transmute_vec.rs

unsafe fn transmute_vec<T, U>(vec: Vec<T>) -> Vec<U> {
    use std::mem;
    let ratio = mem::size_of::<T>() / mem::size_of::<U>();

    let length = vec.len() * ratio;
    let capacity = vec.capacity() * ratio;
    let ptr = vec.as_ptr();

    mem::forget(vec);
    Vec::from_raw_parts(ptr as *mut U, length, capacity)
}