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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 | ||
aa5b395b MZ |
55 | /* architecture-specific bits */ |
56 | #ifdef CONFIG_ZLIB_DFLTCC | |
9fec9f8e | 57 | # include "../zlib_dfltcc/dfltcc_deflate.h" |
aa5b395b MZ |
58 | #else |
59 | #define DEFLATE_RESET_HOOK(strm) do {} while (0) | |
60 | #define DEFLATE_HOOK(strm, flush, bstate) 0 | |
61 | #define DEFLATE_NEED_CHECKSUM(strm) 1 | |
803521b1 | 62 | #define DEFLATE_DFLTCC_ENABLED() 0 |
aa5b395b | 63 | #endif |
1da177e4 LT |
64 | |
65 | /* =========================================================================== | |
66 | * Function prototypes. | |
67 | */ | |
1da177e4 LT |
68 | |
69 | typedef block_state (*compress_func) (deflate_state *s, int flush); | |
70 | /* Compression function. Returns the block state after the call. */ | |
71 | ||
72 | static void fill_window (deflate_state *s); | |
73 | static block_state deflate_stored (deflate_state *s, int flush); | |
74 | static block_state deflate_fast (deflate_state *s, int flush); | |
75 | static block_state deflate_slow (deflate_state *s, int flush); | |
76 | static void lm_init (deflate_state *s); | |
77 | static void putShortMSB (deflate_state *s, uInt b); | |
1da177e4 LT |
78 | static int read_buf (z_streamp strm, Byte *buf, unsigned size); |
79 | static uInt longest_match (deflate_state *s, IPos cur_match); | |
80 | ||
81 | #ifdef DEBUG_ZLIB | |
82 | static void check_match (deflate_state *s, IPos start, IPos match, | |
83 | int length); | |
84 | #endif | |
85 | ||
86 | /* =========================================================================== | |
87 | * Local data | |
88 | */ | |
89 | ||
90 | #define NIL 0 | |
91 | /* Tail of hash chains */ | |
92 | ||
93 | #ifndef TOO_FAR | |
94 | # define TOO_FAR 4096 | |
95 | #endif | |
96 | /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */ | |
97 | ||
98 | #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) | |
99 | /* Minimum amount of lookahead, except at the end of the input file. | |
100 | * See deflate.c for comments about the MIN_MATCH+1. | |
101 | */ | |
102 | ||
aa5b395b MZ |
103 | /* Workspace to be allocated for deflate processing */ |
104 | typedef struct deflate_workspace { | |
105 | /* State memory for the deflator */ | |
106 | deflate_state deflate_memory; | |
107 | #ifdef CONFIG_ZLIB_DFLTCC | |
108 | /* State memory for s390 hardware deflate */ | |
9fec9f8e | 109 | struct dfltcc_deflate_state dfltcc_memory; |
aa5b395b MZ |
110 | #endif |
111 | Byte *window_memory; | |
112 | Pos *prev_memory; | |
113 | Pos *head_memory; | |
114 | char *overlay_memory; | |
115 | } deflate_workspace; | |
116 | ||
117 | #ifdef CONFIG_ZLIB_DFLTCC | |
118 | /* dfltcc_state must be doubleword aligned for DFLTCC call */ | |
119 | static_assert(offsetof(struct deflate_workspace, dfltcc_memory) % 8 == 0); | |
120 | #endif | |
121 | ||
1da177e4 LT |
122 | /* Values for max_lazy_match, good_match and max_chain_length, depending on |
123 | * the desired pack level (0..9). The values given below have been tuned to | |
124 | * exclude worst case performance for pathological files. Better values may be | |
125 | * found for specific files. | |
126 | */ | |
127 | typedef struct config_s { | |
128 | ush good_length; /* reduce lazy search above this match length */ | |
129 | ush max_lazy; /* do not perform lazy search above this match length */ | |
130 | ush nice_length; /* quit search above this match length */ | |
131 | ush max_chain; | |
132 | compress_func func; | |
133 | } config; | |
134 | ||
135 | static const config configuration_table[10] = { | |
136 | /* good lazy nice chain */ | |
137 | /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */ | |
138 | /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */ | |
139 | /* 2 */ {4, 5, 16, 8, deflate_fast}, | |
140 | /* 3 */ {4, 6, 32, 32, deflate_fast}, | |
141 | ||
142 | /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */ | |
143 | /* 5 */ {8, 16, 32, 32, deflate_slow}, | |
144 | /* 6 */ {8, 16, 128, 128, deflate_slow}, | |
145 | /* 7 */ {8, 32, 128, 256, deflate_slow}, | |
146 | /* 8 */ {32, 128, 258, 1024, deflate_slow}, | |
147 | /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */ | |
148 | ||
149 | /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4 | |
150 | * For deflate_fast() (levels <= 3) good is ignored and lazy has a different | |
151 | * meaning. | |
152 | */ | |
153 | ||
154 | #define EQUAL 0 | |
155 | /* result of memcmp for equal strings */ | |
156 | ||
157 | /* =========================================================================== | |
158 | * Update a hash value with the given input byte | |
fd589a8f | 159 | * IN assertion: all calls to UPDATE_HASH are made with consecutive |
1da177e4 LT |
160 | * input characters, so that a running hash key can be computed from the |
161 | * previous key instead of complete recalculation each time. | |
162 | */ | |
163 | #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask) | |
164 | ||
165 | ||
166 | /* =========================================================================== | |
167 | * Insert string str in the dictionary and set match_head to the previous head | |
168 | * of the hash chain (the most recent string with same hash key). Return | |
169 | * the previous length of the hash chain. | |
fd589a8f | 170 | * IN assertion: all calls to INSERT_STRING are made with consecutive |
1da177e4 LT |
171 | * input characters and the first MIN_MATCH bytes of str are valid |
172 | * (except for the last MIN_MATCH-1 bytes of the input file). | |
