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Deprecated Actors Library for Scala
There is a newer version: 2.11.2
package scala.actors

import java.util.concurrent.TimeoutException
import scala.concurrent.util.Duration

/**
 * Trait used for migration of Scala actors to Akka.
 */
@deprecated("ActorRef ought to be used only with the Actor Migration Kit.")
trait ActorRef {

  /**
   * Sends a one-way asynchronous message. E.g. fire-and-forget semantics.
   * 
   *
   * If invoked from within an actor then the actor reference is implicitly passed on as the implicit 'sender' argument.
   * 

   *
   * This actor 'sender' reference is then available in the receiving actor in the 'sender' member variable,
   * if invoked from within an Actor. If not then no sender is available.
   * 
   *   actor ! message
   * 
   * 
   */
  def !(message: Any)(implicit sender: ActorRef = null): Unit

  /**
   * Sends a message asynchronously, returning a future which may eventually hold the reply.
   */
  private[actors] def ?(message: Any, timeout: Duration): Future[Any]

  /**
   * Forwards the message and passes the original sender actor as the sender.
   * 

   * Works with '!' and '?'.
   */
  def forward(message: Any)

  private[actors] def localActor: AbstractActor

}

private[actors] class OutputChannelRef(val actor: OutputChannel[Any]) extends ActorRef {

  override private[actors] def ?(message: Any, timeout: Duration): Future[Any] =
    throw new UnsupportedOperationException("Output channel does not support ?")

  /**
   * Sends a one-way asynchronous message. E.g. fire-and-forget semantics.
   * 

   *
   * 

   * 
   *   actor ! message
   * 
   * 
   */
  def !(message: Any)(implicit sender: ActorRef = null): Unit =
    if (sender != null)
      actor.send(message, sender.localActor)
    else
      actor ! message

  override def equals(that: Any) =
    that.isInstanceOf[OutputChannelRef] && that.asInstanceOf[OutputChannelRef].actor == this.actor

  private[actors] override def localActor: AbstractActor =
    throw new UnsupportedOperationException("Output channel does not have an instance of the actor")

  def forward(message: Any): Unit = throw new UnsupportedOperationException("OutputChannel does not support forward.")

}

private[actors] class ReactorRef(override val actor: Reactor[Any]) extends OutputChannelRef(actor) {

  /**
   * Forwards the message and passes the original sender actor as the sender.
   * 
   * Works with '!' and '?'.
   */
  override def forward(message: Any) = actor.forward(message)

}

private[actors] final class InternalActorRef(override val actor: InternalActor) extends ReactorRef(actor) {

  /**
   * Sends a message asynchronously, returning a future which may eventually hold the reply.
   */
  override private[actors] def ?(message: Any, timeout: Duration): Future[Any] =
    Futures.future {
      val dur = if (timeout.isFinite()) timeout.toMillis else (java.lang.Long.MAX_VALUE >> 2)
      actor !? (dur, message) match {
        case Some(x) => x
        case None => new AskTimeoutException("? operation timed out.")
      }
    }

  override def !(message: Any)(implicit sender: ActorRef = null): Unit =
    if (message == PoisonPill)
      actor.stop('normal)
    else if (sender != null)
      actor.send(message, sender.localActor)
    else
      actor ! message

  private[actors] override def localActor: InternalActor = this.actor
}

/**
 * This is what is used to complete a Future that is returned from an ask/? call,
 * when it times out.
 */
class AskTimeoutException(message: String, cause: Throwable) extends TimeoutException {
  def this(message: String) = this(message, null: Throwable)
}

object PoisonPill