1/* trees.c -- output deflated data using Huffman coding 2 * Copyright (C) 1992-1993 Jean-loup Gailly 3 * This is free software; you can redistribute it and/or modify it under the 4 * terms of the GNU General Public License, see the file COPYING. 5 */ 6 7/* 8 * PURPOSE 9 * 10 * Encode various sets of source values using variable-length 11 * binary code trees. 12 * 13 * DISCUSSION 14 * 15 * The PKZIP "deflation" process uses several Huffman trees. The more 16 * common source values are represented by shorter bit sequences. 17 * 18 * Each code tree is stored in the ZIP file in a compressed form 19 * which is itself a Huffman encoding of the lengths of 20 * all the code strings (in ascending order by source values). 21 * The actual code strings are reconstructed from the lengths in 22 * the UNZIP process, as described in the "application note" 23 * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program. 24 * 25 * REFERENCES 26 * 27 * Lynch, Thomas J. 28 * Data Compression: Techniques and Applications, pp. 53-55. 29 * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7. 30 * 31 * Storer, James A. 32 * Data Compression: Methods and Theory, pp. 49-50. 33 * Computer Science Press, 1988. ISBN 0-7167-8156-5. 34 * 35 * Sedgewick, R. 36 * Algorithms, p290. 37 * Addison-Wesley, 1983. ISBN 0-201-06672-6. 38 * 39 * INTERFACE 40 * 41 * void ct_init (ush *attr, int *methodp) 42 * Allocate the match buffer, initialize the various tables and save 43 * the location of the internal file attribute (ascii/binary) and 44 * method (DEFLATE/STORE) 45 * 46 * void ct_tally (int dist, int lc); 47 * Save the match info and tally the frequency counts. 48 * 49 * long flush_block (char *buf, ulg stored_len, int eof) 50 * Determine the best encoding for the current block: dynamic trees, 51 * static trees or store, and output the encoded block to the zip 52 * file. Returns the total compressed length for the file so far. 53 * 54 */ 55 56#include <ctype.h> 57 58#include "tailor.h" 59#include "gzip.h" 60 61#ifdef RCSID 62static char rcsid[] = "$Id: trees.c 3476 2003-06-11 15:56:10Z darkwyrm $"; 63#endif 64 65/* =========================================================================== 66 * Constants 67 */ 68 69#define MAX_BITS 15 70/* All codes must not exceed MAX_BITS bits */ 71 72#define MAX_BL_BITS 7 73/* Bit length codes must not exceed MAX_BL_BITS bits */ 74 75#define LENGTH_CODES 29 76/* number of length codes, not counting the special END_BLOCK code */ 77 78#define LITERALS 256 79/* number of literal bytes 0..255 */ 80 81#define END_BLOCK 256 82/* end of block literal code */ 83 84#define L_CODES (LITERALS+1+LENGTH_CODES) 85/* number of Literal or Length codes, including the END_BLOCK code */ 86 87#define D_CODES 30 88/* number of distance codes */ 89 90#define BL_CODES 19 91/* number of codes used to transfer the bit lengths */ 92 93 94local int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */ 95 = {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}; 96 97local int near extra_dbits[D_CODES] /* extra bits for each distance code */ 98 = {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}; 99 100local int near extra_blbits[BL_CODES]/* extra bits for each bit length code */ 101 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; 102 103#define STORED_BLOCK 0 104#define STATIC_TREES 1 105#define DYN_TREES 2 106/* The three kinds of block type */ 107 108#ifndef LIT_BUFSIZE 109# ifdef SMALL_MEM 110# define LIT_BUFSIZE 0x2000 111# else 112# ifdef MEDIUM_MEM 113# define LIT_BUFSIZE 0x4000 114# else 115# define LIT_BUFSIZE 0x8000 116# endif 117# endif 118#endif 119#ifndef DIST_BUFSIZE 120# define DIST_BUFSIZE LIT_BUFSIZE 121#endif 122/* Sizes of match buffers for literals/lengths and distances. There are 123 * 4 reasons for limiting LIT_BUFSIZE to 64K: 124 * - frequencies can be kept in 16 bit counters 125 * - if compression is not successful for the first block, all input data is 126 * still in the window so we can still emit a stored block even when input 127 * comes from standard input. (This can also be done for all blocks if 128 * LIT_BUFSIZE is not greater than 32K.) 129 * - if compression is not successful for a file smaller than 64K, we can 130 * even emit a stored file instead of a stored block (saving 5 bytes). 131 * - creating new Huffman trees less frequently may not provide fast 132 * adaptation to changes in the input data statistics. (Take for 133 * example a binary file with poorly compressible code followed by 134 * a highly compressible string table.) Smaller buffer sizes give 135 * fast adaptation but have of course the overhead of transmitting trees 136 * more frequently. 