1 /* +++ trees.c */
2 /* trees.c -- output deflated data using Huffman coding
3 * Copyright (C) 1995-1996 Jean-loup Gailly
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 /* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */
34
35 /* #include "deflate.h" */
36
37 #include <linux/zutil.h>
38 #include <linux/bitrev.h>
39 #include "defutil.h"
40
41 #ifdef DEBUG_ZLIB
42 # include <ctype.h>
43 #endif
44
45 /* ===========================================================================
46 * Constants
47 */
48
49 #define MAX_BL_BITS 7
50 /* Bit length codes must not exceed MAX_BL_BITS bits */
51
52 #define END_BLOCK 256
53 /* end of block literal code */
54
55 #define REP_3_6 16
56 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
57
58 #define REPZ_3_10 17
59 /* repeat a zero length 3-10 times (3 bits of repeat count) */
60
61 #define REPZ_11_138 18
62 /* repeat a zero length 11-138 times (7 bits of repeat count) */
63
64 static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
65 = {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};
66
67 static const int extra_dbits[D_CODES] /* extra bits for each distance code */
68 = {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};
69
70 static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
71 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
72
73 static const uch bl_order[BL_CODES]
74 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
75 /* The lengths of the bit length codes are sent in order of decreasing
76 * probability, to avoid transmitting the lengths for unused bit length codes.
77 */
78
79 #define Buf_size (8 * 2*sizeof(char))
80 /* Number of bits used within bi_buf. (bi_buf might be implemented on
81 * more than 16 bits on some systems.)
82 */
83
84 /* ===========================================================================
85 * Local data. These are initialized only once.
86 */
87
88 static ct_data static_ltree[L_CODES+2];
89 /* The static literal tree. Since the bit lengths are imposed, there is no
90 * need for the L_CODES extra codes used during heap construction. However
91 * The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init
92 * below).
93 */
94
95 static ct_data static_dtree[D_CODES];
96 /* The static distance tree. (Actually a trivial tree since all codes use
97 * 5 bits.)
98 */
99
100 static uch dist_code[512];
101 /* distance codes. The first 256 values correspond to the distances
102 * 3 .. 258, the last 256 values correspond to the top 8 bits of
103 * the 15 bit distances.
104 */
105
106 static uch length_code[MAX_MATCH-MIN_MATCH+1];
107 /* length code for each normalized match length (0 == MIN_MATCH) */
108
109 static int base_length[LENGTH_CODES];
110 /* First normalized length for each code (0 = MIN_MATCH) */
111
112 static int base_dist[D_CODES];
113 /* First normalized distance for each code (0 = distance of 1) */
114
115 struct static_tree_desc_s {
116 const ct_data *static_tree; /* static tree or NULL */
117 const int *extra_bits; /* extra bits for each code or NULL */
118 int extra_base; /* base index for extra_bits */
119 int elems; /* max number of elements in the tree */
120 int max_length; /* max bit length for the codes */
121 };
122
123 static static_tree_desc static_l_desc =
124 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
125
126 static static_tree_desc static_d_desc =
127 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
128
129 static static_tree_desc static_bl_desc =
130 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
131
132 /* ===========================================================================
133 * Local (static) routines in this file.
134 */
135
136 static void tr_static_init (void);
137 static void init_block (deflate_state *s);
138 static void pqdownheap (deflate_state *s, ct_data *tree, int k);
139 static void gen_bitlen (deflate_state *s, tree_desc *desc);
140 static void gen_codes (ct_data *tree, int max_code, ush *bl_count);
141 static void build_tree (deflate_state *s, tree_desc *desc);
142 static void scan_tree (deflate_state *s, ct_data *tree, int max_code);
143 static void send_tree (deflate_state *s, ct_data *tree, int max_code);
144 static int build_bl_tree (deflate_state *s);
145 static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
146 int blcodes);
147 static void compress_block (deflate_state *s, ct_data *ltree,
148 ct_data *dtree);
149 static void set_data_type (deflate_state *s);
150 static void bi_windup (deflate_state *s);
151 static void bi_flush (deflate_state *s);
152 static void copy_block (deflate_state *s, char *buf, unsigned len,
153 int header);
154
155 #ifndef DEBUG_ZLIB
156 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
157 /* Send a code of the given tree. c and tree must not have side effects */
158
159 #else /* DEBUG_ZLIB */
160 # define send_code(s, c, tree) \
161 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
162 send_bits(s, tree[c].Code, tree[c].Len); }
163 #endif
164
165 #define d_code(dist) \
166 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
167 /* Mapping from a distance to a distance code. dist is the distance - 1 and
168 * must not have side effects. dist_code[256] and dist_code[257] are never
169 * used.
