1 /* trees.c -- output deflated data using Huffman coding
2 * Copyright (C) 1995-1998 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.
34 /* #define GEN_TREES_H */
42 /* ===========================================================================
47 /* Bit length codes must not exceed MAX_BL_BITS bits */
50 /* end of block literal code */
53 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
56 /* repeat a zero length 3-10 times (3 bits of repeat count) */
58 #define REPZ_11_138 18
59 /* repeat a zero length 11-138 times (7 bits of repeat count) */
61 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
62 = {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};
64 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
65 = {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};
67 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
68 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
70 local const uch bl_order[BL_CODES]
71 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
72 /* The lengths of the bit length codes are sent in order of decreasing
73 * probability, to avoid transmitting the lengths for unused bit length codes.
76 #define Buf_size (8 * 2*sizeof(char))
77 /* Number of bits used within bi_buf. (bi_buf might be implemented on
78 * more than 16 bits on some systems.)
81 /* ===========================================================================
82 * Local data. These are initialized only once.
85 #define DIST_CODE_LEN 512 /* see definition of array dist_code below */
87 #if defined(GEN_TREES_H) || !defined(STDC)
88 /* non ANSI compilers may not accept trees.h */
90 local ct_data static_ltree[L_CODES+2];
91 /* The static literal tree. Since the bit lengths are imposed, there is no
92 * need for the L_CODES extra codes used during heap construction. However
93 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
97 local ct_data static_dtree[D_CODES];
98 /* The static distance tree. (Actually a trivial tree since all codes use
102 uch _dist_code[DIST_CODE_LEN];
103 /* Distance codes. The first 256 values correspond to the distances
104 * 3 .. 258, the last 256 values correspond to the top 8 bits of
105 * the 15 bit distances.
108 uch _length_code[MAX_MATCH-MIN_MATCH+1];
109 /* length code for each normalized match length (0 == MIN_MATCH) */
111 local int base_length[LENGTH_CODES];
112 /* First normalized length for each code (0 = MIN_MATCH) */
114 local int base_dist[D_CODES];
115 /* First normalized distance for each code (0 = distance of 1) */
119 #endif /* GEN_TREES_H */
121 struct static_tree_desc_s {
122 const ct_data *static_tree; /* static tree or NULL */
123 const intf *extra_bits; /* extra bits for each code or NULL */
124 int extra_base; /* base index for extra_bits */
125 int elems; /* max number of elements in the tree */
126 int max_length; /* max bit length for the codes */
129 local static_tree_desc static_l_desc =
130 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
132 local static_tree_desc static_d_desc =
133 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
135 local static_tree_desc static_bl_desc =
136 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
138 /* ===========================================================================
139 * Local (static) routines in this file.
142 local void tr_static_init OF((void));
143 local void init_block OF((deflate_state *s));
144 local void pqdownheap OF((deflate_state *s, ct_data *tree, int k));
145 local void gen_bitlen OF((deflate_state *s, tree_desc *desc));
146 local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count));
147 local void build_tree OF((deflate_state *s, tree_desc *desc));
148 local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code));
149 local void send_tree OF((deflate_state *s, ct_data *tree, int max_code));
150 local int build_bl_tree OF((deflate_state *s));
151 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
153 local void compress_block OF((deflate_state *s, ct_data *ltree,
155 local void set_data_type OF((deflate_state *s));
156 local unsigned bi_reverse OF((unsigned value, int length));
157 local void bi_windup OF((deflate_state *s));
158 local void bi_flush OF((deflate_state *s));
159 local void copy_block OF((deflate_state *s, charf *buf, unsigned len,
163 local void gen_trees_header OF((void));
167 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
168 /* Send a code of the given tree. c and tree must not have side effects */
171 # define send_code(s, c, tree) \
172 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
173 send_bits(s, tree[c].Code, tree[c].Len); }
176 /* ===========================================================================
177 * Output a short LSB first on the stream.
178 * IN assertion: there is enough room in pendingBuf.
