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
10 * The "deflation" process uses several Huffman trees. The more
11 * common source values are represented by shorter bit sequences.
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.
21 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
22 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
25 * Data Compression: Methods and Theory, pp. 49-50.
26 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
30 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
33 /* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */
35 /* #include "deflate.h" */
37 #include <linux/zutil.h>
44 /* ===========================================================================
49 /* Bit length codes must not exceed MAX_BL_BITS bits */
52 /* end of block literal code */
55 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
58 /* repeat a zero length 3-10 times (3 bits of repeat count) */
60 #define REPZ_11_138 18
61 /* repeat a zero length 11-138 times (7 bits of repeat count) */
63 static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
64 = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
66 static const int extra_dbits[D_CODES] /* extra bits for each distance code */
67 = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
69 static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
70 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
72 static const uch bl_order[BL_CODES]
73 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
74 /* The lengths of the bit length codes are sent in order of decreasing
75 * probability, to avoid transmitting the lengths for unused bit length codes.
78 #define Buf_size (8 * 2*sizeof(char))
79 /* Number of bits used within bi_buf. (bi_buf might be implemented on
80 * more than 16 bits on some systems.)
83 /* ===========================================================================
84 * Local data. These are initialized only once.
87 static ct_data static_ltree[L_CODES+2];
88 /* The static literal tree. Since the bit lengths are imposed, there is no
89 * need for the L_CODES extra codes used during heap construction. However
90 * The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init
94 static ct_data static_dtree[D_CODES];
95 /* The static distance tree. (Actually a trivial tree since all codes use
99 static uch dist_code[512];
100 /* distance codes. The first 256 values correspond to the distances
101 * 3 .. 258, the last 256 values correspond to the top 8 bits of
102 * the 15 bit distances.
105 static uch length_code[MAX_MATCH-MIN_MATCH+1];
106 /* length code for each normalized match length (0 == MIN_MATCH) */
108 static int base_length[LENGTH_CODES];
109 /* First normalized length for each code (0 = MIN_MATCH) */
111 static int base_dist[D_CODES];
112 /* First normalized distance for each code (0 = distance of 1) */
114 struct static_tree_desc_s {
115 const ct_data *static_tree; /* static tree or NULL */
116 const int *extra_bits; /* extra bits for each code or NULL */
117 int extra_base; /* base index for extra_bits */
118 int elems; /* max number of elements in the tree */
119 int max_length; /* max bit length for the codes */
122 static static_tree_desc static_l_desc =
123 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
125 static static_tree_desc static_d_desc =
126 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
128 static static_tree_desc static_bl_desc =
129 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
131 /* ===========================================================================
132 * Local (static) routines in this file.
135 static void tr_static_init (void);
136 static void init_block (deflate_state *s);
137 static void pqdownheap (deflate_state *s, ct_data *tree, int k);
138 static void gen_bitlen (deflate_state *s, tree_desc *desc);
139 static void gen_codes (ct_data *tree, int max_code, ush *bl_count);
140 static void build_tree (deflate_state *s, tree_desc *desc);
141 static void scan_tree (deflate_state *s, ct_data *tree, int max_code);
142 static void send_tree (deflate_state *s, ct_data *tree, int max_code);
143 static int build_bl_tree (deflate_state *s);
144 static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
146 static void compress_block (deflate_state *s, ct_data *ltree,
148 static void set_data_type (deflate_state *s);
149 static unsigned bi_reverse (unsigned value, int length);
150 static void bi_windup (deflate_state *s);
151 static void bi_flush (deflate_state *s);
152 static void copy_block (deflate_state *s, char *buf, unsigned len,
156 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
157 /* Send a code of the given tree. c and tree must not have side effects */
159 #else /* DEBUG_ZLIB */
160 # define send_code(s, c, tree) \
161 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
162 send_bits(s, tree[c].Code, tree[c].Len); }
165 #define d_code(dist) \
166 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
167 /* Mapping from a distance to a distance code. dist is the distance - 1 and
168 * must not have side effects. dist_code[256] and dist_code[257] are never
172 /* ===========================================================================
173 * Send a value on a given number of bits.
