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Java > Open Source Codes > javassist > convert > TransformFieldAccess


1 /*
2  * Javassist, a Java-bytecode translator toolkit.
3  * Copyright (C) 1999-2005 Shigeru Chiba. All Rights Reserved.
4  *
5  * The contents of this file are subject to the Mozilla Public License Version
6  * 1.1 (the "License"); you may not use this file except in compliance with
7  * the License. Alternatively, the contents of this file may be used under
8  * the terms of the GNU Lesser General Public License Version 2.1 or later.
9  *
10  * Software distributed under the License is distributed on an "AS IS" basis,
11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12  * for the specific language governing rights and limitations under the
13  * License.
14  */
15
16 package javassist.convert;
17
18 import javassist.bytecode.*;
19 import javassist.CtClass;
20 import javassist.CtField;
21 import javassist.Modifier;
22
23 final public class TransformFieldAccess extends Transformer {
24     private String JavaDoc newClassname, newFieldname;
25     private String JavaDoc fieldname;
26     private CtClass fieldClass;
27     private boolean isPrivate;
28
29     /* cache */
30     private int newIndex;
31     private ConstPool constPool;
32
33     public TransformFieldAccess(Transformer next, CtField field,
34                                 String JavaDoc newClassname, String JavaDoc newFieldname)
35     {
36         super(next);
37         this.fieldClass = field.getDeclaringClass();
38         this.fieldname = field.getName();
39         this.isPrivate = Modifier.isPrivate(field.getModifiers());
40         this.newClassname = newClassname;
41         this.newFieldname = newFieldname;
42         this.constPool = null;
43     }
44
45     public void initialize(ConstPool cp, CodeAttribute attr) {
46         if (constPool != cp)
47             newIndex = 0;
48     }
49
50     /**
51      * Modify GETFIELD, GETSTATIC, PUTFIELD, and PUTSTATIC so that
52      * a different field is accessed. The new field must be declared
53      * in a superclass of the class in which the original field is
54      * declared.
55      */
56     public int transform(CtClass clazz, int pos,
57                          CodeIterator iterator, ConstPool cp)
58     {
59         int c = iterator.byteAt(pos);
60         if (c == GETFIELD || c == GETSTATIC
61                                 || c == PUTFIELD || c == PUTSTATIC) {
62             int index = iterator.u16bitAt(pos + 1);
63             String JavaDoc typedesc
64                 = TransformReadField.isField(clazz.getClassPool(), cp,
65                                 fieldClass, fieldname, isPrivate, index);
66             if (typedesc != null) {
67                 if (newIndex == 0) {
68                     int nt = cp.addNameAndTypeInfo(newFieldname,
69                                                    typedesc);
70                     newIndex = cp.addFieldrefInfo(
71                                         cp.addClassInfo(newClassname), nt);
72                     constPool = cp;
73                 }
74
75                 iterator.write16bit(newIndex, pos + 1);
76             }
77         }
78
79         return pos;
80     }
81 }
82
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