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deflate.c
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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
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 */
112 } config;
113 
114 static const config configuration_table[10] = {
115 /* good lazy nice chain */
116 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
117 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */
118 /* 2 */ {4, 5, 16, 8, deflate_fast},
119 /* 3 */ {4, 6, 32, 32, deflate_fast},
120 
121 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
122 /* 5 */ {8, 16, 32, 32, deflate_slow},
123 /* 6 */ {8, 16, 128, 128, deflate_slow},
124 /* 7 */ {8, 32, 128, 256, deflate_slow},
125 /* 8 */ {32, 128, 258, 1024, deflate_slow},
126 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
127 
128 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
129  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
130  * meaning.
131  */
132 
133 #define EQUAL 0
134 /* result of memcmp for equal strings */
135 
136 /* ===========================================================================
137  * Update a hash value with the given input byte
138  * IN assertion: all calls to UPDATE_HASH are made with consecutive
139  * input characters, so that a running hash key can be computed from the
140  * previous key instead of complete recalculation each time.
141  */
142 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
143 
144 
145 /* ===========================================================================
146  * Insert string str in the dictionary and set match_head to the previous head
147  * of the hash chain (the most recent string with same hash key). Return
148  * the previous length of the hash chain.
149  * IN assertion: all calls to INSERT_STRING are made with consecutive
150  * input characters and the first MIN_MATCH bytes of str are valid
151  * (except for the last MIN_MATCH-1 bytes of the input file).
152  */
153 #define INSERT_STRING(s, str, match_head) \
154  (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
155  s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
156  s->head[s->ins_h] = (Pos)(str))
157 
158 /* ===========================================================================
159  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
160  * prev[] will be initialized on the fly.
161  */
162 #define CLEAR_HASH(s) \
163  s->head[s->hash_size-1] = NIL; \
164  memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));
165 
166 /* ========================================================================= */
168  z_streamp strm,
169  int level,
170  int method,
171  int windowBits,
172  int memLevel,
173  int strategy
174 )
175 {
176  deflate_state *s;
177  int noheader = 0;
179  char *next;
180 
181  ush *overlay;
182  /* We overlay pending_buf and d_buf+l_buf. This works since the average
183  * output size for (length,distance) codes is <= 24 bits.
184  */
185 
186  if (strm == NULL) return Z_STREAM_ERROR;
187 
188  strm->msg = NULL;
189 
190  if (level == Z_DEFAULT_COMPRESSION) level = 6;
191 
192  mem = (deflate_workspace *) strm->workspace;
193 
194  if (windowBits < 0) { /* undocumented feature: suppress zlib header */
195  noheader = 1;
196  windowBits = -windowBits;
197  }
198  if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
199  windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
200  strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
201  return Z_STREAM_ERROR;
202  }
203 
204  /*
205  * Direct the workspace's pointers to the chunks that were allocated
206  * along with the deflate_workspace struct.
207  */
208  next = (char *) mem;
209  next += sizeof(*mem);
210  mem->window_memory = (Byte *) next;
211  next += zlib_deflate_window_memsize(windowBits);
212  mem->prev_memory = (Pos *) next;
213  next += zlib_deflate_prev_memsize(windowBits);
214  mem->head_memory = (Pos *) next;
215  next += zlib_deflate_head_memsize(memLevel);
216  mem->overlay_memory = next;
217 
218  s = (deflate_state *) &(mem->deflate_memory);
219  strm->state = (struct internal_state *)s;
220  s->strm = strm;
221 
222  s->noheader = noheader;
223  s->w_bits = windowBits;
224  s->w_size = 1 << s->w_bits;
225  s->w_mask = s->w_size - 1;
226 
227  s->hash_bits = memLevel + 7;
228  s->hash_size = 1 << s->hash_bits;
229  s->hash_mask = s->hash_size - 1;
230  s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
231 
232  s->window = (Byte *) mem->window_memory;
233  s->prev = (Pos *) mem->prev_memory;
234  s->head = (Pos *) mem->head_memory;
235 
236  s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
237 
238  overlay = (ush *) mem->overlay_memory;
239  s->pending_buf = (uch *) overlay;
240  s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
241 
242  s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
243  s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
244 
245  s->level = level;
246  s->strategy = strategy;
247  s->method = (Byte)method;
248 
249  return zlib_deflateReset(strm);
250 }
251 
252 /* ========================================================================= */
253 #if 0
254 int zlib_deflateSetDictionary(
255  z_streamp strm,
256  const Byte *dictionary,
257  uInt dictLength
258 )
259 {
260  deflate_state *s;
261  uInt length = dictLength;
262  uInt n;
263  IPos hash_head = 0;
264 
265  if (strm == NULL || strm->state == NULL || dictionary == NULL)
266  return Z_STREAM_ERROR;
267 
268  s = (deflate_state *) strm->state;
269  if (s->status != INIT_STATE) return Z_STREAM_ERROR;
270 
271  strm->adler = zlib_adler32(strm->adler, dictionary, dictLength);
272 
273  if (length < MIN_MATCH) return Z_OK;
274  if (length > MAX_DIST(s)) {
275  length = MAX_DIST(s);
276 #ifndef USE_DICT_HEAD
277  dictionary += dictLength - length; /* use the tail of the dictionary */
278 #endif
279  }
280  memcpy((char *)s->window, dictionary, length);
281  s->strstart = length;
282  s->block_start = (long)length;
283 
284  /* Insert all strings in the hash table (except for the last two bytes).
