refers to a page that has been updated in memory
+   * only, the changes to a dirty page are not yet stored on disk.
+   * Without \ref MDBX_WRITEMAP dirty pages are allocated from memory and
+   * released when a transaction is committed. To reduce overhead, it is
+   * reasonable to release not all ones, but to leave some allocations in
+   * reserve for reuse in the next transaction(s).
+   *
+   * The `MDBX_opt_dp_reserve_limit` allows you to set a limit for such reserve
+   * inside the current process. Default is 1024. */
+  MDBX_opt_dp_reserve_limit,
+
+  /** \brief Controls the in-process limit of dirty pages
+   * for a write transaction.
+   *
+   * \details A 'dirty page' refers to a page that has been updated in memory
+   * only, the changes to a dirty page are not yet stored on disk.
+   * Without \ref MDBX_WRITEMAP dirty pages are allocated from memory and will
+   * be busy until are written to disk. Therefore for a large transactions is
+   * reasonable to limit dirty pages collecting above an some threshold but
+   * spill to disk instead.
+   *
+   * The `MDBX_opt_txn_dp_limit` controls described threshold for the current
+   * process. Default is 65536, it is usually enough for most cases. */
+  MDBX_opt_txn_dp_limit,
+
+  /** \brief Controls the in-process initial allocation size for dirty pages
+   * list of a write transaction. Default is 1024. */
+  MDBX_opt_txn_dp_initial,
+
+  /** \brief Controls the in-process how maximal part of the dirty pages may be
+   * spilled when necessary.
+   *
+   * \details The `MDBX_opt_spill_max_denominator` defines the denominator for
+   * limiting from the top for part of the current dirty pages may be spilled
+   * when the free room for a new dirty pages (i.e. distance to the
+   * `MDBX_opt_txn_dp_limit` threshold) is not enough to perform requested
+   * operation.
+   * Exactly `max_pages_to_spill = dirty_pages - dirty_pages / N`,
+   * where `N` is the value set by `MDBX_opt_spill_max_denominator`.
+   *
+   * Should be in the range 0..255, where zero means no limit, i.e. all dirty
+   * pages could be spilled. Default is 8, i.e. no more than 7/8 of the current
+   * dirty pages may be spilled when reached the condition described above. */
+  MDBX_opt_spill_max_denominator,
+
+  /** \brief Controls the in-process how minimal part of the dirty pages should
+   * be spilled when necessary.
+   *
+   * \details The `MDBX_opt_spill_min_denominator` defines the denominator for
+   * limiting from the bottom for part of the current dirty pages should be
+   * spilled when the free room for a new dirty pages (i.e. distance to the
+   * `MDBX_opt_txn_dp_limit` threshold) is not enough to perform requested
+   * operation.
+   * Exactly `min_pages_to_spill = dirty_pages / N`,
+   * where `N` is the value set by `MDBX_opt_spill_min_denominator`.
+   *
+   * Should be in the range 0..255, where zero means no restriction at the
+   * bottom. Default is 8, i.e. at least the 1/8 of the current dirty pages
+   * should be spilled when reached the condition described above. */
+  MDBX_opt_spill_min_denominator,
+
+  /** \brief Controls the in-process how much of the parent transaction dirty
+   * pages will be spilled while start each child transaction.
+   *
+   * \details The `MDBX_opt_spill_parent4child_denominator` defines the
+   * denominator to determine how much of parent transaction dirty pages will be
+   * spilled explicitly while start each child transaction.
+   * Exactly `pages_to_spill = dirty_pages / N`,
+   * where `N` is the value set by `MDBX_opt_spill_parent4child_denominator`.
+   *
+   * For a stack of nested transactions each dirty page could be spilled only
+   * once, and parent's dirty pages couldn't be spilled while child
+   * transaction(s) are running. Therefore a child transaction could reach
+   * \ref MDBX_TXN_FULL when parent(s) transaction has  spilled too less (and
+   * child reach the limit of dirty pages), either when parent(s) has spilled
+   * too more (since child can't spill already spilled pages). So there is no
+   * universal golden ratio.
+   *
+   * Should be in the range 0..255, where zero means no explicit spilling will
+   * be performed during starting nested transactions.
+   * Default is 0, i.e. by default no spilling performed during starting nested
+   * transactions, that correspond historically behaviour. */
+  MDBX_opt_spill_parent4child_denominator,
+};
+#ifndef __cplusplus
+/** \ingroup c_settings */
+typedef enum MDBX_option_t MDBX_option_t;
+#endif
+
+LIBMDBX_API int mdbx_env_set_option(MDBX_env *env, const MDBX_option_t option,
+                                    const uint64_t value);
+LIBMDBX_API int mdbx_env_get_option(const MDBX_env *env,
+                                    const MDBX_option_t option,
+                                    uint64_t *value);
+
+/** \brief Open an environment instance.
+ * \ingroup c_opening
+ *
+ * Indifferently this function will fails or not, the \ref mdbx_env_close() must
+ * be called later to discard the \ref MDBX_env handle and release associated
+ * resources.
+ *
+ * \param [in] env       An environment handle returned
+ *                       by \ref mdbx_env_create()
+ *
+ * \param [in] pathname  The pathname for the database or the directory in which
+ *                       the database files reside. In the case of directory it
+ *                       must already exist and be writable.
+ *
+ * \param [in] flags     Special options for this environment. This parameter
+ *                       must be set to 0 or by bitwise OR'ing together one
+ *                       or more of the values described above in the
+ *                       \ref env_flags and \ref sync_modes sections.
+ *
+ * Flags set by mdbx_env_set_flags() are also used:
+ *  - \ref MDBX_NOSUBDIR, \ref MDBX_RDONLY, \ref MDBX_EXCLUSIVE,
+ *    \ref MDBX_WRITEMAP, \ref MDBX_NOTLS, \ref MDBX_NORDAHEAD,
+ *    \ref MDBX_NOMEMINIT, \ref MDBX_COALESCE, \ref MDBX_LIFORECLAIM.
+ *    See \ref env_flags section.
+ *
+ *  - \ref MDBX_NOMETASYNC, \ref MDBX_SAFE_NOSYNC, \ref MDBX_UTTERLY_NOSYNC.
+ *    See \ref sync_modes section.
+ *
+ * \note `MDB_NOLOCK` flag don't supported by MDBX,
+ *       try use \ref MDBX_EXCLUSIVE as a replacement.
+ *
+ * \note MDBX don't allow to mix processes with different \ref MDBX_SAFE_NOSYNC
+ *       flags on the same environment.
+ *       In such case \ref MDBX_INCOMPATIBLE will be returned.
+ *
+ * If the database is already exist and parameters specified early by
+ * \ref mdbx_env_set_geometry() are incompatible (i.e. for instance, different
+ * page size) then \ref mdbx_env_open() will return \ref MDBX_INCOMPATIBLE
+ * error.
+ *
+ * \param [in] mode   The UNIX permissions to set on created files.
+ *                    Zero value means to open existing, but do not create.
+ *
+ * \return A non-zero error value on failure and 0 on success,
+ *         some possible errors are:
+ * \retval MDBX_VERSION_MISMATCH The version of the MDBX library doesn't match
+ *                            the version that created the database environment.
+ * \retval MDBX_INVALID       The environment file headers are corrupted.
+ * \retval MDBX_ENOENT        The directory specified by the path parameter
+ *                            doesn't exist.
+ * \retval MDBX_EACCES        The user didn't have permission to access
+ *                            the environment files.
+ * \retval MDBX_EAGAIN        The environment was locked by another process.
+ * \retval MDBX_BUSY          The \ref MDBX_EXCLUSIVE flag was specified and the
+ *                            environment is in use by another process,
+ *                            or the current process tries to open environment
+ *                            more than once.
+ * \retval MDBX_INCOMPATIBLE  Environment is already opened by another process,
+ *                            but with different set of \ref MDBX_SAFE_NOSYNC,
+ *                            \ref MDBX_UTTERLY_NOSYNC flags.
+ *                            Or if the database is already exist and parameters
+ *                            specified early by \ref mdbx_env_set_geometry()
+ *                            are incompatible (i.e. different pagesize, etc).
+ *
+ * \retval MDBX_WANNA_RECOVERY The \ref MDBX_RDONLY flag was specified but
+ *                             read-write access is required to rollback
+ *                             inconsistent state after a system crash.
+ *
+ * \retval MDBX_TOO_LARGE      Database is too large for this process,
+ *                             i.e. 32-bit process tries to open >4Gb database.
+ */
+LIBMDBX_API int mdbx_env_open(MDBX_env *env, const char *pathname,
+                              MDBX_env_flags_t flags, mdbx_mode_t mode);
+
+/** \brief Deletion modes for \ref mdbx_env_delete().
+ * \ingroup c_extra
+ * \see mdbx_env_delete() */
+enum MDBX_env_delete_mode_t {
+  /** \brief Just delete the environment's files and directory if any.
+   * \note On POSIX systems, processes already working with the database will
+   * continue to work without interference until it close the environment.
+   * \note On Windows, the behavior of `MDB_ENV_JUST_DELETE` is different
+   * because the system does not support deleting files that are currently
+   * memory mapped. */
+  MDBX_ENV_JUST_DELETE = 0,
+  /** \brief Make sure that the environment is not being used by other
+   * processes, or return an error otherwise. */
+  MDBX_ENV_ENSURE_UNUSED = 1,
+  /** \brief Wait until other processes closes the environment before deletion.
+   */
+  MDBX_ENV_WAIT_FOR_UNUSED = 2,
+};
+#ifndef __cplusplus
+/** \ingroup c_extra */
+typedef enum MDBX_env_delete_mode_t MDBX_env_delete_mode_t;
+#endif
+
+/** \brief Delete the environment's files in a proper and multiprocess-safe way.
+ * \ingroup c_extra
+ *
+ * \param [in] pathname  The pathname for the database or the directory in which
+ *                       the database files reside.
+ *
+ * \param [in] mode      Special deletion mode for the environment. This
+ *                       parameter must be set to one of the values described
+ *                       above in the \ref MDBX_env_delete_mode_t section.
+ *
+ * \note The \ref MDBX_ENV_JUST_DELETE don't supported on Windows since system
+ * unable to delete a memory-mapped files.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_RESULT_TRUE   No corresponding files or directories were found,
+ *                            so no deletion was performed. */
+LIBMDBX_API int mdbx_env_delete(const char *pathname,
+                                MDBX_env_delete_mode_t mode);
+
+/** \brief Copy an MDBX environment to the specified path, with options.
+ * \ingroup c_extra
+ *
+ * This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need.
+ * \note This call can trigger significant file size growth if run in
+ * parallel with write transactions, because it employs a read-only
+ * transaction. See long-lived transactions under \ref restrictions section.
+ *
+ * \param [in] env    An environment handle returned by mdbx_env_create().
+ *                    It must have already been opened successfully.
+ * \param [in] dest   The pathname of a file in which the copy will reside.
+ *                    This file must not be already exist, but parent directory
+ *                    must be writable.
+ * \param [in] flags  Special options for this operation. This parameter must
+ *                    be set to 0 or by bitwise OR'ing together one or more
+ *                    of the values described here:
+ *
+ *  - \ref MDBX_CP_COMPACT
+ *      Perform compaction while copying: omit free pages and sequentially
+ *      renumber all pages in output. This option consumes little bit more
+ *      CPU for processing, but may running quickly than the default, on
+ *      account skipping free pages.
+ *
+ *  - \ref MDBX_CP_FORCE_DYNAMIC_SIZE
+ *      Force to make resizeable copy, i.e. dynamic size instead of fixed.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_copy(MDBX_env *env, const char *dest,
+                              MDBX_copy_flags_t flags);
+
+/** \brief Copy an environment to the specified file descriptor, with
+ * options. \ingroup c_extra
+ *
+ * This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need.
+ * \see mdbx_env_copy()
+ *
+ * \note This call can trigger significant file size growth if run in
+ *       parallel with write transactions, because it employs a read-only
+ *       transaction. See long-lived transactions under \ref restrictions
+ *       section.
+ *
+ * \note Fails if the environment has suffered a page leak and the destination
+ *       file descriptor is associated with a pipe, socket, or FIFO.
+ *
+ * \param [in] env     An environment handle returned by mdbx_env_create().
+ *                     It must have already been opened successfully.
+ * \param [in] fd      The file descriptor to write the copy to. It must have
+ *                     already been opened for Write access.
+ * \param [in] flags   Special options for this operation. \see mdbx_env_copy()
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_copy2fd(MDBX_env *env, mdbx_filehandle_t fd,
+                                 MDBX_copy_flags_t flags);
+
+/** \brief Statistics for a database in the environment
+ * \ingroup c_statinfo
+ * \see mdbx_env_stat_ex() \see mdbx_dbi_stat() */
+struct MDBX_stat {
+  uint32_t ms_psize; /**< Size of a database page. This is the same for all
+                        databases. */
+  uint32_t ms_depth; /**< Depth (height) of the B-tree */
+  uint64_t ms_branch_pages;   /**< Number of internal (non-leaf) pages */
+  uint64_t ms_leaf_pages;     /**< Number of leaf pages */
+  uint64_t ms_overflow_pages; /**< Number of overflow pages */
+  uint64_t ms_entries;        /**< Number of data items */
+  uint64_t ms_mod_txnid; /**< Transaction ID of committed last modification */
+};
+#ifndef __cplusplus
+/** \ingroup c_statinfo */
+typedef struct MDBX_stat MDBX_stat;
+#endif
+
+/** \brief Return statistics about the MDBX environment.
+ * \ingroup c_statinfo
+ *
+ * At least one of env or txn argument must be non-null. If txn is passed
+ * non-null then stat will be filled accordingly to the given transaction.
+ * Otherwise, if txn is null, then stat will be populated by a snapshot from
+ * the last committed write transaction, and at next time, other information
+ * can be returned.
+ *
+ * Legacy mdbx_env_stat() correspond to calling \ref mdbx_env_stat_ex() with the
+ * null `txn` argument.
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create()
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin()
+ * \param [out] stat   The address of an \ref MDBX_stat structure where
+ *                     the statistics will be copied
+ * \param [in] bytes   The size of \ref MDBX_stat.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_stat_ex(const MDBX_env *env, const MDBX_txn *txn,
+                                 MDBX_stat *stat, size_t bytes);
+
+/** \brief Return statistics about the MDBX environment.
+ * \ingroup c_statinfo
+ * \deprecated Please use mdbx_env_stat_ex() instead. */
+MDBX_DEPRECATED LIBMDBX_INLINE_API(int, mdbx_env_stat,
+                                   (const MDBX_env *env, MDBX_stat *stat,
+                                    size_t bytes)) {
+  return mdbx_env_stat_ex(env, NULL, stat, bytes);
+}
+
+/** \brief Information about the environment
+ * \ingroup c_statinfo
+ * \see mdbx_env_info_ex() */
+struct MDBX_envinfo {
+  struct {
+    uint64_t lower;   /**< Lower limit for datafile size */
+    uint64_t upper;   /**< Upper limit for datafile size */
+    uint64_t current; /**< Current datafile size */
+    uint64_t shrink;  /**< Shrink threshold for datafile */
+    uint64_t grow;    /**< Growth step for datafile */
+  } mi_geo;
+  uint64_t mi_mapsize;             /**< Size of the data memory map */
+  uint64_t mi_last_pgno;           /**< Number of the last used page */
+  uint64_t mi_recent_txnid;        /**< ID of the last committed transaction */
+  uint64_t mi_latter_reader_txnid; /**< ID of the last reader transaction */
+  uint64_t mi_self_latter_reader_txnid; /**< ID of the last reader transaction
+                                           of caller process */
+  uint64_t mi_meta0_txnid, mi_meta0_sign;
+  uint64_t mi_meta1_txnid, mi_meta1_sign;
+  uint64_t mi_meta2_txnid, mi_meta2_sign;
+  uint32_t mi_maxreaders;   /**< Total reader slots in the environment */
+  uint32_t mi_numreaders;   /**< Max reader slots used in the environment */
+  uint32_t mi_dxb_pagesize; /**< Database pagesize */
+  uint32_t mi_sys_pagesize; /**< System pagesize */
+
+  /** \brief A mostly unique ID that is regenerated on each boot.
+
+   As such it can be used to identify the local machine's current boot. MDBX
+   uses such when open the database to determine whether rollback required to
+   the last steady sync point or not. I.e. if current bootid is differ from the
+   value within a database then the system was rebooted and all changes since
+   last steady sync must be reverted for data integrity. Zeros mean that no
+   relevant information is available from the system. */
+  struct {
+    struct {
+      uint64_t x, y;
+    } current, meta0, meta1, meta2;
+  } mi_bootid;
+
+  /** Bytes not explicitly synchronized to disk */
+  uint64_t mi_unsync_volume;
+  /** Current auto-sync threshold, see \ref mdbx_env_set_syncbytes(). */
+  uint64_t mi_autosync_threshold;
+  /** Time since the last steady sync in 1/65536 of second */
+  uint32_t mi_since_sync_seconds16dot16;
+  /** Current auto-sync period in 1/65536 of second,
+   * see \ref mdbx_env_set_syncperiod(). */
+  uint32_t mi_autosync_period_seconds16dot16;
+  /** Time since the last readers check in 1/65536 of second,
+   * see \ref mdbx_reader_check(). */
+  uint32_t mi_since_reader_check_seconds16dot16;
+  /** Current environment mode.
+   * The same as \ref mdbx_env_get_flags() returns. */
+  uint32_t mi_mode;
+};
+#ifndef __cplusplus
+/** \ingroup c_statinfo */
+typedef struct MDBX_envinfo MDBX_envinfo;
+#endif
+
+/** \brief Return information about the MDBX environment.
+ * \ingroup c_statinfo
+ *
+ * At least one of env or txn argument must be non-null. If txn is passed
+ * non-null then stat will be filled accordingly to the given transaction.
+ * Otherwise, if txn is null, then stat will be populated by a snapshot from
+ * the last committed write transaction, and at next time, other information
+ * can be returned.
+ *
+ * Legacy \ref mdbx_env_info() correspond to calling \ref mdbx_env_info_ex()
+ * with the null `txn` argument.
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create()
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin()
+ * \param [out] info   The address of an \ref MDBX_envinfo structure
+ *                     where the information will be copied
+ * \param [in] bytes   The size of \ref MDBX_envinfo.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_info_ex(const MDBX_env *env, const MDBX_txn *txn,
+                                 MDBX_envinfo *info, size_t bytes);
+/** \brief Return information about the MDBX environment.
+ * \ingroup c_statinfo
+ * \deprecated Please use mdbx_env_info_ex() instead. */
+MDBX_DEPRECATED LIBMDBX_INLINE_API(int, mdbx_env_info,
+                                   (const MDBX_env *env, MDBX_envinfo *info,
+                                    size_t bytes)) {
+  return mdbx_env_info_ex(env, NULL, info, bytes);
+}
+
+/** \brief Flush the environment data buffers to disk.
+ * \ingroup c_extra
+ *
+ * Unless the environment was opened with no-sync flags (\ref MDBX_NOMETASYNC,
+ * \ref MDBX_SAFE_NOSYNC and \ref MDBX_UTTERLY_NOSYNC), then
+ * data is always written an flushed to disk when \ref mdbx_txn_commit() is
+ * called. Otherwise \ref mdbx_env_sync() may be called to manually write and
+ * flush unsynced data to disk.
+ *
+ * Besides, \ref mdbx_env_sync_ex() with argument `force=false` may be used to
+ * provide polling mode for lazy/asynchronous sync in conjunction with
+ * \ref mdbx_env_set_syncbytes() and/or \ref mdbx_env_set_syncperiod().
+ *
+ * \note This call is not valid if the environment was opened with MDBX_RDONLY.
+ *
+ * \param [in] env      An environment handle returned by \ref mdbx_env_create()
+ * \param [in] force    If non-zero, force a flush. Otherwise, If force is
+ *                      zero, then will run in polling mode,
+ *                      i.e. it will check the thresholds that were
+ *                      set \ref mdbx_env_set_syncbytes()
+ *                      and/or \ref mdbx_env_set_syncperiod() and perform flush
+ *                      if at least one of the thresholds is reached.
+ *
+ * \param [in] nonblock Don't wait if write transaction
+ *                      is running by other thread.
+ *
+ * \returns A non-zero error value on failure and \ref MDBX_RESULT_TRUE or 0 on
+ *     success. The \ref MDBX_RESULT_TRUE means no data pending for flush
+ *     to disk, and 0 otherwise. Some possible errors are:
+ *
+ * \retval MDBX_EACCES   the environment is read-only.
+ * \retval MDBX_BUSY     the environment is used by other thread
+ *                       and `nonblock=true`.
+ * \retval MDBX_EINVAL   an invalid parameter was specified.
+ * \retval MDBX_EIO      an error occurred during synchronization. */
+LIBMDBX_API int mdbx_env_sync_ex(MDBX_env *env, bool force, bool nonblock);
+
+/** \brief The shortcut to calling \ref mdbx_env_sync_ex() with
+ * the `force=true` and `nonblock=false` arguments.
+ * \ingroup c_extra */
+LIBMDBX_INLINE_API(int, mdbx_env_sync, (MDBX_env * env)) {
+  return mdbx_env_sync_ex(env, true, false);
+}
+
+/** \brief The shortcut to calling \ref mdbx_env_sync_ex() with
+ * the `force=false` and `nonblock=true` arguments.
+ * \ingroup c_extra */
+LIBMDBX_INLINE_API(int, mdbx_env_sync_poll, (MDBX_env * env)) {
+  return mdbx_env_sync_ex(env, false, true);
+}
+
+/** \brief Sets threshold to force flush the data buffers to disk, even any of
+ * \ref MDBX_SAFE_NOSYNC flag in the environment.
+ * \ingroup c_settings
+ *
+ * The threshold value affects all processes which operates with given
+ * environment until the last process close environment or a new value will be
+ * settled.
+ *
+ * Data is always written to disk when \ref mdbx_txn_commit() is called, but
+ * the operating system may keep it buffered. MDBX always flushes the OS buffers
+ * upon commit as well, unless the environment was opened with
+ * \ref MDBX_SAFE_NOSYNC, \ref MDBX_UTTERLY_NOSYNC
+ * or in part \ref MDBX_NOMETASYNC.
+ *
+ * The default is 0, than mean no any threshold checked, and no additional
+ * flush will be made.
+ *
+ * \param [in] env         An environment handle returned by mdbx_env_create().
+ * \param [in] threshold   The size in bytes of summary changes when
+ *                         a synchronous flush would be made.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_INLINE_API(int, mdbx_env_set_syncbytes,
+                   (MDBX_env * env, size_t threshold)) {
+  return mdbx_env_set_option(env, MDBX_opt_sync_bytes, threshold);
+}
+
+/** \brief Sets relative period since the last unsteady commit to force flush
+ * the data buffers to disk, even of \ref MDBX_SAFE_NOSYNC flag in the
+ * environment.
+ *
+ * \ingroup c_settings
+ *
+ * The relative period value affects all processes which operates with given
+ * environment until the last process close environment or a new value will be
+ * settled.
+ *
+ * Data is always written to disk when \ref mdbx_txn_commit() is called, but the
+ * operating system may keep it buffered. MDBX always flushes the OS buffers
+ * upon commit as well, unless the environment was opened with
+ * \ref MDBX_SAFE_NOSYNC or in part \ref MDBX_NOMETASYNC.
+ *
+ * Settled period don't checked asynchronously, but only by the
+ * \ref mdbx_txn_commit() and \ref mdbx_env_sync() functions. Therefore, in
+ * cases where transactions are committed infrequently and/or irregularly,
+ * polling by \ref mdbx_env_sync() may be a reasonable solution to timeout
+ * enforcement.
+ *
+ * The default is 0, than mean no any timeout checked, and no additional
+ * flush will be made.
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ * \param [in] seconds_16dot16  The period in 1/65536 of second when
+ *                              a synchronous flush would be made since
+ *                              the last unsteady commit.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_INLINE_API(int, mdbx_env_set_syncperiod,
+                   (MDBX_env * env, unsigned seconds_16dot16)) {
+  return mdbx_env_set_option(env, MDBX_opt_sync_period, seconds_16dot16);
+}
+
+/** \brief Close the environment and release the memory map.
+ * \ingroup c_opening
+ *
+ * Only a single thread may call this function. All transactions, databases,
+ * and cursors must already be closed before calling this function. Attempts
+ * to use any such handles after calling this function will cause a `SIGSEGV`.
+ * The environment handle will be freed and must not be used again after this
+ * call.
+ *
+ * \param [in] env        An environment handle returned by
+ *                        \ref mdbx_env_create().
+ *
+ * \param [in] dont_sync  A dont'sync flag, if non-zero the last checkpoint
+ *                        will be kept "as is" and may be still "weak" in the
+ *                        \ref MDBX_SAFE_NOSYNC or \ref MDBX_UTTERLY_NOSYNC
+ *                        modes. Such "weak" checkpoint will be ignored on
+ *                        opening next time, and transactions since the last
+ *                        non-weak checkpoint (meta-page update) will rolledback
+ *                        for consistency guarantee.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_BUSY   The write transaction is running by other thread,
+ *                     in such case \ref MDBX_env instance has NOT be destroyed
+ *                     not released!
+ *                     \note If any OTHER error code was returned then
+ *                     given MDBX_env instance has been destroyed and released.
+ *
+ * \retval MDBX_EBADSIGN  Environment handle already closed or not valid,
+ *                        i.e. \ref mdbx_env_close() was already called for the
+ *                        `env` or was not created by \ref mdbx_env_create().
+ *
+ * \retval MDBX_PANIC  If \ref mdbx_env_close_ex() was called in the child
+ *                     process after `fork()`. In this case \ref MDBX_PANIC
+ *                     is expected, i.e. \ref MDBX_env instance was freed in
+ *                     proper manner.
+ *
+ * \retval MDBX_EIO    An error occurred during synchronization. */
+LIBMDBX_API int mdbx_env_close_ex(MDBX_env *env, bool dont_sync);
+
+/** \brief The shortcut to calling \ref mdbx_env_close_ex() with
+ * the `dont_sync=false` argument.
+ * \ingroup c_opening */
+LIBMDBX_INLINE_API(int, mdbx_env_close, (MDBX_env * env)) {
+  return mdbx_env_close_ex(env, false);
+}
+
+/** \brief Set environment flags.
+ * \ingroup c_settings
+ *
+ * This may be used to set some flags in addition to those from
+ * mdbx_env_open(), or to unset these flags.
+ * \see mdbx_env_get_flags()
+ *
+ * \note In contrast to LMDB, the MDBX serialize threads via mutex while
+ * changing the flags. Therefore this function will be blocked while a write
+ * transaction running by other thread, or \ref MDBX_BUSY will be returned if
+ * function called within a write transaction.
+ *
+ * \param [in] env      An environment handle returned
+ *                      by \ref mdbx_env_create().
+ * \param [in] flags    The \ref env_flags to change, bitwise OR'ed together.
+ * \param [in] onoff    A non-zero value sets the flags, zero clears them.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_env_set_flags(MDBX_env *env, MDBX_env_flags_t flags,
+                                   bool onoff);
+
+/** \brief Get environment flags.
+ * \ingroup c_statinfo
+ * \see mdbx_env_set_flags()
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ * \param [out] flags  The address of an integer to store the flags.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL An invalid parameter was specified. */
+LIBMDBX_API int mdbx_env_get_flags(const MDBX_env *env, unsigned *flags);
+
+/** \brief Return the path that was used in mdbx_env_open().
+ * \ingroup c_statinfo
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create()
+ * \param [out] dest   Address of a string pointer to contain the path.
+ *                     This is the actual string in the environment, not a
+ *                     copy. It should not be altered in any way.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_env_get_path(const MDBX_env *env, const char **dest);
+
+/** \brief Return the file descriptor for the given environment.
+ * \ingroup c_statinfo
+ *
+ * \note All MDBX file descriptors have `FD_CLOEXEC` and
+ *       couldn't be used after exec() and or `fork()`.
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ * \param [out] fd   Address of a int to contain the descriptor.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_env_get_fd(const MDBX_env *env, mdbx_filehandle_t *fd);
+
+/** \brief Set all size-related parameters of environment, including page size
+ * and the min/max size of the memory map. \ingroup c_settings
+ *
+ * In contrast to LMDB, the MDBX provide automatic size management of an
+ * database according the given parameters, including shrinking and resizing
+ * on the fly. From user point of view all of these just working. Nevertheless,
+ * it is reasonable to know some details in order to make optimal decisions
+ * when choosing parameters.
+ *
+ * Both \ref mdbx_env_info_ex() and legacy \ref mdbx_env_info() are inapplicable
+ * to read-only opened environment.
+ *
+ * Both \ref mdbx_env_info_ex() and legacy \ref mdbx_env_info() could be called
+ * either before or after \ref mdbx_env_open(), either within the write
+ * transaction running by current thread or not:
+ *
+ *  - In case \ref mdbx_env_info_ex() or legacy \ref mdbx_env_info() was called
+ *    BEFORE \ref mdbx_env_open(), i.e. for closed environment, then the
+ *    specified parameters will be used for new database creation, or will be
+ *    applied during opening if database exists and no other process using it.
+ *
+ *    If the database is already exist, opened with \ref MDBX_EXCLUSIVE or not
+ *    used by any other process, and parameters specified by
+ *    \ref mdbx_env_set_geometry() are incompatible (i.e. for instance,
+ *    different page size) then \ref mdbx_env_open() will return
+ *    \ref MDBX_INCOMPATIBLE error.
+ *
+ *    In another way, if database will opened read-only or will used by other
+ *    process during calling \ref mdbx_env_open() that specified parameters will
+ *    silently discarded (open the database with \ref MDBX_EXCLUSIVE flag
+ *    to avoid this).
+ *
+ *  - In case \ref mdbx_env_info_ex() or legacy \ref mdbx_env_info() was called
+ *    after \ref mdbx_env_open() WITHIN the write transaction running by current
+ *    thread, then specified parameters will be applied as a part of write
+ *    transaction, i.e. will not be visible to any others processes until the
+ *    current write transaction has been committed by the current process.
+ *    However, if transaction will be aborted, then the database file will be
+ *    reverted to the previous size not immediately, but when a next transaction
+ *    will be committed or when the database will be opened next time.
+ *
+ *  - In case \ref mdbx_env_info_ex() or legacy \ref mdbx_env_info() was called
+ *    after \ref mdbx_env_open() but OUTSIDE a write transaction, then MDBX will
+ *    execute internal pseudo-transaction to apply new parameters (but only if
+ *    anything has been changed), and changes be visible to any others processes
+ *    immediately after succesful completion of function.
+ *
+ * Essentially a concept of "automatic size management" is simple and useful:
+ *  - There are the lower and upper bound of the database file size;
+ *  - There is the growth step by which the database file will be increased,
+ *    in case of lack of space.
+ *  - There is the threshold for unused space, beyond which the database file
+ *    will be shrunk.
+ *  - The size of the memory map is also the maximum size of the database.
+ *  - MDBX will automatically manage both the size of the database and the size
+ *    of memory map, according to the given parameters.
+ *
+ * So, there some considerations about choosing these parameters:
+ *  - The lower bound allows you to prevent database shrinking below some
+ *    rational size to avoid unnecessary resizing costs.
+ *  - The upper bound allows you to prevent database growth above some rational
+ *    size. Besides, the upper bound defines the linear address space
+ *    reservation in each process that opens the database. Therefore changing
+ *    the upper bound is costly and may be required reopening environment in
+ *    case of \ref MDBX_UNABLE_EXTEND_MAPSIZE errors, and so on. Therefore, this
+ *    value should be chosen reasonable as large as possible, to accommodate
+ *    future growth of the database.
+ *  - The growth step must be greater than zero to allow the database to grow,
+ *    but also reasonable not too small, since increasing the size by little
+ *    steps will result a large overhead.
+ *  - The shrink threshold must be greater than zero to allow the database
+ *    to shrink but also reasonable not too small (to avoid extra overhead) and
+ *    not less than growth step to avoid up-and-down flouncing.
+ *  - The current size (i.e. size_now argument) is an auxiliary parameter for
+ *    simulation legacy \ref mdbx_env_set_mapsize() and as workaround Windows
+ *    issues (see below).
+ *
+ * Unfortunately, Windows has is a several issues
+ * with resizing of memory-mapped file:
+ *  - Windows unable shrinking a memory-mapped file (i.e memory-mapped section)
+ *    in any way except unmapping file entirely and then map again. Moreover,
+ *    it is impossible in any way if a memory-mapped file is used more than
+ *    one process.
+ *  - Windows does not provide the usual API to augment a memory-mapped file
+ *    (that is, a memory-mapped partition), but only by using "Native API"
+ *    in an undocumented way.
+ *
+ * MDBX bypasses all Windows issues, but at a cost:
+ *  - Ability to resize database on the fly requires an additional lock
+ *    and release `SlimReadWriteLock during` each read-only transaction.
+ *  - During resize all in-process threads should be paused and then resumed.
+ *  - Shrinking of database file is performed only when it used by single
+ *    process, i.e. when a database closes by the last process or opened
+ *    by the first.
+ *  = Therefore, the size_now argument may be useful to set database size
+ *    by the first process which open a database, and thus avoid expensive
+ *    remapping further.
+ *
+ * For create a new database with particular parameters, including the page
+ * size, \ref mdbx_env_set_geometry() should be called after
+ * \ref mdbx_env_create() and before mdbx_env_open(). Once the database is
+ * created, the page size cannot be changed. If you do not specify all or some
+ * of the parameters, the corresponding default values will be used. For
+ * instance, the default for database size is 10485760 bytes.
+ *
+ * If the mapsize is increased by another process, MDBX silently and
+ * transparently adopt these changes at next transaction start. However,
+ * \ref mdbx_txn_begin() will return \ref MDBX_UNABLE_EXTEND_MAPSIZE if new
+ * mapping size could not be applied for current process (for instance if
+ * address space is busy).  Therefore, in the case of
+ * \ref MDBX_UNABLE_EXTEND_MAPSIZE error you need close and reopen the
+ * environment to resolve error.
+ *
+ * \note Actual values may be different than your have specified because of
+ * rounding to specified database page size, the system page size and/or the
+ * size of the system virtual memory management unit. You can get actual values
+ * by \ref mdbx_env_sync_ex() or see by using the tool `mdbx_chk` with the `-v`
+ * option.
+ *
+ * Legacy \ref mdbx_env_set_mapsize() correspond to calling
+ * \ref mdbx_env_set_geometry() with the arguments `size_lower`, `size_now`,
+ * `size_upper` equal to the `size` and `-1` (i.e. default) for all other
+ * parameters.
+ *
+ * \param [in] env         An environment handle returned
+ *                         by \ref mdbx_env_create()
+ *
+ * \param [in] size_lower  The lower bound of database size in bytes.
+ *                         Zero value means "minimal acceptable",
+ *                         and negative means "keep current or use default".
+ *
+ * \param [in] size_now    The size in bytes to setup the database size for
+ *                         now. Zero value means "minimal acceptable", and
+ *                         negative means "keep current or use default". So,
+ *                         it is recommended always pass -1 in this argument
+ *                         except some special cases.
+ *
+ * \param [in] size_upper The upper bound of database size in bytes.
+ *                        Zero value means "minimal acceptable",
+ *                        and negative means "keep current or use default".
+ *                        It is recommended to avoid change upper bound while
+ *                        database is used by other processes or threaded
+ *                        (i.e. just pass -1 in this argument except absolutely
+ *                        necessary). Otherwise you must be ready for
+ *                        \ref MDBX_UNABLE_EXTEND_MAPSIZE error(s), unexpected
+ *                        pauses during remapping and/or system errors like
+ *                        "address busy", and so on. In other words, there
+ *                        is no way to handle a growth of the upper bound
+ *                        robustly because there may be a lack of appropriate
+ *                        system resources (which are extremely volatile in
+ *                        a multi-process multi-threaded environment).
+ *
+ * \param [in] growth_step  The growth step in bytes, must be greater than
+ *                          zero to allow the database to grow. Negative value
+ *                          means "keep current or use default".
+ *
+ * \param [in] shrink_threshold  The shrink threshold in bytes, must be greater
+ *                               than zero to allow the database to shrink and
+ *                               greater than growth_step to avoid shrinking
+ *                               right after grow.
+ *                               Negative value means "keep current
+ *                               or use default". Default is 2*growth_step.
+ *
+ * \param [in] pagesize          The database page size for new database
+ *                               creation or -1 otherwise. Must be power of 2
+ *                               in the range between \ref MDBX_MIN_PAGESIZE and
+ *                               \ref MDBX_MAX_PAGESIZE. Zero value means
+ *                               "minimal acceptable", and negative means
+ *                               "keep current or use default".
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL    An invalid parameter was specified,
+ *                        or the environment has an active write transaction.
+ * \retval MDBX_EPERM     Specific for Windows: Shrinking was disabled before
+ *                        and now it wanna be enabled, but there are reading
+ *                        threads that don't use the additional `SRWL` (that
+ *                        is required to avoid Windows issues).
+ * \retval MDBX_EACCESS   The environment opened in read-only.
+ * \retval MDBX_MAP_FULL  Specified size smaller than the space already
+ *                        consumed by the environment.
+ * \retval MDBX_TOO_LARGE Specified size is too large, i.e. too many pages for
+ *                        given size, or a 32-bit process requests too much
+ *                        bytes for the 32-bit address space. */
+LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
+                                      intptr_t size_now, intptr_t size_upper,
+                                      intptr_t growth_step,
+                                      intptr_t shrink_threshold,
+                                      intptr_t pagesize);
+
+/** \deprecated Please use \ref mdbx_env_set_geometry() instead.
+ * \ingroup c_settings */
+MDBX_DEPRECATED LIBMDBX_INLINE_API(int, mdbx_env_set_mapsize,
+                                   (MDBX_env * env, size_t size)) {
+  return mdbx_env_set_geometry(env, size, size, size, -1, -1, -1);
+}
+
+/** \brief Find out whether to use readahead or not, based on the given database
+ * size and the amount of available memory. \ingroup c_extra
+ *
+ * \param [in] volume      The expected database size in bytes.
+ * \param [in] redundancy  Additional reserve or overload in case of negative
+ *                         value.
+ *
+ * \returns A \ref MDBX_RESULT_TRUE or \ref MDBX_RESULT_FALSE value,
+ *          otherwise the error code:
+ * \retval MDBX_RESULT_TRUE   Readahead is reasonable.
+ * \retval MDBX_RESULT_FALSE  Readahead is NOT reasonable,
+ *                            i.e. \ref MDBX_NORDAHEAD is useful to
+ *                            open environment by \ref mdbx_env_open().
+ * \retval Otherwise the error code. */
+LIBMDBX_API int mdbx_is_readahead_reasonable(size_t volume,
+                                             intptr_t redundancy);
+
+/** \brief Returns the minimal database page size in bytes.
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_INLINE_API(intptr_t, mdbx_limits_pgsize_min,
+                                               (void)) {
+  return MDBX_MIN_PAGESIZE;
+}
+
+/** \brief Returns the maximal database page size in bytes.
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_INLINE_API(intptr_t, mdbx_limits_pgsize_max,
+                                               (void)) {
+  return MDBX_MAX_PAGESIZE;
+}
+
+/** \brief Returns minimal database size in bytes for given page size,
+ * or -1 if pagesize is invalid.
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API intptr_t
+mdbx_limits_dbsize_min(intptr_t pagesize);
+
+/** \brief Returns maximal database size in bytes for given page size,
+ * or -1 if pagesize is invalid.
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API intptr_t
+mdbx_limits_dbsize_max(intptr_t pagesize);
+
+/** \brief Returns maximal key size in bytes for given page size
+ * and database flags, or -1 if pagesize is invalid.
+ * \ingroup c_statinfo
+ * \see db_flags */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API intptr_t
+mdbx_limits_keysize_max(intptr_t pagesize, MDBX_db_flags_t flags);
+
+/** \brief Returns maximal data size in bytes for given page size
+ * and database flags, or -1 if pagesize is invalid.
+ * \ingroup c_statinfo
+ * \see db_flags */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API intptr_t
+mdbx_limits_valsize_max(intptr_t pagesize, MDBX_db_flags_t flags);
+
+/** \brief Returns maximal write transaction size (i.e. limit for summary volume
+ * of dirty pages) in bytes for given page size, or -1 if pagesize is invalid.
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API intptr_t
+mdbx_limits_txnsize_max(intptr_t pagesize);
+
+/** \brief Set the maximum number of threads/reader slots for for all processes
+ * interacts with the database. \ingroup c_settings
+ *
+ * \details This defines the number of slots in the lock table that is used to
+ * track readers in the the environment. The default is about 100 for 4K system
+ * page size. Starting a read-only transaction normally ties a lock table slot
+ * to the current thread until the environment closes or the thread exits. If
+ * \ref MDBX_NOTLS is in use, \ref mdbx_txn_begin() instead ties the slot to the
+ * \ref MDBX_txn object until it or the \ref MDBX_env object is destroyed.
+ * This function may only be called after \ref mdbx_env_create() and before
+ * \ref mdbx_env_open(), and has an effect only when the database is opened by
+ * the first process interacts with the database.
+ * \see mdbx_env_get_maxreaders()
+ *
+ * \param [in] env       An environment handle returned
+ *                       by \ref mdbx_env_create().
+ * \param [in] readers   The maximum number of reader lock table slots.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL   An invalid parameter was specified.
+ * \retval MDBX_EPERM    The environment is already open. */
+LIBMDBX_INLINE_API(int, mdbx_env_set_maxreaders,
+                   (MDBX_env * env, unsigned readers)) {
+  return mdbx_env_set_option(env, MDBX_opt_max_readers, readers);
+}
+
+/** \brief Get the maximum number of threads/reader slots for the environment.
+ * \ingroup c_statinfo
+ * \see mdbx_env_set_maxreaders()
+ *
+ * \param [in] env       An environment handle returned
+ *                       by \ref mdbx_env_create().
+ * \param [out] readers  Address of an integer to store the number of readers.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL   An invalid parameter was specified. */
+LIBMDBX_INLINE_API(int, mdbx_env_get_maxreaders,
+                   (const MDBX_env *env, unsigned *readers)) {
+  int rc = MDBX_EINVAL;
+  if (readers) {
+    uint64_t proxy = 0;
+    rc = mdbx_env_get_option(env, MDBX_opt_max_readers, &proxy);
+    *readers = (unsigned)proxy;
+  }
+  return rc;
+}
+
+/** \brief Set the maximum number of named databases for the environment.
+ * \ingroup c_settings
+ *
+ * This function is only needed if multiple databases will be used in the
+ * environment. Simpler applications that use the environment as a single
+ * unnamed database can ignore this option.
+ * This function may only be called after \ref mdbx_env_create() and before
+ * \ref mdbx_env_open().
+ *
+ * Currently a moderate number of slots are cheap but a huge number gets
+ * expensive: 7-120 words per transaction, and every \ref mdbx_dbi_open()
+ * does a linear search of the opened slots.
+ * \see mdbx_env_get_maxdbs()
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ * \param [in] dbs   The maximum number of databases.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL   An invalid parameter was specified.
+ * \retval MDBX_EPERM    The environment is already open. */
+LIBMDBX_INLINE_API(int, mdbx_env_set_maxdbs, (MDBX_env * env, MDBX_dbi dbs)) {
+  return mdbx_env_set_option(env, MDBX_opt_max_db, dbs);
+}
+
+/** \brief Get the maximum number of named databases for the environment.
+ * \ingroup c_statinfo
+ * \see mdbx_env_set_maxdbs()
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ * \param [out] dbs  Address to store the maximum number of databases.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EINVAL   An invalid parameter was specified. */
+LIBMDBX_INLINE_API(int, mdbx_env_get_maxdbs,
+                   (const MDBX_env *env, MDBX_dbi *dbs)) {
+  int rc = MDBX_EINVAL;
+  if (dbs) {
+    uint64_t proxy = 0;
+    rc = mdbx_env_get_option(env, MDBX_opt_max_db, &proxy);
+    *dbs = (MDBX_dbi)proxy;
+  }
+  return rc;
+}
+
+/** \brief Returns the default size of database page for the current system.
+ * \ingroup c_statinfo
+ * \details Default size of database page depends on the size of the system
+ * page and usually exactly match it. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API size_t mdbx_default_pagesize(void);
+
+/** \brief Get the maximum size of keys can write.
+ * \ingroup c_statinfo
+ *
+ * \param [in] env    An environment handle returned by \ref mdbx_env_create().
+ * \param [in] flags  Database options (\ref MDBX_DUPSORT, \ref MDBX_INTEGERKEY
+ *                    and so on). \see db_flags
+ *
+ * \returns The maximum size of a key can write,
+ *          or -1 if something is wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_env_get_maxkeysize_ex(const MDBX_env *env, MDBX_db_flags_t flags);
+
+/** \brief Get the maximum size of data we can write.
+ * \ingroup c_statinfo
+ *
+ * \param [in] env    An environment handle returned by \ref mdbx_env_create().
+ * \param [in] flags  Database options (\ref MDBX_DUPSORT, \ref MDBX_INTEGERKEY
+ *                    and so on). \see db_flags
+ *
+ * \returns The maximum size of a data can write,
+ *          or -1 if something is wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_env_get_maxvalsize_ex(const MDBX_env *env, MDBX_db_flags_t flags);
+
+/** \deprecated Please use \ref mdbx_env_get_maxkeysize_ex()
+ *              and/or \ref mdbx_env_get_maxvalsize_ex()
+ * \ingroup c_statinfo */
+MDBX_NOTHROW_PURE_FUNCTION MDBX_DEPRECATED LIBMDBX_API int
+mdbx_env_get_maxkeysize(const MDBX_env *env);
+
+/** \brief Set application information associated with the \ref MDBX_env.
+ * \ingroup c_settings
+ * \see mdbx_env_get_userctx()
+ *
+ * \param [in] env  An environment handle returned by \ref mdbx_env_create().
+ * \param [in] ctx  An arbitrary pointer for whatever the application needs.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_set_userctx(MDBX_env *env, void *ctx);
+
+/** \brief Get the application information associated with the MDBX_env.
+ * \ingroup c_statinfo
+ * \see mdbx_env_set_userctx()
+ *
+ * \param [in] env An environment handle returned by \ref mdbx_env_create()
+ * \returns The pointer set by \ref mdbx_env_set_userctx()
+ *          or `NULL` if something wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API void *
+mdbx_env_get_userctx(const MDBX_env *env);
+
+/** \brief Create a transaction with a user provided context pointer
+ * for use with the environment.
+ * \ingroup c_transactions
+ *
+ * The transaction handle may be discarded using \ref mdbx_txn_abort()
+ * or \ref mdbx_txn_commit().
+ * \see mdbx_txn_begin()
+ *
+ * \note A transaction and its cursors must only be used by a single thread,
+ * and a thread may only have a single transaction at a time. If \ref MDBX_NOTLS
+ * is in use, this does not apply to read-only transactions.
+ *
+ * \note Cursors may not span transactions.
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ *
+ * \param [in] parent  If this parameter is non-NULL, the new transaction will
+ *                     be a nested transaction, with the transaction indicated
+ *                     by parent as its parent. Transactions may be nested
+ *                     to any level. A parent transaction and its cursors may
+ *                     not issue any other operations than mdbx_txn_commit and
+ *                     \ref mdbx_txn_abort() while it has active child
+ *                     transactions.
+ *
+ * \param [in] flags   Special options for this transaction. This parameter
+ *                     must be set to 0 or by bitwise OR'ing together one
+ *                     or more of the values described here:
+ *                      - \ref MDBX_RDONLY   This transaction will not perform
+ *                                           any write operations.
+ *
+ *                      - \ref MDBX_TXN_TRY  Do not block when starting
+ *                                           a write transaction.
+ *
+ *                      - \ref MDBX_SAFE_NOSYNC, \ref MDBX_NOMETASYNC.
+ *                        Do not sync data to disk corresponding
+ *                        to \ref MDBX_NOMETASYNC or \ref MDBX_SAFE_NOSYNC
+ *                        description. \see sync_modes
+ *
+ * \param [out] txn    Address where the new MDBX_txn handle will be stored.
+ *
+ * \param [in] context A pointer to application context to be associated with
+ *                     created transaction and could be retrieved by
+ *                     \ref mdbx_txn_get_userctx() until transaction finished.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_PANIC         A fatal error occurred earlier and the
+ *                            environment must be shut down.
+ * \retval MDBX_UNABLE_EXTEND_MAPSIZE  Another process wrote data beyond
+ *                                     this MDBX_env's mapsize and this
+ *                                     environment map must be resized as well.
+ *                                     See \ref mdbx_env_set_mapsize().
+ * \retval MDBX_READERS_FULL  A read-only transaction was requested and
+ *                            the reader lock table is full.
+ *                            See \ref mdbx_env_set_maxreaders().
+ * \retval MDBX_ENOMEM        Out of memory.
+ * \retval MDBX_BUSY          The write transaction is already started by the
+ *                            current thread. */
+LIBMDBX_API int mdbx_txn_begin_ex(MDBX_env *env, MDBX_txn *parent,
+                                  MDBX_txn_flags_t flags, MDBX_txn **txn,
+                                  void *context);
+
+/** \brief Create a transaction for use with the environment.
+ * \ingroup c_transactions
+ *
+ * The transaction handle may be discarded using \ref mdbx_txn_abort()
+ * or \ref mdbx_txn_commit().
+ * \see mdbx_txn_begin_ex()
+ *
+ * \note A transaction and its cursors must only be used by a single thread,
+ * and a thread may only have a single transaction at a time. If \ref MDBX_NOTLS
+ * is in use, this does not apply to read-only transactions.
+ *
+ * \note Cursors may not span transactions.
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ *
+ * \param [in] parent  If this parameter is non-NULL, the new transaction will
+ *                     be a nested transaction, with the transaction indicated
+ *                     by parent as its parent. Transactions may be nested
+ *                     to any level. A parent transaction and its cursors may
+ *                     not issue any other operations than mdbx_txn_commit and
+ *                     \ref mdbx_txn_abort() while it has active child
+ *                     transactions.
+ *
+ * \param [in] flags   Special options for this transaction. This parameter
+ *                     must be set to 0 or by bitwise OR'ing together one
+ *                     or more of the values described here:
+ *                      - \ref MDBX_RDONLY   This transaction will not perform
+ *                                           any write operations.
+ *
+ *                      - \ref MDBX_TXN_TRY  Do not block when starting
+ *                                           a write transaction.
+ *
+ *                      - \ref MDBX_SAFE_NOSYNC, \ref MDBX_NOMETASYNC.
+ *                        Do not sync data to disk corresponding
+ *                        to \ref MDBX_NOMETASYNC or \ref MDBX_SAFE_NOSYNC
+ *                        description. \see sync_modes
+ *
+ * \param [out] txn    Address where the new MDBX_txn handle will be stored.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_PANIC         A fatal error occurred earlier and the
+ *                            environment must be shut down.
+ * \retval MDBX_UNABLE_EXTEND_MAPSIZE  Another process wrote data beyond
+ *                                     this MDBX_env's mapsize and this
+ *                                     environment map must be resized as well.
+ *                                     See \ref mdbx_env_set_mapsize().
+ * \retval MDBX_READERS_FULL  A read-only transaction was requested and
+ *                            the reader lock table is full.
+ *                            See \ref mdbx_env_set_maxreaders().
+ * \retval MDBX_ENOMEM        Out of memory.
+ * \retval MDBX_BUSY          The write transaction is already started by the
+ *                            current thread. */
+LIBMDBX_INLINE_API(int, mdbx_txn_begin,
+                   (MDBX_env * env, MDBX_txn *parent, MDBX_txn_flags_t flags,
+                    MDBX_txn **txn)) {
+  return mdbx_txn_begin_ex(env, parent, flags, txn, NULL);
+}
+
+/** \brief Set application information associated with the \ref MDBX_txn.
+ * \ingroup c_transactions
+ * \see mdbx_txn_get_userctx()
+ *
+ * \param [in] txn  An transaction handle returned by \ref mdbx_txn_begin_ex()
+ *                  or \ref mdbx_txn_begin().
+ * \param [in] ctx  An arbitrary pointer for whatever the application needs.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_txn_set_userctx(MDBX_txn *txn, void *ctx);
+
+/** \brief Get the application information associated with the MDBX_txn.
+ * \ingroup c_transactions
+ * \see mdbx_txn_set_userctx()
+ *
+ * \param [in] txn  An transaction handle returned by \ref mdbx_txn_begin_ex()
+ *                  or \ref mdbx_txn_begin().
+ * \returns The pointer which was passed via the `context` parameter
+ *          of `mdbx_txn_begin_ex()` or set by \ref mdbx_txn_set_userctx(),
+ *          or `NULL` if something wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API void *
+mdbx_txn_get_userctx(const MDBX_txn *txn);
+
+/** \brief Information about the transaction
+ * \ingroup c_statinfo
+ * \see mdbx_txn_info */
+struct MDBX_txn_info {
+  /** The ID of the transaction. For a READ-ONLY transaction, this corresponds
+      to the snapshot being read. */
+  uint64_t txn_id;
+
+  /** For READ-ONLY transaction: the lag from a recent MVCC-snapshot, i.e. the
+     number of committed transaction since read transaction started.
+     For WRITE transaction (provided if `scan_rlt=true`): the lag of the oldest
+     reader from current transaction (i.e. at least 1 if any reader running). */
+  uint64_t txn_reader_lag;
+
+  /** Used space by this transaction, i.e. corresponding to the last used
+   * database page. */
+  uint64_t txn_space_used;
+
+  /** Current size of database file. */
+  uint64_t txn_space_limit_soft;
+
+  /** Upper bound for size the database file, i.e. the value `size_upper`
+     argument of the appropriate call of \ref mdbx_env_set_geometry(). */
+  uint64_t txn_space_limit_hard;
+
+  /** For READ-ONLY transaction: The total size of the database pages that were
+     retired by committed write transactions after the reader's MVCC-snapshot,
+     i.e. the space which would be freed after the Reader releases the
+     MVCC-snapshot for reuse by completion read transaction.
+     For WRITE transaction: The summarized size of the database pages that were
+     retired for now due Copy-On-Write during this transaction. */
+  uint64_t txn_space_retired;
+
+  /** For READ-ONLY transaction: the space available for writer(s) and that
+     must be exhausted for reason to call the Handle-Slow-Readers callback for
+     this read transaction.
+     For WRITE transaction: the space inside transaction
+     that left to `MDBX_TXN_FULL` error. */
+  uint64_t txn_space_leftover;
+
+  /** For READ-ONLY transaction (provided if `scan_rlt=true`): The space that
+     actually become available for reuse when only this transaction will be
+     finished.
+     For WRITE transaction: The summarized size of the dirty database
+     pages that generated during this transaction. */
+  uint64_t txn_space_dirty;
+};
+#ifndef __cplusplus
+/** \ingroup c_statinfo */
+typedef struct MDBX_txn_info MDBX_txn_info;
+#endif
+
+/** \brief Return information about the MDBX transaction.
+ * \ingroup c_statinfo
+ *
+ * \param [in] txn        A transaction handle returned by \ref mdbx_txn_begin()
+ * \param [out] info      The address of an \ref MDBX_txn_info structure
+ *                        where the information will be copied.
+ * \param [in] scan_rlt   The boolean flag controls the scan of the read lock
+ *                        table to provide complete information. Such scan
+ *                        is relatively expensive and you can avoid it
+ *                        if corresponding fields are not needed.
+ *                        See description of \ref MDBX_txn_info.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_txn_info(const MDBX_txn *txn, MDBX_txn_info *info,
+                              bool scan_rlt);
+
+/** \brief Returns the transaction's MDBX_env.
+ * \ingroup c_transactions
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin() */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API MDBX_env *
+mdbx_txn_env(const MDBX_txn *txn);
+
+/** \brief Return the transaction's flags.
+ * \ingroup c_transactions
+ *
+ * This returns the flags associated with this transaction.
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A transaction flags, valid if input is an valid transaction,
+ *          otherwise -1. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int mdbx_txn_flags(const MDBX_txn *txn);
+
+/** \brief Return the transaction's ID.
+ * \ingroup c_statinfo
+ *
+ * This returns the identifier associated with this transaction. For a
+ * read-only transaction, this corresponds to the snapshot being read;
+ * concurrent readers will frequently have the same transaction ID.
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A transaction ID, valid if input is an active transaction,
+ *          otherwise 0. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API uint64_t
+mdbx_txn_id(const MDBX_txn *txn);
+
+/** \brief Latency of commit stages in 1/65536 of seconds units.
+ * \warning This structure may be changed in future releases.
+ * \see mdbx_txn_commit_ex() */
+struct MDBX_commit_latency {
+  /** \brief Duration of preparation (commit child transactions, update
+   * sub-databases records and cursors destroying). */
+  uint32_t preparation;
+  /** \brief Duration of GC/freeDB handling & updation. */
+  uint32_t gc;
+  /** \brief Duration of internal audit if enabled. */
+  uint32_t audit;
+  /** \brief Duration of writing dirty/modified data pages. */
+  uint32_t write;
+  /** \brief Duration of syncing written data to the dist/storage. */
+  uint32_t sync;
+  /** \brief Duration of transaction ending (releasing resources). */
+  uint32_t ending;
+  /** \brief The total duration of a commit. */
+  uint32_t whole;
+};
+#ifndef __cplusplus
+/** \ingroup c_statinfo */
+typedef struct MDBX_commit_latency MDBX_commit_latency;
+#endif
+
+/** \brief Commit all the operations of a transaction into the database and
+ * collect latency information.
+ * \see mdbx_txn_commit()
+ * \ingroup c_statinfo
+ * \warning This function may be changed in future releases. */
+LIBMDBX_API int mdbx_txn_commit_ex(MDBX_txn *txn, MDBX_commit_latency *latency);
+
+/** \brief Commit all the operations of a transaction into the database.
+ * \ingroup c_transactions
+ *
+ * If the current thread is not eligible to manage the transaction then
+ * the \ref MDBX_THREAD_MISMATCH error will returned. Otherwise the transaction
+ * will be committed and its handle is freed. If the transaction cannot
+ * be committed, it will be aborted with the corresponding error returned.
+ *
+ * Thus, a result other than \ref MDBX_THREAD_MISMATCH means that the
+ * transaction is terminated:
+ *  - Resources are released;
+ *  - Transaction handle is invalid;
+ *  - Cursor(s) associated with transaction must not be used, except with
+ *    mdbx_cursor_renew() and \ref mdbx_cursor_close().
+ *    Such cursor(s) must be closed explicitly by \ref mdbx_cursor_close()
+ *    before or after transaction commit, either can be reused with
+ *    \ref mdbx_cursor_renew() until it will be explicitly closed by
+ *    \ref mdbx_cursor_close().
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_RESULT_TRUE      Transaction was aborted since it should
+ *                               be aborted due to previous errors.
+ * \retval MDBX_PANIC            A fatal error occurred earlier
+ *                               and the environment must be shut down.
+ * \retval MDBX_BAD_TXN          Transaction is already finished or never began.
+ * \retval MDBX_EBADSIGN         Transaction object has invalid signature,
+ *                               e.g. transaction was already terminated
+ *                               or memory was corrupted.
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL           Transaction handle is NULL.
+ * \retval MDBX_ENOSPC           No more disk space.
+ * \retval MDBX_EIO              A system-level I/O error occurred.
+ * \retval MDBX_ENOMEM           Out of memory. */
+LIBMDBX_INLINE_API(int, mdbx_txn_commit, (MDBX_txn * txn)) {
+  return mdbx_txn_commit_ex(txn, NULL);
+}
+
+/** \brief Abandon all the operations of the transaction instead of saving them.
+ * \ingroup c_transactions
+ *
+ * The transaction handle is freed. It and its cursors must not be used again
+ * after this call, except with \ref mdbx_cursor_renew() and
+ * \ref mdbx_cursor_close().
+ *
+ * If the current thread is not eligible to manage the transaction then
+ * the \ref MDBX_THREAD_MISMATCH error will returned. Otherwise the transaction
+ * will be aborted and its handle is freed. Thus, a result other than
+ * \ref MDBX_THREAD_MISMATCH means that the transaction is terminated:
+ *  - Resources are released;
+ *  - Transaction handle is invalid;
+ *  - Cursor(s) associated with transaction must not be used, except with
+ *    \ref mdbx_cursor_renew() and \ref mdbx_cursor_close().
+ *    Such cursor(s) must be closed explicitly by \ref mdbx_cursor_close()
+ *    before or after transaction abort, either can be reused with
+ *    \ref mdbx_cursor_renew() until it will be explicitly closed by
+ *    \ref mdbx_cursor_close().
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_PANIC            A fatal error occurred earlier and
+ *                               the environment must be shut down.
+ * \retval MDBX_BAD_TXN          Transaction is already finished or never began.
+ * \retval MDBX_EBADSIGN         Transaction object has invalid signature,
+ *                               e.g. transaction was already terminated
+ *                               or memory was corrupted.
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL           Transaction handle is NULL. */
+LIBMDBX_API int mdbx_txn_abort(MDBX_txn *txn);
+
+/** \brief Marks transaction as broken.
+ * \ingroup c_transactions
+ *
+ * Function keeps the transaction handle and corresponding locks, but it
+ * is not possible to perform any operations in a broken transaction.
+ * Broken transaction must then be aborted explicitly later.
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \see mdbx_txn_abort() \see mdbx_txn_reset() \see mdbx_txn_commit()
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_txn_break(MDBX_txn *txn);
+
+/** \brief Reset a read-only transaction.
+ * \ingroup c_transactions
+ *
+ * Abort the read-only transaction like \ref mdbx_txn_abort(), but keep the
+ * transaction handle. Therefore \ref mdbx_txn_renew() may reuse the handle.
+ * This saves allocation overhead if the process will start a new read-only
+ * transaction soon, and also locking overhead if \ref MDBX_NOTLS is in use. The
+ * reader table lock is released, but the table slot stays tied to its thread
+ * or \ref MDBX_txn. Use \ref mdbx_txn_abort() to discard a reset handle, and to
+ * free its lock table slot if \ref MDBX_NOTLS is in use.
+ *
+ * Cursors opened within the transaction must not be used again after this
+ * call, except with \ref mdbx_cursor_renew() and \ref mdbx_cursor_close().
+ *
+ * Reader locks generally don't interfere with writers, but they keep old
+ * versions of database pages allocated. Thus they prevent the old pages from
+ * being reused when writers commit new data, and so under heavy load the
+ * database size may grow much more rapidly than otherwise.
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_PANIC            A fatal error occurred earlier and
+ *                               the environment must be shut down.
+ * \retval MDBX_BAD_TXN          Transaction is already finished or never began.
+ * \retval MDBX_EBADSIGN         Transaction object has invalid signature,
+ *                               e.g. transaction was already terminated
+ *                               or memory was corrupted.
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL           Transaction handle is NULL. */
+LIBMDBX_API int mdbx_txn_reset(MDBX_txn *txn);
+
+/** \brief Renew a read-only transaction.
+ * \ingroup c_transactions
+ *
+ * This acquires a new reader lock for a transaction handle that had been
+ * released by \ref mdbx_txn_reset(). It must be called before a reset
+ * transaction may be used again.
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_PANIC            A fatal error occurred earlier and
+ *                               the environment must be shut down.
+ * \retval MDBX_BAD_TXN          Transaction is already finished or never began.
+ * \retval MDBX_EBADSIGN         Transaction object has invalid signature,
+ *                               e.g. transaction was already terminated
+ *                               or memory was corrupted.
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL           Transaction handle is NULL. */
+LIBMDBX_API int mdbx_txn_renew(MDBX_txn *txn);
+
+/** \brief The fours integers markers (aka "canary") associated with the
+ * environment. \ingroup c_crud \see mdbx_canary_set() \see mdbx_canary_get()
+ *
+ * The `x`, `y` and `z` values could be set by \ref mdbx_canary_put(), while the
+ * 'v' will be always set to the transaction number. Updated values becomes
+ * visible outside the current transaction only after it was committed. Current
+ * values could be retrieved by \ref mdbx_canary_get(). */
+struct MDBX_canary {
+  uint64_t x, y, z, v;
+};
+#ifndef __cplusplus
+/** \ingroup c_crud */
+typedef struct MDBX_canary MDBX_canary;
+#endif
+
+/** \brief Set integers markers (aka "canary") associated with the environment.
+ * \ingroup c_crud
+ * \see mdbx_canary_get()
+ *
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin()
+ * \param [in] canary  A optional pointer to \ref MDBX_canary structure for `x`,
+ *              `y` and `z` values from.
+ *            - If canary is NOT NULL then the `x`, `y` and `z` values will be
+ *              updated from given canary argument, but the 'v' be always set
+ *              to the current transaction number if at least one `x`, `y` or
+ *              `z` values have changed (i.e. if `x`, `y` and `z` have the same
+ *              values as currently present then nothing will be changes or
+ *              updated).
+ *            - if canary is NULL then the `v` value will be explicitly update
+ *              to the current transaction number without changes `x`, `y` nor
+ *              `z`.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_canary_put(MDBX_txn *txn, const MDBX_canary *canary);
+
+/** \brief Returns fours integers markers (aka "canary") associated with the
+ * environment.
+ * \ingroup c_crud
+ * \see mdbx_canary_set()
+ *
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] canary  The address of an MDBX_canary structure where the
+ *                     information will be copied.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_canary_get(const MDBX_txn *txn, MDBX_canary *canary);
+
+/** \brief A callback function used to compare two keys in a database
+ * \ingroup c_crud
+ * \see mdbx_cmp() \see mdbx_get_keycmp()
+ * \see mdbx_get_datacmp \see mdbx_dcmp() */
+typedef int(MDBX_cmp_func)(const MDBX_val *a,
+                           const MDBX_val *b) MDBX_CXX17_NOEXCEPT;
+
+/** \brief Open or Create a database in the environment.
+ * \ingroup c_dbi
+ *
+ * A database handle denotes the name and parameters of a database,
+ * independently of whether such a database exists. The database handle may be
+ * discarded by calling \ref mdbx_dbi_close(). The old database handle is
+ * returned if the database was already open. The handle may only be closed
+ * once.
+ *
+ * \note A notable difference between MDBX and LMDB is that MDBX make handles
+ * opened for existing databases immediately available for other transactions,
+ * regardless this transaction will be aborted or reset. The REASON for this is
+ * to avoiding the requirement for multiple opening a same handles in
+ * concurrent read transactions, and tracking of such open but hidden handles
+ * until the completion of read transactions which opened them.
+ *
+ * Nevertheless, the handle for the NEWLY CREATED database will be invisible
+ * for other transactions until the this write transaction is successfully
+ * committed. If the write transaction is aborted the handle will be closed
+ * automatically. After a successful commit the such handle will reside in the
+ * shared environment, and may be used by other transactions.
+ *
+ * In contrast to LMDB, the MDBX allow this function to be called from multiple
+ * concurrent transactions or threads in the same process.
+ *
+ * To use named database (with name != NULL), \ref mdbx_env_set_maxdbs()
+ * must be called before opening the environment. Table names are
+ * keys in the internal unnamed database, and may be read but not written.
+ *
+ * \param [in] txn    transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] name   The name of the database to open. If only a single
+ *                    database is needed in the environment,
+ *                    this value may be NULL.
+ * \param [in] flags  Special options for this database. This parameter must
+ *                    be set to 0 or by bitwise OR'ing together one or more
+ *                    of the values described here:
+ *  - \ref MDBX_REVERSEKEY
+ *      Keys are strings to be compared in reverse order, from the end
+ *      of the strings to the beginning. By default, Keys are treated as
+ *      strings and compared from beginning to end.
+ *  - \ref MDBX_INTEGERKEY
+ *      Keys are binary integers in native byte order, either uint32_t or
+ *      uint64_t, and will be sorted as such. The keys must all be of the
+ *      same size and must be aligned while passing as arguments.
+ *  - \ref MDBX_DUPSORT
+ *      Duplicate keys may be used in the database. Or, from another point of
+ *      view, keys may have multiple data items, stored in sorted order. By
+ *      default keys must be unique and may have only a single data item.
+ *  - \ref MDBX_DUPFIXED
+ *      This flag may only be used in combination with \ref MDBX_DUPSORT. This
+ *      option tells the library that the data items for this database are
+ *      all the same size, which allows further optimizations in storage and
+ *      retrieval. When all data items are the same size, the
+ *      \ref MDBX_GET_MULTIPLE, \ref MDBX_NEXT_MULTIPLE and
+ *      \ref MDBX_PREV_MULTIPLE cursor operations may be used to retrieve
+ *      multiple items at once.
+ *  - \ref MDBX_INTEGERDUP
+ *      This option specifies that duplicate data items are binary integers,
+ *      similar to \ref MDBX_INTEGERKEY keys. The data values must all be of the
+ *      same size and must be aligned while passing as arguments.
+ *  - \ref MDBX_REVERSEDUP
+ *      This option specifies that duplicate data items should be compared as
+ *      strings in reverse order (the comparison is performed in the direction
+ *      from the last byte to the first).
+ *  - \ref MDBX_CREATE
+ *      Create the named database if it doesn't exist. This option is not
+ *      allowed in a read-only transaction or a read-only environment.
+ *
+ * \param [out] dbi     Address where the new \ref MDBX_dbi handle
+ *                      will be stored.
+ *
+ * For \ref mdbx_dbi_open_ex() additional arguments allow you to set custom
+ * comparison functions for keys and values (for multimaps).
+ * However, I recommend not using custom comparison functions, but instead
+ * converting the keys to one of the forms that are suitable for built-in
+ * comparators (for instance take look to the \ref value2key).
+ * The reasons to not using custom comparators are:
+ *   - The order of records could not be validated without your code.
+ *     So `mdbx_chk` utility will reports "wrong order" errors
+ *     and the `-i` option is required to ignore ones.
+ *   - A records could not be ordered or sorted without your code.
+ *     So mdbx_load utility should be used with `-a` option to preserve
+ *     input data order.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_NOTFOUND   The specified database doesn't exist in the
+ *                         environment and \ref MDBX_CREATE was not specified.
+ * \retval MDBX_DBS_FULL   Too many databases have been opened.
+ *                         \see mdbx_env_set_maxdbs()
+ * \retval MDBX_INCOMPATIBLE  Database is incompatible with given flags,
+ *                         i.e. the passed flags is different with which the
+ *                         database was created, or the database was already
+ *                         opened with a different comparison function(s).
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread. */
+LIBMDBX_API int mdbx_dbi_open(MDBX_txn *txn, const char *name,
+                              MDBX_db_flags_t flags, MDBX_dbi *dbi);
+
+/** \deprecated Please avoid using custom comparators
+ *              and use mdbx_dbi_open() instead.
+ * \ingroup c_dbi
+ *
+ * \param [in] txn    transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] name   The name of the database to open. If only a single
+ *                    database is needed in the environment,
+ *                    this value may be NULL.
+ * \param [in] flags  Special options for this database.
+ * \param [in] keycmp  Optional custom key comparison function for a database.
+ * \param [in] datacmp Optional custom data comparison function for a database.
+ * \param [out] dbi    Address where the new MDBX_dbi handle will be stored.
+ * \returns A non-zero error value on failure and 0 on success. */
+MDBX_DEPRECATED LIBMDBX_API int
+mdbx_dbi_open_ex(MDBX_txn *txn, const char *name, MDBX_db_flags_t flags,
+                 MDBX_dbi *dbi, MDBX_cmp_func *keycmp, MDBX_cmp_func *datacmp);
+
+/** \defgroup value2key Value-to-Key functions to avoid custom comparators
+ * \see key2value
+ * @{
+ *
+ * The \ref mdbx_key_from_jsonInteger() build a keys which are comparable with
+ * keys created by \ref mdbx_key_from_double(). So this allows mixing `int64_t`
+ * and IEEE754 double values in one index for JSON-numbers with restriction for
+ * integer numbers range corresponding to RFC-7159, i.e. \f$[-2^{53}+1,
+ * 2^{53}-1]\f$. See bottom of page 6 at https://tools.ietf.org/html/rfc7159 */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API uint64_t
+mdbx_key_from_jsonInteger(const int64_t json_integer);
+
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API uint64_t
+mdbx_key_from_double(const double ieee754_64bit);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API uint64_t
+mdbx_key_from_ptrdouble(const double *const ieee754_64bit);
+
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API uint32_t
+mdbx_key_from_float(const float ieee754_32bit);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API uint32_t
+mdbx_key_from_ptrfloat(const float *const ieee754_32bit);
+
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_INLINE_API(uint64_t, mdbx_key_from_int64,
+                                               (const int64_t i64)) {
+  return UINT64_C(0x8000000000000000) + i64;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_INLINE_API(uint32_t, mdbx_key_from_int32,
+                                               (const int32_t i32)) {
+  return UINT32_C(0x80000000) + i32;
+}
+/** @} */
+
+/** \defgroup key2value Key-to-Value functions to avoid custom comparators
+ * \see value2key
+ * @{ */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int64_t
+mdbx_jsonInteger_from_key(const MDBX_val);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API double
+mdbx_double_from_key(const MDBX_val);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API float
+mdbx_float_from_key(const MDBX_val);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int32_t
+mdbx_int32_from_key(const MDBX_val);
+
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int64_t
+mdbx_int64_from_key(const MDBX_val);
+/** @} */
+
+/** \brief Retrieve statistics for a database.
+ * \ingroup c_statinfo
+ *
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi     A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] stat   The address of an \ref MDBX_stat structure where
+ *                     the statistics will be copied.
+ * \param [in] bytes   The size of \ref MDBX_stat.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL   An invalid parameter was specified. */
+LIBMDBX_API int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *stat,
+                              size_t bytes);
+
+/** \brief Retrieve depth (bitmask) information of nested dupsort (multi-value)
+ * B+trees for given database.
+ * \ingroup c_statinfo
+ *
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi     A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] mask   The address of an uint32_t value where the bitmask
+ *                     will be stored.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL       An invalid parameter was specified.
+ * \retval MDBX_RESULT_TRUE  The dbi isn't a dupsort (multi-value) database. */
+LIBMDBX_API int mdbx_dbi_dupsort_depthmask(MDBX_txn *txn, MDBX_dbi dbi,
+                                           uint32_t *mask);
+
+/** \brief DBI state bits returted by \ref mdbx_dbi_flags_ex()
+ * \ingroup c_statinfo
+ * \see mdbx_dbi_flags_ex() */
+enum MDBX_dbi_state_t {
+  /** DB was written in this txn */
+  MDBX_DBI_DIRTY = 0x01,
+  /** Named-DB record is older than txnID */
+  MDBX_DBI_STALE = 0x02,
+  /** Named-DB handle opened in this txn */
+  MDBX_DBI_FRESH = 0x04,
+  /** Named-DB handle created in this txn */
+  MDBX_DBI_CREAT = 0x08,
+};
+#ifndef __cplusplus
+/** \ingroup c_statinfo */
+typedef enum MDBX_dbi_state_t MDBX_dbi_state_t;
+#else
+DEFINE_ENUM_FLAG_OPERATORS(MDBX_dbi_state_t)
+#endif
+
+/** \brief Retrieve the DB flags and status for a database handle.
+ * \ingroup c_statinfo
+ *
+ * \param [in] txn     A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi     A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] flags  Address where the flags will be returned.
