blob: 1653dd9bb01a459aa6105e44b678928c52327c47 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* +++ 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 */
59typedef 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
66typedef block_state (*compress_func) (deflate_state *s, int flush);
67/* Compression function. Returns the block state after the call. */
68
69static void fill_window (deflate_state *s);
70static block_state deflate_stored (deflate_state *s, int flush);
71static block_state deflate_fast (deflate_state *s, int flush);
72static block_state deflate_slow (deflate_state *s, int flush);
73static void lm_init (deflate_state *s);
74static void putShortMSB (deflate_state *s, uInt b);
75static void flush_pending (z_streamp strm);
76static int read_buf (z_streamp strm, Byte *buf, unsigned size);
77static uInt longest_match (deflate_state *s, IPos cur_match);
78
79#ifdef DEBUG_ZLIB
80static 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 */
106typedef 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
114static 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 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 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/* ========================================================================= */
167int zlib_deflateInit_(
168 z_streamp strm,
169 int level,
170 const char *version,
171 int stream_size
172)
173{
174 return zlib_deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS,
175 DEF_MEM_LEVEL,
176 Z_DEFAULT_STRATEGY, version, stream_size);
177 /* To do: ignore strm->next_in if we use it as window */
178}
179
180/* ========================================================================= */
181int zlib_deflateInit2_(
182 z_streamp strm,
183 int level,
184 int method,
185 int windowBits,
186 int memLevel,
187 int strategy,
188 const char *version,
189 int stream_size
190)
191{
192 deflate_state *s;
193 int noheader = 0;
194 static char* my_version = ZLIB_VERSION;
195 deflate_workspace *mem;
196
197 ush *overlay;
198 /* We overlay pending_buf and d_buf+l_buf. This works since the average
199 * output size for (length,distance) codes is <= 24 bits.
200 */
201
202 if (version == NULL || version[0] != my_version[0] ||
203 stream_size != sizeof(z_stream)) {
204 return Z_VERSION_ERROR;
205 }
206 if (strm == NULL) return Z_STREAM_ERROR;
207
208 strm->msg = NULL;
209
210 if (level == Z_DEFAULT_COMPRESSION) level = 6;
211
212 mem = (deflate_workspace *) strm->workspace;
213
214 if (windowBits < 0) { /* undocumented feature: suppress zlib header */
215 noheader = 1;
216 windowBits = -windowBits;
217 }
218 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
219 windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
220 strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
221 return Z_STREAM_ERROR;
222 }
223 s = (deflate_state *) &(mem->deflate_memory);
224 strm->state = (struct internal_state *)s;
225 s->strm = strm;
226
227 s->noheader = noheader;
228 s->w_bits = windowBits;
229 s->w_size = 1 << s->w_bits;
230 s->w_mask = s->w_size - 1;
231
232 s->hash_bits = memLevel + 7;
233 s->hash_size = 1 << s->hash_bits;
234 s->hash_mask = s->hash_size - 1;
235 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
236
237 s->window = (Byte *) mem->window_memory;
238 s->prev = (Pos *) mem->prev_memory;
239 s->head = (Pos *) mem->head_memory;
240
241 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
242
243 overlay = (ush *) mem->overlay_memory;
244 s->pending_buf = (uch *) overlay;
245 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
246
247 s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
248 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
249
250 s->level = level;
251 s->strategy = strategy;
252 s->method = (Byte)method;
253
254 return zlib_deflateReset(strm);
255}
256
257/* ========================================================================= */
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800258#if 0
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259int zlib_deflateSetDictionary(
260 z_streamp strm,
261 const Byte *dictionary,
262 uInt dictLength
263)
264{
265 deflate_state *s;
266 uInt length = dictLength;
267 uInt n;
268 IPos hash_head = 0;
269
270 if (strm == NULL || strm->state == NULL || dictionary == NULL)
271 return Z_STREAM_ERROR;
272
273 s = (deflate_state *) strm->state;
274 if (s->status != INIT_STATE) return Z_STREAM_ERROR;
275
276 strm->adler = zlib_adler32(strm->adler, dictionary, dictLength);
277
278 if (length < MIN_MATCH) return Z_OK;
279 if (length > MAX_DIST(s)) {
280 length = MAX_DIST(s);
281#ifndef USE_DICT_HEAD
282 dictionary += dictLength - length; /* use the tail of the dictionary */
283#endif
284 }
285 memcpy((char *)s->window, dictionary, length);
286 s->strstart = length;
287 s->block_start = (long)length;
288
289 /* Insert all strings in the hash table (except for the last two bytes).
