1 /* trees.c -- output deflated data using Huffman coding
2 * Copyright (C) 1992-1993 Jean-loup Gailly
3 * This is free software; you can redistribute it and/or modify it under the
4 * terms of the GNU General Public License, see the file COPYING.
6 * $FreeBSD: src/gnu/usr.bin/gzip/trees.c,v 1.9 1999/08/27 23:35:53 peter Exp $
7 * $DragonFly: src/gnu/usr.bin/gzip/Attic/trees.c,v 1.2 2003/06/17 04:25:46 dillon Exp $
13 * Encode various sets of source values using variable-length
18 * The PKZIP "deflation" process uses several Huffman trees. The more
19 * common source values are represented by shorter bit sequences.
21 * Each code tree is stored in the ZIP file in a compressed form
22 * which is itself a Huffman encoding of the lengths of
23 * all the code strings (in ascending order by source values).
24 * The actual code strings are reconstructed from the lengths in
25 * the UNZIP process, as described in the "application note"
26 * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
31 * Data Compression: Techniques and Applications, pp. 53-55.
32 * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
35 * Data Compression: Methods and Theory, pp. 49-50.
36 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
40 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
44 * void ct_init (ush *attr, int *methodp)
45 * Allocate the match buffer, initialize the various tables and save
46 * the location of the internal file attribute (ascii/binary) and
47 * method (DEFLATE/STORE)
49 * void ct_tally (int dist, int lc);
50 * Save the match info and tally the frequency counts.
52 * long flush_block (char *buf, ulg stored_len, int eof)
53 * Determine the best encoding for the current block: dynamic trees,
54 * static trees or store, and output the encoded block to the zip
55 * file. Returns the total compressed length for the file so far.
64 /* ===========================================================================
69 /* All codes must not exceed MAX_BITS bits */
72 /* Bit length codes must not exceed MAX_BL_BITS bits */
74 #define LENGTH_CODES 29
75 /* number of length codes, not counting the special END_BLOCK code */
78 /* number of literal bytes 0..255 */
81 /* end of block literal code */
83 #define L_CODES (LITERALS+1+LENGTH_CODES)
84 /* number of Literal or Length codes, including the END_BLOCK code */
87 /* number of distance codes */
90 /* number of codes used to transfer the bit lengths */
93 local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
94 = {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};
96 local int near extra_dbits[D_CODES] /* extra bits for each distance code */
97 = {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};
99 local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
100 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
102 #define STORED_BLOCK 0
103 #define STATIC_TREES 1
105 /* The three kinds of block type */
109 # define LIT_BUFSIZE 0x2000
112 # define LIT_BUFSIZE 0x4000
114 # define LIT_BUFSIZE 0x8000
119 # define DIST_BUFSIZE LIT_BUFSIZE
121 /* Sizes of match buffers for literals/lengths and distances. There are
122 * 4 reasons for limiting LIT_BUFSIZE to 64K:
123 * - frequencies can be kept in 16 bit counters
124 * - if compression is not successful for the first block, all input data is
125 * still in the window so we can still emit a stored block even when input
126 * comes from standard input. (This can also be done for all blocks if
127 * LIT_BUFSIZE is not greater than 32K.)
128 * - if compression is not successful for a file smaller than 64K, we can
129 * even emit a stored file instead of a stored block (saving 5 bytes).
