trees.c revision 17651
1129203Scognet/* trees.c -- output deflated data using Huffman coding 2129203Scognet * Copyright (C) 1995-1996 Jean-loup Gailly 3129203Scognet * For conditions of distribution and use, see copyright notice in zlib.h 4129203Scognet */ 5129203Scognet 6129203Scognet/* 7129203Scognet * ALGORITHM 8129203Scognet * 9129203Scognet * The "deflation" process uses several Huffman trees. The more 10129203Scognet * common source values are represented by shorter bit sequences. 11129203Scognet * 12129203Scognet * Each code tree is stored in a compressed form which is itself 13129203Scognet * a Huffman encoding of the lengths of all the code strings (in 14129203Scognet * ascending order by source values). The actual code strings are 15129203Scognet * reconstructed from the lengths in the inflate process, as described 16129203Scognet * in the deflate specification. 17129203Scognet * 18129203Scognet * REFERENCES 19129203Scognet * 20129203Scognet * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". 21129203Scognet * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc 22129203Scognet * 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/* $Id: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */ 33 34#include "deflate.h" 35 36#ifdef DEBUG 37# include <ctype.h> 38#endif 39 40/* =========================================================================== 41 * Constants 42 */ 43 44#define MAX_BL_BITS 7 45/* Bit length codes must not exceed MAX_BL_BITS bits */ 46 47#define END_BLOCK 256 48/* end of block literal code */ 49 50#define REP_3_6 16 51/* repeat previous bit length 3-6 times (2 bits of repeat count) */ 52 53#define REPZ_3_10 17 54/* repeat a zero length 3-10 times (3 bits of repeat count) */ 55 56#define REPZ_11_138 18 57/* repeat a zero length 11-138 times (7 bits of repeat count) */ 58 59local int extra_lbits[LENGTH_CODES] /* extra bits for each length code */ 60 = {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}; 61 62local int extra_dbits[D_CODES] /* extra bits for each distance code */ 63 = {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}; 64 65local int extra_blbits[BL_CODES]/* extra bits for each bit length code */ 66 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; 67 68local uch bl_order[BL_CODES] 69 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}; 70/* The lengths of the bit length codes are sent in order of decreasing 71 * probability, to avoid transmitting the lengths for unused bit length codes. 72 */ 73 74#define Buf_size (8 * 2*sizeof(char)) 75/* Number of bits used within bi_buf. (bi_buf might be implemented on 76 * more than 16 bits on some systems.) 77 */ 78 79/* =========================================================================== 80 * Local data. These are initialized only once. 81 */ 82 83local ct_data static_ltree[L_CODES+2]; 84/* The static literal tree. Since the bit lengths are imposed, there is no 85 * need for the L_CODES extra codes used during heap construction. However 86 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init 87 * below). 88 */ 89 90local ct_data static_dtree[D_CODES]; 91/* The static distance tree. (Actually a trivial tree since all codes use 92 * 5 bits.) 93 */ 94 95local uch dist_code[512]; 96/* distance codes. The first 256 values correspond to the distances 97 * 3 .. 258, the last 256 values correspond to the top 8 bits of 98 * the 15 bit distances. 99 */ 100 101local uch length_code[MAX_MATCH-MIN_MATCH+1]; 102/* length code for each normalized match length (0 == MIN_MATCH) */ 103 104local int base_length[LENGTH_CODES]; 105/* First normalized length for each code (0 = MIN_MATCH) */ 106 107local int base_dist[D_CODES]; 108/* First normalized distance for each code (0 = distance of 1) */ 109 110struct static_tree_desc_s { 111 ct_data *static_tree; /* static tree or NULL */ 112 intf *extra_bits; /* extra bits for each code or NULL */ 113 int extra_base; /* base index for extra_bits */ 114 int elems; /* max number of elements in the tree */ 115 int max_length; /* max bit length for the codes */ 116}; 117 118local static_tree_desc static_l_desc = 119{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; 120 121local static_tree_desc static_d_desc = 122{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS}; 123 124local static_tree_desc static_bl_desc = 125{(ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS}; 126 127/* =========================================================================== 128 * Local (static) routines in this file. 129 */ 130 131local void tr_static_init OF((void)); 132local void init_block OF((deflate_state *s)); 133local void pqdownheap OF((deflate_state *s, ct_data *tree, int k)); 134local void gen_bitlen OF((deflate_state *s, tree_desc *desc)); 135local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count)); 136local void build_tree OF((deflate_state *s, tree_desc *desc)); 137local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code)); 138local void send_tree OF((deflate_state *s, ct_data *tree, int max_code)); 139local int build_bl_tree OF((deflate_state *s)); 