com.googlecode.concurentlocks.CompositeLock Maven / Gradle / Ivy

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/**
 * Copyright 2013 Niall Gallagher
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.googlecode.concurentlocks;

import java.util.*;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * A lock spanning a group of backing locks. When this composite lock is locked, it locks all backing locks, and when
 * unlocked, it unlocks all backing locks. Employs roll back logic to ensure that either all locks are acquired
 * or no locks are acquired. Locks are unlocked in the reverse of the order in which the were acquired.
 * 
 * This class delegates most of its implementation to the {@link Locks} utility class.
 *
 * @author Niall Gallagher
 */
public class CompositeLock implements Lock {

    final Deque locks;

    public CompositeLock(Lock... locks) {
        this(new LinkedList(Arrays.asList(locks)));
    }

    public CompositeLock(Deque locks) {
        this.locks = locks;
    }

    @Override
    public void lock() {
        Locks.lockAll(locks);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        Locks.lockInterruptiblyAll(locks);
    }
    @Override
    public boolean tryLock() {
        return Locks.tryLockAll(locks);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return Locks.tryLockAll(time, unit, locks);
    }

    @Override
    public void unlock() {
        // Unlock in reverse order...
        Locks.unlockAll(new Iterable() {
            @Override
            public Iterator iterator() {
                return locks.descendingIterator();
            }
        });
    }

    @Override
    public Condition newCondition() {
        throw new UnsupportedOperationException("This lock does not support conditions");
    }
}