/*
    * Copyright 2010 Red Hat, Inc.
    *
    * Red Hat licenses this file to you 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.
   */
  package org.jboss.netty.util.internal;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.AbstractQueuedSynchronizer;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.Lock;
  
  /**
   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
   * @version $Rev: 2115 $, $Date: 2010-02-01 15:21:49 +0900 (Mon, 01 Feb 2010) $
   */
  public final class NonReentrantLock extends AbstractQueuedSynchronizer
                               implements Lock {
  
      private static final long serialVersionUID = -833780837233068610L;
  
      private Thread owner;
  
      public void lock() {
          acquire(1);
      }
  
      public void lockInterruptibly() throws InterruptedException {
          acquireInterruptibly(1);
      }
  
      public boolean tryLock() {
          return tryAcquire(1);
      }
  
      public boolean tryLock(long time, TimeUnit unit)
              throws InterruptedException {
          return tryAcquireNanos(1, unit.toNanos(time));
      }
  
      public void unlock() {
          release(1);
      }
  
      public boolean isHeldByCurrentThread() {
          return isHeldExclusively();
      }
  
      public Condition newCondition() {
          return new ConditionObject();
      }
  
      @Override
      protected final boolean tryAcquire(int acquires) {
          if (compareAndSetState(0, 1)) {
              owner = Thread.currentThread();
              return true;
          }
          return false;
      }
  
      @Override
      protected final boolean tryRelease(int releases) {
          if (Thread.currentThread() != owner) {
              throw new IllegalMonitorStateException();
          }
          owner = null;
          setState(0);
          return true;
      }
  
      @Override
      protected final boolean isHeldExclusively() {
          return getState() != 0 && owner == Thread.currentThread();
      }
  }