akaros/kern/lib/zlib_deflate/deflate.c
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   1/* +++ deflate.c */
   2/* deflate.c -- compress data using the deflation algorithm
   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 depends on being able to identify portions
  11 *      of the input text which are identical to earlier input (within a
  12 *      sliding window trailing behind the input currently being processed).
  13 *
  14 *      The most straightforward technique turns out to be the fastest for
  15 *      most input files: try all possible matches and select the longest.
  16 *      The key feature of this algorithm is that insertions into the string
  17 *      dictionary are very simple and thus fast, and deletions are avoided
  18 *      completely. Insertions are performed at each input character, whereas
  19 *      string matches are performed only when the previous match ends. So it
  20 *      is preferable to spend more time in matches to allow very fast string
  21 *      insertions and avoid deletions. The matching algorithm for small
  22 *      strings is inspired from that of Rabin & Karp. A brute force approach
  23 *      is used to find longer strings when a small match has been found.
  24 *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
  25 *      (by Leonid Broukhis).
  26 *         A previous version of this file used a more sophisticated algorithm
  27 *      (by Fiala and Greene) which is guaranteed to run in linear amortized
  28 *      time, but has a larger average cost, uses more memory and is patented.
  29 *      However the F&G algorithm may be faster for some highly redundant
  30 *      files if the parameter max_chain_length (described below) is too large.
  31 *
  32 *  ACKNOWLEDGEMENTS
  33 *
  34 *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
  35 *      I found it in 'freeze' written by Leonid Broukhis.
  36 *      Thanks to many people for bug reports and testing.
  37 *
  38 *  REFERENCES
  39 *
  40 *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
  41 *      Available in ftp://ds.internic.net/rfc/rfc1951.txt
  42 *
  43 *      A description of the Rabin and Karp algorithm is given in the book
  44 *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
  45 *
  46 *      Fiala,E.R., and Greene,D.H.
  47 *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
  48 *
  49 */
  50
  51#include <zutil.h>
  52#include <assert.h>
  53#include "defutil.h"
  54
  55
  56/* ===========================================================================
  57 *  Function prototypes.
  58 */
  59typedef enum {
  60    need_more,      /* block not completed, need more input or more output */
  61    block_done,     /* block flush performed */
  62    finish_started, /* finish started, need only more output at next deflate */
  63    finish_done     /* finish done, accept no more input or output */
  64} block_state;
  65
  66typedef block_state (*compress_func) (deflate_state *s, int flush);
  67/* Compression function. Returns the block state after the call. */
  68
  69static void fill_window    (deflate_state *s);
  70static block_state deflate_stored (deflate_state *s, int flush);
  71static block_state deflate_fast   (deflate_state *s, int flush);
  72static block_state deflate_slow   (deflate_state *s, int flush);
  73static void lm_init        (deflate_state *s);
  74static void putShortMSB    (deflate_state *s, uInt b);
  75static void flush_pending  (z_streamp strm);
  76static int read_buf        (z_streamp strm, Byte *buf, unsigned size);
  77static uInt longest_match  (deflate_state *s, IPos cur_match);
  78
  79#ifdef DEBUG_ZLIB
  80static  void check_match (deflate_state *s, IPos start, IPos match,
  81                         int length);
  82#endif
  83
  84/* ===========================================================================
  85 * Local data
  86 */
  87
  88#define NIL 0
  89/* Tail of hash chains */
  90
  91#ifndef TOO_FAR
  92#  define TOO_FAR 4096
  93#endif
  94/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
  95
  96#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
  97/* Minimum amount of lookahead, except at the end of the input file.
  98 * See deflate.c for comments about the MIN_MATCH+1.
  99 */
 100
 101/* Values for max_lazy_match, good_match and max_chain_length, depending on
 102 * the desired pack level (0..9). The values given below have been tuned to
 103 * exclude worst case performance for pathological files. Better values may be
 104 * found for specific files.
 105 */
 106typedef struct config_s {
 107   ush good_length; /* reduce lazy search above this match length */
 108   ush max_lazy;    /* do not perform lazy search above this match length */
 109   ush nice_length; /* quit search above this match length */
 110   ush max_chain;
 111   compress_func func;
 112} config;
 113
 114static const config configuration_table[10] = {
 115/*      good lazy nice chain */
 116/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
 117/* 1 */ {4,    4,  8,    4, deflate_fast}, /* maximum speed, no lazy matches */
 118/* 2 */ {4,    5, 16,    8, deflate_fast},
 119/* 3 */ {4,    6, 32,   32, deflate_fast},
 120
 121/* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
 122/* 5 */ {8,   16, 32,   32, deflate_slow},
 123/* 6 */ {8,   16, 128, 128, deflate_slow},
 124/* 7 */ {8,   32, 128, 256, deflate_slow},
 125/* 8 */ {32, 128, 258, 1024, deflate_slow},
 126/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
 127
 128/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
 129 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
 130 * meaning.
