trees.c revision 33908
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/* $FreeBSD: head/lib/libz/trees.c 33908 1998-02-28 06:08:17Z steve $ */ 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 61local 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 64local 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 67local 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 70local 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 90local 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 97local ct_data static_dtree[D_CODES]; 98/* The static distance tree. (Actually a trivial tree since all codes use 99 * 5 bits.) 100 */ 101 102uch _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 108uch _length_code[MAX_MATCH-MIN_MATCH+1]; 109/* length code for each normalized match length (0 == MIN_MATCH) */ 110 111local int base_length[LENGTH_CODES]; 112/* First normalized length for each code (0 = MIN_MATCH) */ 113 114local 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 121struct 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 129local static_tree_desc static_l_desc = 130{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; 131 132local static_tree_desc static_d_desc = 133{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS}; 134 135local 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 142local void tr_static_init OF((void)); 143local void init_block OF((deflate_state *s)); 144local void pqdownheap OF((deflate_state *s, ct_data *tree, int k)); 145local void gen_bitlen OF((deflate_state *s, tree_desc *desc)); 146local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count)); 147local void build_tree OF((deflate_state *s, tree_desc *desc)); 148local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code)); 149local void send_tree OF((deflate_state *s, ct_data *tree, int max_code)); 150local int build_bl_tree OF((deflate_state *s)); 151local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes, 152 int blcodes)); 153local void compress_block OF((deflate_state *s, ct_data *ltree, 154 ct_data *dtree)); 155local void set_data_type OF((deflate_state *s)); 156local unsigned bi_reverse OF((unsigned value, int length)); 157local void bi_windup OF((deflate_state *s)); 158local void bi_flush OF((deflate_state *s)); 159local void copy_block OF((deflate_state *s, charf *buf, unsigned len, 160 int header)); 161 162#ifdef GEN_TREES_H 163local 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 190local void send_bits OF((deflate_state *s, int value, int length)); 191 192local 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#define MAX(a,b) (a >= b ? a : b) 234/* the arguments must not have side effects */ 235 236/* =========================================================================== 237 * Initialize the various 'constant' tables. 238 */ 239local void tr_static_init() 240{ 241#if defined(GEN_TREES_H) || !defined(STDC) 242 static int static_init_done = 0; 243 int n; /* iterates over tree elements */ 244 int bits; /* bit counter */ 245 int length; /* length value */ 246 int code; /* code value */ 247 int dist; /* distance index */ 248 ush bl_count[MAX_BITS+1]; 249 /* number of codes at each bit length for an optimal tree */ 250 251 if (static_init_done) return; 252 253 /* Initialize the mapping length (0..255) -> length code (0..28) */ 254 length = 0; 255 for (code = 0; code < LENGTH_CODES-1; code++) { 256 base_length[code] = length; 257 for (n = 0; n < (1<<extra_lbits[code]); n++) { 258 _length_code[length++] = (uch)code; 259 } 260 } 261 Assert (length == 256, "tr_static_init: length != 256"); 262 /* Note that the length 255 (match length 258) can be represented 263 * in two different ways: code 284 + 5 bits or code 285, so we 264 * overwrite length_code[255] to use the best encoding: 265 */ 266 _length_code[length-1] = (uch)code; 267 268 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 269 dist = 0; 270 for (code = 0 ; code < 16; code++) { 271 base_dist[code] = dist; 272 for (n = 0; n < (1<<extra_dbits[code]); n++) { 273 _dist_code[dist++] = (uch)code; 274 } 275 } 276 Assert (dist == 256, "tr_static_init: dist != 256"); 277 dist >>= 7; /* from now on, all distances are divided by 128 */ 278 for ( ; code < D_CODES; code++) { 279 base_dist[code] = dist << 7; 280 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { 281 _dist_code[256 + dist++] = (uch)code; 282 } 283 } 284 Assert (dist == 256, "tr_static_init: 256+dist != 512"); 285 286 /* Construct the codes of the static literal tree */ 287 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 288 n = 0; 289 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 290 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 