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/Modules/zlib/trees.c

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C | 1219 lines | 762 code | 151 blank | 306 comment | 193 complexity | dff7366a93335d5efc87daeb99ca9a6c MD5 | raw file
   1/* trees.c -- output deflated data using Huffman coding
   2 * Copyright (C) 1995-2005 Jean-loup Gailly
   3 * For conditions of distribution and use, see copyright notice in zlib.h
   4 */
   5
   6/*
   7 *  ALGORITHM
   8 *
   9 *      The "deflation" process uses several Huffman trees. The more
  10 *      common source values are represented by shorter bit sequences.
  11 *
  12 *      Each code tree is stored in a compressed form which is itself
  13 * a Huffman encoding of the lengths of all the code strings (in
  14 * ascending order by source values).  The actual code strings are
  15 * reconstructed from the lengths in the inflate process, as described
  16 * in the deflate specification.
  17 *
  18 *  REFERENCES
  19 *
  20 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
  21 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
  22 *
  23 *      Storer, James A.
  24 *          Data Compression:  Methods and Theory, pp. 49-50.
  25 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
  26 *
  27 *      Sedgewick, R.
  28 *          Algorithms, p290.
  29 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
  30 */
  31
  32/* @(#) $Id$ */
  33
  34/* #define GEN_TREES_H */
  35
  36#include "deflate.h"
  37
  38#ifdef DEBUG
  39#  include <ctype.h>
  40#endif
  41
  42/* ===========================================================================
  43 * Constants
  44 */
  45
  46#define MAX_BL_BITS 7
  47/* Bit length codes must not exceed MAX_BL_BITS bits */
  48
  49#define END_BLOCK 256
  50/* end of block literal code */
  51
  52#define REP_3_6      16
  53/* repeat previous bit length 3-6 times (2 bits of repeat count) */
  54
  55#define REPZ_3_10    17
  56/* repeat a zero length 3-10 times  (3 bits of repeat count) */
  57
  58#define REPZ_11_138  18
  59/* repeat a zero length 11-138 times  (7 bits of repeat count) */
  60
  61local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
  62   = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
  63
  64local const int extra_dbits[D_CODES] /* extra bits for each distance code */
  65   = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
  66
  67local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
  68   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
  69
  70local const uch bl_order[BL_CODES]
  71   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
  72/* The lengths of the bit length codes are sent in order of decreasing
  73 * probability, to avoid transmitting the lengths for unused bit length codes.
  74 */
  75
  76#define Buf_size (8 * 2*sizeof(char))
  77/* Number of bits used within bi_buf. (bi_buf might be implemented on
  78 * more than 16 bits on some systems.)
  79 */
  80
  81/* ===========================================================================
  82 * Local data. These are initialized only once.
  83 */
  84
  85#define DIST_CODE_LEN  512 /* see definition of array dist_code below */
  86
  87#if defined(GEN_TREES_H) || !defined(STDC)
  88/* non ANSI compilers may not accept trees.h */
  89
  90local ct_data static_ltree[L_CODES+2];
  91/* The static literal tree. Since the bit lengths are imposed, there is no
  92 * need for the L_CODES extra codes used during heap construction. However
  93 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
  94 * below).
  95 */
  96
  97local ct_data static_dtree[D_CODES];
  98/* The static distance tree. (Actually a trivial tree since all codes use
  99 * 5 bits.)
 100 */
 101
 102uch _dist_code[DIST_CODE_LEN];
 103/* Distance codes. The first 256 values correspond to the distances
 104 * 3 .. 258, the last 256 values correspond to the top 8 bits of
 105 * the 15 bit distances.
 106 */
 107
 108uch _length_code[MAX_MATCH-MIN_MATCH+1];
 109/* length code for each normalized match length (0 == MIN_MATCH) */
 110
 111local int base_length[LENGTH_CODES];
 112/* First normalized length for each code (0 = MIN_MATCH) */
 113
 114local int base_dist[D_CODES];
 115/* First normalized distance for each code (0 = distance of 1) */
 116
 117#else
 118#  include "trees.h"
 119#endif /* GEN_TREES_H */
 120
 121struct static_tree_desc_s {
 122    const ct_data *static_tree;  /* static tree or NULL */
 123    const intf *extra_bits;      /* extra bits for each code or NULL */
 124    int     extra_base;          /* base index for extra_bits */
 125    int     elems;               /* max number of elements in the tree */
 126    int     max_length;          /* max bit length for the codes */
 127};
 128
 129local static_tree_desc  static_l_desc =
 130{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
 131
 132local static_tree_desc  static_d_desc =
 133{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
 134
 135local static_tree_desc  static_bl_desc =
 136{(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
 137
 138/* ===========================================================================
 139 * Local (static) routines in this file.
 140 */
 141
 142local void tr_static_init OF((void));
 143local void init_block     OF((deflate_state *s));
 144local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
 145local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
 146local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
 147local void build_tree     OF((deflate_state *s, tree_desc *desc));
 148local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 149local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 150local int  build_bl_tree  OF((deflate_state *s));
 151local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
 152                              int blcodes));
 153local void compress_block OF((deflate_state *s, ct_data *ltree,
 154                              ct_data *dtree));
 155local void set_data_type  OF((deflate_state *s));
 156local unsigned bi_reverse OF((unsigned value, int length));
 157local void bi_windup      OF((deflate_state *s));
 158local void bi_flush       OF((deflate_state *s));
 159local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
 160                              int header));
 161
 162#ifdef GEN_TREES_H
 163local void gen_trees_header OF((void));
 164#endif
 165
 166#ifndef DEBUG
 167#  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
 168   /* Send a code of the given tree. c and tree must not have side effects */
 169
 170#else /* DEBUG */
 171#  define send_code(s, c, tree) \
 172     { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
 173       send_bits(s, tree[c].Code, tree[c].Len); }
 174#endif
 175
 176/* ===========================================================================
 177 * Output a short LSB first on the stream.
