/*
 * 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.datasketches.hive.kll;

import org.apache.datasketches.kll.KllFloatsSketch;
import org.apache.datasketches.memory.Memory;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.BytesWritable;

@Description(name = "GetN", value = "_FUNC_(sketch)",
extended = " Returns the total number of observed input values (stream length) from a given KllFloatsSketch.")
@SuppressWarnings("javadoc")
public class GetNUDF extends UDF {

  /**
   * Returns N from a given sketch
   * @param serializedSketch serialized sketch
   * @return stream length
   */
  public Long evaluate(final BytesWritable serializedSketch) {
    if (serializedSketch == null) { return null; }
    final KllFloatsSketch sketch = KllFloatsSketch.heapify(Memory.wrap(serializedSketch.getBytes()));
    return sketch.getN();
  }

}