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17 package org.apache.bcel.generic;
18
19 /***
20 * SWITCH - Branch depending on int value, generates either LOOKUPSWITCH or
21 * TABLESWITCH instruction, depending on whether the match values (int[]) can be
22 * sorted with no gaps between the numbers.
23 *
24 * @version $Id: SWITCH.java 386056 2006-03-15 11:31:56Z tcurdt $
25 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
26 */
27 public final class SWITCH implements CompoundInstruction {
28
29 private int[] match;
30 private InstructionHandle[] targets;
31 private Select instruction;
32 private int match_length;
33
34
35 /***
36 * Template for switch() constructs. If the match array can be
37 * sorted in ascending order with gaps no larger than max_gap
38 * between the numbers, a TABLESWITCH instruction is generated, and
39 * a LOOKUPSWITCH otherwise. The former may be more efficient, but
40 * needs more space.
41 *
42 * Note, that the key array always will be sorted, though we leave
43 * the original arrays unaltered.
44 *
45 * @param match array of match values (case 2: ... case 7: ..., etc.)
46 * @param targets the instructions to be branched to for each case
47 * @param target the default target
48 * @param max_gap maximum gap that may between case branches
49 */
50 public SWITCH(int[] match, InstructionHandle[] targets, InstructionHandle target, int max_gap) {
51 this.match = (int[]) match.clone();
52 this.targets = (InstructionHandle[]) targets.clone();
53 if ((match_length = match.length) < 2) {
54 instruction = new TABLESWITCH(match, targets, target);
55 } else {
56 sort(0, match_length - 1);
57 if (matchIsOrdered(max_gap)) {
58 fillup(max_gap, target);
59 instruction = new TABLESWITCH(this.match, this.targets, target);
60 } else {
61 instruction = new LOOKUPSWITCH(this.match, this.targets, target);
62 }
63 }
64 }
65
66
67 public SWITCH(int[] match, InstructionHandle[] targets, InstructionHandle target) {
68 this(match, targets, target, 1);
69 }
70
71
72 private final void fillup( int max_gap, InstructionHandle target ) {
73 int max_size = match_length + match_length * max_gap;
74 int[] m_vec = new int[max_size];
75 InstructionHandle[] t_vec = new InstructionHandle[max_size];
76 int count = 1;
77 m_vec[0] = match[0];
78 t_vec[0] = targets[0];
79 for (int i = 1; i < match_length; i++) {
80 int prev = match[i - 1];
81 int gap = match[i] - prev;
82 for (int j = 1; j < gap; j++) {
83 m_vec[count] = prev + j;
84 t_vec[count] = target;
85 count++;
86 }
87 m_vec[count] = match[i];
88 t_vec[count] = targets[i];
89 count++;
90 }
91 match = new int[count];
92 targets = new InstructionHandle[count];
93 System.arraycopy(m_vec, 0, match, 0, count);
94 System.arraycopy(t_vec, 0, targets, 0, count);
95 }
96
97
98 /***
99 * Sort match and targets array with QuickSort.
100 */
101 private final void sort( int l, int r ) {
102 int i = l, j = r;
103 int h, m = match[(l + r) / 2];
104 InstructionHandle h2;
105 do {
106 while (match[i] < m) {
107 i++;
108 }
109 while (m < match[j]) {
110 j--;
111 }
112 if (i <= j) {
113 h = match[i];
114 match[i] = match[j];
115 match[j] = h;
116 h2 = targets[i];
117 targets[i] = targets[j];
118 targets[j] = h2;
119 i++;
120 j--;
121 }
122 } while (i <= j);
123 if (l < j) {
124 sort(l, j);
125 }
126 if (i < r) {
127 sort(i, r);
128 }
129 }
130
131
132 /***
133 * @return match is sorted in ascending order with no gap bigger than max_gap?
134 */
135 private final boolean matchIsOrdered( int max_gap ) {
136 for (int i = 1; i < match_length; i++) {
137 if (match[i] - match[i - 1] > max_gap) {
138 return false;
139 }
140 }
141 return true;
142 }
143
144
145 public final InstructionList getInstructionList() {
146 return new InstructionList(instruction);
147 }
148
149
150 public final Instruction getInstruction() {
151 return instruction;
152 }
153 }