 178 * IN assertion: there is enough room in pendingBuf.
 179 */
 180#define put_short(s, w) { \
 181    put_byte(s, (uch)((w) & 0xff)); \
 182    put_byte(s, (uch)((ush)(w) >> 8)); \
 183}
 184
 185/* ===========================================================================
 186 * Send a value on a given number of bits.
 187 * IN assertion: length <= 16 and value fits in length bits.
 188 */
 189#ifdef DEBUG
 190local void send_bits      OF((deflate_state *s, int value, int length));
 191
 192local void send_bits(s, value, length)
 193    deflate_state *s;
 194    int value;  /* value to send */
 195    int length; /* number of bits */
 196{
 197    Tracevv((stderr," l %2d v %4x ", length, value));
 198    Assert(length > 0 && length <= 15, "invalid length");
 199    s->bits_sent += (ulg)length;
 200
 201    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
 202     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
 203     * unused bits in value.
 204     */
 205    if (s->bi_valid > (int)Buf_size - length) {
 206        s->bi_buf |= (value << s->bi_valid);
 207        put_short(s, s->bi_buf);
 208        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
 209        s->bi_valid += length - Buf_size;
 210    } else {
 211        s->bi_buf |= value << s->bi_valid;
 212        s->bi_valid += length;
 213    }
 214}
 215#else /* !DEBUG */
 216
 217#define send_bits(s, value, length) \
 218{ int len = length;\
 219  if (s->bi_valid > (int)Buf_size - len) {\
 220    int val = value;\
 221    s->bi_buf |= (val << s->bi_valid);\
 222    put_short(s, s->bi_buf);\
 223    s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
 224    s->bi_valid += len - Buf_size;\
 225  } else {\
 226    s->bi_buf |= (value) << s->bi_valid;\
 227    s->bi_valid += len;\
 228  }\
 229}
 230#endif /* DEBUG */
 231
 232
 233/* the arguments must not have side effects */
 234
 235/* ===========================================================================
 236 * Initialize the various 'constant' tables.
 237 */
 238local void tr_static_init()
 239{
 240#if defined(GEN_TREES_H) || !defined(STDC)
 241    static int static_init_done = 0;
 242    int n;        /* iterates over tree elements */
 243    int bits;     /* bit counter */
 244    int length;   /* length value */
 245    int code;     /* code value */
 246    int dist;     /* distance index */
 247    ush bl_count[MAX_BITS+1];
 248    /* number of codes at each bit length for an optimal tree */
 249
 250    if (static_init_done) return;
 251
 252    /* For some embedded targets, global variables are not initialized: */
 253    static_l_desc.static_tree = static_ltree;
 254    static_l_desc.extra_bits = extra_lbits;
 255    static_d_desc.static_tree = static_dtree;
 256    static_d_desc.extra_bits = extra_dbits;
 257    static_bl_desc.extra_bits = extra_blbits;
 258
 259    /* Initialize the mapping length (0..255) -> length code (0..28) */
 260    length = 0;
 261    for (code = 0; code < LENGTH_CODES-1; code++) {
 262        base_length[code] = length;
 263        for (n = 0; n < (1<<extra_lbits[code]); n++) {
 264            _length_code[length++] = (uch)code;
 265        }
 266    }
 267    Assert (length == 256, "tr_static_init: length != 256");
 268    /* Note that the length 255 (match length 258) can be represented
 269     * in two different ways: code 284 + 5 bits or code 285, so we
 270     * overwrite length_code[255] to use the best encoding:
 271     */
 272    _length_code[length-1] = (uch)code;
 273
 274    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
 275    dist = 0;
 276    for (code = 0 ; code < 16; code++) {
 277        base_dist[code] = dist;
 278        for (n = 0; n < (1<<extra_dbits[code]); n++) {
 279            _dist_code[dist++] = (uch)code;
 280        }
 281    }
 282    Assert (dist == 256, "tr_static_init: dist != 256");
 283    dist >>= 7; /* from now on, all distances are divided by 128 */
 284    for ( ; code < D_CODES; code++) {
 285        base_dist[code] = dist << 7;
 286        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
 287            _dist_code[256 + dist++] = (uch)code;
 288        }
 289    }
 290    Assert (dist == 256, "tr_static_init: 256+dist != 512");
 291
 292    /* Construct the codes of the static literal tree */
 293    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
 294    n = 0;
 295    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
 296    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
 297    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
 298    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
 299    /* Codes 286 and 287 do not exist, but we must include them in the
 300     * tree construction to get a canonical Huffman tree (longest code
 301     * all ones)
 302     */
 303    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
 304
 305    /* The static distance tree is trivial: */
 306    for (n = 0; n < D_CODES; n++) {
 307        static_dtree[n].Len = 5;
 308        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
 309    }
 310    static_init_done = 1;
 311
 312#  ifdef GEN_TREES_H
 313    gen_trees_header();
 314#  endif
 315#endif /* defined(GEN_TREES_H) || !defined(STDC) */
 316}
 317
 318/* ===========================================================================
 319 * Genererate the file trees.h describing the static trees.
