733 lines
20 KiB
Java
733 lines
20 KiB
Java
/* BitSet.java -- A vector of bits.
|
|
Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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 for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
package java.util;
|
|
import java.io.Serializable;
|
|
|
|
/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
|
|
* hashCode algorithm taken from JDK 1.2 docs.
|
|
*/
|
|
|
|
/**
|
|
* This class can be thought of in two ways. You can see it as a
|
|
* vector of bits or as a set of non-negative integers. The name
|
|
* <code>BitSet</code> is a bit misleading.
|
|
*
|
|
* It is implemented by a bit vector, but its equally possible to see
|
|
* it as set of non-negative integer; each integer in the set is
|
|
* represented by a set bit at the corresponding index. The size of
|
|
* this structure is determined by the highest integer in the set.
|
|
*
|
|
* You can union, intersect and build (symmetric) remainders, by
|
|
* invoking the logical operations and, or, andNot, resp. xor.
|
|
*
|
|
* This implementation is NOT synchronized against concurrent access from
|
|
* multiple threads. Specifically, if one thread is reading from a bitset
|
|
* while another thread is simultaneously modifying it, the results are
|
|
* undefined.
|
|
*
|
|
* @author Jochen Hoenicke
|
|
* @author Tom Tromey <tromey@cygnus.com>
|
|
* @author Eric Blake <ebb9@email.byu.edu>
|
|
* @status updated to 1.4
|
|
*/
|
|
public class BitSet implements Cloneable, Serializable
|
|
{
|
|
/**
|
|
* Compatible with JDK 1.0.
|
|
*/
|
|
private static final long serialVersionUID = 7997698588986878753L;
|
|
|
|
/**
|
|
* A common mask.
|
|
*/
|
|
private static final int LONG_MASK = 0x3f;
|
|
|
|
/**
|
|
* The actual bits.
|
|
* @serial the i'th bit is in bits[i/64] at position i%64 (where position
|
|
* 0 is the least significant).
|
|
*/
|
|
private long[] bits;
|
|
|
|
/**
|
|
* Create a new empty bit set. All bits are initially false.
|
|
*/
|
|
public BitSet()
|
|
{
|
|
this(64);
|
|
}
|
|
|
|
/**
|
|
* Create a new empty bit set, with a given size. This
|
|
* constructor reserves enough space to represent the integers
|
|
* from <code>0</code> to <code>nbits-1</code>.
|
|
*
|
|
* @param nbits the initial size of the bit set
|
|
* @throws NegativeArraySizeException if nbits < 0
|
|
*/
|
|
public BitSet(int nbits)
|
|
{
|
|
int length = nbits >>> 6;
|
|
if ((nbits & LONG_MASK) != 0)
|
|
++length;
|
|
bits = new long[length];
|
|
}
|
|
|
|
/**
|
|
* Performs the logical AND operation on this bit set and the
|
|
* given <code>set</code>. This means it builds the intersection
|
|
* of the two sets. The result is stored into this bit set.
|
|
*
|
|
* @param set the second bit set
|
|
* @throws NullPointerException if set is null
|
|
*/
|
|
public void and(BitSet bs)
|
|
{
|
|
int max = Math.min(bits.length, bs.bits.length);
|
|
int i;
|
|
for (i = 0; i < max; ++i)
|
|
bits[i] &= bs.bits[i];
|
|
while (i < bits.length)
|
|
bits[i++] = 0;
|
|
}
|
|
|
|
/**
|
|
* Performs the logical AND operation on this bit set and the
|
|
* complement of the given <code>set</code>. This means it
|
|
* selects every element in the first set, that isn't in the
|
|
* second set. The result is stored into this bit set.
|
|
*
|
|
* @param set the second bit set
|
|
* @throws NullPointerException if set is null
|
|
* @since 1.2
|
|
*/
|
|
public void andNot(BitSet bs)
|
|
{
|
|
int i = Math.min(bits.length, bs.bits.length);
|
|
while (--i >= 0)
|
|
bits[i] &= ~bs.bits[i];
|
|
}
|
|
|
|
/**
|
|
* Returns the number of bits set to true.
