Junior Checksum

crc32.cs

// Compute a 32-bit big-endian checksum on arr
public static uint Checksum(ReadOnlySpan<byte> arr)
{
    if (arr.Length == 0) return 0;

    uint sum0 = 0, sum1 = 0, sum2 = 0, sum3 = 0;

    for(var i = 0; i<arr.Length; i++)
    {
        switch (i % 4)
        {
            case 0: sum0 += arr[i]; break;
            case 1: sum1 += arr[i]; break;
            case 2: sum2 += arr[i]; break;
            case 3: sum3 += arr[i]; break;
        }
    }

    var sum = sum3+ (sum2 << 8) + (sum1 << 16) + (sum0 << 24);

    return sum;
}