Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
branch: master
Fetching contributors…

Octocat-spinner-32-eaf2f5

Cannot retrieve contributors at this time

file 1114 lines (977 sloc) 40.51 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
/* +++ trees.c */
/* trees.c -- output deflated data using Huffman coding
* Copyright (C) 1995-1996 Jean-loup Gailly
* For conditions of distribution and use, see copyright notice in zlib.h
*/

/*
* ALGORITHM
*
* The "deflation" process uses several Huffman trees. The more
* common source values are represented by shorter bit sequences.
*
* Each code tree is stored in a compressed form which is itself
* a Huffman encoding of the lengths of all the code strings (in
* ascending order by source values). The actual code strings are
* reconstructed from the lengths in the inflate process, as described
* in the deflate specification.
*
* REFERENCES
*
* Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
* Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
*
* Storer, James A.
* Data Compression: Methods and Theory, pp. 49-50.
* Computer Science Press, 1988. ISBN 0-7167-8156-5.
*
* Sedgewick, R.
* Algorithms, p290.
* Addison-Wesley, 1983. ISBN 0-201-06672-6.
*/

/* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */

/* #include "deflate.h" */

#include <linux/zutil.h>
#include "defutil.h"

#ifdef DEBUG_ZLIB
# include <ctype.h>
#endif

/* ===========================================================================
* Constants
*/

#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */

#define END_BLOCK 256
/* end of block literal code */

#define REP_3_6 16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */

#define REPZ_3_10 17
/* repeat a zero length 3-10 times (3 bits of repeat count) */

#define REPZ_11_138 18
/* repeat a zero length 11-138 times (7 bits of repeat count) */

static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
   = {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};

static const int extra_dbits[D_CODES] /* extra bits for each distance code */
   = {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};

static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};

static const uch bl_order[BL_CODES]
   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
/* The lengths of the bit length codes are sent in order of decreasing
* probability, to avoid transmitting the lengths for unused bit length codes.
*/

#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
* more than 16 bits on some systems.)
*/

/* ===========================================================================
* Local data. These are initialized only once.
*/

static ct_data static_ltree[L_CODES+2];
/* The static literal tree. Since the bit lengths are imposed, there is no
* need for the L_CODES extra codes used during heap construction. However
* The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init
* below).
*/

static ct_data static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
* 5 bits.)
*/

static uch dist_code[512];
/* distance codes. The first 256 values correspond to the distances
* 3 .. 258, the last 256 values correspond to the top 8 bits of
* the 15 bit distances.
*/

static uch length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */

static int base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */

static int base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */

struct static_tree_desc_s {
    const ct_data *static_tree; /* static tree or NULL */
    const int *extra_bits; /* extra bits for each code or NULL */
    int extra_base; /* base index for extra_bits */
    int elems; /* max number of elements in the tree */
    int max_length; /* max bit length for the codes */
};

static static_tree_desc static_l_desc =
{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};

static static_tree_desc static_d_desc =
{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};

static static_tree_desc static_bl_desc =
{(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};

/* ===========================================================================
* Local (static) routines in this file.
*/

static void tr_static_init (void);
static void init_block (deflate_state *s);
static void pqdownheap (deflate_state *s, ct_data *tree, int k);
static void gen_bitlen (deflate_state *s, tree_desc *desc);
static void gen_codes (ct_data *tree, int max_code, ush *bl_count);
static void build_tree (deflate_state *s, tree_desc *desc);
static void scan_tree (deflate_state *s, ct_data *tree, int max_code);
static void send_tree (deflate_state *s, ct_data *tree, int max_code);
static int build_bl_tree (deflate_state *s);
static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
                           int blcodes);
static void compress_block (deflate_state *s, ct_data *ltree,
                           ct_data *dtree);
static void set_data_type (deflate_state *s);
static unsigned bi_reverse (unsigned value, int length);
static void bi_windup (deflate_state *s);
static void bi_flush (deflate_state *s);
static void copy_block (deflate_state *s, char *buf, unsigned len,
                           int header);

