Function sort_with_buffer_by_key 

pub fn sort_with_buffer_by_key<T, F: FnMut(&T) -> K, K: Ord>(
    v: &mut [T],
    buffer: &mut [MaybeUninit<T>],
    f: F,
)

Like sort_by_key, except this function does not allocate and uses the passed buffer instead.