Scala example source code file (DelegatingScheduler.scala)

This example Scala source code file (DelegatingScheduler.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

actor, boolean, concurrent, delegatingscheduler, ischeduler, managedblocker, runnable, trackedreactor, unit

The DelegatingScheduler.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2005-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.actors
package scheduler

import scala.concurrent.ManagedBlocker

/**
 * @author Erik Engbrecht
 */
private[actors] trait DelegatingScheduler extends IScheduler {
  protected def makeNewScheduler(): IScheduler

  protected var sched: IScheduler = null

  final def impl = synchronized {
    if ((sched eq null) || (!sched.isActive))
      sched = makeNewScheduler()
    sched
  }

  final def impl_= (scheduler: IScheduler): Unit = synchronized {
    //TODO: if there is already a scheduler, should it be shutdown?
    sched = scheduler
  }

  /**
   * Always active because it will just make a new scheduler if required
   */
  def isActive: Boolean = true

  def execute(fun: => Unit) = impl.execute(fun)

  def execute(task: Runnable) = impl.execute(task)

  override def executeFromActor(task: Runnable) = impl.executeFromActor(task)

  def shutdown(): Unit = synchronized {
    if (sched ne null) {
      sched.shutdown()
      sched = null
    }
  }

  def newActor(actor: TrackedReactor) = synchronized {
    val createNew = if (sched eq null)
      true
    else sched.synchronized {
      if (!sched.isActive)
        true
      else {
        sched.newActor(actor)
        false
      }
    }
    if (createNew) {
      sched = makeNewScheduler()
      sched.newActor(actor)
    }
  }

  def terminated(actor: TrackedReactor) = impl.terminated(actor)

  def onTerminate(actor: TrackedReactor)(f: => Unit) = impl.onTerminate(actor)(f)

  override def managedBlock(blocker: ManagedBlocker): Unit =
    impl.managedBlock(blocker)
}