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 */
44 struct 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 */
95 struct 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. */
115 struct 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
132 struct 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
214 struct 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
253 struct 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 */
dict_reset(struct dictionary * dict,struct xz_buf * b)286 static void XZ_FUNC 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 */
dict_limit(struct dictionary * dict,size_t out_max)300 static void XZ_FUNC 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. */
dict_has_space(const struct dictionary * dict)309 static __always_inline bool XZ_FUNC 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 */
dict_get(const struct dictionary * dict,uint32_t dist)320 static __always_inline uint32_t XZ_FUNC dict_get(
321 const struct dictionary *dict, uint32_t dist)
322 {
323 size_t offset = dict->pos - dist - 1;
324
325 if (dist >= dict->pos)
326 offset += dict->end;
327
328 return dict->full > 0 ? dict->buf[offset] : 0;
329 }
330
331 /*
332 * Put one byte into the dictionary. It is assumed that there is space for it.
333 */
dict_put(struct dictionary * dict,uint8_t byte)334 static inline void XZ_FUNC dict_put(struct dictionary *dict, uint8_t byte)
335 {
336 dict->buf[dict->pos++] = byte;
337
338 if (dict->full < dict->pos)
339 dict->full = dict->pos;
340 }
341
342 /*
343 * Repeat given number of bytes from the given distance. If the distance is
344 * invalid, false is returned. On success, true is returned and *len is
345 * updated to indicate how many bytes were left to be repeated.
346 */
dict_repeat(struct dictionary * dict,uint32_t * len,uint32_t dist)347 static bool XZ_FUNC dict_repeat(
348 struct dictionary *dict, uint32_t *len, uint32_t dist)
349 {
350 size_t back;
351 uint32_t left;
352
353 if (dist >= dict->full || dist >= dict->size)
354 return false;
355
356 left = min_t(size_t, dict->limit - dict->pos, *len);
357 *len -= left;
358
359 back = dict->pos - dist - 1;
360 if (dist >= dict->pos)
361 back += dict->end;
362
363 do {
364 dict->buf[dict->pos++] = dict->buf[back++];
365 if (back == dict->end)
366 back = 0;
367 } while (--left > 0);
368
369 if (dict->full < dict->pos)
370 dict->full = dict->pos;
371
372 return true;
373 }
374
375 /* Copy uncompressed data as is from input to dictionary and output buffers. */
dict_uncompressed(struct dictionary * dict,struct xz_buf * b,uint32_t * left)376 static void XZ_FUNC dict_uncompressed(
377 struct dictionary *dict, struct xz_buf *b, uint32_t *left)
378 {
379 size_t copy_size;
380
381 while (*left > 0 && b->in_pos < b->in_size
382 && b->out_pos < b->out_size) {
383 copy_size = min(b->in_size - b->in_pos,
384 b->out_size - b->out_pos);
385 if (copy_size > dict->end - dict->pos)
386 copy_size = dict->end - dict->pos;
387 if (copy_size > *left)
388 copy_size = *left;
389
390 *left -= copy_size;
391
392 memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
393 dict->pos += copy_size;
394
395 if (dict->full < dict->pos)
396 dict->full = dict->pos;
397
398 if (DEC_IS_MULTI(dict->mode)) {
399 if (dict->pos == dict->end)
400 dict->pos = 0;
401
402 memcpy(b->out + b->out_pos, b->in + b->in_pos,
403 copy_size);
404 }
405
406 dict->start = dict->pos;
407
408 b->out_pos += copy_size;
409 b->in_pos += copy_size;
410 }
411 }
412
413 /*
414 * Flush pending data from dictionary to b->out. It is assumed that there is
415 * enough space in b->out. This is guaranteed because caller uses dict_limit()
416 * before decoding data into the dictionary.
