text: // Copyright (c) the JPEG XL Project
  //
  // 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 LIB_JXL_ENTROPY_CODER_H_
  #define LIB_JXL_ENTROPY_CODER_H_
  
  #include <stddef.h>
  #include <stdint.h>
  
  #include "lib/jxl/ac_context.h"
  #include "lib/jxl/base/compiler_specific.h"
  #include "lib/jxl/dec_bit_reader.h"
  #include "lib/jxl/field_encodings.h"
  
  // Entropy coding and context modeling of DC and AC coefficients, as well as AC
  // strategy and quantization field.
  
  namespace jxl {
  
  static JXL_INLINE int32_t PredictFromTopAndLeft(
      const int32_t* const JXL_RESTRICT row_top,
      const int32_t* const JXL_RESTRICT row, size_t x, int32_t default_val) {
    if (x == 0) {
      return row_top == nullptr ? default_val : row_top[x];
    }
    if (row_top == nullptr) {
      return row[x - 1];
    }
    return (row_top[x] + row[x - 1] + 1) / 2;
  }
  
  static constexpr U32Enc kDCThresholdDist(Bits(4), BitsOffset(8, 16),
                                           BitsOffset(16, 272),
                                           BitsOffset(32, 65808));
  
  static constexpr U32Enc kQFThresholdDist(Bits(2), BitsOffset(3, 4),
                                           BitsOffset(5, 12), BitsOffset(8, 44));
  
  Status DecodeBlockCtxMap(BitReader* br, BlockCtxMap* block_ctx_map);
  
  }  // namespace jxl
  
  #endif  // LIB_JXL_ENTROPY_CODER_H_
  