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1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-1998 Jean-loup Gailly.
3 * For conditions of distribution and use, see copyright notice in zlib.h
4 */
5
6 /*
7 * ALGORITHM
8 *
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).
12 *
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.
30 *
31 * ACKNOWLEDGEMENTS
32 *
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.
36 *
37 * REFERENCES
38 *
39 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
40 * Available in ftp://ds.internic.net/rfc/rfc1951.txt
41 *
42 * A description of the Rabin and Karp algorithm is given in the book
43 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
44 *
45 * Fiala,E.R., and Greene,D.H.
46 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
47 *
48 */
49
50 /* @(#) $Id$ */
51
52 #include "deflate.h"
53
54 const char deflate_copyright[] =
55 " deflate 1.1.3 Copyright 1995-1998 Jean-loup Gailly ";
56 /*
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.
61 */
62
63 /* ===========================================================================
64 * Function prototypes.
65 */
66 typedef enum {
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 */
71 } block_state;
72
73 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
74 /* Compression function. Returns the block state after the call. */
75
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));
79 local block_state deflate_slow OF((deflate_state *s, int flush));
80 local void lm_init OF((deflate_state *s));
81 local void putShortMSB OF((deflate_state *s, uInt b));
82 local void flush_pending OF((z_streamp strm));
83 local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
84 #ifdef ASMV
85 void match_init OF((void)); /* asm code initialization */
86 uInt longest_match OF((deflate_state *s, IPos cur_match));
87 #else
88 local uInt longest_match OF((deflate_state *s, IPos cur_match));
89 #endif
90
91 #ifdef DEBUG
92 local void check_match OF((deflate_state *s, IPos start, IPos match,
93 int length));
94 #endif
95
96 /* ===========================================================================
97 * Local data
98 */
99
100 #define NIL 0
101 /* Tail of hash chains */
102
103 #ifndef TOO_FAR
104 # define TOO_FAR 4096
105 #endif
106 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
107
108 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
109 /* Minimum amount of lookahead, except at the end of the input file.
110 * See deflate.c for comments about the MIN_MATCH+1.
111 */
112
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.
117 */
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 */
122 ush max_chain;
123 compress_func func;
124 } config;
125
126 local const config configuration_table[10] = {
127 /* good lazy nice chain */
128 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
129 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */
130 /* 2 */ {4, 5, 16, 8, deflate_fast},
131 /* 3 */ {4, 6, 32, 32, deflate_fast},
132
133 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
134 /* 5 */ {8, 16, 32, 32, deflate_slow},
135 /* 6 */ {8, 16, 128, 128, deflate_slow},
136 /* 7 */ {8, 32, 128, 256, deflate_slow},
137 /* 8 */ {32, 128, 258, 1024, deflate_slow},
138 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
139
140 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
141 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
142 * meaning.
143 */
144
145 #define EQUAL 0
146 /* result of memcmp for equal strings */
147
148 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
149
150 /* ===========================================================================
151 * Update a hash value with the given input byte
152 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
153 * input characters, so that a running hash key can be computed from the
154 * previous key instead of complete recalculation each time.
155 */
156 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
157
158
159 /* ===========================================================================
160 * Insert string str in the dictionary and set match_head to the previous head
161 * of the hash chain (the most recent string with same hash key). Return
162 * the previous length of the hash chain.
163 * If this file is compiled with -DFASTEST, the compression level is forced
164 * to 1, and no hash chains are maintained.
165 * IN assertion: all calls to to INSERT_STRING are made with consecutive
166 * input characters and the first MIN_MATCH bytes of str are valid
167 * (except for the last MIN_MATCH-1 bytes of the input file).
168 */
169 #ifdef FASTEST
170 #define INSERT_STRING(s, str, match_head) \
171 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
172 match_head = s->head[s->ins_h], \
173 s->head[s->ins_h] = (Pos)(str))
174 #else
175 #define INSERT_STRING(s, str, match_head) \
176 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
177 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
178 s->head[s->ins_h] = (Pos)(str))
179 #endif
180
181 /* ===========================================================================
182 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
183 * prev[] will be initialized on the fly.
184 */
185 #define CLEAR_HASH(s) \
186 s->head[s->hash_size-1] = NIL; \
187 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
188
189 /* ========================================================================= */
190 int ZEXPORT deflateInit_(strm, level, version, stream_size)
191 z_streamp strm;
192 int level;
193 const char *version;
194 int stream_size;
195 {
196 return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
197 Z_DEFAULT_STRATEGY, version, stream_size);
198 /* To do: ignore strm->next_in if we use it as window */
199 }
200
201 /* ========================================================================= */
202 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
203 version, stream_size)
204 z_streamp strm;
205 int level;
206 int method;
207 int windowBits;
208 int memLevel;
209 int strategy;
210 const char *version;
211 int stream_size;
212 {
213 deflate_state *s;
214 int noheader = 0;
215 static const char* my_version = ZLIB_VERSION;
216
217 ushf *overlay;
218 /* We overlay pending_buf and d_buf+l_buf. This works since the average
219 * output size for (length,distance) codes is <= 24 bits.
