Date: Wed, 7 Feb 2007 11:25:49 +0100 (CET) From: "Stefan Bethke" <stb@lassitu.de> To: "Luigi Rizzo" <rizzo@icir.org> Cc: current@freebsd.org Subject: Re: C macro to find the next power of 2 ? Message-ID: <15241.SV0BLFJbGwk=.1170843949.squirrel@koef.zs64.net> In-Reply-To: <20070207004131.A62183@xorpc.icir.org> References: <20070207004131.A62183@xorpc.icir.org>
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On Wed, February 7, 2007 09:41, Luigi Rizzo wrote:
> My problem is that some hardware wants data structures aligned to
> the next power of 2 with respect to their size, and the code
> in question (the ehci driver in case you care) has hardwired
> constants for this, and possibly wrong ones.
>
> It would be nice if one could write
>
> struct foo_desc {
> ...
> };
>
> #define FOO_ALIGN next_power_of_2(sizeof(struct foo_desc))
>
> instead of having to count fields and make guesses on the size
> of pointers and so on.
_Hacker's Delight_ contains many cool tricks, including multiple solutions
for this, IIRC. I'll have a look tonight when I'm back home.
Cheers,
Stefan
--
Stefan Bethke <stb@lassitu.de> +49 170 3460140
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