nucleus/core/kernel/src/main/java/com/sun/enterprise/v3/common/BooleanLatch.java

/*
 * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.enterprise.v3.common;

import java.util.concurrent.locks.AbstractQueuedSynchronizer;

/**
 * Acts like a CountDownLatch except that it only requires a single signal to fire.
 * Because a latch is non-exclusive, it uses the shared acquire and release methods.
 *
 * @author Jerome Dochez
 */
public class BooleanLatch extends AbstractQueuedSynchronizer {
        public boolean isSignalled() { return getState() != 0; }

        public int tryAcquireShared(int ignore) {
            return isSignalled()? 1 : -1;
        }

        public boolean tryReleaseShared(int ignore) {
            setState(1);
            return true;
        }
    }