From 1e698af05bc6e7e520d3f35ef661f34ea6ea359e Mon Sep 17 00:00:00 2001
From: Caleb Jamison <caleb@cbjamo.com>
Date: Wed, 31 Jan 2024 14:04:48 -0500
Subject: Add timeout_at convenience function and example.

---
 embassy-time/src/lib.rs   |  2 +-
 embassy-time/src/timer.rs | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

(limited to 'embassy-time/src')

diff --git a/embassy-time/src/lib.rs b/embassy-time/src/lib.rs
index d27eb92f6..e7efce49c 100644
--- a/embassy-time/src/lib.rs
+++ b/embassy-time/src/lib.rs
@@ -32,7 +32,7 @@ pub use delay::{block_for, Delay};
 pub use duration::Duration;
 pub use embassy_time_driver::TICK_HZ;
 pub use instant::Instant;
-pub use timer::{with_timeout, Ticker, TimeoutError, Timer};
+pub use timer::{timeout_at, with_timeout, Ticker, TimeoutError, Timer};
 
 const fn gcd(a: u64, b: u64) -> u64 {
     if b == 0 {
diff --git a/embassy-time/src/timer.rs b/embassy-time/src/timer.rs
index 565a65cb8..dbce9297c 100644
--- a/embassy-time/src/timer.rs
+++ b/embassy-time/src/timer.rs
@@ -8,7 +8,7 @@ use futures_util::{pin_mut, Stream};
 
 use crate::{Duration, Instant};
 
-/// Error returned by [`with_timeout`] on timeout.
+/// Error returned by [`with_timeout`] and [`timeout_at`] on timeout.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct TimeoutError;
@@ -26,6 +26,19 @@ pub async fn with_timeout<F: Future>(timeout: Duration, fut: F) -> Result<F::Out
     }
 }
 
+/// Runs a given future with a deadline time.
+///
+/// If the future completes before the deadline, its output is returned. Otherwise, on timeout,
+/// work on the future is stopped (`poll` is no longer called), the future is dropped and `Err(TimeoutError)` is returned.
+pub async fn timeout_at<F: Future>(at: Instant, fut: F) -> Result<F::Output, TimeoutError> {
+    let timeout_fut = Timer::at(at);
+    pin_mut!(fut);
+    match select(fut, timeout_fut).await {
+        Either::Left((r, _)) => Ok(r),
+        Either::Right(_) => Err(TimeoutError),
+    }
+}
+
 /// A future that completes at a specified [Instant](struct.Instant.html).
 #[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct Timer {
-- 
cgit