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.
10 * Encode various sets of source values using variable-length
15 * The PKZIP "deflation" process uses several Huffman trees. The more
16 * common source values are represented by shorter bit sequences.
18 * Each code tree is stored in the ZIP file in a compressed form
19 * which is itself a Huffman encoding of the lengths of
20 * all the code strings (in ascending order by source values).
21 * The actual code strings are reconstructed from the lengths in
22 * the UNZIP process, as described in the "application note"
23 * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
28 * Data Compression: Techniques and Applications, pp. 53-55.
29 * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
32 * Data Compression: Methods and Theory, pp. 49-50.
33 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
37 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
41 * void ct_init (ush *attr, int *methodp)
42 * Allocate the match buffer, initialize the various tables and save
43 * the location of the internal file attribute (ascii/binary) and
44 * method (DEFLATE/STORE)
46 * void ct_tally (int dist, int lc);
47 * Save the match info and tally the frequency counts.
49 * off_t flush_block (char *buf, ulg stored_len, int eof)
50 * Determine the best encoding for the current block: dynamic trees,
51 * static trees or store, and output the encoded block to the zip
52 * file. Returns the total compressed length for the file so far.
63 static char rcsid[] = "$Id: trees.c,v 0.12 1993/06/10 13:27:54 jloup Exp $";
66 /* ===========================================================================
71 /* All codes must not exceed MAX_BITS bits */
74 /* Bit length codes must not exceed MAX_BL_BITS bits */
76 #define LENGTH_CODES 29
77 /* number of length codes, not counting the special END_BLOCK code */
80 /* number of literal bytes 0..255 */
83 /* end of block literal code */
85 #define L_CODES (LITERALS+1+LENGTH_CODES)
86 /* number of Literal or Length codes, including the END_BLOCK code */
89 /* number of distance codes */
92 /* number of codes used to transfer the bit lengths */
95 local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
96 = {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};
98 local int near extra_dbits[D_CODES] /* extra bits for each distance code */
99 = {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};
101 local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
102 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
104 #define STORED_BLOCK 0
105 #define STATIC_TREES 1
107 /* The three kinds of block type */
111 # define LIT_BUFSIZE 0x2000
114 # define LIT_BUFSIZE 0x4000
116 # define LIT_BUFSIZE 0x8000
121 # define DIST_BUFSIZE LIT_BUFSIZE
123 /* Sizes of match buffers for literals/lengths and distances. There are
124 * 4 reasons for limiting LIT_BUFSIZE to 64K:
125 * - frequencies can be kept in 16 bit counters
126 * - if compression is not successful for the first block, all input data is
127 * still in the window so we can still emit a stored block even when input
128 * comes from standard input. (This can also be done for all blocks if
129 * LIT_BUFSIZE is not greater than 32K.)
130 * - if compression is not successful for a file smaller than 64K, we can
131 * even emit a stored file instead of a stored block (saving 5 bytes).
132 * - creating new Huffman trees less frequently may not provide fast
133 * adaptation to changes in the input data statistics. (Take for
134 * example a binary file with poorly compressible code followed by
135 * a highly compressible string table.) Smaller buffer sizes give
136 * fast adaptation but have of course the overhead of transmitting trees
138 * - I can't count above 4
139 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
140 * memory at the expense of compression). Some optimizations would be possible
141 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
143 #if LIT_BUFSIZE > INBUFSIZ
144 error cannot overlay l_buf and inbuf
148 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
151 /* repeat a zero length 3-10 times (3 bits of repeat count) */
153 #define REPZ_11_138 18
154 /* repeat a zero length 11-138 times (7 bits of repeat count) */
156 /* ===========================================================================
160 /* Data structure describing a single value and its code string. */
161 typedef struct ct_data {
163 ush freq; /* frequency count */
164 ush code; /* bit string */
167 ush dad; /* father node in Huffman tree */
168 ush len; /* length of bit string */
177 #define HEAP_SIZE (2*L_CODES+1)
178 /* maximum heap size */
180 local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
181 local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
183 local ct_data near static_ltree[L_CODES+2];
184 /* The static literal tree. Since the bit lengths are imposed, there is no
185 * need for the L_CODES extra codes used during heap construction. However
186 * The codes 286 and 287 are needed to build a canonical tree (see ct_init
190 local ct_data near static_dtree[D_CODES];
191 /* The static distance tree. (Actually a trivial tree since all codes use
195 local ct_data near bl_tree[2*BL_CODES+1];
196 /* Huffman tree for the bit lengths */
198 typedef struct tree_desc {
199 ct_data near *dyn_tree; /* the dynamic tree */
200 ct_data near *static_tree; /* corresponding static tree or NULL */
201 int near *extra_bits; /* extra bits for each code or NULL */
202 int extra_base; /* base index for extra_bits */
203 int elems; /* max number of elements in the tree */
204 int max_length; /* max bit length for the codes */
205 int max_code; /* largest code with non zero frequency */
208 local tree_desc near l_desc =
209 {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
211 local tree_desc near d_desc =
212 {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
214 local tree_desc near bl_desc =
215 {bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
218 local ush near bl_count[MAX_BITS+1];
219 /* number of codes at each bit length for an optimal tree */
221 local uch near bl_order[BL_CODES]
222 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
223 /* The lengths of the bit length codes are sent in order of decreasing
224 * probability, to avoid transmitting the lengths for unused bit length codes.
