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1.1.1.2 root 1: /*
2:
3: Copyright (C) 1990-1992 Mark Adler, Richard B. Wales, Jean-loup Gailly,
4: Kai Uwe Rommel and Igor Mandrichenko.
5: Permission is granted to any individual or institution to use, copy, or
6: redistribute this software so long as all of the original files are included
7: unmodified, that it is not sold for profit, and that this copyright notice
8: is retained.
9:
10: */
11:
12: /*
13: * trees.c by Jean-loup Gailly
14: *
15: * This is a new version of im_ctree.c originally written by Richard B. Wales
16: * for the defunct implosion method.
17: *
18: * PURPOSE
19: *
20: * Encode various sets of source values using variable-length
21: * binary code trees.
22: *
23: * DISCUSSION
24: *
25: * The PKZIP "deflation" process uses several Huffman trees. The more
26: * common source values are represented by shorter bit sequences.
27: *
28: * Each code tree is stored in the ZIP file in a compressed form
29: * which is itself a Huffman encoding of the lengths of
30: * all the code strings (in ascending order by source values).
31: * The actual code strings are reconstructed from the lengths in
32: * the UNZIP process, as described in the "application note"
33: * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
34: *
35: * REFERENCES
36: *
37: * Lynch, Thomas J.
38: * Data Compression: Techniques and Applications, pp. 53-55.
39: * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
40: *
41: * Storer, James A.
42: * Data Compression: Methods and Theory, pp. 49-50.
43: * Computer Science Press, 1988. ISBN 0-7167-8156-5.
44: *
45: * Sedgewick, R.
46: * Algorithms, p290.
47: * Addison-Wesley, 1983. ISBN 0-201-06672-6.
48: *
49: * INTERFACE
50: *
51: * void ct_init (ush *attr, int *method)
52: * Allocate the match buffer, initialize the various tables and save
53: * the location of the internal file attribute (ascii/binary) and
54: * method (DEFLATE/STORE)
55: *
56: * void ct_tally (int dist, int lc);
57: * Save the match info and tally the frequency counts.
58: *
59: * long flush_block (char *buf, ulg stored_len, int eof)
60: * Determine the best encoding for the current block: dynamic trees,
61: * static trees or store, and output the encoded block to the zip
62: * file. Returns the total compressed length for the file so far.
63: *
64: */
65:
66: #include <ctype.h>
67: #include "zip.h"
68:
69: /* ===========================================================================
70: * Constants
71: */
72:
73: #define MAX_BITS 15
74: /* All codes must not exceed MAX_BITS bits */
75:
76: #define MAX_BL_BITS 7
77: /* Bit length codes must not exceed MAX_BL_BITS bits */
78:
79: #define LENGTH_CODES 29
80: /* number of length codes, not counting the special END_BLOCK code */
81:
82: #define LITERALS 256
83: /* number of literal bytes 0..255 */
84:
85: #define END_BLOCK 256
86: /* end of block literal code */
87:
88: #define L_CODES (LITERALS+1+LENGTH_CODES)
89: /* number of Literal or Length codes, including the END_BLOCK code */
90:
91: #define D_CODES 30
92: /* number of distance codes */
93:
94: #define BL_CODES 19
95: /* number of codes used to transfer the bit lengths */
96:
97:
98: local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
99: = {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};
100:
101: local int near extra_dbits[D_CODES] /* extra bits for each distance code */
102: = {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};
103:
104: local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
105: = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
106:
107: #define STORED_BLOCK 0
108: #define STATIC_TREES 1
109: #define DYN_TREES 2
110: /* The three kinds of block type */
111:
112: #ifndef LIT_BUFSIZE
113: # ifdef SMALL_MEM
114: # define LIT_BUFSIZE 0x2000
115: # else
116: # ifdef MEDIUM_MEM
117: # define LIT_BUFSIZE 0x4000
118: # else
119: # define LIT_BUFSIZE 0x8000
120: # endif
121: # endif
122: #endif
123: #define DIST_BUFSIZE LIT_BUFSIZE
124: /* Sizes of match buffers for literals/lengths and distances. There are
125: * 4 reasons for limiting LIT_BUFSIZE to 64K:
126: * - frequencies can be kept in 16 bit counters
127: * - if compression is not successful for the first block, all input data is
128: * still in the window so we can still emit a stored block even when input
129: * comes from standard input. (This can also be done for all blocks if
130: * LIT_BUFSIZE is not greater than 32K.)
131: * - if compression is not successful for a file smaller than 64K, we can
132: * even emit a stored file instead of a stored block (saving 5 bytes).
133: * - creating new Huffman trees less frequently may not provide fast
134: * adaptation to changes in the input data statistics. (Take for
135: * example a binary file with poorly compressible code followed by
136: * a highly compressible string table.) Smaller buffer sizes give
137: * fast adaptation but have of course the overhead of transmitting trees
138: * more frequently.
