1 /* trees.c -- output deflated data using Huffman coding
2 * Copyright (C) 1995 Jean-loup Gailly
3 * For conditions of distribution and use, see copyright notice in zlib.h
9 * The "deflation" process uses several Huffman trees. The more
10 * common source values are represented by shorter bit sequences.
12 * Each code tree is stored in a compressed form which is itself
13 * a Huffman encoding of the lengths of all the code strings (in
14 * ascending order by source values). The actual code strings are
15 * reconstructed from the lengths in the inflate process, as described
16 * in the deflate specification.
20 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
21 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
24 * Data Compression: Methods and Theory, pp. 49-50.
25 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
29 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
32 /* $Id: trees.c,v 1.5 1995/05/03 17:27:12 jloup Exp $ */
40 /* ===========================================================================
45 /* Bit length codes must not exceed MAX_BL_BITS bits */
48 /* end of block literal code */
51 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
54 /* repeat a zero length 3-10 times (3 bits of repeat count) */
56 #define REPZ_11_138 18
57 /* repeat a zero length 11-138 times (7 bits of repeat count) */
59 local int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
60 = {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};
62 local int extra_dbits[D_CODES] /* extra bits for each distance code */
63 = {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};
65 local int extra_blbits[BL_CODES]/* extra bits for each bit length code */
66 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
68 local uch bl_order[BL_CODES]
69 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
70 /* The lengths of the bit length codes are sent in order of decreasing
71 * probability, to avoid transmitting the lengths for unused bit length codes.
74 #define Buf_size (8 * 2*sizeof(char))
75 /* Number of bits used within bi_buf. (bi_buf might be implemented on
76 * more than 16 bits on some systems.)
79 /* ===========================================================================
80 * Local data. These are initialized only once.
81 * To do: initialize at compile time to be completely reentrant. ???
84 local ct_data static_ltree[L_CODES+2];
85 /* The static literal tree. Since the bit lengths are imposed, there is no
86 * need for the L_CODES extra codes used during heap construction. However
87 * The codes 286 and 287 are needed to build a canonical tree (see ct_init
91 local ct_data static_dtree[D_CODES];
92 /* The static distance tree. (Actually a trivial tree since all codes use
96 local uch dist_code[512];
97 /* distance codes. The first 256 values correspond to the distances
98 * 3 .. 258, the last 256 values correspond to the top 8 bits of
99 * the 15 bit distances.
102 local uch length_code[MAX_MATCH-MIN_MATCH+1];
103 /* length code for each normalized match length (0 == MIN_MATCH) */
105 local int base_length[LENGTH_CODES];
106 /* First normalized length for each code (0 = MIN_MATCH) */
108 local int base_dist[D_CODES];
109 /* First normalized distance for each code (0 = distance of 1) */
111 struct static_tree_desc_s {
112 ct_data *static_tree; /* static tree or NULL */
113 int *extra_bits; /* extra bits for each code or NULL */
114 int extra_base; /* base index for extra_bits */
115 int elems; /* max number of elements in the tree */
116 int max_length; /* max bit length for the codes */
119 local static_tree_desc static_l_desc =
120 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
122 local static_tree_desc static_d_desc =
123 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
125 local static_tree_desc static_bl_desc =
126 {(ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
128 /* ===========================================================================
129 * Local (static) routines in this file.
132 local void ct_static_init __P((void));
133 local void init_block __P((deflate_state *s));
134 local void pqdownheap __P((deflate_state *s, ct_data *tree, int k));
135 local void gen_bitlen __P((deflate_state *s, tree_desc *desc));
136 local void gen_codes __P((ct_data *tree, int max_code, ush bl_count[]));
137 local void build_tree __P((deflate_state *s, tree_desc *desc));
138 local void scan_tree __P((deflate_state *s, ct_data *tree, int max_code));
139 local void send_tree __P((deflate_state *s, ct_data *tree, int max_code));
140 local int build_bl_tree __P((deflate_state *s));
141 local void send_all_trees __P((deflate_state *s, int lcodes, int dcodes,
143 local void compress_block __P((deflate_state *s, ct_data *ltree,
145 local void set_data_type __P((deflate_state *s));
146 local void send_bits __P((deflate_state *s, int value, int length));
147 local unsigned bi_reverse __P((unsigned value, int length));
148 local void bi_windup __P((deflate_state *s));
149 local void copy_block __P((deflate_state *s, char *buf, unsigned len,
153 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
154 /* Send a code of the given tree. c and tree must not have side effects */
157 # define send_code(s, c, tree) \
158 { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
159 send_bits(s, tree[c].Code, tree[c].Len); }
162 #define d_code(dist) \
163 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
164 /* Mapping from a distance to a distance code. dist is the distance - 1 and
165 * must not have side effects. dist_code[256] and dist_code[257] are never
169 #define MAX(a,b) (a >= b ? a : b)
170 /* the arguments must not have side effects */
172 /* ===========================================================================
173 * Initialize the various 'constant' tables.