417 */
dict_flush(struct dictionary * dict,struct xz_buf * b)418 static uint32_t XZ_FUNC dict_flush(struct dictionary *dict, struct xz_buf *b)
419 {
420 size_t copy_size = dict->pos - dict->start;
421
422 if (DEC_IS_MULTI(dict->mode)) {
423 if (dict->pos == dict->end)
424 dict->pos = 0;
425
426 memcpy(b->out + b->out_pos, dict->buf + dict->start,
427 copy_size);
428 }
429
430 dict->start = dict->pos;
431 b->out_pos += copy_size;
432 return copy_size;
433 }
434
435 /*****************
436 * Range decoder *
437 *****************/
438
439 /* Reset the range decoder. */
rc_reset(struct rc_dec * rc)440 static void XZ_FUNC rc_reset(struct rc_dec *rc)
441 {
442 rc->range = (uint32_t)-1;
443 rc->code = 0;
444 rc->init_bytes_left = RC_INIT_BYTES;
445 }
446
447 /*
448 * Read the first five initial bytes into rc->code if they haven't been
449 * read already. (Yes, the first byte gets completely ignored.)
450 */
rc_read_init(struct rc_dec * rc,struct xz_buf * b)451 static bool XZ_FUNC rc_read_init(struct rc_dec *rc, struct xz_buf *b)
452 {
453 while (rc->init_bytes_left > 0) {
454 if (b->in_pos == b->in_size)
455 return false;
456
457 rc->code = (rc->code << 8) + b->in[b->in_pos++];
458 --rc->init_bytes_left;
459 }
460
461 return true;
462 }
463
464 /* Return true if there may not be enough input for the next decoding loop. */
rc_limit_exceeded(const struct rc_dec * rc)465 static inline bool XZ_FUNC rc_limit_exceeded(const struct rc_dec *rc)
466 {
467 return rc->in_pos > rc->in_limit;
468 }
469
470 /*
471 * Return true if it is possible (from point of view of range decoder) that
472 * we have reached the end of the LZMA chunk.
473 */
rc_is_finished(const struct rc_dec * rc)474 static inline bool XZ_FUNC rc_is_finished(const struct rc_dec *rc)
475 {
476 return rc->code == 0;
477 }
478
479 /* Read the next input byte if needed. */
rc_normalize(struct rc_dec * rc)480 static __always_inline void XZ_FUNC rc_normalize(struct rc_dec *rc)
481 {
482 if (rc->range < RC_TOP_VALUE) {
483 rc->range <<= RC_SHIFT_BITS;
484 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
485 }
486 }
487
488 /*
489 * Decode one bit. In some versions, this function has been split in three
490 * functions so that the compiler is supposed to be able to more easily avoid
491 * an extra branch. In this particular version of the LZMA decoder, this
492 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
493 * on x86). Using a non-split version results in nicer looking code too.
494 *
495 * NOTE: This must return an int. Do not make it return a bool or the speed
496 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
497 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
498 */
rc_bit(struct rc_dec * rc,uint16_t * prob)499 static __always_inline int XZ_FUNC rc_bit(struct rc_dec *rc, uint16_t *prob)
500 {
501 uint32_t bound;
502 int bit;
503
504 rc_normalize(rc);
505 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
506 if (rc->code < bound) {
507 rc->range = bound;
508 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
509 bit = 0;
510 } else {
511 rc->range -= bound;
512 rc->code -= bound;
513 *prob -= *prob >> RC_MOVE_BITS;
514 bit = 1;
515 }
516
517 return bit;
518 }
519
520 /* Decode a bittree starting from the most significant bit. */
rc_bittree(struct rc_dec * rc,uint16_t * probs,uint32_t limit)521 static __always_inline uint32_t XZ_FUNC rc_bittree(
522 struct rc_dec *rc, uint16_t *probs, uint32_t limit)
523 {
524 uint32_t symbol = 1;
525
526 do {
527 if (rc_bit(rc, &probs[symbol]))
528 symbol = (symbol << 1) + 1;
529 else
530 symbol <<= 1;
531 } while (symbol < limit);
532
533 return symbol;
534 }
535
536 /* Decode a bittree starting from the least significant bit. */
rc_bittree_reverse(struct rc_dec * rc,uint16_t * probs,uint32_t * dest,uint32_t limit)537 static __always_inline void XZ_FUNC rc_bittree_reverse(struct rc_dec *rc,
538 uint16_t *probs, uint32_t *dest, uint32_t limit)
539 {
540 uint32_t symbol = 1;
541 uint32_t i = 0;
542
543 do {
544 if (rc_bit(rc, &probs[symbol])) {
545 symbol = (symbol << 1) + 1;
