source: s10k/CommonLibs/zlib-1.2.8/deflate.c @ 1096

Last change on this file since 1096 was 1096, checked in by s10k, 23 months ago

Added zlib, quazip, basicxmlsyntaxhighlighter, conditionalsemaphore and linenumberdisplay libraries. zlib and quazip are pre-compiled, but you can compile them yourself, just delete the dll files (or equivalent binary files to your OS)

File size: 69.8 KB
Line 
1/* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2013 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://tools.ietf.org/html/rfc1951
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
54const char deflate_copyright[] =
55   " deflate 1.2.8 Copyright 1995-2013 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 */
66typedef 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
73typedef block_state (*compress_func) OF((deflate_state *s, int flush));
74/* Compression function. Returns the block state after the call. */
75
76local void fill_window    OF((deflate_state *s));
77local block_state deflate_stored OF((deflate_state *s, int flush));
78local block_state deflate_fast   OF((deflate_state *s, int flush));
79#ifndef FASTEST
80local block_state deflate_slow   OF((deflate_state *s, int flush));
81#endif
82local block_state deflate_rle    OF((deflate_state *s, int flush));
83local block_state deflate_huff   OF((deflate_state *s, int flush));
84local void lm_init        OF((deflate_state *s));
85local void putShortMSB    OF((deflate_state *s, uInt b));
86local void flush_pending  OF((z_streamp strm));
87local 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
92local uInt longest_match  OF((deflate_state *s, IPos cur_match));
93#endif
94
95#ifdef DEBUG
96local  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 */
117typedef 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
126local 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
131local 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
155struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
156#endif
157
158/* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
159#define RANK(f) (((f) << 1) - ((f) > 4 ? 9 : 0))
160
161/* ===========================================================================
162 * Update a hash value with the given input byte
163 * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
164 *    input characters, so that a running hash key can be computed from the
165 *    previous key instead of complete recalculation each time.
166 */
167#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
168
169
170/* ===========================================================================
171 * Insert string str in the dictionary and set match_head to the previous head
172 * of the hash chain (the most recent string with same hash key). Return
173 * the previous length of the hash chain.
174 * If this file is compiled with -DFASTEST, the compression level is forced
175 * to 1, and no hash chains are maintained.
176 * IN  assertion: all calls to to INSERT_STRING are made with consecutive
177 *    input characters and the first MIN_MATCH bytes of str are valid
178 *    (except for the last MIN_MATCH-1 bytes of the input file).
179 */
180#ifdef FASTEST
181#define INSERT_STRING(s, str, match_head) \
182   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
183    match_head = s->head[s->ins_h], \
184    s->head[s->ins_h] = (Pos)(str))
185#else
186#define INSERT_STRING(s, str, match_head) \
187   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
188    match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
189    s->head[s->ins_h] = (Pos)(str))
190#endif
191
192/* ===========================================================================
193 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
194 * prev[] will be initialized on the fly.
195 */
196#define CLEAR_HASH(s) \
197    s->head[s->hash_size-1] = NIL; \
198    zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
199
200/* ========================================================================= */
201int ZEXPORT deflateInit_(strm, level, version, stream_size)
202    z_streamp strm;
203    int level;
204    const char *version;
205    int stream_size;
206{
207    return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
208                         Z_DEFAULT_STRATEGY, version, stream_size);
209    /* To do: ignore strm->next_in if we use it as window */
210}
211
212/* ========================================================================= */
213int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
214                  version, stream_size)
215    z_streamp strm;
216    int  level;
217    int  method;
218    int  windowBits;
219    int  memLevel;
220    int  strategy;
221    const char *version;
222    int stream_size;
223{
224    deflate_state *s;
225    int wrap = 1;
226    static const char my_version[] = ZLIB_VERSION;
227
228    ushf *overlay;
229    /* We overlay pending_buf and d_buf+l_buf. This works since the average
230     * output size for (length,distance) codes is <= 24 bits.
231     */
232
233    if (version == Z_NULL || version[0] != my_version[0] ||
234        stream_size != sizeof(z_stream)) {
235        return Z_VERSION_ERROR;
236    }
237    if (strm == Z_NULL) return Z_STREAM_ERROR;
238
239    strm->msg = Z_NULL;
240    if (strm->zalloc == (alloc_func)0) {
241#ifdef Z_SOLO
242        return Z_STREAM_ERROR;
243#else
244        strm->zalloc = zcalloc;
245        strm->opaque = (voidpf)0;
246#endif
247    }
248    if (strm->zfree == (free_func)0)
249#ifdef Z_SOLO
250        return Z_STREAM_ERROR;
251#else
252        strm->zfree = zcfree;
253#endif
254
255#ifdef FASTEST
256    if (level != 0) level = 1;
257#else
258    if (level == Z_DEFAULT_COMPRESSION) level = 6;
259#endif
260
261    if (windowBits < 0) { /* suppress zlib wrapper */
262        wrap = 0;
263        windowBits = -windowBits;
264    }
265#ifdef GZIP
266    else if (windowBits > 15) {
267        wrap = 2;       /* write gzip wrapper instead */
268        windowBits -= 16;
269    }
270#endif
271    if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
272        windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
273        strategy < 0 || strategy > Z_FIXED) {
274        return Z_STREAM_ERROR;
275    }
276    if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
277    s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
278    if (s == Z_NULL) return Z_MEM_ERROR;
279    strm->state = (struct internal_state FAR *)s;
280    s->strm = strm;
281
282    s->wrap = wrap;
283    s->gzhead = Z_NULL;
284    s->w_bits = windowBits;
285    s->w_size = 1 << s->w_bits;
286    s->w_mask = s->w_size - 1;
287
288    s->hash_bits = memLevel + 7;
289    s->hash_size = 1 << s->hash_bits;
290    s->hash_mask = s->hash_size - 1;
291    s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
292
293    s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
294    s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
295    s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
296
297    s->high_water = 0;      /* nothing written to s->window yet */
298
299    s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
300
301    overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
302    s->pending_buf = (uchf *) overlay;
303    s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
304
305    if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
306        s->pending_buf == Z_NULL) {
307        s->status = FINISH_STATE;
308        strm->msg = ERR_MSG(Z_MEM_ERROR);
309        deflateEnd (strm);
310        return Z_MEM_ERROR;
311    }
312    s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
313    s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
314
315    s->level = level;
316    s->strategy = strategy;
317    s->method = (Byte)method;
318
319    return deflateReset(strm);
320}
321
322/* ========================================================================= */
323int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
324    z_streamp strm;
325    const Bytef *dictionary;
326    uInt  dictLength;
327{
328    deflate_state *s;
329    uInt str, n;
330    int wrap;
331    unsigned avail;
332    z_const unsigned char *next;
333
334    if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
335        return Z_STREAM_ERROR;
336    s = strm->state;
337    wrap = s->wrap;
338    if (wrap == 2 || (wrap == 1 && s->status != INIT_STATE) || s->lookahead)
339        return Z_STREAM_ERROR;
340
341    /* when using zlib wrappers, compute Adler-32 for provided dictionary */
342    if (wrap == 1)
343        strm->adler = adler32(strm->adler, dictionary, dictLength);
344    s->wrap = 0;                    /* avoid computing Adler-32 in read_buf */
345
346    /* if dictionary would fill window, just replace the history */
347    if (dictLength >= s->w_size) {
348        if (wrap == 0) {            /* already empty otherwise */
349            CLEAR_HASH(s);
350            s->strstart = 0;
351            s->block_start = 0L;
352            s->insert = 0;
353        }
354        dictionary += dictLength - s->w_size;  /* use the tail */
