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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.optimize;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.editor.*;
import proguard.classfile.util.*;
import proguard.classfile.visitor.MemberVisitor;
import proguard.optimize.info.ParameterUsageMarker;
/**
* This MemberVisitor removes unused parameters from the code of the methods
* that it visits.
*
* @see ParameterUsageMarker
* @see MethodStaticizer
* @see MethodDescriptorShrinker
* @author Eric Lafortune
*/
public class ParameterShrinker
extends SimplifiedVisitor
implements AttributeVisitor
{
private static final boolean DEBUG = false;
private final MemberVisitor extraVariableMemberVisitor;
private final VariableRemapper variableRemapper = new VariableRemapper();
/**
* Creates a new ParameterShrinker.
*/
public ParameterShrinker()
{
this(null);
}
/**
* Creates a new ParameterShrinker with an extra visitor.
* @param extraVariableMemberVisitor an optional extra visitor for all
* removed parameters.
*/
public ParameterShrinker(MemberVisitor extraVariableMemberVisitor)
{
this.extraVariableMemberVisitor = extraVariableMemberVisitor;
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Get the original parameter size that was saved.
int oldParameterSize = ParameterUsageMarker.getParameterSize(method);
// Compute the new parameter size from the shrunk descriptor.
int newParameterSize =
ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz),
method.getAccessFlags());
if (oldParameterSize > newParameterSize)
{
// Get the total size of the local variable frame.
int maxLocals = codeAttribute.u2maxLocals;
if (DEBUG)
{
System.out.println("ParameterShrinker: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
System.out.println(" Old parameter size = " + oldParameterSize);
System.out.println(" New parameter size = " + newParameterSize);
System.out.println(" Max locals = " + maxLocals);
}
// Create a variable map.
int[] variableMap = new int[maxLocals];
// Move unused parameters right after the parameter block.
int usedParameterIndex = 0;
int unusedParameterIndex = newParameterSize;
for (int parameterIndex = 0; parameterIndex < oldParameterSize; parameterIndex++)
{
// Is the variable required as a parameter?
if (ParameterUsageMarker.isParameterUsed(method, parameterIndex))
{
// Keep the variable as a parameter.
variableMap[parameterIndex] = usedParameterIndex++;
}
else
{
if (DEBUG)
{
System.out.println(" Deleting parameter #"+parameterIndex);
}
// Shift the variable to the unused parameter block,
// in case it is still used as a variable.
variableMap[parameterIndex] = unusedParameterIndex++;
// Visit the method, if required.
if (extraVariableMemberVisitor != null)
{
method.accept(clazz, extraVariableMemberVisitor);
}
}
}
// Fill out the remainder of the map.
for (int variableIndex = oldParameterSize; variableIndex < maxLocals; variableIndex++)
{
variableMap[variableIndex] = variableIndex;
}
// Set the map.
variableRemapper.setVariableMap(variableMap);
// Remap the variables.
variableRemapper.visitCodeAttribute(clazz, method, codeAttribute);
}
}
}