Riddance provides the Registry container, which stores objects and issues unique IDs for them, also known as a "slot map" or an "arena". Features include:

• New IDs can be "reserved" atomically, without locking the Registry. See reserve_id and reserve_ids.
• When the generation of a slot reaches its maximum, the slot is "retired" instead of allowing the generation to roll over to zero. This prevents logic errors from colliding IDs.
• The default [Id] type is 64 bits, but callers that need smallers IDs can use Id32, which has a configurable number of generation bits.
• The recycle_retired method makes it possible to reuse previously retired slots, though it can introduce logic errors if you violate its contract. It's mainly intended for callers who use Id32.
• By default ID types incorporate the T type parameter of the Registry that created them, to avoid confusing IDs from different registries.

Example

use riddance::{Id, Registry};

struct Person {
    name: String,
    friends: Vec<Id<Person>>,
}

let mut people = Registry::new();
let alice_id = people.insert(Person { name: "Alice".into(), friends: vec![] });
let bob_id = people.insert(Person { name: "Bob".into(), friends: vec![] });
people[alice_id].friends.push(bob_id);
people[bob_id].friends.push(alice_id);

people.remove(bob_id);
assert!(people.get(alice_id).is_some());
assert!(people.get(bob_id).is_none());