546 *dest += 1 << i;
547 } else {
548 symbol <<= 1;
549 }
550 } while (++i < limit);
551 }
552
553 /* Decode direct bits (fixed fifty-fifty probability) */
rc_direct(struct rc_dec * rc,uint32_t * dest,uint32_t limit)554 static inline void XZ_FUNC rc_direct(
555 struct rc_dec *rc, uint32_t *dest, uint32_t limit)
556 {
557 uint32_t mask;
558
559 do {
560 rc_normalize(rc);
561 rc->range >>= 1;
562 rc->code -= rc->range;
563 mask = (uint32_t)0 - (rc->code >> 31);
564 rc->code += rc->range & mask;
565 *dest = (*dest << 1) + (mask + 1);
566 } while (--limit > 0);
567 }
568
569 /********
570 * LZMA *
571 ********/
572
573 /* Get pointer to literal coder probability array. */
lzma_literal_probs(struct xz_dec_lzma2 * s)574 static uint16_t * XZ_FUNC lzma_literal_probs(struct xz_dec_lzma2 *s)
575 {
576 uint32_t prev_byte = dict_get(&s->dict, 0);
577 uint32_t low = prev_byte >> (8 - s->lzma.lc);
578 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
579 return s->lzma.literal[low + high];
580 }
581
582 /* Decode a literal (one 8-bit byte) */
lzma_literal(struct xz_dec_lzma2 * s)583 static void XZ_FUNC lzma_literal(struct xz_dec_lzma2 *s)
584 {
585 uint16_t *probs;
586 uint32_t symbol;
587 uint32_t match_byte;
588 uint32_t match_bit;
589 uint32_t offset;
590 uint32_t i;
591
592 probs = lzma_literal_probs(s);
593
594 if (lzma_state_is_literal(s->lzma.state)) {
595 symbol = rc_bittree(&s->rc, probs, 0x100);
596 } else {
597 symbol = 1;
598 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
599 offset = 0x100;
600
601 do {
602 match_bit = match_byte & offset;
603 match_byte <<= 1;
604 i = offset + match_bit + symbol;
605
606 if (rc_bit(&s->rc, &probs[i])) {
607 symbol = (symbol << 1) + 1;
608 offset &= match_bit;
609 } else {
610 symbol <<= 1;
611 offset &= ~match_bit;
612 }
613 } while (symbol < 0x100);
614 }
615
616 dict_put(&s->dict, (uint8_t)symbol);
617 lzma_state_literal(&s->lzma.state);
618 }
619
620 /* Decode the length of the match into s->lzma.len. */
lzma_len(struct xz_dec_lzma2 * s,struct lzma_len_dec * l,uint32_t pos_state)621 static void XZ_FUNC lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
622 uint32_t pos_state)
623 {
624 uint16_t *probs;
625 uint32_t limit;
626
627 if (!rc_bit(&s->rc, &l->choice)) {
628 probs = l->low[pos_state];
629 limit = LEN_LOW_SYMBOLS;
630 s->lzma.len = MATCH_LEN_MIN;
631 } else {
632 if (!rc_bit(&s->rc, &l->choice2)) {
633 probs = l->mid[pos_state];
634 limit = LEN_MID_SYMBOLS;
635 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
636 } else {
637 probs = l->high;
638 limit = LEN_HIGH_SYMBOLS;
639 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
640 + LEN_MID_SYMBOLS;
641 }
642 }
643
644 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
645 }
646
647 /* Decode a match. The distance will be stored in s->lzma.rep0. */
lzma_match(struct xz_dec_lzma2 * s,uint32_t pos_state)648 static void XZ_FUNC lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
649 {
650 uint16_t *probs;
651 uint32_t dist_slot;
652 uint32_t limit;
653
654 lzma_state_match(&s->lzma.state);
655
656 s->lzma.rep3 = s->lzma.rep2;
657 s->lzma.rep2 = s->lzma.rep1;
658 s->lzma.rep1 = s->lzma.rep0;
659
660 lzma_len(s, &s->lzma.match_len_dec, pos_state);
661
662 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
663 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
664
665 if (dist_slot < DIST_MODEL_START) {
666 s->lzma.rep0 = dist_slot;
667 } else {
668 limit = (dist_slot >> 1) - 1;
669 s->lzma.rep0 = 2 + (dist_slot & 1);
670
671 if (dist_slot < DIST_MODEL_END) {
672 s->lzma.rep0 <<= limit;
673 probs = s->lzma.dist_special + s->lzma.rep0
674 - dist_slot - 1;
675 rc_bittree_reverse(&s->rc, probs,
676 &s->lzma.rep0, limit);
677 } else {
678 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
679 s->lzma.rep0 <<= ALIGN_BITS;
680 rc_bittree_reverse(&s->rc, s->lzma.dist_align,
681 &s->lzma.rep0, ALIGN_BITS);
682 }
683 }
684 }
685
686 /*
687 * Decode a repeated match. The distance is one of the four most recently
688 * seen matches. The distance will be stored in s->lzma.rep0.
