PageRenderTime 105ms CodeModel.GetById 23ms app.highlight 71ms RepoModel.GetById 1ms app.codeStats 0ms

/src/FreeImage/Source/ZLib/trees.c

https://bitbucket.org/cabalistic/ogredeps/
C | 1224 lines | 760 code | 153 blank | 311 comment | 195 complexity | 89e7a6b1ee11f2a96a9c97b7ce28a4ce MD5 | raw file
   1/* trees.c -- output deflated data using Huffman coding
   2 * Copyright (C) 1995-2012 Jean-loup Gailly
   3 * detect_data_type() function provided freely by Cosmin Truta, 2006
   4 * For conditions of distribution and use, see copyright notice in zlib.h
   5 */
   6
   7/*
   8 *  ALGORITHM
   9 *
  10 *      The "deflation" process uses several Huffman trees. The more
  11 *      common source values are represented by shorter bit sequences.
  12 *
  13 *      Each code tree is stored in a compressed form which is itself
  14 * a Huffman encoding of the lengths of all the code strings (in
  15 * ascending order by source values).  The actual code strings are
  16 * reconstructed from the lengths in the inflate process, as described
  17 * in the deflate specification.
  18 *
  19 *  REFERENCES
  20 *
  21 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
  22 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
  23 *
  24 *      Storer, James A.
  25 *          Data Compression:  Methods and Theory, pp. 49-50.
  26 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
  27 *
  28 *      Sedgewick, R.
  29 *          Algorithms, p290.
  30 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
  31 */
  32
  33/* @(#) $Id: trees.c,v 1.8 2012/02/05 18:10:25 drolon Exp $ */
  34
  35/* #define GEN_TREES_H */
  36
  37#include "deflate.h"
  38
  39#ifdef DEBUG
  40#  include <ctype.h>
  41#endif
  42
  43/* ===========================================================================
  44 * Constants
  45 */
  46
  47#define MAX_BL_BITS 7
  48/* Bit length codes must not exceed MAX_BL_BITS bits */
  49
  50#define END_BLOCK 256
  51/* end of block literal code */
  52
  53#define REP_3_6      16
  54/* repeat previous bit length 3-6 times (2 bits of repeat count) */
  55
  56#define REPZ_3_10    17
  57/* repeat a zero length 3-10 times  (3 bits of repeat count) */
  58
  59#define REPZ_11_138  18
  60/* repeat a zero length 11-138 times  (7 bits of repeat count) */
  61
  62local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
  63   = {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};
  64
  65local const int extra_dbits[D_CODES] /* extra bits for each distance code */
  66   = {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};
  67
  68local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
  69   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
  70
  71local const uch bl_order[BL_CODES]
  72   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
  73/* The lengths of the bit length codes are sent in order of decreasing
  74 * probability, to avoid transmitting the lengths for unused bit length codes.
  75 */
  76
  77/* ===========================================================================
  78 * Local data. These are initialized only once.
  79 */
  80
  81#define DIST_CODE_LEN  512 /* see definition of array dist_code below */
  82
  83#if defined(GEN_TREES_H) || !defined(STDC)
  84/* non ANSI compilers may not accept trees.h */
  85
  86local ct_data static_ltree[L_CODES+2];
  87/* The static literal tree. Since the bit lengths are imposed, there is no
  88 * need for the L_CODES extra codes used during heap construction. However
  89 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
  90 * below).
  91 */
  92
  93local ct_data static_dtree[D_CODES];
  94/* The static distance tree. (Actually a trivial tree since all codes use
  95 * 5 bits.)
  96 */
  97
  98uch _dist_code[DIST_CODE_LEN];
  99/* Distance codes. The first 256 values correspond to the distances
 100 * 3 .. 258, the last 256 values correspond to the top 8 bits of
 101 * the 15 bit distances.
 102 */
 103
 104uch _length_code[MAX_MATCH-MIN_MATCH+1];
 105/* length code for each normalized match length (0 == MIN_MATCH) */
 106
 107local int base_length[LENGTH_CODES];
 108/* First normalized length for each code (0 = MIN_MATCH) */
 109
 110local int base_dist[D_CODES];
 111/* First normalized distance for each code (0 = distance of 1) */
 112
 113#else
 114#  include "trees.h"
 115#endif /* GEN_TREES_H */
 116
 117struct static_tree_desc_s {
 118    const ct_data *static_tree;  /* static tree or NULL */
 119    const intf *extra_bits;      /* extra bits for each code or NULL */
 120    int     extra_base;          /* base index for extra_bits */
 121    int     elems;               /* max number of elements in the tree */
 122    int     max_length;          /* max bit length for the codes */
 123};
 124
 125local static_tree_desc  static_l_desc =
 126{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
 127
 128local static_tree_desc  static_d_desc =
 129{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
 130
 131local static_tree_desc  static_bl_desc =
 132{(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
 133
 134/* ===========================================================================
 135 * Local (static) routines in this file.
