Converting complex data structures, continued

Example:

If we wished to XDR encode a pointer to the person structure declared as

  struct person   *pp;

we would convert it using

  xdr_reference(xdrs, &pp, sizeof(struct person), xdr_person);

If the XDR stream indicates an encode operation the function follows the pointer and encodes the data it points to by calling xdr_person().

If the XDR stream indicates a decode operation and *pp is NULL the routine allocates memory to hold the structure and makes pp point to that area.

The routine then decodes the data by calling xdr_person() and places the decoded structure into the memory pointed to by pp.

A related routine called xdr_pointer() exists which more correctly understands NULL pointers.

This facility can be used to create functions which encode/decode linked lists and other arbitrarily complex data structures.