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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=8 sts=2 et sw=2 tw=80: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #ifndef MediaTaskQueue_h_

 #define MediaTaskQueue_h_

 #include <queue>

 #include "mozilla/RefPtr.h"

 #include "mozilla/Monitor.h"

 #include "nsThreadUtils.h"

 class nsIRunnable;

 namespace mozilla {

 class SharedThreadPool;

 // Abstracts executing runnables in order in a thread pool. The runnables

 // dispatched to the MediaTaskQueue will be executed in the order in which

 // they're received, and are guaranteed to not be executed concurrently.

 // They may be executed on different threads, and a memory barrier is used

 // to make this threadsafe for objects that aren't already threadsafe.

 class MediaTaskQueue MOZ_FINAL {

   ~MediaTaskQueue();

 public:

   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaTaskQueue)

   MediaTaskQueue(TemporaryRef<SharedThreadPool> aPool);

   nsresult Dispatch(TemporaryRef<nsIRunnable> aRunnable);

   // Removes all pending tasks from the task queue, and blocks until

   // the currently running task (if any) finishes.

   void Flush();

   // Blocks until all tasks finish executing, then shuts down the task queue

   // and exits.

   void Shutdown();

   // Blocks until all task finish executing.

   void AwaitIdle();

   bool IsEmpty();

   // Returns true if the current thread is currently running a Runnable in

   // the task queue. This is for debugging/validation purposes only.

   bool IsCurrentThreadIn();

 private:

   // Blocks until all task finish executing. Called internally by methods

   // that need to wait until the task queue is idle.

   // mQueueMonitor must be held.

   void AwaitIdleLocked();

   RefPtr<SharedThreadPool> mPool;

   // Monitor that protects the queue and mIsRunning;

   Monitor mQueueMonitor;

   // Queue of tasks to run.

   std::queue<RefPtr<nsIRunnable>> mTasks;

   // The thread currently running the task queue. We store a reference

   // to this so that IsCurrentThreadIn() can tell if the current thread

   // is the thread currently running in the task queue.

   RefPtr<nsIThread> mRunningThread;

   // True if we've dispatched an event to the pool to execute events from

   // the queue.

   bool mIsRunning;

   // True if we've started our shutdown process.

   bool mIsShutdown;

   class Runner : public nsRunnable {

   public:

     Runner(MediaTaskQueue* aQueue)

       : mQueue(aQueue)

     {

     }

     NS_METHOD Run() MOZ_OVERRIDE;

   private:

     RefPtr<MediaTaskQueue> mQueue;

   };

 };

 } // namespace mozilla

 #endif // MediaTaskQueue_h_