Line data Source code
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 0 : static void tr_static_init(void)
172 : {
173 0 : static int static_init_done;
174 0 : int n; /* iterates over tree elements */
175 0 : int bits; /* bit counter */
176 0 : int length; /* length value */
177 0 : int code; /* code value */
178 0 : int dist; /* distance index */
179 0 : ush bl_count[MAX_BITS+1];
180 : /* number of codes at each bit length for an optimal tree */
181 :
182 0 : if (static_init_done) return;
183 :
184 : /* Initialize the mapping length (0..255) -> length code (0..28) */
185 : length = 0;
186 0 : for (code = 0; code < LENGTH_CODES-1; code++) {
187 0 : base_length[code] = length;
188 0 : for (n = 0; n < (1<<extra_lbits[code]); n++) {
189 0 : length_code[length++] = (uch)code;
190 : }
191 : }
192 0 : 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 0 : length_code[length-1] = (uch)code;
198 :
199 : /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
200 0 : dist = 0;
201 0 : for (code = 0 ; code < 16; code++) {
202 0 : base_dist[code] = dist;
203 0 : for (n = 0; n < (1<<extra_dbits[code]); n++) {
204 0 : dist_code[dist++] = (uch)code;
205 : }
206 : }
207 0 : Assert (dist == 256, "tr_static_init: dist != 256");
208 0 : dist >>= 7; /* from now on, all distances are divided by 128 */
209 0 : for ( ; code < D_CODES; code++) {
210 0 : base_dist[code] = dist << 7;
211 0 : for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
212 0 : 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 0 : for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
219 : n = 0;
220 0 : while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
221 0 : while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
222 0 : while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
223 0 : 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 0 : gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
229 :
230 : /* The static distance tree is trivial: */
231 0 : for (n = 0; n < D_CODES; n++) {
232 0 : static_dtree[n].Len = 5;
233 0 : static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
234 : }
235 0 : static_init_done = 1;
236 : }
237 :
238 : /* ===========================================================================
239 : * Initialize the tree data structures for a new zlib stream.
240 : */
241 0 : void zlib_tr_init(
242 : deflate_state *s
243 : )
244 : {
245 0 : tr_static_init();
246 :
247 0 : s->compressed_len = 0L;
248 :
249 0 : s->l_desc.dyn_tree = s->dyn_ltree;
250 0 : s->l_desc.stat_desc = &static_l_desc;
251 :
252 0 : s->d_desc.dyn_tree = s->dyn_dtree;
253 0 : s->d_desc.stat_desc = &static_d_desc;
254 :
255 0 : s->bl_desc.dyn_tree = s->bl_tree;
256 0 : s->bl_desc.stat_desc = &static_bl_desc;
257 :
258 0 : s->bi_buf = 0;
259 0 : s->bi_valid = 0;
260 0 : 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 0 : init_block(s);
267 0 : }
268 :
269 : /* ===========================================================================
270 : * Initialize a new block.
