Move toMillis(Duration) to Utils so that it can be reused. (#1114)

* Add toMillis() method to TimeUtils.

* Reuse toMillis() method in impl and exporters.

* Add a note about overflow and precision loss.

* Move toMillis() to Duration.

1 files changed, 11 insertions, 0 deletions

diff --git a/api/src/test/java/io/opencensus/common/DurationTest.java b/api/src/test/java/io/opencensus/common/DurationTest.java
index 40682fc4..d46f2f7a 100644
--- a/api/src/test/java/io/opencensus/common/DurationTest.java
+++ b/api/src/test/java/io/opencensus/common/DurationTest.java
@@ -88,4 +88,15 @@ public class DurationTest {
     assertThat(Duration.create(-25, -42)).isNotEqualTo(Duration.create(-24, -42));
     assertThat(Duration.create(-24, -43)).isNotEqualTo(Duration.create(-24, -42));
   }
+
+  @Test
+  public void toMillis() {
+    assertThat(Duration.toMillis(Duration.create(10, 0))).isEqualTo(10000L);
+    assertThat(Duration.toMillis(Duration.create(10, 1000))).isEqualTo(10000L);
+    assertThat(Duration.toMillis(Duration.create(0, (int) 1e6))).isEqualTo(1L);
+    assertThat(Duration.toMillis(Duration.create(0, 0))).isEqualTo(0L);
+    assertThat(Duration.toMillis(Duration.create(-10, 0))).isEqualTo(-10000L);
+    assertThat(Duration.toMillis(Duration.create(-10, -1000))).isEqualTo(-10000L);
+    assertThat(Duration.toMillis(Duration.create(0, -(int) 1e6))).isEqualTo(-1L);
+  }
 }