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

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Message-ID: <alpine.LFD.2.00.0904251808320.4803@localhost.localdomain>
Date:	Sat, 25 Apr 2009 18:09:11 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Introduce a boolean "single_bit_set" function.

On Fri, 24 Apr 2009, Andrew Morton wrote:

> On Fri, 24 Apr 2009 06:40:39 -0400 (EDT) "Robert P. J. Day" <rpjday@...shcourse.ca> wrote:
>
> >   so it would be a simple matter to define the bit set boolean in
> > terms of hweight_long(), yes?  so what about, in bitops.h:
> >
> >   static inline bool
> >   exactly_one_bit_set(unsigned long w)
> >   {
> > 	return hweight_long(w) == 1;
> >   }
> >
> >   static inline bool
> >   more_than_one_bit_set(unsigned long w)
> >   {
> > 	return hweight_long(w) > 1;
> >   }
> >
> > or something to that effect, *if* people think it's worth it.
> > obviously, none of the above is strictly necessary, but it would make
> > a lot of code semantically cleaner.
> >
>
> Doing plain old
>
> 	if (hweight32(foo) == 1)
>
> (say) at the call sites quite clearly expresses what the code is trying
> to do.

  yes, that seems reasonable.  but would you really prefer "hweight32"
over "hweight_long"?

rday
--

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

        Linux Consulting, Training and Annoying Kernel Pedantry.

Web page:                                          http://crashcourse.ca
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