org.xbib.standardnumber.checksum

Class DihedralGroup

java.lang.Object

org.xbib.standardnumber.checksum.DihedralGroup

All Implemented Interfaces:

Digit

public class DihedralGroup
extends java.lang.Object
implements Digit

Verhoeff’s algorithm for checksum computation.

1. Verhoeff, Error Detecting Decimal Codes, Mathematical Centre Tract 29, The Mathematical Centre, Amsterdam, 1969

Field Summary

Fields

Modifier and Type	Field and Description
private static int[][]	a The dihedral addition matrix A + B = a[A][B].
private static int[]	inverse The dihedral inverse map, A + inverse[A] = 0.
private static int[][]	p pThe ermutation weighting matrix P[position][value].

Constructor Summary

Constructors

Constructor and Description
DihedralGroup()

Method Summary

Modifier and Type	Method and Description
int	compute(java.lang.String digits) Computes the check digit value.
java.lang.String	encode(java.lang.String digits) Add check digits to a string containing digits.
int	getDigit(java.lang.String digits) Extract just the check digit from an encoded string.
java.lang.String	getNumber(java.lang.String digits) Extracts the raw data without the check digits.
boolean	verify(java.lang.String digits) Verify a string that has been encoded with a check digit.

Methods inherited from class java.lang.Object

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

Field Detail

a

private static final int[][] a

The dihedral addition matrix A + B = a[A][B].

inverse

private static final int[] inverse

The dihedral inverse map, A + inverse[A] = 0.

p

private static final int[][] p

pThe ermutation weighting matrix P[position][value].

Constructor Detail

DihedralGroup

public DihedralGroup()

Method Detail

encode

public java.lang.String encode(java.lang.String digits)

Description copied from interface: Digit

Add check digits to a string containing digits.

Specified by:

encode in interface Digit

Parameters:

digits - the input data string containing only digits '0'-'9'

Returns:

a new string containing data and check digits

verify

public boolean verify(java.lang.String digits)

Description copied from interface: Digit

Verify a string that has been encoded with a check digit.

Specified by:

verify in interface Digit

Parameters:

digits - input digits

Returns:

true if valid, false otherwise

compute

public int compute(java.lang.String digits)

Description copied from interface: Digit

Computes the check digit value.

Specified by:

compute in interface Digit

Parameters:

digits - - a string containing data

Returns:

an integer representing the check digit

getDigit

public int getDigit(java.lang.String digits)

Description copied from interface: Digit

Extract just the check digit from an encoded string.

Specified by:

getDigit in interface Digit

Parameters:

digits - input data containing check and data digits

Returns:

the check digit, as an int

getNumber

public java.lang.String getNumber(java.lang.String digits)

Description copied from interface: Digit

Extracts the raw data without the check digits.

Specified by:

getNumber in interface Digit

Returns:

a string without check digits