173 | */ | |
174 | #define INSERT_STRING(s, str, match_head) \ | |
175 | (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ | |
176 | s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \ | |
177 | s->head[s->ins_h] = (Pos)(str)) | |
178 | ||
179 | /* =========================================================================== | |
180 | * Initialize the hash table (avoiding 64K overflow for 16 bit systems). | |
181 | * prev[] will be initialized on the fly. | |
182 | */ | |
183 | #define CLEAR_HASH(s) \ | |
184 | s->head[s->hash_size-1] = NIL; \ | |
185 | memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head)); | |
186 | ||
187 | /* ========================================================================= */ | |
4f3865fb | 188 | int zlib_deflateInit2( |
1da177e4 LT |
189 | z_streamp strm, |
190 | int level, | |
191 | int method, | |
192 | int windowBits, | |
193 | int memLevel, | |
4f3865fb | 194 | int strategy |
1da177e4 LT |
195 | ) |
196 | { | |
197 | deflate_state *s; | |
198 | int noheader = 0; | |
1da177e4 | 199 | deflate_workspace *mem; |
565d76cb | 200 | char *next; |
1da177e4 LT |
201 | |
202 | ush *overlay; | |
203 | /* We overlay pending_buf and d_buf+l_buf. This works since the average | |
204 | * output size for (length,distance) codes is <= 24 bits. | |
205 | */ | |
206 | ||
1da177e4 LT |
207 | if (strm == NULL) return Z_STREAM_ERROR; |
208 | ||
209 | strm->msg = NULL; | |
210 | ||
211 | if (level == Z_DEFAULT_COMPRESSION) level = 6; | |
212 | ||
213 | mem = (deflate_workspace *) strm->workspace; | |
214 | ||
215 | if (windowBits < 0) { /* undocumented feature: suppress zlib header */ | |
216 | noheader = 1; | |
217 | windowBits = -windowBits; | |
218 | } | |
219 | if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || | |
220 | windowBits < 9 || windowBits > 15 || level < 0 || level > 9 || | |
221 | strategy < 0 || strategy > Z_HUFFMAN_ONLY) { | |
222 | return Z_STREAM_ERROR; | |
223 | } | |
565d76cb JK |
224 | |
225 | /* | |
226 | * Direct the workspace's pointers to the chunks that were allocated | |
227 | * along with the deflate_workspace struct. | |
228 | */ | |
229 | next = (char *) mem; | |
230 | next += sizeof(*mem); | |
aa5b395b MZ |
231 | #ifdef CONFIG_ZLIB_DFLTCC |
232 | /* | |
233 | * DFLTCC requires the window to be page aligned. | |
234 | * Thus, we overallocate and take the aligned portion of the buffer. | |
235 | */ | |
236 | mem->window_memory = (Byte *) PTR_ALIGN(next, PAGE_SIZE); | |
237 | #else | |
565d76cb | 238 | mem->window_memory = (Byte *) next; |
aa5b395b | 239 | #endif |
565d76cb JK |
240 | next += zlib_deflate_window_memsize(windowBits); |
241 | mem->prev_memory = (Pos *) next; | |
242 | next += zlib_deflate_prev_memsize(windowBits); | |
243 | mem->head_memory = (Pos *) next; | |
244 | next += zlib_deflate_head_memsize(memLevel); | |
245 | mem->overlay_memory = next; | |
246 | ||
1da177e4 LT |
247 | s = (deflate_state *) &(mem->deflate_memory); |
248 | strm->state = (struct internal_state *)s; | |
249 | s->strm = strm; | |
250 | ||
251 | s->noheader = noheader; | |
252 | s->w_bits = windowBits; | |
253 | s->w_size = 1 << s->w_bits; | |
254 | s->w_mask = s->w_size - 1; | |
255 | ||
256 | s->hash_bits = memLevel + 7; | |
257 | s->hash_size = 1 << s->hash_bits; | |
258 | s->hash_mask = s->hash_size - 1; | |
259 | s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH); | |
260 | ||
261 | s->window = (Byte *) mem->window_memory; | |
262 | s->prev = (Pos *) mem->prev_memory; | |
263 | s->head = (Pos *) mem->head_memory; | |
264 | ||
265 | s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ | |
266 | ||
267 | overlay = (ush *) mem->overlay_memory; | |
268 | s->pending_buf = (uch *) overlay; | |
269 | s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L); | |
270 | ||
271 | s->d_buf = overlay + s->lit_bufsize/sizeof(ush); | |
272 | s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize; | |
273 | ||
274 | s->level = level; | |
275 | s->strategy = strategy; | |
276 | s->method = (Byte)method; | |
277 | ||
278 | return zlib_deflateReset(strm); | |
279 | } | |
280 | ||
1da177e4 LT |
281 | /* ========================================================================= */ |
282 | int zlib_deflateReset( | |
283 | z_streamp strm | |
284 | ) | |
285 | { | |
286 | deflate_state *s; | |
287 | ||
288 | if (strm == NULL || strm->state == NULL) | |
289 | return Z_STREAM_ERROR; | |
290 | ||
291 | strm->total_in = strm->total_out = 0; | |
292 | strm->msg = NULL; | |
293 | strm->data_type = Z_UNKNOWN; | |
294 | ||
295 | s = (deflate_state *)strm->state; | |
296 | s->pending = 0; | |
297 | s->pending_out = s->pending_buf; | |
298 | ||
299 | if (s->noheader < 0) { | |
300 | s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ | |
301 | } | |
302 | s->status = s->noheader ? BUSY_STATE : INIT_STATE; | |
303 | strm->adler = 1; | |
304 | s->last_flush = Z_NO_FLUSH; | |
305 | ||
306 | zlib_tr_init(s); | |
307 | lm_init(s); | |
308 | ||
aa5b395b MZ |
309 | DEFLATE_RESET_HOOK(strm); |
310 | ||
1da177e4 LT |
311 | return Z_OK; |
312 | } | |
313 | ||
1da177e4 LT |
314 | /* ========================================================================= |
315 | * Put a short in the pending buffer. The 16-bit value is put in MSB order. | |
316 | * IN assertion: the stream state is correct and there is enough room in | |
317 | * pending_buf. | |
318 | */ | |
319 | static void putShortMSB( | |
320 | deflate_state *s, | |
321 | uInt b | |
322 | ) | |
323 | { | |
324 | put_byte(s, (Byte)(b >> 8)); | |