140local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes, 141 int blcodes)); 142local void compress_block OF((deflate_state *s, ct_data *ltree, 143 ct_data *dtree)); 144local void set_data_type OF((deflate_state *s)); 145local unsigned bi_reverse OF((unsigned value, int length)); 146local void bi_windup OF((deflate_state *s)); 147local void bi_flush OF((deflate_state *s)); 148local void copy_block OF((deflate_state *s, charf *buf, unsigned len, 149 int header)); 150 151#ifndef DEBUG 152# define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len) 153 /* Send a code of the given tree. c and tree must not have side effects */ 154 155#else /* DEBUG */ 156# define send_code(s, c, tree) \ 157 { if (verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \ 158 send_bits(s, tree[c].Code, tree[c].Len); } 159#endif 160 161#define d_code(dist) \ 162 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)]) 163/* Mapping from a distance to a distance code. dist is the distance - 1 and 164 * must not have side effects. dist_code[256] and dist_code[257] are never 165 * used. 166 */ 167 168/* =========================================================================== 169 * Output a short LSB first on the stream. 170 * IN assertion: there is enough room in pendingBuf. 171 */ 172#define put_short(s, w) { \ 173 put_byte(s, (uch)((w) & 0xff)); \ 174 put_byte(s, (uch)((ush)(w) >> 8)); \ 175} 176 177/* =========================================================================== 178 * Send a value on a given number of bits. 179 * IN assertion: length <= 16 and value fits in length bits. 180 */ 181#ifdef DEBUG 182local void send_bits OF((deflate_state *s, int value, int length)); 183 184local void send_bits(s, value, length) 185 deflate_state *s; 186 int value; /* value to send */ 187 int length; /* number of bits */ 188{ 189 Tracevv((stderr," l %2d v %4x ", length, value)); 190 Assert(length > 0 && length <= 15, "invalid length"); 191 s->bits_sent += (ulg)length; 192 193 /* If not enough room in bi_buf, use (valid) bits from bi_buf and 194 * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid)) 195 * unused bits in value. 196 */ 197 if (s->bi_valid > (int)Buf_size - length) { 198 s->bi_buf |= (value << s->bi_valid); 199 put_short(s, s->bi_buf); 200 s->bi_buf = (ush)value >> (Buf_size - s->bi_valid); 201 s->bi_valid += length - Buf_size; 202 } else { 203 s->bi_buf |= value << s->bi_valid; 204 s->bi_valid += length; 205 } 206} 207#else /* !DEBUG */ 208 209#define send_bits(s, value, length) \ 210{ int len = length;\ 211 if (s->bi_valid > (int)Buf_size - len) {\ 212 int val = value;\ 213 s->bi_buf |= (val << s->bi_valid);\ 214 put_short(s, s->bi_buf);\ 215 s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\ 216 s->bi_valid += len - Buf_size;\ 217 } else {\ 218 s->bi_buf |= (value) << s->bi_valid;\ 219 s->bi_valid += len;\ 220 }\ 221} 222#endif /* DEBUG */ 223 224 225#define MAX(a,b) (a >= b ? a : b) 226/* the arguments must not have side effects */ 227 228/* =========================================================================== 229 * Initialize the various 'constant' tables. In a multi-threaded environment, 230 * this function may be called by two threads concurrently, but this is 231 * harmless since both invocations do exactly the same thing. 232 */ 233local void tr_static_init() 234{ 235 static int static_init_done = 0; 236 int n; /* iterates over tree elements */ 237 int bits; /* bit counter */ 238 int length; /* length value */ 239 int code; /* code value */ 240 int dist; /* distance index */ 241 ush bl_count[MAX_BITS+1]; 242 /* number of codes at each bit length for an optimal tree */ 243 244 if (static_init_done) return; 245 246 /* Initialize the mapping length (0..255) -> length code (0..28) */ 247 length = 0; 248 for (code = 0; code < LENGTH_CODES-1; code++) { 249 base_length[code] = length; 250 for (n = 0; n < (1<<extra_lbits[code]); n++) { 251 length_code[length++] = (uch)code; 252 } 253 } 254 Assert (length == 256, "tr_static_init: length != 256"); 255 /* Note that the length 255 (match length 258) can be represented 256 * in two different ways: code 284 + 5 bits or code 285, so we 257 * overwrite length_code[255] to use the best encoding: 258 */ 259 length_code[length-1] = (uch)code; 260 261 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ 262 dist = 0; 263 for (code = 0 ; code < 16; code++) { 264 base_dist[code] = dist; 265 for (n = 0; n < (1<<extra_dbits[code]); n++) { 266 dist_code[dist++] = (uch)code; 267 } 268 } 269 Assert (dist == 256, "tr_static_init: dist != 256"); 270 dist >>= 7; /* from now on, all distances are divided by 128 */ 271 for ( ; code < D_CODES; code++) { 272 base_dist[code] = dist << 7; 273 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { 274 dist_code[256 + dist++] = (uch)code; 275 } 276 } 277 Assert (dist == 256, "tr_static_init: 256+dist != 512"); 278 279 /* Construct the codes of the static literal tree */ 280 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; 281 n = 0; 282 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; 283 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; 284 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; 285 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; 286 /* Codes 286 and 287 do not exist, but we must include them in the 287 * tree construction to get a canonical Huffman tree (longest code 288 * all ones) 289 */ 290 gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count); 291 292 /* The static distance tree is trivial: */ 293 for (n = 0; n < D_CODES; n++) { 294 static_dtree[n].Len = 5; 295 static_dtree[n].Code = bi_reverse((unsigned)n, 5); 296 } 297 static_init_done = 1; 298} 299 300/* =========================================================================== 301 * Initialize the tree data structures for a new zlib stream. 