ReadWriteLock.java

/*
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation, either version 3 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
 * Lesser General Public License along with this program. If not, see
 * <http://www.gnu.org/licenses/>
 */
package net.slimevoid.library.data;

import net.minecraft.world.World;

/**
 * A standard Multiple Readers / Single Writer lock.
 *
 * @author ali4z
 */
public class ReadWriteLock {
    private int readers = 0;
    private int writers = 0;
    private int writeReq = 0;

    /**
     * Register a read lock position.<br>
     * Waits if no position is available.
     *
     * @throws InterruptedException if any thread interrupted the current thread before or while
     *                              the current thread was waiting for a notification. The
     *                              interrupted status of the current thread is cleared when this
     *                              exception is thrown.
     */
    public synchronized void readLock(World world) throws InterruptedException {
        while (writers > 0 || writeReq > 0) {
            LoggerSlimevoidLib.getInstance("ReadWriteLock").write(world.isRemote,
                    "readLock() - waiting",
                    LoggerSlimevoidLib.LogLevel.INFO);
            wait();
        }
        readers++;
    }

    /**
     * Release a read lock position.
     */
    public synchronized void readUnlock() {
        readers--;
        notifyAll();
    }

    /**
     * Register a write lock position.<br>
     * Waits if no position is available.
     *
     * @throws InterruptedException if any thread interrupted the current thread before or while
     *                              the current thread was waiting for a notification. The
     *                              interrupted status of the current thread is cleared when this
     *                              exception is thrown.
     */
    public synchronized void writeLock(World world) throws InterruptedException {
        writeReq++;
        while (readers > 0 || writers > 0) {
            LoggerSlimevoidLib.getInstance("ReadWriteLock").write(world.isRemote,
                    "writeLock() - waiting",
                    LoggerSlimevoidLib.LogLevel.INFO);
            wait();
        }
        writers++;
        writeReq--;
    }

    /**
     * Release a write lock position.
     */
    public synchronized void writeUnlock() {
        writers--;
        notifyAll();
    }
}