1 ///////////////////////////////////////////////////////////////////////////////
3 /// \file lz_encoder_mf.c
4 /// \brief Match finders
6 // Authors: Igor Pavlov
9 // This file has been put into the public domain.
10 // You can do whatever you want with this file.
12 ///////////////////////////////////////////////////////////////////////////////
14 #include "lz_encoder.h"
15 #include "lz_encoder_hash.h"
16 #include "memcmplen.h"
19 /// \brief Find matches starting from the current byte
21 /// \return The length of the longest match found
23 lzma_mf_find(lzma_mf *mf, uint32_t *count_ptr, lzma_match *matches)
25 // Call the match finder. It returns the number of length-distance
27 // FIXME: Minimum count is zero, what _exactly_ is the maximum?
28 const uint32_t count = mf->find(mf, matches);
30 // Length of the longest match; assume that no matches were found
31 // and thus the maximum length is zero.
32 uint32_t len_best = 0;
36 // Validate the matches.
37 for (uint32_t i = 0; i < count; ++i) {
38 assert(matches[i].len <= mf->nice_len);
39 assert(matches[i].dist < mf->read_pos);
40 assert(memcmp(mf_ptr(mf) - 1,
41 mf_ptr(mf) - matches[i].dist - 2,
42 matches[i].len) == 0);
46 // The last used element in the array contains
48 len_best = matches[count - 1].len;
50 // If a match of maximum search length was found, try to
51 // extend the match to maximum possible length.
52 if (len_best == mf->nice_len) {
53 // The limit for the match length is either the
54 // maximum match length supported by the LZ-based
55 // encoder or the number of bytes left in the
56 // dictionary, whichever is smaller.
57 uint32_t limit = mf_avail(mf) + 1;
58 if (limit > mf->match_len_max)
59 limit = mf->match_len_max;
61 // Pointer to the byte we just ran through
63 const uint8_t *p1 = mf_ptr(mf) - 1;
65 // Pointer to the beginning of the match. We need -1
66 // here because the match distances are zero based.
67 const uint8_t *p2 = p1 - matches[count - 1].dist - 1;
69 len_best = lzma_memcmplen(p1, p2, len_best, limit);
75 // Finally update the read position to indicate that match finder was
76 // run for this dictionary offset.
83 /// Hash value to indicate unused element in the hash. Since we start the
84 /// positions from dict_size + 1, zero is always too far to qualify
85 /// as usable match position.
86 #define EMPTY_HASH_VALUE 0
89 /// Normalization must be done when lzma_mf.offset + lzma_mf.read_pos
90 /// reaches MUST_NORMALIZE_POS.
91 #define MUST_NORMALIZE_POS UINT32_MAX
94 /// \brief Normalizes hash values
96 /// The hash arrays store positions of match candidates. The positions are
97 /// relative to an arbitrary offset that is not the same as the absolute
98 /// offset in the input stream. The relative position of the current byte
99 /// is lzma_mf.offset + lzma_mf.read_pos. The distances of the matches are
100 /// the differences of the current read position and the position found from
103 /// To prevent integer overflows of the offsets stored in the hash arrays,
104 /// we need to "normalize" the stored values now and then. During the
105 /// normalization, we drop values that indicate distance greater than the
106 /// dictionary size, thus making space for new values.
108 normalize(lzma_mf *mf)
110 assert(mf->read_pos + mf->offset == MUST_NORMALIZE_POS);
112 // In future we may not want to touch the lowest bits, because there
113 // may be match finders that use larger resolution than one byte.
114 const uint32_t subvalue
115 = (MUST_NORMALIZE_POS - mf->cyclic_size);
116 // & (~(UINT32_C(1) << 10) - 1);
118 for (uint32_t i = 0; i < mf->hash_count; ++i) {
119 // If the distance is greater than the dictionary size,
120 // we can simply mark the hash element as empty.
121 if (mf->hash[i] <= subvalue)
122 mf->hash[i] = EMPTY_HASH_VALUE;
124 mf->hash[i] -= subvalue;
127 for (uint32_t i = 0; i < mf->sons_count; ++i) {
128 // Do the same for mf->son.
