~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/lib/zlib_deflate/deflate.c

Version: ~ [ linux-5.1-rc1 ] ~ [ linux-5.0.3 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.30 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.107 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.164 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.176 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.136 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.63 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /* +++ deflate.c */
  2 /* deflate.c -- compress data using the deflation algorithm
  3  * Copyright (C) 1995-1996 Jean-loup Gailly.
  4  * For conditions of distribution and use, see copyright notice in zlib.h 
  5  */
  6 
  7 /*
  8  *  ALGORITHM
  9  *
 10  *      The "deflation" process depends on being able to identify portions
 11  *      of the input text which are identical to earlier input (within a
 12  *      sliding window trailing behind the input currently being processed).
 13  *
 14  *      The most straightforward technique turns out to be the fastest for
 15  *      most input files: try all possible matches and select the longest.
 16  *      The key feature of this algorithm is that insertions into the string
 17  *      dictionary are very simple and thus fast, and deletions are avoided
 18  *      completely. Insertions are performed at each input character, whereas
 19  *      string matches are performed only when the previous match ends. So it
 20  *      is preferable to spend more time in matches to allow very fast string
 21  *      insertions and avoid deletions. The matching algorithm for small
 22  *      strings is inspired from that of Rabin & Karp. A brute force approach
 23  *      is used to find longer strings when a small match has been found.
 24  *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
 25  *      (by Leonid Broukhis).
 26  *         A previous version of this file used a more sophisticated algorithm
 27  *      (by Fiala and Greene) which is guaranteed to run in linear amortized
 28  *      time, but has a larger average cost, uses more memory and is patented.
 29  *      However the F&G algorithm may be faster for some highly redundant
 30  *      files if the parameter max_chain_length (described below) is too large.
 31  *
 32  *  ACKNOWLEDGEMENTS
 33  *
 34  *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
 35  *      I found it in 'freeze' written by Leonid Broukhis.
 36  *      Thanks to many people for bug reports and testing.
 37  *
 38  *  REFERENCES
 39  *
 40  *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
 41  *      Available in ftp://ds.internic.net/rfc/rfc1951.txt
 42  *
 43  *      A description of the Rabin and Karp algorithm is given in the book
 44  *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
 45  *
 46  *      Fiala,E.R., and Greene,D.H.
 47  *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
 48  *
 49  */
 50 
 51 #include <linux/module.h>
 52 #include <linux/zutil.h>
 53 #include "defutil.h"
 54 
 55 
 56 /* ===========================================================================
 57  *  Function prototypes.
 58  */
 59 typedef enum {
 60     need_more,      /* block not completed, need more input or more output */
 61     block_done,     /* block flush performed */
 62     finish_started, /* finish started, need only more output at next deflate */
 63     finish_done     /* finish done, accept no more input or output */
 64 } block_state;
 65 
 66 typedef block_state (*compress_func) (deflate_state *s, int flush);
 67 /* Compression function. Returns the block state after the call. */
 68 
 69 static void fill_window    (deflate_state *s);
 70 static block_state deflate_stored (deflate_state *s, int flush);
 71 static block_state deflate_fast   (deflate_state *s, int flush);
 72 static block_state deflate_slow   (deflate_state *s, int flush);
 73 static void lm_init        (deflate_state *s);
 74 static void putShortMSB    (deflate_state *s, uInt b);
 75 static void flush_pending  (z_streamp strm);
 76 static int read_buf        (z_streamp strm, Byte *buf, unsigned size);
 77 static uInt longest_match  (deflate_state *s, IPos cur_match);
 78 
 79 #ifdef DEBUG_ZLIB
 80 static  void check_match (deflate_state *s, IPos start, IPos match,
 81                          int length);
 82 #endif
 83 
 84 /* ===========================================================================
 85  * Local data
 86  */
 87 
 88 #define NIL 0
 89 /* Tail of hash chains */
 90 
 91 #ifndef TOO_FAR
 92 #  define TOO_FAR 4096
 93 #endif
 94 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
 95 
 96 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
 97 /* Minimum amount of lookahead, except at the end of the input file.
 98  * See deflate.c for comments about the MIN_MATCH+1.
 99  */
100 
101 /* Values for max_lazy_match, good_match and max_chain_length, depending on
102  * the desired pack level (0..9). The values given below have been tuned to
103  * exclude worst case performance for pathological files. Better values may be
104  * found for specific files.
