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