kyotocabinet based db driver

first version that compiles
DO NOT USE IT, dragons live there

git-svn-id: http://svn.miranda-ng.org/main/trunk@12580 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c

1 files changed, 1482 insertions, 0 deletions

diff --git a/plugins/Dbx_kyoto/src/kyotocabinet/kcstashdb.h b/plugins/Dbx_kyoto/src/kyotocabinet/kcstashdb.h
new file mode 100644
index 0000000000..2ce5599e7c
--- /dev/null
+++ b/plugins/Dbx_kyoto/src/kyotocabinet/kcstashdb.h
@@ -0,0 +1,1482 @@
+/*************************************************************************************************
+ * Stash database
+ *                                                               Copyright (C) 2009-2012 FAL Labs
+ * This file is part of Kyoto Cabinet.
+ * This program is free software: you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software Foundation, either version
+ * 3 of the License, or any later version.
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License along with this program.
+ * If not, see <http://www.gnu.org/licenses/>.
+ *************************************************************************************************/
+
+
+#ifndef _KCSTASHDB_H                     // duplication check
+#define _KCSTASHDB_H
+
+#include <kccommon.h>
+#include <kcutil.h>
+#include <kcthread.h>
+#include <kcfile.h>
+#include <kccompress.h>
+#include <kccompare.h>
+#include <kcmap.h>
+#include <kcregex.h>
+#include <kcdb.h>
+#include <kcplantdb.h>
+
+namespace kyotocabinet {                 // common namespace
+
+
+/**
+ * Economical on-memory hash database.
+ * @note This class is a concrete class to operate a hash database on memory.  This class can be
+ * inherited but overwriting methods is forbidden.  Before every database operation, it is
+ * necessary to call the StashDB::open method in order to open a database file and connect the
+ * database object to it.  To avoid data missing or corruption, it is important to close every
+ * database file by the StashDB::close method when the database is no longer in use.  It is
+ * forbidden for multible database objects in a process to open the same database at the same
+ * time.  It is forbidden to share a database object with child processes.
+ */
+class StashDB : public BasicDB {
+ public:
+  class Cursor;
+ private:
+  struct Record;
+  struct TranLog;
+  class Repeater;
+  class Setter;
+  class Remover;
+  class ScopedVisitor;
+  /** An alias of list of cursors. */
+  typedef std::list<Cursor*> CursorList;
+  /** An alias of list of transaction logs. */
+  typedef std::list<TranLog> TranLogList;
+  /** The number of slots of the record lock. */
+  static const int32_t RLOCKSLOT = 1024;
+  /** The default bucket number. */
+  static const size_t DEFBNUM = 1048583LL;
+  /** The size of the opaque buffer. */
+  static const size_t OPAQUESIZ = 16;
+  /** The threshold of busy loop and sleep for locking. */
+  static const uint32_t LOCKBUSYLOOP = 8192;
+  /** The mininum number of buckets to use mmap. */
+  static const size_t MAPZMAPBNUM = 32768;
+ public:
+  /**
+   * Cursor to indicate a record.
+   */
+  class Cursor : public BasicDB::Cursor {
+    friend class StashDB;
+   public:
+    /**
+     * Constructor.
+     * @param db the container database object.
+     */
+    explicit Cursor(StashDB* db) : db_(db), bidx_(-1), rbuf_(NULL) {
+      _assert_(db);
+      ScopedRWLock lock(&db_->mlock_, true);
+      db_->curs_.push_back(this);
+    }
+    /**
+     * Destructor.
+     */
+    virtual ~Cursor() {
+      _assert_(true);
+      if (!db_) return;
+      ScopedRWLock lock(&db_->mlock_, true);
+      db_->curs_.remove(this);
+    }
+    /**
+     * Accept a visitor to the current record.
+     * @param visitor a visitor object.
+     * @param writable true for writable operation, or false for read-only operation.
+     * @param step true to move the cursor to the next record, or false for no move.
+     * @return true on success, or false on failure.
+     * @note The operation for each record is performed atomically and other threads accessing
+     * the same record are blocked.  To avoid deadlock, any explicit database operation must not
+     * be performed in this function.
+     */
+    bool accept(Visitor* visitor, bool writable = true, bool step = false) {
+      _assert_(visitor);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      if (writable && !(db_->omode_ & OWRITER)) {
+        db_->set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+        return false;
+      }
+      if (bidx_ < 0) {
+        db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+        return false;
+      }
+      Record rec(rbuf_);
+      size_t vsiz;
+      const char* vbuf = visitor->visit_full(rec.kbuf_, rec.ksiz_, rec.vbuf_, rec.vsiz_, &vsiz);
+      if (vbuf == Visitor::REMOVE) {
+        Repeater repeater(Visitor::REMOVE, 0);
+        db_->accept_impl(rec.kbuf_, rec.ksiz_, &repeater, bidx_);
+      } else if (vbuf == Visitor::NOP) {
+        if (step) step_impl();
+      } else {
+        Repeater repeater(vbuf, vsiz);
+        db_->accept_impl(rec.kbuf_, rec.ksiz_, &repeater, bidx_);
+        if (step && rbuf_) step_impl();
+      }
+      return true;
+    }
+    /**
+     * Jump the cursor to the first record for forward scan.
+     * @return true on success, or false on failure.
+     */
+    bool jump() {
+      _assert_(true);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      bidx_ = 0;
+      rbuf_ = NULL;
+      while (bidx_ < (int64_t)db_->bnum_) {
+        if (db_->buckets_[bidx_]) {
+          rbuf_ = db_->buckets_[bidx_];
+          return true;
+        }
+        bidx_++;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+      bidx_ = -1;
+      return false;
+    }
+    /**
+     * Jump the cursor to a record for forward scan.
+     * @param kbuf the pointer to the key region.
+     * @param ksiz the size of the key region.
+     * @return true on success, or false on failure.
