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1da177e4 LT |
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 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 | /* ========================================================================= */ | |
167 | int 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 | /* ========================================================================= */ | |
181 | int 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 | /* ========================================================================= */ | |
258 | int zlib_deflateSetDictionary( | |
259 | z_streamp strm, | |
260 | const Byte *dictionary, | |
261 | uInt dictLength | |
262 | ) | |
263 | { | |
264 | deflate_state *s; | |
265 | uInt length = dictLength; | |
266 | uInt n; | |
267 | IPos hash_head = 0; | |
268 | ||
269 | if (strm == NULL || strm->state == NULL || dictionary == NULL) | |
270 | return Z_STREAM_ERROR; | |
271 | ||
272 | s = (deflate_state *) strm->state; | |
273 | if (s->status != INIT_STATE) return Z_STREAM_ERROR; | |
274 | ||
275 | strm->adler = zlib_adler32(strm->adler, dictionary, dictLength); | |
276 | ||
277 | if (length < MIN_MATCH) return Z_OK; | |
278 | if (length > MAX_DIST(s)) { | |
279 | length = MAX_DIST(s); | |
280 | #ifndef USE_DICT_HEAD | |
281 | dictionary += dictLength - length; /* use the tail of the dictionary */ | |
282 | #endif | |
283 | } | |
284 | memcpy((char *)s->window, dictionary, length); | |
285 | s->strstart = length; | |
286 | s->block_start = (long)length; | |
287 | ||
288 | /* Insert all strings in the hash table (except for the last two bytes). | |
289 | * s->lookahead stays null, so s->ins_h will be recomputed at the next | |
290 | * call of fill_window. | |
291 | */ | |
292 | s->ins_h = s->window[0]; | |
293 | UPDATE_HASH(s, s->ins_h, s->window[1]); | |
294 | for (n = 0; n <= length - MIN_MATCH; n++) { | |
295 | INSERT_STRING(s, n, hash_head); | |
296 | } | |
297 | if (hash_head) hash_head = 0; /* to make compiler happy */ | |
298 | return Z_OK; | |
299 | } | |
300 | ||
301 | /* ========================================================================= */ | |
302 | int zlib_deflateReset( | |
303 | z_streamp strm | |
304 | ) | |
305 | { | |
306 | deflate_state *s; | |
307 | ||
308 | if (strm == NULL || strm->state == NULL) | |
309 | return Z_STREAM_ERROR; | |
310 | ||
311 | strm->total_in = strm->total_out = 0; | |
312 | strm->msg = NULL; | |
313 | strm->data_type = Z_UNKNOWN; | |
314 | ||
315 | s = (deflate_state *)strm->state; | |
316 | s->pending = 0; | |
317 | s->pending_out = s->pending_buf; | |
318 | ||
319 | if (s->noheader < 0) { | |
320 | s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ | |
321 | } | |
322 | s->status = s->noheader ? BUSY_STATE : INIT_STATE; | |
323 | strm->adler = 1; | |
324 | s->last_flush = Z_NO_FLUSH; | |
325 | ||
326 | zlib_tr_init(s); | |
327 | lm_init(s); | |
328 | ||
329 | return Z_OK; | |
330 | } | |
331 | ||
332 | /* ========================================================================= */ | |
333 | int zlib_deflateParams( | |
334 | z_streamp strm, | |
335 | int level, | |
336 | int strategy | |
337 | ) | |
338 | { | |
339 | deflate_state *s; | |
340 | compress_func func; | |
341 | int err = Z_OK; | |
342 | ||
343 | if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR; | |
344 | s = (deflate_state *) strm->state; | |
345 | ||
346 | if (level == Z_DEFAULT_COMPRESSION) { | |
347 | level = 6; | |
348 | } | |
349 | if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { | |
350 | return Z_STREAM_ERROR; | |
351 | } | |
352 | func = configuration_table[s->level].func; | |
353 | ||
354 | if (func != configuration_table[level].func && strm->total_in != 0) { | |
355 | /* Flush the last buffer: */ | |
356 | err = zlib_deflate(strm, Z_PARTIAL_FLUSH); | |
357 | } | |
358 | if (s->level != level) { | |
359 | s->level = level; | |
360 | s->max_lazy_match = configuration_table[level].max_lazy; | |
361 | s->good_match = configuration_table[level].good_length; | |
362 | s->nice_match = configuration_table[level].nice_length; | |
363 | s->max_chain_length = configuration_table[level].max_chain; | |
364 | } | |
365 | s->strategy = strategy; | |
366 | return err; | |
367 | } | |
368 | ||
369 | /* ========================================================================= | |
370 | * Put a short in the pending buffer. The 16-bit value is put in MSB order. | |
371 | * IN assertion: the stream state is correct and there is enough room in | |
372 | * pending_buf. | |
373 | */ | |
374 | static void putShortMSB( | |
375 | deflate_state *s, | |
376 | uInt b | |
377 | ) | |
378 | { | |
379 | put_byte(s, (Byte)(b >> 8)); | |
380 | put_byte(s, (Byte)(b & 0xff)); | |
381 | } | |
382 | ||
383 | /* ========================================================================= | |
384 | * Flush as much pending output as possible. All deflate() output goes | |
385 | * through this function so some applications may wish to modify it | |
