} else if (u8a[i] === 0xF0) /* F0 90..BF 80..BF 80..BF */ {
      if (i + 3 < len) /* Expect a 2nd, 3rd 3th byte */ {
        if (u8a[i + 1] < 0x90 || u8a[i + 1] > 0xBF) {
          // *message = "After a first byte of F0, expecting 2nd byte between 90 and BF.";
          // *faulty_bytes = 2;