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 intf *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 OF((void));
133 local void init_block OF((deflate_state *s));
134 local void pqdownheap OF((deflate_state *s, ct_data *tree, int k));
135 local void gen_bitlen OF((deflate_state *s, tree_desc *desc));
136 local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count));
137 local void build_tree OF((deflate_state *s, tree_desc *desc));
138 local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code));
139 local void send_tree OF((deflate_state *s, ct_data *tree, int max_code));
140 local int build_bl_tree OF((deflate_state *s));
141 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
143 local void compress_block OF((deflate_state *s, ct_data *ltree,
145 local void set_data_type OF((deflate_state *s));
146 local unsigned bi_reverse OF((unsigned value, int length));
147 local void bi_windup OF((deflate_state *s));
148 local void bi_flush OF((deflate_state *s));
149 local void copy_block OF((deflate_state *s, charf *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 /* ===========================================================================
170 * Output a short LSB first on the stream.
171 * IN assertion: there is enough room in pendingBuf.
173 #define put_short(s, w) { \
174 put_byte(s, (uch)((w) & 0xff)); \
175 put_byte(s, (uch)((ush)(w) >> 8)); \
178 /* ===========================================================================
179 * Send a value on a given number of bits.
180 * IN assertion: length <= 16 and value fits in length bits.
183 local void send_bits OF((deflate_state *s, int value, int length));
185 local void send_bits(s, value, length)
187 int value; /* value to send */
188 int length; /* number of bits */
190 Tracev((stderr," l %2d v %4x ", length, value));
191 Assert(length > 0 && length <= 15, "invalid length");
192 s->bits_sent += (ulg)length;
194 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
195 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
196 * unused bits in value.
198 if (s->bi_valid > (int)Buf_size - length) {
199 s->bi_buf |= (value << s->bi_valid);
200 put_short(s, s->bi_buf);
201 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
202 s->bi_valid += length - Buf_size;
204 s->bi_buf |= value << s->bi_valid;
205 s->bi_valid += length;
210 #define send_bits(s, value, length) \
212 if (s->bi_valid > (int)Buf_size - len) {\
214 s->bi_buf |= (val << s->bi_valid);\
215 put_short(s, s->bi_buf);\
216 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
217 s->bi_valid += len - Buf_size;\
219 s->bi_buf |= (value) << s->bi_valid;\
226 #define MAX(a,b) (a >= b ? a : b)
227 /* the arguments must not have side effects */
229 /* ===========================================================================
230 * Initialize the various 'constant' tables.
231 * To do: do this at compile time.
233 local void ct_static_init()
235 int n; /* iterates over tree elements */
236 int bits; /* bit counter */
237 int length; /* length value */
238 int code; /* code value */
239 int dist; /* distance index */
240 ush bl_count[MAX_BITS+1];
241 /* number of codes at each bit length for an optimal tree */
243 /* Initialize the mapping length (0..255) -> length code (0..28) */
245 for (code = 0; code < LENGTH_CODES-1; code++) {
246 base_length[code] = length;
247 for (n = 0; n < (1<<extra_lbits[code]); n++) {
248 length_code[length++] = (uch)code;
251 Assert (length == 256, "ct_static_init: length != 256");
252 /* Note that the length 255 (match length 258) can be represented
253 * in two different ways: code 284 + 5 bits or code 285, so we
254 * overwrite length_code[255] to use the best encoding:
256 length_code[length-1] = (uch)code;
258 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
260 for (code = 0 ; code < 16; code++) {
261 base_dist[code] = dist;
262 for (n = 0; n < (1<<extra_dbits[code]); n++) {
263 dist_code[dist++] = (uch)code;
266 Assert (dist == 256, "ct_static_init: dist != 256");
267 dist >>= 7; /* from now on, all distances are divided by 128 */
268 for ( ; code < D_CODES; code++) {
269 base_dist[code] = dist << 7;
270 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
271 dist_code[256 + dist++] = (uch)code;
274 Assert (dist == 256, "ct_static_init: 256+dist != 512");
276 /* Construct the codes of the static literal tree */
277 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
279 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
280 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
281 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
282 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
283 /* Codes 286 and 287 do not exist, but we must include them in the
284 * tree construction to get a canonical Huffman tree (longest code
287 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
289 /* The static distance tree is trivial: */
290 for (n = 0; n < D_CODES; n++) {
291 static_dtree[n].Len = 5;
292 static_dtree[n].Code = bi_reverse(n, 5);
296 /* ===========================================================================
297 * Initialize the tree data structures for a new zlib stream.
