Force insert at a given key

[james7132]

Is it possible to forcibly insert a value at a given key? Either by allocating up to a given key, inserting into a vacant entry, or evicting a already occupied one. I'm in a situation where I need to keep multiple slabs and keep the same key between all of them. Would the bookkeeping make this prohibitively expensive?

[Darksonn]

The cost of that would be linear time. The slab stores the list of unused indexes by threading a linked list through the slab. Removing something from that linked list requires traversing the entire linked list to find the position that comes before it.

[Ralith]

An alternative solution to this pattern is to have one slab, used to determine the index and maintain a freelist, and maintain Vec<Option<T>>s on the side that share the same indexes.