+ * \param [out] state  Address where the state will be returned.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_dbi_flags_ex(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
+                                  unsigned *state);
+/** \brief The shortcut to calling \ref mdbx_dbi_flags_ex() with `state=NULL`
+ * for discarding it result. \ingroup c_statinfo */
+LIBMDBX_INLINE_API(int, mdbx_dbi_flags,
+                   (MDBX_txn * txn, MDBX_dbi dbi, unsigned *flags)) {
+  unsigned state;
+  return mdbx_dbi_flags_ex(txn, dbi, flags, &state);
+}
+
+/** \brief Close a database handle. Normally unnecessary.
+ * \ingroup c_dbi
+ *
+ * Closing a database handle is not necessary, but lets \ref mdbx_dbi_open()
+ * reuse the handle value. Usually it's better to set a bigger
+ * \ref mdbx_env_set_maxdbs(), unless that value would be large.
+ *
+ * \note Use with care.
+ * This call is synchronized via mutex with \ref mdbx_dbi_close(), but NOT with
+ * other transactions running by other threads. The "next" version of libmdbx
+ * (\ref MithrilDB) will solve this issue.
+ *
+ * Handles should only be closed if no other threads are going to reference
+ * the database handle or one of its cursors any further. Do not close a handle
+ * if an existing transaction has modified its database. Doing so can cause
+ * misbehavior from database corruption to errors like \ref MDBX_BAD_DBI
+ * (since the DB name is gone).
+ *
+ * \param [in] env  An environment handle returned by \ref mdbx_env_create().
+ * \param [in] dbi  A database handle returned by \ref mdbx_dbi_open().
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_dbi_close(MDBX_env *env, MDBX_dbi dbi);
+
+/** \brief Empty or delete and close a database.
+ * \ingroup c_crud
+ *
+ * \see mdbx_dbi_close() \see mdbx_dbi_open()
+ *
+ * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi  A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] del  `false` to empty the DB, `true` to delete it
+ *                  from the environment and close the DB handle.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_drop(MDBX_txn *txn, MDBX_dbi dbi, bool del);
+
+/** \brief Get items from a database.
+ * \ingroup c_crud
+ *
+ * This function retrieves key/data pairs from the database. The address
+ * and length of the data associated with the specified key are returned
+ * in the structure to which data refers.
+ * If the database supports duplicate keys (\ref MDBX_DUPSORT) then the
+ * first data item for the key will be returned. Retrieval of other
+ * items requires the use of \ref mdbx_cursor_get().
+ *
+ * \note The memory pointed to by the returned values is owned by the
+ * database. The caller need not dispose of the memory, and may not
+ * modify it in any way. For values returned in a read-only transaction
+ * any modification attempts will cause a `SIGSEGV`.
+ *
+ * \note Values returned from the database are valid only until a
+ * subsequent update operation, or the end of the transaction.
+ *
+ * \param [in] txn       A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi       A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key       The key to search for in the database.
+ * \param [in,out] data  The data corresponding to the key.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_NOTFOUND  The key was not in the database.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                         MDBX_val *data);
+
+/** \brief Get items from a database
+ * and optionally number of data items for a given key.
+ *
+ * \ingroup c_crud
+ *
+ * Briefly this function does the same as \ref mdbx_get() with a few
+ * differences:
+ *  1. If values_count is NOT NULL, then returns the count
+ *     of multi-values/duplicates for a given key.
+ *  2. Updates BOTH the key and the data for pointing to the actual key-value
+ *     pair inside the database.
+ *
+ * \param [in] txn           A transaction handle returned
+ *                           by \ref mdbx_txn_begin().
+ * \param [in] dbi           A database handle returned by \ref mdbx_dbi_open().
+ * \param [in,out] key       The key to search for in the database.
+ * \param [in,out] data      The data corresponding to the key.
+ * \param [out] values_count The optional address to return number of values
+ *                           associated with given key:
+ *                            = 0 - in case \ref MDBX_NOTFOUND error;
+ *                            = 1 - exactly for databases
+ *                                  WITHOUT \ref MDBX_DUPSORT;
+ *                            >= 1 for databases WITH \ref MDBX_DUPSORT.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_NOTFOUND  The key was not in the database.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                            MDBX_val *data, size_t *values_count);
+
+/** \brief Get equal or great item from a database.
+ * \ingroup c_crud
+ *
+ * Briefly this function does the same as \ref mdbx_get() with a few
+ * differences:
+ * 1. Return equal or great (due comparison function) key-value
+ *    pair, but not only exactly matching with the key.
+ * 2. On success return \ref MDBX_SUCCESS if key found exactly,
+ *    and \ref MDBX_RESULT_TRUE otherwise. Moreover, for databases with
+ *    \ref MDBX_DUPSORT flag the data argument also will be used to match over
+ *    multi-value/duplicates, and \ref MDBX_SUCCESS will be returned only when
+ *    BOTH the key and the data match exactly.
+ * 3. Updates BOTH the key and the data for pointing to the actual key-value
+ *    pair inside the database.
+ *
+ * \param [in] txn           A transaction handle returned
+ *                           by \ref mdbx_txn_begin().
+ * \param [in] dbi           A database handle returned by \ref mdbx_dbi_open().
+ * \param [in,out] key       The key to search for in the database.
+ * \param [in,out] data      The data corresponding to the key.
+ *
+ * \returns A non-zero error value on failure and \ref MDBX_RESULT_FALSE
+ *          or \ref MDBX_RESULT_TRUE on success (as described above).
+ *          Some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_NOTFOUND      The key was not in the database.
+ * \retval MDBX_EINVAL        An invalid parameter was specified. */
+LIBMDBX_API int mdbx_get_equal_or_great(MDBX_txn *txn, MDBX_dbi dbi,
+                                        MDBX_val *key, MDBX_val *data);
+
+/** \brief Store items into a database.
+ * \ingroup c_crud
+ *
+ * This function stores key/data pairs in the database. The default behavior
+ * is to enter the new key/data pair, replacing any previously existing key
+ * if duplicates are disallowed, or adding a duplicate data item if
+ * duplicates are allowed (see \ref MDBX_DUPSORT).
+ *
+ * \param [in] txn        A transaction handle returned
+ *                        by \ref mdbx_txn_begin().
+ * \param [in] dbi        A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key        The key to store in the database.
+ * \param [in,out] data   The data to store.
+ * \param [in] flags      Special options for this operation.
+ *                        This parameter must be set to 0 or by bitwise OR'ing
+ *                        together one or more of the values described here:
+ *   - \ref MDBX_NODUPDATA
+ *      Enter the new key-value pair only if it does not already appear
+ *      in the database. This flag may only be specified if the database
+ *      was opened with \ref MDBX_DUPSORT. The function will return
+ *      \ref MDBX_KEYEXIST if the key/data pair already appears in the database.
+ *
+ *  - \ref MDBX_NOOVERWRITE
+ *      Enter the new key/data pair only if the key does not already appear
+ *      in the database. The function will return \ref MDBX_KEYEXIST if the key
+ *      already appears in the database, even if the database supports
+ *      duplicates (see \ref  MDBX_DUPSORT). The data parameter will be set
+ *      to point to the existing item.
+ *
+ *  - \ref MDBX_CURRENT
+ *      Update an single existing entry, but not add new ones. The function will
+ *      return \ref MDBX_NOTFOUND if the given key not exist in the database.
+ *      In case multi-values for the given key, with combination of
+ *      the \ref MDBX_ALLDUPS will replace all multi-values,
+ *      otherwise return the \ref MDBX_EMULTIVAL.
+ *
+ *  - \ref MDBX_RESERVE
+ *      Reserve space for data of the given size, but don't copy the given
+ *      data. Instead, return a pointer to the reserved space, which the
+ *      caller can fill in later - before the next update operation or the
+ *      transaction ends. This saves an extra memcpy if the data is being
+ *      generated later. MDBX does nothing else with this memory, the caller
+ *      is expected to modify all of the space requested. This flag must not
+ *      be specified if the database was opened with \ref MDBX_DUPSORT.
+ *
+ *  - \ref MDBX_APPEND
+ *      Append the given key/data pair to the end of the database. This option
+ *      allows fast bulk loading when keys are already known to be in the
+ *      correct order. Loading unsorted keys with this flag will cause
+ *      a \ref MDBX_EKEYMISMATCH error.
+ *
+ *  - \ref MDBX_APPENDDUP
+ *      As above, but for sorted dup data.
+ *
+ *  - \ref MDBX_MULTIPLE
+ *      Store multiple contiguous data elements in a single request. This flag
+ *      may only be specified if the database was opened with
+ *      \ref MDBX_DUPFIXED. With combination the \ref MDBX_ALLDUPS
+ *      will replace all multi-values.
+ *      The data argument must be an array of two \ref MDBX_val. The `iov_len`
+ *      of the first \ref MDBX_val must be the size of a single data element.
+ *      The `iov_base` of the first \ref MDBX_val must point to the beginning
+ *      of the array of contiguous data elements which must be properly aligned
+ *      in case of database with \ref MDBX_INTEGERDUP flag.
+ *      The `iov_len` of the second \ref MDBX_val must be the count of the
+ *      number of data elements to store. On return this field will be set to
+ *      the count of the number of elements actually written. The `iov_base` of
+ *      the second \ref MDBX_val is unused.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_KEYEXIST  The key/value pair already exists in the database.
+ * \retval MDBX_MAP_FULL  The database is full, see \ref mdbx_env_set_mapsize().
+ * \retval MDBX_TXN_FULL  The transaction has too many dirty pages.
+ * \retval MDBX_EACCES    An attempt was made to write
+ *                        in a read-only transaction.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_put(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                         MDBX_val *data, MDBX_put_flags_t flags);
+
+/** \brief Replace items in a database.
+ * \ingroup c_crud
+ *
+ * This function allows to update or delete an existing value at the same time
+ * as the previous value is retrieved. If the argument new_data equal is NULL
+ * zero, the removal is performed, otherwise the update/insert.
+ *
+ * The current value may be in an already changed (aka dirty) page. In this
+ * case, the page will be overwritten during the update, and the old value will
+ * be lost. Therefore, an additional buffer must be passed via old_data
+ * argument initially to copy the old value. If the buffer passed in is too
+ * small, the function will return \ref MDBX_RESULT_TRUE by setting iov_len
+ * field pointed by old_data argument to the appropriate value, without
+ * performing any changes.
+ *
+ * For databases with non-unique keys (i.e. with \ref MDBX_DUPSORT flag),
+ * another use case is also possible, when by old_data argument selects a
+ * specific item from multi-value/duplicates with the same key for deletion or
+ * update. To select this scenario in flags should simultaneously specify
+ * \ref MDBX_CURRENT and \ref MDBX_NOOVERWRITE. This combination is chosen
+ * because it makes no sense, and thus allows you to identify the request of
+ * such a scenario.
+ *
+ * \param [in] txn           A transaction handle returned
+ *                           by \ref mdbx_txn_begin().
+ * \param [in] dbi           A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key           The key to store in the database.
+ * \param [in] new_data      The data to store, if NULL then deletion will
+ *                           be performed.
+ * \param [in,out] old_data  The buffer for retrieve previous value as describe
+ *                           above.
+ * \param [in] flags         Special options for this operation.
+ *                           This parameter must be set to 0 or by bitwise
+ *                           OR'ing together one or more of the values
+ *                           described in \ref mdbx_put() description above,
+ *                           and additionally
+ *                           (\ref MDBX_CURRENT | \ref MDBX_NOOVERWRITE)
+ *                           combination for selection particular item from
+ *                           multi-value/duplicates.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_replace(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                             MDBX_val *new_data, MDBX_val *old_data,
+                             MDBX_put_flags_t flags);
+
+typedef int (*MDBX_preserve_func)(void *context, MDBX_val *target,
+                                  const void *src, size_t bytes);
+LIBMDBX_API int mdbx_replace_ex(MDBX_txn *txn, MDBX_dbi dbi,
+                                const MDBX_val *key, MDBX_val *new_data,
+                                MDBX_val *old_data, MDBX_put_flags_t flags,
+                                MDBX_preserve_func preserver,
+                                void *preserver_context);
+
+/** \brief Delete items from a database.
+ * \ingroup c_crud
+ *
+ * This function removes key/data pairs from the database.
+ *
+ * \note The data parameter is NOT ignored regardless the database does
+ * support sorted duplicate data items or not. If the data parameter
+ * is non-NULL only the matching data item will be deleted. Otherwise, if data
+ * parameter is NULL, any/all value(s) for specified key will be deleted.
+ *
+ * This function will return \ref MDBX_NOTFOUND if the specified key/data
+ * pair is not in the database.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \param [in] txn   A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi   A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key   The key to delete from the database.
+ * \param [in] data  The data to delete.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EACCES   An attempt was made to write
+ *                       in a read-only transaction.
+ * \retval MDBX_EINVAL   An invalid parameter was specified. */
+LIBMDBX_API int mdbx_del(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+                         const MDBX_val *data);
+
+/** \brief Create a cursor handle but not bind it to transaction nor DBI handle.
+ * \ingroup c_cursors
+ *
+ * An capable of operation cursor is associated with a specific transaction and
+ * database. A cursor cannot be used when its database handle is closed. Nor
+ * when its transaction has ended, except with \ref mdbx_cursor_bind() and
+ * \ref mdbx_cursor_renew().
+ * Also it can be discarded with \ref mdbx_cursor_close().
+ *
+ * A cursor must be closed explicitly always, before or after its transaction
+ * ends. It can be reused with \ref mdbx_cursor_bind()
+ * or \ref mdbx_cursor_renew() before finally closing it.
+ *
+ * \note In contrast to LMDB, the MDBX required that any opened cursors can be
+ * reused and must be freed explicitly, regardless ones was opened in a
+ * read-only or write transaction. The REASON for this is eliminates ambiguity
+ * which helps to avoid errors such as: use-after-free, double-free, i.e.
+ * memory corruption and segfaults.
+ *
+ * \param [in] context A pointer to application context to be associated with
+ *                     created cursor and could be retrieved by
+ *                     \ref mdbx_cursor_get_userctx() until cursor closed.
+ *
+ * \returns Created cursor handle or NULL in case out of memory. */
+LIBMDBX_API MDBX_cursor *mdbx_cursor_create(void *context);
+
+/** \brief Set application information associated with the \ref MDBX_cursor.
+ * \ingroup c_cursors
+ * \see mdbx_cursor_get_userctx()
+ *
+ * \param [in] cursor  An cursor handle returned by \ref mdbx_cursor_create()
+ *                     or \ref mdbx_cursor_open().
+ * \param [in] ctx     An arbitrary pointer for whatever the application needs.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_cursor_set_userctx(MDBX_cursor *cursor, void *ctx);
+
+/** \brief Get the application information associated with the MDBX_cursor.
+ * \ingroup c_cursors
+ * \see mdbx_cursor_set_userctx()
+ *
+ * \param [in] cursor  An cursor handle returned by \ref mdbx_cursor_create()
+ *                     or \ref mdbx_cursor_open().
+ * \returns The pointer which was passed via the `context` parameter
+ *          of `mdbx_cursor_create()` or set by \ref mdbx_cursor_set_userctx(),
+ *          or `NULL` if something wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API void *
+mdbx_cursor_get_userctx(const MDBX_cursor *cursor);
+
+/** \brief Bind cursor to specified transaction and DBI handle.
+ * \ingroup c_cursors
+ *
+ * Using of the `mdbx_cursor_bind()` is equivalent to calling
+ * \ref mdbx_cursor_renew() but with specifying an arbitrary dbi handle.
+ *
+ * An capable of operation cursor is associated with a specific transaction and
+ * database. The cursor may be associated with a new transaction,
+ * and referencing a new or the same database handle as it was created with.
+ * This may be done whether the previous transaction is live or dead.
+ *
+ * \note In contrast to LMDB, the MDBX required that any opened cursors can be
+ * reused and must be freed explicitly, regardless ones was opened in a
+ * read-only or write transaction. The REASON for this is eliminates ambiguity
+ * which helps to avoid errors such as: use-after-free, double-free, i.e.
+ * memory corruption and segfaults.
+ *
+ * \param [in] txn      A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi      A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] cursor  A cursor handle returned by \ref mdbx_cursor_create().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *cursor,
+                                 MDBX_dbi dbi);
+
+/** \brief Create a cursor handle for the specified transaction and DBI handle.
+ * \ingroup c_cursors
+ *
+ * Using of the `mdbx_cursor_open()` is equivalent to calling
+ * \ref mdbx_cursor_create() and then \ref mdbx_cursor_bind() functions.
+ *
+ * An capable of operation cursor is associated with a specific transaction and
+ * database. A cursor cannot be used when its database handle is closed. Nor
+ * when its transaction has ended, except with \ref mdbx_cursor_bind() and
+ * \ref mdbx_cursor_renew().
+ * Also it can be discarded with \ref mdbx_cursor_close().
+ *
+ * A cursor must be closed explicitly always, before or after its transaction
+ * ends. It can be reused with \ref mdbx_cursor_bind()
+ * or \ref mdbx_cursor_renew() before finally closing it.
+ *
+ * \note In contrast to LMDB, the MDBX required that any opened cursors can be
+ * reused and must be freed explicitly, regardless ones was opened in a
+ * read-only or write transaction. The REASON for this is eliminates ambiguity
+ * which helps to avoid errors such as: use-after-free, double-free, i.e.
+ * memory corruption and segfaults.
+ *
+ * \param [in] txn      A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi      A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] cursor  Address where the new \ref MDBX_cursor handle will be
+ *                      stored.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi,
+                                 MDBX_cursor **cursor);
+
+/** \brief Close a cursor handle.
+ * \ingroup c_cursors
+ *
+ * The cursor handle will be freed and must not be used again after this call,
+ * but its transaction may still be live.
+ *
+ * \note In contrast to LMDB, the MDBX required that any opened cursors can be
+ * reused and must be freed explicitly, regardless ones was opened in a
+ * read-only or write transaction. The REASON for this is eliminates ambiguity
+ * which helps to avoid errors such as: use-after-free, double-free, i.e.
+ * memory corruption and segfaults.
+ *
+ * \param [in] cursor  A cursor handle returned by \ref mdbx_cursor_open()
+ *                     or \ref mdbx_cursor_create(). */
+LIBMDBX_API void mdbx_cursor_close(MDBX_cursor *cursor);
+
+/** \brief Renew a cursor handle.
+ * \ingroup c_cursors
+ *
+ * An capable of operation cursor is associated with a specific transaction and
+ * database. The cursor may be associated with a new transaction,
+ * and referencing a new or the same database handle as it was created with.
+ * This may be done whether the previous transaction is live or dead.
+ *
+ * Using of the `mdbx_cursor_renew()` is equivalent to calling
+ * \ref mdbx_cursor_bind() with the DBI handle that previously
+ * the cursor was used with.
+ *
+ * \note In contrast to LMDB, the MDBX allow any cursor to be re-used by using
+ * \ref mdbx_cursor_renew(), to avoid unnecessary malloc/free overhead until it
+ * freed by \ref mdbx_cursor_close().
+ *
+ * \param [in] txn      A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] cursor   A cursor handle returned by \ref mdbx_cursor_open().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL  An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_renew(MDBX_txn *txn, MDBX_cursor *cursor);
+
+/** \brief Return the cursor's transaction handle.
+ * \ingroup c_cursors
+ *
+ * \param [in] cursor A cursor handle returned by \ref mdbx_cursor_open(). */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API MDBX_txn *
+mdbx_cursor_txn(const MDBX_cursor *cursor);
+
+/** \brief Return the cursor's database handle.
+ * \ingroup c_cursors
+ *
+ * \param [in] cursor  A cursor handle returned by \ref mdbx_cursor_open(). */
+LIBMDBX_API MDBX_dbi mdbx_cursor_dbi(const MDBX_cursor *cursor);
+
+/** \brief Copy cursor position and state.
+ * \ingroup c_cursors
+ *
+ * \param [in] src       A source cursor handle returned
+ * by \ref mdbx_cursor_create() or \ref mdbx_cursor_open().
+ *
+ * \param [in,out] dest  A destination cursor handle returned
+ * by \ref mdbx_cursor_create() or \ref mdbx_cursor_open().
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_cursor_copy(const MDBX_cursor *src, MDBX_cursor *dest);
+
+/** \brief Retrieve by cursor.
+ * \ingroup c_cursors c_crud
+ *
+ * This function retrieves key/data pairs from the database. The address and
+ * length of the key are returned in the object to which key refers (except
+ * for the case of the \ref MDBX_SET option, in which the key object is
+ * unchanged), and the address and length of the data are returned in the object
+ * to which data refers.
+ * \see mdbx_get()
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ * \param [in,out] key   The key for a retrieved item.
+ * \param [in,out] data  The data of a retrieved item.
+ * \param [in] op        A cursor operation \ref MDBX_cursor_op.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_NOTFOUND  No matching key found.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_get(MDBX_cursor *cursor, MDBX_val *key,
+                                MDBX_val *data, MDBX_cursor_op op);
+
+/** \brief Store by cursor.
+ * \ingroup c_cursors c_crud
+ *
+ * This function stores key/data pairs into the database. The cursor is
+ * positioned at the new item, or on failure usually near it.
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ * \param [in] key       The key operated on.
+ * \param [in,out] data  The data operated on.
+ * \param [in] flags     Options for this operation. This parameter
+ *                       must be set to 0 or by bitwise OR'ing together
+ *                       one or more of the values described here:
+ *  - \ref MDBX_CURRENT
+ *      Replace the item at the current cursor position. The key parameter
+ *      must still be provided, and must match it, otherwise the function
+ *      return \ref MDBX_EKEYMISMATCH. With combination the
+ *      \ref MDBX_ALLDUPS will replace all multi-values.
+ *
+ *      \note MDBX allows (unlike LMDB) you to change the size of the data and
+ *      automatically handles reordering for sorted duplicates
+ *      (see \ref MDBX_DUPSORT).
+ *
+ *  - \ref MDBX_NODUPDATA
+ *      Enter the new key-value pair only if it does not already appear in the
+ *      database. This flag may only be specified if the database was opened
+ *      with \ref MDBX_DUPSORT. The function will return \ref MDBX_KEYEXIST
+ *      if the key/data pair already appears in the database.
+ *
+ *  - \ref MDBX_NOOVERWRITE
+ *      Enter the new key/data pair only if the key does not already appear
+ *      in the database. The function will return \ref MDBX_KEYEXIST if the key
+ *      already appears in the database, even if the database supports
+ *      duplicates (\ref MDBX_DUPSORT).
+ *
+ *  - \ref MDBX_RESERVE
+ *      Reserve space for data of the given size, but don't copy the given
+ *      data. Instead, return a pointer to the reserved space, which the
+ *      caller can fill in later - before the next update operation or the
+ *      transaction ends. This saves an extra memcpy if the data is being
+ *      generated later. This flag must not be specified if the database
+ *      was opened with \ref MDBX_DUPSORT.
+ *
+ *  - \ref MDBX_APPEND
+ *      Append the given key/data pair to the end of the database. No key
+ *      comparisons are performed. This option allows fast bulk loading when
+ *      keys are already known to be in the correct order. Loading unsorted
+ *      keys with this flag will cause a \ref MDBX_KEYEXIST error.
+ *
+ *  - \ref MDBX_APPENDDUP
+ *      As above, but for sorted dup data.
+ *
+ *  - \ref MDBX_MULTIPLE
+ *      Store multiple contiguous data elements in a single request. This flag
+ *      may only be specified if the database was opened with
+ *      \ref MDBX_DUPFIXED. With combination the \ref MDBX_ALLDUPS
+ *      will replace all multi-values.
+ *      The data argument must be an array of two \ref MDBX_val. The `iov_len`
+ *      of the first \ref MDBX_val must be the size of a single data element.
+ *      The `iov_base` of the first \ref MDBX_val must point to the beginning
+ *      of the array of contiguous data elements which must be properly aligned
+ *      in case of database with \ref MDBX_INTEGERDUP flag.
+ *      The `iov_len` of the second \ref MDBX_val must be the count of the
+ *      number of data elements to store. On return this field will be set to
+ *      the count of the number of elements actually written. The `iov_base` of
+ *      the second \ref MDBX_val is unused.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EKEYMISMATCH  The given key value is mismatched to the current
+ *                            cursor position
+ * \retval MDBX_MAP_FULL      The database is full,
+ *                             see \ref mdbx_env_set_mapsize().
+ * \retval MDBX_TXN_FULL      The transaction has too many dirty pages.
+ * \retval MDBX_EACCES        An attempt was made to write in a read-only
+ *                            transaction.
+ * \retval MDBX_EINVAL        An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_put(MDBX_cursor *cursor, const MDBX_val *key,
+                                MDBX_val *data, MDBX_put_flags_t flags);
+
+/** \brief Delete current key/data pair.
+ * \ingroup c_cursors c_crud
+ *
+ * This function deletes the key/data pair to which the cursor refers. This
+ * does not invalidate the cursor, so operations such as \ref MDBX_NEXT can
+ * still be used on it. Both \ref MDBX_NEXT and \ref MDBX_GET_CURRENT will
+ * return the same record after this operation.
+ *
+ * \param [in] cursor  A cursor handle returned by mdbx_cursor_open().
+ * \param [in] flags   Options for this operation. This parameter must be set
+ * to one of the values described here.
+ *
+ *  - \ref MDBX_CURRENT Delete only single entry at current cursor position.
+ *  - \ref MDBX_ALLDUPS
+ *    or \ref MDBX_NODUPDATA (supported for compatibility)
+ *      Delete all of the data items for the current key. This flag has effect
+ *      only for database(s) was created with \ref MDBX_DUPSORT.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_MAP_FULL      The database is full,
+ *                            see \ref mdbx_env_set_mapsize().
+ * \retval MDBX_TXN_FULL      The transaction has too many dirty pages.
+ * \retval MDBX_EACCES        An attempt was made to write in a read-only
+ *                            transaction.
+ * \retval MDBX_EINVAL        An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_del(MDBX_cursor *cursor, MDBX_put_flags_t flags);
+
+/** \brief Return count of duplicates for current key.
+ * \ingroup c_cursors c_crud
+ *
+ * This call is valid for all databases, but reasonable only for that support
+ * sorted duplicate data items \ref MDBX_DUPSORT.
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ * \param [out] pcount   Address where the count will be stored.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
+ *                               by current thread.
+ * \retval MDBX_EINVAL   Cursor is not initialized, or an invalid parameter
+ *                       was specified. */
+LIBMDBX_API int mdbx_cursor_count(const MDBX_cursor *cursor, size_t *pcount);
+
+/** \brief Determines whether the cursor is pointed to a key-value pair or not,
+ * i.e. was not positioned or points to the end of data.
+ * \ingroup c_cursors
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ *
+ * \returns A \ref MDBX_RESULT_TRUE or \ref MDBX_RESULT_FALSE value,
+ *          otherwise the error code:
+ * \retval MDBX_RESULT_TRUE    No more data available or cursor not
+ *                             positioned
+ * \retval MDBX_RESULT_FALSE   A data is available
+ * \retval Otherwise the error code */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_cursor_eof(const MDBX_cursor *cursor);
+
+/** \brief Determines whether the cursor is pointed to the first key-value pair
+ * or not. \ingroup c_cursors
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ *
+ * \returns A MDBX_RESULT_TRUE or MDBX_RESULT_FALSE value,
+ *          otherwise the error code:
+ * \retval MDBX_RESULT_TRUE   Cursor positioned to the first key-value pair
+ * \retval MDBX_RESULT_FALSE  Cursor NOT positioned to the first key-value
+ * pair \retval Otherwise the error code */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_cursor_on_first(const MDBX_cursor *cursor);
+
+/** \brief Determines whether the cursor is pointed to the last key-value pair
+ * or not. \ingroup c_cursors
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ *
+ * \returns A \ref MDBX_RESULT_TRUE or \ref MDBX_RESULT_FALSE value,
+ *          otherwise the error code:
+ * \retval MDBX_RESULT_TRUE   Cursor positioned to the last key-value pair
+ * \retval MDBX_RESULT_FALSE  Cursor NOT positioned to the last key-value pair
+ * \retval Otherwise the error code */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int
+mdbx_cursor_on_last(const MDBX_cursor *cursor);
+
+/** \addtogroup c_rqest
+ * \details \note The estimation result varies greatly depending on the filling
+ * of specific pages and the overall balance of the b-tree:
+ *
+ * 1. The number of items is estimated by analyzing the height and fullness of
+ * the b-tree. The accuracy of the result directly depends on the balance of
+ * the b-tree, which in turn is determined by the history of previous
+ * insert/delete operations and the nature of the data (i.e. variability of
+ * keys length and so on). Therefore, the accuracy of the estimation can vary
+ * greatly in a particular situation.
+ *
+ * 2. To understand the potential spread of results, you should consider a
+ * possible situations basing on the general criteria for splitting and merging
+ * b-tree pages:
+ *  - the page is split into two when there is no space for added data;
+ *  - two pages merge if the result fits in half a page;
+ *  - thus, the b-tree can consist of an arbitrary combination of pages filled
+ *    both completely and only 1/4. Therefore, in the worst case, the result
+ *    can diverge 4 times for each level of the b-tree excepting the first and
+ *    the last.
+ *
+ * 3. In practice, the probability of extreme cases of the above situation is
+ * close to zero and in most cases the error does not exceed a few percent. On
+ * the other hand, it's just a chance you shouldn't overestimate. */
+
+/** \brief Estimates the distance between cursors as a number of elements.
+ * \ingroup c_rqest
+ *
+ * This function performs a rough estimate based only on b-tree pages that are
+ * common for the both cursor's stacks. The results of such estimation can be
+ * used to build and/or optimize query execution plans.
+ *
+ * Please see notes on accuracy of the result in the details
+ * of \ref c_rqest section.
+ *
+ * Both cursors must be initialized for the same database and the same
+ * transaction.
+ *
+ * \param [in] first            The first cursor for estimation.
+ * \param [in] last             The second cursor for estimation.
+ * \param [out] distance_items  The pointer to store estimated distance value,
+ *                              i.e. `*distance_items = distance(first, last)`.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_estimate_distance(const MDBX_cursor *first,
+                                       const MDBX_cursor *last,
+                                       ptrdiff_t *distance_items);
+
+/** \brief Estimates the move distance.
+ * \ingroup c_rqest
+ *
+ * This function performs a rough estimate distance between the current
+ * cursor position and next position after the specified move-operation with
+ * given key and data. The results of such estimation can be used to build
+ * and/or optimize query execution plans. Current cursor position and state are
+ * preserved.
+ *
+ * Please see notes on accuracy of the result in the details
+ * of \ref c_rqest section.
+ *
+ * \param [in] cursor            Cursor for estimation.
+ * \param [in,out] key           The key for a retrieved item.
+ * \param [in,out] data          The data of a retrieved item.
+ * \param [in] move_op           A cursor operation \ref MDBX_cursor_op.
+ * \param [out] distance_items   A pointer to store estimated move distance
+ *                               as the number of elements.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_estimate_move(const MDBX_cursor *cursor, MDBX_val *key,
+                                   MDBX_val *data, MDBX_cursor_op move_op,
+                                   ptrdiff_t *distance_items);
+
+/** \brief Estimates the size of a range as a number of elements.
+ * \ingroup c_rqest
+ *
+ * The results of such estimation can be used to build and/or optimize query
+ * execution plans.
+ *
+ * Please see notes on accuracy of the result in the details
+ * of \ref c_rqest section.
+ *
+ *
+ * \param [in] txn        A transaction handle returned
+ *                        by \ref mdbx_txn_begin().
+ * \param [in] dbi        A database handle returned by  \ref mdbx_dbi_open().
+ * \param [in] begin_key  The key of range beginning or NULL for explicit FIRST.
+ * \param [in] begin_data Optional additional data to seeking among sorted
+ *                        duplicates.
+ *                        Only for \ref MDBX_DUPSORT, NULL otherwise.
+ * \param [in] end_key    The key of range ending or NULL for explicit LAST.
+ * \param [in] end_data   Optional additional data to seeking among sorted
+ *                        duplicates.
+ *                        Only for \ref MDBX_DUPSORT, NULL otherwise.
+ * \param [out] distance_items  A pointer to store range estimation result.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi,
+                                    MDBX_val *begin_key, MDBX_val *begin_data,
+                                    MDBX_val *end_key, MDBX_val *end_data,
+                                    ptrdiff_t *distance_items);
+
+/** \brief The EPSILON value for mdbx_estimate_range()
+ * \ingroup c_rqest */
+#define MDBX_EPSILON ((MDBX_val *)((ptrdiff_t)-1))
+
+/** \brief Determines whether the given address is on a dirty database page of
+ * the transaction or not. \ingroup c_statinfo
+ *
+ * Ultimately, this allows to avoid copy data from non-dirty pages.
+ *
+ * "Dirty" pages are those that have already been changed during a write
+ * transaction. Accordingly, any further changes may result in such pages being
+ * overwritten. Therefore, all functions libmdbx performing changes inside the
+ * database as arguments should NOT get pointers to data in those pages. In
+ * turn, "not dirty" pages before modification will be copied.
+ *
+ * In other words, data from dirty pages must either be copied before being
+ * passed as arguments for further processing or rejected at the argument
+ * validation stage. Thus, `mdbx_is_dirty()` allows you to get rid of
+ * unnecessary copying, and perform a more complete check of the arguments.
+ *
+ * \note The address passed must point to the beginning of the data. This is
+ * the only way to ensure that the actual page header is physically located in
+ * the same memory page, including for multi-pages with long data.
+ *
+ * \note In rare cases the function may return a false positive answer
+ * (\ref MDBX_RESULT_TRUE when data is NOT on a dirty page), but never a false
+ * negative if the arguments are correct.
+ *
+ * \param [in] txn      A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] ptr      The address of data to check.
+ *
+ * \returns A MDBX_RESULT_TRUE or MDBX_RESULT_FALSE value,
+ *          otherwise the error code:
+ * \retval MDBX_RESULT_TRUE    Given address is on the dirty page.
+ * \retval MDBX_RESULT_FALSE   Given address is NOT on the dirty page.
+ * \retval Otherwise the error code. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int mdbx_is_dirty(const MDBX_txn *txn,
+                                                         const void *ptr);
+
+/** \brief Sequence generation for a database.
+ * \ingroup c_crud
+ *
+ * The function allows to create a linear sequence of unique positive integers
+ * for each database. The function can be called for a read transaction to
+ * retrieve the current sequence value, and the increment must be zero.
+ * Sequence changes become visible outside the current write transaction after
+ * it is committed, and discarded on abort.
+ *
+ * \param [in] txn        A transaction handle returned
+ *                        by \ref mdbx_txn_begin().
+ * \param [in] dbi        A database handle returned by \ref mdbx_dbi_open().
+ * \param [out] result    The optional address where the value of sequence
+ *                        before the change will be stored.
+ * \param [in] increment  Value to increase the sequence,
+ *                        must be 0 for read-only transactions.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_RESULT_TRUE   Increasing the sequence has resulted in an
+ *                            overflow and therefore cannot be executed. */
+LIBMDBX_API int mdbx_dbi_sequence(MDBX_txn *txn, MDBX_dbi dbi, uint64_t *result,
+                                  uint64_t increment);
+
+/** \brief Compare two keys according to a particular database.
+ * \ingroup c_crud
+ *
+ * This returns a comparison as if the two data items were keys in the
+ * specified database.
+ *
+ * \warning There ss a Undefined behavior if one of arguments is invalid.
+ *
+ * \param [in] txn   A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi   A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] a     The first item to compare.
+ * \param [in] b     The second item to compare.
+ *
+ * \returns < 0 if a < b, 0 if a == b, > 0 if a > b */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int mdbx_cmp(const MDBX_txn *txn,
+                                                    MDBX_dbi dbi,
+                                                    const MDBX_val *a,
+                                                    const MDBX_val *b);
+
+/** \brief Returns default internal key's comparator for given database flags.
+ * \ingroup c_extra */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API MDBX_cmp_func *
+mdbx_get_keycmp(MDBX_db_flags_t flags);
+
+/** \brief Compare two data items according to a particular database.
+ * \ingroup c_crud
+ *
+ * This returns a comparison as if the two items were data items of the
+ * specified database.
+ *
+ * \warning There ss a Undefined behavior if one of arguments is invalid.
+ *
+ * \param [in] txn   A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi   A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] a     The first item to compare.
+ * \param [in] b     The second item to compare.
+ *
+ * \returns < 0 if a < b, 0 if a == b, > 0 if a > b */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API int mdbx_dcmp(const MDBX_txn *txn,
+                                                     MDBX_dbi dbi,
+                                                     const MDBX_val *a,
+                                                     const MDBX_val *b);
+
+/** \brief Returns default internal data's comparator for given database flags
+ * \ingroup c_extra */
+MDBX_NOTHROW_CONST_FUNCTION LIBMDBX_API MDBX_cmp_func *
+mdbx_get_datacmp(MDBX_db_flags_t flags);
+
+/** \brief A callback function used to enumerate the reader lock table.
+ * \ingroup c_statinfo
+ *
+ * \param [in] ctx           An arbitrary context pointer for the callback.
+ * \param [in] num           The serial number during enumeration,
+ *                           starting from 1.
+ * \param [in] slot          The reader lock table slot number.
+ * \param [in] txnid         The ID of the transaction being read,
+ *                           i.e. the MVCC-snapshot number.
+ * \param [in] lag           The lag from a recent MVCC-snapshot,
+ *                           i.e. the number of committed write transactions
+ *                           since the current read transaction started.
+ * \param [in] pid           The reader process ID.
+ * \param [in] thread        The reader thread ID.
+ * \param [in] bytes_used    The number of last used page in the MVCC-snapshot
+ *                           which being read,
+ *                           i.e. database file can't shrinked beyond this.
+ * \param [in] bytes_retired The total size of the database pages that were
+ *                           retired by committed write transactions after
+ *                           the reader's MVCC-snapshot,
+ *                           i.e. the space which would be freed after
+ *                           the Reader releases the MVCC-snapshot
+ *                           for reuse by completion read transaction.
+ *
+ * \returns < 0 on failure, >= 0 on success. \see mdbx_reader_list() */
+typedef int(MDBX_reader_list_func)(void *ctx, int num, int slot, mdbx_pid_t pid,
+                                   mdbx_tid_t thread, uint64_t txnid,
+                                   uint64_t lag, size_t bytes_used,
+                                   size_t bytes_retained) MDBX_CXX17_NOEXCEPT;
+
+/** \brief Enumerate the entries in the reader lock table.
+ *
+ * \ingroup c_statinfo
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ * \param [in] func    A \ref MDBX_reader_list_func function.
+ * \param [in] ctx     An arbitrary context pointer for the enumeration
+ *                     function.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ * or \ref MDBX_RESULT_TRUE if the reader lock table is empty. */
+LIBMDBX_API int mdbx_reader_list(const MDBX_env *env,
+                                 MDBX_reader_list_func *func, void *ctx);
+
+/** \brief Check for stale entries in the reader lock table.
+ * \ingroup c_extra
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ * \param [out] dead   Number of stale slots that were cleared.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ * or \ref MDBX_RESULT_TRUE if a dead reader(s) found or mutex was recovered. */
+LIBMDBX_API int mdbx_reader_check(MDBX_env *env, int *dead);
+
+/** \brief Returns a lag of the reading for the given transaction.
+ * \ingroup c_statinfo
+ *
+ * Returns an information for estimate how much given read-only
+ * transaction is lagging relative the to actual head.
+ * \deprecated Please use \ref mdbx_txn_info() instead.
+ *
+ * \param [in] txn       A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [out] percent  Percentage of page allocation in the database.
+ *
+ * \returns Number of transactions committed after the given was started for
+ *          read, or negative value on failure. */
+MDBX_DEPRECATED LIBMDBX_API int mdbx_txn_straggler(const MDBX_txn *txn,
+                                                   int *percent);
+
+/** \brief Registers the current thread as a reader for the environment.
+ * \ingroup c_extra
+ *
+ * To perform read operations without blocking, a reader slot must be assigned
+ * for each thread. However, this assignment requires a short-term lock
+ * acquisition which is performed automatically. This function allows you to
+ * assign the reader slot in advance and thus avoid capturing the blocker when
+ * the read transaction starts firstly from current thread.
+ * \see mdbx_thread_unregister()
+ *
+ * \note Threads are registered automatically the first time a read transaction
+ *       starts. Therefore, there is no need to use this function, except in
+ *       special cases.
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ * or \ref MDBX_RESULT_TRUE if thread is already registered. */
+LIBMDBX_API int mdbx_thread_register(const MDBX_env *env);
+
+/** \brief Unregisters the current thread as a reader for the environment.
+ * \ingroup c_extra
+ *
+ * To perform read operations without blocking, a reader slot must be assigned
+ * for each thread. However, the assigned reader slot will remain occupied until
+ * the thread ends or the environment closes. This function allows you to
+ * explicitly release the assigned reader slot.
+ * \see mdbx_thread_register()
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ *
+ * \returns A non-zero error value on failure and 0 on success, or
+ * \ref MDBX_RESULT_TRUE if thread is not registered or already unregistered. */
+LIBMDBX_API int mdbx_thread_unregister(const MDBX_env *env);
+
+/** \brief A Handle-Slow-Readers callback function to resolve database
+ * full/overflow issue due to a reader(s) which prevents the old data from being
+ * recycled.
+ * \ingroup c_err
+ *
+ * Read transactions prevent reuse of pages freed by newer write transactions,
+ * thus the database can grow quickly. This callback will be called when there
+ * is not enough space in the database (i.e. before increasing the database size
+ * or before \ref MDBX_MAP_FULL error) and thus can be used to resolve issues
+ * with a "long-lived" read transactions.
+ * \see long-lived-read
+ *
+ * Using this callback you can choose how to resolve the situation:
+ *   - abort the write transaction with an error;
+ *   - wait for the read transaction(s) to complete;
+ *   - notify a thread performing a long-lived read transaction
+ *     and wait for an effect;
+ *   - kill the thread or whole process that performs the long-lived read
+ *     transaction;
+ *
+ * Depending on the arguments and needs, your implementation may wait,
+ * terminate a process or thread that is performing a long read, or perform
+ * some other action. In doing so it is important that the returned code always
+ * corresponds to the performed action.
+ *
+ * \param [in] env     An environment handle returned by \ref mdbx_env_create().
+ * \param [in] txn     The current write transaction which internally at
+ *                     the \ref MDBX_MAP_FULL condition.
+ * \param [in] pid     A pid of the reader process.
+ * \param [in] tid     A thread_id of the reader thread.
+ * \param [in] laggard An oldest read transaction number on which stalled.
+ * \param [in] gap     A lag from the last committed txn.
+ * \param [in] space   A space that actually become available for reuse after
+ *                     this reader finished. The callback function can take
+ *                     this value into account to evaluate the impact that
+ *                     a long-running transaction has.
+ * \param [in] retry   A retry number starting from 0.
+ *                     If callback has returned 0 at least once, then at end
+ *                     of current handling loop the callback function will be
+ *                     called additionally with negative value to notify about
+ *                     the end of loop. The callback function can use this value
+ *                     to implement timeout logic while waiting for readers.
+ *
+ * \returns The RETURN CODE determines the further actions libmdbx and must
+ *          match the action which was executed by the callback:
+ *
+ * \retval -2 or less  An error condition and the reader was not killed.
+ *
+ * \retval -1          The callback was unable to solve the problem and
+ *                     agreed on \ref MDBX_MAP_FULL error;
+ *                     libmdbx should increase the database size or
+ *                     return \ref MDBX_MAP_FULL error.
+ *
+ * \retval 0 (zero)    The callback solved the problem or just waited for
+ *                     a while, libmdbx should rescan the reader lock table and
+ *                     retry. This also includes a situation when corresponding
+ *                     transaction terminated in normal way by
+ *                     \ref mdbx_txn_abort() or \ref mdbx_txn_reset(),
+ *                     and my be restarted. I.e. reader slot don't needed
+ *                     to be cleaned from transaction.
+ *
+ * \retval 1           Transaction aborted asynchronous and reader slot
+ *                     should be cleared immediately, i.e. read transaction
+ *                     will not continue but \ref mdbx_txn_abort()
+ *                     or \ref mdbx_txn_reset() will be called later.
+ *
+ * \retval 2 or great  The reader process was terminated or killed,
+ *                     and libmdbx should entirely reset reader registration.
+ *
+ * \see mdbx_env_set_hsr() \see mdbx_env_get_hsr()
+ */
+typedef int(MDBX_hsr_func)(const MDBX_env *env, const MDBX_txn *txn,
+                           mdbx_pid_t pid, mdbx_tid_t tid, uint64_t laggard,
+                           unsigned gap, size_t space,
+                           int retry) MDBX_CXX17_NOEXCEPT;
+
+/** \brief Sets a Handle-Slow-Readers callback to resolve database full/overflow
+ * issue due to a reader(s) which prevents the old data from being recycled.
+ * \ingroup c_err
+ *
+ * The callback will only be triggered when the database is full due to a
+ * reader(s) prevents the old data from being recycled.
+ *
+ * \see mdbx_env_get_hsr()
+ * \see long-lived-read
+ *
+ * \param [in] env             An environment handle returned
+ *                             by \ref mdbx_env_create().
+ * \param [in] hsr_callback    A \ref MDBX_hsr_func function
+ *                             or NULL to disable.
+ *
+ * \returns A non-zero error value on failure and 0 on success. */
+LIBMDBX_API int mdbx_env_set_hsr(MDBX_env *env, MDBX_hsr_func *hsr_callback);
+
+/** \brief Gets current Handle-Slow-Readers callback used to resolve database
+ * full/overflow issue due to a reader(s) which prevents the old data from being
+ * recycled.
+ * \see mdbx_env_set_hsr()
+ *
+ * \param [in] env   An environment handle returned by \ref mdbx_env_create().
+ *
+ * \returns A MDBX_hsr_func function or NULL if disabled
+ *          or something wrong. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API MDBX_hsr_func *
+mdbx_env_get_hsr(const MDBX_env *env);
+
+/** \defgroup btree_traversal B-tree Traversal
+ * This is internal API for mdbx_chk tool. You should avoid to use it, except
+ * some extremal special cases.
+ * \ingroup c_extra
+ * @{ */
+
+/** \brief Page types for traverse the b-tree.
+ * \see mdbx_env_pgwalk() \see MDBX_pgvisitor_func */
+enum MDBX_page_type_t {
+  MDBX_page_broken,
+  MDBX_page_meta,
+  MDBX_page_large,
+  MDBX_page_branch,
+  MDBX_page_leaf,
+  MDBX_page_dupfixed_leaf,
+  MDBX_subpage_leaf,
+  MDBX_subpage_dupfixed_leaf,
+  MDBX_subpage_broken,
+};
+#ifndef __cplusplus
+typedef enum MDBX_page_type_t MDBX_page_type_t;
+#endif
+
+/** \brief Pseudo-name for MainDB */
+#define MDBX_PGWALK_MAIN ((const char *)((ptrdiff_t)0))
+/** \brief Pseudo-name for GarbageCollectorDB */
+#define MDBX_PGWALK_GC ((const char *)((ptrdiff_t)-1))
+/** \brief Pseudo-name for MetaPages */
+#define MDBX_PGWALK_META ((const char *)((ptrdiff_t)-2))
+
+/** \brief Callback function for traverse the b-tree. \see mdbx_env_pgwalk() */
+typedef int MDBX_pgvisitor_func(
+    const uint64_t pgno, const unsigned number, void *const ctx, const int deep,
+    const char *const dbi, const size_t page_size, const MDBX_page_type_t type,
+    const MDBX_error_t err, const size_t nentries, const size_t payload_bytes,
+    const size_t header_bytes, const size_t unused_bytes) MDBX_CXX17_NOEXCEPT;
+
+/** \brief B-tree traversal function. */
+LIBMDBX_API int mdbx_env_pgwalk(MDBX_txn *txn, MDBX_pgvisitor_func *visitor,
+                                void *ctx, bool dont_check_keys_ordering);
+
+/** \brief Open an environment instance using specific meta-page
+ * for checking and recovery.
+ *
+ * This function mostly of internal API for `mdbx_chk` utility and subject to
+ * change at any time. Do not use this function to avoid shooting your own
+ * leg(s). */
+LIBMDBX_API int mdbx_env_open_for_recovery(MDBX_env *env, const char *pathname,
+                                           unsigned target_meta,
+                                           bool writeable);
+
+/** \brief Turn database to the specified meta-page.
+ *
+ * This function mostly of internal API for `mdbx_chk` utility and subject to
+ * change at any time. Do not use this function to avoid shooting your own
+ * leg(s). */
+LIBMDBX_API int mdbx_env_turn_for_recovery(MDBX_env *env, unsigned target_meta);
+
+/** @} B-tree Traversal */
+
+/**** Attribute support functions for Nexenta
+ * *******************************************/
+#if defined(MDBX_NEXENTA_ATTRS) || defined(DOXYGEN)
+/** \defgroup nexenta Attribute support functions for Nexenta
+ * \ingroup c_crud
+ * @{ */
+typedef uint_fast64_t mdbx_attr_t;
+
+/** Store by cursor with attribute.
+ *
+ * This function stores key/data pairs into the database. The cursor is
+ * positioned at the new item, or on failure usually near it.
+ *
+ * \note Internally based on \ref MDBX_RESERVE feature,
+ *       therefore doesn't support \ref MDBX_DUPSORT.
+ *
+ * \param [in] cursor  A cursor handle returned by \ref mdbx_cursor_open()
+ * \param [in] key     The key operated on.
+ * \param [in] data    The data operated on.
+ * \param [in] attr    The attribute.
+ * \param [in] flags   Options for this operation. This parameter must be set
+ *                     to 0 or one of the values described here:
+ *  - \ref MDBX_CURRENT
+ *      Replace the item at the current cursor position. The key parameter
+ *      must still be provided, and must match it, otherwise the function
+ *      return \ref MDBX_EKEYMISMATCH.
+ *
+ *  - \ref MDBX_APPEND
+ *      Append the given key/data pair to the end of the database. No key
+ *      comparisons are performed. This option allows fast bulk loading when
+ *      keys are already known to be in the correct order. Loading unsorted
+ *      keys with this flag will cause a \ref MDBX_KEYEXIST error.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_EKEYMISMATCH
+ * \retval MDBX_MAP_FULL  The database is full, see \ref mdbx_env_set_mapsize().
+ * \retval MDBX_TXN_FULL  The transaction has too many dirty pages.
+ * \retval MDBX_EACCES    An attempt was made to write in a read-only
+ *                        transaction.
+ * \retval MDBX_EINVAL    an invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_put_attr(MDBX_cursor *cursor, MDBX_val *key,
+                                     MDBX_val *data, mdbx_attr_t attr,
+                                     MDBX_put_flags_t flags);
+
+/** Store items and attributes into a database.
+ *
+ * This function stores key/data pairs in the database. The default behavior
+ * is to enter the new key/data pair, replacing any previously existing key
+ * if duplicates are disallowed.
+ *
+ * \note Internally based on \ref MDBX_RESERVE feature,
+ *       therefore doesn't support \ref MDBX_DUPSORT.
+ *
+ * \param [in] txn       A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi       A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key       The key to store in the database.
+ * \param [in] attr      The attribute to store in the database.
+ * \param [in,out] data  The data to store.
+ * \param [in] flags     Special options for this operation. This parameter
+ *                       must be set to 0 or by bitwise OR'ing together one or
+ *                       more of the values described here:
+ *  - \ref MDBX_NOOVERWRITE
+ *      Enter the new key/data pair only if the key does not already appear
+ *      in the database. The function will return \ref MDBX_KEYEXIST if the key
+ *      already appears in the database. The data parameter will be set to
+ *      point to the existing item.
+ *
+ *  - \ref MDBX_CURRENT
+ *      Update an single existing entry, but not add new ones. The function
+ *      will return \ref MDBX_NOTFOUND if the given key not exist in the
+ *      database. Or the \ref MDBX_EMULTIVAL in case duplicates for the given
+ *     key.
+ *
+ *  - \ref MDBX_APPEND
+ *      Append the given key/data pair to the end of the database. This option
+ *      allows fast bulk loading when keys are already known to be in the
+ *      correct order. Loading unsorted keys with this flag will cause
+ *      a \ref MDBX_EKEYMISMATCH error.
+ *
+ * \see \ref c_crud_hints "Quick reference for Insert/Update/Delete operations"
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_KEYEXIST
+ * \retval MDBX_MAP_FULL  The database is full, see \ref mdbx_env_set_mapsize().
+ * \retval MDBX_TXN_FULL  The transaction has too many dirty pages.
+ * \retval MDBX_EACCES    An attempt was made to write
+ *                        in a read-only transaction.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_put_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                              MDBX_val *data, mdbx_attr_t attr,
+                              MDBX_put_flags_t flags);
+
+/** Set items attribute from a database.
+ *
+ * This function stores key/data pairs attribute to the database.
+ *
+ * \note Internally based on \ref MDBX_RESERVE feature,
+ *       therefore doesn't support \ref MDBX_DUPSORT.
+ *
+ * \param [in] txn   A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi   A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key   The key to search for in the database.
+ * \param [in] data  The data to be stored or NULL to save previous value.
+ * \param [in] attr  The attribute to be stored.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_NOTFOUND   The key-value pair was not in the database.
+ * \retval MDBX_EINVAL     An invalid parameter was specified. */
+LIBMDBX_API int mdbx_set_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                              MDBX_val *data, mdbx_attr_t attr);
+
+/** Get items attribute from a database cursor.
+ *
+ * This function retrieves key/data pairs from the database. The address and
+ * length of the key are returned in the object to which key refers (except
+ * for the case of the \ref MDBX_SET option, in which the key object is
+ * unchanged), and the address and length of the data are returned in the object
+ * to which data refers.
+ * \see mdbx_get()
+ *
+ * \param [in] cursor    A cursor handle returned by \ref mdbx_cursor_open().
+ * \param [in,out] key   The key for a retrieved item.
+ * \param [in,out] data  The data of a retrieved item.
+ * \param [out] pattr    The pointer to retrieve attribute.
+ * \param [in] op        A cursor operation MDBX_cursor_op.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_NOTFOUND  No matching key found.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_cursor_get_attr(MDBX_cursor *cursor, MDBX_val *key,
+                                     MDBX_val *data, mdbx_attr_t *pattr,
+                                     MDBX_cursor_op op);
+
+/** Get items attribute from a database.
+ *
+ * This function retrieves key/data pairs from the database. The address
+ * and length of the data associated with the specified key are returned
+ * in the structure to which data refers.
+ * If the database supports duplicate keys (see \ref MDBX_DUPSORT) then the
+ * first data item for the key will be returned. Retrieval of other
+ * items requires the use of \ref mdbx_cursor_get().
+ *
+ * \note The memory pointed to by the returned values is owned by the
+ * database. The caller need not dispose of the memory, and may not
+ * modify it in any way. For values returned in a read-only transaction
+ * any modification attempts will cause a `SIGSEGV`.
+ *
+ * \note Values returned from the database are valid only until a
+ * subsequent update operation, or the end of the transaction.
+ *
+ * \param [in] txn       A transaction handle returned by \ref mdbx_txn_begin().
+ * \param [in] dbi       A database handle returned by \ref mdbx_dbi_open().
+ * \param [in] key       The key to search for in the database.
+ * \param [in,out] data  The data corresponding to the key.
+ * \param [out] pattr    The pointer to retrieve attribute.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_NOTFOUND  The key was not in the database.
+ * \retval MDBX_EINVAL    An invalid parameter was specified. */
+LIBMDBX_API int mdbx_get_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                              MDBX_val *data, mdbx_attr_t *pattr);
+/** @} end of Attribute support functions for Nexenta */
+#endif /* MDBX_NEXENTA_ATTRS */
+
+/** @} end of C API */
+
+/*******************************************************************************
+ * Workaround for mmaped-lookahead-cross-page-boundary bug
+ * in an obsolete versions of Elbrus's libc and kernels. */
+#if defined(__e2k__) && defined(MDBX_E2K_MLHCPB_WORKAROUND) &&                 \
+    MDBX_E2K_MLHCPB_WORKAROUND
+LIBMDBX_API int mdbx_e2k_memcmp_bug_workaround(const void *s1, const void *s2,
+                                               size_t n);
+LIBMDBX_API int mdbx_e2k_strcmp_bug_workaround(const char *s1, const char *s2);
+LIBMDBX_API int mdbx_e2k_strncmp_bug_workaround(const char *s1, const char *s2,
+                                                size_t n);
+LIBMDBX_API size_t mdbx_e2k_strlen_bug_workaround(const char *s);
+LIBMDBX_API size_t mdbx_e2k_strnlen_bug_workaround(const char *s,
+                                                   size_t maxlen);
+#ifdef __cplusplus
+namespace std {
+inline int mdbx_e2k_memcmp_bug_workaround(const void *s1, const void *s2,
+                                          size_t n) {
+  return ::mdbx_e2k_memcmp_bug_workaround(s1, s2, n);
+}
+inline int mdbx_e2k_strcmp_bug_workaround(const char *s1, const char *s2) {
+  return ::mdbx_e2k_strcmp_bug_workaround(s1, s2);
+}
+inline int mdbx_e2k_strncmp_bug_workaround(const char *s1, const char *s2,
+                                           size_t n) {
+  return ::mdbx_e2k_strncmp_bug_workaround(s1, s2, n);
+}
+inline size_t mdbx_e2k_strlen_bug_workaround(const char *s) {
+  return ::mdbx_e2k_strlen_bug_workaround(s);
+}
+inline size_t mdbx_e2k_strnlen_bug_workaround(const char *s, size_t maxlen) {
+  return ::mdbx_e2k_strnlen_bug_workaround(s, maxlen);
+}
+} // namespace std
+#endif /* __cplusplus */
+
+#include <string.h>
+#include <strings.h>
+#undef memcmp
+#define memcmp mdbx_e2k_memcmp_bug_workaround
+#undef bcmp
+#define bcmp mdbx_e2k_memcmp_bug_workaround
+#undef strcmp
+#define strcmp mdbx_e2k_strcmp_bug_workaround
+#undef strncmp
+#define strncmp mdbx_e2k_strncmp_bug_workaround
+#undef strlen
+#define strlen mdbx_e2k_strlen_bug_workaround
+#undef strnlen
+#define strnlen mdbx_e2k_strnlen_bug_workaround
+#endif /* MDBX_E2K_MLHCPB_WORKAROUND */
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* LIBMDBX_H */
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx.h++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.h++
new file mode 100644
index 0000000000..5ae3838aeb
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx.h++
@@ -0,0 +1,4707 @@
+/// \file mdbx.h++
+/// \brief The libmdbx C++ API header file (preliminary).
+///
+/// \author Copyright (c) 2020-2021, Leonid Yuriev <leo@yuriev.ru>.
+/// \copyright SPDX-License-Identifier: Apache-2.0
+///
+/// Tested with:
+///  - LCC >= 1.23 (http://www.mcst.ru/lcc),
+///  - GNU C++ >= 4.8,
+///  - clang >= 4.0,
+///  - MSVC >= 19.0 (Visual Studio 2015),
+///    but 19.2x could hang due optimizer bug.
+///
+
+#pragma once
+
+#if (!defined(__cplusplus) || __cplusplus < 201103L) &&                        \
+    !(defined(                                                                 \
+          _MSC_VER) /* MSVC is mad and don't define __cplusplus properly */    \
+      && _MSC_VER == 1900)
+#error "C++11 or better is required"
+#endif
+
+#if (defined(_WIN32) || defined(_WIN64)) && MDBX_AVOID_CRT
+#error "CRT is required for C++ API, the MDBX_AVOID_CRT option must be disabled"
+#endif /* Windows */
+
+#ifndef __has_include
+#define __has_include(header) (0)
+#endif /* __has_include */
+
+#if __has_include(<version>)
+#include <version>
+#endif /* <version> */
+
+/* Disable min/max macros from C' headers */
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+
+#include <algorithm>   // for std::min/max
+#include <cassert>     // for assert()
+#include <cstring>     // for std::strlen, str:memcmp
+#include <exception>   // for std::exception_ptr
+#include <ostream>     // for std::ostream
+#include <sstream>     // for std::ostringstream
+#include <stdexcept>   // for std::invalid_argument
+#include <string>      // for std::string
+#include <type_traits> // for std::is_pod<>, etc.
+#include <vector>      // for std::vector<> as template args
+
+// Unused for now
+// #if defined(__cpp_lib_bit_cast) && __cpp_lib_bit_cast >= 201806L
+// #include <bit>
+// #endif
+
+#if defined(__cpp_lib_memory_resource) && __cpp_lib_memory_resource >= 201603L
+#include <memory_resource>
+#endif
+
+#if defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L
+#include <string_view>
+#endif
+
+#if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L
+#include <filesystem>
+#endif
+
+#include "mdbx.h"
+
+#if defined(DOXYGEN) ||                                                        \
+    defined(__cpp_constexpr) && __cpp_constexpr >= 201603L &&                  \
+        ((defined(_MSC_VER) && _MSC_VER >= 1915) ||                            \
+         (defined(__clang__) && __clang_major__ > 5) ||                        \
+         (defined(__GNUC__) && __GNUC__ > 7) ||                                \
+         (!defined(__GNUC__) && !defined(__clang__) && !defined(_MSC_VER)))
+#define MDBX_CXX17_CONSTEXPR constexpr
+#else
+#define MDBX_CXX17_CONSTEXPR inline
+#endif /* MDBX_CXX17_CONSTEXPR */
+
+#if defined(DOXYGEN) || defined(__cpp_lib_is_constant_evaluated) &&            \
+                            __cpp_lib_is_constant_evaluated >= 201811L &&      \
+                            defined(__cpp_lib_constexpr_string) &&             \
+                            __cpp_lib_constexpr_string >= 201907L
+#define MDBX_CXX20_CONSTEXPR constexpr
+#else
+#define MDBX_CXX20_CONSTEXPR inline
+#endif /* MDBX_CXX20_CONSTEXPR */
+
+#if defined(CONSTEXPR_ASSERT)
+#define MDBX_CONSTEXPR_ASSERT(expr) CONSTEXPR_ASSERT(expr)
+#elif defined NDEBUG
+#define MDBX_CONSTEXPR_ASSERT(expr) void(0)
+#else
+#define MDBX_CONSTEXPR_ASSERT(expr)                                            \
+  ((expr) ? void(0) : [] { assert(!#expr); }())
+#endif /* MDBX_CONSTEXPR_ASSERT */
+
+#ifndef MDBX_LIKELY
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__GNUC__) || __has_builtin(__builtin_expect)) &&                  \
+        !defined(__COVERITY__)
+#define MDBX_LIKELY(cond) __builtin_expect(!!(cond), 1)
+#else
+#define MDBX_LIKELY(x) (x)
+#endif
+#endif /* MDBX_LIKELY */
+
+#ifndef MDBX_UNLIKELY
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__GNUC__) || __has_builtin(__builtin_expect)) &&                  \
+        !defined(__COVERITY__)
+#define MDBX_UNLIKELY(cond) __builtin_expect(!!(cond), 0)
+#else
+#define MDBX_UNLIKELY(x) (x)
+#endif
+#endif /* MDBX_UNLIKELY */
+
+#if defined(DOXYGEN) ||                                                        \
+    (__has_cpp_attribute(fallthrough) &&                                       \
+     (!defined(__clang__) || __clang__ > 4)) ||                                \
+    __cplusplus >= 201703L
+#define MDBX_CXX17_FALLTHROUGH [[fallthrough]]
+#else
+#define MDBX_CXX17_FALLTHROUGH
+#endif /* MDBX_CXX17_FALLTHROUGH */
+
+#if defined(DOXYGEN) || __has_cpp_attribute(likely)
+#define MDBX_CXX20_LIKELY [[likely]]
+#else
+#define MDBX_CXX20_LIKELY
+#endif /* MDBX_CXX20_LIKELY */
+
+#ifndef MDBX_CXX20_UNLIKELY
+#if defined(DOXYGEN) || __has_cpp_attribute(unlikely)
+#define MDBX_CXX20_UNLIKELY [[unlikely]]
+#else
+#define MDBX_CXX20_UNLIKELY
+#endif
+#endif /* MDBX_CXX20_UNLIKELY */
+
+#ifdef _MSC_VER
+#pragma warning(push, 4)
+#pragma warning(disable : 4251) /* 'std::FOO' needs to have dll-interface to   \
+                                   be used by clients of 'mdbx::BAR' */
+#pragma warning(disable : 4275) /* non dll-interface 'std::FOO' used as        \
+                                   base for dll-interface 'mdbx::BAR' */
+/* MSVC is mad and can generate this warning for its own intermediate
+ * automatically generated code, which becomes unreachable after some kinds of
+ * optimization (copy elision, etc). */
+#pragma warning(disable : 4702) /* unreachable code */
+#endif                          /* _MSC_VER (warnings) */
+
+//------------------------------------------------------------------------------
+/// \defgroup cxx_api C++ API
+/// @{
+
+namespace mdbx {
+
+// Functions whose signature depends on the `mdbx::byte` type
+// must be strictly defined as inline!
+#if defined(DOXYGEN) || (defined(__cpp_char8_t) && __cpp_char8_t >= 201811)
+// Wanna using a non-aliasing type to release more power of an optimizer.
+using byte = char8_t;
+#else
+// Wanna not using std::byte since it doesn't add features,
+// but add inconvenient restrictions.
+using byte = unsigned char;
+#endif /* __cpp_char8_t >= 201811*/
+
+/// \copydoc MDBX_version_info
+using version_info = ::MDBX_version_info;
+/// \brief Returns libmdbx version information.
+MDBX_CXX11_CONSTEXPR const version_info &get_version() noexcept;
+/// \copydoc MDBX_build_info
+using build_info = ::MDBX_build_info;
+/// \brief Returns libmdbx build information.
+MDBX_CXX11_CONSTEXPR const build_info &get_build() noexcept;
+
+/// \brief constexpr-compatible strlen().
+static MDBX_CXX17_CONSTEXPR size_t strlen(const char *c_str) noexcept;
+
+struct slice;
+class env;
+class env_managed;
+class txn;
+class txn_managed;
+class cursor;
+class cursor_managed;
+
+/// \brief Legacy default allocator
+/// but it is recommended to use \ref polymorphic_allocator.
+using legacy_allocator = ::std::string::allocator_type;
+
+#if defined(DOXYGEN) ||                                                        \
+    defined(__cpp_lib_memory_resource) && __cpp_lib_memory_resource >= 201603L
+/// \brief Default polymorphic allocator for modern code.
+using polymorphic_allocator = ::std::pmr::string::allocator_type;
+#endif /* __cpp_lib_memory_resource >= 201603L */
+
+/// \brief Default singe-byte string.
+template <class ALLOCATOR = legacy_allocator>
+using string = ::std::basic_string<char, ::std::char_traits<char>, ALLOCATOR>;
+
+using filehandle = ::mdbx_filehandle_t;
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L &&       \
+     (!defined(__MAC_OS_X_VERSION_MIN_REQUIRED) ||                             \
+      __MAC_OS_X_VERSION_MIN_REQUIRED >= 101500))
+#define MDBX_STD_FILESYSTEM_PATH
+using path = ::std::filesystem::path;
+#elif defined(_WIN32) || defined(_WIN64)
+using path = ::std::wstring;
+#else
+using path = ::std::string;
+#endif
+
+/// \brief Transfers C++ exceptions thru C callbacks.
+/// \details Implements saving exceptions before returning
+/// from an C++'s environment to the intermediate C code and re-throwing after
+/// returning from C to the C++'s environment.
+class LIBMDBX_API_TYPE exception_thunk {
+  ::std::exception_ptr captured_;
+
+public:
+  exception_thunk() noexcept = default;
+  exception_thunk(const exception_thunk &) = delete;
+  exception_thunk(exception_thunk &&) = delete;
+  exception_thunk &operator=(const exception_thunk &) = delete;
+  exception_thunk &operator=(exception_thunk &&) = delete;
+  inline bool is_clean() const noexcept;
+  inline void capture() noexcept;
+  inline void rethrow_captured() const;
+};
+
+/// \brief Implements error information and throwing corresponding exceptions.
+class LIBMDBX_API_TYPE error {
+  MDBX_error_t code_;
+  inline error &operator=(MDBX_error_t error_code) noexcept;
+
+public:
+  MDBX_CXX11_CONSTEXPR error(MDBX_error_t error_code) noexcept;
+  error(const error &) = default;
+  error(error &&) = default;
+  error &operator=(const error &) = default;
+  error &operator=(error &&) = default;
+
+  MDBX_CXX11_CONSTEXPR friend bool operator==(const error &a,
+                                              const error &b) noexcept;
+  MDBX_CXX11_CONSTEXPR friend bool operator!=(const error &a,
+                                              const error &b) noexcept;
+
+  MDBX_CXX11_CONSTEXPR bool is_success() const noexcept;
+  MDBX_CXX11_CONSTEXPR bool is_result_true() const noexcept;
+  MDBX_CXX11_CONSTEXPR bool is_result_false() const noexcept;
+  MDBX_CXX11_CONSTEXPR bool is_failure() const noexcept;
+
+  /// \brief Returns error code.
+  MDBX_CXX11_CONSTEXPR MDBX_error_t code() const noexcept;
+
+  /// \brief Returns message for MDBX's errors only and "SYSTEM" for others.
+  const char *what() const noexcept;
+
+  /// \brief Returns message for any errors.
+  ::std::string message() const;
+
+  /// \brief Returns true for MDBX's errors.
+  MDBX_CXX11_CONSTEXPR bool is_mdbx_error() const noexcept;
+  /// \brief Panics on unrecoverable errors inside destructors etc.
+  [[noreturn]] void panic(const char *context_where_when,
+                          const char *func_who_what) const noexcept;
+  [[noreturn]] void throw_exception() const;
+  [[noreturn]] static inline void throw_exception(int error_code);
+  inline void throw_on_failure() const;
+  inline void success_or_throw() const;
+  inline void success_or_throw(const exception_thunk &) const;
+  inline void panic_on_failure(const char *context_where,
+                               const char *func_who) const noexcept;
+  inline void success_or_panic(const char *context_where,
+                               const char *func_who) const noexcept;
+  static inline void throw_on_nullptr(const void *ptr, MDBX_error_t error_code);
+  static inline void success_or_throw(MDBX_error_t error_code);
+  static void success_or_throw(int error_code) {
+    success_or_throw(static_cast<MDBX_error_t>(error_code));
+  }
+  static inline void throw_on_failure(int error_code);
+  static inline bool boolean_or_throw(int error_code);
+  static inline void success_or_throw(int error_code, const exception_thunk &);
+  static inline void panic_on_failure(int error_code, const char *context_where,
+                                      const char *func_who) noexcept;
+  static inline void success_or_panic(int error_code, const char *context_where,
+                                      const char *func_who) noexcept;
+};
+
+/// \brief Base class for all libmdbx's exceptions that are corresponds
+/// to libmdbx errors.
+///
+/// \see MDBX_error_t
+class LIBMDBX_API_TYPE exception : public ::std::runtime_error {
+  using base = ::std::runtime_error;
+  ::mdbx::error error_;
+
+public:
+  exception(const ::mdbx::error &) noexcept;
+  exception(const exception &) = default;
+  exception(exception &&) = default;
+  exception &operator=(const exception &) = default;
+  exception &operator=(exception &&) = default;
+  virtual ~exception() noexcept;
+  const mdbx::error error() const noexcept { return error_; }
+};
+
+/// \brief Fatal exception that lead termination anyway
+/// in dangerous unrecoverable cases.
+class LIBMDBX_API_TYPE fatal : public exception {
+  using base = exception;
+
+public:
+  fatal(const ::mdbx::error &) noexcept;
+  fatal(const exception &src) noexcept : fatal(src.error()) {}
+  fatal(exception &&src) noexcept : fatal(src.error()) {}
+  fatal(const fatal &src) noexcept : fatal(src.error()) {}
+  fatal(fatal &&src) noexcept : fatal(src.error()) {}
+  fatal &operator=(fatal &&) = default;
+  fatal &operator=(const fatal &) = default;
+  virtual ~fatal() noexcept;
+};
+
+#define MDBX_DECLARE_EXCEPTION(NAME)                                           \
+  struct LIBMDBX_API_TYPE NAME : public exception {                            \
+    NAME(const ::mdbx::error &);                                               \
+    virtual ~NAME() noexcept;                                                  \
+  }
+MDBX_DECLARE_EXCEPTION(bad_map_id);
+MDBX_DECLARE_EXCEPTION(bad_transaction);
+MDBX_DECLARE_EXCEPTION(bad_value_size);
+MDBX_DECLARE_EXCEPTION(db_corrupted);
+MDBX_DECLARE_EXCEPTION(db_full);
+MDBX_DECLARE_EXCEPTION(db_invalid);
+MDBX_DECLARE_EXCEPTION(db_too_large);
+MDBX_DECLARE_EXCEPTION(db_unable_extend);
+MDBX_DECLARE_EXCEPTION(db_version_mismatch);
+MDBX_DECLARE_EXCEPTION(db_wanna_write_for_recovery);
+MDBX_DECLARE_EXCEPTION(incompatible_operation);
+MDBX_DECLARE_EXCEPTION(internal_page_full);
+MDBX_DECLARE_EXCEPTION(internal_problem);
+MDBX_DECLARE_EXCEPTION(key_exists);
+MDBX_DECLARE_EXCEPTION(key_mismatch);
+MDBX_DECLARE_EXCEPTION(max_maps_reached);
+MDBX_DECLARE_EXCEPTION(max_readers_reached);
+MDBX_DECLARE_EXCEPTION(multivalue);
+MDBX_DECLARE_EXCEPTION(no_data);
+MDBX_DECLARE_EXCEPTION(not_found);
+MDBX_DECLARE_EXCEPTION(operation_not_permitted);
+MDBX_DECLARE_EXCEPTION(permission_denied_or_not_writeable);
+MDBX_DECLARE_EXCEPTION(reader_slot_busy);
+MDBX_DECLARE_EXCEPTION(remote_media);
+MDBX_DECLARE_EXCEPTION(something_busy);
+MDBX_DECLARE_EXCEPTION(thread_mismatch);
+MDBX_DECLARE_EXCEPTION(transaction_full);
+MDBX_DECLARE_EXCEPTION(transaction_overlapping);
+#undef MDBX_DECLARE_EXCEPTION
+
+[[noreturn]] LIBMDBX_API void throw_too_small_target_buffer();
+[[noreturn]] LIBMDBX_API void throw_max_length_exceeded();
+[[noreturn]] LIBMDBX_API void throw_out_range();
+MDBX_CXX14_CONSTEXPR size_t check_length(size_t bytes);
+
+//------------------------------------------------------------------------------
+
+/// \brief References a data located outside the slice.
+///
+/// The `slice` is similar in many ways to `std::string_view`, but it
+/// implements specific capabilities and manipulates with bytes but
+/// not a characters.
+///
+/// \copydetails MDBX_val
+struct LIBMDBX_API_TYPE slice : public ::MDBX_val {
+  /// \todo slice& operator<<(slice&, ...) for reading
+  /// \todo key-to-value (parse/unpack) functions
+  /// \todo template<class X> key(X); for decoding keys while reading
+
+  enum { max_length = MDBX_MAXDATASIZE };
+
+  /// \brief Create an empty slice.
+  MDBX_CXX11_CONSTEXPR slice() noexcept;
+
+  /// \brief Create a slice that refers to [0,bytes-1] of memory bytes pointed
+  /// by ptr.