291 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 292 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 293 /* Codes 286 and 287 do not exist, but we must include them in the 294 * tree construction to get a canonical Huffman tree (longest code 295 * all ones) 296 */ 297 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count); 298 299 /* The static distance tree is trivial: */ 300 for (n = 0; n < D_CODES; n++) { 301 static_dtree[n].Len = 5; 302 static_dtree[n].Code = bi_reverse((unsigned)n, 5); 303 } 304 static_init_done = 1; 305 306# ifdef GEN_TREES_H 307 gen_trees_header(); 308# endif 309#endif /* defined(GEN_TREES_H) || !defined(STDC) */ 310} 311 312/* =========================================================================== 313 * Genererate the file trees.h describing the static trees. 314 */ 315#ifdef GEN_TREES_H 316# ifndef DEBUG 317# include <stdio.h> 318# endif 319 320# define SEPARATOR(i, last, width) \ 321 ((i) == (last)? "\n};\n\n" : \ 322 ((i) % (width) == (width)-1 ? ",\n" : ", ")) 323 324void gen_trees_header() 325{ 326 FILE *header = fopen("trees.h", "w"); 327 int i; 328 329 Assert (header != NULL, "Can't open trees.h"); 330 fprintf(header, 331 "/* header created automatically with -DGEN_TREES_H */\n\n"); 332 333 fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n"); 334 for (i = 0; i < L_CODES+2; i++) { 335 fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code, 336 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5)); 337 } 338 339 fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n"); 340 for (i = 0; i < D_CODES; i++) { 341 fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code, 342 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5)); 343 } 344 345 fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n"); 346 for (i = 0; i < DIST_CODE_LEN; i++) { 347 fprintf(header, "%2u%s", _dist_code[i], 348 SEPARATOR(i, DIST_CODE_LEN-1, 20)); 349 } 350 351 fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n"); 352 for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) { 353 fprintf(header, "%2u%s", _length_code[i], 354 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20)); 355 } 356 357 fprintf(header, "local const int base_length[LENGTH_CODES] = {\n"); 358 for (i = 0; i < LENGTH_CODES; i++) { 359 fprintf(header, "%1u%s", base_length[i], 360 SEPARATOR(i, LENGTH_CODES-1, 20)); 361 } 362 363 fprintf(header, "local const int base_dist[D_CODES] = {\n"); 364 for (i = 0; i < D_CODES; i++) { 365 fprintf(header, "%5u%s", base_dist[i], 366 SEPARATOR(i, D_CODES-1, 10)); 367 } 368 369 fclose(header); 370} 371#endif /* GEN_TREES_H */ 372 373/* =========================================================================== 374 * Initialize the tree data structures for a new zlib stream. 375 */ 376void _tr_init(s) 377 deflate_state *s; 378{ 379 tr_static_init(); 380 381 s->compressed_len = 0L; 382 383 s->l_desc.dyn_tree = s->dyn_ltree; 384 s->l_desc.stat_desc = &static_l_desc; 385 386 s->d_desc.dyn_tree = s->dyn_dtree; 387 s->d_desc.stat_desc = &static_d_desc; 388 389 s->bl_desc.dyn_tree = s->bl_tree; 390 s->bl_desc.stat_desc = &static_bl_desc; 391 392 s->bi_buf = 0; 393 s->bi_valid = 0; 394 s->last_eob_len = 8; /* enough lookahead for inflate */ 395#ifdef DEBUG 396 s->bits_sent = 0L; 397#endif 398 399 /* Initialize the first block of the first file: */ 400 init_block(s); 401} 402 403/* =========================================================================== 404 * Initialize a new block. 405 */ 406local void init_block(s) 407 deflate_state *s; 408{ 409 int n; /* iterates over tree elements */ 410 411 /* Initialize the trees. */ 412 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; 413 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; 414 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; 415 416 s->dyn_ltree[END_BLOCK].Freq = 1; 417 s->opt_len = s->static_len = 0L; 418 s->last_lit = s->matches = 0; 419} 420 421#define SMALLEST 1 422/* Index within the heap array of least frequent node in the Huffman tree */ 423 424 425/* =========================================================================== 426 * Remove the smallest element from the heap and recreate the heap with 427 * one less element. Updates heap and heap_len. 428 */ 429#define pqremove(s, tree, top) \ 430{\ 431 top = s->heap[SMALLEST]; \ 432 s->heap[SMALLEST] = s->heap[s->heap_len--]; \ 433 pqdownheap(s, tree, SMALLEST); \ 434} 435 436/* =========================================================================== 437 * Compares to subtrees, using the tree depth as tie breaker when 438 * the subtrees have equal frequency. This minimizes the worst case length. 