290 * s->lookahead stays null, so s->ins_h will be recomputed at the next
291 * call of fill_window.
292 */
293 s->ins_h = s->window[0];
294 UPDATE_HASH(s, s->ins_h, s->window[1]);
295 for (n = 0; n <= length - MIN_MATCH; n++) {
296 INSERT_STRING(s, n, hash_head);
297 }
298 if (hash_head) hash_head = 0; /* to make compiler happy */
299 return Z_OK;
300}
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800301#endif /* 0 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302
303/* ========================================================================= */
304int zlib_deflateReset(
305 z_streamp strm
306)
307{
308 deflate_state *s;
309
310 if (strm == NULL || strm->state == NULL)
311 return Z_STREAM_ERROR;
312
313 strm->total_in = strm->total_out = 0;
314 strm->msg = NULL;
315 strm->data_type = Z_UNKNOWN;
316
317 s = (deflate_state *)strm->state;
318 s->pending = 0;
319 s->pending_out = s->pending_buf;
320
321 if (s->noheader < 0) {
322 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
323 }
324 s->status = s->noheader ? BUSY_STATE : INIT_STATE;
325 strm->adler = 1;
326 s->last_flush = Z_NO_FLUSH;
327
328 zlib_tr_init(s);
329 lm_init(s);
330
331 return Z_OK;
332}
333
334/* ========================================================================= */
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800335#if 0
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336int zlib_deflateParams(
337 z_streamp strm,
338 int level,
339 int strategy
340)
341{
342 deflate_state *s;
343 compress_func func;
344 int err = Z_OK;
345
346 if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
347 s = (deflate_state *) strm->state;
348
349 if (level == Z_DEFAULT_COMPRESSION) {
350 level = 6;
351 }
352 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
353 return Z_STREAM_ERROR;
354 }
355 func = configuration_table[s->level].func;
356
357 if (func != configuration_table[level].func && strm->total_in != 0) {
358 /* Flush the last buffer: */
359 err = zlib_deflate(strm, Z_PARTIAL_FLUSH);
360 }
361 if (s->level != level) {
362 s->level = level;
363 s->max_lazy_match = configuration_table[level].max_lazy;
364 s->good_match = configuration_table[level].good_length;
365 s->nice_match = configuration_table[level].nice_length;
366 s->max_chain_length = configuration_table[level].max_chain;
367 }
368 s->strategy = strategy;
369 return err;
370}
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800371#endif /* 0 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372
373/* =========================================================================
374 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
375 * IN assertion: the stream state is correct and there is enough room in
376 * pending_buf.
377 */
378static void putShortMSB(
379 deflate_state *s,
380 uInt b
381)
382{
383 put_byte(s, (Byte)(b >> 8));
384 put_byte(s, (Byte)(b & 0xff));
385}
386
387/* =========================================================================
388 * Flush as much pending output as possible. All deflate() output goes
389 * through this function so some applications may wish to modify it
390 * to avoid allocating a large strm->next_out buffer and copying into it.
391 * (See also read_buf()).
