| // Copyright (c) 2016 The WebM 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 SRC_PARSER_UTILS_H_ |
| #define SRC_PARSER_UTILS_H_ |
| |
| #include <cassert> |
| #include <cstdint> |
| #include <type_traits> |
| |
| #include "webm/reader.h" |
| #include "webm/status.h" |
| |
| namespace webm { |
| |
| // Reads a single byte from the reader, and returns the status of the read. If |
| // the status is not Status::kOkCompleted, then no data was read. |
| Status ReadByte(Reader* reader, std::uint8_t* byte); |
| |
| // Accumulates bytes from the reader into the integer. The integer will be |
| // extracted as a big-endian integer and stored with the native |
| // host-endianness. num_bytes_remaining is the number of bytes to |
| template <typename T> |
| Status AccumulateIntegerBytes(int num_to_read, Reader* reader, T* integer, |
| std::uint64_t* num_actually_read) { |
| static_assert(std::is_integral<T>::value || std::is_enum<T>::value, |
| "T must be an integer or enum type"); |
| // Use unsigned integers for bitwise arithmetic because it's well-defined (as |
| // opposed to signed integers, where left shifting a negative integer is |
| // undefined, for example). |
| using UnsignedT = typename std::make_unsigned<T>::type; |
| |
| assert(reader != nullptr); |
| assert(integer != nullptr); |
| assert(num_actually_read != nullptr); |
| assert(num_to_read >= 0); |
| assert(static_cast<std::size_t>(num_to_read) <= sizeof(T)); |
| |
| *num_actually_read = 0; |
| |
| if (num_to_read < 0 || static_cast<std::size_t>(num_to_read) > sizeof(T)) { |
| return Status(Status::kInvalidElementSize); |
| } |
| |
| for (; num_to_read > 0; --num_to_read) { |
| std::uint8_t byte; |
| const Status status = ReadByte(reader, &byte); |
| if (!status.completed_ok()) { |
| return status; |
| } |
| ++*num_actually_read; |
| *integer = static_cast<T>((static_cast<UnsignedT>(*integer) << 8) | byte); |
| } |
| |
| return Status(Status::kOkCompleted); |
| } |
| |
| } // namespace webm |
| |
| #endif // SRC_PARSER_UTILS_H_ |