org.apache.xpath.VariableStack Maven / Gradle / Ivy
/*
* 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: VariableStack.java 524812 2007-04-02 15:52:03Z zongaro $
*/
package org.apache.xpath;
import javax.xml.transform.TransformerException;
import org.apache.xalan.res.XSLMessages;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
/**
* Defines a class to keep track of a stack for
* template arguments and variables.
*
* This has been changed from the previous incarnations of this
* class to be fairly low level.
* @xsl.usage internal
*/
public class VariableStack implements Cloneable
{
/**
* limitation for 1K
*/
public static final int CLEARLIMITATION= 1024;
/**
* Constructor for a variable stack.
*/
public VariableStack()
{
reset();
}
/**
* Constructor for a variable stack.
* @param initStackSize The initial stack size. Must be at least one. The
* stack can grow if needed.
*/
public VariableStack(int initStackSize)
{
// Allow for twice as many variables as stack link entries
reset(initStackSize, initStackSize*2);
}
/**
* 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 = (XObject[]) _stackFrames.clone();
vs._links = (int[]) _links.clone();
return vs;
}
/**
* The stack frame where all variables and params will be kept.
* @serial
*/
XObject[] _stackFrames;
/**
* The top of the stack frame (_stackFrames).
* @serial
*/
int _frameTop;
/**
* The bottom index of the current frame (relative to _stackFrames).
* @serial
*/
private int _currentFrameBottom;
/**
* The stack of frame positions. I call 'em links because of distant
*
* Motorola 68000 assembler memories. :-)
* @serial
*/
int[] _links;
/**
* 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.
*/
public void reset()
{
// If the stack was previously allocated, assume that about the same
// amount of stack space will be needed again; otherwise, use a very
// large stack size.
int linksSize = (_links == null) ? XPathContext.RECURSIONLIMIT
: _links.length;
int varArraySize = (_stackFrames == null) ? XPathContext.RECURSIONLIMIT * 2
: _stackFrames.length;
reset(linksSize, varArraySize);
}
/**
* Reset the stack to a start position.
* @param linksSize Initial stack size to use
* @param varArraySize Initial variable array size to use
*/
protected void reset(int linksSize, int varArraySize) {
_frameTop = 0;
_linksTop = 0;
// Don't bother reallocating _links array if it exists already
if (_links == null) {
_links = new int[linksSize];
}
// 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;
// Get a clean _stackFrames array and discard the old one.
_stackFrames = new XObject[varArraySize];
}
/**
* 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.
*
* I use the link/unlink concept because of distant
*
* Motorola 68000 assembler memories.
*
* @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, org.apache.xml.utils.QName qname)
throws javax.xml.transform.TransformerException
{
org.apache.xml.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 org.apache.xalan.templates.ElemTemplateElement)
{
org.apache.xalan.templates.ElemVariable vvar;
org.apache.xalan.templates.ElemTemplateElement prev =
(org.apache.xalan.templates.ElemTemplateElement) prefixResolver;
if (!(prev instanceof org.apache.xalan.templates.Stylesheet))
{
while ( !(prev.getParentNode() instanceof org.apache.xalan.templates.Stylesheet) )
{
org.apache.xalan.templates.ElemTemplateElement savedprev = prev;
while (null != (prev = prev.getPreviousSiblingElem()))
{
if (prev instanceof org.apache.xalan.templates.ElemVariable)
{
vvar = (org.apache.xalan.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