umontreal.iro.lecuyer.util

Class BitVector

java.lang.Object

umontreal.iro.lecuyer.util.BitVector

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public class BitVector
extends java.lang.Object
implements java.io.Serializable, java.lang.Cloneable

This class implements vectors of bits and the operations needed to use them. The vectors can be of arbitrary length. The operations provided are all the binary operations available to the int and long primitive types in Java.

All bit operations are present in two forms: a normal form and a self form. The normal form returns a newly created object containing the result, while the self form puts the result in the calling object (this). The return value of the self form is the calling object itself. This is done to allow easier manipulation of the results, making it possible to chain operations.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
BitVector(BitVector that) Creates a copy of the BitVector that.
BitVector(int length) Creates a new BitVector of length length with all its bits set to 0.
BitVector(int[] vect) Creates a new BitVector using the data in vect.
BitVector(int[] vect, int length) Creates a new BitVector of length length using the data in vect.

Method Summary

Modifier and Type	Method and Description
BitVector	and(BitVector that) Returns a BitVector which is the result of the and operator with both the this and that BitVector's.
java.lang.Object	clone() Creates a copy of the BitVector.
void	enlarge(int size) Resizes the BitVector so that its length is equal to size.
void	enlarge(int size, boolean filling) Resizes the BitVector so that its length is equal to size.
boolean	equals(BitVector that) Verifies if two BitVector's have the same length and the same data.
boolean	getBool(int pos) Gives the value of the bit in position pos.
int	getInt(int pos) Returns an int containing all the bits in the interval [pos×32,pos×32 + 31].
BitVector	not() Returns a BitVector which is the result of the not operator on the current BitVector.
BitVector	or(BitVector that) Returns a BitVector which is the result of the or operator with both the this and that BitVector's.
boolean	scalarProduct(BitVector that) Returns the scalar product of two BitVector's modulo 2.
BitVector	selfAnd(BitVector that) Applies the and operator on this with that.
BitVector	selfNot() Applies the not operator on the current BitVector and returns it.
BitVector	selfOr(BitVector that) Applies the or operator on this with that.
BitVector	selfShift(int j) Shift all the bits of the current BitVector j positions to the right if j is positive, and j positions to the left if j is negative.
BitVector	selfXor(BitVector that) Applies the xor operator on this with that.
void	setBool(int pos, boolean value) Sets the value of the bit in position pos.
BitVector	shift(int j) Returns a BitVector equal to the original with all the bits shifted j positions to the right if j is positive, and shifted j positions to the left if j is negative.
int	size() Returns the length of the BitVector.
java.lang.String	toString() Returns a string containing all the bits of the BitVector, starting with the highest order bit and finishing with the lowest order bit.
BitVector	xor(BitVector that) Returns a BitVector which is the result of the xor operator applied on this and that.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

BitVector

public BitVector(int length)

Creates a new BitVector of length length with all its bits set to 0.

Parameters:

length - the length of the BitVector

BitVector

public BitVector(int[] vect,
                 int length)

Creates a new BitVector of length length using the data in vect. Component vect[0] makes the 32 lowest order bits, with vect[1] being the 32 next lowest order bits, and so on. The normal bit order is then used to fill the 32 bits (the first bit is the lowest order bit and the last bit is largest order bit). Note that the sign bit is used as the largest order bit.

Parameters:

vect - the bits data

length - the length of the vector

Throws:

java.lang.IllegalArgumentException - when the length of vect is not compatible with the length provided

BitVector

public BitVector(int[] vect)

Creates a new BitVector using the data in vect. The length of the BitVector is always equals to 32 times the length of vect.

Parameters:

vect - the bits data

BitVector

public BitVector(BitVector that)

Creates a copy of the BitVector that.

Parameters:

that - the BitVector to copy

Method Detail

clone

public java.lang.Object clone()

Creates a copy of the BitVector.

Overrides:

clone in class java.lang.Object

Returns:

a deep copy of the BitVector

equals

public boolean equals(BitVector that)

Verifies if two BitVector's have the same length and the same data.

Parameters:

that - the other BitVector to compare to

Returns:

if the two BitVector's are identiqual

size

public int size()

Returns the length of the BitVector.

Returns:

the length of the BitVector

enlarge

public void enlarge(int size,
                    boolean filling)

Resizes the BitVector so that its length is equal to size. If the BitVector is enlarged, then the newly added bits are given the value 1 if filling is set to true and 0 otherwise.

