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deflate.c

MalwareMustDie Jul 14th, 2015 (edited) 90 Never
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  1. // #MalwareMustDie - tip:
  2. // pipe the encoded to http://www.zlib.net/zpipe.c to decode.
  3. // @unixfreaxjp
  4. //
  5.  
  6. /* deflate.c -- compress data using the deflation algorithm
  7.  * Copyright (C) 1995-2005 Jean-loup Gailly.
  8.  * For conditions of distribution and use, see copyright notice in zlib.h
  9.  */
  10.  
  11. /*
  12.  *  ALGORITHM
  13.  *
  14.  *      The "deflation" process depends on being able to identify portions
  15.  *      of the input text which are identical to earlier input (within a
  16.  *      sliding window trailing behind the input currently being processed).
  17.  *
  18.  *      The most straightforward technique turns out to be the fastest for
  19.  *      most input files: try all possible matches and select the longest.
  20.  *      The key feature of this algorithm is that insertions into the string
  21.  *      dictionary are very simple and thus fast, and deletions are avoided
  22.  *      completely. Insertions are performed at each input character, whereas
  23.  *      string matches are performed only when the previous match ends. So it
  24.  *      is preferable to spend more time in matches to allow very fast string
  25.  *      insertions and avoid deletions. The matching algorithm for small
  26.  *      strings is inspired from that of Rabin & Karp. A brute force approach
  27.  *      is used to find longer strings when a small match has been found.
  28.  *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
  29.  *      (by Leonid Broukhis).
  30.  *         A previous version of this file used a more sophisticated algorithm
  31.  *      (by Fiala and Greene) which is guaranteed to run in linear amortized
  32.  *      time, but has a larger average cost, uses more memory and is patented.
  33.  *      However the F&G algorithm may be faster for some highly redundant
  34.  *      files if the parameter max_chain_length (described below) is too large.
  35.  *
  36.  *  ACKNOWLEDGEMENTS
  37.  *
  38.  *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
  39.  *      I found it in 'freeze' written by Leonid Broukhis.
  40.  *      Thanks to many people for bug reports and testing.
  41.  *
  42.  *  REFERENCES
  43.  *
  44.  *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
  45.  *      Available in http://www.ietf.org/rfc/rfc1951.txt
  46.  *
  47.  *      A description of the Rabin and Karp algorithm is given in the book
  48.  *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
  49.  *
  50.  *      Fiala,E.R., and Greene,D.H.
  51.  *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
  52.  *
  53.  */
  54.  
  55. /* @(#) $Id$ */
  56.  
  57. #include "deflate.h"
  58.  
  59. const char deflate_copyright[] =
  60.    " deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly ";
  61. /*
  62.   If you use the zlib library in a product, an acknowledgment is welcome
  63.   in the documentation of your product. If for some reason you cannot
  64.   include such an acknowledgment, I would appreciate that you keep this
  65.   copyright string in the executable of your product.
  66.  */
  67.  
  68. /* ===========================================================================
  69.  *  Function prototypes.
  70.  */
  71. typedef enum {
  72.     need_more,      /* block not completed, need more input or more output */
  73.     block_done,     /* block flush performed */
  74.     finish_started, /* finish started, need only more output at next deflate */
  75.     finish_done     /* finish done, accept no more input or output */
  76. } block_state;
  77.  
  78. typedef block_state (*compress_func) OF((deflate_state *s, int flush));
  79. /* Compression function. Returns the block state after the call. */
  80.  
  81. local void fill_window    OF((deflate_state *s));
  82. local block_state deflate_stored OF((deflate_state *s, int flush));
  83. local block_state deflate_fast   OF((deflate_state *s, int flush));
  84. #ifndef FASTEST
  85. local block_state deflate_slow   OF((deflate_state *s, int flush));
  86. #endif
  87. local void lm_init        OF((deflate_state *s));
  88. local void putShortMSB    OF((deflate_state *s, uInt b));
  89. local void flush_pending  OF((z_streamp strm));
  90. local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
  91. #ifndef FASTEST
  92. #ifdef ASMV
  93.       void match_init OF((void)); /* asm code initialization */
  94.       uInt longest_match  OF((deflate_state *s, IPos cur_match));
  95. #else
  96. local uInt longest_match  OF((deflate_state *s, IPos cur_match));
  97. #endif
  98. #endif
  99. local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
  100.  
  101. #ifdef DEBUG
  102. local  void check_match OF((deflate_state *s, IPos start, IPos match,
  103.                             int length));
  104. #endif
  105.  
  106. /* ===========================================================================
  107.  * Local data
  108.  */
  109.  
  110. #define NIL 0
  111. /* Tail of hash chains */
  112.  
  113. #ifndef TOO_FAR
  114. #  define TOO_FAR 4096
  115. #endif
  116. /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
  117.  
  118. #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
  119. /* Minimum amount of lookahead, except at the end of the input file.
  120.  * See deflate.c for comments about the MIN_MATCH+1.
  121.  */
  122.  
  123. /* Values for max_lazy_match, good_match and max_chain_length, depending on
  124.  * the desired pack level (0..9). The values given below have been tuned to
  125.  * exclude worst case performance for pathological files. Better values may be
  126.  * found for specific files.
  127.  */
  128. typedef struct config_s {
  129.    ush good_length; /* reduce lazy search above this match length */
  130.    ush max_lazy;    /* do not perform lazy search above this match length */
  131.    ush nice_length; /* quit search above this match length */
  132.    ush max_chain;
  133.    compress_func func;
  134. } config;
  135.  
  136. #ifdef FASTEST
  137. local const config configuration_table[2] = {
  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. #else
  142. local const config configuration_table[10] = {
  143. /*      good lazy nice chain */
  144. /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
  145. /* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
  146. /* 2 */ {4,    5, 16,    8, deflate_fast},
  147. /* 3 */ {4,    6, 32,   32, deflate_fast},
  148.  
  149. /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
  150. /* 5 */ {8,   16, 32,   32, deflate_slow},
  151. /* 6 */ {8,   16, 128, 128, deflate_slow},
  152. /* 7 */ {8,   32, 128, 256, deflate_slow},
  153. /* 8 */ {32, 128, 258, 1024, deflate_slow},
  154. /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
  155. #endif
  156.  
  157. /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
  158.  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
  159.  * meaning.
  160.  */
  161.  
  162. #define EQUAL 0
  163. /* result of memcmp for equal strings */
  164.  
  165. #ifndef NO_DUMMY_DECL
  166. struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
  167. #endif
  168.  
  169. /* ===========================================================================
  170.  * Update a hash value with the given input byte
  171.  * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
  172.  *    input characters, so that a running hash key can be computed from the
  173.  *    previous key instead of complete recalculation each time.
  174.  */
  175. #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
  176.  
  177.  
  178. /* ===========================================================================
  179.  * Insert string str in the dictionary and set match_head to the previous head
  180.  * of the hash chain (the most recent string with same hash key). Return
  181.  * the previous length of the hash chain.
  182.  * If this file is compiled with -DFASTEST, the compression level is forced
  183.  * to 1, and no hash chains are maintained.
  184.  * IN  assertion: all calls to to INSERT_STRING are made with consecutive
  185.  *    input characters and the first MIN_MATCH bytes of str are valid
  186.  *    (except for the last MIN_MATCH-1 bytes of the input file).
  187.  */
  188. #ifdef FASTEST
  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->head[s->ins_h], \
  192.     s->head[s->ins_h] = (Pos)(str))
  193. #else
  194. #define INSERT_STRING(s, str, match_head) \
  195.    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
  196.     match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
  197.     s->head[s->ins_h] = (Pos)(str))
  198. #endif
  199.  
  200. /* ===========================================================================
  201.  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
  202.  * prev[] will be initialized on the fly.
  203.  */
  204. #define CLEAR_HASH(s) \
  205.     s->head[s->hash_size-1] = NIL; \
  206.     zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
  207.  
  208. /* ========================================================================= */
  209. int ZEXPORT deflateInit_(strm, level, version, stream_size)
  210.     z_streamp strm;
  211.     int level;
  212.     const char *version;
  213.     int stream_size;
  214. {
  215.     return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
  216.                          Z_DEFAULT_STRATEGY, version, stream_size);
  217.     /* To do: ignore strm->next_in if we use it as window */
  218. }
  219.  