386 | * to avoid allocating a large strm->next_out buffer and copying into it. | |
387 | * (See also read_buf()). | |
388 | */ | |
389 | static void flush_pending( | |
390 | z_streamp strm | |
391 | ) | |
392 | { | |
393 | deflate_state *s = (deflate_state *) strm->state; | |
394 | unsigned len = s->pending; | |
395 | ||
396 | if (len > strm->avail_out) len = strm->avail_out; | |
397 | if (len == 0) return; | |
398 | ||
399 | if (strm->next_out != NULL) { | |
400 | memcpy(strm->next_out, s->pending_out, len); | |
401 | strm->next_out += len; | |
402 | } | |
403 | s->pending_out += len; | |
404 | strm->total_out += len; | |
405 | strm->avail_out -= len; | |
406 | s->pending -= len; | |
407 | if (s->pending == 0) { | |
408 | s->pending_out = s->pending_buf; | |
409 | } | |
410 | } | |
411 | ||
412 | /* ========================================================================= */ | |
413 | int zlib_deflate( | |
414 | z_streamp strm, | |
415 | int flush | |
416 | ) | |
417 | { | |
418 | int old_flush; /* value of flush param for previous deflate call */ | |
419 | deflate_state *s; | |
420 | ||
421 | if (strm == NULL || strm->state == NULL || | |
422 | flush > Z_FINISH || flush < 0) { | |
423 | return Z_STREAM_ERROR; | |
424 | } | |
425 | s = (deflate_state *) strm->state; | |
426 | ||
427 | if ((strm->next_in == NULL && strm->avail_in != 0) || | |
428 | (s->status == FINISH_STATE && flush != Z_FINISH)) { | |
429 | return Z_STREAM_ERROR; | |
430 | } | |
431 | if (strm->avail_out == 0) return Z_BUF_ERROR; | |
432 | ||
433 | s->strm = strm; /* just in case */ | |
434 | old_flush = s->last_flush; | |
435 | s->last_flush = flush; | |
436 | ||
437 | /* Write the zlib header */ | |
438 | if (s->status == INIT_STATE) { | |
439 | ||
440 | uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; | |
441 | uInt level_flags = (s->level-1) >> 1; | |
442 | ||
443 | if (level_flags > 3) level_flags = 3; | |
444 | header |= (level_flags << 6); | |
445 | if (s->strstart != 0) header |= PRESET_DICT; | |
446 | header += 31 - (header % 31); | |
447 | ||
448 | s->status = BUSY_STATE; | |
449 | putShortMSB(s, header); | |
450 | ||
451 | /* Save the adler32 of the preset dictionary: */ | |
452 | if (s->strstart != 0) { | |
453 | putShortMSB(s, (uInt)(strm->adler >> 16)); | |
454 | putShortMSB(s, (uInt)(strm->adler & 0xffff)); | |
455 | } | |
456 | strm->adler = 1L; | |
457 | } | |
458 | ||
459 | /* Flush as much pending output as possible */ | |
460 | if (s->pending != 0) { | |
461 | flush_pending(strm); | |
462 | if (strm->avail_out == 0) { | |
463 | /* Since avail_out is 0, deflate will be called again with | |
464 | * more output space, but possibly with both pending and | |
465 | * avail_in equal to zero. There won't be anything to do, | |
466 | * but this is not an error situation so make sure we | |
467 | * return OK instead of BUF_ERROR at next call of deflate: | |
468 | */ | |
469 | s->last_flush = -1; | |
470 | return Z_OK; | |
471 | } | |
472 | ||
473 | /* Make sure there is something to do and avoid duplicate consecutive | |
474 | * flushes. For repeated and useless calls with Z_FINISH, we keep | |
475 | * returning Z_STREAM_END instead of Z_BUFF_ERROR. | |
476 | */ | |
477 | } else if (strm->avail_in == 0 && flush <= old_flush && | |
478 | flush != Z_FINISH) { | |
479 | return Z_BUF_ERROR; | |
480 | } | |
481 | ||
482 | /* User must not provide more input after the first FINISH: */ | |
483 | if (s->status == FINISH_STATE && strm->avail_in != 0) { | |
484 | return Z_BUF_ERROR; | |
485 | } | |
486 | ||
487 | /* Start a new block or continue the current one. | |
488 | */ | |
489 | if (strm->avail_in != 0 || s->lookahead != 0 || | |
490 | (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { | |
491 | block_state bstate; | |
492 | ||
493 | bstate = (*(configuration_table[s->level].func))(s, flush); | |
494 | ||
495 | if (bstate == finish_started || bstate == finish_done) { | |
496 | s->status = FINISH_STATE; | |
497 | } | |
498 | if (bstate == need_more || bstate == finish_started) { | |
499 | if (strm->avail_out == 0) { | |
500 | s->last_flush = -1; /* avoid BUF_ERROR next call, see above */ | |
501 | } | |
502 | return Z_OK; | |
503 | /* If flush != Z_NO_FLUSH && avail_out == 0, the next call | |
504 | * of deflate should use the same flush parameter to make sure | |
505 | * that the flush is complete. So we don't have to output an | |
506 | * empty block here, this will be done at next call. This also | |
507 | * ensures that for a very small output buffer, we emit at most | |
508 | * one empty block. | |
509 | */ | |
510 | } | |
511 | if (bstate == block_done) { | |
512 | if (flush == Z_PARTIAL_FLUSH) { | |
513 | zlib_tr_align(s); | |
514 | } else if (flush == Z_PACKET_FLUSH) { | |
515 | /* Output just the 3-bit `stored' block type value, | |
516 | but not a zero length. */ | |
517 | zlib_tr_stored_type_only(s); | |
518 | } else { /* FULL_FLUSH or SYNC_FLUSH */ | |
519 | zlib_tr_stored_block(s, (char*)0, 0L, 0); | |
