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
54 const char deflate_copyright[] =
55 " deflate 1.2.5 Copyright 1995-2010 Jean-loup Gailly and Mark Adler ";
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 block_state deflate_rle OF((deflate_state *s, int flush));
83 local block_state deflate_huff OF((deflate_state *s, int flush));
84 local void lm_init OF((deflate_state *s));
85 local void putShortMSB OF((deflate_state *s, uInt b));
86 local void flush_pending OF((z_streamp strm));
87 local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
89 void match_init OF((void)); /* asm code initialization */
90 uInt longest_match OF((deflate_state *s, IPos cur_match));
92 local uInt longest_match OF((deflate_state *s, IPos cur_match));
96 local void check_match OF((deflate_state *s, IPos start, IPos match,
100 /* ===========================================================================
105 /* Tail of hash chains */
108 # define TOO_FAR 4096
110 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
112 /* Values for max_lazy_match, good_match and max_chain_length, depending on
113 * the desired pack level (0..9). The values given below have been tuned to
114 * exclude worst case performance for pathological files. Better values may be
115 * found for specific files.
117 typedef struct config_s {
118 ush good_length; /* reduce lazy search above this match length */
119 ush max_lazy; /* do not perform lazy search above this match length */
120 ush nice_length; /* quit search above this match length */
126 local const config configuration_table[2] = {
127 /* good lazy nice chain */
128 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
129 /* 1 */ {4, 4, 8, 4, deflate_fast}}; /* max speed, no lazy matches */
131 local const config configuration_table[10] = {
132 /* good lazy nice chain */
133 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
134 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* max speed, no lazy matches */
135 /* 2 */ {4, 5, 16, 8, deflate_fast},
136 /* 3 */ {4, 6, 32, 32, deflate_fast},
138 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
139 /* 5 */ {8, 16, 32, 32, deflate_slow},
140 /* 6 */ {8, 16, 128, 128, deflate_slow},
141 /* 7 */ {8, 32, 128, 256, deflate_slow},
142 /* 8 */ {32, 128, 258, 1024, deflate_slow},
143 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
146 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
147 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
152 /* result of memcmp for equal strings */
154 #ifndef NO_DUMMY_DECL
155 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
158 /* ===========================================================================
159 * Update a hash value with the given input byte
160 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
161 * input characters, so that a running hash key can be computed from the
162 * previous key instead of complete recalculation each time.
164 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
167 /* ===========================================================================
168 * Insert string str in the dictionary and set match_head to the previous head
169 * of the hash chain (the most recent string with same hash key). Return
170 * the previous length of the hash chain.
171 * If this file is compiled with -DFASTEST, the compression level is forced
172 * to 1, and no hash chains are maintained.
173 * IN assertion: all calls to to INSERT_STRING are made with consecutive
174 * input characters and the first MIN_MATCH bytes of str are valid
175 * (except for the last MIN_MATCH-1 bytes of the input file).
178 #define INSERT_STRING(s, str, match_head) \
179 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
180 match_head = s->head[s->ins_h], \
181 s->head[s->ins_h] = (Pos)(str))
183 #define INSERT_STRING(s, str, match_head) \
184 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
185 match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
186 s->head[s->ins_h] = (Pos)(str))
189 /* ===========================================================================
190 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
191 * prev[] will be initialized on the fly.
193 #define CLEAR_HASH(s) \
194 s->head[s->hash_size-1] = NIL; \
195 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
197 /* ========================================================================= */
198 int ZEXPORT deflateInit_(strm, level, version, stream_size)
204 return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
205 Z_DEFAULT_STRATEGY, version, stream_size);
206 /* To do: ignore strm->next_in if we use it as window */
209 /* ========================================================================= */
210 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
211 version, stream_size)
223 static const char my_version[] = ZLIB_VERSION;
226 /* We overlay pending_buf and d_buf+l_buf. This works since the average
227 * output size for (length,distance) codes is <= 24 bits.
230 if (version == Z_NULL || version[0] != my_version[0] ||
231 stream_size != sizeof(z_stream)) {
232 return Z_VERSION_ERROR;
234 if (strm == Z_NULL) return Z_STREAM_ERROR;
237 if (strm->zalloc == (alloc_func)0) {
238 strm->zalloc = zcalloc;
239 strm->opaque = (voidpf)0;
241 if (strm->zfree == (free_func)0) strm->zfree = zcfree;
244 if (level != 0) level = 1;
246 if (level == Z_DEFAULT_COMPRESSION) level = 6;
249 if (windowBits < 0) { /* suppress zlib wrapper */
251 windowBits = -windowBits;
254 else if (windowBits > 15) {
255 wrap = 2; /* write gzip wrapper instead */
259 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
260 windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
261 strategy < 0 || strategy > Z_FIXED) {
262 return Z_STREAM_ERROR;
264 if (windowBits == 8) windowBits = 9; /* until 256-byte window bug fixed */
265 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
266 if (s == Z_NULL) return Z_MEM_ERROR;
267 strm->state = (struct internal_state FAR *)s;
272 s->w_bits = windowBits;
273 s->w_size = 1 << s->w_bits;
274 s->w_mask = s->w_size - 1;
276 s->hash_bits = memLevel + 7;
277 s->hash_size = 1 << s->hash_bits;
278 s->hash_mask = s->hash_size - 1;
279 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
281 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
282 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
283 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
285 s->high_water = 0; /* nothing written to s->window yet */
287 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
289 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
290 s->pending_buf = (uchf *) overlay;
291 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
293 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
294 s->pending_buf == Z_NULL) {
295 s->status = FINISH_STATE;
296 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
300 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
301 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
304 s->strategy = strategy;
305 s->method = (Byte)method;
307 return deflateReset(strm);
310 /* ========================================================================= */
311 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
313 const Bytef *dictionary;
317 uInt length = dictLength;
321 if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
322 strm->state->wrap == 2 ||
323 (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
324 return Z_STREAM_ERROR;
328 strm->adler = adler32(strm->adler, dictionary, dictLength);
330 if (length < MIN_MATCH) return Z_OK;
331 if (length > s->w_size) {
333 dictionary += dictLength - length; /* use the tail of the dictionary */
335 zmemcpy(s->window, dictionary, length);
336 s->strstart = length;
337 s->block_start = (long)length;
339 /* Insert all strings in the hash table (except for the last two bytes).
