    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
    020import java.util.ArrayList;
    021
    022import org.apache.bcel.generic.InstructionHandle;
    023
    024/**
    025 * An InstructionContext offers convenient access to information like control flow successors and such.
    026 *
    027 */
    028public interface InstructionContext {
    029
    030    /**
    031     * This method symbolically executes the Instruction held in the InstructionContext. It "merges in" the incoming
    032     * execution frame situation (see The Java Virtual Machine Specification, 2nd edition, page 146). By so doing, the
    033     * outgoing execution frame situation is calculated.
    034     *
    035     * This method is JustIce-specific and is usually of no sense for users of the ControlFlowGraph class. They should use
    036     * getInstruction().accept(Visitor), possibly in conjunction with the ExecutionVisitor.
    037     *
    038     *
    039     * @see ControlFlowGraph
    040     * @see ExecutionVisitor
    041     * @see #getOutFrame(ArrayList)
    042     * @return true - if and only if the "outgoing" frame situation changed from the one before execute()ing.
    043     */
    044    boolean execute(Frame inFrame, ArrayList<InstructionContext> executionPredecessors, InstConstraintVisitor icv, ExecutionVisitor ev);
    045
    046    /**
    047     * Returns the exception handlers that protect this instruction. They are special control flow successors.
    048     */
    049    ExceptionHandler[] getExceptionHandlers();
    050
    051    Frame getInFrame();
    052
    053    /**
    054     * Returns the InstructionHandle this InstructionContext is wrapped around.
    055     *
    056     * @return The InstructionHandle this InstructionContext is wrapped around.
    057     */
    058    InstructionHandle getInstruction();
    059
    060    /**
    061     * This method returns the outgoing execution frame situation; therefore <B>it has to be calculated by execute(Frame,
    062     * ArrayList) first.</B>
    063     *
    064     * @see #execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor)
    065     */
    066    Frame getOutFrame(ArrayList<InstructionContext> executionPredecessors);
    067
    068    /**
    069     * Returns the usual control flow successors.
    070     *
    071     * @see #getExceptionHandlers()
    072     */
    073    InstructionContext[] getSuccessors();
    074
    075    /**
    076     * The getTag and setTag methods may be used for temporary flagging, such as graph colouring. Nothing in the
    077     * InstructionContext object depends on the value of the tag. JustIce does not use it.
    078     *
    079     * @see #setTag(int tag)
    080     */
    081    int getTag();
    082
    083    /**
    084     * The getTag and setTag methods may be used for temporary flagging, such as graph colouring. Nothing in the
    085     * InstructionContext object depends on the value of the tag. JustIce does not use it.
    086     *
    087     * @see #getTag()
    088     */
    089    void setTag(int tag);
    090}