+  MDBX_CXX14_CONSTEXPR slice(const void *ptr, size_t bytes);
+
+  /// \brief Create a slice that refers to [begin,end] of memory bytes.
+  MDBX_CXX14_CONSTEXPR slice(const void *begin, const void *end);
+
+  /// \brief Create a slice that refers to text[0,strlen(text)-1].
+  template <size_t SIZE>
+  MDBX_CXX14_CONSTEXPR slice(const char (&text)[SIZE]) noexcept
+      : slice(text, SIZE - 1) {
+    MDBX_CONSTEXPR_ASSERT(SIZE > 0 && text[SIZE - 1] == '\0');
+  }
+  /// \brief Create a slice that refers to c_str[0,strlen(c_str)-1].
+  explicit MDBX_CXX17_CONSTEXPR slice(const char *c_str);
+
+  /// \brief Create a slice that refers to the contents of "str".
+  /* 'explicit' to avoid reference to the temporary std::string instance */
+  template <class C, class T, class A>
+  explicit MDBX_CXX20_CONSTEXPR slice(const ::std::basic_string<C, T, A> &str)
+      : slice(str.data(), str.length() * sizeof(C)) {}
+
+  MDBX_CXX14_CONSTEXPR slice(const MDBX_val &src);
+  MDBX_CXX11_CONSTEXPR slice(const slice &) noexcept = default;
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  /// \brief Create a slice that refers to the same contents as "sv"
+  template <class C, class T>
+  explicit MDBX_CXX14_CONSTEXPR slice(const ::std::basic_string_view<C, T> &sv)
+      : slice(sv.data(), sv.data() + sv.length()) {}
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  inline slice(MDBX_val &&src);
+  inline slice(slice &&src) noexcept;
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  slice(::std::basic_string_view<C, T> &&sv) : slice(sv) {
+    sv = {};
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  template <size_t SIZE>
+  static MDBX_CXX14_CONSTEXPR slice wrap(const char (&text)[SIZE]) {
+    return slice(text);
+  }
+
+  template <typename POD>
+  MDBX_CXX14_CONSTEXPR static slice wrap(const POD &pod) {
+    static_assert(::std::is_standard_layout<POD>::value &&
+                      !std::is_pointer<POD>::value,
+                  "Must be a standard layout type!");
+    return slice(&pod, sizeof(pod));
+  }
+
+  inline slice &assign(const void *ptr, size_t bytes);
+  inline slice &assign(const slice &src) noexcept;
+  inline slice &assign(const ::MDBX_val &src);
+  inline slice &assign(slice &&src) noexcept;
+  inline slice &assign(::MDBX_val &&src);
+  inline slice &assign(const void *begin, const void *end);
+  template <class C, class T, class A>
+  slice &assign(const ::std::basic_string<C, T, A> &str) {
+    return assign(str.data(), str.length() * sizeof(C));
+  }
+  inline slice &assign(const char *c_str);
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  slice &assign(const ::std::basic_string_view<C, T> &view) {
+    return assign(view.begin(), view.end());
+  }
+  template <class C, class T>
+  slice &assign(::std::basic_string_view<C, T> &&view) {
+    assign(view);
+    view = {};
+    return *this;
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  slice &operator=(const slice &) noexcept = default;
+  inline slice &operator=(slice &&src) noexcept;
+  inline slice &operator=(::MDBX_val &&src);
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  slice &operator=(const ::std::basic_string_view<C, T> &view) {
+    return assign(view);
+  }
+  template <class C, class T>
+  slice &operator=(::std::basic_string_view<C, T> &&view) {
+    return assign(view);
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  template <class C = char, class T = ::std::char_traits<C>,
+            class A = legacy_allocator>
+  MDBX_CXX20_CONSTEXPR ::std::basic_string<C, T, A>
+  string(const A &allocator = A()) const {
+    static_assert(sizeof(C) == 1, "Must be single byte characters");
+    return ::std::basic_string<C, T, A>(char_ptr(), length(), allocator);
+  }
+
+  template <class C, class T, class A>
+  MDBX_CXX20_CONSTEXPR operator ::std::basic_string<C, T, A>() const {
+    return this->string<C, T, A>();
+  }
+
+  /// \brief Fills the buffer by hexadecimal data dump of slice content.
+  /// \throws std::length_error if given buffer is too small.
+  char *to_hex(char *dest, size_t dest_size, bool uppercase = false,
+               unsigned wrap_width = 0) const;
+
+  /// \brief Returns the buffer size in bytes needed for hexadecimal data dump
+  /// of slice content.
+  MDBX_CXX11_CONSTEXPR size_t
+  to_hex_bytes(unsigned wrap_width = 0) const noexcept {
+    const size_t bytes = length() << 1;
+    return wrap_width ? bytes + bytes / wrap_width : bytes;
+  }
+
+  /// \brief Fills the buffer with data converted from hexadecimal dump
+  /// from slice content.
+  /// \throws std::length_error if given buffer is too small.
+  byte *from_hex(byte *dest, size_t dest_size,
+                 bool ignore_spaces = false) const;
+
+  /// \brief Returns the buffer size in bytes needed for conversion
+  /// hexadecimal dump from slice content to data.
+  MDBX_CXX11_CONSTEXPR size_t from_hex_bytes() const noexcept {
+    return length() >> 1;
+  }
+
+  /// \brief Fills the buffer by [Base58](https://en.wikipedia.org/wiki/Base58)
+  /// data dump of slice content.
+  /// \throws std::length_error if given buffer is too small.
+  char *to_base58(char *dest, size_t dest_size, unsigned wrap_width = 0) const;
+
+  /// \brief Returns the buffer size in bytes needed for
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) data dump of slice content.
+  MDBX_CXX11_CONSTEXPR size_t
+  to_base58_bytes(unsigned wrap_width = 0) const noexcept {
+    const size_t bytes = length() / 8 * 11 + (length() % 8 * 43 + 31) / 32;
+    return wrap_width ? bytes + bytes / wrap_width : bytes;
+  }
+
+  /// \brief Fills the buffer with data converted from
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump from slice content.
+  /// \throws std::length_error if given buffer is too small.
+  byte *from_base58(byte *dest, size_t dest_size,
+                    bool ignore_spaces = false) const;
+
+  /// \brief Returns the buffer size in bytes needed for conversion
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump to data.
+  MDBX_CXX11_CONSTEXPR size_t from_base58_bytes() const noexcept {
+    return length() / 11 * 8 + length() % 11 * 32 / 43;
+  }
+
+  /// \brief Fills the buffer by [Base64](https://en.wikipedia.org/wiki/Base64)
+  /// data dump.
+  /// \throws std::length_error if given buffer is too small.
+  char *to_base64(char *dest, size_t dest_size, unsigned wrap_width = 0) const;
+
+  /// \brief Returns the buffer size in bytes needed for
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) data dump.
+  MDBX_CXX11_CONSTEXPR size_t
+  to_base64_bytes(unsigned wrap_width = 0) const noexcept {
+    const size_t bytes = (length() + 2) / 3 * 4;
+    return wrap_width ? bytes + bytes / wrap_width : bytes;
+  }
+
+  /// \brief Fills the buffer with data converted from
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump.
+  /// \throws std::length_error if given buffer is too small.
+  byte *from_base64(byte *dest, size_t dest_size,
+                    bool ignore_spaces = false) const;
+
+  /// \brief Returns the buffer size in bytes needed for conversion
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump to data.
+  MDBX_CXX11_CONSTEXPR size_t from_base64_bytes() const noexcept {
+    return (length() + 3) / 4 * 3;
+  }
+
+  /// \brief Returns a string with a hexadecimal dump of the slice content.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  hex_encode(bool uppercase = false,
+             const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Decodes hexadecimal dump from the slice content into returned data
+  /// string.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  hex_decode(const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Returns a string with a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of the slice content.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  base58_encode(const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Decodes [Base58](https://en.wikipedia.org/wiki/Base58) dump
+  /// from the slice content into returned data string.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  base58_decode(const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Returns a string with a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump of the slice content.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  base64_encode(const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Decodes [Base64](https://en.wikipedia.org/wiki/Base64) dump
+  /// from the slice content into returned data string.
+  template <class ALLOCATOR = legacy_allocator>
+  inline ::mdbx::string<ALLOCATOR>
+  base64_decode(const ALLOCATOR &allocator = ALLOCATOR()) const;
+
+  /// \brief Checks whether the content of the slice is printable.
+  /// \param [in] disable_utf8 By default if `disable_utf8` is `false` function
+  /// checks that content bytes are printable ASCII-7 characters or a valid UTF8
+  /// sequences. Otherwise, if if `disable_utf8` is `true` function checks that
+  /// content bytes are printable extended 8-bit ASCII codes.
+  MDBX_NOTHROW_PURE_FUNCTION bool
+  is_printable(bool disable_utf8 = false) const noexcept;
+
+  /// \brief Checks whether the content of the slice is a hexadecimal dump.
+  /// \param [in] ignore_spaces If `true` function will skips spaces surrounding
+  /// (before, between and after) a encoded bytes. However, spaces should not
+  /// break a pair of characters encoding a single byte.
+  MDBX_NOTHROW_PURE_FUNCTION bool
+  is_hex(bool ignore_spaces = false) const noexcept;
+  MDBX_NOTHROW_PURE_FUNCTION bool
+
+  /// \brief Checks whether the content of the slice is a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump.
+  /// \param [in] ignore_spaces If `true` function will skips spaces surrounding
+  /// (before, between and after) a encoded bytes. However, spaces should not
+  /// break a code group of characters.
+  is_base58(bool ignore_spaces = false) const noexcept;
+  MDBX_NOTHROW_PURE_FUNCTION bool
+
+  /// \brief Checks whether the content of the slice is a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump.
+  /// \param [in] ignore_spaces If `true` function will skips spaces surrounding
+  /// (before, between and after) a encoded bytes. However, spaces should not
+  /// break a code group of characters.
+  is_base64(bool ignore_spaces = false) const noexcept;
+
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  /// \brief Return a string_view that references the same data as this slice.
+  template <class C, class T>
+  MDBX_CXX11_CONSTEXPR explicit
+  operator ::std::basic_string_view<C, T>() const noexcept {
+    static_assert(sizeof(C) == 1, "Must be single byte characters");
+    return ::std::basic_string_view<C, T>(char_ptr(), length());
+  }
+
+  /// \brief Return a string_view that references the same data as this slice.
+  template <class C = char, class T = ::std::char_traits<C>>
+  MDBX_CXX11_CONSTEXPR ::std::basic_string_view<C, T>
+  string_view() const noexcept {
+    static_assert(sizeof(C) == 1, "Must be single byte characters");
+    return ::std::basic_string_view<C, T>(char_ptr(), length());
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  inline void swap(slice &other) noexcept;
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  void swap(::std::basic_string_view<C, T> &view) noexcept {
+    static_assert(sizeof(C) == 1, "Must be single byte characters");
+    const auto temp = ::std::basic_string_view<C, T>(*this);
+    *this = view;
+    view = temp;
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  /// \brief Returns casted to pointer to byte an address of data.
+  MDBX_CXX11_CONSTEXPR const byte *byte_ptr() const noexcept;
+
+  /// \brief Returns casted to pointer to char an address of data.
+  MDBX_CXX11_CONSTEXPR const char *char_ptr() const noexcept;
+
+  /// \brief Return a pointer to the beginning of the referenced data.
+  MDBX_CXX11_CONSTEXPR const void *data() const noexcept;
+
+  /// \brief Returns the number of bytes.
+  MDBX_CXX11_CONSTEXPR size_t length() const noexcept;
+
+  /// \brief Checks whether the slice is empty.
+  MDBX_CXX11_CONSTEXPR bool empty() const noexcept;
+
+  /// \brief Checks whether the slice data pointer is nullptr.
+  MDBX_CXX11_CONSTEXPR bool is_null() const noexcept;
+
+  /// \brief Returns the number of bytes.
+  MDBX_CXX11_CONSTEXPR size_t size() const noexcept;
+
+  /// \brief Returns true if slice is not empty.
+  MDBX_CXX11_CONSTEXPR operator bool() const noexcept;
+
+  /// \brief Depletes content of slice and make it invalid.
+  inline void invalidate() noexcept;
+
+  /// \brief Makes the slice empty and referencing to nothing.
+  inline void clear() noexcept;
+
+  /// \brief Drops the first "n" bytes from this slice.
+  /// \pre REQUIRES: `n <= size()`
+  inline void remove_prefix(size_t n) noexcept;
+
+  /// \brief Drops the last "n" bytes from this slice.
+  /// \pre REQUIRES: `n <= size()`
+  inline void remove_suffix(size_t n) noexcept;
+
+  /// \brief Drops the first "n" bytes from this slice.
+  /// \throws std::out_of_range if `n > size()`
+  inline void safe_remove_prefix(size_t n);
+
+  /// \brief Drops the last "n" bytes from this slice.
+  /// \throws std::out_of_range if `n > size()`
+  inline void safe_remove_suffix(size_t n);
+
+  /// \brief Checks if the data starts with the given prefix.
+  MDBX_NOTHROW_PURE_FUNCTION inline bool
+  starts_with(const slice &prefix) const noexcept;
+
+  /// \brief Checks if the data ends with the given suffix.
+  MDBX_NOTHROW_PURE_FUNCTION inline bool
+  ends_with(const slice &suffix) const noexcept;
+
+  /// \brief Returns the nth byte in the referenced data.
+  /// \pre REQUIRES: `n < size()`
+  inline byte operator[](size_t n) const noexcept;
+
+  /// \brief Returns the nth byte in the referenced data with bounds checking.
+  /// \throws std::out_of_range if `n >= size()`
+  inline byte at(size_t n) const;
+
+  /// \brief Returns the first "n" bytes of the slice.
+  /// \pre REQUIRES: `n <= size()`
+  inline slice head(size_t n) const noexcept;
+
+  /// \brief Returns the last "n" bytes of the slice.
+  /// \pre REQUIRES: `n <= size()`
+  inline slice tail(size_t n) const noexcept;
+
+  /// \brief Returns the middle "n" bytes of the slice.
+  /// \pre REQUIRES: `from + n <= size()`
+  inline slice middle(size_t from, size_t n) const noexcept;
+
+  /// \brief Returns the first "n" bytes of the slice.
+  /// \throws std::out_of_range if `n >= size()`
+  inline slice safe_head(size_t n) const;
+
+  /// \brief Returns the last "n" bytes of the slice.
+  /// \throws std::out_of_range if `n >= size()`
+  inline slice safe_tail(size_t n) const;
+
+  /// \brief Returns the middle "n" bytes of the slice.
+  /// \throws std::out_of_range if `from + n >= size()`
+  inline slice safe_middle(size_t from, size_t n) const;
+
+  /// \brief Returns the hash value of referenced data.
+  /// \attention Function implementation and returned hash values may changed
+  /// version to version, and in future the t1ha3 will be used here. Therefore
+  /// values obtained from this function shouldn't be persisted anywhere.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX14_CONSTEXPR size_t
+  hash_value() const noexcept;
+
+  /// \brief Three-way fast non-lexicographically length-based comparison.
+  /// \return value:
+  ///   == 0 if "a" == "b",
+  ///   <  0 if "a" shorter than "b",
+  ///   >  0 if "a" longer than "b",
+  ///   <  0 if "a" length-equal and lexicographically less than "b",
+  ///   >  0 if "a" length-equal and lexicographically great than "b".
+  MDBX_NOTHROW_PURE_FUNCTION static inline intptr_t
+  compare_fast(const slice &a, const slice &b) noexcept;
+
+  /// \brief Three-way lexicographically comparison.
+  /// \return value:
+  ///   <  0 if "a" <  "b",
+  ///   == 0 if "a" == "b",
+  ///   >  0 if "a" >  "b".
+  MDBX_NOTHROW_PURE_FUNCTION static inline intptr_t
+  compare_lexicographically(const slice &a, const slice &b) noexcept;
+  friend inline bool operator==(const slice &a, const slice &b) noexcept;
+  friend inline bool operator<(const slice &a, const slice &b) noexcept;
+  friend inline bool operator>(const slice &a, const slice &b) noexcept;
+  friend inline bool operator<=(const slice &a, const slice &b) noexcept;
+  friend inline bool operator>=(const slice &a, const slice &b) noexcept;
+  friend inline bool operator!=(const slice &a, const slice &b) noexcept;
+
+  /// \brief Checks the slice is not refers to null address or has zero length.
+  MDBX_CXX11_CONSTEXPR bool is_valid() const noexcept {
+    return !(iov_base == nullptr && iov_len != 0);
+  }
+
+  /// \brief Build an invalid slice which non-zero length and refers to null
+  /// address.
+  MDBX_CXX11_CONSTEXPR static slice invalid() noexcept {
+    return slice(size_t(-1));
+  }
+
+protected:
+  MDBX_CXX11_CONSTEXPR slice(size_t invalid_length) noexcept
+      : ::MDBX_val({nullptr, invalid_length}) {}
+};
+
+//------------------------------------------------------------------------------
+
+/// \brief The chunk of data stored inside the buffer or located outside it.
+template <class ALLOCATOR = legacy_allocator> class buffer {
+  friend class txn;
+  using silo = ::mdbx::string<ALLOCATOR>;
+  silo silo_;
+  ::mdbx::slice slice_;
+
+  void insulate() {
+    assert(is_reference());
+    silo_.assign(slice_.char_ptr(), slice_.length());
+    slice_.iov_base = const_cast<char *>(silo_.data());
+  }
+
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR const byte *
+  silo_begin() const noexcept {
+    return static_cast<const byte *>(static_cast<const void *>(silo_.data()));
+  }
+
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR const byte *
+  silo_end() const noexcept {
+    return silo_begin() + silo_.capacity();
+  }
+
+  struct data_preserver : public exception_thunk {
+    buffer data;
+    data_preserver(ALLOCATOR &allocator) : data(allocator) {}
+    static int callback(void *context, MDBX_val *target, const void *src,
+                        size_t bytes) noexcept;
+    MDBX_CXX11_CONSTEXPR operator MDBX_preserve_func() const noexcept {
+      return callback;
+    }
+    MDBX_CXX11_CONSTEXPR operator const buffer &() const noexcept {
+      return data;
+    }
+    MDBX_CXX11_CONSTEXPR operator buffer &() noexcept { return data; }
+  };
+
+public:
+  /// \todo buffer& operator<<(buffer&, ...) for writing
+  /// \todo buffer& operator>>(buffer&, ...) for reading (delegated to slice)
+  /// \todo template<class X> key(X) for encoding keys while writing
+
+  using allocator_type = ALLOCATOR;
+  enum : size_t {
+    max_length = MDBX_MAXDATASIZE,
+    default_shrink_threshold = 1024
+  };
+
+  /// \brief Returns the associated allocator.
+  MDBX_CXX20_CONSTEXPR allocator_type get_allocator() const {
+    return silo_.get_allocator();
+  }
+
+  /// \brief Checks whether data chunk stored inside the buffer, otherwise
+  /// buffer just refers to data located outside the buffer.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR bool
+  is_freestanding() const noexcept {
+    return size_t(byte_ptr() - silo_begin()) < silo_.capacity();
+  }
+
+  /// \brief Checks whether the buffer just refers to data located outside
+  /// the buffer, rather than stores it.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR bool
+  is_reference() const noexcept {
+    return !is_freestanding();
+  }
+
+  /// \brief Returns the number of bytes that can be held in currently allocated
+  /// storage.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t
+  capacity() const noexcept {
+    return is_freestanding() ? silo_.capacity() : 0;
+  }
+
+  /// \brief Returns the number of bytes that available in currently allocated
+  /// storage ahead the currently beginning of data.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t
+  headroom() const noexcept {
+    return is_freestanding() ? slice_.byte_ptr() - silo_begin() : 0;
+  }
+
+  /// \brief Returns the number of bytes that available in currently allocated
+  /// storage after the currently data end.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t
+  tailroom() const noexcept {
+    return is_freestanding() ? capacity() - headroom() - slice_.length() : 0;
+  }
+
+  /// \brief Returns casted to const pointer to byte an address of data.
+  MDBX_CXX11_CONSTEXPR const byte *byte_ptr() const noexcept {
+    return slice_.byte_ptr();
+  }
+
+  /// \brief Returns casted to pointer to byte an address of data.
+  /// \pre REQUIRES: The buffer should store data chunk, but not referenced to
+  /// an external one.
+  MDBX_CXX11_CONSTEXPR byte *byte_ptr() noexcept {
+    assert(is_freestanding());
+    return const_cast<byte *>(slice_.byte_ptr());
+  }
+
+  /// \brief Returns casted to const pointer to char an address of data.
+  MDBX_CXX11_CONSTEXPR const char *char_ptr() const noexcept {
+    return slice_.char_ptr();
+  }
+
+  /// \brief Returns casted to pointer to char an address of data.
+  /// \pre REQUIRES: The buffer should store data chunk, but not referenced to
+  /// an external one.
+  MDBX_CXX11_CONSTEXPR char *char_ptr() noexcept {
+    assert(is_freestanding());
+    return const_cast<char *>(slice_.char_ptr());
+  }
+
+  /// \brief Return a const pointer to the beginning of the referenced data.
+  MDBX_CXX11_CONSTEXPR const void *data() const noexcept {
+    return slice_.data();
+  }
+
+  /// \brief Return a pointer to the beginning of the referenced data.
+  /// \pre REQUIRES: The buffer should store data chunk, but not referenced to
+  /// an external one.
+  MDBX_CXX11_CONSTEXPR void *data() noexcept {
+    assert(is_freestanding());
+    return const_cast<void *>(slice_.data());
+  }
+
+  /// \brief Returns the number of bytes.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t
+  length() const noexcept {
+    return MDBX_CONSTEXPR_ASSERT(is_reference() ||
+                                 slice_.length() + headroom() ==
+                                     silo_.length()),
+           slice_.length();
+  }
+
+  void make_freestanding() {
+    if (is_reference())
+      insulate();
+  }
+
+  buffer(const ::mdbx::slice &src, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : silo_(allocator), slice_(src) {
+    if (!make_reference)
+      insulate();
+  }
+
+  buffer(const buffer &src, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : buffer(src.slice_, make_reference, allocator) {}
+
+  buffer(const void *ptr, size_t bytes, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(ptr, bytes), make_reference, allocator) {}
+
+  template <class C, class T, class A>
+  buffer(const ::std::basic_string<C, T, A> &str, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(str), make_reference, allocator) {}
+
+  buffer(const char *c_str, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(c_str), make_reference, allocator) {}
+
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  buffer(const ::std::basic_string_view<C, T> &view, bool make_reference,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(view), make_reference, allocator) {}
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  MDBX_CXX20_CONSTEXPR
+  buffer(const ::mdbx::slice &src,
+         const allocator_type &allocator = allocator_type())
+      : silo_(src.char_ptr(), src.length(), allocator), slice_(silo_) {}
+
+  MDBX_CXX20_CONSTEXPR
+  buffer(const buffer &src, const allocator_type &allocator = allocator_type())
+      : buffer(src.slice_, allocator) {}
+
+  MDBX_CXX20_CONSTEXPR
+  buffer(const void *ptr, size_t bytes,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(ptr, bytes), allocator) {}
+
+  template <class C, class T, class A>
+  MDBX_CXX20_CONSTEXPR
+  buffer(const ::std::basic_string<C, T, A> &str,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(str), allocator) {}
+
+  MDBX_CXX20_CONSTEXPR
+  buffer(const char *c_str, const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(c_str), allocator) {}
+
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  MDBX_CXX20_CONSTEXPR
+  buffer(const ::std::basic_string_view<C, T> &view,
+         const allocator_type &allocator = allocator_type())
+      : buffer(::mdbx::slice(view), allocator) {}
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  inline buffer(size_t head_room, size_t tail_room,
+                const allocator_type &allocator = allocator_type());
+
+  inline buffer(size_t capacity,
+                const allocator_type &allocator = allocator_type());
+
+  inline buffer(size_t head_room, const ::mdbx::slice &src, size_t tail_room,
+                const allocator_type &allocator = allocator_type());
+
+  buffer(size_t head_room, const buffer &src, size_t tail_room,
+         const allocator_type &allocator = allocator_type())
+      : buffer(head_room, src.slice_, tail_room, allocator) {}
+
+  MDBX_CXX20_CONSTEXPR
+  buffer(const allocator_type &allocator = allocator_type()) noexcept
+      : silo_(allocator) {}
+
+  inline buffer(const txn &txn, const ::mdbx::slice &src,
+                const allocator_type &allocator = allocator_type());
+
+  buffer(buffer &&src) noexcept
+      : silo_(::std::move(src.silo_)), slice_(::std::move(src.slice_)) {}
+
+  buffer(silo &&str) noexcept : silo_(::std::move(str)), slice_(silo_) {}
+
+  MDBX_CXX11_CONSTEXPR const ::mdbx::slice &slice() const noexcept {
+    return slice_;
+  }
+
+  MDBX_CXX11_CONSTEXPR operator const ::mdbx::slice &() const noexcept {
+    return slice_;
+  }
+
+  template <typename POD>
+  static buffer wrap(const POD &pod, bool make_reference = false,
+                     const allocator_type &allocator = allocator_type()) {
+    return buffer(::mdbx::slice::wrap(pod), make_reference, allocator);
+  }
+
+  /// \brief Reserves storage.
+  inline void reserve(size_t wanna_headroom, size_t wanna_tailroom,
+                      size_t shrink_threshold = default_shrink_threshold);
+
+  buffer &assign_reference(const void *ptr, size_t bytes) noexcept {
+    silo_.clear();
+    slice_.assign(ptr, bytes);
+    return *this;
+  }
+
+  buffer &assign_freestanding(const void *ptr, size_t bytes) {
+    silo_.assign(static_cast<const typename silo::value_type *>(ptr),
+                 check_length(bytes));
+    slice_.assign(silo_);
+    return *this;
+  }
+
+  void swap(buffer &other)
+#if defined(__cpp_noexcept_function_type) &&                                   \
+    __cpp_noexcept_function_type >= 201510L
+      noexcept(
+          std::allocator_traits<ALLOCATOR>::propagate_on_container_swap::value
+#if defined(__cpp_lib_allocator_traits_is_always_equal) &&                     \
+    __cpp_lib_allocator_traits_is_always_equal >= 201411L
+          || std::allocator_traits<ALLOCATOR>::is_always_equal::value
+#endif /* __cpp_lib_allocator_traits_is_always_equal */
+      )
+#endif /* __cpp_noexcept_function_type */
+          ;
+
+  buffer &assign(buffer &&src)
+#if defined(__cpp_noexcept_function_type) &&                                   \
+    __cpp_noexcept_function_type >= 201510L
+      noexcept(std::allocator_traits<
+                   ALLOCATOR>::propagate_on_container_move_assignment::value
+#if defined(__cpp_lib_allocator_traits_is_always_equal) &&                     \
+    __cpp_lib_allocator_traits_is_always_equal >= 201411L
+               || std::allocator_traits<ALLOCATOR>::is_always_equal::value
+#endif /* __cpp_lib_allocator_traits_is_always_equal */
+      )
+#endif /* __cpp_noexcept_function_type */
+  {
+    silo_.assign(::std::move(src.silo_));
+    slice_.assign(::std::move(src.slice_));
+    return *this;
+  }
+
+  buffer &assign(silo &&src)
+#if defined(__cpp_noexcept_function_type) &&                                   \
+    __cpp_noexcept_function_type >= 201510L
+      noexcept(std::allocator_traits<
+                   ALLOCATOR>::propagate_on_container_move_assignment::value
+#if defined(__cpp_lib_allocator_traits_is_always_equal) &&                     \
+    __cpp_lib_allocator_traits_is_always_equal >= 201411L
+               || std::allocator_traits<ALLOCATOR>::is_always_equal::value
+#endif /* __cpp_lib_allocator_traits_is_always_equal */
+      )
+#endif /* __cpp_noexcept_function_type */
+  {
+    return assign(buffer(::std::move(src)));
+  }
+
+  static buffer clone(const buffer &src,
+                      const allocator_type &allocator = allocator_type()) {
+    return buffer(src.headroom(), src.slice_, src.tailroom(), allocator);
+  }
+
+  buffer &assign(const buffer &src, bool make_reference = false) {
+    return assign(src.slice_, make_reference);
+  }
+
+  buffer &assign(const void *ptr, size_t bytes, bool make_reference = false) {
+    return make_reference ? assign_reference(ptr, bytes)
+                          : assign_freestanding(ptr, bytes);
+  }
+
+  buffer &assign(const ::mdbx::slice &src, bool make_reference = false) {
+    return assign(src.data(), src.length(), make_reference);
+  }
+
+  buffer &assign(const ::MDBX_val &src, bool make_reference = false) {
+    return assign(src.iov_base, src.iov_len, make_reference);
+  }
+
+  buffer &assign(::mdbx::slice &&src, bool make_reference = false) {
+    assign(src.data(), src.length(), make_reference);
+    src.invalidate();
+    return *this;
+  }
+
+  buffer &assign(::MDBX_val &&src, bool make_reference = false) {
+    assign(src.iov_base, src.iov_len, make_reference);
+    src.iov_base = nullptr;
+    return *this;
+  }
+
+  buffer &assign(const void *begin, const void *end,
+                 bool make_reference = false) {
+    return assign(begin,
+                  static_cast<const byte *>(end) -
+                      static_cast<const byte *>(begin),
+                  make_reference);
+  }
+
+  template <class C, class T, class A>
+  buffer &assign(const ::std::basic_string<C, T, A> &str,
+                 bool make_reference = false) {
+    return assign(str.data(), str.length(), make_reference);
+  }
+
+  buffer &assign(const char *c_str, bool make_reference = false) {
+    return assign(c_str, ::mdbx::strlen(c_str), make_reference);
+  }
+
+#if defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L
+  template <class C, class T>
+  buffer &assign(const ::std::basic_string_view<C, T> &view,
+                 bool make_reference = false) {
+    return assign(view.data(), view.length(), make_reference);
+  }
+
+  template <class C, class T>
+  buffer &assign(::std::basic_string_view<C, T> &&view,
+                 bool make_reference = false) {
+    assign(view.data(), view.length(), make_reference);
+    view = {};
+    return *this;
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  buffer &operator=(const buffer &src) { return assign(src); }
+
+  buffer &operator=(buffer &&src) noexcept { return assign(::std::move(src)); }
+
+  buffer &operator=(silo &&src) noexcept { return assign(::std::move(src)); }
+
+  buffer &operator=(const ::mdbx::slice &src) { return assign(src); }
+
+  buffer &operator=(::mdbx::slice &&src) { return assign(::std::move(src)); }
+
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  buffer &operator=(const ::std::basic_string_view<C, T> &view) noexcept {
+    return assign(view);
+  }
+
+  /// \brief Return a string_view that references the data of this buffer.
+  template <class C = char, class T = ::std::char_traits<C>>
+  ::std::basic_string_view<C, T> string_view() const noexcept {
+    return slice_.string_view<C, T>();
+  }
+
+  /// \brief Return a string_view that references the data of this buffer.
+  template <class C, class T>
+  operator ::std::basic_string_view<C, T>() const noexcept {
+    return string_view<C, T>();
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  /// \brief Decodes hexadecimal dump from the given slice to the returned
+  /// buffer.
+  static buffer decode_hex(const ::mdbx::slice &hex,
+                           const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(hex.hex_decode(allocator));
+#else
+    silo data(hex.hex_decode(allocator));
+    return buffer(::std::move(data));
+#endif
+  }
+
+  /// \brief Returns a buffer with a hexadecimal dump of the given slice.
+  static buffer encode_hex(const ::mdbx::slice &data, bool uppercase = false,
+                           const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(data.hex_encode(uppercase, allocator));
+#else
+    silo hex(data.hex_encode(uppercase, allocator));
+    return buffer(::std::move(hex));
+#endif
+  }
+
+  /// \brief Decodes [Base58](https://en.wikipedia.org/wiki/Base58) dump from
+  /// the given slice to the returned buffer.
+  static buffer
+  decode_base58(const ::mdbx::slice &base58,
+                const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(base58.base58_decode(allocator));
+#else
+    silo data(base58.base58_decode(allocator));
+    return buffer(::std::move(data));
+#endif
+  }
+
+  /// \brief Returns a buffer with a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of the given slice.
+  static buffer
+  encode_base58(const ::mdbx::slice &data,
+                const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(data.base58_encode(allocator));
+#else
+    silo base58(data.base58_encode(allocator));
+    return buffer(::std::move(base58));
+#endif
+  }
+
+  /// \brief Decodes [Base64](https://en.wikipedia.org/wiki/Base64) dump from
+  /// the given slice to the returned buffer.
+  static buffer
+  decode_base64(const ::mdbx::slice &base64,
+                const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(base64.base64_decode(allocator));
+#else
+    silo data(base64.base64_decode(allocator));
+    return buffer(::std::move(data));
+#endif
+  }
+
+  /// \brief Returns a buffer with a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump of the given slice.
+  static buffer
+  encode_base64(const ::mdbx::slice &data,
+                const allocator_type &allocator = allocator_type()) {
+#if __cplusplus >= 201703L
+    return buffer(data.base64_encode(allocator));
+#else
+    silo base64(data.base64_encode(allocator));
+    return buffer(::std::move(base64));
+#endif
+  }
+
+  /// \brief Checks whether the string is empty.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR bool empty() const noexcept {
+    return length() == 0;
+  }
+
+  /// \brief Checks whether the data pointer of the buffer is nullptr.
+  MDBX_CXX11_CONSTEXPR bool is_null() const noexcept {
+    return data() == nullptr;
+  }
+
+  /// \brief Returns the number of bytes.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX20_CONSTEXPR size_t size() const noexcept {
+    return length();
+  }
+
+  /// \brief Returns the hash value of the data.
+  /// \attention Function implementation and returned hash values may changed
+  /// version to version, and in future the t1ha3 will be used here. Therefore
+  /// values obtained from this function shouldn't be persisted anywhere.
+  MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX14_CONSTEXPR size_t
+  hash_value() const noexcept {
+    return slice_.hash_value();
+  }
+
+  template <class C = char, class T = ::std::char_traits<C>,
+            class A = legacy_allocator>
+  MDBX_CXX20_CONSTEXPR ::std::basic_string<C, T, A>
+  string(const A &allocator = A()) const {
+    return slice_.string<C, T, A>(allocator);
+  }
+
+  template <class C, class T, class A>
+  MDBX_CXX20_CONSTEXPR operator ::std::basic_string<C, T, A>() const {
+    return this->string<C, T, A>();
+  }
+
+  /// \brief Checks if the data starts with the given prefix.
+  MDBX_NOTHROW_PURE_FUNCTION bool
+  starts_with(const ::mdbx::slice &prefix) const noexcept {
+    return slice_.starts_with(prefix);
+  }
+
+  /// \brief Checks if the data ends with the given suffix.
+  MDBX_NOTHROW_PURE_FUNCTION bool
+  ends_with(const ::mdbx::slice &suffix) const noexcept {
+    return slice_.ends_with(suffix);
+  }
+
+  /// \brief Clears the contents and storage.
+  void clear() noexcept {
+    slice_.clear();
+    silo_.clear();
+  }
+
+  /// \brief Reduces memory usage by freeing unused storage space.
+  void shrink_to_fit(size_t threshold = 64) { reserve(0, 0, threshold); }
+
+  /// \brief Drops the first "n" bytes from the data chunk.
+  /// \pre REQUIRES: `n <= size()`
+  void remove_prefix(size_t n) noexcept { slice_.remove_prefix(n); }
+
+  /// \brief Drops the last "n" bytes from the data chunk.
+  /// \pre REQUIRES: `n <= size()`
+  void remove_suffix(size_t n) noexcept { slice_.remove_suffix(n); }
+
+  /// \brief Drops the first "n" bytes from the data chunk.
+  /// \throws std::out_of_range if `n > size()`
+  void safe_remove_prefix(size_t n) { slice_.safe_remove_prefix(n); }
+
+  /// \brief Drops the last "n" bytes from the data chunk.
+  /// \throws std::out_of_range if `n > size()`
+  void safe_remove_suffix(size_t n) { slice_.safe_remove_suffix(n); }
+
+  /// \brief Accesses the specified byte of data chunk.
+  /// \pre REQUIRES: `n < size()`
+  byte operator[](size_t n) const noexcept { return slice_[n]; }
+
+  /// \brief Accesses the specified byte of data chunk.
+  /// \pre REQUIRES: `n < size()`
+  byte &operator[](size_t n) noexcept {
+    assert(n < size());
+    return byte_ptr()[n];
+  }
+
+  /// \brief Accesses the specified byte of data chunk with bounds checking.
+  /// \throws std::out_of_range if `n >= size()`
+  byte at(size_t n) const { return slice_.at(n); }
+
+  /// \brief Accesses the specified byte of data chunk with bounds checking.
+  /// \throws std::out_of_range if `n >= size()`
+  byte &at(size_t n) {
+    if (MDBX_UNLIKELY(n >= size()))
+      MDBX_CXX20_UNLIKELY throw_out_range();
+    return byte_ptr()[n];
+  }
+
+  /// \brief Returns the first "n" bytes of the data chunk.
+  /// \pre REQUIRES: `n <= size()`
+  ::mdbx::slice head(size_t n) const noexcept { return slice_.head(n); }
+
+  /// \brief Returns the last "n" bytes of the data chunk.
+  /// \pre REQUIRES: `n <= size()`
+  ::mdbx::slice tail(size_t n) const noexcept { return slice_.tail(n); }
+
+  /// \brief Returns the middle "n" bytes of the data chunk.
+  /// \pre REQUIRES: `from + n <= size()`
+  ::mdbx::slice middle(size_t from, size_t n) const noexcept {
+    return slice_.middle(from, n);
+  }
+
+  /// \brief Returns the first "n" bytes of the data chunk.
+  /// \throws std::out_of_range if `n >= size()`
+  ::mdbx::slice safe_head(size_t n) const { return slice_.safe_head(n); }
+
+  /// \brief Returns the last "n" bytes of the data chunk.
+  /// \throws std::out_of_range if `n >= size()`
+  ::mdbx::slice safe_tail(size_t n) const { return slice_.safe_tail(n); }
+
+  /// \brief Returns the middle "n" bytes of the data chunk.
+  /// \throws std::out_of_range if `from + n >= size()`
+  ::mdbx::slice safe_middle(size_t from, size_t n) const {
+    return slice_.safe_middle(from, n);
+  }
+
+  inline buffer &append(const void *src, size_t bytes);
+
+  buffer &append(const ::mdbx::slice &chunk) {
+    return append(chunk.data(), chunk.size());
+  }
+
+  inline buffer &add_header(const void *src, size_t bytes);
+
+  buffer &add_header(const ::mdbx::slice &chunk) {
+    return add_header(chunk.data(), chunk.size());
+  }
+
+  //----------------------------------------------------------------------------
+
+  template <size_t SIZE>
+  static buffer key_from(const char (&text)[SIZE], bool make_reference = true) {
+    return buffer(::mdbx::slice(text), make_reference);
+  }
+
+#if defined(DOXYGEN) ||                                                        \
+    (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
+  template <class C, class T>
+  static buffer key_from(const ::std::basic_string_view<C, T> &src,
+                         bool make_reference = false) {
+    return buffer(src, make_reference);
+  }
+#endif /* __cpp_lib_string_view >= 201606L */
+
+  static buffer key_from(const char *src, bool make_reference = false) {
+    return buffer(src, make_reference);
+  }
+
+  template <class C, class T, class A>
+  static buffer key_from(const ::std::basic_string<C, T, A> &src,
+                         bool make_reference = false) {
+    return buffer(src, make_reference);
+  }
+
+  static buffer key_from(const silo &&src) noexcept {
+    return buffer(::std::move(src));
+  }
+
+  static buffer key_from(const double ieee754_64bit) {
+    return wrap(::mdbx_key_from_double(ieee754_64bit));
+  }
+
+  static buffer key_from(const double *ieee754_64bit) {
+    return wrap(::mdbx_key_from_ptrdouble(ieee754_64bit));
+  }
+
+  static buffer key_from(const uint64_t unsigned_int64) {
+    return wrap(unsigned_int64);
+  }
+
+  static buffer key_from(const int64_t signed_int64) {
+    return wrap(::mdbx_key_from_int64(signed_int64));
+  }
+
+  static buffer key_from_jsonInteger(const int64_t json_integer) {
+    return wrap(::mdbx_key_from_jsonInteger(json_integer));
+  }
+
+  static buffer key_from(const float ieee754_32bit) {
+    return wrap(::mdbx_key_from_float(ieee754_32bit));
+  }
+
+  static buffer key_from(const float *ieee754_32bit) {
+    return wrap(::mdbx_key_from_ptrfloat(ieee754_32bit));
+  }
+
+  static buffer key_from(const uint32_t unsigned_int32) {
+    return wrap(unsigned_int32);
+  }
+
+  static buffer key_from(const int32_t signed_int32) {
+    return wrap(::mdbx_key_from_int32(signed_int32));
+  }
+};
+
+/// \brief Combines data slice with boolean flag to represent result of certain
+/// operations.
+struct value_result {
+  slice value;
+  bool done;
+  value_result(const slice &value, bool done) noexcept
+      : value(value), done(done) {}
+  value_result(const value_result &) noexcept = default;
+  value_result &operator=(const value_result &) noexcept = default;
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept {
+    assert(!done || bool(value));
+    return done;
+  }
+};
+
+/// \brief Combines pair of slices for key and value to represent result of
+/// certain operations.
+struct pair {
+  slice key, value;
+  pair(const slice &key, const slice &value) noexcept
+      : key(key), value(value) {}
+  pair(const pair &) noexcept = default;
+  pair &operator=(const pair &) noexcept = default;
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept {
+    assert(bool(key) == bool(value));
+    return key;
+  }
+};
+
+/// \brief Combines pair of slices for key and value with boolean flag to
+/// represent result of certain operations.
+struct pair_result : public pair {
+  bool done;
+  pair_result(const slice &key, const slice &value, bool done) noexcept
+      : pair(key, value), done(done) {}
+  pair_result(const pair_result &) noexcept = default;
+  pair_result &operator=(const pair_result &) noexcept = default;
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept {
+    assert(!done || (bool(key) && bool(value)));
+    return done;
+  }
+};
+
+//------------------------------------------------------------------------------
+
+/// \brief Loop control constants for readers enumeration functor and other
+/// cases. \see env::enumerate_readers()
+enum loop_control { continue_loop = 0, exit_loop = INT32_MIN };
+
+/// \brief Kinds of the keys and corresponding modes of comparing it.
+enum class key_mode {
+  usual = MDBX_DB_DEFAULTS,  ///< Usual variable length keys with byte-by-byte
+                             ///< lexicographic comparison like `std::memcmp()`.
+  reverse = MDBX_REVERSEKEY, ///< Variable length keys with byte-by-byte
+                             ///< lexicographic comparison in reverse order,
+                             ///< from the end of the keys to the beginning.
+  ordinal = MDBX_INTEGERKEY, ///< Keys are binary integers in native byte order,
+                             ///< either `uint32_t` or `uint64_t`, and will be
+                             ///< sorted as such. The keys must all be of the
+                             ///< same size and must be aligned while passing
+                             ///< as arguments.
+  msgpack = -1 ///< Keys are in [MessagePack](https://msgpack.org/)
+               ///< format with appropriate comparison.
+               ///< \note Not yet implemented and PRs are welcome.
+};
+
+/// \brief Kind of the values and sorted multi-values with corresponding
+/// comparison.
+enum class value_mode {
+  single = MDBX_DB_DEFAULTS, ///< Usual single value for each key. In terms of
+                             ///< keys, they are unique.
+  multi =
+      MDBX_DUPSORT, ///< A more than one data value could be associated with
+                    ///< each key. Internally each key is stored once, and the
+                    ///< corresponding data values are sorted by byte-by-byte
+                    ///< lexicographic comparison like `std::memcmp()`.
+                    ///< In terms of keys, they are not unique, i.e. has
+                    ///< duplicates which are sorted by associated data values.
+#if CONSTEXPR_ENUM_FLAGS_OPERATIONS || defined(DOXYGEN)
+  multi_reverse =
+      MDBX_DUPSORT |
+      MDBX_REVERSEDUP, ///< A more than one data value could be associated with
+                       ///< each key. Internally each key is stored once, and
+                       ///< the corresponding data values are sorted by
+                       ///< byte-by-byte lexicographic comparison in reverse
+                       ///< order, from the end of the keys to the beginning.
+                       ///< In terms of keys, they are not unique, i.e. has
+                       ///< duplicates which are sorted by associated data
+                       ///< values.
+  multi_samelength =
+      MDBX_DUPSORT |
+      MDBX_DUPFIXED, ///< A more than one data value could be associated with
+                     ///< each key, and all data values must be same length.
+                     ///< Internally each key is stored once, and the
+                     ///< corresponding data values are sorted by byte-by-byte
+                     ///< lexicographic comparison like `std::memcmp()`. In
+                     ///< terms of keys, they are not unique, i.e. has
+                     ///< duplicates which are sorted by associated data values.
+  multi_ordinal =
+      MDBX_DUPSORT | MDBX_DUPFIXED |
+      MDBX_INTEGERDUP, ///< A more than one data value could be associated with
+                       ///< each key, and all data values are binary integers in
+                       ///< native byte order, either `uint32_t` or `uint64_t`,
+                       ///< and will be sorted as such. Internally each key is
+                       ///< stored once, and the corresponding data values are
+                       ///< sorted. In terms of keys, they are not unique, i.e.
+                       ///< has duplicates which are sorted by associated data
+                       ///< values.
+  multi_reverse_samelength =
+      MDBX_DUPSORT | MDBX_REVERSEDUP |
+      MDBX_DUPFIXED, ///< A more than one data value could be associated with
+                     ///< each key, and all data values must be same length.
+                     ///< Internally each key is stored once, and the
+                     ///< corresponding data values are sorted by byte-by-byte
+                     ///< lexicographic comparison in reverse order, from the
+                     ///< end of the keys to the beginning. In terms of keys,
+                     ///< they are not unique, i.e. has duplicates which are
+                     ///< sorted by associated data values.
+  msgpack = -1 ///< A more than one data value could be associated with each
+               ///< key. Values are in [MessagePack](https://msgpack.org/)
+               ///< format with appropriate comparison. Internally each key is
+               ///< stored once, and the corresponding data values are sorted.
+               ///< In terms of keys, they are not unique, i.e. has duplicates
+               ///< which are sorted by associated data values.
+               ///< \note Not yet implemented and PRs are welcome.
+#else
+  multi_reverse = uint32_t(MDBX_DUPSORT) | uint32_t(MDBX_REVERSEDUP),
+  multi_samelength = uint32_t(MDBX_DUPSORT) | uint32_t(MDBX_DUPFIXED),
+  multi_ordinal = uint32_t(MDBX_DUPSORT) | uint32_t(MDBX_DUPFIXED) |
+                  uint32_t(MDBX_INTEGERDUP),
+  multi_reverse_samelength = uint32_t(MDBX_DUPSORT) |
+                             uint32_t(MDBX_REVERSEDUP) | uint32_t(MDBX_DUPFIXED)
+#endif
+};
+
+/// \brief A handle for an individual database (key-value spaces) in the
+/// environment.
+/// \see txn::open_map() \see txn::create_map()
+/// \see txn::clear_map() \see txn::drop_map()
+/// \see txn::get_handle_info() \see txn::get_map_stat()
+/// \see env::close_amp()
+/// \see cursor::map()
+struct LIBMDBX_API_TYPE map_handle {
+  MDBX_dbi dbi{0};
+  MDBX_CXX11_CONSTEXPR map_handle() noexcept {}
+  MDBX_CXX11_CONSTEXPR map_handle(MDBX_dbi dbi) noexcept : dbi(dbi) {}
+  map_handle(const map_handle &) noexcept = default;
+  map_handle &operator=(const map_handle &) noexcept = default;
+  operator bool() const noexcept { return dbi != 0; }
+
+  using flags = ::MDBX_db_flags_t;
+  using state = ::MDBX_dbi_state_t;
+  struct LIBMDBX_API_TYPE info {
+    map_handle::flags flags;
+    map_handle::state state;
+    MDBX_CXX11_CONSTEXPR info(map_handle::flags flags,
+                              map_handle::state state) noexcept;
+    info(const info &) noexcept = default;
+    info &operator=(const info &) noexcept = default;
+    MDBX_CXX11_CONSTEXPR ::mdbx::key_mode key_mode() const noexcept;
+    MDBX_CXX11_CONSTEXPR ::mdbx::value_mode value_mode() const noexcept;
+  };
+};
+
+/// \brief Key-value pairs put mode.
+enum put_mode {
+  insert_unique = MDBX_NOOVERWRITE, ///< Insert only unique keys.
+  upsert = MDBX_UPSERT,             ///< Insert or update.
+  update = MDBX_CURRENT,            ///< Update existing, don't insert new.
+};
+
+/// \brief Unmanaged database environment.
+///
+/// Like other unmanaged classes, `env` allows copying and assignment for
+/// instances, but does not destroys the represented underlying object from the
+/// own class destructor.
+///
+/// An environment supports multiple key-value sub-databases (aka key-value
+/// spaces or tables), all residing in the same shared-memory map.
+class LIBMDBX_API_TYPE env {
+  friend class txn;
+
+protected:
+  MDBX_env *handle_{nullptr};
+  MDBX_CXX11_CONSTEXPR env(MDBX_env *ptr) noexcept;
+
+public:
+  MDBX_CXX11_CONSTEXPR env() noexcept = default;
+  env(const env &) noexcept = default;
+  inline env &operator=(env &&other) noexcept;
+  inline env(env &&other) noexcept;
+  inline ~env() noexcept;
+
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept;
+  MDBX_CXX14_CONSTEXPR operator const MDBX_env *() const;
+  MDBX_CXX14_CONSTEXPR operator MDBX_env *();
+  friend MDBX_CXX11_CONSTEXPR bool operator==(const env &a,
+                                              const env &b) noexcept;
+  friend MDBX_CXX11_CONSTEXPR bool operator!=(const env &a,
+                                              const env &b) noexcept;
+
+  //----------------------------------------------------------------------------
+
+  /// Database geometry for size management.
+  struct LIBMDBX_API_TYPE geometry {
+    enum : int64_t {
+      default_value = -1,         ///< Means "keep current or use default"
+      minimal_value = 0,          ///< Means "minimal acceptable"
+      maximal_value = INTPTR_MAX, ///< Means "maximal acceptable"
+      kB = 1000,                  ///< \f$10^{3}\f$ bytes
+      MB = kB * 1000,             ///< \f$10^{6}\f$ bytes
+      GB = MB * 1000,             ///< \f$10^{9}\f$ bytes
+      TB = GB * 1000,             ///< \f$10^{12}\f$ bytes
+      PB = TB * 1000,             ///< \f$10^{15}\f$ bytes
+      EB = PB * 1000,             ///< \f$10^{18}\f$ bytes
+      KiB = 1024,                 ///< \f$2^{10}\f$ bytes
+      MiB = KiB << 10,            ///< \f$2^{20}\f$ bytes
+      GiB = MiB << 10,            ///< \f$2^{30}\f$ bytes
+      TiB = GiB << 10,            ///< \f$2^{40}\f$ bytes
+      PiB = TiB << 10,            ///< \f$2^{50}\f$ bytes
+      EiB = PiB << 10,            ///< \f$2^{60}\f$ bytes
+    };
+
+    /// \brief Tagged type for output to std::ostream
+    struct size {
+      intptr_t bytes;
+      MDBX_CXX11_CONSTEXPR size(intptr_t bytes) noexcept : bytes(bytes) {}
+      MDBX_CXX11_CONSTEXPR operator intptr_t() const noexcept { return bytes; }
+    };
+
+    /// \brief The lower bound of database size in bytes.
+    intptr_t size_lower{minimal_value};
+
+    /// \brief The size in bytes to setup the database size for now.
+    /// \details It is recommended always pass \ref default_value in this
+    /// argument except some special cases.
+    intptr_t size_now{default_value};
+
+    /// \brief The upper bound of database size in bytes.
+    /// \details It is recommended to avoid change upper bound while database is
+    /// used by other processes or threaded (i.e. just pass \ref default_value
+    /// in this argument except absolutely necessary). Otherwise you must be
+    /// ready for \ref MDBX_UNABLE_EXTEND_MAPSIZE error(s), unexpected pauses
+    /// during remapping and/or system errors like "address busy", and so on. In
+    /// other words, there is no way to handle a growth of the upper bound
+    /// robustly because there may be a lack of appropriate system resources
+    /// (which are extremely volatile in a multi-process multi-threaded
+    /// environment).
+    intptr_t size_upper{maximal_value};
+
+    /// \brief The growth step in bytes, must be greater than zero to allow the
+    /// database to grow.
+    intptr_t growth_step{default_value};
+
+    /// \brief The shrink threshold in bytes, must be greater than zero to allow
+    /// the database to shrink.
+    intptr_t shrink_threshold{default_value};
+
+    /// \brief The database page size for new database creation
+    /// or \ref default_value otherwise.
+    /// \details Must be power of 2 in the range between \ref MDBX_MIN_PAGESIZE
+    /// and \ref MDBX_MAX_PAGESIZE.
+    intptr_t pagesize{default_value};
+
+    inline geometry &make_fixed(intptr_t size) noexcept;
+    inline geometry &make_dynamic(intptr_t lower = minimal_value,
+                                  intptr_t upper = maximal_value) noexcept;
+  };
+
+  /// \brief Operation mode.
+  enum mode {
+    readonly,       ///< \copydoc MDBX_RDONLY
+    write_file_io,  // don't available on OpenBSD
+    write_mapped_io ///< \copydoc MDBX_WRITEMAP
+  };
+
+  /// \brief Durability level.
+  enum durability {
+    robust_synchronous,         ///< \copydoc MDBX_SYNC_DURABLE
+    half_synchronous_weak_last, ///< \copydoc MDBX_NOMETASYNC
+    lazy_weak_tail,             ///< \copydoc MDBX_SAFE_NOSYNC
+    whole_fragile               ///< \copydoc MDBX_UTTERLY_NOSYNC
+  };
+
+  /// \brief Garbage reclaiming options.
+  struct LIBMDBX_API_TYPE reclaiming_options {
+    /// \copydoc MDBX_LIFORECLAIM
+    bool lifo{false};
+    /// \copydoc MDBX_COALESCE
+    bool coalesce{false};
+    MDBX_CXX11_CONSTEXPR reclaiming_options() noexcept {}
+    reclaiming_options(MDBX_env_flags_t) noexcept;
+  };
+
+  /// \brief Operate options.
+  struct LIBMDBX_API_TYPE operate_options {
+    /// \copydoc MDBX_NOTLS
+    bool orphan_read_transactions{false};
+    bool nested_write_transactions{false};
+    /// \copydoc MDBX_EXCLUSIVE
+    bool exclusive{false};
+    /// \copydoc MDBX_NORDAHEAD
+    bool disable_readahead{false};
+    /// \copydoc MDBX_NOMEMINIT
+    bool disable_clear_memory{false};
+    MDBX_CXX11_CONSTEXPR operate_options() noexcept {}
+    operate_options(MDBX_env_flags_t) noexcept;
+  };
+
+  /// \brief Operate parameters.
+  struct LIBMDBX_API_TYPE operate_parameters {
+    /// \brief The maximum number of named databases for the environment.
+    /// Zero means default value.
+    unsigned max_maps{0};
+    /// \brief The maximum number of threads/reader slots for the environment.
+    /// Zero means default value.
+    unsigned max_readers{0};
+    env::mode mode{write_mapped_io};
+    env::durability durability{robust_synchronous};
+    env::reclaiming_options reclaiming;
+    env::operate_options options;
+
+    MDBX_CXX11_CONSTEXPR operate_parameters() noexcept {}
+    MDBX_env_flags_t make_flags(bool accede = true, ///< \copydoc MDBX_ACCEDE
+                                bool use_subdirectory = false) const;
+    static env::mode mode_from_flags(MDBX_env_flags_t) noexcept;
+    static env::durability durability_from_flags(MDBX_env_flags_t) noexcept;
+    inline static env::reclaiming_options
+    reclaiming_from_flags(MDBX_env_flags_t flags) noexcept;
+    inline static env::operate_options
+    options_from_flags(MDBX_env_flags_t flags) noexcept;
+    operate_parameters(const env &);
+  };
+
+  /// \brief Returns current operation parameters.
+  inline env::operate_parameters get_operation_parameters() const;
+  /// \brief Returns current operation mode.
+  inline env::mode get_mode() const;
+  /// \brief Returns current durability mode.
+  inline env::durability get_durability() const;
+  /// \brief Returns current reclaiming options.
+  inline env::reclaiming_options get_reclaiming() const;
+  /// \brief Returns current operate options.
+  inline env::operate_options get_options() const;
+
+  /// \brief Returns `true` for a freshly created database,
+  /// but `false` if at least one transaction was committed.
+  bool is_pristine() const;
+
+  /// \brief Checks whether the database is empty.
+  bool is_empty() const;
+
+  /// \brief Returns default page size for current system/platform.
+  static size_t default_pagesize() noexcept {
+    return ::mdbx_default_pagesize();
+  }
+
+  struct limits {
+    limits() = delete;
+    /// \brief Returns the minimal database page size in bytes.
+    static inline size_t pagesize_min() noexcept;
+    /// \brief Returns the maximal database page size in bytes.
+    static inline size_t pagesize_max() noexcept;
+    /// \brief Returns the minimal database size in bytes for specified page
+    /// size.
+    static inline size_t dbsize_min(intptr_t pagesize);
+    /// \brief Returns the maximal database size in bytes for specified page
+    /// size.
+    static inline size_t dbsize_max(intptr_t pagesize);
+    /// \brief Returns the minimal key size in bytes for specified database
+    /// flags.
+    static inline size_t key_min(MDBX_db_flags_t flags) noexcept;
+    /// \brief Returns the minimal key size in bytes for specified keys mode.
+    static inline size_t key_min(key_mode mode) noexcept;
+    /// \brief Returns the maximal key size in bytes for specified page size and
+    /// database flags.
+    static inline size_t key_max(intptr_t pagesize, MDBX_db_flags_t flags);
+    /// \brief Returns the maximal key size in bytes for specified page size and
+    /// keys mode.
+    static inline size_t key_max(intptr_t pagesize, key_mode mode);
+    /// \brief Returns the maximal key size in bytes for given environment and
+    /// database flags.
+    static inline size_t key_max(const env &, MDBX_db_flags_t flags);
+    /// \brief Returns the maximal key size in bytes for given environment and
+    /// keys mode.
+    static inline size_t key_max(const env &, key_mode mode);
+    /// \brief Returns the minimal values size in bytes for specified database
+    /// flags.
+    static inline size_t value_min(MDBX_db_flags_t flags) noexcept;
+    /// \brief Returns the minimal values size in bytes for specified values
+    /// mode.
+    static inline size_t value_min(value_mode) noexcept;
+    /// \brief Returns the maximal value size in bytes for specified page size
+    /// and database flags.
+    static inline size_t value_max(intptr_t pagesize, MDBX_db_flags_t flags);
+    /// \brief Returns the maximal value size in bytes for specified page size
+    /// and values mode.
+    static inline size_t value_max(intptr_t pagesize, value_mode);
+    /// \brief Returns the maximal value size in bytes for given environment and
+    /// database flags.
+    static inline size_t value_max(const env &, MDBX_db_flags_t flags);
+    /// \brief Returns the maximal value size in bytes for specified page size
+    /// and values mode.
+    static inline size_t value_max(const env &, value_mode);
+    /// \brief Returns the maximal write transaction size (i.e. limit for
+    /// summary volume of dirty pages) in bytes for specified page size.
+    static inline size_t transaction_size_max(intptr_t pagesize);
+  };
+
+  /// \brief Returns the minimal database size in bytes for the environment.
+  size_t dbsize_min() const { return limits::dbsize_min(this->get_pagesize()); }
+  /// \brief Returns the maximal database size in bytes for the environment.
+  size_t dbsize_max() const { return limits::dbsize_max(this->get_pagesize()); }
+  /// \brief Returns the minimal key size in bytes for specified keys mode.
+  size_t key_min(key_mode mode) const noexcept { return limits::key_min(mode); }
+  /// \brief Returns the maximal key size in bytes for specified keys mode.
+  size_t key_max(key_mode mode) const { return limits::key_max(*this, mode); }
+  /// \brief Returns the minimal value size in bytes for specified values mode.
+  size_t value_min(value_mode mode) const noexcept {
+    return limits::value_min(mode);
+  }
+  /// \brief Returns the maximal value size in bytes for specified values mode.
+  size_t value_max(value_mode mode) const {
+    return limits::value_max(*this, mode);
+  }
+  /// \brief Returns the maximal write transaction size (i.e. limit for summary
+  /// volume of dirty pages) in bytes.
+  size_t transaction_size_max() const {
+    return limits::transaction_size_max(this->get_pagesize());
+  }
+
+  /// \brief Make a copy (backup) of an existing environment to the specified
+  /// path.
+#ifdef MDBX_STD_FILESYSTEM_PATH
+  env &copy(const ::std::filesystem::path &destination, bool compactify,
+            bool force_dynamic_size = false);
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+#if defined(_WIN32) || defined(_WIN64)
+  env &copy(const ::std::wstring &destination, bool compactify,
+            bool force_dynamic_size = false);
+#endif /* Windows */
+  env &copy(const ::std::string &destination, bool compactify,
+            bool force_dynamic_size = false);
+
+  /// \brief Copy an environment to the specified file descriptor.
+  env &copy(filehandle fd, bool compactify, bool force_dynamic_size = false);
+
+  /// \brief Deletion modes for \ref remove().
+  enum remove_mode {
+    /// \brief Just delete the environment's files and directory if any.
+    /// \note On POSIX systems, processes already working with the database will
+    /// continue to work without interference until it close the environment.
+    /// \note On Windows, the behavior of `just_remove` is different
+    /// because the system does not support deleting files that are currently
+    /// memory mapped.
+    just_remove = MDBX_ENV_JUST_DELETE,
+    /// \brief Make sure that the environment is not being used by other
+    /// processes, or return an error otherwise.
+    ensure_unused = MDBX_ENV_ENSURE_UNUSED,
+    /// \brief Wait until other processes closes the environment before
+    /// deletion.
+    wait_for_unused = MDBX_ENV_WAIT_FOR_UNUSED
+  };
+
+  /// \brief Removes the environment's files in a proper and multiprocess-safe
+  /// way.
+#ifdef MDBX_STD_FILESYSTEM_PATH
+  static bool remove(const ::std::filesystem::path &,
+                     const remove_mode mode = just_remove);
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+#if defined(_WIN32) || defined(_WIN64)
+  static bool remove(const ::std::wstring &,
+                     const remove_mode mode = just_remove);
+#endif /* Windows */
+  static bool remove(const ::std::string &,
+                     const remove_mode mode = just_remove);
+
+  /// \brief Statistics for a database in the MDBX environment.
+  using stat = ::MDBX_stat;
+
+  /// \brief Information about the environment.
+  using info = ::MDBX_envinfo;
+
+  /// \brief Returns snapshot statistics about the MDBX environment.
+  inline stat get_stat() const;
+
+  /// \brief Returns pagesize of this MDBX environment.
+  size_t get_pagesize() const { return get_stat().ms_psize; }
+
+  /// \brief Return snapshot information about the MDBX environment.
+  inline info get_info() const;
+
+  /// \brief Return statistics about the MDBX environment accordingly to the
+  /// specified transaction.
+  inline stat get_stat(const txn &) const;
+
+  /// \brief Return information about the MDBX environment accordingly to the
+  /// specified transaction.
+  inline info get_info(const txn &) const;
+
+  /// \brief Returns the file descriptor for the DXB file of MDBX environment.
+  inline filehandle get_filehandle() const;
+
+  /// \brief Return the path that was used for opening the environment.
+  path get_path() const;
+
+  /// Returns environment flags.
+  inline MDBX_env_flags_t get_flags() const;
+
+  /// \brief Returns the maximum number of threads/reader slots for the
+  /// environment.
+  inline unsigned max_readers() const;
+
+  /// \brief Returns the maximum number of named databases for the environment.
+  inline unsigned max_maps() const;
+
+  /// \brief Returns the application context associated with the environment.
+  inline void *get_context() const noexcept;
+
+  /// \brief Sets the application context associated with the environment.
+  inline env &set_context(void *);
+
+  /// \brief Sets threshold to force flush the data buffers to disk, for
+  /// non-sync durability modes.
+  ///
+  /// The threshold value affects all processes which operates with given
+  /// environment until the last process close environment or a new value will
+  /// be settled.
+  /// Data is always written to disk when \ref txn_managed::commit() is called,
+  /// but the operating system may keep it buffered. MDBX always flushes the OS
+  /// buffers upon commit as well, unless the environment was opened with \ref
+  /// whole_fragile, \ref lazy_weak_tail or in part \ref
+  /// half_synchronous_weak_last. The default is 0, than mean no any threshold
+  /// checked, and no additional flush will be made.
+  ///
+  inline env &set_sync_threshold(size_t bytes);
+
+  /// \brief Sets relative period since the last unsteady commit to force flush
+  /// the data buffers to disk, for non-sync durability modes.
+  ///
+  /// The relative period value affects all processes which operates with given
+  /// environment until the last process close environment or a new value will
+  /// be settled.
+  /// Data is always written to disk when \ref txn_managed::commit() is called,
+  /// but the operating system may keep it buffered. MDBX always flushes the OS
+  /// buffers upon commit as well, unless the environment was opened with \ref
+  /// whole_fragile, \ref lazy_weak_tail or in part \ref
+  /// half_synchronous_weak_last. Settled period don't checked asynchronously,
+  /// but only by the \ref txn_managed::commit() and \ref env::sync_to_disk()
+  /// functions. Therefore, in cases where transactions are committed
+  /// infrequently and/or irregularly, polling by \ref env::poll_sync_to_disk()
+  /// may be a reasonable solution to timeout enforcement. The default is 0,
+  /// than mean no any timeout checked, and no additional flush will be made.
+  ///
+  /// \param [in] seconds_16dot16  The period in 1/65536 of second when a
+  /// synchronous flush would be made since the last unsteady commit.
+  inline env &set_sync_period(unsigned seconds_16dot16);
+
+  /// \brief Sets relative period since the last unsteady commit to force flush
+  /// the data buffers to disk, for non-sync durability modes.
+  ///
+  /// The relative period value affects all processes which operates with given
+  /// environment until the last process close environment or a new value will
+  /// be settled.
+  /// Data is always written to disk when \ref txn_managed::commit() is called,
+  /// but the operating system may keep it buffered. MDBX always flushes the OS
+  /// buffers upon commit as well, unless the environment was opened with \ref
+  /// whole_fragile, \ref lazy_weak_tail or in part \ref
+  /// half_synchronous_weak_last. Settled period don't checked asynchronously,
+  /// but only by the \ref txn_managed::commit() and \ref env::sync_to_disk()
+  /// functions. Therefore, in cases where transactions are committed
+  /// infrequently and/or irregularly, polling by \ref env::poll_sync_to_disk()
+  /// may be a reasonable solution to timeout enforcement. The default is 0,
+  /// than mean no any timeout checked, and no additional flush will be made.
+  ///
+  /// \param [in] seconds  The period in second when a synchronous flush would
+  /// be made since the last unsteady commit.
+  inline env &set_sync_period(double seconds);
+
+  /// \brief Alter environment flags.
+  inline env &alter_flags(MDBX_env_flags_t flags, bool on_off);
+
+  /// \brief Set all size-related parameters of environment.
+  inline env &set_geometry(const geometry &size);
+
+  /// \brief Flush the environment data buffers.
+  /// \return `True` if sync done or no data to sync, or `false` if the
+  /// environment is busy by other thread or none of the thresholds are reached.
+  inline bool sync_to_disk(bool force = true, bool nonblock = false);
+
+  /// \brief Performs non-blocking polling of sync-to-disk thresholds.
+  /// \return `True` if sync done or no data to sync, or `false` if the
+  /// environment is busy by other thread or none of the thresholds are reached.
+  bool poll_sync_to_disk() { return sync_to_disk(false, true); }
+
+  /// \brief Close a key-value map (aka sub-database) handle. Normally
+  /// unnecessary.
+  ///
+  /// Closing a database handle is not necessary, but lets \ref txn::open_map()
+  /// reuse the handle value. Usually it's better to set a bigger
+  /// \ref env::operate_parameters::max_maps, unless that value would be
+  /// large.
+  ///
+  /// \note Use with care.
+  /// This call is synchronized via mutex with other calls \ref close_map(), but
+  /// NOT with other transactions running by other threads. The "next" version
+  /// of libmdbx (\ref MithrilDB) will solve this issue.
+  ///
+  /// Handles should only be closed if no other threads are going to reference
+  /// the database handle or one of its cursors any further. Do not close a
+  /// handle if an existing transaction has modified its database. Doing so can
+  /// cause misbehavior from database corruption to errors like
+  /// \ref MDBX_BAD_DBI (since the DB name is gone).
+  inline void close_map(const map_handle &);
+
+  /// \brief Reader information
+  struct reader_info {
+    int slot;                 ///< The reader lock table slot number.
+    mdbx_pid_t pid;           ///< The reader process ID.
+    mdbx_tid_t thread;        ///< The reader thread ID.
+    uint64_t transaction_id;  ///< The ID of the transaction being read,
+                              ///< i.e. the MVCC-snapshot number.
+    uint64_t transaction_lag; ///< The lag from a recent MVCC-snapshot,
+                              ///< i.e. the number of committed write
+                              /// transactions since the current read
+                              /// transaction started.
+    size_t bytes_used; ///< The number of last used page in the MVCC-snapshot
+                       ///< which being read, i.e. database file can't shrinked
+                       ///< beyond this.
+    size_t bytes_retained; ///< The total size of the database pages that
+                           ///< were retired by committed write transactions
+                           ///< after the reader's MVCC-snapshot, i.e. the space
+                           ///< which would be freed after the Reader releases
+                           ///< the MVCC-snapshot for reuse by completion read
+                           ///< transaction.
+
+    MDBX_CXX11_CONSTEXPR reader_info(int slot, mdbx_pid_t pid,
+                                     mdbx_tid_t thread, uint64_t txnid,
+                                     uint64_t lag, size_t used,
+                                     size_t retained) noexcept;
+  };
+
+  /// \brief Enumerate readers.
+  ///
+  /// The VISITOR class must have `int operator(const reader_info&, int serial)`
+  /// which should return \ref continue_loop (zero) to continue enumeration,
+  /// or any non-zero value to exit.
+  ///
+  /// \returns The last value returned from visitor' functor.
+  template <typename VISITOR> inline int enumerate_readers(VISITOR &visitor);
+
+  /// \brief Checks for stale readers in the lock table and
+  /// return number of cleared slots.
+  inline unsigned check_readers();
+
+  /// \brief Sets a Handle-Slow-Readers callback to resolve database
+  /// full/overflow issue due to a reader(s) which prevents the old data from
+  /// being recycled.
+  ///
+  /// Such callback will be triggered in a case where there is not enough free
+  /// space in the database due to long read transaction(s) which impedes
+  /// reusing the pages of an old MVCC snapshot(s).
+  ///
+  /// Using this callback you can choose how to resolve the situation:
+  ///  - abort the write transaction with an error;
+  ///  - wait for the read transaction(s) to complete;
+  ///  - notify a thread performing a long-lived read transaction
+  ///    and wait for an effect;
+  ///  - kill the thread or whole process that performs the long-lived read
+  ///    transaction;
+  ///
+  /// \see long-lived-read
+  inline env &set_HandleSlowReaders(MDBX_hsr_func *);
+
+  /// \brief Returns the current Handle-Slow-Readers callback used to resolve
+  /// database full/overflow issue due to a reader(s) which prevents the old
+  /// data from being recycled.
+  /// \see set_HandleSlowReaders()
+  inline MDBX_hsr_func *get_HandleSlowReaders() const noexcept;
+
+  /// \brief Starts read (read-only) transaction.
+  inline txn_managed start_read() const;
+
+  /// \brief Creates but not start read transaction.
+  inline txn_managed prepare_read() const;
+
+  /// \brief Starts write (read-write) transaction.
+  inline txn_managed start_write(bool dont_wait = false);
+
+  /// \brief Tries to start write (read-write) transaction without blocking.
+  inline txn_managed try_start_write();
+};
+
+/// \brief Managed database environment.
+///
+/// As other managed classes, `env_managed` destroys the represented underlying
+/// object from the own class destructor, but disallows copying and assignment
+/// for instances.
+///
+/// An environment supports multiple key-value databases (aka key-value spaces
+/// or tables), all residing in the same shared-memory map.
+class LIBMDBX_API_TYPE env_managed : public env {
+  using inherited = env;
+  /// delegated constructor for RAII
+  MDBX_CXX11_CONSTEXPR env_managed(MDBX_env *ptr) noexcept : inherited(ptr) {}
+  void setup(unsigned max_maps, unsigned max_readers = 0);
+
+public:
+  MDBX_CXX11_CONSTEXPR env_managed() noexcept = default;
+
+  /// \brief Open existing database.
+#ifdef MDBX_STD_FILESYSTEM_PATH
+  env_managed(const ::std::filesystem::path &, const operate_parameters &,
+              bool accede = true);
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+#if defined(_WIN32) || defined(_WIN64)
+  env_managed(const ::std::wstring &, const operate_parameters &,
+              bool accede = true);
+#endif /* Windows */
+  env_managed(const ::std::string &, const operate_parameters &,
+              bool accede = true);
+
+  /// \brief Additional parameters for creating a new database.
+  struct create_parameters {
+    env::geometry geometry;
+    mdbx_mode_t file_mode_bits{0640};
+    bool use_subdirectory{false};
+  };
+
+  /// \brief Create new or open existing database.
+#ifdef MDBX_STD_FILESYSTEM_PATH
+  env_managed(const ::std::filesystem::path &, const create_parameters &,
+              const operate_parameters &, bool accede = true);
+#endif /* MDBX_STD_FILESYSTEM_PATH */
+#if defined(_WIN32) || defined(_WIN64)
+  env_managed(const ::std::wstring &, const create_parameters &,
+              const operate_parameters &, bool accede = true);
+#endif /* Windows */
+  env_managed(const ::std::string &, const create_parameters &,
+              const operate_parameters &, bool accede = true);
+
+  /// \brief Explicitly closes the environment and release the memory map.
+  ///
+  /// Only a single thread may call this function. All transactions, databases,
+  /// and cursors must already be closed before calling this function. Attempts
+  /// to use any such handles after calling this function will cause a
+  /// `SIGSEGV`. The environment handle will be freed and must not be used again
+  /// after this call.
+  ///
+  /// \param [in] dont_sync  A dont'sync flag, if non-zero the last checkpoint
+  /// will be kept "as is" and may be still "weak" in the \ref lazy_weak_tail
+  /// or \ref whole_fragile modes. Such "weak" checkpoint will be ignored
+  /// on opening next time, and transactions since the last non-weak checkpoint
+  /// (meta-page update) will rolledback for consistency guarantee.
+  void close(bool dont_sync = false);
+
+  env_managed(env_managed &&) = default;
+  env_managed &operator=(env_managed &&) = default;
+  env_managed(const env_managed &) = delete;
+  env_managed &operator=(const env_managed &) = delete;
+  virtual ~env_managed() noexcept;
+};
+
+/// \brief Unmanaged database transaction.
