Isbn13 Class

Definition

Namespace

Bodu.IO.Hashing.CheckDigits

Assembly

Bodu.IO.Hashing.dll

Package

Bodu.IO.Hashing 1.0.0

Source

Isbn13.cs

Computes the check digit of a 13-digit International Standard Book Number using the ISBN-13 weighted modulus-10 algorithm. This class cannot be inherited.

public sealed class Isbn13 : CheckDigitAlgorithm

Inheritance

object

CheckValueAlgorithm

CheckDigitAlgorithm

Isbn13

Inherited Members

CheckDigitAlgorithm.GetCurrentCheckValue()

CheckValueAlgorithm.Append(char)

CheckValueAlgorithm.CheckLength

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Extension Methods

ComparableExtensions.AtLeast<T>(T, T, IComparer<T>)

ComparableExtensions.AtMost<T>(T, T, IComparer<T>)

ComparableExtensions.IsEqualTo<T>(T, T, IComparer<T>)

ComparableExtensions.Max<T>(T, T, IComparer<T>)

ComparableExtensions.Min<T>(T, T, IComparer<T>)

Examples

// Single-call computation against the 12-digit body.
char check = Isbn13.Compute("978030640615");   // '7'

// Full-sequence validation.
bool ok = Isbn13.IsValid("9780306406157");     // true

// Streaming use when the body is built up incrementally.
var algo = new Isbn13();
algo.Append("978030640615");
char d = algo.GetCurrentCheckDigit();          // '7'

Remarks

The ISBN-13 check scheme, introduced in 2007 by the International ISBN Agency, alternates weights of 1 and 3 across the twelve body digits - the rightmost data digit receives weight 3 - and the check digit is chosen so that the resulting weighted sum is a multiple of ten.

The same algorithm underpins the EAN-13, UPC-A, GTIN-8, and GTIN-14 barcode families - see Ean13 and its siblings for strict-length variants.

Worked example. For the body "978030640615", the computed check digit is '7', and the resulting ISBN-13 "9780306406157" is therefore valid.

important

This algorithm is not cryptographically secure and should not be used for password hashing, digital signatures, or integrity validation in security-sensitive applications.

Constructors

Isbn13()

Initializes a new instance of the Isbn13 class.

public Isbn13()

Properties

AlgorithmName

Gets the canonical name of the algorithm, suitable for diagnostic output and logging.

public override string AlgorithmName { get; }

Property Value

string

A short, stable identifier such as "Luhn", "IBAN", or "ISO 7064 MOD 97-10".

Methods

Append(ReadOnlySpan<char>)

Absorbs the supplied characters into the running check-value state.

public override void Append(ReadOnlySpan<char> body)

Parameters

body ReadOnlySpan<char>

The characters to append. Each element must belong to the algorithm's accepted input alphabet. An empty span is a permitted no-op.

Exceptions

ArgumentOutOfRangeException

Thrown when body contains any character outside the algorithm's accepted input alphabet.

Compute(ReadOnlySpan<char>)

Computes the ISBN-13 check digit for the supplied body of decimal digits without allocating a streaming instance.

public static char Compute(ReadOnlySpan<char> body)

Parameters

body ReadOnlySpan<char>

The body characters. Each must be an ASCII decimal digit ('0' to '9').

Returns

char

The check digit as an ASCII character in the range '0' to '9'.

Exceptions

ArgumentOutOfRangeException

Thrown when body contains any character outside the range '0' to '9'.

GetCurrentCheckDigit()

Returns the check digit computed for the body absorbed since the last Reset() (or since construction).

public override char GetCurrentCheckDigit()

Returns

char

The check digit as an ASCII character in the range '0' to '9'. For an empty body all built-in algorithms return '0'.

Remarks

This call is non-destructive; the running state is unaffected and the method may be invoked any number of times with identical results between appends.

IsValid(ReadOnlySpan<char>)

Determines whether the supplied sequence, comprising a twelve-digit body followed by a trailing ISBN-13 check digit, is consistent - that is, whether the weighted sum evaluates to a multiple of ten.

public static bool IsValid(ReadOnlySpan<char> digitsIncludingCheck)

Parameters

digitsIncludingCheck ReadOnlySpan<char>

The complete sequence including the trailing check digit.

Returns

bool

true if the sequence evaluates as valid under ISBN-13; otherwise, false - including the case where digitsIncludingCheck is empty or contains a character outside the range '0' to '9'.

Reset()

Resets the algorithm to its initial state, discarding any characters previously absorbed.

public override void Reset()

Remarks

Equivalent in behavior to constructing a fresh instance of the same concrete type.

Applies to

Product	Versions
.NET	8, 10