139: * - I can't count above 4
140: * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
141: * memory at the expense of compression). Some optimizations would be possible
142: * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
143: */
144:
145: #define REP_3_6 16
146: /* repeat previous bit length 3-6 times (2 bits of repeat count) */
147:
148: #define REPZ_3_10 17
149: /* repeat a zero length 3-10 times (3 bits of repeat count) */
150:
151: #define REPZ_11_138 18
152: /* repeat a zero length 11-138 times (7 bits of repeat count) */
153:
154: /* ===========================================================================
155: * Local data
156: */
157:
158: /* Data structure describing a single value and its code string. */
159: typedef struct ct_data {
160: union {
161: ush freq; /* frequency count */
162: ush code; /* bit string */
163: } fc;
164: union {
165: ush dad; /* father node in Huffman tree */
166: ush len; /* length of bit string */
167: } dl;
168: } ct_data;
169:
170: #define Freq fc.freq
171: #define Code fc.code
172: #define Dad dl.dad
173: #define Len dl.len
174:
175: #define HEAP_SIZE (2*L_CODES+1)
176: /* maximum heap size */
177:
178: local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
179: local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
180:
181: local ct_data near static_ltree[L_CODES+2];
182: /* The static literal tree. Since the bit lengths are imposed, there is no
183: * need for the L_CODES extra codes used during heap construction. However
184: * The codes 286 and 287 are needed to build a canonical tree (see ct_init
185: * below).
186: */
187:
188: local ct_data near static_dtree[D_CODES];
189: /* The static distance tree. (Actually a trivial tree since all codes use
190: * 5 bits.)
191: */
192:
193: local ct_data near bl_tree[2*BL_CODES+1];
194: /* Huffman tree for the bit lengths */
195:
196: typedef struct tree_desc {
197: ct_data near *dyn_tree; /* the dynamic tree */
198: ct_data near *static_tree; /* corresponding static tree or NULL */
199: int near *extra_bits; /* extra bits for each code or NULL */
200: int extra_base; /* base index for extra_bits */
201: int elems; /* max number of elements in the tree */
202: int max_length; /* max bit length for the codes */
203: int max_code; /* largest code with non zero frequency */
204: } tree_desc;
205:
206: local tree_desc near l_desc =
207: {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
208:
209: local tree_desc near d_desc =
210: {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
211:
212: local tree_desc near bl_desc =
213: {bl_tree, NULL, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
214:
215:
216: local ush near bl_count[MAX_BITS+1];
217: /* number of codes at each bit length for an optimal tree */
218:
219: local uch near bl_order[BL_CODES]
220: = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
221: /* The lengths of the bit length codes are sent in order of decreasing
222: * probability, to avoid transmitting the lengths for unused bit length codes.
223: */
224:
225: local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
226: local int heap_len; /* number of elements in the heap */
227: local int heap_max; /* element of largest frequency */
228: /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
229: * The same heap array is used to build all trees.
230: */
231:
232: local uch near depth[2*L_CODES+1];
233: /* Depth of each subtree used as tie breaker for trees of equal frequency */
234:
235: local uch length_code[MAX_MATCH-MIN_MATCH+1];
236: /* length code for each normalized match length (0 == MIN_MATCH) */
237:
238: local uch dist_code[512];
239: /* distance codes. The first 256 values correspond to the distances
240: * 3 .. 258, the last 256 values correspond to the top 8 bits of
241: * the 15 bit distances.
242: */
243:
244: local int near base_length[LENGTH_CODES];
245: /* First normalized length for each code (0 = MIN_MATCH) */
246:
247: local int near base_dist[D_CODES];
248: /* First normalized distance for each code (0 = distance of 1) */
249:
250: #ifndef DYN_ALLOC
251: local uch far l_buf[LIT_BUFSIZE]; /* buffer for literals/lengths */
252: local ush far d_buf[DIST_BUFSIZE]; /* buffer for distances */
253: #else
254: local uch far *l_buf;
255: local ush far *d_buf;
256: #endif
257:
258: local uch near flag_buf[(LIT_BUFSIZE/8)];
259: /* flag_buf is a bit array distinguishing literals from lengths in
260: * l_buf, and thus indicating the presence or absence of a distance.
261: */
262:
263: local unsigned last_lit; /* running index in l_buf */
264: local unsigned last_dist; /* running index in d_buf */
265: local unsigned last_flags; /* running index in flag_buf */
266: local uch flags; /* current flags not yet saved in flag_buf */
267: local uch flag_bit; /* current bit used in flags */
268: /* bits are filled in flags starting at bit 0 (least significant).
