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, 2437 insertions, 0 deletions

diff --git a/plugins/Dbx_kyoto/src/kyotocabinet/kcdirdb.h b/plugins/Dbx_kyoto/src/kyotocabinet/kcdirdb.h
new file mode 100644
index 0000000000..c80ba2d143
--- /dev/null
+++ b/plugins/Dbx_kyoto/src/kyotocabinet/kcdirdb.h
@@ -0,0 +1,2437 @@
+/*************************************************************************************************
+ * Directory hash 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 _KCDIRDB_H                       // duplication check
+#define _KCDIRDB_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>
+
+#define KCDDBMAGICFILE  "__KCDIR__"      ///< magic file of the directory
+#define KCDDBMETAFILE  "__meta__"        ///< meta data file of the directory
+#define KCDDBOPAQUEFILE  "__opq__"       ///< opaque file of the directory
+#define KCDDBATRANPREFIX  "_x"           ///< prefix of files for auto transaction
+#define KCDDBCHKSUMSEED  "__kyotocabinet__"  ///< seed of the module checksum
+#define KCDDBMAGICEOF  "_EOF_"           ///< magic data for the end of file
+#define KCDDBWALPATHEXT  "wal"           ///< extension of the WAL directory
+#define KCDDBTMPPATHEXT  "tmp"           ///< extension of the temporary directory
+
+namespace kyotocabinet {                 // common namespace
+
+
+/**
+ * Directory hash database.
+ * @note This class is a concrete class to operate a hash database in a directory.  This class
+ * can be inherited but overwriting methods is forbidden.  Before every database operation, it is
+ * necessary to call the DirDB::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 DirDB::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 DirDB : public BasicDB {
+  friend class PlantDB<DirDB, BasicDB::TYPEFOREST>;
+ public:
+  class Cursor;
+ private:
+  struct Record;
+  class ScopedVisitor;
+  /** An alias of list of cursors. */
+  typedef std::list<Cursor*> CursorList;
+  /** An alias of vector of strings. */
+  typedef std::vector<std::string> StringVector;
+  /** The size of the meta data buffer. */
+  static const int64_t METABUFSIZ = 128;
+  /** The magic data for record. */
+  static const uint8_t RECMAGIC = 0xcc;
+  /** The number of slots of the record lock. */
+  static const int32_t RLOCKSLOT = 2048;
+  /** The unit size of a record. */
+  static const int32_t RECUNITSIZ = 32;
+  /** 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;
+ public:
+  /**
+   * Cursor to indicate a record.
+   */
+  class Cursor : public BasicDB::Cursor {
+    friend class DirDB;
+   public:
+    /**
+     * Constructor.
+     * @param db the container database object.
+     */
+    explicit Cursor(DirDB* db) : db_(db), dir_(), alive_(false), name_("") {
+      _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_->writer_)) {
+        db_->set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+        return false;
+      }
+      if (!alive_) {
+        db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+        return false;
+      }
+      bool err = false;
+      const std::string& rpath = db_->path_ + File::PATHCHR + name_;
+      int64_t cnt = db_->count_;
+      Record rec;
+      if (db_->read_record(rpath, &rec)) {
+        if (!db_->accept_visit_full(rec.kbuf, rec.ksiz, rec.vbuf, rec.vsiz, rec.rsiz,
+                                    visitor, rpath, name_.c_str())) err = true;
+        delete[] rec.rbuf;
+        if (alive_ && step && db_->count_ == cnt) {
+          do {
+            if (!dir_.read(&name_)) {
+              if (!disable()) err = true;
+              break;
+            }
+          } while (*name_.c_str() == *KCDDBMAGICFILE);
+        }
+      } else {
+        while (true) {
+          if (!dir_.read(&name_)) {
+            db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+            disable();
+            break;
+          }
+          if (*name_.c_str() == *KCDDBMAGICFILE) continue;
+          const std::string& npath = db_->path_ + File::PATHCHR + name_;
+          if (!File::status(npath)) continue;
+          if (db_->read_record(npath, &rec)) {
+            if (!db_->accept_visit_full(rec.kbuf, rec.ksiz, rec.vbuf, rec.vsiz, rec.rsiz,
+                                        visitor, npath, name_.c_str())) err = true;
+            delete[] rec.rbuf;
+            if (alive_ && step && db_->count_ == cnt) {
+              do {
+                if (!dir_.read(&name_)) {
+                  if (!disable()) err = true;
+                  break;
+                }
+              } while (*name_.c_str() == *KCDDBMAGICFILE);
+            }
+          } else {
+            db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+            err = true;
+          }
+          break;
+        }
+      }
+      return !err;
+    }
+    /**
+     * 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 (alive_ && !disable()) return false;
+      if (db_->omode_ == 0) {
+        db_->set_error(_KCCODELINE_, Error::INVALID, "not opened");
+        return false;
+      }
+      if (!dir_.open(db_->path_)) {
+        db_->set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+        return false;
+      }
+      alive_ = true;
+      do {
+        if (!dir_.read(&name_)) {
+          db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+          disable();
+          return false;
+        }
+      } while (*name_.c_str() == *KCDDBMAGICFILE);
+      return true;
+    }
+    /**
+     * 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 (alive_ && !disable()) return false;
+      if (!dir_.open(db_->path_)) {
+        db_->set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+        return false;
+      }
+      alive_ = true;
+      while (true) {
+        if (!dir_.read(&name_)) {
+          db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+          disable();
+          return false;
+        }
+        if (*name_.c_str() == *KCDDBMAGICFILE) continue;
+        const std::string& rpath = db_->path_ + File::PATHCHR + name_;
+        Record rec;
+        if (db_->read_record(rpath, &rec)) {
+          if (rec.ksiz == ksiz && !std::memcmp(rec.kbuf, kbuf, ksiz)) {
+            delete[] rec.rbuf;
+            break;
+          }
+          delete[] rec.rbuf;
+        } else {
+          db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+          disable();
+          return false;
+        }
+      }
+      return true;
+    }
+    /**
+     * 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 (!alive_) {
+        db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+        return false;
+      }
+      do {
+        if (!dir_.read(&name_)) {
+          db_->set_error(_KCCODELINE_, Error::NOREC, "no record");
+          disable();
+          return false;
+        }
+      } while (*name_.c_str() == *KCDDBMAGICFILE);
+      return true;
+    }
+    /**
+     * 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.
+     */
+    DirDB* db() {
+      _assert_(true);
+      return db_;
+    }
+   private:
+    /**
+     * Disable the cursor.
+     * @return true on success, or false on failure.