 136 */
 137
 138local void tr_static_init OF((void));
 139local void init_block     OF((deflate_state *s));
 140local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
 141local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
 142local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
 143local void build_tree     OF((deflate_state *s, tree_desc *desc));
 144local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 145local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
 146local int  build_bl_tree  OF((deflate_state *s));
 147local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
 148                              int blcodes));
 149local void compress_block OF((deflate_state *s, ct_data *ltree,
 150                              ct_data *dtree));
 151local int  detect_data_type OF((deflate_state *s));
 152local unsigned bi_reverse OF((unsigned value, int length));
 153local void bi_windup      OF((deflate_state *s));
 154local void bi_flush       OF((deflate_state *s));
 155local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
 156                              int header));
 157
 158#ifdef GEN_TREES_H
 159local void gen_trees_header OF((void));
 160#endif
 161
 162#ifndef DEBUG
 163#  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
 164   /* Send a code of the given tree. c and tree must not have side effects */
 165
 166#else /* DEBUG */
 167#  define send_code(s, c, tree) \
 168     { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
 169       send_bits(s, tree[c].Code, tree[c].Len); }
 170#endif
 171
 172/* ===========================================================================
 173 * Output a short LSB first on the stream.
 174 * IN assertion: there is enough room in pendingBuf.
 175 */
 176#define put_short(s, w) { \
 177    put_byte(s, (uch)((w) & 0xff)); \
 178    put_byte(s, (uch)((ush)(w) >> 8)); \
 179}
 180
 181/* ===========================================================================
 182 * Send a value on a given number of bits.
 183 * IN assertion: length <= 16 and value fits in length bits.
 184 */
 185#ifdef DEBUG
 186local void send_bits      OF((deflate_state *s, int value, int length));
 187
 188local void send_bits(s, value, length)
 189    deflate_state *s;
 190    int value;  /* value to send */
 191    int length; /* number of bits */
 192{
 193    Tracevv((stderr," l %2d v %4x ", length, value));
 194    Assert(length > 0 && length <= 15, "invalid length");
 195    s->bits_sent += (ulg)length;
 196
 197    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
 198     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
 199     * unused bits in value.
 200     */
 201    if (s->bi_valid > (int)Buf_size - length) {
 202        s->bi_buf |= (ush)value << s->bi_valid;
 203        put_short(s, s->bi_buf);
 204        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
 205        s->bi_valid += length - Buf_size;
 206    } else {
 207        s->bi_buf |= (ush)value << s->bi_valid;
 208        s->bi_valid += length;
 209    }
 210}
 211#else /* !DEBUG */
 212
 213#define send_bits(s, value, length) \
 214{ int len = length;\
 215  if (s->bi_valid > (int)Buf_size - len) {\
 216    int val = value;\
 217    s->bi_buf |= (ush)val << s->bi_valid;\
 218    put_short(s, s->bi_buf);\
 219    s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
 220    s->bi_valid += len - Buf_size;\
 221  } else {\
 222    s->bi_buf |= (ush)(value) << s->bi_valid;\
 223    s->bi_valid += len;\
 224  }\
 225}
 226#endif /* DEBUG */
 227
 228
 229/* the arguments must not have side effects */
 230
 231/* ===========================================================================
 232 * Initialize the various 'constant' tables.
 233 */
 234local void tr_static_init()
 235{
 236#if defined(GEN_TREES_H) || !defined(STDC)
 237    static int static_init_done = 0;
 238    int n;        /* iterates over tree elements */
 239    int bits;     /* bit counter */
 240    int length;   /* length value */
 241    int code;     /* code value */
 242    int dist;     /* distance index */
 243    ush bl_count[MAX_BITS+1];
 244    /* number of codes at each bit length for an optimal tree */
 245
 246    if (static_init_done) return;
 247
 248    /* For some embedded targets, global variables are not initialized: */
 249#ifdef NO_INIT_GLOBAL_POINTERS
 250    static_l_desc.static_tree = static_ltree;
 251    static_l_desc.extra_bits = extra_lbits;
 252    static_d_desc.static_tree = static_dtree;
 253    static_d_desc.extra_bits = extra_dbits;
 254    static_bl_desc.extra_bits = extra_blbits;
 255#endif
 256
 257    /* Initialize the mapping length (0..255) -> length code (0..28) */
 258    length = 0;
 259    for (code = 0; code < LENGTH_CODES-1; code++) {
 260        base_length[code] = length;
 261        for (n = 0; n < (1<<extra_lbits[code]); n++) {
 262            _length_code[length++] = (uch)code;
 263        }
 264    }
 265    Assert (length == 256, "tr_static_init: length != 256");
 266    /* Note that the length 255 (match length 258) can be represented
 267     * in two different ways: code 284 + 5 bits or code 285, so we
 268     * overwrite length_code[255] to use the best encoding:
 269     */
 270    _length_code[length-1] = (uch)code;
 271
 272    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
 273    dist = 0;
 274    for (code = 0 ; code < 16; code++) {
 275        base_dist[code] = dist;
 276        for (n = 0; n < (1<<extra_dbits[code]); n++) {
 277            _dist_code[dist++] = (uch)code;
 278        }
 279    }
 280    Assert (dist == 256, "tr_static_init: dist != 256");
 281    dist >>= 7; /* from now on, all distances are divided by 128 */
 282    for ( ; code < D_CODES; code++) {
 283        base_dist[code] = dist << 7;
 284        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
 285            _dist_code[256 + dist++] = (uch)code;
 286        }
 287    }
 288    Assert (dist == 256, "tr_static_init: 256+dist != 512");
 289
 290    /* Construct the codes of the static literal tree */
 291    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
 292    n = 0;
 293    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
 294    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
 295    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
 296    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
 297    /* Codes 286 and 287 do not exist, but we must include them in the
 298     * tree construction to get a canonical Huffman tree (longest code
 299     * all ones)
 300     */
 301    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
 302
 303    /* The static distance tree is trivial: */
 304    for (n = 0; n < D_CODES; n++) {
 305        static_dtree[n].Len = 5;
 306        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
 307    }
 308    static_init_done = 1;
 309
 310#  ifdef GEN_TREES_H
 311    gen_trees_header();
 312#  endif
 313#endif /* defined(GEN_TREES_H) || !defined(STDC) */
 314}
 315
 316/* ===========================================================================
 317 * Genererate the file trees.h describing the static trees.
