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/*
 * Copyright 2010-2012 Luca Garulli (l.garulli--at--orientechnologies.com)
 *
 * 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.
 */
package com.orientechnologies.common.concur.resource;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import com.orientechnologies.common.concur.OTimeoutException;

/**
 * Shared resource. Sub classes can acquire and release shared and exclusive locks.
 * 
 * @author Luca Garulli (l.garulli--at--orientechnologies.com)
 * 
 */
public abstract class OSharedResourceTimeout {
  protected final ReadWriteLock lock = new ReentrantReadWriteLock();
  protected int                 timeout;

  public OSharedResourceTimeout(final int timeout) {
    this.timeout = timeout;
  }

  protected void acquireSharedLock() throws OTimeoutException {
    try {
      if (timeout == 0) {
        lock.readLock().lock();
        return;
      } else if (lock.readLock().tryLock(timeout, TimeUnit.MILLISECONDS))
        // OK
        return;
    } catch (InterruptedException e) {
      Thread.currentThread().interrupt();
    }
    throw new OTimeoutException("Timeout on acquiring shared lock against resource: " + this);
  }

  protected void releaseSharedLock() {
    lock.readLock().unlock();
  }

  protected void acquireExclusiveLock() throws OTimeoutException {
    try {
      if (timeout == 0) {
        lock.writeLock().lock();
        return;
      } else if (lock.writeLock().tryLock(timeout, TimeUnit.MILLISECONDS))
        // OK
        return;
    } catch (InterruptedException e) {
      Thread.currentThread().interrupt();
    }
    throw new OTimeoutException("Timeout on acquiring exclusive lock against resource: " + this);
  }

  protected void releaseExclusiveLock() {
    lock.writeLock().unlock();
  }
}