325 | put_byte(s, (Byte)(b & 0xff)); | |
326 | } | |
327 | ||
1da177e4 LT |
328 | /* ========================================================================= */ |
329 | int zlib_deflate( | |
330 | z_streamp strm, | |
331 | int flush | |
332 | ) | |
333 | { | |
334 | int old_flush; /* value of flush param for previous deflate call */ | |
335 | deflate_state *s; | |
336 | ||
337 | if (strm == NULL || strm->state == NULL || | |
338 | flush > Z_FINISH || flush < 0) { | |
339 | return Z_STREAM_ERROR; | |
340 | } | |
341 | s = (deflate_state *) strm->state; | |
342 | ||
343 | if ((strm->next_in == NULL && strm->avail_in != 0) || | |
344 | (s->status == FINISH_STATE && flush != Z_FINISH)) { | |
345 | return Z_STREAM_ERROR; | |
346 | } | |
347 | if (strm->avail_out == 0) return Z_BUF_ERROR; | |
348 | ||
349 | s->strm = strm; /* just in case */ | |
350 | old_flush = s->last_flush; | |
351 | s->last_flush = flush; | |
352 | ||
353 | /* Write the zlib header */ | |
354 | if (s->status == INIT_STATE) { | |
355 | ||
356 | uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; | |
357 | uInt level_flags = (s->level-1) >> 1; | |
358 | ||
359 | if (level_flags > 3) level_flags = 3; | |
360 | header |= (level_flags << 6); | |
361 | if (s->strstart != 0) header |= PRESET_DICT; | |
362 | header += 31 - (header % 31); | |
363 | ||
364 | s->status = BUSY_STATE; | |
365 | putShortMSB(s, header); | |
366 | ||
367 | /* Save the adler32 of the preset dictionary: */ | |
368 | if (s->strstart != 0) { | |
369 | putShortMSB(s, (uInt)(strm->adler >> 16)); | |
370 | putShortMSB(s, (uInt)(strm->adler & 0xffff)); | |
371 | } | |
372 | strm->adler = 1L; | |
373 | } | |
374 | ||
375 | /* Flush as much pending output as possible */ | |
376 | if (s->pending != 0) { | |
377 | flush_pending(strm); | |
378 | if (strm->avail_out == 0) { | |
379 | /* Since avail_out is 0, deflate will be called again with | |
380 | * more output space, but possibly with both pending and | |
381 | * avail_in equal to zero. There won't be anything to do, | |
382 | * but this is not an error situation so make sure we | |
383 | * return OK instead of BUF_ERROR at next call of deflate: | |
384 | */ | |
385 | s->last_flush = -1; | |
386 | return Z_OK; | |
387 | } | |
388 | ||
389 | /* Make sure there is something to do and avoid duplicate consecutive | |
390 | * flushes. For repeated and useless calls with Z_FINISH, we keep | |
391 | * returning Z_STREAM_END instead of Z_BUFF_ERROR. | |
392 | */ | |
393 | } else if (strm->avail_in == 0 && flush <= old_flush && | |
394 | flush != Z_FINISH) { | |
395 | return Z_BUF_ERROR; | |
396 | } | |
397 | ||
398 | /* User must not provide more input after the first FINISH: */ | |
399 | if (s->status == FINISH_STATE && strm->avail_in != 0) { | |
400 | return Z_BUF_ERROR; | |
401 | } | |
402 | ||
403 | /* Start a new block or continue the current one. | |
404 | */ | |
405 | if (strm->avail_in != 0 || s->lookahead != 0 || | |
406 | (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { | |
407 | block_state bstate; | |
408 | ||
aa5b395b MZ |
409 | bstate = DEFLATE_HOOK(strm, flush, &bstate) ? bstate : |
410 | (*(configuration_table[s->level].func))(s, flush); | |
1da177e4 LT |
411 | |
412 | if (bstate == finish_started || bstate == finish_done) { | |
413 | s->status = FINISH_STATE; | |
414 | } | |
415 | if (bstate == need_more || bstate == finish_started) { | |
416 | if (strm->avail_out == 0) { | |
417 | s->last_flush = -1; /* avoid BUF_ERROR next call, see above */ | |
418 | } | |
419 | return Z_OK; | |
420 | /* If flush != Z_NO_FLUSH && avail_out == 0, the next call | |
421 | * of deflate should use the same flush parameter to make sure | |
422 | * that the flush is complete. So we don't have to output an | |
423 | * empty block here, this will be done at next call. This also | |
424 | * ensures that for a very small output buffer, we emit at most | |
425 | * one empty block. | |
426 | */ | |
427 | } | |
428 | if (bstate == block_done) { | |
429 | if (flush == Z_PARTIAL_FLUSH) { | |
430 | zlib_tr_align(s); | |
431 | } else if (flush == Z_PACKET_FLUSH) { | |
432 | /* Output just the 3-bit `stored' block type value, | |
433 | but not a zero length. */ | |
434 | zlib_tr_stored_type_only(s); | |
435 | } else { /* FULL_FLUSH or SYNC_FLUSH */ | |
436 | zlib_tr_stored_block(s, (char*)0, 0L, 0); | |
437 | /* For a full flush, this empty block will be recognized | |
438 | * as a special marker by inflate_sync(). | |
439 | */ | |
440 | if (flush == Z_FULL_FLUSH) { | |
441 | CLEAR_HASH(s); /* forget history */ | |
442 | } | |
443 | } | |
444 | flush_pending(strm); | |
445 | if (strm->avail_out == 0) { | |
446 | s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ | |
447 | return Z_OK; | |
448 | } | |
449 | } | |
450 | } | |
451 | Assert(strm->avail_out > 0, "bug2"); | |
452 | ||
453 | if (flush != Z_FINISH) return Z_OK; | |
1da177e4 | 454 | |
195c5ad9 MZ |
455 | if (!s->noheader) { |
456 | /* Write zlib trailer (adler32) */ | |
457 | putShortMSB(s, (uInt)(strm->adler >> 16)); | |
458 | putShortMSB(s, (uInt)(strm->adler & 0xffff)); | |
459 | } | |
1da177e4 LT |
460 | flush_pending(strm); |
461 | /* If avail_out is zero, the application will call deflate again | |
462 | * to flush the rest. | |
463 | */ | |
195c5ad9 MZ |
464 | if (!s->noheader) { |
465 | s->noheader = -1; /* write the trailer only once! */ | |
466 | } | |
467 | if (s->pending == 0) { | |
468 | Assert(s->bi_valid == 0, "bi_buf not flushed"); | |
469 | return Z_STREAM_END; | |
470 | } | |
