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* Licensed to the Apache Software Foundation (ASF) under one
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* 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,
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* See the License for the specific language governing permissions and
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package com.datastax.dse.driver.internal.core.graph;
import com.datastax.dse.driver.api.core.graph.GraphNode;
import com.datastax.oss.driver.internal.core.util.CountingIterator;
import com.datastax.oss.driver.shaded.guava.common.base.Preconditions;
import java.util.Queue;
import net.jcip.annotations.NotThreadSafe;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
@NotThreadSafe // wraps a mutable queue
class GraphResultIterator extends CountingIterator {
private final Queue data;
private final GraphProtocol graphProtocol;
// Sometimes a traversal can yield the same result multiple times consecutively. To avoid
// duplicating the data, DSE graph sends it only once with a counter indicating how many times
// it's repeated.
private long repeat = 0;
private GraphNode lastGraphNode = null;
GraphResultIterator(Queue data, GraphProtocol graphProtocol) {
super(data.size());
this.data = data;
this.graphProtocol = graphProtocol;
}
@Override
protected GraphNode computeNext() {
if (repeat > 1) {
repeat -= 1;
// Note that we don't make a defensive copy, we assume the client won't mutate the node
return lastGraphNode;
}
GraphNode container = data.poll();
if (container == null) {
return endOfData();
}
if (graphProtocol.isGraphBinary()) {
// results are contained in a Traverser object and not a Map if the protocol
// is GraphBinary
Preconditions.checkState(
container.as(Object.class) instanceof Traverser,
"Graph protocol error. Received object should be a Traverser but it is not.");
Traverser t = container.as(Traverser.class);
this.repeat = t.bulk();
this.lastGraphNode = new ObjectGraphNode(t.get());
return lastGraphNode;
} else {
// The repeat counter is called "bulk" in the JSON payload
GraphNode b = container.getByKey("bulk");
if (b != null) {
this.repeat = b.asLong();
}
lastGraphNode = container.getByKey("result");
return lastGraphNode;
}
}
}