Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422836AbXBAMjR (ORCPT ); Thu, 1 Feb 2007 07:39:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422838AbXBAMjR (ORCPT ); Thu, 1 Feb 2007 07:39:17 -0500 Received: from gockel.physik3.uni-rostock.de ([139.30.44.16]:9929 "EHLO gockel.physik3.uni-rostock.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422836AbXBAMjQ (ORCPT ); Thu, 1 Feb 2007 07:39:16 -0500 Date: Thu, 1 Feb 2007 13:39:15 +0100 (CET) From: Tim Schmielau To: David Howells cc: "Robert P. J. Day" , Linux kernel mailing list , Andrew Morton , Paul Mackerras , galak@kernel.crashing.org Subject: Re: [PATCH] Add "is_power_of_2" checking to log2.h. In-Reply-To: <3565.1170326639@redhat.com> Message-ID: References: <3565.1170326639@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 784 Lines: 23 On Thu, 1 Feb 2007, David Howells wrote: > Robert P. J. Day wrote: > > > +#define is_power_of_4(x) is_power_of_2(x) && (ffs(x) & 1)) > > If this is such a commonly implemented op, it should probably be implemented > globally too. > > I also wonder if there's some better way of implementing it than this, but I > can't think of one offhand. #define is_power_of_2_or_zero(x) ((x & (x-1))==0) #define is_power_of_4(x) (is_power_of_2_or_zero(x) \ && (x & ((typeof(x))0x55555555))) ? Tim - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/