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1.1 root 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.
5: */
6:
7: /*
8: * PURPOSE
9: *
10: * Encode various sets of source values using variable-length
11: * binary code trees.
12: *
13: * DISCUSSION
14: *
15: * The PKZIP "deflation" process uses several Huffman trees. The more
16: * common source values are represented by shorter bit sequences.
17: *
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.
24: *
25: * REFERENCES
26: *
27: * Lynch, Thomas J.
28: * Data Compression: Techniques and Applications, pp. 53-55.
29: * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
30: *
31: * Storer, James A.
32: * Data Compression: Methods and Theory, pp. 49-50.
33: * Computer Science Press, 1988. ISBN 0-7167-8156-5.
34: *
35: * Sedgewick, R.
36: * Algorithms, p290.
37: * Addison-Wesley, 1983. ISBN 0-201-06672-6.
38: *
39: * INTERFACE
40: *
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)
45: *
46: * void ct_tally (int dist, int lc);
47: * Save the match info and tally the frequency counts.
48: *
49: * long 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.
53: *
54: */
55:
56: #include "tailor.h"
57: #include "gzip.h"
58:
59: #include <ctype.h>
60: #include <stdio.h>
61:
62: #ifndef lint
63: static char rcsid[] = "$Id: trees.c,v 0.9 1993/02/10 16:07:22 jloup Exp $";
64: #endif
65:
66: /* ===========================================================================
67: * Constants
68: */
69:
70: #define MAX_BITS 15
71: /* All codes must not exceed MAX_BITS bits */
72:
73: #define MAX_BL_BITS 7
74: /* Bit length codes must not exceed MAX_BL_BITS bits */
75:
76: #define LENGTH_CODES 29
77: /* number of length codes, not counting the special END_BLOCK code */
78:
79: #define LITERALS 256
80: /* number of literal bytes 0..255 */
81:
82: #define END_BLOCK 256
83: /* end of block literal code */
84:
85: #define L_CODES (LITERALS+1+LENGTH_CODES)
86: /* number of Literal or Length codes, including the END_BLOCK code */
87:
88: #define D_CODES 30
89: /* number of distance codes */
90:
91: #define BL_CODES 19
92: /* number of codes used to transfer the bit lengths */
93:
94:
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};
97:
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};
100:
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};
103:
104: #define STORED_BLOCK 0
105: #define STATIC_TREES 1
106: #define DYN_TREES 2
107: /* The three kinds of block type */
108:
109: #ifndef LIT_BUFSIZE
110: # ifdef SMALL_MEM
111: # define LIT_BUFSIZE 0x2000
112: # else
113: # ifdef MEDIUM_MEM
114: # define LIT_BUFSIZE 0x4000
115: # else
116: # define LIT_BUFSIZE 0x8000
117: # endif
118: # endif
119: #endif
120: #ifndef DIST_BUFSIZE
121: # define DIST_BUFSIZE LIT_BUFSIZE
122: #endif
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
137: * more frequently.
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.
142: */
143: #if LIT_BUFSIZE > INBUFSIZ
144: error cannot overlay l_buf and inbuf
145: #endif
146:
147: #define REP_3_6 16
148: /* repeat previous bit length 3-6 times (2 bits of repeat count) */
149:
150: #define REPZ_3_10 17
151: /* repeat a zero length 3-10 times (3 bits of repeat count) */
152:
153: #define REPZ_11_138 18
154: /* repeat a zero length 11-138 times (7 bits of repeat count) */
155:
156: /* ===========================================================================
157: * Local data
158: */
159:
160: /* Data structure describing a single value and its code string. */
161: typedef struct ct_data {
162: union {
163: ush freq; /* frequency count */
164: ush code; /* bit string */
165: } fc;
166: union {
167: ush dad; /* father node in Huffman tree */
168: ush len; /* length of bit string */
169: } dl;
170: } ct_data;
171:
172: #define Freq fc.freq
173: #define Code fc.code
174: #define Dad dl.dad
175: #define Len dl.len
176:
177: #define HEAP_SIZE (2*L_CODES+1)
178: /* maximum heap size */
179:
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 */
182:
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
187: * below).
