1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2004 Jean-loup Gailly.
3 * For conditions of distribution and use, see copyright notice in zlib.h
9 * The "deflation" process depends on being able to identify portions
10 * of the input text which are identical to earlier input (within a
11 * sliding window trailing behind the input currently being processed).
13 * The most straightforward technique turns out to be the fastest for
14 * most input files: try all possible matches and select the longest.
15 * The key feature of this algorithm is that insertions into the string
16 * dictionary are very simple and thus fast, and deletions are avoided
17 * completely. Insertions are performed at each input character, whereas
18 * string matches are performed only when the previous match ends. So it
19 * is preferable to spend more time in matches to allow very fast string
20 * insertions and avoid deletions. The matching algorithm for small
21 * strings is inspired from that of Rabin & Karp. A brute force approach
22 * is used to find longer strings when a small match has been found.
23 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
24 * (by Leonid Broukhis).
25 * A previous version of this file used a more sophisticated algorithm
26 * (by Fiala and Greene) which is guaranteed to run in linear amortized
27 * time, but has a larger average cost, uses more memory and is patented.
28 * However the F&G algorithm may be faster for some highly redundant
29 * files if the parameter max_chain_length (described below) is too large.
33 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
34 * I found it in 'freeze' written by Leonid Broukhis.
35 * Thanks to many people for bug reports and testing.
39 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
40 * Available in http://www.ietf.org/rfc/rfc1951.txt
42 * A description of the Rabin and Karp algorithm is given in the book
43 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
45 * Fiala,E.R., and Greene,D.H.
46 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
54 const char deflate_copyright[] =
55 " deflate 1.2.2.2 Copyright 1995-2004 Jean-loup Gailly ";
57 If you use the zlib library in a product, an acknowledgment is welcome
58 in the documentation of your product. If for some reason you cannot
59 include such an acknowledgment, I would appreciate that you keep this
60 copyright string in the executable of your product.
63 /* ===========================================================================
64 * Function prototypes.
67 need_more, /* block not completed, need more input or more output */
68 block_done, /* block flush performed */
69 finish_started, /* finish started, need only more output at next deflate */
70 finish_done /* finish done, accept no more input or output */
73 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
74 /* Compression function. Returns the block state after the call. */
76 local void fill_window OF((deflate_state *s));
77 local block_state deflate_stored OF((deflate_state *s, int flush));
78 local block_state deflate_fast OF((deflate_state *s, int flush));
80 local block_state deflate_slow OF((deflate_state *s, int flush));
82 local void lm_init OF((deflate_state *s));
83 local void putShortMSB OF((deflate_state *s, uInt b));
84 local void flush_pending OF((z_streamp strm));
85 local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
88 void match_init OF((void)); /* asm code initialization */
89 uInt longest_match OF((deflate_state *s, IPos cur_match));
91 local uInt longest_match OF((deflate_state *s, IPos cur_match));
94 local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
97 local void check_match OF((deflate_state *s, IPos start, IPos match,
101 /* ===========================================================================
106 /* Tail of hash chains */
109 # define TOO_FAR 4096
111 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
113 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
114 /* Minimum amount of lookahead, except at the end of the input file.
115 * See deflate.c for comments about the MIN_MATCH+1.
118 /* Values for max_lazy_match, good_match and max_chain_length, depending on
119 * the desired pack level (0..9). The values given below have been tuned to
120 * exclude worst case performance for pathological files. Better values may be
121 * found for specific files.
123 typedef struct config_s {
124 ush good_length; /* reduce lazy search above this match length */
125 ush max_lazy; /* do not perform lazy search above this match length */
126 ush nice_length; /* quit search above this match length */
132 local const config configuration_table[2] = {
133 /* good lazy nice chain */
134 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
135 /* 1 */ {4, 4, 8, 4, deflate_fast}}; /* max speed, no lazy matches */
137 local const config configuration_table[10] = {
138 /* good lazy nice chain */
139 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
140 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* max speed, no lazy matches */
141 /* 2 */ {4, 5, 16, 8, deflate_fast},
142 /* 3 */ {4, 6, 32, 32, deflate_fast},
144 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
145 /* 5 */ {8, 16, 32, 32, deflate_slow},
146 /* 6 */ {8, 16, 128, 128, deflate_slow},
147 /* 7 */ {8, 32, 128, 256, deflate_slow},
148 /* 8 */ {32, 128, 258, 1024, deflate_slow},
149 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
152 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
153 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
158 /* result of memcmp for equal strings */
160 #ifndef NO_DUMMY_DECL
161 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
164 /* ===========================================================================
165 * Update a hash value with the given input byte
166 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
167 * input characters, so that a running hash key can be computed from the
168 * previous key instead of complete recalculation each time.
170 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
173 /* ===========================================================================
174 * Insert string str in the dictionary and set match_head to the previous head
175 * of the hash chain (the most recent string with same hash key). Return
176 * the previous length of the hash chain.
177 * If this file is compiled with -DFASTEST, the compression level is forced
178 * to 1, and no hash chains are maintained.
179 * IN assertion: all calls to to INSERT_STRING are made with consecutive
180 * input characters and the first MIN_MATCH bytes of str are valid
181 * (except for the last MIN_MATCH-1 bytes of the input file).
