//--BEGIN--pot.h--

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

#ifdef __GNUC__
unsigned ceilPowerOf2(unsigned x);
#else
unsigned __fastcall ceilPowerOf2(unsigned x);
#endif

#ifdef __GNUC__
unsigned floorPowerOf2(unsigned x);
#else
unsigned __fastcall floorPowerOf2(unsigned x);
#endif

//--END--pot.h--
 

//--BEGIN--pot.c--

// Returns the least power of 2 greater than or equal to "x".
// Note that for x=0 and for x>2147483648 this returns 0!
#ifdef __GNUC__
unsigned ceilPowerOf2(unsigned x) {
    unsigned eax;
    __asm__(
        "xor eax,eax\n"
        "dec ecx\n"
        "bsr ecx,ecx\n"
        "cmovz ecx,eax\n"
        "setnz al\n"
        "inc eax\n"
        "shl eax,cl\n"
        : "=a" (eax)
        : "c" (x)
    );
    return eax;
}
#else
__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
    }
}
#endif

// Returns the greatest power of 2 less than or equal to "x".
// Note that for x=0 this returns 0!
#ifdef __GNUC__
unsigned floorPowerOf2(unsigned x) {
    unsigned eax;
    __asm__(
        "xor eax,eax\n"
        "bsr ecx,ecx\n"
        "setnz al\n"
        "shl eax,cl\n"
        : "=a" (eax)
        : "c" (x)
    );
    return eax;
}
#else
__declspec(naked) unsigned __fastcall floorPowerOf2(unsigned x) {
    __asm {
        xor eax,eax
        bsr ecx,ecx
        setnz al
        shl eax,cl
        ret
    }
}
#endif

//--END--pot.c--