Messages in this thread | | | Date | Thu, 1 Feb 2007 22:55:49 +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, Valdis.Kletnieks@vt.edu wrote:
> On Thu, 01 Feb 2007 13:39:15 +0100, Tim Schmielau said: > > #define is_power_of_4(x) (is_power_of_2_or_zero(x) \ > > && (x & ((typeof(x))0x55555555))) > > Those 5's are going to need more magic if x is a 64-bit typeof?
Yeah, I can't count. Make that
#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))0x5555555555555555ull)))
of course.
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