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1 /* trees.c -- output deflated data using Huffman coding
2 * Copyright (C) 1995-2021 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 code, int len));
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
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 */
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 * Generate 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
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 */
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 */
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->sym_next = 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 */
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 */
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 */
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 */
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 */
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 */
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 */
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 the
811 * 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 */
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 */
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 if (stored_len)
874 zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
875 s->pending += stored_len;
876 #ifdef ZLIB_DEBUG
877 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
878 s->compressed_len += (stored_len + 4) << 3;
879 s->bits_sent += 2*16;
880 s->bits_sent += stored_len << 3;
881 #endif
882 }
883
884 /* ===========================================================================
885 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
886 */
887 void ZLIB_INTERNAL _tr_flush_bits(s)
888 deflate_state *s;
889 {
890 bi_flush(s);
891 }
892
893 /* ===========================================================================
894 * Send one empty static block to give enough lookahead for inflate.
895 * This takes 10 bits, of which 7 may remain in the bit buffer.
896 */
897 void ZLIB_INTERNAL _tr_align(s)
898 deflate_state *s;
899 {
900 send_bits(s, STATIC_TREES<<1, 3);
901 send_code(s, END_BLOCK, static_ltree);
902 #ifdef ZLIB_DEBUG
903 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
904 #endif
905 bi_flush(s);
906 }
907
908 /* ===========================================================================
909 * Determine the best encoding for the current block: dynamic trees, static
910 * trees or store, and write out the encoded block.
911 */
912 void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
913 deflate_state *s;
914 charf *buf; /* input block, or NULL if too old */
915 ulg stored_len; /* length of input block */
916 int last; /* one if this is the last block for a file */
917 {
918 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
919 int max_blindex = 0; /* index of last bit length code of non zero freq */
920
921 /* Build the Huffman trees unless a stored block is forced */
922 if (s->level > 0) {
923
924 /* Check if the file is binary or text */
925 if (s->strm->data_type == Z_UNKNOWN)
926 s->strm->data_type = detect_data_type(s);
927
928 /* Construct the literal and distance trees */
929 build_tree(s, (tree_desc *)(&(s->l_desc)));
930 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
931 s->static_len));
932
933 build_tree(s, (tree_desc *)(&(s->d_desc)));
934 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
935 s->static_len));
936 /* At this point, opt_len and static_len are the total bit lengths of
937 * the compressed block data, excluding the tree representations.
938 */
939
940 /* Build the bit length tree for the above two trees, and get the index
941 * in bl_order of the last bit length code to send.
942 */
943 max_blindex = build_bl_tree(s);
944
945 /* Determine the best encoding. Compute the block lengths in bytes. */
946 opt_lenb = (s->opt_len + 3 + 7) >> 3;
947 static_lenb = (s->static_len + 3 + 7) >> 3;
948
949 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
950 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
951 s->sym_next / 3));
952
953 #ifndef FORCE_STATIC
954 if (static_lenb <= opt_lenb || s->strategy == Z_FIXED)
955 #endif
956 opt_lenb = static_lenb;
957
958 } else {
959 Assert(buf != (char*)0, "lost buf");
960 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
961 }
962
963 #ifdef FORCE_STORED
964 if (buf != (char*)0) { /* force stored block */
965 #else
966 if (stored_len + 4 <= opt_lenb && buf != (char*)0) {
967 /* 4: two words for the lengths */
968 #endif
969 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
970 * Otherwise we can't have processed more than WSIZE input bytes since
971 * the last block flush, because compression would have been
972 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
973 * transform a block into a stored block.
