villa.java

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/*************************************************************************************************
 * Java API of Villa, the advanced 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 Villa, the advanced API of QDBM.
 * This class depends on the native library `jqdbm'.
 */
public class Villa 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;
  //----------------------------------------------------------------
  // comparing modes
  //----------------------------------------------------------------
  /** comparing mode: compare by lexical order */
  public static final int CMPLEX = 0;
  /** comparing mode: compare as long integers */
  public static final int CMPNUM = 1;
  /** comparing mode: compare as decimal strings */
  public static final int CMPDEC = 2;
  /** comparing mode: compare as comparable objects */
  public static final int CMPOBJ = 3;
  //----------------------------------------------------------------
  // 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 DDUP = 2;
  //----------------------------------------------------------------
  // jump modes
  //----------------------------------------------------------------
  /** jump mode: jump mode: step forward */
  public static final int JFORWARD = 0;
  /** jump mode: jump mode: step backward */
  public static final int JBACKWARD = 1;
  //----------------------------------------------------------------
  // static initializer
  //----------------------------------------------------------------
  static {
    try {
      System.loadLibrary("jqdbm");
    } catch(UnsatisfiedLinkError e){
      e.printStackTrace();
    }
    vlinit();
  }
  //----------------------------------------------------------------
  // public static methods
  //----------------------------------------------------------------
  /**
   * Get the version information.
   * @return the string of the version information.
   */
  public static synchronized String version(){
    return vlversion();
  }
  /**
   * 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 vlerrmsg(ecode);
  }
  /**
   * Remove a database file.
   * @param name the name of a database file.
   * @throws VillaException if an error occures.
   */
  public static void remove(String name) throws VillaException {
    synchronized(ADBM.class){
      if(vlremove(name) == 0) throw new VillaException(vlecode());
    }
  }
  //----------------------------------------------------------------
  // instance fields
  //----------------------------------------------------------------
  /** Index of the native table for database handles. */
  private int index;
  /** Whether the handle has the transaction or not. */
  private boolean tran;
  /** Monitor for mutual exclusion control. */
  private Object tranmonitor;
  //----------------------------------------------------------------
  // public or protected methods
  //----------------------------------------------------------------
  /**
   * Get the database handle.
   * @param name the name of a database file.
   * @param omode the connection mode: `Villa.OWRITER' as a writer, `Villa.OREADER' as
   * a reader.  If the mode is `Villa.OWRITER', the following may be added by bitwise or:
   * `Villa.OCREAT', which means it creates a new database if not exist, `Villa.OTRUNC',
   * which means it creates a new database regardless if one exists.  Both of `Villa.OREADER'
   * and `Villa.OWRITER' can be added to by bitwise or: `Villa.ONOLCK', which means it opens a
   * database file without file locking.
   * @param cmode the comparing function: `Villa.CMPLEX' comparing keys in lexical order,
   * `Villa.CMPNUM' comparing keys as numbers of big endian, `Villa.CMPDEC' comparing keys as
   * decimal strings, `Villa.CMPOBJ' comparing keys as serialized objects implementing
   * `java.util.Comparable'.  The comparing function should be kept same in the life of a
   * database.
   * @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 `Villa.ONOLCK' is used, the application is
   * responsible for exclusion control.
   */
  public Villa(String name, int omode, int cmode) throws VillaException {
    synchronized(ADBM.class){
      if((index = vlopen(name, omode, cmode)) == -1) throw new VillaException(vlecode());
    }
    tran = false;
    tranmonitor = new Object();
  }
  /**
   * Get the database handle as a reader.
   * The same as `Villa(name, Villa.OREADER, Villa.CMPLEX)'.
   * @see #Villa(java.lang.String, int, int)
   */
  public Villa(String name) throws VillaException {
    this(name, OREADER, CMPLEX);
  }
  /**
   * 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){
        vlclose(index);
        index = -1;
      }
    } finally {
      super.finalize();
    }
  }
  /**
   * Close the database handle.
   * @throws VillaException 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.
   * If the transaction is activated and not committed, it is aborted.
   */
  public void close() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      int rv = vlclose(index);
      index = -1;
      if(rv == 0) throw new VillaException(vlecode());
    }
  }
  /**
   * 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: `Villa.DOVER',
   * which means the specified value overwrites the existing one, `Villa.DKEEP', which means the
   * existing value is kept, `Villa.DDUP', which means duplication of keys is allowed.
   * @throws VillaException if an error occures or replace is cancelled.
   * @note A duplicated record is stored at the tail of the records of the same key.  The cursor
   * becomes unavailable due to updating database.
   */
  public void put(byte[] key, byte[] val, int dmode) throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      if(vlput(index, key, key.length, val, val.length, dmode) == 0)
        throw new VillaException(vlecode());
    }
  }
  /**
   * Store a record with overwrite.
   * The same as `put(key, val, Villa.DOVER)'.
   * @see #put(byte[], byte[], int)
   */
  public void put(byte[] key, byte[] val) throws VillaException {
    put(key, val, DOVER);
  }
  /**
   * Store a record composed of serializable objects.
   * The same as `put(qdbm.Util.serialize(key), qdbm.Util.serialize(val), dmode)'.
   * @see #put(byte[], byte[], int)
   * @note If serialization is failed, an instance of `VillaException' is thrown.
   */
  public void putobj(Object key, Object val, int dmode) throws VillaException {
    byte[] kbuf = Util.serialize(key);
    byte[] vbuf = Util.serialize(val);
    if(kbuf == null || vbuf == null) throw new VillaException();
    put(kbuf, vbuf, dmode);