1 // SPDX-License-Identifier: 0BSD 2 3 /////////////////////////////////////////////////////////////////////////////// 4 // 5 /// \file lz_encoder.h 6 /// \brief LZ in window and match finder API 7 /// 8 // Authors: Igor Pavlov 9 // Lasse Collin 10 // 11 /////////////////////////////////////////////////////////////////////////////// 12 13 #ifndef LZMA_LZ_ENCODER_H 14 #define LZMA_LZ_ENCODER_H 15 16 #include "common.h" 17 18 19 // For now, the dictionary size is limited to 1.5 GiB. This may grow 20 // in the future if needed, but it needs a little more work than just 21 // changing this check. 22 #define IS_ENC_DICT_SIZE_VALID(size) \ 23 ((size) >= LZMA_DICT_SIZE_MIN \ 24 && (size) <= (UINT32_C(1) << 30) + (UINT32_C(1) << 29)) 25 26 27 /// A table of these is used by the LZ-based encoder to hold 28 /// the length-distance pairs found by the match finder. 29 typedef struct { 30 uint32_t len; 31 uint32_t dist; 32 } lzma_match; 33 34 35 typedef struct lzma_mf_s lzma_mf; 36 struct lzma_mf_s { 37 /////////////// 38 // In Window // 39 /////////////// 40 41 /// Pointer to buffer with data to be compressed 42 uint8_t *buffer; 43 44 /// Total size of the allocated buffer (that is, including all 45 /// the extra space) 46 uint32_t size; 47 48 /// Number of bytes that must be kept available in our input history. 49 /// That is, once keep_size_before bytes have been processed, 50 /// buffer[read_pos - keep_size_before] is the oldest byte that 51 /// must be available for reading. 52 uint32_t keep_size_before; 53 54 /// Number of bytes that must be kept in buffer after read_pos. 55 /// That is, read_pos <= write_pos - keep_size_after as long as 56 /// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed 57 /// to reach write_pos so that the last bytes get encoded too. 58 uint32_t keep_size_after; 59 60 /// Match finders store locations of matches using 32-bit integers. 61 /// To avoid adjusting several megabytes of integers every time the 62 /// input window is moved with move_window, we only adjust the 63 /// offset of the buffer. Thus, buffer[value_in_hash_table - offset] 64 /// is the byte pointed by value_in_hash_table. 65 uint32_t offset; 66 67 /// buffer[read_pos] is the next byte to run through the match 68 /// finder. This is incremented in the match finder once the byte 69 /// has been processed. 70 uint32_t read_pos; 71 72 /// Number of bytes that have been ran through the match finder, but 73 /// which haven't been encoded by the LZ-based encoder yet. 74 uint32_t read_ahead; 75 76 /// As long as read_pos is less than read_limit, there is enough 77 /// input available in buffer for at least one encoding loop. 78 /// 79 /// Because of the stateful API, read_limit may and will get greater 80 /// than read_pos quite often. This is taken into account when 81 /// calculating the value for keep_size_after. 82 uint32_t read_limit; 83 84 /// buffer[write_pos] is the first byte that doesn't contain valid 85 /// uncompressed data; that is, the next input byte will be copied 86 /// to buffer[write_pos]. 87 uint32_t write_pos; 88 89 /// Number of bytes not hashed before read_pos. This is needed to 90 /// restart the match finder after LZMA_SYNC_FLUSH. 91 uint32_t pending; 92 93 ////////////////// 94 // Match Finder // 95 ////////////////// 96 97 /// Find matches. Returns the number of distance-length pairs written 98 /// to the matches array. This is called only via lzma_mf_find(). 99 uint32_t (*find)(lzma_mf *mf, lzma_match *matches); 100 101 /// Skips num bytes. This is like find() but doesn't make the 102 /// distance-length pairs available, thus being a little faster. 103 /// This is called only via mf_skip(). 104 void (*skip)(lzma_mf *mf, uint32_t num); 105 106 uint32_t *hash; 107 uint32_t *son; 108 uint32_t cyclic_pos; 109 uint32_t cyclic_size; // Must be dictionary size + 1. 110 uint32_t hash_mask; 111 112 /// Maximum number of loops in the match finder 113 uint32_t depth; 114 115 /// Maximum length of a match that the match finder will try to find. 116 uint32_t nice_len; 117 118 /// Maximum length of a match supported by the LZ-based encoder. 