1 /* trees.c -- output deflated data using Huffman coding
3 Copyright (C) 1997-1999, 2009-2010 Free Software Foundation, Inc.
4 Copyright (C) 1992-1993 Jean-loup Gailly
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software Foundation,
18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
23 * Encode various sets of source values using variable-length
28 * The PKZIP "deflation" process uses several Huffman trees. The more
29 * common source values are represented by shorter bit sequences.
31 * Each code tree is stored in the ZIP file in a compressed form
32 * which is itself a Huffman encoding of the lengths of
33 * all the code strings (in ascending order by source values).
34 * The actual code strings are reconstructed from the lengths in
35 * the UNZIP process, as described in the "application note"
36 * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
41 * Data Compression: Techniques and Applications, pp. 53-55.
42 * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
45 * Data Compression: Methods and Theory, pp. 49-50.
46 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
50 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
54 * void ct_init (ush *attr, int *methodp)
55 * Allocate the match buffer, initialize the various tables and save
56 * the location of the internal file attribute (ascii/binary) and
57 * method (DEFLATE/STORE)
59 * void ct_tally (int dist, int lc);
60 * Save the match info and tally the frequency counts.
62 * off_t flush_block (char *buf, ulg stored_len, int pad, int eof)
63 * Determine the best encoding for the current block: dynamic trees,
64 * static trees or store, and output the encoded block to the zip
65 * file. If pad is set, pads the block to the next
66 * byte. Returns the total compressed length for the file so
76 /* ===========================================================================
81 /* All codes must not exceed MAX_BITS bits */
84 /* Bit length codes must not exceed MAX_BL_BITS bits */
86 #define LENGTH_CODES 29
87 /* number of length codes, not counting the special END_BLOCK code */
90 /* number of literal bytes 0..255 */
93 /* end of block literal code */
95 #define L_CODES (LITERALS+1+LENGTH_CODES)
96 /* number of Literal or Length codes, including the END_BLOCK code */
99 /* number of distance codes */
102 /* number of codes used to transfer the bit lengths */
105 local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
106 = {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};
108 local int near extra_dbits[D_CODES] /* extra bits for each distance code */
109 = {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};
111 local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
112 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
114 #define STORED_BLOCK 0
115 #define STATIC_TREES 1
117 /* The three kinds of block type */
121 # define LIT_BUFSIZE 0x2000
124 # define LIT_BUFSIZE 0x4000
126 # define LIT_BUFSIZE 0x8000
131 # define DIST_BUFSIZE LIT_BUFSIZE
133 /* Sizes of match buffers for literals/lengths and distances. There are
134 * 4 reasons for limiting LIT_BUFSIZE to 64K:
135 * - frequencies can be kept in 16 bit counters
136 * - if compression is not successful for the first block, all input data is
137 * still in the window so we can still emit a stored block even when input
138 * comes from standard input. (This can also be done for all blocks if
139 * LIT_BUFSIZE is not greater than 32K.)
140 * - if compression is not successful for a file smaller than 64K, we can
141 * even emit a stored file instead of a stored block (saving 5 bytes).
