Switch audio synchronization from sleep() based to select() based.

media/audio/shared_memory_util.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/shared_memory_util.h"
-
-#include "base/atomicops.h"
-#include "base/logging.h"
-
-using base::subtle::Atomic32;
-
-static const uint32 kUnknownDataSize = static_cast<uint32>(-1);
-
-namespace media {
-
-uint32 TotalSharedMemorySizeInBytes(uint32 packet_size) {
-  // Need to reserve extra 4 bytes for size of data.
-  return packet_size + sizeof(Atomic32);
-}
-
-uint32 PacketSizeInBytes(uint32 shared_memory_created_size) {
-  return shared_memory_created_size - sizeof(Atomic32);
-}
-
-uint32 GetActualDataSizeInBytes(base::SharedMemory* shared_memory,
-                                uint32 packet_size) {
-  char* ptr = static_cast<char*>(shared_memory->memory()) + packet_size;
-  DCHECK_EQ(0u, reinterpret_cast<size_t>(ptr) & 3);
-
-  // Actual data size stored at the end of the buffer.
-  uint32 actual_data_size =
-      base::subtle::Acquire_Load(reinterpret_cast<volatile Atomic32*>(ptr));
-  return std::min(actual_data_size, packet_size);
-}
-
-void SetActualDataSizeInBytes(void* shared_memory_ptr,
-                              uint32 packet_size,
-                              uint32 actual_data_size) {
-  char* ptr = static_cast<char*>(shared_memory_ptr) + packet_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);
-}
-
-void SetActualDataSizeInBytes(base::SharedMemory* shared_memory,
-                              uint32 packet_size,
-                              uint32 actual_data_size) {
-  SetActualDataSizeInBytes(shared_memory->memory(),
-                           packet_size, actual_data_size);
-}
-
-void SetUnknownDataSize(base::SharedMemory* shared_memory,
-                        uint32 packet_size) {
-  SetActualDataSizeInBytes(shared_memory, packet_size, kUnknownDataSize);
-}
-
-bool IsUnknownDataSize(base::SharedMemory* shared_memory,
-                       uint32 packet_size) {
-  char* ptr = static_cast<char*>(shared_memory->memory()) + packet_size;
-  DCHECK_EQ(0u, reinterpret_cast<size_t>(ptr) & 3);
-
-  // Actual data size stored at the end of the buffer.
-  uint32 actual_data_size =
-      base::subtle::Acquire_Load(reinterpret_cast<volatile Atomic32*>(ptr));
-  return actual_data_size == kUnknownDataSize;
-}
-
-}  // namespace media