 318 */
 319#ifdef GEN_TREES_H
 320#  ifndef DEBUG
 321#    include <stdio.h>
 322#  endif
 323
 324#  define SEPARATOR(i, last, width) \
 325      ((i) == (last)? "\n};\n\n" :    \
 326       ((i) % (width) == (width)-1 ? ",\n" : ", "))
 327
 328void gen_trees_header()
 329{
 330    FILE *header = fopen("trees.h", "w");
 331    int i;
 332
 333    Assert (header != NULL, "Can't open trees.h");
 334    fprintf(header,
 335            "/* header created automatically with -DGEN_TREES_H */\n\n");
 336
 337    fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
 338    for (i = 0; i < L_CODES+2; i++) {
 339        fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
 340                static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
 341    }
 342
 343    fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
 344    for (i = 0; i < D_CODES; i++) {
 345        fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
 346                static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
 347    }
 348
 349    fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
 350    for (i = 0; i < DIST_CODE_LEN; i++) {
 351        fprintf(header, "%2u%s", _dist_code[i],
 352                SEPARATOR(i, DIST_CODE_LEN-1, 20));
 353    }
 354
 355    fprintf(header,
 356        "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
 357    for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
 358        fprintf(header, "%2u%s", _length_code[i],
 359                SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
 360    }
 361
 362    fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
 363    for (i = 0; i < LENGTH_CODES; i++) {
 364        fprintf(header, "%1u%s", base_length[i],
 365                SEPARATOR(i, LENGTH_CODES-1, 20));
 366    }
 367
 368    fprintf(header, "local const int base_dist[D_CODES] = {\n");
 369    for (i = 0; i < D_CODES; i++) {
 370        fprintf(header, "%5u%s", base_dist[i],
 371                SEPARATOR(i, D_CODES-1, 10));
 372    }
 373
 374    fclose(header);
 375}
 376#endif /* GEN_TREES_H */
 377
 378/* ===========================================================================
 379 * Initialize the tree data structures for a new zlib stream.
 380 */
 381void ZLIB_INTERNAL _tr_init(s)
 382    deflate_state *s;
 383{
 384    tr_static_init();
 385
 386    s->l_desc.dyn_tree = s->dyn_ltree;
 387    s->l_desc.stat_desc = &static_l_desc;
 388
 389    s->d_desc.dyn_tree = s->dyn_dtree;
 390    s->d_desc.stat_desc = &static_d_desc;
 391
 392    s->bl_desc.dyn_tree = s->bl_tree;
 393    s->bl_desc.stat_desc = &static_bl_desc;
 394
 395    s->bi_buf = 0;
 396    s->bi_valid = 0;
 397#ifdef DEBUG
 398    s->compressed_len = 0L;
 399    s->bits_sent = 0L;
 400#endif
 401
 402    /* Initialize the first block of the first file: */
 403    init_block(s);
 404}
 405
 406/* ===========================================================================
 407 * Initialize a new block.
 408 */
 409local void init_block(s)
 410    deflate_state *s;
 411{
 412    int n; /* iterates over tree elements */
 413
 414    /* Initialize the trees. */
 415    for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
 416    for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
 417    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
 418
 419    s->dyn_ltree[END_BLOCK].Freq = 1;
 420    s->opt_len = s->static_len = 0L;
 421    s->last_lit = s->matches = 0;
 422}
 423
 424#define SMALLEST 1
 425/* Index within the heap array of least frequent node in the Huffman tree */
 426
 427
 428/* ===========================================================================
 429 * Remove the smallest element from the heap and recreate the heap with
 430 * one less element. Updates heap and heap_len.
 431 */
 432#define pqremove(s, tree, top) \
 433{\
 434    top = s->heap[SMALLEST]; \
 435    s->heap[SMALLEST] = s->heap[s->heap_len--]; \
 436    pqdownheap(s, tree, SMALLEST); \
 437}
 438
 439/* ===========================================================================
 440 * Compares to subtrees, using the tree depth as tie breaker when
 441 * the subtrees have equal frequency. This minimizes the worst case length.
 442 */
 443#define smaller(tree, n, m, depth) \
 444   (tree[n].Freq < tree[m].Freq || \
 445   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
 446
 447/* ===========================================================================
 448 * Restore the heap property by moving down the tree starting at node k,
 449 * exchanging a node with the smallest of its two sons if necessary, stopping
 450 * when the heap property is re-established (each father smaller than its
 451 * two sons).
