linux-kernel - Re: [PATCH] strings: helper for maximum decimal encoding of an unsigned integer

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Message-ID: <20120821221908.GD19185@fieldses.org>
Date:	Tue, 21 Aug 2012 18:19:08 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Jim Rees <rees@...ch.edu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] strings: helper for maximum decimal encoding of an
 unsigned integer

On Tue, Aug 21, 2012 at 11:06:13PM +0100, Al Viro wrote:
> On Tue, Aug 21, 2012 at 05:22:27PM -0400, Jim Rees wrote:
> > J. Bruce Fields wrote:
> > 
> >   From: "J. Bruce Fields" <bfields@...hat.com>
> >   
> >   I've seen a couple examples recently where we've gotten this wrong.
> >   Maybe something like this would help?  Is there some better way?
> >   
> >   (Approximation due to Jim Rees).
> > 
> > Please add Suggested-by: Jim Rees <rees@...ch.edu>.  I'm thinking of
> > patenting the algorithm.
> 
> Is that a joke?  Patenting the fact that log10(256) is 2.408..., which
> is about 2.4, which is 24/10?  I really hope we are Poe'd...  BTW, NAK
> the comment - s/36/26/ in there; check it yourself -
> $ echo '2^(8*27)' | bc
> 105312291668557186697918027683670432318895095400549111254310977536
> which is 66-digit, not 65 as the estimate would be.

Erp, you're right.

Anyway, does something like base10len(type) seem reasonable?  Or define
macros that enumerate the sizes?  (ULONG_STR_MAX or something?)

--b.
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