1 /*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5 /*
6 * Licensed to the Apache Software Foundation (ASF) under one or more
7 * contributor license agreements. See the NOTICE file distributed with
8 * this work for additional information regarding copyright ownership.
9 * The ASF licenses this file to You under the Apache License, Version 2.0
10 * (the "License"); you may not use this file except in compliance with
11 * the License. You may obtain a copy of the License at
12 *
13 * http://www.apache.org/licenses/LICENSE-2.0
14 *
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
20 */
21
22 package com.sun.org.apache.bcel.internal.generic;
23
24 /**
25 * SWITCH - Branch depending on int value, generates either LOOKUPSWITCH or
26 * TABLESWITCH instruction, depending on whether the match values (int[]) can be
27 * sorted with no gaps between the numbers.
28 *
29 */
30 public final class SWITCH implements CompoundInstruction {
31
32 private int[] match;
33 private InstructionHandle[] targets;
34 private Select instruction;
35 private int match_length;
36
37
38 /**
39 * Template for switch() constructs. If the match array can be
40 * sorted in ascending order with gaps no larger than max_gap
41 * between the numbers, a TABLESWITCH instruction is generated, and
42 * a LOOKUPSWITCH otherwise. The former may be more efficient, but
43 * needs more space.
44 *
45 * Note, that the key array always will be sorted, though we leave
46 * the original arrays unaltered.
47 *
48 * @param match array of match values (case 2: ... case 7: ..., etc.)
49 * @param targets the instructions to be branched to for each case
50 * @param target the default target
51 * @param max_gap maximum gap that may between case branches
52 */
53 public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target, final int max_gap) {
54 this.match = match.clone();
55 this.targets = targets.clone();
56 if ((match_length = match.length) < 2) {
57 instruction = new TABLESWITCH(match, targets, target);
58 } else {
59 sort(0, match_length - 1);
60 if (matchIsOrdered(max_gap)) {
61 fillup(max_gap, target);
62 instruction = new TABLESWITCH(this.match, this.targets, target);
63 } else {
64 instruction = new LOOKUPSWITCH(this.match, this.targets, target);
65 }
66 }
67 }
68
69
70 public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target) {
71 this(match, targets, target, 1);
72 }
73
74
75 private void fillup( final int max_gap, final InstructionHandle target ) {
76 final int max_size = match_length + match_length * max_gap;
77 final int[] m_vec = new int[max_size];
78 final InstructionHandle[] t_vec = new InstructionHandle[max_size];
79 int count = 1;
80 m_vec[0] = match[0];
81 t_vec[0] = targets[0];
82 for (int i = 1; i < match_length; i++) {
83 final int prev = match[i - 1];
84 final int gap = match[i] - prev;
85 for (int j = 1; j < gap; j++) {
86 m_vec[count] = prev + j;
87 t_vec[count] = target;
88 count++;
89 }
90 m_vec[count] = match[i];
91 t_vec[count] = targets[i];
92 count++;
93 }
94 match = new int[count];
95 targets = new InstructionHandle[count];
96 System.arraycopy(m_vec, 0, match, 0, count);
97 System.arraycopy(t_vec, 0, targets, 0, count);
98 }
99
100
101 /**
102 * Sort match and targets array with QuickSort.
103 */
104 private void sort( final int l, final int r ) {
105 int i = l;
106 int j = r;
107 int h;
108 final int m = match[(l + r) >>> 1];
109 InstructionHandle h2;
110 do {
111 while (match[i] < m) {
112 i++;
113 }
114 while (m < match[j]) {
115 j--;
116 }
117 if (i <= j) {
118 h = match[i];
119 match[i] = match[j];
120 match[j] = h; // Swap elements
121 h2 = targets[i];
122 targets[i] = targets[j];
123 targets[j] = h2; // Swap instructions, too
124 i++;
125 j--;
126 }
127 } while (i <= j);
128 if (l < j) {
129 sort(l, j);
130 }
131 if (i < r) {
132 sort(i, r);
133 }
134 }
135
136
137 /**
138 * @return match is sorted in ascending order with no gap bigger than max_gap?
139 */
140 private boolean matchIsOrdered( final int max_gap ) {
141 for (int i = 1; i < match_length; i++) {
142 if (match[i] - match[i - 1] > max_gap) {
143 return false;
144 }
145 }
146 return true;
147 }
148
149
150 @Override
151 public InstructionList getInstructionList() {
152 return new InstructionList(instruction);
153 }
154
155
156 public Instruction getInstruction() {
157 return instruction;
158 }
159 }