/* $Id: Utf8Shrinker.java,v 1.26 2004/10/10 20:56:58 eric Exp $ * * ProGuard -- shrinking, optimization, and obfuscation of Java class files. * * Copyright (c) 2002-2004 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.editor.ConstantPoolRemapper;import proguard.classfile.visitor.ClassFileVisitor;/** * This ClassFileVisitor removes UTF-8 constant pool entries that are not marked * as being used. * * @see Utf8UsageMarker * * @author Eric Lafortune */public class Utf8Shrinker implements ClassFileVisitor{    private int[]                cpIndexMap;    private ConstantPoolRemapper constantPoolRemapper;    /**     * Creates a new Utf8Shrinker.     * @param codeLength an estimate of the maximum length of all the code that     *                   will be edited.     */    public Utf8Shrinker(int codeLength)    {        constantPoolRemapper = new ConstantPoolRemapper(codeLength);    }    // Implementations for ClassFileVisitor.    public void visitProgramClassFile(ProgramClassFile programClassFile)    {        // Shift the used constant pool entries together, filling out the        // index map.        programClassFile.u2constantPoolCount =            shrinkConstantPool(programClassFile.constantPool,                               programClassFile.u2constantPoolCount);        // Remap all constant pool references.        constantPoolRemapper.setCpIndexMap(cpIndexMap);        constantPoolRemapper.visitProgramClassFile(programClassFile);    }    public void visitLibraryClassFile(LibraryClassFile libraryClassFile)    {    }    // 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(CpInfo[] constantPool, int length)    {        // Create a new index map, if necessary.        if (cpIndexMap == null ||            cpIndexMap.length < length)        {            cpIndexMap = new int[length];        }        int     counter = 1;        boolean isUsed  = false;        // Shift the used constant pool entries together.        for (int index = 1; index < length; index++)        {            cpIndexMap[index] = counter;            CpInfo cpInfo = constantPool[index];            // Don't update the flag if this is the second half of a long entry.            if (cpInfo != null)            {                isUsed = cpInfo.getTag() != ClassConstants.CONSTANT_Utf8 ||                         Utf8UsageMarker.isUsed(cpInfo);            }            if (isUsed)            {                constantPool[counter++] = cpInfo;            }        }        // Clear the remaining constant pool elements.        for (int index = counter; index < length; index++)        {            constantPool[index] = null;        }        return counter;    }}