269: * Note: these flags are overkill in the current code since we don't
270: * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
271: */
272:
273: local ulg opt_len; /* bit length of current block with optimal trees */
274: local ulg static_len; /* bit length of current block with static trees */
275:
276: local ulg compressed_len; /* total bit length of compressed file */
277:
278: local ulg input_len; /* total byte length of input file */
279: /* input_len is for debugging only since we can get it by other means. */
280:
1.1.1.3 ! root 281: static ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
! 282: static int *file_method; /* pointer to DEFLATE or STORE */
1.1.1.2 root 283:
284: #ifdef DEBUG
285: extern ulg bits_sent; /* bit length of the compressed data */
286: extern ulg isize; /* byte length of input file */
287: #endif
288:
289: extern long block_start; /* window offset of current block */
290: extern unsigned near strstart; /* window offset of current string */
291:
292: /* ===========================================================================
293: * Local (static) routines in this file.
294: */
295:
296: local void init_block OF((void));
297: local void pqdownheap OF((ct_data near *tree, int k));
298: local void gen_bitlen OF((tree_desc near *desc));
299: local void gen_codes OF((ct_data near *tree, int max_code));
300: local void build_tree OF((tree_desc near *desc));
301: local void scan_tree OF((ct_data near *tree, int max_code));
302: local void send_tree OF((ct_data near *tree, int max_code));
303: local int build_bl_tree OF((void));
304: local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
305: local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
306: local void set_file_type OF((void));
307:
308:
309: #ifndef DEBUG
310: # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
311: /* Send a code of the given tree. c and tree must not have side effects */
312:
313: #else /* DEBUG */
314: # define send_code(c, tree) \
315: { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
316: send_bits(tree[c].Code, tree[c].Len); }
317: #endif
318:
319: #define d_code(dist) \
320: ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
321: /* Mapping from a distance to a distance code. dist is the distance - 1 and
322: * must not have side effects. dist_code[256] and dist_code[257] are never
323: * used.
324: */
325:
326: #define MAX(a,b) (a >= b ? a : b)
327: /* the arguments must not have side effects */
328:
329: /* ===========================================================================
330: * Allocate the match buffer, initialize the various tables and save the
331: * location of the internal file attribute (ascii/binary) and method
332: * (DEFLATE/STORE).
333: */
1.1.1.3 ! root 334: void ct_init(attr, Method)
1.1.1.2 root 335: ush *attr; /* pointer to internal file attribute */
1.1.1.3 ! root 336: int *Method; /* pointer to compression method */
1.1.1.2 root 337: {
338: int n; /* iterates over tree elements */
339: int bits; /* bit counter */
340: int length; /* length value */
341: int code; /* code value */
342: int dist; /* distance index */
343:
344: file_type = attr;
1.1.1.3 ! root 345: file_method = Method;
1.1.1.2 root 346: compressed_len = input_len = 0L;
347:
348: #ifdef DYN_ALLOC
349: d_buf = (ush far*) fcalloc(DIST_BUFSIZE, sizeof(ush));
350: l_buf = (uch far*) fcalloc(LIT_BUFSIZE/2, 2);
351: /* Avoid using the value 64K on 16 bit machines */
352: if (l_buf == NULL || d_buf == NULL) error("ct_init: out of memory");
353: #endif
354:
1.1.1.3 ! root 355: if (static_dtree[0].Len != 0) return; /* ct_init already called */
! 356:
1.1.1.2 root 357: /* Initialize the mapping length (0..255) -> length code (0..28) */
358: length = 0;
359: for (code = 0; code < LENGTH_CODES-1; code++) {
360: base_length[code] = length;
361: for (n = 0; n < (1<<extra_lbits[code]); n++) {
362: length_code[length++] = (uch)code;
363: }
364: }
365: Assert (length == 256, "ct_init: length != 256");
366: /* Note that the length 255 (match length 258) can be represented
367: * in two different ways: code 284 + 5 bits or code 285, so we
368: * overwrite length_code[255] to use the best encoding:
369: */
370: length_code[length-1] = (uch)code;
371:
372: /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
373: dist = 0;
374: for (code = 0 ; code < 16; code++) {
375: base_dist[code] = dist;
376: for (n = 0; n < (1<<extra_dbits[code]); n++) {
377: dist_code[dist++] = (uch)code;
378: }
379: }
380: Assert (dist == 256, "ct_init: dist != 256");
381: dist >>= 7; /* from now on, all distances are divided by 128 */
382: for ( ; code < D_CODES; code++) {
383: base_dist[code] = dist << 7;
384: for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
385: dist_code[256 + dist++] = (uch)code;
386: }
387: }
388: Assert (dist == 256, "ct_init: 256+dist != 512");
389:
390: /* Construct the codes of the static literal tree */
391: for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
392: n = 0;
393: while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
394: while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
395: while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
396: while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
397: /* Codes 286 and 287 do not exist, but we must include them in the
398: * tree construction to get a canonical Huffman tree (longest code
399: * all ones)
400: */
401: gen_codes(static_ltree, L_CODES+1);
402:
403: /* The static distance tree is trivial: */
404: for (n = 0; n < D_CODES; n++) {
405: static_dtree[n].Len = 5;
406: static_dtree[n].Code = bi_reverse(n, 5);
407: }
408:
409: /* Initialize the first block of the first file: */
410: init_block();
411: }
412:
1.1.1.3 ! root 413: void ct_free()
! 414: {
! 415: #ifdef DYN_ALLOC
! 416: free(d_buf);
! 417: free(l_buf);
! 418: d_buf = NULL;
! 419: l_buf = NULL;
! 420: #endif
! 421: }
! 422:
1.1.1.2 root 423: /* ===========================================================================
424: * Initialize a new block.
