monix.execution.internal.Trampoline.scala Maven / Gradle / Ivy
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/*
* Copyright (c) 2014-2019 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.execution.internal
import monix.execution.internal.collection.ChunkedArrayQueue
import scala.util.control.NonFatal
import scala.annotation.tailrec
import scala.concurrent.ExecutionContext
private[execution] class Trampoline(underlying: ExecutionContext) {
private def makeQueue(): ChunkedArrayQueue[Runnable] = ChunkedArrayQueue[Runnable](chunkSize = 16)
private[this] var immediateQueue = makeQueue()
private[this] var withinLoop = false
def startLoop(runnable: Runnable): Unit = {
withinLoop = true
try immediateLoop(runnable)
finally {
withinLoop = false
}
}
final def execute(runnable: Runnable): Unit = {
if (!withinLoop) {
startLoop(runnable)
} else {
immediateQueue.enqueue(runnable)
}
}
protected final def forkTheRest(): Unit = {
final class ResumeRun(head: Runnable, rest: ChunkedArrayQueue[Runnable]) extends Runnable {
def run(): Unit = {
immediateQueue.enqueueAll(rest)
immediateLoop(head)
}
}
val head = immediateQueue.dequeue()
if (head ne null) {
val rest = immediateQueue
immediateQueue = makeQueue()
underlying.execute(new ResumeRun(head, rest))
}
}
@tailrec
private final def immediateLoop(task: Runnable): Unit = {
try {
task.run()
} catch {
case ex: Throwable =>
forkTheRest()
if (NonFatal(ex)) underlying.reportFailure(ex)
else throw ex
}
val next = immediateQueue.dequeue()
if (next ne null) immediateLoop(next)
}
}