1 /* trees.c -- output deflated data using Huffman coding 2 * Copyright (C) 1995-2005 Jean-loup Gailly 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6 #pragma ident "@(#)trees.c 1.1 07/03/22 SMI" 7 8 /* 9 * ALGORITHM 10 * 11 * The "deflation" process uses several Huffman trees. The more 12 * common source values are represented by shorter bit sequences. 13 * 14 * Each code tree is stored in a compressed form which is itself 15 * a Huffman encoding of the lengths of all the code strings (in 16 * ascending order by source values). The actual code strings are 17 * reconstructed from the lengths in the inflate process, as described 18 * in the deflate specification. 19 * 20 * REFERENCES 21 * 22 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". 23 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc 24 * 25 * Storer, James A. 26 * Data Compression: Methods and Theory, pp. 49-50. 27 * Computer Science Press, 1988. ISBN 0-7167-8156-5. 28 * 29 * Sedgewick, R. 30 * Algorithms, p290. 31 * Addison-Wesley, 1983. ISBN 0-201-06672-6. 32 */ 33 34 /* #define GEN_TREES_H */ 35 36 #include "deflate.h" 37 38 #ifdef DEBUG 39 # include <ctype.h> 40 #endif 41 42 /* =========================================================================== 43 * Constants 44 */ 45 46 #define MAX_BL_BITS 7 47 /* Bit length codes must not exceed MAX_BL_BITS bits */ 48 49 #define END_BLOCK 256 50 /* end of block literal code */ 51 52 #define REP_3_6 16 53 /* repeat previous bit length 3-6 times (2 bits of repeat count) */ 54 55 #define REPZ_3_10 17 56 /* repeat a zero length 3-10 times (3 bits of repeat count) */ 57 58 #define REPZ_11_138 18 59 /* repeat a zero length 11-138 times (7 bits of repeat count) */ 60 61 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */ 62 = {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}; 63 64 local const int extra_dbits[D_CODES] /* extra bits for each distance code */ 65 = {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}; 66 67 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */ 68 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; 69 70 local const uch bl_order[BL_CODES] 71 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; 72 /* The lengths of the bit length codes are sent in order of decreasing 73 * probability, to avoid transmitting the lengths for unused bit length codes. 74 */ 75 76 #define Buf_size (8 * 2*sizeof(char)) 77 /* Number of bits used within bi_buf. (bi_buf might be implemented on 78 * more than 16 bits on some systems.) 79 */ 80 81 /* =========================================================================== 82 * Local data. These are initialized only once. 83 */ 84 85 #define DIST_CODE_LEN 512 /* see definition of array dist_code below */ 86 87 #if defined(GEN_TREES_H) || !defined(STDC) 88 /* non ANSI compilers may not accept trees.h */ 89 90 local ct_data static_ltree[L_CODES+2]; 91 /* The static literal tree. Since the bit lengths are imposed, there is no 92 * need for the L_CODES extra codes used during heap construction. However 93 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init 94 * below). 95 */ 96 97 local ct_data static_dtree[D_CODES]; 98 /* The static distance tree. (Actually a trivial tree since all codes use 99 * 5 bits.) 100 */ 101 102 uch _dist_code[DIST_CODE_LEN]; 103 /* Distance codes. The first 256 values correspond to the distances 104 * 3 .. 258, the last 256 values correspond to the top 8 bits of 105 * the 15 bit distances. 106 */ 107 108 uch _length_code[MAX_MATCH-MIN_MATCH+1]; 109 /* length code for each normalized match length (0 == MIN_MATCH) */ 110 111 local int base_length[LENGTH_CODES]; 112 /* First normalized length for each code (0 = MIN_MATCH) */ 113 114 local int base_dist[D_CODES]; 115 /* First normalized distance for each code (0 = distance of 1) */ 116 117 #else 118 # include "trees.h" 119 #endif /* GEN_TREES_H */ 120 121 struct static_tree_desc_s { 122 const ct_data *static_tree; /* static tree or NULL */ 123 const intf *extra_bits; /* extra bits for each code or NULL */ 124 int extra_base; /* base index for extra_bits */ 125 int elems; /* max