302 */ 303void _tr_init(s) 304 deflate_state *s; 305{ 306 tr_static_init(); 307 308 s->compressed_len = 0L; 309 310 s->l_desc.dyn_tree = s->dyn_ltree; 311 s->l_desc.stat_desc = &static_l_desc; 312 313 s->d_desc.dyn_tree = s->dyn_dtree; 314 s->d_desc.stat_desc = &static_d_desc; 315 316 s->bl_desc.dyn_tree = s->bl_tree; 317 s->bl_desc.stat_desc = &static_bl_desc; 318 319 s->bi_buf = 0; 320 s->bi_valid = 0; 321 s->last_eob_len = 8; /* enough lookahead for inflate */ 322#ifdef DEBUG 323 s->bits_sent = 0L; 324#endif 325 326 /* Initialize the first block of the first file: */ 327 init_block(s); 328} 329 330/* =========================================================================== 331 * Initialize a new block. 332 */ 333local void init_block(s) 334 deflate_state *s; 335{ 336 int n; /* iterates over tree elements */ 337 338 /* Initialize the trees. */ 339 for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; 340 for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; 341 for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; 342 343 s->dyn_ltree[END_BLOCK].Freq = 1; 344 s->opt_len = s->static_len = 0L; 345 s->last_lit = s->matches = 0; 346} 347 348#define SMALLEST 1 349/* Index within the heap array of least frequent node in the Huffman tree */ 350 351 352/* =========================================================================== 353 * Remove the smallest element from the heap and recreate the heap with 354 * one less element. Updates heap and heap_len. 355 */ 356#define pqremove(s, tree, top) \ 357{\ 358 top = s->heap[SMALLEST]; \ 359 s->heap[SMALLEST] = s->heap[s->heap_len--]; \ 360 pqdownheap(s, tree, SMALLEST); \ 361} 362 363/* =========================================================================== 364 * Compares to subtrees, using the tree depth as tie breaker when 365 * the subtrees have equal frequency. This minimizes the worst case length. 366 */ 367#define smaller(tree, n, m, depth) \ 368 (tree[n].Freq < tree[m].Freq || \ 369 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 370 371/* =========================================================================== 372 * Restore the heap property by moving down the tree starting at node k, 373 * exchanging a node with the smallest of its two sons if necessary, stopping 374 * when the heap property is re-established (each father smaller than its 375 * two sons). 376 */ 377local void pqdownheap(s, tree, k) 378 deflate_state *s; 379 ct_data *tree; /* the tree to restore */ 380 int k; /* node to move down */ 381{ 382 int v = s->heap[k]; 383 int j = k << 1; /* left son of k */ 384 while (j <= s->heap_len) { 385 /* Set j to the smallest of the two sons: */ 386 if (j < s->heap_len && 387 smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { 388 j++; 389 } 390 /* Exit if v is smaller than both sons */ 391 if (smaller(tree, v, s->heap[j], s->depth)) break; 392 393 /* Exchange v with the smallest son */ 394 s->heap[k] = s->heap[j]; k = j; 395 396 /* And continue down the tree, setting j to the left son of k */ 397 j <<= 1; 398 } 399 s->heap[k] = v; 400} 401 402/* =========================================================================== 403 * Compute the optimal bit lengths for a tree and update the total bit length 404 * for the current block. 405 * IN assertion: the fields freq and dad are set, heap[heap_max] and 406 * above are the tree nodes sorted by increasing frequency. 407 * OUT assertions: the field len is set to the optimal bit length, the 408 * array bl_count contains the frequencies for each bit length. 409 * The length opt_len is updated; static_len is also updated if stree is 410 * not null. 411 */ 412local void gen_bitlen(s, desc) 413 deflate_state *s; 414 tree_desc *desc; /* the tree descriptor */ 415{ 416 ct_data *tree = desc->dyn_tree; 417 int max_code = desc->max_code; 418 ct_data *stree = desc->stat_desc->static_tree; 419 intf *extra = desc->stat_desc->extra_bits; 420 int base = desc->stat_desc->extra_base; 421 int max_length = desc->stat_desc->max_length; 422 int h; /* heap index */ 423 int n, m; /* iterate over the tree elements */ 424 int bits; /* bit length */ 425 int xbits; /* extra bits */ 426 ush f; /* frequency */ 427 int overflow = 0; /* number of elements with bit length too large */ 428 429 for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; 430 431 /* In a first pass, compute the optimal bit lengths (which may 432 * overflow in the case of the bit length tree). 