220 */
221
222 if (version == Z_NULL || version[0] != my_version[0] ||
223 stream_size != sizeof(z_stream)) {
224 return Z_VERSION_ERROR;
225 }
226 if (strm == Z_NULL) return Z_STREAM_ERROR;
227
228 strm->msg = Z_NULL;
229 if (strm->zalloc == Z_NULL) {
230 strm->zalloc = zcalloc;
231 strm->opaque = (voidpf)0;
232 }
233 if (strm->zfree == Z_NULL) strm->zfree = zcfree;
234
235 if (level == Z_DEFAULT_COMPRESSION) level = 6;
236 #ifdef FASTEST
237 level = 1;
238 #endif
239
240 if (windowBits < 0) { /* undocumented feature: suppress zlib header */
241 noheader = 1;
242 windowBits = -windowBits;
243 }
244 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
245 windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
246 strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
247 return Z_STREAM_ERROR;
248 }
249 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
250 if (s == Z_NULL) return Z_MEM_ERROR;
251 strm->state = (struct internal_state FAR *)s;
252 s->strm = strm;
253
254 s->noheader = noheader;
255 s->w_bits = windowBits;
256 s->w_size = 1 << s->w_bits;
257 s->w_mask = s->w_size - 1;
258
259 s->hash_bits = memLevel + 7;
260 s->hash_size = 1 << s->hash_bits;
261 s->hash_mask = s->hash_size - 1;
262 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
263
264 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
265 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
266 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
267
268 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
269
270 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
271 s->pending_buf = (uchf *) overlay;
272 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
273
274 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
275 s->pending_buf == Z_NULL) {
276 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
277 deflateEnd (strm);
278 return Z_MEM_ERROR;
279 }
280 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
281 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
282
283 s->level = level;
284 s->strategy = strategy;
285 s->method = (Byte)method;
286
287 return deflateReset(strm);
288 }
289
290 /* ========================================================================= */
291 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
292 z_streamp strm;
293 const Bytef *dictionary;
294 uInt dictLength;
295 {
296 deflate_state *s;
297 uInt length = dictLength;
298 uInt n;
299 IPos hash_head = 0;
300
301 if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
302 strm->state->status != INIT_STATE) return Z_STREAM_ERROR;
303
304 s = strm->state;
305 strm->adler = adler32(strm->adler, dictionary, dictLength);
306
307 if (length < MIN_MATCH) return Z_OK;
308 if (length > MAX_DIST(s)) {
309 length = MAX_DIST(s);
310 #ifndef USE_DICT_HEAD
311 dictionary += dictLength - length; /* use the tail of the dictionary */
312 #endif
313 }
314 zmemcpy(s->window, dictionary, length);
315 s->strstart = length;
316 s->block_start = (long)length;
317
318 /* Insert all strings in the hash table (except for the last two bytes).
319 * s->lookahead stays null, so s->ins_h will be recomputed at the next
320 * call of fill_window.
321 */
322 s->ins_h = s->window[0];
323 UPDATE_HASH(s, s->ins_h, s->window[1]);
324 for (n = 0; n <= length - MIN_MATCH; n++) {
325 INSERT_STRING(s, n, hash_head);
326 }
327 if (hash_head) hash_head = 0; /* to make compiler happy */
328 return Z_OK;
329 }
330
331 /* ========================================================================= */
332 int ZEXPORT deflateReset (strm)
333 z_streamp strm;
334 {
335 deflate_state *s;
336
337 if (strm == Z_NULL || strm->state == Z_NULL ||
338 strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR;
339
340 strm->total_in = strm->total_out = 0;
341 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
342 strm->data_type = Z_UNKNOWN;
343
344 s = (deflate_state *)strm->state;
345 s->pending = 0;
346 s->pending_out = s->pending_buf;
347
348 if (s->noheader < 0) {
349 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
350 }
351 s->status = s->noheader ? BUSY_STATE : INIT_STATE;
352 strm->adler = 1;
353 s->last_flush = Z_NO_FLUSH;
354
355 _tr_init(s);
356 lm_init(s);
357
358 return Z_OK;
359 }
360
361 /* ========================================================================= */
362 int ZEXPORT deflateParams(strm, level, strategy)
363 z_streamp strm;
364 int level;
365 int strategy;
366 {
367 deflate_state *s;
368 compress_func func;
369 int err = Z_OK;
370
371 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
372 s = strm->state;
373
374 if (level == Z_DEFAULT_COMPRESSION) {
375 level = 6;
376 }
377 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
378 return Z_STREAM_ERROR;
379 }
380 func = configuration_table[s->level].func;
381
382 if (func != configuration_table[level].func && strm->total_in != 0) {
383 /* Flush the last buffer: */
384 err = deflate(strm, Z_PARTIAL_FLUSH);
385 }
386 if (s->level != level) {
387 s->level = level;
388 s->max_lazy_match = configuration_table[level].max_lazy;
389 s->good_match = configuration_table[level].good_length;
390 s->nice_match = configuration_table[level].nice_length;
391 s->max_chain_length = configuration_table[level].max_chain;
392 }
393 s->strategy = strategy;
394 return err;
395 }
396
397 /* =========================================================================
398 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
399 * IN assertion: the stream state is correct and there is enough room in
400 * pending_buf.