355        dictLength = s->w_size;
356    }
357
358    /* insert dictionary into window and hash */
359    avail = strm->avail_in;
360    next = strm->next_in;
361    strm->avail_in = dictLength;
362    strm->next_in = (z_const Bytef *)dictionary;
363    fill_window(s);
364    while (s->lookahead >= MIN_MATCH) {
365        str = s->strstart;
366        n = s->lookahead - (MIN_MATCH-1);
367        do {
368            UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
369#ifndef FASTEST
370            s->prev[str & s->w_mask] = s->head[s->ins_h];
371#endif
372            s->head[s->ins_h] = (Pos)str;
373            str++;
374        } while (--n);
375        s->strstart = str;
376        s->lookahead = MIN_MATCH-1;
377        fill_window(s);
378    }
379    s->strstart += s->lookahead;
380    s->block_start = (long)s->strstart;
381    s->insert = s->lookahead;
382    s->lookahead = 0;
383    s->match_length = s->prev_length = MIN_MATCH-1;
384    s->match_available = 0;
385    strm->next_in = next;
386    strm->avail_in = avail;
387    s->wrap = wrap;
388    return Z_OK;
389}
390
391/* ========================================================================= */
392int ZEXPORT deflateResetKeep (strm)
393    z_streamp strm;
394{
395    deflate_state *s;
396
397    if (strm == Z_NULL || strm->state == Z_NULL ||
398        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
399        return Z_STREAM_ERROR;
400    }
401
402    strm->total_in = strm->total_out = 0;
403    strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
404    strm->data_type = Z_UNKNOWN;
405
406    s = (deflate_state *)strm->state;
407    s->pending = 0;
408    s->pending_out = s->pending_buf;
409
410    if (s->wrap < 0) {
411        s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
412    }
413    s->status = s->wrap ? INIT_STATE : BUSY_STATE;
414    strm->adler =
415#ifdef GZIP
416        s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
417#endif
418        adler32(0L, Z_NULL, 0);
419    s->last_flush = Z_NO_FLUSH;
420
421    _tr_init(s);
422
423    return Z_OK;
424}
425
426/* ========================================================================= */
427int ZEXPORT deflateReset (strm)
428    z_streamp strm;
429{
430    int ret;
431
432    ret = deflateResetKeep(strm);
433    if (ret == Z_OK)
434        lm_init(strm->state);
435    return ret;
436}
437
438/* ========================================================================= */
439int ZEXPORT deflateSetHeader (strm, head)
440    z_streamp strm;
441    gz_headerp head;
442{
443    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
444    if (strm->state->wrap != 2) return Z_STREAM_ERROR;
445    strm->state->gzhead = head;
446    return Z_OK;
447}
448
449/* ========================================================================= */
450int ZEXPORT deflatePending (strm, pending, bits)
451    unsigned *pending;
452    int *bits;
453    z_streamp strm;
454{
455    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
456    if (pending != Z_NULL)
457        *pending = strm->state->pending;
458    if (bits != Z_NULL)
459        *bits = strm->state->bi_valid;
460    return Z_OK;
461}
462
463/* ========================================================================= */
464int ZEXPORT deflatePrime (strm, bits, value)
465    z_streamp strm;
466    int bits;
467    int value;
468{
469    deflate_state *s;
470    int put;
471
472    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
473    s = strm->state;
474    if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
475        return Z_BUF_ERROR;
476    do {
477        put = Buf_size - s->bi_valid;
478        if (put > bits)
479            put = bits;
480        s->bi_buf |= (ush)((value & ((1 << put) - 1)) << s->bi_valid);
481        s->bi_valid += put;
482        _tr_flush_bits(s);
483        value >>= put;
484        bits -= put;
485    } while (bits);
486    return Z_OK;
487}
488
489/* ========================================================================= */
490int ZEXPORT deflateParams(strm, level, strategy)
491    z_streamp strm;
492    int level;
493    int strategy;
494{
495    deflate_state *s;
496    compress_func func;
497    int err = Z_OK;
498
499    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
500    s = strm->state;
501
502#ifdef FASTEST
503    if (level != 0) level = 1;
504#else
505    if (level == Z_DEFAULT_COMPRESSION) level = 6;
506#endif
507    if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
508        return Z_STREAM_ERROR;
509    }
510    func = configuration_table[s->level].func;
511
512    if ((strategy != s->strategy || func != configuration_table[level].func) &&
513        strm->total_in != 0) {
514        /* Flush the last buffer: */
515        err = deflate(strm, Z_BLOCK);
516        if (err == Z_BUF_ERROR && s->pending == 0)
517            err = Z_OK;
518    }
519    if (s->level != level) {
520        s->level = level;
521        s->max_lazy_match   = configuration_table[level].max_lazy;
522        s->good_match       = configuration_table[level].good_length;
523        s->nice_match       = configuration_table[level].nice_length;
524        s->max_chain_length = configuration_table[level].max_chain;
525    }
526    s->strategy = strategy;
527    return err;
528}
529
530/* ========================================================================= */
531int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
532    z_streamp strm;
533    int good_length;
534    int max_lazy;
535    int nice_length;
536    int max_chain;
537{
538    deflate_state *s;
539
540    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
541    s = strm->state;
542    s->good_match = good_length;
543    s->max_lazy_match = max_lazy;
544    s->nice_match = nice_length;
545    s->max_chain_length = max_chain;
546    return Z_OK;
547}
548
549/* =========================================================================
550 * For the default windowBits of 15 and memLevel of 8, this function returns
551 * a close to exact, as well as small, upper bound on the compressed size.
552 * They are coded as constants here for a reason--if the #define's are
553 * changed, then this function needs to be changed as well.  The return
554 * value for 15 and 8 only works for those exact settings.
555 *
556 * For any setting other than those defaults for windowBits and memLevel,
557 * the value returned is a conservative worst case for the maximum expansion
558 * resulting from using fixed blocks instead of stored blocks, which deflate
559 * can emit on compressed data for some combinations of the parameters.
560 *
561 * This function could be more sophisticated to provide closer upper bounds for
562 * every combination of windowBits and memLevel.  But even the conservative
563 * upper bound of about 14% expansion does not seem onerous for output buffer
564 * allocation.
565 */
566uLong ZEXPORT deflateBound(strm, sourceLen)
567    z_streamp strm;
568    uLong sourceLen;
569{
570    deflate_state *s;
571    uLong complen, wraplen;
572    Bytef *str;
573
574    /* conservative upper bound for compressed data */
575    complen = sourceLen +
576              ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
577
578    /* if can't get parameters, return conservative bound plus zlib wrapper */
579    if (strm == Z_NULL || strm->state == Z_NULL)
580        return complen + 6;
581
582    /* compute wrapper length */
583    s = strm->state;
584    switch (s->wrap) {
585    case 0:                                 /* raw deflate */
586        wraplen = 0;
587        break;
588    case 1:                                 /* zlib wrapper */
589        wraplen = 6 + (s->strstart ? 4 : 0);
590        break;
591    case 2:                                 /* gzip wrapper */
592        wraplen = 18;
593        if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
594            if (s->gzhead->extra != Z_NULL)
595                wraplen += 2 + s->gzhead->extra_len;
596            str = s->gzhead->name;
597            if (str != Z_NULL)
598                do {
599                    wraplen++;
600                } while (*str++);
601            str = s->gzhead->comment;
602            if (str != Z_NULL)
603                do {
604                    wraplen++;
605                } while (*str++);
606            if (s->gzhead->hcrc)
607                wraplen += 2;
608        }
609        break;
610    default:                                /* for compiler happiness */
611        wraplen = 6;
612    }
613
614    /* if not default parameters, return conservative bound */
615    if (s->w_bits != 15 || s->hash_bits != 8 + 7)
616        return complen + wraplen;
617
618    /* default settings: return tight bound for that case */
619    return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
620           (sourceLen >> 25) + 13 - 6 + wraplen;
621}
622
623/* =========================================================================
624 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
625 * IN assertion: the stream state is correct and there is enough room in
626 * pending_buf.
