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1 /* deflate.c -- compress data using the deflation algorithm
2  * Copyright (C) 1995-2005 Jean-loup Gailly.
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5 
6 /*
7  *  ALGORITHM
8  *
9  *      The "deflation" process depends on being able to identify portions
10  *      of the input text which are identical to earlier input (within a
11  *      sliding window trailing behind the input currently being processed).
12  *
13  *      The most straightforward technique turns out to be the fastest for
14  *      most input files: try all possible matches and select the longest.
15  *      The key feature of this algorithm is that insertions into the string
16  *      dictionary are very simple and thus fast, and deletions are avoided
17  *      completely. Insertions are performed at each input character, whereas
18  *      string matches are performed only when the previous match ends. So it
19  *      is preferable to spend more time in matches to allow very fast string
20  *      insertions and avoid deletions. The matching algorithm for small
21  *      strings is inspired from that of Rabin & Karp. A brute force approach
22  *      is used to find longer strings when a small match has been found.
23  *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
24  *      (by Leonid Broukhis).
25  *         A previous version of this file used a more sophisticated algorithm
26  *      (by Fiala and Greene) which is guaranteed to run in linear amortized
27  *      time, but has a larger average cost, uses more memory and is patented.
28  *      However the F&G algorithm may be faster for some highly redundant
29  *      files if the parameter max_chain_length (described below) is too large.
30  *
31  *  ACKNOWLEDGEMENTS
32  *
33  *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
34  *      I found it in 'freeze' written by Leonid Broukhis.
35  *      Thanks to many people for bug reports and testing.
36  *
37  *  REFERENCES
38  *
39  *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
40  *      Available in http://www.ietf.org/rfc/rfc1951.txt
41  *
42  *      A description of the Rabin and Karp algorithm is given in the book
43  *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
44  *
45  *      Fiala,E.R., and Greene,D.H.
46  *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
47  *
48  */
49 
50 /* @(#) $Id: deflate.c,v 3.6 2005/08/04 19:14:14 tor%cs.brown.edu Exp $ */
51 
52 #include "deflate.h"
53 
54 const char deflate_copyright[] =
55    " deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly ";
56 /*
57   If you use the zlib library in a product, an acknowledgment is welcome
58   in the documentation of your product. If for some reason you cannot
59   include such an acknowledgment, I would appreciate that you keep this
60   copyright string in the executable of your product.
61  */
62 
63 /* ===========================================================================
64  *  Function prototypes.
65  */
66 typedef enum {
67     need_more,      /* block not completed, need more input or more output */
68     block_done,     /* block flush performed */
69     finish_started, /* finish started, need only more output at next deflate */
70     finish_done     /* finish done, accept no more input or output */
71 } block_state;
72 
73 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
74 /* Compression function. Returns the block state after the call. */
75 
76 local void fill_window    OF((deflate_state *s));
77 local block_state deflate_stored OF((deflate_state *s, int flush));
78 local block_state deflate_fast   OF((deflate_state *s, int flush));
79 #ifndef FASTEST
80 local block_state deflate_slow   OF((deflate_state *s, int flush));
81 #endif
82 local void lm_init        OF((deflate_state *s));
83 local void putShortMSB    OF((deflate_state *s, uInt b));
84 local void flush_pending  OF((z_streamp strm));
85 local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
86 #ifndef FASTEST
87 #ifdef ASMV
88       void match_init OF((void)); /* asm code initialization */
89       uInt longest_match  OF((deflate_state *s, IPos cur_match));
90 #else
91 local uInt longest_match  OF((deflate_state *s, IPos cur_match));
92 #endif
93 #endif
94 local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
95 
96 #ifdef DEBUG
97 local  void check_match OF((deflate_state *s, IPos start, IPos match,
98                             int length));
99 #endif
100 
101 /* ===========================================================================
102  * Local data
103  */
104 
105 #define NIL 0
106 /* Tail of hash chains */
107 
108 #ifndef TOO_FAR
109 #  define TOO_FAR 4096
110 #endif
111 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
112 
113 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
114 /* Minimum amount of lookahead, except at the end of the input file.
115  * See deflate.c for comments about the MIN_MATCH+1.
116  */
117 
118 /* Values for max_lazy_match, good_match and max_chain_length, depending on
119  * the desired pack level (0..9). The values given below have been tuned to
120  * exclude worst case performance for pathological files. Better values may be
121  * found for specific files.
122  */
123 typedef struct config_s {
124    ush good_length; /* reduce lazy search above this match length */
125    ush max_lazy;    /* do not perform lazy search above this match length */
126    ush nice_length; /* quit search above this match length */
127    ush max_chain;
128    compress_func func;
129 } config;
130 
131 #ifdef FASTEST
132 local const config configuration_table[2] = {
133 /*      good lazy nice chain */
134 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
135 /* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */
136 #else
137 local const config configuration_table[10] = {
138 /*      good lazy nice chain */
139 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
140 /* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
141 /* 2 */ {4,    5, 16,    8, deflate_fast},
142 /* 3 */ {4,    6, 32,   32, deflate_fast},
143 
144 /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
145 /* 5 */ {8,   16, 32,   32, deflate_slow},
146 /* 6 */ {8,   16, 128, 128, deflate_slow},
147 /* 7 */ {8,   32, 128, 256, deflate_slow},
148 /* 8 */ {32, 128, 258, 1024, deflate_slow},
149 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
150 #endif
151 
152 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
153  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
154  * meaning.
155  */
156 
157 #define EQUAL 0
158 /* result of memcmp for equal strings */
159 
160 #ifndef NO_DUMMY_DECL
161 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
162 #endif
163 
164 /* ===========================================================================
165  * Update a hash value with the given input byte
166  * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
167  *    input characters, so that a running hash key can be computed from the
168  *    previous key instead of complete recalculation each time.
169  */
170 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
171 
172 
173 /* ===========================================================================
174  * Insert string str in the dictionary and set match_head to the previous head
175  * of the hash chain (the most recent string with same hash key). Return
176  * the previous length of the hash chain.
177  * If this file is compiled with -DFASTEST, the compression level is forced
178  * to 1, and no hash chains are maintained.
179  * IN  assertion: all calls to to INSERT_STRING are made with consecutive
180  *    input characters and the first MIN_MATCH bytes of str are valid
181  *    (except for the last MIN_MATCH-1 bytes of the input file).
182  */
183 #ifdef FASTEST
184 #define INSERT_STRING(s, str, match_head) \
185    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
186     match_head = s->head[s->ins_h], \
187     s->head[s->ins_h] = (Pos)(str))
188 #else
189 #define INSERT_STRING(s, str, match_head) \
190    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
191     match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
192     s->head[s->ins_h] = (Pos)(str))
193 #endif
194 
195 /* ===========================================================================
196  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
197  * prev[] will be initialized on the fly.