401 */
402 local void putShortMSB (s, b)
403 deflate_state *s;
404 uInt b;
405 {
406 put_byte(s, (Byte)(b >> 8));
407 put_byte(s, (Byte)(b & 0xff));
408 }
409
410 /* =========================================================================
411 * Flush as much pending output as possible. All deflate() output goes
412 * through this function so some applications may wish to modify it
413 * to avoid allocating a large strm->next_out buffer and copying into it.
414 * (See also read_buf()).
415 */
416 local void flush_pending(strm)
417 z_streamp strm;
418 {
419 unsigned len = strm->state->pending;
420
421 if (len > strm->avail_out) len = strm->avail_out;
422 if (len == 0) return;
423
424 zmemcpy(strm->next_out, strm->state->pending_out, len);
425 strm->next_out += len;
426 strm->state->pending_out += len;
427 strm->total_out += len;
428 strm->avail_out -= len;
429 strm->state->pending -= len;
430 if (strm->state->pending == 0) {
431 strm->state->pending_out = strm->state->pending_buf;
432 }
433 }
434
435 /* ========================================================================= */
436 int ZEXPORT deflate (strm, flush)
437 z_streamp strm;
438 int flush;
439 {
440 int old_flush; /* value of flush param for previous deflate call */
441 deflate_state *s;
442
443 if (strm == Z_NULL || strm->state == Z_NULL ||
444 flush > Z_FINISH || flush < 0) {
445 return Z_STREAM_ERROR;
446 }
447 s = strm->state;
448
449 if (strm->next_out == Z_NULL ||
450 (strm->next_in == Z_NULL && strm->avail_in != 0) ||
451 (s->status == FINISH_STATE && flush != Z_FINISH)) {
452 ERR_RETURN(strm, Z_STREAM_ERROR);
453 }
454 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
455
456 s->strm = strm; /* just in case */
457 old_flush = s->last_flush;
458 s->last_flush = flush;
459
460 /* Write the zlib header */
461 if (s->status == INIT_STATE) {
462
463 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
464 uInt level_flags = (s->level-1) >> 1;
465
466 if (level_flags > 3) level_flags = 3;
467 header |= (level_flags << 6);
468 if (s->strstart != 0) header |= PRESET_DICT;
469 header += 31 - (header % 31);
470
471 s->status = BUSY_STATE;
472 putShortMSB(s, header);
473
474 /* Save the adler32 of the preset dictionary: */
475 if (s->strstart != 0) {
476 putShortMSB(s, (uInt)(strm->adler >> 16));
477 putShortMSB(s, (uInt)(strm->adler & 0xffff));
478 }
479 strm->adler = 1L;
480 }
481
482 /* Flush as much pending output as possible */
483 if (s->pending != 0) {
484 flush_pending(strm);
485 if (strm->avail_out == 0) {
486 /* Since avail_out is 0, deflate will be called again with
487 * more output space, but possibly with both pending and
488 * avail_in equal to zero. There won't be anything to do,
489 * but this is not an error situation so make sure we
490 * return OK instead of BUF_ERROR at next call of deflate:
491 */
492 s->last_flush = -1;
493 return Z_OK;
494 }
495
496 /* Make sure there is something to do and avoid duplicate consecutive
497 * flushes. For repeated and useless calls with Z_FINISH, we keep
498 * returning Z_STREAM_END instead of Z_BUFF_ERROR.
499 */
500 } else if (strm->avail_in == 0 && flush <= old_flush &&
501 flush != Z_FINISH) {
502 ERR_RETURN(strm, Z_BUF_ERROR);
503 }
504
505 /* User must not provide more input after the first FINISH: */
506 if (s->status == FINISH_STATE && strm->avail_in != 0) {
507 ERR_RETURN(strm, Z_BUF_ERROR);
508 }
509
510 /* Start a new block or continue the current one.
511 */
512 if (strm->avail_in != 0 || s->lookahead != 0 ||
513 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
514 block_state bstate;
515
516 bstate = (*(configuration_table[s->level].func))(s, flush);
517
518 if (bstate == finish_started || bstate == finish_done) {
519 s->status = FINISH_STATE;
520 }
521 if (bstate == need_more || bstate == finish_started) {
522 if (strm->avail_out == 0) {
523 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
524 }
525 return Z_OK;
526 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
527 * of deflate should use the same flush parameter to make sure
528 * that the flush is complete. So we don't have to output an
529 * empty block here, this will be done at next call. This also
530 * ensures that for a very small output buffer, we emit at most
531 * one empty block.
532 */
533 }
534 if (bstate == block_done) {
535 if (flush == Z_PARTIAL_FLUSH) {
536 _tr_align(s);
537 } else { /* FULL_FLUSH or SYNC_FLUSH */
538 _tr_stored_block(s, (char*)0, 0L, 0);
539 /* For a full flush, this empty block will be recognized
540 * as a special marker by inflate_sync().
541 */
542 if (flush == Z_FULL_FLUSH) {
543 CLEAR_HASH(s); /* forget history */
544 }
545 }
546 flush_pending(strm);
547 if (strm->avail_out == 0) {
548 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
549 return Z_OK;
550 }
551 }
552 }
553 Assert(strm->avail_out > 0, "bug2");
554
555 if (flush != Z_FINISH) return Z_OK;
556 if (s->noheader) return Z_STREAM_END;
557
558 /* Write the zlib trailer (adler32) */
559 putShortMSB(s, (uInt)(strm->adler >> 16));
560 putShortMSB(s, (uInt)(strm->adler & 0xffff));
561 flush_pending(strm);
562 /* If avail_out is zero, the application will call deflate again
563 * to flush the rest.
