1 /* trees.c -- output deflated data using Huffman coding
2  * Copyright (C) 1995-2005 Jean-loup Gailly
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5 
6 /*
7  *  ALGORITHM
8  *
9  *      The "deflation" process uses several Huffman trees. The more
10  *      common source values are represented by shorter bit sequences.
11  *
12  *      Each code tree is stored in a compressed form which is itself
13  * a Huffman encoding of the lengths of all the code strings (in
14  * ascending order by source values).  The actual code strings are
15  * reconstructed from the lengths in the inflate process, as described
16  * in the deflate specification.
17  *
18  *  REFERENCES
19  *
20  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
21  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
22  *
23  *      Storer, James A.
24  *          Data Compression:  Methods and Theory, pp. 49-50.
25  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
26  *
27  *      Sedgewick, R.
28  *          Algorithms, p290.
29  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
30  */
31 
32 /* @(#) $Id$ */
33 
34 /* #define GEN_TREES_H */
35 
36 #include "deflate.h"
37 
38 #ifdef DEBUG
39 #  include <ctype.h>
40 #endif
41 
42 /* ===========================================================================
43  * Constants
44  */
45 
46 #define MAX_BL_BITS 7
47 /* Bit length codes must not exceed MAX_BL_BITS bits */
48 
49 #define END_BLOCK 256
50 /* end of block literal code */
51 
52 #define REP_3_6      16
53 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
54 
55 #define REPZ_3_10    17
56 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
57 
58 #define REPZ_11_138  18
59 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
60 
61 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
62    = {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};
63 
64 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
65    = {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};
66 
67 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
68    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
69 
70 local const uch bl_order[BL_CODES]
71    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
72 /* The lengths of the bit length codes are sent in order of decreasing
73  * probability, to avoid transmitting the lengths for unused bit length codes.
74  */
75 
76 #define Buf_size (8 * 2*sizeof(char))
77 /* Number of bits used within bi_buf. (bi_buf might be implemented on
78  * more than 16 bits on some systems.)
79  */
80 
81 /* ===========================================================================
82  * Local data. These are initialized only once.
83  */
84 
85 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
86 
87 #if defined(GEN_TREES_H) || !defined(STDC)
88 /* non ANSI compilers may not accept trees.h */
89 
90 local ct_data static_ltree[L_CODES+2];
91 /* The static literal tree. Since the bit lengths are imposed, there is no
92  * need for the L_CODES extra codes used during heap construction. However
93  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
94  * below).
95  */
96 
97 local ct_data static_dtree[D_CODES];
98 /* The static distance tree. (Actually a trivial tree since all codes use
99  * 5 bits.)
100  */
101 
102 uch _dist_code[DIST_CODE_LEN];
103 /* Distance codes. The first 256 values correspond to the distances
104  * 3 .. 258, the last 256 values correspond to the top 8 bits of
105  * the 15 bit distances.
106  */
107 
108 uch _length_code[MAX_MATCH-MIN_MATCH+1];
109 /* length code for each normalized match length (0 == MIN_MATCH) */
110 
111 local int base_length[LENGTH_CODES];
112 /* First normalized length for each code (0 = MIN_MATCH) */
113 
114 local int base_dist[D_CODES];
115 /* First normalized distance for each code (0 = distance of 1) */
116 
117 #else
118 #  include "trees.h"
119 #endif /* GEN_TREES_H */
120 
121 struct static_tree_desc_s {
122     const ct_data *static_tree;  /* static tree or NULL */
123     const intf *extra_bits;      /* extra bits for each code or NULL */
124     int     extra_base;          /* base index for extra_bits */
125     int     elems;               /* max number of elements in the tree */
126     int     max_length;          /* max bit length for the codes */
127 };
128 
129 local static_tree_desc  static_l_desc =
130 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
131 
132 local static_tree_desc  static_d_desc =
133 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
134 
135 local static_tree_desc  static_bl_desc =
136 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
137 
138 /* ===========================================================================
139  * Local (static) routines in this file.
140  */
141 
142 local void tr_static_init OF((void));
143 local void init_block     OF((deflate_state *s));
144 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
145 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
146 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
147 local void build_tree     OF((deflate_state *s, tree_desc *desc));
148 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
149 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
150 local int  build_bl_tree  OF((deflate_state *s));
151 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
152                               int blcodes));
153 local void compress_block OF((deflate_state *s, ct_data *ltree,
154                               ct_data *dtree));
155 local void set_data_type  OF((deflate_state *s));
156 local unsigned bi_reverse OF((unsigned value, int length));
157 local void bi_windup      OF((deflate_state *s));
158 local void bi_flush       OF((deflate_state *s));
159 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
160                               int header));
161 
162 #ifdef GEN_TREES_H
163 local void gen_trees_header OF((void));
164 #endif
165 
166 #ifndef DEBUG
167 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
168    /* Send a code of the given tree. c and tree must not have side effects */
169 
170 #else /* DEBUG */
171 #  define send_code(s, c, tree) \
172      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
173        send_bits(s, tree[c].Code, tree[c].Len); }
174 #endif
175 
176 /* ===========================================================================
177  * Output a short LSB first on the stream.