433 */ 434 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ 435 436 for (h = s->heap_max+1; h < HEAP_SIZE; h++) { 437 n = s->heap[h]; 438 bits = tree[tree[n].Dad].Len + 1; 439 if (bits > max_length) bits = max_length, overflow++; 440 tree[n].Len = (ush)bits; 441 /* We overwrite tree[n].Dad which is no longer needed */ 442 443 if (n > max_code) continue; /* not a leaf node */ 444 445 s->bl_count[bits]++; 446 xbits = 0; 447 if (n >= base) xbits = extra[n-base]; 448 f = tree[n].Freq; 449 s->opt_len += (ulg)f * (bits + xbits); 450 if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); 451 } 452 if (overflow == 0) return; 453 454 Trace((stderr,"\nbit length overflow\n")); 455 /* This happens for example on obj2 and pic of the Calgary corpus */ 456 457 /* Find the first bit length which could increase: */ 458 do { 459 bits = max_length-1; 460 while (s->bl_count[bits] == 0) bits--; 461 s->bl_count[bits]--; /* move one leaf down the tree */ 462 s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ 463 s->bl_count[max_length]--; 464 /* The brother of the overflow item also moves one step up, 465 * but this does not affect bl_count[max_length] 466 */ 467 overflow -= 2; 468 } while (overflow > 0); 469 470 /* Now recompute all bit lengths, scanning in increasing frequency. 471 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all 472 * lengths instead of fixing only the wrong ones. This idea is taken 473 * from 'ar' written by Haruhiko Okumura.) 474 */ 475 for (bits = max_length; bits != 0; bits--) { 476 n = s->bl_count[bits]; 477 while (n != 0) { 478 m = s->heap[--h]; 479 if (m > max_code) continue; 480 if (tree[m].Len != (unsigned) bits) { 481 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); 482 s->opt_len += ((long)bits - (long)tree[m].Len) 483 *(long)tree[m].Freq; 484 tree[m].Len = (ush)bits; 485 } 486 n--; 487 } 488 } 489} 490 491/* =========================================================================== 492 * Generate the codes for a given tree and bit counts (which need not be 493 * optimal). 494 * IN assertion: the array bl_count contains the bit length statistics for 495 * the given tree and the field len is set for all tree elements. 496 * OUT assertion: the field code is set for all tree elements of non 497 * zero code length. 498 */ 499local void gen_codes (tree, max_code, bl_count) 500 ct_data *tree; /* the tree to decorate */ 501 int max_code; /* largest code with non zero frequency */ 502 ushf *bl_count; /* number of codes at each bit length */ 503{ 504 ush next_code[MAX_BITS+1]; /* next code value for each bit length */ 505 ush code = 0; /* running code value */ 506 int bits; /* bit index */ 507 int n; /* code index */ 508 509 /* The distribution counts are first used to generate the code values 510 * without bit reversal. 511 */ 512 for (bits = 1; bits <= MAX_BITS; bits++) { 513 next_code[bits] = code = (code + bl_count[bits-1]) << 1; 514 } 515 /* Check that the bit counts in bl_count are consistent. The last code 516 * must be all ones. 517 */ 518 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, 519 "inconsistent bit counts"); 520 Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); 521 522 for (n = 0; n <= max_code; n++) { 523 int len = tree[n].Len; 524 if (len == 0) continue; 525 /* Now reverse the bits */ 526 tree[n].Code = bi_reverse(next_code[len]++, len); 527 528 Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", 529 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); 530 } 531} 532 533/* =========================================================================== 534 * Construct one Huffman tree and assigns the code bit strings and lengths. 535 * Update the total bit length for the current block. 536 * IN assertion: the field freq is set for all tree elements. 537 * OUT assertions: the fields len and code are set to the optimal bit length 538 * and corresponding code. The length opt_len is updated; static_len is 539 * also updated if stree is not null. The field max_code is set. 540 */ 541local void build_tree(s, desc) 542 deflate_state *s; 543 tree_desc *desc; /* the tree descriptor */ 544{ 545 ct_data *tree = desc->dyn_tree; 546 ct_data *stree = desc->stat_desc->static_tree; 547 int elems = desc->stat_desc->elems; 548 int n, m; /* iterate over heap elements */ 549 int max_code = -1; /* largest code with non zero frequency */ 550 int node; /* new node being created */ 551 552 /* Construct the initial heap, with least frequent element in 553 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. 554 * heap[0] is not used. 555 */ 556 s->heap_len = 0, s->heap_max = HEAP_SIZE; 557 558 for (n = 0; n < elems; n++) { 559 if (tree[n].Freq != 0) { 560 s->heap[++(s->heap_len)] = max_code = n; 561 s->depth[n] = 0; 562 } else { 563 tree[n].Len = 0; 564 } 565 } 566 567 /* The pkzip format requires that at least one distance code exists, 568 * and that at least one bit should be sent even if there is only one 569 * possible code. So to avoid special checks later on we force at least 570 * two codes of non zero frequency. 