1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2014 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.optimize.info;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.*;
25import proguard.classfile.attribute.visitor.*;
26import proguard.classfile.util.SimplifiedVisitor;
27import proguard.evaluation.ConstantValueFactory;
28import proguard.evaluation.value.*;
29
30/**
31 * This class stores some optimization information that can be attached to
32 * a field.
33 *
34 * @author Eric Lafortune
35 */
36public class FieldOptimizationInfo
37extends      SimplifiedVisitor
38implements   AttributeVisitor
39{
40    private static final ParticularValueFactory VALUE_FACTORY          = new ParticularValueFactory();
41    private static final ConstantValueFactory   CONSTANT_VALUE_FACTORY = new ConstantValueFactory(VALUE_FACTORY);
42    private static final InitialValueFactory    INITIAL_VALUE_FACTORY  = new InitialValueFactory(VALUE_FACTORY);
43
44    private boolean        isWritten;
45    private boolean        isRead;
46    private boolean        canBeMadePrivate = true;
47    private ReferenceValue referencedClass;
48    private Value          value;
49
50
51    public FieldOptimizationInfo(Clazz clazz, Field field)
52    {
53        int accessFlags = field.getAccessFlags();
54
55        isWritten =
56        isRead    = (accessFlags & ClassConstants.ACC_VOLATILE) != 0;
57
58        resetValue(clazz, field);
59    }
60
61
62    public FieldOptimizationInfo(FieldOptimizationInfo FieldOptimizationInfo)
63    {
64        this.isWritten        = FieldOptimizationInfo.isWritten;
65        this.isRead           = FieldOptimizationInfo.isRead;
66        this.canBeMadePrivate = FieldOptimizationInfo.canBeMadePrivate;
67        this.referencedClass  = FieldOptimizationInfo.referencedClass;
68        this.value            = FieldOptimizationInfo.value;
69    }
70
71
72    public void setWritten()
73    {
74        isWritten = true;
75    }
76
77
78    public boolean isWritten()
79    {
80        return isWritten;
81    }
82
83
84    public void setRead()
85    {
86        isRead = true;
87    }
88
89
90    public boolean isRead()
91    {
92        return isRead;
93    }
94
95
96    public void setCanNotBeMadePrivate()
97    {
98        canBeMadePrivate = false;
99    }
100
101
102    public boolean canBeMadePrivate()
103    {
104        return canBeMadePrivate;
105    }
106
107
108    public void generalizeReferencedClass(ReferenceValue referencedClass)
109    {
110        this.referencedClass = this.referencedClass != null ?
111            this.referencedClass.generalize(referencedClass) :
112            referencedClass;
113    }
114
115
116    public ReferenceValue getReferencedClass()
117    {
118        return referencedClass;
119    }
120
121
122    public void resetValue(Clazz clazz, Field field)
123    {
124        int accessFlags = field.getAccessFlags();
125
126        value = null;
127
128        // See if we can initialize a static field with a constant value.
129        if ((accessFlags & ClassConstants.ACC_STATIC) != 0)
130        {
131            field.accept(clazz, new AllAttributeVisitor(this));
132        }
133
134        // Otherwise initialize a non-final field with the default value.
135        // Conservatively, even a final field needs to be initialized with the
136        // default value, because it may be accessed before it is set.
137        if (value == null &&
138            (SideEffectInstructionChecker.OPTIMIZE_CONSERVATIVELY ||
139             (accessFlags & ClassConstants.ACC_FINAL) == 0))
140        {
141            value = INITIAL_VALUE_FACTORY.createValue(field.getDescriptor(clazz));
142        }
143    }
144
145
146    public void generalizeValue(Value value)
147    {
148        this.value = this.value != null ?
149            this.value.generalize(value) :
150            value;
151    }
152
153
154    public Value getValue()
155    {
156        return value;
157    }
158
159
160    // Implementations for AttributeVisitor.
161
162    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
163
164
165    public void visitConstantValueAttribute(Clazz clazz, Field field, ConstantValueAttribute constantValueAttribute)
166    {
167        // Retrieve the initial static field value.
168        value = CONSTANT_VALUE_FACTORY.constantValue(clazz, constantValueAttribute.u2constantValueIndex);
169    }
170
171
172    // Small utility methods.
173
174    public static void setFieldOptimizationInfo(Clazz clazz, Field field)
175    {
176        field.setVisitorInfo(new FieldOptimizationInfo(clazz, field));
177    }
178
179
180    public static FieldOptimizationInfo getFieldOptimizationInfo(Field field)
181    {
182        Object visitorInfo = field.getVisitorInfo();
183
184        return visitorInfo instanceof FieldOptimizationInfo ?
185            (FieldOptimizationInfo)visitorInfo :
186            null;
187    }
188}
189