+///
+/// Like other unmanaged classes, `txn` allows copying and assignment for
+/// instances, but does not destroys the represented underlying object from the
+/// own class destructor.
+///
+/// All database operations require a transaction handle. Transactions may be
+/// read-only or read-write.
+class LIBMDBX_API_TYPE txn {
+protected:
+  friend class cursor;
+  MDBX_txn *handle_{nullptr};
+  MDBX_CXX11_CONSTEXPR txn(MDBX_txn *ptr) noexcept;
+
+public:
+  MDBX_CXX11_CONSTEXPR txn() noexcept = default;
+  txn(const txn &) noexcept = default;
+  inline txn &operator=(txn &&other) noexcept;
+  inline txn(txn &&other) noexcept;
+  inline ~txn() noexcept;
+
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept;
+  MDBX_CXX14_CONSTEXPR operator const MDBX_txn *() const;
+  MDBX_CXX14_CONSTEXPR operator MDBX_txn *();
+  friend MDBX_CXX11_CONSTEXPR bool operator==(const txn &a,
+                                              const txn &b) noexcept;
+  friend MDBX_CXX11_CONSTEXPR bool operator!=(const txn &a,
+                                              const txn &b) noexcept;
+
+  /// \brief Returns the transaction's environment.
+  inline ::mdbx::env env() const noexcept;
+  /// \brief Returns transaction's flags.
+  inline MDBX_txn_flags_t flags() const;
+  /// \brief Return the transaction's ID.
+  inline uint64_t id() const;
+
+  /// \brief Checks whether the given data is on a dirty page.
+  inline bool is_dirty(const void *ptr) const;
+
+  /// \brief Checks whether the transaction is read-only.
+  bool is_readonly() const { return (flags() & MDBX_TXN_RDONLY) != 0; }
+
+  /// \brief Checks whether the transaction is read-write.
+  bool is_readwrite() const { return (flags() & MDBX_TXN_RDONLY) == 0; }
+
+  using info = ::MDBX_txn_info;
+  /// \brief Returns information about the MDBX transaction.
+  inline info get_info(bool scan_reader_lock_table = false) const;
+
+  /// \brief Returns maximal write transaction size (i.e. limit for summary
+  /// volume of dirty pages) in bytes.
+  size_t size_max() const { return env().transaction_size_max(); }
+
+  /// \brief Returns current write transaction size (i.e.summary volume of dirty
+  /// pages) in bytes.
+  size_t size_current() const {
+    assert(is_readwrite());
+    return size_t(get_info().txn_space_dirty);
+  }
+
+  //----------------------------------------------------------------------------
+
+  /// \brief Reset a read-only transaction.
+  inline void reset_reading();
+
+  /// \brief Renew a read-only transaction.
+  inline void renew_reading();
+
+  /// \brief Start nested write transaction.
+  txn_managed start_nested();
+
+  /// \brief Opens cursor for specified key-value map handle.
+  inline cursor_managed open_cursor(map_handle map);
+
+  /// \brief Open existing key-value map.
+  inline map_handle open_map(
+      const char *name,
+      const ::mdbx::key_mode key_mode = ::mdbx::key_mode::usual,
+      const ::mdbx::value_mode value_mode = ::mdbx::value_mode::single) const;
+  /// \brief Open existing key-value map.
+  inline map_handle open_map(
+      const ::std::string &name,
+      const ::mdbx::key_mode key_mode = ::mdbx::key_mode::usual,
+      const ::mdbx::value_mode value_mode = ::mdbx::value_mode::single) const;
+
+  /// \brief Create new or open existing key-value map.
+  inline map_handle
+  create_map(const char *name,
+             const ::mdbx::key_mode key_mode = ::mdbx::key_mode::usual,
+             const ::mdbx::value_mode value_mode = ::mdbx::value_mode::single);
+  /// \brief Create new or open existing key-value map.
+  inline map_handle
+  create_map(const ::std::string &name,
+             const ::mdbx::key_mode key_mode = ::mdbx::key_mode::usual,
+             const ::mdbx::value_mode value_mode = ::mdbx::value_mode::single);
+
+  /// \brief Drops key-value map using handle.
+  inline void drop_map(map_handle map);
+  /// \brief Drops key-value map using name.
+  /// \return `True` if the key-value map existed and was deleted, either
+  /// `false` if the key-value map did not exist and there is nothing to delete.
+  bool drop_map(const char *name, bool throw_if_absent = false);
+  /// \brief Drop key-value map.
+  /// \return `True` if the key-value map existed and was deleted, either
+  /// `false` if the key-value map did not exist and there is nothing to delete.
+  inline bool drop_map(const ::std::string &name, bool throw_if_absent = false);
+
+  /// \brief Clear key-value map.
+  inline void clear_map(map_handle map);
+  /// \return `True` if the key-value map existed and was cleared, either
+  /// `false` if the key-value map did not exist and there is nothing to clear.
+  bool clear_map(const char *name, bool throw_if_absent = false);
+  /// \return `True` if the key-value map existed and was cleared, either
+  /// `false` if the key-value map did not exist and there is nothing to clear.
+  inline bool clear_map(const ::std::string &name,
+                        bool throw_if_absent = false);
+
+  using map_stat = ::MDBX_stat;
+  /// \brief Returns statistics for a sub-database.
+  inline map_stat get_map_stat(map_handle map) const;
+  /// \brief Returns depth (bitmask) information of nested dupsort (multi-value)
+  /// B+trees for given database.
+  inline uint32_t get_tree_deepmask(map_handle map) const;
+  /// \brief Returns information about key-value map (aka sub-database) handle.
+  inline map_handle::info get_handle_info(map_handle map) const;
+
+  using canary = ::MDBX_canary;
+  /// \brief Set integers markers (aka "canary") associated with the
+  /// environment.
+  inline txn &put_canary(const canary &);
+  /// \brief Returns fours integers markers (aka "canary") associated with the
+  /// environment.
+  inline canary get_canary() const;
+
+  /// Reads sequence generator associated with a key-value map (aka
+  /// sub-database).
+  inline uint64_t sequence(map_handle map) const;
+  /// \brief Reads and increment sequence generator associated with a key-value
+  /// map (aka sub-database).
+  inline uint64_t sequence(map_handle map, uint64_t increment);
+
+  /// \brief Compare two keys according to a particular key-value map (aka
+  /// sub-database).
+  inline int compare_keys(map_handle map, const slice &a,
+                          const slice &b) const noexcept;
+  /// \brief Compare two values according to a particular key-value map (aka
+  /// sub-database).
+  inline int compare_values(map_handle map, const slice &a,
+                            const slice &b) const noexcept;
+  /// \brief Compare keys of two pairs according to a particular key-value map
+  /// (aka sub-database).
+  inline int compare_keys(map_handle map, const pair &a,
+                          const pair &b) const noexcept;
+  /// \brief Compare values of two pairs according to a particular key-value map
+  /// (aka sub-database).
+  inline int compare_values(map_handle map, const pair &a,
+                            const pair &b) const noexcept;
+
+  /// \brief Get value by key from a key-value map (aka sub-database).
+  inline slice get(map_handle map, const slice &key) const;
+  /// \brief Get first of multi-value and values count by key from a key-value
+  /// multimap (aka sub-database).
+  inline slice get(map_handle map, slice key, size_t &values_count) const;
+  /// \brief Get value by key from a key-value map (aka sub-database).
+  inline slice get(map_handle map, const slice &key,
+                   const slice &value_at_absence) const;
+  /// \brief Get first of multi-value and values count by key from a key-value
+  /// multimap (aka sub-database).
+  inline slice get(map_handle map, slice key, size_t &values_count,
+                   const slice &value_at_absence) const;
+  /// \brief Get value for equal or great key from a database.
+  /// \return Bundle of key-value pair and boolean flag,
+  /// which will be `true` if the exact key was found and `false` otherwise.
+  inline pair_result get_equal_or_great(map_handle map, const slice &key) const;
+  /// \brief Get value for equal or great key from a database.
+  /// \return Bundle of key-value pair and boolean flag,
+  /// which will be `true` if the exact key was found and `false` otherwise.
+  inline pair_result get_equal_or_great(map_handle map, const slice &key,
+                                        const slice &value_at_absence) const;
+
+  inline MDBX_error_t put(map_handle map, const slice &key, slice *value,
+                          MDBX_put_flags_t flags) noexcept;
+  inline void put(map_handle map, const slice &key, slice value,
+                  put_mode mode) noexcept;
+  inline void insert(map_handle map, const slice &key, slice value);
+  inline value_result try_insert(map_handle map, const slice &key, slice value);
+  inline slice insert_reserve(map_handle map, const slice &key,
+                              size_t value_length);
+  inline value_result try_insert_reserve(map_handle map, const slice &key,
+                                         size_t value_length);
+
+  inline void upsert(map_handle map, const slice &key, const slice &value);
+  inline slice upsert_reserve(map_handle map, const slice &key,
+                              size_t value_length);
+
+  inline void update(map_handle map, const slice &key, const slice &value);
+  inline bool try_update(map_handle map, const slice &key, const slice &value);
+  inline slice update_reserve(map_handle map, const slice &key,
+                              size_t value_length);
+  inline value_result try_update_reserve(map_handle map, const slice &key,
+                                         size_t value_length);
+
+  inline bool erase(map_handle map, const slice &key);
+
+  /// \brief Removes the particular multi-value entry of the key.
+  inline bool erase(map_handle map, const slice &key, const slice &value);
+
+  /// \brief Replaces the particular multi-value of the key with a new value.
+  inline void replace(map_handle map, const slice &key, slice old_value,
+                      const slice &new_value);
+
+  /// \brief Removes and return a value of the key.
+  template <class ALLOCATOR>
+  inline buffer<ALLOCATOR> extract(map_handle map, const slice &key,
+                                   const ALLOCATOR &allocator = ALLOCATOR());
+
+  /// \brief Replaces and returns a value of the key with new one.
+  template <class ALLOCATOR>
+  inline buffer<ALLOCATOR> replace(map_handle map, const slice &key,
+                                   const slice &new_value,
+                                   const ALLOCATOR &allocator = ALLOCATOR());
+
+  template <class ALLOCATOR>
+  inline buffer<ALLOCATOR>
+  replace_reserve(map_handle map, const slice &key, slice &new_value,
+                  const ALLOCATOR &allocator = ALLOCATOR());
+
+  /// \brief Adding a key-value pair, provided that ascending order of the keys
+  /// and (optionally) values are preserved.
+  ///
+  /// Instead of splitting the full b+tree pages, the data will be placed on new
+  /// ones. Thus appending is about two times faster than insertion, and the
+  /// pages will be filled in completely mostly but not half as after splitting
+  /// ones. On the other hand, any subsequent insertion or update with an
+  /// increase in the length of the value will be twice as slow, since it will
+  /// require splitting already filled pages.
+  ///
+  /// \param [in] multivalue_order_preserved
+  /// If `multivalue_order_preserved == true` then the same rules applied for
+  /// to pages of nested b+tree of multimap's values.
+  inline void append(map_handle map, const slice &key, const slice &value,
+                     bool multivalue_order_preserved = true);
+
+  size_t put_multiple(map_handle map, const slice &key,
+                      const size_t value_length, const void *values_array,
+                      size_t values_count, put_mode mode,
+                      bool allow_partial = false);
+  template <typename VALUE>
+  void put_multiple(map_handle map, const slice &key,
+                    const std::vector<VALUE> &vector, put_mode mode) {
+    put_multiple(map, key, sizeof(VALUE), vector.data(), vector.size(), mode,
+                 false);
+  }
+
+  inline ptrdiff_t estimate(map_handle map, pair from, pair to) const;
+  inline ptrdiff_t estimate(map_handle map, slice from, slice to) const;
+  inline ptrdiff_t estimate_from_first(map_handle map, slice to) const;
+  inline ptrdiff_t estimate_to_last(map_handle map, slice from) const;
+};
+
+/// \brief Managed database transaction.
+///
+/// As other managed classes, `txn_managed` destroys the represented underlying
+/// object from the own class destructor, but disallows copying and assignment
+/// for instances.
+///
+/// All database operations require a transaction handle. Transactions may be
+/// read-only or read-write.
+class LIBMDBX_API_TYPE txn_managed : public txn {
+  using inherited = txn;
+  friend class env;
+  friend class txn;
+  /// delegated constructor for RAII
+  MDBX_CXX11_CONSTEXPR txn_managed(MDBX_txn *ptr) noexcept : inherited(ptr) {}
+
+public:
+  MDBX_CXX11_CONSTEXPR txn_managed() noexcept = default;
+  txn_managed(txn_managed &&) = default;
+  txn_managed &operator=(txn_managed &&) = default;
+  txn_managed(const txn_managed &) = delete;
+  txn_managed &operator=(const txn_managed &) = delete;
+  ~txn_managed() noexcept;
+
+  //----------------------------------------------------------------------------
+
+  /// \brief Abandon all the operations of the transaction instead of saving
+  /// them.
+  void abort();
+
+  /// \brief Commit all the operations of a transaction into the database.
+  void commit();
+};
+
+/// \brief Unmanaged cursor.
+///
+/// Like other unmanaged classes, `cursor` allows copying and assignment for
+/// instances, but does not destroys the represented underlying object from the
+/// own class destructor.
+///
+/// \copydetails MDBX_cursor
+class LIBMDBX_API_TYPE cursor {
+protected:
+  MDBX_cursor *handle_{nullptr};
+  MDBX_CXX11_CONSTEXPR cursor(MDBX_cursor *ptr) noexcept;
+
+public:
+  MDBX_CXX11_CONSTEXPR cursor() noexcept = default;
+  cursor(const cursor &) noexcept = default;
+  inline cursor &operator=(cursor &&other) noexcept;
+  inline cursor(cursor &&other) noexcept;
+  inline ~cursor() noexcept;
+  MDBX_CXX14_CONSTEXPR operator bool() const noexcept;
+  MDBX_CXX14_CONSTEXPR operator const MDBX_cursor *() const;
+  MDBX_CXX14_CONSTEXPR operator MDBX_cursor *();
+  friend MDBX_CXX11_CONSTEXPR bool operator==(const cursor &a,
+                                              const cursor &b) noexcept;
+  friend MDBX_CXX11_CONSTEXPR bool operator!=(const cursor &a,
+                                              const cursor &b) noexcept;
+
+  enum move_operation {
+    first = MDBX_FIRST,
+    last = MDBX_LAST,
+    next = MDBX_NEXT,
+    previous = MDBX_PREV,
+    get_current = MDBX_GET_CURRENT,
+
+    multi_prevkey_lastvalue = MDBX_PREV_NODUP,
+    multi_currentkey_firstvalue = MDBX_FIRST_DUP,
+    multi_currentkey_prevvalue = MDBX_PREV_DUP,
+    multi_currentkey_nextvalue = MDBX_NEXT_DUP,
+    multi_currentkey_lastvalue = MDBX_LAST_DUP,
+    multi_nextkey_firstvalue = MDBX_NEXT_NODUP,
+
+    multi_find_pair = MDBX_GET_BOTH,
+    multi_exactkey_lowerboundvalue = MDBX_GET_BOTH_RANGE,
+
+    find_key = MDBX_SET,
+    key_exact = MDBX_SET_KEY,
+    key_lowerbound = MDBX_SET_RANGE
+  };
+
+  struct move_result : public pair_result {
+    inline move_result(const cursor &cursor, bool throw_notfound);
+    inline move_result(cursor &cursor, move_operation operation,
+                       bool throw_notfound);
+    inline move_result(cursor &cursor, move_operation operation,
+                       const slice &key, bool throw_notfound);
+    inline move_result(cursor &cursor, move_operation operation,
+                       const slice &key, const slice &value,
+                       bool throw_notfound);
+    move_result(const move_result &) noexcept = default;
+  };
+
+protected:
+  inline bool move(move_operation operation, MDBX_val *key, MDBX_val *value,
+                   bool throw_notfound) const
+      /* fake const, i.e. for some operations */;
+  inline ptrdiff_t estimate(move_operation operation, MDBX_val *key,
+                            MDBX_val *value) const;
+
+public:
+  inline move_result move(move_operation operation, bool throw_notfound);
+  inline move_result to_first(bool throw_notfound = true);
+  inline move_result to_previous(bool throw_notfound = true);
+  inline move_result to_previous_last_multi(bool throw_notfound = true);
+  inline move_result to_current_first_multi(bool throw_notfound = true);
+  inline move_result to_current_prev_multi(bool throw_notfound = true);
+  inline move_result current(bool throw_notfound = true) const;
+  inline move_result to_current_next_multi(bool throw_notfound = true);
+  inline move_result to_current_last_multi(bool throw_notfound = true);
+  inline move_result to_next_first_multi(bool throw_notfound = true);
+  inline move_result to_next(bool throw_notfound = true);
+  inline move_result to_last(bool throw_notfound = true);
+
+  inline move_result move(move_operation operation, const slice &key,
+                          bool throw_notfound);
+  inline move_result find(const slice &key, bool throw_notfound = true);
+  inline move_result lower_bound(const slice &key, bool throw_notfound = true);
+
+  inline move_result move(move_operation operation, const slice &key,
+                          const slice &value, bool throw_notfound);
+  inline move_result find_multivalue(const slice &key, const slice &value,
+                                     bool throw_notfound = true);
+  inline move_result lower_bound_multivalue(const slice &key,
+                                            const slice &value,
+                                            bool throw_notfound = false);
+
+  inline bool seek(const slice &key);
+  inline bool move(move_operation operation, slice &key, slice &value,
+                   bool throw_notfound);
+
+  /// \brief Return count of duplicates for current key.
+  inline size_t count_multivalue() const;
+
+  inline bool eof() const;
+  inline bool on_first() const;
+  inline bool on_last() const;
+  inline ptrdiff_t estimate(slice key, slice value) const;
+  inline ptrdiff_t estimate(slice key) const;
+  inline ptrdiff_t estimate(move_operation operation) const;
+
+  //----------------------------------------------------------------------------
+
+  /// \brief Renew/bind a cursor with a new transaction and previously used
+  /// key-value map handle.
+  inline void renew(::mdbx::txn &txn);
+
+  /// \brief Bind/renew a cursor with a new transaction and specified key-value
+  /// map handle.
+  inline void bind(::mdbx::txn &txn, ::mdbx::map_handle map_handle);
+
+  /// \brief Returns the cursor's transaction.
+  inline ::mdbx::txn txn() const;
+  inline map_handle map() const;
+
+  inline operator ::mdbx::txn() const { return txn(); }
+  inline operator ::mdbx::map_handle() const { return map(); }
+
+  inline MDBX_error_t put(const slice &key, slice *value,
+                          MDBX_put_flags_t flags) noexcept;
+  inline void insert(const slice &key, slice value);
+  inline value_result try_insert(const slice &key, slice value);
+  inline slice insert_reserve(const slice &key, size_t value_length);
+  inline value_result try_insert_reserve(const slice &key, size_t value_length);
+
+  inline void upsert(const slice &key, const slice &value);
+  inline slice upsert_reserve(const slice &key, size_t value_length);
+
+  inline void update(const slice &key, const slice &value);
+  inline bool try_update(const slice &key, const slice &value);
+  inline slice update_reserve(const slice &key, size_t value_length);
+  inline value_result try_update_reserve(const slice &key, size_t value_length);
+
+  inline bool erase(bool whole_multivalue = false);
+};
+
+/// \brief Managed cursor.
+///
+/// As other managed classes, `cursor_managed` destroys the represented
+/// underlying object from the own class destructor, but disallows copying and
+/// assignment for instances.
+///
+/// \copydetails MDBX_cursor
+class LIBMDBX_API_TYPE cursor_managed : public cursor {
+  using inherited = cursor;
+  friend class txn;
+  /// delegated constructor for RAII
+  MDBX_CXX11_CONSTEXPR cursor_managed(MDBX_cursor *ptr) noexcept
+      : inherited(ptr) {}
+
+public:
+  /// \brief Creates a new managed cursor with underlying object.
+  inline cursor_managed();
+
+  /// \brief Explicitly closes the cursor.
+  void close();
+
+  cursor_managed(cursor_managed &&) = default;
+  cursor_managed &operator=(cursor_managed &&) = default;
+  cursor_managed(const cursor_managed &) = delete;
+  cursor_managed &operator=(const cursor_managed &) = delete;
+  ~cursor_managed() noexcept { ::mdbx_cursor_close(handle_); }
+};
+
+//------------------------------------------------------------------------------
+
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const slice &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const pair &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const pair_result &);
+template <class ALLOCATOR>
+inline ::std::ostream &operator<<(::std::ostream &out,
+                                  const buffer<ALLOCATOR> &it) {
+  return (it.is_freestanding()
+              ? out << "buf-" << it.headroom() << "." << it.tailroom()
+              : out << "ref-")
+         << it.slice();
+}
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env::geometry::size &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const env::geometry &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env::operate_parameters &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const env::mode &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env::durability &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env::reclaiming_options &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env::operate_options &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const env_managed::create_parameters &);
+
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const MDBX_log_level_t &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &,
+                                       const MDBX_debug_flags_t &);
+LIBMDBX_API ::std::ostream &operator<<(::std::ostream &, const error &);
+inline ::std::ostream &operator<<(::std::ostream &out,
+                                  const MDBX_error_t &errcode) {
+  return out << error(errcode);
+}
+
+//==============================================================================
+//
+// Inline body of the libmdbx C++ API (preliminary draft)
+//
+
+MDBX_CXX11_CONSTEXPR const version_info &get_version() noexcept {
+  return ::mdbx_version;
+}
+MDBX_CXX11_CONSTEXPR const build_info &get_build() noexcept {
+  return ::mdbx_build;
+}
+
+static MDBX_CXX17_CONSTEXPR size_t strlen(const char *c_str) noexcept {
+#if defined(__cpp_lib_is_constant_evaluated) &&                                \
+    __cpp_lib_is_constant_evaluated >= 201811L
+  if (::std::is_constant_evaluated()) {
+    for (size_t i = 0; c_str; ++i)
+      if (!c_str[i])
+        return i;
+    return 0;
+  }
+#endif /* __cpp_lib_is_constant_evaluated >= 201811 */
+#if defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L
+  return c_str ? ::std::string_view(c_str).length() : 0;
+#else
+  return c_str ? ::std::strlen(c_str) : 0;
+#endif
+}
+
+MDBX_CXX14_CONSTEXPR size_t check_length(size_t bytes) {
+  if (MDBX_UNLIKELY(bytes > size_t(MDBX_MAXDATASIZE)))
+    MDBX_CXX20_UNLIKELY throw_max_length_exceeded();
+  return bytes;
+}
+
+inline bool exception_thunk::is_clean() const noexcept { return !captured_; }
+
+inline void exception_thunk::capture() noexcept {
+  assert(is_clean());
+  captured_ = ::std::current_exception();
+}
+
+inline void exception_thunk::rethrow_captured() const {
+  if (captured_)
+    MDBX_CXX20_UNLIKELY ::std::rethrow_exception(captured_);
+}
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR error::error(MDBX_error_t error_code) noexcept
+    : code_(error_code) {}
+
+inline error &error::operator=(MDBX_error_t error_code) noexcept {
+  code_ = error_code;
+  return *this;
+}
+
+MDBX_CXX11_CONSTEXPR bool operator==(const error &a, const error &b) noexcept {
+  return a.code_ == b.code_;
+}
+
+MDBX_CXX11_CONSTEXPR bool operator!=(const error &a, const error &b) noexcept {
+  return !(a == b);
+}
+
+MDBX_CXX11_CONSTEXPR bool error::is_success() const noexcept {
+  return code_ == MDBX_SUCCESS;
+}
+
+MDBX_CXX11_CONSTEXPR bool error::is_result_true() const noexcept {
+  return code_ == MDBX_RESULT_FALSE;
+}
+
+MDBX_CXX11_CONSTEXPR bool error::is_result_false() const noexcept {
+  return code_ == MDBX_RESULT_TRUE;
+}
+
+MDBX_CXX11_CONSTEXPR bool error::is_failure() const noexcept {
+  return code_ != MDBX_SUCCESS && code_ != MDBX_RESULT_TRUE;
+}
+
+MDBX_CXX11_CONSTEXPR MDBX_error_t error::code() const noexcept { return code_; }
+
+MDBX_CXX11_CONSTEXPR bool error::is_mdbx_error() const noexcept {
+  return (code() >= MDBX_FIRST_LMDB_ERRCODE &&
+          code() <= MDBX_LAST_LMDB_ERRCODE) ||
+         (code() >= MDBX_FIRST_ADDED_ERRCODE &&
+          code() <= MDBX_LAST_ADDED_ERRCODE);
+}
+
+inline void error::throw_exception(int error_code) {
+  const error trouble(static_cast<MDBX_error_t>(error_code));
+  trouble.throw_exception();
+}
+
+inline void error::throw_on_failure() const {
+  if (MDBX_UNLIKELY(is_failure()))
+    MDBX_CXX20_UNLIKELY throw_exception();
+}
+
+inline void error::success_or_throw() const {
+  if (MDBX_UNLIKELY(!is_success()))
+    MDBX_CXX20_UNLIKELY throw_exception();
+}
+
+inline void error::success_or_throw(const exception_thunk &thunk) const {
+  assert(thunk.is_clean() || code() != MDBX_SUCCESS);
+  if (MDBX_UNLIKELY(!is_success())) {
+    MDBX_CXX20_UNLIKELY if (!thunk.is_clean()) thunk.rethrow_captured();
+    else throw_exception();
+  }
+}
+
+inline void error::panic_on_failure(const char *context_where,
+                                    const char *func_who) const noexcept {
+  if (MDBX_UNLIKELY(is_failure()))
+    MDBX_CXX20_UNLIKELY panic(context_where, func_who);
+}
+
+inline void error::success_or_panic(const char *context_where,
+                                    const char *func_who) const noexcept {
+  if (MDBX_UNLIKELY(!is_success()))
+    MDBX_CXX20_UNLIKELY panic(context_where, func_who);
+}
+
+inline void error::throw_on_nullptr(const void *ptr, MDBX_error_t error_code) {
+  if (MDBX_UNLIKELY(ptr == nullptr))
+    MDBX_CXX20_UNLIKELY error(error_code).throw_exception();
+}
+
+inline void error::throw_on_failure(int error_code) {
+  error rc(static_cast<MDBX_error_t>(error_code));
+  rc.throw_on_failure();
+}
+
+inline void error::success_or_throw(MDBX_error_t error_code) {
+  error rc(error_code);
+  rc.success_or_throw();
+}
+
+inline bool error::boolean_or_throw(int error_code) {
+  switch (error_code) {
+  case MDBX_RESULT_FALSE:
+    return false;
+  case MDBX_RESULT_TRUE:
+    return true;
+  default:
+    MDBX_CXX20_UNLIKELY throw_exception(error_code);
+  }
+}
+
+inline void error::success_or_throw(int error_code,
+                                    const exception_thunk &thunk) {
+  error rc(static_cast<MDBX_error_t>(error_code));
+  rc.success_or_throw(thunk);
+}
+
+inline void error::panic_on_failure(int error_code, const char *context_where,
+                                    const char *func_who) noexcept {
+  error rc(static_cast<MDBX_error_t>(error_code));
+  rc.panic_on_failure(context_where, func_who);
+}
+
+inline void error::success_or_panic(int error_code, const char *context_where,
+                                    const char *func_who) noexcept {
+  error rc(static_cast<MDBX_error_t>(error_code));
+  rc.success_or_panic(context_where, func_who);
+}
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR slice::slice() noexcept : ::MDBX_val({nullptr, 0}) {}
+
+MDBX_CXX14_CONSTEXPR slice::slice(const void *ptr, size_t bytes)
+    : ::MDBX_val({const_cast<void *>(ptr), check_length(bytes)}) {}
+
+MDBX_CXX14_CONSTEXPR slice::slice(const void *begin, const void *end)
+    : slice(begin, static_cast<const byte *>(end) -
+                       static_cast<const byte *>(begin)) {}
+
+MDBX_CXX17_CONSTEXPR slice::slice(const char *c_str)
+    : slice(c_str, ::mdbx::strlen(c_str)) {}
+
+MDBX_CXX14_CONSTEXPR slice::slice(const MDBX_val &src)
+    : slice(src.iov_base, src.iov_len) {}
+
+inline slice::slice(MDBX_val &&src) : slice(src) { src.iov_base = nullptr; }
+
+inline slice::slice(slice &&src) noexcept : slice(src) { src.invalidate(); }
+
+inline slice &slice::assign(const void *ptr, size_t bytes) {
+  iov_base = const_cast<void *>(ptr);
+  iov_len = check_length(bytes);
+  return *this;
+}
+
+inline slice &slice::assign(const slice &src) noexcept {
+  iov_base = src.iov_base;
+  iov_len = src.iov_len;
+  return *this;
+}
+
+inline slice &slice::assign(const ::MDBX_val &src) {
+  return assign(src.iov_base, src.iov_len);
+}
+
+slice &slice::assign(slice &&src) noexcept {
+  assign(src);
+  src.invalidate();
+  return *this;
+}
+
+inline slice &slice::assign(::MDBX_val &&src) {
+  assign(src.iov_base, src.iov_len);
+  src.iov_base = nullptr;
+  return *this;
+}
+
+inline slice &slice::assign(const void *begin, const void *end) {
+  return assign(begin, static_cast<const byte *>(end) -
+                           static_cast<const byte *>(begin));
+}
+
+inline slice &slice::assign(const char *c_str) {
+  return assign(c_str, ::mdbx::strlen(c_str));
+}
+
+inline slice &slice::operator=(slice &&src) noexcept {
+  return assign(::std::move(src));
+}
+
+inline slice &slice::operator=(::MDBX_val &&src) {
+  return assign(::std::move(src));
+}
+
+inline void slice::swap(slice &other) noexcept {
+  const auto temp = *this;
+  *this = other;
+  other = temp;
+}
+
+MDBX_CXX11_CONSTEXPR const mdbx::byte *slice::byte_ptr() const noexcept {
+  return static_cast<const byte *>(iov_base);
+}
+
+MDBX_CXX11_CONSTEXPR const char *slice::char_ptr() const noexcept {
+  return static_cast<const char *>(iov_base);
+}
+
+MDBX_CXX11_CONSTEXPR const void *slice::data() const noexcept {
+  return iov_base;
+}
+
+MDBX_CXX11_CONSTEXPR size_t slice::length() const noexcept { return iov_len; }
+
+MDBX_CXX11_CONSTEXPR bool slice::empty() const noexcept {
+  return length() == 0;
+}
+
+MDBX_CXX11_CONSTEXPR bool slice::is_null() const noexcept {
+  return data() == nullptr;
+}
+
+MDBX_CXX11_CONSTEXPR size_t slice::size() const noexcept { return length(); }
+
+MDBX_CXX11_CONSTEXPR slice::operator bool() const noexcept {
+  return !is_null();
+}
+
+inline void slice::invalidate() noexcept { iov_base = nullptr; }
+
+inline void slice::clear() noexcept {
+  iov_base = nullptr;
+  iov_len = 0;
+}
+
+inline void slice::remove_prefix(size_t n) noexcept {
+  assert(n <= size());
+  iov_base = static_cast<byte *>(iov_base) + n;
+  iov_len -= n;
+}
+
+inline void slice::safe_remove_prefix(size_t n) {
+  if (MDBX_UNLIKELY(n > size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  remove_prefix(n);
+}
+
+inline void slice::remove_suffix(size_t n) noexcept {
+  assert(n <= size());
+  iov_len -= n;
+}
+
+inline void slice::safe_remove_suffix(size_t n) {
+  if (MDBX_UNLIKELY(n > size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  remove_suffix(n);
+}
+
+inline bool slice::starts_with(const slice &prefix) const noexcept {
+  return length() >= prefix.length() &&
+         ::std::memcmp(data(), prefix.data(), prefix.length()) == 0;
+}
+
+inline bool slice::ends_with(const slice &suffix) const noexcept {
+  return length() >= suffix.length() &&
+         ::std::memcmp(byte_ptr() + length() - suffix.length(), suffix.data(),
+                       suffix.length()) == 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION MDBX_CXX14_CONSTEXPR size_t
+slice::hash_value() const noexcept {
+  size_t h = length() * 3977471;
+  for (size_t i = 0; i < length(); ++i)
+    h = (h ^ static_cast<const uint8_t *>(data())[i]) * 1664525 + 1013904223;
+  return h ^ 3863194411 * (h >> 11);
+}
+
+inline byte slice::operator[](size_t n) const noexcept {
+  assert(n < size());
+  return byte_ptr()[n];
+}
+
+inline byte slice::at(size_t n) const {
+  if (MDBX_UNLIKELY(n >= size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  return byte_ptr()[n];
+}
+
+inline slice slice::head(size_t n) const noexcept {
+  assert(n <= size());
+  return slice(data(), n);
+}
+
+inline slice slice::tail(size_t n) const noexcept {
+  assert(n <= size());
+  return slice(char_ptr() + size() - n, n);
+}
+
+inline slice slice::middle(size_t from, size_t n) const noexcept {
+  assert(from + n <= size());
+  return slice(char_ptr() + from, n);
+}
+
+inline slice slice::safe_head(size_t n) const {
+  if (MDBX_UNLIKELY(n > size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  return head(n);
+}
+
+inline slice slice::safe_tail(size_t n) const {
+  if (MDBX_UNLIKELY(n > size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  return tail(n);
+}
+
+inline slice slice::safe_middle(size_t from, size_t n) const {
+  if (MDBX_UNLIKELY(n > max_length))
+    MDBX_CXX20_UNLIKELY throw_max_length_exceeded();
+  if (MDBX_UNLIKELY(from + n > size()))
+    MDBX_CXX20_UNLIKELY throw_out_range();
+  return middle(from, n);
+}
+
+inline intptr_t slice::compare_fast(const slice &a, const slice &b) noexcept {
+  const intptr_t diff = a.length() - b.length();
+  return diff ? diff
+              : (a.data() == b.data())
+                    ? 0
+                    : ::std::memcmp(a.data(), b.data(), a.length());
+}
+
+inline intptr_t slice::compare_lexicographically(const slice &a,
+                                                 const slice &b) noexcept {
+  const intptr_t diff =
+      ::std::memcmp(a.data(), b.data(), ::std::min(a.length(), b.length()));
+  return diff ? diff : intptr_t(a.length() - b.length());
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator==(const slice &a,
+                                                  const slice &b) noexcept {
+  return slice::compare_fast(a, b) == 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator<(const slice &a,
+                                                 const slice &b) noexcept {
+  return slice::compare_lexicographically(a, b) < 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator>(const slice &a,
+                                                 const slice &b) noexcept {
+  return slice::compare_lexicographically(a, b) > 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator<=(const slice &a,
+                                                  const slice &b) noexcept {
+  return slice::compare_lexicographically(a, b) <= 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator>=(const slice &a,
+                                                  const slice &b) noexcept {
+  return slice::compare_lexicographically(a, b) >= 0;
+}
+
+MDBX_NOTHROW_PURE_FUNCTION inline bool operator!=(const slice &a,
+                                                  const slice &b) noexcept {
+  return slice::compare_fast(a, b) != 0;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::hex_encode(bool uppercase, const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(to_hex_bytes());
+    result.resize(to_hex(const_cast<char *>(result.data()), result.capacity()) -
+                      result.data(),
+                  uppercase);
+  }
+  return result;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::hex_decode(const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(from_hex_bytes());
+    result.resize(
+        from_hex(static_cast<byte *>(
+                     static_cast<void *>(const_cast<char *>(result.data()))),
+                 result.capacity()) -
+        static_cast<const byte *>(static_cast<const void *>(result.data())));
+  }
+  return result;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::base58_encode(const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(to_base58_bytes());
+    result.resize(
+        to_base58(const_cast<char *>(result.data()), result.capacity()) -
+        result.data());
+  }
+  return result;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::base58_decode(const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(from_base58_bytes());
+    result.resize(
+        from_base58(static_cast<byte *>(
+                        static_cast<void *>(const_cast<char *>(result.data()))),
+                    result.capacity()) -
+        static_cast<const byte *>(static_cast<const void *>(result.data())));
+  }
+  return result;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::base64_encode(const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(to_base64_bytes());
+    result.resize(
+        to_base64(const_cast<char *>(result.data()), result.capacity()) -
+        result.data());
+  }
+  return result;
+}
+
+template <class ALLOCATOR>
+inline ::mdbx::string<ALLOCATOR>
+slice::base64_decode(const ALLOCATOR &allocator) const {
+  ::mdbx::string<ALLOCATOR> result(allocator);
+  if (MDBX_LIKELY(length() > 0)) {
+    result.resize(from_base64_bytes());
+    result.resize(
+        from_base64(static_cast<byte *>(
+                        static_cast<void *>(const_cast<char *>(result.data()))),
+                    result.capacity()) -
+        static_cast<const byte *>(static_cast<const void *>(result.data())));
+  }
+  return result;
+}
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR map_handle::info::info(map_handle::flags flags,
+                                            map_handle::state state) noexcept
+    : flags(flags), state(state) {}
+
+MDBX_CXX11_CONSTEXPR ::mdbx::key_mode
+map_handle::info::key_mode() const noexcept {
+  return ::mdbx::key_mode(flags & (MDBX_REVERSEKEY | MDBX_INTEGERKEY));
+}
+
+MDBX_CXX11_CONSTEXPR ::mdbx::value_mode
+map_handle::info::value_mode() const noexcept {
+  return ::mdbx::value_mode(flags & (MDBX_DUPSORT | MDBX_REVERSEDUP |
+                                     MDBX_DUPFIXED | MDBX_INTEGERDUP));
+}
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR env::env(MDBX_env *ptr) noexcept : handle_(ptr) {}
+
+inline env &env::operator=(env &&other) noexcept {
+  handle_ = other.handle_;
+  other.handle_ = nullptr;
+  return *this;
+}
+
+inline env::env(env &&other) noexcept : handle_(other.handle_) {
+  other.handle_ = nullptr;
+}
+
+inline env::~env() noexcept {
+#ifndef NDEBUG
+  handle_ = reinterpret_cast<MDBX_env *>(uintptr_t(0xDeadBeef));
+#endif
+}
+
+MDBX_CXX14_CONSTEXPR env::operator bool() const noexcept {
+  return handle_ != nullptr;
+}
+
+MDBX_CXX14_CONSTEXPR env::operator const MDBX_env *() const { return handle_; }
+
+MDBX_CXX14_CONSTEXPR env::operator MDBX_env *() { return handle_; }
+
+MDBX_CXX11_CONSTEXPR bool operator==(const env &a, const env &b) noexcept {
+  return a.handle_ == b.handle_;
+}
+
+MDBX_CXX11_CONSTEXPR bool operator!=(const env &a, const env &b) noexcept {
+  return a.handle_ != b.handle_;
+}
+
+inline env::geometry &env::geometry::make_fixed(intptr_t size) noexcept {
+  size_lower = size_now = size_upper = size;
+  growth_step = shrink_threshold = 0;
+  return *this;
+}
+
+inline env::geometry &env::geometry::make_dynamic(intptr_t lower,
+                                                  intptr_t upper) noexcept {
+  size_now = size_lower = lower;
+  size_upper = upper;
+  growth_step = shrink_threshold = default_value;
+  return *this;
+}
+
+inline env::reclaiming_options env::operate_parameters::reclaiming_from_flags(
+    MDBX_env_flags_t flags) noexcept {
+  return reclaiming_options(flags);
+}
+
+inline env::operate_options
+env::operate_parameters::options_from_flags(MDBX_env_flags_t flags) noexcept {
+  return operate_options(flags);
+}
+
+inline size_t env::limits::pagesize_min() noexcept { return MDBX_MIN_PAGESIZE; }
+
+inline size_t env::limits::pagesize_max() noexcept { return MDBX_MAX_PAGESIZE; }
+
+inline size_t env::limits::dbsize_min(intptr_t pagesize) {
+  const intptr_t result = mdbx_limits_dbsize_min(pagesize);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::dbsize_max(intptr_t pagesize) {
+  const intptr_t result = mdbx_limits_dbsize_max(pagesize);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::key_min(MDBX_db_flags_t flags) noexcept {
+  return (flags & MDBX_INTEGERKEY) ? 4 : 0;
+}
+
+inline size_t env::limits::key_min(key_mode mode) noexcept {
+  return key_min(MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::key_max(intptr_t pagesize, MDBX_db_flags_t flags) {
+  const intptr_t result = mdbx_limits_keysize_max(pagesize, flags);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::key_max(intptr_t pagesize, key_mode mode) {
+  return key_max(pagesize, MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::key_max(const env &env, MDBX_db_flags_t flags) {
+  const intptr_t result = mdbx_env_get_maxkeysize_ex(env, flags);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::key_max(const env &env, key_mode mode) {
+  return key_max(env, MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::value_min(MDBX_db_flags_t flags) noexcept {
+  return (flags & MDBX_INTEGERDUP) ? 4 : 0;
+}
+
+inline size_t env::limits::value_min(value_mode mode) noexcept {
+  return value_min(MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::value_max(intptr_t pagesize, MDBX_db_flags_t flags) {
+  const intptr_t result = mdbx_limits_valsize_max(pagesize, flags);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::value_max(intptr_t pagesize, value_mode mode) {
+  return value_max(pagesize, MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::value_max(const env &env, MDBX_db_flags_t flags) {
+  const intptr_t result = mdbx_env_get_maxvalsize_ex(env, flags);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline size_t env::limits::value_max(const env &env, value_mode mode) {
+  return value_max(env, MDBX_db_flags_t(mode));
+}
+
+inline size_t env::limits::transaction_size_max(intptr_t pagesize) {
+  const intptr_t result = mdbx_limits_txnsize_max(pagesize);
+  if (result < 0)
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_EINVAL);
+  return static_cast<size_t>(result);
+}
+
+inline env::operate_parameters env::get_operation_parameters() const {
+  return env::operate_parameters(*this);
+}
+
+inline env::mode env::get_mode() const {
+  return operate_parameters::mode_from_flags(get_flags());
+}
+
+inline env::durability env::get_durability() const {
+  return env::operate_parameters::durability_from_flags(get_flags());
+}
+
+inline env::reclaiming_options env::get_reclaiming() const {
+  return env::operate_parameters::reclaiming_from_flags(get_flags());
+}
+
+inline env::operate_options env::get_options() const {
+  return env::operate_parameters::options_from_flags(get_flags());
+}
+
+inline env::stat env::get_stat() const {
+  env::stat r;
+  error::success_or_throw(::mdbx_env_stat_ex(handle_, nullptr, &r, sizeof(r)));
+  return r;
+}
+
+inline env::stat env::get_stat(const txn &txn) const {
+  env::stat r;
+  error::success_or_throw(::mdbx_env_stat_ex(handle_, txn, &r, sizeof(r)));
+  return r;
+}
+
+inline env::info env::get_info() const {
+  env::info r;
+  error::success_or_throw(::mdbx_env_info_ex(handle_, nullptr, &r, sizeof(r)));
+  return r;
+}
+
+inline env::info env::get_info(const txn &txn) const {
+  env::info r;
+  error::success_or_throw(::mdbx_env_info_ex(handle_, txn, &r, sizeof(r)));
+  return r;
+}
+
+inline filehandle env::get_filehandle() const {
+  filehandle fd;
+  error::success_or_throw(::mdbx_env_get_fd(handle_, &fd));
+  return fd;
+}
+
+inline MDBX_env_flags_t env::get_flags() const {
+  unsigned bits;
+  error::success_or_throw(::mdbx_env_get_flags(handle_, &bits));
+  return MDBX_env_flags_t(bits);
+}
+
+inline unsigned env::max_readers() const {
+  unsigned r;
+  error::success_or_throw(::mdbx_env_get_maxreaders(handle_, &r));
+  return r;
+}
+
+inline unsigned env::max_maps() const {
+  unsigned r;
+  error::success_or_throw(::mdbx_env_get_maxdbs(handle_, &r));
+  return r;
+}
+
+inline void *env::get_context() const noexcept {
+  return mdbx_env_get_userctx(handle_);
+}
+
+inline env &env::set_context(void *ptr) {
+  error::success_or_throw(::mdbx_env_set_userctx(handle_, ptr));
+  return *this;
+}
+
+inline env &env::set_sync_threshold(size_t bytes) {
+  error::success_or_throw(::mdbx_env_set_syncbytes(handle_, bytes));
+  return *this;
+}
+
+inline env &env::set_sync_period(unsigned seconds_16dot16) {
+  error::success_or_throw(::mdbx_env_set_syncperiod(handle_, seconds_16dot16));
+  return *this;
+}
+
+inline env &env::set_sync_period(double seconds) {
+  return set_sync_period(unsigned(seconds * 65536));
+}
+
+inline env &env::alter_flags(MDBX_env_flags_t flags, bool on_off) {
+  error::success_or_throw(::mdbx_env_set_flags(handle_, flags, on_off));
+  return *this;
+}
+
+inline env &env::set_geometry(const geometry &geo) {
+  error::success_or_throw(::mdbx_env_set_geometry(
+      handle_, geo.size_lower, geo.size_now, geo.size_upper, geo.growth_step,
+      geo.shrink_threshold, geo.pagesize));
+  return *this;
+}
+
+inline bool env::sync_to_disk(bool force, bool nonblock) {
+  const int err = ::mdbx_env_sync_ex(handle_, force, nonblock);
+  switch (err) {
+  case MDBX_SUCCESS /* flush done */:
+  case MDBX_RESULT_TRUE /* no data pending for flush to disk */:
+    return true;
+  case MDBX_BUSY /* the environment is used by other thread */:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline void env::close_map(const map_handle &handle) {
+  error::success_or_throw(::mdbx_dbi_close(*this, handle.dbi));
+}
+
+MDBX_CXX11_CONSTEXPR
+env::reader_info::reader_info(int slot, mdbx_pid_t pid, mdbx_tid_t thread,
+                              uint64_t txnid, uint64_t lag, size_t used,
+                              size_t retained) noexcept
+    : slot(slot), pid(pid), thread(thread), transaction_id(txnid),
+      transaction_lag(lag), bytes_used(used), bytes_retained(retained) {}
+
+template <typename VISITOR>
+inline int env::enumerate_readers(VISITOR &visitor) {
+  struct reader_visitor_thunk : public exception_thunk {
+    VISITOR &visitor_;
+    static int cb(void *ctx, int number, int slot, mdbx_pid_t pid,
+                  mdbx_tid_t thread, uint64_t txnid, uint64_t lag, size_t used,
+                  size_t retained) noexcept {
+      reader_visitor_thunk *thunk = static_cast<reader_visitor_thunk *>(ctx);
+      assert(thunk->is_clean());
+      try {
+        const reader_info info(slot, pid, thread, txnid, lag, used, retained);
+        return loop_control(thunk->visitor_(info, number));
+      } catch (... /* capture any exception to rethrow it over C code */) {
+        thunk->capture();
+        return loop_control::exit_loop;
+      }
+    }
+    MDBX_CXX11_CONSTEXPR reader_visitor_thunk(VISITOR &visitor) noexcept
+        : visitor_(visitor) {}
+  };
+  reader_visitor_thunk thunk(visitor);
+  const auto rc = ::mdbx_reader_list(*this, thunk.cb, &thunk);
+  thunk.rethrow_captured();
+  return rc;
+}
+
+inline unsigned env::check_readers() {
+  int dead_count;
+  error::throw_on_failure(::mdbx_reader_check(*this, &dead_count));
+  assert(dead_count >= 0);
+  return static_cast<unsigned>(dead_count);
+}
+
+inline env &env::set_HandleSlowReaders(MDBX_hsr_func *cb) {
+  error::success_or_throw(::mdbx_env_set_hsr(handle_, cb));
+  return *this;
+}
+
+inline MDBX_hsr_func *env::get_HandleSlowReaders() const noexcept {
+  return ::mdbx_env_get_hsr(handle_);
+}
+
+inline txn_managed env::start_read() const {
+  ::MDBX_txn *ptr;
+  error::success_or_throw(
+      ::mdbx_txn_begin(handle_, nullptr, MDBX_TXN_RDONLY, &ptr));
+  assert(ptr != nullptr);
+  return txn_managed(ptr);
+}
+
+inline txn_managed env::prepare_read() const {
+  ::MDBX_txn *ptr;
+  error::success_or_throw(
+      ::mdbx_txn_begin(handle_, nullptr, MDBX_TXN_RDONLY_PREPARE, &ptr));
+  assert(ptr != nullptr);
+  return txn_managed(ptr);
+}
+
+inline txn_managed env::start_write(bool dont_wait) {
+  ::MDBX_txn *ptr;
+  error::success_or_throw(::mdbx_txn_begin(
+      handle_, nullptr, dont_wait ? MDBX_TXN_TRY : MDBX_TXN_READWRITE, &ptr));
+  assert(ptr != nullptr);
+  return txn_managed(ptr);
+}
+
+inline txn_managed env::try_start_write() { return start_write(true); }
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR txn::txn(MDBX_txn *ptr) noexcept : handle_(ptr) {}
+
+inline txn &txn::operator=(txn &&other) noexcept {
+  handle_ = other.handle_;
+  other.handle_ = nullptr;
+  return *this;
+}
+
+inline txn::txn(txn &&other) noexcept : handle_(other.handle_) {
+  other.handle_ = nullptr;
+}
+
+inline txn::~txn() noexcept {
+#ifndef NDEBUG
+  handle_ = reinterpret_cast<MDBX_txn *>(uintptr_t(0xDeadBeef));
+#endif
+}
+
+MDBX_CXX14_CONSTEXPR txn::operator bool() const noexcept {
+  return handle_ != nullptr;
+}
+
+MDBX_CXX14_CONSTEXPR txn::operator const MDBX_txn *() const { return handle_; }
+
+MDBX_CXX14_CONSTEXPR txn::operator MDBX_txn *() { return handle_; }
+
+MDBX_CXX11_CONSTEXPR bool operator==(const txn &a, const txn &b) noexcept {
+  return a.handle_ == b.handle_;
+}
+
+MDBX_CXX11_CONSTEXPR bool operator!=(const txn &a, const txn &b) noexcept {
+  return a.handle_ != b.handle_;
+}
+
+inline bool txn::is_dirty(const void *ptr) const {
+  int err = ::mdbx_is_dirty(handle_, ptr);
+  switch (err) {
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  case MDBX_RESULT_TRUE:
+    return true;
+  case MDBX_RESULT_FALSE:
+    return false;
+  }
+}
+
+inline ::mdbx::env txn::env() const noexcept { return ::mdbx_txn_env(handle_); }
+
+inline MDBX_txn_flags_t txn::flags() const {
+  const int bits = mdbx_txn_flags(handle_);
+  error::throw_on_failure((bits != -1) ? MDBX_SUCCESS : MDBX_BAD_TXN);
+  return static_cast<MDBX_txn_flags_t>(bits);
+}
+
+inline uint64_t txn::id() const {
+  const uint64_t txnid = mdbx_txn_id(handle_);
+  error::throw_on_failure(txnid ? MDBX_SUCCESS : MDBX_BAD_TXN);
+  return txnid;
+}
+
+inline void txn::reset_reading() {
+  error::success_or_throw(::mdbx_txn_reset(handle_));
+}
+
+inline void txn::renew_reading() {
+  error::success_or_throw(::mdbx_txn_renew(handle_));
+}
+
+inline txn::info txn::get_info(bool scan_reader_lock_table) const {
+  txn::info r;
+  error::success_or_throw(::mdbx_txn_info(handle_, &r, scan_reader_lock_table));
+  return r;
+}
+
+inline cursor_managed txn::open_cursor(map_handle map) {
+  MDBX_cursor *ptr;
+  error::success_or_throw(::mdbx_cursor_open(handle_, map.dbi, &ptr));
+  return cursor_managed(ptr);
+}
+
+inline ::mdbx::map_handle
+txn::open_map(const char *name, const ::mdbx::key_mode key_mode,
+              const ::mdbx::value_mode value_mode) const {
+  ::mdbx::map_handle map;
+  error::success_or_throw(::mdbx_dbi_open(
+      handle_, name, MDBX_db_flags_t(key_mode) | MDBX_db_flags_t(value_mode),
+      &map.dbi));
+  assert(map.dbi != 0);
+  return map;
+}
+
+inline ::mdbx::map_handle
+txn::open_map(const ::std::string &name, const ::mdbx::key_mode key_mode,
+              const ::mdbx::value_mode value_mode) const {
+  return open_map(name.c_str(), key_mode, value_mode);
+}
+
+inline ::mdbx::map_handle txn::create_map(const char *name,
+                                          const ::mdbx::key_mode key_mode,
+                                          const ::mdbx::value_mode value_mode) {
+  ::mdbx::map_handle map;
+  error::success_or_throw(::mdbx_dbi_open(
+      handle_, name,
+      MDBX_CREATE | MDBX_db_flags_t(key_mode) | MDBX_db_flags_t(value_mode),
+      &map.dbi));
+  assert(map.dbi != 0);
+  return map;
+}
+
+inline ::mdbx::map_handle txn::create_map(const ::std::string &name,
+                                          const ::mdbx::key_mode key_mode,
+                                          const ::mdbx::value_mode value_mode) {
+  return create_map(name.c_str(), key_mode, value_mode);
+}
+
+inline void txn::drop_map(map_handle map) {
+  error::success_or_throw(::mdbx_drop(handle_, map.dbi, true));
+}
+
+inline bool txn::drop_map(const ::std::string &name, bool throw_if_absent) {
+  return drop_map(name.c_str(), throw_if_absent);
+}
+
+inline void txn::clear_map(map_handle map) {
+  error::success_or_throw(::mdbx_drop(handle_, map.dbi, false));
+}
+
+inline bool txn::clear_map(const ::std::string &name, bool throw_if_absent) {
+  return clear_map(name.c_str(), throw_if_absent);
+}
+
+inline txn::map_stat txn::get_map_stat(map_handle map) const {
+  txn::map_stat r;
+  error::success_or_throw(::mdbx_dbi_stat(handle_, map.dbi, &r, sizeof(r)));
+  return r;
+}
+
+inline uint32_t txn::get_tree_deepmask(map_handle map) const {
+  uint32_t r;
+  error::success_or_throw(::mdbx_dbi_dupsort_depthmask(handle_, map.dbi, &r));
+  return r;
+}
+
+inline map_handle::info txn::get_handle_info(map_handle map) const {
+  unsigned flags, state;
+  error::success_or_throw(
+      ::mdbx_dbi_flags_ex(handle_, map.dbi, &flags, &state));
+  return map_handle::info(MDBX_db_flags_t(flags), MDBX_dbi_state_t(state));
+}
+
+inline txn &txn::put_canary(const txn::canary &canary) {
+  error::success_or_throw(::mdbx_canary_put(handle_, &canary));
+  return *this;
+}
+
+inline txn::canary txn::get_canary() const {
+  txn::canary r;
+  error::success_or_throw(::mdbx_canary_get(handle_, &r));
+  return r;
+}
+
+inline uint64_t txn::sequence(map_handle map) const {
+  uint64_t result;
+  error::success_or_throw(::mdbx_dbi_sequence(handle_, map.dbi, &result, 0));
+  return result;
+}
+
+inline uint64_t txn::sequence(map_handle map, uint64_t increment) {
+  uint64_t result;
+  error::success_or_throw(
+      ::mdbx_dbi_sequence(handle_, map.dbi, &result, increment));
+  return result;
+}
+
+inline int txn::compare_keys(map_handle map, const slice &a,
+                             const slice &b) const noexcept {
+  return ::mdbx_cmp(handle_, map.dbi, &a, &b);
+}
+
+inline int txn::compare_values(map_handle map, const slice &a,
+                               const slice &b) const noexcept {
+  return ::mdbx_dcmp(handle_, map.dbi, &a, &b);
+}
+
+inline int txn::compare_keys(map_handle map, const pair &a,
+                             const pair &b) const noexcept {
+  return compare_keys(map, a.key, b.key);
+}
+
+inline int txn::compare_values(map_handle map, const pair &a,
+                               const pair &b) const noexcept {
+  return compare_values(map, a.value, b.value);
+}
+
+inline slice txn::get(map_handle map, const slice &key) const {
+  slice result;
+  error::success_or_throw(::mdbx_get(handle_, map.dbi, &key, &result));
+  return result;
+}
+
+inline slice txn::get(map_handle map, slice key, size_t &values_count) const {
+  slice result;
+  error::success_or_throw(
+      ::mdbx_get_ex(handle_, map.dbi, &key, &result, &values_count));
+  return result;
+}
+
+inline slice txn::get(map_handle map, const slice &key,
+                      const slice &value_at_absence) const {
+  slice result;
+  const int err = ::mdbx_get(handle_, map.dbi, &key, &result);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return result;
+  case MDBX_NOTFOUND:
+    return value_at_absence;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline slice txn::get(map_handle map, slice key, size_t &values_count,
+                      const slice &value_at_absence) const {
+  slice result;
+  const int err = ::mdbx_get_ex(handle_, map.dbi, &key, &result, &values_count);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return result;
+  case MDBX_NOTFOUND:
+    return value_at_absence;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline pair_result txn::get_equal_or_great(map_handle map,
+                                           const slice &key) const {
+  pair result(key, slice());
+  bool exact = !error::boolean_or_throw(
+      ::mdbx_get_equal_or_great(handle_, map.dbi, &result.key, &result.value));
+  return pair_result(result.key, result.value, exact);
+}
+
+inline pair_result
+txn::get_equal_or_great(map_handle map, const slice &key,
+                        const slice &value_at_absence) const {
+  pair result{key, slice()};
+  const int err =
+      ::mdbx_get_equal_or_great(handle_, map.dbi, &result.key, &result.value);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return pair_result{result.key, result.value, true};
+  case MDBX_RESULT_TRUE:
+    return pair_result{result.key, result.value, false};
+  case MDBX_NOTFOUND:
+    return pair_result{key, value_at_absence, false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline MDBX_error_t txn::put(map_handle map, const slice &key, slice *value,
+                             MDBX_put_flags_t flags) noexcept {
+  return MDBX_error_t(::mdbx_put(handle_, map.dbi, &key, value, flags));
+}
+
+inline void txn::put(map_handle map, const slice &key, slice value,
+                     put_mode mode) noexcept {
+  error::success_or_throw(put(map, key, &value, MDBX_put_flags_t(mode)));
+}
+
+inline void txn::insert(map_handle map, const slice &key, slice value) {
+  error::success_or_throw(
+      put(map, key, &value /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique)));
+}
+
+inline value_result txn::try_insert(map_handle map, const slice &key,
+                                    slice value) {
+  const int err =
+      put(map, key, &value /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique));
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{slice(), true};
+  case MDBX_KEYEXIST:
+    return value_result{value, false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline slice txn::insert_reserve(map_handle map, const slice &key,
+                                 size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(
+      put(map, key, &result /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique) | MDBX_RESERVE));
+  return result;
+}
+
+inline value_result txn::try_insert_reserve(map_handle map, const slice &key,
+                                            size_t value_length) {
+  slice result(nullptr, value_length);
+  const int err =
+      put(map, key, &result /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique) | MDBX_RESERVE);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{result, true};
+  case MDBX_KEYEXIST:
+    return value_result{result, false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline void txn::upsert(map_handle map, const slice &key, const slice &value) {
+  error::success_or_throw(put(map, key, const_cast<slice *>(&value),
+                              MDBX_put_flags_t(put_mode::upsert)));
+}
+
+inline slice txn::upsert_reserve(map_handle map, const slice &key,
+                                 size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(put(
+      map, key, &result, MDBX_put_flags_t(put_mode::upsert) | MDBX_RESERVE));
+  return result;
+}
+
+inline void txn::update(map_handle map, const slice &key, const slice &value) {
+  error::success_or_throw(put(map, key, const_cast<slice *>(&value),
+                              MDBX_put_flags_t(put_mode::update)));
+}
+
+inline bool txn::try_update(map_handle map, const slice &key,
+                            const slice &value) {
+  const int err = put(map, key, const_cast<slice *>(&value),
+                      MDBX_put_flags_t(put_mode::update));
+  switch (err) {
+  case MDBX_SUCCESS:
+    return true;
+  case MDBX_NOTFOUND:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline slice txn::update_reserve(map_handle map, const slice &key,
+                                 size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(put(
+      map, key, &result, MDBX_put_flags_t(put_mode::update) | MDBX_RESERVE));
+  return result;
+}
+
+inline value_result txn::try_update_reserve(map_handle map, const slice &key,
+                                            size_t value_length) {
+  slice result(nullptr, value_length);
+  const int err =
+      put(map, key, &result, MDBX_put_flags_t(put_mode::update) | MDBX_RESERVE);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{result, true};
+  case MDBX_NOTFOUND:
+    return value_result{slice(), false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline bool txn::erase(map_handle map, const slice &key) {
+  const int err = ::mdbx_del(handle_, map.dbi, &key, nullptr);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return true;
+  case MDBX_NOTFOUND:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline bool txn::erase(map_handle map, const slice &key, const slice &value) {
+  const int err = ::mdbx_del(handle_, map.dbi, &key, &value);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return true;
+  case MDBX_NOTFOUND:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline void txn::replace(map_handle map, const slice &key, slice old_value,
+                         const slice &new_value) {
+  error::success_or_throw(::mdbx_replace_ex(
+      handle_, map.dbi, &key, const_cast<slice *>(&new_value), &old_value,
+      MDBX_CURRENT | MDBX_NOOVERWRITE, nullptr, nullptr));
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR> txn::extract(map_handle map, const slice &key,
+                                      const ALLOCATOR &allocator) {
+  typename buffer<ALLOCATOR>::data_preserver result(allocator);
+  error::success_or_throw(::mdbx_replace_ex(handle_, map.dbi, &key, nullptr,
+                                            &result.slice_, MDBX_CURRENT,
+                                            result, &result),
+                          result);
+  return result;
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR> txn::replace(map_handle map, const slice &key,
+                                      const slice &new_value,
+                                      const ALLOCATOR &allocator) {
+  typename buffer<ALLOCATOR>::data_preserver result(allocator);
+  error::success_or_throw(
+      ::mdbx_replace_ex(handle_, map.dbi, &key, const_cast<slice *>(&new_value),
+                        &result.slice_, MDBX_CURRENT, result, &result),
+      result);
+  return result;
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR> txn::replace_reserve(map_handle map, const slice &key,
+                                              slice &new_value,
+                                              const ALLOCATOR &allocator) {
+  typename buffer<ALLOCATOR>::data_preserver result(allocator);
+  error::success_or_throw(
+      ::mdbx_replace_ex(handle_, map.dbi, &key, &new_value, &result.slice_,
+                        MDBX_CURRENT | MDBX_RESERVE, result, &result),
+      result);
+  return result;
+}
+
+inline void txn::append(map_handle map, const slice &key, const slice &value,
+                        bool multivalue_order_preserved) {
+  error::success_or_throw(::mdbx_put(
+      handle_, map.dbi, const_cast<slice *>(&key), const_cast<slice *>(&value),
+      multivalue_order_preserved ? (MDBX_APPEND | MDBX_APPENDDUP)
+                                 : MDBX_APPEND));
+}
+
+inline size_t txn::put_multiple(map_handle map, const slice &key,
+                                const size_t value_length,
+                                const void *values_array, size_t values_count,
+                                put_mode mode, bool allow_partial) {
+  MDBX_val args[2] = {{const_cast<void *>(values_array), value_length},
+                      {nullptr, values_count}};
+  const int err = ::mdbx_put(handle_, map.dbi, const_cast<slice *>(&key), args,
+                             MDBX_put_flags_t(mode) | MDBX_MULTIPLE);
+  switch (err) {
+  case MDBX_SUCCESS:
+    MDBX_CXX20_LIKELY break;
+  case MDBX_KEYEXIST:
+    if (allow_partial)
+      break;
+    mdbx_txn_break(handle_);
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+  return args[1].iov_len /* done item count */;
+}
+
+inline ptrdiff_t txn::estimate(map_handle map, pair from, pair to) const {
+  ptrdiff_t result;
+  error::success_or_throw(mdbx_estimate_range(
+      handle_, map.dbi, &from.key, &from.value, &to.key, &to.value, &result));
+  return result;
+}
+
+inline ptrdiff_t txn::estimate(map_handle map, slice from, slice to) const {
+  ptrdiff_t result;
+  error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, &from, nullptr,
+                                              &to, nullptr, &result));
+  return result;
+}
+
+inline ptrdiff_t txn::estimate_from_first(map_handle map, slice to) const {
+  ptrdiff_t result;
+  error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, nullptr,
+                                              nullptr, &to, nullptr, &result));
+  return result;
+}
+
+inline ptrdiff_t txn::estimate_to_last(map_handle map, slice from) const {
+  ptrdiff_t result;
+  error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, &from, nullptr,
+                                              nullptr, nullptr, &result));
+  return result;
+}
+
+//------------------------------------------------------------------------------
+
+MDBX_CXX11_CONSTEXPR cursor::cursor(MDBX_cursor *ptr) noexcept : handle_(ptr) {}
+
+inline cursor &cursor::operator=(cursor &&other) noexcept {
+  handle_ = other.handle_;
+  other.handle_ = nullptr;
+  return *this;
+}
+
+inline cursor::cursor(cursor &&other) noexcept : handle_(other.handle_) {
+  other.handle_ = nullptr;
+}
+
+inline cursor::~cursor() noexcept {
+#ifndef NDEBUG
+  handle_ = reinterpret_cast<MDBX_cursor *>(uintptr_t(0xDeadBeef));
+#endif
+}
+
+MDBX_CXX14_CONSTEXPR cursor::operator bool() const noexcept {
+  return handle_ != nullptr;
+}
+
+MDBX_CXX14_CONSTEXPR cursor::operator const MDBX_cursor *() const {
+  return handle_;
+}
+
+MDBX_CXX14_CONSTEXPR cursor::operator MDBX_cursor *() { return handle_; }
+
+MDBX_CXX11_CONSTEXPR bool operator==(const cursor &a,
+                                     const cursor &b) noexcept {
+  return a.handle_ == b.handle_;
+}
+
+MDBX_CXX11_CONSTEXPR bool operator!=(const cursor &a,
+                                     const cursor &b) noexcept {
+  return a.handle_ != b.handle_;
+}
+
+inline cursor::move_result::move_result(const cursor &cursor,
+                                        bool throw_notfound)
+    : pair_result(key, value, false) {
+  done = cursor.move(get_current, &key, &value, throw_notfound);
+}
+
+inline cursor::move_result::move_result(cursor &cursor,
+                                        move_operation operation,
+                                        bool throw_notfound)
+    : pair_result(key, value, false) {
+  done = cursor.move(operation, &key, &value, throw_notfound);
+}
+
+inline cursor::move_result::move_result(cursor &cursor,
+                                        move_operation operation,
+                                        const slice &key, bool throw_notfound)
+    : pair_result(key, slice(), false) {
+  this->done = cursor.move(operation, &this->key, &this->value, throw_notfound);
+}
+
+inline cursor::move_result::move_result(cursor &cursor,
+                                        move_operation operation,
+                                        const slice &key, const slice &value,
+                                        bool throw_notfound)
+    : pair_result(key, value, false) {
+  this->done = cursor.move(operation, &this->key, &this->value, throw_notfound);
+}
+
+inline bool cursor::move(move_operation operation, MDBX_val *key,
+                         MDBX_val *value, bool throw_notfound) const {
+  const int err =
+      ::mdbx_cursor_get(handle_, key, value, MDBX_cursor_op(operation));
+  switch (err) {
+  case MDBX_SUCCESS:
+    MDBX_CXX20_LIKELY return true;
+  case MDBX_NOTFOUND:
+    if (!throw_notfound)
+      return false;
+    MDBX_CXX17_FALLTHROUGH /* fallthrough */;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline ptrdiff_t cursor::estimate(move_operation operation, MDBX_val *key,
+                                  MDBX_val *value) const {
+  ptrdiff_t result;
+  error::success_or_throw(::mdbx_estimate_move(
+      *this, key, value, MDBX_cursor_op(operation), &result));
+  return result;
+}
+
+inline ptrdiff_t estimate(const cursor &from, const cursor &to) {
+  ptrdiff_t result;
+  error::success_or_throw(mdbx_estimate_distance(from, to, &result));
+  return result;
+}
+
+inline cursor::move_result cursor::move(move_operation operation,
+                                        bool throw_notfound) {
+  return move_result(*this, operation, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_first(bool throw_notfound) {
+  return move(first, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_previous(bool throw_notfound) {
+  return move(previous, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_previous_last_multi(bool throw_notfound) {
+  return move(multi_prevkey_lastvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_current_first_multi(bool throw_notfound) {
+  return move(multi_currentkey_firstvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_current_prev_multi(bool throw_notfound) {
+  return move(multi_currentkey_prevvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::current(bool throw_notfound) const {
+  return move_result(*this, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_current_next_multi(bool throw_notfound) {
+  return move(multi_currentkey_nextvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_current_last_multi(bool throw_notfound) {
+  return move(multi_currentkey_lastvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_next_first_multi(bool throw_notfound) {
+  return move(multi_nextkey_firstvalue, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_next(bool throw_notfound) {
+  return move(next, throw_notfound);
+}
+
+inline cursor::move_result cursor::to_last(bool throw_notfound) {
+  return move(last, throw_notfound);
+}
+
+inline cursor::move_result cursor::move(move_operation operation,
+                                        const slice &key, bool throw_notfound) {
+  return move_result(*this, operation, key, throw_notfound);
+}
+
+inline cursor::move_result cursor::find(const slice &key, bool throw_notfound) {
+  return move(key_exact, key, throw_notfound);
+}
+
+inline cursor::move_result cursor::lower_bound(const slice &key,
+                                               bool throw_notfound) {
+  return move(key_lowerbound, key, throw_notfound);
+}
+
+inline cursor::move_result cursor::move(move_operation operation,
+                                        const slice &key, const slice &value,
+                                        bool throw_notfound) {
+  return move_result(*this, operation, key, value, throw_notfound);
+}
+
+inline cursor::move_result cursor::find_multivalue(const slice &key,
+                                                   const slice &value,
+                                                   bool throw_notfound) {
+  return move(key_exact, key, value, throw_notfound);
+}
+
+inline cursor::move_result cursor::lower_bound_multivalue(const slice &key,
+                                                          const slice &value,
+                                                          bool throw_notfound) {
+  return move(multi_exactkey_lowerboundvalue, key, value, throw_notfound);
+}
+
+inline bool cursor::seek(const slice &key) {
+  return move(find_key, const_cast<slice *>(&key), nullptr, false);
+}
+
+inline bool cursor::move(move_operation operation, slice &key, slice &value,
+                         bool throw_notfound) {
+  return move(operation, &key, &value, throw_notfound);
+}
+
+inline size_t cursor::count_multivalue() const {
+  size_t result;
+  error::success_or_throw(::mdbx_cursor_count(*this, &result));
+  return result;
+}
+
+inline bool cursor::eof() const {
+  return error::boolean_or_throw(::mdbx_cursor_eof(*this));
+}
+
+inline bool cursor::on_first() const {
+  return error::boolean_or_throw(::mdbx_cursor_on_first(*this));
+}
+
+inline bool cursor::on_last() const {
+  return error::boolean_or_throw(::mdbx_cursor_on_last(*this));
+}
+
+inline ptrdiff_t cursor::estimate(slice key, slice value) const {
+  return estimate(multi_exactkey_lowerboundvalue, &key, &value);
+}
+
+inline ptrdiff_t cursor::estimate(slice key) const {
+  return estimate(key_lowerbound, &key, nullptr);
+}
+
+inline ptrdiff_t cursor::estimate(move_operation operation) const {
+  slice unused_key;
+  return estimate(operation, &unused_key, nullptr);
+}
+
+inline void cursor::renew(::mdbx::txn &txn) {
+  error::success_or_throw(::mdbx_cursor_renew(txn, handle_));
+}
+
+inline void cursor::bind(::mdbx::txn &txn, ::mdbx::map_handle map_handle) {
+  error::success_or_throw(::mdbx_cursor_bind(txn, handle_, map_handle.dbi));
+}
+
+inline txn cursor::txn() const {
+  MDBX_txn *txn = ::mdbx_cursor_txn(handle_);
+  error::throw_on_nullptr(txn, MDBX_EINVAL);
+  return ::mdbx::txn(txn);
+}
+
+inline map_handle cursor::map() const {
+  const MDBX_dbi dbi = ::mdbx_cursor_dbi(handle_);
+  if (MDBX_UNLIKELY(dbi > MDBX_MAX_DBI))
+    error::throw_exception(MDBX_EINVAL);
+  return map_handle(dbi);
+}
+
+inline MDBX_error_t cursor::put(const slice &key, slice *value,
+                                MDBX_put_flags_t flags) noexcept {
+  return MDBX_error_t(::mdbx_cursor_put(handle_, &key, value, flags));
+}
+
+inline void cursor::insert(const slice &key, slice value) {
+  error::success_or_throw(
+      put(key, &value /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique)));
+}
+
+inline value_result cursor::try_insert(const slice &key, slice value) {
+  const int err =
+      put(key, &value /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique));
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{slice(), true};
+  case MDBX_KEYEXIST:
+    return value_result{value, false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline slice cursor::insert_reserve(const slice &key, size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(
+      put(key, &result /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique) | MDBX_RESERVE));
+  return result;
+}
+
+inline value_result cursor::try_insert_reserve(const slice &key,
+                                               size_t value_length) {
+  slice result(nullptr, value_length);
+  const int err =
+      put(key, &result /* takes the present value in case MDBX_KEYEXIST */,
+          MDBX_put_flags_t(put_mode::insert_unique) | MDBX_RESERVE);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{result, true};
+  case MDBX_KEYEXIST:
+    return value_result{result, false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline void cursor::upsert(const slice &key, const slice &value) {
+  error::success_or_throw(put(key, const_cast<slice *>(&value),
+                              MDBX_put_flags_t(put_mode::upsert)));
+}
+
+inline slice cursor::upsert_reserve(const slice &key, size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(
+      put(key, &result, MDBX_put_flags_t(put_mode::upsert) | MDBX_RESERVE));
+  return result;
+}
+
+inline void cursor::update(const slice &key, const slice &value) {
+  error::success_or_throw(put(key, const_cast<slice *>(&value),
+                              MDBX_put_flags_t(put_mode::update)));
+}
+
+inline bool cursor::try_update(const slice &key, const slice &value) {
+  const int err =
+      put(key, const_cast<slice *>(&value), MDBX_put_flags_t(put_mode::update));
+  switch (err) {
+  case MDBX_SUCCESS:
+    return true;
+  case MDBX_NOTFOUND:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline slice cursor::update_reserve(const slice &key, size_t value_length) {
+  slice result(nullptr, value_length);
+  error::success_or_throw(
+      put(key, &result, MDBX_put_flags_t(put_mode::update) | MDBX_RESERVE));
+  return result;
+}
+
+inline value_result cursor::try_update_reserve(const slice &key,
+                                               size_t value_length) {
+  slice result(nullptr, value_length);
+  const int err =
+      put(key, &result, MDBX_put_flags_t(put_mode::update) | MDBX_RESERVE);
+  switch (err) {
+  case MDBX_SUCCESS:
+    return value_result{result, true};
+  case MDBX_NOTFOUND:
+    return value_result{slice(), false};
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+inline bool cursor::erase(bool whole_multivalue) {
+  const int err = ::mdbx_cursor_del(handle_, whole_multivalue ? MDBX_ALLDUPS
+                                                              : MDBX_CURRENT);
+  switch (err) {
+  case MDBX_SUCCESS:
+    MDBX_CXX20_LIKELY return true;
+  case MDBX_NOTFOUND:
+    return false;
+  default:
+    MDBX_CXX20_UNLIKELY error::throw_exception(err);
+  }
+}
+
+//------------------------------------------------------------------------------
+
+inline cursor_managed::cursor_managed()
+    : cursor_managed(::mdbx_cursor_create(nullptr)) {
+  if (MDBX_UNLIKELY(!handle_))
+    MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_ENOMEM);
+}
+
+//------------------------------------------------------------------------------
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR>::buffer(const txn &txn, const ::mdbx::slice &src,
+                                 const ALLOCATOR &allocator)
+    : buffer(src, !txn.is_dirty(src.data()), allocator) {}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR>::buffer(size_t head_room, size_t tail_room,
+                                 const ALLOCATOR &allocator)
+    : silo_(allocator) {
+  if (MDBX_UNLIKELY(head_room > max_length || tail_room > max_length ||
+                    head_room + tail_room > max_length))
+    throw_max_length_exceeded();
+  silo_.reserve(head_room + tail_room);
+  silo_.append(head_room, '\0');
+  slice_.iov_base = const_cast<char *>(silo_.data());
+  assert(slice_.iov_len == 0);
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR>::buffer(size_t capacity, const ALLOCATOR &allocator)
+    : silo_(allocator) {
+  silo_.reserve(check_length(capacity));
+  slice_.iov_base = const_cast<char *>(silo_.data());
+  assert(slice_.iov_len == 0);
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR>::buffer(size_t head_room, const ::mdbx::slice &src,
+                                 size_t tail_room, const ALLOCATOR &allocator)
+    : silo_(allocator) {
+  if (MDBX_UNLIKELY(head_room > max_length || tail_room > max_length ||
+                    head_room + tail_room > max_length - slice_.length()))
+    throw_max_length_exceeded();
+  silo_.reserve(head_room + src.length() + tail_room);
+  silo_.append(head_room, '\0');
+  silo_.append(src.char_ptr(), src.length());
+  slice_.iov_base = const_cast<char *>(silo_.data());
+  slice_.iov_len = src.length();
+}
+
+template <class ALLOCATOR>
+inline void buffer<ALLOCATOR>::reserve(size_t wanna_headroom,
+                                       size_t wanna_tailroom,
+                                       size_t shrink_threshold) {
+  if (MDBX_UNLIKELY(
+          wanna_headroom > max_length || wanna_tailroom > max_length ||
+          wanna_headroom + wanna_tailroom > max_length - slice_.length()))
+    throw_max_length_exceeded();
+
+  wanna_headroom = std::min(std::max(headroom(), wanna_headroom),
+                            wanna_headroom + shrink_threshold);
+  wanna_tailroom = std::min(std::max(tailroom(), wanna_tailroom),
+                            wanna_tailroom + shrink_threshold);
+  const auto wanna_capacity = wanna_headroom + slice_.length() + wanna_tailroom;
+  if (is_reference() || slice_.empty()) {
+    silo_.reserve(wanna_capacity);
+    silo_.resize(wanna_headroom);
+    silo_.append(slice_.char_ptr(), slice_.length());
+  } else {
+    const auto was_headroom = headroom();
+    if (was_headroom > wanna_headroom)
+      silo_.erase(wanna_headroom, was_headroom - wanna_headroom);
+    silo_.reserve(wanna_capacity);
+    if (was_headroom < wanna_headroom)
+      silo_.insert(was_headroom, wanna_headroom - was_headroom, '\0');
+  }
+  slice_.iov_base = const_cast<byte *>(silo_begin()) + wanna_headroom;
+  assert(headroom() >= wanna_headroom &&
+         headroom() <= wanna_headroom + shrink_threshold);
+  assert(tailroom() >= wanna_tailroom &&
+         tailroom() <= wanna_tailroom + shrink_threshold);
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR> &buffer<ALLOCATOR>::append(const void *src,
+                                                    size_t bytes) {
+  if (MDBX_UNLIKELY(tailroom() < check_length(bytes)))
+    reserve(0, bytes);
+  std::memcpy(static_cast<char *>(slice_.iov_base) + size(), src, bytes);
+  slice_.iov_len += bytes;
+  return *this;
+}
+
+template <class ALLOCATOR>
+inline buffer<ALLOCATOR> &buffer<ALLOCATOR>::add_header(const void *src,
+                                                        size_t bytes) {
+  if (MDBX_UNLIKELY(headroom() < check_length(bytes)))
+    reserve(bytes, 0);
+  slice_.iov_base =
+      std::memcpy(static_cast<char *>(slice_.iov_base) - bytes, src, bytes);
+  slice_.iov_len += bytes;
+  return *this;
+}
+
+template <class ALLOCATOR>
+inline void buffer<ALLOCATOR>::swap(buffer &other)
+#if defined(__cpp_noexcept_function_type) &&                                   \
+    __cpp_noexcept_function_type >= 201510L
+    noexcept(
+        std::allocator_traits<ALLOCATOR>::propagate_on_container_swap::value
+#if defined(__cpp_lib_allocator_traits_is_always_equal) &&                     \
+    __cpp_lib_allocator_traits_is_always_equal >= 201411L
+        || std::allocator_traits<ALLOCATOR>::is_always_equal::value
+#endif /* __cpp_lib_allocator_traits_is_always_equal */
+    )
+#endif /* __cpp_noexcept_function_type */
+{
+  if /* checking the equality of allocators to avoid UB */
+#if defined(__cpp_if_constexpr) && __cpp_if_constexpr >= 201606L
+      constexpr
+#endif
+      (!std::allocator_traits<ALLOCATOR>::propagate_on_container_swap::value
+#if defined(__cpp_lib_allocator_traits_is_always_equal) &&                     \
+    __cpp_lib_allocator_traits_is_always_equal >= 201411L
+       && !std::allocator_traits<ALLOCATOR>::is_always_equal::value
+#endif /* __cpp_lib_allocator_traits_is_always_equal */
+      ) {
+    if (MDBX_UNLIKELY(silo_.get_allocator() != other.silo_.get_allocator()))
+      throw std::bad_alloc();
+  }
+  silo_.swap(other.silo_);
+  slice_.swap(other.slice_);
+}
+
+template <class ALLOCATOR>
+inline int buffer<ALLOCATOR>::data_preserver::callback(void *context,
+                                                       MDBX_val *target,
+                                                       const void *src,
+                                                       size_t bytes) noexcept {
+  auto self = static_cast<data_preserver *>(context);
+  assert(self->is_clean());
+  assert(&self->data.slice_ == target);
+  (void)target;
+  try {
+    self->data.assign(src, bytes, false);
+    return MDBX_RESULT_FALSE;
+  } catch (... /* capture any exception to rethrow it over C code */) {
+    self->capture();
+    return MDBX_RESULT_TRUE;
+  }
+}
+
+} // namespace mdbx
+
+//------------------------------------------------------------------------------
+
+namespace std {
+
+inline string to_string(const mdbx::slice &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+template <class ALLOCATOR>
+inline string to_string(const mdbx::buffer<ALLOCATOR> &buffer) {
+  ostringstream out;
+  out << buffer;
+  return out.str();
+}
+
+inline string to_string(const mdbx::pair &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::geometry &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::operate_parameters &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::mode &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::durability &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::reclaiming_options &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env::operate_options &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::env_managed::create_parameters &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const ::MDBX_log_level_t &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const ::MDBX_debug_flags_t &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const mdbx::error &value) {
+  ostringstream out;
+  out << value;
+  return out.str();
+}
+
+inline string to_string(const ::MDBX_error_t &errcode) {
+  return to_string(mdbx::error(errcode));
+}
+
+template <> struct hash<mdbx::slice> {
+  MDBX_CXX14_CONSTEXPR size_t
+  operator()(mdbx::slice const &slice) const noexcept {
+    return slice.hash_value();
+  }
+};
+} // namespace std
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+/// @} end of C++ API
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx_chk.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx_chk.c
new file mode 100644
index 0000000000..a30003be28
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx_chk.c
@@ -0,0 +1,4818 @@
+/* mdbx_chk.c - memory-mapped database check tool */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#ifdef _MSC_VER
+#if _MSC_VER > 1800
+#pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#pragma warning(disable : 4996) /* The POSIX name is deprecated... */
+#endif                          /* _MSC_VER (warnings) */
+
+#define MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+
+typedef struct flagbit {
+  int bit;
+  const char *name;
+} flagbit;
+
+const flagbit dbflags[] = {{MDBX_DUPSORT, "dupsort"},
+                           {MDBX_INTEGERKEY, "integerkey"},
+                           {MDBX_REVERSEKEY, "reversekey"},
+                           {MDBX_DUPFIXED, "dupfixed"},
+                           {MDBX_REVERSEDUP, "reversedup"},
+                           {MDBX_INTEGERDUP, "integerdup"},
+                           {0, nullptr}};
+
+#if defined(_WIN32) || defined(_WIN64)
+/*
+ * POSIX getopt for Windows
+ *
+ * AT&T Public License
+ *
+ * Code given out at the 1985 UNIFORUM conference in Dallas.