170 */
171
172 /* ===========================================================================
173 * Send a value on a given number of bits.
174 * IN assertion: length <= 16 and value fits in length bits.
175 */
176 #ifdef DEBUG_ZLIB
177 static void send_bits (deflate_state *s, int value, int length);
178
179 static void send_bits(
180 deflate_state *s,
181 int value, /* value to send */
182 int length /* number of bits */
183 )
184 {
185 Tracevv((stderr," l %2d v %4x ", length, value));
186 Assert(length > 0 && length <= 15, "invalid length");
187 s->bits_sent += (ulg)length;
188
189 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
190 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
191 * unused bits in value.
192 */
193 if (s->bi_valid > (int)Buf_size - length) {
194 s->bi_buf |= (value << s->bi_valid);
195 put_short(s, s->bi_buf);
196 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
197 s->bi_valid += length - Buf_size;
198 } else {
199 s->bi_buf |= value << s->bi_valid;
200 s->bi_valid += length;
201 }
202 }
203 #else /* !DEBUG_ZLIB */
204
205 #define send_bits(s, value, length) \
206 { int len = length;\
207 if (s->bi_valid > (int)Buf_size - len) {\
208 int val = value;\
209 s->bi_buf |= (val << s->bi_valid);\
210 put_short(s, s->bi_buf);\
211 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
212 s->bi_valid += len - Buf_size;\
213 } else {\
214 s->bi_buf |= (value) << s->bi_valid;\
215 s->bi_valid += len;\
216 }\
217 }
218 #endif /* DEBUG_ZLIB */
219
220 /* ===========================================================================
221 * Initialize the various 'constant' tables. In a multi-threaded environment,
222 * this function may be called by two threads concurrently, but this is
223 * harmless since both invocations do exactly the same thing.
224 */
225 static void tr_static_init(void)
226 {
227 static int static_init_done;
228 int n; /* iterates over tree elements */
229 int bits; /* bit counter */
230 int length; /* length value */
231 int code; /* code value */
232 int dist; /* distance index */
233 ush bl_count[MAX_BITS+1];
234 /* number of codes at each bit length for an optimal tree */
235
236 if (static_init_done) return;
237
238 /* Initialize the mapping length (0..255) -> length code (0..28) */
239 length = 0;
240 for (code = 0; code < LENGTH_CODES-1; code++) {
241 base_length[code] = length;
242 for (n = 0; n < (1<<extra_lbits[code]); n++) {
243 length_code[length++] = (uch)code;
244 }
245 }
246 Assert (length == 256, "tr_static_init: length != 256");
247 /* Note that the length 255 (match length 258) can be represented
248 * in two different ways: code 284 + 5 bits or code 285, so we
249 * overwrite length_code[255] to use the best encoding:
250 */
251 length_code[length-1] = (uch)code;
252
253 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
254 dist = 0;
255 for (code = 0 ; code < 16; code++) {
256 base_dist[code] = dist;
257 for (n = 0; n < (1<<extra_dbits[code]); n++) {
258 dist_code[dist++] = (uch)code;
259 }
260 }
261 Assert (dist == 256, "tr_static_init: dist != 256");
262 dist >>= 7; /* from now on, all distances are divided by 128 */
263 for ( ; code < D_CODES; code++) {
264 base_dist[code] = dist << 7;
265 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
266 dist_code[256 + dist++] = (uch)code;
267 }
268 }
269 Assert (dist == 256, "tr_static_init: 256+dist != 512");
270
271 /* Construct the codes of the static literal tree */
272 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
273 n = 0;
274 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
275 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
276 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
277 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
278 /* Codes 286 and 287 do not exist, but we must include them in the
279 * tree construction to get a canonical Huffman tree (longest code
280 * all ones)
281 */
282 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
283
284 /* The static distance tree is trivial: */
285 for (n = 0; n < D_CODES; n++) {
286 static_dtree[n].Len = 5;
287 static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
288 }
289 static_init_done = 1;
290 }
291
292 /* ===========================================================================
293 * Initialize the tree data structures for a new zlib stream.
