1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
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
53 #include <u-boot/crc.h>
55 const char deflate_copyright[] =
56 " deflate 1.2.5 Copyright 1995-2010 Jean-loup Gailly and Mark Adler ";
58 If you use the zlib library in a product, an acknowledgment is welcome
59 in the documentation of your product. If for some reason you cannot
60 include such an acknowledgment, I would appreciate that you keep this
61 copyright string in the executable of your product.
64 /* ===========================================================================
65 * Function prototypes.
68 need_more, /* block not completed, need more input or more output */
69 block_done, /* block flush performed */
70 finish_started, /* finish started, need only more output at next deflate */
71 finish_done /* finish done, accept no more input or output */
74 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
75 /* Compression function. Returns the block state after the call. */
77 local void fill_window OF((deflate_state *s));
78 local block_state deflate_stored OF((deflate_state *s, int flush));
79 local block_state deflate_fast OF((deflate_state *s, int flush));
81 local block_state deflate_slow OF((deflate_state *s, int flush));
83 local block_state deflate_rle OF((deflate_state *s, int flush));
84 local block_state deflate_huff OF((deflate_state *s, int flush));
85 local void lm_init OF((deflate_state *s));
86 local void putShortMSB OF((deflate_state *s, uInt b));
87 local void flush_pending OF((z_streamp strm));
88 local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
90 void match_init OF((void)); /* asm code initialization */
91 uInt longest_match OF((deflate_state *s, IPos cur_match));
93 local uInt longest_match 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 /* Values for max_lazy_match, good_match and max_chain_length, depending on
114 * the desired pack level (0..9). The values given below have been tuned to
115 * exclude worst case performance for pathological files. Better values may be
116 * found for specific files.
118 typedef struct config_s {
119 ush good_length; /* reduce lazy search above this match length */
120 ush max_lazy; /* do not perform lazy search above this match length */
121 ush nice_length; /* quit search above this match length */
127 local const config configuration_table[2] = {
128 /* good lazy nice chain */
129 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
130 /* 1 */ {4, 4, 8, 4, deflate_fast}}; /* max speed, no lazy matches */
132 local const config configuration_table[10] = {
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 */
136 /* 2 */ {4, 5, 16, 8, deflate_fast},
137 /* 3 */ {4, 6, 32, 32, deflate_fast},
139 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
140 /* 5 */ {8, 16, 32, 32, deflate_slow},
141 /* 6 */ {8, 16, 128, 128, deflate_slow},
142 /* 7 */ {8, 32, 128, 256, deflate_slow},
143 /* 8 */ {32, 128, 258, 1024, deflate_slow},
144 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
147 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
148 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
153 /* result of memcmp for equal strings */
155 #ifndef NO_DUMMY_DECL
156 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
159 /* ===========================================================================
160 * Update a hash value with the given input byte
161 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
162 * input characters, so that a running hash key can be computed from the
163 * previous key instead of complete recalculation each time.
165 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
168 /* ===========================================================================
169 * Insert string str in the dictionary and set match_head to the previous head
170 * of the hash chain (the most recent string with same hash key). Return
171 * the previous length of the hash chain.
172 * If this file is compiled with -DFASTEST, the compression level is forced
173 * to 1, and no hash chains are maintained.
174 * IN assertion: all calls to to INSERT_STRING are made with consecutive
175 * input characters and the first MIN_MATCH bytes of str are valid
176 * (except for the last MIN_MATCH-1 bytes of the input file).
179 #define INSERT_STRING(s, str, match_head) \
180 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
181 match_head = s->head[s->ins_h], \
182 s->head[s->ins_h] = (Pos)(str))
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->prev[(str) & s->w_mask] = s->head[s->ins_h], \
187 s->head[s->ins_h] = (Pos)(str))
190 /* ===========================================================================
191 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
192 * prev[] will be initialized on the fly.
194 #define CLEAR_HASH(s) \
195 s->head[s->hash_size-1] = NIL; \
196 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
198 /* ========================================================================= */
199 int ZEXPORT deflateInit_(strm, level, version, stream_size)
205 return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
206 Z_DEFAULT_STRATEGY, version, stream_size);
207 /* To do: ignore strm->next_in if we use it as window */
210 /* ========================================================================= */
211 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
212 version, stream_size)
224 static const char my_version[] = ZLIB_VERSION;
227 /* We overlay pending_buf and d_buf+l_buf. This works since the average
228 * output size for (length,distance) codes is <= 24 bits.
231 if (version == Z_NULL || version[0] != my_version[0] ||
232 stream_size != sizeof(z_stream)) {
233 return Z_VERSION_ERROR;
235 if (strm == Z_NULL) return Z_STREAM_ERROR;
238 if (strm->zalloc == (alloc_func)0) {
239 strm->zalloc = zcalloc;
240 strm->opaque = (voidpf)0;
242 if (strm->zfree == (free_func)0) strm->zfree = zcfree;
245 if (level != 0) level = 1;
247 if (level == Z_DEFAULT_COMPRESSION) level = 6;
250 if (windowBits < 0) { /* suppress zlib wrapper */
252 windowBits = -windowBits;
255 else if (windowBits > 15) {
256 wrap = 2; /* write gzip wrapper instead */
260 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
261 windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
262 strategy < 0 || strategy > Z_FIXED) {
263 return Z_STREAM_ERROR;
265 if (windowBits == 8) windowBits = 9; /* until 256-byte window bug fixed */
266 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
267 if (s == Z_NULL) return Z_MEM_ERROR;
268 strm->state = (struct internal_state FAR *)s;
273 s->w_bits = windowBits;
274 s->w_size = 1 << s->w_bits;
275 s->w_mask = s->w_size - 1;
277 s->hash_bits = memLevel + 7;
278 s->hash_size = 1 << s->hash_bits;
279 s->hash_mask = s->hash_size - 1;
280 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
282 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
283 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
284 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
286 s->high_water = 0; /* nothing written to s->window yet */
288 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
290 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
291 s->pending_buf = (uchf *) overlay;
292 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
294 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
295 s->pending_buf == Z_NULL) {
296 s->status = FINISH_STATE;
297 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
301 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
302 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
305 s->strategy = strategy;
306 s->method = (Byte)method;
308 return deflateReset(strm);
311 /* ========================================================================= */
312 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
314 const Bytef *dictionary;
318 uInt length = dictLength;
322 if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
323 strm->state->wrap == 2 ||
324 (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
325 return Z_STREAM_ERROR;
329 strm->adler = adler32(strm->adler, dictionary, dictLength);
331 if (length < MIN_MATCH) return Z_OK;
332 if (length > s->w_size) {
334 dictionary += dictLength - length; /* use the tail of the dictionary */
336 zmemcpy(s->window, dictionary, length);
337 s->strstart = length;
338 s->block_start = (long)length;
340 /* Insert all strings in the hash table (except for the last two bytes).
