AbaRoutingNumber Class

Definition

Namespace

Bodu.IO.Hashing.CheckDigits

Assembly

Bodu.IO.Hashing.dll

Package

Bodu.IO.Hashing 1.0.0

Source

AbaRoutingNumber.cs

Computes the check digit of a 9-digit American Bankers Association (ABA) routing transit number using the weighted modulus-10 scheme specified by the US Federal Reserve. This class cannot be inherited.

public sealed class AbaRoutingNumber : CheckDigitAlgorithm

Inheritance

object

CheckValueAlgorithm

CheckDigitAlgorithm

AbaRoutingNumber

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 8-digit body.
char check = AbaRoutingNumber.Compute("01100001");   // '5'

// Full-sequence validation.
bool ok = AbaRoutingNumber.IsValid("011000015");     // true

// Streaming use when the body is built up incrementally.
var algo = new AbaRoutingNumber();
algo.Append("01100001");
char d = algo.GetCurrentCheckDigit();                // '5'

Remarks

The ABA scheme applies the cyclic weight pattern {3, 7, 1} to the first eight digits (weights 3, 7, 1, 3, 7, 1, 3, 7 from left to right). The check digit is chosen so that the full nine-digit sequence yields a weighted sum that is a multiple of ten.

The static helpers on this type enforce a strict 8-digit body length (9-digit full sequence) to match the ABA specification; the streaming surface is length-agnostic to permit chunked input.

Worked example. For the body "01100001" - the leading 8 digits of the Federal Reserve Bank of Boston's routing number - the computed check digit is '5', and the resulting sequence "011000015" 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

AbaRoutingNumber()

Initializes a new instance of the AbaRoutingNumber class.

public AbaRoutingNumber()

Fields

BodyLength

The required body length of 8 decimal digits.

public const int BodyLength = 8

Field Value

int

SequenceLength

The required full-sequence length of 9 decimal digits.

public const int SequenceLength = 9

Field Value

int

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 ABA routing-number 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'.

Remarks

This helper is length-tolerant to support streaming and partial-body use; IsValid(ReadOnlySpan<char>) enforces the strict SequenceLength domain contract for full validation.

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 an eight-digit body followed by a trailing ABA check digit, is consistent.

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 is exactly SequenceLength digits and evaluates as valid under the ABA scheme; otherwise, false - including the case where digitsIncludingCheck is empty, the length is wrong, or a non-digit character is present.

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