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: Operation.java 468655 2006-10-28 07:12:06Z minchau $
20 */
21package org.apache.xpath.operations;
22
23import org.apache.xpath.Expression;
24import org.apache.xpath.ExpressionOwner;
25import org.apache.xpath.XPathContext;
26import org.apache.xpath.XPathVisitor;
27import org.apache.xpath.objects.XObject;
28
29/**
30 * The baseclass for a binary operation.
31 */
32public class Operation extends Expression implements ExpressionOwner
33{
34    static final long serialVersionUID = -3037139537171050430L;
35
36  /** The left operand expression.
37   *  @serial */
38  protected Expression m_left;
39
40  /** The right operand expression.
41   *  @serial */
42  protected Expression m_right;
43
44  /**
45   * This function is used to fixup variables from QNames to stack frame
46   * indexes at stylesheet build time.
47   * @param vars List of QNames that correspond to variables.  This list
48   * should be searched backwards for the first qualified name that
49   * corresponds to the variable reference qname.  The position of the
50   * QName in the vector from the start of the vector will be its position
51   * in the stack frame (but variables above the globalsTop value will need
52   * to be offset to the current stack frame).
53   */
54  public void fixupVariables(java.util.Vector vars, int globalsSize)
55  {
56    m_left.fixupVariables(vars, globalsSize);
57    m_right.fixupVariables(vars, globalsSize);
58  }
59
60
61  /**
62   * Tell if this expression or it's subexpressions can traverse outside
63   * the current subtree.
64   *
65   * @return true if traversal outside the context node's subtree can occur.
66   */
67  public boolean canTraverseOutsideSubtree()
68  {
69
70    if (null != m_left && m_left.canTraverseOutsideSubtree())
71      return true;
72
73    if (null != m_right && m_right.canTraverseOutsideSubtree())
74      return true;
75
76    return false;
77  }
78
79  /**
80   * Set the left and right operand expressions for this operation.
81   *
82   *
83   * @param l The left expression operand.
84   * @param r The right expression operand.
85   */
86  public void setLeftRight(Expression l, Expression r)
87  {
88    m_left = l;
89    m_right = r;
90    l.exprSetParent(this);
91    r.exprSetParent(this);
92  }
93
94  /**
95   * Execute a binary operation by calling execute on each of the operands,
96   * and then calling the operate method on the derived class.
97   *
98   *
99   * @param xctxt The runtime execution context.
100   *
101   * @return The XObject result of the operation.
102   *
103   * @throws javax.xml.transform.TransformerException
104   */
105  public XObject execute(XPathContext xctxt)
106          throws javax.xml.transform.TransformerException
107  {
108
109    XObject left = m_left.execute(xctxt, true);
110    XObject right = m_right.execute(xctxt, true);
111
112    XObject result = operate(left, right);
113    left.detach();
114    right.detach();
115    return result;
116  }
117
118  /**
119   * Apply the operation to two operands, and return the result.
120   *
121   *
122   * @param left non-null reference to the evaluated left operand.
123   * @param right non-null reference to the evaluated right operand.
124   *
125   * @return non-null reference to the XObject that represents the result of the operation.
126   *
127   * @throws javax.xml.transform.TransformerException
128   */
129  public XObject operate(XObject left, XObject right)
130          throws javax.xml.transform.TransformerException
131  {
132    return null;  // no-op
133  }
134
135  /** @return the left operand of binary operation, as an Expression.
136   */
137  public Expression getLeftOperand(){
138    return m_left;
139  }
140
141  /** @return the right operand of binary operation, as an Expression.
142   */
143  public Expression getRightOperand(){
144    return m_right;
145  }
146
147  class LeftExprOwner implements ExpressionOwner
148  {
149    /**
150     * @see ExpressionOwner#getExpression()
151     */
152    public Expression getExpression()
153    {
154      return m_left;
155    }
156
157    /**
158     * @see ExpressionOwner#setExpression(Expression)
159     */
160    public void setExpression(Expression exp)
161    {
162    	exp.exprSetParent(Operation.this);
163    	m_left = exp;
164    }
165  }
166
167  /**
168   * @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
169   */
170  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
171  {
172  	if(visitor.visitBinaryOperation(owner, this))
173  	{
174  		m_left.callVisitors(new LeftExprOwner(), visitor);
175  		m_right.callVisitors(this, visitor);
176  	}
177  }
178
179  /**
180   * @see ExpressionOwner#getExpression()
181   */
182  public Expression getExpression()
183  {
184    return m_right;
185  }
186
187  /**
188   * @see ExpressionOwner#setExpression(Expression)
189   */
190  public void setExpression(Expression exp)
191  {
192  	exp.exprSetParent(this);
193  	m_right = exp;
194  }
195
196  /**
197   * @see Expression#deepEquals(Expression)
198   */
199  public boolean deepEquals(Expression expr)
200  {
201  	if(!isSameClass(expr))
202  		return false;
203
204  	if(!m_left.deepEquals(((Operation)expr).m_left))
205  		return false;
206
207  	if(!m_right.deepEquals(((Operation)expr).m_right))
208  		return false;
209
210  	return true;
211  }
212}
213