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 /* deflate.c -- compress data using the deflation algorithm
  * Copyright (C) 1995-2022 Jean-loup Gailly and Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
 /*
  *  ALGORITHM
  *
  *      The "deflation" process depends on being able to identify portions
  *      of the input text which are identical to earlier input (within a
  *      sliding window trailing behind the input currently being processed).
  *
  *      The most straightforward technique turns out to be the fastest for
  *      most input files: try all possible matches and select the longest.
  *      The key feature of this algorithm is that insertions into the string
  *      dictionary are very simple and thus fast, and deletions are avoided
  *      completely. Insertions are performed at each input character, whereas
  *      string matches are performed only when the previous match ends. So it
  *      is preferable to spend more time in matches to allow very fast string
  *      insertions and avoid deletions. The matching algorithm for small
  *      strings is inspired from that of Rabin & Karp. A brute force approach
  *      is used to find longer strings when a small match has been found.
  *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
  *      (by Leonid Broukhis).
  *         A previous version of this file used a more sophisticated algorithm
  *      (by Fiala and Greene) which is guaranteed to run in linear amortized
  *      time, but has a larger average cost, uses more memory and is patented.
  *      However the F&G algorithm may be faster for some highly redundant
  *      files if the parameter max_chain_length (described below) is too large.
  *
  *  ACKNOWLEDGEMENTS
  *
  *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
  *      I found it in 'freeze' written by Leonid Broukhis.
  *      Thanks to many people for bug reports and testing.
  *
  *  REFERENCES
  *
  *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
  *      Available in http://tools.ietf.org/html/rfc1951
  *
  *      A description of the Rabin and Karp algorithm is given in the book
  *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
  *
  *      Fiala,E.R., and Greene,D.H.
  *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
  *
  */
 
 /* @(#) $Id$ */
 
 #include "deflate.h"
 
 const char deflate_copyright[] =
    " deflate 1.2.13 Copyright 1995-2022 Jean-loup Gailly and Mark Adler ";
 /*
   If you use the zlib library in a product, an acknowledgment is welcome
   in the documentation of your product. If for some reason you cannot
   include such an acknowledgment, I would appreciate that you keep this
   copyright string in the executable of your product.
  */
 
 /* ===========================================================================
  *  Function prototypes.
  */
 typedef enum {
     need_more,      /* block not completed, need more input or more output */
     block_done,     /* block flush performed */
     finish_started, /* finish started, need only more output at next deflate */
     finish_done     /* finish done, accept no more input or output */
 } block_state;
 
 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
 /* Compression function. Returns the block state after the call. */
 
 local int deflateStateCheck      OF((z_streamp strm));
 local void slide_hash     OF((deflate_state *s));
 local void fill_window    OF((deflate_state *s));
 local block_state deflate_stored OF((deflate_state *s, int flush));
 local block_state deflate_fast   OF((deflate_state *s, int flush));
 #ifndef FASTEST
 local block_state deflate_slow   OF((deflate_state *s, int flush));
 #endif
 local block_state deflate_rle    OF((deflate_state *s, int flush));
 local block_state deflate_huff   OF((deflate_state *s, int flush));
 local void lm_init        OF((deflate_state *s));
 local void putShortMSB    OF((deflate_state *s, uInt b));
 local void flush_pending  OF((z_streamp strm));
 local unsigned read_buf   OF((z_streamp strm, Bytef *buf, unsigned size));
 local uInt longest_match  OF((deflate_state *s, IPos cur_match));
 
 #ifdef ZLIB_DEBUG
 local  void check_match OF((deflate_state *s, IPos start, IPos match,
                             int length));
 #endif
 
 /* ===========================================================================
  * Local data
  */
 
 #define NIL 0
 /* Tail of hash chains */
 
 #ifndef TOO_FAR
 #  define TOO_FAR 4096
 #endif
 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
 
 /* Values for max_lazy_match, good_match and max_chain_length, depending on
  * the desired pack level (0..9). The values given below have been tuned to
  * exclude worst case performance for pathological files. Better values may be
  * found for specific files.
  */
 typedef struct config_s {
    ush good_length; /* reduce lazy search above this match length */
    ush max_lazy;    /* do not perform lazy search above this match length */
    ush nice_length; /* quit search above this match length */
    ush max_chain;
    compress_func func;
 } config;
 
 #ifdef FASTEST
 local const config configuration_table[2] = {
 /*      good lazy nice chain */
 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
 /* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */
 #else
 local const config configuration_table[10] = {
 /*      good lazy nice chain */
 /* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */
 /* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
 /* 2 */ {4,    5, 16,    8, deflate_fast},
 /* 3 */ {4,    6, 32,   32, deflate_fast},
 
 /* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
 /* 5 */ {8,   16, 32,   32, deflate_slow},
 /* 6 */ {8,   16, 128, 128, deflate_slow},
 /* 7 */ {8,   32, 128, 256, deflate_slow},
 /* 8 */ {32, 128, 258, 1024, deflate_slow},
 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
 #endif
 
 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
  * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
  * meaning.
  */
 
 /* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
 #define RANK(f) (((f) * 2) - ((f) > 4 ? 9 : 0))
 
 /* ===========================================================================
  * Update a hash value with the given input byte
  * IN  assertion: all calls to UPDATE_HASH are made with consecutive input
  *    characters, so that a running hash key can be computed from the previous
  *    key instead of complete recalculation each time.
  */
 #define UPDATE_HASH(s,h,c) (h = (((h) << s->hash_shift) ^ (c)) & s->hash_mask)
 
 
 /* ===========================================================================
  * Insert string str in the dictionary and set match_head to the previous head
  * of the hash chain (the most recent string with same hash key). Return
  * the previous length of the hash chain.
  * If this file is compiled with -DFASTEST, the compression level is forced
  * to 1, and no hash chains are maintained.
  * IN  assertion: all calls to INSERT_STRING are made with consecutive input
  *    characters and the first MIN_MATCH bytes of str are valid (except for
  *    the last MIN_MATCH-1 bytes of the input file).
  */
 #ifdef FASTEST
 #define INSERT_STRING(s, str, match_head) \
    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
     match_head = s->head[s->ins_h], \
     s->head[s->ins_h] = (Pos)(str))
 #else
 #define INSERT_STRING(s, str, match_head) \
    (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
     match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
     s->head[s->ins_h] = (Pos)(str))
 #endif
 
 /* ===========================================================================
  * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
  * prev[] will be initialized on the fly.
  */
 #define CLEAR_HASH(s) \
     do { \
         s->head[s->hash_size - 1] = NIL; \
         zmemzero((Bytef *)s->head, \
                  (unsigned)(s->hash_size - 1)*sizeof(*s->head)); \
     } while (0)
 
 /* ===========================================================================
  * Slide the hash table when sliding the window down (could be avoided with 32
  * bit values at the expense of memory usage). We slide even when level == 0 to
  * keep the hash table consistent if we switch back to level > 0 later.
  */
 local void slide_hash(s)
     deflate_state *s;
 {
     unsigned n, m;
     Posf *p;
     uInt wsize = s->w_size;
 
     n = s->hash_size;
     p = &s->head[n];
     do {
         m = *--p;
         *p = (Pos)(m >= wsize ? m - wsize : NIL);
     } while (--n);
     n = wsize;
 #ifndef FASTEST
     p = &s->prev[n];
     do {
         m = *--p;
         *p = (Pos)(m >= wsize ? m - wsize : NIL);
         /* If n is not on any hash chain, prev[n] is garbage but
          * its value will never be used.
          */
     } while (--n);
 #endif
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateInit_(strm, level, version, stream_size)
     z_streamp strm;
     int level;
     const char *version;
     int stream_size;
 {
     return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
                          Z_DEFAULT_STRATEGY, version, stream_size);
     /* To do: ignore strm->next_in if we use it as window */
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
                   version, stream_size)
     z_streamp strm;
     int  level;
     int  method;
     int  windowBits;
     int  memLevel;
     int  strategy;
     const char *version;
     int stream_size;
 {
     deflate_state *s;
     int wrap = 1;
     static const char my_version[] = ZLIB_VERSION;
 
     if (version == Z_NULL || version[0] != my_version[0] ||
         stream_size != sizeof(z_stream)) {
         return Z_VERSION_ERROR;
     }
     if (strm == Z_NULL) return Z_STREAM_ERROR;
 
     strm->msg = Z_NULL;
     if (strm->zalloc == (alloc_func)0) {
 #ifdef Z_SOLO
         return Z_STREAM_ERROR;
 #else
         strm->zalloc = zcalloc;
         strm->opaque = (voidpf)0;
 #endif
     }
     if (strm->zfree == (free_func)0)
 #ifdef Z_SOLO
         return Z_STREAM_ERROR;
 #else
         strm->zfree = zcfree;
 #endif
 