174 * IN assertion: length <= 16 and value fits in length bits.
177 static void send_bits (deflate_state *s, int value, int length);
179 static void send_bits(
181 int value, /* value to send */
182 int length /* number of bits */
185 Tracevv((stderr," l %2d v %4x ", length, value));
186 Assert(length > 0 && length <= 15, "invalid length");
187 s->bits_sent += (ulg)length;
189 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
190 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
191 * unused bits in value.
193 if (s->bi_valid > (int)Buf_size - length) {
194 s->bi_buf |= (value << s->bi_valid);
195 put_short(s, s->bi_buf);
196 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
197 s->bi_valid += length - Buf_size;
199 s->bi_buf |= value << s->bi_valid;
200 s->bi_valid += length;
203 #else /* !DEBUG_ZLIB */
205 #define send_bits(s, value, length) \
207 if (s->bi_valid > (int)Buf_size - len) {\
209 s->bi_buf |= (val << s->bi_valid);\
210 put_short(s, s->bi_buf);\
211 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
212 s->bi_valid += len - Buf_size;\
214 s->bi_buf |= (value) << s->bi_valid;\
218 #endif /* DEBUG_ZLIB */
221 #define MAX(a,b) (a >= b ? a : b)
222 /* the arguments must not have side effects */
224 /* ===========================================================================
225 * Initialize the various 'constant' tables. In a multi-threaded environment,
226 * this function may be called by two threads concurrently, but this is
227 * harmless since both invocations do exactly the same thing.
229 static void tr_static_init(void)
231 static int static_init_done;
232 int n; /* iterates over tree elements */
233 int bits; /* bit counter */
234 int length; /* length value */
235 int code; /* code value */
236 int dist; /* distance index */
237 ush bl_count[MAX_BITS+1];
238 /* number of codes at each bit length for an optimal tree */
240 if (static_init_done) return;
242 /* Initialize the mapping length (0..255) -> length code (0..28) */
244 for (code = 0; code < LENGTH_CODES-1; code++) {
245 base_length[code] = length;
246 for (n = 0; n < (1<<extra_lbits[code]); n++) {
247 length_code[length++] = (uch)code;
250 Assert (length == 256, "tr_static_init: length != 256");
251 /* Note that the length 255 (match length 258) can be represented
252 * in two different ways: code 284 + 5 bits or code 285, so we
253 * overwrite length_code[255] to use the best encoding:
255 length_code[length-1] = (uch)code;
257 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
259 for (code = 0 ; code < 16; code++) {
260 base_dist[code] = dist;
261 for (n = 0; n < (1<<extra_dbits[code]); n++) {
262 dist_code[dist++] = (uch)code;
265 Assert (dist == 256, "tr_static_init: dist != 256");
266 dist >>= 7; /* from now on, all distances are divided by 128 */
267 for ( ; code < D_CODES; code++) {
268 base_dist[code] = dist << 7;
269 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
270 dist_code[256 + dist++] = (uch)code;
273 Assert (dist == 256, "tr_static_init: 256+dist != 512");
275 /* Construct the codes of the static literal tree */
276 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
278 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
279 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
280 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
281 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
282 /* Codes 286 and 287 do not exist, but we must include them in the
283 * tree construction to get a canonical Huffman tree (longest code
286 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
288 /* The static distance tree is trivial: */
289 for (n = 0; n < D_CODES; n++) {
290 static_dtree[n].Len = 5;
291 static_dtree[n].Code = bi_reverse((unsigned)n, 5);
293 static_init_done = 1;
296 /* ===========================================================================
297 * Initialize the tree data structures for a new zlib stream.
305 s->compressed_len = 0L;
307 s->l_desc.dyn_tree = s->dyn_ltree;
308 s->l_desc.stat_desc = &static_l_desc;
310 s->d_desc.dyn_tree = s->dyn_dtree;
311 s->d_desc.stat_desc = &static_d_desc;
313 s->bl_desc.dyn_tree = s->bl_tree;
314 s->bl_desc.stat_desc = &static_bl_desc;
318 s->last_eob_len = 8; /* enough lookahead for inflate */
323 /* Initialize the first block of the first file: */
327 /* ===========================================================================
328 * Initialize a new block.
