/*
* Copyright (c) 1999, 2015, Oracle and/or its affiliates. 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.sun.tools.javac.util;
import java.util.Arrays;
/** A class for extensible, mutable bit sets.
*
* <p><b>This is NOT part of any supported API.
* 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 {
// ____________ reset _________
// / UNKNOWN \ <-------- / UNINIT \
// \____________/ | \_________/
// | | |
// |assign | | any
// | ___________ |
// ------> / NORMAL \ <----
// \___________/ |
// | |
// | |
// -----------
// any
protected enum BitsState {
/* A Bits instance is in UNKNOWN state if it has been explicitly reset.
* It is possible to get to this state from any other by calling the
* reset method. An instance in the UNKNOWN state can pass to the
* NORMAL state after being assigned another Bits instance.
*
* Bits instances are final fields in Flow so the UNKNOWN state models
* the null assignment.
*/
UNKNOWN,
/* A Bits instance is in UNINIT when it is created with the default
* constructor but it isn't explicitly reset. The main objective of this
* internal state is to save some memory.
*/
UNINIT,
/* The normal state is reached after creating a Bits instance from an
* existing one or after applying any operation to an instance on UNINIT
* or NORMAL state. From this state a bits instance can pass to the
* UNKNOWN state by calling the reset method.
*/
NORMAL;
static BitsState getState(int[] someBits, boolean reset) {
if (reset) {
return UNKNOWN;
} else {
if (someBits != unassignedBits) {
return NORMAL;
} else {
return UNINIT;
}
}
}
}
private final static int wordlen = 32;
private final static int wordshift = 5;
private final static int wordmask = wordlen - 1;
public int[] bits = null;
// This field will store last version of bits after every change.
private static final int[] unassignedBits = new int[0];
protected BitsState currentState;
/** Construct an initially empty set.
*/
public Bits() {
this(false);
}
public Bits(Bits someBits) {
this(someBits.dup().bits, BitsState.getState(someBits.bits, false));
}
public Bits(boolean reset) {
this(unassignedBits, BitsState.getState(unassignedBits, reset));
}
/** Construct a set consisting initially of given bit vector.
*/
protected Bits(int[] bits, BitsState initState) {
this.bits = bits;
this.currentState = initState;
switch (initState) {
case UNKNOWN:
this.bits = null;
break;
case NORMAL:
Assert.check(bits != unassignedBits);
break;
}
}
protected void sizeTo(int len) {
if (bits.length < len) {
bits = Arrays.copyOf(bits, len);
}
}
/** This set = {}.
*/
public void clear() {
Assert.check(currentState != BitsState.UNKNOWN);
for (int i = 0; i < bits.length; i++) {
bits[i] = 0;
}
currentState = BitsState.NORMAL;
}
public void reset() {
internalReset();
}
protected void internalReset() {
bits = null;
currentState = BitsState.UNKNOWN;
}
public boolean isReset() {
return currentState == BitsState.UNKNOWN;
}
public Bits assign(Bits someBits) {
bits = someBits.dup().bits;
currentState = BitsState.NORMAL;
return this;
}
/** Return a copy of this set.
*/
public Bits dup() {
Assert.check(currentState != BitsState.UNKNOWN);
Bits tmp = new Bits();
tmp.bits = dupBits();
currentState = BitsState.NORMAL;
return tmp;
}
protected int[] dupBits() {
int [] result;
if (currentState != BitsState.NORMAL) {
result = bits;
} else {
result = new int[bits.length];
System.arraycopy(bits, 0, result, 0, bits.length);
}
return result;
}
/** Include x in this set.
*/
public void incl(int x) {
Assert.check(currentState != BitsState.UNKNOWN);
Assert.check(x >= 0);
sizeTo((x >>> wordshift) + 1);
bits[x >>> wordshift] = bits[x >>> wordshift] |
(1 << (x & wordmask));
currentState = BitsState.NORMAL;
}
/** Include [start..limit) in this set.
*/
public void inclRange(int start, int limit) {
Assert.check(currentState != BitsState.UNKNOWN);
sizeTo((limit >>> wordshift) + 1);
for (int x = start; x < limit; x++) {
bits[x >>> wordshift] = bits[x >>> wordshift] |
(1 << (x & wordmask));
}
currentState = BitsState.NORMAL;
}
/** Exclude [start...end] from this set.
*/
public void excludeFrom(int start) {
Assert.check(currentState != BitsState.UNKNOWN);
Bits temp = new Bits();
temp.sizeTo(bits.length);
temp.inclRange(0, start);
internalAndSet(temp);
currentState = BitsState.NORMAL;
}
/** Exclude x from this set.
*/
public void excl(int x) {
Assert.check(currentState != BitsState.UNKNOWN);
Assert.check(x >= 0);
sizeTo((x >>> wordshift) + 1);
bits[x >>> wordshift] = bits[x >>> wordshift] &
~(1 << (x & wordmask));
currentState = BitsState.NORMAL;
}
/** Is x an element of this set?
*/
public boolean isMember(int x) {
Assert.check(currentState != BitsState.UNKNOWN);
return
0 <= x && x < (bits.length << wordshift) &&
(bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
}
/** {@literal this set = this set & xs}.
*/
public Bits andSet(Bits xs) {
Assert.check(currentState != BitsState.UNKNOWN);
internalAndSet(xs);
currentState = BitsState.NORMAL;
return this;
}
protected void internalAndSet(Bits xs) {
Assert.check(currentState != BitsState.UNKNOWN);
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++) {
bits[i] = bits[i] & xs.bits[i];
}
}
/** this set = this set | xs.
*/
public Bits orSet(Bits xs) {
Assert.check(currentState != BitsState.UNKNOWN);
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++) {
bits[i] = bits[i] | xs.bits[i];
}
currentState = BitsState.NORMAL;
return this;
}
/** this set = this set \ xs.
*/
public Bits diffSet(Bits xs) {
Assert.check(currentState != BitsState.UNKNOWN);
for (int i = 0; i < bits.length; i++) {
if (i < xs.bits.length) {
bits[i] = bits[i] & ~xs.bits[i];
}
}
currentState = BitsState.NORMAL;
return this;
}
/** this set = this set ^ xs.
*/
public Bits xorSet(Bits xs) {
Assert.check(currentState != BitsState.UNKNOWN);
sizeTo(xs.bits.length);
for (int i = 0; i < xs.bits.length; i++) {
bits[i] = bits[i] ^ xs.bits[i];
}
currentState = BitsState.NORMAL;
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.check(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>{@code
* for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
* }</pre>
*/
public int nextBit(int x) {
Assert.check(currentState != BitsState.UNKNOWN);
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.
*/
@Override
public String toString() {
if (bits != null && bits.length > 0) {
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);
} else {
return "[]";
}
}
}