com.diozero.api.sandpit.EventQueue Maven / Gradle / Ivy
package com.diozero.api.sandpit;
/*-
* #%L
* Organisation: diozero
* Project: diozero - Core
* Filename: EventQueue.java
*
* This file is part of the diozero project. More information about this project
* can be found at https://www.diozero.com/.
* %%
* Copyright (C) 2016 - 2021 diozero
* %%
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
* #L%
*/
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Consumer;
import com.diozero.api.Event;
import com.diozero.util.DiozeroScheduler;
/**
* Decouple event producers from consumers so that event production isn't
* affected by event consumption
*
* @param the class containing the data fields for individual events
*/
public class EventQueue implements Consumer, Runnable, AutoCloseable {
private final BlockingQueue queue;
private final List> listeners;
private final AtomicBoolean running;
private Future future;
public EventQueue() {
queue = new LinkedBlockingQueue<>();
listeners = new ArrayList<>();
running = new AtomicBoolean();
start();
}
public void addListener(Consumer listener) {
listeners.add(listener);
}
public void removeListener(Consumer listener) {
listeners.remove(listener);
}
/**
* Adds an element to the tail of the queue
*/
@Override
public void accept(T t) {
queue.offer(t);
}
public void start() {
running.set(true);
future = DiozeroScheduler.getNonDaemonInstance().submit(this);
}
@Override
public void run() {
while (running.get()) {
try {
T event = queue.take();
listeners.forEach(listener -> listener.accept(event));
} catch (InterruptedException e) {
running.set(false);
// Set interrupted flag
Thread.currentThread().interrupt();
}
/*-
// Drain the remaining elements on the queue and process them.
final Collection remaining_events = new ArrayList<>();
queue.drainTo(remaining_events);
remaining_events.forEach(event -> listeners.forEach(listener -> listener.accept(event)));
*/
}
}
public void stop() {
running.set(false);
if (future != null) {
future.cancel(true);
}
}
@Override
public void close() {
stop();
}
}