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    1 /* deflate.c -- compress data using the deflation algorithm
    2  * Copyright (C) 1995-2003 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 
   54 const char deflate_copyright[] =
   55    " deflate 1.2.1.1 Copyright 1995-2003 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  */
   66 typedef 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 
   73 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
   74 /* Compression function. Returns the block state after the call. */
   75 
   76 local void fill_window    OF((deflate_state *s));
   77 local block_state deflate_stored OF((deflate_state *s, int flush));
   78 local block_state deflate_fast   OF((deflate_state *s, int flush));
   79 #ifndef FASTEST
   80 local block_state deflate_slow   OF((deflate_state *s, int flush));
   81 #endif
   82 local void lm_init        OF((deflate_state *s));
   83 local void putShortMSB    OF((deflate_state *s, uInt b));
   84 local void flush_pending  OF((z_streamp strm));
   85 local 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
   91 local uInt longest_match  OF((deflate_state *s, IPos cur_match));
   92 #endif
   93 #endif
   94 local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
   95 
   96 #ifdef DEBUG
   97 local  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  */
  123 typedef 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
  132 local 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
  137 local 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
  161 struct 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 /* ========================================================================= */
  204 int 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 /* ========================================================================= */
  216 int 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_RLE) {
  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->w_bits = windowBits;
  278     s->w_size = 1 << s->w_bits;
  279     s->w_mask = s->w_size - 1;
  280 
  281     s->hash_bits = memLevel + 7;
  282     s->hash_size = 1 << s->hash_bits;
  283     s->hash_mask = s->hash_size - 1;
  284     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
  285 
  286     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
  287     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
  288     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
  289 
  290     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
  291 
  292     overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
  293     s->pending_buf = (uchf *) overlay;
  294     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
  295 
  296     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
  297         s->pending_buf == Z_NULL) {
  298         s->status = FINISH_STATE;
  299         strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
  300         deflateEnd (strm);
  301         return Z_MEM_ERROR;
  302     }
  303     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
  304     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
  305 
  306     s->level = level;
  307     s->strategy = strategy;
  308     s->method = (Byte)method;
  309 
  310     return deflateReset(strm);
  311 }
  312 
  313 /* ========================================================================= */
  314 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
  315     z_streamp strm;
  316     const Bytef *dictionary;
  317     uInt  dictLength;
  318 {
  319     deflate_state *s;
  320     uInt length = dictLength;
  321     uInt n;
  322     IPos hash_head = 0;
  323 
  324     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
  325         strm->state->wrap == 2 ||
  326         (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
  327         return Z_STREAM_ERROR;
  328 
  329     s = strm->state;
  330     if (s->wrap)
  331         strm->adler = adler32(strm->adler, dictionary, dictLength);
  332 
  333     if (length < MIN_MATCH) return Z_OK;
  334     if (length > MAX_DIST(s)) {
  335         length = MAX_DIST(s);
  336 #ifndef USE_DICT_HEAD
  337         dictionary += dictLength - length; /* use the tail of the dictionary */
  338 #endif
  339     }
  340     zmemcpy(s->window, dictionary, length);
  341     s->strstart = length;
  342     s->block_start = (long)length;
  343 
  344     /* Insert all strings in the hash table (except for the last two bytes).
  345      * s->lookahead stays null, so s->ins_h will be recomputed at the next
  346      * call of fill_window.
  347      */
  348     s->ins_h = s->window[0];
  349     UPDATE_HASH(s, s->ins_h, s->window[1]);
  350     for (n = 0; n <= length - MIN_MATCH; n++) {
  351         INSERT_STRING(s, n, hash_head);
  352     }
  353     if (hash_head) hash_head = 0;  /* to make compiler happy */
  354     return Z_OK;
  355 }
  356 
  357 /* ========================================================================= */
  358 int ZEXPORT deflateReset (strm)
  359     z_streamp strm;
  360 {
  361     deflate_state *s;
  362 
  363     if (strm == Z_NULL || strm->state == Z_NULL ||
  364         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
  365         return Z_STREAM_ERROR;
  366     }
  367 
  368     strm->total_in = strm->total_out = 0;
  369     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
  370     strm->data_type = Z_UNKNOWN;
  371 
  372     s = (deflate_state *)strm->state;
  373     s->pending = 0;
  374     s->pending_out = s->pending_buf;
  375 
  376     if (s->wrap < 0) {
  377         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
  378     }
  379     s->status = s->wrap ? INIT_STATE : BUSY_STATE;
  380     strm->adler =
  381 #ifdef GZIP
  382         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
  383 #endif
  384         adler32(0L, Z_NULL, 0);
  385     s->last_flush = Z_NO_FLUSH;
  386 
  387     _tr_init(s);
  388     lm_init(s);
  389 
  390     return Z_OK;
  391 }
  392 
  393 /* ========================================================================= */
  394 int ZEXPORT deflatePrime (strm, bits, value)
  395     z_streamp strm;
  396     int bits;
  397     int value;
  398 {
  399     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  400     strm->state->bi_valid = bits;
  401     strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
  402     return Z_OK;
  403 }
  404 
  405 /* ========================================================================= */
  406 int ZEXPORT deflateParams(strm, level, strategy)
  407     z_streamp strm;
  408     int level;
  409     int strategy;
  410 {
  411     deflate_state *s;
  412     compress_func func;
  413     int err = Z_OK;
  414 
  415     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  416     s = strm->state;
  417 
  418 #ifdef FASTEST
  419     if (level != 0) level = 1;
  420 #else
  421     if (level == Z_DEFAULT_COMPRESSION) level = 6;
  422 #endif
  423     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_RLE) {
  424         return Z_STREAM_ERROR;
  425     }
  426     func = configuration_table[s->level].func;
  427 
  428     if (func != configuration_table[level].func && strm->total_in != 0) {
  429         /* Flush the last buffer: */
  430         err = deflate(strm, Z_PARTIAL_FLUSH);
  431     }
  432     if (s->level != level) {
  433         s->level = level;
  434         s->max_lazy_match   = configuration_table[level].max_lazy;
  435         s->good_match       = configuration_table[level].good_length;
  436         s->nice_match       = configuration_table[level].nice_length;
  437         s->max_chain_length = configuration_table[level].max_chain;
  438     }
  439     s->strategy = strategy;
  440     return err;
  441 }
  442 
  443 /* =========================================================================
  444  * For the default windowBits of 15 and memLevel of 8, this function returns
  445  * a close to exact, as well as small, upper bound on the compressed size.
