Moved the fake input stream's processing onto the audio worker thread.

media/audio/fake_audio_consumer.cc

-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "media/audio/fake_audio_consumer.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/cancelable_callback.h"
-#include "base/location.h"
-#include "base/logging.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/single_thread_task_runner.h"
-#include "base/synchronization/lock.h"
-#include "base/threading/thread_checker.h"
-#include "base/time/time.h"
-#include "media/audio/audio_parameters.h"
-#include "media/base/audio_bus.h"
-
-namespace media {
-
-class FakeAudioConsumer::Worker
-    : public base::RefCountedThreadSafe<FakeAudioConsumer::Worker> {
- public:
-  Worker(const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner,
-         const AudioParameters& params);
-
-  bool IsStopped();
-  void Start(const ReadCB& read_cb);
-  void Stop();
-
- private:
-  friend class base::RefCountedThreadSafe<Worker>;
-  ~Worker();
-
-  // Initialize and start regular calls to DoRead() on the worker thread.
-  void DoStart();
-
-  // Cancel any delayed callbacks to DoRead() in the worker loop's queue.
-  void DoCancel();
-
-  // Task that regularly calls |read_cb_| according to the playback rate as
-  // determined by the audio parameters given during construction.  Runs on
-  // the worker loop.
-  void DoRead();
-
-  const scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner_;
-  const scoped_ptr<AudioBus> audio_bus_;
-  const base::TimeDelta buffer_duration_;
-
-  base::Lock read_cb_lock_;  // Held while mutating or running |read_cb_|.
-  ReadCB read_cb_;
-  base::TimeTicks next_read_time_;
-
-  // Used to cancel any delayed tasks still inside the worker loop's queue.
-  base::CancelableClosure read_task_cb_;
-
-  base::ThreadChecker thread_checker_;
-
-  DISALLOW_COPY_AND_ASSIGN(Worker);
-};
-
-FakeAudioConsumer::FakeAudioConsumer(
-    const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner,
-    const AudioParameters& params)
-    : worker_(new Worker(worker_task_runner, params)) {
-}
-
-FakeAudioConsumer::~FakeAudioConsumer() {
-  DCHECK(worker_->IsStopped());
-}
-
-void FakeAudioConsumer::Start(const ReadCB& read_cb) {
-  DCHECK(worker_->IsStopped());
-  worker_->Start(read_cb);
-}
-
-void FakeAudioConsumer::Stop() {
-  worker_->Stop();
-}
-
-FakeAudioConsumer::Worker::Worker(
-    const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner,
-    const AudioParameters& params)
-    : worker_task_runner_(worker_task_runner),
-      audio_bus_(AudioBus::Create(params)),
-      buffer_duration_(base::TimeDelta::FromMicroseconds(
-          params.frames_per_buffer() * base::Time::kMicrosecondsPerSecond /
-          static_cast<float>(params.sample_rate()))) {
-  audio_bus_->Zero();
-
-  // Worker can be constructed on any thread, but will DCHECK that its
-  // Start/Stop methods are called from the same thread.
-  thread_checker_.DetachFromThread();
-}
-
-FakeAudioConsumer::Worker::~Worker() {
-  DCHECK(read_cb_.is_null());
-}
-
-bool FakeAudioConsumer::Worker::IsStopped() {
-  base::AutoLock scoped_lock(read_cb_lock_);
-  return read_cb_.is_null();
-}
-
-void FakeAudioConsumer::Worker::Start(const ReadCB& read_cb)  {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!read_cb.is_null());
-  {
-    base::AutoLock scoped_lock(read_cb_lock_);
-    DCHECK(read_cb_.is_null());
-    read_cb_ = read_cb;
-  }
-  worker_task_runner_->PostTask(FROM_HERE, base::Bind(&Worker::DoStart, this));
-}
-
-void FakeAudioConsumer::Worker::DoStart() {
-  DCHECK(worker_task_runner_->BelongsToCurrentThread());
-  next_read_time_ = base::TimeTicks::Now();
-  read_task_cb_.Reset(base::Bind(&Worker::DoRead, this));
-  read_task_cb_.callback().Run();
-}
-
-void FakeAudioConsumer::Worker::Stop() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  {
-    base::AutoLock scoped_lock(read_cb_lock_);
-    if (read_cb_.is_null())
-      return;
-    read_cb_.Reset();
-  }
-  worker_task_runner_->PostTask(FROM_HERE, base::Bind(&Worker::DoCancel, this));
-}
-
-void FakeAudioConsumer::Worker::DoCancel() {
-  DCHECK(worker_task_runner_->BelongsToCurrentThread());
-  read_task_cb_.Cancel();
-}
-
-void FakeAudioConsumer::Worker::DoRead() {
-  DCHECK(worker_task_runner_->BelongsToCurrentThread());
-
-  {
-    base::AutoLock scoped_lock(read_cb_lock_);
-    if (!read_cb_.is_null())
-      read_cb_.Run(audio_bus_.get());
-  }
-
-  // Need to account for time spent here due to the cost of |read_cb_| as well
-  // as the imprecision of PostDelayedTask().
-  const base::TimeTicks now = base::TimeTicks::Now();
-  base::TimeDelta delay = next_read_time_ + buffer_duration_ - now;
-
-  // If we're behind, find the next nearest ontime interval.
-  if (delay < base::TimeDelta())
-    delay += buffer_duration_ * (-delay / buffer_duration_ + 1);
-  next_read_time_ = now + delay;
-
-  worker_task_runner_->PostDelayedTask(
-      FROM_HERE, read_task_cb_.callback(), delay);
-}
-
-}  // namespace media