media/audio/scoped_task_runner_observer.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/audio/scoped_task_runner_observer.h"
   6
   7 #include "base/bind.h"
   8 #include "base/synchronization/waitable_event.h"
   9
  10 namespace media {
  11
  12 ScopedTaskRunnerObserver::ScopedTaskRunnerObserver(
  13     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
  14     : task_runner_(task_runner) {
  15   ObserveLoopDestruction(true, NULL);
  16 }
  17
  18 ScopedTaskRunnerObserver::~ScopedTaskRunnerObserver() {
  19   ObserveLoopDestruction(false, NULL);
  20 }
  21
  22 void ScopedTaskRunnerObserver::ObserveLoopDestruction(
  23     bool enable,
  24     base::WaitableEvent* done) {
  25   // Note: |done| may be NULL.
  26   if (task_runner_->BelongsToCurrentThread()) {
  27     base::MessageLoop* loop = base::MessageLoop::current();
  28     if (enable) {
  29       loop->AddDestructionObserver(this);
  30     } else {
  31       loop->RemoveDestructionObserver(this);
  32     }
  33   } else {
  34     base::WaitableEvent event(false, false);
  35     if (task_runner_->PostTask(FROM_HERE,
  36             base::Bind(&ScopedTaskRunnerObserver::ObserveLoopDestruction,
  37                        base::Unretained(this), enable, &event))) {
  38       event.Wait();
  39     } else {
  40       // The message loop's thread has already terminated, so no need to wait.
  41     }
  42   }
  43
  44   if (done)
  45     done->Signal();
  46 }
  47
  48 }  // namespace media.