340 * s->lookahead stays null, so s->ins_h will be recomputed at the next
341 * call of fill_window.
343 s->ins_h = s->window[0];
344 UPDATE_HASH(s, s->ins_h, s->window[1]);
345 for (n = 0; n <= length - MIN_MATCH; n++) {
346 INSERT_STRING(s, n, hash_head);
348 if (hash_head) hash_head = 0; /* to make compiler happy */
352 /* ========================================================================= */
353 int ZEXPORT deflateReset (strm)
358 if (strm == Z_NULL || strm->state == Z_NULL ||
359 strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
360 return Z_STREAM_ERROR;
363 strm->total_in = strm->total_out = 0;
364 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
365 strm->data_type = Z_UNKNOWN;
367 s = (deflate_state *)strm->state;
369 s->pending_out = s->pending_buf;
372 s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
374 s->status = s->wrap ? INIT_STATE : BUSY_STATE;
377 s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
379 adler32(0L, Z_NULL, 0);
380 s->last_flush = Z_NO_FLUSH;
388 /* ========================================================================= */
389 int ZEXPORT deflateSetHeader (strm, head)
393 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
394 if (strm->state->wrap != 2) return Z_STREAM_ERROR;
395 strm->state->gzhead = head;
399 /* ========================================================================= */
400 int ZEXPORT deflatePrime (strm, bits, value)
405 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
406 strm->state->bi_valid = bits;
407 strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
411 /* ========================================================================= */
412 int ZEXPORT deflateParams(strm, level, strategy)
421 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
425 if (level != 0) level = 1;
427 if (level == Z_DEFAULT_COMPRESSION) level = 6;
429 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
430 return Z_STREAM_ERROR;
432 func = configuration_table[s->level].func;
434 if ((strategy != s->strategy || func != configuration_table[level].func) &&
435 strm->total_in != 0) {
436 /* Flush the last buffer: */
437 err = deflate(strm, Z_BLOCK);
439 if (s->level != level) {
441 s->max_lazy_match = configuration_table[level].max_lazy;
442 s->good_match = configuration_table[level].good_length;
443 s->nice_match = configuration_table[level].nice_length;
444 s->max_chain_length = configuration_table[level].max_chain;
446 s->strategy = strategy;
450 /* ========================================================================= */
451 int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
460 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
462 s->good_match = good_length;
463 s->max_lazy_match = max_lazy;
464 s->nice_match = nice_length;
465 s->max_chain_length = max_chain;
469 /* =========================================================================
470 * For the default windowBits of 15 and memLevel of 8, this function returns
471 * a close to exact, as well as small, upper bound on the compressed size.
472 * They are coded as constants here for a reason--if the #define's are
473 * changed, then this function needs to be changed as well. The return
474 * value for 15 and 8 only works for those exact settings.
476 * For any setting other than those defaults for windowBits and memLevel,
477 * the value returned is a conservative worst case for the maximum expansion
478 * resulting from using fixed blocks instead of stored blocks, which deflate
479 * can emit on compressed data for some combinations of the parameters.
481 * This function could be more sophisticated to provide closer upper bounds for
482 * every combination of windowBits and memLevel. But even the conservative
483 * upper bound of about 14% expansion does not seem onerous for output buffer
486 uLong ZEXPORT deflateBound(strm, sourceLen)
491 uLong complen, wraplen;
494 /* conservative upper bound for compressed data */
495 complen = sourceLen +
496 ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
498 /* if can't get parameters, return conservative bound plus zlib wrapper */
499 if (strm == Z_NULL || strm->state == Z_NULL)
502 /* compute wrapper length */
505 case 0: /* raw deflate */
508 case 1: /* zlib wrapper */
509 wraplen = 6 + (s->strstart ? 4 : 0);
511 case 2: /* gzip wrapper */
513 if (s->gzhead != Z_NULL) { /* user-supplied gzip header */
514 if (s->gzhead->extra != Z_NULL)
515 wraplen += 2 + s->gzhead->extra_len;
516 str = s->gzhead->name;
521 str = s->gzhead->comment;
530 default: /* for compiler happiness */
534 /* if not default parameters, return conservative bound */
535 if (s->w_bits != 15 || s->hash_bits != 8 + 7)
536 return complen + wraplen;
538 /* default settings: return tight bound for that case */
539 return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
540 (sourceLen >> 25) + 13 - 6 + wraplen;
543 /* =========================================================================
544 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
545 * IN assertion: the stream state is correct and there is enough room in
548 local void putShortMSB (s, b)
552 put_byte(s, (Byte)(b >> 8));
553 put_byte(s, (Byte)(b & 0xff));
556 /* =========================================================================
557 * Flush as much pending output as possible. All deflate() output goes
558 * through this function so some applications may wish to modify it
559 * to avoid allocating a large strm->next_out buffer and copying into it.
560 * (See also read_buf()).