341 * s->lookahead stays null, so s->ins_h will be recomputed at the next
342 * call of fill_window.
344 s->ins_h = s->window[0];
345 UPDATE_HASH(s, s->ins_h, s->window[1]);
346 for (n = 0; n <= length - MIN_MATCH; n++) {
347 INSERT_STRING(s, n, hash_head);
349 if (hash_head) hash_head = 0; /* to make compiler happy */
353 /* ========================================================================= */
354 int ZEXPORT deflateReset (strm)
359 if (strm == Z_NULL || strm->state == Z_NULL ||
360 strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
361 return Z_STREAM_ERROR;
364 strm->total_in = strm->total_out = 0;
365 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
366 strm->data_type = Z_UNKNOWN;
368 s = (deflate_state *)strm->state;
370 s->pending_out = s->pending_buf;
373 s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
375 s->status = s->wrap ? INIT_STATE : BUSY_STATE;
378 s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
380 adler32(0L, Z_NULL, 0);
381 s->last_flush = Z_NO_FLUSH;
389 /* ========================================================================= */
390 int ZEXPORT deflateSetHeader (strm, head)
394 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
395 if (strm->state->wrap != 2) return Z_STREAM_ERROR;
396 strm->state->gzhead = head;
400 /* ========================================================================= */
401 int ZEXPORT deflatePrime (strm, bits, value)
406 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
407 strm->state->bi_valid = bits;
408 strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
412 /* ========================================================================= */
413 int ZEXPORT deflateParams(strm, level, strategy)
422 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
426 if (level != 0) level = 1;
428 if (level == Z_DEFAULT_COMPRESSION) level = 6;
430 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
431 return Z_STREAM_ERROR;
433 func = configuration_table[s->level].func;
435 if ((strategy != s->strategy || func != configuration_table[level].func) &&
436 strm->total_in != 0) {
437 /* Flush the last buffer: */
438 err = deflate(strm, Z_BLOCK);
440 if (s->level != level) {
442 s->max_lazy_match = configuration_table[level].max_lazy;
443 s->good_match = configuration_table[level].good_length;
444 s->nice_match = configuration_table[level].nice_length;
445 s->max_chain_length = configuration_table[level].max_chain;
447 s->strategy = strategy;
451 /* ========================================================================= */
452 int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
461 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
463 s->good_match = good_length;
464 s->max_lazy_match = max_lazy;
465 s->nice_match = nice_length;
466 s->max_chain_length = max_chain;
470 /* =========================================================================
471 * For the default windowBits of 15 and memLevel of 8, this function returns
472 * a close to exact, as well as small, upper bound on the compressed size.
473 * They are coded as constants here for a reason--if the #define's are
474 * changed, then this function needs to be changed as well. The return
475 * value for 15 and 8 only works for those exact settings.
477 * For any setting other than those defaults for windowBits and memLevel,
478 * the value returned is a conservative worst case for the maximum expansion
479 * resulting from using fixed blocks instead of stored blocks, which deflate
480 * can emit on compressed data for some combinations of the parameters.
482 * This function could be more sophisticated to provide closer upper bounds for
483 * every combination of windowBits and memLevel. But even the conservative
484 * upper bound of about 14% expansion does not seem onerous for output buffer
487 uLong ZEXPORT deflateBound(strm, sourceLen)
492 uLong complen, wraplen;
495 /* conservative upper bound for compressed data */
496 complen = sourceLen +
497 ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
499 /* if can't get parameters, return conservative bound plus zlib wrapper */
500 if (strm == Z_NULL || strm->state == Z_NULL)
503 /* compute wrapper length */
506 case 0: /* raw deflate */
509 case 1: /* zlib wrapper */
510 wraplen = 6 + (s->strstart ? 4 : 0);
512 case 2: /* gzip wrapper */
514 if (s->gzhead != Z_NULL) { /* user-supplied gzip header */
515 if (s->gzhead->extra != Z_NULL)
516 wraplen += 2 + s->gzhead->extra_len;
517 str = s->gzhead->name;
522 str = s->gzhead->comment;
531 default: /* for compiler happiness */
535 /* if not default parameters, return conservative bound */
536 if (s->w_bits != 15 || s->hash_bits != 8 + 7)
537 return complen + wraplen;
539 /* default settings: return tight bound for that case */
540 return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
541 (sourceLen >> 25) + 13 - 6 + wraplen;
544 /* =========================================================================
545 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
546 * IN assertion: the stream state is correct and there is enough room in
549 local void putShortMSB (s, b)
553 put_byte(s, (Byte)(b >> 8));
554 put_byte(s, (Byte)(b & 0xff));
557 /* =========================================================================
558 * Flush as much pending output as possible. All deflate() output goes
559 * through this function so some applications may wish to modify it
560 * to avoid allocating a large strm->next_out buffer and copying into it.
