Tianjie Xu | 1c26e2e | 2017-10-26 17:19:41 -0700 | [diff] [blame] | 1 | // Copyright 2017 The Chromium OS Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef _BSDIFF_COMPRESSOR_BUFFER_H_ |
| 6 | #define _BSDIFF_COMPRESSOR_BUFFER_H_ |
| 7 | |
| 8 | #include <stddef.h> |
| 9 | #include <stdint.h> |
| 10 | |
| 11 | #include <vector> |
| 12 | |
| 13 | namespace bsdiff { |
| 14 | |
| 15 | // An utility class to store the output from a compressor. It has a small |
| 16 | // temporary buffer that holds the compressed data every time the compressed |
| 17 | // stream has some output. That buffer is then appended to a list of vectors |
| 18 | // stored in memory. This approach is more efficient than a simple vector |
| 19 | // because it saves some resize / reallocation of memory. And the compressed |
| 20 | // data is copied once no matter how many times we fetch output from the |
| 21 | // compressor. |
| 22 | class CompressorBuffer { |
| 23 | public: |
| 24 | explicit CompressorBuffer(size_t buffer_size) { |
| 25 | comp_buffer_.resize(buffer_size); |
| 26 | } |
| 27 | |
| 28 | size_t buffer_size() { return comp_buffer_.size(); } |
| 29 | uint8_t* buffer_data() { return comp_buffer_.data(); } |
| 30 | |
| 31 | // Concatenate the data in |comp_chunks_| and return the data in the form of |
| 32 | // a single vector. |
| 33 | const std::vector<uint8_t>& GetCompressedData(); |
| 34 | |
| 35 | // Add the data in |comp_buffer_| to the end of |comp_chunks_|. |
| 36 | void AddDataToChunks(size_t data_size); |
| 37 | |
| 38 | private: |
| 39 | // A list of chunks of compressed data. The final compressed representation is |
| 40 | // the concatenation of all the compressed data. |
| 41 | std::vector<std::vector<uint8_t>> comp_chunks_; |
| 42 | |
| 43 | // A concatenated version of the |comp_chunks_|, used to store the compressed |
| 44 | // memory after Finish() is called. |
| 45 | std::vector<uint8_t> comp_data_; |
| 46 | |
| 47 | // A temporary compression buffer for multiple calls to Write(). |
| 48 | std::vector<uint8_t> comp_buffer_; |
| 49 | }; |
| 50 | |
| 51 | } // namespace bsdiff |
| 52 | |
| 53 | #endif // _BSDIFF_COMPRESSOR_BUFFER_H_ |