180 #define put_short(s, w) { \
181 put_byte(s, (uch)((w) & 0xff)); \
182 put_byte(s, (uch)((ush)(w) >> 8)); \
185 /* ===========================================================================
186 * Send a value on a given number of bits.
187 * IN assertion: length <= 16 and value fits in length bits.
190 local void send_bits OF((deflate_state *s, int value, int length));
192 local void send_bits(s, value, length)
194 int value; /* value to send */
195 int length; /* number of bits */
197 Tracevv((stderr," l %2d v %4x ", length, value));
198 Assert(length > 0 && length <= 15, "invalid length");
199 s->bits_sent += (ulg)length;
201 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
202 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
203 * unused bits in value.
205 if (s->bi_valid > (int)Buf_size - length) {
206 s->bi_buf |= (value << s->bi_valid);
207 put_short(s, s->bi_buf);
208 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
209 s->bi_valid += length - Buf_size;
211 s->bi_buf |= value << s->bi_valid;
212 s->bi_valid += length;
217 #define send_bits(s, value, length) \
219 if (s->bi_valid > (int)Buf_size - len) {\
221 s->bi_buf |= (val << s->bi_valid);\
222 put_short(s, s->bi_buf);\
223 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
224 s->bi_valid += len - Buf_size;\
226 s->bi_buf |= (value) << s->bi_valid;\
234 #define MAX(a,b) ((a) >= (b) ? (a) : (b))
236 /* the arguments must not have side effects */
238 /* ===========================================================================
239 * Initialize the various 'constant' tables.
241 local void tr_static_init()
243 #if defined(GEN_TREES_H) || !defined(STDC)
244 static int static_init_done = 0;
245 int n; /* iterates over tree elements */
246 int bits; /* bit counter */
247 int length; /* length value */
248 int code; /* code value */
249 int dist; /* distance index */
250 ush bl_count[MAX_BITS+1];
251 /* number of codes at each bit length for an optimal tree */
253 if (static_init_done) return;
255 /* Initialize the mapping length (0..255) -> length code (0..28) */
257 for (code = 0; code < LENGTH_CODES-1; code++) {
258 base_length[code] = length;
259 for (n = 0; n < (1<<extra_lbits[code]); n++) {
260 _length_code[length++] = (uch)code;
263 Assert (length == 256, "tr_static_init: length != 256");
264 /* Note that the length 255 (match length 258) can be represented
265 * in two different ways: code 284 + 5 bits or code 285, so we
266 * overwrite length_code[255] to use the best encoding:
268 _length_code[length-1] = (uch)code;
270 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
272 for (code = 0 ; code < 16; code++) {
273 base_dist[code] = dist;
274 for (n = 0; n < (1<<extra_dbits[code]); n++) {
275 _dist_code[dist++] = (uch)code;
278 Assert (dist == 256, "tr_static_init: dist != 256");
279 dist >>= 7; /* from now on, all distances are divided by 128 */
280 for ( ; code < D_CODES; code++) {
281 base_dist[code] = dist << 7;
282 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
283 _dist_code[256 + dist++] = (uch)code;
286 Assert (dist == 256, "tr_static_init: 256+dist != 512");
288 /* Construct the codes of the static literal tree */
289 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
291 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
292 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
293 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
294 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
295 /* Codes 286 and 287 do not exist, but we must include them in the
296 * tree construction to get a canonical Huffman tree (longest code
299 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
301 /* The static distance tree is trivial: */
302 for (n = 0; n < D_CODES; n++) {
303 static_dtree[n].Len = 5;
304 static_dtree[n].Code = bi_reverse((unsigned)n, 5);
306 static_init_done = 1;
311 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
314 /* ===========================================================================
315 * Genererate the file trees.h describing the static trees.