330 static void init_block(
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 static void pqdownheap(
377 ct_data *tree, /* the tree to restore */
378 int k /* node to move down */
382 int j = k << 1; /* left son of k */
383 while (j <= s->heap_len) {
384 /* Set j to the smallest of the two sons: */
385 if (j < s->heap_len &&
386 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
389 /* Exit if v is smaller than both sons */
390 if (smaller(tree, v, s->heap[j], s->depth)) break;
392 /* Exchange v with the smallest son */
393 s->heap[k] = s->heap[j]; k = j;
395 /* And continue down the tree, setting j to the left son of k */
401 /* ===========================================================================
402 * Compute the optimal bit lengths for a tree and update the total bit length
403 * for the current block.
404 * IN assertion: the fields freq and dad are set, heap[heap_max] and
405 * above are the tree nodes sorted by increasing frequency.
406 * OUT assertions: the field len is set to the optimal bit length, the
407 * array bl_count contains the frequencies for each bit length.
408 * The length opt_len is updated; static_len is also updated if stree is
411 static void gen_bitlen(
413 tree_desc *desc /* the tree descriptor */
416 ct_data *tree = desc->dyn_tree;
417 int max_code = desc->max_code;
418 const ct_data *stree = desc->stat_desc->static_tree;
419 const int *extra = desc->stat_desc->extra_bits;
420 int base = desc->stat_desc->extra_base;
421 int max_length = desc->stat_desc->max_length;
422 int h; /* heap index */
423 int n, m; /* iterate over the tree elements */
424 int bits; /* bit length */
425 int xbits; /* extra bits */
426 ush f; /* frequency */
427 int overflow = 0; /* number of elements with bit length too large */
429 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
431 /* In a first pass, compute the optimal bit lengths (which may
432 * overflow in the case of the bit length tree).
434 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
436 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
438 bits = tree[tree[n].Dad].Len + 1;
439 if (bits > max_length) bits = max_length, overflow++;
440 tree[n].Len = (ush)bits;
441 /* We overwrite tree[n].Dad which is no longer needed */
443 if (n > max_code) continue; /* not a leaf node */
447 if (n >= base) xbits = extra[n-base];
449 s->opt_len += (ulg)f * (bits + xbits);
450 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
452 if (overflow == 0) return;
454 Trace((stderr,"\nbit length overflow\n"));
455 /* This happens for example on obj2 and pic of the Calgary corpus */
457 /* Find the first bit length which could increase: */
460 while (s->bl_count[bits] == 0) bits--;
461 s->bl_count[bits]--; /* move one leaf down the tree */
462 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
463 s->bl_count[max_length]--;
464 /* The brother of the overflow item also moves one step up,
465 * but this does not affect bl_count[max_length]
468 } while (overflow > 0);
470 /* Now recompute all bit lengths, scanning in increasing frequency.
471 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
472 * lengths instead of fixing only the wrong ones. This idea is taken
473 * from 'ar' written by Haruhiko Okumura.)
475 for (bits = max_length; bits != 0; bits--) {
476 n = s->bl_count[bits];
479 if (m > max_code) continue;
480 if (tree[m].Len != (unsigned) bits) {
481 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
482 s->opt_len += ((long)bits - (long)tree[m].Len)
484 tree[m].Len = (ush)bits;
491 /* ===========================================================================
492 * Generate the codes for a given tree and bit counts (which need not be
494 * IN assertion: the array bl_count contains the bit length statistics for
495 * the given tree and the field len is set for all tree elements.
496 * OUT assertion: the field code is set for all tree elements of non
499 static void gen_codes(
500 ct_data *tree, /* the tree to decorate */
501 int max_code, /* largest code with non zero frequency */
502 ush *bl_count /* number of codes at each bit length */
505 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
506 ush code = 0; /* running code value */
507 int bits; /* bit index */
508 int n; /* code index */
510 /* The distribution counts are first used to generate the code values
511 * without bit reversal.
