xref: /openbmc/u-boot/lib/zlib/deflate.c (revision 7fb46430)
1 /* deflate.c -- compress data using the deflation algorithm
2  * Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
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 /* @(#) $Id$ */
51 
52 #include "deflate.h"
53 
54 const char deflate_copyright[] =
55    " deflate 1.2.5 Copyright 1995-2010 Jean-loup Gailly and Mark Adler ";
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 block_state deflate_rle    OF((deflate_state *s, int flush));
83 local block_state deflate_huff   OF((deflate_state *s, int flush));
84 local void lm_init        OF((deflate_state *s));
85 local void putShortMSB    OF((deflate_state *s, uInt b));
86 local void flush_pending  OF((z_streamp strm));
87 local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
88 #ifdef ASMV
89       void match_init OF((void)); /* asm code initialization */
90       uInt longest_match  OF((deflate_state *s, IPos cur_match));
91 #else
92 local uInt longest_match  OF((deflate_state *s, IPos cur_match));
93 #endif
94 
95 #ifdef DEBUG
96 local  void check_match OF((deflate_state *s, IPos start, IPos match,
97                             int length));
98 #endif
99 
100 /* ===========================================================================
101  * Local data
102  */
103 
104 #define NIL 0
105 /* Tail of hash chains */
106 
107 #ifndef TOO_FAR
108 #  define TOO_FAR 4096
109 #endif
110 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
111 
112 /* Values for max_lazy_match, good_match and max_chain_length, depending on
113  * the desired pack level (0..9). The values given below have been tuned to
114  * exclude worst case performance for pathological files. Better values may be
115  * found for specific files.
116  */
117 typedef struct config_s {
118    ush good_length; /* reduce lazy search above this match length */
119    ush max_lazy;    /* do not perform lazy search above this match length */
120    ush nice_length; /* quit search above this match length */
121    ush max_chain;
122    compress_func func;
123 } config;
124 
125 #ifdef FASTEST
126 local const config configuration_table[2] = {
127 /*      good lazy nice chain */
128 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
129 /* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */
130 #else
131 local const config configuration_table[10] = {
132 /*      good lazy nice chain */
133 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
134 /* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
135 /* 2 */ {4,    5, 16,    8, deflate_fast},
136 /* 3 */ {4,    6, 32,   32, deflate_fast},
137 
138 /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
139 /* 5 */ {8,   16, 32,   32, deflate_slow},
140 /* 6 */ {8,   16, 128, 128, deflate_slow},
141 /* 7 */ {8,   32, 128, 256, deflate_slow},
142 /* 8 */ {32, 128, 258, 1024, deflate_slow},
143 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
144 #endif
145 
146 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
147  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
148  * meaning.
149  */
150 
151 #define EQUAL 0
152 /* result of memcmp for equal strings */
153 
154 #ifndef NO_DUMMY_DECL
155 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
156 #endif
157 
158 /* ===========================================================================
159  * Update a hash value with the given input byte
160  * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
161  *    input characters, so that a running hash key can be computed from the
162  *    previous key instead of complete recalculation each time.
163  */
164 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
165 
166 
167 /* ===========================================================================
168  * Insert string str in the dictionary and set match_head to the previous head
169  * of the hash chain (the most recent string with same hash key). Return
170  * the previous length of the hash chain.
171  * If this file is compiled with -DFASTEST, the compression level is forced
172  * to 1, and no hash chains are maintained.
173  * IN  assertion: all calls to to INSERT_STRING are made with consecutive
174  *    input characters and the first MIN_MATCH bytes of str are valid
175  *    (except for the last MIN_MATCH-1 bytes of the input file).
176  */
177 #ifdef FASTEST
178 #define INSERT_STRING(s, str, match_head) \
179    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
180     match_head = s->head[s->ins_h], \
181     s->head[s->ins_h] = (Pos)(str))
182 #else
183 #define INSERT_STRING(s, str, match_head) \
184    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
185     match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
186     s->head[s->ins_h] = (Pos)(str))
187 #endif
188 
189 /* ===========================================================================
190  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
191  * prev[] will be initialized on the fly.
192  */
193 #define CLEAR_HASH(s) \
194     s->head[s->hash_size-1] = NIL; \
195     zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
196 
197 /* ========================================================================= */
198 int ZEXPORT deflateInit_(strm, level, version, stream_size)
199     z_streamp strm;
200     int level;
201     const char *version;
202     int stream_size;
203 {
204     return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
205                          Z_DEFAULT_STRATEGY, version, stream_size);
206     /* To do: ignore strm->next_in if we use it as window */
207 }
208 
209 /* ========================================================================= */
210 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
211                   version, stream_size)
212     z_streamp strm;
213     int  level;
214     int  method;
215     int  windowBits;
216     int  memLevel;
217     int  strategy;
218     const char *version;
219     int stream_size;
220 {
221     deflate_state *s;
222     int wrap = 1;
223     static const char my_version[] = ZLIB_VERSION;
224 
225     ushf *overlay;
226     /* We overlay pending_buf and d_buf+l_buf. This works since the average
227      * output size for (length,distance) codes is <= 24 bits.
228      */
229 
230     if (version == Z_NULL || version[0] != my_version[0] ||
231         stream_size != sizeof(z_stream)) {
232         return Z_VERSION_ERROR;
233     }
234     if (strm == Z_NULL) return Z_STREAM_ERROR;
235 
236     strm->msg = Z_NULL;
237     if (strm->zalloc == (alloc_func)0) {
238         strm->zalloc = zcalloc;
239         strm->opaque = (voidpf)0;
240     }
241     if (strm->zfree == (free_func)0) strm->zfree = zcfree;
242 
243 #ifdef FASTEST
244     if (level != 0) level = 1;
245 #else
246     if (level == Z_DEFAULT_COMPRESSION) level = 6;
247 #endif
248 
249     if (windowBits < 0) { /* suppress zlib wrapper */
250         wrap = 0;
251         windowBits = -windowBits;
252     }
253 #ifdef GZIP
254     else if (windowBits > 15) {
255         wrap = 2;       /* write gzip wrapper instead */
256         windowBits -= 16;
257     }
258 #endif
259     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
260         windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
261         strategy < 0 || strategy > Z_FIXED) {
262         return Z_STREAM_ERROR;
263     }
264     if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
265     s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
266     if (s == Z_NULL) return Z_MEM_ERROR;
267     strm->state = (struct internal_state FAR *)s;
268     s->strm = strm;
269 
270     s->wrap = wrap;
271     s->gzhead = Z_NULL;
272     s->w_bits = windowBits;
273     s->w_size = 1 << s->w_bits;
274     s->w_mask = s->w_size - 1;
275 
276     s->hash_bits = memLevel + 7;
277     s->hash_size = 1 << s->hash_bits;
278     s->hash_mask = s->hash_size - 1;
279     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
280 
281     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
282     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
283     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
284 
285     s->high_water = 0;      /* nothing written to s->window yet */
286 
287     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
288 
289     overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
290     s->pending_buf = (uchf *) overlay;
291     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
292 
293     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
294         s->pending_buf == Z_NULL) {
295         s->status = FINISH_STATE;
296         strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
297         deflateEnd (strm);
298         return Z_MEM_ERROR;
299     }
300     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
301     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
302 
303     s->level = level;
304     s->strategy = strategy;
305     s->method = (Byte)method;
306 
307     return deflateReset(strm);
308 }
309 
310 /* ========================================================================= */
311 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
312     z_streamp strm;
313     const Bytef *dictionary;
314     uInt  dictLength;
315 {
316     deflate_state *s;
317     uInt length = dictLength;
318     uInt n;
319     IPos hash_head = 0;
320 
321     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
322         strm->state->wrap == 2 ||
323         (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
324         return Z_STREAM_ERROR;
325 
326     s = strm->state;
327     if (s->wrap)
328         strm->adler = adler32(strm->adler, dictionary, dictLength);
329 
330     if (length < MIN_MATCH) return Z_OK;
331     if (length > s->w_size) {
332         length = s->w_size;
333         dictionary += dictLength - length; /* use the tail of the dictionary */
334     }
335     zmemcpy(s->window, dictionary, length);
336     s->strstart = length;
337     s->block_start = (long)length;
338 
339     /* Insert all strings in the hash table (except for the last two bytes).
