1 /* $NetBSD: trees.c,v 1.7 2024/09/22 19:12:27 christos Exp $ */ 2 3 /* trees.c -- output deflated data using Huffman coding 4 * Copyright (C) 1995-2024 Jean-loup Gailly 5 * detect_data_type() function provided freely by Cosmin Truta, 2006 6 * For conditions of distribution and use, see copyright notice in zlib.h 7 */ 8 9 /* 10 * ALGORITHM 11 * 12 * The "deflation" process uses several Huffman trees. The more 13 * common source values are represented by shorter bit sequences. 14 * 15 * Each code tree is stored in a compressed form which is itself 16 * a Huffman encoding of the lengths of all the code strings (in 17 * ascending order by source values). The actual code strings are 18 * reconstructed from the lengths in the inflate process, as described 19 * in the deflate specification. 20 * 21 * REFERENCES 22 * 23 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". 24 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc 25 * 26 * Storer, James A. 27 * Data Compression: Methods and Theory, pp. 49-50. 28 * Computer Science Press, 1988. ISBN 0-7167-8156-5. 29 * 30 * Sedgewick, R. 31 * Algorithms, p290. 32 * Addison-Wesley, 1983. ISBN 0-201-06672-6. 33 */ 34 35 /* @(#) Id */ 36 37 /* #define GEN_TREES_H */ 38 39 #include "deflate.h" 40 41 #ifdef ZLIB_DEBUG 42 # include <ctype.h> 43 #endif 44 45 /* =========================================================================== 46 * Constants 47 */ 48 49 #define MAX_BL_BITS 7 50 /* Bit length codes must not exceed MAX_BL_BITS bits */ 51 52 #define END_BLOCK 256 53 /* end of block literal code */ 54 55 #define REP_3_6 16 56 /* repeat previous bit length 3-6 times (2 bits of repeat count) */ 57 58 #define REPZ_3_10 17 59 /* repeat a zero length 3-10 times (3 bits of repeat count) */ 60 61 #define REPZ_11_138 18 62 /* repeat a zero length 11-138 times (7 bits of repeat count) */ 63 64 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */ 65 = {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}; 66 67 local const int extra_dbits[D_CODES] /* extra bits for each distance code */ 68 = {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}; 69 70 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */ 71 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; 72 73 local const uch bl_order[BL_CODES] 74 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; 75 /* The lengths of the bit length codes are sent in order of decreasing 76 * probability, to avoid transmitting the lengths for unused bit length codes. 77 */ 78 79 /* =========================================================================== 80 * Local data. These are initialized only once. 81 */ 82 83 #define DIST_CODE_LEN 512 /* see definition of array dist_code below */ 84 85 #if defined(GEN_TREES_H) || !defined(STDC) 86 /* non ANSI compilers may not accept trees.h */ 87 88 local ct_data static_ltree[L_CODES+2]; 89 /* The static literal tree. Since the bit lengths are imposed, there is no 90 * need for the L_CODES extra codes used during heap construction. However 91 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init 92 * below). 93 */ 94 95 local ct_data static_dtree[D_CODES]; 96 /* The static distance tree. (Actually a trivial tree since all codes use 97 * 5 bits.) 98 */ 99 100 uch _dist_code[DIST_CODE_LEN]; 101 /* Distance codes. The first 256 values correspond to the distances 102 * 3 .. 258, the last 256 values correspond to the top 8 bits of 103 * the 15 bit distances. 104 */ 105 106 uch _length_code[MAX_MATCH-MIN_MATCH+1]; 107 /* length code for each normalized match length (0 == MIN_MATCH) */ 108 109 local int base_length[LENGTH_CODES]; 110 /* First normalized length for each code (0 = MIN_MATCH) */ 111 112 local int base_dist[D_CODES]; 113 /* First normalized distance for each code (0 = distance of 1) */ 114 115 #else 116 # include "trees.h" 117 #endif /* GEN_TREES_H */ 118 119 struct static_tree_desc_s { 120 const ct_data *static_tree; /* static tree or NULL */ 121 const intf *extra_bits; /* extra bits for each code or NULL */ 122 int extra_base; /* base index for extra_bits */ 123 int elems; /* max number of elements in the tree */ 124 int max_length; /* max bit length for the codes */ 125 }; 126 127 #ifdef NO_INIT_GLOBAL_POINTERS 128 # define TCONST 129 #else 130 # define TCONST const 131 #endif 132 133 local TCONST static_tree_desc static_l_desc = 134 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; 135 136 local TCONST static_tree_desc static_d_desc = 137 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS}; 138 139 local TCONST static_tree_desc static_bl_desc = 140 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS}; 141 142 /* =========================================================================== 143 * Output a short LSB first on the stream. 