commit	152b14b7e9ade7da56179a1576c4820f1eb8beed	[log] [tgz]
author	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Thu Dec 22 11:15:45 2022 +0000
committer	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Thu Dec 22 11:15:45 2022 +0000
tree	a8c0195dcd49ed82252eacb02eecc46b2bc3cc63
parent	937cf38761e486f1118354e658e1abfe30de1660 [diff]
parent	0143fdb2f7dcd63a150f77e08962d379cadb88d6 [diff]

tree: a8c0195dcd49ed82252eacb02eecc46b2bc3cc63

README.md

async-task

Task abstraction for building executors.

To spawn a future onto an executor, we first need to allocate it on the heap and keep some state attached to it. The state indicates whether the future is ready for polling, waiting to be woken up, or completed. Such a stateful future is called a task.

All executors have a queue that holds scheduled tasks:

let (sender, receiver) = flume::unbounded();

A task is created using either spawn(), spawn_local(), or spawn_unchecked() which return a Runnable and a Task:

// A future that will be spawned.
let future = async { 1 + 2 };

// A function that schedules the task when it gets woken up.
let schedule = move |runnable| sender.send(runnable).unwrap();

// Construct a task.
let (runnable, task) = async_task::spawn(future, schedule);

// Push the task into the queue by invoking its schedule function.
runnable.schedule();

The Runnable is used to poll the task's future, and the Task is used to await its output.

Finally, we need a loop that takes scheduled tasks from the queue and runs them:

for runnable in receiver {
    runnable.run();
}

Method run() polls the task's future once. Then, the Runnable vanishes and only reappears when its Waker wakes the task, thus scheduling it to be run again.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.