142 * - creating new Huffman trees less frequently may not provide fast
143 * adaptation to changes in the input data statistics. (Take for
144 * example a binary file with poorly compressible code followed by
145 * a highly compressible string table.) Smaller buffer sizes give
146 * fast adaptation but have of course the overhead of transmitting trees
148 * - I can't count above 4
149 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
150 * memory at the expense of compression). Some optimizations would be possible
151 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
153 #if LIT_BUFSIZE > INBUFSIZ
154 error cannot overlay l_buf and inbuf
158 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
161 /* repeat a zero length 3-10 times (3 bits of repeat count) */
163 #define REPZ_11_138 18
164 /* repeat a zero length 11-138 times (7 bits of repeat count) */
166 /* ===========================================================================
170 /* Data structure describing a single value and its code string. */
171 typedef struct ct_data {
173 ush freq; /* frequency count */
174 ush code; /* bit string */
177 ush dad; /* father node in Huffman tree */
178 ush len; /* length of bit string */
187 #define HEAP_SIZE (2*L_CODES+1)
188 /* maximum heap size */
190 local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
191 local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
193 local ct_data near static_ltree[L_CODES+2];
194 /* The static literal tree. Since the bit lengths are imposed, there is no
195 * need for the L_CODES extra codes used during heap construction. However
196 * The codes 286 and 287 are needed to build a canonical tree (see ct_init
200 local ct_data near static_dtree[D_CODES];
201 /* The static distance tree. (Actually a trivial tree since all codes use
205 local ct_data near bl_tree[2*BL_CODES+1];
206 /* Huffman tree for the bit lengths */
208 typedef struct tree_desc {
209 ct_data near *dyn_tree; /* the dynamic tree */
210 ct_data near *static_tree; /* corresponding static tree or NULL */
211 int near *extra_bits; /* extra bits for each code or NULL */
212 int extra_base; /* base index for extra_bits */
213 int elems; /* max number of elements in the tree */
214 int max_length; /* max bit length for the codes */
215 int max_code; /* largest code with non zero frequency */
218 local tree_desc near l_desc =
219 {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
221 local tree_desc near d_desc =
222 {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
224 local tree_desc near bl_desc =
225 {bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
228 local ush near bl_count[MAX_BITS+1];
229 /* number of codes at each bit length for an optimal tree */
231 local uch near bl_order[BL_CODES]
232 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
233 /* The lengths of the bit length codes are sent in order of decreasing
234 * probability, to avoid transmitting the lengths for unused bit length codes.
237 local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
238 local int heap_len; /* number of elements in the heap */
239 local int heap_max; /* element of largest frequency */
240 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
241 * The same heap array is used to build all trees.
244 local uch near depth[2*L_CODES+1];
245 /* Depth of each subtree used as tie breaker for trees of equal frequency */
247 local uch length_code[MAX_MATCH-MIN_MATCH+1];
248 /* length code for each normalized match length (0 == MIN_MATCH) */
250 local uch dist_code[512];
251 /* distance codes. The first 256 values correspond to the distances
252 * 3 .. 258, the last 256 values correspond to the top 8 bits of
253 * the 15 bit distances.
256 local int near base_length[LENGTH_CODES];
257 /* First normalized length for each code (0 = MIN_MATCH) */
259 local int near base_dist[D_CODES];
260 /* First normalized distance for each code (0 = distance of 1) */
263 /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
265 /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
267 local uch near flag_buf[(LIT_BUFSIZE/8)];
268 /* flag_buf is a bit array distinguishing literals from lengths in
269 * l_buf, thus indicating the presence or absence of a distance.
272 local unsigned last_lit; /* running index in l_buf */
273 local unsigned last_dist; /* running index in d_buf */
274 local unsigned last_flags; /* running index in flag_buf */
275 local uch flags; /* current flags not yet saved in flag_buf */
276 local uch flag_bit; /* current bit used in flags */
277 /* bits are filled in flags starting at bit 0 (least significant).
278 * Note: these flags are overkill in the current code since we don't
279 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
282 local ulg opt_len; /* bit length of current block with optimal trees */
283 local ulg static_len; /* bit length of current block with static trees */
285 local off_t compressed_len; /* total bit length of compressed file */
287 local off_t input_len; /* total byte length of input file */
288 /* input_len is for debugging only since we can get it by other means. */
290 ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
291 int *file_method; /* pointer to DEFLATE or STORE */
294 extern off_t bits_sent; /* bit length of the compressed data */
297 extern long block_start; /* window offset of current block */
298 extern unsigned near strstart; /* window offset of current string */
300 /* ===========================================================================
301 * Local (static) routines in this file.