439 */ 440#define smaller(tree, n, m, depth) \ 441 (tree[n].Freq < tree[m].Freq || \ 442 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 443 444/* =========================================================================== 445 * Restore the heap property by moving down the tree starting at node k, 446 * exchanging a node with the smallest of its two sons if necessary, stopping 447 * when the heap property is re-established (each father smaller than its 448 * two sons). 449 */ 450local void pqdownheap(s, tree, k) 451 deflate_state *s; 452 ct_data *tree; /* the tree to restore */ 453 int k; /* node to move down */ 454{ 455 int v = s->heap[k]; 456 int j = k << 1; /* left son of k */ 457 while (j <= s->heap_len) { 458 /* Set j to the smallest of the two sons: */ 459 if (j < s->heap_len && 460 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { 461 j++; 462 } 463 /* Exit if v is smaller than both sons */ 464 if (smaller(tree, v, s->heap[j], s->depth)) break; 465 466 /* Exchange v with the smallest son */ 467 s->heap[k] = s->heap[j]; k = j; 468 469 /* And continue down the tree, setting j to the left son of k */ 470 j <<= 1; 471 } 472 s->heap[k] = v; 473} 474 475/* =========================================================================== 476 * Compute the optimal bit lengths for a tree and update the total bit length 477 * for the current block. 478 * IN assertion: the fields freq and dad are set, heap[heap_max] and 479 * above are the tree nodes sorted by increasing frequency. 480 * OUT assertions: the field len is set to the optimal bit length, the 481 * array bl_count contains the frequencies for each bit length. 482 * The length opt_len is updated; static_len is also updated if stree is 483 * not null. 484 */ 485local void gen_bitlen(s, desc) 486 deflate_state *s; 487 tree_desc *desc; /* the tree descriptor */ 488{ 489 ct_data *tree = desc->dyn_tree; 490 int max_code = desc->max_code; 491 const ct_data *stree = desc->stat_desc->static_tree; 492 const intf *extra = desc->stat_desc->extra_bits; 493 int base = desc->stat_desc->extra_base; 494 int max_length = desc->stat_desc->max_length; 495 int h; /* heap index */ 496 int n, m; /* iterate over the tree elements */ 497 int bits; /* bit length */ 498 int xbits; /* extra bits */ 499 ush f; /* frequency */ 500 int overflow = 0; /* number of elements with bit length too large */ 501 502 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; 503 504 /* In a first pass, compute the optimal bit lengths (which may 505 * overflow in the case of the bit length tree). 506 */ 507 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ 508 509 for (h = s->heap_max+1; h < HEAP_SIZE; h++) { 510 n = s->heap[h]; 511 bits = tree[tree[n].Dad].Len + 1; 512 if (bits > max_length) bits = max_length, overflow++; 513 tree[n].Len = (ush)bits; 514 /* We overwrite tree[n].Dad which is no longer needed */ 515 516 if (n > max_code) continue; /* not a leaf node */ 517 518 s->bl_count[bits]++; 519 xbits = 0; 520 if (n >= base) xbits = extra[n-base]; 521 f = tree[n].Freq; 522 s->opt_len += (ulg)f * (bits + xbits); 523 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); 524 } 525 if (overflow == 0) return; 526 527 Trace((stderr,"\nbit length overflow\n")); 528 /* This happens for example on obj2 and pic of the Calgary corpus */ 529 530 /* Find the first bit length which could increase: */ 531 do { 532 bits = max_length-1; 533 while (s->bl_count[bits] == 0) bits--; 534 s->bl_count[bits]--; /* move one leaf down the tree */ 535 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ 536 s->bl_count[max_length]--; 537 /* The brother of the overflow item also moves one step up, 538 * but this does not affect bl_count[max_length] 539 */ 540 overflow -= 2; 541 } while (overflow > 0); 542 543 /* Now recompute all bit lengths, scanning in increasing frequency. 544 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 545 * lengths instead of fixing only the wrong ones. This idea is taken 546 * from 'ar' written by Haruhiko Okumura.) 547 */ 548 for (bits = max_length; bits != 0; bits--) { 549 n = s->bl_count[bits]; 550 while (n != 0) { 551 m = s->heap[--h]; 552 if (m > max_code) continue; 553 if (tree[m].Len != (unsigned) bits) { 554 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 555 s->opt_len += ((long)bits - (long)tree[m].Len) 556 *(long)tree[m].Freq; 557 tree[m].Len = (ush)bits; 558 } 559 n--; 560 } 561 } 562} 563 564/* =========================================================================== 565 * Generate the codes for a given tree and bit counts (which need not be 566 * optimal). 567 * IN assertion: the array bl_count contains the bit length statistics for 568 * the given tree and the field len is set for all tree elements. 