XDR(3N-BSD) RISC/os Reference Manual XDR(3N-BSD)
NAME
xdr - library routines for external data representation
SYNOPSIS AND 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.
xdr_array(xdrs, arrp, sizep, maxsize, elsize, elproc)
XDR *xdrs;
char **arrp;
u_int *sizep, maxsize, elsize;
xdrproc_t elproc;
A filter primitive that 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 can-
not exceed maxsize. The parameter elsize 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 succeeds, zero otherwise.
xdr_bool(xdrs, bp)
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.
xdr_bytes(xdrs, sp, sizep, maxsize)
XDR *xdrs;
char **sp;
u_int *sizep, maxsize;
A filter primitive that translates between counted byte
strings and their external representations. The param-
eter 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 one if it succeeds, zero otherwise.
xdr_char(xdrs, cp)
XDR *xdrs;
char *cp;
A filter primitive that translates between C characters
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and their external representations. This routine
returns one if it succeeds, zero otherwise. Note:
encoded characters are not packed, and occupy 4 bytes
each. For arrays of characters, it is worthwhile to
consider xdr_bytes(), xdr_opaque() or xdr_string().
void
xdr_destroy(xdrs)
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.
xdr_double(xdrs, dp)
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 other-
wise.
xdr_enum(xdrs, ep)
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 other-
wise.
xdr_float(xdrs, fp)
XDR *xdrs;
float *fp;
A filter primitive that translates between C floats and
their external representations. This routine returns
one if it succeeds, zero otherwise.
void
xdr_free(proc, objp)
xdrproc_t proc;
char *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).
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u_int
xdr_getpos(xdrs)
XDR *xdrs;
A macro that invokes the get-position routine associ-
ated with the XDR stream, xdrs. The routine returns an
unsigned integer, which indicates the position of the
XDR byte stream. A desirable feature of XDR streams is
that simple arithmetic works with this number, although
the XDR stream instances need not guarantee this.
long *
xdr_inline(xdrs, len)
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.
xdr_int(xdrs, ip)
XDR *xdrs;
int *ip;
A filter primitive that translates between C integers
and their external representations. This routine
returns one if it succeeds, zero otherwise.
xdr_long(xdrs, lp)
XDR *xdrs;
long *lp;
A filter primitive that translates between C long
integers and their external representations. This rou-
tine returns one if it succeeds, zero otherwise.
void
xdrmem_create(xdrs, addr, size, op)
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
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from, a chunk of memory at location addr whose length
is no more than size bytes long. The op determines the
direction of the XDR stream (either XDR_ENCODE,
XDR_DECODE, or XDR_FREE).
xdr_opaque(xdrs, cp, cnt)
XDR *xdrs;
char *cp;
u_int cnt;
A filter primitive that 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 one if
it succeeds, zero otherwise.
xdr_pointer(xdrs, objpp, objsize, xdrobj)
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 represent recursive data structures,
such as binary trees or linked lists.
void
xdrrec_create(xdrs, sendsize, recvsize, handle, readit, writeit)
XDR *xdrs;
u_int sendsize, recvsize;
char *handle;
int (*readit) (), (*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 similar to the system calls read and write, except
that handle is passed to the former routines as the
first parameter. 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.
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xdrrec_endofrecord(xdrs, sendnow)
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.
xdrrec_eof(xdrs)
XDR *xdrs;
int empty;
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.
xdrrec_skiprecord(xdrs)
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 discarded. This routine returns one
if it succeeds, zero otherwise.
xdr_reference(xdrs, pp, size, proc)
XDR *xdrs;
char **pp;
u_int size;
xdrproc_t proc;
A primitive that provides pointer chasing within struc-
tures. 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 filters the structure
between its C form and its external representation.
This routine returns one if it succeeds, zero other-
wise.
Warning: this routine does not understand NULL
pointers. Use xdr_pointer() instead.
xdr_setpos(xdrs, pos)
XDR *xdrs;
u_int pos;
A macro that invokes the set position routine associ-
ated with the XDR stream xdrs. The parameter pos is a
position value obtained from xdr_getpos(). This
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routine returns one if the XDR stream could be reposi-
tioned, 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.
xdr_short(xdrs, sp)
XDR *xdrs;
short *sp;
A filter primitive that translates between C short
integers and their external representations. This rou-
tine returns one if it succeeds, zero otherwise.
void
xdrstdio_create(xdrs, file, op)
XDR *xdrs;
FILE *file;
enum xdr_op op;
This routine initializes the XDR stream object pointed
to by xdrs. The XDR stream data is written to, or read
from, the Standard I/O stream file. The parameter op
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() on the file stream, but never
fclose().
xdr_string(xdrs, sp, maxsize)
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.
xdr_u_char(xdrs, ucp)
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.
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xdr_u_int(xdrs, up)
XDR *xdrs;
unsigned *up;
A filter primitive that translates between C unsigned
integers and their external representations. This rou-
tine returns one if it succeeds, zero otherwise.
xdr_u_long(xdrs, ulp)
XDR *xdrs;
unsigned long *ulp;
A filter primitive that translates between C unsigned
long integers and their external representations. This
routine returns one if it succeeds, zero otherwise.
xdr_u_short(xdrs, usp)
XDR *xdrs;
unsigned short *usp;
A filter primitive that translates between C unsigned
short integers and their external representations.
This routine returns one if it succeeds, zero other-
wise.
xdr_union(xdrs, dscmp, unp, choices, dfault)
XDR *xdrs;
int *dscmp;
char *unp;
struct xdr_discrim *choices;
bool_t (*defaultarm) (); /* may equal NULL */
A filter primitive that translates between a discrim-
inated C union and its corresponding external represen-
tation. 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 discrim-
inant 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.
xdr_vector(xdrs, arrp, size, elsize, elproc)
XDR *xdrs;
char *arrp;
u_int size, elsize;
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xdrproc_t elproc;
A filter primitive that translates between fixed-length
arrays and their corresponding external representa-
tions. 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
filter that translates between the array elements' C
form, and their external representation. This routine
returns one if it succeeds, zero otherwise.
xdr_void()
This routine always returns one. It may be passed to
RPC routines that require a function parameter, where
nothing is to be done.
xdr_wrapstring(xdrs, sp)
XDR *xdrs;
char **sp;
A primitive that calls xdr_string(xdrs,
sp,MAXUN.UNSIGNED ); where is the maximum value of an
unsigned integer. xdr_wrapstring() is handy because
the RPC package passes a maximum of two XDR routines as
parameters, and xdr_string(), one of the most fre-
quently used primitives, requires three. Returns one
if it succeeds, zero otherwise.
SEE ALSO
rpc(3N)
ORIGIN
Sun Microsystems
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