+     */
+    bool jump(const char* kbuf, size_t ksiz) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      bidx_ = -1;
+      rbuf_ = NULL;
+      size_t bidx = db_->hash_record(kbuf, ksiz) % db_->bnum_;
+      char* rbuf = db_->buckets_[bidx];
+      while (rbuf) {
+        Record rec(rbuf);
+        if (rec.ksiz_ == ksiz && !std::memcmp(rec.kbuf_, kbuf, ksiz)) {
+          bidx_ = bidx;
+          rbuf_ = rbuf;
+          return true;
+        }
+        rbuf = rec.child_;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+      return false;
+    }
+    /**
+     * Jump the cursor to a record for forward scan.
+     * @note Equal to the original Cursor::jump method except that the parameter is std::string.
+     */
+    bool jump(const std::string& key) {
+      _assert_(true);
+      return jump(key.c_str(), key.size());
+    }
+    /**
+     * Jump the cursor to the last record for backward scan.
+     * @note This is a dummy implementation for compatibility.
+     */
+    bool jump_back() {
+      _assert_(true);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOIMPL, "not implemented");
+      return false;
+    }
+    /**
+     * Jump the cursor to a record for backward scan.
+     * @note This is a dummy implementation for compatibility.
+     */
+    bool jump_back(const char* kbuf, size_t ksiz) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOIMPL, "not implemented");
+      return false;
+    }
+    /**
+     * Jump the cursor to a record for backward scan.
+     * @note This is a dummy implementation for compatibility.
+     */
+    bool jump_back(const std::string& key) {
+      _assert_(true);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOIMPL, "not implemented");
+      return false;
+    }
+    /**
+     * Step the cursor to the next record.
+     * @return true on success, or false on failure.
+     */
+    bool step() {
+      _assert_(true);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      if (bidx_ < 0) {
+        db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+        return false;
+      }
+      bool err = false;
+      if (!step_impl()) err = true;
+      return !err;
+    }
+    /**
+     * Step the cursor to the previous record.
+     * @note This is a dummy implementation for compatibility.
+     */
+    bool step_back() {
+      _assert_(true);
+      ScopedRWLock lock(&db_->mlock_, true);
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      db_->set_error(_KCCODELINE_, Error::NOIMPL, "not implemented");
+      return false;
+    }
+    /**
+     * Get the database object.
+     * @return the database object.
+     */
+    StashDB* db() {
+      _assert_(true);
+      return db_;
+    }
+   private:
+    /**
+     * Step the cursor to the next record.
+     * @return true on success, or false on failure.
+     */
+    bool step_impl() {
+      _assert_(true);
+      Record rec(rbuf_);
+      rbuf_ = rec.child_;
+      if (!rbuf_) {
+        while (++bidx_ < (int64_t)db_->bnum_) {
+          if (db_->buckets_[bidx_]) {
+            rbuf_ = db_->buckets_[bidx_];
+            return true;
+          }
+        }
+        db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+        bidx_ = -1;
+        return false;
+      }
+      return true;
+    }
+    /** Dummy constructor to forbid the use. */
+    Cursor(const Cursor&);
+    /** Dummy Operator to forbid the use. */
+    Cursor& operator =(const Cursor&);
+    /** The inner database. */
+    StashDB* db_;
+    /** The index of the current bucket. */
+    int64_t bidx_;
+    /** The buffer of the current record. */
+    char* rbuf_;
+  };
+  /**
+   * Default constructor.
+   */
+  explicit StashDB() :
+      mlock_(), rlock_(RLOCKSLOT), flock_(), error_(),
+      logger_(NULL), logkinds_(0), mtrigger_(NULL),
+      omode_(0), curs_(), path_(""), bnum_(DEFBNUM), opaque_(),
+      count_(0), size_(0), buckets_(NULL),
+      tran_(false), trlogs_(), trcount_(0), trsize_(0) {
+    _assert_(true);
+  }
+  /**
+   * Destructor.
+   * @note If the database is not closed, it is closed implicitly.
+   */
+  ~StashDB() {
+    _assert_(true);
+    if (omode_ != 0) close();
+    if (!curs_.empty()) {
+      CursorList::const_iterator cit = curs_.begin();
+      CursorList::const_iterator citend = curs_.end();
+      while (cit != citend) {
+        Cursor* cur = *cit;
+        cur->db_ = NULL;
+        ++cit;
+      }
+    }
+  }
+  /**
+   * Accept a visitor to a record.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @param visitor a visitor object.
+   * @param writable true for writable operation, or false for read-only operation.
+   * @return true on success, or false on failure.
+   * @note The operation for each record is performed atomically and other threads accessing the
+   * same record are blocked.  To avoid deadlock, any explicit database operation must not be
+   * performed in this function.
+   */
+  bool accept(const char* kbuf, size_t ksiz, Visitor* visitor, bool writable = true) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && visitor);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (writable && !(omode_ & OWRITER)) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    size_t bidx = hash_record(kbuf, ksiz) % bnum_;
+    size_t lidx = bidx % RLOCKSLOT;
+    if (writable) {
+      rlock_.lock_writer(lidx);
+    } else {
+      rlock_.lock_reader(lidx);
+    }
+    accept_impl(kbuf, ksiz, visitor, bidx);
+    rlock_.unlock(lidx);
+    return true;
+  }
+  /**
+   * Accept a visitor to multiple records at once.
+   * @param keys specifies a string vector of the keys.
+   * @param visitor a visitor object.
+   * @param writable true for writable operation, or false for read-only operation.
+   * @return true on success, or false on failure.
+   * @note The operations for specified records are performed atomically and other threads
+   * accessing the same records are blocked.  To avoid deadlock, any explicit database operation
+   * must not be performed in this function.