227 local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
228 local int heap_len; /* number of elements in the heap */
229 local int heap_max; /* element of largest frequency */
230 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
231 * The same heap array is used to build all trees.
234 local uch near depth[2*L_CODES+1];
235 /* Depth of each subtree used as tie breaker for trees of equal frequency */
237 local uch length_code[MAX_MATCH-MIN_MATCH+1];
238 /* length code for each normalized match length (0 == MIN_MATCH) */
240 local uch dist_code[512];
241 /* distance codes. The first 256 values correspond to the distances
242 * 3 .. 258, the last 256 values correspond to the top 8 bits of
243 * the 15 bit distances.
246 local int near base_length[LENGTH_CODES];
247 /* First normalized length for each code (0 = MIN_MATCH) */
249 local int near base_dist[D_CODES];
250 /* First normalized distance for each code (0 = distance of 1) */
253 /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
255 /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
257 local uch near flag_buf[(LIT_BUFSIZE/8)];
258 /* flag_buf is a bit array distinguishing literals from lengths in
259 * l_buf, thus indicating the presence or absence of a distance.
262 local unsigned last_lit; /* running index in l_buf */
263 local unsigned last_dist; /* running index in d_buf */
264 local unsigned last_flags; /* running index in flag_buf */
265 local uch flags; /* current flags not yet saved in flag_buf */
266 local uch flag_bit; /* current bit used in flags */
267 /* bits are filled in flags starting at bit 0 (least significant).
268 * Note: these flags are overkill in the current code since we don't
269 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
272 local ulg opt_len; /* bit length of current block with optimal trees */
273 local ulg static_len; /* bit length of current block with static trees */
275 local off_t compressed_len; /* total bit length of compressed file */
277 local off_t input_len; /* total byte length of input file */
278 /* input_len is for debugging only since we can get it by other means. */
280 ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
281 int *file_method; /* pointer to DEFLATE or STORE */
284 extern off_t bits_sent; /* bit length of the compressed data */
287 extern long block_start; /* window offset of current block */
288 extern unsigned near strstart; /* window offset of current string */
290 /* ===========================================================================
291 * Local (static) routines in this file.
