cryptix.util.math

Class BigRegister

Implemented Interfaces:
Cloneable, Serializable
Known Direct Subclasses:
TrinomialLFSR

public class BigRegister
extends java.lang.Object
implements Cloneable, Serializable

Utility class to manage a large bit-register of a given size as a mutable object.

The bits are indexed from 0 (rightmost) to size - 1, (leftmost) where size is this register's designated (at instantiation time) bit capacity.

Copyright © 1995-1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.2 $

Author:
Raif S. Naffah

Field Summary

static int
MAXIMUM_SIZE
Maximum allowed number of bits in a BigRegister object.

Constructor Summary

BigRegister(int size)
Instantiate a BigRegister of a given size with all its bits set to zeroes.

Method Summary

void
and(BigRegister source)
Compute this &= source.
void
andNot(BigRegister source)
Compute this &= ~source.
void
atRandom()
Fill this BigRegister object with random data generated from the default source.
void
atRandom(SecureRandom source)
Fill this BigRegister object with random data generated from a designated source.
int
byteValue()
Return the rightmost byte value in this BigRegister.
void
clearBit(int n)
Set the bit at the designated position to 0; ie.
Object
clone()
Return a reference to a duplicate of this.
int
compareTo(BigRegister x)
Compare this BigRegister's contents to that of the argument, returning -1, 0 or 1 for less than, equal to, or greater than comparison result.
int
countSetBits()
Return the number of bits set (to 1) in this.
void
flipBit(int n)
Flip the value of the bit at the designated position.
int
getBit(int n)
Return 1 or 0 if the designated bit was set or cleared respectively.
long
getBits(int n, int count)
Return count bits starting at offset n framed in a long, right justified and left padded with binary zeroes.
int
getSize()
Return the size of this object as specified at its instantiation time.
int
highestSetBit()
Return the index of the leftmost non-zero bit in this.
int
intValue()
Return the rightmost 32-bit value in this BigRegister as an int.
void
invertOrder()
Invert the bit order of the current contents of this.
boolean
isSameValue(BigRegister x)
Return true if the parameters of the BigRegister x (size and bits) are equal to this one; false otherwise.
void
load(byte[] source)
Copy the bit values from a byte array into this.
void
load(BigRegister source)
Copy the argument's value into this.
long
longValue()
Return the rightmost 64-bit value in this BigRegister as a long.
int
lowestSetBit()
Return the index of the rightmost non-zero bit in this.
void
not()
Compute this = ~this.
void
or(BigRegister source)
Compute this |= source.
void
reset()
Reset to zeroes all this BigRegister's bits.
void
rotateLeft(int n)
Circular left shift over the size of this register.
void
rotateRight(int n)
Circular right shift over the size of this register.
void
setBit(int n)
Set the bit at the designated position to 1.
void
setBits(int n, int count, long value)
Set count bits starting at offset n to a given value.
void
shiftLeft(int n)
Execute a left shift of this BigRegister's contents by a given number of bit positions.
void
shiftRight(int n)
Execute a right shift of this BigRegister's contents by a given number of bit positions.
boolean
testBit(int n)
Return true if the designated bit is set or false otherwise.
byte[]
toByteArray()
Return a copy of this BigRegister's contents in a byte array with the LSB at index position 0.
String
toString()
Return a formatted String representation of the binary contents of this.
BigRegister
valueOf(long n)
Return a BigRegister, of the same size as this set to the specified value.
void
xor(BigRegister source)
Compute this ^= source.

Field Details

MAXIMUM_SIZE

public static final int MAXIMUM_SIZE
Maximum allowed number of bits in a BigRegister object.

Field Value:
4096

Constructor Details

BigRegister

public BigRegister(int size)
Instantiate a BigRegister of a given size with all its bits set to zeroes.

Parameters:
size - Number of meaningful bits in this object.

See Also:
MAXIMUM_SIZE

Method Details

and

public void and(BigRegister source)
Compute this &= source.


andNot

public void andNot(BigRegister source)
Compute this &= ~source.


atRandom

public void atRandom()
Fill this BigRegister object with random data generated from the default source.


atRandom

public void atRandom(SecureRandom source)
Fill this BigRegister object with random data generated from a designated source.


byteValue

public int byteValue()
Return the rightmost byte value in this BigRegister.

Returns:
The rightmost byte value in this.


clearBit

public void clearBit(int n)
Set the bit at the designated position to 0; ie. clear it.

Parameters:
n - The bit position to alter.


clone

public Object clone()
Return a reference to a duplicate of this.


compareTo

public int compareTo(BigRegister x)
Compare this BigRegister's contents to that of the argument, returning -1, 0 or 1 for less than, equal to, or greater than comparison result.

Parameters:
x - A BigRegister object to compare to.

