1 package org.apache.bcel.generic;
2
3 /* ====================================================================
4 * The Apache Software License, Version 1.1
5 *
6 * Copyright (c) 2001 The Apache Software Foundation. All rights
7 * reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
19 * distribution.
20 *
21 * 3. The end-user documentation included with the redistribution,
22 * if any, must include the following acknowledgment:
23 * "This product includes software developed by the
24 * Apache Software Foundation (http://www.apache.org/)."
25 * Alternately, this acknowledgment may appear in the software itself,
26 * if and wherever such third-party acknowledgments normally appear.
27 *
28 * 4. The names "Apache" and "Apache Software Foundation" and
29 * "Apache BCEL" must not be used to endorse or promote products
30 * derived from this software without prior written permission. For
31 * written permission, please contact apache@apache.org.
32 *
33 * 5. Products derived from this software may not be called "Apache",
34 * "Apache BCEL", nor may "Apache" appear in their name, without
35 * prior written permission of the Apache Software Foundation.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
51 * This software consists of voluntary contributions made by many
52 * individuals on behalf of the Apache Software Foundation. For more
53 * information on the Apache Software Foundation, please see
54 * <http://www.apache.org/>.
55 */
56
57 /***
58 * SWITCH - Branch depending on int value, generates either LOOKUPSWITCH or
59 * TABLESWITCH instruction, depending on whether the match values (int[]) can be
60 * sorted with no gaps between the numbers.
61 *
62 * @version $Id: SWITCH.java,v 1.1.1.1 2001/10/29 20:00:27 jvanzyl Exp $
63 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
64 */
65 public final class SWITCH implements CompoundInstruction {
66 private int[] match;
67 private InstructionHandle[] targets;
68 private Select instruction;
69 private int match_length;
70
71 /***
72 * Template for switch() constructs. If the match array can be
73 * sorted in ascending order with gaps no larger than max_gap
74 * between the numbers, a TABLESWITCH instruction is generated, and
75 * a LOOKUPSWITCH otherwise. The former may be more efficient, but
76 * needs more space.
77 *
78 * Note, that the key array always will be sorted, though we leave
79 * the original arrays unaltered.
80 *
81 * @param match array of match values (case 2: ... case 7: ..., etc.)
82 * @param targets the instructions to be branched to for each case
83 * @param target the default target
84 * @param max_gap maximum gap that may between case branches
85 */
86 public SWITCH(int[] match, InstructionHandle[] targets,
87 InstructionHandle target, int max_gap) {
88 this.match = (int[])match.clone();
89 this.targets = (InstructionHandle[])targets.clone();
90
91 if((match_length = match.length) < 2) // (almost) empty switch, or just default
92 instruction = new TABLESWITCH(match, targets, target);
93 else {
94 sort(0, match_length - 1);
95
96 if(matchIsOrdered(max_gap)) {
97 fillup(max_gap, target);
98
99 instruction = new TABLESWITCH(this.match, this.targets, target);
100 }
101 else
102 instruction = new LOOKUPSWITCH(this.match, this.targets, target);
103 }
104 }
105
106 public SWITCH(int[] match, InstructionHandle[] targets,
107 InstructionHandle target) {
108 this(match, targets, target, 1);
109 }
110
111 private final void fillup(int max_gap, InstructionHandle target) {
112 int max_size = match_length + match_length * max_gap;
113 int[] m_vec = new int[max_size];
114 InstructionHandle[] t_vec = new InstructionHandle[max_size];
115 int count = 1;
116
117 m_vec[0] = match[0];
118 t_vec[0] = targets[0];
119
120 for(int i=1; i < match_length; i++) {
121 int prev = match[i-1];
122 int gap = match[i] - prev;
123
124 for(int j=1; j < gap; j++) {
125 m_vec[count] = prev + j;
126 t_vec[count] = target;
127 count++;
128 }
129
130 m_vec[count] = match[i];
131 t_vec[count] = targets[i];
132 count++;
133 }
134
135 match = new int[count];
136 targets = new InstructionHandle[count];
137
138 System.arraycopy(m_vec, 0, match, 0, count);
139 System.arraycopy(t_vec, 0, targets, 0, count);
140 }
141
142 /***
143 * Sort match and targets array with QuickSort.
144 */
145 private final void sort(int l, int r) {
146 int i = l, j = r;
147 int h, m = match[(l + r) / 2];
148 InstructionHandle h2;
149
150 do {
151 while(match[i] < m) i++;
152 while(m < match[j]) j--;
153
154 if(i <= j) {
155 h=match[i]; match[i]=match[j]; match[j]=h; // Swap elements
156 h2=targets[i]; targets[i]=targets[j]; targets[j]=h2; // Swap instructions, too
157 i++; j--;
158 }
159 } while(i <= j);
160
161 if(l < j) sort(l, j);
162 if(i < r) sort(i, r);
163 }
164
165 /***
166 * @return match is sorted in ascending order with no gap bigger than max_gap?
167 */
168 private final boolean matchIsOrdered(int max_gap) {
169 for(int i=1; i < match_length; i++)
170 if(match[i] - match[i-1] > max_gap)
171 return false;
172
173 return true;
174 }
175
176 public final InstructionList getInstructionList() {
177 return new InstructionList(instruction);
178 }
179
180 public final Instruction getInstruction() {
181 return instruction;
182 }
183 }
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