trees.c revision 84228
1/* trees.c -- output deflated data using Huffman coding 2 * Copyright (C) 1995-1998 Jean-loup Gailly 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6/* 7 * ALGORITHM 8 * 9 * The "deflation" process uses several Huffman trees. The more 10 * common source values are represented by shorter bit sequences. 11 * 12 * Each code tree is stored in a compressed form which is itself 13 * a Huffman encoding of the lengths of all the code strings (in 14 * ascending order by source values). The actual code strings are 15 * reconstructed from the lengths in the inflate process, as described 16 * in the deflate specification. 17 * 18 * REFERENCES 19 * 20 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". 21 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc 22 * 23 * Storer, James A. 24 * Data Compression: Methods and Theory, pp. 49-50. 25 * Computer Science Press, 1988. ISBN 0-7167-8156-5. 26 * 27 * Sedgewick, R. 28 * Algorithms, p290. 29 * Addison-Wesley, 1983. ISBN 0-201-06672-6. 30 */ 31 32#include <sys/cdefs.h> 33__FBSDID("$FreeBSD: head/lib/libz/trees.c 84228 2001-09-30 22:39:00Z dillon $"); 34 35/* #define GEN_TREES_H */ 36 37#include "deflate.h" 38 39#ifdef DEBUG 40# include <ctype.h> 41#endif 42 43/* =========================================================================== 44 * Constants 45 */ 46 47#define MAX_BL_BITS 7 48/* Bit length codes must not exceed MAX_BL_BITS bits */ 49 50#define END_BLOCK 256 51/* end of block literal code */ 52 53#define REP_3_6 16 54/* repeat previous bit length 3-6 times (2 bits of repeat count) */ 55 56#define REPZ_3_10 17 57/* repeat a zero length 3-10 times (3 bits of repeat count) */ 58 59#define REPZ_11_138 18 60/* repeat a zero length 11-138 times (7 bits of repeat count) */ 61 62local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */ 63 = {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}; 64 65local const int extra_dbits[D_CODES] /* extra bits for each distance code */ 66 = {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}; 67 68local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */ 69 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; 70 71local const uch bl_order[BL_CODES] 72 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; 73/* The lengths of the bit length codes are sent in order of decreasing 74 * probability, to avoid transmitting the lengths for unused bit length codes. 75 */ 76 77#define Buf_size (8 * 2*sizeof(char)) 78/* Number of bits used within bi_buf. (bi_buf might be implemented on 79 * more than 16 bits on some systems.) 80 */ 81 82/* =========================================================================== 83 * Local data. These are initialized only once. 84 */ 85 86#define DIST_CODE_LEN 512 /* see definition of array dist_code below */ 87 88#if defined(GEN_TREES_H) || !defined(STDC) 89/* non ANSI compilers may not accept trees.h */ 90 91local ct_data static_ltree[L_CODES+2]; 92/* The static literal tree. Since the bit lengths are imposed, there is no 93 * need for the L_CODES extra codes used during heap construction. However 94 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init 95 * below). 96 */ 97 98local ct_data static_dtree[D_CODES]; 99/* The static distance tree. (Actually a trivial tree since all codes use 100 * 5 bits.) 101 */ 102 103uch _dist_code[DIST_CODE_LEN]; 104/* Distance codes. The first 256 values correspond to the distances 105 * 3 .. 258, the last 256 values correspond to the top 8 bits of 106 * the 15 bit distances. 107 */ 108 109uch _length_code[MAX_MATCH-MIN_MATCH+1]; 110/* length code for each normalized match length (0 == MIN_MATCH) */ 111 112local int base_length[LENGTH_CODES]; 113/* First normalized length for each code (0 = MIN_MATCH) */ 114 115local int base_dist[D_CODES]; 116/* First normalized distance for each code (0 = distance of 1) */ 117 118#else 119# include "trees.h" 120#endif /* GEN_TREES_H */ 121 122struct static_tree_desc_s { 123 const ct_data *static_tree; /* static tree or NULL */ 124 const intf *extra_bits; /* extra bits for each code or NULL */ 125 int extra_base; /* base index for extra_bits */ 126 int elems; /* max number of elements in the tree */ 127 int max_length; /* max bit length for the codes */ 128}; 129 130local static_tree_desc static_l_desc = 131{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; 132 133local static_tree_desc static_d_desc = 134{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS}; 135 136local static_tree_desc static_bl_desc = 137{(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS}; 138 139/* =========================================================================== 140 * Local (static) routines in this file. 141 */ 142 143local void tr_static_init OF((void)); 144local void init_block OF((deflate_state *s)); 145local void pqdownheap OF((deflate_state *s, ct_data *tree, int k)); 146local void gen_bitlen OF((deflate_state *s, tree_desc *desc)); 147local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count)); 148local void build_tree OF((deflate_state *s, tree_desc *desc)); 149local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code)); 150local void send_tree OF((deflate_state *s, ct_data *tree, int max_code)); 151local int build_bl_tree