1/*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the  "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 *     http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18/*
19 * $Id: XUnresolvedVariable.java 468643 2006-10-28 06:56:03Z minchau $
20 */
21package org.apache.xalan.templates;
22
23import org.apache.xalan.res.XSLTErrorResources;
24import org.apache.xalan.transformer.TransformerImpl;
25import org.apache.xpath.VariableStack;
26import org.apache.xpath.XPathContext;
27import org.apache.xpath.objects.XObject;
28
29/**
30 * An instance of this class holds unto a variable until
31 * it is executed.  It is used at this time for global
32 * variables which must (we think) forward reference.
33 */
34public class XUnresolvedVariable extends XObject
35{
36    static final long serialVersionUID = -256779804767950188L;
37  /** The node context for execution. */
38  transient private int m_context;
39
40  /** The transformer context for execution. */
41  transient private TransformerImpl m_transformer;
42
43  /** An index to the point in the variable stack where we should
44   * begin variable searches for evaluation of expressions.
45   * This is -1 if m_isTopLevel is false.
46   **/
47  transient private int m_varStackPos = -1;
48
49  /** An index into the variable stack where the variable context
50   * ends, i.e. at the point we should terminate the search.
51   **/
52  transient private int m_varStackContext;
53
54  /** true if this variable or parameter is a global.
55   *  @serial */
56  private boolean m_isGlobal;
57
58  /** true if this variable or parameter is not currently being evaluated. */
59  transient private boolean m_doneEval = true;
60
61  /**
62   * Create an XUnresolvedVariable, that may be executed at a later time.
63   * This is primarily used so that forward referencing works with
64   * global variables.  An XUnresolvedVariable is initially pushed
65   * into the global variable stack, and then replaced with the real
66   * thing when it is accessed.
67   *
68   * @param obj Must be a non-null reference to an ElemVariable.
69   * @param sourceNode The node context for execution.
70   * @param transformer The transformer execution context.
71   * @param varStackPos An index to the point in the variable stack where we should
72   * begin variable searches for evaluation of expressions.
73   * @param varStackContext An index into the variable stack where the variable context
74   * ends, i.e. at the point we should terminate the search.
75   * @param isGlobal true if this is a global variable.
76   */
77  public XUnresolvedVariable(ElemVariable obj, int sourceNode,
78                             TransformerImpl transformer,
79                             int varStackPos, int varStackContext,
80                             boolean isGlobal)
81  {
82    super(obj);
83    m_context = sourceNode;
84    m_transformer = transformer;
85
86    // For globals, this value will have to be updated once we
87    // have determined how many global variables have been pushed.
88    m_varStackPos = varStackPos;
89
90    // For globals, this should zero.
91    m_varStackContext = varStackContext;
92
93    m_isGlobal = isGlobal;
94  }
95
96  /**
97   * For support of literal objects in xpaths.
98   *
99   * @param xctxt The XPath execution context.
100   *
101   * @return This object.
102   *
103   * @throws javax.xml.transform.TransformerException
104   */
105  public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
106  {
107    if (!m_doneEval)
108    {
109      this.m_transformer.getMsgMgr().error
110        (xctxt.getSAXLocator(), XSLTErrorResources.ER_REFERENCING_ITSELF,
111          new Object[]{((ElemVariable)this.object()).getName().getLocalName()});
112    }
113    VariableStack vars = xctxt.getVarStack();
114
115    // These three statements need to be combined into one operation.
116    int currentFrame = vars.getStackFrame();
117    //// vars.setStackFrame(m_varStackPos);
118
119
120    ElemVariable velem = (ElemVariable)m_obj;
121    try
122    {
123      m_doneEval = false;
124      if(-1 != velem.m_frameSize)
125      	vars.link(velem.m_frameSize);
126      XObject var = velem.getValue(m_transformer, m_context);
127      m_doneEval = true;
128      return var;
129    }
130    finally
131    {
132      // These two statements need to be combined into one operation.
133      // vars.setStackFrame(currentFrame);
134
135      if(-1 != velem.m_frameSize)
136	  	vars.unlink(currentFrame);
137    }
138  }
139
140  /**
141   * Set an index to the point in the variable stack where we should
142   * begin variable searches for evaluation of expressions.
143   * This is -1 if m_isTopLevel is false.
144   *
145   * @param top A valid value that specifies where in the variable
146   * stack the search should begin.
147   */
148  public void setVarStackPos(int top)
149  {
150    m_varStackPos = top;
151  }
152
153  /**
154   * Set an index into the variable stack where the variable context
155   * ends, i.e. at the point we should terminate the search.
156   *
157   * @param bottom The point at which the search should terminate, normally
158   * zero for global variables.
159   */
160  public void setVarStackContext(int bottom)
161  {
162    m_varStackContext = bottom;
163  }
164
165  /**
166   * Tell what kind of class this is.
167   *
168   * @return CLASS_UNRESOLVEDVARIABLE
169   */
170  public int getType()
171  {
172    return CLASS_UNRESOLVEDVARIABLE;
173  }
174
175  /**
176   * Given a request type, return the equivalent string.
177   * For diagnostic purposes.
178   *
179   * @return An informational string.
180   */
181  public String getTypeString()
182  {
183    return "XUnresolvedVariable (" + object().getClass().getName() + ")";
184  }
185
186
187}
188