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1   /*
2    * Copyright 1999-2004 The Apache Software Foundation
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.jxpath.ri.compiler;
17  
18  import java.util.Arrays;
19  
20  import org.apache.commons.jxpath.Function;
21  import org.apache.commons.jxpath.JXPathException;
22  import org.apache.commons.jxpath.ri.EvalContext;
23  import org.apache.commons.jxpath.ri.QName;
24  
25  /***
26   * Represents  an element of the parse tree representing an extension function
27   * call.
28   *
29   * @author Dmitri Plotnikov
30   * @version $Revision: 1.13 $ $Date: 2004/03/25 05:42:01 $
31   */
32  public class ExtensionFunction extends Operation {
33  
34      private QName functionName;
35  
36      public ExtensionFunction(QName functionName, Expression args[]) {
37          super(args);
38          this.functionName = functionName;
39      }
40  
41      public QName getFunctionName() {
42          return functionName;
43      }
44  
45      /***
46       * An extension function gets the current context, therefore it MAY be
47       * context dependent.
48       */
49      public boolean computeContextDependent() {
50          return true;
51      }
52  
53      public String toString() {
54          StringBuffer buffer = new StringBuffer();
55          buffer.append(functionName);
56          buffer.append('(');
57          Expression args[] = getArguments();
58          if (args != null) {
59              for (int i = 0; i < args.length; i++) {
60                  if (i > 0) {
61                      buffer.append(", ");
62                  }
63                  buffer.append(args[i]);
64              }
65          }
66          buffer.append(')');
67          return buffer.toString();
68      }
69      
70      public Object compute(EvalContext context) {
71          return computeValue(context);
72      }
73  
74      public Object computeValue(EvalContext context) {
75          Object[] parameters = null;
76          if (args != null) {
77              parameters = new Object[args.length];
78              for (int i = 0; i < args.length; i++) {
79                  parameters[i] = convert(args[i].compute(context));
80              }
81          }
82  
83          Function function =
84              context.getRootContext().getFunction(functionName, parameters);
85          if (function == null) {
86              throw new JXPathException(
87                  "No such function: "
88                      + functionName
89                      + Arrays.asList(parameters));
90          }
91  
92          return function.invoke(context, parameters);
93      }
94      
95      private Object convert(Object object) {
96          if (object instanceof EvalContext) {
97              return ((EvalContext) object).getValue();
98          }
99          return object;
100     }  
101 }