340      * s->lookahead stays null, so s->ins_h will be recomputed at the next
341      * call of fill_window.
342      */
343     s->ins_h = s->window[0];
344     UPDATE_HASH(s, s->ins_h, s->window[1]);
345     for (n = 0; n <= length - MIN_MATCH; n++) {
346         INSERT_STRING(s, n, hash_head);
347     }
348     if (hash_head) hash_head = 0;  /* to make compiler happy */
349     return Z_OK;
350 }
351 
352 /* ========================================================================= */
353 int ZEXPORT deflateReset (strm)
354     z_streamp strm;
355 {
356     deflate_state *s;
357 
358     if (strm == Z_NULL || strm->state == Z_NULL ||
359         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
360         return Z_STREAM_ERROR;
361     }
362 
363     strm->total_in = strm->total_out = 0;
364     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
365     strm->data_type = Z_UNKNOWN;
366 
367     s = (deflate_state *)strm->state;
368     s->pending = 0;
369     s->pending_out = s->pending_buf;
370 
371     if (s->wrap < 0) {
372         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
373     }
374     s->status = s->wrap ? INIT_STATE : BUSY_STATE;
375     strm->adler =
376 #ifdef GZIP
377         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
378 #endif
379         adler32(0L, Z_NULL, 0);
380     s->last_flush = Z_NO_FLUSH;
381 
382     _tr_init(s);
383     lm_init(s);
384 
385     return Z_OK;
386 }
387 
388 /* ========================================================================= */
389 int ZEXPORT deflateSetHeader (strm, head)
390     z_streamp strm;
391     gz_headerp head;
392 {
393     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
394     if (strm->state->wrap != 2) return Z_STREAM_ERROR;
395     strm->state->gzhead = head;
396     return Z_OK;
397 }
398 
399 /* ========================================================================= */
400 int ZEXPORT deflatePrime (strm, bits, value)
401     z_streamp strm;
402     int bits;
403     int value;
404 {
405     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
406     strm->state->bi_valid = bits;
407     strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
408     return Z_OK;
409 }
410 
411 /* ========================================================================= */
412 int ZEXPORT deflateParams(strm, level, strategy)
413     z_streamp strm;
414     int level;
415     int strategy;
416 {
417     deflate_state *s;
418     compress_func func;
419     int err = Z_OK;
420 
421     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
422     s = strm->state;
423 
424 #ifdef FASTEST
425     if (level != 0) level = 1;
426 #else
427     if (level == Z_DEFAULT_COMPRESSION) level = 6;
428 #endif
429     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
430         return Z_STREAM_ERROR;
431     }
432     func = configuration_table[s->level].func;
433 
434     if ((strategy != s->strategy || func != configuration_table[level].func) &&
435         strm->total_in != 0) {
436         /* Flush the last buffer: */
437         err = deflate(strm, Z_BLOCK);
438     }
439     if (s->level != level) {
440         s->level = level;
441         s->max_lazy_match   = configuration_table[level].max_lazy;
442         s->good_match       = configuration_table[level].good_length;
443         s->nice_match       = configuration_table[level].nice_length;
444         s->max_chain_length = configuration_table[level].max_chain;
445     }
446     s->strategy = strategy;
447     return err;
448 }
449 
450 /* ========================================================================= */
451 int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
452     z_streamp strm;
453     int good_length;
454     int max_lazy;
455     int nice_length;
456     int max_chain;
457 {
458     deflate_state *s;
459 
460     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
461     s = strm->state;
462     s->good_match = good_length;
463     s->max_lazy_match = max_lazy;
464     s->nice_match = nice_length;
465     s->max_chain_length = max_chain;
466     return Z_OK;
467 }
468 
469 /* =========================================================================
470  * For the default windowBits of 15 and memLevel of 8, this function returns
471  * a close to exact, as well as small, upper bound on the compressed size.
472  * They are coded as constants here for a reason--if the #define's are
473  * changed, then this function needs to be changed as well.  The return
474  * value for 15 and 8 only works for those exact settings.
475  *
476  * For any setting other than those defaults for windowBits and memLevel,
477  * the value returned is a conservative worst case for the maximum expansion
478  * resulting from using fixed blocks instead of stored blocks, which deflate
479  * can emit on compressed data for some combinations of the parameters.
480  *
481  * This function could be more sophisticated to provide closer upper bounds for
482  * every combination of windowBits and memLevel.  But even the conservative
483  * upper bound of about 14% expansion does not seem onerous for output buffer
484  * allocation.
485  */
486 uLong ZEXPORT deflateBound(strm, sourceLen)
487     z_streamp strm;
488     uLong sourceLen;
489 {
490     deflate_state *s;
491     uLong complen, wraplen;
492     Bytef *str;
493 
494     /* conservative upper bound for compressed data */
495     complen = sourceLen +
496               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
497 
498     /* if can't get parameters, return conservative bound plus zlib wrapper */
499     if (strm == Z_NULL || strm->state == Z_NULL)
500         return complen + 6;
501 
502     /* compute wrapper length */
503     s = strm->state;
504     switch (s->wrap) {
505     case 0:                                 /* raw deflate */
506         wraplen = 0;
507         break;
508     case 1:                                 /* zlib wrapper */
509         wraplen = 6 + (s->strstart ? 4 : 0);
510         break;
511     case 2:                                 /* gzip wrapper */
512         wraplen = 18;
513         if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
514             if (s->gzhead->extra != Z_NULL)
515                 wraplen += 2 + s->gzhead->extra_len;
516             str = s->gzhead->name;
517             if (str != Z_NULL)
518                 do {
519                     wraplen++;
520                 } while (*str++);
521             str = s->gzhead->comment;
522             if (str != Z_NULL)
523                 do {
524                     wraplen++;
525                 } while (*str++);
526             if (s->gzhead->hcrc)
527                 wraplen += 2;
528         }
529         break;
530     default:                                /* for compiler happiness */
531         wraplen = 6;
532     }
533 
534     /* if not default parameters, return conservative bound */
535     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
536         return complen + wraplen;
537 
538     /* default settings: return tight bound for that case */
539     return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
540            (sourceLen >> 25) + 13 - 6 + wraplen;
541 }
542 
543 /* =========================================================================
544  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
545  * IN assertion: the stream state is correct and there is enough room in
546  * pending_buf.
