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	/*
	* 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;

	import javax.xml.transform.TransformerException;

	import com.sun.org.apache.xalan.internal.res.XSLMessages;
	import com.sun.org.apache.xpath.internal.objects.XObject;
	import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

	/**
	* Defines a class to keep track of a stack for
	* template arguments and variables.
	*
	* <p>This has been changed from the previous incarnations of this
	* class to be fairly low level.</p>
	* @xsl.usage internal
	* @LastModified: Nov 2017
	*/
	public class VariableStack implements Cloneable
	{
	/**
	* limitation for 1K
	*/
	public static final int CLEARLIMITATION= 1024;

	/**
	* Constructor for a variable stack.
	*/
	public VariableStack()
	{
	reset();
	}

	/**
	* Returns a clone of this variable stack.
	*
	* @return a clone of this variable stack.
	*
	* @throws CloneNotSupportedException
	*/
	public synchronized Object clone() throws CloneNotSupportedException
	{

	VariableStack vs = (VariableStack) super.clone();

	// I think I can get away with a shallow clone here?
	vs._stackFrames = _stackFrames.clone();
	vs._links = _links.clone();

	return vs;
	}

	/**
	* The stack frame where all variables and params will be kept.
	* @serial
	*/
	XObject[] _stackFrames = new XObject[XPathContext.RECURSIONLIMIT * 2];

	/**
	* The top of the stack frame (<code>_stackFrames</code>).
	* @serial
	*/
	int _frameTop;

	/**
	* The bottom index of the current frame (relative to <code>_stackFrames</code>).
	* @serial
	*/
	private int _currentFrameBottom;

	/**
	* The stack of frame positions. I call 'em links because of distant
	* <a href="http://math.millikin.edu/mprogers/Courses/currentCourses/CS481-ComputerArchitecture/cs481.Motorola68000.html">
	* Motorola 68000 assembler</a> memories. :-)
	* @serial
	*/
	int[] _links = new int[XPathContext.RECURSIONLIMIT];

	/**
	* The top of the links stack.
	*/
	int _linksTop;

	/**
	* Get the element at the given index, regardless of stackframe.
	*
	* @param i index from zero.
	*
	* @return The item at the given index.
	*/
	public XObject elementAt(final int i)
	{
	return _stackFrames[i];
	}

	/**
	* Get size of the stack.
	*
	* @return the total size of the execution stack.
	*/
	public int size()
	{
	return _frameTop;
	}

	/**
	* Reset the stack to a start position.
	*
	* @return the total size of the execution stack.
	*/
	public void reset()
	{

	_frameTop = 0;
	_linksTop = 0;

	// Adding one here to the stack of frame positions will allow us always
	// to look one under without having to check if we're at zero.
	// (As long as the caller doesn't screw up link/unlink.)
	_links[_linksTop++] = 0;
	_stackFrames = new XObject[_stackFrames.length];
	}

	/**
	* Set the current stack frame.
	*
	* @param sf The new stack frame position.
	*/
	public void setStackFrame(int sf)
	{
	_currentFrameBottom = sf;
	}

	/**
	* Get the position from where the search should start,
	* which is either the searchStart property, or the top
	* of the stack if that value is -1.
	*
	* @return The current stack frame position.
	*/
	public int getStackFrame()
	{
	return _currentFrameBottom;
	}

	/**
	* Allocates memory (called a stackframe) on the stack; used to store
	* local variables and parameter arguments.
	*
	* <p>I use the link/unlink concept because of distant
	* <a href="http://math.millikin.edu/mprogers/Courses/currentCourses/CS481-ComputerArchitecture/cs481.Motorola68000.html">
	* Motorola 68000 assembler</a> memories.</p>
	*
	* @param size The size of the stack frame allocation. This ammount should
	* normally be the maximum number of variables that you can have allocated
	* at one time in the new stack frame.
	*
	* @return The bottom of the stack frame, from where local variable addressing
	* should start from.
	*/
	public int link(final int size)
	{

	_currentFrameBottom = _frameTop;
	_frameTop += size;

	if (_frameTop >= _stackFrames.length)
	{
	XObject newsf[] = new XObject[_stackFrames.length + XPathContext.RECURSIONLIMIT + size];

	System.arraycopy(_stackFrames, 0, newsf, 0, _stackFrames.length);

	_stackFrames = newsf;
	}

	if (_linksTop + 1 >= _links.length)
	{
	int newlinks[] = new int[_links.length + (CLEARLIMITATION * 2)];