562 local void flush_pending(strm)
565 unsigned len = strm->state->pending;
567 if (len > strm->avail_out) len = strm->avail_out;
568 if (len == 0) return;
570 zmemcpy(strm->next_out, strm->state->pending_out, len);
571 strm->next_out += len;
572 strm->state->pending_out += len;
573 strm->total_out += len;
574 strm->avail_out -= len;
575 strm->state->pending -= len;
576 if (strm->state->pending == 0) {
577 strm->state->pending_out = strm->state->pending_buf;
581 /* ========================================================================= */
582 int ZEXPORT deflate (strm, flush)
586 int old_flush; /* value of flush param for previous deflate call */
589 if (strm == Z_NULL || strm->state == Z_NULL ||
590 flush > Z_BLOCK || flush < 0) {
591 return Z_STREAM_ERROR;
595 if (s->status == FINISH_STATE && flush != Z_FINISH) {
596 ERR_RETURN(strm, Z_STREAM_ERROR);
598 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
600 s->strm = strm; /* just in case */
601 old_flush = s->last_flush;
602 s->last_flush = flush;
604 /* Write the header */
605 if (s->status == INIT_STATE) {
608 strm->adler = crc32(0L, Z_NULL, 0);
612 if (s->gzhead == Z_NULL) {
618 put_byte(s, s->level == 9 ? 2 :
619 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
621 put_byte(s, OS_CODE);
622 s->status = BUSY_STATE;
625 put_byte(s, (s->gzhead->text ? 1 : 0) +
626 (s->gzhead->hcrc ? 2 : 0) +
627 (s->gzhead->extra == Z_NULL ? 0 : 4) +
628 (s->gzhead->name == Z_NULL ? 0 : 8) +
629 (s->gzhead->comment == Z_NULL ? 0 : 16)
631 put_byte(s, (Byte)(s->gzhead->time & 0xff));
632 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
633 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
634 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
635 put_byte(s, s->level == 9 ? 2 :
636 (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
638 put_byte(s, s->gzhead->os & 0xff);
639 if (s->gzhead->extra != Z_NULL) {
640 put_byte(s, s->gzhead->extra_len & 0xff);
641 put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
644 strm->adler = crc32(strm->adler, s->pending_buf,
647 s->status = EXTRA_STATE;
653 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
656 if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
658 else if (s->level < 6)
660 else if (s->level == 6)
664 header |= (level_flags << 6);
665 if (s->strstart != 0) header |= PRESET_DICT;
666 header += 31 - (header % 31);
668 s->status = BUSY_STATE;
669 putShortMSB(s, header);
671 /* Save the adler32 of the preset dictionary: */
672 if (s->strstart != 0) {
673 putShortMSB(s, (uInt)(strm->adler >> 16));
674 putShortMSB(s, (uInt)(strm->adler & 0xffff));
676 strm->adler = adler32(0L, Z_NULL, 0);
680 if (s->status == EXTRA_STATE) {
681 if (s->gzhead->extra != Z_NULL) {
682 uInt beg = s->pending; /* start of bytes to update crc */
684 while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
685 if (s->pending == s->pending_buf_size) {
686 if (s->gzhead->hcrc && s->pending > beg)
687 strm->adler = crc32(strm->adler, s->pending_buf + beg,
691 if (s->pending == s->pending_buf_size)
694 put_byte(s, s->gzhead->extra[s->gzindex]);
697 if (s->gzhead->hcrc && s->pending > beg)
698 strm->adler = crc32(strm->adler, s->pending_buf + beg,
700 if (s->gzindex == s->gzhead->extra_len) {
702 s->status = NAME_STATE;
706 s->status = NAME_STATE;
708 if (s->status == NAME_STATE) {
709 if (s->gzhead->name != Z_NULL) {
710 uInt beg = s->pending; /* start of bytes to update crc */
714 if (s->pending == s->pending_buf_size) {
715 if (s->gzhead->hcrc && s->pending > beg)
716 strm->adler = crc32(strm->adler, s->pending_buf + beg,
720 if (s->pending == s->pending_buf_size) {
725 val = s->gzhead->name[s->gzindex++];
728 if (s->gzhead->hcrc && s->pending > beg)
729 strm->adler = crc32(strm->adler, s->pending_buf + beg,
733 s->status = COMMENT_STATE;
737 s->status = COMMENT_STATE;
739 if (s->status == COMMENT_STATE) {
740 if (s->gzhead->comment != Z_NULL) {
741 uInt beg = s->pending; /* start of bytes to update crc */
745 if (s->pending == s->pending_buf_size) {
746 if (s->gzhead->hcrc && s->pending > beg)
747 strm->adler = crc32(strm->adler, s->pending_buf + beg,
751 if (s->pending == s->pending_buf_size) {
756 val = s->gzhead->comment[s->gzindex++];
759 if (s->gzhead->hcrc && s->pending > beg)
760 strm->adler = crc32(strm->adler, s->pending_buf + beg,
763 s->status = HCRC_STATE;
766 s->status = HCRC_STATE;
768 if (s->status == HCRC_STATE) {
769 if (s->gzhead->hcrc) {
770 if (s->pending + 2 > s->pending_buf_size)
772 if (s->pending + 2 <= s->pending_buf_size) {
773 put_byte(s, (Byte)(strm->adler & 0xff));
774 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
775 strm->adler = crc32(0L, Z_NULL, 0);
776 s->status = BUSY_STATE;
780 s->status = BUSY_STATE;
784 /* Flush as much pending output as possible */
785 if (s->pending != 0) {
787 if (strm->avail_out == 0) {
788 /* Since avail_out is 0, deflate will be called again with
789 * more output space, but possibly with both pending and
790 * avail_in equal to zero. There won't be anything to do,
791 * but this is not an error situation so make sure we
792 * return OK instead of BUF_ERROR at next call of deflate:
798 /* Make sure there is something to do and avoid duplicate consecutive
799 * flushes. For repeated and useless calls with Z_FINISH, we keep
800 * returning Z_STREAM_END instead of Z_BUF_ERROR.