569 * OUT assertion: the field code is set for all tree elements of non 570 * zero code length. 571 */ 572local void gen_codes (tree, max_code, bl_count) 573 ct_data *tree; /* the tree to decorate */ 574 int max_code; /* largest code with non zero frequency */ 575 ushf *bl_count; /* number of codes at each bit length */ 576{ 577 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 578 ush code = 0; /* running code value */ 579 int bits; /* bit index */ 580 int n; /* code index */ 581 582 /* The distribution counts are first used to generate the code values 583 * without bit reversal. 584 */ 585 for (bits = 1; bits <= MAX_BITS; bits++) { 586 next_code[bits] = code = (code + bl_count[bits-1]) << 1; 587 } 588 /* Check that the bit counts in bl_count are consistent. The last code 589 * must be all ones. 590 */ 591 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, 592 "inconsistent bit counts"); 593 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 594 595 for (n = 0; n <= max_code; n++) { 596 int len = tree[n].Len; 597 if (len == 0) continue; 598 /* Now reverse the bits */ 599 tree[n].Code = bi_reverse(next_code[len]++, len); 600 601 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 602 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); 603 } 604} 605 606/* =========================================================================== 607 * Construct one Huffman tree and assigns the code bit strings and lengths. 608 * Update the total bit length for the current block. 609 * IN assertion: the field freq is set for all tree elements. 610 * OUT assertions: the fields len and code are set to the optimal bit length 611 * and corresponding code. The length opt_len is updated; static_len is 612 * also updated if stree is not null. The field max_code is set. 613 */ 614local void build_tree(s, desc) 615 deflate_state *s; 616 tree_desc *desc; /* the tree descriptor */ 617{ 618 ct_data *tree = desc->dyn_tree; 619 const ct_data *stree = desc->stat_desc->static_tree; 620 int elems = desc->stat_desc->elems; 621 int n, m; /* iterate over heap elements */ 622 int max_code = -1; /* largest code with non zero frequency */ 623 int node; /* new node being created */ 624 625 /* Construct the initial heap, with least frequent element in 626 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. 627 * heap[0] is not used. 628 */ 629 s->heap_len = 0, s->heap_max = HEAP_SIZE; 630 631 for (n = 0; n < elems; n++) { 632 if (tree[n].Freq != 0) { 633 s->heap[++(s->heap_len)] = max_code = n; 634 s->depth[n] = 0; 635 } else { 636 tree[n].Len = 0; 637 } 638 } 639 640 /* The pkzip format requires that at least one distance code exists, 641 * and that at least one bit should be sent even if there is only one 642 * possible code. So to avoid special checks later on we force at least 643 * two codes of non zero frequency. 644 */ 645 while (s->heap_len < 2) { 646 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); 647 tree[node].Freq = 1; 648 s->depth[node] = 0; 649 s->opt_len--; if (stree) s->static_len -= stree[node].Len; 650 /* node is 0 or 1 so it does not have extra bits */ 651 } 652 desc->max_code = max_code; 653 654 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, 655 * establish sub-heaps of increasing lengths: 656 */ 657 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); 658 659 /* Construct the Huffman tree by repeatedly combining the least two 660 * frequent nodes. 661 */ 662 node = elems; /* next internal node of the tree */ 663 do { 664 pqremove(s, tree, n); /* n = node of least frequency */ 665 m = s->heap[SMALLEST]; /* m = node of next least frequency */ 666 667 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ 668 s->heap[--(s->heap_max)] = m; 669 670 /* Create a new node father of n and m */ 671 tree[node].Freq = tree[n].Freq + tree[m].Freq; 672 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1); 673 tree[n].Dad = tree[m].Dad = (ush)node; 674#ifdef DUMP_BL_TREE 675 if (tree == s->bl_tree) { 676 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 677 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 678 } 679#endif 680 /* and insert the new node in the heap */ 681 s->heap[SMALLEST] = node++; 682 pqdownheap(s, tree, SMALLEST); 683 684 } while (s->heap_len >= 2); 685 686 s->heap[--(s->heap_max)] = s->heap[SMALLEST]; 687 688 /* At this point, the fields freq and dad are set. We can now 689 * generate the bit lengths. 