471 | return Z_OK; | |
1da177e4 LT |
472 | } |
473 | ||
474 | /* ========================================================================= */ | |
475 | int zlib_deflateEnd( | |
476 | z_streamp strm | |
477 | ) | |
478 | { | |
479 | int status; | |
480 | deflate_state *s; | |
481 | ||
482 | if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR; | |
483 | s = (deflate_state *) strm->state; | |
484 | ||
485 | status = s->status; | |
486 | if (status != INIT_STATE && status != BUSY_STATE && | |
487 | status != FINISH_STATE) { | |
488 | return Z_STREAM_ERROR; | |
489 | } | |
490 | ||
491 | strm->state = NULL; | |
492 | ||
493 | return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; | |
494 | } | |
495 | ||
1da177e4 LT |
496 | /* =========================================================================== |
497 | * Read a new buffer from the current input stream, update the adler32 | |
498 | * and total number of bytes read. All deflate() input goes through | |
499 | * this function so some applications may wish to modify it to avoid | |
500 | * allocating a large strm->next_in buffer and copying from it. | |
501 | * (See also flush_pending()). | |
502 | */ | |
503 | static int read_buf( | |
504 | z_streamp strm, | |
505 | Byte *buf, | |
506 | unsigned size | |
507 | ) | |
508 | { | |
509 | unsigned len = strm->avail_in; | |
510 | ||
511 | if (len > size) len = size; | |
512 | if (len == 0) return 0; | |
513 | ||
514 | strm->avail_in -= len; | |
515 | ||
aa5b395b MZ |
516 | if (!DEFLATE_NEED_CHECKSUM(strm)) {} |
517 | else if (!((deflate_state *)(strm->state))->noheader) { | |
1da177e4 LT |
518 | strm->adler = zlib_adler32(strm->adler, strm->next_in, len); |
519 | } | |
520 | memcpy(buf, strm->next_in, len); | |
521 | strm->next_in += len; | |
522 | strm->total_in += len; | |
523 | ||
524 | return (int)len; | |
525 | } | |
526 | ||
527 | /* =========================================================================== | |
528 | * Initialize the "longest match" routines for a new zlib stream | |
529 | */ | |
530 | static void lm_init( | |
531 | deflate_state *s | |
532 | ) | |
533 | { | |
534 | s->window_size = (ulg)2L*s->w_size; | |
535 | ||
536 | CLEAR_HASH(s); | |
537 | ||
538 | /* Set the default configuration parameters: | |
539 | */ | |
540 | s->max_lazy_match = configuration_table[s->level].max_lazy; | |
541 | s->good_match = configuration_table[s->level].good_length; | |
542 | s->nice_match = configuration_table[s->level].nice_length; | |
543 | s->max_chain_length = configuration_table[s->level].max_chain; | |
544 | ||
545 | s->strstart = 0; | |
546 | s->block_start = 0L; | |
547 | s->lookahead = 0; | |
548 | s->match_length = s->prev_length = MIN_MATCH-1; | |
549 | s->match_available = 0; | |
550 | s->ins_h = 0; | |
551 | } | |
552 | ||
553 | /* =========================================================================== | |
554 | * Set match_start to the longest match starting at the given string and | |
555 | * return its length. Matches shorter or equal to prev_length are discarded, | |
556 | * in which case the result is equal to prev_length and match_start is | |
557 | * garbage. | |
558 | * IN assertions: cur_match is the head of the hash chain for the current | |
559 | * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 | |
560 | * OUT assertion: the match length is not greater than s->lookahead. | |
561 | */ | |
562 | /* For 80x86 and 680x0, an optimized version will be provided in match.asm or | |
563 | * match.S. The code will be functionally equivalent. | |
564 | */ | |
565 | static uInt longest_match( | |
566 | deflate_state *s, | |
567 | IPos cur_match /* current match */ | |
568 | ) | |
569 | { | |
570 | unsigned chain_length = s->max_chain_length;/* max hash chain length */ | |
571 | register Byte *scan = s->window + s->strstart; /* current string */ | |
572 | register Byte *match; /* matched string */ | |
573 | register int len; /* length of current match */ | |
574 | int best_len = s->prev_length; /* best match length so far */ | |
575 | int nice_match = s->nice_match; /* stop if match long enough */ | |
576 | IPos limit = s->strstart > (IPos)MAX_DIST(s) ? | |
577 | s->strstart - (IPos)MAX_DIST(s) : NIL; | |
578 | /* Stop when cur_match becomes <= limit. To simplify the code, | |
579 | * we prevent matches with the string of window index 0. | |
580 | */ | |
581 | Pos *prev = s->prev; | |
582 | uInt wmask = s->w_mask; | |
583 | ||
584 | #ifdef UNALIGNED_OK | |
585 | /* Compare two bytes at a time. Note: this is not always beneficial. | |
586 | * Try with and without -DUNALIGNED_OK to check. | |
587 | */ | |
588 | register Byte *strend = s->window + s->strstart + MAX_MATCH - 1; | |
589 | register ush scan_start = *(ush*)scan; | |
590 | register ush scan_end = *(ush*)(scan+best_len-1); | |
591 | #else | |
592 | register Byte *strend = s->window + s->strstart + MAX_MATCH; | |
593 | register Byte scan_end1 = scan[best_len-1]; | |
594 | register Byte scan_end = scan[best_len]; | |
595 | #endif | |
596 | ||
597 | /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. | |
598 | * It is easy to get rid of this optimization if necessary. | |
599 | */ | |
600 | Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); | |
601 | ||
602 | /* Do not waste too much time if we already have a good match: */ | |
603 | if (s->prev_length >= s->good_match) { | |
604 | chain_length >>= 2; | |
605 | } | |
606 | /* Do not look for matches beyond the end of the input. This is necessary | |
607 | * to make deflate deterministic. | |
608 | */ | |
