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Unified Diff: media/audio/shared_memory_util.cc

Issue 10826296: Introduce shared_memory_support media target for PPAPI (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Rebase. Created 8 years, 4 months ago
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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
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