transformwritefield.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist.convert;

import javassist.CtClass;
import javassist.CtField;
import javassist.bytecode.*;

final public class TransformWriteField extends TransformReadField {
    public TransformWriteField(Transformer next, CtField field,
                               String methodClassname, String methodName)
    {
        super(next, field, methodClassname, methodName);
    }

    public int transform(CtClass tclazz, int pos, CodeIterator iterator,
                         ConstPool cp) throws BadBytecode
    {
        int c = iterator.byteAt(pos);
        if (c == PUTFIELD || c == PUTSTATIC) {
            int index = iterator.u16bitAt(pos + 1);
            String typedesc = isField(tclazz.getClassPool(), cp,
                                fieldClass, fieldname, isPrivate, index);
            if (typedesc != null) {
                if (c == PUTSTATIC) {
                    CodeAttribute ca = iterator.get();
                    iterator.move(pos);
                    char c0 = typedesc.charAt(0);
                    if (c0 == 'J' || c0 == 'D') {       // long or double
                        // insertGap() may insert 4 bytes.
                        iterator.insertGap(3);
                        iterator.writeByte(ACONST_NULL, pos);
                        iterator.writeByte(DUP_X2, pos + 1);
                        iterator.writeByte(POP, pos + 2);
                        ca.setMaxStack(ca.getMaxStack() + 2);
                    }
                    else {
                        // insertGap() may insert 4 bytes.
                        iterator.insertGap(2);
                        iterator.writeByte(ACONST_NULL, pos);
                        iterator.writeByte(SWAP, pos + 1);
                        ca.setMaxStack(ca.getMaxStack() + 1);
                    }

                    pos = iterator.next();
                }

                int mi = cp.addClassInfo(methodClassname);
                String type = "(Ljava/lang/Object;" + typedesc + ")V";
                int methodref = cp.addMethodrefInfo(mi, methodName, type);
                iterator.writeByte(INVOKESTATIC, pos);
                iterator.write16bit(methodref, pos + 1);
            }
        }

        return pos;
    }
}