285  * s->lookahead stays null, so s->ins_h will be recomputed at the next
286  * call of fill_window.
287  */
288  s->ins_h = s->window[0];
289  UPDATE_HASH(s, s->ins_h, s->window[1]);
290  for (n = 0; n <= length - MIN_MATCH; n++) {
291  INSERT_STRING(s, n, hash_head);
292  }
293  if (hash_head) hash_head = 0; /* to make compiler happy */
294  return Z_OK;
295 }
296 #endif /* 0 */
297 
298 /* ========================================================================= */
300  z_streamp strm
301 )
302 {
303  deflate_state *s;
304 
305  if (strm == NULL || strm->state == NULL)
306  return Z_STREAM_ERROR;
307 
308  strm->total_in = strm->total_out = 0;
309  strm->msg = NULL;
310  strm->data_type = Z_UNKNOWN;
311 
312  s = (deflate_state *)strm->state;
313  s->pending = 0;
314  s->pending_out = s->pending_buf;
315 
316  if (s->noheader < 0) {
317  s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
318  }
319  s->status = s->noheader ? BUSY_STATE : INIT_STATE;
320  strm->adler = 1;
321  s->last_flush = Z_NO_FLUSH;
322 
323  zlib_tr_init(s);
324  lm_init(s);
325 
326  return Z_OK;
327 }
328 
329 /* ========================================================================= */
330 #if 0
331 int zlib_deflateParams(
332  z_streamp strm,
333  int level,
334  int strategy
335 )
336 {
337  deflate_state *s;
339  int err = Z_OK;
340 
341  if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
342  s = (deflate_state *) strm->state;
343 
344  if (level == Z_DEFAULT_COMPRESSION) {
345  level = 6;
346  }
347  if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
348  return Z_STREAM_ERROR;
349  }
350  func = configuration_table[s->level].func;
351 
352  if (func != configuration_table[level].func && strm->total_in != 0) {
353  /* Flush the last buffer: */
354  err = zlib_deflate(strm, Z_PARTIAL_FLUSH);
355  }
356  if (s->level != level) {
357  s->level = level;
358  s->max_lazy_match = configuration_table[level].max_lazy;
359  s->good_match = configuration_table[level].good_length;
360  s->nice_match = configuration_table[level].nice_length;
361  s->max_chain_length = configuration_table[level].max_chain;
362  }
363  s->strategy = strategy;
364  return err;
365 }
366 #endif /* 0 */
367 
368 /* =========================================================================
369  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
370  * IN assertion: the stream state is correct and there is enough room in
371  * pending_buf.
372  */
373 static void putShortMSB(
374  deflate_state *s,
375  uInt b
376 )
377 {
378  put_byte(s, (Byte)(b >> 8));
379  put_byte(s, (Byte)(b & 0xff));
380 }
381 
382 /* =========================================================================
383  * Flush as much pending output as possible. All deflate() output goes
384  * through this function so some applications may wish to modify it
385  * to avoid allocating a large strm->next_out buffer and copying into it.
386  * (See also read_buf()).
