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Deprecated Actors Library for Scala
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2005-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.actors
import java.util.TimerTask
import scala.util.control.ControlThrowable
private[actors] object InternalActor {
private[actors] trait Body[a] {
def andThen[b](other: => b): Unit
}
}
private[actors] trait InternalActor extends AbstractActor with InternalReplyReactor with ActorCanReply with InputChannel[Any] with Serializable {
/* The following two fields are only used when the actor
* suspends by blocking its underlying thread, for example,
* when waiting in a receive or synchronous send.
*/
@volatile
private[actors] var isSuspended = false
/* This field is used to communicate the received message from
* the invocation of send to the place where the thread of
* the receiving actor resumes inside receive/receiveWithin.
*/
@volatile
private var received: Option[Any] = None
protected[actors] override def scheduler: IScheduler = Scheduler
private[actors] override def startSearch(msg: Any, replyTo: OutputChannel[Any], handler: PartialFunction[Any, Any]) =
if (isSuspended) {
() =>
synchronized {
mailbox.append(msg, replyTo)
resumeActor()
}
} else super.startSearch(msg, replyTo, handler)
// we override this method to check `shouldExit` before suspending
private[actors] override def searchMailbox(startMbox: MQueue[Any],
handler: PartialFunction[Any, Any],
resumeOnSameThread: Boolean) {
var tmpMbox = startMbox
var done = false
while (!done) {
val qel = tmpMbox.extractFirst((msg: Any, replyTo: OutputChannel[Any]) => {
senders = List(replyTo)
handler.isDefinedAt(msg)
})
if (tmpMbox ne mailbox)
tmpMbox.foreach((m, s) => mailbox.append(m, s))
if (null eq qel) {
synchronized {
// in mean time new stuff might have arrived
if (!sendBuffer.isEmpty) {
tmpMbox = new MQueue[Any]("Temp")
drainSendBuffer(tmpMbox)
// keep going
} else {
// very important to check for `shouldExit` at this point
// since linked actors might have set it after we checked
// last time (e.g., at the beginning of `react`)
if (shouldExit) exit()
waitingFor = handler
// see Reactor.searchMailbox
throw Actor.suspendException
}
}
} else {
resumeReceiver((qel.msg, qel.session), handler, resumeOnSameThread)
done = true
}
}
}
private[actors] override def makeReaction(fun: () => Unit, handler: PartialFunction[Any, Any], msg: Any): Runnable =
new ActorTask(this, fun, handler, msg)
/** See the companion object's `receive` method. */
def receive[R](f: PartialFunction[Any, R]): R = {
assert(Actor.self(scheduler) == this, "receive from channel belonging to other actor")
synchronized {
if (shouldExit) exit() // links
drainSendBuffer(mailbox)
}
var done = false
while (!done) {
val qel = mailbox.extractFirst((m: Any, replyTo: OutputChannel[Any]) => {
senders = replyTo :: senders
val matches = f.isDefinedAt(m)
senders = senders.tail
matches
})
if (null eq qel) {
synchronized {
// in mean time new stuff might have arrived
if (!sendBuffer.isEmpty) {
drainSendBuffer(mailbox)
// keep going
} else {
waitingFor = f
isSuspended = true
scheduler.managedBlock(blocker)
drainSendBuffer(mailbox)
// keep going
}
}
} else {
received = Some(qel.msg)
senders = qel.session :: senders
done = true
}
}
val result = f(received.get)
received = None
senders = senders.tail
result
}
/** See the companion object's `receiveWithin` method. */
def receiveWithin[R](msec: Long)(f: PartialFunction[Any, R]): R = {
assert(Actor.self(scheduler) == this, "receive from channel belonging to other actor")
synchronized {
if (shouldExit) exit() // links
drainSendBuffer(mailbox)
}
// first, remove spurious TIMEOUT message from mailbox if any
