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