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/Modules/zlib/deflate.c

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   1/* deflate.c -- compress data using the deflation algorithm
   2 * Copyright (C) 1995-2005 Jean-loup Gailly.
   3 * For conditions of distribution and use, see copyright notice in zlib.h
   4 */
   5
   6/*
   7 *  ALGORITHM
   8 *
   9 *      The "deflation" process depends on being able to identify portions
  10 *      of the input text which are identical to earlier input (within a
  11 *      sliding window trailing behind the input currently being processed).
  12 *
  13 *      The most straightforward technique turns out to be the fastest for
  14 *      most input files: try all possible matches and select the longest.
  15 *      The key feature of this algorithm is that insertions into the string
  16 *      dictionary are very simple and thus fast, and deletions are avoided
  17 *      completely. Insertions are performed at each input character, whereas
  18 *      string matches are performed only when the previous match ends. So it
  19 *      is preferable to spend more time in matches to allow very fast string
  20 *      insertions and avoid deletions. The matching algorithm for small
  21 *      strings is inspired from that of Rabin & Karp. A brute force approach
  22 *      is used to find longer strings when a small match has been found.
  23 *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
  24 *      (by Leonid Broukhis).
  25 *         A previous version of this file used a more sophisticated algorithm
  26 *      (by Fiala and Greene) which is guaranteed to run in linear amortized
  27 *      time, but has a larger average cost, uses more memory and is patented.
  28 *      However the F&G algorithm may be faster for some highly redundant
  29 *      files if the parameter max_chain_length (described below) is too large.
  30 *
  31 *  ACKNOWLEDGEMENTS
  32 *
  33 *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
  34 *      I found it in 'freeze' written by Leonid Broukhis.
  35 *      Thanks to many people for bug reports and testing.
  36 *
  37 *  REFERENCES
  38 *
  39 *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
  40 *      Available in http://www.ietf.org/rfc/rfc1951.txt
  41 *
  42 *      A description of the Rabin and Karp algorithm is given in the book
  43 *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
  44 *
  45 *      Fiala,E.R., and Greene,D.H.
  46 *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
  47 *
  48 */
  49
  50/* @(#) $Id$ */
  51
  52#include "deflate.h"
  53
  54const char deflate_copyright[] =
  55   " deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly ";
  56/*
  57  If you use the zlib library in a product, an acknowledgment is welcome
  58  in the documentation of your product. If for some reason you cannot
  59  include such an acknowledgment, I would appreciate that you keep this
  60  copyright string in the executable of your product.
  61 */
  62
  63/* ===========================================================================
  64 *  Function prototypes.
  65 */
  66typedef enum {
  67    need_more,      /* block not completed, need more input or more output */
  68    block_done,     /* block flush performed */
  69    finish_started, /* finish started, need only more output at next deflate */
  70    finish_done     /* finish done, accept no more input or output */
  71} block_state;
  72
  73typedef block_state (*compress_func) OF((deflate_state *s, int flush));
  74/* Compression function. Returns the block state after the call. */
  75
  76local void fill_window    OF((deflate_state *s));
  77local block_state deflate_stored OF((deflate_state *s, int flush));
  78local block_state deflate_fast   OF((deflate_state *s, int flush));
  79#ifndef FASTEST
  80local block_state deflate_slow   OF((deflate_state *s, int flush));
  81#endif
  82local void lm_init        OF((deflate_state *s));
  83local void putShortMSB    OF((deflate_state *s, uInt b));
  84local void flush_pending  OF((z_streamp strm));
  85local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
  86#ifndef FASTEST
  87#ifdef ASMV
  88      void match_init OF((void)); /* asm code initialization */
  89      uInt longest_match  OF((deflate_state *s, IPos cur_match));
  90#else
  91local uInt longest_match  OF((deflate_state *s, IPos cur_match));
  92#endif
  93#endif
  94local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
  95
  96#ifdef DEBUG
  97local  void check_match OF((deflate_state *s, IPos start, IPos match,
  98                            int length));
  99#endif
 100
 101/* ===========================================================================
 102 * Local data
 103 */
 104
 105#define NIL 0
 106/* Tail of hash chains */
 107
 108#ifndef TOO_FAR
 109#  define TOO_FAR 4096
 110#endif
 111/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
 112
 113#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
 114/* Minimum amount of lookahead, except at the end of the input file.
 115 * See deflate.c for comments about the MIN_MATCH+1.
 116 */
 117
 118/* Values for max_lazy_match, good_match and max_chain_length, depending on
 119 * the desired pack level (0..9). The values given below have been tuned to
 120 * exclude worst case performance for pathological files. Better values may be
 121 * found for specific files.
 122 */
 123typedef struct config_s {
 124   ush good_length; /* reduce lazy search above this match length */
 125   ush max_lazy;    /* do not perform lazy search above this match length */
 126   ush nice_length; /* quit search above this match length */
 127   ush max_chain;
 128   compress_func func;
 129} config;
 130
 131#ifdef FASTEST
 132local const config configuration_table[2] = {
 133/*      good lazy nice chain */
 134/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
 135/* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */
 136#else
 137local const config configuration_table[10] = {
 138/*      good lazy nice chain */
 139/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
 140/* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
 141/* 2 */ {4,    5, 16,    8, deflate_fast},
 142/* 3 */ {4,    6, 32,   32, deflate_fast},
 143
 144/* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
 145/* 5 */ {8,   16, 32,   32, deflate_slow},
 146/* 6 */ {8,   16, 128, 128, deflate_slow},
 147/* 7 */ {8,   32, 128, 256, deflate_slow},
 148/* 8 */ {32, 128, 258, 1024, deflate_slow},
 149/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
 150#endif
 151
 152/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
 153 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
 154 * meaning.
