/* deflate.c -- compress data using the deflation algorithm
   * Copyright (C) 1995-2010 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://www.ietf.org/rfc/rfc1951.txt
   *
   *      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 1.2.5 Copyright 1995-2010 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 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 int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));
  #ifdef ASMV
        void match_init OF((void)); /* asm code initialization */
        uInt longest_match  OF((deflate_state *s, IPos cur_match));
  #else
  local uInt longest_match  OF((deflate_state *s, IPos cur_match));
  #endif
  
  #ifdef 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.
   */
  
  #define EQUAL 0
  /* result of memcmp for equal strings */
  
  #ifndef NO_DUMMY_DECL
  struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
  #endif
  
  /* ===========================================================================
   * Update a hash value with the given input byte
   * IN  assertion: all calls to 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 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) \
      s->head[s->hash_size-1] = NIL; \
      zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
  
  /* ========================================================================= */
  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;
  
      ushf *overlay;
      /* We overlay pending_buf and d_buf+l_buf. This works since the average
       * output size for (length,distance) codes is <= 24 bits.
       */
  
      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) {
          strm->zalloc = zcalloc;
          strm->opaque = (voidpf)0;
      }
      if (strm->zfree == (free_func)0) strm->zfree = zcfree;
  
  #ifdef FASTEST
      if (level != 0) level = 1;
  #else
      if (level == Z_DEFAULT_COMPRESSION) level = 6;
  #endif
  
      if (windowBits < 0) { /* suppress zlib wrapper */
          wrap = 0;
          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) {
          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->wrap = wrap;
      s->gzhead = Z_NULL;
      s->w_bits = windowBits;
      s->w_size = 1 << s->w_bits;
      s->w_mask = s->w_size - 1;
  
      s->hash_bits = 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 */
  
      overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
      s->pending_buf = (uchf *) overlay;
      s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
  
      if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
          s->pending_buf == Z_NULL) {
          s->status = FINISH_STATE;
          strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
          deflateEnd (strm);
          return Z_MEM_ERROR;
      }
      s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
      s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
  
      s->level = level;
      s->strategy = strategy;
      s->method = (Byte)method;
  
      return deflateReset(strm);
  }
  
  /* ========================================================================= */
  int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
      z_streamp strm;
      const Bytef *dictionary;
      uInt  dictLength;
  {
      deflate_state *s;
      uInt length = dictLength;
      uInt n;
      IPos hash_head = 0;
  
      if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
          strm->state->wrap == 2 ||
          (strm->state->wrap == 1 && strm->state->status != INIT_STATE))
          return Z_STREAM_ERROR;
  
      s = strm->state;
      if (s->wrap)
          strm->adler = adler32(strm->adler, dictionary, dictLength);
  
      if (length < MIN_MATCH) return Z_OK;
      if (length > s->w_size) {
          length = s->w_size;
          dictionary += dictLength - length; /* use the tail of the dictionary */
      }
      zmemcpy(s->window, dictionary, length);
      s->strstart = length;
      s->block_start = (long)length;
  
      /* Insert all strings in the hash table (except for the last two bytes).
       * s->lookahead stays null, so s->ins_h will be recomputed at the next
       * call of fill_window.
       */
      s->ins_h = s->window[0];
      UPDATE_HASH(s, s->ins_h, s->window[1]);
      for (n = 0; n <= length - MIN_MATCH; n++) {
          INSERT_STRING(s, n, hash_head);
      }
      if (hash_head) hash_head = 0;  /* to make compiler happy */
      return Z_OK;
  }
  
  /* ========================================================================= */
  int ZEXPORT deflateReset (strm)
      z_streamp strm;
  {
      deflate_state *s;
  
      if (strm == Z_NULL || strm->state == Z_NULL ||
          strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
          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 = s->wrap ? INIT_STATE : BUSY_STATE;
      strm->adler =
  #ifdef GZIP
          s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
  #endif
          adler32(0L, Z_NULL, 0);
      s->last_flush = Z_NO_FLUSH;
  