  446  * They are coded as constants here for a reason--if the #define's are
  447  * changed, then this function needs to be changed as well.  The return
  448  * value for 15 and 8 only works for those exact settings.
  449  *
  450  * For any setting other than those defaults for windowBits and memLevel,
  451  * the value returned is a conservative worst case for the maximum expansion
  452  * resulting from using fixed blocks instead of stored blocks, which deflate
  453  * can emit on compressed data for some combinations of the parameters.
  454  *
  455  * This function could be more sophisticated to provide closer upper bounds
  456  * for every combination of windowBits and memLevel, as well as wrap.
  457  * But even the conservative upper bound of about 14% expansion does not
  458  * seem onerous for output buffer allocation.
  459  */
  460 uLong ZEXPORT deflateBound(strm, sourceLen)
  461     z_streamp strm;
  462     uLong sourceLen;
  463 {
  464     deflate_state *s;
  465     uLong destLen;
  466 
  467     /* conservative upper bound */
  468     destLen = sourceLen +
  469               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
  470 
  471     /* if can't get parameters, return conservative bound */
  472     if (strm == Z_NULL || strm->state == Z_NULL)
  473         return destLen;
  474 
  475     /* if not default parameters, return conservative bound */
  476     s = strm->state;
  477     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
  478         return destLen;
  479 
  480     /* default settings: return tight bound for that case */
  481     return compressBound(sourceLen);
  482 }
  483 
  484 /* =========================================================================
  485  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
  486  * IN assertion: the stream state is correct and there is enough room in
  487  * pending_buf.
  488  */
  489 local void putShortMSB (s, b)
  490     deflate_state *s;
  491     uInt b;
  492 {
  493     put_byte(s, (Byte)(b >> 8));
  494     put_byte(s, (Byte)(b & 0xff));
  495 }
  496 
  497 /* =========================================================================
  498  * Flush as much pending output as possible. All deflate() output goes
  499  * through this function so some applications may wish to modify it
  500  * to avoid allocating a large strm->next_out buffer and copying into it.
  501  * (See also read_buf()).
  502  */
  503 local void flush_pending(strm)
  504     z_streamp strm;
  505 {
  506     unsigned len = strm->state->pending;
  507 
  508     if (len > strm->avail_out) len = strm->avail_out;
  509     if (len == 0) return;
  510 
  511     zmemcpy(strm->next_out, strm->state->pending_out, len);
  512     strm->next_out  += len;
  513     strm->state->pending_out  += len;
  514     strm->total_out += len;
  515     strm->avail_out  -= len;
  516     strm->state->pending -= len;
  517     if (strm->state->pending == 0) {
  518         strm->state->pending_out = strm->state->pending_buf;
  519     }
  520 }
  521 
  522 /* ========================================================================= */
  523 int ZEXPORT deflate (strm, flush)
  524     z_streamp strm;
  525     int flush;
  526 {
  527     int old_flush; /* value of flush param for previous deflate call */
  528     deflate_state *s;
  529 
  530     if (strm == Z_NULL || strm->state == Z_NULL ||
  531         flush > Z_FINISH || flush < 0) {
  532         return Z_STREAM_ERROR;
  533     }
  534     s = strm->state;
  535 
  536     if (strm->next_out == Z_NULL ||
  537         (strm->next_in == Z_NULL && strm->avail_in != 0) ||
  538         (s->status == FINISH_STATE && flush != Z_FINISH)) {
  539         ERR_RETURN(strm, Z_STREAM_ERROR);
  540     }
  541     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
  542 
  543     s->strm = strm; /* just in case */
  544     old_flush = s->last_flush;
  545     s->last_flush = flush;
  546 
  547     /* Write the header */
  548     if (s->status == INIT_STATE) {
  549 #ifdef GZIP
  550         if (s->wrap == 2) {
  551             put_byte(s, 31);
  552             put_byte(s, 139);
  553             put_byte(s, 8);
  554             put_byte(s, 0);
  555             put_byte(s, 0);
  556             put_byte(s, 0);
  557             put_byte(s, 0);
  558             put_byte(s, 0);
  559             put_byte(s, s->level == 9 ? 2 :
  560                         (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
  561                          4 : 0));
  562             put_byte(s, 255);
  563             s->status = BUSY_STATE;
  564             strm->adler = crc32(0L, Z_NULL, 0);
  565         }
  566         else
  567 #endif
  568         {
  569             uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
  570             uInt level_flags;
  571 
  572             if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
  573                 level_flags = 0;
  574             else if (s->level < 6)
  575                 level_flags = 1;
  576             else if (s->level == 6)
  577                 level_flags = 2;
  578             else
  579                 level_flags = 3;
  580             header |= (level_flags << 6);
  581             if (s->strstart != 0) header |= PRESET_DICT;
  582             header += 31 - (header % 31);
  583 
  584             s->status = BUSY_STATE;
  585             putShortMSB(s, header);
  586 
  587             /* Save the adler32 of the preset dictionary: */
  588             if (s->strstart != 0) {
  589                 putShortMSB(s, (uInt)(strm->adler >> 16));
  590                 putShortMSB(s, (uInt)(strm->adler & 0xffff));
  591             }
  592             strm->adler = adler32(0L, Z_NULL, 0);
  593         }
  594     }
  595 
  596     /* Flush as much pending output as possible */
  597     if (s->pending != 0) {
  598         flush_pending(strm);
  599         if (strm->avail_out == 0) {
  600             /* Since avail_out is 0, deflate will be called again with
  601              * more output space, but possibly with both pending and
  602              * avail_in equal to zero. There won't be anything to do,
  603              * but this is not an error situation so make sure we
  604              * return OK instead of BUF_ERROR at next call of deflate:
  605              */
  606             s->last_flush = -1;
  607             return Z_OK;
  608         }
  609 
  610     /* Make sure there is something to do and avoid duplicate consecutive
  611      * flushes. For repeated and useless calls with Z_FINISH, we keep
  612      * returning Z_STREAM_END instead of Z_BUF_ERROR.
