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.
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
35 /* #define GEN_TREES_H */
43 /* ===========================================================================
48 /* Bit length codes must not exceed MAX_BL_BITS bits */
51 /* end of block literal code */
54 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
57 /* repeat a zero length 3-10 times (3 bits of repeat count) */
59 #define REPZ_11_138 18
60 /* repeat a zero length 11-138 times (7 bits of repeat count) */
62 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
63 = {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};
65 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
66 = {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};
68 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
69 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
71 local const uch bl_order[BL_CODES]
72 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
73 /* The lengths of the bit length codes are sent in order of decreasing
74 * probability, to avoid transmitting the lengths for unused bit length codes.
77 #define Buf_size (8 * 2*sizeof(char))
78 /* Number of bits used within bi_buf. (bi_buf might be implemented on
79 * more than 16 bits on some systems.)
82 /* ===========================================================================
83 * Local data. These are initialized only once.
86 #define DIST_CODE_LEN 512 /* see definition of array dist_code below */
88 #if defined(GEN_TREES_H) || !defined(STDC)
89 /* non ANSI compilers may not accept trees.h */
91 local ct_data static_ltree[L_CODES+2];
92 /* The static literal tree. Since the bit lengths are imposed, there is no
93 * need for the L_CODES extra codes used during heap construction. However
94 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
98 local ct_data static_dtree[D_CODES];
99 /* The static distance tree. (Actually a trivial tree since all codes use
103 uch _dist_code[DIST_CODE_LEN];
104 /* Distance codes. The first 256 values correspond to the distances
105 * 3 .. 258, the last 256 values correspond to the top 8 bits of
106 * the 15 bit distances.
109 uch _length_code[MAX_MATCH-MIN_MATCH+1];
110 /* length code for each normalized match length (0 == MIN_MATCH) */
112 local int base_length[LENGTH_CODES];
113 /* First normalized length for each code (0 = MIN_MATCH) */
115 local int base_dist[D_CODES];
116 /* First normalized distance for each code (0 = distance of 1) */
120 #endif /* GEN_TREES_H */
122 struct static_tree_desc_s {
123 const ct_data *static_tree; /* static tree or NULL */
124 const intf *extra_bits; /* extra bits for each code or NULL */
125 int extra_base; /* base index for extra_bits */
126 int elems; /* max number of elements in the tree */
127 int max_length; /* max bit length for the codes */
130 local static_tree_desc static_l_desc =
131 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
133 local static_tree_desc static_d_desc =
134 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
136 local static_tree_desc static_bl_desc =
137 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
139 /* ===========================================================================
140 * Local (static) routines in this file.
143 local void tr_static_init OF((void));
144 local void init_block OF((deflate_state *s));
145 local void pqdownheap OF((deflate_state *s, ct_data *tree, int k));
146 local void gen_bitlen OF((deflate_state *s, tree_desc *desc));
147 local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count));
148 local void build_tree OF((deflate_state *s, tree_desc *desc));
149 local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code));
150 local void send_tree OF((deflate_state *s, ct_data *tree, int max_code));
151 local int build_bl_tree OF((deflate_state *s));
152 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
154 local void compress_block OF((deflate_state *s, ct_data *ltree,
156 local void set_data_type OF((deflate_state *s));
157 local unsigned bi_reverse OF((unsigned value, int length));
158 local void bi_windup OF((deflate_state *s));
159 local void bi_flush OF((deflate_state *s));
160 local void copy_block OF((deflate_state *s, charf *buf, unsigned len,
164 local void gen_trees_header OF((void));
168 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
169 /* Send a code of the given tree. c and tree must not have side effects */
172 # define send_code(s, c, tree) \
173 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
174 send_bits(s, tree[c].Code, tree[c].Len); }
177 /* ===========================================================================
178 * Output a short LSB first on the stream.
179 * IN assertion: there is enough room in pendingBuf.
181 #define put_short(s, w) { \
182 put_byte(s, (uch)((w) & 0xff)); \
183 put_byte(s, (uch)((ush)(w) >> 8)); \
186 /* ===========================================================================
187 * Send a value on a given number of bits.
