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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "mojo/core/ipcz_driver/ring_buffer.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include "base/check_op.h"
#include "base/containers/span.h"
#include "base/numerics/safe_math.h"
#include "mojo/core/ipcz_driver/shared_buffer_mapping.h"
namespace mojo::core::ipcz_driver {
RingBuffer::RingBuffer(scoped_refptr<SharedBufferMapping> mapping)
: mapping_(std::move(mapping)) {}
RingBuffer::~RingBuffer() = default;
size_t RingBuffer::Write(base::span<const uint8_t> source) {
auto bytes = MapRange(ComplementRange(data_range_));
const size_t first_chunk_size = std::min(source.size(), bytes.first.size());
const size_t second_chunk_size =
std::min(source.size() - first_chunk_size, bytes.second.size());
bytes.first.copy_prefix_from(source.first(first_chunk_size));
bytes.second.copy_prefix_from(
source.subspan(first_chunk_size, second_chunk_size));
const size_t write_size = first_chunk_size + second_chunk_size;
bool ok = ExtendDataRange(write_size);
DCHECK(ok);
return write_size;
}
bool RingBuffer::WriteAll(base::span<const uint8_t> source) {
if (source.size() > available_capacity()) {
return false;
}
const size_t n = Write(source);
DCHECK_EQ(n, source.size());
return true;
}
size_t RingBuffer::Read(base::span<uint8_t> target) {
const size_t n = Peek(target);
bool ok = DiscardAll(n);
DCHECK(ok);
return n;
}
bool RingBuffer::ReadAll(base::span<uint8_t> target) {
if (target.size() > data_size()) {
return false;
}
const size_t n = Read(target);
DCHECK_EQ(n, target.size());
return true;
}
size_t RingBuffer::Peek(base::span<uint8_t> target) {
auto bytes = MapRange(data_range_);
const size_t first_chunk_size = std::min(target.size(), bytes.first.size());
const size_t second_chunk_size =
std::min(target.size() - first_chunk_size, bytes.second.size());
target.copy_prefix_from(bytes.first.first(first_chunk_size));
target.subspan(first_chunk_size)
.copy_prefix_from(bytes.second.first(second_chunk_size));
return first_chunk_size + second_chunk_size;
}
bool RingBuffer::PeekAll(base::span<uint8_t> target) {
if (target.size() > data_size()) {
return false;
}
const size_t n = Peek(target);
DCHECK_EQ(n, target.size());
return true;
}
size_t RingBuffer::Discard(size_t n) {
const size_t num_bytes = std::min(n, data_size());
bool ok = DiscardAll(num_bytes);
DCHECK(ok);
return num_bytes;
}
bool RingBuffer::DiscardAll(size_t n) {
if (n > data_size()) {
return false;
}
size_t new_offset;
if (!base::CheckAdd(data_range_.offset, n).AssignIfValid(&new_offset)) {
return false;
}
data_range_ = {.offset = new_offset % capacity(), .size = data_size() - n};
return true;
}
bool RingBuffer::ExtendDataRange(size_t n) {
if (n > available_capacity()) {
return false;
}
data_range_.size += n;
return true;
}
void RingBuffer::Serialize(SerializedState& state) {
state.offset = base::checked_cast<uint32_t>(data_range_.offset);
state.size = base::checked_cast<uint32_t>(data_range_.size);
}
bool RingBuffer::Deserialize(const SerializedState& state) {
const uint32_t data_offset = state.offset;
const uint32_t data_size = state.size;
if (data_offset >= capacity() || data_size > capacity()) {
return false;
}
data_range_ = {.offset = data_offset, .size = data_size};
return true;
}
RingBuffer::SplitBytes RingBuffer::MapRange(
const RingBuffer::Range& range) const {
DCHECK_LE(range.offset, capacity());
const size_t first_chunk_size =
std::min(range.size, capacity() - range.offset);
return {
mapping().bytes().subspan(range.offset).first(first_chunk_size),
mapping().bytes().first(range.size - first_chunk_size),
};
}
RingBuffer::Range RingBuffer::ComplementRange(const Range& range) const {
const size_t buffer_size = capacity();
DCHECK_LE(range.offset, buffer_size);
DCHECK_LE(range.size, buffer_size);
const size_t end = range.offset + range.size;
return {
.offset = end >= buffer_size ? end - buffer_size : end,
.size = buffer_size - range.size,
};
}
base::span<uint8_t> RingBuffer::GetAvailableCapacityView() const {
return MapRange(ComplementRange(data_range_)).first;
}
base::span<const uint8_t> RingBuffer::GetReadableDataView() const {
return MapRange(data_range_).first;
}
} // namespace mojo::core::ipcz_driver
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