387  */
388 static void flush_pending(
389  z_streamp strm
390 )
391 {
392  deflate_state *s = (deflate_state *) strm->state;
393  unsigned len = s->pending;
394 
395  if (len > strm->avail_out) len = strm->avail_out;
396  if (len == 0) return;
397 
398  if (strm->next_out != NULL) {
399  memcpy(strm->next_out, s->pending_out, len);
400  strm->next_out += len;
401  }
402  s->pending_out += len;
403  strm->total_out += len;
404  strm->avail_out -= len;
405  s->pending -= len;
406  if (s->pending == 0) {
407  s->pending_out = s->pending_buf;
408  }
409 }
410 
411 /* ========================================================================= */
413  z_streamp strm,
414  int flush
415 )
416 {
417  int old_flush; /* value of flush param for previous deflate call */
418  deflate_state *s;
419 
420  if (strm == NULL || strm->state == NULL ||
421  flush > Z_FINISH || flush < 0) {
422  return Z_STREAM_ERROR;
423  }
424  s = (deflate_state *) strm->state;
425 
426  if ((strm->next_in == NULL && strm->avail_in != 0) ||
427  (s->status == FINISH_STATE && flush != Z_FINISH)) {
428  return Z_STREAM_ERROR;
429  }
430  if (strm->avail_out == 0) return Z_BUF_ERROR;
431 
432  s->strm = strm; /* just in case */
433  old_flush = s->last_flush;
434  s->last_flush = flush;
435 
436  /* Write the zlib header */
437  if (s->status == INIT_STATE) {
438 
439  uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
440  uInt level_flags = (s->level-1) >> 1;
441 
442  if (level_flags > 3) level_flags = 3;
443  header |= (level_flags << 6);
444  if (s->strstart != 0) header |= PRESET_DICT;
445  header += 31 - (header % 31);
446 
447  s->status = BUSY_STATE;
448  putShortMSB(s, header);
449 
450  /* Save the adler32 of the preset dictionary: */
451  if (s->strstart != 0) {
452  putShortMSB(s, (uInt)(strm->adler >> 16));
453  putShortMSB(s, (uInt)(strm->adler & 0xffff));
454  }
455  strm->adler = 1L;
456  }
457 
458  /* Flush as much pending output as possible */
459  if (s->pending != 0) {
460  flush_pending(strm);
461  if (strm->avail_out == 0) {
462  /* Since avail_out is 0, deflate will be called again with
463  * more output space, but possibly with both pending and
464  * avail_in equal to zero. There won't be anything to do,
465  * but this is not an error situation so make sure we
466  * return OK instead of BUF_ERROR at next call of deflate:
467  */
468  s->last_flush = -1;
469  return Z_OK;
470  }
471 
472  /* Make sure there is something to do and avoid duplicate consecutive
473  * flushes. For repeated and useless calls with Z_FINISH, we keep
474  * returning Z_STREAM_END instead of Z_BUFF_ERROR.
475  */
476  } else if (strm->avail_in == 0 && flush <= old_flush &&
477  flush != Z_FINISH) {
478  return Z_BUF_ERROR;
479  }
480 
481  /* User must not provide more input after the first FINISH: */
482  if (s->status == FINISH_STATE && strm->avail_in != 0) {
483  return Z_BUF_ERROR;
484  }
485 
486  /* Start a new block or continue the current one.
487  */
488  if (strm->avail_in != 0 || s->lookahead != 0 ||
489  (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
490  block_state bstate;
491 
492  bstate = (*(configuration_table[s->level].func))(s, flush);
493 
494  if (bstate == finish_started || bstate == finish_done) {
495  s->status = FINISH_STATE;
496  }
497  if (bstate == need_more || bstate == finish_started) {
498  if (strm->avail_out == 0) {
499  s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
500  }
501  return Z_OK;
502  /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
503  * of deflate should use the same flush parameter to make sure
504  * that the flush is complete. So we don't have to output an
505  * empty block here, this will be done at next call. This also
506  * ensures that for a very small output buffer, we emit at most
507  * one empty block.
508  */
509  }
510  if (bstate == block_done) {
511  if (flush == Z_PARTIAL_FLUSH) {
512  zlib_tr_align(s);
513  } else if (flush == Z_PACKET_FLUSH) {
514  /* Output just the 3-bit `stored' block type value,
515  but not a zero length. */
517  } else { /* FULL_FLUSH or SYNC_FLUSH */
518  zlib_tr_stored_block(s, (char*)0, 0L, 0);
519  /* For a full flush, this empty block will be recognized
520  * as a special marker by inflate_sync().
521  */
522  if (flush == Z_FULL_FLUSH) {
523  CLEAR_HASH(s); /* forget history */
524  }
525  }
526  flush_pending(strm);
527  if (strm->avail_out == 0) {
528  s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
529  return Z_OK;
530  }
531  }
532  }
533  Assert(strm->avail_out > 0, "bug2");
534 
535  if (flush != Z_FINISH) return Z_OK;
536  if (s->noheader) return Z_STREAM_END;
537 
538  /* Write the zlib trailer (adler32) */
539  putShortMSB(s, (uInt)(strm->adler >> 16));
540  putShortMSB(s, (uInt)(strm->adler & 0xffff));
541  flush_pending(strm);
542  /* If avail_out is zero, the application will call deflate again
543  * to flush the rest.