627 */
628local void putShortMSB (s, b)
629    deflate_state *s;
630    uInt b;
631{
632    put_byte(s, (Byte)(b >> 8));
633    put_byte(s, (Byte)(b & 0xff));
634}
635
636/* =========================================================================
637 * Flush as much pending output as possible. All deflate() output goes
638 * through this function so some applications may wish to modify it
639 * to avoid allocating a large strm->next_out buffer and copying into it.
640 * (See also read_buf()).
641 */
642local void flush_pending(strm)
643    z_streamp strm;
644{
645    unsigned len;
646    deflate_state *s = strm->state;
647
648    _tr_flush_bits(s);
649    len = s->pending;
650    if (len > strm->avail_out) len = strm->avail_out;
651    if (len == 0) return;
652
653    zmemcpy(strm->next_out, s->pending_out, len);
654    strm->next_out  += len;
655    s->pending_out  += len;
656    strm->total_out += len;
657    strm->avail_out  -= len;
658    s->pending -= len;
659    if (s->pending == 0) {
660        s->pending_out = s->pending_buf;
661    }
662}
663
664/* ========================================================================= */
665int ZEXPORT deflate (strm, flush)
666    z_streamp strm;
667    int flush;
668{
669    int old_flush; /* value of flush param for previous deflate call */
670    deflate_state *s;
671
672    if (strm == Z_NULL || strm->state == Z_NULL ||
673        flush > Z_BLOCK || flush < 0) {
674        return Z_STREAM_ERROR;
675    }
676    s = strm->state;
677
678    if (strm->next_out == Z_NULL ||
679        (strm->next_in == Z_NULL && strm->avail_in != 0) ||
680        (s->status == FINISH_STATE && flush != Z_FINISH)) {
681        ERR_RETURN(strm, Z_STREAM_ERROR);
682    }
683    if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
684
685    s->strm = strm; /* just in case */
686    old_flush = s->last_flush;
687    s->last_flush = flush;
688
689    /* Write the header */
690    if (s->status == INIT_STATE) {
691#ifdef GZIP
692        if (s->wrap == 2) {
693            strm->adler = crc32(0L, Z_NULL, 0);
694            put_byte(s, 31);
695            put_byte(s, 139);
696            put_byte(s, 8);
697            if (s->gzhead == Z_NULL) {
698                put_byte(s, 0);
699                put_byte(s, 0);
700                put_byte(s, 0);
701                put_byte(s, 0);
702                put_byte(s, 0);
703                put_byte(s, s->level == 9 ? 2 :
704                            (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
705                             4 : 0));
706                put_byte(s, OS_CODE);
707                s->status = BUSY_STATE;
708            }
709            else {
710                put_byte(s, (s->gzhead->text ? 1 : 0) +
711                            (s->gzhead->hcrc ? 2 : 0) +
712                            (s->gzhead->extra == Z_NULL ? 0 : 4) +
713                            (s->gzhead->name == Z_NULL ? 0 : 8) +
714                            (s->gzhead->comment == Z_NULL ? 0 : 16)
715                        );
716                put_byte(s, (Byte)(s->gzhead->time & 0xff));
717                put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
718                put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
719                put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
720                put_byte(s, s->level == 9 ? 2 :
721                            (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
722                             4 : 0));
723                put_byte(s, s->gzhead->os & 0xff);
724                if (s->gzhead->extra != Z_NULL) {
725                    put_byte(s, s->gzhead->extra_len & 0xff);
726                    put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
727                }
728                if (s->gzhead->hcrc)
729                    strm->adler = crc32(strm->adler, s->pending_buf,
730                                        s->pending);
731                s->gzindex = 0;
732                s->status = EXTRA_STATE;
733            }
734        }
735        else
736#endif
737        {
738            uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
739            uInt level_flags;
740
741            if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
742                level_flags = 0;
743            else if (s->level < 6)
744                level_flags = 1;
745            else if (s->level == 6)
746                level_flags = 2;
747            else
748                level_flags = 3;
749            header |= (level_flags << 6);
750            if (s->strstart != 0) header |= PRESET_DICT;
751            header += 31 - (header % 31);
752
753            s->status = BUSY_STATE;
754            putShortMSB(s, header);
755
756            /* Save the adler32 of the preset dictionary: */
757            if (s->strstart != 0) {
758                putShortMSB(s, (uInt)(strm->adler >> 16));
759                putShortMSB(s, (uInt)(strm->adler & 0xffff));
760            }
761            strm->adler = adler32(0L, Z_NULL, 0);
762        }
763    }
764#ifdef GZIP
765    if (s->status == EXTRA_STATE) {
766        if (s->gzhead->extra != Z_NULL) {
767            uInt beg = s->pending;  /* start of bytes to update crc */
768
769            while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
770                if (s->pending == s->pending_buf_size) {
771                    if (s->gzhead->hcrc && s->pending > beg)
772                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
773                                            s->pending - beg);
774                    flush_pending(strm);
775                    beg = s->pending;
776                    if (s->pending == s->pending_buf_size)
777                        break;
778                }
779                put_byte(s, s->gzhead->extra[s->gzindex]);
780                s->gzindex++;
781            }
782            if (s->gzhead->hcrc && s->pending > beg)
783                strm->adler = crc32(strm->adler, s->pending_buf + beg,
784                                    s->pending - beg);
785            if (s->gzindex == s->gzhead->extra_len) {
786                s->gzindex = 0;
787                s->status = NAME_STATE;
788            }
789        }
790        else
791            s->status = NAME_STATE;
792    }
793    if (s->status == NAME_STATE) {
794        if (s->gzhead->name != Z_NULL) {
795            uInt beg = s->pending;  /* start of bytes to update crc */
796            int val;
797
798            do {
799                if (s->pending == s->pending_buf_size) {
800                    if (s->gzhead->hcrc && s->pending > beg)
801                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
802                                            s->pending - beg);
803                    flush_pending(strm);
804                    beg = s->pending;
805                    if (s->pending == s->pending_buf_size) {
806                        val = 1;
807                        break;
808                    }
809                }
810                val = s->gzhead->name[s->gzindex++];
811                put_byte(s, val);
812            } while (val != 0);
813            if (s->gzhead->hcrc && s->pending > beg)
814                strm->adler = crc32(strm->adler, s->pending_buf + beg,
815                                    s->pending - beg);
816            if (val == 0) {
817                s->gzindex = 0;
818                s->status = COMMENT_STATE;
819            }
820        }
821        else
822            s->status = COMMENT_STATE;
823    }
824    if (s->status == COMMENT_STATE) {
825        if (s->gzhead->comment != Z_NULL) {
826            uInt beg = s->pending;  /* start of bytes to update crc */
827            int val;
828
829            do {
830                if (s->pending == s->pending_buf_size) {
831                    if (s->gzhead->hcrc && s->pending > beg)
832                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
833                                            s->pending - beg);
834                    flush_pending(strm);
835                    beg = s->pending;
836                    if (s->pending == s->pending_buf_size) {
837                        val = 1;
838                        break;
839                    }
840                }
841                val = s->gzhead->comment[s->gzindex++];
842                put_byte(s, val);
843            } while (val != 0);
844            if (s->gzhead->hcrc && s->pending > beg)
845                strm->adler = crc32(strm->adler, s->pending_buf + beg,
846                                    s->pending - beg);
847            if (val == 0)
848                s->status = HCRC_STATE;
849        }
850        else
851            s->status = HCRC_STATE;
852    }
853    if (s->status == HCRC_STATE) {
854        if (s->gzhead->hcrc) {
855            if (s->pending + 2 > s->pending_buf_size)
856                flush_pending(strm);
857            if (s->pending + 2 <= s->pending_buf_size) {
858                put_byte(s, (Byte)(strm->adler & 0xff));
859                put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
860                strm->adler = crc32(0L, Z_NULL, 0);
861                s->status = BUSY_STATE;
862            }
863        }
864        else
865            s->status = BUSY_STATE;
866    }
867#endif
868
869    /* Flush as much pending output as possible */
870    if (s->pending != 0) {
871        flush_pending(strm);
872        if (strm->avail_out == 0) {
873            /* Since avail_out is 0, deflate will be called again with
874             * more output space, but possibly with both pending and
875             * avail_in equal to zero. There won't be anything to do,
876             * but this is not an error situation so make sure we
877             * return OK instead of BUF_ERROR at next call of deflate:
878             */
879            s->last_flush = -1;
880            return Z_OK;
881        }
882
883    /* Make sure there is something to do and avoid duplicate consecutive
884     * flushes. For repeated and useless calls with Z_FINISH, we keep
885     * returning Z_STREAM_END instead of Z_BUF_ERROR.