322 # define SEPARATOR(i, last, width) \
323 ((i) == (last)? "\n};\n\n" : \
324 ((i) % (width) == (width)-1 ? ",\n" : ", "))
326 void gen_trees_header()
328 FILE *header = fopen("trees.h", "w");
331 Assert (header != NULL, "Can't open trees.h");
333 "/* header created automatically with -DGEN_TREES_H */\n\n");
335 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
336 for (i = 0; i < L_CODES+2; i++) {
337 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
338 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
341 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
342 for (i = 0; i < D_CODES; i++) {
343 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
344 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
347 fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
348 for (i = 0; i < DIST_CODE_LEN; i++) {
349 fprintf(header, "%2u%s", _dist_code[i],
350 SEPARATOR(i, DIST_CODE_LEN-1, 20));
353 fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
354 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
355 fprintf(header, "%2u%s", _length_code[i],
356 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
359 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
360 for (i = 0; i < LENGTH_CODES; i++) {
361 fprintf(header, "%1u%s", base_length[i],
362 SEPARATOR(i, LENGTH_CODES-1, 20));
365 fprintf(header, "local const int base_dist[D_CODES] = {\n");
366 for (i = 0; i < D_CODES; i++) {
367 fprintf(header, "%5u%s", base_dist[i],
368 SEPARATOR(i, D_CODES-1, 10));
373 #endif /* GEN_TREES_H */
375 /* ===========================================================================
376 * Initialize the tree data structures for a new zlib stream.
383 s->compressed_len = 0L;
385 s->l_desc.dyn_tree = s->dyn_ltree;
386 s->l_desc.stat_desc = &static_l_desc;
388 s->d_desc.dyn_tree = s->dyn_dtree;
389 s->d_desc.stat_desc = &static_d_desc;
391 s->bl_desc.dyn_tree = s->bl_tree;
392 s->bl_desc.stat_desc = &static_bl_desc;
396 s->last_eob_len = 8; /* enough lookahead for inflate */
401 /* Initialize the first block of the first file: */
405 /* ===========================================================================
406 * Initialize a new block.
408 local void init_block(s)
411 int n; /* iterates over tree elements */
413 /* Initialize the trees. */
414 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
415 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
416 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
418 s->dyn_ltree[END_BLOCK].Freq = 1;
419 s->opt_len = s->static_len = 0L;
420 s->last_lit = s->matches = 0;
424 /* Index within the heap array of least frequent node in the Huffman tree */
427 /* ===========================================================================
428 * Remove the smallest element from the heap and recreate the heap with
429 * one less element. Updates heap and heap_len.
431 #define pqremove(s, tree, top) \
433 top = s->heap[SMALLEST]; \
434 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
435 pqdownheap(s, tree, SMALLEST); \
438 /* ===========================================================================
439 * Compares to subtrees, using the tree depth as tie breaker when
440 * the subtrees have equal frequency. This minimizes the worst case length.
442 #define smaller(tree, n, m, depth) \
443 (tree[n].Freq < tree[m].Freq || \
444 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
446 /* ===========================================================================
447 * Restore the heap property by moving down the tree starting at node k,
448 * exchanging a node with the smallest of its two sons if necessary, stopping
449 * when the heap property is re-established (each father smaller than its
452 local void pqdownheap(s, tree, k)
454 ct_data *tree; /* the tree to restore */
455 int k; /* node to move down */
458 int j = k << 1; /* left son of k */
459 while (j <= s->heap_len) {
460 /* Set j to the smallest of the two sons: */
461 if (j < s->heap_len &&
462 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
465 /* Exit if v is smaller than both sons */
466 if (smaller(tree, v, s->heap[j], s->depth)) break;
468 /* Exchange v with the smallest son */
469 s->heap[k] = s->heap[j]; k = j;
471 /* And continue down the tree, setting j to the left son of k */
477 /* ===========================================================================
478 * Compute the optimal bit lengths for a tree and update the total bit length
479 * for the current block.
480 * IN assertion: the fields freq and dad are set, heap[heap_max] and
481 * above are the tree nodes sorted by increasing frequency.
482 * OUT assertions: the field len is set to the optimal bit length, the
483 * array bl_count contains the frequencies for each bit length.
