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 /* This class models a sequence of literals and a backward reference copy. */ 8 9 #ifndef BROTLI_ENC_COMMAND_H_ 10 #define BROTLI_ENC_COMMAND_H_ 11 12 #include "../common/constants.h" 13 #include "../common/platform.h" 14 #include <brotli/types.h> 15 #include "./fast_log.h" 16 #include "./params.h" 17 #include "./prefix.h" 18 19 #if defined(__cplusplus) || defined(c_plusplus) 20 extern "C" { 21 #endif 22 23 static uint32_t kInsBase[] = { 0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26, 34, 50, 24 66, 98, 130, 194, 322, 578, 1090, 2114, 6210, 22594 }; 25 static uint32_t kInsExtra[] = { 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 26 5, 5, 6, 7, 8, 9, 10, 12, 14, 24 }; 27 static uint32_t kCopyBase[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 18, 22, 30, 28 38, 54, 70, 102, 134, 198, 326, 582, 1094, 2118 }; 29 static uint32_t kCopyExtra[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 30 4, 4, 5, 5, 6, 7, 8, 9, 10, 24 }; 31 32 static BROTLI_INLINE uint16_t GetInsertLengthCode(size_t insertlen) { 33 if (insertlen < 6) { 34 return (uint16_t)insertlen; 35 } else if (insertlen < 130) { 36 uint32_t nbits = Log2FloorNonZero(insertlen - 2) - 1u; 37 return (uint16_t)((nbits << 1) + ((insertlen - 2) >> nbits) + 2); 38 } else if (insertlen < 2114) { 39 return (uint16_t)(Log2FloorNonZero(insertlen - 66) + 10); 40 } else if (insertlen < 6210) { 41 return 21u; 42 } else if (insertlen < 22594) { 43 return 22u; 44 } else { 45 return 23u; 46 } 47 } 48 49 static BROTLI_INLINE uint16_t GetCopyLengthCode(size_t copylen) { 50 if (copylen < 10) { 51 return (uint16_t)(copylen - 2); 52 } else if (copylen < 134) { 53 uint32_t nbits = Log2FloorNonZero(copylen - 6) - 1u; 54 return (uint16_t)((nbits << 1) + ((copylen - 6) >> nbits) + 4); 55 } else if (copylen < 2118) { 56 return (uint16_t)(Log2FloorNonZero(copylen - 70) + 12); 57 } else { 58 return 23u; 59 } 60 } 61 62 static BROTLI_INLINE uint16_t CombineLengthCodes( 63 uint16_t inscode, uint16_t copycode, BROTLI_BOOL use_last_distance) { 64 uint16_t bits64 = 65 (uint16_t)((copycode & 0x7u) | ((inscode & 0x7u) << 3u)); 66 if (use_last_distance && inscode < 8u && copycode < 16u) { 67 return (copycode < 8u) ? bits64 : (bits64 | 64u); 68 } else { 69 /* Specification: 5 Encoding of ... (last table) */ 70 /* offset = 2 * index, where index is in range [0..8] */ 71 uint32_t offset = 2u * ((copycode >> 3u) + 3u * (inscode >> 3u)); 72 /* All values in specification are K * 64, 73 where K = [2, 3, 6, 4, 5, 8, 7, 9, 10], 74 i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9], 75 K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D. 76 All values in D require only 2 bits to encode. 77 Magic constant is shifted 6 bits left, to avoid final multiplication. */ 78 offset = (offset << 5u) + 0x40u + ((0x520D40u >> offset) & 0xC0u); 79 return (uint16_t)(offset | bits64); 80 } 81 } 82 83 static BROTLI_INLINE void GetLengthCode(size_t insertlen, size_t copylen, 84 BROTLI_BOOL use_last_distance, 85 uint16_t* code) { 86 uint16_t inscode = GetInsertLengthCode(insertlen); 87 uint16_t copycode = GetCopyLengthCode(copylen); 88 *code = CombineLengthCodes(inscode, copycode, use_last_distance); 89 } 90 91 static BROTLI_INLINE uint32_t GetInsertBase(uint16_t inscode) { 92 return kInsBase[inscode]; 93 } 94 95 static BROTLI_INLINE uint32_t GetInsertExtra(uint16_t inscode) { 96 return kInsExtra[inscode]; 97 } 98 99 static BROTLI_INLINE uint32_t GetCopyBase(uint16_t copycode) { 100 return kCopyBase[copycode]; 101 } 102 103 