XDR(3) BSD Library Functions Manual XDR(3)NAME
xdr, xdr_array, xdr_bool, xdr_bytes, xdr_char, xdr_destroy, xdr_double,
xdr_enum, xdr_float, xdr_free, xdr_getpos, xdr_hyper, xdr_inline,
xdr_int, xdr_long, xdr_longlong_t, xdrmem_create, xdr_opaque,
xdr_pointer, xdrrec_create, xdrrec_endofrecord, xdrrec_eof,
xdrrec_skiprecord, xdr_reference, xdr_setpos, xdr_short, xdrstdio_create,
xdr_string, xdr_u_char, xdr_u_hyper, xdr_u_int, xdr_u_long,
xdr_u_longlong_t, xdr_u_short, xdr_union, xdr_vector, xdr_void,
xdr_wrapstring — library routines for external data representation
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <rpc/types.h>
#include <rpc/xdr.h>
See DESCRIPTION for function declarations.
DESCRIPTION
These routines allow C programmers to describe arbitrary data structures
in a machine-independent fashion. Data for remote procedure calls are
transmitted using these routines.
int
xdr_array(XDR *xdrs, char **arrp, u_int *sizep, u_int maxsize,
u_int elsize, xdrproc_t elproc)
A filter primitive that translates between variable-length arrays
and their corresponding external representations. The arrp argu‐
ment 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 elsize argument is the sizeof each of
the array's elements, and elproc is an XDR filter that translates
between the array elements' C form, and their external represen‐
tation. This routine returns one if it succeeds, zero otherwise.
int
xdr_bool(XDR *xdrs, bool_t *bp)
A filter primitive that translates between booleans (C integers)
and their external representations. When encoding data, this
filter produces values of either one or zero. This routine
returns one if it succeeds, zero otherwise.
int
xdr_bytes(XDR *xdrs, char **sp, u_int *sizep, u_int maxsize)
A filter primitive that translates between counted byte strings
and their external representations. The sp argument 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 one if it succeeds, zero otherwise.
int
xdr_char(XDR *xdrs, char *cp)
A filter primitive that translates between C characters and their
external representations. This routine returns one if it suc‐
ceeds, zero otherwise. Note: encoded characters are not packed,
and occupy 4 bytes each. For arrays of characters, it is worth‐
while to consider xdr_bytes(), xdr_opaque() or xdr_string().
void
xdr_destroy(XDR *xdrs)
A macro that invokes the destroy routine associated with the XDR
stream, xdrs. Destruction usually involves freeing private data
structures associated with the stream. Using xdrs after invoking
xdr_destroy() is undefined.
int
xdr_double(XDR *xdrs, double *dp)
A filter primitive that translates between C double precision
numbers and their external representations. This routine returns
one if it succeeds, zero otherwise.
int
xdr_enum(XDR *xdrs, enum_t *ep)
A filter primitive that translates between C enums (actually
integers) and their external representations. This routine
returns one if it succeeds, zero otherwise.
int
xdr_float(XDR *xdrs, float *fp)
A filter primitive that translates between C floats and their
external representations. This routine returns one if it suc‐
ceeds, zero otherwise.
void
xdr_free(xdrproc_t proc, void *objp)
Generic freeing routine. The first argument is the XDR routine
for the object being freed. The second argument is a pointer to
the object itself. Note: the pointer passed to this routine is
not freed, but what it points to is freed (recursively).
u_int
xdr_getpos(XDR *xdrs)
A macro that invokes the get-position routine associated with the
XDR stream, xdrs. The routine returns an unsigned integer, which
indicates the position of the XDR byte stream. A desirable fea‐
ture of XDR streams is that simple arithmetic works with this
number, although the XDR stream instances need not guarantee
this.
int
xdr_hyper(XDR *xdrs, quad_t *llp)
A filter primitive that translates between ANSI C long long inte‐
gers and their external representations. This routine returns
one if it succeeds, zero otherwise.
long *
xdr_inline(XDR *xdrs, int len)
A macro that invokes the in-line routine associated with the XDR
stream, xdrs. The routine returns a pointer to a contiguous
piece of the stream's buffer; len is the byte length of the
desired buffer. Note: pointer is cast to long *.
