Gapotchenko.FX.Data.Integrity.Checksum.Crc32 2022.1.4

Overview

The module provides the implementation of checksum algorithms belonging to CRC-32 family.

Quick Start

Use the following code to calculate a CRC-32 checksum for the specified data:

using Gapotchenko.FX.Data.Integrity.Checksum;

var checksum = Crc32.Standard.ComputeChecksum(data);

If you need to calculate a CRC-32 checksum iteratively then the following approach becomes handy:

var iterator = Crc32.Standard.CreateIterator();

iterator.ComputeBlock(...); // block 1
// ...
iterator.ComputeBlock(...); // block N

// Compute the final checksum:
var checksum = iterator.ComputeFinal();

Available CRC-32 Algorithms

CRC-32 family of cyclic redundancy checks consists of several attested checksum algorithms with predefined parameters:

The check parameter shows what checksum value an algorithm should produce for "123456789" input string interpreted as an ASCII data:

// Get the byte representation of the ASCII string.
var data = Encoding.ASCII.GetBytes("123456789");

// Compute the checksum.
var checksum = Crc32.Standard.ComputeChecksum(data);

// Print out the result (will print "Checksum = 0xcbf43926").
Console.WriteLine("Checksum = 0x{0:x}", checksum);

Recommended CRC-32 Algorithm

Among all other posibilities, it is recommended to use the standard CRC-32 algorithm which comes under CRC-32, CRC-32/ISO-HDLC, CRC-32/ADCCP, CRC-32/V-42, CRC-32/XZ, PKZIP aliases and is available via Crc32.Standard property.

All other predefined algorithms are available as the properties of Crc32.Attested class.

Custom CRC-32 Algorithms

Once in a while, you may encounter a custom CRC-32 algorithm that is neither widely known nor characterized. In that case, you can instantiate a custom checksum algorithm with the desired parameters by hand:

var checksumAlgorithm = new CustomCrc32(poly, init, refin, refout, xorout);

If you want to formalize a custom algorithm even further, you may opt-in to creating a separate class for it with a convenient accessor property:

/// <summary>
/// Defines a custom CRC-32 algorithm.
/// </summary>
sealed class FooCrc32 : CustomCrc32
{
    FooCrc32() :
        base(poly, init, refin, refout, xorout)
    {
    }

    public static FooCrc32 Instance { get; } = new FooCrc32();
}

That would allow you to use the algorithm effortlessly from several places in the codebase later:

var checksum = FooCrc32.Instance.ComputeChecksum(...);