294 */
295 void zlib_tr_init(
296 deflate_state *s
297 )
298 {
299 tr_static_init();
300
301 s->compressed_len = 0L;
302
303 s->l_desc.dyn_tree = s->dyn_ltree;
304 s->l_desc.stat_desc = &static_l_desc;
305
306 s->d_desc.dyn_tree = s->dyn_dtree;
307 s->d_desc.stat_desc = &static_d_desc;
308
309 s->bl_desc.dyn_tree = s->bl_tree;
310 s->bl_desc.stat_desc = &static_bl_desc;
311
312 s->bi_buf = 0;
313 s->bi_valid = 0;
314 s->last_eob_len = 8; /* enough lookahead for inflate */
315 #ifdef DEBUG_ZLIB
316 s->bits_sent = 0L;
317 #endif
318
319 /* Initialize the first block of the first file: */
320 init_block(s);
321 }
322
323 /* ===========================================================================
324 * Initialize a new block.
325 */
326 static void init_block(
327 deflate_state *s
328 )
329 {
330 int n; /* iterates over tree elements */
331
332 /* Initialize the trees. */
333 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
334 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
335 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
336
337 s->dyn_ltree[END_BLOCK].Freq = 1;
338 s->opt_len = s->static_len = 0L;
339 s->last_lit = s->matches = 0;
340 }
341
342 #define SMALLEST 1
343 /* Index within the heap array of least frequent node in the Huffman tree */
344
345
346 /* ===========================================================================
347 * Remove the smallest element from the heap and recreate the heap with
348 * one less element. Updates heap and heap_len.
349 */
350 #define pqremove(s, tree, top) \
351 {\
352 top = s->heap[SMALLEST]; \
353 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
354 pqdownheap(s, tree, SMALLEST); \
355 }
356
357 /* ===========================================================================
358 * Compares to subtrees, using the tree depth as tie breaker when
359 * the subtrees have equal frequency. This minimizes the worst case length.
360 */
361 #define smaller(tree, n, m, depth) \
362 (tree[n].Freq < tree[m].Freq || \
363 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
364
365 /* ===========================================================================
366 * Restore the heap property by moving down the tree starting at node k,
367 * exchanging a node with the smallest of its two sons if necessary, stopping
368 * when the heap property is re-established (each father smaller than its
369 * two sons).
370 */
371 static void pqdownheap(
372 deflate_state *s,
373 ct_data *tree, /* the tree to restore */
374 int k /* node to move down */
375 )
376 {
377 int v = s->heap[k];
378 int j = k << 1; /* left son of k */
379 while (j <= s->heap_len) {
380 /* Set j to the smallest of the two sons: */
381 if (j < s->heap_len &&
382 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
383 j++;
384 }
385 /* Exit if v is smaller than both sons */
386 if (smaller(tree, v, s->heap[j], s->depth)) break;
387
388 /* Exchange v with the smallest son */
389 s->heap[k] = s->heap[j]; k = j;
390
391 /* And continue down the tree, setting j to the left son of k */
392 j <<= 1;
393 }
394 s->heap[k] = v;
395 }
396
397 /* ===========================================================================
398 * Compute the optimal bit lengths for a tree and update the total bit length
399 * for the current block.
400 * IN assertion: the fields freq and dad are set, heap[heap_max] and
401 * above are the tree nodes sorted by increasing frequency.
402 * OUT assertions: the field len is set to the optimal bit length, the
403 * array bl_count contains the frequencies for each bit length.
404 * The length opt_len is updated; static_len is also updated if stree is
405 * not null.
406 */
407 static void gen_bitlen(
408 deflate_state *s,
409 tree_desc *desc /* the tree descriptor */
410 )
411 {
412 ct_data *tree = desc->dyn_tree;
413 int max_code = desc->max_code;
414 const ct_data *stree = desc->stat_desc->static_tree;
415 const int *extra = desc->stat_desc->extra_bits;
416 int base = desc->stat_desc->extra_base;
417 int max_length = desc->stat_desc->max_length;
418 int h; /* heap index */
419 int n, m; /* iterate over the tree elements */
420 int bits; /* bit length */
421 int xbits; /* extra bits */
422 ush f; /* frequency */
423 int overflow = 0; /* number of elements with bit length too large */
424
425 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
426
427 /* In a first pass, compute the optimal bit lengths (which may
428 * overflow in the case of the bit length tree).