 131 */
 132
 133#define EQUAL 0
 134/* result of memcmp for equal strings */
 135
 136/* ===========================================================================
 137 * Update a hash value with the given input byte
 138 * IN  assertion: all calls to UPDATE_HASH are made with consecutive
 139 *    input characters, so that a running hash key can be computed from the
 140 *    previous key instead of complete recalculation each time.
 141 */
 142#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
 143
 144
 145/* ===========================================================================
 146 * Insert string str in the dictionary and set match_head to the previous head
 147 * of the hash chain (the most recent string with same hash key). Return
 148 * the previous length of the hash chain.
 149 * IN  assertion: all calls to INSERT_STRING are made with consecutive
 150 *    input characters and the first MIN_MATCH bytes of str are valid
 151 *    (except for the last MIN_MATCH-1 bytes of the input file).
 152 */
 153#define INSERT_STRING(s, str, match_head) \
 154   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
 155    s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
 156    s->head[s->ins_h] = (Pos)(str))
 157
 158/* ===========================================================================
 159 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
 160 * prev[] will be initialized on the fly.
 161 */
 162#define CLEAR_HASH(s) \
 163    s->head[s->hash_size-1] = NIL; \
 164    memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));
 165
 166/* ========================================================================= */
 167int zlib_deflateInit2(
 168        z_streamp strm,
 169        int  level,
 170        int  method,
 171        int  windowBits,
 172        int  memLevel,
 173        int  strategy
 174)
 175{
 176    deflate_state *s;
 177    int noheader = 0;
 178    deflate_workspace *mem;
 179    char *next;
 180
 181    ush *overlay;
 182    /* We overlay pending_buf and d_buf+l_buf. This works since the average
 183     * output size for (length,distance) codes is <= 24 bits.
 184     */
 185
 186    if (strm == NULL) return Z_STREAM_ERROR;
 187
 188    strm->msg = NULL;
 189
 190    if (level == Z_DEFAULT_COMPRESSION) level = 6;
 191
 192    mem = (deflate_workspace *) strm->workspace;
 193
 194    if (windowBits < 0) { /* undocumented feature: suppress zlib header */
 195        noheader = 1;
 196        windowBits = -windowBits;
 197    }
 198    if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
 199        windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
 200        strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
 201        return Z_STREAM_ERROR;
 202    }
 203
 204    /*
 205     * Direct the workspace's pointers to the chunks that were allocated
 206     * along with the deflate_workspace struct.
 207     */
 208    next = (char *) mem;
 209    next += sizeof(*mem);
 210    mem->window_memory = (Byte *) next;
 211    next += zlib_deflate_window_memsize(windowBits);
 212    mem->prev_memory = (Pos *) next;
 213    next += zlib_deflate_prev_memsize(windowBits);
 214    mem->head_memory = (Pos *) next;
 215    next += zlib_deflate_head_memsize(memLevel);
 216    mem->overlay_memory = next;
 217
 218    s = (deflate_state *) &(mem->deflate_memory);
 219    strm->state = (struct internal_state *)s;
 220    s->strm = strm;
 221
 222    s->noheader = noheader;
 223    s->w_bits = windowBits;
 224    s->w_size = 1 << s->w_bits;
 225    s->w_mask = s->w_size - 1;
 226
 227    s->hash_bits = memLevel + 7;
 228    s->hash_size = 1 << s->hash_bits;
 229    s->hash_mask = s->hash_size - 1;
 230    s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
 231
 232    s->window = (Byte *) mem->window_memory;
 233    s->prev   = (Pos *)  mem->prev_memory;
 234    s->head   = (Pos *)  mem->head_memory;
 235
 236    s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
 237
 238    overlay = (ush *) mem->overlay_memory;
 239    s->pending_buf = (uch *) overlay;
 240    s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
 241
 242    s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
 243    s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
 244
 245    s->level = level;
 246    s->strategy = strategy;
 247    s->method = (Byte)method;
 248
 249    return zlib_deflateReset(strm);
 250}
 251
 252/* ========================================================================= */
 253int zlib_deflateReset(
 254        z_streamp strm
 255)
 256{
 257    deflate_state *s;
 258
 259    if (strm == NULL || strm->state == NULL)
 260        return Z_STREAM_ERROR;
 261
 262    strm->total_in = strm->total_out = 0;
 263    strm->msg = NULL;
 264    strm->data_type = Z_UNKNOWN;
 265
 266    s = (deflate_state *)strm->state;
 267    s->pending = 0;
 268    s->pending_out = s->pending_buf;
 269
 270    if (s->noheader < 0) {
 271        s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
 272    }
 273    s->status = s->noheader ? BUSY_STATE : INIT_STATE;
 274    strm->adler = 1;
 275    s->last_flush = Z_NO_FLUSH;
 276
 277    zlib_tr_init(s);
 278    lm_init(s);
 279
 280    return Z_OK;
 281}
 282
 283/* =========================================================================
 284 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
 285 * IN assertion: the stream state is correct and there is enough room in
 286 * pending_buf.
