xref: /illumos-gate/usr/src/contrib/zlib/trees.c (revision b8382935)
1 /* trees.c -- output deflated data using Huffman coding
2  * Copyright (C) 1995-2017 Jean-loup Gailly
3  * detect_data_type() function provided freely by Cosmin Truta, 2006
4  * For conditions of distribution and use, see copyright notice in zlib.h
5  */
6 
7 /*
8  *  ALGORITHM
9  *
10  *      The "deflation" process uses several Huffman trees. The more
11  *      common source values are represented by shorter bit sequences.
12  *
13  *      Each code tree is stored in a compressed form which is itself
14  * a Huffman encoding of the lengths of all the code strings (in
15  * ascending order by source values).  The actual code strings are
16  * reconstructed from the lengths in the inflate process, as described
17  * in the deflate specification.
18  *
19  *  REFERENCES
20  *
21  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
22  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
23  *
24  *      Storer, James A.
25  *          Data Compression:  Methods and Theory, pp. 49-50.
26  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
27  *
28  *      Sedgewick, R.
29  *          Algorithms, p290.
30  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
31  */
32 
33 /* @(#) $Id$ */
34 
35 /* #define GEN_TREES_H */
36 
37 #include "deflate.h"
38 
39 #ifdef ZLIB_DEBUG
40 #  include <ctype.h>
41 #endif
42 
43 /* ===========================================================================
44  * Constants
45  */
46 
47 #define MAX_BL_BITS 7
48 /* Bit length codes must not exceed MAX_BL_BITS bits */
49 
50 #define END_BLOCK 256
51 /* end of block literal code */
52 
53 #define REP_3_6      16
54 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
55 
56 #define REPZ_3_10    17
57 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
58 
59 #define REPZ_11_138  18
60 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
61 
62 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
63    = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
64 
65 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
66    = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
67 
68 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
69    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
70 
71 local const uch bl_order[BL_CODES]
72    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
73 /* The lengths of the bit length codes are sent in order of decreasing
74  * probability, to avoid transmitting the lengths for unused bit length codes.
75  */
76 
77 /* ===========================================================================
78  * Local data. These are initialized only once.
79  */
80 
81 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
82 
83 #if defined(GEN_TREES_H) || !defined(STDC)
84 /* non ANSI compilers may not accept trees.h */
85 
86 local ct_data static_ltree[L_CODES+2];
87 /* The static literal tree. Since the bit lengths are imposed, there is no
88  * need for the L_CODES extra codes used during heap construction. However
89  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
90  * below).
91  */
92 
93 local ct_data static_dtree[D_CODES];
94 /* The static distance tree. (Actually a trivial tree since all codes use
95  * 5 bits.)
96  */
97 
98 uch _dist_code[DIST_CODE_LEN];
99 /* Distance codes. The first 256 values correspond to the distances
100  * 3 .. 258, the last 256 values correspond to the top 8 bits of
101  * the 15 bit distances.
102  */
103 
104 uch _length_code[MAX_MATCH-MIN_MATCH+1];
105 /* length code for each normalized match length (0 == MIN_MATCH) */
106 
107 local int base_length[LENGTH_CODES];
108 /* First normalized length for each code (0 = MIN_MATCH) */
109 
110 local int base_dist[D_CODES];
111 /* First normalized distance for each code (0 = distance of 1) */
112 
113 #else
114 #  include "trees.h"
115 #endif /* GEN_TREES_H */
116 
117 struct static_tree_desc_s {
118     const ct_data *static_tree;  /* static tree or NULL */
119     const intf *extra_bits;      /* extra bits for each code or NULL */
120     int     extra_base;          /* base index for extra_bits */
121     int     elems;               /* max number of elements in the tree */
122     int     max_length;          /* max bit length for the codes */
123 };
124 
125 local const static_tree_desc  static_l_desc =
126 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
127 
128 local const static_tree_desc  static_d_desc =
129 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
130 
131 local const static_tree_desc  static_bl_desc =
132 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
133 
134 /* ===========================================================================
135  * Local (static) routines in this file.
136  */
137 
138 local void tr_static_init OF((void));
139 local void init_block     OF((deflate_state *s));
140 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
141 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
142 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
143 local void build_tree     OF((deflate_state *s, tree_desc *desc));
144 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
145 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
146 local int  build_bl_tree  OF((deflate_state *s));
147 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
148                               int blcodes));
149 local void compress_block OF((deflate_state *s, const ct_data *ltree,
150                               const ct_data *dtree));
151 local int  detect_data_type OF((deflate_state *s));
152 local unsigned bi_reverse OF((unsigned value, int length));
153 local void bi_windup      OF((deflate_state *s));
154 local void bi_flush       OF((deflate_state *s));
155 
156 #ifdef GEN_TREES_H
157 local void gen_trees_header OF((void));
158 #endif
159 
160 #ifndef ZLIB_DEBUG
161 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
162    /* Send a code of the given tree. c and tree must not have side effects */
163 
164 #else /* !ZLIB_DEBUG */
165 #  define send_code(s, c, tree) \
166      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
167        send_bits(s, tree[c].Code, tree[c].Len); }
168 #endif
169 
170 /* ===========================================================================
171  * Output a short LSB first on the stream.
