1/* 2 * LZMA2 decoder 3 * 4 * Authors: Lasse Collin <lasse.collin@tukaani.org> 5 * Igor Pavlov <http://7-zip.org/> 6 * 7 * This file has been put into the public domain. 8 * You can do whatever you want with this file. 9 */ 10 11#include "xz_private.h" 12#include "xz_lzma2.h" 13 14/* 15 * Range decoder initialization eats the first five bytes of each LZMA chunk. 16 */ 17#define RC_INIT_BYTES 5 18 19/* 20 * Minimum number of usable input buffer to safely decode one LZMA symbol. 21 * The worst case is that we decode 22 bits using probabilities and 26 22 * direct bits. This may decode at maximum of 20 bytes of input. However, 23 * lzma_main() does an extra normalization before returning, thus we 24 * need to put 21 here. 25 */ 26#define LZMA_IN_REQUIRED 21 27 28/* 29 * Dictionary (history buffer) 30 * 31 * These are always true: 32 * start <= pos <= full <= end 33 * pos <= limit <= end 34 * 35 * In multi-call mode, also these are true: 36 * end == size 37 * size <= size_max 38 * allocated <= size 39 * 40 * Most of these variables are size_t to support single-call mode, 41 * in which the dictionary variables address the actual output 42 * buffer directly. 43 */ 44struct dictionary { 45 /* Beginning of the history buffer */ 46 uint8_t *buf; 47 48 /* Old position in buf (before decoding more data) */ 49 size_t start; 50 51 /* Position in buf */ 52 size_t pos; 53 54 /* 55 * How full dictionary is. This is used to detect corrupt input that 56 * would read beyond the beginning of the uncompressed stream. 57 */ 58 size_t full; 59 60 /* Write limit; we don't write to buf[limit] or later bytes. */ 61 size_t limit; 62 63 /* 64 * End of the dictionary buffer. In multi-call mode, this is 65 * the same as the dictionary size. In single-call mode, this 66 * indicates the size of the output buffer. 67 */ 68 size_t end; 69 70 /* 71 * Size of the dictionary as specified in Block Header. This is used 72 * together with "full" to detect corrupt input that would make us 73 * read beyond the beginning of the uncompressed stream. 74 */ 75 uint32_t size; 76 77 /* 78 * Maximum allowed dictionary size in multi-call mode. 79 * This is ignored in single-call mode. 80 */ 81 uint32_t size_max; 82 83 /* 84 * Amount of memory currently allocated for the dictionary. 85 * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC, 86 * size_max is always the same as the allocated size.) 87 */ 88 uint32_t allocated; 89 90 /* Operation mode */ 91 enum xz_mode mode; 92}; 93 94/* Range decoder */ 95struct rc_dec { 96 uint32_t range; 97 uint32_t code; 98 99 /* 100 * Number of initializing bytes remaining to be read 101 * by rc_read_init(). 102 */ 103 uint32_t init_bytes_left; 104 105 /* 106 * Buffer from which we read our input. It can be either 107 * temp.buf or the caller-provided input buffer. 108 */ 109 const uint8_t *in; 110 size_t in_pos; 111 size_t in_limit; 112}; 113 114/* Probabilities for a length decoder. */ 115struct lzma_len_dec { 116 /* Probability of match length being at least 10 */ 117 uint16_t choice; 118 119 /* Probability of match length being at least 18 */ 120 uint16_t choice2; 121 122 /* Probabilities for match lengths 2-9 */ 123 uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS]; 124 125 /* Probabilities for match lengths 10-17 */ 126 uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS]; 127 128 /* Probabilities for match lengths 18-273 */ 129 uint16_t high[LEN_HIGH_SYMBOLS]; 130}; 131 132struct lzma_dec { 133 /* Distances of latest four matches */ 134 uint32_t rep0; 135 uint32_t rep1; 136 uint32_t rep2; 137 uint32_t rep3; 138 139 /* Types of the most recently seen LZMA symbols */ 140 enum lzma_state state; 141 142 /* 143 * Length of a match. This is updated so that dict_repeat can 144 * be called again to finish repeating the whole match. 