425: */
426: local void init_block()
427: {
428: int n; /* iterates over tree elements */
429:
430: /* Initialize the trees. */
431: for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
432: for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
433: for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
434:
435: dyn_ltree[END_BLOCK].Freq = 1;
436: opt_len = static_len = 0L;
437: last_lit = last_dist = last_flags = 0;
438: flags = 0; flag_bit = 1;
439: }
440:
441: #define SMALLEST 1
442: /* Index within the heap array of least frequent node in the Huffman tree */
443:
444:
445: /* ===========================================================================
446: * Remove the smallest element from the heap and recreate the heap with
447: * one less element. Updates heap and heap_len.
448: */
449: #define pqremove(tree, top) \
450: {\
451: top = heap[SMALLEST]; \
452: heap[SMALLEST] = heap[heap_len--]; \
453: pqdownheap(tree, SMALLEST); \
454: }
455:
456: /* ===========================================================================
457: * Compares to subtrees, using the tree depth as tie breaker when
458: * the subtrees have equal frequency. This minimizes the worst case length.
459: */
460: #define smaller(tree, n, m) \
461: (tree[n].Freq < tree[m].Freq || \
462: (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
463:
464: /* ===========================================================================
465: * Restore the heap property by moving down the tree starting at node k,
466: * exchanging a node with the smallest of its two sons if necessary, stopping
467: * when the heap property is re-established (each father smaller than its
468: * two sons).
469: */
470: local void pqdownheap(tree, k)
471: ct_data near *tree; /* the tree to restore */
472: int k; /* node to move down */
473: {
474: int v = heap[k];
475: int j = k << 1; /* left son of k */
476: while (j <= heap_len) {
477: /* Set j to the smallest of the two sons: */
478: if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
479:
480: /* Exit if v is smaller than both sons */
481: if (smaller(tree, v, heap[j])) break;
482:
483: /* Exchange v with the smallest son */
484: heap[k] = heap[j], k = j;
485:
486: /* And continue down the tree, setting j to the left son of k */
487: j <<= 1;
488: }
489: heap[k] = v;
490: }
491:
492: /* ===========================================================================
493: * Compute the optimal bit lengths for a tree and update the total bit length
494: * for the current block.
495: * IN assertion: the fields freq and dad are set, heap[heap_max] and
496: * above are the tree nodes sorted by increasing frequency.
497: * OUT assertions: the field len is set to the optimal bit length, the
498: * array bl_count contains the frequencies for each bit length.
499: * The length opt_len is updated; static_len is also updated if stree is
500: * not null.
501: */
502: local void gen_bitlen(desc)
503: tree_desc near *desc; /* the tree descriptor */
504: {
505: ct_data near *tree = desc->dyn_tree;
506: int near *extra = desc->extra_bits;
507: int base = desc->extra_base;
508: int max_code = desc->max_code;
509: int max_length = desc->max_length;
510: ct_data near *stree = desc->static_tree;
511: int h; /* heap index */
512: int n, m; /* iterate over the tree elements */
513: int bits; /* bit length */
514: int xbits; /* extra bits */
515: ush f; /* frequency */
516: int overflow = 0; /* number of elements with bit length too large */
517:
518: for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
519:
520: /* In a first pass, compute the optimal bit lengths (which may
521: * overflow in the case of the bit length tree).
522: */
523: tree[heap[heap_max]].Len = 0; /* root of the heap */
524:
525: for (h = heap_max+1; h < HEAP_SIZE; h++) {
526: n = heap[h];
527: bits = tree[tree[n].Dad].Len + 1;
528: if (bits > max_length) bits = max_length, overflow++;
529: tree[n].Len = bits;
530: /* We overwrite tree[n].Dad which is no longer needed */
531:
532: if (n > max_code) continue; /* not a leaf node */
533:
534: bl_count[bits]++;
535: xbits = 0;
536: if (n >= base) xbits = extra[n-base];
537: f = tree[n].Freq;
538: opt_len += (ulg)f * (bits + xbits);
539: if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
540: }
541: if (overflow == 0) return;
542:
543: Trace((stderr,"\nbit length overflow\n"));
544: /* This happens for example on obj2 and pic of the Calgary corpus */
545:
546: /* Find the first bit length which could increase: */
547: do {
548: bits = max_length-1;
549: while (bl_count[bits] == 0) bits--;
550: bl_count[bits]--; /* move one leaf down the tree */
551: bl_count[bits+1] += 2; /* move one overflow item as its brother */
552: bl_count[max_length]--;
553: /* The brother of the overflow item also moves one step up,
554: * but this does not affect bl_count[max_length]
555: */
556: overflow -= 2;
557: } while (overflow > 0);
558:
559: /* Now recompute all bit lengths, scanning in increasing frequency.
