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//========================================================================
//Copyright 2011-2012 Mort Bay Consulting Pty. Ltd.
//------------------------------------------------------------------------
//All rights reserved. This program and the accompanying materials
//are made available under the terms of the Eclipse Public License v1.0
//and Apache License v2.0 which accompanies this distribution.
//The Eclipse Public License is available at
//http://www.eclipse.org/legal/epl-v10.html
//The Apache License v2.0 is available at
//http://www.opensource.org/licenses/apache2.0.php
//You may elect to redistribute this code under either of these licenses.
//========================================================================
package org.eclipse.jetty.spdy;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.eclipse.jetty.spdy.api.Handler;
/**
* <p>A {@link Promise} is a {@link Future} that allows a result or a failure to be set,
* so that the {@link Future} will be {@link #isDone() done}.</p>
*
* @param <T> the type of the result object
*/
public class Promise<T> implements Handler<T>, Future<T>
{
private final CountDownLatch latch = new CountDownLatch(1);
private boolean cancelled;
private Throwable failure;
private T promise;
@Override
public void completed(T result)
{
this.promise = result;
latch.countDown();
}
@Override
public void failed(T context, Throwable x)
{
this.failure = x;
latch.countDown();
}
@Override
public boolean cancel(boolean mayInterruptIfRunning)
{
cancelled = true;
latch.countDown();
return true;
}
@Override
public boolean isCancelled()
{
return cancelled;
}
@Override
public boolean isDone()
{
return cancelled || latch.getCount() == 0;
}
@Override
public T get() throws InterruptedException, ExecutionException
{
latch.await();
return result();
}
@Override
public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
{
boolean elapsed = !latch.await(timeout, unit);
if (elapsed)
throw new TimeoutException();
return result();
}
private T result() throws ExecutionException
{
if (isCancelled())
throw new CancellationException();
Throwable failure = this.failure;
if (failure != null)
throw new ExecutionException(failure);
return promise;
}
}
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