1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2002 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 #include "common/setup_before.h"
51 #include "zlib/pvpgn_deflate.h"
52
53 const char deflate_copyright[] =
54 " deflate 1.1.4 Copyright 1995-2002 Jean-loup Gailly ";
55 /*
56 If you use the zlib library in a product, an acknowledgment is welcome
57 in the documentation of your product. If for some reason you cannot
58 include such an acknowledgment, I would appreciate that you keep this
59 copyright string in the executable of your product.
60 */
61
62 /* ===========================================================================
63 * Function prototypes.
64 */
65 typedef enum {
66 need_more, /* block not completed, need more input or more output */
67 block_done, /* block flush performed */
68 finish_started, /* finish started, need only more output at next deflate */
69 finish_done /* finish done, accept no more input or output */
70 } block_state;
71
72 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
73 /* Compression function. Returns the block state after the call. */
74
75 local void fill_window OF((deflate_state *s));
76 local block_state deflate_stored OF((deflate_state *s, int flush));
77 local block_state deflate_fast OF((deflate_state *s, int flush));
78 local block_state deflate_slow OF((deflate_state *s, int flush));
79 local void lm_init OF((deflate_state *s));
80 local void putShortMSB OF((deflate_state *s, uInt b));
81 local void flush_pending OF((z_streamp strm));
82 local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
83 #ifdef ASMV
84 void pvpgn_match_init OF((void)); /* asm code initialization */
85 uInt pvpgn_longest_match OF((deflate_state *s, IPos cur_match));
86 #else
87 local uInt longest_match OF((deflate_state *s, IPos cur_match));
88 #endif
89
90 #ifdef DEBUG
91 local void check_match OF((deflate_state *s, IPos start, IPos match,
92 int length));
93 #endif
94
95 /* ===========================================================================
96 * Local data
97 */
98
99 #define NIL 0
100 /* Tail of hash chains */
101
102 #ifndef TOO_FAR
103 # define TOO_FAR 4096
104 #endif
105 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
106
107 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
108 /* Minimum amount of lookahead, except at the end of the input file.
109 * See deflate.c for comments about the MIN_MATCH+1.
110 */
111
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.
116 */
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 */
121 ush max_chain;
122 compress_func func;
123 } config;
124
125 local const config configuration_table[10] = {
126 /* good lazy nice chain */
127 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
128 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */
129 /* 2 */ {4, 5, 16, 8, deflate_fast},
130 /* 3 */ {4, 6, 32, 32, deflate_fast},
131
132 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
133 /* 5 */ {8, 16, 32, 32, deflate_slow},
134 /* 6 */ {8, 16, 128, 128, deflate_slow},
135 /* 7 */ {8, 32, 128, 256, deflate_slow},
136 /* 8 */ {32, 128, 258, 1024, deflate_slow},
137 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
138
139 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
140 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
141 * meaning.
142 */
143
144 #define EQUAL 0
145 /* result of memcmp for equal strings */
146
147 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
148
149 /* ===========================================================================
150 * Update a hash value with the given input byte
151 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
152 * input characters, so that a running hash key can be computed from the
153 * previous key instead of complete recalculation each time.
154 */
155 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
156
157
158 /* ===========================================================================
159 * Insert string str in the dictionary and set match_head to the previous head
160 * of the hash chain (the most recent string with same hash key). Return
161 * the previous length of the hash chain.
162 * If this file is compiled with -DFASTEST, the compression level is forced
163 * to 1, and no hash chains are maintained.
164 * IN assertion: all calls to to INSERT_STRING are made with consecutive
165 * input characters and the first MIN_MATCH bytes of str are valid
166 * (except for the last MIN_MATCH-1 bytes of the input file).
167 */
168 #ifdef FASTEST
169 #define INSERT_STRING(s, str, match_head) \
170 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
171 match_head = s->head[s->ins_h], \
172 s->head[s->ins_h] = (Pos)(str))
173 #else
174 #define INSERT_STRING(s, str, match_head) \
175 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
176 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
177 s->head[s->ins_h] = (Pos)(str))
178 #endif
179
180 /* ===========================================================================
181 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
182 * prev[] will be initialized on the fly.
183 */
184 #define CLEAR_HASH(s) \
185 s->head[s->hash_size-1] = NIL; \
186 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
187
188 /* ========================================================================= */
pvpgn_deflateInit_(strm,level,version,stream_size)189 int ZEXPORT pvpgn_deflateInit_(strm, level, version, stream_size)
190 z_streamp strm;
191 int level;
192 const char *version;
193 int stream_size;
194 {
195 return pvpgn_deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
196 Z_DEFAULT_STRATEGY, version, stream_size);
197 /* To do: ignore strm->next_in if we use it as window */
198 }
199
200 /* ========================================================================= */
pvpgn_deflateInit2_(strm,level,method,windowBits,memLevel,strategy,version,stream_size)201 int ZEXPORT pvpgn_deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
202 version, stream_size)
203 z_streamp strm;
204 int level;
205 int method;
206 int windowBits;
207 int memLevel;
208 int strategy;
209 const char *version;
210 int stream_size;
211 {
212 deflate_state *s;
213 int noheader = 0;
214 static const char* my_version = ZLIB_VERSION;
215
216 ushf *overlay;
217 /* We overlay pending_buf and d_buf+l_buf. This works since the average
218 * output size for (length,distance) codes is <= 24 bits.