 287 */
 288static void putShortMSB(
 289        deflate_state *s,
 290        uInt b
 291)
 292{
 293    put_byte(s, (Byte)(b >> 8));
 294    put_byte(s, (Byte)(b & 0xff));
 295}
 296
 297/* =========================================================================
 298 * Flush as much pending output as possible. All deflate() output goes
 299 * through this function so some applications may wish to modify it
 300 * to avoid allocating a large strm->next_out buffer and copying into it.
 301 * (See also read_buf()).
 302 */
 303static void flush_pending(
 304        z_streamp strm
 305)
 306{
 307    deflate_state *s = (deflate_state *) strm->state;
 308    unsigned len = s->pending;
 309
 310    if (len > strm->avail_out) len = strm->avail_out;
 311    if (len == 0) return;
 312
 313    if (strm->next_out != NULL) {
 314        memcpy(strm->next_out, s->pending_out, len);
 315        strm->next_out += len;
 316    }
 317    s->pending_out += len;
 318    strm->total_out += len;
 319    strm->avail_out  -= len;
 320    s->pending -= len;
 321    if (s->pending == 0) {
 322        s->pending_out = s->pending_buf;
 323    }
 324}
 325
 326/* ========================================================================= */
 327int zlib_deflate(
 328        z_streamp strm,
 329        int flush
 330)
 331{
 332    int old_flush; /* value of flush param for previous deflate call */
 333    deflate_state *s;
 334
 335    if (strm == NULL || strm->state == NULL ||
 336        flush > Z_FINISH || flush < 0) {
 337        return Z_STREAM_ERROR;
 338    }
 339    s = (deflate_state *) strm->state;
 340
 341    if ((strm->next_in == NULL && strm->avail_in != 0) ||
 342        (s->status == FINISH_STATE && flush != Z_FINISH)) {
 343        return Z_STREAM_ERROR;
 344    }
 345    if (strm->avail_out == 0) return Z_BUF_ERROR;
 346
 347    s->strm = strm; /* just in case */
 348    old_flush = s->last_flush;
 349    s->last_flush = flush;
 350
 351    /* Write the zlib header */
 352    if (s->status == INIT_STATE) {
 353
 354        uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
 355        uInt level_flags = (s->level-1) >> 1;
 356
 357        if (level_flags > 3) level_flags = 3;
 358        header |= (level_flags << 6);
 359        if (s->strstart != 0) header |= PRESET_DICT;
 360        header += 31 - (header % 31);
 361
 362        s->status = BUSY_STATE;
 363        putShortMSB(s, header);
 364
 365        /* Save the adler32 of the preset dictionary: */
 366        if (s->strstart != 0) {
 367            putShortMSB(s, (uInt)(strm->adler >> 16));
 368            putShortMSB(s, (uInt)(strm->adler & 0xffff));
 369        }
 370        strm->adler = 1L;
 371    }
 372
 373    /* Flush as much pending output as possible */
 374    if (s->pending != 0) {
 375        flush_pending(strm);
 376        if (strm->avail_out == 0) {
 377            /* Since avail_out is 0, deflate will be called again with
 378             * more output space, but possibly with both pending and
 379             * avail_in equal to zero. There won't be anything to do,
 380             * but this is not an error situation so make sure we
 381             * return OK instead of BUF_ERROR at next call of deflate:
 382             */
 383            s->last_flush = -1;
 384            return Z_OK;
 385        }
 386
 387    /* Make sure there is something to do and avoid duplicate consecutive
 388     * flushes. For repeated and useless calls with Z_FINISH, we keep
 389     * returning Z_STREAM_END instead of Z_BUFF_ERROR.
 390     */
 391    } else if (strm->avail_in == 0 && flush <= old_flush &&
 392               flush != Z_FINISH) {
 393        return Z_BUF_ERROR;
 394    }
 395
 396    /* User must not provide more input after the first FINISH: */
 397    if (s->status == FINISH_STATE && strm->avail_in != 0) {
 398        return Z_BUF_ERROR;
 399    }
 400
 401    /* Start a new block or continue the current one.
 402     */
 403    if (strm->avail_in != 0 || s->lookahead != 0 ||
 404        (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
 405        block_state bstate;
 406
 407        bstate = (*(configuration_table[s->level].func))(s, flush);
 408
 409        if (bstate == finish_started || bstate == finish_done) {
 410            s->status = FINISH_STATE;
 411        }
 412        if (bstate == need_more || bstate == finish_started) {
 413            if (strm->avail_out == 0) {
 414                s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
 415            }
 416            return Z_OK;
 417            /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
 418             * of deflate should use the same flush parameter to make sure
 419             * that the flush is complete. So we don't have to output an
 420             * empty block here, this will be done at next call. This also
 421             * ensures that for a very small output buffer, we emit at most
 422             * one empty block.
 423             */
 424        }
 425        if (bstate == block_done) {
 426            if (flush == Z_PARTIAL_FLUSH) {
 427                zlib_tr_align(s);
 428            } else if (flush == Z_PACKET_FLUSH) {
 429                /* Output just the 3-bit `stored' block type value,
 430                   but not a zero length. */
 431                zlib_tr_stored_type_only(s);
 432            } else { /* FULL_FLUSH or SYNC_FLUSH */
 433                zlib_tr_stored_block(s, (char*)0, 0L, 0);
 434                /* For a full flush, this empty block will be recognized
 435                 * as a special marker by inflate_sync().
