James Carlson <[EMAIL PROTECTED]> wrote:
> Garrett D'Amore writes:
> > I have macros like those above, yes. (Although in my code it looks more
> > like this:)
> >
> > #define BIT(x) (1UL << (x))
> > ...
> > #define MYMASK BIT(4)
>
> I'm surprised nobody's mentioned C structures with bit fields. I've
> used those to good effect on hardware in the past. (Yes, getting the
> access width right, particularly on writes, can be a pain on some
> devices.)
The C standard grants that these structures are not portable.....
All known C-compilers give a limited portability if you take care of declaring
them the right way.
- You need to use "unsigned char" as type unless you use the IBM
C-compiler
- You may not define them to have more bits than an int
- You take care of alignement
- You take care about Bit-ordering (this may be different from Byte-order
see Plan 9 compiler...)
Cdrecord uses bitfields for SCSI structures but as you see from above, you
definitely need autoconf to get the right definition for the current compile
platform.
Jörg
--
EMail:[EMAIL PROTECTED] (home) Jörg Schilling D-13353 Berlin
[EMAIL PROTECTED] (uni)
[EMAIL PROTECTED] (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
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