429 */
430 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
431
432 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
433 n = s->heap[h];
434 bits = tree[tree[n].Dad].Len + 1;
435 if (bits > max_length) bits = max_length, overflow++;
436 tree[n].Len = (ush)bits;
437 /* We overwrite tree[n].Dad which is no longer needed */
438
439 if (n > max_code) continue; /* not a leaf node */
440
441 s->bl_count[bits]++;
442 xbits = 0;
443 if (n >= base) xbits = extra[n-base];
444 f = tree[n].Freq;
445 s->opt_len += (ulg)f * (bits + xbits);
446 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
447 }
448 if (overflow == 0) return;
449
450 Trace((stderr,"\nbit length overflow\n"));
451 /* This happens for example on obj2 and pic of the Calgary corpus */
452
453 /* Find the first bit length which could increase: */
454 do {
455 bits = max_length-1;
456 while (s->bl_count[bits] == 0) bits--;
457 s->bl_count[bits]--; /* move one leaf down the tree */
458 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
459 s->bl_count[max_length]--;
460 /* The brother of the overflow item also moves one step up,
461 * but this does not affect bl_count[max_length]
462 */
463 overflow -= 2;
464 } while (overflow > 0);
465
466 /* Now recompute all bit lengths, scanning in increasing frequency.
467 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
468 * lengths instead of fixing only the wrong ones. This idea is taken
469 * from 'ar' written by Haruhiko Okumura.)
470 */
471 for (bits = max_length; bits != 0; bits--) {
472 n = s->bl_count[bits];
473 while (n != 0) {
474 m = s->heap[--h];
475 if (m > max_code) continue;
476 if (tree[m].Len != (unsigned) bits) {
477 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
478 s->opt_len += ((long)bits - (long)tree[m].Len)
479 *(long)tree[m].Freq;
480 tree[m].Len = (ush)bits;
481 }
482 n--;
483 }
484 }
485 }
486
487 /* ===========================================================================
488 * Generate the codes for a given tree and bit counts (which need not be
489 * optimal).
490 * IN assertion: the array bl_count contains the bit length statistics for
491 * the given tree and the field len is set for all tree elements.
492 * OUT assertion: the field code is set for all tree elements of non
493 * zero code length.
494 */
495 static void gen_codes(
496 ct_data *tree, /* the tree to decorate */
497 int max_code, /* largest code with non zero frequency */
498 ush *bl_count /* number of codes at each bit length */
499 )
500 {
501 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
502 ush code = 0; /* running code value */
503 int bits; /* bit index */
504 int n; /* code index */
505
506 /* The distribution counts are first used to generate the code values
507 * without bit reversal.
508 */
509 for (bits = 1; bits <= MAX_BITS; bits++) {
510 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
511 }
512 /* Check that the bit counts in bl_count are consistent. The last code
513 * must be all ones.
514 */
515 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
516 "inconsistent bit counts");
517 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
518
519 for (n = 0; n <= max_code; n++) {
520 int len = tree[n].Len;
521 if (len == 0) continue;
522 /* Now reverse the bits */
523 tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);
524
525 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
526 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
527 }
528 }
529
530 /* ===========================================================================
531 * Construct one Huffman tree and assigns the code bit strings and lengths.
532 * Update the total bit length for the current block.
533 * IN assertion: the field freq is set for all tree elements.
534 * OUT assertions: the fields len and code are set to the optimal bit length
535 * and corresponding code. The length opt_len is updated; static_len is
536 * also updated if stree is not null. The field max_code is set.
537 */
538 static void build_tree(
539 deflate_state *s,
540 tree_desc *desc /* the tree descriptor */
541 )
542 {
543 ct_data *tree = desc->dyn_tree;
544 const ct_data *stree = desc->stat_desc->static_tree;
545 int elems = desc->stat_desc->elems;
546 int n, m; /* iterate over heap elements */
547 int max_code = -1; /* largest code with non zero frequency */
548 int node; /* new node being created */
549
550 /* Construct the initial heap, with least frequent element in
551 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
552 * heap[0] is not used.
553 */
554 s->heap_len = 0, s->heap_max = HEAP_SIZE;
555
556 for (n = 0; n < elems; n++) {
557 if (tree[n].Freq != 0) {
558 s->heap[++(s->heap_len)] = max_code = n;
559 s->depth[n] = 0;
560 } else {
561 tree[n].Len = 0;
562 }
563 }
564
565 /* The pkzip format requires that at least one distance code exists,
566 * and that at least one bit should be sent even if there is only one
567 * possible code. So to avoid special checks later on we force at least
568 * two codes of non zero frequency.
