/*

 * H.265 video codec.

 * Copyright (c) 2013-2014 struktur AG, Dirk Farin <farin@struktur.de>

 *

 * This file is part of libde265.

 *

 * libde265 is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation, either version 3 of

 * the License, or (at your option) any later version.

 *

 * libde265 is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with libde265.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef DE265_BITSTREAM_H

#define DE265_BITSTREAM_H

#include <cstdint>

// HEVC (ITU-T H.265, E.3.3) allows ue(v) values up to 2^32-2 (e.g. bit_rate_value_minus1),

// which requires 31 leading zeros in the exp-Golomb code. 32 leading zeros would give a

// minimum codeNum of 2^32-1, which exceeds every syntax element's valid range.

constexpr int MAX_UVLC_LEADING_ZEROS = 31;

constexpr uint32_t UVLC_ERROR = UINT32_MAX;

constexpr int32_t SVLC_ERROR = INT32_MIN;

class bitreader {

public:

  bitreader() = default;

  bitreader(unsigned char* buffer, int len);

  uint32_t get_bits(int n); // n in [0;32]

  uint32_t get_bits_fast(int n); // n in [0;32]

  uint32_t peek_bits(int n);

  void skip_bits(int n);

  void skip_bits_fast(int n);

  void skip_to_byte_boundary();

  void prepare_for_CABAC();

  uint32_t get_uvlc();  // may return UVLC_ERROR

  int32_t  get_svlc();  // may return SVLC_ERROR

  bool check_rbsp_trailing_bits(); // return true if remaining filler bits are all zero

  uint8_t* data = nullptr;

  int bytes_remaining = 0;

private:

  void refill(); // refill to at least 56+1 bits

  uint64_t nextbits = 0; // left-aligned bits

  int nextbits_cnt = 0;

};

#endif