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.\" @(#)xdr.3n  2.2 88/08/03 4.0 RPCSRC; from 1.16 88/03/14 SMI

.\" $FreeBSD: src/lib/libc/xdr/xdr.3,v 1.8 2000/03/02 09:14:05 sheldonh Exp $

.\"

.TH XDR 3 "16 February 1988"

.SH NAME

xdr \- library routines for external data representation

.SH SYNOPSIS AND DESCRIPTION

.LP

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.

.LP

.ft B

.nf

.sp .5

xdr_array(xdrs, arrp, sizep, maxsize, elsize, elproc)

\s-1XDR\s0 *xdrs;

char **arrp;

u_int *sizep, maxsize, elsize;

xdrproc_t elproc;

.fi

.ft R

.IP

A filter primitive that translates between variable-length

arrays

and their corresponding external representations.

The

parameter

.I arrp

is the address of the pointer to the array, while

.I sizep

is the address of the element count of the array;

this element count cannot exceed

.IR maxsize .

The parameter

.I elsize

is the

.I sizeof

each of the array's elements, and

.I elproc

is an

.SM XDR

filter that translates between

the array elements' C form, and their external

representation.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

xdr_bool(xdrs, bp)

\s-1XDR\s0 *xdrs;

bool_t *bp;

.fi

.ft R

.IP

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.

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

xdr_bytes(xdrs, sp, sizep, maxsize)

\s-1XDR\s0 *xdrs;

char **sp;

u_int *sizep, maxsize;

.fi

.ft R

.IP

A filter primitive that translates between counted byte

strings and their external representations.

The parameter

.I sp

is the address of the string pointer.

The length of the

string is located at address

.IR sizep ;

strings cannot be longer than

.IR maxsize .

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_char(xdrs, cp)

\s-1XDR\s0 *xdrs;

char *cp;

.fi

.ft R

.IP

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

.BR xdr_bytes(\|) ,

.B xdr_opaque(\|)

or

.BR xdr_string(\|) .

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

void

xdr_destroy(xdrs)

\s-1XDR\s0 *xdrs;

.fi

.ft R

.IP

A macro that invokes the destroy routine associated with the

.SM XDR

stream,

.IR xdrs .

Destruction usually involves freeing private data structures

associated with the stream.  Using

.I xdrs

after invoking

.B xdr_destroy(\|)

is undefined.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_double(xdrs, dp)

\s-1XDR\s0 *xdrs;

double *dp;

.fi

.ft R

.IP

A filter primitive that translates between C

.B double

precision numbers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_enum(xdrs, ep)

\s-1XDR\s0 *xdrs;

enum_t *ep;

.fi

.ft R

.IP

A filter primitive that translates between C

.BR enum s

(actually integers) and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

xdr_float(xdrs, fp)

\s-1XDR\s0 *xdrs;

float *fp;

.fi

.ft R

.IP

A filter primitive that translates between C

.BR float s

and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 9

.LP

.ft B

.nf

.sp .5

void

xdr_free(proc, objp)

xdrproc_t proc;

char *objp;

.fi

.ft R

.IP

Generic freeing routine.

The first argument is the

.SM 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

.I not

freed, but what it points to

.I is

freed (recursively).

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

u_int

xdr_getpos(xdrs)

\s-1XDR\s0 *xdrs;

.fi

.ft R

.IP

A macro that invokes the get-position routine

associated with the

.SM XDR

stream,

.IR xdrs .

The routine returns an unsigned integer,

which indicates the position of the

.SM XDR

byte stream.

A desirable feature of

.SM XDR

streams is that simple arithmetic works with this number,

although the

.SM XDR

stream instances need not guarantee this.

.br

.if t .ne 4

.LP

.ft B

.nf

.sp .5

.br

long *

xdr_inline(xdrs, len)

\s-1XDR\s0 *xdrs;

int len;

.fi

.ft R

.IP

A macro that invokes the in-line routine associated with the

.SM XDR

stream,

.IR xdrs .

The routine returns a pointer

to a contiguous piece of the stream's buffer;

.I len

is the byte length of the desired buffer.

Note: pointer is cast to

.BR "long *" .

.IP

Warning:

.B xdr_inline(\|)

may return

.SM 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.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_int(xdrs, ip)

\s-1XDR\s0 *xdrs;

int *ip;

.fi

.ft R

.IP

A filter primitive that translates between C integers

and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_long(xdrs, lp)

\s-1XDR\s0 *xdrs;

long *lp;

.fi

.ft R

.IP

A filter primitive that translates between C

.B long

integers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 12

.LP

.ft B

.nf

.sp .5

void

xdrmem_create(xdrs, addr, size, op)

\s-1XDR\s0 *xdrs;

char *addr;

u_int size;

enum xdr_op op;

.fi

.ft R

.IP

This routine initializes the

.SM XDR

stream object pointed to by

.IR xdrs .

