arena-lib 0.2.0

Typed memory arena and slab allocator library. Generational indices, typed arenas (one allocation per type), interned strings, and bump allocation. Zero unsafe leakage into user code.
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    55 out of 55 items documented8 out of 48 items with examples
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  • Source code size: 138.8 kB This is the summed size of all the files inside the crates.io package for this release.
  • Documentation size: 1.54 MB This is the summed size of all files generated by rustdoc for all configured targets
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  • this release: 4s Average build duration of successful builds.
  • all releases: 4s Average build duration of successful builds in releases after 2024-10-23.
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  • jamesgober

Why arena-lib

Allocator-aware Rust normally means juggling three or four crates: one for slab storage, one for handle stability, one for string interning, plus a bump arena for short-lived scratch. arena-lib collects those primitives behind a single, safe, REPS-disciplined surface so you can move fast without paying for it later.

Designed around four guarantees:

  • Typed arenas — one backing allocation per element type, predictable layout, cache-friendly traversal.
  • Generational indices — stable handles that catch use-after-free without reference counting.
  • String interning — O(1) equality and compact storage for repeated identifiers.
  • Bump allocation — short-lived scratch regions that reset in constant time.

Every public path is safe Rust. unsafe lives only in measured, documented internals — never in your call sites.

Status: v0.2.0 (Foundation). The four core primitives — generational arena, string interner, bump arena, and the shared Error type — are live and tested. The 1.0 contract is in place; the 0.5 milestone tunes hot paths and grows the bump arena to multi-chunk.

Quick start

Add the crate to your Cargo.toml:

[dependencies]
arena-lib = "0.2"

End-to-end use of every primitive:

use arena_lib::prelude::*;

fn main() {
    // Generational arena — stable handles, use-after-free detection.
    let mut arena: Arena<&'static str> = Arena::with_capacity(8);
    let alice = arena.insert("alice");
    let bob = arena.insert("bob");
    assert_eq!(arena.get(alice), Some(&"alice"));

    // String interner — O(1) equality on repeated identifiers.
    let mut interner = Interner::with_capacity(8);
    let id_a = interner.intern("user:alice");
    let id_b = interner.intern("user:alice");
    assert_eq!(id_a, id_b);

    // Bump arena — fast scratch, reset in O(1).
    let bump = Bump::with_capacity(64);
    let scratch = bump.alloc([0_u8; 16]);
    assert_eq!(scratch.len(), 16);

    // Removing a slot invalidates its handle without touching the rest.
    assert_eq!(arena.remove(alice), Some("alice"));
    assert!(arena.get(alice).is_none());
    assert!(arena.get(bob).is_some());
}

See docs/API.md for the full reference, including the planned 1.0 surface.

Standards

  • REPS governs every decision. See REPS.md.
  • MSRV: Rust 1.85.
  • Edition: 2024.
  • Cross-platform: Linux, macOS, Windows.

License

Dual-licensed under either of:

at your option.