886     */
887    } else if (strm->avail_in == 0 && RANK(flush) <= RANK(old_flush) &&
888               flush != Z_FINISH) {
889        ERR_RETURN(strm, Z_BUF_ERROR);
890    }
891
892    /* User must not provide more input after the first FINISH: */
893    if (s->status == FINISH_STATE && strm->avail_in != 0) {
894        ERR_RETURN(strm, Z_BUF_ERROR);
895    }
896
897    /* Start a new block or continue the current one.
898     */
899    if (strm->avail_in != 0 || s->lookahead != 0 ||
900        (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
901        block_state bstate;
902
903        bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
904                    (s->strategy == Z_RLE ? deflate_rle(s, flush) :
905                        (*(configuration_table[s->level].func))(s, flush));
906
907        if (bstate == finish_started || bstate == finish_done) {
908            s->status = FINISH_STATE;
909        }
910        if (bstate == need_more || bstate == finish_started) {
911            if (strm->avail_out == 0) {
912                s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
913            }
914            return Z_OK;
915            /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
916             * of deflate should use the same flush parameter to make sure
917             * that the flush is complete. So we don't have to output an
918             * empty block here, this will be done at next call. This also
919             * ensures that for a very small output buffer, we emit at most
920             * one empty block.
921             */
922        }
923        if (bstate == block_done) {
924            if (flush == Z_PARTIAL_FLUSH) {
925                _tr_align(s);
926            } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
927                _tr_stored_block(s, (char*)0, 0L, 0);
928                /* For a full flush, this empty block will be recognized
929                 * as a special marker by inflate_sync().
930                 */
931                if (flush == Z_FULL_FLUSH) {
932                    CLEAR_HASH(s);             /* forget history */
933                    if (s->lookahead == 0) {
934                        s->strstart = 0;
935                        s->block_start = 0L;
936                        s->insert = 0;
937                    }
938                }
939            }
940            flush_pending(strm);
941            if (strm->avail_out == 0) {
942              s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
943              return Z_OK;
944            }
945        }
946    }
947    Assert(strm->avail_out > 0, "bug2");
948
949    if (flush != Z_FINISH) return Z_OK;
950    if (s->wrap <= 0) return Z_STREAM_END;
951
952    /* Write the trailer */
953#ifdef GZIP
954    if (s->wrap == 2) {
955        put_byte(s, (Byte)(strm->adler & 0xff));
956        put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
957        put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
958        put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
959        put_byte(s, (Byte)(strm->total_in & 0xff));
960        put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
961        put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
962        put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
963    }
964    else
965#endif
966    {
967        putShortMSB(s, (uInt)(strm->adler >> 16));
968        putShortMSB(s, (uInt)(strm->adler & 0xffff));
969    }
970    flush_pending(strm);
971    /* If avail_out is zero, the application will call deflate again
972     * to flush the rest.
973     */
974    if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
975    return s->pending != 0 ? Z_OK : Z_STREAM_END;
976}
977
978/* ========================================================================= */
979int ZEXPORT deflateEnd (strm)
980    z_streamp strm;
981{
982    int status;
983
984    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
985
986    status = strm->state->status;
987    if (status != INIT_STATE &&
988        status != EXTRA_STATE &&
989        status != NAME_STATE &&
990        status != COMMENT_STATE &&
991        status != HCRC_STATE &&
992        status != BUSY_STATE &&
993        status != FINISH_STATE) {
994      return Z_STREAM_ERROR;
995    }
996
997    /* Deallocate in reverse order of allocations: */
998    TRY_FREE(strm, strm->state->pending_buf);
999    TRY_FREE(strm, strm->state->head);
1000    TRY_FREE(strm, strm->state->prev);
1001    TRY_FREE(strm, strm->state->window);
1002
1003    ZFREE(strm, strm->state);
1004    strm->state = Z_NULL;
1005
1006    return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
1007}
1008
1009/* =========================================================================
1010 * Copy the source state to the destination state.
1011 * To simplify the source, this is not supported for 16-bit MSDOS (which
1012 * doesn't have enough memory anyway to duplicate compression states).
1013 */
1014int ZEXPORT deflateCopy (dest, source)
1015    z_streamp dest;
1016    z_streamp source;
1017{
1018#ifdef MAXSEG_64K
1019    return Z_STREAM_ERROR;
1020#else
1021    deflate_state *ds;
1022    deflate_state *ss;
1023    ushf *overlay;
1024
1025
1026    if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
1027        return Z_STREAM_ERROR;
1028    }
1029
1030    ss = source->state;
1031
1032    zmemcpy((voidpf)dest, (voidpf)source, sizeof(z_stream));
1033
1034    ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
1035    if (ds == Z_NULL) return Z_MEM_ERROR;
1036    dest->state = (struct internal_state FAR *) ds;
1037    zmemcpy((voidpf)ds, (voidpf)ss, sizeof(deflate_state));
1038    ds->strm = dest;
1039
1040    ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
1041    ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
1042    ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
1043    overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
1044    ds->pending_buf = (uchf *) overlay;
1045
1046    if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
1047        ds->pending_buf == Z_NULL) {
1048        deflateEnd (dest);
1049        return Z_MEM_ERROR;
1050    }
1051    /* following zmemcpy do not work for 16-bit MSDOS */
1052    zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
1053    zmemcpy((voidpf)ds->prev, (voidpf)ss->prev, ds->w_size * sizeof(Pos));
1054    zmemcpy((voidpf)ds->head, (voidpf)ss->head, ds->hash_size * sizeof(Pos));
1055    zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
1056
1057    ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
1058    ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
1059    ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
1060
1061    ds->l_desc.dyn_tree = ds->dyn_ltree;
1062    ds->d_desc.dyn_tree = ds->dyn_dtree;
1063    ds->bl_desc.dyn_tree = ds->bl_tree;
1064
1065    return Z_OK;
1066#endif /* MAXSEG_64K */
1067}
1068
1069/* ===========================================================================
1070 * Read a new buffer from the current input stream, update the adler32
1071 * and total number of bytes read.  All deflate() input goes through
1072 * this function so some applications may wish to modify it to avoid
1073 * allocating a large strm->next_in buffer and copying from it.
1074 * (See also flush_pending()).
