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[xz/debian.git] / src / liblzma / rangecoder / price.h
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1 // SPDX-License-Identifier: 0BSD
3 ///////////////////////////////////////////////////////////////////////////////
4 //
5 /// \file price.h
6 /// \brief Probability price calculation
7 //
8 // Author: Igor Pavlov
9 //
10 ///////////////////////////////////////////////////////////////////////////////
12 #ifndef LZMA_PRICE_H
13 #define LZMA_PRICE_H
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)
20 #define RC_INFINITY_PRICE (UINT32_C(1) << 30)
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];
28 static inline uint32_t
29 rc_bit_price(const probability prob, const uint32_t bit)
31 return lzma_rc_prices[(prob ^ ((UINT32_C(0) - bit)
32 & (RC_BIT_MODEL_TOTAL - 1))) >> RC_MOVE_REDUCING_BITS];
36 static inline uint32_t
37 rc_bit_0_price(const probability prob)
39 return lzma_rc_prices[prob >> RC_MOVE_REDUCING_BITS];
43 static inline uint32_t
44 rc_bit_1_price(const probability prob)
46 return lzma_rc_prices[(prob ^ (RC_BIT_MODEL_TOTAL - 1))
47 >> RC_MOVE_REDUCING_BITS];
51 static inline uint32_t
52 rc_bittree_price(const probability *const probs,
53 const uint32_t bit_levels, uint32_t symbol)
55 uint32_t price = 0;
56 symbol += UINT32_C(1) << bit_levels;
58 do {
59 const uint32_t bit = symbol & 1;
60 symbol >>= 1;
61 price += rc_bit_price(probs[symbol], bit);
62 } while (symbol != 1);
64 return price;
68 static inline uint32_t
69 rc_bittree_reverse_price(const probability *const probs,
70 uint32_t bit_levels, uint32_t symbol)
72 uint32_t price = 0;
73 uint32_t model_index = 1;
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);
82 return price;
86 static inline uint32_t
87 rc_direct_price(const uint32_t bits)
89 return bits << RC_BIT_PRICE_SHIFT_BITS;
92 #endif