571 */ 572 while (s->heap_len < 2) { 573 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); 574 tree[node].Freq = 1; 575 s->depth[node] = 0; 576 s->opt_len--; if (stree) s->static_len -= stree[node].Len; 577 /* node is 0 or 1 so it does not have extra bits */ 578 } 579 desc->max_code = max_code; 580 581 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, 582 * establish sub-heaps of increasing lengths: 583 */ 584 for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); 585 586 /* Construct the Huffman tree by repeatedly combining the least two 587 * frequent nodes. 588 */ 589 node = elems; /* next internal node of the tree */ 590 do { 591 pqremove(s, tree, n); /* n = node of least frequency */ 592 m = s->heap[SMALLEST]; /* m = node of next least frequency */ 593 594 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ 595 s->heap[--(s->heap_max)] = m; 596 597 /* Create a new node father of n and m */ 598 tree[node].Freq = tree[n].Freq + tree[m].Freq; 599 s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1); 600 tree[n].Dad = tree[m].Dad = (ush)node; 601#ifdef DUMP_BL_TREE 602 if (tree == s->bl_tree) { 603 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", 604 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); 605 } 606#endif 607 /* and insert the new node in the heap */ 608 s->heap[SMALLEST] = node++; 609 pqdownheap(s, tree, SMALLEST); 610 611 } while (s->heap_len >= 2); 612 613 s->heap[--(s->heap_max)] = s->heap[SMALLEST]; 614 615 /* At this point, the fields freq and dad are set. We can now 616 * generate the bit lengths. 617 */ 618 gen_bitlen(s, (tree_desc *)desc); 619 620 /* The field len is now set, we can generate the bit codes */ 621 gen_codes ((ct_data *)tree, max_code, s->bl_count); 622} 623 624/* =========================================================================== 625 * Scan a literal or distance tree to determine the frequencies of the codes 626 * in the bit length tree. 627 */ 628local void scan_tree (s, tree, max_code) 629 deflate_state *s; 630 ct_data *tree; /* the tree to be scanned */ 631 int max_code; /* and its largest code of non zero frequency */ 632{ 633 int n; /* iterates over all tree elements */ 634 int prevlen = -1; /* last emitted length */ 635 int curlen; /* length of current code */ 636 int nextlen = tree[0].Len; /* length of next code */ 637 int count = 0; /* repeat count of the current code */ 638 int max_count = 7; /* max repeat count */ 639 int min_count = 4; /* min repeat count */ 640 641 if (nextlen == 0) max_count = 138, min_count = 3; 642 tree[max_code+1].Len = (ush)0xffff; /* guard */ 643 644 for (n = 0; n <= max_code; n++) { 645 curlen = nextlen; nextlen = tree[n+1].Len; 646 if (++count < max_count && curlen == nextlen) { 647 continue; 648 } else if (count < min_count) { 649 s->bl_tree[curlen].Freq += count; 650 } else if (curlen != 0) { 651 if (curlen != prevlen) s->bl_tree[curlen].Freq++; 652 s->bl_tree[REP_3_6].Freq++; 653 } else if (count <= 10) { 654 s->bl_tree[REPZ_3_10].Freq++; 655 } else { 656 s->bl_tree[REPZ_11_138].Freq++; 657 } 658 count = 0; prevlen = curlen; 659 if (nextlen == 0) { 660 max_count = 138, min_count = 3; 661 } else if (curlen == nextlen) { 662 max_count = 6, min_count = 3; 663 } else { 664 max_count = 7, min_count = 4; 665 } 666 } 667} 668 669/* =========================================================================== 670 * Send a literal or distance tree in compressed form, using the codes in 671 * bl_tree. 672 */ 673local void send_tree (s, tree, max_code) 674 deflate_state *s; 675 ct_data *tree; /* the tree to be scanned */ 676 int max_code; /* and its largest code of non zero frequency */ 677{ 678 int n; /* iterates over all tree elements */ 679 int prevlen = -1; /* last emitted length */ 680 int curlen; /* length of current code */ 681 int nextlen = tree[0].Len; /* length of next code */ 682 int count = 0; /* repeat count of the current code */ 683 int max_count = 7; /* max repeat count */ 684 int min_count = 4; /* min repeat count */ 685 686 /* tree[max_code+1].Len = -1; */ /* guard already set */ 687 if (nextlen == 0) max_count = 138, min_count = 3; 688 689 for (n = 0; n <= max_code; n++) { 690 curlen = nextlen; nextlen = tree[n+1].Len; 691 if (++count < max_count && curlen == nextlen) { 692 continue; 693 } else if (count < min_count) { 694 do { send_code(s, curlen, s->bl_tree); } while (--count != 0); 695 696 } else if (curlen != 0) { 697 if (curlen != prevlen) { 698 send_code(s, curlen, s->bl_tree); count--; 699 } 700 Assert(count >= 3 && count <= 6, " 3_6?"); 701 send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); 702 703 } else if (count <= 10) { 704 send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); 705 706 } else { 707 send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); 708 } 709 count = 0; prevlen = curlen; 710 if (nextlen == 0) { 711 max_count = 138, min_count = 3; 712 } else if (curlen == nextlen) { 713 max_count = 6, min_count = 3; 714 } else { 715 max_count = 7, min_count = 4; 716 } 717 } 718} 719 720/* =========================================================================== 721 * Construct the Huffman tree for the bit lengths and return the index in 722 * bl_order of the last bit length code to send. 723 */ 724local int build_bl_tree(s) 725 deflate_state *s; 726{ 727 int max_blindex; /* index of last bit length code of non zero freq */ 728 729 /* Determine the bit length frequencies for literal and distance trees */ 730 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); 731 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); 732 733 /* Build the bit length tree: */ 734 build_tree(s, (tree_desc *)(&(s->bl_desc))); 735 /* opt_len now includes the length of the tree representations, except 736 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. 