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Druid Aggregators based on datasketches lib http://datasketches.github.io/

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.query.aggregation.datasketches.quantiles;

import java.nio.ByteBuffer;

import com.yahoo.memory.Memory;
import com.yahoo.sketches.quantiles.DoublesSketch;

import io.druid.segment.data.ObjectStrategy;

public class DoublesSketchObjectStrategy implements ObjectStrategy
{

  private static final byte[] EMPTY_BYTES = new byte[] {};

  @Override
  public int compare(final DoublesSketch s1, final DoublesSketch s2)
  {
    return DoublesSketchAggregatorFactory.COMPARATOR.compare(s1, s2);
  }

  @Override
  public DoublesSketch fromByteBuffer(final ByteBuffer buffer, final int numBytes)
  {
    if (numBytes == 0) {
      return DoublesSketchOperations.EMPTY_SKETCH;
    }
    return DoublesSketch.wrap(Memory.wrap(buffer).region(buffer.position(), numBytes));
  }

  @Override
  public Class getClazz()
  {
    return DoublesSketch.class;
  }

  @Override
  public byte[] toBytes(final DoublesSketch sketch)
  {
    if (sketch == null || sketch.isEmpty()) {
      return EMPTY_BYTES;
    }
    return sketch.toByteArray(true);
  }

}