 #ifdef FASTEST
     if (level != 0) level = 1;
 #else
     if (level == Z_DEFAULT_COMPRESSION) level = 6;
 #endif
 
     if (windowBits < 0) { /* suppress zlib wrapper */
         wrap = 0;
         if (windowBits < -15)
             return Z_STREAM_ERROR;
         windowBits = -windowBits;
     }
 #ifdef GZIP
     else if (windowBits > 15) {
         wrap = 2;       /* write gzip wrapper instead */
         windowBits -= 16;
     }
 #endif
     if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
         windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
         strategy < 0 || strategy > Z_FIXED || (windowBits == 8 && wrap != 1)) {
         return Z_STREAM_ERROR;
     }
     if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */
     s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
     if (s == Z_NULL) return Z_MEM_ERROR;
     strm->state = (struct internal_state FAR *)s;
     s->strm = strm;
     s->status = INIT_STATE;     /* to pass state test in deflateReset() */
 
     s->wrap = wrap;
     s->gzhead = Z_NULL;
     s->w_bits = (uInt)windowBits;
     s->w_size = 1 << s->w_bits;
     s->w_mask = s->w_size - 1;
 
     s->hash_bits = (uInt)memLevel + 7;
     s->hash_size = 1 << s->hash_bits;
     s->hash_mask = s->hash_size - 1;
     s->hash_shift =  ((s->hash_bits + MIN_MATCH-1) / MIN_MATCH);
 
     s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
     s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));
     s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));
 
     s->high_water = 0;      /* nothing written to s->window yet */
 
     s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
 
     /* We overlay pending_buf and sym_buf. This works since the average size
      * for length/distance pairs over any compressed block is assured to be 31
      * bits or less.
      *
      * Analysis: The longest fixed codes are a length code of 8 bits plus 5
      * extra bits, for lengths 131 to 257. The longest fixed distance codes are
      * 5 bits plus 13 extra bits, for distances 16385 to 32768. The longest
      * possible fixed-codes length/distance pair is then 31 bits total.
      *
      * sym_buf starts one-fourth of the way into pending_buf. So there are
      * three bytes in sym_buf for every four bytes in pending_buf. Each symbol
      * in sym_buf is three bytes -- two for the distance and one for the
      * literal/length. As each symbol is consumed, the pointer to the next
      * sym_buf value to read moves forward three bytes. From that symbol, up to
      * 31 bits are written to pending_buf. The closest the written pending_buf
      * bits gets to the next sym_buf symbol to read is just before the last
      * code is written. At that time, 31*(n - 2) bits have been written, just
      * after 24*(n - 2) bits have been consumed from sym_buf. sym_buf starts at
      * 8*n bits into pending_buf. (Note that the symbol buffer fills when n - 1
      * symbols are written.) The closest the writing gets to what is unread is
      * then n + 14 bits. Here n is lit_bufsize, which is 16384 by default, and
      * can range from 128 to 32768.
      *
      * Therefore, at a minimum, there are 142 bits of space between what is
      * written and what is read in the overlain buffers, so the symbols cannot
      * be overwritten by the compressed data. That space is actually 139 bits,
      * due to the three-bit fixed-code block header.
      *
      * That covers the case where either Z_FIXED is specified, forcing fixed
      * codes, or when the use of fixed codes is chosen, because that choice
      * results in a smaller compressed block than dynamic codes. That latter
      * condition then assures that the above analysis also covers all dynamic
      * blocks. A dynamic-code block will only be chosen to be emitted if it has
      * fewer bits than a fixed-code block would for the same set of symbols.
      * Therefore its average symbol length is assured to be less than 31. So
      * the compressed data for a dynamic block also cannot overwrite the
      * symbols from which it is being constructed.
      */
 
     s->pending_buf = (uchf *) ZALLOC(strm, s->lit_bufsize, 4);
     s->pending_buf_size = (ulg)s->lit_bufsize * 4;
 
     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
         s->pending_buf == Z_NULL) {
         s->status = FINISH_STATE;
         strm->msg = ERR_MSG(Z_MEM_ERROR);
         deflateEnd (strm);
         return Z_MEM_ERROR;
     }
     s->sym_buf = s->pending_buf + s->lit_bufsize;
     s->sym_end = (s->lit_bufsize - 1) * 3;
     /* We avoid equality with lit_bufsize*3 because of wraparound at 64K
      * on 16 bit machines and because stored blocks are restricted to
      * 64K-1 bytes.
      */
 
     s->level = level;
     s->strategy = strategy;
     s->method = (Byte)method;
 
     return deflateReset(strm);
 }
 
 /* =========================================================================
  * Check for a valid deflate stream state. Return 0 if ok, 1 if not.
  */
 local int deflateStateCheck(strm)
     z_streamp strm;
 {
     deflate_state *s;
     if (strm == Z_NULL ||
         strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0)
         return 1;
     s = strm->state;
     if (s == Z_NULL || s->strm != strm || (s->status != INIT_STATE &&
 #ifdef GZIP
                                            s->status != GZIP_STATE &&
 #endif
                                            s->status != EXTRA_STATE &&
                                            s->status != NAME_STATE &&
                                            s->status != COMMENT_STATE &&
                                            s->status != HCRC_STATE &&
                                            s->status != BUSY_STATE &&
                                            s->status != FINISH_STATE))
         return 1;
     return 0;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateSetDictionary(strm, dictionary, dictLength)
     z_streamp strm;
     const Bytef *dictionary;
     uInt  dictLength;
 {
     deflate_state *s;
     uInt str, n;
     int wrap;
     unsigned avail;
     z_const unsigned char *next;
 
     if (deflateStateCheck(strm) || dictionary == Z_NULL)
         return Z_STREAM_ERROR;
     s = strm->state;
     wrap = s->wrap;
     if (wrap == 2 || (wrap == 1 && s->status != INIT_STATE) || s->lookahead)
         return Z_STREAM_ERROR;
 
     /* when using zlib wrappers, compute Adler-32 for provided dictionary */
     if (wrap == 1)
         strm->adler = adler32(strm->adler, dictionary, dictLength);
     s->wrap = 0;                    /* avoid computing Adler-32 in read_buf */
 
     /* if dictionary would fill window, just replace the history */
     if (dictLength >= s->w_size) {
         if (wrap == 0) {            /* already empty otherwise */
             CLEAR_HASH(s);
             s->strstart = 0;
             s->block_start = 0L;
             s->insert = 0;
         }
         dictionary += dictLength - s->w_size;  /* use the tail */
         dictLength = s->w_size;
     }
 
     /* insert dictionary into window and hash */
     avail = strm->avail_in;
     next = strm->next_in;
     strm->avail_in = dictLength;
     strm->next_in = (z_const Bytef *)dictionary;
     fill_window(s);
     while (s->lookahead >= MIN_MATCH) {
         str = s->strstart;
         n = s->lookahead - (MIN_MATCH-1);
         do {
             UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
 #ifndef FASTEST
             s->prev[str & s->w_mask] = s->head[s->ins_h];
 #endif
             s->head[s->ins_h] = (Pos)str;
             str++;
         } while (--n);
         s->strstart = str;
         s->lookahead = MIN_MATCH-1;
         fill_window(s);
     }
     s->strstart += s->lookahead;
     s->block_start = (long)s->strstart;
     s->insert = s->lookahead;
     s->lookahead = 0;
     s->match_length = s->prev_length = MIN_MATCH-1;
     s->match_available = 0;
     strm->next_in = next;
     strm->avail_in = avail;
     s->wrap = wrap;
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateGetDictionary(strm, dictionary, dictLength)
     z_streamp strm;
     Bytef *dictionary;
     uInt  *dictLength;
 {
     deflate_state *s;
     uInt len;
 
     if (deflateStateCheck(strm))
         return Z_STREAM_ERROR;
     s = strm->state;
     len = s->strstart + s->lookahead;
     if (len > s->w_size)
         len = s->w_size;
     if (dictionary != Z_NULL && len)
         zmemcpy(dictionary, s->window + s->strstart + s->lookahead - len, len);
     if (dictLength != Z_NULL)
         *dictLength = len;
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateResetKeep(strm)
     z_streamp strm;
 {
     deflate_state *s;
 
     if (deflateStateCheck(strm)) {
         return Z_STREAM_ERROR;
     }
 
     strm->total_in = strm->total_out = 0;
     strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
     strm->data_type = Z_UNKNOWN;
 
     s = (deflate_state *)strm->state;
     s->pending = 0;
     s->pending_out = s->pending_buf;
 
     if (s->wrap < 0) {
         s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
     }
     s->status =
 #ifdef GZIP
         s->wrap == 2 ? GZIP_STATE :
 #endif
         INIT_STATE;
     strm->adler =
 #ifdef GZIP
         s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
 #endif
         adler32(0L, Z_NULL, 0);
     s->last_flush = -2;
 
     _tr_init(s);
 