 452 */
 453local void pqdownheap(s, tree, k)
 454    deflate_state *s;
 455    ct_data *tree;  /* the tree to restore */
 456    int k;               /* node to move down */
 457{
 458    int v = s->heap[k];
 459    int j = k << 1;  /* left son of k */
 460    while (j <= s->heap_len) {
 461        /* Set j to the smallest of the two sons: */
 462        if (j < s->heap_len &&
 463            smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
 464            j++;
 465        }
 466        /* Exit if v is smaller than both sons */
 467        if (smaller(tree, v, s->heap[j], s->depth)) break;
 468
 469        /* Exchange v with the smallest son */
 470        s->heap[k] = s->heap[j];  k = j;
 471
 472        /* And continue down the tree, setting j to the left son of k */
 473        j <<= 1;
 474    }
 475    s->heap[k] = v;
 476}
 477
 478/* ===========================================================================
 479 * Compute the optimal bit lengths for a tree and update the total bit length
 480 * for the current block.
 481 * IN assertion: the fields freq and dad are set, heap[heap_max] and
 482 *    above are the tree nodes sorted by increasing frequency.
 483 * OUT assertions: the field len is set to the optimal bit length, the
 484 *     array bl_count contains the frequencies for each bit length.
 485 *     The length opt_len is updated; static_len is also updated if stree is
 486 *     not null.
 487 */
 488local void gen_bitlen(s, desc)
 489    deflate_state *s;
 490    tree_desc *desc;    /* the tree descriptor */
 491{
 492    ct_data *tree        = desc->dyn_tree;
 493    int max_code         = desc->max_code;
 494    const ct_data *stree = desc->stat_desc->static_tree;
 495    const intf *extra    = desc->stat_desc->extra_bits;
 496    int base             = desc->stat_desc->extra_base;
 497    int max_length       = desc->stat_desc->max_length;
 498    int h;              /* heap index */
 499    int n, m;           /* iterate over the tree elements */
 500    int bits;           /* bit length */
 501    int xbits;          /* extra bits */
 502    ush f;              /* frequency */
 503    int overflow = 0;   /* number of elements with bit length too large */
 504
 505    for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
 506
 507    /* In a first pass, compute the optimal bit lengths (which may
 508     * overflow in the case of the bit length tree).
 509     */
 510    tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
 511
 512    for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
 513        n = s->heap[h];
 514        bits = tree[tree[n].Dad].Len + 1;
 515        if (bits > max_length) bits = max_length, overflow++;
 516        tree[n].Len = (ush)bits;
 517        /* We overwrite tree[n].Dad which is no longer needed */
 518
 519        if (n > max_code) continue; /* not a leaf node */
 520
 521        s->bl_count[bits]++;
 522        xbits = 0;
 523        if (n >= base) xbits = extra[n-base];
 524        f = tree[n].Freq;
 525        s->opt_len += (ulg)f * (bits + xbits);
 526        if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
 527    }
 528    if (overflow == 0) return;
 529
 530    Trace((stderr,"\nbit length overflow\n"));
 531    /* This happens for example on obj2 and pic of the Calgary corpus */
 532
 533    /* Find the first bit length which could increase: */
 534    do {
 535        bits = max_length-1;
 536        while (s->bl_count[bits] == 0) bits--;
 537        s->bl_count[bits]--;      /* move one leaf down the tree */
 538        s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
 539        s->bl_count[max_length]--;
 540        /* The brother of the overflow item also moves one step up,
 541         * but this does not affect bl_count[max_length]
 542         */
 543        overflow -= 2;
 544    } while (overflow > 0);
 545
 546    /* Now recompute all bit lengths, scanning in increasing frequency.
 547     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
 548     * lengths instead of fixing only the wrong ones. This idea is taken
 549     * from 'ar' written by Haruhiko Okumura.)
 550     */
 551    for (bits = max_length; bits != 0; bits--) {
 552        n = s->bl_count[bits];
 553        while (n != 0) {
 554            m = s->heap[--h];
 555            if (m > max_code) continue;
 556            if ((unsigned) tree[m].Len != (unsigned) bits) {
 557                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
 558                s->opt_len += ((long)bits - (long)tree[m].Len)
 559                              *(long)tree[m].Freq;
 560                tree[m].Len = (ush)bits;
 561            }
 562            n--;
 563        }
 564    }
 565}
 566
 567/* ===========================================================================
 568 * Generate the codes for a given tree and bit counts (which need not be
 569 * optimal).
 570 * IN assertion: the array bl_count contains the bit length statistics for
 571 * the given tree and the field len is set for all tree elements.
 572 * OUT assertion: the field code is set for all tree elements of non
 573 *     zero code length.
 574 */
 575local void gen_codes (tree, max_code, bl_count)
 576    ct_data *tree;             /* the tree to decorate */
 577    int max_code;              /* largest code with non zero frequency */
 578    ushf *bl_count;            /* number of codes at each bit length */
 579{
 580    ush next_code[MAX_BITS+1]; /* next code value for each bit length */
 581    ush code = 0;              /* running code value */
 582    int bits;                  /* bit index */
 583    int n;                     /* code index */
 584
 585    /* The distribution counts are first used to generate the code values
 586     * without bit reversal.
 587     */
 588    for (bits = 1; bits <= MAX_BITS; bits++) {
 589        next_code[bits] = code = (code + bl_count[bits-1]) << 1;
 590    }
 591    /* Check that the bit counts in bl_count are consistent. The last code
 592     * must be all ones.
 593     */
 594    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
 595            "inconsistent bit counts");
 596    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
 597
 598    for (n = 0;  n <= max_code; n++) {
 599        int len = tree[n].Len;
 600        if (len == 0) continue;
 601        /* Now reverse the bits */
 602        tree[n].Code = bi_reverse(next_code[len]++, len);
 603
 604        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
 605             n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
 606    }
 607}
 608
 609/* ===========================================================================
 610 * Construct one Huffman tree and assigns the code bit strings and lengths.