137 * - I can't count above 4 138 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save 139 * memory at the expense of compression). Some optimizations would be possible 140 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE. 141 */ 142#if LIT_BUFSIZE > INBUFSIZ 143 error cannot overlay l_buf and inbuf 144#endif 145 146#define REP_3_6 16 147/* repeat previous bit length 3-6 times (2 bits of repeat count) */ 148 149#define REPZ_3_10 17 150/* repeat a zero length 3-10 times (3 bits of repeat count) */ 151 152#define REPZ_11_138 18 153/* repeat a zero length 11-138 times (7 bits of repeat count) */ 154 155/* =========================================================================== 156 * Local data 157 */ 158 159/* Data structure describing a single value and its code string. */ 160typedef struct ct_data { 161 union { 162 ush freq; /* frequency count */ 163 ush code; /* bit string */ 164 } fc; 165 union { 166 ush dad; /* father node in Huffman tree */ 167 ush len; /* length of bit string */ 168 } dl; 169} ct_data; 170 171#define Freq fc.freq 172#define Code fc.code 173#define Dad dl.dad 174#define Len dl.len 175 176#define HEAP_SIZE (2*L_CODES+1) 177/* maximum heap size */ 178 179local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 180local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */ 181 182local ct_data near static_ltree[L_CODES+2]; 183/* The static literal tree. Since the bit lengths are imposed, there is no 184 * need for the L_CODES extra codes used during heap construction. However 185 * The codes 286 and 287 are needed to build a canonical tree (see ct_init 186 * below). 187 */ 188 189local ct_data near static_dtree[D_CODES]; 190/* The static distance tree. (Actually a trivial tree since all codes use 191 * 5 bits.) 192 */ 193 194local ct_data near bl_tree[2*BL_CODES+1]; 195/* Huffman tree for the bit lengths */ 196 197typedef struct tree_desc { 198 ct_data near *dyn_tree; /* the dynamic tree */ 199 ct_data near *static_tree; /* corresponding static tree or NULL */ 200 int near *extra_bits; /* extra bits for each code or NULL */ 201 int extra_base; /* base index for extra_bits */ 202 int elems; /* max number of elements in the tree */ 203 int max_length; /* max bit length for the codes */ 204 int max_code; /* largest code with non zero frequency */ 205} tree_desc; 206 207local tree_desc near l_desc = 208{dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0}; 209 210local tree_desc near d_desc = 211{dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0}; 212 213local tree_desc near bl_desc = 214{bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0}; 215 216 217local ush near bl_count[MAX_BITS+1]; 218/* number of codes at each bit length for an optimal tree */ 219 220local uch near bl_order[BL_CODES] 221 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; 222/* The lengths of the bit length codes are sent in order of decreasing 223 * probability, to avoid transmitting the lengths for unused bit length codes. 224 */ 225 226local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 227local int heap_len; /* number of elements in the heap */ 228local int heap_max; /* element of largest frequency */ 229/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 230 * The same heap array is used to build all trees. 231 */ 232 233local uch near depth[2*L_CODES+1]; 234/* Depth of each subtree used as tie breaker for trees of equal frequency */ 235 236local uch length_code[MAX_MATCH-MIN_MATCH+1]; 237/* length code for each normalized match length (0 == MIN_MATCH) */ 238 239local uch dist_code[512]; 240/* distance codes. The first 256 values correspond to the distances 241 * 3 .. 258, the last 256 values correspond to the top 8 bits of 242 * the 15 bit distances. 243 */ 244 245local int near base_length[LENGTH_CODES]; 246/* First normalized length for each code (0 = MIN_MATCH) */ 247 248local int near base_dist[D_CODES]; 249/* First normalized distance for each code (0 = distance of 1) */ 250 251#define l_buf inbuf 252/* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */ 253 254/* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */ 255 256local uch near flag_buf[(LIT_BUFSIZE/8)]; 257/* flag_buf is a bit array distinguishing literals from lengths in 258 * l_buf, thus indicating the presence or absence of a distance. 259 */ 260 261local unsigned last_lit; /* running index in l_buf */ 262local unsigned last_dist; /* running index in d_buf */ 263local unsigned last_flags; /* running index in flag_buf */ 264local uch flags; /* current flags not yet saved in flag_buf */ 265local uch flag_bit; /* current bit used in flags */ 266/* bits are filled in flags starting at bit 0 (least significant). 