144 * IN assertion: there is enough room in pendingBuf. 145 */ 146 #define put_short(s, w) { \ 147 put_byte(s, (uch)((w) & 0xff)); \ 148 put_byte(s, (uch)((ush)(w) >> 8)); \ 149 } 150 151 /* =========================================================================== 152 * Reverse the first len bits of a code, using straightforward code (a faster 153 * method would use a table) 154 * IN assertion: 1 <= len <= 15 155 */ 156 local unsigned bi_reverse(unsigned code, int len) { 157 register unsigned res = 0; 158 do { 159 res |= code & 1; 160 code >>= 1, res <<= 1; 161 } while (--len > 0); 162 return res >> 1; 163 } 164 165 /* =========================================================================== 166 * Flush the bit buffer, keeping at most 7 bits in it. 167 */ 168 local void bi_flush(deflate_state *s) { 169 if (s->bi_valid == 16) { 170 put_short(s, s->bi_buf); 171 s->bi_buf = 0; 172 s->bi_valid = 0; 173 } else if (s->bi_valid >= 8) { 174 put_byte(s, (Byte)s->bi_buf); 175 s->bi_buf >>= 8; 176 s->bi_valid -= 8; 177 } 178 } 179 180 /* =========================================================================== 181 * Flush the bit buffer and align the output on a byte boundary 182 */ 183 local void bi_windup(deflate_state *s) { 184 if (s->bi_valid > 8) { 185 put_short(s, s->bi_buf); 186 } else if (s->bi_valid > 0) { 187 put_byte(s, (Byte)s->bi_buf); 188 } 189 s->bi_buf = 0; 190 s->bi_valid = 0; 191 #ifdef ZLIB_DEBUG 192 s->bits_sent = (s->bits_sent + 7) & ~7; 193 #endif 194 } 195 196 /* =========================================================================== 197 * Generate the codes for a given tree and bit counts (which need not be 198 * optimal). 199 * IN assertion: the array bl_count contains the bit length statistics for 200 * the given tree and the field len is set for all tree elements. 201 * OUT assertion: the field code is set for all tree elements of non 202 * zero code length. 203 */ 204 local void gen_codes(ct_data *tree, int max_code, ushf *bl_count) { 205 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 206 unsigned code = 0; /* running code value */ 207 int bits; /* bit index */ 208 int n; /* code index */ 209 210 /* The distribution counts are first used to generate the code values 211 * without bit reversal. 212 */ 213 for (bits = 1; bits <= MAX_BITS; bits++) { 214 code = (code + bl_count[bits - 1]) << 1; 215 next_code[bits] = (ush)code; 216 } 217 /* Check that the bit counts in bl_count are consistent. The last code 218 * must be all ones. 219 */ 220 Assert (code + bl_count[MAX_BITS] - 1 == (1 << MAX_BITS) - 1, 221 "inconsistent bit counts"); 222 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 223 224 for (n = 0; n <= max_code; n++) { 225 int len = tree[n].Len; 226 if (len == 0) continue; 227 /* Now reverse the bits */ 228 tree[n].Code = (ush)bi_reverse(next_code[len]++, len); 229 230 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 231 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len] - 1)); 232 } 233 } 234 235 #ifdef GEN_TREES_H 236 local void gen_trees_header(void); 237 #endif 238 239 #ifndef ZLIB_DEBUG 240 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len) 241 /* Send a code of the given tree. c and tree must not have side effects */ 242 243 #else /* !ZLIB_DEBUG */ 244 # define send_code(s, c, tree) \ 245 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \ 246 send_bits(s, tree[c].Code, tree[c].Len); } 247 #endif 248 249 /* =========================================================================== 250 * Send a value on a given number of bits. 251 * IN assertion: length <= 16 and value fits in length bits. 252 */ 253 #ifdef ZLIB_DEBUG 254 local void send_bits(deflate_state *s, int value, int length) { 255 Tracevv((stderr," l %2d v %4x ", length, value)); 256 Assert(length > 0 && length <= 15, "invalid length"); 257 s->bits_sent += (ulg)length; 258 259 /* If not enough room in bi_buf, use (valid) bits from bi_buf and 260 * (16 - bi_valid) bits from value, leaving (width - (16 - bi_valid)) 261 * unused bits in value. 262 */ 263 if (s->bi_valid > (int)Buf_size - length) { 264 s->bi_buf |= (ush)value << s->bi_valid; 265 put_short(s, s->bi_buf); 266 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid); 267 s->bi_valid += length - Buf_size; 268 } else { 269 s->bi_buf |= (ush)value << s->bi_valid; 270 s->bi_valid += length; 271 } 272 } 273 #else /* !ZLIB_DEBUG */ 274 275 #define send_bits(s, value, length) \ 276 { int len = length;\ 277 if (s->bi_valid > (int)Buf_size - len) {\ 278 int val = (int)value;\ 279 s->bi_buf |= (ush)val << s->bi_valid;\ 280 put_short(s, s->bi_buf);\ 281 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\ 282 s->bi_valid += len - Buf_size;\ 283 } else {\ 284 s->bi_buf |= (ush)(value) << s->bi_valid;\ 285 s->bi_valid += len;\ 286 }\ 287 } 288 #endif /* ZLIB_DEBUG */ 289 290 291 /* the arguments must not have side effects */ 292 293 /* =========================================================================== 294 * Initialize the various 'constant' tables. 