1 | /* |
2 | * Copyright 1999-2005 Sun Microsystems, Inc. All Rights Reserved. |
3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 | * |
5 | * This code is free software; you can redistribute it and/or modify it |
6 | * under the terms of the GNU General Public License version 2 only, as |
7 | * published by the Free Software Foundation. Sun designates this |
8 | * particular file as subject to the "Classpath" exception as provided |
9 | * by Sun in the LICENSE file that accompanied this code. |
10 | * |
11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
14 | * version 2 for more details (a copy is included in the LICENSE file that |
15 | * accompanied this code). |
16 | * |
17 | * You should have received a copy of the GNU General Public License version |
18 | * 2 along with this work; if not, write to the Free Software Foundation, |
19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
20 | * |
21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
23 | * have any questions. |
24 | */ |
25 | |
26 | package com.sun.tools.javac.util; |
27 | |
28 | /** A class for extensible, mutable bit sets. |
29 | * |
30 | * <p><b>This is NOT part of any API supported by Sun Microsystems. If |
31 | * you write code that depends on this, you do so at your own risk. |
32 | * This code and its internal interfaces are subject to change or |
33 | * deletion without notice.</b> |
34 | */ |
35 | public class Bits { |
36 | |
37 | |
38 | private final static int wordlen = 32; |
39 | private final static int wordshift = 5; |
40 | private final static int wordmask = wordlen - 1; |
41 | |
42 | private int[] bits; |
43 | |
44 | /** Construct an initially empty set. |
45 | */ |
46 | public Bits() { |
47 | this(new int[1]); |
48 | } |
49 | |
50 | /** Construct a set consisting initially of given bit vector. |
51 | */ |
52 | public Bits(int[] bits) { |
53 | this.bits = bits; |
54 | } |
55 | |
56 | /** Construct a set consisting initially of given range. |
57 | */ |
58 | public Bits(int start, int limit) { |
59 | this(); |
60 | inclRange(start, limit); |
61 | } |
62 | |
63 | private void sizeTo(int len) { |
64 | if (bits.length < len) { |
65 | int[] newbits = new int[len]; |
66 | System.arraycopy(bits, 0, newbits, 0, bits.length); |
67 | bits = newbits; |
68 | } |
69 | } |
70 | |
71 | /** This set = {}. |
72 | */ |
73 | public void clear() { |
74 | for (int i = 0; i < bits.length; i++) bits[i] = 0; |
75 | } |
76 | |
77 | /** Return a copy of this set. |
78 | */ |
79 | public Bits dup() { |
80 | int[] newbits = new int[bits.length]; |
81 | System.arraycopy(bits, 0, newbits, 0, bits.length); |
82 | return new Bits(newbits); |
83 | } |
84 | |
85 | /** Include x in this set. |
86 | */ |
87 | public void incl(int x) { |
88 | assert x >= 0; |
89 | sizeTo((x >>> wordshift) + 1); |
90 | bits[x >>> wordshift] = bits[x >>> wordshift] | |
91 | (1 << (x & wordmask)); |
92 | } |
93 | |
94 | |
95 | /** Include [start..limit) in this set. |
96 | */ |
97 | public void inclRange(int start, int limit) { |
98 | sizeTo((limit >>> wordshift) + 1); |
99 | for (int x = start; x < limit; x++) |
100 | bits[x >>> wordshift] = bits[x >>> wordshift] | |
101 | (1 << (x & wordmask)); |
102 | } |
103 | |
104 | /** Exclude x from this set. |
105 | */ |
106 | public void excl(int x) { |
107 | assert x >= 0; |
108 | sizeTo((x >>> wordshift) + 1); |
109 | bits[x >>> wordshift] = bits[x >>> wordshift] & |
110 | ~(1 << (x & wordmask)); |
