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Diffstat (limited to 'src/proguard/classfile/editor/NameAndTypeShrinker.java')
| -rw-r--r-- | src/proguard/classfile/editor/NameAndTypeShrinker.java | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/src/proguard/classfile/editor/NameAndTypeShrinker.java b/src/proguard/classfile/editor/NameAndTypeShrinker.java new file mode 100644 index 0000000..650f9ba --- /dev/null +++ b/src/proguard/classfile/editor/NameAndTypeShrinker.java @@ -0,0 +1,188 @@ +/* + * ProGuard -- shrinking, optimization, obfuscation, and preverification + * of Java bytecode. + * + * Copyright (c) 2002-2013 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.editor.ConstantPoolRemapper; +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++) + { + 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_NameAndType || + isUsed(constant); + } + + if (isUsed) + { + constantPool[counter++] = constant; + } + } + + // Clear the remaining constant pool elements. + Arrays.fill(constantPool, counter, length, null); + + return counter; + } +} |