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
|
/*
* 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.util.SimplifiedVisitor;
import java.util.Arrays;
/**
* This AttributeVisitor accumulates specified changes to local variables, and
* then applies these accumulated changes to the code attributes that it visits.
*
* @author Eric Lafortune
*/
public class VariableEditor
extends SimplifiedVisitor
implements AttributeVisitor
{
private boolean modified;
private boolean[] deleted = new boolean[ClassConstants.TYPICAL_VARIABLES_SIZE];
private int[] variableMap = new int[ClassConstants.TYPICAL_VARIABLES_SIZE];
private final VariableRemapper variableRemapper = new VariableRemapper();
/**
* Resets the accumulated code changes.
* @param maxLocals the length of the local variable frame that will be
* edited next.
*/
public void reset(int maxLocals)
{
// Try to reuse the previous array.
if (deleted.length < maxLocals)
{
// Create a new array.
deleted = new boolean[maxLocals];
}
else
{
// Reset the array.
Arrays.fill(deleted, 0, maxLocals, false);
}
modified = false;
}
/**
* Remembers to delete the given variable.
* @param variableIndex the index of the variable to be deleted.
*/
public void deleteVariable(int variableIndex)
{
deleted[variableIndex] = true;
modified = true;
}
/**
* Returns whether the given variable at the given offset has deleted.
*/
public boolean isDeleted(int instructionOffset)
{
return deleted[instructionOffset];
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Avoid doing any work if nothing is changing anyway.
if (!modified)
{
return;
}
int oldMaxLocals = codeAttribute.u2maxLocals;
// Make sure there is a sufficiently large variable map.
if (variableMap.length < oldMaxLocals)
{
variableMap = new int[oldMaxLocals];
}
// Fill out the variable map.
int newVariableIndex = 0;
for (int oldVariableIndex = 0; oldVariableIndex < oldMaxLocals; oldVariableIndex++)
{
variableMap[oldVariableIndex] = deleted[oldVariableIndex] ?
-1 : newVariableIndex++;
}
// Set the map.
variableRemapper.setVariableMap(variableMap);
// Remap the variables.
variableRemapper.visitCodeAttribute(clazz, method, codeAttribute);
// Update the length of local variable frame.
codeAttribute.u2maxLocals = newVariableIndex;
}
}
|
