Function deflate_slow

Picviewer CE+/dist.user.js:6859–7013

(s, flush)

 * no better match at the next window position.
 */
function deflate_slow(s, flush) {
  var hash_head;          /* head of hash chain */
  var bflush;              /* set if current block must be flushed */

  var max_insert;

  /* 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 BS_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 = 0/*NIL*/;
    if (s.lookahead >= MIN_MATCH) {
      /*** INSERT_STRING(s, s.strstart, hash_head); ***/
      s.ins_h = ((s.ins_h << s.hash_shift) ^ s.window[s.strstart + MIN_MATCH - 1]) & s.hash_mask;
      hash_head = s.prev[s.strstart & s.w_mask] = s.head[s.ins_h];
      s.head[s.ins_h] = s.strstart;
      /***/
    }

    /* 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 !== 0/*NIL*/ && s.prev_length < s.max_lazy_match &&
        s.strstart - hash_head <= (s.w_size - MIN_LOOKAHEAD)/*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 || (s.match_length === MIN_MATCH && s.strstart - s.match_start > 4096/*TOO_FAR*/))) {

        /* 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