What is the recommended approach for copying of a message?

[yoloroy]

I'm developing a multiplayer game where the server needs to relay incoming command messages to all other clients in the session. I'm separating commands (reliable messages for input, abilities, etc.) from updates (unreliable messages for game state).

My goal is to avoid deserializing the message on the server and then re-serializing it into a new message, as this adds significant boilerplate.

What I have tried

I attempted to use AddBytes and AddMessage to copy the original message's payload into a new one. The resulting message had the expected size, but the bits within the copy were corrupted and did not correspond to the original data.

var copy = Message.AddMessage(message, 8 * known_constant_for_this_message_type, 0) // returns corrupted data
             // or AddMessage(message) when dealing with incoming message
    .AddInt(senderId) // or other appendage

Workaround: Manual parsing and reconstruction

My current workaround is to manually deserialize the message on the server and then create new Message object, reserializing the data on the next line. This works correctly:

// receiving the data
var player = src.Players[sender];
player.Position = message.GetVector2();
player.Vector = message.GetVector2();
var timestamp = message.GetDouble(); // todo [inter,extra]polation, maybe some simulation and all of that

// reserialization
copy = Message.Create()
    .AddVector2(player.Position)
    .AddVector2(player.Vector)
    .AddDouble(timestamp)
    .AddInt(sender);

While this works, doing it for every command will be tedious, especially for commands that don't affect the game state.

[tom-weiland]

The AddMessage method is definitely intended for this use case.

The resulting message had the expected size, but the bits within the copy were corrupted and did not correspond to the original data.

What do you mean by "corrupted"? Is the change in the data constant/predictable? Is the Message that you're adding the message to an empty message instance? Or does it already have header info in it? It would help if you provided more context for your example that includes where/how both message instances are created.

As for your workaround example, you say that it works, but I'm not actually sure how it would do that because you're using the Message.Create() overload without any parameters, meaning that's returning an empty message instance. copy will contain only your custom data and not any header information, so sending it wouldn't work unless you're taking copy and copying its data into another message instance that does contain header info...