370 lines
11 KiB
Java
370 lines
11 KiB
Java
/*
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* Copyright (c) 1999, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.tools.javac.util;
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import java.util.Arrays;
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/** A class for extensible, mutable bit sets.
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*
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* <p><b>This is NOT part of any supported API.
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* If you write code that depends on this, you do so at your own risk.
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* This code and its internal interfaces are subject to change or
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* deletion without notice.</b>
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*/
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public class Bits {
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// ____________ reset _________
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// / UNKNOWN \ <-------- / UNINIT \
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// \____________/ | \_________/
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// | | |
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// |assign | | any
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// | ___________ |
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// ------> / NORMAL \ <----
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// \___________/ |
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// | |
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// | |
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// -----------
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// any
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protected enum BitsState {
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/* A Bits instance is in UNKNOWN state if it has been explicitly reset.
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* It is possible to get to this state from any other by calling the
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* reset method. An instance in the UNKNOWN state can pass to the
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* NORMAL state after being assigned another Bits instance.
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*
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* Bits instances are final fields in Flow so the UNKNOWN state models
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* the null assignment.
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*/
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UNKNOWN,
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/* A Bits instance is in UNINIT when it is created with the default
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* constructor but it isn't explicitly reset. The main objective of this
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* internal state is to save some memory.
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*/
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UNINIT,
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/* The normal state is reached after creating a Bits instance from an
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* existing one or after applying any operation to an instance on UNINIT
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* or NORMAL state. From this state a bits instance can pass to the
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* UNKNOWN state by calling the reset method.
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*/
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NORMAL;
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static BitsState getState(int[] someBits, boolean reset) {
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if (reset) {
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return UNKNOWN;
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} else {
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if (someBits != unassignedBits) {
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return NORMAL;
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} else {
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return UNINIT;
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}
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}
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}
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}
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private final static int wordlen = 32;
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private final static int wordshift = 5;
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private final static int wordmask = wordlen - 1;
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public int[] bits = null;
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// This field will store last version of bits after every change.
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private static final int[] unassignedBits = new int[0];
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protected BitsState currentState;
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/** Construct an initially empty set.
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*/
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public Bits() {
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this(false);
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}
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public Bits(Bits someBits) {
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this(someBits.dup().bits, BitsState.getState(someBits.bits, false));
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}
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public Bits(boolean reset) {
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this(unassignedBits, BitsState.getState(unassignedBits, reset));
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}
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/** Construct a set consisting initially of given bit vector.
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*/
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protected Bits(int[] bits, BitsState initState) {
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this.bits = bits;
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this.currentState = initState;
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switch (initState) {
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case UNKNOWN:
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this.bits = null;
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break;
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case NORMAL:
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Assert.check(bits != unassignedBits);
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break;
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}
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}
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protected void sizeTo(int len) {
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if (bits.length < len) {
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bits = Arrays.copyOf(bits, len);
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}
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}
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/** This set = {}.
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*/
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public void clear() {
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Assert.check(currentState != BitsState.UNKNOWN);
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for (int i = 0; i < bits.length; i++) {
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bits[i] = 0;
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}
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currentState = BitsState.NORMAL;
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}
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public void reset() {
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internalReset();
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}
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protected void internalReset() {
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bits = null;
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currentState = BitsState.UNKNOWN;
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}
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public boolean isReset() {
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return currentState == BitsState.UNKNOWN;
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}
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public Bits assign(Bits someBits) {
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bits = someBits.dup().bits;
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currentState = BitsState.NORMAL;
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return this;
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}
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/** Return a copy of this set.
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*/
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public Bits dup() {
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Assert.check(currentState != BitsState.UNKNOWN);
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Bits tmp = new Bits();
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tmp.bits = dupBits();
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currentState = BitsState.NORMAL;
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return tmp;
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}
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protected int[] dupBits() {
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int [] result;
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if (currentState != BitsState.NORMAL) {
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result = bits;
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} else {
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result = new int[bits.length];
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System.arraycopy(bits, 0, result, 0, bits.length);
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}
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return result;
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}
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/** Include x in this set.
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*/
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public void incl(int x) {
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Assert.check(currentState != BitsState.UNKNOWN);
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Assert.check(x >= 0, "Value of x " + x);
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sizeTo((x >>> wordshift) + 1);
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bits[x >>> wordshift] = bits[x >>> wordshift] |
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(1 << (x & wordmask));
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currentState = BitsState.NORMAL;
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}
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/** Include [start..limit) in this set.
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*/
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public void inclRange(int start, int limit) {
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Assert.check(currentState != BitsState.UNKNOWN);
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sizeTo((limit >>> wordshift) + 1);
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for (int x = start; x < limit; x++) {
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bits[x >>> wordshift] = bits[x >>> wordshift] |
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(1 << (x & wordmask));
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}
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currentState = BitsState.NORMAL;
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}
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/** Exclude [start...end] from this set.