#ifndef DEBUG_ZLIB
# define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
   /* Send a code of the given tree. c and tree must not have side effects */

#else /* DEBUG_ZLIB */
# define send_code(s, c, tree) \
{ if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
send_bits(s, tree[c].Code, tree[c].Len); }
#endif

#define d_code(dist) \
((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
* must not have side effects. dist_code[256] and dist_code[257] are never
* used.
*/

/* ===========================================================================
* Send a value on a given number of bits.
* IN assertion: length <= 16 and value fits in length bits.
*/
#ifdef DEBUG_ZLIB
static void send_bits (deflate_state *s, int value, int length);

static void send_bits(
deflate_state *s,
int value, /* value to send */
int length /* number of bits */
)
{
    Tracevv((stderr," l %2d v %4x ", length, value));
    Assert(length > 0 && length <= 15, "invalid length");
    s->bits_sent += (ulg)length;

    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
* (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
* unused bits in value.
*/
    if (s->bi_valid > (int)Buf_size - length) {
        s->bi_buf |= (value << s->bi_valid);
        put_short(s, s->bi_buf);
        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
        s->bi_valid += length - Buf_size;
    } else {
        s->bi_buf |= value << s->bi_valid;
        s->bi_valid += length;
    }
}
#else /* !DEBUG_ZLIB */

#define send_bits(s, value, length) \
{ int len = length;\
if (s->bi_valid > (int)Buf_size - len) {\
int val = value;\
s->bi_buf |= (val << s->bi_valid);\
put_short(s, s->bi_buf);\
s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
s->bi_valid += len - Buf_size;\
} else {\
s->bi_buf |= (value) << s->bi_valid;\
s->bi_valid += len;\
}\
}
#endif /* DEBUG_ZLIB */

/* ===========================================================================
* Initialize the various 'constant' tables. In a multi-threaded environment,
* this function may be called by two threads concurrently, but this is
* harmless since both invocations do exactly the same thing.
*/
static void tr_static_init(void)
{
    static int static_init_done;
    int n; /* iterates over tree elements */
    int bits; /* bit counter */
    int length; /* length value */
    int code; /* code value */
    int dist; /* distance index */
    ush bl_count[MAX_BITS+1];
    /* number of codes at each bit length for an optimal tree */

    if (static_init_done) return;

    /* Initialize the mapping length (0..255) -> length code (0..28) */
    length = 0;
    for (code = 0; code < LENGTH_CODES-1; code++) {
        base_length[code] = length;
        for (n = 0; n < (1<<extra_lbits[code]); n++) {
            length_code[length++] = (uch)code;
        }
    }
    Assert (length == 256, "tr_static_init: length != 256");
    /* Note that the length 255 (match length 258) can be represented
* in two different ways: code 284 + 5 bits or code 285, so we
* overwrite length_code[255] to use the best encoding:
*/
    length_code[length-1] = (uch)code;

    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    dist = 0;
    for (code = 0 ; code < 16; code++) {
        base_dist[code] = dist;
        for (n = 0; n < (1<<extra_dbits[code]); n++) {
            dist_code[dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: dist != 256");
    dist >>= 7; /* from now on, all distances are divided by 128 */
    for ( ; code < D_CODES; code++) {
        base_dist[code] = dist << 7;
        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
            dist_code[256 + dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: 256+dist != 512");

    /* Construct the codes of the static literal tree */
    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    n = 0;
    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    /* Codes 286 and 287 do not exist, but we must include them in the
* tree construction to get a canonical Huffman tree (longest code
* all ones)
*/
    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);

    /* The static distance tree is trivial: */
    for (n = 0; n < D_CODES; n++) {
        static_dtree[n].Len = 5;
        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    }
    static_init_done = 1;
}