  220. /* ========================================================================= */
  221. int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
  222.                   version, stream_size)
  223.     z_streamp strm;
  224.     int  level;
  225.     int  method;
  226.     int  windowBits;
  227.     int  memLevel;
  228.     int  strategy;
  229.     const char *version;
  230.     int stream_size;
  231. {
  232.     deflate_state *s;
  233.     int wrap = 1;
  234.     static const char my_version[] = ZLIB_VERSION;
  235.  
  236.     ushf *overlay;
  237.     /* We overlay pending_buf and d_buf+l_buf. This works since the average
  238.      * output size for (length,distance) codes is <= 24 bits.
  239.      */
  240.  
  241.     if (version == Z_NULL || version[0] != my_version[0] ||
  242.         stream_size != sizeof(z_stream)) {
  243.         return Z_VERSION_ERROR;
  244.     }
  245.     if (strm == Z_NULL) return Z_STREAM_ERROR;
  246.  
  247.     strm->msg = Z_NULL;
  248.     if (strm->zalloc == (alloc_func)0) {
  249.         strm->zalloc = zcalloc;
  250.         strm->opaque = (voidpf)0;
  251.     }
  252.     if (strm->zfree == (free_func)0) strm->zfree = zcfree;
  253.  
  254. #ifdef FASTEST
  255.     if (level != 0) level = 1;
  256. #else
  257.     if (level == Z_DEFAULT_COMPRESSION) level = 6;
  258. #endif
  259.  
  260.     if (windowBits < 0) { /* suppress zlib wrapper */
  261.         wrap = 0;
  262.         windowBits = -windowBits;
  263.     }
  264. #ifdef GZIP
  265.     else if (windowBits > 15) {
  266.         wrap = 2;       /* write gzip wrapper instead */
  267.         windowBits -= 16;
  268.     }
  269. #endif
  270.     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
  271.         windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
  272.         strategy < 0 || strategy > Z_FIXED) {
  273.         return Z_STREAM_ERROR;
  274.     }
  275.     if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
  276.     s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
  277.     if (s == Z_NULL) return Z_MEM_ERROR;
  278.     strm->state = (struct internal_state FAR *)s;
  279.     s->strm = strm;
  280.  
  281.     s->wrap = wrap;
  282.     s->gzhead = Z_NULL;
  283.     s->w_bits = windowBits;
  284.     s->w_size = 1 << s->w_bits;
  285.     s->w_mask = s->w_size - 1;
  286.  
  287.     s->hash_bits = memLevel + 7;
  288.     s->hash_size = 1 << s->hash_bits;
  289.     s->hash_mask = s->hash_size - 1;
  290.     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
  291.  
  292.     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
  293.     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
  294.     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
  295.  
  296.     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
  297.  
  298.     overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
  299.     s->pending_buf = (uchf *) overlay;
  300.     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
  301.  
  302.     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
  303.         s->pending_buf == Z_NULL) {
  304.         s->status = FINISH_STATE;
  305.         strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
  306.         deflateEnd (strm);
  307.         return Z_MEM_ERROR;
  308.     }
  309.     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
  310.     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
  311.  
  312.     s->level = level;
  313.     s->strategy = strategy;
  314.     s->method = (Byte)method;
  315.  
  316.     return deflateReset(strm);
  317. }
  318.  
  319. /* ========================================================================= */
  320. int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
  321.     z_streamp strm;
  322.     const Bytef *dictionary;
  323.     uInt  dictLength;
  324. {
  325.     deflate_state *s;
  326.     uInt length = dictLength;
  327.     uInt n;
  328.     IPos hash_head = 0;
  329.  
  330.     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
  331.         strm->state->wrap == 2 ||
  332.         (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
  333.         return Z_STREAM_ERROR;
  334.  
  335.     s = strm->state;
  336.     if (s->wrap)
  337.         strm->adler = adler32(strm->adler, dictionary, dictLength);
  338.  
  339.     if (length < MIN_MATCH) return Z_OK;
  340.     if (length > MAX_DIST(s)) {
  341.         length = MAX_DIST(s);
  342.         dictionary += dictLength - length; /* use the tail of the dictionary */
  343.     }
  344.     zmemcpy(s->window, dictionary, length);
  345.     s->strstart = length;
  346.     s->block_start = (long)length;
  347.  
  348.     /* Insert all strings in the hash table (except for the last two bytes).
  349.      * s->lookahead stays null, so s->ins_h will be recomputed at the next
  350.      * call of fill_window.
  351.      */
  352.     s->ins_h = s->window[0];
  353.     UPDATE_HASH(s, s->ins_h, s->window[1]);
  354.     for (n = 0; n <= length - MIN_MATCH; n++) {
  355.         INSERT_STRING(s, n, hash_head);
  356.     }
  357.     if (hash_head) hash_head = 0;  /* to make compiler happy */
  358.     return Z_OK;
  359. }
  360.  
  361. /* ========================================================================= */
  362. int ZEXPORT deflateReset (strm)
  363.     z_streamp strm;
  364. {
  365.     deflate_state *s;
  366.  
  367.     if (strm == Z_NULL || strm->state == Z_NULL ||
  368.         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
  369.         return Z_STREAM_ERROR;
  370.     }
  371.  
  372.     strm->total_in = strm->total_out = 0;
  373.     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
  374.     strm->data_type = Z_UNKNOWN;
  375.  
  376.     s = (deflate_state *)strm->state;
  377.     s->pending = 0;
  378.     s->pending_out = s->pending_buf;
  379.  
  380.     if (s->wrap < 0) {
  381.         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
  382.     }
  383.     s->status = s->wrap ? INIT_STATE : BUSY_STATE;
  384.     strm->adler =
  385. #ifdef GZIP
  386.         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
  387. #endif
  388.         adler32(0L, Z_NULL, 0);
  389.     s->last_flush = Z_NO_FLUSH;
  390.  
  391.     _tr_init(s);
  392.     lm_init(s);
  393.  
  394.     return Z_OK;
  395. }
  396.  
  397. /* ========================================================================= */
  398. int ZEXPORT deflateSetHeader (strm, head)
  399.     z_streamp strm;
  400.     gz_headerp head;
  401. {
  402.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  403.     if (strm->state->wrap != 2) return Z_STREAM_ERROR;
  404.     strm->state->gzhead = head;
  405.     return Z_OK;
  406. }
  407.  
  408. /* ========================================================================= */
  409. int ZEXPORT deflatePrime (strm, bits, value)
  410.     z_streamp strm;
  411.     int bits;
  412.     int value;
  413. {
  414.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  415.     strm->state->bi_valid = bits;
  416.     strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
  417.     return Z_OK;
  418. }
  419.  
  420. /* ========================================================================= */
  421. int ZEXPORT deflateParams(strm, level, strategy)
  422.     z_streamp strm;
  423.     int level;
  424.     int strategy;
  425. {
  426.     deflate_state *s;
  427.     compress_func func;
  428.     int err = Z_OK;
  429.  
  430.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  431.     s = strm->state;
  432.  
  433. #ifdef FASTEST
  434.     if (level != 0) level = 1;
  435. #else
  436.     if (level == Z_DEFAULT_COMPRESSION) level = 6;
  437. #endif
  438.     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
  439.         return Z_STREAM_ERROR;
  440.     }
  441.     func = configuration_table[s->level].func;
  442.  
  443.     if (func != configuration_table[level].func && strm->total_in != 0) {
  444.         /* Flush the last buffer: */
  445.         err = deflate(strm, Z_PARTIAL_FLUSH);
  446.     }
  447.     if (s->level != level) {
  448.         s->level = level;
  449.         s->max_lazy_match   = configuration_table[level].max_lazy;
  450.         s->good_match       = configuration_table[level].good_length;
  451.         s->nice_match       = configuration_table[level].nice_length;
  452.         s->max_chain_length = configuration_table[level].max_chain;
  453.     }
  454.     s->strategy = strategy;
  455.     return err;
  456. }
  457.  
  458. /* ========================================================================= */
  459. int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
  460.     z_streamp strm;
  461.     int good_length;
  462.     int max_lazy;
  463.     int nice_length;
  464.     int max_chain;
  465. {
  466.     deflate_state *s;
  467.  