+     */
+    bool disable() {
+      bool err = false;
+      if (!dir_.close()) {
+        db_->set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+        err = true;
+      }
+      alive_ = false;
+      return !err;
+    }
+    /** Dummy constructor to forbid the use. */
+    Cursor(const Cursor&);
+    /** Dummy Operator to forbid the use. */
+    Cursor& operator =(const Cursor&);
+    /** The inner database. */
+    DirDB* db_;
+    /** The inner directory stream. */
+    DirStream dir_;
+    /** The flag if alive. */
+    bool alive_;
+    /** The current name. */
+    std::string name_;
+  };
+  /**
+   * Tuning options.
+   */
+  enum Option {
+    TSMALL = 1 << 0,                     ///< dummy for compatibility
+    TLINEAR = 1 << 1,                    ///< dummy for compatibility
+    TCOMPRESS = 1 << 2                   ///< compress each record
+  };
+  /**
+   * Status flags.
+   */
+  enum Flag {
+    FOPEN = 1 << 0,                      ///< dummy for compatibility
+    FFATAL = 1 << 1                      ///< dummy for compatibility
+  };
+  /**
+   * Default constructor.
+   */
+  explicit DirDB() :
+      mlock_(), rlock_(RLOCKSLOT), error_(),
+      logger_(NULL), logkinds_(0), mtrigger_(NULL),
+      omode_(0), writer_(false), autotran_(false), autosync_(false),
+      recov_(false), reorg_(false),
+      file_(), curs_(), path_(""),
+      libver_(LIBVER), librev_(LIBREV), fmtver_(FMTVER), chksum_(0), type_(TYPEDIR),
+      flags_(0), opts_(0), count_(0), size_(0), opaque_(), embcomp_(ZLIBRAWCOMP), comp_(NULL),
+      tran_(false), trhard_(false), trcount_(0), trsize_(0), walpath_(""), tmppath_("") {
+    _assert_(true);
+  }
+  /**
+   * Destructor.
+   * @note If the database is not closed, it is closed implicitly.
+   */
+  virtual ~DirDB() {
+    _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 && !writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    bool err = false;
+    char name[NUMBUFSIZ];
+    size_t lidx = hashpath(kbuf, ksiz, name) % RLOCKSLOT;
+    if (writable) {
+      rlock_.lock_writer(lidx);
+    } else {
+      rlock_.lock_reader(lidx);
+    }
+    if (!accept_impl(kbuf, ksiz, visitor, name)) err = true;
+    rlock_.unlock(lidx);
+    return !err;
+  }
+  /**
+   * 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 && !writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    ScopedVisitor svis(visitor);
+    size_t knum = keys.size();
+    if (knum < 1) return true;
+    bool err = false;
+    struct RecordKey {
+      const char* kbuf;
+      size_t ksiz;
+      char name[NUMBUFSIZ];
+    };
+    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();
+      lidxs.insert(hashpath(rkey->kbuf, rkey->ksiz, rkey->name) % 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;
+      if (!accept_impl(rkey->kbuf, rkey->ksiz, visitor, rkey->name)) {
+        err = true;
+        break;
+      }
+    }
+    lit = lidxs.begin();
+    litend = lidxs.end();
+    while (lit != litend) {
+      rlock_.unlock(*lit);
+      ++lit;
+    }
+    delete[] rkeys;
+    return !err;
+  }
+  /**
+   * 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 && !writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    ScopedVisitor svis(visitor);
+    bool err = false;
+    if (!iterate_impl(visitor, checker)) err = true;
+    trigger_meta(MetaTrigger::ITERATE, "iterate");
+    return !err;
+  }
+  /**
+   * 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 = 0;
+    if (thnum > (size_t)INT8MAX) thnum = INT8MAX;
+    ScopedVisitor svis(visitor);
+    rlock_.lock_reader_all();
+    bool err = false;
+    if (!scan_parallel_impl(visitor, thnum, checker)) err = true;
+    rlock_.unlock_all();
+    trigger_meta(MetaTrigger::ITERATE, "scan_parallel");
+    return !err;
+  }
+  /**
+   * 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 (code == Error::BROKEN || code == Error::SYSTEM) flags_ |= FFATAL;
+    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.  DirDB::OWRITER as a writer, DirDB::OREADER as a
+   * reader.  The following may be added to the writer mode by bitwise-or: DirDB::OCREATE,
+   * which means it creates a new database if the file does not exist, DirDB::OTRUNCATE, which
+   * means it creates a new database regardless if the file exists, DirDB::OAUTOTRAN, which
+   * means each updating operation is performed in implicit transaction, DirDB::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: DirDB::ONOLOCK, which means it opens the database file without file locking,
+   * DirDB::OTRYLOCK, which means locking is performed without blocking, DirDB::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 DirDB::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());
+    writer_ = false;
+    autotran_ = false;
+    autosync_ = false;
+    recov_ = false;
+    reorg_ = false;
+    uint32_t fmode = File::OREADER;
+    if (mode & OWRITER) {
+      writer_ = true;
+      fmode = File::OWRITER;
+      if (mode & OCREATE) fmode |= File::OCREATE;
+      if (mode & OTRUNCATE) fmode |= File::OTRUNCATE;
+      if (mode & OAUTOTRAN) autotran_ = true;
+      if (mode & OAUTOSYNC) autosync_ = true;
+    }
+    if (mode & ONOLOCK) fmode |= File::ONOLOCK;
+    if (mode & OTRYLOCK) fmode |= File::OTRYLOCK;
+    size_t psiz = path.size();
+    while (psiz > 0 && path[psiz-1] == File::PATHCHR) {
+      psiz--;
+    }
+    const std::string& cpath = path.substr(0, psiz);
+    const std::string& magicpath = cpath + File::PATHCHR + KCDDBMAGICFILE;
+    const std::string& metapath = cpath + File::PATHCHR + KCDDBMETAFILE;
+    const std::string& opqpath = cpath + File::PATHCHR + KCDDBOPAQUEFILE;
+    const std::string& walpath = cpath + File::EXTCHR + KCDDBWALPATHEXT;
+    const std::string& tmppath = cpath + File::EXTCHR + KCDDBTMPPATHEXT;
+    bool hot = false;
+    if (writer_ && (mode & OTRUNCATE) && File::status(magicpath)) {
+      if (!file_.open(magicpath, fmode)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+        return false;
+      }
+      if (!remove_files(cpath)) {
+        file_.close();
+        return false;
+      }
+      if (File::status(walpath)) {
+        remove_files(walpath);
+        File::remove_directory(walpath);
+      }
+      if (!file_.close()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+        return false;
+      }
+      const std::string& buf = format_magic(0, 0);
+      if (!File::write_file(magicpath, buf.c_str(), buf.size())) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+        return false;
+      }
+      if (File::status(metapath) && !File::remove(metapath)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+        return false;
+      }
+      if (File::status(opqpath) && !File::remove(opqpath)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+        return false;
+      }
+      hot = true;
+    }
+    File::Status sbuf;
+    if (File::status(cpath, &sbuf)) {
+      if (!sbuf.isdir) {
+        set_error(_KCCODELINE_, Error::NOPERM, "invalid path (not directory)");
+        return false;
+      }
+      if (!File::status(magicpath)) {
+        set_error(_KCCODELINE_, Error::BROKEN, "invalid magic data");
+        return false;
+      }
+      if (!file_.open(magicpath, fmode)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+        return false;
+      }
+    } else if (writer_ && (mode & OCREATE)) {
+      hot = true;
+      if (!File::make_directory(cpath)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "making a directory failed");
+        return false;
