FileLockingStore.java

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors 
 * as indicated by the @author tags. 
 * See the copyright.txt in the distribution for a
 * full listing of individual contributors. 
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License, v. 2.1.
 * This program is distributed in the hope that it will be useful, but WITHOUT A 
 * 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,
 * v.2.1 along with this distribution; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
 * MA  02110-1301, USA.
 * 
 * (C) 2005-2006,
 * @author JBoss Inc.
 */
/*
 * Copyright (C) 1998, 1999, 2000,
 *
 * Arjuna Solutions Limited,
 * Newcastle upon Tyne,
 * Tyne and Wear,
 * UK.  
 *
 * $Id: FileLockingStore.java 2342 2006-03-30 13:06:17Z  $
 */

package com.arjuna.ats.internal.arjuna.objectstore;

import java.io.File;

import com.arjuna.ats.arjuna.common.ObjectStoreEnvironmentBean;
import com.arjuna.ats.arjuna.common.Uid;
import com.arjuna.ats.arjuna.exceptions.ObjectStoreException;
import com.arjuna.ats.arjuna.logging.tsLogger;
import com.arjuna.ats.arjuna.state.InputObjectState;
import com.arjuna.ats.arjuna.state.OutputObjectState;
import com.arjuna.ats.arjuna.utils.FileLock;

/**
 * An refinement of the basic FileSystemStore which provides file-level locking.
 * 
 * @author Mark Little (mark@arjuna.com)
 * @version $Id: FileLockingStore.java 2342 2006-03-30 13:06:17Z $
 * @since JTS 1.0.
 */

public abstract class FileLockingStore extends FileSystemStore
{

    protected abstract InputObjectState read_state (Uid u, String tn, int s)
            throws ObjectStoreException;

    protected abstract boolean remove_state (Uid u, String tn, int s)
            throws ObjectStoreException;

    protected abstract boolean write_state (Uid u, String tn,
            OutputObjectState buff, int s) throws ObjectStoreException;

    public FileLockingStore(ObjectStoreEnvironmentBean objectStoreEnvironmentBean) throws ObjectStoreException
    {
        super(objectStoreEnvironmentBean);
    }

    /**
     * Lock files as we would do on a Unix system.
     */

    protected synchronized boolean lock (File fd, int lmode, boolean create)
    {
        if (tsLogger.logger.isTraceEnabled()) {
            tsLogger.logger.trace("FileLockingStore.lock(" + fd + ", " + FileLock.modeString(lmode) + ", " + create + ")");
        }

        FileLock fileLock = new FileLock(fd);

        return fileLock.lock(lmode, create);
    }

    protected synchronized boolean unlock (File fd)
    {
        if (tsLogger.logger.isTraceEnabled()) {
            tsLogger.logger.trace("FileLockingStore.unlock(" + fd + ")");
        }

        FileLock fileLock = new FileLock(fd);

        return fileLock.unlock();
    }

}