+   */
+  bool accept_bulk(const std::vector<std::string>& keys, Visitor* visitor,
+                   bool writable = true) {
+    _assert_(visitor);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (writable && !(omode_ & OWRITER)) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    ScopedVisitor svis(visitor);
+    size_t knum = keys.size();
+    if (knum < 1) return true;
+    struct RecordKey {
+      const char* kbuf;
+      size_t ksiz;
+      size_t bidx;
+    };
+    RecordKey* rkeys = new RecordKey[knum];
+    std::set<size_t> lidxs;
+    for (size_t i = 0; i < knum; i++) {
+      const std::string& key = keys[i];
+      RecordKey* rkey = rkeys + i;
+      rkey->kbuf = key.data();
+      rkey->ksiz = key.size();
+      rkey->bidx = hash_record(rkey->kbuf, rkey->ksiz) % bnum_;
+      lidxs.insert(rkey->bidx % RLOCKSLOT);
+    }
+    std::set<size_t>::iterator lit = lidxs.begin();
+    std::set<size_t>::iterator litend = lidxs.end();
+    while (lit != litend) {
+      if (writable) {
+        rlock_.lock_writer(*lit);
+      } else {
+        rlock_.lock_reader(*lit);
+      }
+      ++lit;
+    }
+    for (size_t i = 0; i < knum; i++) {
+      RecordKey* rkey = rkeys + i;
+      accept_impl(rkey->kbuf, rkey->ksiz, visitor, rkey->bidx);
+    }
+    lit = lidxs.begin();
+    litend = lidxs.end();
+    while (lit != litend) {
+      rlock_.unlock(*lit);
+      ++lit;
+    }
+    delete[] rkeys;
+    return true;
+  }
+  /**
+   * Iterate to accept a visitor for each record.
+   * @param visitor a visitor object.
+   * @param writable true for writable operation, or false for read-only operation.
+   * @param checker a progress checker object.  If it is NULL, no checking is performed.
+   * @return true on success, or false on failure.
+   * @note The whole iteration is performed atomically and other threads are blocked.  To avoid
+   * deadlock, any explicit database operation must not be performed in this function.
+   */
+  bool iterate(Visitor *visitor, bool writable = true, ProgressChecker* checker = NULL) {
+    _assert_(visitor);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (writable && !(omode_ & OWRITER)) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    ScopedVisitor svis(visitor);
+    int64_t allcnt = count_;
+    if (checker && !checker->check("iterate", "beginning", 0, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    int64_t curcnt = 0;
+    for (size_t i = 0; i < bnum_; i++) {
+      char* rbuf = buckets_[i];
+      while (rbuf) {
+        curcnt++;
+        Record rec(rbuf);
+        rbuf = rec.child_;
+        size_t vsiz;
+        const char* vbuf = visitor->visit_full(rec.kbuf_, rec.ksiz_,
+                                               rec.vbuf_, rec.vsiz_, &vsiz);
+        if (vbuf == Visitor::REMOVE) {
+          Repeater repeater(Visitor::REMOVE, 0);
+          accept_impl(rec.kbuf_, rec.ksiz_, &repeater, i);
+        } else if (vbuf != Visitor::NOP) {
+          Repeater repeater(vbuf, vsiz);
+          accept_impl(rec.kbuf_, rec.ksiz_, &repeater, i);
+        }
+        if (checker && !checker->check("iterate", "processing", curcnt, allcnt)) {
+          set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+          return false;
+        }
+      }
+    }
+    if (checker && !checker->check("iterate", "ending", -1, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    trigger_meta(MetaTrigger::ITERATE, "iterate");
+    return true;
+  }
+  /**
+   * Scan each record in parallel.
+   * @param visitor a visitor object.
+   * @param thnum the number of worker threads.
+   * @param checker a progress checker object.  If it is NULL, no checking is performed.
+   * @return true on success, or false on failure.
+   * @note This function is for reading records and not for updating ones.  The return value of
+   * the visitor is just ignored.  To avoid deadlock, any explicit database operation must not
+   * be performed in this function.
+   */
+  bool scan_parallel(Visitor *visitor, size_t thnum, ProgressChecker* checker = NULL) {
+    _assert_(visitor && thnum <= MEMMAXSIZ);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (thnum < 1) thnum = 1;
+    if (thnum > (size_t)INT8MAX) thnum = INT8MAX;
+    if (thnum > bnum_) thnum = bnum_;
+    ScopedVisitor svis(visitor);
+    int64_t allcnt = count_;
+    if (checker && !checker->check("scan_parallel", "beginning", 0, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    class ThreadImpl : public Thread {
+     public:
+      explicit ThreadImpl() :
+          db_(NULL), visitor_(NULL), checker_(NULL), allcnt_(0),
+          begidx_(0), endidx_(0), error_() {}
+      void init(StashDB* db, Visitor* visitor, ProgressChecker* checker, int64_t allcnt,
+                size_t begidx, size_t endidx) {
+        db_ = db;
+        visitor_ = visitor;
+        checker_ = checker;
+        allcnt_ = allcnt;
+        begidx_ = begidx;
+        endidx_ = endidx;
+      }
+      const Error& error() {
+        return error_;
+      }
+     private:
+      void run() {
+        StashDB* db = db_;
+        Visitor* visitor = visitor_;
+        ProgressChecker* checker = checker_;
+        int64_t allcnt = allcnt_;
+        size_t endidx = endidx_;
+        char** buckets = db->buckets_;
+        for (size_t i = begidx_; i < endidx; i++) {
+          char* rbuf = buckets[i];
+          while (rbuf) {
+            Record rec(rbuf);
+            rbuf = rec.child_;
+            size_t vsiz;
+            visitor->visit_full(rec.kbuf_, rec.ksiz_, rec.vbuf_, rec.vsiz_, &vsiz);
+            if (checker && !checker->check("scan_parallel", "processing", -1, allcnt)) {
+              db->set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+              error_ = db->error();
+              break;
+            }
+          }
+        }
+      }
+      StashDB* db_;
+      Visitor* visitor_;
+      ProgressChecker* checker_;
+      int64_t allcnt_;
+      size_t begidx_;
+      size_t endidx_;
+      Error error_;
+    };
+    bool err = false;
+    rlock_.lock_reader_all();
+    ThreadImpl* threads = new ThreadImpl[thnum];
+    double range = (double)bnum_ / thnum;
+    for (size_t i = 0; i < thnum; i++) {
+      size_t cidx = i * range;
+      size_t nidx = (i + 1) * range;
+      if (i < 1) cidx = 0;
+      if (i >= thnum - 1) nidx = bnum_;
+      ThreadImpl* thread = threads + i;
+      thread->init(this, visitor, checker, allcnt, cidx, nidx);
+      thread->start();
+    }
+    for (size_t i = 0; i < thnum; i++) {
+      ThreadImpl* thread = threads + i;
+      thread->join();
+      if (thread->error() != Error::SUCCESS) {
+        *error_ = thread->error();
+        err = true;
+      }
+    }
+    delete[] threads;
+    rlock_.unlock_all();
+    if (err) return false;
+    if (checker && !checker->check("scan_parallel", "ending", -1, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    trigger_meta(MetaTrigger::ITERATE, "scan_parallel");
+    return true;
+  }
+  /**
+   * Get the last happened error.