564 */
565 s->noheader = -1; /* write the trailer only once! */
566 return s->pending != 0 ? Z_OK : Z_STREAM_END;
567 }
568
569 /* ========================================================================= */
570 int ZEXPORT deflateEnd (strm)
571 z_streamp strm;
572 {
573 int status;
574
575 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
576
577 status = strm->state->status;
578 if (status != INIT_STATE && status != BUSY_STATE &&
579 status != FINISH_STATE) {
580 return Z_STREAM_ERROR;
581 }
582
583 /* Deallocate in reverse order of allocations: */
584 TRY_FREE(strm, strm->state->pending_buf);
585 TRY_FREE(strm, strm->state->head);
586 TRY_FREE(strm, strm->state->prev);
587 TRY_FREE(strm, strm->state->window);
588
589 ZFREE(strm, strm->state);
590 strm->state = Z_NULL;
591
592 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
593 }
594
595 /* =========================================================================
596 * Copy the source state to the destination state.
597 * To simplify the source, this is not supported for 16-bit MSDOS (which
598 * doesn't have enough memory anyway to duplicate compression states).
599 */
600 int ZEXPORT deflateCopy (dest, source)
601 z_streamp dest;
602 z_streamp source;
603 {
604 #ifdef MAXSEG_64K
605 return Z_STREAM_ERROR;
606 #else
607 deflate_state *ds;
608 deflate_state *ss;
609 ushf *overlay;
610
611
612 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
613 return Z_STREAM_ERROR;
614 }
615
616 ss = source->state;
617
618 *dest = *source;
619
620 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
621 if (ds == Z_NULL) return Z_MEM_ERROR;
622 dest->state = (struct internal_state FAR *) ds;
623 *ds = *ss;
624 ds->strm = dest;
625
626 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
627 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
628 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
629 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
630 ds->pending_buf = (uchf *) overlay;
631
632 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
633 ds->pending_buf == Z_NULL) {
634 deflateEnd (dest);
635 return Z_MEM_ERROR;
636 }
637 /* following zmemcpy do not work for 16-bit MSDOS */
638 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
639 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
640 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
641 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
642
643 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
644 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
645 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
646
647 ds->l_desc.dyn_tree = ds->dyn_ltree;
648 ds->d_desc.dyn_tree = ds->dyn_dtree;
649 ds->bl_desc.dyn_tree = ds->bl_tree;
650
651 return Z_OK;
652 #endif
653 }
654
655 /* ===========================================================================
656 * Read a new buffer from the current input stream, update the adler32
657 * and total number of bytes read. All deflate() input goes through
658 * this function so some applications may wish to modify it to avoid
659 * allocating a large strm->next_in buffer and copying from it.
660 * (See also flush_pending()).
661 */
662 local int read_buf(strm, buf, size)
663 z_streamp strm;
664 Bytef *buf;
665 unsigned size;
666 {
667 unsigned len = strm->avail_in;
668
669 if (len > size) len = size;
670 if (len == 0) return 0;
671
672 strm->avail_in -= len;
673
674 if (!strm->state->noheader) {
675 strm->adler = adler32(strm->adler, strm->next_in, len);
676 }
677 zmemcpy(buf, strm->next_in, len);
678 strm->next_in += len;
679 strm->total_in += len;
680
681 return (int)len;
682 }
683
684 /* ===========================================================================
685 * Initialize the "longest match" routines for a new zlib stream
686 */
687 local void lm_init (s)
688 deflate_state *s;
689 {
690 s->window_size = (ulg)2L*s->w_size;
691
692 CLEAR_HASH(s);
693
694 /* Set the default configuration parameters:
695 */
696 s->max_lazy_match = configuration_table[s->level].max_lazy;
697 s->good_match = configuration_table[s->level].good_length;
698 s->nice_match = configuration_table[s->level].nice_length;
699 s->max_chain_length = configuration_table[s->level].max_chain;
700
701 s->strstart = 0;
702 s->block_start = 0L;
703 s->lookahead = 0;
704 s->match_length = s->prev_length = MIN_MATCH-1;
705 s->match_available = 0;
706 s->ins_h = 0;
707 #ifdef ASMV
708 match_init(); /* initialize the asm code */
709 #endif
710 }
711
712 /* ===========================================================================
713 * Set match_start to the longest match starting at the given string and
714 * return its length. Matches shorter or equal to prev_length are discarded,
715 * in which case the result is equal to prev_length and match_start is
716 * garbage.
717 * IN assertions: cur_match is the head of the hash chain for the current
718 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
719 * OUT assertion: the match length is not greater than s->lookahead.
720 */
721 #ifndef ASMV
722 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
723 * match.S. The code will be functionally equivalent.