OF((deflate_state *s)); 152local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes, 153 int blcodes)); 154local void compress_block OF((deflate_state *s, ct_data *ltree, 155 ct_data *dtree)); 156local void set_data_type OF((deflate_state *s)); 157local unsigned bi_reverse OF((unsigned value, int length)); 158local void bi_windup OF((deflate_state *s)); 159local void bi_flush OF((deflate_state *s)); 160local void copy_block OF((deflate_state *s, charf *buf, unsigned len, 161 int header)); 162 163#ifdef GEN_TREES_H 164local void gen_trees_header OF((void)); 165#endif 166 167#ifndef DEBUG 168# define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len) 169 /* Send a code of the given tree. c and tree must not have side effects */ 170 171#else /* DEBUG */ 172# define send_code(s, c, tree) \ 173 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \ 174 send_bits(s, tree[c].Code, tree[c].Len); } 175#endif 176 177/* =========================================================================== 178 * Output a short LSB first on the stream. 179 * IN assertion: there is enough room in pendingBuf. 180 */ 181#define put_short(s, w) { \ 182 put_byte(s, (uch)((w) & 0xff)); \ 183 put_byte(s, (uch)((ush)(w) >> 8)); \ 184} 185 186/* =========================================================================== 187 * Send a value on a given number of bits. 188 * IN assertion: length <= 16 and value fits in length bits. 189 */ 190#ifdef DEBUG 191local void send_bits OF((deflate_state *s, int value, int length)); 192 193local void send_bits(s, value, length) 194 deflate_state *s; 195 int value; /* value to send */ 196 int length; /* number of bits */ 197{ 198 Tracevv((stderr," l %2d v %4x ", length, value)); 199 Assert(length > 0 && length <= 15, "invalid length"); 200 s->bits_sent += (ulg)length; 201 202 /* If not enough room in bi_buf, use (valid) bits from bi_buf and 203 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid)) 204 * unused bits in value. 205 */ 206 if (s->bi_valid > (int)Buf_size - length) { 207 s->bi_buf |= (value << s->bi_valid); 208 put_short(s, s->bi_buf); 209 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid); 210 s->bi_valid += length - Buf_size; 211 } else { 212 s->bi_buf |= value << s->bi_valid; 213 s->bi_valid += length; 214 } 215} 216#else /* !DEBUG */ 217 218#define send_bits(s, value, length) \ 219{ int len = length;\ 220 if (s->bi_valid > (int)Buf_size - len) {\ 221 int val = value;\ 222 s->bi_buf |= (val << s->bi_valid);\ 223 put_short(s, s->bi_buf);\ 224 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\ 225 s->bi_valid += len - Buf_size;\ 226 } else {\ 227 s->bi_buf |= (value) << s->bi_valid;\ 228 s->bi_valid += len;\ 229 }\ 230} 231#endif /* DEBUG */ 232 233 234#define MAX(a,b) (a >= b ? a : b) 235/* the arguments must not have side effects */ 236 237/* =========================================================================== 238 * Initialize the various 'constant' tables. 239 */ 240local void tr_static_init() 241{ 242#if defined(GEN_TREES_H) || !defined(STDC) 243 static int static_init_done = 0; 244 int n; /* iterates over tree elements */ 245 int bits; /* bit counter */ 246 int length; /* length value */ 247 int code; /* code value */ 248 int dist; /* distance index */ 249 ush bl_count[MAX_BITS+1]; 250 /* number of codes at each bit length for an optimal tree */ 251 252 if (static_init_done) return; 253 254 /* For some embedded targets, global variables are not initialized: */ 255 static_l_desc.static_tree = static_ltree; 256 static_l_desc.extra_bits = extra_lbits; 257 static_d_desc.static_tree = static_dtree; 258 static_d_desc.extra_bits = extra_dbits; 259 static_bl_desc.extra_bits = extra_blbits; 260 261 /* Initialize the mapping length (0..255) -> length code (0..28) */ 262 length = 0; 263 for (code = 0; code < LENGTH_CODES-1; code++) { 264 base_length[code] = length; 265 for (n = 0; n < (1<<extra_lbits[code]); n++) { 266 _length_code[length++] = (uch)code; 267 } 268 } 269 Assert (length == 256, "tr_static_init: length != 256"); 270 /* Note that the length 255 (match length 258) can be represented 271 * in two different ways: code 284 + 5 bits or code 285, so we 272 * overwrite length_code[255] to use the best encoding: 273 */ 274 _length_code[length-1] = (uch)code; 275 276 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 277 dist = 0; 278 for (code = 0 ; code < 16; code++) { 279 base_dist[code] = dist; 280 for (n = 0; n < (1<<extra_dbits[code]); n++) { 281 _dist_code[dist++] = (uch)code; 282 } 283 } 284 Assert (dist == 256, "tr_static_init: dist != 256"); 285 dist >>= 7; /* from now on, all distances are divided by 128 */ 286 for ( ; code < D_CODES; code++) { 287 base_dist[code] = dist << 7; 288 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { 289 _dist_code[256 + dist++] = (uch)code; 290 } 291 } 292 Assert (dist == 256, "tr_static_init: 256+dist != 512"); 293 294 /* Construct the codes of the static literal tree */ 295 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 296 n = 0; 297 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 298 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 299 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 300 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 301 /* Codes 286 and 287 do not exist, but we must include them in the 302 * tree construction to get a canonical Huffman tree (longest code 303 * all ones) 304 */ 305 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count); 306 307 /* The static distance tree is trivial: */ 308 for (n = 0; n < D_CODES; n++) { 309 static_dtree[n].Len = 5; 310 static_dtree[n].Code = bi_reverse((unsigned)n, 5); 311 } 312 static_init_done = 1; 313 314# ifdef GEN_TREES_H 315 gen_trees_header(); 316# endif 317#endif /* defined(GEN_TREES_H) || !defined(STDC) */ 318} 319 320/* =========================================================================== 321 * Genererate the file trees.h describing the static trees. 