Index: media/audio/shared_memory_util.cc |
diff --git a/media/audio/shared_memory_util.cc b/media/audio/shared_memory_util.cc |
new file mode 100644 |
index 0000000000000000000000000000000000000000..afb6b33c6661241f1ba2dab824bbf6ec401ae2be |
--- /dev/null |
+++ b/media/audio/shared_memory_util.cc |
@@ -0,0 +1,70 @@ |
+// 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 shared_memory_size) { |
+ char* ptr = static_cast<char*>(shared_memory->memory()) + shared_memory_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, shared_memory_size); |
+} |
+ |
+void SetActualDataSizeInBytes(void* shared_memory_ptr, |
+ uint32 shared_memory_size, |
+ uint32 actual_data_size) { |
+ char* ptr = static_cast<char*>(shared_memory_ptr) + 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); |
+} |
+ |
+void SetActualDataSizeInBytes(base::SharedMemory* shared_memory, |
+ uint32 shared_memory_size, |
+ uint32 actual_data_size) { |
+ SetActualDataSizeInBytes(shared_memory->memory(), |
+ shared_memory_size, actual_data_size); |
+} |
+ |
+void SetUnknownDataSize(base::SharedMemory* shared_memory, |
+ uint32 shared_memory_size) { |
+ SetActualDataSizeInBytes(shared_memory, shared_memory_size, kUnknownDataSize); |
+} |
+ |
+bool IsUnknownDataSize(base::SharedMemory* shared_memory, |
+ uint32 shared_memory_size) { |
+ char* ptr = static_cast<char*>(shared_memory->memory()) + shared_memory_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 |