1 // Copyright (c) 2016 The WebM project authors. All Rights Reserved. 2 // 3 // Use of this source code is governed by a BSD-style license 4 // that can be found in the LICENSE file in the root of the source 5 // tree. An additional intellectual property rights grant can be found 6 // in the file PATENTS. All contributing project authors may 7 // be found in the AUTHORS file in the root of the source tree. 8 #include "src/size_parser.h" 9 10 #include <cassert> 11 #include <cstdint> 12 #include <limits> 13 14 #include "src/bit_utils.h" 15 #include "src/parser_utils.h" 16 #include "webm/element.h" 17 #include "webm/reader.h" 18 #include "webm/status.h" 19 20 namespace webm { 21 22 // Spec references: 23 // http://matroska.org/technical/specs/index.html#EBML_ex 24 // https://github.com/Matroska-Org/ebml-specification/blob/master/specification.markdown#element-data-size Feed(Callback * callback,Reader * reader,std::uint64_t * num_bytes_read)25Status SizeParser::Feed(Callback* callback, Reader* reader, 26 std::uint64_t* num_bytes_read) { 27 assert(callback != nullptr); 28 assert(reader != nullptr); 29 assert(num_bytes_read != nullptr); 30 31 // Within the EBML header, the size can be encoded with 1-4 octets. After 32 // the EBML header, the size can be encoded with 1-8 octets (though not more 33 // than EBMLMaxSizeLength). 34 35 Status status = uint_parser_.Feed(callback, reader, num_bytes_read); 36 37 if (status.code == Status::kInvalidElementValue) { 38 status.code = Status::kInvalidElementSize; 39 } 40 41 return status; 42 } 43 size() const44std::uint64_t SizeParser::size() const { 45 // If all data bits are set, then it represents an unknown element size. 46 const std::uint64_t data_bits = 47 std::numeric_limits<std::uint64_t>::max() >> 48 (57 - 7 * (uint_parser_.encoded_length() - 1)); 49 if (uint_parser_.value() == data_bits) { 50 return kUnknownElementSize; 51 } 52 53 return uint_parser_.value(); 54 } 55 56 } // namespace webm 57