1 /* 2 * Copyright 2019 The libgav1 Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_ 18 #define LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_ 19 20 #include <cstddef> 21 #include <cstdint> 22 23 #include "src/utils/bit_reader.h" 24 #include "src/utils/memory.h" 25 26 namespace libgav1 { 27 28 class RawBitReader final : public BitReader, public Allocable { 29 public: 30 RawBitReader(const uint8_t* data, size_t size); 31 ~RawBitReader() override = default; 32 33 int ReadBit() override; 34 int64_t ReadLiteral(int num_bits) override; // f(n) in the spec. 35 bool ReadInverseSignedLiteral(int num_bits, 36 int* value); // su(1+num_bits) in the spec. 37 bool ReadLittleEndian(int num_bytes, 38 size_t* value); // le(n) in the spec. 39 bool ReadUnsignedLeb128(size_t* value); // leb128() in the spec. 40 // Reads a variable length unsigned number and stores it in |*value|. On a 41 // successful return, |*value| is in the range of 0 to UINT32_MAX - 1, 42 // inclusive. 43 bool ReadUvlc(uint32_t* value); // uvlc() in the spec. 44 bool Finished() const; bit_offset()45 size_t bit_offset() const { return bit_offset_; } 46 // Return the bytes consumed so far (rounded up). byte_offset()47 size_t byte_offset() const { return (bit_offset() + 7) >> 3; } size()48 size_t size() const { return size_; } 49 // Move to the next byte boundary if not already at one. Return false if any 50 // of the bits being skipped over is non-zero. Return true otherwise. If this 51 // function returns false, the reader is left in an undefined state and must 52 // not be used further. section 5.3.5. 53 bool AlignToNextByte(); 54 // Make sure that the trailing bits structure is as expected and skip over it. 55 // section 5.3.4. 56 bool VerifyAndSkipTrailingBits(size_t num_bits); 57 // Skip |num_bytes| bytes. This only works if the current position is at a 58 // byte boundary. The function returns false if the current position is not at 59 // a byte boundary or if skipping |num_bytes| causes the reader to run out of 60 // buffer. Returns true otherwise. 61 bool SkipBytes(size_t num_bytes); 62 // Skip |num_bits| bits. The function returns false if skipping |num_bits| 63 // causes the reader to run out of buffer. Returns true otherwise. 64 bool SkipBits(size_t num_bits); 65 66 private: 67 // Returns true if it is safe to read a literal of size |num_bits|. 68 bool CanReadLiteral(size_t num_bits) const; 69 int ReadBitImpl(); 70 71 const uint8_t* const data_; 72 size_t bit_offset_; 73 const size_t size_; 74 }; 75 76 } // namespace libgav1 77 78 #endif // LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_ 79