duke@1: /*
ohair@798:  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
duke@1:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1:  *
duke@1:  * This code is free software; you can redistribute it and/or modify it
duke@1:  * under the terms of the GNU General Public License version 2 only, as
ohair@554:  * published by the Free Software Foundation.  Oracle designates this
duke@1:  * particular file as subject to the "Classpath" exception as provided
ohair@554:  * by Oracle in the LICENSE file that accompanied this code.
duke@1:  *
duke@1:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@1:  * version 2 for more details (a copy is included in the LICENSE file that
duke@1:  * accompanied this code).
duke@1:  *
duke@1:  * You should have received a copy of the GNU General Public License version
duke@1:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@1:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1:  *
ohair@554:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
ohair@554:  * or visit www.oracle.com if you need additional information or have any
ohair@554:  * questions.
duke@1:  */
duke@1: 
duke@1: package com.sun.tools.javac.util;
duke@1: 
duke@1: /** A class for extensible, mutable bit sets.
duke@1:  *
jjg@581:  *  <p><b>This is NOT part of any supported API.
jjg@581:  *  If you write code that depends on this, you do so at your own risk.
duke@1:  *  This code and its internal interfaces are subject to change or
duke@1:  *  deletion without notice.</b>
duke@1:  */
duke@1: public class Bits {
duke@1: 
duke@1: 
duke@1:     private final static int wordlen = 32;
duke@1:     private final static int wordshift = 5;
duke@1:     private final static int wordmask = wordlen - 1;
duke@1: 
duke@1:     private int[] bits;
duke@1: 
duke@1:     /** Construct an initially empty set.
duke@1:      */
duke@1:     public Bits() {
duke@1:         this(new int[1]);
duke@1:     }
duke@1: 
duke@1:     /** Construct a set consisting initially of given bit vector.
duke@1:      */
duke@1:     public Bits(int[] bits) {
duke@1:         this.bits = bits;
duke@1:     }
duke@1: 
duke@1:     /** Construct a set consisting initially of given range.
duke@1:      */
duke@1:     public Bits(int start, int limit) {
duke@1:         this();
duke@1:         inclRange(start, limit);
duke@1:     }
duke@1: 
duke@1:     private void sizeTo(int len) {
duke@1:         if (bits.length < len) {
duke@1:             int[] newbits = new int[len];
duke@1:             System.arraycopy(bits, 0, newbits, 0, bits.length);
duke@1:             bits = newbits;
duke@1:         }
duke@1:     }
duke@1: 
duke@1:     /** This set = {}.
duke@1:      */
duke@1:     public void clear() {
duke@1:         for (int i = 0; i < bits.length; i++) bits[i] = 0;
duke@1:     }
duke@1: 
duke@1:     /** Return a copy of this set.
duke@1:      */
duke@1:     public Bits dup() {
duke@1:         int[] newbits = new int[bits.length];
duke@1:         System.arraycopy(bits, 0, newbits, 0, bits.length);
duke@1:         return new Bits(newbits);
duke@1:     }
duke@1: 
duke@1:     /** Include x in this set.
duke@1:      */
duke@1:     public void incl(int x) {
duke@1:         assert x >= 0;
duke@1:         sizeTo((x >>> wordshift) + 1);
duke@1:         bits[x >>> wordshift] = bits[x >>> wordshift] |
duke@1:             (1 << (x & wordmask));
duke@1:     }
duke@1: 
duke@1: 
duke@1:     /** Include [start..limit) in this set.
duke@1:      */
duke@1:     public void inclRange(int start, int limit) {
duke@1:         sizeTo((limit >>> wordshift) + 1);
duke@1:         for (int x = start; x < limit; x++)
duke@1:             bits[x >>> wordshift] = bits[x >>> wordshift] |
duke@1:                 (1 << (x & wordmask));
duke@1:     }
duke@1: 
mcimadamore@773:     /** Exclude [start...end] from this set.
mcimadamore@773:      */
mcimadamore@773:     public void excludeFrom(int start) {
mcimadamore@773:         Bits temp = new Bits();
mcimadamore@773:         temp.sizeTo(bits.length);
mcimadamore@773:         temp.inclRange(0, start);
mcimadamore@773:         andSet(temp);
mcimadamore@773:     }
mcimadamore@773: 
duke@1:     /** Exclude x from this set.
duke@1:      */
duke@1:     public void excl(int x) {
duke@1:         assert x >= 0;
duke@1:         sizeTo((x >>> wordshift) + 1);
duke@1:         bits[x >>> wordshift] = bits[x >>> wordshift] &
duke@1:             ~(1 << (x & wordmask));
duke@1:     }
duke@1: 
duke@1:     /** Is x an element of this set?
