1/*
2 * Javassist, a Java-bytecode translator toolkit.
3 * Copyright (C) 1999-2007 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
16package javassist.convert;
17
18import javassist.bytecode.*;
19import javassist.CtClass;
20import javassist.CtField;
21import javassist.Modifier;
22
23final public class TransformFieldAccess extends Transformer {
24    private String newClassname, newFieldname;
25    private String 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 newClassname, String 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 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