188 * IN assertion: length <= 16 and value fits in length bits.
191 local void send_bits OF((deflate_state *s, int value, int length));
193 local void send_bits(s, value, length)
195 int value; /* value to send */
196 int length; /* number of bits */
198 Tracevv((stderr," l %2d v %4x ", length, value));
199 Assert(length > 0 && length <= 15, "invalid length");
200 s->bits_sent += (ulg)length;
202 /* If not enough room in bi_buf, use (valid) bits from bi_buf and
203 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
204 * unused bits in value.
206 if (s->bi_valid > (int)Buf_size - length) {
207 s->bi_buf |= (value << s->bi_valid);
208 put_short(s, s->bi_buf);
209 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
210 s->bi_valid += length - Buf_size;
212 s->bi_buf |= value << s->bi_valid;
213 s->bi_valid += length;
218 #define send_bits(s, value, length) \
220 if (s->bi_valid > (int)Buf_size - len) {\
222 s->bi_buf |= (val << s->bi_valid);\
223 put_short(s, s->bi_buf);\
224 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
225 s->bi_valid += len - Buf_size;\
227 s->bi_buf |= (value) << s->bi_valid;\
234 #define MAX(a,b) (a >= b ? a : b)
235 /* the arguments must not have side effects */
237 /* ===========================================================================
238 * Initialize the various 'constant' tables.
240 local void tr_static_init()
242 #if defined(GEN_TREES_H) || !defined(STDC)
243 static int static_init_done = 0;
244 int n; /* iterates over tree elements */
245 int bits; /* bit counter */
246 int length; /* length value */
247 int code; /* code value */
248 int dist; /* distance index */
249 ush bl_count[MAX_BITS+1];
250 /* number of codes at each bit length for an optimal tree */
252 if (static_init_done) return;
254 /* For some embedded targets, global variables are not initialized: */
255 static_l_desc.static_tree = static_ltree;
256 static_l_desc.extra_bits = extra_lbits;
257 static_d_desc.static_tree = static_dtree;
258 static_d_desc.extra_bits = extra_dbits;
259 static_bl_desc.extra_bits = extra_blbits;
261 /* Initialize the mapping length (0..255) -> length code (0..28) */
263 for (code = 0; code < LENGTH_CODES-1; code++) {
264 base_length[code] = length;
265 for (n = 0; n < (1<<extra_lbits[code]); n++) {
266 _length_code[length++] = (uch)code;
269 Assert (length == 256, "tr_static_init: length != 256");
270 /* Note that the length 255 (match length 258) can be represented
271 * in two different ways: code 284 + 5 bits or code 285, so we
272 * overwrite length_code[255] to use the best encoding:
274 _length_code[length-1] = (uch)code;
276 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
278 for (code = 0 ; code < 16; code++) {
279 base_dist[code] = dist;
280 for (n = 0; n < (1<<extra_dbits[code]); n++) {
281 _dist_code[dist++] = (uch)code;
284 Assert (dist == 256, "tr_static_init: dist != 256");
285 dist >>= 7; /* from now on, all distances are divided by 128 */
286 for ( ; code < D_CODES; code++) {
287 base_dist[code] = dist << 7;
288 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
289 _dist_code[256 + dist++] = (uch)code;
292 Assert (dist == 256, "tr_static_init: 256+dist != 512");
294 /* Construct the codes of the static literal tree */
295 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
297 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
298 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
299 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
300 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
301 /* Codes 286 and 287 do not exist, but we must include them in the
302 * tree construction to get a canonical Huffman tree (longest code
305 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
307 /* The static distance tree is trivial: */
308 for (n = 0; n < D_CODES; n++) {
309 static_dtree[n].Len = 5;
310 static_dtree[n].Code = bi_reverse((unsigned)n, 5);
312 static_init_done = 1;
317 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
320 /* ===========================================================================
321 * Genererate the file trees.h describing the static trees.
