thread pool (untested)

include/blt/std/thread.h

@@ -0,0 +1,119 @@
+/*
+ *  <Short Description>
+ *  Copyright (C) 2023  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef BLT_THREAD_H
+#define BLT_THREAD_H
+
+#include <thread>
+#include <functional>
+#include <string>
+#include <vector>
+#include <queue>
+#include <variant>
+#include <atomic>
+#include <mutex>
+#include <chrono>
+
+namespace blt
+{
+    /**
+     * @tparam queue should we use a queue or execute the same function over and over?
+     */
+    template<bool queue = false>
+    class thread_pool
+    {
+        private:
+            typedef std::function<void()> thread_function;
+            volatile std::atomic_bool should_stop = false;
+            std::vector<std::thread*> threads;
+            std::variant<std::queue<thread_function>, thread_function> func_queue;
+            std::mutex queue_mutex;
+        public:
+            explicit thread_pool(size_t number_of_threads = 8)
+            {
+                for (size_t i = 0; i < number_of_threads; i++)
+                {
+                    threads.push_back(new std::thread([this]() {
+                        while (!should_stop)
+                        {
+                            if constexpr (queue)
+                            {
+                                // should be safe right?
+                                std::unique_lock lock(queue_mutex);
+                                lock.lock();
+                                auto& func_q = std::get<std::queue<thread_function>>(func_queue);
+                                if (func_q.empty())
+                                {
+                                    lock.unlock();
+                                    std::this_thread::sleep_for(std::chrono::milliseconds(16));
+                                    continue;
+                                }
+                                auto func = func_q.front();
+                                func_q.pop();
+                                lock.unlock();
+                                func();
+                            } else
+                            {
+                                {
+                                    std::scoped_lock lock(queue_mutex);
+                                    if (std::holds_alternative<std::queue<thread_function>>(func_queue))
+                                    {
+                                        std::this_thread::sleep_for(std::chrono::milliseconds(16));
+                                        continue;
+                                    }
+                                }
+                                auto& func = std::get<thread_function>(func_queue);
+                                func();
+                            }
+                        }
+                    }));
+                }
+            }
+            
+            inline void execute(const thread_function& func)
+            {
+                std::scoped_lock lock(queue_mutex);
+                if constexpr (queue)
+                {
+                    auto& v = std::get<std::queue<thread_function>>(func_queue);
+                    v.push(func);
+                } else
+                {
+                    func_queue = func;
+                }
+            }
+            
+            inline void stop()
+            {
+                should_stop = true;
+            }
+            
+            ~thread_pool()
+            {
+                should_stop = true;
+                for (auto* t : threads)
+                {
+                    if (t->joinable())
+                        t->join();
+                    delete t;
+                }
+            }
+    };
+}
+
+#endif //BLT_THREAD_H