refactor AudioInputDevice to remove race condition.

content/renderer/media/audio_input_device.h

 // Copyright (c) 2011 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.
 
 // Low-latency audio capturing unit utilizing audio input stream provided
 // by browser process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioInputController                 AudioInputDevice
 //           ^                                  ^
 //           |                                  |
 //           v                  IPC             v
 // AudioInputRendererHost  <---------> AudioInputMessageFilter
 //
 // Transportation of audio samples from the browser to the render process
 // is done by using shared memory in combination with a sync socket pair
 // to generate a low latency transport. The AudioInputDevice user registers
 // an AudioInputDevice::CaptureCallback at construction and will be called
 // by the AudioInputDevice with recorded audio from the underlying audio layers.
 //
 // State sequences.
 //
-//            Task [IO thread]                  IPC [IO thread]
+//         [Capture thread]                [IO thread]
 //
-// Start -> InitializeOnIOThread -----> AudioInputHostMsg_CreateStream ------->
-//     <- OnLowLatencyCreated <- AudioInputMsg_NotifyLowLatencyStreamCreated <-
-//       ---> StartOnIOThread ---------> AudioInputHostMsg_PlayStream -------->
+//         StartOnCaptureThread  --> AddDelegateOnIOThread
+// DelegateAddedOnCaptureThread  <--
+//                               --> AudioInputHostMsg_CreateStream
+//                                   AudioInputMsg_NotifyLowLatencyStreamCreated
+// StartRecordingOnCaptureThread <-- OnLowLatencyCreated
+//                               --> AudioInputHostMsg_RecordStream
 //
 // AudioInputDevice::Capture => low latency audio transport on audio thread =>
 //                               |
-// Stop --> ShutDownOnIOThread ------>  AudioInputHostMsg_CloseStream -> Close
+//         StopOnCaptureThread  --> RemoveDelegateOnIOThread
+// DelegateRemovedOnCaptureThread <--
+//                                --> AudioInputHostMsg_CloseStream
 //
-// This class utilizes three threads during its lifetime, namely:
+// This class utilizes four threads during its lifetime, namely:
 // 1. Creating thread.
 //    Must be the main render thread. Start and Stop should be called on
 //    this thread.
 // 2. IO thread.
 //    The thread within which this class receives all the IPC messages and
 //    IPC communications can only happen in this thread.
 // 3. Audio transport thread.
 //    Responsible for calling the CaptrureCallback and feed audio samples from
 //    the audio layer in the browser process using sync sockets and shared
 //    memory.
+// 4. Capture thread.
+//    The main working thread on which AudioInputDevice runs its methods.
 
 #ifndef CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
 #define CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
 #pragma once
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "base/threading/simple_thread.h"
 #include "content/renderer/media/audio_input_message_filter.h"
 
-struct AudioParameters;
+class AudioInputDeviceEventHandler;
 
 // TODO(henrika): This class is based on the AudioDevice class and it has
 // many components in common. Investigate potential for re-factoring.
 class AudioInputDevice
     : public AudioInputMessageFilter::Delegate,
       public base::DelegateSimpleThread::Delegate,
       public base::RefCountedThreadSafe<AudioInputDevice> {
  public:
   class CaptureCallback {
    public:
     virtual void Capture(const std::vector<float*>& audio_data,
                          size_t number_of_frames,
                          size_t audio_delay_milliseconds) = 0;
    protected:
     virtual ~CaptureCallback() {}
   };
 
   // Methods called on main render thread -------------------------------------
+  // |message_loop_proxy| is the working thread for AudioInputDevice.
   AudioInputDevice(size_t buffer_size,
                    int channels,
                    double sample_rate,
+                   base::MessageLoopProxy* message_loop_proxy,
+                   AudioInputDeviceEventHandler* event_handler,
                    CaptureCallback* callback);
   virtual ~AudioInputDevice();
 
   // Starts audio capturing. Returns |true| on success.
   bool Start();
 
   // Stops audio capturing. Returns |true| on success.
   bool Stop();
 