328 # define SEPARATOR(i, last, width) \
329 ((i) == (last)? "\n};\n\n" : \
330 ((i) % (width) == (width)-1 ? ",\n" : ", "))
332 void gen_trees_header()
334 FILE *header = fopen("trees.h", "w");
337 Assert (header != NULL, "Can't open trees.h");
339 "/* header created automatically with -DGEN_TREES_H */\n\n");
341 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
342 for (i = 0; i < L_CODES+2; i++) {
343 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
344 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
347 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
348 for (i = 0; i < D_CODES; i++) {
349 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
350 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
353 fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
354 for (i = 0; i < DIST_CODE_LEN; i++) {
355 fprintf(header, "%2u%s", _dist_code[i],
356 SEPARATOR(i, DIST_CODE_LEN-1, 20));
359 fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
360 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
361 fprintf(header, "%2u%s", _length_code[i],
362 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
365 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
366 for (i = 0; i < LENGTH_CODES; i++) {
367 fprintf(header, "%1u%s", base_length[i],
368 SEPARATOR(i, LENGTH_CODES-1, 20));
371 fprintf(header, "local const int base_dist[D_CODES] = {\n");
372 for (i = 0; i < D_CODES; i++) {
373 fprintf(header, "%5u%s", base_dist[i],
374 SEPARATOR(i, D_CODES-1, 10));
379 #endif /* GEN_TREES_H */
381 /* ===========================================================================
382 * Initialize the tree data structures for a new zlib stream.
389 s->l_desc.dyn_tree = s->dyn_ltree;
390 s->l_desc.stat_desc = &static_l_desc;
392 s->d_desc.dyn_tree = s->dyn_dtree;
393 s->d_desc.stat_desc = &static_d_desc;
395 s->bl_desc.dyn_tree = s->bl_tree;
396 s->bl_desc.stat_desc = &static_bl_desc;
400 s->last_eob_len = 8; /* enough lookahead for inflate */
402 s->compressed_len = 0L;
406 /* Initialize the first block of the first file: */
410 /* ===========================================================================
411 * Initialize a new block.
413 local void init_block(s)
416 int n; /* iterates over tree elements */
418 /* Initialize the trees. */
419 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
420 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
421 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
423 s->dyn_ltree[END_BLOCK].Freq = 1;
424 s->opt_len = s->static_len = 0L;
425 s->last_lit = s->matches = 0;
429 /* Index within the heap array of least frequent node in the Huffman tree */
432 /* ===========================================================================
433 * Remove the smallest element from the heap and recreate the heap with
434 * one less element. Updates heap and heap_len.
436 #define pqremove(s, tree, top) \
438 top = s->heap[SMALLEST]; \
439 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
440 pqdownheap(s, tree, SMALLEST); \
443 /* ===========================================================================
444 * Compares to subtrees, using the tree depth as tie breaker when
445 * the subtrees have equal frequency. This minimizes the worst case length.
447 #define smaller(tree, n, m, depth) \
448 (tree[n].Freq < tree[m].Freq || \
449 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
451 /* ===========================================================================
452 * Restore the heap property by moving down the tree starting at node k,
453 * exchanging a node with the smallest of its two sons if necessary, stopping
454 * when the heap property is re-established (each father smaller than its
457 local void pqdownheap(s, tree, k)
459 ct_data *tree; /* the tree to restore */
460 int k; /* node to move down */
463 int j = k << 1; /* left son of k */
464 while (j <= s->heap_len) {
465 /* Set j to the smallest of the two sons: */
466 if (j < s->heap_len &&
467 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
470 /* Exit if v is smaller than both sons */
471 if (smaller(tree, v, s->heap[j], s->depth)) break;
473 /* Exchange v with the smallest son */
474 s->heap[k] = s->heap[j]; k = j;
476 /* And continue down the tree, setting j to the left son of k */
482 /* ===========================================================================
483 * Compute the optimal bit lengths for a tree and update the total bit length
484 * for the current block.
485 * IN assertion: the fields freq and dad are set, heap[heap_max] and
486 * above are the tree nodes sorted by increasing frequency.