322 */ 323#ifdef GEN_TREES_H 324# ifndef DEBUG 325# include <stdio.h> 326# endif 327 328# define SEPARATOR(i, last, width) \ 329 ((i) == (last)? "\n};\n\n" : \ 330 ((i) % (width) == (width)-1 ? ",\n" : ", ")) 331 332void gen_trees_header() 333{ 334 FILE *header = fopen("trees.h", "w"); 335 int i; 336 337 Assert (header != NULL, "Can't open trees.h"); 338 fprintf(header, 339 "/* header created automatically with -DGEN_TREES_H */\n\n"); 340 341 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n"); 342 for (i = 0; i < L_CODES+2; i++) { 343 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code, 344 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5)); 345 } 346 347 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n"); 348 for (i = 0; i < D_CODES; i++) { 349 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code, 350 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5)); 351 } 352 353 fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n"); 354 for (i = 0; i < DIST_CODE_LEN; i++) { 355 fprintf(header, "%2u%s", _dist_code[i], 356 SEPARATOR(i, DIST_CODE_LEN-1, 20)); 357 } 358 359 fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n"); 360 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) { 361 fprintf(header, "%2u%s", _length_code[i], 362 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20)); 363 } 364 365 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n"); 366 for (i = 0; i < LENGTH_CODES; i++) { 367 fprintf(header, "%1u%s", base_length[i], 368 SEPARATOR(i, LENGTH_CODES-1, 20)); 369 } 370 371 fprintf(header, "local const int base_dist[D_CODES] = {\n"); 372 for (i = 0; i < D_CODES; i++) { 373 fprintf(header, "%5u%s", base_dist[i], 374 SEPARATOR(i, D_CODES-1, 10)); 375 } 376 377 fclose(header); 378} 379#endif /* GEN_TREES_H */ 380 381/* =========================================================================== 382 * Initialize the tree data structures for a new zlib stream. 383 */ 384void _tr_init(s) 385 deflate_state *s; 386{ 387 tr_static_init(); 388 389 s->l_desc.dyn_tree = s->dyn_ltree; 390 s->l_desc.stat_desc = &static_l_desc; 391 392 s->d_desc.dyn_tree = s->dyn_dtree; 393 s->d_desc.stat_desc = &static_d_desc; 394 395 s->bl_desc.dyn_tree = s->bl_tree; 396 s->bl_desc.stat_desc = &static_bl_desc; 397 398 s->bi_buf = 0; 399 s->bi_valid = 0; 400 s->last_eob_len = 8; /* enough lookahead for inflate */ 401#ifdef DEBUG 402 s->compressed_len = 0L; 403 s->bits_sent = 0L; 404#endif 405 406 /* Initialize the first block of the first file: */ 407 init_block(s); 408} 409 410/* =========================================================================== 411 * Initialize a new block. 412 */ 413local void init_block(s) 414 deflate_state *s; 415{ 416 int n; /* iterates over tree elements */ 417 418 /* Initialize the trees. */ 419 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; 420 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; 421 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; 422 423 s->dyn_ltree[END_BLOCK].Freq = 1; 424 s->opt_len = s->static_len = 0L; 425 s->last_lit = s->matches = 0; 426} 427 428#define SMALLEST 1 429/* Index within the heap array of least frequent node in the Huffman tree */ 430 431 432/* =========================================================================== 433 * Remove the smallest element from the heap and recreate the heap with 434 * one less element. Updates heap and heap_len. 435 */ 436#define pqremove(s, tree, top) \ 437{\ 438 top = s->heap[SMALLEST]; \ 439 s->heap[SMALLEST] = s->heap[s->heap_len--]; \ 440 pqdownheap(s, tree, SMALLEST); \ 441} 442 443/* =========================================================================== 444 * Compares to subtrees, using the tree depth as tie breaker when 445 * the subtrees have equal frequency. This minimizes the worst case length. 446 */ 447#define smaller(tree, n, m, depth) \ 448 (tree[n].Freq < tree[m].Freq || \ 449 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 450 451/* =========================================================================== 452 * Restore the heap property by moving down the tree starting at node k, 453 * exchanging a node with the smallest of its two sons if necessary, stopping 454 * when the heap property is re-established (each father smaller than its 455 * two sons). 