513 for (bits = 1; bits <= MAX_BITS; bits++) {
514 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
516 /* Check that the bit counts in bl_count are consistent. The last code
519 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
520 "inconsistent bit counts");
521 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
523 for (n = 0; n <= max_code; n++) {
524 int len = tree[n].Len;
525 if (len == 0) continue;
526 /* Now reverse the bits */
527 tree[n].Code = bi_reverse(next_code[len]++, len);
529 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
530 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
534 /* ===========================================================================
535 * Construct one Huffman tree and assigns the code bit strings and lengths.
536 * Update the total bit length for the current block.
537 * IN assertion: the field freq is set for all tree elements.
538 * OUT assertions: the fields len and code are set to the optimal bit length
539 * and corresponding code. The length opt_len is updated; static_len is
540 * also updated if stree is not null. The field max_code is set.
542 static void build_tree(
544 tree_desc *desc /* the tree descriptor */
547 ct_data *tree = desc->dyn_tree;
548 const ct_data *stree = desc->stat_desc->static_tree;
549 int elems = desc->stat_desc->elems;
550 int n, m; /* iterate over heap elements */
551 int max_code = -1; /* largest code with non zero frequency */
552 int node; /* new node being created */
554 /* Construct the initial heap, with least frequent element in
555 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
556 * heap[0] is not used.
558 s->heap_len = 0, s->heap_max = HEAP_SIZE;
560 for (n = 0; n < elems; n++) {
561 if (tree[n].Freq != 0) {
562 s->heap[++(s->heap_len)] = max_code = n;
569 /* The pkzip format requires that at least one distance code exists,
570 * and that at least one bit should be sent even if there is only one
571 * possible code. So to avoid special checks later on we force at least
572 * two codes of non zero frequency.
574 while (s->heap_len < 2) {
575 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
578 s->opt_len--; if (stree) s->static_len -= stree[node].Len;
579 /* node is 0 or 1 so it does not have extra bits */
581 desc->max_code = max_code;
583 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
584 * establish sub-heaps of increasing lengths:
586 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
588 /* Construct the Huffman tree by repeatedly combining the least two
591 node = elems; /* next internal node of the tree */
593 pqremove(s, tree, n); /* n = node of least frequency */
594 m = s->heap[SMALLEST]; /* m = node of next least frequency */
596 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
597 s->heap[--(s->heap_max)] = m;
599 /* Create a new node father of n and m */
600 tree[node].Freq = tree[n].Freq + tree[m].Freq;
601 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
602 tree[n].Dad = tree[m].Dad = (ush)node;
604 if (tree == s->bl_tree) {
605 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
606 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
609 /* and insert the new node in the heap */
610 s->heap[SMALLEST] = node++;
611 pqdownheap(s, tree, SMALLEST);
613 } while (s->heap_len >= 2);
615 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
617 /* At this point, the fields freq and dad are set. We can now
618 * generate the bit lengths.
620 gen_bitlen(s, (tree_desc *)desc);
622 /* The field len is now set, we can generate the bit codes */
623 gen_codes ((ct_data *)tree, max_code, s->bl_count);
626 /* ===========================================================================
627 * Scan a literal or distance tree to determine the frequencies of the codes
628 * in the bit length tree.