544  */
545  s->noheader = -1; /* write the trailer only once! */
546  return s->pending != 0 ? Z_OK : Z_STREAM_END;
547 }
548 
549 /* ========================================================================= */
551  z_streamp strm
552 )
553 {
554  int status;
555  deflate_state *s;
556 
557  if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
558  s = (deflate_state *) strm->state;
559 
560  status = s->status;
561  if (status != INIT_STATE && status != BUSY_STATE &&
562  status != FINISH_STATE) {
563  return Z_STREAM_ERROR;
564  }
565 
566  strm->state = NULL;
567 
568  return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
569 }
570 
571 /* =========================================================================
572  * Copy the source state to the destination state.
573  */
574 #if 0
575 int zlib_deflateCopy (
576  z_streamp dest,
578 )
579 {
580 #ifdef MAXSEG_64K
581  return Z_STREAM_ERROR;
582 #else
583  deflate_state *ds;
584  deflate_state *ss;
585  ush *overlay;
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));
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 #endif /* 0 */
628 
629 /* ===========================================================================
630  * Read a new buffer from the current input stream, update the adler32
631  * and total number of bytes read. All deflate() input goes through
632  * this function so some applications may wish to modify it to avoid
633  * allocating a large strm->next_in buffer and copying from it.
634  * (See also flush_pending()).
635  */
636 static int read_buf(
637  z_streamp strm,
638  Byte *buf,
639  unsigned size
640 )
641 {
642  unsigned len = strm->avail_in;
643 
644  if (len > size) len = size;
645  if (len == 0) return 0;
646 
647  strm->avail_in -= len;
648 
649  if (!((deflate_state *)(strm->state))->noheader) {
650  strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
651  }
652  memcpy(buf, strm->next_in, len);
653  strm->next_in += len;
654  strm->total_in += len;
655 
656  return (int)len;
657 }
658 
659 /* ===========================================================================
660  * Initialize the "longest match" routines for a new zlib stream
661  */
662 static void lm_init(
663  deflate_state *s
664 )
665 {
666  s->window_size = (ulg)2L*s->w_size;
667 
668  CLEAR_HASH(s);
669 
670  /* Set the default configuration parameters:
671  */
672  s->max_lazy_match = configuration_table[s->level].max_lazy;
673  s->good_match = configuration_table[s->level].good_length;
674  s->nice_match = configuration_table[s->level].nice_length;
675  s->max_chain_length = configuration_table[s->level].max_chain;
676 
677  s->strstart = 0;
678  s->block_start = 0L;
679  s->lookahead = 0;
680  s->match_length = s->prev_length = MIN_MATCH-1;
681  s->match_available = 0;
682  s->ins_h = 0;
683 }
684 
685 /* ===========================================================================
686  * Set match_start to the longest match starting at the given string and
687  * return its length. Matches shorter or equal to prev_length are discarded,
688  * in which case the result is equal to prev_length and match_start is
689  * garbage.
690  * IN assertions: cur_match is the head of the hash chain for the current
691  * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
692  * OUT assertion: the match length is not greater than s->lookahead.
693  */
694 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
695  * match.S. The code will be functionally equivalent.
696  */
697 static uInt longest_match(
698  deflate_state *s,
699  IPos cur_match /* current match */
700 )
701 {
702  unsigned chain_length = s->max_chain_length;/* max hash chain length */
703  register Byte *scan = s->window + s->strstart; /* current string */
704  register Byte *match; /* matched string */
705  register int len; /* length of current match */
706  int best_len = s->prev_length; /* best match length so far */
707  int nice_match = s->nice_match; /* stop if match long enough */
708  IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
709  s->strstart - (IPos)MAX_DIST(s) : NIL;
710  /* Stop when cur_match becomes <= limit. To simplify the code,
711  * we prevent matches with the string of window index 0.
712  */
713  Pos *prev = s->prev;
714  uInt wmask = s->w_mask;
715 
716 #ifdef UNALIGNED_OK
717  /* Compare two bytes at a time. Note: this is not always beneficial.
718  * Try with and without -DUNALIGNED_OK to check.
719  */
720  register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
721  register ush scan_start = *(ush*)scan;
722  register ush scan_end = *(ush*)(scan+best_len-1);
723 #else
724  register Byte *strend = s->window + s->strstart + MAX_MATCH;
725  register Byte scan_end1 = scan[best_len-1];
726  register Byte scan_end = scan[best_len];
727 #endif
728 
729  /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
730  * It is easy to get rid of this optimization if necessary.
731  */
732  Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
733 
734  /* Do not waste too much time if we already have a good match: */
735  if (s->prev_length >= s->good_match) {
736  chain_length >>= 2;
737  }
738  /* Do not look for matches beyond the end of the input. This is necessary
739  * to make deflate deterministic.