 320 */
 321#ifdef GEN_TREES_H
 322#  ifndef DEBUG
 323#    include <stdio.h>
 324#  endif
 325
 326#  define SEPARATOR(i, last, width) \
 327      ((i) == (last)? "\n};\n\n" :    \
 328       ((i) % (width) == (width)-1 ? ",\n" : ", "))
 329
 330void gen_trees_header()
 331{
 332    FILE *header = fopen("trees.h", "w");
 333    int i;
 334
 335    Assert (header != NULL, "Can't open trees.h");
 336    fprintf(header,
 337            "/* header created automatically with -DGEN_TREES_H */\n\n");
 338
 339    fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
 340    for (i = 0; i < L_CODES+2; i++) {
 341        fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
 342                static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
 343    }
 344
 345    fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
 346    for (i = 0; i < D_CODES; i++) {
 347        fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
 348                static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
 349    }
 350
 351    fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
 352    for (i = 0; i < DIST_CODE_LEN; i++) {
 353        fprintf(header, "%2u%s", _dist_code[i],
 354                SEPARATOR(i, DIST_CODE_LEN-1, 20));
 355    }
 356
 357    fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
 358    for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
 359        fprintf(header, "%2u%s", _length_code[i],
 360                SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
 361    }
 362
 363    fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
 364    for (i = 0; i < LENGTH_CODES; i++) {
 365        fprintf(header, "%1u%s", base_length[i],
 366                SEPARATOR(i, LENGTH_CODES-1, 20));
 367    }
 368
 369    fprintf(header, "local const int base_dist[D_CODES] = {\n");
 370    for (i = 0; i < D_CODES; i++) {
 371        fprintf(header, "%5u%s", base_dist[i],
 372                SEPARATOR(i, D_CODES-1, 10));
 373    }
 374
 375    fclose(header);
 376}
 377#endif /* GEN_TREES_H */
 378
 379/* ===========================================================================
 380 * Initialize the tree data structures for a new zlib stream.
 381 */
 382void _tr_init(s)
 383    deflate_state *s;
 384{
 385    tr_static_init();
 386
 387    s->l_desc.dyn_tree = s->dyn_ltree;
 388    s->l_desc.stat_desc = &static_l_desc;
 389
 390    s->d_desc.dyn_tree = s->dyn_dtree;
 391    s->d_desc.stat_desc = &static_d_desc;
 392
 393    s->bl_desc.dyn_tree = s->bl_tree;
 394    s->bl_desc.stat_desc = &static_bl_desc;
 395
 396    s->bi_buf = 0;
 397    s->bi_valid = 0;
 398    s->last_eob_len = 8; /* enough lookahead for inflate */
 399#ifdef DEBUG
 400    s->compressed_len = 0L;
 401    s->bits_sent = 0L;
 402#endif
 403
 404    /* Initialize the first block of the first file: */
 405    init_block(s);
 406}
 407
 408/* ===========================================================================
 409 * Initialize a new block.
 410 */
 411local void init_block(s)
 412    deflate_state *s;
 413{
 414    int n; /* iterates over tree elements */
 415
 416    /* Initialize the trees. */
 417    for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
 418    for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
 419    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
 420
 421    s->dyn_ltree[END_BLOCK].Freq = 1;
 422    s->opt_len = s->static_len = 0L;
 423    s->last_lit = s->matches = 0;
 424}
 425
 426#define SMALLEST 1
 427/* Index within the heap array of least frequent node in the Huffman tree */
 428
 429
 430/* ===========================================================================
 431 * Remove the smallest element from the heap and recreate the heap with
 432 * one less element. Updates heap and heap_len.
 433 */
 434#define pqremove(s, tree, top) \
 435{\
 436    top = s->heap[SMALLEST]; \
 437    s->heap[SMALLEST] = s->heap[s->heap_len--]; \
 438    pqdownheap(s, tree, SMALLEST); \
 439}
 440
 441/* ===========================================================================
 442 * Compares to subtrees, using the tree depth as tie breaker when
 443 * the subtrees have equal frequency. This minimizes the worst case length.
 444 */
 445#define smaller(tree, n, m, depth) \
 446   (tree[n].Freq < tree[m].Freq || \
 447   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
 448
 449/* ===========================================================================
 450 * Restore the heap property by moving down the tree starting at node k,
 451 * exchanging a node with the smallest of its two sons if necessary, stopping
 452 * when the heap property is re-established (each father smaller than its
 453 * two sons).
 454 */
 455local void pqdownheap(s, tree, k)
 456    deflate_state *s;
 457    ct_data *tree;  /* the tree to restore */
 458    int k;               /* node to move down */
 459{
 460    int v = s->heap[k];
 461    int j = k << 1;  /* left son of k */
 462    while (j <= s->heap_len) {
 463        /* Set j to the smallest of the two sons: */
 464        if (j < s->heap_len &&
 465            smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
 466            j++;
 467        }
 468        /* Exit if v is smaller than both sons */
 469        if (smaller(tree, v, s->heap[j], s->depth)) break;
 470
 471        /* Exchange v with the smallest son */
 472        s->heap[k] = s->heap[j];  k = j;
 473
 474        /* And continue down the tree, setting j to the left son of k */
 475        j <<= 1;
 476    }
 477    s->heap[k] = v;
 478}
 479
 480/* ===========================================================================
 481 * Compute the optimal bit lengths for a tree and update the total bit length
 482 * for the current block.
