/*
 * $Source: /usr/cvsroot/melati/poem/src/main/java/org/melati/poem/transaction/TransactionedSerial.java,v $
 * $Revision: 1.15 $
 *
 * Copyright (C) 2000 William Chesters
 *
 * Part of Melati (http://melati.org), a framework for the rapid
 * development of clean, maintainable web applications.
 *
 * Melati is free software; Permission is granted to copy, distribute
 * and/or modify this software under the terms either:
 *
 * a) the GNU General Public License as published by the Free Software
 *    Foundation; either version 2 of the License, or (at your option)
 *    any later version,
 *
 *    or
 *
 * b) any version of the Melati Software License, as published
 *    at http://melati.org
 *
 * You should have received a copy of the GNU General Public License and
 * the Melati Software License along with this program;
 * if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
 * GNU General Public License and visit http://melati.org to obtain the
 * Melati Software License.
 *
 * Feel free to contact the Developers of Melati (http://melati.org),
 * if you would like to work out a different arrangement than the options
 * outlined here.  It is our intention to allow Melati to be used by as
 * wide an audience as possible.
 *
 * 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.
 *
 * Contact details for copyright holder:
 *
 *     William Chesters <williamc At paneris.org>
 *     http://paneris.org/~williamc
 *     Obrechtstraat 114, 2517VX Den Haag, The Netherlands
 */

package org.melati.poem.transaction;

/**
 * A serial id of an object which is incremented each time 
 * that object is loaded or locked.
 */
public class TransactionedSerial extends Transactioned {

  private long serial = 0L;

  /**
   * Constructor.
   * @param transactionPool the TransactionPool this is relevant to
   */
  public TransactionedSerial(TransactionPool transactionPool) {
    super(transactionPool);
  }

  /**
   * On load increment the Serial for this object.
   * 
   * {@inheritDoc}
   * @see org.melati.poem.transaction.Transactioned#load(org.melati.poem.transaction.Transaction)
   */
  protected void load(Transaction transaction) {
    ++serial;
  }

  /**
   * Return the inheritted validity flag.
   * 
   * {@inheritDoc}
   * @see org.melati.poem.transaction.Transactioned#upToDate(org.melati.poem.transaction.Transaction)
   */
  protected boolean upToDate(Transaction transaction) {
    return valid;
  }

  /**
   * This implementation does nothing.
   * 
   * {@inheritDoc}
   * @see org.melati.poem.transaction.Transactioned#writeDown(org.melati.poem.transaction.Transaction)
   */
  protected void writeDown(Transaction transaction) {
  }

  // 
  // ---------------------
  //  TransactionedSerial
  // ---------------------
  // 

  /**
   * Readlock and return the serial for the given Transaction.
   * @param transaction the Transaction
   * @return the serial for the given Transaction
   */
  public long current(Transaction transaction) {
    readLock(transaction);
    return serial;
  }

  /**
   * Write lock and increment.
   * @param transaction the Transaction
   */
  public void increment(Transaction transaction) {
    writeLock(transaction);
    increment_unlocked();
  }

  /**
   * Increment.
   */
  public void increment_unlocked() {
    ++serial;
  }
}