172  * IN assertion: there is enough room in pendingBuf.
173  */
174 #define put_short(s, w) { \
175     put_byte(s, (uch)((w) & 0xff)); \
176     put_byte(s, (uch)((ush)(w) >> 8)); \
177 }
178 
179 /* ===========================================================================
180  * Send a value on a given number of bits.
181  * IN assertion: length <= 16 and value fits in length bits.
182  */
183 #ifdef ZLIB_DEBUG
184 local void send_bits      OF((deflate_state *s, int value, int length));
185 
send_bits(s,value,length)186 local void send_bits(s, value, length)
187     deflate_state *s;
188     int value;  /* value to send */
189     int length; /* number of bits */
190 {
191     Tracevv((stderr," l %2d v %4x ", length, value));
192     Assert(length > 0 && length <= 15, "invalid length");
193     s->bits_sent += (ulg)length;
194 
195     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
196      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
197      * unused bits in value.
198      */
199     if (s->bi_valid > (int)Buf_size - length) {
200         s->bi_buf |= (ush)value << s->bi_valid;
201         put_short(s, s->bi_buf);
202         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
203         s->bi_valid += length - Buf_size;
204     } else {
205         s->bi_buf |= (ush)value << s->bi_valid;
206         s->bi_valid += length;
207     }
208 }
209 #else /* !ZLIB_DEBUG */
210 
211 #define send_bits(s, value, length) \
212 { int len = length;\
213   if (s->bi_valid > (int)Buf_size - len) {\
214     int val = (int)value;\
215     s->bi_buf |= (ush)val << s->bi_valid;\
216     put_short(s, s->bi_buf);\
217     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
218     s->bi_valid += len - Buf_size;\
219   } else {\
220     s->bi_buf |= (ush)(value) << s->bi_valid;\
221     s->bi_valid += len;\
222   }\
223 }
224 #endif /* ZLIB_DEBUG */
225 
226 
227 /* the arguments must not have side effects */
228 
229 /* ===========================================================================
230  * Initialize the various 'constant' tables.
231  */
tr_static_init()232 local void tr_static_init()
233 {
234 #if defined(GEN_TREES_H) || !defined(STDC)
235     static int static_init_done = 0;
236     int n;        /* iterates over tree elements */
237     int bits;     /* bit counter */
238     int length;   /* length value */
239     int code;     /* code value */
240     int dist;     /* distance index */
241     ush bl_count[MAX_BITS+1];
242     /* number of codes at each bit length for an optimal tree */
243 
244     if (static_init_done) return;
245 
246     /* For some embedded targets, global variables are not initialized: */
247 #ifdef NO_INIT_GLOBAL_POINTERS
248     static_l_desc.static_tree = static_ltree;
249     static_l_desc.extra_bits = extra_lbits;
250     static_d_desc.static_tree = static_dtree;
251     static_d_desc.extra_bits = extra_dbits;
252     static_bl_desc.extra_bits = extra_blbits;
253 #endif
254 
255     /* Initialize the mapping length (0..255) -> length code (0..28) */
256     length = 0;
257     for (code = 0; code < LENGTH_CODES-1; code++) {
258         base_length[code] = length;
259         for (n = 0; n < (1<<extra_lbits[code]); n++) {
260             _length_code[length++] = (uch)code;
261         }
262     }
263     Assert (length == 256, "tr_static_init: length != 256");
264     /* Note that the length 255 (match length 258) can be represented
265      * in two different ways: code 284 + 5 bits or code 285, so we
266      * overwrite length_code[255] to use the best encoding:
267      */
268     _length_code[length-1] = (uch)code;
269 
270     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
271     dist = 0;
272     for (code = 0 ; code < 16; code++) {
273         base_dist[code] = dist;
274         for (n = 0; n < (1<<extra_dbits[code]); n++) {
275             _dist_code[dist++] = (uch)code;
276         }
277     }
278     Assert (dist == 256, "tr_static_init: dist != 256");
279     dist >>= 7; /* from now on, all distances are divided by 128 */
280     for ( ; code < D_CODES; code++) {
281         base_dist[code] = dist << 7;
282         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
283             _dist_code[256 + dist++] = (uch)code;
284         }
285     }
286     Assert (dist == 256, "tr_static_init: 256+dist != 512");
287 
288     /* Construct the codes of the static literal tree */
289     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
290     n = 0;
291     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
292     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
293     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
294     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
295     /* Codes 286 and 287 do not exist, but we must include them in the
296      * tree construction to get a canonical Huffman tree (longest code
297      * all ones)
298      */
299     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
300 
301     /* The static distance tree is trivial: */
302     for (n = 0; n < D_CODES; n++) {
303         static_dtree[n].Len = 5;
304         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
305     }
306     static_init_done = 1;
307 
308 #  ifdef GEN_TREES_H
309     gen_trees_header();
310 #  endif
311 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
312 }
313 
314 /* ===========================================================================
315  * Genererate the file trees.h describing the static trees.
