xref: /aosp_15_r20/external/libwebm/webm_parser/src/parser_utils.h (revision 103e46e4cd4b6efcf6001f23fa8665fb110abf8d)
1*103e46e4SHarish Mahendrakar // Copyright (c) 2016 The WebM project authors. All Rights Reserved.
2*103e46e4SHarish Mahendrakar //
3*103e46e4SHarish Mahendrakar // Use of this source code is governed by a BSD-style license
4*103e46e4SHarish Mahendrakar // that can be found in the LICENSE file in the root of the source
5*103e46e4SHarish Mahendrakar // tree. An additional intellectual property rights grant can be found
6*103e46e4SHarish Mahendrakar // in the file PATENTS.  All contributing project authors may
7*103e46e4SHarish Mahendrakar // be found in the AUTHORS file in the root of the source tree.
8*103e46e4SHarish Mahendrakar #ifndef SRC_PARSER_UTILS_H_
9*103e46e4SHarish Mahendrakar #define SRC_PARSER_UTILS_H_
10*103e46e4SHarish Mahendrakar 
11*103e46e4SHarish Mahendrakar #include <cassert>
12*103e46e4SHarish Mahendrakar #include <cstdint>
13*103e46e4SHarish Mahendrakar #include <type_traits>
14*103e46e4SHarish Mahendrakar 
15*103e46e4SHarish Mahendrakar #include "webm/reader.h"
16*103e46e4SHarish Mahendrakar #include "webm/status.h"
17*103e46e4SHarish Mahendrakar 
18*103e46e4SHarish Mahendrakar namespace webm {
19*103e46e4SHarish Mahendrakar 
20*103e46e4SHarish Mahendrakar // Reads a single byte from the reader, and returns the status of the read. If
21*103e46e4SHarish Mahendrakar // the status is not Status::kOkCompleted, then no data was read.
22*103e46e4SHarish Mahendrakar Status ReadByte(Reader* reader, std::uint8_t* byte);
23*103e46e4SHarish Mahendrakar 
24*103e46e4SHarish Mahendrakar // Accumulates bytes from the reader into the integer. The integer will be
25*103e46e4SHarish Mahendrakar // extracted as a big-endian integer and stored with the native
26*103e46e4SHarish Mahendrakar // host-endianness. num_bytes_remaining is the number of bytes to
27*103e46e4SHarish Mahendrakar template <typename T>
AccumulateIntegerBytes(int num_to_read,Reader * reader,T * integer,std::uint64_t * num_actually_read)28*103e46e4SHarish Mahendrakar Status AccumulateIntegerBytes(int num_to_read, Reader* reader, T* integer,
29*103e46e4SHarish Mahendrakar                               std::uint64_t* num_actually_read) {
30*103e46e4SHarish Mahendrakar   static_assert(std::is_integral<T>::value || std::is_enum<T>::value,
31*103e46e4SHarish Mahendrakar                 "T must be an integer or enum type");
32*103e46e4SHarish Mahendrakar   // Use unsigned integers for bitwise arithmetic because it's well-defined (as
33*103e46e4SHarish Mahendrakar   // opposed to signed integers, where left shifting a negative integer is
34*103e46e4SHarish Mahendrakar   // undefined, for example).
35*103e46e4SHarish Mahendrakar   using UnsignedT = typename std::make_unsigned<T>::type;
36*103e46e4SHarish Mahendrakar 
37*103e46e4SHarish Mahendrakar   assert(reader != nullptr);
38*103e46e4SHarish Mahendrakar   assert(integer != nullptr);
39*103e46e4SHarish Mahendrakar   assert(num_actually_read != nullptr);
40*103e46e4SHarish Mahendrakar   assert(num_to_read >= 0);
41*103e46e4SHarish Mahendrakar   assert(static_cast<std::size_t>(num_to_read) <= sizeof(T));
42*103e46e4SHarish Mahendrakar 
43*103e46e4SHarish Mahendrakar   *num_actually_read = 0;
44*103e46e4SHarish Mahendrakar 
45*103e46e4SHarish Mahendrakar   if (num_to_read < 0 || static_cast<std::size_t>(num_to_read) > sizeof(T)) {
46*103e46e4SHarish Mahendrakar     return Status(Status::kInvalidElementSize);
47*103e46e4SHarish Mahendrakar   }
48*103e46e4SHarish Mahendrakar 
49*103e46e4SHarish Mahendrakar   for (; num_to_read > 0; --num_to_read) {
50*103e46e4SHarish Mahendrakar     std::uint8_t byte;
51*103e46e4SHarish Mahendrakar     const Status status = ReadByte(reader, &byte);
52*103e46e4SHarish Mahendrakar     if (!status.completed_ok()) {
53*103e46e4SHarish Mahendrakar       return status;
54*103e46e4SHarish Mahendrakar     }
55*103e46e4SHarish Mahendrakar     ++*num_actually_read;
56*103e46e4SHarish Mahendrakar     *integer = static_cast<T>((static_cast<UnsignedT>(*integer) << 8) | byte);
57*103e46e4SHarish Mahendrakar   }
58*103e46e4SHarish Mahendrakar 
59*103e46e4SHarish Mahendrakar   return Status(Status::kOkCompleted);
60*103e46e4SHarish Mahendrakar }
61*103e46e4SHarish Mahendrakar 
62*103e46e4SHarish Mahendrakar }  // namespace webm
63*103e46e4SHarish Mahendrakar 
64*103e46e4SHarish Mahendrakar #endif  // SRC_PARSER_UTILS_H_
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