  613      */
  614     } else if (strm->avail_in == 0 && flush <= old_flush &&
  615                flush != Z_FINISH) {
  616         ERR_RETURN(strm, Z_BUF_ERROR);
  617     }
  618 
  619     /* User must not provide more input after the first FINISH: */
  620     if (s->status == FINISH_STATE && strm->avail_in != 0) {
  621         ERR_RETURN(strm, Z_BUF_ERROR);
  622     }
  623 
  624     /* Start a new block or continue the current one.
  625      */
  626     if (strm->avail_in != 0 || s->lookahead != 0 ||
  627         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
  628         block_state bstate;
  629 
  630         bstate = (*(configuration_table[s->level].func))(s, flush);
  631 
  632         if (bstate == finish_started || bstate == finish_done) {
  633             s->status = FINISH_STATE;
  634         }
  635         if (bstate == need_more || bstate == finish_started) {
  636             if (strm->avail_out == 0) {
  637                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
  638             }
  639             return Z_OK;
  640             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
  641              * of deflate should use the same flush parameter to make sure
  642              * that the flush is complete. So we don't have to output an
  643              * empty block here, this will be done at next call. This also
  644              * ensures that for a very small output buffer, we emit at most
  645              * one empty block.
  646              */
  647         }
  648         if (bstate == block_done) {
  649             if (flush == Z_PARTIAL_FLUSH) {
  650           //                _tr_align(s);
  651             } else { /* FULL_FLUSH or SYNC_FLUSH */
  652                 _tr_stored_block(s, (char*)0, 0L, 0);
  653                 /* For a full flush, this empty block will be recognized
  654                  * as a special marker by inflate_sync().
  655                  */
  656                 if (flush == Z_FULL_FLUSH) {
  657                     CLEAR_HASH(s);             /* forget history */
  658                 }
  659             }
  660             flush_pending(strm);
  661             if (strm->avail_out == 0) {
  662               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
  663               return Z_OK;
  664             }
  665         }
  666     }
  667     Assert(strm->avail_out > 0, "bug2");
  668 
  669     if (flush != Z_FINISH) return Z_OK;
  670     if (s->wrap <= 0) return Z_STREAM_END;
  671 
  672     /* Write the trailer */
  673 #ifdef GZIP
  674     if (s->wrap == 2) {
  675         put_byte(s, (Byte)(strm->adler & 0xff));
  676         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
  677         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
  678         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
  679         put_byte(s, (Byte)(strm->total_in & 0xff));
  680         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
  681         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
  682         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
  683     }
  684     else
  685 #endif
  686     {
  687         putShortMSB(s, (uInt)(strm->adler >> 16));
  688         putShortMSB(s, (uInt)(strm->adler & 0xffff));
  689     }
  690     flush_pending(strm);
  691     /* If avail_out is zero, the application will call deflate again
  692      * to flush the rest.
  693      */
  694     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
  695     return s->pending != 0 ? Z_OK : Z_STREAM_END;
  696 }
  697 
  698 /* ========================================================================= */
  699 int ZEXPORT deflateEnd (strm)
  700     z_streamp strm;
  701 {
  702     int status;
  703 
  704     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  705 
  706     status = strm->state->status;
  707     if (status != INIT_STATE && status != BUSY_STATE &&
  708         status != FINISH_STATE) {
  709       return Z_STREAM_ERROR;
  710     }
  711 
  712     /* Deallocate in reverse order of allocations: */
  713     TRY_FREE(strm, strm->state->pending_buf);
  714     TRY_FREE(strm, strm->state->head);
  715     TRY_FREE(strm, strm->state->prev);
  716     TRY_FREE(strm, strm->state->window);
  717 
  718     ZFREE(strm, strm->state);
  719     strm->state = Z_NULL;
  720 
  721     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
  722 }
  723 
  724 /* =========================================================================
  725  * Copy the source state to the destination state.
  726  * To simplify the source, this is not supported for 16-bit MSDOS (which
  727  * doesn't have enough memory anyway to duplicate compression states).