609 | if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; | |
610 | ||
611 | Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); | |
612 | ||
613 | do { | |
614 | Assert(cur_match < s->strstart, "no future"); | |
615 | match = s->window + cur_match; | |
616 | ||
617 | /* Skip to next match if the match length cannot increase | |
618 | * or if the match length is less than 2: | |
619 | */ | |
620 | #if (defined(UNALIGNED_OK) && MAX_MATCH == 258) | |
621 | /* This code assumes sizeof(unsigned short) == 2. Do not use | |
622 | * UNALIGNED_OK if your compiler uses a different size. | |
623 | */ | |
624 | if (*(ush*)(match+best_len-1) != scan_end || | |
625 | *(ush*)match != scan_start) continue; | |
626 | ||
627 | /* It is not necessary to compare scan[2] and match[2] since they are | |
628 | * always equal when the other bytes match, given that the hash keys | |
629 | * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at | |
630 | * strstart+3, +5, ... up to strstart+257. We check for insufficient | |
631 | * lookahead only every 4th comparison; the 128th check will be made | |
632 | * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is | |
633 | * necessary to put more guard bytes at the end of the window, or | |
634 | * to check more often for insufficient lookahead. | |
635 | */ | |
636 | Assert(scan[2] == match[2], "scan[2]?"); | |
637 | scan++, match++; | |
638 | do { | |
639 | } while (*(ush*)(scan+=2) == *(ush*)(match+=2) && | |
640 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
641 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
642 | *(ush*)(scan+=2) == *(ush*)(match+=2) && | |
643 | scan < strend); | |
644 | /* The funny "do {}" generates better code on most compilers */ | |
645 | ||
646 | /* Here, scan <= window+strstart+257 */ | |
647 | Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); | |
648 | if (*scan == *match) scan++; | |
649 | ||
650 | len = (MAX_MATCH - 1) - (int)(strend-scan); | |
651 | scan = strend - (MAX_MATCH-1); | |
652 | ||
653 | #else /* UNALIGNED_OK */ | |
654 | ||
655 | if (match[best_len] != scan_end || | |
656 | match[best_len-1] != scan_end1 || | |
657 | *match != *scan || | |
658 | *++match != scan[1]) continue; | |
659 | ||
660 | /* The check at best_len-1 can be removed because it will be made | |
661 | * again later. (This heuristic is not always a win.) | |
662 | * It is not necessary to compare scan[2] and match[2] since they | |
663 | * are always equal when the other bytes match, given that | |
664 | * the hash keys are equal and that HASH_BITS >= 8. | |
665 | */ | |
666 | scan += 2, match++; | |
667 | Assert(*scan == *match, "match[2]?"); | |
668 | ||
669 | /* We check for insufficient lookahead only every 8th comparison; | |
670 | * the 256th check will be made at strstart+258. | |
671 | */ | |
672 | do { | |
673 | } while (*++scan == *++match && *++scan == *++match && | |
674 | *++scan == *++match && *++scan == *++match && | |
675 | *++scan == *++match && *++scan == *++match && | |
676 | *++scan == *++match && *++scan == *++match && | |
677 | scan < strend); | |
678 | ||
679 | Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); | |
680 | ||
681 | len = MAX_MATCH - (int)(strend - scan); | |
682 | scan = strend - MAX_MATCH; | |
683 | ||
684 | #endif /* UNALIGNED_OK */ | |
685 | ||
686 | if (len > best_len) { | |
687 | s->match_start = cur_match; | |
688 | best_len = len; | |
689 | if (len >= nice_match) break; | |
690 | #ifdef UNALIGNED_OK | |
691 | scan_end = *(ush*)(scan+best_len-1); | |
692 | #else | |
693 | scan_end1 = scan[best_len-1]; | |
694 | scan_end = scan[best_len]; | |
695 | #endif | |
696 | } | |
697 | } while ((cur_match = prev[cur_match & wmask]) > limit | |
698 | && --chain_length != 0); | |
699 | ||
700 | if ((uInt)best_len <= s->lookahead) return best_len; | |
701 | return s->lookahead; | |
702 | } | |
703 | ||
704 | #ifdef DEBUG_ZLIB | |
705 | /* =========================================================================== | |
706 | * Check that the match at match_start is indeed a match. | |
707 | */ | |
708 | static void check_match( | |
709 | deflate_state *s, | |
710 | IPos start, | |
711 | IPos match, | |
712 | int length | |
713 | ) | |
714 | { | |
715 | /* check that the match is indeed a match */ | |
716 | if (memcmp((char *)s->window + match, | |
717 | (char *)s->window + start, length) != EQUAL) { | |
718 | fprintf(stderr, " start %u, match %u, length %d\n", | |
719 | start, match, length); | |
720 | do { | |
721 | fprintf(stderr, "%c%c", s->window[match++], s->window[start++]); | |
722 | } while (--length != 0); | |
723 | z_error("invalid match"); | |
724 | } | |
725 | if (z_verbose > 1) { | |
726 | fprintf(stderr,"\\[%d,%d]", start-match, length); | |
727 | do { putc(s->window[start++], stderr); } while (--length != 0); | |
728 | } | |
729 | } | |
730 | #else | |
731 | # define check_match(s, start, match, length) | |
732 | #endif | |
733 | ||
734 | /* =========================================================================== | |
735 | * Fill the window when the lookahead becomes insufficient. | |
736 | * Updates strstart and lookahead. | |
737 | * | |
738 | * IN assertion: lookahead < MIN_LOOKAHEAD | |
739 | * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD | |
740 | * At least one byte has been read, or avail_in == 0; reads are | |
741 | * performed for at least two bytes (required for the zip translate_eol | |
742 | * option -- not supported here). | |
743 | */ | |
744 | static void fill_window( | |
745 | deflate_state *s | |