392 */
393static void flush_pending(
394 z_streamp strm
395)
396{
397 deflate_state *s = (deflate_state *) strm->state;
398 unsigned len = s->pending;
399
400 if (len > strm->avail_out) len = strm->avail_out;
401 if (len == 0) return;
402
403 if (strm->next_out != NULL) {
404 memcpy(strm->next_out, s->pending_out, len);
405 strm->next_out += len;
406 }
407 s->pending_out += len;
408 strm->total_out += len;
409 strm->avail_out -= len;
410 s->pending -= len;
411 if (s->pending == 0) {
412 s->pending_out = s->pending_buf;
413 }
414}
415
416/* ========================================================================= */
417int zlib_deflate(
418 z_streamp strm,
419 int flush
420)
421{
422 int old_flush; /* value of flush param for previous deflate call */
423 deflate_state *s;
424
425 if (strm == NULL || strm->state == NULL ||
426 flush > Z_FINISH || flush < 0) {
427 return Z_STREAM_ERROR;
428 }
429 s = (deflate_state *) strm->state;
430
431 if ((strm->next_in == NULL && strm->avail_in != 0) ||
432 (s->status == FINISH_STATE && flush != Z_FINISH)) {
433 return Z_STREAM_ERROR;
434 }
435 if (strm->avail_out == 0) return Z_BUF_ERROR;
436
437 s->strm = strm; /* just in case */
438 old_flush = s->last_flush;
439 s->last_flush = flush;
440
441 /* Write the zlib header */
442 if (s->status == INIT_STATE) {
443
444 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
445 uInt level_flags = (s->level-1) >> 1;
446
447 if (level_flags > 3) level_flags = 3;
448 header |= (level_flags << 6);
449 if (s->strstart != 0) header |= PRESET_DICT;
450 header += 31 - (header % 31);
451
452 s->status = BUSY_STATE;
453 putShortMSB(s, header);
454
455 /* Save the adler32 of the preset dictionary: */
456 if (s->strstart != 0) {
457 putShortMSB(s, (uInt)(strm->adler >> 16));
458 putShortMSB(s, (uInt)(strm->adler & 0xffff));
459 }
460 strm->adler = 1L;
461 }
462
463 /* Flush as much pending output as possible */
464 if (s->pending != 0) {
465 flush_pending(strm);
466 if (strm->avail_out == 0) {
467 /* Since avail_out is 0, deflate will be called again with
468 * more output space, but possibly with both pending and
469 * avail_in equal to zero. There won't be anything to do,
470 * but this is not an error situation so make sure we
471 * return OK instead of BUF_ERROR at next call of deflate:
472 */
473 s->last_flush = -1;
474 return Z_OK;
475 }
476
477 /* Make sure there is something to do and avoid duplicate consecutive
478 * flushes. For repeated and useless calls with Z_FINISH, we keep
479 * returning Z_STREAM_END instead of Z_BUFF_ERROR.
480 */
481 } else if (strm->avail_in == 0 && flush <= old_flush &&
482 flush != Z_FINISH) {
483 return Z_BUF_ERROR;
484 }
485
486 /* User must not provide more input after the first FINISH: */
487 if (s->status == FINISH_STATE && strm->avail_in != 0) {
488 return Z_BUF_ERROR;
489 }
490
491 /* Start a new block or continue the current one.
492 */
493 if (strm->avail_in != 0 || s->lookahead != 0 ||
494 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
495 block_state bstate;
496
497 bstate = (*(configuration_table[s->level].func))(s, flush);
498
499 if (bstate == finish_started || bstate == finish_done) {
500 s->status = FINISH_STATE;
501 }
502 if (bstate == need_more || bstate == finish_started) {
503 if (strm->avail_out == 0) {
504 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
505 }
506 return Z_OK;
507 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
508 * of deflate should use the same flush parameter to make sure
509 * that the flush is complete. So we don't have to output an
510 * empty block here, this will be done at next call. This also
511 * ensures that for a very small output buffer, we emit at most
512 * one empty block.
513 */
514 }
515 if (bstate == block_done) {
516 if (flush == Z_PARTIAL_FLUSH) {
517 zlib_tr_align(s);
518 } else if (flush == Z_PACKET_FLUSH) {
519 /* Output just the 3-bit `stored' block type value,
520 but not a zero length. */
521 zlib_tr_stored_type_only(s);
522 } else { /* FULL_FLUSH or SYNC_FLUSH */
523 zlib_tr_stored_block(s, (char*)0, 0L, 0);
524 /* For a full flush, this empty block will be recognized
525 * as a special marker by inflate_sync().
526 */
527 if (flush == Z_FULL_FLUSH) {
528 CLEAR_HASH(s); /* forget history */
529 }
530 }
531 flush_pending(strm);
532 if (strm->avail_out == 0) {
533 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
534 return Z_OK;
535 }
536 }
537 }
538 Assert(strm->avail_out > 0, "bug2");
539
540 if (flush != Z_FINISH) return Z_OK;
541 if (s->noheader) return Z_STREAM_END;
542
543 /* Write the zlib trailer (adler32) */
544 putShortMSB(s, (uInt)(strm->adler >> 16));
545 putShortMSB(s, (uInt)(strm->adler & 0xffff));
546 flush_pending(strm);
547 /* If avail_out is zero, the application will call deflate again
548 * to flush the rest.