145 */ 146 uint32_t len; 147 148 /* 149 * LZMA properties or related bit masks (number of literal 150 * context bits, a mask dervied from the number of literal 151 * position bits, and a mask dervied from the number 152 * position bits) 153 */ 154 uint32_t lc; 155 uint32_t literal_pos_mask; /* (1 << lp) - 1 */ 156 uint32_t pos_mask; /* (1 << pb) - 1 */ 157 158 /* If 1, it's a match. Otherwise it's a single 8-bit literal. */ 159 uint16_t is_match[STATES][POS_STATES_MAX]; 160 161 /* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */ 162 uint16_t is_rep[STATES]; 163 164 /* 165 * If 0, distance of a repeated match is rep0. 166 * Otherwise check is_rep1. 167 */ 168 uint16_t is_rep0[STATES]; 169 170 /* 171 * If 0, distance of a repeated match is rep1. 172 * Otherwise check is_rep2. 173 */ 174 uint16_t is_rep1[STATES]; 175 176 /* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */ 177 uint16_t is_rep2[STATES]; 178 179 /* 180 * If 1, the repeated match has length of one byte. Otherwise 181 * the length is decoded from rep_len_decoder. 182 */ 183 uint16_t is_rep0_long[STATES][POS_STATES_MAX]; 184 185 /* 186 * Probability tree for the highest two bits of the match 187 * distance. There is a separate probability tree for match 188 * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273]. 189 */ 190 uint16_t dist_slot[DIST_STATES][DIST_SLOTS]; 191 192 /* 193 * Probility trees for additional bits for match distance 194 * when the distance is in the range [4, 127]. 195 */ 196 uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END]; 197 198 /* 199 * Probability tree for the lowest four bits of a match 200 * distance that is equal to or greater than 128. 201 */ 202 uint16_t dist_align[ALIGN_SIZE]; 203 204 /* Length of a normal match */ 205 struct lzma_len_dec match_len_dec; 206 207 /* Length of a repeated match */ 208 struct lzma_len_dec rep_len_dec; 209 210 /* Probabilities of literals */ 211 uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE]; 212}; 213 214struct lzma2_dec { 215 /* Position in xz_dec_lzma2_run(). */ 216 enum lzma2_seq { 217 SEQ_CONTROL, 218 SEQ_UNCOMPRESSED_1, 219 SEQ_UNCOMPRESSED_2, 220 SEQ_COMPRESSED_0, 221 SEQ_COMPRESSED_1, 222 SEQ_PROPERTIES, 223 SEQ_LZMA_PREPARE, 224 SEQ_LZMA_RUN, 225 SEQ_COPY 226 } sequence; 227 228 /* Next position after decoding the compressed size of the chunk. */ 229 enum lzma2_seq next_sequence; 230 231 /* Uncompressed size of LZMA chunk (2 MiB at maximum) */ 232 uint32_t uncompressed; 233 234 /* 235 * Compressed size of LZMA chunk or compressed/uncompressed 236 * size of uncompressed chunk (64 KiB at maximum) 237 */ 238 uint32_t compressed; 239 240 /* 241 * True if dictionary reset is needed. This is false before 242 * the first chunk (LZMA or uncompressed). 243 */ 244 bool need_dict_reset; 245 246 /* 247 * True if new LZMA properties are needed. This is false 248 * before the first LZMA chunk. 249 */ 250 bool need_props; 251}; 252 253struct xz_dec_lzma2 { 254 /* 255 * The order below is important on x86 to reduce code size and 256 * it shouldn't hurt on other platforms. Everything up to and 257 * including lzma.pos_mask are in the first 128 bytes on x86-32, 258 * which allows using smaller instructions to access those 259 * variables. On x86-64, fewer variables fit into the first 128 260 * bytes, but this is still the best order without sacrificing 261 * the readability by splitting the structures. 262 */ 263 struct rc_dec rc; 264 struct dictionary dict; 265 struct lzma2_dec lzma2; 266 struct lzma_dec lzma; 267 268 /* 269 * Temporary buffer which holds small number of input bytes between 270 * decoder calls. See lzma2_lzma() for details. 271 */ 272 struct { 273 uint32_t size; 274 uint8_t buf[3 * LZMA_IN_REQUIRED]; 275 } temp; 276}; 277 278/************** 279 * Dictionary * 280 **************/ 281 282/* 283 * Reset the dictionary state. When in single-call mode, set up the beginning 284 * of the dictionary to point to the actual output buffer. 