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/*
* 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.optimize.info;
import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.MemberVisitor;
/**
* This InstructionVisitor marks all fields that are write-only.
*
* @author Eric Lafortune
*/
public class ReadWriteFieldMarker
extends SimplifiedVisitor
implements InstructionVisitor,
ConstantVisitor,
MemberVisitor
{
// Parameters for the visitor methods.
private boolean reading = true;
private boolean writing = true;
// 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)
{
byte opcode = constantInstruction.opcode;
// Check for instructions that involve fields.
switch (opcode)
{
case InstructionConstants.OP_LDC:
case InstructionConstants.OP_LDC_W:
// Mark the field, if any, as being read from and written to.
reading = true;
writing = true;
clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
break;
case InstructionConstants.OP_GETSTATIC:
case InstructionConstants.OP_GETFIELD:
// Mark the field as being read from.
reading = true;
writing = false;
clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
break;
case InstructionConstants.OP_PUTSTATIC:
case InstructionConstants.OP_PUTFIELD:
// Mark the field as being written to.
reading = false;
writing = true;
clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
break;
}
}
// Implementations for ConstantVisitor.
public void visitAnyConstant(Clazz clazz, Constant constant) {}
public void visitStringConstant(Clazz clazz, StringConstant stringConstant)
{
// Mark the referenced field, if any.
stringConstant.referencedMemberAccept(this);
}
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
// Mark the referenced field.
fieldrefConstant.referencedMemberAccept(this);
}
// Implementations for MemberVisitor.
public void visitAnyMember(Clazz Clazz, Member member) {}
public void visitProgramField(ProgramClass programClass, ProgramField programField)
{
// Mark the field if it is being read from.
if (reading)
{
markAsRead(programField);
}
// Mark the field if it is being written to.
if (writing)
{
markAsWritten(programField);
}
}
// Small utility methods.
private static void markAsRead(Field field)
{
FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
if (info != null)
{
info.setRead();
}
}
public static boolean isRead(Field field)
{
FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
return info == null ||
info.isRead();
}
private static void markAsWritten(Field field)
{
FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
if (info != null)
{
info.setWritten();
}
}
public static boolean isWritten(Field field)
{
FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
return info == null ||
info.isWritten();
}
}
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