 611 * Update the total bit length for the current block.
 612 * IN assertion: the field freq is set for all tree elements.
 613 * OUT assertions: the fields len and code are set to the optimal bit length
 614 *     and corresponding code. The length opt_len is updated; static_len is
 615 *     also updated if stree is not null. The field max_code is set.
 616 */
 617local void build_tree(s, desc)
 618    deflate_state *s;
 619    tree_desc *desc; /* the tree descriptor */
 620{
 621    ct_data *tree         = desc->dyn_tree;
 622    const ct_data *stree  = desc->stat_desc->static_tree;
 623    int elems             = desc->stat_desc->elems;
 624    int n, m;          /* iterate over heap elements */
 625    int max_code = -1; /* largest code with non zero frequency */
 626    int node;          /* new node being created */
 627
 628    /* Construct the initial heap, with least frequent element in
 629     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
 630     * heap[0] is not used.
 631     */
 632    s->heap_len = 0, s->heap_max = HEAP_SIZE;
 633
 634    for (n = 0; n < elems; n++) {
 635        if (tree[n].Freq != 0) {
 636            s->heap[++(s->heap_len)] = max_code = n;
 637            s->depth[n] = 0;
 638        } else {
 639            tree[n].Len = 0;
 640        }
 641    }
 642
 643    /* The pkzip format requires that at least one distance code exists,
 644     * and that at least one bit should be sent even if there is only one
 645     * possible code. So to avoid special checks later on we force at least
 646     * two codes of non zero frequency.
 647     */
 648    while (s->heap_len < 2) {
 649        node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
 650        tree[node].Freq = 1;
 651        s->depth[node] = 0;
 652        s->opt_len--; if (stree) s->static_len -= stree[node].Len;
 653        /* node is 0 or 1 so it does not have extra bits */
 654    }
 655    desc->max_code = max_code;
 656
 657    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
 658     * establish sub-heaps of increasing lengths:
 659     */
 660    for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
 661
 662    /* Construct the Huffman tree by repeatedly combining the least two
 663     * frequent nodes.
 664     */
 665    node = elems;              /* next internal node of the tree */
 666    do {
 667        pqremove(s, tree, n);  /* n = node of least frequency */
 668        m = s->heap[SMALLEST]; /* m = node of next least frequency */
 669
 670        s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
 671        s->heap[--(s->heap_max)] = m;
 672
 673        /* Create a new node father of n and m */
 674        tree[node].Freq = tree[n].Freq + tree[m].Freq;
 675        s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
 676                                s->depth[n] : s->depth[m]) + 1);
 677        tree[n].Dad = tree[m].Dad = (ush)node;
 678#ifdef DUMP_BL_TREE
 679        if (tree == s->bl_tree) {
 680            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
 681                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
 682        }
 683#endif
 684        /* and insert the new node in the heap */
 685        s->heap[SMALLEST] = node++;
 686        pqdownheap(s, tree, SMALLEST);
 687
 688    } while (s->heap_len >= 2);
 689
 690    s->heap[--(s->heap_max)] = s->heap[SMALLEST];
 691
 692    /* At this point, the fields freq and dad are set. We can now
 693     * generate the bit lengths.
 694     */
 695    gen_bitlen(s, (tree_desc *)desc);
 696
 697    /* The field len is now set, we can generate the bit codes */
 698    gen_codes ((ct_data *)tree, max_code, s->bl_count);
 699}
 700
 701/* ===========================================================================
 702 * Scan a literal or distance tree to determine the frequencies of the codes
 703 * in the bit length tree.
 704 */
 705local void scan_tree (s, tree, max_code)
 706    deflate_state *s;
 707    ct_data *tree;   /* the tree to be scanned */
 708    int max_code;    /* and its largest code of non zero frequency */
 709{
 710    int n;                     /* iterates over all tree elements */
 711    int prevlen = -1;          /* last emitted length */
 712    int curlen;                /* length of current code */
 713    int nextlen = tree[0].Len; /* length of next code */
 714    int count = 0;             /* repeat count of the current code */
 715    int max_count = 7;         /* max repeat count */
 716    int min_count = 4;         /* min repeat count */
 717
 718    if (nextlen == 0) max_count = 138, min_count = 3;
 719    tree[max_code+1].Len = (ush)0xffff; /* guard */
 720
 721    for (n = 0; n <= max_code; n++) {
 722        curlen = nextlen; nextlen = tree[n+1].Len;
 723        if (++count < max_count && curlen == nextlen) {
 724            continue;
 725        } else if (count < min_count) {
 726            s->bl_tree[curlen].Freq += count;
 727        } else if (curlen != 0) {
 728            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
 729            s->bl_tree[REP_3_6].Freq++;
 730        } else if (count <= 10) {
 731            s->bl_tree[REPZ_3_10].Freq++;
 732        } else {
 733            s->bl_tree[REPZ_11_138].Freq++;
 734        }
 735        count = 0; prevlen = curlen;
 736        if (nextlen == 0) {
 737            max_count = 138, min_count = 3;
 738        } else if (curlen == nextlen) {
 739            max_count = 6, min_count = 3;
 740        } else {
 741            max_count = 7, min_count = 4;
 742        }
 743    }
 744}
 745
 746/* ===========================================================================
 747 * Send a literal or distance tree in compressed form, using the codes in
 748 * bl_tree.
