| // Copyright 2013 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. |
| |
| #ifndef CHROME_COMMON_PARTIAL_CIRCULAR_BUFFER_H_ |
| #define CHROME_COMMON_PARTIAL_CIRCULAR_BUFFER_H_ |
| |
| #include <stdint.h> |
| |
| // A wrapper around a memory buffer that allows circular read and write with a |
| // selectable wrapping position. Buffer layout (after wrap; H is header): |
| // ----------------------------------------------------------- |
| // | H | Beginning | End | Middle | |
| // ----------------------------------------------------------- |
| // ^---- Non-wrapping -----^ ^--------- Wrapping ----------^ |
| // The non-wrapping part is never overwritten. The wrapping part will be |
| // circular. The very first part is the header (see the BufferData struct |
| // below). It consists of the following information: |
| // - Length written to the buffer (not including header). |
| // - Wrapping position. |
| // - End position of buffer. (If the last byte is at x, this will be x + 1.) |
| // Users of wrappers around the same underlying buffer must ensure that writing |
| // is finished before reading is started. |
| class PartialCircularBuffer { |
| public: |
| // Use for reading. |buffer_size| is in bytes and must be larger than the |
| // header size (see above). |
| PartialCircularBuffer(void* buffer, uint32_t buffer_size); |
| |
| // Use for writing. |buffer_size| is in bytes and must be larger than the |
| // header size (see above). If |append| is true, the header data is not reset |
| // and writing will continue were left off, |wrap_position| is then ignored. |
| PartialCircularBuffer(void* buffer, |
| uint32_t buffer_size, |
| uint32_t wrap_position, |
| bool append); |
| |
| uint32_t Read(void* buffer, uint32_t buffer_size); |
| void Write(const void* buffer, uint32_t buffer_size); |
| |
| private: |
| friend class PartialCircularBufferTest; |
| |
| #pragma pack(push) |
| #pragma pack(4) |
| struct BufferData { |
| uint32_t total_written; |
| uint32_t wrap_position; |
| uint32_t end_position; |
| uint8_t data[1]; |
| }; |
| #pragma pack(pop) |
| |
| void DoWrite(const uint8_t* input, uint32_t input_size); |
| |
| // Used for reading and writing. |
| BufferData* buffer_data_; |
| uint32_t memory_buffer_size_; |
| uint32_t data_size_; |
| uint32_t position_; |
| |
| // Used for reading. |
| uint32_t total_read_; |
| }; |
| |
| #endif // CHROME_COMMON_PARTIAL_CIRCULAR_BUFFER_H_ |