The stream's data is written to, or read from,

a chunk of memory at location

.I addr

whose length is no more than

.I size

bytes long.  The

.I op

determines the direction of the

.SM XDR

stream

(either

.BR \s-1XDR_ENCODE\s0 ,

.BR \s-1XDR_DECODE\s0 ,

or

.BR \s-1XDR_FREE\s0 ).

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

xdr_opaque(xdrs, cp, cnt)

\s-1XDR\s0 *xdrs;

char *cp;

u_int cnt;

.fi

.ft R

.IP

A filter primitive that translates between fixed size opaque

data

and its external representation.

The parameter

.I cp

is the address of the opaque object, and

.I cnt

is its size in bytes.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

xdr_pointer(xdrs, objpp, objsize, xdrobj)

\s-1XDR\s0 *xdrs;

char **objpp;

u_int objsize;

xdrproc_t xdrobj;

.fi

.ft R

.IP

Like

.B xdr_reference(\|)

execpt that it serializes

.SM NULL

pointers, whereas

.B xdr_reference(\|)

does not.  Thus,

.B xdr_pointer(\|)

can represent

recursive data structures, such as binary trees or

linked lists.

.br

.if t .ne 15

.LP

.ft B

.nf

.sp .5

void

xdrrec_create(xdrs, sendsize, recvsize, handle, readit, writeit)

\s-1XDR\s0 *xdrs;

u_int sendsize, recvsize;

char *handle;

int (*readit) (\|), (*writeit) (\|);

.fi

.ft R

.IP

This routine initializes the

.SM XDR

stream object pointed to by

.IR xdrs .

The stream's data is written to a buffer of size

.IR sendsize ;

a value of zero indicates the system should use a suitable

default.

The stream's data is read from a buffer of size

.IR recvsize ;

it too can be set to a suitable default by passing a zero

value.

When a stream's output buffer is full,

.I writeit

is called.  Similarly, when a stream's input buffer is empty,

.I readit

is called.  The behavior of these two routines is similar to

the

system calls

.B read

and

.BR write ,

except that

.I handle

is passed to the former routines as the first parameter.

Note: the

.SM XDR

stream's

.I op

field must be set by the caller.

.IP

Warning: this

.SM XDR

stream implements an intermediate record stream.

Therefore there are additional bytes in the stream

to provide record boundary information.

.br

.if t .ne 9

.LP

.ft B

.nf

.sp .5

xdrrec_endofrecord(xdrs, sendnow)

\s-1XDR\s0 *xdrs;

int sendnow;

.fi

.ft R

.IP

This routine can be invoked only on

streams created by

.BR xdrrec_create(\|) .

The data in the output buffer is marked as a completed

record,

and the output buffer is optionally written out if

.I sendnow

is non-zero.

This routine returns one if it succeeds, zero

otherwise.

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

xdrrec_eof(xdrs)

\s-1XDR\s0 *xdrs;

int empty;

.fi

.ft R

.IP

This routine can be invoked only on

streams created by

.BR 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.

.br

.if t .ne 3

.LP

.ft B

.nf

.sp .5

xdrrec_skiprecord(xdrs)

\s-1XDR\s0 *xdrs;

.fi

.ft R

.IP

This routine can be invoked only on

streams created by

.BR xdrrec_create(\|) .

It tells the

.SM 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.

.br

.if t .ne 11

.LP

.ft B

.nf

.sp .5

xdr_reference(xdrs, pp, size, proc)

\s-1XDR\s0 *xdrs;

char **pp;

u_int size;

xdrproc_t proc;

.fi

.ft R

.IP

A primitive that provides pointer chasing within structures.

The parameter

.I pp

is the address of the pointer;

.I size

is the

.I sizeof

the structure that

.I *pp

points to; and

.I proc

is an

.SM XDR

procedure that filters the structure

between its C form and its external representation.

This routine returns one if it succeeds, zero otherwise.

.IP

Warning: this routine does not understand

.SM NULL

pointers.

Use

.B xdr_pointer(\|)

instead.

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

xdr_setpos(xdrs, pos)

\s-1XDR\s0 *xdrs;

u_int pos;

.fi

.ft R

.IP

A macro that invokes the set position routine associated with

the

.SM XDR

stream

.IR xdrs .

The parameter

.I pos

is a position value obtained from

.BR xdr_getpos(\|) .

This routine returns one if the

.SM XDR

stream could be repositioned,

and zero otherwise.

.IP

Warning: it is difficult to reposition some types of

.SM XDR

streams, so this routine may fail with one

type of stream and succeed with another.

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

xdr_short(xdrs, sp)

\s-1XDR\s0 *xdrs;

short *sp;

.fi

.ft R

.IP

A filter primitive that translates between C

.B short

integers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

void

xdrstdio_create(xdrs, file, op)

\s-1XDR\s0 *xdrs;

\s-1FILE\s0 *file;

enum xdr_op op;

.fi

.ft R

.IP

This routine initializes the

.SM XDR

stream object pointed to by

.IR xdrs .

The

.SM XDR

stream data is written to, or read from, the Standard

.B I/O

stream

.IR file .

