com.mastfrog.util.thread.MultiCountdownLatch Maven / Gradle / Ivy

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/*
 * The MIT License
 *
 * Copyright 2017 Tim Boudreau.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.mastfrog.util.thread;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;

/**
 * Like a CountDownLatch but with the ability to release multiple permits
 * in one call.
 *
 * @author Tim Boudreau
 */
public class MultiCountdownLatch {

    private static final class Sync extends AbstractQueuedSynchronizer {

        Sync(int count) {
            setState(count);
        }

        int getCount() {
            return getState();
        }

        void reset(int count) {
            setState(count);
        }

        @Override
        protected int tryAcquireShared(int acquires) {
            return (getState() == 0) ? 1 : -1;
        }

        @Override
        protected boolean tryReleaseShared(int releases) {
            // Decrement count; signal when transition to zero
            for (;;) {
                int c = getState();
                if (c == 0) {
                    return false;
                }
                int nextc = c - releases;
                if (compareAndSetState(c, nextc)) {
                    return nextc == 0;
                }
            }
        }
    }

    private final Sync sync;

    public MultiCountdownLatch(int count) {
        this.sync = new Sync(count);
    }

    public void await() throws InterruptedException {
        sync.acquireSharedInterruptibly(1);
    }

    public boolean await(long timeout, TimeUnit unit)
            throws InterruptedException {
        return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
    }

    public void countDown() {
        countDown(1);
    }

    public void countDown(int qty) {
        sync.releaseShared(qty);
    }

    public long getCount() {
        return sync.getCount();
    }
}