267 * Note: these flags are overkill in the current code since we don't 268 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE. 269 */ 270 271local ulg opt_len; /* bit length of current block with optimal trees */ 272local ulg static_len; /* bit length of current block with static trees */ 273 274local ulg compressed_len; /* total bit length of compressed file */ 275 276local ulg input_len; /* total byte length of input file */ 277/* input_len is for debugging only since we can get it by other means. */ 278 279ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */ 280int *file_method; /* pointer to DEFLATE or STORE */ 281 282#ifdef DEBUG 283extern ulg bits_sent; /* bit length of the compressed data */ 284extern long isize; /* byte length of input file */ 285#endif 286 287extern long block_start; /* window offset of current block */ 288extern unsigned near strstart; /* window offset of current string */ 289 290/* =========================================================================== 291 * Local (static) routines in this file. 292 */ 293 294local void init_block OF((void)); 295local void pqdownheap OF((ct_data near *tree, int k)); 296local void gen_bitlen OF((tree_desc near *desc)); 297local void gen_codes OF((ct_data near *tree, int max_code)); 298local void build_tree OF((tree_desc near *desc)); 299local void scan_tree OF((ct_data near *tree, int max_code)); 300local void send_tree OF((ct_data near *tree, int max_code)); 301local int build_bl_tree OF((void)); 302local void send_all_trees OF((int lcodes, int dcodes, int blcodes)); 303local void compress_block OF((ct_data near *ltree, ct_data near *dtree)); 304local void set_file_type OF((void)); 305 306 307#ifndef DEBUG 308# define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len) 309 /* Send a code of the given tree. c and tree must not have side effects */ 310 311#else /* DEBUG */ 312# define send_code(c, tree) \ 313 { if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \ 314 send_bits(tree[c].Code, tree[c].Len); } 315#endif 316 317#define d_code(dist) \ 318 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)]) 319/* Mapping from a distance to a distance code. dist is the distance - 1 and 320 * must not have side effects. dist_code[256] and dist_code[257] are never 321 * used. 322 */ 323 324#define MAX(a,b) (a >= b ? a : b) 325/* the arguments must not have side effects */ 326 327/* =========================================================================== 328 * Allocate the match buffer, initialize the various tables and save the 329 * location of the internal file attribute (ascii/binary) and method 330 * (DEFLATE/STORE). 331 */ 332void ct_init(attr, methodp) 333 ush *attr; /* pointer to internal file attribute */ 334 int *methodp; /* pointer to compression method */ 335{ 336 int n; /* iterates over tree elements */ 337 int bits; /* bit counter */ 338 int length; /* length value */ 339 int code; /* code value */ 340 int dist; /* distance index */ 341 342 file_type = attr; 343 file_method = methodp; 344 compressed_len = input_len = 0L; 345 346 if (static_dtree[0].Len != 0) return; /* ct_init already called */ 347 348 /* Initialize the mapping length (0..255) -> length code (0..28) */ 349 length = 0; 350 for (code = 0; code < LENGTH_CODES-1; code++) { 351 base_length[code] = length; 352 for (n = 0; n < (1<<extra_lbits[code]); n++) { 353 length_code[length++] = (uch)code; 354 } 355 } 356 Assert (length == 256, "ct_init: length != 256"); 357 /* Note that the length 255 (match length 258) can be represented 358 * in two different ways: code 284 + 5 bits or code 285, so we 359 * overwrite length_code[255] to use the best encoding: 360 */ 361 length_code[length-1] = (uch)code; 362 363 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 364 dist = 0; 365 for (code = 0 ; code < 16; code++) { 366 base_dist[code] = dist; 367 for (n = 0; n < (1<<extra_dbits[code]); n++) { 368 dist_code[dist++] = (uch)code; 369 } 370 } 371 Assert (dist == 256, "ct_init: dist != 256"); 372 dist >>= 7; /* from now on, all distances are divided by 128 */ 373 for ( ; code < D_CODES; code++) { 374 base_dist[code] = dist << 7; 375 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { 376 dist_code[256 + dist++] = (uch)code; 377 } 378 } 379 Assert (dist == 256, "ct_init: 256+dist != 512"); 380 381 /* Construct the codes of the static literal tree */ 382 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 383 n = 0; 384 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 385 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 386 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 387 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 388 /* Codes 286 and 287 do not exist, but we must include them in the 389 * tree construction to get a canonical Huffman tree (longest code 390 * all ones) 391 */ 392 gen_codes((ct_data near *)static_ltree, L_CODES+1); 393 394 /* The static distance tree is trivial: */ 395 for (n = 0; n < D_CODES; n++) { 396 static_dtree[n].Len = 5; 397 static_dtree[n].Code = bi_reverse(n, 5); 398 } 399 400 /* Initialize the first block of the first file: */ 401 init_block(); 402} 403 404/* =========================================================================== 405 * Initialize a new block. 