001/*
002 * Copyright (C) 2012 eXo Platform SAS.
003 *
004 * This is free software; you can redistribute it and/or modify it
005 * under the terms of the GNU Lesser General Public License as
006 * published by the Free Software Foundation; either version 2.1 of
007 * the License, or (at your option) any later version.
008 *
009 * This software is distributed in the hope that it will be useful,
010 * but WITHOUT ANY WARRANTY; without even the implied warranty of
011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 * Lesser General Public License for more details.
013 *
014 * You should have received a copy of the GNU Lesser General Public
015 * License along with this software; if not, write to the Free
016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018 */
019package org.crsh.util;
020
021import java.util.concurrent.*;
022import java.util.concurrent.locks.Lock;
023import java.util.concurrent.locks.ReentrantLock;
024
025public class LatchedFuture<V> implements Future<V> {
026
027  /** . */
028  private V value = null;
029
030  /** . */
031  private final CountDownLatch latch = new CountDownLatch(1);
032
033  /** . */
034  private final Lock lock = new ReentrantLock();
035
036  /** The optional listener. */
037  private FutureListener<V> listener;
038
039  public LatchedFuture() {
040  }
041
042  public LatchedFuture(V value) {
043    set(value);
044  }
045
046  public boolean cancel(boolean b) {
047    return false;
048  }
049
050  public boolean isCancelled() {
051    return false; 
052  }
053
054  public boolean isDone() {
055    return latch.getCount() == 0;
056  }
057
058  public V get() throws InterruptedException, ExecutionException {
059    latch.await();
060    return value;
061  }
062
063  public V get(long l, TimeUnit timeUnit) throws InterruptedException, ExecutionException, TimeoutException {
064    latch.await(l, timeUnit);
065    return value;
066  }
067
068  public void addListener(FutureListener<V> listener) {
069    if (listener == null) {
070      throw new NullPointerException();
071    }
072    lock.lock();
073    try {
074
075      // Avoid double init
076      if (this.listener != null) {
077        throw new IllegalStateException();
078      }
079
080      // Set state
081      this.listener = listener;
082
083      //
084      if (latch.getCount() == 0) {
085        listener.completed(value);
086      }
087
088      //
089    } finally {
090      lock.unlock();
091    }
092  }
093
094  public void set(V value) {
095    lock.lock();
096    try {
097      if (latch.getCount() > 0) {
098        this.value = value;
099        latch.countDown();
100        if (listener != null) {
101          listener.completed(value);
102        }
103      } else {
104        throw new IllegalStateException();
105      }
106    } finally {
107      lock.unlock();
108    }
109  }
110}