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