520 | /* For a full flush, this empty block will be recognized | |
521 | * as a special marker by inflate_sync(). | |
522 | */ | |
523 | if (flush == Z_FULL_FLUSH) { | |
524 | CLEAR_HASH(s); /* forget history */ | |
525 | } | |
526 | } | |
527 | flush_pending(strm); | |
528 | if (strm->avail_out == 0) { | |
529 | s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ | |
530 | return Z_OK; | |
531 | } | |
532 | } | |
533 | } | |
534 | Assert(strm->avail_out > 0, "bug2"); | |
535 | ||
536 | if (flush != Z_FINISH) return Z_OK; | |
537 | if (s->noheader) return Z_STREAM_END; | |
538 | ||
539 | /* Write the zlib trailer (adler32) */ | |
540 | putShortMSB(s, (uInt)(strm->adler >> 16)); | |
541 | putShortMSB(s, (uInt)(strm->adler & 0xffff)); | |
542 | flush_pending(strm); | |
543 | /* If avail_out is zero, the application will call deflate again | |
544 | * to flush the rest. | |
545 | */ | |
546 | s->noheader = -1; /* write the trailer only once! */ | |
547 | return s->pending != 0 ? Z_OK : Z_STREAM_END; | |
548 | } | |
549 | ||
550 | /* ========================================================================= */ | |
551 | int zlib_deflateEnd( | |
552 | z_streamp strm | |
553 | ) | |
554 | { | |
555 | int status; | |
556 | deflate_state *s; | |
557 | ||
558 | if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR; | |
559 | s = (deflate_state *) strm->state; | |
560 | ||
561 | status = s->status; | |
562 | if (status != INIT_STATE && status != BUSY_STATE && | |
563 | status != FINISH_STATE) { | |
564 | return Z_STREAM_ERROR; | |
565 | } | |
566 | ||
567 | strm->state = NULL; | |
568 | ||
569 | return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; | |
570 | } | |
571 | ||
572 | /* ========================================================================= | |
573 | * Copy the source state to the destination state. | |
574 | */ | |
575 | int zlib_deflateCopy ( | |
576 | z_streamp dest, | |
577 | z_streamp source | |
578 | ) | |
579 | { | |
580 | #ifdef MAXSEG_64K | |
581 | return Z_STREAM_ERROR; | |
582 | #else | |
583 | deflate_state *ds; | |
584 | deflate_state *ss; | |
585 | ush *overlay; | |
586 | deflate_workspace *mem; | |
587 | ||
588 | ||
589 | if (source == NULL || dest == NULL || source->state == NULL) { | |
590 | return Z_STREAM_ERROR; | |
591 | } | |
592 | ||
593 | ss = (deflate_state *) source->state; | |
594 | ||
595 | *dest = *source; | |
596 | ||
597 | mem = (deflate_workspace *) dest->workspace; | |
598 | ||
599 | ds = &(mem->deflate_memory); | |
600 | ||
601 | dest->state = (struct internal_state *) ds; | |
602 | *ds = *ss; | |
603 | ds->strm = dest; | |
604 | ||
605 | ds->window = (Byte *) mem->window_memory; | |
606 | ds->prev = (Pos *) mem->prev_memory; | |
607 | ds->head = (Pos *) mem->head_memory; | |
608 | overlay = (ush *) mem->overlay_memory; | |
609 | ds->pending_buf = (uch *) overlay; | |
610 | ||
611 | memcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte)); | |
612 | memcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos)); | |
613 | memcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos)); | |
614 | memcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size); | |
615 | ||
616 | ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf); | |
617 | ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush); | |
618 | ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize; | |
619 | ||
620 | ds->l_desc.dyn_tree = ds->dyn_ltree; | |
621 | ds->d_desc.dyn_tree = ds->dyn_dtree; | |
622 | ds->bl_desc.dyn_tree = ds->bl_tree; | |
623 | ||
624 | return Z_OK; | |
625 | #endif | |
626 | } | |
627 | ||
628 | /* =========================================================================== | |
629 | * Read a new buffer from the current input stream, update the adler32 | |
630 | * and total number of bytes read. All deflate() input goes through | |
631 | * this function so some applications may wish to modify it to avoid | |
632 | * allocating a large strm->next_in buffer and copying from it. | |
633 | * (See also flush_pending()). | |
634 | */ | |
635 | static int read_buf( | |
636 | z_streamp strm, | |
637 | Byte *buf, | |
638 | unsigned size | |
639 | ) | |
640 | { | |
641 | unsigned len = strm->avail_in; | |
642 | ||
643 | if (len > size) len = size; | |
644 | if (len == 0) return 0; | |
645 | ||
646 | strm->avail_in -= len; | |
647 | ||
648 | if (!((deflate_state *)(strm->state))->noheader) { | |
649 | strm->adler = zlib_adler32(strm->adler, strm->next_in, len); | |
650 | } | |
651 | memcpy(buf, strm->next_in, len); | |
652 | strm->next_in += len; | |
653 | strm->total_in += len; | |
654 | ||
655 | return (int)len; | |
656 | } | |
657 | ||
658 | /* =========================================================================== | |
659 | * Initialize the "longest match" routines for a new zlib stream | |
660 | */ | |
661 | static void lm_init( | |
662 | deflate_state *s | |
663 | ) | |
664 | { | |
665 | s->window_size = (ulg)2L*s->w_size; | |
666 | ||