569 */
570 while (s->heap_len < 2) {
571 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
572 tree[node].Freq = 1;
573 s->depth[node] = 0;
574 s->opt_len--; if (stree) s->static_len -= stree[node].Len;
575 /* node is 0 or 1 so it does not have extra bits */
576 }
577 desc->max_code = max_code;
578
579 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
580 * establish sub-heaps of increasing lengths:
581 */
582 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
583
584 /* Construct the Huffman tree by repeatedly combining the least two
585 * frequent nodes.
586 */
587 node = elems; /* next internal node of the tree */
588 do {
589 pqremove(s, tree, n); /* n = node of least frequency */
590 m = s->heap[SMALLEST]; /* m = node of next least frequency */
591
592 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
593 s->heap[--(s->heap_max)] = m;
594
595 /* Create a new node father of n and m */
596 tree[node].Freq = tree[n].Freq + tree[m].Freq;
597 s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);
598 tree[n].Dad = tree[m].Dad = (ush)node;
599 #ifdef DUMP_BL_TREE
600 if (tree == s->bl_tree) {
601 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
602 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
603 }
604 #endif
605 /* and insert the new node in the heap */
606 s->heap[SMALLEST] = node++;
607 pqdownheap(s, tree, SMALLEST);
608
609 } while (s->heap_len >= 2);
610
611 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
612
613 /* At this point, the fields freq and dad are set. We can now
614 * generate the bit lengths.
615 */
616 gen_bitlen(s, (tree_desc *)desc);
617
618 /* The field len is now set, we can generate the bit codes */
619 gen_codes ((ct_data *)tree, max_code, s->bl_count);
620 }
621
622 /* ===========================================================================
623 * Scan a literal or distance tree to determine the frequencies of the codes
624 * in the bit length tree.
625 */
626 static void scan_tree(
627 deflate_state *s,
628 ct_data *tree, /* the tree to be scanned */
629 int max_code /* and its largest code of non zero frequency */
630 )
631 {
632 int n; /* iterates over all tree elements */
633 int prevlen = -1; /* last emitted length */
634 int curlen; /* length of current code */
635 int nextlen = tree[0].Len; /* length of next code */
636 int count = 0; /* repeat count of the current code */
637 int max_count = 7; /* max repeat count */
638 int min_count = 4; /* min repeat count */
639
640 if (nextlen == 0) max_count = 138, min_count = 3;
641 tree[max_code+1].Len = (ush)0xffff; /* guard */
642
643 for (n = 0; n <= max_code; n++) {
644 curlen = nextlen; nextlen = tree[n+1].Len;
645 if (++count < max_count && curlen == nextlen) {
646 continue;
647 } else if (count < min_count) {
648 s->bl_tree[curlen].Freq += count;
649 } else if (curlen != 0) {
650 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
651 s->bl_tree[REP_3_6].Freq++;
652 } else if (count <= 10) {
653 s->bl_tree[REPZ_3_10].Freq++;
654 } else {
655 s->bl_tree[REPZ_11_138].Freq++;
656 }
657 count = 0; prevlen = curlen;
658 if (nextlen == 0) {
659 max_count = 138, min_count = 3;
660 } else if (curlen == nextlen) {
661 max_count = 6, min_count = 3;
662 } else {
663 max_count = 7, min_count = 4;
664 }
665 }
666 }
667
668 /* ===========================================================================
669 * Send a literal or distance tree in compressed form, using the codes in
670 * bl_tree.
671 */
672 static void send_tree(
673 deflate_state *s,
674 ct_data *tree, /* the tree to be scanned */
675 int max_code /* and its largest code of non zero frequency */
676 )
677 {
678 int n; /* iterates over all tree elements */
679 int prevlen = -1; /* last emitted length */
680 int curlen; /* length of current code */
681 int nextlen = tree[0].Len; /* length of next code */
682 int count = 0; /* repeat count of the current code */
683 int max_count = 7; /* max repeat count */
684 int min_count = 4; /* min repeat count */
685
686 /* tree[max_code+1].Len = -1; */ /* guard already set */
687 if (nextlen == 0) max_count = 138, min_count = 3;
688
689 for (n = 0; n <= max_code; n++) {
690 curlen = nextlen; nextlen = tree[n+1].Len;
691 if (++count < max_count && curlen == nextlen) {
692 continue;
693 } else if (count < min_count) {
694 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
695
696 } else if (curlen != 0) {
697 if (curlen != prevlen) {
698 send_code(s, curlen, s->bl_tree); count--;
699 }
700 Assert(count >= 3 && count <= 6, " 3_6?");
701 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
702
703 } else if (count <= 10) {
704 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
705
706 } else {
707 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
708 }
709 count = 0; prevlen = curlen;
710 if (nextlen == 0) {
711 max_count = 138, min_count = 3;
712 } else if (curlen == nextlen) {
713 max_count = 6, min_count = 3;
714 } else {
715 max_count = 7, min_count = 4;
716 }
717 }
718 }
719
720 /* ===========================================================================
721 * Construct the Huffman tree for the bit lengths and return the index in
722 * bl_order of the last bit length code to send.