 155 */
 156
 157#define EQUAL 0
 158/* result of memcmp for equal strings */
 159
 160#ifndef NO_DUMMY_DECL
 161struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
 162#endif
 163
 164/* ===========================================================================
 165 * Update a hash value with the given input byte
 166 * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
 167 *    input characters, so that a running hash key can be computed from the
 168 *    previous key instead of complete recalculation each time.
 169 */
 170#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
 171
 172
 173/* ===========================================================================
 174 * Insert string str in the dictionary and set match_head to the previous head
 175 * of the hash chain (the most recent string with same hash key). Return
 176 * the previous length of the hash chain.
 177 * If this file is compiled with -DFASTEST, the compression level is forced
 178 * to 1, and no hash chains are maintained.
 179 * IN  assertion: all calls to to INSERT_STRING are made with consecutive
 180 *    input characters and the first MIN_MATCH bytes of str are valid
 181 *    (except for the last MIN_MATCH-1 bytes of the input file).
 182 */
 183#ifdef FASTEST
 184#define INSERT_STRING(s, str, match_head) \
 185   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
 186    match_head = s->head[s->ins_h], \
 187    s->head[s->ins_h] = (Pos)(str))
 188#else
 189#define INSERT_STRING(s, str, match_head) \
 190   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
 191    match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
 192    s->head[s->ins_h] = (Pos)(str))
 193#endif
 194
 195/* ===========================================================================
 196 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
 197 * prev[] will be initialized on the fly.
 198 */
 199#define CLEAR_HASH(s) \
 200    s->head[s->hash_size-1] = NIL; \
 201    zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
 202
 203/* ========================================================================= */
 204int ZEXPORT deflateInit_(strm, level, version, stream_size)
 205    z_streamp strm;
 206    int level;
 207    const char *version;
 208    int stream_size;
 209{
 210    return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
 211                         Z_DEFAULT_STRATEGY, version, stream_size);
 212    /* To do: ignore strm->next_in if we use it as window */
 213}
 214
 215/* ========================================================================= */
 216int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
 217                  version, stream_size)
 218    z_streamp strm;
 219    int  level;
 220    int  method;
 221    int  windowBits;
 222    int  memLevel;
 223    int  strategy;
 224    const char *version;
 225    int stream_size;
 226{
 227    deflate_state *s;
 228    int wrap = 1;
 229    static const char my_version[] = ZLIB_VERSION;
 230
 231    ushf *overlay;
 232    /* We overlay pending_buf and d_buf+l_buf. This works since the average
 233     * output size for (length,distance) codes is <= 24 bits.
 234     */
 235
 236    if (version == Z_NULL || version[0] != my_version[0] ||
 237        stream_size != sizeof(z_stream)) {
 238        return Z_VERSION_ERROR;
 239    }
 240    if (strm == Z_NULL) return Z_STREAM_ERROR;
 241
 242    strm->msg = Z_NULL;
 243    if (strm->zalloc == (alloc_func)0) {
 244        strm->zalloc = zcalloc;
 245        strm->opaque = (voidpf)0;
 246    }
 247    if (strm->zfree == (free_func)0) strm->zfree = zcfree;
 248
 249#ifdef FASTEST
 250    if (level != 0) level = 1;
 251#else
 252    if (level == Z_DEFAULT_COMPRESSION) level = 6;
 253#endif
 254
 255    if (windowBits < 0) { /* suppress zlib wrapper */
 256        wrap = 0;
 257        windowBits = -windowBits;
 258    }
 259#ifdef GZIP
 260    else if (windowBits > 15) {
 261        wrap = 2;       /* write gzip wrapper instead */
 262        windowBits -= 16;
 263    }
 264#endif
 265    if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
 266        windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
 267        strategy < 0 || strategy > Z_FIXED) {
 268        return Z_STREAM_ERROR;
 269    }
 270    if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
 271    s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
 272    if (s == Z_NULL) return Z_MEM_ERROR;
 273    strm->state = (struct internal_state FAR *)s;
 274    s->strm = strm;
 275
 276    s->wrap = wrap;
 277    s->gzhead = Z_NULL;
 278    s->w_bits = windowBits;
 279    s->w_size = 1 << s->w_bits;
 280    s->w_mask = s->w_size - 1;
 281
 282    s->hash_bits = memLevel + 7;
 283    s->hash_size = 1 << s->hash_bits;
 284    s->hash_mask = s->hash_size - 1;
 285    s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
 286
 287    s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
 288    s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
 289    s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
 290
 291    s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
 292
 293    overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
 294    s->pending_buf = (uchf *) overlay;
 295    s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
 296
 297    if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
 298        s->pending_buf == Z_NULL) {
 299        s->status = FINISH_STATE;
 300        strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
 301        deflateEnd (strm);
 302        return Z_MEM_ERROR;
 303    }
 304    s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
 305    s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
 306
 307    s->level = level;
 308    s->strategy = strategy;
 309    s->method = (Byte)method;
 310
 311    return deflateReset(strm);
 312}
 313
 314/* ========================================================================= */
 315int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
 316    z_streamp strm;
 317    const Bytef *dictionary;
 318    uInt  dictLength;
 319{
 320    deflate_state *s;
 321    uInt length = dictLength;
 322    uInt n;
 323    IPos hash_head = 0;
 324
 325    if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
 326        strm->state->wrap == 2 ||
 327        (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
 328        return Z_STREAM_ERROR;
 329
 330    s = strm->state;
 331    if (s->wrap)
 332        strm->adler = adler32(strm->adler, dictionary, dictLength);
 333
 334    if (length < MIN_MATCH) return Z_OK;
 335    if (length > MAX_DIST(s)) {
 336        length = MAX_DIST(s);
 337        dictionary += dictLength - length; /* use the tail of the dictionary */
 338    }
 339    zmemcpy(s->window, dictionary, length);
 340    s->strstart = length;
 341    s->block_start = (long)length;
 342
 343    /* Insert all strings in the hash table (except for the last two bytes).
 344     * s->lookahead stays null, so s->ins_h will be recomputed at the next
 345     * call of fill_window.