456 */ 457local void pqdownheap(s, tree, k) 458 deflate_state *s; 459 ct_data *tree; /* the tree to restore */ 460 int k; /* node to move down */ 461{ 462 int v = s->heap[k]; 463 int j = k << 1; /* left son of k */ 464 while (j <= s->heap_len) { 465 /* Set j to the smallest of the two sons: */ 466 if (j < s->heap_len && 467 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { 468 j++; 469 } 470 /* Exit if v is smaller than both sons */ 471 if (smaller(tree, v, s->heap[j], s->depth)) break; 472 473 /* Exchange v with the smallest son */ 474 s->heap[k] = s->heap[j]; k = j; 475 476 /* And continue down the tree, setting j to the left son of k */ 477 j <<= 1; 478 } 479 s->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 */ 492local void gen_bitlen(s, desc) 493 deflate_state *s; 494 tree_desc *desc; /* the tree descriptor */ 495{ 496 ct_data *tree = desc->dyn_tree; 497 int max_code = desc->max_code; 498 const ct_data *stree = desc->stat_desc->static_tree; 499 const intf *extra = desc->stat_desc->extra_bits; 500 int base = desc->stat_desc->extra_base; 501 int max_length = desc->stat_desc->max_length; 502 int h; /* heap index */ 503 int n, m; /* iterate over the tree elements */ 504 int bits; /* bit length */ 505 int xbits; /* extra bits */ 506 ush f; /* frequency */ 507 int overflow = 0; /* number of elements with bit length too large */ 508 509 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; 510 511 /* In a first pass, compute the optimal bit lengths (which may 512 * overflow in the case of the bit length tree). 513 */ 514 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ 515 516 for (h = s->heap_max+1; h < HEAP_SIZE; h++) { 517 n = s->heap[h]; 518 bits = tree[tree[n].Dad].Len + 1; 519 if (bits > max_length) bits = max_length, overflow++; 520 tree[n].Len = (ush)bits; 521 /* We overwrite tree[n].Dad which is no longer needed */ 522 523 if (n > max_code) continue; /* not a leaf node */ 524 525 s->bl_count[bits]++; 526 xbits = 0; 527 if (n >= base) xbits = extra[n-base]; 528 f = tree[n].Freq; 529 s->opt_len += (ulg)f * (bits + xbits); 530 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); 531 } 532 if (overflow == 0) return; 533 534 Trace((stderr,"\nbit length overflow\n")); 535 /* This happens for example on obj2 and pic of the Calgary corpus */ 536 537 /* Find the first bit length which could increase: */ 538 do { 539 bits = max_length-1; 540 while (s->bl_count[bits] == 0) bits--; 541 s->bl_count[bits]--; /* move one leaf down the tree */ 542 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ 543 s->bl_count[max_length]--; 544 /* The brother of the overflow item also moves one step up, 545 * but this does not affect bl_count[max_length] 546 */ 547 overflow -= 2; 548 } while (overflow > 0); 549 550 /* Now recompute all bit lengths, scanning in increasing frequency. 551 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 552 * lengths instead of fixing only the wrong ones. This idea is taken 553 * from 'ar' written by Haruhiko Okumura.) 554 */ 555 for (bits = max_length; bits != 0; bits--) { 556 n = s->bl_count[bits]; 557 while (n != 0) { 558 m = s->heap[--h]; 559 if (m > max_code) continue; 560 if (tree[m].Len != (unsigned) bits) { 561 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 562 s->opt_len += ((long)bits - (long)tree[m].Len) 563 *(long)tree[m].Freq; 564 tree[m].Len = (ush)bits; 565 } 566 n--; 567 } 568 } 569} 570 571/* =========================================================================== 572 * Generate the codes for a given tree and bit counts (which need not be 573 * optimal). 574 * IN assertion: the array bl_count contains the bit length statistics for 575 * the given tree and the field len is set for all tree elements. 576 * OUT assertion: the field code is set for all tree elements of non 577 * zero code length. 578 */ 579local void gen_codes (tree, max_code, bl_count) 580 ct_data *tree; /* the tree to decorate */ 581 int max_code; /* largest code with non zero frequency */ 582 ushf *bl_count; /* number of codes at each bit length */ 583{ 584 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 585 ush code = 0; /* running code value */ 586 int bits; /* bit index */ 587 int n; /* code index */ 588 589 /* The distribution counts are first used to generate the code values 590 * without bit reversal. 591 */ 592 for (bits = 1; bits <= MAX_BITS; bits++) { 593 next_code[bits] = code = (code + bl_count[bits-1]) << 1; 594 } 595 /* Check that the bit counts in bl_count are consistent. The last code 596 * must be all ones. 597 */ 598 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, 599 "inconsistent bit counts"); 600 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 601 602 for (n = 0; n <= max_code; n++) { 603 int len = tree[n].Len; 604 if (len == 0) continue; 605 /* Now reverse the bits */ 606 tree[n].Code = bi_reverse(next_code[len]++, len); 607 608 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 609 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); 610 } 611} 612 613/* =========================================================================== 614 * Construct one Huffman tree and assigns the code bit strings and lengths. 615 * Update the total bit length for the current block. 616 * IN assertion: the field freq is set for all tree elements. 