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  1. /* deflate.c -- compress data using the deflation algorithm
  2.  * Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
  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://tools.ietf.org/html/rfc1951
  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 1.2.8 Copyright 1995-2013 Jean-loup Gailly and Mark Adler ";
  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 block_state deflate_rle    OF((deflate_state *s, int flush));
  83. local block_state deflate_huff   OF((deflate_state *s, int flush));
  84. local void lm_init        OF((deflate_state *s));
  85. local void putShortMSB    OF((deflate_state *s, uInt b));
  86. local void flush_pending  OF((z_streamp strm));
  87. local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
  88. #ifdef ASMV
  89.       void match_init OF((void)); /* asm code initialization */
  90.       uInt longest_match  OF((deflate_state *s, IPos cur_match));
  91. #else
  92. local uInt longest_match  OF((deflate_state *s, IPos cur_match));
  93. #endif
  94.  
  95. #ifdef DEBUG
  96. local  void check_match OF((deflate_state *s, IPos start, IPos match,
  97.                             int length));
  98. #endif
  99.  
  100. /* ===========================================================================
  101.  * Local data
  102.  */
  103.  
  104. #define NIL 0
  105. /* Tail of hash chains */
  106.  
  107. #ifndef TOO_FAR
  108. #  define TOO_FAR 4096
  109. #endif
  110. /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
  111.  
  112. /* Values for max_lazy_match, good_match and max_chain_length, depending on
  113.  * the desired pack level (0..9). The values given below have been tuned to
  114.  * exclude worst case performance for pathological files. Better values may be
  115.  * found for specific files.
  116.  */
  117. typedef struct config_s {
  118.    ush good_length; /* reduce lazy search above this match length */
  119.    ush max_lazy;    /* do not perform lazy search above this match length */
  120.    ush nice_length; /* quit search above this match length */
  121.    ush max_chain;
  122.    compress_func func;
  123. } config;
  124.  
  125. #ifdef FASTEST
  126. local const config configuration_table[2] = {
  127. /*      good lazy nice chain */
  128. /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
  129. /* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */
  130. #else
  131. local const config configuration_table[10] = {
  132. /*      good lazy nice chain */
  133. /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
  134. /* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
  135. /* 2 */ {4,    5, 16,    8, deflate_fast},
  136. /* 3 */ {4,    6, 32,   32, deflate_fast},
  137.  
  138. /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
  139. /* 5 */ {8,   16, 32,   32, deflate_slow},
  140. /* 6 */ {8,   16, 128, 128, deflate_slow},
  141. /* 7 */ {8,   32, 128, 256, deflate_slow},
  142. /* 8 */ {32, 128, 258, 1024, deflate_slow},
  143. /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
  144. #endif
  145.  
  146. /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
  147.  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
  148.  * meaning.
  149.  */
  150.  
  151. #define EQUAL 0
  152. /* result of memcmp for equal strings */
  153.  
  154. #ifndef NO_DUMMY_DECL
  155. struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
  156. #endif
  157.  
  158. /* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
  159. #define RANK(f) (((f) << 1) - ((f) > 4 ? 9 : 0))
  160.  
  161. /* ===========================================================================
  162.  * Update a hash value with the given input byte
  163.  * IN  assertion: all calls to to UPDATE_HASH are made with consecutive
  164.  *    input characters, so that a running hash key can be computed from the
  165.  *    previous key instead of complete recalculation each time.
  166.  */
  167. #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
  168.  
  169.  
  170. /* ===========================================================================
  171.  * Insert string str in the dictionary and set match_head to the previous head
  172.  * of the hash chain (the most recent string with same hash key). Return
  173.  * the previous length of the hash chain.
  174.  * If this file is compiled with -DFASTEST, the compression level is forced
  175.  * to 1, and no hash chains are maintained.
  176.  * IN  assertion: all calls to to INSERT_STRING are made with consecutive
  177.  *    input characters and the first MIN_MATCH bytes of str are valid
  178.  *    (except for the last MIN_MATCH-1 bytes of the input file).
  179.  */
  180. #ifdef FASTEST
  181. #define INSERT_STRING(s, str, match_head) \
  182.    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
  183.     match_head = s->head[s->ins_h], \
  184.     s->head[s->ins_h] = (Pos)(str))
  185. #else
  186. #define INSERT_STRING(s, str, match_head) \
  187.    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
  188.     match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
  189.     s->head[s->ins_h] = (Pos)(str))
  190. #endif
  191.  
  192. /* ===========================================================================
  193.  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
  194.  * prev[] will be initialized on the fly.
  195.  */
  196. #define CLEAR_HASH(s) \
  197.     s->head[s->hash_size-1] = NIL; \
  198.     zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
  199.  
  200. /* ========================================================================= */
  201. int ZEXPORT deflateInit_(strm, level, version, stream_size)
  202.     z_streamp strm;
  203.     int level;
  204.     const char *version;
  205.     int stream_size;
  206. {
  207.     return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
  208.                          Z_DEFAULT_STRATEGY, version, stream_size);
  209.     /* To do: ignore strm->next_in if we use it as window */
  210. }
  211.  
  212. /* ========================================================================= */
  213. int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
  214.                   version, stream_size)
  215.     z_streamp strm;
  216.     int  level;
  217.     int  method;
  218.     int  windowBits;
  219.     int  memLevel;
  220.     int  strategy;
  221.     const char *version;
  222.     int stream_size;
  223. {
  224.     deflate_state *s;
  225.     int wrap = 1;
  226.     static const char my_version[] = ZLIB_VERSION;
  227.  
  228.     ushf *overlay;
  229.     /* We overlay pending_buf and d_buf+l_buf. This works since the average
  230.      * output size for (length,distance) codes is <= 24 bits.
  231.      */
  232.  
  233.     if (version == Z_NULL || version[0] != my_version[0] ||
  234.         stream_size != sizeof(z_stream)) {
  235.         return Z_VERSION_ERROR;
  236.     }
  237.     if (strm == Z_NULL) return Z_STREAM_ERROR;
  238.  
  239.     strm->msg = Z_NULL;
  240.     if (strm->zalloc == (alloc_func)0) {
  241. #ifdef Z_SOLO
  242.         return Z_STREAM_ERROR;
  243. #else
  244.         strm->zalloc = zcalloc;
  245.         strm->opaque = (voidpf)0;
  246. #endif
  247.     }
  248.     if (strm->zfree == (free_func)0)
  249. #ifdef Z_SOLO
  250.         return Z_STREAM_ERROR;
  251. #else
  252.         strm->zfree = zcfree;
  253. #endif
  254.  
  255. #ifdef FASTEST
  256.     if (level != 0) level = 1;
  257. #else
  258.     if (level == Z_DEFAULT_COMPRESSION) level = 6;
  259. #endif
  260.  
  261.     if (windowBits < 0) { /* suppress zlib wrapper */
  262.         wrap = 0;
  263.         windowBits = -windowBits;
  264.     }
  265. #ifdef GZIP
  266.     else if (windowBits > 15) {
  267.         wrap = 2;       /* write gzip wrapper instead */
  268.         windowBits -= 16;
  269.     }
  270. #endif
  271.     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
  272.         windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
  273.         strategy < 0 || strategy > Z_FIXED) {
  274.         return Z_STREAM_ERROR;
  275.     }
  276.     if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
  277.     s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
  278.     if (s == Z_NULL) return Z_MEM_ERROR;
  279.     strm->state = (struct internal_state FAR *)s;
  280.     s->strm = strm;
  281.  
  282.     s->wrap = wrap;
  283.     s->gzhead = Z_NULL;
  284.     s->w_bits = windowBits;
  285.     s->w_size = 1 << s->w_bits;
  286.     s->w_mask = s->w_size - 1;
  287.  
  288.     s->hash_bits = memLevel + 7;
  289.     s->hash_size = 1 << s->hash_bits;
  290.     s->hash_mask = s->hash_size - 1;
  291.     s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
  292.  
  293.     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
  294.     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
  295.     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
  296.  
  297.     s->high_water = 0;      /* nothing written to s->window yet */
  298.  
  299.     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
  300.  
  301.     overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
  302.     s->pending_buf = (uchf *) overlay;
  303.     s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
  304.  
  305.     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
  306.         s->pending_buf == Z_NULL) {
  307.         s->status = FINISH_STATE;
  308.         strm->msg = ERR_MSG(Z_MEM_ERROR);
  309.         deflateEnd (strm);
  310.         return Z_MEM_ERROR;
  311.     }
  312.     s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
  313.     s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
  314.  
  315.     s->level = level;
  316.     s->strategy = strategy;
  317.     s->method = (Byte)method;
  318.  
  319.     return deflateReset(strm);
  320. }
  321.  
  322. /* ========================================================================= */
  323. int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
  324.     z_streamp strm;
  325.     const Bytef *dictionary;
  326.     uInt  dictLength;
  327. {
  328.     deflate_state *s;
  329.     uInt str, n;
  330.     int wrap;
  331.     unsigned avail;
  332.     z_const unsigned char *next;
  333.  