|
|
*
|
|
* @return the number of true bits
|
|
* @since 1.4
|
|
*/
|
|
public int cardinality()
|
|
{
|
|
int card = 0;
|
|
for (int i = bits.length - 1; i >= 0; i--)
|
|
{
|
|
long a = bits[i];
|
|
// Take care of common cases.
|
|
if (a == 0)
|
|
continue;
|
|
if (a == -1)
|
|
{
|
|
card += 64;
|
|
continue;
|
|
}
|
|
|
|
// Successively collapse alternating bit groups into a sum.
|
|
a = ((a >> 1) & 0x5555555555555555L) + (a & 0x5555555555555555L);
|
|
a = ((a >> 2) & 0x3333333333333333L) + (a & 0x3333333333333333L);
|
|
int b = (int) ((a >>> 32) + a);
|
|
b = ((b >> 4) & 0x0f0f0f0f) + (b & 0x0f0f0f0f);
|
|
b = ((b >> 8) & 0x00ff00ff) + (b & 0x00ff00ff);
|
|
card += ((b >> 16) & 0x0000ffff) + (b & 0x0000ffff);
|
|
}
|
|
return card;
|
|
}
|
|
|
|
/**
|
|
* Sets all bits in the set to false.
|
|
*
|
|
* @since 1.4
|
|
*/
|
|
public void clear()
|
|
{
|
|
Arrays.fill(bits, 0);
|
|
}
|
|
|
|
/**
|
|
* Removes the integer <code>bitIndex</code> from this set. That is
|
|
* the corresponding bit is cleared. If the index is not in the set,
|
|
* this method does nothing.
|
|
*
|
|
* @param bitIndex a non-negative integer
|
|
* @throws IndexOutOfBoundsException if bitIndex < 0
|
|
*/
|
|
public void clear(int pos)
|
|
{
|
|
int offset = pos >>> 6;
|
|
ensure(offset);
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
bits[offset] &= ~(1L << pos);
|
|
}
|
|
|
|
/**
|
|
* Sets the bits between from (inclusive) and to (exclusive) to false.
|
|
*
|
|
* @param from the start range (inclusive)
|
|
* @param to the end range (exclusive)
|
|
* @throws IndexOutOfBoundsException if from < 0 || from > to
|
|
* @since 1.4
|
|
*/
|
|
public void clear(int from, int to)
|
|
{
|
|
if (from < 0 || from > to)
|
|
throw new IndexOutOfBoundsException();
|
|
if (from == to)
|
|
return;
|
|
int lo_offset = from >>> 6;
|
|
int hi_offset = to >>> 6;
|
|
ensure(hi_offset);
|
|
if (lo_offset == hi_offset)
|
|
{
|
|
bits[hi_offset] &= ((1L << from) - 1) | (-1L << to);
|
|
return;
|
|
}
|
|
|
|
bits[lo_offset] &= (1L << from) - 1;
|
|
bits[hi_offset] &= -1L << to;
|
|
for (int i = lo_offset + 1; i < hi_offset; i++)
|
|
bits[i] = 0;
|
|
}
|
|
|
|
/**
|
|
* Create a clone of this bit set, that is an instance of the same
|
|
* class and contains the same elements. But it doesn't change when
|
|
* this bit set changes.
|
|
*
|
|
* @return the clone of this object.
|
|
*/
|
|
public Object clone()
|
|
{
|
|
try
|
|
{
|
|
BitSet bs = (BitSet) super.clone();
|
|
bs.bits = (long[]) bits.clone();
|
|
return bs;
|
|
}
|
|
catch (CloneNotSupportedException e)
|
|
{
|
|
// Impossible to get here.
|
|
return null;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns true if the <code>obj</code> is a bit set that contains
|
|
* exactly the same elements as this bit set, otherwise false.
