1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2013 Eric Lafortune (eric@graphics.cornell.edu)
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package proguard.classfile.editor;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.editor.ConstantPoolRemapper;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.ClassVisitor;
import java.util.Arrays;
/**
* This ClassVisitor removes NameAndType constant pool entries that are not
* used.
*
* @author Eric Lafortune
*/
public class NameAndTypeShrinker
extends SimplifiedVisitor
implements ClassVisitor,
ConstantVisitor,
AttributeVisitor
{
// A visitor info flag to indicate the NameAndType constant pool entry is being used.
private static final Object USED = new Object();
private int[] constantIndexMap;
private final ConstantPoolRemapper constantPoolRemapper = new ConstantPoolRemapper();
// Implementations for ClassVisitor.
public void visitProgramClass(ProgramClass programClass)
{
// Mark the NameAndType entries referenced by all other constant pool
// entries.
programClass.constantPoolEntriesAccept(this);
// Mark the NameAndType entries referenced by all EnclosingMethod
// attributes.
programClass.attributesAccept(this);
// Shift the used constant pool entries together, filling out the
// index map.
int newConstantPoolCount =
shrinkConstantPool(programClass.constantPool,
programClass.u2constantPoolCount);
// Remap the references to the constant pool if it has shrunk.
if (newConstantPoolCount < programClass.u2constantPoolCount)
{
programClass.u2constantPoolCount = newConstantPoolCount;
// Remap all constant pool references.
constantPoolRemapper.setConstantIndexMap(constantIndexMap);
constantPoolRemapper.visitProgramClass(programClass);
}
}
// Implementations for ConstantVisitor.
public void visitAnyConstant(Clazz clazz, Constant constant) {}
public void visitInvokeDynamicConstant(Clazz clazz, InvokeDynamicConstant invokeDynamicConstant)
{
markNameAndTypeConstant(clazz, invokeDynamicConstant.u2nameAndTypeIndex);
}
public void visitAnyRefConstant(Clazz clazz, RefConstant refConstant)
{
markNameAndTypeConstant(clazz, refConstant.u2nameAndTypeIndex);
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitEnclosingMethodAttribute(Clazz clazz, EnclosingMethodAttribute enclosingMethodAttribute)
{
if (enclosingMethodAttribute.u2nameAndTypeIndex != 0)
{
markNameAndTypeConstant(clazz, enclosingMethodAttribute.u2nameAndTypeIndex);
}
}
// Small utility methods.
/**
* Marks the given UTF-8 constant pool entry of the given class.
*/
private void markNameAndTypeConstant(Clazz clazz, int index)
{
markAsUsed((NameAndTypeConstant)((ProgramClass)clazz).getConstant(index));
}
/**
* Marks the given VisitorAccepter as being used.
* In this context, the VisitorAccepter will be a NameAndTypeConstant object.
*/
private void markAsUsed(VisitorAccepter visitorAccepter)
{
visitorAccepter.setVisitorInfo(USED);
}
/**
* Returns whether the given VisitorAccepter has been marked as being used.
* In this context, the VisitorAccepter will be a NameAndTypeConstant object.
*/
private boolean isUsed(VisitorAccepter visitorAccepter)
{
return visitorAccepter.getVisitorInfo() == USED;
}
/**
* Removes all NameAndType entries that are not marked as being used
* from the given constant pool.
* @return the new number of entries.
*/
private int shrinkConstantPool(Constant[] constantPool, int length)
{
// Create a new index map, if necessary.
if (constantIndexMap == null ||
constantIndexMap.length < length)
{
constantIndexMap = new int[length];
}
int counter = 1;
boolean isUsed = false;
// Shift the used constant pool entries together.
for (int index = 1; index < length; index++)
{
constantIndexMap[index] = counter;
Constant constant = constantPool[index];
// Don't update the flag if this is the second half of a long entry.
if (constant != null)
{
isUsed = constant.getTag() != ClassConstants.CONSTANT_NameAndType ||
isUsed(constant);
}
if (isUsed)
{
constantPool[counter++] = constant;
}
}
// Clear the remaining constant pool elements.
Arrays.fill(constantPool, counter, length, null);
return counter;
}
}
|
