Add a TimestampConverter that can be used to convert nanoTime to Timestamp. (#160)

* Add a TimestampConverter class that can be used to convert nanoTime to Timestamp.

3 files changed, 65 insertions, 18 deletions

diff --git a/core/src/main/java/com/google/instrumentation/common/Timestamp.java b/core/src/main/java/com/google/instrumentation/common/Timestamp.java
index c1e736dc..c9c8f2a3 100644
--- a/core/src/main/java/com/google/instrumentation/common/Timestamp.java
+++ b/core/src/main/java/com/google/instrumentation/common/Timestamp.java
@@ -13,6 +13,8 @@
 
 package com.google.instrumentation.common;
 
+import javax.annotation.concurrent.Immutable;
+
 /**
  * A representation of an instant in time. The instant is the number of nanoseconds after the number
  * of seconds since the Unix Epoch.
@@ -20,11 +22,13 @@ package com.google.instrumentation.common;
  * <p>Use {@link TimestampFactory#now} to get the current timestamp since epoch
  * (1970-01-01T00:00:00Z).
  */
+@Immutable
 public final class Timestamp {
   private static final long MAX_SECONDS = 315576000000L;
   private static final int MAX_NANOS = 999999999;
   private static final long NUM_MILLIS_PER_SECOND = 1000L;
   private static final int NUM_NANOS_PER_MILLI = 1000 * 1000;
+  private static final long NUM_NANOS_PER_SECOND = NUM_NANOS_PER_MILLI * NUM_MILLIS_PER_SECOND;
   private final long seconds;
   private final int nanos;
 
@@ -40,11 +44,9 @@ public final class Timestamp {
    *
    * @param seconds Represents seconds of UTC time since Unix epoch 1970-01-01T00:00:00Z. Must
    *     be from from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59Z inclusive.
-   *
    * @param nanos Non-negative fractions of a second at nanosecond resolution. Negative
    *     second values with fractions must still have non-negative nanos values that count forward
    *     in time. Must be from 0 to 999,999,999 inclusive.
-   *
    * @return new {@link Timestamp} with specified fields. For invalid inputs, a {@link Timestamp}
    *     of zero is returned.
    */
@@ -59,13 +61,15 @@ public final class Timestamp {
   }
 
   /**
-   * Creates a new timestamp from given milliseconds.
+   * Creates a new timestamp from the given milliseconds.
+   *
+   * @return a new timestamp from the given milliseconds.
    */
   public static Timestamp fromMillis(long millis) {
     long seconds = millis / NUM_MILLIS_PER_SECOND;
     int nanos = (int) (millis % NUM_MILLIS_PER_SECOND) * NUM_NANOS_PER_MILLI;
     if (nanos < 0) {
-      return new Timestamp(seconds - 1, MAX_NANOS + nanos + 1);
+      return new Timestamp(seconds - 1, (int)(nanos + NUM_NANOS_PER_SECOND));
     } else {
       return new Timestamp(seconds, nanos);
     }
@@ -90,6 +94,29 @@ public final class Timestamp {
     return nanos;
   }
 
+  /**
+   * Returns a {@code Timestamp} calculated as this {@code Timestamp} plus some number of
+   * nanoseconds.
+   *
+   * @param nanos the nanoseconds to be added to the current timestamp.
+   * @return a {@code Timestamp} calculated as this {@code Timestamp} plus some number of
+   *     nanoseconds.
+   */
+  public Timestamp addNanos(long nanos) {
+    long newSeconds = seconds + nanos / NUM_NANOS_PER_SECOND;
+    nanos %= NUM_NANOS_PER_SECOND;
+    // Cannot overflow because: abs(nanos) < NUM_NANOS_PER_SECOND AND
+    // this.nanos < NUM_NANOS_PER_SECOND.
+    long newNanos = nanos + this.nanos;
+    newSeconds += (newNanos / NUM_NANOS_PER_SECOND);
+    newNanos %= NUM_NANOS_PER_SECOND;
+    if (newNanos >= 0) {
+      return Timestamp.create(newSeconds, (int) newNanos);
+    } else {
+      return Timestamp.create(newSeconds - 1, (int)(newNanos + NUM_NANOS_PER_SECOND));
+    }
+  }
+
   @Override
   public boolean equals(Object obj) {
     if (obj == this) {
diff --git a/core/src/main/java/com/google/instrumentation/common/TimestampFactory.java b/core/src/main/java/com/google/instrumentation/common/TimestampFactory.java
index 27f14f6a..63762a6b 100644
--- a/core/src/main/java/com/google/instrumentation/common/TimestampFactory.java
+++ b/core/src/main/java/com/google/instrumentation/common/TimestampFactory.java
@@ -38,8 +38,9 @@ public final class TimestampFactory {
     return HANDLER.timeNow();
   }
 
