com.datastax.oss.driver.internal.core.util.collection.QueryPlanBase Maven / Gradle / Ivy
/*
* Copyright DataStax, 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 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.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicInteger;
import net.jcip.annotations.ThreadSafe;
@ThreadSafe
public abstract class QueryPlanBase extends AbstractQueue implements QueryPlan {
private final AtomicInteger nextIndex = new AtomicInteger();
/**
* Returns the nodes in this query plan; the returned array should stay the same across
* invocations.
*
* The declared return type is {@code Object[]} because of implementation details of {@link
* com.datastax.oss.driver.internal.core.loadbalancing.DefaultLoadBalancingPolicy
* DefaultLoadBalancingPolicy} and {@link
* com.datastax.oss.driver.internal.core.loadbalancing.BasicLoadBalancingPolicy
* BasicLoadBalancingPolicy}, but all elements must be instances of {@link Node}, otherwise
* instance methods will fail later.
*/
protected abstract Object[] getNodes();
@Nullable
@Override
public Node poll() {
// We don't handle overflow. In practice it won't be an issue, since the driver stops polling
// once the query plan is empty.
int i = nextIndex.getAndIncrement();
Object[] nodes = getNodes();
return (i >= nodes.length) ? null : (Node) nodes[i];
}
@NonNull
@Override
public Iterator iterator() {
int i = nextIndex.get();
Object[] nodes = getNodes();
if (i >= nodes.length) {
return Collections.emptyIterator();
} else {
return Iterators.forArray(Arrays.copyOfRange(nodes, i, nodes.length, Node[].class));
}
}
@Override
public int size() {
return Math.max(getNodes().length - nextIndex.get(), 0);
}
}