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From: efp90@ecs.soton.ac.uk (Pritchard EF)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Question on AbortIO() and WaitIO()
Message-ID: <7753@ecs.soton.ac.uk>
Date: 21 May 91 11:49:49 GMT
References: <28630@uflorida.cis.ufl.EDU>
Sender: news@ecs.soton.ac.uk
Lines: 61

leh@otter.cis.ufl.edu (Les Hill) writes:

>I have run into a situation which is not clearly documented (to me anyways) in the
>RKM's (v1.2 ?).  Below I have included the relevant fragments of code:
>...
>   struct MsgPort *read_port, *write_port;
>   struct IOExtSer *read_req, *write_req;
>...
>   BYTE dev_error;
>   struct Message *read_msg;
>...
>   /* Clean up */
>   if (!CheckIO(read_req)) {
>      AbortIO(read_req);
>      if (dev_error = WaitIO(read_req)) {
>         printf("Error waiting for aborted read -- %d\n", dev_error);
>         goto cleanup_8;
>      }
>      read_msg = GetMsg(read_port); // not necessary?
>   }
>...

>The situation is this: a CMD_READ request *should* be queued at the device
>(the CheckIO() should confirm this), the CMD_READ request is then aborted and
>a WaitIO() follows as recommended in the RKMs; the WaitIO() returns a -2
>(aborted request.)

>The question that comes to mind is: does WaitIO() dequeue the reply at 
>read_port (read_port is the reply port for read_req) regardless of the error?
>Additionally, do I need the GetMsg()?


Look in the Revised and Updated RKM Libraries and Devices, page 292
under AbortIO(), it states that:

The AbortIO() command may fail; if it succeeds, the device will stop
processing the IORequest, and 
** reply to it earlier than it may have done otherwise. AbortIO() does not  
** remove the IORequest from your replyport... your program must wait for the
** reply message before actually reusing the IORequest...
** If a request has already completed... no action is taken.

So YES, GetMsg() is required
Hope that helps!

>Thanks in advance,

>Les
>-- 
>Extraordinary crimes against the people and the state have to be avenged by
>agents extraordinary.  Two such people are John Steed -- top professional, and
>his partner, Emma Peel -- talented amateur; otherwise known as "The Avengers."
>INTERNET: leh@ufl.edu  UUCP: ...!gatech!uflorida!leh  BITNET: vishnu@UFPINE

E.F.Pritchard.
efp90@uk.ac.soton.ecs
Department of Computer Science,
Southampton University,
Southampton,
Hampshire,
England.