184 #define INSERT_STRING(s, str, match_head) \
185 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
186 match_head = s->head[s->ins_h], \
187 s->head[s->ins_h] = (Pos)(str))
189 #define INSERT_STRING(s, str, match_head) \
190 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
191 match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
192 s->head[s->ins_h] = (Pos)(str))
195 /* ===========================================================================
196 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
197 * prev[] will be initialized on the fly.
199 #define CLEAR_HASH(s) \
200 s->head[s->hash_size-1] = NIL; \
201 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
203 /* ========================================================================= */
204 int ZEXPORT deflateInit_(strm, level, version, stream_size)
210 return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
211 Z_DEFAULT_STRATEGY, version, stream_size);
212 /* To do: ignore strm->next_in if we use it as window */
215 /* ========================================================================= */
216 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
217 version, stream_size)
229 static const char my_version[] = ZLIB_VERSION;
232 /* We overlay pending_buf and d_buf+l_buf. This works since the average
233 * output size for (length,distance) codes is <= 24 bits.
236 if (version == Z_NULL || version[0] != my_version[0] ||
237 stream_size != sizeof(z_stream)) {
238 return Z_VERSION_ERROR;
240 if (strm == Z_NULL) return Z_STREAM_ERROR;
243 if (strm->zalloc == (alloc_func)0) {
244 strm->zalloc = zcalloc;
245 strm->opaque = (voidpf)0;
247 if (strm->zfree == (free_func)0) strm->zfree = zcfree;
250 if (level != 0) level = 1;
252 if (level == Z_DEFAULT_COMPRESSION) level = 6;
255 if (windowBits < 0) { /* suppress zlib wrapper */
257 windowBits = -windowBits;
260 else if (windowBits > 15) {
261 wrap = 2; /* write gzip wrapper instead */
265 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
266 windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
267 strategy < 0 || strategy > Z_FIXED) {
268 return Z_STREAM_ERROR;
270 if (windowBits == 8) windowBits = 9; /* until 256-byte window bug fixed */
271 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
272 if (s == Z_NULL) return Z_MEM_ERROR;
273 strm->state = (struct internal_state FAR *)s;
278 s->w_bits = windowBits;
279 s->w_size = 1 << s->w_bits;
280 s->w_mask = s->w_size - 1;
282 s->hash_bits = memLevel + 7;
283 s->hash_size = 1 << s->hash_bits;
284 s->hash_mask = s->hash_size - 1;
285 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
287 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
288 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
289 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
291 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
293 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
294 s->pending_buf = (uchf *) overlay;
295 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
297 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
298 s->pending_buf == Z_NULL) {
299 s->status = FINISH_STATE;
300 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
304 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
305 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
308 s->strategy = strategy;
309 s->method = (Byte)method;
311 return deflateReset(strm);
314 /* ========================================================================= */
315 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
317 const Bytef *dictionary;
321 uInt length = dictLength;
325 if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
326 strm->state->wrap == 2 ||
327 (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
328 return Z_STREAM_ERROR;
332 strm->adler = adler32(strm->adler, dictionary, dictLength);
334 if (length < MIN_MATCH) return Z_OK;
335 if (length > MAX_DIST(s)) {
336 length = MAX_DIST(s);
337 #ifndef USE_DICT_HEAD
338 dictionary += dictLength - length; /* use the tail of the dictionary */
341 zmemcpy(s->window, dictionary, length);
342 s->strstart = length;
343 s->block_start = (long)length;
345 /* Insert all strings in the hash table (except for the last two bytes).
346 * s->lookahead stays null, so s->ins_h will be recomputed at the next
347 * call of fill_window.
349 s->ins_h = s->window[0];
350 UPDATE_HASH(s, s->ins_h, s->window[1]);
351 for (n = 0; n <= length - MIN_MATCH; n++) {
352 INSERT_STRING(s, n, hash_head);
354 if (hash_head) hash_head = 0; /* to make compiler happy */
358 /* ========================================================================= */
359 int ZEXPORT deflateReset (strm)
364 if (strm == Z_NULL || strm->state == Z_NULL ||
365 strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
366 return Z_STREAM_ERROR;
369 strm->total_in = strm->total_out = 0;
370 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
371 strm->data_type = Z_UNKNOWN;
373 s = (deflate_state *)strm->state;
375 s->pending_out = s->pending_buf;
378 s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
380 s->status = s->wrap ? INIT_STATE : BUSY_STATE;
383 s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
385 adler32(0L, Z_NULL, 0);
386 s->last_flush = Z_NO_FLUSH;
394 /* ========================================================================= */
395 int ZEXPORT deflateSetHeader (strm, head)
399 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
400 if (strm->state->wrap != 2) return Z_STREAM_ERROR;
401 strm->state->gzhead = head;
405 /* ========================================================================= */
406 int ZEXPORT deflatePrime (strm, bits, value)
411 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
412 strm->state->bi_valid = bits;
413 strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
417 /* ========================================================================= */
418 int ZEXPORT deflateParams(strm, level, strategy)
427 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
431 if (level != 0) level = 1;
433 if (level == Z_DEFAULT_COMPRESSION) level = 6;
435 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
436 return Z_STREAM_ERROR;
438 func = configuration_table[s->level].func;
440 if (func != configuration_table[level].func && strm->total_in != 0) {
441 /* Flush the last buffer: */
442 err = deflate(strm, Z_PARTIAL_FLUSH);
444 if (s->level != level) {
446 s->max_lazy_match = configuration_table[level].max_lazy;
447 s->good_match = configuration_table[level].good_length;
448 s->nice_match = configuration_table[level].nice_length;
449 s->max_chain_length = configuration_table[level].max_chain;
451 s->strategy = strategy;
455 /* =========================================================================
456 * For the default windowBits of 15 and memLevel of 8, this function returns
457 * a close to exact, as well as small, upper bound on the compressed size.