	System.arraycopy(_links, 0, newlinks, 0, _links.length);

	_links = newlinks;
	}

	_links[_linksTop++] = _currentFrameBottom;

	return _currentFrameBottom;
	}

	/**
	* Free up the stack frame that was last allocated with
	* {@link #link(int size)}.
	*/
	public void unlink()
	{
	_frameTop = _links[--_linksTop];
	_currentFrameBottom = _links[_linksTop - 1];
	}

	/**
	* Free up the stack frame that was last allocated with
	* {@link #link(int size)}.
	* @param currentFrame The current frame to set to
	* after the unlink.
	*/
	public void unlink(int currentFrame)
	{
	_frameTop = _links[--_linksTop];
	_currentFrameBottom = currentFrame;
	}

	/**
	* Set a local variable or parameter in the current stack frame.
	*
	*
	* @param index Local variable index relative to the current stack
	* frame bottom.
	*
	* @param val The value of the variable that is being set.
	*/
	public void setLocalVariable(int index, XObject val)
	{
	_stackFrames[index + _currentFrameBottom] = val;
	}

	/**
	* Set a local variable or parameter in the specified stack frame.
	*
	*
	* @param index Local variable index relative to the current stack
	* frame bottom.
	* NEEDSDOC @param stackFrame
	*
	* @param val The value of the variable that is being set.
	*/
	public void setLocalVariable(int index, XObject val, int stackFrame)
	{
	_stackFrames[index + stackFrame] = val;
	}

	/**
	* Get a local variable or parameter in the current stack frame.
	*
	*
	* @param xctxt The XPath context, which must be passed in order to
	* lazy evaluate variables.
	*
	* @param index Local variable index relative to the current stack
	* frame bottom.
	*
	* @return The value of the variable.
	*
	* @throws TransformerException
	*/
	public XObject getLocalVariable(XPathContext xctxt, int index)
	throws TransformerException
	{

	index += _currentFrameBottom;

	XObject val = _stackFrames[index];

	if(null == val)
	throw new TransformerException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_VARIABLE_ACCESSED_BEFORE_BIND, null),
	xctxt.getSAXLocator());
	// "Variable accessed before it is bound!", xctxt.getSAXLocator());

	// Lazy execution of variables.
	if (val.getType() == XObject.CLASS_UNRESOLVEDVARIABLE)
	return (_stackFrames[index] = val.execute(xctxt));

	return val;
	}

	/**
	* Get a local variable or parameter in the current stack frame.
	*
	*
	* @param index Local variable index relative to the given
	* frame bottom.
	* NEEDSDOC @param frame
	*
	* @return The value of the variable.
	*
	* @throws TransformerException
	*/
	public XObject getLocalVariable(int index, int frame)
	throws TransformerException
	{

	index += frame;

	XObject val = _stackFrames[index];

	return val;
	}

	/**
	* Get a local variable or parameter in the current stack frame.
	*
	*
	* @param xctxt The XPath context, which must be passed in order to
	* lazy evaluate variables.
	*
	* @param index Local variable index relative to the current stack
	* frame bottom.
	*
	* @return The value of the variable.
	*
	* @throws TransformerException
	*/
	public XObject getLocalVariable(XPathContext xctxt, int index, boolean destructiveOK)
	throws TransformerException
	{

	index += _currentFrameBottom;

	XObject val = _stackFrames[index];

	if(null == val)
	throw new TransformerException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_VARIABLE_ACCESSED_BEFORE_BIND, null),
	xctxt.getSAXLocator());
	// "Variable accessed before it is bound!", xctxt.getSAXLocator());

	// Lazy execution of variables.
	if (val.getType() == XObject.CLASS_UNRESOLVEDVARIABLE)
	return (_stackFrames[index] = val.execute(xctxt));

	return destructiveOK ? val : val.getFresh();
	}

	/**
	* Tell if a local variable has been set or not.
	*
	* @param index Local variable index relative to the current stack
	* frame bottom.
	*
	* @return true if the value at the index is not null.
	*
	* @throws TransformerException
	*/
	public boolean isLocalSet(int index) throws TransformerException
	{
	return (_stackFrames[index + _currentFrameBottom] != null);
	}

	/** NEEDSDOC Field m_nulls */
	private static XObject[] m_nulls = new XObject[CLEARLIMITATION];

	/**
	* Use this to clear the variables in a section of the stack. This is
	* used to clear the parameter section of the stack, so that default param
	* values can tell if they've already been set. It is important to note that
	* this function has a 1K limitation.
	*
	* @param start The start position, relative to the current local stack frame.
	* @param len The number of slots to be cleared.
	*/
	public void clearLocalSlots(int start, int len)
	{

	start += _currentFrameBottom;