130 * - creating new Huffman trees less frequently may not provide fast
131 * adaptation to changes in the input data statistics. (Take for
132 * example a binary file with poorly compressible code followed by
133 * a highly compressible string table.) Smaller buffer sizes give
134 * fast adaptation but have of course the overhead of transmitting trees
136 * - I can't count above 4
137 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
138 * memory at the expense of compression). Some optimizations would be possible
139 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
141 #if LIT_BUFSIZE > INBUFSIZ
142 error cannot overlay l_buf and inbuf
146 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
149 /* repeat a zero length 3-10 times (3 bits of repeat count) */
151 #define REPZ_11_138 18
152 /* repeat a zero length 11-138 times (7 bits of repeat count) */
154 /* ===========================================================================
158 /* Data structure describing a single value and its code string. */
159 typedef struct ct_data {
161 ush freq; /* frequency count */
162 ush code; /* bit string */
165 ush dad; /* father node in Huffman tree */
166 ush len; /* length of bit string */
175 #define HEAP_SIZE (2*L_CODES+1)
176 /* maximum heap size */
178 local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
179 local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
181 local ct_data near static_ltree[L_CODES+2];
182 /* The static literal tree. Since the bit lengths are imposed, there is no
183 * need for the L_CODES extra codes used during heap construction. However
184 * The codes 286 and 287 are needed to build a canonical tree (see ct_init
188 local ct_data near static_dtree[D_CODES];
189 /* The static distance tree. (Actually a trivial tree since all codes use
193 local ct_data near bl_tree[2*BL_CODES+1];
194 /* Huffman tree for the bit lengths */
196 typedef struct tree_desc {
197 ct_data near *dyn_tree; /* the dynamic tree */
198 ct_data near *static_tree; /* corresponding static tree or NULL */
199 int near *extra_bits; /* extra bits for each code or NULL */
200 int extra_base; /* base index for extra_bits */
201 int elems; /* max number of elements in the tree */
202 int max_length; /* max bit length for the codes */
203 int max_code; /* largest code with non zero frequency */
206 local tree_desc near l_desc =
207 {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
209 local tree_desc near d_desc =
210 {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
212 local tree_desc near bl_desc =
213 {bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
216 local ush near bl_count[MAX_BITS+1];
217 /* number of codes at each bit length for an optimal tree */
219 local uch near bl_order[BL_CODES]
220 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
221 /* The lengths of the bit length codes are sent in order of decreasing
222 * probability, to avoid transmitting the lengths for unused bit length codes.
225 local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
226 local int heap_len; /* number of elements in the heap */
227 local int heap_max; /* element of largest frequency */
228 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
229 * The same heap array is used to build all trees.
232 local uch near depth[2*L_CODES+1];
233 /* Depth of each subtree used as tie breaker for trees of equal frequency */
235 local uch length_code[MAX_MATCH-MIN_MATCH+1];
236 /* length code for each normalized match length (0 == MIN_MATCH) */
238 local uch dist_code[512];
239 /* distance codes. The first 256 values correspond to the distances
240 * 3 .. 258, the last 256 values correspond to the top 8 bits of
241 * the 15 bit distances.
244 local int near base_length[LENGTH_CODES];
245 /* First normalized length for each code (0 = MIN_MATCH) */
247 local int near base_dist[D_CODES];
248 /* First normalized distance for each code (0 = distance of 1) */
251 /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
253 /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
255 local uch near flag_buf[(LIT_BUFSIZE/8)];
256 /* flag_buf is a bit array distinguishing literals from lengths in
257 * l_buf, thus indicating the presence or absence of a distance.
260 local unsigned last_lit; /* running index in l_buf */
261 local unsigned last_dist; /* running index in d_buf */
262 local unsigned last_flags; /* running index in flag_buf */
263 local uch flags; /* current flags not yet saved in flag_buf */
264 local uch flag_bit; /* current bit used in flags */
265 /* bits are filled in flags starting at bit 0 (least significant).
266 * Note: these flags are overkill in the current code since we don't
267 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
270 local ulg opt_len; /* bit length of current block with optimal trees */
271 local ulg static_len; /* bit length of current block with static trees */
273 local ulg compressed_len; /* total bit length of compressed file */
275 local ulg input_len; /* total byte length of input file */
276 /* input_len is for debugging only since we can get it by other means. */
278 ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
279 int *file_method; /* pointer to DEFLATE or STORE */
282 extern ulg bits_sent; /* bit length of the compressed data */
283 extern long isize; /* byte length of input file */
286 extern long block_start; /* window offset of current block */
287 extern unsigned near strstart; /* window offset of current string */
289 /* ===========================================================================
290 * Local (static) routines in this file.
