BasicBranchUnit.java revision db267bc191f906f55eaef21a27110cce2ec57fdf 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2009 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 */
21package proguard.evaluation;
22
23import proguard.classfile.Clazz;
24import proguard.classfile.attribute.CodeAttribute;
25import proguard.evaluation.value.InstructionOffsetValue;
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 */
33public class BasicBranchUnit
34implements   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