302 if (static_dtree[0].Len == 0) {
303 ct_static_init(); /* To do: at compile time */
306 s->compressed_len = 0L;
308 s->l_desc.dyn_tree = s->dyn_ltree;
309 s->l_desc.stat_desc = &static_l_desc;
311 s->d_desc.dyn_tree = s->dyn_dtree;
312 s->d_desc.stat_desc = &static_d_desc;
314 s->bl_desc.dyn_tree = s->bl_tree;
315 s->bl_desc.stat_desc = &static_bl_desc;
319 s->last_eob_len = 8; /* enough lookahead for inflate */
324 /* Initialize the first block of the first file: */
328 /* ===========================================================================
329 * Initialize a new block.
331 local void init_block(s)
334 int n; /* iterates over tree elements */
336 /* Initialize the trees. */
337 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
338 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
339 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
341 s->dyn_ltree[END_BLOCK].Freq = 1;
342 s->opt_len = s->static_len = 0L;
343 s->last_lit = s->matches = 0;
347 /* Index within the heap array of least frequent node in the Huffman tree */
350 /* ===========================================================================
351 * Remove the smallest element from the heap and recreate the heap with
352 * one less element. Updates heap and heap_len.
354 #define pqremove(s, tree, top) \
356 top = s->heap[SMALLEST]; \
357 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
358 pqdownheap(s, tree, SMALLEST); \
361 /* ===========================================================================
362 * Compares to subtrees, using the tree depth as tie breaker when
363 * the subtrees have equal frequency. This minimizes the worst case length.
365 #define smaller(tree, n, m, depth) \
366 (tree[n].Freq < tree[m].Freq || \
367 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
369 /* ===========================================================================
370 * Restore the heap property by moving down the tree starting at node k,
371 * exchanging a node with the smallest of its two sons if necessary, stopping
372 * when the heap property is re-established (each father smaller than its
375 local void pqdownheap(s, tree, k)
377 ct_data *tree; /* the tree to restore */
378 int k; /* node to move down */
381 int j = k << 1; /* left son of k */
382 while (j <= s->heap_len) {
383 /* Set j to the smallest of the two sons: */
384 if (j < s->heap_len &&
385 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
388 /* Exit if v is smaller than both sons */
389 if (smaller(tree, v, s->heap[j], s->depth)) break;
391 /* Exchange v with the smallest son */
392 s->heap[k] = s->heap[j]; k = j;
394 /* And continue down the tree, setting j to the left son of k */
400 /* ===========================================================================
401 * Compute the optimal bit lengths for a tree and update the total bit length
402 * for the current block.
403 * IN assertion: the fields freq and dad are set, heap[heap_max] and
404 * above are the tree nodes sorted by increasing frequency.
405 * OUT assertions: the field len is set to the optimal bit length, the
406 * array bl_count contains the frequencies for each bit length.
407 * The length opt_len is updated; static_len is also updated if stree is
410 local void gen_bitlen(s, desc)
412 tree_desc *desc; /* the tree descriptor */
414 ct_data *tree = desc->dyn_tree;
415 int max_code = desc->max_code;
416 ct_data *stree = desc->stat_desc->static_tree;
417 intf *extra = desc->stat_desc->extra_bits;
418 int base = desc->stat_desc->extra_base;
419 int max_length = desc->stat_desc->max_length;
420 int h; /* heap index */
421 int n, m; /* iterate over the tree elements */
422 int bits; /* bit length */
423 int xbits; /* extra bits */
424 ush f; /* frequency */
425 int overflow = 0; /* number of elements with bit length too large */
427 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
429 /* In a first pass, compute the optimal bit lengths (which may
430 * overflow in the case of the bit length tree).
