Flash5/flash/docs/http2/README.md

HTTP/2 in Flash

Flash treats HTTP/1.1 and HTTP/2 as peer transports behind one connection boundary. TLS ALPN or the cleartext prior-knowledge preface selects a protocol once; both paths then feed the same router, Request, Response, handler, trailer, streaming and WebSocket APIs. HTTP/2 adds a bounded frame decoder, HPACK codec, stream state machine, two-level flow control and one serialized writer per connection. Application code does not branch on the wire protocol.

The implementation is deliberately layered:

listener / TLS
    -> protocol negotiation
        -> HTTP/1.1 parser ---------+
        -> HTTP/2 frames + HPACK ----+-> shared request model -> router -> handler
                                         shared response model
        <- HTTP/1.1 serializer -----+
        <- HTTP/2 stream writer ----+

Start here

• HTTP/1.1 hardening — message-boundary rules, timeouts and negotiation.
• Transport — listeners, connection ownership, TLS and virtual threads.
• Message model — shared request/response objects and their lifetime contract.
• Connection and streams — HTTP/2 connection and stream state.
• Flow control — request backpressure and streamed responses.
• Trailers and streaming — the public cross-protocol APIs.
• Cleartext and proxying — prior knowledge and the upstream h2 client.
• WebSockets — RFC 8441 extended CONNECT using the existing WebSocket API.

Wire internals

• Byte primitives — reusable views, scanning and bounded slice lifetimes.
• Serialized writer — the single-owner output path and contention model.
• Frames — frame parsing, validation and error scope.
• HPACK — integer/Huffman coding and static/dynamic table ownership.

Operate and verify

• Security — every HTTP/2 limit, default and abuse control.
• Troubleshooting — GOAWAY/RST_STREAM diagnosis and protocol tracing.
• Compliance — h2spec, interoperability, fuzzing and deliberate omissions.
• Performance and CI baselines — measurements and regression gates, including the comparison with nghttpd.

Design history

Decisions records non-obvious trade-offs and rejected alternatives. The implementation plan is retained as historical engineering evidence; it is not required to use or extend the runtime.