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      1 /*
      2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
      3  *             of Java bytecode.
      4  *
      5  * Copyright (c) 2002-2014 Eric Lafortune (eric (at) graphics.cornell.edu)
      6  *
      7  * This program is free software; you can redistribute it and/or modify it
      8  * under the terms of the GNU General Public License as published by the Free
      9  * Software Foundation; either version 2 of the License, or (at your option)
     10  * any later version.
     11  *
     12  * This program is distributed in the hope that it will be useful, but WITHOUT
     13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     14  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
     15  * more details.
     16  *
     17  * You should have received a copy of the GNU General Public License along
     18  * with this program; if not, write to the Free Software Foundation, Inc.,
     19  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
     20  */
     21 package proguard.classfile.editor;
     22 
     23 import proguard.classfile.*;
     24 import proguard.classfile.constant.Constant;
     25 import proguard.classfile.util.SimplifiedVisitor;
     26 import proguard.classfile.visitor.ClassVisitor;
     27 
     28 import java.util.Arrays;
     29 
     30 /**
     31  * This ClassVisitor sorts the constant pool entries of the program classes
     32  * that it visits. The sorting order is based on the types of the constant pool
     33  * entries in the first place, and on their contents in the second place.
     34  *
     35  * @author Eric Lafortune
     36  */
     37 public class ConstantPoolSorter
     38 extends      SimplifiedVisitor
     39 implements   ClassVisitor
     40 {
     41     private int[]                constantIndexMap       = new int[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
     42     private ComparableConstant[] comparableConstantPool = new ComparableConstant[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
     43     private Constant[]           newConstantPool        = new Constant[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
     44 
     45     private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
     46 
     47 
     48     // Implementations for ClassVisitor.
     49 
     50     public void visitProgramClass(ProgramClass programClass)
     51     {
     52         int constantPoolCount = programClass.u2constantPoolCount;
     53 
     54         // Sort the constant pool and set up an index map.
     55         if (constantIndexMap.length < constantPoolCount)
     56         {
     57             constantIndexMap       = new int[constantPoolCount];
     58             comparableConstantPool = new ComparableConstant[constantPoolCount];
     59             newConstantPool        = new Constant[constantPoolCount];
     60         }
     61 
     62         // Initialize an array whose elements can be compared.
     63         int sortLength = 0;
     64         for (int oldIndex = 1; oldIndex < constantPoolCount; oldIndex++)
     65         {
     66             Constant constant = programClass.constantPool[oldIndex];
     67             if (constant != null)
     68             {
     69                 comparableConstantPool[sortLength++] =
     70                     new ComparableConstant(programClass, oldIndex, constant);
     71             }
     72         }
     73 
     74         // Sort the array.
     75         Arrays.sort(comparableConstantPool, 0, sortLength);
     76 
     77         // Save the sorted elements.
     78         int newLength = 1;
     79         int newIndex  = 1;
     80         ComparableConstant previousComparableConstant = null;
     81         for (int sortIndex = 0; sortIndex < sortLength; sortIndex++)
     82         {
     83             ComparableConstant comparableConstant = comparableConstantPool[sortIndex];
     84 
     85             // Isn't this a duplicate of the previous constant?
     86             if (!comparableConstant.equals(previousComparableConstant))
     87             {
     88                 // Remember the index of the new entry.
     89                 newIndex = newLength;
     90 
     91                 // Copy the sorted constant pool entry over to the constant pool.
     92                 Constant constant = comparableConstant.getConstant();
     93 
     94                 newConstantPool[newLength++] = constant;
     95 
     96                 // Long entries take up two slots, the second of which is null.
     97                 int tag = constant.getTag();
     98                 if (tag == ClassConstants.CONSTANT_Long ||
     99                     tag == ClassConstants.CONSTANT_Double)
    100                 {
    101                     newConstantPool[newLength++] = null;
    102                 }
    103 
    104                 previousComparableConstant = comparableConstant;
    105             }
    106 
    107             // Fill out the map array.
    108             constantIndexMap[comparableConstant.getIndex()] = newIndex;
    109         }
    110 
    111         // Copy the new constant pool over.
    112         System.arraycopy(newConstantPool, 0, programClass.constantPool, 0, newLength);
    113 
    114         // Clear any remaining entries.
    115         Arrays.fill(programClass.constantPool, newLength, constantPoolCount, null);
    116 
    117         programClass.u2constantPoolCount = newLength;
    118 
    119         // Remap all constant pool references.
    120         constantPoolRemapper.setConstantIndexMap(constantIndexMap);
    121         constantPoolRemapper.visitProgramClass(programClass);
    122     }
    123 }
    124