/* ===========================================================================
* Initialize the tree data structures for a new zlib stream.
*/
void zlib_tr_init(
deflate_state *s
)
{
    tr_static_init();

    s->compressed_len = 0L;

    s->l_desc.dyn_tree = s->dyn_ltree;
    s->l_desc.stat_desc = &static_l_desc;

    s->d_desc.dyn_tree = s->dyn_dtree;
    s->d_desc.stat_desc = &static_d_desc;

    s->bl_desc.dyn_tree = s->bl_tree;
    s->bl_desc.stat_desc = &static_bl_desc;

    s->bi_buf = 0;
    s->bi_valid = 0;
    s->last_eob_len = 8; /* enough lookahead for inflate */
#ifdef DEBUG_ZLIB
    s->bits_sent = 0L;
#endif

    /* Initialize the first block of the first file: */
    init_block(s);
}

/* ===========================================================================
* Initialize a new block.
*/
static void init_block(
deflate_state *s
)
{
    int n; /* iterates over tree elements */

    /* Initialize the trees. */
    for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0;
    for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0;
    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;

    s->dyn_ltree[END_BLOCK].Freq = 1;
    s->opt_len = s->static_len = 0L;
    s->last_lit = s->matches = 0;
}

#define SMALLEST 1
/* Index within the heap array of least frequent node in the Huffman tree */


/* ===========================================================================
* Remove the smallest element from the heap and recreate the heap with
* one less element. Updates heap and heap_len.
*/
#define pqremove(s, tree, top) \
{\
top = s->heap[SMALLEST]; \
s->heap[SMALLEST] = s->heap[s->heap_len--]; \
pqdownheap(s, tree, SMALLEST); \
}

/* ===========================================================================
* Compares to subtrees, using the tree depth as tie breaker when
* the subtrees have equal frequency. This minimizes the worst case length.
*/
#define smaller(tree, n, m, depth) \
(tree[n].Freq < tree[m].Freq || \
(tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))

/* ===========================================================================
* Restore the heap property by moving down the tree starting at node k,
* exchanging a node with the smallest of its two sons if necessary, stopping
* when the heap property is re-established (each father smaller than its
* two sons).
*/
static void pqdownheap(
deflate_state *s,
ct_data *tree, /* the tree to restore */
int k /* node to move down */
)
{
    int v = s->heap[k];
    int j = k << 1; /* left son of k */
    while (j <= s->heap_len) {
        /* Set j to the smallest of the two sons: */
        if (j < s->heap_len &&
            smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
            j++;
        }
        /* Exit if v is smaller than both sons */
        if (smaller(tree, v, s->heap[j], s->depth)) break;

        /* Exchange v with the smallest son */
        s->heap[k] = s->heap[j]; k = j;

        /* And continue down the tree, setting j to the left son of k */
        j <<= 1;
    }
    s->heap[k] = v;
}

/* ===========================================================================
* Compute the optimal bit lengths for a tree and update the total bit length
* for the current block.
* IN assertion: the fields freq and dad are set, heap[heap_max] and
* above are the tree nodes sorted by increasing frequency.
* OUT assertions: the field len is set to the optimal bit length, the
* array bl_count contains the frequencies for each bit length.
* The length opt_len is updated; static_len is also updated if stree is
* not null.
*/
static void gen_bitlen(
deflate_state *s,
tree_desc *desc /* the tree descriptor */
)
{
    ct_data *tree = desc->dyn_tree;
    int max_code = desc->max_code;
    const ct_data *stree = desc->stat_desc->static_tree;
    const int *extra = desc->stat_desc->extra_bits;
    int base = desc->stat_desc->extra_base;
    int max_length = desc->stat_desc->max_length;
    int h; /* heap index */
    int n, m; /* iterate over the tree elements */
    int bits; /* bit length */
    int xbits; /* extra bits */
    ush f; /* frequency */
    int overflow = 0; /* number of elements with bit length too large */

    for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;