+      }
+      if (!file_.open(magicpath, fmode)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+        return false;
+      }
+    } else {
+      set_error(_KCCODELINE_, Error::NOREPOS, "open failed (file not found)");
+      return false;
+    }
+    if (hot) {
+      count_ = 0;
+      size_ = 0;
+      comp_ = (opts_ & TCOMPRESS) ? embcomp_ : NULL;
+      libver_ = LIBVER;
+      librev_ = LIBREV;
+      fmtver_ = FMTVER;
+      chksum_ = calc_checksum();
+      if (!dump_meta(metapath)) {
+        file_.close();
+        return false;
+      }
+      std::memset(opaque_, 0, sizeof(opaque_));
+      if (autosync_ && !File::synchronize_whole()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+        file_.close();
+        return false;
+      }
+    } else {
+      if (File::status(walpath, &sbuf)) {
+        if (writer_) {
+          file_.truncate(0);
+        } else {
+          File::write_file(magicpath, "", 0);
+          file_.refresh();
+        }
+        DirStream dir;
+        if (dir.open(walpath)) {
+          std::string name;
+          while (dir.read(&name)) {
+            const std::string& srcpath = walpath + File::PATHCHR + name;
+            const std::string& destpath = cpath + File::PATHCHR + name;
+            File::Status sbuf;
+            if (File::status(srcpath, &sbuf)) {
+              if (sbuf.size > 1) {
+                File::rename(srcpath, destpath);
+              } else {
+                if (File::remove(destpath) || !File::status(destpath)) File::remove(srcpath);
+              }
+            }
+          }
+          dir.close();
+          File::remove_directory(walpath);
+          recov_ = true;
+          report(_KCCODELINE_, Logger::WARN, "recovered by the WAL directory");
+        }
+      }
+      if (!load_meta(metapath)) {
+        file_.close();
+        return false;
+      }
+      comp_ = (opts_ & TCOMPRESS) ? embcomp_ : NULL;
+      uint8_t chksum = calc_checksum();
+      if (chksum != chksum_) {
+        set_error(_KCCODELINE_, Error::INVALID, "invalid module checksum");
+        report(_KCCODELINE_, Logger::WARN, "saved=%02X calculated=%02X",
+               (unsigned)chksum_, (unsigned)chksum);
+        file_.close();
+        return false;
+      }
+      if (!load_magic()) {
+        if (!calc_magic(cpath)) {
+          file_.close();
+          return false;
+        }
+        reorg_ = true;
+        if (!writer_ && !(mode & ONOLOCK)) {
+          const std::string& buf = format_magic(count_, size_);
+          if (!File::write_file(magicpath, buf.c_str(), buf.size())) {
+            set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+            file_.close();
+            return false;
+          }
+          if (!file_.refresh()) {
+            set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+            file_.close();
+            return false;
+          }
+        }
+        report(_KCCODELINE_, Logger::WARN, "re-calculated magic data");
+      }
+    }
+    if (writer_ && !file_.truncate(0)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+      file_.close();
+      return false;
+    }
+    if (File::status(walpath)) {
+      remove_files(walpath);
+      File::remove_directory(walpath);
+    }
+    if (File::status(tmppath)) {
+      remove_files(tmppath);
+      File::remove_directory(tmppath);
+    }
+    omode_ = mode;
+    path_ = cpath;
+    tran_ = false;
+    walpath_ = walpath;
+    tmppath_ = tmppath;
+    load_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());
+    bool err = false;
+    if (tran_ && !abort_transaction()) err = true;
+    if (!disable_cursors()) err = true;
+    if (writer_) {
+      if (!dump_magic()) err = true;
+      if (!dump_opaque()) err = true;
+    }
+    if (!file_.close()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+      err = true;
+    }
+    omode_ = 0;
+    trigger_meta(MetaTrigger::CLOSE, "close");
+    return !err;
+  }
+  /**
+   * 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;
+    }
+    rlock_.lock_reader_all();
+    bool err = false;
+    if (!synchronize_impl(hard, proc, checker)) err = true;
+    trigger_meta(MetaTrigger::SYNCHRONIZE, "synchronize");
+    rlock_.unlock_all();
+    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 (!writer_) {
+        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++;
+      }
+    }
+    trhard_ = hard;
+    if (!begin_transaction_impl()) {
+      mlock_.unlock();
+      return false;
+    }
+    tran_ = true;
+    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 (!writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      mlock_.unlock();
+      return false;
+    }
+    if (tran_) {
+      set_error(_KCCODELINE_, Error::LOGIC, "competition avoided");
+      mlock_.unlock();
+      return false;
+    }
+    trhard_ = hard;
+    if (!begin_transaction_impl()) {
+      mlock_.unlock();
+      return false;
+    }
+    tran_ = true;
+    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;
+    }
+    bool err = false;
+    if (commit) {
+      if (!commit_transaction()) err = true;
+    } else {
+      if (!abort_transaction()) err = true;
+    }
+    tran_ = false;
+    trigger_meta(commit ? MetaTrigger::COMMITTRAN : MetaTrigger::ABORTTRAN, "end_transaction");
+    return !err;
+  }
+  /**
+   * 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;
+    }
+    if (!writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    bool err = false;
+    if (!disable_cursors()) err = true;
+    if (tran_) {
+      DirStream dir;
+      if (dir.open(path_)) {
+        std::string name;
+        while (dir.read(&name)) {
+          if (*name.c_str() == *KCDDBMAGICFILE) continue;
+          const std::string& rpath = path_ + File::PATHCHR + name;
+          const std::string& walpath = walpath_ + File::PATHCHR + name;
+          if (File::status(walpath)) {
+            if (!File::remove(rpath)) {
+              set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+              err = true;
+            }
+          } else if (!File::rename(rpath, walpath)) {
+            set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+            err = true;
+          }
+        }
+        if (!dir.close()) {
+          set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+          err = true;
+        }
+      } else {
+        set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+        err = true;
+      }
+    } else {
+      if (!remove_files(path_)) err = true;
+    }
+    recov_ = false;
+    reorg_ = false;
+    flags_ = 0;
+    std::memset(opaque_, 0, sizeof(opaque_));
+    count_ = 0;
+    size_ = 0;
+    trigger_meta(MetaTrigger::CLEAR, "clear");
+    return !err;
+  }
+  /**
+   * 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)TYPEDIR);
+    (*strmap)["realtype"] = strprintf("%u", (unsigned)type_);
+    (*strmap)["path"] = path_;
+    (*strmap)["libver"] = strprintf("%u", libver_);
+    (*strmap)["librev"] = strprintf("%u", librev_);
+    (*strmap)["fmtver"] = strprintf("%u", fmtver_);
+    (*strmap)["chksum"] = strprintf("%u", chksum_);
+    (*strmap)["flags"] = strprintf("%u", flags_);
+    (*strmap)["opts"] = strprintf("%u", opts_);
+    (*strmap)["recovered"] = strprintf("%d", recov_);
+    (*strmap)["reorganized"] = strprintf("%d", reorg_);
+    if (strmap->count("opaque") > 0)
+      (*strmap)["opaque"] = std::string(opaque_, sizeof(opaque_));
+    (*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 optional features.