484 * The length opt_len is updated; static_len is also updated if stree is
487 local void gen_bitlen(s, desc)
489 tree_desc *desc; /* the tree descriptor */
491 ct_data *tree = desc->dyn_tree;
492 int max_code = desc->max_code;
493 const ct_data *stree = desc->stat_desc->static_tree;
494 const intf *extra = desc->stat_desc->extra_bits;
495 int base = desc->stat_desc->extra_base;
496 int max_length = desc->stat_desc->max_length;
497 int h; /* heap index */
498 int n, m; /* iterate over the tree elements */
499 int bits; /* bit length */
500 int xbits; /* extra bits */
501 ush f; /* frequency */
502 int Overflow = 0; /* number of elements with bit length too large */
504 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
506 /* In a first pass, compute the optimal bit lengths (which may
507 * overflow in the case of the bit length tree).
509 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
511 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
513 bits = tree[tree[n].Dad].Len + 1;
514 if (bits > max_length) bits = max_length, Overflow++;
515 tree[n].Len = (ush)bits;
516 /* We overwrite tree[n].Dad which is no longer needed */
518 if (n > max_code) continue; /* not a leaf node */
522 if (n >= base) xbits = extra[n-base];
524 s->opt_len += (ulg)f * (bits + xbits);
525 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
527 if (Overflow == 0) return;
529 Trace((stderr,"\nbit length overflow\n"));
530 /* This happens for example on obj2 and pic of the Calgary corpus */
532 /* Find the first bit length which could increase: */
535 while (s->bl_count[bits] == 0) bits--;
536 s->bl_count[bits]--; /* move one leaf down the tree */
537 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
538 s->bl_count[max_length]--;
539 /* The brother of the overflow item also moves one step up,
540 * but this does not affect bl_count[max_length]
543 } while (Overflow > 0);
545 /* Now recompute all bit lengths, scanning in increasing frequency.
546 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
547 * lengths instead of fixing only the wrong ones. This idea is taken
548 * from 'ar' written by Haruhiko Okumura.)
550 for (bits = max_length; bits != 0; bits--) {
551 n = s->bl_count[bits];
554 if (m > max_code) continue;
555 if (tree[m].Len != (unsigned) bits) {
556 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
557 s->opt_len += ((long)bits - (long)tree[m].Len)
559 tree[m].Len = (ush)bits;
566 /* ===========================================================================
567 * Generate the codes for a given tree and bit counts (which need not be
569 * IN assertion: the array bl_count contains the bit length statistics for
570 * the given tree and the field len is set for all tree elements.
571 * OUT assertion: the field code is set for all tree elements of non
574 local void gen_codes (tree, max_code, bl_count)
575 ct_data *tree; /* the tree to decorate */
576 int max_code; /* largest code with non zero frequency */
577 ushf *bl_count; /* number of codes at each bit length */
579 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
580 ush code = 0; /* running code value */
581 int bits; /* bit index */
582 int n; /* code index */
584 /* The distribution counts are first used to generate the code values
585 * without bit reversal.
587 for (bits = 1; bits <= MAX_BITS; bits++) {
588 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
590 /* Check that the bit counts in bl_count are consistent. The last code
593 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
594 "inconsistent bit counts");
595 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
597 for (n = 0; n <= max_code; n++) {
598 int len = tree[n].Len;
599 if (len == 0) continue;
600 /* Now reverse the bits */
601 tree[n].Code = bi_reverse(next_code[len]++, len);
603 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
604 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
608 /* ===========================================================================
609 * Construct one Huffman tree and assigns the code bit strings and lengths.
610 * Update the total bit length for the current block.
611 * IN assertion: the field freq is set for all tree elements.
612 * OUT assertions: the fields len and code are set to the optimal bit length
613 * and corresponding code. The length opt_len is updated; static_len is
614 * also updated if stree is not null. The field max_code is set.
616 local void build_tree(s, desc)
618 tree_desc *desc; /* the tree descriptor */
620 ct_data *tree = desc->dyn_tree;
621 const ct_data *stree = desc->stat_desc->static_tree;
622 int elems = desc->stat_desc->elems;
623 int n, m; /* iterate over heap elements */
624 int max_code = -1; /* largest code with non zero frequency */
625 int node; /* new node being created */
627 /* Construct the initial heap, with least frequent element in
628 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
629 * heap[0] is not used.