304 local void init_block OF((void));
305 local void pqdownheap OF((ct_data near *tree, int k));
306 local void gen_bitlen OF((tree_desc near *desc));
307 local void gen_codes OF((ct_data near *tree, int max_code));
308 local void build_tree OF((tree_desc near *desc));
309 local void scan_tree OF((ct_data near *tree, int max_code));
310 local void send_tree OF((ct_data near *tree, int max_code));
311 local int build_bl_tree OF((void));
312 local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
313 local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
314 local void set_file_type OF((void));
318 # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
319 /* Send a code of the given tree. c and tree must not have side effects */
322 # define send_code(c, tree) \
323 { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
324 send_bits(tree[c].Code, tree[c].Len); }
327 #define d_code(dist) \
328 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
329 /* Mapping from a distance to a distance code. dist is the distance - 1 and
330 * must not have side effects. dist_code[256] and dist_code[257] are never
334 #define MAX(a,b) (a >= b ? a : b)
335 /* the arguments must not have side effects */
337 /* ===========================================================================
338 * Allocate the match buffer, initialize the various tables and save the
339 * location of the internal file attribute (ascii/binary) and method
342 void ct_init(attr, methodp)
343 ush *attr; /* pointer to internal file attribute */
344 int *methodp; /* pointer to compression method */
346 int n; /* iterates over tree elements */
347 int bits; /* bit counter */
348 int length; /* length value */
349 int code; /* code value */
350 int dist; /* distance index */
353 file_method = methodp;
354 compressed_len = input_len = 0L;
356 if (static_dtree[0].Len != 0) return; /* ct_init already called */
358 /* Initialize the mapping length (0..255) -> length code (0..28) */
360 for (code = 0; code < LENGTH_CODES-1; code++) {
361 base_length[code] = length;
362 for (n = 0; n < (1<<extra_lbits[code]); n++) {
363 length_code[length++] = (uch)code;
366 Assert (length == 256, "ct_init: length != 256");
367 /* Note that the length 255 (match length 258) can be represented
368 * in two different ways: code 284 + 5 bits or code 285, so we
369 * overwrite length_code[255] to use the best encoding:
371 length_code[length-1] = (uch)code;
373 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
375 for (code = 0 ; code < 16; code++) {
376 base_dist[code] = dist;
377 for (n = 0; n < (1<<extra_dbits[code]); n++) {
378 dist_code[dist++] = (uch)code;
381 Assert (dist == 256, "ct_init: dist != 256");
382 dist >>= 7; /* from now on, all distances are divided by 128 */
383 for ( ; code < D_CODES; code++) {
384 base_dist[code] = dist << 7;
385 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
386 dist_code[256 + dist++] = (uch)code;
389 Assert (dist == 256, "ct_init: 256+dist != 512");
391 /* Construct the codes of the static literal tree */
392 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
394 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
395 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
396 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
397 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
398 /* Codes 286 and 287 do not exist, but we must include them in the
399 * tree construction to get a canonical Huffman tree (longest code
402 gen_codes((ct_data near *)static_ltree, L_CODES+1);
404 /* The static distance tree is trivial: */
405 for (n = 0; n < D_CODES; n++) {
406 static_dtree[n].Len = 5;
407 static_dtree[n].Code = bi_reverse(n, 5);
410 /* Initialize the first block of the first file: */
414 /* ===========================================================================
415 * Initialize a new block.
417 local void init_block()
419 int n; /* iterates over tree elements */
421 /* Initialize the trees. */
422 for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
423 for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
424 for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
426 dyn_ltree[END_BLOCK].Freq = 1;
427 opt_len = static_len = 0L;
428 last_lit = last_dist = last_flags = 0;
429 flags = 0; flag_bit = 1;
433 /* Index within the heap array of least frequent node in the Huffman tree */
436 /* ===========================================================================
437 * Remove the smallest element from the heap and recreate the heap with
438 * one less element. Updates heap and heap_len.
440 #define pqremove(tree, top) \
442 top = heap[SMALLEST]; \
443 heap[SMALLEST] = heap[heap_len--]; \
444 pqdownheap(tree, SMALLEST); \
447 /* ===========================================================================
448 * Compares to subtrees, using the tree depth as tie breaker when
449 * the subtrees have equal frequency. This minimizes the worst case length.
451 #define smaller(tree, n, m) \
452 (tree[n].Freq < tree[m].Freq || \
453 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
455 /* ===========================================================================
456 * Restore the heap property by moving down the tree starting at node k,
457 * exchanging a node with the smallest of its two sons if necessary, stopping
458 * when the heap property is re-established (each father smaller than its
461 local void pqdownheap(tree, k)
462 ct_data near *tree; /* the tree to restore */
463 int k; /* node to move down */
466 int j = k << 1; /* left son of k */
467 while (j <= heap_len) {
468 /* Set j to the smallest of the two sons: */
469 if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
471 /* Exit if v is smaller than both sons */
472 if (smaller(tree, v, heap[j])) break;
474 /* Exchange v with the smallest son */
475 heap[k] = heap[j]; k = j;
477 /* And continue down the tree, setting j to the left son of k */
483 /* ===========================================================================
484 * Compute the optimal bit lengths for a tree and update the total bit length
485 * for the current block.
