package test; import scala.concurrent._; class MailBox with Monitor { private class LinkedList[a] { var elem: a = _; var next: LinkedList[a] = null; } def insert[a](l: LinkedList[a], x: a): LinkedList[a] = { l.next = new LinkedList[a]; l.next.elem = x; l.next.next = l.next; l } private abstract class Receiver { def isDefined(msg: Any): boolean; var msg: Any = null; } private val sent = new LinkedList[Any]; private var lastSent = sent; private val receivers = new LinkedList[Receiver]; private var lastReceiver = receivers; def send(msg: Any): unit = synchronized { var r = receivers, r1 = r.next; while (r1 != null && !r1.elem.isDefined(msg)) { r = r1; r1 = r1.next; } if (r1 != null) { r.next = r1.next; r1.elem.msg = msg; r1.elem.notify; } else { lastSent = insert(lastSent, msg); } } def receive[a](f: PartialFunction[Any, a]): a = { val msg: Any = synchronized { var s = sent, s1 = s.next; while (s1 != null && !f.isDefinedAt(s1.elem)) { s = s1; s1 = s1.next } if (s1 != null) { s.next = s1.next; s1.elem } else { val r = insert(lastReceiver, new Receiver { def isDefined(msg: Any) = f.isDefinedAt(msg); }); lastReceiver = r; r.elem.wait(); r.elem.msg } } f(msg) } def receiveWithin[a](msec: long)(f: PartialFunction[Any, a]): a = { val msg: Any = synchronized { var s = sent, s1 = s.next; while (s1 != null && !f.isDefinedAt(s1.elem)) { s = s1; s1 = s1.next ; } if (s1 != null) { s.next = s1.next; s1.elem } else { val r = insert(lastReceiver, new Receiver { def isDefined(msg: Any) = f.isDefinedAt(msg); }); lastReceiver = r; r.elem.wait(msec); if (r.elem.msg == null) r.elem.msg = TIMEOUT; r.elem.msg } } f(msg) } }