690 */ 691 gen_bitlen(s, (tree_desc *)desc); 692 693 /* The field len is now set, we can generate the bit codes */ 694 gen_codes ((ct_data *)tree, max_code, s->bl_count); 695} 696 697/* =========================================================================== 698 * Scan a literal or distance tree to determine the frequencies of the codes 699 * in the bit length tree. 700 */ 701local void scan_tree (s, tree, max_code) 702 deflate_state *s; 703 ct_data *tree; /* the tree to be scanned */ 704 int max_code; /* and its largest code of non zero frequency */ 705{ 706 int n; /* iterates over all tree elements */ 707 int prevlen = -1; /* last emitted length */ 708 int curlen; /* length of current code */ 709 int nextlen = tree[0].Len; /* length of next code */ 710 int count = 0; /* repeat count of the current code */ 711 int max_count = 7; /* max repeat count */ 712 int min_count = 4; /* min repeat count */ 713 714 if (nextlen == 0) max_count = 138, min_count = 3; 715 tree[max_code+1].Len = (ush)0xffff; /* guard */ 716 717 for (n = 0; n <= max_code; n++) { 718 curlen = nextlen; nextlen = tree[n+1].Len; 719 if (++count < max_count && curlen == nextlen) { 720 continue; 721 } else if (count < min_count) { 722 s->bl_tree[curlen].Freq += count; 723 } else if (curlen != 0) { 724 if (curlen != prevlen) s->bl_tree[curlen].Freq++; 725 s->bl_tree[REP_3_6].Freq++; 726 } else if (count <= 10) { 727 s->bl_tree[REPZ_3_10].Freq++; 728 } else { 729 s->bl_tree[REPZ_11_138].Freq++; 730 } 731 count = 0; prevlen = curlen; 732 if (nextlen == 0) { 733 max_count = 138, min_count = 3; 734 } else if (curlen == nextlen) { 735 max_count = 6, min_count = 3; 736 } else { 737 max_count = 7, min_count = 4; 738 } 739 } 740} 741 742/* =========================================================================== 743 * Send a literal or distance tree in compressed form, using the codes in 744 * bl_tree. 745 */ 746local void send_tree (s, tree, max_code) 747 deflate_state *s; 748 ct_data *tree; /* the tree to be scanned */ 749 int max_code; /* and its largest code of non zero frequency */ 750{ 751 int n; /* iterates over all tree elements */ 752 int prevlen = -1; /* last emitted length */ 753 int curlen; /* length of current code */ 754 int nextlen = tree[0].Len; /* length of next code */ 755 int count = 0; /* repeat count of the current code */ 756 int max_count = 7; /* max repeat count */ 757 int min_count = 4; /* min repeat count */ 758 759 /* tree[max_code+1].Len = -1; */ /* guard already set */ 760 if (nextlen == 0) max_count = 138, min_count = 3; 761 762 for (n = 0; n <= max_code; n++) { 763 curlen = nextlen; nextlen = tree[n+1].Len; 764 if (++count < max_count && curlen == nextlen) { 765 continue; 766 } else if (count < min_count) { 767 do { send_code(s, curlen, s->bl_tree); } while (--count != 0); 768 769 } else if (curlen != 0) { 770 if (curlen != prevlen) { 771 send_code(s, curlen, s->bl_tree); count--; 772 } 773 Assert(count >= 3 && count <= 6, " 3_6?"); 774 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); 775 776 } else if (count <= 10) { 777 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); 778 779 } else { 780 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); 781 } 782 count = 0; prevlen = curlen; 783 if (nextlen == 0) { 784 max_count = 138, min_count = 3; 785 } else if (curlen == nextlen) { 786 max_count = 6, min_count = 3; 787 } else { 788 max_count = 7, min_count = 4; 789 } 790 } 791} 792 793/* =========================================================================== 794 * Construct the Huffman tree for the bit lengths and return the index in 795 * bl_order of the last bit length code to send. 796 */ 797local int build_bl_tree(s) 798 deflate_state *s; 799{ 800 int max_blindex; /* index of last bit length code of non zero freq */ 801 802 /* Determine the bit length frequencies for literal and distance trees */ 803 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); 804 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); 805 806 /* Build the bit length tree: */ 807 build_tree(s, (tree_desc *)(&(s->bl_desc))); 808 /* opt_len now includes the length of the tree representations, except 809 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. 810 */ 811 812 /* Determine the number of bit length codes to send. The pkzip format 813 * requires that at least 4 bit length codes be sent. (appnote.txt says 814 * 3 but the actual value used is 4.) 