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateReset(strm)
     z_streamp strm;
 {
     int ret;
 
     ret = deflateResetKeep(strm);
     if (ret == Z_OK)
         lm_init(strm->state);
     return ret;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateSetHeader(strm, head)
     z_streamp strm;
     gz_headerp head;
 {
     if (deflateStateCheck(strm) || strm->state->wrap != 2)
         return Z_STREAM_ERROR;
     strm->state->gzhead = head;
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflatePending(strm, pending, bits)
     unsigned *pending;
     int *bits;
     z_streamp strm;
 {
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     if (pending != Z_NULL)
         *pending = strm->state->pending;
     if (bits != Z_NULL)
         *bits = strm->state->bi_valid;
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflatePrime(strm, bits, value)
     z_streamp strm;
     int bits;
     int value;
 {
     deflate_state *s;
     int put;
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
     if (bits < 0 || bits > 16 ||
         s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
         return Z_BUF_ERROR;
     do {
         put = Buf_size - s->bi_valid;
         if (put > bits)
             put = bits;
         s->bi_buf |= (ush)((value & ((1 << put) - 1)) << s->bi_valid);
         s->bi_valid += put;
         _tr_flush_bits(s);
         value >>= put;
         bits -= put;
     } while (bits);
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateParams(strm, level, strategy)
     z_streamp strm;
     int level;
     int strategy;
 {
     deflate_state *s;
     compress_func func;
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
 
 #ifdef FASTEST
     if (level != 0) level = 1;
 #else
     if (level == Z_DEFAULT_COMPRESSION) level = 6;
 #endif
     if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
         return Z_STREAM_ERROR;
     }
     func = configuration_table[s->level].func;
 
     if ((strategy != s->strategy || func != configuration_table[level].func) &&
         s->last_flush != -2) {
         /* Flush the last buffer: */
         int err = deflate(strm, Z_BLOCK);
         if (err == Z_STREAM_ERROR)
             return err;
         if (strm->avail_in || (s->strstart - s->block_start) + s->lookahead)
             return Z_BUF_ERROR;
     }
     if (s->level != level) {
         if (s->level == 0 && s->matches != 0) {
             if (s->matches == 1)
                 slide_hash(s);
             else
                 CLEAR_HASH(s);
             s->matches = 0;
         }
         s->level = level;
         s->max_lazy_match   = configuration_table[level].max_lazy;
         s->good_match       = configuration_table[level].good_length;
         s->nice_match       = configuration_table[level].nice_length;
         s->max_chain_length = configuration_table[level].max_chain;
     }
     s->strategy = strategy;
     return Z_OK;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
     z_streamp strm;
     int good_length;
     int max_lazy;
     int nice_length;
     int max_chain;
 {
     deflate_state *s;
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
     s->good_match = (uInt)good_length;
     s->max_lazy_match = (uInt)max_lazy;
     s->nice_match = nice_length;
     s->max_chain_length = (uInt)max_chain;
     return Z_OK;
 }
 
 /* =========================================================================
  * For the default windowBits of 15 and memLevel of 8, this function returns a
  * close to exact, as well as small, upper bound on the compressed size. This
  * is an expansion of ~0.03%, plus a small constant.
  *
  * For any setting other than those defaults for windowBits and memLevel, one
  * of two worst case bounds is returned. This is at most an expansion of ~4% or
  * ~13%, plus a small constant.
  *
  * Both the 0.03% and 4% derive from the overhead of stored blocks. The first
  * one is for stored blocks of 16383 bytes (memLevel == 8), whereas the second
  * is for stored blocks of 127 bytes (the worst case memLevel == 1). The
  * expansion results from five bytes of header for each stored block.
  *
  * The larger expansion of 13% results from a window size less than or equal to
  * the symbols buffer size (windowBits <= memLevel + 7). In that case some of
  * the data being compressed may have slid out of the sliding window, impeding
  * a stored block from being emitted. Then the only choice is a fixed or
  * dynamic block, where a fixed block limits the maximum expansion to 9 bits
  * per 8-bit byte, plus 10 bits for every block. The smallest block size for
  * which this can occur is 255 (memLevel == 2).
  *
  * Shifts are used to approximate divisions, for speed.
  */
 uLong ZEXPORT deflateBound(strm, sourceLen)
     z_streamp strm;
     uLong sourceLen;
 {
     deflate_state *s;
     uLong fixedlen, storelen, wraplen;
 
     /* upper bound for fixed blocks with 9-bit literals and length 255
        (memLevel == 2, which is the lowest that may not use stored blocks) --
        ~13% overhead plus a small constant */
     fixedlen = sourceLen + (sourceLen >> 3) + (sourceLen >> 8) +
                (sourceLen >> 9) + 4;
 
     /* upper bound for stored blocks with length 127 (memLevel == 1) --
        ~4% overhead plus a small constant */
     storelen = sourceLen + (sourceLen >> 5) + (sourceLen >> 7) +
                (sourceLen >> 11) + 7;
 
     /* if can't get parameters, return larger bound plus a zlib wrapper */
     if (deflateStateCheck(strm))
         return (fixedlen > storelen ? fixedlen : storelen) + 6;
 
     /* compute wrapper length */
     s = strm->state;
     switch (s->wrap) {
     case 0:                                 /* raw deflate */
         wraplen = 0;
         break;
     case 1:                                 /* zlib wrapper */
         wraplen = 6 + (s->strstart ? 4 : 0);
         break;
 #ifdef GZIP
     case 2:                                 /* gzip wrapper */
         wraplen = 18;
         if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
             Bytef *str;
             if (s->gzhead->extra != Z_NULL)
                 wraplen += 2 + s->gzhead->extra_len;
             str = s->gzhead->name;
             if (str != Z_NULL)
                 do {
                     wraplen++;
                 } while (*str++);
             str = s->gzhead->comment;
             if (str != Z_NULL)
                 do {
                     wraplen++;
                 } while (*str++);
             if (s->gzhead->hcrc)
                 wraplen += 2;
         }
         break;
 #endif
     default:                                /* for compiler happiness */
         wraplen = 6;
     }
 
     /* if not default parameters, return one of the conservative bounds */
     if (s->w_bits != 15 || s->hash_bits != 8 + 7)
         return (s->w_bits <= s->hash_bits ? fixedlen : storelen) + wraplen;
 
     /* default settings: return tight bound for that case -- ~0.03% overhead
        plus a small constant */
     return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
            (sourceLen >> 25) + 13 - 6 + wraplen;
 }
 
 /* =========================================================================
  * Put a short in the pending buffer. The 16-bit value is put in MSB order.
  * IN assertion: the stream state is correct and there is enough room in
  * pending_buf.
  */
 local void putShortMSB(s, b)
     deflate_state *s;
     uInt b;
 {
     put_byte(s, (Byte)(b >> 8));
     put_byte(s, (Byte)(b & 0xff));
 }
 
 /* =========================================================================
  * Flush as much pending output as possible. All deflate() output, except for
  * some deflate_stored() output, goes through this function so some
  * applications may wish to modify it to avoid allocating a large
  * strm->next_out buffer and copying into it. (See also read_buf()).
  */
 local void flush_pending(strm)
     z_streamp strm;
 {
     unsigned len;
     deflate_state *s = strm->state;
 
     _tr_flush_bits(s);
     len = s->pending;
     if (len > strm->avail_out) len = strm->avail_out;
     if (len == 0) return;
 
     zmemcpy(strm->next_out, s->pending_out, len);
     strm->next_out  += len;
     s->pending_out  += len;
     strm->total_out += len;
     strm->avail_out -= len;
     s->pending      -= len;
     if (s->pending == 0) {
         s->pending_out = s->pending_buf;
     }
 }
 
 /* ===========================================================================
  * Update the header CRC with the bytes s->pending_buf[beg..s->pending - 1].
  */
 #define HCRC_UPDATE(beg) \
     do { \
         if (s->gzhead->hcrc && s->pending > (beg)) \
             strm->adler = crc32(strm->adler, s->pending_buf + (beg), \
                                 s->pending - (beg)); \
     } while (0)
 
 /* ========================================================================= */
 int ZEXPORT deflate(strm, flush)
     z_streamp strm;
     int flush;
 {
     int old_flush; /* value of flush param for previous deflate call */
     deflate_state *s;
 
     if (deflateStateCheck(strm) || flush > Z_BLOCK || flush < 0) {
         return Z_STREAM_ERROR;
     }
     s = strm->state;
 
     if (strm->next_out == Z_NULL ||
         (strm->avail_in != 0 && strm->next_in == Z_NULL) ||
         (s->status == FINISH_STATE && flush != Z_FINISH)) {
         ERR_RETURN(strm, Z_STREAM_ERROR);
     }
     if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
 
     old_flush = s->last_flush;
     s->last_flush = flush;
 
     /* Flush as much pending output as possible */
     if (s->pending != 0) {
         flush_pending(strm);
         if (strm->avail_out == 0) {
             /* Since avail_out is 0, deflate will be called again with
              * more output space, but possibly with both pending and
              * avail_in equal to zero. There won't be anything to do,
              * but this is not an error situation so make sure we
              * return OK instead of BUF_ERROR at next call of deflate:
              */
             s->last_flush = -1;
             return Z_OK;
         }
 
     /* Make sure there is something to do and avoid duplicate consecutive
      * flushes. For repeated and useless calls with Z_FINISH, we keep
      * returning Z_STREAM_END instead of Z_BUF_ERROR.
      */
     } else if (strm->avail_in == 0 && RANK(flush) <= RANK(old_flush) &&
                flush != Z_FINISH) {
         ERR_RETURN(strm, Z_BUF_ERROR);
     }
 