689 */
lzma_rep_match(struct xz_dec_lzma2 * s,uint32_t pos_state)690 static void XZ_FUNC lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
691 {
692 uint32_t tmp;
693
694 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
695 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
696 s->lzma.state][pos_state])) {
697 lzma_state_short_rep(&s->lzma.state);
698 s->lzma.len = 1;
699 return;
700 }
701 } else {
702 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
703 tmp = s->lzma.rep1;
704 } else {
705 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
706 tmp = s->lzma.rep2;
707 } else {
708 tmp = s->lzma.rep3;
709 s->lzma.rep3 = s->lzma.rep2;
710 }
711
712 s->lzma.rep2 = s->lzma.rep1;
713 }
714
715 s->lzma.rep1 = s->lzma.rep0;
716 s->lzma.rep0 = tmp;
717 }
718
719 lzma_state_long_rep(&s->lzma.state);
720 lzma_len(s, &s->lzma.rep_len_dec, pos_state);
721 }
722
723 /* LZMA decoder core */
lzma_main(struct xz_dec_lzma2 * s)724 static bool XZ_FUNC lzma_main(struct xz_dec_lzma2 *s)
725 {
726 uint32_t pos_state;
727
728 /*
729 * If the dictionary was reached during the previous call, try to
730 * finish the possibly pending repeat in the dictionary.
731 */
732 if (dict_has_space(&s->dict) && s->lzma.len > 0)
733 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
734
735 /*
736 * Decode more LZMA symbols. One iteration may consume up to
737 * LZMA_IN_REQUIRED - 1 bytes.
738 */
739 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
740 pos_state = s->dict.pos & s->lzma.pos_mask;
741
742 if (!rc_bit(&s->rc, &s->lzma.is_match[
743 s->lzma.state][pos_state])) {
744 lzma_literal(s);
745 } else {
746 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
747 lzma_rep_match(s, pos_state);
748 else
749 lzma_match(s, pos_state);
750
751 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
752 return false;
753 }
754 }
755
756 /*
757 * Having the range decoder always normalized when we are outside
758 * this function makes it easier to correctly handle end of the chunk.
759 */
760 rc_normalize(&s->rc);
761
762 return true;
763 }
764
765 /*
766 * Reset the LZMA decoder and range decoder state. Dictionary is nore reset
767 * here, because LZMA state may be reset without resetting the dictionary.
768 */
lzma_reset(struct xz_dec_lzma2 * s)769 static void XZ_FUNC lzma_reset(struct xz_dec_lzma2 *s)
770 {
771 uint16_t *probs;
772 size_t i;
773
774 s->lzma.state = STATE_LIT_LIT;
775 s->lzma.rep0 = 0;
776 s->lzma.rep1 = 0;
777 s->lzma.rep2 = 0;
778 s->lzma.rep3 = 0;
779
780 /*
781 * All probabilities are initialized to the same value. This hack
782 * makes the code smaller by avoiding a separate loop for each
783 * probability array.
784 *
785 * This could be optimized so that only that part of literal
786 * probabilities that are actually required. In the common case
787 * we would write 12 KiB less.
