Messages in this thread |  | | Date | Thu, 1 Feb 2007 13:39:15 +0100 (CET) | From | Tim Schmielau <> | Subject | Re: [PATCH] Add "is_power_of_2" checking to log2.h. |
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On Thu, 1 Feb 2007, David Howells wrote: > Robert P. J. Day <rpjday@mindspring.com> 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)))
?
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