+ */
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#endif /* _MSC_VER (warnings) */
+
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+/*----------------------------------------------------------------------------*/
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+int optind = 1;
+int optopt;
+char *optarg;
+
+int getopt(int argc, char *const argv[], const char *opts) {
+  static int sp = 1;
+  int c;
+  const char *cp;
+
+  if (sp == 1) {
+    if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
+      return EOF;
+    else if (strcmp(argv[optind], "--") == 0) {
+      optind++;
+      return EOF;
+    }
+  }
+  optopt = c = argv[optind][sp];
+  if (c == ':' || (cp = strchr(opts, c)) == NULL) {
+    fprintf(stderr, "%s: %s -- %c\n", argv[0], "illegal option", c);
+    if (argv[optind][++sp] == '\0') {
+      optind++;
+      sp = 1;
+    }
+    return '?';
+  }
+  if (*++cp == ':') {
+    if (argv[optind][sp + 1] != '\0')
+      optarg = &argv[optind++][sp + 1];
+    else if (++optind >= argc) {
+      fprintf(stderr, "%s: %s -- %c\n", argv[0], "option requires an argument",
+              c);
+      sp = 1;
+      return '?';
+    } else
+      optarg = argv[optind++];
+    sp = 1;
+  } else {
+    if (argv[optind][++sp] == '\0') {
+      sp = 1;
+      optind++;
+    }
+    optarg = NULL;
+  }
+  return c;
+}
+
+static volatile BOOL user_break;
+static BOOL WINAPI ConsoleBreakHandlerRoutine(DWORD dwCtrlType) {
+  (void)dwCtrlType;
+  user_break = 1;
+  return true;
+}
+
+static uint64_t GetMilliseconds(void) {
+  LARGE_INTEGER Counter, Frequency;
+  return (QueryPerformanceFrequency(&Frequency) &&
+          QueryPerformanceCounter(&Counter))
+             ? Counter.QuadPart * 1000ul / Frequency.QuadPart
+             : 0;
+}
+
+#else /* WINDOWS */
+
+static volatile sig_atomic_t user_break;
+static void signal_handler(int sig) {
+  (void)sig;
+  user_break = 1;
+}
+
+#endif /* !WINDOWS */
+
+#define EXIT_INTERRUPTED (EXIT_FAILURE + 4)
+#define EXIT_FAILURE_SYS (EXIT_FAILURE + 3)
+#define EXIT_FAILURE_MDBX (EXIT_FAILURE + 2)
+#define EXIT_FAILURE_CHECK_MAJOR (EXIT_FAILURE + 1)
+#define EXIT_FAILURE_CHECK_MINOR EXIT_FAILURE
+
+typedef struct {
+  const char *name;
+  struct {
+    uint64_t branch, large_count, large_volume, leaf;
+    uint64_t subleaf_dupsort, leaf_dupfixed, subleaf_dupfixed;
+    uint64_t total, empty, other;
+  } pages;
+  uint64_t payload_bytes;
+  uint64_t lost_bytes;
+} walk_dbi_t;
+
+struct {
+  short *pagemap;
+  uint64_t total_payload_bytes;
+  uint64_t pgcount;
+  walk_dbi_t
+      dbi[MDBX_MAX_DBI + CORE_DBS + /* account pseudo-entry for meta */ 1];
+} walk;
+
+#define dbi_free walk.dbi[FREE_DBI]
+#define dbi_main walk.dbi[MAIN_DBI]
+#define dbi_meta walk.dbi[CORE_DBS]
+
+int envflags = MDBX_RDONLY | MDBX_EXCLUSIVE;
+MDBX_env *env;
+MDBX_txn *txn;
+MDBX_envinfo envinfo;
+MDBX_stat envstat;
+size_t userdb_count, skipped_subdb;
+uint64_t total_unused_bytes, reclaimable_pages, gc_pages, alloc_pages,
+    unused_pages, backed_pages;
+unsigned verbose;
+bool ignore_wrong_order, quiet, dont_traversal;
+const char *only_subdb;
+int stuck_meta = -1;
+
+struct problem {
+  struct problem *pr_next;
+  size_t count;
+  const char *caption;
+};
+
+struct problem *problems_list;
+uint64_t total_problems;
+
+static void MDBX_PRINTF_ARGS(1, 2) print(const char *msg, ...) {
+  if (!quiet) {
+    va_list args;
+
+    fflush(stderr);
+    va_start(args, msg);
+    vfprintf(stdout, msg, args);
+    va_end(args);
+  }
+}
+
+static void va_log(MDBX_log_level_t level, const char *msg, va_list args) {
+  static const char *const prefixes[] = {
+      "!!!fatal: ",       " ! " /* error */,      " ~ " /* warning */,
+      "   " /* notice */, "   // " /* verbose */, "   //// " /* debug */,
+      "   ////// " /* trace */
+  };
+
+  FILE *out = stdout;
+  if (level <= MDBX_LOG_ERROR) {
+    total_problems++;
+    out = stderr;
+  }
+
+  if (!quiet && verbose + 1 >= (unsigned)level) {
+    fflush(nullptr);
+    fputs(prefixes[level], out);
+    vfprintf(out, msg, args);
+    if (msg[strlen(msg) - 1] != '\n')
+      fputc('\n', out);
+    fflush(nullptr);
+  }
+
+  if (level == MDBX_LOG_FATAL) {
+    exit(EXIT_FAILURE_MDBX);
+    abort();
+  }
+}
+
+static void MDBX_PRINTF_ARGS(1, 2) error(const char *msg, ...) {
+  va_list args;
+  va_start(args, msg);
+  va_log(MDBX_LOG_ERROR, msg, args);
+  va_end(args);
+}
+
+static void logger(MDBX_log_level_t level, const char *function, int line,
+                   const char *msg, va_list args) {
+  (void)line;
+  (void)function;
+  if (level < MDBX_LOG_EXTRA)
+    va_log(level, msg, args);
+}
+
+static int check_user_break(void) {
+  switch (user_break) {
+  case 0:
+    return MDBX_SUCCESS;
+  case 1:
+    print(" - interrupted by signal\n");
+    fflush(nullptr);
+    user_break = 2;
+  }
+  return MDBX_EINTR;
+}
+
+static void pagemap_cleanup(void) {
+  for (size_t i = CORE_DBS + /* account pseudo-entry for meta */ 1;
+       i < ARRAY_LENGTH(walk.dbi); ++i) {
+    if (walk.dbi[i].name) {
+      mdbx_free((void *)walk.dbi[i].name);
+      walk.dbi[i].name = nullptr;
+    }
+  }
+
+  mdbx_free(walk.pagemap);
+  walk.pagemap = nullptr;
+}
+
+static walk_dbi_t *pagemap_lookup_dbi(const char *dbi_name, bool silent) {
+  static walk_dbi_t *last;
+
+  if (dbi_name == MDBX_PGWALK_MAIN)
+    return &dbi_main;
+  if (dbi_name == MDBX_PGWALK_GC)
+    return &dbi_free;
+  if (dbi_name == MDBX_PGWALK_META)
+    return &dbi_meta;
+
+  if (last && strcmp(last->name, dbi_name) == 0)
+    return last;
+
+  walk_dbi_t *dbi = walk.dbi + CORE_DBS + /* account pseudo-entry for meta */ 1;
+  for (; dbi < ARRAY_END(walk.dbi) && dbi->name; ++dbi) {
+    if (strcmp(dbi->name, dbi_name) == 0)
+      return last = dbi;
+  }
+
+  if (verbose > 0 && !silent) {
+    print(" - found '%s' area\n", dbi_name);
+    fflush(nullptr);
+  }
+
+  if (dbi == ARRAY_END(walk.dbi))
+    return nullptr;
+
+  dbi->name = mdbx_strdup(dbi_name);
+  return last = dbi;
+}
+
+static void MDBX_PRINTF_ARGS(4, 5)
+    problem_add(const char *object, uint64_t entry_number, const char *msg,
+                const char *extra, ...) {
+  total_problems++;
+
+  if (!quiet) {
+    int need_fflush = 0;
+    struct problem *p;
+
+    for (p = problems_list; p; p = p->pr_next)
+      if (p->caption == msg)
+        break;
+
+    if (!p) {
+      p = mdbx_calloc(1, sizeof(*p));
+      p->caption = msg;
+      p->pr_next = problems_list;
+      problems_list = p;
+      need_fflush = 1;
+    }
+
+    p->count++;
+    if (verbose > 1) {
+      print("     %s #%" PRIu64 ": %s", object, entry_number, msg);
+      if (extra) {
+        va_list args;
+        printf(" (");
+        va_start(args, extra);
+        vfprintf(stdout, extra, args);
+        va_end(args);
+        printf(")");
+      }
+      printf("\n");
+      if (need_fflush)
+        fflush(nullptr);
+    }
+  }
+}
+
+static struct problem *problems_push(void) {
+  struct problem *p = problems_list;
+  problems_list = nullptr;
+  return p;
+}
+
+static size_t problems_pop(struct problem *list) {
+  size_t count = 0;
+
+  if (problems_list) {
+    int i;
+
+    print(" - problems: ");
+    for (i = 0; problems_list; ++i) {
+      struct problem *p = problems_list->pr_next;
+      count += problems_list->count;
+      print("%s%s (%" PRIuPTR ")", i ? ", " : "", problems_list->caption,
+            problems_list->count);
+      mdbx_free(problems_list);
+      problems_list = p;
+    }
+    print("\n");
+    fflush(nullptr);
+  }
+
+  problems_list = list;
+  return count;
+}
+
+static int pgvisitor(const uint64_t pgno, const unsigned pgnumber,
+                     void *const ctx, const int deep,
+                     const char *const dbi_name_or_tag, const size_t page_size,
+                     const MDBX_page_type_t pagetype, const MDBX_error_t err,
+                     const size_t nentries, const size_t payload_bytes,
+                     const size_t header_bytes, const size_t unused_bytes) {
+  (void)ctx;
+  if (deep > 42) {
+    problem_add("deep", deep, "too large", nullptr);
+    return MDBX_CORRUPTED /* avoid infinite loop/recursion */;
+  }
+
+  walk_dbi_t *dbi = pagemap_lookup_dbi(dbi_name_or_tag, false);
+  if (!dbi)
+    return MDBX_ENOMEM;
+
+  const size_t page_bytes = payload_bytes + header_bytes + unused_bytes;
+  walk.pgcount += pgnumber;
+
+  const char *pagetype_caption;
+  bool branch = false;
+  switch (pagetype) {
+  default:
+    problem_add("page", pgno, "unknown page-type", "type %u, deep %i",
+                (unsigned)pagetype, deep);
+    pagetype_caption = "unknown";
+    dbi->pages.other += pgnumber;
+    break;
+  case MDBX_page_broken:
+    pagetype_caption = "broken";
+    dbi->pages.other += pgnumber;
+    break;
+  case MDBX_subpage_broken:
+    pagetype_caption = "broken-subpage";
+    break;
+  case MDBX_page_meta:
+    pagetype_caption = "meta";
+    dbi->pages.other += pgnumber;
+    break;
+  case MDBX_page_large:
+    pagetype_caption = "large";
+    dbi->pages.large_volume += pgnumber;
+    dbi->pages.large_count += 1;
+    break;
+  case MDBX_page_branch:
+    pagetype_caption = "branch";
+    dbi->pages.branch += pgnumber;
+    branch = true;
+    break;
+  case MDBX_page_leaf:
+    pagetype_caption = "leaf";
+    dbi->pages.leaf += pgnumber;
+    break;
+  case MDBX_page_dupfixed_leaf:
+    pagetype_caption = "leaf-dupfixed";
+    dbi->pages.leaf_dupfixed += pgnumber;
+    break;
+  case MDBX_subpage_leaf:
+    pagetype_caption = "subleaf-dupsort";
+    dbi->pages.subleaf_dupsort += 1;
+    break;
+  case MDBX_subpage_dupfixed_leaf:
+    pagetype_caption = "subleaf-dupfixed";
+    dbi->pages.subleaf_dupfixed += 1;
+    break;
+  }
+
+  if (pgnumber) {
+    if (verbose > 3 && (!only_subdb || strcmp(only_subdb, dbi->name) == 0)) {
+      if (pgnumber == 1)
+        print("     %s-page %" PRIu64, pagetype_caption, pgno);
+      else
+        print("     %s-span %" PRIu64 "[%u]", pagetype_caption, pgno, pgnumber);
+      print(" of %s: header %" PRIiPTR ", payload %" PRIiPTR
+            ", unused %" PRIiPTR ", deep %i\n",
+            dbi->name, header_bytes, payload_bytes, unused_bytes, deep);
+    }
+
+    bool already_used = false;
+    for (unsigned n = 0; n < pgnumber; ++n) {
+      uint64_t spanpgno = pgno + n;
+      if (spanpgno >= alloc_pages)
+        problem_add("page", spanpgno, "wrong page-no",
+                    "%s-page: %" PRIu64 " > %" PRIu64 ", deep %i",
+                    pagetype_caption, spanpgno, alloc_pages, deep);
+      else if (walk.pagemap[spanpgno]) {
+        walk_dbi_t *coll_dbi = &walk.dbi[walk.pagemap[spanpgno] - 1];
+        problem_add("page", spanpgno,
+                    (branch && coll_dbi == dbi) ? "loop" : "already used",
+                    "%s-page: by %s, deep %i", pagetype_caption, coll_dbi->name,
+                    deep);
+        already_used = true;
+      } else {
+        walk.pagemap[spanpgno] = (short)(dbi - walk.dbi + 1);
+        dbi->pages.total += 1;
+      }
+    }
+
+    if (already_used)
+      return branch ? MDBX_RESULT_TRUE /* avoid infinite loop/recursion */
+                    : MDBX_SUCCESS;
+  }
+
+  if (MDBX_IS_ERROR(err)) {
+    problem_add("page", pgno, "invalid/corrupted", "%s-page", pagetype_caption);
+  } else {
+    if (unused_bytes > page_size)
+      problem_add("page", pgno, "illegal unused-bytes",
+                  "%s-page: %u < %" PRIuPTR " < %u", pagetype_caption, 0,
+                  unused_bytes, envstat.ms_psize);
+
+    if (header_bytes < (int)sizeof(long) ||
+        (size_t)header_bytes >= envstat.ms_psize - sizeof(long))
+      problem_add("page", pgno, "illegal header-length",
+                  "%s-page: %" PRIuPTR " < %" PRIuPTR " < %" PRIuPTR,
+                  pagetype_caption, sizeof(long), header_bytes,
+                  envstat.ms_psize - sizeof(long));
+    if (payload_bytes < 1) {
+      if (nentries > 1) {
+        problem_add("page", pgno, "zero size-of-entry",
+                    "%s-page: payload %" PRIuPTR " bytes, %" PRIuPTR " entries",
+                    pagetype_caption, payload_bytes, nentries);
+        /* if ((size_t)header_bytes + unused_bytes < page_size) {
+          // LY: hush a misuse error
+          page_bytes = page_size;
+        } */
+      } else {
+        problem_add("page", pgno, "empty",
+                    "%s-page: payload %" PRIuPTR " bytes, %" PRIuPTR
+                    " entries, deep %i",
+                    pagetype_caption, payload_bytes, nentries, deep);
+        dbi->pages.empty += 1;
+      }
+    }
+
+    if (pgnumber) {
+      if (page_bytes != page_size) {
+        problem_add("page", pgno, "misused",
+                    "%s-page: %" PRIuPTR " != %" PRIuPTR " (%" PRIuPTR
+                    "h + %" PRIuPTR "p + %" PRIuPTR "u), deep %i",
+                    pagetype_caption, page_size, page_bytes, header_bytes,
+                    payload_bytes, unused_bytes, deep);
+        if (page_size > page_bytes)
+          dbi->lost_bytes += page_size - page_bytes;
+      } else {
+        dbi->payload_bytes += payload_bytes + header_bytes;
+        walk.total_payload_bytes += payload_bytes + header_bytes;
+      }
+    }
+  }
+
+  return check_user_break();
+}
+
+typedef int(visitor)(const uint64_t record_number, const MDBX_val *key,
+                     const MDBX_val *data);
+static int process_db(MDBX_dbi dbi_handle, char *dbi_name, visitor *handler,
+                      bool silent);
+
+static int handle_userdb(const uint64_t record_number, const MDBX_val *key,
+                         const MDBX_val *data) {
+  (void)record_number;
+  (void)key;
+  (void)data;
+  return check_user_break();
+}
+
+static int handle_freedb(const uint64_t record_number, const MDBX_val *key,
+                         const MDBX_val *data) {
+  char *bad = "";
+  pgno_t *iptr = data->iov_base;
+
+  if (key->iov_len != sizeof(txnid_t))
+    problem_add("entry", record_number, "wrong txn-id size",
+                "key-size %" PRIiPTR, key->iov_len);
+  else {
+    txnid_t txnid;
+    memcpy(&txnid, key->iov_base, sizeof(txnid));
+    if (txnid < 1 || txnid > envinfo.mi_recent_txnid)
+      problem_add("entry", record_number, "wrong txn-id", "%" PRIaTXN, txnid);
+    else {
+      if (data->iov_len < sizeof(pgno_t) || data->iov_len % sizeof(pgno_t))
+        problem_add("entry", txnid, "wrong idl size", "%" PRIuPTR,
+                    data->iov_len);
+      size_t number = (data->iov_len >= sizeof(pgno_t)) ? *iptr++ : 0;
+      if (number < 1 || number > MDBX_PGL_LIMIT)
+        problem_add("entry", txnid, "wrong idl length", "%" PRIuPTR, number);
+      else if ((number + 1) * sizeof(pgno_t) > data->iov_len) {
+        problem_add("entry", txnid, "trimmed idl",
+                    "%" PRIuSIZE " > %" PRIuSIZE " (corruption)",
+                    (number + 1) * sizeof(pgno_t), data->iov_len);
+        number = data->iov_len / sizeof(pgno_t) - 1;
+      } else if (data->iov_len - (number + 1) * sizeof(pgno_t) >=
+                 /* LY: allow gap up to one page. it is ok
+                  * and better than shink-and-retry inside mdbx_update_gc() */
+                 envstat.ms_psize)
+        problem_add("entry", txnid, "extra idl space",
+                    "%" PRIuSIZE " < %" PRIuSIZE " (minor, not a trouble)",
+                    (number + 1) * sizeof(pgno_t), data->iov_len);
+
+      gc_pages += number;
+      if (envinfo.mi_latter_reader_txnid > txnid)
+        reclaimable_pages += number;
+
+      pgno_t prev = MDBX_PNL_ASCENDING ? NUM_METAS - 1 : txn->mt_next_pgno;
+      pgno_t span = 1;
+      for (unsigned i = 0; i < number; ++i) {
+        if (check_user_break())
+          return MDBX_EINTR;
+        const pgno_t pgno = iptr[i];
+        if (pgno < NUM_METAS)
+          problem_add("entry", txnid, "wrong idl entry",
+                      "pgno %" PRIaPGNO " < meta-pages %u", pgno, NUM_METAS);
+        else if (pgno >= backed_pages)
+          problem_add("entry", txnid, "wrong idl entry",
+                      "pgno %" PRIaPGNO " > backed-pages %" PRIu64, pgno,
+                      backed_pages);
+        else if (pgno >= alloc_pages)
+          problem_add("entry", txnid, "wrong idl entry",
+                      "pgno %" PRIaPGNO " > alloc-pages %" PRIu64, pgno,
+                      alloc_pages - 1);
+        else {
+          if (MDBX_PNL_DISORDERED(prev, pgno)) {
+            bad = " [bad sequence]";
+            problem_add("entry", txnid, "bad sequence",
+                        "%" PRIaPGNO " %c [%u].%" PRIaPGNO, prev,
+                        (prev == pgno) ? '=' : (MDBX_PNL_ASCENDING ? '>' : '<'),
+                        i, pgno);
+          }
+          if (walk.pagemap) {
+            int idx = walk.pagemap[pgno];
+            if (idx == 0)
+              walk.pagemap[pgno] = -1;
+            else if (idx > 0)
+              problem_add("page", pgno, "already used", "by %s",
+                          walk.dbi[idx - 1].name);
+            else
+              problem_add("page", pgno, "already listed in GC", nullptr);
+          }
+        }
+        prev = pgno;
+        while (i + span < number &&
+               iptr[i + span] == (MDBX_PNL_ASCENDING ? pgno_add(pgno, span)
+                                                     : pgno_sub(pgno, span)))
+          ++span;
+      }
+      if (verbose > 3 && !only_subdb) {
+        print("     transaction %" PRIaTXN ", %" PRIuPTR
+              " pages, maxspan %" PRIaPGNO "%s\n",
+              txnid, number, span, bad);
+        if (verbose > 4) {
+          for (unsigned i = 0; i < number; i += span) {
+            const pgno_t pgno = iptr[i];
+            for (span = 1;
+                 i + span < number &&
+                 iptr[i + span] == (MDBX_PNL_ASCENDING ? pgno_add(pgno, span)
+                                                       : pgno_sub(pgno, span));
+                 ++span)
+              ;
+            if (span > 1) {
+              print("    %9" PRIaPGNO "[%" PRIaPGNO "]\n", pgno, span);
+            } else
+              print("    %9" PRIaPGNO "\n", pgno);
+          }
+        }
+      }
+    }
+  }
+
+  return check_user_break();
+}
+
+static int equal_or_greater(const MDBX_val *a, const MDBX_val *b) {
+  return (a->iov_len == b->iov_len &&
+          memcmp(a->iov_base, b->iov_base, a->iov_len) == 0)
+             ? 0
+             : 1;
+}
+
+static int handle_maindb(const uint64_t record_number, const MDBX_val *key,
+                         const MDBX_val *data) {
+  char *name;
+  int rc;
+  size_t i;
+
+  name = key->iov_base;
+  for (i = 0; i < key->iov_len; ++i) {
+    if (name[i] < ' ')
+      return handle_userdb(record_number, key, data);
+  }
+
+  name = mdbx_malloc(key->iov_len + 1);
+  memcpy(name, key->iov_base, key->iov_len);
+  name[key->iov_len] = '\0';
+  userdb_count++;
+
+  rc = process_db(~0u, name, handle_userdb, false);
+  mdbx_free(name);
+  if (rc != MDBX_INCOMPATIBLE)
+    return rc;
+
+  return handle_userdb(record_number, key, data);
+}
+
+static const char *db_flags2keymode(unsigned flags) {
+  flags &= (MDBX_REVERSEKEY | MDBX_INTEGERKEY);
+  switch (flags) {
+  case 0:
+    return "usual";
+  case MDBX_REVERSEKEY:
+    return "reserve";
+  case MDBX_INTEGERKEY:
+    return "ordinal";
+  case MDBX_REVERSEKEY | MDBX_INTEGERKEY:
+    return "msgpack";
+  default:
+    assert(false);
+    __unreachable();
+  }
+}
+
+static const char *db_flags2valuemode(unsigned flags) {
+  flags &= (MDBX_DUPSORT | MDBX_REVERSEDUP | MDBX_DUPFIXED | MDBX_INTEGERDUP);
+  switch (flags) {
+  case 0:
+    return "single";
+  case MDBX_DUPSORT:
+    return "multi";
+  case MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_REVERSEDUP:
+    return "multi-reverse";
+  case MDBX_DUPFIXED:
+  case MDBX_DUPSORT | MDBX_DUPFIXED:
+    return "multi-samelength";
+  case MDBX_DUPFIXED | MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_REVERSEDUP:
+    return "multi-reverse-samelength";
+  case MDBX_INTEGERDUP:
+  case MDBX_DUPSORT | MDBX_INTEGERDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERDUP:
+  case MDBX_DUPFIXED | MDBX_INTEGERDUP:
+    return "multi-ordinal";
+  case MDBX_INTEGERDUP | MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_INTEGERDUP | MDBX_REVERSEDUP:
+    return "multi-msgpack";
+  case MDBX_DUPFIXED | MDBX_INTEGERDUP | MDBX_REVERSEDUP:
+  case MDBX_DUPSORT | MDBX_DUPFIXED | MDBX_INTEGERDUP | MDBX_REVERSEDUP:
+    return "reserved";
+  default:
+    assert(false);
+    __unreachable();
+  }
+}
+
+static int process_db(MDBX_dbi dbi_handle, char *dbi_name, visitor *handler,
+                      bool silent) {
+  MDBX_cursor *mc;
+  MDBX_stat ms;
+  MDBX_val key, data;
+  MDBX_val prev_key, prev_data;
+  unsigned flags;
+  int rc, i;
+  struct problem *saved_list;
+  uint64_t problems_count;
+
+  uint64_t record_count = 0, dups = 0;
+  uint64_t key_bytes = 0, data_bytes = 0;
+
+  if ((MDBX_TXN_FINISHED | MDBX_TXN_ERROR) & mdbx_txn_flags(txn)) {
+    print(" ! abort processing '%s' due to a previous error\n",
+          dbi_name ? dbi_name : "@MAIN");
+    return MDBX_BAD_TXN;
+  }
+
+  if (dbi_handle == ~0u) {
+    rc = mdbx_dbi_open_ex(
+        txn, dbi_name, MDBX_DB_ACCEDE, &dbi_handle,
+        (dbi_name && ignore_wrong_order) ? equal_or_greater : nullptr,
+        (dbi_name && ignore_wrong_order) ? equal_or_greater : nullptr);
+    if (rc) {
+      if (!dbi_name ||
+          rc !=
+              MDBX_INCOMPATIBLE) /* LY: mainDB's record is not a user's DB. */ {
+        error("mdbx_open '%s' failed, error %d %s\n",
+              dbi_name ? dbi_name : "main", rc, mdbx_strerror(rc));
+      }
+      return rc;
+    }
+  }
+
+  if (dbi_handle >= CORE_DBS && dbi_name && only_subdb &&
+      strcmp(only_subdb, dbi_name) != 0) {
+    if (verbose) {
+      print("Skip processing '%s'...\n", dbi_name);
+      fflush(nullptr);
+    }
+    skipped_subdb++;
+    return MDBX_SUCCESS;
+  }
+
+  if (!silent && verbose) {
+    print("Processing '%s'...\n", dbi_name ? dbi_name : "@MAIN");
+    fflush(nullptr);
+  }
+
+  rc = mdbx_dbi_flags(txn, dbi_handle, &flags);
+  if (rc) {
+    error("mdbx_dbi_flags failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return rc;
+  }
+
+  rc = mdbx_dbi_stat(txn, dbi_handle, &ms, sizeof(ms));
+  if (rc) {
+    error("mdbx_dbi_stat failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return rc;
+  }
+
+  if (!silent && verbose) {
+    print(" - key-value kind: %s-key => %s-value", db_flags2keymode(flags),
+          db_flags2valuemode(flags));
+    if (verbose > 1) {
+      print(", flags:");
+      if (!flags)
+        print(" none");
+      else {
+        for (i = 0; dbflags[i].bit; i++)
+          if (flags & dbflags[i].bit)
+            print(" %s", dbflags[i].name);
+      }
+      if (verbose > 2)
+        print(" (0x%02X), dbi-id %d", flags, dbi_handle);
+    }
+    print("\n");
+    if (ms.ms_mod_txnid)
+      print(" - last modification txn#%" PRIu64 "\n", ms.ms_mod_txnid);
+    if (verbose > 1) {
+      print(" - page size %u, entries %" PRIu64 "\n", ms.ms_psize,
+            ms.ms_entries);
+      print(" - b-tree depth %u, pages: branch %" PRIu64 ", leaf %" PRIu64
+            ", overflow %" PRIu64 "\n",
+            ms.ms_depth, ms.ms_branch_pages, ms.ms_leaf_pages,
+            ms.ms_overflow_pages);
+    }
+  }
+
+  walk_dbi_t *dbi = (dbi_handle < CORE_DBS)
+                        ? &walk.dbi[dbi_handle]
+                        : pagemap_lookup_dbi(dbi_name, true);
+  if (!dbi) {
+    error("too many DBIs or out of memory\n");
+    return MDBX_ENOMEM;
+  }
+  if (!dont_traversal) {
+    const uint64_t subtotal_pages =
+        ms.ms_branch_pages + ms.ms_leaf_pages + ms.ms_overflow_pages;
+    if (subtotal_pages != dbi->pages.total)
+      error("%s pages mismatch (%" PRIu64 " != walked %" PRIu64 ")\n",
+            "subtotal", subtotal_pages, dbi->pages.total);
+    if (ms.ms_branch_pages != dbi->pages.branch)
+      error("%s pages mismatch (%" PRIu64 " != walked %" PRIu64 ")\n", "branch",
+            ms.ms_branch_pages, dbi->pages.branch);
+    const uint64_t allleaf_pages = dbi->pages.leaf + dbi->pages.leaf_dupfixed;
+    if (ms.ms_leaf_pages != allleaf_pages)
+      error("%s pages mismatch (%" PRIu64 " != walked %" PRIu64 ")\n",
+            "all-leaf", ms.ms_leaf_pages, allleaf_pages);
+    if (ms.ms_overflow_pages != dbi->pages.large_volume)
+      error("%s pages mismatch (%" PRIu64 " != walked %" PRIu64 ")\n",
+            "large/overlow", ms.ms_overflow_pages, dbi->pages.large_volume);
+  }
+  rc = mdbx_cursor_open(txn, dbi_handle, &mc);
+  if (rc) {
+    error("mdbx_cursor_open failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return rc;
+  }
+
+  if (ignore_wrong_order) { /* for debugging with enabled assertions */
+    mc->mc_flags |= C_SKIPORD;
+    if (mc->mc_xcursor)
+      mc->mc_xcursor->mx_cursor.mc_flags |= C_SKIPORD;
+  }
+
+  const size_t maxkeysize = mdbx_env_get_maxkeysize_ex(env, flags);
+  saved_list = problems_push();
+  prev_key.iov_base = nullptr;
+  prev_key.iov_len = 0;
+  prev_data.iov_base = nullptr;
+  prev_data.iov_len = 0;
+  rc = mdbx_cursor_get(mc, &key, &data, MDBX_FIRST);
+  while (rc == MDBX_SUCCESS) {
+    rc = check_user_break();
+    if (rc)
+      goto bailout;
+
+    bool bad_key = false;
+    if (key.iov_len > maxkeysize) {
+      problem_add("entry", record_count, "key length exceeds max-key-size",
+                  "%" PRIuPTR " > %" PRIuPTR, key.iov_len, maxkeysize);
+      bad_key = true;
+    } else if ((flags & MDBX_INTEGERKEY) && key.iov_len != sizeof(uint64_t) &&
+               key.iov_len != sizeof(uint32_t)) {
+      problem_add("entry", record_count, "wrong key length",
+                  "%" PRIuPTR " != 4or8", key.iov_len);
+      bad_key = true;
+    }
+
+    bool bad_data = false;
+    if ((flags & MDBX_INTEGERDUP) && data.iov_len != sizeof(uint64_t) &&
+        data.iov_len != sizeof(uint32_t)) {
+      problem_add("entry", record_count, "wrong data length",
+                  "%" PRIuPTR " != 4or8", data.iov_len);
+      bad_data = true;
+    }
+
+    if (prev_key.iov_base && !bad_data) {
+      if ((flags & MDBX_DUPFIXED) && prev_data.iov_len != data.iov_len) {
+        problem_add("entry", record_count, "different data length",
+                    "%" PRIuPTR " != %" PRIuPTR, prev_data.iov_len,
+                    data.iov_len);
+        bad_data = true;
+      }
+
+      if (!bad_key) {
+        int cmp = mdbx_cmp(txn, dbi_handle, &key, &prev_key);
+        if (cmp == 0) {
+          ++dups;
+          if ((flags & MDBX_DUPSORT) == 0) {
+            problem_add("entry", record_count, "duplicated entries", nullptr);
+            if (data.iov_len == prev_data.iov_len &&
+                memcmp(data.iov_base, prev_data.iov_base, data.iov_len) == 0) {
+              problem_add("entry", record_count, "complete duplicate", nullptr);
+            }
+          } else if (!bad_data) {
+            cmp = mdbx_dcmp(txn, dbi_handle, &data, &prev_data);
+            if (cmp == 0) {
+              problem_add("entry", record_count, "complete duplicate", nullptr);
+            } else if (cmp < 0 && !ignore_wrong_order) {
+              problem_add("entry", record_count, "wrong order of multi-values",
+                          nullptr);
+            }
+          }
+        } else if (cmp < 0 && !ignore_wrong_order) {
+          problem_add("entry", record_count, "wrong order of entries", nullptr);
+        }
+      }
+    } else if (verbose) {
+      if (flags & MDBX_INTEGERKEY)
+        print(" - fixed key-size %" PRIuPTR "\n", key.iov_len);
+      if (flags & (MDBX_INTEGERDUP | MDBX_DUPFIXED))
+        print(" - fixed data-size %" PRIuPTR "\n", data.iov_len);
+    }
+
+    if (handler) {
+      rc = handler(record_count, &key, &data);
+      if (MDBX_IS_ERROR(rc))
+        goto bailout;
+    }
+
+    record_count++;
+    key_bytes += key.iov_len;
+    data_bytes += data.iov_len;
+
+    if (!bad_key)
+      prev_key = key;
+    if (!bad_data)
+      prev_data = data;
+    rc = mdbx_cursor_get(mc, &key, &data, MDBX_NEXT);
+  }
+  if (rc != MDBX_NOTFOUND)
+    error("mdbx_cursor_get failed, error %d %s\n", rc, mdbx_strerror(rc));
+  else
+    rc = 0;
+
+  if (record_count != ms.ms_entries)
+    problem_add("entry", record_count, "different number of entries",
+                "%" PRIu64 " != %" PRIu64, record_count, ms.ms_entries);
+bailout:
+  problems_count = problems_pop(saved_list);
+  if (!silent && verbose) {
+    print(" - summary: %" PRIu64 " records, %" PRIu64 " dups, %" PRIu64
+          " key's bytes, %" PRIu64 " data's "
+          "bytes, %" PRIu64 " problems\n",
+          record_count, dups, key_bytes, data_bytes, problems_count);
+    fflush(nullptr);
+  }
+
+  mdbx_cursor_close(mc);
+  return (rc || problems_count) ? MDBX_RESULT_TRUE : MDBX_SUCCESS;
+}
+
+static void usage(char *prog) {
+  fprintf(stderr,
+          "usage: %s [-V] [-v] [-q] [-c] [-0|1|2] [-w] [-d] [-i] [-s subdb] "
+          "dbpath\n"
+          "  -V\t\tprint version and exit\n"
+          "  -v\t\tmore verbose, could be used multiple times\n"
+          "  -q\t\tbe quiet\n"
+          "  -c\t\tforce cooperative mode (don't try exclusive)\n"
+          "  -w\t\twrite-mode checking\n"
+          "  -d\t\tdisable page-by-page traversal of B-tree\n"
+          "  -i\t\tignore wrong order errors (for custom comparators case)\n"
+          "  -s subdb\tprocess a specific subdatabase only\n"
+          "  -0|1|2\tforce using specific meta-page 0, or 2 for checking\n"
+          "  -t\t\tturn to a specified meta-page on successful check\n"
+          "  -T\t\tturn to a specified meta-page EVEN ON UNSUCCESSFUL CHECK!\n",
+          prog);
+  exit(EXIT_INTERRUPTED);
+}
+
+static __inline bool meta_ot(txnid_t txn_a, uint64_t sign_a, txnid_t txn_b,
+                             uint64_t sign_b, const bool wanna_steady) {
+  if (txn_a == txn_b)
+    return SIGN_IS_STEADY(sign_b);
+
+  if (wanna_steady && SIGN_IS_STEADY(sign_a) != SIGN_IS_STEADY(sign_b))
+    return SIGN_IS_STEADY(sign_b);
+
+  return txn_a < txn_b;
+}
+
+static __inline bool meta_eq(txnid_t txn_a, uint64_t sign_a, txnid_t txn_b,
+                             uint64_t sign_b) {
+  if (txn_a != txn_b)
+    return false;
+
+  if (SIGN_IS_STEADY(sign_a) != SIGN_IS_STEADY(sign_b))
+    return false;
+
+  return true;
+}
+
+static __inline int meta_recent(const bool wanna_steady) {
+  if (meta_ot(envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+              envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign, wanna_steady))
+    return meta_ot(envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign,
+                   envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign, wanna_steady)
+               ? 1
+               : 2;
+  else
+    return meta_ot(envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+                   envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign, wanna_steady)
+               ? 2
+               : 0;
+}
+
+static __inline int meta_tail(int head) {
+  switch (head) {
+  case 0:
+    return meta_ot(envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign,
+                   envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign, true)
+               ? 1
+               : 2;
+  case 1:
+    return meta_ot(envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+                   envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign, true)
+               ? 0
+               : 2;
+  case 2:
+    return meta_ot(envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+                   envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign, true)
+               ? 0
+               : 1;
+  default:
+    assert(false);
+    return -1;
+  }
+}
+
+static int meta_head(void) { return meta_recent(false); }
+
+void verbose_meta(int num, txnid_t txnid, uint64_t sign, uint64_t bootid_x,
+                  uint64_t bootid_y) {
+  const bool have_bootid = (bootid_x | bootid_y) != 0;
+  const bool bootid_match = bootid_x == envinfo.mi_bootid.current.x &&
+                            bootid_y == envinfo.mi_bootid.current.y;
+
+  print(" - meta-%d: ", num);
+  switch (sign) {
+  case MDBX_DATASIGN_NONE:
+    print("no-sync/legacy");
+    break;
+  case MDBX_DATASIGN_WEAK:
+    print("weak-%s", bootid_match ? (have_bootid ? "intact (same boot-id)"
+                                                 : "unknown (no boot-id")
+                                  : "dead");
+    break;
+  default:
+    print("steady");
+    break;
+  }
+  print(" txn#%" PRIu64, txnid);
+
+  const int head = meta_head();
+  if (num == head)
+    print(", head");
+  else if (num == meta_tail(head))
+    print(", tail");
+  else
+    print(", stay");
+
+  if (stuck_meta >= 0) {
+    if (num == stuck_meta)
+      print(", forced for checking");
+  } else if (txnid > envinfo.mi_recent_txnid &&
+             (envflags & (MDBX_EXCLUSIVE | MDBX_RDONLY)) == MDBX_EXCLUSIVE)
+    print(", rolled-back %" PRIu64 " (%" PRIu64 " >>> %" PRIu64 ")",
+          txnid - envinfo.mi_recent_txnid, txnid, envinfo.mi_recent_txnid);
+  print("\n");
+}
+
+static uint64_t get_meta_txnid(const unsigned meta_id) {
+  switch (meta_id) {
+  default:
+    assert(false);
+    error("unexpected meta_id %u\n", meta_id);
+    return 0;
+  case 0:
+    return envinfo.mi_meta0_txnid;
+  case 1:
+    return envinfo.mi_meta1_txnid;
+  case 2:
+    return envinfo.mi_meta2_txnid;
+  }
+}
+
+static void print_size(const char *prefix, const uint64_t value,
+                       const char *suffix) {
+  const char sf[] =
+      "KMGTPEZY"; /* LY: Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta! */
+  double k = 1024.0;
+  size_t i;
+  for (i = 0; sf[i + 1] && value / k > 1000.0; ++i)
+    k *= 1024;
+  print("%s%" PRIu64 " (%.2f %cb)%s", prefix, value, value / k, sf[i], suffix);
+}
+
+int main(int argc, char *argv[]) {
+  int rc;
+  char *prog = argv[0];
+  char *envname;
+  int problems_maindb = 0, problems_freedb = 0, problems_meta = 0;
+  bool write_locked = false;
+  bool turn_meta = false;
+  bool force_turn_meta = false;
+
+  double elapsed;
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t timestamp_start, timestamp_finish;
+  timestamp_start = GetMilliseconds();
+#else
+  struct timespec timestamp_start, timestamp_finish;
+  if (clock_gettime(CLOCK_MONOTONIC, &timestamp_start)) {
+    rc = errno;
+    error("clock_gettime failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return EXIT_FAILURE_SYS;
+  }
+#endif
+
+  dbi_meta.name = "@META";
+  dbi_free.name = "@GC";
+  dbi_main.name = "@MAIN";
+  atexit(pagemap_cleanup);
+
+  if (argc < 2)
+    usage(prog);
+
+  for (int i; (i = getopt(argc, argv,
+                          "0"
+                          "1"
+                          "2"
+                          "T"
+                          "V"
+                          "v"
+                          "q"
+                          "n"
+                          "w"
+                          "c"
+                          "t"
+                          "d"
+                          "i"
+                          "s:")) != EOF;) {
+    switch (i) {
+    case 'V':
+      printf("mdbx_chk version %d.%d.%d.%d\n"
+             " - source: %s %s, commit %s, tree %s\n"
+             " - anchor: %s\n"
+             " - build: %s for %s by %s\n"
+             " - flags: %s\n"
+             " - options: %s\n",
+             mdbx_version.major, mdbx_version.minor, mdbx_version.release,
+             mdbx_version.revision, mdbx_version.git.describe,
+             mdbx_version.git.datetime, mdbx_version.git.commit,
+             mdbx_version.git.tree, mdbx_sourcery_anchor, mdbx_build.datetime,
+             mdbx_build.target, mdbx_build.compiler, mdbx_build.flags,
+             mdbx_build.options);
+      return EXIT_SUCCESS;
+    case 'v':
+      verbose++;
+      break;
+    case '0':
+      stuck_meta = 0;
+      break;
+    case '1':
+      stuck_meta = 1;
+      break;
+    case '2':
+      stuck_meta = 2;
+      break;
+    case 't':
+      turn_meta = true;
+      break;
+    case 'T':
+      turn_meta = force_turn_meta = true;
+      quiet = false;
+      if (verbose < 2)
+        verbose = 2;
+      break;
+    case 'q':
+      quiet = true;
+      break;
+    case 'n':
+      envflags |= MDBX_NOSUBDIR;
+      break;
+    case 'w':
+      envflags &= ~MDBX_RDONLY;
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+      /* Temporary `workaround` for OpenBSD kernel's flaw.
+       * See https://github.com/erthink/libmdbx/issues/67 */
+      envflags |= MDBX_WRITEMAP;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+      break;
+    case 'c':
+      envflags = (envflags & ~MDBX_EXCLUSIVE) | MDBX_ACCEDE;
+      break;
+    case 'd':
+      dont_traversal = true;
+      break;
+    case 's':
+      if (only_subdb && strcmp(only_subdb, optarg))
+        usage(prog);
+      only_subdb = optarg;
+      break;
+    case 'i':
+      ignore_wrong_order = true;
+      break;
+    default:
+      usage(prog);
+    }
+  }
+
+  if (optind != argc - 1)
+    usage(prog);
+
+  rc = MDBX_SUCCESS;
+  if (stuck_meta >= 0 && (envflags & MDBX_EXCLUSIVE) == 0) {
+    error("exclusive mode is required to using specific meta-page(%d) for "
+          "checking.\n",
+          stuck_meta);
+    rc = EXIT_INTERRUPTED;
+  }
+  if (turn_meta) {
+    if (stuck_meta < 0) {
+      error("meta-page must be specified (by -0, -1 or -2 options) to turn to "
+            "it.\n");
+      rc = EXIT_INTERRUPTED;
+    }
+    if (envflags & MDBX_RDONLY) {
+      error("write-mode must be enabled to turn to the specified meta-page.\n");
+      rc = EXIT_INTERRUPTED;
+    }
+    if (only_subdb || dont_traversal) {
+      error("whole database checking with tree-traversal are required to turn "
+            "to the specified meta-page.\n");
+      rc = EXIT_INTERRUPTED;
+    }
+  }
+  if (rc)
+    exit(rc);
+
+#if defined(_WIN32) || defined(_WIN64)
+  SetConsoleCtrlHandler(ConsoleBreakHandlerRoutine, true);
+#else
+#ifdef SIGPIPE
+  signal(SIGPIPE, signal_handler);
+#endif
+#ifdef SIGHUP
+  signal(SIGHUP, signal_handler);
+#endif
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+#endif /* !WINDOWS */
+
+  envname = argv[optind];
+  print("mdbx_chk %s (%s, T-%s)\nRunning for %s in 'read-%s' mode...\n",
+        mdbx_version.git.describe, mdbx_version.git.datetime,
+        mdbx_version.git.tree, envname,
+        (envflags & MDBX_RDONLY) ? "only" : "write");
+  fflush(nullptr);
+  mdbx_setup_debug((verbose < MDBX_LOG_TRACE - 1)
+                       ? (MDBX_log_level_t)(verbose + 1)
+                       : MDBX_LOG_TRACE,
+                   MDBX_DBG_LEGACY_OVERLAP, logger);
+
+  rc = mdbx_env_create(&env);
+  if (rc) {
+    error("mdbx_env_create failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return rc < 0 ? EXIT_FAILURE_MDBX : EXIT_FAILURE_SYS;
+  }
+
+  rc = mdbx_env_set_maxdbs(env, MDBX_MAX_DBI);
+  if (rc) {
+    error("mdbx_env_set_maxdbs failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+
+  if (stuck_meta >= 0) {
+    rc = mdbx_env_open_for_recovery(env, envname, stuck_meta,
+                                    (envflags & MDBX_RDONLY) ? false : true);
+  } else {
+    rc = mdbx_env_open(env, envname, envflags, 0);
+    if ((envflags & MDBX_EXCLUSIVE) &&
+        (rc == MDBX_BUSY ||
+#if defined(_WIN32) || defined(_WIN64)
+         rc == ERROR_LOCK_VIOLATION || rc == ERROR_SHARING_VIOLATION
+#else
+         rc == EBUSY || rc == EAGAIN
+#endif
+         )) {
+      envflags &= ~MDBX_EXCLUSIVE;
+      rc = mdbx_env_open(env, envname, envflags | MDBX_ACCEDE, 0);
+    }
+  }
+
+  if (rc) {
+    error("mdbx_env_open failed, error %d %s\n", rc, mdbx_strerror(rc));
+    if (rc == MDBX_WANNA_RECOVERY && (envflags & MDBX_RDONLY))
+      print("Please run %s in the read-write mode (with '-w' option).\n", prog);
+    goto bailout;
+  }
+  if (verbose)
+    print(" - %s mode\n",
+          (envflags & MDBX_EXCLUSIVE) ? "monopolistic" : "cooperative");
+
+  if ((envflags & (MDBX_RDONLY | MDBX_EXCLUSIVE)) == 0) {
+    rc = mdbx_txn_lock(env, false);
+    if (rc != MDBX_SUCCESS) {
+      error("mdbx_txn_lock failed, error %d %s\n", rc, mdbx_strerror(rc));
+      goto bailout;
+    }
+    write_locked = true;
+  }
+
+  rc = mdbx_txn_begin(env, nullptr, MDBX_TXN_RDONLY, &txn);
+  if (rc) {
+    error("mdbx_txn_begin() failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+
+  rc = mdbx_env_info_ex(env, txn, &envinfo, sizeof(envinfo));
+  if (rc) {
+    error("mdbx_env_info failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+  if (verbose) {
+    print(" - current boot-id ");
+    if (envinfo.mi_bootid.current.x | envinfo.mi_bootid.current.y)
+      print("%016" PRIx64 "-%016" PRIx64 "\n", envinfo.mi_bootid.current.x,
+            envinfo.mi_bootid.current.y);
+    else
+      print("unavailable\n");
+  }
+
+  rc = mdbx_env_stat_ex(env, txn, &envstat, sizeof(envstat));
+  if (rc) {
+    error("mdbx_env_stat failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+
+  mdbx_filehandle_t dxb_fd;
+  rc = mdbx_env_get_fd(env, &dxb_fd);
+  if (rc) {
+    error("mdbx_env_get_fd failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+
+  uint64_t dxb_filesize = 0;
+#if defined(_WIN32) || defined(_WIN64)
+  {
+    BY_HANDLE_FILE_INFORMATION info;
+    if (!GetFileInformationByHandle(dxb_fd, &info))
+      rc = GetLastError();
+    else
+      dxb_filesize = info.nFileSizeLow | (uint64_t)info.nFileSizeHigh << 32;
+  }
+#else
+  {
+    struct stat st;
+    STATIC_ASSERT_MSG(sizeof(off_t) <= sizeof(uint64_t),
+                      "libmdbx requires 64-bit file I/O on 64-bit systems");
+    if (fstat(dxb_fd, &st))
+      rc = errno;
+    else
+      dxb_filesize = st.st_size;
+  }
+#endif
+  if (rc) {
+    error("mdbx_filesize failed, error %d %s\n", rc, mdbx_strerror(rc));
+    goto bailout;
+  }
+
+  errno = 0;
+  const uint64_t dxbfile_pages = dxb_filesize / envinfo.mi_dxb_pagesize;
+  alloc_pages = txn->mt_next_pgno;
+  backed_pages = envinfo.mi_geo.current / envinfo.mi_dxb_pagesize;
+  if (backed_pages > dxbfile_pages) {
+    print(" ! backed-pages %" PRIu64 " > file-pages %" PRIu64 "\n",
+          backed_pages, dxbfile_pages);
+    ++problems_meta;
+  }
+  if (dxbfile_pages < NUM_METAS)
+    print(" ! file-pages %" PRIu64 " < %u\n", dxbfile_pages, NUM_METAS);
+  if (backed_pages < NUM_METAS)
+    print(" ! backed-pages %" PRIu64 " < %u\n", backed_pages, NUM_METAS);
+  if (backed_pages < NUM_METAS || dxbfile_pages < NUM_METAS)
+    goto bailout;
+  if (backed_pages > MAX_PAGENO) {
+    print(" ! backed-pages %" PRIu64 " > max-pages %" PRIaPGNO "\n",
+          backed_pages, MAX_PAGENO);
+    ++problems_meta;
+    backed_pages = MAX_PAGENO;
+  }
+
+  if ((envflags & (MDBX_EXCLUSIVE | MDBX_RDONLY)) != MDBX_RDONLY) {
+    if (backed_pages > dxbfile_pages) {
+      print(" ! backed-pages %" PRIu64 " > file-pages %" PRIu64 "\n",
+            backed_pages, dxbfile_pages);
+      ++problems_meta;
+      backed_pages = dxbfile_pages;
+    }
+    if (alloc_pages > backed_pages) {
+      print(" ! alloc-pages %" PRIu64 " > backed-pages %" PRIu64 "\n",
+            alloc_pages, backed_pages);
+      ++problems_meta;
+      alloc_pages = backed_pages;
+    }
+  } else {
+    /* LY: DB may be shrinked by writer down to the allocated pages. */
+    if (alloc_pages > backed_pages) {
+      print(" ! alloc-pages %" PRIu64 " > backed-pages %" PRIu64 "\n",
+            alloc_pages, backed_pages);
+      ++problems_meta;
+      alloc_pages = backed_pages;
+    }
+    if (alloc_pages > dxbfile_pages) {
+      print(" ! alloc-pages %" PRIu64 " > file-pages %" PRIu64 "\n",
+            alloc_pages, dxbfile_pages);
+      ++problems_meta;
+      alloc_pages = dxbfile_pages;
+    }
+    if (backed_pages > dxbfile_pages)
+      backed_pages = dxbfile_pages;
+  }
+
+  if (verbose) {
+    print(" - pagesize %u (%u system), max keysize %d..%d"
+          ", max readers %u\n",
+          envinfo.mi_dxb_pagesize, envinfo.mi_sys_pagesize,
+          mdbx_env_get_maxkeysize_ex(env, MDBX_DUPSORT),
+          mdbx_env_get_maxkeysize_ex(env, 0), envinfo.mi_maxreaders);
+    print_size(" - mapsize ", envinfo.mi_mapsize, "\n");
+    if (envinfo.mi_geo.lower == envinfo.mi_geo.upper)
+      print_size(" - fixed datafile: ", envinfo.mi_geo.current, "");
+    else {
+      print_size(" - dynamic datafile: ", envinfo.mi_geo.lower, "");
+      print_size(" .. ", envinfo.mi_geo.upper, ", ");
+      print_size("+", envinfo.mi_geo.grow, ", ");
+      print_size("-", envinfo.mi_geo.shrink, "\n");
+      print_size(" - current datafile: ", envinfo.mi_geo.current, "");
+    }
+    printf(", %" PRIu64 " pages\n",
+           envinfo.mi_geo.current / envinfo.mi_dxb_pagesize);
+#if defined(_WIN32) || defined(_WIN64)
+    if (envinfo.mi_geo.shrink && envinfo.mi_geo.current != envinfo.mi_geo.upper)
+      print(
+          "                     WARNING: Due Windows system limitations a "
+          "file couldn't\n                     be truncated while the database "
+          "is opened. So, the size\n                     database file "
+          "of may by large than the database itself,\n                     "
+          "until it will be closed or reopened in read-write mode.\n");
+#endif
+    print(" - transactions: recent %" PRIu64 ", latter reader %" PRIu64
+          ", lag %" PRIi64 "\n",
+          envinfo.mi_recent_txnid, envinfo.mi_latter_reader_txnid,
+          envinfo.mi_recent_txnid - envinfo.mi_latter_reader_txnid);
+
+    verbose_meta(0, envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+                 envinfo.mi_bootid.meta0.x, envinfo.mi_bootid.meta0.y);
+    verbose_meta(1, envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign,
+                 envinfo.mi_bootid.meta1.x, envinfo.mi_bootid.meta1.y);
+    verbose_meta(2, envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign,
+                 envinfo.mi_bootid.meta2.x, envinfo.mi_bootid.meta2.y);
+  }
+
+  if (verbose > 1)
+    print(" - performs check for meta-pages clashes\n");
+  if (meta_eq(envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign,
+              envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign)) {
+    print(" ! meta-%d and meta-%d are clashed\n", 0, 1);
+    ++problems_meta;
+  }
+  if (meta_eq(envinfo.mi_meta1_txnid, envinfo.mi_meta1_sign,
+              envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign)) {
+    print(" ! meta-%d and meta-%d are clashed\n", 1, 2);
+    ++problems_meta;
+  }
+  if (meta_eq(envinfo.mi_meta2_txnid, envinfo.mi_meta2_sign,
+              envinfo.mi_meta0_txnid, envinfo.mi_meta0_sign)) {
+    print(" ! meta-%d and meta-%d are clashed\n", 2, 0);
+    ++problems_meta;
+  }
+
+  const unsigned steady_meta_id = meta_recent(true);
+  const uint64_t steady_meta_txnid = get_meta_txnid(steady_meta_id);
+  const unsigned weak_meta_id = meta_recent(false);
+  const uint64_t weak_meta_txnid = get_meta_txnid(weak_meta_id);
+  if (envflags & MDBX_EXCLUSIVE) {
+    if (verbose > 1)
+      print(" - performs full check recent-txn-id with meta-pages\n");
+    if (steady_meta_txnid != envinfo.mi_recent_txnid) {
+      print(" ! steady meta-%d txn-id mismatch recent-txn-id (%" PRIi64
+            " != %" PRIi64 ")\n",
+            steady_meta_id, steady_meta_txnid, envinfo.mi_recent_txnid);
+      ++problems_meta;
+    }
+  } else if (write_locked) {
+    if (verbose > 1)
+      print(" - performs lite check recent-txn-id with meta-pages (not a "
+            "monopolistic mode)\n");
+    if (weak_meta_txnid != envinfo.mi_recent_txnid) {
+      print(" ! weak meta-%d txn-id mismatch recent-txn-id (%" PRIi64
+            " != %" PRIi64 ")\n",
+            weak_meta_id, weak_meta_txnid, envinfo.mi_recent_txnid);
+      ++problems_meta;
+    }
+  } else if (verbose) {
+    print(" - skip check recent-txn-id with meta-pages (monopolistic or "
+          "read-write mode only)\n");
+  }
+  total_problems += problems_meta;
+
+  if (!dont_traversal) {
+    struct problem *saved_list;
+    size_t traversal_problems;
+    uint64_t empty_pages, lost_bytes;
+
+    print("Traversal b-tree by txn#%" PRIaTXN "...\n", txn->mt_txnid);
+    fflush(nullptr);
+    walk.pagemap = mdbx_calloc((size_t)backed_pages, sizeof(*walk.pagemap));
+    if (!walk.pagemap) {
+      rc = errno ? errno : MDBX_ENOMEM;
+      error("calloc failed, error %d %s\n", rc, mdbx_strerror(rc));
+      goto bailout;
+    }
+
+    saved_list = problems_push();
+    rc = mdbx_env_pgwalk(txn, pgvisitor, nullptr,
+                         true /* always skip key ordering checking to avoid
+                               MDBX_CORRUPTED when using custom comparators */);
+    traversal_problems = problems_pop(saved_list);
+
+    if (rc) {
+      if (rc != MDBX_EINTR || !check_user_break())
+        error("mdbx_env_pgwalk failed, error %d %s\n", rc, mdbx_strerror(rc));
+      goto bailout;
+    }
+
+    for (uint64_t n = 0; n < alloc_pages; ++n)
+      if (!walk.pagemap[n])
+        unused_pages += 1;
+
+    empty_pages = lost_bytes = 0;
+    for (walk_dbi_t *dbi = &dbi_main; dbi < ARRAY_END(walk.dbi) && dbi->name;
+         ++dbi) {
+      empty_pages += dbi->pages.empty;
+      lost_bytes += dbi->lost_bytes;
+    }
+
+    if (verbose) {
+      uint64_t total_page_bytes = walk.pgcount * envstat.ms_psize;
+      print(" - pages: walked %" PRIu64 ", left/unused %" PRIu64 "\n",
+            walk.pgcount, unused_pages);
+      if (verbose > 1) {
+        for (walk_dbi_t *dbi = walk.dbi; dbi < ARRAY_END(walk.dbi) && dbi->name;
+             ++dbi) {
+          print("     %s: subtotal %" PRIu64, dbi->name, dbi->pages.total);
+          if (dbi->pages.other && dbi->pages.other != dbi->pages.total)
+            print(", other %" PRIu64, dbi->pages.other);
+          if (dbi->pages.branch)
+            print(", branch %" PRIu64, dbi->pages.branch);
+          if (dbi->pages.large_count)
+            print(", large %" PRIu64, dbi->pages.large_count);
+          uint64_t all_leaf = dbi->pages.leaf + dbi->pages.leaf_dupfixed;
+          if (all_leaf) {
+            print(", leaf %" PRIu64, all_leaf);
+            if (verbose > 2 &&
+                (dbi->pages.leaf_dupfixed | dbi->pages.subleaf_dupsort |
+                 dbi->pages.subleaf_dupsort))
+              print(" (usual %" PRIu64 ", sub-dupsort %" PRIu64
+                    ", dupfixed %" PRIu64 ", sub-dupfixed %" PRIu64 ")",
+                    dbi->pages.leaf, dbi->pages.subleaf_dupsort,
+                    dbi->pages.leaf_dupfixed, dbi->pages.subleaf_dupfixed);
+          }
+          print("\n");
+        }
+      }
+
+      if (verbose > 1)
+        print(" - usage: total %" PRIu64 " bytes, payload %" PRIu64
+              " (%.1f%%), unused "
+              "%" PRIu64 " (%.1f%%)\n",
+              total_page_bytes, walk.total_payload_bytes,
+              walk.total_payload_bytes * 100.0 / total_page_bytes,
+              total_page_bytes - walk.total_payload_bytes,
+              (total_page_bytes - walk.total_payload_bytes) * 100.0 /
+                  total_page_bytes);
+      if (verbose > 2) {
+        for (walk_dbi_t *dbi = walk.dbi; dbi < ARRAY_END(walk.dbi) && dbi->name;
+             ++dbi)
+          if (dbi->pages.total) {
+            uint64_t dbi_bytes = dbi->pages.total * envstat.ms_psize;
+            print("     %s: subtotal %" PRIu64 " bytes (%.1f%%),"
+                  " payload %" PRIu64 " (%.1f%%), unused %" PRIu64 " (%.1f%%)",
+                  dbi->name, dbi_bytes, dbi_bytes * 100.0 / total_page_bytes,
+                  dbi->payload_bytes, dbi->payload_bytes * 100.0 / dbi_bytes,
+                  dbi_bytes - dbi->payload_bytes,
+                  (dbi_bytes - dbi->payload_bytes) * 100.0 / dbi_bytes);
+            if (dbi->pages.empty)
+              print(", %" PRIu64 " empty pages", dbi->pages.empty);
+            if (dbi->lost_bytes)
+              print(", %" PRIu64 " bytes lost", dbi->lost_bytes);
+            print("\n");
+          } else
+            print("     %s: empty\n", dbi->name);
+      }
+      print(" - summary: average fill %.1f%%",
+            walk.total_payload_bytes * 100.0 / total_page_bytes);
+      if (empty_pages)
+        print(", %" PRIu64 " empty pages", empty_pages);
+      if (lost_bytes)
+        print(", %" PRIu64 " bytes lost", lost_bytes);
+      print(", %" PRIuPTR " problems\n", traversal_problems);
+    }
+  } else if (verbose) {
+    print("Skipping b-tree walk...\n");
+    fflush(nullptr);
+  }
+
+  if (!verbose)
+    print("Iterating DBIs...\n");
+  problems_maindb = process_db(~0u, /* MAIN_DBI */ nullptr, nullptr, false);
+  problems_freedb = process_db(FREE_DBI, "@GC", handle_freedb, false);
+
+  if (verbose) {
+    uint64_t value = envinfo.mi_mapsize / envstat.ms_psize;
+    double percent = value / 100.0;
+    print(" - space: %" PRIu64 " total pages", value);
+    print(", backed %" PRIu64 " (%.1f%%)", backed_pages,
+          backed_pages / percent);
+    print(", allocated %" PRIu64 " (%.1f%%)", alloc_pages,
+          alloc_pages / percent);
+
+    if (verbose > 1) {
+      value = envinfo.mi_mapsize / envstat.ms_psize - alloc_pages;
+      print(", remained %" PRIu64 " (%.1f%%)", value, value / percent);
+
+      value = dont_traversal ? alloc_pages - gc_pages : walk.pgcount;
+      print(", used %" PRIu64 " (%.1f%%)", value, value / percent);
+
+      print(", gc %" PRIu64 " (%.1f%%)", gc_pages, gc_pages / percent);
+
+      value = gc_pages - reclaimable_pages;
+      print(", detained %" PRIu64 " (%.1f%%)", value, value / percent);
+
+      print(", reclaimable %" PRIu64 " (%.1f%%)", reclaimable_pages,
+            reclaimable_pages / percent);
+    }
+
+    value =
+        envinfo.mi_mapsize / envstat.ms_psize - alloc_pages + reclaimable_pages;
+    print(", available %" PRIu64 " (%.1f%%)\n", value, value / percent);
+  }
+
+  if (problems_maindb == 0 && problems_freedb == 0) {
+    if (!dont_traversal &&
+        (envflags & (MDBX_EXCLUSIVE | MDBX_RDONLY)) != MDBX_RDONLY) {
+      if (walk.pgcount != alloc_pages - gc_pages) {
+        error("used pages mismatch (%" PRIu64 "(walked) != %" PRIu64
+              "(allocated - GC))\n",
+              walk.pgcount, alloc_pages - gc_pages);
+      }
+      if (unused_pages != gc_pages) {
+        error("gc pages mismatch (%" PRIu64 "(expected) != %" PRIu64 "(GC))\n",
+              unused_pages, gc_pages);
+      }
+    } else if (verbose) {
+      print(" - skip check used and gc pages (btree-traversal with "
+            "monopolistic or read-write mode only)\n");
+    }
+
+    if (!process_db(MAIN_DBI, nullptr, handle_maindb, true)) {
+      if (!userdb_count && verbose)
+        print(" - does not contain multiple databases\n");
+    }
+  }
+
+  if (rc == 0 && total_problems == 1 && problems_meta == 1 && !dont_traversal &&
+      (envflags & MDBX_RDONLY) == 0 && !only_subdb && stuck_meta < 0 &&
+      steady_meta_txnid < envinfo.mi_recent_txnid) {
+    print("Perform sync-to-disk for make steady checkpoint at txn-id #%" PRIi64
+          "\n",
+          envinfo.mi_recent_txnid);
+    fflush(nullptr);
+    if (write_locked) {
+      mdbx_txn_unlock(env);
+      write_locked = false;
+    }
+    rc = mdbx_env_sync_ex(env, true, false);
+    if (rc != MDBX_SUCCESS)
+      error("mdbx_env_pgwalk failed, error %d %s\n", rc, mdbx_strerror(rc));
+    else {
+      total_problems -= 1;
+      problems_meta -= 1;
+    }
+  }
+
+  if (turn_meta && stuck_meta >= 0 && !dont_traversal && !only_subdb &&
+      (envflags & (MDBX_RDONLY | MDBX_EXCLUSIVE)) == MDBX_EXCLUSIVE) {
+    const bool successful_check = (rc | total_problems | problems_meta) == 0;
+    if (successful_check || force_turn_meta) {
+      fflush(nullptr);
+      print(" = Performing turn to the specified meta-page (%d) due to %s!\n",
+            stuck_meta,
+            successful_check ? "successful check" : "the -T option was given");
+      fflush(nullptr);
+      rc = mdbx_env_turn_for_recovery(env, stuck_meta);
+      if (rc != MDBX_SUCCESS)
+        error("mdbx_env_turn_for_recovery failed, error %d %s\n", rc,
+              mdbx_strerror(rc));
+    } else {
+      print(" = Skipping turn to the specified meta-page (%d) due to "
+            "unsuccessful check!\n",
+            stuck_meta);
+    }
+  }
+
+bailout:
+  if (txn)
+    mdbx_txn_abort(txn);
+  if (write_locked) {
+    mdbx_txn_unlock(env);
+    write_locked = false;
+  }
+  if (env) {
+    const bool dont_sync = rc != 0 || total_problems;
+    mdbx_env_close_ex(env, dont_sync);
+  }
+  fflush(nullptr);
+  if (rc) {
+    if (rc < 0)
+      return user_break ? EXIT_INTERRUPTED : EXIT_FAILURE_SYS;
+    return EXIT_FAILURE_MDBX;
+  }
+
+#if defined(_WIN32) || defined(_WIN64)
+  timestamp_finish = GetMilliseconds();
+  elapsed = (timestamp_finish - timestamp_start) * 1e-3;
+#else
+  if (clock_gettime(CLOCK_MONOTONIC, &timestamp_finish)) {
+    rc = errno;
+    error("clock_gettime failed, error %d %s\n", rc, mdbx_strerror(rc));
+    return EXIT_FAILURE_SYS;
+  }
+  elapsed = timestamp_finish.tv_sec - timestamp_start.tv_sec +
+            (timestamp_finish.tv_nsec - timestamp_start.tv_nsec) * 1e-9;
+#endif /* !WINDOWS */
+
+  if (total_problems) {
+    print("Total %" PRIu64 " error%s detected, elapsed %.3f seconds.\n",
+          total_problems, (total_problems > 1) ? "s are" : " is", elapsed);
+    if (problems_meta || problems_maindb || problems_freedb)
+      return EXIT_FAILURE_CHECK_MAJOR;
+    return EXIT_FAILURE_CHECK_MINOR;
+  }
+  print("No error is detected, elapsed %.3f seconds\n", elapsed);
+  return EXIT_SUCCESS;
+}
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx_copy.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx_copy.c
new file mode 100644
index 0000000000..faec17ac15
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx_copy.c
@@ -0,0 +1,3270 @@
+/* mdbx_copy.c - memory-mapped database backup tool */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#ifdef _MSC_VER
+#if _MSC_VER > 1800
+#pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#pragma warning(disable : 4996) /* The POSIX name is deprecated... */
+#endif                          /* _MSC_VER (warnings) */
+
+#define MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#if defined(_WIN32) || defined(_WIN64)
+/*
+ * POSIX getopt for Windows
+ *
+ * AT&T Public License
+ *
+ * Code given out at the 1985 UNIFORUM conference in Dallas.
