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The XPath engine used by HtmlUnit.
There is a newer version: 4.7.0
/*
 * 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.htmlunit.xpath.compiler;

/**
 * Like IntVector, but used only for the OpMap array. Length of array is kept in the m_lengthPos
 * position of the array. Only the required methods are in included here.
 */
public class OpMapVector {

  /** Size of blocks to allocate */
  protected final int m_blocksize;

  /** Array of ints */
  protected int[] m_map; // IntStack is trying to see this directly

  /** Position where size of array is kept */
  protected int m_lengthPos;

  /** Size of array */
  protected int m_mapSize;

  /**
   * Construct a OpMapVector, using the given block size.
   *
   * @param blocksize Size of block to allocate
   */
  public OpMapVector(final int blocksize, final int increaseSize, final int lengthPos) {
    m_blocksize = increaseSize;
    m_mapSize = blocksize;
    m_lengthPos = lengthPos;
    m_map = new int[blocksize];
  }

  /**
   * Get the nth element.
   *
   * @param i index of object to get
   * @return object at given index
   */
  public final int elementAt(final int i) {
    return m_map[i];
  }

  /**
   * Sets the component at the specified index of this vector to be the specified object. The
   * previous component at that position is discarded.
   *
   * The index must be a value greater than or equal to 0 and less than the current size of the
   * vector.
   *
   * @param value object to set
   * @param index Index of where to set the object
   */
  public final void setElementAt(final int value, final int index) {
    if (index >= m_mapSize) {
      final int oldSize = m_mapSize;

      m_mapSize += m_blocksize;

      final int[] newMap = new int[m_mapSize];

      System.arraycopy(m_map, 0, newMap, 0, oldSize);

      m_map = newMap;
    }

    m_map[index] = value;
  }

  /*
   * Reset the array to the supplied size. No checking is done.
   *
   * @param size The size to trim to.
   */
  public final void setToSize(final int size) {

    final int[] newMap = new int[size];

    System.arraycopy(m_map, 0, newMap, 0, m_map[m_lengthPos]);

    m_mapSize = size;
    m_map = newMap;
  }
}