737 */ 738 739 /* Determine the number of bit length codes to send. The pkzip format 740 * requires that at least 4 bit length codes be sent. (appnote.txt says 741 * 3 but the actual value used is 4.) 742 */ 743 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { 744 if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; 745 } 746 /* Update opt_len to include the bit length tree and counts */ 747 s->opt_len += 3*(max_blindex+1) + 5+5+4; 748 Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", 749 s->opt_len, s->static_len)); 750 751 return max_blindex; 752} 753 754/* =========================================================================== 755 * Send the header for a block using dynamic Huffman trees: the counts, the 756 * lengths of the bit length codes, the literal tree and the distance tree. 757 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. 758 */ 759local void send_all_trees(s, lcodes, dcodes, blcodes) 760 deflate_state *s; 761 int lcodes, dcodes, blcodes; /* number of codes for each tree */ 762{ 763 int rank; /* index in bl_order */ 764 765 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); 766 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, 767 "too many codes"); 768 Tracev((stderr, "\nbl counts: ")); 769 send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */ 770 send_bits(s, dcodes-1, 5); 771 send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */ 772 for (rank = 0; rank < blcodes; rank++) { 773 Tracev((stderr, "\nbl code %2d ", bl_order[rank])); 774 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); 775 } 776 Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); 777 778 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ 779 Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); 780 781 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ 782 Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); 783} 784 785/* =========================================================================== 786 * Send a stored block 787 */ 788void _tr_stored_block(s, buf, stored_len, eof) 789 deflate_state *s; 790 charf *buf; /* input block */ 791 ulg stored_len; /* length of input block */ 792 int eof; /* true if this is the last block for a file */ 793{ 794 send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */ 795 s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; 796 s->compressed_len += (stored_len + 4) << 3; 797 798 copy_block(s, buf, (unsigned)stored_len, 1); /* with header */ 799} 800 801/* =========================================================================== 802 * Send one empty static block to give enough lookahead for inflate. 803 * This takes 10 bits, of which 7 may remain in the bit buffer. 804 * The current inflate code requires 9 bits of lookahead. If the 805 * last two codes for the previous block (real code plus EOB) were coded 806 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode 807 * the last real code. In this case we send two empty static blocks instead 808 * of one. (There are no problems if the previous block is stored or fixed.) 809 * To simplify the code, we assume the worst case of last real code encoded 810 * on one bit only. 811 */ 812void _tr_align(s) 813 deflate_state *s; 814{ 815 send_bits(s, STATIC_TREES<<1, 3); 816 send_code(s, END_BLOCK, static_ltree); 817 s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ 818 bi_flush(s); 819 /* Of the 10 bits for the empty block, we have already sent 820 * (10 - bi_valid) bits. The lookahead for the last real code (before 821 * the EOB of the previous block) was thus at least one plus the length 822 * of the EOB plus what we have just sent of the empty static block. 