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1.1 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:
281: ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
282: int *file_method; /* pointer to DEFLATE or STORE */
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: */
334: void ct_init(attr, method)
335: ush *attr; /* pointer to internal file attribute */
336: int *method; /* pointer to compression method */
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;
345: file_method = method;
346: compressed_len = input_len = 0L;
347:
348: if (static_dtree[0].Len != 0) return; /* ct_init already called */
349:
350: #ifdef DYN_ALLOC
351: d_buf = (ush far*) fcalloc(DIST_BUFSIZE, sizeof(ush));
352: l_buf = (uch far*) fcalloc(LIT_BUFSIZE/2, 2);
353: /* Avoid using the value 64K on 16 bit machines */
354: if (l_buf == NULL || d_buf == NULL) error("ct_init: out of memory");
355: #endif
356:
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:
413: /* ===========================================================================
414: * Initialize a new block.
415: */
416: local void init_block()
417: {
418: int n; /* iterates over tree elements */
419:
420: /* Initialize the trees. */
421: for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
422: for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
423: for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
424:
425: dyn_ltree[END_BLOCK].Freq = 1;
426: opt_len = static_len = 0L;
427: last_lit = last_dist = last_flags = 0;
428: flags = 0; flag_bit = 1;
429: }
430:
431: #define SMALLEST 1
432: /* Index within the heap array of least frequent node in the Huffman tree */
433:
434:
435: /* ===========================================================================
436: * Remove the smallest element from the heap and recreate the heap with
437: * one less element. Updates heap and heap_len.
438: */
439: #define pqremove(tree, top) \
440: {\
441: top = heap[SMALLEST]; \
442: heap[SMALLEST] = heap[heap_len--]; \
443: pqdownheap(tree, SMALLEST); \
444: }
445:
446: /* ===========================================================================
447: * Compares to subtrees, using the tree depth as tie breaker when
448: * the subtrees have equal frequency. This minimizes the worst case length.
449: */
450: #define smaller(tree, n, m) \
451: (tree[n].Freq < tree[m].Freq || \
452: (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
453:
454: /* ===========================================================================
455: * Restore the heap property by moving down the tree starting at node k,
456: * exchanging a node with the smallest of its two sons if necessary, stopping
457: * when the heap property is re-established (each father smaller than its
458: * two sons).
459: */
460: local void pqdownheap(tree, k)
461: ct_data near *tree; /* the tree to restore */
462: int k; /* node to move down */
463: {
464: int v = heap[k];
465: int j = k << 1; /* left son of k */
466: while (j <= heap_len) {
467: /* Set j to the smallest of the two sons: */
468: if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
469:
470: /* Exit if v is smaller than both sons */
471: if (smaller(tree, v, heap[j])) break;
472:
473: /* Exchange v with the smallest son */
474: heap[k] = heap[j], k = j;
475:
476: /* And continue down the tree, setting j to the left son of k */
477: j <<= 1;
478: }
479: heap[k] = v;
480: }
481:
482: /* ===========================================================================
483: * Compute the optimal bit lengths for a tree and update the total bit length
484: * for the current block.
485: * IN assertion: the fields freq and dad are set, heap[heap_max] and
486: * above are the tree nodes sorted by increasing frequency.
487: * OUT assertions: the field len is set to the optimal bit length, the
488: * array bl_count contains the frequencies for each bit length.
489: * The length opt_len is updated; static_len is also updated if stree is
490: * not null.
491: */
492: local void gen_bitlen(desc)
493: tree_desc near *desc; /* the tree descriptor */
494: {
495: ct_data near *tree = desc->dyn_tree;
496: int near *extra = desc->extra_bits;
497: int base = desc->extra_base;
498: int max_code = desc->max_code;
499: int max_length = desc->max_length;
500: ct_data near *stree = desc->static_tree;
501: int h; /* heap index */
502: int n, m; /* iterate over the tree elements */
503: int bits; /* bit length */
504: int xbits; /* extra bits */
505: ush f; /* frequency */
506: int overflow = 0; /* number of elements with bit length too large */
507:
508: for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
509:
510: /* In a first pass, compute the optimal bit lengths (which may
511: * overflow in the case of the bit length tree).
