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ADDMHF

ADDMHF

Section: PVM Version 3.4 (3PVM) Updated: 1 April, 1997
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NAME

pvm_addmhf, pvm_delmhf - Install or remove message-handler functions.

 

SYNOPSIS

C       int mhid = pvm_addmhf( int src, int tag, int ctx, int (*func)(int mid) )

int info = pvm_delmhf( int mhid )
Fortran Not available

 

PARAMETERS

src
The tid of the sender.
tag
The tag sent with the message.
ctx
The context sent with the message.
func
Function to call when message received.
mhid
Message handler id.
info
Result code.
mid
Message buffer identifier for new active receive buffer.

 

DESCRIPTION

pvm_addmhf specifies a function that will be called whenever libpvm copies in a message whose header fields of src, tag, and ctx match those provided to pvm_addmhf().

The src and tag fields may be left unspecified (wildcard) by setting to -1.

The calling sequence of the message handler function is:

        int handler( int mid )

Where mid is the bufid of the received message. The handler function can be used to unpack and process the received message buffer. PVM automatically saves the current send and receive buffers, so the handler need not worry about interfering with message buffers in the regular program flow. PVM also sets the current receive buffer to the received message (using pvm_setrbuf()) before invoking the message handler, so the message can be unpacked directly. PVM will free this message buffer when the message handler returns, if the handler has not already done so. But, any other message buffers created by the handler routine should be freed using pvm_freebuf() before returning.

Note: Operation in the message handler context is somewhat restricted. The function may call some PVM functions, but not others. For example, it may compose and send a reply message as shown:

        pvm_packf( "%+ %s", PvmDataDefault, "got your message" );
        pvm_send( tid, tag );
        pvm_freebuf( pvm_setsbuf( 0 ) );

or equivalently:

        pvm_setsbuf( pvm_mkbuf( PvmDataDefault ) );
        pvm_pkstr( "got your message" );
        pvm_send( tid, tag );
        pvm_freebuf( pvm_setsbuf( 0 ) );

but is not allowed to call certain other PVM communication functions, such as multicast or receive.

pvm_addmhf returns the id number of the newly created message handler if successful; this number may be passed to pvm_delmhf to remove the entry. There is no guarantee to the ordering of id values returned by pvm_addmhf, or to the order in which message handlers will be invoked. PvmExists is returned if the handler already exists.

pvm_delmhf returns PvmOk if successful. PvmBadParam if pvm_delmhf is passed a negative id value. PvmNotFound if the id value is not found.

 

EXAMPLES

        /* Print a message when hosts are added to virtual machine */

        int
        hostAdded( int mid )
        {
                int n;
                pvm_unpackf( "%d", &n );
                printf( "*** %d new hosts just added ***\n", n );
        }

        void
        main()
        {
                int src, tag, ctx;

                . . .

                src = -1;
                tag = 99;
                ctx = -1;

                pvm_addmhf( src, tag, ctx, hostAdded );
                pvm_notify( PvmHostAdd, 99, -1, (int *) NULL );

                . . .
        }

 

ERRORS

The following error conditions can be returned by pvm_addmhf():
PvmExists
Can't insert as handler already exists with same (tag, ctx, src) including "wild-cards" (those set to -1)

The following error conditions can be returned by pvm_delmhf():

PvmBadParam
Invalid (negative) mhid passed in.
PvmNotFound
Message handler mhid does not exist.

 

SEE ALSO

pvm_setrbuf(3PVM), pvm_setsbuf(3PVM), pvm_freebuf(3PVM)


 

Index

NAME
SYNOPSIS
PARAMETERS
DESCRIPTION
EXAMPLES
ERRORS
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 21:53:18 GMT, April 16, 2011