RE: [Gm2] two versions of DeviceTablePtrValue

[Martin Kalbfuß]

I only need one did for all channels of my module? I thought every
channel needs its own did.

Am Samstag, den 05.06.2010, 10:04 -0400 schrieb Breeden, Thomas (tmb):
> Yes, the "CAST(IOLink.DeviceTablePtr, cid)" does not look so good.
> 
> Using "IOLink.DeviceTablePtrValue (cid, MyDid)" to get the pointer should not 
> be
> a problem in your custom stream implementation, since your module is the
> one that does the "IOLink.AllocateDeviceId (MyDid)" on initialization, and 
> knows
> what the value of MyDid is.
> 
> However, I don't see how one could implement IOChan procedures without
> using the CAST(), since something like IOChan's 
>  PROCEDURE RawWrite(cid:ChanId; from:ADDRESS; locsToWrite:CARDINAL);
> does not have the DeviceId associated with the passed ChanId.
> 
> If seems like it must assume that the ChanId is the DeviceTablePtr in order 
> to find the
> correct device callback routine:
>     did := CAST(IOLink.DeviceTablePtr, cid);
>     did^.doRawWrite(did, from, locsToWrite);
> 
> I suspect that Rick Sutcliffe would be the best person to explain the 
> architecture
> here.
> 
> regards,
> 
> Tom
> address@hidden
> 
> > From: gm2-bounces On Behalf Of Martin Kalbfuß address@hidden
> > Sent: Saturday, June 05, 2010 7:30 AM
> > To: GNU Modula-2
> > Subject: Re: [Gm2] two versions of DeviceTablePtrValue
> >
> > I still wonder how to implement your own channel the right way. There's
> > no ISO conform way. to obtain the did out of the cid, because
> > DeviceTablePtrValue needs the did as parameter.
> >
> > To implement an open/close pair for your custom stream like
> >
> > OpenMyChannel(VAR cid : IOChan.ChanId);
> > CloseMyCannel(VAR cid : IOChan.ChanId);
> > 
> > you have to store the did externally in an array or something similar.
> > Do you think that's the right way to do it?
> 
> > From: gm2-bounces On Behalf Of Martin Kalbfuß address@hidden
> > Sent: Friday, June 04, 2010 6:32 PM
> > To: GNU Modula-2
> > Subject: RE: [Gm2] iso streams
> > 
> > Many thanks,
> > 
> > I wonder, that there's no default implementation of
> > such a stream.
> > 
> > I had a look at your code. I've seen, that you did a cast
> > 
>  > p := SYSTEM.CAST(IOLink.DeviceTablePtr, cid);
> > 
> > Is this standard conform? There is a function to get the table.
> 
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