823 */ 824 if (1 + s->last_eob_len + 10 - s->bi_valid < 9) { 825 send_bits(s, STATIC_TREES<<1, 3); 826 send_code(s, END_BLOCK, static_ltree); 827 s->compressed_len += 10L; 828 bi_flush(s); 829 } 830 s->last_eob_len = 7; 831} 832 833/* =========================================================================== 834 * Determine the best encoding for the current block: dynamic trees, static 835 * trees or store, and output the encoded block to the zip file. This function 836 * returns the total compressed length for the file so far. 837 */ 838ulg _tr_flush_block(s, buf, stored_len, eof) 839 deflate_state *s; 840 charf *buf; /* input block, or NULL if too old */ 841 ulg stored_len; /* length of input block */ 842 int eof; /* true if this is the last block for a file */ 843{ 844 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ 845 int max_blindex = 0; /* index of last bit length code of non zero freq */ 846 847 /* Build the Huffman trees unless a stored block is forced */ 848 if (s->level > 0) { 849 850 /* Check if the file is ascii or binary */ 851 if (s->data_type == Z_UNKNOWN) set_data_type(s); 852 853 /* Construct the literal and distance trees */ 854 build_tree(s, (tree_desc *)(&(s->l_desc))); 855 Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len, 856 s->static_len)); 857 858 build_tree(s, (tree_desc *)(&(s->d_desc))); 859 Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len, 860 s->static_len)); 861 /* At this point, opt_len and static_len are the total bit lengths of 862 * the compressed block data, excluding the tree representations. 863 */ 864 865 /* Build the bit length tree for the above two trees, and get the index 866 * in bl_order of the last bit length code to send. 867 */ 868 max_blindex = build_bl_tree(s); 869 870 /* Determine the best encoding. Compute first the block length in bytes*/ 871 opt_lenb = (s->opt_len+3+7)>>3; 872 static_lenb = (s->static_len+3+7)>>3; 873 874 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", 875 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, 876 s->last_lit)); 877 878 if (static_lenb <= opt_lenb) opt_lenb = static_lenb; 879 880 } else { 881 Assert(buf != (char*)0, "lost buf"); 882 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */ 883 } 884 885 /* If compression failed and this is the first and last block, 886 * and if the .zip file can be seeked (to rewrite the local header), 887 * the whole file is transformed into a stored file: 888 */ 889#ifdef STORED_FILE_OK 890# ifdef FORCE_STORED_FILE 891 if (eof && s->compressed_len == 0L) { /* force stored file */ 892# else 893 if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) { 894# endif 895 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */ 896 if (buf == (charf*)0) error ("block vanished"); 897 898 copy_block(buf, (unsigned)stored_len, 0); /* without header */ 899 s->compressed_len = stored_len << 3; 900 s->method = STORED; 901 } else 902#endif /* STORED_FILE_OK */ 903 904#ifdef FORCE_STORED 905 if (buf != (char*)0) { /* force stored block */ 906#else 907 if (stored_len+4 <= opt_lenb && buf != (char*)0) { 908 /* 4: two words for the lengths */ 909#endif 910 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. 911 * Otherwise we can't have processed more than WSIZE input bytes since 912 * the last block flush, because compression would have been 913 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to 914 * transform a block into a stored block. 915 */ 916 _tr_stored_block(s, buf, stored_len, eof); 917 918#ifdef FORCE_STATIC 919 } else if (static_lenb >= 0) { /* force static trees */ 920#else 921 } else if (static_lenb == opt_lenb) { 922#endif 923 send_bits(s, (STATIC_TREES<<1)+eof, 3); 924 compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree); 925 s->compressed_len += 3 + s->static_len; 926 } else { 927 send_bits(s, (DYN_TREES<<1)+eof, 3); 928 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1, 929 max_blindex+1); 930 compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree); 931 s->compressed_len += 3 + s->opt_len; 932 } 933 Assert (s->compressed_len == s->bits_sent, "bad compressed size"); 934 init_block(s); 935 936 if (eof) { 937 bi_windup(s); 938 s->compressed_len += 7; /* align on byte boundary */ 939 } 940 Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3, 941 s->compressed_len-7*eof)); 942 943 return s->compressed_len >> 3; 944} 945 946/* =========================================================================== 947 * Save the match info and tally the frequency counts. Return true if 948 * the current block must be flushed. 949 */ 950int _tr_tally (s, dist, lc) 951 deflate_state *s; 952 unsigned dist; /* distance of matched string */ 953 unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ 954{ 955 s->d_buf[s->last_lit] = (ush)dist; 956 s->l_buf[s->last_lit++] = (uch)lc; 957 if (dist == 0) { 958 /* lc is the unmatched char */ 959 s->dyn_ltree[lc].Freq++; 960 } else { 961 s->matches++; 962 /* Here, lc is the match length - MIN_MATCH */ 963 dist--; /* dist = match distance - 1 */ 964 Assert((ush)dist < (ush)MAX_DIST(s) && 965 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && 966 (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match"); 967 968 s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++; 969 s->dyn_dtree[d_code(dist)].Freq++; 970 } 971 972 /* Try to guess if it is profitable to stop the current block here */ 973 if (s->level > 2 && (s->last_lit & 0xfff) == 0) { 974 /* Compute an upper bound for the compressed length */ 975 ulg out_length = (ulg)s->last_lit*8L; 976 ulg in_length = (ulg)((long)s->strstart - s->block_start); 977 int dcode; 978 for (dcode = 0; dcode < D_CODES; dcode++) { 979 out_length += (ulg)s->dyn_dtree[dcode].Freq * 980 (5L+extra_dbits[dcode]); 981 } 982 out_length >>= 3; 983 Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", 984 s->last_lit, in_length, out_length, 985 100L - out_length*100L/in_length)); 986 if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1; 987 } 988 return (s->last_lit == s->lit_bufsize-1); 989 /* We avoid equality with lit_bufsize because of wraparound at 64K 990 * on 16 bit machines and because stored blocks are restricted to 991 * 64K-1 bytes. 