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