monifu.reactive.internals.builders.amb.scala Maven / Gradle / Ivy
/*
* Copyright (c) 2014-2016 by its authors. Some rights reserved.
* See the project homepage at: https://monix.io
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package monifu.reactive.internals.builders
import monifu.concurrent.Scheduler
import monifu.concurrent.atomic.{Atomic, AtomicInt}
import monifu.reactive.Ack.Cancel
import monifu.reactive.{Ack, Observable, Observer}
import scala.concurrent.Future
private[reactive] object amb {
/**
* Given a list of source Observables, emits all of the items from the first of
* these Observables to emit an item and cancel the rest.
*/
def apply[T](source: Observable[T]*): Observable[T] = {
// helper function used for creating a subscription that uses `finishLine` as guard
def createSubscription(observable: Observable[T], observer: Observer[T], finishLine: AtomicInt, idx: Int)(implicit s: Scheduler): Unit =
observable.onSubscribe(new Observer[T] {
def onNext(elem: T): Future[Ack] = {
if (finishLine.get == idx || finishLine.compareAndSet(0, idx))
observer.onNext(elem)
else
Cancel
}
def onError(ex: Throwable): Unit = {
if (finishLine.get == idx || finishLine.compareAndSet(0, idx))
observer.onError(ex)
}
def onComplete(): Unit = {
if (finishLine.get == idx || finishLine.compareAndSet(0, idx))
observer.onComplete()
}
})
Observable.create { subscriber =>
import subscriber.scheduler
val finishLine = Atomic(0)
var idx = 0
for (observable <- source) {
createSubscription(observable, subscriber, finishLine, idx + 1)
idx += 1
}
// if the list of observables was empty, just
// emit `onComplete`
if (idx == 0) subscriber.onComplete()
}
}
}
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