 483 * IN assertion: the fields freq and dad are set, heap[heap_max] and
 484 *    above are the tree nodes sorted by increasing frequency.
 485 * OUT assertions: the field len is set to the optimal bit length, the
 486 *     array bl_count contains the frequencies for each bit length.
 487 *     The length opt_len is updated; static_len is also updated if stree is
 488 *     not null.
 489 */
 490local void gen_bitlen(s, desc)
 491    deflate_state *s;
 492    tree_desc *desc;    /* the tree descriptor */
 493{
 494    ct_data *tree        = desc->dyn_tree;
 495    int max_code         = desc->max_code;
 496    const ct_data *stree = desc->stat_desc->static_tree;
 497    const intf *extra    = desc->stat_desc->extra_bits;
 498    int base             = desc->stat_desc->extra_base;
 499    int max_length       = desc->stat_desc->max_length;
 500    int h;              /* heap index */
 501    int n, m;           /* iterate over the tree elements */
 502    int bits;           /* bit length */
 503    int xbits;          /* extra bits */
 504    ush f;              /* frequency */
 505    int overflow = 0;   /* number of elements with bit length too large */
 506
 507    for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
 508
 509    /* In a first pass, compute the optimal bit lengths (which may
 510     * overflow in the case of the bit length tree).
 511     */
 512    tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
 513
 514    for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
 515        n = s->heap[h];
 516        bits = tree[tree[n].Dad].Len + 1;
 517        if (bits > max_length) bits = max_length, overflow++;
 518        tree[n].Len = (ush)bits;
 519        /* We overwrite tree[n].Dad which is no longer needed */
 520
 521        if (n > max_code) continue; /* not a leaf node */
 522
 523        s->bl_count[bits]++;
 524        xbits = 0;
 525        if (n >= base) xbits = extra[n-base];
 526        f = tree[n].Freq;
 527        s->opt_len += (ulg)f * (bits + xbits);
 528        if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
 529    }
 530    if (overflow == 0) return;
 531
 532    Trace((stderr,"\nbit length overflow\n"));
 533    /* This happens for example on obj2 and pic of the Calgary corpus */
 534
 535    /* Find the first bit length which could increase: */
 536    do {
 537        bits = max_length-1;
 538        while (s->bl_count[bits] == 0) bits--;
 539        s->bl_count[bits]--;      /* move one leaf down the tree */
 540        s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
 541        s->bl_count[max_length]--;
 542        /* The brother of the overflow item also moves one step up,
 543         * but this does not affect bl_count[max_length]
 544         */
 545        overflow -= 2;
 546    } while (overflow > 0);
 547
 548    /* Now recompute all bit lengths, scanning in increasing frequency.
 549     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
 550     * lengths instead of fixing only the wrong ones. This idea is taken
 551     * from 'ar' written by Haruhiko Okumura.)
 552     */
 553    for (bits = max_length; bits != 0; bits--) {
 554        n = s->bl_count[bits];
 555        while (n != 0) {
 556            m = s->heap[--h];
 557            if (m > max_code) continue;
 558            if ((unsigned) tree[m].Len != (unsigned) bits) {
 559                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
 560                s->opt_len += ((long)bits - (long)tree[m].Len)
 561                              *(long)tree[m].Freq;
 562                tree[m].Len = (ush)bits;
 563            }
 564            n--;
 565        }
 566    }
 567}
 568
 569/* ===========================================================================
 570 * Generate the codes for a given tree and bit counts (which need not be
 571 * optimal).
 572 * IN assertion: the array bl_count contains the bit length statistics for
 573 * the given tree and the field len is set for all tree elements.
 574 * OUT assertion: the field code is set for all tree elements of non
 575 *     zero code length.
 576 */
 577local void gen_codes (tree, max_code, bl_count)
 578    ct_data *tree;             /* the tree to decorate */
 579    int max_code;              /* largest code with non zero frequency */
 580    ushf *bl_count;            /* number of codes at each bit length */
 581{
 582    ush next_code[MAX_BITS+1]; /* next code value for each bit length */
 583    ush code = 0;              /* running code value */
 584    int bits;                  /* bit index */
 585    int n;                     /* code index */
 586
 587    /* The distribution counts are first used to generate the code values
 588     * without bit reversal.
 589     */
 590    for (bits = 1; bits <= MAX_BITS; bits++) {
 591        next_code[bits] = code = (code + bl_count[bits-1]) << 1;
 592    }
 593    /* Check that the bit counts in bl_count are consistent. The last code
 594     * must be all ones.
 595     */
 596    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
 597            "inconsistent bit counts");
 598    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
 599
 600    for (n = 0;  n <= max_code; n++) {
 601        int len = tree[n].Len;
 602        if (len == 0) continue;
 603        /* Now reverse the bits */
 604        tree[n].Code = bi_reverse(next_code[len]++, len);
 605
 606        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
 607             n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
 608    }
 609}
 610
 611/* ===========================================================================
 612 * Construct one Huffman tree and assigns the code bit strings and lengths.
 613 * Update the total bit length for the current block.