178  * IN assertion: there is enough room in pendingBuf.
179  */
180 #define put_short(s, w) { \
181     put_byte(s, (uch)((w) & 0xff)); \
182     put_byte(s, (uch)((ush)(w) >> 8)); \
183 }
184 
185 /* ===========================================================================
186  * Send a value on a given number of bits.
187  * IN assertion: length <= 16 and value fits in length bits.
188  */
189 #ifdef DEBUG
190 local void send_bits      OF((deflate_state *s, int value, int length));
191 
send_bits(s,value,length)192 local void send_bits(s, value, length)
193     deflate_state *s;
194     int value;  /* value to send */
195     int length; /* number of bits */
196 {
197     Tracevv((stderr," l %2d v %4x ", length, value));
198     Assert(length > 0 && length <= 15, "invalid length");
199     s->bits_sent += (ulg)length;
200 
201     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
202      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
203      * unused bits in value.
204      */
205     if (s->bi_valid > (int)Buf_size - length) {
206         s->bi_buf |= (value << s->bi_valid);
207         put_short(s, s->bi_buf);
208         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
209         s->bi_valid += length - Buf_size;
210     } else {
211         s->bi_buf |= value << s->bi_valid;
212         s->bi_valid += length;
213     }
214 }
215 #else /* !DEBUG */
216 
217 #define send_bits(s, value, length) \
218 { int len = length;\
219   if (s->bi_valid > (int)Buf_size - len) {\
220     int val = value;\
221     s->bi_buf |= (val << s->bi_valid);\
222     put_short(s, s->bi_buf);\
223     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
224     s->bi_valid += len - Buf_size;\
225   } else {\
226     s->bi_buf |= (value) << s->bi_valid;\
227     s->bi_valid += len;\
228   }\
229 }
230 #endif /* DEBUG */
231 
232 
233 /* the arguments must not have side effects */
234 
235 /* ===========================================================================
236  * Initialize the various 'constant' tables.
237  */
tr_static_init()238 local void tr_static_init()
239 {
240 #if defined(GEN_TREES_H) || !defined(STDC)
241     static int static_init_done = 0;
242     int n;        /* iterates over tree elements */
243     int bits;     /* bit counter */
244     int length;   /* length value */
245     int code;     /* code value */
246     int dist;     /* distance index */
247     ush bl_count[MAX_BITS+1];
248     /* number of codes at each bit length for an optimal tree */
249 
250     if (static_init_done) return;
251 
252     /* For some embedded targets, global variables are not initialized: */
253     static_l_desc.static_tree = static_ltree;
254     static_l_desc.extra_bits = extra_lbits;
255     static_d_desc.static_tree = static_dtree;
256     static_d_desc.extra_bits = extra_dbits;
257     static_bl_desc.extra_bits = extra_blbits;
258 
259     /* Initialize the mapping length (0..255) -> length code (0..28) */
260     length = 0;
261     for (code = 0; code < LENGTH_CODES-1; code++) {
262         base_length[code] = length;
263         for (n = 0; n < (1<<extra_lbits[code]); n++) {
264             _length_code[length++] = (uch)code;
265         }
266     }
267     Assert (length == 256, "tr_static_init: length != 256");
268     /* Note that the length 255 (match length 258) can be represented
269      * in two different ways: code 284 + 5 bits or code 285, so we
270      * overwrite length_code[255] to use the best encoding:
271      */
272     _length_code[length-1] = (uch)code;
273 
274     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
275     dist = 0;
276     for (code = 0 ; code < 16; code++) {
277         base_dist[code] = dist;
278         for (n = 0; n < (1<<extra_dbits[code]); n++) {
279             _dist_code[dist++] = (uch)code;
280         }
281     }
282     Assert (dist == 256, "tr_static_init: dist != 256");
283     dist >>= 7; /* from now on, all distances are divided by 128 */
284     for ( ; code < D_CODES; code++) {
285         base_dist[code] = dist << 7;
286         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
287             _dist_code[256 + dist++] = (uch)code;
288         }
289     }
290     Assert (dist == 256, "tr_static_init: 256+dist != 512");
291 
292     /* Construct the codes of the static literal tree */
293     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
294     n = 0;
295     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
296     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
297     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
298     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
299     /* Codes 286 and 287 do not exist, but we must include them in the
300      * tree construction to get a canonical Huffman tree (longest code
301      * all ones)
302      */
303     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
304 
305     /* The static distance tree is trivial: */
306     for (n = 0; n < D_CODES; n++) {
307         static_dtree[n].Len = 5;
308         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
309     }
310     static_init_done = 1;
311 
312 #  ifdef GEN_TREES_H
313     gen_trees_header();
314 #  endif
315 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
316 }
317 
318 /* ===========================================================================
319  * Genererate the file trees.h describing the static trees.