406 */ 407local void init_block() 408{ 409 int n; /* iterates over tree elements */ 410 411 /* Initialize the trees. */ 412 for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0; 413 for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0; 414 for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0; 415 416 dyn_ltree[END_BLOCK].Freq = 1; 417 opt_len = static_len = 0L; 418 last_lit = last_dist = last_flags = 0; 419 flags = 0; flag_bit = 1; 420} 421 422#define SMALLEST 1 423/* Index within the heap array of least frequent node in the Huffman tree */ 424 425 426/* =========================================================================== 427 * Remove the smallest element from the heap and recreate the heap with 428 * one less element. Updates heap and heap_len. 429 */ 430#define pqremove(tree, top) \ 431{\ 432 top = heap[SMALLEST]; \ 433 heap[SMALLEST] = heap[heap_len--]; \ 434 pqdownheap(tree, SMALLEST); \ 435} 436 437/* =========================================================================== 438 * Compares to subtrees, using the tree depth as tie breaker when 439 * the subtrees have equal frequency. This minimizes the worst case length. 440 */ 441#define smaller(tree, n, m) \ 442 (tree[n].Freq < tree[m].Freq || \ 443 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 444 445/* =========================================================================== 446 * Restore the heap property by moving down the tree starting at node k, 447 * exchanging a node with the smallest of its two sons if necessary, stopping 448 * when the heap property is re-established (each father smaller than its 449 * two sons). 450 */ 451local void pqdownheap(tree, k) 452 ct_data near *tree; /* the tree to restore */ 453 int k; /* node to move down */ 454{ 455 int v = heap[k]; 456 int j = k << 1; /* left son of k */ 457 while (j <= heap_len) { 458 /* Set j to the smallest of the two sons: */ 459 if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++; 460 461 /* Exit if v is smaller than both sons */ 462 if (smaller(tree, v, heap[j])) break; 463 464 /* Exchange v with the smallest son */ 465 heap[k] = heap[j]; k = j; 466 467 /* And continue down the tree, setting j to the left son of k */ 468 j <<= 1; 469 } 470 heap[k] = v; 471} 472 473/* =========================================================================== 474 * Compute the optimal bit lengths for a tree and update the total bit length 475 * for the current block. 476 * IN assertion: the fields freq and dad are set, heap[heap_max] and 477 * above are the tree nodes sorted by increasing frequency. 478 * OUT assertions: the field len is set to the optimal bit length, the 479 * array bl_count contains the frequencies for each bit length. 480 * The length opt_len is updated; static_len is also updated if stree is 481 * not null. 482 */ 483local void gen_bitlen(desc) 484 tree_desc near *desc; /* the tree descriptor */ 485{ 486 ct_data near *tree = desc->dyn_tree; 487 int near *extra = desc->extra_bits; 488 int base = desc->extra_base; 489 int max_code = desc->max_code; 490 int max_length = desc->max_length; 491 ct_data near *stree = desc->static_tree; 492 int h; /* heap index */ 493 int n, m; /* iterate over the tree elements */ 494 int bits; /* bit length */ 495 int xbits; /* extra bits */ 496 ush f; /* frequency */ 497 int overflow = 0; /* number of elements with bit length too large */ 498 499 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 500 501 /* In a first pass, compute the optimal bit lengths (which may 502 * overflow in the case of the bit length tree). 503 */ 504 tree[heap[heap_max]].Len = 0; /* root of the heap */ 505 506 for (h = heap_max+1; h < HEAP_SIZE; h++) { 507 n = heap[h]; 508 bits = tree[tree[n].Dad].Len + 1; 509 if (bits > max_length) bits = max_length, overflow++; 510 tree[n].Len = (ush)bits; 511 /* We overwrite tree[n].Dad which is no longer needed */ 512 513 if (n > max_code) continue; /* not a leaf node */ 514 515 bl_count[bits]++; 516 xbits = 0; 517 if (n >= base) xbits = extra[n-base]; 518 f = tree[n].Freq; 519 opt_len += (ulg)f * (bits + xbits); 520 if (stree) static_len += (ulg)f * (stree[n].Len + xbits); 521 } 522 if (overflow == 0) return; 523 524 Trace((stderr,"\nbit length overflow\n")); 525 /* This happens for example on obj2 and pic of the Calgary corpus */ 526 527 /* Find the first bit length which could increase: */ 528 do { 529 bits = max_length-1; 530 while (bl_count[bits] == 0) bits--; 531 bl_count[bits]--; /* move one leaf down the tree */ 532 bl_count[bits+1] += 2; /* move one overflow item as its brother */ 533 bl_count[max_length]--; 534 /* The brother of the overflow item also moves one step up, 535 * but this does not affect bl_count[max_length] 536 */ 537 overflow -= 2; 538 } while (overflow > 0); 539 540 /* Now recompute all bit lengths, scanning in increasing frequency. 541 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 542 * lengths instead of fixing only the wrong ones. This idea is taken 543 * from 'ar' written by Haruhiko Okumura.) 