     /* User must not provide more input after the first FINISH: */
     if (s->status == FINISH_STATE && strm->avail_in != 0) {
         ERR_RETURN(strm, Z_BUF_ERROR);
     }
 
     /* Write the header */
     if (s->status == INIT_STATE && s->wrap == 0)
         s->status = BUSY_STATE;
     if (s->status == INIT_STATE) {
         /* zlib header */
         uInt header = (Z_DEFLATED + ((s->w_bits - 8) << 4)) << 8;
         uInt level_flags;
 
         if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
             level_flags = 0;
         else if (s->level < 6)
             level_flags = 1;
         else if (s->level == 6)
             level_flags = 2;
         else
             level_flags = 3;
         header |= (level_flags << 6);
         if (s->strstart != 0) header |= PRESET_DICT;
         header += 31 - (header % 31);
 
         putShortMSB(s, header);
 
         /* Save the adler32 of the preset dictionary: */
         if (s->strstart != 0) {
             putShortMSB(s, (uInt)(strm->adler >> 16));
             putShortMSB(s, (uInt)(strm->adler & 0xffff));
         }
         strm->adler = adler32(0L, Z_NULL, 0);
         s->status = BUSY_STATE;
 
         /* Compression must start with an empty pending buffer */
         flush_pending(strm);
         if (s->pending != 0) {
             s->last_flush = -1;
             return Z_OK;
         }
     }
 #ifdef GZIP
     if (s->status == GZIP_STATE) {
         /* gzip header */
         strm->adler = crc32(0L, Z_NULL, 0);
         put_byte(s, 31);
         put_byte(s, 139);
         put_byte(s, 8);
         if (s->gzhead == Z_NULL) {
             put_byte(s, 0);
             put_byte(s, 0);
             put_byte(s, 0);
             put_byte(s, 0);
             put_byte(s, 0);
             put_byte(s, s->level == 9 ? 2 :
                      (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                       4 : 0));
             put_byte(s, OS_CODE);
             s->status = BUSY_STATE;
 
             /* Compression must start with an empty pending buffer */
             flush_pending(strm);
             if (s->pending != 0) {
                 s->last_flush = -1;
                 return Z_OK;
             }
         }
         else {
             put_byte(s, (s->gzhead->text ? 1 : 0) +
                      (s->gzhead->hcrc ? 2 : 0) +
                      (s->gzhead->extra == Z_NULL ? 0 : 4) +
                      (s->gzhead->name == Z_NULL ? 0 : 8) +
                      (s->gzhead->comment == Z_NULL ? 0 : 16)
                      );
             put_byte(s, (Byte)(s->gzhead->time & 0xff));
             put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
             put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
             put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
             put_byte(s, s->level == 9 ? 2 :
                      (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                       4 : 0));
             put_byte(s, s->gzhead->os & 0xff);
             if (s->gzhead->extra != Z_NULL) {
                 put_byte(s, s->gzhead->extra_len & 0xff);
                 put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
             }
             if (s->gzhead->hcrc)
                 strm->adler = crc32(strm->adler, s->pending_buf,
                                     s->pending);
             s->gzindex = 0;
             s->status = EXTRA_STATE;
         }
     }
     if (s->status == EXTRA_STATE) {
         if (s->gzhead->extra != Z_NULL) {
             ulg beg = s->pending;   /* start of bytes to update crc */
             uInt left = (s->gzhead->extra_len & 0xffff) - s->gzindex;
             while (s->pending + left > s->pending_buf_size) {
                 uInt copy = s->pending_buf_size - s->pending;
                 zmemcpy(s->pending_buf + s->pending,
                         s->gzhead->extra + s->gzindex, copy);
                 s->pending = s->pending_buf_size;
                 HCRC_UPDATE(beg);
                 s->gzindex += copy;
                 flush_pending(strm);
                 if (s->pending != 0) {
                     s->last_flush = -1;
                     return Z_OK;
                 }
                 beg = 0;
                 left -= copy;
             }
             zmemcpy(s->pending_buf + s->pending,
                     s->gzhead->extra + s->gzindex, left);
             s->pending += left;
             HCRC_UPDATE(beg);
             s->gzindex = 0;
         }
         s->status = NAME_STATE;
     }
     if (s->status == NAME_STATE) {
         if (s->gzhead->name != Z_NULL) {
             ulg beg = s->pending;   /* start of bytes to update crc */
             int val;
             do {
                 if (s->pending == s->pending_buf_size) {
                     HCRC_UPDATE(beg);
                     flush_pending(strm);
                     if (s->pending != 0) {
                         s->last_flush = -1;
                         return Z_OK;
                     }
                     beg = 0;
                 }
                 val = s->gzhead->name[s->gzindex++];
                 put_byte(s, val);
             } while (val != 0);
             HCRC_UPDATE(beg);
             s->gzindex = 0;
         }
         s->status = COMMENT_STATE;
     }
     if (s->status == COMMENT_STATE) {
         if (s->gzhead->comment != Z_NULL) {
             ulg beg = s->pending;   /* start of bytes to update crc */
             int val;
             do {
                 if (s->pending == s->pending_buf_size) {
                     HCRC_UPDATE(beg);
                     flush_pending(strm);
                     if (s->pending != 0) {
                         s->last_flush = -1;
                         return Z_OK;
                     }
                     beg = 0;
                 }
                 val = s->gzhead->comment[s->gzindex++];
                 put_byte(s, val);
             } while (val != 0);
             HCRC_UPDATE(beg);
         }
         s->status = HCRC_STATE;
     }
     if (s->status == HCRC_STATE) {
         if (s->gzhead->hcrc) {
             if (s->pending + 2 > s->pending_buf_size) {
                 flush_pending(strm);
                 if (s->pending != 0) {
                     s->last_flush = -1;
                     return Z_OK;
                 }
             }
             put_byte(s, (Byte)(strm->adler & 0xff));
             put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
             strm->adler = crc32(0L, Z_NULL, 0);
         }
         s->status = BUSY_STATE;
 
         /* Compression must start with an empty pending buffer */
         flush_pending(strm);
         if (s->pending != 0) {
             s->last_flush = -1;
             return Z_OK;
         }
     }
 #endif
 
     /* Start a new block or continue the current one.
      */
     if (strm->avail_in != 0 || s->lookahead != 0 ||
         (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
         block_state bstate;
 
         bstate = s->level == 0 ? deflate_stored(s, flush) :
                  s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
                  s->strategy == Z_RLE ? deflate_rle(s, flush) :
                  (*(configuration_table[s->level].func))(s, flush);
 
         if (bstate == finish_started || bstate == finish_done) {
             s->status = FINISH_STATE;
         }
         if (bstate == need_more || bstate == finish_started) {
             if (strm->avail_out == 0) {
                 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
             }
             return Z_OK;
             /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
              * of deflate should use the same flush parameter to make sure
              * that the flush is complete. So we don't have to output an
              * empty block here, this will be done at next call. This also
              * ensures that for a very small output buffer, we emit at most
              * one empty block.
              */
         }
         if (bstate == block_done) {
             if (flush == Z_PARTIAL_FLUSH) {
                 _tr_align(s);
             } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
                 _tr_stored_block(s, (char*)0, 0L, 0);
                 /* For a full flush, this empty block will be recognized
                  * as a special marker by inflate_sync().
                  */
                 if (flush == Z_FULL_FLUSH) {
                     CLEAR_HASH(s);             /* forget history */
                     if (s->lookahead == 0) {
                         s->strstart = 0;
                         s->block_start = 0L;
                         s->insert = 0;
                     }
                 }
             }
             flush_pending(strm);
             if (strm->avail_out == 0) {
               s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
               return Z_OK;
             }
         }
     }
 
     if (flush != Z_FINISH) return Z_OK;
     if (s->wrap <= 0) return Z_STREAM_END;
 
     /* Write the trailer */
 #ifdef GZIP
     if (s->wrap == 2) {
         put_byte(s, (Byte)(strm->adler & 0xff));
         put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
         put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
         put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
         put_byte(s, (Byte)(strm->total_in & 0xff));
         put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
         put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
         put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
     }
     else
 #endif
     {
         putShortMSB(s, (uInt)(strm->adler >> 16));
         putShortMSB(s, (uInt)(strm->adler & 0xffff));
     }
     flush_pending(strm);
     /* If avail_out is zero, the application will call deflate again
      * to flush the rest.
      */
     if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
     return s->pending != 0 ? Z_OK : Z_STREAM_END;
 }
 
 /* ========================================================================= */
 int ZEXPORT deflateEnd(strm)
     z_streamp strm;
 {
     int status;
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
 
     status = strm->state->status;
 
     /* Deallocate in reverse order of allocations: */
     TRY_FREE(strm, strm->state->pending_buf);
     TRY_FREE(strm, strm->state->head);
     TRY_FREE(strm, strm->state->prev);
     TRY_FREE(strm, strm->state->window);
 