294 local void init_block OF((void));
295 local void pqdownheap OF((ct_data near *tree, int k));
296 local void gen_bitlen OF((tree_desc near *desc));
297 local void gen_codes OF((ct_data near *tree, int max_code));
298 local void build_tree OF((tree_desc near *desc));
299 local void scan_tree OF((ct_data near *tree, int max_code));
300 local void send_tree OF((ct_data near *tree, int max_code));
301 local int build_bl_tree OF((void));
302 local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
303 local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
304 local void set_file_type OF((void));
308 # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
309 /* Send a code of the given tree. c and tree must not have side effects */
312 # define send_code(c, tree) \
313 { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
314 send_bits(tree[c].Code, tree[c].Len); }
317 #define d_code(dist) \
318 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
319 /* Mapping from a distance to a distance code. dist is the distance - 1 and
320 * must not have side effects. dist_code[256] and dist_code[257] are never
324 #define MAX(a,b) (a >= b ? a : b)
325 /* the arguments must not have side effects */
327 /* ===========================================================================
328 * Allocate the match buffer, initialize the various tables and save the
329 * location of the internal file attribute (ascii/binary) and method
332 void ct_init(attr, methodp)
333 ush *attr; /* pointer to internal file attribute */
334 int *methodp; /* pointer to compression method */
336 int n; /* iterates over tree elements */
337 int bits; /* bit counter */
338 int length; /* length value */
339 int code; /* code value */
340 int dist; /* distance index */
343 file_method = methodp;
344 compressed_len = input_len = 0L;
346 if (static_dtree[0].Len != 0) return; /* ct_init already called */
348 /* Initialize the mapping length (0..255) -> length code (0..28) */
350 for (code = 0; code < LENGTH_CODES-1; code++) {
351 base_length[code] = length;
352 for (n = 0; n < (1<<extra_lbits[code]); n++) {
353 length_code[length++] = (uch)code;
356 Assert (length == 256, "ct_init: length != 256");
357 /* Note that the length 255 (match length 258) can be represented
358 * in two different ways: code 284 + 5 bits or code 285, so we
359 * overwrite length_code[255] to use the best encoding:
361 length_code[length-1] = (uch)code;
363 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
365 for (code = 0 ; code < 16; code++) {
366 base_dist[code] = dist;
367 for (n = 0; n < (1<<extra_dbits[code]); n++) {
368 dist_code[dist++] = (uch)code;
371 Assert (dist == 256, "ct_init: dist != 256");
372 dist >>= 7; /* from now on, all distances are divided by 128 */
373 for ( ; code < D_CODES; code++) {
374 base_dist[code] = dist << 7;
375 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
376 dist_code[256 + dist++] = (uch)code;
379 Assert (dist == 256, "ct_init: 256+dist != 512");
381 /* Construct the codes of the static literal tree */
382 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
384 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
385 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
386 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
387 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
388 /* Codes 286 and 287 do not exist, but we must include them in the
389 * tree construction to get a canonical Huffman tree (longest code
392 gen_codes((ct_data near *)static_ltree, L_CODES+1);
394 /* The static distance tree is trivial: */
395 for (n = 0; n < D_CODES; n++) {
396 static_dtree[n].Len = 5;
397 static_dtree[n].Code = bi_reverse(n, 5);
400 /* Initialize the first block of the first file: */
404 /* ===========================================================================
405 * Initialize a new block.
407 local void init_block()
409 int n; /* iterates over tree elements */
411 /* Initialize the trees. */
412 for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
413 for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
414 for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
416 dyn_ltree[END_BLOCK].Freq = 1;
417 opt_len = static_len = 0L;
418 last_lit = last_dist = last_flags = 0;
419 flags = 0; flag_bit = 1;
423 /* Index within the heap array of least frequent node in the Huffman tree */
426 /* ===========================================================================
427 * Remove the smallest element from the heap and recreate the heap with
428 * one less element. Updates heap and heap_len.
430 #define pqremove(tree, top) \
432 top = heap[SMALLEST]; \
433 heap[SMALLEST] = heap[heap_len--]; \
434 pqdownheap(tree, SMALLEST); \
437 /* ===========================================================================
438 * Compares to subtrees, using the tree depth as tie breaker when
439 * the subtrees have equal frequency. This minimizes the worst case length.
441 #define smaller(tree, n, m) \
442 (tree[n].Freq < tree[m].Freq || \
443 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
445 /* ===========================================================================
446 * Restore the heap property by moving down the tree starting at node k,
447 * exchanging a node with the smallest of its two sons if necessary, stopping
448 * when the heap property is re-established (each father smaller than its
451 local void pqdownheap(tree, k)
452 ct_data near *tree; /* the tree to restore */
453 int k; /* node to move down */
456 int j = k << 1; /* left son of k */
457 while (j <= heap_len) {
458 /* Set j to the smallest of the two sons: */
459 if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
461 /* Exit if v is smaller than both sons */
462 if (smaller(tree, v, heap[j])) break;
464 /* Exchange v with the smallest son */
465 heap[k] = heap[j]; k = j;
467 /* And continue down the tree, setting j to the left son of k */
473 /* ===========================================================================
474 * Compute the optimal bit lengths for a tree and update the total bit length
475 * for the current block.
476 * IN assertion: the fields freq and dad are set, heap[heap_max] and
477 * above are the tree nodes sorted by increasing frequency.
478 * OUT assertions: the field len is set to the optimal bit length, the
479 * array bl_count contains the frequencies for each bit length.
