Use multiple shared memory buffers cyclically for audio capture.

media/audio/audio_output_device.cc

Index: media/audio/audio_output_device.cc
===================================================================
--- media/audio/audio_output_device.cc	(revision 185810)
+++ media/audio/audio_output_device.cc	(working copy)
@@ -22,7 +22,7 @@
     : public AudioDeviceThread::Callback {
  public:
   AudioThreadCallback(const AudioParameters& audio_parameters,
-                      base::SharedMemoryHandle memory,
+                      SharedMemoryHandleVector memory,
                       int memory_length,
                       AudioRendererSink::RenderCallback* render_callback);
   virtual ~AudioThreadCallback();
@@ -30,7 +30,7 @@
   virtual void MapSharedMemory() OVERRIDE;
 
   // Called whenever we receive notifications about pending data.
-  virtual void Process(int pending_data) OVERRIDE;
+  virtual void Process(int pending_data, int index) OVERRIDE;
 
  private:
   AudioRendererSink::RenderCallback* render_callback_;
@@ -48,6 +48,7 @@
       stream_id_(0),
       state_(IDLE),
       play_on_start_(true),
+      audio_thread_(false),
       stopping_hack_(false) {
   CHECK(ipc_);
 }
@@ -226,7 +227,9 @@
 
   DCHECK(audio_thread_.IsStopped());
   audio_callback_.reset(new AudioOutputDevice::AudioThreadCallback(
-      audio_parameters_, handle, length, callback_));
+      audio_parameters_,
+      AudioDeviceThread::Callback::SharedMemoryHandleVector(1, handle),
+      length, callback_));
   audio_thread_.Start(audio_callback_.get(), socket_handle,
       "AudioOutputDevice");
   state_ = PAUSED;
@@ -252,7 +255,7 @@
 
 AudioOutputDevice::AudioThreadCallback::AudioThreadCallback(
     const AudioParameters& audio_parameters,
-    base::SharedMemoryHandle memory,
+    SharedMemoryHandleVector memory,
     int memory_length,
     AudioRendererSink::RenderCallback* render_callback)
     : AudioDeviceThread::Callback(audio_parameters,
@@ -265,7 +268,9 @@
 }
 
 void AudioOutputDevice::AudioThreadCallback::MapSharedMemory() {
-  shared_memory_.Map(TotalSharedMemorySizeInBytes(memory_length_));
+  DCHECK_EQ(shared_memory_.size(), 1u);
+  base::SharedMemory* shared_buffer = shared_memory_[0];
+  shared_buffer->Map(TotalSharedMemorySizeInBytes(memory_length_));
 
   // Calculate output and input memory size.
   int output_memory_size = AudioBus::CalculateMemorySize(audio_parameters_);
@@ -279,22 +284,24 @@
   DCHECK_EQ(memory_length_, io_size);
 
   output_bus_ =
-      AudioBus::WrapMemory(audio_parameters_, shared_memory_.memory());
+      AudioBus::WrapMemory(audio_parameters_, shared_buffer->memory());
 
   if (input_channels > 0) {
     // The input data is after the output data.
     char* input_data =
-        static_cast<char*>(shared_memory_.memory()) + output_memory_size;
+        static_cast<char*>(shared_buffer->memory()) + output_memory_size;
     input_bus_ =
         AudioBus::WrapMemory(input_channels, frames, input_data);
   }
 }
 
 // Called whenever we receive notifications about pending data.
-void AudioOutputDevice::AudioThreadCallback::Process(int pending_data) {
+void AudioOutputDevice::AudioThreadCallback::Process(
+    int pending_data, int index) {
+  base::SharedMemory* shared_buffer = shared_memory_[0];
   if (pending_data == kPauseMark) {
-    memset(shared_memory_.memory(), 0, memory_length_);
-    SetActualDataSizeInBytes(&shared_memory_, memory_length_, 0);
+    memset(shared_buffer->memory(), 0, memory_length_);
+    SetActualDataSizeInBytes(shared_buffer, memory_length_, 0);
     return;
   }
 
@@ -325,7 +332,7 @@
   // relying on AudioSyncReader::Read() to parse this with that in mind.  Rename
   // these methods to Set/GetActualFrameCount().
   SetActualDataSizeInBytes(
-      &shared_memory_, memory_length_,
+      shared_buffer, memory_length_,
       num_frames * sizeof(*output_bus_->channel(0)) * output_bus_->channels());
 }