219 */
220
221 if (version == Z_NULL || version[0] != my_version[0] ||
222 stream_size != sizeof(z_stream)) {
223 return Z_VERSION_ERROR;
224 }
225 if (strm == Z_NULL) return Z_STREAM_ERROR;
226
227 strm->msg = Z_NULL;
228 if (strm->zalloc == Z_NULL) {
229 strm->zalloc = pvpgn_zcalloc;
230 strm->opaque = (voidpf)0;
231 }
232 if (strm->zfree == Z_NULL) strm->zfree = pvpgn_zcfree;
233
234 if (level == Z_DEFAULT_COMPRESSION) level = 6;
235 #ifdef FASTEST
236 level = 1;
237 #endif
238
239 if (windowBits < 0) { /* undocumented feature: suppress zlib header */
240 noheader = 1;
241 windowBits = -windowBits;
242 }
243 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
244 windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
245 strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
246 return Z_STREAM_ERROR;
247 }
248 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
249 if (s == Z_NULL) return Z_MEM_ERROR;
250 strm->state = (struct internal_state FAR *)s;
251 s->strm = strm;
252
253 s->noheader = noheader;
254 s->w_bits = windowBits;
255 s->w_size = 1 << s->w_bits;
256 s->w_mask = s->w_size - 1;
257
258 s->hash_bits = memLevel + 7;
259 s->hash_size = 1 << s->hash_bits;
260 s->hash_mask = s->hash_size - 1;
261 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
262
263 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
264 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
265 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
266
267 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
268
269 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
270 s->pending_buf = (uchf *) overlay;
271 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
272
273 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
274 s->pending_buf == Z_NULL) {
275 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
276 pvpgn_deflateEnd (strm);
277 return Z_MEM_ERROR;
278 }
279 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
280 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
281
282 s->level = level;
283 s->strategy = strategy;
284 s->method = (Byte)method;
285
286 return pvpgn_deflateReset(strm);
287 }
288
289 /* ========================================================================= */
pvpgn_deflateReset(strm)290 int ZEXPORT pvpgn_deflateReset (strm)
291 z_streamp strm;
292 {
293 deflate_state *s;
294
295 if (strm == Z_NULL || strm->state == Z_NULL ||
296 strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR;
297
298 strm->total_in = strm->total_out = 0;
299 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
300 strm->data_type = Z_UNKNOWN;
301
302 s = (deflate_state *)strm->state;
303 s->pending = 0;
304 s->pending_out = s->pending_buf;
305
306 if (s->noheader < 0) {
307 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
308 }
309 s->status = s->noheader ? BUSY_STATE : INIT_STATE;
310 strm->adler = 1;
311 s->last_flush = Z_NO_FLUSH;
312
313 pvpgn_tr_init(s);
314 lm_init(s);
315
316 return Z_OK;
317 }
318
319 /* =========================================================================
320 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
321 * IN assertion: the stream state is correct and there is enough room in
322 * pending_buf.
323 */
putShortMSB(s,b)324 local void putShortMSB (s, b)
325 deflate_state *s;
326 uInt b;
327 {
328 put_byte(s, (Byte)(b >> 8));
329 put_byte(s, (Byte)(b & 0xff));
330 }
331
332 /* =========================================================================
333 * Flush as much pending output as possible. All deflate() output goes
334 * through this function so some applications may wish to modify it
335 * to avoid allocating a large strm->next_out buffer and copying into it.
336 * (See also read_buf()).