188: */
189:
190: local ct_data near static_dtree[D_CODES];
191: /* The static distance tree. (Actually a trivial tree since all codes use
192: * 5 bits.)
193: */
194:
195: local ct_data near bl_tree[2*BL_CODES+1];
196: /* Huffman tree for the bit lengths */
197:
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 */
206: } tree_desc;
207:
208: local tree_desc near l_desc =
209: {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
210:
211: local tree_desc near d_desc =
212: {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
213:
214: local tree_desc near bl_desc =
215: {bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
216:
217:
218: local ush near bl_count[MAX_BITS+1];
219: /* number of codes at each bit length for an optimal tree */
220:
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.
225: */
226:
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.
232: */
233:
234: local uch near depth[2*L_CODES+1];
235: /* Depth of each subtree used as tie breaker for trees of equal frequency */
236:
237: local uch length_code[MAX_MATCH-MIN_MATCH+1];
238: /* length code for each normalized match length (0 == MIN_MATCH) */
239:
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.
244: */
245:
246: local int near base_length[LENGTH_CODES];
247: /* First normalized length for each code (0 = MIN_MATCH) */
248:
249: local int near base_dist[D_CODES];
250: /* First normalized distance for each code (0 = distance of 1) */
251:
252: #define l_buf inbuf
253: /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
254:
255: /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
256:
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.
260: */
261:
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.
270: */
271:
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 */
274:
275: local ulg compressed_len; /* total bit length of compressed file */
276:
277: local ulg input_len; /* total byte length of input file */
278: /* input_len is for debugging only since we can get it by other means. */
279:
280: ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
281: int *file_method; /* pointer to DEFLATE or STORE */
282:
283: #ifdef DEBUG
284: extern ulg bits_sent; /* bit length of the compressed data */
285: extern long isize; /* byte length of input file */
286: #endif
287:
288: extern long block_start; /* window offset of current block */
289: extern unsigned near strstart; /* window offset of current string */
290:
291: /* ===========================================================================
292: * Local (static) routines in this file.
293: */
294:
295: local void init_block OF((void));
296: local void pqdownheap OF((ct_data near *tree, int k));
297: local void gen_bitlen OF((tree_desc near *desc));
298: local void gen_codes OF((ct_data near *tree, int max_code));
299: local void build_tree OF((tree_desc near *desc));
300: local void scan_tree OF((ct_data near *tree, int max_code));
301: local void send_tree OF((ct_data near *tree, int max_code));
302: local int build_bl_tree OF((void));
303: local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
304: local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
305: local void set_file_type OF((void));
306:
307:
308: #ifndef DEBUG
309: # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
310: /* Send a code of the given tree. c and tree must not have side effects */
311:
312: #else /* DEBUG */
313: # define send_code(c, tree) \
314: { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
315: send_bits(tree[c].Code, tree[c].Len); }
316: #endif
317:
318: #define d_code(dist) \
319: ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
320: /* Mapping from a distance to a distance code. dist is the distance - 1 and
321: * must not have side effects. dist_code[256] and dist_code[257] are never
322: * used.
323: */
324:
325: #define MAX(a,b) (a >= b ? a : b)
326: /* the arguments must not have side effects */
327:
328: /* ===========================================================================
329: * Allocate the match buffer, initialize the various tables and save the
330: * location of the internal file attribute (ascii/binary) and method
331: * (DEFLATE/STORE).