320  */
321 #ifdef GEN_TREES_H
322 #  ifndef DEBUG
323 #    include <stdio.h>
324 #  endif
325 
326 #  define SEPARATOR(i, last, width) \
327       ((i) == (last)? "\n};\n\n" :    \
328        ((i) % (width) == (width)-1 ? ",\n" : ", "))
329 
gen_trees_header()330 void gen_trees_header()
331 {
332     FILE *header = fopen("trees.h", "w");
333     int i;
334 
335     Assert (header != NULL, "Can't open trees.h");
336     fprintf(header,
337             "/* header created automatically with -DGEN_TREES_H */\n\n");
338 
339     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
340     for (i = 0; i < L_CODES+2; i++) {
341         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
342                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
343     }
344 
345     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
346     for (i = 0; i < D_CODES; i++) {
347         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
348                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
349     }
350 
351     fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
352     for (i = 0; i < DIST_CODE_LEN; i++) {
353         fprintf(header, "%2u%s", _dist_code[i],
354                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
355     }
356 
357     fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
358     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
359         fprintf(header, "%2u%s", _length_code[i],
360                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
361     }
362 
363     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
364     for (i = 0; i < LENGTH_CODES; i++) {
365         fprintf(header, "%1u%s", base_length[i],
366                 SEPARATOR(i, LENGTH_CODES-1, 20));
367     }
368 
369     fprintf(header, "local const int base_dist[D_CODES] = {\n");
370     for (i = 0; i < D_CODES; i++) {
371         fprintf(header, "%5u%s", base_dist[i],
372                 SEPARATOR(i, D_CODES-1, 10));
373     }
374 
375     fclose(header);
376 }
377 #endif /* GEN_TREES_H */
378 
379 /* ===========================================================================
380  * Initialize the tree data structures for a new zlib stream.
381  */
_tr_init(s)382 void _tr_init(s)
383     deflate_state *s;
384 {
385     tr_static_init();
386 
387     s->l_desc.dyn_tree = s->dyn_ltree;
388     s->l_desc.stat_desc = &static_l_desc;
389 
390     s->d_desc.dyn_tree = s->dyn_dtree;
391     s->d_desc.stat_desc = &static_d_desc;
392 
393     s->bl_desc.dyn_tree = s->bl_tree;
394     s->bl_desc.stat_desc = &static_bl_desc;
395 
396     s->bi_buf = 0;
397     s->bi_valid = 0;
398     s->last_eob_len = 8; /* enough lookahead for inflate */
399 #ifdef DEBUG
400     s->compressed_len = 0L;
401     s->bits_sent = 0L;
402 #endif
403 
404     /* Initialize the first block of the first file: */
405     init_block(s);
406 }
407 
408 /* ===========================================================================
409  * Initialize a new block.
410  */
init_block(s)411 local void init_block(s)
412     deflate_state *s;
413 {
414     int n; /* iterates over tree elements */
415 
416     /* Initialize the trees. */
417     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
418     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
419     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
420 
421     s->dyn_ltree[END_BLOCK].Freq = 1;
422     s->opt_len = s->static_len = 0L;
423     s->last_lit = s->matches = 0;
424 }
425 
426 #define SMALLEST 1
427 /* Index within the heap array of least frequent node in the Huffman tree */
428 
429 
430 /* ===========================================================================
431  * Remove the smallest element from the heap and recreate the heap with
432  * one less element. Updates heap and heap_len.
433  */
434 #define pqremove(s, tree, top) \
435 {\
436     top = s->heap[SMALLEST]; \
437     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
438     pqdownheap(s, tree, SMALLEST); \
439 }
440 
441 /* ===========================================================================
442  * Compares to subtrees, using the tree depth as tie breaker when
443  * the subtrees have equal frequency. This minimizes the worst case length.
444  */
445 #define smaller(tree, n, m, depth) \
446    (tree[n].Freq < tree[m].Freq || \
447    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
448 
449 /* ===========================================================================
450  * Restore the heap property by moving down the tree starting at node k,
451  * exchanging a node with the smallest of its two sons if necessary, stopping
452  * when the heap property is re-established (each father smaller than its
453  * two sons).
454  */
pqdownheap(s,tree,k)455 local void pqdownheap(s, tree, k)
456     deflate_state *s;
457     ct_data *tree;  /* the tree to restore */
458     int k;               /* node to move down */
459 {
460     int v = s->heap[k];
461     int j = k << 1;  /* left son of k */
462     while (j <= s->heap_len) {
463         /* Set j to the smallest of the two sons: */
464         if (j < s->heap_len &&
465             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
466             j++;
467         }
468         /* Exit if v is smaller than both sons */
469         if (smaller(tree, v, s->heap[j], s->depth)) break;
470 
471         /* Exchange v with the smallest son */
472         s->heap[k] = s->heap[j];  k = j;
473 
474         /* And continue down the tree, setting j to the left son of k */
475         j <<= 1;
476     }
477     s->heap[k] = v;
478 }
479 
480 /* ===========================================================================
481  * Compute the optimal bit lengths for a tree and update the total bit length
482  * for the current block.
483  * IN assertion: the fields freq and dad are set, heap[heap_max] and
484  *    above are the tree nodes sorted by increasing frequency.
485  * OUT assertions: the field len is set to the optimal bit length, the
486  *     array bl_count contains the frequencies for each bit length.
