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

package scala.actors

import scala.util.control.ControlThrowable
import java.util.{Timer, TimerTask}
import scala.language.implicitConversions

/**
* Provides functions for the definition of actors, as well as actor
* operations, such as `receive`, `react`, `reply`, etc.
*
* @author Philipp Haller
*/
@deprecated("Use the akka.actor package instead. For migration from the scala.actors package refer to the Actors Migration Guide.", "2.11.0")
object Actor extends Combinators {

  /** State of an actor.
*
* - '''New''' -
* Not yet started
* - '''Runnable''' -
* Executing
* - '''Suspended''' -
* Suspended, waiting in a `react`
* - '''TimedSuspended''' -
* Suspended, waiting in a `reactWithin`
* - '''Blocked''' -
* Blocked waiting in a `receive`
* - '''TimedBlocked''' -
* Blocked waiting in a `receiveWithin`
* - '''Terminated''' -
* Actor has terminated
*/
  object State extends Enumeration {
    val New,
        Runnable,
        Suspended,
        TimedSuspended,
        Blocked,
        TimedBlocked,
        Terminated = Value
  }

  private[actors] val tl = new ThreadLocal[InternalReplyReactor]

  // timer thread runs as daemon
  private[actors] val timer = new Timer(true)

  private[actors] val suspendException = new SuspendActorControl

  /**
* Returns the currently executing actor. Should be used instead
* of `'''this'''` in all blocks of code executed by actors.
*
* @return returns the currently executing actor.
*/
  def self: Actor = self(Scheduler).asInstanceOf[Actor]

  private[actors] def self(sched: IScheduler): InternalActor =
    rawSelf(sched).asInstanceOf[InternalActor]

  private[actors] def rawSelf: InternalReplyReactor =
    rawSelf(Scheduler)

  private[actors] def rawSelf(sched: IScheduler): InternalReplyReactor = {
    val s = tl.get
    if (s eq null) {
      val r = new ActorProxy(Thread.currentThread, sched)
      tl.set(r)
      r
    } else
      s
  }

  private def parentScheduler: IScheduler = {
    val s = tl.get
    if (s eq null) Scheduler else s.scheduler
  }

  /**
* Resets an actor proxy associated with the current thread.
* It replaces the implicit `ActorProxy` instance
* of the current thread (if any) with a new instance.
*
* This permits to re-use the current thread as an actor
* even if its `ActorProxy` has died for some reason.
*/
  def resetProxy() {
    val a = tl.get
    if ((null ne a) && a.isInstanceOf[ActorProxy])
      tl.set(new ActorProxy(Thread.currentThread, parentScheduler))
  }

  /**
* Removes any reference to an `Actor` instance
* currently stored in thread-local storage.
*
* This allows to release references from threads that are potentially
* long-running or being re-used (e.g. inside a thread pool). Permanent
* references in thread-local storage are a potential memory leak.
*/
  def clearSelf() {
    tl set null
  }

  /**
* Factory method for creating and starting an actor.
*
* @example {{{
* import scala.actors.Actor._
* ...
* val a = actor {
* ...
* }
* }}}
*
* @param body the code block to be executed by the newly created actor
* @return the newly created actor. Note that it is automatically started.
*/
  def actor(body: => Unit): Actor = {
    val a = new Actor {
      def act() = body
      override final val scheduler: IScheduler = parentScheduler
    }
    a.start()
    a
  }

  /**
* Factory method for creating actors whose
* body is defined using a `Responder`.
*
* @example {{{
* import scala.actors.Actor._
* import Responder.exec
* ...
* val a = reactor {
* for {
* res <- b !! MyRequest;
* if exec(println("result: "+res))
* } yield {}
* }
* }}}
*
* @param body the `Responder` to be executed by the newly created actor
* @return the newly created actor. Note that it is automatically started.
*/
  def reactor(body: => Responder[Unit]): Actor = {
    val a = new Actor {
      def act() {
        Responder.run(body)
      }
      override final val scheduler: IScheduler = parentScheduler
    }
    a.start()
    a
  }

  /**
* Receives the next message from the mailbox of the current actor `self`.
*/
  def ? : Any = self.?

  /**
* Receives a message from the mailbox of `self`. Blocks if no message
* matching any of the cases of `f` can be received.
*
* @example {{{
* receive {
* case "exit" => println("exiting")
* case 42 => println("got the answer")
* case x:Int => println("got an answer")
* }
* }}}
*
* @param f a partial function specifying patterns and actions
* @return the result of processing the received message
*/
  def receive[A](f: PartialFunction[Any, A]): A =
    self.receive(f)

  /**
* Receives a message from the mailbox of `self`. Blocks at most `msec`
* milliseconds if no message matching any of the cases of `f` can be
* received. If no message could be received the `TIMEOUT` action is
* executed if specified.
*
* @param msec the time span before timeout
* @param f a partial function specifying patterns and actions
* @return the result of processing the received message
*/
  def receiveWithin[R](msec: Long)(f: PartialFunction[Any, R]): R =
    self.receiveWithin(msec)(f)

  /**
* Lightweight variant of `receive`.
*
* Actions in `f` have to contain the rest of the computation of `self`,
* as this method will never return.
*
* A common method of continuting the computation is to send a message
* to another actor:
* {{{
* react {
* case Get(from) =>
* react {
* case Put(x) => from ! x
* }
* }
* }}}
*
* Another common method is to use `loop` to continuously `react` to messages:
* {{{
* loop {
* react {
* case Msg(data) => // process data
* }
* }
* }}}
*
* @param f a partial function specifying patterns and actions
* @return this function never returns
*/
  def react(f: PartialFunction[Any, Unit]): Nothing =
    rawSelf.react(f)

