| /* |
| * 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(); |
| } |
| } |