547  */
548 local void putShortMSB (s, b)
549     deflate_state *s;
550     uInt b;
551 {
552     put_byte(s, (Byte)(b >> 8));
553     put_byte(s, (Byte)(b & 0xff));
554 }
555 
556 /* =========================================================================
557  * Flush as much pending output as possible. All deflate() output goes
558  * through this function so some applications may wish to modify it
559  * to avoid allocating a large strm->next_out buffer and copying into it.
560  * (See also read_buf()).
561  */
562 local void flush_pending(strm)
563     z_streamp strm;
564 {
565     unsigned len = strm->state->pending;
566 
567     if (len > strm->avail_out) len = strm->avail_out;
568     if (len == 0) return;
569 
570     zmemcpy(strm->next_out, strm->state->pending_out, len);
571     strm->next_out  += len;
572     strm->state->pending_out  += len;
573     strm->total_out += len;
574     strm->avail_out  -= len;
575     strm->state->pending -= len;
576     if (strm->state->pending == 0) {
577         strm->state->pending_out = strm->state->pending_buf;
578     }
579 }
580 
581 /* ========================================================================= */
582 int ZEXPORT deflate (strm, flush)
583     z_streamp strm;
584     int flush;
585 {
586     int old_flush; /* value of flush param for previous deflate call */
587     deflate_state *s;
588 
589     if (strm == Z_NULL || strm->state == Z_NULL ||
590         flush > Z_BLOCK || flush < 0) {
591         return Z_STREAM_ERROR;
592     }
593     s = strm->state;
594 
595     if (s->status == FINISH_STATE && flush != Z_FINISH) {
596         ERR_RETURN(strm, Z_STREAM_ERROR);
597     }
598     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
599 
600     s->strm = strm; /* just in case */
601     old_flush = s->last_flush;
602     s->last_flush = flush;
603 
604     /* Write the header */
605     if (s->status == INIT_STATE) {
606 #ifdef GZIP
607         if (s->wrap == 2) {
608             strm->adler = crc32(0L, Z_NULL, 0);
609             put_byte(s, 31);
610             put_byte(s, 139);
611             put_byte(s, 8);
612             if (s->gzhead == Z_NULL) {
613                 put_byte(s, 0);
614                 put_byte(s, 0);
615                 put_byte(s, 0);
616                 put_byte(s, 0);
617                 put_byte(s, 0);
618                 put_byte(s, s->level == 9 ? 2 :
619                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
620                              4 : 0));
621                 put_byte(s, OS_CODE);
622                 s->status = BUSY_STATE;
623             }
624             else {
625                 put_byte(s, (s->gzhead->text ? 1 : 0) +
626                             (s->gzhead->hcrc ? 2 : 0) +
627                             (s->gzhead->extra == Z_NULL ? 0 : 4) +
628                             (s->gzhead->name == Z_NULL ? 0 : 8) +
629                             (s->gzhead->comment == Z_NULL ? 0 : 16)
630                         );
631                 put_byte(s, (Byte)(s->gzhead->time & 0xff));
632                 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
633                 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
634                 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
635                 put_byte(s, s->level == 9 ? 2 :
636                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
637                              4 : 0));
638                 put_byte(s, s->gzhead->os & 0xff);
639                 if (s->gzhead->extra != Z_NULL) {
640                     put_byte(s, s->gzhead->extra_len & 0xff);
641                     put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
642                 }
643                 if (s->gzhead->hcrc)
644                     strm->adler = crc32(strm->adler, s->pending_buf,
645                                         s->pending);
646                 s->gzindex = 0;
647                 s->status = EXTRA_STATE;
648             }
649         }
650         else
651 #endif
652         {
653             uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
654             uInt level_flags;
655 
656             if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
657                 level_flags = 0;
658             else if (s->level < 6)
659                 level_flags = 1;
660             else if (s->level == 6)
661                 level_flags = 2;
662             else
663                 level_flags = 3;
664             header |= (level_flags << 6);
665             if (s->strstart != 0) header |= PRESET_DICT;
666             header += 31 - (header % 31);
667 
668             s->status = BUSY_STATE;
669             putShortMSB(s, header);
670 
671             /* Save the adler32 of the preset dictionary: */
672             if (s->strstart != 0) {
673                 putShortMSB(s, (uInt)(strm->adler >> 16));
674                 putShortMSB(s, (uInt)(strm->adler & 0xffff));
675             }
676             strm->adler = adler32(0L, Z_NULL, 0);
677         }
678     }
679 #ifdef GZIP
680     if (s->status == EXTRA_STATE) {
681         if (s->gzhead->extra != Z_NULL) {
682             uInt beg = s->pending;  /* start of bytes to update crc */
683 
684             while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
685                 if (s->pending == s->pending_buf_size) {
686                     if (s->gzhead->hcrc && s->pending > beg)
687                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
688                                             s->pending - beg);
689                     flush_pending(strm);
690                     beg = s->pending;
691                     if (s->pending == s->pending_buf_size)
692                         break;
693                 }
694                 put_byte(s, s->gzhead->extra[s->gzindex]);
695                 s->gzindex++;
696             }
697             if (s->gzhead->hcrc && s->pending > beg)
698                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
699                                     s->pending - beg);
700             if (s->gzindex == s->gzhead->extra_len) {
701                 s->gzindex = 0;
702                 s->status = NAME_STATE;
703             }
704         }
705         else
706             s->status = NAME_STATE;
707     }
708     if (s->status == NAME_STATE) {
709         if (s->gzhead->name != Z_NULL) {
710             uInt beg = s->pending;  /* start of bytes to update crc */
711             int val;
712 
713             do {
714                 if (s->pending == s->pending_buf_size) {
715                     if (s->gzhead->hcrc && s->pending > beg)
716                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
717                                             s->pending - beg);
718                     flush_pending(strm);
719                     beg = s->pending;
720                     if (s->pending == s->pending_buf_size) {
721                         val = 1;
722                         break;
723                     }
724                 }
725                 val = s->gzhead->name[s->gzindex++];
726                 put_byte(s, val);
727             } while (val != 0);
728             if (s->gzhead->hcrc && s->pending > beg)
729                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
730                                     s->pending - beg);
731             if (val == 0) {
732                 s->gzindex = 0;
733                 s->status = COMMENT_STATE;
734             }
735         }
736         else
737             s->status = COMMENT_STATE;
738     }
739     if (s->status == COMMENT_STATE) {
740         if (s->gzhead->comment != Z_NULL) {
741             uInt beg = s->pending;  /* start of bytes to update crc */
742             int val;
743 
744             do {
745                 if (s->pending == s->pending_buf_size) {
746                     if (s->gzhead->hcrc && s->pending > beg)
747                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
748                                             s->pending - beg);
749                     flush_pending(strm);
750                     beg = s->pending;
751                     if (s->pending == s->pending_buf_size) {
752                         val = 1;
753                         break;
754                     }
755                 }
756                 val = s->gzhead->comment[s->gzindex++];
757                 put_byte(s, val);
758             } while (val != 0);
759             if (s->gzhead->hcrc && s->pending > beg)
760                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
761                                     s->pending - beg);
762             if (val == 0)
763                 s->status = HCRC_STATE;
764         }
765         else
766             s->status = HCRC_STATE;
767     }
768     if (s->status == HCRC_STATE) {
769         if (s->gzhead->hcrc) {
770             if (s->pending + 2 > s->pending_buf_size)
771                 flush_pending(strm);
772             if (s->pending + 2 <= s->pending_buf_size) {
773                 put_byte(s, (Byte)(strm->adler & 0xff));
774                 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
775                 strm->adler = crc32(0L, Z_NULL, 0);
776                 s->status = BUSY_STATE;
777             }
778         }
779         else
780             s->status = BUSY_STATE;
781     }
782 #endif
783 
784     /* Flush as much pending output as possible */
785     if (s->pending != 0) {
786         flush_pending(strm);
787         if (strm->avail_out == 0) {
788             /* Since avail_out is 0, deflate will be called again with
789              * more output space, but possibly with both pending and
790              * avail_in equal to zero. There won't be anything to do,
791              * but this is not an error situation so make sure we
792              * return OK instead of BUF_ERROR at next call of deflate:
793              */
794             s->last_flush = -1;
795             return Z_OK;
796         }
797 
798     /* Make sure there is something to do and avoid duplicate consecutive
799      * flushes. For repeated and useless calls with Z_FINISH, we keep
800      * returning Z_STREAM_END instead of Z_BUF_ERROR.
