CompileTimeFunction


1   package net.sf.saxon.functions;
2   import net.sf.saxon.expr.Expression;
3   import net.sf.saxon.expr.StaticContext;
4   import net.sf.saxon.expr.XPathContext;
5   import net.sf.saxon.om.Item;
6   import net.sf.saxon.om.SequenceIterator;
7   import net.sf.saxon.trans.XPathException;
8   
9   /**
10  * Abtract class representing a function call that is always rewritten at compile-time:
11  * it can never be executed
12  */
13  
14  public abstract class CompileTimeFunction extends SystemFunction {
15  
16      /**
17      * preEvaluate: this method suppresses compile-time evaluation by doing nothing.
18       * (this is because the default implementation of preEvaluate() calls evaluate() which
19       * is not available for these functions)
20      */
21  
22      public Expression preEvaluate(StaticContext env) throws XPathException {
23          return this;
24      }
25  
26      /**
27      * Evaluate as a single item
28      */
29  
30      public final Item evaluateItem(XPathContext c) throws XPathException {
31          throw new IllegalStateException  ("Function " + getName(c) + " should have been resolved at compile-time");
32      }
33  
34      /**
35      * Iterate over the results of the function
36      */
37  
38      public final SequenceIterator iterate(XPathContext c) {
39          throw new IllegalStateException  ("Function " + getName(c) + " should have been resolved at compile-time");
40      }
41  
42      private String   getName(XPathContext c) {
43          return getDisplayName(c.getController().getNamePool());
44      }
45  
46  }
47  
48  
49  
50  
51  //
52  // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
53  // you may not use this file except in compliance with the License. You may obtain a copy of the
54  // License at http://www.mozilla.org/MPL/
55  //
56  // Software distributed under the License is distributed on an "AS IS" basis,
57  // WITHOUT WARRANTY OF ANY KIND, either express or implied.
58  // See the License for the specific language governing rights and limitations under the License.
59  //
60  // The Original Code is: all this file.
61  //
62  // The Initial Developer of the Original Code is Michael H. Kay
63  //
64  // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
65  //
66  // Contributor(s): none.
67  //
68
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