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Date: Wed, 19 Feb 2003 09:27:02 -0800
From: Tim Kientzle <kientzle@acm.org>
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To: Dag-Erling Smorgrav <des@ofug.org>
Cc: phk@phk.freebsd.dk, Paul Herman <pherman@frenchfries.net>,
	Peter Jeremy <peterjeremy@optushome.com.au>,
	FreeBSD Hackers <hackers@FreeBSD.ORG>
Subject: Re: arc4random() range
References: <86890.1045646060@critter.freebsd.dk> <xzpsmukwqqb.fsf@flood.ping.uio.no>
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Dag-Erling Smorgrav wrote:

> phk@phk.freebsd.dk writes:
> 
>>Well, I'm right in principle but wrong in current practice, at
>>the very least make it:
>>
>>#define arc4random31()   (arc4random() & RAND_MAX)
>>
> 
> or rather
> 
> #define arc4random31()   (arc4random() % (RAND_MAX + 1))
> 
> to avoid relying on RAND_MAX being one less than a power of two.
> 
> DES
> 


Nope.  Because RAND_MAX is one less than a power of two,
you run into integer overflow problems, which PHK's
version avoids.


Tim Kientzle


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