mailbox.extractFirst((m: Any, replyTo: OutputChannel[Any]) => m == TIMEOUT)
val receiveTimeout = () => {
if (f.isDefinedAt(TIMEOUT)) {
received = Some(TIMEOUT)
senders = this :: senders
} else
sys.error("unhandled timeout")
}
var done = false
while (!done) {
val qel = mailbox.extractFirst((m: Any, replyTo: OutputChannel[Any]) => {
senders = replyTo :: senders
val matches = f.isDefinedAt(m)
senders = senders.tail
matches
})
if (null eq qel) {
val todo = synchronized {
// in mean time new stuff might have arrived
if (!sendBuffer.isEmpty) {
drainSendBuffer(mailbox)
// keep going
() => {}
} else if (msec == 0L) {
done = true
receiveTimeout
} else {
if (onTimeout.isEmpty) {
if (!f.isDefinedAt(TIMEOUT))
sys.error("unhandled timeout")
val thisActor = this
onTimeout = Some(new TimerTask {
def run() {
thisActor.send(TIMEOUT, thisActor)
}
})
Actor.timer.schedule(onTimeout.get, msec)
}
// It is possible that !onTimeout.isEmpty, but TIMEOUT is not yet in mailbox
// See SI-4759
waitingFor = f
received = None
isSuspended = true
scheduler.managedBlock(blocker)
drainSendBuffer(mailbox)
// keep going
() => {}
}
}
todo()
} else {
synchronized {
if (!onTimeout.isEmpty) {
onTimeout.get.cancel()
onTimeout = None
}
}
received = Some(qel.msg)
senders = qel.session :: senders
done = true
}
}
val result = f(received.get)
received = None
senders = senders.tail
result
}
/** See the companion object's `react` method. */
override def react(handler: PartialFunction[Any, Unit]): Nothing = {
synchronized {
if (shouldExit) exit()
}
super.react(handler)
}
/** See the companion object's `reactWithin` method. */
override def reactWithin(msec: Long)(handler: PartialFunction[Any, Unit]): Nothing = {
synchronized {
if (shouldExit) exit()
}
super.reactWithin(msec)(handler)
}
/** Receives the next message from the mailbox */
def ? : Any = receive {
case x => x
}
// guarded by lock of this
// never throws SuspendActorControl
private[actors] override def scheduleActor(f: PartialFunction[Any, Any], msg: Any) =
if (f eq null) {
// do nothing (timeout is handled instead)
} else {
val task = new ActorTask(this, null, f, msg)
scheduler executeFromActor task
}
/* Used for notifying scheduler when blocking inside receive/receiveWithin. */
private object blocker extends scala.concurrent.ManagedBlocker {
def block() = {
InternalActor.this.suspendActor()
true
}
def isReleasable =
!InternalActor.this.isSuspended
}
private def suspendActor() = synchronized {
while (isSuspended) {
try {
wait()
} catch {
case _: InterruptedException =>
}
}
// links: check if we should exit
if (shouldExit) exit()
}
private def resumeActor() {
isSuspended = false
notify()
}
private[actors] override def exiting = synchronized {
_state == Actor.State.Terminated
}
// guarded by this
private[actors] override def dostart() {
// Reset various flags.
//
// Note that we do *not* reset `trapExit`. The reason is that
// users should be able to set the field in the constructor
// and before `act` is called.
exitReason = 'normal
shouldExit = false
super.dostart()
}
override def start(): InternalActor = synchronized {
super.start()
this
}
/** State of this actor */
override def getState: Actor.State.Value = synchronized {
if (isSuspended) {
if (onTimeout.isEmpty)
Actor.State.Blocked
else
Actor.State.TimedBlocked
} else
super.getState
}
// guarded by this
private[actors] var links: List[AbstractActor] = Nil
/**
* Links self to actor to.
*
* @param to the actor to link to
* @return the parameter actor
*/
def link(to: AbstractActor): AbstractActor = {
assert(Actor.self(scheduler) == this, "link called on actor different from self")
this linkTo to
to linkTo this
to
}
/**
* Links self to actor to.