  468.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  469.     s = strm->state;
  470.     s->good_match = good_length;
  471.     s->max_lazy_match = max_lazy;
  472.     s->nice_match = nice_length;
  473.     s->max_chain_length = max_chain;
  474.     return Z_OK;
  475. }
  476.  
  477. /* =========================================================================
  478.  * For the default windowBits of 15 and memLevel of 8, this function returns
  479.  * a close to exact, as well as small, upper bound on the compressed size.
  480.  * They are coded as constants here for a reason--if the #define's are
  481.  * changed, then this function needs to be changed as well.  The return
  482.  * value for 15 and 8 only works for those exact settings.
  483.  *
  484.  * For any setting other than those defaults for windowBits and memLevel,
  485.  * the value returned is a conservative worst case for the maximum expansion
  486.  * resulting from using fixed blocks instead of stored blocks, which deflate
  487.  * can emit on compressed data for some combinations of the parameters.
  488.  *
  489.  * This function could be more sophisticated to provide closer upper bounds
  490.  * for every combination of windowBits and memLevel, as well as wrap.
  491.  * But even the conservative upper bound of about 14% expansion does not
  492.  * seem onerous for output buffer allocation.
  493.  */
  494. uLong ZEXPORT deflateBound(strm, sourceLen)
  495.     z_streamp strm;
  496.     uLong sourceLen;
  497. {
  498.     deflate_state *s;
  499.     uLong destLen;
  500.  
  501.     /* conservative upper bound */
  502.     destLen = sourceLen +
  503.               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
  504.  
  505.     /* if can't get parameters, return conservative bound */
  506.     if (strm == Z_NULL || strm->state == Z_NULL)
  507.         return destLen;
  508.  
  509.     /* if not default parameters, return conservative bound */
  510.     s = strm->state;
  511.     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
  512.         return destLen;
  513.  
  514.     /* default settings: return tight bound for that case */
  515.     return compressBound(sourceLen);
  516. }
  517.  
  518. /* =========================================================================
  519.  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
  520.  * IN assertion: the stream state is correct and there is enough room in
  521.  * pending_buf.
  522.  */
  523. local void putShortMSB (s, b)
  524.     deflate_state *s;
  525.     uInt b;
  526. {
  527.     put_byte(s, (Byte)(b >> 8));
  528.     put_byte(s, (Byte)(b & 0xff));
  529. }
  530.  
  531. /* =========================================================================
  532.  * Flush as much pending output as possible. All deflate() output goes
  533.  * through this function so some applications may wish to modify it
  534.  * to avoid allocating a large strm->next_out buffer and copying into it.
  535.  * (See also read_buf()).
  536.  */
  537. local void flush_pending(strm)
  538.     z_streamp strm;
  539. {
  540.     unsigned len = strm->state->pending;
  541.  
  542.     if (len > strm->avail_out) len = strm->avail_out;
  543.     if (len == 0) return;
  544.  
  545.     zmemcpy(strm->next_out, strm->state->pending_out, len);
  546.     strm->next_out  += len;
  547.     strm->state->pending_out  += len;
  548.     strm->total_out += len;
  549.     strm->avail_out  -= len;
  550.     strm->state->pending -= len;
  551.     if (strm->state->pending == 0) {
  552.         strm->state->pending_out = strm->state->pending_buf;
  553.     }
  554. }
  555.  
  556. /* ========================================================================= */
  557. int ZEXPORT deflate (strm, flush)
  558.     z_streamp strm;
  559.     int flush;
  560. {
  561.     int old_flush; /* value of flush param for previous deflate call */
  562.     deflate_state *s;
  563.  
  564.     if (strm == Z_NULL || strm->state == Z_NULL ||
  565.         flush > Z_FINISH || flush < 0) {
  566.         return Z_STREAM_ERROR;
  567.     }
  568.     s = strm->state;
  569.  
  570.     if (strm->next_out == Z_NULL ||
  571.         (strm->next_in == Z_NULL && strm->avail_in != 0) ||
  572.         (s->status == FINISH_STATE && flush != Z_FINISH)) {
  573.         ERR_RETURN(strm, Z_STREAM_ERROR);
  574.     }
  575.     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
  576.  
  577.     s->strm = strm; /* just in case */
  578.     old_flush = s->last_flush;
  579.     s->last_flush = flush;
  580.  
  581.     /* Write the header */
  582.     if (s->status == INIT_STATE) {
  583. #ifdef GZIP
  584.         if (s->wrap == 2) {
  585.             strm->adler = crc32(0L, Z_NULL, 0);
  586.             put_byte(s, 31);
  587.             put_byte(s, 139);
  588.             put_byte(s, 8);
  589.             if (s->gzhead == NULL) {
  590.                 put_byte(s, 0);
  591.                 put_byte(s, 0);
  592.                 put_byte(s, 0);
  593.                 put_byte(s, 0);
  594.                 put_byte(s, 0);
  595.                 put_byte(s, s->level == 9 ? 2 :
  596.                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
  597.                              4 : 0));
  598.                 put_byte(s, OS_CODE);
  599.                 s->status = BUSY_STATE;
  600.             }
  601.             else {
  602.                 put_byte(s, (s->gzhead->text ? 1 : 0) +
  603.                             (s->gzhead->hcrc ? 2 : 0) +
  604.                             (s->gzhead->extra == Z_NULL ? 0 : 4) +
  605.                             (s->gzhead->name == Z_NULL ? 0 : 8) +
  606.                             (s->gzhead->comment == Z_NULL ? 0 : 16)
  607.                         );
  608.                 put_byte(s, (Byte)(s->gzhead->time & 0xff));
  609.                 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
  610.                 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
  611.                 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
  612.                 put_byte(s, s->level == 9 ? 2 :
  613.                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
  614.                              4 : 0));
  615.                 put_byte(s, s->gzhead->os & 0xff);
  616.                 if (s->gzhead->extra != NULL) {
  617.                     put_byte(s, s->gzhead->extra_len & 0xff);
  618.                     put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
  619.                 }
  620.                 if (s->gzhead->hcrc)
  621.                     strm->adler = crc32(strm->adler, s->pending_buf,
  622.                                         s->pending);
  623.                 s->gzindex = 0;
  624.                 s->status = EXTRA_STATE;
  625.             }
  626.         }
  627.         else
  628. #endif
  629.         {
  630.             uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
  631.             uInt level_flags;
  632.  
  633.             if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
  634.                 level_flags = 0;
  635.             else if (s->level < 6)
  636.                 level_flags = 1;
  637.             else if (s->level == 6)
  638.                 level_flags = 2;
  639.             else
  640.                 level_flags = 3;
  641.             header |= (level_flags << 6);
  642.             if (s->strstart != 0) header |= PRESET_DICT;
  643.             header += 31 - (header % 31);
  644.  
  645.             s->status = BUSY_STATE;
  646.             putShortMSB(s, header);
  647.  
  648.             /* Save the adler32 of the preset dictionary: */
  649.             if (s->strstart != 0) {
  650.                 putShortMSB(s, (uInt)(strm->adler >> 16));
  651.                 putShortMSB(s, (uInt)(strm->adler & 0xffff));
  652.             }
  653.             strm->adler = adler32(0L, Z_NULL, 0);
  654.         }
  655.     }
  656. #ifdef GZIP
  657.     if (s->status == EXTRA_STATE) {
  658.         if (s->gzhead->extra != NULL) {
  659.             uInt beg = s->pending;  /* start of bytes to update crc */
  660.  
  661.             while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
  662.                 if (s->pending == s->pending_buf_size) {
  663.                     if (s->gzhead->hcrc && s->pending > beg)
  664.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  665.                                             s->pending - beg);
  666.                     flush_pending(strm);
  667.                     beg = s->pending;
  668.                     if (s->pending == s->pending_buf_size)
  669.                         break;
  670.                 }
  671.                 put_byte(s, s->gzhead->extra[s->gzindex]);
  672.                 s->gzindex++;
  673.             }
  674.             if (s->gzhead->hcrc && s->pending > beg)
  675.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  676.                                     s->pending - beg);
  677.             if (s->gzindex == s->gzhead->extra_len) {
  678.                 s->gzindex = 0;
  679.                 s->status = NAME_STATE;
  680.             }
  681.         }
  682.         else
  683.             s->status = NAME_STATE;
  684.     }
  685.     if (s->status == NAME_STATE) {
  686.         if (s->gzhead->name != NULL) {
  687.             uInt beg = s->pending;  /* start of bytes to update crc */
  688.             int val;
  689.  