512: */
513: tree[heap[heap_max]].Len = 0; /* root of the heap */
514:
515: for (h = heap_max+1; h < HEAP_SIZE; h++) {
516: n = heap[h];
517: bits = tree[tree[n].Dad].Len + 1;
518: if (bits > max_length) bits = max_length, overflow++;
519: tree[n].Len = bits;
520: /* We overwrite tree[n].Dad which is no longer needed */
521:
522: if (n > max_code) continue; /* not a leaf node */
523:
524: bl_count[bits]++;
525: xbits = 0;
526: if (n >= base) xbits = extra[n-base];
527: f = tree[n].Freq;
528: opt_len += (ulg)f * (bits + xbits);
529: if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
530: }
531: if (overflow == 0) return;
532:
533: Trace((stderr,"\nbit length overflow\n"));
534: /* This happens for example on obj2 and pic of the Calgary corpus */
535:
536: /* Find the first bit length which could increase: */
537: do {
538: bits = max_length-1;
539: while (bl_count[bits] == 0) bits--;
540: bl_count[bits]--; /* move one leaf down the tree */
541: bl_count[bits+1] += 2; /* move one overflow item as its brother */
542: bl_count[max_length]--;
543: /* The brother of the overflow item also moves one step up,
544: * but this does not affect bl_count[max_length]
545: */
546: overflow -= 2;
547: } while (overflow > 0);
548:
549: /* Now recompute all bit lengths, scanning in increasing frequency.
550: * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
551: * lengths instead of fixing only the wrong ones. This idea is taken
552: * from 'ar' written by Haruhiko Okumura.)
553: */
554: for (bits = max_length; bits != 0; bits--) {
555: n = bl_count[bits];
556: while (n != 0) {
557: m = heap[--h];
558: if (m > max_code) continue;
559: if (tree[m].Len != (unsigned) bits) {
560: Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
561: opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
562: tree[m].Len = bits;
563: }
564: n--;
565: }
566: }
567: }
568:
569: /* ===========================================================================
570: * Generate the codes for a given tree and bit counts (which need not be
571: * optimal).
572: * IN assertion: the array bl_count contains the bit length statistics for
573: * the given tree and the field len is set for all tree elements.
574: * OUT assertion: the field code is set for all tree elements of non
575: * zero code length.
576: */
577: local void gen_codes (tree, max_code)
578: ct_data near *tree; /* the tree to decorate */
579: int max_code; /* largest code with non zero frequency */
580: {
581: ush next_code[MAX_BITS+1]; /* next code value for each bit length */
582: ush code = 0; /* running code value */
583: int bits; /* bit index */
584: int n; /* code index */
585:
586: /* The distribution counts are first used to generate the code values
587: * without bit reversal.
588: */
589: for (bits = 1; bits <= MAX_BITS; bits++) {
590: next_code[bits] = code = (code + bl_count[bits-1]) << 1;
591: }
592: /* Check that the bit counts in bl_count are consistent. The last code
593: * must be all ones.
594: */
595: Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
596: "inconsistent bit counts");
597: Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
598:
599: for (n = 0; n <= max_code; n++) {
600: int len = tree[n].Len;
601: if (len == 0) continue;
602: /* Now reverse the bits */
603: tree[n].Code = bi_reverse(next_code[len]++, len);
604:
605: Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
606: n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
607: }
608: }
609:
610: /* ===========================================================================
611: * Construct one Huffman tree and assigns the code bit strings and lengths.
612: * Update the total bit length for the current block.
613: * IN assertion: the field freq is set for all tree elements.
614: * OUT assertions: the fields len and code are set to the optimal bit length
615: * and corresponding code. The length opt_len is updated; static_len is
616: * also updated if stree is not null. The field max_code is set.
617: */
618: local void build_tree(desc)
619: tree_desc near *desc; /* the tree descriptor */
620: {
621: ct_data near *tree = desc->dyn_tree;
622: ct_data near *stree = desc->static_tree;
623: int elems = desc->elems;
624: int n, m; /* iterate over heap elements */
625: int max_code = -1; /* largest code with non zero frequency */
626: int node = elems; /* next internal node of the tree */
627:
628: /* Construct the initial heap, with least frequent element in
629: * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
630: * heap[0] is not used.