487  *     The length opt_len is updated; static_len is also updated if stree is
488  *     not null.
489  */
gen_bitlen(s,desc)490 local void gen_bitlen(s, desc)
491     deflate_state *s;
492     tree_desc *desc;    /* the tree descriptor */
493 {
494     ct_data *tree        = desc->dyn_tree;
495     int max_code         = desc->max_code;
496     const ct_data *stree = desc->stat_desc->static_tree;
497     const intf *extra    = desc->stat_desc->extra_bits;
498     int base             = desc->stat_desc->extra_base;
499     int max_length       = desc->stat_desc->max_length;
500     int h;              /* heap index */
501     int n, m;           /* iterate over the tree elements */
502     int bits;           /* bit length */
503     int xbits;          /* extra bits */
504     ush f;              /* frequency */
505     int overflow = 0;   /* number of elements with bit length too large */
506 
507     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
508 
509     /* In a first pass, compute the optimal bit lengths (which may
510      * overflow in the case of the bit length tree).
511      */
512     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
513 
514     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
515         n = s->heap[h];
516         bits = tree[tree[n].Dad].Len + 1;
517         if (bits > max_length) bits = max_length, overflow++;
518         tree[n].Len = (ush)bits;
519         /* We overwrite tree[n].Dad which is no longer needed */
520 
521         if (n > max_code) continue; /* not a leaf node */
522 
523         s->bl_count[bits]++;
524         xbits = 0;
525         if (n >= base) xbits = extra[n-base];
526         f = tree[n].Freq;
527         s->opt_len += (ulg)f * (bits + xbits);
528         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
529     }
530     if (overflow == 0) return;
531 
532     Trace((stderr,"\nbit length overflow\n"));
533     /* This happens for example on obj2 and pic of the Calgary corpus */
534 
535     /* Find the first bit length which could increase: */
536     do {
537         bits = max_length-1;
538         while (s->bl_count[bits] == 0) bits--;
539         s->bl_count[bits]--;      /* move one leaf down the tree */
540         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
541         s->bl_count[max_length]--;
542         /* The brother of the overflow item also moves one step up,
543          * but this does not affect bl_count[max_length]
544          */
545         overflow -= 2;
546     } while (overflow > 0);
547 
548     /* Now recompute all bit lengths, scanning in increasing frequency.
549      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
550      * lengths instead of fixing only the wrong ones. This idea is taken
551      * from 'ar' written by Haruhiko Okumura.)
552      */
553     for (bits = max_length; bits != 0; bits--) {
554         n = s->bl_count[bits];
555         while (n != 0) {
556             m = s->heap[--h];
557             if (m > max_code) continue;
558             if ((unsigned) tree[m].Len != (unsigned) bits) {
559                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
560                 s->opt_len += ((long)bits - (long)tree[m].Len)
561                               *(long)tree[m].Freq;
562                 tree[m].Len = (ush)bits;
563             }
564             n--;
565         }
566     }
567 }
568 
569 /* ===========================================================================
570  * Generate the codes for a given tree and bit counts (which need not be
571  * optimal).
572  * IN assertion: the array bl_count contains the bit length statistics for
573  * the given tree and the field len is set for all tree elements.
574  * OUT assertion: the field code is set for all tree elements of non
575  *     zero code length.
576  */
gen_codes(tree,max_code,bl_count)577 local void gen_codes (tree, max_code, bl_count)
578     ct_data *tree;             /* the tree to decorate */
579     int max_code;              /* largest code with non zero frequency */
580     ushf *bl_count;            /* number of codes at each bit length */
581 {
582     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
583     ush code = 0;              /* running code value */
584     int bits;                  /* bit index */
585     int n;                     /* code index */
586 
587     /* The distribution counts are first used to generate the code values
588      * without bit reversal.
589      */
590     for (bits = 1; bits <= MAX_BITS; bits++) {
591         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
592     }
593     /* Check that the bit counts in bl_count are consistent. The last code
594      * must be all ones.
595      */
596     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
597             "inconsistent bit counts");
598     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
599 
600     for (n = 0;  n <= max_code; n++) {
601         int len = tree[n].Len;
602         if (len == 0) continue;
603         /* Now reverse the bits */
604         tree[n].Code = bi_reverse(next_code[len]++, len);
605 
606         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
607              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
608     }
609 }
610 
611 /* ===========================================================================
612  * Construct one Huffman tree and assigns the code bit strings and lengths.
613  * Update the total bit length for the current block.
614  * IN assertion: the field freq is set for all tree elements.
615  * OUT assertions: the fields len and code are set to the optimal bit length
616  *     and corresponding code. The length opt_len is updated; static_len is
617  *     also updated if stree is not null. The field max_code is set.
618  */
build_tree(s,desc)619 local void build_tree(s, desc)
620     deflate_state *s;
621     tree_desc *desc; /* the tree descriptor */
622 {
623     ct_data *tree         = desc->dyn_tree;
624     const ct_data *stree  = desc->stat_desc->static_tree;
625     int elems             = desc->stat_desc->elems;
626     int n, m;          /* iterate over heap elements */
627     int max_code = -1; /* largest code with non zero frequency */
628     int node;          /* new node being created */
629 
630     /* Construct the initial heap, with least frequent element in
631      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
632      * heap[0] is not used.