432 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
434 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
436 bits = tree[tree[n].Dad].Len + 1;
437 if (bits > max_length) bits = max_length, overflow++;
438 tree[n].Len = (ush)bits;
439 /* We overwrite tree[n].Dad which is no longer needed */
441 if (n > max_code) continue; /* not a leaf node */
445 if (n >= base) xbits = extra[n-base];
447 s->opt_len += (ulg)f * (bits + xbits);
448 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
450 if (overflow == 0) return;
452 Trace((stderr,"\nbit length overflow\n"));
453 /* This happens for example on obj2 and pic of the Calgary corpus */
455 /* Find the first bit length which could increase: */
458 while (s->bl_count[bits] == 0) bits--;
459 s->bl_count[bits]--; /* move one leaf down the tree */
460 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
461 s->bl_count[max_length]--;
462 /* The brother of the overflow item also moves one step up,
463 * but this does not affect bl_count[max_length]
466 } while (overflow > 0);
468 /* Now recompute all bit lengths, scanning in increasing frequency.
469 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
470 * lengths instead of fixing only the wrong ones. This idea is taken
471 * from 'ar' written by Haruhiko Okumura.)
473 for (bits = max_length; bits != 0; bits--) {
474 n = s->bl_count[bits];
477 if (m > max_code) continue;
478 if (tree[m].Len != (unsigned) bits) {
479 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
480 s->opt_len += ((long)bits - (long)tree[m].Len)
482 tree[m].Len = (ush)bits;
489 /* ===========================================================================
490 * Generate the codes for a given tree and bit counts (which need not be
492 * IN assertion: the array bl_count contains the bit length statistics for
493 * the given tree and the field len is set for all tree elements.
494 * OUT assertion: the field code is set for all tree elements of non
497 local void gen_codes (tree, max_code, bl_count)
498 ct_data *tree; /* the tree to decorate */
499 int max_code; /* largest code with non zero frequency */
500 ushf *bl_count; /* number of codes at each bit length */
502 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
503 ush code = 0; /* running code value */
504 int bits; /* bit index */
505 int n; /* code index */
507 /* The distribution counts are first used to generate the code values
508 * without bit reversal.
510 for (bits = 1; bits <= MAX_BITS; bits++) {
511 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
513 /* Check that the bit counts in bl_count are consistent. The last code
516 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
517 "inconsistent bit counts");
518 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
520 for (n = 0; n <= max_code; n++) {
521 int len = tree[n].Len;
522 if (len == 0) continue;
523 /* Now reverse the bits */
524 tree[n].Code = bi_reverse(next_code[len]++, len);
526 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
527 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
531 /* ===========================================================================
532 * Construct one Huffman tree and assigns the code bit strings and lengths.
533 * Update the total bit length for the current block.
534 * IN assertion: the field freq is set for all tree elements.
535 * OUT assertions: the fields len and code are set to the optimal bit length
536 * and corresponding code. The length opt_len is updated; static_len is
537 * also updated if stree is not null. The field max_code is set.
539 local void build_tree(s, desc)
541 tree_desc *desc; /* the tree descriptor */
543 ct_data *tree = desc->dyn_tree;
544 ct_data *stree = desc->stat_desc->static_tree;
545 int elems = desc->stat_desc->elems;
546 int n, m; /* iterate over heap elements */
547 int max_code = -1; /* largest code with non zero frequency */
548 int node; /* new node being created */
550 /* Construct the initial heap, with least frequent element in
551 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
552 * heap[0] is not used.
