NAME
xdr - library routines for external data representation SYNOPSIS AND DESCRIPTION These routines allow C programmers to describe arbitrary data struc‐
tures in a machine-independent fashion. Data for remote procedure calls are transmitted using these routines. The prototypes below are declared in
and make use of the following types: typedef int boolt; typedef boolt (*xdrprocti) (XDR *, void *,...); For the declaration of the XDR type, see . boolt xdrarray(XDR *xdrs, char **arrp, unsigned int *sizep, unsigned int maxsize, unsigned int elsize, xdrproct 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 suc‐ ceeds, zero otherwise. boolt xdrbool(XDR *xdrs, boolt *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. boolt xdrbytes(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. boolt xdrchar(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 xdrbytes(), xdropaque() or xdrstring(). void xdrdestroy(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 invok‐ ing xdrdestroy() is undefined. boolt xdrdouble(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. boolt xdrenum(XDR *xdrs, enumt *ep); A filter primitive that translates between C enums (actually integers) and their external representations. This routine returns one if it succeeds, zero otherwise. boolt xdrfloat(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 xdrfree(xdrproct 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 xdrgetpos(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 desir‐ able feature of XDR streams is that simple arithmetic works with this number, although the XDR stream instances need not guaran‐ tee this. long *xdrinline(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: xdrinline() 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. boolt xdrint(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. boolt xdrlong(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 xdrmemcreate(XDR *xdrs, char *addr, unsigned int size, enum xdrop 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 XDRENCODE, XDRDECODE, or XDRFREE). boolt xdropaque(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. boolt xdrpointer(XDR *xdrs, char **objpp, unsigned int objsize, xdrproct xdrobj); Like xdrreference() except that it serializes NULL pointers, whereas xdrreference() does not. Thus, xdrpointer() can rep‐ resent recursive data structures, such as binary trees or linked lists. void xdrreccreate(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 send‐ size; a value of zero indicates the system should use a suitable default. The stream's data is read from a buffer of size recv‐ size; 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, rea‐ dit 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: this XDR stream implements an intermediate record stream. Therefore there are additional bytes in the stream to provide record boundary information. boolt xdrrecendofrecord(XDR *xdrs, int sendnow); This routine can be invoked only on streams created by xdr‐ reccreate(). The data in the output buffer is marked as a com‐ pleted record, and the output buffer is optionally written out if sendnow is nonzero. This routine returns one if it succeeds, zero otherwise. boolt xdrreceof(XDR *xdrs); This routine can be invoked only on streams created by xdr‐ reccreate(). After consuming the rest of the current record in the stream, this routine returns one if the stream has no more input, zero otherwise. boolt xdrrecskiprecord(XDR *xdrs); This routine can be invoked only on streams created by xdr‐ reccreate(). 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 other‐ wise. boolt xdrreference(XDR *xdrs, char **pp, unsigned int size, xdrproct 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 pro‐ cedure that filters the structure between its C form and its external representation. This routine returns one if it suc‐ ceeds, zero otherwise. Warning: this routine does not understand NULL pointers. Use xdrpointer() instead. xdrsetpos(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 xdrgetpos(). 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. boolt xdrshort(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 xdrstdiocreate(XDR *xdrs, FILE *file, enum xdrop 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 XDRENCODE, XDRDECODE, or XDRFREE). Warning: the destroy routine associated with such XDR streams calls fflush(3) on the file stream, but never fclose(3). boolt xdrstring(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 other‐ wise. boolt xdruchar(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. boolt xdruint(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. boolt xdrulong(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. boolt xdrushort(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. boolt xdrunion(XDR *xdrs, int *dscmp, char *unp, struct xdrdiscrim *choices, xdrproct 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 enumt. Next the union located at unp is translated. The argument choices is a pointer to an array of xdrdiscrim() 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 xdrdiscrim() 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. boolt xdrvector(XDR *xdrs, char *arrp, unsigned int size, unsigned int elsize, xdrproct 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 suc‐ ceeds, zero otherwise. boolt xdrvoid(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. boolt xdrwrapstring(XDR *xdrs, char **sp); A primitive that calls xdrstring(xdrs, sp,MAXUN.UNSIGNED ); where MAXUN.UNSIGNED is the maximum value of an unsigned inte‐ ger. xdrwrapstring() is handy because the RPC package passes a maximum of two XDR routines as arguments, and xdrstring(), one of the most frequently used primitives, requires three. Returns one if it succeeds, zero otherwise. SEE ALSO rpc(3) 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. COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2007-12-30 XDR(3)