  690.             do {
  691.                 if (s->pending == s->pending_buf_size) {
  692.                     if (s->gzhead->hcrc && s->pending > beg)
  693.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  694.                                             s->pending - beg);
  695.                     flush_pending(strm);
  696.                     beg = s->pending;
  697.                     if (s->pending == s->pending_buf_size) {
  698.                         val = 1;
  699.                         break;
  700.                     }
  701.                 }
  702.                 val = s->gzhead->name[s->gzindex++];
  703.                 put_byte(s, val);
  704.             } while (val != 0);
  705.             if (s->gzhead->hcrc && s->pending > beg)
  706.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  707.                                     s->pending - beg);
  708.             if (val == 0) {
  709.                 s->gzindex = 0;
  710.                 s->status = COMMENT_STATE;
  711.             }
  712.         }
  713.         else
  714.             s->status = COMMENT_STATE;
  715.     }
  716.     if (s->status == COMMENT_STATE) {
  717.         if (s->gzhead->comment != NULL) {
  718.             uInt beg = s->pending;  /* start of bytes to update crc */
  719.             int val;
  720.  
  721.             do {
  722.                 if (s->pending == s->pending_buf_size) {
  723.                     if (s->gzhead->hcrc && s->pending > beg)
  724.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  725.                                             s->pending - beg);
  726.                     flush_pending(strm);
  727.                     beg = s->pending;
  728.                     if (s->pending == s->pending_buf_size) {
  729.                         val = 1;
  730.                         break;
  731.                     }
  732.                 }
  733.                 val = s->gzhead->comment[s->gzindex++];
  734.                 put_byte(s, val);
  735.             } while (val != 0);
  736.             if (s->gzhead->hcrc && s->pending > beg)
  737.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  738.                                     s->pending - beg);
  739.             if (val == 0)
  740.                 s->status = HCRC_STATE;
  741.         }
  742.         else
  743.             s->status = HCRC_STATE;
  744.     }
  745.     if (s->status == HCRC_STATE) {
  746.         if (s->gzhead->hcrc) {
  747.             if (s->pending + 2 > s->pending_buf_size)
  748.                 flush_pending(strm);
  749.             if (s->pending + 2 <= s->pending_buf_size) {
  750.                 put_byte(s, (Byte)(strm->adler & 0xff));
  751.                 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
  752.                 strm->adler = crc32(0L, Z_NULL, 0);
  753.                 s->status = BUSY_STATE;
  754.             }
  755.         }
  756.         else
  757.             s->status = BUSY_STATE;
  758.     }
  759. #endif
  760.  
  761.     /* Flush as much pending output as possible */
  762.     if (s->pending != 0) {
  763.         flush_pending(strm);
  764.         if (strm->avail_out == 0) {
  765.             /* Since avail_out is 0, deflate will be called again with
  766.              * more output space, but possibly with both pending and
  767.              * avail_in equal to zero. There won't be anything to do,
  768.              * but this is not an error situation so make sure we
  769.              * return OK instead of BUF_ERROR at next call of deflate:
  770.              */
  771.             s->last_flush = -1;
  772.             return Z_OK;
  773.         }
  774.  
  775.     /* Make sure there is something to do and avoid duplicate consecutive
  776.      * flushes. For repeated and useless calls with Z_FINISH, we keep
  777.      * returning Z_STREAM_END instead of Z_BUF_ERROR.
  778.      */
  779.     } else if (strm->avail_in == 0 && flush <= old_flush &&
  780.                flush != Z_FINISH) {
  781.         ERR_RETURN(strm, Z_BUF_ERROR);
  782.     }
  783.  
  784.     /* User must not provide more input after the first FINISH: */
  785.     if (s->status == FINISH_STATE && strm->avail_in != 0) {
  786.         ERR_RETURN(strm, Z_BUF_ERROR);
  787.     }
  788.  
  789.     /* Start a new block or continue the current one.
  790.      */
  791.     if (strm->avail_in != 0 || s->lookahead != 0 ||
  792.         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
  793.         block_state bstate;
  794.  
  795.         bstate = (*(configuration_table[s->level].func))(s, flush);
  796.  
  797.         if (bstate == finish_started || bstate == finish_done) {
  798.             s->status = FINISH_STATE;
  799.         }
  800.         if (bstate == need_more || bstate == finish_started) {
  801.             if (strm->avail_out == 0) {
  802.                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
  803.             }
  804.             return Z_OK;
  805.             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
  806.              * of deflate should use the same flush parameter to make sure
  807.              * that the flush is complete. So we don't have to output an
  808.              * empty block here, this will be done at next call. This also
  809.              * ensures that for a very small output buffer, we emit at most
  810.              * one empty block.
  811.              */
  812.         }
  813.         if (bstate == block_done) {
  814.             if (flush == Z_PARTIAL_FLUSH) {
  815.                 _tr_align(s);
  816.             } else { /* FULL_FLUSH or SYNC_FLUSH */
  817.                 _tr_stored_block(s, (char*)0, 0L, 0);
  818.                 /* For a full flush, this empty block will be recognized
  819.                  * as a special marker by inflate_sync().
  820.                  */
  821.                 if (flush == Z_FULL_FLUSH) {
  822.                     CLEAR_HASH(s);             /* forget history */
  823.                 }
  824.             }
  825.             flush_pending(strm);
  826.             if (strm->avail_out == 0) {
  827.               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
  828.               return Z_OK;
  829.             }
  830.         }
  831.     }
  832.     Assert(strm->avail_out > 0, "bug2");
  833.  
  834.     if (flush != Z_FINISH) return Z_OK;
  835.     if (s->wrap <= 0) return Z_STREAM_END;
  836.  
  837.     /* Write the trailer */
  838. #ifdef GZIP
  839.     if (s->wrap == 2) {
  840.         put_byte(s, (Byte)(strm->adler & 0xff));
  841.         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
  842.         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
  843.         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
  844.         put_byte(s, (Byte)(strm->total_in & 0xff));
  845.         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
  846.         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
  847.         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
  848.     }
  849.     else
  850. #endif
  851.     {
  852.         putShortMSB(s, (uInt)(strm->adler >> 16));
  853.         putShortMSB(s, (uInt)(strm->adler & 0xffff));
  854.     }
  855.     flush_pending(strm);
  856.     /* If avail_out is zero, the application will call deflate again
  857.      * to flush the rest.
  858.      */
  859.     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
  860.     return s->pending != 0 ? Z_OK : Z_STREAM_END;
  861. }
  862.  
  863. /* ========================================================================= */
  864. int ZEXPORT deflateEnd (strm)
  865.     z_streamp strm;
  866. {
  867.     int status;
  868.  
  869.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  870.  
  871.     status = strm->state->status;
  872.     if (status != INIT_STATE &&
  873.         status != EXTRA_STATE &&
  874.         status != NAME_STATE &&
  875.         status != COMMENT_STATE &&
  876.         status != HCRC_STATE &&
  877.         status != BUSY_STATE &&
  878.         status != FINISH_STATE) {
  879.       return Z_STREAM_ERROR;
  880.     }
  881.  
  882.     /* Deallocate in reverse order of allocations: */
  883.     TRY_FREE(strm, strm->state->pending_buf);
  884.     TRY_FREE(strm, strm->state->head);
  885.     TRY_FREE(strm, strm->state->prev);
  886.     TRY_FREE(strm, strm->state->window);
  887.  
  888.     ZFREE(strm, strm->state);
  889.     strm->state = Z_NULL;
  890.  
  891.     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
  892. }
  893.  
  894. /* =========================================================================
  895.  * Copy the source state to the destination state.
  896.  * To simplify the source, this is not supported for 16-bit MSDOS (which
  897.  * doesn't have enough memory anyway to duplicate compression states).
  898.  */
  899. int ZEXPORT deflateCopy (dest, source)
  900.     z_streamp dest;
  901.     z_streamp source;
  902. {
  903. #ifdef MAXSEG_64K
  904.     return Z_STREAM_ERROR;
  905. #else
  906.     deflate_state *ds;
  907.     deflate_state *ss;
  908.     ushf *overlay;
  909.  
  910.  
  911.     if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
  912.         return Z_STREAM_ERROR;
  913.     }
  914.  
