.\" $Id: pvm_setminfo.3,v 1.1 1996/09/23 22:06:14 pvmsrc Exp $
.TH SETMINFO 3PVM "13 March, 1996" "" "PVM Version 3.4"
.SH NAME
pvm_getminfo,
pvm_setminfo \- Get or set header information of a message.

.SH SYNOPSIS
.nf
.ft B
C	int info = pvm_getminfo( int bufid, struct pvmminfo *mi )
.br
	int info = pvm_setminfo( int bufid, struct pvmminfo *mi )
.br

Fortran	call pvmfgetminfo( bufid, len, ctx, tag, wid, enc, crc,
                           src, dst, info )
	call pvmfsetminfo( bufid, ctx, tag, wid, src, dst, info )
.fi

.SH PARAMETERS
.IP bufid 0.8i
Message buffer identifier.
.IP mi
Struct containing header information.
.IP info
Result code.
.PP
For a description of the Fortran parameters,
see below.

.SH DESCRIPTION
These functions read and set information passed in message headers,
which may be of interest to certain applications.
Typically,
they will be used when it is necessary to get the message context or
wait id to use the same values in a reply message.

The fields affected are:
.IP len
The length in bytes of the body of the message.
This will be equal to the actual size of the data packed,
if \fIPvmDataRaw\fR is used,
otherwise it may include pad bytes.
.IP ctx
The context sent with the message.
.IP tag
The tag sent with the message.
.IP wid
Wait Identifier, used to match a reply message to the corresponding request.
.IP enc
Message Encoding,
either the \fIdata signature\fR of the sender,
or 0x10000000 for XDR.
.IP crc
The CRC checksum of the message body.
.IP src
The tid of the sender.
.IP dst
The tid of the destination.
.PP
All fields may be read,
but only \fIctx\fR, \fItag\fR, \fIwid\fR, \fIsrc\fR and \fIdst\fR
may be set.

pvm_getmwid and pvm_setmwid return PvmOk if successful,
or else a negative error code.

.SH EXAMPLES
.nf
	/* return a message to a caller with the same tag and wait id */
	struct pvmminfo mi1, mi2;

	pvm_recv(-1, -1);
	/* ... process, compose reply message */
	pvm_getminfo(pvm_getrbuf(), &mi1);
	pvm_getminfo(pvm_getsbuf(), &mi2);
	mi2.wid = mi1.wid;
	pvm_send(mi1.src, mi1.tag);

.SH ERRORS
The following error conditions can be returned by
pvm_getmwid or pvm_setmwid:
.IP PvmBadParam
Invalid value for \fIbufid\fR or \fImi\fR argument.
.IP PvmNoSuchBuf
Message buffer \fIbufid\fR doesn't exist.
.PP
.SH SEE ALSO
pvm_bufinfo(3PVM)