code: /*
   * 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.
   */
  /*
   * $Id$
   */
  package org.apache.xml.utils;
  
  import java.util.EmptyStackException;
  
  /**
   * Implement a stack of simple integers.
   *
   * %OPT%
   * This is currently based on ObjectVector, which permits fast acess but pays a
   * heavy recopying penalty if/when its size is increased. If we expect deep
   * stacks, we should consider a version based on ChunkedObjectVector.
   * @xsl.usage internal
   */
  public class ObjectStack extends ObjectVector
  {
  
    /**
     * Default constructor.  Note that the default
     * block size is very small, for small lists.
     */
    public ObjectStack()
    {
      super();
    }
  
    /**
     * Construct a ObjectVector, using the given block size.
     *
     * @param blocksize Size of block to allocate
     */
    public ObjectStack(int blocksize)
    {
      super(blocksize);
    }
  
    /**
     * Copy constructor for ObjectStack
     * 
     * @param v ObjectStack to copy
     */
    public ObjectStack (ObjectStack v)
    {
    	super(v);
    }
    
    /**
     * Pushes an item onto the top of this stack.
     *
     * @param   i   the int to be pushed onto this stack.
     * @return  the <code>item</code> argument.
     */
    public Object push(Object i)
    {
  
      if ((m_firstFree + 1) >= m_mapSize)
      {
        m_mapSize += m_blocksize;
  
        Object newMap[] = new Object[m_mapSize];
  
        System.arraycopy(m_map, 0, newMap, 0, m_firstFree + 1);
  
        m_map = newMap;
      }
  
      m_map[m_firstFree] = i;
  
      m_firstFree++;
  
      return i;
    }
  
    /**
     * Removes the object at the top of this stack and returns that
     * object as the value of this function.
     *
     * @return     The object at the top of this stack.
     */
    public Object pop()
    {
      Object val = m_map[--m_firstFree];
      m_map[m_firstFree] = null;
      
      return val;
    }
  
    /**
     * Quickly pops a number of items from the stack.
     */
  
    public void quickPop(int n)
    {
      m_firstFree -= n;
    }
  
    /**
     * Looks at the object at the top of this stack without removing it
     * from the stack.
     *
     * @return     the object at the top of this stack.
     * @throws  EmptyStackException  if this stack is empty.
     */
    public Object peek()
    {
      try {
        return m_map[m_firstFree - 1];
      }
      catch (ArrayIndexOutOfBoundsException e)
      {
        throw new EmptyStackException();
      }
    }
  
    /**
     * Looks at the object at the position the stack counting down n items.
     *
     * @param n The number of items down, indexed from zero.
     * @return     the object at n items down.
     * @throws  EmptyStackException  if this stack is empty.
     */
    public Object peek(int n)
    {
      try {
        return m_map[m_firstFree-(1+n)];
      }
      catch (ArrayIndexOutOfBoundsException e)
      {
        throw new EmptyStackException();
      }
    }
  
    /**
     * Sets an object at a the top of the statck
     *
     *
     * @param val object to set at the top
     * @throws  EmptyStackException  if this stack is empty.
     */
    public void setTop(Object val)
    {
      try {
        m_map[m_firstFree - 1] = val;
      }
      catch (ArrayIndexOutOfBoundsException e)
      {
        throw new EmptyStackException();
      }
    }
  
    /**
     * Tests if this stack is empty.
     *
     * @return  <code>true</code> if this stack is empty;
     *          <code>false</code> otherwise.
     * @since   JDK1.0
     */
    public boolean empty()
    {
      return m_firstFree == 0;
    }
  
    /**
     * Returns where an object is on this stack.
     *
     * @param   o   the desired object.
     * @return  the distance from the top of the stack where the object is]
     *          located; the return value <code>-1</code> indicates that the
     *          object is not on the stack.
     * @since   JDK1.0
     */
    public int search(Object o)
    {
  
      int i = lastIndexOf(o);
  
      if (i >= 0)
      {
        return size() - i;
      }
  
      return -1;
    }
  
    /**
     * Returns clone of current ObjectStack
     * 
     * @return clone of current ObjectStack
     */
    public Object clone()
      throws CloneNotSupportedException
    {
    	return (ObjectStack) super.clone();
    }  
    
  }
  