332: */
333: void ct_init(attr, methodp)
334: ush *attr; /* pointer to internal file attribute */
335: int *methodp; /* pointer to compression method */
336: {
337: int n; /* iterates over tree elements */
338: int bits; /* bit counter */
339: int length; /* length value */
340: int code; /* code value */
341: int dist; /* distance index */
342:
343: file_type = attr;
344: file_method = methodp;
345: compressed_len = input_len = 0L;
346:
347: if (static_dtree[0].Len != 0) return; /* ct_init already called */
348:
349: /* Initialize the mapping length (0..255) -> length code (0..28) */
350: length = 0;
351: for (code = 0; code < LENGTH_CODES-1; code++) {
352: base_length[code] = length;
353: for (n = 0; n < (1<<extra_lbits[code]); n++) {
354: length_code[length++] = (uch)code;
355: }
356: }
357: Assert (length == 256, "ct_init: length != 256");
358: /* Note that the length 255 (match length 258) can be represented
359: * in two different ways: code 284 + 5 bits or code 285, so we
360: * overwrite length_code[255] to use the best encoding:
361: */
362: length_code[length-1] = (uch)code;
363:
364: /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
365: dist = 0;
366: for (code = 0 ; code < 16; code++) {
367: base_dist[code] = dist;
368: for (n = 0; n < (1<<extra_dbits[code]); n++) {
369: dist_code[dist++] = (uch)code;
370: }
371: }
372: Assert (dist == 256, "ct_init: dist != 256");
373: dist >>= 7; /* from now on, all distances are divided by 128 */
374: for ( ; code < D_CODES; code++) {
375: base_dist[code] = dist << 7;
376: for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
377: dist_code[256 + dist++] = (uch)code;
378: }
379: }
380: Assert (dist == 256, "ct_init: 256+dist != 512");
381:
382: /* Construct the codes of the static literal tree */
383: for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
384: n = 0;
385: while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
386: while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
387: while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
388: while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
389: /* Codes 286 and 287 do not exist, but we must include them in the
390: * tree construction to get a canonical Huffman tree (longest code
391: * all ones)
392: */
393: gen_codes((ct_data near *)static_ltree, L_CODES+1);
394:
395: /* The static distance tree is trivial: */
396: for (n = 0; n < D_CODES; n++) {
397: static_dtree[n].Len = 5;
398: static_dtree[n].Code = bi_reverse(n, 5);
399: }
400:
401: /* Initialize the first block of the first file: */
402: init_block();
403: }
404:
405: /* ===========================================================================
406: * Initialize a new block.
407: */
408: local void init_block()
409: {
410: int n; /* iterates over tree elements */
411:
412: /* Initialize the trees. */
413: for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
414: for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
415: for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
416:
417: dyn_ltree[END_BLOCK].Freq = 1;
418: opt_len = static_len = 0L;
419: last_lit = last_dist = last_flags = 0;
420: flags = 0; flag_bit = 1;
421: }
422:
423: #define SMALLEST 1
424: /* Index within the heap array of least frequent node in the Huffman tree */
425:
426:
427: /* ===========================================================================
428: * Remove the smallest element from the heap and recreate the heap with
429: * one less element. Updates heap and heap_len.
430: */
431: #define pqremove(tree, top) \
432: {\
433: top = heap[SMALLEST]; \
434: heap[SMALLEST] = heap[heap_len--]; \
435: pqdownheap(tree, SMALLEST); \
436: }
437:
438: /* ===========================================================================
439: * Compares to subtrees, using the tree depth as tie breaker when
440: * the subtrees have equal frequency. This minimizes the worst case length.
441: */
442: #define smaller(tree, n, m) \
443: (tree[n].Freq < tree[m].Freq || \
444: (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
445:
446: /* ===========================================================================
447: * Restore the heap property by moving down the tree starting at node k,
448: * exchanging a node with the smallest of its two sons if necessary, stopping
449: * when the heap property is re-established (each father smaller than its
450: * two sons).
451: */
452: local void pqdownheap(tree, k)
453: ct_data near *tree; /* the tree to restore */
454: int k; /* node to move down */
455: {
456: int v = heap[k];
457: int j = k << 1; /* left son of k */
458: while (j <= heap_len) {
459: /* Set j to the smallest of the two sons: */
460: if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
461:
462: /* Exit if v is smaller than both sons */
463: if (smaller(tree, v, heap[j])) break;
464:
465: /* Exchange v with the smallest son */
466: heap[k] = heap[j]; k = j;
467:
468: /* And continue down the tree, setting j to the left son of k */
469: j <<= 1;
470: }
471: heap[k] = v;
472: }
473:
474: /* ===========================================================================
475: * Compute the optimal bit lengths for a tree and update the total bit length
476: * for the current block.
477: * IN assertion: the fields freq and dad are set, heap[heap_max] and
478: * above are the tree nodes sorted by increasing frequency.
