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Java > Open Source Codes > org > apache > bcel > verifier > structurals > InstructionContext


1 /*
2  * Copyright 2000-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package org.apache.bcel.verifier.structurals;
18
19
20 import java.util.ArrayList JavaDoc;
21 import org.apache.bcel.generic.InstructionHandle;
22
23 /**
24  * An InstructionContext offers convenient access
25  * to information like control flow successors and
26  * such.
27  *
28  * @version $Id: InstructionContext.java 382272 2006-03-02 03:31:46Z tcurdt $
29  * @author Enver Haase
30  */
31 public interface InstructionContext{
32
33     /**
34      * The getTag and setTag methods may be used for
35      * temporary flagging, such as graph colouring.
36      * Nothing in the InstructionContext object depends
37      * on the value of the tag. JustIce does not use it.
38      *
39      * @see #setTag(int tag)
40      */
41     public int getTag();
42
43     /**
44      * The getTag and setTag methods may be used for
45      * temporary flagging, such as graph colouring.
46      * Nothing in the InstructionContext object depends
47      * on the value of the tag. JustIce does not use it.
48      *
49      * @see #getTag()
50      */
51     public void setTag(int tag);
52
53     /**
54      * This method symbolically executes the Instruction
55      * held in the InstructionContext.
56      * It "merges in" the incoming execution frame situation
57      * (see The Java Virtual Machine Specification, 2nd
58      * edition, page 146).
59      * By so doing, the outgoing execution frame situation
60      * is calculated.
61      *
62      * This method is JustIce-specific and is usually of
63      * no sense for users of the ControlFlowGraph class.
64      * They should use getInstruction().accept(Visitor),
65      * possibly in conjunction with the ExecutionVisitor.
66      *
67      *
68      * @see ControlFlowGraph
69      * @see ExecutionVisitor
70      * @see #getOutFrame(ArrayList)
71      * @return true - if and only if the "outgoing" frame situation
72      * changed from the one before execute()ing.
73      */
74     boolean execute(Frame inFrame, ArrayList JavaDoc executionPredecessors, InstConstraintVisitor icv, ExecutionVisitor ev);
75
76     Frame getInFrame();
77
78     /**
79      * This method returns the outgoing execution frame situation;
80      * therefore <B>it has to be calculated by execute(Frame, ArrayList)
81      * first.</B>
82      *
83      * @see #execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor)
84      */
85     Frame getOutFrame(ArrayList JavaDoc executionPredecessors);
86     
87     /**
88      * Returns the InstructionHandle this InstructionContext is wrapped around.
89      *
90      * @return The InstructionHandle this InstructionContext is wrapped around.
91      */
92     InstructionHandle getInstruction();
93
94     /**
95      * Returns the usual control flow successors.
96      * @see #getExceptionHandlers()
97      */
98     InstructionContext[] getSuccessors();
99
100     /**
101      * Returns the exception handlers that protect this instruction.
102      * They are special control flow successors.
103      */
104     ExceptionHandler[] getExceptionHandlers();
105 }
106
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