723 */
724 static int build_bl_tree(
725 deflate_state *s
726 )
727 {
728 int max_blindex; /* index of last bit length code of non zero freq */
729
730 /* Determine the bit length frequencies for literal and distance trees */
731 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
732 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
733
734 /* Build the bit length tree: */
735 build_tree(s, (tree_desc *)(&(s->bl_desc)));
736 /* opt_len now includes the length of the tree representations, except
737 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
738 */
739
740 /* Determine the number of bit length codes to send. The pkzip format
741 * requires that at least 4 bit length codes be sent. (appnote.txt says
742 * 3 but the actual value used is 4.)
743 */
744 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
745 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
746 }
747 /* Update opt_len to include the bit length tree and counts */
748 s->opt_len += 3*(max_blindex+1) + 5+5+4;
749 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
750 s->opt_len, s->static_len));
751
752 return max_blindex;
753 }
754
755 /* ===========================================================================
756 * Send the header for a block using dynamic Huffman trees: the counts, the
757 * lengths of the bit length codes, the literal tree and the distance tree.
758 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
759 */
760 static void send_all_trees(
761 deflate_state *s,
762 int lcodes, /* number of codes for each tree */
763 int dcodes, /* number of codes for each tree */
764 int blcodes /* number of codes for each tree */
765 )
766 {
767 int rank; /* index in bl_order */
768
769 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
770 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
771 "too many codes");
772 Tracev((stderr, "\nbl counts: "));
773 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
774 send_bits(s, dcodes-1, 5);
775 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
776 for (rank = 0; rank < blcodes; rank++) {
777 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
778 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
779 }
780 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
781
782 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
783 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
784
785 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
786 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
787 }
788
789 /* ===========================================================================
790 * Send a stored block
791 */
792 void zlib_tr_stored_block(
793 deflate_state *s,
794 char *buf, /* input block */
795 ulg stored_len, /* length of input block */
796 int eof /* true if this is the last block for a file */
797 )
798 {
799 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
800 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
801 s->compressed_len += (stored_len + 4) << 3;
802
803 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
804 }
805
806 /* Send just the `stored block' type code without any length bytes or data.
807 */
808 void zlib_tr_stored_type_only(
809 deflate_state *s
810 )
811 {
812 send_bits(s, (STORED_BLOCK << 1), 3);
813 bi_windup(s);
814 s->compressed_len = (s->compressed_len + 3) & ~7L;
815 }
816
817
818 /* ===========================================================================
819 * Send one empty static block to give enough lookahead for inflate.
820 * This takes 10 bits, of which 7 may remain in the bit buffer.
821 * The current inflate code requires 9 bits of lookahead. If the
822 * last two codes for the previous block (real code plus EOB) were coded
823 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
824 * the last real code. In this case we send two empty static blocks instead
825 * of one. (There are no problems if the previous block is stored or fixed.)
826 * To simplify the code, we assume the worst case of last real code encoded
827 * on one bit only.
828 */
829 void zlib_tr_align(
830 deflate_state *s
831 )
832 {
833 send_bits(s, STATIC_TREES<<1, 3);
834 send_code(s, END_BLOCK, static_ltree);
835 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
836 bi_flush(s);
837 /* Of the 10 bits for the empty block, we have already sent
838 * (10 - bi_valid) bits. The lookahead for the last real code (before
839 * the EOB of the previous block) was thus at least one plus the length
840 * of the EOB plus what we have just sent of the empty static block.
