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 pin::Pin,
9 rc::Rc,
10 sync::{
11 atomic::{AtomicBool, Ordering::SeqCst},
12 Arc,
13 },
14 task::{Context, Poll},
15 time::Duration,
16};
17use util::TryFutureExt;
18use waker_fn::waker_fn;
19
20#[derive(Clone)]
21pub struct BackgroundExecutor {
22 dispatcher: Arc<dyn PlatformDispatcher>,
23}
24
25#[derive(Clone)]
26pub struct ForegroundExecutor {
27 dispatcher: Arc<dyn PlatformDispatcher>,
28 not_send: PhantomData<Rc<()>>,
29}
30
31#[must_use]
32pub enum Task<T> {
33 Ready(Option<T>),
34 Spawned(async_task::Task<T>),
35}
36
37impl<T> Task<T> {
38 pub fn ready(val: T) -> Self {
39 Task::Ready(Some(val))
40 }
41
42 pub fn detach(self) {
43 match self {
44 Task::Ready(_) => {}
45 Task::Spawned(task) => task.detach(),
46 }
47 }
48}
49
50impl<E, T> Task<Result<T, E>>
51where
52 T: 'static + Send,
53 E: 'static + Send + Debug,
54{
55 pub fn detach_and_log_err(self, cx: &mut AppContext) {
56 cx.background_executor().spawn(self.log_err()).detach();
57 }
58}
59
60impl<T> Future for Task<T> {
61 type Output = T;
62
63 fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
64 match unsafe { self.get_unchecked_mut() } {
65 Task::Ready(val) => Poll::Ready(val.take().unwrap()),
66 Task::Spawned(task) => task.poll(cx),
67 }
68 }
69}
70
71impl BackgroundExecutor {
72 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
73 Self { dispatcher }
74 }
75
76 /// Enqueues the given closure to be run on any thread. The closure returns
77 /// a future which will be run to completion on any available thread.
78 pub fn spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
79 where
80 R: Send + 'static,
81 {
82 let dispatcher = self.dispatcher.clone();
83 let (runnable, task) =
84 async_task::spawn(future, move |runnable| dispatcher.dispatch(runnable));
85 runnable.schedule();
86 Task::Spawned(task)
87 }
88
89 #[cfg(any(test, feature = "test-support"))]
90 pub fn block_test<R>(&self, future: impl Future<Output = R>) -> R {
91 self.block_internal(false, future)
92 }
93
94 pub fn block<R>(&self, future: impl Future<Output = R>) -> R {
95 self.block_internal(true, future)
96 }
97
98 pub(crate) fn block_internal<R>(
99 &self,
100 background_only: bool,
101 future: impl Future<Output = R>,
102 ) -> R {
103 pin_mut!(future);
104 let (parker, unparker) = parking::pair();
105 let awoken = Arc::new(AtomicBool::new(false));
106 let awoken2 = awoken.clone();
107
108 let waker = waker_fn(move || {
109 awoken2.store(true, SeqCst);
110 unparker.unpark();
111 });
112 let mut cx = std::task::Context::from_waker(&waker);
113
114 loop {
115 match future.as_mut().poll(&mut cx) {
116 Poll::Ready(result) => return result,
117 Poll::Pending => {
118 if !self.dispatcher.poll(background_only) {
119 if awoken.swap(false, SeqCst) {
120 continue;
121 }
122
123 #[cfg(any(test, feature = "test-support"))]
124 if let Some(test) = self.dispatcher.as_test() {
125 if !test.parking_allowed() {
126 let mut backtrace_message = String::new();
127 if let Some(backtrace) = test.waiting_backtrace() {
128 backtrace_message =
129 format!("\nbacktrace of waiting future:\n{:?}", backtrace);
130 }
131 panic!("parked with nothing left to run\n{:?}", backtrace_message)
132 }
133 }
134 parker.park();
135 }
136 }
137 }
138 }
139 }
140
141 pub fn block_with_timeout<R>(
142 &self,
143 duration: Duration,
144 future: impl Future<Output = R>,
145 ) -> Result<R, impl Future<Output = R>> {
146 let mut future = Box::pin(future.fuse());
147 if duration.is_zero() {
148 return Err(future);
149 }
150
151 let mut timer = self.timer(duration).fuse();
152 let timeout = async {
153 futures::select_biased! {
154 value = future => Ok(value),
155 _ = timer => Err(()),
156 }
157 };
158 match self.block(timeout) {
159 Ok(value) => Ok(value),