788 */
789 probs = s->lzma.is_match[0];
790 for (i = 0; i < PROBS_TOTAL; ++i)
791 probs[i] = RC_BIT_MODEL_TOTAL / 2;
792
793 rc_reset(&s->rc);
794 }
795
796 /*
797 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
798 * from the decoded lp and pb values. On success, the LZMA decoder state is
799 * reset and true is returned.
800 */
lzma_props(struct xz_dec_lzma2 * s,uint8_t props)801 static bool XZ_FUNC lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
802 {
803 if (props > (4 * 5 + 4) * 9 + 8)
804 return false;
805
806 s->lzma.pos_mask = 0;
807 while (props >= 9 * 5) {
808 props -= 9 * 5;
809 ++s->lzma.pos_mask;
810 }
811
812 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
813
814 s->lzma.literal_pos_mask = 0;
815 while (props >= 9) {
816 props -= 9;
817 ++s->lzma.literal_pos_mask;
818 }
819
820 s->lzma.lc = props;
821
822 if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
823 return false;
824
825 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
826
827 lzma_reset(s);
828
829 return true;
830 }
831
832 /*********
833 * LZMA2 *
834 *********/
835
836 /*
837 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
838 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
839 * wrapper function takes care of making the LZMA decoder's assumption safe.
840 *
841 * As long as there is plenty of input left to be decoded in the current LZMA
842 * chunk, we decode directly from the caller-supplied input buffer until
843 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
844 * s->temp.buf, which (hopefully) gets filled on the next call to this
845 * function. We decode a few bytes from the temporary buffer so that we can
846 * continue decoding from the caller-supplied input buffer again.
847 */
lzma2_lzma(struct xz_dec_lzma2 * s,struct xz_buf * b)848 static bool XZ_FUNC lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
849 {
850 size_t in_avail;
851 uint32_t tmp;
852
853 in_avail = b->in_size - b->in_pos;
854 if (s->temp.size > 0 || s->lzma2.compressed == 0) {
855 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
856 if (tmp > s->lzma2.compressed - s->temp.size)
857 tmp = s->lzma2.compressed - s->temp.size;
858 if (tmp > in_avail)
859 tmp = in_avail;
860
861 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
862
863 if (s->temp.size + tmp == s->lzma2.compressed) {
864 memzero(s->temp.buf + s->temp.size + tmp,
865 sizeof(s->temp.buf)
866 - s->temp.size - tmp);
867 s->rc.in_limit = s->temp.size + tmp;
868 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
869 s->temp.size += tmp;
870 b->in_pos += tmp;
871 return true;
872 } else {
873 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
874 }
875
876 s->rc.in = s->temp.buf;
877 s->rc.in_pos = 0;
878
879 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
880 return false;
881
882 s->lzma2.compressed -= s->rc.in_pos;
883
884 if (s->rc.in_pos < s->temp.size) {
885 s->temp.size -= s->rc.in_pos;
886 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
887 s->temp.size);
888 return true;
889 }
890
891 b->in_pos += s->rc.in_pos - s->temp.size;
892 s->temp.size = 0;
893 }
894
895 in_avail = b->in_size - b->in_pos;
896 if (in_avail >= LZMA_IN_REQUIRED) {
897 s->rc.in = b->in;
898 s->rc.in_pos = b->in_pos;
899
900 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
901 s->rc.in_limit = b->in_pos + s->lzma2.compressed;
902 else
903 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
904
905 if (!lzma_main(s))
906 return false;
907
908 in_avail = s->rc.in_pos - b->in_pos;
909 if (in_avail > s->lzma2.compressed)
910 return false;
911
912 s->lzma2.compressed -= in_avail;
913 b->in_pos = s->rc.in_pos;
914 }
915
916 in_avail = b->in_size - b->in_pos;
917 if (in_avail < LZMA_IN_REQUIRED) {
918 if (in_avail > s->lzma2.compressed)
919 in_avail = s->lzma2.compressed;
920
921 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
922 s->temp.size = in_avail;
923 b->in_pos += in_avail;
924 }
925
926 return true;
927 }
928
929 /*
930 * Take care of the LZMA2 control layer, and forward the job of actual LZMA
931 * decoding or copying of uncompressed chunks to other functions.
