async_local_executor/
executor.rs

1use crate::tls::{executor, try_executor};
2use async_local_channel::oneshot;
3use slotmap::new_key_type;
4use slotmap::{Key, SlotMap};
5use std::fmt::Debug;
6use std::pin::{Pin, pin};
7use std::sync::Arc;
8use std::task::Wake;
9use std::task::Waker;
10use std::task::{Context, Poll};
11
12new_key_type! { pub struct TaskId; }
13
14type WakerFn = Arc<dyn Fn(TaskHandle) + Send + Sync>;
15
16struct WakerData {
17    handle: TaskHandle,
18    f: WakerFn,
19}
20
21impl Wake for WakerData {
22    fn wake(self: Arc<Self>) {
23        (self.f)(self.handle);
24    }
25
26    fn wake_by_ref(self: &Arc<Self>) {
27        (self.f)(self.handle);
28    }
29}
30
31fn create_waker(handle: TaskHandle, f: WakerFn) -> Waker {
32    Waker::from(Arc::new(WakerData { handle, f }))
33}
34
35type LocalFuture = Pin<Box<dyn Future<Output = ()>>>;
36
37struct Task {
38    future: LocalFuture,
39    waker: Waker,
40}
41
42#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
43pub struct TaskHandle {
44    id: TaskId,
45}
46
47impl Debug for TaskHandle {
48    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
49        self.id.data().fmt(f)
50    }
51}
52
53impl TaskHandle {
54    #[inline]
55    pub fn tick(self) {
56        if let Some(ticker) = { executor().ticker(self) } {
57            ticker.tick();
58        }
59    }
60}
61
62#[must_use]
63pub struct Ticker {
64    handle: TaskHandle,
65    task: Task,
66}
67
68impl Ticker {
69    #[inline]
70    pub fn tick(mut self) {
71        let mut context = Context::from_waker(&self.task.waker);
72        if pin!(&mut self.task.future).poll(&mut context).is_ready() {
73            executor().task_completed(self.handle);
74        } else {
75            executor().return_poller(self);
76        }
77    }
78}
79
80#[must_use = "tasks get canceled when dropped, use `.detach()` to run them in the background"]
81pub struct JoinHandle<T> {
82    handle: TaskHandle,
83    result: oneshot::Receiver<T>,
84    detached: bool,
85}
86
87impl<T> Debug for JoinHandle<T> {
88    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
89        f.debug_struct("JoinHandle")
90            .field("task", &self.handle)
91            .finish()
92    }
93}
94
95impl<T> JoinHandle<T> {
96    const fn new(handle: TaskHandle, result: oneshot::Receiver<T>) -> Self {
97        Self {
98            handle,
99            result,
100            detached: false,
101        }
102    }
103
104    #[inline]
105    pub fn detach(mut self) {
106        self.detached = true;
107    }
108
109    #[inline]
110    #[must_use]
111    pub fn result(&self) -> Option<T> {
112        self.result.try_recv()
113    }
114}
115
116impl<T: 'static> Future for JoinHandle<T> {
117    type Output = T;
118
119    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
120        match pin!(self.result.recv()).poll(cx) {
121            Poll::Ready(value) => Poll::Ready(value.unwrap()),
122            Poll::Pending => Poll::Pending,
123        }
124    }
125}
126
127impl<T> Drop for JoinHandle<T> {
128    #[inline]
129    fn drop(&mut self) {
130        if !self.detached
131            && let Some(mut executor) = try_executor()
132        {
133            executor.task_completed(self.handle);
134        }
135    }
136}
137
138pub struct Executor {
139    tasks: SlotMap<TaskId, Option<Task>>,
140    waker_fn: WakerFn,
141}
142
143impl Debug for Executor {
144    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
145        f.debug_tuple("Executor").field(&self.tasks.len()).finish()
146    }
147}
148
149impl Executor {
150    #[inline]
151    pub fn new<F: Fn(TaskHandle) + Send + Sync + 'static>(f: F) -> Self {
152        Self {
153            tasks: SlotMap::with_key(),
154            waker_fn: Arc::new(f),
155        }
156    }
157
158    pub(crate) fn spawn_local<F>(&mut self, future: F) -> JoinHandle<F::Output>
159    where
160        F: Future + 'static,
161        F::Output: 'static,
162    {
163        let (tx, rx) = oneshot::channel();
164        let future = async {
165            let res = future.await;
166            let _ = tx.send(res);
167        };
168        let waker_fn = self.waker_fn.clone();
169        let future = Box::pin(future);
170        let id = self.tasks.insert_with_key(|id| {
171            let waker = create_waker(TaskHandle { id }, waker_fn);
172            Some(Task { future, waker })
173        });
174        let handle = TaskHandle { id };
175        (self.waker_fn)(handle);
176        JoinHandle::new(handle, rx.activate())
177    }
178
179    fn ticker(&mut self, handle: TaskHandle) -> Option<Ticker> {
180        let task = self.tasks.get_mut(handle.id)?.take()?;
181        Some(Ticker { handle, task })
182    }
183
184    fn task_completed(&mut self, handle: TaskHandle) {
185        self.tasks.remove(handle.id);
186    }
187
188    fn return_poller(&mut self, ticker: Ticker) {
189        self.tasks[ticker.handle.id] = Some(ticker.task);
190    }
191}
async_local_executor/executor.rs

async_local_executor/
executor.rs