801      */
802     } else if (strm->avail_in == 0 && flush <= old_flush &&
803                flush != Z_FINISH) {
804         ERR_RETURN(strm, Z_BUF_ERROR);
805     }
806 
807     /* User must not provide more input after the first FINISH: */
808     if (s->status == FINISH_STATE && strm->avail_in != 0) {
809         ERR_RETURN(strm, Z_BUF_ERROR);
810     }
811 
812     /* Start a new block or continue the current one.
813      */
814     if (strm->avail_in != 0 || s->lookahead != 0 ||
815         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
816         block_state bstate;
817 
818         bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
819                     (s->strategy == Z_RLE ? deflate_rle(s, flush) :
820                         (*(configuration_table[s->level].func))(s, flush));
821 
822         if (bstate == finish_started || bstate == finish_done) {
823             s->status = FINISH_STATE;
824         }
825         if (bstate == need_more || bstate == finish_started) {
826             if (strm->avail_out == 0) {
827                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
828             }
829             return Z_OK;
830             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
831              * of deflate should use the same flush parameter to make sure
832              * that the flush is complete. So we don't have to output an
833              * empty block here, this will be done at next call. This also
834              * ensures that for a very small output buffer, we emit at most
835              * one empty block.
836              */
837         }
838         if (bstate == block_done) {
839             if (flush == Z_PARTIAL_FLUSH) {
840                 _tr_align(s);
841             } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
842                 _tr_stored_block(s, (char*)0, 0L, 0);
843                 /* For a full flush, this empty block will be recognized
844                  * as a special marker by inflate_sync().
845                  */
846                 if (flush == Z_FULL_FLUSH) {
847                     CLEAR_HASH(s);             /* forget history */
848                     if (s->lookahead == 0) {
849                         s->strstart = 0;
850                         s->block_start = 0L;
851                     }
852                 }
853             }
854             flush_pending(strm);
855             if (strm->avail_out == 0) {
856               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
857               return Z_OK;
858             }
859         }
860     }
861     Assert(strm->avail_out > 0, "bug2");
862 
863     if (flush != Z_FINISH) return Z_OK;
864     if (s->wrap <= 0) return Z_STREAM_END;
865 
866     /* Write the trailer */
867 #ifdef GZIP
868     if (s->wrap == 2) {
869         put_byte(s, (Byte)(strm->adler & 0xff));
870         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
871         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
872         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
873         put_byte(s, (Byte)(strm->total_in & 0xff));
874         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
875         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
876         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
877     }
878     else
879 #endif
880     {
881         putShortMSB(s, (uInt)(strm->adler >> 16));
882         putShortMSB(s, (uInt)(strm->adler & 0xffff));
883     }
884     flush_pending(strm);
885     /* If avail_out is zero, the application will call deflate again
886      * to flush the rest.
887      */
888     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
889     return s->pending != 0 ? Z_OK : Z_STREAM_END;
890 }
891 
892 /* ========================================================================= */
893 int ZEXPORT deflateEnd (strm)
894     z_streamp strm;
895 {
896     int status;
897 
898     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
899 
900     status = strm->state->status;
901     if (status != INIT_STATE &&
902         status != EXTRA_STATE &&
903         status != NAME_STATE &&
904         status != COMMENT_STATE &&
905         status != HCRC_STATE &&
906         status != BUSY_STATE &&
907         status != FINISH_STATE) {
908       return Z_STREAM_ERROR;
909     }
910 
911     /* Deallocate in reverse order of allocations: */
912     TRY_FREE(strm, strm->state->pending_buf);
913     TRY_FREE(strm, strm->state->head);
914     TRY_FREE(strm, strm->state->prev);
915     TRY_FREE(strm, strm->state->window);
916 
917     ZFREE(strm, strm->state);
918     strm->state = Z_NULL;
919 
920     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
921 }
922 
923 /* =========================================================================
924  * Copy the source state to the destination state.
925  * To simplify the source, this is not supported for 16-bit MSDOS (which
926  * doesn't have enough memory anyway to duplicate compression states).
927  */
928 int ZEXPORT deflateCopy (dest, source)
929     z_streamp dest;
930     z_streamp source;
931 {
932 #ifdef MAXSEG_64K
933     return Z_STREAM_ERROR;
934 #else
935     deflate_state *ds;
936     deflate_state *ss;
937     ushf *overlay;
938 
939 
940     if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
941         return Z_STREAM_ERROR;
942     }
943 
944     ss = source->state;
945 
946     zmemcpy(dest, source, sizeof(z_stream));
947 
948     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
949     if (ds == Z_NULL) return Z_MEM_ERROR;
950     dest->state = (struct internal_state FAR *) ds;
951     zmemcpy(ds, ss, sizeof(deflate_state));
952     ds->strm = dest;
953 
954     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
955     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
956     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
957     overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
958     ds->pending_buf = (uchf *) overlay;
959 
960     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
961         ds->pending_buf == Z_NULL) {
962         deflateEnd (dest);
963         return Z_MEM_ERROR;
964     }
965     /* following zmemcpy do not work for 16-bit MSDOS */
966     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
967     zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
968     zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
969     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
970 
971     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
972     ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
973     ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
974 
975     ds->l_desc.dyn_tree = ds->dyn_ltree;
976     ds->d_desc.dyn_tree = ds->dyn_dtree;
977     ds->bl_desc.dyn_tree = ds->bl_tree;
978 
979     return Z_OK;
980 #endif /* MAXSEG_64K */
981 }
982 
983 /* ===========================================================================
984  * Read a new buffer from the current input stream, update the adler32
985  * and total number of bytes read.  All deflate() input goes through
986  * this function so some applications may wish to modify it to avoid
987  * allocating a large strm->next_in buffer and copying from it.
988  * (See also flush_pending()).