337 */
flush_pending(strm)338 local void flush_pending(strm)
339 z_streamp strm;
340 {
341 unsigned len = strm->state->pending;
342
343 if (len > strm->avail_out) len = strm->avail_out;
344 if (len == 0) return;
345
346 zmemcpy(strm->next_out, strm->state->pending_out, len);
347 strm->next_out += len;
348 strm->state->pending_out += len;
349 strm->total_out += len;
350 strm->avail_out -= len;
351 strm->state->pending -= len;
352 if (strm->state->pending == 0) {
353 strm->state->pending_out = strm->state->pending_buf;
354 }
355 }
356
357 /* ========================================================================= */
pvpgn_deflate(strm,flush)358 int ZEXPORT pvpgn_deflate (strm, flush)
359 z_streamp strm;
360 int flush;
361 {
362 int old_flush; /* value of flush param for previous deflate call */
363 deflate_state *s;
364
365 if (strm == Z_NULL || strm->state == Z_NULL ||
366 flush > Z_FINISH || flush < 0) {
367 return Z_STREAM_ERROR;
368 }
369 s = strm->state;
370
371 if (strm->next_out == Z_NULL ||
372 (strm->next_in == Z_NULL && strm->avail_in != 0) ||
373 (s->status == FINISH_STATE && flush != Z_FINISH)) {
374 ERR_RETURN(strm, Z_STREAM_ERROR);
375 }
376 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
377
378 s->strm = strm; /* just in case */
379 old_flush = s->last_flush;
380 s->last_flush = flush;
381
382 /* Write the zlib header */
383 if (s->status == INIT_STATE) {
384
385 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
386 uInt level_flags = (s->level-1) >> 1;
387
388 if (level_flags > 3) level_flags = 3;
389 header |= (level_flags << 6);
390 if (s->strstart != 0) header |= PRESET_DICT;
391 header += 31 - (header % 31);
392
393 s->status = BUSY_STATE;
394 putShortMSB(s, header);
395
396 /* Save the adler32 of the preset dictionary: */
397 if (s->strstart != 0) {
398 putShortMSB(s, (uInt)(strm->adler >> 16));
399 putShortMSB(s, (uInt)(strm->adler & 0xffff));
400 }
401 strm->adler = 1L;
402 }
403
404 /* Flush as much pending output as possible */
405 if (s->pending != 0) {
406 flush_pending(strm);
407 if (strm->avail_out == 0) {
408 /* Since avail_out is 0, deflate will be called again with
409 * more output space, but possibly with both pending and
410 * avail_in equal to zero. There won't be anything to do,
411 * but this is not an error situation so make sure we
412 * return OK instead of BUF_ERROR at next call of deflate:
413 */
414 s->last_flush = -1;
415 return Z_OK;
416 }
417
418 /* Make sure there is something to do and avoid duplicate consecutive
419 * flushes. For repeated and useless calls with Z_FINISH, we keep
420 * returning Z_STREAM_END instead of Z_BUFF_ERROR.
421 */
422 } else if (strm->avail_in == 0 && flush <= old_flush &&
423 flush != Z_FINISH) {
424 ERR_RETURN(strm, Z_BUF_ERROR);
425 }
426
427 /* User must not provide more input after the first FINISH: */
428 if (s->status == FINISH_STATE && strm->avail_in != 0) {
429 ERR_RETURN(strm, Z_BUF_ERROR);
430 }
431
432 /* Start a new block or continue the current one.
433 */
434 if (strm->avail_in != 0 || s->lookahead != 0 ||
435 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
436 block_state bstate;
437
438 bstate = (*(configuration_table[s->level].func))(s, flush);
439
440 if (bstate == finish_started || bstate == finish_done) {
441 s->status = FINISH_STATE;
442 }
443 if (bstate == need_more || bstate == finish_started) {
444 if (strm->avail_out == 0) {
445 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
446 }
447 return Z_OK;
448 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
449 * of deflate should use the same flush parameter to make sure
450 * that the flush is complete. So we don't have to output an
451 * empty block here, this will be done at next call. This also
452 * ensures that for a very small output buffer, we emit at most
453 * one empty block.
454 */
455 }
456 if (bstate == block_done) {
457 if (flush == Z_PARTIAL_FLUSH) {
458 pvpgn_tr_align(s);
459 } else { /* FULL_FLUSH or SYNC_FLUSH */
460 pvpgn_tr_stored_block(s, (char*)0, 0L, 0);
461 /* For a full flush, this empty block will be recognized
462 * as a special marker by inflate_sync().
463 */
464 if (flush == Z_FULL_FLUSH) {
465 CLEAR_HASH(s); /* forget history */
466 }
467 }
468 flush_pending(strm);
469 if (strm->avail_out == 0) {
470 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
471 return Z_OK;
472 }
473 }
474 }
475 Assert(strm->avail_out > 0, "bug2");
476
477 if (flush != Z_FINISH) return Z_OK;
478 if (s->noheader) return Z_STREAM_END;
479
480 /* Write the zlib trailer (adler32) */
481 putShortMSB(s, (uInt)(strm->adler >> 16));
482 putShortMSB(s, (uInt)(strm->adler & 0xffff));
483 flush_pending(strm);
484 /* If avail_out is zero, the application will call deflate again
485 * to flush the rest.
486 */
487 s->noheader = -1; /* write the trailer only once! */
488 return s->pending != 0 ? Z_OK : Z_STREAM_END;
489 }
490
491 /* ========================================================================= */
pvpgn_deflateEnd(strm)492 int ZEXPORT pvpgn_deflateEnd (strm)
493 z_streamp strm;
494 {
495 int status;
496
497 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
498
499 status = strm->state->status;
500 if (status != INIT_STATE && status != BUSY_STATE &&
501 status != FINISH_STATE) {
502 return Z_STREAM_ERROR;
503 }
504
505 /* Deallocate in reverse order of allocations: */
506 TRY_FREE(strm, strm->state->pending_buf);
507 TRY_FREE(strm, strm->state->head);
508 TRY_FREE(strm, strm->state->prev);
509 TRY_FREE(strm, strm->state->window);
510
511 ZFREE(strm, strm->state);
512 strm->state = Z_NULL;
513
514 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
515 }
516
517 /* =========================================================================
518 * Copy the source state to the destination state.
