depot.java

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/*************************************************************************************************
 * Java API of Depot, the basic API of QDBM
 *                                                      Copyright (C) 2000-2003 Mikio Hirabayashi
 * This file is part of QDBM, Quick Database Manager.
 * QDBM is free software; you can redistribute it and/or modify it under the terms of the GNU
 * Lesser General Public License as published by the Free Software Foundation; either version
 * 2.1 of the License or any later version.  QDBM 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 Lesser General Public License for more
 * details.
 * You should have received a copy of the GNU Lesser General Public License along with QDBM; if
 * not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 * 02111-1307 USA.
 *************************************************************************************************/


package qdbm;



/**
 * The Java API of Depot, the basic API of QDBM.
 * This class depends on the native library `jqdbm'.
 */
public class Depot implements ADBM {
  //----------------------------------------------------------------
  // error codes
  //----------------------------------------------------------------
  /** error code: no error */
  public static final int ENOERR = 0;
  /** error code: with fatal error */
  public static final int EFATAL = 1;
  /** error code: invalid mode */
  public static final int EMODE = 2;
  /** error code: broken database file */
  public static final int EBROKEN = 3;
  /** error code: existing record */
  public static final int EKEEP = 4;
  /** error code: no item found */
  public static final int ENOITEM = 5;
  /** error code: memory allocation error */
  public static final int EALLOC = 6;
  /** error code: memory mapping error */
  public static final int EMAP = 7;
  /** error code: open error */
  public static final int EOPEN = 8;
  /** error code: close error */
  public static final int ECLOSE = 9;
  /** error code: trunc error */
  public static final int ETRUNC = 10;
  /** error code: sync error */
  public static final int ESYNC = 11;
  /** error code: stat error */
  public static final int ESTAT = 12;
  /** error code: seek error */
  public static final int ESEEK = 13;
  /** error code: read error */
  public static final int EREAD = 14;
  /** error code: write error */
  public static final int EWRITE = 15;
  /** error code: lock error */
  public static final int ELOCK = 16;
  /** error code: unlink error */
  public static final int EUNLINK = 17;
  /** error code: mkdir error */
  public static final int EMKDIR = 18;
  /** error code: rmdir error */
  public static final int ERMDIR = 19;
  /** error code: miscellaneous error */
  public static final int EMISC = 20;
  //----------------------------------------------------------------
  // open modes
  //----------------------------------------------------------------
  /** open mode: open as a reader */
  public static final int OREADER = 1 << 0;
  /** open mode: open as a writer */
  public static final int OWRITER = 1 << 1;
  /** open mode: writer creating */
  public static final int OCREAT = 1 << 2;
  /** open mode: writer truncating */
  public static final int OTRUNC = 1 << 3;
  /** open mode: open without locking */
  public static final int ONOLCK = 1 << 4;
  //----------------------------------------------------------------
  // write modes
  //----------------------------------------------------------------
  /** write mode: overwrite the existing value */
  public static final int DOVER = 0;
  /** write mode: keep the existing value */
  public static final int DKEEP = 1;
  /** write mode: concatenate values */
  public static final int DCAT = 2;
  //----------------------------------------------------------------
  // static initializer
  //----------------------------------------------------------------
  static {
    try {
      System.loadLibrary("jqdbm");
    } catch(UnsatisfiedLinkError e){
      e.printStackTrace();
    }
    dpinit();
  }
  //----------------------------------------------------------------
  // public static methods
  //----------------------------------------------------------------
  /**
   * Get the version information.
   * @return the string of the version information.
   */
  public static synchronized String version(){
    return dpversion();
  }
  /**
   * Get an error message.
   * @param ecode an error code.
   * @return the message string of the error code.
   */
  public static synchronized String errmsg(int ecode){
    return dperrmsg(ecode);
  }
  /**
   * Remove a database file.
   * @param name the name of a database file.
   * @throws DepotException if an error occures.
   */
  public static void remove(String name) throws DepotException {
    synchronized(ADBM.class){
      if(dpremove(name) == 0) throw new DepotException(dpecode());
    }
  }
  //----------------------------------------------------------------
  // instance fields
  //----------------------------------------------------------------
  /** Index of the native table for database handles. */
  private int index;
