xdr_init_encode — Initialize a struct xdr_stream for sending data.
pointer to xdr_stream struct
pointer to XDR buffer in which to encode data
current pointer inside XDR buffer
at the moment the RPC client only passes the length of our scratch buffer in the xdr_buf's header kvec. Previously this meant we needed to call xdr_adjust_iovec after encoding the data. With the new scheme, the xdr_stream manages the details of the buffer length, and takes care of adjusting the kvec length for us.