561 * (See also read_buf()).
563 local void flush_pending(strm)
566 unsigned len = strm->state->pending;
568 if (len > strm->avail_out) len = strm->avail_out;
569 if (len == 0) return;
571 zmemcpy(strm->next_out, strm->state->pending_out, len);
572 strm->next_out += len;
573 strm->state->pending_out += len;
574 strm->total_out += len;
575 strm->avail_out -= len;
576 strm->state->pending -= len;
577 if (strm->state->pending == 0) {
578 strm->state->pending_out = strm->state->pending_buf;
582 /* ========================================================================= */
583 int ZEXPORT deflate (strm, flush)
587 int old_flush; /* value of flush param for previous deflate call */
590 if (strm == Z_NULL || strm->state == Z_NULL ||
591 flush > Z_BLOCK || flush < 0) {
592 return Z_STREAM_ERROR;
596 if (s->status == FINISH_STATE && flush != Z_FINISH) {
597 ERR_RETURN(strm, Z_STREAM_ERROR);
599 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
601 s->strm = strm; /* just in case */
602 old_flush = s->last_flush;
603 s->last_flush = flush;
605 /* Write the header */
606 if (s->status == INIT_STATE) {
609 strm->adler = crc32(0L, Z_NULL, 0);
613 if (s->gzhead == Z_NULL) {
619 put_byte(s, s->level == 9 ? 2 :
620 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
622 put_byte(s, OS_CODE);
623 s->status = BUSY_STATE;
626 put_byte(s, (s->gzhead->text ? 1 : 0) +
627 (s->gzhead->hcrc ? 2 : 0) +
628 (s->gzhead->extra == Z_NULL ? 0 : 4) +
629 (s->gzhead->name == Z_NULL ? 0 : 8) +
630 (s->gzhead->comment == Z_NULL ? 0 : 16)
632 put_byte(s, (Byte)(s->gzhead->time & 0xff));
633 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
634 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
635 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
636 put_byte(s, s->level == 9 ? 2 :
637 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
639 put_byte(s, s->gzhead->os & 0xff);
640 if (s->gzhead->extra != Z_NULL) {
641 put_byte(s, s->gzhead->extra_len & 0xff);
642 put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
645 strm->adler = crc32(strm->adler, s->pending_buf,
648 s->status = EXTRA_STATE;
654 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
657 if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
659 else if (s->level < 6)
661 else if (s->level == 6)
665 header |= (level_flags << 6);
666 if (s->strstart != 0) header |= PRESET_DICT;
667 header += 31 - (header % 31);
669 s->status = BUSY_STATE;
670 putShortMSB(s, header);
672 /* Save the adler32 of the preset dictionary: */
673 if (s->strstart != 0) {
674 putShortMSB(s, (uInt)(strm->adler >> 16));
675 putShortMSB(s, (uInt)(strm->adler & 0xffff));
677 strm->adler = adler32(0L, Z_NULL, 0);
681 if (s->status == EXTRA_STATE) {
682 if (s->gzhead->extra != Z_NULL) {
683 uInt beg = s->pending; /* start of bytes to update crc */
685 while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
686 if (s->pending == s->pending_buf_size) {
687 if (s->gzhead->hcrc && s->pending > beg)
688 strm->adler = crc32(strm->adler, s->pending_buf + beg,
692 if (s->pending == s->pending_buf_size)
695 put_byte(s, s->gzhead->extra[s->gzindex]);
698 if (s->gzhead->hcrc && s->pending > beg)
699 strm->adler = crc32(strm->adler, s->pending_buf + beg,
701 if (s->gzindex == s->gzhead->extra_len) {
703 s->status = NAME_STATE;
707 s->status = NAME_STATE;
709 if (s->status == NAME_STATE) {
710 if (s->gzhead->name != Z_NULL) {
711 uInt beg = s->pending; /* start of bytes to update crc */
715 if (s->pending == s->pending_buf_size) {
716 if (s->gzhead->hcrc && s->pending > beg)
717 strm->adler = crc32(strm->adler, s->pending_buf + beg,
721 if (s->pending == s->pending_buf_size) {
726 val = s->gzhead->name[s->gzindex++];
729 if (s->gzhead->hcrc && s->pending > beg)
730 strm->adler = crc32(strm->adler, s->pending_buf + beg,
734 s->status = COMMENT_STATE;
738 s->status = COMMENT_STATE;
740 if (s->status == COMMENT_STATE) {
741 if (s->gzhead->comment != Z_NULL) {
742 uInt beg = s->pending; /* start of bytes to update crc */
746 if (s->pending == s->pending_buf_size) {
747 if (s->gzhead->hcrc && s->pending > beg)
748 strm->adler = crc32(strm->adler, s->pending_buf + beg,
752 if (s->pending == s->pending_buf_size) {
757 val = s->gzhead->comment[s->gzindex++];
760 if (s->gzhead->hcrc && s->pending > beg)
761 strm->adler = crc32(strm->adler, s->pending_buf + beg,
764 s->status = HCRC_STATE;
767 s->status = HCRC_STATE;
769 if (s->status == HCRC_STATE) {
770 if (s->gzhead->hcrc) {
771 if (s->pending + 2 > s->pending_buf_size)
773 if (s->pending + 2 <= s->pending_buf_size) {
774 put_byte(s, (Byte)(strm->adler & 0xff));
775 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
776 strm->adler = crc32(0L, Z_NULL, 0);
777 s->status = BUSY_STATE;
781 s->status = BUSY_STATE;
785 /* Flush as much pending output as possible */
786 if (s->pending != 0) {
788 if (strm->avail_out == 0) {
789 /* Since avail_out is 0, deflate will be called again with
790 * more output space, but possibly with both pending and
791 * avail_in equal to zero. There won't be anything to do,
792 * but this is not an error situation so make sure we
793 * return OK instead of BUF_ERROR at next call of deflate:
799 /* Make sure there is something to do and avoid duplicate consecutive
800 * flushes. For repeated and useless calls with Z_FINISH, we keep
801 * returning Z_STREAM_END instead of Z_BUF_ERROR.