  728  */
  729 int ZEXPORT deflateCopy (dest, source)
  730     z_streamp dest;
  731     z_streamp source;
  732 {
  733 #ifdef MAXSEG_64K
  734     return Z_STREAM_ERROR;
  735 #else
  736     deflate_state *ds;
  737     deflate_state *ss;
  738     ushf *overlay;
  739 
  740 
  741     if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
  742         return Z_STREAM_ERROR;
  743     }
  744 
  745     ss = source->state;
  746 
  747     *dest = *source;
  748 
  749     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
  750     if (ds == Z_NULL) return Z_MEM_ERROR;
  751     dest->state = (struct internal_state FAR *) ds;
  752     *ds = *ss;
  753     ds->strm = dest;
  754 
  755     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
  756     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
  757     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
  758     overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
  759     ds->pending_buf = (uchf *) overlay;
  760 
  761     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
  762         ds->pending_buf == Z_NULL) {
  763         deflateEnd (dest);
  764         return Z_MEM_ERROR;
  765     }
  766     /* following zmemcpy do not work for 16-bit MSDOS */
  767     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
  768     zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
  769     zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
  770     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
  771 
  772     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
  773     ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
  774     ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
  775 
  776     ds->l_desc.dyn_tree = ds->dyn_ltree;
  777     ds->d_desc.dyn_tree = ds->dyn_dtree;
  778     ds->bl_desc.dyn_tree = ds->bl_tree;
  779 
  780     return Z_OK;
  781 #endif /* MAXSEG_64K */
  782 }
  783 
  784 /* ===========================================================================
  785  * Read a new buffer from the current input stream, update the adler32
  786  * and total number of bytes read.  All deflate() input goes through
  787  * this function so some applications may wish to modify it to avoid
  788  * allocating a large strm->next_in buffer and copying from it.
  789  * (See also flush_pending()).
  790  */
  791 local int read_buf(strm, buf, size)
  792     z_streamp strm;
  793     Bytef *buf;
  794     unsigned size;
  795 {
  796     unsigned len = strm->avail_in;
  797 
  798     if (len > size) len = size;
  799     if (len == 0) return 0;
  800 
  801     strm->avail_in  -= len;
  802 
  803     if (strm->state->wrap == 1) {
  804         strm->adler = adler32(strm->adler, strm->next_in, len);
  805     }
  806 #ifdef GZIP
  807     else if (strm->state->wrap == 2) {
  808         strm->adler = crc32(strm->adler, strm->next_in, len);
  809     }
  810 #endif
  811     zmemcpy(buf, strm->next_in, len);
  812     strm->next_in  += len;
  813     strm->total_in += len;
  814 
  815     return (int)len;
  816 }
  817 
  818 /* ===========================================================================
  819  * Initialize the "longest match" routines for a new zlib stream
  820  */
  821 local void lm_init (s)
  822     deflate_state *s;
  823 {
  824     s->window_size = (ulg)2L*s->w_size;
  825 
  826     CLEAR_HASH(s);
  827 
  828     /* Set the default configuration parameters:
  829      */
  830     s->max_lazy_match   = configuration_table[s->level].max_lazy;
  831     s->good_match       = configuration_table[s->level].good_length;
  832     s->nice_match       = configuration_table[s->level].nice_length;
  833     s->max_chain_length = configuration_table[s->level].max_chain;
  834 
  835     s->strstart = 0;
  836     s->block_start = 0L;
  837     s->lookahead = 0;
  838     s->match_length = s->prev_length = MIN_MATCH-1;
  839     s->match_available = 0;
  840     s->ins_h = 0;
  841 #ifdef ASMV
  842     match_init(); /* initialize the asm code */
  843 #endif
  844 }
  845 
  846 #ifndef FASTEST
  847 /* ===========================================================================
  848  * Set match_start to the longest match starting at the given string and
  849  * return its length. Matches shorter or equal to prev_length are discarded,
  850  * in which case the result is equal to prev_length and match_start is
  851  * garbage.
  852  * IN assertions: cur_match is the head of the hash chain for the current
  853  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
  854  * OUT assertion: the match length is not greater than s->lookahead.
  855  */
  856 #ifndef ASMV
  857 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
  858  * match.S. The code will be functionally equivalent.
  859  */
  860 local uInt longest_match(s, cur_match)
  861     deflate_state *s;
  862     IPos cur_match;                             /* current match */
  863 {
  864     unsigned chain_length = s->max_chain_length;/* max hash chain length */
  865     register Bytef *scan = s->window + s->strstart; /* current string */
  866     register Bytef *match;                       /* matched string */
  867     register int len;                           /* length of current match */
  868     int best_len = s->prev_length;              /* best match length so far */
  869     int nice_match = s->nice_match;             /* stop if match long enough */
  870     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
  871         s->strstart - (IPos)MAX_DIST(s) : NIL;
  872     /* Stop when cur_match becomes <= limit. To simplify the code,
  873      * we prevent matches with the string of window index 0.
  874      */
  875     Posf *prev = s->prev;
  876     uInt wmask = s->w_mask;
  877 
  878 #ifdef UNALIGNED_OK
  879     /* Compare two bytes at a time. Note: this is not always beneficial.
  880      * Try with and without -DUNALIGNED_OK to check.
  881      */
  882     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
  883     register ush scan_start = *(ushf*)scan;
  884     register ush scan_end   = *(ushf*)(scan+best_len-1);
  885 #else
  886     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
  887     register Byte scan_end1  = scan[best_len-1];
  888     register Byte scan_end   = scan[best_len];
  889 #endif
  890 
  891     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
  892      * It is easy to get rid of this optimization if necessary.
  893      */
  894     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
  895 
  896     /* Do not waste too much time if we already have a good match: */
  897     if (s->prev_length >= s->good_match) {
  898         chain_length >>= 2;
  899     }
  900     /* Do not look for matches beyond the end of the input. This is necessary
  901      * to make deflate deterministic.
