3 files changed, 125 insertions, 58 deletions

diff --git a/lib/work.h b/lib/work.h
deleted file mode 100644
index c780e13..0000000
--- a/lib/work.h
+++ /dev/null
@@ -1,12 +0,0 @@
-#pragma once
-
-#include <special_members.hpp>
-
-class Work {
-public:
-	virtual ~Work() = default;
-	NO_COPY(Work);
-	NO_MOVE(Work);
-
-	virtual void doWork() = 0;
-};
diff --git a/lib/worker.cpp b/lib/worker.cpp
index fd255c7..45fb6df 100644
--- a/lib/worker.cpp
+++ b/lib/worker.cpp
@@ -1,27 +1,24 @@
 #include "worker.h"
-#if __cpp_lib_semaphore
-#	include "work.h"
-#	include <algorithm>
-#	include <iterator>
-#	include <mutex>
+#include <algorithm>
+#include <iterator>
+#include <mutex>
+
+Worker Worker::instance;
 
 Worker::Worker() : todoLen {0}
 {
 	std::generate_n(std::back_inserter(threads), std::thread::hardware_concurrency(), [this]() {
-		return std::thread {&Worker::worker, this};
+		return std::jthread {&Worker::worker, this};
 	});
 }
 
 Worker::~Worker()
 {
 	todoLen.release(std::thread::hardware_concurrency());
-	std::for_each(threads.begin(), threads.end(), [](auto & th) {
-		th.join();
-	});
 }
 
 void
-Worker::addWork(WorkPtr j)
+Worker::addWorkPtr(WorkPtr j)
 {
 	std::lock_guard<std::mutex> lck {todoMutex};
 	todoLen.release();
@@ -45,4 +42,24 @@ Worker::worker()
 		j->doWork();
 	}
 }
-#endif
+
+void
+Worker::assist()
+{
+	auto job = [this]() {
+		using namespace std::chrono_literals;
+		if (todoLen.try_acquire_for(100us)) {
+			if (std::lock_guard<std::mutex> lck {todoMutex}; todo.size()) {
+				WorkPtr x = std::move(todo.front());
+				if (x) {
+					todo.pop_front();
+				}
+				return x;
+			}
+		}
+		return WorkPtr {};
+	};
+	if (auto j = job()) {
+		j->doWork();
+	}
+}
diff --git a/lib/worker.h b/lib/worker.h
index 7cd06f9..d9a5a6f 100644
--- a/lib/worker.h
+++ b/lib/worker.h
@@ -1,60 +1,122 @@
 #pragma once
 
+#include <deque>
+#include <functional>
+#include <future>
+#include <memory>
+#include <mutex>
+#include <semaphore>
+#include <special_members.hpp>
+#include <thread>
 #include <utility>
-class Work;
-
-#if __cpp_lib_semaphore
-#	include <deque>
-#	include <memory>
-#	include <mutex>
-#	include <semaphore>
-#	include <special_members.hpp>
-#	include <thread>
-#	include <vector>
+#include <vector>
 
 class Worker {
 public:
+	class WorkItem {
+	protected:
+		WorkItem(Worker * worker) : worker {worker} { }
+		virtual ~WorkItem() = default;
+		NO_MOVE(WorkItem);
+		NO_COPY(WorkItem);
+
+		void
+		assist() const
+		{
+			worker->assist();
+		}
+		Worker * worker;
+
+	public:
+		virtual void doWork() = 0;
+	};
+
+	template<typename T> class WorkItemT : public WorkItem {
+	public:
+		T
+		get()
+		{
+			using namespace std::chrono_literals;
+			while (future.wait_for(0s) == std::future_status::timeout) {
+				assist();
+			}
+			return future.get();
+		}
+
+	protected:
+		WorkItemT(Worker * worker) : WorkItem {worker} { }
+
+		std::promise<T> promise;
+		std::future<T> future {promise.get_future()};
+		friend Worker;
+	};
+
+	template<typename... Params>
+	static auto
+	addWork(Params &&... params)
+	{
+		return instance.addWorkImpl(std::forward<Params>(params)...);
+	}
+	template<typename T> using WorkPtrT = std::shared_ptr<WorkItemT<T>>;
+
+private:
+	template<typename T, typename... Params> class WorkItemTImpl : public WorkItemT<T> {
+	public:
+		WorkItemTImpl(Worker * worker, Params &&... params) :
+			WorkItemT<T> {worker}, params {std::forward<Params>(params)...}
+		{
+		}
+
+	private:
+		void
+		doWork() override
+		{
+			try {
+				if constexpr (std::is_void_v<T>) {
+					std::apply(std::invoke<Params &...>, params);
+					WorkItemT<T>::promise.set_value();
+				}
+				else {
+					WorkItemT<T>::promise.set_value(std::apply(std::invoke<Params &...>, params));
+				}
+			}
+			catch (...) {
+				WorkItemT<T>::promise.set_exception(std::current_exception());
+			}
+		}
+
+		std::tuple<Params...> params;
+	};
+
 	Worker();
 	~Worker();
 
 	NO_COPY(Worker);
 	NO_MOVE(Worker);
 
-	using WorkPtr = std::unique_ptr<Work>;
+	using WorkPtr = std::shared_ptr<WorkItem>;
 
-	template<typename T, typename... Params>
-	void
-	addWork(Params &&... params)
-		requires std::is_base_of_v<Work, T>
+	template<typename... Params>
+	auto
+	addWorkImpl(Params &&... params)
 	{
-		addWork(std::make_unique<T>(std::forward<Params>(params)...));
+		using T = decltype(std::invoke(std::forward<Params>(params)...));
+		auto work = std::make_shared<WorkItemTImpl<T, Params...>>(this, std::forward<Params>(params)...);
+		addWorkPtr(work);
+		return work;
 	}
 
-	void addWork(WorkPtr w);
-
-private:
+	void addWorkPtr(WorkPtr w);
 	void worker();
+	void assist();
 
-	using Threads = std::vector<std::thread>;
+	using Threads = std::vector<std::jthread>;
 	using ToDo = std::deque<WorkPtr>;
 
-	Threads threads;
 	ToDo todo;
 	std::counting_semaphore<16> todoLen;
 	std::mutex todoMutex;
-};
-
-#else
+	Threads threads;
 
-class Worker {
-public:
-	template<typename T, typename... Params>
-	void
-	addWork(Params &&... params)
-		requires std::is_base_of_v<Work, T>
-	{
-		T(std::forward<Params>(params)...).doWork();
-	}
+	static Worker instance;
 };
-
-#endif