285 */ 286static void dict_reset(struct dictionary *dict, struct xz_buf *b) 287{ 288 if (DEC_IS_SINGLE(dict->mode)) { 289 dict->buf = b->out + b->out_pos; 290 dict->end = b->out_size - b->out_pos; 291 } 292 293 dict->start = 0; 294 dict->pos = 0; 295 dict->limit = 0; 296 dict->full = 0; 297} 298 299/* Set dictionary write limit */ 300static void dict_limit(struct dictionary *dict, size_t out_max) 301{ 302 if (dict->end - dict->pos <= out_max) 303 dict->limit = dict->end; 304 else 305 dict->limit = dict->pos + out_max; 306} 307 308/* Return true if at least one byte can be written into the dictionary. */ 309static inline bool dict_has_space(const struct dictionary *dict) 310{ 311 return dict->pos < dict->limit; 312} 313 314/* 315 * Get a byte from the dictionary at the given distance. The distance is 316 * assumed to valid, or as a special case, zero when the dictionary is 317 * still empty. This special case is needed for single-call decoding to 318 * avoid writing a '\0' to the end of the destination buffer. 319 */ 320static inline uint32_t dict_get(const struct dictionary *dict, uint32_t dist) 321{ 322 size_t offset = dict->pos - dist - 1; 323 324 if (dist >= dict->pos) 325 offset += dict->end; 326 327 return dict->full > 0 ? dict->buf[offset] : 0; 328} 329 330/* 331 * Put one byte into the dictionary. It is assumed that there is space for it. 332 */ 333static inline void dict_put(struct dictionary *dict, uint8_t byte) 334{ 335 dict->buf[dict->pos++] = byte; 336 337 if (dict->full < dict->pos) 338 dict->full = dict->pos; 339} 340 341/* 342 * Repeat given number of bytes from the given distance. If the distance is 343 * invalid, false is returned. On success, true is returned and *len is 344 * updated to indicate how many bytes were left to be repeated. 345 */ 346static bool dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist) 347{ 348 size_t back; 349 uint32_t left; 350 351 if (dist >= dict->full || dist >= dict->size) 352 return false; 353 354 left = min_t(size_t, dict->limit - dict->pos, *len); 355 *len -= left; 356 357 back = dict->pos - dist - 1; 358 if (dist >= dict->pos) 359 back += dict->end; 360 361 do { 362 dict->buf[dict->pos++] = dict->buf[back++]; 363 if (back == dict->end) 364 back = 0; 365 } while (--left > 0); 366 367 if (dict->full < dict->pos) 368 dict->full = dict->pos; 369 370 return true; 371} 372 373/* Copy uncompressed data as is from input to dictionary and output buffers. */ 374static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b, 375 uint32_t *left) 376{ 377 size_t copy_size; 378 379 while (*left > 0 && b->in_pos < b->in_size 380 && b->out_pos < b->out_size) { 381 copy_size = min(b->in_size - b->in_pos, 382 b->out_size - b->out_pos); 383 if (copy_size > dict->end - dict->pos) 384 copy_size = dict->end - dict->pos; 385 if (copy_size > *left) 386 copy_size = *left; 387 388 *left -= copy_size; 389 390 memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size); 391 dict->pos += copy_size; 392 393 if (dict->full < dict->pos) 394 dict->full = dict->pos; 395 396 if (DEC_IS_MULTI(dict->mode)) { 397 if (dict->pos == dict->end) 398 dict->pos = 0; 399 400 memcpy(b->out + b->out_pos, b->in + b->in_pos, 401 copy_size); 402 } 403 404 dict->start = dict->pos; 405 406 b->out_pos += copy_size; 407 b->in_pos += copy_size; 408 } 409} 410 411/* 412 * Flush pending data from dictionary to b->out. It is assumed that there is 413 * enough space in b->out. This is guaranteed because caller uses dict_limit() 414 * before decoding data into the dictionary. 415 */ 416static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b) 417{ 418 size_t copy_size = dict->pos - dict->start; 419 420 if (DEC_IS_MULTI(dict->mode)) { 421 if (dict->pos == dict->end) 422 dict->pos = 0; 423 424 memcpy(b->out + b->out_pos, dict->buf + dict->start, 425 copy_size); 426 } 427 428 dict->start = dict->pos; 429 b->out_pos += copy_size; 430 return copy_size; 431} 432 433/***************** 434 * Range decoder * 435 *****************/ 436 437/* Reset the range decoder. */ 438static void rc_reset(struct rc_dec *rc) 439{ 440 rc->range = (uint32_t)-1; 441 rc->code = 0; 442 rc->init_bytes_left = RC_INIT_BYTES; 443} 444 445/* 446 * Read the first five initial bytes into rc->code if they haven't been 447 * read already. (Yes, the first byte gets completely ignored.) 