xdr_complex(3rpc)

xdr_complex: xdr_array, xdr_bytes, xdr_opaque, xdr_pointer, xdr_reference, xdr_string, xdr_union, xdr_vector, xdr_wrapstring -- library routines for external data representation

Synopsis

cc [options] file -lnsl

#include <rpc/xdr.h>

bool_t xdr_array(XDR *xdrs, caddr_t *arrp, u_int *sizep,
	const u_int maxsize, const u_int elsize,
	const xdrproc_t elproc);

bool_t xdr_bytes(XDR *xdrs, char **sp, u_int *sizep,
	const u_int maxsize);

bool_t xdr_opaque(XDR *xdrs, caddr_t cp, const u_int cnt);

bool_t xdr_pointer(XDR *xdrs, char **objpp, u_int objsize,
	const xdrproc_t xdrobj);

bool_t xdr_reference(XDR *xdrs, caddr_t *pp, u_int size,
	const xdrproc_t proc);

bool_t xdr_string(XDR *xdrs, char **sp, const u_int maxsize);

bool_t xdr_union(XDR *xdrs, enum_t *dscmp, char *unp,
	const struct xdr_discrim *choices,
	const bool_t (*defaultarm)(const XDR *, const char *,
		const int));

bool_t xdr_vector(XDR *xdrs, char *arrp, const u_int size,
	const u_int elsize, const xdrproc_t elproc);

bool_t xdr_wrapstring(XDR *xdrs, char **sp);

Description

XDR library routines allow C programmers to describe complex data structures in a machine-independent fashion. Protocols such as remote procedure calls (RPC) use these routines to describe the format of the data. These routines are the XDR library routines for complex data structures. They require the creation of XDR stream (see xdr_create(3rpc)).

Routines

See rpc(3rpc) for the definition of the XDR data structure.

bool_t
xdr_array(XDR *xdrs, caddr_t *arrp, u_int *sizep, const u_int maxsize,
	const u_int elsize, const xdrproc_t elproc);

xdr_array translates between variable-length arrays and their corresponding external representations. The parameter arrp is the address of the pointer to the array, while sizep is the address of the element count of the array; this element count cannot exceed maxsize. The parameter elsize is the sizeof each of the array's elements, and elproc is an XDR routine that translates between the array elements' C form and their external representation. This routine returns 1 if it succeeds, 0 otherwise.

bool_t
xdr_bytes(XDR *xdrs, char **sp, u_int *sizep, const u_int maxsize);

xdr_bytes translates between counted byte strings and their external representations. The parameter sp is the address of the string pointer. The length of the string is located at address sizep; strings cannot be longer than maxsize. This routine returns 1 if it succeeds, 0 otherwise.

bool_t
xdr_opaque(XDR *xdrs, caddr_t cp, const u_int cnt);

xdr_opaque translates between fixed size opaque data and its external representation. The parameter cp is the address of the opaque object, and cnt is its size in bytes. This routine returns 1 if it succeeds, 0 otherwise.

bool_t
xdr_pointer(XDR *xdrs, char **objpp, u_int objsize,
	const xdrproc_t xdrobj);

Like xdr_reference except that it serializes NULL pointers, whereas xdr_reference does not. Thus, xdr_pointer can represent recursive data structures, such as binary trees or linked lists.

bool_t
xdr_reference(XDR *xdrs, caddr_t *pp, u_int size, const xdrproc_t proc);

xdr_reference provides pointer chasing within structures. The parameter pp is the address of the pointer; size is the sizeof the structure that *pp points to; and proc is an XDR procedure that translates the structure between its C form and its external representation. This routine returns 1 if it succeeds, 0 otherwise.

Note: this routine does not understand NULL pointers. Use xdr_pointer instead.

bool_t
xdr_string(XDR *xdrs, char **sp, const u_int maxsize);

xdr_string translates between C strings and their corresponding external representations. Strings cannot be longer than maxsize. Note: sp is the address of the string's pointer. This routine returns 1 if it succeeds, 0 otherwise.

bool_t
xdr_union(XDR *xdrs, enum_t *dscmp, char *unp,
	const struct xdr_discrim *choices,
	const bool_t (*defaultarm)(const XDR *, const char *, const int));

xdr_union translates between a discriminated C union and its corresponding external representation. It first translates the discriminant of the union located at dscmp. This discriminant is always an enum_t. Next the union located at unp is translated. The parameter choices is a pointer to an array of xdr_discrim structures. Each structure contains an ordered pair of [value, proc]. If the union's discriminant is equal to the associated value, then the proc is called to translate the union. The end of the xdr_discrim structure array is denoted by a routine of value NULL. If the discriminant is not found in the choices array, then the defaultarm procedure is called (if it is not NULL). Returns 1 if it succeeds, 0 otherwise.

bool_t
xdr_vector(XDR *xdrs, char *arrp, const u_int size,
	const u_int elsize, const xdrproc_t elproc);

xdr_vector translates between fixed-length arrays and their corresponding external representations. The parameter arrp is the address of the pointer to the array, while size is the element count of the array. The parameter elsize is the sizeof each of the array's elements, and elproc is an XDR routine that translates between the array elements' C form and their external representation. This routine returns 1 if it succeeds, 0 otherwise.

   bool_t
   xdr_wrapstring(XDR *xdrs, char **sp);

A routine that calls xdr_string with arguments xdrs, sp, maxuint, where maxuint is the maximum value of an unsigned integer.

Many routines, such as xdr_array, xdr_pointer and xdr_vector take a function pointer of type xdrproc_t, which takes two arguments. xdr_string, one of the most frequently used routines, requires three arguments, while xdr_wrapstring only requires two. For these routines, xdr_wrapstring is desirable. This routine returns 1 if it succeeds, 0 otherwise.

References

rpc(3rpc), xdr_admin(3rpc), xdr_create(3rpc), xdr_simple(3rpc)