add macOS implementation

macos/include/ThreadPool.hpp

@@ -0,0 +1,79 @@
+/*
+ * This file is licensed under the zlib/libpng license, included in this
+ * distribution in the file COPYING.
+ */
+
+#include <future>
+#include <thread>
+#include <deque>
+#include <vector>
+#include <utility>
+#include <chrono>
+#include <functional>
+#include <type_traits>
+
+#ifndef _THREADPOOL_HPP
+#define _THREADPOOL_HPP
+
+namespace polyvox {
+
+class ThreadPool {
+	std::vector<std::thread> pool;
+	bool stop;
+
+	std::mutex access;
+	std::condition_variable cond;
+	std::deque<std::function<void()>> tasks;
+
+public:
+	explicit ThreadPool(int nr = 1) : stop(false) {
+		while(nr-->0) {
+			add_worker();
+		}
+	}
+	~ThreadPool() {
+		stop = true;
+		for(std::thread &t : pool) {
+			t.join();
+		}
+		pool.clear();
+	}
+
+	template<class Rt>
+	auto add_task(std::packaged_task<Rt()>& pt) -> std::future<Rt> {
+		std::unique_lock<std::mutex> lock(access);
+
+		auto ret = pt.get_future();
+		tasks.push_back([pt=std::make_shared<std::packaged_task<Rt()>>(std::move(pt))]{ (*pt)();});
+
+		cond.notify_one();
+
+		return ret;
+	}
+
+private:
+	void add_worker() {
+		std::thread t([this]() {
+			while(!stop) {
+				std::function<void()> task;
+				{
+					std::unique_lock<std::mutex> lock(access);
+					if(tasks.empty()) {
+						cond.wait_for(lock, std::chrono::duration<int, std::milli>(5));
+						continue;
+					}
+					task = std::move(tasks.front());
+					tasks.pop_front();
+				}
+				task();
+			}
+		});
+		pool.push_back(std::move(t));
+	}
+};
+
+}
+
+#endif//_THREADPOOL_HPP
+
+// vim: syntax=cpp11