| /* |
| * ProGuard -- shrinking, optimization, obfuscation, and preverification |
| * of Java bytecode. |
| * |
| * Copyright (c) 2002-2014 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.peephole; |
| |
| import proguard.classfile.*; |
| import proguard.classfile.attribute.*; |
| import proguard.classfile.attribute.visitor.AttributeVisitor; |
| import proguard.classfile.editor.VariableEditor; |
| import proguard.classfile.util.*; |
| import proguard.classfile.visitor.MemberVisitor; |
| import proguard.optimize.*; |
| import proguard.optimize.info.*; |
| |
| /** |
| * This MemberVisitor removes unused local variables from the code of the methods |
| * that it visits. |
| * |
| * @see ParameterUsageMarker |
| * @see MethodStaticizer |
| * @see MethodDescriptorShrinker |
| * @author Eric Lafortune |
| */ |
| public class VariableShrinker |
| extends SimplifiedVisitor |
| implements AttributeVisitor |
| { |
| private static final boolean DEBUG = false; |
| |
| |
| private final MemberVisitor extraVariableMemberVisitor; |
| |
| private final VariableUsageMarker variableUsageMarker = new VariableUsageMarker(); |
| private final VariableEditor variableEditor = new VariableEditor(); |
| |
| |
| /** |
| * Creates a new VariableShrinker. |
| */ |
| public VariableShrinker() |
| { |
| this(null); |
| } |
| |
| |
| /** |
| * Creates a new VariableShrinker with an extra visitor. |
| * @param extraVariableMemberVisitor an optional extra visitor for all |
| * removed variables. |
| */ |
| public VariableShrinker(MemberVisitor extraVariableMemberVisitor) |
| { |
| this.extraVariableMemberVisitor = extraVariableMemberVisitor; |
| } |
| |
| |
| // Implementations for AttributeVisitor. |
| |
| public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} |
| |
| |
| public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) |
| { |
| if ((method.getAccessFlags() & ClassConstants.ACC_ABSTRACT) == 0) |
| { |
| // Compute the parameter size. |
| int parameterSize = |
| ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz), |
| method.getAccessFlags()); |
| |
| // Get the total size of the local variable frame. |
| int maxLocals = codeAttribute.u2maxLocals; |
| |
| if (DEBUG) |
| { |
| System.out.println("VariableShrinker: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz)); |
| System.out.println(" Parameter size = " + parameterSize); |
| System.out.println(" Max locals = " + maxLocals); |
| } |
| |
| // Figure out the local variables that are used by the code. |
| variableUsageMarker.visitCodeAttribute(clazz, method, codeAttribute); |
| |
| // Delete unused local variables from the local variable frame. |
| variableEditor.reset(maxLocals); |
| |
| for (int variableIndex = parameterSize; variableIndex < maxLocals; variableIndex++) |
| { |
| // Is the variable not required? |
| if (!variableUsageMarker.isVariableUsed(variableIndex)) |
| { |
| if (DEBUG) |
| { |
| System.out.println(" Deleting local variable #"+variableIndex); |
| } |
| |
| // Delete the unused variable. |
| variableEditor.deleteVariable(variableIndex); |
| |
| // Visit the method, if required. |
| if (extraVariableMemberVisitor != null) |
| { |
| method.accept(clazz, extraVariableMemberVisitor); |
| } |
| } |
| } |
| |
| // Shift all remaining parameters and variables in the byte code. |
| variableEditor.visitCodeAttribute(clazz, method, codeAttribute); |
| } |
| } |
| } |