 749 */
 750local void send_tree (s, tree, max_code)
 751    deflate_state *s;
 752    ct_data *tree; /* the tree to be scanned */
 753    int max_code;       /* and its largest code of non zero frequency */
 754{
 755    int n;                     /* iterates over all tree elements */
 756    int prevlen = -1;          /* last emitted length */
 757    int curlen;                /* length of current code */
 758    int nextlen = tree[0].Len; /* length of next code */
 759    int count = 0;             /* repeat count of the current code */
 760    int max_count = 7;         /* max repeat count */
 761    int min_count = 4;         /* min repeat count */
 762
 763    /* tree[max_code+1].Len = -1; */  /* guard already set */
 764    if (nextlen == 0) max_count = 138, min_count = 3;
 765
 766    for (n = 0; n <= max_code; n++) {
 767        curlen = nextlen; nextlen = tree[n+1].Len;
 768        if (++count < max_count && curlen == nextlen) {
 769            continue;
 770        } else if (count < min_count) {
 771            do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
 772
 773        } else if (curlen != 0) {
 774            if (curlen != prevlen) {
 775                send_code(s, curlen, s->bl_tree); count--;
 776            }
 777            Assert(count >= 3 && count <= 6, " 3_6?");
 778            send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
 779
 780        } else if (count <= 10) {
 781            send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
 782
 783        } else {
 784            send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
 785        }
 786        count = 0; prevlen = curlen;
 787        if (nextlen == 0) {
 788            max_count = 138, min_count = 3;
 789        } else if (curlen == nextlen) {
 790            max_count = 6, min_count = 3;
 791        } else {
 792            max_count = 7, min_count = 4;
 793        }
 794    }
 795}
 796
 797/* ===========================================================================
 798 * Construct the Huffman tree for the bit lengths and return the index in
 799 * bl_order of the last bit length code to send.
 800 */
 801local int build_bl_tree(s)
 802    deflate_state *s;
 803{
 804    int max_blindex;  /* index of last bit length code of non zero freq */
 805
 806    /* Determine the bit length frequencies for literal and distance trees */
 807    scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
 808    scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
 809
 810    /* Build the bit length tree: */
 811    build_tree(s, (tree_desc *)(&(s->bl_desc)));
 812    /* opt_len now includes the length of the tree representations, except
 813     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
 814     */
 815
 816    /* Determine the number of bit length codes to send. The pkzip format
 817     * requires that at least 4 bit length codes be sent. (appnote.txt says
 818     * 3 but the actual value used is 4.)
 819     */
 820    for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
 821        if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
 822    }
 823    /* Update opt_len to include the bit length tree and counts */
 824    s->opt_len += 3*(max_blindex+1) + 5+5+4;
 825    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
 826            s->opt_len, s->static_len));
 827
 828    return max_blindex;
 829}
 830
 831/* ===========================================================================
 832 * Send the header for a block using dynamic Huffman trees: the counts, the
 833 * lengths of the bit length codes, the literal tree and the distance tree.
 834 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
 835 */
 836local void send_all_trees(s, lcodes, dcodes, blcodes)
 837    deflate_state *s;
 838    int lcodes, dcodes, blcodes; /* number of codes for each tree */
 839{
 840    int rank;                    /* index in bl_order */
 841
 842    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
 843    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
 844            "too many codes");
 845    Tracev((stderr, "\nbl counts: "));
 846    send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
 847    send_bits(s, dcodes-1,   5);
 848    send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
 849    for (rank = 0; rank < blcodes; rank++) {
 850        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
 851        send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
 852    }
 853    Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
 854
 855    send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
 856    Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
 857
 858    send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
 859    Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
 860}
 861
 862/* ===========================================================================
 863 * Send a stored block
 864 */
 865void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
 866    deflate_state *s;
 867    charf *buf;       /* input block */
 868    ulg stored_len;   /* length of input block */
 869    int last;         /* one if this is the last block for a file */
 870{
 871    send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
 872#ifdef DEBUG
 873    s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
 874    s->compressed_len += (stored_len + 4) << 3;
 875#endif
 876    copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
 877}
 878
 879/* ===========================================================================
 880 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
 881 */
 882void ZLIB_INTERNAL _tr_flush_bits(s)
 883    deflate_state *s;
 884{
 885    bi_flush(s);
 886}
 887
 888/* ===========================================================================
 889 * Send one empty static block to give enough lookahead for inflate.
 890 * This takes 10 bits, of which 7 may remain in the bit buffer.
 891 */
 892void ZLIB_INTERNAL _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}
 902
 903/* ===========================================================================
 904 * Determine the best encoding for the current block: dynamic trees, static
 905 * trees or store, and output the encoded block to the zip file.