295 */ 296 local void tr_static_init(void) { 297 #if defined(GEN_TREES_H) || !defined(STDC) 298 static int static_init_done = 0; 299 int n; /* iterates over tree elements */ 300 int bits; /* bit counter */ 301 int length; /* length value */ 302 int code; /* code value */ 303 int dist; /* distance index */ 304 ush bl_count[MAX_BITS+1]; 305 /* number of codes at each bit length for an optimal tree */ 306 307 if (static_init_done) return; 308 309 /* For some embedded targets, global variables are not initialized: */ 310 #ifdef NO_INIT_GLOBAL_POINTERS 311 static_l_desc.static_tree = static_ltree; 312 static_l_desc.extra_bits = extra_lbits; 313 static_d_desc.static_tree = static_dtree; 314 static_d_desc.extra_bits = extra_dbits; 315 static_bl_desc.extra_bits = extra_blbits; 316 #endif 317 318 /* Initialize the mapping length (0..255) -> length code (0..28) */ 319 length = 0; 320 for (code = 0; code < LENGTH_CODES-1; code++) { 321 base_length[code] = length; 322 for (n = 0; n < (1 << extra_lbits[code]); n++) { 323 _length_code[length++] = (uch)code; 324 } 325 } 326 Assert (length == 256, "tr_static_init: length != 256"); 327 /* Note that the length 255 (match length 258) can be represented 328 * in two different ways: code 284 + 5 bits or code 285, so we 329 * overwrite length_code[255] to use the best encoding: 330 */ 331 _length_code[length - 1] = (uch)code; 332 333 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 334 dist = 0; 335 for (code = 0 ; code < 16; code++) { 336 base_dist[code] = dist; 337 for (n = 0; n < (1 << extra_dbits[code]); n++) { 338 _dist_code[dist++] = (uch)code; 339 } 340 } 341 Assert (dist == 256, "tr_static_init: dist != 256"); 342 dist >>= 7; /* from now on, all distances are divided by 128 */ 343 for ( ; code < D_CODES; code++) { 344 base_dist[code] = dist << 7; 345 for (n = 0; n < (1 << (extra_dbits[code] - 7)); n++) { 346 _dist_code[256 + dist++] = (uch)code; 347 } 348 } 349 Assert (dist == 256, "tr_static_init: 256 + dist != 512"); 350 351 /* Construct the codes of the static literal tree */ 352 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 353 n = 0; 354 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 355 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 356 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 357 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 358 /* Codes 286 and 287 do not exist, but we must include them in the 359 * tree construction to get a canonical Huffman tree (longest code 360 * all ones) 361 */ 362 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count); 363 364 /* The static distance tree is trivial: */ 365 for (n = 0; n < D_CODES; n++) { 366 static_dtree[n].Len = 5; 367 static_dtree[n].Code = bi_reverse((unsigned)n, 5); 368 } 369 static_init_done = 1; 370 371 # ifdef GEN_TREES_H 372 gen_trees_header(); 373 # endif 374 #endif /* defined(GEN_TREES_H) || !defined(STDC) */ 375 } 376 377 /* =========================================================================== 378 * Generate the file trees.h describing the static trees. 379 */ 380 #ifdef GEN_TREES_H 381 # ifndef ZLIB_DEBUG 382 # include <stdio.h> 383 # endif 384 385 # define SEPARATOR(i, last, width) \ 386 ((i) == (last)? "\n};\n\n" : \ 387 ((i) % (width) == (width) - 1 ? ",\n" : ", ")) 388 389 void gen_trees_header(void) { 390 FILE *header = fopen("trees.h", "w"); 391 int i; 392 393 Assert (header != NULL, "Can't open trees.h"); 394 fprintf(header, 395 "/* header created automatically with -DGEN_TREES_H */\n\n"); 396 397 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n"); 398 for (i = 0; i < L_CODES+2; i++) { 399 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code, 400 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5)); 401 } 402 403 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n"); 404 for (i = 0; i < D_CODES; i++) { 405 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code, 406 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5)); 407 } 408 409 fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n"); 410 for (i = 0; i < DIST_CODE_LEN; i++) { 411 fprintf(header, "%2u%s", _dist_code[i], 412 SEPARATOR(i, DIST_CODE_LEN-1, 20)); 413 } 414 415 fprintf(header, 416 "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n"); 417 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) { 418 fprintf(header, "%2u%s", _length_code[i], 419 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20)); 420 } 421 422 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n"); 423 for (i = 0; i < LENGTH_CODES; i++) { 424 fprintf(header, "%1u%s", base_length[i], 425 SEPARATOR(i, LENGTH_CODES-1, 20)); 426 } 427 428 fprintf(header, "local const int base_dist[D_CODES] = {\n"); 429 for (i = 0; i < D_CODES; i++) { 430 fprintf(header, "%5u%s", base_dist[i], 431 SEPARATOR(i, D_CODES-1, 10)); 432 } 433 434 fclose(header); 435 } 436 #endif /* GEN_TREES_H */ 437 438 /* =========================================================================== 439 * Initialize a new block. 