xdr — library routines for external data representation
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]](../stylesheet/note.png) | Note | 
|---|---|
| Encoded characters are not packed, and
                      occupy 4 bytes each. For arrays of
                      characters, it is worthwhile to consider
                       | 
| 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]](../stylesheet/note.png) | 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]](../stylesheet/note.png) | Note | 
|---|---|
| Pointer is cast to long *. | 
| ![[Warning]](../stylesheet/warning.png) | Warning | 
|---|---|
| 
 | 
| 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]](../stylesheet/note.png) | Note | 
|---|---|
| The XDR stream's  | 
| ![[Warning]](../stylesheet/warning.png) | Warning | 
|---|---|
| This XDR stream implements an intermediate record stream. Therefore there are additional bytes in the stream to provide record boundary information. | 
| 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]](../stylesheet/warning.png) | Warning | 
|---|---|
| This routine does not understand NULL
                      pointers. Use  | 
| bool_t
                  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]](../stylesheet/warning.png) | 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).
| 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]](../stylesheet/note.png) | Note | 
|---|---|
| 
 | 
| 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.
The following manuals:
eXternal Data Representation Standard: Protocol Specification
eXternal Data Representation: Sun Technical Notes
XDR: External Data Representation Standard, RFC 1014, Sun Microsystems, Inc., USC-ISI.
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| This page was taken from the 4.4BSD-Lite CDROM (BSD license) (#)xdr.3n 2.2 88/08/03 4.0 RPCSRC; from 1.16 88/03/14 SMI 2007-12-30, mtk, Convert function prototypes to modern C syntax |