293 local void init_block OF((void));
294 local void pqdownheap OF((ct_data near *tree, int k));
295 local void gen_bitlen OF((tree_desc near *desc));
296 local void gen_codes OF((ct_data near *tree, int max_code));
297 local void build_tree OF((tree_desc near *desc));
298 local void scan_tree OF((ct_data near *tree, int max_code));
299 local void send_tree OF((ct_data near *tree, int max_code));
300 local int build_bl_tree OF((void));
301 local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
302 local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
303 local void set_file_type OF((void));
307 # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
308 /* Send a code of the given tree. c and tree must not have side effects */
311 # define send_code(c, tree) \
312 { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
313 send_bits(tree[c].Code, tree[c].Len); }
316 #define d_code(dist) \
317 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
318 /* Mapping from a distance to a distance code. dist is the distance - 1 and
319 * must not have side effects. dist_code[256] and dist_code[257] are never
323 #define MAX(a,b) (a >= b ? a : b)
324 /* the arguments must not have side effects */
326 /* ===========================================================================
327 * Allocate the match buffer, initialize the various tables and save the
328 * location of the internal file attribute (ascii/binary) and method
331 void ct_init(attr, methodp)
332 ush *attr; /* pointer to internal file attribute */
333 int *methodp; /* pointer to compression method */
335 int n; /* iterates over tree elements */
336 int bits; /* bit counter */
337 int length; /* length value */
338 int code; /* code value */
339 int dist; /* distance index */
342 file_method = methodp;
343 compressed_len = input_len = 0L;
345 if (static_dtree[0].Len != 0) return; /* ct_init already called */
347 /* Initialize the mapping length (0..255) -> length code (0..28) */
349 for (code = 0; code < LENGTH_CODES-1; code++) {
350 base_length[code] = length;
351 for (n = 0; n < (1<<extra_lbits[code]); n++) {
352 length_code[length++] = (uch)code;
355 Assert (length == 256, "ct_init: length != 256");
356 /* Note that the length 255 (match length 258) can be represented
357 * in two different ways: code 284 + 5 bits or code 285, so we
358 * overwrite length_code[255] to use the best encoding:
360 length_code[length-1] = (uch)code;
362 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
364 for (code = 0 ; code < 16; code++) {
365 base_dist[code] = dist;
366 for (n = 0; n < (1<<extra_dbits[code]); n++) {
367 dist_code[dist++] = (uch)code;
370 Assert (dist == 256, "ct_init: dist != 256");
371 dist >>= 7; /* from now on, all distances are divided by 128 */
372 for ( ; code < D_CODES; code++) {
373 base_dist[code] = dist << 7;
374 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
375 dist_code[256 + dist++] = (uch)code;
378 Assert (dist == 256, "ct_init: 256+dist != 512");
380 /* Construct the codes of the static literal tree */
381 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
383 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
384 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
385 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
386 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
387 /* Codes 286 and 287 do not exist, but we must include them in the
388 * tree construction to get a canonical Huffman tree (longest code
391 gen_codes((ct_data near *)static_ltree, L_CODES+1);
393 /* The static distance tree is trivial: */
394 for (n = 0; n < D_CODES; n++) {
395 static_dtree[n].Len = 5;
396 static_dtree[n].Code = bi_reverse(n, 5);
399 /* Initialize the first block of the first file: */
403 /* ===========================================================================
404 * Initialize a new block.