440 */ 441 local void init_block(deflate_state *s) { 442 int n; /* iterates over tree elements */ 443 444 /* Initialize the trees. */ 445 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; 446 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; 447 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; 448 449 s->dyn_ltree[END_BLOCK].Freq = 1; 450 s->opt_len = s->static_len = 0L; 451 s->sym_next = s->matches = 0; 452 } 453 454 /* =========================================================================== 455 * Initialize the tree data structures for a new zlib stream. 456 */ 457 void ZLIB_INTERNAL _tr_init(deflate_state *s) { 458 tr_static_init(); 459 460 s->l_desc.dyn_tree = s->dyn_ltree; 461 s->l_desc.stat_desc = &static_l_desc; 462 463 s->d_desc.dyn_tree = s->dyn_dtree; 464 s->d_desc.stat_desc = &static_d_desc; 465 466 s->bl_desc.dyn_tree = s->bl_tree; 467 s->bl_desc.stat_desc = &static_bl_desc; 468 469 s->bi_buf = 0; 470 s->bi_valid = 0; 471 #ifdef ZLIB_DEBUG 472 s->compressed_len = 0L; 473 s->bits_sent = 0L; 474 #endif 475 476 /* Initialize the first block of the first file: */ 477 init_block(s); 478 } 479 480 #define SMALLEST 1 481 /* Index within the heap array of least frequent node in the Huffman tree */ 482 483 484 /* =========================================================================== 485 * Remove the smallest element from the heap and recreate the heap with 486 * one less element. Updates heap and heap_len. 487 */ 488 #define pqremove(s, tree, top) \ 489 {\ 490 top = s->heap[SMALLEST]; \ 491 s->heap[SMALLEST] = s->heap[s->heap_len--]; \ 492 pqdownheap(s, tree, SMALLEST); \ 493 } 494 495 /* =========================================================================== 496 * Compares to subtrees, using the tree depth as tie breaker when 497 * the subtrees have equal frequency. This minimizes the worst case length. 498 */ 499 #define smaller(tree, n, m, depth) \ 500 (tree[n].Freq < tree[m].Freq || \ 501 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 502 503 /* =========================================================================== 504 * Restore the heap property by moving down the tree starting at node k, 505 * exchanging a node with the smallest of its two sons if necessary, stopping 506 * when the heap property is re-established (each father smaller than its 507 * two sons). 508 */ 509 local void pqdownheap(deflate_state *s, ct_data *tree, int k) { 510 int v = s->heap[k]; 511 int j = k << 1; /* left son of k */ 512 while (j <= s->heap_len) { 513 /* Set j to the smallest of the two sons: */ 514 if (j < s->heap_len && 515 smaller(tree, s->heap[j + 1], s->heap[j], s->depth)) { 516 j++; 517 } 518 /* Exit if v is smaller than both sons */ 519 if (smaller(tree, v, s->heap[j], s->depth)) break; 520 521 /* Exchange v with the smallest son */ 522 s->heap[k] = s->heap[j]; k = j; 523 524 /* And continue down the tree, setting j to the left son of k */ 525 j <<= 1; 526 } 527 s->heap[k] = v; 528 } 529 530 /* =========================================================================== 531 * Compute the optimal bit lengths for a tree and update the total bit length 532 * for the current block. 533 * IN assertion: the fields freq and dad are set, heap[heap_max] and 534 * above are the tree nodes sorted by increasing frequency. 535 * OUT assertions: the field len is set to the optimal bit length, the 536 * array bl_count contains the frequencies for each bit length. 537 * The length opt_len is updated; static_len is also updated if stree is 538 * not null. 539 */ 540 local void gen_bitlen(deflate_state *s, tree_desc *desc) { 541 ct_data *tree = desc->dyn_tree; 542 int max_code = desc->max_code; 543 const ct_data *stree = desc->stat_desc->static_tree; 544 const intf *extra = desc->stat_desc->extra_bits; 545 int base = desc->stat_desc->extra_base; 546 int max_length = desc->stat_desc->max_length; 547 int h; /* heap index */ 548 int n, m; /* iterate over the tree elements */ 549 int bits; /* bit length */ 550 int xbits; /* extra bits */ 551 ush f; /* frequency */ 552 int overflow = 0; /* number of elements with bit length too large */ 553 554 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; 555 556 /* In a first pass, compute the optimal bit lengths (which may 557 * overflow in the case of the bit length tree). 