Tribblix: manual page: xdr

XDR_COMPLEX(3NSL) Networking Services Library Functions XDR_COMPLEX(3NSL)

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 streams. See
xdr_create(3NSL).

Routines

See rpc(3NSL) for the definition of the XDR data structure. Note that
any buffers passed to the XDR routines must be properly aligned. It
is suggested either that malloc() be used to allocate these buffers,
or that the programmer insure that the buffer address is divisible
evenly by four.

#include <rpc/xdr.h>

bool_t xdr_array(XDR *xdrs, caddr_t *arrp, uint_t *sizep, const
uint_t maxsize, const uint_t 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 size of each of the
array's elements, and elproc is an XDR routine that translates
between the array elements' C form and their external
representation. If *aarp is NULL when decoding, xdr_array()
allocates memory and *aarp points to it. This routine returns
TRUE if it succeeds, FALSE otherwise.

bool_t xdr_bytes(XDR *xdrs, char **sp, uint_t *sizep, const uint_t
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. If *sp is NULL
when decoding, xdr_bytes() allocates memory and *sp points to it.
This routine returns TRUE if it succeeds, FALSE otherwise.

bool_t xdr_opaque(XDR *xdrs, caddr_t cp, const uint_t 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
TRUE if it succeeds, FALSE otherwise.

bool_t xdr_pointer(XDR *xdrs, char **objpp, uint_t 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. If *objpp is NULL when decoding, xdr_pointer()
allocates memory and *objpp points to it.

bool_t xdr_reference(XDR *xdrs, caddr_t *pp, uint_t 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. If *pp is NULL when decoding, xdr_reference()
allocates memory and *pp points to it. 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 uint_t 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. If *sp is NULL
when decoding, xdr_string() allocates memory and *sp points to
it. This routine returns TRUE if it succeeds, FALSE otherwise.
Note: xdr_string() can be used to send an empty string (""), but
not a null string.

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

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). It
returns TRUE if it succeeds, FALSE otherwise.

bool_t xdr_vector(XDR *xdrs, char *arrp, const uint_t size, const
uint_t 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 TRUE if it succeeds, FALSE
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 TRUE if it succeeds, FALSE
otherwise.

ATTRIBUTES

NAME

DESCRIPTION

Routines

ATTRIBUTES

SEE ALSO