From: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
To: Jan Engelhardt <jengelh@inai.de>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
linux-kernel@vger.kernel.org, Jim Rees <rees@umich.edu>
Subject: Re: [PATCH] strings: helper for maximum decimal encoding of an unsigned integer
Date: Fri, 14 Sep 2012 11:17:54 +0200 [thread overview]
Message-ID: <1347614276.26071.15.camel@thorin> (raw)
In-Reply-To: <alpine.LNX.2.01.1209100803060.22738@frira.zrqbmnf.qr>
On Mon, 2012-09-10 at 08:19 +0200, Jan Engelhardt wrote:
> On Tuesday 2012-08-21 23:29, J. Bruce Fields wrote:
[...]
> >+/*
> >+ * length of the decimal representation of an unsigned integer. Just an
> >+ * approximation, but it's right for types of size 1 to 36 bytes:
> >+ */
> >+#define base10len(i) (sizeof(i) * 24 / 10 + 1)
>
> gcc provides... "interesting" features at times.
>
> /* for unsigned "i"s */
> #define base10len(i) ((const int[]){1,3,5,8,10,13,15,17,20}[i])
Shouldn't that have been
---- snip ----
#define base10len(i) ((const int[]){1,3,5,8,10,13,15,17,20}[sizeof(i)])
---- snip ----
?
A pure K&R-C version would use a string:
---- snip ----
#define base10len(i) "\0x1\0x3\0x5\0x8\0x0A\0x0D\0x0F\0x11\0x14"[sizeof(i)]
---- snip ----
(if I converted them properly into hexadecimal) and that gives a "char"
which is happily promoted to whatever one needs in that place.
Kind regards,
Bernd
--
Bernd Petrovitsch Email : bernd@petrovitsch.priv.at
LUGA : http://www.luga.at
next prev parent reply other threads:[~2012-09-14 9:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 21:29 [PATCH] strings: helper for maximum decimal encoding of an unsigned integer J. Bruce Fields
2012-08-21 21:22 ` Jim Rees
2012-08-21 22:06 ` Al Viro
2012-08-21 22:19 ` J. Bruce Fields
2012-08-22 0:03 ` Jim Rees
2012-09-10 6:19 ` Jan Engelhardt
2012-09-14 9:17 ` Bernd Petrovitsch [this message]
2012-09-14 12:30 ` Jim Rees
2012-09-14 13:14 ` J. Bruce Fields
2012-09-14 13:18 ` Bernd Petrovitsch
2012-09-14 13:51 ` Jim Rees
2012-09-14 13:37 ` Jan Engelhardt
2012-09-14 13:54 ` Jim Rees
2012-09-14 12:59 ` Jan Engelhardt
2012-09-14 13:46 ` Jim Rees
2012-09-14 14:25 ` Jan Engelhardt
2012-09-14 15:00 ` Bernd Petrovitsch
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