new_pow2.c

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#include <sys/math.h>
 
uint64_t next_pow2(uint64_t n)
{
    if (n <= 1)
    {
        return 2;
    }
 
    if ((n > 0 && (n & (n - 1)) == 0))
    {
        return n;
    }
 
    n--;
    n |= n >> 1;
    n |= n >> 2;
    n |= n >> 4;
    n |= n >> 8;
    n |= n >> 16;
    n |= n >> 32;
    n++;
 
    if (n == 0)
    {
        return (UINT64_MAX >> 1) + 1;
    }
 
    return n;
}