 346     */
 347    s->ins_h = s->window[0];
 348    UPDATE_HASH(s, s->ins_h, s->window[1]);
 349    for (n = 0; n <= length - MIN_MATCH; n++) {
 350        INSERT_STRING(s, n, hash_head);
 351    }
 352    if (hash_head) hash_head = 0;  /* to make compiler happy */
 353    return Z_OK;
 354}
 355
 356/* ========================================================================= */
 357int ZEXPORT deflateReset (strm)
 358    z_streamp strm;
 359{
 360    deflate_state *s;
 361
 362    if (strm == Z_NULL || strm->state == Z_NULL ||
 363        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
 364        return Z_STREAM_ERROR;
 365    }
 366
 367    strm->total_in = strm->total_out = 0;
 368    strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
 369    strm->data_type = Z_UNKNOWN;
 370
 371    s = (deflate_state *)strm->state;
 372    s->pending = 0;
 373    s->pending_out = s->pending_buf;
 374
 375    if (s->wrap < 0) {
 376        s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
 377    }
 378    s->status = s->wrap ? INIT_STATE : BUSY_STATE;
 379    strm->adler =
 380#ifdef GZIP
 381        s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
 382#endif
 383        adler32(0L, Z_NULL, 0);
 384    s->last_flush = Z_NO_FLUSH;
 385
 386    _tr_init(s);
 387    lm_init(s);
 388
 389    return Z_OK;
 390}
 391
 392/* ========================================================================= */
 393int ZEXPORT deflateSetHeader (strm, head)
 394    z_streamp strm;
 395    gz_headerp head;
 396{
 397    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
 398    if (strm->state->wrap != 2) return Z_STREAM_ERROR;
 399    strm->state->gzhead = head;
 400    return Z_OK;
 401}
 402
 403/* ========================================================================= */
 404int ZEXPORT deflatePrime (strm, bits, value)
 405    z_streamp strm;
 406    int bits;
 407    int value;
 408{
 409    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
 410    strm->state->bi_valid = bits;
 411    strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
 412    return Z_OK;
 413}
 414
 415/* ========================================================================= */
 416int ZEXPORT deflateParams(strm, level, strategy)
 417    z_streamp strm;
 418    int level;
 419    int strategy;
 420{
 421    deflate_state *s;
 422    compress_func func;
 423    int err = Z_OK;
 424
 425    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
 426    s = strm->state;
 427
 428#ifdef FASTEST
 429    if (level != 0) level = 1;
 430#else
 431    if (level == Z_DEFAULT_COMPRESSION) level = 6;
 432#endif
 433    if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
 434        return Z_STREAM_ERROR;
 435    }
 436    func = configuration_table[s->level].func;
 437
 438    if (func != configuration_table[level].func && strm->total_in != 0) {
 439        /* Flush the last buffer: */
 440        err = deflate(strm, Z_PARTIAL_FLUSH);
 441    }
 442    if (s->level != level) {
 443        s->level = level;
 444        s->max_lazy_match   = configuration_table[level].max_lazy;
 445        s->good_match       = configuration_table[level].good_length;
 446        s->nice_match       = configuration_table[level].nice_length;
 447        s->max_chain_length = configuration_table[level].max_chain;
 448    }
 449    s->strategy = strategy;
 450    return err;
 451}
 452
 453/* ========================================================================= */
 454int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
 455    z_streamp strm;
 456    int good_length;
 457    int max_lazy;
 458    int nice_length;
 459    int max_chain;
 460{
 461    deflate_state *s;
 462
 463    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
 464    s = strm->state;
 465    s->good_match = good_length;
 466    s->max_lazy_match = max_lazy;
 467    s->nice_match = nice_length;
 468    s->max_chain_length = max_chain;
 469    return Z_OK;
 470}
 471
 472/* =========================================================================
 473 * For the default windowBits of 15 and memLevel of 8, this function returns
 474 * a close to exact, as well as small, upper bound on the compressed size.
 475 * They are coded as constants here for a reason--if the #define's are
 476 * changed, then this function needs to be changed as well.  The return
 477 * value for 15 and 8 only works for those exact settings.
 478 *
 479 * For any setting other than those defaults for windowBits and memLevel,
 480 * the value returned is a conservative worst case for the maximum expansion
 481 * resulting from using fixed blocks instead of stored blocks, which deflate
 482 * can emit on compressed data for some combinations of the parameters.
 483 *
 484 * This function could be more sophisticated to provide closer upper bounds
 485 * for every combination of windowBits and memLevel, as well as wrap.
 486 * But even the conservative upper bound of about 14% expansion does not
 487 * seem onerous for output buffer allocation.
 488 */
 489uLong ZEXPORT deflateBound(strm, sourceLen)
 490    z_streamp strm;
 491    uLong sourceLen;
 492{
 493    deflate_state *s;
 494    uLong destLen;
 495
 496    /* conservative upper bound */
 497    destLen = sourceLen +
 498              ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
 499
 500    /* if can't get parameters, return conservative bound */
 501    if (strm == Z_NULL || strm->state == Z_NULL)
 502        return destLen;
 503
 504    /* if not default parameters, return conservative bound */
 505    s = strm->state;
 506    if (s->w_bits != 15 || s->hash_bits != 8 + 7)
 507        return destLen;
 508
 509    /* default settings: return tight bound for that case */
 510    return compressBound(sourceLen);
 511}
 512
 513/* =========================================================================
 514 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
 515 * IN assertion: the stream state is correct and there is enough room in
 516 * pending_buf.
 517 */
 518local void putShortMSB (s, b)
 519    deflate_state *s;
 520    uInt b;
 521{
 522    put_byte(s, (Byte)(b >> 8));
 523    put_byte(s, (Byte)(b & 0xff));
 524}
 525
 526/* =========================================================================
 527 * Flush as much pending output as possible. All deflate() output goes
 528 * through this function so some applications may wish to modify it
 529 * to avoid allocating a large strm->next_out buffer and copying into it.
