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

    A filter primitive that translates between a variable-length byte
    array and its external representation. The length of the array
    is located at sizep; the array cannot be longer than maxsize. If
    *bpp is NULL, xdr_bytes allocates maxsize bytes.