  915.     ss = source->state;
  916.  
  917.     zmemcpy(dest, source, sizeof(z_stream));
  918.  
  919.     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
  920.     if (ds == Z_NULL) return Z_MEM_ERROR;
  921.     dest->state = (struct internal_state FAR *) ds;
  922.     zmemcpy(ds, ss, sizeof(deflate_state));
  923.     ds->strm = dest;
  924.  
  925.     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
  926.     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
  927.     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
  928.     overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
  929.     ds->pending_buf = (uchf *) overlay;
  930.  
  931.     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
  932.         ds->pending_buf == Z_NULL) {
  933.         deflateEnd (dest);
  934.         return Z_MEM_ERROR;
  935.     }
  936.     /* following zmemcpy do not work for 16-bit MSDOS */
  937.     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
  938.     zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
  939.     zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
  940.     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
  941.  
  942.     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
  943.     ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
  944.     ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
  945.  
  946.     ds->l_desc.dyn_tree = ds->dyn_ltree;
  947.     ds->d_desc.dyn_tree = ds->dyn_dtree;
  948.     ds->bl_desc.dyn_tree = ds->bl_tree;
  949.  
  950.     return Z_OK;
  951. #endif /* MAXSEG_64K */
  952. }
  953.  
  954. /* ===========================================================================
  955.  * Read a new buffer from the current input stream, update the adler32
  956.  * and total number of bytes read.  All deflate() input goes through
  957.  * this function so some applications may wish to modify it to avoid
  958.  * allocating a large strm->next_in buffer and copying from it.
  959.  * (See also flush_pending()).
  960.  */
  961. local int read_buf(strm, buf, size)
  962.     z_streamp strm;
  963.     Bytef *buf;
  964.     unsigned size;
  965. {
  966.     unsigned len = strm->avail_in;
  967.  
  968.     if (len > size) len = size;
  969.     if (len == 0) return 0;
  970.  
  971.     strm->avail_in  -= len;
  972.  
  973.     if (strm->state->wrap == 1) {
  974.         strm->adler = adler32(strm->adler, strm->next_in, len);
  975.     }
  976. #ifdef GZIP
  977.     else if (strm->state->wrap == 2) {
  978.         strm->adler = crc32(strm->adler, strm->next_in, len);
  979.     }
  980. #endif
  981.     zmemcpy(buf, strm->next_in, len);
  982.     strm->next_in  += len;
  983.     strm->total_in += len;
  984.  
  985.     return (int)len;
  986. }
  987.  
  988. /* ===========================================================================
  989.  * Initialize the "longest match" routines for a new zlib stream
  990.  */
  991. local void lm_init (s)
  992.     deflate_state *s;
  993. {
  994.     s->window_size = (ulg)2L*s->w_size;
  995.  
  996.     CLEAR_HASH(s);
  997.  
  998.     /* Set the default configuration parameters:
  999.      */
  1000.     s->max_lazy_match   = configuration_table[s->level].max_lazy;
  1001.     s->good_match       = configuration_table[s->level].good_length;
  1002.     s->nice_match       = configuration_table[s->level].nice_length;
  1003.     s->max_chain_length = configuration_table[s->level].max_chain;
  1004.  
  1005.     s->strstart = 0;
  1006.     s->block_start = 0L;
  1007.     s->lookahead = 0;
  1008.     s->match_length = s->prev_length = MIN_MATCH-1;
  1009.     s->match_available = 0;
  1010.     s->ins_h = 0;
  1011. #ifndef FASTEST
  1012. #ifdef ASMV
  1013.     match_init(); /* initialize the asm code */
  1014. #endif
  1015. #endif
  1016. }
  1017.  
  1018. #ifndef FASTEST
  1019. /* ===========================================================================
  1020.  * Set match_start to the longest match starting at the given string and
  1021.  * return its length. Matches shorter or equal to prev_length are discarded,
  1022.  * in which case the result is equal to prev_length and match_start is
  1023.  * garbage.
  1024.  * IN assertions: cur_match is the head of the hash chain for the current
  1025.  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
  1026.  * OUT assertion: the match length is not greater than s->lookahead.
  1027.  */
  1028. #ifndef ASMV
  1029. /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
  1030.  * match.S. The code will be functionally equivalent.
  1031.  */
  1032. local uInt longest_match(s, cur_match)
  1033.     deflate_state *s;
  1034.     IPos cur_match;                             /* current match */
  1035. {
  1036.     unsigned chain_length = s->max_chain_length;/* max hash chain length */
  1037.     register Bytef *scan = s->window + s->strstart; /* current string */
  1038.     register Bytef *match;                       /* matched string */
  1039.     register int len;                           /* length of current match */
  1040.     int best_len = s->prev_length;              /* best match length so far */
  1041.     int nice_match = s->nice_match;             /* stop if match long enough */
  1042.     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
  1043.         s->strstart - (IPos)MAX_DIST(s) : NIL;
  1044.     /* Stop when cur_match becomes <= limit. To simplify the code,
  1045.      * we prevent matches with the string of window index 0.
  1046.      */
  1047.     Posf *prev = s->prev;
  1048.     uInt wmask = s->w_mask;
  1049.  
  1050. #ifdef UNALIGNED_OK
  1051.     /* Compare two bytes at a time. Note: this is not always beneficial.
  1052.      * Try with and without -DUNALIGNED_OK to check.
  1053.      */
  1054.     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
  1055.     register ush scan_start = *(ushf*)scan;
  1056.     register ush scan_end   = *(ushf*)(scan+best_len-1);
  1057. #else
  1058.     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
  1059.     register Byte scan_end1  = scan[best_len-1];
  1060.     register Byte scan_end   = scan[best_len];
  1061. #endif
  1062.  
  1063.     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
  1064.      * It is easy to get rid of this optimization if necessary.
  1065.      */
  1066.     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
  1067.  
  1068.     /* Do not waste too much time if we already have a good match: */
  1069.     if (s->prev_length >= s->good_match) {
  1070.         chain_length >>= 2;
  1071.     }
  1072.     /* Do not look for matches beyond the end of the input. This is necessary
  1073.      * to make deflate deterministic.
  1074.      */
  1075.     if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
  1076.  
  1077.     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
  1078.  
  1079.     do {
  1080.         Assert(cur_match < s->strstart, "no future");
  1081.         match = s->window + cur_match;
  1082.  
  1083.         /* Skip to next match if the match length cannot increase
  1084.          * or if the match length is less than 2.  Note that the checks below
  1085.          * for insufficient lookahead only occur occasionally for performance
  1086.          * reasons.  Therefore uninitialized memory will be accessed, and
  1087.          * conditional jumps will be made that depend on those values.
  1088.          * However the length of the match is limited to the lookahead, so
  1089.          * the output of deflate is not affected by the uninitialized values.
  1090.          */
  1091. #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
  1092.         /* This code assumes sizeof(unsigned short) == 2. Do not use
  1093.          * UNALIGNED_OK if your compiler uses a different size.
  1094.          */
  1095.         if (*(ushf*)(match+best_len-1) != scan_end ||
  1096.             *(ushf*)match != scan_start) continue;
  1097.  
  1098.         /* It is not necessary to compare scan[2] and match[2] since they are
  1099.          * always equal when the other bytes match, given that the hash keys
  1100.          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
  1101.          * strstart+3, +5, ... up to strstart+257. We check for insufficient
  1102.          * lookahead only every 4th comparison; the 128th check will be made
  1103.          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
  1104.          * necessary to put more guard bytes at the end of the window, or
  1105.          * to check more often for insufficient lookahead.
  1106.          */
  1107.         Assert(scan[2] == match[2], "scan[2]?");
  1108.         scan++, match++;
  1109.         do {
  1110.         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1111.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1112.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1113.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1114.                  scan < strend);
  1115.         /* The funny "do {}" generates better code on most compilers */
  1116.  
  1117.         /* Here, scan <= window+strstart+257 */
  1118.         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1119.         if (*scan == *match) scan++;
  1120.  
  1121.         len = (MAX_MATCH - 1) - (int)(strend-scan);
  1122.         scan = strend - (MAX_MATCH-1);
  1123.  
  1124. #else /* UNALIGNED_OK */
  1125.  
  1126.         if (match[best_len]   != scan_end  ||
  1127.             match[best_len-1] != scan_end1 ||
  1128.             *match            != *scan     ||
  1129.             *++match          != scan[1])      continue;
  1130.  