746 | ) | |
747 | { | |
748 | register unsigned n, m; | |
749 | register Pos *p; | |
750 | unsigned more; /* Amount of free space at the end of the window. */ | |
751 | uInt wsize = s->w_size; | |
752 | ||
753 | do { | |
754 | more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); | |
755 | ||
756 | /* Deal with !@#$% 64K limit: */ | |
757 | if (more == 0 && s->strstart == 0 && s->lookahead == 0) { | |
758 | more = wsize; | |
759 | ||
760 | } else if (more == (unsigned)(-1)) { | |
761 | /* Very unlikely, but possible on 16 bit machine if strstart == 0 | |
762 | * and lookahead == 1 (input done one byte at time) | |
763 | */ | |
764 | more--; | |
765 | ||
766 | /* If the window is almost full and there is insufficient lookahead, | |
767 | * move the upper half to the lower one to make room in the upper half. | |
768 | */ | |
769 | } else if (s->strstart >= wsize+MAX_DIST(s)) { | |
770 | ||
771 | memcpy((char *)s->window, (char *)s->window+wsize, | |
772 | (unsigned)wsize); | |
773 | s->match_start -= wsize; | |
774 | s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ | |
775 | s->block_start -= (long) wsize; | |
776 | ||
777 | /* Slide the hash table (could be avoided with 32 bit values | |
778 | at the expense of memory usage). We slide even when level == 0 | |
779 | to keep the hash table consistent if we switch back to level > 0 | |
780 | later. (Using level 0 permanently is not an optimal usage of | |
781 | zlib, so we don't care about this pathological case.) | |
782 | */ | |
783 | n = s->hash_size; | |
784 | p = &s->head[n]; | |
785 | do { | |
786 | m = *--p; | |
787 | *p = (Pos)(m >= wsize ? m-wsize : NIL); | |
788 | } while (--n); | |
789 | ||
790 | n = wsize; | |
791 | p = &s->prev[n]; | |
792 | do { | |
793 | m = *--p; | |
794 | *p = (Pos)(m >= wsize ? m-wsize : NIL); | |
795 | /* If n is not on any hash chain, prev[n] is garbage but | |
796 | * its value will never be used. | |
797 | */ | |
798 | } while (--n); | |
799 | more += wsize; | |
800 | } | |
801 | if (s->strm->avail_in == 0) return; | |
802 | ||
803 | /* If there was no sliding: | |
804 | * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && | |
805 | * more == window_size - lookahead - strstart | |
806 | * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) | |
807 | * => more >= window_size - 2*WSIZE + 2 | |
808 | * In the BIG_MEM or MMAP case (not yet supported), | |
809 | * window_size == input_size + MIN_LOOKAHEAD && | |
810 | * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. | |
811 | * Otherwise, window_size == 2*WSIZE so more >= 2. | |
812 | * If there was sliding, more >= WSIZE. So in all cases, more >= 2. | |
813 | */ | |
814 | Assert(more >= 2, "more < 2"); | |
815 | ||
816 | n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more); | |
817 | s->lookahead += n; | |
818 | ||
819 | /* Initialize the hash value now that we have some input: */ | |
820 | if (s->lookahead >= MIN_MATCH) { | |
821 | s->ins_h = s->window[s->strstart]; | |
822 | UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); | |
823 | #if MIN_MATCH != 3 | |
824 | Call UPDATE_HASH() MIN_MATCH-3 more times | |
825 | #endif | |
826 | } | |
827 | /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, | |
828 | * but this is not important since only literal bytes will be emitted. | |
829 | */ | |
830 | ||
831 | } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); | |
832 | } | |
833 | ||
834 | /* =========================================================================== | |
835 | * Flush the current block, with given end-of-file flag. | |
836 | * IN assertion: strstart is set to the end of the current match. | |
837 | */ | |
838 | #define FLUSH_BLOCK_ONLY(s, eof) { \ | |
839 | zlib_tr_flush_block(s, (s->block_start >= 0L ? \ | |
840 | (char *)&s->window[(unsigned)s->block_start] : \ | |
841 | NULL), \ | |
842 | (ulg)((long)s->strstart - s->block_start), \ | |
843 | (eof)); \ | |
844 | s->block_start = s->strstart; \ | |
845 | flush_pending(s->strm); \ | |
846 | Tracev((stderr,"[FLUSH]")); \ | |
847 | } | |
848 | ||
849 | /* Same but force premature exit if necessary. */ | |
850 | #define FLUSH_BLOCK(s, eof) { \ | |
851 | FLUSH_BLOCK_ONLY(s, eof); \ | |
852 | if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \ | |
853 | } | |
854 | ||
855 | /* =========================================================================== | |
856 | * Copy without compression as much as possible from the input stream, return | |
857 | * the current block state. | |
858 | * This function does not insert new strings in the dictionary since | |
859 | * uncompressible data is probably not useful. This function is used | |
860 | * only for the level=0 compression option. | |
861 | * NOTE: this function should be optimized to avoid extra copying from | |
862 | * window to pending_buf. | |
863 | */ | |
864 | static block_state deflate_stored( | |
865 | deflate_state *s, | |
866 | int flush | |
867 | ) | |
868 | { | |
869 | /* Stored blocks are limited to 0xffff bytes, pending_buf is limited | |
870 | * to pending_buf_size, and each stored block has a 5 byte header: | |
871 | */ | |
872 | ulg max_block_size = 0xffff; | |
873 | ulg max_start; | |
874 | ||
875 | if (max_block_size > s->pending_buf_size - 5) { | |
876 | max_block_size = s->pending_buf_size - 5; | |
877 | } | |
878 | ||
879 | /* Copy as much as possible from input to output: */ | |
880 | for (;;) { | |
881 | /* Fill the window as much as possible: */ | |
882 | if (s->lookahead <= 1) { | |
883 | ||
884 | Assert(s->strstart < s->w_size+MAX_DIST(s) || | |