549 */
550 s->noheader = -1; /* write the trailer only once! */
551 return s->pending != 0 ? Z_OK : Z_STREAM_END;
552}
553
554/* ========================================================================= */
555int zlib_deflateEnd(
556 z_streamp strm
557)
558{
559 int status;
560 deflate_state *s;
561
562 if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
563 s = (deflate_state *) strm->state;
564
565 status = s->status;
566 if (status != INIT_STATE && status != BUSY_STATE &&
567 status != FINISH_STATE) {
568 return Z_STREAM_ERROR;
569 }
570
571 strm->state = NULL;
572
573 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
574}
575
576/* =========================================================================
577 * Copy the source state to the destination state.
578 */
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800579#if 0
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580int zlib_deflateCopy (
581 z_streamp dest,
582 z_streamp source
583)
584{
585#ifdef MAXSEG_64K
586 return Z_STREAM_ERROR;
587#else
588 deflate_state *ds;
589 deflate_state *ss;
590 ush *overlay;
591 deflate_workspace *mem;
592
593
594 if (source == NULL || dest == NULL || source->state == NULL) {
595 return Z_STREAM_ERROR;
596 }
597
598 ss = (deflate_state *) source->state;
599
600 *dest = *source;
601
602 mem = (deflate_workspace *) dest->workspace;
603
604 ds = &(mem->deflate_memory);
605
606 dest->state = (struct internal_state *) ds;
607 *ds = *ss;
608 ds->strm = dest;
609
610 ds->window = (Byte *) mem->window_memory;
611 ds->prev = (Pos *) mem->prev_memory;
612 ds->head = (Pos *) mem->head_memory;
613 overlay = (ush *) mem->overlay_memory;
614 ds->pending_buf = (uch *) overlay;
615
616 memcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
617 memcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
618 memcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
619 memcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
620
621 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
622 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
623 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
624
625 ds->l_desc.dyn_tree = ds->dyn_ltree;
626 ds->d_desc.dyn_tree = ds->dyn_dtree;
627 ds->bl_desc.dyn_tree = ds->bl_tree;
628
629 return Z_OK;
630#endif
631}
Adrian Bunk87c2ce32006-01-09 20:54:07 -0800632#endif /* 0 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633
634/* ===========================================================================
635 * Read a new buffer from the current input stream, update the adler32
636 * and total number of bytes read. All deflate() input goes through
637 * this function so some applications may wish to modify it to avoid
638 * allocating a large strm->next_in buffer and copying from it.
639 * (See also flush_pending()).
640 */
641static int read_buf(
642 z_streamp strm,
643 Byte *buf,
644 unsigned size
645)
646{
647 unsigned len = strm->avail_in;
648
649 if (len > size) len = size;
650 if (len == 0) return 0;
651
652 strm->avail_in -= len;
653
654 if (!((deflate_state *)(strm->state))->noheader) {
655 strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
656 }
657 memcpy(buf, strm->next_in, len);
658 strm->next_in += len;
659 strm->total_in += len;
660
661 return (int)len;
662}
663
664/* ===========================================================================
665 * Initialize the "longest match" routines for a new zlib stream
666 */
667static void lm_init(
668 deflate_state *s
669)
670{
671 s->window_size = (ulg)2L*s->w_size;
672
673 CLEAR_HASH(s);
674
675 /* Set the default configuration parameters:
676 */
677 s->max_lazy_match = configuration_table[s->level].max_lazy;
678 s->good_match = configuration_table[s->level].good_length;
679 s->nice_match = configuration_table[s->level].nice_length;
680 s->max_chain_length = configuration_table[s->level].max_chain;
681
682 s->strstart = 0;
683 s->block_start = 0L;
684 s->lookahead = 0;
685 s->match_length = s->prev_length = MIN_MATCH-1;
686 s->match_available = 0;
687 s->ins_h = 0;
688}
689
690/* ===========================================================================
691 * Set match_start to the longest match starting at the given string and
692 * return its length. Matches shorter or equal to prev_length are discarded,
693 * in which case the result is equal to prev_length and match_start is
694 * garbage.
695 * IN assertions: cur_match is the head of the hash chain for the current
696 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
697 * OUT assertion: the match length is not greater than s->lookahead.
698 */
699/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
700 * match.S. The code will be functionally equivalent.