+ */
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#endif /* _MSC_VER (warnings) */
+
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+/*----------------------------------------------------------------------------*/
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+int optind = 1;
+int optopt;
+char *optarg;
+
+int getopt(int argc, char *const argv[], const char *opts) {
+  static int sp = 1;
+  int c;
+  const char *cp;
+
+  if (sp == 1) {
+    if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
+      return EOF;
+    else if (strcmp(argv[optind], "--") == 0) {
+      optind++;
+      return EOF;
+    }
+  }
+  optopt = c = argv[optind][sp];
+  if (c == ':' || (cp = strchr(opts, c)) == NULL) {
+    fprintf(stderr, "%s: %s -- %c\n", argv[0], "illegal option", c);
+    if (argv[optind][++sp] == '\0') {
+      optind++;
+      sp = 1;
+    }
+    return '?';
+  }
+  if (*++cp == ':') {
+    if (argv[optind][sp + 1] != '\0')
+      optarg = &argv[optind++][sp + 1];
+    else if (++optind >= argc) {
+      fprintf(stderr, "%s: %s -- %c\n", argv[0], "option requires an argument",
+              c);
+      sp = 1;
+      return '?';
+    } else
+      optarg = argv[optind++];
+    sp = 1;
+  } else {
+    if (argv[optind][++sp] == '\0') {
+      sp = 1;
+      optind++;
+    }
+    optarg = NULL;
+  }
+  return c;
+}
+
+static volatile BOOL user_break;
+static BOOL WINAPI ConsoleBreakHandlerRoutine(DWORD dwCtrlType) {
+  (void)dwCtrlType;
+  user_break = true;
+  return true;
+}
+
+#else /* WINDOWS */
+
+static volatile sig_atomic_t user_break;
+static void signal_handler(int sig) {
+  (void)sig;
+  user_break = 1;
+}
+
+#endif /* !WINDOWS */
+
+static void usage(const char *prog) {
+  fprintf(stderr,
+          "usage: %s [-V] [-q] [-c] src_path [dest_path]\n"
+          "  -V\t\tprint version and exit\n"
+          "  -q\t\tbe quiet\n"
+          "  -c\t\tenable compactification (skip unused pages)\n"
+          "  src_path\tsource database\n"
+          "  dest_path\tdestination (stdout if not specified)\n",
+          prog);
+  exit(EXIT_FAILURE);
+}
+
+int main(int argc, char *argv[]) {
+  int rc;
+  MDBX_env *env = NULL;
+  const char *progname = argv[0], *act;
+  unsigned flags = MDBX_RDONLY;
+  unsigned cpflags = 0;
+  bool quiet = false;
+
+  for (; argc > 1 && argv[1][0] == '-'; argc--, argv++) {
+    if (argv[1][1] == 'n' && argv[1][2] == '\0')
+      flags |= MDBX_NOSUBDIR;
+    else if (argv[1][1] == 'c' && argv[1][2] == '\0')
+      cpflags |= MDBX_CP_COMPACT;
+    else if (argv[1][1] == 'q' && argv[1][2] == '\0')
+      quiet = true;
+    else if ((argv[1][1] == 'h' && argv[1][2] == '\0') ||
+             strcmp(argv[1], "--help") == 0)
+      usage(progname);
+    else if (argv[1][1] == 'V' && argv[1][2] == '\0') {
+      printf("mdbx_copy version %d.%d.%d.%d\n"
+             " - source: %s %s, commit %s, tree %s\n"
+             " - anchor: %s\n"
+             " - build: %s for %s by %s\n"
+             " - flags: %s\n"
+             " - options: %s\n",
+             mdbx_version.major, mdbx_version.minor, mdbx_version.release,
+             mdbx_version.revision, mdbx_version.git.describe,
+             mdbx_version.git.datetime, mdbx_version.git.commit,
+             mdbx_version.git.tree, mdbx_sourcery_anchor, mdbx_build.datetime,
+             mdbx_build.target, mdbx_build.compiler, mdbx_build.flags,
+             mdbx_build.options);
+      return EXIT_SUCCESS;
+    } else
+      argc = 0;
+  }
+
+  if (argc < 2 || argc > 3)
+    usage(progname);
+
+#if defined(_WIN32) || defined(_WIN64)
+  SetConsoleCtrlHandler(ConsoleBreakHandlerRoutine, true);
+#else
+#ifdef SIGPIPE
+  signal(SIGPIPE, signal_handler);
+#endif
+#ifdef SIGHUP
+  signal(SIGHUP, signal_handler);
+#endif
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+#endif /* !WINDOWS */
+
+  if (!quiet) {
+    fprintf((argc == 2) ? stderr : stdout,
+            "mdbx_copy %s (%s, T-%s)\nRunning for copy %s to %s...\n",
+            mdbx_version.git.describe, mdbx_version.git.datetime,
+            mdbx_version.git.tree, argv[1], (argc == 2) ? "stdout" : argv[2]);
+    fflush(NULL);
+  }
+
+  act = "opening environment";
+  rc = mdbx_env_create(&env);
+  if (rc == MDBX_SUCCESS) {
+    rc = mdbx_env_open(env, argv[1], flags, 0640);
+  }
+  if (rc == MDBX_SUCCESS) {
+    act = "copying";
+    if (argc == 2) {
+      mdbx_filehandle_t fd;
+#if defined(_WIN32) || defined(_WIN64)
+      fd = GetStdHandle(STD_OUTPUT_HANDLE);
+#else
+      fd = fileno(stdout);
+#endif
+      rc = mdbx_env_copy2fd(env, fd, cpflags);
+    } else
+      rc = mdbx_env_copy(env, argv[2], cpflags);
+  }
+  if (rc)
+    fprintf(stderr, "%s: %s failed, error %d (%s)\n", progname, act, rc,
+            mdbx_strerror(rc));
+  mdbx_env_close(env);
+
+  return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx_dump.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx_dump.c
new file mode 100644
index 0000000000..abf82b0d7c
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx_dump.c
@@ -0,0 +1,3626 @@
+/* mdbx_dump.c - memory-mapped database dump tool */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#ifdef _MSC_VER
+#if _MSC_VER > 1800
+#pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#pragma warning(disable : 4996) /* The POSIX name is deprecated... */
+#endif                          /* _MSC_VER (warnings) */
+
+#define MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#include <ctype.h>
+
+#define PRINT 1
+#define GLOBAL 2
+static int mode = GLOBAL;
+
+typedef struct flagbit {
+  int bit;
+  char *name;
+} flagbit;
+
+flagbit dbflags[] = {{MDBX_REVERSEKEY, "reversekey"},
+                     {MDBX_DUPSORT, "dupsort"},
+                     {MDBX_INTEGERKEY, "integerkey"},
+                     {MDBX_DUPFIXED, "dupfixed"},
+                     {MDBX_INTEGERDUP, "integerdup"},
+                     {MDBX_REVERSEDUP, "reversedup"},
+                     {0, nullptr}};
+
+#if defined(_WIN32) || defined(_WIN64)
+/*
+ * POSIX getopt for Windows
+ *
+ * AT&T Public License
+ *
+ * Code given out at the 1985 UNIFORUM conference in Dallas.
+ */
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#endif /* _MSC_VER (warnings) */
+
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+/*----------------------------------------------------------------------------*/
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+int optind = 1;
+int optopt;
+char *optarg;
+
+int getopt(int argc, char *const argv[], const char *opts) {
+  static int sp = 1;
+  int c;
+  const char *cp;
+
+  if (sp == 1) {
+    if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
+      return EOF;
+    else if (strcmp(argv[optind], "--") == 0) {
+      optind++;
+      return EOF;
+    }
+  }
+  optopt = c = argv[optind][sp];
+  if (c == ':' || (cp = strchr(opts, c)) == NULL) {
+    fprintf(stderr, "%s: %s -- %c\n", argv[0], "illegal option", c);
+    if (argv[optind][++sp] == '\0') {
+      optind++;
+      sp = 1;
+    }
+    return '?';
+  }
+  if (*++cp == ':') {
+    if (argv[optind][sp + 1] != '\0')
+      optarg = &argv[optind++][sp + 1];
+    else if (++optind >= argc) {
+      fprintf(stderr, "%s: %s -- %c\n", argv[0], "option requires an argument",
+              c);
+      sp = 1;
+      return '?';
+    } else
+      optarg = argv[optind++];
+    sp = 1;
+  } else {
+    if (argv[optind][++sp] == '\0') {
+      sp = 1;
+      optind++;
+    }
+    optarg = NULL;
+  }
+  return c;
+}
+
+static volatile BOOL user_break;
+static BOOL WINAPI ConsoleBreakHandlerRoutine(DWORD dwCtrlType) {
+  (void)dwCtrlType;
+  user_break = true;
+  return true;
+}
+
+#else /* WINDOWS */
+
+static volatile sig_atomic_t user_break;
+static void signal_handler(int sig) {
+  (void)sig;
+  user_break = 1;
+}
+
+#endif /* !WINDOWS */
+
+static const char hexc[] = "0123456789abcdef";
+
+static void dumpbyte(unsigned char c) {
+  putchar(hexc[c >> 4]);
+  putchar(hexc[c & 0xf]);
+}
+
+static void text(MDBX_val *v) {
+  unsigned char *c, *end;
+
+  putchar(' ');
+  c = v->iov_base;
+  end = c + v->iov_len;
+  while (c < end) {
+    if (isprint(*c) && *c != '\\') {
+      putchar(*c);
+    } else {
+      putchar('\\');
+      dumpbyte(*c);
+    }
+    c++;
+  }
+  putchar('\n');
+}
+
+static void dumpval(MDBX_val *v) {
+  unsigned char *c, *end;
+
+  putchar(' ');
+  c = v->iov_base;
+  end = c + v->iov_len;
+  while (c < end)
+    dumpbyte(*c++);
+  putchar('\n');
+}
+
+bool quiet = false, rescue = false;
+const char *prog;
+static void error(const char *func, int rc) {
+  fprintf(stderr, "%s: %s() error %d %s\n", prog, func, rc, mdbx_strerror(rc));
+}
+
+/* Dump in BDB-compatible format */
+static int dump_sdb(MDBX_txn *txn, MDBX_dbi dbi, char *name) {
+  unsigned int flags;
+  int rc = mdbx_dbi_flags(txn, dbi, &flags);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_flags", rc);
+    return rc;
+  }
+
+  MDBX_stat ms;
+  rc = mdbx_dbi_stat(txn, dbi, &ms, sizeof(ms));
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_stat", rc);
+    return rc;
+  }
+
+  MDBX_envinfo info;
+  rc = mdbx_env_info_ex(mdbx_txn_env(txn), txn, &info, sizeof(info));
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_info_ex", rc);
+    return rc;
+  }
+
+  printf("VERSION=3\n");
+  if (mode & GLOBAL) {
+    mode -= GLOBAL;
+    if (info.mi_geo.upper != info.mi_geo.lower)
+      printf("geometry=l%" PRIu64 ",c%" PRIu64 ",u%" PRIu64 ",s%" PRIu64
+             ",g%" PRIu64 "\n",
+             info.mi_geo.lower, info.mi_geo.current, info.mi_geo.upper,
+             info.mi_geo.shrink, info.mi_geo.grow);
+    printf("mapsize=%" PRIu64 "\n", info.mi_geo.upper);
+    printf("maxreaders=%u\n", info.mi_maxreaders);
+
+    MDBX_canary canary;
+    rc = mdbx_canary_get(txn, &canary);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_canary_get", rc);
+      return rc;
+    }
+    if (canary.v)
+      printf("canary=v%" PRIu64 ",x%" PRIu64 ",y%" PRIu64 ",z%" PRIu64 "\n",
+             canary.v, canary.x, canary.y, canary.z);
+  }
+  printf("format=%s\n", mode & PRINT ? "print" : "bytevalue");
+  if (name)
+    printf("database=%s\n", name);
+  printf("type=btree\n");
+  printf("db_pagesize=%u\n", ms.ms_psize);
+  /* if (ms.ms_mod_txnid)
+    printf("txnid=%" PRIaTXN "\n", ms.ms_mod_txnid);
+  else if (!name)
+    printf("txnid=%" PRIaTXN "\n", mdbx_txn_id(txn)); */
+
+  printf("duplicates=%d\n", (flags & (MDBX_DUPSORT | MDBX_DUPFIXED |
+                                      MDBX_INTEGERDUP | MDBX_REVERSEDUP))
+                                ? 1
+                                : 0);
+  for (int i = 0; dbflags[i].bit; i++)
+    if (flags & dbflags[i].bit)
+      printf("%s=1\n", dbflags[i].name);
+
+  uint64_t sequence;
+  rc = mdbx_dbi_sequence(txn, dbi, &sequence, 0);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_sequence", rc);
+    return rc;
+  }
+  if (sequence)
+    printf("sequence=%" PRIu64 "\n", sequence);
+
+  printf("HEADER=END\n"); /*-------------------------------------------------*/
+
+  MDBX_cursor *cursor;
+  MDBX_val key, data;
+  rc = mdbx_cursor_open(txn, dbi, &cursor);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_cursor_open", rc);
+    return rc;
+  }
+  if (MDBX_DEBUG > 0 && rescue) {
+    cursor->mc_flags |= C_SKIPORD;
+    if (cursor->mc_xcursor)
+      cursor->mc_xcursor->mx_cursor.mc_flags |= C_SKIPORD;
+  }
+
+  while ((rc = mdbx_cursor_get(cursor, &key, &data, MDBX_NEXT)) ==
+         MDBX_SUCCESS) {
+    if (user_break) {
+      rc = MDBX_EINTR;
+      break;
+    }
+    if (mode & PRINT) {
+      text(&key);
+      text(&data);
+    } else {
+      dumpval(&key);
+      dumpval(&data);
+    }
+  }
+  printf("DATA=END\n");
+  if (rc == MDBX_NOTFOUND)
+    rc = MDBX_SUCCESS;
+  if (unlikely(rc != MDBX_SUCCESS))
+    error("mdbx_cursor_get", rc);
+
+  mdbx_cursor_close(cursor);
+  return rc;
+}
+
+static void usage(void) {
+  fprintf(stderr,
+          "usage: %s [-V] [-q] [-f file] [-l] [-p] [-a|-s subdb] [-r] "
+          "dbpath\n"
+          "  -V\t\tprint version and exit\n"
+          "  -q\t\tbe quiet\n"
+          "  -f\t\twrite to file instead of stdout\n"
+          "  -l\t\tlist subDBs and exit\n"
+          "  -p\t\tuse printable characters\n"
+          "  -a\t\tdump main DB and all subDBs,\n"
+          "    \t\tby default dump only the main DB\n"
+          "  -s\t\tdump only the named subDB\n"
+          "  -r\t\trescue mode (ignore errors to dump corrupted DB)\n",
+          prog);
+  exit(EXIT_FAILURE);
+}
+
+static int equal_or_greater(const MDBX_val *a, const MDBX_val *b) {
+  return (a->iov_len == b->iov_len &&
+          memcmp(a->iov_base, b->iov_base, a->iov_len) == 0)
+             ? 0
+             : 1;
+}
+
+int main(int argc, char *argv[]) {
+  int i, rc;
+  MDBX_env *env;
+  MDBX_txn *txn;
+  MDBX_dbi dbi;
+  prog = argv[0];
+  char *envname;
+  char *subname = nullptr, *buf4free = nullptr;
+  unsigned envflags = 0;
+  bool alldbs = false, list = false;
+
+  if (argc < 2)
+    usage();
+
+  while ((i = getopt(argc, argv,
+                     "a"
+                     "f:"
+                     "l"
+                     "n"
+                     "p"
+                     "s:"
+                     "V"
+                     "r"
+                     "q")) != EOF) {
+    switch (i) {
+    case 'V':
+      printf("mdbx_dump version %d.%d.%d.%d\n"
+             " - source: %s %s, commit %s, tree %s\n"
+             " - anchor: %s\n"
+             " - build: %s for %s by %s\n"
+             " - flags: %s\n"
+             " - options: %s\n",
+             mdbx_version.major, mdbx_version.minor, mdbx_version.release,
+             mdbx_version.revision, mdbx_version.git.describe,
+             mdbx_version.git.datetime, mdbx_version.git.commit,
+             mdbx_version.git.tree, mdbx_sourcery_anchor, mdbx_build.datetime,
+             mdbx_build.target, mdbx_build.compiler, mdbx_build.flags,
+             mdbx_build.options);
+      return EXIT_SUCCESS;
+    case 'l':
+      list = true;
+      /*FALLTHROUGH*/;
+      __fallthrough;
+    case 'a':
+      if (subname)
+        usage();
+      alldbs = true;
+      break;
+    case 'f':
+      if (freopen(optarg, "w", stdout) == nullptr) {
+        fprintf(stderr, "%s: %s: reopen: %s\n", prog, optarg,
+                mdbx_strerror(errno));
+        exit(EXIT_FAILURE);
+      }
+      break;
+    case 'n':
+      envflags |= MDBX_NOSUBDIR;
+      break;
+    case 'p':
+      mode |= PRINT;
+      break;
+    case 's':
+      if (alldbs)
+        usage();
+      subname = optarg;
+      break;
+    case 'q':
+      quiet = true;
+      break;
+    case 'r':
+      rescue = true;
+      break;
+    default:
+      usage();
+    }
+  }
+
+  if (optind != argc - 1)
+    usage();
+
+#if defined(_WIN32) || defined(_WIN64)
+  SetConsoleCtrlHandler(ConsoleBreakHandlerRoutine, true);
+#else
+#ifdef SIGPIPE
+  signal(SIGPIPE, signal_handler);
+#endif
+#ifdef SIGHUP
+  signal(SIGHUP, signal_handler);
+#endif
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+#endif /* !WINDOWS */
+
+  envname = argv[optind];
+  if (!quiet) {
+    fprintf(stderr, "mdbx_dump %s (%s, T-%s)\nRunning for %s...\n",
+            mdbx_version.git.describe, mdbx_version.git.datetime,
+            mdbx_version.git.tree, envname);
+    fflush(nullptr);
+  }
+
+  rc = mdbx_env_create(&env);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_create", rc);
+    return EXIT_FAILURE;
+  }
+
+  if (alldbs || subname) {
+    rc = mdbx_env_set_maxdbs(env, 2);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_set_maxdbs", rc);
+      goto env_close;
+    }
+  }
+
+  rc = mdbx_env_open(
+      env, envname,
+      envflags | (rescue ? MDBX_RDONLY | MDBX_EXCLUSIVE : MDBX_RDONLY), 0);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_open", rc);
+    goto env_close;
+  }
+
+  rc = mdbx_txn_begin(env, nullptr, MDBX_TXN_RDONLY, &txn);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_txn_begin", rc);
+    goto env_close;
+  }
+
+  rc = mdbx_dbi_open(txn, subname, MDBX_DB_ACCEDE, &dbi);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_open", rc);
+    goto txn_abort;
+  }
+
+  if (alldbs) {
+    assert(dbi == MAIN_DBI);
+
+    MDBX_cursor *cursor;
+    rc = mdbx_cursor_open(txn, MAIN_DBI, &cursor);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_cursor_open", rc);
+      goto txn_abort;
+    }
+    if (MDBX_DEBUG > 0 && rescue) {
+      cursor->mc_flags |= C_SKIPORD;
+      if (cursor->mc_xcursor)
+        cursor->mc_xcursor->mx_cursor.mc_flags |= C_SKIPORD;
+    }
+
+    bool have_raw = false;
+    int count = 0;
+    MDBX_val key;
+    while (MDBX_SUCCESS ==
+           (rc = mdbx_cursor_get(cursor, &key, nullptr, MDBX_NEXT_NODUP))) {
+      if (user_break) {
+        rc = MDBX_EINTR;
+        break;
+      }
+
+      if (memchr(key.iov_base, '\0', key.iov_len))
+        continue;
+      subname = mdbx_realloc(buf4free, key.iov_len + 1);
+      if (!subname) {
+        rc = MDBX_ENOMEM;
+        break;
+      }
+
+      buf4free = subname;
+      memcpy(subname, key.iov_base, key.iov_len);
+      subname[key.iov_len] = '\0';
+
+      MDBX_dbi sub_dbi;
+      rc = mdbx_dbi_open_ex(txn, subname, MDBX_DB_ACCEDE, &sub_dbi,
+                            rescue ? equal_or_greater : nullptr,
+                            rescue ? equal_or_greater : nullptr);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        if (rc == MDBX_INCOMPATIBLE) {
+          have_raw = true;
+          continue;
+        }
+        error("mdbx_dbi_open", rc);
+        if (!rescue)
+          break;
+      } else {
+        count++;
+        if (list) {
+          printf("%s\n", subname);
+        } else {
+          rc = dump_sdb(txn, sub_dbi, subname);
+          if (unlikely(rc != MDBX_SUCCESS)) {
+            if (!rescue)
+              break;
+            fprintf(stderr, "%s: %s: ignore %s for `%s` and continue\n", prog,
+                    envname, mdbx_strerror(rc), subname);
+            /* Here is a hack for rescue mode, don't do that:
+             *  - we should restart transaction in case error due
+             *    database corruption;
+             *  - but we won't close cursor, reopen and re-positioning it
+             *    for new a transaction;
+             *  - this is possible since DB is opened in read-only exclusive
+             *    mode and transaction is the same, i.e. has the same address
+             *    and so on. */
+            rc = mdbx_txn_reset(txn);
+            if (unlikely(rc != MDBX_SUCCESS)) {
+              error("mdbx_txn_reset", rc);
+              goto env_close;
+            }
+            rc = mdbx_txn_renew(txn);
+            if (unlikely(rc != MDBX_SUCCESS)) {
+              error("mdbx_txn_renew", rc);
+              goto env_close;
+            }
+          }
+        }
+        rc = mdbx_dbi_close(env, sub_dbi);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          error("mdbx_dbi_close", rc);
+          break;
+        }
+      }
+    }
+    mdbx_cursor_close(cursor);
+    cursor = nullptr;
+
+    if (have_raw && (!count /* || rescue */))
+      rc = dump_sdb(txn, MAIN_DBI, nullptr);
+    else if (!count) {
+      fprintf(stderr, "%s: %s does not contain multiple databases\n", prog,
+              envname);
+      rc = MDBX_NOTFOUND;
+    }
+  } else {
+    rc = dump_sdb(txn, dbi, subname);
+  }
+
+  switch (rc) {
+  case MDBX_NOTFOUND:
+    rc = MDBX_SUCCESS;
+  case MDBX_SUCCESS:
+    break;
+  case MDBX_EINTR:
+    fprintf(stderr, "Interrupted by signal/user\n");
+    break;
+  default:
+    if (unlikely(rc != MDBX_SUCCESS))
+      error("mdbx_cursor_get", rc);
+  }
+
+  mdbx_dbi_close(env, dbi);
+txn_abort:
+  mdbx_txn_abort(txn);
+env_close:
+  mdbx_env_close(env);
+  free(buf4free);
+
+  return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx_load.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx_load.c
new file mode 100644
index 0000000000..fc0021bf1c
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx_load.c
@@ -0,0 +1,3965 @@
+/* mdbx_load.c - memory-mapped database load tool */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#ifdef _MSC_VER
+#if _MSC_VER > 1800
+#pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#pragma warning(disable : 4996) /* The POSIX name is deprecated... */
+#endif                          /* _MSC_VER (warnings) */
+
+#define MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#include <ctype.h>
+
+#if defined(_WIN32) || defined(_WIN64)
+/*
+ * POSIX getopt for Windows
+ *
+ * AT&T Public License
+ *
+ * Code given out at the 1985 UNIFORUM conference in Dallas.
+ */
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#endif /* _MSC_VER (warnings) */
+
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+/*----------------------------------------------------------------------------*/
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+int optind = 1;
+int optopt;
+char *optarg;
+
+int getopt(int argc, char *const argv[], const char *opts) {
+  static int sp = 1;
+  int c;
+  const char *cp;
+
+  if (sp == 1) {
+    if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
+      return EOF;
+    else if (strcmp(argv[optind], "--") == 0) {
+      optind++;
+      return EOF;
+    }
+  }
+  optopt = c = argv[optind][sp];
+  if (c == ':' || (cp = strchr(opts, c)) == NULL) {
+    fprintf(stderr, "%s: %s -- %c\n", argv[0], "illegal option", c);
+    if (argv[optind][++sp] == '\0') {
+      optind++;
+      sp = 1;
+    }
+    return '?';
+  }
+  if (*++cp == ':') {
+    if (argv[optind][sp + 1] != '\0')
+      optarg = &argv[optind++][sp + 1];
+    else if (++optind >= argc) {
+      fprintf(stderr, "%s: %s -- %c\n", argv[0], "option requires an argument",
+              c);
+      sp = 1;
+      return '?';
+    } else
+      optarg = argv[optind++];
+    sp = 1;
+  } else {
+    if (argv[optind][++sp] == '\0') {
+      sp = 1;
+      optind++;
+    }
+    optarg = NULL;
+  }
+  return c;
+}
+
+static volatile BOOL user_break;
+static BOOL WINAPI ConsoleBreakHandlerRoutine(DWORD dwCtrlType) {
+  (void)dwCtrlType;
+  user_break = true;
+  return true;
+}
+
+#else /* WINDOWS */
+
+static volatile sig_atomic_t user_break;
+static void signal_handler(int sig) {
+  (void)sig;
+  user_break = 1;
+}
+
+#endif /* !WINDOWS */
+
+static char *prog;
+static size_t lineno;
+static void error(const char *func, int rc) {
+  if (lineno)
+    fprintf(stderr, "%s: at input line %" PRIiSIZE ": %s() error %d, %s\n",
+            prog, lineno, func, rc, mdbx_strerror(rc));
+  else
+    fprintf(stderr, "%s: %s() error %d %s\n", prog, func, rc,
+            mdbx_strerror(rc));
+}
+
+static char *valstr(char *line, const char *item) {
+  const size_t len = strlen(item);
+  if (strncmp(line, item, len) != 0)
+    return nullptr;
+  if (line[len] != '=') {
+    if (line[len] > ' ')
+      return nullptr;
+    fprintf(stderr, "%s: line %" PRIiSIZE ": unexpected line format for '%s'\n",
+            prog, lineno, item);
+    exit(EXIT_FAILURE);
+  }
+  char *ptr = strchr(line, '\n');
+  if (ptr)
+    *ptr = '\0';
+  return line + len + 1;
+}
+
+static bool valnum(char *line, const char *item, uint64_t *value) {
+  char *str = valstr(line, item);
+  if (!str)
+    return false;
+
+  char *end = nullptr;
+  *value = strtoull(str, &end, 0);
+  if (end && *end) {
+    fprintf(stderr,
+            "%s: line %" PRIiSIZE ": unexpected number format for '%s'\n", prog,
+            lineno, item);
+    exit(EXIT_FAILURE);
+  }
+  return true;
+}
+
+static bool valbool(char *line, const char *item, bool *value) {
+  uint64_t u64;
+  if (!valnum(line, item, &u64))
+    return false;
+
+  if (u64 > 1) {
+    fprintf(stderr, "%s: line %" PRIiSIZE ": unexpected value for '%s'\n", prog,
+            lineno, item);
+    exit(EXIT_FAILURE);
+  }
+  *value = u64 != 0;
+  return true;
+}
+
+/*----------------------------------------------------------------------------*/
+
+static char *subname = nullptr;
+static int dbi_flags;
+static txnid_t txnid;
+static uint64_t sequence;
+static MDBX_canary canary;
+static MDBX_envinfo envinfo;
+
+#define PRINT 1
+#define NOHDR 2
+#define GLOBAL 4
+static int mode = GLOBAL;
+
+static MDBX_val kbuf, dbuf;
+
+#define STRLENOF(s) (sizeof(s) - 1)
+
+typedef struct flagbit {
+  unsigned bit;
+  char *name;
+  unsigned len;
+} flagbit;
+
+#define S(s) s, STRLENOF(s)
+
+flagbit dbflags[] = {
+    {MDBX_REVERSEKEY, S("reversekey")}, {MDBX_DUPSORT, S("duplicates")},
+    {MDBX_DUPSORT, S("dupsort")},       {MDBX_INTEGERKEY, S("integerkey")},
+    {MDBX_DUPFIXED, S("dupfixed")},     {MDBX_INTEGERDUP, S("integerdup")},
+    {MDBX_REVERSEDUP, S("reversedup")}, {0, nullptr, 0}};
+
+static int readhdr(void) {
+  /* reset parameters */
+  if (subname) {
+    free(subname);
+    subname = nullptr;
+  }
+  dbi_flags = 0;
+  txnid = 0;
+  sequence = 0;
+
+  while (true) {
+    errno = 0;
+    if (fgets(dbuf.iov_base, (int)dbuf.iov_len, stdin) == nullptr)
+      return errno ? errno : EOF;
+    if (user_break)
+      return MDBX_EINTR;
+
+    lineno++;
+    uint64_t u64;
+
+    if (valnum(dbuf.iov_base, "VERSION", &u64)) {
+      if (u64 != 3) {
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": unsupported value %" PRIu64
+                " for %s\n",
+                prog, lineno, u64, "VERSION");
+        exit(EXIT_FAILURE);
+      }
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "db_pagesize", &u64)) {
+      if (!(mode & GLOBAL) && envinfo.mi_dxb_pagesize != u64)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore value %" PRIu64
+                " for '%s' in non-global context\n",
+                prog, lineno, u64, "db_pagesize");
+      else if (u64 < MDBX_MIN_PAGESIZE || u64 > MDBX_MAX_PAGESIZE)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore unsupported value %" PRIu64
+                " for %s\n",
+                prog, lineno, u64, "db_pagesize");
+      else
+        envinfo.mi_dxb_pagesize = (uint32_t)u64;
+      continue;
+    }
+
+    char *str = valstr(dbuf.iov_base, "format");
+    if (str) {
+      if (strcmp(str, "print") == 0) {
+        mode |= PRINT;
+        continue;
+      }
+      if (strcmp(str, "bytevalue") == 0) {
+        mode &= ~PRINT;
+        continue;
+      }
+      fprintf(stderr, "%s: line %" PRIiSIZE ": unsupported value '%s' for %s\n",
+              prog, lineno, str, "format");
+      exit(EXIT_FAILURE);
+    }
+
+    str = valstr(dbuf.iov_base, "database");
+    if (str) {
+      if (*str) {
+        free(subname);
+        subname = mdbx_strdup(str);
+        if (!subname) {
+          perror("strdup()");
+          exit(EXIT_FAILURE);
+        }
+      }
+      continue;
+    }
+
+    str = valstr(dbuf.iov_base, "type");
+    if (str) {
+      if (strcmp(str, "btree") != 0) {
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": unsupported value '%s' for %s\n", prog,
+                lineno, str, "type");
+        free(subname);
+        exit(EXIT_FAILURE);
+      }
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "mapaddr", &u64)) {
+      if (u64)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore unsupported value 0x%" PRIx64
+                " for %s\n",
+                prog, lineno, u64, "mapaddr");
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "mapsize", &u64)) {
+      if (!(mode & GLOBAL))
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore value %" PRIu64
+                " for '%s' in non-global context\n",
+                prog, lineno, u64, "mapsize");
+      else if (u64 < MIN_MAPSIZE || u64 > MAX_MAPSIZE64)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore unsupported value 0x%" PRIx64
+                " for %s\n",
+                prog, lineno, u64, "mapsize");
+      else
+        envinfo.mi_mapsize = (size_t)u64;
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "maxreaders", &u64)) {
+      if (!(mode & GLOBAL))
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore value %" PRIu64
+                " for '%s' in non-global context\n",
+                prog, lineno, u64, "maxreaders");
+      else if (u64 < 1 || u64 > MDBX_READERS_LIMIT)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore unsupported value 0x%" PRIx64
+                " for %s\n",
+                prog, lineno, u64, "maxreaders");
+      else
+        envinfo.mi_maxreaders = (int)u64;
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "txnid", &u64)) {
+      if (u64 < MIN_TXNID || u64 > MAX_TXNID)
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore unsupported value 0x%" PRIx64
+                " for %s\n",
+                prog, lineno, u64, "txnid");
+      txnid = u64;
+      continue;
+    }
+
+    if (valnum(dbuf.iov_base, "sequence", &u64)) {
+      sequence = u64;
+      continue;
+    }
+
+    str = valstr(dbuf.iov_base, "geometry");
+    if (str) {
+      if (!(mode & GLOBAL))
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore values %s"
+                " for '%s' in non-global context\n",
+                prog, lineno, str, "geometry");
+      else if (sscanf(str,
+                      "l%" PRIu64 ",c%" PRIu64 ",u%" PRIu64 ",s%" PRIu64
+                      ",g%" PRIu64,
+                      &envinfo.mi_geo.lower, &envinfo.mi_geo.current,
+                      &envinfo.mi_geo.upper, &envinfo.mi_geo.shrink,
+                      &envinfo.mi_geo.grow) != 5) {
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": unexpected line format for '%s'\n",
+                prog, lineno, "geometry");
+        exit(EXIT_FAILURE);
+      }
+      continue;
+    }
+
+    str = valstr(dbuf.iov_base, "canary");
+    if (str) {
+      if (!(mode & GLOBAL))
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": ignore values %s"
+                " for '%s' in non-global context\n",
+                prog, lineno, str, "canary");
+      else if (sscanf(str, "v%" PRIu64 ",x%" PRIu64 ",y%" PRIu64 ",z%" PRIu64,
+                      &canary.v, &canary.x, &canary.y, &canary.z) != 4) {
+        fprintf(stderr,
+                "%s: line %" PRIiSIZE ": unexpected line format for '%s'\n",
+                prog, lineno, "canary");
+        exit(EXIT_FAILURE);
+      }
+      continue;
+    }
+
+    for (int i = 0; dbflags[i].bit; i++) {
+      bool value = false;
+      if (valbool(dbuf.iov_base, dbflags[i].name, &value)) {
+        if (value)
+          dbi_flags |= dbflags[i].bit;
+        else
+          dbi_flags &= ~dbflags[i].bit;
+        goto next;
+      }
+    }
+
+    str = valstr(dbuf.iov_base, "HEADER");
+    if (str) {
+      if (strcmp(str, "END") == 0)
+        return MDBX_SUCCESS;
+    }
+
+    fprintf(stderr,
+            "%s: line %" PRIiSIZE ": unrecognized keyword ignored: %s\n", prog,
+            lineno, (char *)dbuf.iov_base);
+  next:;
+  }
+  return EOF;
+}
+
+static int badend(void) {
+  fprintf(stderr, "%s: line %" PRIiSIZE ": unexpected end of input\n", prog,
+          lineno);
+  return errno ? errno : MDBX_ENODATA;
+}
+
+static int unhex(unsigned char *c2) {
+  int x, c;
+  x = *c2++ & 0x4f;
+  if (x & 0x40)
+    x -= 55;
+  c = x << 4;
+  x = *c2 & 0x4f;
+  if (x & 0x40)
+    x -= 55;
+  c |= x;
+  return c;
+}
+
+static int readline(MDBX_val *out, MDBX_val *buf) {
+  unsigned char *c1, *c2, *end;
+  size_t len, l2;
+  int c;
+
+  if (user_break)
+    return MDBX_EINTR;
+
+  errno = 0;
+  if (!(mode & NOHDR)) {
+    c = fgetc(stdin);
+    if (c == EOF)
+      return errno ? errno : EOF;
+    if (c != ' ') {
+      lineno++;
+      errno = 0;
+      if (fgets(buf->iov_base, (int)buf->iov_len, stdin)) {
+        if (c == 'D' && !strncmp(buf->iov_base, "ATA=END", STRLENOF("ATA=END")))
+          return EOF;
+      }
+      return badend();
+    }
+  }
+  if (fgets(buf->iov_base, (int)buf->iov_len, stdin) == nullptr)
+    return errno ? errno : EOF;
+  lineno++;
+
+  c1 = buf->iov_base;
+  len = strlen((char *)c1);
+  l2 = len;
+
+  /* Is buffer too short? */
+  while (c1[len - 1] != '\n') {
+    buf->iov_base = mdbx_realloc(buf->iov_base, buf->iov_len * 2);
+    if (!buf->iov_base) {
+      fprintf(stderr, "%s: line %" PRIiSIZE ": out of memory, line too long\n",
+              prog, lineno);
+      return MDBX_ENOMEM;
+    }
+    c1 = buf->iov_base;
+    c1 += l2;
+    errno = 0;
+    if (fgets((char *)c1, (int)buf->iov_len + 1, stdin) == nullptr)
+      return errno ? errno : EOF;
+    buf->iov_len *= 2;
+    len = strlen((char *)c1);
+    l2 += len;
+  }
+  c1 = c2 = buf->iov_base;
+  len = l2;
+  c1[--len] = '\0';
+  end = c1 + len;
+
+  if (mode & PRINT) {
+    while (c2 < end) {
+      if (unlikely(*c2 == '\\')) {
+        if (c2[1] == '\\') {
+          *c1++ = '\\';
+        } else {
+          if (c2 + 3 > end || !isxdigit(c2[1]) || !isxdigit(c2[2]))
+            return badend();
+          *c1++ = (char)unhex(++c2);
+        }
+        c2 += 2;
+      } else {
+        /* copies are redundant when no escapes were used */
+        *c1++ = *c2++;
+      }
+    }
+  } else {
+    /* odd length not allowed */
+    if (len & 1)
+      return badend();
+    while (c2 < end) {
+      if (!isxdigit(*c2) || !isxdigit(c2[1]))
+        return badend();
+      *c1++ = (char)unhex(c2);
+      c2 += 2;
+    }
+  }
+  c2 = out->iov_base = buf->iov_base;
+  out->iov_len = c1 - c2;
+
+  return MDBX_SUCCESS;
+}
+
+static void usage(void) {
+  fprintf(stderr,
+          "usage: %s "
+          "[-V] [-q] [-a] [-f file] [-s name] [-N] [-p] [-T] [-r] [-n] dbpath\n"
+          "  -V\t\tprint version and exit\n"
+          "  -q\t\tbe quiet\n"
+          "  -a\t\tappend records in input order (required for custom "
+          "comparators)\n"
+          "  -f file\tread from file instead of stdin\n"
+          "  -s name\tload into named subDB\n"
+          "  -N\t\tdon't overwrite existing records when loading, just skip "
+          "ones\n"
+          "  -p\t\tpurge subDB before loading\n"
+          "  -T\t\tread plaintext\n"
+          "  -r\t\trescue mode (ignore errors to load corrupted DB dump)\n"
+          "  -n\t\tdon't use subdirectory for newly created database "
+          "(MDBX_NOSUBDIR)\n",
+          prog);
+  exit(EXIT_FAILURE);
+}
+
+static int equal_or_greater(const MDBX_val *a, const MDBX_val *b) {
+  return (a->iov_len == b->iov_len &&
+          memcmp(a->iov_base, b->iov_base, a->iov_len) == 0)
+             ? 0
+             : 1;
+}
+
+int main(int argc, char *argv[]) {
+  int i, rc;
+  MDBX_env *env = nullptr;
+  MDBX_txn *txn = nullptr;
+  MDBX_cursor *mc = nullptr;
+  MDBX_dbi dbi;
+  char *envname = nullptr;
+  int envflags = MDBX_SAFE_NOSYNC | MDBX_ACCEDE, putflags = MDBX_UPSERT;
+  bool quiet = false;
+  bool rescue = false;
+  bool purge = false;
+
+  prog = argv[0];
+  if (argc < 2)
+    usage();
+
+  while ((i = getopt(argc, argv,
+                     "a"
+                     "f:"
+                     "n"
+                     "s:"
+                     "N"
+                     "p"
+                     "T"
+                     "V"
+                     "r"
+                     "q")) != EOF) {
+    switch (i) {
+    case 'V':
+      printf("mdbx_load version %d.%d.%d.%d\n"
+             " - source: %s %s, commit %s, tree %s\n"
+             " - anchor: %s\n"
+             " - build: %s for %s by %s\n"
+             " - flags: %s\n"
+             " - options: %s\n",
+             mdbx_version.major, mdbx_version.minor, mdbx_version.release,
+             mdbx_version.revision, mdbx_version.git.describe,
+             mdbx_version.git.datetime, mdbx_version.git.commit,
+             mdbx_version.git.tree, mdbx_sourcery_anchor, mdbx_build.datetime,
+             mdbx_build.target, mdbx_build.compiler, mdbx_build.flags,
+             mdbx_build.options);
+      return EXIT_SUCCESS;
+    case 'a':
+      putflags |= MDBX_APPEND;
+      break;
+    case 'f':
+      if (freopen(optarg, "r", stdin) == nullptr) {
+        fprintf(stderr, "%s: %s: open: %s\n", prog, optarg,
+                mdbx_strerror(errno));
+        exit(EXIT_FAILURE);
+      }
+      break;
+    case 'n':
+      envflags |= MDBX_NOSUBDIR;
+      break;
+    case 's':
+      subname = mdbx_strdup(optarg);
+      break;
+    case 'N':
+      putflags |= MDBX_NOOVERWRITE | MDBX_NODUPDATA;
+      break;
+    case 'p':
+      purge = true;
+      break;
+    case 'T':
+      mode |= NOHDR | PRINT;
+      break;
+    case 'q':
+      quiet = true;
+      break;
+    case 'r':
+      rescue = true;
+      break;
+    default:
+      usage();
+    }
+  }
+
+  if (optind != argc - 1)
+    usage();
+
+#if defined(_WIN32) || defined(_WIN64)
+  SetConsoleCtrlHandler(ConsoleBreakHandlerRoutine, true);
+#else
+#ifdef SIGPIPE
+  signal(SIGPIPE, signal_handler);
+#endif
+#ifdef SIGHUP
+  signal(SIGHUP, signal_handler);
+#endif
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+#endif /* !WINDOWS */
+
+  envname = argv[optind];
+  if (!quiet)
+    printf("mdbx_load %s (%s, T-%s)\nRunning for %s...\n",
+           mdbx_version.git.describe, mdbx_version.git.datetime,
+           mdbx_version.git.tree, envname);
+  fflush(nullptr);
+
+  dbuf.iov_len = 4096;
+  dbuf.iov_base = mdbx_malloc(dbuf.iov_len);
+  if (!dbuf.iov_base) {
+    rc = MDBX_ENOMEM;
+    error("value-buffer", rc);
+    goto env_close;
+  }
+
+  /* read first header for mapsize= */
+  if (!(mode & NOHDR)) {
+    rc = readhdr();
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      if (rc == EOF)
+        rc = MDBX_ENODATA;
+      error("readheader", rc);
+      goto env_close;
+    }
+  }
+
+  rc = mdbx_env_create(&env);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_create", rc);
+    return EXIT_FAILURE;
+  }
+
+  mdbx_env_set_maxdbs(env, 2);
+  if (envinfo.mi_maxreaders) {
+    rc = mdbx_env_set_maxreaders(env, envinfo.mi_maxreaders);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_set_maxreaders", rc);
+      goto env_close;
+    }
+  }
+
+  if (envinfo.mi_geo.current | envinfo.mi_mapsize) {
+    if (envinfo.mi_geo.current) {
+      rc = mdbx_env_set_geometry(
+          env, (intptr_t)envinfo.mi_geo.lower, (intptr_t)envinfo.mi_geo.current,
+          (intptr_t)envinfo.mi_geo.upper, (intptr_t)envinfo.mi_geo.shrink,
+          (intptr_t)envinfo.mi_geo.grow,
+          envinfo.mi_dxb_pagesize ? (intptr_t)envinfo.mi_dxb_pagesize : -1);
+    } else {
+      if (envinfo.mi_mapsize > MAX_MAPSIZE) {
+        fprintf(
+            stderr,
+            "Database size is too large for current system (mapsize=%" PRIu64
+            " is great than system-limit %zu)\n",
+            envinfo.mi_mapsize, (size_t)MAX_MAPSIZE);
+        goto env_close;
+      }
+      rc = mdbx_env_set_geometry(
+          env, (intptr_t)envinfo.mi_mapsize, (intptr_t)envinfo.mi_mapsize,
+          (intptr_t)envinfo.mi_mapsize, 0, 0,
+          envinfo.mi_dxb_pagesize ? (intptr_t)envinfo.mi_dxb_pagesize : -1);
+    }
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_set_geometry", rc);
+      goto env_close;
+    }
+  }
+
+  rc = mdbx_env_open(env, envname, envflags, 0664);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_open", rc);
+    goto env_close;
+  }
+
+  kbuf.iov_len = mdbx_env_get_maxvalsize_ex(env, 0) + 1;
+  if (kbuf.iov_len >= INTPTR_MAX / 2) {
+    fprintf(stderr, "mdbx_env_get_maxkeysize() failed, returns %zu\n",
+            kbuf.iov_len);
+    goto env_close;
+  }
+
+  kbuf.iov_base = malloc(kbuf.iov_len);
+  if (!kbuf.iov_base) {
+    rc = MDBX_ENOMEM;
+    error("key-buffer", rc);
+    goto env_close;
+  }
+
+  while (rc == MDBX_SUCCESS) {
+    if (user_break) {
+      rc = MDBX_EINTR;
+      break;
+    }
+
+    rc = mdbx_txn_begin(env, nullptr, 0, &txn);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_txn_begin", rc);
+      goto env_close;
+    }
+
+    if (mode & GLOBAL) {
+      mode -= GLOBAL;
+      if (canary.v | canary.x | canary.y | canary.z) {
+        rc = mdbx_canary_put(txn, &canary);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          error("mdbx_canary_put", rc);
+          goto txn_abort;
+        }
+      }
+    }
+
+    const char *const dbi_name = subname ? subname : "@MAIN";
+    rc =
+        mdbx_dbi_open_ex(txn, subname, dbi_flags | MDBX_CREATE, &dbi,
+                         (putflags & MDBX_APPEND) ? equal_or_greater : nullptr,
+                         (putflags & MDBX_APPEND) ? equal_or_greater : nullptr);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_dbi_open_ex", rc);
+      goto txn_abort;
+    }
+
+    uint64_t present_sequence;
+    rc = mdbx_dbi_sequence(txn, dbi, &present_sequence, 0);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_dbi_sequence", rc);
+      goto txn_abort;
+    }
+    if (present_sequence > sequence) {
+      fprintf(stderr,
+              "present sequence for '%s' value (%" PRIu64
+              ") is greater than loaded (%" PRIu64 ")\n",
+              dbi_name, present_sequence, sequence);
+      rc = MDBX_RESULT_TRUE;
+      goto txn_abort;
+    }
+    if (present_sequence < sequence) {
+      rc = mdbx_dbi_sequence(txn, dbi, nullptr, sequence - present_sequence);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_dbi_sequence", rc);
+        goto txn_abort;
+      }
+    }
+
+    if (purge) {
+      rc = mdbx_drop(txn, dbi, false);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_drop", rc);
+        goto txn_abort;
+      }
+    }
+
+    if (putflags & MDBX_APPEND)
+      putflags = (dbi_flags & MDBX_DUPSORT) ? putflags | MDBX_APPENDDUP
+                                            : putflags & ~MDBX_APPENDDUP;
+
+    rc = mdbx_cursor_open(txn, dbi, &mc);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_cursor_open", rc);
+      goto txn_abort;
+    }
+
+    int batch = 0;
+    while (rc == MDBX_SUCCESS) {
+      MDBX_val key, data;
+      rc = readline(&key, &kbuf);
+      if (rc == EOF)
+        break;
+
+      if (rc == MDBX_SUCCESS)
+        rc = readline(&data, &dbuf);
+      if (rc) {
+        fprintf(stderr, "%s: line %" PRIiSIZE ": failed to read key value\n",
+                prog, lineno);
+        goto txn_abort;
+      }
+
+      rc = mdbx_cursor_put(mc, &key, &data, putflags);
+      if (rc == MDBX_KEYEXIST && putflags)
+        continue;
+      if (rc == MDBX_BAD_VALSIZE && rescue) {
+        fprintf(stderr, "%s: skip line %" PRIiSIZE ": due %s\n", prog, lineno,
+                mdbx_strerror(rc));
+        continue;
+      }
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_cursor_put", rc);
+        goto txn_abort;
+      }
+      batch++;
+
+      MDBX_txn_info txn_info;
+      rc = mdbx_txn_info(txn, &txn_info, false);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_txn_info", rc);
+        goto txn_abort;
+      }
+
+      if (batch == 10000 || txn_info.txn_space_dirty > MEGABYTE * 256) {
+        rc = mdbx_txn_commit(txn);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          error("mdbx_txn_commit", rc);
+          goto env_close;
+        }
+        batch = 0;
+
+        rc = mdbx_txn_begin(env, nullptr, 0, &txn);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          error("mdbx_txn_begin", rc);
+          goto env_close;
+        }
+        rc = mdbx_cursor_bind(txn, mc, dbi);
+        if (unlikely(rc != MDBX_SUCCESS)) {
+          error("mdbx_cursor_bind", rc);
+          goto txn_abort;
+        }
+      }
+    }
+
+    mdbx_cursor_close(mc);
+    mc = nullptr;
+    rc = mdbx_txn_commit(txn);
+    txn = nullptr;
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_txn_commit", rc);
+      goto env_close;
+    }
+    if (subname) {
+      assert(dbi != MAIN_DBI);
+      rc = mdbx_dbi_close(env, dbi);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_dbi_close", rc);
+        goto env_close;
+      }
+    } else {
+      assert(dbi == MAIN_DBI);
+    }
+
+    /* try read next header */
+    if (!(mode & NOHDR))
+      rc = readhdr();
+    else if (ferror(stdin) || feof(stdin))
+      break;
+  }
+
+  switch (rc) {
+  case EOF:
+    rc = MDBX_SUCCESS;
+  case MDBX_SUCCESS:
+    break;
+  case MDBX_EINTR:
+    fprintf(stderr, "Interrupted by signal/user\n");
+    break;
+  default:
+    if (unlikely(rc != MDBX_SUCCESS))
+      error("readline", rc);
+  }
+
+txn_abort:
+  mdbx_cursor_close(mc);
+  mdbx_txn_abort(txn);
+env_close:
+  mdbx_env_close(env);
+  free(kbuf.iov_base);
+  free(dbuf.iov_base);
+
+  return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/plugins/Dbx_mdbx/src/libmdbx/mdbx_stat.c b/plugins/Dbx_mdbx/src/libmdbx/mdbx_stat.c
new file mode 100644
index 0000000000..30e9e5cc29
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/mdbx_stat.c
@@ -0,0 +1,3611 @@
+/* mdbx_stat.c - memory-mapped database status tool */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#ifdef _MSC_VER
+#if _MSC_VER > 1800
+#pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#pragma warning(disable : 4996) /* The POSIX name is deprecated... */
+#endif                          /* _MSC_VER (warnings) */
+
+#define MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>. */
+
+#define MDBX_BUILD_SOURCERY 37ec6726f69ef69c4e52fcfb87d700f44f37246b1b635f455d2a429776a8eec6_v0_9_2_136_g9f0ff86
+#ifdef MDBX_CONFIG_H
+#include MDBX_CONFIG_H
+#endif
+
+#define LIBMDBX_INTERNALS
+#ifdef MDBX_TOOLS
+#define MDBX_DEPRECATED
+#endif /* MDBX_TOOLS */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+/* In case the MDBX_DEBUG is undefined set it corresponding to NDEBUG */
+#ifndef MDBX_DEBUG
+#   ifdef NDEBUG
+#       define MDBX_DEBUG 0
+#   else
+#       define MDBX_DEBUG 1
+#   endif
+#endif
+
+/* Undefine the NDEBUG if debugging is enforced by MDBX_DEBUG */
+#if MDBX_DEBUG
+#   undef NDEBUG
+#endif
+
+#ifdef MDBX_ALLOY
+/* Amalgamated build */
+#   define MDBX_INTERNAL_FUNC static
+#   define MDBX_INTERNAL_VAR static
+#else
+/* Non-amalgamated build */
+#   define MDBX_INTERNAL_FUNC
+#   define MDBX_INTERNAL_VAR extern
+#endif /* MDBX_ALLOY */
+
+#ifndef MDBX_DISABLE_GNU_SOURCE
+#define MDBX_DISABLE_GNU_SOURCE 0
+#endif
+#if MDBX_DISABLE_GNU_SOURCE
+#undef _GNU_SOURCE
+#elif (defined(__linux__) || defined(__gnu_linux__)) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+/* Should be defined before any includes */
+#ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+#endif
+
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE
+#endif
+
+#ifdef _MSC_VER
+#   if _MSC_FULL_VER < 190024234
+        /* Actually libmdbx was not tested with compilers older than 19.00.24234 (Visual Studio 2015 Update 3).
+         * But you could remove this #error and try to continue at your own risk.
+         * In such case please don't rise up an issues related ONLY to old compilers.
+         */
+#       error "At least \"Microsoft C/C++ Compiler\" version 19.00.24234 (Visual Studio 2015 Update 3) is required."
+#   endif
+#   ifndef _CRT_SECURE_NO_WARNINGS
+#       define _CRT_SECURE_NO_WARNINGS
+#   endif
+#if _MSC_VER > 1800
+#   pragma warning(disable : 4464) /* relative include path contains '..' */
+#endif
+#if _MSC_VER > 1913
+#   pragma warning(disable : 5045) /* Compiler will insert Spectre mitigation... */
+#endif
+#pragma warning(disable : 4710) /* 'xyz': function not inlined */
+#pragma warning(disable : 4711) /* function 'xyz' selected for automatic inline expansion */
+#pragma warning(disable : 4201) /* nonstandard extension used : nameless struct / union */
+#pragma warning(disable : 4702) /* unreachable code */
+#pragma warning(disable : 4706) /* assignment within conditional expression */
+#pragma warning(disable : 4127) /* conditional expression is constant */
+#pragma warning(disable : 4324) /* 'xyz': structure was padded due to alignment specifier */
+#pragma warning(disable : 4310) /* cast truncates constant value */
+#pragma warning(disable : 4820) /* bytes padding added after data member for alignment */
+#pragma warning(disable : 4548) /* expression before comma has no effect; expected expression with side - effect */
+#pragma warning(disable : 4366) /* the result of the unary '&' operator may be unaligned */
+#pragma warning(disable : 4200) /* nonstandard extension used: zero-sized array in struct/union */
+#pragma warning(disable : 4204) /* nonstandard extension used: non-constant aggregate initializer */
+#pragma warning(disable : 4505) /* unreferenced local function has been removed */
+#endif                          /* _MSC_VER (warnings) */
+
+#include "mdbx.h"
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+
+#ifndef __GNUC_PREREQ
+#   if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#       define __GNUC_PREREQ(maj, min) \
+          ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GNUC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GNUC_PREREQ */
+
+#ifndef __CLANG_PREREQ
+#   ifdef __clang__
+#       define __CLANG_PREREQ(maj,min) \
+          ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+#   else
+#       define __CLANG_PREREQ(maj,min) (0)
+#   endif
+#endif /* __CLANG_PREREQ */
+
+#ifndef __GLIBC_PREREQ
+#   if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
+#       define __GLIBC_PREREQ(maj, min) \
+          ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
+#   else
+#       define __GLIBC_PREREQ(maj, min) (0)
+#   endif
+#endif /* __GLIBC_PREREQ */
+
+#ifndef __has_warning
+#   define __has_warning(x) (0)
+#endif
+
+#ifndef __has_include
+#   define __has_include(x) (0)
+#endif
+
+#if __has_feature(thread_sanitizer)
+#   define __SANITIZE_THREAD__ 1
+#endif
+
+#if __has_feature(address_sanitizer)
+#   define __SANITIZE_ADDRESS__ 1
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __extern_C
+#   ifdef __cplusplus
+#       define __extern_C extern "C"
+#   else
+#       define __extern_C
+#   endif
+#endif /* __extern_C */
+
+#if !defined(nullptr) && !defined(__cplusplus) || (__cplusplus < 201103L && !defined(_MSC_VER))
+#   define nullptr NULL
+#endif
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef __always_inline
+#   if defined(__GNUC__) || __has_attribute(__always_inline__)
+#       define __always_inline __inline __attribute__((__always_inline__))
+#   elif defined(_MSC_VER)
+#       define __always_inline __forceinline
+#   else
+#       define __always_inline
+#   endif
+#endif /* __always_inline */
+
+#ifndef __noinline
+#   if defined(__GNUC__) || __has_attribute(__noinline__)
+#       define __noinline __attribute__((__noinline__))
+#   elif defined(_MSC_VER)
+#       define __noinline __declspec(noinline)
+#   else
+#       define __noinline
+#   endif
+#endif /* __noinline */
+
+#ifndef __must_check_result
+#   if defined(__GNUC__) || __has_attribute(__warn_unused_result__)
+#       define __must_check_result __attribute__((__warn_unused_result__))
+#   else
+#       define __must_check_result
+#   endif
+#endif /* __must_check_result */
+
+#ifndef __maybe_unused
+#   if defined(__GNUC__) || __has_attribute(__unused__)
+#       define __maybe_unused __attribute__((__unused__))
+#   else
+#       define __maybe_unused
+#   endif
+#endif /* __maybe_unused */
+
+#if !defined(__noop) && !defined(_MSC_VER)
+#   define __noop(...) do {} while(0)
+#endif /* __noop */
+
+#ifndef __fallthrough
+#  if defined(__cplusplus) && (__has_cpp_attribute(fallthrough) &&             \
+     (!defined(__clang__) || __clang__ > 4)) || __cplusplus >= 201703L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(8, 0) && defined(__cplusplus) && __cplusplus >= 201103L
+#    define __fallthrough [[fallthrough]]
+#  elif __GNUC_PREREQ(7, 0) &&                                                 \
+    (!defined(__LCC__) || (__LCC__ == 124 && __LCC_MINOR__ >= 12) ||           \
+     (__LCC__ == 125 && __LCC_MINOR__ >= 5) || (__LCC__ >= 126))
+#    define __fallthrough __attribute__((__fallthrough__))
+#  elif defined(__clang__) && defined(__cplusplus) && __cplusplus >= 201103L &&\
+    __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#    define __fallthrough [[clang::fallthrough]]
+#  else
+#    define __fallthrough
+#  endif
+#endif /* __fallthrough */
+
+#ifndef __unreachable
+#   if __GNUC_PREREQ(4,5) || __has_builtin(__builtin_unreachable)
+#       define __unreachable() __builtin_unreachable()
+#   elif defined(_MSC_VER)
+#       define __unreachable() __assume(0)
+#   else
+#       define __unreachable() __noop()
+#   endif
+#endif /* __unreachable */
+
+#ifndef __prefetch
+#   if defined(__GNUC__) || defined(__clang__) || __has_builtin(__builtin_prefetch)
+#       define __prefetch(ptr) __builtin_prefetch(ptr)
+#   else
+#       define __prefetch(ptr) __noop(ptr)
+#   endif
+#endif /* __prefetch */
+
+#ifndef __nothrow
+#   if defined(__cplusplus)
+#       if __cplusplus < 201703L
+#           define __nothrow throw()
+#       else
+#           define __nothrow noexcept(true)
+#       endif /* __cplusplus */
+#   elif defined(__GNUC__) || __has_attribute(__nothrow__)
+#       define __nothrow __attribute__((__nothrow__))
+#   elif defined(_MSC_VER) && defined(__cplusplus)
+#       define __nothrow __declspec(nothrow)
+#   else
+#       define __nothrow
+#   endif
+#endif /* __nothrow */
+
+#ifndef __hidden
+#   if defined(__GNUC__) || __has_attribute(__visibility__)
+#       define __hidden __attribute__((__visibility__("hidden")))
+#   else
+#       define __hidden
+#   endif
+#endif /* __hidden */
+
+#ifndef __optimize
+#   if defined(__OPTIMIZE__)
+#       if (defined(__GNUC__) && !defined(__clang__)) || __has_attribute(__optimize__)
+#           define __optimize(ops) __attribute__((__optimize__(ops)))
+#       else
+#           define __optimize(ops)
+#       endif
+#   else
+#       define __optimize(ops)
+#   endif
+#endif /* __optimize */
+
+#ifndef __hot
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __hot __attribute__((__hot__)) __optimize(3)
+#       elif defined(__clang__) && !__has_attribute(__hot_) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put frequently used functions in separate section */
+#           define __hot __attribute__((__section__("text.hot"))) __optimize("O3")
+#       elif defined(__GNUC__) || __has_attribute(__hot__)
+#           define __hot __attribute__((__hot__)) __optimize("O3")
+#       else
+#           define __hot  __optimize("O3")
+#       endif
+#   else
+#       define __hot
+#   endif
+#endif /* __hot */
+
+#ifndef __cold
+#   if defined(__OPTIMIZE__)
+#       if defined(__e2k__)
+#           define __cold __attribute__((__cold__)) __optimize(1)
+#       elif defined(__clang__) && !__has_attribute(cold) \
+        && __has_attribute(__section__) && (defined(__linux__) || defined(__gnu_linux__))
+            /* just put infrequently used functions in separate section */
+#           define __cold __attribute__((__section__("text.unlikely"))) __optimize("Os")
+#       elif defined(__GNUC__) || __has_attribute(cold)
+#           define __cold __attribute__((__cold__)) __optimize("Os")
+#       else
+#           define __cold __optimize("Os")
+#       endif
+#   else
+#       define __cold
+#   endif
+#endif /* __cold */
+
+#ifndef __flatten
+#   if defined(__OPTIMIZE__) && (defined(__GNUC__) || __has_attribute(__flatten__))
+#       define __flatten __attribute__((__flatten__))
+#   else
+#       define __flatten
+#   endif
+#endif /* __flatten */
+
+#ifndef likely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define likely(cond) __builtin_expect(!!(cond), 1)
+#   else
+#       define likely(x) (!!(x))
+#   endif
+#endif /* likely */
+
+#ifndef unlikely
+#   if (defined(__GNUC__) || __has_builtin(__builtin_expect)) && !defined(__COVERITY__)
+#       define unlikely(cond) __builtin_expect(!!(cond), 0)
+#   else
+#       define unlikely(x) (!!(x))
+#   endif
+#endif /* unlikely */
+
+#ifndef __anonymous_struct_extension__
+#   if defined(__GNUC__)
+#       define __anonymous_struct_extension__ __extension__
+#   else
+#       define __anonymous_struct_extension__
+#   endif
+#endif /* __anonymous_struct_extension__ */
+
+#ifndef __Wpedantic_format_voidptr
+    static __inline __maybe_unused const void* MDBX_PURE_FUNCTION
+        __Wpedantic_format_voidptr(const void* ptr) {return ptr;}
+#   define __Wpedantic_format_voidptr(ARG) __Wpedantic_format_voidptr(ARG)
+#endif /* __Wpedantic_format_voidptr */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(MDBX_USE_VALGRIND)
+#   include <valgrind/memcheck.h>
+#   ifndef VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE
+        /* LY: available since Valgrind 3.10 */
+#       define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#       define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   endif
+#elif !defined(RUNNING_ON_VALGRIND)
+#   define VALGRIND_CREATE_MEMPOOL(h,r,z)
+#   define VALGRIND_DESTROY_MEMPOOL(h)
+#   define VALGRIND_MEMPOOL_TRIM(h,a,s)
+#   define VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#   define VALGRIND_MEMPOOL_FREE(h,a)
+#   define VALGRIND_MEMPOOL_CHANGE(h,a,b,s)
+#   define VALGRIND_MAKE_MEM_NOACCESS(a,s)
+#   define VALGRIND_MAKE_MEM_DEFINED(a,s)
+#   define VALGRIND_MAKE_MEM_UNDEFINED(a,s)
+#   define VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE(a,s)
+#   define VALGRIND_CHECK_MEM_IS_ADDRESSABLE(a,s) (0)
+#   define VALGRIND_CHECK_MEM_IS_DEFINED(a,s) (0)
+#   define RUNNING_ON_VALGRIND (0)
+#endif /* MDBX_USE_VALGRIND */
+
+#ifdef __SANITIZE_ADDRESS__
+#   include <sanitizer/asan_interface.h>
+#elif !defined(ASAN_POISON_MEMORY_REGION)
+#   define ASAN_POISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#   define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+        ((void)(addr), (void)(size))
+#endif /* __SANITIZE_ADDRESS__ */
+
+/*----------------------------------------------------------------------------*/
+
+#ifndef ARRAY_LENGTH
+#   ifdef __cplusplus
+        template <typename T, size_t N>
+        char (&__ArraySizeHelper(T (&array)[N]))[N];
+#       define ARRAY_LENGTH(array) (sizeof(::__ArraySizeHelper(array)))
+#   else
+#       define ARRAY_LENGTH(array) (sizeof(array) / sizeof(array[0]))
+#   endif
+#endif /* ARRAY_LENGTH */
+
+#ifndef ARRAY_END
+#   define ARRAY_END(array) (&array[ARRAY_LENGTH(array)])
+#endif /* ARRAY_END */
+
+#ifndef STRINGIFY
+#   define STRINGIFY_HELPER(x) #x
+#   define STRINGIFY(x) STRINGIFY_HELPER(x)
+#endif /* STRINGIFY */
+
+#define CONCAT(a,b) a##b
+#define XCONCAT(a,b) CONCAT(a,b)
+
+#ifndef offsetof
+#   define offsetof(type, member)  __builtin_offsetof(type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#   define container_of(ptr, type, member) \
+        ((type *)((char *)(ptr) - offsetof(type, member)))
+#endif /* container_of */
+
+#define MDBX_TETRAD(a, b, c, d)                                                \
+  ((uint32_t)(a) << 24 | (uint32_t)(b) << 16 | (uint32_t)(c) << 8 | (d))
+
+#define MDBX_STRING_TETRAD(str) MDBX_TETRAD(str[0], str[1], str[2], str[3])
+
+#define FIXME "FIXME: " __FILE__ ", " STRINGIFY(__LINE__)
+
+#ifndef STATIC_ASSERT_MSG
+#   if defined(static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) static_assert(expr, msg)
+#   elif defined(_STATIC_ASSERT)
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif defined(_MSC_VER)
+#       include <crtdbg.h>
+#       define STATIC_ASSERT_MSG(expr, msg) _STATIC_ASSERT(expr)
+#   elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) \
+          || __has_feature(c_static_assert)
+#       define STATIC_ASSERT_MSG(expr, msg) _Static_assert(expr, msg)
+#   else
+#       define STATIC_ASSERT_MSG(expr, msg) switch (0) {case 0:case (expr):;}
+#   endif
+#endif /* STATIC_ASSERT */
+
+#ifndef STATIC_ASSERT
+#   define STATIC_ASSERT(expr) STATIC_ASSERT_MSG(expr, #expr)
+#endif
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__GNUC__) && !__GNUC_PREREQ(4,2)
+    /* Actually libmdbx was not tested with compilers older than GCC 4.2.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required GCC >= 4.2"
+#endif
+
+#if defined(__clang__) && !__CLANG_PREREQ(3,8)
+    /* Actually libmdbx was not tested with CLANG older than 3.8.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old compilers.
+     */
+#   warning "libmdbx required CLANG >= 3.8"
+#endif
+
+#if defined(__GLIBC__) && !__GLIBC_PREREQ(2,12)
+    /* Actually libmdbx was not tested with something older than glibc 2.12.
+     * But you could ignore this warning at your own risk.
+     * In such case please don't rise up an issues related ONLY to old systems.
+     */
+#   warning "libmdbx was only tested with GLIBC >= 2.12."
+#endif
+
+#ifdef __SANITIZE_THREAD__
+#   warning "libmdbx don't compatible with ThreadSanitizer, you will get a lot of false-positive issues."
+#endif /* __SANITIZE_THREAD__ */
+
+#if __has_warning("-Wnested-anon-types")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wnested-anon-types"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wnested-anon-types"
+#   else
+#      pragma warning disable "nested-anon-types"
+#   endif
+#endif /* -Wnested-anon-types */
+
+#if __has_warning("-Wconstant-logical-operand")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Wconstant-logical-operand"
+#   else
+#      pragma warning disable "constant-logical-operand"
+#   endif
+#endif /* -Wconstant-logical-operand */
+
+#if defined(__LCC__) && (__LCC__ <= 121)
+    /* bug #2798 */
+#   pragma diag_suppress alignment_reduction_ignored
+#elif defined(__ICC)
+#   pragma warning(disable: 3453 1366)
+#elif __has_warning("-Walignment-reduction-ignored")
+#   if defined(__clang__)
+#       pragma clang diagnostic ignored "-Walignment-reduction-ignored"
+#   elif defined(__GNUC__)
+#       pragma GCC diagnostic ignored "-Walignment-reduction-ignored"
+#   else
+#       pragma warning disable "alignment-reduction-ignored"
+#   endif
+#endif /* -Walignment-reduction-ignored */
+
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */
+
+/*
+ * Copyright 2015-2021 Leonid Yuriev <leo@yuriev.ru>
+ * and other libmdbx authors: please see AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#endif                          /* _MSC_VER (warnings) */
+
+#if defined(_WIN32) || defined(_WIN64)
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#if !defined(_NO_CRT_STDIO_INLINE) && MDBX_BUILD_SHARED_LIBRARY &&             \
+    !defined(MDBX_TOOLS) && MDBX_AVOID_CRT
+#define _NO_CRT_STDIO_INLINE
+#endif
+#elif !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif /* Windows */
+
+/*----------------------------------------------------------------------------*/
+/* C99 includes */
+#include <inttypes.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+/* C11 stdalign.h */
+#if __has_include(<stdalign.h>)
+#include <stdalign.h>
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define alignas(N) _Alignas(N)
+#elif defined(_MSC_VER)
+#define alignas(N) __declspec(align(N))
+#elif __has_attribute(__aligned__) || defined(__GNUC__)
+#define alignas(N) __attribute__((__aligned__(N)))
+#else
+#error "FIXME: Required _alignas() or equivalent."