+   * @return the last happened error.
+   */
+  Error error() const {
+    _assert_(true);
+    return error_;
+  }
+  /**
+   * Set the error information.
+   * @param file the file name of the program source code.
+   * @param line the line number of the program source code.
+   * @param func the function name of the program source code.
+   * @param code an error code.
+   * @param message a supplement message.
+   */
+  void set_error(const char* file, int32_t line, const char* func,
+                 Error::Code code, const char* message) {
+    _assert_(file && line > 0 && func && message);
+    error_->set(code, message);
+    if (logger_) {
+      Logger::Kind kind = code == Error::BROKEN || code == Error::SYSTEM ?
+          Logger::ERROR : Logger::INFO;
+      if (kind & logkinds_)
+        report(file, line, func, kind, "%d: %s: %s", code, Error::codename(code), message);
+    }
+  }
+  /**
+   * Open a database file.
+   * @param path the path of a database file.
+   * @param mode the connection mode.  StashDB::OWRITER as a writer, StashDB::OREADER as a
+   * reader.  The following may be added to the writer mode by bitwise-or: StashDB::OCREATE,
+   * which means it creates a new database if the file does not exist, StashDB::OTRUNCATE, which
+   * means it creates a new database regardless if the file exists, StashDB::OAUTOTRAN, which
+   * means each updating operation is performed in implicit transaction, StashDB::OAUTOSYNC,
+   * which means each updating operation is followed by implicit synchronization with the file
+   * system.  The following may be added to both of the reader mode and the writer mode by
+   * bitwise-or: StashDB::ONOLOCK, which means it opens the database file without file locking,
+   * StashDB::OTRYLOCK, which means locking is performed without blocking, StashDB::ONOREPAIR,
+   * which means the database file is not repaired implicitly even if file destruction is
+   * detected.
+   * @return true on success, or false on failure.
+   * @note Every opened database must be closed by the StashDB::close method when it is no
+   * longer in use.  It is not allowed for two or more database objects in the same process to
+   * keep their connections to the same database file at the same time.
+   */
+  bool open(const std::string& path, uint32_t mode = OWRITER | OCREATE) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    report(_KCCODELINE_, Logger::DEBUG, "opening the database (path=%s)", path.c_str());
+    omode_ = mode;
+    path_.append(path);
+    if (bnum_ >= MAPZMAPBNUM) {
+      buckets_ = (char**)mapalloc(sizeof(*buckets_) * bnum_);
+    } else {
+      buckets_ = new char*[bnum_];
+      for (size_t i = 0; i < bnum_; i++) {
+        buckets_[i] = NULL;
+      }
+    }
+    std::memset(opaque_, 0, sizeof(opaque_));
+    trigger_meta(MetaTrigger::OPEN, "open");
+    return true;
+  }
+  /**
+   * Close the database file.
+   * @return true on success, or false on failure.
+   */
+  bool close() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    report(_KCCODELINE_, Logger::DEBUG, "closing the database (path=%s)", path_.c_str());
+    tran_ = false;
+    trlogs_.clear();
+    for (size_t i = 0; i < bnum_; i++) {
+      char* rbuf = buckets_[i];
+      while (rbuf) {
+        Record rec(rbuf);
+        char* child = rec.child_;
+        delete[] rbuf;
+        rbuf = child;
+      }
+    }
+    if (bnum_ >= MAPZMAPBNUM) {
+      mapfree(buckets_);
+    } else {
+      delete[] buckets_;
+    }
+    path_.clear();
+    omode_ = 0;
+    trigger_meta(MetaTrigger::CLOSE, "close");
+    return true;
+  }
+  /**
+   * Synchronize updated contents with the file and the device.
+   * @param hard true for physical synchronization with the device, or false for logical
+   * synchronization with the file system.
+   * @param proc a postprocessor object.  If it is NULL, no postprocessing is performed.
+   * @param checker a progress checker object.  If it is NULL, no checking is performed.
+   * @return true on success, or false on failure.
+   * @note The operation of the postprocessor is performed atomically and other threads accessing
+   * the same record are blocked.  To avoid deadlock, any explicit database operation must not
+   * be performed in this function.
+   */
+  bool synchronize(bool hard = false, FileProcessor* proc = NULL,
+                   ProgressChecker* checker = NULL) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    bool err = false;
+    if ((omode_ & OWRITER) && checker &&
+        !checker->check("synchronize", "nothing to be synchronized", -1, -1)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    if (proc) {
+      if (checker && !checker->check("synchronize", "running the post processor", -1, -1)) {
+        set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+        return false;
+      }
+      if (!proc->process(path_, count_, size_impl())) {
+        set_error(_KCCODELINE_, Error::LOGIC, "postprocessing failed");
+        err = true;
+      }
+    }
+    trigger_meta(MetaTrigger::SYNCHRONIZE, "synchronize");
+    return !err;
+  }
+  /**
+   * Occupy database by locking and do something meanwhile.
+   * @param writable true to use writer lock, or false to use reader lock.
+   * @param proc a processor object.  If it is NULL, no processing is performed.
+   * @return true on success, or false on failure.
+   * @note The operation of the processor is performed atomically and other threads accessing
+   * the same record are blocked.  To avoid deadlock, any explicit database operation must not
+   * be performed in this function.
+   */
+  bool occupy(bool writable = true, FileProcessor* proc = NULL) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, writable);
+    bool err = false;
+    if (proc && !proc->process(path_, count_, size_impl())) {
+      set_error(_KCCODELINE_, Error::LOGIC, "processing failed");
+      err = true;
+    }
+    trigger_meta(MetaTrigger::OCCUPY, "occupy");
+    return !err;
+  }
+  /**
+   * Begin transaction.