 906 */
 907void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
 908    deflate_state *s;
 909    charf *buf;       /* input block, or NULL if too old */
 910    ulg stored_len;   /* length of input block */
 911    int last;         /* one if this is the last block for a file */
 912{
 913    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
 914    int max_blindex = 0;  /* index of last bit length code of non zero freq */
 915
 916    /* Build the Huffman trees unless a stored block is forced */
 917    if (s->level > 0) {
 918
 919        /* Check if the file is binary or text */
 920        if (s->strm->data_type == Z_UNKNOWN)
 921            s->strm->data_type = detect_data_type(s);
 922
 923        /* Construct the literal and distance trees */
 924        build_tree(s, (tree_desc *)(&(s->l_desc)));
 925        Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
 926                s->static_len));
 927
 928        build_tree(s, (tree_desc *)(&(s->d_desc)));
 929        Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
 930                s->static_len));
 931        /* At this point, opt_len and static_len are the total bit lengths of
 932         * the compressed block data, excluding the tree representations.
 933         */
 934
 935        /* Build the bit length tree for the above two trees, and get the index
 936         * in bl_order of the last bit length code to send.
 937         */
 938        max_blindex = build_bl_tree(s);
 939
 940        /* Determine the best encoding. Compute the block lengths in bytes. */
 941        opt_lenb = (s->opt_len+3+7)>>3;
 942        static_lenb = (s->static_len+3+7)>>3;
 943
 944        Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
 945                opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
 946                s->last_lit));
 947
 948        if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
 949
 950    } else {
 951        Assert(buf != (char*)0, "lost buf");
 952        opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
 953    }
 954
 955#ifdef FORCE_STORED
 956    if (buf != (char*)0) { /* force stored block */
 957#else
 958    if (stored_len+4 <= opt_lenb && buf != (char*)0) {
 959                       /* 4: two words for the lengths */
 960#endif
 961        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
 962         * Otherwise we can't have processed more than WSIZE input bytes since
 963         * the last block flush, because compression would have been
 964         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
 965         * transform a block into a stored block.
 966         */
 967        _tr_stored_block(s, buf, stored_len, last);
 968
 969#ifdef FORCE_STATIC
 970    } else if (static_lenb >= 0) { /* force static trees */
 971#else
 972    } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
 973#endif
 974        send_bits(s, (STATIC_TREES<<1)+last, 3);
 975        compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
 976#ifdef DEBUG
 977        s->compressed_len += 3 + s->static_len;
 978#endif
 979    } else {
 980        send_bits(s, (DYN_TREES<<1)+last, 3);
 981        send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
 982                       max_blindex+1);
 983        compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
 984#ifdef DEBUG
 985        s->compressed_len += 3 + s->opt_len;
 986#endif
 987    }
 988    Assert (s->compressed_len == s->bits_sent, "bad compressed size");
 989    /* The above check is made mod 2^32, for files larger than 512 MB
 990     * and uLong implemented on 32 bits.
 991     */
 992    init_block(s);
 993
 994    if (last) {
 995        bi_windup(s);
 996#ifdef DEBUG
 997        s->compressed_len += 7;  /* align on byte boundary */
 998#endif
 999    }
1000    Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
1001           s->compressed_len-7*last));
1002}
1003
1004/* ===========================================================================
1005 * Save the match info and tally the frequency counts. Return true if
1006 * the current block must be flushed.
1007 */
1008int ZLIB_INTERNAL _tr_tally (s, dist, lc)
1009    deflate_state *s;
1010    unsigned dist;  /* distance of matched string */
1011    unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
1012{
1013    s->d_buf[s->last_lit] = (ush)dist;
1014    s->l_buf[s->last_lit++] = (uch)lc;
1015    if (dist == 0) {
1016        /* lc is the unmatched char */
1017        s->dyn_ltree[lc].Freq++;
1018    } else {
1019        s->matches++;
1020        /* Here, lc is the match length - MIN_MATCH */
1021        dist--;             /* dist = match distance - 1 */
1022        Assert((ush)dist < (ush)MAX_DIST(s) &&
1023               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
1024               (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
1025
1026        s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
1027        s->dyn_dtree[d_code(dist)].Freq++;
1028    }
1029
1030#ifdef TRUNCATE_BLOCK
1031    /* Try to guess if it is profitable to stop the current block here */
1032    if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
1033        /* Compute an upper bound for the compressed length */
1034        ulg out_length = (ulg)s->last_lit*8L;
1035        ulg in_length = (ulg)((long)s->strstart - s->block_start);
1036        int dcode;
1037        for (dcode = 0; dcode < D_CODES; dcode++) {
1038            out_length += (ulg)s->dyn_dtree[dcode].Freq *
1039                (5L+extra_dbits[dcode]);
1040        }
1041        out_length >>= 3;
1042        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
1043               s->last_lit, in_length, out_length,
1044               100L - out_length*100L/in_length));
1045        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
1046    }
1047#endif
1048    return (s->last_lit == s->lit_bufsize-1);
1049    /* We avoid equality with lit_bufsize because of wraparound at 64K
1050     * on 16 bit machines and because stored blocks are restricted to
1051     * 64K-1 bytes.
