Bit Shifting in Place [closed]

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I was just wondering if there was a way to bit shift a number "in place"? I've googled exactly that, and I can't find anything that pertains to what I want to do. Say I have the number 0b01001101, and I want to shift it twice to the right "in place", appending any numbers that fall off to the beginning. So it would look like 0b01010011. Is there any function in c++ that would allow me to bit shift left or right like that?

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You want to implement a rotational shift

Here's a templatized version that should work with all types of ints (including shorts, chars, ints, and unsigned/signed alike).

template<class T>
T rotate_shift_right(T x, int shift)
{
    if ((shift > 0) && (shift < (sizeof(x)*8)))
    {
        x = ((unsigned)x >> shift) | (x << (sizeof(x) * 8 - shift));
    }
    return x;
}

template<class T>
T rotate_shift_left(T x, int shift)
{
    if ((shift > 0) && (shift < (sizeof(x)*8)))
    {
        x = (x << shift) | (((unsigned)x) >> (sizeof(x) * 8 - shift));
    }
    return x;
}

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Write one yourself, I think it's not hard.

First store the right two bits,and then do the bit shift.Finally fill the left two bits with the stored bits.

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Using the assembly instruction ror and getting the carry flag's value each time should do the work.

int rotate(int x, int n)
{
    for(int i = 0; i < n; i++) {
        __asm {
            ror   x, 1            ; rotate and store limit bit in cf
            lahf                  ; get part of flags in ah
            and   ah, 1           ; get only the cf
            shl   eax, 31         ; put it at the end
            and   x, eax          ; and store in x
        }
    }

    return x;
}

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I think shifting it and then anding the last byte onto the beginning should work.

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No, you should create your custom one

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This is implemented as vendor-specific extensions. For MSVC, you can use _rotl8, _rotl16 (or _rotr* for rotating to the right). Not sure about GCC, but you can always drop to assembly and use the rol or ror.