841 */
842 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
843 send_bits(s, STATIC_TREES<<1, 3);
844 send_code(s, END_BLOCK, static_ltree);
845 s->compressed_len += 10L;
846 bi_flush(s);
847 }
848 s->last_eob_len = 7;
849 }
850
851 /* ===========================================================================
852 * Determine the best encoding for the current block: dynamic trees, static
853 * trees or store, and output the encoded block to the zip file. This function
854 * returns the total compressed length for the file so far.
855 */
856 ulg zlib_tr_flush_block(
857 deflate_state *s,
858 char *buf, /* input block, or NULL if too old */
859 ulg stored_len, /* length of input block */
860 int eof /* true if this is the last block for a file */
861 )
862 {
863 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
864 int max_blindex = 0; /* index of last bit length code of non zero freq */
865
866 /* Build the Huffman trees unless a stored block is forced */
867 if (s->level > 0) {
868
869 /* Check if the file is ascii or binary */
870 if (s->data_type == Z_UNKNOWN) set_data_type(s);
871
872 /* Construct the literal and distance trees */
873 build_tree(s, (tree_desc *)(&(s->l_desc)));
874 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
875 s->static_len));
876
877 build_tree(s, (tree_desc *)(&(s->d_desc)));
878 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
879 s->static_len));
880 /* At this point, opt_len and static_len are the total bit lengths of
881 * the compressed block data, excluding the tree representations.
882 */
883
884 /* Build the bit length tree for the above two trees, and get the index
885 * in bl_order of the last bit length code to send.
886 */
887 max_blindex = build_bl_tree(s);
888
889 /* Determine the best encoding. Compute first the block length in bytes*/
890 opt_lenb = (s->opt_len+3+7)>>3;
891 static_lenb = (s->static_len+3+7)>>3;
892
893 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
894 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
895 s->last_lit));
896
897 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
898
899 } else {
900 Assert(buf != (char*)0, "lost buf");
901 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
902 }
903
904 /* If compression failed and this is the first and last block,
905 * and if the .zip file can be seeked (to rewrite the local header),
906 * the whole file is transformed into a stored file:
907 */
908 #ifdef STORED_FILE_OK
909 # ifdef FORCE_STORED_FILE
910 if (eof && s->compressed_len == 0L) { /* force stored file */
911 # else
912 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
913 # endif
914 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
915 if (buf == (char*)0) error ("block vanished");
916
917 copy_block(s, buf, (unsigned)stored_len, 0); /* without header */
918 s->compressed_len = stored_len << 3;
919 s->method = STORED;
920 } else
921 #endif /* STORED_FILE_OK */
922
923 #ifdef FORCE_STORED
924 if (buf != (char*)0) { /* force stored block */
925 #else
926 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
927 /* 4: two words for the lengths */
928 #endif
929 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
930 * Otherwise we can't have processed more than WSIZE input bytes since
931 * the last block flush, because compression would have been
932 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
933 * transform a block into a stored block.
934 */
935 zlib_tr_stored_block(s, buf, stored_len, eof);
936
937 #ifdef FORCE_STATIC
938 } else if (static_lenb >= 0) { /* force static trees */
939 #else
940 } else if (static_lenb == opt_lenb) {
941 #endif
942 send_bits(s, (STATIC_TREES<<1)+eof, 3);
943 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
944 s->compressed_len += 3 + s->static_len;
945 } else {
946 send_bits(s, (DYN_TREES<<1)+eof, 3);
947 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
948 max_blindex+1);
949 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
950 s->compressed_len += 3 + s->opt_len;
951 }
952 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
953 init_block(s);
954
955 if (eof) {
956 bi_windup(s);
957 s->compressed_len += 7; /* align on byte boundary */
958 }
959 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
960 s->compressed_len-7*eof));
961
962 return s->compressed_len >> 3;
963 }
964
965 /* ===========================================================================
966 * Save the match info and tally the frequency counts. Return true if
967 * the current block must be flushed.
