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/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999-2003 Shigeru Chiba. All Rights Reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package javassist.convert;
import javassist.bytecode.*;
import javassist.CtClass;
import javassist.CannotCompileException;
final public class TransformNew extends Transformer {
private int nested;
private String classname, trapClass, trapMethod;
public TransformNew(Transformer next,
String classname, String trapClass, String trapMethod) {
super(next);
this.classname = classname;
this.trapClass = trapClass;
this.trapMethod = trapMethod;
}
public void initialize(ConstPool cp, CodeAttribute attr) {
nested = 0;
}
/**
* Replace a sequence of
* NEW classname
* DUP
* ...
* INVOKESPECIAL
* with
* NOP
* NOP
* ...
* INVOKESTATIC trapMethod in trapClass
*/
public int transform(CtClass clazz, int pos, CodeIterator iterator,
ConstPool cp) throws CannotCompileException
{
int index;
int c = iterator.byteAt(pos);
if (c == NEW) {
index = iterator.u16bitAt(pos + 1);
if (cp.getClassInfo(index).equals(classname)) {
if (iterator.byteAt(pos + 3) != DUP)
throw new CannotCompileException(
"NEW followed by no DUP was found");
iterator.writeByte(NOP, pos);
iterator.writeByte(NOP, pos + 1);
iterator.writeByte(NOP, pos + 2);
iterator.writeByte(NOP, pos + 3);
++nested;
}
}
else if (c == INVOKESPECIAL) {
index = iterator.u16bitAt(pos + 1);
int typedesc = cp.isConstructor(classname, index);
if (typedesc != 0 && nested > 0) {
int methodref = computeMethodref(typedesc, cp);
iterator.writeByte(INVOKESTATIC, pos);
iterator.write16bit(methodref, pos + 1);
--nested;
}
}
return pos;
}
private int computeMethodref(int typedesc, ConstPool cp) {
int classIndex = cp.addClassInfo(trapClass);
int mnameIndex = cp.addUtf8Info(trapMethod);
typedesc = cp.addUtf8Info(
Descriptor.changeReturnType(classname,
cp.getUtf8Info(typedesc)));
return cp.addMethodrefInfo(classIndex,
cp.addNameAndTypeInfo(mnameIndex, typedesc));
}
}
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