fn i_from_slice<T>(slice: &[u8]) -> Option<T>
{
    let n = std::mem::size_of::<T>();
    if slice.len() == n {
        let mut buf = vec![0; n];
        buf.copy_from_slice(slice);
        Some(unsafe { std::mem::transmute_copy(&buf) })
    } else {
        None
    }
}

fn main() {
    let x = [0xFF,0xFF]; // should transmute to be 65535
    println!("{:?}", i_from_slice::<u16>(&x));
}