+   * @param hard true for physical synchronization with the device, or false for logical
+   * synchronization with the file system.
+   * @return true on success, or false on failure.
+   */
+  bool begin_transaction(bool hard = false) {
+    _assert_(true);
+    uint32_t wcnt = 0;
+    while (true) {
+      mlock_.lock_writer();
+      if (omode_ == 0) {
+        set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        mlock_.unlock();
+        return false;
+      }
+      if (!(omode_ & OWRITER)) {
+        set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+        mlock_.unlock();
+        return false;
+      }
+      if (!tran_) break;
+      mlock_.unlock();
+      if (wcnt >= LOCKBUSYLOOP) {
+        Thread::chill();
+      } else {
+        Thread::yield();
+        wcnt++;
+      }
+    }
+    tran_ = true;
+    trcount_ = count_;
+    trsize_ = size_;
+    trigger_meta(MetaTrigger::BEGINTRAN, "begin_transaction");
+    mlock_.unlock();
+    return true;
+  }
+  /**
+   * Try to begin transaction.
+   * @param hard true for physical synchronization with the device, or false for logical
+   * synchronization with the file system.
+   * @return true on success, or false on failure.
+   */
+  bool begin_transaction_try(bool hard = false) {
+    _assert_(true);
+    mlock_.lock_writer();
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      mlock_.unlock();
+      return false;
+    }
+    if (!(omode_ & OWRITER)) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      mlock_.unlock();
+      return false;
+    }
+    if (tran_) {
+      set_error(_KCCODELINE_, Error::LOGIC, "competition avoided");
+      mlock_.unlock();
+      return false;
+    }
+    tran_ = true;
+    trcount_ = count_;
+    trsize_ = size_;
+    trigger_meta(MetaTrigger::BEGINTRAN, "begin_transaction_try");
+    mlock_.unlock();
+    return true;
+  }
+  /**
+   * End transaction.
+   * @param commit true to commit the transaction, or false to abort the transaction.
+   * @return true on success, or false on failure.
+   */
+  bool end_transaction(bool commit = true) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (!tran_) {
+      set_error(_KCCODELINE_, Error::INVALID, "not in transaction");
+      return false;
+    }
+    if (!commit) {
+      disable_cursors();
+      apply_trlogs();
+      count_ = trcount_;
+      size_ = trsize_;
+    }
+    trlogs_.clear();
+    tran_ = false;
+    trigger_meta(commit ? MetaTrigger::COMMITTRAN : MetaTrigger::ABORTTRAN, "end_transaction");
+    return true;
+  }
+  /**
+   * Remove all records.
+   * @return true on success, or false on failure.
+   */
+  bool clear() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    disable_cursors();
+    if (count_ > 0) {
+      for (size_t i = 0; i < bnum_; i++) {
+        char* rbuf = buckets_[i];
+        while (rbuf) {
+          Record rec(rbuf);
+          char* child = rec.child_;
+          delete[] rbuf;
+          rbuf = child;
+        }
+        buckets_[i] = NULL;
+      }
+      count_ = 0;
+      size_ = 0;
+    }
+    std::memset(opaque_, 0, sizeof(opaque_));
+    trigger_meta(MetaTrigger::CLEAR, "clear");
+    return true;
+  }
+  /**
+   * Get the number of records.
+   * @return the number of records, or -1 on failure.
+   */
+  int64_t count() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return -1;
+    }
+    return count_;
+  }
+  /**
+   * Get the size of the database file.
+   * @return the size of the database file in bytes, or -1 on failure.
+   */
+  int64_t size() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return -1;
+    }
+    return size_impl();
+  }
+  /**
+   * Get the path of the database file.
+   * @return the path of the database file, or an empty string on failure.
+   */
+  std::string path() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return "";
+    }
+    return path_;
+  }
+  /**
+   * Get the miscellaneous status information.
+   * @param strmap a string map to contain the result.
+   * @return true on success, or false on failure.
+   */
+  bool status(std::map<std::string, std::string>* strmap) {
+    _assert_(strmap);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    (*strmap)["type"] = strprintf("%u", (unsigned)TYPESTASH);
+    (*strmap)["realtype"] = strprintf("%u", (unsigned)TYPESTASH);
+    (*strmap)["path"] = path_;
+    if (strmap->count("opaque") > 0)
+      (*strmap)["opaque"] = std::string(opaque_, sizeof(opaque_));
+    if (strmap->count("bnum_used") > 0) {
+      int64_t cnt = 0;
+      for (size_t i = 0; i < bnum_; i++) {
+        if (buckets_[i]) cnt++;
+      }
+      (*strmap)["bnum_used"] = strprintf("%lld", (long long)cnt);
+    }
+    (*strmap)["count"] = strprintf("%lld", (long long)count_);
+    (*strmap)["size"] = strprintf("%lld", (long long)size_impl());
+    return true;
+  }
+  /**
+   * Create a cursor object.
+   * @return the return value is the created cursor object.
+   * @note Because the object of the return value is allocated by the constructor, it should be
+   * released with the delete operator when it is no longer in use.
+   */
+  Cursor* cursor() {
+    _assert_(true);
+    return new Cursor(this);
+  }
+  /**
+   * Write a log message.
+   * @param file the file name of the program source code.
+   * @param line the line number of the program source code.
+   * @param func the function name of the program source code.
+   * @param kind the kind of the event.  Logger::DEBUG for debugging, Logger::INFO for normal
+   * information, Logger::WARN for warning, and Logger::ERROR for fatal error.
+   * @param message the supplement message.
+   */
+  void log(const char* file, int32_t line, const char* func, Logger::Kind kind,
+           const char* message) {
+    _assert_(file && line > 0 && func && message);
+    ScopedRWLock lock(&mlock_, false);
+    if (!logger_) return;
+    logger_->log(file, line, func, kind, message);
+  }
+  /**
+   * Set the internal logger.
+   * @param logger the logger object.
