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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.security.AccessController;
	import sun.security.action.GetIntegerAction;
	import jdk.internal.misc.InnocuousThread;

	/**
	* Defines static methods to invoke a completion handler or arbitrary task.
	*/

	class Invoker {
	private Invoker() { }

	// maximum number of completion handlers that may be invoked on the current
	// thread before it re-directs invocations to the thread pool. This helps
	// avoid stack overflow and lessens the risk of starvation.
	private static final int maxHandlerInvokeCount = AccessController.doPrivileged(
	new GetIntegerAction("sun.nio.ch.maxCompletionHandlersOnStack", 16));

	// Per-thread object with reference to channel group and a counter for
	// the number of completion handlers invoked. This should be reset to 0
	// when all completion handlers have completed.
	static class GroupAndInvokeCount {
	private final AsynchronousChannelGroupImpl group;
	private int handlerInvokeCount;
	GroupAndInvokeCount(AsynchronousChannelGroupImpl group) {
	this.group = group;
	}
	AsynchronousChannelGroupImpl group() {
	return group;
	}
	int invokeCount() {
	return handlerInvokeCount;
	}
	void setInvokeCount(int value) {
	handlerInvokeCount = value;
	}
	void resetInvokeCount() {
	handlerInvokeCount = 0;
	}
	void incrementInvokeCount() {
	handlerInvokeCount++;
	}
	}
	private static final ThreadLocal<GroupAndInvokeCount> myGroupAndInvokeCount =
	new ThreadLocal<GroupAndInvokeCount>() {
	@Override protected GroupAndInvokeCount initialValue() {
	return null;
	}
	};

	/**
	* Binds this thread to the given group
	*/
	static void bindToGroup(AsynchronousChannelGroupImpl group) {
	myGroupAndInvokeCount.set(new GroupAndInvokeCount(group));
	}

	/**
	* Returns the GroupAndInvokeCount object for this thread.
	*/
	static GroupAndInvokeCount getGroupAndInvokeCount() {
	return myGroupAndInvokeCount.get();
	}

	/**
	* Returns true if the current thread is in a channel group's thread pool
	*/
	static boolean isBoundToAnyGroup() {
	return myGroupAndInvokeCount.get() != null;
	}

	/**
	* Returns true if the current thread is in the given channel's thread
	* pool and we haven't exceeded the maximum number of handler frames on
	* the stack.
	*/
	static boolean mayInvokeDirect(GroupAndInvokeCount myGroupAndInvokeCount,
	AsynchronousChannelGroupImpl group)
	{
	if ((myGroupAndInvokeCount != null) &&
	(myGroupAndInvokeCount.group() == group) &&
	(myGroupAndInvokeCount.invokeCount() < maxHandlerInvokeCount))
	{
	return true;
	}
	return false;
	}

	/**
	* Invoke handler without checking the thread identity or number of handlers
	* on the thread stack.
	*/
	static <V,A> void invokeUnchecked(CompletionHandler<V,? super A> handler,
	A attachment,
	V value,
	Throwable exc)
	{
	if (exc == null) {
	handler.completed(value, attachment);
	} else {
	handler.failed(exc, attachment);
	}

	// clear interrupt
	Thread.interrupted();

	// clear thread locals when in default thread pool
	if (System.getSecurityManager() != null) {
	Thread me = Thread.currentThread();
	if (me instanceof InnocuousThread) {
	GroupAndInvokeCount thisGroupAndInvokeCount = myGroupAndInvokeCount.get();
	((InnocuousThread)me).eraseThreadLocals();
	if (thisGroupAndInvokeCount != null) {
	myGroupAndInvokeCount.set(thisGroupAndInvokeCount);
	}
	}
	}
	}

	/**
	* Invoke handler assuming thread identity already checked
	*/
	static <V,A> void invokeDirect(GroupAndInvokeCount myGroupAndInvokeCount,
	CompletionHandler<V,? super A> handler,
	A attachment,
	V result,
	Throwable exc)
	{
	myGroupAndInvokeCount.incrementInvokeCount();
	Invoker.invokeUnchecked(handler, attachment, result, exc);
	}

