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* 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 com.datastax.oss.driver.internal.core.util.collection;
import com.datastax.oss.driver.api.core.metadata.Node;
import com.datastax.oss.driver.shaded.guava.common.collect.Iterators;
import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;
import java.util.AbstractQueue;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicInteger;
import net.jcip.annotations.ThreadSafe;
/** A query plan that encompasses many child plans, and consumes them one by one. */
@ThreadSafe
public class CompositeQueryPlan extends AbstractQueue implements QueryPlan {
private final Queue[] plans;
private final AtomicInteger currentPlan = new AtomicInteger(0);
@SafeVarargs
public CompositeQueryPlan(@NonNull Queue... plans) {
if (plans.length == 0) {
throw new IllegalArgumentException("at least one child plan must be provided");
}
for (Queue plan : plans) {
if (plan == null) {
throw new NullPointerException("child plan cannot be null");
}
}
this.plans = plans;
}
@Nullable
@Override
public Node poll() {
while (true) {
int current = currentPlan.get();
Queue plan = plans[current];
Node n = plan.poll();
if (n != null) {
return n;
}
int next = current + 1;
if (next == plans.length) {
return null;
}
currentPlan.compareAndSet(current, next);
}
}
@NonNull
@Override
public Iterator iterator() {
List> its = new ArrayList<>(plans.length);
for (Queue plan : plans) {
its.add(plan.iterator());
}
return Iterators.concat(its.iterator());
}
@Override
public int size() {
int size = 0;
for (Queue plan : plans) {
size += plan.size();
}
return size;
}
}