815 */ 816 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { 817 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; 818 } 819 /* Update opt_len to include the bit length tree and counts */ 820 s->opt_len += 3*(max_blindex+1) + 5+5+4; 821 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", 822 s->opt_len, s->static_len)); 823 824 return max_blindex; 825} 826 827/* =========================================================================== 828 * Send the header for a block using dynamic Huffman trees: the counts, the 829 * lengths of the bit length codes, the literal tree and the distance tree. 830 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 831 */ 832local void send_all_trees(s, lcodes, dcodes, blcodes) 833 deflate_state *s; 834 int lcodes, dcodes, blcodes; /* number of codes for each tree */ 835{ 836 int rank; /* index in bl_order */ 837 838 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); 839 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, 840 "too many codes"); 841 Tracev((stderr, "\nbl counts: ")); 842 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */ 843 send_bits(s, dcodes-1, 5); 844 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */ 845 for (rank = 0; rank < blcodes; rank++) { 846 Tracev((stderr, "\nbl code %2d ", bl_order[rank])); 847 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); 848 } 849 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); 850 851 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ 852 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); 853 854 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ 855 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); 856} 857 858/* =========================================================================== 859 * Send a stored block 860 */ 861void _tr_stored_block(s, buf, stored_len, eof) 862 deflate_state *s; 863 charf *buf; /* input block */ 864 ulg stored_len; /* length of input block */ 865 int eof; /* true if this is the last block for a file */ 866{ 867 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */ 868 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; 869 s->compressed_len += (stored_len + 4) << 3; 870 871 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */ 872} 873 874/* =========================================================================== 875 * Send one empty static block to give enough lookahead for inflate. 876 * This takes 10 bits, of which 7 may remain in the bit buffer. 877 * The current inflate code requires 9 bits of lookahead. If the 878 * last two codes for the previous block (real code plus EOB) were coded 879 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode 880 * the last real code. In this case we send two empty static blocks instead 881 * of one. (There are no problems if the previous block is stored or fixed.) 882 * To simplify the code, we assume the worst case of last real code encoded 883 * on one bit only. 884 */ 885void _tr_align(s) 886 deflate_state *s; 887{ 888 send_bits(s, STATIC_TREES<<1, 3); 889 send_code(s, END_BLOCK, static_ltree); 890 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ 891 bi_flush(s); 892 /* Of the 10 bits for the empty block, we have already sent 893 * (10 - bi_valid) bits. The lookahead for the last real code (before 894 * the EOB of the previous block) was thus at least one plus the length 895 * of the EOB plus what we have just sent of the empty static block. 896 */ 897 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) { 898 send_bits(s, STATIC_TREES<<1, 3); 899 send_code(s, END_BLOCK, static_ltree); 900 s->compressed_len += 10L; 901 bi_flush(s); 902 } 903 s->last_eob_len = 7; 904} 905 906/* =========================================================================== 907 * Determine the best encoding for the current block: dynamic trees, static 908 * trees or store, and output the encoded block to the zip file. This function 909 * returns the total compressed length for the file so far. 910 */ 911ulg _tr_flush_block(s, buf, stored_len, eof) 912 deflate_state *s; 913 charf *buf; /* input block, or NULL if too old */ 914 ulg stored_len; /* length of input block */ 915 int eof; /* true if this is the last block for a file */ 916{ 917 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 918 int max_blindex = 0; /* index of last bit length code of non zero freq */ 919 920 /* Build the Huffman trees unless a stored block is forced */ 921 if (s->level > 0) { 922 923 /* Check if the file is ascii or binary */ 924 if (s->data_type == Z_UNKNOWN) set_data_type(s); 925 926 /* Construct the literal and distance trees */ 927 build_tree(s, (tree_desc *)(&(s->l_desc))); 928 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len, 929 s->static_len)); 930 931 build_tree(s, (tree_desc *)(&(s->d_desc))); 932 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len, 933 s->static_len)); 934 /* At this point, opt_len and static_len are the total bit lengths of 935 * the compressed block data, excluding the tree representations. 