974 */
975 _tr_stored_block(s, buf, stored_len, last);
976
977 } else if (static_lenb == opt_lenb) {
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 */
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 (dist==0) */
1018 {
1019 s->sym_buf[s->sym_next++] = (uch)dist;
1020 s->sym_buf[s->sym_next++] = (uch)(dist >> 8);
1021 s->sym_buf[s->sym_next++] = (uch)lc;
1022 if (dist == 0) {
1023 /* lc is the unmatched char */
1024 s->dyn_ltree[lc].Freq++;
1025 } else {
1026 s->matches++;
1027 /* Here, lc is the match length - MIN_MATCH */
1028 dist--; /* dist = match distance - 1 */
1029 Assert((ush)dist < (ush)MAX_DIST(s) &&
1030 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1031 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match");
1032
1033 s->dyn_ltree[_length_code[lc] + LITERALS + 1].Freq++;
1034 s->dyn_dtree[d_code(dist)].Freq++;
1035 }
1036 return (s->sym_next == s->sym_end);
1037 }
1038
1039 /* ===========================================================================
1040 * Send the block data compressed using the given Huffman trees
1041 */
1042 local void compress_block(s, ltree, dtree)
1043 deflate_state *s;
1044 const ct_data *ltree; /* literal tree */
1045 const ct_data *dtree; /* distance tree */
1046 {
1047 unsigned dist; /* distance of matched string */
1048 int lc; /* match length or unmatched char (if dist == 0) */
1049 unsigned sx = 0; /* running index in sym_buf */
1050 unsigned code; /* the code to send */
1051 int extra; /* number of extra bits to send */
1052
1053 if (s->sym_next != 0) do {
1054 dist = s->sym_buf[sx++] & 0xff;
1055 dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;
1056 lc = s->sym_buf[sx++];
1057 if (dist == 0) {
1058 send_code(s, lc, ltree); /* send a literal byte */
1059 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1060 } else {
1061 /* Here, lc is the match length - MIN_MATCH */
1062 code = _length_code[lc];
1063 send_code(s, code + LITERALS + 1, ltree); /* send length code */
1064 extra = extra_lbits[code];
1065 if (extra != 0) {
1066 lc -= base_length[code];
1067 send_bits(s, lc, extra); /* send the extra length bits */
1068 }
1069 dist--; /* dist is now the match distance - 1 */
1070 code = d_code(dist);
1071 Assert (code < D_CODES, "bad d_code");
1072
1073 send_code(s, code, dtree); /* send the distance code */
1074 extra = extra_dbits[code];
1075 if (extra != 0) {
1076 dist -= (unsigned)base_dist[code];
1077 send_bits(s, dist, extra); /* send the extra distance bits */
1078 }
1079 } /* literal or match pair ? */
1080
1081 /* Check that the overlay between pending_buf and sym_buf is ok: */
1082 Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow");
1083
1084 } while (sx < s->sym_next);
1085
1086 send_code(s, END_BLOCK, ltree);
1087 }
1088
1089 /* ===========================================================================
1090 * Check if the data type is TEXT or BINARY, using the following algorithm:
1091 * - TEXT if the two conditions below are satisfied:
1092 * a) There are no non-portable control characters belonging to the
1093 * "block list" (0..6, 14..25, 28..31).
1094 * b) There is at least one printable character belonging to the
1095 * "allow list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
1096 * - BINARY otherwise.
1097 * - The following partially-portable control characters form a
1098 * "gray list" that is ignored in this detection algorithm:
1099 * (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
1100 * IN assertion: the fields Freq of dyn_ltree are set.
1101 */
1102 local int detect_data_type(s)
1103 deflate_state *s;
1104 {
1105 /* block_mask is the bit mask of block-listed bytes
1106 * set bits 0..6, 14..25, and 28..31
1107 * 0xf3ffc07f = binary 11110011111111111100000001111111
1108 */
1109 unsigned long block_mask = 0xf3ffc07fUL;
1110 int n;
1111
1112 /* Check for non-textual ("block-listed") bytes. */
1113 for (n = 0; n <= 31; n++, block_mask >>= 1)
1114 if ((block_mask & 1) && (s->dyn_ltree[n].Freq != 0))
1115 return Z_BINARY;
1116
1117 /* Check for textual ("allow-listed") bytes. */
1118 if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
1119 || s->dyn_ltree[13].Freq != 0)
1120 return Z_TEXT;
1121 for (n = 32; n < LITERALS; n++)
1122 if (s->dyn_ltree[n].Freq != 0)
1123 return Z_TEXT;
1124
1125 /* There are no "block-listed" or "allow-listed" bytes:
1126 * this stream either is empty or has tolerated ("gray-listed") bytes only.
1127 */
1128 return Z_BINARY;
1129 }
1130
1131 /* ===========================================================================
1132 * Reverse the first len bits of a code, using straightforward code (a faster
1133 * method would use a table)
1134 * IN assertion: 1 <= len <= 15
1135 */
1136 local unsigned bi_reverse(code, len)
1137 unsigned code; /* the value to invert */
1138 int len; /* its bit length */
1139 {
1140 register unsigned res = 0;
1141 do {
1142 res |= code & 1;
1143 code >>= 1, res <<= 1;
1144 } while (--len > 0);
1145 return res >> 1;
1146 }
1147
1148 /* ===========================================================================
1149 * Flush the bit buffer, keeping at most 7 bits in it.
1150 */
1151 local void bi_flush(s)
1152 deflate_state *s;
1153 {
1154 if (s->bi_valid == 16) {
1155 put_short(s, s->bi_buf);
1156 s->bi_buf = 0;
1157 s->bi_valid = 0;
1158 } else if (s->bi_valid >= 8) {
1159 put_byte(s, (Byte)s->bi_buf);
1160 s->bi_buf >>= 8;
1161 s->bi_valid -= 8;
1162 }
1163 }
1164
1165 /* ===========================================================================
1166 * Flush the bit buffer and align the output on a byte boundary
1167 */
1168 local void bi_windup(s)
1169 deflate_state *s;
1170 {
1171 if (s->bi_valid > 8) {
1172 put_short(s, s->bi_buf);
1173 } else if (s->bi_valid > 0) {
1174 put_byte(s, (Byte)s->bi_buf);
1175 }
1176 s->bi_buf = 0;
1177 s->bi_valid = 0;
1178 #ifdef ZLIB_DEBUG
1179 s->bits_sent = (s->bits_sent + 7) & ~7;
1180 #endif
1181 }
1182