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//! A function that runs a future to completion on a dedicated thread.
use std::future::Future;
use std::sync::Arc;
use std::thread;
use async_task::Task;
use smol::future;
/// Spawns a future on a new dedicated thread.
///
/// The returned task can be used to await the output of the future.
fn spawn_on_thread<F, T>(future: F) -> Task<T>
where
F: Future<Output = T> + Send + 'static,
T: Send + 'static,
{
// Create a channel that holds the task when it is scheduled for running.
let (sender, receiver) = flume::unbounded();
let sender = Arc::new(sender);
let s = Arc::downgrade(&sender);
// Wrap the future into one that disconnects the channel on completion.
let future = async move {
// When the inner future completes, the sender gets dropped and disconnects the channel.
let _sender = sender;
future.await
};
// Create a task that is scheduled by sending it into the channel.
let schedule = move |runnable| s.upgrade().unwrap().send(runnable).unwrap();
let (runnable, task) = async_task::spawn(future, schedule);
// Schedule the task by sending it into the channel.
runnable.schedule();
// Spawn a thread running the task to completion.
thread::spawn(move || {
// Keep taking the task from the channel and running it until completion.
for runnable in receiver {
runnable.run();
}
});
task
}
fn main() {
// Spawn a future on a dedicated thread.
future::block_on(spawn_on_thread(async {
println!("Hello, world!");
}));
}
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