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/**
* Copyright (C) 2009-2014 Typesafe Inc.
*/
package akka.dispatch.sysmsg
import scala.annotation.tailrec
import akka.actor.{ ActorInitializationException, InternalActorRef, ActorRef, PossiblyHarmful }
import akka.actor.DeadLetterSuppression
import akka.actor.DeadLetterSuppression
/**
* INTERNAL API
*
* Helper companion object for [[akka.dispatch.sysmsg.LatestFirstSystemMessageList]] and
* [[akka.dispatch.sysmsg.EarliestFirstSystemMessageList]]
*/
private[akka] object SystemMessageList {
final val LNil: LatestFirstSystemMessageList = new LatestFirstSystemMessageList(null)
final val ENil: EarliestFirstSystemMessageList = new EarliestFirstSystemMessageList(null)
@tailrec
private[sysmsg] def sizeInner(head: SystemMessage, acc: Int): Int = if (head eq null) acc else sizeInner(head.next, acc + 1)
@tailrec
private[sysmsg] def reverseInner(head: SystemMessage, acc: SystemMessage): SystemMessage = {
if (head eq null) acc else {
val next = head.next
head.next = acc
reverseInner(next, head)
}
}
}
/**
*
* INTERNAL API
*
* Value class supporting list operations on system messages. The `next` field of [[SystemMessage]]
* is hidden, and can only accessed through the value classes [[akka.dispatch.sysmsg.LatestFirstSystemMessageList]] and
* [[akka.dispatch.sysmsg.EarliestFirstSystemMessageList]], abstracting over the fact that system messages are the
* list nodes themselves. If used properly, this stays a compile time construct without any allocation overhead.
*
* This list is mutable.
*
* The type of the list also encodes that the messages contained are in reverse order, i.e. the head of the list is the
* latest appended element.
*
*/
private[akka] class LatestFirstSystemMessageList(val head: SystemMessage) extends AnyVal {
import SystemMessageList._
/**
* Indicates if the list is empty or not. This operation has constant cost.
*/
final def isEmpty: Boolean = head eq null
/**
* Indicates if the list has at least one element or not. This operation has constant cost.
*/
final def nonEmpty: Boolean = head ne null
/**
* Indicates if the list is empty or not. This operation has constant cost.
*/
final def size: Int = sizeInner(head, 0)
/**
* Gives back the list containing all the elements except the first. This operation has constant cost.
*
* *Warning:* as the underlying list nodes (the [[SystemMessage]] instances) are mutable, care
* should be taken when passing the tail to other methods. [[akka.dispatch.sysmsg.SystemMessage#unlink]] should be
* called on the head if one wants to detach the tail permanently.
*/
final def tail: LatestFirstSystemMessageList = new LatestFirstSystemMessageList(head.next)
/**
* Reverses the list. This operation mutates the underlying list. The cost of the call to reverse is linear in the
* number of elements.
*
* The type of the returned list is of the opposite order: [[akka.dispatch.sysmsg.EarliestFirstSystemMessageList]]
*/
final def reverse: EarliestFirstSystemMessageList = new EarliestFirstSystemMessageList(reverseInner(head, null))
/**
* Attaches a message to the current head of the list. This operation has constant cost.
*/
final def ::(msg: SystemMessage): LatestFirstSystemMessageList = {
assert(msg ne null)
msg.next = head
new LatestFirstSystemMessageList(msg)
}
}
/**
*
* INTERNAL API
*
* Value class supporting list operations on system messages. The `next` field of [[SystemMessage]]
* is hidden, and can only accessed through the value classes [[akka.dispatch.sysmsg.LatestFirstSystemMessageList]] and
* [[akka.dispatch.sysmsg.EarliestFirstSystemMessageList]], abstracting over the fact that system messages are the
* list nodes themselves. If used properly, this stays a compile time construct without any allocation overhead.
*
* This list is mutable.
*
* This list type also encodes that the messages contained are in reverse order, i.e. the head of the list is the
* latest appended element.
*
*/
private[akka] class EarliestFirstSystemMessageList(val head: SystemMessage) extends AnyVal {
import SystemMessageList._
/**
* Indicates if the list is empty or not. This operation has constant cost.
*/
final def isEmpty: Boolean = head eq null
/**
* Indicates if the list has at least one element or not. This operation has constant cost.
*/
final def nonEmpty: Boolean = head ne null
/**
* Indicates if the list is empty or not. This operation has constant cost.