631: */
632: heap_len = 0, heap_max = HEAP_SIZE;
633:
634: for (n = 0; n < elems; n++) {
635: if (tree[n].Freq != 0) {
636: heap[++heap_len] = max_code = n;
637: depth[n] = 0;
638: } else {
639: tree[n].Len = 0;
640: }
641: }
642:
643: /* The pkzip format requires that at least one distance code exists,
644: * and that at least one bit should be sent even if there is only one
645: * possible code. So to avoid special checks later on we force at least
646: * two codes of non zero frequency.
647: */
648: while (heap_len < 2) {
649: int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
650: tree[new].Freq = 1;
651: depth[new] = 0;
652: opt_len--; if (stree) static_len -= stree[new].Len;
653: /* new is 0 or 1 so it does not have extra bits */
654: }
655: desc->max_code = max_code;
656:
657: /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
658: * establish sub-heaps of increasing lengths:
659: */
660: for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
661:
662: /* Construct the Huffman tree by repeatedly combining the least two
663: * frequent nodes.
664: */
665: do {
666: pqremove(tree, n); /* n = node of least frequency */
667: m = heap[SMALLEST]; /* m = node of next least frequency */
668:
669: heap[--heap_max] = n; /* keep the nodes sorted by frequency */
670: heap[--heap_max] = m;
671:
672: /* Create a new node father of n and m */
673: tree[node].Freq = tree[n].Freq + tree[m].Freq;
674: depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
675: tree[n].Dad = tree[m].Dad = node;
676: #ifdef DUMP_BL_TREE
677: if (tree == bl_tree) {
678: fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
679: node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
680: }
681: #endif
682: /* and insert the new node in the heap */
683: heap[SMALLEST] = node++;
684: pqdownheap(tree, SMALLEST);
685:
686: } while (heap_len >= 2);
687:
688: heap[--heap_max] = heap[SMALLEST];
689:
690: /* At this point, the fields freq and dad are set. We can now
691: * generate the bit lengths.
692: */
693: gen_bitlen(desc);
694:
695: /* The field len is now set, we can generate the bit codes */
696: gen_codes (tree, max_code);
697: }
698:
699: /* ===========================================================================
700: * Scan a literal or distance tree to determine the frequencies of the codes
701: * in the bit length tree. Updates opt_len to take into account the repeat
702: * counts. (The contribution of the bit length codes will be added later
703: * during the construction of bl_tree.)
704: */
705: local void scan_tree (tree, max_code)
706: ct_data near *tree; /* the tree to be scanned */
707: int max_code; /* and its largest code of non zero frequency */
708: {
709: int n; /* iterates over all tree elements */
710: int prevlen = -1; /* last emitted length */
711: int curlen; /* length of current code */
712: int nextlen = tree[0].Len; /* length of next code */
713: int count = 0; /* repeat count of the current code */
714: int max_count = 7; /* max repeat count */
715: int min_count = 4; /* min repeat count */
716:
717: if (nextlen == 0) max_count = 138, min_count = 3;
718: tree[max_code+1].Len = (ush)-1; /* guard */
719:
720: for (n = 0; n <= max_code; n++) {
721: curlen = nextlen; nextlen = tree[n+1].Len;
722: if (++count < max_count && curlen == nextlen) {
723: continue;
724: } else if (count < min_count) {
725: bl_tree[curlen].Freq += count;
726: } else if (curlen != 0) {
727: if (curlen != prevlen) bl_tree[curlen].Freq++;
728: bl_tree[REP_3_6].Freq++;
729: } else if (count <= 10) {
730: bl_tree[REPZ_3_10].Freq++;
731: } else {
732: bl_tree[REPZ_11_138].Freq++;
733: }
734: count = 0; prevlen = curlen;
735: if (nextlen == 0) {
736: max_count = 138, min_count = 3;
737: } else if (curlen == nextlen) {
738: max_count = 6, min_count = 3;
739: } else {
740: max_count = 7, min_count = 4;
741: }
742: }
743: }
744:
745: /* ===========================================================================
746: * Send a literal or distance tree in compressed form, using the codes in
747: * bl_tree.
