twidbits.h File Reference

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Functions
FORCEINLINE ULONG	CountNumberOfBits (_In_ UINT32 n)
	Return the number of bits set in a 32-bit integer.

Function Documentation

CountNumberOfBits()

FORCEINLINE ULONG CountNumberOfBits

(

_In_ UINT32

n

)

Return the number of bits set in a 32-bit integer.

Note

Equivalent to __popcnt().

Definition at line 22 of file twidbits.h.

{
#ifdef HAVE___BUILTIN_POPCOUNT
    return __popcnt(n);
#else
    n -= ((n >> 1) & 0x55555555);
    n =  (((n >> 2) & 0x33333333) + (n & 0x33333333));
#if 0
    n =  (((n >> 4) + n) & 0x0f0f0f0f);
    n += (n >> 8);
    n += (n >> 16);
    return (n & 0x3f);
#else
    return (((n >> 4) + n) & 0x0f0f0f0f) * 0x01010101 >> 24;
#endif
#endif /* HAVE___BUILTIN_POPCOUNT */
}

Referenced by PixelBitmasksToBpp().