631 s->heap_len = 0, s->heap_max = HEAP_SIZE;
633 for (n = 0; n < elems; n++) {
634 if (tree[n].Freq != 0) {
635 s->heap[++(s->heap_len)] = max_code = n;
642 /* The pkzip format requires that at least one distance code exists,
643 * and that at least one bit should be sent even if there is only one
644 * possible code. So to avoid special checks later on we force at least
645 * two codes of non zero frequency.
647 while (s->heap_len < 2) {
648 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
651 s->opt_len--; if (stree) s->static_len -= stree[node].Len;
652 /* node is 0 or 1 so it does not have extra bits */
654 desc->max_code = max_code;
656 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
657 * establish sub-heaps of increasing lengths:
659 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
661 /* Construct the Huffman tree by repeatedly combining the least two
664 node = elems; /* next internal node of the tree */
666 pqremove(s, tree, n); /* n = node of least frequency */
667 m = s->heap[SMALLEST]; /* m = node of next least frequency */
669 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
670 s->heap[--(s->heap_max)] = m;
672 /* Create a new node father of n and m */
673 tree[node].Freq = tree[n].Freq + tree[m].Freq;
674 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
675 tree[n].Dad = tree[m].Dad = (ush)node;
677 if (tree == s->bl_tree) {
678 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
679 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
682 /* and insert the new node in the heap */
683 s->heap[SMALLEST] = node++;
684 pqdownheap(s, tree, SMALLEST);
686 } while (s->heap_len >= 2);
688 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
690 /* At this point, the fields freq and dad are set. We can now
691 * generate the bit lengths.
693 gen_bitlen(s, (tree_desc *)desc);
695 /* The field len is now set, we can generate the bit codes */
696 gen_codes ((ct_data *)tree, max_code, s->bl_count);
699 /* ===========================================================================
700 * Scan a literal or distance tree to determine the frequencies of the codes
701 * in the bit length tree.
703 local void scan_tree (s, tree, max_code)
705 ct_data *tree; /* the tree to be scanned */
706 int max_code; /* and its largest code of non zero frequency */
708 int n; /* iterates over all tree elements */
709 int prevlen = -1; /* last emitted length */
710 int curlen; /* length of current code */
711 int nextlen = tree[0].Len; /* length of next code */
712 int count = 0; /* repeat count of the current code */
713 int max_count = 7; /* max repeat count */
714 int min_count = 4; /* min repeat count */
716 if (nextlen == 0) max_count = 138, min_count = 3;
717 tree[max_code+1].Len = (ush)0xffff; /* guard */
719 for (n = 0; n <= max_code; n++) {
720 curlen = nextlen; nextlen = tree[n+1].Len;
721 if (++count < max_count && curlen == nextlen) {
723 } else if (count < min_count) {
724 s->bl_tree[curlen].Freq += count;
725 } else if (curlen != 0) {
726 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
727 s->bl_tree[REP_3_6].Freq++;
728 } else if (count <= 10) {
729 s->bl_tree[REPZ_3_10].Freq++;
731 s->bl_tree[REPZ_11_138].Freq++;
733 count = 0; prevlen = curlen;
735 max_count = 138, min_count = 3;
736 } else if (curlen == nextlen) {
737 max_count = 6, min_count = 3;
739 max_count = 7, min_count = 4;
744 /* ===========================================================================
745 * Send a literal or distance tree in compressed form, using the codes in
748 local void send_tree (s, tree, max_code)
750 ct_data *tree; /* the tree to be scanned */
751 int max_code; /* and its largest code of non zero frequency */
753 int n; /* iterates over all tree elements */
754 int prevlen = -1; /* last emitted length */
755 int curlen; /* length of current code */
756 int nextlen = tree[0].Len; /* length of next code */
757 int count = 0; /* repeat count of the current code */
758 int max_count = 7; /* max repeat count */
759 int min_count = 4; /* min repeat count */
761 /* tree[max_code+1].Len = -1; */ /* guard already set */
762 if (nextlen == 0) max_count = 138, min_count = 3;
764 for (n = 0; n <= max_code; n++) {
765 curlen = nextlen; nextlen = tree[n+1].Len;
766 if (++count < max_count && curlen == nextlen) {
768 } else if (count < min_count) {
769 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
771 } else if (curlen != 0) {
772 if (curlen != prevlen) {
773 send_code(s, curlen, s->bl_tree); count--;
775 Assert(count >= 3 && count <= 6, " 3_6?");
776 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
778 } else if (count <= 10) {
779 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
782 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
784 count = 0; prevlen = curlen;
786 max_count = 138, min_count = 3;
787 } else if (curlen == nextlen) {
788 max_count = 6, min_count = 3;
790 max_count = 7, min_count = 4;
795 /* ===========================================================================
796 * Construct the Huffman tree for the bit lengths and return the index in
797 * bl_order of the last bit length code to send.