174 * To do: do this at compile time.
176 local void ct_static_init()
178 int n; /* iterates over tree elements */
179 int bits; /* bit counter */
180 int length; /* length value */
181 int code; /* code value */
182 int dist; /* distance index */
183 ush bl_count[MAX_BITS+1];
184 /* number of codes at each bit length for an optimal tree */
186 /* Initialize the mapping length (0..255) -> length code (0..28) */
188 for (code = 0; code < LENGTH_CODES-1; code++) {
189 base_length[code] = length;
190 for (n = 0; n < (1<<extra_lbits[code]); n++) {
191 length_code[length++] = (uch)code;
194 Assert (length == 256, "ct_static_init: length != 256");
195 /* Note that the length 255 (match length 258) can be represented
196 * in two different ways: code 284 + 5 bits or code 285, so we
197 * overwrite length_code[255] to use the best encoding:
199 length_code[length-1] = (uch)code;
201 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
203 for (code = 0 ; code < 16; code++) {
204 base_dist[code] = dist;
205 for (n = 0; n < (1<<extra_dbits[code]); n++) {
206 dist_code[dist++] = (uch)code;
209 Assert (dist == 256, "ct_static_init: dist != 256");
210 dist >>= 7; /* from now on, all distances are divided by 128 */
211 for ( ; code < D_CODES; code++) {
212 base_dist[code] = dist << 7;
213 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
214 dist_code[256 + dist++] = (uch)code;
217 Assert (dist == 256, "ct_static_init: 256+dist != 512");
219 /* Construct the codes of the static literal tree */
220 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
222 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
223 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
224 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
225 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
226 /* Codes 286 and 287 do not exist, but we must include them in the
227 * tree construction to get a canonical Huffman tree (longest code
230 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
232 /* The static distance tree is trivial: */
233 for (n = 0; n < D_CODES; n++) {
234 static_dtree[n].Len = 5;
235 static_dtree[n].Code = bi_reverse(n, 5);
239 /* ===========================================================================
240 * Initialize the tree data structures for a new zlib stream.
245 if (static_dtree[0].Len == 0) {
246 ct_static_init(); /* To do: at compile time */
249 s->compressed_len = 0L;
251 s->l_desc.dyn_tree = s->dyn_ltree;
252 s->l_desc.stat_desc = &static_l_desc;
254 s->d_desc.dyn_tree = s->dyn_dtree;
255 s->d_desc.stat_desc = &static_d_desc;
257 s->bl_desc.dyn_tree = s->bl_tree;
258 s->bl_desc.stat_desc = &static_bl_desc;
266 /* Initialize the first block of the first file: */
270 /* ===========================================================================
271 * Initialize a new block.
273 local void init_block(s)
276 int n; /* iterates over tree elements */
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;
283 s->dyn_ltree[END_BLOCK].Freq = 1;
284 s->opt_len = s->static_len = 0L;
285 s->last_lit = s->matches = 0;
289 /* Index within the heap array of least frequent node in the Huffman tree */
292 /* ===========================================================================
293 * Remove the smallest element from the heap and recreate the heap with
294 * one less element. Updates heap and heap_len.
296 #define pqremove(s, tree, top) \
298 top = s->heap[SMALLEST]; \
299 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
300 pqdownheap(s, tree, SMALLEST); \
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.
