// Copyright (c) 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Note: ported from Chromium commit head: 60f9667
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#ifndef SHARED_MEMORY_REGION_H_
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#define SHARED_MEMORY_REGION_H_
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#include "base/memory/shared_memory.h"
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#include "bitstream_buffer.h"
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namespace media {
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// Helper class to access a region of a SharedMemory. Different from
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// SharedMemory, in which the |offset| of function MapAt() must be aligned to
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// the value of |SysInfo::VMAllocationGranularity()|, the |offset| of a
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// SharedMemoryRegion needs not to be aligned, this class hides the details
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// and returns the mapped address of the given offset.
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class SharedMemoryRegion {
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public:
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// Creates a SharedMemoryRegion.
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// The mapped memory region begins at |offset| bytes from the start of the
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// shared memory and the length is |size|. It will take the ownership of
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// the |handle| and release the resource when being destroyed. Different
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// from SharedMemory, the |offset| needs not to be aligned to the value of
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// |SysInfo::VMAllocationGranularity()|.
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SharedMemoryRegion(const base::SharedMemoryHandle& handle,
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off_t offset,
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size_t size,
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bool read_only);
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// Creates a SharedMemoryRegion from the given |bistream_buffer|.
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SharedMemoryRegion(const BitstreamBuffer& bitstream_buffer, bool read_only);
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// Maps the shared memory into the caller's address space.
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// Return true on success, false otherwise.
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bool Map();
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// Gets a pointer to the mapped region if it has been mapped via Map().
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// Returns |nullptr| if it is not mapped. The returned pointer points
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// to the memory at the offset previously passed to the constructor.
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void* memory();
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size_t size() const { return size_; }
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private:
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base::SharedMemory shm_;
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off_t offset_;
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size_t size_;
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size_t alignment_size_;
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DISALLOW_COPY_AND_ASSIGN(SharedMemoryRegion);
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};
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} // namespace media
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#endif // SHARED_MEMORY_REGION_H_
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