Stream buffering in cupertino_http StreamedRequest

[Vovcharaa]

Related #974
StreamQueue is buffering everything it can consume before sending it to the remote.
This still prevents tracking upload progress or sending large files.

http/pkgs/cupertino_http/lib/src/cupertino_api.dart

Lines 124 to 127 in b206771

	ncb.NSInputStream _streamToNSInputStream(Stream<List<int>> stream) {
	const maxReadAheadSize = 4096;
	final queue = StreamQueue(stream);
	final port = ReceivePort();

http/pkgs/cupertino_http/lib/src/cupertino_client.dart

Lines 219 to 228 in b206771

	static Future<(bool, Stream<List<int>>)> _hasData(
	Stream<List<int>> stream) async {
	final queue = StreamQueue(stream);
	while (await queue.hasNext && (await queue.peek).isEmpty) {
	await queue.next;
	}
	return (await queue.hasNext, queue.rest);
	}

[Vovcharaa]

@brianquinlan Perhaps, I misunderstood how StreamController(sync: true) is working.
I want to be able to send data into the StreamingRequest sink with knowledge of how much of the data is sent to the server. But I can't track progress if something is buffering my data before it is sent to the server.
When I am sending chunks of data with an artificial delay between them, I can see these chunks on the server as they are sent. So streaming request is definitely working, but not as I expected it will be.
Is it actually possible to track uploading progress in StreamedRequest?

[brianquinlan]

From #974:
Could you include the stream that you are sending? AFAIK, _hasData is only buffering the first non-empty List in the stream.

_streamToNSInputStream is only providing data when requested to by the Apple's client implementation and is, in my experience, providing less data than requested.

I don't think that you can accurately track uploading progress using StreamedRequest unless the request is "large" and the input stream emits List<int> whose size is significantly less than the total request size.

How much data are you sending on how many List<int>s are in your Stream?