    /* In a first pass, compute the optimal bit lengths (which may
* overflow in the case of the bit length tree).
*/
    tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */

    for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
        n = s->heap[h];
        bits = tree[tree[n].Dad].Len + 1;
        if (bits > max_length) bits = max_length, overflow++;
        tree[n].Len = (ush)bits;
        /* We overwrite tree[n].Dad which is no longer needed */

        if (n > max_code) continue; /* not a leaf node */

        s->bl_count[bits]++;
        xbits = 0;
        if (n >= base) xbits = extra[n-base];
        f = tree[n].Freq;
        s->opt_len += (ulg)f * (bits + xbits);
        if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
    }
    if (overflow == 0) return;

    Trace((stderr,"\nbit length overflow\n"));
    /* This happens for example on obj2 and pic of the Calgary corpus */

    /* Find the first bit length which could increase: */
    do {
        bits = max_length-1;
        while (s->bl_count[bits] == 0) bits--;
        s->bl_count[bits]--; /* move one leaf down the tree */
        s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
        s->bl_count[max_length]--;
        /* The brother of the overflow item also moves one step up,
* but this does not affect bl_count[max_length]
*/
        overflow -= 2;
    } while (overflow > 0);

    /* Now recompute all bit lengths, scanning in increasing frequency.
* h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
* lengths instead of fixing only the wrong ones. This idea is taken
* from 'ar' written by Haruhiko Okumura.)
*/
    for (bits = max_length; bits != 0; bits--) {
        n = s->bl_count[bits];
        while (n != 0) {
            m = s->heap[--h];
            if (m > max_code) continue;
            if (tree[m].Len != (unsigned) bits) {
                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
                s->opt_len += ((long)bits - (long)tree[m].Len)
                              *(long)tree[m].Freq;
                tree[m].Len = (ush)bits;
            }
            n--;
        }
    }
}

/* ===========================================================================
* Generate the codes for a given tree and bit counts (which need not be
* optimal).
* IN assertion: the array bl_count contains the bit length statistics for
* the given tree and the field len is set for all tree elements.
* OUT assertion: the field code is set for all tree elements of non
* zero code length.
*/
static void gen_codes(
ct_data *tree, /* the tree to decorate */
int max_code, /* largest code with non zero frequency */
ush *bl_count /* number of codes at each bit length */
)
{
    ush next_code[MAX_BITS+1]; /* next code value for each bit length */
    ush code = 0; /* running code value */
    int bits; /* bit index */
    int n; /* code index */

    /* The distribution counts are first used to generate the code values
* without bit reversal.
*/
    for (bits = 1; bits <= MAX_BITS; bits++) {
        next_code[bits] = code = (code + bl_count[bits-1]) << 1;
    }
    /* Check that the bit counts in bl_count are consistent. The last code
* must be all ones.
*/
    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
            "inconsistent bit counts");
    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));

    for (n = 0; n <= max_code; n++) {
        int len = tree[n].Len;
        if (len == 0) continue;
        /* Now reverse the bits */
        tree[n].Code = bi_reverse(next_code[len]++, len);

        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
             n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
    }
}

/* ===========================================================================
* Construct one Huffman tree and assigns the code bit strings and lengths.
* Update the total bit length for the current block.
* IN assertion: the field freq is set for all tree elements.
* OUT assertions: the fields len and code are set to the optimal bit length
* and corresponding code. The length opt_len is updated; static_len is
* also updated if stree is not null. The field max_code is set.
*/
static void build_tree(
deflate_state *s,
tree_desc *desc /* the tree descriptor */
)
{
    ct_data *tree = desc->dyn_tree;
    const ct_data *stree = desc->stat_desc->static_tree;
    int elems = desc->stat_desc->elems;
    int n, m; /* iterate over heap elements */
    int max_code = -1; /* largest code with non zero frequency */
    int node; /* new node being created */

    /* Construct the initial heap, with least frequent element in
* heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
* heap[0] is not used.
*/
    s->heap_len = 0, s->heap_max = HEAP_SIZE;

    for (n = 0; n < elems; n++) {
        if (tree[n].Freq != 0) {
            s->heap[++(s->heap_len)] = max_code = n;
            s->depth[n] = 0;
        } else {
            tree[n].Len = 0;
        }
    }