519 * To simplify the source, this is not supported for 16-bit MSDOS (which
520 * doesn't have enough memory anyway to duplicate compression states).
521 */
pvpgn_deflateCopy(dest,source)522 int ZEXPORT pvpgn_deflateCopy (dest, source)
523 z_streamp dest;
524 z_streamp source;
525 {
526 #ifdef MAXSEG_64K
527 return Z_STREAM_ERROR;
528 #else
529 deflate_state *ds;
530 deflate_state *ss;
531 ushf *overlay;
532
533
534 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
535 return Z_STREAM_ERROR;
536 }
537
538 ss = source->state;
539
540 *dest = *source;
541
542 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
543 if (ds == Z_NULL) return Z_MEM_ERROR;
544 dest->state = (struct internal_state FAR *) ds;
545 *ds = *ss;
546 ds->strm = dest;
547
548 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
549 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
550 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
551 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
552 ds->pending_buf = (uchf *) overlay;
553
554 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
555 ds->pending_buf == Z_NULL) {
556 pvpgn_deflateEnd (dest);
557 return Z_MEM_ERROR;
558 }
559 /* following zmemcpy do not work for 16-bit MSDOS */
560 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
561 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
562 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
563 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
564
565 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
566 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
567 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
568
569 ds->l_desc.dyn_tree = ds->dyn_ltree;
570 ds->d_desc.dyn_tree = ds->dyn_dtree;
571 ds->bl_desc.dyn_tree = ds->bl_tree;
572
573 return Z_OK;
574 #endif
575 }
576
577 /* ===========================================================================
578 * Read a new buffer from the current input stream, update the adler32
579 * and total number of bytes read. All deflate() input goes through
580 * this function so some applications may wish to modify it to avoid
581 * allocating a large strm->next_in buffer and copying from it.
582 * (See also flush_pending()).
583 */
read_buf(strm,buf,size)584 local int read_buf(strm, buf, size)
585 z_streamp strm;
586 Bytef *buf;
587 unsigned size;
588 {
589 unsigned len = strm->avail_in;
590
591 if (len > size) len = size;
592 if (len == 0) return 0;
593
594 strm->avail_in -= len;
595
596 if (!strm->state->noheader) {
597 strm->adler = pvpgn_adler32(strm->adler, strm->next_in, len);
598 }
599 zmemcpy(buf, strm->next_in, len);
600 strm->next_in += len;
601 strm->total_in += len;
602
603 return (int)len;
604 }
605
606 /* ===========================================================================
607 * Initialize the "longest match" routines for a new zlib stream
608 */
lm_init(s)609 local void lm_init (s)
610 deflate_state *s;
611 {
612 s->window_size = (ulg)2L*s->w_size;
613
614 CLEAR_HASH(s);
615
616 /* Set the default configuration parameters:
617 */
618 s->max_lazy_match = configuration_table[s->level].max_lazy;
619 s->good_match = configuration_table[s->level].good_length;
620 s->nice_match = configuration_table[s->level].nice_length;
621 s->max_chain_length = configuration_table[s->level].max_chain;
622
623 s->strstart = 0;
624 s->block_start = 0L;
625 s->lookahead = 0;
626 s->match_length = s->prev_length = MIN_MATCH-1;
627 s->match_available = 0;
628 s->ins_h = 0;
629 #ifdef ASMV
630 match_init(); /* initialize the asm code */
631 #endif
632 }
633
634 /* ===========================================================================
635 * Set match_start to the longest match starting at the given string and
636 * return its length. Matches shorter or equal to prev_length are discarded,
637 * in which case the result is equal to prev_length and match_start is
638 * garbage.
639 * IN assertions: cur_match is the head of the hash chain for the current
640 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
641 * OUT assertion: the match length is not greater than s->lookahead.
642 */
643 #ifndef ASMV
644 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
645 * match.S. The code will be functionally equivalent.
646 */
647 #ifndef FASTEST
longest_match(s,cur_match)648 local uInt longest_match(s, cur_match)
649 deflate_state *s;
650 IPos cur_match; /* current match */
651 {
652 unsigned chain_length = s->max_chain_length;/* max hash chain length */
653 register Bytef *scan = s->window + s->strstart; /* current string */
654 register Bytef *match; /* matched string */
655 register int len; /* length of current match */
656 int best_len = s->prev_length; /* best match length so far */
657 int nice_match = s->nice_match; /* stop if match long enough */
658 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
659 s->strstart - (IPos)MAX_DIST(s) : NIL;
660 /* Stop when cur_match becomes <= limit. To simplify the code,
661 * we prevent matches with the string of window index 0.
662 */
663 Posf *prev = s->prev;
664 uInt wmask = s->w_mask;
665
666 #ifdef UNALIGNED_OK
667 /* Compare two bytes at a time. Note: this is not always beneficial.
668 * Try with and without -DUNALIGNED_OK to check.
669 */
670 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
671 register ush scan_start = *(ushf*)scan;
672 register ush scan_end = *(ushf*)(scan+best_len-1);
673 #else
674 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
675 register Byte scan_end1 = scan[best_len-1];
676 register Byte scan_end = scan[best_len];
677 #endif
678
679 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
680 * It is easy to get rid of this optimization if necessary.