static BROTLI_INLINE uint32_t GetCopyExtra(uint16_t copycode) { 104 return kCopyExtra[copycode]; 105 } 106 107 typedef struct Command { 108 uint32_t insert_len_; 109 /* Stores copy_len in low 25 bits and copy_code - copy_len in high 7 bit. */ 110 uint32_t copy_len_; 111 /* Stores distance extra bits. */ 112 uint32_t dist_extra_; 113 uint16_t cmd_prefix_; 114 /* Stores distance code in low 10 bits 115 and number of extra bits in high 6 bits. */ 116 uint16_t dist_prefix_; 117 } Command; 118 119 /* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */ 120 static BROTLI_INLINE void InitCommand(Command* self, 121 const BrotliDistanceParams* dist, size_t insertlen, 122 size_t copylen, int copylen_code_delta, size_t distance_code) { 123 /* Don't rely on signed int representation, use honest casts. */ 124 uint32_t delta = (uint8_t)((int8_t)copylen_code_delta); 125 self->insert_len_ = (uint32_t)insertlen; 126 self->copy_len_ = (uint32_t)(copylen | (delta << 25)); 127 /* The distance prefix and extra bits are stored in this Command as if 128 npostfix and ndirect were 0, they are only recomputed later after the 129 clustering if needed. */ 130 PrefixEncodeCopyDistance( 131 distance_code, dist->num_direct_distance_codes, 132 dist->distance_postfix_bits, &self->dist_prefix_, &self->dist_extra_); 133 GetLengthCode( 134 insertlen, (size_t)((int)copylen + copylen_code_delta), 135 TO_BROTLI_BOOL((self->dist_prefix_ & 0x3FF) == 0), &self->cmd_prefix_); 136 } 137 138 static BROTLI_INLINE void InitInsertCommand(Command* self, size_t insertlen) { 139 self->insert_len_ = (uint32_t)insertlen; 140 self->copy_len_ = 4 << 25; 141 self->dist_extra_ = 0; 142 self->dist_prefix_ = BROTLI_NUM_DISTANCE_SHORT_CODES; 143 GetLengthCode(insertlen, 4, BROTLI_FALSE, &self->cmd_prefix_); 144 } 145 146 static BROTLI_INLINE uint32_t CommandRestoreDistanceCode( 147 const Command* self, const BrotliDistanceParams* dist) { 148 if ((self->dist_prefix_ & 0x3FFu) < 149 BROTLI_NUM_DISTANCE_SHORT_CODES + dist->num_direct_distance_codes) { 150 return self->dist_prefix_ & 0x3FFu; 151 } else { 152 uint32_t dcode = self->dist_prefix_ & 0x3FFu; 153 uint32_t nbits = self->dist_prefix_ >> 10; 154 uint32_t extra = self->dist_extra_; 155 uint32_t postfix_mask = (1U << dist->distance_postfix_bits) - 1U; 156 uint32_t hcode = (dcode - dist->num_direct_distance_codes - 157 BROTLI_NUM_DISTANCE_SHORT_CODES) >> 158 dist->distance_postfix_bits; 159 uint32_t lcode = (dcode - dist->num_direct_distance_codes - 160 BROTLI_NUM_DISTANCE_SHORT_CODES) & postfix_mask; 161 uint32_t offset = ((2U + (hcode & 1U)) << nbits) - 4U; 162 return ((offset + extra) << dist->distance_postfix_bits) + lcode + 163 dist->num_direct_distance_codes + BROTLI_NUM_DISTANCE_SHORT_CODES; 164 } 165 } 166 167 static BROTLI_INLINE uint32_t CommandDistanceContext(const Command* self) { 168 uint32_t r = self->cmd_prefix_ >> 6; 169 uint32_t c = self->cmd_prefix_ & 7; 170 if ((r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2)) { 171 return c; 172 } 173 return 3; 174 } 175 176 static BROTLI_INLINE uint32_t CommandCopyLen(const Command* self) { 177 return self->copy_len_ & 0x1FFFFFF; 178 } 179 180 static BROTLI_INLINE uint32_t CommandCopyLenCode(const Command* self) { 181 uint32_t modifier = self->copy_len_ >> 25; 182 int32_t delta = (int8_t)((uint8_t)(modifier | ((modifier & 0x40) << 1))); 183 return (uint32_t)((int32_t)(self->copy_len_ & 0x1FFFFFF) + delta); 184 } 185 186 #if defined(__cplusplus) || defined(c_plusplus) 187 } /* extern "C" */ 188 #endif 189 190 #endif /* BROTLI_ENC_COMMAND_H_ */ 191