+   * @param opts the optional features by bitwise-or: DirDB::TCOMPRESS to compress each record.
+   * @return true on success, or false on failure.
+   */
+  bool tune_options(int8_t opts) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    opts_ = opts;
+    return true;
+  }
+  /**
+   * Set the data compressor.
+   * @param comp the data compressor object.
+   * @return true on success, or false on failure.
+   */
+  bool tune_compressor(Compressor* comp) {
+    _assert_(comp);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    embcomp_ = comp;
+    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 (!writer_) {
+      set_error(_KCCODELINE_, Error::NOPERM, "permission denied");
+      return false;
+    }
+    bool err = false;
+    if (!dump_opaque()) err = true;
+    return !err;
+  }
+  /**
+   * Get the status flags.
+   * @note This is a dummy implementation for compatibility.
+   */
+  uint8_t flags() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return 0;
+  }
+ 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);
+  }
+  /**
+   * Set the database type.
+   * @param type the database type.
+   * @return true on success, or false on failure.
+   */
+  bool tune_type(int8_t type) {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, true);
+    if (omode_ != 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "already opened");
+      return false;
+    }
+    type_ = type;
+    return true;
+  }
+  /**
+   * Get the library version.
+   * @return the library version, or 0 on failure.
+   */
+  uint8_t libver() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return libver_;
+  }
+  /**
+   * Get the library revision.
+   * @return the library revision, or 0 on failure.
+   */
+  uint8_t librev() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return librev_;
+  }
+  /**
+   * Get the format version.
+   * @return the format version, or 0 on failure.
+   */
+  uint8_t fmtver() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return fmtver_;
+  }
+  /**
+   * Get the module checksum.
+   * @return the module checksum, or 0 on failure.
+   */
+  uint8_t chksum() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return chksum_;
+  }
+  /**
+   * Get the database type.
+   * @return the database type, or 0 on failure.
+   */
+  uint8_t type() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return type_;
+  }
+  /**
+   * Get the options.
+   * @return the options, or 0 on failure.
+   */
+  uint8_t opts() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return 0;
+    }
+    return opts_;
+  }
+  /**
+   * Get the data compressor.
+   * @return the data compressor, or NULL on failure.
+   */
+  Compressor* comp() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return NULL;
+    }
+    return comp_;
+  }
+  /**
+   * Check whether the database was recovered or not.
+   * @return true if recovered, or false if not.
+   */
+  bool recovered() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    return recov_;
+  }
+  /**
+   * Check whether the database was reorganized or not.
+   * @return true if reorganized, or false if not.
+   */
+  bool reorganized() {
+    _assert_(true);
+    ScopedRWLock lock(&mlock_, false);
+    if (omode_ == 0) {
+      set_error(_KCCODELINE_, Error::INVALID, "not opened");
+      return false;
+    }
+    return reorg_;
+  }
+ private:
+  /**
+   * Set the power of the alignment of record size.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool tune_alignment(int8_t apow) {
+    return true;
+  }
+  /**
+   * Set the power of the capacity of the free block pool.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool tune_fbp(int8_t fpow) {
+    return true;
+  }
+  /**
+   * Set the number of buckets of the hash table.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool tune_buckets(int64_t bnum) {
+    return true;
+  }
+  /**
+   * Set the size of the internal memory-mapped region.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool tune_map(int64_t msiz) {
+    return true;
+  }
+  /**
+   * Set the unit step number of auto defragmentation.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool tune_defrag(int64_t dfunit) {
+    return true;
+  }
+  /**
+   * Perform defragmentation of the file.
+   * @note This is a dummy implementation for compatibility.
+   */
+  bool defrag(int64_t step = 0) {
+    return true;
+  }
+  /**
+   * Get the alignment power.
+   * @note This is a dummy implementation for compatibility.
+   */
+  uint8_t apow() {
+    return 0;
+  }
+  /**
+   * Get the free block pool power.
+   * @note This is a dummy implementation for compatibility.
+   */
+  uint8_t fpow() {
+    return 0;
+  }
+  /**
+   * Get the bucket number.
+   * @note This is a dummy implementation for compatibility.
+   */
+  int64_t bnum() {
+    return 1;
+  }
+  /**
+   * Get the size of the internal memory-mapped region.
+   * @note This is a dummy implementation for compatibility.
+   */
+  int64_t msiz() {
+    return 0;
+  }
+  /**
+   * Get the unit step number of auto defragmentation.
+   * @note This is a dummy implementation for compatibility.
+   */
+  int64_t dfunit() {
+    return 0;
+  }
+ private:
+  /**
+   * Record data.
+   */
+  struct Record {
+    char* rbuf;                          ///< record buffer
+    size_t rsiz;                         ///< record size
+    const char* kbuf;                    ///< key buffer
+    size_t ksiz;                         ///< key size
+    const char* vbuf;                    ///< value buffer
+    size_t vsiz;                         ///< value size
+  };
+  /**
+   * 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
+  };
+  /**
+   * Dump the magic data into the file.
+   * @return true on success, or false on failure.
+   */
+  bool dump_magic() {
+    _assert_(true);
+    const std::string& buf = format_magic(count_, size_);
+    if (!file_.write(0, buf.c_str(), buf.size())) {
+      set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+      return false;
+    }
+    return true;
+  }
+  /**
+   * Format the magic data.
+   * @return the result string.
+   */
+  std::string format_magic(int64_t count, int64_t size) {
+    return strprintf("%lld\n%lld\n%s\n", (long long)count, (long long)size, KCDDBMAGICEOF);
+  }
+  /**
+   * Load the magic data from the file.
