media/audio/scoped_loop_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_loop_observer.h"
   6
   7 #include "base/bind.h"
   8 #include "base/synchronization/waitable_event.h"
   9
  10 namespace media {
  11
  12 ScopedLoopObserver::ScopedLoopObserver(
  13     const scoped_refptr<base::MessageLoopProxy>& loop)
  14     : loop_(loop) {
  15   ObserveLoopDestruction(true, NULL);
  16 }
  17
  18 ScopedLoopObserver::~ScopedLoopObserver() {
  19   ObserveLoopDestruction(false, NULL);
  20 }
  21
  22 void ScopedLoopObserver::ObserveLoopDestruction(bool enable,
  23                                                 base::WaitableEvent* done) {
  24   // Note: |done| may be NULL.
  25   if (loop_->BelongsToCurrentThread()) {
  26     MessageLoop* loop = MessageLoop::current();
  27     if (enable) {
  28       loop->AddDestructionObserver(this);
  29     } else {
  30       loop->RemoveDestructionObserver(this);
  31     }
  32   } else {
  33     base::WaitableEvent event(false, false);
  34     if (loop_->PostTask(FROM_HERE,
  35             base::Bind(&ScopedLoopObserver::ObserveLoopDestruction,
  36                        base::Unretained(this), enable, &event))) {
  37       event.Wait();
  38     } else {
  39       // The message loop's thread has already terminated, so no need to wait.
  40     }
  41   }
  42
  43   if (done)
  44     done->Signal();
  45 }
  46
  47 }  // namespace media.