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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.obfuscate;
import proguard.classfile.*;
import proguard.classfile.constant.Constant;
import proguard.classfile.editor.ConstantPoolRemapper;
import proguard.classfile.visitor.ClassVisitor;
/**
* This ClassVisitor removes UTF-8 constant pool entries that are not marked
* as being used.
*
* @see Utf8UsageMarker
*
* @author Eric Lafortune
*/
public class Utf8Shrinker implements ClassVisitor
{
private int[] constantIndexMap = new int[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
// Implementations for ClassVisitor.
public void visitProgramClass(ProgramClass programClass)
{
// Shift the used constant pool entries together, filling out the
// index map.
programClass.u2constantPoolCount =
shrinkConstantPool(programClass.constantPool,
programClass.u2constantPoolCount);
// Remap all constant pool references.
constantPoolRemapper.setConstantIndexMap(constantIndexMap);
constantPoolRemapper.visitProgramClass(programClass);
}
public void visitLibraryClass(LibraryClass libraryClass)
{
}
// Small utility methods.
/**
* Removes all UTF-8 entries that are not marked as being used
* from the given constant pool.
* @return the new number of entries.
*/
private int shrinkConstantPool(Constant[] constantPool, int length)
{
// Create a new index map, if necessary.
if (constantIndexMap.length < length)
{
constantIndexMap = new int[length];
}
int counter = 1;
boolean isUsed = false;
// Shift the used constant pool entries together.
for (int index = 1; index < length; index++)
{
constantIndexMap[index] = counter;
Constant constant = constantPool[index];
// Don't update the flag if this is the second half of a long entry.
if (constant != null)
{
isUsed = constant.getTag() != ClassConstants.CONSTANT_Utf8 ||
Utf8UsageMarker.isUsed(constant);
}
if (isUsed)
{
constantPool[counter++] = constant;
}
}
// Clear the remaining constant pool elements.
for (int index = counter; index < length; index++)
{
constantPool[index] = null;
}
return counter;
}
}
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