486 * IN assertion: the fields freq and dad are set, heap[heap_max] and
487 * above are the tree nodes sorted by increasing frequency.
488 * OUT assertions: the field len is set to the optimal bit length, the
489 * array bl_count contains the frequencies for each bit length.
490 * The length opt_len is updated; static_len is also updated if stree is
493 local void gen_bitlen(desc)
494 tree_desc near *desc; /* the tree descriptor */
496 ct_data near *tree = desc->dyn_tree;
497 int near *extra = desc->extra_bits;
498 int base = desc->extra_base;
499 int max_code = desc->max_code;
500 int max_length = desc->max_length;
501 ct_data near *stree = desc->static_tree;
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++) 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[heap[heap_max]].Len = 0; /* root of the heap */
516 for (h = 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 opt_len += (ulg)f * (bits + xbits);
530 if (stree) 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 (bl_count[bits] == 0) bits--;
541 bl_count[bits]--; /* move one leaf down the tree */
542 bl_count[bits+1] += 2; /* move one overflow item as its brother */
543 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--) {
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 opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
563 tree[m].Len = (ush)bits;
570 /* ===========================================================================
571 * Generate the codes for a given tree and bit counts (which need not be
573 * IN assertion: the array bl_count contains the bit length statistics for
574 * the given tree and the field len is set for all tree elements.
575 * OUT assertion: the field code is set for all tree elements of non
578 local void gen_codes (tree, max_code)
579 ct_data near *tree; /* the tree to decorate */
580 int max_code; /* largest code with non zero frequency */
582 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
583 ush code = 0; /* running code value */
584 int bits; /* bit index */
585 int n; /* code index */
587 /* The distribution counts are first used to generate the code values
588 * without bit reversal.
590 for (bits = 1; bits <= MAX_BITS; bits++) {
591 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
593 /* Check that the bit counts in bl_count are consistent. The last code
596 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
597 "inconsistent bit counts");
598 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
600 for (n = 0; n <= max_code; n++) {
601 int len = tree[n].Len;
602 if (len == 0) continue;
603 /* Now reverse the bits */
604 tree[n].Code = bi_reverse(next_code[len]++, len);
606 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
607 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
611 /* ===========================================================================
612 * Construct one Huffman tree and assigns the code bit strings and lengths.
613 * Update the total bit length for the current block.
614 * IN assertion: the field freq is set for all tree elements.
615 * OUT assertions: the fields len and code are set to the optimal bit length
616 * and corresponding code. The length opt_len is updated; static_len is
617 * also updated if stree is not null. The field max_code is set.
619 local void build_tree(desc)
620 tree_desc near *desc; /* the tree descriptor */
622 ct_data near *tree = desc->dyn_tree;
623 ct_data near *stree = desc->static_tree;
624 int elems = desc->elems;
625 int n, m; /* iterate over heap elements */
626 int max_code = -1; /* largest code with non zero frequency */
627 int node = elems; /* next internal node of the tree */
629 /* Construct the initial heap, with least frequent element in
630 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
631 * heap[0] is not used.
633 heap_len = 0, heap_max = HEAP_SIZE;
635 for (n = 0; n < elems; n++) {
636 if (tree[n].Freq != 0) {
637 heap[++heap_len] = max_code = n;
644 /* The pkzip format requires that at least one distance code exists,
645 * and that at least one bit should be sent even if there is only one
646 * possible code. So to avoid special checks later on we force at least
647 * two codes of non zero frequency.
