Path: utzoo!mnetor!uunet!husc6!im4u!ut-sally!utah-cs!thomson
From: thomson@utah-cs.UUCP (Richard A Thomson)
Newsgroups: comp.sys.amiga.tech
Subject: Re: WaitPort, GetMsg, ReplyMsg
Message-ID: <5417@utah-cs.UUCP>
Date: 19 Apr 88 05:37:09 GMT
References: <8804182050.AA15158@cory.Berkeley.EDU>
Reply-To: thomson@cs.utah.edu.UUCP (Richard A Thomson)
Organization: University of Utah CS Dept
Lines: 38

In article <8804182050.AA15158@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:
>:In article <GumbyFooArticleNumber> I (Richard Thomson) wrote:
>:This tells me that after the WaitPort call, message will point to the
>:first message in the list.  The funny thing is that when I do a GetMsg(port)
>:I get a different address, although it also is listed as returning a pointer
>:to the first message in the port's message list.  What's going on here?
>
>	WaitPort() does NOT remove the message from the port.  you should
>NEVER ReplyMsg() without GetMsg() it first.  I.E.:
>
>	WaitPort(port);
>	message = GetMsg(port);
> 	code = message->Code;
> 	class = message->Class;
> 	ReplyMsg(message);
>
>					-Matt

The part about WaitPort not removing the message is clear and Matt's above
example is what I used, although it actually looks like this:

    [ FORTHer's version ]		[ C hack's version :-]
    port GetMsg ?DUP 0= IF		if ((message = GetMsg(port)) == 0) {
	port WaitPort DROP		    WaitPort(port);
	port GetMsg THEN		    message = GetMsg(port); }
    DUP +imCode MsgCode !		MsgCode = message->Code;
    DUP +imClass @			class = message->Class;
    SWAP ReplyMsg			ReplyMsg(message);

My question still remains unanswered, though.  The documentation for WaitPort
and GetMsg says that they both "return a pointer to the first message", but
they return different pointers!

					-- Rich Thomson
-- 
					-- Rich
Richard Thomson		3190 MEB, University of Utah, Salt Lake City, UT 84112
thomson@cs.utah.edu	(801) 584-4555: Talk to a machine, they're lonely.