633      */
634     s->heap_len = 0, s->heap_max = HEAP_SIZE;
635 
636     for (n = 0; n < elems; n++) {
637         if (tree[n].Freq != 0) {
638             s->heap[++(s->heap_len)] = max_code = n;
639             s->depth[n] = 0;
640         } else {
641             tree[n].Len = 0;
642         }
643     }
644 
645     /* The pkzip format requires that at least one distance code exists,
646      * and that at least one bit should be sent even if there is only one
647      * possible code. So to avoid special checks later on we force at least
648      * two codes of non zero frequency.
649      */
650     while (s->heap_len < 2) {
651         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
652         tree[node].Freq = 1;
653         s->depth[node] = 0;
654         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
655         /* node is 0 or 1 so it does not have extra bits */
656     }
657     desc->max_code = max_code;
658 
659     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
660      * establish sub-heaps of increasing lengths:
661      */
662     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
663 
664     /* Construct the Huffman tree by repeatedly combining the least two
665      * frequent nodes.
666      */
667     node = elems;              /* next internal node of the tree */
668     do {
669         pqremove(s, tree, n);  /* n = node of least frequency */
670         m = s->heap[SMALLEST]; /* m = node of next least frequency */
671 
672         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
673         s->heap[--(s->heap_max)] = m;
674 
675         /* Create a new node father of n and m */
676         tree[node].Freq = tree[n].Freq + tree[m].Freq;
677         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
678                                 s->depth[n] : s->depth[m]) + 1);
679         tree[n].Dad = tree[m].Dad = (ush)node;
680 #ifdef DUMP_BL_TREE
681         if (tree == s->bl_tree) {
682             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
683                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
684         }
685 #endif
686         /* and insert the new node in the heap */
687         s->heap[SMALLEST] = node++;
688         pqdownheap(s, tree, SMALLEST);
689 
690     } while (s->heap_len >= 2);
691 
692     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
693 
694     /* At this point, the fields freq and dad are set. We can now
695      * generate the bit lengths.
696      */
697     gen_bitlen(s, (tree_desc *)desc);
698 
699     /* The field len is now set, we can generate the bit codes */
700     gen_codes ((ct_data *)tree, max_code, s->bl_count);
701 }
702 
703 /* ===========================================================================
704  * Scan a literal or distance tree to determine the frequencies of the codes
705  * in the bit length tree.
706  */
scan_tree(s,tree,max_code)707 local void scan_tree (s, tree, max_code)
708     deflate_state *s;
709     ct_data *tree;   /* the tree to be scanned */
710     int max_code;    /* and its largest code of non zero frequency */
711 {
712     int n;                     /* iterates over all tree elements */
713     int prevlen = -1;          /* last emitted length */
714     int curlen;                /* length of current code */
715     int nextlen = tree[0].Len; /* length of next code */
716     int count = 0;             /* repeat count of the current code */
717     int max_count = 7;         /* max repeat count */
718     int min_count = 4;         /* min repeat count */
719 
720     if (nextlen == 0) max_count = 138, min_count = 3;
721     tree[max_code+1].Len = (ush)0xffff; /* guard */
722 
723     for (n = 0; n <= max_code; n++) {
724         curlen = nextlen; nextlen = tree[n+1].Len;
725         if (++count < max_count && curlen == nextlen) {
726             continue;
727         } else if (count < min_count) {
728             s->bl_tree[curlen].Freq += count;
729         } else if (curlen != 0) {
730             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
731             s->bl_tree[REP_3_6].Freq++;
732         } else if (count <= 10) {
733             s->bl_tree[REPZ_3_10].Freq++;
734         } else {
735             s->bl_tree[REPZ_11_138].Freq++;
736         }
737         count = 0; prevlen = curlen;
738         if (nextlen == 0) {
739             max_count = 138, min_count = 3;
740         } else if (curlen == nextlen) {
741             max_count = 6, min_count = 3;
742         } else {
743             max_count = 7, min_count = 4;
744         }
745     }
746 }
747 
748 /* ===========================================================================
749  * Send a literal or distance tree in compressed form, using the codes in
750  * bl_tree.