458 * They are coded as constants here for a reason--if the #define's are
459 * changed, then this function needs to be changed as well. The return
460 * value for 15 and 8 only works for those exact settings.
462 * For any setting other than those defaults for windowBits and memLevel,
463 * the value returned is a conservative worst case for the maximum expansion
464 * resulting from using fixed blocks instead of stored blocks, which deflate
465 * can emit on compressed data for some combinations of the parameters.
467 * This function could be more sophisticated to provide closer upper bounds
468 * for every combination of windowBits and memLevel, as well as wrap.
469 * But even the conservative upper bound of about 14% expansion does not
470 * seem onerous for output buffer allocation.
472 uLong ZEXPORT deflateBound(strm, sourceLen)
479 /* conservative upper bound */
480 destLen = sourceLen +
481 ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
483 /* if can't get parameters, return conservative bound */
484 if (strm == Z_NULL || strm->state == Z_NULL)
487 /* if not default parameters, return conservative bound */
489 if (s->w_bits != 15 || s->hash_bits != 8 + 7)
492 /* default settings: return tight bound for that case */
493 return compressBound(sourceLen);
496 /* =========================================================================
497 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
498 * IN assertion: the stream state is correct and there is enough room in
501 local void putShortMSB (s, b)
505 put_byte(s, (Byte)(b >> 8));
506 put_byte(s, (Byte)(b & 0xff));
509 /* =========================================================================
510 * Flush as much pending output as possible. All deflate() output goes
511 * through this function so some applications may wish to modify it
512 * to avoid allocating a large strm->next_out buffer and copying into it.
513 * (See also read_buf()).
515 local void flush_pending(strm)
518 unsigned len = strm->state->pending;
520 if (len > strm->avail_out) len = strm->avail_out;
521 if (len == 0) return;
523 zmemcpy(strm->next_out, strm->state->pending_out, len);
524 strm->next_out += len;
525 strm->state->pending_out += len;
526 strm->total_out += len;
527 strm->avail_out -= len;
528 strm->state->pending -= len;
529 if (strm->state->pending == 0) {
530 strm->state->pending_out = strm->state->pending_buf;
534 /* ========================================================================= */
535 int ZEXPORT deflate (strm, flush)
539 int old_flush; /* value of flush param for previous deflate call */
542 if (strm == Z_NULL || strm->state == Z_NULL ||
543 flush > Z_FINISH || flush < 0) {
544 return Z_STREAM_ERROR;
548 if (strm->next_out == Z_NULL ||
549 (strm->next_in == Z_NULL && strm->avail_in != 0) ||
550 (s->status == FINISH_STATE && flush != Z_FINISH)) {
551 ERR_RETURN(strm, Z_STREAM_ERROR);
553 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
555 s->strm = strm; /* just in case */
556 old_flush = s->last_flush;
557 s->last_flush = flush;
559 /* Write the header */
560 if (s->status == INIT_STATE) {
563 strm->adler = crc32(0L, Z_NULL, 0);
567 if (s->gzhead == NULL) {
573 put_byte(s, s->level == 9 ? 2 :
574 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
576 put_byte(s, OS_CODE);
577 s->status = BUSY_STATE;
580 put_byte(s, (s->gzhead->text ? 1 : 0) +
581 (s->gzhead->hcrc ? 2 : 0) +
582 (s->gzhead->extra == Z_NULL ? 0 : 4) +
583 (s->gzhead->name == Z_NULL ? 0 : 8) +
584 (s->gzhead->comment == Z_NULL ? 0 : 16)
586 put_byte(s, s->gzhead->time & 0xff);
587 put_byte(s, (s->gzhead->time >> 8) & 0xff);
588 put_byte(s, (s->gzhead->time >> 16) & 0xff);
589 put_byte(s, (s->gzhead->time >> 24) & 0xff);
590 put_byte(s, s->level == 9 ? 2 :
591 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
593 put_byte(s, s->gzhead->os & 0xff);
594 if (s->gzhead->extra != NULL) {
595 put_byte(s, s->gzhead->extra_len & 0xff);
596 put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
599 strm->adler = crc32(strm->adler, s->pending_buf,
602 s->status = EXTRA_STATE;
608 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
611 if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
613 else if (s->level < 6)
615 else if (s->level == 6)
619 header |= (level_flags << 6);
620 if (s->strstart != 0) header |= PRESET_DICT;
621 header += 31 - (header % 31);
623 s->status = BUSY_STATE;
624 putShortMSB(s, header);
626 /* Save the adler32 of the preset dictionary: */
627 if (s->strstart != 0) {
628 putShortMSB(s, (uInt)(strm->adler >> 16));
629 putShortMSB(s, (uInt)(strm->adler & 0xffff));
631 strm->adler = adler32(0L, Z_NULL, 0);
635 if (s->status == EXTRA_STATE) {
636 if (s->gzhead->extra != NULL) {
637 int beg = s->pending; /* start of bytes to update crc */
639 while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
640 if (s->pending == s->pending_buf_size) {
641 if (s->gzhead->hcrc && s->pending > beg)
642 strm->adler = crc32(strm->adler, s->pending_buf + beg,
646 if (s->pending == s->pending_buf_size)
649 put_byte(s, s->gzhead->extra[s->gzindex]);
652 if (s->gzhead->hcrc && s->pending > beg)
653 strm->adler = crc32(strm->adler, s->pending_buf + beg,
655 if (s->gzindex == s->gzhead->extra_len) {
657 s->status = NAME_STATE;
661 s->status = NAME_STATE;