748: */
749: local void send_tree (tree, max_code)
750: ct_data near *tree; /* the tree to be scanned */
751: int max_code; /* and its largest code of non zero frequency */
752: {
753: int n; /* iterates over all tree elements */
754: int prevlen = -1; /* last emitted length */
755: int curlen; /* length of current code */
756: int nextlen = tree[0].Len; /* length of next code */
757: int count = 0; /* repeat count of the current code */
758: int max_count = 7; /* max repeat count */
759: int min_count = 4; /* min repeat count */
760:
761: /* tree[max_code+1].Len = -1; */ /* guard already set */
762: if (nextlen == 0) max_count = 138, min_count = 3;
763:
764: for (n = 0; n <= max_code; n++) {
765: curlen = nextlen; nextlen = tree[n+1].Len;
766: if (++count < max_count && curlen == nextlen) {
767: continue;
768: } else if (count < min_count) {
769: do { send_code(curlen, bl_tree); } while (--count != 0);
770:
771: } else if (curlen != 0) {
772: if (curlen != prevlen) {
773: send_code(curlen, bl_tree); count--;
774: }
775: Assert(count >= 3 && count <= 6, " 3_6?");
776: send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
777:
778: } else if (count <= 10) {
779: send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
780:
781: } else {
782: send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
783: }
784: count = 0; prevlen = curlen;
785: if (nextlen == 0) {
786: max_count = 138, min_count = 3;
787: } else if (curlen == nextlen) {
788: max_count = 6, min_count = 3;
789: } else {
790: max_count = 7, min_count = 4;
791: }
792: }
793: }
794:
795: /* ===========================================================================
796: * Construct the Huffman tree for the bit lengths and return the index in
797: * bl_order of the last bit length code to send.
798: */
799: local int build_bl_tree()
800: {
801: int max_blindex; /* index of last bit length code of non zero freq */
802:
803: /* Determine the bit length frequencies for literal and distance trees */
804: scan_tree(dyn_ltree, l_desc.max_code);
805: scan_tree(dyn_dtree, d_desc.max_code);
806:
807: /* Build the bit length tree: */
808: build_tree(&bl_desc);
809: /* opt_len now includes the length of the tree representations, except
810: * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
811: */
812:
813: /* Determine the number of bit length codes to send. The pkzip format
814: * requires that at least 4 bit length codes be sent. (appnote.txt says
815: * 3 but the actual value used is 4.)
816: */
817: for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
818: if (bl_tree[bl_order[max_blindex]].Len != 0) break;
819: }
820: /* Update opt_len to include the bit length tree and counts */
821: opt_len += 3*(max_blindex+1) + 5+5+4;
822: Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len));
823:
824: return max_blindex;
825: }
826:
827: /* ===========================================================================
828: * Send the header for a block using dynamic Huffman trees: the counts, the
829: * lengths of the bit length codes, the literal tree and the distance tree.
830: * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
831: */
832: local void send_all_trees(lcodes, dcodes, blcodes)
833: int lcodes, dcodes, blcodes; /* number of codes for each tree */
834: {
835: int rank; /* index in bl_order */
836:
837: Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
838: Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
839: "too many codes");
840: Tracev((stderr, "\nbl counts: "));
841: send_bits(lcodes-257, 5); /* not -255 as stated in appnote.txt */
842: send_bits(dcodes-1, 5);
843: send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
844: for (rank = 0; rank < blcodes; rank++) {
845: Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
846: send_bits(bl_tree[bl_order[rank]].Len, 3);
847: }
848: Tracev((stderr, "\nbl tree: sent %ld", bits_sent));
849:
850: send_tree(dyn_ltree, lcodes-1); /* send the literal tree */
851: Tracev((stderr, "\nlit tree: sent %ld", bits_sent));
852:
853: send_tree(dyn_dtree, dcodes-1); /* send the distance tree */
854: Tracev((stderr, "\ndist tree: sent %ld", bits_sent));
855: }
856:
857: /* ===========================================================================
858: * Determine the best encoding for the current block: dynamic trees, static
859: * trees or store, and output the encoded block to the zip file. This function
860: * returns the total compressed length for the file so far.
