Simplified AudioOutputStream interface.

media/audio/linux/alsa_output.h

 // Copyright (c) 2010 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.
 //
 // Creates an output stream based on the ALSA PCM interface.
 //
 // On device write failure, the stream will move itself to an invalid state.
 // No more data will be pulled from the data source, or written to the device.
 // All calls to public API functions will either no-op themselves, or return an
 // error if possible.  Specifically, If the stream is in an error state, Open()
 // will return false, and Start() will call OnError() immediately on the
 // provided callback.
 //
 // TODO(ajwong): The OnClose() and OnError() calling needing fixing.
 //
 // If the stream is successfully opened, Close() must be called before the
 // stream is deleted as Close() is responsible for ensuring resource cleanup
 // occurs.
 //
 // This object's thread-safety is a little tricky.  This object's public API
 // can only be called from the thread that created the object.  Calling the
 // public APIs in any method that may cause concurrent execution will result in
 // a race condition.  When modifying the code in this class, please read the
 // threading assumptions at the top of the implementation file to avoid
 // introducing race conditions between tasks posted to the internal
 // message_loop, and the thread calling the public APIs.
+//
+// TODO(sergeyu): AlsaPcmOutputStream is always created and used from the
+// audio thread (i.e. |client_thread_loop_| and |message_loop_| always point
+// to the same thread), so it doesn't need to be thread-safe anymore.
+//
+// TODO(sergeyu): Remove refcounter from AlsaPcmOutputStream and use
+// ScopedRunnableMethodFactory to create tasks.
 
 #ifndef MEDIA_AUDIO_LINUX_ALSA_OUTPUT_H_
 #define MEDIA_AUDIO_LINUX_ALSA_OUTPUT_H_
 
 #include <alsa/asoundlib.h>
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/lock.h"
@@ skipping 35 matching lines @@
   // |message_loop|.
   //
   // If unsure of what to use for |device_name|, use |kAutoSelectDevice|.
   AlsaPcmOutputStream(const std::string& device_name,
                       AudioParameters params,
                       AlsaWrapper* wrapper,
                       AudioManagerLinux* manager,
                       MessageLoop* message_loop);
 
   // Implementation of AudioOutputStream.
-  virtual bool Open(uint32 packet_size);
+  virtual bool Open();
   virtual void Close();
   virtual void Start(AudioSourceCallback* callback);
   virtual void Stop();
   virtual void SetVolume(double volume);
   virtual void GetVolume(double* volume);
 
  private:
   friend class base::RefCountedThreadSafe<AlsaPcmOutputStream>;
   friend class AlsaPcmOutputStreamTest;
   FRIEND_TEST_ALL_PREFIXES(AlsaPcmOutputStreamTest,
@@ skipping 27 matching lines @@
     kInError = 0,
     kCreated,
     kIsOpened,
     kIsPlaying,
     kIsStopped,
     kIsClosed
   };
   friend std::ostream& operator<<(std::ostream& os, InternalState);
 
   // Various tasks that complete actions started in the public API.
-  void OpenTask(uint32 packet_size);
+  void OpenTask();
   void StartTask();
   void CloseTask();
 
   // Functions to get another packet from the data source and write it into the
   // ALSA device.
   void BufferPacket(bool* source_exhausted);
   void WritePacket();
   void WriteTask();
   void ScheduleNextWrite(bool source_exhausted);
 
@@ skipping 31 matching lines @@
     // API for Proxying calls to the AudioSourceCallback provided during
     // Start().  These APIs are threadsafe.
     //
     // TODO(ajwong): This is necessary because the ownership semantics for the
     // |source_callback_| object are incorrect in AudioRenderHost. The callback
     // is passed into the output stream, but ownership is not transfered which
     // requires a synchronization on access of the |source_callback_| to avoid
     // using a deleted callback.
     uint32 OnMoreData(AudioOutputStream* stream, uint8* dest,
                       uint32 max_size, AudioBuffersState buffers_state);
-    void OnClose(AudioOutputStream* stream);
     void OnError(AudioOutputStream* stream, int code);
 
     // Changes the AudioSourceCallback to proxy calls to.  Pass in NULL to
     // release ownership of the currently registered callback.
     void set_source_callback(AudioSourceCallback* callback);
 
    private:
     Lock lock_;
 
     InternalState state_;
@@ skipping 11 matching lines @@
   const std::string requested_device_name_;
   const snd_pcm_format_t pcm_format_;
   const uint32 channels_;
   const uint32 sample_rate_;
   const uint32 bytes_per_sample_;
   const uint32 bytes_per_frame_;
 
   // Device configuration data. Populated after OpenTask() completes.
   std::string device_name_;
   bool should_downmix_;
-  uint32 latency_micros_;
   uint32 packet_size_;
   uint32 micros_per_packet_;
+  uint32 latency_micros_;
   uint32 bytes_per_output_frame_;
   uint32 alsa_buffer_frames_;
 
   // Flag indicating the code should stop reading from the data source or
   // writing to the ALSA device.  This is set because the device has entered
   // an unrecoverable error state, or the ClosedTask() has executed.
   bool stop_stream_;
 
   // Wrapper class to invoke all the ALSA functions.
   AlsaWrapper* wrapper_;
@@ skipping 13 matching lines @@
   MessageLoop* client_thread_loop_;
 
   // The message loop responsible for querying the data source, and writing to
   // the output device.
   MessageLoop* message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(AlsaPcmOutputStream);
 };
 
 #endif  // MEDIA_AUDIO_LINUX_ALSA_OUTPUT_H_