monix.reactive.internal.operators.TakeLastOperator.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
import monix.execution.Ack.Continue
import monix.reactive.Observable
import monix.reactive.Observable.Operator
import monix.reactive.observers.Subscriber
import scala.collection.mutable
private[reactive] final class TakeLastOperator[A](n: Int) extends Operator[A, A] {
def apply(out: Subscriber[A]): Subscriber[A] = {
require(n > 0, "n should be strictly positive")
new Subscriber.Sync[A] {
implicit val scheduler = out.scheduler
private[this] val queue = mutable.Queue.empty[A]
private[this] var queued = 0
def onNext(elem: A): Ack = {
queue.enqueue(elem)
if (queued < n)
queued += 1
else
queue.dequeue()
Continue
}
def onComplete(): Unit = {
Observable.fromIterable(queue).unsafeSubscribeFn(out)
}
def onError(ex: Throwable): Unit = {
out.onError(ex)
}
}
}
}