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*/
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public void excludeFrom(int start) {
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Assert.check(currentState != BitsState.UNKNOWN);
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Bits temp = new Bits();
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temp.sizeTo(bits.length);
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temp.inclRange(0, start);
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internalAndSet(temp);
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currentState = BitsState.NORMAL;
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}
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/** Exclude x from this set.
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*/
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public void excl(int x) {
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Assert.check(currentState != BitsState.UNKNOWN);
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Assert.check(x >= 0);
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sizeTo((x >>> wordshift) + 1);
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bits[x >>> wordshift] = bits[x >>> wordshift] &
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~(1 << (x & wordmask));
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currentState = BitsState.NORMAL;
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}
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/** Is x an element of this set?
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*/
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public boolean isMember(int x) {
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Assert.check(currentState != BitsState.UNKNOWN);
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return
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0 <= x && x < (bits.length << wordshift) &&
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(bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
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}
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/** {@literal this set = this set & xs}.
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*/
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public Bits andSet(Bits xs) {
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Assert.check(currentState != BitsState.UNKNOWN);
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internalAndSet(xs);
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currentState = BitsState.NORMAL;
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return this;
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}
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protected void internalAndSet(Bits xs) {
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Assert.check(currentState != BitsState.UNKNOWN);
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sizeTo(xs.bits.length);
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for (int i = 0; i < xs.bits.length; i++) {
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bits[i] = bits[i] & xs.bits[i];
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}
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}
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/** this set = this set | xs.
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*/
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public Bits orSet(Bits xs) {
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Assert.check(currentState != BitsState.UNKNOWN);
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sizeTo(xs.bits.length);
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for (int i = 0; i < xs.bits.length; i++) {
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bits[i] = bits[i] | xs.bits[i];
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}
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currentState = BitsState.NORMAL;
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return this;
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}
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/** this set = this set \ xs.
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*/
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public Bits diffSet(Bits xs) {
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Assert.check(currentState != BitsState.UNKNOWN);
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for (int i = 0; i < bits.length; i++) {
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if (i < xs.bits.length) {
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bits[i] = bits[i] & ~xs.bits[i];
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}
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}
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currentState = BitsState.NORMAL;
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return this;
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}
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/** this set = this set ^ xs.
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*/
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public Bits xorSet(Bits xs) {
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Assert.check(currentState != BitsState.UNKNOWN);
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sizeTo(xs.bits.length);
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for (int i = 0; i < xs.bits.length; i++) {
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bits[i] = bits[i] ^ xs.bits[i];
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}
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currentState = BitsState.NORMAL;
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return this;
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}
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/** Count trailing zero bits in an int. Algorithm from "Hacker's
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* Delight" by Henry S. Warren Jr. (figure 5-13)
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*/
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private static int trailingZeroBits(int x) {
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Assert.check(wordlen == 32);
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if (x == 0) {
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return 32;
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}
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int n = 1;
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if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }
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if ((x & 0x00ff) == 0) { n += 8; x >>>= 8; }
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if ((x & 0x000f) == 0) { n += 4; x >>>= 4; }
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if ((x & 0x0003) == 0) { n += 2; x >>>= 2; }
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return n - (x&1);
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}
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/** Return the index of the least bit position ≥ x that is set.
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* If none are set, returns -1. This provides a nice way to iterate
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* over the members of a bit set:
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* <pre>{@code
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* for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
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* }</pre>
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*/
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public int nextBit(int x) {
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Assert.check(currentState != BitsState.UNKNOWN);
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int windex = x >>> wordshift;
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if (windex >= bits.length) {
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return -1;
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}
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int word = bits[windex] & ~((1 << (x & wordmask))-1);
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while (true) {
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if (word != 0) {
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return (windex << wordshift) + trailingZeroBits(word);
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}
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windex++;
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if (windex >= bits.length) {
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return -1;
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}
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word = bits[windex];
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}
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}
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/** a string representation of this set.
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*/
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@Override
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public String toString() {
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if (bits != null && bits.length > 0) {
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char[] digits = new char[bits.length * wordlen];
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for (int i = 0; i < bits.length * wordlen; i++) {
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digits[i] = isMember(i) ? '1' : '0';
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}
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return new String(digits);
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} else {
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return "[]";
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}
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}
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/** Test Bits.nextBit(int). */
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public static void main(String[] args) {
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java.util.Random r = new java.util.Random();
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Bits bits = new Bits();
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for (int i=0; i<125; i++) {
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int k;
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do {
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k = r.nextInt(250);
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} while (bits.isMember(k));
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System.out.println("adding " + k);
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bits.incl(k);
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}
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int count = 0;
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for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
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System.out.println("found " + i);
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count ++;
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}
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if (count != 125) {
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throw new Error();
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}
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}
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}
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