/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwt.internal.Lock;

import tango.core.Thread;
import tango.core.sync.Mutex;
import tango.core.sync.Condition;
import tango.core.Exception;

import dwt.dwthelper.utils;

/**
 * Instance of this represent a recursive monitor.
 */
public class Lock
{
    int count, waitCount;
    Thread owner;
    Mutex mutex;
    Condition cond;

    public this ()
    {
        mutex = new Mutex;
        cond = new Condition(mutex);
    }

    /**
     * Locks the monitor and returns the lock count. If
     * the lock is owned by another thread, wait until
     * the lock is released.
     *
     * @return the lock count
     */
    public int lock ()
    {
        synchronized (mutex)
        {
            Thread current = Thread.getThis();
            if (owner !is current)
            {
                waitCount++;
                while (count > 0)
                {
                    try
                    {
                        cond.wait();
                    }
                    catch (SyncException e)
                    {
                    /* Wait forever, just like synchronized blocks */
                    }
                }
                --waitCount;
                owner = current;
            }
            return ++count;
        }
    }

    /**
     * Unlocks the monitor. If the current thread is not
     * the monitor owner, do nothing.
     */
    public void unlock ()
    {
        synchronized (mutex)
        {
            Thread current = Thread.getThis();
            if (owner is current)
            {
                if (--count is 0)
                {
                    owner = null;
                    if (waitCount > 0)
                        cond.notifyAll();
                }
            }
        }
    }
}