617 * OUT assertions: the fields len and code are set to the optimal bit length 618 * and corresponding code. The length opt_len is updated; static_len is 619 * also updated if stree is not null. The field max_code is set. 620 */ 621local void build_tree(s, desc) 622 deflate_state *s; 623 tree_desc *desc; /* the tree descriptor */ 624{ 625 ct_data *tree = desc->dyn_tree; 626 const ct_data *stree = desc->stat_desc->static_tree; 627 int elems = desc->stat_desc->elems; 628 int n, m; /* iterate over heap elements */ 629 int max_code = -1; /* largest code with non zero frequency */ 630 int node; /* new node being created */ 631 632 /* Construct the initial heap, with least frequent element in 633 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. 634 * heap[0] is not used. 635 */ 636 s->heap_len = 0, s->heap_max = HEAP_SIZE; 637 638 for (n = 0; n < elems; n++) { 639 if (tree[n].Freq != 0) { 640 s->heap[++(s->heap_len)] = max_code = n; 641 s->depth[n] = 0; 642 } else { 643 tree[n].Len = 0; 644 } 645 } 646 647 /* The pkzip format requires that at least one distance code exists, 648 * and that at least one bit should be sent even if there is only one 649 * possible code. So to avoid special checks later on we force at least 650 * two codes of non zero frequency. 651 */ 652 while (s->heap_len < 2) { 653 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); 654 tree[node].Freq = 1; 655 s->depth[node] = 0; 656 s->opt_len--; if (stree) s->static_len -= stree[node].Len; 657 /* node is 0 or 1 so it does not have extra bits */ 658 } 659 desc->max_code = max_code; 660 661 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, 662 * establish sub-heaps of increasing lengths: 663 */ 664 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); 665 666 /* Construct the Huffman tree by repeatedly combining the least two 667 * frequent nodes. 668 */ 669 node = elems; /* next internal node of the tree */ 670 do { 671 pqremove(s, tree, n); /* n = node of least frequency */ 672 m = s->heap[SMALLEST]; /* m = node of next least frequency */ 673 674 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ 675 s->heap[--(s->heap_max)] = m; 676 677 /* Create a new node father of n and m */ 678 tree[node].Freq = tree[n].Freq + tree[m].Freq; 679 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1); 680 tree[n].Dad = tree[m].Dad = (ush)node; 681#ifdef DUMP_BL_TREE 682 if (tree == s->bl_tree) { 683 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 684 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 685 } 686#endif 687 /* and insert the new node in the heap */ 688 s->heap[SMALLEST] = node++; 689 pqdownheap(s, tree, SMALLEST); 690 691 } while (s->heap_len >= 2); 692 693 s->heap[--(s->heap_max)] = s->heap[SMALLEST]; 694 695 /* At this point, the fields freq and dad are set. We can now 696 * generate the bit lengths. 697 */ 698 gen_bitlen(s, (tree_desc *)desc); 699 700 /* The field len is now set, we can generate the bit codes */ 701 gen_codes ((ct_data *)tree, max_code, s->bl_count); 702} 703 704/* =========================================================================== 705 * Scan a literal or distance tree to determine the frequencies of the codes 706 * in the bit length tree. 707 */ 708local void scan_tree (s, tree, max_code) 709 deflate_state *s; 710 ct_data *tree; /* the tree to be scanned */ 711 int max_code; /* and its largest code of non zero frequency */ 712{ 713 int n; /* iterates over all tree elements */ 714 int prevlen = -1; /* last emitted length */ 715 int curlen; /* length of current code */ 716 int nextlen = tree[0].Len; /* length of next code */ 717 int count = 0; /* repeat count of the current code */ 718 int max_count = 7; /* max repeat count */ 719 int min_count = 4; /* min repeat count */ 720 721 if (nextlen == 0) max_count = 138, min_count = 3; 722 tree[max_code+1].Len = (ush)0xffff; /* guard */ 723 724 for (n = 0; n <= max_code; n++) { 725 curlen = nextlen; nextlen = tree[n+1].Len; 726 if (++count < max_count && curlen == nextlen) { 727 continue; 728 } else if (count < min_count) { 729 s->bl_tree[curlen].Freq += count; 730 } else if (curlen != 0) { 731 if (curlen != prevlen) s->bl_tree[curlen].Freq++; 732 s->bl_tree[REP_3_6].Freq++; 733 } else if (count <= 10) { 734 s->bl_tree[REPZ_3_10].Freq++; 735 } else { 736 s->bl_tree[REPZ_11_138].Freq++; 737 } 738 count = 0; prevlen = curlen; 739 if (nextlen == 0) { 740 max_count = 138, min_count = 3; 741 } else if (curlen == nextlen) { 742 max_count = 6, min_count = 3; 743 } else { 744 max_count = 7, min_count = 4; 745 } 746 } 747} 748 749/* =========================================================================== 750 * Send a literal or distance tree in compressed form, using the codes in 751 * bl_tree. 752 */ 753local void send_tree (s, tree, max_code) 754 deflate_state *s; 755 ct_data *tree; /* the tree to be scanned */ 756 int max_code; /* and its largest code of non zero frequency */ 757{ 758 int n; /* iterates over all tree elements */ 759 int prevlen = -1; /* last emitted length */ 760 int curlen; /* length of current code */ 761 int nextlen = tree[0].Len; /* length of next code */ 762 int count = 0; /* repeat count of the current code */ 763 int max_count = 7; /* max repeat count */ 764 int min_count = 4; /* min repeat count */ 765 766 /* tree[max_code+1].Len = -1; */ /* guard already set */ 767 if (nextlen == 0) max_count = 138, min_count = 3; 768 769 for (n = 0; n <= max_code; n++) { 770 curlen = nextlen; nextlen = tree[n+1].Len; 771 if (++count < max_count && curlen == nextlen) { 772 continue; 773 } else if (count < min_count) { 774 do { send_code(s, curlen, s->bl_tree); } while (--count != 0); 775 776 } else if (curlen != 0) { 777 if (curlen != prevlen) { 778 send_code(s, curlen, s->bl_tree); count--; 779 } 780 Assert(count >= 3 && count <= 6, " 3_6?"); 781 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); 782 783 } else if (count <= 10) { 784 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); 785 786 } else { 787 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); 788 } 789 count = 0; prevlen = curlen; 790 if (nextlen == 0) { 791 max_count = 138, min_count = 3; 792 } else if (curlen == nextlen) { 793 max_count = 6, min_count = 3; 794 } else { 795 max_count = 7, min_count = 4; 796 } 797 } 798} 799 800/* =========================================================================== 801 * Construct the Huffman tree for the bit lengths and return the index in 802 * bl_order of the last bit length code to send. 803 */ 804local int build_bl_tree(s) 805 deflate_state *s; 806{ 807 int max_blindex; /* index of last bit length code of non zero freq */ 808 809 /* Determine the bit length frequencies for literal and distance trees */ 810 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); 811 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); 812 813 /* Build the bit length tree: */ 814 build_tree(s, (tree_desc *)(&(s->bl_desc))); 815 /* opt_len now includes the length of the tree representations, except 816 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. 817 */ 818 819 /* Determine the number of bit length codes to send. The pkzip format 820 * requires that at least 4 bit length codes be sent. (appnote.txt says 821 * 3 but the actual value used is 4.) 822 */ 823 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { 824 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; 825 } 826 /* Update opt_len to include the bit length tree and counts */ 827 s->opt_len += 3*(max_blindex+1) + 5+5+4; 828 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", 829 s->opt_len, s->static_len)); 830 831 return max_blindex; 832} 833 834/* =========================================================================== 835 * Send the header for a block using dynamic Huffman trees: the counts, the 836 * lengths of the bit length codes, the literal tree and the distance tree. 837 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 838 */ 839local void send_all_trees(s, lcodes, dcodes, blcodes) 840 deflate_state *s; 841 int lcodes, dcodes, blcodes; /* number of codes for each tree */ 842{ 843 int rank; /* index in bl_order */ 844 845 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); 846 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, 847 "too many codes"); 848 Tracev((stderr, "\nbl counts: ")); 849 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */ 850 send_bits(s, dcodes-1, 5); 851 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */ 852 for (rank = 0; rank < blcodes; rank++) { 853 Tracev((stderr, "\nbl code %2d ", bl_order[rank])); 854 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); 855 } 856 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); 857 858 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ 859 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); 860 861 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ 862 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); 863} 864 865/* =========================================================================== 866 * Send a stored block 867 */ 868void _tr_stored_block(s, buf, stored_len, eof) 869 deflate_state *s; 870 charf *buf; /* input block */ 871 ulg stored_len; /* length of input block */ 872 int eof; /* true if this is the last block for a file */ 873{ 874 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */ 875#ifdef DEBUG 876 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; 877 s->compressed_len += (stored_len + 4) << 3; 878#endif 879 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */ 880} 881 882/* =========================================================================== 883 * Send one empty static block to give enough lookahead for inflate. 884 * This takes 10 bits, of which 7 may remain in the bit buffer. 885 * The current inflate code requires 9 bits of lookahead. If the 886 * last two codes for the previous block (real code plus EOB) were coded 887 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode 888 * the last real code. In this case we send two empty static blocks instead 889 * of one. (There are no problems if the previous block is stored or fixed.) 890 * To simplify the code, we assume the worst case of last real code encoded 891 * on one bit only. 892 */ 893void _tr_align(s) 894 deflate_state *s; 895{ 896 send_bits(s, STATIC_TREES<<1, 3); 897 send_code(s, END_BLOCK, static_ltree); 898#ifdef DEBUG 899 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ 900#endif 901 bi_flush(s); 902 /* Of the 10 bits for the empty block, we have already sent 903 * (10 - bi_valid) bits. The lookahead for the last real code (before 904 * the EOB of the previous block) was thus at least one plus the length 905 * of the EOB plus what we have just sent of the empty static block. 