1 /* +++ deflate.c */
2 /* deflate.c -- compress data using the deflation algorithm
3 * Copyright (C) 1995-1996 Jean-loup Gailly.
4 * For conditions of distribution and use, see copyright notice in zlib.h
5 */
6
7 /*
8 * ALGORITHM
9 *
10 * The "deflation" process depends on being able to identify portions
11 * of the input text which are identical to earlier input (within a
12 * sliding window trailing behind the input currently being processed).
13 *
14 * The most straightforward technique turns out to be the fastest for
15 * most input files: try all possible matches and select the longest.
16 * The key feature of this algorithm is that insertions into the string
17 * dictionary are very simple and thus fast, and deletions are avoided
18 * completely. Insertions are performed at each input character, whereas
19 * string matches are performed only when the previous match ends. So it
20 * is preferable to spend more time in matches to allow very fast string
21 * insertions and avoid deletions. The matching algorithm for small
22 * strings is inspired from that of Rabin & Karp. A brute force approach
23 * is used to find longer strings when a small match has been found.
24 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
25 * (by Leonid Broukhis).
26 * A previous version of this file used a more sophisticated algorithm
27 * (by Fiala and Greene) which is guaranteed to run in linear amortized
28 * time, but has a larger average cost, uses more memory and is patented.
29 * However the F&G algorithm may be faster for some highly redundant
30 * files if the parameter max_chain_length (described below) is too large.
31 *
32 * ACKNOWLEDGEMENTS
33 *
34 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
35 * I found it in 'freeze' written by Leonid Broukhis.
36 * Thanks to many people for bug reports and testing.
37 *
38 * REFERENCES
39 *
40 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
41 * Available in ftp://ds.internic.net/rfc/rfc1951.txt
42 *
43 * A description of the Rabin and Karp algorithm is given in the book
44 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
45 *
46 * Fiala,E.R., and Greene,D.H.
47 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
48 *
49 */
50
51 #include <linux/module.h>
52 #include <linux/zutil.h>
53 #include "defutil.h"
54
55
56 /* ===========================================================================
57 * Function prototypes.
58 */
59 typedef enum {
60 need_more, /* block not completed, need more input or more output */
61 block_done, /* block flush performed */
62 finish_started, /* finish started, need only more output at next deflate */
63 finish_done /* finish done, accept no more input or output */
64 } block_state;
65
66 typedef block_state (*compress_func) (deflate_state *s, int flush);
67 /* Compression function. Returns the block state after the call. */
68
69 static void fill_window (deflate_state *s);
70 static block_state deflate_stored (deflate_state *s, int flush);
71 static block_state deflate_fast (deflate_state *s, int flush);
72 static block_state deflate_slow (deflate_state *s, int flush);
73 static void lm_init (deflate_state *s);
74 static void putShortMSB (deflate_state *s, uInt b);
75 static void flush_pending (z_streamp strm);
76 static int read_buf (z_streamp strm, Byte *buf, unsigned size);
77 static uInt longest_match (deflate_state *s, IPos cur_match);
78
79 #ifdef DEBUG_ZLIB
80 static void check_match (deflate_state *s, IPos start, IPos match,
81 int length);
82 #endif
83
84 /* ===========================================================================
85 * Local data
86 */
87
88 #define NIL 0
89 /* Tail of hash chains */
90
91 #ifndef TOO_FAR
92 # define TOO_FAR 4096
93 #endif
94 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
95
96 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
97 /* Minimum amount of lookahead, except at the end of the input file.
98 * See deflate.c for comments about the MIN_MATCH+1.
99 */
100
101 /* Values for max_lazy_match, good_match and max_chain_length, depending on
102 * the desired pack level (0..9). The values given below have been tuned to
103 * exclude worst case performance for pathological files. Better values may be
104 * found for specific files.
105 */
106 typedef struct config_s {
107 ush good_length; /* reduce lazy search above this match length */
108 ush max_lazy; /* do not perform lazy search above this match length */
109 ush nice_length; /* quit search above this match length */
110 ush max_chain;
111 compress_func func;
112 } config;
113
114 static const config configuration_table[10] = {
115 /* good lazy nice chain */
116 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
117 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */
118 /* 2 */ {4, 5, 16, 8, deflate_fast},
119 /* 3 */ {4, 6, 32, 32, deflate_fast},
120
121 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
122 /* 5 */ {8, 16, 32, 32, deflate_slow},
123 /* 6 */ {8, 16, 128, 128, deflate_slow},
124 /* 7 */ {8, 32, 128, 256, deflate_slow},
125 /* 8 */ {32, 128, 258, 1024, deflate_slow},
126 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
127
128 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
129 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
130 * meaning.