885 | s->block_start >= (long)s->w_size, "slide too late"); | |
886 | ||
887 | fill_window(s); | |
888 | if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; | |
889 | ||
890 | if (s->lookahead == 0) break; /* flush the current block */ | |
891 | } | |
892 | Assert(s->block_start >= 0L, "block gone"); | |
893 | ||
894 | s->strstart += s->lookahead; | |
895 | s->lookahead = 0; | |
896 | ||
897 | /* Emit a stored block if pending_buf will be full: */ | |
898 | max_start = s->block_start + max_block_size; | |
899 | if (s->strstart == 0 || (ulg)s->strstart >= max_start) { | |
900 | /* strstart == 0 is possible when wraparound on 16-bit machine */ | |
901 | s->lookahead = (uInt)(s->strstart - max_start); | |
902 | s->strstart = (uInt)max_start; | |
903 | FLUSH_BLOCK(s, 0); | |
904 | } | |
905 | /* Flush if we may have to slide, otherwise block_start may become | |
906 | * negative and the data will be gone: | |
907 | */ | |
908 | if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { | |
909 | FLUSH_BLOCK(s, 0); | |
910 | } | |
911 | } | |
912 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
913 | return flush == Z_FINISH ? finish_done : block_done; | |
914 | } | |
915 | ||
916 | /* =========================================================================== | |
917 | * Compress as much as possible from the input stream, return the current | |
918 | * block state. | |
919 | * This function does not perform lazy evaluation of matches and inserts | |
920 | * new strings in the dictionary only for unmatched strings or for short | |
921 | * matches. It is used only for the fast compression options. | |
922 | */ | |
923 | static block_state deflate_fast( | |
924 | deflate_state *s, | |
925 | int flush | |
926 | ) | |
927 | { | |
928 | IPos hash_head = NIL; /* head of the hash chain */ | |
929 | int bflush; /* set if current block must be flushed */ | |
930 | ||
931 | for (;;) { | |
932 | /* Make sure that we always have enough lookahead, except | |
933 | * at the end of the input file. We need MAX_MATCH bytes | |
934 | * for the next match, plus MIN_MATCH bytes to insert the | |
935 | * string following the next match. | |
936 | */ | |
937 | if (s->lookahead < MIN_LOOKAHEAD) { | |
938 | fill_window(s); | |
939 | if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { | |
940 | return need_more; | |
941 | } | |
942 | if (s->lookahead == 0) break; /* flush the current block */ | |
943 | } | |
944 | ||
945 | /* Insert the string window[strstart .. strstart+2] in the | |
946 | * dictionary, and set hash_head to the head of the hash chain: | |
947 | */ | |
948 | if (s->lookahead >= MIN_MATCH) { | |
949 | INSERT_STRING(s, s->strstart, hash_head); | |
950 | } | |
951 | ||
952 | /* Find the longest match, discarding those <= prev_length. | |
953 | * At this point we have always match_length < MIN_MATCH | |
954 | */ | |
955 | if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { | |
956 | /* To simplify the code, we prevent matches with the string | |
957 | * of window index 0 (in particular we have to avoid a match | |
958 | * of the string with itself at the start of the input file). | |
959 | */ | |
960 | if (s->strategy != Z_HUFFMAN_ONLY) { | |
961 | s->match_length = longest_match (s, hash_head); | |
962 | } | |
963 | /* longest_match() sets match_start */ | |
964 | } | |
965 | if (s->match_length >= MIN_MATCH) { | |
966 | check_match(s, s->strstart, s->match_start, s->match_length); | |
967 | ||
968 | bflush = zlib_tr_tally(s, s->strstart - s->match_start, | |
969 | s->match_length - MIN_MATCH); | |
970 | ||
971 | s->lookahead -= s->match_length; | |
972 | ||
973 | /* Insert new strings in the hash table only if the match length | |
974 | * is not too large. This saves time but degrades compression. | |
975 | */ | |
976 | if (s->match_length <= s->max_insert_length && | |
977 | s->lookahead >= MIN_MATCH) { | |
978 | s->match_length--; /* string at strstart already in hash table */ | |
979 | do { | |
980 | s->strstart++; | |
981 | INSERT_STRING(s, s->strstart, hash_head); | |
982 | /* strstart never exceeds WSIZE-MAX_MATCH, so there are | |
983 | * always MIN_MATCH bytes ahead. | |
984 | */ | |
985 | } while (--s->match_length != 0); | |
986 | s->strstart++; | |
987 | } else { | |
988 | s->strstart += s->match_length; | |
989 | s->match_length = 0; | |
990 | s->ins_h = s->window[s->strstart]; | |
991 | UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); | |
992 | #if MIN_MATCH != 3 | |
993 | Call UPDATE_HASH() MIN_MATCH-3 more times | |
994 | #endif | |
995 | /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not | |
996 | * matter since it will be recomputed at next deflate call. | |
997 | */ | |
998 | } | |
999 | } else { | |
1000 | /* No match, output a literal byte */ | |
1001 | Tracevv((stderr,"%c", s->window[s->strstart])); | |
1002 | bflush = zlib_tr_tally (s, 0, s->window[s->strstart]); | |
1003 | s->lookahead--; | |
1004 | s->strstart++; | |
1005 | } | |
1006 | if (bflush) FLUSH_BLOCK(s, 0); | |
1007 | } | |
1008 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
1009 | return flush == Z_FINISH ? finish_done : block_done; | |
1010 | } | |
1011 | ||
1012 | /* =========================================================================== | |
1013 | * Same as above, but achieves better compression. We use a lazy | |
1014 | * evaluation for matches: a match is finally adopted only if there is | |
1015 | * no better match at the next window position. | |
1016 | */ | |
1017 | static block_state deflate_slow( | |