487 * OUT assertions: the field len is set to the optimal bit length, the
488 * array bl_count contains the frequencies for each bit length.
489 * The length opt_len is updated; static_len is also updated if stree is
492 local void gen_bitlen(s, desc)
494 tree_desc *desc; /* the tree descriptor */
496 ct_data *tree = desc->dyn_tree;
497 int max_code = desc->max_code;
498 const ct_data *stree = desc->stat_desc->static_tree;
499 const intf *extra = desc->stat_desc->extra_bits;
500 int base = desc->stat_desc->extra_base;
501 int max_length = desc->stat_desc->max_length;
502 int h; /* heap index */
503 int n, m; /* iterate over the tree elements */
504 int bits; /* bit length */
505 int xbits; /* extra bits */
506 ush f; /* frequency */
507 int overflow = 0; /* number of elements with bit length too large */
509 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
511 /* In a first pass, compute the optimal bit lengths (which may
512 * overflow in the case of the bit length tree).
514 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
516 for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
518 bits = tree[tree[n].Dad].Len + 1;
519 if (bits > max_length) bits = max_length, overflow++;
520 tree[n].Len = (ush)bits;
521 /* We overwrite tree[n].Dad which is no longer needed */
523 if (n > max_code) continue; /* not a leaf node */
527 if (n >= base) xbits = extra[n-base];
529 s->opt_len += (ulg)f * (bits + xbits);
530 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
532 if (overflow == 0) return;
534 Trace((stderr,"\nbit length overflow\n"));
535 /* This happens for example on obj2 and pic of the Calgary corpus */
537 /* Find the first bit length which could increase: */
540 while (s->bl_count[bits] == 0) bits--;
541 s->bl_count[bits]--; /* move one leaf down the tree */
542 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
543 s->bl_count[max_length]--;
544 /* The brother of the overflow item also moves one step up,
545 * but this does not affect bl_count[max_length]
548 } while (overflow > 0);
550 /* Now recompute all bit lengths, scanning in increasing frequency.
551 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
552 * lengths instead of fixing only the wrong ones. This idea is taken
553 * from 'ar' written by Haruhiko Okumura.)
555 for (bits = max_length; bits != 0; bits--) {
556 n = s->bl_count[bits];
559 if (m > max_code) continue;
560 if (tree[m].Len != (unsigned) bits) {
561 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
562 s->opt_len += ((long)bits - (long)tree[m].Len)
564 tree[m].Len = (ush)bits;
571 /* ===========================================================================
572 * Generate the codes for a given tree and bit counts (which need not be
574 * IN assertion: the array bl_count contains the bit length statistics for
575 * the given tree and the field len is set for all tree elements.
576 * OUT assertion: the field code is set for all tree elements of non
579 local void gen_codes (tree, max_code, bl_count)
580 ct_data *tree; /* the tree to decorate */
581 int max_code; /* largest code with non zero frequency */
582 ushf *bl_count; /* number of codes at each bit length */
584 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
585 ush code = 0; /* running code value */
586 int bits; /* bit index */
587 int n; /* code index */
589 /* The distribution counts are first used to generate the code values
590 * without bit reversal.
592 for (bits = 1; bits <= MAX_BITS; bits++) {
593 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
595 /* Check that the bit counts in bl_count are consistent. The last code
598 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
599 "inconsistent bit counts");
600 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
602 for (n = 0; n <= max_code; n++) {
603 int len = tree[n].Len;
604 if (len == 0) continue;
605 /* Now reverse the bits */
606 tree[n].Code = bi_reverse(next_code[len]++, len);
608 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
609 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
613 /* ===========================================================================
614 * Construct one Huffman tree and assigns the code bit strings and lengths.
615 * Update the total bit length for the current block.
616 * IN assertion: the field freq is set for all tree elements.
617 * OUT assertions: the fields len and code are set to the optimal bit length
618 * and corresponding code. The length opt_len is updated; static_len is
619 * also updated if stree is not null. The field max_code is set.