906 */ 907 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) { 908 send_bits(s, STATIC_TREES<<1, 3); 909 send_code(s, END_BLOCK, static_ltree); 910#ifdef DEBUG 911 s->compressed_len += 10L; 912#endif 913 bi_flush(s); 914 } 915 s->last_eob_len = 7; 916} 917 918/* =========================================================================== 919 * Determine the best encoding for the current block: dynamic trees, static 920 * trees or store, and output the encoded block to the zip file. 921 */ 922void _tr_flush_block(s, buf, stored_len, eof) 923 deflate_state *s; 924 charf *buf; /* input block, or NULL if too old */ 925 ulg stored_len; /* length of input block */ 926 int eof; /* true if this is the last block for a file */ 927{ 928 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 929 int max_blindex = 0; /* index of last bit length code of non zero freq */ 930 931 /* Build the Huffman trees unless a stored block is forced */ 932 if (s->level > 0) { 933 934 /* Check if the file is ascii or binary */ 935 if (s->data_type == Z_UNKNOWN) set_data_type(s); 936 937 /* Construct the literal and distance trees */ 938 build_tree(s, (tree_desc *)(&(s->l_desc))); 939 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len, 940 s->static_len)); 941 942 build_tree(s, (tree_desc *)(&(s->d_desc))); 943 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len, 944 s->static_len)); 945 /* At this point, opt_len and static_len are the total bit lengths of 946 * the compressed block data, excluding the tree representations. 947 */ 948 949 /* Build the bit length tree for the above two trees, and get the index 950 * in bl_order of the last bit length code to send. 951 */ 952 max_blindex = build_bl_tree(s); 953 954 /* Determine the best encoding. Compute first the block length in bytes*/ 955 opt_lenb = (s->opt_len+3+7)>>3; 956 static_lenb = (s->static_len+3+7)>>3; 957 958 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", 959 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, 960 s->last_lit)); 961 962 if (static_lenb <= opt_lenb) opt_lenb = static_lenb; 963 964 } else { 965 Assert(buf != (char*)0, "lost buf"); 966 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */ 967 } 968 969#ifdef FORCE_STORED 970 if (buf != (char*)0) { /* force stored block */ 971#else 972 if (stored_len+4 <= opt_lenb && buf != (char*)0) { 973 /* 4: two words for the lengths */ 974#endif 975 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. 976 * Otherwise we can't have processed more than WSIZE input bytes since 977 * the last block flush, because compression would have been 978 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to 979 * transform a block into a stored block. 980 */ 981 _tr_stored_block(s, buf, stored_len, eof); 982 983#ifdef FORCE_STATIC 984 } else if (static_lenb >= 0) { /* force static trees */ 985#else 986 } else if (static_lenb == opt_lenb) { 987#endif 988 send_bits(s, (STATIC_TREES<<1)+eof, 3); 989 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree); 990#ifdef DEBUG 991 s->compressed_len += 3 + s->static_len; 992#endif 993 } else { 994 send_bits(s, (DYN_TREES<<1)+eof, 3); 995 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1, 996 max_blindex+1); 997 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree); 998#ifdef DEBUG 999 s->compressed_len += 3 + s->opt_len; 1000#endif 1001 } 1002 Assert (s->compressed_len == s->bits_sent, "bad compressed size"); 1003 /* The above check is made mod 2^32, for files larger than 512 MB 1004 * and uLong implemented on 32 bits. 1005 */ 1006 init_block(s); 1007 1008 if (eof) { 1009 bi_windup(s); 1010#ifdef DEBUG 1011 s->compressed_len += 7; /* align on byte boundary */ 1012#endif 1013 } 1014 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3, 1015 s->compressed_len-7*eof)); 1016} 1017 1018/* =========================================================================== 1019 * Save the match info and tally the frequency counts. Return true if 1020 * the current block must be flushed. 1021 */ 1022int _tr_tally (s, dist, lc) 1023 deflate_state *s; 1024 unsigned dist; /* distance of matched string */ 1025 unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ 1026{ 1027 s->d_buf[s->last_lit] = (ush)dist; 1028 s->l_buf[s->last_lit++] = (uch)lc; 1029 if (dist == 0) { 1030 /* lc is the unmatched char */ 1031 s->dyn_ltree[lc].Freq++; 1032 } else { 1033 s->matches++; 1034 /* Here, lc is the match length - MIN_MATCH */ 1035 dist--; /* dist = match distance - 1 */ 1036 Assert((ush)dist < (ush)MAX_DIST(s) && 1037 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && 1038 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match"); 1039 1040 s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++; 1041 s->dyn_dtree[d_code(dist)].Freq++; 1042 } 1043 1044#ifdef TRUNCATE_BLOCK 1045 /* Try to guess if it is profitable to stop the current block here */ 1046 if ((s->last_lit & 0x1fff) == 0 && s->level > 2) { 1047 /* Compute an upper bound for the compressed length */ 1048 ulg out_length = (ulg)s->last_lit*8L; 1049 ulg in_length = (ulg)((long)s->strstart - s->block_start); 1050 int dcode; 1051 for (dcode = 0; dcode < D_CODES; dcode++) { 1052 out_length += (ulg)s->dyn_dtree[dcode].Freq * 1053 (5L+extra_dbits[dcode]); 1054 } 1055 out_length >>= 3; 1056 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", 1057 s->last_lit, in_length, out_length, 1058 100L - out_length*100L/in_length)); 1059 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1; 1060 } 1061#endif 1062 return (s->last_lit == s->lit_bufsize-1); 1063 /* We avoid equality with lit_bufsize because of wraparound at 64K 1064 * on 16 bit machines and because stored blocks are restricted to 1065 * 64K-1 bytes. 