content: /*
   * 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
   *
   *     https://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.avro.hadoop.util;
  
  import java.util.Comparator;
  
  /**
   * Compares Avro string data (data with schema <i>"string"</i>).
   *
   * <p>
   * The only case where comparing Avro objects does not work using their natural
   * order is when the schema is <i>"string"</i>. The Avro string schema maps to
   * the Java <code>CharSequence</code> interface, which does not define
   * <code>equals</code>, <code>hashCode</code>, or <code>compareTo</code>.
   * </p>
   *
   * <p>
   * Using this comparator enables comparisons between <code>String</code> and
   * <code>Utf8</code> objects that are both valid when working with Avro strings.
   * </p>
   *
   * @param <T> The type of object to compare.
   */
  public class AvroCharSequenceComparator<T> implements Comparator<T> {
    /** A singleton instance. */
    public static final AvroCharSequenceComparator<CharSequence> INSTANCE = new AvroCharSequenceComparator<>();
  
    /** {@inheritDoc} */
    @Override
    public int compare(T o1, T o2) {
      if (!(o1 instanceof CharSequence) || !(o2 instanceof CharSequence)) {
        throw new RuntimeException("Attempted use of AvroCharSequenceComparator on non-CharSequence objects: "
            + o1.getClass().getName() + " and " + o2.getClass().getName());
      }
      return compareCharSequence((CharSequence) o1, (CharSequence) o2);
    }
  
    /**
     * Compares the CharSequences <code>o1</code> and <code>o2</code>.
     *
     * @param o1 The left charsequence.
     * @param o2 The right charsequence.
     * @return a negative integer, zero, or a positive integer if the first argument
     *         is less than, equal to, or greater than the second, respectively.
     */
    private int compareCharSequence(CharSequence o1, CharSequence o2) {
      for (int i = 0; i < Math.max(o1.length(), o2.length()); i++) {
        int charComparison = compareCharacter(o1, o2, i);
        if (0 != charComparison) {
          return charComparison;
        }
      }
      return 0;
    }
  
    /**
     * Compares the characters of <code>o1</code> and <code>o2</code> at index
     * <code>index</code>.
     *
     * @param o1    The left charsequence.
     * @param o2    The right charsequence.
     * @param index The zero-based index into the charsequences to compare.
     * @return a negative integer, zero, or a positive integer if the first argument
     *         is less than, equal to, or greater than the second, respectively.
     */
    private int compareCharacter(CharSequence o1, CharSequence o2, int index) {
      if (index < o1.length() && index < o2.length()) {
        return Character.compare(o1.charAt(index), o2.charAt(index));
      }
      if (index >= o1.length() && index >= o2.length()) {
        return 0;
      }
      return o1.length() - o2.length();
    }
  }
  