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]))
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
317 local void pqdownheap(s, tree, k)
319 ct_data *tree; /* the tree to restore */
320 int k; /* node to move down */
323 int j = k << 1; /* left son of k */
324 while (j <= s->heap_len) {
325 /* Set j to the smallest of the two sons: */
326 if (j < s->heap_len &&
327 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
330 /* Exit if v is smaller than both sons */
331 if (smaller(tree, v, s->heap[j], s->depth)) break;
333 /* Exchange v with the smallest son */
334 s->heap[k] = s->heap[j]; k = j;
336 /* And continue down the tree, setting j to the left son of k */
342 /* ===========================================================================
343 * Compute the optimal bit lengths for a tree and update the total bit length
344 * for the current block.
345 * IN assertion: the fields freq and dad are set, heap[heap_max] and
346 * above are the tree nodes sorted by increasing frequency.
347 * OUT assertions: the field len is set to the optimal bit length, the
348 * array bl_count contains the frequencies for each bit length.
349 * The length opt_len is updated; static_len is also updated if stree is
352 local void gen_bitlen(s, desc)
354 tree_desc *desc; /* the tree descriptor */
356 ct_data *tree = desc->dyn_tree;
357 int max_code = desc->max_code;
358 ct_data *stree = desc->stat_desc->static_tree;
359 int *extra = desc->stat_desc->extra_bits;
360 int base = desc->stat_desc->extra_base;
361 int max_length = desc->stat_desc->max_length;
362 int h; /* heap index */
363 int n, m; /* iterate over the tree elements */
364 int bits; /* bit length */
365 int xbits; /* extra bits */
366 ush f; /* frequency */
367 int overflow = 0; /* number of elements with bit length too large */
369 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
371 /* In a first pass, compute the optimal bit lengths (which may
372 * overflow in the case of the bit length tree).
374 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
376 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
378 bits = tree[tree[n].Dad].Len + 1;
379 if (bits > max_length) bits = max_length, overflow++;
380 tree[n].Len = (ush)bits;
381 /* We overwrite tree[n].Dad which is no longer needed */
383 if (n > max_code) continue; /* not a leaf node */
387 if (n >= base) xbits = extra[n-base];
389 s->opt_len += (ulg)f * (bits + xbits);
390 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
392 if (overflow == 0) return;
394 Trace((stderr,"\nbit length overflow\n"));
395 /* This happens for example on obj2 and pic of the Calgary corpus */
397 /* Find the first bit length which could increase: */
400 while (s->bl_count[bits] == 0) bits--;
401 s->bl_count[bits]--; /* move one leaf down the tree */
402 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
403 s->bl_count[max_length]--;
404 /* The brother of the overflow item also moves one step up,
405 * but this does not affect bl_count[max_length]
408 } while (overflow > 0);
410 /* Now recompute all bit lengths, scanning in increasing frequency.
411 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
412 * lengths instead of fixing only the wrong ones. This idea is taken
413 * from 'ar' written by Haruhiko Okumura.)
415 for (bits = max_length; bits != 0; bits--) {
416 n = s->bl_count[bits];
419 if (m > max_code) continue;
420 if (tree[m].Len != (unsigned) bits) {
421 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
422 s->opt_len += ((long)bits - (long)tree[m].Len)
424 tree[m].Len = (ush)bits;
431 /* ===========================================================================
432 * Generate the codes for a given tree and bit counts (which need not be
434 * IN assertion: the array bl_count contains the bit length statistics for
435 * the given tree and the field len is set for all tree elements.
436 * OUT assertion: the field code is set for all tree elements of non
439 local void gen_codes (tree, max_code, bl_count)
440 ct_data *tree; /* the tree to decorate */
441 int max_code; /* largest code with non zero frequency */
442 ush bl_count[]; /* number of codes at each bit length */
444 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
445 ush code = 0; /* running code value */
446 int bits; /* bit index */
447 int n; /* code index */
449 /* The distribution counts are first used to generate the code values
450 * without bit reversal.