861: */
862: ulg flush_block(buf, stored_len, eof)
863: char *buf; /* input block, or NULL if too old */
864: ulg stored_len; /* length of input block */
865: int eof; /* true if this is the last block for a file */
866: {
867: ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
868: int max_blindex; /* index of last bit length code of non zero freq */
869:
870: flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
871:
872: /* Check if the file is ascii or binary */
873: if (*file_type == (ush)UNKNOWN) set_file_type();
874:
875: /* Construct the literal and distance trees */
876: build_tree(&l_desc);
877: Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len));
878:
879: build_tree(&d_desc);
880: Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len));
881: /* At this point, opt_len and static_len are the total bit lengths of
882: * the compressed block data, excluding the tree representations.
883: */
884:
885: /* Build the bit length tree for the above two trees, and get the index
886: * in bl_order of the last bit length code to send.
887: */
888: max_blindex = build_bl_tree();
889:
890: /* Determine the best encoding. Compute first the block length in bytes */
891: opt_lenb = (opt_len+3+7)>>3;
892: static_lenb = (static_len+3+7)>>3;
893: input_len += stored_len; /* for debugging only */
894:
895: Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
896: opt_lenb, opt_len, static_lenb, static_len, stored_len,
897: last_lit, last_dist));
898:
899: if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
900:
901: #ifdef ZIP /* not ok for PGP */
902: /* If compression failed and this is the first and last block,
903: * and if the zip file can be seeked (to rewrite the local header),
904: * the whole file is transformed into a stored file:
905: */
906: #ifdef FORCE_METHOD
907: if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
908: #else
909: if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
910: #endif
911: /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
912: if (buf == NULL) error ("block vanished");
913:
914: copy_block(buf, (unsigned)stored_len, 0); /* without header */
915: compressed_len = stored_len << 3;
916: *file_method = STORE;
917: } else
918: #endif /* ZIP */
919:
920: #ifdef FORCE_METHOD
921: if (level == 2 && buf != NULL) { /* force stored block */
922: #else
923: if (stored_len+4 <= opt_lenb && buf != NULL) {
924: /* 4: two words for the lengths */
925: #endif
926: /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
927: * Otherwise we can't have processed more than WSIZE input bytes since
928: * the last block flush, because compression would have been
929: * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
930: * transform a block into a stored block.
931: */
932: send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
933: compressed_len = (compressed_len + 3 + 7) & ~7L;
934: compressed_len += (stored_len + 4) << 3;
935:
936: copy_block(buf, (unsigned)stored_len, 1); /* with header */
937:
938: #ifdef FORCE_METHOD
939: } else if (level == 3) { /* force static trees */
940: #else
941: } else if (static_lenb == opt_lenb) {
942: #endif
943: send_bits((STATIC_TREES<<1)+eof, 3);
944: compress_block(static_ltree, static_dtree);
945: compressed_len += 3 + static_len;
946: } else {
947: send_bits((DYN_TREES<<1)+eof, 3);
948: send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
949: compress_block(dyn_ltree, dyn_dtree);
950: compressed_len += 3 + opt_len;
951: }
952: Assert (compressed_len == bits_sent, "bad compressed size");
953: init_block();
954:
955: if (eof) {
956: Assert (input_len == isize, "bad input size");
957: bi_windup();
958: compressed_len += 7; /* align on byte boundary */
959: }
960: Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3,
961: compressed_len-7*eof));
962:
963: return compressed_len >> 3;
964: }
965:
966: /* ===========================================================================
967: * Save the match info and tally the frequency counts. Return true if
968: * the current block must be flushed.
