Use modulo operation to convert nanosecond to Duration

Author: tiif

src/tools/miri/src/clock.rs

@@ -39,13 +39,14 @@ impl Instant {
                 InstantKind::Virtual { nanoseconds },
                 InstantKind::Virtual { nanoseconds: earlier },
             ) => {
-                // If it exceeded u64::MAX nanosecond, we will just keep u64::MAX nanosecond,
-                // Duration can't take in more than u64::MAX.
-                let duration = match u64::try_from(nanoseconds.saturating_sub(earlier)) {
-                    Ok(nanosecond) => Duration::from_nanos(nanosecond),
-                    Err(_err) => Duration::from_nanos(u64::MAX),
-                };
-                Duration::new(duration.as_secs(), duration.subsec_nanos())
+                // It is possible for second to overflow because u64::MAX < (u128::MAX / 1e9).
+                let seconds = u64::try_from(
+                    nanoseconds.saturating_sub(earlier).saturating_div(1_000_000_000),
+                )
+                .unwrap();
+                // It is impossible for nanosecond to overflow because u32::MAX > 1e9.
+                let nanosecond = u32::try_from(nanoseconds.wrapping_rem(1_000_000_000)).unwrap();
+                Duration::new(seconds, nanosecond)
             }
             _ => panic!("all `Instant` must be of the same kind"),
         }