989  */
990 local int read_buf(strm, buf, size)
991     z_streamp strm;
992     Bytef *buf;
993     unsigned size;
994 {
995     unsigned len = strm->avail_in;
996 
997     if (len > size) len = size;
998     if (len == 0) return 0;
999 
1000     strm->avail_in  -= len;
1001 
1002     if (strm->state->wrap == 1) {
1003         strm->adler = adler32(strm->adler, strm->next_in, len);
1004     }
1005 #ifdef GZIP
1006     else if (strm->state->wrap == 2) {
1007         strm->adler = crc32(strm->adler, strm->next_in, len);
1008     }
1009 #endif
1010     zmemcpy(buf, strm->next_in, len);
1011     strm->next_in  += len;
1012     strm->total_in += len;
1013 
1014     return (int)len;
1015 }
1016 
1017 /* ===========================================================================
1018  * Initialize the "longest match" routines for a new zlib stream
1019  */
1020 local void lm_init (s)
1021     deflate_state *s;
1022 {
1023     s->window_size = (ulg)2L*s->w_size;
1024 
1025     CLEAR_HASH(s);
1026 
1027     /* Set the default configuration parameters:
1028      */
1029     s->max_lazy_match   = configuration_table[s->level].max_lazy;
1030     s->good_match       = configuration_table[s->level].good_length;
1031     s->nice_match       = configuration_table[s->level].nice_length;
1032     s->max_chain_length = configuration_table[s->level].max_chain;
1033 
1034     s->strstart = 0;
1035     s->block_start = 0L;
1036     s->lookahead = 0;
1037     s->match_length = s->prev_length = MIN_MATCH-1;
1038     s->match_available = 0;
1039     s->ins_h = 0;
1040 #ifndef FASTEST
1041 #ifdef ASMV
1042     match_init(); /* initialize the asm code */
1043 #endif
1044 #endif
1045 }
1046 
1047 #ifndef FASTEST
1048 /* ===========================================================================
1049  * Set match_start to the longest match starting at the given string and
1050  * return its length. Matches shorter or equal to prev_length are discarded,
1051  * in which case the result is equal to prev_length and match_start is
1052  * garbage.
1053  * IN assertions: cur_match is the head of the hash chain for the current
1054  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1055  * OUT assertion: the match length is not greater than s->lookahead.
1056  */
1057 #ifndef ASMV
1058 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1059  * match.S. The code will be functionally equivalent.
1060  */
1061 local uInt longest_match(s, cur_match)
1062     deflate_state *s;
1063     IPos cur_match;                             /* current match */
1064 {
1065     unsigned chain_length = s->max_chain_length;/* max hash chain length */
1066     register Bytef *scan = s->window + s->strstart; /* current string */
1067     register Bytef *match;                       /* matched string */
1068     register int len;                           /* length of current match */
1069     int best_len = s->prev_length;              /* best match length so far */
1070     int nice_match = s->nice_match;             /* stop if match long enough */
1071     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1072         s->strstart - (IPos)MAX_DIST(s) : NIL;
1073     /* Stop when cur_match becomes <= limit. To simplify the code,
1074      * we prevent matches with the string of window index 0.
1075      */
1076     Posf *prev = s->prev;
1077     uInt wmask = s->w_mask;
1078 
1079 #ifdef UNALIGNED_OK
1080     /* Compare two bytes at a time. Note: this is not always beneficial.
1081      * Try with and without -DUNALIGNED_OK to check.
1082      */
1083     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1084     register ush scan_start = *(ushf*)scan;
1085     register ush scan_end   = *(ushf*)(scan+best_len-1);
1086 #else
1087     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1088     register Byte scan_end1  = scan[best_len-1];
1089     register Byte scan_end   = scan[best_len];
1090 #endif
1091 
1092     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1093      * It is easy to get rid of this optimization if necessary.
1094      */
1095     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1096 
1097     /* Do not waste too much time if we already have a good match: */
1098     if (s->prev_length >= s->good_match) {
1099         chain_length >>= 2;
1100     }
1101     /* Do not look for matches beyond the end of the input. This is necessary
1102      * to make deflate deterministic.
1103      */
1104     if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1105 
1106     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1107 
1108     do {
1109         Assert(cur_match < s->strstart, "no future");
1110         match = s->window + cur_match;
1111 
1112         /* Skip to next match if the match length cannot increase
1113          * or if the match length is less than 2.  Note that the checks below
1114          * for insufficient lookahead only occur occasionally for performance
1115          * reasons.  Therefore uninitialized memory will be accessed, and
1116          * conditional jumps will be made that depend on those values.
1117          * However the length of the match is limited to the lookahead, so
1118          * the output of deflate is not affected by the uninitialized values.
1119          */
1120 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1121         /* This code assumes sizeof(unsigned short) == 2. Do not use
1122          * UNALIGNED_OK if your compiler uses a different size.
1123          */
1124         if (*(ushf*)(match+best_len-1) != scan_end ||
1125             *(ushf*)match != scan_start) continue;
1126 
1127         /* It is not necessary to compare scan[2] and match[2] since they are
1128          * always equal when the other bytes match, given that the hash keys
1129          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1130          * strstart+3, +5, ... up to strstart+257. We check for insufficient
1131          * lookahead only every 4th comparison; the 128th check will be made
1132          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1133          * necessary to put more guard bytes at the end of the window, or
1134          * to check more often for insufficient lookahead.
1135          */
1136         Assert(scan[2] == match[2], "scan[2]?");
1137         scan++, match++;
1138         do {
1139         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1140                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1141                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1142                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1143                  scan < strend);
1144         /* The funny "do {}" generates better code on most compilers */
1145 
1146         /* Here, scan <= window+strstart+257 */
1147         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1148         if (*scan == *match) scan++;
1149 
1150         len = (MAX_MATCH - 1) - (int)(strend-scan);
1151         scan = strend - (MAX_MATCH-1);
1152 
1153 #else /* UNALIGNED_OK */
1154 
1155         if (match[best_len]   != scan_end  ||
1156             match[best_len-1] != scan_end1 ||
1157             *match            != *scan     ||
1158             *++match          != scan[1])      continue;
1159 
1160         /* The check at best_len-1 can be removed because it will be made
1161          * again later. (This heuristic is not always a win.)
1162          * It is not necessary to compare scan[2] and match[2] since they
1163          * are always equal when the other bytes match, given that
1164          * the hash keys are equal and that HASH_BITS >= 8.
1165          */
1166         scan += 2, match++;
1167         Assert(*scan == *match, "match[2]?");
1168 
1169         /* We check for insufficient lookahead only every 8th comparison;
1170          * the 256th check will be made at strstart+258.
1171          */
1172         do {
1173         } while (*++scan == *++match && *++scan == *++match &&
1174                  *++scan == *++match && *++scan == *++match &&
1175                  *++scan == *++match && *++scan == *++match &&
1176                  *++scan == *++match && *++scan == *++match &&
1177                  scan < strend);
1178 
1179         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1180 
1181         len = MAX_MATCH - (int)(strend - scan);
1182         scan = strend - MAX_MATCH;
1183 
1184 #endif /* UNALIGNED_OK */
1185 
1186         if (len > best_len) {
1187             s->match_start = cur_match;
1188             best_len = len;
1189             if (len >= nice_match) break;
1190 #ifdef UNALIGNED_OK
1191             scan_end = *(ushf*)(scan+best_len-1);
1192 #else
1193             scan_end1  = scan[best_len-1];
1194             scan_end   = scan[best_len];
1195 #endif
1196         }
1197     } while ((cur_match = prev[cur_match & wmask]) > limit
1198              && --chain_length != 0);
1199 
1200     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1201     return s->lookahead;
1202 }
1203 #endif /* ASMV */
1204 
1205 #else /* FASTEST */
1206 
1207 /* ---------------------------------------------------------------------------
1208  * Optimized version for FASTEST only
1209  */
1210 local uInt longest_match(s, cur_match)
1211     deflate_state *s;
1212     IPos cur_match;                             /* current match */
1213 {
1214     register Bytef *scan = s->window + s->strstart; /* current string */
1215     register Bytef *match;                       /* matched string */
1216     register int len;                           /* length of current match */
1217     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1218 
1219     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1220      * It is easy to get rid of this optimization if necessary.