198  */
199 #define CLEAR_HASH(s) \
200     s->head[s->hash_size-1] = NIL; \
201     zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
202 
203 /* ========================================================================= */
deflateInit_(strm,level,version,stream_size)204 int ZEXPORT deflateInit_(strm, level, version, stream_size)
205     z_streamp strm;
206     int level;
207     const char *version;
208     int stream_size;
209 {
210     return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
211                          Z_DEFAULT_STRATEGY, version, stream_size);
212     /* To do: ignore strm->next_in if we use it as window */
213 }
214 
215 /* ========================================================================= */
deflateInit2_(strm,level,method,windowBits,memLevel,strategy,version,stream_size)216 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
217                   version, stream_size)
218     z_streamp strm;
219     int  level;
220     int  method;
221     int  windowBits;
222     int  memLevel;
223     int  strategy;
224     const char *version;
225     int stream_size;
226 {
227     deflate_state *s;
228     int wrap = 1;
229     static const char my_version[] = ZLIB_VERSION;
230 
231     ushf *overlay;
232     /* We overlay pending_buf and d_buf+l_buf. This works since the average
233      * output size for (length,distance) codes is <= 24 bits.
234      */
235 
236     if (version == Z_NULL || version[0] != my_version[0] ||
237         stream_size != sizeof(z_stream)) {
238         return Z_VERSION_ERROR;
239     }
240     if (strm == Z_NULL) return Z_STREAM_ERROR;
241 
242     strm->msg = Z_NULL;
243     if (strm->zalloc == (alloc_func)0) {
244         strm->zalloc = zcalloc;
245         strm->opaque = (voidpf)0;
246     }
247     if (strm->zfree == (free_func)0) strm->zfree = zcfree;
248 
249 #ifdef FASTEST
250     if (level != 0) level = 1;
251 #else
252     if (level == Z_DEFAULT_COMPRESSION) level = 6;
253 #endif
254 
255     if (windowBits < 0) { /* suppress zlib wrapper */
256         wrap = 0;
257         windowBits = -windowBits;
258     }
259 #ifdef GZIP
260     else if (windowBits > 15) {
261         wrap = 2;       /* write gzip wrapper instead */
262         windowBits -= 16;
263     }
264 #endif
265     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
266         windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
267         strategy < 0 || strategy > Z_FIXED) {
268         return Z_STREAM_ERROR;
269     }
270     if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
271     s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
272     if (s == Z_NULL) return Z_MEM_ERROR;
273     strm->state = (struct internal_state FAR *)s;
274     s->strm = strm;
275 
276     s->wrap = wrap;
277     s->gzhead = Z_NULL;
278     s->w_bits = windowBits;
279     s->w_size = 1 << s->w_bits;
280     s->w_mask = s->w_size - 1;
281 
282     s->hash_bits = memLevel + 7;
283     s->hash_size = 1 << s->hash_bits;
284     s->hash_mask = s->hash_size - 1;
285     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
286 
287     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
288     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
289     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
290 
291     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
292 
293     overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
294     s->pending_buf = (uchf *) overlay;
295     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
296 
297     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
298         s->pending_buf == Z_NULL) {
299         s->status = FINISH_STATE;
300         strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
301         deflateEnd (strm);
302         return Z_MEM_ERROR;
303     }
304     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
305     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
306 
307     s->level = level;
308     s->strategy = strategy;
309     s->method = (Byte)method;
310 
311     return deflateReset(strm);
312 }
313 
314 /* ========================================================================= */
deflateSetDictionary(strm,dictionary,dictLength)315 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
316     z_streamp strm;
317     const Bytef *dictionary;
318     uInt  dictLength;
319 {
320     deflate_state *s;
321     uInt length = dictLength;
322     uInt n;
323     IPos hash_head = 0;
324 
325     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
326         strm->state->wrap == 2 ||
327         (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
328         return Z_STREAM_ERROR;
329 
330     s = strm->state;
331     if (s->wrap)
332         strm->adler = adler32(strm->adler, dictionary, dictLength);
333 
334     if (length < MIN_MATCH) return Z_OK;
335     if (length > MAX_DIST(s)) {
336         length = MAX_DIST(s);
337         dictionary += dictLength - length; /* use the tail of the dictionary */
338     }
339     zmemcpy(s->window, dictionary, length);
340     s->strstart = length;
341     s->block_start = (long)length;
342 
343     /* Insert all strings in the hash table (except for the last two bytes).
344      * s->lookahead stays null, so s->ins_h will be recomputed at the next
345      * call of fill_window.
346      */
347     s->ins_h = s->window[0];
348     UPDATE_HASH(s, s->ins_h, s->window[1]);
349     for (n = 0; n <= length - MIN_MATCH; n++) {
350         INSERT_STRING(s, n, hash_head);
351     }
352     if (hash_head) hash_head = 0;  /* to make compiler happy */
353     return Z_OK;
354 }
355 
356 /* ========================================================================= */
deflateReset(strm)357 int ZEXPORT deflateReset (strm)
358     z_streamp strm;
359 {
360     deflate_state *s;
361 
362     if (strm == Z_NULL || strm->state == Z_NULL ||
363         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
364         return Z_STREAM_ERROR;
365     }
366 
367     strm->total_in = strm->total_out = 0;
368     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
369     strm->data_type = Z_UNKNOWN;
370 
371     s = (deflate_state *)strm->state;
372     s->pending = 0;
373     s->pending_out = s->pending_buf;
374 
375     if (s->wrap < 0) {
376         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
377     }
378     s->status = s->wrap ? INIT_STATE : BUSY_STATE;
379     strm->adler =
380 #ifdef GZIP
381         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
382 #endif
383         adler32(0L, Z_NULL, 0);
384     s->last_flush = Z_NO_FLUSH;
385 
386     _tr_init(s);
387     lm_init(s);
388 
389     return Z_OK;
390 }
391 
392 /* ========================================================================= */
deflateSetHeader(strm,head)393 int ZEXPORT deflateSetHeader (strm, head)
394     z_streamp strm;
395     gz_headerp head;
396 {
397     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
398     if (strm->state->wrap != 2) return Z_STREAM_ERROR;
399     strm->state->gzhead = head;
400     return Z_OK;
401 }
402 
403 /* ========================================================================= */
deflatePrime(strm,bits,value)404 int ZEXPORT deflatePrime (strm, bits, value)
405     z_streamp strm;
406     int bits;
407     int value;
408 {
409     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
410     strm->state->bi_valid = bits;
411     strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
412     return Z_OK;
413 }
414 
415 /* ========================================================================= */
deflateParams(strm,level,strategy)416 int ZEXPORT deflateParams(strm, level, strategy)
417     z_streamp strm;
418     int level;
419     int strategy;
420 {
421     deflate_state *s;
422     compress_func func;
423     int err = Z_OK;
424 
425     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
426     s = strm->state;
427 
428 #ifdef FASTEST
429     if (level != 0) level = 1;
430 #else
431     if (level == Z_DEFAULT_COMPRESSION) level = 6;
432 #endif
433     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
434         return Z_STREAM_ERROR;
435     }
436     func = configuration_table[s->level].func;
437 
438     if (func != configuration_table[level].func && strm->total_in != 0) {
439         /* Flush the last buffer: */
440         err = deflate(strm, Z_PARTIAL_FLUSH);
441     }
442     if (s->level != level) {
443         s->level = level;
444         s->max_lazy_match   = configuration_table[level].max_lazy;
445         s->good_match       = configuration_table[level].good_length;
446         s->nice_match       = configuration_table[level].nice_length;
447         s->max_chain_length = configuration_table[level].max_chain;
448     }
449     s->strategy = strategy;
450     return err;
451 }
452 
453 /* ========================================================================= */
deflateTune(strm,good_length,max_lazy,nice_length,max_chain)454 int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
455     z_streamp strm;
456     int good_length;
457     int max_lazy;
458     int nice_length;
459     int max_chain;
460 {
461     deflate_state *s;
462 
463     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
464     s = strm->state;
465     s->good_match = good_length;
466     s->max_lazy_match = max_lazy;
467     s->nice_match = nice_length;
468     s->max_chain_length = max_chain;
469     return Z_OK;
470 }
471 
472 /* =========================================================================
473  * For the default windowBits of 15 and memLevel of 8, this function returns
474  * a close to exact, as well as small, upper bound on the compressed size.