554 s->heap_len = 0, s->heap_max = HEAP_SIZE;
556 for (n = 0; n < elems; n++) {
557 if (tree[n].Freq != 0) {
558 s->heap[++(s->heap_len)] = max_code = n;
565 /* The pkzip format requires that at least one distance code exists,
566 * and that at least one bit should be sent even if there is only one
567 * possible code. So to avoid special checks later on we force at least
568 * two codes of non zero frequency.
570 while (s->heap_len < 2) {
571 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
574 s->opt_len--; if (stree) s->static_len -= stree[node].Len;
575 /* node is 0 or 1 so it does not have extra bits */
577 desc->max_code = max_code;
579 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
580 * establish sub-heaps of increasing lengths:
582 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
584 /* Construct the Huffman tree by repeatedly combining the least two
587 node = elems; /* next internal node of the tree */
589 pqremove(s, tree, n); /* n = node of least frequency */
590 m = s->heap[SMALLEST]; /* m = node of next least frequency */
592 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
593 s->heap[--(s->heap_max)] = m;
595 /* Create a new node father of n and m */
596 tree[node].Freq = tree[n].Freq + tree[m].Freq;
597 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
598 tree[n].Dad = tree[m].Dad = (ush)node;
600 if (tree == s->bl_tree) {
601 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
602 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
605 /* and insert the new node in the heap */
606 s->heap[SMALLEST] = node++;
607 pqdownheap(s, tree, SMALLEST);
609 } while (s->heap_len >= 2);
611 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
613 /* At this point, the fields freq and dad are set. We can now
614 * generate the bit lengths.
616 gen_bitlen(s, (tree_desc *)desc);
618 /* The field len is now set, we can generate the bit codes */
619 gen_codes ((ct_data *)tree, max_code, s->bl_count);
622 /* ===========================================================================
623 * Scan a literal or distance tree to determine the frequencies of the codes
624 * in the bit length tree.
626 local void scan_tree (s, tree, max_code)
628 ct_data *tree; /* the tree to be scanned */
629 int max_code; /* and its largest code of non zero frequency */
631 int n; /* iterates over all tree elements */
632 int prevlen = -1; /* last emitted length */
633 int curlen; /* length of current code */
634 int nextlen = tree[0].Len; /* length of next code */
635 int count = 0; /* repeat count of the current code */
636 int max_count = 7; /* max repeat count */
637 int min_count = 4; /* min repeat count */
639 if (nextlen == 0) max_count = 138, min_count = 3;
640 tree[max_code+1].Len = (ush)0xffff; /* guard */
642 for (n = 0; n <= max_code; n++) {
643 curlen = nextlen; nextlen = tree[n+1].Len;
644 if (++count < max_count && curlen == nextlen) {
646 } else if (count < min_count) {
647 s->bl_tree[curlen].Freq += count;
648 } else if (curlen != 0) {
649 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
650 s->bl_tree[REP_3_6].Freq++;
651 } else if (count <= 10) {
652 s->bl_tree[REPZ_3_10].Freq++;
654 s->bl_tree[REPZ_11_138].Freq++;
656 count = 0; prevlen = curlen;
658 max_count = 138, min_count = 3;
659 } else if (curlen == nextlen) {
660 max_count = 6, min_count = 3;
662 max_count = 7, min_count = 4;
667 /* ===========================================================================
668 * Send a literal or distance tree in compressed form, using the codes in
671 local void send_tree (s, tree, max_code)
673 ct_data *tree; /* the tree to be scanned */
674 int max_code; /* and its largest code of non zero frequency */
676 int n; /* iterates over all tree elements */
677 int prevlen = -1; /* last emitted length */
678 int curlen; /* length of current code */
679 int nextlen = tree[0].Len; /* length of next code */
680 int count = 0; /* repeat count of the current code */
681 int max_count = 7; /* max repeat count */
682 int min_count = 4; /* min repeat count */
684 /* tree[max_code+1].Len = -1; */ /* guard already set */
685 if (nextlen == 0) max_count = 138, min_count = 3;
687 for (n = 0; n <= max_code; n++) {
688 curlen = nextlen; nextlen = tree[n+1].Len;
689 if (++count < max_count && curlen == nextlen) {
691 } else if (count < min_count) {
692 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
694 } else if (curlen != 0) {
695 if (curlen != prevlen) {
696 send_code(s, curlen, s->bl_tree); count--;
698 Assert(count >= 3 && count <= 6, " 3_6?");
699 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
701 } else if (count <= 10) {
702 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
705 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
707 count = 0; prevlen = curlen;
709 max_count = 138, min_count = 3;
710 } else if (curlen == nextlen) {
711 max_count = 6, min_count = 3;
713 max_count = 7, min_count = 4;
718 /* ===========================================================================
719 * Construct the Huffman tree for the bit lengths and return the index in
720 * bl_order of the last bit length code to send.
