From 511b75a446ee7ba4b20ddadfb9aedee59564c5f0 Mon Sep 17 00:00:00 2001
From: folex <0xdxdy@gmail.com>
Date: Tue, 19 May 2020 22:35:44 +0300
Subject: [PATCH 1/2] add checked_duration_since & saturating_duration_since

---
 src/wasm.rs | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/src/wasm.rs b/src/wasm.rs
index 57ee1e6..65f4e89 100644
--- a/src/wasm.rs
+++ b/src/wasm.rs
@@ -70,6 +70,18 @@ impl Instant {
     pub fn elapsed(&self) -> Duration {
         Instant::now() - *self
     }
+
+    pub fn saturating_duration_since(&self, earlier: Instant) -> Duration {
+        self.checked_duration_since(earlier).unwrap_or(Duration::new(0, 0))
+    }
+
+    pub fn checked_duration_since(&self, earlier: Instant) -> Option<Duration> {
+        if self.inner >= earlier.inner {
+            Some(*self - earlier)
+        } else {
+            None
+        }
+    }
 }
 
 impl Add<Duration> for Instant {
@@ -188,3 +200,25 @@ impl SubAssign<Duration> for SystemTime {
         *self = *self - rhs;
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn instant_checked_duration_since_nopanic() {
+        let now = Instant::now();
+        let earlier = now - Duration::new(1, 0);
+        let later = now + Duration::new(1, 0);
+        assert_eq!(earlier.checked_duration_since(now), None);
+        assert_eq!(later.checked_duration_since(now), Some(Duration::new(1, 0)));
+        assert_eq!(now.checked_duration_since(now), Some(Duration::new(0, 0)));
+    }
+
+    #[test]
+    fn instant_saturating_duration_since_nopanic() {
+        let a = Instant::now();
+        let ret = (a - Duration::new(1, 0)).saturating_duration_since(a);
+        assert_eq!(ret, Duration::new(0, 0));
+    }
+}
\ No newline at end of file

From 5facff3900abaf021a0985078035b24d4f4b8af6 Mon Sep 17 00:00:00 2001
From: folex <0xdxdy@gmail.com>
Date: Tue, 19 May 2020 23:03:13 +0300
Subject: [PATCH 2/2] newline

---
 src/wasm.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wasm.rs b/src/wasm.rs
index 65f4e89..62eff0c 100644
--- a/src/wasm.rs
+++ b/src/wasm.rs
@@ -221,4 +221,4 @@ mod tests {
         let ret = (a - Duration::new(1, 0)).saturating_duration_since(a);
         assert_eq!(ret, Duration::new(0, 0));
     }
-}
\ No newline at end of file
+}