558 */ 559 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ 560 561 for (h = s->heap_max + 1; h < HEAP_SIZE; h++) { 562 n = s->heap[h]; 563 bits = tree[tree[n].Dad].Len + 1; 564 if (bits > max_length) bits = max_length, overflow++; 565 tree[n].Len = (ush)bits; 566 /* We overwrite tree[n].Dad which is no longer needed */ 567 568 if (n > max_code) continue; /* not a leaf node */ 569 570 s->bl_count[bits]++; 571 xbits = 0; 572 if (n >= base) xbits = extra[n - base]; 573 f = tree[n].Freq; 574 s->opt_len += (ulg)f * (unsigned)(bits + xbits); 575 if (stree) s->static_len += (ulg)f * (unsigned)(stree[n].Len + xbits); 576 } 577 if (overflow == 0) return; 578 579 Tracev((stderr,"\nbit length overflow\n")); 580 /* This happens for example on obj2 and pic of the Calgary corpus */ 581 582 /* Find the first bit length which could increase: */ 583 do { 584 bits = max_length - 1; 585 while (s->bl_count[bits] == 0) bits--; 586 s->bl_count[bits]--; /* move one leaf down the tree */ 587 s->bl_count[bits + 1] += 2; /* move one overflow item as its brother */ 588 s->bl_count[max_length]--; 589 /* The brother of the overflow item also moves one step up, 590 * but this does not affect bl_count[max_length] 591 */ 592 overflow -= 2; 593 } while (overflow > 0); 594 595 /* Now recompute all bit lengths, scanning in increasing frequency. 596 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 597 * lengths instead of fixing only the wrong ones. This idea is taken 598 * from 'ar' written by Haruhiko Okumura.) 599 */ 600 for (bits = max_length; bits != 0; bits--) { 601 n = s->bl_count[bits]; 602 while (n != 0) { 603 m = s->heap[--h]; 604 if (m > max_code) continue; 605 if ((unsigned) tree[m].Len != (unsigned) bits) { 606 Tracev((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 607 s->opt_len += ((ulg)bits - tree[m].Len) * tree[m].Freq; 608 tree[m].Len = (ush)bits; 609 } 610 n--; 611 } 612 } 613 } 614 615 #ifdef DUMP_BL_TREE 616 # include <stdio.h> 617 #endif 618 619 /* =========================================================================== 620 * Construct one Huffman tree and assigns the code bit strings and lengths. 621 * Update the total bit length for the current block. 622 * IN assertion: the field freq is set for all tree elements. 623 * OUT assertions: the fields len and code are set to the optimal bit length 624 * and corresponding code. The length opt_len is updated; static_len is 625 * also updated if stree is not null. The field max_code is set. 626 */ 627 local void build_tree(deflate_state *s, tree_desc *desc) { 628 ct_data *tree = desc->dyn_tree; 629 const ct_data *stree = desc->stat_desc->static_tree; 630 int elems = desc->stat_desc->elems; 631 int n, m; /* iterate over heap elements */ 632 int max_code = -1; /* largest code with non zero frequency */ 633 int node; /* new node being created */ 634 635 /* Construct the initial heap, with least frequent element in 636 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n + 1]. 637 * heap[0] is not used. 638 */ 639 s->heap_len = 0, s->heap_max = HEAP_SIZE; 640 641 for (n = 0; n < elems; n++) { 642 if (tree[n].Freq != 0) { 643 s->heap[++(s->heap_len)] = max_code = n; 644 s->depth[n] = 0; 645 } else { 646 tree[n].Len = 0; 647 } 648 } 649 650 /* The pkzip format requires that at least one distance code exists, 651 * and that at least one bit should be sent even if there is only one 652 * possible code. So to avoid special checks later on we force at least 653 * two codes of non zero frequency. 654 */ 655 while (s->heap_len < 2) { 656 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); 657 tree[node].Freq = 1; 658 s->depth[node] = 0; 659 s->opt_len--; if (stree) s->static_len -= stree[node].Len; 660 /* node is 0 or 1 so it does not have extra bits */ 661 } 662 desc->max_code = max_code; 663 664 /* The elements heap[heap_len/2 + 1 .. heap_len] are leaves of the tree, 665 * establish sub-heaps of increasing lengths: 666 */ 667 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); 668 669 /* Construct the Huffman tree by repeatedly combining the least two 670 * frequent nodes. 671 */ 672 node = elems; /* next internal node of the tree */ 673 do { 674 pqremove(s, tree, n); /* n = node of least frequency */ 675 m = s->heap[SMALLEST]; /* m = node of next least frequency */ 676 677 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ 678 s->heap[--(s->heap_max)] = m; 679 680 /* Create a new node father of n and m */ 681 tree[node].Freq = tree[n].Freq + tree[m].Freq; 682 s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ? 