722 local int build_bl_tree(s)
725 int max_blindex; /* index of last bit length code of non zero freq */
727 /* Determine the bit length frequencies for literal and distance trees */
728 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
729 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
731 /* Build the bit length tree: */
732 build_tree(s, (tree_desc *)(&(s->bl_desc)));
733 /* opt_len now includes the length of the tree representations, except
734 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
737 /* Determine the number of bit length codes to send. The pkzip format
738 * requires that at least 4 bit length codes be sent. (appnote.txt says
739 * 3 but the actual value used is 4.)
741 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
742 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
744 /* Update opt_len to include the bit length tree and counts */
745 s->opt_len += 3*(max_blindex+1) + 5+5+4;
746 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
747 s->opt_len, s->static_len));
752 /* ===========================================================================
753 * Send the header for a block using dynamic Huffman trees: the counts, the
754 * lengths of the bit length codes, the literal tree and the distance tree.
755 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
757 local void send_all_trees(s, lcodes, dcodes, blcodes)
759 int lcodes, dcodes, blcodes; /* number of codes for each tree */
761 int rank; /* index in bl_order */
763 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
764 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
766 Tracev((stderr, "\nbl counts: "));
767 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
768 send_bits(s, dcodes-1, 5);
769 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
770 for (rank = 0; rank < blcodes; rank++) {
771 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
772 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
774 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
776 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
777 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
779 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
780 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
783 /* ===========================================================================
784 * Send a stored block
786 void ct_stored_block(s, buf, stored_len, eof)
788 charf *buf; /* input block */
789 ulg stored_len; /* length of input block */
790 int eof; /* true if this is the last block for a file */
792 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
793 s->compressed_len = (s->compressed_len + 3 + 7) & ~7L;
794 s->compressed_len += (stored_len + 4) << 3;
796 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
799 /* ===========================================================================
800 * Send one empty static block to give enough lookahead for inflate.
801 * This takes 10 bits, of which 7 may remain in the bit buffer.
802 * The current inflate code requires 9 bits of lookahead. If the EOB
803 * code for the previous block was coded on 5 bits or less, inflate
804 * may have only 5+3 bits of lookahead to decode this EOB.
805 * (There are no problems if the previous block is stored or fixed.)
810 send_bits(s, STATIC_TREES<<1, 3);
811 send_code(s, END_BLOCK, static_ltree);
812 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
814 /* Of the 10 bits for the empty block, we have already sent
815 * (10 - bi_valid) bits. The lookahead for the EOB of the previous
816 * block was thus its length plus what we have just sent.
818 if (s->last_eob_len + 10 - s->bi_valid < 9) {
819 send_bits(s, STATIC_TREES<<1, 3);
820 send_code(s, END_BLOCK, static_ltree);
821 s->compressed_len += 10L;
827 /* ===========================================================================
828 * Determine the best encoding for the current block: dynamic trees, static
829 * trees or store, and output the encoded block to the zip file. This function
830 * returns the total compressed length for the file so far.