  902      */
  903     if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
  904 
  905     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
  906 
  907     do {
  908         Assert(cur_match < s->strstart, "no future");
  909         match = s->window + cur_match;
  910 
  911         /* Skip to next match if the match length cannot increase
  912          * or if the match length is less than 2:
  913          */
  914 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
  915         /* This code assumes sizeof(unsigned short) == 2. Do not use
  916          * UNALIGNED_OK if your compiler uses a different size.
  917          */
  918         if (*(ushf*)(match+best_len-1) != scan_end ||
  919             *(ushf*)match != scan_start) continue;
  920 
  921         /* It is not necessary to compare scan[2] and match[2] since they are
  922          * always equal when the other bytes match, given that the hash keys
  923          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
  924          * strstart+3, +5, ... up to strstart+257. We check for insufficient
  925          * lookahead only every 4th comparison; the 128th check will be made
  926          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
  927          * necessary to put more guard bytes at the end of the window, or
  928          * to check more often for insufficient lookahead.
  929          */
  930         Assert(scan[2] == match[2], "scan[2]?");
  931         scan++, match++;
  932         do {
  933         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  934                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  935                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  936                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  937                  scan < strend);
  938         /* The funny "do {}" generates better code on most compilers */
  939 
  940         /* Here, scan <= window+strstart+257 */
  941         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  942         if (*scan == *match) scan++;
  943 
  944         len = (MAX_MATCH - 1) - (int)(strend-scan);
  945         scan = strend - (MAX_MATCH-1);
  946 
  947 #else /* UNALIGNED_OK */
  948 
  949         if (match[best_len]   != scan_end  ||
  950             match[best_len-1] != scan_end1 ||
  951             *match            != *scan     ||
  952             *++match          != scan[1])      continue;
  953 
  954         /* The check at best_len-1 can be removed because it will be made
  955          * again later. (This heuristic is not always a win.)
  956          * It is not necessary to compare scan[2] and match[2] since they
  957          * are always equal when the other bytes match, given that
  958          * the hash keys are equal and that HASH_BITS >= 8.
  959          */
  960         scan += 2, match++;
  961         Assert(*scan == *match, "match[2]?");
  962 
  963         /* We check for insufficient lookahead only every 8th comparison;
  964          * the 256th check will be made at strstart+258.
  965          */
  966         do {
  967         } while (*++scan == *++match && *++scan == *++match &&
  968                  *++scan == *++match && *++scan == *++match &&
  969                  *++scan == *++match && *++scan == *++match &&
  970                  *++scan == *++match && *++scan == *++match &&
  971                  scan < strend);
  972 
  973         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  974 
  975         len = MAX_MATCH - (int)(strend - scan);
  976         scan = strend - MAX_MATCH;
  977 
  978 #endif /* UNALIGNED_OK */
  979 
  980         if (len > best_len) {
  981             s->match_start = cur_match;
  982             best_len = len;
  983             if (len >= nice_match) break;
  984 #ifdef UNALIGNED_OK
  985             scan_end = *(ushf*)(scan+best_len-1);
  986 #else
  987             scan_end1  = scan[best_len-1];
  988             scan_end   = scan[best_len];
  989 #endif
  990         }
  991     } while ((cur_match = prev[cur_match & wmask]) > limit
  992              && --chain_length != 0);
  993 
  994     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
  995     return s->lookahead;
  996 }
  997 #endif /* ASMV */
  998 #endif /* FASTEST */
  999 
 1000 /* ---------------------------------------------------------------------------
 1001  * Optimized version for level == 1 or strategy == Z_RLE only
 1002  */
 1003 local uInt longest_match_fast(s, cur_match)
 1004     deflate_state *s;
 1005     IPos cur_match;                             /* current match */
 1006 {
 1007     register Bytef *scan = s->window + s->strstart; /* current string */
 1008     register Bytef *match;                       /* matched string */
 1009     register int len;                           /* length of current match */
 1010     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
 1011 
 1012     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
 1013      * It is easy to get rid of this optimization if necessary.
 1014      */
 1015     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
 1016 
 1017     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
 1018 
 1019     Assert(cur_match < s->strstart, "no future");
 1020 
 1021     match = s->window + cur_match;
 1022 
 1023     /* Return failure if the match length is less than 2:
 1024      */
 1025     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
 1026 
 1027     /* The check at best_len-1 can be removed because it will be made
 1028      * again later. (This heuristic is not always a win.)
 1029      * It is not necessary to compare scan[2] and match[2] since they
 1030      * are always equal when the other bytes match, given that
 1031      * the hash keys are equal and that HASH_BITS >= 8.
 1032      */
 1033     scan += 2, match += 2;
 1034     Assert(*scan == *match, "match[2]?");
 1035 
 1036     /* We check for insufficient lookahead only every 8th comparison;
 1037      * the 256th check will be made at strstart+258.
 1038      */
 1039     do {
 1040     } while (*++scan == *++match && *++scan == *++match &&
 1041              *++scan == *++match && *++scan == *++match &&
 1042              *++scan == *++match && *++scan == *++match &&
 1043              *++scan == *++match && *++scan == *++match &&
 1044              scan < strend);
 1045 
 1046     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
 1047 
 1048     len = MAX_MATCH - (int)(strend - scan);
 1049 
 1050     if (len < MIN_MATCH) return MIN_MATCH - 1;
 1051 
 1052     s->match_start = cur_match;
 1053     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
 1054 }
 1055 
 1056 #ifdef DEBUG
 1057 /* ===========================================================================
 1058  * Check that the match at match_start is indeed a match.
