1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       price.h
4 /// \brief      Probability price calculation
5 //
6 //  Author:     Igor Pavlov
7 //
8 //  This file has been put into the public domain.
9 //  You can do whatever you want with this file.
10 //
11 ///////////////////////////////////////////////////////////////////////////////
12 
13 #ifndef LZMA_PRICE_H
14 #define LZMA_PRICE_H
15 
16 
17 #define RC_MOVE_REDUCING_BITS 4
18 #define RC_BIT_PRICE_SHIFT_BITS 4
19 #define RC_PRICE_TABLE_SIZE (RC_BIT_MODEL_TOTAL >> RC_MOVE_REDUCING_BITS)
20 
21 #define RC_INFINITY_PRICE (UINT32_C(1) << 30)
22 
23 
24 /// Lookup table for the inline functions defined in this file.
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
93