  334.     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
  335.         return Z_STREAM_ERROR;
  336.     s = strm->state;
  337.     wrap = s->wrap;
  338.     if (wrap == 2 || (wrap == 1 && s->status != INIT_STATE) || s->lookahead)
  339.         return Z_STREAM_ERROR;
  340.  
  341.     /* when using zlib wrappers, compute Adler-32 for provided dictionary */
  342.     if (wrap == 1)
  343.         strm->adler = adler32(strm->adler, dictionary, dictLength);
  344.     s->wrap = 0;                    /* avoid computing Adler-32 in read_buf */
  345.  
  346.     /* if dictionary would fill window, just replace the history */
  347.     if (dictLength >= s->w_size) {
  348.         if (wrap == 0) {            /* already empty otherwise */
  349.             CLEAR_HASH(s);
  350.             s->strstart = 0;
  351.             s->block_start = 0L;
  352.             s->insert = 0;
  353.         }
  354.         dictionary += dictLength - s->w_size;  /* use the tail */
  355.         dictLength = s->w_size;
  356.     }
  357.  
  358.     /* insert dictionary into window and hash */
  359.     avail = strm->avail_in;
  360.     next = strm->next_in;
  361.     strm->avail_in = dictLength;
  362.     strm->next_in = (z_const Bytef *)dictionary;
  363.     fill_window(s);
  364.     while (s->lookahead >= MIN_MATCH) {
  365.         str = s->strstart;
  366.         n = s->lookahead - (MIN_MATCH-1);
  367.         do {
  368.             UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
  369. #ifndef FASTEST
  370.             s->prev[str & s->w_mask] = s->head[s->ins_h];
  371. #endif
  372.             s->head[s->ins_h] = (Pos)str;
  373.             str++;
  374.         } while (--n);
  375.         s->strstart = str;
  376.         s->lookahead = MIN_MATCH-1;
  377.         fill_window(s);
  378.     }
  379.     s->strstart += s->lookahead;
  380.     s->block_start = (long)s->strstart;
  381.     s->insert = s->lookahead;
  382.     s->lookahead = 0;
  383.     s->match_length = s->prev_length = MIN_MATCH-1;
  384.     s->match_available = 0;
  385.     strm->next_in = next;
  386.     strm->avail_in = avail;
  387.     s->wrap = wrap;
  388.     return Z_OK;
  389. }
  390.  
  391. /* ========================================================================= */
  392. int ZEXPORT deflateResetKeep (strm)
  393.     z_streamp strm;
  394. {
  395.     deflate_state *s;
  396.  
  397.     if (strm == Z_NULL || strm->state == Z_NULL ||
  398.         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
  399.         return Z_STREAM_ERROR;
  400.     }
  401.  
  402.     strm->total_in = strm->total_out = 0;
  403.     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
  404.     strm->data_type = Z_UNKNOWN;
  405.  
  406.     s = (deflate_state *)strm->state;
  407.     s->pending = 0;
  408.     s->pending_out = s->pending_buf;
  409.  
  410.     if (s->wrap < 0) {
  411.         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
  412.     }
  413.     s->status = s->wrap ? INIT_STATE : BUSY_STATE;
  414.     strm->adler =
  415. #ifdef GZIP
  416.         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
  417. #endif
  418.         adler32(0L, Z_NULL, 0);
  419.     s->last_flush = Z_NO_FLUSH;
  420.  
  421.     _tr_init(s);
  422.  
  423.     return Z_OK;
  424. }
  425.  
  426. /* ========================================================================= */
  427. int ZEXPORT deflateReset (strm)
  428.     z_streamp strm;
  429. {
  430.     int ret;
  431.  
  432.     ret = deflateResetKeep(strm);
  433.     if (ret == Z_OK)
  434.         lm_init(strm->state);
  435.     return ret;
  436. }
  437.  
  438. /* ========================================================================= */
  439. int ZEXPORT deflateSetHeader (strm, head)
  440.     z_streamp strm;
  441.     gz_headerp head;
  442. {
  443.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  444.     if (strm->state->wrap != 2) return Z_STREAM_ERROR;
  445.     strm->state->gzhead = head;
  446.     return Z_OK;
  447. }
  448.  
  449. /* ========================================================================= */
  450. int ZEXPORT deflatePending (strm, pending, bits)
  451.     unsigned *pending;
  452.     int *bits;
  453.     z_streamp strm;
  454. {
  455.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  456.     if (pending != Z_NULL)
  457.         *pending = strm->state->pending;
  458.     if (bits != Z_NULL)
  459.         *bits = strm->state->bi_valid;
  460.     return Z_OK;
  461. }
  462.  
  463. /* ========================================================================= */
  464. int ZEXPORT deflatePrime (strm, bits, value)
  465.     z_streamp strm;
  466.     int bits;
  467.     int value;
  468. {
  469.     deflate_state *s;
  470.     int put;
  471.  
  472.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  473.     s = strm->state;
  474.     if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
  475.         return Z_BUF_ERROR;
  476.     do {
  477.         put = Buf_size - s->bi_valid;
  478.         if (put > bits)
  479.             put = bits;
  480.         s->bi_buf |= (ush)((value & ((1 << put) - 1)) << s->bi_valid);
  481.         s->bi_valid += put;
  482.         _tr_flush_bits(s);
  483.         value >>= put;
  484.         bits -= put;
  485.     } while (bits);
  486.     return Z_OK;
  487. }
  488.  
  489. /* ========================================================================= */
  490. int ZEXPORT deflateParams(strm, level, strategy)
  491.     z_streamp strm;
  492.     int level;
  493.     int strategy;
  494. {
  495.     deflate_state *s;
  496.     compress_func func;
  497.     int err = Z_OK;
  498.  
  499.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  500.     s = strm->state;
  501.  
  502. #ifdef FASTEST
  503.     if (level != 0) level = 1;
  504. #else
  505.     if (level == Z_DEFAULT_COMPRESSION) level = 6;
  506. #endif
  507.     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
  508.         return Z_STREAM_ERROR;
  509.     }
  510.     func = configuration_table[s->level].func;
  511.  
  512.     if ((strategy != s->strategy || func != configuration_table[level].func) &&
  513.         strm->total_in != 0) {
  514.         /* Flush the last buffer: */
  515.         err = deflate(strm, Z_BLOCK);
  516.         if (err == Z_BUF_ERROR && s->pending == 0)
  517.             err = Z_OK;
  518.     }
  519.     if (s->level != level) {
  520.         s->level = level;
  521.         s->max_lazy_match   = configuration_table[level].max_lazy;
  522.         s->good_match       = configuration_table[level].good_length;
  523.         s->nice_match       = configuration_table[level].nice_length;
  524.         s->max_chain_length = configuration_table[level].max_chain;
  525.     }
  526.     s->strategy = strategy;
  527.     return err;
  528. }
  529.  
  530. /* ========================================================================= */
  531. int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
  532.     z_streamp strm;
  533.     int good_length;
  534.     int max_lazy;
  535.     int nice_length;
  536.     int max_chain;
  537. {
  538.     deflate_state *s;
  539.  
  540.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  541.     s = strm->state;
  542.     s->good_match = good_length;
  543.     s->max_lazy_match = max_lazy;
  544.     s->nice_match = nice_length;
  545.     s->max_chain_length = max_chain;
  546.     return Z_OK;
  547. }
  548.  
  549. /* =========================================================================
  550.  * For the default windowBits of 15 and memLevel of 8, this function returns
  551.  * a close to exact, as well as small, upper bound on the compressed size.
  552.  * They are coded as constants here for a reason--if the #define's are
  553.  * changed, then this function needs to be changed as well.  The return
  554.  * value for 15 and 8 only works for those exact settings.
  555.  *
  556.  * For any setting other than those defaults for windowBits and memLevel,
  557.  * the value returned is a conservative worst case for the maximum expansion
  558.  * resulting from using fixed blocks instead of stored blocks, which deflate
  559.  * can emit on compressed data for some combinations of the parameters.
  560.  *
  561.  * This function could be more sophisticated to provide closer upper bounds for
  562.  * every combination of windowBits and memLevel.  But even the conservative
  563.  * upper bound of about 14% expansion does not seem onerous for output buffer
  564.  * allocation.
  565.  */
  566. uLong ZEXPORT deflateBound(strm, sourceLen)
  567.     z_streamp strm;
  568.     uLong sourceLen;
  569. {
  570.     deflate_state *s;
  571.     uLong complen, wraplen;
  572.     Bytef *str;
  573.  
  574.     /* conservative upper bound for compressed data */
  575.     complen = sourceLen +
  576.               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
  577.  
  578.     /* if can't get parameters, return conservative bound plus zlib wrapper */
  579.     if (strm == Z_NULL || strm->state == Z_NULL)
  580.         return complen + 6;
  581.  
