001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 * 017 */ 018package org.apache.bcel.verifier.structurals; 019 020 021import java.util.ArrayList; 022 023import org.apache.bcel.generic.InstructionHandle; 024 025/** 026 * An InstructionContext offers convenient access 027 * to information like control flow successors and 028 * such. 029 * 030 * @version $Id: InstructionContext.java 1806200 2017-08-25 16:33:06Z ggregory $ 031 */ 032public interface InstructionContext{ 033 034 /** 035 * The getTag and setTag methods may be used for 036 * temporary flagging, such as graph colouring. 037 * Nothing in the InstructionContext object depends 038 * on the value of the tag. JustIce does not use it. 039 * 040 * @see #setTag(int tag) 041 */ 042 int getTag(); 043 044 /** 045 * The getTag and setTag methods may be used for 046 * temporary flagging, such as graph colouring. 047 * Nothing in the InstructionContext object depends 048 * on the value of the tag. JustIce does not use it. 049 * 050 * @see #getTag() 051 */ 052 void setTag(int tag); 053 054 /** 055 * This method symbolically executes the Instruction 056 * held in the InstructionContext. 057 * It "merges in" the incoming execution frame situation 058 * (see The Java Virtual Machine Specification, 2nd 059 * edition, page 146). 060 * By so doing, the outgoing execution frame situation 061 * is calculated. 062 * 063 * This method is JustIce-specific and is usually of 064 * no sense for users of the ControlFlowGraph class. 065 * They should use getInstruction().accept(Visitor), 066 * possibly in conjunction with the ExecutionVisitor. 067 * 068 * 069 * @see ControlFlowGraph 070 * @see ExecutionVisitor 071 * @see #getOutFrame(ArrayList) 072 * @return true - if and only if the "outgoing" frame situation 073 * changed from the one before execute()ing. 074 */ 075 boolean execute(Frame inFrame, ArrayList<InstructionContext> executionPredecessors, 076 InstConstraintVisitor icv, ExecutionVisitor ev); 077 078 Frame getInFrame(); 079 080 /** 081 * This method returns the outgoing execution frame situation; 082 * therefore <B>it has to be calculated by execute(Frame, ArrayList) 083 * first.</B> 084 * 085 * @see #execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor) 086 */ 087 Frame getOutFrame(ArrayList<InstructionContext> executionPredecessors); 088 089 /** 090 * Returns the InstructionHandle this InstructionContext is wrapped around. 091 * 092 * @return The InstructionHandle this InstructionContext is wrapped around. 093 */ 094 InstructionHandle getInstruction(); 095 096 /** 097 * Returns the usual control flow successors. 098 * @see #getExceptionHandlers() 099 */ 100 InstructionContext[] getSuccessors(); 101 102 /** 103 * Returns the exception handlers that protect this instruction. 104 * They are special control flow successors. 105 */ 106 ExceptionHandler[] getExceptionHandlers(); 107}