 1059  */
 1060 local void check_match(s, start, match, length)
 1061     deflate_state *s;
 1062     IPos start, match;
 1063     int length;
 1064 {
 1065     /* check that the match is indeed a match */
 1066     if (zmemcmp(s->window + match,
 1067                 s->window + start, length) != EQUAL) {
 1068         fprintf(stderr, " start %u, match %u, length %d\n",
 1069                 start, match, length);
 1070         do {
 1071             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
 1072         } while (--length != 0);
 1073         z_error("invalid match");
 1074     }
 1075     if (z_verbose > 1) {
 1076         fprintf(stderr,"\\[%d,%d]", start-match, length);
 1077         do { putc(s->window[start++], stderr); } while (--length != 0);
 1078     }
 1079 }
 1080 #else
 1081 #  define check_match(s, start, match, length)
 1082 #endif /* DEBUG */
 1083 
 1084 /* ===========================================================================
 1085  * Fill the window when the lookahead becomes insufficient.
 1086  * Updates strstart and lookahead.
 1087  *
 1088  * IN assertion: lookahead < MIN_LOOKAHEAD
 1089  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
 1090  *    At least one byte has been read, or avail_in == 0; reads are
 1091  *    performed for at least two bytes (required for the zip translate_eol
 1092  *    option -- not supported here).
 1093  */
 1094 local void fill_window(s)
 1095     deflate_state *s;
 1096 {
 1097     register unsigned n, m;
 1098     register Posf *p;
 1099     unsigned more;    /* Amount of free space at the end of the window. */
 1100     uInt wsize = s->w_size;
 1101 
 1102     do {
 1103         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
 1104 
 1105         /* Deal with !@#$% 64K limit: */
 1106         if (sizeof(int) <= 2) {
 1107             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
 1108                 more = wsize;
 1109 
 1110             } else if (more == (unsigned)(-1)) {
 1111                 /* Very unlikely, but possible on 16 bit machine if
 1112                  * strstart == 0 && lookahead == 1 (input done a byte at time)
 1113                  */
 1114                 more--;
 1115             }
 1116         }
 1117 
 1118         /* If the window is almost full and there is insufficient lookahead,
 1119          * move the upper half to the lower one to make room in the upper half.
 1120          */
 1121         if (s->strstart >= wsize+MAX_DIST(s)) {
 1122 
 1123             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
 1124             s->match_start -= wsize;
 1125             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
 1126             s->block_start -= (long) wsize;
 1127 
 1128             /* Slide the hash table (could be avoided with 32 bit values
 1129                at the expense of memory usage). We slide even when level == 0
 1130                to keep the hash table consistent if we switch back to level > 0
 1131                later. (Using level 0 permanently is not an optimal usage of
 1132                zlib, so we don't care about this pathological case.)
 1133              */
 1134             n = s->hash_size;
 1135             p = &s->head[n];
 1136             do {
 1137                 m = *--p;
 1138                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
 1139             } while (--n);
 1140 
 1141             n = wsize;
 1142 #ifndef FASTEST
 1143             p = &s->prev[n];
 1144             do {
 1145                 m = *--p;
 1146                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
 1147                 /* If n is not on any hash chain, prev[n] is garbage but
 1148                  * its value will never be used.
 1149                  */
 1150             } while (--n);
 1151 #endif
 1152             more += wsize;
 1153         }
 1154         if (s->strm->avail_in == 0) return;
 1155 
 1156         /* If there was no sliding:
 1157          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
 1158          *    more == window_size - lookahead - strstart
 1159          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
 1160          * => more >= window_size - 2*WSIZE + 2
 1161          * In the BIG_MEM or MMAP case (not yet supported),
 1162          *   window_size == input_size + MIN_LOOKAHEAD  &&
 1163          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
 1164          * Otherwise, window_size == 2*WSIZE so more >= 2.
 1165          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
 1166          */
 1167         Assert(more >= 2, "more < 2");
 1168 
 1169         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
 1170         s->lookahead += n;
 1171 
 1172         /* Initialize the hash value now that we have some input: */
 1173         if (s->lookahead >= MIN_MATCH) {
 1174             s->ins_h = s->window[s->strstart];
 1175             UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
 1176 #if MIN_MATCH != 3
 1177             Call UPDATE_HASH() MIN_MATCH-3 more times
 1178 #endif
 1179         }
 1180         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
 1181          * but this is not important since only literal bytes will be emitted.
 1182          */
 1183 
 1184     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
 1185 }
 1186 
 1187 /* ===========================================================================
 1188  * Flush the current block, with given end-of-file flag.
 1189  * IN assertion: strstart is set to the end of the current match.
 1190  */
 1191 #define FLUSH_BLOCK_ONLY(s, eof) { \
 1192    _tr_flush_block(s, (s->block_start >= 0L ? \
 1193                    (charf *)&s->window[(unsigned)s->block_start] : \
 1194                    (charf *)Z_NULL), \
 1195                 (ulg)((long)s->strstart - s->block_start), \
 1196                 (eof)); \
 1197    s->block_start = s->strstart; \
 1198    flush_pending(s->strm); \
 1199    Tracev((stderr,"[FLUSH]")); \
 1200 }
 1201 
 1202 /* Same but force premature exit if necessary. */
 1203 #define FLUSH_BLOCK(s, eof) { \
 1204    FLUSH_BLOCK_ONLY(s, eof); \
 1205    if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
 1206 }
 1207 
 1208 /* ===========================================================================
 1209  * Copy without compression as much as possible from the input stream, return
 1210  * the current block state.
 1211  * This function does not insert new strings in the dictionary since
 1212  * uncompressible data is probably not useful. This function is used
 1213  * only for the level=0 compression option.
 1214  * NOTE: this function should be optimized to avoid extra copying from
 1215  * window to pending_buf.