799 local int build_bl_tree(s)
802 int max_blindex; /* index of last bit length code of non zero freq */
804 /* Determine the bit length frequencies for literal and distance trees */
805 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
806 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
808 /* Build the bit length tree: */
809 build_tree(s, (tree_desc *)(&(s->bl_desc)));
810 /* opt_len now includes the length of the tree representations, except
811 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
814 /* Determine the number of bit length codes to send. The pkzip format
815 * requires that at least 4 bit length codes be sent. (appnote.txt says
816 * 3 but the actual value used is 4.)
818 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
819 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
821 /* Update opt_len to include the bit length tree and counts */
822 s->opt_len += 3*(max_blindex+1) + 5+5+4;
823 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
824 s->opt_len, s->static_len));
829 /* ===========================================================================
830 * Send the header for a block using dynamic Huffman trees: the counts, the
831 * lengths of the bit length codes, the literal tree and the distance tree.
832 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
834 local void send_all_trees(s, lcodes, dcodes, blcodes)
836 int lcodes, dcodes, blcodes; /* number of codes for each tree */
838 int rank; /* index in bl_order */
840 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
841 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
843 Tracev((stderr, "\nbl counts: "));
844 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
845 send_bits(s, dcodes-1, 5);
846 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
847 for (rank = 0; rank < blcodes; rank++) {
848 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
849 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
851 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
853 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
854 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
856 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
857 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
860 /* ===========================================================================
861 * Send a stored block
863 void _tr_stored_block(s, buf, stored_len, eof)
865 charf *buf; /* input block */
866 ulg stored_len; /* length of input block */
867 int eof; /* true if this is the last block for a file */
869 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
870 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
871 s->compressed_len += (stored_len + 4) << 3;
873 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
876 /* ===========================================================================
877 * Send one empty static block to give enough lookahead for inflate.
878 * This takes 10 bits, of which 7 may remain in the bit buffer.
879 * The current inflate code requires 9 bits of lookahead. If the
880 * last two codes for the previous block (real code plus EOB) were coded
881 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
882 * the last real code. In this case we send two empty static blocks instead
883 * of one. (There are no problems if the previous block is stored or fixed.)
884 * To simplify the code, we assume the worst case of last real code encoded
890 send_bits(s, STATIC_TREES<<1, 3);
891 send_code(s, END_BLOCK, static_ltree);
892 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
894 /* Of the 10 bits for the empty block, we have already sent
895 * (10 - bi_valid) bits. The lookahead for the last real code (before
896 * the EOB of the previous block) was thus at least one plus the length
897 * of the EOB plus what we have just sent of the empty static block.
899 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
900 send_bits(s, STATIC_TREES<<1, 3);
901 send_code(s, END_BLOCK, static_ltree);
902 s->compressed_len += 10L;
908 /* ===========================================================================
909 * Determine the best encoding for the current block: dynamic trees, static
910 * trees or store, and output the encoded block to the zip file. This function
911 * returns the total compressed length for the file so far.