  582.     /* compute wrapper length */
  583.     s = strm->state;
  584.     switch (s->wrap) {
  585.     case 0:                                 /* raw deflate */
  586.         wraplen = 0;
  587.         break;
  588.     case 1:                                 /* zlib wrapper */
  589.         wraplen = 6 + (s->strstart ? 4 : 0);
  590.         break;
  591.     case 2:                                 /* gzip wrapper */
  592.         wraplen = 18;
  593.         if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
  594.             if (s->gzhead->extra != Z_NULL)
  595.                 wraplen += 2 + s->gzhead->extra_len;
  596.             str = s->gzhead->name;
  597.             if (str != Z_NULL)
  598.                 do {
  599.                     wraplen++;
  600.                 } while (*str++);
  601.             str = s->gzhead->comment;
  602.             if (str != Z_NULL)
  603.                 do {
  604.                     wraplen++;
  605.                 } while (*str++);
  606.             if (s->gzhead->hcrc)
  607.                 wraplen += 2;
  608.         }
  609.         break;
  610.     default:                                /* for compiler happiness */
  611.         wraplen = 6;
  612.     }
  613.  
  614.     /* if not default parameters, return conservative bound */
  615.     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
  616.         return complen + wraplen;
  617.  
  618.     /* default settings: return tight bound for that case */
  619.     return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
  620.            (sourceLen >> 25) + 13 - 6 + wraplen;
  621. }
  622.  
  623. /* =========================================================================
  624.  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
  625.  * IN assertion: the stream state is correct and there is enough room in
  626.  * pending_buf.
  627.  */
  628. local void putShortMSB (s, b)
  629.     deflate_state *s;
  630.     uInt b;
  631. {
  632.     put_byte(s, (Byte)(b >> 8));
  633.     put_byte(s, (Byte)(b & 0xff));
  634. }
  635.  
  636. /* =========================================================================
  637.  * Flush as much pending output as possible. All deflate() output goes
  638.  * through this function so some applications may wish to modify it
  639.  * to avoid allocating a large strm->next_out buffer and copying into it.
  640.  * (See also read_buf()).
  641.  */
  642. local void flush_pending(strm)
  643.     z_streamp strm;
  644. {
  645.     unsigned len;
  646.     deflate_state *s = strm->state;
  647.  
  648.     _tr_flush_bits(s);
  649.     len = s->pending;
  650.     if (len > strm->avail_out) len = strm->avail_out;
  651.     if (len == 0) return;
  652.  
  653.     zmemcpy(strm->next_out, s->pending_out, len);
  654.     strm->next_out  += len;
  655.     s->pending_out  += len;
  656.     strm->total_out += len;
  657.     strm->avail_out  -= len;
  658.     s->pending -= len;
  659.     if (s->pending == 0) {
  660.         s->pending_out = s->pending_buf;
  661.     }
  662. }
  663.  
  664. /* ========================================================================= */
  665. int ZEXPORT deflate (strm, flush)
  666.     z_streamp strm;
  667.     int flush;
  668. {
  669.     int old_flush; /* value of flush param for previous deflate call */
  670.     deflate_state *s;
  671.  
  672.     if (strm == Z_NULL || strm->state == Z_NULL ||
  673.         flush > Z_BLOCK || flush < 0) {
  674.         return Z_STREAM_ERROR;
  675.     }
  676.     s = strm->state;
  677.  
  678.     if (strm->next_out == Z_NULL ||
  679.         (strm->next_in == Z_NULL && strm->avail_in != 0) ||
  680.         (s->status == FINISH_STATE && flush != Z_FINISH)) {
  681.         ERR_RETURN(strm, Z_STREAM_ERROR);
  682.     }
  683.     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
  684.  
  685.     s->strm = strm; /* just in case */
  686.     old_flush = s->last_flush;
  687.     s->last_flush = flush;
  688.  
  689.     /* Write the header */
  690.     if (s->status == INIT_STATE) {
  691. #ifdef GZIP
  692.         if (s->wrap == 2) {
  693.             strm->adler = crc32(0L, Z_NULL, 0);
  694.             put_byte(s, 31);
  695.             put_byte(s, 139);
  696.             put_byte(s, 8);
  697.             if (s->gzhead == Z_NULL) {
  698.                 put_byte(s, 0);
  699.                 put_byte(s, 0);
  700.                 put_byte(s, 0);
  701.                 put_byte(s, 0);
  702.                 put_byte(s, 0);
  703.                 put_byte(s, s->level == 9 ? 2 :
  704.                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
  705.                              4 : 0));
  706.                 put_byte(s, OS_CODE);
  707.                 s->status = BUSY_STATE;
  708.             }
  709.             else {
  710.                 put_byte(s, (s->gzhead->text ? 1 : 0) +
  711.                             (s->gzhead->hcrc ? 2 : 0) +
  712.                             (s->gzhead->extra == Z_NULL ? 0 : 4) +
  713.                             (s->gzhead->name == Z_NULL ? 0 : 8) +
  714.                             (s->gzhead->comment == Z_NULL ? 0 : 16)
  715.                         );
  716.                 put_byte(s, (Byte)(s->gzhead->time & 0xff));
  717.                 put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
  718.                 put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
  719.                 put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
  720.                 put_byte(s, s->level == 9 ? 2 :
  721.                             (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
  722.                              4 : 0));
  723.                 put_byte(s, s->gzhead->os & 0xff);
  724.                 if (s->gzhead->extra != Z_NULL) {
  725.                     put_byte(s, s->gzhead->extra_len & 0xff);
  726.                     put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
  727.                 }
  728.                 if (s->gzhead->hcrc)
  729.                     strm->adler = crc32(strm->adler, s->pending_buf,
  730.                                         s->pending);
  731.                 s->gzindex = 0;
  732.                 s->status = EXTRA_STATE;
  733.             }
  734.         }
  735.         else
  736. #endif
  737.         {
  738.             uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
  739.             uInt level_flags;
  740.  
  741.             if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
  742.                 level_flags = 0;
  743.             else if (s->level < 6)
  744.                 level_flags = 1;
  745.             else if (s->level == 6)
  746.                 level_flags = 2;
  747.             else
  748.                 level_flags = 3;
  749.             header |= (level_flags << 6);
  750.             if (s->strstart != 0) header |= PRESET_DICT;
  751.             header += 31 - (header % 31);
  752.  
  753.             s->status = BUSY_STATE;
  754.             putShortMSB(s, header);
  755.  
  756.             /* Save the adler32 of the preset dictionary: */
  757.             if (s->strstart != 0) {
  758.                 putShortMSB(s, (uInt)(strm->adler >> 16));
  759.                 putShortMSB(s, (uInt)(strm->adler & 0xffff));
  760.             }
  761.             strm->adler = adler32(0L, Z_NULL, 0);
  762.         }
  763.     }
  764. #ifdef GZIP
  765.     if (s->status == EXTRA_STATE) {
  766.         if (s->gzhead->extra != Z_NULL) {
  767.             uInt beg = s->pending;  /* start of bytes to update crc */
  768.  
  769.             while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
  770.                 if (s->pending == s->pending_buf_size) {
  771.                     if (s->gzhead->hcrc && s->pending > beg)
  772.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  773.                                             s->pending - beg);
  774.                     flush_pending(strm);
  775.                     beg = s->pending;
  776.                     if (s->pending == s->pending_buf_size)
  777.                         break;
  778.                 }
  779.                 put_byte(s, s->gzhead->extra[s->gzindex]);
  780.                 s->gzindex++;
  781.             }
  782.             if (s->gzhead->hcrc && s->pending > beg)
  783.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  784.                                     s->pending - beg);
  785.             if (s->gzindex == s->gzhead->extra_len) {
  786.                 s->gzindex = 0;
  787.                 s->status = NAME_STATE;
  788.             }
  789.         }
  790.         else
  791.             s->status = NAME_STATE;
  792.     }
  793.     if (s->status == NAME_STATE) {
  794.         if (s->gzhead->name != Z_NULL) {
  795.             uInt beg = s->pending;  /* start of bytes to update crc */
  796.             int val;
  797.  
  798.             do {
  799.                 if (s->pending == s->pending_buf_size) {
  800.                     if (s->gzhead->hcrc && s->pending > beg)
  801.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  802.                                             s->pending - beg);
  803.                     flush_pending(strm);
  804.                     beg = s->pending;
  805.                     if (s->pending == s->pending_buf_size) {
  806.                         val = 1;
  807.                         break;
  808.                     }
  809.                 }
  810.                 val = s->gzhead->name[s->gzindex++];
  811.                 put_byte(s, val);
  812.             } while (val != 0);
  813.             if (s->gzhead->hcrc && s->pending > beg)
  814.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  815.                                     s->pending - beg);
  816.             if (val == 0) {
  817.                 s->gzindex = 0;
  818.                 s->status = COMMENT_STATE;
  819.             }
  820.         }
  821.         else
  822.             s->status = COMMENT_STATE;
  823.     }
  824.     if (s->status == COMMENT_STATE) {
  825.         if (s->gzhead->comment != Z_NULL) {
  826.             uInt beg = s->pending;  /* start of bytes to update crc */
  827.             int val;
  828.  