480 * The length opt_len is updated; static_len is also updated if stree is
483 local void gen_bitlen(desc)
484 tree_desc near *desc; /* the tree descriptor */
486 ct_data near *tree = desc->dyn_tree;
487 int near *extra = desc->extra_bits;
488 int base = desc->extra_base;
489 int max_code = desc->max_code;
490 int max_length = desc->max_length;
491 ct_data near *stree = desc->static_tree;
492 int h; /* heap index */
493 int n, m; /* iterate over the tree elements */
494 int bits; /* bit length */
495 int xbits; /* extra bits */
496 ush f; /* frequency */
497 int overflow = 0; /* number of elements with bit length too large */
499 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
501 /* In a first pass, compute the optimal bit lengths (which may
502 * overflow in the case of the bit length tree).
504 tree[heap[heap_max]].Len = 0; /* root of the heap */
506 for (h = heap_max+1; h < HEAP_SIZE; h++) {
508 bits = tree[tree[n].Dad].Len + 1;
509 if (bits > max_length) bits = max_length, overflow++;
510 tree[n].Len = (ush)bits;
511 /* We overwrite tree[n].Dad which is no longer needed */
513 if (n > max_code) continue; /* not a leaf node */
517 if (n >= base) xbits = extra[n-base];
519 opt_len += (ulg)f * (bits + xbits);
520 if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
522 if (overflow == 0) return;
524 Trace((stderr,"\nbit length overflow\n"));
525 /* This happens for example on obj2 and pic of the Calgary corpus */
527 /* Find the first bit length which could increase: */
530 while (bl_count[bits] == 0) bits--;
531 bl_count[bits]--; /* move one leaf down the tree */
532 bl_count[bits+1] += 2; /* move one overflow item as its brother */
533 bl_count[max_length]--;
534 /* The brother of the overflow item also moves one step up,
535 * but this does not affect bl_count[max_length]
538 } while (overflow > 0);
540 /* Now recompute all bit lengths, scanning in increasing frequency.
541 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
542 * lengths instead of fixing only the wrong ones. This idea is taken
543 * from 'ar' written by Haruhiko Okumura.)
545 for (bits = max_length; bits != 0; bits--) {
549 if (m > max_code) continue;
550 if (tree[m].Len != (unsigned) bits) {
551 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
552 opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
553 tree[m].Len = (ush)bits;
560 /* ===========================================================================
561 * Generate the codes for a given tree and bit counts (which need not be
563 * IN assertion: the array bl_count contains the bit length statistics for
564 * the given tree and the field len is set for all tree elements.
565 * OUT assertion: the field code is set for all tree elements of non
568 local void gen_codes (tree, max_code)
569 ct_data near *tree; /* the tree to decorate */
570 int max_code; /* largest code with non zero frequency */
572 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
573 ush code = 0; /* running code value */
574 int bits; /* bit index */
575 int n; /* code index */
577 /* The distribution counts are first used to generate the code values
578 * without bit reversal.
580 for (bits = 1; bits <= MAX_BITS; bits++) {
581 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
583 /* Check that the bit counts in bl_count are consistent. The last code
586 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
587 "inconsistent bit counts");
588 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
590 for (n = 0; n <= max_code; n++) {
591 int len = tree[n].Len;
592 if (len == 0) continue;
593 /* Now reverse the bits */
594 tree[n].Code = bi_reverse(next_code[len]++, len);
596 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
597 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
601 /* ===========================================================================
602 * Construct one Huffman tree and assigns the code bit strings and lengths.
603 * Update the total bit length for the current block.
604 * IN assertion: the field freq is set for all tree elements.
605 * OUT assertions: the fields len and code are set to the optimal bit length
606 * and corresponding code. The length opt_len is updated; static_len is
607 * also updated if stree is not null. The field max_code is set.
609 local void build_tree(desc)
610 tree_desc near *desc; /* the tree descriptor */
612 ct_data near *tree = desc->dyn_tree;
613 ct_data near *stree = desc->static_tree;
614 int elems = desc->elems;
615 int n, m; /* iterate over heap elements */
616 int max_code = -1; /* largest code with non zero frequency */
617 int node = elems; /* next internal node of the tree */
619 /* Construct the initial heap, with least frequent element in
620 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
621 * heap[0] is not used.
