Added Timer class to be used in testing and more.

Signed-off-by: Jonas Bonér <jonas@jonasboner.com>

akka-actor/src/main/scala/akka/util/Duration.scala

@@ -8,6 +8,35 @@ import java.util.concurrent.TimeUnit
 import TimeUnit._
 import java.lang.{ Long ⇒ JLong, Double ⇒ JDouble }
 
+class TimerException(message: String) extends RuntimeException(message)
+
+/**
+ * Simple timer class.
+ * Usage:
+ * <pre>
+ *   import akka.util.duration._
+ *   import akka.util.Timer
+ *
+ *   val timer = Timer(30.seconds)
+ *   while (timer.isTicking) { ... }
+ * </pre>
+ */
+case class Timer(duration: Duration, throwExceptionOnTimeout: Boolean = false) {
+  val startTimeInMillis = System.currentTimeMillis
+  val timeoutInMillis = duration.toMillis
+
+  /**
+   * Returns true while the timer is ticking. After that it either throws and exception or
+   * returns false. Depending on if the 'throwExceptionOnTimeout' argument is true or false.
+   */
+  def isTicking: Boolean = {
+    if (!(timeoutInMillis > (System.currentTimeMillis - startTimeInMillis))) {
+      if (throwExceptionOnTimeout) throw new TimerException("Time out after " + duration)
+      else false
+    } else true
+  }
+}
+
 object Duration {
   def apply(length: Long, unit: TimeUnit): Duration = new FiniteDuration(length, unit)
   def apply(length: Double, unit: TimeUnit): Duration = fromNanos(unit.toNanos(1) * length)