+   * @param kinds kinds of logged messages by bitwise-or: Logger::DEBUG for debugging,
+   * Logger::INFO for normal information, Logger::WARN for warning, and Logger::ERROR for fatal
+   * error.
+   * @return true on success, or false on failure.
+   */
+  bool tune_logger(Logger* logger, uint32_t kinds = Logger::WARN | Logger::ERROR) {
+    _assert_(logger);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    logger_ = logger;
+    logkinds_ = kinds;
+    return true;
+  }
+  /**
+   * Set the internal meta operation trigger.
+   * @param trigger the trigger object.
+   * @return true on success, or false on failure.
+   */
+  bool tune_meta_trigger(MetaTrigger* trigger) {
+    _assert_(trigger);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    mtrigger_ = trigger;
+    return true;
+  }
+  /**
+   * Set the number of buckets of the hash table.
+   * @param bnum the number of buckets of the hash table.
+   * @return true on success, or false on failure.
+   */
+  bool tune_buckets(int64_t bnum) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    bnum_ = bnum >= 0 ? bnum : DEFBNUM;
+    if (bnum_ > (size_t)INT16MAX) bnum_ = nearbyprime(bnum_);
+    return true;
+  }
+  /**
+   * Get the opaque data.
+   * @return the pointer to the opaque data region, whose size is 16 bytes.
+   */
+  char* opaque() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return NULL;
+    }
+    return opaque_;
+  }
+  /**
+   * Synchronize the opaque data.
+   * @return true on success, or false on failure.
+   */
+  bool synchronize_opaque() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    if (!(omode_ & OWRITER)) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    return true;
+  }
+ protected:
+  /**
+   * Report a message for debugging.
+   * @param file the file name of the program source code.
+   * @param line the line number of the program source code.
+   * @param func the function name of the program source code.
+   * @param kind the kind of the event.  Logger::DEBUG for debugging, Logger::INFO for normal
+   * information, Logger::WARN for warning, and Logger::ERROR for fatal error.
+   * @param format the printf-like format string.
+   * @param ... used according to the format string.
+   */
+  void report(const char* file, int32_t line, const char* func, Logger::Kind kind,
+              const char* format, ...) {
+    _assert_(file && line > 0 && func && format);
+    if (!logger_ || !(kind & logkinds_)) return;
+    std::string message;
+    strprintf(&message, "%s: ", path_.empty() ? "-" : path_.c_str());
+    va_list ap;
+    va_start(ap, format);
+    vstrprintf(&message, format, ap);
+    va_end(ap);
+    logger_->log(file, line, func, kind, message.c_str());
+  }
+  /**
+   * Report a message for debugging with variable number of arguments.
+   * @param file the file name of the program source code.
+   * @param line the line number of the program source code.
+   * @param func the function name of the program source code.
+   * @param kind the kind of the event.  Logger::DEBUG for debugging, Logger::INFO for normal
+   * information, Logger::WARN for warning, and Logger::ERROR for fatal error.
+   * @param format the printf-like format string.
+   * @param ap used according to the format string.
+   */
+  void report_valist(const char* file, int32_t line, const char* func, Logger::Kind kind,
+                     const char* format, va_list ap) {
+    _assert_(file && line > 0 && func && format);
+    if (!logger_ || !(kind & logkinds_)) return;
+    std::string message;
+    strprintf(&message, "%s: ", path_.empty() ? "-" : path_.c_str());
+    vstrprintf(&message, format, ap);
+    logger_->log(file, line, func, kind, message.c_str());
+  }
+  /**
+   * Report the content of a binary buffer for debugging.
+   * @param file the file name of the epicenter.
+   * @param line the line number of the epicenter.
+   * @param func the function name of the program source code.
+   * @param kind the kind of the event.  Logger::DEBUG for debugging, Logger::INFO for normal
+   * information, Logger::WARN for warning, and Logger::ERROR for fatal error.
+   * @param name the name of the information.
+   * @param buf the binary buffer.
+   * @param size the size of the binary buffer
+   */
+  void report_binary(const char* file, int32_t line, const char* func, Logger::Kind kind,
+                     const char* name, const char* buf, size_t size) {
+    _assert_(file && line > 0 && func && name && buf && size <= MEMMAXSIZ);
+    if (!logger_) return;
+    char* hex = hexencode(buf, size);
+    report(file, line, func, kind, "%s=%s", name, hex);
+    delete[] hex;
+  }
+  /**
+   * Trigger a meta database operation.
+   * @param kind the kind of the event.  MetaTrigger::OPEN for opening, MetaTrigger::CLOSE for
+   * closing, MetaTrigger::CLEAR for clearing, MetaTrigger::ITERATE for iteration,
+   * MetaTrigger::SYNCHRONIZE for synchronization, MetaTrigger::BEGINTRAN for beginning
+   * transaction, MetaTrigger::COMMITTRAN for committing transaction, MetaTrigger::ABORTTRAN
+   * for aborting transaction, and MetaTrigger::MISC for miscellaneous operations.
+   * @param message the supplement message.
+   */
+  void trigger_meta(MetaTrigger::Kind kind, const char* message) {
+    _assert_(message);
+    if (mtrigger_) mtrigger_->trigger(kind, message);
+  }
+ private:
+  /**
+   * Record data.
