1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/classes/com/sun/tools/javac/util/Bits.java Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,222 @@
1.4 +/*
1.5 + * Copyright 1999-2005 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Sun designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Sun in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.25 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.26 + * have any questions.
1.27 + */
1.28 +
1.29 +package com.sun.tools.javac.util;
1.30 +
1.31 +/** A class for extensible, mutable bit sets.
1.32 + *
1.33 + * <p><b>This is NOT part of any API supported by Sun Microsystems. If
1.34 + * you write code that depends on this, you do so at your own risk.
1.35 + * This code and its internal interfaces are subject to change or
1.36 + * deletion without notice.</b>
1.37 + */
1.38 +public class Bits {
1.39 +
1.40 +
1.41 + private final static int wordlen = 32;
1.42 + private final static int wordshift = 5;
1.43 + private final static int wordmask = wordlen - 1;
1.44 +
1.45 + private int[] bits;
1.46 +
1.47 + /** Construct an initially empty set.
1.48 + */
1.49 + public Bits() {
1.50 + this(new int[1]);
1.51 + }
1.52 +
1.53 + /** Construct a set consisting initially of given bit vector.
1.54 + */
1.55 + public Bits(int[] bits) {
1.56 + this.bits = bits;
1.57 + }
1.58 +
1.59 + /** Construct a set consisting initially of given range.
1.60 + */
1.61 + public Bits(int start, int limit) {
1.62 + this();
1.63 + inclRange(start, limit);
1.64 + }
1.65 +
1.66 + private void sizeTo(int len) {
1.67 + if (bits.length < len) {
1.68 + int[] newbits = new int[len];
1.69 + System.arraycopy(bits, 0, newbits, 0, bits.length);
1.70 + bits = newbits;
1.71 + }
1.72 + }
1.73 +
1.74 + /** This set = {}.
1.75 + */
1.76 + public void clear() {
1.77 + for (int i = 0; i < bits.length; i++) bits[i] = 0;
1.78 + }
1.79 +
1.80 + /** Return a copy of this set.
1.81 + */
1.82 + public Bits dup() {
1.83 + int[] newbits = new int[bits.length];
1.84 + System.arraycopy(bits, 0, newbits, 0, bits.length);
1.85 + return new Bits(newbits);
1.86 + }
1.87 +
1.88 + /** Include x in this set.
1.89 + */
1.90 + public void incl(int x) {
1.91 + assert x >= 0;
1.92 + sizeTo((x >>> wordshift) + 1);
1.93 + bits[x >>> wordshift] = bits[x >>> wordshift] |
1.94 + (1 << (x & wordmask));
1.95 + }
1.96 +
1.97 +
1.98 + /** Include [start..limit) in this set.
1.99 + */
1.100 + public void inclRange(int start, int limit) {
1.101 + sizeTo((limit >>> wordshift) + 1);
1.102 + for (int x = start; x < limit; x++)
1.103 + bits[x >>> wordshift] = bits[x >>> wordshift] |
1.104 + (1 << (x & wordmask));
1.105 + }
1.106 +
1.107 + /** Exclude x from this set.
1.108 + */
1.109 + public void excl(int x) {
1.110 + assert x >= 0;
1.111 + sizeTo((x >>> wordshift) + 1);
1.112 + bits[x >>> wordshift] = bits[x >>> wordshift] &
1.113 + ~(1 << (x & wordmask));
1.114 + }
1.115 +
1.116 + /** Is x an element of this set?
1.117 + */
1.118 + public boolean isMember(int x) {
1.119 + return
1.120 + 0 <= x && x < (bits.length << wordshift) &&
1.121 + (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
1.122 + }
1.123 +
1.124 + /** this set = this set & xs.
1.125 + */
1.126 + public Bits andSet(Bits xs) {
1.127 + sizeTo(xs.bits.length);
1.128 + for (int i = 0; i < xs.bits.length; i++)
1.129 + bits[i] = bits[i] & xs.bits[i];
1.130 + return this;
1.131 + }
1.132 +
1.133 + /** this set = this set | xs.
1.134 + */
1.135 + public Bits orSet(Bits xs) {
1.136 + sizeTo(xs.bits.length);
1.137 + for (int i = 0; i < xs.bits.length; i++)
1.138 + bits[i] = bits[i] | xs.bits[i];
1.139 + return this;
1.140 + }
1.141 +
1.142 + /** this set = this set \ xs.
1.143 + */
1.144 + public Bits diffSet(Bits xs) {
1.145 + for (int i = 0; i < bits.length; i++) {
1.146 + if (i < xs.bits.length) {
1.147 + bits[i] = bits[i] & ~xs.bits[i];
1.148 + }
1.149 + }
1.150 + return this;
1.151 + }
1.152 +
1.153 + /** this set = this set ^ xs.
1.154 + */
1.155 + public Bits xorSet(Bits xs) {
1.156 + sizeTo(xs.bits.length);
1.157 + for (int i = 0; i < xs.bits.length; i++)
1.158 + bits[i] = bits[i] ^ xs.bits[i];
1.159 + return this;
1.160 + }
1.161 +
1.162 + /** Count trailing zero bits in an int. Algorithm from "Hacker's
1.163 + * Delight" by Henry S. Warren Jr. (figure 5-13)
1.164 + */
1.165 + private static int trailingZeroBits(int x) {
1.166 + assert wordlen == 32;
1.167 + if (x == 0) return 32;
1.168 + int n = 1;
1.169 + if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }
1.170 + if ((x & 0x00ff) == 0) { n += 8; x >>>= 8; }
1.171 + if ((x & 0x000f) == 0) { n += 4; x >>>= 4; }
1.172 + if ((x & 0x0003) == 0) { n += 2; x >>>= 2; }
1.173 + return n - (x&1);
1.174 + }
1.175 +
1.176 + /** Return the index of the least bit position >= x that is set.
1.177 + * If none are set, returns -1. This provides a nice way to iterate
1.178 + * over the members of a bit set:
1.179 + * <pre>
1.180 + * for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
1.181 + * </pre>
1.182 + */
1.183 + public int nextBit(int x) {
1.184 + int windex = x >>> wordshift;
1.185 + if (windex >= bits.length) return -1;
1.186 + int word = bits[windex] & ~((1 << (x & wordmask))-1);
1.187 + while (true) {
1.188 + if (word != 0)
1.189 + return (windex << wordshift) + trailingZeroBits(word);
1.190 + windex++;
1.191 + if (windex >= bits.length) return -1;
1.192 + word = bits[windex];
1.193 + }
1.194 + }
1.195 +
1.196 + /** a string representation of this set.
1.197 + */
1.198 + public String toString() {
1.199 + char[] digits = new char[bits.length * wordlen];
1.200 + for (int i = 0; i < bits.length * wordlen; i++)
1.201 + digits[i] = isMember(i) ? '1' : '0';
1.202 + return new String(digits);
1.203 + }
1.204 +
1.205 + /** Test Bits.nextBit(int). */
1.206 + public static void main(String[] args) {
1.207 + java.util.Random r = new java.util.Random();
1.208 + Bits bits = new Bits();
1.209 + int dupCount = 0;
1.210 + for (int i=0; i<125; i++) {
1.211 + int k;
1.212 + do {
1.213 + k = r.nextInt(250);
1.214 + } while (bits.isMember(k));
1.215 + System.out.println("adding " + k);
1.216 + bits.incl(k);
1.217 + }
1.218 + int count = 0;
1.219 + for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
1.220 + System.out.println("found " + i);
1.221 + count ++;
1.222 + }
1.223 + if (count != 125) throw new Error();
1.224 + }
1.225 +}