316  */
317 #ifdef GEN_TREES_H
318 #  ifndef ZLIB_DEBUG
319 #    include <stdio.h>
320 #  endif
321 
322 #  define SEPARATOR(i, last, width) \
323       ((i) == (last)? "\n};\n\n" :    \
324        ((i) % (width) == (width)-1 ? ",\n" : ", "))
325 
gen_trees_header()326 void gen_trees_header()
327 {
328     FILE *header = fopen("trees.h", "w");
329     int i;
330 
331     Assert (header != NULL, "Can't open trees.h");
332     fprintf(header,
333             "/* header created automatically with -DGEN_TREES_H */\n\n");
334 
335     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
336     for (i = 0; i < L_CODES+2; i++) {
337         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
338                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
339     }
340 
341     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
342     for (i = 0; i < D_CODES; i++) {
343         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
344                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
345     }
346 
347     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
348     for (i = 0; i < DIST_CODE_LEN; i++) {
349         fprintf(header, "%2u%s", _dist_code[i],
350                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
351     }
352 
353     fprintf(header,
354         "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
355     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
356         fprintf(header, "%2u%s", _length_code[i],
357                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
358     }
359 
360     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
361     for (i = 0; i < LENGTH_CODES; i++) {
362         fprintf(header, "%1u%s", base_length[i],
363                 SEPARATOR(i, LENGTH_CODES-1, 20));
364     }
365 
366     fprintf(header, "local const int base_dist[D_CODES] = {\n");
367     for (i = 0; i < D_CODES; i++) {
368         fprintf(header, "%5u%s", base_dist[i],
369                 SEPARATOR(i, D_CODES-1, 10));
370     }
371 
372     fclose(header);
373 }
374 #endif /* GEN_TREES_H */
375 
376 /* ===========================================================================
377  * Initialize the tree data structures for a new zlib stream.
378  */
_tr_init(s)379 void ZLIB_INTERNAL _tr_init(s)
380     deflate_state *s;
381 {
382     tr_static_init();
383 
384     s->l_desc.dyn_tree = s->dyn_ltree;
385     s->l_desc.stat_desc = &static_l_desc;
386 
387     s->d_desc.dyn_tree = s->dyn_dtree;
388     s->d_desc.stat_desc = &static_d_desc;
389 
390     s->bl_desc.dyn_tree = s->bl_tree;
391     s->bl_desc.stat_desc = &static_bl_desc;
392 
393     s->bi_buf = 0;
394     s->bi_valid = 0;
395 #ifdef ZLIB_DEBUG
396     s->compressed_len = 0L;
397     s->bits_sent = 0L;
398 #endif
399 
400     /* Initialize the first block of the first file: */
401     init_block(s);
402 }
403 
404 /* ===========================================================================
405  * Initialize a new block.
406  */
init_block(s)407 local void init_block(s)
408     deflate_state *s;
409 {
410     int n; /* iterates over tree elements */
411 
412     /* Initialize the trees. */
413     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
414     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
415     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
416 
417     s->dyn_ltree[END_BLOCK].Freq = 1;
418     s->opt_len = s->static_len = 0L;
419     s->last_lit = s->matches = 0;
420 }
421 
422 #define SMALLEST 1
423 /* Index within the heap array of least frequent node in the Huffman tree */
424 
425 
426 /* ===========================================================================
427  * Remove the smallest element from the heap and recreate the heap with
428  * one less element. Updates heap and heap_len.
429  */
430 #define pqremove(s, tree, top) \
431 {\
432     top = s->heap[SMALLEST]; \
433     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
434     pqdownheap(s, tree, SMALLEST); \
435 }
436 
437 /* ===========================================================================
438  * Compares to subtrees, using the tree depth as tie breaker when
439  * the subtrees have equal frequency. This minimizes the worst case length.
440  */
441 #define smaller(tree, n, m, depth) \
442    (tree[n].Freq < tree[m].Freq || \
443    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
444 
445 /* ===========================================================================
446  * Restore the heap property by moving down the tree starting at node k,
447  * exchanging a node with the smallest of its two sons if necessary, stopping
448  * when the heap property is re-established (each father smaller than its
449  * two sons).
450  */
pqdownheap(s,tree,k)451 local void pqdownheap(s, tree, k)
452     deflate_state *s;
453     ct_data *tree;  /* the tree to restore */
454     int k;               /* node to move down */
455 {
456     int v = s->heap[k];
457     int j = k << 1;  /* left son of k */
458     while (j <= s->heap_len) {
459         /* Set j to the smallest of the two sons: */
460         if (j < s->heap_len &&
461             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
462             j++;
463         }
464         /* Exit if v is smaller than both sons */
465         if (smaller(tree, v, s->heap[j], s->depth)) break;
466 
467         /* Exchange v with the smallest son */
468         s->heap[k] = s->heap[j];  k = j;
469 
470         /* And continue down the tree, setting j to the left son of k */
471         j <<= 1;
472     }
473     s->heap[k] = v;
474 }
475 
476 /* ===========================================================================
477  * Compute the optimal bit lengths for a tree and update the total bit length
478  * for the current block.
479  * IN assertion: the fields freq and dad are set, heap[heap_max] and
480  *    above are the tree nodes sorted by increasing frequency.