  829.             do {
  830.                 if (s->pending == s->pending_buf_size) {
  831.                     if (s->gzhead->hcrc && s->pending > beg)
  832.                         strm->adler = crc32(strm->adler, s->pending_buf + beg,
  833.                                             s->pending - beg);
  834.                     flush_pending(strm);
  835.                     beg = s->pending;
  836.                     if (s->pending == s->pending_buf_size) {
  837.                         val = 1;
  838.                         break;
  839.                     }
  840.                 }
  841.                 val = s->gzhead->comment[s->gzindex++];
  842.                 put_byte(s, val);
  843.             } while (val != 0);
  844.             if (s->gzhead->hcrc && s->pending > beg)
  845.                 strm->adler = crc32(strm->adler, s->pending_buf + beg,
  846.                                     s->pending - beg);
  847.             if (val == 0)
  848.                 s->status = HCRC_STATE;
  849.         }
  850.         else
  851.             s->status = HCRC_STATE;
  852.     }
  853.     if (s->status == HCRC_STATE) {
  854.         if (s->gzhead->hcrc) {
  855.             if (s->pending + 2 > s->pending_buf_size)
  856.                 flush_pending(strm);
  857.             if (s->pending + 2 <= s->pending_buf_size) {
  858.                 put_byte(s, (Byte)(strm->adler & 0xff));
  859.                 put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
  860.                 strm->adler = crc32(0L, Z_NULL, 0);
  861.                 s->status = BUSY_STATE;
  862.             }
  863.         }
  864.         else
  865.             s->status = BUSY_STATE;
  866.     }
  867. #endif
  868.  
  869.     /* Flush as much pending output as possible */
  870.     if (s->pending != 0) {
  871.         flush_pending(strm);
  872.         if (strm->avail_out == 0) {
  873.             /* Since avail_out is 0, deflate will be called again with
  874.              * more output space, but possibly with both pending and
  875.              * avail_in equal to zero. There won't be anything to do,
  876.              * but this is not an error situation so make sure we
  877.              * return OK instead of BUF_ERROR at next call of deflate:
  878.              */
  879.             s->last_flush = -1;
  880.             return Z_OK;
  881.         }
  882.  
  883.     /* Make sure there is something to do and avoid duplicate consecutive
  884.      * flushes. For repeated and useless calls with Z_FINISH, we keep
  885.      * returning Z_STREAM_END instead of Z_BUF_ERROR.
  886.      */
  887.     } else if (strm->avail_in == 0 && RANK(flush) <= RANK(old_flush) &&
  888.                flush != Z_FINISH) {
  889.         ERR_RETURN(strm, Z_BUF_ERROR);
  890.     }
  891.  
  892.     /* User must not provide more input after the first FINISH: */
  893.     if (s->status == FINISH_STATE && strm->avail_in != 0) {
  894.         ERR_RETURN(strm, Z_BUF_ERROR);
  895.     }
  896.  
  897.     /* Start a new block or continue the current one.
  898.      */
  899.     if (strm->avail_in != 0 || s->lookahead != 0 ||
  900.         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
  901.         block_state bstate;
  902.  
  903.         bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
  904.                     (s->strategy == Z_RLE ? deflate_rle(s, flush) :
  905.                         (*(configuration_table[s->level].func))(s, flush));
  906.  
  907.         if (bstate == finish_started || bstate == finish_done) {
  908.             s->status = FINISH_STATE;
  909.         }
  910.         if (bstate == need_more || bstate == finish_started) {
  911.             if (strm->avail_out == 0) {
  912.                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
  913.             }
  914.             return Z_OK;
  915.             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
  916.              * of deflate should use the same flush parameter to make sure
  917.              * that the flush is complete. So we don't have to output an
  918.              * empty block here, this will be done at next call. This also
  919.              * ensures that for a very small output buffer, we emit at most
  920.              * one empty block.
  921.              */
  922.         }
  923.         if (bstate == block_done) {
  924.             if (flush == Z_PARTIAL_FLUSH) {
  925.                 _tr_align(s);
  926.             } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
  927.                 _tr_stored_block(s, (char*)0, 0L, 0);
  928.                 /* For a full flush, this empty block will be recognized
  929.                  * as a special marker by inflate_sync().
  930.                  */
  931.                 if (flush == Z_FULL_FLUSH) {
  932.                     CLEAR_HASH(s);             /* forget history */
  933.                     if (s->lookahead == 0) {
  934.                         s->strstart = 0;
  935.                         s->block_start = 0L;
  936.                         s->insert = 0;
  937.                     }
  938.                 }
  939.             }
  940.             flush_pending(strm);
  941.             if (strm->avail_out == 0) {
  942.               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
  943.               return Z_OK;
  944.             }
  945.         }
  946.     }
  947.     Assert(strm->avail_out > 0, "bug2");
  948.  
  949.     if (flush != Z_FINISH) return Z_OK;
  950.     if (s->wrap <= 0) return Z_STREAM_END;
  951.  
  952.     /* Write the trailer */
  953. #ifdef GZIP
  954.     if (s->wrap == 2) {
  955.         put_byte(s, (Byte)(strm->adler & 0xff));
  956.         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
  957.         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
  958.         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
  959.         put_byte(s, (Byte)(strm->total_in & 0xff));
  960.         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
  961.         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
  962.         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
  963.     }
  964.     else
  965. #endif
  966.     {
  967.         putShortMSB(s, (uInt)(strm->adler >> 16));
  968.         putShortMSB(s, (uInt)(strm->adler & 0xffff));
  969.     }
  970.     flush_pending(strm);
  971.     /* If avail_out is zero, the application will call deflate again
  972.      * to flush the rest.
  973.      */
  974.     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
  975.     return s->pending != 0 ? Z_OK : Z_STREAM_END;
  976. }
  977.  
  978. /* ========================================================================= */
  979. int ZEXPORT deflateEnd (strm)
  980.     z_streamp strm;
  981. {
  982.     int status;
  983.  
  984.     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  985.  
  986.     status = strm->state->status;
  987.     if (status != INIT_STATE &&
  988.         status != EXTRA_STATE &&
  989.         status != NAME_STATE &&
  990.         status != COMMENT_STATE &&
  991.         status != HCRC_STATE &&
  992.         status != BUSY_STATE &&
  993.         status != FINISH_STATE) {
  994.       return Z_STREAM_ERROR;
  995.     }
  996.  
  997.     /* Deallocate in reverse order of allocations: */
  998.     TRY_FREE(strm, strm->state->pending_buf);
  999.     TRY_FREE(strm, strm->state->head);
  1000.     TRY_FREE(strm, strm->state->prev);
  1001.     TRY_FREE(strm, strm->state->window);
  1002.  
  1003.     ZFREE(strm, strm->state);
  1004.     strm->state = Z_NULL;
  1005.  
  1006.     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
  1007. }
  1008.  
  1009. /* =========================================================================
  1010.  * Copy the source state to the destination state.
  1011.  * To simplify the source, this is not supported for 16-bit MSDOS (which
  1012.  * doesn't have enough memory anyway to duplicate compression states).
  1013.  */
  1014. int ZEXPORT deflateCopy (dest, source)
  1015.     z_streamp dest;
  1016.     z_streamp source;
  1017. {
  1018. #ifdef MAXSEG_64K
  1019.     return Z_STREAM_ERROR;
  1020. #else
  1021.     deflate_state *ds;
  1022.     deflate_state *ss;
  1023.     ushf *overlay;
  1024.  
  1025.  
  1026.     if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
  1027.         return Z_STREAM_ERROR;
  1028.     }
  1029.  
  1030.     ss = source->state;
  1031.  
  1032.     zmemcpy((voidpf)dest, (voidpf)source, sizeof(z_stream));
  1033.  
  1034.     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
  1035.     if (ds == Z_NULL) return Z_MEM_ERROR;
  1036.     dest->state = (struct internal_state FAR *) ds;
  1037.     zmemcpy((voidpf)ds, (voidpf)ss, sizeof(deflate_state));
  1038.     ds->strm = dest;
  1039.  
  1040.     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
  1041.     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
  1042.     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
  1043.     overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
  1044.     ds->pending_buf = (uchf *) overlay;
  1045.  
  1046.     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
  1047.         ds->pending_buf == Z_NULL) {
  1048.         deflateEnd (dest);
  1049.         return Z_MEM_ERROR;
  1050.     }
  1051.     /* following zmemcpy do not work for 16-bit MSDOS */
  1052.     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
  1053.     zmemcpy((voidpf)ds->prev, (voidpf)ss->prev, ds->w_size * sizeof(Pos));
  1054.     zmemcpy((voidpf)ds->head, (voidpf)ss->head, ds->hash_size * sizeof(Pos));
  1055.     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
  1056.  
  1057.     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
  1058.     ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
  1059.     ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
  1060.  
  1061.     ds->l_desc.dyn_tree = ds->dyn_ltree;
  1062.     ds->d_desc.dyn_tree = ds->dyn_dtree;
  1063.     ds->bl_desc.dyn_tree = ds->bl_tree;
  1064.  
  1065.     return Z_OK;
  1066. #endif /* MAXSEG_64K */
  1067. }
  1068.  
  1069. /* ===========================================================================
  1070.  * Read a new buffer from the current input stream, update the adler32
  1071.  * and total number of bytes read.  All deflate() input goes through
  1072.  * this function so some applications may wish to modify it to avoid
  1073.  * allocating a large strm->next_in buffer and copying from it.