803 } else if (strm->avail_in == 0 && flush <= old_flush &&
805 ERR_RETURN(strm, Z_BUF_ERROR);
808 /* User must not provide more input after the first FINISH: */
809 if (s->status == FINISH_STATE && strm->avail_in != 0) {
810 ERR_RETURN(strm, Z_BUF_ERROR);
813 /* Start a new block or continue the current one.
815 if (strm->avail_in != 0 || s->lookahead != 0 ||
816 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
819 bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
820 (s->strategy == Z_RLE ? deflate_rle(s, flush) :
821 (*(configuration_table[s->level].func))(s, flush));
823 if (bstate == finish_started || bstate == finish_done) {
824 s->status = FINISH_STATE;
826 if (bstate == need_more || bstate == finish_started) {
827 if (strm->avail_out == 0) {
828 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
831 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
832 * of deflate should use the same flush parameter to make sure
833 * that the flush is complete. So we don't have to output an
834 * empty block here, this will be done at next call. This also
835 * ensures that for a very small output buffer, we emit at most
839 if (bstate == block_done) {
840 if (flush == Z_PARTIAL_FLUSH) {
842 } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
843 _tr_stored_block(s, (char*)0, 0L, 0);
844 /* For a full flush, this empty block will be recognized
845 * as a special marker by inflate_sync().
847 if (flush == Z_FULL_FLUSH) {
848 CLEAR_HASH(s); /* forget history */
849 if (s->lookahead == 0) {
856 if (strm->avail_out == 0) {
857 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
862 Assert(strm->avail_out > 0, "bug2");
864 if (flush != Z_FINISH) return Z_OK;
865 if (s->wrap <= 0) return Z_STREAM_END;
867 /* Write the trailer */
870 put_byte(s, (Byte)(strm->adler & 0xff));
871 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
872 put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
873 put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
874 put_byte(s, (Byte)(strm->total_in & 0xff));
875 put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
876 put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
877 put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
882 putShortMSB(s, (uInt)(strm->adler >> 16));
883 putShortMSB(s, (uInt)(strm->adler & 0xffff));
886 /* If avail_out is zero, the application will call deflate again
889 if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
890 return s->pending != 0 ? Z_OK : Z_STREAM_END;
893 /* ========================================================================= */
894 int ZEXPORT deflateEnd (strm)
899 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
901 status = strm->state->status;
902 if (status != INIT_STATE &&
903 status != EXTRA_STATE &&
904 status != NAME_STATE &&
905 status != COMMENT_STATE &&
906 status != HCRC_STATE &&
907 status != BUSY_STATE &&
908 status != FINISH_STATE) {
909 return Z_STREAM_ERROR;
912 /* Deallocate in reverse order of allocations: */
913 TRY_FREE(strm, strm->state->pending_buf);
914 TRY_FREE(strm, strm->state->head);
915 TRY_FREE(strm, strm->state->prev);
916 TRY_FREE(strm, strm->state->window);
918 ZFREE(strm, strm->state);
919 strm->state = Z_NULL;
921 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
924 /* =========================================================================
925 * Copy the source state to the destination state.
926 * To simplify the source, this is not supported for 16-bit MSDOS (which
927 * doesn't have enough memory anyway to duplicate compression states).
929 int ZEXPORT deflateCopy (dest, source)
934 return Z_STREAM_ERROR;
941 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
942 return Z_STREAM_ERROR;
947 zmemcpy(dest, source, sizeof(z_stream));
949 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
950 if (ds == Z_NULL) return Z_MEM_ERROR;
951 dest->state = (struct internal_state FAR *) ds;
952 zmemcpy(ds, ss, sizeof(deflate_state));
955 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
956 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
957 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
958 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
959 ds->pending_buf = (uchf *) overlay;
961 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
962 ds->pending_buf == Z_NULL) {
966 /* following zmemcpy do not work for 16-bit MSDOS */
967 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
968 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
969 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
970 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
972 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
973 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
974 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
976 ds->l_desc.dyn_tree = ds->dyn_ltree;
977 ds->d_desc.dyn_tree = ds->dyn_dtree;
978 ds->bl_desc.dyn_tree = ds->bl_tree;
981 #endif /* MAXSEG_64K */
984 /* ===========================================================================
985 * Read a new buffer from the current input stream, update the adler32
986 * and total number of bytes read. All deflate() input goes through
987 * this function so some applications may wish to modify it to avoid
988 * allocating a large strm->next_in buffer and copying from it.
989 * (See also flush_pending()).
