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