|
|
*
|
|
* @param obj the object to compare to
|
|
* @return true if obj equals this bit set
|
|
*/
|
|
public boolean equals(Object obj)
|
|
{
|
|
if (!(obj instanceof BitSet))
|
|
return false;
|
|
BitSet bs = (BitSet) obj;
|
|
int max = Math.min(bits.length, bs.bits.length);
|
|
int i;
|
|
for (i = 0; i < max; ++i)
|
|
if (bits[i] != bs.bits[i])
|
|
return false;
|
|
// If one is larger, check to make sure all extra bits are 0.
|
|
for (int j = i; j < bits.length; ++j)
|
|
if (bits[j] != 0)
|
|
return false;
|
|
for (int j = i; j < bs.bits.length; ++j)
|
|
if (bs.bits[j] != 0)
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Sets the bit at the index to the opposite value.
|
|
*
|
|
* @param index the index of the bit
|
|
* @throws IndexOutOfBoundsException if index is negative
|
|
* @since 1.4
|
|
*/
|
|
public void flip(int index)
|
|
{
|
|
int offset = index >>> 6;
|
|
ensure(offset);
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
bits[offset] ^= 1L << index;
|
|
}
|
|
|
|
/**
|
|
* Sets a range of bits to the opposite value.
|
|
*
|
|
* @param from the low index (inclusive)
|
|
* @param to the high index (exclusive)
|
|
* @throws IndexOutOfBoundsException if from > to || from < 0
|
|
* @since 1.4
|
|
*/
|
|
public void flip(int from, int to)
|
|
{
|
|
if (from < 0 || from > to)
|
|
throw new IndexOutOfBoundsException();
|
|
if (from == to)
|
|
return;
|
|
int lo_offset = from >>> 6;
|
|
int hi_offset = to >>> 6;
|
|
ensure(hi_offset);
|
|
if (lo_offset == hi_offset)
|
|
{
|
|
bits[hi_offset] ^= (-1L << from) & ((1L << to) - 1);
|
|
return;
|
|
}
|
|
|
|
bits[lo_offset] ^= -1L << from;
|
|
bits[hi_offset] ^= (1L << to) - 1;
|
|
for (int i = lo_offset + 1; i < hi_offset; i++)
|
|
bits[i] ^= -1;
|
|
}
|
|
|
|
/**
|
|
* Returns true if the integer <code>bitIndex</code> is in this bit
|
|
* set, otherwise false.
|
|
*
|
|
* @param pos a non-negative integer
|
|
* @return the value of the bit at the specified index
|
|
* @throws IndexOutOfBoundsException if the index is negative
|
|
*/
|
|
public boolean get(int pos)
|
|
{
|
|
int offset = pos >>> 6;
|
|
if (offset >= bits.length)
|
|
return false;
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
return (bits[offset] & (1L << pos)) != 0;
|
|
}
|
|
|
|
/**
|
|
* Returns a new <code>BitSet</code> composed of a range of bits from
|
|
* this one.
