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.
The prototypes below are declared in <rpc/xdr.h> and
make use of the following types:
typedef int bool_t;
typedef bool_t (*xdrproc_t) (XDR *, void *,...);
For the declaration of the XDR type, see
<rpc/xdr.h>.
bool_t xdr_array(XDR *xdrs, char **arrp, unsigned int *sizep,
unsigned int maxsize, unsigned int elsize,
xdrproc_t elproc);
- A filter primitive that translates between variable-length arrays and
their corresponding external representations. The argument 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 argument 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.
bool_t 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.
bool_t xdr_bytes(XDR *xdrs, char **sp, unsigned int *sizep,
unsigned int maxsize);
- A filter primitive that translates between counted byte strings and their
external representations. The argument 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.
bool_t xdr_char(XDR *xdrs, char *cp);
- A filter primitive that translates between C characters 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(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.
bool_t 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.
bool_t 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.
bool_t xdr_float(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(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).
unsigned 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 feature of XDR
streams is that simple arithmetic works with this number, although the XDR
stream instances need not guarantee this.
long *xdr_inline(XDR *xdrs, int len);
- A macro that invokes the inline 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.
bool_t xdr_int(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.
bool_t 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.
void xdrmem_create(XDR *xdrs, char *addr, unsigned 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 determines the direction of the XDR stream (either
XDR_ENCODE, XDR_DECODE, or XDR_FREE).
bool_t xdr_opaque(XDR *xdrs, char *cp, unsigned int cnt);
- A filter primitive that translates between fixed size opaque data and its
external representation. The argument cp is the address of the
opaque object, and cnt is its size in bytes. This routine returns
one if it succeeds, zero otherwise.
bool_t xdr_pointer(XDR *xdrs, char **objpp,
unsigned 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(XDR *xdrs, unsigned int sendsize,
unsigned int recvsize, char *handle,
int (*readit) (char *, char *, int),
int (*writeit) (char *, char *, int));
- 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(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: to read from an XDR stream created by this API, you'll need to
call xdrrec_skiprecord() first before calling any other XDR APIs.
This inserts additional bytes in the stream to provide record boundary
information. Also, XDR streams created with different xdr*_create
APIs are not compatible for the same reason.
bool_t 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 nonzero. This routine returns one if it succeeds, zero
otherwise.
bool_t 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.
bool_t 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 discarded. This
routine returns one if it succeeds, zero otherwise.
bool_t xdr_reference(XDR *xdrs, char **pp, unsigned int size,
xdrproc_t proc);
- A primitive that provides pointer chasing within structures. The argument
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
otherwise.
- Warning: this routine does not understand null pointers. Use
xdr_pointer() instead.
xdr_setpos(XDR *xdrs, unsigned int pos);
- A macro that invokes the set position routine associated with the XDR
stream xdrs. The argument pos 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.
bool_t 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.
void xdrstdio_create(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 stdio stream
file. The argument 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(3) on the file stream, but never
fclose(3).
bool_t xdr_string(XDR *xdrs, char **sp, unsigned 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.
bool_t 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.
bool_t 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.
bool_t xdr_u_long(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.
bool_t xdr_u_short(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 otherwise.
bool_t xdr_union(XDR *xdrs, int *dscmp, char *unp,
struct xdr_discrim *choices,
xdrproc_t defaultarm); /* may equal NULL */
- 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 argument 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 one if it succeeds, zero otherwise.
bool_t xdr_vector(XDR *xdrs, char *arrp, unsigned int size,
unsigned int elsize, xdrproc_t elproc);
- A filter primitive that translates between fixed-length arrays and their
corresponding external representations. The argument arrp is the
address of the pointer to the array, while size is the element
count of the array. The argument 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.
bool_t xdr_void(void);
- This routine always returns one. It may be passed to RPC routines that
require a function argument, where nothing is to be done.
bool_t 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.
xdr_wrapstring() 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.