131 */
132
133 #define EQUAL 0
134 /* result of memcmp for equal strings */
135
136 /* ===========================================================================
137 * Update a hash value with the given input byte
138 * IN assertion: all calls to UPDATE_HASH are made with consecutive
139 * input characters, so that a running hash key can be computed from the
140 * previous key instead of complete recalculation each time.
141 */
142 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
143
144
145 /* ===========================================================================
146 * Insert string str in the dictionary and set match_head to the previous head
147 * of the hash chain (the most recent string with same hash key). Return
148 * the previous length of the hash chain.
149 * IN assertion: all calls to INSERT_STRING are made with consecutive
150 * input characters and the first MIN_MATCH bytes of str are valid
151 * (except for the last MIN_MATCH-1 bytes of the input file).
152 */
153 #define INSERT_STRING(s, str, match_head) \
154 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
155 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
156 s->head[s->ins_h] = (Pos)(str))
157
158 /* ===========================================================================
159 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
160 * prev[] will be initialized on the fly.
161 */
162 #define CLEAR_HASH(s) \
163 s->head[s->hash_size-1] = NIL; \
164 memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));
165
166 /* ========================================================================= */
167 int zlib_deflateInit2(
168 z_streamp strm,
169 int level,
170 int method,
171 int windowBits,
172 int memLevel,
173 int strategy
174 )
175 {
176 deflate_state *s;
177 int noheader = 0;
178 deflate_workspace *mem;
179 char *next;
180
181 ush *overlay;
182 /* We overlay pending_buf and d_buf+l_buf. This works since the average
183 * output size for (length,distance) codes is <= 24 bits.
184 */
185
186 if (strm == NULL) return Z_STREAM_ERROR;
187
188 strm->msg = NULL;
189
190 if (level == Z_DEFAULT_COMPRESSION) level = 6;
191
192 mem = (deflate_workspace *) strm->workspace;
193
194 if (windowBits < 0) { /* undocumented feature: suppress zlib header */
195 noheader = 1;
196 windowBits = -windowBits;
197 }
198 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
199 windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
200 strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
201 return Z_STREAM_ERROR;
202 }
203
204 /*
205 * Direct the workspace's pointers to the chunks that were allocated
206 * along with the deflate_workspace struct.
207 */
208 next = (char *) mem;
209 next += sizeof(*mem);
210 mem->window_memory = (Byte *) next;
211 next += zlib_deflate_window_memsize(windowBits);
212 mem->prev_memory = (Pos *) next;
213 next += zlib_deflate_prev_memsize(windowBits);
214 mem->head_memory = (Pos *) next;
215 next += zlib_deflate_head_memsize(memLevel);
216 mem->overlay_memory = next;
217
218 s = (deflate_state *) &(mem->deflate_memory);
219 strm->state = (struct internal_state *)s;
220 s->strm = strm;
221
222 s->noheader = noheader;
223 s->w_bits = windowBits;
224 s->w_size = 1 << s->w_bits;
225 s->w_mask = s->w_size - 1;
226
227 s->hash_bits = memLevel + 7;
228 s->hash_size = 1 << s->hash_bits;
229 s->hash_mask = s->hash_size - 1;
230 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
231
232 s->window = (Byte *) mem->window_memory;
233 s->prev = (Pos *) mem->prev_memory;
234 s->head = (Pos *) mem->head_memory;
235
236 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
237
238 overlay = (ush *) mem->overlay_memory;
239 s->pending_buf = (uch *) overlay;
240 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
241
242 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
243 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
244
245 s->level = level;
246 s->strategy = strategy;
247 s->method = (Byte)method;
248
249 return zlib_deflateReset(strm);
250 }
251
252 /* ========================================================================= */
253 int zlib_deflateReset(
254 z_streamp strm
255 )
256 {
257 deflate_state *s;
258
259 if (strm == NULL || strm->state == NULL)
260 return Z_STREAM_ERROR;
261
262 strm->total_in = strm->total_out = 0;
263 strm->msg = NULL;
264 strm->data_type = Z_UNKNOWN;
265
266 s = (deflate_state *)strm->state;
267 s->pending = 0;
268 s->pending_out = s->pending_buf;
269
270 if (s->noheader < 0) {
271 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
272 }
273 s->status = s->noheader ? BUSY_STATE : INIT_STATE;
274 strm->adler = 1;
275 s->last_flush = Z_NO_FLUSH;
276
277 zlib_tr_init(s);
278 lm_init(s);
279
280 return Z_OK;
281 }
282
283 /* =========================================================================
284 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
285 * IN assertion: the stream state is correct and there is enough room in
286 * pending_buf.
