This commit asserts that continuation frames are an implementation
detail of the websocket layer, and should remain hidden from the
application layer. That is:
- a codec should write only frames to the wire, and read only frames from the wire
- when sending messages, the websocket implementation should break large
text and binary messages into continuation frames -- the application should
not have to be aware of this.
- when receiving messages, the websocket implementation should reconstitute
continuation frames into their original messages -- the application should
not have to handle this.
- the application should only have to send and receive complete websocket messages
Here, the reconstitution of continuation frames into their original messages is
done by the Stream implementation of actix_web_actors::ws::WsStream, by adding
a continuation frame buffer and not issuing a Poll::Ready(Some(Ok)) result until
a complete message has been buffered. A test in actix_web_actors::tests::test_ws.rs
checks this.
The breaking of large message payloads into sequential continuation frames is
done by the addition of an actix_http::ws::frame_iters module, which introduces
two structs ContinuationBins and ContinuationTexts. These are iterators over
either single Frame::Binary or Frame::Text frames, if the payloads are small,
or over sequences of Frame::Continuation's with appropriate Items FirstBinary/FirstText,
Continue, and Last. New tests in actix_http::ws::frame_iters verify this
functionality.
Huston Bokinsky
Nikolay Kim