1   package org.apache.bcel.verifier.structurals;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
5    *
6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
7    * reserved.
8    *
9    * Redistribution and use in source and binary forms, with or without
10   * modification, are permitted provided that the following conditions
11   * are met:
12   *
13   * 1. Redistributions of source code must retain the above copyright
14   *    notice, this list of conditions and the following disclaimer.
15   *
16   * 2. Redistributions in binary form must reproduce the above copyright
17   *    notice, this list of conditions and the following disclaimer in
18   *    the documentation and/or other materials provided with the
19   *    distribution.
20   *
21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
23   *       "This product includes software developed by the
24   *        Apache Software Foundation (http://www.apache.org/)."
25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
27   *
28   * 4. The names "Apache" and "Apache Software Foundation" and
29   *    "Apache BCEL" must not be used to endorse or promote products
30   *    derived from this software without prior written permission. For
31   *    written permission, please contact apache@apache.org.
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50   *
51   * This software consists of voluntary contributions made by many
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55   */
56  
57  import org.apache.bcel.generic.InstructionHandle;
58  import java.util.ArrayList;
59  import java.util.Iterator;
60  
61  /***
62   * An InstructionContext offers convenient access
63   * to information like control flow successors and
64   * such.
65   *
66   * @version $Id: InstructionContext.java,v 1.1.1.1 2001/10/29 20:00:41 jvanzyl Exp $
67   * @author <A HREF="http://www.inf.fu-berlin.de/~ehaase"/>Enver Haase</A>
68   */
69  public interface InstructionContext{
70  
71  	/***
72  	 * The getTag and setTag methods may be used for
73  	 * temporary flagging, such as graph colouring.
74  	 * Nothing in the InstructionContext object depends
75  	 * on the value of the tag. JustIce does not use it.
76  	 * 
77  	 * @see #setTag(int tag)
78  	 */
79  	public int getTag();
80  
81  	/***
82  	 * The getTag and setTag methods may be used for
83  	 * temporary flagging, such as graph colouring.
84  	 * Nothing in the InstructionContext object depends
85  	 * on the value of the tag. JustIce does not use it.
86  	 * 
87  	 * @see #getTag()
88  	 */
89  	public void setTag(int tag);
90  
91  	/***
92  	 * This method symbolically executes the Instruction
93  	 * held in the InstructionContext.
94  	 * It "merges in" the incoming execution frame situation
95  	 * (see The Java Virtual Machine Specification, 2nd
96  	 * edition, page 146).
97  	 * By so doing, the outgoing execution frame situation
98  	 * is calculated.
99  	 *
100 	 * This method is JustIce-specific and is usually of
101 	 * no sense for users of the ControlFlowGraph class.
102 	 * They should use getInstruction().accept(Visitor),
103 	 * possibly in conjunction with the ExecutionVisitor.
104 	 * 
105 	 *
106 	 * @see ControlFlowGraph
107 	 * @see ExecutionVisitor
108 	 * @see #getOutFrame(ArrayList)
109 	 * @return true -  if and only if the "outgoing" frame situation
110 	 * changed from the one before execute()ing.
111 	 */
112 	boolean execute(Frame inFrame, ArrayList executionPredecessors, InstConstraintVisitor icv, ExecutionVisitor ev);
113 
114 	/***
115 	 * This method returns the outgoing execution frame situation;
116 	 * therefore <B>it has to be calculated by execute(Frame, ArrayList)
117 	 * first.</B>
118 	 *
119 	 * @see #execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor)
120 	 */
121 	Frame getOutFrame(ArrayList executionPredecessors);
122 	
123 	/***
124 	 * Returns the InstructionHandle this InstructionContext is wrapped around.
125 	 *
126 	 * @return The InstructionHandle this InstructionContext is wrapped around.
127 	 */
128 	InstructionHandle getInstruction();
129 
130 	/***
131 	 * Returns the usual control flow successors.
132 	 * @see #getExceptionHandlers()
133 	 */
134 	InstructionContext[] getSuccessors();
135 
136 	/***
137 	 * Returns the exception handlers that protect this instruction.
138 	 * They are special control flow successors.
139 	 */
140 	ExceptionHandler[] getExceptionHandlers();
141 }
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