|
|
*
|
|
* @param from the low index (inclusive)
|
|
* @param to the high index (exclusive)
|
|
* @throws IndexOutOfBoundsException if from > to || from < 0
|
|
* @since 1.4
|
|
*/
|
|
public BitSet get(int from, int to)
|
|
{
|
|
if (from < 0 || from > to)
|
|
throw new IndexOutOfBoundsException();
|
|
BitSet bs = new BitSet(to - from);
|
|
int lo_offset = from >>> 6;
|
|
if (lo_offset >= bits.length)
|
|
return bs;
|
|
|
|
int lo_bit = from & LONG_MASK;
|
|
int hi_offset = to >>> 6;
|
|
if (lo_bit == 0)
|
|
{
|
|
int len = Math.min(hi_offset - lo_offset + 1, bits.length - lo_offset);
|
|
System.arraycopy(bits, lo_offset, bs.bits, 0, len);
|
|
if (hi_offset < bits.length)
|
|
bs.bits[hi_offset - lo_offset] &= (1L << to) - 1;
|
|
return bs;
|
|
}
|
|
|
|
int len = Math.min(hi_offset, bits.length - 1);
|
|
int reverse = ~lo_bit;
|
|
int i;
|
|
for (i = 0; lo_offset < len; lo_offset++, i++)
|
|
bs.bits[i] = ((bits[lo_offset] >>> lo_bit)
|
|
| (bits[lo_offset + 1] << reverse));
|
|
if ((to & LONG_MASK) > lo_bit)
|
|
bs.bits[i++] = bits[lo_offset] >>> lo_bit;
|
|
if (hi_offset < bits.length)
|
|
bs.bits[i - 1] &= (1L << (to - from)) - 1;
|
|
return bs;
|
|
}
|
|
|
|
/**
|
|
* Returns a hash code value for this bit set. The hash code of
|
|
* two bit sets containing the same integers is identical. The algorithm
|
|
* used to compute it is as follows:
|
|
*
|
|
* Suppose the bits in the BitSet were to be stored in an array of
|
|
* long integers called <code>bits</code>, in such a manner that
|
|
* bit <code>k</code> is set in the BitSet (for non-negative values
|
|
* of <code>k</code>) if and only if
|
|
*
|
|
* <pre>
|
|
* ((k/64) < bits.length) && ((bits[k/64] & (1L << (bit % 64))) != 0)
|
|
* </pre>
|
|
*
|
|
* Then the following definition of the hashCode method
|
|
* would be a correct implementation of the actual algorithm:
|
|
*
|
|
* <pre>
|
|
* public int hashCode() {
|
|
* long h = 1234;
|
|
* for (int i = bits.length-1; i>=0; i--) {
|
|
* h ^= bits[i] * (i + 1);
|
|
* }
|
|
* return (int)((h >> 32) ^ h);
|
|
* }
|
|
* </pre>
|
|
*
|
|
* Note that the hash code values changes, if the set is changed.
|
|
*
|
|
* @return the hash code value for this bit set.
|
|
*/
|
|
public int hashCode()
|
|
{
|
|
long h = 1234;
|
|
for (int i = bits.length; i > 0; )
|
|
h ^= i * bits[--i];
|
|
return (int) ((h >> 32) ^ h);
|
|
}
|
|
|
|
/**
|
|
* Returns true if the specified BitSet and this one share at least one
|
|
* common true bit.
|
|
*
|
|
* @param set the set to check for intersection
|
|
* @return true if the sets intersect
|
|
* @throws NullPointerException if set is null
|
|
* @since 1.4
|
|
*/
|
|
public boolean intersects(BitSet set)
|
|
{
|
|
int i = Math.min(bits.length, set.bits.length);
|
|
while (--i >= 0)
|
|
if ((bits[i] & set.bits[i]) != 0)
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Returns true if this set contains no true bits.
|
|
*
|
|
* @return true if all bits are false
|
|
* @since 1.4
|
|
*/
|
|
public boolean isEmpty()
|
|
{
|
|
for (int i = bits.length - 1; i >= 0; i--)
|
|
if (bits[i] != 0)
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Returns the logical number of bits actually used by this bit
|
|
* set. It returns the index of the highest set bit plus one.
|
|
* Note that this method doesn't return the number of set bits.
|
|
*
|
|
* @return the index of the highest set bit plus one.
|
|
*/
|
|
public int length()
|
|
{
|
|
// Set i to highest index that contains a non-zero value.
|
|
int i;
|
|
for (i = bits.length - 1; i >= 0 && bits[i] == 0; --i)
|
|
;
|
|
|
|
// if i < 0 all bits are cleared.
|
|
if (i < 0)
|
|
return 0;
|
|
|
|
// Now determine the exact length.
|
|
long b = bits[i];
|
|
int len = (i + 1) * 64;
|
|
// b >= 0 checks if the highest bit is zero.
