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From: bj@cbmvax.commodore.com (Brian Jackson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Question on AbortIO() and WaitIO()
Message-ID: <21785@cbmvax.commodore.com>
Date: 22 May 91 03:07:56 GMT
References: <28630@uflorida.cis.ufl.EDU> <7753@ecs.soton.ac.uk>
Reply-To: bj@cbmvax.commodore.com (Brian Jackson)
Organization: Commodore, West Chester, PA
Lines: 58

In article <7753@ecs.soton.ac.uk> efp90@ecs.soton.ac.uk (Pritchard EF) writes:
>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!

The GetMsg() is *not* required. He is (properly) doing a WaitIO()
after the AbortIO() call and WaitIO() *does* remove the message.

>E.F.Pritchard.

Brian

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 | Brian Jackson  Software Engineer, Commodore-Amiga Inc.  GEnie: B.J. |
 | bj@cbmvax.cbm.commodore.com    or  ...{uunet|rutgers}!cbmvax!bj     |
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