     ZFREE(strm, strm->state);
     strm->state = Z_NULL;
 
     return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
 }
 
 /* =========================================================================
  * Copy the source state to the destination state.
  * To simplify the source, this is not supported for 16-bit MSDOS (which
  * doesn't have enough memory anyway to duplicate compression states).
  */
 int ZEXPORT deflateCopy(dest, source)
     z_streamp dest;
     z_streamp source;
 {
 #ifdef MAXSEG_64K
     return Z_STREAM_ERROR;
 #else
     deflate_state *ds;
     deflate_state *ss;
 
 
     if (deflateStateCheck(source) || dest == Z_NULL) {
         return Z_STREAM_ERROR;
     }
 
     ss = source->state;
 
     zmemcpy((voidpf)dest, (voidpf)source, sizeof(z_stream));
 
     ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
     if (ds == Z_NULL) return Z_MEM_ERROR;
     dest->state = (struct internal_state FAR *) ds;
     zmemcpy((voidpf)ds, (voidpf)ss, sizeof(deflate_state));
     ds->strm = dest;
 
     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
     ds->pending_buf = (uchf *) ZALLOC(dest, ds->lit_bufsize, 4);
 
     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
         ds->pending_buf == Z_NULL) {
         deflateEnd (dest);
         return Z_MEM_ERROR;
     }
     /* following zmemcpy do not work for 16-bit MSDOS */
     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
     zmemcpy((voidpf)ds->prev, (voidpf)ss->prev, ds->w_size * sizeof(Pos));
     zmemcpy((voidpf)ds->head, (voidpf)ss->head, ds->hash_size * sizeof(Pos));
     zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
 
     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
     ds->sym_buf = ds->pending_buf + ds->lit_bufsize;
 
     ds->l_desc.dyn_tree = ds->dyn_ltree;
     ds->d_desc.dyn_tree = ds->dyn_dtree;
     ds->bl_desc.dyn_tree = ds->bl_tree;
 
     return Z_OK;
 #endif /* MAXSEG_64K */
 }
 
 /* ===========================================================================
  * Read a new buffer from the current input stream, update the adler32
  * and total number of bytes read.  All deflate() input goes through
  * this function so some applications may wish to modify it to avoid
  * allocating a large strm->next_in buffer and copying from it.
  * (See also flush_pending()).
  */
 local unsigned read_buf(strm, buf, size)
     z_streamp strm;
     Bytef *buf;
     unsigned size;
 {
     unsigned len = strm->avail_in;
 
     if (len > size) len = size;
     if (len == 0) return 0;
 
     strm->avail_in  -= len;
 
     zmemcpy(buf, strm->next_in, len);
     if (strm->state->wrap == 1) {
         strm->adler = adler32(strm->adler, buf, len);
     }
 #ifdef GZIP
     else if (strm->state->wrap == 2) {
         strm->adler = crc32(strm->adler, buf, len);
     }
 #endif
     strm->next_in  += len;
     strm->total_in += len;
 
     return len;
 }
 
 /* ===========================================================================
  * Initialize the "longest match" routines for a new zlib stream
  */
 local void lm_init(s)
     deflate_state *s;
 {
     s->window_size = (ulg)2L*s->w_size;
 
     CLEAR_HASH(s);
 
     /* Set the default configuration parameters:
      */
     s->max_lazy_match   = configuration_table[s->level].max_lazy;
     s->good_match       = configuration_table[s->level].good_length;
     s->nice_match       = configuration_table[s->level].nice_length;
     s->max_chain_length = configuration_table[s->level].max_chain;
 
     s->strstart = 0;
     s->block_start = 0L;
     s->lookahead = 0;
     s->insert = 0;
     s->match_length = s->prev_length = MIN_MATCH-1;
     s->match_available = 0;
     s->ins_h = 0;
 }
 
 #ifndef FASTEST
 /* ===========================================================================
  * Set match_start to the longest match starting at the given string and
  * return its length. Matches shorter or equal to prev_length are discarded,
  * in which case the result is equal to prev_length and match_start is
  * garbage.
  * IN assertions: cur_match is the head of the hash chain for the current
  *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
  * OUT assertion: the match length is not greater than s->lookahead.
  */
 local uInt longest_match(s, cur_match)
     deflate_state *s;
     IPos cur_match;                             /* current match */
 {
     unsigned chain_length = s->max_chain_length;/* max hash chain length */
     register Bytef *scan = s->window + s->strstart; /* current string */
     register Bytef *match;                      /* matched string */
     register int len;                           /* length of current match */
     int best_len = (int)s->prev_length;         /* best match length so far */
     int nice_match = s->nice_match;             /* stop if match long enough */
     IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
         s->strstart - (IPos)MAX_DIST(s) : NIL;
     /* Stop when cur_match becomes <= limit. To simplify the code,
      * we prevent matches with the string of window index 0.
      */
     Posf *prev = s->prev;
     uInt wmask = s->w_mask;
 
 #ifdef UNALIGNED_OK
     /* Compare two bytes at a time. Note: this is not always beneficial.
      * Try with and without -DUNALIGNED_OK to check.
      */
     register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
     register ush scan_start = *(ushf*)scan;
     register ush scan_end   = *(ushf*)(scan + best_len - 1);
 #else
     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
     register Byte scan_end1  = scan[best_len - 1];
     register Byte scan_end   = scan[best_len];
 #endif
 
     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
      * It is easy to get rid of this optimization if necessary.
      */
     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
 
     /* Do not waste too much time if we already have a good match: */
     if (s->prev_length >= s->good_match) {
         chain_length >>= 2;
     }
     /* Do not look for matches beyond the end of the input. This is necessary
      * to make deflate deterministic.
      */
     if ((uInt)nice_match > s->lookahead) nice_match = (int)s->lookahead;
 
     Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
            "need lookahead");
 
     do {
         Assert(cur_match < s->strstart, "no future");
         match = s->window + cur_match;
 
         /* Skip to next match if the match length cannot increase
          * or if the match length is less than 2.  Note that the checks below
          * for insufficient lookahead only occur occasionally for performance
          * reasons.  Therefore uninitialized memory will be accessed, and
          * conditional jumps will be made that depend on those values.
          * However the length of the match is limited to the lookahead, so
          * the output of deflate is not affected by the uninitialized values.
          */
 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
         /* This code assumes sizeof(unsigned short) == 2. Do not use
          * UNALIGNED_OK if your compiler uses a different size.
          */
         if (*(ushf*)(match + best_len - 1) != scan_end ||
             *(ushf*)match != scan_start) continue;
 
         /* It is not necessary to compare scan[2] and match[2] since they are
          * always equal when the other bytes match, given that the hash keys
          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
          * strstart + 3, + 5, up to strstart + 257. We check for insufficient
          * lookahead only every 4th comparison; the 128th check will be made
          * at strstart + 257. If MAX_MATCH-2 is not a multiple of 8, it is
          * necessary to put more guard bytes at the end of the window, or
          * to check more often for insufficient lookahead.
          */
         Assert(scan[2] == match[2], "scan[2]?");
         scan++, match++;
         do {
         } while (*(ushf*)(scan += 2) == *(ushf*)(match += 2) &&
                  *(ushf*)(scan += 2) == *(ushf*)(match += 2) &&
                  *(ushf*)(scan += 2) == *(ushf*)(match += 2) &&
                  *(ushf*)(scan += 2) == *(ushf*)(match += 2) &&
                  scan < strend);
         /* The funny "do {}" generates better code on most compilers */
 
         /* Here, scan <= window + strstart + 257 */
         Assert(scan <= s->window + (unsigned)(s->window_size - 1),
                "wild scan");
         if (*scan == *match) scan++;
 
         len = (MAX_MATCH - 1) - (int)(strend - scan);
         scan = strend - (MAX_MATCH-1);
 
 #else /* UNALIGNED_OK */
 
         if (match[best_len]     != scan_end  ||
             match[best_len - 1] != scan_end1 ||
             *match              != *scan     ||
             *++match            != scan[1])      continue;
 
         /* The check at best_len - 1 can be removed because it will be made
          * again later. (This heuristic is not always a win.)
          * It is not necessary to compare scan[2] and match[2] since they
          * are always equal when the other bytes match, given that
          * the hash keys are equal and that HASH_BITS >= 8.
          */
         scan += 2, match++;
         Assert(*scan == *match, "match[2]?");
 
         /* We check for insufficient lookahead only every 8th comparison;
          * the 256th check will be made at strstart + 258.
          */
         do {
         } while (*++scan == *++match && *++scan == *++match &&
                  *++scan == *++match && *++scan == *++match &&
                  *++scan == *++match && *++scan == *++match &&
                  *++scan == *++match && *++scan == *++match &&
                  scan < strend);
 
         Assert(scan <= s->window + (unsigned)(s->window_size - 1),
                "wild scan");
 
         len = MAX_MATCH - (int)(strend - scan);
         scan = strend - MAX_MATCH;
 