1066 */ 1067} 1068 1069/* =========================================================================== 1070 * Send the block data compressed using the given Huffman trees 1071 */ 1072local void compress_block(s, ltree, dtree) 1073 deflate_state *s; 1074 ct_data *ltree; /* literal tree */ 1075 ct_data *dtree; /* distance tree */ 1076{ 1077 unsigned dist; /* distance of matched string */ 1078 int lc; /* match length or unmatched char (if dist == 0) */ 1079 unsigned lx = 0; /* running index in l_buf */ 1080 unsigned code; /* the code to send */ 1081 int extra; /* number of extra bits to send */ 1082 1083 if (s->last_lit != 0) do { 1084 dist = s->d_buf[lx]; 1085 lc = s->l_buf[lx++]; 1086 if (dist == 0) { 1087 send_code(s, lc, ltree); /* send a literal byte */ 1088 Tracecv(isgraph(lc), (stderr," '%c' ", lc)); 1089 } else { 1090 /* Here, lc is the match length - MIN_MATCH */ 1091 code = _length_code[lc]; 1092 send_code(s, code+LITERALS+1, ltree); /* send the length code */ 1093 extra = extra_lbits[code]; 1094 if (extra != 0) { 1095 lc -= base_length[code]; 1096 send_bits(s, lc, extra); /* send the extra length bits */ 1097 } 1098 dist--; /* dist is now the match distance - 1 */ 1099 code = d_code(dist); 1100 Assert (code < D_CODES, "bad d_code"); 1101 1102 send_code(s, code, dtree); /* send the distance code */ 1103 extra = extra_dbits[code]; 1104 if (extra != 0) { 1105 dist -= base_dist[code]; 1106 send_bits(s, dist, extra); /* send the extra distance bits */ 1107 } 1108 } /* literal or match pair ? */ 1109 1110 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */ 1111 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow"); 1112 1113 } while (lx < s->last_lit); 1114 1115 send_code(s, END_BLOCK, ltree); 1116 s->last_eob_len = ltree[END_BLOCK].Len; 1117} 1118 1119/* =========================================================================== 1120 * Set the data type to ASCII or BINARY, using a crude approximation: 1121 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. 1122 * IN assertion: the fields freq of dyn_ltree are set and the total of all 1123 * frequencies does not exceed 64K (to fit in an int on 16 bit machines). 1124 */ 1125local void set_data_type(s) 1126 deflate_state *s; 1127{ 1128 int n = 0; 1129 unsigned ascii_freq = 0; 1130 unsigned bin_freq = 0; 1131 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq; 1132 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq; 1133 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq; 1134 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII); 1135} 1136 1137/* =========================================================================== 1138 * Reverse the first len bits of a code, using straightforward code (a faster 1139 * method would use a table) 1140 * IN assertion: 1 <= len <= 15 1141 */ 1142local unsigned bi_reverse(code, len) 1143 unsigned code; /* the value to invert */ 1144 int len; /* its bit length */ 1145{ 1146 register unsigned res = 0; 1147 do { 1148 res |= code & 1; 1149 code >>= 1, res <<= 1; 1150 } while (--len > 0); 1151 return res >> 1; 1152} 1153 1154/* =========================================================================== 1155 * Flush the bit buffer, keeping at most 7 bits in it. 1156 */ 1157local void bi_flush(s) 1158 deflate_state *s; 1159{ 1160 if (s->bi_valid == 16) { 1161 put_short(s, s->bi_buf); 1162 s->bi_buf = 0; 1163 s->bi_valid = 0; 1164 } else if (s->bi_valid >= 8) { 1165 put_byte(s, (Byte)s->bi_buf); 1166 s->bi_buf >>= 8; 1167 s->bi_valid -= 8; 1168 } 1169} 1170 1171/* =========================================================================== 1172 * Flush the bit buffer and align the output on a byte boundary 1173 */ 1174local void bi_windup(s) 1175 deflate_state *s; 1176{ 1177 if (s->bi_valid > 8) { 1178 put_short(s, s->bi_buf); 1179 } else if (s->bi_valid > 0) { 1180 put_byte(s, (Byte)s->bi_buf); 1181 } 1182 s->bi_buf = 0; 1183 s->bi_valid = 0; 1184#ifdef DEBUG 1185 s->bits_sent = (s->bits_sent+7) & ~7; 1186#endif 1187} 1188 1189/* =========================================================================== 1190 * Copy a stored block, storing first the length and its 1191 * one's complement if requested. 1192 */ 1193local void copy_block(s, buf, len, header) 1194 deflate_state *s; 1195 charf *buf; /* the input data */ 1196 unsigned len; /* its length */ 1197 int header; /* true if block header must be written */ 1198{ 1199 bi_windup(s); /* align on byte boundary */ 1200 s->last_eob_len = 8; /* enough lookahead for inflate */ 1201 1202 if (header) { 1203 put_short(s, (ush)len); 1204 put_short(s, (ush)~len); 1205#ifdef DEBUG 1206 s->bits_sent += 2*16; 1207#endif 1208 } 1209#ifdef DEBUG 1210 s->bits_sent += (ulg)len<<3; 1211#endif 1212 while (len--) { 1213 put_byte(s, *buf++); 1214 } 1215} 1216