From: hat AT se-46 DOT wpa DOT wtb DOT tue DOT nl ()
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Unions...
Date: 26 May 1998 14:57:45 GMT
Organization: Eindhoven University of Technology, The Netherlands
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References: <6keg38$mia$1 AT infa DOT central DOT susx DOT ac DOT uk>
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[Posted and mailed]

In article <6keg38$mia$1 AT infa DOT central DOT susx DOT ac DOT uk>,
	andrewda AT cogs DOT susx DOT ac DOT uk (Andrew Smythe Davidson) writes:
> Basically I'm looing for a way to create a structure full of registers, some
> of which are 16bit, some 8 bit, and some either 8 or 16. Rather than have to
> access it in a regs.?.? way like Union REGS regs would give me I'd like to be
> able to refer to the 8/16 bit registers either as, for example, regs.a or
> regs.ah/regs.al. Is there anyway of doing this without introducing an extra
> level into the structure?

Yes, just #define the double regs reference to a single reference.

So if you want to access regs.a[0] as regs.al, just define

#define al a[0]

(and don't use al anywhere else).

BTW, by using unions in this way you assume a certain memory layout
which is neither portable across different compilers, nor across platforms.

IMHO you'd better think a bit more, and come up with a data structure
which is portable. At least you can then assume that the code might work
on the next version of DJGPP.


Albert
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