/**
* Copyright 2009 Google Inc.
*
* 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 org.waveprotocol.box.server.waveserver;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
import java.util.Set;
/**
* Provides global, simple, deterministic single-threaded events based on global ticks.
*/
public class Ticker {
/** An easy number of ticks easy to divide, add, and multiply. */
public static final int EASY_TICKS = (2 * 2 * 2 * 2) * (3 * 3 * 3);
private int globalTicks = 0;
private final Multimap<Integer, Runnable> tickers = ArrayListMultimap.create();
/**
* Add an event to run after the global tick counter has run to the given number of ticks. The
* event will be run immediately if the ticks were in the past.
*/
public void runAt(int ticks, Runnable doneEvent) {
int finishedAt = ticks - globalTicks;
if (finishedAt <= 0) {
doneEvent.run();
} else {
tickers.put(finishedAt, doneEvent);
}
}
/**
* Advance the global tick counter and run finished events.
*/
public void tick(int ticks) {
globalTicks += ticks;
Set<Integer> tickerView = ImmutableSet.copyOf(tickers.keySet());
for (int i : tickerView) {
if (i <= globalTicks) {
for (Runnable doneEvent : tickers.get(i)) {
doneEvent.run();
}
tickers.removeAll(i);
}
}
}
}