802 } else if (strm->avail_in == 0 && flush <= old_flush &&
804 ERR_RETURN(strm, Z_BUF_ERROR);
807 /* User must not provide more input after the first FINISH: */
808 if (s->status == FINISH_STATE && strm->avail_in != 0) {
809 ERR_RETURN(strm, Z_BUF_ERROR);
812 /* Start a new block or continue the current one.
814 if (strm->avail_in != 0 || s->lookahead != 0 ||
815 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
818 bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
819 (s->strategy == Z_RLE ? deflate_rle(s, flush) :
820 (*(configuration_table[s->level].func))(s, flush));
822 if (bstate == finish_started || bstate == finish_done) {
823 s->status = FINISH_STATE;
825 if (bstate == need_more || bstate == finish_started) {
826 if (strm->avail_out == 0) {
827 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
830 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
831 * of deflate should use the same flush parameter to make sure
832 * that the flush is complete. So we don't have to output an
833 * empty block here, this will be done at next call. This also
834 * ensures that for a very small output buffer, we emit at most
838 if (bstate == block_done) {
839 if (flush == Z_PARTIAL_FLUSH) {
841 } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
842 _tr_stored_block(s, (char*)0, 0L, 0);
843 /* For a full flush, this empty block will be recognized
844 * as a special marker by inflate_sync().
846 if (flush == Z_FULL_FLUSH) {
847 CLEAR_HASH(s); /* forget history */
848 if (s->lookahead == 0) {
855 if (strm->avail_out == 0) {
856 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
861 Assert(strm->avail_out > 0, "bug2");
863 if (flush != Z_FINISH) return Z_OK;
864 if (s->wrap <= 0) return Z_STREAM_END;
866 /* Write the trailer */
869 put_byte(s, (Byte)(strm->adler & 0xff));
870 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
871 put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
872 put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
873 put_byte(s, (Byte)(strm->total_in & 0xff));
874 put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
875 put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
876 put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
881 putShortMSB(s, (uInt)(strm->adler >> 16));
882 putShortMSB(s, (uInt)(strm->adler & 0xffff));
885 /* If avail_out is zero, the application will call deflate again
888 if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
889 return s->pending != 0 ? Z_OK : Z_STREAM_END;
892 /* ========================================================================= */
893 int ZEXPORT deflateEnd (strm)
898 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
900 status = strm->state->status;
901 if (status != INIT_STATE &&
902 status != EXTRA_STATE &&
903 status != NAME_STATE &&
904 status != COMMENT_STATE &&
905 status != HCRC_STATE &&
906 status != BUSY_STATE &&
907 status != FINISH_STATE) {
908 return Z_STREAM_ERROR;
911 /* Deallocate in reverse order of allocations: */
912 TRY_FREE(strm, strm->state->pending_buf);
913 TRY_FREE(strm, strm->state->head);
914 TRY_FREE(strm, strm->state->prev);
915 TRY_FREE(strm, strm->state->window);
917 ZFREE(strm, strm->state);
918 strm->state = Z_NULL;
920 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
923 /* =========================================================================
924 * Copy the source state to the destination state.
925 * To simplify the source, this is not supported for 16-bit MSDOS (which
926 * doesn't have enough memory anyway to duplicate compression states).
928 int ZEXPORT deflateCopy (dest, source)
933 return Z_STREAM_ERROR;
940 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
941 return Z_STREAM_ERROR;
946 zmemcpy(dest, source, sizeof(z_stream));
948 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
949 if (ds == Z_NULL) return Z_MEM_ERROR;
950 dest->state = (struct internal_state FAR *) ds;
951 zmemcpy(ds, ss, sizeof(deflate_state));
954 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
955 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
956 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
957 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
958 ds->pending_buf = (uchf *) overlay;
960 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
961 ds->pending_buf == Z_NULL) {
965 /* following zmemcpy do not work for 16-bit MSDOS */
966 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
967 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
968 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
969 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
971 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
972 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
973 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
975 ds->l_desc.dyn_tree = ds->dyn_ltree;
976 ds->d_desc.dyn_tree = ds->dyn_dtree;
977 ds->bl_desc.dyn_tree = ds->bl_tree;
980 #endif /* MAXSEG_64K */
983 /* ===========================================================================
984 * Read a new buffer from the current input stream, update the adler32
985 * and total number of bytes read. All deflate() input goes through
986 * this function so some applications may wish to modify it to avoid
987 * allocating a large strm->next_in buffer and copying from it.
988 * (See also flush_pending()).
990 local int read_buf(strm, buf, size)
995 unsigned len = strm->avail_in;
997 if (len > size) len = size;
998 if (len == 0) return 0;
1000 strm->avail_in -= len;
1002 if (strm->state->wrap == 1) {
1003 strm->adler = adler32(strm->adler, strm->next_in, len);
1006 else if (strm->state->wrap == 2) {
1007 strm->adler = crc32(strm->adler, strm->next_in, len);
1010 zmemcpy(buf, strm->next_in, len);
1011 strm->next_in += len;
1012 strm->total_in += len;
1017 /* ===========================================================================
1018 * Initialize the "longest match" routines for a new zlib stream
1020 local void lm_init (s)
1023 s->window_size = (ulg)2L*s->w_size;
1027 /* Set the default configuration parameters:
1029 s->max_lazy_match = configuration_table[s->level].max_lazy;
1030 s->good_match = configuration_table[s->level].good_length;
1031 s->nice_match = configuration_table[s->level].nice_length;
1032 s->max_chain_length = configuration_table[s->level].max_chain;
1035 s->block_start = 0L;
1037 s->match_length = s->prev_length = MIN_MATCH-1;
1038 s->match_available = 0;
1042 match_init(); /* initialize the asm code */
1048 /* ===========================================================================
1049 * Set match_start to the longest match starting at the given string and
1050 * return its length. Matches shorter or equal to prev_length are discarded,
1051 * in which case the result is equal to prev_length and match_start is
1053 * IN assertions: cur_match is the head of the hash chain for the current
1054 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1055 * OUT assertion: the match length is not greater than s->lookahead.
