kc3-lang/brotli/enc/bit_cost.h

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• Hash : 81480011
  Author :
  Date : 2016-08-23T14:40:33
  

  Move "public" to "include/brotli"
  

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• enc/bit_cost.h

• /* Copyright 2013 Google Inc. All Rights Reserved.
  
     Distributed under MIT license.
     See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
  */
  
  /* Functions to estimate the bit cost of Huffman trees. */
  
  #ifndef BROTLI_ENC_BIT_COST_H_
  #define BROTLI_ENC_BIT_COST_H_
  
  #include <brotli/types.h>
  #include "./fast_log.h"
  #include "./histogram.h"
  #include "./port.h"
  
  #if defined(__cplusplus) || defined(c_plusplus)
  extern "C" {
  #endif
  
  static BROTLI_INLINE double ShannonEntropy(const uint32_t *population,
                                             size_t size, size_t *total) {
    size_t sum = 0;
    double retval = 0;
    const uint32_t *population_end = population + size;
    size_t p;
    if (size & 1) {
      goto odd_number_of_elements_left;
    }
    while (population < population_end) {
      p = *population++;
      sum += p;
      retval -= (double)p * FastLog2(p);
   odd_number_of_elements_left:
      p = *population++;
      sum += p;
      retval -= (double)p * FastLog2(p);
    }
    if (sum) retval += (double)sum * FastLog2(sum);
    *total = sum;
    return retval;
  }
  
  static BROTLI_INLINE double BitsEntropy(
      const uint32_t *population, size_t size) {
    size_t sum;
    double retval = ShannonEntropy(population, size, &sum);
    if (retval < sum) {
      /* At least one bit per literal is needed. */
      retval = (double)sum;
    }
    return retval;
  }
  
  BROTLI_INTERNAL double BrotliPopulationCostLiteral(const HistogramLiteral*);
  BROTLI_INTERNAL double BrotliPopulationCostCommand(const HistogramCommand*);
  BROTLI_INTERNAL double BrotliPopulationCostDistance(const HistogramDistance*);
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }  /* extern "C" */
  #endif
  
  #endif  /* BROTLI_ENC_BIT_COST_H_ */
  

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