add full WebSocket (RFC 6455) client/server support for zenhttp (#792)

* This branch adds full WebSocket (RFC 6455) support to the HTTP server layer, covering both transport backends, a client, and tests.

- **`websocket.h`** -- Core interfaces: `WebSocketOpcode`, `WebSocketMessage`, `WebSocketConnection` (ref-counted), and `IWebSocketHandler`. Services opt in to WebSocket support by implementing `IWebSocketHandler` alongside their existing `HttpService`.
- **`httpwsclient.h`** -- `HttpWsClient`: an ASIO-backed `ws://` client with both standalone (own thread) and shared `io_context` modes. Supports connect timeout and optional auth token injection via `IWsClientHandler` callbacks.

- **`wsasio.cpp/h`** -- `WsAsioConnection`: WebSocket over ASIO TCP. Takes over the socket after the HTTP 101 handshake and runs an async read/write loop with a queued write path (guarded by `RwLock`).
- **`wshttpsys.cpp/h`** -- `WsHttpSysConnection`: WebSocket over http.sys opaque-mode connections (Windows only). Uses `HttpReceiveRequestEntityBody` / `HttpSendResponseEntityBody` via IOCP, sharing the same threadpool as normal http.sys traffic. Self-ref lifetime management ensures graceful drain of outstanding async ops.
- **`httpsys_iocontext.h`** -- Tagged `OVERLAPPED` wrapper (`HttpSysIoContext`) used to distinguish normal HTTP transactions from WebSocket read/write completions in the single IOCP callback.

- **`wsframecodec.cpp/h`** -- `WsFrameCodec`: static helpers for parsing (unmasked and masked) and building (unmasked server frames and masked client frames) RFC 6455 frames across all three payload length encodings (7-bit, 16-bit, 64-bit). Also computes `Sec-WebSocket-Accept` keys.

- **`clients/httpwsclient.cpp`** -- `HttpWsClient::Impl`: ASIO-based client that performs the HTTP upgrade handshake, then hands off to the frame codec for the read loop. Manages its own `io_context` thread or plugs into an external one.

- **`httpasio.cpp`** -- ASIO server now detects `Upgrade: websocket` requests, checks the matching `HttpService` for `IWebSocketHandler` via `dynamic_cast`, performs the RFC 6455 handshake (101 response), and spins up a `WsAsioConnection`.
- **`httpsys.cpp`** -- Same upgrade detection and handshake logic for the http.sys backend, using `WsHttpSysConnection` and `HTTP_SEND_RESPONSE_FLAG_OPAQUE`.
- **`httpparser.cpp/h`** -- Extended to surface the `Upgrade` / `Connection` / `Sec-WebSocket-Key` headers needed by the handshake.
- **`httpcommon.h`** -- Minor additions (probably new header constants or response codes for the WS upgrade).
- **`httpserver.h`** -- Small interface changes to support WebSocket registration.
- **`zenhttp.cpp` / `xmake.lua`** -- New source files wired in; build config updated.

- **Unit tests** (`websocket.framecodec`): round-trip encode/decode for text, binary, close frames; all three payload sizes; masked and unmasked variants; RFC 6455 `Sec-WebSocket-Accept` test vector.
- **Integration tests** (`websocket.integration`): full ASIO server tests covering handshake (101), normal HTTP coexistence, echo, server-push broadcast, client close handshake, ping/pong auto-response, sequential messages, and rejection of upgrades on non-WS services.
- **Client tests** (`websocket.client`): `HttpWsClient` connect+echo+close, connection failure (bad port -> close code 1006), and server-initiated close.

* changed HttpRequestParser::ParseCurrentHeader to use switch instead of if/else chain

* remove spurious printf

---------

Co-authored-by: Stefan Boberg <[email protected]>

1 files changed, 40 insertions, 0 deletions

diff --git a/src/zenhttp/servers/httpsys_iocontext.h b/src/zenhttp/servers/httpsys_iocontext.h
new file mode 100644
index 000000000..4f8a97012
--- /dev/null
+++ b/src/zenhttp/servers/httpsys_iocontext.h
@@ -0,0 +1,40 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#if ZEN_WITH_HTTPSYS
+#	define _WINSOCKAPI_
+#	include <zencore/windows.h>
+
+#	include <cstdint>
+
+namespace zen {
+
+/**
+ * Tagged OVERLAPPED wrapper for http.sys IOCP dispatch
+ *
+ * Both HttpSysTransaction (for normal HTTP request I/O) and WsHttpSysConnection
+ * (for WebSocket read/write) embed this struct.  The single IoCompletionCallback
+ * bound to the request queue uses the ContextType tag to dispatch to the correct
+ * handler.
+ *
+ * The Overlapped member must be first so that CONTAINING_RECORD works to recover
+ * the HttpSysIoContext from the OVERLAPPED pointer provided by the threadpool.
+ */
+struct HttpSysIoContext
+{
+	OVERLAPPED Overlapped{};
+
+	enum class Type : uint8_t
+	{
+		kTransaction,
+		kWebSocketRead,
+		kWebSocketWrite,
+	} ContextType = Type::kTransaction;
+
+	void* Owner = nullptr;
+};
+
+}  // namespace zen
+
+#endif	// ZEN_WITH_HTTPSYS