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