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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.*;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.optimize.info.VariableUsageMarker;
/**
* This AttributeVisitor cleans up unused variables in all attributes that it
* visits.
*
* @author Eric Lafortune
*/
public class VariableCleaner
extends SimplifiedVisitor
implements AttributeVisitor
{
private final VariableUsageMarker variableUsageMarker = new VariableUsageMarker();
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Figure out the local variables that are used by the code.
variableUsageMarker.visitCodeAttribute(clazz, method, codeAttribute);
// Clean up the variables of the attributes.
codeAttribute.attributesAccept(clazz, method, this);
}
public void visitLocalVariableTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTableAttribute localVariableTableAttribute)
{
// Clean up local variables that aren't used.
localVariableTableAttribute.u2localVariableTableLength =
removeEmptyLocalVariables(localVariableTableAttribute.localVariableTable,
localVariableTableAttribute.u2localVariableTableLength,
codeAttribute.u2maxLocals);
}
public void visitLocalVariableTypeTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeTableAttribute localVariableTypeTableAttribute)
{
// Clean up local variables that aren't used.
localVariableTypeTableAttribute.u2localVariableTypeTableLength =
removeEmptyLocalVariableTypes(localVariableTypeTableAttribute.localVariableTypeTable,
localVariableTypeTableAttribute.u2localVariableTypeTableLength,
codeAttribute.u2maxLocals);
}
// Small utility methods.
/**
* Returns the given list of local variables, without the ones that aren't
* used
*/
private int removeEmptyLocalVariables(LocalVariableInfo[] localVariableInfos,
int localVariableInfoCount,
int maxLocals)
{
// Overwrite all empty local variable entries.
int newIndex = 0;
for (int index = 0; index < localVariableInfoCount && index < maxLocals; index++)
{
if (variableUsageMarker.isVariableUsed(index))
{
localVariableInfos[newIndex++] = localVariableInfos[index];
}
}
// Clean up any remaining array elements.
for (int index = newIndex; index < localVariableInfoCount; index++)
{
localVariableInfos[index] = null;
}
return newIndex;
}
/**
* Returns the given list of local variable types, without the ones that
* aren't used
*/
private int removeEmptyLocalVariableTypes(LocalVariableTypeInfo[] localVariableTypeInfos,
int localVariableTypeInfoCount,
int maxLocals)
{
// Overwrite all empty local variable type entries.
int newIndex = 0;
for (int index = 0; index < localVariableTypeInfoCount && index < maxLocals; index++)
{
if (variableUsageMarker.isVariableUsed(index))
{
localVariableTypeInfos[newIndex++] = localVariableTypeInfos[index];
}
}
// Clean up any remaining array elements.
for (int index = newIndex; index < localVariableTypeInfoCount; index++)
{
localVariableTypeInfos[index] = null;
}
return newIndex;
}
}
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