544 */ 545 for (bits = max_length; bits != 0; bits--) { 546 n = bl_count[bits]; 547 while (n != 0) { 548 m = heap[--h]; 549 if (m > max_code) continue; 550 if (tree[m].Len != (unsigned) bits) { 551 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 552 opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq; 553 tree[m].Len = (ush)bits; 554 } 555 n--; 556 } 557 } 558} 559 560/* =========================================================================== 561 * Generate the codes for a given tree and bit counts (which need not be 562 * optimal). 563 * IN assertion: the array bl_count contains the bit length statistics for 564 * the given tree and the field len is set for all tree elements. 565 * OUT assertion: the field code is set for all tree elements of non 566 * zero code length. 567 */ 568local void gen_codes (tree, max_code) 569 ct_data near *tree; /* the tree to decorate */ 570 int max_code; /* largest code with non zero frequency */ 571{ 572 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 573 ush code = 0; /* running code value */ 574 int bits; /* bit index */ 575 int n; /* code index */ 576 577 /* The distribution counts are first used to generate the code values 578 * without bit reversal. 579 */ 580 for (bits = 1; bits <= MAX_BITS; bits++) { 581 next_code[bits] = code = (code + bl_count[bits-1]) << 1; 582 } 583 /* Check that the bit counts in bl_count are consistent. The last code 584 * must be all ones. 585 */ 586 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, 587 "inconsistent bit counts"); 588 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 589 590 for (n = 0; n <= max_code; n++) { 591 int len = tree[n].Len; 592 if (len == 0) continue; 593 /* Now reverse the bits */ 594 tree[n].Code = bi_reverse(next_code[len]++, len); 595 596 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 597 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); 598 } 599} 600 601/* =========================================================================== 602 * Construct one Huffman tree and assigns the code bit strings and lengths. 603 * Update the total bit length for the current block. 604 * IN assertion: the field freq is set for all tree elements. 605 * OUT assertions: the fields len and code are set to the optimal bit length 606 * and corresponding code. The length opt_len is updated; static_len is 607 * also updated if stree is not null. The field max_code is set. 608 */ 609local void build_tree(desc) 610 tree_desc near *desc; /* the tree descriptor */ 611{ 612 ct_data near *tree = desc->dyn_tree; 613 ct_data near *stree = desc->static_tree; 614 int elems = desc->elems; 615 int n, m; /* iterate over heap elements */ 616 int max_code = -1; /* largest code with non zero frequency */ 617 int node = elems; /* next internal node of the tree */ 618 619 /* Construct the initial heap, with least frequent element in 620 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. 621 * heap[0] is not used. 622 */ 623 heap_len = 0, heap_max = HEAP_SIZE; 624 625 for (n = 0; n < elems; n++) { 626 if (tree[n].Freq != 0) { 627 heap[++heap_len] = max_code = n; 628 depth[n] = 0; 629 } else { 630 tree[n].Len = 0; 631 } 632 } 633 634 /* The pkzip format requires that at least one distance code exists, 635 * and that at least one bit should be sent even if there is only one 636 * possible code. So to avoid special checks later on we force at least 637 * two codes of non zero frequency. 638 */ 639 while (heap_len < 2) { 640 int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0); 641 tree[new].Freq = 1; 642 depth[new] = 0; 643 opt_len--; if (stree) static_len -= stree[new].Len; 644 /* new is 0 or 1 so it does not have extra bits */ 645 } 646 desc->max_code = max_code; 647 648 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, 649 * establish sub-heaps of increasing lengths: 650 */ 651 for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n); 652 653 /* Construct the Huffman tree by repeatedly combining the least two 654 * frequent nodes. 655 */ 656 do { 657 pqremove(tree, n); /* n = node of least frequency */ 658 m = heap[SMALLEST]; /* m = node of next least frequency */ 659 660 heap[--heap_max] = n; /* keep the nodes sorted by frequency */ 661 heap[--heap_max] = m; 662 663 /* Create a new node father of n and m */ 664 tree[node].Freq = tree[n].Freq + tree[m].Freq; 665 depth[node] = (uch) (MAX(depth[n], depth[m]) + 1); 666 tree[n].Dad = tree[m].Dad = (ush)node; 667#ifdef DUMP_BL_TREE 668 if (tree == bl_tree) { 669 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 670 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 671 } 672#endif 673 /* and insert the new node in the heap */ 674 heap[SMALLEST] = node++; 675 pqdownheap(tree, SMALLEST); 676 677 } while (heap_len >= 2); 678 679 heap[--heap_max] = heap[SMALLEST]; 680 681 /* At this point, the fields freq and dad are set. We can now 682 * generate the bit lengths. 