Dense and Sparse vector for faster O(1) lookup, insert and removal (no order)

dense.rs

#[derive(Debug)]
pub struct DenseVecStorage<T>
where
    T: Component,
{
    components: Vec<T>,
    entity_ids: Vec<usize>,
    component_ids: Vec<usize>,
}

impl<T> DenseVecStorage<T>
where
    T: Component,
{
    fn new() -> Self {
        DenseVecStorage {
            components: Vec::new(),
            entity_ids: Vec::new(),
            component_ids: Vec::new(),
        }
    }

    unsafe fn get(&self, id: &usize) -> &T {
        let component_id = self.component_ids.get_unchecked(*id);
        self.components.get_unchecked(*component_id)
    }

    unsafe fn get_mut(&mut self, id: &usize) -> &mut T {
        let component_id = self.component_ids.get_unchecked(*id);
        self.components.get_unchecked_mut(*component_id)
    }

    unsafe fn insert(&mut self, id: &usize, component: T) {
        let id = *id;
        if self.component_ids.len() <= id {
            let delta = id + 1 - self.component_ids.len();
            self.component_ids.reserve(delta);
            self.component_ids.set_len(id + 1);
        }
        *self.component_ids.get_unchecked_mut(id) = self.components.len();
        self.entity_ids.push(id);
        self.components.push(component);
    }

    // . We swap the element to be removed with the element at the end of the list, then pop that element off the end:
    unsafe fn remove(&mut self, id: &usize) -> T {
        let id = *id;
        let component_id = *self.component_ids.get_unchecked(id);
        let last = *self.entity_ids.last().unwrap();
        *self.component_ids.get_unchecked_mut(last) = component_id;
        self.entity_ids.swap_remove(component_id);
        self.components.swap_remove(component_id)
    }
}