Table of Contents

CrcStandard Class

Definition

Namespace
Bodu.IO.Hashing.Checksums
Assembly
Bodu.IO.Hashing.dll
Package
Bodu.IO.Hashing 1.0.0
Source
CrcStandard.Catalog.cs

Immutable parameter bundle that fully describes a CRC variant - width, polynomial, initial value, input/output bit reflection, and final XOR - and serves as the lookup key into the RevEng catalogue used by Crc.

public sealed class CrcStandard : ISerializable, IEquatable<CrcStandard>
Inheritance
CrcStandard
Implements
Inherited Members
Extension Methods

Examples

using Bodu.IO.Hashing.Checksums;

// 1. Direct named accessor - most callers want exactly this.
var crc = new Crc(CrcStandard.CRC32_ISOHDLC);

// 2. Data-driven look-up - pick the variant from a configuration value.
CrcStandards configured = Enum.Parse<CrcStandards>(config["CrcVariant"]);
var configuredCrc = new Crc(CrcStandard.Get(configured));

// 3. Look-up by alias - accept legacy or vendor names supplied by users.
CrcStandard pkzip = CrcStandard.FromName("PKZIP");      // same instance as CRC32_ISOHDLC
CrcStandard ccitt = CrcStandard.FromName("CRC-CCITT");  // resolves to CRC16_KERMIT

// 4. Custom variant (not in the RevEng catalogue): a 12-bit CRC with bespoke parameters.
var custom = new CrcStandard(
    name:         "CRC-12/MY-SPEC",
    size:         12,
    polynomial:   0x80F,
    initialValue: 0x000,
    reflectIn:    false,
    reflectOut:   false,
    xOrOut:       0x000);

Remarks

Every CRC variant in the wild differs from every other along the same five dimensions - the polynomial, the initial register value, whether input bits are reflected as they enter the register, whether the final register is reflected on the way out, and what value the register is XOR-ed with at the end. CRC-32/ISO-HDLC and CRC-32/BZIP2 share a polynomial but disagree on reflection; CRC-16/MODBUS and CRC-16/USB share nearly everything but the initial value. CrcStandard captures one such parameter bundle as an immutable, equatable, serializable value, decoupling the choice of variant from the engine that runs it.

Three ways to obtain a standard.

How it pairs with Crc. The hash engine reads Polynomial and ReflectIn to fetch (or build) a precomputed lookup table from CrcLookupTableCache, seeds the running register with InitialValue, and applies ReflectOut + XOrOut when emitting the final digest. Multiple Crc instances configured with the same CrcStandard share the same lookup table, so creating fresh engines for the same standard is inexpensive.

Equality and serialization. CrcStandard is a value-style type: two instances are equal iff every parameter matches (the Name is informational only and does not affect identity). ISerializable support is provided so a chosen standard can survive process boundaries unchanged.

Coverage and limits. Sizes are constrained to MinSize..MaxSize bits; any wider variant in the RevEng catalogue (currently only CRC-82/DARC) is intentionally omitted because it will not fit in the ulong-backed register. Instances are immutable and therefore safe to share across threads.

Constructors

CrcStandard(string, int, ulong, ulong, bool, bool, ulong)

Initializes a new instance of the CrcStandard class with the specified parameters.

public CrcStandard(string name, int size, ulong polynomial, ulong initialValue, bool reflectIn, bool reflectOut, ulong xOrOut)

Parameters

name string

The name of the CRC standard.

size int

The size, in bits, of the CRC checksum.

polynomial ulong

The CRC polynomial value.

initialValue ulong

The initial value used for the CRC calculation.

reflectIn bool

Indicates whether to reflect the input during the CRC calculation.

reflectOut bool

Indicates whether to reflect the output during the CRC calculation.

xOrOut ulong

The value to XOR the final output with.

Exceptions

ArgumentException

name is null or empty.

ArgumentOutOfRangeException

size is less than MinSize or greater than MaxSize; or polynomial, initialValue, or xOrOut does not fit in size bits.