683 */ 684 gen_bitlen((tree_desc near *)desc); 685 686 /* The field len is now set, we can generate the bit codes */ 687 gen_codes ((ct_data near *)tree, max_code); 688} 689 690/* =========================================================================== 691 * Scan a literal or distance tree to determine the frequencies of the codes 692 * in the bit length tree. Updates opt_len to take into account the repeat 693 * counts. (The contribution of the bit length codes will be added later 694 * during the construction of bl_tree.) 695 */ 696local void scan_tree (tree, max_code) 697 ct_data near *tree; /* the tree to be scanned */ 698 int max_code; /* and its largest code of non zero frequency */ 699{ 700 int n; /* iterates over all tree elements */ 701 int prevlen = -1; /* last emitted length */ 702 int curlen; /* length of current code */ 703 int nextlen = tree[0].Len; /* length of next code */ 704 int count = 0; /* repeat count of the current code */ 705 int max_count = 7; /* max repeat count */ 706 int min_count = 4; /* min repeat count */ 707 708 if (nextlen == 0) max_count = 138, min_count = 3; 709 tree[max_code+1].Len = (ush)0xffff; /* guard */ 710 711 for (n = 0; n <= max_code; n++) { 712 curlen = nextlen; nextlen = tree[n+1].Len; 713 if (++count < max_count && curlen == nextlen) { 714 continue; 715 } else if (count < min_count) { 716 bl_tree[curlen].Freq += count; 717 } else if (curlen != 0) { 718 if (curlen != prevlen) bl_tree[curlen].Freq++; 719 bl_tree[REP_3_6].Freq++; 720 } else if (count <= 10) { 721 bl_tree[REPZ_3_10].Freq++; 722 } else { 723 bl_tree[REPZ_11_138].Freq++; 724 } 725 count = 0; prevlen = curlen; 726 if (nextlen == 0) { 727 max_count = 138, min_count = 3; 728 } else if (curlen == nextlen) { 729 max_count = 6, min_count = 3; 730 } else { 731 max_count = 7, min_count = 4; 732 } 733 } 734} 735 736/* =========================================================================== 737 * Send a literal or distance tree in compressed form, using the codes in 738 * bl_tree. 739 */ 740local void send_tree (tree, max_code) 741 ct_data near *tree; /* the tree to be scanned */ 742 int max_code; /* and its largest code of non zero frequency */ 743{ 744 int n; /* iterates over all tree elements */ 745 int prevlen = -1; /* last emitted length */ 746 int curlen; /* length of current code */ 747 int nextlen = tree[0].Len; /* length of next code */ 748 int count = 0; /* repeat count of the current code */ 749 int max_count = 7; /* max repeat count */ 750 int min_count = 4; /* min repeat count */ 751 752 /* tree[max_code+1].Len = -1; */ /* guard already set */ 753 if (nextlen == 0) max_count = 138, min_count = 3; 754 755 for (n = 0; n <= max_code; n++) { 756 curlen = nextlen; nextlen = tree[n+1].Len; 757 if (++count < max_count && curlen == nextlen) { 758 continue; 759 } else if (count < min_count) { 760 do { send_code(curlen, bl_tree); } while (--count != 0); 761 762 } else if (curlen != 0) { 763 if (curlen != prevlen) { 764 send_code(curlen, bl_tree); count--; 765 } 766 Assert(count >= 3 && count <= 6, " 3_6?"); 767 send_code(REP_3_6, bl_tree); send_bits(count-3, 2); 768 769 } else if (count <= 10) { 770 send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3); 771 772 } else { 773 send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7); 774 } 775 count = 0; prevlen = curlen; 776 if (nextlen == 0) { 777 max_count = 138, min_count = 3; 778 } else if (curlen == nextlen) { 779 max_count = 6, min_count = 3; 780 } else { 781 max_count = 7, min_count = 4; 782 } 783 } 784} 785 786/* =========================================================================== 787 * Construct the Huffman tree for the bit lengths and return the index in 788 * bl_order of the last bit length code to send. 789 */ 790local int build_bl_tree() 791{ 792 int max_blindex; /* index of last bit length code of non zero freq */ 793 794 /* Determine the bit length frequencies for literal and distance trees */ 795 scan_tree((ct_data near *)dyn_ltree, l_desc.max_code); 796 scan_tree((ct_data near *)dyn_dtree, d_desc.max_code); 797 798 /* Build the bit length tree: */ 799 build_tree((tree_desc near *)(&bl_desc)); 800 /* opt_len now includes the length of the tree representations, except 801 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. 802 */ 803 804 /* Determine the number of bit length codes to send. The pkzip format 805 * requires that at least 4 bit length codes be sent. (appnote.txt says 806 * 3 but the actual value used is 4.) 