| //! A simple single-threaded executor. |
| |
| use std::future::Future; |
| use std::panic::catch_unwind; |
| use std::thread; |
| |
| use async_task::{JoinHandle, Runnable}; |
| use futures_lite::future; |
| use once_cell::sync::Lazy; |
| |
| /// Spawns a future on the executor. |
| fn spawn<F, T>(future: F) -> JoinHandle<T> |
| where |
| F: Future<Output = T> + Send + 'static, |
| T: Send + 'static, |
| { |
| // A channel 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 for simplicity. |
| let _ignore_panic = catch_unwind(|| runnable.run()); |
| } |
| }); |
| |
| sender |
| }); |
| |
| // Create a task that is scheduled by sending itself into the channel. |
| let schedule = |t| QUEUE.send(t).unwrap(); |
| let (runnable, handle) = async_task::spawn(future, schedule); |
| |
| // Schedule the task by sending it into the channel. |
| runnable.schedule(); |
| |
| handle |
| } |
| |
| fn main() { |
| // Spawn a future and await its result. |
| let handle = spawn(async { |
| println!("Hello, world!"); |
| }); |
| future::block_on(handle); |
| } |