 530 * (See also read_buf()).
 531 */
 532local void flush_pending(strm)
 533    z_streamp strm;
 534{
 535    unsigned len = strm->state->pending;
 536
 537    if (len > strm->avail_out) len = strm->avail_out;
 538    if (len == 0) return;
 539
 540    zmemcpy(strm->next_out, strm->state->pending_out, len);
 541    strm->next_out  += len;
 542    strm->state->pending_out  += len;
 543    strm->total_out += len;
 544    strm->avail_out  -= len;
 545    strm->state->pending -= len;
 546    if (strm->state->pending == 0) {
 547        strm->state->pending_out = strm->state->pending_buf;
 548    }
 549}
 550
 551/* ========================================================================= */
 552int ZEXPORT deflate (strm, flush)
 553    z_streamp strm;
 554    int flush;
 555{
 556    int old_flush; /* value of flush param for previous deflate call */
 557    deflate_state *s;
 558
 559    if (strm == Z_NULL || strm->state == Z_NULL ||
 560        flush > Z_FINISH || flush < 0) {
 561        return Z_STREAM_ERROR;
 562    }
 563    s = strm->state;
 564
 565    if (strm->next_out == Z_NULL ||
 566        (strm->next_in == Z_NULL && strm->avail_in != 0) ||
 567        (s->status == FINISH_STATE && flush != Z_FINISH)) {
 568        ERR_RETURN(strm, Z_STREAM_ERROR);
 569    }
 570    if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
 571
 572    s->strm = strm; /* just in case */
 573    old_flush = s->last_flush;
 574    s->last_flush = flush;
 575
 576    /* Write the header */
 577    if (s->status == INIT_STATE) {
 578#ifdef GZIP
 579        if (s->wrap == 2) {
 580            strm->adler = crc32(0L, Z_NULL, 0);
 581            put_byte(s, 31);
 582            put_byte(s, 139);
 583            put_byte(s, 8);
 584            if (s->gzhead == NULL) {
 585                put_byte(s, 0);
 586                put_byte(s, 0);
 587                put_byte(s, 0);
 588                put_byte(s, 0);
 589                put_byte(s, 0);
 590                put_byte(s, s->level == 9 ? 2 :
 591                            (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
 592                             4 : 0));
 593                put_byte(s, OS_CODE);
 594                s->status = BUSY_STATE;
 595            }
 596            else {
 597                put_byte(s, (s->gzhead->text ? 1 : 0) +
 598                            (s->gzhead->hcrc ? 2 : 0) +
 599                            (s->gzhead->extra == Z_NULL ? 0 : 4) +
 600                            (s->gzhead->name == Z_NULL ? 0 : 8) +
 601                            (s->gzhead->comment == Z_NULL ? 0 : 16)
 602                        );
 603                put_byte(s, (Byte)(s->gzhead->time & 0xff));
 604                put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
 605                put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
 606                put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
 607                put_byte(s, s->level == 9 ? 2 :
 608                            (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
 609                             4 : 0));
 610                put_byte(s, s->gzhead->os & 0xff);
 611                if (s->gzhead->extra != NULL) {
 612                    put_byte(s, s->gzhead->extra_len & 0xff);
 613                    put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
 614                }
 615                if (s->gzhead->hcrc)
 616                    strm->adler = crc32(strm->adler, s->pending_buf,
 617                                        s->pending);
 618                s->gzindex = 0;
 619                s->status = EXTRA_STATE;
 620            }
 621        }
 622        else
 623#endif
 624        {
 625            uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
 626            uInt level_flags;
 627
 628            if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
 629                level_flags = 0;
 630            else if (s->level < 6)
 631                level_flags = 1;
 632            else if (s->level == 6)
 633                level_flags = 2;
 634            else
 635                level_flags = 3;
 636            header |= (level_flags << 6);
 637            if (s->strstart != 0) header |= PRESET_DICT;
 638            header += 31 - (header % 31);
 639
 640            s->status = BUSY_STATE;
 641            putShortMSB(s, header);
 642
 643            /* Save the adler32 of the preset dictionary: */
 644            if (s->strstart != 0) {
 645                putShortMSB(s, (uInt)(strm->adler >> 16));
 646                putShortMSB(s, (uInt)(strm->adler & 0xffff));
 647            }
 648            strm->adler = adler32(0L, Z_NULL, 0);
 649        }
 650    }
 651#ifdef GZIP
 652    if (s->status == EXTRA_STATE) {
 653        if (s->gzhead->extra != NULL) {
 654            uInt beg = s->pending;  /* start of bytes to update crc */
 655
 656            while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
 657                if (s->pending == s->pending_buf_size) {
 658                    if (s->gzhead->hcrc && s->pending > beg)
 659                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
 660                                            s->pending - beg);
 661                    flush_pending(strm);
 662                    beg = s->pending;
 663                    if (s->pending == s->pending_buf_size)
 664                        break;
 665                }
 666                put_byte(s, s->gzhead->extra[s->gzindex]);
 667                s->gzindex++;
 668            }
 669            if (s->gzhead->hcrc && s->pending > beg)
 670                strm->adler = crc32(strm->adler, s->pending_buf + beg,
 671                                    s->pending - beg);
 672            if (s->gzindex == s->gzhead->extra_len) {
 673                s->gzindex = 0;
 674                s->status = NAME_STATE;
 675            }
 676        }
 677        else
 678            s->status = NAME_STATE;
 679    }
 680    if (s->status == NAME_STATE) {
 681        if (s->gzhead->name != NULL) {
 682            uInt beg = s->pending;  /* start of bytes to update crc */
 683            int val;
 684
 685            do {
 686                if (s->pending == s->pending_buf_size) {
 687                    if (s->gzhead->hcrc && s->pending > beg)
 688                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
 689                                            s->pending - beg);
 690                    flush_pending(strm);
 691                    beg = s->pending;
 692                    if (s->pending == s->pending_buf_size) {