968 */
969 int zlib_tr_tally(
970 deflate_state *s,
971 unsigned dist, /* distance of matched string */
972 unsigned lc /* match length-MIN_MATCH or unmatched char (if dist==0) */
973 )
974 {
975 s->d_buf[s->last_lit] = (ush)dist;
976 s->l_buf[s->last_lit++] = (uch)lc;
977 if (dist == 0) {
978 /* lc is the unmatched char */
979 s->dyn_ltree[lc].Freq++;
980 } else {
981 s->matches++;
982 /* Here, lc is the match length - MIN_MATCH */
983 dist--; /* dist = match distance - 1 */
984 Assert((ush)dist < (ush)MAX_DIST(s) &&
985 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
986 (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match");
987
988 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
989 s->dyn_dtree[d_code(dist)].Freq++;
990 }
991
992 /* Try to guess if it is profitable to stop the current block here */
993 if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
994 /* Compute an upper bound for the compressed length */
995 ulg out_length = (ulg)s->last_lit*8L;
996 ulg in_length = (ulg)((long)s->strstart - s->block_start);
997 int dcode;
998 for (dcode = 0; dcode < D_CODES; dcode++) {
999 out_length += (ulg)s->dyn_dtree[dcode].Freq *
1000 (5L+extra_dbits[dcode]);
1001 }
1002 out_length >>= 3;
1003 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1004 s->last_lit, in_length, out_length,
1005 100L - out_length*100L/in_length));
1006 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1007 }
1008 return (s->last_lit == s->lit_bufsize-1);
1009 /* We avoid equality with lit_bufsize because of wraparound at 64K
1010 * on 16 bit machines and because stored blocks are restricted to
1011 * 64K-1 bytes.
1012 */
1013 }
1014
1015 /* ===========================================================================
1016 * Send the block data compressed using the given Huffman trees
1017 */
1018 static void compress_block(
1019 deflate_state *s,
1020 ct_data *ltree, /* literal tree */
1021 ct_data *dtree /* distance tree */
1022 )
1023 {
1024 unsigned dist; /* distance of matched string */
1025 int lc; /* match length or unmatched char (if dist == 0) */
1026 unsigned lx = 0; /* running index in l_buf */
1027 unsigned code; /* the code to send */
1028 int extra; /* number of extra bits to send */
1029
1030 if (s->last_lit != 0) do {
1031 dist = s->d_buf[lx];
1032 lc = s->l_buf[lx++];
1033 if (dist == 0) {
1034 send_code(s, lc, ltree); /* send a literal byte */
1035 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1036 } else {
1037 /* Here, lc is the match length - MIN_MATCH */
1038 code = length_code[lc];
1039 send_code(s, code+LITERALS+1, ltree); /* send the length code */
1040 extra = extra_lbits[code];
1041 if (extra != 0) {
1042 lc -= base_length[code];
1043 send_bits(s, lc, extra); /* send the extra length bits */
1044 }
1045 dist--; /* dist is now the match distance - 1 */
1046 code = d_code(dist);
1047 Assert (code < D_CODES, "bad d_code");
1048
1049 send_code(s, code, dtree); /* send the distance code */
1050 extra = extra_dbits[code];
1051 if (extra != 0) {
1052 dist -= base_dist[code];
1053 send_bits(s, dist, extra); /* send the extra distance bits */
1054 }
1055 } /* literal or match pair ? */
1056
1057 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1058 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1059
1060 } while (lx < s->last_lit);
1061
1062 send_code(s, END_BLOCK, ltree);
1063 s->last_eob_len = ltree[END_BLOCK].Len;
1064 }
1065
1066 /* ===========================================================================
1067 * Set the data type to ASCII or BINARY, using a crude approximation:
1068 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1069 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1070 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1071 */
1072 static void set_data_type(
1073 deflate_state *s
1074 )
1075 {
1076 int n = 0;
1077 unsigned ascii_freq = 0;
1078 unsigned bin_freq = 0;
1079 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1080 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1081 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1082 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1083 }
1084
1085 /* ===========================================================================
1086 * Copy a stored block, storing first the length and its
1087 * one's complement if requested.
1088 */
1089 static void copy_block(
1090 deflate_state *s,
1091 char *buf, /* the input data */
1092 unsigned len, /* its length */
1093 int header /* true if block header must be written */
1094 )
1095 {
1096 bi_windup(s); /* align on byte boundary */
1097 s->last_eob_len = 8; /* enough lookahead for inflate */
1098
1099 if (header) {
1100 put_short(s, (ush)len);
1101 put_short(s, (ush)~len);
1102 #ifdef DEBUG_ZLIB
1103 s->bits_sent += 2*16;
1104 #endif
1105 }
1106 #ifdef DEBUG_ZLIB
1107 s->bits_sent += (ulg)len<<3;
1108 #endif
1109 /* bundle up the put_byte(s, *buf++) calls */
1110 memcpy(&s->pending_buf[s->pending], buf, len);
1111 s->pending += len;
1112 }
1113