/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.wave.testing;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.Semaphore;
/**
* A executor which defers execution until requested.
*
* This class is designed to be used as an in-thread fake of an executor, and is
* not thread safe.
*
* @author anorth@google.com (Alex North)
*/
public final class DeferredExecutor implements Executor {
private final Semaphore numTasks = new Semaphore(0);
private List<Runnable> thingsToExecute = Lists.newArrayList();
private boolean shutdownCalled = false;
@Override
public void execute(Runnable command) throws RejectedExecutionException {
if (shutdownCalled) {
throw new RejectedExecutionException();
}
thingsToExecute.add(command);
numTasks.release();
}
public List<Runnable> shutdown() {
shutdownCalled = true;
runQueuedCommands();
List<Runnable> unexecuted = Lists.newArrayList(thingsToExecute);
thingsToExecute.clear();
return unexecuted;
}
public boolean isShutdown() {
return shutdownCalled;
}
public void checkShutdown() {
Preconditions.checkState(isShutdown(), "Not shut down");
Preconditions.checkState(thingsToExecute.size() == 0, "Still has things to execute");
}
/**
* Runs all commands which have been scheduled and removes them from the
* queue. Commands are executed in the calling thread.
*
* Note that commands scheduled as a result of executed commands are not
* immediately run.
*
* @see #runAllCommands
*/
public void runQueuedCommands() {
List<Runnable> thingsToExecuteNow = thingsToExecute;
thingsToExecute = new ArrayList<Runnable>();
for (Runnable r : thingsToExecuteNow) {
r.run();
}
}
/**
* Runs commands until no commands remain to run.
*/
public void runAllCommands() {
while (!thingsToExecute.isEmpty()) {
runQueuedCommands();
}
}
/**
* Waits for howMany tasks to be submitted.
*/
public void waitForTasks(int howMany) {
numTasks.acquireUninterruptibly(howMany);
}
}