740  */
741  if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
742 
743  Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
744 
745  do {
746  Assert(cur_match < s->strstart, "no future");
747  match = s->window + cur_match;
748 
749  /* Skip to next match if the match length cannot increase
750  * or if the match length is less than 2:
751  */
752 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
753  /* This code assumes sizeof(unsigned short) == 2. Do not use
754  * UNALIGNED_OK if your compiler uses a different size.
755  */
756  if (*(ush*)(match+best_len-1) != scan_end ||
757  *(ush*)match != scan_start) continue;
758 
759  /* It is not necessary to compare scan[2] and match[2] since they are
760  * always equal when the other bytes match, given that the hash keys
761  * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
762  * strstart+3, +5, ... up to strstart+257. We check for insufficient
763  * lookahead only every 4th comparison; the 128th check will be made
764  * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
765  * necessary to put more guard bytes at the end of the window, or
766  * to check more often for insufficient lookahead.
767  */
768  Assert(scan[2] == match[2], "scan[2]?");
769  scan++, match++;
770  do {
771  } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
772  *(ush*)(scan+=2) == *(ush*)(match+=2) &&
773  *(ush*)(scan+=2) == *(ush*)(match+=2) &&
774  *(ush*)(scan+=2) == *(ush*)(match+=2) &&
775  scan < strend);
776  /* The funny "do {}" generates better code on most compilers */
777 
778  /* Here, scan <= window+strstart+257 */
779  Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
780  if (*scan == *match) scan++;
781 
782  len = (MAX_MATCH - 1) - (int)(strend-scan);
783  scan = strend - (MAX_MATCH-1);
784 
785 #else /* UNALIGNED_OK */
786 
787  if (match[best_len] != scan_end ||
788  match[best_len-1] != scan_end1 ||
789  *match != *scan ||
790  *++match != scan[1]) continue;
791 
792  /* The check at best_len-1 can be removed because it will be made
793  * again later. (This heuristic is not always a win.)
794  * It is not necessary to compare scan[2] and match[2] since they
795  * are always equal when the other bytes match, given that
796  * the hash keys are equal and that HASH_BITS >= 8.
797  */
798  scan += 2, match++;
799  Assert(*scan == *match, "match[2]?");
800 
801  /* We check for insufficient lookahead only every 8th comparison;
802  * the 256th check will be made at strstart+258.
803  */
804  do {
805  } while (*++scan == *++match && *++scan == *++match &&
806  *++scan == *++match && *++scan == *++match &&
807  *++scan == *++match && *++scan == *++match &&
808  *++scan == *++match && *++scan == *++match &&
809  scan < strend);
810 
811  Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
812 
813  len = MAX_MATCH - (int)(strend - scan);
814  scan = strend - MAX_MATCH;
815 
816 #endif /* UNALIGNED_OK */
817 
818  if (len > best_len) {
819  s->match_start = cur_match;
820  best_len = len;
821  if (len >= nice_match) break;
822 #ifdef UNALIGNED_OK
823  scan_end = *(ush*)(scan+best_len-1);
824 #else
825  scan_end1 = scan[best_len-1];
826  scan_end = scan[best_len];
827 #endif
828  }
829  } while ((cur_match = prev[cur_match & wmask]) > limit
830  && --chain_length != 0);
831 
832  if ((uInt)best_len <= s->lookahead) return best_len;
833  return s->lookahead;
834 }
835 
836 #ifdef DEBUG_ZLIB
837 /* ===========================================================================
838  * Check that the match at match_start is indeed a match.
839  */
840 static void check_match(
841  deflate_state *s,
842  IPos start,
843  IPos match,
844  int length
845 )
846 {
847  /* check that the match is indeed a match */
848  if (memcmp((char *)s->window + match,
849  (char *)s->window + start, length) != EQUAL) {
850  fprintf(stderr, " start %u, match %u, length %d\n",
851  start, match, length);
852  do {
853  fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
854  } while (--length != 0);
855  z_error("invalid match");
856  }
857  if (z_verbose > 1) {
858  fprintf(stderr,"\\[%d,%d]", start-match, length);
859  do { putc(s->window[start++], stderr); } while (--length != 0);
860  }
861 }
862 #else
863 # define check_match(s, start, match, length)
864 #endif
865 
866 /* ===========================================================================
867  * Fill the window when the lookahead becomes insufficient.
868  * Updates strstart and lookahead.
869  *
870  * IN assertion: lookahead < MIN_LOOKAHEAD
871  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
872  * At least one byte has been read, or avail_in == 0; reads are
873  * performed for at least two bytes (required for the zip translate_eol
874  * option -- not supported here).
