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.classfile.attribute.preverification;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.CodeAttribute;
25import proguard.classfile.attribute.preverification.visitor.StackMapFrameVisitor;
26
27/**
28 * This abstract class represents a stack map frame. Specific types
29 * of entries are subclassed from it.
30 *
31 * @author Eric Lafortune
32 */
33public abstract class StackMapFrame implements VisitorAccepter
34{
35    public static final int SAME_ZERO_FRAME          =   0;
36    public static final int SAME_ONE_FRAME           =  64;
37    public static final int SAME_ONE_FRAME_EXTENDED  = 247;
38    public static final int LESS_ZERO_FRAME          = 248;
39    public static final int SAME_ZERO_FRAME_EXTENDED = 251;
40    public static final int MORE_ZERO_FRAME          = 252;
41    public static final int FULL_FRAME               = 255;
42
43
44    public int u2offsetDelta;
45
46    /**
47     * An extra field in which visitors can store information.
48     */
49    public Object visitorInfo;
50
51
52
53    /**
54     * Returns the bytecode offset delta relative to the previous stack map
55     * frame.
56     */
57    public int getOffsetDelta()
58    {
59        return u2offsetDelta;
60    }
61
62
63    // Abstract methods to be implemented by extensions.
64
65    /**
66     * Returns the stack map frame tag that specifies the entry type.
67     */
68    public abstract int getTag();
69
70
71    /**
72     * Accepts the given visitor.
73     */
74    public abstract void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, StackMapFrameVisitor stackMapFrameVisitor);
75
76
77    // Implementations for VisitorAccepter.
78
79    public Object getVisitorInfo()
80    {
81        return visitorInfo;
82    }
83
84    public void setVisitorInfo(Object visitorInfo)
85    {
86        this.visitorInfo = visitorInfo;
87    }
88
89
90    // Implementations for Object.
91
92    public boolean equals(Object object)
93    {
94        if (object == null ||
95            this.getClass() != object.getClass())
96        {
97            return false;
98        }
99
100        StackMapFrame other = (StackMapFrame)object;
101
102        return this.u2offsetDelta == other.u2offsetDelta;
103    }
104
105
106    public int hashCode()
107    {
108        return getClass().hashCode() ^
109               u2offsetDelta;
110    }
111
112
113    public String toString()
114    {
115        return "[" + u2offsetDelta + "] ";
116    }
117}
118