683 s->depth[n] : s->depth[m]) + 1); 684 tree[n].Dad = tree[m].Dad = (ush)node; 685 #ifdef DUMP_BL_TREE 686 if (tree == s->bl_tree) { 687 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 688 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 689 } 690 #endif 691 /* and insert the new node in the heap */ 692 s->heap[SMALLEST] = node++; 693 pqdownheap(s, tree, SMALLEST); 694 695 } while (s->heap_len >= 2); 696 697 s->heap[--(s->heap_max)] = s->heap[SMALLEST]; 698 699 /* At this point, the fields freq and dad are set. We can now 700 * generate the bit lengths. 701 */ 702 gen_bitlen(s, (tree_desc *)desc); 703 704 /* The field len is now set, we can generate the bit codes */ 705 gen_codes ((ct_data *)tree, max_code, s->bl_count); 706 } 707 708 /* =========================================================================== 709 * Scan a literal or distance tree to determine the frequencies of the codes 710 * in the bit length tree. 711 */ 712 local void scan_tree(deflate_state *s, ct_data *tree, int max_code) { 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 */ 753 local void send_tree(deflate_state *s, ct_data *tree, int max_code) { 754 int n; /* iterates over all tree elements */ 755 int prevlen = -1; /* last emitted length */ 756 int curlen; /* length of current code */ 757 int nextlen = tree[0].Len; /* length of next code */ 758 int count = 0; /* repeat count of the current code */ 759 int max_count = 7; /* max repeat count */ 760 int min_count = 4; /* min repeat count */ 761 762 /* tree[max_code + 1].Len = -1; */ /* guard already set */ 763 if (nextlen == 0) max_count = 138, min_count = 3; 764 765 for (n = 0; n <= max_code; n++) { 766 curlen = nextlen; nextlen = tree[n + 1].Len; 767 if (++count < max_count && curlen == nextlen) { 768 continue; 769 } else if (count < min_count) { 770 do { send_code(s, curlen, s->bl_tree); } while (--count != 0); 771 772 } else if (curlen != 0) { 773 if (curlen != prevlen) { 774 send_code(s, curlen, s->bl_tree); count--; 775 } 776 Assert(count >= 3 && count <= 6, " 3_6?"); 777 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count - 3, 2); 778 779 } else if (count <= 10) { 780 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count - 3, 3); 781 782 } else { 783 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count - 11, 7); 784 } 785 count = 0; prevlen = curlen; 786 if (nextlen == 0) { 787 max_count = 138, min_count = 3; 788 } else if (curlen == nextlen) { 789 max_count = 6, min_count = 3; 790 } else { 791 max_count = 7, min_count = 4; 792 } 793 } 794 } 795 796 /* =========================================================================== 797 * Construct the Huffman tree for the bit lengths and return the index in 798 * bl_order of the last bit length code to send. 799 */ 800 local int build_bl_tree(deflate_state *s) { 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(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); 805 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); 806 807 /* Build the bit length tree: */ 808 build_tree(s, (tree_desc *)(&(s->bl_desc))); 809 /* opt_len now includes the length of the tree representations, except the 810 * 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 (s->bl_tree[bl_order[max_blindex]].Len != 0) break; 819 } 820 /* Update opt_len to include the bit length tree and counts */ 821 s->opt_len += 3*((ulg)max_blindex + 1) + 5 + 5 + 4; 822 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", 823 s->opt_len, s->static_len)); 824 825 return max_blindex; 826 } 827 828 /* =========================================================================== 829 * Send the header for a block using dynamic Huffman trees: the counts, the 830 * lengths of the bit length codes, the literal tree and the distance tree. 831 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 832 */ 833 local void send_all_trees(deflate_state *s, int lcodes, int dcodes, 834 int blcodes) { 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(s, lcodes - 257, 5); /* not +255 as stated in appnote.txt */ 842 send_bits(s, dcodes - 1, 5); 843 send_bits(s, 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(s, s->bl_tree[bl_order[rank]].Len, 3); 847 } 848 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); 849 850 send_tree(s, (ct_data *)s->dyn_ltree, lcodes - 1); /* literal tree */ 851 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); 852 853 send_tree(s, (ct_data *)s->dyn_dtree, dcodes - 1); /* distance tree */ 854 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); 855 } 856 857 /* =========================================================================== 858 * Send a stored block 859 */ 860 void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf, 861 ulg stored_len, int last) { 862 send_bits(s, (STORED_BLOCK<<1) + last, 