1052     */
1053}
1054
1055/* ===========================================================================
1056 * Send the block data compressed using the given Huffman trees
1057 */
1058local void compress_block(s, ltree, dtree)
1059    deflate_state *s;
1060    ct_data *ltree; /* literal tree */
1061    ct_data *dtree; /* distance tree */
1062{
1063    unsigned dist;      /* distance of matched string */
1064    int lc;             /* match length or unmatched char (if dist == 0) */
1065    unsigned lx = 0;    /* running index in l_buf */
1066    unsigned code;      /* the code to send */
1067    int extra;          /* number of extra bits to send */
1068
1069    if (s->last_lit != 0) do {
1070        dist = s->d_buf[lx];
1071        lc = s->l_buf[lx++];
1072        if (dist == 0) {
1073            send_code(s, lc, ltree); /* send a literal byte */
1074            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1075        } else {
1076            /* Here, lc is the match length - MIN_MATCH */
1077            code = _length_code[lc];
1078            send_code(s, code+LITERALS+1, ltree); /* send the length code */
1079            extra = extra_lbits[code];
1080            if (extra != 0) {
1081                lc -= base_length[code];
1082                send_bits(s, lc, extra);       /* send the extra length bits */
1083            }
1084            dist--; /* dist is now the match distance - 1 */
1085            code = d_code(dist);
1086            Assert (code < D_CODES, "bad d_code");
1087
1088            send_code(s, code, dtree);       /* send the distance code */
1089            extra = extra_dbits[code];
1090            if (extra != 0) {
1091                dist -= base_dist[code];
1092                send_bits(s, dist, extra);   /* send the extra distance bits */
1093            }
1094        } /* literal or match pair ? */
1095
1096        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1097        Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
1098               "pendingBuf overflow");
1099
1100    } while (lx < s->last_lit);
1101
1102    send_code(s, END_BLOCK, ltree);
1103}
1104
1105/* ===========================================================================
1106 * Check if the data type is TEXT or BINARY, using the following algorithm:
1107 * - TEXT if the two conditions below are satisfied:
1108 *    a) There are no non-portable control characters belonging to the
1109 *       "black list" (0..6, 14..25, 28..31).
1110 *    b) There is at least one printable character belonging to the
1111 *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
1112 * - BINARY otherwise.
1113 * - The following partially-portable control characters form a
1114 *   "gray list" that is ignored in this detection algorithm:
1115 *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
1116 * IN assertion: the fields Freq of dyn_ltree are set.
1117 */
1118local int detect_data_type(s)
1119    deflate_state *s;
1120{
1121    /* black_mask is the bit mask of black-listed bytes
1122     * set bits 0..6, 14..25, and 28..31
1123     * 0xf3ffc07f = binary 11110011111111111100000001111111
1124     */
1125    unsigned long black_mask = 0xf3ffc07fUL;
1126    int n;
1127
1128    /* Check for non-textual ("black-listed") bytes. */
1129    for (n = 0; n <= 31; n++, black_mask >>= 1)
1130        if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
1131            return Z_BINARY;
1132
1133    /* Check for textual ("white-listed") bytes. */
1134    if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
1135            || s->dyn_ltree[13].Freq != 0)
1136        return Z_TEXT;
1137    for (n = 32; n < LITERALS; n++)
1138        if (s->dyn_ltree[n].Freq != 0)
1139            return Z_TEXT;
1140
1141    /* There are no "black-listed" or "white-listed" bytes:
1142     * this stream either is empty or has tolerated ("gray-listed") bytes only.
1143     */
1144    return Z_BINARY;
1145}
1146
1147/* ===========================================================================
1148 * Reverse the first len bits of a code, using straightforward code (a faster
1149 * method would use a table)
1150 * IN assertion: 1 <= len <= 15
1151 */
1152local unsigned bi_reverse(code, len)
1153    unsigned code; /* the value to invert */
1154    int len;       /* its bit length */
1155{
1156    register unsigned res = 0;
1157    do {
1158        res |= code & 1;
1159        code >>= 1, res <<= 1;
1160    } while (--len > 0);
1161    return res >> 1;
1162}
1163
1164/* ===========================================================================
1165 * Flush the bit buffer, keeping at most 7 bits in it.
1166 */
1167local void bi_flush(s)
1168    deflate_state *s;
1169{
1170    if (s->bi_valid == 16) {
1171        put_short(s, s->bi_buf);
1172        s->bi_buf = 0;
1173        s->bi_valid = 0;
1174    } else if (s->bi_valid >= 8) {
1175        put_byte(s, (Byte)s->bi_buf);
1176        s->bi_buf >>= 8;
1177        s->bi_valid -= 8;
1178    }
1179}
1180
1181/* ===========================================================================
1182 * Flush the bit buffer and align the output on a byte boundary
1183 */
1184local void bi_windup(s)
1185    deflate_state *s;
1186{
1187    if (s->bi_valid > 8) {
1188        put_short(s, s->bi_buf);
1189    } else if (s->bi_valid > 0) {
1190        put_byte(s, (Byte)s->bi_buf);
1191    }
1192    s->bi_buf = 0;
1193    s->bi_valid = 0;
1194#ifdef DEBUG
1195    s->bits_sent = (s->bits_sent+7) & ~7;
1196#endif
1197}
1198
1199/* ===========================================================================
1200 * Copy a stored block, storing first the length and its
1201 * one's complement if requested.
1202 */
1203local void copy_block(s, buf, len, header)
1204    deflate_state *s;
1205    charf    *buf;    /* the input data */
1206    unsigned len;     /* its length */
1207    int      header;  /* true if block header must be written */
1208{
1209    bi_windup(s);        /* align on byte boundary */
1210
1211    if (header) {
1212        put_short(s, (ush)len);
1213        put_short(s, (ush)~len);
1214#ifdef DEBUG
1215        s->bits_sent += 2*16;
1216#endif
1217    }
1218#ifdef DEBUG
1219    s->bits_sent += (ulg)len<<3;
1220#endif
1221    while (len--) {
1222        put_byte(s, *buf++);
1223    }
1224}