Custom StreamingCallbackToken for http_request_streaming_callback

[lastmjs]

Also on the forum: https://forum.dfinity.org/t/custom-streamingcallbacktoken/9379

This issue has come up while implementing https://github.com/dfinity/certified-assets/issues/10

I would like some clarification on StreamingCallbackToken and http_request_streaming_callback. I might need to modify the StreamingCallbackToken or implement a custom http_request_streaming_callback, but I am not sure if I am able to do that.

Is http_request_streaming_callback a special function? I assume I could name the function anything I want when creating StreamingStrategy::Callback, is that correct?

If that's the case, can I also change the StreamingCallbackToken parameter?

The problem I am trying to solve is that of 206 Partial Content responses. I need to return very custom slices of content, because the client could request any range of bytes on an asset. The default http_request_streaming_callback does not quite offer the flexibility I need. I think I can hack it with the current StreamingCallbackToken, but is there a possibility of implementing my own?

[lastmjs]

Maybe a simpler question is, can I implement custom streaming strategies? If so, how would I do that?

There is this StreamingStrategy enum:

enum StreamingStrategy {
    Callback {
        callback: Func,
        token: StreamingCallbackToken,
    },
}

I would like to somehow provide a custom callback and token to implement my special strategy.

[paulyoung]

I suspect you’d need to extend StreamingStrategy here: https://github.com/dfinity/agent-rs/blob/a8bb38e2079c935fc4deec0128c05319a43e5551/ic-utils/src/interfaces/http_request.rs#L39

and then match on it here, providing the implementation: https://github.com/dfinity/icx-proxy/blob/6cee84ace323c846f670d2eefdd292aa1b986f08/src/main.rs#L261