479: * OUT assertions: the field len is set to the optimal bit length, the
480: * array bl_count contains the frequencies for each bit length.
481: * The length opt_len is updated; static_len is also updated if stree is
482: * not null.
483: */
484: local void gen_bitlen(desc)
485: tree_desc near *desc; /* the tree descriptor */
486: {
487: ct_data near *tree = desc->dyn_tree;
488: int near *extra = desc->extra_bits;
489: int base = desc->extra_base;
490: int max_code = desc->max_code;
491: int max_length = desc->max_length;
492: ct_data near *stree = desc->static_tree;
493: int h; /* heap index */
494: int n, m; /* iterate over the tree elements */
495: int bits; /* bit length */
496: int xbits; /* extra bits */
497: ush f; /* frequency */
498: int overflow = 0; /* number of elements with bit length too large */
499:
500: for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
501:
502: /* In a first pass, compute the optimal bit lengths (which may
503: * overflow in the case of the bit length tree).
504: */
505: tree[heap[heap_max]].Len = 0; /* root of the heap */
506:
507: for (h = heap_max+1; h < HEAP_SIZE; h++) {
508: n = heap[h];
509: bits = tree[tree[n].Dad].Len + 1;
510: if (bits > max_length) bits = max_length, overflow++;
511: tree[n].Len = (ush)bits;
512: /* We overwrite tree[n].Dad which is no longer needed */
513:
514: if (n > max_code) continue; /* not a leaf node */
515:
516: bl_count[bits]++;
517: xbits = 0;
518: if (n >= base) xbits = extra[n-base];
519: f = tree[n].Freq;
520: opt_len += (ulg)f * (bits + xbits);
521: if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
522: }
523: if (overflow == 0) return;
524:
525: Trace((stderr,"\nbit length overflow\n"));
526: /* This happens for example on obj2 and pic of the Calgary corpus */
527:
528: /* Find the first bit length which could increase: */
529: do {
530: bits = max_length-1;
531: while (bl_count[bits] == 0) bits--;
532: bl_count[bits]--; /* move one leaf down the tree */
533: bl_count[bits+1] += 2; /* move one overflow item as its brother */
534: bl_count[max_length]--;
535: /* The brother of the overflow item also moves one step up,
536: * but this does not affect bl_count[max_length]
537: */
538: overflow -= 2;
539: } while (overflow > 0);
540:
541: /* Now recompute all bit lengths, scanning in increasing frequency.
542: * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
543: * lengths instead of fixing only the wrong ones. This idea is taken
544: * from 'ar' written by Haruhiko Okumura.)
545: */
546: for (bits = max_length; bits != 0; bits--) {
547: n = bl_count[bits];
548: while (n != 0) {
549: m = heap[--h];
550: if (m > max_code) continue;
551: if (tree[m].Len != (unsigned) bits) {
552: Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
553: opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
554: tree[m].Len = (ush)bits;
555: }
556: n--;
557: }
558: }
559: }
560:
561: /* ===========================================================================
562: * Generate the codes for a given tree and bit counts (which need not be
563: * optimal).
564: * IN assertion: the array bl_count contains the bit length statistics for
565: * the given tree and the field len is set for all tree elements.
566: * OUT assertion: the field code is set for all tree elements of non
567: * zero code length.
568: */
569: local void gen_codes (tree, max_code)
570: ct_data near *tree; /* the tree to decorate */
571: int max_code; /* largest code with non zero frequency */
572: {
573: ush next_code[MAX_BITS+1]; /* next code value for each bit length */
574: ush code = 0; /* running code value */
575: int bits; /* bit index */
576: int n; /* code index */
577:
578: /* The distribution counts are first used to generate the code values
579: * without bit reversal.
580: */
581: for (bits = 1; bits <= MAX_BITS; bits++) {
582: next_code[bits] = code = (code + bl_count[bits-1]) << 1;
583: }
584: /* Check that the bit counts in bl_count are consistent. The last code
585: * must be all ones.
586: */
587: Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
588: "inconsistent bit counts");
589: Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
590:
591: for (n = 0; n <= max_code; n++) {
592: int len = tree[n].Len;
593: if (len == 0) continue;
594: /* Now reverse the bits */
595: tree[n].Code = bi_reverse(next_code[len]++, len);
596:
597: Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
598: n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
599: }
600: }
601:
602: /* ===========================================================================
603: * Construct one Huffman tree and assigns the code bit strings and lengths.