663 if (s->status == NAME_STATE) {
664 if (s->gzhead->name != NULL) {
665 int beg = s->pending; /* start of bytes to update crc */
669 if (s->pending == s->pending_buf_size) {
670 if (s->gzhead->hcrc && s->pending > beg)
671 strm->adler = crc32(strm->adler, s->pending_buf + beg,
675 if (s->pending == s->pending_buf_size) {
680 val = s->gzhead->name[s->gzindex++];
683 if (s->gzhead->hcrc && s->pending > beg)
684 strm->adler = crc32(strm->adler, s->pending_buf + beg,
688 s->status = COMMENT_STATE;
692 s->status = COMMENT_STATE;
694 if (s->status == COMMENT_STATE) {
695 if (s->gzhead->comment != NULL) {
696 int beg = s->pending; /* start of bytes to update crc */
700 if (s->pending == s->pending_buf_size) {
701 if (s->gzhead->hcrc && s->pending > beg)
702 strm->adler = crc32(strm->adler, s->pending_buf + beg,
706 if (s->pending == s->pending_buf_size) {
711 val = s->gzhead->comment[s->gzindex++];
714 if (s->gzhead->hcrc && s->pending > beg)
715 strm->adler = crc32(strm->adler, s->pending_buf + beg,
718 s->status = HCRC_STATE;
721 s->status = HCRC_STATE;
723 if (s->status == HCRC_STATE) {
724 if (s->gzhead->hcrc) {
725 if (s->pending + 2 > s->pending_buf_size)
727 if (s->pending + 2 <= s->pending_buf_size) {
728 put_byte(s, strm->adler & 0xff);
729 put_byte(s, (strm->adler >> 8) & 0xff);
730 strm->adler = crc32(0L, Z_NULL, 0);
731 s->status = BUSY_STATE;
735 s->status = BUSY_STATE;
739 /* Flush as much pending output as possible */
740 if (s->pending != 0) {
742 if (strm->avail_out == 0) {
743 /* Since avail_out is 0, deflate will be called again with
744 * more output space, but possibly with both pending and
745 * avail_in equal to zero. There won't be anything to do,
746 * but this is not an error situation so make sure we
747 * return OK instead of BUF_ERROR at next call of deflate:
753 /* Make sure there is something to do and avoid duplicate consecutive
754 * flushes. For repeated and useless calls with Z_FINISH, we keep
755 * returning Z_STREAM_END instead of Z_BUF_ERROR.
757 } else if (strm->avail_in == 0 && flush <= old_flush &&
759 ERR_RETURN(strm, Z_BUF_ERROR);
762 /* User must not provide more input after the first FINISH: */
763 if (s->status == FINISH_STATE && strm->avail_in != 0) {
764 ERR_RETURN(strm, Z_BUF_ERROR);
767 /* Start a new block or continue the current one.
769 if (strm->avail_in != 0 || s->lookahead != 0 ||
770 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
773 bstate = (*(configuration_table[s->level].func))(s, flush);
775 if (bstate == finish_started || bstate == finish_done) {
776 s->status = FINISH_STATE;
778 if (bstate == need_more || bstate == finish_started) {
779 if (strm->avail_out == 0) {
780 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
783 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
784 * of deflate should use the same flush parameter to make sure
785 * that the flush is complete. So we don't have to output an
786 * empty block here, this will be done at next call. This also
787 * ensures that for a very small output buffer, we emit at most
791 if (bstate == block_done) {
792 if (flush == Z_PARTIAL_FLUSH) {
794 } else { /* FULL_FLUSH or SYNC_FLUSH */
795 _tr_stored_block(s, (char*)0, 0L, 0);
796 /* For a full flush, this empty block will be recognized
797 * as a special marker by inflate_sync().
799 if (flush == Z_FULL_FLUSH) {
800 CLEAR_HASH(s); /* forget history */
804 if (strm->avail_out == 0) {
805 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
810 Assert(strm->avail_out > 0, "bug2");
812 if (flush != Z_FINISH) return Z_OK;
813 if (s->wrap <= 0) return Z_STREAM_END;
815 /* Write the trailer */
818 put_byte(s, (Byte)(strm->adler & 0xff));
819 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
820 put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
821 put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
822 put_byte(s, (Byte)(strm->total_in & 0xff));
823 put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
824 put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
825 put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
830 putShortMSB(s, (uInt)(strm->adler >> 16));
831 putShortMSB(s, (uInt)(strm->adler & 0xffff));
834 /* If avail_out is zero, the application will call deflate again
837 if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
838 return s->pending != 0 ? Z_OK : Z_STREAM_END;
841 /* ========================================================================= */
842 int ZEXPORT deflateEnd (strm)
847 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
849 status = strm->state->status;
850 if (status != INIT_STATE &&
851 status != EXTRA_STATE &&
852 status != NAME_STATE &&
853 status != COMMENT_STATE &&
854 status != HCRC_STATE &&
855 status != BUSY_STATE &&
856 status != FINISH_STATE) {
857 return Z_STREAM_ERROR;
860 /* Deallocate in reverse order of allocations: */
861 TRY_FREE(strm, strm->state->pending_buf);
862 TRY_FREE(strm, strm->state->head);
863 TRY_FREE(strm, strm->state->prev);
864 TRY_FREE(strm, strm->state->window);
866 ZFREE(strm, strm->state);
867 strm->state = Z_NULL;
869 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
872 /* =========================================================================
873 * Copy the source state to the destination state.
