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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2005-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.actors
/**
* This class is used by our efficient message queue
* implementation.
*
* @version 0.9.9
* @author Philipp Haller
*/
@serializable
class MessageQueueElement(val msg: Any, val session: OutputChannel[Any], var next: MessageQueueElement) {
def this() = this(null, null, null)
def this(msg: Any, session: OutputChannel[Any]) = this(msg, session, null)
}
/**
* The class <code>MessageQueue</code> provides an efficient
* implementation of a message queue specialized for this actor
* library. Classes in this package are supposed to be the only
* clients of this class.
*
* @version 0.9.9
* @author Philipp Haller
*/
@serializable
class MessageQueue(protected val label: String) {
protected var first: MessageQueueElement = null
protected var last: MessageQueueElement = null // last eq null iff list is empty
private var _size = 0
def size = _size
final def isEmpty = last eq null
protected def changeSize(diff: Int) = {
_size += diff
}
def append(msg: Any, session: OutputChannel[Any]) {
changeSize(1) // size always increases by 1
val el = new MessageQueueElement(msg, session)
if (isEmpty) first = el
else last.next = el
last = el
}
def foreach(f: (Any, OutputChannel[Any]) => Unit) {
var curr = first
while (curr != null) {
f(curr.msg, curr.session)
curr = curr.next
}
}
def foldLeft[B](z: B)(f: (B, Any) => B): B = {
var acc = z
var curr = first
while (curr != null) {
acc = f(acc, curr.msg)
curr = curr.next
}
acc
}
/** Returns the n-th msg that satisfies the predicate
* without removing it.
*/
def get(n: Int)(p: Any => Boolean): Option[Any] = {
var pos = 0
def test(msg: Any): Boolean =
p(msg) && (pos == n || { pos += 1; false })
var curr = first
while (curr != null)
if (test(curr.msg)) return Some(curr.msg) // early return
else curr = curr.next
None
}
/** Removes the n-th msg that satisfies the predicate.
*/
def remove(n: Int)(p: Any => Boolean): Option[(Any, OutputChannel[Any])] =
removeInternal(n)(p) map (x => (x.msg, x.session))
def extractFirst(p: Any => Boolean): MessageQueueElement =
removeInternal(0)(p) orNull
private def removeInternal(n: Int)(p: Any => Boolean): Option[MessageQueueElement] = {
var pos = 0
def foundMsg(x: MessageQueueElement) = {
changeSize(-1)
Some(x)
}
def test(msg: Any): Boolean =
p(msg) && (pos == n || { pos += 1 ; false })
if (isEmpty) // early return
return None
// special handling if returning the head
if (test(first.msg)) {
val res = first
first = first.next
if (res eq last)
last = null
foundMsg(res)
}
else {
var curr = first.next // init to element #2
var prev = first
while (curr != null) {
if (test(curr.msg)) {
prev.next = curr.next
if (curr eq last)
last = prev
return foundMsg(curr) // early return
}
else {
prev = curr
curr = curr.next
}
}
// not found
None
}
}
}
/** Debugging trait.
*/
private[actors] trait MessageQueueTracer extends MessageQueue
{
private val queueNumber = MessageQueueTracer.getQueueNumber
override def append(msg: Any, session: OutputChannel[Any]) {
super.append(msg, session)
printQueue("APPEND %s" format msg)
}
override def get(n: Int)(p: Any => Boolean): Option[Any] = {
val res = super.get(n)(p)
printQueue("GET %s" format res)
res
}
override def remove(n: Int)(p: Any => Boolean): Option[(Any, OutputChannel[Any])] = {
val res = super.remove(n)(p)
printQueue("REMOVE %s" format res)
res
}
override def extractFirst(p: Any => Boolean): MessageQueueElement = {
val res = super.extractFirst(p)
printQueue("EXTRACT_FIRST %s" format res)
res
}
private def printQueue(msg: String) = {
def firstMsg = if (first eq null) "null" else first.msg
def lastMsg = if (last eq null) "null" else last.msg
println("[%s size=%d] [%s] first = %s, last = %s".format(this, size, msg, firstMsg, lastMsg))
}
override def toString() = "%s:%d".format(label, queueNumber)
}
object MessageQueueTracer {
// for tracing purposes
private var queueNumberAssigner = 0
private def getQueueNumber = synchronized {
queueNumberAssigner += 1
queueNumberAssigner
}
}
|