number of elements in the tree */ 126 int max_length; /* max bit length for the codes */ 127 }; 128 129 local static_tree_desc static_l_desc = 130 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; 131 132 local static_tree_desc static_d_desc = 133 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS}; 134 135 local static_tree_desc static_bl_desc = 136 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS}; 137 138 /* =========================================================================== 139 * Local (static) routines in this file. 140 */ 141 142 local void tr_static_init OF((void)); 143 local void init_block OF((deflate_state *s)); 144 local void pqdownheap OF((deflate_state *s, ct_data *tree, int k)); 145 local void gen_bitlen OF((deflate_state *s, tree_desc *desc)); 146 local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count)); 147 local void build_tree OF((deflate_state *s, tree_desc *desc)); 148 local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code)); 149 local void send_tree OF((deflate_state *s, ct_data *tree, int max_code)); 150 local int build_bl_tree OF((deflate_state *s)); 151 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes, 152 int blcodes)); 153 local void compress_block OF((deflate_state *s, ct_data *ltree, 154 ct_data *dtree)); 155 local void set_data_type OF((deflate_state *s)); 156 local unsigned bi_reverse OF((unsigned value, int length)); 157 local void bi_windup OF((deflate_state *s)); 158 local void bi_flush OF((deflate_state *s)); 159 local void copy_block OF((deflate_state *s, charf *buf, unsigned len, 160 int header)); 161 162 #ifdef GEN_TREES_H 163 local void gen_trees_header OF((void)); 164 #endif 165 166 #ifndef DEBUG 167 # define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len) 168 /* Send a code of the given tree. c and tree must not have side effects */ 169 170 #else /* DEBUG */ 171 # define send_code(s, c, tree) \ 172 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \ 173 send_bits(s, tree[c].Code, tree[c].Len); } 174 #endif 175 176 /* =========================================================================== 177 * Output a short LSB first on the stream. 178 * IN assertion: there is enough room in pendingBuf. 179 */ 180 #define put_short(s, w) { \ 181 put_byte(s, (uch)((w) & 0xff)); \ 182 put_byte(s, (uch)((ush)(w) >> 8)); \ 183 } 184 185 /* =========================================================================== 186 * Send a value on a given number of bits. 187 * IN assertion: length <= 16 and value fits in length bits. 188 */ 189 #ifdef DEBUG 190 local void send_bits OF((deflate_state *s, int value, int length)); 191 192 local void send_bits(s, value, length) 193 deflate_state *s; 194 int value; /* value to send */ 195 int length; /* number of bits */ 196 { 197 Tracevv((stderr," l %2d v %4x ", length, value)); 198 Assert(length > 0 && length <= 15, "invalid length"); 199 s->bits_sent += (ulg)length; 200 201 /* If not enough room in bi_buf, use (valid) bits from bi_buf and 202 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid)) 203 * unused bits in value. 204 */ 205 if (s->bi_valid > (int)Buf_size - length) { 206 s->bi_buf |= (value << s->bi_valid); 207 put_short(s, s->bi_buf); 208 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid); 209 s->bi_valid += length - Buf_size; 210 } else { 211 s->bi_buf |= value << s->bi_valid; 212 s->bi_valid += length; 213 } 214 } 215 #else /* !DEBUG */ 216 217 #define send_bits(s, value, length) \ 218 { int len = length;\ 219 if (s->bi_valid > (int)Buf_size - len) {\ 220 int val = value;\ 221 s->bi_buf |= (val << s->bi_valid);\ 222 put_short(s, s->bi_buf);\ 223 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\ 224 s->bi_valid += len - Buf_size;\ 225 } else {\ 226 s->bi_buf |= (value) << s->bi_valid;\ 227 s->bi_valid += len;\ 228 }\ 229 } 230 #endif /* DEBUG */ 231 232 233 /* the arguments must not have side effects */ 234 235 /* =========================================================================== 236 * Initialize the various 'constant' tables. 