Class EtherCatType12DLPDU

scapy/contrib/ethercat.py:281–355

Type12 message base class

class EtherCatType12DLPDU(Packet):
    """
    Type12 message base class
    """
    def post_build(self, pkt, pay):
        """

        set next attr automatically if not set explicitly by user

        :param pkt: raw string containing the current layer
        :param pay: raw string containing the payload
        :return: <new current layer> + payload
        """

        data_len = len(self.data)
        if data_len > 2047:
            raise ValueError('payload size {} exceeds maximum length {} '
                             'of data size.'.format(data_len, 2047))

        if self.next is not None:
            has_next = True if self.next else False
        else:
            if pay:
                has_next = True
            else:
                has_next = False

        if has_next:
            next_flag = bytearray([pkt[7] | 0b10000000])
        else:
            next_flag = bytearray([pkt[7] & 0b01111111])

        return pkt[:7] + next_flag + pkt[8:] + pay

    def guess_payload_class(self, payload):

        try:
            dlpdu_type = payload[0]
            return EtherCat.ETHERCAT_TYPE12_DLPDU_TYPES[dlpdu_type]

        except KeyError:
            log_runtime.error(
                '{}.guess_payload_class() - unknown or invalid '
                'DLPDU type'.format(self.__class__.__name__))
            return Packet.guess_payload_class(self, payload)

    # structure templates lacking leading cmd-attribute
    PHYSICAL_ADDRESSING_DESC = [
        ByteField('idx', 0),
        LEShortField('adp', 0),
        LEShortField('ado', 0),
        LEBitFieldLenField('len', None, 11, count_of='data'),
        LEBitField('_reserved', 0, 3),
        LEBitEnumField('c', 0, 1, ETHERCAT_TYPE_12_CIRCULATING_FRAME),
        LEBitEnumField('next', None, 1, ETHERCAT_TYPE_12_NEXT_FRAME),
        LEShortField('irq', 0),
        FieldListField('data', [], ByteField('', 0x00),
                       count_from=lambda pkt: pkt.len),