 614 * IN assertion: the field freq is set for all tree elements.
 615 * OUT assertions: the fields len and code are set to the optimal bit length
 616 *     and corresponding code. The length opt_len is updated; static_len is
 617 *     also updated if stree is not null. The field max_code is set.
 618 */
 619local void build_tree(s, desc)
 620    deflate_state *s;
 621    tree_desc *desc; /* the tree descriptor */
 622{
 623    ct_data *tree         = desc->dyn_tree;
 624    const ct_data *stree  = desc->stat_desc->static_tree;
 625    int elems             = desc->stat_desc->elems;
 626    int n, m;          /* iterate over heap elements */
 627    int max_code = -1; /* largest code with non zero frequency */
 628    int node;          /* new node being created */
 629
 630    /* Construct the initial heap, with least frequent element in
 631     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
 632     * heap[0] is not used.
 633     */
 634    s->heap_len = 0, s->heap_max = HEAP_SIZE;
 635
 636    for (n = 0; n < elems; n++) {
 637        if (tree[n].Freq != 0) {
 638            s->heap[++(s->heap_len)] = max_code = n;
 639            s->depth[n] = 0;
 640        } else {
 641            tree[n].Len = 0;
 642        }
 643    }
 644
 645    /* The pkzip format requires that at least one distance code exists,
 646     * and that at least one bit should be sent even if there is only one
 647     * possible code. So to avoid special checks later on we force at least
 648     * two codes of non zero frequency.
 649     */
 650    while (s->heap_len < 2) {
 651        node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
 652        tree[node].Freq = 1;
 653        s->depth[node] = 0;
 654        s->opt_len--; if (stree) s->static_len -= stree[node].Len;
 655        /* node is 0 or 1 so it does not have extra bits */
 656    }
 657    desc->max_code = max_code;
 658
 659    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
 660     * establish sub-heaps of increasing lengths:
 661     */
 662    for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
 663
 664    /* Construct the Huffman tree by repeatedly combining the least two
 665     * frequent nodes.
 666     */
 667    node = elems;              /* next internal node of the tree */
 668    do {
 669        pqremove(s, tree, n);  /* n = node of least frequency */
 670        m = s->heap[SMALLEST]; /* m = node of next least frequency */
 671
 672        s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
 673        s->heap[--(s->heap_max)] = m;
 674
 675        /* Create a new node father of n and m */
 676        tree[node].Freq = tree[n].Freq + tree[m].Freq;
 677        s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
 678                                s->depth[n] : s->depth[m]) + 1);
 679        tree[n].Dad = tree[m].Dad = (ush)node;
 680#ifdef DUMP_BL_TREE
 681        if (tree == s->bl_tree) {
 682            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
 683                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
 684        }
 685#endif
 686        /* and insert the new node in the heap */
 687        s->heap[SMALLEST] = node++;
 688        pqdownheap(s, tree, SMALLEST);
 689
 690    } while (s->heap_len >= 2);
 691
 692    s->heap[--(s->heap_max)] = s->heap[SMALLEST];
 693
 694    /* At this point, the fields freq and dad are set. We can now
 695     * generate the bit lengths.
 696     */
 697    gen_bitlen(s, (tree_desc *)desc);
 698
 699    /* The field len is now set, we can generate the bit codes */
 700    gen_codes ((ct_data *)tree, max_code, s->bl_count);
 701}
 702
 703/* ===========================================================================
 704 * Scan a literal or distance tree to determine the frequencies of the codes
 705 * in the bit length tree.
 706 */
 707local void scan_tree (s, tree, max_code)
 708    deflate_state *s;
 709    ct_data *tree;   /* the tree to be scanned */
 710    int max_code;    /* and its largest code of non zero frequency */
 711{
 712    int n;                     /* iterates over all tree elements */
 713    int prevlen = -1;          /* last emitted length */
 714    int curlen;                /* length of current code */
 715    int nextlen = tree[0].Len; /* length of next code */
 716    int count = 0;             /* repeat count of the current code */
 717    int max_count = 7;         /* max repeat count */
 718    int min_count = 4;         /* min repeat count */
 719
 720    if (nextlen == 0) max_count = 138, min_count = 3;
 721    tree[max_code+1].Len = (ush)0xffff; /* guard */
 722
 723    for (n = 0; n <= max_code; n++) {
 724        curlen = nextlen; nextlen = tree[n+1].Len;
 725        if (++count < max_count && curlen == nextlen) {
 726            continue;
 727        } else if (count < min_count) {
 728            s->bl_tree[curlen].Freq += count;
 729        } else if (curlen != 0) {
 730            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
 731            s->bl_tree[REP_3_6].Freq++;
 732        } else if (count <= 10) {
 733            s->bl_tree[REPZ_3_10].Freq++;
 734        } else {
 735            s->bl_tree[REPZ_11_138].Freq++;
 736        }
 737        count = 0; prevlen = curlen;
 738        if (nextlen == 0) {
 739            max_count = 138, min_count = 3;
 740        } else if (curlen == nextlen) {
 741            max_count = 6, min_count = 3;
 742        } else {
 743            max_count = 7, min_count = 4;
 744        }
 745    }
 746}
 747
 748/* ===========================================================================
 749 * Send a literal or distance tree in compressed form, using the codes in
 750 * bl_tree.