832 ulg ct_flush_block(s, buf, stored_len, eof)
834 charf *buf; /* input block, or NULL if too old */
835 ulg stored_len; /* length of input block */
836 int eof; /* true if this is the last block for a file */
838 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
839 int max_blindex; /* index of last bit length code of non zero freq */
841 /* Check if the file is ascii or binary */
842 if (s->data_type == UNKNOWN) set_data_type(s);
844 /* Construct the literal and distance trees */
845 build_tree(s, (tree_desc *)(&(s->l_desc)));
846 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
849 build_tree(s, (tree_desc *)(&(s->d_desc)));
850 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
852 /* At this point, opt_len and static_len are the total bit lengths of
853 * the compressed block data, excluding the tree representations.
856 /* Build the bit length tree for the above two trees, and get the index
857 * in bl_order of the last bit length code to send.
859 max_blindex = build_bl_tree(s);
861 /* Determine the best encoding. Compute first the block length in bytes */
862 opt_lenb = (s->opt_len+3+7)>>3;
863 static_lenb = (s->static_len+3+7)>>3;
865 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
866 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
869 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
871 /* If compression failed and this is the first and last block,
872 * and if the .zip file can be seeked (to rewrite the local header),
873 * the whole file is transformed into a stored file:
875 #ifdef STORED_FILE_OK
876 # ifdef FORCE_STORED_FILE
877 if (eof && compressed_len == 0L) { /* force stored file */
879 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
881 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
882 if (buf == (charf*)0) error ("block vanished");
884 copy_block(buf, (unsigned)stored_len, 0); /* without header */
885 s->compressed_len = stored_len << 3;
888 #endif /* STORED_FILE_OK */
891 if (buf != (char*)0) { /* force stored block */
893 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
894 /* 4: two words for the lengths */
896 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
897 * Otherwise we can't have processed more than WSIZE input bytes since
898 * the last block flush, because compression would have been
899 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
900 * transform a block into a stored block.
902 ct_stored_block(s, buf, stored_len, eof);
905 } else if (static_lenb >= 0) { /* force static trees */
907 } else if (static_lenb == opt_lenb) {
909 send_bits(s, (STATIC_TREES<<1)+eof, 3);
910 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
911 s->compressed_len += 3 + s->static_len;
913 send_bits(s, (DYN_TREES<<1)+eof, 3);
914 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
916 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
917 s->compressed_len += 3 + s->opt_len;
919 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
924 s->compressed_len += 7; /* align on byte boundary */
926 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
927 s->compressed_len-7*eof));
929 return s->compressed_len >> 3;
932 /* ===========================================================================
933 * Save the match info and tally the frequency counts. Return true if
934 * the current block must be flushed.