875  */
876 static void fill_window(
877  deflate_state *s
878 )
879 {
880  register unsigned n, m;
881  register Pos *p;
882  unsigned more; /* Amount of free space at the end of the window. */
883  uInt wsize = s->w_size;
884 
885  do {
886  more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
887 
888  /* Deal with !@#$% 64K limit: */
889  if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
890  more = wsize;
891 
892  } else if (more == (unsigned)(-1)) {
893  /* Very unlikely, but possible on 16 bit machine if strstart == 0
894  * and lookahead == 1 (input done one byte at time)
895  */
896  more--;
897 
898  /* If the window is almost full and there is insufficient lookahead,
899  * move the upper half to the lower one to make room in the upper half.
900  */
901  } else if (s->strstart >= wsize+MAX_DIST(s)) {
902 
903  memcpy((char *)s->window, (char *)s->window+wsize,
904  (unsigned)wsize);
905  s->match_start -= wsize;
906  s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
907  s->block_start -= (long) wsize;
908 
909  /* Slide the hash table (could be avoided with 32 bit values
910  at the expense of memory usage). We slide even when level == 0
911  to keep the hash table consistent if we switch back to level > 0
912  later. (Using level 0 permanently is not an optimal usage of
913  zlib, so we don't care about this pathological case.)
914  */
915  n = s->hash_size;
916  p = &s->head[n];
917  do {
918  m = *--p;
919  *p = (Pos)(m >= wsize ? m-wsize : NIL);
920  } while (--n);
921 
922  n = wsize;
923  p = &s->prev[n];
924  do {
925  m = *--p;
926  *p = (Pos)(m >= wsize ? m-wsize : NIL);
927  /* If n is not on any hash chain, prev[n] is garbage but
928  * its value will never be used.
929  */
930  } while (--n);
931  more += wsize;
932  }
933  if (s->strm->avail_in == 0) return;
934 
935  /* If there was no sliding:
936  * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
937  * more == window_size - lookahead - strstart
938  * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
939  * => more >= window_size - 2*WSIZE + 2
940  * In the BIG_MEM or MMAP case (not yet supported),
941  * window_size == input_size + MIN_LOOKAHEAD &&
942  * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
943  * Otherwise, window_size == 2*WSIZE so more >= 2.
944  * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
945  */
946  Assert(more >= 2, "more < 2");
947 
948  n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
949  s->lookahead += n;
950 
951  /* Initialize the hash value now that we have some input: */
952  if (s->lookahead >= MIN_MATCH) {
953  s->ins_h = s->window[s->strstart];
954  UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
955 #if MIN_MATCH != 3
956  Call UPDATE_HASH() MIN_MATCH-3 more times
957 #endif
958  }
959  /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
960  * but this is not important since only literal bytes will be emitted.
961  */
962 
963  } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
964 }
965 
966 /* ===========================================================================
967  * Flush the current block, with given end-of-file flag.
968  * IN assertion: strstart is set to the end of the current match.
969  */
970 #define FLUSH_BLOCK_ONLY(s, eof) { \
971  zlib_tr_flush_block(s, (s->block_start >= 0L ? \
972  (char *)&s->window[(unsigned)s->block_start] : \
973  NULL), \
974  (ulg)((long)s->strstart - s->block_start), \
975  (eof)); \
976  s->block_start = s->strstart; \
977  flush_pending(s->strm); \
978  Tracev((stderr,"[FLUSH]")); \
979 }
980 
981 /* Same but force premature exit if necessary. */
982 #define FLUSH_BLOCK(s, eof) { \
983  FLUSH_BLOCK_ONLY(s, eof); \
984  if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
985 }
986 
987 /* ===========================================================================
988  * Copy without compression as much as possible from the input stream, return
989  * the current block state.
990  * This function does not insert new strings in the dictionary since
991  * uncompressible data is probably not useful. This function is used
992  * only for the level=0 compression option.
993  * NOTE: this function should be optimized to avoid extra copying from
994  * window to pending_buf.
995  */
996 static block_state deflate_stored(
997  deflate_state *s,
998  int flush
999 )
1000 {
1001  /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1002  * to pending_buf_size, and each stored block has a 5 byte header:
1003  */
1004  ulg max_block_size = 0xffff;
1005  ulg max_start;
1006 
1007  if (max_block_size > s->pending_buf_size - 5) {
1008  max_block_size = s->pending_buf_size - 5;
1009  }
1010 
1011  /* Copy as much as possible from input to output: */
1012  for (;;) {
1013  /* Fill the window as much as possible: */
1014  if (s->lookahead <= 1) {
1015 
1016  Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1017  s->block_start >= (long)s->w_size, "slide too late");
1018 
1019  fill_window(s);
1020  if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1021 
1022  if (s->lookahead == 0) break; /* flush the current block */
1023  }
1024  Assert(s->block_start >= 0L, "block gone");
1025 
1026  s->strstart += s->lookahead;
1027  s->lookahead = 0;
1028 
1029  /* Emit a stored block if pending_buf will be full: */
1030  max_start = s->block_start + max_block_size;
1031  if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1032  /* strstart == 0 is possible when wraparound on 16-bit machine */
1033  s->lookahead = (uInt)(s->strstart - max_start);
1034  s->strstart = (uInt)max_start;
1035  FLUSH_BLOCK(s, 0);
1036  }
1037  /* Flush if we may have to slide, otherwise block_start may become
1038  * negative and the data will be gone:
1039  */
1040  if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1041  FLUSH_BLOCK(s, 0);
1042  }
1043  }
1044  FLUSH_BLOCK(s, flush == Z_FINISH);
1045  return flush == Z_FINISH ? finish_done : block_done;
1046 }
1047 
1048 /* ===========================================================================
1049  * Compress as much as possible from the input stream, return the current
1050  * block state.
