From: Ian Molton <spyro@armlinux.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] hex <-> int conversion routines.
Date: Sat, 23 Feb 2002 02:30:07 +0000 [thread overview]
Message-ID: <20020223023007.7e929392.spyro@armlinux.org> (raw)
In-Reply-To: <a4ucfg$tfa$1@cesium.transmeta.com>
In-Reply-To: <02021919493204.00447@jakob> <200202191902.g1JJ2wx28246@frodo.gams.co.at> <a4ucfg$tfa$1@cesium.transmeta.com>
On a sunny 19 Feb 2002 12:27:28 -0800 H. Peter Anvin gathered a sheaf of
electrons and etched in their motions the following immortal words:
> extern const char inthex_digits[];
> static __inline__ char inthex_nybble(int x)
> {
> return inthex_digits[x & 15];
> }
What about the following? It maintains the exact behaviour of the original,
but can be smaller if it doesnt have to deal with >15 in the input (then it
wont need the x &= 0x0f).
It would be 3 cycles for <10 and 4 for >=10 on ARM. I'd imagine this would
be a little quicker than a load from memory as in the above example.
plus it doesnt waste 16 bytes of RAM in a lookup table.
static inline char inthex_nybble(int x){
x &= 0x0f;
return x<10?x^48:x+87;
}
Just a thought...
next prev parent reply other threads:[~2002-02-23 2:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-19 15:39 [PATCH] hex <-> int conversion routines Jakob Kemi
2002-02-19 15:52 ` Martin Dalecki
2002-02-19 18:49 ` Jakob Kemi
2002-02-19 19:02 ` Bernd Petrovitsch
2002-02-19 20:27 ` H. Peter Anvin
2002-02-23 2:30 ` Ian Molton [this message]
2002-02-19 19:04 ` H. Peter Anvin
2002-02-20 10:25 ` Martin Dalecki
2002-02-19 16:51 ` Richard B. Johnson
2002-02-19 18:02 ` Linus Torvalds
2002-02-19 20:29 ` george anzinger
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