237 */ 238 local void tr_static_init() 239 { 240 #if defined(GEN_TREES_H) || !defined(STDC) 241 static int static_init_done = 0; 242 int n; /* iterates over tree elements */ 243 int bits; /* bit counter */ 244 int length; /* length value */ 245 int code; /* code value */ 246 int dist; /* distance index */ 247 ush bl_count[MAX_BITS+1]; 248 /* number of codes at each bit length for an optimal tree */ 249 250 if (static_init_done) return; 251 252 /* For some embedded targets, global variables are not initialized: */ 253 static_l_desc.static_tree = static_ltree; 254 static_l_desc.extra_bits = extra_lbits; 255 static_d_desc.static_tree = static_dtree; 256 static_d_desc.extra_bits = extra_dbits; 257 static_bl_desc.extra_bits = extra_blbits; 258 259 /* Initialize the mapping length (0..255) -> length code (0..28) */ 260 length = 0; 261 for (code = 0; code < LENGTH_CODES-1; code++) { 262 base_length[code] = length; 263 for (n = 0; n < (1<<extra_lbits[code]); n++) { 264 _length_code[length++] = (uch)code; 265 } 266 } 267 Assert (length == 256, "tr_static_init: length != 256"); 268 /* Note that the length 255 (match length 258) can be represented 269 * in two different ways: code 284 + 5 bits or code 285, so we 270 * overwrite length_code[255] to use the best encoding: 271 */ 272 _length_code[length-1] = (uch)code; 273 274 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 275 dist = 0; 276 for (code = 0 ; code < 16; code++) { 277 base_dist[code] = dist; 278 for (n = 0; n < (1<<extra_dbits[code]); n++) { 279 _dist_code[dist++] = (uch)code; 280 } 281 } 282 Assert (dist == 256, "tr_static_init: dist != 256"); 283 dist >>= 7; /* from now on, all distances are divided by 128 */ 284 for ( ; code < D_CODES; code++) { 285 base_dist[code] = dist << 7; 286 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { 287 _dist_code[256 + dist++] = (uch)code; 288 } 289 } 290 Assert (dist == 256, "tr_static_init: 256+dist != 512"); 291 292 /* Construct the codes of the static literal tree */ 293 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 294 n = 0; 295 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 296 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 297 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 298 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 299 /* Codes 286 and 287 do not exist, but we must include them in the 300 * tree construction to get a canonical Huffman tree (longest code 301 * all ones) 302 */ 303 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count); 304 305 /* The static distance tree is trivial: */ 306 for (n = 0; n < D_CODES; n++) { 307 static_dtree[n].Len = 5; 308 static_dtree[n].Code = bi_reverse((unsigned)n, 5); 309 } 310 static_init_done = 1; 311 312 # ifdef GEN_TREES_H 313 gen_trees_header(); 314 # endif 315 #endif /* defined(GEN_TREES_H) || !defined(STDC) */ 316 } 317 318 /* =========================================================================== 319 * Genererate the file trees.h describing the static trees. 320 */ 321 #ifdef GEN_TREES_H 322 # ifndef DEBUG 323 # include <stdio.h> 324 # endif 325 326 # define SEPARATOR(i, last, width) \ 327 ((i) == (last)? "\n};\n\n" : \ 328 ((i) % (width) == (width)-1 ? ",\n" : ", ")) 329 330 void gen_trees_header() 331 { 332 FILE *header = fopen("trees.h", "w"); 333 int i; 334 335 Assert (header != NULL, "Can't open trees.h"); 336 fprintf(header, 337 "/* header created automatically with -DGEN_TREES_H */\n\n"); 338 339 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n"); 340 for (i = 0; i < L_CODES+2; i++) { 341 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code, 342 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5)); 343 } 344 345 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n"); 346 for (i = 0; i < D_CODES; i++) { 347 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code, 348 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5)); 349 } 350 351 fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n"); 352 for (i = 0; i < DIST_CODE_LEN; i++) { 353 fprintf(header, "%2u%s", _dist_code[i], 354 SEPARATOR(i, DIST_CODE_LEN-1, 20)); 355 } 356 357 fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n"); 