1051  * This function does not perform lazy evaluation of matches and inserts
1052  * new strings in the dictionary only for unmatched strings or for short
1053  * matches. It is used only for the fast compression options.
1054  */
1055 static block_state deflate_fast(
1056  deflate_state *s,
1057  int flush
1058 )
1059 {
1060  IPos hash_head = NIL; /* head of the hash chain */
1061  int bflush; /* set if current block must be flushed */
1062 
1063  for (;;) {
1064  /* Make sure that we always have enough lookahead, except
1065  * at the end of the input file. We need MAX_MATCH bytes
1066  * for the next match, plus MIN_MATCH bytes to insert the
1067  * string following the next match.
1068  */
1069  if (s->lookahead < MIN_LOOKAHEAD) {
1070  fill_window(s);
1071  if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1072  return need_more;
1073  }
1074  if (s->lookahead == 0) break; /* flush the current block */
1075  }
1076 
1077  /* Insert the string window[strstart .. strstart+2] in the
1078  * dictionary, and set hash_head to the head of the hash chain:
1079  */
1080  if (s->lookahead >= MIN_MATCH) {
1081  INSERT_STRING(s, s->strstart, hash_head);
1082  }
1083 
1084  /* Find the longest match, discarding those <= prev_length.
1085  * At this point we have always match_length < MIN_MATCH
1086  */
1087  if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1088  /* To simplify the code, we prevent matches with the string
1089  * of window index 0 (in particular we have to avoid a match
1090  * of the string with itself at the start of the input file).
1091  */
1092  if (s->strategy != Z_HUFFMAN_ONLY) {
1093  s->match_length = longest_match (s, hash_head);
1094  }
1095  /* longest_match() sets match_start */
1096  }
1097  if (s->match_length >= MIN_MATCH) {
1099 
1100  bflush = zlib_tr_tally(s, s->strstart - s->match_start,
1101  s->match_length - MIN_MATCH);
1102 
1103  s->lookahead -= s->match_length;
1104 
1105  /* Insert new strings in the hash table only if the match length
1106  * is not too large. This saves time but degrades compression.
1107  */
1108  if (s->match_length <= s->max_insert_length &&
1109  s->lookahead >= MIN_MATCH) {
1110  s->match_length--; /* string at strstart already in hash table */
1111  do {
1112  s->strstart++;
1113  INSERT_STRING(s, s->strstart, hash_head);
1114  /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1115  * always MIN_MATCH bytes ahead.
1116  */
1117  } while (--s->match_length != 0);
1118  s->strstart++;
1119  } else {
1120  s->strstart += s->match_length;
1121  s->match_length = 0;
1122  s->ins_h = s->window[s->strstart];
1123  UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1124 #if MIN_MATCH != 3
1125  Call UPDATE_HASH() MIN_MATCH-3 more times
1126 #endif
1127  /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1128  * matter since it will be recomputed at next deflate call.
1129  */
1130  }
1131  } else {
1132  /* No match, output a literal byte */
1133  Tracevv((stderr,"%c", s->window[s->strstart]));
1134  bflush = zlib_tr_tally (s, 0, s->window[s->strstart]);
1135  s->lookahead--;
1136  s->strstart++;
1137  }
1138  if (bflush) FLUSH_BLOCK(s, 0);
1139  }
1140  FLUSH_BLOCK(s, flush == Z_FINISH);
1141  return flush == Z_FINISH ? finish_done : block_done;
1142 }
1143 
1144 /* ===========================================================================
1145  * Same as above, but achieves better compression. We use a lazy
1146  * evaluation for matches: a match is finally adopted only if there is
1147  * no better match at the next window position.
