linux-kernel - Re: [PATCH] consolidate all within() implementations

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Message-ID: <OFC011E4F1.61EF5440-ONC1257450.0038CB52-C1257450.003A0375@de.ibm.com>
Date:	Wed, 21 May 2008 12:33:40 +0200
From:	Peter 1 Oberparleiter <Peter.Oberparleiter@...ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Harvey Harrison <harvey.harrison@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] consolidate all within() implementations

Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote on 21.05.2008 12:04:26:
> > +static inline int addr_within_len(const void *addr, const void 
*start,
> > +              size_t len)
> > +{
> > +   return ((unsigned long) addr >= (unsigned long) start) &&
> > +          ((unsigned long) addr < ((unsigned long) start + len));
> > +}
> 
> might be my braindamage, but I'd have written it like:
> 
> static inline int 
> addr_within_len(const void *addr, const void *start, size_t len)
> {
>    return (unsigned long)addr - (unsigned long)start < len;
> }

Definitely another way to put it. In my opinion the intention of the
implementation is more easily understood though when spelling it out
as (a>=b) && (a<c).

> static inline int
> addr_within(const void *add, const void *start, const void *end)
> {
>    return addr_within_len(addr, start, 
>          (unsigned long)end - (unsigned long)start);
> }

For empty ranges (start > end), this produces different (less expected)
results than the previous version.


Regards,
  Peter
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