 436                 */
 437                if (flush == Z_FULL_FLUSH) {
 438                    CLEAR_HASH(s);             /* forget history */
 439                }
 440            }
 441            flush_pending(strm);
 442            if (strm->avail_out == 0) {
 443              s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
 444              return Z_OK;
 445            }
 446        }
 447    }
 448    Assert(strm->avail_out > 0, "bug2");
 449
 450    if (flush != Z_FINISH) return Z_OK;
 451    if (s->noheader) return Z_STREAM_END;
 452
 453    /* Write the zlib trailer (adler32) */
 454    putShortMSB(s, (uInt)(strm->adler >> 16));
 455    putShortMSB(s, (uInt)(strm->adler & 0xffff));
 456    flush_pending(strm);
 457    /* If avail_out is zero, the application will call deflate again
 458     * to flush the rest.
 459     */
 460    s->noheader = -1; /* write the trailer only once! */
 461    return s->pending != 0 ? Z_OK : Z_STREAM_END;
 462}
 463
 464/* ========================================================================= */
 465int zlib_deflateEnd(
 466        z_streamp strm
 467)
 468{
 469    int status;
 470    deflate_state *s;
 471
 472    if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
 473    s = (deflate_state *) strm->state;
 474
 475    status = s->status;
 476    if (status != INIT_STATE && status != BUSY_STATE &&
 477        status != FINISH_STATE) {
 478      return Z_STREAM_ERROR;
 479    }
 480
 481    strm->state = NULL;
 482
 483    return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
 484}
 485
 486/* ===========================================================================
 487 * Read a new buffer from the current input stream, update the adler32
 488 * and total number of bytes read.  All deflate() input goes through
 489 * this function so some applications may wish to modify it to avoid
 490 * allocating a large strm->next_in buffer and copying from it.
 491 * (See also flush_pending()).
 492 */
 493static int read_buf(
 494        z_streamp strm,
 495        Byte *buf,
 496        unsigned size
 497)
 498{
 499    unsigned len = strm->avail_in;
 500
 501    if (len > size) len = size;
 502    if (len == 0) return 0;
 503
 504    strm->avail_in  -= len;
 505
 506    if (!((deflate_state *)(strm->state))->noheader) {
 507        strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
 508    }
 509    memcpy(buf, strm->next_in, len);
 510    strm->next_in  += len;
 511    strm->total_in += len;
 512
 513    return (int)len;
 514}
 515
 516/* ===========================================================================
 517 * Initialize the "longest match" routines for a new zlib stream
 518 */
 519static void lm_init(
 520        deflate_state *s
 521)
 522{
 523    s->window_size = (ulg)2L*s->w_size;
 524
 525    CLEAR_HASH(s);
 526
 527    /* Set the default configuration parameters:
 528     */
 529    s->max_lazy_match   = configuration_table[s->level].max_lazy;
 530    s->good_match       = configuration_table[s->level].good_length;
 531    s->nice_match       = configuration_table[s->level].nice_length;
 532    s->max_chain_length = configuration_table[s->level].max_chain;
 533
 534    s->strstart = 0;
 535    s->block_start = 0L;
 536    s->lookahead = 0;
 537    s->match_length = s->prev_length = MIN_MATCH-1;
 538    s->match_available = 0;
 539    s->ins_h = 0;
 540}
 541
 542/* ===========================================================================
 543 * Set match_start to the longest match starting at the given string and
 544 * return its length. Matches shorter or equal to prev_length are discarded,
 545 * in which case the result is equal to prev_length and match_start is
 546 * garbage.
 547 * IN assertions: cur_match is the head of the hash chain for the current
 548 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
 549 * OUT assertion: the match length is not greater than s->lookahead.
 550 */
 551/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
 552 * match.S. The code will be functionally equivalent.
 553 */
 554static uInt longest_match(
 555        deflate_state *s,
 556        IPos cur_match                  /* current match */
 557)
 558{
 559    unsigned chain_length = s->max_chain_length;/* max hash chain length */
 560    register Byte *scan = s->window + s->strstart; /* current string */
 561    register Byte *match;                       /* matched string */
 562    register int len;                           /* length of current match */
 563    int best_len = s->prev_length;              /* best match length so far */
 564    int nice_match = s->nice_match;             /* stop if match long enough */
 565    IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
 566        s->strstart - (IPos)MAX_DIST(s) : NIL;
 567    /* Stop when cur_match becomes <= limit. To simplify the code,
 568     * we prevent matches with the string of window index 0.
 569     */
 570    Pos *prev = s->prev;
 571    uInt wmask = s->w_mask;
 572
 573#ifdef UNALIGNED_OK
 574    /* Compare two bytes at a time. Note: this is not always beneficial.
 575     * Try with and without -DUNALIGNED_OK to check.