271 : */
272 0 : static void init_block(
273 : deflate_state *s
274 : )
275 : {
276 0 : int n; /* iterates over tree elements */
277 :
278 : /* Initialize the trees. */
279 0 : for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
280 0 : for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
281 0 : for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
282 :
283 0 : s->dyn_ltree[END_BLOCK].Freq = 1;
284 0 : s->opt_len = s->static_len = 0L;
285 0 : s->last_lit = s->matches = 0;
286 0 : }
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 0 : 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 0 : int v = s->heap[k];
324 0 : int j = k << 1; /* left son of k */
325 0 : while (j <= s->heap_len) {
326 : /* Set j to the smallest of the two sons: */
327 0 : if (j < s->heap_len &&
328 0 : smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
329 0 : j++;
330 : }
331 : /* Exit if v is smaller than both sons */
332 0 : if (smaller(tree, v, s->heap[j], s->depth)) break;
333 :
334 : /* Exchange v with the smallest son */
335 0 : s->heap[k] = s->heap[j]; k = j;
336 :
337 : /* And continue down the tree, setting j to the left son of k */
338 0 : j <<= 1;
339 : }
340 0 : s->heap[k] = v;
341 0 : }
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 0 : static void gen_bitlen(
354 : deflate_state *s,
355 : tree_desc *desc /* the tree descriptor */
356 : )
357 : {
358 0 : ct_data *tree = desc->dyn_tree;
359 0 : int max_code = desc->max_code;
360 0 : const ct_data *stree = desc->stat_desc->static_tree;
361 0 : const int *extra = desc->stat_desc->extra_bits;
362 0 : int base = desc->stat_desc->extra_base;
363 0 : int max_length = desc->stat_desc->max_length;
364 0 : int h; /* heap index */
365 0 : int n, m; /* iterate over the tree elements */
366 0 : int bits; /* bit length */
367 0 : int xbits; /* extra bits */
368 0 : ush f; /* frequency */
369 0 : int overflow = 0; /* number of elements with bit length too large */
370 :
371 0 : 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 0 : tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
377 :
378 0 : for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
379 0 : n = s->heap[h];
380 0 : bits = tree[tree[n].Dad].Len + 1;
381 0 : if (bits > max_length) bits = max_length, overflow++;
382 0 : tree[n].Len = (ush)bits;
383 : /* We overwrite tree[n].Dad which is no longer needed */
384 :
385 0 : if (n > max_code) continue; /* not a leaf node */
386 :
387 0 : s->bl_count[bits]++;
388 0 : xbits = 0;
389 0 : if (n >= base) xbits = extra[n-base];
390 0 : f = tree[n].Freq;
391 0 : s->opt_len += (ulg)f * (bits + xbits);
392 0 : if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
393 : }
394 0 : if (overflow == 0) return;
395 :
396 0 : 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 0 : do {
401 0 : bits = max_length-1;
402 0 : while (s->bl_count[bits] == 0) bits--;
403 0 : s->bl_count[bits]--; /* move one leaf down the tree */
404 0 : s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
405 0 : 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 0 : overflow -= 2;
410 0 : } 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 0 : for (bits = max_length; bits != 0; bits--) {
418 0 : n = s->bl_count[bits];
419 0 : while (n != 0) {
420 0 : m = s->heap[--h];
421 0 : if (m > max_code) continue;
422 0 : if (tree[m].Len != (unsigned) bits) {
423 0 : Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
424 0 : s->opt_len += ((long)bits - (long)tree[m].Len)
425 0 : *(long)tree[m].Freq;
426 0 : tree[m].Len = (ush)bits;
427 : }
428 0 : 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 0 : 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 0 : ush next_code[MAX_BITS+1]; /* next code value for each bit length */
448 0 : ush code = 0; /* running code value */
449 0 : int bits; /* bit index */
450 0 : int n; /* code index */
451 :
452 : /* The distribution counts are first used to generate the code values
453 : * without bit reversal.
454 : */
455 0 : for (bits = 1; bits <= MAX_BITS; bits++) {
456 0 : 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 0 : for (n = 0; n <= max_code; n++) {
466 0 : int len = tree[n].Len;
467 0 : if (len == 0) continue;
468 : /* Now reverse the bits */
469 0 : 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 0 : n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
473 : }
474 0 : }
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 0 : static void build_tree(
485 : deflate_state *s,
486 : tree_desc *desc /* the tree descriptor */
487 : )
488 : {
489 0 : ct_data *tree = desc->dyn_tree;
490 0 : const ct_data *stree = desc->stat_desc->static_tree;
491 0 : int elems = desc->stat_desc->elems;
492 0 : int n, m; /* iterate over heap elements */
493 0 : int max_code = -1; /* largest code with non zero frequency */
494 0 : 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 0 : s->heap_len = 0, s->heap_max = HEAP_SIZE;
501 :
502 0 : for (n = 0; n < elems; n++) {
503 0 : if (tree[n].Freq != 0) {
504 0 : s->heap[++(s->heap_len)] = max_code = n;
505 0 : s->depth[n] = 0;
506 : } else {
507 0 : 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 0 : while (s->heap_len < 2) {
517 0 : node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
518 0 : tree[node].Freq = 1;
519 0 : s->depth[node] = 0;
520 0 : 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 0 : 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 0 : 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 0 : do {
535 0 : pqremove(s, tree, n); /* n = node of least frequency */
536 0 : m = s->heap[SMALLEST]; /* m = node of next least frequency */
537 :
538 0 : s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
539 0 : s->heap[--(s->heap_max)] = m;
540 :
541 : /* Create a new node father of n and m */
542 0 : tree[node].Freq = tree[n].Freq + tree[m].Freq;
543 0 : s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);
544 0 : 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 0 : s->heap[SMALLEST] = node++;
553 0 : pqdownheap(s, tree, SMALLEST);
554 :
555 0 : } while (s->heap_len >= 2);
556 :
557 0 : 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 0 : gen_bitlen(s, (tree_desc *)desc);
563 :
564 : /* The field len is now set, we can generate the bit codes */
565 0 : gen_codes ((ct_data *)tree, max_code, s->bl_count);
566 0 : }
567 :
568 : /* ===========================================================================
569 : * Scan a literal or distance tree to determine the frequencies of the codes
570 : * in the bit length tree.