160 Err(_) => Err(future),
161 }
162 }
163
164 pub async fn scoped<'scope, F>(&self, scheduler: F)
165 where
166 F: FnOnce(&mut Scope<'scope>),
167 {
168 let mut scope = Scope::new(self.clone());
169 (scheduler)(&mut scope);
170 let spawned = mem::take(&mut scope.futures)
171 .into_iter()
172 .map(|f| self.spawn(f))
173 .collect::<Vec<_>>();
174 for task in spawned {
175 task.await;
176 }
177 }
178
179 pub fn timer(&self, duration: Duration) -> Task<()> {
180 let (runnable, task) = async_task::spawn(async move {}, {
181 let dispatcher = self.dispatcher.clone();
182 move |runnable| dispatcher.dispatch_after(duration, runnable)
183 });
184 runnable.schedule();
185 Task::Spawned(task)
186 }
187
188 #[cfg(any(test, feature = "test-support"))]
189 pub fn start_waiting(&self) {
190 self.dispatcher.as_test().unwrap().start_waiting();
191 }
192
193 #[cfg(any(test, feature = "test-support"))]
194 pub fn finish_waiting(&self) {
195 self.dispatcher.as_test().unwrap().finish_waiting();
196 }
197
198 #[cfg(any(test, feature = "test-support"))]
199 pub fn simulate_random_delay(&self) -> impl Future<Output = ()> {
200 self.dispatcher.as_test().unwrap().simulate_random_delay()
201 }
202
203 #[cfg(any(test, feature = "test-support"))]
204 pub fn advance_clock(&self, duration: Duration) {
205 self.dispatcher.as_test().unwrap().advance_clock(duration)
206 }
207
208 #[cfg(any(test, feature = "test-support"))]
209 pub fn run_until_parked(&self) {
210 self.dispatcher.as_test().unwrap().run_until_parked()
211 }
212
213 #[cfg(any(test, feature = "test-support"))]
214 pub fn allow_parking(&self) {
215 self.dispatcher.as_test().unwrap().allow_parking();
216 }
217
218 pub fn num_cpus(&self) -> usize {
219 num_cpus::get()
220 }
221
222 pub fn is_main_thread(&self) -> bool {
223 self.dispatcher.is_main_thread()
224 }
225}
226
227impl ForegroundExecutor {
228 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
229 Self {
230 dispatcher,
231 not_send: PhantomData,
232 }
233 }
234
235 /// Enqueues the given closure to be run on any thread. The closure returns
236 /// a future which will be run to completion on any available thread.
237 pub fn spawn<R>(&self, future: impl Future<Output = R> + 'static) -> Task<R>
238 where
239 R: 'static,
240 {
241 let dispatcher = self.dispatcher.clone();
242 let (runnable, task) = async_task::spawn_local(future, move |runnable| {
243 dispatcher.dispatch_on_main_thread(runnable)
244 });
245 runnable.schedule();
246 Task::Spawned(task)
247 }
248}
249
250pub struct Scope<'a> {
251 executor: BackgroundExecutor,
252 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
253 tx: Option<mpsc::Sender<()>>,
254 rx: mpsc::Receiver<()>,
255 lifetime: PhantomData<&'a ()>,
256}
257
258impl<'a> Scope<'a> {
259 fn new(executor: BackgroundExecutor) -> Self {
260 let (tx, rx) = mpsc::channel(1);
261 Self {
262 executor,
263 tx: Some(tx),
264 rx,
265 futures: Default::default(),
266 lifetime: PhantomData,
267 }
268 }
269
270 pub fn spawn<F>(&mut self, f: F)
271 where
272 F: Future<Output = ()> + Send + 'a,
273 {
274 let tx = self.tx.clone().unwrap();
275
276 // Safety: The 'a lifetime is guaranteed to outlive any of these futures because
277 // dropping this `Scope` blocks until all of the futures have resolved.
278 let f = unsafe {
279 mem::transmute::<
280 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
281 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
282 >(Box::pin(async move {
283 f.await;
284 drop(tx);
285 }))
286 };
287 self.futures.push(f);
288 }
289}
290
291impl<'a> Drop for Scope<'a> {
292 fn drop(&mut self) {
293 self.tx.take().unwrap();
294
295 // Wait until the channel is closed, which means that all of the spawned
296 // futures have resolved.
297 self.executor.block(self.rx.next());
298 }
299}