Initial commit of libspinscale library

include/spinscale/asynchronousContinuation.h

@@ -0,0 +1,158 @@
+#ifndef ASYNCHRONOUS_CONTINUATION_H
+#define ASYNCHRONOUS_CONTINUATION_H
+
+#include <functional>
+#include <memory>
+#include <exception>
+#include <spinscale/componentThread.h>
+#include <spinscale/callback.h>
+#include <spinscale/callableTracer.h>
+#include <spinscale/asynchronousContinuationChainLink.h>
+
+
+namespace sscl {
+
+/**
+ * AsynchronousContinuation - Template base class for async sequence management
+ *
+ * This template provides a common pattern for managing asynchronous operations
+ * that need to maintain object lifetime through a sequence of callbacks.
+ *
+ * The template parameter OriginalCbFnT represents the signature of the original
+ * callback that will be invoked when the async sequence completes.
+ */
+template <class OriginalCbFnT>
+class AsynchronousContinuation
+:	public AsynchronousContinuationChainLink
+{
+public:
+	explicit AsynchronousContinuation(Callback<OriginalCbFnT> originalCb)
+	: originalCallback(std::move(originalCb))
+	{}
+
+	/**		EXPLANATION:
+	 * Each numbered segmented sequence persists the lifetime of the
+	 * continuation object by taking a copy of its shared_ptr.
+	 */
+	typedef void (SegmentFn)(
+		std::shared_ptr<AsynchronousContinuation<OriginalCbFnT>>
+			lifetimePreservingConveyance);
+
+	/**	EXPLANATION:
+	 * When an exception is thrown in a an async callee, which pertains to an
+	 * error in the data given by the caller, we ought not to throw the
+	 * exception within the callee. Instead, we should store the exception
+	 * in the continuation object and return it to the caller.
+	 *
+	 * The caller should then call checkException() to rethrow it on its
+	 * own stack.
+	 *
+	 * This macro should be used by the caller to bubble the exception to the
+	 * caller.
+	 */
+	#define CALLEE_SETEXC(continuation, type, exc_obj) \
+		(continuation)->exception = std::make_exception_ptr<type>(exc_obj)
+
+	#define CALLEE_SETEXC_CALLCB(continuation, type, exc_obj) \
+		do { \
+			CALLEE_SETEXC(continuation, type, exc_obj); \
+			(continuation)->callOriginalCb(); \
+		} while(0)
+
+	#define CALLEE_SETEXC_CALLCB_RET(continuation, type, exc_obj) \
+		do { \
+			CALLEE_SETEXC_CALLCB(continuation, type, exc_obj); \
+			return; \
+		} while(0)
+
+	// Call this in the caller to rethrow the exception.
+	void checkException()
+	{
+		if (exception)
+			{ std::rethrow_exception(exception); }
+	}
+
+	// Implement the virtual method from AsynchronousContinuationChainLink
+	virtual std::shared_ptr<AsynchronousContinuationChainLink>
+	getCallersContinuationShPtr() const override
+		{ return originalCallback.callerContinuation; }
+
+public:
+	Callback<OriginalCbFnT> originalCallback;
+	std::exception_ptr exception;
+};
+
+/**
+ * NonPostedAsynchronousContinuation - For continuations that don't post
+ * callbacks
+ *
+ * Note: We intentionally do not create a
+ * LockedNonPostedAsynchronousContinuation because the only way to implement
+ * non-posted locking would be via busy-spinning or sleeplocks. This would
+ * eliminate the throughput advantage from our Qspinning mechanism, which
+ * relies on re-posting to the io_service queue when locks are unavailable.
+ */
+template <class OriginalCbFnT>
+class NonPostedAsynchronousContinuation
+:	public AsynchronousContinuation<OriginalCbFnT>
+{
+public:
+	explicit NonPostedAsynchronousContinuation(
+		Callback<OriginalCbFnT> originalCb)
+	:	AsynchronousContinuation<OriginalCbFnT>(originalCb)
+	{}
+
+	/**
+	 * @brief Call the original callback with perfect forwarding
+	 * (immediate execution)
+	 *
+	 * This implementation calls the original callback immediately without
+	 * posting to any thread or queue. Used for non-posted continuations.
+	 *
+	 * @param args Arguments to forward to the original callback
+	 */
+	template<typename... Args>
+	void callOriginalCb(Args&&... args)
+	{
+		if (AsynchronousContinuation<OriginalCbFnT>::originalCallback
+			.callbackFn)
+		{
+			AsynchronousContinuation<OriginalCbFnT>::originalCallback
+				.callbackFn(std::forward<Args>(args)...);
+		}
+	}
+};
+
+template <class OriginalCbFnT>
+class PostedAsynchronousContinuation
+:	public AsynchronousContinuation<OriginalCbFnT>
+{
+public:
+	PostedAsynchronousContinuation(
+		const std::shared_ptr<ComponentThread> &caller,
+		Callback<OriginalCbFnT> originalCbFn)
+	:	AsynchronousContinuation<OriginalCbFnT>(originalCbFn),
+	caller(caller)
+	{}
+
+	template<typename... Args>
+	void callOriginalCb(Args&&... args)
+	{
+		if (AsynchronousContinuation<OriginalCbFnT>::originalCallback
+			.callbackFn)
+		{
+			caller->getIoService().post(
+				STC(std::bind(
+					AsynchronousContinuation<OriginalCbFnT>::originalCallback
+						.callbackFn,
+					std::forward<Args>(args)...)));
+		}
+	}
+
+public:
+	std::shared_ptr<ComponentThread> caller;
+};
+
+} // namespace sscl
+
+#endif // ASYNCHRONOUS_CONTINUATION_H