481  * OUT assertions: the field len is set to the optimal bit length, the
482  *     array bl_count contains the frequencies for each bit length.
483  *     The length opt_len is updated; static_len is also updated if stree is
484  *     not null.
485  */
gen_bitlen(s,desc)486 local void gen_bitlen(s, desc)
487     deflate_state *s;
488     tree_desc *desc;    /* the tree descriptor */
489 {
490     ct_data *tree        = desc->dyn_tree;
491     int max_code         = desc->max_code;
492     const ct_data *stree = desc->stat_desc->static_tree;
493     const intf *extra    = desc->stat_desc->extra_bits;
494     int base             = desc->stat_desc->extra_base;
495     int max_length       = desc->stat_desc->max_length;
496     int h;              /* heap index */
497     int n, m;           /* iterate over the tree elements */
498     int bits;           /* bit length */
499     int xbits;          /* extra bits */
500     ush f;              /* frequency */
501     int overflow = 0;   /* number of elements with bit length too large */
502 
503     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
504 
505     /* In a first pass, compute the optimal bit lengths (which may
506      * overflow in the case of the bit length tree).
507      */
508     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
509 
510     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
511         n = s->heap[h];
512         bits = tree[tree[n].Dad].Len + 1;
513         if (bits > max_length) bits = max_length, overflow++;
514         tree[n].Len = (ush)bits;
515         /* We overwrite tree[n].Dad which is no longer needed */
516 
517         if (n > max_code) continue; /* not a leaf node */
518 
519         s->bl_count[bits]++;
520         xbits = 0;
521         if (n >= base) xbits = extra[n-base];
522         f = tree[n].Freq;
523         s->opt_len += (ulg)f * (unsigned)(bits + xbits);
524         if (stree) s->static_len += (ulg)f * (unsigned)(stree[n].Len + xbits);
525     }
526     if (overflow == 0) return;
527 
528     Tracev((stderr,"\nbit length overflow\n"));
529     /* This happens for example on obj2 and pic of the Calgary corpus */
530 
531     /* Find the first bit length which could increase: */
532     do {
533         bits = max_length-1;
534         while (s->bl_count[bits] == 0) bits--;
535         s->bl_count[bits]--;      /* move one leaf down the tree */
536         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
537         s->bl_count[max_length]--;
538         /* The brother of the overflow item also moves one step up,
539          * but this does not affect bl_count[max_length]
540          */
541         overflow -= 2;
542     } while (overflow > 0);
543 
544     /* Now recompute all bit lengths, scanning in increasing frequency.
545      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
546      * lengths instead of fixing only the wrong ones. This idea is taken
547      * from 'ar' written by Haruhiko Okumura.)
548      */
549     for (bits = max_length; bits != 0; bits--) {
550         n = s->bl_count[bits];
551         while (n != 0) {
552             m = s->heap[--h];
553             if (m > max_code) continue;
554             if ((unsigned) tree[m].Len != (unsigned) bits) {
555                 Tracev((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
556                 s->opt_len += ((ulg)bits - tree[m].Len) * tree[m].Freq;
557                 tree[m].Len = (ush)bits;
558             }
559             n--;
560         }
561     }
562 }
563 
564 /* ===========================================================================
565  * Generate the codes for a given tree and bit counts (which need not be
566  * optimal).
567  * IN assertion: the array bl_count contains the bit length statistics for
568  * the given tree and the field len is set for all tree elements.
569  * OUT assertion: the field code is set for all tree elements of non
570  *     zero code length.
571  */
gen_codes(tree,max_code,bl_count)572 local void gen_codes (tree, max_code, bl_count)
573     ct_data *tree;             /* the tree to decorate */
574     int max_code;              /* largest code with non zero frequency */
575     ushf *bl_count;            /* number of codes at each bit length */
576 {
577     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
578     unsigned code = 0;         /* running code value */
579     int bits;                  /* bit index */
580     int n;                     /* code index */
581 
582     /* The distribution counts are first used to generate the code values
583      * without bit reversal.
584      */
585     for (bits = 1; bits <= MAX_BITS; bits++) {
586         code = (code + bl_count[bits-1]) << 1;
587         next_code[bits] = (ush)code;
588     }
589     /* Check that the bit counts in bl_count are consistent. The last code
590      * must be all ones.
591      */
592     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
593             "inconsistent bit counts");
594     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
595 
596     for (n = 0;  n <= max_code; n++) {
597         int len = tree[n].Len;
598         if (len == 0) continue;
599         /* Now reverse the bits */
600         tree[n].Code = (ush)bi_reverse(next_code[len]++, len);
601 
602         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
603              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
604     }
605 }
606 
607 /* ===========================================================================
608  * Construct one Huffman tree and assigns the code bit strings and lengths.
609  * Update the total bit length for the current block.
610  * IN assertion: the field freq is set for all tree elements.
611  * OUT assertions: the fields len and code are set to the optimal bit length
612  *     and corresponding code. The length opt_len is updated; static_len is
613  *     also updated if stree is not null. The field max_code is set.