560: * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
561: * lengths instead of fixing only the wrong ones. This idea is taken
562: * from 'ar' written by Haruhiko Okumura.)
563: */
564: for (bits = max_length; bits != 0; bits--) {
565: n = bl_count[bits];
566: while (n != 0) {
567: m = heap[--h];
568: if (m > max_code) continue;
569: if (tree[m].Len != (unsigned) bits) {
570: Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
571: opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
572: tree[m].Len = bits;
573: }
574: n--;
575: }
576: }
577: }
578:
579: /* ===========================================================================
580: * Generate the codes for a given tree and bit counts (which need not be
581: * optimal).
582: * IN assertion: the array bl_count contains the bit length statistics for
583: * the given tree and the field len is set for all tree elements.
584: * OUT assertion: the field code is set for all tree elements of non
585: * zero code length.
586: */
587: local void gen_codes (tree, max_code)
588: ct_data near *tree; /* the tree to decorate */
589: int max_code; /* largest code with non zero frequency */
590: {
591: ush next_code[MAX_BITS+1]; /* next code value for each bit length */
592: ush code = 0; /* running code value */
593: int bits; /* bit index */
594: int n; /* code index */
595:
596: /* The distribution counts are first used to generate the code values
597: * without bit reversal.
598: */
599: for (bits = 1; bits <= MAX_BITS; bits++) {
600: next_code[bits] = code = (code + bl_count[bits-1]) << 1;
601: }
602: /* Check that the bit counts in bl_count are consistent. The last code
603: * must be all ones.
604: */
605: Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
606: "inconsistent bit counts");
607: Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
608:
609: for (n = 0; n <= max_code; n++) {
610: int len = tree[n].Len;
611: if (len == 0) continue;
612: /* Now reverse the bits */
613: tree[n].Code = bi_reverse(next_code[len]++, len);
614:
615: Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
616: n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
617: }
618: }
619:
620: /* ===========================================================================
621: * Construct one Huffman tree and assigns the code bit strings and lengths.
622: * Update the total bit length for the current block.
623: * IN assertion: the field freq is set for all tree elements.
624: * OUT assertions: the fields len and code are set to the optimal bit length
625: * and corresponding code. The length opt_len is updated; static_len is
626: * also updated if stree is not null. The field max_code is set.
627: */
628: local void build_tree(desc)
629: tree_desc near *desc; /* the tree descriptor */
630: {
631: ct_data near *tree = desc->dyn_tree;
632: ct_data near *stree = desc->static_tree;
633: int elems = desc->elems;
634: int n, m; /* iterate over heap elements */
635: int max_code = -1; /* largest code with non zero frequency */
636: int node = elems; /* next internal node of the tree */
637:
638: /* Construct the initial heap, with least frequent element in
639: * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
640: * heap[0] is not used.
641: */
642: heap_len = 0, heap_max = HEAP_SIZE;
643:
644: for (n = 0; n < elems; n++) {
645: if (tree[n].Freq != 0) {
646: heap[++heap_len] = max_code = n;
647: depth[n] = 0;
648: } else {
649: tree[n].Len = 0;
650: }
651: }
652:
653: /* The pkzip format requires that at least one distance code exists,
654: * and that at least one bit should be sent even if there is only one
655: * possible code. So to avoid special checks later on we force at least
656: * two codes of non zero frequency.
657: */
658: while (heap_len < 2) {
659: int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
660: tree[new].Freq = 1;
661: depth[new] = 0;
662: opt_len--; if (stree) static_len -= stree[new].Len;
663: /* new is 0 or 1 so it does not have extra bits */
664: }
665: desc->max_code = max_code;
666:
667: /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
668: * establish sub-heaps of increasing lengths:
669: */
670: for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
671:
672: /* Construct the Huffman tree by repeatedly combining the least two
673: * frequent nodes.
674: */
675: do {
676: pqremove(tree, n); /* n = node of least frequency */
677: m = heap[SMALLEST]; /* m = node of next least frequency */
678:
679: heap[--heap_max] = n; /* keep the nodes sorted by frequency */
680: heap[--heap_max] = m;
681:
682: /* Create a new node father of n and m */
683: tree[node].Freq = tree[n].Freq + tree[m].Freq;
684: depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
685: tree[n].Dad = tree[m].Dad = node;
686: #ifdef DUMP_BL_TREE
687: if (tree == bl_tree) {
688: fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
689: node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
690: }
691: #endif
692: /* and insert the new node in the heap */
693: heap[SMALLEST] = node++;
694: pqdownheap(tree, SMALLEST);
695:
696: } while (heap_len >= 2);
697:
698: heap[--heap_max] = heap[SMALLEST];
699:
700: /* At this point, the fields freq and dad are set. We can now
701: * generate the bit lengths.
