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Diffstat (limited to 'src/proguard/classfile/editor/VariableEditor.java')
-rw-r--r-- | src/proguard/classfile/editor/VariableEditor.java | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/proguard/classfile/editor/VariableEditor.java b/src/proguard/classfile/editor/VariableEditor.java new file mode 100644 index 0000000..a583b49 --- /dev/null +++ b/src/proguard/classfile/editor/VariableEditor.java @@ -0,0 +1,129 @@ +/* + * 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.AttributeVisitor; +import proguard.classfile.util.SimplifiedVisitor; + +/** + * This AttributeVisitor accumulates specified changes to local variables, and + * then applies these accumulated changes to the code attributes that it visits. + * + * @author Eric Lafortune + */ +public class VariableEditor +extends SimplifiedVisitor +implements AttributeVisitor +{ + private boolean modified; + + private boolean[] deleted = new boolean[ClassConstants.TYPICAL_VARIABLES_SIZE]; + private int[] variableMap = new int[ClassConstants.TYPICAL_VARIABLES_SIZE]; + + private final VariableRemapper variableRemapper = new VariableRemapper(); + + + /** + * Resets the accumulated code changes. + * @param maxLocals the length of the local variable frame that will be + * edited next. + */ + public void reset(int maxLocals) + { + // Try to reuse the previous array. + if (deleted.length < maxLocals) + { + deleted = new boolean[maxLocals]; + } + else + { + for (int index = 0; index < maxLocals; index++) + { + deleted[index] = false; + } + } + + modified = false; + } + + + /** + * Remembers to delete the given variable. + * @param variableIndex the index of the variable to be deleted. + */ + public void deleteVariable(int variableIndex) + { + deleted[variableIndex] = true; + + modified = true; + } + + + /** + * Returns whether the given variable at the given offset has deleted. + */ + public boolean isDeleted(int instructionOffset) + { + return deleted[instructionOffset]; + } + + + // Implementations for AttributeVisitor. + + public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} + + + public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) + { + // Avoid doing any work if nothing is changing anyway. + if (!modified) + { + return; + } + + int oldMaxLocals = codeAttribute.u2maxLocals; + + // Make sure there is a sufficiently large variable map. + if (variableMap.length < oldMaxLocals) + { + variableMap = new int[oldMaxLocals]; + } + + // Fill out the variable map. + int newVariableIndex = 0; + for (int oldVariableIndex = 0; oldVariableIndex < oldMaxLocals; oldVariableIndex++) + { + variableMap[oldVariableIndex] = deleted[oldVariableIndex] ? + -1 : newVariableIndex++; + } + + // Set the map. + variableRemapper.setVariableMap(variableMap); + + // Remap the variables. + variableRemapper.visitCodeAttribute(clazz, method, codeAttribute); + + // Update the length of local variable frame. + codeAttribute.u2maxLocals = newVariableIndex; + } +} |