1075 */
1076local int read_buf(strm, buf, size)
1077    z_streamp strm;
1078    Bytef *buf;
1079    unsigned size;
1080{
1081    unsigned len = strm->avail_in;
1082
1083    if (len > size) len = size;
1084    if (len == 0) return 0;
1085
1086    strm->avail_in  -= len;
1087
1088    zmemcpy(buf, strm->next_in, len);
1089    if (strm->state->wrap == 1) {
1090        strm->adler = adler32(strm->adler, buf, len);
1091    }
1092#ifdef GZIP
1093    else if (strm->state->wrap == 2) {
1094        strm->adler = crc32(strm->adler, buf, len);
1095    }
1096#endif
1097    strm->next_in  += len;
1098    strm->total_in += len;
1099
1100    return (int)len;
1101}
1102
1103/* ===========================================================================
1104 * Initialize the "longest match" routines for a new zlib stream
1105 */
1106local void lm_init (s)
1107    deflate_state *s;
1108{
1109    s->window_size = (ulg)2L*s->w_size;
1110
1111    CLEAR_HASH(s);
1112
1113    /* Set the default configuration parameters:
1114     */
1115    s->max_lazy_match   = configuration_table[s->level].max_lazy;
1116    s->good_match       = configuration_table[s->level].good_length;
1117    s->nice_match       = configuration_table[s->level].nice_length;
1118    s->max_chain_length = configuration_table[s->level].max_chain;
1119
1120    s->strstart = 0;
1121    s->block_start = 0L;
1122    s->lookahead = 0;
1123    s->insert = 0;
1124    s->match_length = s->prev_length = MIN_MATCH-1;
1125    s->match_available = 0;
1126    s->ins_h = 0;
1127#ifndef FASTEST
1128#ifdef ASMV
1129    match_init(); /* initialize the asm code */
1130#endif
1131#endif
1132}
1133
1134#ifndef FASTEST
1135/* ===========================================================================
1136 * Set match_start to the longest match starting at the given string and
1137 * return its length. Matches shorter or equal to prev_length are discarded,
1138 * in which case the result is equal to prev_length and match_start is
1139 * garbage.
1140 * IN assertions: cur_match is the head of the hash chain for the current
1141 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1142 * OUT assertion: the match length is not greater than s->lookahead.
1143 */
1144#ifndef ASMV
1145/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1146 * match.S. The code will be functionally equivalent.
1147 */
1148local uInt longest_match(s, cur_match)
1149    deflate_state *s;
1150    IPos cur_match;                             /* current match */
1151{
1152    unsigned chain_length = s->max_chain_length;/* max hash chain length */
1153    register Bytef *scan = s->window + s->strstart; /* current string */
1154    register Bytef *match;                       /* matched string */
1155    register int len;                           /* length of current match */
1156    int best_len = s->prev_length;              /* best match length so far */
1157    int nice_match = s->nice_match;             /* stop if match long enough */
1158    IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1159        s->strstart - (IPos)MAX_DIST(s) : NIL;
1160    /* Stop when cur_match becomes <= limit. To simplify the code,
1161     * we prevent matches with the string of window index 0.
1162     */
1163    Posf *prev = s->prev;
1164    uInt wmask = s->w_mask;
1165
1166#ifdef UNALIGNED_OK
1167    /* Compare two bytes at a time. Note: this is not always beneficial.
1168     * Try with and without -DUNALIGNED_OK to check.
1169     */
1170    register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1171    register ush scan_start = *(ushf*)scan;
1172    register ush scan_end   = *(ushf*)(scan+best_len-1);
1173#else
1174    register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1175    register Byte scan_end1  = scan[best_len-1];
1176    register Byte scan_end   = scan[best_len];
1177#endif
1178
1179    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1180     * It is easy to get rid of this optimization if necessary.
1181     */
1182    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1183
1184    /* Do not waste too much time if we already have a good match: */
1185    if (s->prev_length >= s->good_match) {
1186        chain_length >>= 2;
1187    }
1188    /* Do not look for matches beyond the end of the input. This is necessary
1189     * to make deflate deterministic.
1190     */
1191    if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1192
1193    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1194
1195    do {
1196        Assert(cur_match < s->strstart, "no future");
1197        match = s->window + cur_match;
1198
1199        /* Skip to next match if the match length cannot increase
1200         * or if the match length is less than 2.  Note that the checks below
1201         * for insufficient lookahead only occur occasionally for performance
1202         * reasons.  Therefore uninitialized memory will be accessed, and
1203         * conditional jumps will be made that depend on those values.
1204         * However the length of the match is limited to the lookahead, so
1205         * the output of deflate is not affected by the uninitialized values.
1206         */
1207#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1208        /* This code assumes sizeof(unsigned short) == 2. Do not use
1209         * UNALIGNED_OK if your compiler uses a different size.
1210         */
1211        if (*(ushf*)(match+best_len-1) != scan_end ||
1212            *(ushf*)match != scan_start) continue;
1213
1214        /* It is not necessary to compare scan[2] and match[2] since they are
1215         * always equal when the other bytes match, given that the hash keys
1216         * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1217         * strstart+3, +5, ... up to strstart+257. We check for insufficient
1218         * lookahead only every 4th comparison; the 128th check will be made
1219         * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1220         * necessary to put more guard bytes at the end of the window, or
1221         * to check more often for insufficient lookahead.
1222         */
1223        Assert(scan[2] == match[2], "scan[2]?");
1224        scan++, match++;
1225        do {
1226        } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1227                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1228                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1229                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1230                 scan < strend);
1231        /* The funny "do {}" generates better code on most compilers */
1232
1233        /* Here, scan <= window+strstart+257 */
1234        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1235        if (*scan == *match) scan++;
1236
1237        len = (MAX_MATCH - 1) - (int)(strend-scan);
1238        scan = strend - (MAX_MATCH-1);
1239
1240#else /* UNALIGNED_OK */
1241
1242        if (match[best_len]   != scan_end  ||
1243            match[best_len-1] != scan_end1 ||
1244            *match            != *scan     ||
1245            *++match          != scan[1])      continue;
1246
1247        /* The check at best_len-1 can be removed because it will be made
1248         * again later. (This heuristic is not always a win.)
1249         * It is not necessary to compare scan[2] and match[2] since they
1250         * are always equal when the other bytes match, given that
1251         * the hash keys are equal and that HASH_BITS >= 8.
1252         */
1253        scan += 2, match++;
1254        Assert(*scan == *match, "match[2]?");
1255
1256        /* We check for insufficient lookahead only every 8th comparison;
1257         * the 256th check will be made at strstart+258.
1258         */
1259        do {
1260        } while (*++scan == *++match && *++scan == *++match &&
1261                 *++scan == *++match && *++scan == *++match &&
1262                 *++scan == *++match && *++scan == *++match &&
1263                 *++scan == *++match && *++scan == *++match &&
1264                 scan < strend);
1265
1266        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1267
1268        len = MAX_MATCH - (int)(strend - scan);
1269        scan = strend - MAX_MATCH;
1270
1271#endif /* UNALIGNED_OK */
1272
1273        if (len > best_len) {
1274            s->match_start = cur_match;
1275            best_len = len;
1276            if (len >= nice_match) break;
1277#ifdef UNALIGNED_OK
1278            scan_end = *(ushf*)(scan+best_len-1);
1279#else
1280            scan_end1  = scan[best_len-1];
1281            scan_end   = scan[best_len];
1282#endif
1283        }
1284    } while ((cur_match = prev[cur_match & wmask]) > limit
1285             && --chain_length != 0);
1286
1287    if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1288    return s->lookahead;
1289}
1290#endif /* ASMV */
1291
1292#else /* FASTEST */
1293
1294/* ---------------------------------------------------------------------------
1295 * Optimized version for FASTEST only
1296 */
1297local uInt longest_match(s, cur_match)
1298    deflate_state *s;
1299    IPos cur_match;                             /* current match */
1300{
1301    register Bytef *scan = s->window + s->strstart; /* current string */
1302    register Bytef *match;                       /* matched string */
1303    register int len;                           /* length of current match */
1304    register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1305
1306    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1307     * It is easy to get rid of this optimization if necessary.