623 heap_len = 0, heap_max = HEAP_SIZE;
625 for (n = 0; n < elems; n++) {
626 if (tree[n].Freq != 0) {
627 heap[++heap_len] = max_code = n;
634 /* The pkzip format requires that at least one distance code exists,
635 * and that at least one bit should be sent even if there is only one
636 * possible code. So to avoid special checks later on we force at least
637 * two codes of non zero frequency.
639 while (heap_len < 2) {
640 int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
643 opt_len--; if (stree) static_len -= stree[new].Len;
644 /* new is 0 or 1 so it does not have extra bits */
646 desc->max_code = max_code;
648 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
649 * establish sub-heaps of increasing lengths:
651 for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
653 /* Construct the Huffman tree by repeatedly combining the least two
657 pqremove(tree, n); /* n = node of least frequency */
658 m = heap[SMALLEST]; /* m = node of next least frequency */
660 heap[--heap_max] = n; /* keep the nodes sorted by frequency */
661 heap[--heap_max] = m;
663 /* Create a new node father of n and m */
664 tree[node].Freq = tree[n].Freq + tree[m].Freq;
665 depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
666 tree[n].Dad = tree[m].Dad = (ush)node;
668 if (tree == bl_tree) {
669 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
670 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
673 /* and insert the new node in the heap */
674 heap[SMALLEST] = node++;
675 pqdownheap(tree, SMALLEST);
677 } while (heap_len >= 2);
679 heap[--heap_max] = heap[SMALLEST];
681 /* At this point, the fields freq and dad are set. We can now
682 * generate the bit lengths.
684 gen_bitlen((tree_desc near *)desc);
686 /* The field len is now set, we can generate the bit codes */
687 gen_codes ((ct_data near *)tree, max_code);
690 /* ===========================================================================
691 * Scan a literal or distance tree to determine the frequencies of the codes
692 * in the bit length tree. Updates opt_len to take into account the repeat
693 * counts. (The contribution of the bit length codes will be added later
694 * during the construction of bl_tree.)
696 local void scan_tree (tree, max_code)
697 ct_data near *tree; /* the tree to be scanned */
698 int max_code; /* and its largest code of non zero frequency */
700 int n; /* iterates over all tree elements */
701 int prevlen = -1; /* last emitted length */
702 int curlen; /* length of current code */
703 int nextlen = tree[0].Len; /* length of next code */
704 int count = 0; /* repeat count of the current code */
705 int max_count = 7; /* max repeat count */
706 int min_count = 4; /* min repeat count */
708 if (nextlen == 0) max_count = 138, min_count = 3;
709 tree[max_code+1].Len = (ush)0xffff; /* guard */
711 for (n = 0; n <= max_code; n++) {
712 curlen = nextlen; nextlen = tree[n+1].Len;
713 if (++count < max_count && curlen == nextlen) {
715 } else if (count < min_count) {
716 bl_tree[curlen].Freq += count;
717 } else if (curlen != 0) {
718 if (curlen != prevlen) bl_tree[curlen].Freq++;
719 bl_tree[REP_3_6].Freq++;
720 } else if (count <= 10) {
721 bl_tree[REPZ_3_10].Freq++;
723 bl_tree[REPZ_11_138].Freq++;
725 count = 0; prevlen = curlen;
727 max_count = 138, min_count = 3;
728 } else if (curlen == nextlen) {
729 max_count = 6, min_count = 3;
731 max_count = 7, min_count = 4;
736 /* ===========================================================================
737 * Send a literal or distance tree in compressed form, using the codes in
740 local void send_tree (tree, max_code)
741 ct_data near *tree; /* the tree to be scanned */
742 int max_code; /* and its largest code of non zero frequency */
744 int n; /* iterates over all tree elements */
745 int prevlen = -1; /* last emitted length */
746 int curlen; /* length of current code */
747 int nextlen = tree[0].Len; /* length of next code */
748 int count = 0; /* repeat count of the current code */
749 int max_count = 7; /* max repeat count */
750 int min_count = 4; /* min repeat count */
752 /* tree[max_code+1].Len = -1; */ /* guard already set */
753 if (nextlen == 0) max_count = 138, min_count = 3;
755 for (n = 0; n <= max_code; n++) {
756 curlen = nextlen; nextlen = tree[n+1].Len;
757 if (++count < max_count && curlen == nextlen) {
759 } else if (count < min_count) {
760 do { send_code(curlen, bl_tree); } while (--count != 0);
762 } else if (curlen != 0) {
763 if (curlen != prevlen) {
764 send_code(curlen, bl_tree); count--;
766 Assert(count >= 3 && count <= 6, " 3_6?");
767 send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
769 } else if (count <= 10) {
770 send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
773 send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
775 count = 0; prevlen = curlen;
777 max_count = 138, min_count = 3;
778 } else if (curlen == nextlen) {
779 max_count = 6, min_count = 3;
781 max_count = 7, min_count = 4;
786 /* ===========================================================================
787 * Construct the Huffman tree for the bit lengths and return the index in
788 * bl_order of the last bit length code to send.
