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# runloop [](https://crates.io/crates/runloop) [](https://travis-ci.org/ttaubert/rust-runloop) [](LICENSE)
This crate provides a cancelable `RunLoop` to simplify writing non-blocking
polling threads.
## Usage
The closure passed to `RunLoop::new()` or `RunLoop::new_with_timeout()` will be
called once and is executed in the newly spawned thread. It should periodically
check, via the given callback argument named `alive` in the below examples,
whether the runloop was requested to terminate.
`RunLoop::alive()` allows the owning thread to check whether the runloop is
still alive. This can be useful for debugging (e.g. assertions) or early
returns on failure in the passed closure.
`RunLoop::cancel()` will request the runloop to terminate. If the runloop is
still active it will join the thread and block. If the runloop already
terminated on its own this will be a no-op.
### Example: An endless runloop
A runloop does not have to terminate on its own, it can wait until the
`cancel()` method is called.
```rust
// This runloop runs until we stop it.
let rloop = RunLoop::new(|alive| {
while alive() { /* endless loop */ }
})?;
// Loop a few times.
thread::sleep_ms(500);
assert!(rloop.alive());
// This will cause `alive()` to return false
// and block until the thread was joined.
rloop.cancel();
```
### Example: A runloop with a timeout
Creating a runloop via `new_with_timeout()` ensures that `alive()` returns
`false` after the given duration.
```rust
// This runloop will time out after 10ms.
let rloop = RunLoop::new_with_timeout(|alive| {
while alive() { /* endless loop */ }
}, 10)?;
// Wait for the timeout.
while rloop.alive() { /* loop */ }
// This won't block anymore, it's a no-op.
// The runloop has already terminated.
rloop.cancel();
```
### Example: A runloop with channels
As a runloop will run the given closure in a newly spawned thread it requires
channels and similar utilities to communicate back to the owning thread.
```rust
let (tx, rx) = channel();
// This runloop will send a lot of numbers.
let rloop = RunLoop::new(move |alive| {
let mut counter = 0u64;
while alive() {
tx.send(counter).unwrap();
counter += 1;
}
})?;
// Wait until we receive a specific number.
while rx.recv().unwrap() < 50 { /* loop */ }
// We've seen enough.
rloop.cancel();
```
## License
`runloop` is distributed under the terms of the Mozilla Public License, v. 2.0.
See [LICENSE](LICENSE) for details.
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