614  */
build_tree(s,desc)615 local void build_tree(s, desc)
616     deflate_state *s;
617     tree_desc *desc; /* the tree descriptor */
618 {
619     ct_data *tree         = desc->dyn_tree;
620     const ct_data *stree  = desc->stat_desc->static_tree;
621     int elems             = desc->stat_desc->elems;
622     int n, m;          /* iterate over heap elements */
623     int max_code = -1; /* largest code with non zero frequency */
624     int node;          /* new node being created */
625 
626     /* Construct the initial heap, with least frequent element in
627      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
628      * heap[0] is not used.
629      */
630     s->heap_len = 0, s->heap_max = HEAP_SIZE;
631 
632     for (n = 0; n < elems; n++) {
633         if (tree[n].Freq != 0) {
634             s->heap[++(s->heap_len)] = max_code = n;
635             s->depth[n] = 0;
636         } else {
637             tree[n].Len = 0;
638         }
639     }
640 
641     /* The pkzip format requires that at least one distance code exists,
642      * and that at least one bit should be sent even if there is only one
643      * possible code. So to avoid special checks later on we force at least
644      * two codes of non zero frequency.
645      */
646     while (s->heap_len < 2) {
647         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
648         tree[node].Freq = 1;
649         s->depth[node] = 0;
650         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
651         /* node is 0 or 1 so it does not have extra bits */
652     }
653     desc->max_code = max_code;
654 
655     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
656      * establish sub-heaps of increasing lengths:
657      */
658     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
659 
660     /* Construct the Huffman tree by repeatedly combining the least two
661      * frequent nodes.
662      */
663     node = elems;              /* next internal node of the tree */
664     do {
665         pqremove(s, tree, n);  /* n = node of least frequency */
666         m = s->heap[SMALLEST]; /* m = node of next least frequency */
667 
668         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
669         s->heap[--(s->heap_max)] = m;
670 
671         /* Create a new node father of n and m */
672         tree[node].Freq = tree[n].Freq + tree[m].Freq;
673         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
674                                 s->depth[n] : s->depth[m]) + 1);
675         tree[n].Dad = tree[m].Dad = (ush)node;
676 #ifdef DUMP_BL_TREE
677         if (tree == s->bl_tree) {
678             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
679                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
680         }
681 #endif
682         /* and insert the new node in the heap */
683         s->heap[SMALLEST] = node++;
684         pqdownheap(s, tree, SMALLEST);
685 
686     } while (s->heap_len >= 2);
687 
688     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
689 
690     /* At this point, the fields freq and dad are set. We can now
691      * generate the bit lengths.
692      */
693     gen_bitlen(s, (tree_desc *)desc);
694 
695     /* The field len is now set, we can generate the bit codes */
696     gen_codes ((ct_data *)tree, max_code, s->bl_count);
697 }
698 
699 /* ===========================================================================
700  * Scan a literal or distance tree to determine the frequencies of the codes
701  * in the bit length tree.
702  */
scan_tree(s,tree,max_code)703 local void scan_tree (s, tree, max_code)
704     deflate_state *s;
705     ct_data *tree;   /* the tree to be scanned */
706     int max_code;    /* and its largest code of non zero frequency */
707 {
708     int n;                     /* iterates over all tree elements */
709     int prevlen = -1;          /* last emitted length */
710     int curlen;                /* length of current code */
711     int nextlen = tree[0].Len; /* length of next code */
712     int count = 0;             /* repeat count of the current code */
713     int max_count = 7;         /* max repeat count */
714     int min_count = 4;         /* min repeat count */
715 
716     if (nextlen == 0) max_count = 138, min_count = 3;
717     tree[max_code+1].Len = (ush)0xffff; /* guard */
718 
719     for (n = 0; n <= max_code; n++) {
720         curlen = nextlen; nextlen = tree[n+1].Len;
721         if (++count < max_count && curlen == nextlen) {
722             continue;
723         } else if (count < min_count) {
724             s->bl_tree[curlen].Freq += count;
725         } else if (curlen != 0) {
726             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
727             s->bl_tree[REP_3_6].Freq++;
728         } else if (count <= 10) {
729             s->bl_tree[REPZ_3_10].Freq++;
730         } else {
731             s->bl_tree[REPZ_11_138].Freq++;
732         }
733         count = 0; prevlen = curlen;
734         if (nextlen == 0) {
735             max_count = 138, min_count = 3;
736         } else if (curlen == nextlen) {
737             max_count = 6, min_count = 3;
738         } else {
739             max_count = 7, min_count = 4;
740         }
741     }
742 }
743 
744 /* ===========================================================================
745  * Send a literal or distance tree in compressed form, using the codes in
746  * bl_tree.