702: */
703: gen_bitlen(desc);
704:
705: /* The field len is now set, we can generate the bit codes */
706: gen_codes (tree, max_code);
707: }
708:
709: /* ===========================================================================
710: * Scan a literal or distance tree to determine the frequencies of the codes
711: * in the bit length tree. Updates opt_len to take into account the repeat
712: * counts. (The contribution of the bit length codes will be added later
713: * during the construction of bl_tree.)
714: */
715: local void scan_tree (tree, max_code)
716: ct_data near *tree; /* the tree to be scanned */
717: int max_code; /* and its largest code of non zero frequency */
718: {
719: int n; /* iterates over all tree elements */
720: int prevlen = -1; /* last emitted length */
721: int curlen; /* length of current code */
722: int nextlen = tree[0].Len; /* length of next code */
723: int count = 0; /* repeat count of the current code */
724: int max_count = 7; /* max repeat count */
725: int min_count = 4; /* min repeat count */
726:
727: if (nextlen == 0) max_count = 138, min_count = 3;
728: tree[max_code+1].Len = (ush)-1; /* guard */
729:
730: for (n = 0; n <= max_code; n++) {
731: curlen = nextlen; nextlen = tree[n+1].Len;
732: if (++count < max_count && curlen == nextlen) {
733: continue;
734: } else if (count < min_count) {
735: bl_tree[curlen].Freq += count;
736: } else if (curlen != 0) {
737: if (curlen != prevlen) bl_tree[curlen].Freq++;
738: bl_tree[REP_3_6].Freq++;
739: } else if (count <= 10) {
740: bl_tree[REPZ_3_10].Freq++;
741: } else {
742: bl_tree[REPZ_11_138].Freq++;
743: }
744: count = 0; prevlen = curlen;
745: if (nextlen == 0) {
746: max_count = 138, min_count = 3;
747: } else if (curlen == nextlen) {
748: max_count = 6, min_count = 3;
749: } else {
750: max_count = 7, min_count = 4;
751: }
752: }
753: }
754:
755: /* ===========================================================================
756: * Send a literal or distance tree in compressed form, using the codes in
757: * bl_tree.
758: */
759: local void send_tree (tree, max_code)
760: ct_data near *tree; /* the tree to be scanned */
761: int max_code; /* and its largest code of non zero frequency */
762: {
763: int n; /* iterates over all tree elements */
764: int prevlen = -1; /* last emitted length */
765: int curlen; /* length of current code */
766: int nextlen = tree[0].Len; /* length of next code */
767: int count = 0; /* repeat count of the current code */
768: int max_count = 7; /* max repeat count */
769: int min_count = 4; /* min repeat count */
770:
771: /* tree[max_code+1].Len = -1; */ /* guard already set */
772: if (nextlen == 0) max_count = 138, min_count = 3;
773:
774: for (n = 0; n <= max_code; n++) {
775: curlen = nextlen; nextlen = tree[n+1].Len;
776: if (++count < max_count && curlen == nextlen) {
777: continue;
778: } else if (count < min_count) {
779: do { send_code(curlen, bl_tree); } while (--count != 0);
780:
781: } else if (curlen != 0) {
782: if (curlen != prevlen) {
783: send_code(curlen, bl_tree); count--;
784: }
785: Assert(count >= 3 && count <= 6, " 3_6?");
786: send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
787:
788: } else if (count <= 10) {
789: send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
790:
791: } else {
792: send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
793: }
794: count = 0; prevlen = curlen;
795: if (nextlen == 0) {
796: max_count = 138, min_count = 3;
797: } else if (curlen == nextlen) {
798: max_count = 6, min_count = 3;
799: } else {
800: max_count = 7, min_count = 4;
801: }
802: }
803: }
804:
805: /* ===========================================================================
806: * Construct the Huffman tree for the bit lengths and return the index in
807: * bl_order of the last bit length code to send.
808: */
809: local int build_bl_tree()
810: {
811: int max_blindex; /* index of last bit length code of non zero freq */
812:
813: /* Determine the bit length frequencies for literal and distance trees */
814: scan_tree(dyn_ltree, l_desc.max_code);
815: scan_tree(dyn_dtree, d_desc.max_code);
816:
817: /* Build the bit length tree: */
818: build_tree(&bl_desc);
819: /* opt_len now includes the length of the tree representations, except
820: * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
821: */
822:
823: /* Determine the number of bit length codes to send. The pkzip format
824: * requires that at least 4 bit length codes be sent. (appnote.txt says
825: * 3 but the actual value used is 4.)
826: */
827: for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
828: if (bl_tree[bl_order[max_blindex]].Len != 0) break;
829: }
830: /* Update opt_len to include the bit length tree and counts */
831: opt_len += 3*(max_blindex+1) + 5+5+4;
832: Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len));
833:
834: return max_blindex;
835: }
836:
837: /* ===========================================================================
838: * Send the header for a block using dynamic Huffman trees: the counts, the
839: * lengths of the bit length codes, the literal tree and the distance tree.