751  */
send_tree(s,tree,max_code)752 local void send_tree (s, tree, max_code)
753     deflate_state *s;
754     ct_data *tree; /* the tree to be scanned */
755     int max_code;       /* and its largest code of non zero frequency */
756 {
757     int n;                     /* iterates over all tree elements */
758     int prevlen = -1;          /* last emitted length */
759     int curlen;                /* length of current code */
760     int nextlen = tree[0].Len; /* length of next code */
761     int count = 0;             /* repeat count of the current code */
762     int max_count = 7;         /* max repeat count */
763     int min_count = 4;         /* min repeat count */
764 
765     /* tree[max_code+1].Len = -1; */  /* guard already set */
766     if (nextlen == 0) max_count = 138, min_count = 3;
767 
768     for (n = 0; n <= max_code; n++) {
769         curlen = nextlen; nextlen = tree[n+1].Len;
770         if (++count < max_count && curlen == nextlen) {
771             continue;
772         } else if (count < min_count) {
773             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
774 
775         } else if (curlen != 0) {
776             if (curlen != prevlen) {
777                 send_code(s, curlen, s->bl_tree); count--;
778             }
779             Assert(count >= 3 && count <= 6, " 3_6?");
780             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
781 
782         } else if (count <= 10) {
783             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
784 
785         } else {
786             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
787         }
788         count = 0; prevlen = curlen;
789         if (nextlen == 0) {
790             max_count = 138, min_count = 3;
791         } else if (curlen == nextlen) {
792             max_count = 6, min_count = 3;
793         } else {
794             max_count = 7, min_count = 4;
795         }
796     }
797 }
798 
799 /* ===========================================================================
800  * Construct the Huffman tree for the bit lengths and return the index in
801  * bl_order of the last bit length code to send.
802  */
build_bl_tree(s)803 local int build_bl_tree(s)
804     deflate_state *s;
805 {
806     int max_blindex;  /* index of last bit length code of non zero freq */
807 
808     /* Determine the bit length frequencies for literal and distance trees */
809     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
810     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
811 
812     /* Build the bit length tree: */
813     build_tree(s, (tree_desc *)(&(s->bl_desc)));
814     /* opt_len now includes the length of the tree representations, except
815      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
816      */
817 
818     /* Determine the number of bit length codes to send. The pkzip format
819      * requires that at least 4 bit length codes be sent. (appnote.txt says
820      * 3 but the actual value used is 4.)
821      */
822     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
823         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
824     }
825     /* Update opt_len to include the bit length tree and counts */
826     s->opt_len += 3*(max_blindex+1) + 5+5+4;
827     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
828             s->opt_len, s->static_len));
829 
830     return max_blindex;
831 }
832 
833 /* ===========================================================================
834  * Send the header for a block using dynamic Huffman trees: the counts, the
835  * lengths of the bit length codes, the literal tree and the distance tree.
836  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
837  */
send_all_trees(s,lcodes,dcodes,blcodes)838 local void send_all_trees(s, lcodes, dcodes, blcodes)
839     deflate_state *s;
840     int lcodes, dcodes, blcodes; /* number of codes for each tree */
841 {
842     int rank;                    /* index in bl_order */
843 
844     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
845     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
846             "too many codes");
847     Tracev((stderr, "\nbl counts: "));
848     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
849     send_bits(s, dcodes-1,   5);
850     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
851     for (rank = 0; rank < blcodes; rank++) {
852         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
853         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
854     }
855     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
856 
857     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
858     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
859 
860     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
861     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
862 }
863 
864 /* ===========================================================================
865  * Send a stored block
866  */
_tr_stored_block(s,buf,stored_len,eof)867 void _tr_stored_block(s, buf, stored_len, eof)
868     deflate_state *s;
869     charf *buf;       /* input block */
870     ulg stored_len;   /* length of input block */
871     int eof;          /* true if this is the last block for a file */
872 {
873     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
874 #ifdef DEBUG
875     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
876     s->compressed_len += (stored_len + 4) << 3;
877 #endif
878     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
879 }
880 
881 /* ===========================================================================
882  * Send one empty static block to give enough lookahead for inflate.
883  * This takes 10 bits, of which 7 may remain in the bit buffer.
884  * The current inflate code requires 9 bits of lookahead. If the
885  * last two codes for the previous block (real code plus EOB) were coded
886  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
887  * the last real code. In this case we send two empty static blocks instead
888  * of one. (There are no problems if the previous block is stored or fixed.)
889  * To simplify the code, we assume the worst case of last real code encoded
890  * on one bit only.
891  */
_tr_align(s)892 void _tr_align(s)
893     deflate_state *s;
894 {
895     send_bits(s, STATIC_TREES<<1, 3);
896     send_code(s, END_BLOCK, static_ltree);
897 #ifdef DEBUG
898     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
899 #endif
900     bi_flush(s);
901     /* Of the 10 bits for the empty block, we have already sent
902      * (10 - bi_valid) bits. The lookahead for the last real code (before
903      * the EOB of the previous block) was thus at least one plus the length
904      * of the EOB plus what we have just sent of the empty static block.
905      */
906     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
907         send_bits(s, STATIC_TREES<<1, 3);
908         send_code(s, END_BLOCK, static_ltree);
909 #ifdef DEBUG
910         s->compressed_len += 10L;
911 #endif
912         bi_flush(s);
913     }
914     s->last_eob_len = 7;
915 }
916 
917 /* ===========================================================================
918  * Determine the best encoding for the current block: dynamic trees, static
919  * trees or store, and output the encoded block to the zip file.
