Fixed internal overflow on subtraiton in elapsed and duration

1 files changed, 4 insertions, 2 deletions

diff --git a/src/cyccnt.rs b/src/cyccnt.rs
index 86969cb1..338bbbea 100644
--- a/src/cyccnt.rs
+++ b/src/cyccnt.rs
@@ -38,12 +38,14 @@ impl Instant {
 
     /// Returns the amount of time elapsed since this instant was created.
     pub fn elapsed(&self) -> Duration {
-        Instant::now() - *self
+        let diff = Instant::now().inner.wrapping_sub(self.inner);
+        assert!(diff >= 0, "instant now is earlier than self");
+        Duration { inner: diff as u32 }
     }
 
     /// Returns the amount of time elapsed from another instant to this one.
     pub fn duration_since(&self, earlier: Instant) -> Duration {
-        let diff = self.inner - earlier.inner;
+        let diff = self.inner.wrapping_sub(earlier.inner);
         assert!(diff >= 0, "second instant is later than self");
         Duration { inner: diff as u32 }
     }