287 */
288 static void putShortMSB(
289 deflate_state *s,
290 uInt b
291 )
292 {
293 put_byte(s, (Byte)(b >> 8));
294 put_byte(s, (Byte)(b & 0xff));
295 }
296
297 /* =========================================================================
298 * Flush as much pending output as possible. All deflate() output goes
299 * through this function so some applications may wish to modify it
300 * to avoid allocating a large strm->next_out buffer and copying into it.
301 * (See also read_buf()).
302 */
303 static void flush_pending(
304 z_streamp strm
305 )
306 {
307 deflate_state *s = (deflate_state *) strm->state;
308 unsigned len = s->pending;
309
310 if (len > strm->avail_out) len = strm->avail_out;
311 if (len == 0) return;
312
313 if (strm->next_out != NULL) {
314 memcpy(strm->next_out, s->pending_out, len);
315 strm->next_out += len;
316 }
317 s->pending_out += len;
318 strm->total_out += len;
319 strm->avail_out -= len;
320 s->pending -= len;
321 if (s->pending == 0) {
322 s->pending_out = s->pending_buf;
323 }
324 }
325
326 /* ========================================================================= */
327 int zlib_deflate(
328 z_streamp strm,
329 int flush
330 )
331 {
332 int old_flush; /* value of flush param for previous deflate call */
333 deflate_state *s;
334
335 if (strm == NULL || strm->state == NULL ||
336 flush > Z_FINISH || flush < 0) {
337 return Z_STREAM_ERROR;
338 }
339 s = (deflate_state *) strm->state;
340
341 if ((strm->next_in == NULL && strm->avail_in != 0) ||
342 (s->status == FINISH_STATE && flush != Z_FINISH)) {
343 return Z_STREAM_ERROR;
344 }
345 if (strm->avail_out == 0) return Z_BUF_ERROR;
346
347 s->strm = strm; /* just in case */
348 old_flush = s->last_flush;
349 s->last_flush = flush;
350
351 /* Write the zlib header */
352 if (s->status == INIT_STATE) {
353
354 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
355 uInt level_flags = (s->level-1) >> 1;
356
357 if (level_flags > 3) level_flags = 3;
358 header |= (level_flags << 6);
359 if (s->strstart != 0) header |= PRESET_DICT;
360 header += 31 - (header % 31);
361
362 s->status = BUSY_STATE;
363 putShortMSB(s, header);
364
365 /* Save the adler32 of the preset dictionary: */
366 if (s->strstart != 0) {
367 putShortMSB(s, (uInt)(strm->adler >> 16));
368 putShortMSB(s, (uInt)(strm->adler & 0xffff));
369 }
370 strm->adler = 1L;
371 }
372
373 /* Flush as much pending output as possible */
374 if (s->pending != 0) {
375 flush_pending(strm);
376 if (strm->avail_out == 0) {
377 /* Since avail_out is 0, deflate will be called again with
378 * more output space, but possibly with both pending and
379 * avail_in equal to zero. There won't be anything to do,
380 * but this is not an error situation so make sure we
381 * return OK instead of BUF_ERROR at next call of deflate:
382 */
383 s->last_flush = -1;
384 return Z_OK;
385 }
386
387 /* Make sure there is something to do and avoid duplicate consecutive
388 * flushes. For repeated and useless calls with Z_FINISH, we keep
389 * returning Z_STREAM_END instead of Z_BUFF_ERROR.
390 */
391 } else if (strm->avail_in == 0 && flush <= old_flush &&
392 flush != Z_FINISH) {
393 return Z_BUF_ERROR;
394 }
395
396 /* User must not provide more input after the first FINISH: */
397 if (s->status == FINISH_STATE && strm->avail_in != 0) {
398 return Z_BUF_ERROR;
399 }
400
401 /* Start a new block or continue the current one.
402 */
403 if (strm->avail_in != 0 || s->lookahead != 0 ||
404 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
405 block_state bstate;
406
407 bstate = (*(configuration_table[s->level].func))(s, flush);
408
409 if (bstate == finish_started || bstate == finish_done) {
410 s->status = FINISH_STATE;
411 }
412 if (bstate == need_more || bstate == finish_started) {
413 if (strm->avail_out == 0) {
414 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
415 }
416 return Z_OK;
417 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
418 * of deflate should use the same flush parameter to make sure
419 * that the flush is complete. So we don't have to output an
420 * empty block here, this will be done at next call. This also
421 * ensures that for a very small output buffer, we emit at most
422 * one empty block.
423 */
424 }
425 if (bstate == block_done) {
426 if (flush == Z_PARTIAL_FLUSH) {
427 zlib_tr_align(s);
428 } else if (flush == Z_PACKET_FLUSH) {
429 /* Output just the 3-bit `stored' block type value,
430 but not a zero length. */
431 zlib_tr_stored_type_only(s);
432 } else { /* FULL_FLUSH or SYNC_FLUSH */
433 zlib_tr_stored_block(s, (char*)0, 0L, 0);
434 /* For a full flush, this empty block will be recognized
435 * as a special marker by inflate_sync().
