Add Duration.toMillis() method and tests. (#535)

3 files changed, 24 insertions, 0 deletions

diff --git a/core/src/main/java/io/opencensus/stats/View.java b/core/src/main/java/io/opencensus/stats/View.java
index 9dbebf53..d5ad4b09 100644
--- a/core/src/main/java/io/opencensus/stats/View.java
+++ b/core/src/main/java/io/opencensus/stats/View.java
@@ -206,6 +206,9 @@ public abstract class View {
       /**
        * Constructs an interval {@code Window} that has a finite explicit {@code Duration}.
        *
+       * <p>The {@code Duration} should be able to round to milliseconds. Currently interval window
+       * cannot have smaller {@code Duration} such as microseconds or nanoseconds.
+       *
        * @return an interval {@code Window}.
        */
       public static Interval create(Duration duration) {
diff --git a/core_impl/src/main/java/io/opencensus/implcore/stats/MutableViewData.java b/core_impl/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
index aeefd498..86db9b3a 100644
--- a/core_impl/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
+++ b/core_impl/src/main/java/io/opencensus/implcore/stats/MutableViewData.java
@@ -20,6 +20,7 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import io.opencensus.common.Clock;
+import io.opencensus.common.Duration;
 import io.opencensus.common.Function;
 import io.opencensus.common.Functions;
 import io.opencensus.common.Timestamp;
@@ -68,6 +69,9 @@ import javax.annotation.Nullable;
  */
 final class MutableViewData {
 
+  private static final long MILLIS_PER_SECOND = 1000L;
+  private static final long NANOS_PER_MILLI = 1000 * 1000;
+
   private static final Function<TagString, TagValue> GET_STRING_TAG_VALUE =
       new Function<TagString, TagValue>() {
         @Override
@@ -224,6 +228,11 @@ final class MutableViewData {
     return tagValues;
   }
 
+  // Returns the milliseconds representation of a Duration.
+  static long toMillis(Duration duration) {
+    return duration.getSeconds() * MILLIS_PER_SECOND + duration.getNanos() / NANOS_PER_MILLI;
+  }
+
   /**
    * Create an empty {@link MutableAggregation} based on the given {@link Aggregation}.
    *
diff --git a/core_impl/src/test/java/io/opencensus/implcore/stats/MutableViewDataTest.java b/core_impl/src/test/java/io/opencensus/implcore/stats/MutableViewDataTest.java
index d4259ccd..ba7a8b39 100644
--- a/core_impl/src/test/java/io/opencensus/implcore/stats/MutableViewDataTest.java
+++ b/core_impl/src/test/java/io/opencensus/implcore/stats/MutableViewDataTest.java
@@ -17,8 +17,10 @@
 package io.opencensus.implcore.stats;
 
 import static com.google.common.truth.Truth.assertThat;
+import static io.opencensus.implcore.stats.MutableViewData.toMillis;
 
 import com.google.common.collect.ImmutableMap;
+import io.opencensus.common.Duration;
 import io.opencensus.implcore.stats.MutableAggregation.MutableCount;
 import io.opencensus.implcore.stats.MutableAggregation.MutableHistogram;
 import io.opencensus.implcore.stats.MutableAggregation.MutableMean;
@@ -130,4 +132,14 @@ public class MutableViewDataTest {
         StdDevData.create(0))
         .inOrder();
   }
+
+  @Test
+  public void testDurationToMillis() {
+    assertThat(toMillis(Duration.create(0, 0))).isEqualTo(0);
+    assertThat(toMillis(Duration.create(0, 987000000))).isEqualTo(987);
+    assertThat(toMillis(Duration.create(3, 456000000))).isEqualTo(3456);
+    assertThat(toMillis(Duration.create(0, -1000000))).isEqualTo(-1);
+    assertThat(toMillis(Duration.create(-1, 0))).isEqualTo(-1000);
+    assertThat(toMillis(Duration.create(-3, -456000000))).isEqualTo(-3456);
+  }
 }