 1216  */
 1217 local block_state deflate_stored(s, flush)
 1218     deflate_state *s;
 1219     int flush;
 1220 {
 1221     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
 1222      * to pending_buf_size, and each stored block has a 5 byte header:
 1223      */
 1224     ulg max_block_size = 0xffff;
 1225     ulg max_start;
 1226 
 1227     if (max_block_size > s->pending_buf_size - 5) {
 1228         max_block_size = s->pending_buf_size - 5;
 1229     }
 1230 
 1231     /* Copy as much as possible from input to output: */
 1232     for (;;) {
 1233         /* Fill the window as much as possible: */
 1234         if (s->lookahead <= 1) {
 1235 
 1236             Assert(s->strstart < s->w_size+MAX_DIST(s) ||
 1237                    s->block_start >= (long)s->w_size, "slide too late");
 1238 
 1239             fill_window(s);
 1240             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
 1241 
 1242             if (s->lookahead == 0) break; /* flush the current block */
 1243         }
 1244         Assert(s->block_start >= 0L, "block gone");
 1245 
 1246         s->strstart += s->lookahead;
 1247         s->lookahead = 0;
 1248 
 1249         /* Emit a stored block if pending_buf will be full: */
 1250         max_start = s->block_start + max_block_size;
 1251         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
 1252             /* strstart == 0 is possible when wraparound on 16-bit machine */
 1253             s->lookahead = (uInt)(s->strstart - max_start);
 1254             s->strstart = (uInt)max_start;
 1255             FLUSH_BLOCK(s, 0);
 1256         }
 1257         /* Flush if we may have to slide, otherwise block_start may become
 1258          * negative and the data will be gone:
 1259          */
 1260         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
 1261             FLUSH_BLOCK(s, 0);
 1262         }
 1263     }
 1264     FLUSH_BLOCK(s, flush == Z_FINISH);
 1265     return flush == Z_FINISH ? finish_done : block_done;
 1266 }
 1267 
 1268 /* ===========================================================================
 1269  * Compress as much as possible from the input stream, return the current
 1270  * block state.
 1271  * This function does not perform lazy evaluation of matches and inserts
 1272  * new strings in the dictionary only for unmatched strings or for short
 1273  * matches. It is used only for the fast compression options.
 1274  */
 1275 local block_state deflate_fast(s, flush)
 1276     deflate_state *s;
 1277     int flush;
 1278 {
 1279     IPos hash_head = NIL; /* head of the hash chain */
 1280     int bflush;           /* set if current block must be flushed */
 1281 
 1282     for (;;) {
 1283         /* Make sure that we always have enough lookahead, except
 1284          * at the end of the input file. We need MAX_MATCH bytes
 1285          * for the next match, plus MIN_MATCH bytes to insert the
 1286          * string following the next match.
 1287          */
 1288         if (s->lookahead < MIN_LOOKAHEAD) {
 1289             fill_window(s);
 1290             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
 1291                 return need_more;
 1292             }
 1293             if (s->lookahead == 0) break; /* flush the current block */
 1294         }
 1295 
 1296         /* Insert the string window[strstart .. strstart+2] in the
 1297          * dictionary, and set hash_head to the head of the hash chain:
 1298          */
 1299         if (s->lookahead >= MIN_MATCH) {
 1300             INSERT_STRING(s, s->strstart, hash_head);
 1301         }
 1302 
 1303         /* Find the longest match, discarding those <= prev_length.
 1304          * At this point we have always match_length < MIN_MATCH
 1305          */
 1306         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
 1307             /* To simplify the code, we prevent matches with the string
 1308              * of window index 0 (in particular we have to avoid a match
 1309              * of the string with itself at the start of the input file).
 1310              */
 1311 #ifdef FASTEST
 1312             if ((s->strategy < Z_HUFFMAN_ONLY) ||
 1313                 (s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
 1314                 s->match_length = longest_match_fast (s, hash_head);
 1315             }
 1316 #else
 1317             if (s->strategy < Z_HUFFMAN_ONLY) {
 1318                 s->match_length = longest_match (s, hash_head);
 1319             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
 1320                 s->match_length = longest_match_fast (s, hash_head);
 1321             }
 1322 #endif
 1323             /* longest_match() or longest_match_fast() sets match_start */
 1324         }
 1325         if (s->match_length >= MIN_MATCH) {
 1326             check_match(s, s->strstart, s->match_start, s->match_length);
 1327 
 1328             _tr_tally_dist(s, s->strstart - s->match_start,
 1329                            s->match_length - MIN_MATCH, bflush);
 1330 
 1331             s->lookahead -= s->match_length;
 1332 
 1333             /* Insert new strings in the hash table only if the match length
 1334              * is not too large. This saves time but degrades compression.
 1335              */
 1336 #ifndef FASTEST
 1337             if (s->match_length <= s->max_insert_length &&
 1338                 s->lookahead >= MIN_MATCH) {
 1339                 s->match_length--; /* string at strstart already in table */
 1340                 do {
 1341                     s->strstart++;
 1342                     INSERT_STRING(s, s->strstart, hash_head);
 1343                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
 1344                      * always MIN_MATCH bytes ahead.
 1345                      */
 1346                 } while (--s->match_length != 0);
 1347                 s->strstart++;
 1348             } else
 1349 #endif
 1350             {
 1351                 s->strstart += s->match_length;
 1352                 s->match_length = 0;
 1353                 s->ins_h = s->window[s->strstart];
 1354                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
 1355 #if MIN_MATCH != 3
 1356                 Call UPDATE_HASH() MIN_MATCH-3 more times
 1357 #endif
 1358                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
 1359                  * matter since it will be recomputed at next deflate call.
