proguard.optimize.peephole.WrapperClassUseSimplifier Maven / Gradle / Ivy
/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2018 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.optimize.peephole;
import proguard.classfile.*;
import proguard.classfile.attribute.Attribute;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.constant.ClassConstant;
import proguard.classfile.constant.Constant;
import proguard.classfile.constant.FieldrefConstant;
import proguard.classfile.constant.MethodrefConstant;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.editor.CodeAttributeEditor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.ClassVisitor;
import proguard.optimize.info.WrapperClassMarker;
/**
* This AttributeVisitor simplifies the use of retargeted wrapper classes in
* the code attributes that it visits. More specifically, it replaces
* "new Wrapper(targetClass)" by "targetClass", and
* "wrapper.field" by "wrapper".
* You still need to retarget all class references, replacing references to
* the wrapper class by references to the target class.
*
* @see WrapperClassMarker
* @see ClassMerger
* @see RetargetedClassFilter
* @see TargetClassChanger
* @author Eric Lafortune
*/
public class WrapperClassUseSimplifier
extends SimplifiedVisitor
implements AttributeVisitor,
InstructionVisitor,
ConstantVisitor,
ClassVisitor
{
//*
private static final boolean DEBUG = false;
/*/
private static boolean DEBUG = System.getProperty("wc") != null;
//*/
private final InstructionVisitor extraInstructionVisitor;
private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor(true, true);
// Fields acting as parameters and return values for the visitor methods.
private Clazz wrappedClass;
private Instruction popInstruction;
/**
* Creates a new WrapperClassUseSimplifier.
*/
public WrapperClassUseSimplifier()
{
this(null);
}
/**
* Creates a new WrapperClassUseSimplifier.
* @param extraInstructionVisitor an optional extra visitor for all
* simplified instructions.
*/
public WrapperClassUseSimplifier(InstructionVisitor extraInstructionVisitor)
{
this.extraInstructionVisitor = extraInstructionVisitor;
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
if (DEBUG)
{
System.out.println("WrapperClassUseSimplifier: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
}
int codeLength = codeAttribute.u4codeLength;
// Reset the code changes.
codeAttributeEditor.reset(codeLength);
// Edit the instructions.
codeAttribute.instructionsAccept(clazz, method, this);
// Apply all accumulated changes to the code.
codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
}
// Implementations for InstructionVisitor.
public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
{
switch (constantInstruction.opcode)
{
case InstructionConstants.OP_NEW:
{
// Is it instantiating a wrapper class?
if (isReferencingWrapperClass(clazz, constantInstruction.constantIndex))
{
// Is the next instruction a typical dup instruction?
int nextOffset = offset + constantInstruction.length(offset);
popInstruction = InstructionFactory.create(codeAttribute.code, nextOffset);
switch (popInstruction.canonicalOpcode())
{
case InstructionConstants.OP_DUP:
{
// Delete the new and dup instructions:
// new Wrapper
// dup
codeAttributeEditor.deleteInstruction(offset);
codeAttributeEditor.deleteInstruction(nextOffset);
popInstruction = null;
break;
}
case InstructionConstants.OP_ASTORE:
{
// Replace the new instance by a dummy null
// and remember to store the target instance:
// new Wrapper -> aconst_null
// astore x -> remember
// aload x
codeAttributeEditor.replaceInstruction(offset, new SimpleInstruction(InstructionConstants.OP_ACONST_NULL));
break;
}
default:
{
// Replace the new instance by a dummy null
// and remember to pop the target instance:
// new Wrapper -> aconst_null
codeAttributeEditor.replaceInstruction(offset, new SimpleInstruction(InstructionConstants.OP_ACONST_NULL));
popInstruction = new SimpleInstruction(InstructionConstants.OP_POP);
}
}
if (extraInstructionVisitor != null)
{
extraInstructionVisitor.visitConstantInstruction(clazz, method, codeAttribute, offset, constantInstruction);
}
}
break;
}
case InstructionConstants.OP_INVOKESPECIAL:
{
// Is it initializing a wrapper class?
if (isReferencingWrapperClass(clazz, constantInstruction.constantIndex))
{
// Do we have a special pop instruction?
// TODO: May still fail with nested initializers.
if (popInstruction == null)
{
// Delete the initializer invocation (with the
// wrapper instance no longer on the stack):
// Wrapper.(target) -> target
codeAttributeEditor.deleteInstruction(offset);
}
else
{
// Delete the initializer invocation, and store
// the target instance again:
// invokespecial Wrapper.(target) -> astore x / pop
codeAttributeEditor.replaceInstruction(offset, new Instruction[]
{
popInstruction,
new SimpleInstruction(InstructionConstants.OP_POP),
});
}
}
break;
}
case InstructionConstants.OP_GETFIELD:
{
// Is it retrieving the field of the wrapper class?
if (isReferencingWrapperClass(clazz, constantInstruction.constantIndex))
{
// Delete the retrieval:
// wrapper.field -> wrapper.
codeAttributeEditor.deleteInstruction(offset);
}
break;
}
}
}
// Implementations for ConstantVisitor.
public void visitAnyConstant(Clazz clazz, Constant constant) {}
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
// Is the constant retrieving from a wrapper class?
fieldrefConstant.referencedClassAccept(this);
}
public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
{
if (methodrefConstant.getName(clazz).equals(ClassConstants.METHOD_NAME_INIT))
{
// Is the constant referring to a wrapper class?
methodrefConstant.referencedClassAccept(this);
}
}
public void visitClassConstant(Clazz clazz, ClassConstant classConstant)
{
// Is the constant referring to a wrapper class?
classConstant.referencedClassAccept(this);
}
// Implementations for ClassVisitor.
public void visitLibraryClass(LibraryClass libraryClass) {}
public void visitProgramClass(ProgramClass programClass)
{
wrappedClass = ClassMerger.getTargetClass(programClass);
}
// Small utility methods.
/**
* Returns whether the constant at the given offset is referencing a
* wrapper class (different from the given class) that is being retargeted.
*/
private boolean isReferencingWrapperClass(Clazz clazz, int constantIndex)
{
wrappedClass = null;
clazz.constantPoolEntryAccept(constantIndex, this);
return wrappedClass != null;
}
}
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