452 for (bits = 1; bits <= MAX_BITS; bits++) {
453 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
455 /* Check that the bit counts in bl_count are consistent. The last code
458 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
459 "inconsistent bit counts");
460 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
462 for (n = 0; n <= max_code; n++) {
463 int len = tree[n].Len;
464 if (len == 0) continue;
465 /* Now reverse the bits */
466 tree[n].Code = bi_reverse(next_code[len]++, len);
468 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
469 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
473 /* ===========================================================================
474 * Construct one Huffman tree and assigns the code bit strings and lengths.
475 * Update the total bit length for the current block.
476 * IN assertion: the field freq is set for all tree elements.
477 * OUT assertions: the fields len and code are set to the optimal bit length
478 * and corresponding code. The length opt_len is updated; static_len is
479 * also updated if stree is not null. The field max_code is set.
481 local void build_tree(s, desc)
483 tree_desc *desc; /* the tree descriptor */
485 ct_data *tree = desc->dyn_tree;
486 ct_data *stree = desc->stat_desc->static_tree;
487 int elems = desc->stat_desc->elems;
488 int n, m; /* iterate over heap elements */
489 int max_code = -1; /* largest code with non zero frequency */
490 int node = elems; /* next internal node of the tree */
491 int new; /* new node being created */
493 /* Construct the initial heap, with least frequent element in
494 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
495 * heap[0] is not used.
497 s->heap_len = 0, s->heap_max = HEAP_SIZE;
499 for (n = 0; n < elems; n++) {
500 if (tree[n].Freq != 0) {
501 s->heap[++(s->heap_len)] = max_code = n;
508 /* The pkzip format requires that at least one distance code exists,
509 * and that at least one bit should be sent even if there is only one
510 * possible code. So to avoid special checks later on we force at least
511 * two codes of non zero frequency.
513 while (s->heap_len < 2) {
514 new = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
517 s->opt_len--; if (stree) s->static_len -= stree[new].Len;
518 /* new is 0 or 1 so it does not have extra bits */
520 desc->max_code = max_code;
522 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
523 * establish sub-heaps of increasing lengths:
525 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
527 /* Construct the Huffman tree by repeatedly combining the least two
531 pqremove(s, tree, n); /* n = node of least frequency */
532 m = s->heap[SMALLEST]; /* m = node of next least frequency */
534 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
535 s->heap[--(s->heap_max)] = m;
537 /* Create a new node father of n and m */
538 tree[node].Freq = tree[n].Freq + tree[m].Freq;
539 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
540 tree[n].Dad = tree[m].Dad = (ush)node;
542 if (tree == s->bl_tree) {
543 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
544 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
547 /* and insert the new node in the heap */
548 s->heap[SMALLEST] = node++;
549 pqdownheap(s, tree, SMALLEST);
551 } while (s->heap_len >= 2);
553 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
555 /* At this point, the fields freq and dad are set. We can now
556 * generate the bit lengths.
558 gen_bitlen(s, (tree_desc *)desc);
560 /* The field len is now set, we can generate the bit codes */
561 gen_codes ((ct_data *)tree, max_code, s->bl_count);
564 /* ===========================================================================
565 * Scan a literal or distance tree to determine the frequencies of the codes
566 * in the bit length tree.