      _tr_init(s);
      lm_init(s);
  
      return Z_OK;
  }
  
  /* ========================================================================= */
  int ZEXPORT deflateSetHeader (strm, head)
      z_streamp strm;
      gz_headerp head;
  {
      if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
      if (strm->state->wrap != 2) return Z_STREAM_ERROR;
      strm->state->gzhead = head;
      return Z_OK;
  }
  
  /* ========================================================================= */
  int ZEXPORT deflatePrime (strm, bits, value)
      z_streamp strm;
      int bits;
      int value;
  {
      if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
      strm->state->bi_valid = bits;
      strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
      return Z_OK;
  }
  
  /* ========================================================================= */
  int ZEXPORT deflateParams(strm, level, strategy)
      z_streamp strm;
      int level;
      int strategy;
  {
      deflate_state *s;
      compress_func func;
      int err = Z_OK;
  
      if (strm == Z_NULL || strm->state == Z_NULL) 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) &&
          strm->total_in != 0) {
          /* Flush the last buffer: */
          err = deflate(strm, Z_BLOCK);
      }
      if (s->level != level) {
          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 err;
  }
  
  /* ========================================================================= */
  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 (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
      s = strm->state;
      s->good_match = good_length;
      s->max_lazy_match = max_lazy;
      s->nice_match = nice_length;
      s->max_chain_length = 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.
   * They are coded as constants here for a reason--if the #define's are
   * changed, then this function needs to be changed as well.  The return
   * value for 15 and 8 only works for those exact settings.
   *
   * For any setting other than those defaults for windowBits and memLevel,
   * the value returned is a conservative worst case for the maximum expansion
   * resulting from using fixed blocks instead of stored blocks, which deflate
   * can emit on compressed data for some combinations of the parameters.
   *
   * This function could be more sophisticated to provide closer upper bounds for
   * every combination of windowBits and memLevel.  But even the conservative
   * upper bound of about 14% expansion does not seem onerous for output buffer
   * allocation.
   */
  uLong ZEXPORT deflateBound(strm, sourceLen)
      z_streamp strm;
      uLong sourceLen;
  {
      deflate_state *s;
      uLong complen, wraplen;
      Bytef *str;
  
      /* conservative upper bound for compressed data */
      complen = sourceLen +
                ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
  
      /* if can't get parameters, return conservative bound plus zlib wrapper */
      if (strm == Z_NULL || strm->state == Z_NULL)
          return complen + 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;
      case 2:                                 /* gzip wrapper */
          wraplen = 18;
          if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
              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;
      default:                                /* for compiler happiness */
          wraplen = 6;
      }
  
      /* if not default parameters, return conservative bound */
      if (s->w_bits != 15 || s->hash_bits != 8 + 7)
          return complen + wraplen;
  
      /* default settings: return tight bound for that case */
      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 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 = strm->state->pending;
  
      if (len > strm->avail_out) len = strm->avail_out;
      if (len == 0) return;
  
      zmemcpy(strm->next_out, strm->state->pending_out, len);
      strm->next_out  += len;
      strm->state->pending_out  += len;
      strm->total_out += len;
      strm->avail_out  -= len;
      strm->state->pending -= len;
      if (strm->state->pending == 0) {
          strm->state->pending_out = strm->state->pending_buf;
      }
  }
  
  /* ========================================================================= */
  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 (strm == Z_NULL || strm->state == Z_NULL ||
          flush > Z_BLOCK || flush < 0) {
          return Z_STREAM_ERROR;
      }
      s = strm->state;
  
      if (s->status == FINISH_STATE && flush != Z_FINISH) {
          ERR_RETURN(strm, Z_STREAM_ERROR);
      }
      if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
  
      s->strm = strm; /* just in case */
      old_flush = s->last_flush;
      s->last_flush = flush;
  