724 */
725 #ifndef FASTEST
726 local uInt longest_match(s, cur_match)
727 deflate_state *s;
728 IPos cur_match; /* current match */
729 {
730 unsigned chain_length = s->max_chain_length;/* max hash chain length */
731 register Bytef *scan = s->window + s->strstart; /* current string */
732 register Bytef *match; /* matched string */
733 register int len; /* length of current match */
734 int best_len = s->prev_length; /* best match length so far */
735 int nice_match = s->nice_match; /* stop if match long enough */
736 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
737 s->strstart - (IPos)MAX_DIST(s) : NIL;
738 /* Stop when cur_match becomes <= limit. To simplify the code,
739 * we prevent matches with the string of window index 0.
740 */
741 Posf *prev = s->prev;
742 uInt wmask = s->w_mask;
743
744 #ifdef UNALIGNED_OK
745 /* Compare two bytes at a time. Note: this is not always beneficial.
746 * Try with and without -DUNALIGNED_OK to check.
747 */
748 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
749 register ush scan_start = *(ushf*)scan;
750 register ush scan_end = *(ushf*)(scan+best_len-1);
751 #else
752 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
753 register Byte scan_end1 = scan[best_len-1];
754 register Byte scan_end = scan[best_len];
755 #endif
756
757 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
758 * It is easy to get rid of this optimization if necessary.
759 */
760 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
761
762 /* Do not waste too much time if we already have a good match: */
763 if (s->prev_length >= s->good_match) {
764 chain_length >>= 2;
765 }
766 /* Do not look for matches beyond the end of the input. This is necessary
767 * to make deflate deterministic.
768 */
769 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
770
771 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
772
773 do {
774 Assert(cur_match < s->strstart, "no future");
775 match = s->window + cur_match;
776
777 /* Skip to next match if the match length cannot increase
778 * or if the match length is less than 2:
779 */
780 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
781 /* This code assumes sizeof(unsigned short) == 2. Do not use
782 * UNALIGNED_OK if your compiler uses a different size.
783 */
784 if (*(ushf*)(match+best_len-1) != scan_end ||
785 *(ushf*)match != scan_start) continue;
786
787 /* It is not necessary to compare scan[2] and match[2] since they are
788 * always equal when the other bytes match, given that the hash keys
789 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
790 * strstart+3, +5, ... up to strstart+257. We check for insufficient
791 * lookahead only every 4th comparison; the 128th check will be made
792 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
793 * necessary to put more guard bytes at the end of the window, or
794 * to check more often for insufficient lookahead.
795 */
796 Assert(scan[2] == match[2], "scan[2]?");
797 scan++, match++;
798 do {
799 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
800 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
801 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
802 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
803 scan < strend);
804 /* The funny "do {}" generates better code on most compilers */
805
806 /* Here, scan <= window+strstart+257 */
807 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
808 if (*scan == *match) scan++;
809
810 len = (MAX_MATCH - 1) - (int)(strend-scan);
811 scan = strend - (MAX_MATCH-1);
812
813 #else /* UNALIGNED_OK */
814
815 if (match[best_len] != scan_end ||
816 match[best_len-1] != scan_end1 ||
817 *match != *scan ||
818 *++match != scan[1]) continue;
819
820 /* The check at best_len-1 can be removed because it will be made
821 * again later. (This heuristic is not always a win.)
822 * It is not necessary to compare scan[2] and match[2] since they
823 * are always equal when the other bytes match, given that
824 * the hash keys are equal and that HASH_BITS >= 8.
825 */
826 scan += 2, match++;
827 Assert(*scan == *match, "match[2]?");
828
829 /* We check for insufficient lookahead only every 8th comparison;
830 * the 256th check will be made at strstart+258.
831 */
832 do {
833 } while (*++scan == *++match && *++scan == *++match &&
834 *++scan == *++match && *++scan == *++match &&
835 *++scan == *++match && *++scan == *++match &&
836 *++scan == *++match && *++scan == *++match &&
837 scan < strend);
838
839 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
840
841 len = MAX_MATCH - (int)(strend - scan);
842 scan = strend - MAX_MATCH;
843
844 #endif /* UNALIGNED_OK */
845
846 if (len > best_len) {
847 s->match_start = cur_match;
848 best_len = len;
849 if (len >= nice_match) break;
850 #ifdef UNALIGNED_OK
851 scan_end = *(ushf*)(scan+best_len-1);
852 #else
853 scan_end1 = scan[best_len-1];
854 scan_end = scan[best_len];
855 #endif
856 }
857 } while ((cur_match = prev[cur_match & wmask]) > limit
858 && --chain_length != 0);
859
860 if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
861 return s->lookahead;
862 }
863
864 #else /* FASTEST */
865 /* ---------------------------------------------------------------------------
866 * Optimized version for level == 1 only
867 */
868 local uInt longest_match(s, cur_match)
869 deflate_state *s;
870 IPos cur_match; /* current match */
871 {
872 register Bytef *scan = s->window + s->strstart; /* current string */
873 register Bytef *match; /* matched string */
874 register int len; /* length of current match */
875 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
876
877 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
878 * It is easy to get rid of this optimization if necessary.
879 */
880 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
881
882 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
883
884 Assert(cur_match < s->strstart, "no future");
885
886 match = s->window + cur_match;
887
888 /* Return failure if the match length is less than 2:
889 */
890 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
891
892 /* The check at best_len-1 can be removed because it will be made
893 * again later. (This heuristic is not always a win.)