475  * They are coded as constants here for a reason--if the #define's are
476  * changed, then this function needs to be changed as well.  The return
477  * value for 15 and 8 only works for those exact settings.
478  *
479  * For any setting other than those defaults for windowBits and memLevel,
480  * the value returned is a conservative worst case for the maximum expansion
481  * resulting from using fixed blocks instead of stored blocks, which deflate
482  * can emit on compressed data for some combinations of the parameters.
483  *
484  * This function could be more sophisticated to provide closer upper bounds
485  * for every combination of windowBits and memLevel, as well as wrap.
486  * But even the conservative upper bound of about 14% expansion does not
487  * seem onerous for output buffer allocation.
488  */
deflateBound(strm,sourceLen)489 uLong ZEXPORT deflateBound(strm, sourceLen)
490     z_streamp strm;
491     uLong sourceLen;
492 {
493     deflate_state *s;
494     uLong destLen;
495 
496     /* conservative upper bound */
497     destLen = sourceLen +
498               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
499 
500     /* if can't get parameters, return conservative bound */
501     if (strm == Z_NULL || strm->state == Z_NULL)
502         return destLen;
503 
504     /* if not default parameters, return conservative bound */
505     s = strm->state;
506     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
507         return destLen;
508 
509     /* default settings: return tight bound for that case */
510     return compressBound(sourceLen);
511 }
512 
513 /* =========================================================================
514  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
515  * IN assertion: the stream state is correct and there is enough room in
516  * pending_buf.
517  */
putShortMSB(s,b)518 local void putShortMSB (s, b)
519     deflate_state *s;
520     uInt b;
521 {
522     put_byte(s, (Byte)(b >> 8));
523     put_byte(s, (Byte)(b & 0xff));
524 }
525 
526 /* =========================================================================
527  * Flush as much pending output as possible. All deflate() output goes
528  * through this function so some applications may wish to modify it
529  * to avoid allocating a large strm->next_out buffer and copying into it.
530  * (See also read_buf()).
531  */
flush_pending(strm)532 local void flush_pending(strm)
533     z_streamp strm;
534 {
535     unsigned len = strm->state->pending;
536 
537     if (len > strm->avail_out) len = strm->avail_out;
538     if (len == 0) return;
539 
540     zmemcpy(strm->next_out, strm->state->pending_out, len);
541     strm->next_out  += len;
542     strm->state->pending_out  += len;
543     strm->total_out += len;
544     strm->avail_out  -= len;
545     strm->state->pending -= len;
546     if (strm->state->pending == 0) {
547         strm->state->pending_out = strm->state->pending_buf;
548     }
549 }
550 
551 /* ========================================================================= */
deflate(strm,flush)552 int ZEXPORT deflate (strm, flush)
553     z_streamp strm;
554     int flush;
555 {
556     int old_flush; /* value of flush param for previous deflate call */
557     deflate_state *s;
558 
559     if (strm == Z_NULL || strm->state == Z_NULL ||
560         flush > Z_FINISH || flush < 0) {
561         return Z_STREAM_ERROR;
562     }
563     s = strm->state;
564 
565     if (strm->next_out == Z_NULL ||
566         (strm->next_in == Z_NULL && strm->avail_in != 0) ||
567         (s->status == FINISH_STATE && flush != Z_FINISH)) {
568         ERR_RETURN(strm, Z_STREAM_ERROR);
569     }
570     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
571 
572     s->strm = strm; /* just in case */
573     old_flush = s->last_flush;
574     s->last_flush = flush;
575 
576     /* Write the header */
577     if (s->status == INIT_STATE) {
578 #ifdef GZIP
579         if (s->wrap == 2) {
580             strm->adler = crc32(0L, Z_NULL, 0);
581             put_byte(s, 31);
582             put_byte(s, 139);
583             put_byte(s, 8);
584             if (s->gzhead == NULL) {
585                 put_byte(s, 0);
586                 put_byte(s, 0);
587                 put_byte(s, 0);
588                 put_byte(s, 0);
589                 put_byte(s, 0);
590                 put_byte(s, s->level == 9 ? 2 :
591                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
592                              4 : 0));
593                 put_byte(s, OS_CODE);
594                 s->status = BUSY_STATE;
595             }
596             else {
597                 put_byte(s, (s->gzhead->text ? 1 : 0) +
598                             (s->gzhead->hcrc ? 2 : 0) +
599                             (s->gzhead->extra == Z_NULL ? 0 : 4) +
600                             (s->gzhead->name == Z_NULL ? 0 : 8) +
601                             (s->gzhead->comment == Z_NULL ? 0 : 16)
602                         );
603                 put_byte(s, (Byte)(s->gzhead->time & 0xff));
604                 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
605                 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
606                 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
607                 put_byte(s, s->level == 9 ? 2 :
608                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
609                              4 : 0));
610                 put_byte(s, s->gzhead->os & 0xff);
611                 if (s->gzhead->extra != NULL) {
612                     put_byte(s, s->gzhead->extra_len & 0xff);
613                     put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
614                 }
615                 if (s->gzhead->hcrc)
616                     strm->adler = crc32(strm->adler, s->pending_buf,
617                                         s->pending);
618                 s->gzindex = 0;
619                 s->status = EXTRA_STATE;
620             }
621         }
622         else
623 #endif
624         {
625             uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
626             uInt level_flags;
627 
628             if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
629                 level_flags = 0;
630             else if (s->level < 6)
631                 level_flags = 1;
632             else if (s->level == 6)
633                 level_flags = 2;
634             else
635                 level_flags = 3;
636             header |= (level_flags << 6);
637             if (s->strstart != 0) header |= PRESET_DICT;
638             header += 31 - (header % 31);
639 
640             s->status = BUSY_STATE;
641             putShortMSB(s, header);
642 
643             /* Save the adler32 of the preset dictionary: */
644             if (s->strstart != 0) {
645                 putShortMSB(s, (uInt)(strm->adler >> 16));
646                 putShortMSB(s, (uInt)(strm->adler & 0xffff));
647             }
648             strm->adler = adler32(0L, Z_NULL, 0);
649         }
650     }
651 #ifdef GZIP
652     if (s->status == EXTRA_STATE) {
653         if (s->gzhead->extra != NULL) {
654             uInt beg = s->pending;  /* start of bytes to update crc */
655 
656             while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
657                 if (s->pending == s->pending_buf_size) {
658                     if (s->gzhead->hcrc && s->pending > beg)
659                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
660                                             s->pending - beg);
661                     flush_pending(strm);
662                     beg = s->pending;
663                     if (s->pending == s->pending_buf_size)
664                         break;
665                 }
666                 put_byte(s, s->gzhead->extra[s->gzindex]);
667                 s->gzindex++;
668             }
669             if (s->gzhead->hcrc && s->pending > beg)
670                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
671                                     s->pending - beg);
672             if (s->gzindex == s->gzhead->extra_len) {
673                 s->gzindex = 0;
674                 s->status = NAME_STATE;
675             }
676         }
677         else
678             s->status = NAME_STATE;
679     }
680     if (s->status == NAME_STATE) {
681         if (s->gzhead->name != NULL) {
682             uInt beg = s->pending;  /* start of bytes to update crc */