406 local void init_block()
408 int n; /* iterates over tree elements */
410 /* Initialize the trees. */
411 for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
412 for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
413 for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
415 dyn_ltree[END_BLOCK].Freq = 1;
416 opt_len = static_len = 0L;
417 last_lit = last_dist = last_flags = 0;
418 flags = 0; flag_bit = 1;
422 /* Index within the heap array of least frequent node in the Huffman tree */
425 /* ===========================================================================
426 * Remove the smallest element from the heap and recreate the heap with
427 * one less element. Updates heap and heap_len.
429 #define pqremove(tree, top) \
431 top = heap[SMALLEST]; \
432 heap[SMALLEST] = heap[heap_len--]; \
433 pqdownheap(tree, SMALLEST); \
436 /* ===========================================================================
437 * Compares to subtrees, using the tree depth as tie breaker when
438 * the subtrees have equal frequency. This minimizes the worst case length.
440 #define smaller(tree, n, m) \
441 (tree[n].Freq < tree[m].Freq || \
442 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
444 /* ===========================================================================
445 * Restore the heap property by moving down the tree starting at node k,
446 * exchanging a node with the smallest of its two sons if necessary, stopping
447 * when the heap property is re-established (each father smaller than its
450 local void pqdownheap(tree, k)
451 ct_data near *tree; /* the tree to restore */
452 int k; /* node to move down */
455 int j = k << 1; /* left son of k */
456 while (j <= heap_len) {
457 /* Set j to the smallest of the two sons: */
458 if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
460 /* Exit if v is smaller than both sons */
461 if (smaller(tree, v, heap[j])) break;
463 /* Exchange v with the smallest son */
464 heap[k] = heap[j]; k = j;
466 /* And continue down the tree, setting j to the left son of k */
472 /* ===========================================================================
473 * Compute the optimal bit lengths for a tree and update the total bit length
474 * for the current block.
475 * IN assertion: the fields freq and dad are set, heap[heap_max] and
476 * above are the tree nodes sorted by increasing frequency.
477 * OUT assertions: the field len is set to the optimal bit length, the
478 * array bl_count contains the frequencies for each bit length.
479 * The length opt_len is updated; static_len is also updated if stree is
482 local void gen_bitlen(desc)
483 tree_desc near *desc; /* the tree descriptor */
485 ct_data near *tree = desc->dyn_tree;
486 int near *extra = desc->extra_bits;
487 int base = desc->extra_base;
488 int max_code = desc->max_code;
489 int max_length = desc->max_length;
490 ct_data near *stree = desc->static_tree;
491 int h; /* heap index */
492 int n, m; /* iterate over the tree elements */
493 int bits; /* bit length */
494 int xbits; /* extra bits */
495 ush f; /* frequency */
496 int overflow = 0; /* number of elements with bit length too large */
498 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
500 /* In a first pass, compute the optimal bit lengths (which may
501 * overflow in the case of the bit length tree).
503 tree[heap[heap_max]].Len = 0; /* root of the heap */
505 for (h = heap_max+1; h < HEAP_SIZE; h++) {
507 bits = tree[tree[n].Dad].Len + 1;
508 if (bits > max_length) bits = max_length, overflow++;
509 tree[n].Len = (ush)bits;
510 /* We overwrite tree[n].Dad which is no longer needed */
512 if (n > max_code) continue; /* not a leaf node */
516 if (n >= base) xbits = extra[n-base];
518 opt_len += (ulg)f * (bits + xbits);
519 if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
521 if (overflow == 0) return;
523 Trace((stderr,"\nbit length overflow\n"));
524 /* This happens for example on obj2 and pic of the Calgary corpus */
526 /* Find the first bit length which could increase: */
529 while (bl_count[bits] == 0) bits--;
530 bl_count[bits]--; /* move one leaf down the tree */
531 bl_count[bits+1] += 2; /* move one overflow item as its brother */
532 bl_count[max_length]--;
533 /* The brother of the overflow item also moves one step up,
534 * but this does not affect bl_count[max_length]
537 } while (overflow > 0);
539 /* Now recompute all bit lengths, scanning in increasing frequency.
540 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
541 * lengths instead of fixing only the wrong ones. This idea is taken
542 * from 'ar' written by Haruhiko Okumura.)
544 for (bits = max_length; bits != 0; bits--) {
548 if (m > max_code) continue;
549 if (tree[m].Len != (unsigned) bits) {
550 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
551 opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
552 tree[m].Len = (ush)bits;
559 /* ===========================================================================
560 * Generate the codes for a given tree and bit counts (which need not be
562 * IN assertion: the array bl_count contains the bit length statistics for
563 * the given tree and the field len is set for all tree elements.
564 * OUT assertion: the field code is set for all tree elements of non
567 local void gen_codes (tree, max_code)
568 ct_data near *tree; /* the tree to decorate */
569 int max_code; /* largest code with non zero frequency */
571 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
572 ush code = 0; /* running code value */
573 int bits; /* bit index */
574 int n; /* code index */
576 /* The distribution counts are first used to generate the code values
577 * without bit reversal.
579 for (bits = 1; bits <= MAX_BITS; bits++) {
580 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
582 /* Check that the bit counts in bl_count are consistent. The last code
585 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
586 "inconsistent bit counts");
587 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
589 for (n = 0; n <= max_code; n++) {
590 int len = tree[n].Len;
591 if (len == 0) continue;
592 /* Now reverse the bits */
593 tree[n].Code = bi_reverse(next_code[len]++, len);
595 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
596 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
600 /* ===========================================================================
601 * Construct one Huffman tree and assigns the code bit strings and lengths.
602 * Update the total bit length for the current block.
603 * IN assertion: the field freq is set for all tree elements.
604 * OUT assertions: the fields len and code are set to the optimal bit length
605 * and corresponding code. The length opt_len is updated; static_len is
606 * also updated if stree is not null. The field max_code is set.
608 local void build_tree(desc)
609 tree_desc near *desc; /* the tree descriptor */
611 ct_data near *tree = desc->dyn_tree;
612 ct_data near *stree = desc->static_tree;
613 int elems = desc->elems;
614 int n, m; /* iterate over heap elements */
615 int max_code = -1; /* largest code with non zero frequency */
616 int node = elems; /* next internal node of the tree */
618 /* Construct the initial heap, with least frequent element in
619 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
620 * heap[0] is not used.
622 heap_len = 0, heap_max = HEAP_SIZE;
624 for (n = 0; n < elems; n++) {
625 if (tree[n].Freq != 0) {
626 heap[++heap_len] = max_code = n;
633 /* The pkzip format requires that at least one distance code exists,
634 * and that at least one bit should be sent even if there is only one
635 * possible code. So to avoid special checks later on we force at least
636 * two codes of non zero frequency.
638 while (heap_len < 2) {
639 int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
642 opt_len--; if (stree) static_len -= stree[new].Len;
643 /* new is 0 or 1 so it does not have extra bits */
645 desc->max_code = max_code;
647 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
648 * establish sub-heaps of increasing lengths:
650 for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
652 /* Construct the Huffman tree by repeatedly combining the least two
656 pqremove(tree, n); /* n = node of least frequency */
657 m = heap[SMALLEST]; /* m = node of next least frequency */
659 heap[--heap_max] = n; /* keep the nodes sorted by frequency */
660 heap[--heap_max] = m;
662 /* Create a new node father of n and m */
663 tree[node].Freq = tree[n].Freq + tree[m].Freq;
664 depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
665 tree[n].Dad = tree[m].Dad = (ush)node;
667 if (tree == bl_tree) {
668 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
669 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
672 /* and insert the new node in the heap */
673 heap[SMALLEST] = node++;
674 pqdownheap(tree, SMALLEST);
676 } while (heap_len >= 2);
678 heap[--heap_max] = heap[SMALLEST];
680 /* At this point, the fields freq and dad are set. We can now
681 * generate the bit lengths.