duke@1:      */
duke@1:     public boolean isMember(int x) {
duke@1:         return
duke@1:             0 <= x && x < (bits.length << wordshift) &&
duke@1:             (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
duke@1:     }
duke@1: 
duke@1:     /** this set = this set & xs.
duke@1:      */
duke@1:     public Bits andSet(Bits xs) {
duke@1:         sizeTo(xs.bits.length);
duke@1:         for (int i = 0; i < xs.bits.length; i++)
duke@1:             bits[i] = bits[i] & xs.bits[i];
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** this set = this set | xs.
duke@1:      */
duke@1:     public Bits orSet(Bits xs) {
duke@1:         sizeTo(xs.bits.length);
duke@1:         for (int i = 0; i < xs.bits.length; i++)
duke@1:             bits[i] = bits[i] | xs.bits[i];
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** this set = this set \ xs.
duke@1:      */
duke@1:     public Bits diffSet(Bits xs) {
duke@1:         for (int i = 0; i < bits.length; i++) {
duke@1:             if (i < xs.bits.length) {
duke@1:                 bits[i] = bits[i] & ~xs.bits[i];
duke@1:             }
duke@1:         }
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** this set = this set ^ xs.
duke@1:      */
duke@1:     public Bits xorSet(Bits xs) {
duke@1:         sizeTo(xs.bits.length);
duke@1:         for (int i = 0; i < xs.bits.length; i++)
duke@1:             bits[i] = bits[i] ^ xs.bits[i];
duke@1:         return this;
duke@1:     }
duke@1: 
duke@1:     /** Count trailing zero bits in an int. Algorithm from "Hacker's
duke@1:      *  Delight" by Henry S. Warren Jr. (figure 5-13)
duke@1:      */
duke@1:     private static int trailingZeroBits(int x) {
duke@1:         assert wordlen == 32;
duke@1:         if (x == 0) return 32;
duke@1:         int n = 1;
duke@1:         if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }
duke@1:         if ((x & 0x00ff) == 0) { n +=  8; x >>>=  8; }
duke@1:         if ((x & 0x000f) == 0) { n +=  4; x >>>=  4; }
duke@1:         if ((x & 0x0003) == 0) { n +=  2; x >>>=  2; }
duke@1:         return n - (x&1);
duke@1:     }
duke@1: 
duke@1:     /** Return the index of the least bit position >= x that is set.
duke@1:      *  If none are set, returns -1.  This provides a nice way to iterate
duke@1:      *  over the members of a bit set:
duke@1:      *  <pre>
duke@1:      *  for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
duke@1:      *  </pre>
duke@1:      */
duke@1:     public int nextBit(int x) {
duke@1:         int windex = x >>> wordshift;
duke@1:         if (windex >= bits.length) return -1;
duke@1:         int word = bits[windex] & ~((1 << (x & wordmask))-1);
duke@1:         while (true) {
duke@1:             if (word != 0)
duke@1:                 return (windex << wordshift) + trailingZeroBits(word);
duke@1:             windex++;
duke@1:             if (windex >= bits.length) return -1;
duke@1:             word = bits[windex];
duke@1:         }
duke@1:     }
duke@1: 
duke@1:     /** a string representation of this set.
duke@1:      */
duke@1:     public String toString() {
duke@1:         char[] digits = new char[bits.length * wordlen];
duke@1:         for (int i = 0; i < bits.length * wordlen; i++)
duke@1:             digits[i] = isMember(i) ? '1' : '0';
duke@1:         return new String(digits);
duke@1:     }
duke@1: 
duke@1:     /** Test Bits.nextBit(int). */
duke@1:     public static void main(String[] args) {
duke@1:         java.util.Random r = new java.util.Random();
duke@1:         Bits bits = new Bits();
duke@1:         int dupCount = 0;
duke@1:         for (int i=0; i<125; i++) {
duke@1:             int k;
duke@1:             do {
duke@1:                 k = r.nextInt(250);
duke@1:             } while (bits.isMember(k));
duke@1:             System.out.println("adding " + k);
duke@1:             bits.incl(k);
duke@1:         }
duke@1:         int count = 0;
duke@1:         for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
duke@1:             System.out.println("found " + i);
duke@1:             count ++;
duke@1:         }
duke@1:         if (count != 125) throw new Error();
duke@1:     }
duke@1: }