Add toMsg method to Time class (osrf#44)

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

Author: jacobperron

rcljava/src/main/java/org/ros2/rcljava/Time.java

@@ -60,6 +60,14 @@ public Time(final long secs, final long nanos, final ClockType ct) {
     this.nanoseconds = TimeUnit.SECONDS.toNanos(secs) + nanos;
   }
 
+  public builtin_interfaces.msg.Time toMsg() {
+    long seconds = this.nanoseconds / 1000000000;
+    long nanos = this.nanoseconds % 1000000000;
+    builtin_interfaces.msg.Time msg = new builtin_interfaces.msg.Time();
+    msg.setSec((int)seconds);
+    msg.setNanosec((int)nanos);
+    return msg;
+  }
 
   public long nanoseconds() {
     return nanoseconds;

rcljava/src/test/java/org/ros2/rcljava/TimeTest.java

@@ -50,6 +50,16 @@ public final void testTimeNoArgConstructor() {
     assertEquals(ClockType.SYSTEM_TIME, time.clockType());
   }
 
+  @Test
+  public final void testTimeFromMsgConstructor() {
+    builtin_interfaces.msg.Time timeMsg = new builtin_interfaces.msg.Time();
+    timeMsg.setSec(42);
+    timeMsg.setNanosec(100);
+    Time time = new Time(timeMsg, ClockType.SYSTEM_TIME);
+    assertEquals(42000000100L, time.nanoseconds());
+    assertEquals(ClockType.SYSTEM_TIME, time.clockType());
+  }
+
   @Test
   public final void testTimeNanos() {
     Time time = new Time(45, ClockType.SYSTEM_TIME);
@@ -73,4 +83,29 @@ public final void testTimeBadSecs() {
   public final void testTimeBadNanos() {
     Time time = new Time(0, -45, ClockType.SYSTEM_TIME);
   }
+
+  @Test
+  public final void testTimeToMsg() {
+    {
+      Time time = new Time();
+      builtin_interfaces.msg.Time timeMsgOut = time.toMsg();
+      assertEquals(0, timeMsgOut.getSec());
+      assertEquals(0, timeMsgOut.getNanosec());
+    }
+    {
+      builtin_interfaces.msg.Time timeMsg = new builtin_interfaces.msg.Time();
+      timeMsg.setSec(42);
+      timeMsg.setNanosec(100);
+      Time time = new Time(timeMsg, ClockType.SYSTEM_TIME);
+      builtin_interfaces.msg.Time timeMsgOut = time.toMsg();
+      assertEquals(42, timeMsgOut.getSec());
+      assertEquals(100, timeMsgOut.getNanosec());
+    }
+    {
+      Time time = new Time(0, 45, ClockType.SYSTEM_TIME);
+      builtin_interfaces.msg.Time timeMsgOut = time.toMsg();
+      assertEquals(0, timeMsgOut.getSec());
+      assertEquals(45, timeMsgOut.getNanosec());
+    }
+  }
 }