790 local int build_bl_tree()
792 int max_blindex; /* index of last bit length code of non zero freq */
794 /* Determine the bit length frequencies for literal and distance trees */
795 scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
796 scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
798 /* Build the bit length tree: */
799 build_tree((tree_desc near *)(&bl_desc));
800 /* opt_len now includes the length of the tree representations, except
801 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
804 /* Determine the number of bit length codes to send. The pkzip format
805 * requires that at least 4 bit length codes be sent. (appnote.txt says
806 * 3 but the actual value used is 4.)
808 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
809 if (bl_tree[bl_order[max_blindex]].Len != 0) break;
811 /* Update opt_len to include the bit length tree and counts */
812 opt_len += 3*(max_blindex+1) + 5+5+4;
813 Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", opt_len, static_len));
818 /* ===========================================================================
819 * Send the header for a block using dynamic Huffman trees: the counts, the
820 * lengths of the bit length codes, the literal tree and the distance tree.
821 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
823 local void send_all_trees(lcodes, dcodes, blcodes)
824 int lcodes, dcodes, blcodes; /* number of codes for each tree */
826 int rank; /* index in bl_order */
828 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
829 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
831 Tracev((stderr, "\nbl counts: "));
832 send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
833 send_bits(dcodes-1, 5);
834 send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
835 for (rank = 0; rank < blcodes; rank++) {
836 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
837 send_bits(bl_tree[bl_order[rank]].Len, 3);
840 send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
842 send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
845 /* ===========================================================================
846 * Determine the best encoding for the current block: dynamic trees, static
847 * trees or store, and output the encoded block to the zip file. This function
848 * returns the total compressed length for the file so far.
850 off_t flush_block(buf, stored_len, eof)
851 char *buf; /* input block, or NULL if too old */
852 ulg stored_len; /* length of input block */
853 int eof; /* true if this is the last block for a file */
855 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
856 int max_blindex; /* index of last bit length code of non zero freq */
858 flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
860 /* Check if the file is ascii or binary */
861 if (*file_type == (ush)UNKNOWN) set_file_type();
863 /* Construct the literal and distance trees */
864 build_tree((tree_desc near *)(&l_desc));
865 Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len));
867 build_tree((tree_desc near *)(&d_desc));
868 Tracev((stderr, "\ndist data: dyn %lu, stat %lu", opt_len, static_len));
869 /* At this point, opt_len and static_len are the total bit lengths of
870 * the compressed block data, excluding the tree representations.
873 /* Build the bit length tree for the above two trees, and get the index
874 * in bl_order of the last bit length code to send.
876 max_blindex = build_bl_tree();
878 /* Determine the best encoding. Compute first the block length in bytes */
879 opt_lenb = (opt_len+3+7)>>3;
880 static_lenb = (static_len+3+7)>>3;
881 input_len += stored_len; /* for debugging only */
883 Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
884 opt_lenb, opt_len, static_lenb, static_len, stored_len,
885 last_lit, last_dist));
887 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
889 /* If compression failed and this is the first and last block,
890 * and if the zip file can be seeked (to rewrite the local header),
891 * the whole file is transformed into a stored file:
894 if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
896 if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
898 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
899 if (buf == (char*)0) error ("block vanished");
901 copy_block(buf, (unsigned)stored_len, 0); /* without header */
902 compressed_len = stored_len << 3;
903 *file_method = STORED;
906 } else if (level == 2 && buf != (char*)0) { /* force stored block */
908 } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
909 /* 4: two words for the lengths */
911 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
912 * Otherwise we can't have processed more than WSIZE input bytes since
913 * the last block flush, because compression would have been
914 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
915 * transform a block into a stored block.