649 while (heap_len < 2) {
650 int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
653 opt_len--; if (stree) static_len -= stree[new].Len;
654 /* new is 0 or 1 so it does not have extra bits */
656 desc->max_code = max_code;
658 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
659 * establish sub-heaps of increasing lengths:
661 for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
663 /* Construct the Huffman tree by repeatedly combining the least two
667 pqremove(tree, n); /* n = node of least frequency */
668 m = heap[SMALLEST]; /* m = node of next least frequency */
670 heap[--heap_max] = n; /* keep the nodes sorted by frequency */
671 heap[--heap_max] = m;
673 /* Create a new node father of n and m */
674 tree[node].Freq = tree[n].Freq + tree[m].Freq;
675 depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
676 tree[n].Dad = tree[m].Dad = (ush)node;
678 if (tree == bl_tree) {
679 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
680 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
683 /* and insert the new node in the heap */
684 heap[SMALLEST] = node++;
685 pqdownheap(tree, SMALLEST);
687 } while (heap_len >= 2);
689 heap[--heap_max] = heap[SMALLEST];
691 /* At this point, the fields freq and dad are set. We can now
692 * generate the bit lengths.
694 gen_bitlen((tree_desc near *)desc);
696 /* The field len is now set, we can generate the bit codes */
697 gen_codes ((ct_data near *)tree, max_code);
700 /* ===========================================================================
701 * Scan a literal or distance tree to determine the frequencies of the codes
702 * in the bit length tree. Updates opt_len to take into account the repeat
703 * counts. (The contribution of the bit length codes will be added later
704 * during the construction of bl_tree.)
706 local void scan_tree (tree, max_code)
707 ct_data near *tree; /* the tree to be scanned */
708 int max_code; /* and its largest code of non zero frequency */
710 int n; /* iterates over all tree elements */
711 int prevlen = -1; /* last emitted length */
712 int curlen; /* length of current code */
713 int nextlen = tree[0].Len; /* length of next code */
714 int count = 0; /* repeat count of the current code */
715 int max_count = 7; /* max repeat count */
716 int min_count = 4; /* min repeat count */
718 if (nextlen == 0) max_count = 138, min_count = 3;
719 tree[max_code+1].Len = (ush)0xffff; /* guard */
721 for (n = 0; n <= max_code; n++) {
722 curlen = nextlen; nextlen = tree[n+1].Len;
723 if (++count < max_count && curlen == nextlen) {
725 } else if (count < min_count) {
726 bl_tree[curlen].Freq += count;
727 } else if (curlen != 0) {
728 if (curlen != prevlen) bl_tree[curlen].Freq++;
729 bl_tree[REP_3_6].Freq++;
730 } else if (count <= 10) {
731 bl_tree[REPZ_3_10].Freq++;
733 bl_tree[REPZ_11_138].Freq++;
735 count = 0; prevlen = curlen;
737 max_count = 138, min_count = 3;
738 } else if (curlen == nextlen) {
739 max_count = 6, min_count = 3;
741 max_count = 7, min_count = 4;
746 /* ===========================================================================
747 * Send a literal or distance tree in compressed form, using the codes in
750 local void send_tree (tree, max_code)
751 ct_data near *tree; /* the tree to be scanned */
752 int max_code; /* and its largest code of non zero frequency */
754 int n; /* iterates over all tree elements */
755 int prevlen = -1; /* last emitted length */
756 int curlen; /* length of current code */
757 int nextlen = tree[0].Len; /* length of next code */
758 int count = 0; /* repeat count of the current code */
759 int max_count = 7; /* max repeat count */
760 int min_count = 4; /* min repeat count */
762 /* tree[max_code+1].Len = -1; */ /* guard already set */
763 if (nextlen == 0) max_count = 138, min_count = 3;
765 for (n = 0; n <= max_code; n++) {
766 curlen = nextlen; nextlen = tree[n+1].Len;
767 if (++count < max_count && curlen == nextlen) {
769 } else if (count < min_count) {
770 do { send_code(curlen, bl_tree); } while (--count != 0);
772 } else if (curlen != 0) {
773 if (curlen != prevlen) {
774 send_code(curlen, bl_tree); count--;
776 Assert(count >= 3 && count <= 6, " 3_6?");
777 send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
779 } else if (count <= 10) {
780 send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
783 send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
785 count = 0; prevlen = curlen;
787 max_count = 138, min_count = 3;
788 } else if (curlen == nextlen) {
789 max_count = 6, min_count = 3;
791 max_count = 7, min_count = 4;
796 /* ===========================================================================
797 * Construct the Huffman tree for the bit lengths and return the index in
798 * bl_order of the last bit length code to send.
