autocommit 2022-01-06 19:08:32 CET

src/utils/asyncevent.rs

@@ -0,0 +1,41 @@
+use crate::NumCell;
+use std::cell::Cell;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll, Waker};
+
+#[derive(Default)]
+pub struct AsyncEvent {
+    triggers: NumCell<u32>,
+    waker: Cell<Option<Waker>>,
+}
+
+impl AsyncEvent {
+    pub fn trigger(&self) {
+        self.triggers.fetch_add(1);
+        if let Some(waker) = self.waker.take() {
+            waker.wake();
+        }
+    }
+
+    pub fn triggered(&self) -> AsyncEventTriggered {
+        AsyncEventTriggered { ae: self }
+    }
+}
+
+pub struct AsyncEventTriggered<'a> {
+    ae: &'a AsyncEvent,
+}
+
+impl<'a> Future for AsyncEventTriggered<'a> {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        if self.ae.triggers.replace(0) == 0 {
+            self.ae.waker.set(Some(cx.waker().clone()));
+            Poll::Pending
+        } else {
+            Poll::Ready(())
+        }
+    }
+}