621 local void build_tree(s, desc)
623 tree_desc *desc; /* the tree descriptor */
625 ct_data *tree = desc->dyn_tree;
626 const ct_data *stree = desc->stat_desc->static_tree;
627 int elems = desc->stat_desc->elems;
628 int n, m; /* iterate over heap elements */
629 int max_code = -1; /* largest code with non zero frequency */
630 int node; /* new node being created */
632 /* Construct the initial heap, with least frequent element in
633 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
634 * heap[0] is not used.
636 s->heap_len = 0, s->heap_max = HEAP_SIZE;
638 for (n = 0; n < elems; n++) {
639 if (tree[n].Freq != 0) {
640 s->heap[++(s->heap_len)] = max_code = n;
647 /* The pkzip format requires that at least one distance code exists,
648 * and that at least one bit should be sent even if there is only one
649 * possible code. So to avoid special checks later on we force at least
650 * two codes of non zero frequency.
652 while (s->heap_len < 2) {
653 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
656 s->opt_len--; if (stree) s->static_len -= stree[node].Len;
657 /* node is 0 or 1 so it does not have extra bits */
659 desc->max_code = max_code;
661 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
662 * establish sub-heaps of increasing lengths:
664 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
666 /* Construct the Huffman tree by repeatedly combining the least two
669 node = elems; /* next internal node of the tree */
671 pqremove(s, tree, n); /* n = node of least frequency */
672 m = s->heap[SMALLEST]; /* m = node of next least frequency */
674 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
675 s->heap[--(s->heap_max)] = m;
677 /* Create a new node father of n and m */
678 tree[node].Freq = tree[n].Freq + tree[m].Freq;
679 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
680 tree[n].Dad = tree[m].Dad = (ush)node;
682 if (tree == s->bl_tree) {
683 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
684 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
687 /* and insert the new node in the heap */
688 s->heap[SMALLEST] = node++;
689 pqdownheap(s, tree, SMALLEST);
691 } while (s->heap_len >= 2);
693 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
695 /* At this point, the fields freq and dad are set. We can now
696 * generate the bit lengths.
698 gen_bitlen(s, (tree_desc *)desc);
700 /* The field len is now set, we can generate the bit codes */
701 gen_codes ((ct_data *)tree, max_code, s->bl_count);
704 /* ===========================================================================
705 * Scan a literal or distance tree to determine the frequencies of the codes
706 * in the bit length tree.
708 local void scan_tree (s, tree, max_code)
710 ct_data *tree; /* the tree to be scanned */
711 int max_code; /* and its largest code of non zero frequency */
713 int n; /* iterates over all tree elements */
714 int prevlen = -1; /* last emitted length */
715 int curlen; /* length of current code */
716 int nextlen = tree[0].Len; /* length of next code */
717 int count = 0; /* repeat count of the current code */
718 int max_count = 7; /* max repeat count */
719 int min_count = 4; /* min repeat count */
721 if (nextlen == 0) max_count = 138, min_count = 3;
722 tree[max_code+1].Len = (ush)0xffff; /* guard */
724 for (n = 0; n <= max_code; n++) {
725 curlen = nextlen; nextlen = tree[n+1].Len;
726 if (++count < max_count && curlen == nextlen) {
728 } else if (count < min_count) {
729 s->bl_tree[curlen].Freq += count;
730 } else if (curlen != 0) {
731 if (curlen != prevlen) s->bl_tree[curlen].Freq++;
732 s->bl_tree[REP_3_6].Freq++;
733 } else if (count <= 10) {
734 s->bl_tree[REPZ_3_10].Freq++;
736 s->bl_tree[REPZ_11_138].Freq++;
738 count = 0; prevlen = curlen;
740 max_count = 138, min_count = 3;
741 } else if (curlen == nextlen) {
742 max_count = 6, min_count = 3;
744 max_count = 7, min_count = 4;
749 /* ===========================================================================
750 * Send a literal or distance tree in compressed form, using the codes in
753 local void send_tree (s, tree, max_code)
755 ct_data *tree; /* the tree to be scanned */
756 int max_code; /* and its largest code of non zero frequency */
758 int n; /* iterates over all tree elements */
759 int prevlen = -1; /* last emitted length */
760 int curlen; /* length of current code */
761 int nextlen = tree[0].Len; /* length of next code */
762 int count = 0; /* repeat count of the current code */
763 int max_count = 7; /* max repeat count */
764 int min_count = 4; /* min repeat count */
766 /* tree[max_code+1].Len = -1; */ /* guard already set */
767 if (nextlen == 0) max_count = 138, min_count = 3;
769 for (n = 0; n <= max_code; n++) {
770 curlen = nextlen; nextlen = tree[n+1].Len;
