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// Copyright (c) 2012 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 "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/shared_memory.h"
#include "base/sync_socket.h"
#include "base/synchronization/lock.h"
#include "media/base/media_export.h"
#include "media/audio/audio_parameters.h"
#include "media/audio/shared_memory_util.h"
class MessageLoop;
namespace media {
class AudioBus;
// Data transfer between browser and render process uses a combination
// of sync sockets and shared memory. To read from the socket and render
// data, we use a worker thread, a.k.a. the AudioDeviceThread, which reads
// data from the browser via the socket and fills the shared memory from the
// audio thread via the AudioDeviceThread::Callback interface/class.
// For more details see the documentation in audio_device.h.
// TODO(tommi): Multiple audio input/output device instances should be able to
// share the same thread instead of spinning one per instance.
class MEDIA_EXPORT AudioDeviceThread {
// This is the callback interface/base class that Audio[Output|Input]Device
// implements to render input/output data. The callbacks run on the
// thread owned by AudioDeviceThread.
class Callback {
Callback(const AudioParameters& audio_parameters,
int input_channels,
base::SharedMemoryHandle memory,
int memory_length);
virtual ~Callback();
// One time initialization for the callback object on the audio thread.
void InitializeOnAudioThread();
// Derived implementations must call shared_memory_.Map appropriately
// before Process can be called.
virtual void MapSharedMemory() = 0;
// Called whenever we receive notifications about pending data.
virtual void Process(int pending_data) = 0;
// Protected so that derived classes can access directly.
// The variables are 'const' since values are calculated/set in the
// constructor and must never change.
const AudioParameters audio_parameters_;
const int input_channels_;
const int samples_per_ms_;
const int bytes_per_ms_;
base::SharedMemory shared_memory_;
const int memory_length_;
// Starts the audio thread. The thread must not already be running.
void Start(AudioDeviceThread::Callback* callback,
base::SyncSocket::Handle socket,
const char* thread_name);
// This tells the audio thread to stop and clean up the data.
// The method can stop the thread synchronously or asynchronously.
// In the latter case, the thread will still be running after Stop()
// returns, but the callback pointer is cleared so no further callbacks will
// be made (IOW after Stop() returns, it is safe to delete the callback).
// The |loop_for_join| parameter is required for asynchronous operation
// in order to join the worker thread and close the thread handle later via a
// posted task.
// If set to NULL, function will wait for the thread to exit before returning.
void Stop(MessageLoop* loop_for_join);
// Returns true if the thread is stopped or stopping.
bool IsStopped();
// Our own private SimpleThread override. We implement this in a
// private class so that we get the following benefits:
// 1) AudioDeviceThread doesn't expose SimpleThread methods.
// I.e. the caller can't call Start()/Stop() - which would be bad.
// 2) We override ThreadMain to add additional on-thread initialization
// while still synchronized with SimpleThread::Start() to provide
// reliable initialization.
class Thread;
base::Lock thread_lock_;
scoped_refptr<AudioDeviceThread::Thread> thread_;
} // namespace media.