894 * It is not necessary to compare scan[2] and match[2] since they
895 * are always equal when the other bytes match, given that
896 * the hash keys are equal and that HASH_BITS >= 8.
897 */
898 scan += 2, match += 2;
899 Assert(*scan == *match, "match[2]?");
900
901 /* We check for insufficient lookahead only every 8th comparison;
902 * the 256th check will be made at strstart+258.
903 */
904 do {
905 } while (*++scan == *++match && *++scan == *++match &&
906 *++scan == *++match && *++scan == *++match &&
907 *++scan == *++match && *++scan == *++match &&
908 *++scan == *++match && *++scan == *++match &&
909 scan < strend);
910
911 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
912
913 len = MAX_MATCH - (int)(strend - scan);
914
915 if (len < MIN_MATCH) return MIN_MATCH - 1;
916
917 s->match_start = cur_match;
918 return len <= s->lookahead ? len : s->lookahead;
919 }
920 #endif /* FASTEST */
921 #endif /* ASMV */
922
923 #ifdef DEBUG
924 /* ===========================================================================
925 * Check that the match at match_start is indeed a match.
926 */
927 local void check_match(s, start, match, length)
928 deflate_state *s;
929 IPos start, match;
930 int length;
931 {
932 /* check that the match is indeed a match */
933 if (zmemcmp(s->window + match,
934 s->window + start, length) != EQUAL) {
935 fprintf(stderr, " start %u, match %u, length %d\n",
936 start, match, length);
937 do {
938 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
939 } while (--length != 0);
940 z_error("invalid match");
941 }
942 if (z_verbose > 1) {
943 fprintf(stderr,"\\[%d,%d]", start-match, length);
944 do { putc(s->window[start++], stderr); } while (--length != 0);
945 }
946 }
947 #else
948 # define check_match(s, start, match, length)
949 #endif
950
951 /* ===========================================================================
952 * Fill the window when the lookahead becomes insufficient.
953 * Updates strstart and lookahead.
954 *
955 * IN assertion: lookahead < MIN_LOOKAHEAD
956 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
957 * At least one byte has been read, or avail_in == 0; reads are
958 * performed for at least two bytes (required for the zip translate_eol
959 * option -- not supported here).
960 */
961 local void fill_window(s)
962 deflate_state *s;
963 {
964 register unsigned n, m;
965 register Posf *p;
966 unsigned more; /* Amount of free space at the end of the window. */
967 uInt wsize = s->w_size;
968
969 do {
970 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
971
972 /* Deal with !@#$% 64K limit: */
973 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
974 more = wsize;
975
976 } else if (more == (unsigned)(-1)) {
977 /* Very unlikely, but possible on 16 bit machine if strstart == 0
978 * and lookahead == 1 (input done one byte at time)
979 */
980 more--;
981
982 /* If the window is almost full and there is insufficient lookahead,
983 * move the upper half to the lower one to make room in the upper half.
984 */
985 } else if (s->strstart >= wsize+MAX_DIST(s)) {
986
987 zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
988 s->match_start -= wsize;
989 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
990 s->block_start -= (long) wsize;
991
992 /* Slide the hash table (could be avoided with 32 bit values
993 at the expense of memory usage). We slide even when level == 0
994 to keep the hash table consistent if we switch back to level > 0
995 later. (Using level 0 permanently is not an optimal usage of
996 zlib, so we don't care about this pathological case.)
997 */
998 n = s->hash_size;
999 p = &s->head[n];
1000 do {
1001 m = *--p;
1002 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1003 } while (--n);
1004
1005 n = wsize;
1006 #ifndef FASTEST
1007 p = &s->prev[n];
1008 do {
1009 m = *--p;
1010 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1011 /* If n is not on any hash chain, prev[n] is garbage but
1012 * its value will never be used.
1013 */
1014 } while (--n);
1015 #endif
1016 more += wsize;
1017 }
1018 if (s->strm->avail_in == 0) return;
1019
1020 /* If there was no sliding:
1021 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1022 * more == window_size - lookahead - strstart
1023 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1024 * => more >= window_size - 2*WSIZE + 2
1025 * In the BIG_MEM or MMAP case (not yet supported),
1026 * window_size == input_size + MIN_LOOKAHEAD &&
1027 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1028 * Otherwise, window_size == 2*WSIZE so more >= 2.
1029 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1030 */
1031 Assert(more >= 2, "more < 2");
1032
1033 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1034 s->lookahead += n;
1035
1036 /* Initialize the hash value now that we have some input: */
1037 if (s->lookahead >= MIN_MATCH) {
1038 s->ins_h = s->window[s->strstart];
1039 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1040 #if MIN_MATCH != 3
1041 Call UPDATE_HASH() MIN_MATCH-3 more times
1042 #endif
1043 }
1044 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1045 * but this is not important since only literal bytes will be emitted.
1046 */
1047
1048 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1049 }
1050
1051 /* ===========================================================================
1052 * Flush the current block, with given end-of-file flag.
1053 * IN assertion: strstart is set to the end of the current match.
