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From: dcl@ncsc1.ATT.COM (Dave Love)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Pointer Initialization
Message-ID: <717@ncsc1.ATT.COM>
Date: 27 Dec 90 17:14:45 GMT
References: <4241@mindlink.UUCP>
Organization: National Customer Support Center
Lines: 48

In article <4241@mindlink.UUCP> a976@mindlink.UUCP (Ron Tarrant) writes:
>> kzyx@vax5.cit.cornell.edu writes:
>>        What is the correct way to initialize a structure pointer to access
>> the hardware under ANSI (Aztec C 5.0d)
>>
>
>It's not a good idea to access the hardware directly. It means you have to
>update your code every time there is system software and makes it harder (if
>I'm not mistaken) to go from one Amiga model to another.
>
Agreed.

>>                struct myblitterstruct *myblitterpointer;
>> 
>
>This initializes your structure pointer. If you already have a structure of
>this type defined, that is. If you also have an actual
>structure of this type declared, then make your pointer point to it like this:
>
>        myblitterstruct = &OriginalBlitterStruct
>
>But when you point your pointer at something in the hardware you're asking for
>trouble. In fact, I'm not sure it can even be done.
>-Ron

To get to the hardware you need something like the following line
(assuming you want myblitterpointer to point to the actual blitter
registers):

	struct myblitterstruct *myblitterpointer = 
		(struct myblitterstruct *)(0x00000000L);

where 0x00000000 is replaced by the appropriate hardware address (Sorry,
I don't have my RKM's handy so I can't give the correct address).


DISCLAIMER:  Using techniques similar to this in production code
will probably result in the end of the world as we know it. :)
However, going straight to the hardware was, for me, the best way
to learn about the blitter.  Once I was comfortable with what the
blitter did (and why), it was fairly simple to find "approved" ways
to use it.

-- 
 Dave Love  
 UUCP: dcl@ncsc1.att.com  CI$: 75126,2223   bix: dlove  

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