667 | CLEAR_HASH(s); | |
668 | ||
669 | /* Set the default configuration parameters: | |
670 | */ | |
671 | s->max_lazy_match = configuration_table[s->level].max_lazy; | |
672 | s->good_match = configuration_table[s->level].good_length; | |
673 | s->nice_match = configuration_table[s->level].nice_length; | |
674 | s->max_chain_length = configuration_table[s->level].max_chain; | |
675 | ||
676 | s->strstart = 0; | |
677 | s->block_start = 0L; | |
678 | s->lookahead = 0; | |
679 | s->match_length = s->prev_length = MIN_MATCH-1; | |
680 | s->match_available = 0; | |
681 | s->ins_h = 0; | |
682 | } | |
683 | ||
684 | /* =========================================================================== | |
685 | * Set match_start to the longest match starting at the given string and | |
686 | * return its length. Matches shorter or equal to prev_length are discarded, | |
687 | * in which case the result is equal to prev_length and match_start is | |
688 | * garbage. | |
689 | * IN assertions: cur_match is the head of the hash chain for the current | |
690 | * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 | |
691 | * OUT assertion: the match length is not greater than s->lookahead. | |
692 | */ | |
693 | /* For 80x86 and 680x0, an optimized version will be provided in match.asm or | |
694 | * match.S. The code will be functionally equivalent. | |
695 | */ | |
696 | static uInt longest_match( | |
697 | deflate_state *s, | |
698 | IPos cur_match /* current match */ | |
699 | ) | |
700 | { | |
701 | unsigned chain_length = s->max_chain_length;/* max hash chain length */ | |
702 | register Byte *scan = s->window + s->strstart; /* current string */ | |
703 | register Byte *match; /* matched string */ | |
704 | register int len; /* length of current match */ | |
705 | int best_len = s->prev_length; /* best match length so far */ | |
706 | int nice_match = s->nice_match; /* stop if match long enough */ | |
707 | IPos limit = s->strstart > (IPos)MAX_DIST(s) ? | |
708 | s->strstart - (IPos)MAX_DIST(s) : NIL; | |
709 | /* Stop when cur_match becomes <= limit. To simplify the code, | |
710 | * we prevent matches with the string of window index 0. | |
711 | */ | |
712 | Pos *prev = s->prev; | |
713 | uInt wmask = s->w_mask; | |
714 | ||
715 | #ifdef UNALIGNED_OK | |
716 | /* Compare two bytes at a time. Note: this is not always beneficial. | |
717 | * Try with and without -DUNALIGNED_OK to check. | |
718 | */ | |
719 | register Byte *strend = s->window + s->strstart + MAX_MATCH - 1; | |
720 | register ush scan_start = *(ush*)scan; | |
721 | register ush scan_end = *(ush*)(scan+best_len-1); | |
722 | #else | |
723 | register Byte *strend = s->window + s->strstart + MAX_MATCH; | |
724 | register Byte scan_end1 = scan[best_len-1]; | |
725 | register Byte scan_end = scan[best_len]; | |
726 | #endif | |
727 | ||
728 | /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. | |
729 | * It is easy to get rid of this optimization if necessary. | |
730 | */ | |
731 | Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); | |
732 | ||
733 | /* Do not waste too much time if we already have a good match: */ | |
734 | if (s->prev_length >= s->good_match) { | |
735 | chain_length >>= 2; | |
736 | } | |
737 | /* Do not look for matches beyond the end of the input. This is necessary | |
738 | * to make deflate deterministic. | |
739 | */ | |
740 | if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; | |
741 | ||
742 | Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); | |
743 | ||
744 | do { | |
745 | Assert(cur_match < s->strstart, "no future"); | |
746 | match = s->window + cur_match; | |
747 | ||
748 | /* Skip to next match if the match length cannot increase | |
749 | * or if the match length is less than 2: | |
750 | */ | |
751 | #if (defined(UNALIGNED_OK) && MAX_MATCH == 258) | |
752 | /* This code assumes sizeof(unsigned short) == 2. Do not use | |
753 | * UNALIGNED_OK if your compiler uses a different size. | |
754 | */ | |
755 | if (*(ush*)(match+best_len-1) != scan_end || | |
756 | *(ush*)match != scan_start) continue; | |
757 | ||
758 | /* It is not necessary to compare scan[2] and match[2] since they are | |
759 | * always equal when the other bytes match, given that the hash keys | |
760 | * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at | |
761 | * strstart+3, +5, ... up to strstart+257. We check for insufficient | |
762 | * lookahead only every 4th comparison; the 128th check will be made | |
763 | * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is | |
764 | * necessary to put more guard bytes at the end of the window, or | |
765 | * to check more often for insufficient lookahead. | |
766 | */ | |
767 | Assert(scan[2] == match[2], "scan[2]?"); | |
768 | scan++, match++; | |
769 | do { | |
770 | } while (*(ush*)(scan+=2) == *(ush*)(match+=2) && | |
771 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
772 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
773 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