991 local int read_buf(strm, buf, size)
996 unsigned len = strm->avail_in;
998 if (len > size) len = size;
999 if (len == 0) return 0;
1001 strm->avail_in -= len;
1003 if (strm->state->wrap == 1) {
1004 strm->adler = adler32(strm->adler, strm->next_in, len);
1007 else if (strm->state->wrap == 2) {
1008 strm->adler = crc32(strm->adler, strm->next_in, len);
1011 zmemcpy(buf, strm->next_in, len);
1012 strm->next_in += len;
1013 strm->total_in += len;
1018 /* ===========================================================================
1019 * Initialize the "longest match" routines for a new zlib stream
1021 local void lm_init (s)
1024 s->window_size = (ulg)2L*s->w_size;
1028 /* Set the default configuration parameters:
1030 s->max_lazy_match = configuration_table[s->level].max_lazy;
1031 s->good_match = configuration_table[s->level].good_length;
1032 s->nice_match = configuration_table[s->level].nice_length;
1033 s->max_chain_length = configuration_table[s->level].max_chain;
1036 s->block_start = 0L;
1038 s->match_length = s->prev_length = MIN_MATCH-1;
1039 s->match_available = 0;
1043 match_init(); /* initialize the asm code */
1049 /* ===========================================================================
1050 * Set match_start to the longest match starting at the given string and
1051 * return its length. Matches shorter or equal to prev_length are discarded,
1052 * in which case the result is equal to prev_length and match_start is
1054 * IN assertions: cur_match is the head of the hash chain for the current
1055 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1056 * OUT assertion: the match length is not greater than s->lookahead.
1059 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1060 * match.S. The code will be functionally equivalent.
1062 local uInt longest_match(s, cur_match)
1064 IPos cur_match; /* current match */
1066 unsigned chain_length = s->max_chain_length;/* max hash chain length */
1067 register Bytef *scan = s->window + s->strstart; /* current string */
1068 register Bytef *match; /* matched string */
1069 register int len; /* length of current match */
1070 int best_len = s->prev_length; /* best match length so far */
1071 int nice_match = s->nice_match; /* stop if match long enough */
1072 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1073 s->strstart - (IPos)MAX_DIST(s) : NIL;
1074 /* Stop when cur_match becomes <= limit. To simplify the code,
1075 * we prevent matches with the string of window index 0.
1077 Posf *prev = s->prev;
1078 uInt wmask = s->w_mask;
1081 /* Compare two bytes at a time. Note: this is not always beneficial.
1082 * Try with and without -DUNALIGNED_OK to check.
1084 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1085 register ush scan_start = *(ushf*)scan;
1086 register ush scan_end = *(ushf*)(scan+best_len-1);
1088 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1089 register Byte scan_end1 = scan[best_len-1];
1090 register Byte scan_end = scan[best_len];
1093 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1094 * It is easy to get rid of this optimization if necessary.
1096 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1098 /* Do not waste too much time if we already have a good match: */
1099 if (s->prev_length >= s->good_match) {
1102 /* Do not look for matches beyond the end of the input. This is necessary
1103 * to make deflate deterministic.
1105 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1107 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1110 Assert(cur_match < s->strstart, "no future");
1111 match = s->window + cur_match;
1113 /* Skip to next match if the match length cannot increase
1114 * or if the match length is less than 2. Note that the checks below
1115 * for insufficient lookahead only occur occasionally for performance
1116 * reasons. Therefore uninitialized memory will be accessed, and
1117 * conditional jumps will be made that depend on those values.
1118 * However the length of the match is limited to the lookahead, so
1119 * the output of deflate is not affected by the uninitialized values.
1121 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1122 /* This code assumes sizeof(unsigned short) == 2. Do not use
1123 * UNALIGNED_OK if your compiler uses a different size.
1125 if (*(ushf*)(match+best_len-1) != scan_end ||
1126 *(ushf*)match != scan_start) continue;
1128 /* It is not necessary to compare scan[2] and match[2] since they are
1129 * always equal when the other bytes match, given that the hash keys
1130 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1131 * strstart+3, +5, ... up to strstart+257. We check for insufficient
1132 * lookahead only every 4th comparison; the 128th check will be made
1133 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1134 * necessary to put more guard bytes at the end of the window, or
1135 * to check more often for insufficient lookahead.
1137 Assert(scan[2] == match[2], "scan[2]?");
1140 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1141 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1142 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1143 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1145 /* The funny "do {}" generates better code on most compilers */
1147 /* Here, scan <= window+strstart+257 */
1148 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1149 if (*scan == *match) scan++;
1151 len = (MAX_MATCH - 1) - (int)(strend-scan);
1152 scan = strend - (MAX_MATCH-1);
1154 #else /* UNALIGNED_OK */
1156 if (match[best_len] != scan_end ||
1157 match[best_len-1] != scan_end1 ||
1159 *++match != scan[1]) continue;
1161 /* The check at best_len-1 can be removed because it will be made
1162 * again later. (This heuristic is not always a win.)
1163 * It is not necessary to compare scan[2] and match[2] since they
1164 * are always equal when the other bytes match, given that
1165 * the hash keys are equal and that HASH_BITS >= 8.
1168 Assert(*scan == *match, "match[2]?");
1170 /* We check for insufficient lookahead only every 8th comparison;
1171 * the 256th check will be made at strstart+258.
1174 } while (*++scan == *++match && *++scan == *++match &&
1175 *++scan == *++match && *++scan == *++match &&
1176 *++scan == *++match && *++scan == *++match &&
1177 *++scan == *++match && *++scan == *++match &&
1180 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1182 len = MAX_MATCH - (int)(strend - scan);
1183 scan = strend - MAX_MATCH;
1185 #endif /* UNALIGNED_OK */
1187 if (len > best_len) {
1188 s->match_start = cur_match;
1190 if (len >= nice_match) break;
1192 scan_end = *(ushf*)(scan+best_len-1);
1194 scan_end1 = scan[best_len-1];
1195 scan_end = scan[best_len];
1198 } while ((cur_match = prev[cur_match & wmask]) > limit
1199 && --chain_length != 0);
1201 if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1202 return s->lookahead;
1208 /* ---------------------------------------------------------------------------
1209 * Optimized version for FASTEST only
1211 local uInt longest_match(s, cur_match)
1213 IPos cur_match; /* current match */
1215 register Bytef *scan = s->window + s->strstart; /* current string */
1216 register Bytef *match; /* matched string */
1217 register int len; /* length of current match */
1218 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1220 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1221 * It is easy to get rid of this optimization if necessary.
