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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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 * as provided by Sun in the GPL Version 2 section of the License file that
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 * elects to include this software in this distribution under the [CDDL or GPL
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package com.sun.org.apache.bcel.internal.verifier.structurals;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */

import com.sun.org.apache.bcel.internal.generic.*;
import com.sun.org.apache.bcel.internal.verifier.exc.*;
import java.util.*;

/**
 * This class implements a stack used for symbolic JVM stack simulation.
 * [It's used an an operand stack substitute.]
 * Elements of this stack are com.sun.org.apache.bcel.internal.generic.Type objects.
 *
 * @version $Id: OperandStack.java,v 1.3 2007-07-19 04:35:00 ofung Exp $
 * @author Enver Haase
 */
public class OperandStack{

	/** We hold the stack information here. */
	private ArrayList stack = new ArrayList();

	/** The maximum number of stack slots this OperandStack instance may hold. */
	private int maxStack;

	/**
	 * Creates an empty stack with a maximum of maxStack slots.
	 */
	public OperandStack(int maxStack){
		this.maxStack = maxStack;
	}

	/**
	 * Creates an otherwise empty stack with a maximum of maxStack slots and
	 * the ObjectType 'obj' at the top.
	 */
	public OperandStack(int maxStack, ObjectType obj){
		this.maxStack = maxStack;
		this.push(obj);
	}	
	/**
	 * Returns a deep copy of this object; that means, the clone operates
	 * on a new stack. However, the Type objects on the stack are
	 * shared.
	 */
	protected Object clone(){
		OperandStack newstack = new OperandStack(this.maxStack);
		newstack.stack = (ArrayList) this.stack.clone();
		return newstack;
	}

	/**
	 * Clears the stack.
	 */
	public void clear(){
		stack = new ArrayList();
	}

	/**
	 * Returns true if and only if this OperandStack
	 * equals another, meaning equal lengths and equal
	 * objects on the stacks.
	 */
	public boolean equals(Object o){
		if (!(o instanceof OperandStack)) return false;
		OperandStack s = (OperandStack) o;
		return this.stack.equals(s.stack);
	}

	/**
	 * Returns a (typed!) clone of this.
	 *
	 * @see #clone()
	 */
	public OperandStack getClone(){
		return (OperandStack) this.clone();
	}

	/**
	 * Returns true IFF this OperandStack is empty.
   */
	public boolean isEmpty(){
		return stack.isEmpty();
	}

	/**
	 * Returns the number of stack slots this stack can hold.
	 */
	public int maxStack(){
		return this.maxStack;
	}

	/**
	 * Returns the element on top of the stack. The element is not popped off the stack!
	 */
	public Type peek(){
		return peek(0);
	}

	/**
   * Returns the element that's i elements below the top element; that means,
   * iff i==0 the top element is returned. The element is not popped off the stack!
   */
	public Type peek(int i){
		return (Type) stack.get(size()-i-1);
	}

	/**
	 * Returns the element on top of the stack. The element is popped off the stack.
	 */
	public Type pop(){
		Type e = (Type) stack.remove(size()-1);
		return e;
	}

	/**
	 * Pops i elements off the stack. ALWAYS RETURNS "null"!!!
	 */
	public Type pop(int i){
		for (int j=0; j= maxStack){
			throw new AssertionViolatedException("OperandStack too small, should have thrown proper Exception elsewhere. Stack: "+this);
		}
		stack.add(type);
	}

	/**
	 * Returns the size of this OperandStack; that means, how many Type objects there are.
	 */
	int size(){
		return stack.size();
	}

	/**
	 * Returns the number of stack slots used.
	 * @see #maxStack()
	 */	
	public int slotsUsed(){
		/*  XXX change this to a better implementation using a variable
		    that keeps track of the actual slotsUsed()-value monitoring
		    all push()es and pop()s.
		*/
		int slots = 0;
		for (int i=0; i