771 if (++count < max_count && curlen == nextlen) {
773 } else if (count < min_count) {
774 do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
776 } else if (curlen != 0) {
777 if (curlen != prevlen) {
778 send_code(s, curlen, s->bl_tree); count--;
780 Assert(count >= 3 && count <= 6, " 3_6?");
781 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
783 } else if (count <= 10) {
784 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
787 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
789 count = 0; prevlen = curlen;
791 max_count = 138, min_count = 3;
792 } else if (curlen == nextlen) {
793 max_count = 6, min_count = 3;
795 max_count = 7, min_count = 4;
800 /* ===========================================================================
801 * Construct the Huffman tree for the bit lengths and return the index in
802 * bl_order of the last bit length code to send.
804 local int build_bl_tree(s)
807 int max_blindex; /* index of last bit length code of non zero freq */
809 /* Determine the bit length frequencies for literal and distance trees */
810 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
811 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
813 /* Build the bit length tree: */
814 build_tree(s, (tree_desc *)(&(s->bl_desc)));
815 /* opt_len now includes the length of the tree representations, except
816 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
819 /* Determine the number of bit length codes to send. The pkzip format
820 * requires that at least 4 bit length codes be sent. (appnote.txt says
821 * 3 but the actual value used is 4.)
823 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
824 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
826 /* Update opt_len to include the bit length tree and counts */
827 s->opt_len += 3*(max_blindex+1) + 5+5+4;
828 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
829 s->opt_len, s->static_len));
834 /* ===========================================================================
835 * Send the header for a block using dynamic Huffman trees: the counts, the
836 * lengths of the bit length codes, the literal tree and the distance tree.
837 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
839 local void send_all_trees(s, lcodes, dcodes, blcodes)
841 int lcodes, dcodes, blcodes; /* number of codes for each tree */
843 int rank; /* index in bl_order */
845 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
846 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
848 Tracev((stderr, "\nbl counts: "));
849 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
850 send_bits(s, dcodes-1, 5);
851 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
852 for (rank = 0; rank < blcodes; rank++) {
853 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
854 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
856 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
858 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
859 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
861 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
862 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
865 /* ===========================================================================
866 * Send a stored block
868 void _tr_stored_block(s, buf, stored_len, eof)
870 charf *buf; /* input block */
871 ulg stored_len; /* length of input block */
872 int eof; /* true if this is the last block for a file */
874 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
876 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
877 s->compressed_len += (stored_len + 4) << 3;
879 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
882 /* ===========================================================================
883 * Send one empty static block to give enough lookahead for inflate.
884 * This takes 10 bits, of which 7 may remain in the bit buffer.
885 * The current inflate code requires 9 bits of lookahead. If the
886 * last two codes for the previous block (real code plus EOB) were coded
887 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
888 * the last real code. In this case we send two empty static blocks instead
889 * of one. (There are no problems if the previous block is stored or fixed.)
890 * To simplify the code, we assume the worst case of last real code encoded
896 send_bits(s, STATIC_TREES<<1, 3);
897 send_code(s, END_BLOCK, static_ltree);
899 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
902 /* Of the 10 bits for the empty block, we have already sent
903 * (10 - bi_valid) bits. The lookahead for the last real code (before
904 * the EOB of the previous block) was thus at least one plus the length
905 * of the EOB plus what we have just sent of the empty static block.