436 */
437 if (flush == Z_FULL_FLUSH) {
438 CLEAR_HASH(s); /* forget history */
439 }
440 }
441 flush_pending(strm);
442 if (strm->avail_out == 0) {
443 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
444 return Z_OK;
445 }
446 }
447 }
448 Assert(strm->avail_out > 0, "bug2");
449
450 if (flush != Z_FINISH) return Z_OK;
451 if (s->noheader) return Z_STREAM_END;
452
453 /* Write the zlib trailer (adler32) */
454 putShortMSB(s, (uInt)(strm->adler >> 16));
455 putShortMSB(s, (uInt)(strm->adler & 0xffff));
456 flush_pending(strm);
457 /* If avail_out is zero, the application will call deflate again
458 * to flush the rest.
459 */
460 s->noheader = -1; /* write the trailer only once! */
461 return s->pending != 0 ? Z_OK : Z_STREAM_END;
462 }
463
464 /* ========================================================================= */
465 int zlib_deflateEnd(
466 z_streamp strm
467 )
468 {
469 int status;
470 deflate_state *s;
471
472 if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
473 s = (deflate_state *) strm->state;
474
475 status = s->status;
476 if (status != INIT_STATE && status != BUSY_STATE &&
477 status != FINISH_STATE) {
478 return Z_STREAM_ERROR;
479 }
480
481 strm->state = NULL;
482
483 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
484 }
485
486 /* ===========================================================================
487 * Read a new buffer from the current input stream, update the adler32
488 * and total number of bytes read. All deflate() input goes through
489 * this function so some applications may wish to modify it to avoid
490 * allocating a large strm->next_in buffer and copying from it.
491 * (See also flush_pending()).
492 */
493 static int read_buf(
494 z_streamp strm,
495 Byte *buf,
496 unsigned size
497 )
498 {
499 unsigned len = strm->avail_in;
500
501 if (len > size) len = size;
502 if (len == 0) return 0;
503
504 strm->avail_in -= len;
505
506 if (!((deflate_state *)(strm->state))->noheader) {
507 strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
508 }
509 memcpy(buf, strm->next_in, len);
510 strm->next_in += len;
511 strm->total_in += len;
512
513 return (int)len;
514 }
515
516 /* ===========================================================================
517 * Initialize the "longest match" routines for a new zlib stream
518 */
519 static void lm_init(
520 deflate_state *s
521 )
522 {
523 s->window_size = (ulg)2L*s->w_size;
524
525 CLEAR_HASH(s);
526
527 /* Set the default configuration parameters:
528 */
529 s->max_lazy_match = configuration_table[s->level].max_lazy;
530 s->good_match = configuration_table[s->level].good_length;
531 s->nice_match = configuration_table[s->level].nice_length;
532 s->max_chain_length = configuration_table[s->level].max_chain;
533
534 s->strstart = 0;
535 s->block_start = 0L;
536 s->lookahead = 0;
537 s->match_length = s->prev_length = MIN_MATCH-1;
538 s->match_available = 0;
539 s->ins_h = 0;
540 }
541
542 /* ===========================================================================
543 * Set match_start to the longest match starting at the given string and
544 * return its length. Matches shorter or equal to prev_length are discarded,
545 * in which case the result is equal to prev_length and match_start is
546 * garbage.
547 * IN assertions: cur_match is the head of the hash chain for the current
548 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
549 * OUT assertion: the match length is not greater than s->lookahead.
550 */
551 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
552 * match.S. The code will be functionally equivalent.
553 */
554 static uInt longest_match(
555 deflate_state *s,
556 IPos cur_match /* current match */
557 )
558 {
559 unsigned chain_length = s->max_chain_length;/* max hash chain length */
560 register Byte *scan = s->window + s->strstart; /* current string */
561 register Byte *match; /* matched string */
562 register int len; /* length of current match */
563 int best_len = s->prev_length; /* best match length so far */
564 int nice_match = s->nice_match; /* stop if match long enough */
565 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
566 s->strstart - (IPos)MAX_DIST(s) : NIL;
567 /* Stop when cur_match becomes <= limit. To simplify the code,
568 * we prevent matches with the string of window index 0.
569 */
570 Pos *prev = s->prev;
571 uInt wmask = s->w_mask;
572
573 #ifdef UNALIGNED_OK
574 /* Compare two bytes at a time. Note: this is not always beneficial.
575 * Try with and without -DUNALIGNED_OK to check.
