bb-tools/proguard4.7/src/proguard/shrink/ClassShrinker.java
/*
* 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.shrink;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.annotation.*;
import proguard.classfile.attribute.annotation.visitor.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.constant.*;
import proguard.classfile.editor.*;
import proguard.classfile.util.*;
import proguard.classfile.visitor.*;
import java.util.Arrays;
/**
* This ClassVisitor removes constant pool entries, class members, and other
* class elements that are not marked as being used.
*
* @see UsageMarker
*
* @author Eric Lafortune
*/
public class ClassShrinker
extends SimplifiedVisitor
implements ClassVisitor,
MemberVisitor,
AttributeVisitor,
AnnotationVisitor,
ElementValueVisitor
{
private final UsageMarker usageMarker;
private int[] constantIndexMap = new int[ClassConstants.TYPICAL_CONSTANT_POOL_SIZE];
private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
/**
* Creates a new ClassShrinker.
* @param usageMarker the usage marker that is used to mark the classes
* and class members.
*/
public ClassShrinker(UsageMarker usageMarker)
{
this.usageMarker = usageMarker;
}
// Implementations for ClassVisitor.
public void visitProgramClass(ProgramClass programClass)
{
// Shrink the arrays for constant pool, interfaces, fields, methods,
// and class attributes.
programClass.u2interfacesCount =
shrinkConstantIndexArray(programClass.constantPool,
programClass.u2interfaces,
programClass.u2interfacesCount);
// Shrinking the constant pool also sets up an index map.
int newConstantPoolCount =
shrinkConstantPool(programClass.constantPool,
programClass.u2constantPoolCount);
programClass.u2fieldsCount =
shrinkArray(programClass.fields,
programClass.u2fieldsCount);
programClass.u2methodsCount =
shrinkArray(programClass.methods,
programClass.u2methodsCount);
programClass.u2attributesCount =
shrinkArray(programClass.attributes,
programClass.u2attributesCount);
// Compact the remaining fields, methods, and attributes,
// and remap their references to the constant pool.
programClass.fieldsAccept(this);
programClass.methodsAccept(this);
programClass.attributesAccept(this);
// 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);
}
// Remove the unused interfaces from the class signature.
programClass.attributesAccept(new SignatureShrinker());
// Compact the extra field pointing to the subclasses of this class.
programClass.subClasses =
shrinkToNewArray(programClass.subClasses);
}
public void visitLibraryClass(LibraryClass libraryClass)
{
// Library classes are left unchanged.
// Compact the extra field pointing to the subclasses of this class.
libraryClass.subClasses =
shrinkToNewArray(libraryClass.subClasses);
}
// Implementations for MemberVisitor.
public void visitProgramMember(ProgramClass programClass, ProgramMember programMember)
{
// Shrink the attributes array.
programMember.u2attributesCount =
shrinkArray(programMember.attributes,
programMember.u2attributesCount);
// Shrink any attributes.
programMember.attributesAccept(programClass, this);
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitBootstrapMethodsAttribute(Clazz clazz, BootstrapMethodsAttribute bootstrapMethodsAttribute)
{
// Shrink the array of BootstrapMethodInfo objects.
bootstrapMethodsAttribute.u2bootstrapMethodsCount =
shrinkArray(bootstrapMethodsAttribute.bootstrapMethods,
bootstrapMethodsAttribute.u2bootstrapMethodsCount);
}
public void visitInnerClassesAttribute(Clazz clazz, InnerClassesAttribute innerClassesAttribute)
{
// Shrink the array of InnerClassesInfo objects.
innerClassesAttribute.u2classesCount =
shrinkArray(innerClassesAttribute.classes,
innerClassesAttribute.u2classesCount);
}
public void visitEnclosingMethodAttribute(Clazz clazz, EnclosingMethodAttribute enclosingMethodAttribute)
{
// Sometimes, a class is still referenced (apparently as a dummy class),
// but its enclosing method is not. Then remove the reference to
// the enclosing method.
// E.g. the anonymous inner class javax.swing.JList$1 is defined inside
// a constructor of javax.swing.JList, but it is also referenced as a
// dummy argument in a constructor of javax.swing.JList$ListSelectionHandler.
if (enclosingMethodAttribute.referencedMethod != null &&
!usageMarker.isUsed(enclosingMethodAttribute.referencedMethod))
{
enclosingMethodAttribute.u2nameAndTypeIndex = 0;
enclosingMethodAttribute.referencedMethod = null;
}
}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Shrink the attributes array.
codeAttribute.u2attributesCount =
shrinkArray(codeAttribute.attributes,
codeAttribute.u2attributesCount);
}
public void visitAnyAnnotationsAttribute(Clazz clazz, AnnotationsAttribute annotationsAttribute)
{
// Shrink the annotations array.
annotationsAttribute.u2annotationsCount =
shrinkArray(annotationsAttribute.annotations,
annotationsAttribute.u2annotationsCount);
// Shrink the annotations themselves.
annotationsAttribute.annotationsAccept(clazz, this);
}
public void visitAnyParameterAnnotationsAttribute(Clazz clazz, Method method, ParameterAnnotationsAttribute parameterAnnotationsAttribute)
{
// Loop over all parameters.
for (int parameterIndex = 0; parameterIndex < parameterAnnotationsAttribute.u2parametersCount; parameterIndex++)
{
// Shrink the parameter annotations array.
