Утилитный функции по работе с числами степени двойки

inline bool isPowerOf2(unsigned x) {
    if (x<1) return false;
    return (x&(x-1))==0;
}

// Returns the least power of 2 greater than or equal to "x".
// Note that for x=0 and for x>2147483648 this returns 0!
__declspec(naked) unsigned __fastcall ceilPowerOf2(unsigned x) {
    __asm {
        xor eax,eax
        dec ecx
        bsr ecx,ecx
        cmovz ecx,eax
        setnz al
        inc eax
        shl eax,cl
        ret
    }
}

// Returns the greatest power of 2 less than or equal to "x".
// Note that for x=0 this returns 0!
__declspec(naked) unsigned __fastcall floorPowerOf2(unsigned x) {
    __asm {
        xor eax,eax
        bsr ecx,ecx
        setnz al
        shl eax,cl
        ret
    }
}