568 local void scan_tree (s, tree, max_code)
570 ct_data *tree; /* the tree to be scanned */
571 int max_code; /* and its largest code of non zero frequency */
573 int n; /* iterates over all tree elements */
574 int prevlen = -1; /* last emitted length */
575 int curlen; /* length of current code */
576 int nextlen = tree[0].Len; /* length of next code */
577 int count = 0; /* repeat count of the current code */
578 int max_count = 7; /* max repeat count */
579 int min_count = 4; /* min repeat count */
581 if (nextlen == 0) max_count = 138, min_count = 3;
582 tree[max_code+1].Len = (ush)0xffff; /* guard */
584 for (n = 0; n <= max_code; n++) {
585 curlen = nextlen; nextlen = tree[n+1].Len;
586 if (++count < max_count && curlen == nextlen) {
588 } else if (count < min_count) {
589 s->bl_tree[curlen].Freq += count;
590 } else if (curlen != 0) {
591 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
592 s->bl_tree[REP_3_6].Freq++;
593 } else if (count <= 10) {
594 s->bl_tree[REPZ_3_10].Freq++;
596 s->bl_tree[REPZ_11_138].Freq++;
598 count = 0; prevlen = curlen;
600 max_count = 138, min_count = 3;
601 } else if (curlen == nextlen) {
602 max_count = 6, min_count = 3;
604 max_count = 7, min_count = 4;
609 /* ===========================================================================
610 * Send a literal or distance tree in compressed form, using the codes in
613 local void send_tree (s, tree, max_code)
615 ct_data *tree; /* the tree to be scanned */
616 int max_code; /* and its largest code of non zero frequency */
618 int n; /* iterates over all tree elements */
619 int prevlen = -1; /* last emitted length */
620 int curlen; /* length of current code */
621 int nextlen = tree[0].Len; /* length of next code */
622 int count = 0; /* repeat count of the current code */
623 int max_count = 7; /* max repeat count */
624 int min_count = 4; /* min repeat count */
626 /* tree[max_code+1].Len = -1; */ /* guard already set */
627 if (nextlen == 0) max_count = 138, min_count = 3;
629 for (n = 0; n <= max_code; n++) {
630 curlen = nextlen; nextlen = tree[n+1].Len;
631 if (++count < max_count && curlen == nextlen) {
633 } else if (count < min_count) {
634 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
636 } else if (curlen != 0) {
637 if (curlen != prevlen) {
638 send_code(s, curlen, s->bl_tree); count--;
640 Assert(count >= 3 && count <= 6, " 3_6?");
641 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
643 } else if (count <= 10) {
644 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
647 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
649 count = 0; prevlen = curlen;
651 max_count = 138, min_count = 3;
652 } else if (curlen == nextlen) {
653 max_count = 6, min_count = 3;
655 max_count = 7, min_count = 4;
660 /* ===========================================================================
661 * Construct the Huffman tree for the bit lengths and return the index in
662 * bl_order of the last bit length code to send.
664 local int build_bl_tree(s)
667 int max_blindex; /* index of last bit length code of non zero freq */
669 /* Determine the bit length frequencies for literal and distance trees */
670 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
671 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
673 /* Build the bit length tree: */
674 build_tree(s, (tree_desc *)(&(s->bl_desc)));
675 /* opt_len now includes the length of the tree representations, except
676 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
679 /* Determine the number of bit length codes to send. The pkzip format
680 * requires that at least 4 bit length codes be sent. (appnote.txt says
681 * 3 but the actual value used is 4.)
683 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
684 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
686 /* Update opt_len to include the bit length tree and counts */
687 s->opt_len += 3*(max_blindex+1) + 5+5+4;
688 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
689 s->opt_len, s->static_len));
694 /* ===========================================================================
695 * Send the header for a block using dynamic Huffman trees: the counts, the
696 * lengths of the bit length codes, the literal tree and the distance tree.
697 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
699 local void send_all_trees(s, lcodes, dcodes, blcodes)
701 int lcodes, dcodes, blcodes; /* number of codes for each tree */
703 int rank; /* index in bl_order */
705 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
706 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
708 Tracev((stderr, "\nbl counts: "));
709 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
710 send_bits(s, dcodes-1, 5);
711 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
712 for (rank = 0; rank < blcodes; rank++) {
713 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
714 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
716 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
718 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
719 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
721 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
722 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
725 /* ===========================================================================
726 * Send a stored block
728 void ct_stored_block(s, buf, stored_len, eof)
730 char *buf; /* input block */
731 ulg stored_len; /* length of input block */
732 int eof; /* true if this is the last block for a file */
734 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
735 s->compressed_len = (s->compressed_len + 3 + 7) & ~7L;
736 s->compressed_len += (stored_len + 4) << 3;
738 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
741 /* ===========================================================================
742 * Send one empty static block to give enough lookahead for inflate
747 send_bits(s, STATIC_TREES<<1, 3);
748 send_code(s, END_BLOCK, static_ltree);
749 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
752 /* ===========================================================================
753 * Determine the best encoding for the current block: dynamic trees, static
754 * trees or store, and output the encoded block to the zip file. This function
755 * returns the total compressed length for the file so far.
