/* Title: Pure/System/event_bus.scala
Author: Makarius
Generic event bus with multiple receiving actors.
*/
package isabelle
import scala.actors.Actor, Actor._
import scala.collection.mutable.ListBuffer
class Event_Bus[Event]
{
/* receivers */
private val receivers = new ListBuffer[Actor]
def += (r: Actor) { synchronized { receivers += r } }
def + (r: Actor): Event_Bus[Event] = { this += r; this }
def += (f: Event => Unit) {
this += actor { loop { react { case x => f(x.asInstanceOf[Event]) } } }
}
def + (f: Event => Unit): Event_Bus[Event] = { this += f; this }
def -= (r: Actor) { synchronized { receivers -= r } }
def - (r: Actor) = { this -= r; this }
/* event invocation */
def event(x: Event) { synchronized { receivers.foreach(_ ! x) } }
/* await global condition -- triggered via bus events */
def await(cond: => Boolean)
{
case object Wait
val a = new Actor {
def act {
if (cond) react { case Wait => reply(()); exit(Wait) }
else {
loop {
react {
case trigger if trigger != Wait =>
if (cond) { react { case Wait => reply(()); exit(Wait) } }
}
}
}
}
}
this += a
a.start
a !? Wait
this -= a
}
}