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Date: Sat, 23 Feb 2002 02:30:07 +0000
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.
Message-Id: <20020223023007.7e929392.spyro@armlinux.org>
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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...
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