1308     */
1309    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1310
1311    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1312
1313    Assert(cur_match < s->strstart, "no future");
1314
1315    match = s->window + cur_match;
1316
1317    /* Return failure if the match length is less than 2:
1318     */
1319    if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1320
1321    /* The check at best_len-1 can be removed because it will be made
1322     * again later. (This heuristic is not always a win.)
1323     * It is not necessary to compare scan[2] and match[2] since they
1324     * are always equal when the other bytes match, given that
1325     * the hash keys are equal and that HASH_BITS >= 8.
1326     */
1327    scan += 2, match += 2;
1328    Assert(*scan == *match, "match[2]?");
1329
1330    /* We check for insufficient lookahead only every 8th comparison;
1331     * the 256th check will be made at strstart+258.
1332     */
1333    do {
1334    } while (*++scan == *++match && *++scan == *++match &&
1335             *++scan == *++match && *++scan == *++match &&
1336             *++scan == *++match && *++scan == *++match &&
1337             *++scan == *++match && *++scan == *++match &&
1338             scan < strend);
1339
1340    Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1341
1342    len = MAX_MATCH - (int)(strend - scan);
1343
1344    if (len < MIN_MATCH) return MIN_MATCH - 1;
1345
1346    s->match_start = cur_match;
1347    return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1348}
1349
1350#endif /* FASTEST */
1351
1352#ifdef DEBUG
1353/* ===========================================================================
1354 * Check that the match at match_start is indeed a match.
1355 */
1356local void check_match(s, start, match, length)
1357    deflate_state *s;
1358    IPos start, match;
1359    int length;
1360{
1361    /* check that the match is indeed a match */
1362    if (zmemcmp(s->window + match,
1363                s->window + start, length) != EQUAL) {
1364        fprintf(stderr, " start %u, match %u, length %d\n",
1365                start, match, length);
1366        do {
1367            fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1368        } while (--length != 0);
1369        z_error("invalid match");
1370    }
1371    if (z_verbose > 1) {
1372        fprintf(stderr,"\\[%d,%d]", start-match, length);
1373        do { putc(s->window[start++], stderr); } while (--length != 0);
1374    }
1375}
1376#else
1377#  define check_match(s, start, match, length)
1378#endif /* DEBUG */
1379
1380/* ===========================================================================
1381 * Fill the window when the lookahead becomes insufficient.
1382 * Updates strstart and lookahead.
1383 *
1384 * IN assertion: lookahead < MIN_LOOKAHEAD
1385 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1386 *    At least one byte has been read, or avail_in == 0; reads are
1387 *    performed for at least two bytes (required for the zip translate_eol
1388 *    option -- not supported here).
1389 */
1390local void fill_window(s)
1391    deflate_state *s;
1392{
1393    register unsigned n, m;
1394    register Posf *p;
1395    unsigned more;    /* Amount of free space at the end of the window. */
1396    uInt wsize = s->w_size;
1397
1398    Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");
1399
1400    do {
1401        more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1402
1403        /* Deal with !@#$% 64K limit: */
1404        if (sizeof(int) <= 2) {
1405            if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1406                more = wsize;
1407
1408            } else if (more == (unsigned)(-1)) {
1409                /* Very unlikely, but possible on 16 bit machine if
1410                 * strstart == 0 && lookahead == 1 (input done a byte at time)
1411                 */
1412                more--;
1413            }
1414        }
1415
1416        /* If the window is almost full and there is insufficient lookahead,
1417         * move the upper half to the lower one to make room in the upper half.
1418         */
1419        if (s->strstart >= wsize+MAX_DIST(s)) {
1420
1421            zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1422            s->match_start -= wsize;
1423            s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
1424            s->block_start -= (long) wsize;
1425
1426            /* Slide the hash table (could be avoided with 32 bit values
1427               at the expense of memory usage). We slide even when level == 0
1428               to keep the hash table consistent if we switch back to level > 0
1429               later. (Using level 0 permanently is not an optimal usage of
1430               zlib, so we don't care about this pathological case.)
1431             */
1432            n = s->hash_size;
1433            p = &s->head[n];
1434            do {
1435                m = *--p;
1436                *p = (Pos)(m >= wsize ? m-wsize : NIL);
1437            } while (--n);
1438
1439            n = wsize;
1440#ifndef FASTEST
1441            p = &s->prev[n];
1442            do {
1443                m = *--p;
1444                *p = (Pos)(m >= wsize ? m-wsize : NIL);
1445                /* If n is not on any hash chain, prev[n] is garbage but
1446                 * its value will never be used.
1447                 */
1448            } while (--n);
1449#endif
1450            more += wsize;
1451        }
1452        if (s->strm->avail_in == 0) break;
1453
1454        /* If there was no sliding:
1455         *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1456         *    more == window_size - lookahead - strstart
1457         * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1458         * => more >= window_size - 2*WSIZE + 2
1459         * In the BIG_MEM or MMAP case (not yet supported),
1460         *   window_size == input_size + MIN_LOOKAHEAD  &&
1461         *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1462         * Otherwise, window_size == 2*WSIZE so more >= 2.
1463         * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1464         */
1465        Assert(more >= 2, "more < 2");
1466
1467        n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1468        s->lookahead += n;
1469
1470        /* Initialize the hash value now that we have some input: */
1471        if (s->lookahead + s->insert >= MIN_MATCH) {
1472            uInt str = s->strstart - s->insert;
1473            s->ins_h = s->window[str];
1474            UPDATE_HASH(s, s->ins_h, s->window[str + 1]);
1475#if MIN_MATCH != 3
1476            Call UPDATE_HASH() MIN_MATCH-3 more times
1477#endif
1478            while (s->insert) {
1479                UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
1480#ifndef FASTEST
1481                s->prev[str & s->w_mask] = s->head[s->ins_h];
1482#endif
1483                s->head[s->ins_h] = (Pos)str;
1484                str++;
1485                s->insert--;
1486                if (s->lookahead + s->insert < MIN_MATCH)
1487                    break;
1488            }
1489        }
1490        /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1491         * but this is not important since only literal bytes will be emitted.
1492         */
1493
1494    } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1495
1496    /* If the WIN_INIT bytes after the end of the current data have never been
1497     * written, then zero those bytes in order to avoid memory check reports of
1498     * the use of uninitialized (or uninitialised as Julian writes) bytes by
1499     * the longest match routines.  Update the high water mark for the next
1500     * time through here.  WIN_INIT is set to MAX_MATCH since the longest match
1501     * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
1502     */
1503    if (s->high_water < s->window_size) {
1504        ulg curr = s->strstart + (ulg)(s->lookahead);
1505        ulg init;
1506
1507        if (s->high_water < curr) {
1508            /* Previous high water mark below current data -- zero WIN_INIT
1509             * bytes or up to end of window, whichever is less.
1510             */
1511            init = s->window_size - curr;
1512            if (init > WIN_INIT)
1513                init = WIN_INIT;
1514            zmemzero(s->window + curr, (unsigned)init);
1515            s->high_water = curr + init;
1516        }
1517        else if (s->high_water < (ulg)curr + WIN_INIT) {
1518            /* High water mark at or above current data, but below current data
1519             * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
1520             * to end of window, whichever is less.
1521             */
1522            init = (ulg)curr + WIN_INIT - s->high_water;
1523            if (init > s->window_size - s->high_water)
1524                init = s->window_size - s->high_water;
1525            zmemzero(s->window + s->high_water, (unsigned)init);
1526            s->high_water += init;
1527        }
1528    }
1529
1530    Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
1531           "not enough room for search");
1532}
1533
1534/* ===========================================================================
1535 * Flush the current block, with given end-of-file flag.
