| /* |
| * ProGuard -- shrinking, optimization, obfuscation, and preverification |
| * of Java bytecode. |
| * |
| * Copyright (c) 2002-2014 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.attribute.*; |
| import proguard.classfile.attribute.visitor.AttributeVisitor; |
| import proguard.classfile.constant.*; |
| import proguard.classfile.constant.visitor.ConstantVisitor; |
| import proguard.classfile.util.SimplifiedVisitor; |
| import proguard.classfile.visitor.ClassVisitor; |
| |
| import java.util.Arrays; |
| |
| |
| /** |
| * This ClassVisitor removes NameAndType constant pool entries that are not |
| * used. |
| * |
| * @author Eric Lafortune |
| */ |
| public class NameAndTypeShrinker |
| extends SimplifiedVisitor |
| implements ClassVisitor, |
| ConstantVisitor, |
| AttributeVisitor |
| { |
| // A visitor info flag to indicate the NameAndType constant pool entry is being used. |
| private static final Object USED = new Object(); |
| |
| private int[] constantIndexMap; |
| private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper(); |
| |
| |
| // Implementations for ClassVisitor. |
| |
| public void visitProgramClass(ProgramClass programClass) |
| { |
| // Mark the NameAndType entries referenced by all other constant pool |
| // entries. |
| programClass.constantPoolEntriesAccept(this); |
| |
| // Mark the NameAndType entries referenced by all EnclosingMethod |
| // attributes. |
| programClass.attributesAccept(this); |
| |
| // Shift the used constant pool entries together, filling out the |
| // index map. |
| int newConstantPoolCount = |
| shrinkConstantPool(programClass.constantPool, |
| programClass.u2constantPoolCount); |
| |
| // Remap the references to the constant pool if it has shrunk. |
| if (newConstantPoolCount < programClass.u2constantPoolCount) |
| { |
| programClass.u2constantPoolCount = newConstantPoolCount; |
| |
| // Remap all constant pool references. |
| constantPoolRemapper.setConstantIndexMap(constantIndexMap); |
| constantPoolRemapper.visitProgramClass(programClass); |
| } |
| } |
| |
| |
| // Implementations for ConstantVisitor. |
| |
| public void visitAnyConstant(Clazz clazz, Constant constant) {} |
| |
| |
| public void visitInvokeDynamicConstant(Clazz clazz, InvokeDynamicConstant invokeDynamicConstant) |
| { |
| markNameAndTypeConstant(clazz, invokeDynamicConstant.u2nameAndTypeIndex); |
| } |
| |
| |
| public void visitAnyRefConstant(Clazz clazz, RefConstant refConstant) |
| { |
| markNameAndTypeConstant(clazz, refConstant.u2nameAndTypeIndex); |
| } |
| |
| |
| // Implementations for AttributeVisitor. |
| |
| public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} |
| |
| |
| public void visitEnclosingMethodAttribute(Clazz clazz, EnclosingMethodAttribute enclosingMethodAttribute) |
| { |
| if (enclosingMethodAttribute.u2nameAndTypeIndex != 0) |
| { |
| markNameAndTypeConstant(clazz, enclosingMethodAttribute.u2nameAndTypeIndex); |
| } |
| } |
| |
| |
| // Small utility methods. |
| |
| /** |
| * Marks the given UTF-8 constant pool entry of the given class. |
| */ |
| private void markNameAndTypeConstant(Clazz clazz, int index) |
| { |
| markAsUsed((NameAndTypeConstant)((ProgramClass)clazz).getConstant(index)); |
| } |
| |
| |
| /** |
| * Marks the given VisitorAccepter as being used. |
| * In this context, the VisitorAccepter will be a NameAndTypeConstant object. |
| */ |
| private void markAsUsed(VisitorAccepter visitorAccepter) |
| { |
| visitorAccepter.setVisitorInfo(USED); |
| } |
| |
| |
| /** |
| * Returns whether the given VisitorAccepter has been marked as being used. |
| * In this context, the VisitorAccepter will be a NameAndTypeConstant object. |
| */ |
| private boolean isUsed(VisitorAccepter visitorAccepter) |
| { |
| return visitorAccepter.getVisitorInfo() == USED; |
| } |
| |
| |
| /** |
| * Removes all NameAndType 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 == null || |
| 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++) |
| { |
| Constant constant = constantPool[index]; |
| |
| // Is the constant being used? Don't update the flag if this is the |
| // second half of a long entry. |
| if (constant != null) |
| { |
| isUsed = constant.getTag() != ClassConstants.CONSTANT_NameAndType || |
| isUsed(constant); |
| } |
| |
| if (isUsed) |
| { |
| // Remember the new index. |
| constantIndexMap[index] = counter; |
| |
| // Shift the constant pool entry. |
| constantPool[counter++] = constant; |
| } |
| else |
| { |
| // Remember an invalid index. |
| constantIndexMap[index] = -1; |
| } |
| } |
| |
| // Clear the remaining constant pool elements. |
| Arrays.fill(constantPool, counter, length, null); |
| |
| return counter; |
| } |
| } |