701 */
702static uInt longest_match(
703 deflate_state *s,
704 IPos cur_match /* current match */
705)
706{
707 unsigned chain_length = s->max_chain_length;/* max hash chain length */
708 register Byte *scan = s->window + s->strstart; /* current string */
709 register Byte *match; /* matched string */
710 register int len; /* length of current match */
711 int best_len = s->prev_length; /* best match length so far */
712 int nice_match = s->nice_match; /* stop if match long enough */
713 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
714 s->strstart - (IPos)MAX_DIST(s) : NIL;
715 /* Stop when cur_match becomes <= limit. To simplify the code,
716 * we prevent matches with the string of window index 0.
717 */
718 Pos *prev = s->prev;
719 uInt wmask = s->w_mask;
720
721#ifdef UNALIGNED_OK
722 /* Compare two bytes at a time. Note: this is not always beneficial.
723 * Try with and without -DUNALIGNED_OK to check.
724 */
725 register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
726 register ush scan_start = *(ush*)scan;
727 register ush scan_end = *(ush*)(scan+best_len-1);
728#else
729 register Byte *strend = s->window + s->strstart + MAX_MATCH;
730 register Byte scan_end1 = scan[best_len-1];
731 register Byte scan_end = scan[best_len];
732#endif
733
734 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
735 * It is easy to get rid of this optimization if necessary.
736 */
737 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
738
739 /* Do not waste too much time if we already have a good match: */
740 if (s->prev_length >= s->good_match) {
741 chain_length >>= 2;
742 }
743 /* Do not look for matches beyond the end of the input. This is necessary
744 * to make deflate deterministic.
745 */
746 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
747
748 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
749
750 do {
751 Assert(cur_match < s->strstart, "no future");
752 match = s->window + cur_match;
753
754 /* Skip to next match if the match length cannot increase
755 * or if the match length is less than 2:
756 */
757#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
758 /* This code assumes sizeof(unsigned short) == 2. Do not use
759 * UNALIGNED_OK if your compiler uses a different size.
760 */
761 if (*(ush*)(match+best_len-1) != scan_end ||
762 *(ush*)match != scan_start) continue;
763
764 /* It is not necessary to compare scan[2] and match[2] since they are
765 * always equal when the other bytes match, given that the hash keys
766 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
767 * strstart+3, +5, ... up to strstart+257. We check for insufficient
768 * lookahead only every 4th comparison; the 128th check will be made
769 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
770 * necessary to put more guard bytes at the end of the window, or
771 * to check more often for insufficient lookahead.
772 */
773 Assert(scan[2] == match[2], "scan[2]?");
774 scan++, match++;
775 do {
776 } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
777 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
778 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
779 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
780 scan < strend);
781 /* The funny "do {}" generates better code on most compilers */
782
783 /* Here, scan <= window+strstart+257 */
784 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
785 if (*scan == *match) scan++;
786
787 len = (MAX_MATCH - 1) - (int)(strend-scan);
788 scan = strend - (MAX_MATCH-1);
789
790#else /* UNALIGNED_OK */
791
792 if (match[best_len] != scan_end ||
793 match[best_len-1] != scan_end1 ||
794 *match != *scan ||
795 *++match != scan[1]) continue;
796
797 /* The check at best_len-1 can be removed because it will be made
798 * again later. (This heuristic is not always a win.)
799 * It is not necessary to compare scan[2] and match[2] since they
800 * are always equal when the other bytes match, given that
801 * the hash keys are equal and that HASH_BITS >= 8.
802 */
803 scan += 2, match++;
804 Assert(*scan == *match, "match[2]?");
805
806 /* We check for insufficient lookahead only every 8th comparison;
807 * the 256th check will be made at strstart+258.