448 */ 449static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b) 450{ 451 while (rc->init_bytes_left > 0) { 452 if (b->in_pos == b->in_size) 453 return false; 454 455 rc->code = (rc->code << 8) + b->in[b->in_pos++]; 456 --rc->init_bytes_left; 457 } 458 459 return true; 460} 461 462/* Return true if there may not be enough input for the next decoding loop. */ 463static inline bool rc_limit_exceeded(const struct rc_dec *rc) 464{ 465 return rc->in_pos > rc->in_limit; 466} 467 468/* 469 * Return true if it is possible (from point of view of range decoder) that 470 * we have reached the end of the LZMA chunk. 471 */ 472static inline bool rc_is_finished(const struct rc_dec *rc) 473{ 474 return rc->code == 0; 475} 476 477/* Read the next input byte if needed. */ 478static __always_inline void rc_normalize(struct rc_dec *rc) 479{ 480 if (rc->range < RC_TOP_VALUE) { 481 rc->range <<= RC_SHIFT_BITS; 482 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++]; 483 } 484} 485 486/* 487 * Decode one bit. In some versions, this function has been splitted in three 488 * functions so that the compiler is supposed to be able to more easily avoid 489 * an extra branch. In this particular version of the LZMA decoder, this 490 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3 491 * on x86). Using a non-splitted version results in nicer looking code too. 492 * 493 * NOTE: This must return an int. Do not make it return a bool or the speed 494 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care, 495 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.) 496 */ 497static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob) 498{ 499 uint32_t bound; 500 int bit; 501 502 rc_normalize(rc); 503 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob; 504 if (rc->code < bound) { 505 rc->range = bound; 506 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS; 507 bit = 0; 508 } else { 509 rc->range -= bound; 510 rc->code -= bound; 511 *prob -= *prob >> RC_MOVE_BITS; 512 bit = 1; 513 } 514 515 return bit; 516} 517 518/* Decode a bittree starting from the most significant bit. */ 519static __always_inline uint32_t rc_bittree(struct rc_dec *rc, 520 uint16_t *probs, uint32_t limit) 521{ 522 uint32_t symbol = 1; 523 524 do { 525 if (rc_bit(rc, &probs[symbol])) 526 symbol = (symbol << 1) + 1; 527 else 528 symbol <<= 1; 529 } while (symbol < limit); 530 531 return symbol; 532} 533 534/* Decode a bittree starting from the least significant bit. */ 535static __always_inline void rc_bittree_reverse(struct rc_dec *rc, 536 uint16_t *probs, 537 uint32_t *dest, uint32_t limit) 538{ 539 uint32_t symbol = 1; 540 uint32_t i = 0; 541 542 do { 543 if (rc_bit(rc, &probs[symbol])) { 544 symbol = (symbol << 1) + 1; 545 *dest += 1 << i; 546 } else { 547 symbol <<= 1; 548 } 549 } while (++i < limit); 550} 551 552/* Decode direct bits (fixed fifty-fifty probability) */ 553static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit) 554{ 555 uint32_t mask; 556 557 do { 558 rc_normalize(rc); 559 rc->range >>= 1; 560 rc->code -= rc->range; 561 mask = (uint32_t)0 - (rc->code >> 31); 562 rc->code += rc->range & mask; 563 *dest = (*dest << 1) + (mask + 1); 564 } while (--limit > 0); 565} 566 567/******** 568 * LZMA * 569 ********/ 570 571/* Get pointer to literal coder probability array. */ 572static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s) 573{ 574 uint32_t prev_byte = dict_get(&s->dict, 0); 575 uint32_t low = prev_byte >> (8 - s->lzma.lc); 576 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc; 577 return s->lzma.literal[low + high]; 578} 579 580/* Decode a literal (one 8-bit byte) */ 