C# checksum

在C#中，可以使用不同的算法来计算数据的校验和。以下是一些常见的校验和算法示例：

1. CRC32校验和：

using System;
using System.Security.Cryptography;

public static class ChecksumHelper
{
    public static uint CalculateCRC32(byte[] data)
    {
        using (var crc32 = new CRC32())
        {
            return crc32.ComputeHash(data);
        }
    }
}

public class CRC32 : HashAlgorithm
{
    private const uint Polynomial = 0xEDB88320;
    private uint[] table;
    private uint crc;

    public CRC32()
    {
        table = InitializeTable(Polynomial);
        crc = 0xffffffff;
    }

    public override void Initialize()
    {
        crc = 0xffffffff;
    }

    protected override void HashCore(byte[] array, int ibStart, int cbSize)
    {
        crc ^= 0xffffffff;

        for (int i = ibStart; i < ibStart + cbSize; i++)
        {
            crc = (crc >> 8) ^ table[array[i] ^ crc & 0xff];
        }

        crc ^= 0xffffffff;
    }

    protected override byte[] HashFinal()
    {
        byte[] hash = new byte[4];
        hash[0] = (byte)((crc >> 24) & 0xff);
        hash[1] = (byte)((crc >> 16) & 0xff);
        hash[2] = (byte)((crc >> 8) & 0xff);
        hash[3] = (byte)(crc & 0xff);
        return hash;
    }

    private static uint[] InitializeTable(uint polynomial)
    {
        uint[] table = new uint[256];

        for (uint i = 0; i < 256; i++)
        {
            uint entry = i;
            for (int j = 0; j < 8; j++)
            {
                if ((entry & 1) == 1)
                {
                    entry = (entry >> 1) ^ polynomial;
                }
                else
                {
                    entry >>= 1;
                }
            }
            table[i] = entry;
        }

        return table;
    }
}

使用示例:

byte[] data = { 0x01, 0x02, 0x03, 0x04 };
uint crc32Checksum = ChecksumHelper.CalculateCRC32(data);
Console.WriteLine($"CRC32 checksum: 0x{crc32Checksum:X8}");

2. MD5校验和：

using System;
using System.Security.Cryptography;
using System.Text;

public static class ChecksumHelper
{
    public static string CalculateMD5(string input)
    {
        using (var md5 = MD5.Create())
        {
            byte[] inputBytes = Encoding.UTF8.GetBytes(input);
            byte[] hashBytes = md5.ComputeHash(inputBytes);

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < hashBytes.Length; i++)
            {
                sb.Append(hashBytes[i].ToString("X2"));
            }

            return sb.ToString();
        }
    }
}

使用示例:

string input = "Hello, world!";
string md5Checksum = ChecksumHelper.CalculateMD5(input);
Console.WriteLine($"MD5 checksum: {md5Checksum}");

这些示例展示了如何在C#中计算CRC32和MD5校验和。根据你的需求，你可以选择适合的校验和算法来计算数据的校验和。