808 */
809 do {
810 } while (*++scan == *++match && *++scan == *++match &&
811 *++scan == *++match && *++scan == *++match &&
812 *++scan == *++match && *++scan == *++match &&
813 *++scan == *++match && *++scan == *++match &&
814 scan < strend);
815
816 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
817
818 len = MAX_MATCH - (int)(strend - scan);
819 scan = strend - MAX_MATCH;
820
821#endif /* UNALIGNED_OK */
822
823 if (len > best_len) {
824 s->match_start = cur_match;
825 best_len = len;
826 if (len >= nice_match) break;
827#ifdef UNALIGNED_OK
828 scan_end = *(ush*)(scan+best_len-1);
829#else
830 scan_end1 = scan[best_len-1];
831 scan_end = scan[best_len];
832#endif
833 }
834 } while ((cur_match = prev[cur_match & wmask]) > limit
835 && --chain_length != 0);
836
837 if ((uInt)best_len <= s->lookahead) return best_len;
838 return s->lookahead;
839}
840
841#ifdef DEBUG_ZLIB
842/* ===========================================================================
843 * Check that the match at match_start is indeed a match.
844 */
845static void check_match(
846 deflate_state *s,
847 IPos start,
848 IPos match,
849 int length
850)
851{
852 /* check that the match is indeed a match */
853 if (memcmp((char *)s->window + match,
854 (char *)s->window + start, length) != EQUAL) {
855 fprintf(stderr, " start %u, match %u, length %d\n",
856 start, match, length);
857 do {
858 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
859 } while (--length != 0);
860 z_error("invalid match");
861 }
862 if (z_verbose > 1) {
863 fprintf(stderr,"\\[%d,%d]", start-match, length);
864 do { putc(s->window[start++], stderr); } while (--length != 0);
865 }
866}
867#else
868# define check_match(s, start, match, length)
869#endif
870
871/* ===========================================================================
872 * Fill the window when the lookahead becomes insufficient.
873 * Updates strstart and lookahead.
874 *
875 * IN assertion: lookahead < MIN_LOOKAHEAD
876 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
877 * At least one byte has been read, or avail_in == 0; reads are
878 * performed for at least two bytes (required for the zip translate_eol
879 * option -- not supported here).
880 */
881static void fill_window(
882 deflate_state *s
883)
884{
885 register unsigned n, m;
886 register Pos *p;
887 unsigned more; /* Amount of free space at the end of the window. */
888 uInt wsize = s->w_size;
889
890 do {
891 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
892
893 /* Deal with !@#$% 64K limit: */
894 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
895 more = wsize;
896
897 } else if (more == (unsigned)(-1)) {
898 /* Very unlikely, but possible on 16 bit machine if strstart == 0
899 * and lookahead == 1 (input done one byte at time)
900 */
901 more--;
902
903 /* If the window is almost full and there is insufficient lookahead,
904 * move the upper half to the lower one to make room in the upper half.
905 */
906 } else if (s->strstart >= wsize+MAX_DIST(s)) {
907
908 memcpy((char *)s->window, (char *)s->window+wsize,
909 (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 p = &s->prev[n];
929 do {
930 m = *--p;
931 *p = (Pos)(m >= wsize ? m-wsize : NIL);
932 /* If n is not on any hash chain, prev[n] is garbage but
933 * its value will never be used.
934 */
935 } while (--n);
936 more += wsize;
937 }
938 if (s->strm->avail_in == 0) return;
939
940 /* If there was no sliding:
941 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
942 * more == window_size - lookahead - strstart
943 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
944 * => more >= window_size - 2*WSIZE + 2
945 * In the BIG_MEM or MMAP case (not yet supported),
946 * window_size == input_size + MIN_LOOKAHEAD &&
947 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
948 * Otherwise, window_size == 2*WSIZE so more >= 2.
949 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
950 */
951 Assert(more >= 2, "more < 2");
952
953 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
954 s->lookahead += n;
955
956 /* Initialize the hash value now that we have some input: */
957 if (s->lookahead >= MIN_MATCH) {
958 s->ins_h = s->window[s->strstart];
959 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
960#if MIN_MATCH != 3
961 Call UPDATE_HASH() MIN_MATCH-3 more times
962#endif
963 }
964 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
965 * but this is not important since only literal bytes will be emitted.
966 */
967
968 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
969}
970
971/* ===========================================================================
972 * Flush the current block, with given end-of-file flag.
973 * IN assertion: strstart is set to the end of the current match.