|
|
while (b >= 0)
|
|
{
|
|
--len;
|
|
b <<= 1;
|
|
}
|
|
|
|
return len;
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the next false bit, from the specified bit
|
|
* (inclusive).
|
|
*
|
|
* @param from the start location
|
|
* @return the first false bit
|
|
* @throws IndexOutOfBoundsException if from is negative
|
|
* @since 1.4
|
|
*/
|
|
public int nextClearBit(int from)
|
|
{
|
|
int offset = from >>> 6;
|
|
long mask = 1L << from;
|
|
while (offset < bits.length)
|
|
{
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
long h = bits[offset];
|
|
do
|
|
{
|
|
if ((h & mask) == 0)
|
|
return from;
|
|
mask <<= 1;
|
|
from++;
|
|
}
|
|
while (mask != 0);
|
|
mask = 1;
|
|
offset++;
|
|
}
|
|
return from;
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the next true bit, from the specified bit
|
|
* (inclusive). If there is none, -1 is returned. You can iterate over
|
|
* all true bits with this loop:<br>
|
|
* <pre>
|
|
* for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i + 1))
|
|
* { // operate on i here }
|
|
* </pre>
|
|
*
|
|
* @param from the start location
|
|
* @return the first true bit, or -1
|
|
* @throws IndexOutOfBoundsException if from is negative
|
|
* @since 1.4
|
|
*/
|
|
public int nextSetBit(int from)
|
|
{
|
|
int offset = from >>> 6;
|
|
long mask = 1L << from;
|
|
while (offset < bits.length)
|
|
{
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
long h = bits[offset];
|
|
do
|
|
{
|
|
if ((h & mask) != 0)
|
|
return from;
|
|
mask <<= 1;
|
|
from++;
|
|
}
|
|
while (mask != 0);
|
|
mask = 1;
|
|
offset++;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/**
|
|
* Performs the logical OR operation on this bit set and the
|
|
* given <code>set</code>. This means it builds the union
|
|
* of the two sets. The result is stored into this bit set, which
|
|
* grows as necessary.
|
|
*
|
|
* @param bs the second bit set
|
|
* @throws NullPointerException if bs is null
|
|
*/
|
|
public void or(BitSet bs)
|
|
{
|
|
ensure(bs.bits.length - 1);
|
|
for (int i = bs.bits.length - 1; i >= 0; i--)
|
|
bits[i] |= bs.bits[i];
|
|
}
|
|
|
|
/**
|
|
* Add the integer <code>bitIndex</code> to this set. That is
|
|
* the corresponding bit is set to true. If the index was already in
|
|
* the set, this method does nothing. The size of this structure
|
|
* is automatically increased as necessary.
|
|
*
|
|
* @param pos a non-negative integer.
|
|
* @throws IndexOutOfBoundsException if pos is negative
|
|
*/
|
|
public void set(int pos)
|
|
{
|
|
int offset = pos >>> 6;
|
|
ensure(offset);
|
|
// ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,
|
|
// so we'll just let that be our exception.
|
|
bits[offset] |= 1L << pos;
|
|
}
|
|
|
|
/**
|
|
* Sets the bit at the given index to the specified value. The size of
|
|
* this structure is automatically increased as necessary.
|
|
*
|
|
* @param index the position to set
|
|
* @param value the value to set it to
|
|
* @throws IndexOutOfBoundsException if index is negative
|
|
* @since 1.4
|
|
*/
|
|
public void set(int index, boolean value)
|
|
{
|
|
if (value)
|
|
set(index);
|
|
else
|
|
clear(index);
|
|
}
|
|
|
|
/**
|
|
* Sets the bits between from (inclusive) and to (exclusive) to true.
