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/*
* Copyright 2000-2014 JetBrains s.r.o.
*
* 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 com.intellij.util.concurrency;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.Queue;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
public class BoundedTaskExecutor implements Executor {
protected final Executor myBackendExecutor;
private final int myMaxTasks;
private final AtomicInteger myInProgress = new AtomicInteger(0);
private final Queue<FutureTask> myTaskQueue = new LinkedBlockingQueue<FutureTask>();
private final Runnable USER_TASK_RUNNER = new Runnable() {
@Override
public void run() {
final FutureTask task = myTaskQueue.poll();
try {
if (task != null && !task.isCancelled()) {
task.run();
}
}
finally {
myInProgress.decrementAndGet();
if (!myTaskQueue.isEmpty()) {
processQueue();
}
}
}
};
public BoundedTaskExecutor(@NotNull Executor backendExecutor, int maxSimultaneousTasks) {
myBackendExecutor = backendExecutor;
assert maxSimultaneousTasks >= 1 : maxSimultaneousTasks;
myMaxTasks = Math.max(maxSimultaneousTasks, 1);
}
@Override
public void execute(@NotNull Runnable task) {
submit(task);
}
@NotNull
public Future<?> submit(@NotNull Runnable task) {
final RunnableFuture<Void> future = queueTask(new FutureTask<Void>(task, null));
if (future == null) {
throw new RuntimeException("Failed to queue task: " + task);
}
return future;
}
@NotNull
public <T> Future<T> submit(@NotNull Callable<T> task) {
final RunnableFuture<T> future = queueTask(new FutureTask<T>(task));
if (future == null) {
throw new RuntimeException("Failed to queue task: " + task);
}
return future;
}
@Nullable
private <T> RunnableFuture<T> queueTask(@NotNull FutureTask<T> futureTask) {
if (myTaskQueue.offer(futureTask)) {
processQueue();
return futureTask;
}
return null;
}
protected void processQueue() {
while (true) {
final int count = myInProgress.get();
if (count >= myMaxTasks) {
return;
}
if (myInProgress.compareAndSet(count, count + 1)) {
break;
}
}
myBackendExecutor.execute(USER_TASK_RUNNER);
}
}
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