571 : */
572 0 : 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 0 : int n; /* iterates over all tree elements */
579 0 : int prevlen = -1; /* last emitted length */
580 0 : int curlen; /* length of current code */
581 0 : int nextlen = tree[0].Len; /* length of next code */
582 0 : int count = 0; /* repeat count of the current code */
583 0 : int max_count = 7; /* max repeat count */
584 0 : int min_count = 4; /* min repeat count */
585 :
586 0 : if (nextlen == 0) max_count = 138, min_count = 3;
587 0 : tree[max_code+1].Len = (ush)0xffff; /* guard */
588 :
589 0 : for (n = 0; n <= max_code; n++) {
590 0 : curlen = nextlen; nextlen = tree[n+1].Len;
591 0 : if (++count < max_count && curlen == nextlen) {
592 0 : continue;
593 0 : } else if (count < min_count) {
594 0 : s->bl_tree[curlen].Freq += count;
595 0 : } else if (curlen != 0) {
596 0 : if (curlen != prevlen) s->bl_tree[curlen].Freq++;
597 0 : s->bl_tree[REP_3_6].Freq++;
598 0 : } else if (count <= 10) {
599 0 : s->bl_tree[REPZ_3_10].Freq++;
600 : } else {
601 0 : s->bl_tree[REPZ_11_138].Freq++;
602 : }
603 0 : count = 0; prevlen = curlen;
604 0 : if (nextlen == 0) {
605 : max_count = 138, min_count = 3;
606 0 : } else if (curlen == nextlen) {
607 : max_count = 6, min_count = 3;
608 : } else {
609 0 : max_count = 7, min_count = 4;
610 : }
611 : }
612 0 : }
613 :
614 : /* ===========================================================================
615 : * Send a literal or distance tree in compressed form, using the codes in
616 : * bl_tree.
617 : */
618 0 : 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 0 : int n; /* iterates over all tree elements */
625 0 : int prevlen = -1; /* last emitted length */
626 0 : int curlen; /* length of current code */
627 0 : int nextlen = tree[0].Len; /* length of next code */
628 0 : int count = 0; /* repeat count of the current code */
629 0 : int max_count = 7; /* max repeat count */
630 0 : int min_count = 4; /* min repeat count */
631 :
632 : /* tree[max_code+1].Len = -1; */ /* guard already set */
633 0 : if (nextlen == 0) max_count = 138, min_count = 3;
634 :
635 0 : for (n = 0; n <= max_code; n++) {
636 0 : curlen = nextlen; nextlen = tree[n+1].Len;
637 0 : if (++count < max_count && curlen == nextlen) {
638 0 : continue;
639 0 : } else if (count < min_count) {
640 0 : do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
641 :
642 0 : } else if (curlen != 0) {
643 0 : if (curlen != prevlen) {
644 0 : send_code(s, curlen, s->bl_tree); count--;
645 : }
646 0 : Assert(count >= 3 && count <= 6, " 3_6?");
647 0 : send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
648 :
649 0 : } else if (count <= 10) {
650 0 : send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
651 :
652 : } else {
653 0 : send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
654 : }
655 0 : count = 0; prevlen = curlen;
656 0 : if (nextlen == 0) {
657 : max_count = 138, min_count = 3;
658 0 : } else if (curlen == nextlen) {
659 : max_count = 6, min_count = 3;
660 : } else {
661 0 : max_count = 7, min_count = 4;
662 : }
663 : }
664 0 : }
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 0 : static int build_bl_tree(
671 : deflate_state *s
672 : )
673 : {
674 0 : 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 0 : scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
678 0 : scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
679 :
680 : /* Build the bit length tree: */
681 0 : 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 0 : for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
691 0 : 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 0 : s->opt_len += 3*(max_blindex+1) + 5+5+4;
695 : Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
696 0 : s->opt_len, s->static_len));
697 :
698 0 : 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 0 : 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 0 : int rank; /* index in bl_order */
714 :
715 0 : Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
716 : Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
717 0 : "too many codes");
718 0 : Tracev((stderr, "\nbl counts: "));
