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//! A simple single-threaded executor.
use std::future::Future;
use std::panic::catch_unwind;
use std::thread;
use async_task::{Runnable, Task};
use once_cell::sync::Lazy;
use smol::future;
/// Spawns a future on the executor.
fn spawn<F, T>(future: F) -> Task<T>
where
F: Future<Output = T> + Send + 'static,
T: Send + 'static,
{
// A queue that holds scheduled tasks.
static QUEUE: Lazy<flume::Sender<Runnable>> = Lazy::new(|| {
let (sender, receiver) = flume::unbounded::<Runnable>();
// Start the executor thread.
thread::spawn(|| {
for runnable in receiver {
// Ignore panics inside futures.
let _ignore_panic = catch_unwind(|| runnable.run());
}
});
sender
});
// Create a task that is scheduled by pushing it into the queue.
let schedule = |runnable| QUEUE.send(runnable).unwrap();
let (runnable, task) = async_task::spawn(future, schedule);
// Schedule the task by pushing it into the queue.
runnable.schedule();
task
}
fn main() {
// Spawn a future and await its result.
let task = spawn(async {
println!("Hello, world!");
});
future::block_on(task);
}
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