774 | scan < strend); | |
775 | /* The funny "do {}" generates better code on most compilers */ | |
776 | ||
777 | /* Here, scan <= window+strstart+257 */ | |
778 | Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); | |
779 | if (*scan == *match) scan++; | |
780 | ||
781 | len = (MAX_MATCH - 1) - (int)(strend-scan); | |
782 | scan = strend - (MAX_MATCH-1); | |
783 | ||
784 | #else /* UNALIGNED_OK */ | |
785 | ||
786 | if (match[best_len] != scan_end || | |
787 | match[best_len-1] != scan_end1 || | |
788 | *match != *scan || | |
789 | *++match != scan[1]) continue; | |
790 | ||
791 | /* The check at best_len-1 can be removed because it will be made | |
792 | * again later. (This heuristic is not always a win.) | |
793 | * It is not necessary to compare scan[2] and match[2] since they | |
794 | * are always equal when the other bytes match, given that | |
795 | * the hash keys are equal and that HASH_BITS >= 8. | |
796 | */ | |
797 | scan += 2, match++; | |
798 | Assert(*scan == *match, "match[2]?"); | |
799 | ||
800 | /* We check for insufficient lookahead only every 8th comparison; | |
801 | * the 256th check will be made at strstart+258. | |
802 | */ | |
803 | do { | |
804 | } while (*++scan == *++match && *++scan == *++match && | |
805 | *++scan == *++match && *++scan == *++match && | |
806 | *++scan == *++match && *++scan == *++match && | |
807 | *++scan == *++match && *++scan == *++match && | |
808 | scan < strend); | |
809 | ||
810 | Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); | |
811 | ||
812 | len = MAX_MATCH - (int)(strend - scan); | |
813 | scan = strend - MAX_MATCH; | |
814 | ||
815 | #endif /* UNALIGNED_OK */ | |
816 | ||
817 | if (len > best_len) { | |
818 | s->match_start = cur_match; | |
819 | best_len = len; | |
820 | if (len >= nice_match) break; | |
821 | #ifdef UNALIGNED_OK | |
822 | scan_end = *(ush*)(scan+best_len-1); | |
823 | #else | |
824 | scan_end1 = scan[best_len-1]; | |
825 | scan_end = scan[best_len]; | |
826 | #endif | |
827 | } | |
828 | } while ((cur_match = prev[cur_match & wmask]) > limit | |
829 | && --chain_length != 0); | |
830 | ||
831 | if ((uInt)best_len <= s->lookahead) return best_len; | |
832 | return s->lookahead; | |
833 | } | |
834 | ||
835 | #ifdef DEBUG_ZLIB | |
836 | /* =========================================================================== | |
837 | * Check that the match at match_start is indeed a match. | |
838 | */ | |
839 | static void check_match( | |
840 | deflate_state *s, | |
841 | IPos start, | |
842 | IPos match, | |
843 | int length | |
844 | ) | |
845 | { | |
846 | /* check that the match is indeed a match */ | |
847 | if (memcmp((char *)s->window + match, | |
848 | (char *)s->window + start, length) != EQUAL) { | |
849 | fprintf(stderr, " start %u, match %u, length %d\n", | |
850 | start, match, length); | |
851 | do { | |
852 | fprintf(stderr, "%c%c", s->window[match++], s->window[start++]); | |
853 | } while (--length != 0); | |
854 | z_error("invalid match"); | |
855 | } | |
856 | if (z_verbose > 1) { | |
857 | fprintf(stderr,"\\[%d,%d]", start-match, length); | |
858 | do { putc(s->window[start++], stderr); } while (--length != 0); | |
859 | } | |
860 | } | |
861 | #else | |
862 | # define check_match(s, start, match, length) | |
863 | #endif | |
864 | ||
865 | /* =========================================================================== | |
866 | * Fill the window when the lookahead becomes insufficient. | |
867 | * Updates strstart and lookahead. | |
868 | * | |
869 | * IN assertion: lookahead < MIN_LOOKAHEAD | |
870 | * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD | |
871 | * At least one byte has been read, or avail_in == 0; reads are | |
872 | * performed for at least two bytes (required for the zip translate_eol | |
873 | * option -- not supported here). | |
874 | */ | |
875 | static void fill_window( | |
876 | deflate_state *s | |
877 | ) | |
878 | { | |
879 | register unsigned n, m; | |
880 | register Pos *p; | |
881 | unsigned more; /* Amount of free space at the end of the window. */ | |
882 | uInt wsize = s->w_size; | |
883 | ||
884 | do { | |
885 | more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); | |
886 | ||
887 | /* Deal with !@#$% 64K limit: */ | |
888 | if (more == 0 && s->strstart == 0 && s->lookahead == 0) { | |
889 | more = wsize; | |
890 | ||
891 | } else if (more == (unsigned)(-1)) { | |
892 | /* Very unlikely, but possible on 16 bit machine if strstart == 0 | |
893 | * and lookahead == 1 (input done one byte at time) | |
894 | */ | |
895 | more--; | |
896 | ||
897 | /* If the window is almost full and there is insufficient lookahead, | |
898 | * move the upper half to the lower one to make room in the upper half. | |
899 | */ | |
900 | } else if (s->strstart >= wsize+MAX_DIST(s)) { | |
901 | ||
902 | memcpy((char *)s->window, (char *)s->window+wsize, | |
903 | (unsigned)wsize); | |
904 | s->match_start -= wsize; | |
905 | s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ | |
906 | s->block_start -= (long) wsize; | |
907 | ||
908 | /* Slide the hash table (could be avoided with 32 bit values | |
909 | at the expense of memory usage). We slide even when level == 0 | |
910 | to keep the hash table consistent if we switch back to level > 0 | |
911 | later. (Using level 0 permanently is not an optimal usage of | |
912 | zlib, so we don't care about this pathological case.) | |
913 | */ | |
914 | n = s->hash_size; | |
915 | p = &s->head[n]; | |
916 | do { | |
917 | m = *--p; | |
918 | *p = (Pos)(m >= wsize ? m-wsize : NIL); | |
919 | } while (--n); | |
920 | ||
921 | n = wsize; | |
922 | p = &s->prev[n]; | |
923 | do { | |
924 | m = *--p; | |
925 | *p = (Pos)(m >= wsize ? m-wsize : NIL); | |
926 | /* If n is not on any hash chain, prev[n] is garbage but | |
927 | * its value will never be used. | |
928 | */ | |
929 | } while (--n); | |
930 | more += wsize; | |
931 | } | |
932 | if (s->strm->avail_in == 0) return; | |
933 | ||
934 | /* If there was no sliding: | |
935 | * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && | |
936 | * more == window_size - lookahead - strstart | |
937 | * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) | |
938 | * => more >= window_size - 2*WSIZE + 2 | |
939 | * In the BIG_MEM or MMAP case (not yet supported), | |
940 | * window_size == input_size + MIN_LOOKAHEAD && | |
941 | * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. | |
942 | * Otherwise, window_size == 2*WSIZE so more >= 2. | |
943 | * If there was sliding, more >= WSIZE. So in all cases, more >= 2. | |
944 | */ | |
945 | Assert(more >= 2, "more < 2"); | |
946 | ||
947 | n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more); | |
948 | s->lookahead += n; | |
949 | ||
950 | /* Initialize the hash value now that we have some input: */ | |
951 | if (s->lookahead >= MIN_MATCH) { | |
952 | s->ins_h = s->window[s->strstart]; | |
953 | UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); | |
954 | #if MIN_MATCH != 3 | |
955 | Call UPDATE_HASH() MIN_MATCH-3 more times | |
956 | #endif | |
957 | } | |
958 | /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, | |
959 | * but this is not important since only literal bytes will be emitted. | |
960 | */ | |
961 | ||
962 | } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); | |
963 | } | |
964 | ||
965 | /* =========================================================================== | |
966 | * Flush the current block, with given end-of-file flag. | |
967 | * IN assertion: strstart is set to the end of the current match. | |
968 | */ | |
969 | #define FLUSH_BLOCK_ONLY(s, eof) { \ | |
970 | zlib_tr_flush_block(s, (s->block_start >= 0L ? \ | |
971 | (char *)&s->window[(unsigned)s->block_start] : \ | |
972 | NULL), \ | |
973 | (ulg)((long)s->strstart - s->block_start), \ | |
974 | (eof)); \ | |
975 | s->block_start = s->strstart; \ | |
976 | flush_pending(s->strm); \ | |
977 | Tracev((stderr,"[FLUSH]")); \ | |
978 | } | |
979 | ||
980 | /* Same but force premature exit if necessary. */ | |
981 | #define FLUSH_BLOCK(s, eof) { \ | |
982 | FLUSH_BLOCK_ONLY(s, eof); \ | |
983 | if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \ | |
984 | } | |
985 | ||
986 | /* =========================================================================== | |
987 | * Copy without compression as much as possible from the input stream, return | |
988 | * the current block state. | |
989 | * This function does not insert new strings in the dictionary since | |
990 | * uncompressible data is probably not useful. This function is used | |
991 | * only for the level=0 compression option. | |
992 | * NOTE: this function should be optimized to avoid extra copying from | |
993 | * window to pending_buf. | |
994 | */ | |
995 | static block_state deflate_stored( | |
996 | deflate_state *s, | |
997 | int flush | |
998 | ) | |
999 | { | |
1000 | /* Stored blocks are limited to 0xffff bytes, pending_buf is limited | |
1001 | * to pending_buf_size, and each stored block has a 5 byte header: | |
1002 | */ | |
1003 | ulg max_block_size = 0xffff; | |
1004 | ulg max_start; | |
1005 | ||
1006 | if (max_block_size > s->pending_buf_size - 5) { | |
1007 | max_block_size = s->pending_buf_size - 5; | |
1008 | } | |
1009 | ||
1010 | /* Copy as much as possible from input to output: */ | |
1011 | for (;;) { | |
1012 | /* Fill the window as much as possible: */ | |
1013 | if (s->lookahead <= 1) { | |
1014 | ||
1015 | Assert(s->strstart < s->w_size+MAX_DIST(s) || | |
1016 | s->block_start >= (long)s->w_size, "slide too late"); | |
1017 | ||
1018 | fill_window(s); | |
1019 | if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; | |
1020 | ||
1021 | if (s->lookahead == 0) break; /* flush the current block */ | |
1022 | } | |
1023 | Assert(s->block_start >= 0L, "block gone"); | |
1024 | ||
1025 | s->strstart += s->lookahead; | |
1026 | s->lookahead = 0; | |
1027 | ||
1028 | /* Emit a stored block if pending_buf will be full: */ | |