    /* The pkzip format requires that at least one distance code exists,
* and that at least one bit should be sent even if there is only one
* possible code. So to avoid special checks later on we force at least
* two codes of non zero frequency.
*/
    while (s->heap_len < 2) {
        node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
        tree[node].Freq = 1;
        s->depth[node] = 0;
        s->opt_len--; if (stree) s->static_len -= stree[node].Len;
        /* node is 0 or 1 so it does not have extra bits */
    }
    desc->max_code = max_code;

    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
* establish sub-heaps of increasing lengths:
*/
    for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);

    /* Construct the Huffman tree by repeatedly combining the least two
* frequent nodes.
*/
    node = elems; /* next internal node of the tree */
    do {
        pqremove(s, tree, n); /* n = node of least frequency */
        m = s->heap[SMALLEST]; /* m = node of next least frequency */

        s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
        s->heap[--(s->heap_max)] = m;

        /* Create a new node father of n and m */
        tree[node].Freq = tree[n].Freq + tree[m].Freq;
        s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);
        tree[n].Dad = tree[m].Dad = (ush)node;
#ifdef DUMP_BL_TREE
        if (tree == s->bl_tree) {
            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
        }
#endif
        /* and insert the new node in the heap */
        s->heap[SMALLEST] = node++;
        pqdownheap(s, tree, SMALLEST);

    } while (s->heap_len >= 2);

    s->heap[--(s->heap_max)] = s->heap[SMALLEST];

    /* At this point, the fields freq and dad are set. We can now
* generate the bit lengths.
*/
    gen_bitlen(s, (tree_desc *)desc);

    /* The field len is now set, we can generate the bit codes */
    gen_codes ((ct_data *)tree, max_code, s->bl_count);
}

/* ===========================================================================
* Scan a literal or distance tree to determine the frequencies of the codes
* in the bit length tree.
*/
static void scan_tree(
deflate_state *s,
ct_data *tree, /* the tree to be scanned */
int max_code /* and its largest code of non zero frequency */
)
{
    int n; /* iterates over all tree elements */
    int prevlen = -1; /* last emitted length */
    int curlen; /* length of current code */
    int nextlen = tree[0].Len; /* length of next code */
    int count = 0; /* repeat count of the current code */
    int max_count = 7; /* max repeat count */
    int min_count = 4; /* min repeat count */

    if (nextlen == 0) max_count = 138, min_count = 3;
    tree[max_code+1].Len = (ush)0xffff; /* guard */

    for (n = 0; n <= max_code; n++) {
        curlen = nextlen; nextlen = tree[n+1].Len;
        if (++count < max_count && curlen == nextlen) {
            continue;
        } else if (count < min_count) {
            s->bl_tree[curlen].Freq += count;
        } else if (curlen != 0) {
            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
            s->bl_tree[REP_3_6].Freq++;
        } else if (count <= 10) {
            s->bl_tree[REPZ_3_10].Freq++;
        } else {
            s->bl_tree[REPZ_11_138].Freq++;
        }
        count = 0; prevlen = curlen;
        if (nextlen == 0) {
            max_count = 138, min_count = 3;
        } else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
        } else {
            max_count = 7, min_count = 4;
        }
    }
}

/* ===========================================================================
* Send a literal or distance tree in compressed form, using the codes in
* bl_tree.
*/
static void send_tree(
deflate_state *s,
ct_data *tree, /* the tree to be scanned */
int max_code /* and its largest code of non zero frequency */
)
{
    int n; /* iterates over all tree elements */
    int prevlen = -1; /* last emitted length */
    int curlen; /* length of current code */
    int nextlen = tree[0].Len; /* length of next code */
    int count = 0; /* repeat count of the current code */
    int max_count = 7; /* max repeat count */
    int min_count = 4; /* min repeat count */

    /* tree[max_code+1].Len = -1; */ /* guard already set */
    if (nextlen == 0) max_count = 138, min_count = 3;

    for (n = 0; n <= max_code; n++) {
        curlen = nextlen; nextlen = tree[n+1].Len;
        if (++count < max_count && curlen == nextlen) {
            continue;
        } else if (count < min_count) {
            do { send_code(s, curlen, s->bl_tree); } while (--count != 0);