  1131.         /* The check at best_len-1 can be removed because it will be made
  1132.          * again later. (This heuristic is not always a win.)
  1133.          * It is not necessary to compare scan[2] and match[2] since they
  1134.          * are always equal when the other bytes match, given that
  1135.          * the hash keys are equal and that HASH_BITS >= 8.
  1136.          */
  1137.         scan += 2, match++;
  1138.         Assert(*scan == *match, "match[2]?");
  1139.  
  1140.         /* We check for insufficient lookahead only every 8th comparison;
  1141.          * the 256th check will be made at strstart+258.
  1142.          */
  1143.         do {
  1144.         } while (*++scan == *++match && *++scan == *++match &&
  1145.                  *++scan == *++match && *++scan == *++match &&
  1146.                  *++scan == *++match && *++scan == *++match &&
  1147.                  *++scan == *++match && *++scan == *++match &&
  1148.                  scan < strend);
  1149.  
  1150.         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1151.  
  1152.         len = MAX_MATCH - (int)(strend - scan);
  1153.         scan = strend - MAX_MATCH;
  1154.  
  1155. #endif /* UNALIGNED_OK */
  1156.  
  1157.         if (len > best_len) {
  1158.             s->match_start = cur_match;
  1159.             best_len = len;
  1160.             if (len >= nice_match) break;
  1161. #ifdef UNALIGNED_OK
  1162.             scan_end = *(ushf*)(scan+best_len-1);
  1163. #else
  1164.             scan_end1  = scan[best_len-1];
  1165.             scan_end   = scan[best_len];
  1166. #endif
  1167.         }
  1168.     } while ((cur_match = prev[cur_match & wmask]) > limit
  1169.              && --chain_length != 0);
  1170.  
  1171.     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
  1172.     return s->lookahead;
  1173. }
  1174. #endif /* ASMV */
  1175. #endif /* FASTEST */
  1176.  
  1177. /* ---------------------------------------------------------------------------
  1178.  * Optimized version for level == 1 or strategy == Z_RLE only
  1179.  */
  1180. local uInt longest_match_fast(s, cur_match)
  1181.     deflate_state *s;
  1182.     IPos cur_match;                             /* current match */
  1183. {
  1184.     register Bytef *scan = s->window + s->strstart; /* current string */
  1185.     register Bytef *match;                       /* matched string */
  1186.     register int len;                           /* length of current match */
  1187.     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
  1188.  
  1189.     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
  1190.      * It is easy to get rid of this optimization if necessary.
  1191.      */
  1192.     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
  1193.  
  1194.     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
  1195.  
  1196.     Assert(cur_match < s->strstart, "no future");
  1197.  
  1198.     match = s->window + cur_match;
  1199.  
  1200.     /* Return failure if the match length is less than 2:
  1201.      */
  1202.     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
  1203.  
  1204.     /* The check at best_len-1 can be removed because it will be made
  1205.      * again later. (This heuristic is not always a win.)
  1206.      * It is not necessary to compare scan[2] and match[2] since they
  1207.      * are always equal when the other bytes match, given that
  1208.      * the hash keys are equal and that HASH_BITS >= 8.
  1209.      */
  1210.     scan += 2, match += 2;
  1211.     Assert(*scan == *match, "match[2]?");
  1212.  
  1213.     /* We check for insufficient lookahead only every 8th comparison;
  1214.      * the 256th check will be made at strstart+258.
  1215.      */
  1216.     do {
  1217.     } while (*++scan == *++match && *++scan == *++match &&
  1218.              *++scan == *++match && *++scan == *++match &&
  1219.              *++scan == *++match && *++scan == *++match &&
  1220.              *++scan == *++match && *++scan == *++match &&
  1221.              scan < strend);
  1222.  
  1223.     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1224.  
  1225.     len = MAX_MATCH - (int)(strend - scan);
  1226.  
  1227.     if (len < MIN_MATCH) return MIN_MATCH - 1;
  1228.  
  1229.     s->match_start = cur_match;
  1230.     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
  1231. }
  1232.  
  1233. #ifdef DEBUG
  1234. /* ===========================================================================
  1235.  * Check that the match at match_start is indeed a match.
  1236.  */
  1237. local void check_match(s, start, match, length)
  1238.     deflate_state *s;
  1239.     IPos start, match;
  1240.     int length;
  1241. {
  1242.     /* check that the match is indeed a match */
  1243.     if (zmemcmp(s->window + match,
  1244.                 s->window + start, length) != EQUAL) {
  1245.         fprintf(stderr, " start %u, match %u, length %d\n",
  1246.                 start, match, length);
  1247.         do {
  1248.             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
  1249.         } while (--length != 0);
  1250.         z_error("invalid match");
  1251.     }
  1252.     if (z_verbose > 1) {
  1253.         fprintf(stderr,"\\[%d,%d]", start-match, length);
  1254.         do { putc(s->window[start++], stderr); } while (--length != 0);
  1255.     }
  1256. }
  1257. #else
  1258. #  define check_match(s, start, match, length)
  1259. #endif /* DEBUG */
  1260.  
  1261. /* ===========================================================================
  1262.  * Fill the window when the lookahead becomes insufficient.
  1263.  * Updates strstart and lookahead.
  1264.  *
  1265.  * IN assertion: lookahead < MIN_LOOKAHEAD
  1266.  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
  1267.  *    At least one byte has been read, or avail_in == 0; reads are
  1268.  *    performed for at least two bytes (required for the zip translate_eol
  1269.  *    option -- not supported here).
  1270.  */
  1271. local void fill_window(s)
  1272.     deflate_state *s;
  1273. {
  1274.     register unsigned n, m;
  1275.     register Posf *p;
  1276.     unsigned more;    /* Amount of free space at the end of the window. */
  1277.     uInt wsize = s->w_size;
  1278.  
  1279.     do {
  1280.         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
  1281.  
  1282.         /* Deal with !@#$% 64K limit: */
  1283.         if (sizeof(int) <= 2) {
  1284.             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
  1285.                 more = wsize;
  1286.  
  1287.             } else if (more == (unsigned)(-1)) {
  1288.                 /* Very unlikely, but possible on 16 bit machine if
  1289.                  * strstart == 0 && lookahead == 1 (input done a byte at time)
  1290.                  */
  1291.                 more--;
  1292.             }
  1293.         }
  1294.  
  1295.         /* If the window is almost full and there is insufficient lookahead,
  1296.          * move the upper half to the lower one to make room in the upper half.
  1297.          */
  1298.         if (s->strstart >= wsize+MAX_DIST(s)) {
  1299.  
  1300.             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
  1301.             s->match_start -= wsize;
  1302.             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
  1303.             s->block_start -= (long) wsize;
  1304.  
  1305.             /* Slide the hash table (could be avoided with 32 bit values
  1306.                at the expense of memory usage). We slide even when level == 0
  1307.                to keep the hash table consistent if we switch back to level > 0
  1308.                later. (Using level 0 permanently is not an optimal usage of
  1309.                zlib, so we don't care about this pathological case.)
  1310.              */
  1311.             /* %%% avoid this when Z_RLE */
  1312.             n = s->hash_size;
  1313.             p = &s->head[n];
  1314.             do {
  1315.                 m = *--p;
  1316.                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
  1317.             } while (--n);
  1318.  
  1319.             n = wsize;
  1320. #ifndef FASTEST
  1321.             p = &s->prev[n];
  1322.             do {
  1323.                 m = *--p;
  1324.                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
  1325.                 /* If n is not on any hash chain, prev[n] is garbage but
  1326.                  * its value will never be used.
  1327.                  */
  1328.             } while (--n);
  1329. #endif
  1330.             more += wsize;
  1331.         }
  1332.         if (s->strm->avail_in == 0) return;
  1333.  
  1334.         /* If there was no sliding:
  1335.          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
  1336.          *    more == window_size - lookahead - strstart
  1337.          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
  1338.          * => more >= window_size - 2*WSIZE + 2
  1339.          * In the BIG_MEM or MMAP case (not yet supported),
  1340.          *   window_size == input_size + MIN_LOOKAHEAD  &&
  1341.          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
  1342.          * Otherwise, window_size == 2*WSIZE so more >= 2.