932 */
xz_dec_lzma2_run(struct xz_dec_lzma2 * s,struct xz_buf * b)933 XZ_EXTERN NOINLINE enum xz_ret XZ_FUNC xz_dec_lzma2_run(
934 struct xz_dec_lzma2 *s, struct xz_buf *b)
935 {
936 uint32_t tmp;
937
938 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
939 switch (s->lzma2.sequence) {
940 case SEQ_CONTROL:
941 /*
942 * LZMA2 control byte
943 *
944 * Exact values:
945 * 0x00 End marker
946 * 0x01 Dictionary reset followed by
947 * an uncompressed chunk
948 * 0x02 Uncompressed chunk (no dictionary reset)
949 *
950 * Highest three bits (s->control & 0xE0):
951 * 0xE0 Dictionary reset, new properties and state
952 * reset, followed by LZMA compressed chunk
953 * 0xC0 New properties and state reset, followed
954 * by LZMA compressed chunk (no dictionary
955 * reset)
956 * 0xA0 State reset using old properties,
957 * followed by LZMA compressed chunk (no
958 * dictionary reset)
959 * 0x80 LZMA chunk (no dictionary or state reset)
960 *
961 * For LZMA compressed chunks, the lowest five bits
962 * (s->control & 1F) are the highest bits of the
963 * uncompressed size (bits 16-20).
964 *
965 * A new LZMA2 stream must begin with a dictionary
966 * reset. The first LZMA chunk must set new
967 * properties and reset the LZMA state.
968 *
969 * Values that don't match anything described above
970 * are invalid and we return XZ_DATA_ERROR.
971 */
972 tmp = b->in[b->in_pos++];
973
974 if (tmp == 0x00)
975 return XZ_STREAM_END;
976
977 if (tmp >= 0xE0 || tmp == 0x01) {
978 s->lzma2.need_props = true;
979 s->lzma2.need_dict_reset = false;
980 dict_reset(&s->dict, b);
981 } else if (s->lzma2.need_dict_reset) {
982 return XZ_DATA_ERROR;
983 }
984
985 if (tmp >= 0x80) {
986 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
987 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
988
989 if (tmp >= 0xC0) {
990 /*
991 * When there are new properties,
992 * state reset is done at
993 * SEQ_PROPERTIES.
994 */
995 s->lzma2.need_props = false;
996 s->lzma2.next_sequence
997 = SEQ_PROPERTIES;
998 } else if (s->lzma2.need_props) {
999 return XZ_DATA_ERROR;
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 } else if (b->out_pos == b->out_size
1082 || (b->in_pos == b->in_size
1083 && s->temp.size
1084 < s->lzma2.compressed)) {
1085 return XZ_OK;
1086 }
1087
1088 break;
1089
1090 case SEQ_COPY:
1091 dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1092 if (s->lzma2.compressed > 0)
1093 return XZ_OK;
1094
1095 s->lzma2.sequence = SEQ_CONTROL;
1096 break;
1097 }
1098 }
1099
1100 return XZ_OK;
1101 }
1102
xz_dec_lzma2_create(enum xz_mode mode,uint32_t dict_max)1103 XZ_EXTERN struct xz_dec_lzma2 * XZ_FUNC xz_dec_lzma2_create(
1104 enum xz_mode mode, uint32_t dict_max)
1105 {
1106 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1107 if (s == NULL)
1108 return NULL;
1109
1110 s->dict.mode = mode;
1111 s->dict.size_max = dict_max;
1112
1113 if (DEC_IS_PREALLOC(mode)) {
1114 s->dict.buf = vmalloc(dict_max);
1115 if (s->dict.buf == NULL) {
1116 kfree(s);
1117 return NULL;
1118 }
1119 } else if (DEC_IS_DYNALLOC(mode)) {
1120 s->dict.buf = NULL;
1121 s->dict.allocated = 0;
1122 }
1123
1124 return s;
1125 }
1126
xz_dec_lzma2_reset(struct xz_dec_lzma2 * s,uint8_t props)1127 XZ_EXTERN enum xz_ret XZ_FUNC xz_dec_lzma2_reset(
1128 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
xz_dec_lzma2_end(struct xz_dec_lzma2 * s)1165 XZ_EXTERN void XZ_FUNC 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