Fields

MaxSize

The maximum size allowed for a CRC standard (in bits).

public const int MaxSize = 64

Field Value

int

MinSize

The minimum size allowed for a CRC standard (in bits).

public const int MinSize = 1

Field Value

int

Properties

All

Gets a snapshot of every supported CRC standard in the catalogue, in declaration order.

public static IReadOnlyList<CrcStandard> All { get; }

Property Value

IReadOnlyList<CrcStandard>

A read-only list containing one CrcStandard per canonical entry.

Remarks

The backing array is built lazily on first access and then memoised, so merely loading this type does not construct any CrcStandard instances. Aliases are not included as separate entries; use FromName(string) to resolve an alias to its canonical instance.

CRC16_ARC

Gets the CRC-16/ARC CRC standard (aliases include CRC-16, CRC-IBM, CRC-16/LHA). The de-facto generic 16-bit CRC.

public static CrcStandard CRC16_ARC { get; }

Property Value

CrcStandard
See Also

CRC16_IBM3740

Gets the CRC-16/IBM-3740 CRC standard (aliases CRC-16/AUTOSAR, CRC-16/CCITT-FALSE). The widely-used "CCITT-false" variant.

public static CrcStandard CRC16_IBM3740 { get; }

Property Value

CrcStandard
See Also

CRC16_KERMIT

Gets the CRC-16/KERMIT CRC standard (aliases CRC-16/BLUETOOTH, CRC-16/CCITT, CRC-CCITT). Used by Kermit and Bluetooth.

public static CrcStandard CRC16_KERMIT { get; }

Property Value

CrcStandard
See Also

CRC16_MODBUS

Gets the CRC-16/MODBUS CRC standard (alias MODBUS). Used by Modbus RTU over serial.

public static CrcStandard CRC16_MODBUS { get; }

Property Value

CrcStandard
See Also

CRC16_XMODEM

Gets the CRC-16/XMODEM CRC standard (aliases CRC-16/ACORN, XMODEM, ZMODEM). Used by XMODEM and ZMODEM.

public static CrcStandard CRC16_XMODEM { get; }

Property Value

CrcStandard
See Also

CRC32_BZIP2

Gets the CRC-32/BZIP2 CRC standard (aliases CRC-32/AAL5, CRC-32/DECT-B, B-CRC-32). Used by bzip2 and AAL5.

public static CrcStandard CRC32_BZIP2 { get; }

Property Value

CrcStandard
See Also

CRC32_ISCSI

Gets the CRC-32/ISCSI CRC standard (aliases CRC-32C, CRC-32/CASTAGNOLI, CRC-32/NVME, CRC-32/BASE91-C, CRC-32/INTERLAKEN). Castagnoli polynomial used by iSCSI, SCTP, Btrfs, ext4, NVMe, and many modern protocols.

public static CrcStandard CRC32_ISCSI { get; }

Property Value

CrcStandard
See Also

CRC32_ISOHDLC

Gets the CRC-32/ISO-HDLC CRC standard (aliases CRC-32, PKZIP, CRC-32/XZ, CRC-32/ADCCP, CRC-32/V-42). The canonical CRC-32 used by zlib, PNG, Ethernet, PKZIP, and the default standard used by Crc().

public static CrcStandard CRC32_ISOHDLC { get; }

Property Value

CrcStandard

Remarks

Width 32, polynomial 0x04C11DB7, initial value 0xFFFFFFFF, reflected input and output, final XOR 0xFFFFFFFF.

See Also

CRC64_ECMA182

Gets the CRC-64/ECMA-182 CRC standard (alias CRC-64). Specified by ECMA-182 for DLT tape formats.

public static CrcStandard CRC64_ECMA182 { get; }

Property Value

CrcStandard
See Also

CRC64_XZ

Gets the CRC-64/XZ CRC standard (alias CRC-64/GO-ECMA). Used by the XZ compressed file format and the Go crc64 ECMA table.

public static CrcStandard CRC64_XZ { get; }

Property Value

CrcStandard
See Also

CRC8_MAXIMDOW

Gets the CRC-8/MAXIM-DOW CRC standard (aliases CRC-8/MAXIM, DOW-CRC). Used by Maxim / Dallas 1-Wire devices.

public static CrcStandard CRC8_MAXIMDOW { get; }

Property Value

CrcStandard
See Also

CRC8_SMBUS

Gets the CRC-8/SMBUS CRC standard (alias CRC-8). Width 8, polynomial 0x07, initial value 0x00, no reflection, XOR out 0x00.

public static CrcStandard CRC8_SMBUS { get; }

Property Value

CrcStandard

Remarks

The canonical "CRC-8" used by SMBus (System Management Bus) and the de-facto generic 8-bit CRC.