 #endif /* UNALIGNED_OK */
 
         if (len > best_len) {
             s->match_start = cur_match;
             best_len = len;
             if (len >= nice_match) break;
 #ifdef UNALIGNED_OK
             scan_end = *(ushf*)(scan + best_len - 1);
 #else
             scan_end1  = scan[best_len - 1];
             scan_end   = scan[best_len];
 #endif
         }
     } while ((cur_match = prev[cur_match & wmask]) > limit
              && --chain_length != 0);
 
     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
     return s->lookahead;
 }
 
 #else /* FASTEST */
 
 /* ---------------------------------------------------------------------------
  * Optimized version for FASTEST only
  */
 local uInt longest_match(s, cur_match)
     deflate_state *s;
     IPos cur_match;                             /* current match */
 {
     register Bytef *scan = s->window + s->strstart; /* current string */
     register Bytef *match;                       /* matched string */
     register int len;                           /* length of current match */
     register Bytef *strend = s->window + s->strstart + MAX_MATCH;
 
     /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
      * It is easy to get rid of this optimization if necessary.
      */
     Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
 
     Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
            "need lookahead");
 
     Assert(cur_match < s->strstart, "no future");
 
     match = s->window + cur_match;
 
     /* Return failure if the match length is less than 2:
      */
     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
 
     /* The check at best_len - 1 can be removed because it will be made
      * again later. (This heuristic is not always a win.)
      * It is not necessary to compare scan[2] and match[2] since they
      * are always equal when the other bytes match, given that
      * the hash keys are equal and that HASH_BITS >= 8.
      */
     scan += 2, match += 2;
     Assert(*scan == *match, "match[2]?");
 
     /* We check for insufficient lookahead only every 8th comparison;
      * the 256th check will be made at strstart + 258.
      */
     do {
     } while (*++scan == *++match && *++scan == *++match &&
              *++scan == *++match && *++scan == *++match &&
              *++scan == *++match && *++scan == *++match &&
              *++scan == *++match && *++scan == *++match &&
              scan < strend);
 
     Assert(scan <= s->window + (unsigned)(s->window_size - 1), "wild scan");
 
     len = MAX_MATCH - (int)(strend - scan);
 
     if (len < MIN_MATCH) return MIN_MATCH - 1;
 
     s->match_start = cur_match;
     return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
 }
 
 #endif /* FASTEST */
 
 #ifdef ZLIB_DEBUG
 
 #define EQUAL 0
 /* result of memcmp for equal strings */
 
 /* ===========================================================================
  * Check that the match at match_start is indeed a match.
  */
 local void check_match(s, start, match, length)
     deflate_state *s;
     IPos start, match;
     int length;
 {
     /* check that the match is indeed a match */
     if (zmemcmp(s->window + match,
                 s->window + start, length) != EQUAL) {
         fprintf(stderr, " start %u, match %u, length %d\n",
                 start, match, length);
         do {
             fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
         } while (--length != 0);
         z_error("invalid match");
     }
     if (z_verbose > 1) {
         fprintf(stderr,"\\[%d,%d]", start - match, length);
         do { putc(s->window[start++], stderr); } while (--length != 0);
     }
 }
 #else
 #  define check_match(s, start, match, length)
 #endif /* ZLIB_DEBUG */
 
 /* ===========================================================================
  * Fill the window when the lookahead becomes insufficient.
  * Updates strstart and lookahead.
  *
  * IN assertion: lookahead < MIN_LOOKAHEAD
  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
  *    At least one byte has been read, or avail_in == 0; reads are
  *    performed for at least two bytes (required for the zip translate_eol
  *    option -- not supported here).
  */
 local void fill_window(s)
     deflate_state *s;
 {
     unsigned n;
     unsigned more;    /* Amount of free space at the end of the window. */
     uInt wsize = s->w_size;
 
     Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");
 
     do {
         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
 
         /* Deal with !@#$% 64K limit: */
         if (sizeof(int) <= 2) {
             if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
                 more = wsize;
 
             } else if (more == (unsigned)(-1)) {
                 /* Very unlikely, but possible on 16 bit machine if
                  * strstart == 0 && lookahead == 1 (input done a byte at time)
                  */
                 more--;
             }
         }
 
         /* If the window is almost full and there is insufficient lookahead,
          * move the upper half to the lower one to make room in the upper half.
          */
         if (s->strstart >= wsize + MAX_DIST(s)) {
 
             zmemcpy(s->window, s->window + wsize, (unsigned)wsize - more);
             s->match_start -= wsize;
             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
             s->block_start -= (long) wsize;
             if (s->insert > s->strstart)
                 s->insert = s->strstart;
             slide_hash(s);
             more += wsize;
         }
         if (s->strm->avail_in == 0) break;
 
         /* If there was no sliding:
          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
          *    more == window_size - lookahead - strstart
          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
          * => more >= window_size - 2*WSIZE + 2
          * In the BIG_MEM or MMAP case (not yet supported),
          *   window_size == input_size + MIN_LOOKAHEAD  &&
          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
          * Otherwise, window_size == 2*WSIZE so more >= 2.
          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
          */
         Assert(more >= 2, "more < 2");
 
         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
         s->lookahead += n;
 
         /* Initialize the hash value now that we have some input: */
         if (s->lookahead + s->insert >= MIN_MATCH) {
             uInt str = s->strstart - s->insert;
             s->ins_h = s->window[str];
             UPDATE_HASH(s, s->ins_h, s->window[str + 1]);
 #if MIN_MATCH != 3
             Call UPDATE_HASH() MIN_MATCH-3 more times
 #endif
             while (s->insert) {
                 UPDATE_HASH(s, s->ins_h, s->window[str + MIN_MATCH-1]);
 #ifndef FASTEST
                 s->prev[str & s->w_mask] = s->head[s->ins_h];
 #endif
                 s->head[s->ins_h] = (Pos)str;
                 str++;
                 s->insert--;
                 if (s->lookahead + s->insert < MIN_MATCH)
                     break;
             }
         }
         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
          * but this is not important since only literal bytes will be emitted.
          */
 
     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
 
     /* If the WIN_INIT bytes after the end of the current data have never been
      * written, then zero those bytes in order to avoid memory check reports of
      * the use of uninitialized (or uninitialised as Julian writes) bytes by
      * the longest match routines.  Update the high water mark for the next
      * time through here.  WIN_INIT is set to MAX_MATCH since the longest match
      * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
      */
     if (s->high_water < s->window_size) {
         ulg curr = s->strstart + (ulg)(s->lookahead);
         ulg init;
 
         if (s->high_water < curr) {
             /* Previous high water mark below current data -- zero WIN_INIT
              * bytes or up to end of window, whichever is less.
              */
             init = s->window_size - curr;
             if (init > WIN_INIT)
                 init = WIN_INIT;
             zmemzero(s->window + curr, (unsigned)init);
             s->high_water = curr + init;
         }
         else if (s->high_water < (ulg)curr + WIN_INIT) {
             /* High water mark at or above current data, but below current data
              * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
              * to end of window, whichever is less.
              */
             init = (ulg)curr + WIN_INIT - s->high_water;
             if (init > s->window_size - s->high_water)
                 init = s->window_size - s->high_water;
             zmemzero(s->window + s->high_water, (unsigned)init);
             s->high_water += init;
         }
     }
 
     Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
            "not enough room for search");
 }
 
 /* ===========================================================================
  * Flush the current block, with given end-of-file flag.
  * IN assertion: strstart is set to the end of the current match.
  */
 #define FLUSH_BLOCK_ONLY(s, last) { \
    _tr_flush_block(s, (s->block_start >= 0L ? \
                    (charf *)&s->window[(unsigned)s->block_start] : \
                    (charf *)Z_NULL), \
                 (ulg)((long)s->strstart - s->block_start), \
                 (last)); \
    s->block_start = s->strstart; \
    flush_pending(s->strm); \
    Tracev((stderr,"[FLUSH]")); \
 }
 
 /* Same but force premature exit if necessary. */
 #define FLUSH_BLOCK(s, last) { \
    FLUSH_BLOCK_ONLY(s, last); \
    if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
 }
 
 /* Maximum stored block length in deflate format (not including header). */
 #define MAX_STORED 65535
 
 /* Minimum of a and b. */
 #define MIN(a, b) ((a) > (b) ? (b) : (a))
 
 /* ===========================================================================
  * Copy without compression as much as possible from the input stream, return
  * the current block state.
  *
  * In case deflateParams() is used to later switch to a non-zero compression
  * level, s->matches (otherwise unused when storing) keeps track of the number
  * of hash table slides to perform. If s->matches is 1, then one hash table
  * slide will be done when switching. If s->matches is 2, the maximum value
  * allowed here, then the hash table will be cleared, since two or more slides
  * is the same as a clear.
  *
  * deflate_stored() is written to minimize the number of times an input byte is
  * copied. It is most efficient with large input and output buffers, which
  * maximizes the opportunities to have a single copy from next_in to next_out.
  */
 local block_state deflate_stored(s, flush)
     deflate_state *s;
     int flush;
 {
     /* Smallest worthy block size when not flushing or finishing. By default
      * this is 32K. This can be as small as 507 bytes for memLevel == 1. For
      * large input and output buffers, the stored block size will be larger.
      */
     unsigned min_block = MIN(s->pending_buf_size - 5, s->w_size);
 