630 static void scan_tree(
632 ct_data *tree, /* the tree to be scanned */
633 int max_code /* and its largest code of non zero frequency */
636 int n; /* iterates over all tree elements */
637 int prevlen = -1; /* last emitted length */
638 int curlen; /* length of current code */
639 int nextlen = tree[0].Len; /* length of next code */
640 int count = 0; /* repeat count of the current code */
641 int max_count = 7; /* max repeat count */
642 int min_count = 4; /* min repeat count */
644 if (nextlen == 0) max_count = 138, min_count = 3;
645 tree[max_code+1].Len = (ush)0xffff; /* guard */
647 for (n = 0; n <= max_code; n++) {
648 curlen = nextlen; nextlen = tree[n+1].Len;
649 if (++count < max_count && curlen == nextlen) {
651 } else if (count < min_count) {
652 s->bl_tree[curlen].Freq += count;
653 } else if (curlen != 0) {
654 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
655 s->bl_tree[REP_3_6].Freq++;
656 } else if (count <= 10) {
657 s->bl_tree[REPZ_3_10].Freq++;
659 s->bl_tree[REPZ_11_138].Freq++;
661 count = 0; prevlen = curlen;
663 max_count = 138, min_count = 3;
664 } else if (curlen == nextlen) {
665 max_count = 6, min_count = 3;
667 max_count = 7, min_count = 4;
672 /* ===========================================================================
673 * Send a literal or distance tree in compressed form, using the codes in
676 static void send_tree(
678 ct_data *tree, /* the tree to be scanned */
679 int max_code /* and its largest code of non zero frequency */
682 int n; /* iterates over all tree elements */
683 int prevlen = -1; /* last emitted length */
684 int curlen; /* length of current code */
685 int nextlen = tree[0].Len; /* length of next code */
686 int count = 0; /* repeat count of the current code */
687 int max_count = 7; /* max repeat count */
688 int min_count = 4; /* min repeat count */
690 /* tree[max_code+1].Len = -1; */ /* guard already set */
691 if (nextlen == 0) max_count = 138, min_count = 3;
693 for (n = 0; n <= max_code; n++) {
694 curlen = nextlen; nextlen = tree[n+1].Len;
695 if (++count < max_count && curlen == nextlen) {
697 } else if (count < min_count) {
698 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
700 } else if (curlen != 0) {
701 if (curlen != prevlen) {
702 send_code(s, curlen, s->bl_tree); count--;
704 Assert(count >= 3 && count <= 6, " 3_6?");
705 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
707 } else if (count <= 10) {
708 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
711 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
713 count = 0; prevlen = curlen;
715 max_count = 138, min_count = 3;
716 } else if (curlen == nextlen) {
717 max_count = 6, min_count = 3;
719 max_count = 7, min_count = 4;
724 /* ===========================================================================
725 * Construct the Huffman tree for the bit lengths and return the index in
726 * bl_order of the last bit length code to send.
728 static int build_bl_tree(
732 int max_blindex; /* index of last bit length code of non zero freq */
734 /* Determine the bit length frequencies for literal and distance trees */
735 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
736 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
738 /* Build the bit length tree: */
739 build_tree(s, (tree_desc *)(&(s->bl_desc)));
740 /* opt_len now includes the length of the tree representations, except
741 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
744 /* Determine the number of bit length codes to send. The pkzip format
745 * requires that at least 4 bit length codes be sent. (appnote.txt says
746 * 3 but the actual value used is 4.)
748 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
749 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
751 /* Update opt_len to include the bit length tree and counts */
752 s->opt_len += 3*(max_blindex+1) + 5+5+4;
753 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
754 s->opt_len, s->static_len));
759 /* ===========================================================================
760 * Send the header for a block using dynamic Huffman trees: the counts, the
761 * lengths of the bit length codes, the literal tree and the distance tree.
762 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
764 static void send_all_trees(
766 int lcodes, /* number of codes for each tree */
767 int dcodes, /* number of codes for each tree */
768 int blcodes /* number of codes for each tree */
771 int rank; /* index in bl_order */
773 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
774 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
776 Tracev((stderr, "\nbl counts: "));
777 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
778 send_bits(s, dcodes-1, 5);
779 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
780 for (rank = 0; rank < blcodes; rank++) {
781 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
782 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
784 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
786 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
787 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
789 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
790 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
793 /* ===========================================================================
794 * Send a stored block
796 void zlib_tr_stored_block(
798 char *buf, /* input block */
799 ulg stored_len, /* length of input block */
800 int eof /* true if this is the last block for a file */
803 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
804 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
805 s->compressed_len += (stored_len + 4) << 3;
807 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
810 /* Send just the `stored block' type code without any length bytes or data.