604: * Update the total bit length for the current block.
605: * IN assertion: the field freq is set for all tree elements.
606: * OUT assertions: the fields len and code are set to the optimal bit length
607: * and corresponding code. The length opt_len is updated; static_len is
608: * also updated if stree is not null. The field max_code is set.
609: */
610: local void build_tree(desc)
611: tree_desc near *desc; /* the tree descriptor */
612: {
613: ct_data near *tree = desc->dyn_tree;
614: ct_data near *stree = desc->static_tree;
615: int elems = desc->elems;
616: int n, m; /* iterate over heap elements */
617: int max_code = -1; /* largest code with non zero frequency */
618: int node = elems; /* next internal node of the tree */
619:
620: /* Construct the initial heap, with least frequent element in
621: * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
622: * heap[0] is not used.
623: */
624: heap_len = 0, heap_max = HEAP_SIZE;
625:
626: for (n = 0; n < elems; n++) {
627: if (tree[n].Freq != 0) {
628: heap[++heap_len] = max_code = n;
629: depth[n] = 0;
630: } else {
631: tree[n].Len = 0;
632: }
633: }
634:
635: /* The pkzip format requires that at least one distance code exists,
636: * and that at least one bit should be sent even if there is only one
637: * possible code. So to avoid special checks later on we force at least
638: * two codes of non zero frequency.
639: */
640: while (heap_len < 2) {
641: int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
642: tree[new].Freq = 1;
643: depth[new] = 0;
644: opt_len--; if (stree) static_len -= stree[new].Len;
645: /* new is 0 or 1 so it does not have extra bits */
646: }
647: desc->max_code = max_code;
648:
649: /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
650: * establish sub-heaps of increasing lengths:
651: */
652: for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
653:
654: /* Construct the Huffman tree by repeatedly combining the least two
655: * frequent nodes.
656: */
657: do {
658: pqremove(tree, n); /* n = node of least frequency */
659: m = heap[SMALLEST]; /* m = node of next least frequency */
660:
661: heap[--heap_max] = n; /* keep the nodes sorted by frequency */
662: heap[--heap_max] = m;
663:
664: /* Create a new node father of n and m */
665: tree[node].Freq = tree[n].Freq + tree[m].Freq;
666: depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
667: tree[n].Dad = tree[m].Dad = (ush)node;
668: #ifdef DUMP_BL_TREE
669: if (tree == bl_tree) {
670: fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
671: node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
672: }
673: #endif
674: /* and insert the new node in the heap */
675: heap[SMALLEST] = node++;
676: pqdownheap(tree, SMALLEST);
677:
678: } while (heap_len >= 2);
679:
680: heap[--heap_max] = heap[SMALLEST];
681:
682: /* At this point, the fields freq and dad are set. We can now
683: * generate the bit lengths.
684: */
685: gen_bitlen((tree_desc near *)desc);
686:
687: /* The field len is now set, we can generate the bit codes */
688: gen_codes ((ct_data near *)tree, max_code);
689: }
690:
691: /* ===========================================================================
692: * Scan a literal or distance tree to determine the frequencies of the codes
693: * in the bit length tree. Updates opt_len to take into account the repeat
694: * counts. (The contribution of the bit length codes will be added later
695: * during the construction of bl_tree.)