681 */
682 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
683
684 /* Do not waste too much time if we already have a good match: */
685 if (s->prev_length >= s->good_match) {
686 chain_length >>= 2;
687 }
688 /* Do not look for matches beyond the end of the input. This is necessary
689 * to make deflate deterministic.
690 */
691 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
692
693 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
694
695 do {
696 Assert(cur_match < s->strstart, "no future");
697 match = s->window + cur_match;
698
699 /* Skip to next match if the match length cannot increase
700 * or if the match length is less than 2:
701 */
702 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
703 /* This code assumes sizeof(unsigned short) == 2. Do not use
704 * UNALIGNED_OK if your compiler uses a different size.
705 */
706 if (*(ushf*)(match+best_len-1) != scan_end ||
707 *(ushf*)match != scan_start) continue;
708
709 /* It is not necessary to compare scan[2] and match[2] since they are
710 * always equal when the other bytes match, given that the hash keys
711 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
712 * strstart+3, +5, ... up to strstart+257. We check for insufficient
713 * lookahead only every 4th comparison; the 128th check will be made
714 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
715 * necessary to put more guard bytes at the end of the window, or
716 * to check more often for insufficient lookahead.
717 */
718 Assert(scan[2] == match[2], "scan[2]?");
719 scan++, match++;
720 do {
721 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
722 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
723 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
724 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
725 scan < strend);
726 /* The funny "do {}" generates better code on most compilers */
727
728 /* Here, scan <= window+strstart+257 */
729 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
730 if (*scan == *match) scan++;
731
732 len = (MAX_MATCH - 1) - (int)(strend-scan);
733 scan = strend - (MAX_MATCH-1);
734
735 #else /* UNALIGNED_OK */
736
737 if (match[best_len] != scan_end ||
738 match[best_len-1] != scan_end1 ||
739 *match != *scan ||
740 *++match != scan[1]) continue;
741
742 /* The check at best_len-1 can be removed because it will be made
743 * again later. (This heuristic is not always a win.)
744 * It is not necessary to compare scan[2] and match[2] since they
745 * are always equal when the other bytes match, given that
746 * the hash keys are equal and that HASH_BITS >= 8.
747 */
748 scan += 2, match++;
749 Assert(*scan == *match, "match[2]?");
750
751 /* We check for insufficient lookahead only every 8th comparison;
752 * the 256th check will be made at strstart+258.
753 */
754 do {
755 } while (*++scan == *++match && *++scan == *++match &&
756 *++scan == *++match && *++scan == *++match &&
757 *++scan == *++match && *++scan == *++match &&
758 *++scan == *++match && *++scan == *++match &&
759 scan < strend);
760
761 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
762
763 len = MAX_MATCH - (int)(strend - scan);
764 scan = strend - MAX_MATCH;
765
766 #endif /* UNALIGNED_OK */
767
768 if (len > best_len) {
769 s->match_start = cur_match;
770 best_len = len;
771 if (len >= nice_match) break;
772 #ifdef UNALIGNED_OK
773 scan_end = *(ushf*)(scan+best_len-1);
774 #else
775 scan_end1 = scan[best_len-1];
776 scan_end = scan[best_len];
777 #endif
778 }
779 } while ((cur_match = prev[cur_match & wmask]) > limit
780 && --chain_length != 0);
781
782 if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
783 return s->lookahead;
784 }
785
786 #else /* FASTEST */
787 /* ---------------------------------------------------------------------------
788 * Optimized version for level == 1 only
789 */
longest_match(s,cur_match)790 local uInt longest_match(s, cur_match)
791 deflate_state *s;
792 IPos cur_match; /* current match */
793 {
794 register Bytef *scan = s->window + s->strstart; /* current string */
795 register Bytef *match; /* matched string */
796 register int len; /* length of current match */
797 register Bytef *strend = s->window + s->strstart + MAX_MATCH;
798
799 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
800 * It is easy to get rid of this optimization if necessary.
801 */
802 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
803
804 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
805
806 Assert(cur_match < s->strstart, "no future");
807
808 match = s->window + cur_match;
809
810 /* Return failure if the match length is less than 2:
811 */
812 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
813
814 /* The check at best_len-1 can be removed because it will be made
815 * again later. (This heuristic is not always a win.)
816 * It is not necessary to compare scan[2] and match[2] since they
817 * are always equal when the other bytes match, given that
818 * the hash keys are equal and that HASH_BITS >= 8.
819 */
820 scan += 2, match += 2;
821 Assert(*scan == *match, "match[2]?");
822
823 /* We check for insufficient lookahead only every 8th comparison;
824 * the 256th check will be made at strstart+258.
