Impl NonViralNonPostingInvoker; rename other invokers around posting behaviour

include/spinscale/co/nonPostingPromise.h

@@ -0,0 +1,108 @@
+#ifndef NON_POSTING_PROMISE_H
+#define NON_POSTING_PROMISE_H
+
+#include <config.h>
+#include <coroutine>
+#include <exception>
+#include <functional>
+#include <iostream>
+#include <thread>
+#include <utility>
+
+#include <spinscale/co/coQutex.h>
+#include <spinscale/co/promiseChainLink.h>
+#include <spinscale/co/promises.h>
+
+namespace sscl::co {
+
+struct NonPostingPromise
+:	public PromiseChainLink
+{
+	/**	Completion work must run from this awaiter's await_suspend, not
+	 *	synchronously inside promise.final_suspend() before it returns: the
+	 *	hidden coroutine segment index in the coroutine state is only advanced
+	 *	after final_suspend exits. See docs/prompts/post-to-and-back-in-invokables.md.
+	 */
+	struct FinalSuspendNonPostingInvoker
+	:	public std::suspend_always
+	{
+		explicit FinalSuspendNonPostingInvoker(NonPostingPromise &calleePromiseIn) noexcept
+		:	calleePromise(calleePromiseIn)
+		{}
+
+		bool await_suspend(std::coroutine_handle<> const) noexcept
+		{
+			if (calleePromise.callerLambda)
+			{
+#ifdef CONFIG_LIBSSCL_DEBUG_CO
+				std::cout << "final_suspend" << ": " << std::this_thread::get_id()
+					<< " Non-viral non-posting: invoking callerLambda directly.\n";
+#endif
+				if (calleePromise.returnValues.myExceptionPtr) {
+					std::rethrow_exception(
+						calleePromise.returnValues.myExceptionPtr);
+				}
+
+				calleePromise.callerLambda();
+			}
+			return true;
+		}
+
+		NonPostingPromise &calleePromise;
+	};
+
+	NonPostingPromise() noexcept
+	: returnValues()
+	{}
+
+	template <typename... TailArgs>
+	NonPostingPromise(
+		std::exception_ptr &callerExceptionPtr,
+		std::function<void()> callerLambdaIn,
+		TailArgs &&...) noexcept
+	: returnValues(callerExceptionPtr),
+	callerLambda(std::move(callerLambdaIn))
+	{}
+
+	~NonPostingPromise() noexcept
+	{
+#ifdef CONFIG_LIBSSCL_DEBUG_CO
+		std::cout << __func__ << ": " << std::this_thread::get_id() << " Destructing.\n";
+#endif
+	}
+
+	std::suspend_never initial_suspend() noexcept
+		{ return {}; }
+
+	auto final_suspend() noexcept
+		{ return FinalSuspendNonPostingInvoker(*this); }
+
+	void return_void() noexcept
+		{ return; }
+
+	void unhandled_exception() noexcept
+	{
+		returnValues.myExceptionPtr = std::current_exception();
+	}
+
+	void removeAcquiredLock(CoQutex &coQutex) noexcept override
+	{
+		eraseFirstMatchingAcquiredLock(coQutex);
+	}
+
+	void setSelfSchedHandle(std::coroutine_handle<> schedHandle) noexcept
+	{
+		selfSchedHandle = schedHandle;
+	}
+
+	ReturnValues<void> returnValues;
+	std::function<void()> callerLambda;
+	std::coroutine_handle<> selfSchedHandle;
+
+	template <typename>
+	friend class NonPostingInvoker;
+};
+
+} // namespace sscl::co
+
+#endif // NON_POSTING_PROMISE_H