Moved implementation away with pimpl aka cheshire cat pattern

src/impl/threadpool.hpp

@@ -0,0 +1,124 @@
+/**
+ * Copyright (c) 2020 Paul-Louis Ageneau
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef RTC_IMPL_THREADPOOL_H
+#define RTC_IMPL_THREADPOOL_H
+
+#include "include.hpp"
+#include "init.hpp"
+
+#include <chrono>
+#include <condition_variable>
+#include <deque>
+#include <functional>
+#include <future>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <stdexcept>
+#include <thread>
+#include <vector>
+
+namespace rtc::impl {
+
+template <class F, class... Args>
+using invoke_future_t = std::future<std::invoke_result_t<std::decay_t<F>, std::decay_t<Args>...>>;
+
+class ThreadPool final {
+public:
+	using clock = std::chrono::steady_clock;
+
+	static ThreadPool &Instance();
+
+	ThreadPool(const ThreadPool &) = delete;
+	ThreadPool &operator=(const ThreadPool &) = delete;
+	ThreadPool(ThreadPool &&) = delete;
+	ThreadPool &operator=(ThreadPool &&) = delete;
+
+	int count() const;
+	void spawn(int count = 1);
+	void join();
+	void run();
+	bool runOne();
+
+	template <class F, class... Args>
+	auto enqueue(F &&f, Args &&...args) -> invoke_future_t<F, Args...>;
+
+	template <class F, class... Args>
+	auto schedule(clock::duration delay, F &&f, Args &&...args) -> invoke_future_t<F, Args...>;
+
+	template <class F, class... Args>
+	auto schedule(clock::time_point time, F &&f, Args &&...args) -> invoke_future_t<F, Args...>;
+
+protected:
+	ThreadPool();
+	~ThreadPool();
+
+	std::function<void()> dequeue(); // returns null function if joining
+
+	std::vector<std::thread> mWorkers;
+	int mWaitingWorkers = 0;
+	std::atomic<bool> mJoining = false;
+
+	struct Task {
+		clock::time_point time;
+		std::function<void()> func;
+		bool operator>(const Task &other) const { return time > other.time; }
+		bool operator<(const Task &other) const { return time < other.time; }
+	};
+	std::priority_queue<Task, std::deque<Task>, std::greater<Task>> mTasks;
+
+	std::condition_variable mTasksCondition, mWaitingCondition;
+	mutable std::mutex mMutex, mWorkersMutex;
+};
+
+template <class F, class... Args>
+auto ThreadPool::enqueue(F &&f, Args &&...args) -> invoke_future_t<F, Args...> {
+	return schedule(clock::now(), std::forward<F>(f), std::forward<Args>(args)...);
+}
+
+template <class F, class... Args>
+auto ThreadPool::schedule(clock::duration delay, F &&f, Args &&...args)
+    -> invoke_future_t<F, Args...> {
+	return schedule(clock::now() + delay, std::forward<F>(f), std::forward<Args>(args)...);
+}
+
+template <class F, class... Args>
+auto ThreadPool::schedule(clock::time_point time, F &&f, Args &&...args)
+    -> invoke_future_t<F, Args...> {
+	std::unique_lock lock(mMutex);
+	using R = std::invoke_result_t<std::decay_t<F>, std::decay_t<Args>...>;
+	auto bound = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
+	auto task = std::make_shared<std::packaged_task<R()>>([bound = std::move(bound)]() mutable {
+		try {
+			return bound();
+		} catch (const std::exception &e) {
+			PLOG_WARNING << e.what();
+			throw;
+		}
+	});
+	std::future<R> result = task->get_future();
+
+	mTasks.push({time, [task = std::move(task), token = Init::Token()]() { return (*task)(); }});
+	mTasksCondition.notify_one();
+	return result;
+}
+
+} // namespace rtc::impl
+
+#endif