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/*
* Copyright 2019 The libgav1 Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_
#define LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_
#include <cstddef>
#include <cstdint>
#include "src/utils/bit_reader.h"
#include "src/utils/memory.h"
namespace libgav1 {
class RawBitReader : public BitReader, public Allocable {
public:
RawBitReader(const uint8_t* data, size_t size);
~RawBitReader() override = default;
int ReadBit() override;
int64_t ReadLiteral(int num_bits) override; // f(n) in the spec.
bool ReadInverseSignedLiteral(int num_bits,
int* value); // su(1+num_bits) in the spec.
bool ReadLittleEndian(int num_bytes,
size_t* value); // le(n) in the spec.
bool ReadUnsignedLeb128(size_t* value); // leb128() in the spec.
// Reads a variable length unsigned number and stores it in |*value|. On a
// successful return, |*value| is in the range of 0 to UINT32_MAX − 1,
// inclusive.
bool ReadUvlc(uint32_t* value); // uvlc() in the spec.
bool Finished() const;
size_t bit_offset() const { return bit_offset_; }
// Return the bytes consumed so far (rounded up).
size_t byte_offset() const { return (bit_offset() + 7) >> 3; }
size_t size() const { return size_; }
// Move to the next byte boundary if not already at one. Return false if any
// of the bits being skipped over is non-zero. Return true otherwise. If this
// function returns false, the reader is left in an undefined state and must
// not be used further. section 5.3.5.
bool AlignToNextByte();
// Make sure that the trailing bits structure is as expected and skip over it.
// section 5.3.4.
bool VerifyAndSkipTrailingBits(size_t num_bits);
// Skip |num_bytes| bytes. This only works if the current position is at a
// byte boundary. The function returns false if the current position is not at
// a byte boundary or if skipping |num_bytes| causes the reader to run out of
// buffer. Returns true otherwise.
bool SkipBytes(size_t num_bytes);
// Skip |num_bits| bits. The function returns false if skipping |num_bits|
// causes the reader to run out of buffer. Returns true otherwise.
bool SkipBits(size_t num_bits);
private:
// Returns true if it is safe to read a literal of size |num_bits|.
bool CanReadLiteral(size_t num_bits) const;
int ReadBitImpl();
const uint8_t* const data_;
size_t bit_offset_;
const size_t size_;
};
} // namespace libgav1
#endif // LIBGAV1_SRC_UTILS_RAW_BIT_READER_H_
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