See Also

InitialValue

Gets the initial value used in the CRC calculation.

public ulong InitialValue { get; }

Property Value

ulong

The initial value for the CRC calculation.

Name

Gets the name of the CRC standard.

public string Name { get; }

Property Value

string

The name of the CRC algorithm.

Polynomial

Gets the polynomial used in the CRC calculation.

public ulong Polynomial { get; }

Property Value

ulong

The polynomial value used in the CRC calculation.

ReflectIn

Gets a value indicating whether the input data is reflected during the CRC calculation.

public bool ReflectIn { get; }

Property Value

bool

true if input data is reflected; otherwise, false.

ReflectOut

Gets a value indicating whether the CRC result is reflected before XORing with XOrOut.

public bool ReflectOut { get; }

Property Value

bool

true if the result is reflected; otherwise, false.

Size

Gets the size, in bits, of the CRC checksum.

public int Size { get; }

Property Value

int

The size of the CRC in bits.

XOrOut

Gets the value to XOR the final CRC result with.

public ulong XOrOut { get; }

Property Value

ulong

The XOR value for the final CRC result.

Methods

Equals(CrcStandard?)

Determines whether the current CrcStandard object is equal to another CrcStandard object.

public bool Equals(CrcStandard? other)

Parameters

other CrcStandard

The other CrcStandard object to compare.

Returns

bool

true if other has the same identity-bearing parameters ( Size, Polynomial, InitialValue, ReflectIn, ReflectOut, and XOrOut); otherwise, false. Name is informational and is intentionally excluded from equality.

Equals(object?)

Determines whether the specified object is equal to the current object.

public override bool Equals(object? obj)

Parameters

obj object

The object to compare with the current object.

Returns

bool

true if the specified object is equal to the current object; otherwise, false.

FromName(string)

Resolves a catalogue entry by its canonical name or any of its published aliases.

public static CrcStandard FromName(string name)

Parameters

name string

The canonical CRC standard name, or an alias. Comparison is ordinal and case-sensitive.

Returns

CrcStandard

The shared CrcStandard instance for name.

Exceptions

ArgumentNullException

name is null.

KeyNotFoundException

No catalogue entry matching name exists.

Get(CrcStandards)

Materialises - or retrieves from cache - the CrcStandard identified by the given enum value.

public static CrcStandard Get(CrcStandards standard)

Parameters

standard CrcStandards

The catalogue entry to resolve. Must be a defined CrcStandards value.

Returns

CrcStandard

The shared CrcStandard instance for standard.

Remarks

The first call for a given value constructs a new CrcStandard from the packed catalogue data and races to publish it into the per-entry cache. Subsequent calls - including concurrent calls - return the same instance, so reference equality is stable.

Exceptions

ArgumentOutOfRangeException

standard is not a defined enum value.

GetHashCode()

Serves as the default hash function.

public override int GetHashCode()

Returns

int

A hash code for the current object.

TryFromName(string?, out CrcStandard?)

Attempts to resolve a catalogue entry by its canonical name or alias without throwing.

public static bool TryFromName(string? name, out CrcStandard? standard)

Parameters

name string

The canonical CRC standard name or alias to look up.

standard CrcStandard

When this method returns, contains the matching CrcStandard if found; otherwise, null.

Returns

bool

true if a catalogue entry was found; otherwise, false.

Explicit Interface Implementations

ISerializable.GetObjectData(SerializationInfo, StreamingContext)

Populates a SerializationInfo with the data needed to serialize the target object.

void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)

Parameters

info SerializationInfo

The SerializationInfo to populate with data.

context StreamingContext

The destination (see StreamingContext) for this serialization.

Exceptions

SecurityException

The caller does not have the required permission.

Applies to

ProductVersions
.NET8, 10

See Also

Crc
CrcStandards
CrcLookupTableCache