code: function f1(d, m, r) {
      const t = m + d;
      const I = (t << r) | (t >>> (32 - r));
      return ((sBox[0][I >>> 24] ^ sBox[1][(I >>> 16) & 255]) - sBox[2][(I >>> 8) & 255]) + sBox[3][I & 255];
    }
docs: These are the three 'f' functions. See RFC 2144, section 2.2.