1 | /* Copyright 2013 Google Inc. All Rights Reserved. |
2 | |
3 | Distributed under MIT license. |
4 | See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
5 | */ |
6 | |
7 | /* Utilities for building Huffman decoding tables. */ |
8 | |
9 | #ifndef BROTLI_DEC_HUFFMAN_H_ |
10 | #define BROTLI_DEC_HUFFMAN_H_ |
11 | |
12 | #include "../common/platform.h" |
13 | #include <brotli/types.h> |
14 | |
15 | #if defined(__cplusplus) || defined(c_plusplus) |
16 | extern "C" { |
17 | #endif |
18 | |
19 | #define BROTLI_HUFFMAN_MAX_CODE_LENGTH 15 |
20 | |
21 | /* Maximum possible Huffman table size for an alphabet size of (index * 32), |
22 | max code length 15 and root table bits 8. */ |
23 | static const uint16_t kMaxHuffmanTableSize[] = { |
24 | 256, 402, 436, 468, 500, 534, 566, 598, 630, 662, 694, 726, 758, 790, 822, |
25 | 854, 886, 920, 952, 984, 1016, 1048, 1080, 1112, 1144, 1176, 1208, 1240, 1272, |
26 | 1304, 1336, 1368, 1400, 1432, 1464, 1496, 1528}; |
27 | /* BROTLI_NUM_BLOCK_LEN_SYMBOLS == 26 */ |
28 | #define BROTLI_HUFFMAN_MAX_SIZE_26 396 |
29 | /* BROTLI_MAX_BLOCK_TYPE_SYMBOLS == 258 */ |
30 | #define BROTLI_HUFFMAN_MAX_SIZE_258 632 |
31 | /* BROTLI_MAX_CONTEXT_MAP_SYMBOLS == 272 */ |
32 | #define BROTLI_HUFFMAN_MAX_SIZE_272 646 |
33 | |
34 | #define BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH 5 |
35 | |
36 | #if ((defined(BROTLI_TARGET_ARMV7) || defined(BROTLI_TARGET_ARMV8_32)) && \ |
37 | BROTLI_GNUC_HAS_ATTRIBUTE(aligned, 2, 7, 0)) |
38 | #define BROTLI_HUFFMAN_CODE_FAST_LOAD |
39 | #endif |
40 | |
41 | #if !defined(BROTLI_HUFFMAN_CODE_FAST_LOAD) |
42 | /* Do not create this struct directly - use the ConstructHuffmanCode |
43 | * constructor below! */ |
44 | typedef struct { |
45 | uint8_t bits; /* number of bits used for this symbol */ |
46 | uint16_t value; /* symbol value or table offset */ |
47 | } HuffmanCode; |
48 | |
49 | static BROTLI_INLINE HuffmanCode ConstructHuffmanCode(const uint8_t bits, |
50 | const uint16_t value) { |
51 | HuffmanCode h; |
52 | h.bits = bits; |
53 | h.value = value; |
54 | return h; |
55 | } |
56 | |
57 | /* Please use the following macros to optimize HuffmanCode accesses in hot |
58 | * paths. |
59 | * |
60 | * For example, assuming |table| contains a HuffmanCode pointer: |
61 | * |
62 | * BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(table); |
63 | * BROTLI_HC_ADJUST_TABLE_INDEX(table, index_into_table); |
64 | * *bits = BROTLI_HC_GET_BITS(table); |
65 | * *value = BROTLI_HC_GET_VALUE(table); |
66 | * BROTLI_HC_ADJUST_TABLE_INDEX(table, offset); |
67 | * *bits2 = BROTLI_HC_GET_BITS(table); |
68 | * *value2 = BROTLI_HC_GET_VALUE(table); |
69 | * |
70 | */ |
71 | |
72 | #define BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(H) |
73 | #define BROTLI_HC_ADJUST_TABLE_INDEX(H, V) H += (V) |
74 | |
75 | /* These must be given a HuffmanCode pointer! */ |
76 | #define BROTLI_HC_FAST_LOAD_BITS(H) (H->bits) |
77 | #define BROTLI_HC_FAST_LOAD_VALUE(H) (H->value) |
78 | |
79 | #else /* BROTLI_HUFFMAN_CODE_FAST_LOAD */ |
80 | |
81 | typedef BROTLI_ALIGNED(4) uint32_t HuffmanCode; |
82 | |
83 | static BROTLI_INLINE HuffmanCode ConstructHuffmanCode(const uint8_t bits, |
84 | const uint16_t value) { |
85 | return ((value & 0xFFFF) << 16) | (bits & 0xFF); |
86 | } |
87 | |
88 | #define BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(H) uint32_t __fastload_##H = (*H) |
89 | #define BROTLI_HC_ADJUST_TABLE_INDEX(H, V) H += (V); __fastload_##H = (*H) |
90 | |
91 | /* These must be given a HuffmanCode pointer! */ |
92 | #define BROTLI_HC_FAST_LOAD_BITS(H) ((__fastload_##H) & 0xFF) |
93 | #define BROTLI_HC_FAST_LOAD_VALUE(H) ((__fastload_##H) >> 16) |
94 | #endif /* BROTLI_HUFFMAN_CODE_FAST_LOAD */ |
95 | |
96 | /* Builds Huffman lookup table assuming code lengths are in symbol order. */ |
97 | BROTLI_INTERNAL void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* root_table, |
98 | const uint8_t* const code_lengths, uint16_t* count); |
99 | |
100 | /* Builds Huffman lookup table assuming code lengths are in symbol order. |
101 | Returns size of resulting table. */ |
102 | BROTLI_INTERNAL uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table, |
103 | int root_bits, const uint16_t* const symbol_lists, uint16_t* count_arg); |
104 | |
105 | /* Builds a simple Huffman table. The |num_symbols| parameter is to be |
106 | interpreted as follows: 0 means 1 symbol, 1 means 2 symbols, |
107 | 2 means 3 symbols, 3 means 4 symbols with lengths [2, 2, 2, 2], |
108 | 4 means 4 symbols with lengths [1, 2, 3, 3]. */ |
109 | BROTLI_INTERNAL uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table, |
110 | int root_bits, uint16_t* symbols, uint32_t num_symbols); |
111 | |
112 | /* Contains a collection of Huffman trees with the same alphabet size. */ |
113 | /* max_symbol is needed due to simple codes since log2(alphabet_size) could be |
114 | greater than log2(max_symbol). */ |
115 | typedef struct { |
116 | HuffmanCode** htrees; |
117 | HuffmanCode* codes; |
118 | uint16_t alphabet_size; |
119 | uint16_t max_symbol; |
120 | uint16_t num_htrees; |
121 | } HuffmanTreeGroup; |
122 | |
123 | #if defined(__cplusplus) || defined(c_plusplus) |
124 | } /* extern "C" */ |
125 | #endif |
126 | |
127 | #endif /* BROTLI_DEC_HUFFMAN_H_ */ |
128 | |