936 int ct_tally (s, dist, lc)
938 int dist; /* distance of matched string */
939 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
941 s->d_buf[s->last_lit] = (ush)dist;
942 s->l_buf[s->last_lit++] = (uch)lc;
944 /* lc is the unmatched char */
945 s->dyn_ltree[lc].Freq++;
948 /* Here, lc is the match length - MIN_MATCH */
949 dist--; /* dist = match distance - 1 */
950 Assert((ush)dist < (ush)MAX_DIST(s) &&
951 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
952 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
954 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
955 s->dyn_dtree[d_code(dist)].Freq++;
958 /* Try to guess if it is profitable to stop the current block here */
959 if (s->level > 2 && (s->last_lit & 0xfff) == 0) {
960 /* Compute an upper bound for the compressed length */
961 ulg out_length = (ulg)s->last_lit*8L;
962 ulg in_length = (ulg)s->strstart - s->block_start;
964 for (dcode = 0; dcode < D_CODES; dcode++) {
965 out_length += (ulg)s->dyn_dtree[dcode].Freq *
966 (5L+extra_dbits[dcode]);
969 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
970 s->last_lit, in_length, out_length,
971 100L - out_length*100L/in_length));
972 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
974 return (s->last_lit == s->lit_bufsize-1);
975 /* We avoid equality with lit_bufsize because of wraparound at 64K
976 * on 16 bit machines and because stored blocks are restricted to
981 /* ===========================================================================
982 * Send the block data compressed using the given Huffman trees
984 local void compress_block(s, ltree, dtree)
986 ct_data *ltree; /* literal tree */
987 ct_data *dtree; /* distance tree */
989 unsigned dist; /* distance of matched string */
990 int lc; /* match length or unmatched char (if dist == 0) */
991 unsigned lx = 0; /* running index in l_buf */
992 unsigned code; /* the code to send */
993 int extra; /* number of extra bits to send */
995 if (s->last_lit != 0) do {
999 send_code(s, lc, ltree); /* send a literal byte */
1000 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1002 /* Here, lc is the match length - MIN_MATCH */
1003 code = length_code[lc];
1004 send_code(s, code+LITERALS+1, ltree); /* send the length code */
1005 extra = extra_lbits[code];
1007 lc -= base_length[code];
1008 send_bits(s, lc, extra); /* send the extra length bits */
1010 dist--; /* dist is now the match distance - 1 */
1011 code = d_code(dist);
1012 Assert (code < D_CODES, "bad d_code");
1014 send_code(s, code, dtree); /* send the distance code */
1015 extra = extra_dbits[code];
1017 dist -= base_dist[code];
1018 send_bits(s, dist, extra); /* send the extra distance bits */
1020 } /* literal or match pair ? */
1022 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1023 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1025 } while (lx < s->last_lit);
1027 send_code(s, END_BLOCK, ltree);
1028 s->last_eob_len = ltree[END_BLOCK].Len;
1031 /* ===========================================================================
1032 * Set the data type to ASCII or BINARY, using a crude approximation:
1033 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1034 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1035 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1037 local void set_data_type(s)
1041 unsigned ascii_freq = 0;
1042 unsigned bin_freq = 0;
1043 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1044 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1045 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1046 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? BINARY : ASCII);
1049 /* ===========================================================================
1050 * Reverse the first len bits of a code, using straightforward code (a faster
1051 * method would use a table)
1052 * IN assertion: 1 <= len <= 15
1054 local unsigned bi_reverse(code, len)
1055 unsigned code; /* the value to invert */
1056 int len; /* its bit length */
1058 register unsigned res = 0;
1061 code >>= 1, res <<= 1;
1062 } while (--len > 0);
1066 /* ===========================================================================
1067 * Flush the bit buffer, keeping at most 7 bits in it.
1069 local void bi_flush(s)
1072 if (s->bi_valid == 16) {
1073 put_short(s, s->bi_buf);
1076 } else if (s->bi_valid >= 8) {
1077 put_byte(s, (Byte)s->bi_buf);
1083 /* ===========================================================================
1084 * Flush the bit buffer and align the output on a byte boundary
1086 local void bi_windup(s)
1089 if (s->bi_valid > 8) {
1090 put_short(s, s->bi_buf);
1091 } else if (s->bi_valid > 0) {
1092 put_byte(s, (Byte)s->bi_buf);
1097 s->bits_sent = (s->bits_sent+7) & ~7;
1101 /* ===========================================================================
1102 * Copy a stored block, storing first the length and its
1103 * one's complement if requested.
1105 local void copy_block(s, buf, len, header)
1107 charf *buf; /* the input data */
1108 unsigned len; /* its length */
1109 int header; /* true if block header must be written */
1111 bi_windup(s); /* align on byte boundary */
1112 s->last_eob_len = 8; /* enough lookahead for inflate */
1115 put_short(s, (ush)len);
1116 put_short(s, (ush)~len);
1118 s->bits_sent += 2*16;
1122 s->bits_sent += (ulg)len<<3;
1125 put_byte(s, *buf++);