Change inheritance to:

eis_object
    ^
    |
eis_ccsds_packet

eis_object
    ^
    |
eis_ccsds_interface
^                 ^
|                 |
eis_ccsds_reader  eis_ccsds_writer


eis_ccsds_packet
      *
      | has-a
      |
eis_ccsds_interface