  1074.  * (See also flush_pending()).
  1075.  */
  1076. local int read_buf(strm, buf, size)
  1077.     z_streamp strm;
  1078.     Bytef *buf;
  1079.     unsigned size;
  1080. {
  1081.     unsigned len = strm->avail_in;
  1082.  
  1083.     if (len > size) len = size;
  1084.     if (len == 0) return 0;
  1085.  
  1086.     strm->avail_in  -= len;
  1087.  
  1088.     zmemcpy(buf, strm->next_in, len);
  1089.     if (strm->state->wrap == 1) {
  1090.         strm->adler = adler32(strm->adler, buf, len);
  1091.     }
  1092. #ifdef GZIP
  1093.     else if (strm->state->wrap == 2) {
  1094.         strm->adler = crc32(strm->adler, buf, len);
  1095.     }
  1096. #endif
  1097.     strm->next_in  += len;
  1098.     strm->total_in += len;
  1099.  
  1100.     return (int)len;
  1101. }
  1102.  
  1103. /* ===========================================================================
  1104.  * Initialize the "longest match" routines for a new zlib stream
  1105.  */
  1106. local void lm_init (s)
  1107.     deflate_state *s;
  1108. {
  1109.     s->window_size = (ulg)2L*s->w_size;
  1110.  
  1111.     CLEAR_HASH(s);
  1112.  
  1113.     /* Set the default configuration parameters:
  1114.      */
  1115.     s->max_lazy_match   = configuration_table[s->level].max_lazy;
  1116.     s->good_match       = configuration_table[s->level].good_length;
  1117.     s->nice_match       = configuration_table[s->level].nice_length;
  1118.     s->max_chain_length = configuration_table[s->level].max_chain;
  1119.  
  1120.     s->strstart = 0;
  1121.     s->block_start = 0L;
  1122.     s->lookahead = 0;
  1123.     s->insert = 0;
  1124.     s->match_length = s->prev_length = MIN_MATCH-1;
  1125.     s->match_available = 0;
  1126.     s->ins_h = 0;
  1127. #ifndef FASTEST
  1128. #ifdef ASMV
  1129.     match_init(); /* initialize the asm code */
  1130. #endif
  1131. #endif
  1132. }
  1133.  
  1134. #ifndef FASTEST
  1135. /* ===========================================================================
  1136.  * Set match_start to the longest match starting at the given string and
  1137.  * return its length. Matches shorter or equal to prev_length are discarded,
  1138.  * in which case the result is equal to prev_length and match_start is
  1139.  * garbage.
  1140.  * IN assertions: cur_match is the head of the hash chain for the current
  1141.  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
  1142.  * OUT assertion: the match length is not greater than s->lookahead.
  1143.  */
  1144. #ifndef ASMV
  1145. /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
  1146.  * match.S. The code will be functionally equivalent.
  1147.  */
  1148. local uInt longest_match(s, cur_match)
  1149.     deflate_state *s;
  1150.     IPos cur_match;                             /* current match */
  1151. {
  1152.     unsigned chain_length = s->max_chain_length;/* max hash chain length */
  1153.     register Bytef *scan = s->window + s->strstart; /* current string */
  1154.     register Bytef *match;                       /* matched string */
  1155.     register int len;                           /* length of current match */
  1156.     int best_len = s->prev_length;              /* best match length so far */
  1157.     int nice_match = s->nice_match;             /* stop if match long enough */
  1158.     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
  1159.         s->strstart - (IPos)MAX_DIST(s) : NIL;
  1160.     /* Stop when cur_match becomes <= limit. To simplify the code,
  1161.      * we prevent matches with the string of window index 0.
  1162.      */
  1163.     Posf *prev = s->prev;
  1164.     uInt wmask = s->w_mask;
  1165.  
  1166. #ifdef UNALIGNED_OK
  1167.     /* Compare two bytes at a time. Note: this is not always beneficial.
  1168.      * Try with and without -DUNALIGNED_OK to check.
  1169.      */
  1170.     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
  1171.     register ush scan_start = *(ushf*)scan;
  1172.     register ush scan_end   = *(ushf*)(scan+best_len-1);
  1173. #else
  1174.     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
  1175.     register Byte scan_end1  = scan[best_len-1];
  1176.     register Byte scan_end   = scan[best_len];
  1177. #endif
  1178.  
  1179.     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
  1180.      * It is easy to get rid of this optimization if necessary.
  1181.      */
  1182.     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
  1183.  
  1184.     /* Do not waste too much time if we already have a good match: */
  1185.     if (s->prev_length >= s->good_match) {
  1186.         chain_length >>= 2;
  1187.     }
  1188.     /* Do not look for matches beyond the end of the input. This is necessary
  1189.      * to make deflate deterministic.
  1190.      */
  1191.     if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
  1192.  
  1193.     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
  1194.  
  1195.     do {
  1196.         Assert(cur_match < s->strstart, "no future");
  1197.         match = s->window + cur_match;
  1198.  
  1199.         /* Skip to next match if the match length cannot increase
  1200.          * or if the match length is less than 2.  Note that the checks below
  1201.          * for insufficient lookahead only occur occasionally for performance
  1202.          * reasons.  Therefore uninitialized memory will be accessed, and
  1203.          * conditional jumps will be made that depend on those values.
  1204.          * However the length of the match is limited to the lookahead, so
  1205.          * the output of deflate is not affected by the uninitialized values.
  1206.          */
  1207. #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
  1208.         /* This code assumes sizeof(unsigned short) == 2. Do not use
  1209.          * UNALIGNED_OK if your compiler uses a different size.
  1210.          */
  1211.         if (*(ushf*)(match+best_len-1) != scan_end ||
  1212.             *(ushf*)match != scan_start) continue;
  1213.  
  1214.         /* It is not necessary to compare scan[2] and match[2] since they are
  1215.          * always equal when the other bytes match, given that the hash keys
  1216.          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
  1217.          * strstart+3, +5, ... up to strstart+257. We check for insufficient
  1218.          * lookahead only every 4th comparison; the 128th check will be made
  1219.          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
  1220.          * necessary to put more guard bytes at the end of the window, or
  1221.          * to check more often for insufficient lookahead.
  1222.          */
  1223.         Assert(scan[2] == match[2], "scan[2]?");
  1224.         scan++, match++;
  1225.         do {
  1226.         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1227.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1228.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1229.                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
  1230.                  scan < strend);
  1231.         /* The funny "do {}" generates better code on most compilers */
  1232.  
  1233.         /* Here, scan <= window+strstart+257 */
  1234.         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1235.         if (*scan == *match) scan++;
  1236.  
  1237.         len = (MAX_MATCH - 1) - (int)(strend-scan);
  1238.         scan = strend - (MAX_MATCH-1);
  1239.  
  1240. #else /* UNALIGNED_OK */
  1241.  
  1242.         if (match[best_len]   != scan_end  ||
  1243.             match[best_len-1] != scan_end1 ||
  1244.             *match            != *scan     ||
  1245.             *++match          != scan[1])      continue;
  1246.  
  1247.         /* The check at best_len-1 can be removed because it will be made
  1248.          * again later. (This heuristic is not always a win.)
  1249.          * It is not necessary to compare scan[2] and match[2] since they
  1250.          * are always equal when the other bytes match, given that
  1251.          * the hash keys are equal and that HASH_BITS >= 8.
  1252.          */
  1253.         scan += 2, match++;
  1254.         Assert(*scan == *match, "match[2]?");
  1255.  
  1256.         /* We check for insufficient lookahead only every 8th comparison;
  1257.          * the 256th check will be made at strstart+258.
  1258.          */
  1259.         do {
  1260.         } while (*++scan == *++match && *++scan == *++match &&
  1261.                  *++scan == *++match && *++scan == *++match &&
  1262.                  *++scan == *++match && *++scan == *++match &&
  1263.                  *++scan == *++match && *++scan == *++match &&
  1264.                  scan < strend);
  1265.  
  1266.         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1267.  
  1268.         len = MAX_MATCH - (int)(strend - scan);
  1269.         scan = strend - MAX_MATCH;
  1270.  
  1271. #endif /* UNALIGNED_OK */
  1272.  
  1273.         if (len > best_len) {
  1274.             s->match_start = cur_match;
  1275.             best_len = len;
  1276.             if (len >= nice_match) break;
  1277. #ifdef UNALIGNED_OK
  1278.             scan_end = *(ushf*)(scan+best_len-1);
  1279. #else
  1280.             scan_end1  = scan[best_len-1];
  1281.             scan_end   = scan[best_len];
  1282. #endif
  1283.         }
  1284.     } while ((cur_match = prev[cur_match & wmask]) > limit
  1285.              && --chain_length != 0);
  1286.  
  1287.     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
  1288.     return s->lookahead;
  1289. }
  1290. #endif /* ASMV */
  1291.  
  1292. #else /* FASTEST */
  1293.  