581static void lzma_literal(struct xz_dec_lzma2 *s) 582{ 583 uint16_t *probs; 584 uint32_t symbol; 585 uint32_t match_byte; 586 uint32_t match_bit; 587 uint32_t offset; 588 uint32_t i; 589 590 probs = lzma_literal_probs(s); 591 592 if (lzma_state_is_literal(s->lzma.state)) { 593 symbol = rc_bittree(&s->rc, probs, 0x100); 594 } else { 595 symbol = 1; 596 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1; 597 offset = 0x100; 598 599 do { 600 match_bit = match_byte & offset; 601 match_byte <<= 1; 602 i = offset + match_bit + symbol; 603 604 if (rc_bit(&s->rc, &probs[i])) { 605 symbol = (symbol << 1) + 1; 606 offset &= match_bit; 607 } else { 608 symbol <<= 1; 609 offset &= ~match_bit; 610 } 611 } while (symbol < 0x100); 612 } 613 614 dict_put(&s->dict, (uint8_t)symbol); 615 lzma_state_literal(&s->lzma.state); 616} 617 618/* Decode the length of the match into s->lzma.len. */ 619static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l, 620 uint32_t pos_state) 621{ 622 uint16_t *probs; 623 uint32_t limit; 624 625 if (!rc_bit(&s->rc, &l->choice)) { 626 probs = l->low[pos_state]; 627 limit = LEN_LOW_SYMBOLS; 628 s->lzma.len = MATCH_LEN_MIN; 629 } else { 630 if (!rc_bit(&s->rc, &l->choice2)) { 631 probs = l->mid[pos_state]; 632 limit = LEN_MID_SYMBOLS; 633 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS; 634 } else { 635 probs = l->high; 636 limit = LEN_HIGH_SYMBOLS; 637 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS 638 + LEN_MID_SYMBOLS; 639 } 640 } 641 642 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit; 643} 644 645/* Decode a match. The distance will be stored in s->lzma.rep0. */ 646static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state) 647{ 648 uint16_t *probs; 649 uint32_t dist_slot; 650 uint32_t limit; 651 652 lzma_state_match(&s->lzma.state); 653 654 s->lzma.rep3 = s->lzma.rep2; 655 s->lzma.rep2 = s->lzma.rep1; 656 s->lzma.rep1 = s->lzma.rep0; 657 658 lzma_len(s, &s->lzma.match_len_dec, pos_state); 659 660 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)]; 661 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS; 662 663 if (dist_slot < DIST_MODEL_START) { 664 s->lzma.rep0 = dist_slot; 665 } else { 666 limit = (dist_slot >> 1) - 1; 667 s->lzma.rep0 = 2 + (dist_slot & 1); 668 669 if (dist_slot < DIST_MODEL_END) { 670 s->lzma.rep0 <<= limit; 671 probs = s->lzma.dist_special + s->lzma.rep0 672 - dist_slot - 1; 673 rc_bittree_reverse(&s->rc, probs, 674 &s->lzma.rep0, limit); 675 } else { 676 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS); 677 s->lzma.rep0 <<= ALIGN_BITS; 678 rc_bittree_reverse(&s->rc, s->lzma.dist_align, 679 &s->lzma.rep0, ALIGN_BITS); 680 } 681 } 682} 683 684/* 685 * Decode a repeated match. The distance is one of the four most recently 686 * seen matches. The distance will be stored in s->lzma.rep0. 687 */ 688static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state) 689{ 690 uint32_t tmp; 691 692 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) { 693 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[ 694 s->lzma.state][pos_state])) { 695 lzma_state_short_rep(&s->lzma.state); 696 s->lzma.len = 1; 697 return; 698 } 699 } else { 700 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) { 701 tmp = s->lzma.rep1; 702 } else { 703 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) { 704 tmp = s->lzma.rep2; 705 } else { 706 tmp = s->lzma.rep3; 707 s->lzma.rep3 = s->lzma.rep2; 708 } 709 710 s->lzma.rep2 = s->lzma.rep1; 711 } 712 713 s->lzma.rep1 = s->lzma.rep0; 714 s->lzma.rep0 = tmp; 715 } 716 717 lzma_state_long_rep(&s->lzma.state); 718 lzma_len(s, &s->lzma.rep_len_dec, pos_state); 719} 720 721/* LZMA decoder core */ 722static bool lzma_main(struct xz_dec_lzma2 *s) 723{ 724 uint32_t pos_state; 725 726 /* 727 * If the dictionary was reached during the previous call, try to 728 * finish the possibly pending repeat in the dictionary. 