Function fill_window

Picviewer CE+/dist.user.js:6477–6622

(s)

 *    option -- not supported here).
 */
function fill_window(s) {
  var _w_size = s.w_size;
  var p, n, m, more, str;

  //Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");

  do {
    more = s.window_size - s.lookahead - s.strstart;

    // JS ints have 32 bit, block below not needed
    /* 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 >= _w_size + (_w_size - MIN_LOOKAHEAD)) {

      utils.arraySet(s.window, s.window, _w_size, _w_size, 0);
      s.match_start -= _w_size;
      s.strstart -= _w_size;
      /* we now have strstart >= MAX_DIST */
      s.block_start -= _w_size;

      /* 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 = n;
      do {
        m = s.head[--p];
        s.head[p] = (m >= _w_size ? m - _w_size : 0);
      } while (--n);

      n = _w_size;
      p = n;
      do {
        m = s.prev[--p];
        s.prev[p] = (m >= _w_size ? m - _w_size : 0);
        /* If n is not on any hash chain, prev[n] is garbage but
         * its value will never be used.
         */
      } while (--n);