        } else if (curlen != 0) {
            if (curlen != prevlen) {
                send_code(s, curlen, s->bl_tree); count--;
            }
            Assert(count >= 3 && count <= 6, " 3_6?");
            send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);

        } else if (count <= 10) {
            send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);

        } else {
            send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
        }
        count = 0; prevlen = curlen;
        if (nextlen == 0) {
            max_count = 138, min_count = 3;
        } else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
        } else {
            max_count = 7, min_count = 4;
        }
    }
}

/* ===========================================================================
* Construct the Huffman tree for the bit lengths and return the index in
* bl_order of the last bit length code to send.
*/
static int build_bl_tree(
deflate_state *s
)
{
    int max_blindex; /* index of last bit length code of non zero freq */

    /* Determine the bit length frequencies for literal and distance trees */
    scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
    scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);

    /* Build the bit length tree: */
    build_tree(s, (tree_desc *)(&(s->bl_desc)));
    /* opt_len now includes the length of the tree representations, except
* the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
*/

    /* Determine the number of bit length codes to send. The pkzip format
* requires that at least 4 bit length codes be sent. (appnote.txt says
* 3 but the actual value used is 4.)
*/
    for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
        if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
    }
    /* Update opt_len to include the bit length tree and counts */
    s->opt_len += 3*(max_blindex+1) + 5+5+4;
    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
            s->opt_len, s->static_len));

    return max_blindex;
}

/* ===========================================================================
* Send the header for a block using dynamic Huffman trees: the counts, the
* lengths of the bit length codes, the literal tree and the distance tree.
* IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
*/
static void send_all_trees(
deflate_state *s,
int lcodes, /* number of codes for each tree */
int dcodes, /* number of codes for each tree */
int blcodes /* number of codes for each tree */
)
{
    int rank; /* index in bl_order */

    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
            "too many codes");
    Tracev((stderr, "\nbl counts: "));
    send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
    send_bits(s, dcodes-1, 5);
    send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */
    for (rank = 0; rank < blcodes; rank++) {
        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
        send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
    }
    Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));

    send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
    Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));

    send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
    Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
}

/* ===========================================================================
* Send a stored block
*/
void zlib_tr_stored_block(
deflate_state *s,
char *buf, /* input block */
ulg stored_len, /* length of input block */
int eof /* true if this is the last block for a file */
)
{
    send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
    s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
    s->compressed_len += (stored_len + 4) << 3;

    copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
}

/* Send just the `stored block' type code without any length bytes or data.
*/
void zlib_tr_stored_type_only(
deflate_state *s
)
{
    send_bits(s, (STORED_BLOCK << 1), 3);
    bi_windup(s);
    s->compressed_len = (s->compressed_len + 3) & ~7L;
}


/* ===========================================================================
* Send one empty static block to give enough lookahead for inflate.
* This takes 10 bits, of which 7 may remain in the bit buffer.
* The current inflate code requires 9 bits of lookahead. If the
* last two codes for the previous block (real code plus EOB) were coded
* on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
* the last real code. In this case we send two empty static blocks instead
* of one. (There are no problems if the previous block is stored or fixed.)
* To simplify the code, we assume the worst case of last real code encoded
* on one bit only.
*/
void zlib_tr_align(
deflate_state *s
)
{
    send_bits(s, STATIC_TREES<<1, 3);
    send_code(s, END_BLOCK, static_ltree);
    s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
    bi_flush(s);
    /* Of the 10 bits for the empty block, we have already sent
* (10 - bi_valid) bits. The lookahead for the last real code (before
* the EOB of the previous block) was thus at least one plus the length
* of the EOB plus what we have just sent of the empty static block.
*/
    if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
        send_bits(s, STATIC_TREES<<1, 3);
        send_code(s, END_BLOCK, static_ltree);
        s->compressed_len += 10L;
        bi_flush(s);
    }
    s->last_eob_len = 7;
}

