org.apache.pinot.segment.local.utils.IdMap Maven / Gradle / Ivy

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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.local.utils;

import java.io.Closeable;


/**
 * Interface for a map from Key to auto-generated contiguous integer Id's.
 *
 * @param 
 */
public interface IdMap extends Closeable {
  int INVALID_ID = -1;

  /**
   * Puts the specified key into the map. The id for the key is auto-generated as follows:
   *
   *  If key does not exist in the map, it is inserted into the map with a new id which is equal to number of
   * elements in the map before the key is inserted. For example, the first key inserted will have id of 0, second
   * will have an id of 1, and so on. 
   *
   *  If key already exists in the map, then it keeps its original id.
   *
   * @param key Key to be inserted into the map.
   *
   * @return Returns the id for the key.
   */
  int put(Key key);

  /**
   * Returns the id associated with the specified key.
   *
   *  Returns the id of the key if it exists. 
   *  Returns {@link IdMap#INVALID_ID} if the key does not exist in the map. 
   *
   * @param key Key to get.
   * @return Id of the key.
   */
  int getId(Key key);

  /**
   * Returns the key associated with the specified id.
   *
   *  Returns the id of the key if it exists. 
   *  Returns null if the key does not exist in the map. 
   *
   * @param id id for which to get the key.
   * @return Key for the id.
   */
  Key getKey(int id);

  /**
   * Returns the current size of the map, zero if the map is empty.
   * @return Size of the map.
   */
  int size();
}