800 local int build_bl_tree()
802 int max_blindex; /* index of last bit length code of non zero freq */
804 /* Determine the bit length frequencies for literal and distance trees */
805 scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
806 scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
808 /* Build the bit length tree: */
809 build_tree((tree_desc near *)(&bl_desc));
810 /* opt_len now includes the length of the tree representations, except
811 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
814 /* Determine the number of bit length codes to send. The pkzip format
815 * requires that at least 4 bit length codes be sent. (appnote.txt says
816 * 3 but the actual value used is 4.)
818 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
819 if (bl_tree[bl_order[max_blindex]].Len != 0) break;
821 /* Update opt_len to include the bit length tree and counts */
822 opt_len += 3*(max_blindex+1) + 5+5+4;
823 Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", opt_len, static_len));
828 /* ===========================================================================
829 * Send the header for a block using dynamic Huffman trees: the counts, the
830 * lengths of the bit length codes, the literal tree and the distance tree.
831 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
833 local void send_all_trees(lcodes, dcodes, blcodes)
834 int lcodes, dcodes, blcodes; /* number of codes for each tree */
836 int rank; /* index in bl_order */
838 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
839 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
841 Tracev((stderr, "\nbl counts: "));
842 send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
843 send_bits(dcodes-1, 5);
844 send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
845 for (rank = 0; rank < blcodes; rank++) {
846 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
847 send_bits(bl_tree[bl_order[rank]].Len, 3);
850 send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
852 send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
855 /* ===========================================================================
856 * Determine the best encoding for the current block: dynamic trees, static
857 * trees or store, and output the encoded block to the zip file. This function
858 * returns the total compressed length for the file so far.
860 off_t flush_block(buf, stored_len, pad, eof)
861 char *buf; /* input block, or NULL if too old */
862 ulg stored_len; /* length of input block */
863 int pad; /* pad output to byte boundary */
864 int eof; /* true if this is the last block for a file */
866 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
867 int max_blindex; /* index of last bit length code of non zero freq */
869 flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
871 /* Check if the file is ascii or binary */
872 if (*file_type == (ush)UNKNOWN) set_file_type();
874 /* Construct the literal and distance trees */
875 build_tree((tree_desc near *)(&l_desc));
876 Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len));
878 build_tree((tree_desc near *)(&d_desc));
879 Tracev((stderr, "\ndist data: dyn %lu, stat %lu", opt_len, static_len));
880 /* At this point, opt_len and static_len are the total bit lengths of
881 * the compressed block data, excluding the tree representations.
884 /* Build the bit length tree for the above two trees, and get the index
885 * in bl_order of the last bit length code to send.
887 max_blindex = build_bl_tree();
889 /* Determine the best encoding. Compute first the block length in bytes */
890 opt_lenb = (opt_len+3+7)>>3;
891 static_lenb = (static_len+3+7)>>3;
892 input_len += stored_len; /* for debugging only */
894 Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
895 opt_lenb, opt_len, static_lenb, static_len, stored_len,
896 last_lit, last_dist));
898 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
900 /* If compression failed and this is the first and last block,
901 * and if the zip file can be seeked (to rewrite the local header),
902 * the whole file is transformed into a stored file:
905 if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
907 if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
909 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
911 gzip_error ("block vanished");
913 copy_block(buf, (unsigned)stored_len, 0); /* without header */
914 compressed_len = stored_len << 3;
915 *file_method = STORED;
918 } else if (level == 2 && buf != (char*)0) { /* force stored block */
920 } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
921 /* 4: two words for the lengths */
923 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
924 * Otherwise we can't have processed more than WSIZE input bytes since
925 * the last block flush, because compression would have been
926 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
927 * transform a block into a stored block.
