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
   *
   *    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.arrow.algorithm.search;
  
  import org.apache.arrow.algorithm.sort.VectorValueComparator;
  import org.apache.arrow.vector.ValueVector;
  
  /** Search for the range of a particular element in the target vector. */
  public class VectorRangeSearcher {
  
    /** Result returned when a search fails. */
    public static final int SEARCH_FAIL_RESULT = -1;
  
    /**
     * Search for the first occurrence of an element. The search is based on the binary search
     * algorithm. So the target vector must be sorted.
     *
     * @param targetVector the vector from which to perform the search.
     * @param comparator the criterion for the comparison.
     * @param keyVector the vector containing the element to search.
     * @param keyIndex the index of the search key in the key vector.
     * @param <V> the vector type.
     * @return the index of the first matched element if any, and -1 otherwise.
     */
    public static <V extends ValueVector> int getFirstMatch(
        V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
      comparator.attachVectors(keyVector, targetVector);
  
      int ret = SEARCH_FAIL_RESULT;
  
      int low = 0;
      int high = targetVector.getValueCount() - 1;
  
      while (low <= high) {
        int mid = low + (high - low) / 2;
        int result = comparator.compare(keyIndex, mid);
        if (result < 0) {
          // the key is smaller
          high = mid - 1;
        } else if (result > 0) {
          // the key is larger
          low = mid + 1;
        } else {
          // an equal element is found
          // continue to go left-ward
          ret = mid;
          high = mid - 1;
        }
      }
      return ret;
    }
  
    /**
     * Search for the last occurrence of an element. The search is based on the binary search
     * algorithm. So the target vector must be sorted.
     *
     * @param targetVector the vector from which to perform the search.
     * @param comparator the criterion for the comparison.
     * @param keyVector the vector containing the element to search.
     * @param keyIndex the index of the search key in the key vector.
     * @param <V> the vector type.
     * @return the index of the last matched element if any, and -1 otherwise.
     */
    public static <V extends ValueVector> int getLastMatch(
        V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
      comparator.attachVectors(keyVector, targetVector);
  
      int ret = SEARCH_FAIL_RESULT;
  
      int low = 0;
      int high = targetVector.getValueCount() - 1;
  
      while (low <= high) {
        int mid = low + (high - low) / 2;
        int result = comparator.compare(keyIndex, mid);
        if (result < 0) {
          // the key is smaller
          high = mid - 1;
        } else if (result > 0) {
          // the key is larger
          low = mid + 1;
        } else {
          // an equal element is found,
          // continue to go right-ward
          ret = mid;
          low = mid + 1;
        }
      }
      return ret;
    }
  }
  