Bit rotation question/challenge

[Afgdr]

On Saturday, 30 January 2021 at 13:30:49 UTC, burt wrote:
> I have a static array of `ubyte`s of arbitrary size:
>
> ```d
> ubyte[4] x = [ // in reality, ubyte[64]
>     0b00001000,
>     0b00000001,
>     0b00010101,
>     0b11110010,
> ];
> ```
>
> Now I want to bit-rotate the array as if it is one big integer. 
> So:
>
> ```d
> ubyte[n] rotateRight(size_t n)(ref const ubyte[n] array, uint 
> rotation)
> {
>     // ?
> }
> // same for rotateLeft
>
> ubyte[4] y = [
>     0b11111001,
>     0b00000100,
>     0b00000000,
>     0b10001010,
> ];
> assert(x.rotateRight(9) == y);
> assert(y.rotateLeft(9) == x);
> ```
>
> Any ideas how this could be achieved? I.e. what should go at 
> the "?" for rotateRight and rotateLeft?

cast as uint and shift. cast the result as ubyte[4].