lucene/core/src/java/org/apache/lucene/util/BytesRefComparator.java

/*
 * 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.lucene.util;

import java.util.Comparator;

/**
 * Specialized {@link BytesRef} comparator that {@link
 * FixedLengthBytesRefArray#iterator(Comparator)} has optimizations for.
 *
 * @lucene.internal
 */
public abstract class BytesRefComparator implements Comparator<BytesRef> {

  final int comparedBytesCount;

  /**
   * Sole constructor.
   *
   * @param comparedBytesCount the maximum number of bytes to compare.
   */
  protected BytesRefComparator(int comparedBytesCount) {
    this.comparedBytesCount = comparedBytesCount;
  }

  /**
   * Return the unsigned byte to use for comparison at index {@code i}, or {@code -1} if all bytes
   * that are useful for comparisons are exhausted. This may only be called with a value of {@code
   * i} between {@code 0} included and {@code comparedBytesCount} excluded.
   */
  protected abstract int byteAt(BytesRef ref, int i);

  @Override
  public int compare(BytesRef o1, BytesRef o2) {
    for (int i = 0; i < comparedBytesCount; ++i) {
      final int b1 = byteAt(o1, i);
      final int b2 = byteAt(o2, i);
      if (b1 != b2) {
        return b1 - b2;
      } else if (b1 == -1) {
        break;
      }
    }
    return 0;
  }
}