358 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) { 359 fprintf(header, "%2u%s", _length_code[i], 360 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20)); 361 } 362 363 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n"); 364 for (i = 0; i < LENGTH_CODES; i++) { 365 fprintf(header, "%1u%s", base_length[i], 366 SEPARATOR(i, LENGTH_CODES-1, 20)); 367 } 368 369 fprintf(header, "local const int base_dist[D_CODES] = {\n"); 370 for (i = 0; i < D_CODES; i++) { 371 fprintf(header, "%5u%s", base_dist[i], 372 SEPARATOR(i, D_CODES-1, 10)); 373 } 374 375 fclose(header); 376 } 377 #endif /* GEN_TREES_H */ 378 379 /* =========================================================================== 380 * Initialize the tree data structures for a new zlib stream. 381 */ 382 void _tr_init(s) 383 deflate_state *s; 384 { 385 tr_static_init(); 386 387 s->l_desc.dyn_tree = s->dyn_ltree; 388 s->l_desc.stat_desc = &static_l_desc; 389 390 s->d_desc.dyn_tree = s->dyn_dtree; 391 s->d_desc.stat_desc = &static_d_desc; 392 393 s->bl_desc.dyn_tree = s->bl_tree; 394 s->bl_desc.stat_desc = &static_bl_desc; 395 396 s->bi_buf = 0; 397 s->bi_valid = 0; 398 s->last_eob_len = 8; /* enough lookahead for inflate */ 399 #ifdef DEBUG 400 s->compressed_len = 0L; 401 s->bits_sent = 0L; 402 #endif 403 404 /* Initialize the first block of the first file: */ 405 init_block(s); 406 } 407 408 /* =========================================================================== 409 * Initialize a new block. 410 */ 411 local void init_block(s) 412 deflate_state *s; 413 { 414 int n; /* iterates over tree elements */ 415 416 /* Initialize the trees. */ 417 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; 418 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; 419 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; 420 421 s->dyn_ltree[END_BLOCK].Freq = 1; 422 s->opt_len = s->static_len = 0L; 423 s->last_lit = s->matches = 0; 424 } 425 426 #define SMALLEST 1 427 /* Index within the heap array of least frequent node in the Huffman tree */ 428 429 430 /* =========================================================================== 431 * Remove the smallest element from the heap and recreate the heap with 432 * one less element. Updates heap and heap_len. 433 */ 434 #define pqremove(s, tree, top) \ 435 {\ 436 top = s->heap[SMALLEST]; \ 437 s->heap[SMALLEST] = s->heap[s->heap_len--]; \ 438 pqdownheap(s, tree, SMALLEST); \ 439 } 440 441 /* =========================================================================== 442 * Compares to subtrees, using the tree depth as tie breaker when 443 * the subtrees have equal frequency. This minimizes the worst case length. 444 */ 445 #define smaller(tree, n, m, depth) \ 446 (tree[n].Freq < tree[m].Freq || \ 447 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 448 449 /* =========================================================================== 450 * Restore the heap property by moving down the tree starting at node k, 451 * exchanging a node with the smallest of its two sons if necessary, stopping 452 * when the heap property is re-established (each father smaller than its 453 * two sons). 454 */ 455 local void pqdownheap(s, tree, k) 456 deflate_state *s; 457 ct_data *tree; /* the tree to restore */ 458 int k; /* node to move down */ 459 { 460 int v = s->heap[k]; 461 int j = k << 1; /* left son of k */ 462 while (j <= s->heap_len) { 463 /* Set j to the smallest of the two sons: */ 464 if (j < s->heap_len && 465 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { 466 j++; 467 } 468 /* Exit if v is smaller than both sons */ 469 if (smaller(tree, v, s->heap[j], s->depth)) break; 470 471 /* Exchange v with the smallest son */ 472 s->heap[k] = s->heap[j]; k = j; 473 474 /* And continue down the tree, setting j to the left son of k */ 475 j <<= 1; 476 } 477 s->heap[k] = v; 478 } 479 480 /* =========================================================================== 481 * Compute the optimal bit lengths for a tree and update the total bit length 482 * for the current block. 