netdev - Re: [PATCH] Update jhash.h with the new version of Jenkins' hash

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Date:	Thu, 12 Feb 2009 00:23:35 +0100
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] Update jhash.h with the new version of Jenkins' hash

On Wed, Feb 11, 2009 at 11:50:38PM +0100, Jozsef Kadlecsik wrote:
> On Wed, 11 Feb 2009, Micha? Miros?aw wrote:
> > On Wed, Feb 11, 2009 at 11:19:20AM +0100, Jozsef Kadlecsik wrote:
> > >  /* The golden ration: an arbitrary value */
> > > -#define JHASH_GOLDEN_RATIO	0x9e3779b9
> > > +#define JHASH_GOLDEN_RATIO	0xdeadbeef
> > I have a stupid question: if this is arbitrary value, then why not
> > just get rid of it (IOW use zero as it's used in addition)?
> lookup3() is a quite generic hash function and it supports 0-byte strings 
> as input keys too. If the input key is a 0-byte string and the arbitrary 
> value is zero, then the hash value simply equal to the initval. In order 
> to avoid that case, the arbitrary value must be nonzero.

Double-hashing, of course! I really need more sleep. Sorry for the noise. :>

Best Regards,
Michał Mirosław

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