 576     */
 577    register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
 578    register ush scan_start = *(ush*)scan;
 579    register ush scan_end   = *(ush*)(scan+best_len-1);
 580#else
 581    register Byte *strend = s->window + s->strstart + MAX_MATCH;
 582    register Byte scan_end1  = scan[best_len-1];
 583    register Byte scan_end   = scan[best_len];
 584#endif
 585
 586    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
 587     * It is easy to get rid of this optimization if necessary.
 588     */
 589    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
 590
 591    /* Do not waste too much time if we already have a good match: */
 592    if (s->prev_length >= s->good_match) {
 593        chain_length >>= 2;
 594    }
 595    /* Do not look for matches beyond the end of the input. This is necessary
 596     * to make deflate deterministic.
 597     */
 598    if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
 599
 600    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
 601
 602    do {
 603        Assert(cur_match < s->strstart, "no future");
 604        match = s->window + cur_match;
 605
 606        /* Skip to next match if the match length cannot increase
 607         * or if the match length is less than 2:
 608         */
 609#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
 610        /* This code assumes sizeof(unsigned short) == 2. Do not use
 611         * UNALIGNED_OK if your compiler uses a different size.
 612         */
 613        if (*(ush*)(match+best_len-1) != scan_end ||
 614            *(ush*)match != scan_start) continue;
 615
 616        /* It is not necessary to compare scan[2] and match[2] since they are
 617         * always equal when the other bytes match, given that the hash keys
 618         * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
 619         * strstart+3, +5, ... up to strstart+257. We check for insufficient
 620         * lookahead only every 4th comparison; the 128th check will be made
 621         * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
 622         * necessary to put more guard bytes at the end of the window, or
 623         * to check more often for insufficient lookahead.
 624         */
 625        Assert(scan[2] == match[2], "scan[2]?");
 626        scan++, match++;
 627        do {
 628        } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
 629                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
 630                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
 631                 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
 632                 scan < strend);
 633        /* The funny "do {}" generates better code on most compilers */
 634
 635        /* Here, scan <= window+strstart+257 */
 636        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
 637        if (*scan == *match) scan++;
 638
 639        len = (MAX_MATCH - 1) - (int)(strend-scan);
 640        scan = strend - (MAX_MATCH-1);
 641
 642#else /* UNALIGNED_OK */
 643
 644        if (match[best_len]   != scan_end  ||
 645            match[best_len-1] != scan_end1 ||
 646            *match            != *scan     ||
 647            *++match          != scan[1])      continue;
 648
 649        /* The check at best_len-1 can be removed because it will be made
 650         * again later. (This heuristic is not always a win.)
 651         * It is not necessary to compare scan[2] and match[2] since they
 652         * are always equal when the other bytes match, given that
 653         * the hash keys are equal and that HASH_BITS >= 8.
 654         */
 655        scan += 2, match++;
 656        Assert(*scan == *match, "match[2]?");
 657
 658        /* We check for insufficient lookahead only every 8th comparison;
 659         * the 256th check will be made at strstart+258.
 660         */
 661        do {
 662        } while (*++scan == *++match && *++scan == *++match &&
 663                 *++scan == *++match && *++scan == *++match &&
 664                 *++scan == *++match && *++scan == *++match &&
 665                 *++scan == *++match && *++scan == *++match &&
 666                 scan < strend);
 667
 668        Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
 669
 670        len = MAX_MATCH - (int)(strend - scan);
 671        scan = strend - MAX_MATCH;
 672
 673#endif /* UNALIGNED_OK */
 674
 675        if (len > best_len) {
 676            s->match_start = cur_match;
 677            best_len = len;
 678            if (len >= nice_match) break;
 679#ifdef UNALIGNED_OK
 680            scan_end = *(ush*)(scan+best_len-1);
 681#else
 682            scan_end1  = scan[best_len-1];
 683            scan_end   = scan[best_len];
 684#endif
 685        }
 686    } while ((cur_match = prev[cur_match & wmask]) > limit
 687             && --chain_length != 0);
 688
 689    if ((uInt)best_len <= s->lookahead) return best_len;
 690    return s->lookahead;
 691}
 692
 693#ifdef DEBUG_ZLIB
 694/* ===========================================================================
 695 * Check that the match at match_start is indeed a match.
 696 */
 697static void check_match(
 698        deflate_state *s,
 699        IPos start,
 700        IPos match,
 701        int length
 702)
 703{
 704    /* check that the match is indeed a match */
 705    if (memcmp((char *)s->window + match,
 706                (char *)s->window + start, length) != EQUAL) {
 707        fprintf(stderr, " start %u, match %u, length %d\n",
 708                start, match, length);
 709        do {
 710            fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
 711        } while (--length != 0);
 712        z_error("invalid match");
 713    }
 714    if (z_verbose > 1) {
 715        fprintf(stderr,"\\[%d,%d]", start-match, length);
 716        do { putc(s->window[start++], stderr); } while (--length != 0);
 717    }
 718}
 719#else
 720#  define check_match(s, start, match, length)
 721#endif
 722
 723/* ===========================================================================
 724 * Fill the window when the lookahead becomes insufficient.
