DataType for storing a long serial number (10 bytes)

Question

We have a device which has a 10 byte serial number which must be read into our application and stored into a .net datatype. In the device it is stored as an unsigned 10-byte (80-bit) number. I don't expect we will be performing any mathematical operations on this number, but only displaying it to the user.

The .NET framework doesn't have a built in UNIT128 to store this datatype. My suggestion for storing this datatype is to create a 10 element byte array and read in the data into this array. Are there any better solutions to this problem?

Note: I have seen in this question that a GUID is a 128 byte signed integer, but it seems like a bad idea to use a GUID in this fashion. Any other suggestions?

Answer 1

You should use a byte array.

Answer 2

If you're only displaying it, why not use a string? If you want additional security against accidental changes, you could even wrap that into some business object.

Answer 3

I agree with @SLaks, you should use a byte array. However, BigInteger, http://msdn.microsoft.com/en-us/library/system.numerics.biginteger.aspx, might also work, since it theoretically has no lower/upper bounds. This is for .NET 4 only. Byte array would still be a better choice though.

Answer 4

If you're not doing calculations on the number, what wrong with System.String?

Answer 5

You have few options. Any they depend on how you will use the data. You can pack it into a Guid, use a byte array, use a custom Struct, or pack it as Base64 or HEX and stuff it into a string.

[StructLayout( LayoutKind.Explicit)]
public struct MyStruct
{
    public MyStruct(byte[] buffer)
    {
        if (buffer.Length != 10)
            throw new ArgumentOutOfRangeException();
        High = BitConverter.ToUInt16(buffer, 0);
        Low = BitConverter.ToUInt64(buffer, 2);
    }
    [FieldOffset(0)]
    public ushort High;  //2 bytes
    [FieldOffset(2)]
    public ulong Low;    //8 bytes

    public byte[] Bytes
    {
        get
        {
            return BitConverter.GetBytes(High)
                .Concat(BitConverter.GetBytes(Low))
                .ToArray();
        }
    }
    public override string ToString()
    {
        return Convert.ToBase64String(Bytes);
    }
    public static MyStruct Parse(string toParse)
    {
        var bytes = Convert.FromBase64String(toParse);
        return new MyStruct(bytes);
    }
}