|
|
*
|
|
* @param from the start range (inclusive)
|
|
* @param to the end range (exclusive)
|
|
* @throws IndexOutOfBoundsException if from < 0 || from > to
|
|
* @since 1.4
|
|
*/
|
|
public void set(int from, int to)
|
|
{
|
|
if (from < 0 || from > to)
|
|
throw new IndexOutOfBoundsException();
|
|
if (from == to)
|
|
return;
|
|
int lo_offset = from >>> 6;
|
|
int hi_offset = to >>> 6;
|
|
ensure(hi_offset);
|
|
if (lo_offset == hi_offset)
|
|
{
|
|
bits[hi_offset] |= (-1L << from) & ((1L << to) - 1);
|
|
return;
|
|
}
|
|
|
|
bits[lo_offset] |= -1L << from;
|
|
bits[hi_offset] |= (1L << to) - 1;
|
|
for (int i = lo_offset + 1; i < hi_offset; i++)
|
|
bits[i] = -1;
|
|
}
|
|
|
|
/**
|
|
* Sets the bits between from (inclusive) and to (exclusive) to the
|
|
* specified value.
|
|
*
|
|
* @param from the start range (inclusive)
|
|
* @param to the end range (exclusive)
|
|
* @param value the value to set it to
|
|
* @throws IndexOutOfBoundsException if from < 0 || from > to
|
|
* @since 1.4
|
|
*/
|
|
public void set(int from, int to, boolean value)
|
|
{
|
|
if (value)
|
|
set(from, to);
|
|
else
|
|
clear(from, to);
|
|
}
|
|
|
|
/**
|
|
* Returns the number of bits actually used by this bit set. Note
|
|
* that this method doesn't return the number of set bits, and that
|
|
* future requests for larger bits will make this automatically grow.
|
|
*
|
|
* @return the number of bits currently used.
|
|
*/
|
|
public int size()
|
|
{
|
|
return bits.length * 64;
|
|
}
|
|
|
|
/**
|
|
* Returns the string representation of this bit set. This
|
|
* consists of a comma separated list of the integers in this set
|
|
* surrounded by curly braces. There is a space after each comma.
|
|
* A sample string is thus "{1, 3, 53}".
|
|
* @return the string representation.
|
|
*/
|
|
public String toString()
|
|
{
|
|
StringBuffer r = new StringBuffer("{");
|
|
boolean first = true;
|
|
for (int i = 0; i < bits.length; ++i)
|
|
{
|
|
long bit = 1;
|
|
long word = bits[i];
|
|
if (word == 0)
|
|
continue;
|
|
for (int j = 0; j < 64; ++j)
|
|
{
|
|
if ((word & bit) != 0)
|
|
{
|
|
if (! first)
|
|
r.append(", ");
|
|
r.append(64 * i + j);
|
|
first = false;
|
|
}
|
|
bit <<= 1;
|
|
}
|
|
}
|
|
return r.append("}").toString();
|
|
}
|
|
|
|
/**
|
|
* Performs the logical XOR operation on this bit set and the
|
|
* given <code>set</code>. This means it builds the symmetric
|
|
* remainder of the two sets (the elements that are in one set,
|
|
* but not in the other). The result is stored into this bit set,
|
|
* which grows as necessary.
|
|
*
|
|
* @param bs the second bit set
|
|
* @throws NullPointerException if bs is null
|
|
*/
|
|
public void xor(BitSet bs)
|
|
{
|
|
ensure(bs.bits.length - 1);
|
|
for (int i = bs.bits.length - 1; i >= 0; i--)
|
|
bits[i] ^= bs.bits[i];
|
|
}
|
|
|
|
/**
|
|
* Make sure the vector is big enough.
|
|
*
|
|
* @param lastElt the size needed for the bits array
|
|
*/
|
|
private final void ensure(int lastElt)
|
|
{
|
|
if (lastElt >= bits.length)
|
|
{
|
|
long[] nd = new long[lastElt + 1];
|
|
System.arraycopy(bits, 0, nd, 0, bits.length);
|
|
bits = nd;
|
|
}
|
|
}
|
|
}
|