 725 * Updates strstart and lookahead.
 726 *
 727 * IN assertion: lookahead < MIN_LOOKAHEAD
 728 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
 729 *    At least one byte has been read, or avail_in == 0; reads are
 730 *    performed for at least two bytes (required for the zip translate_eol
 731 *    option -- not supported here).
 732 */
 733static void fill_window(
 734        deflate_state *s
 735)
 736{
 737    register unsigned n, m;
 738    register Pos *p;
 739    unsigned more;    /* Amount of free space at the end of the window. */
 740    uInt wsize = s->w_size;
 741
 742    do {
 743        more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
 744
 745        /* Deal with !@#$% 64K limit: */
 746        if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
 747            more = wsize;
 748
 749        } else if (more == (unsigned)(-1)) {
 750            /* Very unlikely, but possible on 16 bit machine if strstart == 0
 751             * and lookahead == 1 (input done one byte at time)
 752             */
 753            more--;
 754
 755        /* If the window is almost full and there is insufficient lookahead,
 756         * move the upper half to the lower one to make room in the upper half.
 757         */
 758        } else if (s->strstart >= wsize+MAX_DIST(s)) {
 759
 760            memcpy((char *)s->window, (char *)s->window+wsize,
 761                   (unsigned)wsize);
 762            s->match_start -= wsize;
 763            s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
 764            s->block_start -= (long) wsize;
 765
 766            /* Slide the hash table (could be avoided with 32 bit values
 767               at the expense of memory usage). We slide even when level == 0
 768               to keep the hash table consistent if we switch back to level > 0
 769               later. (Using level 0 permanently is not an optimal usage of
 770               zlib, so we don't care about this pathological case.)
 771             */
 772            n = s->hash_size;
 773            p = &s->head[n];
 774            do {
 775                m = *--p;
 776                *p = (Pos)(m >= wsize ? m-wsize : NIL);
 777            } while (--n);
 778
 779            n = wsize;
 780            p = &s->prev[n];
 781            do {
 782                m = *--p;
 783                *p = (Pos)(m >= wsize ? m-wsize : NIL);
 784                /* If n is not on any hash chain, prev[n] is garbage but
 785                 * its value will never be used.
 786                 */
 787            } while (--n);
 788            more += wsize;
 789        }
 790        if (s->strm->avail_in == 0) return;
 791
 792        /* If there was no sliding:
 793         *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
 794         *    more == window_size - lookahead - strstart
 795         * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
 796         * => more >= window_size - 2*WSIZE + 2
 797         * In the BIG_MEM or MMAP case (not yet supported),
 798         *   window_size == input_size + MIN_LOOKAHEAD  &&
 799         *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
 800         * Otherwise, window_size == 2*WSIZE so more >= 2.
 801         * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
 802         */
 803        Assert(more >= 2, "more < 2");
 804
 805        n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
 806        s->lookahead += n;
 807
 808        /* Initialize the hash value now that we have some input: */
 809        if (s->lookahead >= MIN_MATCH) {
 810            s->ins_h = s->window[s->strstart];
 811            UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
 812#if MIN_MATCH != 3
 813            Call UPDATE_HASH() MIN_MATCH-3 more times
 814#endif
 815        }
 816        /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
 817         * but this is not important since only literal bytes will be emitted.
 818         */
 819
 820    } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
 821}
 822
 823/* ===========================================================================
 824 * Flush the current block, with given end-of-file flag.
 825 * IN assertion: strstart is set to the end of the current match.
 826 */
 827#define FLUSH_BLOCK_ONLY(s, eof) { \
 828   zlib_tr_flush_block(s, (s->block_start >= 0L ? \
 829                   (char *)&s->window[(unsigned)s->block_start] : \
 830                   NULL), \
 831                (ulg)((long)s->strstart - s->block_start), \
 832                (eof)); \
 833   s->block_start = s->strstart; \
 834   flush_pending(s->strm); \
 835   Tracev((stderr,"[FLUSH]")); \
 836}
 837
 838/* Same but force premature exit if necessary. */
 839#define FLUSH_BLOCK(s, eof) { \
 840   FLUSH_BLOCK_ONLY(s, eof); \
 841   if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
 842}
 843
 844/* ===========================================================================
 845 * Copy without compression as much as possible from the input stream, return
 846 * the current block state.
 847 * This function does not insert new strings in the dictionary since
 848 * uncompressible data is probably not useful. This function is used
 849 * only for the level=0 compression option.
 850 * NOTE: this function should be optimized to avoid extra copying from
 851 * window to pending_buf.
