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/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2013 Eric Lafortune (eric@graphics.cornell.edu)
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program 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 General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package proguard.classfile.editor;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
/**
* This AttributeVisitor remaps variable indexes in all attributes that it
* visits, based on a given index map.
*
* @author Eric Lafortune
*/
public class VariableRemapper
extends SimplifiedVisitor
implements AttributeVisitor,
InstructionVisitor,
LocalVariableInfoVisitor,
LocalVariableTypeInfoVisitor
{
private static final boolean DEBUG = false;
private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor();
private int[] variableMap;
/**
* Sets the given mapping of old variable indexes to their new indexes.
* Variables that should disappear can be mapped to -1.
*/
public void setVariableMap(int[] variableMap)
{
this.variableMap = variableMap;
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
if (DEBUG)
{
System.out.println("VariableRemapper: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
for (int index= 0; index < codeAttribute.u2maxLocals; index++)
{
System.out.println(" v"+index+" -> "+variableMap[index]);
}
}
// Remap the variables of the attributes, before editing the code and
// cleaning up its local variable frame.
codeAttribute.attributesAccept(clazz, method, this);
// Initially, the code attribute editor doesn't contain any changes.
codeAttributeEditor.reset(codeAttribute.u4codeLength);
// Remap the variables of the instructions.
codeAttribute.instructionsAccept(clazz, method, this);
// Apply the code atribute editor.
codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
}
public void visitLocalVariableTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTableAttribute localVariableTableAttribute)
{
// Remap the variable references of the local variables.
localVariableTableAttribute.localVariablesAccept(clazz, method, codeAttribute, this);
}
public void visitLocalVariableTypeTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeTableAttribute localVariableTypeTableAttribute)
{
// Remap the variable references of the local variables.
localVariableTypeTableAttribute.localVariablesAccept(clazz, method, codeAttribute, this);
}
// Implementations for LocalVariableInfoVisitor.
public void visitLocalVariableInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableInfo localVariableInfo)
{
localVariableInfo.u2index =
remapVariable(localVariableInfo.u2index);
}
// Implementations for LocalVariableTypeInfoVisitor.
public void visitLocalVariableTypeInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeInfo localVariableTypeInfo)
{
localVariableTypeInfo.u2index =
remapVariable(localVariableTypeInfo.u2index);
}
// Implementations for InstructionVisitor.
public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
{
// Is the new variable index different from the original one?
int oldVariableIndex = variableInstruction.variableIndex;
int newVariableIndex = remapVariable(oldVariableIndex);
if (newVariableIndex != oldVariableIndex)
{
// Replace the instruction.
Instruction replacementInstruction =
new VariableInstruction(variableInstruction.opcode,
newVariableIndex,
variableInstruction.constant);
codeAttributeEditor.replaceInstruction(offset, replacementInstruction);
}
}
// Small utility methods.
/**
* Returns the new variable index of the given variable.
*/
private int remapVariable(int variableIndex)
{
return variableMap[variableIndex];
}
}
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