913 ulg _tr_flush_block(s, buf, stored_len, eof)
915 charf *buf; /* input block, or NULL if too old */
916 ulg stored_len; /* length of input block */
917 int eof; /* true if this is the last block for a file */
919 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
920 int max_blindex = 0; /* index of last bit length code of non zero freq */
922 /* Build the Huffman trees unless a stored block is forced */
925 /* Check if the file is ascii or binary */
926 if (s->data_type == Z_UNKNOWN) set_data_type(s);
928 /* Construct the literal and distance trees */
929 build_tree(s, (tree_desc *)(&(s->l_desc)));
930 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
933 build_tree(s, (tree_desc *)(&(s->d_desc)));
934 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
936 /* At this point, opt_len and static_len are the total bit lengths of
937 * the compressed block data, excluding the tree representations.
940 /* Build the bit length tree for the above two trees, and get the index
941 * in bl_order of the last bit length code to send.
943 max_blindex = build_bl_tree(s);
945 /* Determine the best encoding. Compute first the block length in bytes*/
946 opt_lenb = (s->opt_len+3+7)>>3;
947 static_lenb = (s->static_len+3+7)>>3;
949 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
950 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
953 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
956 Assert(buf != (char*)0, "lost buf");
957 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
960 /* If compression failed and this is the first and last block,
961 * and if the .zip file can be seeked (to rewrite the local header),
962 * the whole file is transformed into a stored file:
964 #ifdef STORED_FILE_OK
965 # ifdef FORCE_STORED_FILE
966 if (eof && s->compressed_len == 0L) { /* force stored file */
968 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
970 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
971 if (buf == (charf*)0) error ("block vanished");
973 copy_block(buf, (unsigned)stored_len, 0); /* without header */
974 s->compressed_len = stored_len << 3;
977 #endif /* STORED_FILE_OK */
980 if (buf != (char*)0) { /* force stored block */
982 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
983 /* 4: two words for the lengths */
985 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
986 * Otherwise we can't have processed more than WSIZE input bytes since
987 * the last block flush, because compression would have been
988 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
989 * transform a block into a stored block.
991 _tr_stored_block(s, buf, stored_len, eof);
994 } else if (static_lenb >= 0) { /* force static trees */
996 } else if (static_lenb == opt_lenb) {
998 send_bits(s, (STATIC_TREES<<1)+eof, 3);
999 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
1000 s->compressed_len += 3 + s->static_len;
1002 send_bits(s, (DYN_TREES<<1)+eof, 3);
1003 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
1005 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
1006 s->compressed_len += 3 + s->opt_len;
1008 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
1013 s->compressed_len += 7; /* align on byte boundary */
1015 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1016 s->compressed_len-7*eof));
1018 return s->compressed_len >> 3;
1021 /* ===========================================================================
1022 * Save the match info and tally the frequency counts. Return true if
1023 * the current block must be flushed.