111 | } |
112 | |
113 | /** Is x an element of this set? |
114 | */ |
115 | public boolean isMember(int x) { |
116 | return |
117 | 0 <= x && x < (bits.length << wordshift) && |
118 | (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0; |
119 | } |
120 | |
121 | /** this set = this set & xs. |
122 | */ |
123 | public Bits andSet(Bits xs) { |
124 | sizeTo(xs.bits.length); |
125 | for (int i = 0; i < xs.bits.length; i++) |
126 | bits[i] = bits[i] & xs.bits[i]; |
127 | return this; |
128 | } |
129 | |
130 | /** this set = this set | xs. |
131 | */ |
132 | public Bits orSet(Bits xs) { |
133 | sizeTo(xs.bits.length); |
134 | for (int i = 0; i < xs.bits.length; i++) |
135 | bits[i] = bits[i] | xs.bits[i]; |
136 | return this; |
137 | } |
138 | |
139 | /** this set = this set \ xs. |
140 | */ |
141 | public Bits diffSet(Bits xs) { |
142 | for (int i = 0; i < bits.length; i++) { |
143 | if (i < xs.bits.length) { |
144 | bits[i] = bits[i] & ~xs.bits[i]; |
145 | } |
146 | } |
147 | return this; |
148 | } |
149 | |
150 | /** this set = this set ^ xs. |
151 | */ |
152 | public Bits xorSet(Bits xs) { |
153 | sizeTo(xs.bits.length); |
154 | for (int i = 0; i < xs.bits.length; i++) |
155 | bits[i] = bits[i] ^ xs.bits[i]; |
156 | return this; |
157 | } |
158 | |
159 | /** Count trailing zero bits in an int. Algorithm from "Hacker's |
160 | * Delight" by Henry S. Warren Jr. (figure 5-13) |
161 | */ |
162 | private static int trailingZeroBits(int x) { |
163 | assert wordlen == 32; |
164 | if (x == 0) return 32; |
165 | int n = 1; |
166 | if ((x & 0xffff) == 0) { n += 16; x >>>= 16; } |
167 | if ((x & 0x00ff) == 0) { n += 8; x >>>= 8; } |
168 | if ((x & 0x000f) == 0) { n += 4; x >>>= 4; } |
169 | if ((x & 0x0003) == 0) { n += 2; x >>>= 2; } |
170 | return n - (x&1); |
171 | } |
172 | |
173 | /** Return the index of the least bit position >= x that is set. |
174 | * If none are set, returns -1. This provides a nice way to iterate |
175 | * over the members of a bit set: |
176 | * <pre> |
177 | * for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ... |
178 | * </pre> |
179 | */ |
180 | public int nextBit(int x) { |
181 | int windex = x >>> wordshift; |
182 | if (windex >= bits.length) return -1; |
183 | int word = bits[windex] & ~((1 << (x & wordmask))-1); |
184 | while (true) { |
185 | if (word != 0) |
186 | return (windex << wordshift) + trailingZeroBits(word); |
187 | windex++; |
188 | if (windex >= bits.length) return -1; |
189 | word = bits[windex]; |
190 | } |
191 | } |
192 | |
193 | /** a string representation of this set. |
194 | */ |
195 | public String toString() { |
196 | char[] digits = new char[bits.length * wordlen]; |
197 | for (int i = 0; i < bits.length * wordlen; i++) |
198 | digits[i] = isMember(i) ? '1' : '0'; |
199 | return new String(digits); |
200 | } |
201 | |
202 | /** Test Bits.nextBit(int). */ |
203 | public static void main(String[] args) { |
204 | java.util.Random r = new java.util.Random(); |
205 | Bits bits = new Bits(); |
206 | int dupCount = 0; |
207 | for (int i=0; i<125; i++) { |
208 | int k; |
209 | do { |
210 | k = r.nextInt(250); |
211 | } while (bits.isMember(k)); |
212 | System.out.println("adding " + k); |
213 | bits.incl(k); |
214 | } |
215 | int count = 0; |
216 | for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) { |
217 | System.out.println("found " + i); |
218 | count ++; |
219 | } |
220 | if (count != 125) throw new Error(); |
221 | } |
222 | } |