1223 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1225 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1227 Assert(cur_match < s->strstart, "no future");
1229 match = s->window + cur_match;
1231 /* Return failure if the match length is less than 2:
1233 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1235 /* The check at best_len-1 can be removed because it will be made
1236 * again later. (This heuristic is not always a win.)
1237 * It is not necessary to compare scan[2] and match[2] since they
1238 * are always equal when the other bytes match, given that
1239 * the hash keys are equal and that HASH_BITS >= 8.
1241 scan += 2, match += 2;
1242 Assert(*scan == *match, "match[2]?");
1244 /* We check for insufficient lookahead only every 8th comparison;
1245 * the 256th check will be made at strstart+258.
1248 } while (*++scan == *++match && *++scan == *++match &&
1249 *++scan == *++match && *++scan == *++match &&
1250 *++scan == *++match && *++scan == *++match &&
1251 *++scan == *++match && *++scan == *++match &&
1254 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1256 len = MAX_MATCH - (int)(strend - scan);
1258 if (len < MIN_MATCH) return MIN_MATCH - 1;
1260 s->match_start = cur_match;
1261 return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1264 #endif /* FASTEST */
1267 /* ===========================================================================
1268 * Check that the match at match_start is indeed a match.
1270 local void check_match(s, start, match, length)
1275 /* check that the match is indeed a match */
1276 if (zmemcmp(s->window + match,
1277 s->window + start, length) != EQUAL) {
1278 fprintf(stderr, " start %u, match %u, length %d\n",
1279 start, match, length);
1281 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1282 } while (--length != 0);
1283 z_error("invalid match");
1285 if (z_verbose > 1) {
1286 fprintf(stderr,"\\[%d,%d]", start-match, length);
1287 do { putc(s->window[start++], stderr); } while (--length != 0);
1291 # define check_match(s, start, match, length)
1294 /* ===========================================================================
1295 * Fill the window when the lookahead becomes insufficient.
1296 * Updates strstart and lookahead.
1298 * IN assertion: lookahead < MIN_LOOKAHEAD
1299 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1300 * At least one byte has been read, or avail_in == 0; reads are
1301 * performed for at least two bytes (required for the zip translate_eol
1302 * option -- not supported here).
1304 local void fill_window(s)
1307 register unsigned n, m;
1309 unsigned more; /* Amount of free space at the end of the window. */
1310 uInt wsize = s->w_size;
1313 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1315 /* Deal with !@#$% 64K limit: */
1316 if (sizeof(int) <= 2) {
1317 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1320 } else if (more == (unsigned)(-1)) {
1321 /* Very unlikely, but possible on 16 bit machine if
1322 * strstart == 0 && lookahead == 1 (input done a byte at time)
1328 /* If the window is almost full and there is insufficient lookahead,
1329 * move the upper half to the lower one to make room in the upper half.
1331 if (s->strstart >= wsize+MAX_DIST(s)) {
1333 zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1334 s->match_start -= wsize;
1335 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
1336 s->block_start -= (long) wsize;
1338 /* Slide the hash table (could be avoided with 32 bit values
1339 at the expense of memory usage). We slide even when level == 0
1340 to keep the hash table consistent if we switch back to level > 0
1341 later. (Using level 0 permanently is not an optimal usage of
1342 zlib, so we don't care about this pathological case.)
1348 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1356 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1357 /* If n is not on any hash chain, prev[n] is garbage but
1358 * its value will never be used.
1364 if (s->strm->avail_in == 0) return;
1366 /* If there was no sliding:
1367 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1368 * more == window_size - lookahead - strstart
1369 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1370 * => more >= window_size - 2*WSIZE + 2
1371 * In the BIG_MEM or MMAP case (not yet supported),
1372 * window_size == input_size + MIN_LOOKAHEAD &&
1373 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1374 * Otherwise, window_size == 2*WSIZE so more >= 2.
1375 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1377 Assert(more >= 2, "more < 2");
1379 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1382 /* Initialize the hash value now that we have some input: */
1383 if (s->lookahead >= MIN_MATCH) {
1384 s->ins_h = s->window[s->strstart];
1385 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1387 Call UPDATE_HASH() MIN_MATCH-3 more times
1390 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1391 * but this is not important since only literal bytes will be emitted.
1394 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1396 /* If the WIN_INIT bytes after the end of the current data have never been
1397 * written, then zero those bytes in order to avoid memory check reports of
1398 * the use of uninitialized (or uninitialised as Julian writes) bytes by
1399 * the longest match routines. Update the high water mark for the next
1400 * time through here. WIN_INIT is set to MAX_MATCH since the longest match
1401 * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
1403 if (s->high_water < s->window_size) {
1404 ulg curr = s->strstart + (ulg)(s->lookahead);
1407 if (s->high_water < curr) {
1408 /* Previous high water mark below current data -- zero WIN_INIT
1409 * bytes or up to end of window, whichever is less.
1411 init = s->window_size - curr;
1412 if (init > WIN_INIT)
1414 zmemzero(s->window + curr, (unsigned)init);
1415 s->high_water = curr + init;
1417 else if (s->high_water < (ulg)curr + WIN_INIT) {
1418 /* High water mark at or above current data, but below current data
1419 * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
1420 * to end of window, whichever is less.
1422 init = (ulg)curr + WIN_INIT - s->high_water;
1423 if (init > s->window_size - s->high_water)
1424 init = s->window_size - s->high_water;
1425 zmemzero(s->window + s->high_water, (unsigned)init);
1426 s->high_water += init;
1431 /* ===========================================================================
1432 * Flush the current block, with given end-of-file flag.
1433 * IN assertion: strstart is set to the end of the current match.