 1360                  */
 1361             }
 1362         } else {
 1363             /* No match, output a literal byte */
 1364             Tracevv((stderr,"%c", s->window[s->strstart]));
 1365             _tr_tally_lit (s, s->window[s->strstart], bflush);
 1366             s->lookahead--;
 1367             s->strstart++;
 1368         }
 1369         if (bflush) FLUSH_BLOCK(s, 0);
 1370     }
 1371     FLUSH_BLOCK(s, flush == Z_FINISH);
 1372     return flush == Z_FINISH ? finish_done : block_done;
 1373 }
 1374 
 1375 #ifndef FASTEST
 1376 /* ===========================================================================
 1377  * Same as above, but achieves better compression. We use a lazy
 1378  * evaluation for matches: a match is finally adopted only if there is
 1379  * no better match at the next window position.
 1380  */
 1381 local block_state deflate_slow(s, flush)
 1382     deflate_state *s;
 1383     int flush;
 1384 {
 1385     IPos hash_head = NIL;    /* head of hash chain */
 1386     int bflush;              /* set if current block must be flushed */
 1387 
 1388     /* Process the input block. */
 1389     for (;;) {
 1390         /* Make sure that we always have enough lookahead, except
 1391          * at the end of the input file. We need MAX_MATCH bytes
 1392          * for the next match, plus MIN_MATCH bytes to insert the
 1393          * string following the next match.
 1394          */
 1395         if (s->lookahead < MIN_LOOKAHEAD) {
 1396             fill_window(s);
 1397             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
 1398                 return need_more;
 1399             }
 1400             if (s->lookahead == 0) break; /* flush the current block */
 1401         }
 1402 
 1403         /* Insert the string window[strstart .. strstart+2] in the
 1404          * dictionary, and set hash_head to the head of the hash chain:
 1405          */
 1406         if (s->lookahead >= MIN_MATCH) {
 1407             INSERT_STRING(s, s->strstart, hash_head);
 1408         }
 1409 
 1410         /* Find the longest match, discarding those <= prev_length.
 1411          */
 1412         s->prev_length = s->match_length, s->prev_match = s->match_start;
 1413         s->match_length = MIN_MATCH-1;
 1414 
 1415         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
 1416             s->strstart - hash_head <= MAX_DIST(s)) {
 1417             /* To simplify the code, we prevent matches with the string
 1418              * of window index 0 (in particular we have to avoid a match
 1419              * of the string with itself at the start of the input file).
 1420              */
 1421             if (s->strategy < Z_HUFFMAN_ONLY) {
 1422                 s->match_length = longest_match (s, hash_head);
 1423             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
 1424                 s->match_length = longest_match_fast (s, hash_head);
 1425             }
 1426             /* longest_match() or longest_match_fast() sets match_start */
 1427 
 1428             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
 1429 #if TOO_FAR <= 32767
 1430                 || (s->match_length == MIN_MATCH &&
 1431                     s->strstart - s->match_start > TOO_FAR)
 1432 #endif
 1433                 )) {
 1434 
 1435                 /* If prev_match is also MIN_MATCH, match_start is garbage
 1436                  * but we will ignore the current match anyway.
 1437                  */
 1438                 s->match_length = MIN_MATCH-1;
 1439             }
 1440         }
 1441         /* If there was a match at the previous step and the current
 1442          * match is not better, output the previous match:
 1443          */
 1444         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
 1445             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
 1446             /* Do not insert strings in hash table beyond this. */
 1447 
 1448             check_match(s, s->strstart-1, s->prev_match, s->prev_length);
 1449 
 1450             _tr_tally_dist(s, s->strstart -1 - s->prev_match,
 1451                            s->prev_length - MIN_MATCH, bflush);
 1452 
 1453             /* Insert in hash table all strings up to the end of the match.
 1454              * strstart-1 and strstart are already inserted. If there is not
 1455              * enough lookahead, the last two strings are not inserted in
 1456              * the hash table.
 1457              */
 1458             s->lookahead -= s->prev_length-1;
 1459             s->prev_length -= 2;
 1460             do {
 1461                 if (++s->strstart <= max_insert) {
 1462                     INSERT_STRING(s, s->strstart, hash_head);
 1463                 }
 1464             } while (--s->prev_length != 0);
 1465             s->match_available = 0;
 1466             s->match_length = MIN_MATCH-1;
 1467             s->strstart++;
 1468 
 1469             if (bflush) FLUSH_BLOCK(s, 0);
 1470 
 1471         } else if (s->match_available) {
 1472             /* If there was no match at the previous position, output a
 1473              * single literal. If there was a match but the current match
 1474              * is longer, truncate the previous match to a single literal.
 1475              */
 1476             Tracevv((stderr,"%c", s->window[s->strstart-1]));
 1477             _tr_tally_lit(s, s->window[s->strstart-1], bflush);
 1478             if (bflush) {
 1479                 FLUSH_BLOCK_ONLY(s, 0);
 1480             }
 1481             s->strstart++;
 1482             s->lookahead--;
 1483             if (s->strm->avail_out == 0) return need_more;
 1484         } else {
 1485             /* There is no previous match to compare with, wait for
 1486              * the next step to decide.
 1487              */
 1488             s->match_available = 1;
 1489             s->strstart++;
 1490             s->lookahead--;
 1491         }
 1492     }
 1493     Assert (flush != Z_NO_FLUSH, "no flush?");
 1494     if (s->match_available) {
 1495         Tracevv((stderr,"%c", s->window[s->strstart-1]));
 1496         _tr_tally_lit(s, s->window[s->strstart-1], bflush);
 1497         s->match_available = 0;
 1498     }
 1499     FLUSH_BLOCK(s, flush == Z_FINISH);
 1500     return flush == Z_FINISH ? finish_done : block_done;
 1501 }
 1502 #endif /* FASTEST */