Warning: xdr_inline() may return NULL (0) if it cannot allocate a
contiguous piece of a buffer. Therefore the behavior may vary
among stream instances; it exists for the sake of efficiency.
int
xdr_int(XDR *xdrs, int *ip)
A filter primitive that translates between C integers and their
external representations. This routine returns one if it suc‐
ceeds, zero otherwise.
int
xdr_long(XDR *xdrs, long *lp)
A filter primitive that translates between C long integers and
their external representations. This routine returns one if it
succeeds, zero otherwise.
int
xdr_longlong_t(XDR *xdrs, quad_t *llp)
A filter primitive that translates between ANSI C long long inte‐
gers and their external representations. This routine returns
one if it succeeds, zero otherwise.
void
xdrmem_create(XDR *xdrs, char *addr, u_int size, enum xdr_op op)
This routine initializes the XDR stream object pointed to by
xdrs. The stream's data is written to, or read from, a chunk of
memory at location addr whose length is no more than size bytes
long. The op argument determines the direction of the XDR stream
(either XDR_ENCODE, XDR_DECODE, or XDR_FREE).
int
xdr_opaque(XDR *xdrs, char *cp, u_int cnt)
A filter primitive that translates between fixed size opaque data
and its external representation. The cp argument is the address
of the opaque object, and cnt is its size in bytes. This routine
returns one if it succeeds, zero otherwise.
int
xdr_pointer(XDR *xdrs, char **objpp, u_int objsize, xdrproc_t xdrobj)
Like xdr_reference() except that it serializes NULL pointers,
whereas xdr_reference() does not. Thus, xdr_pointer() can repre‐
sent recursive data structures, such as binary trees or linked
lists.
void
xdrrec_create(XDR *xdrs, u_int sendsize, u_int recvsize, void *handle,
int (*readit)(), int (*writeit)())
This routine initializes the XDR stream object pointed to by
xdrs. The stream's data is written to a buffer of size sendsize;
a value of zero indicates the system should use a suitable
default. The stream's data is read from a buffer of size
recvsize; it too can be set to a suitable default by passing a
zero value. When a stream's output buffer is full, writeit() is
called. Similarly, when a stream's input buffer is empty,
readit() is called. The behavior of these two routines is simi‐
lar to the system calls read(2) and write(2), except that handle
is passed to the former routines as the first argument. Note:
the XDR stream's op field must be set by the caller.
Warning: this XDR stream implements an intermediate record
stream. Therefore there are additional bytes in the stream to
provide record boundary information.
int
xdrrec_endofrecord(XDR *xdrs, int sendnow)
This routine can be invoked only on streams created by
xdrrec_create(). The data in the output buffer is marked as a
completed record, and the output buffer is optionally written out
if sendnow is non-zero. This routine returns one if it succeeds,
zero otherwise.
int
xdrrec_eof(XDR *xdrs)
This routine can be invoked only on streams created by
xdrrec_create(). After consuming the rest of the current record
in the stream, this routine returns one if the stream has no more
input, zero otherwise.
int
xdrrec_skiprecord(XDR *xdrs)
This routine can be invoked only on streams created by
xdrrec_create(). It tells the XDR implementation that the rest
of the current record in the stream's input buffer should be dis‐
carded. This routine returns one if it succeeds, zero otherwise.
int
xdr_reference(XDR *xdrs, char **pp, u_int size, xdrproc_t proc)
A primitive that provides pointer chasing within structures. The
pp argument is the address of the pointer; size is the sizeof the
structure that *pp points to; and proc is an XDR procedure that
filters the structure between its C form and its external repre‐
sentation. This routine returns one if it succeeds, zero other‐
wise.