3); /* send block type */ 863 bi_windup(s); /* align on byte boundary */ 864 put_short(s, (ush)stored_len); 865 put_short(s, (ush)~stored_len); 866 if (stored_len) 867 zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len); 868 s->pending += stored_len; 869 #ifdef ZLIB_DEBUG 870 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; 871 s->compressed_len += (stored_len + 4) << 3; 872 s->bits_sent += 2*16; 873 s->bits_sent += stored_len << 3; 874 #endif 875 } 876 877 /* =========================================================================== 878 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits) 879 */ 880 void ZLIB_INTERNAL _tr_flush_bits(deflate_state *s) { 881 bi_flush(s); 882 } 883 884 /* =========================================================================== 885 * Send one empty static block to give enough lookahead for inflate. 886 * This takes 10 bits, of which 7 may remain in the bit buffer. 887 */ 888 void ZLIB_INTERNAL _tr_align(deflate_state *s) { 889 send_bits(s, STATIC_TREES<<1, 3); 890 send_code(s, END_BLOCK, static_ltree); 891 #ifdef ZLIB_DEBUG 892 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ 893 #endif 894 bi_flush(s); 895 } 896 897 /* =========================================================================== 898 * Send the block data compressed using the given Huffman trees 899 */ 900 local void compress_block(deflate_state *s, const ct_data *ltree, 901 const ct_data *dtree) { 902 unsigned dist; /* distance of matched string */ 903 int lc; /* match length or unmatched char (if dist == 0) */ 904 unsigned sx = 0; /* running index in symbol buffers */ 905 unsigned code; /* the code to send */ 906 int extra; /* number of extra bits to send */ 907 908 if (s->sym_next != 0) do { 909 #ifdef LIT_MEM 910 dist = s->d_buf[sx]; 911 lc = s->l_buf[sx++]; 912 #else 913 dist = s->sym_buf[sx++] & 0xff; 914 dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8; 915 lc = s->sym_buf[sx++]; 916 #endif 917 if (dist == 0) { 918 send_code(s, lc, ltree); /* send a literal byte */ 919 Tracecv(isgraph(lc), (stderr," '%c' ", lc)); 920 } else { 921 /* Here, lc is the match length - MIN_MATCH */ 922 code = _length_code[lc]; 923 send_code(s, code + LITERALS + 1, ltree); /* send length code */ 924 extra = extra_lbits[code]; 925 if (extra != 0) { 926 lc -= base_length[code]; 927 send_bits(s, lc, extra); /* send the extra length bits */ 928 } 929 dist--; /* dist is now the match distance - 1 */ 930 code = d_code(dist); 931 Assert (code < D_CODES, "bad d_code"); 932 933 send_code(s, code, dtree); /* send the distance code */ 934 extra = extra_dbits[code]; 935 if (extra != 0) { 936 dist -= (unsigned)base_dist[code]; 937 send_bits(s, dist, extra); /* send the extra distance bits */ 938 } 939 } /* literal or match pair ? */ 940 941 /* Check for no overlay of pending_buf on needed symbols */ 942 #ifdef LIT_MEM 943 Assert(s->pending < 2 * (s->lit_bufsize + sx), "pendingBuf overflow"); 944 #else 945 Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow"); 946 #endif 947 948 } while (sx < s->sym_next); 949 950 send_code(s, END_BLOCK, ltree); 951 } 952 953 /* =========================================================================== 954 * Check if the data type is TEXT or BINARY, using the following algorithm: 955 * - TEXT if the two conditions below are satisfied: 956 * a) There are no non-portable control characters belonging to the 957 * "block list" (0..6, 14..25, 28..31). 958 * b) There is at least one printable character belonging to the 959 * "allow list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255). 960 * - BINARY otherwise. 961 * - The following partially-portable control characters form a 962 * "gray list" that is ignored in this detection algorithm: 963 * (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}). 964 * IN assertion: the fields Freq of dyn_ltree are set. 965 */ 966 local int detect_data_type(deflate_state *s) { 967 /* block_mask is the bit mask of block-listed bytes 968 * set bits 0..6, 14..25, and 28..31 969 * 0xf3ffc07f = binary 11110011111111111100000001111111 970 */ 971 unsigned long block_mask = 0xf3ffc07fUL; 972 int n; 973 974 /* Check for non-textual ("block-listed") bytes. */ 975 for (n = 0; n <= 31; n++, block_mask >>= 1) 976 if ((block_mask & 1) && (s->dyn_ltree[n].Freq != 0)) 977 return Z_BINARY; 978 979 /* Check for textual ("allow-listed") bytes. */ 980 if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0 981 || s->dyn_ltree[13].Freq != 0) 982 return Z_TEXT; 983 for (n = 32; n < LITERALS; n++) 984 if (s->dyn_ltree[n].Freq != 0) 985 return Z_TEXT; 986 987 /* There are no "block-listed" or "allow-listed" bytes: 988 * this stream either is empty or has tolerated ("gray-listed") bytes only. 989 */ 990 return Z_BINARY; 991 } 992 993 /* =========================================================================== 994 * Determine the best encoding for the current block: dynamic trees, static 995 * trees or store, and write out the encoded block. 