alfresco-community-repo/source/java/org/alfresco/filesys/locking/FileLock.java

/*
 * Copyright (C) 2005 Alfresco, Inc.
 *
 * 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.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */
package org.alfresco.filesys.locking;

/**
 * File Lock Class
 * <p>
 * Contains the details of a single file lock.
 */
public class FileLock
{

    // Constants

    public static final long LockWholeFile = 0xFFFFFFFFFFFFFFFFL;

    // Start lock offset and length

    private long m_offset;
    private long m_length;

    // Owner process id

    private int m_pid;

    /**
     * Class constructor
     * 
     * @param offset long
     * @param len long
     * @param pid int
     */
    public FileLock(long offset, long len, int pid)
    {
        setOffset(offset);
        setLength(len);
        setProcessId(pid);
    }

    /**
     * Get the starting lock offset
     * 
     * @return long Starting lock offset.
     */
    public final long getOffset()
    {
        return m_offset;
    }

    /**
     * Set the starting lock offset.
     * 
     * @param long Starting lock offset
     */
    public final void setOffset(long offset)
    {
        m_offset = offset;
    }

    /**
     * Get the locked section length
     * 
     * @return long Locked section length
     */
    public final long getLength()
    {
        return m_length;
    }

    /**
     * Set the locked section length
     * 
     * @param long Locked section length
     */
    public final void setLength(long len)
    {
        if (len < 0)
            m_length = LockWholeFile;
        else
            m_length = len;
    }

    /**
     * Get the owner process id for the lock
     * 
     * @return int
     */
    public final int getProcessId()
    {
        return m_pid;
    }

    /**
     * Deterine if the lock is locking the whole file
     * 
     * @return boolean
     */
    public final boolean isWholeFile()
    {
        return m_length == LockWholeFile ? true : false;
    }

    /**
     * Set the process id of the owner of this lock
     * 
     * @param pid int
     */
    public final void setProcessId(int pid)
    {
        m_pid = pid;
    }

    /**
     * Check if the specified locks byte range overlaps this locks byte range.
     * 
     * @param lock FileLock
     */
    public final boolean hasOverlap(FileLock lock)
    {
        return hasOverlap(lock.getOffset(), lock.getLength());
    }

    /**
     * Check if the specified locks byte range overlaps this locks byte range.
     * 
     * @param offset long
     * @param len long
     */
    public final boolean hasOverlap(long offset, long len)
    {

        //  Check if the lock is for the whole file
        
        if ( isWholeFile())
            return true;
            
        //  Check if the locks overlap

        long endOff = getOffset() + ( getLength() - 1);
        
        if (getOffset() < offset && endOff < offset)
            return false;

        endOff = offset + ( len - 1);
        
        if ( getOffset() > endOff)
            return false;

        //  Locks overlap

        return true;
    }

    /**
     * Return the lock details as a string
     * 
     * @return String
     */
    public String toString()
    {
        StringBuffer str = new StringBuffer();

        str.append("[PID=");
        str.append(getProcessId());
        str.append(",Offset=");
        str.append(getOffset());
        str.append(",Len=");
        str.append(getLength());
        str.append("]");

        return str.toString();
    }
}