1435 #define FLUSH_BLOCK_ONLY(s, last) { \
1436 _tr_flush_block(s, (s->block_start >= 0L ? \
1437 (charf *)&s->window[(unsigned)s->block_start] : \
1439 (ulg)((long)s->strstart - s->block_start), \
1441 s->block_start = s->strstart; \
1442 flush_pending(s->strm); \
1443 Tracev((stderr,"[FLUSH]")); \
1446 /* Same but force premature exit if necessary. */
1447 #define FLUSH_BLOCK(s, last) { \
1448 FLUSH_BLOCK_ONLY(s, last); \
1449 if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
1452 /* ===========================================================================
1453 * Copy without compression as much as possible from the input stream, return
1454 * the current block state.
1455 * This function does not insert new strings in the dictionary since
1456 * uncompressible data is probably not useful. This function is used
1457 * only for the level=0 compression option.
1458 * NOTE: this function should be optimized to avoid extra copying from
1459 * window to pending_buf.
1461 local block_state deflate_stored(s, flush)
1465 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1466 * to pending_buf_size, and each stored block has a 5 byte header:
1468 ulg max_block_size = 0xffff;
1471 if (max_block_size > s->pending_buf_size - 5) {
1472 max_block_size = s->pending_buf_size - 5;
1475 /* Copy as much as possible from input to output: */
1477 /* Fill the window as much as possible: */
1478 if (s->lookahead <= 1) {
1480 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1481 s->block_start >= (long)s->w_size, "slide too late");
1484 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1486 if (s->lookahead == 0) break; /* flush the current block */
1488 Assert(s->block_start >= 0L, "block gone");
1490 s->strstart += s->lookahead;
1493 /* Emit a stored block if pending_buf will be full: */
1494 max_start = s->block_start + max_block_size;
1495 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1496 /* strstart == 0 is possible when wraparound on 16-bit machine */
1497 s->lookahead = (uInt)(s->strstart - max_start);
1498 s->strstart = (uInt)max_start;
1501 /* Flush if we may have to slide, otherwise block_start may become
1502 * negative and the data will be gone:
1504 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1508 FLUSH_BLOCK(s, flush == Z_FINISH);
1509 return flush == Z_FINISH ? finish_done : block_done;
1512 /* ===========================================================================
1513 * Compress as much as possible from the input stream, return the current
1515 * This function does not perform lazy evaluation of matches and inserts
1516 * new strings in the dictionary only for unmatched strings or for short
1517 * matches. It is used only for the fast compression options.
1519 local block_state deflate_fast(s, flush)
1523 IPos hash_head; /* head of the hash chain */
1524 int bflush; /* set if current block must be flushed */
1527 /* Make sure that we always have enough lookahead, except
1528 * at the end of the input file. We need MAX_MATCH bytes
1529 * for the next match, plus MIN_MATCH bytes to insert the
1530 * string following the next match.
1532 if (s->lookahead < MIN_LOOKAHEAD) {
1534 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1537 if (s->lookahead == 0) break; /* flush the current block */
1540 /* Insert the string window[strstart .. strstart+2] in the
1541 * dictionary, and set hash_head to the head of the hash chain:
1544 if (s->lookahead >= MIN_MATCH) {
1545 INSERT_STRING(s, s->strstart, hash_head);
1548 /* Find the longest match, discarding those <= prev_length.
1549 * At this point we have always match_length < MIN_MATCH
1551 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1552 /* To simplify the code, we prevent matches with the string
1553 * of window index 0 (in particular we have to avoid a match
1554 * of the string with itself at the start of the input file).
1556 s->match_length = longest_match (s, hash_head);
1557 /* longest_match() sets match_start */
1559 if (s->match_length >= MIN_MATCH) {
1560 check_match(s, s->strstart, s->match_start, s->match_length);
1562 _tr_tally_dist(s, s->strstart - s->match_start,
1563 s->match_length - MIN_MATCH, bflush);
1565 s->lookahead -= s->match_length;
1567 /* Insert new strings in the hash table only if the match length
1568 * is not too large. This saves time but degrades compression.
1571 if (s->match_length <= s->max_insert_length &&
1572 s->lookahead >= MIN_MATCH) {
1573 s->match_length--; /* string at strstart already in table */
1576 INSERT_STRING(s, s->strstart, hash_head);
1577 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1578 * always MIN_MATCH bytes ahead.
1580 } while (--s->match_length != 0);
1585 s->strstart += s->match_length;
1586 s->match_length = 0;
1587 s->ins_h = s->window[s->strstart];
1588 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1590 Call UPDATE_HASH() MIN_MATCH-3 more times
1592 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1593 * matter since it will be recomputed at next deflate call.
1597 /* No match, output a literal byte */
1598 Tracevv((stderr,"%c", s->window[s->strstart]));
1599 _tr_tally_lit (s, s->window[s->strstart], bflush);
1603 if (bflush) FLUSH_BLOCK(s, 0);
1605 FLUSH_BLOCK(s, flush == Z_FINISH);
1606 return flush == Z_FINISH ? finish_done : block_done;
1610 /* ===========================================================================
1611 * Same as above, but achieves better compression. We use a lazy
1612 * evaluation for matches: a match is finally adopted only if there is
1613 * no better match at the next window position.
1615 local block_state deflate_slow(s, flush)
1619 IPos hash_head; /* head of hash chain */
1620 int bflush; /* set if current block must be flushed */
1622 /* Process the input block. */
1624 /* Make sure that we always have enough lookahead, except
1625 * at the end of the input file. We need MAX_MATCH bytes
1626 * for the next match, plus MIN_MATCH bytes to insert the
1627 * string following the next match.