840: * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
841: */
842: local void send_all_trees(lcodes, dcodes, blcodes)
843: int lcodes, dcodes, blcodes; /* number of codes for each tree */
844: {
845: int rank; /* index in bl_order */
846:
847: Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
848: Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
849: "too many codes");
850: Tracev((stderr, "\nbl counts: "));
851: send_bits(lcodes-257, 5); /* not -255 as stated in appnote.txt */
852: send_bits(dcodes-1, 5);
853: send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
854: for (rank = 0; rank < blcodes; rank++) {
855: Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
856: send_bits(bl_tree[bl_order[rank]].Len, 3);
857: }
858: Tracev((stderr, "\nbl tree: sent %ld", bits_sent));
859:
860: send_tree(dyn_ltree, lcodes-1); /* send the literal tree */
861: Tracev((stderr, "\nlit tree: sent %ld", bits_sent));
862:
863: send_tree(dyn_dtree, dcodes-1); /* send the distance tree */
864: Tracev((stderr, "\ndist tree: sent %ld", bits_sent));
865: }
866:
867: /* ===========================================================================
868: * Determine the best encoding for the current block: dynamic trees, static
869: * trees or store, and output the encoded block to the zip file. This function
870: * returns the total compressed length for the file so far.
871: */
872: ulg flush_block(buf, stored_len, eof)
873: char *buf; /* input block, or NULL if too old */
874: ulg stored_len; /* length of input block */
875: int eof; /* true if this is the last block for a file */
876: {
877: ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
878: int max_blindex; /* index of last bit length code of non zero freq */
879:
880: flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
881:
882: /* Check if the file is ascii or binary */
883: if (*file_type == (ush)UNKNOWN) set_file_type();
884:
885: /* Construct the literal and distance trees */
886: build_tree(&l_desc);
887: Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len));
888:
889: build_tree(&d_desc);
890: Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len));
891: /* At this point, opt_len and static_len are the total bit lengths of
892: * the compressed block data, excluding the tree representations.
893: */
894:
895: /* Build the bit length tree for the above two trees, and get the index
896: * in bl_order of the last bit length code to send.
897: */
898: max_blindex = build_bl_tree();
899:
900: /* Determine the best encoding. Compute first the block length in bytes */
901: opt_lenb = (opt_len+3+7)>>3;
902: static_lenb = (static_len+3+7)>>3;
903: input_len += stored_len; /* for debugging only */
904:
905: Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
906: opt_lenb, opt_len, static_lenb, static_len, stored_len,
907: last_lit, last_dist));
908:
909: if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
910:
911: #ifdef ZIP /* not ok for PGP */
912: /* If compression failed and this is the first and last block,
913: * and if the zip file can be seeked (to rewrite the local header),
914: * the whole file is transformed into a stored file:
915: */
916: #ifdef FORCE_METHOD
917: if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
918: #else
919: if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
920: #endif
921: /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
922: if (buf == NULL) error ("block vanished");
923:
924: copy_block(buf, (unsigned)stored_len, 0); /* without header */
925: compressed_len = stored_len << 3;
926: *file_method = STORE;
927: } else
928: #endif /* ZIP */
929:
930: #ifdef FORCE_METHOD
931: if (level == 2 && buf != NULL) { /* force stored block */
932: #else
1.1.1.3 ! root 933: if ((stored_len+4 <= opt_lenb) && (buf != (char *)NULL)) {
1.1.1.2 root 934: /* 4: two words for the lengths */
935: #endif
936: /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
937: * Otherwise we can't have processed more than WSIZE input bytes since
938: * the last block flush, because compression would have been
939: * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
940: * transform a block into a stored block.
941: */
942: send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
943: compressed_len = (compressed_len + 3 + 7) & ~7L;
944: compressed_len += (stored_len + 4) << 3;
945:
946: copy_block(buf, (unsigned)stored_len, 1); /* with header */
947:
948: #ifdef FORCE_METHOD
949: } else if (level == 3) { /* force static trees */
950: #else
951: } else if (static_lenb == opt_lenb) {
952: #endif
953: send_bits((STATIC_TREES<<1)+eof, 3);
954: compress_block(static_ltree, static_dtree);
955: compressed_len += 3 + static_len;
956: } else {
957: send_bits((DYN_TREES<<1)+eof, 3);
958: send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
959: compress_block(dyn_ltree, dyn_dtree);
960: compressed_len += 3 + opt_len;
961: }
962: Assert (compressed_len == bits_sent, "bad compressed size");
963: init_block();
964:
965: if (eof) {
966: #ifndef ZIP
967: /* Wipe out sensitive data for pgp */
968: # ifdef DYN_ALLOC
969: extern uch *window;
970: # else
971: extern uch window[];
972: # endif
973: memset(window, 0, (unsigned)(2*WSIZE-1)); /* -1 needed if WSIZE=32K */
974: #endif /* ZIP */
975:
976: #if 0
977: Assert (input_len == isize, "bad input size");
978: #endif
979: bi_windup();
980: compressed_len += 7; /* align on byte boundary */
981: }
982: Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3,
983: compressed_len-7*eof));
984:
985: return compressed_len >> 3;
986: }
987:
988: /* ===========================================================================
989: * Save the match info and tally the frequency counts. Return true if
990: * the current block must be flushed.
