1use crate::{AppContext, PlatformDispatcher};
2use futures::{channel::mpsc, pin_mut, FutureExt};
3use smol::prelude::*;
4use std::{
5 fmt::Debug,
6 marker::PhantomData,
7 mem,
8 num::NonZeroUsize,
9 pin::Pin,
10 rc::Rc,
11 sync::{
12 atomic::{AtomicBool, AtomicUsize, Ordering::SeqCst},
13 Arc,
14 },
15 task::{Context, Poll},
16 time::Duration,
17};
18use util::TryFutureExt;
19use waker_fn::waker_fn;
20
21#[cfg(any(test, feature = "test-support"))]
22use rand::rngs::StdRng;
23
24#[derive(Clone)]
25pub struct BackgroundExecutor {
26 dispatcher: Arc<dyn PlatformDispatcher>,
27}
28
29#[derive(Clone)]
30pub struct ForegroundExecutor {
31 dispatcher: Arc<dyn PlatformDispatcher>,
32 not_send: PhantomData<Rc<()>>,
33}
34
35#[must_use]
36#[derive(Debug)]
37pub enum Task<T> {
38 Ready(Option<T>),
39 Spawned(async_task::Task<T>),
40}
41
42impl<T> Task<T> {
43 pub fn ready(val: T) -> Self {
44 Task::Ready(Some(val))
45 }
46
47 pub fn detach(self) {
48 match self {
49 Task::Ready(_) => {}
50 Task::Spawned(task) => task.detach(),
51 }
52 }
53}
54
55impl<E, T> Task<Result<T, E>>
56where
57 T: 'static,
58 E: 'static + Debug,
59{
60 pub fn detach_and_log_err(self, cx: &mut AppContext) {
61 cx.foreground_executor().spawn(self.log_err()).detach();
62 }
63}
64
65impl<T> Future for Task<T> {
66 type Output = T;
67
68 fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
69 match unsafe { self.get_unchecked_mut() } {
70 Task::Ready(val) => Poll::Ready(val.take().unwrap()),
71 Task::Spawned(task) => task.poll(cx),
72 }
73 }
74}
75
76#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
77pub struct TaskLabel(NonZeroUsize);
78
79impl TaskLabel {
80 pub fn new() -> Self {
81 static NEXT_TASK_LABEL: AtomicUsize = AtomicUsize::new(1);
82 Self(NEXT_TASK_LABEL.fetch_add(1, SeqCst).try_into().unwrap())
83 }
84}
85
86type AnyLocalFuture<R> = Pin<Box<dyn 'static + Future<Output = R>>>;
87
88type AnyFuture<R> = Pin<Box<dyn 'static + Send + Future<Output = R>>>;
89
90impl BackgroundExecutor {
91 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
92 Self { dispatcher }
93 }
94
95 /// Enqueues the given future to be run to completion on a background thread.
96 pub fn spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
97 where
98 R: Send + 'static,
99 {
100 self.spawn_internal::<R>(Box::pin(future), None)
101 }
102
103 /// Enqueues the given future to be run to completion on a background thread.
104 /// The given label can be used to control the priority of the task in tests.
105 pub fn spawn_labeled<R>(
106 &self,
107 label: TaskLabel,
108 future: impl Future<Output = R> + Send + 'static,
109 ) -> Task<R>
110 where
111 R: Send + 'static,
112 {
113 self.spawn_internal::<R>(Box::pin(future), Some(label))
114 }
115
116 fn spawn_internal<R: Send + 'static>(
117 &self,
118 future: AnyFuture<R>,
119 label: Option<TaskLabel>,
120 ) -> Task<R> {
121 let dispatcher = self.dispatcher.clone();
122 let (runnable, task) =
123 async_task::spawn(future, move |runnable| dispatcher.dispatch(runnable, label));
124 runnable.schedule();
125 Task::Spawned(task)
126 }
127
128 #[cfg(any(test, feature = "test-support"))]
129 #[track_caller]
130 pub fn block_test<R>(&self, future: impl Future<Output = R>) -> R {
131 self.block_internal(false, future)
132 }
133
134 pub fn block<R>(&self, future: impl Future<Output = R>) -> R {
135 self.block_internal(true, future)
136 }
137
138 #[track_caller]
139 pub(crate) fn block_internal<R>(
140 &self,
141 background_only: bool,
142 future: impl Future<Output = R>,
143 ) -> R {
144 pin_mut!(future);
145 let unparker = self.dispatcher.unparker();
146 let awoken = Arc::new(AtomicBool::new(false));
147
148 let waker = waker_fn({
149 let awoken = awoken.clone();
150 move || {
151 awoken.store(true, SeqCst);
152 unparker.unpark();
153 }
154 });
155 let mut cx = std::task::Context::from_waker(&waker);
156
157 loop {
158 match future.as_mut().poll(&mut cx) {
159 Poll::Ready(result) => return result,
160 Poll::Pending => {
161 if !self.dispatcher.tick(background_only) {
162 if awoken.swap(false, SeqCst) {
163 continue;
164 }
165
166 #[cfg(any(test, feature = "test-support"))]
167 if let Some(test) = self.dispatcher.as_test() {
168 if !test.parking_allowed() {
169 let mut backtrace_message = String::new();
170 if let Some(backtrace) = test.waiting_backtrace() {
171 backtrace_message =
172 format!("\nbacktrace of waiting future:\n{:?}", backtrace);
173 }
174 panic!("parked with nothing left to run\n{:?}", backtrace_message)
175 }
176 }
177
178 self.dispatcher.park();
179 }
180 }
181 }
182 }
183 }
184
185 pub fn block_with_timeout<R>(
186 &self,
187 duration: Duration,
188 future: impl Future<Output = R>,
189 ) -> Result<R, impl Future<Output = R>> {