  1294. /* ---------------------------------------------------------------------------
  1295.  * Optimized version for FASTEST only
  1296.  */
  1297. local uInt longest_match(s, cur_match)
  1298.     deflate_state *s;
  1299.     IPos cur_match;                             /* current match */
  1300. {
  1301.     register Bytef *scan = s->window + s->strstart; /* current string */
  1302.     register Bytef *match;                       /* matched string */
  1303.     register int len;                           /* length of current match */
  1304.     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
  1305.  
  1306.     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
  1307.      * It is easy to get rid of this optimization if necessary.
  1308.      */
  1309.     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
  1310.  
  1311.     Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
  1312.  
  1313.     Assert(cur_match < s->strstart, "no future");
  1314.  
  1315.     match = s->window + cur_match;
  1316.  
  1317.     /* Return failure if the match length is less than 2:
  1318.      */
  1319.     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
  1320.  
  1321.     /* The check at best_len-1 can be removed because it will be made
  1322.      * again later. (This heuristic is not always a win.)
  1323.      * It is not necessary to compare scan[2] and match[2] since they
  1324.      * are always equal when the other bytes match, given that
  1325.      * the hash keys are equal and that HASH_BITS >= 8.
  1326.      */
  1327.     scan += 2, match += 2;
  1328.     Assert(*scan == *match, "match[2]?");
  1329.  
  1330.     /* We check for insufficient lookahead only every 8th comparison;
  1331.      * the 256th check will be made at strstart+258.
  1332.      */
  1333.     do {
  1334.     } while (*++scan == *++match && *++scan == *++match &&
  1335.              *++scan == *++match && *++scan == *++match &&
  1336.              *++scan == *++match && *++scan == *++match &&
  1337.              *++scan == *++match && *++scan == *++match &&
  1338.              scan < strend);
  1339.  
  1340.     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
  1341.  
  1342.     len = MAX_MATCH - (int)(strend - scan);
  1343.  
  1344.     if (len < MIN_MATCH) return MIN_MATCH - 1;
  1345.  
  1346.     s->match_start = cur_match;
  1347.     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
  1348. }
  1349.  
  1350. #endif /* FASTEST */
  1351.  
  1352. #ifdef DEBUG
  1353. /* ===========================================================================
  1354.  * Check that the match at match_start is indeed a match.
  1355.  */
  1356. local void check_match(s, start, match, length)
  1357.     deflate_state *s;
  1358.     IPos start, match;
  1359.     int length;
  1360. {
  1361.     /* check that the match is indeed a match */
  1362.     if (zmemcmp(s->window + match,
  1363.                 s->window + start, length) != EQUAL) {
  1364.         fprintf(stderr, " start %u, match %u, length %d\n",
  1365.                 start, match, length);
  1366.         do {
  1367.             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
  1368.         } while (--length != 0);
  1369.         z_error("invalid match");
  1370.     }
  1371.     if (z_verbose > 1) {
  1372.         fprintf(stderr,"\\[%d,%d]", start-match, length);
  1373.         do { putc(s->window[start++], stderr); } while (--length != 0);
  1374.     }
  1375. }
  1376. #else
  1377. #  define check_match(s, start, match, length)
  1378. #endif /* DEBUG */
  1379.  
  1380. /* ===========================================================================
  1381.  * Fill the window when the lookahead becomes insufficient.
  1382.  * Updates strstart and lookahead.
  1383.  *
  1384.  * IN assertion: lookahead < MIN_LOOKAHEAD
  1385.  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
  1386.  *    At least one byte has been read, or avail_in == 0; reads are
  1387.  *    performed for at least two bytes (required for the zip translate_eol
  1388.  *    option -- not supported here).
  1389.  */
  1390. local void fill_window(s)
  1391.     deflate_state *s;
  1392. {
  1393.     register unsigned n, m;
  1394.     register Posf *p;
  1395.     unsigned more;    /* Amount of free space at the end of the window. */
  1396.     uInt wsize = s->w_size;
  1397.  
  1398.     Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");
  1399.  
  1400.     do {
  1401.         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
  1402.  
  1403.         /* Deal with !@#$% 64K limit: */
  1404.         if (sizeof(int) <= 2) {
  1405.             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
  1406.                 more = wsize;
  1407.  
  1408.             } else if (more == (unsigned)(-1)) {
  1409.                 /* Very unlikely, but possible on 16 bit machine if
  1410.                  * strstart == 0 && lookahead == 1 (input done a byte at time)
  1411.                  */
  1412.                 more--;
  1413.             }
  1414.         }
  1415.  
  1416.         /* If the window is almost full and there is insufficient lookahead,
  1417.          * move the upper half to the lower one to make room in the upper half.
  1418.          */
  1419.         if (s->strstart >= wsize+MAX_DIST(s)) {
  1420.  
  1421.             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
  1422.             s->match_start -= wsize;
  1423.             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
  1424.             s->block_start -= (long) wsize;
  1425.  
  1426.             /* Slide the hash table (could be avoided with 32 bit values
  1427.                at the expense of memory usage). We slide even when level == 0
  1428.                to keep the hash table consistent if we switch back to level > 0
  1429.                later. (Using level 0 permanently is not an optimal usage of
  1430.                zlib, so we don't care about this pathological case.)
  1431.              */
  1432.             n = s->hash_size;
  1433.             p = &s->head[n];
  1434.             do {
  1435.                 m = *--p;
  1436.                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
  1437.             } while (--n);
  1438.  
  1439.             n = wsize;
  1440. #ifndef FASTEST
  1441.             p = &s->prev[n];
  1442.             do {
  1443.                 m = *--p;
  1444.                 *p = (Pos)(m >= wsize ? m-wsize : NIL);
  1445.                 /* If n is not on any hash chain, prev[n] is garbage but
  1446.                  * its value will never be used.
  1447.                  */
  1448.             } while (--n);
  1449. #endif
  1450.             more += wsize;
  1451.         }
  1452.         if (s->strm->avail_in == 0) break;
  1453.  
  1454.         /* If there was no sliding:
  1455.          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
  1456.          *    more == window_size - lookahead - strstart
  1457.          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
  1458.          * => more >= window_size - 2*WSIZE + 2
  1459.          * In the BIG_MEM or MMAP case (not yet supported),
  1460.          *   window_size == input_size + MIN_LOOKAHEAD  &&
  1461.          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
  1462.          * Otherwise, window_size == 2*WSIZE so more >= 2.
  1463.          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
  1464.          */
  1465.         Assert(more >= 2, "more < 2");
  1466.  
  1467.         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
  1468.         s->lookahead += n;
  1469.  
  1470.         /* Initialize the hash value now that we have some input: */
  1471.         if (s->lookahead + s->insert >= MIN_MATCH) {
  1472.             uInt str = s->strstart - s->insert;
  1473.             s->ins_h = s->window[str];
  1474.             UPDATE_HASH(s, s->ins_h, s->window[str + 1]);
  1475. #if MIN_MATCH != 3
  1476.             Call UPDATE_HASH() MIN_MATCH-3 more times
  1477. #endif
  1478.             while (s->insert) {
  1479.                 UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
  1480. #ifndef FASTEST
  1481.                 s->prev[str & s->w_mask] = s->head[s->ins_h];
  1482. #endif
  1483.                 s->head[s->ins_h] = (Pos)str;
  1484.                 str++;
  1485.                 s->insert--;
  1486.                 if (s->lookahead + s->insert < MIN_MATCH)
  1487.                     break;
  1488.             }
  1489.         }
  1490.         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
  1491.          * but this is not important since only literal bytes will be emitted.
  1492.          */
  1493.  
  1494.     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
  1495.  
  1496.     /* If the WIN_INIT bytes after the end of the current data have never been
  1497.      * written, then zero those bytes in order to avoid memory check reports of
  1498.      * the use of uninitialized (or uninitialised as Julian writes) bytes by
  1499.      * the longest match routines.  Update the high water mark for the next
  1500.      * time through here.  WIN_INIT is set to MAX_MATCH since the longest match
  1501.      * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
  1502.      */
  1503.     if (s->high_water < s->window_size) {
  1504.         ulg curr = s->strstart + (ulg)(s->lookahead);
  1505.         ulg init;
  1506.  
  1507.         if (s->high_water < curr) {
  1508.             /* Previous high water mark below current data -- zero WIN_INIT
  1509.              * bytes or up to end of window, whichever is less.
  1510.              */
  1511.             init = s->window_size - curr;
  1512.             if (init > WIN_INIT)
  1513.                 init = WIN_INIT;
  1514.             zmemzero(s->window + curr, (unsigned)init);
  1515.             s->high_water = curr + init;
  1516.         }
  1517.         else if (s->high_water < (ulg)curr + WIN_INIT) {
  1518.             /* High water mark at or above current data, but below current data
  1519.              * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
  1520.              * to end of window, whichever is less.
  1521.              */
  1522.             init = (ulg)curr + WIN_INIT - s->high_water;
  1523.             if (init > s->window_size - s->high_water)
  1524.                 init = s->window_size - s->high_water;
  1525.             zmemzero(s->window + s->high_water, (unsigned)init);
  1526.             s->high_water += init;
  1527.         }
  1528.     }
  1529.  
  1530.     Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
  1531.            "not enough room for search");
  1532. }
  1533.  
