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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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;
  
  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 boolean tryAcquire(int acquires) {
          if (compareAndSetState(0, 1)) {
              owner = Thread.currentThread();
              return true;
          }
          return false;
      }
  
      @Override
      protected boolean tryRelease(int releases) {
          if (Thread.currentThread() != owner) {
              throw new IllegalMonitorStateException();
          }
          owner = null;
          setState(0);
          return true;
      }
  
      @Override
      protected boolean isHeldExclusively() {
          return getState() != 0 && owner == Thread.currentThread();
      }
  }