monix.reactive.internal.operators.ThrottleLastObservable.scala Maven / Gradle / Ivy
/*
* Copyright (c) 2014-2020 by The Monix Project Developers.
* 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 monix.reactive.internal.operators
import monix.execution.Ack.{Continue, Stop}
import monix.execution.cancelables.{CompositeCancelable, SingleAssignCancelable}
import monix.execution.{Ack, Cancelable}
import monix.reactive.Observable
import monix.reactive.observers.Subscriber
import scala.concurrent.Future
private[reactive] final class ThrottleLastObservable[+A, S](
source: Observable[A],
sampler: Observable[S],
shouldRepeatOnSilence: Boolean)
extends Observable[A] {
def unsafeSubscribeFn(downstream: Subscriber[A]): Cancelable = {
val upstreamSubscription = SingleAssignCancelable()
val samplerSubscription = SingleAssignCancelable()
val composite = CompositeCancelable(upstreamSubscription, samplerSubscription)
upstreamSubscription := source.unsafeSubscribeFn(new Subscriber.Sync[A] { upstreamSubscriber =>
implicit val scheduler = downstream.scheduler
// Value is volatile to keep write to lastValue visible
// after this one is seen as being true
@volatile private[this] var hasValue = false
// MUST BE written before `hasValue = true`
private[this] var lastValue: A = _
// To be written in onComplete/onError, to be read from tick
private[this] var upstreamIsDone = false
// MUST BE synchronized by `upstreamSubscriber`.
private[this] var downstreamIsDone = false
def onNext(elem: A): Ack =
if (downstreamIsDone) Stop
else {
lastValue = elem
hasValue = true
Continue
}
def onError(ex: Throwable): Unit =
upstreamSubscriber.synchronized {
if (!downstreamIsDone) {
downstreamIsDone = true
samplerSubscription.cancel()
downstream.onError(ex)
}
}
def onComplete(): Unit =
upstreamSubscriber.synchronized {
upstreamIsDone = true
}
samplerSubscription := sampler.unsafeSubscribeFn(new Subscriber[S] { self =>
implicit val scheduler = downstream.scheduler
def onNext(elem: S): Future[Ack] =
upstreamSubscriber.synchronized(signalNext())
def onError(ex: Throwable): Unit =
upstreamSubscriber.onError(ex)
def onComplete(): Unit =
upstreamSubscriber.synchronized {
upstreamIsDone = true
signalNext()
}
def signalNext(): Future[Ack] =
if (downstreamIsDone) Stop
else {
val next =
if (!hasValue) Continue
else {
hasValue = shouldRepeatOnSilence
val ack = downstream.onNext(lastValue)
ack.syncOnStopOrFailure { _ =>
downstreamIsDone = true
upstreamSubscription.cancel()
}
}
if (!upstreamIsDone) next
else {
downstreamIsDone = true
upstreamSubscription.cancel()
if (next ne Stop) downstream.onComplete()
Stop
}
}
})
})
composite
}
}