/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
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 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
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 */
package com.sun.enterprise.util;

/**
 * Based on Concurrent Programming in Java, Second Edition,
 * by Doug Lea, page 266
 *
 */

public class SemaphoreImpl implements Semaphore {

    private long numPermits_;

    public SemaphoreImpl(long initialPermits) {
        numPermits_ = initialPermits;
    }

    public synchronized void release() {
        numPermits_++;
        notify();
    }

    public void acquire() throws InterruptedException {
        if( Thread.interrupted()) {
            throw new InterruptedException();
        }
        
        synchronized (this) {
            try {
                while( numPermits_ <= 0 ) {
                    wait();
                } 
                numPermits_--;
            } catch( InterruptedException ie) {
                notify();
                throw ie;
            }
        }
    }

}