483 * IN assertion: the fields freq and dad are set, heap[heap_max] and 484 * above are the tree nodes sorted by increasing frequency. 485 * OUT assertions: the field len is set to the optimal bit length, the 486 * array bl_count contains the frequencies for each bit length. 487 * The length opt_len is updated; static_len is also updated if stree is 488 * not null. 489 */ 490 local void gen_bitlen(s, desc) 491 deflate_state *s; 492 tree_desc *desc; /* the tree descriptor */ 493 { 494 ct_data *tree = desc->dyn_tree; 495 int max_code = desc->max_code; 496 const ct_data *stree = desc->stat_desc->static_tree; 497 const intf *extra = desc->stat_desc->extra_bits; 498 int base = desc->stat_desc->extra_base; 499 int max_length = desc->stat_desc->max_length; 500 int h; /* heap index */ 501 int n, m; /* iterate over the tree elements */ 502 int bits; /* bit length */ 503 int xbits; /* extra bits */ 504 ush f; /* frequency */ 505 int overflow = 0; /* number of elements with bit length too large */ 506 507 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; 508 509 /* In a first pass, compute the optimal bit lengths (which may 510 * overflow in the case of the bit length tree). 511 */ 512 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ 513 514 for (h = s->heap_max+1; h < HEAP_SIZE; h++) { 515 n = s->heap[h]; 516 bits = tree[tree[n].Dad].Len + 1; 517 if (bits > max_length) bits = max_length, overflow++; 518 tree[n].Len = (ush)bits; 519 /* We overwrite tree[n].Dad which is no longer needed */ 520 521 if (n > max_code) continue; /* not a leaf node */ 522 523 s->bl_count[bits]++; 524 xbits = 0; 525 if (n >= base) xbits = extra[n-base]; 526 f = tree[n].Freq; 527 s->opt_len += (ulg)f * (bits + xbits); 528 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); 529 } 530 if (overflow == 0) return; 531 532 Trace((stderr,"\nbit length overflow\n")); 533 /* This happens for example on obj2 and pic of the Calgary corpus */ 534 535 /* Find the first bit length which could increase: */ 536 do { 537 bits = max_length-1; 538 while (s->bl_count[bits] == 0) bits--; 539 s->bl_count[bits]--; /* move one leaf down the tree */ 540 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ 541 s->bl_count[max_length]--; 542 /* The brother of the overflow item also moves one step up, 543 * but this does not affect bl_count[max_length] 544 */ 545 overflow -= 2; 546 } while (overflow > 0); 547 548 /* Now recompute all bit lengths, scanning in increasing frequency. 549 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 550 * lengths instead of fixing only the wrong ones. This idea is taken 551 * from 'ar' written by Haruhiko Okumura.) 552 */ 553 for (bits = max_length; bits != 0; bits--) { 554 n = s->bl_count[bits]; 555 while (n != 0) { 556 m = s->heap[--h]; 557 if (m > max_code) continue; 558 if ((unsigned) tree[m].Len != (unsigned) bits) { 559 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 560 s->opt_len += ((long)bits - (long)tree[m].Len) 561 *(long)tree[m].Freq; 562 tree[m].Len = (ush)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, bl_count) 578 ct_data *tree; /* the tree to decorate */ 579 int max_code; /* largest code with non zero frequency */ 580 ushf *bl_count; /* number of codes at each bit length */ 581 { 582 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 583 ush code = 0; /* running code value */ 584 int bits; /* bit index */ 585 int n; /* code index */ 586 587 /* The distribution counts are first used to generate the code values 588 * without bit reversal. 589 */ 590 for (bits = 1; bits <= MAX_BITS; bits++) { 591 next_code[bits] = code = (code + bl_count[bits-1]) << 1; 592 } 593 /* Check that the bit counts in bl_count are consistent. The last code 594 * must be all ones. 595 */ 596 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, 597 "inconsistent bit counts"); 598 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 599 600 for (n = 0; n <= max_code; n++) { 601 int len = tree[n].Len; 602 if (len == 0) continue; 603 /* Now reverse the bits */ 604 tree[n].Code = bi_reverse(next_code[len]++, len); 605 606 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 607 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); 608 } 609 } 610 611 /* =========================================================================== 612 * Construct one Huffman tree and assigns the code bit strings and lengths. 