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	/*
	* Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.nio.ch;

	import java.nio.channels.*;
	import java.util.concurrent.*;
	import java.io.IOException;

	/**
	* A Future for a pending I/O operation. A PendingFuture allows for the
	* attachment of an additional arbitrary context object and a timer task.
	*/

	final class PendingFuture<V,A> implements Future<V> {
	private static final CancellationException CANCELLED =
	new CancellationException();

	private final AsynchronousChannel channel;
	private final CompletionHandler<V,? super A> handler;
	private final A attachment;

	// true if result (or exception) is available
	private volatile boolean haveResult;
	private volatile V result;
	private volatile Throwable exc;

	// latch for waiting (created lazily if needed)
	private CountDownLatch latch;

	// optional timer task that is cancelled when result becomes available
	private Future<?> timeoutTask;

	// optional context object
	private volatile Object context;

	PendingFuture(AsynchronousChannel channel,
	CompletionHandler<V,? super A> handler,
	A attachment,
	Object context)
	{
	this.channel = channel;
	this.handler = handler;
	this.attachment = attachment;
	this.context = context;
	}

	PendingFuture(AsynchronousChannel channel,
	CompletionHandler<V,? super A> handler,
	A attachment)
	{
	this.channel = channel;
	this.handler = handler;
	this.attachment = attachment;
	}

	PendingFuture(AsynchronousChannel channel) {
	this(channel, null, null);
	}

	PendingFuture(AsynchronousChannel channel, Object context) {
	this(channel, null, null, context);
	}

	AsynchronousChannel channel() {
	return channel;
	}

	CompletionHandler<V,? super A> handler() {
	return handler;
	}

	A attachment() {
	return attachment;
	}

	void setContext(Object context) {
	this.context = context;
	}

	Object getContext() {
	return context;
	}

	void setTimeoutTask(Future<?> task) {
	synchronized (this) {
	if (haveResult) {
	task.cancel(false);
	} else {
	this.timeoutTask = task;
	}
	}
	}

	// creates latch if required; return true if caller needs to wait
	private boolean prepareForWait() {
	synchronized (this) {
	if (haveResult) {
	return false;
	} else {
	if (latch == null)
	latch = new CountDownLatch(1);
	return true;
	}
	}
	}

	/**
	* Sets the result, or a no-op if the result or exception is already set.
	*/
	void setResult(V res) {
	synchronized (this) {
	if (haveResult)
	return;
	result = res;
	haveResult = true;
	if (timeoutTask != null)
	timeoutTask.cancel(false);
	if (latch != null)
	latch.countDown();
	}
	}

	/**
	* Sets the result, or a no-op if the result or exception is already set.
	*/
	void setFailure(Throwable x) {
	if (!(x instanceof IOException) && !(x instanceof SecurityException))
	x = new IOException(x);
	synchronized (this) {
	if (haveResult)
	return;
	exc = x;
	haveResult = true;
	if (timeoutTask != null)
	timeoutTask.cancel(false);
	if (latch != null)
	latch.countDown();
	}
	}

	/**
	* Sets the result
	*/
	void setResult(V res, Throwable x) {
	if (x == null) {
	setResult(res);
	} else {
	setFailure(x);
	}
	}

	@Override
	public V get() throws ExecutionException, InterruptedException {
	if (!haveResult) {
	boolean needToWait = prepareForWait();
	if (needToWait)
	latch.await();
	}
	if (exc != null) {
	if (exc == CANCELLED)
	throw new CancellationException();
	throw new ExecutionException(exc);
	}
	return result;
	}

	@Override
	public V get(long timeout, TimeUnit unit)
	throws ExecutionException, InterruptedException, TimeoutException
	{
	if (!haveResult) {
	boolean needToWait = prepareForWait();
	if (needToWait)
	if (!latch.await(timeout, unit)) throw new TimeoutException();
	}
	if (exc != null) {
	if (exc == CANCELLED)
	throw new CancellationException();
	throw new ExecutionException(exc);
	}
	return result;
	}

	Throwable exception() {
	return (exc != CANCELLED) ? exc : null;
	}

	V value() {
	return result;
	}

	@Override
	public boolean isCancelled() {
	return (exc == CANCELLED);
	}

	@Override
	public boolean isDone() {
	return haveResult;
	}

	@Override
	public boolean cancel(boolean mayInterruptIfRunning) {
	synchronized (this) {
	if (haveResult)
	return false; // already completed

	// notify channel
	if (channel() instanceof Cancellable)
	((Cancellable)channel()).onCancel(this);

	// set result and cancel timer
	exc = CANCELLED;
	haveResult = true;
	if (timeoutTask != null)
	timeoutTask.cancel(false);
	}

	// close channel if forceful cancel
	if (mayInterruptIfRunning) {
	try {
	channel().close();
	} catch (IOException ignore) { }
	}

	// release waiters
	if (latch != null)
	latch.countDown();
	return true;
	}
	}

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