974 */
975#define FLUSH_BLOCK_ONLY(s, eof) { \
976 zlib_tr_flush_block(s, (s->block_start >= 0L ? \
977 (char *)&s->window[(unsigned)s->block_start] : \
978 NULL), \
979 (ulg)((long)s->strstart - s->block_start), \
980 (eof)); \
981 s->block_start = s->strstart; \
982 flush_pending(s->strm); \
983 Tracev((stderr,"[FLUSH]")); \
984}
985
986/* Same but force premature exit if necessary. */
987#define FLUSH_BLOCK(s, eof) { \
988 FLUSH_BLOCK_ONLY(s, eof); \
989 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
990}
991
992/* ===========================================================================
993 * Copy without compression as much as possible from the input stream, return
994 * the current block state.
995 * This function does not insert new strings in the dictionary since
996 * uncompressible data is probably not useful. This function is used
997 * only for the level=0 compression option.
998 * NOTE: this function should be optimized to avoid extra copying from
999 * window to pending_buf.
1000 */
1001static block_state deflate_stored(
1002 deflate_state *s,
1003 int flush
1004)
1005{
1006 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1007 * to pending_buf_size, and each stored block has a 5 byte header:
1008 */
1009 ulg max_block_size = 0xffff;
1010 ulg max_start;
1011
1012 if (max_block_size > s->pending_buf_size - 5) {
1013 max_block_size = s->pending_buf_size - 5;
1014 }
1015
1016 /* Copy as much as possible from input to output: */
1017 for (;;) {
1018 /* Fill the window as much as possible: */
1019 if (s->lookahead <= 1) {
1020
1021 Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1022 s->block_start >= (long)s->w_size, "slide too late");
1023
1024 fill_window(s);
1025 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1026
1027 if (s->lookahead == 0) break; /* flush the current block */
1028 }
1029 Assert(s->block_start >= 0L, "block gone");
1030
1031 s->strstart += s->lookahead;
1032 s->lookahead = 0;
1033
1034 /* Emit a stored block if pending_buf will be full: */
1035 max_start = s->block_start + max_block_size;
1036 if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1037 /* strstart == 0 is possible when wraparound on 16-bit machine */
1038 s->lookahead = (uInt)(s->strstart - max_start);
1039 s->strstart = (uInt)max_start;
1040 FLUSH_BLOCK(s, 0);
1041 }
1042 /* Flush if we may have to slide, otherwise block_start may become
1043 * negative and the data will be gone:
1044 */
1045 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1046 FLUSH_BLOCK(s, 0);
1047 }
1048 }
1049 FLUSH_BLOCK(s, flush == Z_FINISH);
1050 return flush == Z_FINISH ? finish_done : block_done;
1051}
1052
1053/* ===========================================================================
1054 * Compress as much as possible from the input stream, return the current
1055 * block state.
1056 * This function does not perform lazy evaluation of matches and inserts
1057 * new strings in the dictionary only for unmatched strings or for short
1058 * matches. It is used only for the fast compression options.
1059 */
1060static block_state deflate_fast(
1061 deflate_state *s,
1062 int flush
1063)
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 bflush = zlib_tr_tally(s, s->strstart - s->match_start,
1106 s->match_length - MIN_MATCH);
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 if (s->match_length <= s->max_insert_length &&
1114 s->lookahead >= MIN_MATCH) {
1115 s->match_length--; /* string at strstart already in hash table */
1116 do {
1117 s->strstart++;
1118 INSERT_STRING(s, s->strstart, hash_head);
1119 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1120 * always MIN_MATCH bytes ahead.
1121 */
1122 } while (--s->match_length != 0);
1123 s->strstart++;
1124 } else {
1125 s->strstart += s->match_length;
1126 s->match_length = 0;
1127 s->ins_h = s->window[s->strstart];
1128 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1129#if MIN_MATCH != 3
1130 Call UPDATE_HASH() MIN_MATCH-3 more times
1131#endif
1132 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1133 * matter since it will be recomputed at next deflate call.
1134 */
1135 }
1136 } else {
1137 /* No match, output a literal byte */
1138 Tracevv((stderr,"%c", s->window[s->strstart]));
1139 bflush = zlib_tr_tally (s, 0, s->window[s->strstart]);
1140 s->lookahead--;
1141 s->strstart++;
1142 }
1143 if (bflush) FLUSH_BLOCK(s, 0);
1144 }
1145 FLUSH_BLOCK(s, flush == Z_FINISH);
1146 return flush == Z_FINISH ? finish_done : block_done;
1147}
1148
1149/* ===========================================================================
1150 * Same as above, but achieves better compression. We use a lazy
1151 * evaluation for matches: a match is finally adopted only if there is
1152 * no better match at the next window position.
