Use multiple shared memory buffers cyclically for audio capture.

content/browser/renderer_host/media/audio_input_renderer_host.cc

 // 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 "content/browser/renderer_host/media/audio_input_renderer_host.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
 #include "base/process.h"
 #include "base/shared_memory.h"
 #include "content/browser/renderer_host/media/audio_input_device_manager.h"
 #include "content/browser/renderer_host/media/audio_input_sync_writer.h"
 #include "content/browser/renderer_host/media/media_stream_manager.h"
 #include "content/browser/renderer_host/media/web_contents_audio_input_stream.h"
 #include "content/browser/renderer_host/media/web_contents_capture_util.h"
 #include "content/common/media/audio_messages.h"
 
 namespace content {
 
 struct AudioInputRendererHost::AudioEntry {
   AudioEntry();
   ~AudioEntry();
 
   // The AudioInputController that manages the audio input stream.
   scoped_refptr<media::AudioInputController> controller;
 
   // The audio input stream ID in the render view.
   int stream_id;
 
-  // Shared memory for transmission of the audio data.
+  // Shared memory for transmission of the audio data. It has
+  // |shared_memory_segment_count| equal lengthed segments.
   base::SharedMemory shared_memory;
+  int shared_memory_segment_count;
 
   // The synchronous writer to be used by the controller. We have the
   // ownership of the writer.
   scoped_ptr<media::AudioInputController::SyncWriter> writer;
 
   // Set to true after we called Close() for the controller.
   bool pending_close;
 };
 
 AudioInputRendererHost::AudioEntry::AudioEntry()
     : stream_id(0),
+      shared_memory_segment_count(0),
       pending_close(false) {
 }
 
 AudioInputRendererHost::AudioEntry::~AudioEntry() {}
 
 AudioInputRendererHost::AudioInputRendererHost(
     media::AudioManager* audio_manager,
     MediaStreamManager* media_stream_manager)
     : audio_manager_(audio_manager),
       media_stream_manager_(media_stream_manager) {
@@ skipping 95 matching lines @@
   // If we failed to prepare the sync socket for the renderer then we fail
   // the construction of audio input stream.
   if (!writer->PrepareForeignSocketHandle(peer_handle(),
                                           &foreign_socket_handle)) {
     DeleteEntryOnError(entry);
     return;
   }
 
   Send(new AudioInputMsg_NotifyStreamCreated(entry->stream_id,
       foreign_memory_handle, foreign_socket_handle,
-      entry->shared_memory.created_size()));
+      entry->shared_memory.created_size(),
+      entry->shared_memory_segment_count));
 }
 
 void AudioInputRendererHost::DoSendRecordingMessage(
     media::AudioInputController* controller) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   // TODO(henrika): See crbug.com/115262 for details on why this method
   // should be implemented.
 }
 
 void AudioInputRendererHost::DoHandleError(
@@ skipping 33 matching lines @@
 
   // Add the session entry to the map.
   session_entries_[session_id] = stream_id;
 
   // Start the device with the session_id. If the device is started
   // successfully, OnDeviceStarted() callback will be triggered.
   media_stream_manager_->audio_input_device_manager()->Start(session_id, this);
 }
 
 void AudioInputRendererHost::OnCreateStream(
-    int stream_id, const media::AudioParameters& params,
-    const std::string& device_id, bool automatic_gain_control) {
+    int stream_id,
+    const media::AudioParameters& params,
+    const std::string& device_id,
+    bool automatic_gain_control,
+    int shared_memory_count) {
   VLOG(1) << "AudioInputRendererHost::OnCreateStream(stream_id="
           << stream_id << ")";
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   // media::AudioParameters is validated in the deserializer.
   if (LookupById(stream_id) != NULL) {
     SendErrorMessage(stream_id);
     return;
   }
 
   media::AudioParameters audio_params(params);
 
   if (media_stream_manager_->audio_input_device_manager()->
       ShouldUseFakeDevice()) {
     audio_params.Reset(media::AudioParameters::AUDIO_FAKE,
                        params.channel_layout(), 0, params.sample_rate(),
                        params.bits_per_sample(), params.frames_per_buffer());
   }
 
   uint32 buffer_size = audio_params.GetBytesPerBuffer();
 
   // Create a new AudioEntry structure.
   scoped_ptr<AudioEntry> entry(new AudioEntry());
 
-  uint32 mem_size = sizeof(media::AudioInputBufferParameters) + buffer_size;
+  uint32 segment_size =
+      sizeof(media::AudioInputBufferParameters) + buffer_size;
+  entry->shared_memory_segment_count = shared_memory_count;
 
   // Create the shared memory and share it with the renderer process
   // using a new SyncWriter object.
-  if (!entry->shared_memory.CreateAndMapAnonymous(mem_size)) {
+  if (!entry->shared_memory.CreateAndMapAnonymous(
+      segment_size * entry->shared_memory_segment_count)) {
     // If creation of shared memory failed then send an error message.
     SendErrorMessage(stream_id);
     return;
   }
 
   scoped_ptr<AudioInputSyncWriter> writer(
-      new AudioInputSyncWriter(&entry->shared_memory));
+      new AudioInputSyncWriter(&entry->shared_memory,
+                               entry->shared_memory_segment_count));
 
   if (!writer->Init()) {
     SendErrorMessage(stream_id);
     return;
   }
 
   // If we have successfully created the SyncWriter then assign it to the
   // entry and construct an AudioInputController.
   entry->writer.reset(writer.release());
   if (WebContentsCaptureUtil::IsWebContentsDeviceId(device_id)) {
@@ skipping 197 matching lines @@
   for (SessionEntryMap::iterator it = session_entries_.begin();
        it != session_entries_.end(); ++it) {
     if (stream_id == it->second) {
       return it->first;
     }
   }
   return 0;
 }
 
 }  // namespace content