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/**
 * 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.pinot.segment.spi.partition;

import com.google.common.base.Preconditions;


/**
 * Hash code partition function, where:
 * 
 *    partitionId = value.hashCode() % {@link #_numPartitions}
 * 
 */
public class HashCodePartitionFunction implements PartitionFunction {
  private static final String NAME = "HashCode";
  private final int _numPartitions;

  public HashCodePartitionFunction(int numPartitions) {
    Preconditions.checkArgument(numPartitions > 0, "Number of partitions must be > 0, specified", numPartitions);
    _numPartitions = numPartitions;
  }

  @Override
  public int getPartition(Object value) {
    return abs(value.toString().hashCode()) % _numPartitions;
  }

  @Override
  public String getName() {
    return NAME;
  }

  @Override
  public int getNumPartitions() {
    return _numPartitions;
  }

  // Keep it for backward-compatibility, use getName() instead
  @Override
  public String toString() {
    return NAME;
  }

  // NOTE: This matches the Utils.abs() in Kafka
  private static int abs(int n) {
    return (n == Integer.MIN_VALUE) ? 0 : Math.abs(n);
  }
}