576 */
577 register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
578 register ush scan_start = *(ush*)scan;
579 register ush scan_end = *(ush*)(scan+best_len-1);
580 #else
581 register Byte *strend = s->window + s->strstart + MAX_MATCH;
582 register Byte scan_end1 = scan[best_len-1];
583 register Byte scan_end = scan[best_len];
584 #endif
585
586 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
587 * It is easy to get rid of this optimization if necessary.
588 */
589 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
590
591 /* Do not waste too much time if we already have a good match: */
592 if (s->prev_length >= s->good_match) {
593 chain_length >>= 2;
594 }
595 /* Do not look for matches beyond the end of the input. This is necessary
596 * to make deflate deterministic.
597 */
598 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
599
600 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
601
602 do {
603 Assert(cur_match < s->strstart, "no future");
604 match = s->window + cur_match;
605
606 /* Skip to next match if the match length cannot increase
607 * or if the match length is less than 2:
608 */
609 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
610 /* This code assumes sizeof(unsigned short) == 2. Do not use
611 * UNALIGNED_OK if your compiler uses a different size.
612 */
613 if (*(ush*)(match+best_len-1) != scan_end ||
614 *(ush*)match != scan_start) continue;
615
616 /* It is not necessary to compare scan[2] and match[2] since they are
617 * always equal when the other bytes match, given that the hash keys
618 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
619 * strstart+3, +5, ... up to strstart+257. We check for insufficient
620 * lookahead only every 4th comparison; the 128th check will be made
621 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
622 * necessary to put more guard bytes at the end of the window, or
623 * to check more often for insufficient lookahead.
624 */
625 Assert(scan[2] == match[2], "scan[2]?");
626 scan++, match++;
627 do {
628 } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
629 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
630 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
631 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
632 scan < strend);
633 /* The funny "do {}" generates better code on most compilers */
634
635 /* Here, scan <= window+strstart+257 */
636 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
637 if (*scan == *match) scan++;
638
639 len = (MAX_MATCH - 1) - (int)(strend-scan);
640 scan = strend - (MAX_MATCH-1);
641
642 #else /* UNALIGNED_OK */
643
644 if (match[best_len] != scan_end ||
645 match[best_len-1] != scan_end1 ||
646 *match != *scan ||
647 *++match != scan[1]) continue;
648
649 /* The check at best_len-1 can be removed because it will be made
650 * again later. (This heuristic is not always a win.)
651 * It is not necessary to compare scan[2] and match[2] since they
652 * are always equal when the other bytes match, given that
653 * the hash keys are equal and that HASH_BITS >= 8.
654 */
655 scan += 2, match++;
656 Assert(*scan == *match, "match[2]?");
657
658 /* We check for insufficient lookahead only every 8th comparison;
659 * the 256th check will be made at strstart+258.
660 */
661 do {
662 } while (*++scan == *++match && *++scan == *++match &&
663 *++scan == *++match && *++scan == *++match &&
664 *++scan == *++match && *++scan == *++match &&
665 *++scan == *++match && *++scan == *++match &&
666 scan < strend);
667
668 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
669
670 len = MAX_MATCH - (int)(strend - scan);
671 scan = strend - MAX_MATCH;
672
673 #endif /* UNALIGNED_OK */
674
675 if (len > best_len) {
676 s->match_start = cur_match;
677 best_len = len;
678 if (len >= nice_match) break;
679 #ifdef UNALIGNED_OK
680 scan_end = *(ush*)(scan+best_len-1);
681 #else
682 scan_end1 = scan[best_len-1];
683 scan_end = scan[best_len];
684 #endif
685 }
686 } while ((cur_match = prev[cur_match & wmask]) > limit
687 && --chain_length != 0);
688
689 if ((uInt)best_len <= s->lookahead) return best_len;
690 return s->lookahead;
691 }
692
693 #ifdef DEBUG_ZLIB
694 /* ===========================================================================
695 * Check that the match at match_start is indeed a match.
696 */
697 static void check_match(
698 deflate_state *s,
699 IPos start,
700 IPos match,
701 int length
702 )
703 {
704 /* check that the match is indeed a match */
705 if (memcmp((char *)s->window + match,
706 (char *)s->window + start, length) != EQUAL) {
707 fprintf(stderr, " start %u, match %u, length %d\n",
708 start, match, length);
709 do {
710 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
711 } while (--length != 0);
712 z_error("invalid match");
713 }
714 if (z_verbose > 1) {
715 fprintf(stderr,"\\[%d,%d]", start-match, length);
716 do { putc(s->window[start++], stderr); } while (--length != 0);
717 }
718 }
719 #else
720 # define check_match(s, start, match, length)
721 #endif
722
723 /* ===========================================================================
724 * Fill the window when the lookahead becomes insufficient.