+   */
+  struct Record {
+    /** constructor */
+    Record(char* child, const char* kbuf, uint64_t ksiz, const char* vbuf, uint64_t vsiz) :
+        child_(child), kbuf_(kbuf), ksiz_(ksiz), vbuf_(vbuf), vsiz_(vsiz) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ);
+    }
+    /** constructor */
+    Record(const char* rbuf) :
+        child_(NULL), kbuf_(NULL), ksiz_(0), vbuf_(NULL), vsiz_(0) {
+      _assert_(rbuf);
+      deserialize(rbuf);
+    }
+    /** overwrite the buffer */
+    void overwrite(char* rbuf, const char* vbuf, size_t vsiz) {
+      _assert_(rbuf && vbuf && vsiz <= MEMMAXSIZ);
+      char* wp = rbuf + sizeof(child_) + sizevarnum(ksiz_) + ksiz_;
+      wp += writevarnum(wp, vsiz);
+      std::memcpy(wp, vbuf, vsiz);
+    }
+    /** serialize data into a buffer */
+    char* serialize() {
+      _assert_(true);
+      uint64_t rsiz = sizeof(child_) + sizevarnum(ksiz_) + ksiz_ + sizevarnum(vsiz_) + vsiz_;
+      char* rbuf = new char[rsiz];
+      char* wp = rbuf;
+      *(char**)wp = child_;
+      wp += sizeof(child_);
+      wp += writevarnum(wp, ksiz_);
+      std::memcpy(wp, kbuf_, ksiz_);
+      wp += ksiz_;
+      wp += writevarnum(wp, vsiz_);
+      std::memcpy(wp, vbuf_, vsiz_);
+      return rbuf;
+    }
+    /** deserialize a buffer into object */
+    void deserialize(const char* rbuf) {
+      _assert_(rbuf);
+      const char* rp = rbuf;
+      child_ = *(char**)rp;
+      rp += sizeof(child_);
+      rp += readvarnum(rp, sizeof(ksiz_), &ksiz_);
+      kbuf_ = rp;
+      rp += ksiz_;
+      rp += readvarnum(rp, sizeof(vsiz_), &vsiz_);
+      vbuf_ = rp;
+    }
+    /** print debug info */
+    void print() {
+      std::cout << "child:" << (void*)child_ << std::endl;
+      std::cout << "key:" << std::string(kbuf_, ksiz_) << std::endl;
+      std::cout << "value:" << std::string(vbuf_, vsiz_) << std::endl;
+      std::cout << "ksiz:" << ksiz_ << std::endl;
+      std::cout << "vsiz:" << vsiz_ << std::endl;
+    }
+    char* child_;                        ///< region of the child
+    const char* kbuf_;                   ///< region of the key
+    uint64_t ksiz_;                      ///< size of the key
+    const char* vbuf_;                   ///< region of the value
+    uint64_t vsiz_;                      ///< size of the key
+  };
+  /**
+   * Transaction log.
+   */
+  struct TranLog {
+    bool full;                           ///< flag whether full
+    std::string key;                     ///< old key
+    std::string value;                   ///< old value
+    /** constructor for a full record */
+    explicit TranLog(const char* kbuf, size_t ksiz, const char* vbuf, size_t vsiz) :
+        full(true), key(kbuf, ksiz), value(vbuf, vsiz) {
+      _assert_(true);
+    }
+    /** constructor for an empty record */
+    explicit TranLog(const char* kbuf, size_t ksiz) : full(false), key(kbuf, ksiz) {
+      _assert_(true);
+    }
+  };
+  /**
+   * Repeating visitor.
+   */
+  class Repeater : public Visitor {
+   public:
+    /** constructor */
+    explicit Repeater(const char* vbuf, size_t vsiz) : vbuf_(vbuf), vsiz_(vsiz) {}
+   private:
+    /** process a full record */
+    const char* visit_full(const char* kbuf, size_t ksiz,
+                           const char* vbuf, size_t vsiz, size_t* sp) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ && sp);
+      *sp = vsiz_;
+      return vbuf_;
+    }
+    const char* vbuf_;                   ///< region of the value
+    size_t vsiz_;                        ///< size of the value
+  };
+  /**
+   * Setting visitor.
+   */
+  class Setter : public Visitor {
+   public:
+    /** constructor */
+    explicit Setter(const char* vbuf, size_t vsiz) : vbuf_(vbuf), vsiz_(vsiz) {}
+   private:
+    /** process a full record */
+    const char* visit_full(const char* kbuf, size_t ksiz,
+                           const char* vbuf, size_t vsiz, size_t* sp) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ && sp);
+      *sp = vsiz_;
+      return vbuf_;
+    }
+    /** process an empty record */
+    const char* visit_empty(const char* kbuf, size_t ksiz, size_t* sp) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ && sp);
+      *sp = vsiz_;
+      return vbuf_;
+    }
+    const char* vbuf_;                   ///< region of the value
+    size_t vsiz_;                        ///< size of the value
+  };
+  /**
+   * Removing visitor.
+   */
+  class Remover : public Visitor {
+   private:
+    /** visit a record */
+    const char* visit_full(const char* kbuf, size_t ksiz,
+                           const char* vbuf, size_t vsiz, size_t* sp) {
+      _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ && sp);
+      return REMOVE;
+    }
+  };
+  /**
+   * Scoped visitor.
+   */
+  class ScopedVisitor {
+   public:
+    /** constructor */
+    explicit ScopedVisitor(Visitor* visitor) : visitor_(visitor) {
+      _assert_(visitor);
+      visitor_->visit_before();
+    }
+    /** destructor */
+    ~ScopedVisitor() {
+      _assert_(true);
+      visitor_->visit_after();
+    }
+   private:
+    Visitor* visitor_;                   ///< visitor
+  };
+  /**
+   * Accept a visitor to a record.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @param visitor a visitor object.
+   * @param bidx the bucket index.