119 /// If the longest match found by the match finder is nice_len, 120 /// mf_find() tries to expand it up to match_len_max bytes. 121 uint32_t match_len_max; 122 123 /// When running out of input, binary tree match finders need to know 124 /// if it is due to flushing or finishing. The action is used also 125 /// by the LZ-based encoders themselves. 126 lzma_action action; 127 128 /// Number of elements in hash[] 129 uint32_t hash_count; 130 131 /// Number of elements in son[] 132 uint32_t sons_count; 133 }; 134 135 136 typedef struct { 137 /// Extra amount of data to keep available before the "actual" 138 /// dictionary. 139 size_t before_size; 140 141 /// Size of the history buffer 142 size_t dict_size; 143 144 /// Extra amount of data to keep available after the "actual" 145 /// dictionary. 146 size_t after_size; 147 148 /// Maximum length of a match that the LZ-based encoder can accept. 149 /// This is used to extend matches of length nice_len to the 150 /// maximum possible length. 151 size_t match_len_max; 152 153 /// Match finder will search matches up to this length. 154 /// This must be less than or equal to match_len_max. 155 size_t nice_len; 156 157 /// Type of the match finder to use 158 lzma_match_finder match_finder; 159 160 /// Maximum search depth 161 uint32_t depth; 162 163 /// Initial dictionary for the match finder to search. 164 const uint8_t *preset_dict; 165 166 /// If the preset dictionary is NULL, this value is ignored. 167 /// Otherwise this member must indicate the preset dictionary's 168 /// buffer size. If this size is larger than dict_size, then only 169 /// the dict_size sized tail of the preset_dict will be used. 170 uint32_t preset_dict_size; 171 172 } lzma_lz_options; 173 174 175 // The total usable buffer space at any moment outside the match finder: 176 // before_size + dict_size + after_size + match_len_max 177 // 178 // In reality, there's some extra space allocated to prevent the number of 179 // memmove() calls reasonable. The bigger the dict_size is, the bigger 180 // this extra buffer will be since with bigger dictionaries memmove() would 181 // also take longer. 182 // 183 // A single encoder loop in the LZ-based encoder may call the match finder 184 // (mf_find() or mf_skip()) at most after_size times. In other words, 185 // a single encoder loop may increment lzma_mf.read_pos at most after_size 186 // times. Since matches are looked up to 187 // lzma_mf.buffer[lzma_mf.read_pos + match_len_max - 1], the total 188 // amount of extra buffer needed after dict_size becomes 189 // after_size + match_len_max. 190 // 191 // before_size has two uses. The first one is to keep literals available 192 // in cases when the LZ-based encoder has made some read ahead. 193 // TODO: Maybe this could be changed by making the LZ-based encoders to 194 // store the actual literals as they do with length-distance pairs. 195 // 196 // Algorithms such as LZMA2 first try to compress a chunk, and then check 197 // if the encoded result is smaller than the uncompressed one. If the chunk 198 // was incompressible, it is better to store it in uncompressed form in 199 // the output stream. To do this, the whole uncompressed chunk has to be 200 // still available in the history buffer. before_size achieves that. 201 202 203 typedef struct { 204 /// Data specific to the LZ-based encoder 205 void *coder; 206 207 /// Function to encode from *dict to out[] 208 lzma_ret (*code)(void *coder, 209 lzma_mf *restrict mf, uint8_t *restrict out, 210 size_t *restrict out_pos, size_t out_size); 211 212 /// Free allocated resources 213 void (*end)(void *coder, const lzma_allocator *allocator); 214 215 /// Update the options in the middle of the encoding. 216 lzma_ret (*options_update)(void *coder, const lzma_filter *filter); 217 218 /// Set maximum allowed output size 219 lzma_ret (*set_out_limit)(void *coder, uint64_t *uncomp_size, 220 uint64_t out_limit); 221 222 } lzma_lz_encoder; 223 224 225 // Basic steps: 226 // 1. Input gets copied into the dictionary. 