/*

 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.

 */

/*

 * 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 com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.DTMIterator;

import com.sun.org.apache.xml.internal.utils.WrappedRuntimeException;

import java.util.ArrayList;

import java.util.List;

/**

 * Pool of object of a given type to pick from to help memory usage

 * @xsl.usage internal

 * @LastModified: Oct 2017

 */

public final class IteratorPool implements java.io.Serializable

{

    static final long serialVersionUID = -460927331149566998L;

  /**

   * Type of objects in this pool.

   */

  private final DTMIterator m_orig;

  /**

   * Stack of given objects this points to.

   */

  private final List<DTMIterator> m_freeStack;

  /**

   * Constructor IteratorPool

   *

   * @param original The original iterator from which all others will be cloned.

   */

  public IteratorPool(DTMIterator original)

  {

    m_orig = original;

    m_freeStack = new ArrayList<>();

  }

  /**

   * Get an instance of the given object in this pool

   *

   * @return An instance of the given object

   */

  public synchronized DTMIterator getInstanceOrThrow()

    throws CloneNotSupportedException

  {

    // Check if the pool is empty.

    if (m_freeStack.isEmpty())

    {

      // Create a new object if so.

      return (DTMIterator)m_orig.clone();

    }

    else

    {

      // Remove object from end of free pool.

      DTMIterator result = m_freeStack.remove(m_freeStack.size() - 1);

      return result;

    }

  }

  /**

   * Get an instance of the given object in this pool

   *

   * @return An instance of the given object

   */

  public synchronized DTMIterator getInstance()

  {

    // Check if the pool is empty.

    if (m_freeStack.isEmpty())

    {

      // Create a new object if so.

      try

      {

        return (DTMIterator)m_orig.clone();

      }

      catch (Exception ex)

      {

        throw new WrappedRuntimeException(ex);

      }

    }

    else

    {

      // Remove object from end of free pool.

      DTMIterator result = m_freeStack.remove(m_freeStack.size() - 1);

      return result;

    }

  }

  /**

   * Add an instance of the given object to the pool

   *

   *

   * @param obj Object to add.

   */

  public synchronized void freeInstance(DTMIterator obj)

  {

    m_freeStack.add(obj);

  }

}