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.xalan.templates;
  
  import org.apache.xalan.res.XSLTErrorResources;
  import org.apache.xalan.transformer.TransformerImpl;
  import org.apache.xpath.VariableStack;
  import org.apache.xpath.XPathContext;
  import org.apache.xpath.objects.XObject;
  
  /**
   * An instance of this class holds unto a variable until 
   * it is executed.  It is used at this time for global 
   * variables which must (we think) forward reference.
   */
  public class XUnresolvedVariable extends XObject
  {  
      static final long serialVersionUID = -256779804767950188L;
    /** The node context for execution. */
    transient private int m_context;
    
    /** The transformer context for execution. */
    transient private TransformerImpl m_transformer;
    
    /** An index to the point in the variable stack where we should
     * begin variable searches for evaluation of expressions.
     * This is -1 if m_isTopLevel is false. 
     **/
    transient private int m_varStackPos = -1;
  
    /** An index into the variable stack where the variable context 
     * ends, i.e. at the point we should terminate the search. 
     **/
    transient private int m_varStackContext;
    
    /** true if this variable or parameter is a global.
     *  @serial */
    private boolean m_isGlobal;
    
    /** true if this variable or parameter is not currently being evaluated. */
    transient private boolean m_doneEval = true;
    
    /**
     * Create an XUnresolvedVariable, that may be executed at a later time.
     * This is primarily used so that forward referencing works with 
     * global variables.  An XUnresolvedVariable is initially pushed 
     * into the global variable stack, and then replaced with the real 
     * thing when it is accessed.
     *
     * @param obj Must be a non-null reference to an ElemVariable.
     * @param sourceNode The node context for execution.
     * @param transformer The transformer execution context.
     * @param varStackPos An index to the point in the variable stack where we should
     * begin variable searches for evaluation of expressions.
     * @param varStackContext An index into the variable stack where the variable context 
     * ends, i.e. at the point we should terminate the search.
     * @param isGlobal true if this is a global variable.
     */
    public XUnresolvedVariable(ElemVariable obj, int sourceNode, 
                               TransformerImpl transformer,
                               int varStackPos, int varStackContext,
                               boolean isGlobal)
    {
      super(obj);
      m_context = sourceNode;
      m_transformer = transformer;
      
      // For globals, this value will have to be updated once we 
      // have determined how many global variables have been pushed.
      m_varStackPos = varStackPos;
      
      // For globals, this should zero.
      m_varStackContext = varStackContext;
      
      m_isGlobal = isGlobal;
    }
      
    /**
     * For support of literal objects in xpaths.
     *
     * @param xctxt The XPath execution context.
     *
     * @return This object.
     *
     * @throws javax.xml.transform.TransformerException
     */
    public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
    {
      if (!m_doneEval) 
      {
        this.m_transformer.getMsgMgr().error      
          (xctxt.getSAXLocator(), XSLTErrorResources.ER_REFERENCING_ITSELF, 
            new Object[]{((ElemVariable)this.object()).getName().getLocalName()}); 
      }
      VariableStack vars = xctxt.getVarStack();
      
      // These three statements need to be combined into one operation.
      int currentFrame = vars.getStackFrame();
      //// vars.setStackFrame(m_varStackPos);
     
  
      ElemVariable velem = (ElemVariable)m_obj;
      try
      {
        m_doneEval = false;
        if(-1 != velem.m_frameSize)
        	vars.link(velem.m_frameSize);
        XObject var = velem.getValue(m_transformer, m_context);
        m_doneEval = true;
        return var;
      }
      finally
      {
        // These two statements need to be combined into one operation.
        // vars.setStackFrame(currentFrame);
        
        if(-1 != velem.m_frameSize)
  	  	vars.unlink(currentFrame);
      }
    }
    
    /**
     * Set an index to the point in the variable stack where we should
     * begin variable searches for evaluation of expressions.
     * This is -1 if m_isTopLevel is false. 
     * 
     * @param top A valid value that specifies where in the variable 
     * stack the search should begin.
     */
    public void setVarStackPos(int top)
    {
      m_varStackPos = top;
    }
  
    /**
     * Set an index into the variable stack where the variable context 
     * ends, i.e. at the point we should terminate the search.
     * 
     * @param bottom The point at which the search should terminate, normally 
     * zero for global variables.
     */
    public void setVarStackContext(int bottom)
    {
      m_varStackContext = bottom;
    }
    
    /**
     * Tell what kind of class this is.
     *
     * @return CLASS_UNRESOLVEDVARIABLE
     */
    public int getType()
    {
      return CLASS_UNRESOLVEDVARIABLE;
    }
    
    /**
     * Given a request type, return the equivalent string.
     * For diagnostic purposes.
     *
     * @return An informational string.
     */
    public String getTypeString()
    {
      return "XUnresolvedVariable (" + object().getClass().getName() + ")";
    }
  
  
  }
  