+   * @return true on success, or false on failure.
+   */
+  bool load_magic() {
+    _assert_(true);
+    char buf[NUMBUFSIZ*3];
+    size_t len = file_.size();
+    if (len > sizeof(buf) - 1) len = sizeof(buf) - 1;
+    if (!file_.read(0, buf, len)) return false;
+    buf[len] = '\0';
+    char* rp = buf;
+    int64_t count = atoi(rp);
+    char* pv = std::strchr(rp, '\n');
+    if (!pv) return false;
+    rp = pv + 1;
+    int64_t size = atoi(rp);
+    pv = std::strchr(rp, '\n');
+    if (!pv) return false;
+    rp = pv + 1;
+    if (std::strlen(rp) < sizeof(KCDDBMAGICEOF) - 1 ||
+        std::memcmp(rp, KCDDBMAGICEOF, sizeof(KCDDBMAGICEOF) - 1)) return false;
+    flags_ = 0;
+    count_ = count;
+    size_ = size;
+    return true;
+  }
+  /**
+   * Calculate magic data.
+   * @param cpath the path of the database file.
+   * @return true on success, or false on failure.
+   */
+  bool calc_magic(const std::string& cpath) {
+    _assert_(true);
+    count_ = 0;
+    size_ = 0;
+    DirStream dir;
+    if (!dir.open(cpath)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+      return false;
+    }
+    bool err = false;
+    std::string name;
+    while (dir.read(&name)) {
+      if (*name.c_str() == *KCDDBMAGICFILE) continue;
+      const std::string& rpath = cpath + File::PATHCHR + name;
+      File::Status sbuf;
+      if (File::status(rpath, &sbuf)) {
+        if (sbuf.size >= 4) {
+          count_ += 1;
+          size_ += sbuf.size - 4;
+        } else {
+          File::remove(rpath);
+        }
+      } else {
+        set_error(_KCCODELINE_, Error::SYSTEM, "checking the status of a file failed");
+        err = true;
+      }
+    }
+    if (!dir.close()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Calculate the module checksum.
+   * @return the module checksum.
+   */
+  uint8_t calc_checksum() {
+    _assert_(true);
+    const char* kbuf = KCDDBCHKSUMSEED;
+    size_t ksiz = sizeof(KCDDBCHKSUMSEED) - 1;
+    char* zbuf = NULL;
+    size_t zsiz = 0;
+    if (comp_) {
+      zbuf = comp_->compress(kbuf, ksiz, &zsiz);
+      if (!zbuf) return 0;
+      kbuf = zbuf;
+      ksiz = zsiz;
+    }
+    char name[NUMBUFSIZ];
+    uint32_t hash = hashpath(kbuf, ksiz, name);
+    hash += hashmurmur(name, std::strlen(name));
+    delete[] zbuf;
+    return hash;
+  }
+  /**
+   * Dump the meta data into the file.
+   * @param metapath the path of the meta data file.
+   * @return true on success, or false on failure.
+   */
+  bool dump_meta(const std::string& metapath) {
+    _assert_(true);
+    bool err = false;
+    char buf[METABUFSIZ];
+    char* wp = buf;
+    wp += std::sprintf(wp, "%u\n", libver_);
+    wp += std::sprintf(wp, "%u\n", librev_);
+    wp += std::sprintf(wp, "%u\n", fmtver_);
+    wp += std::sprintf(wp, "%u\n", chksum_);
+    wp += std::sprintf(wp, "%u\n", type_);
+    wp += std::sprintf(wp, "%u\n", opts_);
+    wp += std::sprintf(wp, "%s\n", KCDDBMAGICEOF);
+    if (!File::write_file(metapath, buf, wp - buf)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Load the meta data from the file.
+   * @param metapath the path of the meta data file.
+   * @return true on success, or false on failure.
+   */
+  bool load_meta(const std::string& metapath) {
+    _assert_(true);
+    int64_t size;
+    char* buf = File::read_file(metapath, &size, METABUFSIZ);
+    if (!buf) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "reading a file failed");
+      return false;
+    }
+    std::string str(buf, size);
+    delete[] buf;
+    std::vector<std::string> elems;
+    if (strsplit(str, '\n', &elems) < 7 || elems[6] != KCDDBMAGICEOF) {
+      set_error(_KCCODELINE_, Error::BROKEN, "invalid meta data file");
+      return false;
+    }
+    libver_ = atoi(elems[0].c_str());
+    librev_ = atoi(elems[1].c_str());
+    fmtver_ = atoi(elems[2].c_str());
+    chksum_ = atoi(elems[3].c_str());
+    type_ = atoi(elems[4].c_str());
+    opts_ = atoi(elems[5].c_str());
+    return true;
+  }
+  /**
+   * Dump the opaque data into the file.
+   * @return true on success, or false on failure.
+   */
+  bool dump_opaque() {
+    _assert_(true);
+    bool err = false;
+    const std::string& opath = path_ + File::PATHCHR + KCDDBOPAQUEFILE;
+    if (!File::write_file(opath, opaque_, sizeof(opaque_))) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Load the opaque data from the file.
+   * @return true on success, or false on failure.
+   */
+  void load_opaque() {
+    _assert_(true);
+    std::memset(opaque_, 0, sizeof(opaque_));
+    const std::string& opath = path_ + File::PATHCHR + KCDDBOPAQUEFILE;
+    int64_t size;
+    char* buf = File::read_file(opath, &size, sizeof(opaque_));
+    if (buf) {
+      std::memcpy(opaque_, buf, size);
+      delete[] buf;
+    }
+  }
+  /**
+   * Remove inner files.
+   * @param cpath the path of the database file.
+   * @return true on success, or false on failure.
+   */
+  bool remove_files(const std::string& cpath) {
+    _assert_(true);
+    DirStream dir;
+    if (!dir.open(cpath)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+      return false;
+    }
+    bool err = false;
+    std::string name;
+    while (dir.read(&name)) {
+      if (*name.c_str() == *KCDDBMAGICFILE) continue;
+      const std::string& rpath = cpath + File::PATHCHR + name;
+      if (!File::remove(rpath)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+        err = true;
+      }
+    }
+    if (!dir.close()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Read a record.
+   * @param rpath the path of the record.
+   * @param rec the record structure.
+   * @return true on success, or false on failure.