996 */ 997 void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf, 998 ulg stored_len, int last) { 999 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 1000 int max_blindex = 0; /* index of last bit length code of non zero freq */ 1001 1002 /* Build the Huffman trees unless a stored block is forced */ 1003 if (s->level > 0) { 1004 1005 /* Check if the file is binary or text */ 1006 if (s->strm->data_type == Z_UNKNOWN) 1007 s->strm->data_type = detect_data_type(s); 1008 1009 /* Construct the literal and distance trees */ 1010 build_tree(s, (tree_desc *)(&(s->l_desc))); 1011 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len, 1012 s->static_len)); 1013 1014 build_tree(s, (tree_desc *)(&(s->d_desc))); 1015 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len, 1016 s->static_len)); 1017 /* At this point, opt_len and static_len are the total bit lengths of 1018 * the compressed block data, excluding the tree representations. 1019 */ 1020 1021 /* Build the bit length tree for the above two trees, and get the index 1022 * in bl_order of the last bit length code to send. 1023 */ 1024 max_blindex = build_bl_tree(s); 1025 1026 /* Determine the best encoding. Compute the block lengths in bytes. */ 1027 opt_lenb = (s->opt_len + 3 + 7) >> 3; 1028 static_lenb = (s->static_len + 3 + 7) >> 3; 1029 1030 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", 1031 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, 1032 s->sym_next / 3)); 1033 1034 #ifndef FORCE_STATIC 1035 if (static_lenb <= opt_lenb || s->strategy == Z_FIXED) 1036 #endif 1037 opt_lenb = static_lenb; 1038 1039 } else { 1040 Assert(buf != (char*)0, "lost buf"); 1041 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */ 1042 } 1043 1044 #ifdef FORCE_STORED 1045 if (buf != (char*)0) { /* force stored block */ 1046 #else 1047 if (stored_len + 4 <= opt_lenb && buf != (char*)0) { 1048 /* 4: two words for the lengths */ 1049 #endif 1050 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. 1051 * Otherwise we can't have processed more than WSIZE input bytes since 1052 * the last block flush, because compression would have been 1053 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to 1054 * transform a block into a stored block. 1055 */ 1056 _tr_stored_block(s, buf, stored_len, last); 1057 1058 } else if (static_lenb == opt_lenb) { 1059 send_bits(s, (STATIC_TREES<<1) + last, 3); 1060 compress_block(s, (const ct_data *)static_ltree, 1061 (const ct_data *)static_dtree); 1062 #ifdef ZLIB_DEBUG 1063 s->compressed_len += 3 + s->static_len; 1064 #endif 1065 } else { 1066 send_bits(s, (DYN_TREES<<1) + last, 3); 1067 send_all_trees(s, s->l_desc.max_code + 1, s->d_desc.max_code + 1, 1068 max_blindex + 1); 1069 compress_block(s, (const ct_data *)s->dyn_ltree, 1070 (const ct_data *)s->dyn_dtree); 1071 #ifdef ZLIB_DEBUG 1072 s->compressed_len += 3 + s->opt_len; 1073 #endif 1074 } 1075 Assert (s->compressed_len == s->bits_sent, "bad compressed size"); 1076 /* The above check is made mod 2^32, for files larger than 512 MB 1077 * and uLong implemented on 32 bits. 1078 */ 1079 init_block(s); 1080 1081 if (last) { 1082 bi_windup(s); 1083 #ifdef ZLIB_DEBUG 1084 s->compressed_len += 7; /* align on byte boundary */ 1085 #endif 1086 } 1087 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len >> 3, 1088 s->compressed_len - 7*last)); 1089 } 1090 1091 /* =========================================================================== 1092 * Save the match info and tally the frequency counts. Return true if 1093 * the current block must be flushed. 1094 */ 1095 int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc) { 1096 #ifdef LIT_MEM 1097 s->d_buf[s->sym_next] = (ush)dist; 1098 s->l_buf[s->sym_next++] = (uch)lc; 1099 #else 1100 s->sym_buf[s->sym_next++] = (uch)dist; 1101 s->sym_buf[s->sym_next++] = (uch)(dist >> 8); 1102 s->sym_buf[s->sym_next++] = (uch)lc; 1103 #endif 1104 if (dist == 0) { 1105 /* lc is the unmatched char */ 1106 s->dyn_ltree[lc].Freq++; 1107 } else { 1108 s->matches++; 1109 /* Here, lc is the match length - MIN_MATCH */ 1110 dist--; /* dist = match distance - 1 */ 1111 Assert((ush)dist < (ush)MAX_DIST(s) && 1112 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && 1113 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match"); 1114 1115 s->dyn_ltree[_length_code[lc] + LITERALS + 1].Freq++; 1116 s->dyn_dtree[d_code(dist)].Freq++; 1117 } 1118 return (s->sym_next == s->sym_end); 1119 } 1120
Indexes created Sat Sep 20 22:09:52 GMT 2025