1029 | max_start = s->block_start + max_block_size; | |
1030 | if (s->strstart == 0 || (ulg)s->strstart >= max_start) { | |
1031 | /* strstart == 0 is possible when wraparound on 16-bit machine */ | |
1032 | s->lookahead = (uInt)(s->strstart - max_start); | |
1033 | s->strstart = (uInt)max_start; | |
1034 | FLUSH_BLOCK(s, 0); | |
1035 | } | |
1036 | /* Flush if we may have to slide, otherwise block_start may become | |
1037 | * negative and the data will be gone: | |
1038 | */ | |
1039 | if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { | |
1040 | FLUSH_BLOCK(s, 0); | |
1041 | } | |
1042 | } | |
1043 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
1044 | return flush == Z_FINISH ? finish_done : block_done; | |
1045 | } | |
1046 | ||
1047 | /* =========================================================================== | |
1048 | * Compress as much as possible from the input stream, return the current | |
1049 | * block state. | |
1050 | * This function does not perform lazy evaluation of matches and inserts | |
1051 | * new strings in the dictionary only for unmatched strings or for short | |
1052 | * matches. It is used only for the fast compression options. | |
1053 | */ | |
1054 | static block_state deflate_fast( | |
1055 | deflate_state *s, | |
1056 | int flush | |
1057 | ) | |
1058 | { | |
1059 | IPos hash_head = NIL; /* head of the hash chain */ | |
1060 | int bflush; /* set if current block must be flushed */ | |
1061 | ||
1062 | for (;;) { | |
1063 | /* Make sure that we always have enough lookahead, except | |
1064 | * at the end of the input file. We need MAX_MATCH bytes | |
1065 | * for the next match, plus MIN_MATCH bytes to insert the | |
1066 | * string following the next match. | |
1067 | */ | |
1068 | if (s->lookahead < MIN_LOOKAHEAD) { | |
1069 | fill_window(s); | |
1070 | if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { | |
1071 | return need_more; | |
1072 | } | |
1073 | if (s->lookahead == 0) break; /* flush the current block */ | |
1074 | } | |
1075 | ||
1076 | /* Insert the string window[strstart .. strstart+2] in the | |
1077 | * dictionary, and set hash_head to the head of the hash chain: | |
1078 | */ | |
1079 | if (s->lookahead >= MIN_MATCH) { | |
1080 | INSERT_STRING(s, s->strstart, hash_head); | |
1081 | } | |
1082 | ||
1083 | /* Find the longest match, discarding those <= prev_length. | |
1084 | * At this point we have always match_length < MIN_MATCH | |
1085 | */ | |
1086 | if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { | |
1087 | /* To simplify the code, we prevent matches with the string | |
1088 | * of window index 0 (in particular we have to avoid a match | |
1089 | * of the string with itself at the start of the input file). | |
1090 | */ | |
1091 | if (s->strategy != Z_HUFFMAN_ONLY) { | |
1092 | s->match_length = longest_match (s, hash_head); | |
1093 | } | |
1094 | /* longest_match() sets match_start */ | |
1095 | } | |
1096 | if (s->match_length >= MIN_MATCH) { | |
1097 | check_match(s, s->strstart, s->match_start, s->match_length); | |
1098 | ||
1099 | bflush = zlib_tr_tally(s, s->strstart - s->match_start, | |
1100 | s->match_length - MIN_MATCH); | |
1101 | ||
1102 | s->lookahead -= s->match_length; | |
1103 | ||
1104 | /* Insert new strings in the hash table only if the match length | |
1105 | * is not too large. This saves time but degrades compression. | |
1106 | */ | |
1107 | if (s->match_length <= s->max_insert_length && | |
1108 | s->lookahead >= MIN_MATCH) { | |
1109 | s->match_length--; /* string at strstart already in hash table */ | |
1110 | do { | |
1111 | s->strstart++; | |
1112 | INSERT_STRING(s, s->strstart, hash_head); | |
1113 | /* strstart never exceeds WSIZE-MAX_MATCH, so there are | |
1114 | * always MIN_MATCH bytes ahead. | |
1115 | */ | |
1116 | } while (--s->match_length != 0); | |
1117 | s->strstart++; | |
1118 | } else { | |
1119 | s->strstart += s->match_length; | |
1120 | s->match_length = 0; | |
1121 | s->ins_h = s->window[s->strstart]; | |
1122 | UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); | |
1123 | #if MIN_MATCH != 3 | |
1124 | Call UPDATE_HASH() MIN_MATCH-3 more times | |
1125 | #endif | |
1126 | /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not | |
1127 | * matter since it will be recomputed at next deflate call. | |
1128 | */ | |
1129 | } | |
1130 | } else { | |
1131 | /* No match, output a literal byte */ | |
1132 | Tracevv((stderr,"%c", s->window[s->strstart])); | |
1133 | bflush = zlib_tr_tally (s, 0, s->window[s->strstart]); | |
1134 | s->lookahead--; | |
1135 | s->strstart++; | |
1136 | } | |
1137 | if (bflush) FLUSH_BLOCK(s, 0); | |
1138 | } | |
1139 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
1140 | return flush == Z_FINISH ? finish_done : block_done; | |
1141 | } | |
1142 | ||
1143 | /* =========================================================================== | |
1144 | * Same as above, but achieves better compression. We use a lazy | |