683 gen_bitlen((tree_desc near *)desc);
685 /* The field len is now set, we can generate the bit codes */
686 gen_codes ((ct_data near *)tree, max_code);
689 /* ===========================================================================
690 * Scan a literal or distance tree to determine the frequencies of the codes
691 * in the bit length tree. Updates opt_len to take into account the repeat
692 * counts. (The contribution of the bit length codes will be added later
693 * during the construction of bl_tree.)
695 local void scan_tree (tree, max_code)
696 ct_data near *tree; /* the tree to be scanned */
697 int max_code; /* and its largest code of non zero frequency */
699 int n; /* iterates over all tree elements */
700 int prevlen = -1; /* last emitted length */
701 int curlen; /* length of current code */
702 int nextlen = tree[0].Len; /* length of next code */
703 int count = 0; /* repeat count of the current code */
704 int max_count = 7; /* max repeat count */
705 int min_count = 4; /* min repeat count */
707 if (nextlen == 0) max_count = 138, min_count = 3;
708 tree[max_code+1].Len = (ush)0xffff; /* guard */
710 for (n = 0; n <= max_code; n++) {
711 curlen = nextlen; nextlen = tree[n+1].Len;
712 if (++count < max_count && curlen == nextlen) {
714 } else if (count < min_count) {
715 bl_tree[curlen].Freq += count;
716 } else if (curlen != 0) {
717 if (curlen != prevlen) bl_tree[curlen].Freq++;
718 bl_tree[REP_3_6].Freq++;
719 } else if (count <= 10) {
720 bl_tree[REPZ_3_10].Freq++;
722 bl_tree[REPZ_11_138].Freq++;
724 count = 0; prevlen = curlen;
726 max_count = 138, min_count = 3;
727 } else if (curlen == nextlen) {
728 max_count = 6, min_count = 3;
730 max_count = 7, min_count = 4;
735 /* ===========================================================================
736 * Send a literal or distance tree in compressed form, using the codes in
739 local void send_tree (tree, max_code)
740 ct_data near *tree; /* the tree to be scanned */
741 int max_code; /* and its largest code of non zero frequency */
743 int n; /* iterates over all tree elements */
744 int prevlen = -1; /* last emitted length */
745 int curlen; /* length of current code */
746 int nextlen = tree[0].Len; /* length of next code */
747 int count = 0; /* repeat count of the current code */
748 int max_count = 7; /* max repeat count */
749 int min_count = 4; /* min repeat count */
751 /* tree[max_code+1].Len = -1; */ /* guard already set */
752 if (nextlen == 0) max_count = 138, min_count = 3;
754 for (n = 0; n <= max_code; n++) {
755 curlen = nextlen; nextlen = tree[n+1].Len;
756 if (++count < max_count && curlen == nextlen) {
758 } else if (count < min_count) {
759 do { send_code(curlen, bl_tree); } while (--count != 0);
761 } else if (curlen != 0) {
762 if (curlen != prevlen) {
763 send_code(curlen, bl_tree); count--;
765 Assert(count >= 3 && count <= 6, " 3_6?");
766 send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
768 } else if (count <= 10) {
769 send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
772 send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
774 count = 0; prevlen = curlen;
776 max_count = 138, min_count = 3;
777 } else if (curlen == nextlen) {
778 max_count = 6, min_count = 3;
780 max_count = 7, min_count = 4;
785 /* ===========================================================================
786 * Construct the Huffman tree for the bit lengths and return the index in
787 * bl_order of the last bit length code to send.
789 local int build_bl_tree()
791 int max_blindex; /* index of last bit length code of non zero freq */
793 /* Determine the bit length frequencies for literal and distance trees */
794 scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
795 scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
797 /* Build the bit length tree: */
798 build_tree((tree_desc near *)(&bl_desc));
799 /* opt_len now includes the length of the tree representations, except
800 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
803 /* Determine the number of bit length codes to send. The pkzip format
804 * requires that at least 4 bit length codes be sent. (appnote.txt says
805 * 3 but the actual value used is 4.)