  1343.          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
  1344.          */
  1345.         Assert(more >= 2, "more < 2");
  1346.  
  1347.         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
  1348.         s->lookahead += n;
  1349.  
  1350.         /* Initialize the hash value now that we have some input: */
  1351.         if (s->lookahead >= MIN_MATCH) {
  1352.             s->ins_h = s->window[s->strstart];
  1353.             UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
  1354. #if MIN_MATCH != 3
  1355.             Call UPDATE_HASH() MIN_MATCH-3 more times
  1356. #endif
  1357.         }
  1358.         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
  1359.          * but this is not important since only literal bytes will be emitted.
  1360.          */
  1361.  
  1362.     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
  1363. }
  1364.  
  1365. /* ===========================================================================
  1366.  * Flush the current block, with given end-of-file flag.
  1367.  * IN assertion: strstart is set to the end of the current match.
  1368.  */
  1369. #define FLUSH_BLOCK_ONLY(s, eof) { \
  1370.    _tr_flush_block(s, (s->block_start >= 0L ? \
  1371.                    (charf *)&s->window[(unsigned)s->block_start] : \
  1372.                    (charf *)Z_NULL), \
  1373.                 (ulg)((long)s->strstart - s->block_start), \
  1374.                 (eof)); \
  1375.    s->block_start = s->strstart; \
  1376.    flush_pending(s->strm); \
  1377.    Tracev((stderr,"[FLUSH]")); \
  1378. }
  1379.  
  1380. /* Same but force premature exit if necessary. */
  1381. #define FLUSH_BLOCK(s, eof) { \
  1382.    FLUSH_BLOCK_ONLY(s, eof); \
  1383.    if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
  1384. }
  1385.  
  1386. /* ===========================================================================
  1387.  * Copy without compression as much as possible from the input stream, return
  1388.  * the current block state.
  1389.  * This function does not insert new strings in the dictionary since
  1390.  * uncompressible data is probably not useful. This function is used
  1391.  * only for the level=0 compression option.
  1392.  * NOTE: this function should be optimized to avoid extra copying from
  1393.  * window to pending_buf.
  1394.  */
  1395. local block_state deflate_stored(s, flush)
  1396.     deflate_state *s;
  1397.     int flush;
  1398. {
  1399.     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
  1400.      * to pending_buf_size, and each stored block has a 5 byte header:
  1401.      */
  1402.     ulg max_block_size = 0xffff;
  1403.     ulg max_start;
  1404.  
  1405.     if (max_block_size > s->pending_buf_size - 5) {
  1406.         max_block_size = s->pending_buf_size - 5;
  1407.     }
  1408.  
  1409.     /* Copy as much as possible from input to output: */
  1410.     for (;;) {
  1411.         /* Fill the window as much as possible: */
  1412.         if (s->lookahead <= 1) {
  1413.  
  1414.             Assert(s->strstart < s->w_size+MAX_DIST(s) ||
  1415.                    s->block_start >= (long)s->w_size, "slide too late");
  1416.  
  1417.             fill_window(s);
  1418.             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
  1419.  
  1420.             if (s->lookahead == 0) break; /* flush the current block */
  1421.         }
  1422.         Assert(s->block_start >= 0L, "block gone");
  1423.  
  1424.         s->strstart += s->lookahead;
  1425.         s->lookahead = 0;
  1426.  
  1427.         /* Emit a stored block if pending_buf will be full: */
  1428.         max_start = s->block_start + max_block_size;
  1429.         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
  1430.             /* strstart == 0 is possible when wraparound on 16-bit machine */
  1431.             s->lookahead = (uInt)(s->strstart - max_start);
  1432.             s->strstart = (uInt)max_start;
  1433.             FLUSH_BLOCK(s, 0);
  1434.         }
  1435.         /* Flush if we may have to slide, otherwise block_start may become
  1436.          * negative and the data will be gone:
  1437.          */
  1438.         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
  1439.             FLUSH_BLOCK(s, 0);
  1440.         }
  1441.     }
  1442.     FLUSH_BLOCK(s, flush == Z_FINISH);
  1443.     return flush == Z_FINISH ? finish_done : block_done;
  1444. }
  1445.  
  1446. /* ===========================================================================
  1447.  * Compress as much as possible from the input stream, return the current
  1448.  * block state.
  1449.  * This function does not perform lazy evaluation of matches and inserts
  1450.  * new strings in the dictionary only for unmatched strings or for short
  1451.  * matches. It is used only for the fast compression options.
  1452.  */
  1453. local block_state deflate_fast(s, flush)
  1454.     deflate_state *s;
  1455.     int flush;
  1456. {
  1457.     IPos hash_head = NIL; /* head of the hash chain */
  1458.     int bflush;           /* set if current block must be flushed */
  1459.  
  1460.     for (;;) {
  1461.         /* Make sure that we always have enough lookahead, except
  1462.          * at the end of the input file. We need MAX_MATCH bytes
  1463.          * for the next match, plus MIN_MATCH bytes to insert the
  1464.          * string following the next match.
  1465.          */
  1466.         if (s->lookahead < MIN_LOOKAHEAD) {
  1467.             fill_window(s);
  1468.             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
  1469.                 return need_more;
  1470.             }
  1471.             if (s->lookahead == 0) break; /* flush the current block */
  1472.         }
  1473.  
  1474.         /* Insert the string window[strstart .. strstart+2] in the
  1475.          * dictionary, and set hash_head to the head of the hash chain:
  1476.          */
  1477.         if (s->lookahead >= MIN_MATCH) {
  1478.             INSERT_STRING(s, s->strstart, hash_head);
  1479.         }
  1480.  
  1481.         /* Find the longest match, discarding those <= prev_length.
  1482.          * At this point we have always match_length < MIN_MATCH
  1483.          */
  1484.         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
  1485.             /* To simplify the code, we prevent matches with the string
  1486.              * of window index 0 (in particular we have to avoid a match
  1487.              * of the string with itself at the start of the input file).
  1488.              */
  1489. #ifdef FASTEST
  1490.             if ((s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) ||
  1491.                 (s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
  1492.                 s->match_length = longest_match_fast (s, hash_head);
  1493.             }
  1494. #else
  1495.             if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
  1496.                 s->match_length = longest_match (s, hash_head);
  1497.             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
  1498.                 s->match_length = longest_match_fast (s, hash_head);
  1499.             }
  1500. #endif
  1501.             /* longest_match() or longest_match_fast() sets match_start */
  1502.         }
  1503.         if (s->match_length >= MIN_MATCH) {
  1504.             check_match(s, s->strstart, s->match_start, s->match_length);
  1505.  
  1506.             _tr_tally_dist(s, s->strstart - s->match_start,
  1507.                            s->match_length - MIN_MATCH, bflush);
  1508.  
  1509.             s->lookahead -= s->match_length;
  1510.  
  1511.             /* Insert new strings in the hash table only if the match length
  1512.              * is not too large. This saves time but degrades compression.
  1513.              */
  1514. #ifndef FASTEST
  1515.             if (s->match_length <= s->max_insert_length &&
  1516.                 s->lookahead >= MIN_MATCH) {
  1517.                 s->match_length--; /* string at strstart already in table */
  1518.                 do {
  1519.                     s->strstart++;
  1520.                     INSERT_STRING(s, s->strstart, hash_head);
  1521.                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
  1522.                      * always MIN_MATCH bytes ahead.
  1523.                      */
  1524.                 } while (--s->match_length != 0);
  1525.                 s->strstart++;
  1526.             } else
  1527. #endif
  1528.             {
  1529.                 s->strstart += s->match_length;
  1530.                 s->match_length = 0;
  1531.                 s->ins_h = s->window[s->strstart];
  1532.                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
  1533. #if MIN_MATCH != 3
  1534.                 Call UPDATE_HASH() MIN_MATCH-3 more times
  1535. #endif
  1536.                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
  1537.                  * matter since it will be recomputed at next deflate call.
  1538.                  */
  1539.             }
  1540.         } else {
  1541.             /* No match, output a literal byte */
  1542.             Tracevv((stderr,"%c", s->window[s->strstart]));
  1543.             _tr_tally_lit (s, s->window[s->strstart], bflush);
  1544.             s->lookahead--;
  1545.             s->strstart++;
  1546.         }
  1547.         if (bflush) FLUSH_BLOCK(s, 0);
  1548.     }
  1549.     FLUSH_BLOCK(s, flush == Z_FINISH);
  1550.     return flush == Z_FINISH ? finish_done : block_done;
  1551. }
  1552.  