807 */ 808 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { 809 if (bl_tree[bl_order[max_blindex]].Len != 0) break; 810 } 811 /* Update opt_len to include the bit length tree and counts */ 812 opt_len += 3*(max_blindex+1) + 5+5+4; 813 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, static_len)); 814 815 return max_blindex; 816} 817 818/* =========================================================================== 819 * Send the header for a block using dynamic Huffman trees: the counts, the 820 * lengths of the bit length codes, the literal tree and the distance tree. 821 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 822 */ 823local void send_all_trees(lcodes, dcodes, blcodes) 824 int lcodes, dcodes, blcodes; /* number of codes for each tree */ 825{ 826 int rank; /* index in bl_order */ 827 828 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); 829 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, 830 "too many codes"); 831 Tracev((stderr, "\nbl counts: ")); 832 send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */ 833 send_bits(dcodes-1, 5); 834 send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */ 835 for (rank = 0; rank < blcodes; rank++) { 836 Tracev((stderr, "\nbl code %2d ", bl_order[rank])); 837 send_bits(bl_tree[bl_order[rank]].Len, 3); 838 } 839 Tracev((stderr, "\nbl tree: sent %ld", bits_sent)); 840 841 send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */ 842 Tracev((stderr, "\nlit tree: sent %ld", bits_sent)); 843 844 send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */ 845 Tracev((stderr, "\ndist tree: sent %ld", bits_sent)); 846} 847 848/* =========================================================================== 849 * Determine the best encoding for the current block: dynamic trees, static 850 * trees or store, and output the encoded block to the zip file. This function 851 * returns the total compressed length for the file so far. 852 */ 853ulg flush_block(buf, stored_len, eof) 854 char *buf; /* input block, or NULL if too old */ 855 ulg stored_len; /* length of input block */ 856 int eof; /* true if this is the last block for a file */ 857{ 858 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 859 int max_blindex; /* index of last bit length code of non zero freq */ 860 861 flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */ 862 863 /* Check if the file is ascii or binary */ 864 if (*file_type == (ush)UNKNOWN) set_file_type(); 865 866 /* Construct the literal and distance trees */ 867 build_tree((tree_desc near *)(&l_desc)); 868 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len)); 869 870 build_tree((tree_desc near *)(&d_desc)); 871 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, static_len)); 872 /* At this point, opt_len and static_len are the total bit lengths of 873 * the compressed block data, excluding the tree representations. 874 */ 875 876 /* Build the bit length tree for the above two trees, and get the index 877 * in bl_order of the last bit length code to send. 878 */ 879 max_blindex = build_bl_tree(); 880 881 /* Determine the best encoding. Compute first the block length in bytes */ 882 opt_lenb = (opt_len+3+7)>>3; 883 static_lenb = (static_len+3+7)>>3; 884 input_len += stored_len; /* for debugging only */ 885 886 Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ", 887 opt_lenb, opt_len, static_lenb, static_len, stored_len, 888 last_lit, last_dist)); 889 890 if (static_lenb <= opt_lenb) opt_lenb = static_lenb; 891 892 /* If compression failed and this is the first and last block, 893 * and if the zip file can be seeked (to rewrite the local header), 894 * the whole file is transformed into a stored file: 895 */ 896#ifdef FORCE_METHOD 897 if (level == 1 && eof && compressed_len == 0L) { /* force stored file */ 898#else 899 if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) { 900#endif 901 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */ 902 if (buf == (char*)0) error ("block vanished"); 903 904 copy_block(buf, (unsigned)stored_len, 0); /* without header */ 905 compressed_len = stored_len << 3; 906 *file_method = STORED; 907 908#ifdef FORCE_METHOD 909 } else if (level == 2 && buf != (char*)0) { /* force stored block */ 910#else 911 } else if (stored_len+4 <= opt_lenb && buf != (char*)0) { 912 /* 4: two words for the lengths */ 913#endif 914 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. 915 * Otherwise we can't have processed more than WSIZE input bytes since 916 * the last block flush, because compression would have been 917 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to 918 * transform a block into a stored block. 919 */ 920 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */ 921 compressed_len = (compressed_len + 3 + 7) & ~7L; 922 compressed_len += (stored_len + 4) << 3; 923 924 copy_block(buf, (unsigned)stored_len, 1); /* with header */ 925 926#ifdef FORCE_METHOD 927 } else if (level == 3) { /* force static trees */ 928#else 929 } else if (static_lenb == opt_lenb) { 930#endif 931 send_bits((STATIC_TREES<<1)+eof, 3); 932 compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree); 933 compressed_len += 3 + static_len; 934 } else { 935 send_bits((DYN_TREES<<1)+eof, 3); 936 send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1); 937 compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree); 938 compressed_len += 3 + opt_len; 939 } 940 Assert (compressed_len == bits_sent, "bad compressed size"); 941 init_block(); 942 943 if (eof) { 944 Assert (input_len == isize, "bad input size"); 945 bi_windup(); 946 compressed_len += 7; /* align on byte boundary */ 947 } 948 Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3, 949 compressed_len-7*eof)); 950 951 return compressed_len >> 3; 952} 953 954/* =========================================================================== 955 * Save the match info and tally the frequency counts. Return true if 956 * the current block must be flushed. 