https://github.com/bevyengine/atomicow

A `Cow`-like data structure where owned data is stored inside an `Arc`.
https://github.com/bevyengine/atomicow

Last synced: 3 months ago
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A `Cow`-like data structure where owned data is stored inside an `Arc`.

• Host: GitHub
• URL: https://github.com/bevyengine/atomicow
• Owner: bevyengine
• License: apache-2.0
• Created: 2024-08-26T20:12:30.000Z (10 months ago)
• Default Branch: main
• Last Pushed: 2025-03-21T04:25:55.000Z (3 months ago)
• Last Synced: 2025-03-29T21:02:57.120Z (3 months ago)
• Language: Rust
• Size: 34.2 KB
• Stars: 29
• Watchers: 3
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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# `atomicow`



![License](https://img.shields.io/badge/license-MIT%2FApache-blue.svg)

[![Crates.io](https://img.shields.io/crates/v/atomicow.svg)](https://crates.io/crates/atomicow)

[![Downloads](https://img.shields.io/crates/d/atomicow.svg)](https://crates.io/crates/atomicow)

[![Docs](https://docs.rs/atomicow/badge.svg)](https://docs.rs/atomicow/latest/atomicow/)

A [`Cow`](https://doc.rust-lang.org/std/borrow/enum.Cow.html)-like data structure where owned data is stored inside an [`Arc`](https://doc.rust-lang.org/std/sync/struct.Arc.html).

Here's what it looks like:

```rust, ignore

pub enum CowArc<'a, T: ?Sized + 'static> {

    Borrowed(&'a T),

    Static(&'static T),

    Owned(Arc),

}

```

As implied by the `Cow` name, this type allows for cheap immutable reference, but can be converted into a shared owned form via cloning when lifetime extension is required.

This data structure is particularly useful for `str` or other values with a static lifetime,

as might be used in structures such as asset paths.

A `'static str` stored in a `CowArc` can be cloned without allocations or bookkeeping,

while owned values are shared by reference-counting in a thread-safe fashion.

## Comparison to the `cow_arc` crate

The similar [`cow_arc`](https://docs.rs/cow_arc/latest/cow_arc/) crate already exists.

How does `atomicow` differ?

Put simply: `cow_arc`'s data structure is just a wrapper over an `Arc`.

While this is exactly what you need in some use cases,

the enum structure used in `atomicow` is both more transparent and more flexible.

## Contributing

This crate is maintained by the Bevy organization, and is intended to be tiny, stable, zero-dependency, and broadly useful.

[Issues](https://github.com/bevyengine/atomicow/issues) and [pull requests](https://github.com/bevyengine/atomicow/pulls) are genuinely welcome!