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