992 */ 993} 994 995/* =========================================================================== 996 * Send the block data compressed using the given Huffman trees 997 */ 998local void compress_block(s, ltree, dtree) 999 deflate_state *s; 1000 ct_data *ltree; /* literal tree */ 1001 ct_data *dtree; /* distance tree */ 1002{ 1003 unsigned dist; /* distance of matched string */ 1004 int lc; /* match length or unmatched char (if dist == 0) */ 1005 unsigned lx = 0; /* running index in l_buf */ 1006 unsigned code; /* the code to send */ 1007 int extra; /* number of extra bits to send */ 1008 1009 if (s->last_lit != 0) do { 1010 dist = s->d_buf[lx]; 1011 lc = s->l_buf[lx++]; 1012 if (dist == 0) { 1013 send_code(s, lc, ltree); /* send a literal byte */ 1014 Tracecv(isgraph(lc), (stderr," '%c' ", lc)); 1015 } else { 1016 /* Here, lc is the match length - MIN_MATCH */ 1017 code = length_code[lc]; 1018 send_code(s, code+LITERALS+1, ltree); /* send the length code */ 1019 extra = extra_lbits[code]; 1020 if (extra != 0) { 1021 lc -= base_length[code]; 1022 send_bits(s, lc, extra); /* send the extra length bits */ 1023 } 1024 dist--; /* dist is now the match distance - 1 */ 1025 code = d_code(dist); 1026 Assert (code < D_CODES, "bad d_code"); 1027 1028 send_code(s, code, dtree); /* send the distance code */ 1029 extra = extra_dbits[code]; 1030 if (extra != 0) { 1031 dist -= base_dist[code]; 1032 send_bits(s, dist, extra); /* send the extra distance bits */ 1033 } 1034 } /* literal or match pair ? */ 1035 1036 /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */ 1037 Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow"); 1038 1039 } while (lx < s->last_lit); 1040 1041 send_code(s, END_BLOCK, ltree); 1042 s->last_eob_len = ltree[END_BLOCK].Len; 1043} 1044 1045/* =========================================================================== 1046 * Set the data type to ASCII or BINARY, using a crude approximation: 1047 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. 1048 * IN assertion: the fields freq of dyn_ltree are set and the total of all 1049 * frequencies does not exceed 64K (to fit in an int on 16 bit machines). 1050 */ 1051local void set_data_type(s) 1052 deflate_state *s; 1053{ 1054 int n = 0; 1055 unsigned ascii_freq = 0; 1056 unsigned bin_freq = 0; 1057 while (n < 7) bin_freq += s->dyn_ltree[n++].Freq; 1058 while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq; 1059 while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq; 1060 s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII); 1061} 1062 1063/* =========================================================================== 1064 * Reverse the first len bits of a code, using straightforward code (a faster 1065 * method would use a table) 1066 * IN assertion: 1 <= len <= 15 1067 */ 1068local unsigned bi_reverse(code, len) 1069 unsigned code; /* the value to invert */ 1070 int len; /* its bit length */ 1071{ 1072 register unsigned res = 0; 1073 do { 1074 res |= code & 1; 1075 code >>= 1, res <<= 1; 1076 } while (--len > 0); 1077 return res >> 1; 1078} 1079 1080/* =========================================================================== 1081 * Flush the bit buffer, keeping at most 7 bits in it. 1082 */ 1083local void bi_flush(s) 1084 deflate_state *s; 1085{ 1086 if (s->bi_valid == 16) { 1087 put_short(s, s->bi_buf); 1088 s->bi_buf = 0; 1089 s->bi_valid = 0; 1090 } else if (s->bi_valid >= 8) { 1091 put_byte(s, (Byte)s->bi_buf); 1092 s->bi_buf >>= 8; 1093 s->bi_valid -= 8; 1094 } 1095} 1096 1097/* =========================================================================== 1098 * Flush the bit buffer and align the output on a byte boundary 1099 */ 1100local void bi_windup(s) 1101 deflate_state *s; 1102{ 1103 if (s->bi_valid > 8) { 1104 put_short(s, s->bi_buf); 1105 } else if (s->bi_valid > 0) { 1106 put_byte(s, (Byte)s->bi_buf); 1107 } 1108 s->bi_buf = 0; 1109 s->bi_valid = 0; 1110#ifdef DEBUG 1111 s->bits_sent = (s->bits_sent+7) & ~7; 1112#endif 1113} 1114 1115/* =========================================================================== 1116 * Copy a stored block, storing first the length and its 1117 * one's complement if requested. 1118 */ 1119local void copy_block(s, buf, len, header) 1120 deflate_state *s; 1121 charf *buf; /* the input data */ 1122 unsigned len; /* its length */ 1123 int header; /* true if block header must be written */ 1124{ 1125 bi_windup(s); /* align on byte boundary */ 1126 s->last_eob_len = 8; /* enough lookahead for inflate */ 1127 1128 if (header) { 1129 put_short(s, (ush)len); 1130 put_short(s, (ush)~len); 1131#ifdef DEBUG 1132 s->bits_sent += 2*16; 1133#endif 1134 } 1135#ifdef DEBUG 1136 s->bits_sent += (ulg)len<<3; 1137#endif 1138 while (len--) { 1139 put_byte(s, *buf++); 1140 } 1141} 1142