729 */ 730 if (dict_has_space(&s->dict) && s->lzma.len > 0) 731 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0); 732 733 /* 734 * Decode more LZMA symbols. One iteration may consume up to 735 * LZMA_IN_REQUIRED - 1 bytes. 736 */ 737 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) { 738 pos_state = s->dict.pos & s->lzma.pos_mask; 739 740 if (!rc_bit(&s->rc, &s->lzma.is_match[ 741 s->lzma.state][pos_state])) { 742 lzma_literal(s); 743 } else { 744 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state])) 745 lzma_rep_match(s, pos_state); 746 else 747 lzma_match(s, pos_state); 748 749 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0)) 750 return false; 751 } 752 } 753 754 /* 755 * Having the range decoder always normalized when we are outside 756 * this function makes it easier to correctly handle end of the chunk. 757 */ 758 rc_normalize(&s->rc); 759 760 return true; 761} 762 763/* 764 * Reset the LZMA decoder and range decoder state. Dictionary is nore reset 765 * here, because LZMA state may be reset without resetting the dictionary. 766 */ 767static void lzma_reset(struct xz_dec_lzma2 *s) 768{ 769 uint16_t *probs; 770 size_t i; 771 772 s->lzma.state = STATE_LIT_LIT; 773 s->lzma.rep0 = 0; 774 s->lzma.rep1 = 0; 775 s->lzma.rep2 = 0; 776 s->lzma.rep3 = 0; 777 778 /* 779 * All probabilities are initialized to the same value. This hack 780 * makes the code smaller by avoiding a separate loop for each 781 * probability array. 782 * 783 * This could be optimized so that only that part of literal 784 * probabilities that are actually required. In the common case 785 * we would write 12 KiB less. 786 */ 787 probs = s->lzma.is_match[0]; 788 for (i = 0; i < PROBS_TOTAL; ++i) 789 probs[i] = RC_BIT_MODEL_TOTAL / 2; 790 791 rc_reset(&s->rc); 792} 793 794/* 795 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks 796 * from the decoded lp and pb values. On success, the LZMA decoder state is 797 * reset and true is returned. 798 */ 799static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props) 800{ 801 if (props > (4 * 5 + 4) * 9 + 8) 802 return false; 803 804 s->lzma.pos_mask = 0; 805 while (props >= 9 * 5) { 806 props -= 9 * 5; 807 ++s->lzma.pos_mask; 808 } 809 810 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1; 811 812 s->lzma.literal_pos_mask = 0; 813 while (props >= 9) { 814 props -= 9; 815 ++s->lzma.literal_pos_mask; 816 } 817 818 s->lzma.lc = props; 819 820 if (s->lzma.lc + s->lzma.literal_pos_mask > 4) 821 return false; 822 823 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1; 824 825 lzma_reset(s); 826 827 return true; 828} 829 830/********* 831 * LZMA2 * 832 *********/ 833 834/* 835 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't 836 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This 837 * wrapper function takes care of making the LZMA decoder's assumption safe. 838 * 839 * As long as there is plenty of input left to be decoded in the current LZMA 840 * chunk, we decode directly from the caller-supplied input buffer until 841 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into 842 * s->temp.buf, which (hopefully) gets filled on the next call to this 843 * function. We decode a few bytes from the temporary buffer so that we can 844 * continue decoding from the caller-supplied input buffer again. 845 */ 846static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b) 847{ 848 size_t in_avail; 849 uint32_t tmp; 850 851 in_avail = b->in_size - b->in_pos; 852 if (s->temp.size > 0 || s->lzma2.compressed == 0) { 853 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size; 854 if (tmp > s->lzma2.compressed - s->temp.size) 855 tmp = s->lzma2.compressed - s->temp.size; 856 if (tmp > in_avail) 857 tmp = in_avail; 858 859 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp); 860 861 if (s->temp.size + tmp == s->lzma2.compressed) { 862 memzero(s->temp.buf + s->temp.size + tmp, 863 sizeof(s->temp.buf) 864 - s->temp.size - tmp); 865 