<?php
/*
 * Gallery - a web based photo album viewer and editor
 * Copyright (C) 2000-2008 Bharat Mediratta
 *
 * 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 2 of the License, or (at
 * your option) 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA  02110-1301, USA.
 */

GalleryCoreApi::requireOnce('modules/core/classes/GalleryLockSystem.class');

/**
 * Database backed locking.  This is less efficient than filesystem based locking,
 * but is more reliable and portable.
 *
 * @package GalleryCore
 * @subpackage Classes
 * @author Bharat Mediratta <bharat@menalto.com>
 * @version $Revision: 17580 $
 */
class DatabaseLockSystem extends GalleryLockSystem {

    /**
     * @see GalleryLockSystem::_acquireLock
     */
    function _acquireLock($ids, $timeout, $lockType) {
	global $gallery;
	$storage =& $gallery->getStorage();

	if ($lockType == LOCK_WRITE) {
	    list ($ret, $lock) = $storage->acquireWriteLock($ids, $timeout);
	    if ($ret) {
		return array($ret, null);
	    }
	} else {
	    list ($ret, $lock) = $storage->acquireReadLock($ids, $timeout);
	    if ($ret) {
		return array($ret, null);
	    }
	}

	$this->_locks[$lock['lockId']] = $lock;
	return array(null, $lock['lockId']);
    }

    /**
     * @see GalleryLockSystem::_releaseLocksNow
     */
    function _releaseLocksNow($locks) {
	global $gallery;
	$storage =& $gallery->getStorage();

	$ret = $storage->releaseLocks(array_keys($locks));
	if ($ret) {
	    return $ret;
	}

	return null;
    }

    /**
     * @see GalleryLockSystem:_removeObjectsFromLock
     */
    function _removeObjectsFromLock(&$lock, $ids) {
	global $gallery;
	$storage =& $gallery->getStorage();

	$ret = $storage->removeIdsFromLock($lock, $ids);
	if ($ret) {
	    return $ret;
	}
	foreach ($ids as $id) {
	    unset($lock['ids'][$id]);
	}
	return null;
    }

    /**
     * @see GalleryLockSystem:_moveObjectsBetweenLocks
     */
    function _moveObjectsBetweenLocks($relock, $newLockId) {
	global $gallery;
	$storage =& $gallery->getStorage();

	$ret = $storage->moveIdsBetweenLocks(
		$relock, $newLockId, $this->_locks[$newLockId]['type']);
	if ($ret) {
	    return $ret;
	}
	$ret = parent::_moveObjectsBetweenLocks($relock, $newLockId);
	if ($ret) {
	    return $ret;
	}
	return null;
    }

    /**
     * @see GalleryLockSystem::_newLockId
     */
    function _newLockId() {
	global $gallery;
	$storage =& $gallery->getStorage();

	list ($ret, $lockId) = $storage->newLockId();
	if ($ret) {
	    return array($ret, null);
	}
	return array(null, $lockId);
    }

    /**
     * @see GalleryLockSystem::refreshLocks
     */
    function refreshLocks($freshUntil) {
	global $gallery;

	if (!empty($this->_locks)) {
	    $storage =& $gallery->getStorage();
	    $ret = $storage->refreshLocks(array_keys($this->_locks), $freshUntil);
	    if ($ret) {
		return $ret;
	    }
	}

	return null;
    }
}
?>