	System.arraycopy(m_nulls, 0, _stackFrames, start, len);
	}

	/**
	* Set a global variable or parameter in the global stack frame.
	*
	*
	* @param index Local variable index relative to the global stack frame
	* bottom.
	*
	* @param val The value of the variable that is being set.
	*/
	public void setGlobalVariable(final int index, final XObject val)
	{
	_stackFrames[index] = val;
	}

	/**
	* Get a global variable or parameter from the global stack frame.
	*
	*
	* @param xctxt The XPath context, which must be passed in order to
	* lazy evaluate variables.
	*
	* @param index Global variable index relative to the global stack
	* frame bottom.
	*
	* @return The value of the variable.
	*
	* @throws TransformerException
	*/
	public XObject getGlobalVariable(XPathContext xctxt, final int index)
	throws TransformerException
	{

	XObject val = _stackFrames[index];

	// Lazy execution of variables.
	if (val.getType() == XObject.CLASS_UNRESOLVEDVARIABLE)
	return (_stackFrames[index] = val.execute(xctxt));

	return val;
	}

	/**
	* Get a global variable or parameter from the global stack frame.
	*
	*
	* @param xctxt The XPath context, which must be passed in order to
	* lazy evaluate variables.
	*
	* @param index Global variable index relative to the global stack
	* frame bottom.
	*
	* @return The value of the variable.
	*
	* @throws TransformerException
	*/
	public XObject getGlobalVariable(XPathContext xctxt, final int index, boolean destructiveOK)
	throws TransformerException
	{

	XObject val = _stackFrames[index];

	// Lazy execution of variables.
	if (val.getType() == XObject.CLASS_UNRESOLVEDVARIABLE)
	return (_stackFrames[index] = val.execute(xctxt));

	return destructiveOK ? val : val.getFresh();
	}

	/**
	* Get a variable based on it's qualified name.
	* This is for external use only.
	*
	* @param xctxt The XPath context, which must be passed in order to
	* lazy evaluate variables.
	*
	* @param qname The qualified name of the variable.
	*
	* @return The evaluated value of the variable.
	*
	* @throws javax.xml.transform.TransformerException
	*/
	public XObject getVariableOrParam(
	XPathContext xctxt, com.sun.org.apache.xml.internal.utils.QName qname)
	throws javax.xml.transform.TransformerException
	{

	// J2SE does not support Xalan interpretive
	/*
	com.sun.org.apache.xml.internal.utils.PrefixResolver prefixResolver =
	xctxt.getNamespaceContext();

	// Get the current ElemTemplateElement, which must be pushed in as the
	// prefix resolver, and then walk backwards in document order, searching
	// for an xsl:param element or xsl:variable element that matches our
	// qname. If we reach the top level, use the StylesheetRoot's composed
	// list of top level variables and parameters.

	if (prefixResolver instanceof com.sun.org.apache.xalan.internal.templates.ElemTemplateElement)
	{

	com.sun.org.apache.xalan.internal.templates.ElemVariable vvar;

	com.sun.org.apache.xalan.internal.templates.ElemTemplateElement prev =
	(com.sun.org.apache.xalan.internal.templates.ElemTemplateElement) prefixResolver;

	if (!(prev instanceof com.sun.org.apache.xalan.internal.templates.Stylesheet))
	{
	while ( !(prev.getParentNode() instanceof com.sun.org.apache.xalan.internal.templates.Stylesheet) )
	{
	com.sun.org.apache.xalan.internal.templates.ElemTemplateElement savedprev = prev;

	while (null != (prev = prev.getPreviousSiblingElem()))
	{
	if (prev instanceof com.sun.org.apache.xalan.internal.templates.ElemVariable)
	{
	vvar = (com.sun.org.apache.xalan.internal.templates.ElemVariable) prev;

	if (vvar.getName().equals(qname))
	return getLocalVariable(xctxt, vvar.getIndex());
	}
	}
	prev = savedprev.getParentElem();
	}
	}

	vvar = prev.getStylesheetRoot().getVariableOrParamComposed(qname);
	if (null != vvar)
	return getGlobalVariable(xctxt, vvar.getIndex());
	}
	*/

	throw new javax.xml.transform.TransformerException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_VAR_NOT_RESOLVABLE, new Object[]{qname.toString()})); //"Variable not resolvable: " + qname);
	}
	} // end VariableStack

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