696: */
697: local void scan_tree (tree, max_code)
698: ct_data near *tree; /* the tree to be scanned */
699: int max_code; /* and its largest code of non zero frequency */
700: {
701: int n; /* iterates over all tree elements */
702: int prevlen = -1; /* last emitted length */
703: int curlen; /* length of current code */
704: int nextlen = tree[0].Len; /* length of next code */
705: int count = 0; /* repeat count of the current code */
706: int max_count = 7; /* max repeat count */
707: int min_count = 4; /* min repeat count */
708:
709: if (nextlen == 0) max_count = 138, min_count = 3;
710: tree[max_code+1].Len = (ush)-1; /* guard */
711:
712: for (n = 0; n <= max_code; n++) {
713: curlen = nextlen; nextlen = tree[n+1].Len;
714: if (++count < max_count && curlen == nextlen) {
715: continue;
716: } else if (count < min_count) {
717: bl_tree[curlen].Freq += count;
718: } else if (curlen != 0) {
719: if (curlen != prevlen) bl_tree[curlen].Freq++;
720: bl_tree[REP_3_6].Freq++;
721: } else if (count <= 10) {
722: bl_tree[REPZ_3_10].Freq++;
723: } else {
724: bl_tree[REPZ_11_138].Freq++;
725: }
726: count = 0; prevlen = curlen;
727: if (nextlen == 0) {
728: max_count = 138, min_count = 3;
729: } else if (curlen == nextlen) {
730: max_count = 6, min_count = 3;
731: } else {
732: max_count = 7, min_count = 4;
733: }
734: }
735: }
736:
737: /* ===========================================================================
738: * Send a literal or distance tree in compressed form, using the codes in
739: * bl_tree.
740: */
741: local void send_tree (tree, max_code)
742: ct_data near *tree; /* the tree to be scanned */
743: int max_code; /* and its largest code of non zero frequency */
744: {
745: int n; /* iterates over all tree elements */
746: int prevlen = -1; /* last emitted length */
747: int curlen; /* length of current code */
748: int nextlen = tree[0].Len; /* length of next code */
749: int count = 0; /* repeat count of the current code */
750: int max_count = 7; /* max repeat count */
751: int min_count = 4; /* min repeat count */
752:
753: /* tree[max_code+1].Len = -1; */ /* guard already set */
754: if (nextlen == 0) max_count = 138, min_count = 3;
755:
756: for (n = 0; n <= max_code; n++) {
757: curlen = nextlen; nextlen = tree[n+1].Len;
758: if (++count < max_count && curlen == nextlen) {
759: continue;
760: } else if (count < min_count) {
761: do { send_code(curlen, bl_tree); } while (--count != 0);
762:
763: } else if (curlen != 0) {
764: if (curlen != prevlen) {
765: send_code(curlen, bl_tree); count--;
766: }
767: Assert(count >= 3 && count <= 6, " 3_6?");
768: send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
769:
770: } else if (count <= 10) {
771: send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
772:
773: } else {
774: send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
775: }
776: count = 0; prevlen = curlen;
777: if (nextlen == 0) {
778: max_count = 138, min_count = 3;
779: } else if (curlen == nextlen) {
780: max_count = 6, min_count = 3;
781: } else {
782: max_count = 7, min_count = 4;
783: }
784: }
785: }
786:
787: /* ===========================================================================
788: * Construct the Huffman tree for the bit lengths and return the index in
789: * bl_order of the last bit length code to send.
790: */
791: local int build_bl_tree()
792: {
793: int max_blindex; /* index of last bit length code of non zero freq */
794:
795: /* Determine the bit length frequencies for literal and distance trees */
796: scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
797: scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
798:
799: /* Build the bit length tree: */
800: build_tree((tree_desc near *)(&bl_desc));
801: /* opt_len now includes the length of the tree representations, except
802: * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
803: */
804:
805: /* Determine the number of bit length codes to send. The pkzip format
806: * requires that at least 4 bit length codes be sent. (appnote.txt says
807: * 3 but the actual value used is 4.)
808: */
809: for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
810: if (bl_tree[bl_order[max_blindex]].Len != 0) break;
811: }
812: /* Update opt_len to include the bit length tree and counts */
813: opt_len += 3*(max_blindex+1) + 5+5+4;
814: Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len));
815:
816: return max_blindex;
817: }
818:
819: /* ===========================================================================
820: * Send the header for a block using dynamic Huffman trees: the counts, the
821: * lengths of the bit length codes, the literal tree and the distance tree.
