nghttp2: streamed response bodies, and the ASP.NET sample moves into the Playground

[MDA2AV]

nghttp2 streams response bodies now. It always could - our shim was the part that couldn't.

The gap was ours, not nghttp2's

nghttp2_data_provider, NGHTTP2_ERR_DEFERRED and nghttp2_session_resume_data exist for exactly this. ioxide_nghttp2_shim.c only ever exposed the whole-body submit, so there was nothing for a writer to push into. That makes this mostly a C change.

Three new entry points:

ih2_submit_response_stream	opens a stream with a provider and no bytes
ih2_stream_write	appends a chunk and resumes the deferred stream
ih2_stream_close	no more body; END_STREAM follows what is queued

The behaviour actually lives in read_body: on an empty window it now returns NGHTTP2_ERR_DEFERRED for a streamed body instead of flagging EOF. That is what holds a stream open through a slow producer rather than truncating it at its first quiet moment.

It is a PULL, and the C# hides that

Nghttp2ResponseWriter is an IBufferWriter<byte> and reads like a push, but underneath nghttp2 asks for bytes when it is ready to frame them. So a flush here means handed over, not on the wire - nghttp2 owns frame boundaries and timing. ioxide.http2 owns its own framing and stages a DATA frame the moment you flush; that difference is the whole reason this needed native work instead of a C# writer.

Verified on the wire

A byte count cannot tell streaming from one coalesced blob, so nghttp was the check:

recv HEADERS  (END_HEADERS, no END_STREAM)
recv DATA x8  (1024 each - one per flush)
recv DATA len=0 ; END_STREAM

/feed streams 251 MB in three seconds. The regression test counts frames, not bytes, for the same reason.

One bug worth recording because it will catch the next person: resume_data returns INVALID_ARGUMENT when the stream is not currently deferred, which happens whenever a write beats nghttp2 to it - most of them. Treating it as an error killed the connection after a single chunk: the finite case returned 0 bytes and /feed stopped dead at 1024.

Also here

Examples.AspNet was the last thing left at the repo root from the old Examples project. It moves to Playground/AspNet and is verified still serving on the io_uring transport.

0.4.177 across eleven packages. ioxide.nghttp2 is the one carrying a changed native library, and the packed nupkg was checked to contain the rebuilt .so exporting all three new symbols.

Not done

• Request-body streaming. The shim already delivers chunks as they arrive (on_data_chunk_recv), so a reader is nearly all C# - but nghttp2 credits the flow-control window automatically, so it would be a reader with no backpressure. Real credit-as-you-read needs nghttp2_option_set_no_auto_window_update plus nghttp2_session_consume.
• The .so is linux-x64 only, built from nghttp2 master rather than a pinned tag. Worth pinning before a release goes out on it.

Unit 36, Chaos 47, Http 38, E2E 46 - all 0 failed, 0 skipped.