  1534. /* ===========================================================================
  1535.  * Flush the current block, with given end-of-file flag.
  1536.  * IN assertion: strstart is set to the end of the current match.
  1537.  */
  1538. #define FLUSH_BLOCK_ONLY(s, last) { \
  1539.    _tr_flush_block(s, (s->block_start >= 0L ? \
  1540.                    (charf *)&s->window[(unsigned)s->block_start] : \
  1541.                    (charf *)Z_NULL), \
  1542.                 (ulg)((long)s->strstart - s->block_start), \
  1543.                 (last)); \
  1544.    s->block_start = s->strstart; \
  1545.    flush_pending(s->strm); \
  1546.    Tracev((stderr,"[FLUSH]")); \
  1547. }
  1548.  
  1549. /* Same but force premature exit if necessary. */
  1550. #define FLUSH_BLOCK(s, last) { \
  1551.    FLUSH_BLOCK_ONLY(s, last); \
  1552.    if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
  1553. }
  1554.  
  1555. /* ===========================================================================
  1556.  * Copy without compression as much as possible from the input stream, return
  1557.  * the current block state.
  1558.  * This function does not insert new strings in the dictionary since
  1559.  * uncompressible data is probably not useful. This function is used
  1560.  * only for the level=0 compression option.
  1561.  * NOTE: this function should be optimized to avoid extra copying from
  1562.  * window to pending_buf.
  1563.  */
  1564. local block_state deflate_stored(s, flush)
  1565.     deflate_state *s;
  1566.     int flush;
  1567. {
  1568.     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
  1569.      * to pending_buf_size, and each stored block has a 5 byte header:
  1570.      */
  1571.     ulg max_block_size = 0xffff;
  1572.     ulg max_start;
  1573.  
  1574.     if (max_block_size > s->pending_buf_size - 5) {
  1575.         max_block_size = s->pending_buf_size - 5;
  1576.     }
  1577.  
  1578.     /* Copy as much as possible from input to output: */
  1579.     for (;;) {
  1580.         /* Fill the window as much as possible: */
  1581.         if (s->lookahead <= 1) {
  1582.  
  1583.             Assert(s->strstart < s->w_size+MAX_DIST(s) ||
  1584.                    s->block_start >= (long)s->w_size, "slide too late");
  1585.  
  1586.             fill_window(s);
  1587.             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
  1588.  
  1589.             if (s->lookahead == 0) break; /* flush the current block */
  1590.         }
  1591.         Assert(s->block_start >= 0L, "block gone");
  1592.  
  1593.         s->strstart += s->lookahead;
  1594.         s->lookahead = 0;
  1595.  
  1596.         /* Emit a stored block if pending_buf will be full: */
  1597.         max_start = s->block_start + max_block_size;
  1598.         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
  1599.             /* strstart == 0 is possible when wraparound on 16-bit machine */
  1600.             s->lookahead = (uInt)(s->strstart - max_start);
  1601.             s->strstart = (uInt)max_start;
  1602.             FLUSH_BLOCK(s, 0);
  1603.         }
  1604.         /* Flush if we may have to slide, otherwise block_start may become
  1605.          * negative and the data will be gone:
  1606.          */
  1607.         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
  1608.             FLUSH_BLOCK(s, 0);
  1609.         }
  1610.     }
  1611.     s->insert = 0;
  1612.     if (flush == Z_FINISH) {
  1613.         FLUSH_BLOCK(s, 1);
  1614.         return finish_done;
  1615.     }
  1616.     if ((long)s->strstart > s->block_start)
  1617.         FLUSH_BLOCK(s, 0);
  1618.     return block_done;
  1619. }
  1620.  
  1621. /* ===========================================================================
  1622.  * Compress as much as possible from the input stream, return the current
  1623.  * block state.
  1624.  * This function does not perform lazy evaluation of matches and inserts
  1625.  * new strings in the dictionary only for unmatched strings or for short
  1626.  * matches. It is used only for the fast compression options.
  1627.  */
  1628. local block_state deflate_fast(s, flush)
  1629.     deflate_state *s;
  1630.     int flush;
  1631. {
  1632.     IPos hash_head;       /* head of the hash chain */
  1633.     int bflush;           /* set if current block must be flushed */
  1634.  
  1635.     for (;;) {
  1636.         /* Make sure that we always have enough lookahead, except
  1637.          * at the end of the input file. We need MAX_MATCH bytes
  1638.          * for the next match, plus MIN_MATCH bytes to insert the
  1639.          * string following the next match.
  1640.          */
  1641.         if (s->lookahead < MIN_LOOKAHEAD) {
  1642.             fill_window(s);
  1643.             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
  1644.                 return need_more;
  1645.             }
  1646.             if (s->lookahead == 0) break; /* flush the current block */
  1647.         }
  1648.  
  1649.         /* Insert the string window[strstart .. strstart+2] in the
  1650.          * dictionary, and set hash_head to the head of the hash chain:
  1651.          */
  1652.         hash_head = NIL;
  1653.         if (s->lookahead >= MIN_MATCH) {
  1654.             INSERT_STRING(s, s->strstart, hash_head);
  1655.         }
  1656.  
  1657.         /* Find the longest match, discarding those <= prev_length.
  1658.          * At this point we have always match_length < MIN_MATCH
  1659.          */
  1660.         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
  1661.             /* To simplify the code, we prevent matches with the string
  1662.              * of window index 0 (in particular we have to avoid a match
  1663.              * of the string with itself at the start of the input file).
  1664.              */
  1665.             s->match_length = longest_match (s, hash_head);
  1666.             /* longest_match() sets match_start */
  1667.         }
  1668.         if (s->match_length >= MIN_MATCH) {
  1669.             check_match(s, s->strstart, s->match_start, s->match_length);
  1670.  
  1671.             _tr_tally_dist(s, s->strstart - s->match_start,
  1672.                            s->match_length - MIN_MATCH, bflush);
  1673.  
  1674.             s->lookahead -= s->match_length;
  1675.  
  1676.             /* Insert new strings in the hash table only if the match length
  1677.              * is not too large. This saves time but degrades compression.
  1678.              */
  1679. #ifndef FASTEST
  1680.             if (s->match_length <= s->max_insert_length &&
  1681.                 s->lookahead >= MIN_MATCH) {
  1682.                 s->match_length--; /* string at strstart already in table */
  1683.                 do {
  1684.                     s->strstart++;
  1685.                     INSERT_STRING(s, s->strstart, hash_head);
  1686.                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
  1687.                      * always MIN_MATCH bytes ahead.
  1688.                      */
  1689.                 } while (--s->match_length != 0);
  1690.                 s->strstart++;
  1691.             } else
  1692. #endif
  1693.             {
  1694.                 s->strstart += s->match_length;
  1695.                 s->match_length = 0;
  1696.                 s->ins_h = s->window[s->strstart];
  1697.                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
  1698. #if MIN_MATCH != 3
  1699.                 Call UPDATE_HASH() MIN_MATCH-3 more times
  1700. #endif
  1701.                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
  1702.                  * matter since it will be recomputed at next deflate call.
  1703.                  */
  1704.             }
  1705.         } else {
  1706.             /* No match, output a literal byte */
  1707.             Tracevv((stderr,"%c", s->window[s->strstart]));
  1708.             _tr_tally_lit (s, s->window[s->strstart], bflush);
  1709.             s->lookahead--;
  1710.             s->strstart++;
  1711.         }
  1712.         if (bflush) FLUSH_BLOCK(s, 0);
  1713.     }
  1714.     s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
  1715.     if (flush == Z_FINISH) {
  1716.         FLUSH_BLOCK(s, 1);
  1717.         return finish_done;
  1718.     }
  1719.     if (s->last_lit)
  1720.         FLUSH_BLOCK(s, 0);
  1721.     return block_done;
  1722. }
  1723.  
  1724. #ifndef FASTEST
  1725. /* ===========================================================================
  1726.  * Same as above, but achieves better compression. We use a lazy
  1727.  * evaluation for matches: a match is finally adopted only if there is
  1728.  * no better match at the next window position.
  1729.  */
  1730. local block_state deflate_slow(s, flush)
  1731.     deflate_state *s;
  1732.     int flush;
  1733. {
  1734.     IPos hash_head;          /* head of hash chain */
  1735.     int bflush;              /* set if current block must be flushed */
  1736.  
  1737.     /* Process the input block. */
  1738.     for (;;) {
  1739.         /* Make sure that we always have enough lookahead, except
  1740.          * at the end of the input file. We need MAX_MATCH bytes
  1741.          * for the next match, plus MIN_MATCH bytes to insert the
  1742.          * string following the next match.
  1743.          */
  1744.         if (s->lookahead < MIN_LOOKAHEAD) {
  1745.             fill_window(s);
  1746.             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
  1747.                 return need_more;
  1748.             }
  1749.             if (s->lookahead == 0) break; /* flush the current block */
  1750.         }
  1751.  
