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// 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
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