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0.1.0 | Nov 17, 2018 |
#120 in Concurrency
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ThreadBound<T>
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.
[dependencies]
threadbound = "0.1"
Version requirement: rustc 1.31+
Example
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);
}
License
Licensed under either of Apache License, Version 2.0 or MIT license at your option.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.