1148  */
1149 static block_state deflate_slow(
1150  deflate_state *s,
1151  int flush
1152 )
1153 {
1154  IPos hash_head = NIL; /* head of hash chain */
1155  int bflush; /* set if current block must be flushed */
1156 
1157  /* Process the input block. */
1158  for (;;) {
1159  /* Make sure that we always have enough lookahead, except
1160  * at the end of the input file. We need MAX_MATCH bytes
1161  * for the next match, plus MIN_MATCH bytes to insert the
1162  * string following the next match.
1163  */
1164  if (s->lookahead < MIN_LOOKAHEAD) {
1165  fill_window(s);
1166  if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1167  return need_more;
1168  }
1169  if (s->lookahead == 0) break; /* flush the current block */
1170  }
1171 
1172  /* Insert the string window[strstart .. strstart+2] in the
1173  * dictionary, and set hash_head to the head of the hash chain:
1174  */
1175  if (s->lookahead >= MIN_MATCH) {
1176  INSERT_STRING(s, s->strstart, hash_head);
1177  }
1178 
1179  /* Find the longest match, discarding those <= prev_length.
1180  */
1182  s->match_length = MIN_MATCH-1;
1183 
1184  if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1185  s->strstart - hash_head <= MAX_DIST(s)) {
1186  /* To simplify the code, we prevent matches with the string
1187  * of window index 0 (in particular we have to avoid a match
1188  * of the string with itself at the start of the input file).
1189  */
1190  if (s->strategy != Z_HUFFMAN_ONLY) {
1191  s->match_length = longest_match (s, hash_head);
1192  }
1193  /* longest_match() sets match_start */
1194 
1195  if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1196  (s->match_length == MIN_MATCH &&
1197  s->strstart - s->match_start > TOO_FAR))) {
1198 
1199  /* If prev_match is also MIN_MATCH, match_start is garbage
1200  * but we will ignore the current match anyway.
1201  */
1202  s->match_length = MIN_MATCH-1;
1203  }
1204  }
1205  /* If there was a match at the previous step and the current
1206  * match is not better, output the previous match:
1207  */
1208  if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1209  uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1210  /* Do not insert strings in hash table beyond this. */
1211 
1212  check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1213 
1214  bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match,
1215  s->prev_length - MIN_MATCH);
1216 
1217  /* Insert in hash table all strings up to the end of the match.
1218  * strstart-1 and strstart are already inserted. If there is not
1219  * enough lookahead, the last two strings are not inserted in
1220  * the hash table.
1221  */
1222  s->lookahead -= s->prev_length-1;
1223  s->prev_length -= 2;
1224  do {
1225  if (++s->strstart <= max_insert) {
1226  INSERT_STRING(s, s->strstart, hash_head);
1227  }
1228  } while (--s->prev_length != 0);
1229  s->match_available = 0;
1230  s->match_length = MIN_MATCH-1;
1231  s->strstart++;
1232 
1233  if (bflush) FLUSH_BLOCK(s, 0);
1234 
1235  } else if (s->match_available) {
1236  /* If there was no match at the previous position, output a
1237  * single literal. If there was a match but the current match
1238  * is longer, truncate the previous match to a single literal.
1239  */
1240  Tracevv((stderr,"%c", s->window[s->strstart-1]));
1241  if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) {
1242  FLUSH_BLOCK_ONLY(s, 0);
1243  }
1244  s->strstart++;
1245  s->lookahead--;
1246  if (s->strm->avail_out == 0) return need_more;
1247  } else {
1248  /* There is no previous match to compare with, wait for
1249  * the next step to decide.
1250  */
1251  s->match_available = 1;
1252  s->strstart++;
1253  s->lookahead--;
1254  }
1255  }
1256  Assert (flush != Z_NO_FLUSH, "no flush?");
1257  if (s->match_available) {
1258  Tracevv((stderr,"%c", s->window[s->strstart-1]));
1259  zlib_tr_tally (s, 0, s->window[s->strstart-1]);
1260  s->match_available = 0;
1261  }
1262  FLUSH_BLOCK(s, flush == Z_FINISH);
1263  return flush == Z_FINISH ? finish_done : block_done;
1264 }
1265 
1266 int zlib_deflate_workspacesize(int windowBits, int memLevel)
1267 {
1268  if (windowBits < 0) /* undocumented feature: suppress zlib header */
1269  windowBits = -windowBits;
1270 
1271  /* Since the return value is typically passed to vmalloc() unchecked... */
1272  BUG_ON(memLevel < 1 || memLevel > MAX_MEM_LEVEL || windowBits < 9 ||
1273  windowBits > 15);
1274 
1275  return sizeof(deflate_workspace)
1276  + zlib_deflate_window_memsize(windowBits)
1277  + zlib_deflate_prev_memsize(windowBits)
1278  + zlib_deflate_head_memsize(memLevel)
1279  + zlib_deflate_overlay_memsize(memLevel);
1280 }