StructLayout to convert byte array to short

Question

Sorry about the horrible title but I honestly have know idea what I want nor what is wrong...

Basically I have a struct (well I have 250+ structs but they all follow the same idea) that looks like this:

[StructLayout(LayoutKind.Explicit)]
public struct GenericPacket
{
    [FieldOffset(0)]
    public byte[] data;

    [FieldOffset(0)]
    public short packetid;
}

The issue is that a byte array is a reference type and a short is a value type and it won't allow the fieldoffset to be set to the same memory location...

I would really hate to have to remove all the structs I've written just to do it a different way. So here is my question, how can I use this in a way that works. Basically what I'm going to do is this:

socket.Receive(buff, 0, 0, SocketFlags.None);
GenericPacket packet = new GenericPacket();
packet.data = buff;
Console.WriteLine(packet.packetid);

It refuses to even compile as it doesn't want to generate the struct /:

Before anyone suggests other methods, the reason I am doing this is it needs ultra high speeds... I could use a ByteReader and other methods (eg. BitConverter) but it needs to be a tad faster than that...

I started with Bitwise shifts but I needed a more 'dynamic' way to do it because after I have a packet ID I then read it with another struct, for example:

[StructLayout(LayoutKind.Explicit)]
public struct _03k
{
    [FieldOffset(0)]
    byte[] data;

    [FieldOffset(0)]
    short packetid;
    [FieldOffset(2)]
    short @null;
    [FieldOffset(4)]
    int major;
    [FieldOffset(8)]
    int minor;
    [FieldOffset(12)]
    int build;
}

Instead of having to have a lot of inline "Bitwise shits" I simply want an easy AND very fast way of doing this... Seems I got the fast just not the easy /:

PLEASE HELP! Unsafe code is ok, but prefer a managed version too.

FAIL :(: Just remembered you can convert Value types to Reference types by boxing them (casting to type object). This does however remove the REAL return type and says it just is an object, is there anyway with XML Documentation that you can lie about the return type? DOESN'T WORK SADLY D:

UPDATE: OK, now I have:

public struct GenericPacket
{
    public short packetid;

    public static GenericPacket ReadUsingPointer(byte[] data)
    {
        unsafe
        {
            fixed (byte* packet = &data[0])
            {
                return *(GenericPacket*)packet;
            }
        }
    }
}

But its a bit annoying having to call a method everytime to convert it :( Anyone got any more suggestions?

Thanks, JD

Answer 1

What I finally settled on was a struct with an implicit conversion operator that called the ReadByPointer method.

public struct GenericPacket
{
    public short packetid;

    public static GenericPacket ReadUsingPointer(byte[] data)
    {
        unsafe
        {
            fixed (byte* packet = &data[0])
            {
                return *(GenericPacket*)packet;
            }
        }
    }

    static public implicit operator GenericPacket(byte[] value) 
    {
        return GenericPacket.ReadUsingPointer(value);
    }
}

This allows you to do the following:

GenericPacket packet = bufferFromReceive;

Thanks -jD