825 */
826 do {
827 } while (*++scan == *++match && *++scan == *++match &&
828 *++scan == *++match && *++scan == *++match &&
829 *++scan == *++match && *++scan == *++match &&
830 *++scan == *++match && *++scan == *++match &&
831 scan < strend);
832
833 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
834
835 len = MAX_MATCH - (int)(strend - scan);
836
837 if (len < MIN_MATCH) return MIN_MATCH - 1;
838
839 s->match_start = cur_match;
840 return len <= s->lookahead ? len : s->lookahead;
841 }
842 #endif /* FASTEST */
843 #endif /* ASMV */
844
845 #ifdef DEBUG
846 /* ===========================================================================
847 * Check that the match at match_start is indeed a match.
848 */
check_match(s,start,match,length)849 local void check_match(s, start, match, length)
850 deflate_state *s;
851 IPos start, match;
852 int length;
853 {
854 /* check that the match is indeed a match */
855 if (zmemcmp(s->window + match,
856 s->window + start, length) != EQUAL) {
857 fprintf(stderr, " start %u, match %u, length %d\n",
858 start, match, length);
859 do {
860 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
861 } while (--length != 0);
862 z_error("invalid match");
863 }
864 if (z_verbose > 1) {
865 fprintf(stderr,"\\[%d,%d]", start-match, length);
866 do { putc(s->window[start++], stderr); } while (--length != 0);
867 }
868 }
869 #else
870 # define check_match(s, start, match, length)
871 #endif
872
873 /* ===========================================================================
874 * Fill the window when the lookahead becomes insufficient.
875 * Updates strstart and lookahead.
876 *
877 * IN assertion: lookahead < MIN_LOOKAHEAD
878 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
879 * At least one byte has been read, or avail_in == 0; reads are
880 * performed for at least two bytes (required for the zip translate_eol
881 * option -- not supported here).
882 */
fill_window(s)883 local void fill_window(s)
884 deflate_state *s;
885 {
886 register unsigned n, m;
887 register Posf *p;
888 unsigned more; /* Amount of free space at the end of the window. */
889 uInt wsize = s->w_size;
890
891 do {
892 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
893
894 /* Deal with !@#$% 64K limit: */
895 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
896 more = wsize;
897
898 } else if (more == (unsigned)(-1)) {
899 /* Very unlikely, but possible on 16 bit machine if strstart == 0
900 * and lookahead == 1 (input done one byte at time)
901 */
902 more--;
903
904 /* If the window is almost full and there is insufficient lookahead,
905 * move the upper half to the lower one to make room in the upper half.
906 */
907 } else if (s->strstart >= wsize+MAX_DIST(s)) {
908
909 zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
910 s->match_start -= wsize;
911 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
912 s->block_start -= (long) wsize;
913
914 /* Slide the hash table (could be avoided with 32 bit values
915 at the expense of memory usage). We slide even when level == 0
916 to keep the hash table consistent if we switch back to level > 0
917 later. (Using level 0 permanently is not an optimal usage of
918 zlib, so we don't care about this pathological case.)
919 */
920 n = s->hash_size;
921 p = &s->head[n];
922 do {
923 m = *--p;
924 *p = (Pos)(m >= wsize ? m-wsize : NIL);
925 } while (--n);
926
927 n = wsize;
928 #ifndef FASTEST
929 p = &s->prev[n];
930 do {
931 m = *--p;
932 *p = (Pos)(m >= wsize ? m-wsize : NIL);
933 /* If n is not on any hash chain, prev[n] is garbage but
934 * its value will never be used.
935 */
936 } while (--n);
937 #endif
938 more += wsize;
939 }
940 if (s->strm->avail_in == 0) return;
941
942 /* If there was no sliding:
943 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
944 * more == window_size - lookahead - strstart
945 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
946 * => more >= window_size - 2*WSIZE + 2
947 * In the BIG_MEM or MMAP case (not yet supported),
948 * window_size == input_size + MIN_LOOKAHEAD &&
949 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
950 * Otherwise, window_size == 2*WSIZE so more >= 2.
951 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
952 */
953 Assert(more >= 2, "more < 2");
954
955 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
956 s->lookahead += n;
957
958 /* Initialize the hash value now that we have some input: */
959 if (s->lookahead >= MIN_MATCH) {
960 s->ins_h = s->window[s->strstart];
961 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
962 #if MIN_MATCH != 3
963 Call UPDATE_HASH() MIN_MATCH-3 more times
964 #endif
965 }
966 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
967 * but this is not important since only literal bytes will be emitted.
968 */
969
970 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
971 }
972
973 /* ===========================================================================
974 * Flush the current block, with given end-of-file flag.
975 * IN assertion: strstart is set to the end of the current match.
976 */
977 #define FLUSH_BLOCK_ONLY(s, eof) { \
978 pvpgn_tr_flush_block(s, (s->block_start >= 0L ? \
979 (charf *)&s->window[(unsigned)s->block_start] : \
980 (charf *)Z_NULL), \
981 (ulg)((long)s->strstart - s->block_start), \
982 (eof)); \
983 s->block_start = s->strstart; \
984 flush_pending(s->strm); \
985 Tracev((stderr,"[FLUSH]")); \
986 }
987
988 /* Same but force premature exit if necessary. */
989 #define FLUSH_BLOCK(s, eof) { \
990 FLUSH_BLOCK_ONLY(s, eof); \
991 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
992 }
993
994 /* ===========================================================================
995 * Copy without compression as much as possible from the input stream, return
996 * the current block state.
