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Java > Open Source Codes > proguard > evaluation > BasicBranchUnit


1 /*
2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
3  * of Java bytecode.
4  *
5  * Copyright (c) 2002-2007 Eric Lafortune (eric@graphics.cornell.edu)
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License as published by the Free
9  * Software Foundation; either version 2 of the License, or (at your option)
10  * any later version.
11  *
12  * This program is distributed in the hope that it will be useful, but WITHOUT
13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15  * more details.
16  *
17  * You should have received a copy of the GNU General Public License along
18  * with this program; if not, write to the Free Software Foundation, Inc.,
19  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20  */
21 package proguard.evaluation;
22
23 import proguard.evaluation.value.*;
24 import proguard.classfile.Clazz;
25 import proguard.classfile.attribute.CodeAttribute;
26
27 /**
28  * This BranchUnit remembers the branch unit commands that are invoked on it.
29  * I doesn't consider conditions when branching.
30  *
31  * @author Eric Lafortune
32  */
33 public class BasicBranchUnit
34 implements BranchUnit
35 {
36     private boolean wasCalled;
37     private InstructionOffsetValue traceBranchTargets;
38
39
40     /**
41      * Resets the flag that tells whether any of the branch unit commands was
42      * called.
43      */
44     public void resetCalled()
45     {
46         wasCalled = false;
47     }
48
49     /**
50      * Sets the flag that tells whether any of the branch unit commands was
51      * called.
52      */
53     protected void setCalled()
54     {
55         wasCalled = true;
56     }
57
58     /**
59      * Returns whether any of the branch unit commands was called.
60      */
61     public boolean wasCalled()
62     {
63         return wasCalled;
64     }
65
66
67     /**
68      * Sets the initial branch targets, which will be updated as the branch
69      * methods of the branch unit are called.
70      */
71     public void setTraceBranchTargets(InstructionOffsetValue branchTargets)
72     {
73         this.traceBranchTargets = branchTargets;
74     }
75
76     public InstructionOffsetValue getTraceBranchTargets()
77     {
78         return traceBranchTargets;
79     }
80
81
82     // Implementations for BranchUnit.
83
84     public void branch(Clazz clazz,
85                        CodeAttribute codeAttribute,
86                        int offset,
87                        int branchTarget)
88     {
89         // Override the branch targets.
90 traceBranchTargets = new InstructionOffsetValue(branchTarget);
91
92         wasCalled = true;
93     }
94
95
96     public void branchConditionally(Clazz clazz,
97                                     CodeAttribute codeAttribute,
98                                     int offset,
99                                     int branchTarget,
100                                     int conditional)
101     {
102         // Accumulate the branch targets.
103 traceBranchTargets =
104             traceBranchTargets.generalize(new InstructionOffsetValue(branchTarget)).instructionOffsetValue();
105
106         wasCalled = true;
107     }
108
109
110     public void returnFromMethod()
111     {
112         // Stop processing this block.
113 traceBranchTargets = InstructionOffsetValue.EMPTY_VALUE;
114
115         wasCalled = true;
116     }
117
118
119     public void throwException()
120     {
121         // Stop processing this block.
122 traceBranchTargets = InstructionOffsetValue.EMPTY_VALUE;
123
124         wasCalled = true;
125     }
126 }
127
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