iterator-test-harness/src/main/java/org/apache/accumulo/iteratortest/SimpleKVReusingIterator.java

/*
 * 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.apache.accumulo.iteratortest;

import java.io.IOException;
import java.util.Collection;
import java.util.Map;

import org.apache.accumulo.core.data.ByteSequence;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Range;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.iterators.IteratorEnvironment;
import org.apache.accumulo.core.iterators.SortedKeyValueIterator;

/**
 * Internally, Accumulo reuses the same instance of Key and Value to reduce the number of objects to
 * be garbage collected. This iterator simulates that.
 */
public class SimpleKVReusingIterator implements SortedKeyValueIterator<Key,Value> {

  private final SortedKeyValueIterator<Key,Value> source;
  private final Key topKey = new Key();
  private final Value topValue = new Value();

  public SimpleKVReusingIterator(SortedKeyValueIterator<Key,Value> source) {
    this.source = source;
  }

  @Override
  public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options,
      IteratorEnvironment env) throws IOException {
    this.source.init(source, options, env);
  }

  @Override
  public boolean hasTop() {
    return source.hasTop();
  }

  @Override
  public void next() throws IOException {
    source.next();
    load();
  }

  @Override
  public void seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive)
      throws IOException {
    source.seek(range, columnFamilies, inclusive);
    load();
  }

  @Override
  public Key getTopKey() {
    return topKey;
  }

  @Override
  public Value getTopValue() {
    return topValue;
  }

  @Override
  public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env) {
    SortedKeyValueIterator<Key,Value> newSource = source.deepCopy(env);
    return new SimpleKVReusingIterator(newSource);
  }

  private void load() {
    if (hasTop()) {
      topKey.set(source.getTopKey());
      topValue.set(source.getTopValue().get());
    }
  }
}