parameterAnnotationsAttribute.u2parameterAnnotationsCount[parameterIndex] =
shrinkArray(parameterAnnotationsAttribute.parameterAnnotations[parameterIndex],
parameterAnnotationsAttribute.u2parameterAnnotationsCount[parameterIndex]);
}
// Shrink the annotations themselves.
parameterAnnotationsAttribute.annotationsAccept(clazz, method, this);
}
// Implementations for AnnotationVisitor.
public void visitAnnotation(Clazz clazz, Annotation annotation)
{
// Shrink the element values array.
annotation.u2elementValuesCount =
shrinkArray(annotation.elementValues,
annotation.u2elementValuesCount);
// Shrink the element values themselves.
annotation.elementValuesAccept(clazz, this);
}
/**
* This AttributeVisitor updates the Utf8 constants of class signatures,
* removing any unused interfaces.
*/
private class SignatureShrinker
extends SimplifiedVisitor
implements AttributeVisitor
{
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitSignatureAttribute(Clazz clazz, SignatureAttribute signatureAttribute)
{
Clazz[] referencedClasses = signatureAttribute.referencedClasses;
if (referencedClasses != null)
{
// Go over the generic definitions, superclass and implemented interfaces.
String signature = clazz.getString(signatureAttribute.u2signatureIndex);
InternalTypeEnumeration internalTypeEnumeration =
new InternalTypeEnumeration(signature);
StringBuffer newSignatureBuffer = new StringBuffer();
int referencedClassIndex = 0;
int newReferencedClassIndex = 0;
while (internalTypeEnumeration.hasMoreTypes())
{
// Consider the classes referenced by this signature.
String type = internalTypeEnumeration.nextType();
int classCount = new DescriptorClassEnumeration(type).classCount();
Clazz referencedClass = referencedClasses[referencedClassIndex];
if (referencedClass == null ||
usageMarker.isUsed(referencedClass))
{
// Append the superclass or interface.
newSignatureBuffer.append(type);
// Copy the referenced classes.
for (int counter = 0; counter < classCount; counter++)
{
referencedClasses[newReferencedClassIndex++] =
referencedClasses[referencedClassIndex++];
}
}
else
{
// Skip the referenced classes.
referencedClassIndex += classCount;
}
}
if (newReferencedClassIndex < referencedClassIndex)
{
// Update the signature.
((Utf8Constant)((ProgramClass)clazz).constantPool[signatureAttribute.u2signatureIndex]).setString(newSignatureBuffer.toString());
// Clear the unused entries.
while (newReferencedClassIndex < referencedClassIndex)
{
referencedClasses[newReferencedClassIndex++] = null;
}
}
}
}
}
// Implementations for ElementValueVisitor.
public void visitAnyElementValue(Clazz clazz, Annotation annotation, ElementValue elementValue) {}
public void visitAnnotationElementValue(Clazz clazz, Annotation annotation, AnnotationElementValue annotationElementValue)
{
// Shrink the contained annotation.
annotationElementValue.annotationAccept(clazz, this);
}
public void visitArrayElementValue(Clazz clazz, Annotation annotation, ArrayElementValue arrayElementValue)
{
// Shrink the element values array.
arrayElementValue.u2elementValuesCount =
shrinkArray(arrayElementValue.elementValues,
arrayElementValue.u2elementValuesCount);
// Shrink the element values themselves.
arrayElementValue.elementValuesAccept(clazz, annotation, this);
}
// Small utility methods.
/**
* Removes all 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)
{
if (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 = usageMarker.isUsed(constant);
}
if (isUsed)
{
constantPool[counter++] = constant;
}
}
// Clear the remaining constant pool elements.
Arrays.fill(constantPool, counter, length, null);
return counter;
}
/**
* Removes all indices that point to unused constant pool entries
* from the given array.
* @return the new number of indices.
*/
private int shrinkConstantIndexArray(Constant[] constantPool, int[] array, int length)
{
int counter = 0;
// Shift the used objects together.
for (int index = 0; index < length; index++)
{
if (usageMarker.isUsed(constantPool[array[index]]))
{
array[counter++] = array[index];
}
}
// Clear the remaining array elements.
Arrays.fill(array, counter, length, 0);
return counter;
}
/**
* Removes all Clazz objects that are not marked as being used
* from the given array and returns the remaining objects in a an array
* of the right size.
* @return the new array.
*/
private Clazz[] shrinkToNewArray(Clazz[] array)
{
if (array == null)
{
return null;
}
// Shrink the given array in-place.
int length = shrinkArray(array, array.length);
if (length == 0)
{
return null;
}
// Return immediately if the array is of right size already.
if (length == array.length)
{
return array;
}
// Copy the remaining elements into a new array of the right size.
Clazz[] newArray = new Clazz[length];
System.arraycopy(array, 0, newArray, 0, length);
return newArray;
}
/**
* Removes all VisitorAccepter objects that are not marked as being used
* from the given array.
* @return the new number of VisitorAccepter objects.
*/
private int shrinkArray(VisitorAccepter[] array, int length)
{
int counter = 0;
// Shift the used objects together.
for (int index = 0; index < length; index++)
{
if (usageMarker.isUsed(array[index]))
{
array[counter++] = array[index];
}
}
// Clear any remaining array elements.
if (counter < length)
{
Arrays.fill(array, counter, length, null);
}
return counter;
}
}