src/liblzma/rangecoder/price.h

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       price.h
   6 /// \brief      Probability price calculation
   7 //
   8 //  Author:     Igor Pavlov
   9 //
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 #ifndef LZMA_PRICE_H
  13 #define LZMA_PRICE_H
  14
  15
  16 #define RC_MOVE_REDUCING_BITS 4
  17 #define RC_BIT_PRICE_SHIFT_BITS 4
  18 #define RC_PRICE_TABLE_SIZE (RC_BIT_MODEL_TOTAL >> RC_MOVE_REDUCING_BITS)
  19
  20 #define RC_INFINITY_PRICE (UINT32_C(1) << 30)
  21
  22
  23 /// Lookup table for the inline functions defined in this file.
  24 lzma_attr_visibility_hidden
  25 extern const uint8_t lzma_rc_prices[RC_PRICE_TABLE_SIZE];
  26
  27
  28 static inline uint32_t
  29 rc_bit_price(const probability prob, const uint32_t bit)
  30 {
  31         return lzma_rc_prices[(prob ^ ((UINT32_C(0) - bit)
  32                         & (RC_BIT_MODEL_TOTAL - 1))) >> RC_MOVE_REDUCING_BITS];
  33 }
  34
  35
  36 static inline uint32_t
  37 rc_bit_0_price(const probability prob)
  38 {
  39         return lzma_rc_prices[prob >> RC_MOVE_REDUCING_BITS];
  40 }
  41
  42
  43 static inline uint32_t
  44 rc_bit_1_price(const probability prob)
  45 {
  46         return lzma_rc_prices[(prob ^ (RC_BIT_MODEL_TOTAL - 1))
  47                         >> RC_MOVE_REDUCING_BITS];
  48 }
  49
  50
  51 static inline uint32_t
  52 rc_bittree_price(const probability *const probs,
  53                 const uint32_t bit_levels, uint32_t symbol)
  54 {
  55         uint32_t price = 0;
  56         symbol += UINT32_C(1) << bit_levels;
  57
  58         do {
  59                 const uint32_t bit = symbol & 1;
  60                 symbol >>= 1;
  61                 price += rc_bit_price(probs[symbol], bit);
  62         } while (symbol != 1);
  63
  64         return price;
  65 }
  66
  67
  68 static inline uint32_t
  69 rc_bittree_reverse_price(const probability *const probs,
  70                 uint32_t bit_levels, uint32_t symbol)
  71 {
  72         uint32_t price = 0;
  73         uint32_t model_index = 1;
  74
  75         do {
  76                 const uint32_t bit = symbol & 1;
  77                 symbol >>= 1;
  78                 price += rc_bit_price(probs[model_index], bit);
  79                 model_index = (model_index << 1) + bit;
  80         } while (--bit_levels != 0);
  81
  82         return price;
  83 }
  84
  85
  86 static inline uint32_t
  87 rc_direct_price(const uint32_t bits)
  88 {
  89          return bits << RC_BIT_PRICE_SHIFT_BITS;
  90 }
  91
  92 #endif