 751 */
 752local void send_tree (s, tree, max_code)
 753    deflate_state *s;
 754    ct_data *tree; /* the tree to be scanned */
 755    int max_code;       /* and its largest code of non zero frequency */
 756{
 757    int n;                     /* iterates over all tree elements */
 758    int prevlen = -1;          /* last emitted length */
 759    int curlen;                /* length of current code */
 760    int nextlen = tree[0].Len; /* length of next code */
 761    int count = 0;             /* repeat count of the current code */
 762    int max_count = 7;         /* max repeat count */
 763    int min_count = 4;         /* min repeat count */
 764
 765    /* tree[max_code+1].Len = -1; */  /* guard already set */
 766    if (nextlen == 0) max_count = 138, min_count = 3;
 767
 768    for (n = 0; n <= max_code; n++) {
 769        curlen = nextlen; nextlen = tree[n+1].Len;
 770        if (++count < max_count && curlen == nextlen) {
 771            continue;
 772        } else if (count < min_count) {
 773            do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
 774
 775        } else if (curlen != 0) {
 776            if (curlen != prevlen) {
 777                send_code(s, curlen, s->bl_tree); count--;
 778            }
 779            Assert(count >= 3 && count <= 6, " 3_6?");
 780            send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
 781
 782        } else if (count <= 10) {
 783            send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
 784
 785        } else {
 786            send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
 787        }
 788        count = 0; prevlen = curlen;
 789        if (nextlen == 0) {
 790            max_count = 138, min_count = 3;
 791        } else if (curlen == nextlen) {
 792            max_count = 6, min_count = 3;
 793        } else {
 794            max_count = 7, min_count = 4;
 795        }
 796    }
 797}
 798
 799/* ===========================================================================
 800 * Construct the Huffman tree for the bit lengths and return the index in
 801 * bl_order of the last bit length code to send.
 802 */
 803local int build_bl_tree(s)
 804    deflate_state *s;
 805{
 806    int max_blindex;  /* index of last bit length code of non zero freq */
 807
 808    /* Determine the bit length frequencies for literal and distance trees */
 809    scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
 810    scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
 811
 812    /* Build the bit length tree: */
 813    build_tree(s, (tree_desc *)(&(s->bl_desc)));
 814    /* opt_len now includes the length of the tree representations, except
 815     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
 816     */
 817
 818    /* Determine the number of bit length codes to send. The pkzip format
 819     * requires that at least 4 bit length codes be sent. (appnote.txt says
 820     * 3 but the actual value used is 4.)
 821     */
 822    for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
 823        if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
 824    }
 825    /* Update opt_len to include the bit length tree and counts */
 826    s->opt_len += 3*(max_blindex+1) + 5+5+4;
 827    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
 828            s->opt_len, s->static_len));
 829
 830    return max_blindex;
 831}
 832
 833/* ===========================================================================
 834 * Send the header for a block using dynamic Huffman trees: the counts, the
 835 * lengths of the bit length codes, the literal tree and the distance tree.
 836 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
 837 */
 838local void send_all_trees(s, lcodes, dcodes, blcodes)
 839    deflate_state *s;
 840    int lcodes, dcodes, blcodes; /* number of codes for each tree */
 841{
 842    int rank;                    /* index in bl_order */
 843
 844    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
 845    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
 846            "too many codes");
 847    Tracev((stderr, "\nbl counts: "));
 848    send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
 849    send_bits(s, dcodes-1,   5);
 850    send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
 851    for (rank = 0; rank < blcodes; rank++) {
 852        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
 853        send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
 854    }
 855    Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
 856
 857    send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
 858    Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
 859
 860    send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
 861    Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
 862}
 863
 864/* ===========================================================================
 865 * Send a stored block
 866 */
 867void _tr_stored_block(s, buf, stored_len, eof)
 868    deflate_state *s;
 869    charf *buf;       /* input block */
 870    ulg stored_len;   /* length of input block */
 871    int eof;          /* true if this is the last block for a file */
 872{
 873    send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
 874#ifdef DEBUG
 875    s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
 876    s->compressed_len += (stored_len + 4) << 3;
 877#endif
 878    copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
 879}
 880
 881/* ===========================================================================
 882 * Send one empty static block to give enough lookahead for inflate.
 883 * This takes 10 bits, of which 7 may remain in the bit buffer.
 884 * The current inflate code requires 9 bits of lookahead. If the
 885 * last two codes for the previous block (real code plus EOB) were coded
 886 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
 887 * the last real code. In this case we send two empty static blocks instead
 888 * of one. (There are no problems if the previous block is stored or fixed.)
 889 * To simplify the code, we assume the worst case of last real code encoded
 890 * on one bit only.
 891 */
 892void _tr_align(s)
 893    deflate_state *s;
 894{
 895    send_bits(s, STATIC_TREES<<1, 3);
 896    send_code(s, END_BLOCK, static_ltree);
 897#ifdef DEBUG
 898    s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
 899#endif
 900    bi_flush(s);
 901    /* Of the 10 bits for the empty block, we have already sent
 902     * (10 - bi_valid) bits. The lookahead for the last real code (before
 903     * the EOB of the previous block) was thus at least one plus the length
 904     * of the EOB plus what we have just sent of the empty static block.