     /* Copy as many min_block or larger stored blocks directly to next_out as
      * possible. If flushing, copy the remaining available input to next_out as
      * stored blocks, if there is enough space.
      */
     unsigned len, left, have, last = 0;
     unsigned used = s->strm->avail_in;
     do {
         /* Set len to the maximum size block that we can copy directly with the
          * available input data and output space. Set left to how much of that
          * would be copied from what's left in the window.
          */
         len = MAX_STORED;       /* maximum deflate stored block length */
         have = (s->bi_valid + 42) >> 3;         /* number of header bytes */
         if (s->strm->avail_out < have)          /* need room for header */
             break;
             /* maximum stored block length that will fit in avail_out: */
         have = s->strm->avail_out - have;
         left = s->strstart - s->block_start;    /* bytes left in window */
         if (len > (ulg)left + s->strm->avail_in)
             len = left + s->strm->avail_in;     /* limit len to the input */
         if (len > have)
             len = have;                         /* limit len to the output */
 
         /* If the stored block would be less than min_block in length, or if
          * unable to copy all of the available input when flushing, then try
          * copying to the window and the pending buffer instead. Also don't
          * write an empty block when flushing -- deflate() does that.
          */
         if (len < min_block && ((len == 0 && flush != Z_FINISH) ||
                                 flush == Z_NO_FLUSH ||
                                 len != left + s->strm->avail_in))
             break;
 
         /* Make a dummy stored block in pending to get the header bytes,
          * including any pending bits. This also updates the debugging counts.
          */
         last = flush == Z_FINISH && len == left + s->strm->avail_in ? 1 : 0;
         _tr_stored_block(s, (char *)0, 0L, last);
 
         /* Replace the lengths in the dummy stored block with len. */
         s->pending_buf[s->pending - 4] = len;
         s->pending_buf[s->pending - 3] = len >> 8;
         s->pending_buf[s->pending - 2] = ~len;
         s->pending_buf[s->pending - 1] = ~len >> 8;
 
         /* Write the stored block header bytes. */
         flush_pending(s->strm);
 
 #ifdef ZLIB_DEBUG
         /* Update debugging counts for the data about to be copied. */
         s->compressed_len += len << 3;
         s->bits_sent += len << 3;
 #endif
 
         /* Copy uncompressed bytes from the window to next_out. */
         if (left) {
             if (left > len)
                 left = len;
             zmemcpy(s->strm->next_out, s->window + s->block_start, left);
             s->strm->next_out += left;
             s->strm->avail_out -= left;
             s->strm->total_out += left;
             s->block_start += left;
             len -= left;
         }
 
         /* Copy uncompressed bytes directly from next_in to next_out, updating
          * the check value.
          */
         if (len) {
             read_buf(s->strm, s->strm->next_out, len);
             s->strm->next_out += len;
             s->strm->avail_out -= len;
             s->strm->total_out += len;
         }
     } while (last == 0);
 
     /* Update the sliding window with the last s->w_size bytes of the copied
      * data, or append all of the copied data to the existing window if less
      * than s->w_size bytes were copied. Also update the number of bytes to
      * insert in the hash tables, in the event that deflateParams() switches to
      * a non-zero compression level.
      */
     used -= s->strm->avail_in;      /* number of input bytes directly copied */
     if (used) {
         /* If any input was used, then no unused input remains in the window,
          * therefore s->block_start == s->strstart.
          */
         if (used >= s->w_size) {    /* supplant the previous history */
             s->matches = 2;         /* clear hash */
             zmemcpy(s->window, s->strm->next_in - s->w_size, s->w_size);
             s->strstart = s->w_size;
             s->insert = s->strstart;
         }
         else {
             if (s->window_size - s->strstart <= used) {
                 /* Slide the window down. */
                 s->strstart -= s->w_size;
                 zmemcpy(s->window, s->window + s->w_size, s->strstart);
                 if (s->matches < 2)
                     s->matches++;   /* add a pending slide_hash() */
                 if (s->insert > s->strstart)
                     s->insert = s->strstart;
             }
             zmemcpy(s->window + s->strstart, s->strm->next_in - used, used);
             s->strstart += used;
             s->insert += MIN(used, s->w_size - s->insert);
         }
         s->block_start = s->strstart;
     }
     if (s->high_water < s->strstart)
         s->high_water = s->strstart;
 
     /* If the last block was written to next_out, then done. */
     if (last)
         return finish_done;
 
     /* If flushing and all input has been consumed, then done. */
     if (flush != Z_NO_FLUSH && flush != Z_FINISH &&
         s->strm->avail_in == 0 && (long)s->strstart == s->block_start)
         return block_done;
 
     /* Fill the window with any remaining input. */
     have = s->window_size - s->strstart;
     if (s->strm->avail_in > have && s->block_start >= (long)s->w_size) {
         /* Slide the window down. */
         s->block_start -= s->w_size;
         s->strstart -= s->w_size;
         zmemcpy(s->window, s->window + s->w_size, s->strstart);
         if (s->matches < 2)
             s->matches++;           /* add a pending slide_hash() */
         have += s->w_size;          /* more space now */
         if (s->insert > s->strstart)
             s->insert = s->strstart;
     }
     if (have > s->strm->avail_in)
         have = s->strm->avail_in;
     if (have) {
         read_buf(s->strm, s->window + s->strstart, have);
         s->strstart += have;
         s->insert += MIN(have, s->w_size - s->insert);
     }
     if (s->high_water < s->strstart)
         s->high_water = s->strstart;
 
     /* There was not enough avail_out to write a complete worthy or flushed
      * stored block to next_out. Write a stored block to pending instead, if we
      * have enough input for a worthy block, or if flushing and there is enough
      * room for the remaining input as a stored block in the pending buffer.
      */
     have = (s->bi_valid + 42) >> 3;         /* number of header bytes */
         /* maximum stored block length that will fit in pending: */
     have = MIN(s->pending_buf_size - have, MAX_STORED);
     min_block = MIN(have, s->w_size);
     left = s->strstart - s->block_start;
     if (left >= min_block ||
         ((left || flush == Z_FINISH) && flush != Z_NO_FLUSH &&
          s->strm->avail_in == 0 && left <= have)) {
         len = MIN(left, have);
         last = flush == Z_FINISH && s->strm->avail_in == 0 &&
                len == left ? 1 : 0;
         _tr_stored_block(s, (charf *)s->window + s->block_start, len, last);
         s->block_start += len;
         flush_pending(s->strm);
     }
 
     /* We've done all we can with the available input and output. */
     return last ? finish_started : need_more;
 }
 
 /* ===========================================================================
  * Compress as much as possible from the input stream, return the current
  * block state.
  * This function does not perform lazy evaluation of matches and inserts
  * new strings in the dictionary only for unmatched strings or for short
  * matches. It is used only for the fast compression options.
  */
 local block_state deflate_fast(s, flush)
     deflate_state *s;
     int flush;
 {
     IPos hash_head;       /* head of the hash chain */
     int bflush;           /* set if current block must be flushed */
 
     for (;;) {
         /* Make sure that we always have enough lookahead, except
          * at the end of the input file. We need MAX_MATCH bytes
          * for the next match, plus MIN_MATCH bytes to insert the
          * string following the next match.
          */
         if (s->lookahead < MIN_LOOKAHEAD) {
             fill_window(s);
             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                 return need_more;
             }
             if (s->lookahead == 0) break; /* flush the current block */
         }
 
         /* Insert the string window[strstart .. strstart + 2] in the
          * dictionary, and set hash_head to the head of the hash chain:
          */
         hash_head = NIL;
         if (s->lookahead >= MIN_MATCH) {
             INSERT_STRING(s, s->strstart, hash_head);
         }
 
         /* Find the longest match, discarding those <= prev_length.
          * At this point we have always match_length < MIN_MATCH
          */
         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
             /* To simplify the code, we prevent matches with the string
              * of window index 0 (in particular we have to avoid a match
              * of the string with itself at the start of the input file).
              */
             s->match_length = longest_match (s, hash_head);
             /* longest_match() sets match_start */
         }
         if (s->match_length >= MIN_MATCH) {
             check_match(s, s->strstart, s->match_start, s->match_length);
 
             _tr_tally_dist(s, s->strstart - s->match_start,
                            s->match_length - MIN_MATCH, bflush);
 
             s->lookahead -= s->match_length;
 