1058 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1059 * match.S. The code will be functionally equivalent.
1061 local uInt longest_match(s, cur_match)
1063 IPos cur_match; /* current match */
1065 unsigned chain_length = s->max_chain_length;/* max hash chain length */
1066 register Bytef *scan = s->window + s->strstart; /* current string */
1067 register Bytef *match; /* matched string */
1068 register int len; /* length of current match */
1069 int best_len = s->prev_length; /* best match length so far */
1070 int nice_match = s->nice_match; /* stop if match long enough */
1071 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1072 s->strstart - (IPos)MAX_DIST(s) : NIL;
1073 /* Stop when cur_match becomes <= limit. To simplify the code,
1074 * we prevent matches with the string of window index 0.
1076 Posf *prev = s->prev;
1077 uInt wmask = s->w_mask;
1080 /* Compare two bytes at a time. Note: this is not always beneficial.
1081 * Try with and without -DUNALIGNED_OK to check.
1083 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1084 register ush scan_start = *(ushf*)scan;
1085 register ush scan_end = *(ushf*)(scan+best_len-1);
1087 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1088 register Byte scan_end1 = scan[best_len-1];
1089 register Byte scan_end = scan[best_len];
1092 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1093 * It is easy to get rid of this optimization if necessary.
1095 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1097 /* Do not waste too much time if we already have a good match: */
1098 if (s->prev_length >= s->good_match) {
1101 /* Do not look for matches beyond the end of the input. This is necessary
1102 * to make deflate deterministic.
1104 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1106 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1109 Assert(cur_match < s->strstart, "no future");
1110 match = s->window + cur_match;
1112 /* Skip to next match if the match length cannot increase
1113 * or if the match length is less than 2. Note that the checks below
1114 * for insufficient lookahead only occur occasionally for performance
1115 * reasons. Therefore uninitialized memory will be accessed, and
1116 * conditional jumps will be made that depend on those values.
1117 * However the length of the match is limited to the lookahead, so
1118 * the output of deflate is not affected by the uninitialized values.
1120 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1121 /* This code assumes sizeof(unsigned short) == 2. Do not use
1122 * UNALIGNED_OK if your compiler uses a different size.
1124 if (*(ushf*)(match+best_len-1) != scan_end ||
1125 *(ushf*)match != scan_start) continue;
1127 /* It is not necessary to compare scan[2] and match[2] since they are
1128 * always equal when the other bytes match, given that the hash keys
1129 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1130 * strstart+3, +5, ... up to strstart+257. We check for insufficient
1131 * lookahead only every 4th comparison; the 128th check will be made
1132 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1133 * necessary to put more guard bytes at the end of the window, or
1134 * to check more often for insufficient lookahead.
1136 Assert(scan[2] == match[2], "scan[2]?");
1139 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1140 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1141 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1142 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1144 /* The funny "do {}" generates better code on most compilers */
1146 /* Here, scan <= window+strstart+257 */
1147 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1148 if (*scan == *match) scan++;
1150 len = (MAX_MATCH - 1) - (int)(strend-scan);
1151 scan = strend - (MAX_MATCH-1);
1153 #else /* UNALIGNED_OK */
1155 if (match[best_len] != scan_end ||
1156 match[best_len-1] != scan_end1 ||
1158 *++match != scan[1]) continue;
1160 /* The check at best_len-1 can be removed because it will be made
1161 * again later. (This heuristic is not always a win.)
1162 * It is not necessary to compare scan[2] and match[2] since they
1163 * are always equal when the other bytes match, given that
1164 * the hash keys are equal and that HASH_BITS >= 8.
1167 Assert(*scan == *match, "match[2]?");
1169 /* We check for insufficient lookahead only every 8th comparison;
1170 * the 256th check will be made at strstart+258.
1173 } while (*++scan == *++match && *++scan == *++match &&
1174 *++scan == *++match && *++scan == *++match &&
1175 *++scan == *++match && *++scan == *++match &&
1176 *++scan == *++match && *++scan == *++match &&
1179 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1181 len = MAX_MATCH - (int)(strend - scan);
1182 scan = strend - MAX_MATCH;
1184 #endif /* UNALIGNED_OK */
1186 if (len > best_len) {
1187 s->match_start = cur_match;
1189 if (len >= nice_match) break;
1191 scan_end = *(ushf*)(scan+best_len-1);
1193 scan_end1 = scan[best_len-1];
1194 scan_end = scan[best_len];
1197 } while ((cur_match = prev[cur_match & wmask]) > limit
1198 && --chain_length != 0);
1200 if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1201 return s->lookahead;
1207 /* ---------------------------------------------------------------------------
1208 * Optimized version for FASTEST only
1210 local uInt longest_match(s, cur_match)
1212 IPos cur_match; /* current match */
1214 register Bytef *scan = s->window + s->strstart; /* current string */
1215 register Bytef *match; /* matched string */
1216 register int len; /* length of current match */
1217 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1219 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1220 * It is easy to get rid of this optimization if necessary.