757 ulg ct_flush_block(s, buf, stored_len, eof)
759 char *buf; /* input block, or NULL if too old */
760 ulg stored_len; /* length of input block */
761 int eof; /* true if this is the last block for a file */
763 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
764 int max_blindex; /* index of last bit length code of non zero freq */
766 /* Check if the file is ascii or binary */
767 if (s->data_type == UNKNOWN) set_data_type(s);
769 /* Construct the literal and distance trees */
770 build_tree(s, (tree_desc *)(&(s->l_desc)));
771 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
774 build_tree(s, (tree_desc *)(&(s->d_desc)));
775 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
777 /* At this point, opt_len and static_len are the total bit lengths of
778 * the compressed block data, excluding the tree representations.
781 /* Build the bit length tree for the above two trees, and get the index
782 * in bl_order of the last bit length code to send.
784 max_blindex = build_bl_tree(s);
786 /* Determine the best encoding. Compute first the block length in bytes */
787 opt_lenb = (s->opt_len+3+7)>>3;
788 static_lenb = (s->static_len+3+7)>>3;
790 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
791 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
794 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
796 /* If compression failed and this is the first and last block,
797 * and if the .zip file can be seeked (to rewrite the local header),
798 * the whole file is transformed into a stored file:
800 #ifdef STORED_FILE_OK
801 # ifdef FORCE_STORED_FILE
802 if (eof && compressed_len == 0L) { /* force stored file */
804 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
806 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
807 if (buf == (char*)0) error ("block vanished");
809 copy_block(buf, (unsigned)stored_len, 0); /* without header */
810 s->compressed_len = stored_len << 3;
813 #endif /* STORED_FILE_OK */
816 if (buf != (char*)0) { /* force stored block */
818 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
819 /* 4: two words for the lengths */
821 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
822 * Otherwise we can't have processed more than WSIZE input bytes since
823 * the last block flush, because compression would have been
824 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
825 * transform a block into a stored block.
827 ct_stored_block(s, buf, stored_len, eof);
830 } else if (static_lenb >= 0) { /* force static trees */
832 } else if (static_lenb == opt_lenb) {
834 send_bits(s, (STATIC_TREES<<1)+eof, 3);
835 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
836 s->compressed_len += 3 + s->static_len;
838 send_bits(s, (DYN_TREES<<1)+eof, 3);
839 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
841 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
842 s->compressed_len += 3 + s->opt_len;
844 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
849 s->compressed_len += 7; /* align on byte boundary */
851 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
852 s->compressed_len-7*eof));
854 return s->compressed_len >> 3;
857 /* ===========================================================================
858 * Save the match info and tally the frequency counts. Return true if
859 * the current block must be flushed.
861 int ct_tally (s, dist, lc)
863 int dist; /* distance of matched string */
864 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
866 s->d_buf[s->last_lit] = (ush)dist;
867 s->l_buf[s->last_lit++] = (uch)lc;
869 /* lc is the unmatched char */
870 s->dyn_ltree[lc].Freq++;
873 /* Here, lc is the match length - MIN_MATCH */
874 dist--; /* dist = match distance - 1 */
875 Assert((ush)dist < (ush)MAX_DIST(s) &&
876 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
877 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
879 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
880 s->dyn_dtree[d_code(dist)].Freq++;
883 /* Try to guess if it is profitable to stop the current block here */
884 if (s->level > 2 && (s->last_lit & 0xfff) == 0) {
885 /* Compute an upper bound for the compressed length */
886 ulg out_length = (ulg)s->last_lit*8L;
887 ulg in_length = (ulg)s->strstart - s->block_start;
889 for (dcode = 0; dcode < D_CODES; dcode++) {
890 out_length += (ulg)s->dyn_dtree[dcode].Freq *
891 (5L+extra_dbits[dcode]);
894 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
895 s->last_lit, in_length, out_length,
896 100L - out_length*100L/in_length));
897 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
899 return (s->last_lit == s->lit_bufsize-1);
900 /* We avoid equality with lit_bufsize because of wraparound at 64K