	/**
	* Invokes the handler. If the current thread is in the channel group's
	* thread pool then the handler is invoked directly, otherwise it is
	* invoked indirectly.
	*/
	static <V,A> void invoke(AsynchronousChannel channel,
	CompletionHandler<V,? super A> handler,
	A attachment,
	V result,
	Throwable exc)
	{
	boolean invokeDirect = false;
	boolean identityOkay = false;
	GroupAndInvokeCount thisGroupAndInvokeCount = myGroupAndInvokeCount.get();
	if (thisGroupAndInvokeCount != null) {
	if ((thisGroupAndInvokeCount.group() == ((Groupable)channel).group()))
	identityOkay = true;
	if (identityOkay &&
	(thisGroupAndInvokeCount.invokeCount() < maxHandlerInvokeCount))
	{
	// group match
	invokeDirect = true;
	}
	}
	if (invokeDirect) {
	invokeDirect(thisGroupAndInvokeCount, handler, attachment, result, exc);
	} else {
	try {
	invokeIndirectly(channel, handler, attachment, result, exc);
	} catch (RejectedExecutionException ree) {
	// channel group shutdown; fallback to invoking directly
	// if the current thread has the right identity.
	if (identityOkay) {
	invokeDirect(thisGroupAndInvokeCount,
	handler, attachment, result, exc);
	} else {
	throw new ShutdownChannelGroupException();
	}
	}
	}
	}

	/**
	* Invokes the handler indirectly via the channel group's thread pool.
	*/
	static <V,A> void invokeIndirectly(AsynchronousChannel channel,
	final CompletionHandler<V,? super A> handler,
	final A attachment,
	final V result,
	final Throwable exc)
	{
	try {
	((Groupable)channel).group().executeOnPooledThread(new Runnable() {
	public void run() {
	GroupAndInvokeCount thisGroupAndInvokeCount =
	myGroupAndInvokeCount.get();
	if (thisGroupAndInvokeCount != null)
	thisGroupAndInvokeCount.setInvokeCount(1);
	invokeUnchecked(handler, attachment, result, exc);
	}
	});
	} catch (RejectedExecutionException ree) {
	throw new ShutdownChannelGroupException();
	}
	}

	/**
	* Invokes the handler "indirectly" in the given Executor
	*/
	static <V,A> void invokeIndirectly(final CompletionHandler<V,? super A> handler,
	final A attachment,
	final V value,
	final Throwable exc,
	Executor executor)
	{
	try {
	executor.execute(new Runnable() {
	public void run() {
	invokeUnchecked(handler, attachment, value, exc);
	}
	});
	} catch (RejectedExecutionException ree) {
	throw new ShutdownChannelGroupException();
	}
	}

	/**
	* Invokes the given task on the thread pool associated with the given
	* channel. If the current thread is in the thread pool then the task is
	* invoked directly.
	*/
	static void invokeOnThreadInThreadPool(Groupable channel,
	Runnable task)
	{
	boolean invokeDirect;
	GroupAndInvokeCount thisGroupAndInvokeCount = myGroupAndInvokeCount.get();
	AsynchronousChannelGroupImpl targetGroup = channel.group();
	if (thisGroupAndInvokeCount == null) {
	invokeDirect = false;
	} else {
	invokeDirect = (thisGroupAndInvokeCount.group == targetGroup);
	}
	try {
	if (invokeDirect) {
	task.run();
	} else {
	targetGroup.executeOnPooledThread(task);
	}
	} catch (RejectedExecutionException ree) {
	throw new ShutdownChannelGroupException();
	}
	}

	/**
	* Invoke handler with completed result. This method does not check the
	* thread identity or the number of handlers on the thread stack.
	*/
	static <V,A> void invokeUnchecked(PendingFuture<V,A> future) {
	assert future.isDone();
	CompletionHandler<V,? super A> handler = future.handler();
	if (handler != null) {
	invokeUnchecked(handler,
	future.attachment(),
	future.value(),
	future.exception());
	}
	}

	/**
	* Invoke handler with completed result. If the current thread is in the
	* channel group's thread pool then the handler is invoked directly,
	* otherwise it is invoked indirectly.
	*/
	static <V,A> void invoke(PendingFuture<V,A> future) {
	assert future.isDone();
	CompletionHandler<V,? super A> handler = future.handler();
	if (handler != null) {
	invoke(future.channel(),
	handler,
	future.attachment(),
	future.value(),
	future.exception());
	}
	}

	/**
	* Invoke handler with completed result. The handler is invoked indirectly,
	* via the channel group's thread pool.
	*/
	static <V,A> void invokeIndirectly(PendingFuture<V,A> future) {
	assert future.isDone();
	CompletionHandler<V,? super A> handler = future.handler();
	if (handler != null) {
	invokeIndirectly(future.channel(),
	handler,
	future.attachment(),
	future.value(),
	future.exception());
	}
	}
	}

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