1222 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1224 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1226 Assert(cur_match < s->strstart, "no future");
1228 match = s->window + cur_match;
1230 /* Return failure if the match length is less than 2:
1232 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1234 /* The check at best_len-1 can be removed because it will be made
1235 * again later. (This heuristic is not always a win.)
1236 * It is not necessary to compare scan[2] and match[2] since they
1237 * are always equal when the other bytes match, given that
1238 * the hash keys are equal and that HASH_BITS >= 8.
1240 scan += 2, match += 2;
1241 Assert(*scan == *match, "match[2]?");
1243 /* We check for insufficient lookahead only every 8th comparison;
1244 * the 256th check will be made at strstart+258.
1247 } while (*++scan == *++match && *++scan == *++match &&
1248 *++scan == *++match && *++scan == *++match &&
1249 *++scan == *++match && *++scan == *++match &&
1250 *++scan == *++match && *++scan == *++match &&
1253 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1255 len = MAX_MATCH - (int)(strend - scan);
1257 if (len < MIN_MATCH) return MIN_MATCH - 1;
1259 s->match_start = cur_match;
1260 return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1263 #endif /* FASTEST */
1266 /* ===========================================================================
1267 * Check that the match at match_start is indeed a match.
1269 local void check_match(s, start, match, length)
1274 /* check that the match is indeed a match */
1275 if (zmemcmp(s->window + match,
1276 s->window + start, length) != EQUAL) {
1277 fprintf(stderr, " start %u, match %u, length %d\n",
1278 start, match, length);
1280 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1281 } while (--length != 0);
1282 z_error("invalid match");
1284 if (z_verbose > 1) {
1285 fprintf(stderr,"\\[%d,%d]", start-match, length);
1286 do { putc(s->window[start++], stderr); } while (--length != 0);
1290 # define check_match(s, start, match, length)
1293 /* ===========================================================================
1294 * Fill the window when the lookahead becomes insufficient.
1295 * Updates strstart and lookahead.
1297 * IN assertion: lookahead < MIN_LOOKAHEAD
1298 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1299 * At least one byte has been read, or avail_in == 0; reads are
1300 * performed for at least two bytes (required for the zip translate_eol
1301 * option -- not supported here).
1303 local void fill_window(s)
1306 register unsigned n, m;
1308 unsigned more; /* Amount of free space at the end of the window. */
1309 uInt wsize = s->w_size;
1312 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1314 /* Deal with !@#$% 64K limit: */
1315 if (sizeof(int) <= 2) {
1316 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1319 } else if (more == (unsigned)(-1)) {
1320 /* Very unlikely, but possible on 16 bit machine if
1321 * strstart == 0 && lookahead == 1 (input done a byte at time)
1327 /* If the window is almost full and there is insufficient lookahead,
1328 * move the upper half to the lower one to make room in the upper half.
1330 if (s->strstart >= wsize+MAX_DIST(s)) {
1332 zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1333 s->match_start -= wsize;
1334 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
1335 s->block_start -= (long) wsize;
1337 /* Slide the hash table (could be avoided with 32 bit values
1338 at the expense of memory usage). We slide even when level == 0
1339 to keep the hash table consistent if we switch back to level > 0
1340 later. (Using level 0 permanently is not an optimal usage of
1341 zlib, so we don't care about this pathological case.)
1347 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1355 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1356 /* If n is not on any hash chain, prev[n] is garbage but
1357 * its value will never be used.
1363 if (s->strm->avail_in == 0) return;
1365 /* If there was no sliding:
1366 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1367 * more == window_size - lookahead - strstart
1368 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1369 * => more >= window_size - 2*WSIZE + 2
1370 * In the BIG_MEM or MMAP case (not yet supported),
1371 * window_size == input_size + MIN_LOOKAHEAD &&
1372 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1373 * Otherwise, window_size == 2*WSIZE so more >= 2.
1374 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1376 Assert(more >= 2, "more < 2");
1378 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1381 /* Initialize the hash value now that we have some input: */
1382 if (s->lookahead >= MIN_MATCH) {
1383 s->ins_h = s->window[s->strstart];
1384 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1386 Call UPDATE_HASH() MIN_MATCH-3 more times
1389 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1390 * but this is not important since only literal bytes will be emitted.
1393 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1395 /* If the WIN_INIT bytes after the end of the current data have never been
1396 * written, then zero those bytes in order to avoid memory check reports of
1397 * the use of uninitialized (or uninitialised as Julian writes) bytes by
1398 * the longest match routines. Update the high water mark for the next
1399 * time through here. WIN_INIT is set to MAX_MATCH since the longest match
1400 * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
1402 if (s->high_water < s->window_size) {
1403 ulg curr = s->strstart + (ulg)(s->lookahead);
1406 if (s->high_water < curr) {
1407 /* Previous high water mark below current data -- zero WIN_INIT
1408 * bytes or up to end of window, whichever is less.
1410 init = s->window_size - curr;
1411 if (init > WIN_INIT)
1413 zmemzero(s->window + curr, (unsigned)init);
1414 s->high_water = curr + init;
1416 else if (s->high_water < (ulg)curr + WIN_INIT) {
1417 /* High water mark at or above current data, but below current data
1418 * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
1419 * to end of window, whichever is less.
1421 init = (ulg)curr + WIN_INIT - s->high_water;
1422 if (init > s->window_size - s->high_water)
1423 init = s->window_size - s->high_water;
1424 zmemzero(s->window + s->high_water, (unsigned)init);
1425 s->high_water += init;
1430 /* ===========================================================================
1431 * Flush the current block, with given end-of-file flag.
1432 * IN assertion: strstart is set to the end of the current match.
