MultiCharCheckDigitAlgorithm Class

Definition

Namespace

Bodu.IO.Hashing.CheckDigits

Assembly

Bodu.IO.Hashing.dll

Package

Bodu.IO.Hashing 1.0.0

Source

MultiCharCheckDigitAlgorithm.cs

Represents the abstract base class from which check-digit algorithms that emit a fixed-length multi-character check code - most notably ISO 7064 MOD 97-10 and its derivatives (IBAN, LEI) - derive.

public abstract class MultiCharCheckDigitAlgorithm : CheckValueAlgorithm

Inheritance

object

CheckValueAlgorithm

MultiCharCheckDigitAlgorithm

Derived

Iban

Iso7064Mod97_10

Lei

Inherited Members

CheckValueAlgorithm.Append(ReadOnlySpan<char>)

CheckValueAlgorithm.Append(char)

CheckValueAlgorithm.Reset()

CheckValueAlgorithm.AlgorithmName

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

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

// Use a concrete derivative through the abstract surface - IBAN emits a two-digit check.
MultiCharCheckDigitAlgorithm algo = new Iban();
algo.Append("GBWEST12345698765432");                 // country code + BBAN

Span<char> check = stackalloc char[algo.CheckLength];
algo.GetCurrentCheckDigits(check);                   // "82"

Remarks

Parallel in design to CheckDigitAlgorithm, this base generalizes the output from a single character to a run of CheckLength decimal digits, and broadens the input to whichever subset of ASCII the concrete algorithm accepts via InputAlphabet.

Like the rest of this family, the type is intentionally separate from the byte-stream oriented NonCryptographicHashAlgorithm and does not derive from it. A non-cryptographic hash produces a fixed-length opaque byte digest over arbitrary input; a check code performs error detection over a constrained ASCII text alphabet and emits a short run of char values. The families are kept distinct by design rather than unified under one base type.

The streaming surface - Append(ReadOnlySpan<char>), Reset(), and the two GetCurrentCheckDigits overloads - will nonetheless feel familiar to anyone who has used a hash algorithm: input is accumulated, the computation can be restarted, and reading the current check code is non-destructive and idempotent. That resemblance is incidental convenience, not a shared contract. Concrete implementations document their empty-body behavior.

Instances are not thread-safe. Each thread that needs a running check should construct its own instance.

important

Check-digit algorithms are error-detection primitives, not cryptographic functions. They must not be used for password hashing, digital signatures, or integrity validation in security-sensitive applications.

Constructors

MultiCharCheckDigitAlgorithm()

Initializes a new instance of the MultiCharCheckDigitAlgorithm class.

protected MultiCharCheckDigitAlgorithm()

Properties

CheckLength

Gets the fixed number of decimal-digit characters emitted as the trailing check code.

public override abstract int CheckLength { get; }

Property Value

int

A positive integer; for example, 2 for ISO 7064 MOD 97-10.

InputAlphabet

Gets the subset of ASCII from which this algorithm accepts body characters.

public abstract CheckDigitInputAlphabet InputAlphabet { get; }

Property Value

CheckDigitInputAlphabet

The declared input alphabet.

Methods

GetCurrentCheckDigits()

Returns the current check code as a newly allocated string.

public string GetCurrentCheckDigits()

Returns

string

A string of length CheckLength containing the trailing check characters.

Remarks

Allocating convenience wrapper over GetCurrentCheckDigits(Span<char>). Prefer the span overload in hot paths where the allocation is undesirable.

GetCurrentCheckDigits(Span<char>)

Writes the current check code into the supplied destination span.

public abstract int GetCurrentCheckDigits(Span<char> destination)

Parameters

destination Span<char>

The span to receive the trailing check characters. Must be at least CheckLength in length.

Returns

int

The number of characters written, always equal to CheckLength.

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.

Exceptions

ArgumentException

Thrown when destination is shorter than CheckLength.

GetCurrentCheckValue()

Returns the check value computed for the body absorbed since the last Reset() (or since construction) as a newly allocated string.

public override sealed string GetCurrentCheckValue()

Returns

string

A string of length CheckLength containing the check value.

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. The single-character branches also expose the result as a char via GetCurrentCheckDigit(), which avoids the string allocation.

Applies to

Product	Versions
.NET	8, 10

See Also

CheckDigitAlgorithm

AlphanumericCheckDigitAlgorithm

NonCryptographicHashAlgorithm