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/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2009 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.AttributeVisitor;
import proguard.classfile.util.SimplifiedVisitor;
/**
* This AttributeVisitor accumulates specified changes to local variables, and
* then applies these accumulated changes to the code attributes that it visits.
*
* @author Eric Lafortune
*/
public class VariableEditor
extends SimplifiedVisitor
implements AttributeVisitor
{
private boolean modified;
private boolean[] deleted = new boolean[ClassConstants.TYPICAL_VARIABLES_SIZE];
private int[] variableMap = new int[ClassConstants.TYPICAL_VARIABLES_SIZE];
private final VariableRemapper variableRemapper = new VariableRemapper();
/**
* Resets the accumulated code changes.
* @param maxLocals the length of the local variable frame that will be
* edited next.
*/
public void reset(int maxLocals)
{
// Try to reuse the previous array.
if (deleted.length < maxLocals)
{
deleted = new boolean[maxLocals];
}
else
{
for (int index = 0; index < maxLocals; index++)
{
deleted[index] = false;
}
}
modified = false;
}
/**
* Remembers to delete the given variable.
* @param variableIndex the index of the variable to be deleted.
*/
public void deleteVariable(int variableIndex)
{
deleted[variableIndex] = true;
modified = true;
}
/**
* Returns whether the given variable at the given offset has deleted.
*/
public boolean isDeleted(int instructionOffset)
{
return deleted[instructionOffset];
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Avoid doing any work if nothing is changing anyway.
if (!modified)
{
return;
}
int oldMaxLocals = codeAttribute.u2maxLocals;
// Make sure there is a sufficiently large variable map.
if (variableMap.length < oldMaxLocals)
{
variableMap = new int[oldMaxLocals];
}
// Fill out the variable map.
int newVariableIndex = 0;
for (int oldVariableIndex = 0; oldVariableIndex < oldMaxLocals; oldVariableIndex++)
{
variableMap[oldVariableIndex] = deleted[oldVariableIndex] ?
-1 : newVariableIndex++;
}
// Set the map.
variableRemapper.setVariableMap(variableMap);
// Remap the variables.
variableRemapper.visitCodeAttribute(clazz, method, codeAttribute);
// Update the length of local variable frame.
codeAttribute.u2maxLocals = newVariableIndex;
}
}
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