874 * To simplify the source, this is not supported for 16-bit MSDOS (which
875 * doesn't have enough memory anyway to duplicate compression states).
877 int ZEXPORT deflateCopy (dest, source)
882 return Z_STREAM_ERROR;
889 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
890 return Z_STREAM_ERROR;
895 zmemcpy(dest, source, sizeof(z_stream));
897 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
898 if (ds == Z_NULL) return Z_MEM_ERROR;
899 dest->state = (struct internal_state FAR *) ds;
900 zmemcpy(ds, ss, sizeof(deflate_state));
903 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
904 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
905 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
906 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
907 ds->pending_buf = (uchf *) overlay;
909 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
910 ds->pending_buf == Z_NULL) {
914 /* following zmemcpy do not work for 16-bit MSDOS */
915 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
916 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
917 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
918 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
920 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
921 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
922 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
924 ds->l_desc.dyn_tree = ds->dyn_ltree;
925 ds->d_desc.dyn_tree = ds->dyn_dtree;
926 ds->bl_desc.dyn_tree = ds->bl_tree;
929 #endif /* MAXSEG_64K */
932 /* ===========================================================================
933 * Read a new buffer from the current input stream, update the adler32
934 * and total number of bytes read. All deflate() input goes through
935 * this function so some applications may wish to modify it to avoid
936 * allocating a large strm->next_in buffer and copying from it.
937 * (See also flush_pending()).
939 local int read_buf(strm, buf, size)
944 unsigned len = strm->avail_in;
946 if (len > size) len = size;
947 if (len == 0) return 0;
949 strm->avail_in -= len;
951 if (strm->state->wrap == 1) {
952 strm->adler = adler32(strm->adler, strm->next_in, len);
955 else if (strm->state->wrap == 2) {
956 strm->adler = crc32(strm->adler, strm->next_in, len);
959 zmemcpy(buf, strm->next_in, len);
960 strm->next_in += len;
961 strm->total_in += len;
966 /* ===========================================================================
967 * Initialize the "longest match" routines for a new zlib stream
969 local void lm_init (s)
972 s->window_size = (ulg)2L*s->w_size;
976 /* Set the default configuration parameters:
978 s->max_lazy_match = configuration_table[s->level].max_lazy;
979 s->good_match = configuration_table[s->level].good_length;
980 s->nice_match = configuration_table[s->level].nice_length;
981 s->max_chain_length = configuration_table[s->level].max_chain;
986 s->match_length = s->prev_length = MIN_MATCH-1;
987 s->match_available = 0;
990 match_init(); /* initialize the asm code */
995 /* ===========================================================================
996 * Set match_start to the longest match starting at the given string and
997 * return its length. Matches shorter or equal to prev_length are discarded,
998 * in which case the result is equal to prev_length and match_start is
1000 * IN assertions: cur_match is the head of the hash chain for the current
1001 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1002 * OUT assertion: the match length is not greater than s->lookahead.
1005 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1006 * match.S. The code will be functionally equivalent.
1008 local uInt longest_match(s, cur_match)
1010 IPos cur_match; /* current match */
1012 unsigned chain_length = s->max_chain_length;/* max hash chain length */
1013 register Bytef *scan = s->window + s->strstart; /* current string */
1014 register Bytef *match; /* matched string */
1015 register int len; /* length of current match */
1016 int best_len = s->prev_length; /* best match length so far */
1017 int nice_match = s->nice_match; /* stop if match long enough */
1018 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1019 s->strstart - (IPos)MAX_DIST(s) : NIL;
1020 /* Stop when cur_match becomes <= limit. To simplify the code,
1021 * we prevent matches with the string of window index 0.
1023 Posf *prev = s->prev;
1024 uInt wmask = s->w_mask;
1027 /* Compare two bytes at a time. Note: this is not always beneficial.
1028 * Try with and without -DUNALIGNED_OK to check.
1030 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1031 register ush scan_start = *(ushf*)scan;
1032 register ush scan_end = *(ushf*)(scan+best_len-1);
1034 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1035 register Byte scan_end1 = scan[best_len-1];
1036 register Byte scan_end = scan[best_len];
1039 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1040 * It is easy to get rid of this optimization if necessary.
1042 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1044 /* Do not waste too much time if we already have a good match: */
1045 if (s->prev_length >= s->good_match) {
1048 /* Do not look for matches beyond the end of the input. This is necessary
1049 * to make deflate deterministic.
1051 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1053 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1056 Assert(cur_match < s->strstart, "no future");
1057 match = s->window + cur_match;
1059 /* Skip to next match if the match length cannot increase
1060 * or if the match length is less than 2. Note that the checks below
1061 * for insufficient lookahead only occur occasionally for performance
1062 * reasons. Therefore uninitialized memory will be accessed, and
1063 * conditional jumps will be made that depend on those values.
1064 * However the length of the match is limited to the lookahead, so
1065 * the output of deflate is not affected by the uninitialized values.
