Function ReceiveFunctionCall

src/backend/utils/fmgr/fmgr.c:1588–1624

* Call a previously-looked-up datatype binary-input function. * * "buf" may be NULL to indicate we are reading a NULL. In this case * the caller should assume the result is NULL, but we'll call the receive * function anyway if it's not strict. So this is almost but not quite * the same as FunctionCall3. */

 * the same as FunctionCall3.
 */
Datum
ReceiveFunctionCall(FmgrInfo *flinfo, StringInfo buf,
					Oid typioparam, int32 typmod)
{
	LOCAL_FCINFO(fcinfo, 3);
	Datum		result;

	if (buf == NULL && flinfo->fn_strict)
		return (Datum) 0;		/* just return null result */

	InitFunctionCallInfoData(*fcinfo, flinfo, 3, InvalidOid, NULL, NULL);

	fcinfo->args[0].value = PointerGetDatum(buf);
	fcinfo->args[0].isnull = false;
	fcinfo->args[1].value = ObjectIdGetDatum(typioparam);
	fcinfo->args[1].isnull = false;
	fcinfo->args[2].value = Int32GetDatum(typmod);
	fcinfo->args[2].isnull = false;

	result = FunctionCallInvoke(fcinfo);

	/* Should get null result if and only if buf is NULL */
	if (buf == NULL)
	{
		if (!fcinfo->isnull)
			elog(ERROR, "receive function %u returned non-NULL",
				 flinfo->fn_oid);
	}
	else
	{
		if (fcinfo->isnull)
			elog(ERROR, "receive function %u returned NULL",
				 flinfo->fn_oid);
	}

	return result;
}

/*
 * Call a previously-looked-up datatype binary-output function.