991: */
992: int ct_tally (dist, lc)
993: int dist; /* distance of matched string */
994: int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
995: {
996: l_buf[last_lit++] = (uch)lc;
997: if (dist == 0) {
998: /* lc is the unmatched char */
999: dyn_ltree[lc].Freq++;
1000: } else {
1001: /* Here, lc is the match length - MIN_MATCH */
1002: dist--; /* dist = match distance - 1 */
1003: Assert((ush)dist < (ush)MAX_DIST &&
1004: (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1005: (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
1006:
1007: dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
1008: dyn_dtree[d_code(dist)].Freq++;
1009:
1010: d_buf[last_dist++] = dist;
1011: flags |= flag_bit;
1012: }
1013: flag_bit <<= 1;
1014:
1015: /* Output the flags if they fill a byte: */
1016: if ((last_lit & 7) == 0) {
1017: flag_buf[last_flags++] = flags;
1018: flags = 0, flag_bit = 1;
1019: }
1020: /* Try to guess if it is profitable to stop the current block here */
1021: if (level > 2 && (last_lit & 0xfff) == 0) {
1022: /* Compute an upper bound for the compressed length */
1023: ulg out_length = (ulg)last_lit*8L;
1024: ulg in_length = (ulg)strstart-block_start;
1025: int dcode;
1026: for (dcode = 0; dcode < D_CODES; dcode++) {
1027: out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
1028: }
1029: out_length >>= 3;
1030: Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
1031: last_lit, last_dist, in_length, out_length,
1032: 100L - out_length*100L/in_length));
1033: if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1034: }
1035: return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1036: /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1037: * on 16 bit machines and because stored blocks are restricted to
1038: * 64K-1 bytes.
1039: */
1040: }
1041:
1042: /* ===========================================================================
1043: * Send the block data compressed using the given Huffman trees
1044: */
1045: local void compress_block(ltree, dtree)
1046: ct_data near *ltree; /* literal tree */
1047: ct_data near *dtree; /* distance tree */
1048: {
1049: unsigned dist; /* distance of matched string */
1050: int lc; /* match length or unmatched char (if dist == 0) */
1051: unsigned lx = 0; /* running index in l_buf */
1052: unsigned dx = 0; /* running index in d_buf */
1053: unsigned fx = 0; /* running index in flag_buf */
1054: uch flag = 0; /* current flags */
1055: unsigned code; /* the code to send */
1056: int extra; /* number of extra bits to send */
1057:
1058: if (last_lit != 0) do {
1059: if ((lx & 7) == 0) flag = flag_buf[fx++];
1060: lc = l_buf[lx++];
1061: if ((flag & 1) == 0) {
1062: send_code(lc, ltree); /* send a literal byte */
1063: Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1064: } else {
1065: /* Here, lc is the match length - MIN_MATCH */
1066: code = length_code[lc];
1067: send_code(code+LITERALS+1, ltree); /* send the length code */
1068: extra = extra_lbits[code];
1069: if (extra != 0) {
1070: lc -= base_length[code];
1071: send_bits(lc, extra); /* send the extra length bits */
1072: }
1073: dist = d_buf[dx++];
1074: /* Here, dist is the match distance - 1 */
1075: code = d_code(dist);
1076: Assert (code < D_CODES, "bad d_code");
1077:
1078: send_code(code, dtree); /* send the distance code */
1079: extra = extra_dbits[code];
1080: if (extra != 0) {
1081: dist -= base_dist[code];
1082: send_bits(dist, extra); /* send the extra distance bits */
1083: }
1084: } /* literal or match pair ? */
1085: flag >>= 1;
1086: } while (lx < last_lit);
1087:
1088: send_code(END_BLOCK, ltree);
1089: }
1090:
1091: /* ===========================================================================
1092: * Set the file type to ASCII or BINARY, using a crude approximation:
1093: * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1094: * IN assertion: the fields freq of dyn_ltree are set and the total of all
1095: * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1096: */
1097: local void set_file_type()
1098: {
1099: int n = 0;
1100: unsigned ascii_freq = 0;
1101: unsigned bin_freq = 0;
1102: while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1103: while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1104: while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1105: *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1106: #ifdef ZIP
1107: if (*file_type == BINARY && translate_eol) {
1108: warn("-l used on binary file", "");
1109: }
1110: #endif
1111: }
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