*/
final def size: Int = sizeInner(head, 0)
/**
* Gives back the list containing all the elements except the first. This operation has constant cost.
*
* *Warning:* as the underlying list nodes (the [[SystemMessage]] instances) are mutable, care
* should be taken when passing the tail to other methods. [[akka.dispatch.sysmsg.SystemMessage#unlink]] should be
* called on the head if one wants to detach the tail permanently.
*/
final def tail: EarliestFirstSystemMessageList = new EarliestFirstSystemMessageList(head.next)
/**
* Reverses the list. This operation mutates the underlying list. The cost of the call to reverse is linear in the
* number of elements.
*
* The type of the returned list is of the opposite order: [[akka.dispatch.sysmsg.LatestFirstSystemMessageList]]
*/
final def reverse: LatestFirstSystemMessageList = new LatestFirstSystemMessageList(reverseInner(head, null))
/**
* Attaches a message to the current head of the list. This operation has constant cost.
*/
final def ::(msg: SystemMessage): EarliestFirstSystemMessageList = {
assert(msg ne null)
msg.next = head
new EarliestFirstSystemMessageList(msg)
}
/**
* Prepends a list in a reversed order to the head of this list. The prepended list will be reversed during the process.
*
* Example: (3, 4, 5) reversePrepend (2, 1, 0) == (0, 1, 2, 3, 4, 5)
*
* The cost of this operation is linear in the size of the list that is to be prepended.
*/
final def reverse_:::(other: LatestFirstSystemMessageList): EarliestFirstSystemMessageList = {
var remaining = other
var result = this
while (remaining.nonEmpty) {
val msg = remaining.head
remaining = remaining.tail
result ::= msg
}
result
}
}
/**
* System messages are handled specially: they form their own queue within
* each actor’s mailbox. This queue is encoded in the messages themselves to
* avoid extra allocations and overhead. The next pointer is a normal var, and
* it does not need to be volatile because in the enqueuing method its update
* is immediately succeeded by a volatile write and all reads happen after the
* volatile read in the dequeuing thread. Afterwards, the obtained list of
* system messages is handled in a single thread only and not ever passed around,
* hence no further synchronization is needed.
*
* INTERNAL API
*
* ➡➡➡ NEVER SEND THE SAME SYSTEM MESSAGE OBJECT TO TWO ACTORS ⬅⬅⬅
*/
private[akka] sealed trait SystemMessage extends PossiblyHarmful with Serializable {
// Next fields are only modifiable via the SystemMessageList value class
@transient
private[sysmsg] var next: SystemMessage = _
def unlink(): Unit = next = null
def unlinked: Boolean = next eq null
}
/**
* INTERNAL API
*/
private[akka] trait StashWhenWaitingForChildren
/**
* INTERNAL API
*/
private[akka] trait StashWhenFailed
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Create(failure: Option[ActorInitializationException]) extends SystemMessage // sent to self from Dispatcher.register
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Recreate(cause: Throwable) extends SystemMessage with StashWhenWaitingForChildren // sent to self from ActorCell.restart
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Suspend() extends SystemMessage with StashWhenWaitingForChildren // sent to self from ActorCell.suspend
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Resume(causedByFailure: Throwable) extends SystemMessage with StashWhenWaitingForChildren // sent to self from ActorCell.resume
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Terminate() extends SystemMessage with DeadLetterSuppression // sent to self from ActorCell.stop
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Supervise(child: ActorRef, async: Boolean) extends SystemMessage // sent to supervisor ActorRef from ActorCell.start
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Watch(watchee: InternalActorRef, watcher: InternalActorRef) extends SystemMessage // sent to establish a DeathWatch
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Unwatch(watchee: ActorRef, watcher: ActorRef) extends SystemMessage // sent to tear down a DeathWatch
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case object NoMessage extends SystemMessage // switched into the mailbox to signal termination
/**
* INTERNAL API
*/
@SerialVersionUID(1L)
private[akka] case class Failed(child: ActorRef, cause: Throwable, uid: Int) extends SystemMessage
with StashWhenFailed
with StashWhenWaitingForChildren
@SerialVersionUID(1L)
private[akka] case class DeathWatchNotification(
actor: ActorRef,
existenceConfirmed: Boolean,
addressTerminated: Boolean) extends SystemMessage with DeadLetterSuppression
