diff options
Diffstat (limited to 'src/proguard/classfile/editor/VariableRemapper.java')
-rw-r--r-- | src/proguard/classfile/editor/VariableRemapper.java | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/proguard/classfile/editor/VariableRemapper.java b/src/proguard/classfile/editor/VariableRemapper.java new file mode 100644 index 0000000..590cd4e --- /dev/null +++ b/src/proguard/classfile/editor/VariableRemapper.java @@ -0,0 +1,197 @@ +/* + * ProGuard -- shrinking, optimization, obfuscation, and preverification + * of Java bytecode. + * + * Copyright (c) 2002-2009 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.classfile.editor; + +import proguard.classfile.*; +import proguard.classfile.attribute.*; +import proguard.classfile.attribute.visitor.*; +import proguard.classfile.instruction.*; +import proguard.classfile.instruction.visitor.InstructionVisitor; +import proguard.classfile.util.SimplifiedVisitor; + +/** + * This AttributeVisitor remaps variable indexes in all attributes that it + * visits, based on a given index map. + * + * @author Eric Lafortune + */ +public class VariableRemapper +extends SimplifiedVisitor +implements AttributeVisitor, + InstructionVisitor, + LocalVariableInfoVisitor, + LocalVariableTypeInfoVisitor +{ + private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor(); + + private int[] variableMap; + + + /** + * Sets the given mapping of old variable indexes to their new indexes. + * Variables that should disappear can be mapped to -1. + */ + public void setVariableMap(int[] variableMap) + { + this.variableMap = variableMap; + } + + + // Implementations for AttributeVisitor. + + public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} + + + public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) + { + // Initially, the code attribute editor doesn't contain any changes. + codeAttributeEditor.reset(codeAttribute.u4codeLength); + + // Remap the variables of the instructions. + codeAttribute.instructionsAccept(clazz, method, this); + + // Apply the code atribute editor. + codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute); + + // Remap the variables of the attributes. + codeAttribute.attributesAccept(clazz, method, this); + } + + + public void visitLocalVariableTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTableAttribute localVariableTableAttribute) + { + // Remap the variable references of the local variables. + localVariableTableAttribute.localVariablesAccept(clazz, method, codeAttribute, this); + + // Remove local variables that haven't been mapped. + localVariableTableAttribute.u2localVariableTableLength = + removeEmptyLocalVariables(localVariableTableAttribute.localVariableTable, + localVariableTableAttribute.u2localVariableTableLength); + } + + + public void visitLocalVariableTypeTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeTableAttribute localVariableTypeTableAttribute) + { + // Remap the variable references of the local variables. + localVariableTypeTableAttribute.localVariablesAccept(clazz, method, codeAttribute, this); + + // Remove local variables that haven't been mapped. + localVariableTypeTableAttribute.u2localVariableTypeTableLength = + removeEmptyLocalVariableTypes(localVariableTypeTableAttribute.localVariableTypeTable, + localVariableTypeTableAttribute.u2localVariableTypeTableLength); + } + + + // Implementations for LocalVariableInfoVisitor. + + public void visitLocalVariableInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableInfo localVariableInfo) + { + localVariableInfo.u2index = + remapVariable(localVariableInfo.u2index); + } + + + // Implementations for LocalVariableTypeInfoVisitor. + + public void visitLocalVariableTypeInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, LocalVariableTypeInfo localVariableTypeInfo) + { + localVariableTypeInfo.u2index = + remapVariable(localVariableTypeInfo.u2index); + } + + + // Implementations for InstructionVisitor. + + public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {} + + + public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction) + { + // Is the new variable index different from the original one? + int oldVariableIndex = variableInstruction.variableIndex; + int newVariableIndex = remapVariable(oldVariableIndex); + if (newVariableIndex != oldVariableIndex) + { + // Replace the instruction. + Instruction replacementInstruction = + new VariableInstruction(variableInstruction.opcode, + newVariableIndex, + variableInstruction.constant).shrink(); + + codeAttributeEditor.replaceInstruction(offset, replacementInstruction); + } + } + + + // Small utility methods. + + /** + * Returns the new variable index of the given variable. + */ + private int remapVariable(int variableIndex) + { + return variableMap[variableIndex]; + } + + + /** + * Returns the given list of local variables, without the ones that have + * been removed. + */ + private int removeEmptyLocalVariables(LocalVariableInfo[] localVariableInfos, + int localVariableInfoCount) + { + // Overwrite all empty local variable entries. + int newIndex = 0; + for (int index = 0; index < localVariableInfoCount; index++) + { + LocalVariableInfo localVariableInfo = localVariableInfos[index]; + if (localVariableInfo.u2index >= 0) + { + localVariableInfos[newIndex++] = localVariableInfo; + } + } + + return newIndex; + } + + + /** + * Returns the given list of local variable types, without the ones that + * have been removed. + */ + private int removeEmptyLocalVariableTypes(LocalVariableTypeInfo[] localVariableTypeInfos, + int localVariableTypeInfoCount) + { + // Overwrite all empty local variable type entries. + int newIndex = 0; + for (int index = 0; index < localVariableTypeInfoCount; index++) + { + LocalVariableTypeInfo localVariableTypeInfo = localVariableTypeInfos[index]; + if (localVariableTypeInfo.u2index >= 0) + { + localVariableTypeInfos[newIndex++] = localVariableTypeInfo; + } + } + + return newIndex; + } +} |