1067 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1068 /* This code assumes sizeof(unsigned short) == 2. Do not use
1069 * UNALIGNED_OK if your compiler uses a different size.
1071 if (*(ushf*)(match+best_len-1) != scan_end ||
1072 *(ushf*)match != scan_start) continue;
1074 /* It is not necessary to compare scan[2] and match[2] since they are
1075 * always equal when the other bytes match, given that the hash keys
1076 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1077 * strstart+3, +5, ... up to strstart+257. We check for insufficient
1078 * lookahead only every 4th comparison; the 128th check will be made
1079 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1080 * necessary to put more guard bytes at the end of the window, or
1081 * to check more often for insufficient lookahead.
1083 Assert(scan[2] == match[2], "scan[2]?");
1086 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1087 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1088 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1089 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1091 /* The funny "do {}" generates better code on most compilers */
1093 /* Here, scan <= window+strstart+257 */
1094 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1095 if (*scan == *match) scan++;
1097 len = (MAX_MATCH - 1) - (int)(strend-scan);
1098 scan = strend - (MAX_MATCH-1);
1100 #else /* UNALIGNED_OK */
1102 if (match[best_len] != scan_end ||
1103 match[best_len-1] != scan_end1 ||
1105 *++match != scan[1]) continue;
1107 /* The check at best_len-1 can be removed because it will be made
1108 * again later. (This heuristic is not always a win.)
1109 * It is not necessary to compare scan[2] and match[2] since they
1110 * are always equal when the other bytes match, given that
1111 * the hash keys are equal and that HASH_BITS >= 8.
1114 Assert(*scan == *match, "match[2]?");
1116 /* We check for insufficient lookahead only every 8th comparison;
1117 * the 256th check will be made at strstart+258.
1120 } while (*++scan == *++match && *++scan == *++match &&
1121 *++scan == *++match && *++scan == *++match &&
1122 *++scan == *++match && *++scan == *++match &&
1123 *++scan == *++match && *++scan == *++match &&
1126 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1128 len = MAX_MATCH - (int)(strend - scan);
1129 scan = strend - MAX_MATCH;
1131 #endif /* UNALIGNED_OK */
1133 if (len > best_len) {
1134 s->match_start = cur_match;
1136 if (len >= nice_match) break;
1138 scan_end = *(ushf*)(scan+best_len-1);
1140 scan_end1 = scan[best_len-1];
1141 scan_end = scan[best_len];
1144 } while ((cur_match = prev[cur_match & wmask]) > limit
1145 && --chain_length != 0);
1147 if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1148 return s->lookahead;
1151 #endif /* FASTEST */
1153 /* ---------------------------------------------------------------------------
1154 * Optimized version for level == 1 or strategy == Z_RLE only
1156 local uInt longest_match_fast(s, cur_match)
1158 IPos cur_match; /* current match */
1160 register Bytef *scan = s->window + s->strstart; /* current string */
1161 register Bytef *match; /* matched string */
1162 register int len; /* length of current match */
1163 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1165 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1166 * It is easy to get rid of this optimization if necessary.
1168 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1170 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1172 Assert(cur_match < s->strstart, "no future");
1174 match = s->window + cur_match;
1176 /* Return failure if the match length is less than 2:
1178 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1180 /* The check at best_len-1 can be removed because it will be made
1181 * again later. (This heuristic is not always a win.)
1182 * It is not necessary to compare scan[2] and match[2] since they
1183 * are always equal when the other bytes match, given that
1184 * the hash keys are equal and that HASH_BITS >= 8.
1186 scan += 2, match += 2;
1187 Assert(*scan == *match, "match[2]?");
1189 /* We check for insufficient lookahead only every 8th comparison;
1190 * the 256th check will be made at strstart+258.
1193 } while (*++scan == *++match && *++scan == *++match &&
1194 *++scan == *++match && *++scan == *++match &&
1195 *++scan == *++match && *++scan == *++match &&
1196 *++scan == *++match && *++scan == *++match &&
1199 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1201 len = MAX_MATCH - (int)(strend - scan);
1203 if (len < MIN_MATCH) return MIN_MATCH - 1;
1205 s->match_start = cur_match;
1206 return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1210 /* ===========================================================================
1211 * Check that the match at match_start is indeed a match.
1213 local void check_match(s, start, match, length)
1218 /* check that the match is indeed a match */
1219 if (zmemcmp(s->window + match,
1220 s->window + start, length) != EQUAL) {
1221 fprintf(stderr, " start %u, match %u, length %d\n",
1222 start, match, length);
1224 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1225 } while (--length != 0);
1226 z_error("invalid match");
1228 if (z_verbose > 1) {
1229 fprintf(stderr,"\\[%d,%d]", start-match, length);
1230 do { putc(s->window[start++], stderr); } while (--length != 0);
1234 # define check_match(s, start, match, length)
1237 /* ===========================================================================
1238 * Fill the window when the lookahead becomes insufficient.
1239 * Updates strstart and lookahead.
1241 * IN assertion: lookahead < MIN_LOOKAHEAD
1242 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1243 * At least one byte has been read, or avail_in == 0; reads are
1244 * performed for at least two bytes (required for the zip translate_eol
1245 * option -- not supported here).
