code: function _makeBitReversal() {
      var i = 0,
          j = 0,
          k = 0;
      _bitrev[0] = 0;
      while(++i < _n) {
        k = _n >> 1;
        while(k <= j) {
          j -= k;
          k >>= 1;
        }
        j += k;
        _bitrev[i] = j;
      }
    }
docs: make bit reversal table