linux-kernel - Re: [PATCH 3/4] lib: vsprintf: Optimize put_dec

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <xa1t4nmncw03.fsf@mina86.com>
Date:	Mon, 24 Sep 2012 16:53:48 +0200
From:	Michal Nazarewicz <mpn@...gle.com>
To:	George Spelvin <linux@...izon.com>, akpm@...ux-foundation.org,
	linux@...izon.com, rabin@....in
Cc:	hughd@...gle.com, linux-kernel@...r.kernel.org,
	vda.linux@...glemail.com
Subject: Re: [PATCH 3/4] lib: vsprintf: Optimize put_dec_trunc8

On Mon, Sep 24 2012, George Spelvin wrote:
> The fix is straightforward:
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index e755083..9872855 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -180,8 +180,6 @@ char *put_dec_trunc8(char *buf, unsigned r)
>  		*buf++ = q - 10*r;
>  	}
>  
> -	if (r == 0)
> -		return buf;
>  	q      = (r * 0x199a) >> 16;	/* r <= 9999 */
>  	*buf++ = (r - 10 * q)  + '0';
>  	if (q == 0)
>
> Inspired by Michal Nazarewicz, I have some ideas for more tweaking to
> that code.

Ah, right.  I also thought about that first but than started worrying
that it could produce unnecessary zeros if the loop iterates at least
once and exits with r being zero, but now I see that this cannot happen
since if the loop condition was true, r >= 10000 and it has been divided
by 10000 in the loop so now it's at least 1.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--

Content of type "application/pgp-signature" skipped