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ProGuard is a free shrinker, optimizer, obfuscator, and preverifier for Java bytecode
/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2020 Guardsquare NV
*
* 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.constant.visitor.ConstantVisitor;
import proguard.classfile.editor.*;
import proguard.classfile.util.*;
import proguard.classfile.visitor.*;
import proguard.util.*;
import java.util.*;
/**
* This ClassVisitor removes constant pool entries, class members, and other
* class elements that are not marked as being used.
*
* @see ClassUsageMarker
*
* @author Eric Lafortune
*/
public class ClassShrinker
implements ClassVisitor,
MemberVisitor,
AttributeVisitor,
RecordComponentInfoVisitor,
AnnotationVisitor,
ElementValueVisitor
{
private final SimpleUsageMarker usageMarker;
private int[] constantIndexMap = new int[ClassEstimates.TYPICAL_CONSTANT_POOL_SIZE];
private int[] bootstrapMethodIndexMap = new int[ClassEstimates.TYPICAL_CONSTANT_POOL_SIZE];
private final MyAttributeShrinker attributeShrinker = new MyAttributeShrinker();
private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
private final BootstrapMethodRemapper bootstrapMethodRemapper = new BootstrapMethodRemapper();
private final MySignatureCleaner signatureCleaner = new MySignatureCleaner();
/**
* Creates a new ClassShrinker.
* @param usageMarker the usage marker that is used to mark the classes
* and class members.
*/
public ClassShrinker(SimpleUsageMarker usageMarker)
{
this.usageMarker = usageMarker;
}
// Implementations for ClassVisitor.
@Override
public void visitAnyClass(Clazz clazz)
{
throw new UnsupportedOperationException(this.getClass().getName() + " does not support " + clazz.getClass().getName());
}
@Override
public void visitProgramClass(ProgramClass programClass)
{
// Mark the classes with processing flags if fields or methods are removed
// (used for configuration debugging).
programClass.fieldsAccept(
new UsedMemberFilter(usageMarker, null,
new MemberAccessFilter(AccessConstants.PUBLIC, 0,
new MemberToClassVisitor(
new MultiClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_FIELDS),
new ProcessingFlagSetter(ProcessingFlags.REMOVED_PUBLIC_FIELDS)
)),
new MemberToClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_FIELDS)))));
programClass.methodsAccept(
new UsedMemberFilter(usageMarker, null,
new ConstructorMethodFilter(
new MemberAccessFilter(AccessConstants.PUBLIC, 0,
new MemberToClassVisitor(
new MultiClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_CONSTRUCTORS),
new ProcessingFlagSetter(ProcessingFlags.REMOVED_PUBLIC_CONSTRUCTORS)
)),
new MemberToClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_CONSTRUCTORS))),
new MemberAccessFilter(AccessConstants.PUBLIC, 0,
new MemberToClassVisitor(
new MultiClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_METHODS),
new ProcessingFlagSetter(ProcessingFlags.REMOVED_PUBLIC_METHODS)
)),
new MemberToClassVisitor(
new ProcessingFlagSetter(ProcessingFlags.REMOVED_METHODS))))));
// Shrink the arrays for constant pool, interfaces, fields, methods,
// and class attributes.
if (programClass.u2interfacesCount > 0)
{
new InterfaceDeleter(shrinkInterfaceFlags(programClass), true)
.visitProgramClass(programClass);
}
// Shrink the arrays for nest members and permitted subclasses.
programClass.attributesAccept(attributeShrinker);
// Shrink the constant pool, also setting up an index map.
int newConstantPoolCount =
shrinkConstantPool(programClass.constantPool,
programClass.u2constantPoolCount);
int oldFieldsCount = programClass.u2fieldsCount;
programClass.u2fieldsCount =
shrinkArray(programClass.fields,
programClass.u2fieldsCount);
if (programClass.u2fieldsCount < oldFieldsCount)
{
programClass.processingFlags |= ProcessingFlags.REMOVED_FIELDS;
}
int oldMethodsCount = programClass.u2methodsCount;
programClass.u2methodsCount =
shrinkArray(programClass.methods,
programClass.u2methodsCount);
if (programClass.u2methodsCount < oldMethodsCount)
{
programClass.processingFlags |= ProcessingFlags.REMOVED_METHODS;
}
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);
}
// Replace any unused classes in the signatures.
programClass.fieldsAccept(new AllAttributeVisitor(signatureCleaner));
programClass.methodsAccept(new AllAttributeVisitor(signatureCleaner));
programClass.attributesAccept(signatureCleaner);
// Compact the extra field pointing to the subclasses of this class.
programClass.subClassCount =
shrinkArray(programClass.subClasses,
programClass.subClassCount);
}
@Override
public void visitLibraryClass(LibraryClass libraryClass)
{
// Library classes are left unchanged.