613 * Update the total bit length for the current block. 614 * IN assertion: the field freq is set for all tree elements. 615 * OUT assertions: the fields len and code are set to the optimal bit length 616 * and corresponding code. The length opt_len is updated; static_len is 617 * also updated if stree is not null. The field max_code is set. 618 */ 619 local void build_tree(s, desc) 620 deflate_state *s; 621 tree_desc *desc; /* the tree descriptor */ 622 { 623 ct_data *tree = desc->dyn_tree; 624 const ct_data *stree = desc->stat_desc->static_tree; 625 int elems = desc->stat_desc->elems; 626 int n, m; /* iterate over heap elements */ 627 int max_code = -1; /* largest code with non zero frequency */ 628 int node; /* new node being created */ 629 630 /* Construct the initial heap, with least frequent element in 631 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. 632 * heap[0] is not used. 633 */ 634 s->heap_len = 0, s->heap_max = HEAP_SIZE; 635 636 for (n = 0; n < elems; n++) { 637 if (tree[n].Freq != 0) { 638 s->heap[++(s->heap_len)] = max_code = n; 639 s->depth[n] = 0; 640 } else { 641 tree[n].Len = 0; 642 } 643 } 644 645 /* The pkzip format requires that at least one distance code exists, 646 * and that at least one bit should be sent even if there is only one 647 * possible code. So to avoid special checks later on we force at least 648 * two codes of non zero frequency. 649 */ 650 while (s->heap_len < 2) { 651 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); 652 tree[node].Freq = 1; 653 s->depth[node] = 0; 654 s->opt_len--; if (stree) s->static_len -= stree[node].Len; 655 /* node is 0 or 1 so it does not have extra bits */ 656 } 657 desc->max_code = max_code; 658 659 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, 660 * establish sub-heaps of increasing lengths: 661 */ 662 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); 663 664 /* Construct the Huffman tree by repeatedly combining the least two 665 * frequent nodes. 666 */ 667 node = elems; /* next internal node of the tree */ 668 do { 669 pqremove(s, tree, n); /* n = node of least frequency */ 670 m = s->heap[SMALLEST]; /* m = node of next least frequency */ 671 672 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ 673 s->heap[--(s->heap_max)] = m; 674 675 /* Create a new node father of n and m */ 676 tree[node].Freq = tree[n].Freq + tree[m].Freq; 677 s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ? 678 s->depth[n] : s->depth[m]) + 1); 679 tree[n].Dad = tree[m].Dad = (ush)node; 680 #ifdef DUMP_BL_TREE 681 if (tree == s->bl_tree) { 682 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 683 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 684 } 685 #endif 686 /* and insert the new node in the heap */ 687 s->heap[SMALLEST] = node++; 688 pqdownheap(s, tree, SMALLEST); 689 690 } while (s->heap_len >= 2); 691 692 s->heap[--(s->heap_max)] = s->heap[SMALLEST]; 693 694 /* At this point, the fields freq and dad are set. We can now 695 * generate the bit lengths. 696 */ 697 gen_bitlen(s, (tree_desc *)desc); 698 699 /* The field len is now set, we can generate the bit codes */ 700 gen_codes ((ct_data *)tree, max_code, s->bl_count); 701 } 702 703 /* =========================================================================== 704 * Scan a literal or distance tree to determine the frequencies of the codes 705 * in the bit length tree. 706 */ 707 local void scan_tree (s, tree, max_code) 708 deflate_state *s; 709 ct_data *tree; /* the tree to be scanned */ 710 int max_code; /* and its largest code of non zero frequency */ 711 { 712 int n; /* iterates over all tree elements */ 713 int prevlen = -1; /* last emitted length */ 714 int curlen; /* length of current code */ 715 int nextlen = tree[0].Len; /* length of next code */ 716 int count = 0; /* repeat count of the current code */ 717 int max_count = 7; /* max repeat count */ 718 int min_count = 4; /* min repeat