1054 */
1055 #define FLUSH_BLOCK_ONLY(s, eof) { \
1056 _tr_flush_block(s, (s->block_start >= 0L ? \
1057 (charf *)&s->window[(unsigned)s->block_start] : \
1058 (charf *)Z_NULL), \
1059 (ulg)((long)s->strstart - s->block_start), \
1060 (eof)); \
1061 s->block_start = s->strstart; \
1062 flush_pending(s->strm); \
1063 Tracev((stderr,"[FLUSH]")); \
1064 }
1065
1066 /* Same but force premature exit if necessary. */
1067 #define FLUSH_BLOCK(s, eof) { \
1068 FLUSH_BLOCK_ONLY(s, eof); \
1069 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
1070 }
1071
1072 /* ===========================================================================
1073 * Copy without compression as much as possible from the input stream, return
1074 * the current block state.
1075 * This function does not insert new strings in the dictionary since
1076 * uncompressible data is probably not useful. This function is used
1077 * only for the level=0 compression option.
1078 * NOTE: this function should be optimized to avoid extra copying from
1079 * window to pending_buf.
1080 */
1081 local block_state deflate_stored(s, flush)
1082 deflate_state *s;
1083 int flush;
1084 {
1085 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1086 * to pending_buf_size, and each stored block has a 5 byte header:
1087 */
1088 ulg max_block_size = 0xffff;
1089 ulg max_start;
1090
1091 if (max_block_size > s->pending_buf_size - 5) {
1092 max_block_size = s->pending_buf_size - 5;
1093 }
1094
1095 /* Copy as much as possible from input to output: */
1096 for (;;) {
1097 /* Fill the window as much as possible: */
1098 if (s->lookahead <= 1) {
1099
1100 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1101 s->block_start >= (long)s->w_size, "slide too late");
1102
1103 fill_window(s);
1104 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1105
1106 if (s->lookahead == 0) break; /* flush the current block */
1107 }
1108 Assert(s->block_start >= 0L, "block gone");
1109
1110 s->strstart += s->lookahead;
1111 s->lookahead = 0;
1112
1113 /* Emit a stored block if pending_buf will be full: */
1114 max_start = s->block_start + max_block_size;
1115 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1116 /* strstart == 0 is possible when wraparound on 16-bit machine */
1117 s->lookahead = (uInt)(s->strstart - max_start);
1118 s->strstart = (uInt)max_start;
1119 FLUSH_BLOCK(s, 0);
1120 }
1121 /* Flush if we may have to slide, otherwise block_start may become
1122 * negative and the data will be gone:
1123 */
1124 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1125 FLUSH_BLOCK(s, 0);
1126 }
1127 }
1128 FLUSH_BLOCK(s, flush == Z_FINISH);
1129 return flush == Z_FINISH ? finish_done : block_done;
1130 }
1131
1132 /* ===========================================================================
1133 * Compress as much as possible from the input stream, return the current
1134 * block state.
1135 * This function does not perform lazy evaluation of matches and inserts
1136 * new strings in the dictionary only for unmatched strings or for short
1137 * matches. It is used only for the fast compression options.
1138 */
1139 local block_state deflate_fast(s, flush)
1140 deflate_state *s;
1141 int flush;
1142 {
1143 IPos hash_head = NIL; /* head of the hash chain */
1144 int bflush; /* set if current block must be flushed */
1145
1146 for (;;) {
1147 /* Make sure that we always have enough lookahead, except
1148 * at the end of the input file. We need MAX_MATCH bytes
1149 * for the next match, plus MIN_MATCH bytes to insert the
1150 * string following the next match.
1151 */
1152 if (s->lookahead < MIN_LOOKAHEAD) {
1153 fill_window(s);
1154 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1155 return need_more;
1156 }
1157 if (s->lookahead == 0) break; /* flush the current block */
1158 }
1159
1160 /* Insert the string window[strstart .. strstart+2] in the
1161 * dictionary, and set hash_head to the head of the hash chain:
1162 */
1163 if (s->lookahead >= MIN_MATCH) {
1164 INSERT_STRING(s, s->strstart, hash_head);
1165 }
1166
1167 /* Find the longest match, discarding those <= prev_length.
1168 * At this point we have always match_length < MIN_MATCH
1169 */
1170 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1171 /* To simplify the code, we prevent matches with the string
1172 * of window index 0 (in particular we have to avoid a match
1173 * of the string with itself at the start of the input file).
1174 */
1175 if (s->strategy != Z_HUFFMAN_ONLY) {
1176 s->match_length = longest_match (s, hash_head);
1177 }
1178 /* longest_match() sets match_start */
1179 }
1180 if (s->match_length >= MIN_MATCH) {
1181 check_match(s, s->strstart, s->match_start, s->match_length);
1182
1183 _tr_tally_dist(s, s->strstart - s->match_start,
1184 s->match_length - MIN_MATCH, bflush);
1185
1186 s->lookahead -= s->match_length;
1187
1188 /* Insert new strings in the hash table only if the match length
1189 * is not too large. This saves time but degrades compression.
1190 */
1191 #ifndef FASTEST
1192 if (s->match_length <= s->max_insert_length &&
1193 s->lookahead >= MIN_MATCH) {
1194 s->match_length--; /* string at strstart already in hash table */
1195 do {
1196 s->strstart++;
1197 INSERT_STRING(s, s->strstart, hash_head);
1198 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1199 * always MIN_MATCH bytes ahead.
