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 */
019 package org.crsh.util;
020
021 import java.util.concurrent.*;
022 import java.util.concurrent.locks.Lock;
023 import java.util.concurrent.locks.ReentrantLock;
024
025 public 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 }