683             int val;
684 
685             do {
686                 if (s->pending == s->pending_buf_size) {
687                     if (s->gzhead->hcrc && s->pending > beg)
688                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
689                                             s->pending - beg);
690                     flush_pending(strm);
691                     beg = s->pending;
692                     if (s->pending == s->pending_buf_size) {
693                         val = 1;
694                         break;
695                     }
696                 }
697                 val = s->gzhead->name[s->gzindex++];
698                 put_byte(s, val);
699             } while (val != 0);
700             if (s->gzhead->hcrc && s->pending > beg)
701                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
702                                     s->pending - beg);
703             if (val == 0) {
704                 s->gzindex = 0;
705                 s->status = COMMENT_STATE;
706             }
707         }
708         else
709             s->status = COMMENT_STATE;
710     }
711     if (s->status == COMMENT_STATE) {
712         if (s->gzhead->comment != NULL) {
713             uInt beg = s->pending;  /* start of bytes to update crc */
714             int val;
715 
716             do {
717                 if (s->pending == s->pending_buf_size) {
718                     if (s->gzhead->hcrc && s->pending > beg)
719                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
720                                             s->pending - beg);
721                     flush_pending(strm);
722                     beg = s->pending;
723                     if (s->pending == s->pending_buf_size) {
724                         val = 1;
725                         break;
726                     }
727                 }
728                 val = s->gzhead->comment[s->gzindex++];
729                 put_byte(s, val);
730             } while (val != 0);
731             if (s->gzhead->hcrc && s->pending > beg)
732                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
733                                     s->pending - beg);
734             if (val == 0)
735                 s->status = HCRC_STATE;
736         }
737         else
738             s->status = HCRC_STATE;
739     }
740     if (s->status == HCRC_STATE) {
741         if (s->gzhead->hcrc) {
742             if (s->pending + 2 > s->pending_buf_size)
743                 flush_pending(strm);
744             if (s->pending + 2 <= s->pending_buf_size) {
745                 put_byte(s, (Byte)(strm->adler & 0xff));
746                 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
747                 strm->adler = crc32(0L, Z_NULL, 0);
748                 s->status = BUSY_STATE;
749             }
750         }
751         else
752             s->status = BUSY_STATE;
753     }
754 #endif
755 
756     /* Flush as much pending output as possible */
757     if (s->pending != 0) {
758         flush_pending(strm);
759         if (strm->avail_out == 0) {
760             /* Since avail_out is 0, deflate will be called again with
761              * more output space, but possibly with both pending and
762              * avail_in equal to zero. There won't be anything to do,
763              * but this is not an error situation so make sure we
764              * return OK instead of BUF_ERROR at next call of deflate:
765              */
766             s->last_flush = -1;
767             return Z_OK;
768         }
769 
770     /* Make sure there is something to do and avoid duplicate consecutive
771      * flushes. For repeated and useless calls with Z_FINISH, we keep
772      * returning Z_STREAM_END instead of Z_BUF_ERROR.
773      */
774     } else if (strm->avail_in == 0 && flush <= old_flush &&
775                flush != Z_FINISH) {
776         ERR_RETURN(strm, Z_BUF_ERROR);
777     }
778 
779     /* User must not provide more input after the first FINISH: */
780     if (s->status == FINISH_STATE && strm->avail_in != 0) {
781         ERR_RETURN(strm, Z_BUF_ERROR);
782     }
783 
784     /* Start a new block or continue the current one.
785      */
786     if (strm->avail_in != 0 || s->lookahead != 0 ||
787         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
788         block_state bstate;
789 
790         bstate = (*(configuration_table[s->level].func))(s, flush);
791 
792         if (bstate == finish_started || bstate == finish_done) {
793             s->status = FINISH_STATE;
794         }
795         if (bstate == need_more || bstate == finish_started) {
796             if (strm->avail_out == 0) {
797                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
798             }
799             return Z_OK;
800             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
801              * of deflate should use the same flush parameter to make sure
802              * that the flush is complete. So we don't have to output an
803              * empty block here, this will be done at next call. This also
804              * ensures that for a very small output buffer, we emit at most
805              * one empty block.
806              */
807         }
808         if (bstate == block_done) {
809             if (flush == Z_PARTIAL_FLUSH) {
810                 _tr_align(s);
811             } else { /* FULL_FLUSH or SYNC_FLUSH */
812                 _tr_stored_block(s, (char*)0, 0L, 0);
813                 /* For a full flush, this empty block will be recognized
814                  * as a special marker by inflate_sync().
815                  */
816                 if (flush == Z_FULL_FLUSH) {
817                     CLEAR_HASH(s);             /* forget history */
818                 }
819             }
820             flush_pending(strm);
821             if (strm->avail_out == 0) {
822               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
823               return Z_OK;
824             }
825         }
826     }
827     Assert(strm->avail_out > 0, "bug2");
828 
829     if (flush != Z_FINISH) return Z_OK;
830     if (s->wrap <= 0) return Z_STREAM_END;
831 
832     /* Write the trailer */
833 #ifdef GZIP
834     if (s->wrap == 2) {
835         put_byte(s, (Byte)(strm->adler & 0xff));
836         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
837         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
838         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
839         put_byte(s, (Byte)(strm->total_in & 0xff));
840         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
841         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
842         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
843     }
844     else
845 #endif
846     {
847         putShortMSB(s, (uInt)(strm->adler >> 16));
848         putShortMSB(s, (uInt)(strm->adler & 0xffff));
849     }
850     flush_pending(strm);
851     /* If avail_out is zero, the application will call deflate again
852      * to flush the rest.
853      */
854     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
855     return s->pending != 0 ? Z_OK : Z_STREAM_END;
856 }
857 
858 /* ========================================================================= */
deflateEnd(strm)859 int ZEXPORT deflateEnd (strm)
860     z_streamp strm;
861 {
862     int status;
863 
864     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
865 
866     status = strm->state->status;
867     if (status != INIT_STATE &&
868         status != EXTRA_STATE &&
869         status != NAME_STATE &&
870         status != COMMENT_STATE &&
871         status != HCRC_STATE &&
872         status != BUSY_STATE &&
873         status != FINISH_STATE) {
874       return Z_STREAM_ERROR;
875     }
876 
877     /* Deallocate in reverse order of allocations: */
878     TRY_FREE(strm, strm->state->pending_buf);
879     TRY_FREE(strm, strm->state->head);
880     TRY_FREE(strm, strm->state->prev);
881     TRY_FREE(strm, strm->state->window);
882 
883     ZFREE(strm, strm->state);
884     strm->state = Z_NULL;
885 
886     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
887 }
888 
889 /* =========================================================================
890  * Copy the source state to the destination state.
891  * To simplify the source, this is not supported for 16-bit MSDOS (which
892  * doesn't have enough memory anyway to duplicate compression states).