      /* Write the header */
      if (s->status == INIT_STATE) {
  #ifdef GZIP
          if (s->wrap == 2) {
              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;
              }
              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;
              }
          }
          else
  #endif
          {
              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);
  
              s->status = BUSY_STATE;
              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);
          }
      }
  #ifdef GZIP
      if (s->status == EXTRA_STATE) {
          if (s->gzhead->extra != Z_NULL) {
              uInt beg = s->pending;  /* start of bytes to update crc */
  
              while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
                  if (s->pending == s->pending_buf_size) {
                      if (s->gzhead->hcrc && s->pending > beg)
                          strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                              s->pending - beg);
                      flush_pending(strm);
                      beg = s->pending;
                      if (s->pending == s->pending_buf_size)
                          break;
                  }
                  put_byte(s, s->gzhead->extra[s->gzindex]);
                  s->gzindex++;
              }
              if (s->gzhead->hcrc && s->pending > beg)
                  strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                      s->pending - beg);
              if (s->gzindex == s->gzhead->extra_len) {
                  s->gzindex = 0;
                  s->status = NAME_STATE;
              }
          }
          else
              s->status = NAME_STATE;
      }
      if (s->status == NAME_STATE) {
          if (s->gzhead->name != Z_NULL) {
              uInt beg = s->pending;  /* start of bytes to update crc */
              int val;
  
              do {
                  if (s->pending == s->pending_buf_size) {
                      if (s->gzhead->hcrc && s->pending > beg)
                          strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                              s->pending - beg);
                      flush_pending(strm);
                      beg = s->pending;
                      if (s->pending == s->pending_buf_size) {
                          val = 1;
                          break;
                      }
                  }
                  val = s->gzhead->name[s->gzindex++];
                  put_byte(s, val);
              } while (val != 0);
              if (s->gzhead->hcrc && s->pending > beg)
                  strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                      s->pending - beg);
              if (val == 0) {
                  s->gzindex = 0;
                  s->status = COMMENT_STATE;
              }
          }
          else
              s->status = COMMENT_STATE;
      }
      if (s->status == COMMENT_STATE) {
          if (s->gzhead->comment != Z_NULL) {
              uInt beg = s->pending;  /* start of bytes to update crc */
              int val;
  
              do {
                  if (s->pending == s->pending_buf_size) {
                      if (s->gzhead->hcrc && s->pending > beg)
                          strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                              s->pending - beg);
                      flush_pending(strm);
                      beg = s->pending;
                      if (s->pending == s->pending_buf_size) {
                          val = 1;
                          break;
                      }
                  }
                  val = s->gzhead->comment[s->gzindex++];
                  put_byte(s, val);
              } while (val != 0);
              if (s->gzhead->hcrc && s->pending > beg)
                  strm->adler = crc32(strm->adler, s->pending_buf + beg,
                                      s->pending - beg);
              if (val == 0)
                  s->status = HCRC_STATE;
          }
          else
              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 + 2 <= s->pending_buf_size) {
                  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;
              }
          }
          else
              s->status = BUSY_STATE;
      }
  #endif
  
      /* 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 && flush <= 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);
      }
  
      /* 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->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;
                      }
                  }
              }
              flush_pending(strm);
              if (strm->avail_out == 0) {
                s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
                return Z_OK;
              }
          }
      }
      Assert(strm->avail_out > 0, "bug2");
  
      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 (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
  
      status = strm->state->status;
      if (status != INIT_STATE &&
          status != EXTRA_STATE &&
          status != NAME_STATE &&
          status != COMMENT_STATE &&
          status != HCRC_STATE &&
          status != BUSY_STATE &&
          status != FINISH_STATE) {
        return Z_STREAM_ERROR;
      }
  
      /* 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;
      ushf *overlay;
  
  
      if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
          return Z_STREAM_ERROR;
      }
  
      ss = source->state;
  
      zmemcpy(dest, 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(ds, 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));
      overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
      ds->pending_buf = (uchf *) overlay;
  
