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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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/*******************************************************************************
 * Copyright (c) 2003, 2012 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     James Blackburn (Broadcom Corp.) - Bug 311863 Ordered Lock lost after interrupt
 *******************************************************************************/
package org.eclipse.core.internal.jobs;

import java.util.Objects;

public class Semaphore {
	protected long notifications;
	protected Runnable runnable;
	private static final int NANOS_IN_MS = 1_000_000;

	public Semaphore(Runnable runnable) {
		this.runnable = runnable;
		notifications = 0;
	}

	/**
	 * Attempts to acquire this semaphore.  Returns true if it was successfully acquired,
	 * and false otherwise.
	 */
	public synchronized boolean acquire(long delay) throws InterruptedException {
		if (Thread.interrupted())
			throw new InterruptedException();
		long start = System.nanoTime();
		long timeLeft = delay;
		while (true) {
			if (notifications > 0) {
				notifications--;
				return true;
			}
			if (timeLeft <= 0)
				return false;
			wait(timeLeft);
			timeLeft = ((start - System.nanoTime()) / NANOS_IN_MS) + delay;
		}
	}

	/**
	 * Attempt to acquire the semaphore without waiting.
	 * Returns true if successfully acquired, false otherwise.
	 */
	public synchronized boolean attempt() {
		if (notifications > 0) {
			notifications--;
			return true;
		}
		return false;
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == null) {
			return false;
		}
		if (!(obj instanceof Semaphore)) {
			return false;
		}
		return (runnable == ((Semaphore) obj).runnable);
	}

	@Override
	public int hashCode() {
		return Objects.hashCode(runnable);
	}

	public synchronized void release() {
		notifications++;
		notifyAll();
	}

	// for debug only
	@Override
	public String toString() {
		return "Semaphore(" + runnable + ")"; //$NON-NLS-1$ //$NON-NLS-2$
	}
}