  1752.         /* Insert the string window[strstart .. strstart+2] in the
  1753.          * dictionary, and set hash_head to the head of the hash chain:
  1754.          */
  1755.         hash_head = NIL;
  1756.         if (s->lookahead >= MIN_MATCH) {
  1757.             INSERT_STRING(s, s->strstart, hash_head);
  1758.         }
  1759.  
  1760.         /* Find the longest match, discarding those <= prev_length.
  1761.          */
  1762.         s->prev_length = s->match_length, s->prev_match = s->match_start;
  1763.         s->match_length = MIN_MATCH-1;
  1764.  
  1765.         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
  1766.             s->strstart - hash_head <= MAX_DIST(s)) {
  1767.             /* To simplify the code, we prevent matches with the string
  1768.              * of window index 0 (in particular we have to avoid a match
  1769.              * of the string with itself at the start of the input file).
  1770.              */
  1771.             s->match_length = longest_match (s, hash_head);
  1772.             /* longest_match() sets match_start */
  1773.  
  1774.             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
  1775. #if TOO_FAR <= 32767
  1776.                 || (s->match_length == MIN_MATCH &&
  1777.                     s->strstart - s->match_start > TOO_FAR)
  1778. #endif
  1779.                 )) {
  1780.  
  1781.                 /* If prev_match is also MIN_MATCH, match_start is garbage
  1782.                  * but we will ignore the current match anyway.
  1783.                  */
  1784.                 s->match_length = MIN_MATCH-1;
  1785.             }
  1786.         }
  1787.         /* If there was a match at the previous step and the current
  1788.          * match is not better, output the previous match:
  1789.          */
  1790.         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
  1791.             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
  1792.             /* Do not insert strings in hash table beyond this. */
  1793.  
  1794.             check_match(s, s->strstart-1, s->prev_match, s->prev_length);
  1795.  
  1796.             _tr_tally_dist(s, s->strstart -1 - s->prev_match,
  1797.                            s->prev_length - MIN_MATCH, bflush);
  1798.  
  1799.             /* Insert in hash table all strings up to the end of the match.
  1800.              * strstart-1 and strstart are already inserted. If there is not
  1801.              * enough lookahead, the last two strings are not inserted in
  1802.              * the hash table.
  1803.              */
  1804.             s->lookahead -= s->prev_length-1;
  1805.             s->prev_length -= 2;
  1806.             do {
  1807.                 if (++s->strstart <= max_insert) {
  1808.                     INSERT_STRING(s, s->strstart, hash_head);
  1809.                 }
  1810.             } while (--s->prev_length != 0);
  1811.             s->match_available = 0;
  1812.             s->match_length = MIN_MATCH-1;
  1813.             s->strstart++;
  1814.  
  1815.             if (bflush) FLUSH_BLOCK(s, 0);
  1816.  
  1817.         } else if (s->match_available) {
  1818.             /* If there was no match at the previous position, output a
  1819.              * single literal. If there was a match but the current match
  1820.              * is longer, truncate the previous match to a single literal.
  1821.              */
  1822.             Tracevv((stderr,"%c", s->window[s->strstart-1]));
  1823.             _tr_tally_lit(s, s->window[s->strstart-1], bflush);
  1824.             if (bflush) {
  1825.                 FLUSH_BLOCK_ONLY(s, 0);
  1826.             }
  1827.             s->strstart++;
  1828.             s->lookahead--;
  1829.             if (s->strm->avail_out == 0) return need_more;
  1830.         } else {
  1831.             /* There is no previous match to compare with, wait for
  1832.              * the next step to decide.
  1833.              */
  1834.             s->match_available = 1;
  1835.             s->strstart++;
  1836.             s->lookahead--;
  1837.         }
  1838.     }
  1839.     Assert (flush != Z_NO_FLUSH, "no flush?");
  1840.     if (s->match_available) {
  1841.         Tracevv((stderr,"%c", s->window[s->strstart-1]));
  1842.         _tr_tally_lit(s, s->window[s->strstart-1], bflush);
  1843.         s->match_available = 0;
  1844.     }
  1845.     s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
  1846.     if (flush == Z_FINISH) {
  1847.         FLUSH_BLOCK(s, 1);
  1848.         return finish_done;
  1849.     }
  1850.     if (s->last_lit)
  1851.         FLUSH_BLOCK(s, 0);
  1852.     return block_done;
  1853. }
  1854. #endif /* FASTEST */
  1855.  
  1856. /* ===========================================================================
  1857.  * For Z_RLE, simply look for runs of bytes, generate matches only of distance
  1858.  * one.  Do not maintain a hash table.  (It will be regenerated if this run of
  1859.  * deflate switches away from Z_RLE.)
  1860.  */
  1861. local block_state deflate_rle(s, flush)
  1862.     deflate_state *s;
  1863.     int flush;
  1864. {
  1865.     int bflush;             /* set if current block must be flushed */
  1866.     uInt prev;              /* byte at distance one to match */
  1867.     Bytef *scan, *strend;   /* scan goes up to strend for length of run */
  1868.  
  1869.     for (;;) {
  1870.         /* Make sure that we always have enough lookahead, except
  1871.          * at the end of the input file. We need MAX_MATCH bytes
  1872.          * for the longest run, plus one for the unrolled loop.
  1873.          */
  1874.         if (s->lookahead <= MAX_MATCH) {
  1875.             fill_window(s);
  1876.             if (s->lookahead <= MAX_MATCH && flush == Z_NO_FLUSH) {
  1877.                 return need_more;
  1878.             }
  1879.             if (s->lookahead == 0) break; /* flush the current block */
  1880.         }
  1881.  
  1882.         /* See how many times the previous byte repeats */
  1883.         s->match_length = 0;
  1884.         if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
  1885.             scan = s->window + s->strstart - 1;
  1886.             prev = *scan;
  1887.             if (prev == *++scan && prev == *++scan && prev == *++scan) {
  1888.                 strend = s->window + s->strstart + MAX_MATCH;
  1889.                 do {
  1890.                 } while (prev == *++scan && prev == *++scan &&
  1891.                          prev == *++scan && prev == *++scan &&
  1892.                          prev == *++scan && prev == *++scan &&
  1893.                          prev == *++scan && prev == *++scan &&
  1894.                          scan < strend);
  1895.                 s->match_length = MAX_MATCH - (int)(strend - scan);
  1896.                 if (s->match_length > s->lookahead)
  1897.                     s->match_length = s->lookahead;
  1898.             }
  1899.             Assert(scan <= s->window+(uInt)(s->window_size-1), "wild scan");
  1900.         }
  1901.  
  1902.         /* Emit match if have run of MIN_MATCH or longer, else emit literal */
  1903.         if (s->match_length >= MIN_MATCH) {
  1904.             check_match(s, s->strstart, s->strstart - 1, s->match_length);
  1905.  
  1906.             _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
  1907.  
  1908.             s->lookahead -= s->match_length;
  1909.             s->strstart += s->match_length;
  1910.             s->match_length = 0;
  1911.         } else {
  1912.             /* No match, output a literal byte */
  1913.             Tracevv((stderr,"%c", s->window[s->strstart]));
  1914.             _tr_tally_lit (s, s->window[s->strstart], bflush);
  1915.             s->lookahead--;
  1916.             s->strstart++;
  1917.         }
  1918.         if (bflush) FLUSH_BLOCK(s, 0);
  1919.     }
  1920.     s->insert = 0;
  1921.     if (flush == Z_FINISH) {
  1922.         FLUSH_BLOCK(s, 1);
  1923.         return finish_done;
  1924.     }
  1925.     if (s->last_lit)
  1926.         FLUSH_BLOCK(s, 0);
  1927.     return block_done;
  1928. }
  1929.  
  1930. /* ===========================================================================
  1931.  * For Z_HUFFMAN_ONLY, do not look for matches.  Do not maintain a hash table.
  1932.  * (It will be regenerated if this run of deflate switches away from Huffman.)
  1933.  */
  1934. local block_state deflate_huff(s, flush)
  1935.     deflate_state *s;
  1936.     int flush;
  1937. {
  1938.     int bflush;             /* set if current block must be flushed */
  1939.  
  1940.     for (;;) {
  1941.         /* Make sure that we have a literal to write. */
  1942.         if (s->lookahead == 0) {
  1943.             fill_window(s);
  1944.             if (s->lookahead == 0) {
  1945.                 if (flush == Z_NO_FLUSH)
  1946.                     return need_more;
  1947.                 break;      /* flush the current block */
  1948.             }
  1949.         }
  1950.  
  1951.         /* Output a literal byte */
  1952.         s->match_length = 0;
  1953.         Tracevv((stderr,"%c", s->window[s->strstart]));
  1954.         _tr_tally_lit (s, s->window[s->strstart], bflush);
  1955.         s->lookahead--;
  1956.         s->strstart++;
  1957.         if (bflush) FLUSH_BLOCK(s, 0);
  1958.     }
  1959.     s->insert = 0;
  1960.     if (flush == Z_FINISH) {
  1961.         FLUSH_BLOCK(s, 1);
  1962.         return finish_done;
  1963.     }
  1964.     if (s->last_lit)
  1965.         FLUSH_BLOCK(s, 0);
  1966.     return block_done;
  1967. }
  1968.