count */ 719 720 if (nextlen == 0) max_count = 138, min_count = 3; 721 tree[max_code+1].Len = (ush)0xffff; /* guard */ 722 723 for (n = 0; n <= max_code; n++) { 724 curlen = nextlen; nextlen = tree[n+1].Len; 725 if (++count < max_count && curlen == nextlen) { 726 continue; 727 } else if (count < min_count) { 728 s->bl_tree[curlen].Freq += count; 729 } else if (curlen != 0) { 730 if (curlen != prevlen) s->bl_tree[curlen].Freq++; 731 s->bl_tree[REP_3_6].Freq++; 732 } else if (count <= 10) { 733 s->bl_tree[REPZ_3_10].Freq++; 734 } else { 735 s->bl_tree[REPZ_11_138].Freq++; 736 } 737 count = 0; prevlen = curlen; 738 if (nextlen == 0) { 739 max_count = 138, min_count = 3; 740 } else if (curlen == nextlen) { 741 max_count = 6, min_count = 3; 742 } else { 743 max_count = 7, min_count = 4; 744 } 745 } 746 } 747 748 /* =========================================================================== 749 * Send a literal or distance tree in compressed form, using the codes in 750 * bl_tree. 751 */ 752 local void send_tree (s, tree, max_code) 753 deflate_state *s; 754 ct_data *tree; /* the tree to be scanned */ 755 int max_code; /* and its largest code of non zero frequency */ 756 { 757 int n; /* iterates over all tree elements */ 758 int prevlen = -1; /* last emitted length */ 759 int curlen; /* length of current code */ 760 int nextlen = tree[0].Len; /* length of next code */ 761 int count = 0; /* repeat count of the current code */ 762 int max_count = 7; /* max repeat count */ 763 int min_count = 4; /* min repeat count */ 764 765 /* tree[max_code+1].Len = -1; */ /* guard already set */ 766 if (nextlen == 0) max_count = 138, min_count = 3; 767 768 for (n = 0; n <= max_code; n++) { 769 curlen = nextlen; nextlen = tree[n+1].Len; 770 if (++count < max_count && curlen == nextlen) { 771 continue; 772 } else if (count < min_count) { 773 do { send_code(s, curlen, s->bl_tree); } while (--count != 0); 774 775 } else if (curlen != 0) { 776 if (curlen != prevlen) { 777 send_code(s, curlen, s->bl_tree); count--; 778 } 779 Assert(count >= 3 && count <= 6, " 3_6?"); 780 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); 781 782 } else if (count <= 10) { 783 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); 784 785 } else { 786 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); 787 } 788 count = 0; prevlen = curlen; 789 if (nextlen == 0) { 790 max_count = 138, min_count = 3; 791 } else if (curlen == nextlen) { 792 max_count = 6, min_count = 3; 793 } else { 794 max_count = 7, min_count = 4; 795 } 796 } 797 } 798 799 /* =========================================================================== 800 * Construct the Huffman tree for the bit lengths and return the index in 801 * bl_order of the last bit length code to send. 802 */ 803 local int build_bl_tree(s) 804 deflate_state *s; 805 { 806 int max_blindex; /* index of last bit length code of non zero freq */ 807 808 /* Determine the bit length frequencies for literal and distance trees */ 809 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); 810 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); 811 812 /* Build the bit length tree: */ 813 build_tree(s, (tree_desc *)(&(s->bl_desc))); 814 /* opt_len now includes the length of the tree representations, except 815 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. 816 */ 817 818 /* Determine the number of bit length codes to send. The pkzip format 819 * requires that at least 4 bit length codes be sent. (appnote.txt says 820 * 3 but the actual value used is 4.) 