130 // NOTE: There may be uninitialized elements in mf->son.
131 // Valgrind may complain that the "if" below depends on
132 // an uninitialized value. In this case it is safe to ignore
133 // the warning. See also the comments in lz_encoder_init()
135 if (mf->son[i] <= subvalue)
136 mf->son[i] = EMPTY_HASH_VALUE;
138 mf->son[i] -= subvalue;
141 // Update offset to match the new locations.
142 mf->offset -= subvalue;
148 /// Mark the current byte as processed from point of view of the match finder.
150 move_pos(lzma_mf *mf)
152 if (++mf->cyclic_pos == mf->cyclic_size)
156 assert(mf->read_pos <= mf->write_pos);
158 if (unlikely(mf->read_pos + mf->offset == UINT32_MAX))
163 /// When flushing, we cannot run the match finder unless there is nice_len
164 /// bytes available in the dictionary. Instead, we skip running the match
165 /// finder (indicating that no match was found), and count how many bytes we
166 /// have ignored this way.
168 /// When new data is given after the flushing was completed, the match finder
169 /// is restarted by rewinding mf->read_pos backwards by mf->pending. Then
170 /// the missed bytes are added to the hash using the match finder's skip
171 /// function (with small amount of input, it may start using mf->pending
172 /// again if flushing).
174 /// Due to this rewinding, we don't touch cyclic_pos or test for
175 /// normalization. It will be done when the match finder's skip function
176 /// catches up after a flush.
178 move_pending(lzma_mf *mf)
181 assert(mf->read_pos <= mf->write_pos);
186 /// Calculate len_limit and determine if there is enough input to run
187 /// the actual match finder code. Sets up "cur" and "pos". This macro
188 /// is used by all find functions and binary tree skip functions. Hash
189 /// chain skip function doesn't need len_limit so a simpler code is used
191 #define header(is_bt, len_min, ret_op) \
192 uint32_t len_limit = mf_avail(mf); \
193 if (mf->nice_len <= len_limit) { \
194 len_limit = mf->nice_len; \
195 } else if (len_limit < (len_min) \
196 || (is_bt && mf->action == LZMA_SYNC_FLUSH)) { \
197 assert(mf->action != LZMA_RUN); \
201 const uint8_t *cur = mf_ptr(mf); \
202 const uint32_t pos = mf->read_pos + mf->offset
205 /// Header for find functions. "return 0" indicates that zero matches
207 #define header_find(is_bt, len_min) \
208 header(is_bt, len_min, return 0); \
209 uint32_t matches_count = 0
212 /// Header for a loop in a skip function. "continue" tells to skip the rest
213 /// of the code in the loop.
214 #define header_skip(is_bt, len_min) \
215 header(is_bt, len_min, continue)
218 /// Calls hc_find_func() or bt_find_func() and calculates the total number
219 /// of matches found. Updates the dictionary position and returns the number
220 /// of matches found.
221 #define call_find(func, len_best) \
223 matches_count = func(len_limit, pos, cur, cur_match, mf->depth, \
224 mf->son, mf->cyclic_pos, mf->cyclic_size, \
225 matches + matches_count, len_best) \
228 return matches_count; \
236 #if defined(HAVE_MF_HC3) || defined(HAVE_MF_HC4)
239 /// \param len_limit Don't look for matches longer than len_limit.
240 /// \param pos lzma_mf.read_pos + lzma_mf.offset
241 /// \param cur Pointer to current byte (mf_ptr(mf))
242 /// \param cur_match Start position of the current match candidate
243 /// \param depth Maximum length of the hash chain
244 /// \param son lzma_mf.son (contains the hash chain)
245 /// \param cyclic_pos
246 /// \param cyclic_size
247 /// \param matches Array to hold the matches.
248 /// \param len_best The length of the longest match found so far.