+   */
+  bool read_record(const std::string& rpath, Record* rec) {
+    _assert_(rec);
+    int64_t rsiz;
+    char* rbuf = File::read_file(rpath, &rsiz);
+    if (!rbuf) return false;
+    rec->rsiz = rsiz;
+    if (comp_) {
+      size_t zsiz;
+      char* zbuf = comp_->decompress(rbuf, rsiz, &zsiz);
+      if (!zbuf) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "data decompression failed");
+        delete[] rbuf;
+        return false;
+      }
+      delete[] rbuf;
+      rbuf = zbuf;
+      rsiz = zsiz;
+    }
+    const char* rp = rbuf;
+    if (rsiz < 4 || *(const unsigned char*)rp != RECMAGIC) {
+      set_error(_KCCODELINE_, Error::BROKEN, "invalid magic data of a record");
+      report(_KCCODELINE_, Logger::WARN, "rpath=%s", rpath.c_str());
+      report_binary(_KCCODELINE_, Logger::WARN, "rbuf", rbuf, rsiz);
+      delete[] rbuf;
+      return false;
+    }
+    rp++;
+    uint64_t num;
+    size_t step = readvarnum(rp, rsiz, &num);
+    rp += step;
+    rsiz -= step;
+    size_t ksiz = num;
+    if (rsiz < 2) {
+      report(_KCCODELINE_, Logger::WARN, "rpath=%s", rpath.c_str());
+      delete[] rbuf;
+      return false;
+    }
+    step = readvarnum(rp, rsiz, &num);
+    rp += step;
+    rsiz -= step;
+    size_t vsiz = num;
+    if (rsiz < 1 + (int64_t)ksiz + (int64_t)vsiz ||
+        ((const unsigned char*)rp)[ksiz+vsiz] != RECMAGIC) {
+      set_error(_KCCODELINE_, Error::BROKEN, "too short record");
+      report(_KCCODELINE_, Logger::WARN, "rpath=%s", rpath.c_str());
+      delete[] rbuf;
+      return false;
+    }
+    rec->rbuf = rbuf;
+    rec->kbuf = rp;
+    rec->ksiz = ksiz;
+    rec->vbuf = rp + ksiz;
+    rec->vsiz = vsiz;
+    return true;
+  }
+  /**
+   * Write a record.
+   * @param rpath the path of the record.
+   * @param name the file name of the record.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @param vbuf the pointer to the value region.
+   * @param vsiz the size of the value region.
+   * @param wsp the pointer to the variable into which the size of the written record is
+   * assigned.
+   * @return true on success, or false on failure.
+   */
+  bool write_record(const std::string& rpath, const char* name, const char* kbuf, size_t ksiz,
+                    const char* vbuf, size_t vsiz, size_t* wsp) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ && wsp);
+    bool err = false;
+    char* rbuf = new char[NUMBUFSIZ*2+ksiz+vsiz];
+    char* wp = rbuf;
+    *(wp++) = RECMAGIC;
+    wp += writevarnum(wp, ksiz);
+    wp += writevarnum(wp, vsiz);
+    std::memcpy(wp, kbuf, ksiz);
+    wp += ksiz;
+    std::memcpy(wp, vbuf, vsiz);
+    wp += vsiz;
+    *(wp++) = RECMAGIC;
+    size_t rsiz = wp - rbuf;
+    if (comp_) {
+      size_t zsiz;
+      char* zbuf = comp_->compress(rbuf, rsiz, &zsiz);
+      if (!zbuf) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "data compression failed");
+        delete[] rbuf;
+        *wsp = 0;
+        return false;
+      }
+      delete[] rbuf;
+      rbuf = zbuf;
+      rsiz = zsiz;
+    }
+    if (autotran_ && !tran_) {
+      const std::string& tpath = path_ + File::PATHCHR + KCDDBATRANPREFIX + name;
+      if (!File::write_file(tpath, rbuf, rsiz)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+        err = true;
+      }
+      if (!File::rename(tpath, rpath)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+        err = true;
+        File::remove(tpath);
+      }
+    } else {
+      if (!File::write_file(rpath, rbuf, rsiz)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "writing a file failed");
+        err = true;
+      }
+    }
+    delete[] rbuf;
+    *wsp = rsiz;
+    return !err;
+  }
+  /**
+   * Disable all cursors.
+   * @return true on success, or false on failure.
+   */
+  bool disable_cursors() {
+    _assert_(true);
+    if (curs_.empty()) return true;
+    bool err = false;
+    CursorList::const_iterator cit = curs_.begin();
+    CursorList::const_iterator citend = curs_.end();
+    while (cit != citend) {
+      Cursor* cur = *cit;
+      if (cur->alive_ && !cur->disable()) err = true;
+      ++cit;
+    }
+    return !err;
+  }
+  /**
+   * Escape cursors on a free block.
+   * @param rpath the file path of the record.
+   * @param name the file name of the record.
+   * @return true on success, or false on failure.
+   */
+  bool escape_cursors(const std::string& rpath, const char* name) {
+    bool err = false;
+    if (curs_.empty()) return true;
+    CursorList::const_iterator cit = curs_.begin();
+    CursorList::const_iterator citend = curs_.end();
+    while (cit != citend) {
+      Cursor* cur = *cit;
+      if (cur->alive_ && cur->name_ == name) {
+        do {
+          if (!cur->dir_.read(&cur->name_)) {
+            if (!cur->disable()) err = true;
+            break;
+          }
+        } while (*cur->name_.c_str() == *KCDDBMAGICFILE);
+      }
+      ++cit;
+    }
+    return !err;
+  }
+  /**
+   * 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 name the encoded key.
+   * @return true on success, or false on failure.
+   */
+  bool accept_impl(const char* kbuf, size_t ksiz, Visitor* visitor, const char* name) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && visitor && name);
+    bool err = false;
+    const std::string& rpath = path_ + File::PATHCHR + name;
+    Record rec;
+    if (read_record(rpath, &rec)) {
+      if (rec.ksiz == ksiz || !std::memcmp(rec.kbuf, kbuf, ksiz)) {
+        if (!accept_visit_full(kbuf, ksiz, rec.vbuf, rec.vsiz, rec.rsiz,
+                               visitor, rpath, name)) err = true;
+      } else {
+        set_error(_KCCODELINE_, Error::LOGIC, "collision of the hash values");
+        err = true;
+      }
+      delete[] rec.rbuf;
+    } else {
+      if (!accept_visit_empty(kbuf, ksiz, visitor, rpath, name)) err = true;
+    }
+    return !err;
+  }
+  /**
+   * Accept the visit_full method.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @param vbuf the pointer to the value region.
+   * @param vsiz the size of the value region.
+   * @param osiz the old size of the record.
+   * @param visitor a visitor object.
+   * @param rpath the file path of the record.
+   * @param name the file name of the record.
+   * @return true on success, or false on failure.
