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Date: Thu, 12 Feb 2009 10:16:39 +0100
From: Patrick McHardy <kaber@trash.net>
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To: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
CC: wli@movementarian.org, linux-kernel@vger.kernel.org,
       netdev@vger.kernel.org, netfilter-devel@vger.kernel.org,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH] Update jhash.h with the new version of Jenkins' hash
References: <alpine.DEB.2.00.0902111107480.15665@blackhole.kfki.hu> <20090212001223.GA5757@movementarian.org> <alpine.DEB.2.00.0902121006440.18739@blackhole.kfki.hu>
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Jozsef Kadlecsik wrote:
> -#define __jhash_mix(a, b, c) \
> +#define __rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
> +
> +/* __jhash_mix - mix 3 32-bit values reversibly. */
> +#define __jhash_mix(a,b,c) \
> +{ \
> +  a -= c;  a ^= __rot(c, 4);  c += b; \
> +  b -= a;  b ^= __rot(a, 6);  a += c; \
> +  c -= b;  c ^= __rot(b, 8);  b += a; \
> +  a -= c;  a ^= __rot(c,16);  c += b; \
> +  b -= a;  b ^= __rot(a,19);  a += c; \
> +  c -= b;  c ^= __rot(b, 4);  b += a; \
> +}

include/linux/bitops.h includes multiple rot variants. rol32()
looks approriate.