1434 #define FLUSH_BLOCK_ONLY(s, last) { \
1435 _tr_flush_block(s, (s->block_start >= 0L ? \
1436 (charf *)&s->window[(unsigned)s->block_start] : \
1438 (ulg)((long)s->strstart - s->block_start), \
1440 s->block_start = s->strstart; \
1441 flush_pending(s->strm); \
1442 Tracev((stderr,"[FLUSH]")); \
1445 /* Same but force premature exit if necessary. */
1446 #define FLUSH_BLOCK(s, last) { \
1447 FLUSH_BLOCK_ONLY(s, last); \
1448 if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
1451 /* ===========================================================================
1452 * Copy without compression as much as possible from the input stream, return
1453 * the current block state.
1454 * This function does not insert new strings in the dictionary since
1455 * uncompressible data is probably not useful. This function is used
1456 * only for the level=0 compression option.
1457 * NOTE: this function should be optimized to avoid extra copying from
1458 * window to pending_buf.
1460 local block_state deflate_stored(s, flush)
1464 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1465 * to pending_buf_size, and each stored block has a 5 byte header:
1467 ulg max_block_size = 0xffff;
1470 if (max_block_size > s->pending_buf_size - 5) {
1471 max_block_size = s->pending_buf_size - 5;
1474 /* Copy as much as possible from input to output: */
1476 /* Fill the window as much as possible: */
1477 if (s->lookahead <= 1) {
1479 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1480 s->block_start >= (long)s->w_size, "slide too late");
1483 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1485 if (s->lookahead == 0) break; /* flush the current block */
1487 Assert(s->block_start >= 0L, "block gone");
1489 s->strstart += s->lookahead;
1492 /* Emit a stored block if pending_buf will be full: */
1493 max_start = s->block_start + max_block_size;
1494 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1495 /* strstart == 0 is possible when wraparound on 16-bit machine */
1496 s->lookahead = (uInt)(s->strstart - max_start);
1497 s->strstart = (uInt)max_start;
1500 /* Flush if we may have to slide, otherwise block_start may become
1501 * negative and the data will be gone:
1503 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1507 FLUSH_BLOCK(s, flush == Z_FINISH);
1508 return flush == Z_FINISH ? finish_done : block_done;
1511 /* ===========================================================================
1512 * Compress as much as possible from the input stream, return the current
1514 * This function does not perform lazy evaluation of matches and inserts
1515 * new strings in the dictionary only for unmatched strings or for short
1516 * matches. It is used only for the fast compression options.
1518 local block_state deflate_fast(s, flush)
1522 IPos hash_head; /* head of the hash chain */
1523 int bflush; /* set if current block must be flushed */
1526 /* Make sure that we always have enough lookahead, except
1527 * at the end of the input file. We need MAX_MATCH bytes
1528 * for the next match, plus MIN_MATCH bytes to insert the
1529 * string following the next match.
1531 if (s->lookahead < MIN_LOOKAHEAD) {
1533 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1536 if (s->lookahead == 0) break; /* flush the current block */
1539 /* Insert the string window[strstart .. strstart+2] in the
1540 * dictionary, and set hash_head to the head of the hash chain:
1543 if (s->lookahead >= MIN_MATCH) {
1544 INSERT_STRING(s, s->strstart, hash_head);
1547 /* Find the longest match, discarding those <= prev_length.
1548 * At this point we have always match_length < MIN_MATCH
1550 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1551 /* To simplify the code, we prevent matches with the string
1552 * of window index 0 (in particular we have to avoid a match
1553 * of the string with itself at the start of the input file).
1555 s->match_length = longest_match (s, hash_head);
1556 /* longest_match() sets match_start */
1558 if (s->match_length >= MIN_MATCH) {
1559 check_match(s, s->strstart, s->match_start, s->match_length);
1561 _tr_tally_dist(s, s->strstart - s->match_start,
1562 s->match_length - MIN_MATCH, bflush);
1564 s->lookahead -= s->match_length;
1566 /* Insert new strings in the hash table only if the match length
1567 * is not too large. This saves time but degrades compression.
1570 if (s->match_length <= s->max_insert_length &&
1571 s->lookahead >= MIN_MATCH) {
1572 s->match_length--; /* string at strstart already in table */
1575 INSERT_STRING(s, s->strstart, hash_head);
1576 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1577 * always MIN_MATCH bytes ahead.
1579 } while (--s->match_length != 0);
1584 s->strstart += s->match_length;
1585 s->match_length = 0;
1586 s->ins_h = s->window[s->strstart];
1587 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1589 Call UPDATE_HASH() MIN_MATCH-3 more times
1591 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1592 * matter since it will be recomputed at next deflate call.
1596 /* No match, output a literal byte */
1597 Tracevv((stderr,"%c", s->window[s->strstart]));
1598 _tr_tally_lit (s, s->window[s->strstart], bflush);
1602 if (bflush) FLUSH_BLOCK(s, 0);
1604 FLUSH_BLOCK(s, flush == Z_FINISH);
1605 return flush == Z_FINISH ? finish_done : block_done;
1609 /* ===========================================================================
1610 * Same as above, but achieves better compression. We use a lazy
1611 * evaluation for matches: a match is finally adopted only if there is
1612 * no better match at the next window position.
1614 local block_state deflate_slow(s, flush)
1618 IPos hash_head; /* head of hash chain */
1619 int bflush; /* set if current block must be flushed */
1621 /* Process the input block. */
1623 /* Make sure that we always have enough lookahead, except
1624 * at the end of the input file. We need MAX_MATCH bytes
1625 * for the next match, plus MIN_MATCH bytes to insert the
1626 * string following the next match.