812 void zlib_tr_stored_type_only(
816 send_bits(s, (STORED_BLOCK << 1), 3);
818 s->compressed_len = (s->compressed_len + 3) & ~7L;
822 /* ===========================================================================
823 * Send one empty static block to give enough lookahead for inflate.
824 * This takes 10 bits, of which 7 may remain in the bit buffer.
825 * The current inflate code requires 9 bits of lookahead. If the
826 * last two codes for the previous block (real code plus EOB) were coded
827 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
828 * the last real code. In this case we send two empty static blocks instead
829 * of one. (There are no problems if the previous block is stored or fixed.)
830 * To simplify the code, we assume the worst case of last real code encoded
837 send_bits(s, STATIC_TREES<<1, 3);
838 send_code(s, END_BLOCK, static_ltree);
839 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
841 /* Of the 10 bits for the empty block, we have already sent
842 * (10 - bi_valid) bits. The lookahead for the last real code (before
843 * the EOB of the previous block) was thus at least one plus the length
844 * of the EOB plus what we have just sent of the empty static block.
846 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
847 send_bits(s, STATIC_TREES<<1, 3);
848 send_code(s, END_BLOCK, static_ltree);
849 s->compressed_len += 10L;
855 /* ===========================================================================
856 * Determine the best encoding for the current block: dynamic trees, static
857 * trees or store, and output the encoded block to the zip file. This function
858 * returns the total compressed length for the file so far.
860 ulg zlib_tr_flush_block(
862 char *buf, /* input block, or NULL if too old */
863 ulg stored_len, /* length of input block */
864 int eof /* true if this is the last block for a file */
867 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
868 int max_blindex = 0; /* index of last bit length code of non zero freq */
870 /* Build the Huffman trees unless a stored block is forced */
873 /* Check if the file is ascii or binary */
874 if (s->data_type == Z_UNKNOWN) set_data_type(s);
876 /* Construct the literal and distance trees */
877 build_tree(s, (tree_desc *)(&(s->l_desc)));
878 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
881 build_tree(s, (tree_desc *)(&(s->d_desc)));
882 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
884 /* At this point, opt_len and static_len are the total bit lengths of
885 * the compressed block data, excluding the tree representations.
888 /* Build the bit length tree for the above two trees, and get the index
889 * in bl_order of the last bit length code to send.
891 max_blindex = build_bl_tree(s);
893 /* Determine the best encoding. Compute first the block length in bytes*/
894 opt_lenb = (s->opt_len+3+7)>>3;
895 static_lenb = (s->static_len+3+7)>>3;
897 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
898 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
901 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
904 Assert(buf != (char*)0, "lost buf");
905 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
908 /* If compression failed and this is the first and last block,
909 * and if the .zip file can be seeked (to rewrite the local header),
910 * the whole file is transformed into a stored file:
912 #ifdef STORED_FILE_OK
913 # ifdef FORCE_STORED_FILE
914 if (eof && s->compressed_len == 0L) { /* force stored file */
916 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
918 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
919 if (buf == (char*)0) error ("block vanished");
921 copy_block(s, buf, (unsigned)stored_len, 0); /* without header */
922 s->compressed_len = stored_len << 3;
925 #endif /* STORED_FILE_OK */
928 if (buf != (char*)0) { /* force stored block */
930 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
931 /* 4: two words for the lengths */
933 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
934 * Otherwise we can't have processed more than WSIZE input bytes since
935 * the last block flush, because compression would have been
936 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
937 * transform a block into a stored block.
939 zlib_tr_stored_block(s, buf, stored_len, eof);
942 } else if (static_lenb >= 0) { /* force static trees */
944 } else if (static_lenb == opt_lenb) {
946 send_bits(s, (STATIC_TREES<<1)+eof, 3);
947 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
948 s->compressed_len += 3 + s->static_len;
950 send_bits(s, (DYN_TREES<<1)+eof, 3);
951 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
953 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
954 s->compressed_len += 3 + s->opt_len;
956 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
961 s->compressed_len += 7; /* align on byte boundary */
963 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
964 s->compressed_len-7*eof));
966 return s->compressed_len >> 3;
969 /* ===========================================================================
970 * Save the match info and tally the frequency counts. Return true if
971 * the current block must be flushed.