             /* Insert new strings in the hash table only if the match length
              * is not too large. This saves time but degrades compression.
              */
 #ifndef FASTEST
             if (s->match_length <= s->max_insert_length &&
                 s->lookahead >= MIN_MATCH) {
                 s->match_length--; /* string at strstart already in table */
                 do {
                     s->strstart++;
                     INSERT_STRING(s, s->strstart, hash_head);
                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are
                      * always MIN_MATCH bytes ahead.
                      */
                 } while (--s->match_length != 0);
                 s->strstart++;
             } else
 #endif
             {
                 s->strstart += s->match_length;
                 s->match_length = 0;
                 s->ins_h = s->window[s->strstart];
                 UPDATE_HASH(s, s->ins_h, s->window[s->strstart + 1]);
 #if MIN_MATCH != 3
                 Call UPDATE_HASH() MIN_MATCH-3 more times
 #endif
                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
                  * matter since it will be recomputed at next deflate call.
                  */
             }
         } else {
             /* No match, output a literal byte */
             Tracevv((stderr,"%c", s->window[s->strstart]));
             _tr_tally_lit(s, s->window[s->strstart], bflush);
             s->lookahead--;
             s->strstart++;
         }
         if (bflush) FLUSH_BLOCK(s, 0);
     }
     s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
     if (flush == Z_FINISH) {
         FLUSH_BLOCK(s, 1);
         return finish_done;
     }
     if (s->sym_next)
         FLUSH_BLOCK(s, 0);
     return block_done;
 }
 
 #ifndef FASTEST
 /* ===========================================================================
  * Same as above, but achieves better compression. We use a lazy
  * evaluation for matches: a match is finally adopted only if there is
  * no better match at the next window position.
  */
 local block_state deflate_slow(s, flush)
     deflate_state *s;
     int flush;
 {
     IPos hash_head;          /* head of hash chain */
     int bflush;              /* set if current block must be flushed */
 
     /* Process the input block. */
     for (;;) {
         /* Make sure that we always have enough lookahead, except
          * at the end of the input file. We need MAX_MATCH bytes
          * for the next match, plus MIN_MATCH bytes to insert the
          * string following the next match.
          */
         if (s->lookahead < MIN_LOOKAHEAD) {
             fill_window(s);
             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                 return need_more;
             }
             if (s->lookahead == 0) break; /* flush the current block */
         }
 
         /* Insert the string window[strstart .. strstart + 2] in the
          * dictionary, and set hash_head to the head of the hash chain:
          */
         hash_head = NIL;
         if (s->lookahead >= MIN_MATCH) {
             INSERT_STRING(s, s->strstart, hash_head);
         }
 
         /* Find the longest match, discarding those <= prev_length.
          */
         s->prev_length = s->match_length, s->prev_match = s->match_start;
         s->match_length = MIN_MATCH-1;
 
         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
             s->strstart - hash_head <= MAX_DIST(s)) {
             /* To simplify the code, we prevent matches with the string
              * of window index 0 (in particular we have to avoid a match
              * of the string with itself at the start of the input file).
              */
             s->match_length = longest_match (s, hash_head);
             /* longest_match() sets match_start */
 
             if (s->match_length <= 5 && (s->strategy == Z_FILTERED
 #if TOO_FAR <= 32767
                 || (s->match_length == MIN_MATCH &&
                     s->strstart - s->match_start > TOO_FAR)
 #endif
                 )) {
 
                 /* If prev_match is also MIN_MATCH, match_start is garbage
                  * but we will ignore the current match anyway.
                  */
                 s->match_length = MIN_MATCH-1;
             }
         }
         /* If there was a match at the previous step and the current
          * match is not better, output the previous match:
          */
         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
             /* Do not insert strings in hash table beyond this. */
 
             check_match(s, s->strstart - 1, s->prev_match, s->prev_length);
 
             _tr_tally_dist(s, s->strstart - 1 - s->prev_match,
                            s->prev_length - MIN_MATCH, bflush);
 
             /* Insert in hash table all strings up to the end of the match.
              * strstart - 1 and strstart are already inserted. If there is not
              * enough lookahead, the last two strings are not inserted in
              * the hash table.
              */
             s->lookahead -= s->prev_length - 1;
             s->prev_length -= 2;
             do {
                 if (++s->strstart <= max_insert) {
                     INSERT_STRING(s, s->strstart, hash_head);
                 }
             } while (--s->prev_length != 0);
             s->match_available = 0;
             s->match_length = MIN_MATCH-1;
             s->strstart++;
 
             if (bflush) FLUSH_BLOCK(s, 0);
 
         } else if (s->match_available) {
             /* If there was no match at the previous position, output a
              * single literal. If there was a match but the current match
              * is longer, truncate the previous match to a single literal.
              */
             Tracevv((stderr,"%c", s->window[s->strstart - 1]));
             _tr_tally_lit(s, s->window[s->strstart - 1], bflush);
             if (bflush) {
                 FLUSH_BLOCK_ONLY(s, 0);
             }
             s->strstart++;
             s->lookahead--;
             if (s->strm->avail_out == 0) return need_more;
         } else {
             /* There is no previous match to compare with, wait for
              * the next step to decide.
              */
             s->match_available = 1;
             s->strstart++;
             s->lookahead--;
         }
     }
     Assert (flush != Z_NO_FLUSH, "no flush?");
     if (s->match_available) {
         Tracevv((stderr,"%c", s->window[s->strstart - 1]));
         _tr_tally_lit(s, s->window[s->strstart - 1], bflush);
         s->match_available = 0;
     }
     s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
     if (flush == Z_FINISH) {
         FLUSH_BLOCK(s, 1);
         return finish_done;
     }
     if (s->sym_next)
         FLUSH_BLOCK(s, 0);
     return block_done;
 }
 #endif /* FASTEST */
 
 /* ===========================================================================
  * For Z_RLE, simply look for runs of bytes, generate matches only of distance
  * one.  Do not maintain a hash table.  (It will be regenerated if this run of
  * deflate switches away from Z_RLE.)
  */
 local block_state deflate_rle(s, flush)
     deflate_state *s;
     int flush;
 {
     int bflush;             /* set if current block must be flushed */
     uInt prev;              /* byte at distance one to match */
     Bytef *scan, *strend;   /* scan goes up to strend for length of run */
 
     for (;;) {
         /* Make sure that we always have enough lookahead, except
          * at the end of the input file. We need MAX_MATCH bytes
          * for the longest run, plus one for the unrolled loop.
          */
         if (s->lookahead <= MAX_MATCH) {
             fill_window(s);
             if (s->lookahead <= MAX_MATCH && flush == Z_NO_FLUSH) {
                 return need_more;
             }
             if (s->lookahead == 0) break; /* flush the current block */
         }
 
         /* See how many times the previous byte repeats */
         s->match_length = 0;
         if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
             scan = s->window + s->strstart - 1;
             prev = *scan;
             if (prev == *++scan && prev == *++scan && prev == *++scan) {
                 strend = s->window + s->strstart + MAX_MATCH;
                 do {
                 } while (prev == *++scan && prev == *++scan &&
                          prev == *++scan && prev == *++scan &&
                          prev == *++scan && prev == *++scan &&
                          prev == *++scan && prev == *++scan &&
                          scan < strend);
                 s->match_length = MAX_MATCH - (uInt)(strend - scan);
                 if (s->match_length > s->lookahead)
                     s->match_length = s->lookahead;
             }
             Assert(scan <= s->window + (uInt)(s->window_size - 1),
                    "wild scan");
         }
 
         /* Emit match if have run of MIN_MATCH or longer, else emit literal */
         if (s->match_length >= MIN_MATCH) {
             check_match(s, s->strstart, s->strstart - 1, s->match_length);
 
             _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
 
             s->lookahead -= s->match_length;
             s->strstart += s->match_length;
             s->match_length = 0;
         } else {
             /* No match, output a literal byte */
             Tracevv((stderr,"%c", s->window[s->strstart]));
             _tr_tally_lit(s, s->window[s->strstart], bflush);
             s->lookahead--;
             s->strstart++;
         }
         if (bflush) FLUSH_BLOCK(s, 0);
     }
     s->insert = 0;
     if (flush == Z_FINISH) {
         FLUSH_BLOCK(s, 1);
         return finish_done;
     }
     if (s->sym_next)
         FLUSH_BLOCK(s, 0);
     return block_done;
 }
 
 /* ===========================================================================
  * For Z_HUFFMAN_ONLY, do not look for matches.  Do not maintain a hash table.
  * (It will be regenerated if this run of deflate switches away from Huffman.)
  */
 local block_state deflate_huff(s, flush)
     deflate_state *s;
     int flush;
 {
     int bflush;             /* set if current block must be flushed */
 
     for (;;) {
         /* Make sure that we have a literal to write. */
         if (s->lookahead == 0) {
             fill_window(s);
             if (s->lookahead == 0) {
                 if (flush == Z_NO_FLUSH)
                     return need_more;
                 break;      /* flush the current block */
             }
         }
 
         /* Output a literal byte */
         s->match_length = 0;
         Tracevv((stderr,"%c", s->window[s->strstart]));
         _tr_tally_lit(s, s->window[s->strstart], bflush);
         s->lookahead--;
         s->strstart++;
         if (bflush) FLUSH_BLOCK(s, 0);
     }
     s->insert = 0;
     if (flush == Z_FINISH) {
         FLUSH_BLOCK(s, 1);
         return finish_done;
     }
     if (s->sym_next)
         FLUSH_BLOCK(s, 0);
     return block_done;
 }

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