VMS Help TCPIP Services, Programming Interfaces, RPC XDR Routines, xdr_reference, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 xdrs
    A pointer to an XDR stream handle created by one of the XDR
    stream handle creation routines.
 objpp
    A pointer to a pointer to the structure containing the data being
    converted. If objpp is zero, the xdr_reference routine allocates
    the necessary storage when decoding. This argument must be non-
    zero during encoding.
 objsize
    The size of the structure in bytes.
 objproc
    The XDR procedure that filters the structure between its local
    form and its external representation.