*
* @param to the actor to link to
* @return the parameter actor
*/
def link(to: ActorRef): ActorRef = {
this.link(to.localActor)
to
}
/**
* Unidirectional linking. For migration purposes only
*/
private[actors] def watch(subject: ActorRef): ActorRef = {
assert(Actor.self(scheduler) == this, "link called on actor different from self")
subject.localActor linkTo this
subject
}
/**
* Unidirectional linking. For migration purposes only
*/
private[actors] def unwatch(subject: ActorRef): ActorRef = {
assert(Actor.self(scheduler) == this, "link called on actor different from self")
subject.localActor unlinkFrom this
subject
}
/**
* 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 = {
assert(Actor.self(scheduler) == this, "link called on actor different from self")
val a = new Actor {
def act() = body
override final val scheduler: IScheduler = InternalActor.this.scheduler
}
link(a)
a.start()
a
}
private[actors] def linkTo(to: AbstractActor) = synchronized {
links = to :: links
}
/**
* Unlinks self from actor from.
*/
def unlink(from: AbstractActor) {
assert(Actor.self(scheduler) == this, "unlink called on actor different from self")
this unlinkFrom from
from unlinkFrom this
}
/**
* Unlinks self from actor from.
*/
def unlink(from: ActorRef) {
unlink(from.localActor)
}
private[actors] def unlinkFrom(from: AbstractActor) = synchronized {
links = links.filterNot(from.==)
}
@volatile
private[actors] var _trapExit = false
def trapExit = _trapExit
def trapExit_=(value: Boolean) = _trapExit = value
// guarded by this
private var exitReason: AnyRef = 'normal
// guarded by this
private[actors] var shouldExit = false
/**
*
* 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.
*
*/
protected[actors] def exit(reason: AnyRef): Nothing = {
synchronized {
exitReason = reason
}
exit()
}
/**
* Terminates with exit reason 'normal.
*/
protected[actors] override def exit(): Nothing = {
val todo = synchronized {
if (!links.isEmpty)
exitLinked()
else
() => {}
}
todo()
super.exit()
}
// Assume !links.isEmpty
// guarded by this
private[actors] def exitLinked(): () => Unit = {
_state = Actor.State.Terminated
// reset waitingFor, otherwise getState returns Suspended
waitingFor = Reactor.waitingForNone
// remove this from links
val mylinks = links.filterNot(this.==)
// unlink actors
mylinks.foreach(unlinkFrom(_))
// return closure that locks linked actors
() => {
mylinks.foreach((linked: AbstractActor) => {
linked.synchronized {
if (!linked.exiting) {
linked.unlinkFrom(this)
linked.exit(this, exitReason)
}
}
})
}
}
// Assume !links.isEmpty
// guarded by this
private[actors] def exitLinked(reason: AnyRef): () => Unit = {
exitReason = reason
exitLinked()
}
// Assume !this.exiting
private[actors] def exit(from: AbstractActor, reason: AnyRef) {
if (trapExit) {
this ! Exit(from, reason)
} else if (reason != 'normal)
stop(reason)
}
/* Requires qualified private, because RemoteActor must
* register a termination handler.
*/
private[actors] def onTerminate(f: => Unit) {
scheduler.onTerminate(this) { f }
}
private[actors] def stop(reason: AnyRef): Unit = {
synchronized {
shouldExit = true
exitReason = reason
// resume this Actor in a way that
// causes it to exit
// (because shouldExit == true)
if (isSuspended)
resumeActor()
else if (waitingFor ne Reactor.waitingForNone) {
waitingFor = Reactor.waitingForNone
// it doesn't matter what partial function we are passing here
val task = new ActorTask(this, null, waitingFor, null)
scheduler execute task
/* Here we should not throw a SuspendActorControl,
since the current method is called from an actor that
is in the process of exiting.
Therefore, the contract for scheduleActor is that
it never throws a SuspendActorControl.
*/
}
}
}
}
/**
* Used as the timeout pattern in
*
* receiveWithin and
*
* reactWithin.
*
* @example {{{
* receiveWithin(500) {
* case (x, y) => ...
* case TIMEOUT => ...
* }
* }}}
*
* @author Philipp Haller
*/
case object TIMEOUT
/**
* Sent to an actor
* with `trapExit` set to `true` whenever one of its linked actors
* terminates.
*
* @param from the actor that terminated
* @param reason the reason that caused the actor to terminate
*/
case class Exit(from: AbstractActor, reason: AnyRef)
/**
* Manages control flow of actor executions.
*
* @author Philipp Haller
*/
private[actors] class SuspendActorControl extends ControlThrowable
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