Returns:
-1, 0, +1 If the contents of this object are respectively less than, equal to, or greater than those of the argument.


countSetBits

public int countSetBits()
Return the number of bits set (to 1) in this.

Returns:
The number of set bits in this.


flipBit

public void flipBit(int n)
Flip the value of the bit at the designated position.

Parameters:
n - The bit position to alter.


getBit

public int getBit(int n)
Return 1 or 0 if the designated bit was set or cleared respectively.

Parameters:
n - The index of the bit to retrieve.


getBits

public long getBits(int n,
                    int count)
Return count bits starting at offset n framed in a long, right justified and left padded with binary zeroes.

Parameters:
n - The index of the first bit to retrieve.
count - Number of bits to retrieve.

Returns:
Right justified count bits starting from bit index n in a java long.


getSize

public int getSize()
Return the size of this object as specified at its instantiation time.

Returns:
The size of this object as specified at its instantiation time.


highestSetBit

public int highestSetBit()
Return the index of the leftmost non-zero bit in this.

Returns:
Index of the leftmost non-zero bit in this, or -1 if all bits are zeroes.


intValue

public int intValue()
Return the rightmost 32-bit value in this BigRegister as an int.

Returns:
The rightmost 32-bit value in this as an int.


invertOrder

public void invertOrder()
Invert the bit order of the current contents of this.


isSameValue

public boolean isSameValue(BigRegister x)
Return true if the parameters of the BigRegister x (size and bits) are equal to this one; false otherwise.

NOTE: the equals method is not used, because this is a mutable object (see the requirements for equals in the Java Language Spec).

Parameters:
x - BigRegister to test for equality.

Returns:
true iff x has equal size and contents.


load

public void load(byte[] source)
Copy the bit values from a byte array into this. Byte array order is assumed to have its Least Significant Byte (LSB) at index position 0. This format mirrors that of the output returned by the toByteArray() method.

Bits unprovided for in the source array are cleared. It is a more tolerant way of initialising a register than that obtained by invoking the same method with a BigRegister argument.

Parameters:
source - The source bits organised in a byte array with their LSB at index 0.

See Also:
toByteArray()


load

public void load(BigRegister source)
Copy the argument's value into this.


longValue

public long longValue()
Return the rightmost 64-bit value in this BigRegister as a long.

Returns:
The rightmost 64-bit value in this as a long.


lowestSetBit

public int lowestSetBit()
Return the index of the rightmost non-zero bit in this.

Returns:
Index of the rightmost non-zero bit in this, or -1 if all bits are zeroes.


not

public void not()
Compute this = ~this.


or

public void or(BigRegister source)
Compute this |= source.


reset

public void reset()
Reset to zeroes all this BigRegister's bits.


rotateLeft

public void rotateLeft(int n)
Circular left shift over the size of this register.

Effectively compute this = this << n | this >> (size - n).

If the number of positions to rotate by is negative, then a right instead of left rotation is executed.


rotateRight

public void rotateRight(int n)
Circular right shift over the size of this register.

Effectively compute this = this >> n | this << (size - n).

If the number of positions to rotate by is negative, then a left instead of right rotation is executed.


setBit

public void setBit(int n)
Set the bit at the designated position to 1.

Parameters:
n - The bit position to alter.


setBits

public void setBits(int n,
                    int count,
                    long value)
Set count bits starting at offset n to a given value.

Parameters:
n - The index of the first bit to set.
count - Number of bits to set.
value - New bits value, right justified in a long.


shiftLeft

public void shiftLeft(int n)
Execute a left shift of this BigRegister's contents by a given number of bit positions. If the number is negative, a right shift is executed.

Parameters:
n - Number of bit positions to shift by. If this value is negative then a shift in the opposite direction is executed.


shiftRight

public void shiftRight(int n)
Execute a right shift of this BigRegister's contents by a given number of bit positions. If the number is negative, a left shift is executed.

Parameters:
n - Number of bit positions to shift by. If this value is negative then a shift in the opposite direction is executed.


testBit

public boolean testBit(int n)
Return true if the designated bit is set or false otherwise.

Parameters:
n - Index of the bit to test.

Returns:
true if the designated bit is set or false otherwise.


toByteArray

public byte[] toByteArray()
Return a copy of this BigRegister's contents in a byte array with the LSB at index position 0. This format is compatible with the load([B) method of this class.

Returns:
The bits of this in a byte array with the LSB at index position 0.


toString

public String toString()
Return a formatted String representation of the binary contents of this.

Returns:
A formatted string representation of the binary contents of this.


valueOf

public BigRegister valueOf(long n)
Return a BigRegister, of the same size as this set to the specified value.

Returns:
A BigRegister, of the same size as this set to the specified value.


xor

public void xor(BigRegister source)
Compute this ^= source.