Parameters:

size - the new size of the BitVector

filling - the state of the new bits

enlarge

public void enlarge(int size)

Resizes the BitVector so that its length is equal to size. Any new bit added is set to 0.

Parameters:

size - the new size of the BitVector

getBool

public boolean getBool(int pos)

Gives the value of the bit in position pos. If the value is 1, returns true; otherwise, returns false.

Parameters:

pos - the position of the checked bit

Returns:

the value of the bit as a boolean

Throws:

java.lang.ArrayIndexOutOfBoundsException - if pos is outside the range of the BitVector

setBool

public void setBool(int pos,
                    boolean value)

Sets the value of the bit in position pos. If value is equal to true, sets it to 1; otherwise, sets it to 0.

Parameters:

pos - the position of the bit to modify

value - the new value of the bit as a boolean

Throws:

java.lang.ArrayIndexOutOfBoundsException - if pos is outside the range of the BitVector

getInt

public int getInt(int pos)

Returns an int containing all the bits in the interval [pos×32,pos×32 + 31].

Parameters:

pos - the selected position

Returns:

the int at the specified position

Throws:

java.lang.ArrayIndexOutOfBoundsException - if pos is outside the range of the BitVector

toString

public java.lang.String toString()

Returns a string containing all the bits of the BitVector, starting with the highest order bit and finishing with the lowest order bit. The bits are grouped by groups of 8 bits for ease of reading.

Overrides:

toString in class java.lang.Object

Returns:

all the bits of the BitVector

not

public BitVector not()

Returns a BitVector which is the result of the not operator on the current BitVector. The not operator is equivalent to the ~ operator in Java and thus swap all bits (bits previously set to 0 become 1 and bits previously set to 1 become 0).

Returns:

the effect of the not operator

selfNot

public BitVector selfNot()

Applies the not operator on the current BitVector and returns it.

Returns:

the BitVector itself

xor

public BitVector xor(BitVector that)

Returns a BitVector which is the result of the xor operator applied on this and that. The xor operator is equivalent to the ^ operator in Java. All bits which were set to 0 in one of the vector and to 1 in the other vector are set to 1. The others are set to 0. This is equivalent to the addition in modulo 2 arithmetic.

Parameters:

that - the second operand to the xor operator

Returns:

the result of the xor operation

selfXor

public BitVector selfXor(BitVector that)

Applies the xor operator on this with that. Stores the result in this and returns it.

Parameters:

that - the second operand to the xor operator

Returns:

this

and

public BitVector and(BitVector that)

Returns a BitVector which is the result of the and operator with both the this and that BitVector's. The and operator is equivalent to the & operator in Java. Only bits which are set to 1 in both this and that are set to 1 in the result, all the others are set to 0.

Parameters:

that - the second operand to the and operator

Returns:

the result of the and operation

selfAnd

public BitVector selfAnd(BitVector that)

Applies the and operator on this with that. Stores the result in this and returns it.

Parameters:

that - the second operand to the and operator

Returns:

this

or

public BitVector or(BitVector that)

Returns a BitVector which is the result of the or operator with both the this and that BitVector's. The or operator is equivalent to the | operator in Java. Only bits which are set to 0 in both this and that are set to to 0 in the result, all the others are set to 1.

Parameters:

that - the second operand to the or operator

Returns:

the result of the or operation

selfOr

public BitVector selfOr(BitVector that)

Applies the or operator on this with that. Stores the result in this and returns it.

Parameters:

that - the second operand to the or operator

Returns:

this

shift

public BitVector shift(int j)

Returns a BitVector equal to the original with all the bits shifted j positions to the right if j is positive, and shifted j positions to the left if j is negative. The new bits that appears to the left or to the right are set to 0. If j is positive, this operation is equivalent to the »> operator in Java, otherwise, it is equivalent to the « operator.

Parameters:

j - the size of the shift

Returns:

the shifted BitVector

selfShift

public BitVector selfShift(int j)

Shift all the bits of the current BitVector j positions to the right if j is positive, and j positions to the left if j is negative. The new bits that appears to the left or to the rigth are set to 0. Returns this.

Parameters:

j - the size of the shift

Returns:

this

scalarProduct

public boolean scalarProduct(BitVector that)

Returns the scalar product of two BitVector's modulo 2. It returns true if there is an odd number of bits with a value of 1 in the result of the and operator applied on this and that, and returns false otherwise.

Parameters:

that - the other BitVector with which to do the scalar product

Returns:

the scalar product