1153 */
1154static block_state deflate_slow(
1155 deflate_state *s,
1156 int flush
1157)
1158{
1159 IPos hash_head = NIL; /* head of hash chain */
1160 int bflush; /* set if current block must be flushed */
1161
1162 /* Process the input block. */
1163 for (;;) {
1164 /* Make sure that we always have enough lookahead, except
1165 * at the end of the input file. We need MAX_MATCH bytes
1166 * for the next match, plus MIN_MATCH bytes to insert the
1167 * string following the next match.
1168 */
1169 if (s->lookahead < MIN_LOOKAHEAD) {
1170 fill_window(s);
1171 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1172 return need_more;
1173 }
1174 if (s->lookahead == 0) break; /* flush the current block */
1175 }
1176
1177 /* Insert the string window[strstart .. strstart+2] in the
1178 * dictionary, and set hash_head to the head of the hash chain:
1179 */
1180 if (s->lookahead >= MIN_MATCH) {
1181 INSERT_STRING(s, s->strstart, hash_head);
1182 }
1183
1184 /* Find the longest match, discarding those <= prev_length.
1185 */
1186 s->prev_length = s->match_length, s->prev_match = s->match_start;
1187 s->match_length = MIN_MATCH-1;
1188
1189 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1190 s->strstart - hash_head <= MAX_DIST(s)) {
1191 /* To simplify the code, we prevent matches with the string
1192 * of window index 0 (in particular we have to avoid a match
1193 * of the string with itself at the start of the input file).
1194 */
1195 if (s->strategy != Z_HUFFMAN_ONLY) {
1196 s->match_length = longest_match (s, hash_head);
1197 }
1198 /* longest_match() sets match_start */
1199
1200 if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1201 (s->match_length == MIN_MATCH &&
1202 s->strstart - s->match_start > TOO_FAR))) {
1203
1204 /* If prev_match is also MIN_MATCH, match_start is garbage
1205 * but we will ignore the current match anyway.
1206 */
1207 s->match_length = MIN_MATCH-1;
1208 }
1209 }
1210 /* If there was a match at the previous step and the current
1211 * match is not better, output the previous match:
1212 */
1213 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1214 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1215 /* Do not insert strings in hash table beyond this. */
1216
1217 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1218
1219 bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match,
1220 s->prev_length - MIN_MATCH);
1221
1222 /* Insert in hash table all strings up to the end of the match.
1223 * strstart-1 and strstart are already inserted. If there is not
1224 * enough lookahead, the last two strings are not inserted in
1225 * the hash table.
1226 */
1227 s->lookahead -= s->prev_length-1;
1228 s->prev_length -= 2;
1229 do {
1230 if (++s->strstart <= max_insert) {
1231 INSERT_STRING(s, s->strstart, hash_head);
1232 }
1233 } while (--s->prev_length != 0);
1234 s->match_available = 0;
1235 s->match_length = MIN_MATCH-1;
1236 s->strstart++;
1237
1238 if (bflush) FLUSH_BLOCK(s, 0);
1239
1240 } else if (s->match_available) {
1241 /* If there was no match at the previous position, output a
1242 * single literal. If there was a match but the current match
1243 * is longer, truncate the previous match to a single literal.
1244 */
1245 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1246 if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) {
1247 FLUSH_BLOCK_ONLY(s, 0);
1248 }
1249 s->strstart++;
1250 s->lookahead--;
1251 if (s->strm->avail_out == 0) return need_more;
1252 } else {
1253 /* There is no previous match to compare with, wait for
1254 * the next step to decide.
1255 */
1256 s->match_available = 1;
1257 s->strstart++;
1258 s->lookahead--;
1259 }
1260 }
1261 Assert (flush != Z_NO_FLUSH, "no flush?");
1262 if (s->match_available) {
1263 Tracevv((stderr,"%c", s->window[s->strstart-1]));
1264 zlib_tr_tally (s, 0, s->window[s->strstart-1]);
1265 s->match_available = 0;
1266 }
1267 FLUSH_BLOCK(s, flush == Z_FINISH);
1268 return flush == Z_FINISH ? finish_done : block_done;
1269}
1270
1271int zlib_deflate_workspacesize(void)
1272{
1273 return sizeof(deflate_workspace);
1274}