1247 local void fill_window(s)
1250 register unsigned n, m;
1252 unsigned more; /* Amount of free space at the end of the window. */
1253 uInt wsize = s->w_size;
1256 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1258 /* Deal with !@#$% 64K limit: */
1259 if (sizeof(int) <= 2) {
1260 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1263 } else if (more == (unsigned)(-1)) {
1264 /* Very unlikely, but possible on 16 bit machine if
1265 * strstart == 0 && lookahead == 1 (input done a byte at time)
1271 /* If the window is almost full and there is insufficient lookahead,
1272 * move the upper half to the lower one to make room in the upper half.
1274 if (s->strstart >= wsize+MAX_DIST(s)) {
1276 zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1277 s->match_start -= wsize;
1278 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
1279 s->block_start -= (long) wsize;
1281 /* Slide the hash table (could be avoided with 32 bit values
1282 at the expense of memory usage). We slide even when level == 0
1283 to keep the hash table consistent if we switch back to level > 0
1284 later. (Using level 0 permanently is not an optimal usage of
1285 zlib, so we don't care about this pathological case.)
1291 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1299 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1300 /* If n is not on any hash chain, prev[n] is garbage but
1301 * its value will never be used.
1307 if (s->strm->avail_in == 0) return;
1309 /* If there was no sliding:
1310 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1311 * more == window_size - lookahead - strstart
1312 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1313 * => more >= window_size - 2*WSIZE + 2
1314 * In the BIG_MEM or MMAP case (not yet supported),
1315 * window_size == input_size + MIN_LOOKAHEAD &&
1316 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1317 * Otherwise, window_size == 2*WSIZE so more >= 2.
1318 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1320 Assert(more >= 2, "more < 2");
1322 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1325 /* Initialize the hash value now that we have some input: */
1326 if (s->lookahead >= MIN_MATCH) {
1327 s->ins_h = s->window[s->strstart];
1328 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1330 Call UPDATE_HASH() MIN_MATCH-3 more times
1333 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1334 * but this is not important since only literal bytes will be emitted.
1337 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1340 /* ===========================================================================
1341 * Flush the current block, with given end-of-file flag.
1342 * IN assertion: strstart is set to the end of the current match.
1344 #define FLUSH_BLOCK_ONLY(s, eof) { \
1345 _tr_flush_block(s, (s->block_start >= 0L ? \
1346 (charf *)&s->window[(unsigned)s->block_start] : \
1348 (ulg)((long)s->strstart - s->block_start), \
1350 s->block_start = s->strstart; \
1351 flush_pending(s->strm); \
1352 Tracev((stderr,"[FLUSH]")); \
1355 /* Same but force premature exit if necessary. */
1356 #define FLUSH_BLOCK(s, eof) { \
1357 FLUSH_BLOCK_ONLY(s, eof); \
1358 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
1361 /* ===========================================================================
1362 * Copy without compression as much as possible from the input stream, return
1363 * the current block state.
1364 * This function does not insert new strings in the dictionary since
1365 * uncompressible data is probably not useful. This function is used
1366 * only for the level=0 compression option.
1367 * NOTE: this function should be optimized to avoid extra copying from
1368 * window to pending_buf.
1370 local block_state deflate_stored(s, flush)
1374 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1375 * to pending_buf_size, and each stored block has a 5 byte header:
1377 ulg max_block_size = 0xffff;
1380 if (max_block_size > s->pending_buf_size - 5) {
1381 max_block_size = s->pending_buf_size - 5;
1384 /* Copy as much as possible from input to output: */
1386 /* Fill the window as much as possible: */
1387 if (s->lookahead <= 1) {
1389 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1390 s->block_start >= (long)s->w_size, "slide too late");
1393 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1395 if (s->lookahead == 0) break; /* flush the current block */
1397 Assert(s->block_start >= 0L, "block gone");
1399 s->strstart += s->lookahead;
1402 /* Emit a stored block if pending_buf will be full: */
1403 max_start = s->block_start + max_block_size;
1404 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1405 /* strstart == 0 is possible when wraparound on 16-bit machine */
1406 s->lookahead = (uInt)(s->strstart - max_start);
1407 s->strstart = (uInt)max_start;
1410 /* Flush if we may have to slide, otherwise block_start may become
1411 * negative and the data will be gone:
1413 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1417 FLUSH_BLOCK(s, flush == Z_FINISH);
1418 return flush == Z_FINISH ? finish_done : block_done;
1421 /* ===========================================================================
1422 * Compress as much as possible from the input stream, return the current
1424 * This function does not perform lazy evaluation of matches and inserts
1425 * new strings in the dictionary only for unmatched strings or for short
1426 * matches. It is used only for the fast compression options.
1428 local block_state deflate_fast(s, flush)
1432 IPos hash_head = NIL; /* head of the hash chain */
1433 int bflush; /* set if current block must be flushed */
1436 /* Make sure that we always have enough lookahead, except
1437 * at the end of the input file. We need MAX_MATCH bytes
1438 * for the next match, plus MIN_MATCH bytes to insert the
1439 * string following the next match.
1441 if (s->lookahead < MIN_LOOKAHEAD) {
1443 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1446 if (s->lookahead == 0) break; /* flush the current block */
1449 /* Insert the string window[strstart .. strstart+2] in the
1450 * dictionary, and set hash_head to the head of the hash chain:
1452 if (s->lookahead >= MIN_MATCH) {
1453 INSERT_STRING(s, s->strstart, hash_head);
1456 /* Find the longest match, discarding those <= prev_length.
1457 * At this point we have always match_length < MIN_MATCH
1459 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1460 /* To simplify the code, we prevent matches with the string
1461 * of window index 0 (in particular we have to avoid a match
1462 * of the string with itself at the start of the input file).