907 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
908 send_bits(s, STATIC_TREES<<1, 3);
909 send_code(s, END_BLOCK, static_ltree);
911 s->compressed_len += 10L;
918 /* ===========================================================================
919 * Determine the best encoding for the current block: dynamic trees, static
920 * trees or store, and output the encoded block to the zip file.
922 void _tr_flush_block(s, buf, stored_len, eof)
924 charf *buf; /* input block, or NULL if too old */
925 ulg stored_len; /* length of input block */
926 int eof; /* true if this is the last block for a file */
928 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
929 int max_blindex = 0; /* index of last bit length code of non zero freq */
931 /* Build the Huffman trees unless a stored block is forced */
934 /* Check if the file is ascii or binary */
935 if (s->data_type == Z_UNKNOWN) set_data_type(s);
937 /* Construct the literal and distance trees */
938 build_tree(s, (tree_desc *)(&(s->l_desc)));
939 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
942 build_tree(s, (tree_desc *)(&(s->d_desc)));
943 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
945 /* At this point, opt_len and static_len are the total bit lengths of
946 * the compressed block data, excluding the tree representations.
949 /* Build the bit length tree for the above two trees, and get the index
950 * in bl_order of the last bit length code to send.
952 max_blindex = build_bl_tree(s);
954 /* Determine the best encoding. Compute first the block length in bytes*/
955 opt_lenb = (s->opt_len+3+7)>>3;
956 static_lenb = (s->static_len+3+7)>>3;
958 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
959 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
962 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
965 Assert(buf != (char*)0, "lost buf");
966 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
970 if (buf != (char*)0) { /* force stored block */
972 if (stored_len+4 <= opt_lenb && buf != (char*)0) {
973 /* 4: two words for the lengths */
975 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
976 * Otherwise we can't have processed more than WSIZE input bytes since
977 * the last block flush, because compression would have been
978 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
979 * transform a block into a stored block.
981 _tr_stored_block(s, buf, stored_len, eof);
984 } else if (static_lenb >= 0) { /* force static trees */
986 } else if (static_lenb == opt_lenb) {
988 send_bits(s, (STATIC_TREES<<1)+eof, 3);
989 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
991 s->compressed_len += 3 + s->static_len;
994 send_bits(s, (DYN_TREES<<1)+eof, 3);
995 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
997 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
999 s->compressed_len += 3 + s->opt_len;
1002 Assert (s->compressed_len == s->bits_sent, "bad compressed size");
1003 /* The above check is made mod 2^32, for files larger than 512 MB
1004 * and uLong implemented on 32 bits.
1011 s->compressed_len += 7; /* align on byte boundary */
1014 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1015 s->compressed_len-7*eof));
1018 /* ===========================================================================
1019 * Save the match info and tally the frequency counts. Return true if
1020 * the current block must be flushed.
