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      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 
     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 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