725 * Updates strstart and lookahead.
726 *
727 * IN assertion: lookahead < MIN_LOOKAHEAD
728 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
729 * At least one byte has been read, or avail_in == 0; reads are
730 * performed for at least two bytes (required for the zip translate_eol
731 * option -- not supported here).
732 */
733 static void fill_window(
734 deflate_state *s
735 )
736 {
737 register unsigned n, m;
738 register Pos *p;
739 unsigned more; /* Amount of free space at the end of the window. */
740 uInt wsize = s->w_size;
741
742 do {
743 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
744
745 /* Deal with !@#$% 64K limit: */
746 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
747 more = wsize;
748
749 } else if (more == (unsigned)(-1)) {
750 /* Very unlikely, but possible on 16 bit machine if strstart == 0
751 * and lookahead == 1 (input done one byte at time)
752 */
753 more--;
754
755 /* If the window is almost full and there is insufficient lookahead,
756 * move the upper half to the lower one to make room in the upper half.
757 */
758 } else if (s->strstart >= wsize+MAX_DIST(s)) {
759
760 memcpy((char *)s->window, (char *)s->window+wsize,
761 (unsigned)wsize);
762 s->match_start -= wsize;
763 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
764 s->block_start -= (long) wsize;
765
766 /* Slide the hash table (could be avoided with 32 bit values
767 at the expense of memory usage). We slide even when level == 0
768 to keep the hash table consistent if we switch back to level > 0
769 later. (Using level 0 permanently is not an optimal usage of
770 zlib, so we don't care about this pathological case.)
771 */
772 n = s->hash_size;
773 p = &s->head[n];
774 do {
775 m = *--p;
776 *p = (Pos)(m >= wsize ? m-wsize : NIL);
777 } while (--n);
778
779 n = wsize;
780 p = &s->prev[n];
781 do {
782 m = *--p;
783 *p = (Pos)(m >= wsize ? m-wsize : NIL);
784 /* If n is not on any hash chain, prev[n] is garbage but
785 * its value will never be used.
786 */
787 } while (--n);
788 more += wsize;
789 }
790 if (s->strm->avail_in == 0) return;
791
792 /* If there was no sliding:
793 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
794 * more == window_size - lookahead - strstart
795 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
796 * => more >= window_size - 2*WSIZE + 2
797 * In the BIG_MEM or MMAP case (not yet supported),
798 * window_size == input_size + MIN_LOOKAHEAD &&
799 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
800 * Otherwise, window_size == 2*WSIZE so more >= 2.
801 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
802 */
803 Assert(more >= 2, "more < 2");
804
805 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
806 s->lookahead += n;
807
808 /* Initialize the hash value now that we have some input: */
809 if (s->lookahead >= MIN_MATCH) {
810 s->ins_h = s->window[s->strstart];
811 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
812 #if MIN_MATCH != 3
813 Call UPDATE_HASH() MIN_MATCH-3 more times
814 #endif
815 }
816 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
817 * but this is not important since only literal bytes will be emitted.
818 */
819
820 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
821 }
822
823 /* ===========================================================================
824 * Flush the current block, with given end-of-file flag.
825 * IN assertion: strstart is set to the end of the current match.
826 */
827 #define FLUSH_BLOCK_ONLY(s, eof) { \
828 zlib_tr_flush_block(s, (s->block_start >= 0L ? \
829 (char *)&s->window[(unsigned)s->block_start] : \
830 NULL), \
831 (ulg)((long)s->strstart - s->block_start), \
832 (eof)); \
833 s->block_start = s->strstart; \
834 flush_pending(s->strm); \
835 Tracev((stderr,"[FLUSH]")); \
836 }
837
838 /* Same but force premature exit if necessary. */
839 #define FLUSH_BLOCK(s, eof) { \
840 FLUSH_BLOCK_ONLY(s, eof); \
841 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
842 }
843
844 /* ===========================================================================
845 * Copy without compression as much as possible from the input stream, return
846 * the current block state.
847 * This function does not insert new strings in the dictionary since
848 * uncompressible data is probably not useful. This function is used
849 * only for the level=0 compression option.
850 * NOTE: this function should be optimized to avoid extra copying from
851 * window to pending_buf.