1628 if (s->lookahead < MIN_LOOKAHEAD) {
1630 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1633 if (s->lookahead == 0) break; /* flush the current block */
1636 /* Insert the string window[strstart .. strstart+2] in the
1637 * dictionary, and set hash_head to the head of the hash chain:
1640 if (s->lookahead >= MIN_MATCH) {
1641 INSERT_STRING(s, s->strstart, hash_head);
1644 /* Find the longest match, discarding those <= prev_length.
1646 s->prev_length = s->match_length, s->prev_match = s->match_start;
1647 s->match_length = MIN_MATCH-1;
1649 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1650 s->strstart - hash_head <= MAX_DIST(s)) {
1651 /* To simplify the code, we prevent matches with the string
1652 * of window index 0 (in particular we have to avoid a match
1653 * of the string with itself at the start of the input file).
1655 s->match_length = longest_match (s, hash_head);
1656 /* longest_match() sets match_start */
1658 if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1659 #if TOO_FAR <= 32767
1660 || (s->match_length == MIN_MATCH &&
1661 s->strstart - s->match_start > TOO_FAR)
1665 /* If prev_match is also MIN_MATCH, match_start is garbage
1666 * but we will ignore the current match anyway.
1668 s->match_length = MIN_MATCH-1;
1671 /* If there was a match at the previous step and the current
1672 * match is not better, output the previous match:
1674 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1675 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1676 /* Do not insert strings in hash table beyond this. */
1678 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1680 _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1681 s->prev_length - MIN_MATCH, bflush);
1683 /* Insert in hash table all strings up to the end of the match.
1684 * strstart-1 and strstart are already inserted. If there is not
1685 * enough lookahead, the last two strings are not inserted in
1688 s->lookahead -= s->prev_length-1;
1689 s->prev_length -= 2;
1691 if (++s->strstart <= max_insert) {
1692 INSERT_STRING(s, s->strstart, hash_head);
1694 } while (--s->prev_length != 0);
1695 s->match_available = 0;
1696 s->match_length = MIN_MATCH-1;
1699 if (bflush) FLUSH_BLOCK(s, 0);
1701 } else if (s->match_available) {
1702 /* If there was no match at the previous position, output a
1703 * single literal. If there was a match but the current match
1704 * is longer, truncate the previous match to a single literal.
1706 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1707 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1709 FLUSH_BLOCK_ONLY(s, 0);
1713 if (s->strm->avail_out == 0) return need_more;
1715 /* There is no previous match to compare with, wait for
1716 * the next step to decide.
1718 s->match_available = 1;
1723 Assert (flush != Z_NO_FLUSH, "no flush?");
1724 if (s->match_available) {
1725 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1726 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1727 s->match_available = 0;
1729 FLUSH_BLOCK(s, flush == Z_FINISH);
1730 return flush == Z_FINISH ? finish_done : block_done;
1732 #endif /* FASTEST */
1734 /* ===========================================================================
1735 * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1736 * one. Do not maintain a hash table. (It will be regenerated if this run of
1737 * deflate switches away from Z_RLE.)
1739 local block_state deflate_rle(s, flush)
1743 int bflush; /* set if current block must be flushed */
1744 uInt prev; /* byte at distance one to match */
1745 Bytef *scan, *strend; /* scan goes up to strend for length of run */
1748 /* Make sure that we always have enough lookahead, except
1749 * at the end of the input file. We need MAX_MATCH bytes
1750 * for the longest encodable run.
1752 if (s->lookahead < MAX_MATCH) {
1754 if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1757 if (s->lookahead == 0) break; /* flush the current block */
1760 /* See how many times the previous byte repeats */
1761 s->match_length = 0;
1762 if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
1763 scan = s->window + s->strstart - 1;
1765 if (prev == *++scan && prev == *++scan && prev == *++scan) {
1766 strend = s->window + s->strstart + MAX_MATCH;
1768 } while (prev == *++scan && prev == *++scan &&
1769 prev == *++scan && prev == *++scan &&
1770 prev == *++scan && prev == *++scan &&
1771 prev == *++scan && prev == *++scan &&
1773 s->match_length = MAX_MATCH - (int)(strend - scan);
1774 if (s->match_length > s->lookahead)
1775 s->match_length = s->lookahead;
1779 /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1780 if (s->match_length >= MIN_MATCH) {
1781 check_match(s, s->strstart, s->strstart - 1, s->match_length);
1783 _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
1785 s->lookahead -= s->match_length;
1786 s->strstart += s->match_length;
1787 s->match_length = 0;
1789 /* No match, output a literal byte */
1790 Tracevv((stderr,"%c", s->window[s->strstart]));
1791 _tr_tally_lit (s, s->window[s->strstart], bflush);
1795 if (bflush) FLUSH_BLOCK(s, 0);
1797 FLUSH_BLOCK(s, flush == Z_FINISH);
1798 return flush == Z_FINISH ? finish_done : block_done;
1801 /* ===========================================================================
1802 * For Z_HUFFMAN_ONLY, do not look for matches. Do not maintain a hash table.
1803 * (It will be regenerated if this run of deflate switches away from Huffman.)
1805 local block_state deflate_huff(s, flush)
1809 int bflush; /* set if current block must be flushed */
1812 /* Make sure that we have a literal to write. */
1813 if (s->lookahead == 0) {
1815 if (s->lookahead == 0) {
1816 if (flush == Z_NO_FLUSH)
1818 break; /* flush the current block */
1822 /* Output a literal byte */
1823 s->match_length = 0;
1824 Tracevv((stderr,"%c", s->window[s->strstart]));
1825 _tr_tally_lit (s, s->window[s->strstart], bflush);
1828 if (bflush) FLUSH_BLOCK(s, 0);
1830 FLUSH_BLOCK(s, flush == Z_FINISH);
1831 return flush == Z_FINISH ? finish_done : block_done;