901 * on 16 bit machines and because stored blocks are restricted to
906 /* ===========================================================================
907 * Send the block data compressed using the given Huffman trees
909 local void compress_block(s, ltree, dtree)
911 ct_data *ltree; /* literal tree */
912 ct_data *dtree; /* distance tree */
914 unsigned dist; /* distance of matched string */
915 int lc; /* match length or unmatched char (if dist == 0) */
916 unsigned lx = 0; /* running index in l_buf */
917 unsigned code; /* the code to send */
918 int extra; /* number of extra bits to send */
920 if (s->last_lit != 0) do {
924 send_code(s, lc, ltree); /* send a literal byte */
925 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
927 /* Here, lc is the match length - MIN_MATCH */
928 code = length_code[lc];
929 send_code(s, code+LITERALS+1, ltree); /* send the length code */
930 extra = extra_lbits[code];
932 lc -= base_length[code];
933 send_bits(s, lc, extra); /* send the extra length bits */
935 dist--; /* dist is now the match distance - 1 */
937 Assert (code < D_CODES, "bad d_code");
939 send_code(s, code, dtree); /* send the distance code */
940 extra = extra_dbits[code];
942 dist -= base_dist[code];
943 send_bits(s, dist, extra); /* send the extra distance bits */
945 } /* literal or match pair ? */
947 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
948 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
950 } while (lx < s->last_lit);
952 send_code(s, END_BLOCK, ltree);
955 /* ===========================================================================
956 * Set the data type to ASCII or BINARY, using a crude approximation:
957 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
958 * IN assertion: the fields freq of dyn_ltree are set and the total of all
959 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
961 local void set_data_type(s)
965 unsigned ascii_freq = 0;
966 unsigned bin_freq = 0;
967 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
968 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
969 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
970 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? BINARY : ASCII);
973 /* ===========================================================================
974 * Output a short LSB first on the stream.
975 * IN assertion: there is enough room in pendingBuf.
977 #define put_short(s, w) { \
978 put_byte(s, (uch)((w) & 0xff)); \
979 put_byte(s, (uch)((ush)(w) >> 8)); \
982 /* ===========================================================================
983 * Send a value on a given number of bits.
984 * IN assertion: length <= 16 and value fits in length bits.
986 local void send_bits(s, value, length)
988 int value; /* value to send */
989 int length; /* number of bits */
992 Tracev((stderr," l %2d v %4x ", length, value));
993 Assert(length > 0 && length <= 15, "invalid length");
994 s->bits_sent += (ulg)length;
996 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
997 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
998 * unused bits in value.
1000 if (s->bi_valid > (int)Buf_size - length) {
1001 s->bi_buf |= (value << s->bi_valid);
1002 put_short(s, s->bi_buf);
1003 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
1004 s->bi_valid += length - Buf_size;
1006 s->bi_buf |= value << s->bi_valid;
1007 s->bi_valid += length;
1011 /* ===========================================================================
1012 * Reverse the first len bits of a code, using straightforward code (a faster
1013 * method would use a table)
1014 * IN assertion: 1 <= len <= 15
1016 local unsigned bi_reverse(code, len)
1017 unsigned code; /* the value to invert */
1018 int len; /* its bit length */
1020 register unsigned res = 0;
1023 code >>= 1, res <<= 1;
1024 } while (--len > 0);
1028 /* ===========================================================================
1029 * Write out any remaining bits in an incomplete byte.
1031 local void bi_windup(s)
1034 if (s->bi_valid > 8) {
1035 put_short(s, s->bi_buf);
1036 } else if (s->bi_valid > 0) {
1037 put_byte(s, (Byte)s->bi_buf);
1042 s->bits_sent = (s->bits_sent+7) & ~7;
1046 /* ===========================================================================
1047 * Copy a stored block, storing first the length and its
1048 * one's complement if requested.
1050 local void copy_block(s, buf, len, header)
1052 char *buf; /* the input data */
1053 unsigned len; /* its length */
1054 int header; /* true if block header must be written */
1056 bi_windup(s); /* align on byte boundary */
1059 put_short(s, (ush)len);
1060 put_short(s, (ush)~len);
1062 s->bits_sent += 2*16;
1066 s->bits_sent += (ulg)len<<3;
1069 put_byte(s, *buf++);