   // Sets the capture volume scaling, with range [0.0, 1.0] inclusive.
   // Returns |true| on success.
   bool SetVolume(double volume);
 
   // Gets the capture volume scaling, with range [0.0, 1.0] inclusive.
   // Returns |true| on success.
   bool GetVolume(double* volume);
 
   double sample_rate() const { return sample_rate_; }
   size_t buffer_size() const { return buffer_size_; }
 
   // Methods called on IO thread ----------------------------------------------
   // AudioInputMessageFilter::Delegate impl., called by AudioInputMessageFilter
   virtual void OnLowLatencyCreated(base::SharedMemoryHandle handle,
                                    base::SyncSocket::Handle socket_handle,
                                    uint32 length);
   virtual void OnVolume(double volume);
 
  private:
-  // Methods called on IO thread ----------------------------------------------
-  // The following methods are tasks posted on the IO thread that needs to
-  // be executed on that thread. They interact with AudioInputMessageFilter and
-  // sends IPC messages on that thread.
-  void InitializeOnIOThread(const AudioParameters& params);
-  void StartOnIOThread();
-  void ShutDownOnIOThread();
-  void SetVolumeOnIOThread(double volume);
+  enum State {
+    kStarting,
+    kStarted,
+    kPaused,
+    kStopped,
+    kStopping,
+    kError,
+  };
 
+  // Methods called on main working thread for AudioInputDevice ---------------
+  // The following methods are tasks posted on capture thread that needs to
+  // be executed on that thread.
+  void StartOnCaptureThread();
+  void StartRecordingOnCaptureThread(base::SharedMemoryHandle handle,
+                                     base::SyncSocket::Handle socket_handle,
+                                     uint32 length);
+  void StopOnCaptureThread();
+  void SetVolumeOnCaptureThread(double volume);
+  void OnDelegateAddedOnCaptureThread(int32 stream_id);
+  void OnDelegateRemovedOnCaptureThread();
   void Send(IPC::Message* message);
 
   // Method called on the audio thread ----------------------------------------
   // Calls the client's callback for capturing audio.
   void FireCaptureCallback();
 
   // DelegateSimpleThread::Delegate implementation.
   virtual void Run();
 
+  // Add/Remove delegate on IO thread------------------------------------------
+  void AddDelegateOnIOThread();
+  void RemoveDelegateOnIOThread(int32 stream_id);
+
+  // IPC message stuff.
+  base::SharedMemory* shared_memory() { return shared_memory_.get(); }
+  base::SyncSocket* socket() { return socket_.get(); }
+  void* shared_memory_data() { return shared_memory()->memory(); }
+
   // Format
   size_t buffer_size_;  // in sample-frames
   int channels_;
   int bits_per_sample_;
   double sample_rate_;
 
   CaptureCallback* callback_;
+  AudioInputDeviceEventHandler* event_handler_;
 
   // The client callback receives captured audio here.
   std::vector<float*> audio_data_;
 
   // The client stores the last reported audio delay in this member.
   // The delay shall reflect the amount of audio which still resides in
   // the input buffer, i.e., the expected audio input delay.
   int audio_delay_milliseconds_;
 
   // The current volume scaling [0.0, 1.0] of the audio stream.
   double volume_;
 
+  // The working thread for AudioInputDevice.
+  scoped_refptr<base::MessageLoopProxy> capture_message_loop_proxy_;
+
+  State state_;
+
   // Callbacks for capturing audio occur on this thread.
   scoped_ptr<base::DelegateSimpleThread> audio_thread_;
 
-  // IPC message stuff.
-  base::SharedMemory* shared_memory() { return shared_memory_.get(); }
-  base::SyncSocket* socket() { return socket_.get(); }
-  void* shared_memory_data() { return shared_memory()->memory(); }
-
   // Cached audio input message filter (lives on the main render thread).
   scoped_refptr<AudioInputMessageFilter> filter_;
 
   // Our stream ID on the message filter. Only modified on the IO thread.
   int32 stream_id_;
 
   scoped_ptr<base::SharedMemory> shared_memory_;
   scoped_ptr<base::SyncSocket> socket_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioInputDevice);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_