969: */
970: int ct_tally (dist, lc)
971: int dist; /* distance of matched string */
972: int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
973: {
974: l_buf[last_lit++] = (uch)lc;
975: if (dist == 0) {
976: /* lc is the unmatched char */
977: dyn_ltree[lc].Freq++;
978: } else {
979: /* Here, lc is the match length - MIN_MATCH */
980: dist--; /* dist = match distance - 1 */
981: Assert((ush)dist < (ush)MAX_DIST &&
982: (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
983: (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
984:
985: dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
986: dyn_dtree[d_code(dist)].Freq++;
987:
988: d_buf[last_dist++] = dist;
989: flags |= flag_bit;
990: }
991: flag_bit <<= 1;
992:
993: /* Output the flags if they fill a byte: */
994: if ((last_lit & 7) == 0) {
995: flag_buf[last_flags++] = flags;
996: flags = 0, flag_bit = 1;
997: }
998: /* Try to guess if it is profitable to stop the current block here */
999: if (level > 2 && (last_lit & 0xfff) == 0) {
1000: /* Compute an upper bound for the compressed length */
1001: ulg out_length = (ulg)last_lit*8L;
1002: ulg in_length = (ulg)strstart-block_start;
1003: int dcode;
1004: for (dcode = 0; dcode < D_CODES; dcode++) {
1005: out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
1006: }
1007: out_length >>= 3;
1008: Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
1009: last_lit, last_dist, in_length, out_length,
1010: 100L - out_length*100L/in_length));
1011: if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1012: }
1013: return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1014: /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1015: * on 16 bit machines and because stored blocks are restricted to
1016: * 64K-1 bytes.
1017: */
1018: }
1019:
1020: /* ===========================================================================
1021: * Send the block data compressed using the given Huffman trees
1022: */
1023: local void compress_block(ltree, dtree)
1024: ct_data near *ltree; /* literal tree */
1025: ct_data near *dtree; /* distance tree */
1026: {
1027: unsigned dist; /* distance of matched string */
1028: int lc; /* match length or unmatched char (if dist == 0) */
1029: unsigned lx = 0; /* running index in l_buf */
1030: unsigned dx = 0; /* running index in d_buf */
1031: unsigned fx = 0; /* running index in flag_buf */
1032: uch flag = 0; /* current flags */
1033: unsigned code; /* the code to send */
1034: int extra; /* number of extra bits to send */
1035:
1036: if (last_lit != 0) do {
1037: if ((lx & 7) == 0) flag = flag_buf[fx++];
1038: lc = l_buf[lx++];
1039: if ((flag & 1) == 0) {
1040: send_code(lc, ltree); /* send a literal byte */
1041: Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1042: } else {
1043: /* Here, lc is the match length - MIN_MATCH */
1044: code = length_code[lc];
1045: send_code(code+LITERALS+1, ltree); /* send the length code */
1046: extra = extra_lbits[code];
1047: if (extra != 0) {
1048: lc -= base_length[code];
1049: send_bits(lc, extra); /* send the extra length bits */
1050: }
1051: dist = d_buf[dx++];
1052: /* Here, dist is the match distance - 1 */
1053: code = d_code(dist);
1054: Assert (code < D_CODES, "bad d_code");
1055:
1056: send_code(code, dtree); /* send the distance code */
1057: extra = extra_dbits[code];
1058: if (extra != 0) {
1059: dist -= base_dist[code];
1060: send_bits(dist, extra); /* send the extra distance bits */
1061: }
1062: } /* literal or match pair ? */
1063: flag >>= 1;
1064: } while (lx < last_lit);
1065:
1066: send_code(END_BLOCK, ltree);
1067: }
1068:
1069: /* ===========================================================================
1070: * Set the file type to ASCII or BINARY, using a crude approximation:
1071: * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1072: * IN assertion: the fields freq of dyn_ltree are set and the total of all
1073: * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1074: */
1075: local void set_file_type()
1076: {
1077: int n = 0;
1078: unsigned ascii_freq = 0;
1079: unsigned bin_freq = 0;
1080: while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1081: while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1082: while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1083: *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1084: #ifdef ZIP
1085: if (*file_type == BINARY && translate_eol) {
1086: warn("-l used on binary file", "");
1087: }
1088: #endif
1089: }
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