852 */
853 static block_state deflate_stored(
854 deflate_state *s,
855 int flush
856 )
857 {
858 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
859 * to pending_buf_size, and each stored block has a 5 byte header:
860 */
861 ulg max_block_size = 0xffff;
862 ulg max_start;
863
864 if (max_block_size > s->pending_buf_size - 5) {
865 max_block_size = s->pending_buf_size - 5;
866 }
867
868 /* Copy as much as possible from input to output: */
869 for (;;) {
870 /* Fill the window as much as possible: */
871 if (s->lookahead <= 1) {
872
873 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
874 s->block_start >= (long)s->w_size, "slide too late");
875
876 fill_window(s);
877 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
878
879 if (s->lookahead == 0) break; /* flush the current block */
880 }
881 Assert(s->block_start >= 0L, "block gone");
882
883 s->strstart += s->lookahead;
884 s->lookahead = 0;
885
886 /* Emit a stored block if pending_buf will be full: */
887 max_start = s->block_start + max_block_size;
888 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
889 /* strstart == 0 is possible when wraparound on 16-bit machine */
890 s->lookahead = (uInt)(s->strstart - max_start);
891 s->strstart = (uInt)max_start;
892 FLUSH_BLOCK(s, 0);
893 }
894 /* Flush if we may have to slide, otherwise block_start may become
895 * negative and the data will be gone:
896 */
897 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
898 FLUSH_BLOCK(s, 0);
899 }
900 }
901 FLUSH_BLOCK(s, flush == Z_FINISH);
902 return flush == Z_FINISH ? finish_done : block_done;
903 }
904
905 /* ===========================================================================
906 * Compress as much as possible from the input stream, return the current
907 * block state.
908 * This function does not perform lazy evaluation of matches and inserts
909 * new strings in the dictionary only for unmatched strings or for short
910 * matches. It is used only for the fast compression options.
911 */
912 static block_state deflate_fast(
913 deflate_state *s,
914 int flush
915 )
916 {
917 IPos hash_head = NIL; /* head of the hash chain */
918 int bflush; /* set if current block must be flushed */
919
920 for (;;) {
921 /* Make sure that we always have enough lookahead, except
922 * at the end of the input file. We need MAX_MATCH bytes
923 * for the next match, plus MIN_MATCH bytes to insert the
924 * string following the next match.
925 */
926 if (s->lookahead < MIN_LOOKAHEAD) {
927 fill_window(s);
928 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
929 return need_more;
930 }
931 if (s->lookahead == 0) break; /* flush the current block */
932 }
933
934 /* Insert the string window[strstart .. strstart+2] in the
935 * dictionary, and set hash_head to the head of the hash chain:
936 */
937 if (s->lookahead >= MIN_MATCH) {
938 INSERT_STRING(s, s->strstart, hash_head);
939 }
940
941 /* Find the longest match, discarding those <= prev_length.
942 * At this point we have always match_length < MIN_MATCH
943 */
944 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
945 /* To simplify the code, we prevent matches with the string
946 * of window index 0 (in particular we have to avoid a match
947 * of the string with itself at the start of the input file).
948 */
949 if (s->strategy != Z_HUFFMAN_ONLY) {
950 s->match_length = longest_match (s, hash_head);
951 }
952 /* longest_match() sets match_start */
953 }
954 if (s->match_length >= MIN_MATCH) {
955 check_match(s, s->strstart, s->match_start, s->match_length);
956
957 bflush = zlib_tr_tally(s, s->strstart - s->match_start,
958 s->match_length - MIN_MATCH);
959
960 s->lookahead -= s->match_length;
961
962 /* Insert new strings in the hash table only if the match length
963 * is not too large. This saves time but degrades compression.
964 */
965 if (s->match_length <= s->max_insert_length &&
966 s->lookahead >= MIN_MATCH) {
967 s->match_length--; /* string at strstart already in hash table */
968 do {
969 s->strstart++;
970 INSERT_STRING(s, s->strstart, hash_head);
971 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
972 * always MIN_MATCH bytes ahead.
973 */
974 } while (--s->match_length != 0);
975 s->strstart++;
976 } else {
977 s->strstart += s->match_length;
978 s->match_length = 0;
979 s->ins_h = s->window[s->strstart];
980 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
981 #if MIN_MATCH != 3
982 Call UPDATE_HASH() MIN_MATCH-3 more times
983 #endif
984 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
985 * matter since it will be recomputed at next deflate call.
986 */
987 }
988 } else {
989 /* No match, output a literal byte */
990 Tracevv((stderr,"%c", s->window[s->strstart]));
991 bflush = zlib_tr_tally (s, 0, s->window[s->strstart]);
992 s->lookahead--;
993 s->strstart++;
994 }
995 if (bflush) FLUSH_BLOCK(s, 0);
996 }
997 FLUSH_BLOCK(s, flush == Z_FINISH);
998 return flush == Z_FINISH ? finish_done : block_done;
999 }
1000
1001 /* ===========================================================================
1002 * Same as above, but achieves better compression. We use a lazy
1003 * evaluation for matches: a match is finally adopted only if there is
1004 * no better match at the next window position.