1465 if ((s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) ||
1466 (s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
1467 s->match_length = longest_match_fast (s, hash_head);
1470 if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1471 s->match_length = longest_match (s, hash_head);
1472 } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1473 s->match_length = longest_match_fast (s, hash_head);
1476 /* longest_match() or longest_match_fast() sets match_start */
1478 if (s->match_length >= MIN_MATCH) {
1479 check_match(s, s->strstart, s->match_start, s->match_length);
1481 _tr_tally_dist(s, s->strstart - s->match_start,
1482 s->match_length - MIN_MATCH, bflush);
1484 s->lookahead -= s->match_length;
1486 /* Insert new strings in the hash table only if the match length
1487 * is not too large. This saves time but degrades compression.
1490 if (s->match_length <= s->max_insert_length &&
1491 s->lookahead >= MIN_MATCH) {
1492 s->match_length--; /* string at strstart already in table */
1495 INSERT_STRING(s, s->strstart, hash_head);
1496 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1497 * always MIN_MATCH bytes ahead.
1499 } while (--s->match_length != 0);
1504 s->strstart += s->match_length;
1505 s->match_length = 0;
1506 s->ins_h = s->window[s->strstart];
1507 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1509 Call UPDATE_HASH() MIN_MATCH-3 more times
1511 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1512 * matter since it will be recomputed at next deflate call.
1516 /* No match, output a literal byte */
1517 Tracevv((stderr,"%c", s->window[s->strstart]));
1518 _tr_tally_lit (s, s->window[s->strstart], bflush);
1522 if (bflush) FLUSH_BLOCK(s, 0);
1524 FLUSH_BLOCK(s, flush == Z_FINISH);
1525 return flush == Z_FINISH ? finish_done : block_done;
1529 /* ===========================================================================
1530 * Same as above, but achieves better compression. We use a lazy
1531 * evaluation for matches: a match is finally adopted only if there is
1532 * no better match at the next window position.
1534 local block_state deflate_slow(s, flush)
1538 IPos hash_head = NIL; /* head of hash chain */
1539 int bflush; /* set if current block must be flushed */
1541 /* Process the input block. */
1543 /* Make sure that we always have enough lookahead, except
1544 * at the end of the input file. We need MAX_MATCH bytes
1545 * for the next match, plus MIN_MATCH bytes to insert the
1546 * string following the next match.
1548 if (s->lookahead < MIN_LOOKAHEAD) {
1550 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1553 if (s->lookahead == 0) break; /* flush the current block */
1556 /* Insert the string window[strstart .. strstart+2] in the
1557 * dictionary, and set hash_head to the head of the hash chain:
1559 if (s->lookahead >= MIN_MATCH) {
1560 INSERT_STRING(s, s->strstart, hash_head);
1563 /* Find the longest match, discarding those <= prev_length.
1565 s->prev_length = s->match_length, s->prev_match = s->match_start;
1566 s->match_length = MIN_MATCH-1;
1568 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1569 s->strstart - hash_head <= MAX_DIST(s)) {
1570 /* To simplify the code, we prevent matches with the string
1571 * of window index 0 (in particular we have to avoid a match
1572 * of the string with itself at the start of the input file).
1574 if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1575 s->match_length = longest_match (s, hash_head);
1576 } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1577 s->match_length = longest_match_fast (s, hash_head);
1579 /* longest_match() or longest_match_fast() sets match_start */
1581 if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1582 #if TOO_FAR <= 32767
1583 || (s->match_length == MIN_MATCH &&
1584 s->strstart - s->match_start > TOO_FAR)
1588 /* If prev_match is also MIN_MATCH, match_start is garbage
1589 * but we will ignore the current match anyway.
1591 s->match_length = MIN_MATCH-1;
1594 /* If there was a match at the previous step and the current
1595 * match is not better, output the previous match:
1597 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1598 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1599 /* Do not insert strings in hash table beyond this. */
1601 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1603 _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1604 s->prev_length - MIN_MATCH, bflush);
1606 /* Insert in hash table all strings up to the end of the match.
1607 * strstart-1 and strstart are already inserted. If there is not
1608 * enough lookahead, the last two strings are not inserted in
1611 s->lookahead -= s->prev_length-1;
1612 s->prev_length -= 2;
1614 if (++s->strstart <= max_insert) {
1615 INSERT_STRING(s, s->strstart, hash_head);
1617 } while (--s->prev_length != 0);
1618 s->match_available = 0;
1619 s->match_length = MIN_MATCH-1;
1622 if (bflush) FLUSH_BLOCK(s, 0);
1624 } else if (s->match_available) {
1625 /* If there was no match at the previous position, output a
1626 * single literal. If there was a match but the current match
1627 * is longer, truncate the previous match to a single literal.
1629 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1630 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1632 FLUSH_BLOCK_ONLY(s, 0);
1636 if (s->strm->avail_out == 0) return need_more;
1638 /* There is no previous match to compare with, wait for
1639 * the next step to decide.
1641 s->match_available = 1;
1646 Assert (flush != Z_NO_FLUSH, "no flush?");
1647 if (s->match_available) {
1648 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1649 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1650 s->match_available = 0;
1652 FLUSH_BLOCK(s, flush == Z_FINISH);
1653 return flush == Z_FINISH ? finish_done : block_done;
1655 #endif /* FASTEST */