1221      */
1222     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1223 
1224     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1225 
1226     Assert(cur_match < s->strstart, "no future");
1227 
1228     match = s->window + cur_match;
1229 
1230     /* Return failure if the match length is less than 2:
1231      */
1232     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1233 
1234     /* The check at best_len-1 can be removed because it will be made
1235      * again later. (This heuristic is not always a win.)
1236      * It is not necessary to compare scan[2] and match[2] since they
1237      * are always equal when the other bytes match, given that
1238      * the hash keys are equal and that HASH_BITS >= 8.
1239      */
1240     scan += 2, match += 2;
1241     Assert(*scan == *match, "match[2]?");
1242 
1243     /* We check for insufficient lookahead only every 8th comparison;
1244      * the 256th check will be made at strstart+258.
1245      */
1246     do {
1247     } while (*++scan == *++match && *++scan == *++match &&
1248              *++scan == *++match && *++scan == *++match &&
1249              *++scan == *++match && *++scan == *++match &&
1250              *++scan == *++match && *++scan == *++match &&
1251              scan < strend);
1252 
1253     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1254 
1255     len = MAX_MATCH - (int)(strend - scan);
1256 
1257     if (len < MIN_MATCH) return MIN_MATCH - 1;
1258 
1259     s->match_start = cur_match;
1260     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1261 }
1262 
1263 #endif /* FASTEST */
1264 
1265 #ifdef DEBUG
1266 /* ===========================================================================
1267  * Check that the match at match_start is indeed a match.
1268  */
1269 local void check_match(s, start, match, length)
1270     deflate_state *s;
1271     IPos start, match;
1272     int length;
1273 {
1274     /* check that the match is indeed a match */
1275     if (zmemcmp(s->window + match,
1276                 s->window + start, length) != EQUAL) {
1277         fprintf(stderr, " start %u, match %u, length %d\n",
1278                 start, match, length);
1279         do {
1280             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1281         } while (--length != 0);
1282         z_error("invalid match");
1283     }
1284     if (z_verbose > 1) {
1285         fprintf(stderr,"\\[%d,%d]", start-match, length);
1286         do { putc(s->window[start++], stderr); } while (--length != 0);
1287     }
1288 }
1289 #else
1290 #  define check_match(s, start, match, length)
1291 #endif /* DEBUG */
1292 
1293 /* ===========================================================================
1294  * Fill the window when the lookahead becomes insufficient.
1295  * Updates strstart and lookahead.
1296  *
1297  * IN assertion: lookahead < MIN_LOOKAHEAD
1298  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1299  *    At least one byte has been read, or avail_in == 0; reads are
1300  *    performed for at least two bytes (required for the zip translate_eol
1301  *    option -- not supported here).
1302  */
1303 local void fill_window(s)
1304     deflate_state *s;
1305 {
1306     register unsigned n, m;
1307     register Posf *p;
1308     unsigned more;    /* Amount of free space at the end of the window. */
1309     uInt wsize = s->w_size;
1310 
1311     do {
1312         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1313 
1314         /* Deal with !@#$% 64K limit: */
1315         if (sizeof(int) <= 2) {
1316             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1317                 more = wsize;
1318 
1319             } else if (more == (unsigned)(-1)) {
1320                 /* Very unlikely, but possible on 16 bit machine if
1321                  * strstart == 0 && lookahead == 1 (input done a byte at time)
1322                  */
1323                 more--;
1324             }
1325         }
1326 
1327         /* If the window is almost full and there is insufficient lookahead,
1328          * move the upper half to the lower one to make room in the upper half.
1329          */
1330         if (s->strstart >= wsize+MAX_DIST(s)) {
1331 
1332             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1333             s->match_start -= wsize;
1334             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
1335             s->block_start -= (long) wsize;
1336 
1337             /* Slide the hash table (could be avoided with 32 bit values
1338                at the expense of memory usage). We slide even when level == 0
1339                to keep the hash table consistent if we switch back to level > 0
1340                later. (Using level 0 permanently is not an optimal usage of
1341                zlib, so we don't care about this pathological case.)
1342              */
1343             n = s->hash_size;
1344             p = &s->head[n];
1345             do {
1346                 m = *--p;
1347                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1348             } while (--n);
1349 
1350             n = wsize;
1351 #ifndef FASTEST
1352             p = &s->prev[n];
1353             do {
1354                 m = *--p;
1355                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
1356                 /* If n is not on any hash chain, prev[n] is garbage but
1357                  * its value will never be used.
1358                  */
1359             } while (--n);
1360 #endif
1361             more += wsize;
1362         }
1363         if (s->strm->avail_in == 0) return;
1364 
1365         /* If there was no sliding:
1366          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1367          *    more == window_size - lookahead - strstart
1368          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1369          * => more >= window_size - 2*WSIZE + 2
1370          * In the BIG_MEM or MMAP case (not yet supported),
1371          *   window_size == input_size + MIN_LOOKAHEAD  &&
1372          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1373          * Otherwise, window_size == 2*WSIZE so more >= 2.
1374          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1375          */
1376         Assert(more >= 2, "more < 2");
1377 
1378         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1379         s->lookahead += n;
1380 
1381         /* Initialize the hash value now that we have some input: */
1382         if (s->lookahead >= MIN_MATCH) {
1383             s->ins_h = s->window[s->strstart];
1384             UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1385 #if MIN_MATCH != 3
1386             Call UPDATE_HASH() MIN_MATCH-3 more times
1387 #endif
1388         }
1389         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1390          * but this is not important since only literal bytes will be emitted.
1391          */
1392 
1393     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1394 
1395     /* If the WIN_INIT bytes after the end of the current data have never been
1396      * written, then zero those bytes in order to avoid memory check reports of
1397      * the use of uninitialized (or uninitialised as Julian writes) bytes by
1398      * the longest match routines.  Update the high water mark for the next
1399      * time through here.  WIN_INIT is set to MAX_MATCH since the longest match
1400      * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
1401      */
1402     if (s->high_water < s->window_size) {
1403         ulg curr = s->strstart + (ulg)(s->lookahead);
1404         ulg init;
1405 
1406         if (s->high_water < curr) {
1407             /* Previous high water mark below current data -- zero WIN_INIT
1408              * bytes or up to end of window, whichever is less.
1409              */
1410             init = s->window_size - curr;
1411             if (init > WIN_INIT)
1412                 init = WIN_INIT;
1413             zmemzero(s->window + curr, (unsigned)init);
1414             s->high_water = curr + init;
1415         }
1416         else if (s->high_water < (ulg)curr + WIN_INIT) {
1417             /* High water mark at or above current data, but below current data
1418              * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
1419              * to end of window, whichever is less.
1420              */
1421             init = (ulg)curr + WIN_INIT - s->high_water;
1422             if (init > s->window_size - s->high_water)
1423                 init = s->window_size - s->high_water;
1424             zmemzero(s->window + s->high_water, (unsigned)init);
1425             s->high_water += init;
1426         }
1427     }
1428 }
1429 
1430 /* ===========================================================================
1431  * Flush the current block, with given end-of-file flag.