893  */
deflateCopy(dest,source)894 int ZEXPORT deflateCopy (dest, source)
895     z_streamp dest;
896     z_streamp source;
897 {
898 #ifdef MAXSEG_64K
899     return Z_STREAM_ERROR;
900 #else
901     deflate_state *ds;
902     deflate_state *ss;
903     ushf *overlay;
904 
905 
906     if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
907         return Z_STREAM_ERROR;
908     }
909 
910     ss = source->state;
911 
912     zmemcpy(dest, source, sizeof(z_stream));
913 
914     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
915     if (ds == Z_NULL) return Z_MEM_ERROR;
916     dest->state = (struct internal_state FAR *) ds;
917     zmemcpy(ds, ss, sizeof(deflate_state));
918     ds->strm = dest;
919 
920     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
921     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
922     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
923     overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
924     ds->pending_buf = (uchf *) overlay;
925 
926     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
927         ds->pending_buf == Z_NULL) {
928         deflateEnd (dest);
929         return Z_MEM_ERROR;
930     }
931     /* following zmemcpy do not work for 16-bit MSDOS */
932     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
933     zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
934     zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
935     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
936 
937     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
938     ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
939     ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
940 
941     ds->l_desc.dyn_tree = ds->dyn_ltree;
942     ds->d_desc.dyn_tree = ds->dyn_dtree;
943     ds->bl_desc.dyn_tree = ds->bl_tree;
944 
945     return Z_OK;
946 #endif /* MAXSEG_64K */
947 }
948 
949 /* ===========================================================================
950  * Read a new buffer from the current input stream, update the adler32
951  * and total number of bytes read.  All deflate() input goes through
952  * this function so some applications may wish to modify it to avoid
953  * allocating a large strm->next_in buffer and copying from it.
954  * (See also flush_pending()).
955  */
read_buf(strm,buf,size)956 local int read_buf(strm, buf, size)
957     z_streamp strm;
958     Bytef *buf;
959     unsigned size;
960 {
961     unsigned len = strm->avail_in;
962 
963     if (len > size) len = size;
964     if (len == 0) return 0;
965 
966     strm->avail_in  -= len;
967 
968     if (strm->state->wrap == 1) {
969         strm->adler = adler32(strm->adler, strm->next_in, len);
970     }
971 #ifdef GZIP
972     else if (strm->state->wrap == 2) {
973         strm->adler = crc32(strm->adler, strm->next_in, len);
974     }
975 #endif
976     zmemcpy(buf, strm->next_in, len);
977     strm->next_in  += len;
978     strm->total_in += len;
979 
980     return (int)len;
981 }
982 
983 /* ===========================================================================
984  * Initialize the "longest match" routines for a new zlib stream
985  */
lm_init(s)986 local void lm_init (s)
987     deflate_state *s;
988 {
989     s->window_size = (ulg)2L*s->w_size;
990 
991     CLEAR_HASH(s);
992 
993     /* Set the default configuration parameters:
994      */
995     s->max_lazy_match   = configuration_table[s->level].max_lazy;
996     s->good_match       = configuration_table[s->level].good_length;
997     s->nice_match       = configuration_table[s->level].nice_length;
998     s->max_chain_length = configuration_table[s->level].max_chain;
999 
1000     s->strstart = 0;
1001     s->block_start = 0L;
1002     s->lookahead = 0;
1003     s->match_length = s->prev_length = MIN_MATCH-1;
1004     s->match_available = 0;
1005     s->ins_h = 0;
1006 #ifndef FASTEST
1007 #ifdef ASMV
1008     match_init(); /* initialize the asm code */
1009 #endif
1010 #endif
1011 }
1012 
1013 #ifndef FASTEST
1014 /* ===========================================================================
1015  * Set match_start to the longest match starting at the given string and
1016  * return its length. Matches shorter or equal to prev_length are discarded,
1017  * in which case the result is equal to prev_length and match_start is
1018  * garbage.
1019  * IN assertions: cur_match is the head of the hash chain for the current
1020  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1021  * OUT assertion: the match length is not greater than s->lookahead.
1022  */
1023 #ifndef ASMV
1024 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1025  * match.S. The code will be functionally equivalent.
1026  */
longest_match(s,cur_match)1027 local uInt longest_match(s, cur_match)
1028     deflate_state *s;
1029     IPos cur_match;                             /* current match */
1030 {
1031     unsigned chain_length = s->max_chain_length;/* max hash chain length */
1032     register Bytef *scan = s->window + s->strstart; /* current string */
1033     register Bytef *match;                       /* matched string */
1034     register int len;                           /* length of current match */
1035     int best_len = s->prev_length;              /* best match length so far */
1036     int nice_match = s->nice_match;             /* stop if match long enough */
1037     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1038         s->strstart - (IPos)MAX_DIST(s) : NIL;
1039     /* Stop when cur_match becomes <= limit. To simplify the code,
1040      * we prevent matches with the string of window index 0.
1041      */
1042     Posf *prev = s->prev;
1043     uInt wmask = s->w_mask;
1044 
1045 #ifdef UNALIGNED_OK
1046     /* Compare two bytes at a time. Note: this is not always beneficial.
1047      * Try with and without -DUNALIGNED_OK to check.
1048      */
1049     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1050     register ush scan_start = *(ushf*)scan;
1051     register ush scan_end   = *(ushf*)(scan+best_len-1);
1052 #else
1053     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1054     register Byte scan_end1  = scan[best_len-1];
1055     register Byte scan_end   = scan[best_len];
1056 #endif
1057 
1058     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1059      * It is easy to get rid of this optimization if necessary.
1060      */
1061     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1062 
1063     /* Do not waste too much time if we already have a good match: */
1064     if (s->prev_length >= s->good_match) {
1065         chain_length >>= 2;
1066     }
1067     /* Do not look for matches beyond the end of the input. This is necessary
1068      * to make deflate deterministic.
1069      */
1070     if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1071 
1072     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1073 
1074     do {
1075         Assert(cur_match < s->strstart, "no future");
1076         match = s->window + cur_match;
1077 
1078         /* Skip to next match if the match length cannot increase
1079          * or if the match length is less than 2.  Note that the checks below
1080          * for insufficient lookahead only occur occasionally for performance
1081          * reasons.  Therefore uninitialized memory will be accessed, and
1082          * conditional jumps will be made that depend on those values.
1083          * However the length of the match is limited to the lookahead, so
1084          * the output of deflate is not affected by the uninitialized values.
1085          */
1086 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1087         /* This code assumes sizeof(unsigned short) == 2. Do not use
1088          * UNALIGNED_OK if your compiler uses a different size.
1089          */
1090         if (*(ushf*)(match+best_len-1) != scan_end ||
1091             *(ushf*)match != scan_start) continue;
1092 
1093         /* It is not necessary to compare scan[2] and match[2] since they are
1094          * always equal when the other bytes match, given that the hash keys
1095          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1096          * strstart+3, +5, ... up to strstart+257. We check for insufficient
1097          * lookahead only every 4th comparison; the 128th check will be made
1098          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1099          * necessary to put more guard bytes at the end of the window, or
1100          * to check more often for insufficient lookahead.