// Compact the extra field pointing to the subclasses of this class.
libraryClass.subClassCount =
shrinkArray(libraryClass.subClasses,
libraryClass.subClassCount);
}
// 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.
int newBootstrapMethodsCount =
shrinkBootstrapMethodArray(bootstrapMethodsAttribute.bootstrapMethods,
bootstrapMethodsAttribute.u2bootstrapMethodsCount);
if (newBootstrapMethodsCount < bootstrapMethodsAttribute.u2bootstrapMethodsCount)
{
bootstrapMethodsAttribute.u2bootstrapMethodsCount = newBootstrapMethodsCount;
// Remap all bootstrap method references.
bootstrapMethodRemapper.setBootstrapMethodIndexMap(bootstrapMethodIndexMap);
clazz.constantPoolEntriesAccept(bootstrapMethodRemapper);
}
}
public void visitRecordAttribute(Clazz clazz, RecordAttribute recordAttribute)
{
// Shrink the array of RecordComponentInfo objects.
recordAttribute.u2componentsCount =
shrinkArray(recordAttribute.components,
recordAttribute.u2componentsCount);
// Shrink the attributes of the remaining components.
recordAttribute.componentsAccept(clazz, this);
}
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);
// Shrink the attributes themselves.
codeAttribute.attributesAccept(clazz, method, this);
}
public void visitLocalVariableTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTableAttribute localVariableTableAttribute)
{
// Shrink the local variable info array.
localVariableTableAttribute.u2localVariableTableLength =
shrinkArray(localVariableTableAttribute.localVariableTable,
localVariableTableAttribute.u2localVariableTableLength);
}
public void visitLocalVariableTypeTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeTableAttribute localVariableTypeTableAttribute)
{
// Shrink the local variable type info array.
localVariableTypeTableAttribute.u2localVariableTypeTableLength =
shrinkArray(localVariableTypeTableAttribute.localVariableTypeTable,
localVariableTypeTableAttribute.u2localVariableTypeTableLength);
}
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.u1parametersCount; 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 RecordComponentInfoVisitor.
public void visitRecordComponentInfo(Clazz clazz, RecordComponentInfo recordComponentInfo)
{
// Shrink the attributes array.
recordComponentInfo.u2attributesCount =
shrinkArray(recordComponentInfo.attributes,
recordComponentInfo.u2attributesCount);
// Shrink the remaining attributes.
recordComponentInfo.attributesAccept(clazz, 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 shrinks the nest members in the nest member
* attributes and the permitted subclasses in the permitted subclasses
* attributes that it visits.
*/
private class MyAttributeShrinker
implements AttributeVisitor
{
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitNestMembersAttribute(Clazz clazz, NestMembersAttribute nestMembersAttribute)
{
// Shrink the array of nest member indices.
// We must do this before the corresponding constants are remapped.
nestMembersAttribute.u2classesCount =
shrinkConstantIndexArray(((ProgramClass)clazz).constantPool,
nestMembersAttribute.u2classes,
nestMembersAttribute.u2classesCount);
}
public void visitPermittedSubclassesAttribute(Clazz clazz, PermittedSubclassesAttribute permittedSubclassesAttribute)
{
// Shrink the array of nest member indices.
// We must do this before the corresponding constants are remapped.
permittedSubclassesAttribute.u2classesCount =
shrinkConstantIndexArray(((ProgramClass)clazz).constantPool,
permittedSubclassesAttribute.u2classes,
permittedSubclassesAttribute.u2classesCount);
}
}
/**
* This AttributeVisitor updates the Utf8 constants of signatures
* of classes, fields, and methods.
*/
private class MySignatureCleaner
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 classes in the signature.
String signature = signatureAttribute.getSignature(clazz);
DescriptorClassEnumeration classEnumeration =
new DescriptorClassEnumeration(signature);
int referencedClassIndex = 0;
// Start construction a new signature.
StringBuffer newSignatureBuffer = new StringBuffer();
newSignatureBuffer.append(classEnumeration.nextFluff());
while (classEnumeration.hasMoreClassNames())
{
String className = classEnumeration.nextClassName();
// Replace the class name if it is unused.
Clazz referencedClass = referencedClasses[referencedClassIndex];
if (referencedClass != null &&
!usageMarker.isUsed(referencedClass))
{
className = ClassConstants.NAME_JAVA_LANG_OBJECT;
referencedClasses[referencedClassIndex] = null;
}
// Use a short name if it's an inner class after a '.'
