[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    xdr_create(3N) manual page Table of Contents

Name

xdr_create, xdr_destroy, xdrmem_create, xdrrec_create, xdrstdio_create - library routines for external data representation stream creation

MT-Level

MT-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 with the creation of XDR streams. XDR streams have to be created before any data can be translated into XDR format.

Routines

See rpc(3N) for the definition of the XDR , CLIENT , and SVCXPRT data structures. 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>

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.

void xdrmem_create(XDR *xdrs, const caddr_t addr, const u_int size, const 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 less than size bytes long. The op determines the direction of the XDR stream (either XDR_ENCODE , XDR_DECODE , or XDR_FREE ).

void xdrrec_create(XDR *xdrs, const u_int sendsz, const u_int recvsz, const caddr_t handle, const int (*readit)(const void *read_handle, char *buf, const int len), const int (*writeit)(const void *write_handle, const char *buf, const int len));

This routine initializes the
read-oriented XDR stream object pointed to by xdrs. The stream’s data is written to a buffer of size sendsz; a value of 0 indicates the system should use a suitable default. The stream’s data is read from a buffer of size recvsz; it too can be set to a suitable default by passing a 0 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() (see read(2) and write(2) , respectively), except that an appropriate handle (read_handle or write_handle) is passed to the former routines as the first parameter instead of a file descriptor. 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.

void xdrstdio_create(XDR *xdrs, FILE *file, const 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() (see fclose(3S) ).

Failure of any of these functions can be detected by first initializing the x_ops field in the XDR structure (xdrs->x_ops) to NULL before calling the xdr*_create() function. After the return from the xdr*_create() function, if the x_ops field is still NULL , the call has failed. If the x_ops field contains some other value, the call can be assumed to have succeeded.

See Also

read(2) , write(2) , malloc(3C) , rpc(3N) , xdr_admin(3N) , xdr_complex(3N) , xdr_simple(3N) , fclose(3S)

Table of Contents