1022 int _tr_tally (s, dist, lc)
1024 unsigned dist; /* distance of matched string */
1025 unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
1027 s->d_buf[s->last_lit] = (ush)dist;
1028 s->l_buf[s->last_lit++] = (uch)lc;
1030 /* lc is the unmatched char */
1031 s->dyn_ltree[lc].Freq++;
1034 /* Here, lc is the match length - MIN_MATCH */
1035 dist--; /* dist = match distance - 1 */
1036 Assert((ush)dist < (ush)MAX_DIST(s) &&
1037 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1038 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match");
1040 s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1041 s->dyn_dtree[d_code(dist)].Freq++;
1044 #ifdef TRUNCATE_BLOCK
1045 /* Try to guess if it is profitable to stop the current block here */
1046 if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1047 /* Compute an upper bound for the compressed length */
1048 ulg out_length = (ulg)s->last_lit*8L;
1049 ulg in_length = (ulg)((long)s->strstart - s->block_start);
1051 for (dcode = 0; dcode < D_CODES; dcode++) {
1052 out_length += (ulg)s->dyn_dtree[dcode].Freq *
1053 (5L+extra_dbits[dcode]);
1056 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1057 s->last_lit, in_length, out_length,
1058 100L - out_length*100L/in_length));
1059 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1062 return (s->last_lit == s->lit_bufsize-1);
1063 /* We avoid equality with lit_bufsize because of wraparound at 64K
1064 * on 16 bit machines and because stored blocks are restricted to
1069 /* ===========================================================================
1070 * Send the block data compressed using the given Huffman trees
1072 local void compress_block(s, ltree, dtree)
1074 ct_data *ltree; /* literal tree */
1075 ct_data *dtree; /* distance tree */
1077 unsigned dist; /* distance of matched string */
1078 int lc; /* match length or unmatched char (if dist == 0) */
1079 unsigned lx = 0; /* running index in l_buf */
1080 unsigned code; /* the code to send */
1081 int extra; /* number of extra bits to send */
1083 if (s->last_lit != 0) do {
1084 dist = s->d_buf[lx];
1085 lc = s->l_buf[lx++];
1087 send_code(s, lc, ltree); /* send a literal byte */
1088 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1090 /* Here, lc is the match length - MIN_MATCH */
1091 code = _length_code[lc];
1092 send_code(s, code+LITERALS+1, ltree); /* send the length code */
1093 extra = extra_lbits[code];
1095 lc -= base_length[code];
1096 send_bits(s, lc, extra); /* send the extra length bits */
1098 dist--; /* dist is now the match distance - 1 */
1099 code = d_code(dist);
1100 Assert (code < D_CODES, "bad d_code");
1102 send_code(s, code, dtree); /* send the distance code */
1103 extra = extra_dbits[code];
1105 dist -= base_dist[code];
1106 send_bits(s, dist, extra); /* send the extra distance bits */
1108 } /* literal or match pair ? */
1110 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1111 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1113 } while (lx < s->last_lit);
1115 send_code(s, END_BLOCK, ltree);
1116 s->last_eob_len = ltree[END_BLOCK].Len;
1119 /* ===========================================================================
1120 * Set the data type to ASCII or BINARY, using a crude approximation:
1121 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1122 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1123 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1125 local void set_data_type(s)
1129 unsigned ascii_freq = 0;
1130 unsigned bin_freq = 0;
1131 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
1132 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
1133 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1134 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1137 /* ===========================================================================
1138 * Reverse the first len bits of a code, using straightforward code (a faster
1139 * method would use a table)
1140 * IN assertion: 1 <= len <= 15
1142 local unsigned bi_reverse(code, len)
1143 unsigned code; /* the value to invert */
1144 int len; /* its bit length */
1146 register unsigned res = 0;
1149 code >>= 1, res <<= 1;
1150 } while (--len > 0);
1154 /* ===========================================================================
1155 * Flush the bit buffer, keeping at most 7 bits in it.
1157 local void bi_flush(s)
1160 if (s->bi_valid == 16) {
1161 put_short(s, s->bi_buf);
1164 } else if (s->bi_valid >= 8) {
1165 put_byte(s, (Byte)s->bi_buf);
1171 /* ===========================================================================
1172 * Flush the bit buffer and align the output on a byte boundary
1174 local void bi_windup(s)
1177 if (s->bi_valid > 8) {
1178 put_short(s, s->bi_buf);
1179 } else if (s->bi_valid > 0) {
1180 put_byte(s, (Byte)s->bi_buf);
1185 s->bits_sent = (s->bits_sent+7) & ~7;
1189 /* ===========================================================================
1190 * Copy a stored block, storing first the length and its
1191 * one's complement if requested.
1193 local void copy_block(s, buf, len, header)
1195 charf *buf; /* the input data */
1196 unsigned len; /* its length */
1197 int header; /* true if block header must be written */
1199 bi_windup(s); /* align on byte boundary */
1200 s->last_eob_len = 8; /* enough lookahead for inflate */
1203 put_short(s, (ush)len);
1204 put_short(s, (ush)~len);
1206 s->bits_sent += 2*16;
1210 s->bits_sent += (ulg)len<<3;
1213 put_byte(s, *buf++);