 852 */
 853static block_state deflate_stored(
 854        deflate_state *s,
 855        int flush
 856)
 857{
 858    /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
 859     * to pending_buf_size, and each stored block has a 5 byte header:
 860     */
 861    ulg max_block_size = 0xffff;
 862    ulg max_start;
 863
 864    if (max_block_size > s->pending_buf_size - 5) {
 865        max_block_size = s->pending_buf_size - 5;
 866    }
 867
 868    /* Copy as much as possible from input to output: */
 869    for (;;) {
 870        /* Fill the window as much as possible: */
 871        if (s->lookahead <= 1) {
 872
 873            Assert(s->strstart < s->w_size+MAX_DIST(s) ||
 874                   s->block_start >= (long)s->w_size, "slide too late");
 875
 876            fill_window(s);
 877            if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
 878
 879            if (s->lookahead == 0) break; /* flush the current block */
 880        }
 881        Assert(s->block_start >= 0L, "block gone");
 882
 883        s->strstart += s->lookahead;
 884        s->lookahead = 0;
 885
 886        /* Emit a stored block if pending_buf will be full: */
 887        max_start = s->block_start + max_block_size;
 888        if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
 889            /* strstart == 0 is possible when wraparound on 16-bit machine */
 890            s->lookahead = (uInt)(s->strstart - max_start);
 891            s->strstart = (uInt)max_start;
 892            FLUSH_BLOCK(s, 0);
 893        }
 894        /* Flush if we may have to slide, otherwise block_start may become
 895         * negative and the data will be gone:
 896         */
 897        if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
 898            FLUSH_BLOCK(s, 0);
 899        }
 900    }
 901    FLUSH_BLOCK(s, flush == Z_FINISH);
 902    return flush == Z_FINISH ? finish_done : block_done;
 903}
 904
 905/* ===========================================================================
 906 * Compress as much as possible from the input stream, return the current
 907 * block state.
 908 * This function does not perform lazy evaluation of matches and inserts
 909 * new strings in the dictionary only for unmatched strings or for short
 910 * matches. It is used only for the fast compression options.
 911 */
 912static block_state deflate_fast(
 913        deflate_state *s,
 914        int flush
 915)
 916{
 917    IPos hash_head = NIL; /* head of the hash chain */
 918    int bflush;           /* set if current block must be flushed */
 919
 920    for (;;) {
 921        /* Make sure that we always have enough lookahead, except
 922         * at the end of the input file. We need MAX_MATCH bytes
 923         * for the next match, plus MIN_MATCH bytes to insert the
 924         * string following the next match.
 925         */
 926        if (s->lookahead < MIN_LOOKAHEAD) {
 927            fill_window(s);
 928            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
 929                return need_more;
 930            }
 931            if (s->lookahead == 0) break; /* flush the current block */
 932        }
 933
 934        /* Insert the string window[strstart .. strstart+2] in the
 935         * dictionary, and set hash_head to the head of the hash chain:
 936         */
 937        if (s->lookahead >= MIN_MATCH) {
 938            INSERT_STRING(s, s->strstart, hash_head);
 939        }
 940
 941        /* Find the longest match, discarding those <= prev_length.
 942         * At this point we have always match_length < MIN_MATCH
 943         */
 944        if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
 945            /* To simplify the code, we prevent matches with the string
 946             * of window index 0 (in particular we have to avoid a match
 947             * of the string with itself at the start of the input file).
 948             */
 949            if (s->strategy != Z_HUFFMAN_ONLY) {
 950                s->match_length = longest_match (s, hash_head);
 951            }
 952            /* longest_match() sets match_start */
 953        }
 954        if (s->match_length >= MIN_MATCH) {
 955            check_match(s, s->strstart, s->match_start, s->match_length);
 956
 957            bflush = zlib_tr_tally(s, s->strstart - s->match_start,
 958                               s->match_length - MIN_MATCH);
 959
 960            s->lookahead -= s->match_length;
 961
 962            /* Insert new strings in the hash table only if the match length
 963             * is not too large. This saves time but degrades compression.
 964             */
 965            if (s->match_length <= s->max_insert_length &&
 966                s->lookahead >= MIN_MATCH) {
 967                s->match_length--; /* string at strstart already in hash table */
 968                do {
 969                    s->strstart++;
 970                    INSERT_STRING(s, s->strstart, hash_head);
 971                    /* strstart never exceeds WSIZE-MAX_MATCH, so there are
 972                     * always MIN_MATCH bytes ahead.
 973                     */
 974                } while (--s->match_length != 0);
 975                s->strstart++;
 976            } else {
 977                s->strstart += s->match_length;
 978                s->match_length = 0;
 979                s->ins_h = s->window[s->strstart];
 980                UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
 981#if MIN_MATCH != 3
 982                Call UPDATE_HASH() MIN_MATCH-3 more times
 983#endif
 984                /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
 985                 * matter since it will be recomputed at next deflate call.
 986                 */
 987            }
 988        } else {
 989            /* No match, output a literal byte */
 990            Tracevv((stderr,"%c", s->window[s->strstart]));
 991            bflush = zlib_tr_tally (s, 0, s->window[s->strstart]);
 992            s->lookahead--;
 993            s->strstart++;
 994        }
 995        if (bflush) FLUSH_BLOCK(s, 0);
 996    }
 997    FLUSH_BLOCK(s, flush == Z_FINISH);
 998    return flush == Z_FINISH ? finish_done : block_done;
 999}
1000
1001/* ===========================================================================
1002 * Same as above, but achieves better compression. We use a lazy
1003 * evaluation for matches: a match is finally adopted only if there is
1004 * no better match at the next window position.