251 const uint32_t len_limit,
253 const uint8_t *const cur,
257 const uint32_t cyclic_pos,
258 const uint32_t cyclic_size,
262 son[cyclic_pos] = cur_match;
265 const uint32_t delta = pos - cur_match;
266 if (depth-- == 0 || delta >= cyclic_size)
269 const uint8_t *const pb = cur - delta;
270 cur_match = son[cyclic_pos - delta
271 + (delta > cyclic_pos ? cyclic_size : 0)];
273 if (pb[len_best] == cur[len_best] && pb[0] == cur[0]) {
274 uint32_t len = lzma_memcmplen(pb, cur, 1, len_limit);
276 if (len_best < len) {
279 matches->dist = delta - 1;
282 if (len == len_limit)
290 #define hc_find(len_best) \
291 call_find(hc_find_func, len_best)
296 mf->son[mf->cyclic_pos] = cur_match; \
305 lzma_mf_hc3_find(lzma_mf *mf, lzma_match *matches)
307 header_find(false, 3);
311 const uint32_t delta2 = pos - mf->hash[hash_2_value];
312 const uint32_t cur_match = mf->hash[FIX_3_HASH_SIZE + hash_value];
314 mf->hash[hash_2_value] = pos;
315 mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
317 uint32_t len_best = 2;
319 if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
320 len_best = lzma_memcmplen(cur - delta2, cur,
321 len_best, len_limit);
323 matches[0].len = len_best;
324 matches[0].dist = delta2 - 1;
327 if (len_best == len_limit) {
329 return 1; // matches_count
338 lzma_mf_hc3_skip(lzma_mf *mf, uint32_t amount)
341 if (mf_avail(mf) < 3) {
346 const uint8_t *cur = mf_ptr(mf);
347 const uint32_t pos = mf->read_pos + mf->offset;
351 const uint32_t cur_match
352 = mf->hash[FIX_3_HASH_SIZE + hash_value];
354 mf->hash[hash_2_value] = pos;
355 mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
359 } while (--amount != 0);
366 lzma_mf_hc4_find(lzma_mf *mf, lzma_match *matches)
368 header_find(false, 4);
372 uint32_t delta2 = pos - mf->hash[hash_2_value];
373 const uint32_t delta3
374 = pos - mf->hash[FIX_3_HASH_SIZE + hash_3_value];
375 const uint32_t cur_match = mf->hash[FIX_4_HASH_SIZE + hash_value];
377 mf->hash[hash_2_value ] = pos;
378 mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
379 mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
381 uint32_t len_best = 1;
383 if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
386 matches[0].dist = delta2 - 1;
390 if (delta2 != delta3 && delta3 < mf->cyclic_size
391 && *(cur - delta3) == *cur) {
393 matches[matches_count++].dist = delta3 - 1;
397 if (matches_count != 0) {
398 len_best = lzma_memcmplen(cur - delta2, cur,
399 len_best, len_limit);
401 matches[matches_count - 1].len = len_best;
403 if (len_best == len_limit) {
405 return matches_count;
417 lzma_mf_hc4_skip(lzma_mf *mf, uint32_t amount)
420 if (mf_avail(mf) < 4) {
425 const uint8_t *cur = mf_ptr(mf);
426 const uint32_t pos = mf->read_pos + mf->offset;
430 const uint32_t cur_match
431 = mf->hash[FIX_4_HASH_SIZE + hash_value];
433 mf->hash[hash_2_value] = pos;
434 mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
435 mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
439 } while (--amount != 0);
448 #if defined(HAVE_MF_BT2) || defined(HAVE_MF_BT3) || defined(HAVE_MF_BT4)
451 const uint32_t len_limit,
453 const uint8_t *const cur,
457 const uint32_t cyclic_pos,
458 const uint32_t cyclic_size,
462 uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
463 uint32_t *ptr1 = son + (cyclic_pos << 1);
469 const uint32_t delta = pos - cur_match;
470 if (depth-- == 0 || delta >= cyclic_size) {
471 *ptr0 = EMPTY_HASH_VALUE;
472 *ptr1 = EMPTY_HASH_VALUE;
476 uint32_t *const pair = son + ((cyclic_pos - delta
477 + (delta > cyclic_pos ? cyclic_size : 0))
480 const uint8_t *const pb = cur - delta;