822: * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
823: */
824: local void send_all_trees(lcodes, dcodes, blcodes)
825: int lcodes, dcodes, blcodes; /* number of codes for each tree */
826: {
827: int rank; /* index in bl_order */
828:
829: Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
830: Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
831: "too many codes");
832: Tracev((stderr, "\nbl counts: "));
833: send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
834: send_bits(dcodes-1, 5);
835: send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
836: for (rank = 0; rank < blcodes; rank++) {
837: Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
838: send_bits(bl_tree[bl_order[rank]].Len, 3);
839: }
840: Tracev((stderr, "\nbl tree: sent %ld", bits_sent));
841:
842: send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
843: Tracev((stderr, "\nlit tree: sent %ld", bits_sent));
844:
845: send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
846: Tracev((stderr, "\ndist tree: sent %ld", bits_sent));
847: }
848:
849: /* ===========================================================================
850: * Determine the best encoding for the current block: dynamic trees, static
851: * trees or store, and output the encoded block to the zip file. This function
852: * returns the total compressed length for the file so far.
853: */
854: ulg flush_block(buf, stored_len, eof)
855: char *buf; /* input block, or NULL if too old */
856: ulg stored_len; /* length of input block */
857: int eof; /* true if this is the last block for a file */
858: {
859: ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
860: int max_blindex; /* index of last bit length code of non zero freq */
861:
862: flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
863:
864: /* Check if the file is ascii or binary */
865: if (*file_type == (ush)UNKNOWN) set_file_type();
866:
867: /* Construct the literal and distance trees */
868: build_tree((tree_desc near *)(&l_desc));
869: Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len));
870:
871: build_tree((tree_desc near *)(&d_desc));
872: Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len));
873: /* At this point, opt_len and static_len are the total bit lengths of
874: * the compressed block data, excluding the tree representations.
875: */
876:
877: /* Build the bit length tree for the above two trees, and get the index
878: * in bl_order of the last bit length code to send.
879: */
880: max_blindex = build_bl_tree();
881:
882: /* Determine the best encoding. Compute first the block length in bytes */
883: opt_lenb = (opt_len+3+7)>>3;
884: static_lenb = (static_len+3+7)>>3;
885: input_len += stored_len; /* for debugging only */
886:
887: Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
888: opt_lenb, opt_len, static_lenb, static_len, stored_len,
889: last_lit, last_dist));
890:
891: if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
892:
893: /* If compression failed and this is the first and last block,
894: * and if the zip file can be seeked (to rewrite the local header),
895: * the whole file is transformed into a stored file:
896: */
897: #ifdef FORCE_METHOD
898: if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
899: #else
900: if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
901: #endif
902: /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
903: if (buf == (char*)0) error ("block vanished");
904:
905: copy_block(buf, (unsigned)stored_len, 0); /* without header */
906: compressed_len = stored_len << 3;
907: *file_method = STORED;
908:
909: #ifdef FORCE_METHOD
910: } else if (level == 2 && buf != (char*)0) { /* force stored block */
911: #else
912: } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
913: /* 4: two words for the lengths */
914: #endif
915: /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
916: * Otherwise we can't have processed more than WSIZE input bytes since
917: * the last block flush, because compression would have been
918: * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
919: * transform a block into a stored block.
920: */
921: send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
922: compressed_len = (compressed_len + 3 + 7) & ~7L;
923: compressed_len += (stored_len + 4) << 3;
924:
925: copy_block(buf, (unsigned)stored_len, 1); /* with header */
926:
927: #ifdef FORCE_METHOD
928: } else if (level == 3) { /* force static trees */
929: #else
930: } else if (static_lenb == opt_lenb) {
931: #endif
932: send_bits((STATIC_TREES<<1)+eof, 3);
933: compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
934: compressed_len += 3 + static_len;
935: } else {
936: send_bits((DYN_TREES<<1)+eof, 3);
937: send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
938: compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
939: compressed_len += 3 + opt_len;
940: }
941: Assert (compressed_len == bits_sent, "bad compressed size");
942: init_block();
943:
944: if (eof) {
945: Assert (input_len == isize, "bad input size");
946: bi_windup();
947: compressed_len += 7; /* align on byte boundary */
948: }
949: Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3,
950: compressed_len-7*eof));
951:
952: return compressed_len >> 3;
953: }
954:
955: /* ===========================================================================
956: * Save the match info and tally the frequency counts. Return true if
957: * the current block must be flushed.