1005 */
1006static block_state deflate_slow(
1007        deflate_state *s,
1008        int flush
1009)
1010{
1011    IPos hash_head = NIL;    /* head of hash chain */
1012    int bflush;              /* set if current block must be flushed */
1013
1014    /* Process the input block. */
1015    for (;;) {
1016        /* Make sure that we always have enough lookahead, except
1017         * at the end of the input file. We need MAX_MATCH bytes
1018         * for the next match, plus MIN_MATCH bytes to insert the
1019         * string following the next match.
1020         */
1021        if (s->lookahead < MIN_LOOKAHEAD) {
1022            fill_window(s);
1023            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1024                return need_more;
1025            }
1026            if (s->lookahead == 0) break; /* flush the current block */
1027        }
1028
1029        /* Insert the string window[strstart .. strstart+2] in the
1030         * dictionary, and set hash_head to the head of the hash chain:
1031         */
1032        if (s->lookahead >= MIN_MATCH) {
1033            INSERT_STRING(s, s->strstart, hash_head);
1034        }
1035
1036        /* Find the longest match, discarding those <= prev_length.
1037         */
1038        s->prev_length = s->match_length, s->prev_match = s->match_start;
1039        s->match_length = MIN_MATCH-1;
1040
1041        if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1042            s->strstart - hash_head <= MAX_DIST(s)) {
1043            /* To simplify the code, we prevent matches with the string
1044             * of window index 0 (in particular we have to avoid a match
1045             * of the string with itself at the start of the input file).
1046             */
1047            if (s->strategy != Z_HUFFMAN_ONLY) {
1048                s->match_length = longest_match (s, hash_head);
1049            }
1050            /* longest_match() sets match_start */
1051
1052            if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
1053                 (s->match_length == MIN_MATCH &&
1054                  s->strstart - s->match_start > TOO_FAR))) {
1055
1056                /* If prev_match is also MIN_MATCH, match_start is garbage
1057                 * but we will ignore the current match anyway.
1058                 */
1059                s->match_length = MIN_MATCH-1;
1060            }
1061        }
1062        /* If there was a match at the previous step and the current
1063         * match is not better, output the previous match:
1064         */
1065        if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1066            uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1067            /* Do not insert strings in hash table beyond this. */
1068
1069            check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1070
1071            bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match,
1072                                   s->prev_length - MIN_MATCH);
1073
1074            /* Insert in hash table all strings up to the end of the match.
1075             * strstart-1 and strstart are already inserted. If there is not
1076             * enough lookahead, the last two strings are not inserted in
1077             * the hash table.
1078             */
1079            s->lookahead -= s->prev_length-1;
1080            s->prev_length -= 2;
1081            do {
1082                if (++s->strstart <= max_insert) {
1083                    INSERT_STRING(s, s->strstart, hash_head);
1084                }
1085            } while (--s->prev_length != 0);
1086            s->match_available = 0;
1087            s->match_length = MIN_MATCH-1;
1088            s->strstart++;
1089
1090            if (bflush) FLUSH_BLOCK(s, 0);
1091
1092        } else if (s->match_available) {
1093            /* If there was no match at the previous position, output a
1094             * single literal. If there was a match but the current match
1095             * is longer, truncate the previous match to a single literal.
1096             */
1097            Tracevv((stderr,"%c", s->window[s->strstart-1]));
1098            if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) {
1099                FLUSH_BLOCK_ONLY(s, 0);
1100            }
1101            s->strstart++;
1102            s->lookahead--;
1103            if (s->strm->avail_out == 0) return need_more;
1104        } else {
1105            /* There is no previous match to compare with, wait for
1106             * the next step to decide.
1107             */
1108            s->match_available = 1;
1109            s->strstart++;
1110            s->lookahead--;
1111        }
1112    }
1113    Assert (flush != Z_NO_FLUSH, "no flush?");
1114    if (s->match_available) {
1115        Tracevv((stderr,"%c", s->window[s->strstart-1]));
1116        zlib_tr_tally (s, 0, s->window[s->strstart-1]);
1117        s->match_available = 0;
1118    }
1119    FLUSH_BLOCK(s, flush == Z_FINISH);
1120    return flush == Z_FINISH ? finish_done : block_done;
1121}
1122
1123int zlib_deflate_workspacesize(int windowBits, int memLevel)
1124{
1125    if (windowBits < 0) /* undocumented feature: suppress zlib header */
1126        windowBits = -windowBits;
1127
1128    /* Since the return value is typically passed to vmalloc() unchecked... */
1129    assert(!(memLevel < 1 || memLevel > MAX_MEM_LEVEL || windowBits < 9 || windowBits > 15));
1130
1131    return sizeof(deflate_workspace)
1132        + zlib_deflate_window_memsize(windowBits)
1133        + zlib_deflate_prev_memsize(windowBits)
1134        + zlib_deflate_head_memsize(memLevel)
1135        + zlib_deflate_overlay_memsize(memLevel);
1136}
1137