  //----------------------------------------------------------------
  // public or protected methods
  //----------------------------------------------------------------
  /**
   * Get the database handle.
   * @param name the name of a database file.
   * @param omode the connection mode: `Depot.OWRITER' as a writer, `Depot.OREADER' as
   * a reader.  If the mode is `Depot.OWRITER', the following may be added by bitwise or:
   * `Depot.OCREAT', which means it creates a new database if not exist, `Depot.OTRUNC',
   * which means it creates a new database regardless if one exists.  Both of `Depot.OREADER'
   * and `Depot.OWRITER' can be added to by bitwise or: `Depot.ONOLCK', which means it opens a
   * database file without file locking.
   * @param bnum the number of elements of the bucket array.  If it is not more than 0,
   * the default value is specified.  The size of a bucket array is determined on creating,
   * and can not be changed except for by optimization of the database.  Suggested size of a
   * bucket array is about from 0.5 to 4 times of the number of all records to store.
   * @throws DepotException if an error occures.
   * @note While connecting as a writer, an exclusive lock is invoked to the database file.
   * While connecting as a reader, a shared lock is invoked to the database file.  The thread
   * blocks until the lock is achieved.  If `Depot.ONOLCK' is used, the application is
   * responsible for exclusion control.
   */
  public Depot(String name, int omode, int bnum) throws DepotException {
    synchronized(ADBM.class){
      if((index = dpopen(name, omode, bnum)) == -1) throw new DepotException(dpecode());
    }
  }
  /**
   * Get the database handle as a reader.
   * The same as `Depot(name, Depot.OREADER, -1)'.
   * @see #Depot(java.lang.String, int, int)
   */
  public Depot(String name) throws DepotException {
    this(name, OREADER, -1);
  }
  /**
   * Release the resources.
   * @note If the database handle is not closed yet, it is closed.  Every database should be
   * closed explicitly.  Do not cast the duty on the gerbage collection.
   */
  protected void finalize() throws Throwable {
    try {
      if(index < 0) return;
      synchronized(ADBM.class){
        dpclose(index);
        index = -1;
      }
    } finally {
      super.finalize();
    }
  }
  /**
   * Close the database handle.
   * @throws DepotException if an error occures.
   * @note Updating a database is assured to be written when the handle is closed.  If a
   * writer opens a database but does not close it appropriately, the database will be broken.
   */
  public void close() throws DepotException {
    if(index < 0) throw new DepotException();
    synchronized(ADBM.class){
      int rv = dpclose(index);
      index = -1;
      if(rv == 0) throw new DepotException(dpecode());
    }
  }
  /**
   * Store a record.
   * @param key a byte array of a key.
   * @param val a byte array of a value.
   * @param dmode behavior when the key overlaps, by the following values: `Depot.DOVER',
   * which means the specified value overwrites the existing one, `Depot.DKEEP', which means the
   * existing value is kept, `Depot.DCAT', which means the specified value is concatenated at
   * the end of the existing value.
   * @throws DepotException if an error occures or replace is cancelled.
   */
  public void put(byte[] key, byte[] val, int dmode) throws DepotException {
    if(index < 0) throw new DepotException();
    synchronized(ADBM.class){
      if(dpput(index, key, key.length, val, val.length, dmode) == 0)
        throw new DepotException(dpecode());
    }
  }
  /**
   * Store a record with overwrite.
   * The same as `put(key, val, Depot.DOVER)'.
   * @see #put(byte[], byte[], int)
   */
  public void put(byte[] key, byte[] val) throws DepotException {
    put(key, val, DOVER);
  }
  /**
   * Delete a record.
   * @param key a byte array of a key.
   * @throws DepotException if an error occures or no record corresponds.
   */
  public void out(byte[] key) throws DepotException {
    if(index < 0) throw new DepotException();
    synchronized(ADBM.class){
      if(dpout(index, key, key.length) == 0) throw new DepotException(dpecode());
    }
  }
  /**
   * Retrieve a record.
   * @param key a byte array of a key.
   * @param start the array index of the beginning of the value to be read.
   * @param max the max size to read with.  If it is negative, the size is unlimited.
   * @return a byte array of the value of the corresponding record.
   * @throws DepotException if an error occures, no record corresponds, or the size of the value
   * of the corresponding record is less than the index specified by the parameter `start'.
   */
  public byte[] get(byte[] key, int start, int max) throws DepotException {
    if(index < 0) throw new DepotException();
    synchronized(ADBM.class){
      byte[] val = dpget(index, key, key.length, start, max);
      if(val == null) throw new DepotException(dpecode());
      return val;
    }
  }
  /**
   * Retrieve whole value of a record.
   * The same as `get(key, 0, -1)'.
   * @see #get(byte[], int, int)
   */
  public byte[] get(byte[] key) throws DepotException {
    return get(key, 0, -1);