807 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
808 if (bl_tree[bl_order[max_blindex]].Len != 0) break;
810 /* Update opt_len to include the bit length tree and counts */
811 opt_len += 3*(max_blindex+1) + 5+5+4;
812 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len));
817 /* ===========================================================================
818 * Send the header for a block using dynamic Huffman trees: the counts, the
819 * lengths of the bit length codes, the literal tree and the distance tree.
820 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
822 local void send_all_trees(lcodes, dcodes, blcodes)
823 int lcodes, dcodes, blcodes; /* number of codes for each tree */
825 int rank; /* index in bl_order */
827 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
828 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
830 Tracev((stderr, "\nbl counts: "));
831 send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
832 send_bits(dcodes-1, 5);
833 send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
834 for (rank = 0; rank < blcodes; rank++) {
835 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
836 send_bits(bl_tree[bl_order[rank]].Len, 3);
838 Tracev((stderr, "\nbl tree: sent %ld", bits_sent));
840 send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
841 Tracev((stderr, "\nlit tree: sent %ld", bits_sent));
843 send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
844 Tracev((stderr, "\ndist tree: sent %ld", bits_sent));
847 /* ===========================================================================
848 * Determine the best encoding for the current block: dynamic trees, static
849 * trees or store, and output the encoded block to the zip file. This function
850 * returns the total compressed length for the file so far.
852 ulg flush_block(buf, stored_len, eof)
853 char *buf; /* input block, or NULL if too old */
854 ulg stored_len; /* length of input block */
855 int eof; /* true if this is the last block for a file */
857 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
858 int max_blindex; /* index of last bit length code of non zero freq */
860 flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
862 /* Check if the file is ascii or binary */
863 if (*file_type == (ush)UNKNOWN) set_file_type();
865 /* Construct the literal and distance trees */
866 build_tree((tree_desc near *)(&l_desc));
867 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len));
869 build_tree((tree_desc near *)(&d_desc));
870 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len));
871 /* At this point, opt_len and static_len are the total bit lengths of
872 * the compressed block data, excluding the tree representations.
875 /* Build the bit length tree for the above two trees, and get the index
876 * in bl_order of the last bit length code to send.
878 max_blindex = build_bl_tree();
880 /* Determine the best encoding. Compute first the block length in bytes */
881 opt_lenb = (opt_len+3+7)>>3;
882 static_lenb = (static_len+3+7)>>3;
883 input_len += stored_len; /* for debugging only */
885 Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
886 opt_lenb, opt_len, static_lenb, static_len, stored_len,
887 last_lit, last_dist));
889 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
891 /* If compression failed and this is the first and last block,
892 * and if the zip file can be seeked (to rewrite the local header),
893 * the whole file is transformed into a stored file:
896 if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
898 if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
900 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
901 if (buf == (char*)0) error ("block vanished");
903 copy_block(buf, (unsigned)stored_len, 0); /* without header */
904 compressed_len = stored_len << 3;
905 *file_method = STORED;
908 } else if (level == 2 && buf != (char*)0) { /* force stored block */
910 } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
911 /* 4: two words for the lengths */
913 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
914 * Otherwise we can't have processed more than WSIZE input bytes since
915 * the last block flush, because compression would have been
916 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
917 * transform a block into a stored block.
919 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
920 compressed_len = (compressed_len + 3 + 7) & ~7L;
921 compressed_len += (stored_len + 4) << 3;
923 copy_block(buf, (unsigned)stored_len, 1); /* with header */
926 } else if (level == 3) { /* force static trees */
928 } else if (static_lenb == opt_lenb) {
930 send_bits((STATIC_TREES<<1)+eof, 3);
931 compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
932 compressed_len += 3 + static_len;
934 send_bits((DYN_TREES<<1)+eof, 3);
935 send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
936 compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
937 compressed_len += 3 + opt_len;
939 Assert (compressed_len == bits_sent, "bad compressed size");
943 Assert (input_len == isize, "bad input size");
945 compressed_len += 7; /* align on byte boundary */
947 Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3,
948 compressed_len-7*eof));
950 return compressed_len >> 3;
953 /* ===========================================================================
954 * Save the match info and tally the frequency counts. Return true if
955 * the current block must be flushed.