920  */
_tr_flush_block(s,buf,stored_len,eof)921 void _tr_flush_block(s, buf, stored_len, eof)
922     deflate_state *s;
923     charf *buf;       /* input block, or NULL if too old */
924     ulg stored_len;   /* length of input block */
925     int eof;          /* true if this is the last block for a file */
926 {
927     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
928     int max_blindex = 0;  /* index of last bit length code of non zero freq */
929 
930     /* Build the Huffman trees unless a stored block is forced */
931     if (s->level > 0) {
932 
933         /* Check if the file is binary or text */
934         if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN)
935             set_data_type(s);
936 
937         /* Construct the literal and distance trees */
938         build_tree(s, (tree_desc *)(&(s->l_desc)));
939         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
940                 s->static_len));
941 
942         build_tree(s, (tree_desc *)(&(s->d_desc)));
943         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
944                 s->static_len));
945         /* At this point, opt_len and static_len are the total bit lengths of
946          * the compressed block data, excluding the tree representations.
947          */
948 
949         /* Build the bit length tree for the above two trees, and get the index
950          * in bl_order of the last bit length code to send.
951          */
952         max_blindex = build_bl_tree(s);
953 
954         /* Determine the best encoding. Compute the block lengths in bytes. */
955         opt_lenb = (s->opt_len+3+7)>>3;
956         static_lenb = (s->static_len+3+7)>>3;
957 
958         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
959                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
960                 s->last_lit));
961 
962         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
963 
964     } else {
965         Assert(buf != (char*)0, "lost buf");
966         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
967     }
968 
969 #ifdef FORCE_STORED
970     if (buf != (char*)0) { /* force stored block */
971 #else
972     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
973                        /* 4: two words for the lengths */
974 #endif
975         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
976          * Otherwise we can't have processed more than WSIZE input bytes since
977          * the last block flush, because compression would have been
978          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
979          * transform a block into a stored block.
980          */
981         _tr_stored_block(s, buf, stored_len, eof);
982 
983 #ifdef FORCE_STATIC
984     } else if (static_lenb >= 0) { /* force static trees */
985 #else
986     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
987 #endif
988         send_bits(s, (STATIC_TREES<<1)+eof, 3);
989         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
990 #ifdef DEBUG
991         s->compressed_len += 3 + s->static_len;
992 #endif
993     } else {
994         send_bits(s, (DYN_TREES<<1)+eof, 3);
995         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
996                        max_blindex+1);
997         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
998 #ifdef DEBUG
999         s->compressed_len += 3 + s->opt_len;
1000 #endif
1001     }
1002     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
1003     /* The above check is made mod 2^32, for files larger than 512 MB
1004      * and uLong implemented on 32 bits.
1005      */
1006     init_block(s);
1007 
1008     if (eof) {
1009         bi_windup(s);
1010 #ifdef DEBUG
1011         s->compressed_len += 7;  /* align on byte boundary */
1012 #endif
1013     }
1014     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1015            s->compressed_len-7*eof));
1016 }
1017 
1018 /* ===========================================================================
1019  * Save the match info and tally the frequency counts. Return true if
1020  * the current block must be flushed.
1021  */
_tr_tally(s,dist,lc)1022 int _tr_tally (s, dist, lc)
1023     deflate_state *s;
1024     unsigned dist;  /* distance of matched string */
1025     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
1026 {
1027     s->d_buf[s->last_lit] = (ush)dist;
1028     s->l_buf[s->last_lit++] = (uch)lc;
1029     if (dist == 0) {
1030         /* lc is the unmatched char */
1031         s->dyn_ltree[lc].Freq++;
1032     } else {
1033         s->matches++;
1034         /* Here, lc is the match length - MIN_MATCH */
1035         dist--;             /* dist = match distance - 1 */
1036         Assert((ush)dist < (ush)MAX_DIST(s) &&
1037                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1038                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
1039 
1040         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1041         s->dyn_dtree[d_code(dist)].Freq++;
1042     }
1043 
1044 #ifdef TRUNCATE_BLOCK
1045     /* Try to guess if it is profitable to stop the current block here */
1046     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1047         /* Compute an upper bound for the compressed length */
1048         ulg out_length = (ulg)s->last_lit*8L;
1049         ulg in_length = (ulg)((long)s->strstart - s->block_start);
1050         int dcode;
1051         for (dcode = 0; dcode < D_CODES; dcode++) {
1052             out_length += (ulg)s->dyn_dtree[dcode].Freq *
1053                 (5L+extra_dbits[dcode]);
1054         }
1055         out_length >>= 3;
1056         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1057                s->last_lit, in_length, out_length,
1058                100L - out_length*100L/in_length));
1059         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1060     }
1061 #endif
1062     return (s->last_lit == s->lit_bufsize-1);
1063     /* We avoid equality with lit_bufsize because of wraparound at 64K
1064      * on 16 bit machines and because stored blocks are restricted to
1065      * 64K-1 bytes.