      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(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
      zmemcpy(ds->head, 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->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
      ds->l_buf = ds->pending_buf + (1+sizeof(ush))*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 int 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;
  
      if (strm->state->wrap == 1) {
          strm->adler = adler32(strm->adler, strm->next_in, len);
      }
  #ifdef GZIP
      else if (strm->state->wrap == 2) {
          strm->adler = crc32(strm->adler, strm->next_in, len);
      }
  #endif
      zmemcpy(buf, strm->next_in, len);
      strm->next_in  += len;
      strm->total_in += len;
  
      return (int)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->match_length = s->prev_length = MIN_MATCH-1;
      s->match_available = 0;
      s->ins_h = 0;
  #ifndef FASTEST
  #ifdef ASMV
      match_init(); /* initialize the asm code */
  #endif
  #endif
  }
  
  #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.
   */
  #ifndef ASMV
  /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
   * match.S. The code will be functionally equivalent.
   */
  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 = 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 = 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;
  }
  #endif /* ASMV */
  
  #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 DEBUG
  /* ===========================================================================
   * 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
  ",
                  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 /* 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;
  {
      register unsigned n, m;
      register Posf *p;
      unsigned more;    /* Amount of free space at the end of the window. */
      uInt wsize = s->w_size;
  
      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);
              s->match_start -= wsize;
              s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
              s->block_start -= (long) wsize;
  
              /* Slide the hash table (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. (Using level 0 permanently is not an optimal usage of
                 zlib, so we don't care about this pathological case.)
               */
              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
              more += wsize;
          }
          if (s->strm->avail_in == 0) return;
  
          /* 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 >= MIN_MATCH) {
              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 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;
          }
      }
  }
  
  /* ===========================================================================
   * 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; \
  }
  
  /* ===========================================================================
   * Copy without compression as much as possible from the input stream, return
   * the current block state.
   * This function does not insert new strings in the dictionary since
   * uncompressible data is probably not useful. This function is used
   * only for the level=0 compression option.
   * NOTE: this function should be optimized to avoid extra copying from
   * window to pending_buf.
   */
  local block_state deflate_stored(s, flush)
      deflate_state *s;
      int flush;
  {
      /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
       * to pending_buf_size, and each stored block has a 5 byte header:
       */
      ulg max_block_size = 0xffff;
      ulg max_start;
  
      if (max_block_size > s->pending_buf_size - 5) {
          max_block_size = s->pending_buf_size - 5;
      }
  
      /* Copy as much as possible from input to output: */
      for (;;) {
          /* Fill the window as much as possible: */
          if (s->lookahead <= 1) {
  
              Assert(s->strstart < s->w_size+MAX_DIST(s) ||
                     s->block_start >= (long)s->w_size, "slide too late");
  
              fill_window(s);
              if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
  
              if (s->lookahead == 0) break; /* flush the current block */
          }
          Assert(s->block_start >= 0L, "block gone");
  
          s->strstart += s->lookahead;
          s->lookahead = 0;
  
          /* Emit a stored block if pending_buf will be full: */
          max_start = s->block_start + max_block_size;
          if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
              /* strstart == 0 is possible when wraparound on 16-bit machine */
              s->lookahead = (uInt)(s->strstart - max_start);
              s->strstart = (uInt)max_start;
              FLUSH_BLOCK(s, 0);
          }
          /* Flush if we may have to slide, otherwise block_start may become
           * negative and the data will be gone:
           */
          if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
              FLUSH_BLOCK(s, 0);
          }
      }
      FLUSH_BLOCK(s, flush == Z_FINISH);
      return flush == Z_FINISH ? finish_done : block_done;
  }
  
  /* ===========================================================================
   * 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);
      }
      FLUSH_BLOCK(s, flush == Z_FINISH);
      return flush == Z_FINISH ? finish_done : 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;
      }
      FLUSH_BLOCK(s, flush == Z_FINISH);
      return flush == Z_FINISH ? finish_done : 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 encodable run.
           */
          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 - (int)(strend - scan);
                  if (s->match_length > s->lookahead)
                      s->match_length = s->lookahead;
              }
          }
  
          /* 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);
      }
      FLUSH_BLOCK(s, flush == Z_FINISH);
      return flush == Z_FINISH ? finish_done : 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);
      }
      FLUSH_BLOCK(s, flush == Z_FINISH);
      return flush == Z_FINISH ? finish_done : block_done;
  }