Method addfield

scapy/layers/can.py:296–329

(self, pkt, s, val)

        return self.fmt[-1] == "f"

    def addfield(self, pkt, s, val):
        # type: (Packet, bytes, Optional[Union[int, float]]) -> bytes
        if not isinstance(pkt, SignalPacket):
            raise Scapy_Exception("Only use SignalFields in a SignalPacket")

        val = self.i2m(pkt, val)

        if self._is_little_endian():
            msb_pos = self.start + self.size - 1
            lsb_pos = self.start
            shift = lsb_pos
            fmt = "<Q"
        else:
            msb_pos = self.start
            lsb_pos = self._lsb_lookup(self.start, self.size)
            shift = (64 - self._msb_lookup(msb_pos) - self.size)
            fmt = ">Q"

        field_len = max(msb_pos, lsb_pos) // 8 + 1
        if len(s) < field_len:
            s += b"\x00" * (field_len - len(s))

        if self._is_float_number():
            int_val = struct.unpack(self.fmt[0] + "I",
                                    struct.pack(self.fmt, val))[0]  # type: int
        elif self._is_signed_number():
            int_val = self._convert_to_unsigned(int(val), self.size)
        else:
            int_val = cast(int, val)

        pkt_val = struct.unpack(fmt, (s + b"\x00" * 8)[:8])[0]
        pkt_val |= int_val << shift
        tmp_s = struct.pack(fmt, pkt_val)
        return tmp_s[:len(s)]

    def getfield(self, pkt, s):
        # type: (Packet, bytes) -> Tuple[bytes, Union[int, float]]