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 * @version $Id$
30 */
31 public final class SWITCH implements CompoundInstruction {
32
33 private int[] match;
34 private InstructionHandle[] targets;
35 private Select instruction;
36 private int match_length;
37
38
39 /**
40 * Template for switch() constructs. If the match array can be
41 * sorted in ascending order with gaps no larger than max_gap
42 * between the numbers, a TABLESWITCH instruction is generated, and
43 * a LOOKUPSWITCH otherwise. The former may be more efficient, but
44 * needs more space.
45 *
46 * Note, that the key array always will be sorted, though we leave
47 * the original arrays unaltered.
48 *
49 * @param match array of match values (case 2: ... case 7: ..., etc.)
50 * @param targets the instructions to be branched to for each case
51 * @param target the default target
52 * @param max_gap maximum gap that may between case branches
53 */
54 public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target, final int max_gap) {
55 this.match = match.clone();
56 this.targets = targets.clone();
57 if ((match_length = match.length) < 2) {
58 instruction = new TABLESWITCH(match, targets, target);
59 } else {
60 sort(0, match_length - 1);
61 if (matchIsOrdered(max_gap)) {
62 fillup(max_gap, target);
63 instruction = new TABLESWITCH(this.match, this.targets, target);
64 } else {
65 instruction = new LOOKUPSWITCH(this.match, this.targets, target);
66 }
67 }
68 }
69
70
71 public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target) {
72 this(match, targets, target, 1);
73 }
74
75
76 private void fillup( final int max_gap, final InstructionHandle target ) {
77 final int max_size = match_length + match_length * max_gap;
78 final int[] m_vec = new int[max_size];
79 final InstructionHandle[] t_vec = new InstructionHandle[max_size];
80 int count = 1;
81 m_vec[0] = match[0];
82 t_vec[0] = targets[0];
83 for (int i = 1; i < match_length; i++) {
84 final int prev = match[i - 1];
85 final int gap = match[i] - prev;
86 for (int j = 1; j < gap; j++) {
87 m_vec[count] = prev + j;
88 t_vec[count] = target;
89 count++;
90 }
91 m_vec[count] = match[i];
92 t_vec[count] = targets[i];
93 count++;
94 }
95 match = new int[count];
96 targets = new InstructionHandle[count];
97 System.arraycopy(m_vec, 0, match, 0, count);
98 System.arraycopy(t_vec, 0, targets, 0, count);
99 }
100
101
102 /**
103 * Sort match and targets array with QuickSort.
104 */
105 private void sort( final int l, final int r ) {
106 int i = l;
107 int j = r;
108 int h;
109 final int m = match[(l + r) / 2];
110 InstructionHandle h2;
111 do {
112 while (match[i] < m) {
113 i++;
114 }
115 while (m < match[j]) {
116 j--;
117 }
118 if (i <= j) {
119 h = match[i];
120 match[i] = match[j];
121 match[j] = h; // Swap elements
122 h2 = targets[i];
123 targets[i] = targets[j];
124 targets[j] = h2; // Swap instructions, too
125 i++;
126 j--;
127 }
128 } while (i <= j);
129 if (l < j) {
130 sort(l, j);
131 }
132 if (i < r) {
133 sort(i, r);
134 }
135 }
136
137
138 /**
139 * @return match is sorted in ascending order with no gap bigger than max_gap?
140 */
141 private boolean matchIsOrdered( final int max_gap ) {
142 for (int i = 1; i < match_length; i++) {
143 if (match[i] - match[i - 1] > max_gap) {
144 return false;
145 }
146 }
147 return true;
148 }
149
150
151 @Override
152 public final InstructionList getInstructionList() {
153 return new InstructionList(instruction);
154 }
155
156
157 public final Instruction getInstruction() {
158 return instruction;
159 }
160 }