957 */ 958int ct_tally (dist, lc) 959 int dist; /* distance of matched string */ 960 int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ 961{ 962 l_buf[last_lit++] = (uch)lc; 963 if (dist == 0) { 964 /* lc is the unmatched char */ 965 dyn_ltree[lc].Freq++; 966 } else { 967 /* Here, lc is the match length - MIN_MATCH */ 968 dist--; /* dist = match distance - 1 */ 969 Assert((ush)dist < (ush)MAX_DIST && 970 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && 971 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match"); 972 973 dyn_ltree[length_code[lc]+LITERALS+1].Freq++; 974 dyn_dtree[d_code(dist)].Freq++; 975 976 d_buf[last_dist++] = (ush)dist; 977 flags |= flag_bit; 978 } 979 flag_bit <<= 1; 980 981 /* Output the flags if they fill a byte: */ 982 if ((last_lit & 7) == 0) { 983 flag_buf[last_flags++] = flags; 984 flags = 0, flag_bit = 1; 985 } 986 /* Try to guess if it is profitable to stop the current block here */ 987 if (level > 2 && (last_lit & 0xfff) == 0) { 988 /* Compute an upper bound for the compressed length */ 989 ulg out_length = (ulg)last_lit*8L; 990 ulg in_length = (ulg)strstart-block_start; 991 int dcode; 992 for (dcode = 0; dcode < D_CODES; dcode++) { 993 out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]); 994 } 995 out_length >>= 3; 996 Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ", 997 last_lit, last_dist, in_length, out_length, 998 100L - out_length*100L/in_length)); 999 if (last_dist < last_lit/2 && out_length < in_length/2) return 1; 1000 } 1001 return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE); 1002 /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K 1003 * on 16 bit machines and because stored blocks are restricted to 1004 * 64K-1 bytes. 1005 */ 1006} 1007 1008/* =========================================================================== 1009 * Send the block data compressed using the given Huffman trees 1010 */ 1011local void compress_block(ltree, dtree) 1012 ct_data near *ltree; /* literal tree */ 1013 ct_data near *dtree; /* distance tree */ 1014{ 1015 unsigned dist; /* distance of matched string */ 1016 int lc; /* match length or unmatched char (if dist == 0) */ 1017 unsigned lx = 0; /* running index in l_buf */ 1018 unsigned dx = 0; /* running index in d_buf */ 1019 unsigned fx = 0; /* running index in flag_buf */ 1020 uch flag = 0; /* current flags */ 1021 unsigned code; /* the code to send */ 1022 int extra; /* number of extra bits to send */ 1023 1024 if (last_lit != 0) do { 1025 if ((lx & 7) == 0) flag = flag_buf[fx++]; 1026 lc = l_buf[lx++]; 1027 if ((flag & 1) == 0) { 1028 send_code(lc, ltree); /* send a literal byte */ 1029 Tracecv(isgraph(lc), (stderr," '%c' ", lc)); 1030 } else { 1031 /* Here, lc is the match length - MIN_MATCH */ 1032 code = length_code[lc]; 1033 send_code(code+LITERALS+1, ltree); /* send the length code */ 1034 extra = extra_lbits[code]; 1035 if (extra != 0) { 1036 lc -= base_length[code]; 1037 send_bits(lc, extra); /* send the extra length bits */ 1038 } 1039 dist = d_buf[dx++]; 1040 /* Here, dist is the match distance - 1 */ 1041 code = d_code(dist); 1042 Assert (code < D_CODES, "bad d_code"); 1043 1044 send_code(code, dtree); /* send the distance code */ 1045 extra = extra_dbits[code]; 1046 if (extra != 0) { 1047 dist -= base_dist[code]; 1048 send_bits(dist, extra); /* send the extra distance bits */ 1049 } 1050 } /* literal or match pair ? */ 1051 flag >>= 1; 1052 } while (lx < last_lit); 1053 1054 send_code(END_BLOCK, ltree); 1055} 1056 1057/* =========================================================================== 1058 * Set the file type to ASCII or BINARY, using a crude approximation: 1059 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. 1060 * IN assertion: the fields freq of dyn_ltree are set and the total of all 1061 * frequencies does not exceed 64K (to fit in an int on 16 bit machines). 1062 */ 1063local void set_file_type() 1064{ 1065 int n = 0; 1066 unsigned ascii_freq = 0; 1067 unsigned bin_freq = 0; 1068 while (n < 7) bin_freq += dyn_ltree[n++].Freq; 1069 while (n < 128) ascii_freq += dyn_ltree[n++].Freq; 1070 while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq; 1071 *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII; 1072 if (*file_type == BINARY && translate_eol) { 1073 warn("-l used on binary file", ""); 1074 } 1075} 1076