// separator.
else if (classEnumeration.isInnerClassName())
{
className = className.substring(className.lastIndexOf(TypeConstants.INNER_CLASS_SEPARATOR)+1);
}
referencedClassIndex++;
newSignatureBuffer.append(className);
newSignatureBuffer.append(classEnumeration.nextFluff());
}
// Update the signature.
((Utf8Constant)((ProgramClass)clazz).constantPool[signatureAttribute.u2signatureIndex]).setString(newSignatureBuffer.toString());
}
}
}
// 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. Creates a map from the old indices to the new indices
* as a side effect.
* @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];
// Is the constant being used? Don't update the flag if this is the
// second half of a long entry.
if (constant != null)
{
isUsed = usageMarker.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;
}
/**
* Creates an array marking unused constant pool entries for all the
* elements in the given array of constant pool indices.
* @return an array of flags indicating unused elements.
*/
private boolean[] shrinkFlags(Constant[] constantPool, int[] array, int length)
{
boolean[] unused = new boolean[length];
// Remember the unused constants.
for (int index = 0; index < length; index++)
{
if (!usageMarker.isUsed(constantPool[array[index]]))
{
unused[index] = true;
}
}
return unused;
}
/**
* Creates an array marking unused constant pool entries for all the
* elements in the given array of constant pool indices, pointing to
* class constants of interfaces.
* @return an array of flags indicating unused elements.
*/
private boolean[] shrinkInterfaceFlags(ProgramClass programClass)
{
Constant[] constantPool = programClass.constantPool;
int[] interfaces = programClass.u2interfaces;
int interfacesCount = programClass.u2interfacesCount;
// Collect the names of all indirectly implemented interfaces, unless
// they are kept or the class itself is kept. That avoids problems if
// some code applies reflection to the list of interfaces.
Set indirectlyImplementedInterfaces = new HashSet();
if ((programClass.getProcessingFlags() & ProcessingFlags.DONT_SHRINK) == 0)
{
ConstantVisitor interfaceNameCollector =
new ReferencedClassVisitor(
new UsedClassFilter(usageMarker,
new ClassHierarchyTraveler(false, true, true, false,
new ProgramClassFilter(
new UsedClassFilter(usageMarker,
new ClassAccessFilter(AccessConstants.INTERFACE, 0,
new ClassProcessingFlagFilter(0, ProcessingFlags.DONT_SHRINK,
new ClassNameCollector(indirectlyImplementedInterfaces))))))));
programClass.superClassConstantAccept(interfaceNameCollector);
programClass.interfaceConstantsAccept(interfaceNameCollector);
}
boolean[] unused = new boolean[interfacesCount];
// Remember the unused or unnecessary constants.
for (int index = 0; index < interfacesCount; index++)
{
// The interface may be unused, or it may be unnecessary in the
// list of implemented interfaces, if a superclass/interface
// already implements it.
ClassConstant interfaceClassConstant =
(ClassConstant)constantPool[interfaces[index]];
String interfaceClassName =
interfaceClassConstant.getName(programClass);
if (!usageMarker.isUsed(interfaceClassConstant) ||
indirectlyImplementedInterfaces.contains(interfaceClassName))
{
unused[index] = true;
}
}
return unused;
}
/**
* 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 entries that are not marked as being used from the given
* array of bootstrap methods. Creates a map from the old indices to the
* new indices as a side effect.
* @return the new number of entries.
*/
private int shrinkBootstrapMethodArray(BootstrapMethodInfo[] bootstrapMethods, int length)
{
if (bootstrapMethodIndexMap.length < length)
{
bootstrapMethodIndexMap = new int[length];
}
int counter = 0;
// Shift the used bootstrap methods together.
for (int index = 0; index < length; index++)
{
BootstrapMethodInfo bootstrapMethod = bootstrapMethods[index];
// Is the entry being used?
if (usageMarker.isUsed(bootstrapMethod))
{
// Remember the new index.
bootstrapMethodIndexMap[index] = counter;
// Shift the entry.
bootstrapMethods[counter++] = bootstrapMethod;
}
else
{
// Remember an invalid index.
bootstrapMethodIndexMap[index] = -1;
}
}
// Clear the remaining bootstrap methods.
Arrays.fill(bootstrapMethods, counter, length, null);
return counter;
}
/**
* Removes all Processable objects that are not marked as being used
* from the given array.
* @return the new number of Processable objects.
*/
private int shrinkArray(Processable[] array, int length)
{
int counter = 0;
// Shift the used objects together.
for (int index = 0; index < length; index++)
{
Processable processable = array[index];
if (usageMarker.isUsed(processable))
{
array[counter++] = processable;
}
}
// Clear any remaining array elements.
if (counter < length)
{
Arrays.fill(array, counter, length, null);
}
return counter;
}
}
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