The parameter

.I op

determines the direction of the

.SM XDR

stream (either

.BR \s-1XDR_ENCODE\s0 ,

.BR \s-1XDR_DECODE\s0 ,

or

.BR \s-1XDR_FREE\s0 ).

.IP

Warning: the destroy routine associated with such

.SM XDR

streams calls

.B fflush(\|)

on the

.I file

stream, but never

.BR fclose(\|) .

.br

.if t .ne 9

.LP

.ft B

.nf

.sp .5

xdr_string(xdrs, sp, maxsize)

\s-1XDR\s0

*xdrs;

char **sp;

u_int maxsize;

.fi

.ft R

.IP

A filter primitive that translates between C strings and

their

corresponding external representations.

Strings cannot be longer than

.IR maxsize .

Note:

.I sp

is the address of the string's pointer.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 8

.LP

.ft B

.nf

.sp .5

xdr_u_char(xdrs, ucp)

\s-1XDR\s0 *xdrs;

unsigned char *ucp;

.fi

.ft R

.IP

A filter primitive that translates between

.B unsigned

C characters and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 9

.LP

.ft B

.nf

.sp .5

xdr_u_int(xdrs, up)

\s-1XDR\s0 *xdrs;

unsigned *up;

.fi

.ft R

.IP

A filter primitive that translates between C

.B unsigned

integers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_u_long(xdrs, ulp)

\s-1XDR\s0 *xdrs;

unsigned long *ulp;

.fi

.ft R

.IP

A filter primitive that translates between C

.B "unsigned long"

integers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 7

.LP

.ft B

.nf

.sp .5

xdr_u_short(xdrs, usp)

\s-1XDR\s0 *xdrs;

unsigned short *usp;

.fi

.ft R

.IP

A filter primitive that translates between C

.B "unsigned short"

integers and their external representations.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 16

.LP

.ft B

.nf

.sp .5

xdr_union(xdrs, dscmp, unp, choices, dfault)

\s-1XDR\s0 *xdrs;

int *dscmp;

char *unp;

struct xdr_discrim *choices;

bool_t (*defaultarm) (\|);  /* may equal \s-1NULL\s0 */

.fi

.ft R

.IP

A filter primitive that translates between a discriminated C

.B union

and its corresponding external representation.

It first

translates the discriminant of the union located at

.IR dscmp .

This discriminant is always an

.BR enum_t .

Next the union located at

.I unp

is translated.  The parameter

.I choices

is a pointer to an array of

.B xdr_discrim(\|)

structures.

Each structure contains an ordered pair of

.RI [ value , proc ].

If the union's discriminant is equal to the associated

.IR value ,

then the

.I proc

is called to translate the union.  The end of the

.B xdr_discrim(\|)

structure array is denoted by a routine of value

.SM NULL\s0.

If the discriminant is not found in the

.I choices

array, then the

.I defaultarm

procedure is called (if it is not

.SM NULL\s0).

Returns one if it succeeds, zero otherwise.

.br

.if t .ne 6

.LP

.ft B

.nf

.sp .5

xdr_vector(xdrs, arrp, size, elsize, elproc)

\s-1XDR\s0 *xdrs;

char *arrp;

u_int size, elsize;

xdrproc_t elproc;

.fi

.ft R

.IP

A filter primitive that translates between fixed-length

arrays

and their corresponding external representations.  The

parameter

.I arrp

is the address of the pointer to the array, while

.I size

is the element count of the array.  The parameter

.I elsize

is the

.I sizeof

each of the array's elements, and

.I elproc

is an

.SM XDR

filter that translates between

the array elements' C form, and their external

representation.

This routine returns one if it succeeds, zero otherwise.

.br

.if t .ne 5

.LP

.ft B

.nf

.sp .5

xdr_void(\|)

.fi

.ft R

.IP

This routine always returns one.

It may be passed to

.SM RPC

routines that require a function parameter,

where nothing is to be done.

.br

.if t .ne 10

.LP

.ft B

.nf

.sp .5

xdr_wrapstring(xdrs, sp)

\s-1XDR\s0 *xdrs;

char **sp;

.fi

.ft R

.IP

A primitive that calls

.B "xdr_string(xdrs, sp,\s-1MAXUN.UNSIGNED\s0 );"

where

.B

.SM MAXUN.UNSIGNED

is the maximum value of an unsigned integer.

.B xdr_wrapstring(\|)

is handy because the

.SM RPC

package passes a maximum of two

.SM XDR

routines as parameters, and

.BR xdr_string(\|) ,

one of the most frequently used primitives, requires three.

Returns one if it succeeds, zero otherwise.

.SH SEE ALSO

.BR rpc (3)

.LP

The following manuals:

.RS

.ft I

eXternal Data Representation Standard: Protocol Specification

.br

eXternal Data Representation: Sun Technical Notes

.ft R

.br

.IR "\s-1XDR\s0: External Data Representation Standard" ,

.SM RFC1014, Sun Microsystems, Inc.,

.SM USC-ISI\s0.