NAME

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

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(3N)].

Routines

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

     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.

Warning:   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 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(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.

SEE ALSO

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