 905     */
 906    if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
 907        send_bits(s, STATIC_TREES<<1, 3);
 908        send_code(s, END_BLOCK, static_ltree);
 909#ifdef DEBUG
 910        s->compressed_len += 10L;
 911#endif
 912        bi_flush(s);
 913    }
 914    s->last_eob_len = 7;
 915}
 916
 917/* ===========================================================================
 918 * Determine the best encoding for the current block: dynamic trees, static
 919 * trees or store, and output the encoded block to the zip file.
 920 */
 921void _tr_flush_block(s, buf, stored_len, eof)
 922    deflate_state *s;
 923    charf *buf;       /* input block, or NULL if too old */
 924    ulg stored_len;   /* length of input block */
 925    int eof;          /* true if this is the last block for a file */
 926{
 927    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
 928    int max_blindex = 0;  /* index of last bit length code of non zero freq */
 929
 930    /* Build the Huffman trees unless a stored block is forced */
 931    if (s->level > 0) {
 932
 933        /* Check if the file is binary or text */
 934        if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN)
 935            set_data_type(s);
 936
 937        /* Construct the literal and distance trees */
 938        build_tree(s, (tree_desc *)(&(s->l_desc)));
 939        Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
 940                s->static_len));
 941
 942        build_tree(s, (tree_desc *)(&(s->d_desc)));
 943        Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
 944                s->static_len));
 945        /* At this point, opt_len and static_len are the total bit lengths of
 946         * the compressed block data, excluding the tree representations.
 947         */
 948
 949        /* Build the bit length tree for the above two trees, and get the index
 950         * in bl_order of the last bit length code to send.
 951         */
 952        max_blindex = build_bl_tree(s);
 953
 954        /* Determine the best encoding. Compute the block lengths in bytes. */
 955        opt_lenb = (s->opt_len+3+7)>>3;
 956        static_lenb = (s->static_len+3+7)>>3;
 957
 958        Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
 959                opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
 960                s->last_lit));
 961
 962        if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
 963
 964    } else {
 965        Assert(buf != (char*)0, "lost buf");
 966        opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
 967    }
 968
 969#ifdef FORCE_STORED
 970    if (buf != (char*)0) { /* force stored block */
 971#else
 972    if (stored_len+4 <= opt_lenb && buf != (char*)0) {
 973                       /* 4: two words for the lengths */
 974#endif
 975        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
 976         * Otherwise we can't have processed more than WSIZE input bytes since
 977         * the last block flush, because compression would have been
 978         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
 979         * transform a block into a stored block.
 980         */
 981        _tr_stored_block(s, buf, stored_len, eof);
 982
 983#ifdef FORCE_STATIC
 984    } else if (static_lenb >= 0) { /* force static trees */
 985#else
 986    } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
 987#endif
 988        send_bits(s, (STATIC_TREES<<1)+eof, 3);
 989        compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
 990#ifdef DEBUG
 991        s->compressed_len += 3 + s->static_len;
 992#endif
 993    } else {
 994        send_bits(s, (DYN_TREES<<1)+eof, 3);
 995        send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
 996                       max_blindex+1);
 997        compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
 998#ifdef DEBUG
 999        s->compressed_len += 3 + s->opt_len;
1000#endif
1001    }
1002    Assert (s->compressed_len == s->bits_sent, "bad compressed size");
1003    /* The above check is made mod 2^32, for files larger than 512 MB
1004     * and uLong implemented on 32 bits.
1005     */
1006    init_block(s);
1007
1008    if (eof) {
1009        bi_windup(s);
1010#ifdef DEBUG
1011        s->compressed_len += 7;  /* align on byte boundary */
1012#endif
1013    }
1014    Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1015           s->compressed_len-7*eof));
1016}
1017
1018/* ===========================================================================
1019 * Save the match info and tally the frequency counts. Return true if
1020 * the current block must be flushed.
1021 */
1022int _tr_tally (s, dist, lc)
1023    deflate_state *s;
1024    unsigned dist;  /* distance of matched string */
1025    unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
1026{
1027    s->d_buf[s->last_lit] = (ush)dist;
1028    s->l_buf[s->last_lit++] = (uch)lc;
1029    if (dist == 0) {
1030        /* lc is the unmatched char */
1031        s->dyn_ltree[lc].Freq++;
1032    } else {
1033        s->matches++;
1034        /* Here, lc is the match length - MIN_MATCH */
1035        dist--;             /* dist = match distance - 1 */
1036        Assert((ush)dist < (ush)MAX_DIST(s) &&
1037               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1038               (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
1039
1040        s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1041        s->dyn_dtree[d_code(dist)].Freq++;
1042    }
1043
1044#ifdef TRUNCATE_BLOCK
1045    /* Try to guess if it is profitable to stop the current block here */
1046    if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1047        /* Compute an upper bound for the compressed length */
1048        ulg out_length = (ulg)s->last_lit*8L;
1049        ulg in_length = (ulg)((long)s->strstart - s->block_start);
1050        int dcode;
1051        for (dcode = 0; dcode < D_CODES; dcode++) {
1052            out_length += (ulg)s->dyn_dtree[dcode].Freq *
1053                (5L+extra_dbits[dcode]);
1054        }
1055        out_length >>= 3;
1056        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1057               s->last_lit, in_length, out_length,
1058               100L - out_length*100L/in_length));
1059        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1060    }
1061#endif
1062    return (s->last_lit == s->lit_bufsize-1);
1063    /* We avoid equality with lit_bufsize because of wraparound at 64K
1064     * on 16 bit machines and because stored blocks are restricted to
1065     * 64K-1 bytes.