1101          */
1102         Assert(scan[2] == match[2], "scan[2]?");
1103         scan++, match++;
1104         do {
1105         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1106                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1107                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1108                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1109                  scan < strend);
1110         /* The funny "do {}" generates better code on most compilers */
1111 
1112         /* Here, scan <= window+strstart+257 */
1113         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1114         if (*scan == *match) scan++;
1115 
1116         len = (MAX_MATCH - 1) - (int)(strend-scan);
1117         scan = strend - (MAX_MATCH-1);
1118 
1119 #else /* UNALIGNED_OK */
1120 
1121         if (match[best_len]   != scan_end  ||
1122             match[best_len-1] != scan_end1 ||
1123             *match            != *scan     ||
1124             *++match          != scan[1])      continue;
1125 
1126         /* The check at best_len-1 can be removed because it will be made
1127          * again later. (This heuristic is not always a win.)
1128          * It is not necessary to compare scan[2] and match[2] since they
1129          * are always equal when the other bytes match, given that
1130          * the hash keys are equal and that HASH_BITS >= 8.
1131          */
1132         scan += 2, match++;
1133         Assert(*scan == *match, "match[2]?");
1134 
1135         /* We check for insufficient lookahead only every 8th comparison;
1136          * the 256th check will be made at strstart+258.
1137          */
1138         do {
1139         } while (*++scan == *++match && *++scan == *++match &&
1140                  *++scan == *++match && *++scan == *++match &&
1141                  *++scan == *++match && *++scan == *++match &&
1142                  *++scan == *++match && *++scan == *++match &&
1143                  scan < strend);
1144 
1145         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1146 
1147         len = MAX_MATCH - (int)(strend - scan);
1148         scan = strend - MAX_MATCH;
1149 
1150 #endif /* UNALIGNED_OK */
1151 
1152         if (len > best_len) {
1153             s->match_start = cur_match;
1154             best_len = len;
1155             if (len >= nice_match) break;
1156 #ifdef UNALIGNED_OK
1157             scan_end = *(ushf*)(scan+best_len-1);
1158 #else
1159             scan_end1  = scan[best_len-1];
1160             scan_end   = scan[best_len];
1161 #endif
1162         }
1163     } while ((cur_match = prev[cur_match & wmask]) > limit
1164              && --chain_length != 0);
1165 
1166     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1167     return s->lookahead;
1168 }
1169 #endif /* ASMV */
1170 #endif /* FASTEST */
1171 
1172 /* ---------------------------------------------------------------------------
1173  * Optimized version for level == 1 or strategy == Z_RLE only
1174  */
longest_match_fast(s,cur_match)1175 local uInt longest_match_fast(s, cur_match)
1176     deflate_state *s;
1177     IPos cur_match;                             /* current match */
1178 {
1179     register Bytef *scan = s->window + s->strstart; /* current string */
1180     register Bytef *match;                       /* matched string */
1181     register int len;                           /* length of current match */
1182     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1183 
1184     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1185      * It is easy to get rid of this optimization if necessary.
1186      */
1187     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1188 
1189     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1190 
1191     Assert(cur_match < s->strstart, "no future");
1192 
1193     match = s->window + cur_match;
1194 
1195     /* Return failure if the match length is less than 2:
1196      */
1197     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1198 
1199     /* The check at best_len-1 can be removed because it will be made
1200      * again later. (This heuristic is not always a win.)
1201      * It is not necessary to compare scan[2] and match[2] since they
1202      * are always equal when the other bytes match, given that
1203      * the hash keys are equal and that HASH_BITS >= 8.
1204      */
1205     scan += 2, match += 2;
1206     Assert(*scan == *match, "match[2]?");
1207 
1208     /* We check for insufficient lookahead only every 8th comparison;
1209      * the 256th check will be made at strstart+258.
1210      */
1211     do {
1212     } while (*++scan == *++match && *++scan == *++match &&
1213              *++scan == *++match && *++scan == *++match &&
1214              *++scan == *++match && *++scan == *++match &&
1215              *++scan == *++match && *++scan == *++match &&
1216              scan < strend);
1217 
1218     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1219 
1220     len = MAX_MATCH - (int)(strend - scan);
1221 
1222     if (len < MIN_MATCH) return MIN_MATCH - 1;
1223 
1224     s->match_start = cur_match;
1225     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1226 }
1227 
1228 #ifdef DEBUG
1229 /* ===========================================================================
1230  * Check that the match at match_start is indeed a match.
1231  */
check_match(s,start,match,length)1232 local void check_match(s, start, match, length)
1233     deflate_state *s;
1234     IPos start, match;
1235     int length;
1236 {
1237     /* check that the match is indeed a match */
1238     if (zmemcmp(s->window + match,
1239                 s->window + start, length) != EQUAL) {
1240         fprintf(stderr, " start %u, match %u, length %d\n",
1241                 start, match, length);
1242         do {
1243             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1244         } while (--length != 0);
1245         z_error("invalid match");
1246     }
1247     if (z_verbose > 1) {
1248         fprintf(stderr,"\\[%d,%d]", start-match, length);
1249         do { putc(s->window[start++], stderr); } while (--length != 0);
1250     }
1251 }
1252 #else
1253 #  define check_match(s, start, match, length)
1254 #endif /* DEBUG */
1255 
1256 /* ===========================================================================
1257  * Fill the window when the lookahead becomes insufficient.
1258  * Updates strstart and lookahead.
1259  *
1260  * IN assertion: lookahead < MIN_LOOKAHEAD
1261  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1262  *    At least one byte has been read, or avail_in == 0; reads are
1263  *    performed for at least two bytes (required for the zip translate_eol
1264  *    option -- not supported here).
1265  */
fill_window(s)1266 local void fill_window(s)
1267     deflate_state *s;
1268 {
1269     register unsigned n, m;
1270     register Posf *p;
1271     unsigned more;    /* Amount of free space at the end of the window. */
1272     uInt wsize = s->w_size;
1273 
1274     do {
1275         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1276 
1277         /* Deal with !@#$% 64K limit: */
1278         if (sizeof(int) <= 2) {
1279             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1280                 more = wsize;
1281 
1282             } else if (more == (unsigned)(-1)) {
1283                 /* Very unlikely, but possible on 16 bit machine if
1284                  * strstart == 0 && lookahead == 1 (input done a byte at time)
1285                  */
1286                 more--;
1287             }
1288         }
1289 
1290         /* If the window is almost full and there is insufficient lookahead,
1291          * move the upper half to the lower one to make room in the upper half.
1292          */
1293         if (s->strstart >= wsize+MAX_DIST(s)) {
1294 
1295             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1296             s->match_start -= wsize;
1297             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
1298             s->block_start -= (long) wsize;
1299 
1300             /* Slide the hash table (could be avoided with 32 bit values
1301                at the expense of memory usage). We slide even when level == 0
1302                to keep the hash table consistent if we switch back to level > 0
1303                later. (Using level 0 permanently is not an optimal usage of
1304                zlib, so we don't care about this pathological case.)
1305              */
1306             /* %%% avoid this when Z_RLE */
1307             n = s->hash_size;
1308             p = &s->head[n];
1309             do {
1310                 m = *--p;
1311                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1312             } while (--n);
1313 
1314             n = wsize;
1315 #ifndef FASTEST
1316             p = &s->prev[n];
1317             do {
1318                 m = *--p;
1319                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1320                 /* If n is not on any hash chain, prev[n] is garbage but
1321                  * its value will never be used.