227 // 2. Data in dictionary gets run through the match finder byte by byte. 228 // 3. The literals and matches are encoded using e.g. LZMA. 229 // 230 // The bytes that have been ran through the match finder, but not encoded yet, 231 // are called 'read ahead'. 232 233 234 /// Get how many bytes the match finder hashes in its initial step. 235 /// This is also the minimum nice_len value with the match finder. 236 static inline uint32_t 237 mf_get_hash_bytes(lzma_match_finder match_finder) 238 { 239 return (uint32_t)match_finder & 0x0F; 240 } 241 242 243 /// Get pointer to the first byte not ran through the match finder 244 static inline const uint8_t * 245 mf_ptr(const lzma_mf *mf) 246 { 247 return mf->buffer + mf->read_pos; 248 } 249 250 251 /// Get the number of bytes that haven't been ran through the match finder yet. 252 static inline uint32_t 253 mf_avail(const lzma_mf *mf) 254 { 255 return mf->write_pos - mf->read_pos; 256 } 257 258 259 /// Get the number of bytes that haven't been encoded yet (some of these 260 /// bytes may have been ran through the match finder though). 261 static inline uint32_t 262 mf_unencoded(const lzma_mf *mf) 263 { 264 return mf->write_pos - mf->read_pos + mf->read_ahead; 265 } 266 267 268 /// Calculate the absolute offset from the beginning of the most recent 269 /// dictionary reset. Only the lowest four bits are important, so there's no 270 /// problem that we don't know the 64-bit size of the data encoded so far. 271 /// 272 /// NOTE: When moving the input window, we need to do it so that the lowest 273 /// bits of dict->read_pos are not modified to keep this macro working 274 /// as intended. 275 static inline uint32_t 276 mf_position(const lzma_mf *mf) 277 { 278 return mf->read_pos - mf->read_ahead; 279 } 280 281 282 /// Since everything else begins with mf_, use it also for lzma_mf_find(). 283 #define mf_find lzma_mf_find 284 285 286 /// Skip the given number of bytes. This is used when a good match was found. 287 /// For example, if mf_find() finds a match of 200 bytes long, the first byte 288 /// of that match was already consumed by mf_find(), and the rest 199 bytes 289 /// have to be skipped with mf_skip(mf, 199). 290 static inline void 291 mf_skip(lzma_mf *mf, uint32_t amount) 292 { 293 if (amount != 0) { 294 mf->skip(mf, amount); 295 mf->read_ahead += amount; 296 } 297 } 298 299 300 /// Copies at most *left number of bytes from the history buffer 301 /// to out[]. This is needed by LZMA2 to encode uncompressed chunks. 302 static inline void 303 mf_read(lzma_mf *mf, uint8_t *out, size_t *out_pos, size_t out_size, 304 size_t *left) 305 { 306 const size_t out_avail = out_size - *out_pos; 307 const size_t copy_size = my_min(out_avail, *left); 308 309 assert(mf->read_ahead == 0); 310 assert(mf->read_pos >= *left); 311 312 memcpy(out + *out_pos, mf->buffer + mf->read_pos - *left, 313 copy_size); 314 315 *out_pos += copy_size; 316 *left -= copy_size; 317 return; 318 } 319 320 321 extern lzma_ret lzma_lz_encoder_init( 322 lzma_next_coder *next, const lzma_allocator *allocator, 323 const lzma_filter_info *filters, 324 lzma_ret (*lz_init)(lzma_lz_encoder *lz, 325 const lzma_allocator *allocator, 326 lzma_vli id, const void *options, 327 lzma_lz_options *lz_options)); 328 329 330 extern uint64_t lzma_lz_encoder_memusage(const lzma_lz_options *lz_options); 331 332 333 // These are only for LZ encoder's internal use. 334 extern uint32_t lzma_mf_find( 335 lzma_mf *mf, uint32_t *count, lzma_match *matches); 336 337 extern uint32_t lzma_mf_hc3_find(lzma_mf *dict, lzma_match *matches); 338 extern void lzma_mf_hc3_skip(lzma_mf *dict, uint32_t amount); 339 340 extern uint32_t lzma_mf_hc4_find(lzma_mf *dict, lzma_match *matches); 341 extern void lzma_mf_hc4_skip(lzma_mf *dict, uint32_t amount); 342 343 extern uint32_t lzma_mf_bt2_find(lzma_mf *dict, lzma_match *matches); 344 extern void lzma_mf_bt2_skip(lzma_mf *dict, uint32_t amount); 345 346 extern uint32_t lzma_mf_bt3_find(lzma_mf *dict, lzma_match *matches); 347 extern void lzma_mf_bt3_skip(lzma_mf *dict, uint32_t amount); 348 349 extern uint32_t lzma_mf_bt4_find(lzma_mf *dict, lzma_match *matches); 350 extern void lzma_mf_bt4_skip(lzma_mf *dict, uint32_t amount); 351 352 #endif 353