/* ===========================================================================
* Determine the best encoding for the current block: dynamic trees, static
* trees or store, and output the encoded block to the zip file. This function
* returns the total compressed length for the file so far.
*/
ulg zlib_tr_flush_block(
deflate_state *s,
char *buf, /* input block, or NULL if too old */
ulg stored_len, /* length of input block */
int eof /* true if this is the last block for a file */
)
{
    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
    int max_blindex = 0; /* index of last bit length code of non zero freq */

    /* Build the Huffman trees unless a stored block is forced */
    if (s->level > 0) {

/* Check if the file is ascii or binary */
if (s->data_type == Z_UNKNOWN) set_data_type(s);

/* Construct the literal and distance trees */
build_tree(s, (tree_desc *)(&(s->l_desc)));
Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
s->static_len));

build_tree(s, (tree_desc *)(&(s->d_desc)));
Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
s->static_len));
/* At this point, opt_len and static_len are the total bit lengths of
* the compressed block data, excluding the tree representations.
*/

/* Build the bit length tree for the above two trees, and get the index
* in bl_order of the last bit length code to send.
*/
max_blindex = build_bl_tree(s);

/* Determine the best encoding. Compute first the block length in bytes*/
opt_lenb = (s->opt_len+3+7)>>3;
static_lenb = (s->static_len+3+7)>>3;

Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
s->last_lit));

if (static_lenb <= opt_lenb) opt_lenb = static_lenb;

    } else {
        Assert(buf != (char*)0, "lost buf");
opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
    }

    /* If compression failed and this is the first and last block,
* and if the .zip file can be seeked (to rewrite the local header),
* the whole file is transformed into a stored file:
*/
#ifdef STORED_FILE_OK
# ifdef FORCE_STORED_FILE
    if (eof && s->compressed_len == 0L) { /* force stored file */
# else
    if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
# endif
        /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
        if (buf == (char*)0) error ("block vanished");

        copy_block(s, buf, (unsigned)stored_len, 0); /* without header */
        s->compressed_len = stored_len << 3;
        s->method = STORED;
    } else
#endif /* STORED_FILE_OK */

#ifdef FORCE_STORED
    if (buf != (char*)0) { /* force stored block */
#else
    if (stored_len+4 <= opt_lenb && buf != (char*)0) {
                       /* 4: two words for the lengths */
#endif
        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
* Otherwise we can't have processed more than WSIZE input bytes since
* the last block flush, because compression would have been
* successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
* transform a block into a stored block.
*/
        zlib_tr_stored_block(s, buf, stored_len, eof);

#ifdef FORCE_STATIC
    } else if (static_lenb >= 0) { /* force static trees */
#else
    } else if (static_lenb == opt_lenb) {
#endif
        send_bits(s, (STATIC_TREES<<1)+eof, 3);
        compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
        s->compressed_len += 3 + s->static_len;
    } else {
        send_bits(s, (DYN_TREES<<1)+eof, 3);
        send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
                       max_blindex+1);
        compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
        s->compressed_len += 3 + s->opt_len;
    }
    Assert (s->compressed_len == s->bits_sent, "bad compressed size");
    init_block(s);

    if (eof) {
        bi_windup(s);
        s->compressed_len += 7; /* align on byte boundary */
    }
    Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
           s->compressed_len-7*eof));

    return s->compressed_len >> 3;
}

/* ===========================================================================
* Save the match info and tally the frequency counts. Return true if
* the current block must be flushed.
*/
int zlib_tr_tally(
deflate_state *s,
unsigned dist, /* distance of matched string */
unsigned lc /* match length-MIN_MATCH or unmatched char (if dist==0) */
)
{
    s->d_buf[s->last_lit] = (ush)dist;
    s->l_buf[s->last_lit++] = (uch)lc;
    if (dist == 0) {
        /* lc is the unmatched char */
        s->dyn_ltree[lc].Freq++;
    } else {
        s->matches++;
        /* Here, lc is the match length - MIN_MATCH */
        dist--; /* dist = match distance - 1 */
        Assert((ush)dist < (ush)MAX_DIST(s) &&
               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
               (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match");

        s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
        s->dyn_dtree[d_code(dist)].Freq++;
    }