719 0 : send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
720 0 : send_bits(s, dcodes-1, 5);
721 0 : send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
722 0 : for (rank = 0; rank < blcodes; rank++) {
723 0 : Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
724 0 : send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
725 : }
726 0 : Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
727 :
728 0 : send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
729 0 : Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
730 :
731 0 : send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
732 0 : Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
733 0 : }
734 :
735 : /* ===========================================================================
736 : * Send a stored block
737 : */
738 0 : 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 0 : send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
746 0 : s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
747 0 : s->compressed_len += (stored_len + 4) << 3;
748 :
749 0 : copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
750 0 : }
751 :
752 : /* Send just the `stored block' type code without any length bytes or data.
753 : */
754 0 : void zlib_tr_stored_type_only(
755 : deflate_state *s
756 : )
757 : {
758 0 : send_bits(s, (STORED_BLOCK << 1), 3);
759 0 : bi_windup(s);
760 0 : s->compressed_len = (s->compressed_len + 3) & ~7L;
761 0 : }
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 0 : void zlib_tr_align(
776 : deflate_state *s
777 : )
778 : {
779 0 : send_bits(s, STATIC_TREES<<1, 3);
780 0 : send_code(s, END_BLOCK, static_ltree);
781 0 : s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
782 0 : 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 0 : if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
789 0 : send_bits(s, STATIC_TREES<<1, 3);
790 0 : send_code(s, END_BLOCK, static_ltree);
791 0 : s->compressed_len += 10L;
792 0 : bi_flush(s);
793 : }
794 0 : s->last_eob_len = 7;
795 0 : }
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 0 : 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 0 : ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
810 0 : 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 0 : if (s->level > 0) {
814 :
815 : /* Check if the file is ascii or binary */
816 0 : if (s->data_type == Z_UNKNOWN) set_data_type(s);
817 :
818 : /* Construct the literal and distance trees */
819 0 : build_tree(s, (tree_desc *)(&(s->l_desc)));
820 : Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
821 0 : s->static_len));
822 :
823 0 : build_tree(s, (tree_desc *)(&(s->d_desc)));
824 : Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
825 0 : 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 0 : max_blindex = build_bl_tree(s);
834 :
835 : /* Determine the best encoding. Compute first the block length in bytes*/
836 0 : opt_lenb = (s->opt_len+3+7)>>3;
837 0 : 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 0 : s->last_lit));
842 :
843 0 : if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
844 :
845 : } else {
846 0 : Assert(buf != (char*)0, "lost buf");
847 0 : 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 0 : 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 0 : 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 0 : } else if (static_lenb == opt_lenb) {
887 : #endif
888 0 : send_bits(s, (STATIC_TREES<<1)+eof, 3);
889 0 : compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
890 0 : s->compressed_len += 3 + s->static_len;
891 : } else {
892 0 : send_bits(s, (DYN_TREES<<1)+eof, 3);
893 0 : send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
894 : max_blindex+1);
895 0 : compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
896 0 : s->compressed_len += 3 + s->opt_len;
897 : }
898 0 : Assert (s->compressed_len == s->bits_sent, "bad compressed size");
899 0 : init_block(s);
900 :
901 0 : if (eof) {
902 0 : bi_windup(s);
903 0 : s->compressed_len += 7; /* align on byte boundary */
904 : }
905 : Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
906 0 : s->compressed_len-7*eof));
907 :