 693                        val = 1;
 694                        break;
 695                    }
 696                }
 697                val = s->gzhead->name[s->gzindex++];
 698                put_byte(s, val);
 699            } while (val != 0);
 700            if (s->gzhead->hcrc && s->pending > beg)
 701                strm->adler = crc32(strm->adler, s->pending_buf + beg,
 702                                    s->pending - beg);
 703            if (val == 0) {
 704                s->gzindex = 0;
 705                s->status = COMMENT_STATE;
 706            }
 707        }
 708        else
 709            s->status = COMMENT_STATE;
 710    }
 711    if (s->status == COMMENT_STATE) {
 712        if (s->gzhead->comment != NULL) {
 713            uInt beg = s->pending;  /* start of bytes to update crc */
 714            int val;
 715
 716            do {
 717                if (s->pending == s->pending_buf_size) {
 718                    if (s->gzhead->hcrc && s->pending > beg)
 719                        strm->adler = crc32(strm->adler, s->pending_buf + beg,
 720                                            s->pending - beg);
 721                    flush_pending(strm);
 722                    beg = s->pending;
 723                    if (s->pending == s->pending_buf_size) {
 724                        val = 1;
 725                        break;
 726                    }
 727                }
 728                val = s->gzhead->comment[s->gzindex++];
 729                put_byte(s, val);
 730            } while (val != 0);
 731            if (s->gzhead->hcrc && s->pending > beg)
 732                strm->adler = crc32(strm->adler, s->pending_buf + beg,
 733                                    s->pending - beg);
 734            if (val == 0)
 735                s->status = HCRC_STATE;
 736        }
 737        else
 738            s->status = HCRC_STATE;
 739    }
 740    if (s->status == HCRC_STATE) {
 741        if (s->gzhead->hcrc) {
 742            if (s->pending + 2 > s->pending_buf_size)
 743                flush_pending(strm);
 744            if (s->pending + 2 <= s->pending_buf_size) {
 745                put_byte(s, (Byte)(strm->adler & 0xff));
 746                put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
 747                strm->adler = crc32(0L, Z_NULL, 0);
 748                s->status = BUSY_STATE;
 749            }
 750        }
 751        else
 752            s->status = BUSY_STATE;
 753    }
 754#endif
 755
 756    /* Flush as much pending output as possible */
 757    if (s->pending != 0) {
 758        flush_pending(strm);
 759        if (strm->avail_out == 0) {
 760            /* Since avail_out is 0, deflate will be called again with
 761             * more output space, but possibly with both pending and
 762             * avail_in equal to zero. There won't be anything to do,
 763             * but this is not an error situation so make sure we
 764             * return OK instead of BUF_ERROR at next call of deflate:
 765             */
 766            s->last_flush = -1;
 767            return Z_OK;
 768        }
 769
 770    /* Make sure there is something to do and avoid duplicate consecutive
 771     * flushes. For repeated and useless calls with Z_FINISH, we keep
 772     * returning Z_STREAM_END instead of Z_BUF_ERROR.
 773     */
 774    } else if (strm->avail_in == 0 && flush <= old_flush &&
 775               flush != Z_FINISH) {
 776        ERR_RETURN(strm, Z_BUF_ERROR);
 777    }
 778
 779    /* User must not provide more input after the first FINISH: */
 780    if (s->status == FINISH_STATE && strm->avail_in != 0) {
 781        ERR_RETURN(strm, Z_BUF_ERROR);
 782    }
 783
 784    /* Start a new block or continue the current one.
 785     */
 786    if (strm->avail_in != 0 || s->lookahead != 0 ||
 787        (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
 788        block_state bstate;
 789
 790        bstate = (*(configuration_table[s->level].func))(s, flush);
 791
 792        if (bstate == finish_started || bstate == finish_done) {
 793            s->status = FINISH_STATE;
 794        }
 795        if (bstate == need_more || bstate == finish_started) {
 796            if (strm->avail_out == 0) {
 797                s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
 798            }
 799            return Z_OK;
 800            /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
 801             * of deflate should use the same flush parameter to make sure
 802             * that the flush is complete. So we don't have to output an
 803             * empty block here, this will be done at next call. This also
 804             * ensures that for a very small output buffer, we emit at most
 805             * one empty block.
 806             */
 807        }
 808        if (bstate == block_done) {
 809            if (flush == Z_PARTIAL_FLUSH) {
 810                _tr_align(s);
 811            } else { /* FULL_FLUSH or SYNC_FLUSH */
 812                _tr_stored_block(s, (char*)0, 0L, 0);
 813                /* For a full flush, this empty block will be recognized
 814                 * as a special marker by inflate_sync().
 815                 */
 816                if (flush == Z_FULL_FLUSH) {
 817                    CLEAR_HASH(s);             /* forget history */
 818                }
 819            }
 820            flush_pending(strm);
 821            if (strm->avail_out == 0) {
 822              s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
 823              return Z_OK;
 824            }
 825        }
 826    }
 827    Assert(strm->avail_out > 0, "bug2");
 828
 829    if (flush != Z_FINISH) return Z_OK;
 830    if (s->wrap <= 0) return Z_STREAM_END;
 831
 832    /* Write the trailer */
 833#ifdef GZIP
 834    if (s->wrap == 2) {
 835        put_byte(s, (Byte)(strm->adler & 0xff));
 836        put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
 837        put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
 838        put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
 839        put_byte(s, (Byte)(strm->total_in & 0xff));
 840        put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
 841        put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
 842        put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
 843    }
 844    else
 845#endif
 846    {
 847        putShortMSB(s, (uInt)(strm->adler >> 16));
 848        putShortMSB(s, (uInt)(strm->adler & 0xffff));
 849    }
 850    flush_pending(strm);
 851    /* If avail_out is zero, the application will call deflate again
 852     * to flush the rest.