1322                  */
1323             } while (--n);
1324 #endif
1325             more += wsize;
1326         }
1327         if (s->strm->avail_in == 0) return;
1328 
1329         /* If there was no sliding:
1330          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1331          *    more == window_size - lookahead - strstart
1332          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1333          * => more >= window_size - 2*WSIZE + 2
1334          * In the BIG_MEM or MMAP case (not yet supported),
1335          *   window_size == input_size + MIN_LOOKAHEAD  &&
1336          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1337          * Otherwise, window_size == 2*WSIZE so more >= 2.
1338          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1339          */
1340         Assert(more >= 2, "more < 2");
1341 
1342         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1343         s->lookahead += n;
1344 
1345         /* Initialize the hash value now that we have some input: */
1346         if (s->lookahead >= MIN_MATCH) {
1347             s->ins_h = s->window[s->strstart];
1348             UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1349 #if MIN_MATCH != 3
1350             Call UPDATE_HASH() MIN_MATCH-3 more times
1351 #endif
1352         }
1353         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1354          * but this is not important since only literal bytes will be emitted.
1355          */
1356 
1357     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1358 }
1359 
1360 /* ===========================================================================
1361  * Flush the current block, with given end-of-file flag.
1362  * IN assertion: strstart is set to the end of the current match.
1363  */
1364 #define FLUSH_BLOCK_ONLY(s, eof) { \
1365    _tr_flush_block(s, (s->block_start >= 0L ? \
1366                    (charf *)&s->window[(unsigned)s->block_start] : \
1367                    (charf *)Z_NULL), \
1368                 (ulg)((long)s->strstart - s->block_start), \
1369                 (eof)); \
1370    s->block_start = s->strstart; \
1371    flush_pending(s->strm); \
1372    Tracev((stderr,"[FLUSH]")); \
1373 }
1374 
1375 /* Same but force premature exit if necessary. */
1376 #define FLUSH_BLOCK(s, eof) { \
1377    FLUSH_BLOCK_ONLY(s, eof); \
1378    if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
1379 }
1380 
1381 /* ===========================================================================
1382  * Copy without compression as much as possible from the input stream, return
1383  * the current block state.
1384  * This function does not insert new strings in the dictionary since
1385  * uncompressible data is probably not useful. This function is used
1386  * only for the level=0 compression option.
1387  * NOTE: this function should be optimized to avoid extra copying from
1388  * window to pending_buf.
1389  */
deflate_stored(s,flush)1390 local block_state deflate_stored(s, flush)
1391     deflate_state *s;
1392     int flush;
1393 {
1394     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1395      * to pending_buf_size, and each stored block has a 5 byte header:
1396      */
1397     ulg max_block_size = 0xffff;
1398     ulg max_start;
1399 
1400     if (max_block_size > s->pending_buf_size - 5) {
1401         max_block_size = s->pending_buf_size - 5;
1402     }
1403 
1404     /* Copy as much as possible from input to output: */
1405     for (;;) {
1406         /* Fill the window as much as possible: */
1407         if (s->lookahead <= 1) {
1408 
1409             Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1410                    s->block_start >= (long)s->w_size, "slide too late");
1411 
1412             fill_window(s);
1413             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1414 
1415             if (s->lookahead == 0) break; /* flush the current block */
1416         }
1417         Assert(s->block_start >= 0L, "block gone");
1418 
1419         s->strstart += s->lookahead;
1420         s->lookahead = 0;
1421 
1422         /* Emit a stored block if pending_buf will be full: */
1423         max_start = s->block_start + max_block_size;
1424         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1425             /* strstart == 0 is possible when wraparound on 16-bit machine */
1426             s->lookahead = (uInt)(s->strstart - max_start);
1427             s->strstart = (uInt)max_start;
1428             FLUSH_BLOCK(s, 0);
1429         }
1430         /* Flush if we may have to slide, otherwise block_start may become
1431          * negative and the data will be gone:
1432          */
1433         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1434             FLUSH_BLOCK(s, 0);
1435         }
1436     }
1437     FLUSH_BLOCK(s, flush == Z_FINISH);
1438     return flush == Z_FINISH ? finish_done : block_done;
1439 }
1440 
1441 /* ===========================================================================
1442  * Compress as much as possible from the input stream, return the current
1443  * block state.
1444  * This function does not perform lazy evaluation of matches and inserts
1445  * new strings in the dictionary only for unmatched strings or for short
1446  * matches. It is used only for the fast compression options.
1447  */
deflate_fast(s,flush)1448 local block_state deflate_fast(s, flush)
1449     deflate_state *s;
1450     int flush;
1451 {
1452     IPos hash_head = NIL; /* head of the hash chain */
1453     int bflush;           /* set if current block must be flushed */
1454 
1455     for (;;) {
1456         /* Make sure that we always have enough lookahead, except
1457          * at the end of the input file. We need MAX_MATCH bytes
1458          * for the next match, plus MIN_MATCH bytes to insert the
1459          * string following the next match.
1460          */
1461         if (s->lookahead < MIN_LOOKAHEAD) {
1462             fill_window(s);
1463             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1464                 return need_more;
1465             }
1466             if (s->lookahead == 0) break; /* flush the current block */
1467         }
1468 
1469         /* Insert the string window[strstart .. strstart+2] in the
1470          * dictionary, and set hash_head to the head of the hash chain:
1471          */
1472         if (s->lookahead >= MIN_MATCH) {
1473             INSERT_STRING(s, s->strstart, hash_head);
1474         }
1475 
1476         /* Find the longest match, discarding those <= prev_length.
1477          * At this point we have always match_length < MIN_MATCH
1478          */
1479         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1480             /* To simplify the code, we prevent matches with the string
1481              * of window index 0 (in particular we have to avoid a match
1482              * of the string with itself at the start of the input file).
1483              */
1484 #ifdef FASTEST
1485             if ((s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) ||
1486                 (s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
1487                 s->match_length = longest_match_fast (s, hash_head);
1488             }
1489 #else
1490             if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1491                 s->match_length = longest_match (s, hash_head);
1492             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1493                 s->match_length = longest_match_fast (s, hash_head);
1494             }
1495 #endif
1496             /* longest_match() or longest_match_fast() sets match_start */
1497         }
1498         if (s->match_length >= MIN_MATCH) {
1499             check_match(s, s->strstart, s->match_start, s->match_length);
1500 
1501             _tr_tally_dist(s, s->strstart - s->match_start,
1502                            s->match_length - MIN_MATCH, bflush);
1503 
1504             s->lookahead -= s->match_length;
1505 
1506             /* Insert new strings in the hash table only if the match length
1507              * is not too large. This saves time but degrades compression.
1508              */
1509 #ifndef FASTEST
1510             if (s->match_length <= s->max_insert_length &&
1511                 s->lookahead >= MIN_MATCH) {
1512                 s->match_length--; /* string at strstart already in table */
1513                 do {
1514                     s->strstart++;
1515                     INSERT_STRING(s, s->strstart, hash_head);
1516                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1517                      * always MIN_MATCH bytes ahead.
1518                      */
1519                 } while (--s->match_length != 0);
1520                 s->strstart++;
1521             } else
1522 #endif
1523             {
1524                 s->strstart += s->match_length;
1525                 s->match_length = 0;
1526                 s->ins_h = s->window[s->strstart];
1527                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1528 #if MIN_MATCH != 3
1529                 Call UPDATE_HASH() MIN_MATCH-3 more times
1530 #endif
1531                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1532                  * matter since it will be recomputed at next deflate call.