+   */
+  bool accept_visit_full(const char* kbuf, size_t ksiz, const char* vbuf, size_t vsiz,
+                         size_t osiz, Visitor *visitor, const std::string& rpath,
+                         const char* name) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && vbuf && vsiz <= MEMMAXSIZ && visitor);
+    bool err = false;
+    size_t rsiz;
+    const char* rbuf = visitor->visit_full(kbuf, ksiz, vbuf, vsiz, &rsiz);
+    if (rbuf == Visitor::REMOVE) {
+      if (tran_) {
+        const std::string& walpath = walpath_ + File::PATHCHR + name;
+        if (File::status(walpath)) {
+          if (!File::remove(rpath)) {
+            set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+            err = true;
+          }
+        } else if (!File::rename(rpath, walpath)) {
+          set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+          err = true;
+        }
+      } else {
+        if (!File::remove(rpath)) {
+          set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+          err = true;
+        }
+      }
+      if (!escape_cursors(rpath, name)) err = true;
+      count_ -= 1;
+      size_ -= osiz;
+      if (autosync_ && !File::synchronize_whole()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+        err = true;
+      }
+    } else if (rbuf != Visitor::NOP) {
+      if (tran_) {
+        const std::string& walpath = walpath_ + File::PATHCHR + name;
+        if (!File::status(walpath) && !File::rename(rpath, walpath)) {
+          set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+          err = true;
+        }
+      }
+      size_t wsiz;
+      if (!write_record(rpath, name, kbuf, ksiz, rbuf, rsiz, &wsiz)) err = true;
+      size_ += (int64_t)wsiz - (int64_t)osiz;
+      if (autosync_ && !File::synchronize_whole()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+        err = true;
+      }
+    }
+    return !err;
+  }
+  /**
+   * Accept the visit_empty method.
+   * @param kbuf the pointer to the key region.
+   * @param ksiz the size of the key region.
+   * @param visitor a visitor object.
+   * @param rpath the file path of the record.
+   * @param name the file name of the record.
+   * @return true on success, or false on failure.
+   */
+  bool accept_visit_empty(const char* kbuf, size_t ksiz,
+                          Visitor *visitor, const std::string& rpath, const char* name) {
+    _assert_(kbuf && ksiz <= MEMMAXSIZ && visitor);
+    bool err = false;
+    size_t rsiz;
+    const char* rbuf = visitor->visit_empty(kbuf, ksiz, &rsiz);
+    if (rbuf != Visitor::NOP && rbuf != Visitor::REMOVE) {
+      if (tran_) {
+        const std::string& walpath = walpath_ + File::PATHCHR + name;
+        if (!File::status(walpath) && !File::write_file(walpath, "", 0)) {
+          set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+          err = true;
+        }
+      }
+      size_t wsiz;
+      if (!write_record(rpath, name, kbuf, ksiz, rbuf, rsiz, &wsiz)) err = true;
+      count_ += 1;
+      size_ += wsiz;
+      if (autosync_ && !File::synchronize_whole()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+        err = true;
+      }
+    }
+    return !err;
+  }
+  /**
+   * Iterate to accept a visitor for each record.
+   * @param visitor a visitor object.
+   * @param checker a progress checker object.
+   * @return true on success, or false on failure.
+   */
+  bool iterate_impl(Visitor* visitor, ProgressChecker* checker) {
+    _assert_(visitor);
+    int64_t allcnt = count_;
+    if (checker && !checker->check("iterate", "beginning", 0, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    DirStream dir;
+    if (!dir.open(path_)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+      return false;
+    }
+    bool err = false;
+    std::string name;
+    int64_t curcnt = 0;
+    while (dir.read(&name)) {
+      if (*name.c_str() == *KCDDBMAGICFILE) continue;
+      const std::string& rpath = path_ + File::PATHCHR + name;
+      Record rec;
+      if (read_record(rpath, &rec)) {
+        if (!accept_visit_full(rec.kbuf, rec.ksiz, rec.vbuf, rec.vsiz, rec.rsiz,
+                               visitor, rpath, name.c_str())) err = true;
+        delete[] rec.rbuf;
+      } else {
+        set_error(_KCCODELINE_, Error::BROKEN, "missing record");
+        err = true;
+      }
+      curcnt++;
+      if (checker && !checker->check("iterate", "processing", curcnt, allcnt)) {
+        set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+        err = true;
+        break;
+      }
+    }
+    if (!dir.close()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+      err = true;
+    }
+    if (checker && !checker->check("iterate", "ending", -1, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Scan each record in parallel.
+   * @param visitor a visitor object.
+   * @param thnum the number of worker threads.
+   * @param checker a progress checker object.
+   * @return true on success, or false on failure.
+   */
+  bool scan_parallel_impl(Visitor *visitor, size_t thnum, ProgressChecker* checker) {
+    _assert_(visitor && thnum <= MEMMAXSIZ);
+    int64_t allcnt = count_;
+    if (checker && !checker->check("scan_parallel", "beginning", -1, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      return false;
+    }
+    DirStream dir;
+    if (!dir.open(path_)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+      return false;
+    }
+    class ThreadImpl : public Thread {
+     public:
+      explicit ThreadImpl() :
+          db_(NULL), visitor_(NULL), checker_(NULL), allcnt_(0),
+          dir_(NULL), itmtx_(NULL), error_() {}
+      void init(DirDB* db, Visitor* visitor, ProgressChecker* checker, int64_t allcnt,
+                DirStream* dir, Mutex* itmtx) {
+        db_ = db;
+        visitor_ = visitor;
+        checker_ = checker;
+        allcnt_ = allcnt;
+        dir_ = dir;
+        itmtx_ = itmtx;
+      }
+      const Error& error() {
+        return error_;
+      }
+     private:
+      void run() {
+        DirDB* db = db_;
+        Visitor* visitor = visitor_;
+        ProgressChecker* checker = checker_;
+        int64_t allcnt = allcnt_;
+        DirStream* dir = dir_;
+        Mutex* itmtx = itmtx_;
+        const std::string& path = db->path_;
+        while (true) {
+          itmtx->lock();
+          std::string name;
+          if (!dir->read(&name)) {
+            itmtx->unlock();
+            break;
+          }
+          itmtx->unlock();
+          if (*name.c_str() == *KCDDBMAGICFILE) continue;
+          const std::string& rpath = path + File::PATHCHR + name;
+          Record rec;
+          if (db->read_record(rpath, &rec)) {
+            size_t vsiz;
+            visitor->visit_full(rec.kbuf, rec.ksiz, rec.vbuf, rec.vsiz, &vsiz);
+            delete[] rec.rbuf;
+          } else {
+            error_ = db->error();
+            break;
+          }
+          if (checker && !checker->check("scan_parallel", "processing", -1, allcnt)) {
+            db->set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+            error_ = db->error();
+            break;
+          }
+        }
+      }
+      DirDB* db_;
+      Visitor* visitor_;
+      ProgressChecker* checker_;
+      int64_t allcnt_;
+      DirStream* dir_;
+      Mutex* itmtx_;
+      Error error_;
+    };
+    bool err = false;
+    Mutex itmtx;
+    ThreadImpl* threads = new ThreadImpl[thnum];
+    for (size_t i = 0; i < thnum; i++) {
+      ThreadImpl* thread = threads + i;
+      thread->init(this, visitor, checker, allcnt, &dir, &itmtx);
+    }
+    for (size_t i = 0; i < thnum; i++) {
+      ThreadImpl* thread = threads + i;
+      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;
+    if (!dir.close()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+      err = true;
+    }
+    if (checker && !checker->check("scan_parallel", "ending", -1, allcnt)) {
+      set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * 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.