 853     */
 854    if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
 855    return s->pending != 0 ? Z_OK : Z_STREAM_END;
 856}
 857
 858/* ========================================================================= */
 859int ZEXPORT deflateEnd (strm)
 860    z_streamp strm;
 861{
 862    int status;
 863
 864    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
 865
 866    status = strm->state->status;
 867    if (status != INIT_STATE &&
 868        status != EXTRA_STATE &&
 869        status != NAME_STATE &&
 870        status != COMMENT_STATE &&
 871        status != HCRC_STATE &&
 872        status != BUSY_STATE &&
 873        status != FINISH_STATE) {
 874      return Z_STREAM_ERROR;
 875    }
 876
 877    /* Deallocate in reverse order of allocations: */
 878    TRY_FREE(strm, strm->state->pending_buf);
 879    TRY_FREE(strm, strm->state->head);
 880    TRY_FREE(strm, strm->state->prev);
 881    TRY_FREE(strm, strm->state->window);
 882
 883    ZFREE(strm, strm->state);
 884    strm->state = Z_NULL;
 885
 886    return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
 887}
 888
 889/* =========================================================================
 890 * Copy the source state to the destination state.
 891 * To simplify the source, this is not supported for 16-bit MSDOS (which
 892 * doesn't have enough memory anyway to duplicate compression states).
 893 */
 894int ZEXPORT deflateCopy (dest, source)
 895    z_streamp dest;
 896    z_streamp source;
 897{
 898#ifdef MAXSEG_64K
 899    return Z_STREAM_ERROR;
 900#else
 901    deflate_state *ds;
 902    deflate_state *ss;
 903    ushf *overlay;
 904
 905
 906    if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
 907        return Z_STREAM_ERROR;
 908    }
 909
 910    ss = source->state;
 911
 912    zmemcpy(dest, source, sizeof(z_stream));
 913
 914    ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
 915    if (ds == Z_NULL) return Z_MEM_ERROR;
 916    dest->state = (struct internal_state FAR *) ds;
 917    zmemcpy(ds, ss, sizeof(deflate_state));
 918    ds->strm = dest;
 919
 920    ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
 921    ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
 922    ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
 923    overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
 924    ds->pending_buf = (uchf *) overlay;
 925
 926    if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
 927        ds->pending_buf == Z_NULL) {
 928        deflateEnd (dest);
 929        return Z_MEM_ERROR;
 930    }
 931    /* following zmemcpy do not work for 16-bit MSDOS */
 932    zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
 933    zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
 934    zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
 935    zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
 936
 937    ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
 938    ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
 939    ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
 940
 941    ds->l_desc.dyn_tree = ds->dyn_ltree;
 942    ds->d_desc.dyn_tree = ds->dyn_dtree;
 943    ds->bl_desc.dyn_tree = ds->bl_tree;
 944
 945    return Z_OK;
 946#endif /* MAXSEG_64K */
 947}
 948
 949/* ===========================================================================
 950 * Read a new buffer from the current input stream, update the adler32
 951 * and total number of bytes read.  All deflate() input goes through
 952 * this function so some applications may wish to modify it to avoid
 953 * allocating a large strm->next_in buffer and copying from it.
 954 * (See also flush_pending()).
 955 */
 956local int read_buf(strm, buf, size)
 957    z_streamp strm;
 958    Bytef *buf;
 959    unsigned size;
 960{
 961    unsigned len = strm->avail_in;
 962
 963    if (len > size) len = size;
 964    if (len == 0) return 0;
 965
 966    strm->avail_in  -= len;
 967
 968    if (strm->state->wrap == 1) {
 969        strm->adler = adler32(strm->adler, strm->next_in, len);
 970    }
 971#ifdef GZIP
 972    else if (strm->state->wrap == 2) {
 973        strm->adler = crc32(strm->adler, strm->next_in, len);
 974    }
 975#endif
 976    zmemcpy(buf, strm->next_in, len);
 977    strm->next_in  += len;
 978    strm->total_in += len;
 979
 980    return (int)len;
 981}
 982
 983/* ===========================================================================
 984 * Initialize the "longest match" routines for a new zlib stream
 985 */
 986local void lm_init (s)
 987    deflate_state *s;
 988{
 989    s->window_size = (ulg)2L*s->w_size;
 990
 991    CLEAR_HASH(s);
 992
 993    /* Set the default configuration parameters:
 994     */
 995    s->max_lazy_match   = configuration_table[s->level].max_lazy;
 996    s->good_match       = configuration_table[s->level].good_length;
 997    s->nice_match       = configuration_table[s->level].nice_length;
 998    s->max_chain_length = configuration_table[s->level].max_chain;
 999
1000    s->strstart = 0;
1001    s->block_start = 0L;
1002    s->lookahead = 0;
1003    s->match_length = s->prev_length = MIN_MATCH-1;
1004    s->match_available = 0;
1005    s->ins_h = 0;
1006#ifndef FASTEST
1007#ifdef ASMV
1008    match_init(); /* initialize the asm code */
1009#endif
1010#endif
1011}
1012
1013#ifndef FASTEST
1014/* ===========================================================================
1015 * Set match_start to the longest match starting at the given string and
1016 * return its length. Matches shorter or equal to prev_length are discarded,
1017 * in which case the result is equal to prev_length and match_start is
1018 * garbage.
1019 * IN assertions: cur_match is the head of the hash chain for the current
1020 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1021 * OUT assertion: the match length is not greater than s->lookahead.
1022 */
1023#ifndef ASMV
1024/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1025 * match.S. The code will be functionally equivalent.
1026 */
1027local uInt longest_match(s, cur_match)
1028    deflate_state *s;
1029    IPos cur_match;                             /* current match */
1030{
1031    unsigned chain_length = s->max_chain_length;/* max hash chain length */
1032    register Bytef *scan = s->window + s->strstart; /* current string */
1033    register Bytef *match;                       /* matched string */
1034    register int len;                           /* length of current match */
1035    int best_len = s->prev_length;              /* best match length so far */
1036    int nice_match = s->nice_match;             /* stop if match long enough */
1037    IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1038        s->strstart - (IPos)MAX_DIST(s) : NIL;
1039    /* Stop when cur_match becomes <= limit. To simplify the code,
1040     * we prevent matches with the string of window index 0.
