Handling length information

[jonasdroste]

I have to handle a binary protocol that's modelled by the provided class structure. Currently I'm wondering how to handle the length information as I need to do calculations depending which subtype is used. Furthermore I'm wondering how to calculate the size of the whole Payload field an feed that into PayloadLength

    public class Packet
    {
        [FieldOrder(0)]
        public byte ProtocolVersion { get; set; }

        [FieldOrder(1)]
        public byte InvProtocolVersion { get; set; }

        [FieldOrder(2)]
        public dPayloadType PayloadType { get; set; }

        [FieldOrder(4)]
        [Subtype(nameof(PayloadType), dPayloadType.GenericNACK, typeof(GenericNACKPayload))]
        [Subtype(nameof(PayloadType), dPayloadType.Request, typeof(Request))]
        [Subtype(nameof(PayloadType), dPayloadType.UserData, typeof(UserData))]
        public dPayload Payload { get; set; }        
    }
    public class dPayload
    {
        [FieldOrder(0)]
        public UInt32 PayloadLength { get; set; }
    }
    public class GenericNACKPayload : dPayload
    {
        [FieldOrder(0)]
        [FieldLength(1)]
        public byte NackCode { get; set; }
    }

    public class Request : dPayload
    {
        [FieldOrder(0)]
        public byte[] EID { get; set; } // Size is equal to PayloadLength 
    }

    public class UserData : dPayload
    {
        [FieldOrder(0)]
        public byte SA { get; set; }
        [FieldOrder(1)]
        public byte TA { get; set; }
        [FieldOrder(2)]
        public byte[] UD { get; set; } // Size is equal to PayloadLength - 2
    }

[jefffhaynes]

I’m only looking at it on my phone at the moment so it’s hard to say but I think if you simply inject a “payload container” object you can limit the length of the payload object and it should all come out in the wash.

On Thu, Mar 19, 2020 at 3:59 AM Jonas Droste notifications@github.com wrote:

I have to handle a binary protocol that's modelled by the provided class structure. Currently I'm wondering how to handle the length information as I need to do calculations depending which subtype is used. Furthermore I'm wondering how to calculate the size of the whole Payload field an feed that into PayloadLength

public class Packet
{
    [FieldOrder(0)]
    public byte ProtocolVersion { get; set; }

    [FieldOrder(1)]
    public byte InvProtocolVersion { get; set; }

    [FieldOrder(2)]
    public dPayloadType PayloadType { get; set; }

    [FieldOrder(4)]
    [Subtype(nameof(PayloadType), dPayloadType.GenericNACK, typeof(GenericNACKPayload))]
    [Subtype(nameof(PayloadType), dPayloadType.Request, typeof(Request))]
    [Subtype(nameof(PayloadType), dPayloadType.UserData, typeof(UserData))]
    public dPayload Payload { get; set; }
}
public class dPayload
{
    [FieldOrder(0)]
    public UInt32 PayloadLength { get; set; }
}
public class GenericNACKPayload : dPayload
{
    [FieldOrder(0)]
    [FieldLength(1)]
    public byte NackCode { get; set; }
}

public class Request : dPayload
{
    [FieldOrder(0)]
    public byte[] EID { get; set; } // Size is equal to PayloadLength
}

public class UserData : dPayload
{
    [FieldOrder(0)]
    public byte SA { get; set; }
    [FieldOrder(1)]
    public byte TA { get; set; }
    [FieldOrder(2)]
    public byte[] UD { get; set; } // Size is equal to PayloadLength - 2
}

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/jefffhaynes/BinarySerializer/issues/151, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACKIUR2EH4EUPQG3DFDQC3TRIHGGPANCNFSM4LPCZFRA .

-- If you want to build a ship, don't drum up people together to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea.

Antoine de Saint-Exupery

[jefffhaynes]

Looking at it now you don't even need to add anything, just move your length definition to the packet like this:

public class Packet
{
    [FieldOrder(0)]
    public byte ProtocolVersion { get; set; }

    [FieldOrder(1)]
    public byte InvProtocolVersion { get; set; }

    [FieldOrder(2)]
    public dPayloadType PayloadType { get; set; }

    [FieldOrder(3)]
    public UInt32 PayloadLength { get; set; }

    [FieldOrder(4)]
    [FieldLength(nameof(PayloadLength))]
    [Subtype(nameof(PayloadType), dPayloadType.GenericNACK, typeof(GenericNACKPayload))]
    [Subtype(nameof(PayloadType), dPayloadType.Request, typeof(Request))]
    [Subtype(nameof(PayloadType), dPayloadType.UserData, typeof(UserData))]
    public dPayload Payload { get; set; }
}

public abstract class dPayload
{
}

If I'm not mistaken, this should match the format you're trying to achieve.

[jefffhaynes]

Closing this. Please reopen if I'm missing something or you need more help with this.