957 int ct_tally (dist, lc)
958 int dist; /* distance of matched string */
959 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
961 l_buf[last_lit++] = (uch)lc;
963 /* lc is the unmatched char */
964 dyn_ltree[lc].Freq++;
966 /* Here, lc is the match length - MIN_MATCH */
967 dist--; /* dist = match distance - 1 */
968 Assert((ush)dist < (ush)MAX_DIST &&
969 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
970 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
972 dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
973 dyn_dtree[d_code(dist)].Freq++;
975 d_buf[last_dist++] = (ush)dist;
980 /* Output the flags if they fill a byte: */
981 if ((last_lit & 7) == 0) {
982 flag_buf[last_flags++] = flags;
983 flags = 0, flag_bit = 1;
985 /* Try to guess if it is profitable to stop the current block here */
986 if (level > 2 && (last_lit & 0xfff) == 0) {
987 /* Compute an upper bound for the compressed length */
988 ulg out_length = (ulg)last_lit*8L;
989 ulg in_length = (ulg)strstart-block_start;
991 for (dcode = 0; dcode < D_CODES; dcode++) {
992 out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
995 Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
996 last_lit, last_dist, in_length, out_length,
997 100L - out_length*100L/in_length));
998 if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1000 return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1001 /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1002 * on 16 bit machines and because stored blocks are restricted to
1007 /* ===========================================================================
1008 * Send the block data compressed using the given Huffman trees
1010 local void compress_block(ltree, dtree)
1011 ct_data near *ltree; /* literal tree */
1012 ct_data near *dtree; /* distance tree */
1014 unsigned dist; /* distance of matched string */
1015 int lc; /* match length or unmatched char (if dist == 0) */
1016 unsigned lx = 0; /* running index in l_buf */
1017 unsigned dx = 0; /* running index in d_buf */
1018 unsigned fx = 0; /* running index in flag_buf */
1019 uch flag = 0; /* current flags */
1020 unsigned code; /* the code to send */
1021 int extra; /* number of extra bits to send */
1023 if (last_lit != 0) do {
1024 if ((lx & 7) == 0) flag = flag_buf[fx++];
1026 if ((flag & 1) == 0) {
1027 send_code(lc, ltree); /* send a literal byte */
1028 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1030 /* Here, lc is the match length - MIN_MATCH */
1031 code = length_code[lc];
1032 send_code(code+LITERALS+1, ltree); /* send the length code */
1033 extra = extra_lbits[code];
1035 lc -= base_length[code];
1036 send_bits(lc, extra); /* send the extra length bits */
1039 /* Here, dist is the match distance - 1 */
1040 code = d_code(dist);
1041 Assert (code < D_CODES, "bad d_code");
1043 send_code(code, dtree); /* send the distance code */
1044 extra = extra_dbits[code];
1046 dist -= base_dist[code];
1047 send_bits(dist, extra); /* send the extra distance bits */
1049 } /* literal or match pair ? */
1051 } while (lx < last_lit);
1053 send_code(END_BLOCK, ltree);
1056 /* ===========================================================================
1057 * Set the file type to ASCII or BINARY, using a crude approximation:
1058 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1059 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1060 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1062 local void set_file_type()
1065 unsigned ascii_freq = 0;
1066 unsigned bin_freq = 0;
1067 while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1068 while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1069 while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1070 *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1071 if (*file_type == BINARY && translate_eol) {
1072 WARN((stderr, "-l used on binary file"));