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Systems includes */
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif /* Apple OSX & iOS */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+    defined(__BSD__) || defined(__bsdi__) || defined(__DragonFly__) ||         \
+    defined(__APPLE__) || defined(__MACH__)
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <vm/vm_param.h>
+#elif defined(__OpenBSD__) || defined(__NetBSD__)
+#include <uvm/uvm_param.h>
+#else
+#define SYSCTL_LEGACY_NONCONST_MIB
+#endif
+#ifndef __MACH__
+#include <sys/vmmeter.h>
+#endif
+#else
+#include <malloc.h>
+#if !(defined(__sun) || defined(__SVR4) || defined(__svr4__) ||                \
+      defined(_WIN32) || defined(_WIN64))
+#include <mntent.h>
+#endif /* !Solaris */
+#endif /* !xBSD */
+
+#if defined(__FreeBSD__) || __has_include(<malloc_np.h>)
+#include <malloc_np.h>
+#endif
+
+#if defined(__APPLE__) || defined(__MACH__) || __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif /* MacOS */
+
+#if defined(__MACH__)
+#include <mach/host_info.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+#include <uuid/uuid.h>
+#undef P_DIRTY
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+#include <linux/sysctl.h>
+#include <sched.h>
+#include <sys/sendfile.h>
+#include <sys/statfs.h>
+#endif /* Linux */
+
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 0
+#endif
+
+#ifndef _XOPEN_SOURCE_EXTENDED
+#define _XOPEN_SOURCE_EXTENDED 0
+#else
+#include <utmpx.h>
+#endif /* _XOPEN_SOURCE_EXTENDED */
+
+#if defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#include <kstat.h>
+#include <sys/mnttab.h>
+/* On Solaris, it's easier to add a missing prototype rather than find a
+ * combination of #defines that break nothing. */
+__extern_C key_t ftok(const char *, int);
+#endif /* SunOS/Solaris */
+
+#if defined(_WIN32) || defined(_WIN64)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <excpt.h>
+#include <tlhelp32.h>
+#include <windows.h>
+#include <winnt.h>
+#include <winternl.h>
+#define HAVE_SYS_STAT_H
+#define HAVE_SYS_TYPES_H
+typedef HANDLE mdbx_thread_t;
+typedef unsigned mdbx_thread_key_t;
+#define MDBX_OSAL_SECTION HANDLE
+#define MAP_FAILED NULL
+#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
+#define THREAD_CALL WINAPI
+#define THREAD_RESULT DWORD
+typedef struct {
+  HANDLE mutex;
+  HANDLE event[2];
+} mdbx_condpair_t;
+typedef CRITICAL_SECTION mdbx_fastmutex_t;
+
+#if MDBX_AVOID_CRT
+#ifndef mdbx_malloc
+static inline void *mdbx_malloc(size_t bytes) {
+  return LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_malloc */
+
+#ifndef mdbx_calloc
+static inline void *mdbx_calloc(size_t nelem, size_t size) {
+  return LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, nelem * size);
+}
+#endif /* mdbx_calloc */
+
+#ifndef mdbx_realloc
+static inline void *mdbx_realloc(void *ptr, size_t bytes) {
+  return ptr ? LocalReAlloc(ptr, bytes, LMEM_MOVEABLE)
+             : LocalAlloc(LMEM_FIXED, bytes);
+}
+#endif /* mdbx_realloc */
+
+#ifndef mdbx_free
+#define mdbx_free LocalFree
+#endif /* mdbx_free */
+#else
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup _strdup
+#endif /* MDBX_AVOID_CRT */
+
+#ifndef snprintf
+#define snprintf _snprintf /* ntdll */
+#endif
+
+#ifndef vsnprintf
+#define vsnprintf _vsnprintf /* ntdll */
+#endif
+
+#else /*----------------------------------------------------------------------*/
+
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/uio.h>
+#include <unistd.h>
+typedef pthread_t mdbx_thread_t;
+typedef pthread_key_t mdbx_thread_key_t;
+#define INVALID_HANDLE_VALUE (-1)
+#define THREAD_CALL
+#define THREAD_RESULT void *
+typedef struct {
+  pthread_mutex_t mutex;
+  pthread_cond_t cond[2];
+} mdbx_condpair_t;
+typedef pthread_mutex_t mdbx_fastmutex_t;
+#define mdbx_malloc malloc
+#define mdbx_calloc calloc
+#define mdbx_realloc realloc
+#define mdbx_free free
+#define mdbx_strdup strdup
+#endif /* Platform */
+
+#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
+/* malloc_usable_size() already provided */
+#elif defined(__APPLE__)
+#define malloc_usable_size(ptr) malloc_size(ptr)
+#elif defined(_MSC_VER) && !MDBX_AVOID_CRT
+#define malloc_usable_size(ptr) _msize(ptr)
+#endif /* malloc_usable_size */
+
+#ifdef __ANDROID_API__
+#include <android/log.h>
+#if __ANDROID_API__ >= 21
+#include <sys/sendfile.h>
+#endif
+#endif /* Android */
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(HAVE_SYS_STAT_H) || __has_include(<sys/stat.h>)
+#include <sys/stat.h>
+#endif
+#if defined(HAVE_SYS_TYPES_H) || __has_include(<sys/types.h>)
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_FILE_H) || __has_include(<sys/file.h>)
+#include <sys/file.h>
+#endif
+/* *INDENT-ON* */
+/* clang-format on */
+
+#ifndef SSIZE_MAX
+#define SSIZE_MAX INTPTR_MAX
+#endif
+
+#if !defined(MADV_DODUMP) && defined(MADV_CORE)
+#define MADV_DODUMP MADV_CORE
+#endif /* MADV_CORE -> MADV_DODUMP */
+
+#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
+#define MADV_DONTDUMP MADV_NOCORE
+#endif /* MADV_NOCORE -> MADV_DONTDUMP */
+
+#if defined(i386) || defined(__386) || defined(__i386) || defined(__i386__) || \
+    defined(i486) || defined(__i486) || defined(__i486__) ||                   \
+    defined(i586) | defined(__i586) || defined(__i586__) || defined(i686) ||   \
+    defined(__i686) || defined(__i686__) || defined(_M_IX86) ||                \
+    defined(_X86_) || defined(__THW_INTEL__) || defined(__I86__) ||            \
+    defined(__INTEL__) || defined(__x86_64) || defined(__x86_64__) ||          \
+    defined(__amd64__) || defined(__amd64) || defined(_M_X64) ||               \
+    defined(_M_AMD64) || defined(__IA32__) || defined(__INTEL__)
+#ifndef __ia32__
+/* LY: define neutral __ia32__ for x86 and x86-64 */
+#define __ia32__ 1
+#endif /* __ia32__ */
+#if !defined(__amd64__) && (defined(__x86_64) || defined(__x86_64__) ||        \
+                            defined(__amd64) || defined(_M_X64))
+/* LY: define trusty __amd64__ for all AMD64/x86-64 arch */
+#define __amd64__ 1
+#endif /* __amd64__ */
+#endif /* all x86 */
+
+#if (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+#error                                                                         \
+    "Sanity checking failed: Two's complement, reasonably sized integer types"
+#endif
+
+#if UINTPTR_MAX > 0xffffFFFFul || ULONG_MAX > 0xffffFFFFul
+#define MDBX_WORDBITS 64
+#else
+#define MDBX_WORDBITS 32
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+/* Compiler's includes for builtins/intrinsics */
+
+#if defined(_MSC_VER) || defined(__INTEL_COMPILER)
+#include <intrin.h>
+#elif __GNUC_PREREQ(4, 4) || defined(__clang__)
+#if defined(__ia32__) || defined(__e2k__)
+#include <x86intrin.h>
+#endif /* __ia32__ */
+#if defined(__ia32__)
+#include <cpuid.h>
+#endif /* __ia32__ */
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+#include <mbarrier.h>
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+#include <machine/sys/inline.h>
+#elif defined(__IBMC__) && defined(__powerpc)
+#include <atomic.h>
+#elif defined(_AIX)
+#include <builtins.h>
+#include <sys/atomic_op.h>
+#elif (defined(__osf__) && defined(__DECC)) || defined(__alpha)
+#include <c_asm.h>
+#include <machine/builtins.h>
+#elif defined(__MWERKS__)
+/* CodeWarrior - troubles ? */
+#pragma gcc_extensions
+#elif defined(__SNC__)
+/* Sony PS3 - troubles ? */
+#elif defined(__hppa__) || defined(__hppa)
+#include <machine/inline.h>
+#else
+#error Unsupported C compiler, please use GNU C 4.4 or newer
+#endif /* Compiler */
+
+/*----------------------------------------------------------------------------*/
+/* Byteorder */
+
+#if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) ||           \
+    !defined(__ORDER_BIG_ENDIAN__)
+
+/* *INDENT-OFF* */
+/* clang-format off */
+#if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID_API__) ||  \
+    defined(HAVE_ENDIAN_H) || __has_include(<endian.h>)
+#include <endian.h>
+#elif defined(__APPLE__) || defined(__MACH__) || defined(__OpenBSD__) ||       \
+    defined(HAVE_MACHINE_ENDIAN_H) || __has_include(<machine/endian.h>)
+#include <machine/endian.h>
+#elif defined(HAVE_SYS_ISA_DEFS_H) || __has_include(<sys/isa_defs.h>)
+#include <sys/isa_defs.h>
+#elif (defined(HAVE_SYS_TYPES_H) && defined(HAVE_SYS_ENDIAN_H)) ||             \
+    (__has_include(<sys/types.h>) && __has_include(<sys/endian.h>))
+#include <sys/endian.h>
+#include <sys/types.h>
+#elif defined(__bsdi__) || defined(__DragonFly__) || defined(__FreeBSD__) ||   \
+    defined(__NetBSD__) ||                              \
+    defined(HAVE_SYS_PARAM_H) || __has_include(<sys/param.h>)
+#include <sys/param.h>
+#endif /* OS */
+/* *INDENT-ON* */
+/* clang-format on */
+
+#if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ __LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ __BIG_ENDIAN
+#define __BYTE_ORDER__ __BYTE_ORDER
+#elif defined(_BYTE_ORDER) && defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN)
+#define __ORDER_LITTLE_ENDIAN__ _LITTLE_ENDIAN
+#define __ORDER_BIG_ENDIAN__ _BIG_ENDIAN
+#define __BYTE_ORDER__ _BYTE_ORDER
+#else
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#define __ORDER_BIG_ENDIAN__ 4321
+
+#if defined(__LITTLE_ENDIAN__) ||                                              \
+    (defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)) ||                      \
+    defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) ||    \
+    defined(__MIPSEL__) || defined(_MIPSEL) || defined(__MIPSEL) ||            \
+    defined(_M_ARM) || defined(_M_ARM64) || defined(__e2k__) ||                \
+    defined(__elbrus_4c__) || defined(__elbrus_8c__) || defined(__bfin__) ||   \
+    defined(__BFIN__) || defined(__ia64__) || defined(_IA64) ||                \
+    defined(__IA64__) || defined(__ia64) || defined(_M_IA64) ||                \
+    defined(__itanium__) || defined(__ia32__) || defined(__CYGWIN__) ||        \
+    defined(_WIN64) || defined(_WIN32) || defined(__TOS_WIN__) ||              \
+    defined(__WINDOWS__)
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+
+#elif defined(__BIG_ENDIAN__) ||                                               \
+    (defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)) ||                      \
+    defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) ||    \
+    defined(__MIPSEB__) || defined(_MIPSEB) || defined(__MIPSEB) ||            \
+    defined(__m68k__) || defined(M68000) || defined(__hppa__) ||               \
+    defined(__hppa) || defined(__HPPA__) || defined(__sparc__) ||              \
+    defined(__sparc) || defined(__370__) || defined(__THW_370__) ||            \
+    defined(__s390__) || defined(__s390x__) || defined(__SYSC_ZARCH__)
+#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
+
+#else
+#error __BYTE_ORDER__ should be defined.
+#endif /* Arch */
+
+#endif
+#endif /* __BYTE_ORDER__ || __ORDER_LITTLE_ENDIAN__ || __ORDER_BIG_ENDIAN__ */
+
+/* Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files. */
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline size_t
+mdbx_syspagesize(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return sysconf(_SC_PAGE_SIZE);
+#endif
+}
+
+typedef struct mdbx_mmap_param {
+  union {
+    void *address;
+    uint8_t *dxb;
+    struct MDBX_lockinfo *lck;
+  };
+  mdbx_filehandle_t fd;
+  size_t limit;   /* mapping length, but NOT a size of file nor DB */
+  size_t current; /* mapped region size, i.e. the size of file and DB */
+#if defined(_WIN32) || defined(_WIN64)
+  uint64_t filesize /* in-process cache of a file size. */;
+#endif
+#ifdef MDBX_OSAL_SECTION
+  MDBX_OSAL_SECTION section;
+#endif
+} mdbx_mmap_t;
+
+typedef union bin128 {
+  __anonymous_struct_extension__ struct { uint64_t x, y; };
+  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
+} bin128_t;
+
+#if defined(_WIN32) || defined(_WIN64)
+typedef union MDBX_srwlock {
+  struct {
+    long volatile readerCount;
+    long volatile writerCount;
+  };
+  RTL_SRWLOCK native;
+} MDBX_srwlock;
+#endif /* Windows */
+
+#ifdef __cplusplus
+extern void mdbx_osal_jitter(bool tiny);
+#else
+
+/*----------------------------------------------------------------------------*/
+/* Atomics */
+
+#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && (__has_include(<cstdatomic>) || __has_extension(cxx_atomic))
+#include <cstdatomic>
+#define MDBX_HAVE_C11ATOMICS
+#elif !defined(__cplusplus) &&                                                 \
+    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
+    !defined(__STDC_NO_ATOMICS__) &&                                           \
+    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
+     !(defined(__GNUC__) || defined(__clang__)))
+#include <stdatomic.h>
+#define MDBX_HAVE_C11ATOMICS
+#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
+#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
+                                   'size_t' to 'LONGLONG' */
+#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
+                                   'std::size_t', possible loss of data */
+#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
+                                   'long', possible loss of data */
+#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
+#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
+#elif defined(__APPLE__)
+#include <libkern/OSAtomic.h>
+#else
+#error FIXME atomic-ops
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Memory/Compiler barriers, cache coherence */
+
+#if __has_include(<sys/cachectl.h>)
+#include <sys/cachectl.h>
+#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS should have explicit cache control */
+#include <sys/cachectl.h>
+#endif
+
+static __maybe_unused __inline void mdbx_compiler_barrier(void) {
+#if defined(__clang__) || defined(__GNUC__)
+  __asm__ __volatile__("" ::: "memory");
+#elif defined(_MSC_VER)
+  _ReadWriteBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+  __memory_barrier();
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __compiler_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __fence();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+static __maybe_unused __inline void mdbx_memory_barrier(void) {
+#ifdef MDBX_HAVE_C11ATOMICS
+  atomic_thread_fence(memory_order_seq_cst);
+#elif defined(__ATOMIC_SEQ_CST)
+#ifdef __clang__
+  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
+#else
+  __atomic_thread_fence(__ATOMIC_SEQ_CST);
+#endif
+#elif defined(__clang__) || defined(__GNUC__)
+  __sync_synchronize();
+#elif defined(_WIN32) || defined(_WIN64)
+  MemoryBarrier();
+#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
+#if defined(__ia32__)
+  _mm_mfence();
+#else
+  __mf();
+#endif
+#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
+  __machine_rw_barrier();
+#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
+    (defined(HP_IA64) || defined(__ia64))
+  _Asm_mf();
+#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
+    defined(__ppc64__) || defined(__powerpc64__)
+  __lwsync();
+#else
+#error "Could not guess the kind of compiler, please report to us."
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* libc compatibility stuff */
+
+#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
+    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
+#define mdbx_asprintf asprintf
+#define mdbx_vasprintf vasprintf
+#else
+MDBX_INTERNAL_FUNC MDBX_PRINTF_ARGS(2, 3) int __maybe_unused
+    mdbx_asprintf(char **strp, const char *fmt, ...);
+MDBX_INTERNAL_FUNC int mdbx_vasprintf(char **strp, const char *fmt, va_list ap);
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* OS abstraction layer stuff */
+
+/* max bytes to write in one call */
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_WRITE UINT32_C(0x01000000)
+#else
+#define MAX_WRITE UINT32_C(0x3fff0000)
+#endif
+
+#if defined(__linux__) || defined(__gnu_linux__)
+MDBX_INTERNAL_VAR uint32_t mdbx_linux_kernel_version;
+MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
+#endif /* Linux */
+
+#ifndef mdbx_strdup
+LIBMDBX_API char *mdbx_strdup(const char *str);
+#endif
+
+static __maybe_unused __inline int mdbx_get_errno(void) {
+#if defined(_WIN32) || defined(_WIN64)
+  DWORD rc = GetLastError();
+#else
+  int rc = errno;
+#endif
+  return rc;
+}
+
+#ifndef mdbx_memalign_alloc
+MDBX_INTERNAL_FUNC int mdbx_memalign_alloc(size_t alignment, size_t bytes,
+                                           void **result);
+#endif
+#ifndef mdbx_memalign_free
+MDBX_INTERNAL_FUNC void mdbx_memalign_free(void *ptr);
+#endif
+
+MDBX_INTERNAL_FUNC int mdbx_condpair_init(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_lock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_unlock(mdbx_condpair_t *condpair);
+MDBX_INTERNAL_FUNC int mdbx_condpair_signal(mdbx_condpair_t *condpair,
+                                            bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_wait(mdbx_condpair_t *condpair, bool part);
+MDBX_INTERNAL_FUNC int mdbx_condpair_destroy(mdbx_condpair_t *condpair);
+
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_init(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_acquire(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_release(mdbx_fastmutex_t *fastmutex);
+MDBX_INTERNAL_FUNC int mdbx_fastmutex_destroy(mdbx_fastmutex_t *fastmutex);
+
+MDBX_INTERNAL_FUNC int mdbx_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
+                                    int iovcnt, uint64_t offset,
+                                    size_t expected_written);
+MDBX_INTERNAL_FUNC int mdbx_pread(mdbx_filehandle_t fd, void *buf, size_t count,
+                                  uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_pwrite(mdbx_filehandle_t fd, const void *buf,
+                                   size_t count, uint64_t offset);
+MDBX_INTERNAL_FUNC int mdbx_write(mdbx_filehandle_t fd, const void *buf,
+                                  size_t count);
+
+MDBX_INTERNAL_FUNC int
+mdbx_thread_create(mdbx_thread_t *thread,
+                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
+                   void *arg);
+MDBX_INTERNAL_FUNC int mdbx_thread_join(mdbx_thread_t thread);
+
+enum mdbx_syncmode_bits {
+  MDBX_SYNC_NONE = 0,
+  MDBX_SYNC_DATA = 1,
+  MDBX_SYNC_SIZE = 2,
+  MDBX_SYNC_IODQ = 4
+};
+
+MDBX_INTERNAL_FUNC int mdbx_fsync(mdbx_filehandle_t fd,
+                                  const enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_ftruncate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL_FUNC int mdbx_fseek(mdbx_filehandle_t fd, uint64_t pos);
+MDBX_INTERNAL_FUNC int mdbx_filesize(mdbx_filehandle_t fd, uint64_t *length);
+
+enum mdbx_openfile_purpose {
+  MDBX_OPEN_DXB_READ = 0,
+  MDBX_OPEN_DXB_LAZY = 1,
+  MDBX_OPEN_DXB_DSYNC = 2,
+  MDBX_OPEN_LCK = 3,
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
+};
+
+MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
+                                     const MDBX_env *env, const char *pathname,
+                                     mdbx_filehandle_t *fd,
+                                     mdbx_mode_t unix_mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
+
+#define MMAP_OPTION_TRUNCATE 1
+#define MMAP_OPTION_SEMAPHORE 2
+MDBX_INTERNAL_FUNC int mdbx_mmap(const int flags, mdbx_mmap_t *map,
+                                 const size_t must, const size_t limit,
+                                 const unsigned options);
+MDBX_INTERNAL_FUNC int mdbx_munmap(mdbx_mmap_t *map);
+MDBX_INTERNAL_FUNC int mdbx_mresize(int flags, mdbx_mmap_t *map, size_t current,
+                                    size_t wanna, const bool may_move);
+#if defined(_WIN32) || defined(_WIN64)
+typedef struct {
+  unsigned limit, count;
+  HANDLE handles[31];
+} mdbx_handle_array_t;
+MDBX_INTERNAL_FUNC int
+mdbx_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
+MDBX_INTERNAL_FUNC int
+mdbx_resume_threads_after_remap(mdbx_handle_array_t *array);
+#endif /* Windows */
+MDBX_INTERNAL_FUNC int mdbx_msync(mdbx_mmap_t *map, size_t offset,
+                                  size_t length,
+                                  enum mdbx_syncmode_bits mode_bits);
+MDBX_INTERNAL_FUNC int mdbx_check_fs_rdonly(mdbx_filehandle_t handle,
+                                            const char *pathname, int err);
+
+static __maybe_unused __inline uint32_t mdbx_getpid(void) {
+  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
+#if defined(_WIN32) || defined(_WIN64)
+  return GetCurrentProcessId();
+#else
+  return getpid();
+#endif
+}
+
+static __maybe_unused __inline uintptr_t mdbx_thread_self(void) {
+  mdbx_tid_t thunk;
+  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
+#if defined(_WIN32) || defined(_WIN64)
+  thunk = GetCurrentThreadId();
+#else
+  thunk = pthread_self();
+#endif
+  return (uintptr_t)thunk;
+}
+
+MDBX_INTERNAL_FUNC void __maybe_unused mdbx_osal_jitter(bool tiny);
+MDBX_INTERNAL_FUNC uint64_t mdbx_osal_monotime(void);
+MDBX_INTERNAL_FUNC uint64_t
+mdbx_osal_16dot16_to_monotime(uint32_t seconds_16dot16);
+MDBX_INTERNAL_FUNC uint32_t mdbx_osal_monotime_to_16dot16(uint64_t monotime);
+
+MDBX_INTERNAL_FUNC bin128_t mdbx_osal_bootid(void);
+/*----------------------------------------------------------------------------*/
+/* lck stuff */
+
+/// \brief Initialization of synchronization primitives linked with MDBX_env
+///   instance both in LCK-file and within the current process.
+/// \param
+///   global_uniqueness_flag = true - denotes that there are no other processes
+///     working with DB and LCK-file. Thus the function MUST initialize
+///     shared synchronization objects in memory-mapped LCK-file.
+///   global_uniqueness_flag = false - denotes that at least one process is
+///     already working with DB and LCK-file, including the case when DB
+///     has already been opened in the current process. Thus the function
+///     MUST NOT initialize shared synchronization objects in memory-mapped
+///     LCK-file that are already in use.
+/// \return Error code or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_init(MDBX_env *env,
+                                     MDBX_env *inprocess_neighbor,
+                                     int global_uniqueness_flag);
+
+/// \brief Disconnects from shared interprocess objects and destructs
+///   synchronization objects linked with MDBX_env instance
+///   within the current process.
+/// \param
+///   inprocess_neighbor = NULL - if the current process does not have other
+///     instances of MDBX_env linked with the DB being closed.
+///     Thus the function MUST check for other processes working with DB or
+///     LCK-file, and keep or destroy shared synchronization objects in
+///     memory-mapped LCK-file depending on the result.
+///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
+///     (anyone of there is several) working with DB or LCK-file within the
+///     current process. Thus the function MUST NOT try to acquire exclusive
+///     lock and/or try to destruct shared synchronization objects linked with
+///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
+///     of other instances of MDBX_env within the current process, e.g.
+///     restore POSIX-fcntl locks after the closing of file descriptors.
+/// \return Error code (MDBX_PANIC) or zero on success.
+MDBX_INTERNAL_FUNC int mdbx_lck_destroy(MDBX_env *env,
+                                        MDBX_env *inprocess_neighbor);
+
+/// \brief Connects to shared interprocess locking objects and tries to acquire
+///   the maximum lock level (shared if exclusive is not available)
+///   Depending on implementation or/and platform (Windows) this function may
+///   acquire the non-OS super-level lock (e.g. for shared synchronization
+///   objects initialization), which will be downgraded to OS-exclusive or
+///   shared via explicit calling of mdbx_lck_downgrade().
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
+///     the current process is the first and only after the last use of DB.
+///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
+///     DB has already been opened and now is used by other processes.
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_lck_seize(MDBX_env *env);
+
+/// \brief Downgrades the level of initially acquired lock to
+///   operational level specified by argument. The reson for such downgrade:
+///    - unblocking of other processes that are waiting for access, i.e.
+///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
+///      should be made aware that access is unavailable rather than
+///      wait for it.
+///    - freeing locks that interfere file operation (especially for Windows)
+///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
+///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
+///   operational lock.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env);
+
+/// \brief Locks LCK-file or/and table of readers for (de)registering.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rdt_lock(MDBX_env *env);
+
+/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
+MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env);
+
+/// \brief Acquires lock for DB change (on writing transaction start)
+///   Reading transactions will not be blocked.
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+/// \return Error code or zero on success
+LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);
+
+/// \brief Releases lock once DB changes is made (after writing transaction
+///   has finished).
+///   Declared as LIBMDBX_API because it is used in mdbx_chk.
+LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);
+
+/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
+///   the current process. The function does no more than needed for
+///   the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env);
+
+/// \brief Resets alive-flag of reader presence (indicative lock)
+///   for PID of the current process. The function does no more than needed
+///   for the correct working of mdbx_rpid_check() in other processes.
+/// \return Error code or zero on success
+MDBX_INTERNAL_FUNC int mdbx_rpid_clear(MDBX_env *env);
+
+/// \brief Checks for reading process status with the given pid with help of
+///   alive-flag of presence (indicative lock) or using another way.
+/// \return
+///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
+///     and working with DB (indicative lock is present).
+///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
+///     or not working with DB (indicative lock is not present).
+///   Otherwise (not 0 and not -1) - error code.
+MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, uint32_t pid);
+
+#if defined(_WIN32) || defined(_WIN64)
+
+typedef void(WINAPI *MDBX_srwlock_function)(MDBX_srwlock *);
+MDBX_INTERNAL_VAR MDBX_srwlock_function mdbx_srwlock_Init,
+    mdbx_srwlock_AcquireShared, mdbx_srwlock_ReleaseShared,
+    mdbx_srwlock_AcquireExclusive, mdbx_srwlock_ReleaseExclusive;
+
+typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
+    mdbx_GetFileInformationByHandleEx;
+
+typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
+    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
+    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
+    _Out_opt_ LPDWORD lpMaximumComponentLength,
+    _Out_opt_ LPDWORD lpFileSystemFlags,
+    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
+MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
+    mdbx_GetVolumeInformationByHandleW;
+
+typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
+                                                      _Out_ LPWSTR lpszFilePath,
+                                                      _In_ DWORD cchFilePath,
+                                                      _In_ DWORD dwFlags);
+MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;
+
+typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
+    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
+    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
+MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
+    mdbx_SetFileInformationByHandle;
+
+typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
+    IN HANDLE FileHandle, IN OUT HANDLE Event,
+    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
+    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
+    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
+    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
+MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;
+
+typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
+MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;
+
+#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
+typedef struct _WIN32_MEMORY_RANGE_ENTRY {
+  PVOID VirtualAddress;
+  SIZE_T NumberOfBytes;
+} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
+#endif /* Windows 8.x */
+
+typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
+    HANDLE hProcess, ULONG_PTR NumberOfEntries,
+    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
+MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;
+
+#if 0 /* LY: unused for now */
+#if !defined(_WIN32_WINNT_WIN81) || _WIN32_WINNT < _WIN32_WINNT_WIN81
+typedef enum OFFER_PRIORITY {
+  VmOfferPriorityVeryLow = 1,
+  VmOfferPriorityLow,
+  VmOfferPriorityBelowNormal,
+  VmOfferPriorityNormal
+} OFFER_PRIORITY;
+#endif /* Windows 8.1 */
+
+typedef DWORD(WINAPI *MDBX_DiscardVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_DiscardVirtualMemory mdbx_DiscardVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_ReclaimVirtualMemory)(PVOID VirtualAddress,
+                                                 SIZE_T Size);
+MDBX_INTERNAL_VAR MDBX_ReclaimVirtualMemory mdbx_ReclaimVirtualMemory;
+
+typedef DWORD(WINAPI *MDBX_OfferVirtualMemory(
+  PVOID          VirtualAddress,
+  SIZE_T         Size,
+  OFFER_PRIORITY Priority
+);
+MDBX_INTERNAL_VAR MDBX_OfferVirtualMemory mdbx_OfferVirtualMemory;
+#endif /* unused for now */
+
+typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;
+
+typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
+                                              IN PLARGE_INTEGER NewSectionSize);
+MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;
+
+static __inline bool mdbx_RunningUnderWine(void) {
+  return !mdbx_NtExtendSection;
+}
+
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
+#endif /* Windows */
+
+#endif /* !__cplusplus */
+
+/*----------------------------------------------------------------------------*/
+
+#if defined(_MSC_VER) && _MSC_VER >= 1900
+/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
+ * for internal format-args checker. */
+#undef PRIuPTR
+#undef PRIiPTR
+#undef PRIdPTR
+#undef PRIxPTR
+#define PRIuPTR "Iu"
+#define PRIiPTR "Ii"
+#define PRIdPTR "Id"
+#define PRIxPTR "Ix"
+#define PRIuSIZE "zu"
+#define PRIiSIZE "zi"
+#define PRIdSIZE "zd"
+#define PRIxSIZE "zx"
+#endif /* fix PRI*PTR for _MSC_VER */
+
+#ifndef PRIuSIZE
+#define PRIuSIZE PRIuPTR
+#define PRIiSIZE PRIiPTR
+#define PRIdSIZE PRIdPTR
+#define PRIxSIZE PRIxPTR
+#endif /* PRI*SIZE macros for MSVC */
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#define mdbx_sourcery_anchor XCONCAT(mdbx_sourcery_, MDBX_BUILD_SOURCERY)
+#if defined(MDBX_TOOLS)
+extern LIBMDBX_API const char *const mdbx_sourcery_anchor;
+#endif
+
+/*******************************************************************************
+ *******************************************************************************
+ *******************************************************************************
+ *
+ *
+ *         ####   #####    #####     #     ####   #    #   ####
+ *        #    #  #    #     #       #    #    #  ##   #  #
+ *        #    #  #    #     #       #    #    #  # #  #   ####
+ *        #    #  #####      #       #    #    #  #  # #       #
+ *        #    #  #          #       #    #    #  #   ##  #    #
+ *         ####   #          #       #     ####   #    #   ####
+ *
+ *
+ */
+
+/** \defgroup build_option Build options
+ * The libmdbx build options.
+ @{ */
+
+#ifdef DOXYGEN
+/* !!! Actually this is a fake definitions     !!!
+ * !!! for documentation generation by Doxygen !!! */
+
+/** Controls enabling of debugging features.
+ *
+ *  - `MDBX_DEBUG = 0` (by default) Disables any debugging features at all,
+ *                     including logging and assertion controls.
+ *                     Logging level and corresponding debug flags changing
+ *                     by \ref mdbx_setup_debug() will not have effect.
+ *  - `MDBX_DEBUG > 0` Enables code for the debugging features (logging,
+ *                     assertions checking and internal audit).
+ *                     Simultaneously sets the default logging level
+ *                     to the `MDBX_DEBUG` value.
+ *                     Also enables \ref MDBX_DBG_AUDIT if `MDBX_DEBUG >= 2`.
+ *
+ * \ingroup build_option */
+#define MDBX_DEBUG 0...7
+
+/** Disables using of GNU libc extensions. */
+#define MDBX_DISABLE_GNU_SOURCE 0 or 1
+
+#endif /* DOXYGEN */
+
+/** Using fcntl(F_FULLFSYNC) with 5-10 times slowdown */
+#define MDBX_OSX_WANNA_DURABILITY 0
+/** Using fsync() with chance of data lost on power failure */
+#define MDBX_OSX_WANNA_SPEED 1
+
+#ifndef MDBX_OSX_SPEED_INSTEADOF_DURABILITY
+/** Choices \ref MDBX_OSX_WANNA_DURABILITY or \ref MDBX_OSX_WANNA_SPEED
+ * for OSX & iOS */
+#define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
+#endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
+
+/** Controls checking PID against reuse DB environment after the fork() */
+#ifndef MDBX_ENV_CHECKPID
+#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+/* PID check could be omitted:
+ *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
+ *    mapped pages will not be available for child process.
+ *  - in Windows where fork() not available. */
+#define MDBX_ENV_CHECKPID 0
+#else
+#define MDBX_ENV_CHECKPID 1
+#endif
+#define MDBX_ENV_CHECKPID_CONFIG "AUTO=" STRINGIFY(MDBX_ENV_CHECKPID)
+#else
+#define MDBX_ENV_CHECKPID_CONFIG STRINGIFY(MDBX_ENV_CHECKPID)
+#endif /* MDBX_ENV_CHECKPID */
+
+/** Controls checking transaction owner thread against misuse transactions from
+ * other threads. */
+#ifndef MDBX_TXN_CHECKOWNER
+#define MDBX_TXN_CHECKOWNER 1
+#define MDBX_TXN_CHECKOWNER_CONFIG "AUTO=" STRINGIFY(MDBX_TXN_CHECKOWNER)
+#else
+#define MDBX_TXN_CHECKOWNER_CONFIG STRINGIFY(MDBX_TXN_CHECKOWNER)
+#endif /* MDBX_TXN_CHECKOWNER */
+
+/** Does a system have battery-backed Real-Time Clock or just a fake. */
+#ifndef MDBX_TRUST_RTC
+#if defined(__linux__) || defined(__gnu_linux__) || defined(__NetBSD__) ||     \
+    defined(__OpenBSD__)
+#define MDBX_TRUST_RTC 0 /* a lot of embedded systems have a fake RTC */
+#else
+#define MDBX_TRUST_RTC 1
+#endif
+#define MDBX_TRUST_RTC_CONFIG "AUTO=" STRINGIFY(MDBX_TRUST_RTC)
+#else
+#define MDBX_TRUST_RTC_CONFIG STRINGIFY(MDBX_TRUST_RTC)
+#endif /* MDBX_TRUST_RTC */
+
+/** Controls online database auto-compactification during write-transactions. */
+#ifndef MDBX_ENABLE_REFUND
+#define MDBX_ENABLE_REFUND 1
+#endif
+#if !(MDBX_ENABLE_REFUND == 0 || MDBX_ENABLE_REFUND == 1)
+#error MDBX_ENABLE_REFUND must be defined as 0 or 1
+#endif /* MDBX_ENABLE_REFUND */
+
+/** Controls sort order of internal page number lists.
+ * The database format depend on this option and libmdbx builded with different
+ * option value are incompatible. */
+#ifndef MDBX_PNL_ASCENDING
+#define MDBX_PNL_ASCENDING 0
+#endif
+#if !(MDBX_PNL_ASCENDING == 0 || MDBX_PNL_ASCENDING == 1)
+#error MDBX_PNL_ASCENDING must be defined as 0 or 1
+#endif /* MDBX_PNL_ASCENDING */
+
+//------------------------------------------------------------------------------
+
+/** Win32 File Locking API for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_WIN32FILES -1
+
+/** SystemV IPC semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_SYSV 5
+
+/** POSIX-1 Shared anonymous semaphores for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX1988 1988
+
+/** POSIX-2001 Shared Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2001 2001
+
+/** POSIX-2008 Robust Mutexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_POSIX2008 2008
+
+/** BeOS Benaphores, aka Futexes for \ref MDBX_LOCKING */
+#define MDBX_LOCKING_BENAPHORE 1995
+
+/** Advanced: Choices the locking implementation (autodetection by default). */
+#if defined(_WIN32) || defined(_WIN64)
+#define MDBX_LOCKING MDBX_LOCKING_WIN32FILES
+#else
+#ifndef MDBX_LOCKING
+#if defined(_POSIX_THREAD_PROCESS_SHARED) &&                                   \
+    _POSIX_THREAD_PROCESS_SHARED >= 200112L && !defined(__FreeBSD__)
+
+/* Some platforms define the EOWNERDEAD error code even though they
+ * don't support Robust Mutexes. If doubt compile with -MDBX_LOCKING=2001. */
+#if defined(EOWNERDEAD) && _POSIX_THREAD_PROCESS_SHARED >= 200809L &&          \
+    ((defined(_POSIX_THREAD_ROBUST_PRIO_INHERIT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_INHERIT > 0) ||                                \
+     (defined(_POSIX_THREAD_ROBUST_PRIO_PROTECT) &&                            \
+      _POSIX_THREAD_ROBUST_PRIO_PROTECT > 0) ||                                \
+     defined(PTHREAD_MUTEX_ROBUST) || defined(PTHREAD_MUTEX_ROBUST_NP)) &&     \
+    (!defined(__GLIBC__) ||                                                    \
+     __GLIBC_PREREQ(2, 10) /* troubles with Robust mutexes before 2.10 */)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2008
+#else
+#define MDBX_LOCKING MDBX_LOCKING_POSIX2001
+#endif
+#elif defined(__sun) || defined(__SVR4) || defined(__svr4__)
+#define MDBX_LOCKING MDBX_LOCKING_POSIX1988
+#else
+#define MDBX_LOCKING MDBX_LOCKING_SYSV
+#endif
+#define MDBX_LOCKING_CONFIG "AUTO=" STRINGIFY(MDBX_LOCKING)
+#else
+#define MDBX_LOCKING_CONFIG STRINGIFY(MDBX_LOCKING)
+#endif /* MDBX_LOCKING */
+#endif /* !Windows */
+
+/** Advanced: Using POSIX OFD-locks (autodetection by default). */
+#ifndef MDBX_USE_OFDLOCKS
+#if defined(F_OFD_SETLK) && defined(F_OFD_SETLKW) && defined(F_OFD_GETLK) &&   \
+    !defined(MDBX_SAFE4QEMU) &&                                                \
+    !defined(__sun) /* OFD-lock are broken on Solaris */
+#define MDBX_USE_OFDLOCKS 1
+#else
+#define MDBX_USE_OFDLOCKS 0
+#endif
+#define MDBX_USE_OFDLOCKS_CONFIG "AUTO=" STRINGIFY(MDBX_USE_OFDLOCKS)
+#else
+#define MDBX_USE_OFDLOCKS_CONFIG STRINGIFY(MDBX_USE_OFDLOCKS)
+#endif /* MDBX_USE_OFDLOCKS */
+
+/** Advanced: Using sendfile() syscall (autodetection by default). */
+#ifndef MDBX_USE_SENDFILE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     !defined(__ANDROID_API__)) ||                                             \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
+#define MDBX_USE_SENDFILE 1
+#else
+#define MDBX_USE_SENDFILE 0
+#endif
+#endif /* MDBX_USE_SENDFILE */
+
+/** Advanced: Using copy_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_COPYFILERANGE
+#if __GLIBC_PREREQ(2, 27) && defined(_GNU_SOURCE)
+#define MDBX_USE_COPYFILERANGE 1
+#else
+#define MDBX_USE_COPYFILERANGE 0
+#endif
+#endif /* MDBX_USE_COPYFILERANGE */
+
+/** Advanced: Using sync_file_range() syscall (autodetection by default). */
+#ifndef MDBX_USE_SYNCFILERANGE
+#if ((defined(__linux__) || defined(__gnu_linux__)) &&                         \
+     defined(SYNC_FILE_RANGE_WRITE) && !defined(__ANDROID_API__)) ||           \
+    (defined(__ANDROID_API__) && __ANDROID_API__ >= 26)
+#define MDBX_USE_SYNCFILERANGE 1
+#else
+#define MDBX_USE_SYNCFILERANGE 0
+#endif
+#endif /* MDBX_USE_SYNCFILERANGE */
+
+//------------------------------------------------------------------------------
+
+#ifndef MDBX_CPU_WRITEBACK_INCOHERENT
+#if defined(__ia32__) || defined(__e2k__) || defined(__hppa) ||                \
+    defined(__hppa__) || defined(DOXYGEN)
+#define MDBX_CPU_WRITEBACK_INCOHERENT 0
+#else
+#define MDBX_CPU_WRITEBACK_INCOHERENT 1
+#endif
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+#ifndef MDBX_MMAP_INCOHERENT_FILE_WRITE
+#ifdef __OpenBSD__
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 1
+#else
+#define MDBX_MMAP_INCOHERENT_FILE_WRITE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#ifndef MDBX_MMAP_INCOHERENT_CPU_CACHE
+#if defined(__mips) || defined(__mips__) || defined(__mips64) ||               \
+    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
+    defined(__MWERKS__) || defined(__sgi)
+/* MIPS has cache coherency issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 1
+#else
+/* LY: assume no relevant mmap/dcache issues. */
+#define MDBX_MMAP_INCOHERENT_CPU_CACHE 0
+#endif
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#ifndef MDBX_64BIT_ATOMIC
+#if MDBX_WORDBITS >= 64 || defined(DOXYGEN)
+#define MDBX_64BIT_ATOMIC 1
+#else
+#define MDBX_64BIT_ATOMIC 0
+#endif
+#define MDBX_64BIT_ATOMIC_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_ATOMIC)
+#else
+#define MDBX_64BIT_ATOMIC_CONFIG STRINGIFY(MDBX_64BIT_ATOMIC)
+#endif /* MDBX_64BIT_ATOMIC */
+
+#ifndef MDBX_64BIT_CAS
+#if defined(ATOMIC_LLONG_LOCK_FREE)
+#if ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__GCC_ATOMIC_LLONG_LOCK_FREE)
+#if __GCC_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(__CLANG_ATOMIC_LLONG_LOCK_FREE)
+#if __CLANG_ATOMIC_LLONG_LOCK_FREE > 1
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS 0
+#endif
+#elif defined(_MSC_VER) || defined(__APPLE__) || defined(DOXYGEN)
+#define MDBX_64BIT_CAS 1
+#else
+#define MDBX_64BIT_CAS MDBX_64BIT_ATOMIC
+#endif
+#define MDBX_64BIT_CAS_CONFIG "AUTO=" STRINGIFY(MDBX_64BIT_CAS)
+#else
+#define MDBX_64BIT_CAS_CONFIG STRINGIFY(MDBX_64BIT_CAS)
+#endif /* MDBX_64BIT_CAS */
+
+#if !defined(MDBX_UNALIGNED_OK)
+#if defined(_MSC_VER)
+#define MDBX_UNALIGNED_OK 1 /* avoid MSVC misoptimization */
+#elif __CLANG_PREREQ(5, 0) || __GNUC_PREREQ(5, 0)
+#define MDBX_UNALIGNED_OK 0 /* expecting optimization is well done */
+#elif (defined(__ia32__) || defined(__ARM_FEATURE_UNALIGNED)) &&               \
+    !defined(__ALIGNED__)
+#define MDBX_UNALIGNED_OK 1
+#else
+#define MDBX_UNALIGNED_OK 0
+#endif
+#endif /* MDBX_UNALIGNED_OK */
+
+#ifndef MDBX_CACHELINE_SIZE
+#if defined(SYSTEM_CACHE_ALIGNMENT_SIZE)
+#define MDBX_CACHELINE_SIZE SYSTEM_CACHE_ALIGNMENT_SIZE
+#elif defined(__ia64__) || defined(__ia64) || defined(_M_IA64)
+#define MDBX_CACHELINE_SIZE 128
+#else
+#define MDBX_CACHELINE_SIZE 64
+#endif
+#endif /* MDBX_CACHELINE_SIZE */
+
+/** @} end of build options */
+/*******************************************************************************
+ *******************************************************************************
+ ******************************************************************************/
+
+/*----------------------------------------------------------------------------*/
+/* Basic constants and types */
+
+typedef union {
+  volatile uint32_t weak;
+#ifdef MDBX_HAVE_C11ATOMICS
+  volatile _Atomic uint32_t c11a;
+#endif /* MDBX_HAVE_C11ATOMICS */
+} MDBX_atomic_uint32_t;
+
+typedef union {
+  volatile uint64_t weak;
+#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
+  volatile _Atomic uint64_t c11a;
+#endif
+#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
+  __anonymous_struct_extension__ struct {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    MDBX_atomic_uint32_t low, high;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    MDBX_atomic_uint32_t high, low;
+#else
+#error "FIXME: Unsupported byte order"
+#endif /* __BYTE_ORDER__ */
+  };
+#endif
+} MDBX_atomic_uint64_t;
+
+/* The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted. */
+#define MDBX_MINKEYS 2
+
+/* A stamp that identifies a file as an MDBX file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches. */
+#define MDBX_MAGIC UINT64_C(/* 56-bit prime */ 0x59659DBDEF4C11)
+
+/* The version number for a database's datafile format. */
+#define MDBX_DATA_VERSION 2
+/* The version number for a database's lockfile format. */
+#define MDBX_LOCK_VERSION 3
+
+/* handle for the DB used to track free pages. */
+#define FREE_DBI 0
+/* handle for the default DB. */
+#define MAIN_DBI 1
+/* Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS 2
+
+/* Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS 3
+
+/* A page number in the database.
+ *
+ * MDBX uses 32 bit for page numbers. This limits database
+ * size up to 2^44 bytes, in case of 4K pages. */
+typedef uint32_t pgno_t;
+typedef MDBX_atomic_uint32_t atomic_pgno_t;
+#define PRIaPGNO PRIu32
+#define MAX_PAGENO UINT32_C(0x7FFFffff)
+#define MIN_PAGENO NUM_METAS
+
+#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)
+
+/* A transaction ID. */
+typedef uint64_t txnid_t;
+typedef MDBX_atomic_uint64_t atomic_txnid_t;
+#define PRIaTXN PRIi64
+#define MIN_TXNID UINT64_C(1)
+#define MAX_TXNID (SAFE64_INVALID_THRESHOLD - 1)
+#define INITIAL_TXNID (MIN_TXNID + NUM_METAS - 1)
+#define INVALID_TXNID UINT64_MAX
+/* LY: for testing non-atomic 64-bit txnid on 32-bit arches.
+ * #define MDBX_TXNID_STEP (UINT32_MAX / 3) */
+#ifndef MDBX_TXNID_STEP
+#if MDBX_64BIT_CAS
+#define MDBX_TXNID_STEP 1u
+#else
+#define MDBX_TXNID_STEP 2u
+#endif
+#endif /* MDBX_TXNID_STEP */
+
+/* Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty. */
+typedef uint16_t indx_t;
+
+#define MEGABYTE ((size_t)1 << 20)
+
+/*----------------------------------------------------------------------------*/
+/* Core structures for database and shared memory (i.e. format definition) */
+#pragma pack(push, 1)
+
+/* Information about a single database in the environment. */
+typedef struct MDBX_db {
+  uint16_t md_flags;        /* see mdbx_dbi_open */
+  uint16_t md_depth;        /* depth of this tree */
+  uint32_t md_xsize;        /* key-size for MDBX_DUPFIXED (LEAF2 pages) */
+  pgno_t md_root;           /* the root page of this tree */
+  pgno_t md_branch_pages;   /* number of internal pages */
+  pgno_t md_leaf_pages;     /* number of leaf pages */
+  pgno_t md_overflow_pages; /* number of overflow pages */
+  uint64_t md_seq;          /* table sequence counter */
+  uint64_t md_entries;      /* number of data items */
+  uint64_t md_mod_txnid;    /* txnid of last committed modification */
+} MDBX_db;
+
+/* database size-related parameters */
+typedef struct mdbx_geo_t {
+  uint16_t grow;   /* datafile growth step in pages */
+  uint16_t shrink; /* datafile shrink threshold in pages */
+  pgno_t lower;    /* minimal size of datafile in pages */
+  pgno_t upper;    /* maximal size of datafile in pages */
+  pgno_t now;      /* current size of datafile in pages */
+  pgno_t next;     /* first unused page in the datafile,
+                    * but actually the file may be shorter. */
+} mdbx_geo_t;
+
+/* Meta page content.
+ * A meta page is the start point for accessing a database snapshot.
+ * Pages 0-1 are meta pages. Transaction N writes meta page (N % 2). */
+typedef struct MDBX_meta {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with MDBX_DATA_VERSION. */
+  uint32_t mm_magic_and_version[2];
+
+  /* txnid that committed this page, the first of a two-phase-update pair */
+  uint32_t mm_txnid_a[2];
+
+  uint16_t mm_extra_flags;  /* extra DB flags, zero (nothing) for now */
+  uint8_t mm_validator_id;  /* ID of checksum and page validation method,
+                             * zero (nothing) for now */
+  uint8_t mm_extra_pagehdr; /* extra bytes in the page header,
+                             * zero (nothing) for now */
+
+  mdbx_geo_t mm_geo; /* database size-related parameters */
+
+  MDBX_db mm_dbs[CORE_DBS]; /* first is free space, 2nd is main db */
+                            /* The size of pages used in this DB */
+#define mm_psize mm_dbs[FREE_DBI].md_xsize
+/* Any persistent environment flags, see mdbx_env */
+#define mm_flags mm_dbs[FREE_DBI].md_flags
+  MDBX_canary mm_canary;
+
+#define MDBX_DATASIGN_NONE 0u
+#define MDBX_DATASIGN_WEAK 1u
+#define SIGN_IS_STEADY(sign) ((sign) > MDBX_DATASIGN_WEAK)
+#define META_IS_STEADY(meta)                                                   \
+  SIGN_IS_STEADY(unaligned_peek_u64(4, (meta)->mm_datasync_sign))
+  uint32_t mm_datasync_sign[2];
+
+  /* txnid that committed this page, the second of a two-phase-update pair */
+  uint32_t mm_txnid_b[2];
+
+  /* Number of non-meta pages which were put in GC after COW. May be 0 in case
+   * DB was previously handled by libmdbx without corresponding feature.
+   * This value in couple with mr_snapshot_pages_retired allows fast estimation
+   * of "how much reader is restraining GC recycling". */
+  uint32_t mm_pages_retired[2];
+
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  bin128_t mm_bootid;
+
+} MDBX_meta;
+
+/* Common header for all page types. The page type depends on mp_flags.
+ *
+ * P_BRANCH and P_LEAF pages have unsorted 'MDBX_node's at the end, with
+ * sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages
+ * omit mp_ptrs and pack sorted MDBX_DUPFIXED values after the page header.
+ *
+ * P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of F_BIGDATA nodes.
+ *
+ * P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * P_META pages contain MDBX_meta, the start point of an MDBX snapshot.
+ *
+ * Each non-metapage up to MDBX_meta.mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a GC record. */
+typedef struct MDBX_page {
+  union {
+    struct MDBX_page *mp_next; /* for in-memory list of freed pages */
+    uint64_t mp_txnid;         /* txnid that committed this page */
+  };
+  uint16_t mp_leaf2_ksize; /* key size if this is a LEAF2 page */
+#define P_BRANCH 0x01      /* branch page */
+#define P_LEAF 0x02        /* leaf page */
+#define P_OVERFLOW 0x04    /* overflow page */
+#define P_META 0x08        /* meta page */
+#define P_DIRTY 0x10       /* dirty page, also set for P_SUBP pages */
+#define P_LEAF2 0x20       /* for MDBX_DUPFIXED records */
+#define P_SUBP 0x40        /* for MDBX_DUPSORT sub-pages */
+#define P_LOOSE 0x4000     /* page was dirtied then freed, can be reused */
+#define P_KEEP 0x8000      /* leave this page alone during spill */
+  uint16_t mp_flags;
+  union {
+    __anonymous_struct_extension__ struct {
+      indx_t mp_lower; /* lower bound of free space */
+      indx_t mp_upper; /* upper bound of free space */
+    };
+    uint32_t mp_pages; /* number of overflow pages */
+  };
+  pgno_t mp_pgno; /* page number */
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  indx_t mp_ptrs[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_page;
+
+/* Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ ((unsigned)offsetof(MDBX_page, mp_ptrs))
+
+#pragma pack(pop)
+
+#if MDBX_LOCKING == MDBX_LOCKING_WIN32FILES
+#define MDBX_CLOCK_SIGN UINT32_C(0xF10C)
+typedef void mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_SYSV
+
+#define MDBX_CLOCK_SIGN UINT32_C(0xF18D)
+typedef mdbx_pid_t mdbx_ipclock_t;
+#ifndef EOWNERDEAD
+#define EOWNERDEAD MDBX_RESULT_TRUE
+#endif
+
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX2001 ||                                \
+    MDBX_LOCKING == MDBX_LOCKING_POSIX2008
+#define MDBX_CLOCK_SIGN UINT32_C(0x8017)
+typedef pthread_mutex_t mdbx_ipclock_t;
+#elif MDBX_LOCKING == MDBX_LOCKING_POSIX1988
+#define MDBX_CLOCK_SIGN UINT32_C(0xFC29)
+typedef sem_t mdbx_ipclock_t;
+#else
+#error "FIXME"
+#endif /* MDBX_LOCKING */
+
+#if MDBX_LOCKING > MDBX_LOCKING_SYSV && !defined(__cplusplus)
+MDBX_INTERNAL_FUNC int mdbx_ipclock_stub(mdbx_ipclock_t *ipc);
+MDBX_INTERNAL_FUNC int mdbx_ipclock_destroy(mdbx_ipclock_t *ipc);
+#endif /* MDBX_LOCKING */
+
+/* Reader Lock Table
+ *
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent
+ * read transactions started by the same thread need no further locking to
+ * proceed.
+ *
+ * If MDBX_NOTLS is set, the slot address is not saved in thread-specific data.
+ * No reader table is used if the database is on a read-only filesystem.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use. Old transactions
+ * that have discarded any data pages can then have those pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together. */
+
+/* The actual reader record, with cacheline padding. */
+typedef struct MDBX_reader {
+  /* Current Transaction ID when this transaction began, or (txnid_t)-1.
+   * Multiple readers that start at the same time will probably have the
+   * same ID here. Again, it's not important to exclude them from
+   * anything; all we need to know is which version of the DB they
+   * started from so we can avoid overwriting any data used in that
+   * particular version. */
+  MDBX_atomic_uint64_t /* txnid_t */ mr_txnid;
+
+  /* The information we store in a single slot of the reader table.
+   * In addition to a transaction ID, we also record the process and
+   * thread ID that owns a slot, so that we can detect stale information,
+   * e.g. threads or processes that went away without cleaning up.
+   *
+   * NOTE: We currently don't check for stale records.
+   * We simply re-init the table when we know that we're the only process
+   * opening the lock file. */
+
+  /* The thread ID of the thread owning this txn. */
+  MDBX_atomic_uint64_t mr_tid;
+
+  /* The process ID of the process owning this reader txn. */
+  MDBX_atomic_uint32_t mr_pid;
+
+  /* The number of pages used in the reader's MVCC snapshot,
+   * i.e. the value of meta->mm_geo.next and txn->mt_next_pgno */
+  atomic_pgno_t mr_snapshot_pages_used;
+  /* Number of retired pages at the time this reader starts transaction. So,
+   * at any time the difference mm_pages_retired - mr_snapshot_pages_retired
+   * will give the number of pages which this reader restraining from reuse. */
+  MDBX_atomic_uint64_t mr_snapshot_pages_retired;
+} MDBX_reader;
+
+/* The header for the reader table (a memory-mapped lock file). */
+typedef struct MDBX_lockinfo {
+  /* Stamp identifying this as an MDBX file.
+   * It must be set to MDBX_MAGIC with with MDBX_LOCK_VERSION. */
+  uint64_t mti_magic_and_version;
+
+  /* Format of this lock file. Must be set to MDBX_LOCK_FORMAT. */
+  uint32_t mti_os_and_format;
+
+  /* Flags which environment was opened. */
+  MDBX_atomic_uint32_t mti_envmode;
+
+  /* Threshold of un-synced-with-disk pages for auto-sync feature,
+   * zero means no-threshold, i.e. auto-sync is disabled. */
+  atomic_pgno_t mti_autosync_threshold;
+
+  /* Low 32-bit of txnid with which meta-pages was synced,
+   * i.e. for sync-polling in the MDBX_NOMETASYNC mode. */
+  MDBX_atomic_uint32_t mti_meta_sync_txnid;
+
+  /* Period for timed auto-sync feature, i.e. at the every steady checkpoint
+   * the mti_unsynced_timeout sets to the current_time + mti_autosync_period.
+   * The time value is represented in a suitable system-dependent form, for
+   * example clock_gettime(CLOCK_BOOTTIME) or clock_gettime(CLOCK_MONOTONIC).
+   * Zero means timed auto-sync is disabled. */
+  MDBX_atomic_uint64_t mti_autosync_period;
+
+  /* Marker to distinguish uniqueness of DB/CLK.*/
+  MDBX_atomic_uint64_t mti_bait_uniqueness;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Write transaction lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  atomic_txnid_t mti_oldest_reader;
+
+  /* Timestamp of the last steady sync. Value is represented in a suitable
+   * system-dependent form, for example clock_gettime(CLOCK_BOOTTIME) or
+   * clock_gettime(CLOCK_MONOTONIC). */
+  MDBX_atomic_uint64_t mti_sync_timestamp;
+
+  /* Number un-synced-with-disk pages for auto-sync feature. */
+  atomic_pgno_t mti_unsynced_pages;
+
+  /* Number of page which was discarded last time by madvise(MADV_FREE). */
+  atomic_pgno_t mti_discarded_tail;
+
+  /* Timestamp of the last readers check. */
+  MDBX_atomic_uint64_t mti_reader_check_timestamp;
+
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+
+  /* Readeaders registration lock. */
+#if MDBX_LOCKING > 0
+      mdbx_ipclock_t mti_rlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  /* The number of slots that have been used in the reader table.
+   * This always records the maximum count, it is not decremented
+   * when readers release their slots. */
+  MDBX_atomic_uint32_t mti_numreaders;
+  MDBX_atomic_uint32_t mti_readers_refresh_flag;
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
+      MDBX_reader mti_readers[] /* dynamic size */;
+#endif /* C99 */
+} MDBX_lockinfo;
+
+/* Lockfile format signature: version, features and field layout */
+#define MDBX_LOCK_FORMAT                                                       \
+  (MDBX_CLOCK_SIGN * 27733 + (unsigned)sizeof(MDBX_reader) * 13 +              \
+   (unsigned)offsetof(MDBX_reader, mr_snapshot_pages_used) * 251 +             \
+   (unsigned)offsetof(MDBX_lockinfo, mti_oldest_reader) * 83 +                 \
+   (unsigned)offsetof(MDBX_lockinfo, mti_numreaders) * 37 +                    \
+   (unsigned)offsetof(MDBX_lockinfo, mti_readers) * 29)
+
+#define MDBX_DATA_MAGIC                                                        \
+  ((MDBX_MAGIC << 8) + MDBX_PNL_ASCENDING * 64 + MDBX_DATA_VERSION)
+#define MDBX_DATA_MAGIC_DEVEL ((MDBX_MAGIC << 8) + 255)
+
+#define MDBX_LOCK_MAGIC ((MDBX_MAGIC << 8) + MDBX_LOCK_VERSION)
+
+#ifndef MDBX_ASSUME_MALLOC_OVERHEAD
+#define MDBX_ASSUME_MALLOC_OVERHEAD (sizeof(void *) * 2u)
+#endif /* MDBX_ASSUME_MALLOC_OVERHEAD */
+
+/* The maximum size of a database page.
+ *
+ * It is 64K, but value-PAGEHDRSZ must fit in MDBX_page.mp_upper.
+ *
+ * MDBX will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable. */
+#define MAX_PAGESIZE MDBX_MAX_PAGESIZE
+#define MIN_PAGESIZE MDBX_MIN_PAGESIZE
+
+#define MIN_MAPSIZE (MIN_PAGESIZE * MIN_PAGENO)
+#if defined(_WIN32) || defined(_WIN64)
+#define MAX_MAPSIZE32 UINT32_C(0x38000000)
+#else
+#define MAX_MAPSIZE32 UINT32_C(0x7f000000)
+#endif
+#define MAX_MAPSIZE64 (MAX_PAGENO * (uint64_t)MAX_PAGESIZE)
+
+#if MDBX_WORDBITS >= 64
+#define MAX_MAPSIZE MAX_MAPSIZE64
+#define MDBX_READERS_LIMIT                                                     \
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+#define MDBX_PGL_LIMIT MAX_PAGENO
+#else
+#define MDBX_READERS_LIMIT 1024
+#define MAX_MAPSIZE MAX_MAPSIZE32
+#define MDBX_PGL_LIMIT (MAX_MAPSIZE32 / MIN_PAGESIZE)
+#endif /* MDBX_WORDBITS */
+
+/*----------------------------------------------------------------------------*/
+
+/* An PNL is an Page Number List, a sorted array of IDs.
+ * The first element of the array is a counter for how many actual page-numbers
+ * are in the list. By default PNLs are sorted in descending order, this allow
+ * cut off a page with lowest pgno (at the tail) just truncating the list. The
+ * sort order of PNLs is controlled by the MDBX_PNL_ASCENDING build option. */
+typedef pgno_t *MDBX_PNL;
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_ORDERED(first, last) ((first) < (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) >= (last))
+#else
+#define MDBX_PNL_ORDERED(first, last) ((first) > (last))
+#define MDBX_PNL_DISORDERED(first, last) ((first) <= (last))
+#endif
+
+/* List of txnid, only for MDBX_txn.tw.lifo_reclaimed */
+typedef txnid_t *MDBX_TXL;
+
+/* An Dirty-Page list item is an pgno/pointer pair. */
+typedef struct MDBX_dp {
+  pgno_t pgno;
+  MDBX_page *ptr;
+} MDBX_dp;
+
+/* An DPL (dirty-page list) is a sorted array of MDBX_DPs. */
+typedef struct MDBX_dpl {
+  unsigned sorted;
+  unsigned length;
+  unsigned allocated;
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  MDBX_dp items[] /* dynamic size with holes at zero and after the last */;
+#endif
+} MDBX_dpl;
+
+/* PNL sizes */
+#define MDBX_PNL_GRANULATE 1024
+#define MDBX_PNL_INITIAL                                                       \
+  (MDBX_PNL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(pgno_t))
+
+#define MDBX_TXL_GRANULATE 32
+#define MDBX_TXL_INITIAL                                                       \
+  (MDBX_TXL_GRANULATE - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+#define MDBX_TXL_MAX                                                           \
+  ((1u << 17) - 2 - MDBX_ASSUME_MALLOC_OVERHEAD / sizeof(txnid_t))
+
+#define MDBX_PNL_ALLOCLEN(pl) ((pl)[-1])
+#define MDBX_PNL_SIZE(pl) ((pl)[0])
+#define MDBX_PNL_FIRST(pl) ((pl)[1])
+#define MDBX_PNL_LAST(pl) ((pl)[MDBX_PNL_SIZE(pl)])
+#define MDBX_PNL_BEGIN(pl) (&(pl)[1])
+#define MDBX_PNL_END(pl) (&(pl)[MDBX_PNL_SIZE(pl) + 1])
+
+#if MDBX_PNL_ASCENDING
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_FIRST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_LAST(pl)
+#else
+#define MDBX_PNL_LEAST(pl) MDBX_PNL_LAST(pl)
+#define MDBX_PNL_MOST(pl) MDBX_PNL_FIRST(pl)
+#endif
+
+#define MDBX_PNL_SIZEOF(pl) ((MDBX_PNL_SIZE(pl) + 1) * sizeof(pgno_t))
+#define MDBX_PNL_IS_EMPTY(pl) (MDBX_PNL_SIZE(pl) == 0)
+
+/*----------------------------------------------------------------------------*/
+/* Internal structures */
+
+/* Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment. */
+typedef struct MDBX_dbx {
+  MDBX_val md_name;                /* name of the database */
+  MDBX_cmp_func *md_cmp;           /* function for comparing keys */
+  MDBX_cmp_func *md_dcmp;          /* function for comparing data items */
+  size_t md_klen_min, md_klen_max; /* min/max key length for the database */
+  size_t md_vlen_min,
+      md_vlen_max; /* min/max value/data length for the database */
+} MDBX_dbx;
+
+/* A database transaction.
+ * Every operation requires a transaction handle. */
+struct MDBX_txn {
+#define MDBX_MT_SIGNATURE UINT32_C(0x93D53A31)
+  size_t mt_signature;
+  MDBX_txn *mt_parent; /* parent of a nested txn */
+  /* Nested txn under this txn, set together with flag MDBX_TXN_HAS_CHILD */
+  MDBX_txn *mt_child;
+  mdbx_geo_t mt_geo;
+  /* next unallocated page */
+#define mt_next_pgno mt_geo.next
+  /* corresponding to the current size of datafile */
+#define mt_end_pgno mt_geo.now
+
+  /* Transaction Flags */
+  /* mdbx_txn_begin() flags */
+#define MDBX_TXN_RO_BEGIN_FLAGS (MDBX_TXN_RDONLY | MDBX_TXN_RDONLY_PREPARE)
+#define MDBX_TXN_RW_BEGIN_FLAGS                                                \
+  (MDBX_TXN_NOMETASYNC | MDBX_TXN_NOSYNC | MDBX_TXN_TRY)
+  /* Additional flag for mdbx_sync_locked() */
+#define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
+
+  /* internal txn flags */
+#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
+#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
+#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
+#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
+#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
+  /* most operations on the txn are currently illegal */
+#define MDBX_TXN_BLOCKED                                                       \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
+
+#define TXN_FLAGS                                                              \
+  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
+   MDBX_TXN_HAS_CHILD)
+
+#if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
+    ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
+     MDBX_SHRINK_ALLOWED)
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+  unsigned mt_flags;
+  /* The ID of this transaction. IDs are integers incrementing from 1.
+   * Only committed write transactions increment the ID. If a transaction
+   * aborts, the ID may be re-used by the next writer. */
+  txnid_t mt_txnid;
+  MDBX_env *mt_env; /* the DB environment */
+  /* Array of records for each DB known in the environment. */
+  MDBX_dbx *mt_dbxs;
+  /* Array of MDBX_db records for each known DB */
+  MDBX_db *mt_dbs;
+  /* Array of sequence numbers for each DB handle */
+  unsigned *mt_dbiseqs;
+
+  /* Transaction DBI Flags */
+#define DBI_DIRTY MDBX_DBI_DIRTY /* DB was written in this txn */
+#define DBI_STALE MDBX_DBI_STALE /* Named-DB record is older than txnID */
+#define DBI_FRESH MDBX_DBI_FRESH /* Named-DB handle opened in this txn */
+#define DBI_CREAT MDBX_DBI_CREAT /* Named-DB handle created in this txn */
+#define DBI_VALID 0x10           /* DB handle is valid, see also DB_VALID */
+#define DBI_USRVALID 0x20        /* As DB_VALID, but not set for FREE_DBI */
+#define DBI_DUPDATA 0x40         /* DB is MDBX_DUPSORT data */
+#define DBI_AUDITED 0x80         /* Internal flag for accounting during audit */
+  /* Array of flags for each DB */
+  uint8_t *mt_dbistate;
+  /* Number of DB records in use, or 0 when the txn is finished.
+   * This number only ever increments until the txn finishes; we
+   * don't decrement it when individual DB handles are closed. */
+  MDBX_dbi mt_numdbs;
+  size_t mt_owner; /* thread ID that owns this transaction */
+  MDBX_canary mt_canary;
+  void *mt_userctx; /* User-settable context */
+
+  union {
+    struct {
+      /* For read txns: This thread/txn's reader table slot, or NULL. */
+      MDBX_reader *reader;
+    } to;
+    struct {
+      /* In write txns, array of cursors for each DB */
+      MDBX_cursor **cursors;
+      pgno_t *reclaimed_pglist; /* Reclaimed GC pages */
+      txnid_t last_reclaimed;   /* ID of last used record */
+#if MDBX_ENABLE_REFUND
+      pgno_t loose_refund_wl /* FIXME: describe */;
+#endif /* MDBX_ENABLE_REFUND */
+      /* dirtylist room: Dirty array size - dirty pages visible to this txn.
+       * Includes ancestor txns' dirty pages not hidden by other txns'
+       * dirty/spilled pages. Thus commit(nested txn) has room to merge
+       * dirtylist into mt_parent after freeing hidden mt_parent pages. */
+      unsigned dirtyroom;
+      /* For write txns: Modified pages. Sorted when not MDBX_WRITEMAP. */
+      MDBX_dpl *dirtylist;
+      /* The list of reclaimed txns from GC */
+      MDBX_TXL lifo_reclaimed;
+      /* The list of pages that became unused during this transaction. */
+      MDBX_PNL retired_pages;
+      /* The list of loose pages that became unused and may be reused
+       * in this transaction, linked through `mp_next`. */
+      MDBX_page *loose_pages;
+      /* Number of loose pages (tw.loose_pages) */
+      unsigned loose_count;
+      /* The sorted list of dirty pages we temporarily wrote to disk
+       * because the dirty list was full. page numbers in here are
+       * shifted left by 1, deleted slots have the LSB set. */
+      MDBX_PNL spill_pages;
+      unsigned spill_least_removed;
+    } tw;
+  };
+};
+
+#if MDBX_WORDBITS >= 64
+#define CURSOR_STACK 32
+#else
+#define CURSOR_STACK 24
+#endif
+
+struct MDBX_xcursor;
+
+/* Cursors are used for all DB operations.
+ * A cursor holds a path of (page pointer, key index) from the DB
+ * root to a position in the DB, plus other state. MDBX_DUPSORT
+ * cursors include an xcursor to the current data item. Write txns
+ * track their cursors and keep them up to date when data moves.
+ * Exception: An xcursor's pointer to a P_SUBP page can be stale.
+ * (A node with F_DUPDATA but no F_SUBDATA contains a subpage). */
+struct MDBX_cursor {
+#define MDBX_MC_LIVE UINT32_C(0xFE05D5B1)
+#define MDBX_MC_READY4CLOSE UINT32_C(0x2817A047)
+#define MDBX_MC_WAIT4EOT UINT32_C(0x90E297A7)
+  uint32_t mc_signature;
+  /* The database handle this cursor operates on */
+  MDBX_dbi mc_dbi;
+  /* Next cursor on this DB in this txn */
+  MDBX_cursor *mc_next;
+  /* Backup of the original cursor if this cursor is a shadow */
+  MDBX_cursor *mc_backup;
+  /* Context used for databases with MDBX_DUPSORT, otherwise NULL */
+  struct MDBX_xcursor *mc_xcursor;
+  /* The transaction that owns this cursor */
+  MDBX_txn *mc_txn;
+  /* The database record for this cursor */
+  MDBX_db *mc_db;
+  /* The database auxiliary record for this cursor */
+  MDBX_dbx *mc_dbx;
+  /* The mt_dbistate for this database */
+  uint8_t *mc_dbistate;
+  unsigned mc_snum; /* number of pushed pages */
+  unsigned mc_top;  /* index of top page, normally mc_snum-1 */
+
+  /* Cursor state flags. */
+#define C_INITIALIZED 0x01 /* cursor has been initialized and is valid */
+#define C_EOF 0x02         /* No more data */
+#define C_SUB 0x04         /* Cursor is a sub-cursor */
+#define C_DEL 0x08         /* last op was a cursor_del */
+#define C_UNTRACK 0x10     /* Un-track cursor when closing */
+#define C_RECLAIMING 0x20  /* GC lookup is prohibited */
+#define C_GCFREEZE 0x40    /* reclaimed_pglist must not be updated */
+
+  /* Cursor checking flags. */
+#define C_COPYING 0x100  /* skip key-value length check (copying simplify) */
+#define C_UPDATING 0x200 /* update/rebalance pending */
+#define C_RETIRING 0x400 /* refs to child pages may be invalid */
+#define C_SKIPORD 0x800  /* don't check keys ordering */
+
+  unsigned mc_flags;              /* see mdbx_cursor */
+  MDBX_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
+  indx_t mc_ki[CURSOR_STACK];     /* stack of page indices */
+};
+
+/* Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB. */
+typedef struct MDBX_xcursor {
+  /* A sub-cursor for traversing the Dup DB */
+  MDBX_cursor mx_cursor;
+  /* The database record for this Dup DB */
+  MDBX_db mx_db;
+  /* The auxiliary DB record for this Dup DB */
+  MDBX_dbx mx_dbx;
+  /* The mt_dbistate for this Dup DB */
+  uint8_t mx_dbistate;
+} MDBX_xcursor;
+
+typedef struct MDBX_cursor_couple {
+  MDBX_cursor outer;
+  void *mc_userctx; /* User-settable context */
+  MDBX_xcursor inner;
+} MDBX_cursor_couple;
+
+/* The database environment. */
+struct MDBX_env {
+#define MDBX_ME_SIGNATURE UINT32_C(0x9A899641)
+  MDBX_atomic_uint32_t me_signature;
+  /* Failed to update the meta page. Probably an I/O error. */
+#define MDBX_FATAL_ERROR UINT32_C(0x80000000)
+  /* Some fields are initialized. */
+#define MDBX_ENV_ACTIVE UINT32_C(0x20000000)
+  /* me_txkey is set */
+#define MDBX_ENV_TXKEY UINT32_C(0x10000000)
+  /* Legacy MDBX_MAPASYNC (prior v0.9) */
+#define MDBX_DEPRECATED_MAPASYNC UINT32_C(0x100000)
+#define ENV_INTERNAL_FLAGS (MDBX_FATAL_ERROR | MDBX_ENV_ACTIVE | MDBX_ENV_TXKEY)
+  uint32_t me_flags;
+  mdbx_mmap_t me_dxb_mmap; /* The main data file */
+#define me_map me_dxb_mmap.dxb
+#define me_lazy_fd me_dxb_mmap.fd
+  mdbx_filehandle_t me_dsync_fd;
+  mdbx_mmap_t me_lck_mmap; /* The lock file */
+#define me_lfd me_lck_mmap.fd
+#define me_lck me_lck_mmap.lck
+
+  unsigned me_psize;    /* DB page size, initialized from me_os_psize */
+  uint8_t me_psize2log; /* log2 of DB page size */
+  int8_t me_stuck_meta; /* recovery-only: target meta page or less that zero */
+  unsigned me_os_psize; /* OS page size, from mdbx_syspagesize() */
+  unsigned me_maxreaders; /* size of the reader table */
+  mdbx_fastmutex_t me_dbi_lock;
+  MDBX_dbi me_numdbs;         /* number of DBs opened */
+  MDBX_dbi me_maxdbs;         /* size of the DB table */
+  uint32_t me_pid;            /* process ID of this env */
+  mdbx_thread_key_t me_txkey; /* thread-key for readers */
+  char *me_pathname;          /* path to the DB files */
+  void *me_pbuf;              /* scratch area for DUPSORT put() */
+  MDBX_txn *me_txn;           /* current write transaction */
+  MDBX_txn *me_txn0;          /* prealloc'd write transaction */
+
+  /* write-txn lock */
+#if MDBX_LOCKING == MDBX_LOCKING_SYSV
+  union {
+    key_t key;
+    int semid;
+  } me_sysv_ipc;
+#endif /* MDBX_LOCKING == MDBX_LOCKING_SYSV */
+
+#if MDBX_LOCKING > 0
+  mdbx_ipclock_t *me_wlock;
+#endif /* MDBX_LOCKING > 0 */
+
+  MDBX_dbx *me_dbxs;         /* array of static DB info */
+  uint16_t *me_dbflags;      /* array of flags from MDBX_db.md_flags */
+  unsigned *me_dbiseqs;      /* array of dbi sequence numbers */
+  atomic_txnid_t *me_oldest; /* ID of oldest reader last time we looked */
+  MDBX_page *me_dp_reserve;  /* list of malloc'd blocks for re-use */
+  /* PNL of pages that became unused in a write txn */
+  MDBX_PNL me_retired_pages;
+  /* Number of freelist items that can fit in a single overflow page */
+  unsigned me_maxgc_ov1page;
+  unsigned me_branch_nodemax; /* max size of a branch-node */
+  uint32_t me_live_reader;    /* have liveness lock in reader table */
+  void *me_userctx;           /* User-settable context */
+  MDBX_atomic_uint64_t *me_sync_timestamp;
+  MDBX_atomic_uint64_t *me_autosync_period;
+  atomic_pgno_t *me_unsynced_pages;
+  atomic_pgno_t *me_autosync_threshold;
+  atomic_pgno_t *me_discarded_tail;
+  MDBX_atomic_uint32_t *me_meta_sync_txnid;
+  MDBX_hsr_func *me_hsr_callback; /* Callback for kicking laggard readers */
+  unsigned me_dp_reserve_len;
+  struct {
+    unsigned dp_reserve_limit;
+    unsigned rp_augment_limit;
+    unsigned dp_limit;
+    unsigned dp_initial;
+    uint8_t dp_loose_limit;
+    uint8_t spill_max_denominator;
+    uint8_t spill_min_denominator;
+    uint8_t spill_parent4child_denominator;
+  } me_options;
+  struct {
+#if MDBX_LOCKING > 0
+    mdbx_ipclock_t wlock;
+#endif /* MDBX_LOCKING > 0 */
+    atomic_txnid_t oldest;
+    MDBX_atomic_uint64_t sync_timestamp;
+    MDBX_atomic_uint64_t autosync_period;
+    atomic_pgno_t autosync_pending;
+    atomic_pgno_t autosync_threshold;
+    atomic_pgno_t discarded_tail;
+    MDBX_atomic_uint32_t meta_sync_txnid;
+  } me_lckless_stub;
+#if MDBX_DEBUG
+  MDBX_assert_func *me_assert_func; /*  Callback for assertion failures */
+#endif
+#ifdef MDBX_USE_VALGRIND
+  int me_valgrind_handle;
+#endif
+#if defined(MDBX_USE_VALGRIND) || defined(__SANITIZE_ADDRESS__)
+  pgno_t me_poison_edge;
+#endif /* MDBX_USE_VALGRIND || __SANITIZE_ADDRESS__ */
+  MDBX_env *me_lcklist_next;
+
+  /* struct me_dbgeo used for accepting db-geo params from user for the new
+   * database creation, i.e. when mdbx_env_set_geometry() was called before
+   * mdbx_env_open(). */
+  struct {
+    size_t lower;  /* minimal size of datafile */
+    size_t upper;  /* maximal size of datafile */
+    size_t now;    /* current size of datafile */
+    size_t grow;   /* step to grow datafile */
+    size_t shrink; /* threshold to shrink datafile */
+  } me_dbgeo;
+
+#if defined(_WIN32) || defined(_WIN64)
+  MDBX_srwlock me_remap_guard;
+  /* Workaround for LockFileEx and WriteFile multithread bug */
+  CRITICAL_SECTION me_windowsbug_lock;
+#else
+  mdbx_fastmutex_t me_remap_guard;
+#endif
+};
+
+#ifndef __cplusplus
+/*----------------------------------------------------------------------------*/
+/* Debug and Logging stuff */
+
+#define MDBX_RUNTIME_FLAGS_INIT                                                \
+  ((MDBX_DEBUG) > 0) * MDBX_DBG_ASSERT + ((MDBX_DEBUG) > 1) * MDBX_DBG_AUDIT
+
+extern uint8_t mdbx_runtime_flags;
+extern uint8_t mdbx_loglevel;
+extern MDBX_debug_func *mdbx_debug_logger;
+
+MDBX_INTERNAL_FUNC void MDBX_PRINTF_ARGS(4, 5)
+    mdbx_debug_log(int level, const char *function, int line, const char *fmt,
+                   ...) MDBX_PRINTF_ARGS(4, 5);
+MDBX_INTERNAL_FUNC void mdbx_debug_log_va(int level, const char *function,
+                                          int line, const char *fmt,
+                                          va_list args);
+
+#define mdbx_log_enabled(msg) unlikely(msg <= mdbx_loglevel)
+
+#if MDBX_DEBUG
+
+#define mdbx_assert_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_ASSERT)
+
+#define mdbx_audit_enabled() unlikely(mdbx_runtime_flags &MDBX_DBG_AUDIT)
+
+#else /* MDBX_DEBUG */
+
+#define mdbx_audit_enabled() (0)
+
+#if !defined(NDEBUG) || defined(MDBX_FORCE_ASSERTIONS)
+#define mdbx_assert_enabled() (1)
+#else
+#define mdbx_assert_enabled() (0)
+#endif /* NDEBUG */
+
+#endif /* MDBX_DEBUG */
+
+#if !MDBX_DEBUG && defined(__ANDROID_API__)
+#define mdbx_assert_fail(env, msg, func, line)                                 \
+  __android_log_assert(msg, "mdbx", "%s:%u", func, line)
+#else
+void mdbx_assert_fail(const MDBX_env *env, const char *msg, const char *func,
+                      int line);
+#endif
+
+#define mdbx_debug_extra(fmt, ...)                                             \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, __func__, __LINE__, fmt, __VA_ARGS__);    \
+  } while (0)
+
+#define mdbx_debug_extra_print(fmt, ...)                                       \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_EXTRA))                        \
+      mdbx_debug_log(MDBX_LOG_EXTRA, NULL, 0, fmt, __VA_ARGS__);               \
+  } while (0)
+
+#define mdbx_trace(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_TRACE))                        \
+      mdbx_debug_log(MDBX_LOG_TRACE, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_debug(fmt, ...)                                                   \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_DEBUG))                        \
+      mdbx_debug_log(MDBX_LOG_DEBUG, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_verbose(fmt, ...)                                                 \
+  do {                                                                         \
+    if (MDBX_DEBUG && mdbx_log_enabled(MDBX_LOG_VERBOSE))                      \
+      mdbx_debug_log(MDBX_LOG_VERBOSE, __func__, __LINE__, fmt "\n",           \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_notice(fmt, ...)                                                  \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_NOTICE))                                     \
+      mdbx_debug_log(MDBX_LOG_NOTICE, __func__, __LINE__, fmt "\n",            \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_warning(fmt, ...)                                                 \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_WARN))                                       \
+      mdbx_debug_log(MDBX_LOG_WARN, __func__, __LINE__, fmt "\n",              \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_error(fmt, ...)                                                   \
+  do {                                                                         \
+    if (mdbx_log_enabled(MDBX_LOG_ERROR))                                      \
+      mdbx_debug_log(MDBX_LOG_ERROR, __func__, __LINE__, fmt "\n",             \
+                     __VA_ARGS__);                                             \
+  } while (0)
+
+#define mdbx_fatal(fmt, ...)                                                   \
+  mdbx_debug_log(MDBX_LOG_FATAL, __func__, __LINE__, fmt "\n", __VA_ARGS__);
+
+#define mdbx_ensure_msg(env, expr, msg)                                        \
+  do {                                                                         \
+    if (unlikely(!(expr)))                                                     \
+      mdbx_assert_fail(env, msg, __func__, __LINE__);                          \
+  } while (0)
+
+#define mdbx_ensure(env, expr) mdbx_ensure_msg(env, expr, #expr)
+
+/* assert(3) variant in environment context */
+#define mdbx_assert(env, expr)                                                 \
+  do {                                                                         \
+    if (mdbx_assert_enabled())                                                 \
+      mdbx_ensure(env, expr);                                                  \
+  } while (0)
+
+/* assert(3) variant in cursor context */
+#define mdbx_cassert(mc, expr) mdbx_assert((mc)->mc_txn->mt_env, expr)
+
+/* assert(3) variant in transaction context */
+#define mdbx_tassert(txn, expr) mdbx_assert((txn)->mt_env, expr)
+
+#ifndef MDBX_TOOLS /* Avoid using internal mdbx_assert() */
+#undef assert
+#define assert(expr) mdbx_assert(NULL, expr)
+#endif
+
+/*----------------------------------------------------------------------------*/
+/* Cache coherence and mmap invalidation */
+
+#if MDBX_CPU_WRITEBACK_INCOHERENT
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_memory_barrier()
+#else
+#define mdbx_flush_incoherent_cpu_writeback() mdbx_compiler_barrier()
+#endif /* MDBX_CPU_WRITEBACK_INCOHERENT */
+
+static __maybe_unused __inline void
+mdbx_flush_incoherent_mmap(void *addr, size_t nbytes, const intptr_t pagesize) {
+#if MDBX_MMAP_INCOHERENT_FILE_WRITE
+  char *const begin = (char *)(-pagesize & (intptr_t)addr);
+  char *const end =
+      (char *)(-pagesize & (intptr_t)((char *)addr + nbytes + pagesize - 1));
+  int err = msync(begin, end - begin, MS_SYNC | MS_INVALIDATE) ? errno : 0;
+  mdbx_assert(nullptr, err == 0);
+  (void)err;
+#else
+  (void)pagesize;
+#endif /* MDBX_MMAP_INCOHERENT_FILE_WRITE */
+
+#if MDBX_MMAP_INCOHERENT_CPU_CACHE
+#ifdef DCACHE
+  /* MIPS has cache coherency issues.