958: */
959: int ct_tally (dist, lc)
960: int dist; /* distance of matched string */
961: int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
962: {
963: l_buf[last_lit++] = (uch)lc;
964: if (dist == 0) {
965: /* lc is the unmatched char */
966: dyn_ltree[lc].Freq++;
967: } else {
968: /* Here, lc is the match length - MIN_MATCH */
969: dist--; /* dist = match distance - 1 */
970: Assert((ush)dist < (ush)MAX_DIST &&
971: (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
972: (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
973:
974: dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
975: dyn_dtree[d_code(dist)].Freq++;
976:
977: d_buf[last_dist++] = (ush)dist;
978: flags |= flag_bit;
979: }
980: flag_bit <<= 1;
981:
982: /* Output the flags if they fill a byte: */
983: if ((last_lit & 7) == 0) {
984: flag_buf[last_flags++] = flags;
985: flags = 0, flag_bit = 1;
986: }
987: /* Try to guess if it is profitable to stop the current block here */
988: if (level > 2 && (last_lit & 0xfff) == 0) {
989: /* Compute an upper bound for the compressed length */
990: ulg out_length = (ulg)last_lit*8L;
991: ulg in_length = (ulg)strstart-block_start;
992: int dcode;
993: for (dcode = 0; dcode < D_CODES; dcode++) {
994: out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
995: }
996: out_length >>= 3;
997: Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
998: last_lit, last_dist, in_length, out_length,
999: 100L - out_length*100L/in_length));
1000: if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1001: }
1002: return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1003: /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1004: * on 16 bit machines and because stored blocks are restricted to
1005: * 64K-1 bytes.
1006: */
1007: }
1008:
1009: /* ===========================================================================
1010: * Send the block data compressed using the given Huffman trees
1011: */
1012: local void compress_block(ltree, dtree)
1013: ct_data near *ltree; /* literal tree */
1014: ct_data near *dtree; /* distance tree */
1015: {
1016: unsigned dist; /* distance of matched string */
1017: int lc; /* match length or unmatched char (if dist == 0) */
1018: unsigned lx = 0; /* running index in l_buf */
1019: unsigned dx = 0; /* running index in d_buf */
1020: unsigned fx = 0; /* running index in flag_buf */
1021: uch flag = 0; /* current flags */
1022: unsigned code; /* the code to send */
1023: int extra; /* number of extra bits to send */
1024:
1025: if (last_lit != 0) do {
1026: if ((lx & 7) == 0) flag = flag_buf[fx++];
1027: lc = l_buf[lx++];
1028: if ((flag & 1) == 0) {
1029: send_code(lc, ltree); /* send a literal byte */
1030: Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1031: } else {
1032: /* Here, lc is the match length - MIN_MATCH */
1033: code = length_code[lc];
1034: send_code(code+LITERALS+1, ltree); /* send the length code */
1035: extra = extra_lbits[code];
1036: if (extra != 0) {
1037: lc -= base_length[code];
1038: send_bits(lc, extra); /* send the extra length bits */
1039: }
1040: dist = d_buf[dx++];
1041: /* Here, dist is the match distance - 1 */
1042: code = d_code(dist);
1043: Assert (code < D_CODES, "bad d_code");
1044:
1045: send_code(code, dtree); /* send the distance code */
1046: extra = extra_dbits[code];
1047: if (extra != 0) {
1048: dist -= base_dist[code];
1049: send_bits(dist, extra); /* send the extra distance bits */
1050: }
1051: } /* literal or match pair ? */
1052: flag >>= 1;
1053: } while (lx < last_lit);
1054:
1055: send_code(END_BLOCK, ltree);
1056: }
1057:
1058: /* ===========================================================================
1059: * Set the file type to ASCII or BINARY, using a crude approximation:
1060: * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1061: * IN assertion: the fields freq of dyn_ltree are set and the total of all
1062: * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1063: */
1064: local void set_file_type()
1065: {
1066: int n = 0;
1067: unsigned ascii_freq = 0;
1068: unsigned bin_freq = 0;
1069: while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1070: while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1071: while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1072: *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1073: if (*file_type == BINARY && translate_eol) {
1074: warn("-l used on binary file", "");
1075: }
1076: }
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