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Name

xdr_admin, xdr_control, xdr_getpos, xdr_inline, xdrrec_endofrecord, xdrrec_eof, xdrrec_readbytes, xdrrec_skiprecord, xdr_setpos, xdr_sizeof - library routines for external data representation

MT-Level

Safe

Description

XDR library routines allow C programmers to describe arbitrary data structures in a machine-independent fashion. Protocols such as remote procedure calls (RPC ) use these routines to describe the format of the data.

These routines deal specifically with the management of the XDR stream.

Routines

See rpc(3N) for the definition of the XDR data structure. Note that any buffers passed to the XDR routines must be properly aligned. It is suggested that malloc(3C) be used to allocate these buffers or that the programmer insure that the buffer address is divisible evenly by four.

#include <rpc/xdr.h>

bool_t xdr_control( XDR *xdrs, int req, void *info);

A function macro to change or retrieve various information
about an XDR stream. req indicates the type of operation and info is a pointer to the information. The supported values of req, their argument types and what they do are:

XDR_GET_BYTES_AVAIL xdr_bytesrec *return number ofbytes left unconsumed in the stream and a flag indicating whether or not this is the last fragment.

u_int xdr_getpos(const 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. Therefore, applications written for portability should not depend on this feature.

long *xdr_inline(XDR *xdrs, const 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, and applications written for portability should not depend on this feature.

bool_t xdrrec_endofrecord(XDR * xdrs , int sendnow);

This routine can be invoked only on
streams created by xdrrec_create() (see xdr_create(3N) ). 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 TRUE if it succeeds, FALSE 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 TRUE if there is no more data in the stream’s input buffer. It returns FALSE if there is additional data in the stream’s input buffer.

int xdrrec_readbytes(XDR *xdrs, caddr_t addr, u_int nbytes);

This routine can be invoked only on streams created by
xdrrec_create(). It attempts to read nbytes bytes from the XDR stream into the buffer pointed to by addr. On success this routine returns the number of bytes read, -1 on failure. A return value of 0 indicates an end of record.

bool_t xdrrec_skiprecord(XDR *xdrs);

This routine can be invoked only on
streams created by xdrrec_create() (see xdr_create(3N) ). It tells the XDR implementation that the rest of the current record in the stream’s input buffer should be discarded. This routine returns TRUE if it succeeds, FALSE otherwise.

bool_t xdr_setpos(XDR *xdrs, const u_int pos);

A macro that invokes the set position routine associated with the
XDR stream xdrs. The parameter pos is a position value obtained from xdr_getpos(). This routine returns TRUE if the XDR stream was repositioned, and FALSE 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. Therefore, applications written for portability should not depend on this feature.

unsigned long xdr_sizeof(xdrproc_t func, void *data);

This routine returns the number of bytes required to encode
data using the XDR filter function func, excluding potential overhead such as RPC headers or record markers. O is returned on error. This information might be used to select between transport protocols, or to determine the buffer size for various lower levels of RPC client and server creation routines, or to allocate storage when XDR is used outside of the RPC subsystem.

See Also

malloc(3C) , rpc(3N) , xdr_complex(3N) , xdr_create(3N) , xdr_simple(3N)

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