1018 | deflate_state *s, | |
1019 | int flush | |
1020 | ) | |
1021 | { | |
1022 | IPos hash_head = NIL; /* head of hash chain */ | |
1023 | int bflush; /* set if current block must be flushed */ | |
1024 | ||
1025 | /* Process the input block. */ | |
1026 | for (;;) { | |
1027 | /* Make sure that we always have enough lookahead, except | |
1028 | * at the end of the input file. We need MAX_MATCH bytes | |
1029 | * for the next match, plus MIN_MATCH bytes to insert the | |
1030 | * string following the next match. | |
1031 | */ | |
1032 | if (s->lookahead < MIN_LOOKAHEAD) { | |
1033 | fill_window(s); | |
1034 | if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { | |
1035 | return need_more; | |
1036 | } | |
1037 | if (s->lookahead == 0) break; /* flush the current block */ | |
1038 | } | |
1039 | ||
1040 | /* Insert the string window[strstart .. strstart+2] in the | |
1041 | * dictionary, and set hash_head to the head of the hash chain: | |
1042 | */ | |
1043 | if (s->lookahead >= MIN_MATCH) { | |
1044 | INSERT_STRING(s, s->strstart, hash_head); | |
1045 | } | |
1046 | ||
1047 | /* Find the longest match, discarding those <= prev_length. | |
1048 | */ | |
1049 | s->prev_length = s->match_length, s->prev_match = s->match_start; | |
1050 | s->match_length = MIN_MATCH-1; | |
1051 | ||
1052 | if (hash_head != NIL && s->prev_length < s->max_lazy_match && | |
1053 | s->strstart - hash_head <= MAX_DIST(s)) { | |
1054 | /* To simplify the code, we prevent matches with the string | |
1055 | * of window index 0 (in particular we have to avoid a match | |
1056 | * of the string with itself at the start of the input file). | |
1057 | */ | |
1058 | if (s->strategy != Z_HUFFMAN_ONLY) { | |
1059 | s->match_length = longest_match (s, hash_head); | |
1060 | } | |
1061 | /* longest_match() sets match_start */ | |
1062 | ||
1063 | if (s->match_length <= 5 && (s->strategy == Z_FILTERED || | |
1064 | (s->match_length == MIN_MATCH && | |
1065 | s->strstart - s->match_start > TOO_FAR))) { | |
1066 | ||
1067 | /* If prev_match is also MIN_MATCH, match_start is garbage | |
1068 | * but we will ignore the current match anyway. | |
1069 | */ | |
1070 | s->match_length = MIN_MATCH-1; | |
1071 | } | |
1072 | } | |
1073 | /* If there was a match at the previous step and the current | |
1074 | * match is not better, output the previous match: | |
1075 | */ | |
1076 | if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { | |
1077 | uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; | |
1078 | /* Do not insert strings in hash table beyond this. */ | |
1079 | ||
1080 | check_match(s, s->strstart-1, s->prev_match, s->prev_length); | |
1081 | ||
1082 | bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match, | |
1083 | s->prev_length - MIN_MATCH); | |
1084 | ||
1085 | /* Insert in hash table all strings up to the end of the match. | |
1086 | * strstart-1 and strstart are already inserted. If there is not | |
1087 | * enough lookahead, the last two strings are not inserted in | |
1088 | * the hash table. | |
1089 | */ | |
1090 | s->lookahead -= s->prev_length-1; | |
1091 | s->prev_length -= 2; | |
1092 | do { | |
1093 | if (++s->strstart <= max_insert) { | |
1094 | INSERT_STRING(s, s->strstart, hash_head); | |
1095 | } | |
1096 | } while (--s->prev_length != 0); | |
1097 | s->match_available = 0; | |
1098 | s->match_length = MIN_MATCH-1; | |
1099 | s->strstart++; | |
1100 | ||
1101 | if (bflush) FLUSH_BLOCK(s, 0); | |
1102 | ||
1103 | } else if (s->match_available) { | |
1104 | /* If there was no match at the previous position, output a | |
1105 | * single literal. If there was a match but the current match | |
1106 | * is longer, truncate the previous match to a single literal. | |
1107 | */ | |
1108 | Tracevv((stderr,"%c", s->window[s->strstart-1])); | |
1109 | if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) { | |
1110 | FLUSH_BLOCK_ONLY(s, 0); | |
1111 | } | |
1112 | s->strstart++; | |
1113 | s->lookahead--; | |
1114 | if (s->strm->avail_out == 0) return need_more; | |
1115 | } else { | |
1116 | /* There is no previous match to compare with, wait for | |
1117 | * the next step to decide. | |
1118 | */ | |
1119 | s->match_available = 1; | |
1120 | s->strstart++; | |
1121 | s->lookahead--; | |
1122 | } | |
1123 | } | |
1124 | Assert (flush != Z_NO_FLUSH, "no flush?"); | |
1125 | if (s->match_available) { | |
1126 | Tracevv((stderr,"%c", s->window[s->strstart-1])); | |
1127 | zlib_tr_tally (s, 0, s->window[s->strstart-1]); | |
1128 | s->match_available = 0; | |
1129 | } | |
1130 | FLUSH_BLOCK(s, flush == Z_FINISH); | |
1131 | return flush == Z_FINISH ? finish_done : block_done; | |
1132 | } | |
1133 | ||
565d76cb | 1134 | int zlib_deflate_workspacesize(int windowBits, int memLevel) |
1da177e4 | 1135 | { |
565d76cb JK |
1136 | if (windowBits < 0) /* undocumented feature: suppress zlib header */ |
1137 | windowBits = -windowBits; | |
1138 | ||
1139 | /* Since the return value is typically passed to vmalloc() unchecked... */ | |
1140 | BUG_ON(memLevel < 1 || memLevel > MAX_MEM_LEVEL || windowBits < 9 || | |
1141 | windowBits > 15); | |
1142 | ||
1143 | return sizeof(deflate_workspace) | |
1144 | + zlib_deflate_window_memsize(windowBits) | |
1145 | + zlib_deflate_prev_memsize(windowBits) | |
1146 | + zlib_deflate_head_memsize(memLevel) | |
1147 | + zlib_deflate_overlay_memsize(memLevel); | |
1da177e4 | 1148 | } |
803521b1 MZ |
1149 | |
1150 | int zlib_deflate_dfltcc_enabled(void) | |
1151 | { | |
1152 | return DEFLATE_DFLTCC_ENABLED(); | |
1153 | } |