com.google.uzaygezen.core

Class BitSetMath

java.lang.Object

com.google.uzaygezen.core.BitSetMath

public class BitSetMath
extends Object

BitSet utilities. Unless otherwise specified, when seen as numbers the bit sets here are considered to be in little-endian format.

Author:

Daniel Aioanei

Method Summary

Methods

Modifier and Type	Method and Description
static void	copy(BitSet from, BitSet to) Makes the bit set to equal to from.
static void	extractBitRange(BitSet chi, int from, int to, BitSet r) Unfortunately BitSet.get cannot reuse an existing instance so we have this method for exactly that purpose.
static void	grayCode(BitSet i) Computes i's gray code in-place.
static void	grayCodeInverse(BitSet i) Given the gray code of a number, it computes that number in-place.
static int	increment(BitSet i) Increments the given bit set in-place, looking at it as a little-endian value with no bit sign (always non-negative).
static long	littleEndianBitSetToNonNegativeLong(BitSet bs) Produces a long from a little endian bit set.
static void	nonNegativeLongToLittleEndianBitSet(long value, BitSet bs) Computes the little endian representation of a non-negative long.
static void	rotate(BitSet bs, int n, int count) Rotates the lowest n bits by count positions in-place.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

increment

public static int increment(BitSet i)

Increments the given bit set in-place, looking at it as a little-endian value with no bit sign (always non-negative).

Returns:

trailing set bit count of the result. Same as trailing clear bit count of the input.

rotate

public static void rotate(BitSet bs,
          int n,
          int count)

Rotates the lowest n bits by count positions in-place. The bits of index higher than or equal to n are not affected.

Parameters:

bs - input-output

n - the number of lowest bits to rotate

count - right rotation if positive; left rotation if negative; no rotation at all if zero.

extractBitRange

public static void extractBitRange(BitSet chi,
                   int from,
                   int to,
                   BitSet r)

Unfortunately BitSet.get cannot reuse an existing instance so we have this method for exactly that purpose.

Parameters:

chi - original bit set to extract bits from

from - inclusive start of range to extract

to - exclusive end of range to extract

r - output

grayCode

public static void grayCode(BitSet i)

Computes i's gray code in-place.

Parameters:

i - input-output

grayCodeInverse

public static void grayCodeInverse(BitSet i)

Given the gray code of a number, it computes that number in-place.

Parameters:

i - input-output

copy

public static void copy(BitSet from,
        BitSet to)

Makes the bit set to equal to from.

Parameters:

from - source

to - destination

littleEndianBitSetToNonNegativeLong

public static long littleEndianBitSetToNonNegativeLong(BitSet bs)

Produces a long from a little endian bit set.

Parameters:

bs - little endian base 2 number representation

Returns:

the same number as bs, but represented as long

nonNegativeLongToLittleEndianBitSet

public static void nonNegativeLongToLittleEndianBitSet(long value,
                                       BitSet bs)

Computes the little endian representation of a non-negative long. This is the inverse of littleEndianBitSetToNonNegativeLong(java.util.BitSet).

Parameters:

value - input

bs - output