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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
package collection
package mutable
/** `Publisher[A,This]` objects publish events of type `A`
* to all registered subscribers. When subscribing, a subscriber may specify
* a filter which can be used to constrain the number of events sent to the
* subscriber. Subscribers may suspend their subscription, or reactivate a
* suspended subscription. Class `Publisher` is typically used
* as a mixin. The abstract type `Pub` models the type of the publisher itself.
*
* @tparam Evt type of the published event.
*
* @author Matthias Zenger
* @author Martin Odersky
* @version 2.8
* @since 1
*/
trait Publisher[Evt] {
type Pub <: Publisher[Evt]
type Sub = Subscriber[Evt, Pub]
type Filter = Evt => Boolean
/** The publisher itself of type `Pub`. Implemented by a cast from `this` here.
* Needs to be overridden if the actual publisher is different from `this`.
*/
protected val self: Pub = this.asInstanceOf[Pub]
private val filters = new HashMap[Sub, Set[Filter]] with MultiMap[Sub, Filter]
private val suspended = new HashSet[Sub]
def subscribe(sub: Sub) { subscribe(sub, event => true) }
def subscribe(sub: Sub, filter: Filter) { filters.addBinding(sub, filter) }
def suspendSubscription(sub: Sub) { suspended += sub }
def activateSubscription(sub: Sub) { suspended -= sub }
def removeSubscription(sub: Sub) { filters -= sub }
def removeSubscriptions() { filters.clear() }
protected def publish(event: Evt) {
filters.keys.foreach(sub =>
if (!suspended.contains(sub) &&
filters.entryExists(sub, p => p(event)))
sub.notify(self, event)
)
}
/** Checks if two publishers are structurally identical.
*
* @return true, iff both publishers contain the same sequence of elements.
*/
override def equals(obj: Any): Boolean = obj match {
case that: Publisher[_] => filters == that.filters && suspended == that.suspended
case _ => false
}
}
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