1005 */
1006 static block_state deflate_slow(
1007 deflate_state *s,
1008 int flush
1009 )
1010 {
1011 IPos hash_head = NIL; /* head of hash chain */
1012 int bflush; /* set if current block must be flushed */
1013
1014 /* Process the input block. */
1015 for (;;) {
1016 /* Make sure that we always have enough lookahead, except
1017 * at the end of the input file. We need MAX_MATCH bytes
1018 * for the next match, plus MIN_MATCH bytes to insert the
1019 * string following the next match.
1020 */
1021 if (s->lookahead < MIN_LOOKAHEAD) {
1022 fill_window(s);
1023 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1024 return need_more;
1025 }
1026 if (s->lookahead == 0) break; /* flush the current block */
1027 }
1028
1029 /* Insert the string window[strstart .. strstart+2] in the
1030 * dictionary, and set hash_head to the head of the hash chain:
1031 */
1032 if (s->lookahead >= MIN_MATCH) {
1033 INSERT_STRING(s, s->strstart, hash_head);
1034 }
1035
1036 /* Find the longest match, discarding those <= prev_length.
1037 */
1038 s->prev_length = s->match_length, s->prev_match = s->match_start;
1039 s->match_length = MIN_MATCH-1;
1040
1041 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1042 s->strstart - hash_head <= MAX_DIST(s)) {
1043 /* To simplify the code, we prevent matches with the string
1044 * of window index 0 (in particular we have to avoid a match
1045 * of the string with itself at the start of the input file).
1046 */
1047 if (s->strategy != Z_HUFFMAN_ONLY) {
1048 s->match_length = longest_match (s, hash_head);
1049 }
1050 /* longest_match() sets match_start */
1051
1052 if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1053 (s->match_length == MIN_MATCH &&
1054 s->strstart - s->match_start > TOO_FAR))) {
1055
1056 /* If prev_match is also MIN_MATCH, match_start is garbage
1057 * but we will ignore the current match anyway.
1058 */
1059 s->match_length = MIN_MATCH-1;
1060 }
1061 }
1062 /* If there was a match at the previous step and the current
1063 * match is not better, output the previous match:
1064 */
1065 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1066 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1067 /* Do not insert strings in hash table beyond this. */
1068
1069 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1070
1071 bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match,
1072 s->prev_length - MIN_MATCH);
1073
1074 /* Insert in hash table all strings up to the end of the match.
1075 * strstart-1 and strstart are already inserted. If there is not
1076 * enough lookahead, the last two strings are not inserted in
1077 * the hash table.
1078 */
1079 s->lookahead -= s->prev_length-1;
1080 s->prev_length -= 2;
1081 do {
1082 if (++s->strstart <= max_insert) {
1083 INSERT_STRING(s, s->strstart, hash_head);
1084 }
1085 } while (--s->prev_length != 0);
1086 s->match_available = 0;
1087 s->match_length = MIN_MATCH-1;
1088 s->strstart++;
1089
1090 if (bflush) FLUSH_BLOCK(s, 0);
1091
1092 } else if (s->match_available) {
1093 /* If there was no match at the previous position, output a
1094 * single literal. If there was a match but the current match
1095 * is longer, truncate the previous match to a single literal.
1096 */
1097 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1098 if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) {
1099 FLUSH_BLOCK_ONLY(s, 0);
1100 }
1101 s->strstart++;
1102 s->lookahead--;
1103 if (s->strm->avail_out == 0) return need_more;
1104 } else {
1105 /* There is no previous match to compare with, wait for
1106 * the next step to decide.
1107 */
1108 s->match_available = 1;
1109 s->strstart++;
1110 s->lookahead--;
1111 }
1112 }
1113 Assert (flush != Z_NO_FLUSH, "no flush?");
1114 if (s->match_available) {
1115 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1116 zlib_tr_tally (s, 0, s->window[s->strstart-1]);
1117 s->match_available = 0;
1118 }
1119 FLUSH_BLOCK(s, flush == Z_FINISH);
1120 return flush == Z_FINISH ? finish_done : block_done;
1121 }
1122
1123 int zlib_deflate_workspacesize(int windowBits, int memLevel)
1124 {
1125 if (windowBits < 0) /* undocumented feature: suppress zlib header */
1126 windowBits = -windowBits;
1127
1128 /* Since the return value is typically passed to vmalloc() unchecked... */
1129 BUG_ON(memLevel < 1 || memLevel > MAX_MEM_LEVEL || windowBits < 9 ||
1130 windowBits > 15);
1131
1132 return sizeof(deflate_workspace)
1133 + zlib_deflate_window_memsize(windowBits)
1134 + zlib_deflate_prev_memsize(windowBits)
1135 + zlib_deflate_head_memsize(memLevel)
1136 + zlib_deflate_overlay_memsize(memLevel);
1137 }