997 * This function does not insert new strings in the dictionary since
998 * uncompressible data is probably not useful. This function is used
999 * only for the level=0 compression option.
1000 * NOTE: this function should be optimized to avoid extra copying from
1001 * window to pending_buf.
1002 */
deflate_stored(s,flush)1003 local block_state deflate_stored(s, flush)
1004 deflate_state *s;
1005 int flush;
1006 {
1007 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1008 * to pending_buf_size, and each stored block has a 5 byte header:
1009 */
1010 ulg max_block_size = 0xffff;
1011 ulg max_start;
1012
1013 if (max_block_size > s->pending_buf_size - 5) {
1014 max_block_size = s->pending_buf_size - 5;
1015 }
1016
1017 /* Copy as much as possible from input to output: */
1018 for (;;) {
1019 /* Fill the window as much as possible: */
1020 if (s->lookahead <= 1) {
1021
1022 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1023 s->block_start >= (long)s->w_size, "slide too late");
1024
1025 fill_window(s);
1026 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1027
1028 if (s->lookahead == 0) break; /* flush the current block */
1029 }
1030 Assert(s->block_start >= 0L, "block gone");
1031
1032 s->strstart += s->lookahead;
1033 s->lookahead = 0;
1034
1035 /* Emit a stored block if pending_buf will be full: */
1036 max_start = s->block_start + max_block_size;
1037 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1038 /* strstart == 0 is possible when wraparound on 16-bit machine */
1039 s->lookahead = (uInt)(s->strstart - max_start);
1040 s->strstart = (uInt)max_start;
1041 FLUSH_BLOCK(s, 0);
1042 }
1043 /* Flush if we may have to slide, otherwise block_start may become
1044 * negative and the data will be gone:
1045 */
1046 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1047 FLUSH_BLOCK(s, 0);
1048 }
1049 }
1050 FLUSH_BLOCK(s, flush == Z_FINISH);
1051 return flush == Z_FINISH ? finish_done : block_done;
1052 }
1053
1054 /* ===========================================================================
1055 * Compress as much as possible from the input stream, return the current
1056 * block state.
1057 * This function does not perform lazy evaluation of matches and inserts
1058 * new strings in the dictionary only for unmatched strings or for short
1059 * matches. It is used only for the fast compression options.
1060 */
deflate_fast(s,flush)1061 local block_state deflate_fast(s, flush)
1062 deflate_state *s;
1063 int flush;
1064 {
1065 IPos hash_head = NIL; /* head of the hash chain */
1066 int bflush; /* set if current block must be flushed */
1067
1068 for (;;) {
1069 /* Make sure that we always have enough lookahead, except
1070 * at the end of the input file. We need MAX_MATCH bytes
1071 * for the next match, plus MIN_MATCH bytes to insert the
1072 * string following the next match.
1073 */
1074 if (s->lookahead < MIN_LOOKAHEAD) {
1075 fill_window(s);
1076 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1077 return need_more;
1078 }
1079 if (s->lookahead == 0) break; /* flush the current block */
1080 }
1081
1082 /* Insert the string window[strstart .. strstart+2] in the
1083 * dictionary, and set hash_head to the head of the hash chain:
1084 */
1085 if (s->lookahead >= MIN_MATCH) {
1086 INSERT_STRING(s, s->strstart, hash_head);
1087 }
1088
1089 /* Find the longest match, discarding those <= prev_length.
1090 * At this point we have always match_length < MIN_MATCH
1091 */
1092 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1093 /* To simplify the code, we prevent matches with the string
1094 * of window index 0 (in particular we have to avoid a match
1095 * of the string with itself at the start of the input file).
1096 */
1097 if (s->strategy != Z_HUFFMAN_ONLY) {
1098 s->match_length = longest_match (s, hash_head);
1099 }
1100 /* longest_match() sets match_start */
1101 }
1102 if (s->match_length >= MIN_MATCH) {
1103 check_match(s, s->strstart, s->match_start, s->match_length);
1104
1105 _tr_tally_dist(s, s->strstart - s->match_start,
1106 s->match_length - MIN_MATCH, bflush);
1107
1108 s->lookahead -= s->match_length;
1109
1110 /* Insert new strings in the hash table only if the match length
1111 * is not too large. This saves time but degrades compression.
1112 */
1113 #ifndef FASTEST
1114 if (s->match_length <= s->max_insert_length &&
1115 s->lookahead >= MIN_MATCH) {
1116 s->match_length--; /* string at strstart already in hash table */
1117 do {
1118 s->strstart++;
1119 INSERT_STRING(s, s->strstart, hash_head);
1120 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1121 * always MIN_MATCH bytes ahead.
