RECVF(3PVM)							  RECVF(3PVM)

NAME
  pvm_recvf - Redefines	the comparison function	used to	accept messages.

SYNOPSIS
  C	  int (*old)() = pvm_recvf( int	(*new)(	int bufid, int tid, int	tag
  ))

  Fortran NOT AVAILABLE

DISCUSSION
  The routine pvm_recvf	defines	the comparison function	to be used by the
  pvm_recv, pvm_nrecv, and pvm_probe functions.	 It is available as a means
  to customize PVM message passing.  pvm_recvf sets a user supplied com-
  parison function to evaluate messages	for receiving.

  recvf	returns	the old	value of the matching function,	or 0 if	the old	func-
  tion was the default matcher

  pvm_recvf is intended	for sophisticated C programmers	who understand the
  function of such routines (like signal) and who require a receive routine
  that can match on more complex message contexts than the default provides.

MATCHING FUNCTION
  The default comparison function evaluates the	source and message tag asso-
  ciated with all incoming messages.

PARAMETERS

  tid	  Integer task identifier of sending process supplied by the user.

  tag	  Integer message tag supplied by the user.

  bufid	  Integer message buffer identifier.

  The matching function	should return:

       Value	 Action	taken
	< 0	   return immediately with this	error code
	  0	   do not pick this message
	  1	   pick	this message and do not	scan the rest
	> 1	   pick	this highest ranked message after
		 scanning them all

Example: Implementing probe with recvf

  #include <pvm3.h>

  static int foundit = 0;

  static int
  foo_match(mid, tid, code)
       int mid;
       int tid;
       int code;
  {
       int t, c, cc;

       if ((cc = pvm_bufinfo(mid, (int*)0, &c, &t)) < 0)
	    return cc;

       if ((tid	= -1 || tid =	t) && (code = -1 || code = c))
	    foundit = 1;

       return 0;
  }

  int
  probe(src, code)
  {
       int (*omatch)();
       int cc;

       omatch =	pvm_recvf(foo_match);

       foundit = 0;

       if ((cc = pvm_nrecv(src,	code)) < 0)
	    return cc;

       pvm_recvf(omatch);

       return foundit;
  }

ERRORS
  No error conditions are returned by pvm_recvf

SEE ALSO
  pvm_recv(3PVM), pvm_nrecv(3PVM), pvm_probe(3PVM), pvm_trecv(3PVM)