+   */
+  void accept_impl(const char* kbuf, size_t ksiz, Visitor* visitor, size_t bidx) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && visitor);
+    char* rbuf = buckets_[bidx];
+    char** entp = buckets_ + bidx;
+    while (rbuf) {
+      Record rec(rbuf);
+      if (rec.ksiz_ == ksiz && !std::memcmp(rec.kbuf_, kbuf, ksiz)) {
+        size_t vsiz;
+        const char* vbuf = visitor->visit_full(rec.kbuf_, rec.ksiz_,
+                                               rec.vbuf_, rec.vsiz_, &vsiz);
+        if (vbuf == Visitor::REMOVE) {
+          if (tran_) {
+            ScopedMutex lock(&flock_);
+            TranLog log(rec.kbuf_, rec.ksiz_, rec.vbuf_, rec.vsiz_);
+            trlogs_.push_back(log);
+          }
+          count_ -= 1;
+          size_ -= rec.ksiz_ + rec.vsiz_;
+          escape_cursors(rbuf);
+          *entp = rec.child_;
+          delete[] rbuf;
+        } else if (vbuf != Visitor::NOP) {
+          if (tran_) {
+            ScopedMutex lock(&flock_);
+            TranLog log(rec.kbuf_, rec.ksiz_, rec.vbuf_, rec.vsiz_);
+            trlogs_.push_back(log);
+          }
+          int32_t oh = (int32_t)sizevarnum(vsiz) - (int32_t)sizevarnum(rec.vsiz_);
+          int64_t diff = (int64_t)rec.vsiz_ - (int64_t)(vsiz + oh);
+          size_ += (int64_t)vsiz - (int64_t)rec.vsiz_;
+          if (diff >= 0) {
+            rec.overwrite(rbuf, vbuf, vsiz);
+          } else {
+            Record nrec(rec.child_, kbuf, ksiz, vbuf, vsiz);
+            char* nbuf = nrec.serialize();
+            adjust_cursors(rbuf, nbuf);
+            *entp = nbuf;
+            delete[] rbuf;
+          }
+        }
+        return;
+      }
+      entp = (char**)rbuf;
+      rbuf = rec.child_;
+    }
+    size_t vsiz;
+    const char* vbuf = visitor->visit_empty(kbuf, ksiz, &vsiz);
+    if (vbuf != Visitor::REMOVE && vbuf != Visitor::NOP) {
+      if (tran_) {
+        ScopedMutex lock(&flock_);
+        TranLog log(kbuf, ksiz);
+        trlogs_.push_back(log);
+      }
+      Record nrec(NULL, kbuf, ksiz, vbuf, vsiz);
+      *entp = nrec.serialize();
+      count_ += 1;
+      size_ += ksiz + vsiz;
+    }
+  }
+  /**
+   * Get the hash value of a record.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @return the hash value.
+   */
+  size_t hash_record(const char* kbuf, size_t ksiz) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ);
+    return hashmurmur(kbuf, ksiz);
+  }
+  /**
+   * Get the size of the database file.
+   * @return the size of the database file in bytes.
+   */
+  int64_t size_impl() {
+    _assert_(true);
+    return bnum_ * sizeof(*buckets_) + count_ * (4 + sizeof(void*)) + size_;
+  }
+  /**
+   * Escape cursors on a shifted or removed records.
+   * @param rbuf the record buffer.
+   */
+  void escape_cursors(char* rbuf) {
+    _assert_(rbuf);
+    ScopedMutex lock(&flock_);
+    if (curs_.empty()) return;
+    CursorList::const_iterator cit = curs_.begin();
+    CursorList::const_iterator citend = curs_.end();
+    while (cit != citend) {
+      Cursor* cur = *cit;
+      if (cur->rbuf_ == rbuf) cur->step_impl();
+      ++cit;
+    }
+  }
+  /**
+   * Adjust cursors on re-allocated records.
+   * @param obuf the old address.
+   * @param nbuf the new address.
+   */
+  void adjust_cursors(char* obuf, char* nbuf) {
+    _assert_(obuf && nbuf);
+    ScopedMutex lock(&flock_);
+    if (curs_.empty()) return;
+    CursorList::const_iterator cit = curs_.begin();
+    CursorList::const_iterator citend = curs_.end();
+    while (cit != citend) {
+      Cursor* cur = *cit;
+      if (cur->rbuf_ == obuf) cur->rbuf_ = nbuf;
+      ++cit;
+    }
+  }
+  /**
+   * Disable all cursors.
+   */
+  void disable_cursors() {
+    _assert_(true);
+    ScopedMutex lock(&flock_);
+    CursorList::const_iterator cit = curs_.begin();
+    CursorList::const_iterator citend = curs_.end();
+    while (cit != citend) {
+      Cursor* cur = *cit;
+      cur->bidx_ = -1;
+      cur->rbuf_ = NULL;
+      ++cit;
+    }
+  }
+  /**
+   * Apply transaction logs.
+   */
+  void apply_trlogs() {
+    _assert_(true);
+    TranLogList::const_iterator it = trlogs_.end();
+    TranLogList::const_iterator itbeg = trlogs_.begin();
+    while (it != itbeg) {
+      --it;
+      const char* kbuf = it->key.c_str();
+      size_t ksiz = it->key.size();
+      const char* vbuf = it->value.c_str();
+      size_t vsiz = it->value.size();
+      size_t bidx = hash_record(kbuf, ksiz) % bnum_;
+      if (it->full) {
+        Setter setter(vbuf, vsiz);
+        accept_impl(kbuf, ksiz, &setter, bidx);
+      } else {
+        Remover remover;
+        accept_impl(kbuf, ksiz, &remover, bidx);
+      }
+    }
+  }
+  /** Dummy constructor to forbid the use. */
+  StashDB(const StashDB&);
+  /** Dummy Operator to forbid the use. */
+  StashDB& operator =(const StashDB&);
+  /** The method lock. */
+  RWLock mlock_;
+  /** The record locks. */
+  SlottedRWLock rlock_;
+  /** The file lock. */
+  Mutex flock_;
+  /** The last happened error. */
+  TSD<Error> error_;
+  /** The internal logger. */
+  Logger* logger_;
+  /** The kinds of logged messages. */
+  uint32_t logkinds_;
+  /** The internal meta operation trigger. */
+  MetaTrigger* mtrigger_;
+  /** The open mode. */
+  uint32_t omode_;
+  /** The cursor objects. */
+  CursorList curs_;
+  /** The path of the database file. */
+  std::string path_;
+  /** The number of buckets. */
+  size_t bnum_;
+  /** The opaque data. */
+  char opaque_[OPAQUESIZ];
+  /** The record number. */
+  AtomicInt64 count_;
+  /** The total size of records. */
+  AtomicInt64 size_;
+  /** The bucket array. */
+  char** buckets_;
+  /** The flag whether in transaction. */
+  bool tran_;
+  /** The list of transaction logs. */
+  TranLogList trlogs_;
+  /** The count history for transaction. */
+  int64_t trcount_;
+  /** The size history for transaction. */
+  int64_t trsize_;
+};
+
+
+}                                        // common namespace
+
+#endif                                   // duplication check
+
+// END OF FILE