/*
* Copyright 1999-2005 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package com.sun.tools.javac.util;
/** A class for extensible, mutable bit sets.
*
* <p><b>This is NOT part of any API supported by Sun Microsystems. If
* you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.</b>
*/
public class Bits {
private final static int wordlen = 32;
private final static int wordshift = 5;
private final static int wordmask = wordlen - 1;
private int[] bits;
/** Construct an initially empty set.
*/
public Bits() {
this(new int[1]);
}
/** Construct a set consisting initially of given bit vector.
*/
public Bits(int[] bits) {
this.bits = bits;
}
/** Construct a set consisting initially of given range.
*/
public Bits(int start, int limit) {
this();
inclRange(start, limit);
}
private void sizeTo(int len) {
if (bits.length < len) {
int[] newbits = new int[len];
System.arraycopy(bits, 0, newbits, 0, bits.length);
bits = newbits;
}
}
/** This set = {}.
*/
public void clear() {
for (int i = 0; i < bits.length; i++) bits[i] = 0;
}
/** Return a copy of this set.
*/
public Bits dup() {
int[] newbits = new int[bits.length];
System.arraycopy(bits, 0, newbits, 0, bits.length);
return new Bits(newbits);
}
/** Include x in this set.
*/
public void incl(int x) {
assert x >= 0;
sizeTo((x >>> wordshift) + 1);
bits[x >>> wordshift] = bits[x >>> wordshift] |
(1 << (x & wordmask));
}
/** Include [start..limit) in this set.
*/
public void inclRange(int start, int limit) {
sizeTo((limit >>> wordshift) + 1);
for (int x = start; x < limit; x++)
bits[x >>> wordshift] = bits[x >>> wordshift] |
(1 << (x & wordmask));
}
/** Exclude x from this set.
*/
public void excl(int x) {
assert x >= 0;
sizeTo((x >>> wordshift) + 1);
bits[x >>> wordshift] = bits[x >>> wordshift] &
~(1 << (x & wordmask));
}
/** Is x an element of this set?
*/
public boolean isMember(int x) {
return
0 <= x && x < (bits.length << wordshift) &&
(bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
}
/** this set = this set & xs.
*/
public Bits andSet(Bits xs) {
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++)
bits[i] = bits[i] & xs.bits[i];
return this;
}
/** this set = this set | xs.
*/
public Bits orSet(Bits xs) {
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++)
bits[i] = bits[i] | xs.bits[i];
return this;
}
/** this set = this set \ xs.
*/
public Bits diffSet(Bits xs) {
for (int i = 0; i < bits.length; i++) {
if (i < xs.bits.length) {
bits[i] = bits[i] & ~xs.bits[i];
}
}
return this;
}
/** this set = this set ^ xs.
*/
public Bits xorSet(Bits xs) {
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++)
bits[i] = bits[i] ^ xs.bits[i];
return this;
}
/** Count trailing zero bits in an int. Algorithm from "Hacker's
* Delight" by Henry S. Warren Jr. (figure 5-13)
*/
private static int trailingZeroBits(int x) {
assert wordlen == 32;
if (x == 0) return 32;
int n = 1;
if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }
if ((x & 0x00ff) == 0) { n += 8; x >>>= 8; }
if ((x & 0x000f) == 0) { n += 4; x >>>= 4; }
if ((x & 0x0003) == 0) { n += 2; x >>>= 2; }
return n - (x&1);
}
/** Return the index of the least bit position >= x that is set.
* If none are set, returns -1. This provides a nice way to iterate
* over the members of a bit set:
* <pre>
* for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
* </pre>
*/
public int nextBit(int x) {
int windex = x >>> wordshift;
if (windex >= bits.length) return -1;
int word = bits[windex] & ~((1 << (x & wordmask))-1);
while (true) {
if (word != 0)
return (windex << wordshift) + trailingZeroBits(word);
windex++;
if (windex >= bits.length) return -1;
word = bits[windex];
}
}
/** a string representation of this set.
*/
public String toString() {
char[] digits = new char[bits.length * wordlen];
for (int i = 0; i < bits.length * wordlen; i++)
digits[i] = isMember(i) ? '1' : '0';
return new String(digits);
}
/** Test Bits.nextBit(int). */
public static void main(String[] args) {
java.util.Random r = new java.util.Random();
Bits bits = new Bits();
int dupCount = 0;
for (int i=0; i<125; i++) {
int k;
do {
k = r.nextInt(250);
} while (bits.isMember(k));
System.out.println("adding " + k);
bits.incl(k);
}
int count = 0;
for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
System.out.println("found " + i);
count ++;
}
if (count != 125) throw new Error();
}
}