ppapi/shared_impl/ppb_audio_shared.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 "ppapi/shared_impl/ppb_audio_shared.h"

#include "base/logging.h"
#include "ppapi/shared_impl/ppapi_globals.h"

using base::subtle::Atomic32;

namespace ppapi {

#if defined(OS_NACL)
namespace {
// Because this is static, the function pointers will be NULL initially.
PP_ThreadFunctions thread_functions;
}
#endif  // defined(OS_NACL)

// FIXME: The following two functions (TotalSharedMemorySizeInBytes,
// SetActualDataSizeInBytes) are copied from audio_util.cc.
// Remove these functions once a minimal media library is provided for them.
// code.google.com/p/chromium/issues/detail?id=123203

uint32 TotalSharedMemorySizeInBytes(uint32 packet_size) {
  // Need to reserve extra 4 bytes for size of data.
  return packet_size + sizeof(Atomic32);
}

void SetActualDataSizeInBytes(base::SharedMemory* shared_memory,
                              uint32 shared_memory_size,
                              uint32 actual_data_size) {
  char* ptr = static_cast<char*>(shared_memory->memory()) + shared_memory_size;
  DCHECK_EQ(0u, reinterpret_cast<size_t>(ptr) & 3);

  // Set actual data size at the end of the buffer.
  base::subtle::Release_Store(reinterpret_cast<volatile Atomic32*>(ptr),
                              actual_data_size);
}

const int PPB_Audio_Shared::kPauseMark = -1;

PPB_Audio_Shared::PPB_Audio_Shared()
    : playing_(false),
      shared_memory_size_(0),
#if defined(OS_NACL)
      thread_id_(0),
      thread_active_(false),
#endif
      callback_(NULL),
      user_data_(NULL) {
}

PPB_Audio_Shared::~PPB_Audio_Shared() {
  StopThread();
}

void PPB_Audio_Shared::SetCallback(PPB_Audio_Callback callback,
                                   void* user_data) {
  callback_ = callback;
  user_data_ = user_data;
}

void PPB_Audio_Shared::SetStartPlaybackState() {
  DCHECK(!playing_);
#if !defined(OS_NACL)
  DCHECK(!audio_thread_.get());
#else
  DCHECK(!thread_active_);
#endif
  // If the socket doesn't exist, that means that the plugin has started before
  // the browser has had a chance to create all the shared memory info and
  // notify us. This is a common case. In this case, we just set the playing_
  // flag and the playback will automatically start when that data is available
  // in SetStreamInfo.
  playing_ = true;
  StartThread();
}

void PPB_Audio_Shared::SetStopPlaybackState() {
  DCHECK(playing_);
  StopThread();
  playing_ = false;
}

void PPB_Audio_Shared::SetStreamInfo(
    PP_Instance instance,
    base::SharedMemoryHandle shared_memory_handle,
    size_t shared_memory_size,
    base::SyncSocket::Handle socket_handle) {
  socket_.reset(new base::CancelableSyncSocket(socket_handle));
  shared_memory_.reset(new base::SharedMemory(shared_memory_handle, false));
  shared_memory_size_ = shared_memory_size;

  if (!shared_memory_->Map(TotalSharedMemorySizeInBytes(shared_memory_size_))) {
    PpapiGlobals::Get()->LogWithSource(instance, PP_LOGLEVEL_WARNING, "",
      "Failed to map shared memory for PPB_Audio_Shared.");
  }

  StartThread();
}

void PPB_Audio_Shared::StartThread() {
  // Don't start the thread unless all our state is set up correctly.
  if (!playing_ || !callback_ || !socket_.get() || !shared_memory_->memory())
    return;
  // Clear contents of shm buffer before starting audio thread. This will
  // prevent a burst of static if for some reason the audio thread doesn't
  // start up quickly enough.
  memset(shared_memory_->memory(), 0, shared_memory_size_);
#if !defined(OS_NACL)
  DCHECK(!audio_thread_.get());
  audio_thread_.reset(new base::DelegateSimpleThread(
      this, "plugin_audio_thread"));
  audio_thread_->Start();
#else
  // Use NaCl's special API for IRT code that creates threads that call back
  // into user code.
  if (NULL == thread_functions.thread_create ||
      NULL == thread_functions.thread_join)
    return;

  int result = thread_functions.thread_create(&thread_id_, CallRun, this);
  DCHECK_EQ(result, 0);
  thread_active_ = true;
#endif
}

void PPB_Audio_Shared::StopThread() {
  // Shut down the socket to escape any hanging |Receive|s.
  if (socket_.get())
    socket_->Shutdown();
  #if !defined(OS_NACL)
  if (audio_thread_.get()) {
    audio_thread_->Join();
    audio_thread_.reset();
  }
#else
  if (thread_active_) {
    int result = thread_functions.thread_join(thread_id_);
    DCHECK_EQ(0, result);
    thread_active_ = false;
  }
#endif
}

#if defined(OS_NACL)
// static
void PPB_Audio_Shared::SetThreadFunctions(
    const struct PP_ThreadFunctions* functions) {
  DCHECK(thread_functions.thread_create == NULL);
  DCHECK(thread_functions.thread_join == NULL);
  thread_functions = *functions;
}

// static
void PPB_Audio_Shared::CallRun(void* self) {
  PPB_Audio_Shared* audio = static_cast<PPB_Audio_Shared*>(self);
  audio->Run();
}
#endif

void PPB_Audio_Shared::Run() {
  int pending_data;
  void* buffer = shared_memory_->memory();

  while (sizeof(pending_data) ==
      socket_->Receive(&pending_data, sizeof(pending_data)) &&
      pending_data != kPauseMark) {
    callback_(buffer, shared_memory_size_, user_data_);

    // Let the host know we are done.
    SetActualDataSizeInBytes(shared_memory_.get(), shared_memory_size_,
        shared_memory_size_);
  }
}

}  // namespace ppapi