1536 * IN assertion: strstart is set to the end of the current match.
1537 */
1538#define FLUSH_BLOCK_ONLY(s, last) { \
1539   _tr_flush_block(s, (s->block_start >= 0L ? \
1540                   (charf *)&s->window[(unsigned)s->block_start] : \
1541                   (charf *)Z_NULL), \
1542                (ulg)((long)s->strstart - s->block_start), \
1543                (last)); \
1544   s->block_start = s->strstart; \
1545   flush_pending(s->strm); \
1546   Tracev((stderr,"[FLUSH]")); \
1547}
1548
1549/* Same but force premature exit if necessary. */
1550#define FLUSH_BLOCK(s, last) { \
1551   FLUSH_BLOCK_ONLY(s, last); \
1552   if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
1553}
1554
1555/* ===========================================================================
1556 * Copy without compression as much as possible from the input stream, return
1557 * the current block state.
1558 * This function does not insert new strings in the dictionary since
1559 * uncompressible data is probably not useful. This function is used
1560 * only for the level=0 compression option.
1561 * NOTE: this function should be optimized to avoid extra copying from
1562 * window to pending_buf.
1563 */
1564local block_state deflate_stored(s, flush)
1565    deflate_state *s;
1566    int flush;
1567{
1568    /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1569     * to pending_buf_size, and each stored block has a 5 byte header:
1570     */
1571    ulg max_block_size = 0xffff;
1572    ulg max_start;
1573
1574    if (max_block_size > s->pending_buf_size - 5) {
1575        max_block_size = s->pending_buf_size - 5;
1576    }
1577
1578    /* Copy as much as possible from input to output: */
1579    for (;;) {
1580        /* Fill the window as much as possible: */
1581        if (s->lookahead <= 1) {
1582
1583            Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1584                   s->block_start >= (long)s->w_size, "slide too late");
1585
1586            fill_window(s);
1587            if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1588
1589            if (s->lookahead == 0) break; /* flush the current block */
1590        }
1591        Assert(s->block_start >= 0L, "block gone");
1592
1593        s->strstart += s->lookahead;
1594        s->lookahead = 0;
1595
1596        /* Emit a stored block if pending_buf will be full: */
1597        max_start = s->block_start + max_block_size;
1598        if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1599            /* strstart == 0 is possible when wraparound on 16-bit machine */
1600            s->lookahead = (uInt)(s->strstart - max_start);
1601            s->strstart = (uInt)max_start;
1602            FLUSH_BLOCK(s, 0);
1603        }
1604        /* Flush if we may have to slide, otherwise block_start may become
1605         * negative and the data will be gone:
1606         */
1607        if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1608            FLUSH_BLOCK(s, 0);
1609        }
1610    }
1611    s->insert = 0;
1612    if (flush == Z_FINISH) {
1613        FLUSH_BLOCK(s, 1);
1614        return finish_done;
1615    }
1616    if ((long)s->strstart > s->block_start)
1617        FLUSH_BLOCK(s, 0);
1618    return block_done;
1619}
1620
1621/* ===========================================================================
1622 * Compress as much as possible from the input stream, return the current
1623 * block state.
1624 * This function does not perform lazy evaluation of matches and inserts
1625 * new strings in the dictionary only for unmatched strings or for short
1626 * matches. It is used only for the fast compression options.
1627 */
1628local block_state deflate_fast(s, flush)
1629    deflate_state *s;
1630    int flush;
1631{
1632    IPos hash_head;       /* head of the hash chain */
1633    int bflush;           /* set if current block must be flushed */
1634
1635    for (;;) {
1636        /* Make sure that we always have enough lookahead, except
1637         * at the end of the input file. We need MAX_MATCH bytes
1638         * for the next match, plus MIN_MATCH bytes to insert the
1639         * string following the next match.
1640         */
1641        if (s->lookahead < MIN_LOOKAHEAD) {
1642            fill_window(s);
1643            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1644                return need_more;
1645            }
1646            if (s->lookahead == 0) break; /* flush the current block */
1647        }
1648
1649        /* Insert the string window[strstart .. strstart+2] in the
1650         * dictionary, and set hash_head to the head of the hash chain:
1651         */
1652        hash_head = NIL;
1653        if (s->lookahead >= MIN_MATCH) {
1654            INSERT_STRING(s, s->strstart, hash_head);
1655        }
1656
1657        /* Find the longest match, discarding those <= prev_length.
1658         * At this point we have always match_length < MIN_MATCH
1659         */
1660        if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1661            /* To simplify the code, we prevent matches with the string
1662             * of window index 0 (in particular we have to avoid a match
1663             * of the string with itself at the start of the input file).
1664             */
1665            s->match_length = longest_match (s, hash_head);
1666            /* longest_match() sets match_start */
1667        }
1668        if (s->match_length >= MIN_MATCH) {
1669            check_match(s, s->strstart, s->match_start, s->match_length);
1670
1671            _tr_tally_dist(s, s->strstart - s->match_start,
1672                           s->match_length - MIN_MATCH, bflush);
1673
1674            s->lookahead -= s->match_length;
1675
1676            /* Insert new strings in the hash table only if the match length
1677             * is not too large. This saves time but degrades compression.
1678             */
1679#ifndef FASTEST
1680            if (s->match_length <= s->max_insert_length &&
1681                s->lookahead >= MIN_MATCH) {
1682                s->match_length--; /* string at strstart already in table */
1683                do {
1684                    s->strstart++;
1685                    INSERT_STRING(s, s->strstart, hash_head);
1686                    /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1687                     * always MIN_MATCH bytes ahead.
1688                     */
1689                } while (--s->match_length != 0);
1690                s->strstart++;
1691            } else
1692#endif
1693            {
1694                s->strstart += s->match_length;
1695                s->match_length = 0;
1696                s->ins_h = s->window[s->strstart];
1697                UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1698#if MIN_MATCH != 3
1699                Call UPDATE_HASH() MIN_MATCH-3 more times
1700#endif
1701                /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1702                 * matter since it will be recomputed at next deflate call.
1703                 */
1704            }
1705        } else {
1706            /* No match, output a literal byte */
1707            Tracevv((stderr,"%c", s->window[s->strstart]));
1708            _tr_tally_lit (s, s->window[s->strstart], bflush);
1709            s->lookahead--;
1710            s->strstart++;
1711        }
1712        if (bflush) FLUSH_BLOCK(s, 0);
1713    }
1714    s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
1715    if (flush == Z_FINISH) {
1716        FLUSH_BLOCK(s, 1);
1717        return finish_done;
1718    }
1719    if (s->last_lit)
1720        FLUSH_BLOCK(s, 0);
1721    return block_done;
1722}
1723
1724#ifndef FASTEST
1725/* ===========================================================================
1726 * Same as above, but achieves better compression. We use a lazy
1727 * evaluation for matches: a match is finally adopted only if there is
1728 * no better match at the next window position.
1729 */
1730local block_state deflate_slow(s, flush)
1731    deflate_state *s;
1732    int flush;
1733{
1734    IPos hash_head;          /* head of hash chain */
1735    int bflush;              /* set if current block must be flushed */
1736
1737    /* Process the input block. */
1738    for (;;) {
1739        /* Make sure that we always have enough lookahead, except
1740         * at the end of the input file. We need MAX_MATCH bytes
1741         * for the next match, plus MIN_MATCH bytes to insert the
1742         * string following the next match.
1743         */
1744        if (s->lookahead < MIN_LOOKAHEAD) {
1745            fill_window(s);
1746            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1747                return need_more;
1748            }
1749            if (s->lookahead == 0) break; /* flush the current block */
1750        }
1751
1752        /* Insert the string window[strstart .. strstart+2] in the
1753         * dictionary, and set hash_head to the head of the hash chain:
1754         */
1755        hash_head = NIL;
1756        if (s->lookahead >= MIN_MATCH) {
1757            INSERT_STRING(s, s->strstart, hash_head);
1758        }
1759
1760        /* Find the longest match, discarding those <= prev_length.
