Added an implementation of From<Time> for Duration

src/lib.rs

@@ -248,7 +248,7 @@ pub mod num {
     #[cfg(not(feature = "std"))]
     pub use num_traits::float::FloatCore as Float;
 
-    pub use num_traits::{pow, FromPrimitive, Num, One, Saturating, Signed, Zero};
+    pub use num_traits::{pow, AsPrimitive, FromPrimitive, Num, One, Saturating, Signed, Zero};
 
     #[cfg(feature = "bigint-support")]
     pub use num_bigint::{BigInt, BigUint};

src/si/time.rs

@@ -1,5 +1,7 @@
 //! Time (base unit second, s<sup>1</sup>).
 
+use ::lib::time::Duration;
+
 quantity! {
     /// Time (base unit second, s<sup>1</sup>).
     quantity: Time; "time";
@@ -44,3 +46,44 @@ quantity! {
         @year: 3.1536_E7; "a", "year", "years";
     }
 }
+
+impl<U, V> From<Time<U, V>> for Duration
+where
+    U: ::si::Units<V> + ?Sized,
+    V: ::num::Num + ::num::AsPrimitive<u64> + ::num::AsPrimitive<u32> + ::Conversion<V> + ::lib::cmp::PartialOrd,
+    second: ::Conversion<V, T = V::T>,
+    nanosecond: ::Conversion<V, T = V::T>,
+{
+    fn from(mut t: Time<U, V>) -> Duration {
+        if t < Time::<U, V>::new::<second>(V::zero()) {
+            t = Time::<U, V>::new::<second>(V::zero()) - t
+        }
+        let secs = t.get::<second>().as_();
+        let nanos = (t % Time::<U, V>::new::<second>(V::one())).get::<nanosecond>().as_();
+        Duration::new(secs, nanos)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    storage_types! {
+        types: Float;
+
+        use ::lib::time::Duration;
+        use si::quantities::*;
+        use si::time::second;
+
+        #[test]
+        fn from() {
+            let t = Time::new::<second>(-21.5);
+            let d: Duration = t.into();
+            assert_eq!(d.as_secs(), 21);
+            assert!(499_999_999 <= d.subsec_nanos() && d.subsec_nanos() <= 500_000_001);
+
+            let t = Time::new::<second>(12.345);
+            let d: Duration = t.into();
+            assert_eq!(d.as_secs(), 12);
+            assert!(344_999_500 <= d.subsec_nanos() && d.subsec_nanos() <= 345_000_500);
+        }
+    }
+}