975 unsigned dist, /* distance of matched string */
976 unsigned lc /* match length-MIN_MATCH or unmatched char (if dist==0) */
979 s->d_buf[s->last_lit] = (ush)dist;
980 s->l_buf[s->last_lit++] = (uch)lc;
982 /* lc is the unmatched char */
983 s->dyn_ltree[lc].Freq++;
986 /* Here, lc is the match length - MIN_MATCH */
987 dist--; /* dist = match distance - 1 */
988 Assert((ush)dist < (ush)MAX_DIST(s) &&
989 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
990 (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match");
992 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
993 s->dyn_dtree[d_code(dist)].Freq++;
996 /* Try to guess if it is profitable to stop the current block here */
997 if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
998 /* Compute an upper bound for the compressed length */
999 ulg out_length = (ulg)s->last_lit*8L;
1000 ulg in_length = (ulg)((long)s->strstart - s->block_start);
1002 for (dcode = 0; dcode < D_CODES; dcode++) {
1003 out_length += (ulg)s->dyn_dtree[dcode].Freq *
1004 (5L+extra_dbits[dcode]);
1007 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1008 s->last_lit, in_length, out_length,
1009 100L - out_length*100L/in_length));
1010 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1012 return (s->last_lit == s->lit_bufsize-1);
1013 /* We avoid equality with lit_bufsize because of wraparound at 64K
1014 * on 16 bit machines and because stored blocks are restricted to
1019 /* ===========================================================================
1020 * Send the block data compressed using the given Huffman trees
1022 static void compress_block(
1024 ct_data *ltree, /* literal tree */
1025 ct_data *dtree /* distance tree */
1028 unsigned dist; /* distance of matched string */
1029 int lc; /* match length or unmatched char (if dist == 0) */
1030 unsigned lx = 0; /* running index in l_buf */
1031 unsigned code; /* the code to send */
1032 int extra; /* number of extra bits to send */
1034 if (s->last_lit != 0) do {
1035 dist = s->d_buf[lx];
1036 lc = s->l_buf[lx++];
1038 send_code(s, lc, ltree); /* send a literal byte */
1039 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1041 /* Here, lc is the match length - MIN_MATCH */
1042 code = length_code[lc];
1043 send_code(s, code+LITERALS+1, ltree); /* send the length code */
1044 extra = extra_lbits[code];
1046 lc -= base_length[code];
1047 send_bits(s, lc, extra); /* send the extra length bits */
1049 dist--; /* dist is now the match distance - 1 */
1050 code = d_code(dist);
1051 Assert (code < D_CODES, "bad d_code");
1053 send_code(s, code, dtree); /* send the distance code */
1054 extra = extra_dbits[code];
1056 dist -= base_dist[code];
1057 send_bits(s, dist, extra); /* send the extra distance bits */
1059 } /* literal or match pair ? */
1061 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1062 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1064 } while (lx < s->last_lit);
1066 send_code(s, END_BLOCK, ltree);
1067 s->last_eob_len = ltree[END_BLOCK].Len;
1070 /* ===========================================================================
1071 * Set the data type to ASCII or BINARY, using a crude approximation:
1072 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1073 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1074 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1076 static void set_data_type(
1081 unsigned ascii_freq = 0;
1082 unsigned bin_freq = 0;
1083 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1084 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1085 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1086 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1089 /* ===========================================================================
1090 * Copy a stored block, storing first the length and its
1091 * one's complement if requested.
1093 static void copy_block(
1095 char *buf, /* the input data */
1096 unsigned len, /* its length */
1097 int header /* true if block header must be written */
1100 bi_windup(s); /* align on byte boundary */
1101 s->last_eob_len = 8; /* enough lookahead for inflate */
1104 put_short(s, (ush)len);
1105 put_short(s, (ush)~len);
1107 s->bits_sent += 2*16;
1111 s->bits_sent += (ulg)len<<3;
1113 /* bundle up the put_byte(s, *buf++) calls */
1114 memcpy(&s->pending_buf[s->pending], buf, len);