1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.compress.harmony.unpack200.bytecode.forms;
18
19 import java.util.Arrays;
20
21 import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
22 import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;
23
24 public class LookupSwitchForm extends SwitchForm {
25
26 public LookupSwitchForm(final int opcode, final String name) {
27 super(opcode, name);
28 }
29
30 @Override
31 public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
32 final int caseCount = operandManager.nextCaseCount();
33 final int defaultPc = operandManager.nextLabel();
34 final int[] caseValues = new int[caseCount];
35 Arrays.setAll(caseValues, i -> operandManager.nextCaseValues());
36 final int[] casePcs = new int[caseCount];
37 Arrays.setAll(casePcs, i -> operandManager.nextLabel());
38
39 final int[] labelsArray = new int[caseCount + 1];
40 labelsArray[0] = defaultPc;
41 System.arraycopy(casePcs, 0, labelsArray, 1, caseCount + 1 - 1);
42 byteCode.setByteCodeTargets(labelsArray);
43
44 // All this gets dumped into the rewrite bytes of the
45 // poor bytecode.
46
47 // Unlike most byte codes, the LookupSwitch is a
48 // variable-sized bytecode. Because of this, the
49 // rewrite array has to be defined here individually
50 // for each bytecode, rather than in the ByteCodeForm
51 // class.
52
53 // First, there's the bytecode. Then there are 0-3
54 // bytes of padding so that the first (default)
55 // label is on a 4-byte offset.
56 final int padLength = 3 - codeLength % 4;
57 final int rewriteSize = 1 + padLength + 4 // defaultbytes
58 + 4 // npairs
59 + 4 * caseValues.length + 4 * casePcs.length;
60
61 final int[] newRewrite = new int[rewriteSize];
62 int rewriteIndex = 0;
63
64 // Fill in what we can now
65 // opcode
66 newRewrite[rewriteIndex++] = byteCode.getOpcode();
67
68 // padding
69 for (int index = 0; index < padLength; index++) {
70 newRewrite[rewriteIndex++] = 0;
71 }
72
73 // defaultbyte
74 // This gets overwritten by fixUpByteCodeTargets
75 newRewrite[rewriteIndex++] = -1;
76 newRewrite[rewriteIndex++] = -1;
77 newRewrite[rewriteIndex++] = -1;
78 newRewrite[rewriteIndex++] = -1;
79
80 // npairs
81 final int npairsIndex = rewriteIndex;
82 setRewrite4Bytes(caseValues.length, npairsIndex, newRewrite);
83 rewriteIndex += 4;
84
85 // match-offset pairs
86 // The caseValues aren't overwritten, but the
87 // casePcs will get overwritten by fixUpByteCodeTargets
88 for (final int caseValue : caseValues) {
89 // match
90 setRewrite4Bytes(caseValue, rewriteIndex, newRewrite);
91 rewriteIndex += 4;
92 // offset
93 newRewrite[rewriteIndex++] = -1;
94 newRewrite[rewriteIndex++] = -1;
95 newRewrite[rewriteIndex++] = -1;
96 newRewrite[rewriteIndex++] = -1;
97 }
98 byteCode.setRewrite(newRewrite);
99 }
100 }