1 files changed, 139 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/time/interval.rs b/third_party/rust/tokio/src/time/interval.rs
new file mode 100644
index 0000000000..090e2d1f05
--- /dev/null
+++ b/third_party/rust/tokio/src/time/interval.rs
@@ -0,0 +1,139 @@
+use crate::future::poll_fn;
+use crate::time::{delay_until, Delay, Duration, Instant};
+
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+/// Creates new `Interval` that yields with interval of `duration`. The first
+/// tick completes immediately.
+///
+/// An interval will tick indefinitely. At any time, the `Interval` value can be
+/// dropped. This cancels the interval.
+///
+/// This function is equivalent to `interval_at(Instant::now(), period)`.
+///
+/// # Panics
+///
+/// This function panics if `period` is zero.
+///
+/// # Examples
+///
+/// ```
+/// use tokio::time::{self, Duration};
+///
+/// #[tokio::main]
+/// async fn main() {
+///     let mut interval = time::interval(Duration::from_millis(10));
+///
+///     interval.tick().await;
+///     interval.tick().await;
+///     interval.tick().await;
+///
+///     // approximately 20ms have elapsed.
+/// }
+/// ```
+pub fn interval(period: Duration) -> Interval {
+    assert!(period > Duration::new(0, 0), "`period` must be non-zero.");
+
+    interval_at(Instant::now(), period)
+}
+
+/// Creates new `Interval` that yields with interval of `period` with the
+/// first tick completing at `at`.
+///
+/// An interval will tick indefinitely. At any time, the `Interval` value can be
+/// dropped. This cancels the interval.
+///
+/// # Panics
+///
+/// This function panics if `period` is zero.
+///
+/// # Examples
+///
+/// ```
+/// use tokio::time::{interval_at, Duration, Instant};
+///
+/// #[tokio::main]
+/// async fn main() {
+///     let start = Instant::now() + Duration::from_millis(50);
+///     let mut interval = interval_at(start, Duration::from_millis(10));
+///
+///     interval.tick().await;
+///     interval.tick().await;
+///     interval.tick().await;
+///
+///     // approximately 70ms have elapsed.
+/// }
+/// ```
+pub fn interval_at(start: Instant, period: Duration) -> Interval {
+    assert!(period > Duration::new(0, 0), "`period` must be non-zero.");
+
+    Interval {
+        delay: delay_until(start),
+        period,
+    }
+}
+
+/// Stream returned by [`interval`](interval) and [`interval_at`](interval_at).
+#[derive(Debug)]
+pub struct Interval {
+    /// Future that completes the next time the `Interval` yields a value.
+    delay: Delay,
+
+    /// The duration between values yielded by `Interval`.
+    period: Duration,
+}
+
+impl Interval {
+    #[doc(hidden)] // TODO: document
+    pub fn poll_tick(&mut self, cx: &mut Context<'_>) -> Poll<Instant> {
+        // Wait for the delay to be done
+        ready!(Pin::new(&mut self.delay).poll(cx));
+
+        // Get the `now` by looking at the `delay` deadline
+        let now = self.delay.deadline();
+
+        // The next interval value is `duration` after the one that just
+        // yielded.
+        let next = now + self.period;
+        self.delay.reset(next);
+
+        // Return the current instant
+        Poll::Ready(now)
+    }
+
+    /// Completes when the next instant in the interval has been reached.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::time;
+    ///
+    /// use std::time::Duration;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let mut interval = time::interval(Duration::from_millis(10));
+    ///
+    ///     interval.tick().await;
+    ///     interval.tick().await;
+    ///     interval.tick().await;
+    ///
+    ///     // approximately 20ms have elapsed.
+    /// }
+    /// ```
+    #[allow(clippy::should_implement_trait)] // TODO: rename (tokio-rs/tokio#1261)
+    pub async fn tick(&mut self) -> Instant {
+        poll_fn(|cx| self.poll_tick(cx)).await
+    }
+}
+
+#[cfg(feature = "stream")]
+impl crate::stream::Stream for Interval {
+    type Item = Instant;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Instant>> {
+        Poll::Ready(Some(ready!(self.poll_tick(cx))))
+    }
+}