Warning: this routine does not understand NULL pointers. Use
xdr_pointer() instead.
int
xdr_setpos(XDR *xdrs, u_int pos)
A macro that invokes the set position routine associated with the
XDR stream xdrs. The pos argument is a position value obtained
from xdr_getpos(). This routine returns one if the XDR stream
could be repositioned, and zero otherwise.
Warning: it is difficult to reposition some types of XDR streams,
so this routine may fail with one type of stream and succeed with
another.
int
xdr_short(XDR *xdrs, short *sp)
A filter primitive that translates between C short integers and
their external representations. This routine returns one if it
succeeds, zero otherwise.
#ifdef _STDIO_H_
/* XDR using stdio library */
void
xdrstdio_create(XDR *xdrs, FILE *file, enum xdr_op op)
#endif
This routine initializes the XDR stream object pointed to by
xdrs. The XDR stream data is written to, or read from, the Stan‐
dard I/O stream file. The op argument determines the direction
of the XDR stream (either XDR_ENCODE, XDR_DECODE, or XDR_FREE).
Warning: the destroy routine associated with such XDR streams
calls fflush(3) on the file stream, but never fclose(3).
int
xdr_string(XDR *xdrs, char **sp, u_int maxsize)
A filter primitive that 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 one if it succeeds, zero otherwise.
int
xdr_u_char(XDR *xdrs, unsigned char *ucp)
A filter primitive that translates between unsigned C characters
and their external representations. This routine returns one if
it succeeds, zero otherwise.
int
xdr_u_hyper(XDR *xdrs, u_quad_t *ullp)
A filter primitive that translates between unsigned ANSI C long
long integers and their external representations. This routine
returns one if it succeeds, zero otherwise.
int
xdr_u_int(XDR *xdrs, unsigned *up)
A filter primitive that translates between C unsigned integers
and their external representations. This routine returns one if
it succeeds, zero otherwise.
int
xdr_u_long(XDR *xdrs, unsigned long *ulp)
A filter primitive that translates between C unsigned long inte‐
gers and their external representations. This routine returns
one if it succeeds, zero otherwise.
int
xdr_u_longlong_t(XDR *xdrs, u_quad_t *ullp)
A filter primitive that translates between unsigned ANSI C long
long integers and their external representations. This routine
returns one if it succeeds, zero otherwise.
int
xdr_u_short(XDR *xdrs, unsigned short *usp)
A filter primitive that translates between C unsigned short inte‐
gers and their external representations. This routine returns
one if it succeeds, zero otherwise.
int
xdr_union(XDR *xdrs, enum_t *dscmp, char *unp,
const struct xdr_discrim *choices, xdrproc_t defaultarm)
A filter primitive that 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 choices argument 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 one if it succeeds, zero otherwise.
int
xdr_vector(XDR *xdrs, char *arrp, u_int size, u_int elsize,
xdrproc_t elproc)
A filter primitive that translates between fixed-length arrays
and their corresponding external representations. The arrp argu‐
ment is the address of the pointer to the array, while size is
the element count of the array. The elsize argument is the
sizeof each of the array's elements, and elproc is an XDR filter
that translates between the array elements' C form, and their
external representation. This routine returns one if it suc‐
ceeds, zero otherwise.
int
xdr_void(void)
This routine always returns one. It may be passed to RPC rou‐
tines that require a function argument, where nothing is to be
done.
int
xdr_wrapstring(XDR *xdrs, char **sp)
A primitive that calls xdr_string(xdrs, sp, MAXUN.UNSIGNED);
where MAXUN.UNSIGNED is the maximum value of an unsigned integer.
The xdr_wrapstring() function is handy because the RPC package
passes a maximum of two XDR routines as arguments, and
xdr_string(), one of the most frequently used primitives,
requires three. Returns one if it succeeds, zero otherwise.
SEE ALSOrpc(3)
eXternal Data Representation Standard: Protocol Specification.
eXternal Data Representation: Sun Technical Notes.
XDR: External Data Representation Standard, Sun Microsystems, Inc.,
USC-ISI, RFC1014.
BSD February 16, 1988 BSD