    /* Try to guess if it is profitable to stop the current block here */
    if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
        /* Compute an upper bound for the compressed length */
        ulg out_length = (ulg)s->last_lit*8L;
        ulg in_length = (ulg)((long)s->strstart - s->block_start);
        int dcode;
        for (dcode = 0; dcode < D_CODES; dcode++) {
            out_length += (ulg)s->dyn_dtree[dcode].Freq *
                (5L+extra_dbits[dcode]);
        }
        out_length >>= 3;
        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
               s->last_lit, in_length, out_length,
               100L - out_length*100L/in_length));
        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
    }
    return (s->last_lit == s->lit_bufsize-1);
    /* We avoid equality with lit_bufsize because of wraparound at 64K
* on 16 bit machines and because stored blocks are restricted to
* 64K-1 bytes.
*/
}

/* ===========================================================================
* Send the block data compressed using the given Huffman trees
*/
static void compress_block(
deflate_state *s,
ct_data *ltree, /* literal tree */
ct_data *dtree /* distance tree */
)
{
    unsigned dist; /* distance of matched string */
    int lc; /* match length or unmatched char (if dist == 0) */
    unsigned lx = 0; /* running index in l_buf */
    unsigned code; /* the code to send */
    int extra; /* number of extra bits to send */

    if (s->last_lit != 0) do {
        dist = s->d_buf[lx];
        lc = s->l_buf[lx++];
        if (dist == 0) {
            send_code(s, lc, ltree); /* send a literal byte */
            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
        } else {
            /* Here, lc is the match length - MIN_MATCH */
            code = length_code[lc];
            send_code(s, code+LITERALS+1, ltree); /* send the length code */
            extra = extra_lbits[code];
            if (extra != 0) {
                lc -= base_length[code];
                send_bits(s, lc, extra); /* send the extra length bits */
            }
            dist--; /* dist is now the match distance - 1 */
            code = d_code(dist);
            Assert (code < D_CODES, "bad d_code");

            send_code(s, code, dtree); /* send the distance code */
            extra = extra_dbits[code];
            if (extra != 0) {
                dist -= base_dist[code];
                send_bits(s, dist, extra); /* send the extra distance bits */
            }
        } /* literal or match pair ? */

        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
        Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");

    } while (lx < s->last_lit);

    send_code(s, END_BLOCK, ltree);
    s->last_eob_len = ltree[END_BLOCK].Len;
}

/* ===========================================================================
* Set the data type to ASCII or BINARY, using a crude approximation:
* binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
* IN assertion: the fields freq of dyn_ltree are set and the total of all
* frequencies does not exceed 64K (to fit in an int on 16 bit machines).
*/
static void set_data_type(
deflate_state *s
)
{
    int n = 0;
    unsigned ascii_freq = 0;
    unsigned bin_freq = 0;
    while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
    while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
    while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
    s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
}

/* ===========================================================================
* Copy a stored block, storing first the length and its
* one's complement if requested.
*/
static void copy_block(
deflate_state *s,
char *buf, /* the input data */
unsigned len, /* its length */
int header /* true if block header must be written */
)
{
    bi_windup(s); /* align on byte boundary */
    s->last_eob_len = 8; /* enough lookahead for inflate */

    if (header) {
        put_short(s, (ush)len);
        put_short(s, (ush)~len);
#ifdef DEBUG_ZLIB
        s->bits_sent += 2*16;
#endif
    }
#ifdef DEBUG_ZLIB
    s->bits_sent += (ulg)len<<3;
#endif
    /* bundle up the put_byte(s, *buf++) calls */
    memcpy(&s->pending_buf[s->pending], buf, len);
    s->pending += len;
}

Something went wrong with that request. Please try again.