event/net/CoConnectSocket: a coroutine wrapper for ConnectSocket

src/event/net/CoConnectSocket.hxx

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <[email protected]>
+
+#pragma once
+
+#include "ConnectSocket.hxx"
+#include "net/UniqueSocketDescriptor.hxx"
+#include "co/Compat.hxx"
+
+class CoConnectSocket final : ConnectSocketHandler {
+	ConnectSocket connect;
+
+	std::coroutine_handle<> continuation;
+
+	UniqueSocketDescriptor value;
+
+	std::exception_ptr error;
+
+public:
+	CoConnectSocket(EventLoop &event_loop,
+			const auto &address,
+			Event::Duration timeout) noexcept
+		:connect(event_loop, *this)
+	{
+		connect.Connect(address, timeout);
+	}
+
+	auto operator co_await() noexcept {
+		struct Awaitable final {
+			CoConnectSocket &task;
+
+			bool await_ready() const noexcept {
+				return !task.connect.IsPending();
+			}
+
+			std::coroutine_handle<> await_suspend(std::coroutine_handle<> _continuation) noexcept {
+				task.continuation = _continuation;
+				return std::noop_coroutine();
+			}
+
+			decltype(auto) await_resume() {
+				if (task.error)
+					std::rethrow_exception(task.error);
+
+				return std::move(task.value);
+			}
+		};
+
+		return Awaitable{*this};
+	}
+
+private:
+	/* virtual methods from ConnectSocketHandler */
+	void OnSocketConnectSuccess(UniqueSocketDescriptor fd) noexcept override {
+		value = std::move(fd);
+
+		if (continuation)
+			continuation.resume();
+	}
+
+	void OnSocketConnectError(std::exception_ptr _error) noexcept override {
+		error = std::move(_error);
+
+		if (continuation)
+			continuation.resume();
+	}
+};