AsyncResponseStream is not streaming

[y3nd]

Hello,
I would like to use AsyncResponseStream similarly to what I do with a Serial stream. I need to send several 10th of kilobytes in binary and I have heap size issue.
Since a bufferSize is specified, I had initially understood that it would push data to the client progressively and maybe block the writes to slow down like Serial do (i think).
I then noticed that the content-length was set on the response and since headers should be sent before the body, I understood that it was entirely buffered and not sent like a stream.
I then used .availableForWrite to prevent filling the buffer but it seems not implemented.

From user POV, what is the purpose of bufferSize here and how could send the response progressively, maybe by specifying the content length before and using another async response type ?

Thanks

[mathieucarbou]

Hello,

There is an example about serving a big html fie using a small buffer and with caching headers here:

https://github.com/mathieucarbou/ESPAsyncWebServer/blob/main/examples/SimpleServer/SimpleServer.ino#L472-L504

[mathieucarbou]

AsyncResponseStream is badly named: it is not streaming: it is just implementing the Print interface and collects the data into the buffer, allocated with bufferSize bytes.

If it was really streaming, its API should have been like that:

AsyncResponseStream(const char* contentType, Stream& stream, size_t chunkBufferSize);

and the callback as seen in the link above would then read the stream and fill the chunk buffer.

Note: this is nearly what AsyncStreamResponse does.

You have:

• AsyncStreamResponse
• AsyncResponseStream

AsyncWebServerResponse* AsyncWebServerRequest::beginResponse(Stream& stream, const char* contentType, size_t len, AwsTemplateProcessor callback) {

very confusing... ;-)