  /**
* Lightweight variant of `receiveWithin`.
*
* Actions in `f` have to contain the rest of the computation of `self`,
* as this method will never return.
*
* @param msec the time span before timeout
* @param f a partial function specifying patterns and actions
* @return this function never returns
*/
  def reactWithin(msec: Long)(f: PartialFunction[Any, Unit]): Nothing =
    self.reactWithin(msec)(f)

  def eventloop(f: PartialFunction[Any, Unit]): Nothing =
    rawSelf.react(new RecursiveProxyHandler(rawSelf, f))

  private class RecursiveProxyHandler(a: InternalReplyReactor, f: PartialFunction[Any, Unit])
          extends PartialFunction[Any, Unit] {
    def isDefinedAt(m: Any): Boolean =
      true // events are immediately removed from the mailbox
    def apply(m: Any) {
      if (f.isDefinedAt(m)) f(m)
      a.react(this)
    }
  }

  /**
* Returns the actor which sent the last received message.
*/
  def sender: OutputChannel[Any] =
    rawSelf.internalSender

  /**
* Sends `msg` to the actor waiting in a call to `!?`.
*/
  def reply(msg: Any): Unit =
    rawSelf.reply(msg)

  /**
* Sends `()` to the actor waiting in a call to `!?`.
*/
  def reply(): Unit =
    rawSelf.reply(())

  /**
* Returns the number of messages in `self`'s mailbox
*
* @return the number of messages in `self`'s mailbox
*/
  def mailboxSize: Int = rawSelf.mailboxSize

  /**
* Converts a synchronous event-based operation into
* an asynchronous `Responder`.
*
* @example {{{
* val adder = reactor {
* for {
* _ <- respondOn(react) { case Add(a, b) => reply(a+b) }
* } yield {}
* }
* }}}
*/
  def respondOn[A, B](fun: PartialFunction[A, Unit] => Nothing):
    PartialFunction[A, B] => Responder[B] =
      (caseBlock: PartialFunction[A, B]) => new Responder[B] {
        def respond(k: B => Unit) = fun(caseBlock andThen k)
      }

  private[actors] trait Body[a] {
    def andThen[b](other: => b): Unit
  }

  implicit def mkBody[a](body: => a) = new InternalActor.Body[a] {
    def andThen[b](other: => b): Unit = rawSelf.seq(body, other)
  }

  /**
* Links `self` to actor `to`.
*
* @param to the actor to link to
* @return the parameter actor
*/
  def link(to: AbstractActor): AbstractActor = self.link(to)

  /**
* Links `self` to the actor defined by `body`.
*
* @param body the body of the actor to link to
* @return the parameter actor
*/
  def link(body: => Unit): Actor = self.link(body)

  /**
* Unlinks `self` from actor `from`.
*
* @param from the actor to unlink from
*/
  def unlink(from: AbstractActor): Unit = self.unlink(from)

  /**
* Terminates execution of `self` with the following effect on
* linked actors:
*
* For each linked actor `a` with `trapExit` set to `'''true'''`,
* send message `Exit(self, reason)` to `a`.
*
* For each linked actor `a` with `trapExit` set to `'''false'''`
* (default), call `a.exit(reason)` if `reason != 'normal`.
*/
  def exit(reason: AnyRef): Nothing = self.exit(reason)

  /**
* Terminates execution of `self` with the following effect on
* linked actors:
*
* For each linked actor `a` with `trapExit` set to `'''true'''`,
* send message `Exit(self, 'normal)` to `a`.
*/
  def exit(): Nothing = rawSelf.exit()

}

/** Provides lightweight, concurrent actors. Actors are created by extending
* the `Actor` trait (alternatively, one of the factory methods in its
* companion object can be used). The behavior of an `Actor` subclass is
* defined by implementing its `act` method:
* {{{
* class MyActor extends Actor {
* def act() {
* // actor behavior goes here
* }
* }
* }}}
* A new `Actor` instance is started by invoking its `start` method.
*
* '''Note:''' care must be taken when invoking thread-blocking methods other
* than those provided by the `Actor` trait or its companion object (such as
* `receive`). Blocking the underlying thread inside an actor may lead to
* starvation of other actors. This also applies to actors hogging their
* thread for a long time between invoking `receive`/`react`.
*
* If actors use blocking operations (for example, methods for blocking I/O),
* there are several options:
*
* - The run-time system can be configured to use a larger thread pool size
* (for example, by setting the `actors.corePoolSize` JVM property).
* - The `scheduler` method of the `Actor` trait can be overridden to return a
* `ResizableThreadPoolScheduler`, which resizes its thread pool to
* avoid starvation caused by actors that invoke arbitrary blocking methods.
* - The `actors.enableForkJoin` JVM property can be set to `false`, in which
* case a `ResizableThreadPoolScheduler` is used by default to execute actors.
*
* The main ideas of the implementation are explained in the two papers
*
* - [[http://lampwww.epfl.ch/~odersky/papers/jmlc06.pdf Event-Based
* Programming without Inversion of Control]],
* Philipp Haller and Martin Odersky, ''Proc. JMLC 2006'', and
* - [[http://lamp.epfl.ch/~phaller/doc/haller07coord.pdf Actors that
* Unify Threads and Events]],
* Philipp Haller and Martin Odersky, ''Proc. COORDINATION 2007''.
*
* @author Philipp Haller
*
* @define actor actor
* @define channel actor's mailbox
*/
@SerialVersionUID(-781154067877019505L)
@deprecated("Use the akka.actor package instead. For migration from the scala.actors package refer to the Actors Migration Guide.", "2.11.0")
trait Actor extends InternalActor with ReplyReactor {

  override def start(): Actor = synchronized {
    super.start()
    this
  }

  }

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