1761         */
1762        s->prev_length = s->match_length, s->prev_match = s->match_start;
1763        s->match_length = MIN_MATCH-1;
1764
1765        if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1766            s->strstart - hash_head <= MAX_DIST(s)) {
1767            /* To simplify the code, we prevent matches with the string
1768             * of window index 0 (in particular we have to avoid a match
1769             * of the string with itself at the start of the input file).
1770             */
1771            s->match_length = longest_match (s, hash_head);
1772            /* longest_match() sets match_start */
1773
1774            if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1775#if TOO_FAR <= 32767
1776                || (s->match_length == MIN_MATCH &&
1777                    s->strstart - s->match_start > TOO_FAR)
1778#endif
1779                )) {
1780
1781                /* If prev_match is also MIN_MATCH, match_start is garbage
1782                 * but we will ignore the current match anyway.
1783                 */
1784                s->match_length = MIN_MATCH-1;
1785            }
1786        }
1787        /* If there was a match at the previous step and the current
1788         * match is not better, output the previous match:
1789         */
1790        if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1791            uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1792            /* Do not insert strings in hash table beyond this. */
1793
1794            check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1795
1796            _tr_tally_dist(s, s->strstart -1 - s->prev_match,
1797                           s->prev_length - MIN_MATCH, bflush);
1798
1799            /* Insert in hash table all strings up to the end of the match.
1800             * strstart-1 and strstart are already inserted. If there is not
1801             * enough lookahead, the last two strings are not inserted in
1802             * the hash table.
1803             */
1804            s->lookahead -= s->prev_length-1;
1805            s->prev_length -= 2;
1806            do {
1807                if (++s->strstart <= max_insert) {
1808                    INSERT_STRING(s, s->strstart, hash_head);
1809                }
1810            } while (--s->prev_length != 0);
1811            s->match_available = 0;
1812            s->match_length = MIN_MATCH-1;
1813            s->strstart++;
1814
1815            if (bflush) FLUSH_BLOCK(s, 0);
1816
1817        } else if (s->match_available) {
1818            /* If there was no match at the previous position, output a
1819             * single literal. If there was a match but the current match
1820             * is longer, truncate the previous match to a single literal.
1821             */
1822            Tracevv((stderr,"%c", s->window[s->strstart-1]));
1823            _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1824            if (bflush) {
1825                FLUSH_BLOCK_ONLY(s, 0);
1826            }
1827            s->strstart++;
1828            s->lookahead--;
1829            if (s->strm->avail_out == 0) return need_more;
1830        } else {
1831            /* There is no previous match to compare with, wait for
1832             * the next step to decide.
1833             */
1834            s->match_available = 1;
1835            s->strstart++;
1836            s->lookahead--;
1837        }
1838    }
1839    Assert (flush != Z_NO_FLUSH, "no flush?");
1840    if (s->match_available) {
1841        Tracevv((stderr,"%c", s->window[s->strstart-1]));
1842        _tr_tally_lit(s, s->window[s->strstart-1], bflush);
1843        s->match_available = 0;
1844    }
1845    s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
1846    if (flush == Z_FINISH) {
1847        FLUSH_BLOCK(s, 1);
1848        return finish_done;
1849    }
1850    if (s->last_lit)
1851        FLUSH_BLOCK(s, 0);
1852    return block_done;
1853}
1854#endif /* FASTEST */
1855
1856/* ===========================================================================
1857 * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1858 * one.  Do not maintain a hash table.  (It will be regenerated if this run of
1859 * deflate switches away from Z_RLE.)
1860 */
1861local block_state deflate_rle(s, flush)
1862    deflate_state *s;
1863    int flush;
1864{
1865    int bflush;             /* set if current block must be flushed */
1866    uInt prev;              /* byte at distance one to match */
1867    Bytef *scan, *strend;   /* scan goes up to strend for length of run */
1868
1869    for (;;) {
1870        /* Make sure that we always have enough lookahead, except
1871         * at the end of the input file. We need MAX_MATCH bytes
1872         * for the longest run, plus one for the unrolled loop.
1873         */
1874        if (s->lookahead <= MAX_MATCH) {
1875            fill_window(s);
1876            if (s->lookahead <= MAX_MATCH && flush == Z_NO_FLUSH) {
1877                return need_more;
1878            }
1879            if (s->lookahead == 0) break; /* flush the current block */
1880        }
1881
1882        /* See how many times the previous byte repeats */
1883        s->match_length = 0;
1884        if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
1885            scan = s->window + s->strstart - 1;
1886            prev = *scan;
1887            if (prev == *++scan && prev == *++scan && prev == *++scan) {
1888                strend = s->window + s->strstart + MAX_MATCH;
1889                do {
1890                } while (prev == *++scan && prev == *++scan &&
1891                         prev == *++scan && prev == *++scan &&
1892                         prev == *++scan && prev == *++scan &&
1893                         prev == *++scan && prev == *++scan &&
1894                         scan < strend);
1895                s->match_length = MAX_MATCH - (int)(strend - scan);
1896                if (s->match_length > s->lookahead)
1897                    s->match_length = s->lookahead;
1898            }
1899            Assert(scan <= s->window+(uInt)(s->window_size-1), "wild scan");
1900        }
1901
1902        /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1903        if (s->match_length >= MIN_MATCH) {
1904            check_match(s, s->strstart, s->strstart - 1, s->match_length);
1905
1906            _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
1907
1908            s->lookahead -= s->match_length;
1909            s->strstart += s->match_length;
1910            s->match_length = 0;
1911        } else {
1912            /* No match, output a literal byte */
1913            Tracevv((stderr,"%c", s->window[s->strstart]));
1914            _tr_tally_lit (s, s->window[s->strstart], bflush);
1915            s->lookahead--;
1916            s->strstart++;
1917        }
1918        if (bflush) FLUSH_BLOCK(s, 0);
1919    }
1920    s->insert = 0;
1921    if (flush == Z_FINISH) {
1922        FLUSH_BLOCK(s, 1);
1923        return finish_done;
1924    }
1925    if (s->last_lit)
1926        FLUSH_BLOCK(s, 0);
1927    return block_done;
1928}
1929
1930/* ===========================================================================
1931 * For Z_HUFFMAN_ONLY, do not look for matches.  Do not maintain a hash table.
1932 * (It will be regenerated if this run of deflate switches away from Huffman.)
1933 */
1934local block_state deflate_huff(s, flush)
1935    deflate_state *s;
1936    int flush;
1937{
1938    int bflush;             /* set if current block must be flushed */
1939
1940    for (;;) {
1941        /* Make sure that we have a literal to write. */
1942        if (s->lookahead == 0) {
1943            fill_window(s);
1944            if (s->lookahead == 0) {
1945                if (flush == Z_NO_FLUSH)
1946                    return need_more;
1947                break;      /* flush the current block */
1948            }
1949        }
1950
1951        /* Output a literal byte */
1952        s->match_length = 0;
1953        Tracevv((stderr,"%c", s->window[s->strstart]));
1954        _tr_tally_lit (s, s->window[s->strstart], bflush);
1955        s->lookahead--;
1956        s->strstart++;
1957        if (bflush) FLUSH_BLOCK(s, 0);
1958    }
1959    s->insert = 0;
1960    if (flush == Z_FINISH) {
1961        FLUSH_BLOCK(s, 1);
1962        return finish_done;
1963    }
1964    if (s->last_lit)
1965        FLUSH_BLOCK(s, 0);
1966    return block_done;
1967}
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