481 uint32_t len = my_min(len0, len1);
483 if (pb[len] == cur[len]) {
484 len = lzma_memcmplen(pb, cur, len + 1, len_limit);
486 if (len_best < len) {
489 matches->dist = delta - 1;
492 if (len == len_limit) {
500 if (pb[len] < cur[len]) {
517 const uint32_t len_limit,
519 const uint8_t *const cur,
523 const uint32_t cyclic_pos,
524 const uint32_t cyclic_size)
526 uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
527 uint32_t *ptr1 = son + (cyclic_pos << 1);
533 const uint32_t delta = pos - cur_match;
534 if (depth-- == 0 || delta >= cyclic_size) {
535 *ptr0 = EMPTY_HASH_VALUE;
536 *ptr1 = EMPTY_HASH_VALUE;
540 uint32_t *pair = son + ((cyclic_pos - delta
541 + (delta > cyclic_pos ? cyclic_size : 0))
543 const uint8_t *pb = cur - delta;
544 uint32_t len = my_min(len0, len1);
546 if (pb[len] == cur[len]) {
547 len = lzma_memcmplen(pb, cur, len + 1, len_limit);
549 if (len == len_limit) {
556 if (pb[len] < cur[len]) {
571 #define bt_find(len_best) \
572 call_find(bt_find_func, len_best)
576 bt_skip_func(len_limit, pos, cur, cur_match, mf->depth, \
577 mf->son, mf->cyclic_pos, \
587 lzma_mf_bt2_find(lzma_mf *mf, lzma_match *matches)
589 header_find(true, 2);
593 const uint32_t cur_match = mf->hash[hash_value];
594 mf->hash[hash_value] = pos;
601 lzma_mf_bt2_skip(lzma_mf *mf, uint32_t amount)
604 header_skip(true, 2);
608 const uint32_t cur_match = mf->hash[hash_value];
609 mf->hash[hash_value] = pos;
613 } while (--amount != 0);
620 lzma_mf_bt3_find(lzma_mf *mf, lzma_match *matches)
622 header_find(true, 3);
626 const uint32_t delta2 = pos - mf->hash[hash_2_value];
627 const uint32_t cur_match = mf->hash[FIX_3_HASH_SIZE + hash_value];
629 mf->hash[hash_2_value] = pos;
630 mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
632 uint32_t len_best = 2;
634 if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
635 len_best = lzma_memcmplen(
636 cur, cur - delta2, len_best, len_limit);
638 matches[0].len = len_best;
639 matches[0].dist = delta2 - 1;
642 if (len_best == len_limit) {
644 return 1; // matches_count
653 lzma_mf_bt3_skip(lzma_mf *mf, uint32_t amount)
656 header_skip(true, 3);
660 const uint32_t cur_match
661 = mf->hash[FIX_3_HASH_SIZE + hash_value];
663 mf->hash[hash_2_value] = pos;
664 mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
668 } while (--amount != 0);
675 lzma_mf_bt4_find(lzma_mf *mf, lzma_match *matches)
677 header_find(true, 4);
681 uint32_t delta2 = pos - mf->hash[hash_2_value];
682 const uint32_t delta3
683 = pos - mf->hash[FIX_3_HASH_SIZE + hash_3_value];
684 const uint32_t cur_match = mf->hash[FIX_4_HASH_SIZE + hash_value];
686 mf->hash[hash_2_value] = pos;
687 mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
688 mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
690 uint32_t len_best = 1;
692 if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
695 matches[0].dist = delta2 - 1;
699 if (delta2 != delta3 && delta3 < mf->cyclic_size
700 && *(cur - delta3) == *cur) {
702 matches[matches_count++].dist = delta3 - 1;
706 if (matches_count != 0) {
707 len_best = lzma_memcmplen(
708 cur, cur - delta2, len_best, len_limit);
710 matches[matches_count - 1].len = len_best;
712 if (len_best == len_limit) {
714 return matches_count;
726 lzma_mf_bt4_skip(lzma_mf *mf, uint32_t amount)
729 header_skip(true, 4);
733 const uint32_t cur_match
734 = mf->hash[FIX_4_HASH_SIZE + hash_value];
736 mf->hash[hash_2_value] = pos;
737 mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
738 mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
742 } while (--amount != 0);