s->rc.in_limit = s->temp.size + tmp; 866 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) { 867 s->temp.size += tmp; 868 b->in_pos += tmp; 869 return true; 870 } else { 871 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED; 872 } 873 874 s->rc.in = s->temp.buf; 875 s->rc.in_pos = 0; 876 877 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp) 878 return false; 879 880 s->lzma2.compressed -= s->rc.in_pos; 881 882 if (s->rc.in_pos < s->temp.size) { 883 s->temp.size -= s->rc.in_pos; 884 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos, 885 s->temp.size); 886 return true; 887 } 888 889 b->in_pos += s->rc.in_pos - s->temp.size; 890 s->temp.size = 0; 891 } 892 893 in_avail = b->in_size - b->in_pos; 894 if (in_avail >= LZMA_IN_REQUIRED) { 895 s->rc.in = b->in; 896 s->rc.in_pos = b->in_pos; 897 898 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED) 899 s->rc.in_limit = b->in_pos + s->lzma2.compressed; 900 else 901 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED; 902 903 if (!lzma_main(s)) 904 return false; 905 906 in_avail = s->rc.in_pos - b->in_pos; 907 if (in_avail > s->lzma2.compressed) 908 return false; 909 910 s->lzma2.compressed -= in_avail; 911 b->in_pos = s->rc.in_pos; 912 } 913 914 in_avail = b->in_size - b->in_pos; 915 if (in_avail < LZMA_IN_REQUIRED) { 916 if (in_avail > s->lzma2.compressed) 917 in_avail = s->lzma2.compressed; 918 919 memcpy(s->temp.buf, b->in + b->in_pos, in_avail); 920 s->temp.size = in_avail; 921 b->in_pos += in_avail; 922 } 923 924 return true; 925} 926 927/* 928 * Take care of the LZMA2 control layer, and forward the job of actual LZMA 929 * decoding or copying of uncompressed chunks to other functions. 930 */ 931XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s, 932 struct xz_buf *b) 933{ 934 uint32_t tmp; 935 936 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) { 937 switch (s->lzma2.sequence) { 938 case SEQ_CONTROL: 939 /* 940 * LZMA2 control byte 941 * 942 * Exact values: 943 * 0x00 End marker 944 * 0x01 Dictionary reset followed by 945 * an uncompressed chunk 946 * 0x02 Uncompressed chunk (no dictionary reset) 947 * 948 * Highest three bits (s->control & 0xE0): 949 * 0xE0 Dictionary reset, new properties and state 950 * reset, followed by LZMA compressed chunk 951 * 0xC0 New properties and state reset, followed 952 * by LZMA compressed chunk (no dictionary 953 * reset) 954 * 0xA0 State reset using old properties, 955 * followed by LZMA compressed chunk (no 956 * dictionary reset) 957 * 0x80 LZMA chunk (no dictionary or state reset) 958 * 959 * For LZMA compressed chunks, the lowest five bits 960 * (s->control & 1F) are the highest bits of the 961 * uncompressed size (bits 16-20). 962 * 963 * A new LZMA2 stream must begin with a dictionary 964 * reset. The first LZMA chunk must set new 965 * properties and reset the LZMA state. 966 * 967 * Values that don't match anything described above 968 * are invalid and we return XZ_DATA_ERROR. 969 */ 970 tmp = b->in[b->in_pos++]; 971 972 if (tmp == 0x00) 973 return XZ_STREAM_END; 974 975 if (tmp >= 0xE0 || tmp == 0x01) { 976 s->lzma2.need_props = true; 977 s->lzma2.need_dict_reset = false; 978 dict_reset(&s->dict, b); 979 } else if (s->lzma2.need_dict_reset) { 980 return XZ_DATA_ERROR; 981 } 982 983 if (tmp >= 0x80) { 984 s->lzma2.uncompressed = (tmp & 0x1F) << 16; 985 s->lzma2.sequence = SEQ_UNCOMPRESSED_1; 986 987 if (tmp >= 0xC0) { 988 /* 989 * When there are new properties, 990 * state reset is done at 991 * SEQ_PROPERTIES. 