XDR uses to keep track of where it is in the message being processed; it
includes a flag that indicates whether this routine is being used to encode
or decode the message. In other words, routines like xdr item are used on
both the client and the server. Note that the application programmer can
either write the routine xdr item by hand or use a stub compiler called rpcgen
(not shown) to generate this encoding/decoding routine. In the latter
case, rpcgen takes the remote procedure that defines the data structure
item as input and outputs the corresponding stub.