1025 int _tr_tally (s, dist, lc)
1027 unsigned dist; /* distance of matched string */
1028 unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
1030 s->d_buf[s->last_lit] = (ush)dist;
1031 s->l_buf[s->last_lit++] = (uch)lc;
1033 /* lc is the unmatched char */
1034 s->dyn_ltree[lc].Freq++;
1037 /* Here, lc is the match length - MIN_MATCH */
1038 dist--; /* dist = match distance - 1 */
1039 Assert((ush)dist < (ush)MAX_DIST(s) &&
1040 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1041 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match");
1043 s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1044 s->dyn_dtree[d_code(dist)].Freq++;
1047 #ifdef TRUNCATE_BLOCK
1048 /* Try to guess if it is profitable to stop the current block here */
1049 if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1050 /* Compute an upper bound for the compressed length */
1051 ulg out_length = (ulg)s->last_lit*8L;
1052 ulg in_length = (ulg)((long)s->strstart - s->block_start);
1054 for (dcode = 0; dcode < D_CODES; dcode++) {
1055 out_length += (ulg)s->dyn_dtree[dcode].Freq *
1056 (5L+extra_dbits[dcode]);
1059 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1060 s->last_lit, in_length, out_length,
1061 100L - out_length*100L/in_length));
1062 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1065 return (s->last_lit == s->lit_bufsize-1);
1066 /* We avoid equality with lit_bufsize because of wraparound at 64K
1067 * on 16 bit machines and because stored blocks are restricted to
1072 /* ===========================================================================
1073 * Send the block data compressed using the given Huffman trees
1075 local void compress_block(s, ltree, dtree)
1077 ct_data *ltree; /* literal tree */
1078 ct_data *dtree; /* distance tree */
1080 unsigned dist; /* distance of matched string */
1081 int lc; /* match length or unmatched char (if dist == 0) */
1082 unsigned lx = 0; /* running index in l_buf */
1083 unsigned code; /* the code to send */
1084 int extra; /* number of extra bits to send */
1086 if (s->last_lit != 0) do {
1087 dist = s->d_buf[lx];
1088 lc = s->l_buf[lx++];
1090 send_code(s, lc, ltree); /* send a literal byte */
1091 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1093 /* Here, lc is the match length - MIN_MATCH */
1094 code = _length_code[lc];
1095 send_code(s, code+LITERALS+1, ltree); /* send the length code */
1096 extra = extra_lbits[code];
1098 lc -= base_length[code];
1099 send_bits(s, lc, extra); /* send the extra length bits */
1101 dist--; /* dist is now the match distance - 1 */
1102 code = d_code(dist);
1103 Assert (code < D_CODES, "bad d_code");
1105 send_code(s, code, dtree); /* send the distance code */
1106 extra = extra_dbits[code];
1108 dist -= base_dist[code];
1109 send_bits(s, dist, extra); /* send the extra distance bits */
1111 } /* literal or match pair ? */
1113 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1114 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1116 } while (lx < s->last_lit);
1118 send_code(s, END_BLOCK, ltree);
1119 s->last_eob_len = ltree[END_BLOCK].Len;
1122 /* ===========================================================================
1123 * Set the data type to ASCII or BINARY, using a crude approximation:
1124 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1125 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1126 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1128 local void set_data_type(s)
1132 unsigned ascii_freq = 0;
1133 unsigned bin_freq = 0;
1134 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1135 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1136 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1137 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1140 /* ===========================================================================
1141 * Reverse the first len bits of a code, using straightforward code (a faster
1142 * method would use a table)
1143 * IN assertion: 1 <= len <= 15
1145 local unsigned bi_reverse(code, len)
1146 unsigned code; /* the value to invert */
1147 int len; /* its bit length */
1149 register unsigned res = 0;
1152 code >>= 1, res <<= 1;
1153 } while (--len > 0);
1157 /* ===========================================================================
1158 * Flush the bit buffer, keeping at most 7 bits in it.
1160 local void bi_flush(s)
1163 if (s->bi_valid == 16) {
1164 put_short(s, s->bi_buf);
1167 } else if (s->bi_valid >= 8) {
1168 put_byte(s, (Byte)s->bi_buf);
1174 /* ===========================================================================
1175 * Flush the bit buffer and align the output on a byte boundary
1177 local void bi_windup(s)
1180 if (s->bi_valid > 8) {
1181 put_short(s, s->bi_buf);
1182 } else if (s->bi_valid > 0) {
1183 put_byte(s, (Byte)s->bi_buf);
1188 s->bits_sent = (s->bits_sent+7) & ~7;
1192 /* ===========================================================================
1193 * Copy a stored block, storing first the length and its
1194 * one's complement if requested.
1196 local void copy_block(s, buf, len, header)
1198 charf *buf; /* the input data */
1199 unsigned len; /* its length */
1200 int header; /* true if block header must be written */
1202 bi_windup(s); /* align on byte boundary */
1203 s->last_eob_len = 8; /* enough lookahead for inflate */
1206 put_short(s, (ush)len);
1207 put_short(s, (ush)~len);
1209 s->bits_sent += 2*16;
1213 s->bits_sent += (ulg)len<<3;
1216 put_byte(s, *buf++);