Crate thunderdome

Thunderdome is a ~gladitorial~ generational arena inspired by generational-arena, slotmap, and slab. It provides constant time insertion, lookup, and removal via small (8 byte) keys returned from Arena.

Thunderdome's key type, Index, is still 8 bytes when put inside of an Option<T> thanks to Rust's NonZero* types.

Basic Examples

let mut arena = Arena::new();

let foo = arena.insert("Foo");
let bar = arena.insert("Bar");

assert_eq!(arena[foo], "Foo");
assert_eq!(arena[bar], "Bar");

arena[bar] = "Replaced";
assert_eq!(arena[bar], "Replaced");

let foo_value = arena.remove(foo);
assert_eq!(foo_value, Some("Foo"));

// The slot previously used by foo will be reused for baz
let baz = arena.insert("Baz");
assert_eq!(arena[baz], "Baz");

// foo is no longer a valid key
assert_eq!(arena.get(foo), None);

Comparison With Similar Crates

Feature	Thunderdome	generational-arena	slotmap	slab
Generational Indices¹	Yes	Yes	Yes	No
size_of::<Index>()	8	16	8	8
size_of::<Option<Index>>()	8	24	8	16
Max Elements	2³²	2⁶⁴	2³²	2⁶⁴
Non-Copy Values	Yes	Yes	Sorta²	Yes
no_std Support	No	Yes	No	No
Serde Support	No	Yes	Yes	No

• Sizes calculated on rustc 1.44.0-x86_64-pc-windows-msvc
• See the Thunderdome comparison Cargo.toml for versions of each library tested.

1. Generational indices help solve the ABA Problem, which can cause dangling keys to mistakenly access newly-inserted data.
2. slotmap's SlotMap and HopSlotMap require values to be Copy on stable Rust versions. slotmap's DenseSlotMap type supports non-Copy types on stable, but has different performance trade-offs.

Minimum Supported Rust Version (MSRV)

Thunderdome supports Rust 1.34.1 and newer. Until Thunderdome reaches 1.0, changes to the MSRV will require major version bumps. After 1.0, MSRV changes will only require minor version bumps, but will need significant justification.

Structs

Arena	Container that can have elements inserted into it and removed from it.
Drain	See Arena::drain.
Index	Index type for Arena that has a generation attached to it.