villa.java

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   */
  public int fsiz() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      int rv = vlfsiz(index);
      if(rv == -1) throw new VillaException(vlecode());
      return rv;
    }
  }
  /**
   * Get the number of the leaf nodes of B+ tree.
   * @return the number of the leaf nodes.
   * @throws VillaException if an error occures.
   */
  public int lnum() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      int rv = vllnum(index);
      if(rv == -1) throw new VillaException(vlecode());
      return rv;
    }
  }
  /**
   * Get the number of the non-leaf nodes of B+ tree.
   * @return the number of the non-leaf nodes.
   * @throws VillaException if an error occures.
   */
  public int nnum() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      int rv = vlnnum(index);
      if(rv == -1) throw new VillaException(vlecode());
      return rv;
    }
  }
  /**
   * Get the number of the records stored in a database.
   * @return the number of the records stored in the database.
   * @throws VillaException if an error occures.
   */
  public int rnum() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      int rv = vlrnum(index);
      if(rv == -1) throw new VillaException(vlecode());
      return rv;
    }
  }
  /**
   * Check whether the database handle is a writer or not.
   * @return true if the handle is a writer, false if not.
   * @throws VillaException if an error occures.
   */
  public boolean writable() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      return vlwritable(index) == 0 ? false : true;
    }
  }
  /**
   * Check whether the database has a fatal error or not.
   * @return true if the database has a fatal error, false if not.
   * @throws VillaException if an error occures.
   */
  public boolean fatalerror() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      return vlfatalerror(index) == 0 ? false : true;
    }
  }
  /**
   * Begin the transaction.
   * @throws VillaException if an error occures.
   * @note If a thread is already in the transaction, the other threads block until the prius
   * is out of the transaction.  Only one transaction can be activated with a database handle
   * at the same time.
   */
  public void tranbegin() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(tranmonitor){
      while(tran){
        try {
          tranmonitor.wait();
        } catch(InterruptedException e){
          e.printStackTrace();
          throw new VillaException();
        }
      }
      tran = true;
    }
    synchronized(ADBM.class){
      if(vltranbegin(index) == 0){
        tran = false;
        throw new VillaException(vlecode());
      }
    }
  }
  /**
   * Commit the transaction.
   * @throws VillaException if an error occures.
   * @note Updating a database in the transaction is fixed when it is committed successfully.
   * Any other thread except for the one which began the transaction should not call this method.
   */
  public void trancommit() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      if(vltrancommit(index) == 0){
        synchronized(tranmonitor){
          tran = false;
          tranmonitor.notify();
        }
        throw new VillaException(vlecode());
      }
    }
    synchronized(tranmonitor){
      tran = false;
      tranmonitor.notify();
    }
  }
  /**
   * Abort the transaction.
   * @throws VillaException if an error occures.
   * @note Updating a database in the transaction is discarded when it is aborted.  The state
   * of the database is rollbacked to before transaction.  Any other thread except for the one
   * which began the transaction should not call this method.
   */
  public void tranabort() throws VillaException {
    if(index < 0) throw new VillaException();
    synchronized(ADBM.class){
      if(vltranabort(index) == 0){
        synchronized(tranmonitor){
          tran = false;
          tranmonitor.notify();
        }
        throw new VillaException(vlecode());
      }
    }
    synchronized(tranmonitor){
      tran = false;
      tranmonitor.notify();
    }
  }
  /**
   * Store a record.
   * @param key a byte array of a key.
   * @param val a byte array of a value.
   * @param replace whether the existing value is to be overwritten or not.
   * @throws VillaException if an error occures or replace is cancelled.
   */
  public void store(byte[] key, byte[] val, boolean replace) throws VillaException {
    put(key, val, replace ? DOVER : DKEEP);
  }
  /**
   * Delete a record.
   * @param key a byte array of a key.
   * @throws VillaException if an error occures or no record corresponds.
   */
  public void delete(byte[] key) throws VillaException {
    out(key);
  }
  /**
   * Fetch a record.
   * @param key a byte array of a key.
   * @return a byte array of the value of the corresponding record.
   * @throws VillaException if an error occures or no record corresponds.
   */
  public byte[] fetch(byte[] key) throws VillaException {
    return get(key);
  }
  /**
   * Get the first key.
   * @return a byte array of the key of the first record.
   * @throws VillaException if an error occures or no record corresponds.
   */
  public byte[] firstkey() throws VillaException {
    curfirst();
    return curkey();
  }
  /**
   * Get the next key.
   * @return a byte array of the key of the next record.
   * @throws VillaException if an error occures or no record corresponds.
   */
  public byte[] nextkey() throws VillaException {
    curnext();
    return curkey();
  }
  /**
   * Check whether a fatal error occured or not.
   * @return true if the database has a fatal error, false if not.
   * @throws VillaException if an error occures.
   */
  public boolean error() throws VillaException {
    return fatalerror();
  }
  //----------------------------------------------------------------
  // private methods
  //----------------------------------------------------------------
  /**
   * Compare keys of two records as serialized objects implementing `java.util.Comparable'.
   * @param abuf serialized data of one object.
   * @param bbuf serialized data of the other object.
   * @return positive if the former is big, negative if the latter is big, 0 if both are
   * equivalent.
   */
  private static final int objcompare(byte[] abuf, byte[] bbuf){
    Object a = Util.deserialize(abuf);
    Object b = Util.deserialize(bbuf);
    if(a != null && b == null) return 1;
    if(a == null && b != null) return -1;
    if(a == null && b == null) return 0;
    try {
      return ((Comparable)a).compareTo(b);
    } catch(ClassCastException e){
      return 0;
    }
  }
  //----------------------------------------------------------------
  // native methods
  //----------------------------------------------------------------
  private static synchronized final native void vlinit();
  private static synchronized final native String vlversion();
  private static synchronized final native int vlecode();
  private static synchronized final native String vlerrmsg(int ecode);

  private static synchronized final native int vlopen(String name, int omode, int cmode);
  private static synchronized final native int vlclose(int index);
  private static synchronized final native int vlput(int index, byte[] key, int ksiz,
                                                     byte[] val, int vsiz, int dmode);
  private static synchronized final native int vlout(int index, byte[] key, int ksiz);
  private static synchronized final native byte[] vlget(int index, byte[] key, int ksiz);
  private static synchronized final native int vlvnum(int index, byte[] key, int ksiz);
  private static synchronized final native int vlcurfirst(int index);
  private static synchronized final native int vlcurlast(int index);
  private static synchronized final native int vlcurprev(int index);
  private static synchronized final native int vlcurnext(int index);
  private static synchronized final native int vlcurjump(int index, byte[] key, int ksiz,
                                                         int jmode);
  private static synchronized final native byte[] vlcurkey(int index);
  private static synchronized final native byte[] vlcurval(int index);
  private static synchronized final native void vlsettuning(int index, int lrecmax, int nidxmax,
                                                            int lcnum, int ncnum);
  private static synchronized final native int vlsync(int index);
  private static synchronized final native int vloptimize(int index);
  private static synchronized final native String vlname(int index);
  private static synchronized final native int vlfsiz(int index);
  private static synchronized final native int vllnum(int index);
  private static synchronized final native int vlnnum(int index);
  private static synchronized final native int vlrnum(int index);
  private static synchronized final native int vlwritable(int index);
  private static synchronized final native int vlfatalerror(int index);
  private static synchronized final native int vltranbegin(int index);
  private static synchronized final native int vltrancommit(int index);
  private static synchronized final native int vltranabort(int index);
  private static synchronized final native int vlremove(String name);
}



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