Add atomic_shared.hpp for possible future use

include/raii/atomic_shared.hpp

@@ -0,0 +1,98 @@
+/**
+	This file is a part of rexy's matrix client
+	Copyright (C) 2019 rexy712
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Affero 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 Affero General Public License for more details.
+
+	You should have received a copy of the GNU Affero General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef RAII_ATOMIC_SHARED_HPP
+#define RAII_ATOMIC_SHARED_HPP
+
+#include <memory> //shared_ptr
+#include <atomic> //atomic_shared_ptr
+
+#if __cplusplus > 201703L //newer than c++17
+
+namespace raii{
+	template<class T>
+	using atomic_shared_ptr = std::atomic<std::shared_ptr<T>>;
+}
+
+#else //c++17 or older
+
+namespace raii{
+
+	template<class T>
+	class atomic_shared_ptr
+	{
+	private:
+		static constexpr bool is_always_lock_free = (ATOMIC_POINTER_LOCK_FREE == 2);
+
+	private:
+		std::shared_ptr<T> m_data;
+
+	public:
+		constexpr atomic_shared_ptr(void)noexcept = default;
+		atomic_shared_ptr(std::shared_ptr<T> desired)noexcept:
+			m_data(std::move(desired)){}
+		atomic_shared_ptr(const atomic_shared_ptr&) = delete;
+
+		void operator=(const atomic_shared_ptr&) = delete;
+		void operator=(std::shared_ptr<T> desired)noexcept{
+			store(desired);
+		}
+		bool is_lock_free(void)const noexcept{
+			return std::atomic_is_lock_free(&m_data);
+		}
+		void store(std::shared_ptr<T> desired, std::memory_order order = std::memory_order_seq_cst)noexcept{
+			return std::atomic_store_explicit(&m_data, desired, order);
+		}
+		std::shared_ptr<T> load(std::memory_order order = std::memory_order_seq_cst)const noexcept{
+			return std::atomic_load(&m_data);
+		}
+		operator std::shared_ptr<T>(void)const noexcept{
+			return load();
+		}
+		std::shared_ptr<T> exchange(std::shared_ptr<T> desired, std::memory_order order = std::memory_order_seq_cst)noexcept{
+			return std::atomic_exchange_explicit(&m_data, desired, order);
+		}
+		bool compare_exchange_strong(std::shared_ptr<T>& expected, std::shared_ptr<T> desired, std::memory_order success, std::memory_order failure)noexcept{
+			return std::atomic_compare_exchange_strong_explicit(&m_data, &expected, desired, success, failure);
+		}
+		bool compare_exchange_strong(std::shared_ptr<T>& expected, std::shared_ptr<T> desired, std::memory_order order = std::memory_order_seq_cst)noexcept{
+			std::memory_order fail_order = order;
+			if(fail_order == std::memory_order_acq_rel)
+				fail_order = std::memory_order_acquire;
+			else if(fail_order == std::memory_order_release)
+				fail_order = std::memory_order_relaxed;
+			return compare_exchange_strong(expected, desired, order, fail_order);
+		}
+		bool compare_exchange_weak(std::shared_ptr<T>& expected, std::shared_ptr<T> desired, std::memory_order success, std::memory_order failure)noexcept{
+			return std::atomic_compare_exchange_weak_explicit(&m_data, &expected, desired, success, failure);
+		}
+		bool compare_exchange_weak(std::shared_ptr<T>& expected, std::shared_ptr<T> desired, std::memory_order order = std::memory_order_seq_cst)noexcept{
+			std::memory_order fail_order = order;
+			if(fail_order == std::memory_order_acq_rel)
+				fail_order = std::memory_order_acquire;
+			else if(fail_order == std::memory_order_release)
+				fail_order = std::memory_order_relaxed;
+			return compare_exchange_weak(expected, desired, order, fail_order);
+		}
+	};
+
+}
+
+#endif //__cplusplus
+
+#endif //RAII_ATOMIC_SHARED_HPP