fast_log_2

#include <stdio.h>
int fast_log_2(int x)
{
    float f;
    unsigned long d, ex;
    f = (float)x;
    d = *(unsigned long *)&f;
    ex = (d>>23) & 0xFF;
    return ex - 127;
    
}
int main(void) {
    printf("Hello World! %d\n", fast_log_2(255));
    return 0;
}