1432  * IN assertion: strstart is set to the end of the current match.
1433  */
1434 #define FLUSH_BLOCK_ONLY(s, last) { \
1435    _tr_flush_block(s, (s->block_start >= 0L ? \
1436                    (charf *)&s->window[(unsigned)s->block_start] : \
1437                    (charf *)Z_NULL), \
1438                 (ulg)((long)s->strstart - s->block_start), \
1439                 (last)); \
1440    s->block_start = s->strstart; \
1441    flush_pending(s->strm); \
1442    Tracev((stderr,"[FLUSH]")); \
1443 }
1444 
1445 /* Same but force premature exit if necessary. */
1446 #define FLUSH_BLOCK(s, last) { \
1447    FLUSH_BLOCK_ONLY(s, last); \
1448    if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
1449 }
1450 
1451 /* ===========================================================================
1452  * Copy without compression as much as possible from the input stream, return
1453  * the current block state.
1454  * This function does not insert new strings in the dictionary since
1455  * uncompressible data is probably not useful. This function is used
1456  * only for the level=0 compression option.
1457  * NOTE: this function should be optimized to avoid extra copying from
1458  * window to pending_buf.
1459  */
1460 local block_state deflate_stored(s, flush)
1461     deflate_state *s;
1462     int flush;
1463 {
1464     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1465      * to pending_buf_size, and each stored block has a 5 byte header:
1466      */
1467     ulg max_block_size = 0xffff;
1468     ulg max_start;
1469 
1470     if (max_block_size > s->pending_buf_size - 5) {
1471         max_block_size = s->pending_buf_size - 5;
1472     }
1473 
1474     /* Copy as much as possible from input to output: */
1475     for (;;) {
1476         /* Fill the window as much as possible: */
1477         if (s->lookahead <= 1) {
1478 
1479             Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1480                    s->block_start >= (long)s->w_size, "slide too late");
1481 
1482             fill_window(s);
1483             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1484 
1485             if (s->lookahead == 0) break; /* flush the current block */
1486         }
1487         Assert(s->block_start >= 0L, "block gone");
1488 
1489         s->strstart += s->lookahead;
1490         s->lookahead = 0;
1491 
1492         /* Emit a stored block if pending_buf will be full: */
1493         max_start = s->block_start + max_block_size;
1494         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1495             /* strstart == 0 is possible when wraparound on 16-bit machine */
1496             s->lookahead = (uInt)(s->strstart - max_start);
1497             s->strstart = (uInt)max_start;
1498             FLUSH_BLOCK(s, 0);
1499         }
1500         /* Flush if we may have to slide, otherwise block_start may become
1501          * negative and the data will be gone:
1502          */
1503         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1504             FLUSH_BLOCK(s, 0);
1505         }
1506     }
1507     FLUSH_BLOCK(s, flush == Z_FINISH);
1508     return flush == Z_FINISH ? finish_done : block_done;
1509 }
1510 
1511 /* ===========================================================================
1512  * Compress as much as possible from the input stream, return the current
1513  * block state.
1514  * This function does not perform lazy evaluation of matches and inserts
1515  * new strings in the dictionary only for unmatched strings or for short
1516  * matches. It is used only for the fast compression options.
1517  */
1518 local block_state deflate_fast(s, flush)
1519     deflate_state *s;
1520     int flush;
1521 {
1522     IPos hash_head;       /* head of the hash chain */
1523     int bflush;           /* set if current block must be flushed */
1524 
1525     for (;;) {
1526         /* Make sure that we always have enough lookahead, except
1527          * at the end of the input file. We need MAX_MATCH bytes
1528          * for the next match, plus MIN_MATCH bytes to insert the
1529          * string following the next match.
1530          */
1531         if (s->lookahead < MIN_LOOKAHEAD) {
1532             fill_window(s);
1533             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1534                 return need_more;
1535             }
1536             if (s->lookahead == 0) break; /* flush the current block */
1537         }
1538 
1539         /* Insert the string window[strstart .. strstart+2] in the
1540          * dictionary, and set hash_head to the head of the hash chain:
1541          */
1542         hash_head = NIL;
1543         if (s->lookahead >= MIN_MATCH) {
1544             INSERT_STRING(s, s->strstart, hash_head);
1545         }
1546 
1547         /* Find the longest match, discarding those <= prev_length.
1548          * At this point we have always match_length < MIN_MATCH
1549          */
1550         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1551             /* To simplify the code, we prevent matches with the string
1552              * of window index 0 (in particular we have to avoid a match
1553              * of the string with itself at the start of the input file).
1554              */
1555             s->match_length = longest_match (s, hash_head);
1556             /* longest_match() sets match_start */
1557         }
1558         if (s->match_length >= MIN_MATCH) {
1559             check_match(s, s->strstart, s->match_start, s->match_length);
1560 
1561             _tr_tally_dist(s, s->strstart - s->match_start,
1562                            s->match_length - MIN_MATCH, bflush);
1563 
1564             s->lookahead -= s->match_length;
1565 
1566             /* Insert new strings in the hash table only if the match length
1567              * is not too large. This saves time but degrades compression.
1568              */
1569 #ifndef FASTEST
1570             if (s->match_length <= s->max_insert_length &&
1571                 s->lookahead >= MIN_MATCH) {
1572                 s->match_length--; /* string at strstart already in table */
1573                 do {
1574                     s->strstart++;
1575                     INSERT_STRING(s, s->strstart, hash_head);
1576                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1577                      * always MIN_MATCH bytes ahead.
1578                      */
1579                 } while (--s->match_length != 0);
1580                 s->strstart++;
1581             } else
1582 #endif
1583             {
1584                 s->strstart += s->match_length;
1585                 s->match_length = 0;
1586                 s->ins_h = s->window[s->strstart];
1587                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1588 #if MIN_MATCH != 3
1589                 Call UPDATE_HASH() MIN_MATCH-3 more times
1590 #endif
1591                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1592                  * matter since it will be recomputed at next deflate call.
1593                  */
1594             }
1595         } else {
1596             /* No match, output a literal byte */
1597             Tracevv((stderr,"%c", s->window[s->strstart]));
1598             _tr_tally_lit (s, s->window[s->strstart], bflush);
1599             s->lookahead--;
1600             s->strstart++;
1601         }
1602         if (bflush) FLUSH_BLOCK(s, 0);
1603     }
1604     FLUSH_BLOCK(s, flush == Z_FINISH);
1605     return flush == Z_FINISH ? finish_done : block_done;
1606 }
1607 
1608 #ifndef FASTEST
1609 /* ===========================================================================
1610  * Same as above, but achieves better compression. We use a lazy
1611  * evaluation for matches: a match is finally adopted only if there is
1612  * no better match at the next window position.
1613  */
1614 local block_state deflate_slow(s, flush)
1615     deflate_state *s;
1616     int flush;
1617 {
1618     IPos hash_head;          /* head of hash chain */
1619     int bflush;              /* set if current block must be flushed */
1620 
1621     /* Process the input block. */
1622     for (;;) {
1623         /* Make sure that we always have enough lookahead, except
1624          * at the end of the input file. We need MAX_MATCH bytes
1625          * for the next match, plus MIN_MATCH bytes to insert the
1626          * string following the next match.