1533                  */
1534             }
1535         } else {
1536             /* No match, output a literal byte */
1537             Tracevv((stderr,"%c", s->window[s->strstart]));
1538             _tr_tally_lit (s, s->window[s->strstart], bflush);
1539             s->lookahead--;
1540             s->strstart++;
1541         }
1542         if (bflush) FLUSH_BLOCK(s, 0);
1543     }
1544     FLUSH_BLOCK(s, flush == Z_FINISH);
1545     return flush == Z_FINISH ? finish_done : block_done;
1546 }
1547 
1548 #ifndef FASTEST
1549 /* ===========================================================================
1550  * Same as above, but achieves better compression. We use a lazy
1551  * evaluation for matches: a match is finally adopted only if there is
1552  * no better match at the next window position.
1553  */
deflate_slow(s,flush)1554 local block_state deflate_slow(s, flush)
1555     deflate_state *s;
1556     int flush;
1557 {
1558     IPos hash_head = NIL;    /* head of hash chain */
1559     int bflush;              /* set if current block must be flushed */
1560 
1561     /* Process the input block. */
1562     for (;;) {
1563         /* Make sure that we always have enough lookahead, except
1564          * at the end of the input file. We need MAX_MATCH bytes
1565          * for the next match, plus MIN_MATCH bytes to insert the
1566          * string following the next match.
1567          */
1568         if (s->lookahead < MIN_LOOKAHEAD) {
1569             fill_window(s);
1570             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1571                 return need_more;
1572             }
1573             if (s->lookahead == 0) break; /* flush the current block */
1574         }
1575 
1576         /* Insert the string window[strstart .. strstart+2] in the
1577          * dictionary, and set hash_head to the head of the hash chain:
1578          */
1579         if (s->lookahead >= MIN_MATCH) {
1580             INSERT_STRING(s, s->strstart, hash_head);
1581         }
1582 
1583         /* Find the longest match, discarding those <= prev_length.
1584          */
1585         s->prev_length = s->match_length, s->prev_match = s->match_start;
1586         s->match_length = MIN_MATCH-1;
1587 
1588         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1589             s->strstart - hash_head <= MAX_DIST(s)) {
1590             /* To simplify the code, we prevent matches with the string
1591              * of window index 0 (in particular we have to avoid a match
1592              * of the string with itself at the start of the input file).
1593              */
1594             if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1595                 s->match_length = longest_match (s, hash_head);
1596             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1597                 s->match_length = longest_match_fast (s, hash_head);
1598             }
1599             /* longest_match() or longest_match_fast() sets match_start */
1600 
1601             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1602 #if TOO_FAR <= 32767
1603                 || (s->match_length == MIN_MATCH &&
1604                     s->strstart - s->match_start > TOO_FAR)
1605 #endif
1606                 )) {
1607 
1608                 /* If prev_match is also MIN_MATCH, match_start is garbage
1609                  * but we will ignore the current match anyway.
1610                  */
1611                 s->match_length = MIN_MATCH-1;
1612             }
1613         }
1614         /* If there was a match at the previous step and the current
1615          * match is not better, output the previous match:
1616          */
1617         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1618             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1619             /* Do not insert strings in hash table beyond this. */
1620 
1621             check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1622 
1623             _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1624                            s->prev_length - MIN_MATCH, bflush);
1625 
1626             /* Insert in hash table all strings up to the end of the match.
1627              * strstart-1 and strstart are already inserted. If there is not
1628              * enough lookahead, the last two strings are not inserted in
1629              * the hash table.
1630              */
1631             s->lookahead -= s->prev_length-1;
1632             s->prev_length -= 2;
1633             do {
1634                 if (++s->strstart <= max_insert) {
1635                     INSERT_STRING(s, s->strstart, hash_head);
1636                 }
1637             } while (--s->prev_length != 0);
1638             s->match_available = 0;
1639             s->match_length = MIN_MATCH-1;
1640             s->strstart++;
1641 
1642             if (bflush) FLUSH_BLOCK(s, 0);
1643 
1644         } else if (s->match_available) {
1645             /* If there was no match at the previous position, output a
1646              * single literal. If there was a match but the current match
1647              * is longer, truncate the previous match to a single literal.
1648              */
1649             Tracevv((stderr,"%c", s->window[s->strstart-1]));
1650             _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1651             if (bflush) {
1652                 FLUSH_BLOCK_ONLY(s, 0);
1653             }
1654             s->strstart++;
1655             s->lookahead--;
1656             if (s->strm->avail_out == 0) return need_more;
1657         } else {
1658             /* There is no previous match to compare with, wait for
1659              * the next step to decide.
1660              */
1661             s->match_available = 1;
1662             s->strstart++;
1663             s->lookahead--;
1664         }
1665     }
1666     Assert (flush != Z_NO_FLUSH, "no flush?");
1667     if (s->match_available) {
1668         Tracevv((stderr,"%c", s->window[s->strstart-1]));
1669         _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1670         s->match_available = 0;
1671     }
1672     FLUSH_BLOCK(s, flush == Z_FINISH);
1673     return flush == Z_FINISH ? finish_done : block_done;
1674 }
1675 #endif /* FASTEST */
1676 
1677 #if 0
1678 /* ===========================================================================
1679  * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1680  * one.  Do not maintain a hash table.  (It will be regenerated if this run of
1681  * deflate switches away from Z_RLE.)
1682  */
1683 local block_state deflate_rle(s, flush)
1684     deflate_state *s;
1685     int flush;
1686 {
1687     int bflush;         /* set if current block must be flushed */
1688     uInt run;           /* length of run */
1689     uInt max;           /* maximum length of run */
1690     uInt prev;          /* byte at distance one to match */
1691     Bytef *scan;        /* scan for end of run */
1692 
1693     for (;;) {
1694         /* Make sure that we always have enough lookahead, except
1695          * at the end of the input file. We need MAX_MATCH bytes
1696          * for the longest encodable run.
1697          */
1698         if (s->lookahead < MAX_MATCH) {
1699             fill_window(s);
1700             if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1701                 return need_more;
1702             }
1703             if (s->lookahead == 0) break; /* flush the current block */
1704         }
1705 
1706         /* See how many times the previous byte repeats */
1707         run = 0;
1708         if (s->strstart > 0) {      /* if there is a previous byte, that is */
1709             max = s->lookahead < MAX_MATCH ? s->lookahead : MAX_MATCH;
1710             scan = s->window + s->strstart - 1;
1711             prev = *scan++;
1712             do {
1713                 if (*scan++ != prev)
1714                     break;
1715             } while (++run < max);
1716         }
1717 
1718         /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1719         if (run >= MIN_MATCH) {
1720             check_match(s, s->strstart, s->strstart - 1, run);
1721             _tr_tally_dist(s, 1, run - MIN_MATCH, bflush);
1722             s->lookahead -= run;
1723             s->strstart += run;
1724         } else {
1725             /* No match, output a literal byte */
1726             Tracevv((stderr,"%c", s->window[s->strstart]));
1727             _tr_tally_lit (s, s->window[s->strstart], bflush);
1728             s->lookahead--;
1729             s->strstart++;
1730         }
1731         if (bflush) FLUSH_BLOCK(s, 0);
1732     }
1733     FLUSH_BLOCK(s, flush == Z_FINISH);
1734     return flush == Z_FINISH ? finish_done : block_done;
1735 }
1736 #endif
1737