From e6bf005d263c4ef36170008072b85e92ff672ec4 Mon Sep 17 00:00:00 2001
From: Woody Chow <woodychow@google.com>
Date: Mon, 14 Jun 2021 15:49:54 +0900
Subject: [PATCH] cros_async: Add TimerAsync::sleep

to reduce boilerplate code.

BUG=None
TEST=cargo test

Change-Id: Ia1485b63453145e0b0dfaa6730caee34b52bc0b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2960408
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Woody Chow <woodychow@google.com>
---
 cros_async/src/lib.rs   |  7 +++++++
 cros_async/src/timer.rs | 24 +++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/cros_async/src/lib.rs b/cros_async/src/lib.rs
index cfe4baae02..0cc4405598 100644
--- a/cros_async/src/lib.rs
+++ b/cros_async/src/lib.rs
@@ -83,6 +83,7 @@ pub use io_ext::{
 pub use mem::{BackingMemory, MemRegion};
 pub use poll_source::PollSource;
 pub use select::SelectResult;
+pub use sys_util;
 pub use timer::TimerAsync;
 pub use uring_executor::URingExecutor;
 pub use uring_source::UringSource;
@@ -102,6 +103,12 @@ pub enum Error {
     /// Error from the uring executor.
     #[error("Failure in the uring executor: {0}")]
     URingExecutor(uring_executor::Error),
+    /// Error from TimerFd.
+    #[error("Failure in TimerFd: {0}")]
+    TimerFd(sys_util::Error),
+    /// Error from TimerFd.
+    #[error("Failure in TimerAsync: {0}")]
+    TimerAsync(AsyncError),
 }
 pub type Result<T> = std::result::Result<T, Error>;
 
diff --git a/cros_async/src/timer.rs b/cros_async/src/timer.rs
index 7069c7b470..b1c2fb1fc0 100644
--- a/cros_async/src/timer.rs
+++ b/cros_async/src/timer.rs
@@ -6,7 +6,7 @@ use std::time::Duration;
 
 use sys_util::{Result as SysResult, TimerFd};
 
-use crate::{AsyncResult, Executor, IntoAsync, IoSourceExt};
+use crate::{AsyncResult, Error, Executor, IntoAsync, IoSourceExt};
 #[cfg(test)]
 use crate::{FdExecutor, URingExecutor};
 
@@ -36,6 +36,15 @@ impl TimerAsync {
         self.io_source.read_u64().await
     }
 
+    /// Async sleep for the given duration
+    pub async fn sleep(ex: &Executor, dur: Duration) -> std::result::Result<(), Error> {
+        let tfd = TimerFd::new().map_err(Error::TimerFd)?;
+        tfd.reset(dur, None).map_err(Error::TimerFd)?;
+        let t = TimerAsync::new(tfd, ex).map_err(Error::TimerAsync)?;
+        t.next_val().await.map_err(Error::TimerAsync)?;
+        Ok(())
+    }
+
     /// Sets the timer to expire after `dur`.  If `interval` is not `None` it represents
     /// the period for repeated expirations after the initial expiration.  Otherwise
     /// the timer will expire just once.  Cancels any existing duration and repeating interval.
@@ -96,4 +105,17 @@ mod tests {
         let ex = FdExecutor::new().unwrap();
         ex.run_until(this_test(&ex)).unwrap();
     }
+
+    #[test]
+    fn timer() {
+        async fn this_test(ex: &Executor) -> () {
+            let dur = Duration::from_millis(200);
+            let now = Instant::now();
+            TimerAsync::sleep(ex, dur).await.expect("unable to sleep");
+            assert!(now.elapsed() >= dur);
+        }
+
+        let ex = Executor::new().expect("creating an executor failed");
+        ex.run_until(this_test(&ex)).unwrap();
+    }
 }