code: function() {
      var b = this.buffer, o = this.offset, carry = 1;
      for (var i = o + 7; i >= o; i--) {
        var v = (b[i] ^ 0xff) + carry;
        b[i] = v & 0xff;
        carry = v >> 8;
      }
    }
docs: Do in-place 2's compliment.  See
  http://en.wikipedia.org/wiki/Two's_complement