747  */
send_tree(s,tree,max_code)748 local void send_tree (s, tree, max_code)
749     deflate_state *s;
750     ct_data *tree; /* the tree to be scanned */
751     int max_code;       /* and its largest code of non zero frequency */
752 {
753     int n;                     /* iterates over all tree elements */
754     int prevlen = -1;          /* last emitted length */
755     int curlen;                /* length of current code */
756     int nextlen = tree[0].Len; /* length of next code */
757     int count = 0;             /* repeat count of the current code */
758     int max_count = 7;         /* max repeat count */
759     int min_count = 4;         /* min repeat count */
760 
761     /* tree[max_code+1].Len = -1; */  /* guard already set */
762     if (nextlen == 0) max_count = 138, min_count = 3;
763 
764     for (n = 0; n <= max_code; n++) {
765         curlen = nextlen; nextlen = tree[n+1].Len;
766         if (++count < max_count && curlen == nextlen) {
767             continue;
768         } else if (count < min_count) {
769             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
770 
771         } else if (curlen != 0) {
772             if (curlen != prevlen) {
773                 send_code(s, curlen, s->bl_tree); count--;
774             }
775             Assert(count >= 3 && count <= 6, " 3_6?");
776             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
777 
778         } else if (count <= 10) {
779             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
780 
781         } else {
782             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
783         }
784         count = 0; prevlen = curlen;
785         if (nextlen == 0) {
786             max_count = 138, min_count = 3;
787         } else if (curlen == nextlen) {
788             max_count = 6, min_count = 3;
789         } else {
790             max_count = 7, min_count = 4;
791         }
792     }
793 }
794 
795 /* ===========================================================================
796  * Construct the Huffman tree for the bit lengths and return the index in
797  * bl_order of the last bit length code to send.
798  */
build_bl_tree(s)799 local int build_bl_tree(s)
800     deflate_state *s;
801 {
802     int max_blindex;  /* index of last bit length code of non zero freq */
803 
804     /* Determine the bit length frequencies for literal and distance trees */
805     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
806     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
807 
808     /* Build the bit length tree: */
809     build_tree(s, (tree_desc *)(&(s->bl_desc)));
810     /* opt_len now includes the length of the tree representations, except
811      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
812      */
813 
814     /* Determine the number of bit length codes to send. The pkzip format
815      * requires that at least 4 bit length codes be sent. (appnote.txt says
816      * 3 but the actual value used is 4.)
817      */
818     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
819         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
820     }
821     /* Update opt_len to include the bit length tree and counts */
822     s->opt_len += 3*((ulg)max_blindex+1) + 5+5+4;
823     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
824             s->opt_len, s->static_len));
825 
826     return max_blindex;
827 }
828 
829 /* ===========================================================================
830  * Send the header for a block using dynamic Huffman trees: the counts, the
831  * lengths of the bit length codes, the literal tree and the distance tree.
832  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
833  */
send_all_trees(s,lcodes,dcodes,blcodes)834 local void send_all_trees(s, lcodes, dcodes, blcodes)
835     deflate_state *s;
836     int lcodes, dcodes, blcodes; /* number of codes for each tree */
837 {
838     int rank;                    /* index in bl_order */
839 
840     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
841     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
842             "too many codes");
843     Tracev((stderr, "\nbl counts: "));
844     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
845     send_bits(s, dcodes-1,   5);
846     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
847     for (rank = 0; rank < blcodes; rank++) {
848         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
849         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
850     }
851     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
852 
853     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
854     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
855 
856     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
857     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
858 }
859 
860 /* ===========================================================================
861  * Send a stored block
862  */
_tr_stored_block(s,buf,stored_len,last)863 void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
864     deflate_state *s;
865     charf *buf;       /* input block */
866     ulg stored_len;   /* length of input block */
867     int last;         /* one if this is the last block for a file */
868 {
869     send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
870     bi_windup(s);        /* align on byte boundary */
871     put_short(s, (ush)stored_len);
872     put_short(s, (ush)~stored_len);
873     zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
874     s->pending += stored_len;
875 #ifdef ZLIB_DEBUG
876     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
877     s->compressed_len += (stored_len + 4) << 3;
878     s->bits_sent += 2*16;
879     s->bits_sent += stored_len<<3;
880 #endif
881 }
882 
883 /* ===========================================================================
884  * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
885  */
_tr_flush_bits(s)886 void ZLIB_INTERNAL _tr_flush_bits(s)
887     deflate_state *s;
888 {
889     bi_flush(s);
890 }
891 
892 /* ===========================================================================
893  * Send one empty static block to give enough lookahead for inflate.
894  * This takes 10 bits, of which 7 may remain in the bit buffer.
895  */
_tr_align(s)896 void ZLIB_INTERNAL _tr_align(s)
897     deflate_state *s;
898 {
899     send_bits(s, STATIC_TREES<<1, 3);
900     send_code(s, END_BLOCK, static_ltree);
901 #ifdef ZLIB_DEBUG
902     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
903 #endif
904     bi_flush(s);
905 }
906 
907 /* ===========================================================================
908  * Determine the best encoding for the current block: dynamic trees, static
909  * trees or store, and write out the encoded block.