1629 if (s->lookahead < MIN_LOOKAHEAD) {
1631 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1634 if (s->lookahead == 0) break; /* flush the current block */
1637 /* Insert the string window[strstart .. strstart+2] in the
1638 * dictionary, and set hash_head to the head of the hash chain:
1641 if (s->lookahead >= MIN_MATCH) {
1642 INSERT_STRING(s, s->strstart, hash_head);
1645 /* Find the longest match, discarding those <= prev_length.
1647 s->prev_length = s->match_length, s->prev_match = s->match_start;
1648 s->match_length = MIN_MATCH-1;
1650 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1651 s->strstart - hash_head <= MAX_DIST(s)) {
1652 /* To simplify the code, we prevent matches with the string
1653 * of window index 0 (in particular we have to avoid a match
1654 * of the string with itself at the start of the input file).
1656 s->match_length = longest_match (s, hash_head);
1657 /* longest_match() sets match_start */
1659 if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1660 #if TOO_FAR <= 32767
1661 || (s->match_length == MIN_MATCH &&
1662 s->strstart - s->match_start > TOO_FAR)
1666 /* If prev_match is also MIN_MATCH, match_start is garbage
1667 * but we will ignore the current match anyway.
1669 s->match_length = MIN_MATCH-1;
1672 /* If there was a match at the previous step and the current
1673 * match is not better, output the previous match:
1675 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1676 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1677 /* Do not insert strings in hash table beyond this. */
1679 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1681 _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1682 s->prev_length - MIN_MATCH, bflush);
1684 /* Insert in hash table all strings up to the end of the match.
1685 * strstart-1 and strstart are already inserted. If there is not
1686 * enough lookahead, the last two strings are not inserted in
1689 s->lookahead -= s->prev_length-1;
1690 s->prev_length -= 2;
1692 if (++s->strstart <= max_insert) {
1693 INSERT_STRING(s, s->strstart, hash_head);
1695 } while (--s->prev_length != 0);
1696 s->match_available = 0;
1697 s->match_length = MIN_MATCH-1;
1700 if (bflush) FLUSH_BLOCK(s, 0);
1702 } else if (s->match_available) {
1703 /* If there was no match at the previous position, output a
1704 * single literal. If there was a match but the current match
1705 * is longer, truncate the previous match to a single literal.
1707 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1708 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1710 FLUSH_BLOCK_ONLY(s, 0);
1714 if (s->strm->avail_out == 0) return need_more;
1716 /* There is no previous match to compare with, wait for
1717 * the next step to decide.
1719 s->match_available = 1;
1724 Assert (flush != Z_NO_FLUSH, "no flush?");
1725 if (s->match_available) {
1726 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1727 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1728 s->match_available = 0;
1730 FLUSH_BLOCK(s, flush == Z_FINISH);
1731 return flush == Z_FINISH ? finish_done : block_done;
1733 #endif /* FASTEST */
1735 /* ===========================================================================
1736 * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1737 * one. Do not maintain a hash table. (It will be regenerated if this run of
1738 * deflate switches away from Z_RLE.)
1740 local block_state deflate_rle(s, flush)
1744 int bflush; /* set if current block must be flushed */
1745 uInt prev; /* byte at distance one to match */
1746 Bytef *scan, *strend; /* scan goes up to strend for length of run */
1749 /* Make sure that we always have enough lookahead, except
1750 * at the end of the input file. We need MAX_MATCH bytes
1751 * for the longest encodable run.
1753 if (s->lookahead < MAX_MATCH) {
1755 if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1758 if (s->lookahead == 0) break; /* flush the current block */
1761 /* See how many times the previous byte repeats */
1762 s->match_length = 0;
1763 if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
1764 scan = s->window + s->strstart - 1;
1766 if (prev == *++scan && prev == *++scan && prev == *++scan) {
1767 strend = s->window + s->strstart + MAX_MATCH;
1769 } while (prev == *++scan && prev == *++scan &&
1770 prev == *++scan && prev == *++scan &&
1771 prev == *++scan && prev == *++scan &&
1772 prev == *++scan && prev == *++scan &&
1774 s->match_length = MAX_MATCH - (int)(strend - scan);
1775 if (s->match_length > s->lookahead)
1776 s->match_length = s->lookahead;
1780 /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1781 if (s->match_length >= MIN_MATCH) {
1782 check_match(s, s->strstart, s->strstart - 1, s->match_length);
1784 _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
1786 s->lookahead -= s->match_length;
1787 s->strstart += s->match_length;
1788 s->match_length = 0;
1790 /* No match, output a literal byte */
1791 Tracevv((stderr,"%c", s->window[s->strstart]));
1792 _tr_tally_lit (s, s->window[s->strstart], bflush);
1796 if (bflush) FLUSH_BLOCK(s, 0);
1798 FLUSH_BLOCK(s, flush == Z_FINISH);
1799 return flush == Z_FINISH ? finish_done : block_done;
1802 /* ===========================================================================
1803 * For Z_HUFFMAN_ONLY, do not look for matches. Do not maintain a hash table.
1804 * (It will be regenerated if this run of deflate switches away from Huffman.)
1806 local block_state deflate_huff(s, flush)
1810 int bflush; /* set if current block must be flushed */
1813 /* Make sure that we have a literal to write. */
1814 if (s->lookahead == 0) {
1816 if (s->lookahead == 0) {
1817 if (flush == Z_NO_FLUSH)
1819 break; /* flush the current block */
1823 /* Output a literal byte */
1824 s->match_length = 0;
1825 Tracevv((stderr,"%c", s->window[s->strstart]));
1826 _tr_tally_lit (s, s->window[s->strstart], bflush);
1829 if (bflush) FLUSH_BLOCK(s, 0);
1831 FLUSH_BLOCK(s, flush == Z_FINISH);
1832 return flush == Z_FINISH ? finish_done : block_done;