arrayref::array_mut_ref!

macro_rules! array_mut_ref {
    ($arr:expr, $offset:expr, $len:expr) => {{
        {
            #[inline]
            unsafe fn as_array<T>(slice: &mut[T]) -> &mut[T; $len] {
                &mut *(slice.as_mut_ptr() as *mut [_; $len])
            }
            let slice = &mut $arr[$offset..$offset+$len];
            unsafe {
                as_array(slice)
            }
        }
    }}
}

You can use array_mut_ref to generate a mutable array reference to a subset of a sliceable bit of data (which could be an array, or a slice, or a Vec).