910  */
_tr_flush_block(s,buf,stored_len,last)911 void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
912     deflate_state *s;
913     charf *buf;       /* input block, or NULL if too old */
914     ulg stored_len;   /* length of input block */
915     int last;         /* one if this is the last block for a file */
916 {
917     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
918     int max_blindex = 0;  /* index of last bit length code of non zero freq */
919 
920     /* Build the Huffman trees unless a stored block is forced */
921     if (s->level > 0) {
922 
923         /* Check if the file is binary or text */
924         if (s->strm->data_type == Z_UNKNOWN)
925             s->strm->data_type = detect_data_type(s);
926 
927         /* Construct the literal and distance trees */
928         build_tree(s, (tree_desc *)(&(s->l_desc)));
929         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
930                 s->static_len));
931 
932         build_tree(s, (tree_desc *)(&(s->d_desc)));
933         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
934                 s->static_len));
935         /* At this point, opt_len and static_len are the total bit lengths of
936          * the compressed block data, excluding the tree representations.
937          */
938 
939         /* Build the bit length tree for the above two trees, and get the index
940          * in bl_order of the last bit length code to send.
941          */
942         max_blindex = build_bl_tree(s);
943 
944         /* Determine the best encoding. Compute the block lengths in bytes. */
945         opt_lenb = (s->opt_len+3+7)>>3;
946         static_lenb = (s->static_len+3+7)>>3;
947 
948         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
949                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
950                 s->last_lit));
951 
952         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
953 
954     } else {
955         Assert(buf != (char*)0, "lost buf");
956         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
957     }
958 
959 #ifdef FORCE_STORED
960     if (buf != (char*)0) { /* force stored block */
961 #else
962     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
963                        /* 4: two words for the lengths */
964 #endif
965         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
966          * Otherwise we can't have processed more than WSIZE input bytes since
967          * the last block flush, because compression would have been
968          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
969          * transform a block into a stored block.
970          */
971         _tr_stored_block(s, buf, stored_len, last);
972 
973 #ifdef FORCE_STATIC
974     } else if (static_lenb >= 0) { /* force static trees */
975 #else
976     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
977 #endif
978         send_bits(s, (STATIC_TREES<<1)+last, 3);
979         compress_block(s, (const ct_data *)static_ltree,
980                        (const ct_data *)static_dtree);
981 #ifdef ZLIB_DEBUG
982         s->compressed_len += 3 + s->static_len;
983 #endif
984     } else {
985         send_bits(s, (DYN_TREES<<1)+last, 3);
986         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
987                        max_blindex+1);
988         compress_block(s, (const ct_data *)s->dyn_ltree,
989                        (const ct_data *)s->dyn_dtree);
990 #ifdef ZLIB_DEBUG
991         s->compressed_len += 3 + s->opt_len;
992 #endif
993     }
994     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
995     /* The above check is made mod 2^32, for files larger than 512 MB
996      * and uLong implemented on 32 bits.
997      */
998     init_block(s);
999 
1000     if (last) {
1001         bi_windup(s);
1002 #ifdef ZLIB_DEBUG
1003         s->compressed_len += 7;  /* align on byte boundary */
1004 #endif
1005     }
1006     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1007            s->compressed_len-7*last));
1008 }
1009 
1010 /* ===========================================================================
1011  * Save the match info and tally the frequency counts. Return true if
1012  * the current block must be flushed.
1013  */
_tr_tally(s,dist,lc)1014 int ZLIB_INTERNAL _tr_tally (s, dist, lc)
1015     deflate_state *s;
1016     unsigned dist;  /* distance of matched string */
1017     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
1018 {
1019     s->d_buf[s->last_lit] = (ush)dist;
1020     s->l_buf[s->last_lit++] = (uch)lc;
1021     if (dist == 0) {
1022         /* lc is the unmatched char */
1023         s->dyn_ltree[lc].Freq++;
1024     } else {
1025         s->matches++;
1026         /* Here, lc is the match length - MIN_MATCH */
1027         dist--;             /* dist = match distance - 1 */
1028         Assert((ush)dist < (ush)MAX_DIST(s) &&
1029                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1030                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
1031 
1032         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1033         s->dyn_dtree[d_code(dist)].Freq++;
1034     }
1035 
1036 #ifdef TRUNCATE_BLOCK
1037     /* Try to guess if it is profitable to stop the current block here */
1038     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1039         /* Compute an upper bound for the compressed length */
1040         ulg out_length = (ulg)s->last_lit*8L;
1041         ulg in_length = (ulg)((long)s->strstart - s->block_start);
1042         int dcode;
1043         for (dcode = 0; dcode < D_CODES; dcode++) {
1044             out_length += (ulg)s->dyn_dtree[dcode].Freq *
1045                 (5L+extra_dbits[dcode]);
1046         }
1047         out_length >>= 3;
1048         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1049                s->last_lit, in_length, out_length,
1050                100L - out_length*100L/in_length));
1051         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1052     }
1053 #endif
1054     return (s->last_lit == s->lit_bufsize-1);
1055     /* We avoid equality with lit_bufsize because of wraparound at 64K
1056      * on 16 bit machines and because stored blocks are restricted to
1057      * 64K-1 bytes.