-  // This class cannot be final because in case of java8 runtime we can have a better granularity
-  // timestamp.
+  /**
+   * Interface to get the current {@link Timestamp}.
+   */
   interface Handler {
     Timestamp timeNow();
   }
diff --git a/core/src/test/java/com/google/instrumentation/common/TimestampTest.java b/core/src/test/java/com/google/instrumentation/common/TimestampTest.java
index 1e994def..d41733a7 100644
--- a/core/src/test/java/com/google/instrumentation/common/TimestampTest.java
+++ b/core/src/test/java/com/google/instrumentation/common/TimestampTest.java
@@ -10,23 +10,19 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public class TimestampTest {
   @Test
-  public void testTimestampCreate() {
+  public void timestampCreate() {
     assertThat(Timestamp.create(24, 42).getSeconds()).isEqualTo(24);
     assertThat(Timestamp.create(24, 42).getNanos()).isEqualTo(42);
     assertThat(Timestamp.create(-24, 42).getSeconds()).isEqualTo(-24);
     assertThat(Timestamp.create(-24, 42).getNanos()).isEqualTo(42);
-    assertThat(Timestamp.create(315576000000L, 999999999).getSeconds())
-        .isEqualTo(315576000000L);
-    assertThat(Timestamp.create(315576000000L, 999999999).getNanos())
-        .isEqualTo(999999999);
-    assertThat(Timestamp.create(-315576000000L, 999999999).getSeconds())
-        .isEqualTo(-315576000000L);
-    assertThat(Timestamp.create(-315576000000L, 999999999).getNanos())
-        .isEqualTo(999999999);
+    assertThat(Timestamp.create(315576000000L, 999999999).getSeconds()).isEqualTo(315576000000L);
+    assertThat(Timestamp.create(315576000000L, 999999999).getNanos()).isEqualTo(999999999);
+    assertThat(Timestamp.create(-315576000000L, 999999999).getSeconds()).isEqualTo(-315576000000L);
+    assertThat(Timestamp.create(-315576000000L, 999999999).getNanos()).isEqualTo(999999999);
   }
 
   @Test
-  public void testTimestampCreateInvalidInput() {
+  public void timestampCreate_InvalidInput() {
     assertThat(Timestamp.create(-315576000001L, 0)).isEqualTo(Timestamp.create(0, 0));
     assertThat(Timestamp.create(315576000001L, 0)).isEqualTo(Timestamp.create(0, 0));
     assertThat(Timestamp.create(1, 1000000000)).isEqualTo(Timestamp.create(0, 0));
@@ -36,20 +32,43 @@ public class TimestampTest {
   }
 
   @Test
-  public void testTimestampFromMillis() {
+  public void timestampFromMillis() {
     assertThat(Timestamp.fromMillis(0)).isEqualTo(Timestamp.create(0, 0));
     assertThat(Timestamp.fromMillis(987)).isEqualTo(Timestamp.create(0, 987000000));
     assertThat(Timestamp.fromMillis(3456)).isEqualTo(Timestamp.create(3, 456000000));
   }
 
   @Test
-  public void testTimestampFromMillisNegative() {
+  public void timestampFromMillis_Negative() {
     assertThat(Timestamp.fromMillis(-1)).isEqualTo(Timestamp.create(-1, 999000000));
     assertThat(Timestamp.fromMillis(-999)).isEqualTo(Timestamp.create(-1, 1000000));
     assertThat(Timestamp.fromMillis(-3456)).isEqualTo(Timestamp.create(-4, 544000000));
   }
 
   @Test
+  public void timestampAddNanos() {
+    Timestamp timestamp = Timestamp.create(1234, 223);
+    assertThat(timestamp.addNanos(0)).isEqualTo(timestamp);
+    assertThat(timestamp.addNanos(999999777)).isEqualTo(Timestamp.create(1235, 0));
+    assertThat(timestamp.addNanos(1300200500)).isEqualTo(Timestamp.create(1235, 300200723));
+    assertThat(timestamp.addNanos(1999999777)).isEqualTo(Timestamp.create(1236, 0));
+    assertThat(timestamp.addNanos(9876543789L)).isEqualTo(Timestamp.create(1243, 876544012));
+    assertThat(timestamp.addNanos(Long.MAX_VALUE))
+        .isEqualTo(Timestamp.create(1234L + 9223372036L, 223 + 854775807));
+  }
+
+  @Test
+  public void timestampAddNanos_Negative() {
+    Timestamp timestamp = Timestamp.create(1234, 223);
+    assertThat(timestamp.addNanos(-223)).isEqualTo(Timestamp.create(1234, 0));
+    assertThat(timestamp.addNanos(-1000000223)).isEqualTo(Timestamp.create(1233, 0));
+    assertThat(timestamp.addNanos(-1300200500)).isEqualTo(Timestamp.create(1232, 699799723));
+    assertThat(timestamp.addNanos(-4123456213L)).isEqualTo(Timestamp.create(1229, 876544010));
+    assertThat(timestamp.addNanos(Long.MIN_VALUE))
+        .isEqualTo(Timestamp.create(1234L - 9223372036L - 1, 223 + 145224192));
+  }
+
+  @Test
   public void testTimestampEqual() {
     // Positive tests.
     assertThat(Timestamp.create(0, 0)).isEqualTo(Timestamp.create(0, 0));