190 let mut future = Box::pin(future.fuse());
191 if duration.is_zero() {
192 return Err(future);
193 }
194
195 let mut timer = self.timer(duration).fuse();
196 let timeout = async {
197 futures::select_biased! {
198 value = future => Ok(value),
199 _ = timer => Err(()),
200 }
201 };
202 match self.block(timeout) {
203 Ok(value) => Ok(value),
204 Err(_) => Err(future),
205 }
206 }
207
208 pub async fn scoped<'scope, F>(&self, scheduler: F)
209 where
210 F: FnOnce(&mut Scope<'scope>),
211 {
212 let mut scope = Scope::new(self.clone());
213 (scheduler)(&mut scope);
214 let spawned = mem::take(&mut scope.futures)
215 .into_iter()
216 .map(|f| self.spawn(f))
217 .collect::<Vec<_>>();
218 for task in spawned {
219 task.await;
220 }
221 }
222
223 pub fn timer(&self, duration: Duration) -> Task<()> {
224 let (runnable, task) = async_task::spawn(async move {}, {
225 let dispatcher = self.dispatcher.clone();
226 move |runnable| dispatcher.dispatch_after(duration, runnable)
227 });
228 runnable.schedule();
229 Task::Spawned(task)
230 }
231
232 #[cfg(any(test, feature = "test-support"))]
233 pub fn start_waiting(&self) {
234 self.dispatcher.as_test().unwrap().start_waiting();
235 }
236
237 #[cfg(any(test, feature = "test-support"))]
238 pub fn finish_waiting(&self) {
239 self.dispatcher.as_test().unwrap().finish_waiting();
240 }
241
242 #[cfg(any(test, feature = "test-support"))]
243 pub fn simulate_random_delay(&self) -> impl Future<Output = ()> {
244 self.dispatcher.as_test().unwrap().simulate_random_delay()
245 }
246
247 #[cfg(any(test, feature = "test-support"))]
248 pub fn deprioritize(&self, task_label: TaskLabel) {
249 self.dispatcher.as_test().unwrap().deprioritize(task_label)
250 }
251
252 #[cfg(any(test, feature = "test-support"))]
253 pub fn advance_clock(&self, duration: Duration) {
254 self.dispatcher.as_test().unwrap().advance_clock(duration)
255 }
256
257 #[cfg(any(test, feature = "test-support"))]
258 pub fn tick(&self) -> bool {
259 self.dispatcher.as_test().unwrap().tick(false)
260 }
261
262 #[cfg(any(test, feature = "test-support"))]
263 pub fn run_until_parked(&self) {
264 self.dispatcher.as_test().unwrap().run_until_parked()
265 }
266
267 #[cfg(any(test, feature = "test-support"))]
268 pub fn allow_parking(&self) {
269 self.dispatcher.as_test().unwrap().allow_parking();
270 }
271
272 #[cfg(any(test, feature = "test-support"))]
273 pub fn rng(&self) -> StdRng {
274 self.dispatcher.as_test().unwrap().rng()
275 }
276
277 pub fn num_cpus(&self) -> usize {
278 num_cpus::get()
279 }
280
281 pub fn is_main_thread(&self) -> bool {
282 self.dispatcher.is_main_thread()
283 }
284}
285
286impl ForegroundExecutor {
287 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
288 Self {
289 dispatcher,
290 not_send: PhantomData,
291 }
292 }
293
294 /// Enqueues the given closure to be run on any thread. The closure returns
295 /// a future which will be run to completion on any available thread.
296 pub fn spawn<R>(&self, future: impl Future<Output = R> + 'static) -> Task<R>
297 where
298 R: 'static,
299 {
300 let dispatcher = self.dispatcher.clone();
301 fn inner<R: 'static>(
302 dispatcher: Arc<dyn PlatformDispatcher>,
303 future: AnyLocalFuture<R>,
304 ) -> Task<R> {
305 let (runnable, task) = async_task::spawn_local(future, move |runnable| {
306 dispatcher.dispatch_on_main_thread(runnable)
307 });
308 runnable.schedule();
309 Task::Spawned(task)
310 }
311 inner::<R>(dispatcher, Box::pin(future))
312 }
313}
314
315pub struct Scope<'a> {
316 executor: BackgroundExecutor,
317 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
318 tx: Option<mpsc::Sender<()>>,
319 rx: mpsc::Receiver<()>,
320 lifetime: PhantomData<&'a ()>,
321}
322
323impl<'a> Scope<'a> {
324 fn new(executor: BackgroundExecutor) -> Self {
325 let (tx, rx) = mpsc::channel(1);
326 Self {
327 executor,
328 tx: Some(tx),
329 rx,
330 futures: Default::default(),
331 lifetime: PhantomData,
332 }
333 }
334
335 pub fn spawn<F>(&mut self, f: F)
336 where
337 F: Future<Output = ()> + Send + 'a,
338 {
339 let tx = self.tx.clone().unwrap();
340
341 // Safety: The 'a lifetime is guaranteed to outlive any of these futures because
342 // dropping this `Scope` blocks until all of the futures have resolved.
343 let f = unsafe {
344 mem::transmute::<
345 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
346 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
347 >(Box::pin(async move {
348 f.await;
349 drop(tx);
350 }))
351 };
352 self.futures.push(f);
353 }
354}
355
356impl<'a> Drop for Scope<'a> {
357 fn drop(&mut self) {
358 self.tx.take().unwrap();
359
360 // Wait until the channel is closed, which means that all of the spawned
361 // futures have resolved.
362 self.executor.block(self.rx.next());
363 }
364}