/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2011 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.constant.Constant;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.ClassVisitor;
import java.util.Arrays;
/**
* This ClassVisitor sorts the constant pool entries of the program classes
* that it visits. The sorting order is based on the types of the constant pool
* entries in the first place, and on their contents in the second place.
*
* @author Eric Lafortune
*/
public class ConstantPoolSorter
extends SimplifiedVisitor
implements ClassVisitor
{
private int[] constantIndexMap = new int[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
private ComparableConstant[] comparableConstantPool = new ComparableConstant[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
private Constant[] newConstantPool = new Constant[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
// Implementations for ClassVisitor.
public void visitProgramClass(ProgramClass programClass)
{
int constantPoolCount = programClass.u2constantPoolCount;
// Sort the constant pool and set up an index map.
if (constantIndexMap.length < constantPoolCount)
{
constantIndexMap = new int[constantPoolCount];
comparableConstantPool = new ComparableConstant[constantPoolCount];
newConstantPool = new Constant[constantPoolCount];
}
// Initialize an array whose elements can be compared.
int sortLength = 0;
for (int oldIndex = 1; oldIndex < constantPoolCount; oldIndex++)
{
Constant constant = programClass.constantPool[oldIndex];
if (constant != null)
{
comparableConstantPool[sortLength++] =
new ComparableConstant(programClass, oldIndex, constant);
}
}
// Sort the array.
Arrays.sort(comparableConstantPool, 0, sortLength);
// Save the sorted elements.
int newLength = 1;
int newIndex = 1;
ComparableConstant previousComparableConstant = null;
for (int sortIndex = 0; sortIndex < sortLength; sortIndex++)
{
ComparableConstant comparableConstant = comparableConstantPool[sortIndex];
// Isn't this a duplicate of the previous constant?
if (!comparableConstant.equals(previousComparableConstant))
{
// Remember the index of the new entry.
newIndex = newLength;
// Copy the sorted constant pool entry over to the constant pool.
Constant constant = comparableConstant.getConstant();
newConstantPool[newLength++] = constant;
// Long entries take up two slots, the second of which is null.
int tag = constant.getTag();
if (tag == ClassConstants.CONSTANT_Long ||
tag == ClassConstants.CONSTANT_Double)
{
newConstantPool[newLength++] = null;
}
previousComparableConstant = comparableConstant;
}
// Fill out the map array.
constantIndexMap[comparableConstant.getIndex()] = newIndex;
}
// Copy the new constant pool over.
System.arraycopy(newConstantPool, 0, programClass.constantPool, 0, newLength);
// Clear any remaining entries.
for (int index = newLength; index < constantPoolCount; index++)
{
programClass.constantPool[index] = null;
}
programClass.u2constantPoolCount = newLength;
// Remap all constant pool references.
constantPoolRemapper.setConstantIndexMap(constantIndexMap);
constantPoolRemapper.visitProgramClass(programClass);
}
}