917 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
918 compressed_len = (compressed_len + 3 + 7) & ~7L;
919 compressed_len += (stored_len + 4) << 3;
921 copy_block(buf, (unsigned)stored_len, 1); /* with header */
924 } else if (level == 3) { /* force static trees */
926 } else if (static_lenb == opt_lenb) {
928 send_bits((STATIC_TREES<<1)+eof, 3);
929 compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
930 compressed_len += 3 + static_len;
932 send_bits((DYN_TREES<<1)+eof, 3);
933 send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
934 compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
935 compressed_len += 3 + opt_len;
937 Assert (compressed_len == bits_sent, "bad compressed size");
941 Assert (input_len == bytes_in, "bad input size");
943 compressed_len += 7; /* align on byte boundary */
946 return compressed_len >> 3;
949 /* ===========================================================================
950 * Save the match info and tally the frequency counts. Return true if
951 * the current block must be flushed.
953 int ct_tally (dist, lc)
954 int dist; /* distance of matched string */
955 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
957 l_buf[last_lit++] = (uch)lc;
959 /* lc is the unmatched char */
960 dyn_ltree[lc].Freq++;
962 /* Here, lc is the match length - MIN_MATCH */
963 dist--; /* dist = match distance - 1 */
964 Assert((ush)dist < (ush)MAX_DIST &&
965 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
966 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
968 dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
969 dyn_dtree[d_code(dist)].Freq++;
971 d_buf[last_dist++] = (ush)dist;
976 /* Output the flags if they fill a byte: */
977 if ((last_lit & 7) == 0) {
978 flag_buf[last_flags++] = flags;
979 flags = 0, flag_bit = 1;
981 /* Try to guess if it is profitable to stop the current block here */
982 if (level > 2 && (last_lit & 0xfff) == 0) {
983 /* Compute an upper bound for the compressed length */
984 ulg out_length = (ulg)last_lit*8L;
985 ulg in_length = (ulg)strstart-block_start;
987 for (dcode = 0; dcode < D_CODES; dcode++) {
988 out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
991 Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
992 last_lit, last_dist, in_length, out_length,
993 100L - out_length*100L/in_length));
994 if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
996 return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
997 /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
998 * on 16 bit machines and because stored blocks are restricted to
1003 /* ===========================================================================
1004 * Send the block data compressed using the given Huffman trees
1006 local void compress_block(ltree, dtree)
1007 ct_data near *ltree; /* literal tree */
1008 ct_data near *dtree; /* distance tree */
1010 unsigned dist; /* distance of matched string */
1011 int lc; /* match length or unmatched char (if dist == 0) */
1012 unsigned lx = 0; /* running index in l_buf */
1013 unsigned dx = 0; /* running index in d_buf */
1014 unsigned fx = 0; /* running index in flag_buf */
1015 uch flag = 0; /* current flags */
1016 unsigned code; /* the code to send */
1017 int extra; /* number of extra bits to send */
1019 if (last_lit != 0) do {
1020 if ((lx & 7) == 0) flag = flag_buf[fx++];
1022 if ((flag & 1) == 0) {
1023 send_code(lc, ltree); /* send a literal byte */
1024 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1026 /* Here, lc is the match length - MIN_MATCH */
1027 code = length_code[lc];
1028 send_code(code+LITERALS+1, ltree); /* send the length code */
1029 extra = extra_lbits[code];
1031 lc -= base_length[code];
1032 send_bits(lc, extra); /* send the extra length bits */
1035 /* Here, dist is the match distance - 1 */
1036 code = d_code(dist);
1037 Assert (code < D_CODES, "bad d_code");
1039 send_code(code, dtree); /* send the distance code */
1040 extra = extra_dbits[code];
1042 dist -= base_dist[code];
1043 send_bits(dist, extra); /* send the extra distance bits */
1045 } /* literal or match pair ? */
1047 } while (lx < last_lit);
1049 send_code(END_BLOCK, ltree);
1052 /* ===========================================================================
1053 * Set the file type to ASCII or BINARY, using a crude approximation:
1054 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1055 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1056 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1058 local void set_file_type()
1061 unsigned ascii_freq = 0;
1062 unsigned bin_freq = 0;
1063 while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1064 while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1065 while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1066 *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1067 if (*file_type == BINARY && translate_eol) {
1068 warning ("-l used on binary file");