1066     */
1067}
1068
1069/* ===========================================================================
1070 * Send the block data compressed using the given Huffman trees
1071 */
1072local void compress_block(s, ltree, dtree)
1073    deflate_state *s;
1074    ct_data *ltree; /* literal tree */
1075    ct_data *dtree; /* distance tree */
1076{
1077    unsigned dist;      /* distance of matched string */
1078    int lc;             /* match length or unmatched char (if dist == 0) */
1079    unsigned lx = 0;    /* running index in l_buf */
1080    unsigned code;      /* the code to send */
1081    int extra;          /* number of extra bits to send */
1082
1083    if (s->last_lit != 0) do {
1084        dist = s->d_buf[lx];
1085        lc = s->l_buf[lx++];
1086        if (dist == 0) {
1087            send_code(s, lc, ltree); /* send a literal byte */
1088            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1089        } else {
1090            /* Here, lc is the match length - MIN_MATCH */
1091            code = _length_code[lc];
1092            send_code(s, code+LITERALS+1, ltree); /* send the length code */
1093            extra = extra_lbits[code];
1094            if (extra != 0) {
1095                lc -= base_length[code];
1096                send_bits(s, lc, extra);       /* send the extra length bits */
1097            }
1098            dist--; /* dist is now the match distance - 1 */
1099            code = d_code(dist);
1100            Assert (code < D_CODES, "bad d_code");
1101
1102            send_code(s, code, dtree);       /* send the distance code */
1103            extra = extra_dbits[code];
1104            if (extra != 0) {
1105                dist -= base_dist[code];
1106                send_bits(s, dist, extra);   /* send the extra distance bits */
1107            }
1108        } /* literal or match pair ? */
1109
1110        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1111        Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
1112               "pendingBuf overflow");
1113
1114    } while (lx < s->last_lit);
1115
1116    send_code(s, END_BLOCK, ltree);
1117    s->last_eob_len = ltree[END_BLOCK].Len;
1118}
1119
1120/* ===========================================================================
1121 * Set the data type to BINARY or TEXT, using a crude approximation:
1122 * set it to Z_TEXT if all symbols are either printable characters (33 to 255)
1123 * or white spaces (9 to 13, or 32); or set it to Z_BINARY otherwise.
1124 * IN assertion: the fields Freq of dyn_ltree are set.
1125 */
1126local void set_data_type(s)
1127    deflate_state *s;
1128{
1129    int n;
1130
1131    for (n = 0; n < 9; n++)
1132        if (s->dyn_ltree[n].Freq != 0)
1133            break;
1134    if (n == 9)
1135        for (n = 14; n < 32; n++)
1136            if (s->dyn_ltree[n].Freq != 0)
1137                break;
1138    s->strm->data_type = (n == 32) ? Z_TEXT : Z_BINARY;
1139}
1140
1141/* ===========================================================================
1142 * Reverse the first len bits of a code, using straightforward code (a faster
1143 * method would use a table)
1144 * IN assertion: 1 <= len <= 15
1145 */
1146local unsigned bi_reverse(code, len)
1147    unsigned code; /* the value to invert */
1148    int len;       /* its bit length */
1149{
1150    register unsigned res = 0;
1151    do {
1152        res |= code & 1;
1153        code >>= 1, res <<= 1;
1154    } while (--len > 0);
1155    return res >> 1;
1156}
1157
1158/* ===========================================================================
1159 * Flush the bit buffer, keeping at most 7 bits in it.
1160 */
1161local void bi_flush(s)
1162    deflate_state *s;
1163{
1164    if (s->bi_valid == 16) {
1165        put_short(s, s->bi_buf);
1166        s->bi_buf = 0;
1167        s->bi_valid = 0;
1168    } else if (s->bi_valid >= 8) {
1169        put_byte(s, (Byte)s->bi_buf);
1170        s->bi_buf >>= 8;
1171        s->bi_valid -= 8;
1172    }
1173}
1174
1175/* ===========================================================================
1176 * Flush the bit buffer and align the output on a byte boundary
1177 */
1178local void bi_windup(s)
1179    deflate_state *s;
1180{
1181    if (s->bi_valid > 8) {
1182        put_short(s, s->bi_buf);
1183    } else if (s->bi_valid > 0) {
1184        put_byte(s, (Byte)s->bi_buf);
1185    }
1186    s->bi_buf = 0;
1187    s->bi_valid = 0;
1188#ifdef DEBUG
1189    s->bits_sent = (s->bits_sent+7) & ~7;
1190#endif
1191}
1192
1193/* ===========================================================================
1194 * Copy a stored block, storing first the length and its
1195 * one's complement if requested.
1196 */
1197local void copy_block(s, buf, len, header)
1198    deflate_state *s;
1199    charf    *buf;    /* the input data */
1200    unsigned len;     /* its length */
1201    int      header;  /* true if block header must be written */
1202{
1203    bi_windup(s);        /* align on byte boundary */
1204    s->last_eob_len = 8; /* enough lookahead for inflate */
1205
1206    if (header) {
1207        put_short(s, (ush)len);
1208        put_short(s, (ush)~len);
1209#ifdef DEBUG
1210        s->bits_sent += 2*16;
1211#endif
1212    }
1213#ifdef DEBUG
1214    s->bits_sent += (ulg)len<<3;
1215#endif
1216    while (len--) {
1217        put_byte(s, *buf++);
1218    }
1219}