LookUpSwitchInstruction.java revision b72c5c2e5482cf10117b2b25f642f7616b2326c3 
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.instruction;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.CodeAttribute;
25import proguard.classfile.instruction.visitor.InstructionVisitor;
26
27/**
28 * This Instruction represents a simple instruction without variable arguments
29 * or constant pool references.
30 *
31 * @author Eric Lafortune
32 */
33public class LookUpSwitchInstruction extends SwitchInstruction
34{
35    public int[] cases;
36
37
38    /**
39     * Creates an uninitialized LookUpSwitchInstruction.
40     */
41    public LookUpSwitchInstruction() {}
42
43
44    /**
45     * Creates a new LookUpSwitchInstruction with the given arguments.
46     */
47    public LookUpSwitchInstruction(byte  opcode,
48                                   int   defaultOffset,
49                                   int[] cases,
50                                   int[] jumpOffsets)
51    {
52        this.opcode        = opcode;
53        this.defaultOffset = defaultOffset;
54        this.cases         = cases;
55        this.jumpOffsets   = jumpOffsets;
56    }
57
58
59    /**
60     * Copies the given instruction into this instruction.
61     * @param lookUpSwitchInstruction the instruction to be copied.
62     * @return this instruction.
63     */
64    public LookUpSwitchInstruction copy(LookUpSwitchInstruction lookUpSwitchInstruction)
65    {
66        this.opcode        = lookUpSwitchInstruction.opcode;
67        this.defaultOffset = lookUpSwitchInstruction.defaultOffset;
68        this.cases         = lookUpSwitchInstruction.cases;
69        this.jumpOffsets   = lookUpSwitchInstruction.jumpOffsets;
70
71        return this;
72    }
73
74
75    // Implementations for Instruction.
76
77    public Instruction shrink()
78    {
79        // There aren't any ways to shrink this instruction.
80        return this;
81    }
82
83    protected void readInfo(byte[] code, int offset)
84    {
85        // Skip up to three padding bytes.
86        offset += -offset & 3;
87
88        // Read the two 32-bit arguments.
89        defaultOffset       = readInt(code, offset); offset += 4;
90        int jumpOffsetCount = readInt(code, offset); offset += 4;
91
92        // Read the matches-offset pairs.
93        cases       = new int[jumpOffsetCount];
94        jumpOffsets = new int[jumpOffsetCount];
95
96        for (int index = 0; index < jumpOffsetCount; index++)
97        {
98            cases[index]       = readInt(code, offset); offset += 4;
99            jumpOffsets[index] = readInt(code, offset); offset += 4;
100        }
101    }
102
103
104    protected void writeInfo(byte[] code, int offset)
105    {
106        // Write up to three padding bytes.
107        while ((offset & 3) != 0)
108        {
109            writeByte(code, offset++, 0);
110        }
111
112        // Write the two 32-bit arguments.
113        writeInt(code, offset, defaultOffset); offset += 4;
114        writeInt(code, offset, cases.length);  offset += 4;
115
116        // Write the matches-offset pairs.
117        for (int index = 0; index < cases.length; index++)
118        {
119            writeInt(code, offset, cases[index]);       offset += 4;
120            writeInt(code, offset, jumpOffsets[index]); offset += 4;
121        }
122    }
123
124
125    public int length(int offset)
126    {
127        return 1 + (-(offset+1) & 3) + 8 + cases.length * 8;
128    }
129
130
131    public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor)
132    {
133        instructionVisitor.visitLookUpSwitchInstruction(clazz, method, codeAttribute, offset, this);
134    }
135}
136