| /* |
| * 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.*; |
| import proguard.classfile.instruction.*; |
| import proguard.classfile.util.SimplifiedVisitor; |
| import proguard.optimize.info.ExceptionInstructionChecker; |
| |
| /** |
| * This AttributeVisitor removes exception handlers that are unreachable in the |
| * code attributes that it visits. |
| * |
| * @author Eric Lafortune |
| */ |
| public class UnreachableExceptionRemover |
| extends SimplifiedVisitor |
| implements AttributeVisitor, |
| ExceptionInfoVisitor |
| { |
| private final ExceptionInfoVisitor extraExceptionInfoVisitor; |
| |
| |
| /** |
| * Creates a new UnreachableExceptionRemover. |
| */ |
| public UnreachableExceptionRemover() |
| { |
| this(null); |
| } |
| |
| |
| /** |
| * Creates a new UnreachableExceptionRemover. |
| * @param extraExceptionInfoVisitor an optional extra visitor for all |
| * removed exceptions. |
| */ |
| public UnreachableExceptionRemover(ExceptionInfoVisitor extraExceptionInfoVisitor) |
| { |
| this.extraExceptionInfoVisitor = extraExceptionInfoVisitor; |
| } |
| |
| |
| // Implementations for AttributeVisitor. |
| |
| public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} |
| |
| |
| public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) |
| { |
| // Go over the exception table. |
| codeAttribute.exceptionsAccept(clazz, method, this); |
| |
| // Remove exceptions with empty code blocks. |
| codeAttribute.u2exceptionTableLength = |
| removeEmptyExceptions(codeAttribute.exceptionTable, |
| codeAttribute.u2exceptionTableLength); |
| } |
| |
| |
| // Implementations for ExceptionInfoVisitor. |
| |
| public void visitExceptionInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo) |
| { |
| if (!mayThrowExceptions(clazz, |
| method, |
| codeAttribute, |
| exceptionInfo.u2startPC, |
| exceptionInfo.u2endPC)) |
| { |
| // Make the code block empty. |
| exceptionInfo.u2endPC = exceptionInfo.u2startPC; |
| |
| if (extraExceptionInfoVisitor != null) |
| { |
| extraExceptionInfoVisitor.visitExceptionInfo(clazz, method, codeAttribute, exceptionInfo); |
| } |
| } |
| } |
| |
| |
| // Small utility methods. |
| |
| /** |
| * Returns whether the specified block of code may throw exceptions. |
| */ |
| private boolean mayThrowExceptions(Clazz clazz, |
| Method method, |
| CodeAttribute codeAttribute, |
| int startOffset, |
| int endOffset) |
| { |
| byte[] code = codeAttribute.code; |
| |
| // Go over all instructions. |
| int offset = startOffset; |
| while (offset < endOffset) |
| { |
| // Get the current instruction. |
| Instruction instruction = InstructionFactory.create(code, offset); |
| |
| // Check if it may be throwing exceptions. |
| if (instruction.mayThrowExceptions()) |
| { |
| return true; |
| } |
| |
| // Go to the next instruction. |
| offset += instruction.length(offset); |
| } |
| |
| return false; |
| } |
| |
| |
| /** |
| * Returns the given list of exceptions, without the ones that have empty |
| * code blocks. |
| */ |
| private int removeEmptyExceptions(ExceptionInfo[] exceptionInfos, |
| int exceptionInfoCount) |
| { |
| // Overwrite all empty exceptions. |
| int newIndex = 0; |
| for (int index = 0; index < exceptionInfoCount; index++) |
| { |
| ExceptionInfo exceptionInfo = exceptionInfos[index]; |
| if (exceptionInfo.u2startPC < exceptionInfo.u2endPC) |
| { |
| exceptionInfos[newIndex++] = exceptionInfo; |
| } |
| } |
| |
| return newIndex; |
| } |
| } |