105  */
106 typedef struct config_s {
107    ush good_length; /* reduce lazy search above this match length */
108    ush max_lazy;    /* do not perform lazy search above this match length */
109    ush nice_length; /* quit search above this match length */
110    ush max_chain;
111    compress_func func;
112 } config;
113 
114 static const config configuration_table[10] = {
115 /*      good lazy nice chain */
116 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
117 /* 1 */ {4,    4,  8,    4, deflate_fast}, /* maximum speed, no lazy matches */
118 /* 2 */ {4,    5, 16,    8, deflate_fast},
119 /* 3 */ {4,    6, 32,   32, deflate_fast},
120 
121 /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
122 /* 5 */ {8,   16, 32,   32, deflate_slow},
123 /* 6 */ {8,   16, 128, 128, deflate_slow},
124 /* 7 */ {8,   32, 128, 256, deflate_slow},
125 /* 8 */ {32, 128, 258, 1024, deflate_slow},
126 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
127 
128 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
129  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
130  * meaning.
131  */
132 
133 #define EQUAL 0
134 /* result of memcmp for equal strings */
135 
136 /* ===========================================================================
137  * Update a hash value with the given input byte
138  * IN  assertion: all calls to UPDATE_HASH are made with consecutive
139  *    input characters, so that a running hash key can be computed from the
140  *    previous key instead of complete recalculation each time.
141  */
142 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
143 
144 
145 /* ===========================================================================
146  * Insert string str in the dictionary and set match_head to the previous head
147  * of the hash chain (the most recent string with same hash key). Return
148  * the previous length of the hash chain.
149  * IN  assertion: all calls to INSERT_STRING are made with consecutive
150  *    input characters and the first MIN_MATCH bytes of str are valid
151  *    (except for the last MIN_MATCH-1 bytes of the input file).
152  */
153 #define INSERT_STRING(s, str, match_head) \
154    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
155     s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
156     s->head[s->ins_h] = (Pos)(str))
157 
158 /* ===========================================================================
159  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
160  * prev[] will be initialized on the fly.
161  */
162 #define CLEAR_HASH(s) \
163     s->head[s->hash_size-1] = NIL; \
164     memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));
165 
166 /* ========================================================================= */
167 int zlib_deflateInit2(
168         z_streamp strm,
169         int  level,
170         int  method,
171         int  windowBits,
172         int  memLevel,
173         int  strategy
174 )
175 {
176     deflate_state *s;
177     int noheader = 0;
178     deflate_workspace *mem;
179     char *next;
180 
181     ush *overlay;
182     /* We overlay pending_buf and d_buf+l_buf. This works since the average
183      * output size for (length,distance) codes is <= 24 bits.
184      */
185 
186     if (strm == NULL) return Z_STREAM_ERROR;
187 
188     strm->msg = NULL;
189 
190     if (level == Z_DEFAULT_COMPRESSION) level = 6;
191 
192     mem = (deflate_workspace *) strm->workspace;
193 
194     if (windowBits < 0) { /* undocumented feature: suppress zlib header */
195         noheader = 1;
196         windowBits = -windowBits;
197     }
198     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
199         windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
200         strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
201         return Z_STREAM_ERROR;
202     }
203 
204     /*
205      * Direct the workspace's pointers to the chunks that were allocated
206      * along with the deflate_workspace struct.
207      */
208     next = (char *) mem;
209     next += sizeof(*mem);
210     mem->window_memory = (Byte *) next;
211     next += zlib_deflate_window_memsize(windowBits);
212     mem->prev_memory = (Pos *) next;
213     next += zlib_deflate_prev_memsize(windowBits);
214     mem->head_memory = (Pos *) next;
215     next += zlib_deflate_head_memsize(memLevel);
216     mem->overlay_memory = next;
217 
218     s = (deflate_state *) &(mem->deflate_memory);
219     strm->state = (struct internal_state *)s;
220     s->strm = strm;
221 
222     s->noheader = noheader;
223     s->w_bits = windowBits;
224     s->w_size = 1 << s->w_bits;
225     s->w_mask = s->w_size - 1;
226 
227     s->hash_bits = memLevel + 7;
228     s->hash_size = 1 << s->hash_bits;
229     s->hash_mask = s->hash_size - 1;
230     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
231 
232     s->window = (Byte *) mem->window_memory;
233     s->prev   = (Pos *)  mem->prev_memory;
234     s->head   = (Pos *)  mem->head_memory;
235 
236     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
237 
238     overlay = (ush *) mem->overlay_memory;
239     s->pending_buf = (uch *) overlay;
240     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
241 
242     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
243     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
244 
245     s->level = level;
246     s->strategy = strategy;
247     s->method = (Byte)method;
248 
249     return zlib_deflateReset(strm);
250 }
251 
252 /* ========================================================================= */
253 #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 /* ========================================================================= */
299 int zlib_deflateReset(
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;
338     compress_func func;
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 /* ========================================================================= */
412 int zlib_deflate(
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. */
516                 zlib_tr_stored_type_only(s);
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 /* ========================================================================= */
550 int zlib_deflateEnd(
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,
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 #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) {
1098             check_match(s, s->strstart, s->match_start, s->match_length);
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          */
1181         s->prev_length = s->match_length, s->prev_match = s->match_start;
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 }
1281 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp