1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2013 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.editor;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.*;
25
26import java.util.Arrays;
27
28/**
29 * This class can add and delete interfaces to and from classes. References to
30 * the constant pool must be filled out beforehand.
31 *
32 * @author Eric Lafortune
33 */
34public class InterfacesEditor
35{
36    private final ProgramClass targetClass;
37
38
39    /**
40     * Creates a new InterfacesEditor that will edit interfaces in the given
41     * target class.
42     */
43    public InterfacesEditor(ProgramClass targetClass)
44    {
45        this.targetClass = targetClass;
46    }
47
48
49    /**
50     * Adds the specified interface to the target class, if it isn't present yet.
51     */
52    public void addInterface(int interfaceConstantIndex)
53    {
54        // Is the interface not yet present?
55        if (findInterfaceIndex(interfaceConstantIndex) < 0)
56        {
57            int   interfacesCount = targetClass.u2interfacesCount++;
58            int[] interfaces      = targetClass.u2interfaces;
59
60            // Is the array too small to contain the additional interface?
61            if (interfaces.length <= interfacesCount)
62            {
63                // Create a new array and copy the interfaces into it.
64                int[] newinterfaces = new int[interfacesCount + 1];
65                System.arraycopy(interfaces, 0, newinterfaces, 0, interfacesCount);
66                interfaces = newinterfaces;
67
68                targetClass.u2interfaces = interfaces;
69            }
70
71            // Append the interface.
72            interfaces[interfacesCount] = interfaceConstantIndex;
73        }
74    }
75
76
77    /**
78     * Deletes the given interface from the target class, if it is present.
79     */
80    public void deleteInterface(int interfaceConstantIndex)
81    {
82        // Is the interface already present?
83        int interfaceIndex = findInterfaceIndex(interfaceConstantIndex);
84        if (interfaceIndex >= 0)
85        {
86            int   interfacesCount = --targetClass.u2interfacesCount;
87            int[] interfaces      = targetClass.u2interfaces;
88
89            // Shift the other interfaces in the array.
90            for (int index = interfaceIndex; index < interfacesCount; index++)
91            {
92                interfaces[index] = interfaces[index + 1];
93            }
94
95            // Clear the remaining entry in the array.
96            interfaces[interfacesCount] = 0;
97        }
98    }
99
100
101    // Small utility methods.
102
103    /**
104     * Finds the index of the specified interface in the list of interfaces of
105     * the target class.
106     */
107    private int findInterfaceIndex(int interfaceConstantIndex)
108    {
109        int   interfacesCount = targetClass.u2interfacesCount;
110        int[] interfaces      = targetClass.u2interfaces;
111
112        for (int index = 0; index < interfacesCount; index++)
113        {
114            if (interfaces[index] == interfaceConstantIndex)
115              {
116                  return index;
117              }
118        }
119
120        return -1;
121    }
122}