#box #collection #dyn #dst

no-std tinybox

Like Box, but with an optimization that avoids allocations for small data-structures

4 releases (2 breaking)

0.3.1 Jan 4, 2023
0.3.0 Jan 3, 2023
0.2.0 Jan 7, 2022
0.1.0 Jan 7, 2022

#363 in Data structures

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Crates.io docs.rs license: MIT/Apache-2.0 Rust CI

TinyBox is like Box, but with an optimization that avoids allocations for small data-structures. This works by storing the value-bits inside the box itself, when the data-structure fits inside a pointer. This is especially usefull for dynamically sized types like traits.


This example stores a value inside the TinyBox without requireing an allocation.

use tinybox::TinyBox;
let boxed = TinyBox::new(1234usize);
assert_eq!(1234, *boxed)

This looks not very usefull, because the value can be stored inside a usize variable without TinyBox. Here is an more useful example that uses dyn-traits. The tinybox! macro is used to coerce the value to a dyn-trait in stable-rust.

use std::any::{Any,TypeId};
use tinybox::{tinybox, TinyBox};
let boxed: TinyBox<dyn Any> = tinybox!(dyn Any => 1234usize);
assert_eq!(TypeId::of::<usize>(), (*boxed).type_id());
assert_eq!(1234, *boxed.downcast::<usize>().unwrap());


This crate should also work without std. No additional configuration required.


This repository is licensed under either of

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

No runtime deps