linux-kernel - Re: [PATCH] Introduce a boolean "single_bit

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Message-ID: <alpine.LFD.2.00.0905280830150.31093@localhost.localdomain>
Date:	Thu, 28 May 2009 08:32:07 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Petr Tesarik <ptesarik@...e.cz>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] Introduce a boolean "single_bit_set" function.

On Thu, 28 May 2009, Petr Tesarik wrote:

> Robert P. J. Day píše v Čt 23. 04. 2009 v 13:43 -0400:
> > A boolean single_bit_set() routine would simplify the numerous
> > constructs of the form (((n & (n - 1)) == 0)) when testing for
> > single-bitness.
> >
> > Signed-off-by: Robert P. J. Day <rpjday@...shcourse.ca>
> >
> > ---
> >
> > This is similar to the current is_power_of_2() routine defined in
> > include/linux/log2.h, which is mathematically identical but,
> > semantically, should be defined independently just so the code is more
> > readable.
> >
> > I'm open to an alternative function name.
>
> ispow2() ?
>
> Because what it really does is to check that a value is a power of two,
> doesn'it.

  by the way, a search for places in the code that are candidates for
this kind of rewriting can be seen at one of my wiki kernel cleanup
pages:

  http://www.crashcourse.ca/wiki/index.php/The_style_script

scroll down, you'll see a section entitled "Testing for power of 2 or
a single bit set".  lots of potential for clarification if people
think it's worth it.

rday
--

========================================================================
Robert P. J. Day                               Waterloo, Ontario, CANADA

        Linux Consulting, Training and Annoying Kernel Pedantry.

Web page:                                          http://crashcourse.ca
Linked In:                             http://www.linkedin.com/in/rpjday
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