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// 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 "chrome/common/partial_circular_buffer.h"
#include <algorithm>
#include "base/logging.h"
namespace {
inline uint32 Min3(uint32 a, uint32 b, uint32 c) {
return std::min(a, std::min(b, c));
}
} // namespace
PartialCircularBuffer::PartialCircularBuffer(void* buffer,
uint32 buffer_size)
: buffer_data_(reinterpret_cast<BufferData*>(buffer)),
memory_buffer_size_(buffer_size),
data_size_(0),
position_(0),
total_read_(0) {
uint32 header_size =
buffer_data_->data - reinterpret_cast<uint8*>(buffer_data_);
data_size_ = memory_buffer_size_ - header_size;
DCHECK(buffer_data_);
DCHECK_GE(memory_buffer_size_, header_size);
DCHECK_LE(buffer_data_->total_written, data_size_);
DCHECK_LT(buffer_data_->wrap_position, data_size_);
DCHECK_LT(buffer_data_->end_position, data_size_);
}
PartialCircularBuffer::PartialCircularBuffer(void* buffer,
uint32 buffer_size,
uint32 wrap_position,
bool append)
: buffer_data_(reinterpret_cast<BufferData*>(buffer)),
memory_buffer_size_(buffer_size),
data_size_(0),
position_(0),
total_read_(0) {
uint32 header_size =
buffer_data_->data - reinterpret_cast<uint8*>(buffer_data_);
data_size_ = memory_buffer_size_ - header_size;
DCHECK(buffer_data_);
DCHECK_GE(memory_buffer_size_, header_size);
if (append) {
DCHECK_LT(buffer_data_->wrap_position, data_size_);
position_ = buffer_data_->end_position;
} else {
DCHECK_LT(wrap_position, data_size_);
buffer_data_->total_written = 0;
buffer_data_->wrap_position = wrap_position;
buffer_data_->end_position = 0;
}
}
uint32 PartialCircularBuffer::Read(void* buffer, uint32 buffer_size) {
DCHECK(buffer_data_);
if (total_read_ >= buffer_data_->total_written)
return 0;
uint8* buffer_uint8 = reinterpret_cast<uint8*>(buffer);
uint32 read = 0;
// Read from beginning part.
if (position_ < buffer_data_->wrap_position) {
uint32 to_wrap_pos = buffer_data_->wrap_position - position_;
uint32 to_eow = buffer_data_->total_written - total_read_;
uint32 to_read = Min3(buffer_size, to_wrap_pos, to_eow);
memcpy(buffer_uint8, buffer_data_->data + position_, to_read);
position_ += to_read;
total_read_ += to_read;
read += to_read;
if (position_ == buffer_data_->wrap_position &&
buffer_data_->total_written == data_size_) {
// We've read all the beginning part, set the position to the middle part.
// (The second condition above checks if the wrapping part is filled, i.e.
// writing has wrapped.)
position_ = buffer_data_->end_position;
}
if (read >= buffer_size) {
DCHECK_EQ(read, buffer_size);
return read;
}
if (read >= to_eow) {
DCHECK_EQ(read, to_eow);
DCHECK_EQ(total_read_, buffer_data_->total_written);
return read;
}
}
// Read from middle part.
DCHECK_GE(position_, buffer_data_->wrap_position);
if (position_ >= buffer_data_->end_position) {
uint32 remaining_buffer_size = buffer_size - read;
uint32 to_eof = data_size_ - position_;
uint32 to_eow = buffer_data_->total_written - total_read_;
uint32 to_read = Min3(remaining_buffer_size, to_eof, to_eow);
memcpy(buffer_uint8 + read, buffer_data_->data + position_, to_read);
position_ += to_read;
total_read_ += to_read;
read += to_read;
if (position_ == data_size_) {
// We've read all the middle part, set position to the end part.
position_ = buffer_data_->wrap_position;
}
if (read >= buffer_size) {
DCHECK_EQ(read, buffer_size);
return read;
}
if (total_read_ >= buffer_data_->total_written) {
DCHECK_EQ(total_read_, buffer_data_->total_written);
return read;
}
}
// Read from end part.
DCHECK_GE(position_, buffer_data_->wrap_position);
DCHECK_LT(position_, buffer_data_->end_position);
uint32 remaining_buffer_size = buffer_size - read;
uint32 to_eob = buffer_data_->end_position - position_;
uint32 to_eow = buffer_data_->total_written - total_read_;
uint32 to_read = Min3(remaining_buffer_size, to_eob, to_eow);
memcpy(buffer_uint8 + read, buffer_data_->data + position_, to_read);
position_ += to_read;
total_read_ += to_read;
read += to_read;
DCHECK_LE(read, buffer_size);
DCHECK_LE(total_read_, buffer_data_->total_written);
return read;
}
void PartialCircularBuffer::Write(const void* buffer, uint32 buffer_size) {
DCHECK(buffer_data_);
const uint8* input = static_cast<const uint8*>(buffer);
uint32 wrap_position = buffer_data_->wrap_position;
uint32 cycle_size = data_size_ - wrap_position;
// First write the non-wrapping part.
if (position_ < wrap_position) {
uint32 space_left = wrap_position - position_;
uint32 write_size = std::min(buffer_size, space_left);
DoWrite(input, write_size);
input += write_size;
buffer_size -= write_size;
}
// Skip the part that would overlap.
if (buffer_size > cycle_size) {
uint32 skip = buffer_size - cycle_size;
input += skip;
buffer_size -= skip;
position_ = wrap_position + (position_ - wrap_position + skip) % cycle_size;
}
// Finally write the wrapping part.
DoWrite(input, buffer_size);
}
void PartialCircularBuffer::DoWrite(const uint8* input, uint32 input_size) {
DCHECK_LT(position_, data_size_);
buffer_data_->total_written =
std::min(buffer_data_->total_written + input_size, data_size_);
// Write() skips any overlapping part, so this loop will run at most twice.
while (input_size > 0) {
uint32 space_left = data_size_ - position_;
uint32 write_size = std::min(input_size, space_left);
memcpy(buffer_data_->data + position_, input, write_size);
input += write_size;
input_size -= write_size;
position_ += write_size;
if (position_ >= data_size_) {
DCHECK_EQ(position_, data_size_);
position_ = buffer_data_->wrap_position;
}
}
buffer_data_->end_position = position_;
}
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