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