  1553. #ifndef FASTEST
  1554. /* ===========================================================================
  1555.  * Same as above, but achieves better compression. We use a lazy
  1556.  * evaluation for matches: a match is finally adopted only if there is
  1557.  * no better match at the next window position.
  1558.  */
  1559. local block_state deflate_slow(s, flush)
  1560.     deflate_state *s;
  1561.     int flush;
  1562. {
  1563.     IPos hash_head = NIL;    /* head of hash chain */
  1564.     int bflush;              /* set if current block must be flushed */
  1565.  
  1566.     /* Process the input block. */
  1567.     for (;;) {
  1568.         /* Make sure that we always have enough lookahead, except
  1569.          * at the end of the input file. We need MAX_MATCH bytes
  1570.          * for the next match, plus MIN_MATCH bytes to insert the
  1571.          * string following the next match.
  1572.          */
  1573.         if (s->lookahead < MIN_LOOKAHEAD) {
  1574.             fill_window(s);
  1575.             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
  1576.                 return need_more;
  1577.             }
  1578.             if (s->lookahead == 0) break; /* flush the current block */
  1579.         }
  1580.  
  1581.         /* Insert the string window[strstart .. strstart+2] in the
  1582.          * dictionary, and set hash_head to the head of the hash chain:
  1583.          */
  1584.         if (s->lookahead >= MIN_MATCH) {
  1585.             INSERT_STRING(s, s->strstart, hash_head);
  1586.         }
  1587.  
  1588.         /* Find the longest match, discarding those <= prev_length.
  1589.          */
  1590.         s->prev_length = s->match_length, s->prev_match = s->match_start;
  1591.         s->match_length = MIN_MATCH-1;
  1592.  
  1593.         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
  1594.             s->strstart - hash_head <= MAX_DIST(s)) {
  1595.             /* To simplify the code, we prevent matches with the string
  1596.              * of window index 0 (in particular we have to avoid a match
  1597.              * of the string with itself at the start of the input file).
  1598.              */
  1599.             if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
  1600.                 s->match_length = longest_match (s, hash_head);
  1601.             } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
  1602.                 s->match_length = longest_match_fast (s, hash_head);
  1603.             }
  1604.             /* longest_match() or longest_match_fast() sets match_start */
  1605.  
  1606.             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
  1607. #if TOO_FAR <= 32767
  1608.                 || (s->match_length == MIN_MATCH &&
  1609.                     s->strstart - s->match_start > TOO_FAR)
  1610. #endif
  1611.                 )) {
  1612.  
  1613.                 /* If prev_match is also MIN_MATCH, match_start is garbage
  1614.                  * but we will ignore the current match anyway.
  1615.                  */
  1616.                 s->match_length = MIN_MATCH-1;
  1617.             }
  1618.         }
  1619.         /* If there was a match at the previous step and the current
  1620.          * match is not better, output the previous match:
  1621.          */
  1622.         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
  1623.             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
  1624.             /* Do not insert strings in hash table beyond this. */
  1625.  
  1626.             check_match(s, s->strstart-1, s->prev_match, s->prev_length);
  1627.  
  1628.             _tr_tally_dist(s, s->strstart -1 - s->prev_match,
  1629.                            s->prev_length - MIN_MATCH, bflush);
  1630.  
  1631.             /* Insert in hash table all strings up to the end of the match.
  1632.              * strstart-1 and strstart are already inserted. If there is not
  1633.              * enough lookahead, the last two strings are not inserted in
  1634.              * the hash table.
  1635.              */
  1636.             s->lookahead -= s->prev_length-1;
  1637.             s->prev_length -= 2;
  1638.             do {
  1639.                 if (++s->strstart <= max_insert) {
  1640.                     INSERT_STRING(s, s->strstart, hash_head);
  1641.                 }
  1642.             } while (--s->prev_length != 0);
  1643.             s->match_available = 0;
  1644.             s->match_length = MIN_MATCH-1;
  1645.             s->strstart++;
  1646.  
  1647.             if (bflush) FLUSH_BLOCK(s, 0);
  1648.  
  1649.         } else if (s->match_available) {
  1650.             /* If there was no match at the previous position, output a
  1651.              * single literal. If there was a match but the current match
  1652.              * is longer, truncate the previous match to a single literal.
  1653.              */
  1654.             Tracevv((stderr,"%c", s->window[s->strstart-1]));
  1655.             _tr_tally_lit(s, s->window[s->strstart-1], bflush);
  1656.             if (bflush) {
  1657.                 FLUSH_BLOCK_ONLY(s, 0);
  1658.             }
  1659.             s->strstart++;
  1660.             s->lookahead--;
  1661.             if (s->strm->avail_out == 0) return need_more;
  1662.         } else {
  1663.             /* There is no previous match to compare with, wait for
  1664.              * the next step to decide.
  1665.              */
  1666.             s->match_available = 1;
  1667.             s->strstart++;
  1668.             s->lookahead--;
  1669.         }
  1670.     }
  1671.     Assert (flush != Z_NO_FLUSH, "no flush?");
  1672.     if (s->match_available) {
  1673.         Tracevv((stderr,"%c", s->window[s->strstart-1]));
  1674.         _tr_tally_lit(s, s->window[s->strstart-1], bflush);
  1675.         s->match_available = 0;
  1676.     }
  1677.     FLUSH_BLOCK(s, flush == Z_FINISH);
  1678.     return flush == Z_FINISH ? finish_done : block_done;
  1679. }
  1680. #endif /* FASTEST */
  1681.  
  1682. #if 0
  1683. /* ===========================================================================
  1684.  * For Z_RLE, simply look for runs of bytes, generate matches only of distance
  1685.  * one.  Do not maintain a hash table.  (It will be regenerated if this run of
  1686.  * deflate switches away from Z_RLE.)
  1687.  */
  1688. local block_state deflate_rle(s, flush)
  1689.     deflate_state *s;
  1690.     int flush;
  1691. {
  1692.     int bflush;         /* set if current block must be flushed */
  1693.     uInt run;           /* length of run */
  1694.     uInt max;           /* maximum length of run */
  1695.     uInt prev;          /* byte at distance one to match */
  1696.     Bytef *scan;        /* scan for end of run */
  1697.  
  1698.     for (;;) {
  1699.         /* Make sure that we always have enough lookahead, except
  1700.          * at the end of the input file. We need MAX_MATCH bytes
  1701.          * for the longest encodable run.
  1702.          */
  1703.         if (s->lookahead < MAX_MATCH) {
  1704.             fill_window(s);
  1705.             if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
  1706.                 return need_more;
  1707.             }
  1708.             if (s->lookahead == 0) break; /* flush the current block */
  1709.         }
  1710.  
  1711.         /* See how many times the previous byte repeats */
  1712.         run = 0;
  1713.         if (s->strstart > 0) {      /* if there is a previous byte, that is */
  1714.             max = s->lookahead < MAX_MATCH ? s->lookahead : MAX_MATCH;
  1715.             scan = s->window + s->strstart - 1;
  1716.             prev = *scan++;
  1717.             do {
  1718.                 if (*scan++ != prev)
  1719.                     break;
  1720.             } while (++run < max);
  1721.         }
  1722.  
  1723.         /* Emit match if have run of MIN_MATCH or longer, else emit literal */
  1724.         if (run >= MIN_MATCH) {
  1725.             check_match(s, s->strstart, s->strstart - 1, run);
  1726.             _tr_tally_dist(s, 1, run - MIN_MATCH, bflush);
  1727.             s->lookahead -= run;
  1728.             s->strstart += run;
  1729.         } else {
  1730.             /* No match, output a literal byte */
  1731.             Tracevv((stderr,"%c", s->window[s->strstart]));
  1732.             _tr_tally_lit (s, s->window[s->strstart], bflush);
  1733.             s->lookahead--;
  1734.             s->strstart++;
  1735.         }
  1736.         if (bflush) FLUSH_BLOCK(s, 0);
  1737.     }
  1738.     FLUSH_BLOCK(s, flush == Z_FINISH);
  1739.     return flush == Z_FINISH ? finish_done : block_done;
  1740. }
  1741. #endif
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