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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.internal.util.concurrent;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

import junit.framework.TestCase;

/**
 * @author dsmith
 *
 */
public class ReentrantSemaphoreJUnitTest extends TestCase {
  
  public void test() throws Throwable {
    final ReentrantSemaphore sem = new ReentrantSemaphore(2);
    
    sem.acquire();
    sem.acquire();
    assertEquals(1, sem.availablePermits());
    sem.release();
    sem.release();
    assertEquals(2, sem.availablePermits());
    
    final CountDownLatch testDone = new CountDownLatch(1);
    final CountDownLatch semsAquired = new CountDownLatch(2);
    
    final AtomicReference failure = new AtomicReference();
    
    Thread t1 = new Thread() {
      public void run() {
        try { 
          sem.acquire();
          sem.acquire();
          sem.acquire();
          semsAquired.countDown();
          testDone.await();
          sem.release();
          sem.release();
          sem.release();
        } catch(Exception e) {
          failure.compareAndSet(null, e);
        }
      }
    };
    t1.start();
    
    Thread t2 = new Thread() {
      public void run() {
        try {
          sem.acquire();
          sem.acquire();
          sem.acquire();
          semsAquired.countDown();
          testDone.await();
          sem.release();
          sem.release();
          sem.release();
        } catch(Exception e) {
          failure.compareAndSet(null, e);
        }
      }
    };
    t2.start();
    
    Thread t3 = new Thread() {
      public void run() {
        try {
          semsAquired.await();
          assertEquals(0, sem.availablePermits());
          assertFalse(sem.tryAcquire(1, TimeUnit.SECONDS));
        } catch(Exception e) {
          failure.compareAndSet(null, e);
        }
      }
    };
    t3.start();
    
    t3.join();
    testDone.countDown();
    t2.join();
    t1.join();
    
    if(failure.get() != null) {
      throw failure.get();
    }
    
    assertEquals(2, sem.availablePermits());
  }

}