InstructionSequencesReplacer.java revision 8a6199f0c36a778f22394364347a301b0b28e94b 
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.optimize.peephole;
22
23import proguard.classfile.constant.Constant;
24import proguard.classfile.editor.CodeAttributeEditor;
25import proguard.classfile.instruction.Instruction;
26import proguard.classfile.instruction.visitor.*;
27
28/**
29 * This InstructionVisitor replaces multiple instruction sequences at once.
30 *
31 * @see InstructionSequenceReplacer
32 * @author Eric Lafortune
33 */
34public class InstructionSequencesReplacer
35extends      MultiInstructionVisitor
36implements   InstructionVisitor
37{
38    private static final int PATTERN_INDEX     = 0;
39    private static final int REPLACEMENT_INDEX = 1;
40
41
42    /**
43     * Creates a new InstructionSequencesReplacer.
44     * @param patternConstants        any constants referenced by the pattern
45     *                                instruction.
46     * @param instructionSequences    the instruction sequences to be replaced,
47     *                                with subsequently the sequence pair index,
48     *                                the patten/replacement index (0 or 1),
49     *                                and the instruction index in the sequence.
50     * @param branchTargetFinder      a branch target finder that has been
51     *                                initialized to indicate branch targets
52     *                                in the visited code.
53     * @param codeAttributeEditor     a code editor that can be used for
54     *                                accumulating changes to the code.
55     */
56    public InstructionSequencesReplacer(Constant[]          patternConstants,
57                                        Instruction[][][]   instructionSequences,
58                                        BranchTargetFinder  branchTargetFinder,
59                                        CodeAttributeEditor codeAttributeEditor)
60    {
61        this(patternConstants,
62             instructionSequences,
63             branchTargetFinder,
64             codeAttributeEditor,
65             null);
66    }
67
68
69    /**
70     * Creates a new InstructionSequenceReplacer.
71     * @param patternConstants        any constants referenced by the pattern
72     *                                instruction.
73     * @param instructionSequences    the instruction sequences to be replaced,
74     *                                with subsequently the sequence pair index,
75     *                                the patten/replacement index (0 or 1),
76     *                                and the instruction index in the sequence.
77     * @param branchTargetFinder      a branch target finder that has been
78     *                                initialized to indicate branch targets
79     *                                in the visited code.
80     * @param codeAttributeEditor     a code editor that can be used for
81     *                                accumulating changes to the code.
82     * @param extraInstructionVisitor an optional extra visitor for all deleted
83     *                                load instructions.
84     */
85    public InstructionSequencesReplacer(Constant[]          patternConstants,
86                                        Instruction[][][]   instructionSequences,
87                                        BranchTargetFinder  branchTargetFinder,
88                                        CodeAttributeEditor codeAttributeEditor,
89                                        InstructionVisitor  extraInstructionVisitor)
90    {
91        super(createInstructionSequenceReplacers(patternConstants,
92                                                 instructionSequences,
93                                                 branchTargetFinder,
94                                                 codeAttributeEditor,
95                                                 extraInstructionVisitor));
96    }
97
98
99    /**
100     * Creates an array of InstructionSequenceReplacer instances.
101     * @param patternConstants        any constants referenced by the pattern
102     *                                instruction.
103     * @param instructionSequences    the instruction sequences to be replaced,
104     *                                with subsequently the sequence pair index,
105     *                                the from/to index (0 or 1), and the
106     *                                instruction index in the sequence.
107     * @param branchTargetFinder      a branch target finder that has been
108     *                                initialized to indicate branch targets
109     *                                in the visited code.
110     * @param codeAttributeEditor     a code editor that can be used for
111     *                                accumulating changes to the code.
112     * @param extraInstructionVisitor an optional extra visitor for all deleted
113     *                                load instructions.
114     */
115    private static InstructionVisitor[] createInstructionSequenceReplacers(Constant[]          patternConstants,
116                                                                           Instruction[][][]   instructionSequences,
117                                                                           BranchTargetFinder  branchTargetFinder,
118                                                                           CodeAttributeEditor codeAttributeEditor,
119                                                                           InstructionVisitor  extraInstructionVisitor)
120    {
121        InstructionVisitor[] instructionSequenceReplacers =
122            new InstructionSequenceReplacer[instructionSequences.length];
123
124        for (int index = 0; index < instructionSequenceReplacers.length; index++)
125        {
126            Instruction[][] instructionSequencePair = instructionSequences[index];
127            instructionSequenceReplacers[index] =
128                new InstructionSequenceReplacer(patternConstants,
129                                                instructionSequencePair[PATTERN_INDEX],
130                                                instructionSequencePair[REPLACEMENT_INDEX],
131                                                branchTargetFinder,
132                                                codeAttributeEditor,
133                                                extraInstructionVisitor);
134        }
135
136        return instructionSequenceReplacers;
137    }
138}
139