+   * Note: for any nbytes >= on-chip cache size, entire is flushed. */
+  cacheflush(addr, nbytes, DCACHE);
+#else
+#error "Oops, cacheflush() not available"
+#endif /* DCACHE */
+#endif /* MDBX_MMAP_INCOHERENT_CPU_CACHE */
+
+#if !MDBX_MMAP_INCOHERENT_FILE_WRITE && !MDBX_MMAP_INCOHERENT_CPU_CACHE
+  (void)addr;
+  (void)nbytes;
+#endif
+}
+
+/*----------------------------------------------------------------------------*/
+/* Internal prototypes */
+
+MDBX_INTERNAL_FUNC int mdbx_cleanup_dead_readers(MDBX_env *env, int rlocked,
+                                                 int *dead);
+MDBX_INTERNAL_FUNC int mdbx_rthc_alloc(mdbx_thread_key_t *key,
+                                       MDBX_reader *begin, MDBX_reader *end);
+MDBX_INTERNAL_FUNC void mdbx_rthc_remove(const mdbx_thread_key_t key);
+
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_init(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_global_dtor(void);
+MDBX_INTERNAL_FUNC void mdbx_rthc_thread_dtor(void *ptr);
+
+static __maybe_unused __inline void mdbx_jitter4testing(bool tiny) {
+#if MDBX_DEBUG
+  if (MDBX_DBG_JITTER & mdbx_runtime_flags)
+    mdbx_osal_jitter(tiny);
+#else
+  (void)tiny;
+#endif
+}
+
+#endif /* !__cplusplus */
+
+#define MDBX_IS_ERROR(rc)                                                      \
+  ((rc) != MDBX_RESULT_TRUE && (rc) != MDBX_RESULT_FALSE)
+
+/* Internal error codes, not exposed outside libmdbx */
+#define MDBX_NO_ROOT (MDBX_LAST_ADDED_ERRCODE + 10)
+
+/* Debugging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc)                                                               \
+  (((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+
+/* Key size which fits in a DKBUF. */
+#define DKBUF_MAXKEYSIZE 511 /* FIXME */
+
+#if MDBX_DEBUG
+#define DKBUF char _kbuf[DKBUF_MAXKEYSIZE * 4 + 2]
+#define DKEY(x) mdbx_dump_val(x, _kbuf, DKBUF_MAXKEYSIZE * 2 + 1)
+#define DVAL(x)                                                                \
+  mdbx_dump_val(x, _kbuf + DKBUF_MAXKEYSIZE * 2 + 1, DKBUF_MAXKEYSIZE * 2 + 1)
+#else
+#define DKBUF ((void)(0))
+#define DKEY(x) ("-")
+#define DVAL(x) ("-")
+#endif
+
+/* An invalid page number.
+ * Mainly used to denote an empty tree. */
+#define P_INVALID (~(pgno_t)0)
+
+/* Test if the flags f are set in a flag word w. */
+#define F_ISSET(w, f) (((w) & (f)) == (f))
+
+/* Round n up to an even number. */
+#define EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+/* Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should
+ * always set  the size explicitly using mdbx_env_set_mapsize(). */
+#define DEFAULT_MAPSIZE MEGABYTE
+
+/* Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. The 61 is a prime number,
+ * and such readers plus a couple mutexes fit into single 4KB page.
+ * Applications should set the table size using mdbx_env_set_maxreaders(). */
+#define DEFAULT_READERS 61
+
+/* Test if a page is a leaf page */
+#define IS_LEAF(p) (((p)->mp_flags & P_LEAF) != 0)
+/* Test if a page is a LEAF2 page */
+#define IS_LEAF2(p) unlikely(((p)->mp_flags & P_LEAF2) != 0)
+/* Test if a page is a branch page */
+#define IS_BRANCH(p) (((p)->mp_flags & P_BRANCH) != 0)
+/* Test if a page is an overflow page */
+#define IS_OVERFLOW(p) unlikely(((p)->mp_flags & P_OVERFLOW) != 0)
+/* Test if a page is a sub page */
+#define IS_SUBP(p) (((p)->mp_flags & P_SUBP) != 0)
+/* Test if a page is dirty */
+#define IS_DIRTY(p) (((p)->mp_flags & P_DIRTY) != 0)
+
+#define PAGETYPE(p) ((p)->mp_flags & (P_BRANCH | P_LEAF | P_LEAF2 | P_OVERFLOW))
+
+/* Header for a single key/data pair within a page.
+ * Used in pages of type P_BRANCH and P_LEAF without P_LEAF2.
+ * We guarantee 2-byte alignment for 'MDBX_node's.
+ *
+ * Leaf node flags describe node contents.  F_BIGDATA says the node's
+ * data part is the page number of an overflow page with actual data.
+ * F_DUPDATA and F_SUBDATA can be combined giving duplicate data in
+ * a sub-page/sub-database, and named databases (just F_SUBDATA). */
+typedef struct MDBX_node {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  union {
+    uint32_t mn_dsize;
+    uint32_t mn_pgno32;
+  };
+  uint8_t mn_flags; /* see mdbx_node flags */
+  uint8_t mn_extra;
+  uint16_t mn_ksize; /* key size */
+#else
+  uint16_t mn_ksize; /* key size */
+  uint8_t mn_extra;
+  uint8_t mn_flags; /* see mdbx_node flags */
+  union {
+    uint32_t mn_pgno32;
+    uint32_t mn_dsize;
+  };
+#endif /* __BYTE_ORDER__ */
+
+  /* mdbx_node Flags */
+#define F_BIGDATA 0x01 /* data put on overflow page */
+#define F_SUBDATA 0x02 /* data is a sub-database */
+#define F_DUPDATA 0x04 /* data has duplicates */
+
+  /* valid flags for mdbx_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA | F_SUBDATA | MDBX_RESERVE | MDBX_APPEND)
+
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) ||              \
+    (!defined(__cplusplus) && defined(_MSC_VER))
+  uint8_t mn_data[] /* key and data are appended here */;
+#endif /* C99 */
+} MDBX_node;
+
+#define DB_PERSISTENT_FLAGS                                                    \
+  (MDBX_REVERSEKEY | MDBX_DUPSORT | MDBX_INTEGERKEY | MDBX_DUPFIXED |          \
+   MDBX_INTEGERDUP | MDBX_REVERSEDUP)
+
+/* mdbx_dbi_open() flags */
+#define DB_USABLE_FLAGS (DB_PERSISTENT_FLAGS | MDBX_CREATE | MDBX_DB_ACCEDE)
+
+#define DB_VALID 0x8000 /* DB handle is valid, for me_dbflags */
+#define DB_INTERNAL_FLAGS DB_VALID
+
+#if DB_INTERNAL_FLAGS & DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+#if DB_PERSISTENT_FLAGS & ~DB_USABLE_FLAGS
+#error "Oops, some flags overlapped or wrong"
+#endif
+
+/* max number of pages to commit in one writev() call */
+#define MDBX_COMMIT_PAGES 64
+#if defined(IOV_MAX) && IOV_MAX < MDBX_COMMIT_PAGES /* sysconf(_SC_IOV_MAX) */
+#undef MDBX_COMMIT_PAGES
+#define MDBX_COMMIT_PAGES IOV_MAX
+#endif
+
+/*
+ *                /
+ *                | -1, a < b
+ * CMP2INT(a,b) = <  0, a == b
+ *                |  1, a > b
+ *                \
+ */
+#if 1
+/* LY: fast enough on most systems */
+#define CMP2INT(a, b) (((b) > (a)) ? -1 : (a) > (b))
+#else
+#define CMP2INT(a, b) (((a) > (b)) - ((b) > (a)))
+#endif
+
+/* Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDBX_NOSPILL 0x8000
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_add(pgno_t base, pgno_t augend) {
+  assert(base <= MAX_PAGENO);
+  return (augend < MAX_PAGENO - base) ? base + augend : MAX_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __maybe_unused __inline pgno_t
+pgno_sub(pgno_t base, pgno_t subtrahend) {
+  assert(base >= MIN_PAGENO);
+  return (subtrahend < base - MIN_PAGENO) ? base - subtrahend : MIN_PAGENO;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused bool
+is_powerof2(size_t x) {
+  return (x & (x - 1)) == 0;
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+floor_powerof2(size_t value, size_t granularity) {
+  assert(is_powerof2(granularity));
+  return value & ~(granularity - 1);
+}
+
+MDBX_NOTHROW_CONST_FUNCTION static __always_inline __maybe_unused size_t
+ceil_powerof2(size_t value, size_t granularity) {
+  return floor_powerof2(value + granularity - 1, granularity);
+}
+
+/* Only a subset of the mdbx_env flags can be changed
+ * at runtime. Changing other flags requires closing the
+ * environment and re-opening it with the new flags. */
+#define ENV_CHANGEABLE_FLAGS                                                   \
+  (MDBX_SAFE_NOSYNC | MDBX_NOMETASYNC | MDBX_DEPRECATED_MAPASYNC |             \
+   MDBX_NOMEMINIT | MDBX_COALESCE | MDBX_PAGEPERTURB | MDBX_ACCEDE)
+#define ENV_CHANGELESS_FLAGS                                                   \
+  (MDBX_NOSUBDIR | MDBX_RDONLY | MDBX_WRITEMAP | MDBX_NOTLS | MDBX_NORDAHEAD | \
+   MDBX_LIFORECLAIM | MDBX_EXCLUSIVE)
+#define ENV_USABLE_FLAGS (ENV_CHANGEABLE_FLAGS | ENV_CHANGELESS_FLAGS)
+
+#if !defined(__cplusplus) || defined(__cpp_constexpr)
+static __maybe_unused void static_checks(void) {
+  STATIC_ASSERT_MSG(INT16_MAX - CORE_DBS == MDBX_MAX_DBI,
+                    "Oops, MDBX_MAX_DBI or CORE_DBS?");
+  STATIC_ASSERT_MSG((unsigned)(MDBX_DB_ACCEDE | MDBX_CREATE) ==
+                        ((DB_USABLE_FLAGS | DB_INTERNAL_FLAGS) &
+                         (ENV_USABLE_FLAGS | ENV_INTERNAL_FLAGS)),
+                    "Oops, some flags overlapped or wrong");
+  STATIC_ASSERT_MSG((ENV_INTERNAL_FLAGS & ENV_USABLE_FLAGS) == 0,
+                    "Oops, some flags overlapped or wrong");
+}
+#endif /* Disabled for MSVC 19.0 (VisualStudio 2015) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#if defined(_WIN32) || defined(_WIN64)
+/*
+ * POSIX getopt for Windows
+ *
+ * AT&T Public License
+ *
+ * Code given out at the 1985 UNIFORUM conference in Dallas.
+ */
+
+/*----------------------------------------------------------------------------*/
+/* Microsoft compiler generates a lot of warning for self includes... */
+
+#ifdef _MSC_VER
+#pragma warning(push, 1)
+#pragma warning(disable : 4548) /* expression before comma has no effect;      \
+                                   expected expression with side - effect */
+#pragma warning(disable : 4530) /* C++ exception handler used, but unwind      \
+                                 * semantics are not enabled. Specify /EHsc */
+#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling  \
+                                 * mode specified; termination on exception is \
+                                 * not guaranteed. Specify /EHsc */
+#if !defined(_CRT_SECURE_NO_WARNINGS)
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+#endif /* _MSC_VER (warnings) */
+
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+/*----------------------------------------------------------------------------*/
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+int optind = 1;
+int optopt;
+char *optarg;
+
+int getopt(int argc, char *const argv[], const char *opts) {
+  static int sp = 1;
+  int c;
+  const char *cp;
+
+  if (sp == 1) {
+    if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
+      return EOF;
+    else if (strcmp(argv[optind], "--") == 0) {
+      optind++;
+      return EOF;
+    }
+  }
+  optopt = c = argv[optind][sp];
+  if (c == ':' || (cp = strchr(opts, c)) == NULL) {
+    fprintf(stderr, "%s: %s -- %c\n", argv[0], "illegal option", c);
+    if (argv[optind][++sp] == '\0') {
+      optind++;
+      sp = 1;
+    }
+    return '?';
+  }
+  if (*++cp == ':') {
+    if (argv[optind][sp + 1] != '\0')
+      optarg = &argv[optind++][sp + 1];
+    else if (++optind >= argc) {
+      fprintf(stderr, "%s: %s -- %c\n", argv[0], "option requires an argument",
+              c);
+      sp = 1;
+      return '?';
+    } else
+      optarg = argv[optind++];
+    sp = 1;
+  } else {
+    if (argv[optind][++sp] == '\0') {
+      sp = 1;
+      optind++;
+    }
+    optarg = NULL;
+  }
+  return c;
+}
+
+static volatile BOOL user_break;
+static BOOL WINAPI ConsoleBreakHandlerRoutine(DWORD dwCtrlType) {
+  (void)dwCtrlType;
+  user_break = true;
+  return true;
+}
+
+#else /* WINDOWS */
+
+static volatile sig_atomic_t user_break;
+static void signal_handler(int sig) {
+  (void)sig;
+  user_break = 1;
+}
+
+#endif /* !WINDOWS */
+
+static void print_stat(MDBX_stat *ms) {
+  printf("  Pagesize: %u\n", ms->ms_psize);
+  printf("  Tree depth: %u\n", ms->ms_depth);
+  printf("  Branch pages: %" PRIu64 "\n", ms->ms_branch_pages);
+  printf("  Leaf pages: %" PRIu64 "\n", ms->ms_leaf_pages);
+  printf("  Overflow pages: %" PRIu64 "\n", ms->ms_overflow_pages);
+  printf("  Entries: %" PRIu64 "\n", ms->ms_entries);
+}
+
+static void usage(const char *prog) {
+  fprintf(stderr,
+          "usage: %s [-V] [-e] [-f[f[f]]] [-r[r]] [-a|-s name] dbpath\n"
+          "  -V\t\tprint version and exit\n"
+          "  -e\t\tshow whole DB info\n"
+          "  -f\t\tshow GC info\n"
+          "  -r\t\tshow readers\n"
+          "  -a\t\tprint stat of main DB and all subDBs\n"
+          "  \t\t(default) print stat of only the main DB\n"
+          "  -s name\tprint stat of only the named subDB\n",
+          prog);
+  exit(EXIT_FAILURE);
+}
+
+static int reader_list_func(void *ctx, int num, int slot, mdbx_pid_t pid,
+                            mdbx_tid_t thread, uint64_t txnid, uint64_t lag,
+                            size_t bytes_used, size_t bytes_retained) {
+  (void)ctx;
+  if (num == 1)
+    printf("Reader Table\n"
+           "   #\tslot\t%6s %*s %20s %10s %13s %13s\n",
+           "pid", (int)sizeof(size_t) * 2, "thread", "txnid", "lag", "used",
+           "retained");
+
+  printf(" %3d)\t[%d]\t%6" PRIdSIZE " %*" PRIxPTR, num, slot, (size_t)pid,
+         (int)sizeof(size_t) * 2, (uintptr_t)thread);
+  if (txnid)
+    printf(" %20" PRIu64 " %10" PRIu64 " %12.1fM %12.1fM\n", txnid, lag,
+           bytes_used / 1048576.0, bytes_retained / 1048576.0);
+  else
+    printf(" %20s %10s %13s %13s\n", "-", "0", "0", "0");
+
+  return user_break ? MDBX_RESULT_TRUE : MDBX_RESULT_FALSE;
+}
+
+const char *prog;
+static void error(const char *func, int rc) {
+  fprintf(stderr, "%s: %s() error %d %s\n", prog, func, rc, mdbx_strerror(rc));
+}
+
+int main(int argc, char *argv[]) {
+  int o, rc;
+  MDBX_env *env;
+  MDBX_txn *txn;
+  MDBX_dbi dbi;
+  MDBX_stat mst;
+  MDBX_envinfo mei;
+  prog = argv[0];
+  char *envname;
+  char *subname = nullptr;
+  int alldbs = 0, envinfo = 0, envflags = 0, freinfo = 0, rdrinfo = 0;
+
+  if (argc < 2)
+    usage(prog);
+
+  while ((o = getopt(argc, argv,
+                     "V"
+                     "a"
+                     "e"
+                     "f"
+                     "n"
+                     "r"
+                     "s:")) != EOF) {
+    switch (o) {
+    case 'V':
+      printf("mdbx_stat version %d.%d.%d.%d\n"
+             " - source: %s %s, commit %s, tree %s\n"
+             " - anchor: %s\n"
+             " - build: %s for %s by %s\n"
+             " - flags: %s\n"
+             " - options: %s\n",
+             mdbx_version.major, mdbx_version.minor, mdbx_version.release,
+             mdbx_version.revision, mdbx_version.git.describe,
+             mdbx_version.git.datetime, mdbx_version.git.commit,
+             mdbx_version.git.tree, mdbx_sourcery_anchor, mdbx_build.datetime,
+             mdbx_build.target, mdbx_build.compiler, mdbx_build.flags,
+             mdbx_build.options);
+      return EXIT_SUCCESS;
+    case 'a':
+      if (subname)
+        usage(prog);
+      alldbs++;
+      break;
+    case 'e':
+      envinfo++;
+      break;
+    case 'f':
+      freinfo++;
+      break;
+    case 'n':
+      envflags |= MDBX_NOSUBDIR;
+      break;
+    case 'r':
+      rdrinfo++;
+      break;
+    case 's':
+      if (alldbs)
+        usage(prog);
+      subname = optarg;
+      break;
+    default:
+      usage(prog);
+    }
+  }
+
+  if (optind != argc - 1)
+    usage(prog);
+
+#if defined(_WIN32) || defined(_WIN64)
+  SetConsoleCtrlHandler(ConsoleBreakHandlerRoutine, true);
+#else
+#ifdef SIGPIPE
+  signal(SIGPIPE, signal_handler);
+#endif
+#ifdef SIGHUP
+  signal(SIGHUP, signal_handler);
+#endif
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+#endif /* !WINDOWS */
+
+  envname = argv[optind];
+  envname = argv[optind];
+  printf("mdbx_stat %s (%s, T-%s)\nRunning for %s...\n",
+         mdbx_version.git.describe, mdbx_version.git.datetime,
+         mdbx_version.git.tree, envname);
+  fflush(nullptr);
+
+  rc = mdbx_env_create(&env);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_create", rc);
+    return EXIT_FAILURE;
+  }
+
+  if (alldbs || subname) {
+    rc = mdbx_env_set_maxdbs(env, 2);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_set_maxdbs", rc);
+      goto env_close;
+    }
+  }
+
+  rc = mdbx_env_open(env, envname, envflags | MDBX_RDONLY, 0664);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_env_open", rc);
+    goto env_close;
+  }
+
+  rc = mdbx_txn_begin(env, nullptr, MDBX_TXN_RDONLY, &txn);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_txn_begin", rc);
+    goto txn_abort;
+  }
+
+  if (envinfo || freinfo) {
+    rc = mdbx_env_info_ex(env, txn, &mei, sizeof(mei));
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_info_ex", rc);
+      goto txn_abort;
+    }
+  } else {
+    /* LY: zap warnings from gcc */
+    memset(&mei, 0, sizeof(mei));
+  }
+
+  if (envinfo) {
+    rc = mdbx_env_stat_ex(env, txn, &mst, sizeof(mst));
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_env_stat_ex", rc);
+      goto txn_abort;
+    }
+    printf("Environment Info\n");
+    printf("  Pagesize: %u\n", mst.ms_psize);
+    if (mei.mi_geo.lower != mei.mi_geo.upper) {
+      printf("  Dynamic datafile: %" PRIu64 "..%" PRIu64 " bytes (+%" PRIu64
+             "/-%" PRIu64 "), %" PRIu64 "..%" PRIu64 " pages (+%" PRIu64
+             "/-%" PRIu64 ")\n",
+             mei.mi_geo.lower, mei.mi_geo.upper, mei.mi_geo.grow,
+             mei.mi_geo.shrink, mei.mi_geo.lower / mst.ms_psize,
+             mei.mi_geo.upper / mst.ms_psize, mei.mi_geo.grow / mst.ms_psize,
+             mei.mi_geo.shrink / mst.ms_psize);
+      printf("  Current mapsize: %" PRIu64 " bytes, %" PRIu64 " pages \n",
+             mei.mi_mapsize, mei.mi_mapsize / mst.ms_psize);
+      printf("  Current datafile: %" PRIu64 " bytes, %" PRIu64 " pages\n",
+             mei.mi_geo.current, mei.mi_geo.current / mst.ms_psize);
+#if defined(_WIN32) || defined(_WIN64)
+      if (mei.mi_geo.shrink && mei.mi_geo.current != mei.mi_geo.upper)
+        printf("                    WARNING: Due Windows system limitations a "
+               "file couldn't\n                    be truncated while database "
+               "is opened. So, the size of\n                    database file "
+               "may by large than the database itself,\n                    "
+               "until it will be closed or reopened in read-write mode.\n");
+#endif
+    } else {
+      printf("  Fixed datafile: %" PRIu64 " bytes, %" PRIu64 " pages\n",
+             mei.mi_geo.current, mei.mi_geo.current / mst.ms_psize);
+    }
+    printf("  Last transaction ID: %" PRIu64 "\n", mei.mi_recent_txnid);
+    printf("  Latter reader transaction ID: %" PRIu64 " (%" PRIi64 ")\n",
+           mei.mi_latter_reader_txnid,
+           mei.mi_latter_reader_txnid - mei.mi_recent_txnid);
+    printf("  Max readers: %u\n", mei.mi_maxreaders);
+    printf("  Number of reader slots uses: %u\n", mei.mi_numreaders);
+  } else {
+    /* LY: zap warnings from gcc */
+    memset(&mst, 0, sizeof(mst));
+  }
+
+  if (rdrinfo) {
+    rc = mdbx_reader_list(env, reader_list_func, nullptr);
+    if (MDBX_IS_ERROR(rc)) {
+      error("mdbx_reader_list", rc);
+      goto txn_abort;
+    }
+    if (rc == MDBX_RESULT_TRUE)
+      printf("Reader Table is empty\n");
+    else if (rc == MDBX_SUCCESS && rdrinfo > 1) {
+      int dead;
+      rc = mdbx_reader_check(env, &dead);
+      if (MDBX_IS_ERROR(rc)) {
+        error("mdbx_reader_check", rc);
+        goto txn_abort;
+      }
+      if (rc == MDBX_RESULT_TRUE) {
+        printf("  %d stale readers cleared.\n", dead);
+        rc = mdbx_reader_list(env, reader_list_func, nullptr);
+        if (rc == MDBX_RESULT_TRUE)
+          printf("  Now Reader Table is empty\n");
+      } else
+        printf("  No stale readers.\n");
+    }
+    if (!(subname || alldbs || freinfo))
+      goto txn_abort;
+  }
+
+  if (freinfo) {
+    printf("Garbage Collection\n");
+    dbi = 0;
+    MDBX_cursor *cursor;
+    rc = mdbx_cursor_open(txn, dbi, &cursor);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_cursor_open", rc);
+      goto txn_abort;
+    }
+    rc = mdbx_dbi_stat(txn, dbi, &mst, sizeof(mst));
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_dbi_stat", rc);
+      goto txn_abort;
+    }
+    print_stat(&mst);
+
+    pgno_t pages = 0, *iptr;
+    pgno_t reclaimable = 0;
+    MDBX_val key, data;
+    while (MDBX_SUCCESS ==
+           (rc = mdbx_cursor_get(cursor, &key, &data, MDBX_NEXT))) {
+      if (user_break) {
+        rc = MDBX_EINTR;
+        break;
+      }
+      iptr = data.iov_base;
+      const pgno_t number = *iptr++;
+
+      pages += number;
+      if (envinfo && mei.mi_latter_reader_txnid > *(txnid_t *)key.iov_base)
+        reclaimable += number;
+
+      if (freinfo > 1) {
+        char *bad = "";
+        pgno_t prev =
+            MDBX_PNL_ASCENDING ? NUM_METAS - 1 : (pgno_t)mei.mi_last_pgno + 1;
+        pgno_t span = 1;
+        for (unsigned i = 0; i < number; ++i) {
+          pgno_t pg = iptr[i];
+          if (MDBX_PNL_DISORDERED(prev, pg))
+            bad = " [bad sequence]";
+          prev = pg;
+          while (i + span < number &&
+                 iptr[i + span] == (MDBX_PNL_ASCENDING ? pgno_add(pg, span)
+                                                       : pgno_sub(pg, span)))
+            ++span;
+        }
+        printf("    Transaction %" PRIaTXN ", %" PRIaPGNO
+               " pages, maxspan %" PRIaPGNO "%s\n",
+               *(txnid_t *)key.iov_base, number, span, bad);
+        if (freinfo > 2) {
+          for (unsigned i = 0; i < number; i += span) {
+            const pgno_t pg = iptr[i];
+            for (span = 1;
+                 i + span < number &&
+                 iptr[i + span] == (MDBX_PNL_ASCENDING ? pgno_add(pg, span)
+                                                       : pgno_sub(pg, span));
+                 ++span)
+              ;
+            if (span > 1)
+              printf("     %9" PRIaPGNO "[%" PRIaPGNO "]\n", pg, span);
+            else
+              printf("     %9" PRIaPGNO "\n", pg);
+          }
+        }
+      }
+    }
+    mdbx_cursor_close(cursor);
+    cursor = nullptr;
+
+    switch (rc) {
+    case MDBX_SUCCESS:
+    case MDBX_NOTFOUND:
+      break;
+    case MDBX_EINTR:
+      fprintf(stderr, "Interrupted by signal/user\n");
+      goto txn_abort;
+    default:
+      error("mdbx_cursor_get", rc);
+      goto txn_abort;
+    }
+
+    if (envinfo) {
+      uint64_t value = mei.mi_mapsize / mst.ms_psize;
+      double percent = value / 100.0;
+      printf("Page Usage\n");
+      printf("  Total: %" PRIu64 " 100%%\n", value);
+
+      value = mei.mi_geo.current / mst.ms_psize;
+      printf("  Backed: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = mei.mi_last_pgno + 1;
+      printf("  Allocated: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = mei.mi_mapsize / mst.ms_psize - (mei.mi_last_pgno + 1);
+      printf("  Remained: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = mei.mi_last_pgno + 1 - pages;
+      printf("  Used: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = pages;
+      printf("  GC: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = pages - reclaimable;
+      printf("  Retained: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value = reclaimable;
+      printf("  Reclaimable: %" PRIu64 " %.1f%%\n", value, value / percent);
+
+      value =
+          mei.mi_mapsize / mst.ms_psize - (mei.mi_last_pgno + 1) + reclaimable;
+      printf("  Available: %" PRIu64 " %.1f%%\n", value, value / percent);
+    } else
+      printf("  GC: %" PRIaPGNO " pages\n", pages);
+  }
+
+  rc = mdbx_dbi_open(txn, subname, MDBX_DB_ACCEDE, &dbi);
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_open", rc);
+    goto txn_abort;
+  }
+  rc = mdbx_dbi_stat(txn, dbi, &mst, sizeof(mst));
+  if (unlikely(rc != MDBX_SUCCESS)) {
+    error("mdbx_dbi_stat", rc);
+    goto txn_abort;
+  }
+  printf("Status of %s\n", subname ? subname : "Main DB");
+  print_stat(&mst);
+
+  if (alldbs) {
+    MDBX_cursor *cursor;
+    rc = mdbx_cursor_open(txn, dbi, &cursor);
+    if (unlikely(rc != MDBX_SUCCESS)) {
+      error("mdbx_cursor_open", rc);
+      goto txn_abort;
+    }
+
+    MDBX_val key;
+    while (MDBX_SUCCESS ==
+           (rc = mdbx_cursor_get(cursor, &key, nullptr, MDBX_NEXT_NODUP))) {
+      MDBX_dbi subdbi;
+      if (memchr(key.iov_base, '\0', key.iov_len))
+        continue;
+      subname = mdbx_malloc(key.iov_len + 1);
+      memcpy(subname, key.iov_base, key.iov_len);
+      subname[key.iov_len] = '\0';
+      rc = mdbx_dbi_open(txn, subname, MDBX_DB_ACCEDE, &subdbi);
+      if (rc == MDBX_SUCCESS)
+        printf("Status of %s\n", subname);
+      mdbx_free(subname);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        if (rc == MDBX_INCOMPATIBLE)
+          continue;
+        error("mdbx_dbi_open", rc);
+        goto txn_abort;
+      }
+
+      rc = mdbx_dbi_stat(txn, subdbi, &mst, sizeof(mst));
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_dbi_stat", rc);
+        goto txn_abort;
+      }
+      print_stat(&mst);
+
+      rc = mdbx_dbi_close(env, subdbi);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_dbi_close", rc);
+        goto txn_abort;
+      }
+    }
+    mdbx_cursor_close(cursor);
+    cursor = nullptr;
+  }
+
+  switch (rc) {
+  case MDBX_SUCCESS:
+  case MDBX_NOTFOUND:
+    break;
+  case MDBX_EINTR:
+    fprintf(stderr, "Interrupted by signal/user\n");
+    break;
+  default:
+    if (unlikely(rc != MDBX_SUCCESS))
+      error("mdbx_cursor_get", rc);
+  }
+
+  mdbx_dbi_close(env, dbi);
+txn_abort:
+  mdbx_txn_abort(txn);
+env_close:
+  mdbx_env_close(env);
+
+  return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/plugins/Dbx_mdbx/src/libmdbx/ntdll.def b/plugins/Dbx_mdbx/src/libmdbx/ntdll.def
new file mode 100644
index 0000000000..f974ea6380
--- /dev/null
+++ b/plugins/Dbx_mdbx/src/libmdbx/ntdll.def
@@ -0,0 +1,1246 @@
+LIBRARY ntdll
+EXPORTS
+CsrAllocateCaptureBuffer
+CsrAllocateMessagePointer
+CsrCaptureMessageBuffer
+CsrCaptureMessageMultiUnicodeStringsInPlace
+CsrCaptureMessageString
+CsrCaptureTimeout
+CsrClientCallServer
+CsrClientConnectToServer
+CsrFreeCaptureBuffer
+CsrGetProcessId
+CsrIdentifyAlertableThread
+CsrSetPriorityClass
+DbgBreakPoint
+DbgPrint
+DbgPrintEx
+DbgPrintReturnControlC
+DbgPrompt
+DbgQueryDebugFilterState
+DbgSetDebugFilterState
+DbgUiConnectToDbg
+DbgUiContinue
+DbgUiConvertStateChangeStructure
+DbgUiDebugActiveProcess
+DbgUiGetThreadDebugObject
+DbgUiIssueRemoteBreakin
+DbgUiRemoteBreakin
+DbgUiSetThreadDebugObject
+DbgUiStopDebugging
+DbgUiWaitStateChange
+DbgUserBreakPoint
+KiRaiseUserExceptionDispatcher
+KiUserApcDispatcher
+KiUserCallbackDispatcher
+KiUserExceptionDispatcher
+LdrAccessResource
+LdrAddRefDll
+LdrDisableThreadCalloutsForDll
+LdrEnumResources
+LdrEnumerateLoadedModules
+LdrFindEntryForAddress
+LdrFindResourceDirectory_U
+LdrFindResourceEx_U
+LdrFindResource_U
+LdrFlushAlternateResourceModules
+LdrGetDllHandle
+LdrGetDllHandleEx
+LdrGetProcedureAddress
+LdrInitShimEngineDynamic
+LdrInitializeThunk
+LdrLoadAlternateResourceModule
+LdrLoadDll
+LdrLockLoaderLock
+LdrProcessRelocationBlock
+LdrQueryImageFileExecutionOptions
+LdrQueryProcessModuleInformation
+LdrSetAppCompatDllRedirectionCallback
+LdrSetDllManifestProber
+LdrShutdownProcess
+LdrShutdownThread
+LdrUnloadAlternateResourceModule
+LdrUnloadDll
+LdrUnlockLoaderLock
+LdrVerifyImageMatchesChecksum
+NlsAnsiCodePage
+NlsMbCodePageTag
+NlsMbOemCodePageTag
+NtAcceptConnectPort
+NtAccessCheck
+NtAccessCheckAndAuditAlarm
+NtAccessCheckByType
+NtAccessCheckByTypeAndAuditAlarm
+NtAccessCheckByTypeResultList
+NtAccessCheckByTypeResultListAndAuditAlarm
+NtAccessCheckByTypeResultListAndAuditAlarmByHandle
+NtAddAtom
+NtAddBootEntry
+NtAdjustGroupsToken
+NtAdjustPrivilegesToken
+NtAlertResumeThread
+NtAlertThread
+NtAllocateLocallyUniqueId
+NtAllocateUserPhysicalPages
+NtAllocateUuids
+NtAllocateVirtualMemory
+NtAreMappedFilesTheSame
+NtAssignProcessToJobObject
+NtCallbackReturn
+NtCancelIoFile
+NtCancelTimer
+NtClearEvent
+NtClose
+NtCloseObjectAuditAlarm
+NtCompactKeys
+NtCompareTokens
+NtCompleteConnectPort
+NtCompressKey
+NtConnectPort
+NtContinue
+NtCreateDebugObject
+NtCreateDirectoryObject
+NtCreateEvent
+NtCreateEventPair
+NtCreateFile
+NtCreateIoCompletion
+NtCreateJobObject
+NtCreateJobSet
+NtCreateKey
+NtCreateKeyedEvent
+NtCreateMailslotFile
+NtCreateMutant
+NtCreateNamedPipeFile
+NtCreatePagingFile
+NtCreatePort
+NtCreateProcess
+NtCreateProcessEx
+NtCreateProfile
+NtCreateSection
+NtCreateSemaphore
+NtCreateSymbolicLinkObject
+NtCreateThread
+NtCreateTimer
+NtCreateToken
+NtCreateWaitablePort
+NtDebugActiveProcess
+NtDebugContinue
+NtDelayExecution
+NtDeleteAtom
+NtDeleteBootEntry
+NtDeleteFile
+NtDeleteKey
+NtDeleteObjectAuditAlarm
+NtDeleteValueKey
+NtDeviceIoControlFile
+NtDisplayString
+NtDuplicateObject
+NtDuplicateToken
+NtEnumerateBootEntries
+NtEnumerateKey
+NtEnumerateSystemEnvironmentValuesEx
+NtEnumerateValueKey
+NtExtendSection
+NtFilterToken
+NtFindAtom
+NtFlushBuffersFile
+NtFlushInstructionCache
+NtFlushKey
+NtFlushVirtualMemory
+NtFlushWriteBuffer
+NtFreeUserPhysicalPages
+NtFreeVirtualMemory
+NtFsControlFile
+NtGetContextThread
+NtGetDevicePowerState
+NtGetWriteWatch
+NtImpersonateAnonymousToken
+NtImpersonateClientOfPort
+NtImpersonateThread
+NtInitializeRegistry
+NtInitiatePowerAction
+NtIsProcessInJob
+NtIsSystemResumeAutomatic
+NtListenPort
+NtLoadDriver
+NtLoadKey
+NtLoadKey2
+NtLockFile
+NtLockProductActivationKeys
+NtLockRegistryKey
+NtLockVirtualMemory
+NtMakePermanentObject
+NtMakeTemporaryObject
+NtMapUserPhysicalPages
+NtMapUserPhysicalPagesScatter
+NtMapViewOfSection
+NtModifyBootEntry
+NtNotifyChangeDirectoryFile
+NtNotifyChangeKey
+NtNotifyChangeMultipleKeys
+NtOpenDirectoryObject
+NtOpenEvent
+NtOpenEventPair
+NtOpenFile
+NtOpenIoCompletion
+NtOpenJobObject
+NtOpenKey
+NtOpenKeyedEvent
+NtOpenMutant
+NtOpenObjectAuditAlarm
+NtOpenProcess
+NtOpenProcessToken
+NtOpenProcessTokenEx
+NtOpenSection
+NtOpenSemaphore
+NtOpenSymbolicLinkObject
+NtOpenThread
+NtOpenThreadToken
+NtOpenThreadTokenEx
+NtOpenTimer
+NtPlugPlayControl
+NtPowerInformation
+NtPrivilegeCheck
+NtPrivilegeObjectAuditAlarm
+NtPrivilegedServiceAuditAlarm
+NtProtectVirtualMemory
+NtPulseEvent
+NtQueryAttributesFile
+NtQueryBootEntryOrder
+NtQueryBootOptions
+NtQueryDebugFilterState
+NtQueryDefaultLocale
+NtQueryDefaultUILanguage
+NtQueryDirectoryFile
+NtQueryDirectoryObject
+NtQueryEaFile
+NtQueryEvent
+NtQueryFullAttributesFile
+NtQueryInformationAtom
+NtQueryInformationFile
+NtQueryInformationJobObject
+NtQueryInformationPort
+NtQueryInformationProcess
+NtQueryInformationThread
+NtQueryInformationToken
+NtQueryInstallUILanguage
+NtQueryIntervalProfile
+NtQueryIoCompletion
+NtQueryKey
+NtQueryMultipleValueKey
+NtQueryMutant
+NtQueryObject
+NtQueryOpenSubKeys
+NtQueryPerformanceCounter
+NtQueryPortInformationProcess
+NtQueryQuotaInformationFile
+NtQuerySection
+NtQuerySecurityObject
+NtQuerySemaphore
+NtQuerySymbolicLinkObject
+NtQuerySystemEnvironmentValue
+NtQuerySystemEnvironmentValueEx
+NtQuerySystemInformation
+NtQuerySystemTime
+NtQueryTimer
+NtQueryTimerResolution
+NtQueryValueKey
+NtQueryVirtualMemory
+NtQueryVolumeInformationFile
+NtQueueApcThread
+NtRaiseException
+NtRaiseHardError
+NtReadFile
+NtReadFileScatter
+NtReadRequestData
+NtReadVirtualMemory
+NtRegisterThreadTerminatePort
+NtReleaseKeyedEvent
+NtReleaseMutant
+NtReleaseSemaphore
+NtRemoveIoCompletion
+NtRemoveProcessDebug
+NtRenameKey
+NtReplaceKey
+NtReplyPort
+NtReplyWaitReceivePort
+NtReplyWaitReceivePortEx
+NtReplyWaitReplyPort
+NtRequestPort
+NtRequestWaitReplyPort
+NtResetEvent
+NtResetWriteWatch
+NtRestoreKey
+NtResumeProcess
+NtResumeThread
+NtSaveKey
+NtSaveKeyEx
+NtSaveMergedKeys
+NtSecureConnectPort
+NtSetBootEntryOrder
+NtSetBootOptions
+NtSetContextThread
+NtSetDebugFilterState
+NtSetDefaultHardErrorPort
+NtSetDefaultLocale
+NtSetDefaultUILanguage
+NtSetEaFile
+NtSetEvent
+NtSetEventBoostPriority
+NtSetHighEventPair
+NtSetHighWaitLowEventPair
+NtSetInformationDebugObject
+NtSetInformationFile
+NtSetInformationJobObject
+NtSetInformationKey
+NtSetInformationObject
+NtSetInformationProcess
+NtSetInformationThread
+NtSetInformationToken
+NtSetIntervalProfile
+NtSetIoCompletion
+NtSetLdtEntries
+NtSetLowEventPair
+NtSetLowWaitHighEventPair
+NtSetQuotaInformationFile
+NtSetSecurityObject
+NtSetSystemEnvironmentValue
+NtSetSystemEnvironmentValueEx
+NtSetSystemInformation
+NtSetSystemPowerState
+NtSetSystemTime
+NtSetThreadExecutionState
+NtSetTimer
+NtSetTimerResolution
+NtSetUuidSeed
+NtSetValueKey
+NtSetVolumeInformationFile
+NtShutdownSystem
+NtSignalAndWaitForSingleObject
+NtStartProfile
+NtStopProfile
+NtSuspendProcess
+NtSuspendThread
+NtSystemDebugControl
+NtTerminateJobObject
+NtTerminateProcess
+NtTerminateThread
+NtTestAlert
+NtTraceEvent
+NtTranslateFilePath
+NtUnloadDriver
+NtUnloadKey
+NtUnloadKeyEx
+NtUnlockFile
+NtUnlockVirtualMemory
+NtUnmapViewOfSection
+NtVdmControl
+NtWaitForDebugEvent
+NtWaitForKeyedEvent
+NtWaitForMultipleObjects
+NtWaitForSingleObject
+NtWaitHighEventPair
+NtWaitLowEventPair
+NtWriteFile
+NtWriteFileGather
+NtWriteRequestData
+NtWriteVirtualMemory
+NtYieldExecution
+PfxFindPrefix
+PfxInitialize
+PfxInsertPrefix
+PfxRemovePrefix
+RtlAbortRXact
+RtlAbsoluteToSelfRelativeSD
+RtlAcquirePebLock
+RtlAcquireResourceExclusive
+RtlAcquireResourceShared
+RtlActivateActivationContext
+RtlActivateActivationContextEx
+RtlActivateActivationContextUnsafeFast
+RtlAddAccessAllowedAce
+RtlAddAccessAllowedAceEx
+RtlAddAccessAllowedObjectAce
+RtlAddAccessDeniedAce
+RtlAddAccessDeniedAceEx
+RtlAddAccessDeniedObjectAce
+RtlAddAce
+RtlAddActionToRXact
+RtlAddAtomToAtomTable
+RtlAddAttributeActionToRXact
+RtlAddAuditAccessAce
+RtlAddAuditAccessAceEx
+RtlAddAuditAccessObjectAce
+RtlAddCompoundAce
+RtlAddRefActivationContext
+RtlAddRefMemoryStream
+RtlAddVectoredExceptionHandler
+RtlAddressInSectionTable
+RtlAdjustPrivilege
+RtlAllocateAndInitializeSid
+RtlAllocateHandle
+RtlAllocateHeap
+RtlAnsiCharToUnicodeChar
+RtlAnsiStringToUnicodeSize
+RtlAnsiStringToUnicodeString
+RtlAppendAsciizToString
+RtlAppendPathElement
+RtlAppendStringToString
+RtlAppendUnicodeStringToString
+RtlAppendUnicodeToString
+RtlApplicationVerifierStop
+RtlApplyRXact
+RtlApplyRXactNoFlush
+RtlAreAllAccessesGranted
+RtlAreAnyAccessesGranted
+RtlAreBitsClear
+RtlAreBitsSet
+RtlAssert
+RtlCancelTimer
+RtlCaptureContext
+RtlCaptureStackBackTrace
+RtlCharToInteger
+RtlCheckForOrphanedCriticalSections
+RtlCheckRegistryKey
+RtlClearAllBits
+RtlClearBits
+RtlCloneMemoryStream
+RtlCommitMemoryStream
+RtlCompactHeap
+RtlCompareMemory
+RtlCompareMemoryUlong
+RtlCompareString
+RtlCompareUnicodeString
+RtlCompressBuffer
+RtlComputeCrc32
+RtlComputeImportTableHash
+RtlComputePrivatizedDllName_U
+RtlConsoleMultiByteToUnicodeN
+RtlConvertExclusiveToShared
+RtlConvertSharedToExclusive
+RtlConvertSidToUnicodeString
+RtlConvertToAutoInheritSecurityObject
+RtlCopyLuid
+RtlCopyLuidAndAttributesArray
+RtlCopyMemoryStreamTo
+RtlCopyOutOfProcessMemoryStreamTo
+RtlCopySecurityDescriptor
+RtlCopySid
+RtlCopySidAndAttributesArray
+RtlCopyString
+RtlCopyUnicodeString
+RtlCreateAcl
+RtlCreateActivationContext
+RtlCreateAndSetSD
+RtlCreateAtomTable
+RtlCreateBootStatusDataFile
+RtlCreateEnvironment
+RtlCreateHeap
+RtlCreateProcessParameters
+RtlCreateQueryDebugBuffer
+RtlCreateRegistryKey
+RtlCreateSecurityDescriptor
+RtlCreateServiceSid
+RtlCreateSystemVolumeInformationFolder
+RtlCreateTagHeap
+RtlCreateTimer
+RtlCreateTimerQueue
+RtlCreateUnicodeString
+RtlCreateUnicodeStringFromAsciiz
+RtlCreateUserProcess
+RtlCreateUserSecurityObject
+RtlCreateUserThread
+RtlCustomCPToUnicodeN
+RtlCutoverTimeToSystemTime
+RtlDeNormalizeProcessParams
+RtlDeactivateActivationContext
+RtlDeactivateActivationContextUnsafeFast
+RtlDebugPrintTimes
+RtlDecodePointer
+RtlDecodeSystemPointer
+RtlDecompressBuffer
+RtlDecompressFragment
+RtlDefaultNpAcl
+RtlDelete
+RtlDeleteAce
+RtlDeleteAtomFromAtomTable
+RtlDeleteCriticalSection
+RtlDeleteElementGenericTable
+RtlDeleteElementGenericTableAvl
+RtlDeleteNoSplay
+RtlDeleteRegistryValue
+RtlDeleteResource
+RtlDeleteSecurityObject
+RtlDeleteTimer
+RtlDeleteTimerQueue
+RtlDeleteTimerQueueEx
+RtlDeregisterWait
+RtlDeregisterWaitEx
+RtlDestroyAtomTable
+RtlDestroyEnvironment
+RtlDestroyHandleTable
+RtlDestroyHeap
+RtlDestroyProcessParameters
+RtlDestroyQueryDebugBuffer
+RtlDetermineDosPathNameType_U
+RtlDllShutdownInProgress
+RtlDnsHostNameToComputerName
+RtlDoesFileExists_U
+RtlDosApplyFileIsolationRedirection_Ustr
+RtlDosPathNameToNtPathName_U
+RtlDosSearchPath_U
+RtlDosSearchPath_Ustr
+RtlDowncaseUnicodeChar
+RtlDowncaseUnicodeString
+RtlDumpResource
+RtlDuplicateUnicodeString
+RtlEmptyAtomTable
+RtlEnableEarlyCriticalSectionEventCreation
+RtlEncodePointer
+RtlEncodeSystemPointer
+RtlEnterCriticalSection
+RtlEnumProcessHeaps
+RtlEnumerateGenericTable
+RtlEnumerateGenericTableAvl
+RtlEnumerateGenericTableLikeADirectory
+RtlEnumerateGenericTableWithoutSplaying
+RtlEnumerateGenericTableWithoutSplayingAvl
+RtlEqualComputerName
+RtlEqualDomainName
+RtlEqualLuid
+RtlEqualPrefixSid
+RtlEqualSid
+RtlEqualString
+RtlEqualUnicodeString
+RtlEraseUnicodeString
+RtlExitUserThread
+RtlExpandEnvironmentStrings_U
+RtlFillMemory
+RtlFinalReleaseOutOfProcessMemoryStream
+RtlFindActivationContextSectionGuid
+RtlFindActivationContextSectionString
+RtlFindCharInUnicodeString
+RtlFindClearBits
+RtlFindClearBitsAndSet
+RtlFindClearRuns
+RtlFindLastBackwardRunClear
+RtlFindLeastSignificantBit
+RtlFindLongestRunClear
+RtlFindMessage
+RtlFindMostSignificantBit
+RtlFindNextForwardRunClear
+RtlFindSetBits
+RtlFindSetBitsAndClear
+RtlFirstEntrySList
+RtlFirstFreeAce
+RtlFlushSecureMemoryCache
+RtlFormatCurrentUserKeyPath
+RtlFormatMessage
+RtlFreeAnsiString
+RtlFreeHandle
+RtlFreeHeap
+RtlFreeOemString
+RtlFreeSid
+RtlFreeThreadActivationContextStack
+RtlFreeUnicodeString
+RtlGUIDFromString
+RtlGenerate8dot3Name
+RtlGetAce
+RtlGetActiveActivationContext
+RtlGetCallersAddress
+RtlGetCompressionWorkSpaceSize
+RtlGetControlSecurityDescriptor
+RtlGetCurrentDirectory_U
+RtlGetCurrentPeb
+RtlGetDaclSecurityDescriptor
+RtlGetElementGenericTable
+RtlGetElementGenericTableAvl
+RtlGetFrame
+RtlGetFullPathName_U
+RtlGetGroupSecurityDescriptor
+RtlGetLastNtStatus
+RtlGetLastWin32Error
+RtlGetLengthWithoutLastFullDosOrNtPathElement
+RtlGetLengthWithoutTrailingPathSeperators
+RtlGetLongestNtPathLength
+RtlGetNativeSystemInformation
+RtlGetNtGlobalFlags
+RtlGetNtProductType
+RtlGetNtVersionNumbers
+RtlGetOwnerSecurityDescriptor
+RtlGetProcessHeaps
+RtlGetSaclSecurityDescriptor
+RtlGetSecurityDescriptorRMControl
+RtlGetSetBootStatusData
+RtlGetUnloadEventTrace
+RtlGetUserInfoHeap
+RtlGetVersion
+RtlHashUnicodeString
+RtlIdentifierAuthoritySid
+RtlImageDirectoryEntryToData
+RtlImageNtHeader
+RtlImageRvaToSection
+RtlImageRvaToVa
+RtlImpersonateSelf
+RtlInitAnsiString
+RtlInitCodePageTable
+RtlInitMemoryStream
+RtlInitNlsTables
+RtlInitOutOfProcessMemoryStream
+RtlInitString
+RtlInitUnicodeString
+RtlInitUnicodeStringEx
+RtlInitializeAtomPackage
+RtlInitializeBitMap
+RtlInitializeContext
+RtlInitializeCriticalSection
+RtlInitializeCriticalSectionAndSpinCount
+RtlInitializeGenericTable
+RtlInitializeGenericTableAvl
+RtlInitializeHandleTable
+RtlInitializeRXact
+RtlInitializeResource
+RtlInitializeSListHead
+RtlInitializeSid
+RtlInsertElementGenericTable
+RtlInsertElementGenericTableAvl
+RtlInt64ToUnicodeString
+RtlIntegerToChar
+RtlIntegerToUnicodeString
+RtlInterlockedFlushSList
+RtlInterlockedPopEntrySList
+RtlInterlockedPushEntrySList
+RtlInterlockedPushListSList
+RtlIpv4AddressToStringA
+RtlIpv4AddressToStringExA
+RtlIpv4AddressToStringExW
+RtlIpv4AddressToStringW
+RtlIpv4StringToAddressA
+RtlIpv4StringToAddressExA
+RtlIpv4StringToAddressExW
+RtlIpv4StringToAddressW
+RtlIpv6AddressToStringA
+RtlIpv6AddressToStringExA
+RtlIpv6AddressToStringExW
+RtlIpv6AddressToStringW
+RtlIpv6StringToAddressA
+RtlIpv6StringToAddressExA
+RtlIpv6StringToAddressExW
+RtlIpv6StringToAddressW
+RtlIsActivationContextActive
+RtlIsDosDeviceName_U
+RtlIsGenericTableEmpty
+RtlIsGenericTableEmptyAvl
+RtlIsNameLegalDOS8Dot3
+RtlIsTextUnicode
+RtlIsThreadWithinLoaderCallout
+RtlIsValidHandle
+RtlIsValidIndexHandle
+RtlLargeIntegerToChar
+RtlLeaveCriticalSection
+RtlLengthRequiredSid
+RtlLengthSecurityDescriptor
+RtlLengthSid
+RtlLocalTimeToSystemTime
+RtlLockBootStatusData
+RtlLockHeap
+RtlLockMemoryStreamRegion
+RtlLogStackBackTrace
+RtlLookupAtomInAtomTable
+RtlLookupElementGenericTable
+RtlLookupElementGenericTableAvl
+RtlMakeSelfRelativeSD
+RtlMapGenericMask
+RtlMapSecurityErrorToNtStatus
+RtlMoveMemory
+RtlMultiAppendUnicodeStringBuffer
+RtlMultiByteToUnicodeN
+RtlMultiByteToUnicodeSize
+RtlNewInstanceSecurityObject
+RtlNewSecurityGrantedAccess
+RtlNewSecurityObject
+RtlNewSecurityObjectEx
+RtlNewSecurityObjectWithMultipleInheritance
+RtlNormalizeProcessParams
+RtlNtPathNameToDosPathName
+RtlNtStatusToDosError
+RtlNtStatusToDosErrorNoTeb
+RtlNumberGenericTableElements
+RtlNumberGenericTableElementsAvl
+RtlNumberOfClearBits
+RtlNumberOfSetBits
+RtlOemStringToUnicodeSize
+RtlOemStringToUnicodeString
+RtlOemToUnicodeN
+RtlOpenCurrentUser
+RtlPcToFileHeader
+RtlPinAtomInAtomTable
+RtlPopFrame
+RtlPrefixString
+RtlPrefixUnicodeString
+RtlProtectHeap
+RtlPushFrame
+RtlQueryAtomInAtomTable
+RtlQueryDepthSList
+RtlQueryEnvironmentVariable_U
+RtlQueryHeapInformation
+RtlQueryInformationAcl
+RtlQueryInformationActivationContext
+RtlQueryInformationActiveActivationContext
+RtlQueryInterfaceMemoryStream
+RtlQueryProcessBackTraceInformation
+RtlQueryProcessDebugInformation
+RtlQueryProcessHeapInformation
+RtlQueryProcessLockInformation
+RtlQueryRegistryValues
+RtlQuerySecurityObject
+RtlQueryTagHeap
+RtlQueryTimeZoneInformation
+RtlQueueApcWow64Thread
+RtlQueueWorkItem
+RtlRaiseException
+RtlRaiseStatus
+RtlRandom
+RtlRandomEx
+RtlReAllocateHeap
+RtlReadMemoryStream
+RtlReadOutOfProcessMemoryStream
+RtlRealPredecessor
+RtlRealSuccessor
+RtlRegisterSecureMemoryCacheCallback
+RtlRegisterWait
+RtlReleaseActivationContext
+RtlReleaseMemoryStream
+RtlReleasePebLock
+RtlReleaseResource
+RtlRemoteCall
+RtlRemoveVectoredExceptionHandler
+RtlResetRtlTranslations
+RtlRestoreLastWin32Error
+RtlRevertMemoryStream
+RtlRunDecodeUnicodeString
+RtlRunEncodeUnicodeString
+RtlSecondsSince1970ToTime
+RtlSecondsSince1980ToTime
+RtlSeekMemoryStream
+RtlSelfRelativeToAbsoluteSD
+RtlSelfRelativeToAbsoluteSD2
+RtlSetAllBits
+RtlSetAttributesSecurityDescriptor
+RtlSetBits
+RtlSetControlSecurityDescriptor
+RtlSetCriticalSectionSpinCount
+RtlSetCurrentDirectory_U
+RtlSetCurrentEnvironment
+RtlSetDaclSecurityDescriptor
+RtlSetEnvironmentVariable
+RtlSetGroupSecurityDescriptor
+RtlSetHeapInformation
+RtlSetInformationAcl
+RtlSetIoCompletionCallback
+RtlSetLastWin32Error
+RtlSetLastWin32ErrorAndNtStatusFromNtStatus
+RtlSetMemoryStreamSize
+RtlSetOwnerSecurityDescriptor
+RtlSetProcessIsCritical
+RtlSetSaclSecurityDescriptor
+RtlSetSecurityDescriptorRMControl
+RtlSetSecurityObject
+RtlSetSecurityObjectEx
+RtlSetThreadIsCritical
+RtlSetThreadPoolStartFunc
+RtlSetTimeZoneInformation
+RtlSetTimer
+RtlSetUserFlagsHeap
+RtlSetUserValueHeap
+RtlSizeHeap
+RtlSplay
+RtlStartRXact
+RtlStatMemoryStream
+RtlStringFromGUID
+RtlSubAuthorityCountSid
+RtlSubAuthoritySid
+RtlSubtreePredecessor
+RtlSubtreeSuccessor
+RtlSystemTimeToLocalTime
+RtlTimeFieldsToTime
+RtlTimeToElapsedTimeFields
+RtlTimeToSecondsSince1970
+RtlTimeToSecondsSince1980
+RtlTimeToTimeFields
+RtlTraceDatabaseAdd
+RtlTraceDatabaseCreate
+RtlTraceDatabaseDestroy
+RtlTraceDatabaseEnumerate
+RtlTraceDatabaseFind
+RtlTraceDatabaseLock
+RtlTraceDatabaseUnlock
+RtlTraceDatabaseValidate
+RtlTryEnterCriticalSection
+RtlUnhandledExceptionFilter
+RtlUnhandledExceptionFilter2
+RtlUnicodeStringToAnsiSize
+RtlUnicodeStringToAnsiString
+RtlUnicodeStringToCountedOemString
+RtlUnicodeStringToInteger
+RtlUnicodeStringToOemSize
+RtlUnicodeStringToOemString
+RtlUnicodeToCustomCPN
+RtlUnicodeToMultiByteN
+RtlUnicodeToMultiByteSize
+RtlUnicodeToOemN
+RtlUniform
+RtlUnlockBootStatusData
+RtlUnlockHeap
+RtlUnlockMemoryStreamRegion
+RtlUnwind
+RtlUpcaseUnicodeChar
+RtlUpcaseUnicodeString
+RtlUpcaseUnicodeStringToAnsiString
+RtlUpcaseUnicodeStringToCountedOemString
+RtlUpcaseUnicodeStringToOemString
+RtlUpcaseUnicodeToCustomCPN
+RtlUpcaseUnicodeToMultiByteN
+RtlUpcaseUnicodeToOemN
+RtlUpdateTimer
+RtlUpperChar
+RtlUpperString
+RtlValidAcl
+RtlValidRelativeSecurityDescriptor
+RtlValidSecurityDescriptor
+RtlValidSid
+RtlValidateHeap
+RtlValidateProcessHeaps
+RtlValidateUnicodeString
+RtlVerifyVersionInfo
+RtlWalkFrameChain
+RtlWalkHeap
+RtlWriteMemoryStream
+RtlWriteRegistryValue
+RtlZeroHeap
+RtlZeroMemory
+RtlZombifyActivationContext
+RtlpApplyLengthFunction
+RtlpEnsureBufferSize
+RtlpNotOwnerCriticalSection
+RtlpNtCreateKey
+RtlpNtEnumerateSubKey
+RtlpNtMakeTemporaryKey
+RtlpNtOpenKey
+RtlpNtQueryValueKey
+RtlpNtSetValueKey
+RtlpUnWaitCriticalSection
+RtlpWaitForCriticalSection
+RtlxAnsiStringToUnicodeSize
+RtlxOemStringToUnicodeSize
+RtlxUnicodeStringToAnsiSize
+RtlxUnicodeStringToOemSize
+VerSetConditionMask
+ZwAcceptConnectPort
+ZwAccessCheck
+ZwAccessCheckAndAuditAlarm
+ZwAccessCheckByType
+ZwAccessCheckByTypeAndAuditAlarm
+ZwAccessCheckByTypeResultList
+ZwAccessCheckByTypeResultListAndAuditAlarm
+ZwAccessCheckByTypeResultListAndAuditAlarmByHandle
+ZwAddAtom
+ZwAddBootEntry
+ZwAdjustGroupsToken
+ZwAdjustPrivilegesToken
+ZwAlertResumeThread
+ZwAlertThread
+ZwAllocateLocallyUniqueId
+ZwAllocateUserPhysicalPages
+ZwAllocateUuids
+ZwAllocateVirtualMemory
+ZwAreMappedFilesTheSame
+ZwAssignProcessToJobObject
+ZwCallbackReturn
+ZwCancelIoFile
+ZwCancelTimer
+ZwClearEvent
+ZwClose
+ZwCloseObjectAuditAlarm
+ZwCompactKeys
+ZwCompareTokens
+ZwCompleteConnectPort
+ZwCompressKey
+ZwConnectPort
+ZwContinue
+ZwCreateDebugObject
+ZwCreateDirectoryObject
+ZwCreateEvent
+ZwCreateEventPair
+ZwCreateFile
+ZwCreateIoCompletion
+ZwCreateJobObject
+ZwCreateJobSet
+ZwCreateKey
+ZwCreateKeyedEvent
+ZwCreateMailslotFile
+ZwCreateMutant
+ZwCreateNamedPipeFile
+ZwCreatePagingFile
+ZwCreatePort
+ZwCreateProcess
+ZwCreateProcessEx
+ZwCreateProfile
+ZwCreateSection
+ZwCreateSemaphore
+ZwCreateSymbolicLinkObject
+ZwCreateThread
+ZwCreateTimer
+ZwCreateToken
+ZwCreateWaitablePort
+ZwDebugActiveProcess
+ZwDebugContinue
+ZwDelayExecution
+ZwDeleteAtom
+ZwDeleteBootEntry
+ZwDeleteFile
+ZwDeleteKey
+ZwDeleteObjectAuditAlarm
+ZwDeleteValueKey
+ZwDeviceIoControlFile
+ZwDisplayString
+ZwDuplicateObject
+ZwDuplicateToken
+ZwEnumerateBootEntries
+ZwEnumerateKey
+ZwEnumerateSystemEnvironmentValuesEx
+ZwEnumerateValueKey
+ZwExtendSection
+ZwFilterToken
+ZwFindAtom
+ZwFlushBuffersFile
+ZwFlushInstructionCache
+ZwFlushKey
+ZwFlushVirtualMemory
+ZwFlushWriteBuffer
+ZwFreeUserPhysicalPages
+ZwFreeVirtualMemory
+ZwFsControlFile
+ZwGetContextThread
+ZwGetDevicePowerState
+ZwGetWriteWatch
+ZwImpersonateAnonymousToken
+ZwImpersonateClientOfPort
+ZwImpersonateThread
+ZwInitializeRegistry
+ZwInitiatePowerAction
+ZwIsProcessInJob
+ZwIsSystemResumeAutomatic
+ZwListenPort
+ZwLoadDriver
+ZwLoadKey
+ZwLoadKey2
+ZwLockFile
+ZwLockProductActivationKeys
+ZwLockRegistryKey
+ZwLockVirtualMemory
+ZwMakePermanentObject
+ZwMakeTemporaryObject
+ZwMapUserPhysicalPages
+ZwMapUserPhysicalPagesScatter
+ZwMapViewOfSection
+ZwModifyBootEntry
+ZwNotifyChangeDirectoryFile
+ZwNotifyChangeKey
+ZwNotifyChangeMultipleKeys
+ZwOpenDirectoryObject
+ZwOpenEvent
+ZwOpenEventPair
+ZwOpenFile
+ZwOpenIoCompletion
+ZwOpenJobObject
+ZwOpenKey
+ZwOpenKeyedEvent
+ZwOpenMutant
+ZwOpenObjectAuditAlarm
+ZwOpenProcess
+ZwOpenProcessToken
+ZwOpenProcessTokenEx
+ZwOpenSection
+ZwOpenSemaphore
+ZwOpenSymbolicLinkObject
+ZwOpenThread
+ZwOpenThreadToken
+ZwOpenThreadTokenEx
+ZwOpenTimer
+ZwPlugPlayControl
+ZwPowerInformation
+ZwPrivilegeCheck
+ZwPrivilegeObjectAuditAlarm
+ZwPrivilegedServiceAuditAlarm
+ZwProtectVirtualMemory
+ZwPulseEvent
+ZwQueryAttributesFile
+ZwQueryBootEntryOrder
+ZwQueryBootOptions
+ZwQueryDebugFilterState
+ZwQueryDefaultLocale
+ZwQueryDefaultUILanguage
+ZwQueryDirectoryFile
+ZwQueryDirectoryObject
+ZwQueryEaFile
+ZwQueryEvent
+ZwQueryFullAttributesFile
+ZwQueryInformationAtom
+ZwQueryInformationFile
+ZwQueryInformationJobObject
+ZwQueryInformationPort
+ZwQueryInformationProcess
+ZwQueryInformationThread
+ZwQueryInformationToken
+ZwQueryInstallUILanguage
+ZwQueryIntervalProfile
+ZwQueryIoCompletion
+ZwQueryKey
+ZwQueryMultipleValueKey
+ZwQueryMutant
+ZwQueryObject
+ZwQueryOpenSubKeys
+ZwQueryPerformanceCounter
+ZwQueryPortInformationProcess
+ZwQueryQuotaInformationFile
+ZwQuerySection
+ZwQuerySecurityObject
+ZwQuerySemaphore
+ZwQuerySymbolicLinkObject
+ZwQuerySystemEnvironmentValue
+ZwQuerySystemEnvironmentValueEx
+ZwQuerySystemInformation
+ZwQuerySystemTime
+ZwQueryTimer
+ZwQueryTimerResolution
+ZwQueryValueKey
+ZwQueryVirtualMemory
+ZwQueryVolumeInformationFile
+ZwQueueApcThread
+ZwRaiseException
+ZwRaiseHardError
+ZwReadFile
+ZwReadFileScatter
+ZwReadRequestData
+ZwReadVirtualMemory
+ZwRegisterThreadTerminatePort
+ZwReleaseKeyedEvent
+ZwReleaseMutant
+ZwReleaseSemaphore
+ZwRemoveIoCompletion
+ZwRemoveProcessDebug
+ZwRenameKey
+ZwReplaceKey
+ZwReplyPort
+ZwReplyWaitReceivePort
+ZwReplyWaitReceivePortEx
+ZwReplyWaitReplyPort
+ZwRequestPort
+ZwRequestWaitReplyPort
+ZwResetEvent
+ZwResetWriteWatch
+ZwRestoreKey
+ZwResumeProcess
+ZwResumeThread
+ZwSaveKey
+ZwSaveKeyEx
+ZwSaveMergedKeys
+ZwSecureConnectPort
+ZwSetBootEntryOrder
+ZwSetBootOptions
+ZwSetContextThread
+ZwSetDebugFilterState
+ZwSetDefaultHardErrorPort
+ZwSetDefaultLocale
+ZwSetDefaultUILanguage
+ZwSetEaFile
+ZwSetEvent
+ZwSetEventBoostPriority
+ZwSetHighEventPair
+ZwSetHighWaitLowEventPair
+ZwSetInformationDebugObject
+ZwSetInformationFile
+ZwSetInformationJobObject
+ZwSetInformationKey
+ZwSetInformationObject
+ZwSetInformationProcess
+ZwSetInformationThread
+ZwSetInformationToken
+ZwSetIntervalProfile
+ZwSetIoCompletion
+ZwSetLdtEntries
+ZwSetLowEventPair
+ZwSetLowWaitHighEventPair
+ZwSetQuotaInformationFile
+ZwSetSecurityObject
+ZwSetSystemEnvironmentValue
+ZwSetSystemEnvironmentValueEx
+ZwSetSystemInformation
+ZwSetSystemPowerState
+ZwSetSystemTime
+ZwSetThreadExecutionState
+ZwSetTimer
+ZwSetTimerResolution
+ZwSetUuidSeed
+ZwSetValueKey
+ZwSetVolumeInformationFile
+ZwShutdownSystem
+ZwSignalAndWaitForSingleObject
+ZwStartProfile
+ZwStopProfile
+ZwSuspendProcess
+ZwSuspendThread
+ZwSystemDebugControl
+ZwTerminateJobObject
+ZwTerminateProcess
+ZwTerminateThread
+ZwTestAlert
+ZwTraceEvent
+ZwTranslateFilePath
+ZwUnloadDriver
+ZwUnloadKey
+ZwUnloadKeyEx
+ZwUnlockFile
+ZwUnlockVirtualMemory
+ZwUnmapViewOfSection
+ZwVdmControl
+ZwWaitForDebugEvent
+ZwWaitForKeyedEvent
+ZwWaitForMultipleObjects
+ZwWaitForSingleObject
+ZwWaitHighEventPair
+ZwWaitLowEventPair
+ZwWriteFile
+ZwWriteFileGather
+ZwWriteRequestData
+ZwWriteVirtualMemory
+ZwYieldExecution
+__isascii
+__iscsym
+__iscsymf
+__toascii
+_alldiv
+_alldvrm
+_allmul
+_allrem
+_allshl
+_allshr
+_atoi64
+_aulldiv
+_aulldvrm
+_aullrem
+_aullshr
+_fltused
+_i64toa
+_i64tow
+_itoa
+_itow
+_lfind
+_ltoa
+_ltow
+_memccpy
+_memicmp
+_snprintf
+_snwprintf
+_splitpath
+_strcmpi
+_stricmp
+_strlwr
+_strnicmp
+_strupr
+_ui64toa
+_ui64tow
+_ultoa
+_ultow
+_vsnprintf
+_vsnwprintf
+_wcsicmp
+_wcslwr
+_wcsnicmp
+_wcsupr
+_wtoi
+_wtoi64
+_wtol
+abs
+atan
+atoi
+atol
+bsearch
+ceil
+cos
+fabs
+floor
+isalnum
+isalpha
+iscntrl
+isdigit
+isgraph
+islower
+isprint
+ispunct
+isspace
+isupper
+iswalpha
+iswctype
+iswdigit
+iswlower
+iswspace
+iswxdigit
+isxdigit
+labs
+log
+mbstowcs
+memchr
+memcmp
+memcpy
+memmove
+memset
+pow
+qsort
+sin
+sprintf
+sqrt
+sscanf
+strcat
+strchr
+strcmp
+strcpy
+strcspn
+strlen
+strncat
+strncmp
+strncpy
+strpbrk
+strrchr
+strspn
+strstr
+strtol
+strtoul
+swprintf
+tan
+tolower
+toupper
+towlower
+towupper
+vDbgPrintEx
+vDbgPrintExWithPrefix
+vsprintf
+wcscat
+wcschr
+wcscmp
+wcscpy
+wcscspn
+wcslen
+wcsncat
+wcsncmp
+wcsncpy
+wcspbrk
+wcsrchr
+wcsspn
+wcsstr
+wcstol
+wcstombs
+wcstoul
+__C_specific_handler
+_except_handler4_common
diff --git a/plugins/Dbx_mdbx/src/stdafx.h b/plugins/Dbx_mdbx/src/stdafx.h
index 5cf483183f..7c5f564922 100644
--- a/plugins/Dbx_mdbx/src/stdafx.h
+++ b/plugins/Dbx_mdbx/src/stdafx.h
@@ -52,7 +52,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #include <m_gui.h>

 #include <m_skin.h>

 

-#include "../../Libs/libmdbx/src/mdbx.h"

+#include "libmdbx/mdbx.h"

 

 #ifndef thread_local

 #	define thread_local __declspec(thread)