1145 | * evaluation for matches: a match is finally adopted only if there is | |
1146 | * no better match at the next window position. | |
1147 | */ | |
1148 | static block_state deflate_slow( | |
1149 | deflate_state *s, | |
1150 | int flush | |
1151 | ) | |
1152 | { | |
1153 | IPos hash_head = NIL; /* head of hash chain */ | |
1154 | int bflush; /* set if current block must be flushed */ | |
1155 | ||
1156 | /* Process the input block. */ | |
1157 | for (;;) { | |
1158 | /* Make sure that we always have enough lookahead, except | |
1159 | * at the end of the input file. We need MAX_MATCH bytes | |
1160 | * for the next match, plus MIN_MATCH bytes to insert the | |
1161 | * string following the next match. | |
1162 | */ | |
1163 | if (s->lookahead < MIN_LOOKAHEAD) { | |
1164 | fill_window(s); | |
1165 | if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { | |
1166 | return need_more; | |
1167 | } | |
1168 | if (s->lookahead == 0) break; /* flush the current block */ | |
1169 | } | |
1170 | ||
1171 | /* Insert the string window[strstart .. strstart+2] in the | |
1172 | * dictionary, and set hash_head to the head of the hash chain: | |
1173 | */ | |
1174 | if (s->lookahead >= MIN_MATCH) { | |
1175 | INSERT_STRING(s, s->strstart, hash_head); | |
1176 | } | |
1177 | ||
1178 | /* Find the longest match, discarding those <= prev_length. | |
1179 | */ | |
1180 | s->prev_length = s->match_length, s->prev_match = s->match_start; | |
1181 | s->match_length = MIN_MATCH-1; | |
1182 | ||
1183 | if (hash_head != NIL && s->prev_length < s->max_lazy_match && | |
1184 | s->strstart - hash_head <= MAX_DIST(s)) { | |
1185 | /* To simplify the code, we prevent matches with the string | |
1186 | * of window index 0 (in particular we have to avoid a match | |
1187 | * of the string with itself at the start of the input file). | |
1188 | */ | |
1189 | if (s->strategy != Z_HUFFMAN_ONLY) { | |
1190 | s->match_length = longest_match (s, hash_head); | |
1191 | } | |
1192 | /* longest_match() sets match_start */ | |
1193 | ||
1194 | if (s->match_length <= 5 && (s->strategy == Z_FILTERED || | |
1195 | (s->match_length == MIN_MATCH && | |
1196 | s->strstart - s->match_start > TOO_FAR))) { | |
1197 | ||
1198 | /* If prev_match is also MIN_MATCH, match_start is garbage | |
1199 | * but we will ignore the current match anyway. | |
1200 | */ | |
1201 | s->match_length = MIN_MATCH-1; | |
1202 | } | |
1203 | } | |
1204 | /* If there was a match at the previous step and the current | |
1205 | * match is not better, output the previous match: | |
1206 | */ | |
1207 | if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { | |
1208 | uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; | |
1209 | /* Do not insert strings in hash table beyond this. */ | |
1210 | ||
1211 | check_match(s, s->strstart-1, s->prev_match, s->prev_length); | |
1212 | ||
1213 | bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match, | |
1214 | s->prev_length - MIN_MATCH); | |
1215 | ||
1216 | /* Insert in hash table all strings up to the end of the match. | |
1217 | * strstart-1 and strstart are already inserted. If there is not | |
1218 | * enough lookahead, the last two strings are not inserted in | |
1219 | * the hash table. | |
1220 | */ | |
1221 | s->lookahead -= s->prev_length-1; | |
1222 | s->prev_length -= 2; | |
1223 | do { | |
1224 | if (++s->strstart <= max_insert) { | |
1225 | INSERT_STRING(s, s->strstart, hash_head); | |
1226 | } | |
1227 | } while (--s->prev_length != 0); | |
1228 | s->match_available = 0; | |
1229 | s->match_length = MIN_MATCH-1; | |
1230 | s->strstart++; | |
1231 | ||
1232 | if (bflush) FLUSH_BLOCK(s, 0); | |
1233 | ||
1234 | } else if (s->match_available) { | |
1235 | /* If there was no match at the previous position, output a | |
1236 | * single literal. If there was a match but the current match | |
1237 | * is longer, truncate the previous match to a single literal. | |
1238 | */ | |
1239 | Tracevv((stderr,"%c", s->window[s->strstart-1])); | |
1240 | if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) { | |
1241 | FLUSH_BLOCK_ONLY(s, 0); | |
1242 | } | |
1243 | s->strstart++; | |
1244 | s->lookahead--; | |
1245 | if (s->strm->avail_out == 0) return need_more; | |
1246 | } else { | |
1247 | /* There is no previous match to compare with, wait for | |
1248 | * the next step to decide. | |
1249 | */ | |
1250 | s->match_available = 1; | |
1251 | s->strstart++; | |
1252 | s->lookahead--; | |
1253 | } | |
1254 | } | |
1255 | Assert (flush != Z_NO_FLUSH, "no flush?"); | |
1256 | if (s->match_available) { | |
1257 | Tracevv((stderr,"%c", s->window[s->strstart-1])); | |
1258 | zlib_tr_tally (s, 0, s->window[s->strstart-1]); | |
1259 | s->match_available = 0; | |
1260 | } | |
1261 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
1262 | return flush == Z_FINISH ? finish_done : block_done; | |
1263 | } | |
1264 | ||
1265 | int zlib_deflate_workspacesize(void) | |
1266 | { | |
1267 | return sizeof(deflate_workspace); | |
1268 | } |