| /* |
| * Copyright (c) 2021 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #ifndef NET_DCSCTP_PACKET_BOUNDED_BYTE_WRITER_H_ |
| #define NET_DCSCTP_PACKET_BOUNDED_BYTE_WRITER_H_ |
| |
| #include <algorithm> |
| |
| #include "api/array_view.h" |
| |
| namespace dcsctp { |
| |
| // TODO(boivie): These generic functions - and possibly this entire class - |
| // could be a candidate to have added to rtc_base/. They should use compiler |
| // intrinsics as well. |
| namespace internal { |
| // Stores a 8-bit unsigned word at `data`. |
| inline void StoreBigEndian8(uint8_t* data, uint8_t val) { |
| data[0] = val; |
| } |
| |
| // Stores a 16-bit unsigned word at `data`. |
| inline void StoreBigEndian16(uint8_t* data, uint16_t val) { |
| data[0] = val >> 8; |
| data[1] = val; |
| } |
| |
| // Stores a 32-bit unsigned word at `data`. |
| inline void StoreBigEndian32(uint8_t* data, uint32_t val) { |
| data[0] = val >> 24; |
| data[1] = val >> 16; |
| data[2] = val >> 8; |
| data[3] = val; |
| } |
| } // namespace internal |
| |
| // BoundedByteWriter wraps an ArrayView and divides it into two parts; A fixed |
| // size - which is the template parameter - and a variable size, which is what |
| // remains in `data` after the `FixedSize`. |
| // |
| // The BoundedByteWriter provides methods to write big endian numbers to the |
| // FixedSize portion of the buffer, and these are written with static bounds |
| // checking, to avoid out-of-bounds accesses without a run-time penalty. |
| // |
| // The variable sized portion can either be used to create sub-writers, which |
| // themselves would provide compile-time bounds-checking, or data can be copied |
| // to it. |
| template <int FixedSize> |
| class BoundedByteWriter { |
| public: |
| explicit BoundedByteWriter(rtc::ArrayView<uint8_t> data) : data_(data) { |
| RTC_CHECK(data.size() >= FixedSize); |
| } |
| |
| template <size_t offset> |
| void Store8(uint8_t value) { |
| static_assert(offset + sizeof(uint8_t) <= FixedSize, "Out-of-bounds"); |
| internal::StoreBigEndian8(&data_[offset], value); |
| } |
| |
| template <size_t offset> |
| void Store16(uint16_t value) { |
| static_assert(offset + sizeof(uint16_t) <= FixedSize, "Out-of-bounds"); |
| static_assert((offset % sizeof(uint16_t)) == 0, "Unaligned access"); |
| internal::StoreBigEndian16(&data_[offset], value); |
| } |
| |
| template <size_t offset> |
| void Store32(uint32_t value) { |
| static_assert(offset + sizeof(uint32_t) <= FixedSize, "Out-of-bounds"); |
| static_assert((offset % sizeof(uint32_t)) == 0, "Unaligned access"); |
| internal::StoreBigEndian32(&data_[offset], value); |
| } |
| |
| template <size_t SubSize> |
| BoundedByteWriter<SubSize> sub_writer(size_t variable_offset) { |
| RTC_CHECK(FixedSize + variable_offset + SubSize <= data_.size()); |
| |
| return BoundedByteWriter<SubSize>( |
| data_.subview(FixedSize + variable_offset, SubSize)); |
| } |
| |
| void CopyToVariableData(rtc::ArrayView<const uint8_t> source) { |
| size_t copy_size = std::min(source.size(), data_.size() - FixedSize); |
| if (source.data() == nullptr || copy_size == 0) { |
| return; |
| } |
| memcpy(data_.data() + FixedSize, source.data(), copy_size); |
| } |
| |
| private: |
| rtc::ArrayView<uint8_t> data_; |
| }; |
| } // namespace dcsctp |
| |
| #endif // NET_DCSCTP_PACKET_BOUNDED_BYTE_WRITER_H_ |