992 */ 993 s->lzma2.need_props = false; 994 s->lzma2.next_sequence 995 = SEQ_PROPERTIES; 996 997 } else if (s->lzma2.need_props) { 998 return XZ_DATA_ERROR; 999 1000 } else { 1001 s->lzma2.next_sequence 1002 = SEQ_LZMA_PREPARE; 1003 if (tmp >= 0xA0) 1004 lzma_reset(s); 1005 } 1006 } else { 1007 if (tmp > 0x02) 1008 return XZ_DATA_ERROR; 1009 1010 s->lzma2.sequence = SEQ_COMPRESSED_0; 1011 s->lzma2.next_sequence = SEQ_COPY; 1012 } 1013 1014 break; 1015 1016 case SEQ_UNCOMPRESSED_1: 1017 s->lzma2.uncompressed 1018 += (uint32_t)b->in[b->in_pos++] << 8; 1019 s->lzma2.sequence = SEQ_UNCOMPRESSED_2; 1020 break; 1021 1022 case SEQ_UNCOMPRESSED_2: 1023 s->lzma2.uncompressed 1024 += (uint32_t)b->in[b->in_pos++] + 1; 1025 s->lzma2.sequence = SEQ_COMPRESSED_0; 1026 break; 1027 1028 case SEQ_COMPRESSED_0: 1029 s->lzma2.compressed 1030 = (uint32_t)b->in[b->in_pos++] << 8; 1031 s->lzma2.sequence = SEQ_COMPRESSED_1; 1032 break; 1033 1034 case SEQ_COMPRESSED_1: 1035 s->lzma2.compressed 1036 += (uint32_t)b->in[b->in_pos++] + 1; 1037 s->lzma2.sequence = s->lzma2.next_sequence; 1038 break; 1039 1040 case SEQ_PROPERTIES: 1041 if (!lzma_props(s, b->in[b->in_pos++])) 1042 return XZ_DATA_ERROR; 1043 1044 s->lzma2.sequence = SEQ_LZMA_PREPARE; 1045 1046 case SEQ_LZMA_PREPARE: 1047 if (s->lzma2.compressed < RC_INIT_BYTES) 1048 return XZ_DATA_ERROR; 1049 1050 if (!rc_read_init(&s->rc, b)) 1051 return XZ_OK; 1052 1053 s->lzma2.compressed -= RC_INIT_BYTES; 1054 s->lzma2.sequence = SEQ_LZMA_RUN; 1055 1056 case SEQ_LZMA_RUN: 1057 /* 1058 * Set dictionary limit to indicate how much we want 1059 * to be encoded at maximum. Decode new data into the 1060 * dictionary. Flush the new data from dictionary to 1061 * b->out. Check if we finished decoding this chunk. 1062 * In case the dictionary got full but we didn't fill 1063 * the output buffer yet, we may run this loop 1064 * multiple times without changing s->lzma2.sequence. 1065 */ 1066 dict_limit(&s->dict, min_t(size_t, 1067 b->out_size - b->out_pos, 1068 s->lzma2.uncompressed)); 1069 if (!lzma2_lzma(s, b)) 1070 return XZ_DATA_ERROR; 1071 1072 s->lzma2.uncompressed -= dict_flush(&s->dict, b); 1073 1074 if (s->lzma2.uncompressed == 0) { 1075 if (s->lzma2.compressed > 0 || s->lzma.len > 0 1076 || !rc_is_finished(&s->rc)) 1077 return XZ_DATA_ERROR; 1078 1079 rc_reset(&s->rc); 1080 s->lzma2.sequence = SEQ_CONTROL; 1081 1082 } else if (b->out_pos == b->out_size 1083 || (b->in_pos == b->in_size 1084 && s->temp.size 1085 < s->lzma2.compressed)) { 1086 return XZ_OK; 1087 } 1088 1089 break; 1090 1091 case SEQ_COPY: 1092 dict_uncompressed(&s->dict, b, &s->lzma2.compressed); 1093 if (s->lzma2.compressed > 0) 1094 return XZ_OK; 1095 1096 s->lzma2.sequence = SEQ_CONTROL; 1097 break; 1098 } 1099 } 1100 1101 return XZ_OK; 1102} 1103 1104XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode, 1105 uint32_t dict_max) 1106{ 1107 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL); 1108 if (s == NULL) 1109 return NULL; 1110 1111 s->dict.mode = mode; 1112 s->dict.size_max = dict_max; 1113 1114 if (DEC_IS_PREALLOC(mode)) { 1115 s->dict.buf = vmalloc(dict_max); 1116 if (s->dict.buf == NULL) { 1117 kfree(s); 1118 return NULL; 1119 } 1120 } else if (DEC_IS_DYNALLOC(mode)) { 1121 s->dict.buf = NULL; 1122 s->dict.allocated = 0; 1123 } 1124 1125 return s; 1126} 1127 1128XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props) 1129{ 1130 /* This limits dictionary size to 3 GiB to keep parsing simpler. */ 1131 if (props > 39) 1132 return XZ_OPTIONS_ERROR; 1133 1134 s->dict.size = 2 + (props & 1); 1135 s->dict.size <<= (props >> 1) + 11; 1136 1137 if (DEC_IS_MULTI(s->dict.mode)) { 1138 if (s->dict.size > s->dict.size_max) 1139 return XZ_MEMLIMIT_ERROR; 1140 1141 s->dict.end = s->dict.size; 1142 1143 if (DEC_IS_DYNALLOC(s->dict.mode)) { 1144 if (s->dict.allocated < s->dict.size) { 1145 vfree(s->dict.buf); 1146 s->dict.buf = vmalloc(s->dict.size); 1147 if (s->dict.buf == NULL) { 1148 s->dict.allocated = 0; 1149 return XZ_MEM_ERROR; 1150 } 1151 } 1152 } 1153 } 1154 1155 s->lzma.len = 0; 1156 1157 s->lzma2.sequence = SEQ_CONTROL; 1158 s->lzma2.need_dict_reset = true; 1159 1160 s->temp.size = 0; 1161 1162 return XZ_OK; 1163} 1164 1165XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s) 1166{ 1167 if (DEC_IS_MULTI(s->dict.mode)) 1168 vfree(s->dict.buf); 1169 1170 kfree(s); 1171} 1172