1200 */
1201 } while (--s->match_length != 0);
1202 s->strstart++;
1203 } else
1204 #endif
1205 {
1206 s->strstart += s->match_length;
1207 s->match_length = 0;
1208 s->ins_h = s->window[s->strstart];
1209 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1210 #if MIN_MATCH != 3
1211 Call UPDATE_HASH() MIN_MATCH-3 more times
1212 #endif
1213 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1214 * matter since it will be recomputed at next deflate call.
1215 */
1216 }
1217 } else {
1218 /* No match, output a literal byte */
1219 Tracevv((stderr,"%c", s->window[s->strstart]));
1220 _tr_tally_lit (s, s->window[s->strstart], bflush);
1221 s->lookahead--;
1222 s->strstart++;
1223 }
1224 if (bflush) FLUSH_BLOCK(s, 0);
1225 }
1226 FLUSH_BLOCK(s, flush == Z_FINISH);
1227 return flush == Z_FINISH ? finish_done : block_done;
1228 }
1229
1230 /* ===========================================================================
1231 * Same as above, but achieves better compression. We use a lazy
1232 * evaluation for matches: a match is finally adopted only if there is
1233 * no better match at the next window position.
1234 */
1235 local block_state deflate_slow(s, flush)
1236 deflate_state *s;
1237 int flush;
1238 {
1239 IPos hash_head = NIL; /* head of hash chain */
1240 int bflush; /* set if current block must be flushed */
1241
1242 /* Process the input block. */
1243 for (;;) {
1244 /* Make sure that we always have enough lookahead, except
1245 * at the end of the input file. We need MAX_MATCH bytes
1246 * for the next match, plus MIN_MATCH bytes to insert the
1247 * string following the next match.
1248 */
1249 if (s->lookahead < MIN_LOOKAHEAD) {
1250 fill_window(s);
1251 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1252 return need_more;
1253 }
1254 if (s->lookahead == 0) break; /* flush the current block */
1255 }
1256
1257 /* Insert the string window[strstart .. strstart+2] in the
1258 * dictionary, and set hash_head to the head of the hash chain:
1259 */
1260 if (s->lookahead >= MIN_MATCH) {
1261 INSERT_STRING(s, s->strstart, hash_head);
1262 }
1263
1264 /* Find the longest match, discarding those <= prev_length.
1265 */
1266 s->prev_length = s->match_length, s->prev_match = s->match_start;
1267 s->match_length = MIN_MATCH-1;
1268
1269 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1270 s->strstart - hash_head <= MAX_DIST(s)) {
1271 /* To simplify the code, we prevent matches with the string
1272 * of window index 0 (in particular we have to avoid a match
1273 * of the string with itself at the start of the input file).
1274 */
1275 if (s->strategy != Z_HUFFMAN_ONLY) {
1276 s->match_length = longest_match (s, hash_head);
1277 }
1278 /* longest_match() sets match_start */
1279
1280 if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1281 (s->match_length == MIN_MATCH &&
1282 s->strstart - s->match_start > TOO_FAR))) {
1283
1284 /* If prev_match is also MIN_MATCH, match_start is garbage
1285 * but we will ignore the current match anyway.
1286 */
1287 s->match_length = MIN_MATCH-1;
1288 }
1289 }
1290 /* If there was a match at the previous step and the current
1291 * match is not better, output the previous match:
1292 */
1293 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1294 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1295 /* Do not insert strings in hash table beyond this. */
1296
1297 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1298
1299 _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1300 s->prev_length - MIN_MATCH, bflush);
1301
1302 /* Insert in hash table all strings up to the end of the match.
1303 * strstart-1 and strstart are already inserted. If there is not
1304 * enough lookahead, the last two strings are not inserted in
1305 * the hash table.
1306 */
1307 s->lookahead -= s->prev_length-1;
1308 s->prev_length -= 2;
1309 do {
1310 if (++s->strstart <= max_insert) {
1311 INSERT_STRING(s, s->strstart, hash_head);
1312 }
1313 } while (--s->prev_length != 0);
1314 s->match_available = 0;
1315 s->match_length = MIN_MATCH-1;
1316 s->strstart++;
1317
1318 if (bflush) FLUSH_BLOCK(s, 0);
1319
1320 } else if (s->match_available) {
1321 /* If there was no match at the previous position, output a
1322 * single literal. If there was a match but the current match
1323 * is longer, truncate the previous match to a single literal.
1324 */
1325 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1326 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1327 if (bflush) {
1328 FLUSH_BLOCK_ONLY(s, 0);
1329 }
1330 s->strstart++;
1331 s->lookahead--;
1332 if (s->strm->avail_out == 0) return need_more;
1333 } else {
1334 /* There is no previous match to compare with, wait for
1335 * the next step to decide.
1336 */
1337 s->match_available = 1;
1338 s->strstart++;
1339 s->lookahead--;
1340 }
1341 }
1342 Assert (flush != Z_NO_FLUSH, "no flush?");
1343 if (s->match_available) {
1344 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1345 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1346 s->match_available = 0;
1347 }
1348 FLUSH_BLOCK(s, flush == Z_FINISH);
1349 return flush == Z_FINISH ? finish_done : block_done;
1350 }