929 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
930 compressed_len = (compressed_len + 3 + 7) & ~7L;
931 compressed_len += (stored_len + 4) << 3;
933 copy_block(buf, (unsigned)stored_len, 1); /* with header */
936 } else if (level == 3) { /* force static trees */
938 } else if (static_lenb == opt_lenb) {
940 send_bits((STATIC_TREES<<1)+eof, 3);
941 compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
942 compressed_len += 3 + static_len;
944 send_bits((DYN_TREES<<1)+eof, 3);
945 send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
946 compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
947 compressed_len += 3 + opt_len;
949 Assert (compressed_len == bits_sent, "bad compressed size");
953 Assert (input_len == bytes_in, "bad input size");
955 compressed_len += 7; /* align on byte boundary */
956 } else if (pad && (compressed_len % 8) != 0) {
957 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
958 compressed_len = (compressed_len + 3 + 7) & ~7L;
959 copy_block(buf, 0, 1); /* with header */
962 return compressed_len >> 3;
965 /* ===========================================================================
966 * Save the match info and tally the frequency counts. Return true if
967 * the current block must be flushed.
969 int ct_tally (dist, lc)
970 int dist; /* distance of matched string */
971 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
973 l_buf[last_lit++] = (uch)lc;
975 /* lc is the unmatched char */
976 dyn_ltree[lc].Freq++;
978 /* Here, lc is the match length - MIN_MATCH */
979 dist--; /* dist = match distance - 1 */
980 Assert((ush)dist < (ush)MAX_DIST &&
981 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
982 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
984 dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
985 dyn_dtree[d_code(dist)].Freq++;
987 d_buf[last_dist++] = (ush)dist;
992 /* Output the flags if they fill a byte: */
993 if ((last_lit & 7) == 0) {
994 flag_buf[last_flags++] = flags;
995 flags = 0, flag_bit = 1;
997 /* Try to guess if it is profitable to stop the current block here */
998 if (level > 2 && (last_lit & 0xfff) == 0) {
999 /* Compute an upper bound for the compressed length */
1000 ulg out_length = (ulg)last_lit*8L;
1001 ulg in_length = (ulg)strstart-block_start;
1003 for (dcode = 0; dcode < D_CODES; dcode++) {
1004 out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
1007 Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
1008 last_lit, last_dist, in_length, out_length,
1009 100L - out_length*100L/in_length));
1010 if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1012 return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1013 /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1014 * on 16 bit machines and because stored blocks are restricted to
1019 /* ===========================================================================
1020 * Send the block data compressed using the given Huffman trees
1022 local void compress_block(ltree, dtree)
1023 ct_data near *ltree; /* literal tree */
1024 ct_data near *dtree; /* distance tree */
1026 unsigned dist; /* distance of matched string */
1027 int lc; /* match length or unmatched char (if dist == 0) */
1028 unsigned lx = 0; /* running index in l_buf */
1029 unsigned dx = 0; /* running index in d_buf */
1030 unsigned fx = 0; /* running index in flag_buf */
1031 uch flag = 0; /* current flags */
1032 unsigned code; /* the code to send */
1033 int extra; /* number of extra bits to send */
1035 if (last_lit != 0) do {
1036 if ((lx & 7) == 0) flag = flag_buf[fx++];
1038 if ((flag & 1) == 0) {
1039 send_code(lc, ltree); /* send a literal byte */
1040 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1042 /* Here, lc is the match length - MIN_MATCH */
1043 code = length_code[lc];
1044 send_code(code+LITERALS+1, ltree); /* send the length code */
1045 extra = extra_lbits[code];
1047 lc -= base_length[code];
1048 send_bits(lc, extra); /* send the extra length bits */
1051 /* Here, dist is the match distance - 1 */
1052 code = d_code(dist);
1053 Assert (code < D_CODES, "bad d_code");
1055 send_code(code, dtree); /* send the distance code */
1056 extra = extra_dbits[code];
1058 dist -= base_dist[code];
1059 send_bits(dist, extra); /* send the extra distance bits */
1061 } /* literal or match pair ? */
1063 } while (lx < last_lit);
1065 send_code(END_BLOCK, ltree);
1068 /* ===========================================================================
1069 * Set the file type to ASCII or BINARY, using a crude approximation:
1070 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1071 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1072 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1074 local void set_file_type()
1077 unsigned ascii_freq = 0;
1078 unsigned bin_freq = 0;
1079 while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1080 while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1081 while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1082 *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1083 if (*file_type == BINARY && translate_eol) {
1084 warning ("-l used on binary file");