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ThreadBound\<T\>
================
[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/threadbound-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/threadbound)
[<img alt="crates.io" src="https://img.shields.io/crates/v/threadbound.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/threadbound)
[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-threadbound-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/threadbound)
[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/threadbound/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/threadbound/actions?query=branch%3Amaster)
ThreadBound is a wrapper that binds a value to its original thread. The wrapper
gets to be [`Sync`] and [`Send`] but only the original thread on which the
ThreadBound was constructed can retrieve the underlying value.
[`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
[`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
```toml
[dependencies]
threadbound = "0.1"
```
*Version requirement: rustc 1.31+*
<br>
### Example
```rust
extern crate threadbound;
use std::marker::PhantomData;
use std::rc::Rc;
use std::sync::Arc;
use threadbound::ThreadBound;
// Neither Send nor Sync. Maybe the index points into a
// thread-local interner.
#[derive(Copy, Clone)]
struct Span {
index: u32,
marker: PhantomData<Rc<()>>,
}
// Error types are always supposed to be Send and Sync.
// We can use ThreadBound to make it so.
struct Error {
span: ThreadBound<Span>,
message: String,
}
fn main() {
let err = Error {
span: ThreadBound::new(Span {
index: 99,
marker: PhantomData,
}),
message: "fearless concurrency".to_owned(),
};
// Original thread can see the contents.
assert_eq!(err.span.get_ref().unwrap().index, 99);
let err = Arc::new(err);
let err2 = err.clone();
std::thread::spawn(move || {
// Other threads cannot get access. Maybe they use
// a default value or a different codepath.
assert!(err2.span.get_ref().is_none());
});
// Original thread can still see the contents.
assert_eq!(err.span.get_ref().unwrap().index, 99);
}
```
<br>
#### License
<sup>
Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
</sup>
<br>
<sub>
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
be dual licensed as above, without any additional terms or conditions.
</sub>
|