821 */ 822 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { 823 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; 824 } 825 /* Update opt_len to include the bit length tree and counts */ 826 s->opt_len += 3*(max_blindex+1) + 5+5+4; 827 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", 828 s->opt_len, s->static_len)); 829 830 return max_blindex; 831 } 832 833 /* =========================================================================== 834 * Send the header for a block using dynamic Huffman trees: the counts, the 835 * lengths of the bit length codes, the literal tree and the distance tree. 836 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 837 */ 838 local void send_all_trees(s, lcodes, dcodes, blcodes) 839 deflate_state *s; 840 int lcodes, dcodes, blcodes; /* number of codes for each tree */ 841 { 842 int rank; /* index in bl_order */ 843 844 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); 845 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, 846 "too many codes"); 847 Tracev((stderr, "\nbl counts: ")); 848 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */ 849 send_bits(s, dcodes-1, 5); 850 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */ 851 for (rank = 0; rank < blcodes; rank++) { 852 Tracev((stderr, "\nbl code %2d ", bl_order[rank])); 853 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); 854 } 855 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); 856 857 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ 858 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); 859 860 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ 861 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); 862 } 863 864 /* =========================================================================== 865 * Send a stored block 866 */ 867 void _tr_stored_block(s, buf, stored_len, eof) 868 deflate_state *s; 869 charf *buf; /* input block */ 870 ulg stored_len; /* length of input block */ 871 int eof; /* true if this is the last block for a file */ 872 { 873 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */ 874 #ifdef DEBUG 875 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; 876 s->compressed_len += (stored_len + 4) << 3; 877 #endif 878 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */ 879 } 880 881 /* =========================================================================== 882 * Send one empty static block to give enough lookahead for inflate. 883 * This takes 10 bits, of which 7 may remain in the bit buffer. 884 * The current inflate code requires 9 bits of lookahead. If the 885 * last two codes for the previous block (real code plus EOB) were coded 886 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode 887 * the last real code. In this case we send two empty static blocks instead 888 * of one. (There are no problems if the previous block is stored or fixed.) 889 * To simplify the code, we assume the worst case of last real code encoded 890 * on one bit only. 891 */ 892 void _tr_align(s) 893 deflate_state *s; 894 { 895 send_bits(s, STATIC_TREES<<1, 3); 896 send_code(s, END_BLOCK, static_ltree); 897 #ifdef DEBUG 898 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ 899 #endif 900 bi_flush(s); 901 /* Of the 10 bits for the empty block, we have already sent 902 * (10 - bi_valid) bits. The lookahead for the last real code (before 903 * the EOB of the previous block) was thus at least one plus the length 904 * of the EOB plus what we have just sent of the empty static block. 905 */ 906 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) { 907 send_bits(s, STATIC_TREES<<1, 3); 908 send_code(s, END_BLOCK, static_ltree); 909 #ifdef DEBUG 910 s->compressed_len += 10L; 911 #endif 912 bi_flush(s); 913 } 914 s->last_eob_len = 7; 915 } 916 917 /* =========================================================================== 918 * Determine the best encoding for the current block: dynamic trees, static 919 * trees or store, and output the encoded block to the zip file. 920 */ 921 void _tr_flush_block(s, buf, stored_len, eof) 922 deflate_state *s; 923 charf *buf; /* input block, or NULL if too old */ 924 ulg stored_len; /* length of input block */ 925 int eof; /* true if this is the last block for a file */ 926 { 927 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 928 int max_blindex = 0; /* index of last bit length code of non zero freq */ 929 930 /* Build the Huffman trees unless a stored block is forced */ 931 if (s->level > 0) { 932 933 /* Check if the file is binary or text */ 934 if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN) 935 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 the block lengths in bytes. */ 955 opt_lenb = (s->opt_len+3+7)>>3; <