1041     */
1042    Posf *prev = s->prev;
1043    uInt wmask = s->w_mask;
1044
1045#ifdef UNALIGNED_OK
1046    /* Compare two bytes at a time. Note: this is not always beneficial.
1047     * Try with and without -DUNALIGNED_OK to check.
1048     */
1049    register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1050    register ush scan_start = *(ushf*)scan;
1051    register ush scan_end   = *(ushf*)(scan+best_len-1);
1052#else
1053    register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1054    register Byte scan_end1  = scan[best_len-1];
1055    register Byte scan_end   = scan[best_len];
1056#endif
1057
1058    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1059     * It is easy to get rid of this optimization if necessary.
1060     */
1061    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1062
1063    /* Do not waste too much time if we already have a good match: */
1064    if (s->prev_length >= s->good_match) {
1065        chain_length >>= 2;
1066    }
1067    /* Do not look for matches beyond the end of the input. This is necessary
1068     * to make deflate deterministic.
1069     */
1070    if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1071
1072    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1073
1074    do {
1075        Assert(cur_match < s->strstart, "no future");
1076        match = s->window + cur_match;
1077
1078        /* Skip to next match if the match length cannot increase
1079         * or if the match length is less than 2.  Note that the checks below
1080         * for insufficient lookahead only occur occasionally for performance
1081         * reasons.  Therefore uninitialized memory will be accessed, and
1082         * conditional jumps will be made that depend on those values.
1083         * However the length of the match is limited to the lookahead, so
1084         * the output of deflate is not affected by the uninitialized values.
1085         */
1086#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1087        /* This code assumes sizeof(unsigned short) == 2. Do not use
1088         * UNALIGNED_OK if your compiler uses a different size.
1089         */
1090        if (*(ushf*)(match+best_len-1) != scan_end ||
1091            *(ushf*)match != scan_start) continue;
1092
1093        /* It is not necessary to compare scan[2] and match[2] since they are
1094         * always equal when the other bytes match, given that the hash keys
1095         * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1096         * strstart+3, +5, ... up to strstart+257. We check for insufficient
1097         * lookahead only every 4th comparison; the 128th check will be made
1098         * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1099         * necessary to put more guard bytes at the end of the window, or
1100         * to check more often for insufficient lookahead.
1101         */
1102        Assert(scan[2] == match[2], "scan[2]?");
1103        scan++, match++;
1104        do {
1105        } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1106                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1107                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1108                 *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1109                 scan < strend);
1110        /* The funny "do {}" generates better code on most compilers */
1111
1112        /* Here, scan <= window+strstart+257 */
1113        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1114        if (*scan == *match) scan++;
1115
1116        len = (MAX_MATCH - 1) - (int)(strend-scan);
1117        scan = strend - (MAX_MATCH-1);
1118
1119#else /* UNALIGNED_OK */
1120
1121        if (match[best_len]   != scan_end  ||
1122            match[best_len-1] != scan_end1 ||
1123            *match            != *scan     ||
1124            *++match          != scan[1])      continue;
1125
1126        /* The check at best_len-1 can be removed because it will be made
1127         * again later. (This heuristic is not always a win.)
1128         * It is not necessary to compare scan[2] and match[2] since they
1129         * are always equal when the other bytes match, given that
1130         * the hash keys are equal and that HASH_BITS >= 8.
1131         */
1132        scan += 2, match++;
1133        Assert(*scan == *match, "match[2]?");
1134
1135        /* We check for insufficient lookahead only every 8th comparison;
1136         * the 256th check will be made at strstart+258.
1137         */
1138        do {
1139        } while (*++scan == *++match && *++scan == *++match &&
1140                 *++scan == *++match && *++scan == *++match &&
1141                 *++scan == *++match && *++scan == *++match &&
1142                 *++scan == *++match && *++scan == *++match &&
1143                 scan < strend);
1144
1145        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1146
1147        len = MAX_MATCH - (int)(strend - scan);
1148        scan = strend - MAX_MATCH;
1149
1150#endif /* UNALIGNED_OK */
1151
1152        if (len > best_len) {
1153            s->match_start = cur_match;
1154            best_len = len;
1155            if (len >= nice_match) break;
1156#ifdef UNALIGNED_OK
1157            scan_end = *(ushf*)(scan+best_len-1);
1158#else
1159            scan_end1  = scan[best_len-1];
1160            scan_end   = scan[best_len];
1161#endif
1162        }
1163    } while ((cur_match = prev[cur_match & wmask]) > limit
1164             && --chain_length != 0);
1165
1166    if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1167    return s->lookahead;
1168}
1169#endif /* ASMV */
1170#endif /* FASTEST */
1171
1172/* ---------------------------------------------------------------------------
1173 * Optimized version for level == 1 or strategy == Z_RLE only
1174 */
1175local uInt longest_match_fast(s, cur_match)
1176    deflate_state *s;
1177    IPos cur_match;                             /* current match */
1178{
1179    register Bytef *scan = s->window + s->strstart; /* current string */
1180    register Bytef *match;                       /* matched string */
1181    register int len;                           /* length of current match */
1182    register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1183
1184    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1185     * It is easy to get rid of this optimization if necessary.
1186     */
1187    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1188
1189    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1190
1191    Assert(cur_match < s->strstart, "no future");
1192
1193    match = s->window + cur_match;
1194
1195    /* Return failure if the match length is less than 2:
1196     */
1197    if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1198
1199    /* The check at best_len-1 can be removed because it will be made
1200     * again later. (This heuristic is not always a win.)
1201     * It is not necessary to compare scan[2] and match[2] since they
1202     * are always equal when the other bytes match, given that
1203     * the hash keys are equal and that HASH_BITS >= 8.