908 0 : 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 0 : 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 0 : s->d_buf[s->last_lit] = (ush)dist;
922 0 : s->l_buf[s->last_lit++] = (uch)lc;
923 0 : if (dist == 0) {
924 : /* lc is the unmatched char */
925 0 : s->dyn_ltree[lc].Freq++;
926 : } else {
927 0 : s->matches++;
928 : /* Here, lc is the match length - MIN_MATCH */
929 0 : dist--; /* dist = match distance - 1 */
930 : Assert((ush)dist < (ush)MAX_DIST(s) &&
931 : (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
932 0 : (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match");
933 :
934 0 : s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
935 0 : s->dyn_dtree[d_code(dist)].Freq++;
936 : }
937 :
938 : /* Try to guess if it is profitable to stop the current block here */
939 0 : if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
940 : /* Compute an upper bound for the compressed length */
941 0 : ulg out_length = (ulg)s->last_lit*8L;
942 0 : ulg in_length = (ulg)((long)s->strstart - s->block_start);
943 0 : int dcode;
944 0 : for (dcode = 0; dcode < D_CODES; dcode++) {
945 0 : out_length += (ulg)s->dyn_dtree[dcode].Freq *
946 0 : (5L+extra_dbits[dcode]);
947 : }
948 0 : out_length >>= 3;
949 : Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
950 : s->last_lit, in_length, out_length,
951 0 : 100L - out_length*100L/in_length));
952 0 : if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
953 : }
954 0 : 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 0 : static void compress_block(
965 : deflate_state *s,
966 : ct_data *ltree, /* literal tree */
967 : ct_data *dtree /* distance tree */
968 : )
969 : {
970 0 : unsigned dist; /* distance of matched string */
971 0 : int lc; /* match length or unmatched char (if dist == 0) */
972 0 : unsigned lx = 0; /* running index in l_buf */
973 0 : unsigned code; /* the code to send */
974 0 : int extra; /* number of extra bits to send */
975 :
976 0 : if (s->last_lit != 0) do {
977 0 : dist = s->d_buf[lx];
978 0 : lc = s->l_buf[lx++];
979 0 : if (dist == 0) {
980 0 : 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 0 : code = length_code[lc];
985 0 : send_code(s, code+LITERALS+1, ltree); /* send the length code */
986 0 : extra = extra_lbits[code];
987 0 : if (extra != 0) {
988 0 : lc -= base_length[code];
989 0 : send_bits(s, lc, extra); /* send the extra length bits */
990 : }
991 0 : dist--; /* dist is now the match distance - 1 */
992 0 : code = d_code(dist);
993 0 : Assert (code < D_CODES, "bad d_code");
994 :
995 0 : send_code(s, code, dtree); /* send the distance code */
996 0 : extra = extra_dbits[code];
997 0 : if (extra != 0) {
998 0 : dist -= base_dist[code];
999 0 : 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 0 : Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1005 :
1006 0 : } while (lx < s->last_lit);
1007 :
1008 0 : send_code(s, END_BLOCK, ltree);
1009 0 : s->last_eob_len = ltree[END_BLOCK].Len;
1010 0 : }
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 0 : static void set_data_type(
1019 : deflate_state *s
1020 : )
1021 : {
1022 0 : int n = 0;
1023 0 : unsigned ascii_freq = 0;
1024 0 : unsigned bin_freq = 0;
1025 0 : while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1026 0 : while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1027 0 : while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1028 0 : s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1029 0 : }
1030 :
1031 : /* ===========================================================================
1032 : * Copy a stored block, storing first the length and its
1033 : * one's complement if requested.
1034 : */
1035 0 : 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 0 : bi_windup(s); /* align on byte boundary */
1043 0 : s->last_eob_len = 8; /* enough lookahead for inflate */
1044 :
1045 0 : if (header) {
1046 0 : put_short(s, (ush)len);
1047 0 : 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 0 : memcpy(&s->pending_buf[s->pending], buf, len);
1057 0 : s->pending += len;
1058 0 : }
1059 :
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