936 */ 937 938 /* Build the bit length tree for the above two trees, and get the index 939 * in bl_order of the last bit length code to send. 940 */ 941 max_blindex = build_bl_tree(s); 942 943 /* Determine the best encoding. Compute first the block length in bytes*/ 944 opt_lenb = (s->opt_len+3+7)>>3; 945 static_lenb = (s->static_len+3+7)>>3; 946 947 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", 948 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, 949 s->last_lit)); 950 951 if (static_lenb <= opt_lenb) opt_lenb = static_lenb; 952 953 } else { 954 Assert(buf != (char*)0, "lost buf"); 955 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */ 956 } 957 958 /* If compression failed and this is the first and last block, 959 * and if the .zip file can be seeked (to rewrite the local header), 960 * the whole file is transformed into a stored file: 961 */ 962#ifdef STORED_FILE_OK 963# ifdef FORCE_STORED_FILE 964 if (eof && s->compressed_len == 0L) { /* force stored file */ 965# else 966 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) { 967# endif 968 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */ 969 if (buf == (charf*)0) error ("block vanished"); 970 971 copy_block(buf, (unsigned)stored_len, 0); /* without header */ 972 s->compressed_len = stored_len << 3; 973 s->method = STORED; 974 } else 975#endif /* STORED_FILE_OK */ 976 977#ifdef FORCE_STORED 978 if (buf != (char*)0) { /* force stored block */ 979#else 980 if (stored_len+4 <= opt_lenb && buf != (char*)0) { 981 /* 4: two words for the lengths */ 982#endif 983 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. 984 * Otherwise we can't have processed more than WSIZE input bytes since 985 * the last block flush, because compression would have been 986 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to 987 * transform a block into a stored block. 988 */ 989 _tr_stored_block(s, buf, stored_len, eof); 990 991#ifdef FORCE_STATIC 992 } else if (static_lenb >= 0) { /* force static trees */ 993#else 994 } else if (static_lenb == opt_lenb) { 995#endif 996 send_bits(s, (STATIC_TREES<<1)+eof, 3); 997 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree); 998 s->compressed_len += 3 + s->static_len; 999 } else { 1000 send_bits(s, (DYN_TREES<<1)+eof, 3); 1001 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1, 1002 max_blindex+1); 1003 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree); 1004 s->compressed_len += 3 + s->opt_len; 1005 } 1006 Assert (s->compressed_len == s->bits_sent, "bad compressed size"); 1007 init_block(s); 1008 1009 if (eof) { 1010 bi_windup(s); 1011 s->compressed_len += 7; /* align on byte boundary */ 1012 } 1013 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3, 1014 s->compressed_len-7*eof)); 1015 1016 return s->compressed_len >> 3; 1017} 1018 1019/* =========================================================================== 1020 * Save the match info and tally the frequency counts. Return true if 1021 * the current block must be flushed. 1022 */ 1023int _tr_tally (s, dist, lc) 1024 deflate_state *s; 1025 unsigned dist; /* distance of matched string */ 1026 unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ 1027{ 1028 s->d_buf[s->last_lit] = (ush)dist; 1029 s->l_buf[s->last_lit++] = (uch)lc; 1030 if (dist == 0) { 1031 /* lc is the unmatched char */ 1032 s->dyn_ltree[lc].Freq++; 1033 } else { 1034 s->matches++; 1035 /* Here, lc is the match length - MIN_MATCH */ 1036 dist--; /* dist = match distance - 1 */ 1037 Assert((ush)dist < (ush)MAX_DIST(s) && 1038 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && 1039 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match"); 1040 1041 s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++; 1042 s->dyn_dtree[d_code(dist)].Freq++; 1043 } 1044 1045#ifdef TRUNCATE_BLOCK 1046 /* Try to guess if it is profitable to stop the current block here */ 1047 if ((s->last_lit & 0x1fff) == 0 && s->level > 2) { 1048 /* Compute an upper bound for the compressed length */ 1049 ulg out_length = (ulg)s->last_lit*8L; 1050 ulg in_length = (ulg)((long)s->strstart - s->block_start); 1051 int dcode; 1052 for (dcode = 0; dcode < D_CODES; dcode++) { 1053 out_length += (ulg)s->dyn_dtree[dcode].Freq * 1054 (5L+extra_dbits[dcode]); 1055 } 1056 out_length >>= 3; 1057 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", 1058 s->last_lit, in_length, out_length, 1059 100L - out_length*100L/in_length)); 1060 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1; 1061 } 1062#endif 1063 return (s->last_lit == s->lit_bufsize-1); 1064 /* We avoid equality with lit_bufsize because of wraparound at 64K 1065 * on 16 bit machines and because stored blocks are restricted to 1066 * 64K-1 bytes. 