1627          */
1628         if (s->lookahead < MIN_LOOKAHEAD) {
1629             fill_window(s);
1630             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1631                 return need_more;
1632             }
1633             if (s->lookahead == 0) break; /* flush the current block */
1634         }
1635 
1636         /* Insert the string window[strstart .. strstart+2] in the
1637          * dictionary, and set hash_head to the head of the hash chain:
1638          */
1639         hash_head = NIL;
1640         if (s->lookahead >= MIN_MATCH) {
1641             INSERT_STRING(s, s->strstart, hash_head);
1642         }
1643 
1644         /* Find the longest match, discarding those <= prev_length.
1645          */
1646         s->prev_length = s->match_length, s->prev_match = s->match_start;
1647         s->match_length = MIN_MATCH-1;
1648 
1649         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1650             s->strstart - hash_head <= MAX_DIST(s)) {
1651             /* To simplify the code, we prevent matches with the string
1652              * of window index 0 (in particular we have to avoid a match
1653              * of the string with itself at the start of the input file).
1654              */
1655             s->match_length = longest_match (s, hash_head);
1656             /* longest_match() sets match_start */
1657 
1658             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1659 #if TOO_FAR <= 32767
1660                 || (s->match_length == MIN_MATCH &&
1661                     s->strstart - s->match_start > TOO_FAR)
1662 #endif
1663                 )) {
1664 
1665                 /* If prev_match is also MIN_MATCH, match_start is garbage
1666                  * but we will ignore the current match anyway.
1667                  */
1668                 s->match_length = MIN_MATCH-1;
1669             }
1670         }
1671         /* If there was a match at the previous step and the current
1672          * match is not better, output the previous match:
1673          */
1674         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1675             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1676             /* Do not insert strings in hash table beyond this. */
1677 
1678             check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1679 
1680             _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1681                            s->prev_length - MIN_MATCH, bflush);
1682 
1683             /* Insert in hash table all strings up to the end of the match.
1684              * strstart-1 and strstart are already inserted. If there is not
1685              * enough lookahead, the last two strings are not inserted in
1686              * the hash table.
1687              */
1688             s->lookahead -= s->prev_length-1;
1689             s->prev_length -= 2;
1690             do {
1691                 if (++s->strstart <= max_insert) {
1692                     INSERT_STRING(s, s->strstart, hash_head);
1693                 }
1694             } while (--s->prev_length != 0);
1695             s->match_available = 0;
1696             s->match_length = MIN_MATCH-1;
1697             s->strstart++;
1698 
1699             if (bflush) FLUSH_BLOCK(s, 0);
1700 
1701         } else if (s->match_available) {
1702             /* If there was no match at the previous position, output a
1703              * single literal. If there was a match but the current match
1704              * is longer, truncate the previous match to a single literal.
1705              */
1706             Tracevv((stderr,"%c", s->window[s->strstart-1]));
1707             _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1708             if (bflush) {
1709                 FLUSH_BLOCK_ONLY(s, 0);
1710             }
1711             s->strstart++;
1712             s->lookahead--;
1713             if (s->strm->avail_out == 0) return need_more;
1714         } else {
1715             /* There is no previous match to compare with, wait for
1716              * the next step to decide.
1717              */
1718             s->match_available = 1;
1719             s->strstart++;
1720             s->lookahead--;
1721         }
1722     }
1723     Assert (flush != Z_NO_FLUSH, "no flush?");
1724     if (s->match_available) {
1725         Tracevv((stderr,"%c", s->window[s->strstart-1]));
1726         _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1727         s->match_available = 0;
1728     }
1729     FLUSH_BLOCK(s, flush == Z_FINISH);
1730     return flush == Z_FINISH ? finish_done : block_done;
1731 }
1732 #endif /* FASTEST */
1733 
1734 /* ===========================================================================
1735  * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1736  * one.  Do not maintain a hash table.  (It will be regenerated if this run of
1737  * deflate switches away from Z_RLE.)
1738  */
1739 local block_state deflate_rle(s, flush)
1740     deflate_state *s;
1741     int flush;
1742 {
1743     int bflush;             /* set if current block must be flushed */
1744     uInt prev;              /* byte at distance one to match */
1745     Bytef *scan, *strend;   /* scan goes up to strend for length of run */
1746 
1747     for (;;) {
1748         /* Make sure that we always have enough lookahead, except
1749          * at the end of the input file. We need MAX_MATCH bytes
1750          * for the longest encodable run.
1751          */
1752         if (s->lookahead < MAX_MATCH) {
1753             fill_window(s);
1754             if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1755                 return need_more;
1756             }
1757             if (s->lookahead == 0) break; /* flush the current block */
1758         }
1759 
1760         /* See how many times the previous byte repeats */
1761         s->match_length = 0;
1762         if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
1763             scan = s->window + s->strstart - 1;
1764             prev = *scan;
1765             if (prev == *++scan && prev == *++scan && prev == *++scan) {
1766                 strend = s->window + s->strstart + MAX_MATCH;
1767                 do {
1768                 } while (prev == *++scan && prev == *++scan &&
1769                          prev == *++scan && prev == *++scan &&
1770                          prev == *++scan && prev == *++scan &&
1771                          prev == *++scan && prev == *++scan &&
1772                          scan < strend);
1773                 s->match_length = MAX_MATCH - (int)(strend - scan);
1774                 if (s->match_length > s->lookahead)
1775                     s->match_length = s->lookahead;
1776             }
1777         }
1778 
1779         /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1780         if (s->match_length >= MIN_MATCH) {
1781             check_match(s, s->strstart, s->strstart - 1, s->match_length);
1782 
1783             _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
1784 
1785             s->lookahead -= s->match_length;
1786             s->strstart += s->match_length;
1787             s->match_length = 0;
1788         } else {
1789             /* No match, output a literal byte */
1790             Tracevv((stderr,"%c", s->window[s->strstart]));
1791             _tr_tally_lit (s, s->window[s->strstart], bflush);
1792             s->lookahead--;
1793             s->strstart++;
1794         }
1795         if (bflush) FLUSH_BLOCK(s, 0);
1796     }
1797     FLUSH_BLOCK(s, flush == Z_FINISH);
1798     return flush == Z_FINISH ? finish_done : block_done;
1799 }
1800 
1801 /* ===========================================================================
1802  * For Z_HUFFMAN_ONLY, do not look for matches.  Do not maintain a hash table.
1803  * (It will be regenerated if this run of deflate switches away from Huffman.)
1804  */
1805 local block_state deflate_huff(s, flush)
1806     deflate_state *s;
1807     int flush;
1808 {
1809     int bflush;             /* set if current block must be flushed */
1810 
1811     for (;;) {
1812         /* Make sure that we have a literal to write. */
1813         if (s->lookahead == 0) {
1814             fill_window(s);
1815             if (s->lookahead == 0) {
1816                 if (flush == Z_NO_FLUSH)
1817                     return need_more;
1818                 break;      /* flush the current block */
1819             }
1820         }
1821 
1822         /* Output a literal byte */
1823         s->match_length = 0;
1824         Tracevv((stderr,"%c", s->window[s->strstart]));
1825         _tr_tally_lit (s, s->window[s->strstart], bflush);
1826         s->lookahead--;
1827         s->strstart++;
1828         if (bflush) FLUSH_BLOCK(s, 0);
1829     }
1830     FLUSH_BLOCK(s, flush == Z_FINISH);
1831     return flush == Z_FINISH ? finish_done : block_done;
1832 }
1833