1122 */
1123 } while (--s->match_length != 0);
1124 s->strstart++;
1125 } else
1126 #endif
1127 {
1128 s->strstart += s->match_length;
1129 s->match_length = 0;
1130 s->ins_h = s->window[s->strstart];
1131 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1132 #if MIN_MATCH != 3
1133 Call UPDATE_HASH() MIN_MATCH-3 more times
1134 #endif
1135 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1136 * matter since it will be recomputed at next deflate call.
1137 */
1138 }
1139 } else {
1140 /* No match, output a literal byte */
1141 Tracevv((stderr,"%c", s->window[s->strstart]));
1142 _tr_tally_lit (s, s->window[s->strstart], bflush);
1143 s->lookahead--;
1144 s->strstart++;
1145 }
1146 if (bflush) FLUSH_BLOCK(s, 0);
1147 }
1148 FLUSH_BLOCK(s, flush == Z_FINISH);
1149 return flush == Z_FINISH ? finish_done : block_done;
1150 }
1151
1152 /* ===========================================================================
1153 * Same as above, but achieves better compression. We use a lazy
1154 * evaluation for matches: a match is finally adopted only if there is
1155 * no better match at the next window position.
1156 */
deflate_slow(s,flush)1157 local block_state deflate_slow(s, flush)
1158 deflate_state *s;
1159 int flush;
1160 {
1161 IPos hash_head = NIL; /* head of hash chain */
1162 int bflush; /* set if current block must be flushed */
1163
1164 /* Process the input block. */
1165 for (;;) {
1166 /* Make sure that we always have enough lookahead, except
1167 * at the end of the input file. We need MAX_MATCH bytes
1168 * for the next match, plus MIN_MATCH bytes to insert the
1169 * string following the next match.
1170 */
1171 if (s->lookahead < MIN_LOOKAHEAD) {
1172 fill_window(s);
1173 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1174 return need_more;
1175 }
1176 if (s->lookahead == 0) break; /* flush the current block */
1177 }
1178
1179 /* Insert the string window[strstart .. strstart+2] in the
1180 * dictionary, and set hash_head to the head of the hash chain:
1181 */
1182 if (s->lookahead >= MIN_MATCH) {
1183 INSERT_STRING(s, s->strstart, hash_head);
1184 }
1185
1186 /* Find the longest match, discarding those <= prev_length.
1187 */
1188 s->prev_length = s->match_length, s->prev_match = s->match_start;
1189 s->match_length = MIN_MATCH-1;
1190
1191 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1192 s->strstart - hash_head <= MAX_DIST(s)) {
1193 /* To simplify the code, we prevent matches with the string
1194 * of window index 0 (in particular we have to avoid a match
1195 * of the string with itself at the start of the input file).
1196 */
1197 if (s->strategy != Z_HUFFMAN_ONLY) {
1198 s->match_length = longest_match (s, hash_head);
1199 }
1200 /* longest_match() sets match_start */
1201
1202 if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1203 (s->match_length == MIN_MATCH &&
1204 s->strstart - s->match_start > TOO_FAR))) {
1205
1206 /* If prev_match is also MIN_MATCH, match_start is garbage
1207 * but we will ignore the current match anyway.
1208 */
1209 s->match_length = MIN_MATCH-1;
1210 }
1211 }
1212 /* If there was a match at the previous step and the current
1213 * match is not better, output the previous match:
1214 */
1215 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1216 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1217 /* Do not insert strings in hash table beyond this. */
1218
1219 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1220
1221 _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1222 s->prev_length - MIN_MATCH, bflush);
1223
1224 /* Insert in hash table all strings up to the end of the match.
1225 * strstart-1 and strstart are already inserted. If there is not
1226 * enough lookahead, the last two strings are not inserted in
1227 * the hash table.
1228 */
1229 s->lookahead -= s->prev_length-1;
1230 s->prev_length -= 2;
1231 do {
1232 if (++s->strstart <= max_insert) {
1233 INSERT_STRING(s, s->strstart, hash_head);
1234 }
1235 } while (--s->prev_length != 0);
1236 s->match_available = 0;
1237 s->match_length = MIN_MATCH-1;
1238 s->strstart++;
1239
1240 if (bflush) FLUSH_BLOCK(s, 0);
1241
1242 } else if (s->match_available) {
1243 /* If there was no match at the previous position, output a
1244 * single literal. If there was a match but the current match
1245 * is longer, truncate the previous match to a single literal.
1246 */
1247 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1248 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1249 if (bflush) {
1250 FLUSH_BLOCK_ONLY(s, 0);
1251 }
1252 s->strstart++;
1253 s->lookahead--;
1254 if (s->strm->avail_out == 0) return need_more;
1255 } else {
1256 /* There is no previous match to compare with, wait for
1257 * the next step to decide.
1258 */
1259 s->match_available = 1;
1260 s->strstart++;
1261 s->lookahead--;
1262 }
1263 }
1264 Assert (flush != Z_NO_FLUSH, "no flush?");
1265 if (s->match_available) {
1266 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1267 _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1268 s->match_available = 0;
1269 }
1270 FLUSH_BLOCK(s, flush == Z_FINISH);
1271 return flush == Z_FINISH ? finish_done : block_done;
1272 }
1273