1067 */ 1068} 1069 1070/* =========================================================================== 1071 * Send the block data compressed using the given Huffman trees 1072 */ 1073local void compress_block(s, ltree, dtree) 1074 deflate_state *s; 1075 ct_data *ltree; /* literal tree */ 1076 ct_data *dtree; /* distance tree */ 1077{ 1078 unsigned dist; /* distance of matched string */ 1079 int lc; /* match length or unmatched char (if dist == 0) */ 1080 unsigned lx = 0; /* running index in l_buf */ 1081 unsigned code; /* the code to send */ 1082 int extra; /* number of extra bits to send */ 1083 1084 if (s->last_lit != 0) do { 1085 dist = s->d_buf[lx]; 1086 lc = s->l_buf[lx++]; 1087 if (dist == 0) { 1088 send_code(s, lc, ltree); /* send a literal byte */ 1089 Tracecv(isgraph(lc), (stderr," '%c' ", lc)); 1090 } else { 1091 /* Here, lc is the match length - MIN_MATCH */ 1092 code = _length_code[lc]; 1093 send_code(s, code+LITERALS+1, ltree); /* send the length code */ 1094 extra = extra_lbits[code]; 1095 if (extra != 0) { 1096 lc -= base_length[code]; 1097 send_bits(s, lc, extra); /* send the extra length bits */ 1098 } 1099 dist--; /* dist is now the match distance - 1 */ 1100 code = d_code(dist); 1101 Assert (code < D_CODES, "bad d_code"); 1102 1103 send_code(s, code, dtree); /* send the distance code */ 1104 extra = extra_dbits[code]; 1105 if (extra != 0) { 1106 dist -= base_dist[code]; 1107 send_bits(s, dist, extra); /* send the extra distance bits */ 1108 } 1109 } /* literal or match pair ? */ 1110 1111 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */ 1112 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow"); 1113 1114 } while (lx < s->last_lit); 1115 1116 send_code(s, END_BLOCK, ltree); 1117 s->last_eob_len = ltree[END_BLOCK].Len; 1118} 1119 1120/* =========================================================================== 1121 * Set the data type to ASCII or BINARY, using a crude approximation: 1122 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. 1123 * IN assertion: the fields freq of dyn_ltree are set and the total of all 1124 * frequencies does not exceed 64K (to fit in an int on 16 bit machines). 1125 */ 1126local void set_data_type(s) 1127 deflate_state *s; 1128{ 1129 int n = 0; 1130 unsigned ascii_freq = 0; 1131 unsigned bin_freq = 0; 1132 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq; 1133 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq; 1134 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq; 1135 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII); 1136} 1137 1138/* =========================================================================== 1139 * Reverse the first len bits of a code, using straightforward code (a faster 1140 * method would use a table) 1141 * IN assertion: 1 <= len <= 15 1142 */ 1143local unsigned bi_reverse(code, len) 1144 unsigned code; /* the value to invert */ 1145 int len; /* its bit length */ 1146{ 1147 register unsigned res = 0; 1148 do { 1149 res |= code & 1; 1150 code >>= 1, res <<= 1; 1151 } while (--len > 0); 1152 return res >> 1; 1153} 1154 1155/* =========================================================================== 1156 * Flush the bit buffer, keeping at most 7 bits in it. 1157 */ 1158local void bi_flush(s) 1159 deflate_state *s; 1160{ 1161 if (s->bi_valid == 16) { 1162 put_short(s, s->bi_buf); 1163 s->bi_buf = 0; 1164 s->bi_valid = 0; 1165 } else if (s->bi_valid >= 8) { 1166 put_byte(s, (Byte)s->bi_buf); 1167 s->bi_buf >>= 8; 1168 s->bi_valid -= 8; 1169 } 1170} 1171 1172/* =========================================================================== 1173 * Flush the bit buffer and align the output on a byte boundary 1174 */ 1175local void bi_windup(s) 1176 deflate_state *s; 1177{ 1178 if (s->bi_valid > 8) { 1179 put_short(s, s->bi_buf); 1180 } else if (s->bi_valid > 0) { 1181 put_byte(s, (Byte)s->bi_buf); 1182 } 1183 s->bi_buf = 0; 1184 s->bi_valid = 0; 1185#ifdef DEBUG 1186 s->bits_sent = (s->bits_sent+7) & ~7; 1187#endif 1188} 1189 1190/* =========================================================================== 1191 * Copy a stored block, storing first the length and its 1192 * one's complement if requested. 1193 */ 1194local void copy_block(s, buf, len, header) 1195 deflate_state *s; 1196 charf *buf; /* the input data */ 1197 unsigned len; /* its length */ 1198 int header; /* true if block header must be written */ 1199{ 1200 bi_windup(s); /* align on byte boundary */ 1201 s->last_eob_len = 8; /* enough lookahead for inflate */ 1202 1203 if (header) { 1204 put_short(s, (ush)len); 1205 put_short(s, (ush)~len); 1206#ifdef DEBUG 1207 s->bits_sent += 2*16; 1208#endif 1209 } 1210#ifdef DEBUG 1211 s->bits_sent += (ulg)len<<3; 1212#endif 1213 while (len--) { 1214 put_byte(s, *buf++); 1215 } 1216} 1217