1066      */
1067 }
1068 
1069 /* ===========================================================================
1070  * Send the block data compressed using the given Huffman trees
1071  */
compress_block(s,ltree,dtree)1072 local void compress_block(s, ltree, dtree)
1073     deflate_state *s;
1074     ct_data *ltree; /* literal tree */
1075     ct_data *dtree; /* distance tree */
1076 {
1077     unsigned dist;      /* distance of matched string */
1078     int lc;             /* match length or unmatched char (if dist == 0) */
1079     unsigned lx = 0;    /* running index in l_buf */
1080     unsigned code;      /* the code to send */
1081     int extra;          /* number of extra bits to send */
1082 
1083     if (s->last_lit != 0) do {
1084         dist = s->d_buf[lx];
1085         lc = s->l_buf[lx++];
1086         if (dist == 0) {
1087             send_code(s, lc, ltree); /* send a literal byte */
1088             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1089         } else {
1090             /* Here, lc is the match length - MIN_MATCH */
1091             code = _length_code[lc];
1092             send_code(s, code+LITERALS+1, ltree); /* send the length code */
1093             extra = extra_lbits[code];
1094             if (extra != 0) {
1095                 lc -= base_length[code];
1096                 send_bits(s, lc, extra);       /* send the extra length bits */
1097             }
1098             dist--; /* dist is now the match distance - 1 */
1099             code = d_code(dist);
1100             Assert (code < D_CODES, "bad d_code");
1101 
1102             send_code(s, code, dtree);       /* send the distance code */
1103             extra = extra_dbits[code];
1104             if (extra != 0) {
1105                 dist -= base_dist[code];
1106                 send_bits(s, dist, extra);   /* send the extra distance bits */
1107             }
1108         } /* literal or match pair ? */
1109 
1110         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1111         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
1112                "pendingBuf overflow");
1113 
1114     } while (lx < s->last_lit);
1115 
1116     send_code(s, END_BLOCK, ltree);
1117     s->last_eob_len = ltree[END_BLOCK].Len;
1118 }
1119 
1120 /* ===========================================================================
1121  * Set the data type to BINARY or TEXT, using a crude approximation:
1122  * set it to Z_TEXT if all symbols are either printable characters (33 to 255)
1123  * or white spaces (9 to 13, or 32); or set it to Z_BINARY otherwise.
1124  * IN assertion: the fields Freq of dyn_ltree are set.
1125  */
set_data_type(s)1126 local void set_data_type(s)
1127     deflate_state *s;
1128 {
1129     int n;
1130 
1131     for (n = 0; n < 9; n++)
1132         if (s->dyn_ltree[n].Freq != 0)
1133             break;
1134     if (n == 9)
1135         for (n = 14; n < 32; n++)
1136             if (s->dyn_ltree[n].Freq != 0)
1137                 break;
1138     s->strm->data_type = (n == 32) ? Z_TEXT : Z_BINARY;
1139 }
1140 
1141 /* ===========================================================================
1142  * Reverse the first len bits of a code, using straightforward code (a faster
1143  * method would use a table)
1144  * IN assertion: 1 <= len <= 15
1145  */
bi_reverse(code,len)1146 local unsigned bi_reverse(code, len)
1147     unsigned code; /* the value to invert */
1148     int len;       /* its bit length */
1149 {
1150     register unsigned res = 0;
1151     do {
1152         res |= code & 1;
1153         code >>= 1, res <<= 1;
1154     } while (--len > 0);
1155     return res >> 1;
1156 }
1157 
1158 /* ===========================================================================
1159  * Flush the bit buffer, keeping at most 7 bits in it.
1160  */
bi_flush(s)1161 local void bi_flush(s)
1162     deflate_state *s;
1163 {
1164     if (s->bi_valid == 16) {
1165         put_short(s, s->bi_buf);
1166         s->bi_buf = 0;
1167         s->bi_valid = 0;
1168     } else if (s->bi_valid >= 8) {
1169         put_byte(s, (Byte)s->bi_buf);
1170         s->bi_buf >>= 8;
1171         s->bi_valid -= 8;
1172     }
1173 }
1174 
1175 /* ===========================================================================
1176  * Flush the bit buffer and align the output on a byte boundary
1177  */
bi_windup(s)1178 local void bi_windup(s)
1179     deflate_state *s;
1180 {
1181     if (s->bi_valid > 8) {
1182         put_short(s, s->bi_buf);
1183     } else if (s->bi_valid > 0) {
1184         put_byte(s, (Byte)s->bi_buf);
1185     }
1186     s->bi_buf = 0;
1187     s->bi_valid = 0;
1188 #ifdef DEBUG
1189     s->bits_sent = (s->bits_sent+7) & ~7;
1190 #endif
1191 }
1192 
1193 /* ===========================================================================
1194  * Copy a stored block, storing first the length and its
1195  * one's complement if requested.
1196  */
copy_block(s,buf,len,header)1197 local void copy_block(s, buf, len, header)
1198     deflate_state *s;
1199     charf    *buf;    /* the input data */
1200     unsigned len;     /* its length */
1201     int      header;  /* true if block header must be written */
1202 {
1203     bi_windup(s);        /* align on byte boundary */
1204     s->last_eob_len = 8; /* enough lookahead for inflate */
1205 
1206     if (header) {
1207         put_short(s, (ush)len);
1208         put_short(s, (ush)~len);
1209 #ifdef DEBUG
1210         s->bits_sent += 2*16;
1211 #endif
1212     }
1213 #ifdef DEBUG
1214     s->bits_sent += (ulg)len<<3;
1215 #endif
1216     while (len--) {
1217         put_byte(s, *buf++);
1218     }
1219 }
1220