1204     */
1205    scan += 2, match += 2;
1206    Assert(*scan == *match, "match[2]?");
1207
1208    /* We check for insufficient lookahead only every 8th comparison;
1209     * the 256th check will be made at strstart+258.
1210     */
1211    do {
1212    } while (*++scan == *++match && *++scan == *++match &&
1213             *++scan == *++match && *++scan == *++match &&
1214             *++scan == *++match && *++scan == *++match &&
1215             *++scan == *++match && *++scan == *++match &&
1216             scan < strend);
1217
1218    Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1219
1220    len = MAX_MATCH - (int)(strend - scan);
1221
1222    if (len < MIN_MATCH) return MIN_MATCH - 1;
1223
1224    s->match_start = cur_match;
1225    return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1226}
1227
1228#ifdef DEBUG
1229/* ===========================================================================
1230 * Check that the match at match_start is indeed a match.
1231 */
1232local void check_match(s, start, match, length)
1233    deflate_state *s;
1234    IPos start, match;
1235    int length;
1236{
1237    /* check that the match is indeed a match */
1238    if (zmemcmp(s->window + match,
1239                s->window + start, length) != EQUAL) {
1240        fprintf(stderr, " start %u, match %u, length %d\n",
1241                start, match, length);
1242        do {
1243            fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1244        } while (--length != 0);
1245        z_error("invalid match");
1246    }
1247    if (z_verbose > 1) {
1248        fprintf(stderr,"\\[%d,%d]", start-match, length);
1249        do { putc(s->window[start++], stderr); } while (--length != 0);
1250    }
1251}
1252#else
1253#  define check_match(s, start, match, length)
1254#endif /* DEBUG */
1255
1256/* ===========================================================================
1257 * Fill the window when the lookahead becomes insufficient.
1258 * Updates strstart and lookahead.
1259 *
1260 * IN assertion: lookahead < MIN_LOOKAHEAD
1261 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1262 *    At least one byte has been read, or avail_in == 0; reads are
1263 *    performed for at least two bytes (required for the zip translate_eol
1264 *    option -- not supported here).
1265 */
1266local void fill_window(s)
1267    deflate_state *s;
1268{
1269    register unsigned n, m;
1270    register Posf *p;
1271    unsigned more;    /* Amount of free space at the end of the window. */
1272    uInt wsize = s->w_size;
1273
1274    do {
1275        more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1276
1277        /* Deal with !@#$% 64K limit: */
1278        if (sizeof(int) <= 2) {
1279            if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1280                more = wsize;
1281
1282            } else if (more == (unsigned)(-1)) {
1283                /* Very unlikely, but possible on 16 bit machine if
1284                 * strstart == 0 && lookahead == 1 (input done a byte at time)
1285                 */
1286                more--;
1287            }
1288        }
1289
1290        /* If the window is almost full and there is insufficient lookahead,
1291         * move the upper half to the lower one to make room in the upper half.
1292         */
1293        if (s->strstart >= wsize+MAX_DIST(s)) {
1294
1295            zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1296            s->match_start -= wsize;
1297            s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
1298            s->block_start -= (long) wsize;
1299
1300            /* Slide the hash table (could be avoided with 32 bit values
1301               at the expense of memory usage). We slide even when level == 0
1302               to keep the hash table consistent if we switch back to level > 0
1303               later. (Using level 0 permanently is not an optimal usage of
1304               zlib, so we don't care about this pathological case.)
1305             */
1306            /* %%% avoid this when Z_RLE */
1307            n = s->hash_size;
1308            p = &s->head[n];
1309            do {
1310                m = *--p;
1311                *p = (Pos)(m >= wsize ? m-wsize : NIL);
1312            } while (--n);
1313
1314            n = wsize;
1315#ifndef FASTEST
1316            p = &s->prev[n];
1317            do {
1318                m = *--p;
1319                *p = (Pos)(m >= wsize ? m-wsize : NIL);
1320                /* If n is not on any hash chain, prev[n] is garbage but
1321                 * its value will never be used.
1322                 */
1323            } while (--n);
1324#endif
1325            more += wsize;
1326        }
1327        if (s->strm->avail_in == 0) return;
1328
1329        /* If there was no sliding:
1330         *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1331         *    more == window_size - lookahead - strstart
1332         * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1333         * => more >= window_size - 2*WSIZE + 2
1334         * In the BIG_MEM or MMAP case (not yet supported),
1335         *   window_size == input_size + MIN_LOOKAHEAD  &&
1336         *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1337         * Otherwise, window_size == 2*WSIZE so more >= 2.
1338         * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1339         */
1340        Assert(more >= 2, "more < 2");
1341
1342        n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1343        s->lookahead += n;
1344
1345        /* Initialize the hash value now that we have some input: */
1346        if (s->lookahead >= MIN_MATCH) {
1347            s->ins_h = s->window[s->strstart];
1348            UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1349#if MIN_MATCH != 3
1350            Call UPDATE_HASH() MIN_MATCH-3 more times
1351#endif
1352        }
1353        /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1354         * but this is not important since only literal bytes will be emitted.
1355         */
1356
1357    } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1358}
1359
1360/* ===========================================================================
1361 * Flush the current block, with given end-of-file flag.
1362 * IN assertion: strstart is set to the end of the current match.
1363 */
1364#define FLUSH_BLOCK_ONLY(s, eof) { \
1365   _tr_flush_block(s, (s->block_start >= 0L ? \
1366                   (charf *)&s->window[(unsigned)s->block_start] : \
1367                   (charf *)Z_NULL), \
1368                (ulg)((long)s->strstart - s->block_start), \
1369                (eof)); \
1370   s->block_start = s->strstart; \
1371   flush_pending(s->strm); \
1372   Tracev((stderr,"[FLUSH]")); \
1373}
1374
1375/* Same but force premature exit if necessary…

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