docs: private static void cdiv(double xr, double xi, double yr, double yi, double[] buf, int off) {
      if(abs(yr) > abs(yi)) {
        final double r = yi / yr, d = yr + r * yi;
        buf[off] = (xr + r * xi) / d;
        buf[off + 1] = (xi - r * xr) / d;
      }
      else {
        final double r = yr / yi, d = yi + r * yr;
        buf[off] = (r * xr + xi) / d;
        buf[off + 1] = (r * xi - xr) / d;
      }
    }