/*

 * Copyright 2008-2009 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.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;

/**

 * 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.

     */

    @SuppressWarnings("unchecked")

    static <V,A> void invokeUnchecked(CompletionHandler<V,? super A> handler,

                                      AbstractFuture<V,A> result)

    {

        if (handler != null && !result.isCancelled()) {

            Throwable exc = result.exception();

            if (exc == null) {

                handler.completed(result.value(), result.attachment());

            } else {

                handler.failed(exc, result.attachment());

            }

            // clear interrupt

            Thread.interrupted();

        }

    }

    /**

     * Invoke handler after incrementing the invoke count.

     */

    static <V,A> void invokeDirect(GroupAndInvokeCount myGroupAndInvokeCount,

                                   CompletionHandler<V,? super A> handler,

                                   AbstractFuture<V,A> result)

    {

        myGroupAndInvokeCount.incrementInvokeCount();

        invokeUnchecked(handler, result);

    }

    /**

     * 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(CompletionHandler<V,? super A> handler,

                             AbstractFuture<V,A> result)

    {

        if (handler != null) {

            boolean invokeDirect = false;

            boolean identityOkay = false;

            GroupAndInvokeCount thisGroupAndInvokeCount = myGroupAndInvokeCount.get();

            if (thisGroupAndInvokeCount != null) {

                AsynchronousChannel channel = result.channel();

                if ((thisGroupAndInvokeCount.group() == ((Groupable)channel).group()))

                    identityOkay = true;

                if (identityOkay &&

                    (thisGroupAndInvokeCount.invokeCount() < maxHandlerInvokeCount))

                {

                    // group match

                    invokeDirect = true;

                }

            }

            if (invokeDirect) {

                thisGroupAndInvokeCount.incrementInvokeCount();

                invokeUnchecked(handler, result);

            } else {

                try {

                    invokeIndirectly(handler, result);

                } catch (RejectedExecutionException ree) {

                    // channel group shutdown; fallback to invoking directly

                    // if the current thread has the right identity.

                    if (identityOkay) {

                        invokeUnchecked(handler, result);

                    } else {

                        throw new ShutdownChannelGroupException();

                    }

                }

            }

        }

    }

    /**

     * Invokes the handler "indirectly" in the channel group's thread pool.

     */

    static <V,A> void invokeIndirectly(final CompletionHandler<V,? super A> handler,

                                       final AbstractFuture<V,A> result)

    {

        if (handler != null) {

            AsynchronousChannel channel = result.channel();

            try {

                ((Groupable)channel).group().executeOnPooledThread(new Runnable() {

                    public void run() {

                        GroupAndInvokeCount thisGroupAndInvokeCount =

                            myGroupAndInvokeCount.get();

                        if (thisGroupAndInvokeCount != null)

                            thisGroupAndInvokeCount.setInvokeCount(1);

                        invokeUnchecked(handler, result);

                    }

                });

            } 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 AbstractFuture<V,A> result,

                                       Executor executor)

    {

        if (handler != null) {

            try {

                executor.execute(new Runnable() {

                    public void run() {

                        invokeUnchecked(handler, result);

                    }

                });

            } 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();

        }

    }

}