blob: dca31b3f88066777ec3481313bd9aa09f247ceeb [file] [log] [blame]
// 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.
#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 {
// 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);
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_;