Use multiple shared memory buffers cyclically for audio capture.

media/audio/audio_device_thread.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 "media/audio/audio_device_thread.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 10 matching lines @@
 
 // The actual worker thread implementation.  It's very bare bones and much
 // simpler than SimpleThread (no synchronization in Start, etc) and supports
 // joining the thread handle asynchronously via a provided message loop even
 // after the Thread object itself has been deleted.
 class AudioDeviceThread::Thread
     : public PlatformThread::Delegate,
       public base::RefCountedThreadSafe<AudioDeviceThread::Thread> {
  public:
   Thread(AudioDeviceThread::Callback* callback,
+         bool read_index,
          base::SyncSocket::Handle socket,
          const char* thread_name);
 
   void Start();
 
   // Stops the thread.  If |loop_for_join| is non-NULL, the function posts
   // a task to join (close) the thread handle later instead of waiting for
   // the thread.  If loop_for_join is NULL, then the function waits
   // synchronously for the thread to terminate.
   void Stop(MessageLoop* loop_for_join);
 
  private:
   friend class base::RefCountedThreadSafe<AudioDeviceThread::Thread>;
   virtual ~Thread();
 
   // Overrides from PlatformThread::Delegate.
   virtual void ThreadMain() OVERRIDE;
 
   // Runs the loop that reads from the socket.
   void Run();
 
  private:
   base::PlatformThreadHandle thread_;
   AudioDeviceThread::Callback* callback_;
+  bool read_index_;
   base::CancelableSyncSocket socket_;
   base::Lock callback_lock_;
   const char* thread_name_;
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 // AudioDeviceThread implementation
 
-AudioDeviceThread::AudioDeviceThread() {
+AudioDeviceThread::AudioDeviceThread(bool read_index)
+    : read_index_(read_index) {
 }
 
 AudioDeviceThread::~AudioDeviceThread() {
   DCHECK(!thread_);
 }
 
 void AudioDeviceThread::Start(AudioDeviceThread::Callback* callback,
                               base::SyncSocket::Handle socket,
                               const char* thread_name) {
   base::AutoLock auto_lock(thread_lock_);
   CHECK(thread_ == NULL);
-  thread_ = new AudioDeviceThread::Thread(callback, socket, thread_name);
+  thread_ = new AudioDeviceThread::Thread(
+      callback, read_index_, socket, thread_name);
   thread_->Start();
 }
 
 void AudioDeviceThread::Stop(MessageLoop* loop_for_join) {
   base::AutoLock auto_lock(thread_lock_);
   if (thread_) {
     thread_->Stop(loop_for_join);
     thread_ = NULL;
   }
 }
 
 bool AudioDeviceThread::IsStopped() {
   base::AutoLock auto_lock(thread_lock_);
   return thread_ == NULL;
 }
 
 // AudioDeviceThread::Thread implementation
 AudioDeviceThread::Thread::Thread(AudioDeviceThread::Callback* callback,
+                                  bool read_index,
                                   base::SyncSocket::Handle socket,
                                   const char* thread_name)
     : thread_(base::kNullThreadHandle),
       callback_(callback),
+      read_index_(read_index),
       socket_(socket),
       thread_name_(thread_name) {
 }
 
 AudioDeviceThread::Thread::~Thread() {
   DCHECK_EQ(thread_, base::kNullThreadHandle) << "Stop wasn't called";
 }
 
 void AudioDeviceThread::Thread::Start() {
   base::AutoLock auto_lock(callback_lock_);
@@ skipping 45 matching lines @@
   Run();
 
   // Release the reference for the thread. Note that after this, the Thread
   // instance will most likely be deleted.
   Release();
 }
 
 void AudioDeviceThread::Thread::Run() {
   while (true) {
     int pending_data = 0;
+    int pending_id = 0;
     size_t bytes_read = socket_.Receive(&pending_data, sizeof(pending_data));
     if (bytes_read != sizeof(pending_data)) {
       DCHECK_EQ(bytes_read, 0U);
       break;
     }
 
+    if (read_index_) {
+      size_t bytes_read = socket_.Receive(&pending_id, sizeof(pending_id));
+      if (bytes_read != sizeof(pending_id)) {
+        DCHECK_EQ(bytes_read, 0U);
+        break;
+      }
+    }
+
     base::AutoLock auto_lock(callback_lock_);
     if (callback_)
-      callback_->Process(pending_data);
+      callback_->Process(pending_data, pending_id);
   }
 }
 
 // AudioDeviceThread::Callback implementation
 
 AudioDeviceThread::Callback::Callback(
     const AudioParameters& audio_parameters,
-    base::SharedMemoryHandle memory, int memory_length)
+    SharedMemoryHandleVector& memory,
+    int memory_length)
     : audio_parameters_(audio_parameters),
       samples_per_ms_(audio_parameters.sample_rate() / 1000),
       bytes_per_ms_(audio_parameters.channels() *
                     (audio_parameters_.bits_per_sample() / 8) *
                     samples_per_ms_),
-      shared_memory_(memory, false),
       memory_length_(memory_length) {
   CHECK_NE(bytes_per_ms_, 0);  // Catch division by zero early.
   CHECK_NE(samples_per_ms_, 0);
+  shared_memory_.resize(memory.size());
+  for (size_t id = 0; id < shared_memory_.size(); ++id)
+    shared_memory_[id] = new base::SharedMemory(memory[id], false);
 }
 
 AudioDeviceThread::Callback::~Callback() {}
 
 void AudioDeviceThread::Callback::InitializeOnAudioThread() {
   MapSharedMemory();
-  DCHECK(shared_memory_.memory() != NULL);
+  for (size_t id = 0; id < shared_memory_.size(); ++id)
+    DCHECK(shared_memory_[id]->memory() != NULL);
 }
 
 }  // namespace media.