1058      */
1059 }
1060 
1061 /* ===========================================================================
1062  * Send the block data compressed using the given Huffman trees
1063  */
compress_block(s,ltree,dtree)1064 local void compress_block(s, ltree, dtree)
1065     deflate_state *s;
1066     const ct_data *ltree; /* literal tree */
1067     const ct_data *dtree; /* distance tree */
1068 {
1069     unsigned dist;      /* distance of matched string */
1070     int lc;             /* match length or unmatched char (if dist == 0) */
1071     unsigned lx = 0;    /* running index in l_buf */
1072     unsigned code;      /* the code to send */
1073     int extra;          /* number of extra bits to send */
1074 
1075     if (s->last_lit != 0) do {
1076         dist = s->d_buf[lx];
1077         lc = s->l_buf[lx++];
1078         if (dist == 0) {
1079             send_code(s, lc, ltree); /* send a literal byte */
1080             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1081         } else {
1082             /* Here, lc is the match length - MIN_MATCH */
1083             code = _length_code[lc];
1084             send_code(s, code+LITERALS+1, ltree); /* send the length code */
1085             extra = extra_lbits[code];
1086             if (extra != 0) {
1087                 lc -= base_length[code];
1088                 send_bits(s, lc, extra);       /* send the extra length bits */
1089             }
1090             dist--; /* dist is now the match distance - 1 */
1091             code = d_code(dist);
1092             Assert (code < D_CODES, "bad d_code");
1093 
1094             send_code(s, code, dtree);       /* send the distance code */
1095             extra = extra_dbits[code];
1096             if (extra != 0) {
1097                 dist -= (unsigned)base_dist[code];
1098                 send_bits(s, dist, extra);   /* send the extra distance bits */
1099             }
1100         } /* literal or match pair ? */
1101 
1102         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1103         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
1104                "pendingBuf overflow");
1105 
1106     } while (lx < s->last_lit);
1107 
1108     send_code(s, END_BLOCK, ltree);
1109 }
1110 
1111 /* ===========================================================================
1112  * Check if the data type is TEXT or BINARY, using the following algorithm:
1113  * - TEXT if the two conditions below are satisfied:
1114  *    a) There are no non-portable control characters belonging to the
1115  *       "black list" (0..6, 14..25, 28..31).
1116  *    b) There is at least one printable character belonging to the
1117  *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
1118  * - BINARY otherwise.
1119  * - The following partially-portable control characters form a
1120  *   "gray list" that is ignored in this detection algorithm:
1121  *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
1122  * IN assertion: the fields Freq of dyn_ltree are set.
1123  */
detect_data_type(s)1124 local int detect_data_type(s)
1125     deflate_state *s;
1126 {
1127     /* black_mask is the bit mask of black-listed bytes
1128      * set bits 0..6, 14..25, and 28..31
1129      * 0xf3ffc07f = binary 11110011111111111100000001111111
1130      */
1131     unsigned long black_mask = 0xf3ffc07fUL;
1132     int n;
1133 
1134     /* Check for non-textual ("black-listed") bytes. */
1135     for (n = 0; n <= 31; n++, black_mask >>= 1)
1136         if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
1137             return Z_BINARY;
1138 
1139     /* Check for textual ("white-listed") bytes. */
1140     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
1141             || s->dyn_ltree[13].Freq != 0)
1142         return Z_TEXT;
1143     for (n = 32; n < LITERALS; n++)
1144         if (s->dyn_ltree[n].Freq != 0)
1145             return Z_TEXT;
1146 
1147     /* There are no "black-listed" or "white-listed" bytes:
1148      * this stream either is empty or has tolerated ("gray-listed") bytes only.
1149      */
1150     return Z_BINARY;
1151 }
1152 
1153 /* ===========================================================================
1154  * Reverse the first len bits of a code, using straightforward code (a faster
1155  * method would use a table)
1156  * IN assertion: 1 <= len <= 15
1157  */
bi_reverse(code,len)1158 local unsigned bi_reverse(code, len)
1159     unsigned code; /* the value to invert */
1160     int len;       /* its bit length */
1161 {
1162     register unsigned res = 0;
1163     do {
1164         res |= code & 1;
1165         code >>= 1, res <<= 1;
1166     } while (--len > 0);
1167     return res >> 1;
1168 }
1169 
1170 /* ===========================================================================
1171  * Flush the bit buffer, keeping at most 7 bits in it.
1172  */
bi_flush(s)1173 local void bi_flush(s)
1174     deflate_state *s;
1175 {
1176     if (s->bi_valid == 16) {
1177         put_short(s, s->bi_buf);
1178         s->bi_buf = 0;
1179         s->bi_valid = 0;
1180     } else if (s->bi_valid >= 8) {
1181         put_byte(s, (Byte)s->bi_buf);
1182         s->bi_buf >>= 8;
1183         s->bi_valid -= 8;
1184     }
1185 }
1186 
1187 /* ===========================================================================
1188  * Flush the bit buffer and align the output on a byte boundary
1189  */
bi_windup(s)1190 local void bi_windup(s)
1191     deflate_state *s;
1192 {
1193     if (s->bi_valid > 8) {
1194         put_short(s, s->bi_buf);
1195     } else if (s->bi_valid > 0) {
1196         put_byte(s, (Byte)s->bi_buf);
1197     }
1198     s->bi_buf = 0;
1199     s->bi_valid = 0;
1200 #ifdef ZLIB_DEBUG
1201     s->bits_sent = (s->bits_sent+7) & ~7;
1202 #endif
1203 }
1204