+   * @param checker a progress checker object.
+   * @return true on success, or false on failure.
+   */
+  bool synchronize_impl(bool hard, FileProcessor* proc, ProgressChecker* checker) {
+    _assert_(true);
+    bool err = false;
+    if (writer_) {
+      if (checker && !checker->check("synchronize", "dumping the magic data", -1, -1)) {
+        set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+        return false;
+      }
+      if (!dump_magic()) err = true;
+      if (checker && !checker->check("synchronize", "synchronizing the directory", -1, -1)) {
+        set_error(_KCCODELINE_, Error::LOGIC, "checker failed");
+        return false;
+      }
+      if (hard && !File::synchronize_whole()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+        err = true;
+      }
+    }
+    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;
+      }
+    }
+    if (writer_ && !file_.truncate(0)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, file_.error());
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Begin transaction.
+   * @return true on success, or false on failure.
+   */
+  bool begin_transaction_impl() {
+    _assert_(true);
+    if (!File::make_directory(walpath_)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "making a directory failed");
+      return false;
+    }
+    if (trhard_ && !File::synchronize_whole()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+      return false;
+    }
+    trcount_ = count_;
+    trsize_ = size_;
+    return true;
+  }
+  /**
+   * Commit transaction.
+   * @return true on success, or false on failure.
+   */
+  bool commit_transaction() {
+    _assert_(true);
+    bool err = false;
+    if (!File::rename(walpath_, tmppath_)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "renaming a directory failed");
+      err = true;
+    }
+    if (!remove_files(tmppath_)) err = true;
+    if (!File::remove_directory(tmppath_)) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "removing a directory failed");
+      return false;
+    }
+    if (trhard_ && !File::synchronize_whole()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Abort transaction.
+   * @return true on success, or false on failure.
+   */
+  bool abort_transaction() {
+    _assert_(true);
+    bool err = false;
+    if (!disable_cursors()) err = true;
+    DirStream dir;
+    if (dir.open(walpath_)) {
+      std::string name;
+      while (dir.read(&name)) {
+        const std::string& srcpath = walpath_ + File::PATHCHR + name;
+        const std::string& destpath = path_ + File::PATHCHR + name;
+        File::Status sbuf;
+        if (File::status(srcpath, &sbuf)) {
+          if (sbuf.size > 1) {
+            if (!File::rename(srcpath, destpath)) {
+              set_error(_KCCODELINE_, Error::SYSTEM, "renaming a file failed");
+              err = true;
+            }
+          } else {
+            if (File::remove(destpath) || !File::status(destpath)) {
+              if (!File::remove(srcpath)) {
+                set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+                err = true;
+              }
+            } else {
+              set_error(_KCCODELINE_, Error::SYSTEM, "removing a file failed");
+              err = true;
+            }
+          }
+        } else {
+          set_error(_KCCODELINE_, Error::SYSTEM, "checking a file failed");
+          err = true;
+        }
+      }
+      if (!dir.close()) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "closing a directory failed");
+        err = true;
+      }
+      if (!File::remove_directory(walpath_)) {
+        set_error(_KCCODELINE_, Error::SYSTEM, "removing a directory failed");
+        err = true;
+      }
+    } else {
+      set_error(_KCCODELINE_, Error::SYSTEM, "opening a directory failed");
+      err = true;
+    }
+    count_ = trcount_;
+    size_ = trsize_;
+    if (trhard_ && !File::synchronize_whole()) {
+      set_error(_KCCODELINE_, Error::SYSTEM, "synchronizing the file system failed");
+      err = true;
+    }
+    return !err;
+  }
+  /**
+   * Get the size of the database file.
+   * @return the size of the database file in bytes.
+   */
+  int64_t size_impl() {
+    return size_ + count_ * RECUNITSIZ;
+  }
+  /** Dummy constructor to forbid the use. */
+  DirDB(const DirDB&);
+  /** Dummy Operator to forbid the use. */
+  DirDB& operator =(const DirDB&);
+  /** The method lock. */
+  RWLock mlock_;
+  /** The record locks. */
+  SlottedRWLock rlock_;
+  /** 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 flag for writer. */
+  bool writer_;
+  /** The flag for auto transaction. */
+  bool autotran_;
+  /** The flag for auto synchronization. */
+  bool autosync_;
+  /** The flag for recovered. */
+  bool recov_;
+  /** The flag for reorganized. */
+  bool reorg_;
+  /** The file for magic data. */
+  File file_;
+  /** The cursor objects. */
+  CursorList curs_;
+  /** The path of the database file. */
+  std::string path_;
+  /** The library version. */
+  uint8_t libver_;
+  /** The library revision. */
+  uint8_t librev_;
+  /** The format revision. */
+  uint8_t fmtver_;
+  /** The module checksum. */
+  uint8_t chksum_;
+  /** The database type. */
+  uint8_t type_;
+  /** The status flags. */
+  uint8_t flags_;
+  /** The options. */
+  uint8_t opts_;
+  /** The record number. */
+  AtomicInt64 count_;
+  /** The total size of records. */
+  AtomicInt64 size_;
+  /** The opaque data. */
+  char opaque_[OPAQUESIZ];
+  /** The embedded data compressor. */
+  Compressor* embcomp_;
+  /** The data compressor. */
+  Compressor* comp_;
+  /** The compression checksum. */
+  bool tran_;
+  /** The flag whether hard transaction. */
+  bool trhard_;
+  /** The old count before transaction. */
+  int64_t trcount_;
+  /** The old size before transaction. */
+  int64_t trsize_;
+  /** The WAL directory for transaction. */
+  std::string walpath_;
+  /** The temporary directory. */
+  std::string tmppath_;
+};
+
+
+/** An alias of the directory tree database. */
+typedef PlantDB<DirDB, BasicDB::TYPEFOREST> ForestDB;
+
+
+}                                        // common namespace
+
+#endif                                   // duplication check
+
+// END OF FILE