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Date: Wed, 7 Feb 2007 11:25:49 +0100 (CET)
From: "Stefan Bethke" <stb@lassitu.de>
To: "Luigi Rizzo" <rizzo@icir.org>
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Cc: current@freebsd.org
Subject: Re: C macro to find the next power of 2 ?
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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