[ox/std] Add Optional

deps/ox/src/ox/std/CMakeLists.txt

@@ -80,6 +80,7 @@ install(
 		memops.hpp
 		memory.hpp
 		new.hpp
+		optional.hpp
 		random.hpp
 		std.hpp
 		stddef.hpp

deps/ox/src/ox/std/optional.hpp

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2015 - 2021 gary@drinkingtea.net
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include "bit.hpp"
+#include "initializerlist.hpp"
+#include "iterator.hpp"
+#include "new.hpp"
+#include "types.hpp"
+#include "utility.hpp"
+
+namespace ox {
+
+template<typename T, std::size_t buffSize = sizeof(T)>
+class Optional {
+	private:
+		T *m_ptr = nullptr;
+		char m_data[buffSize];
+
+	public:
+		Optional() noexcept = default;
+
+		Optional(const Optional &other) {
+			if (m_ptr) {
+				m_ptr->~T();
+			}
+			if (other.m_ptr) {
+				m_ptr = new(m_data) T(*other.m_ptr);
+			} else {
+				m_ptr = nullptr;
+			}
+		}
+
+		Optional(const Optional &&other) noexcept {
+			if (m_ptr) {
+				m_ptr->~T();
+			}
+			if (other.m_ptr) {
+				m_ptr = new(m_data) T(std::move(*other.m_ptr));
+			} else {
+				m_ptr = nullptr;
+			}
+		}
+
+		template<typename U = T>
+		constexpr U *get() noexcept {
+			return m_ptr;
+		}
+
+		template<typename U = T>
+		constexpr const U *get() const noexcept {
+			return m_ptr;
+		}
+
+		constexpr T &operator*() & noexcept {
+			return m_ptr;
+		}
+
+		constexpr const T &operator*() const & noexcept {
+			return m_ptr;
+		}
+
+		constexpr T &&operator*() && noexcept {
+			return m_ptr;
+		}
+
+		constexpr const T &&operator*() const && noexcept {
+			return m_ptr;
+		}
+
+		constexpr T *operator->() noexcept {
+			return m_ptr;
+		}
+
+		constexpr const T *operator->() const noexcept {
+			return m_ptr;
+		}
+
+		Optional &operator=(const Optional &other) {
+			if (this == &other) {
+				return *this;
+			}
+			if (m_ptr) {
+				m_ptr->~T();
+			}
+			if (other.m_ptr) {
+				m_ptr = new(m_data) T(*other.m_ptr);
+			} else {
+				m_ptr = nullptr;
+			}
+			return *this;
+		}
+
+		Optional &operator=(Optional &&other) noexcept {
+			if (this == &other) {
+				return *this;
+			}
+			if (m_ptr) {
+				m_ptr->~T();
+			}
+			if (other.m_ptr) {
+				m_ptr = new(m_data) T(std::move(*other.m_ptr));
+			} else {
+				m_ptr = nullptr;
+			}
+			return *this;
+		}
+
+		template<class... Args>
+		constexpr T &emplace(Args &&...args) {
+			m_ptr = new (m_data) T(ox::forward<Args>(args)...);
+			return *m_ptr;
+		}
+
+		template<typename U, class... Args>
+		constexpr T &emplace_subclass(Args &&...args) {
+			static_assert(sizeof(U) <= buffSize, "Subclass is too large for this Optional");
+			m_ptr = new (m_data) U(ox::forward<Args>(args)...);
+			return *m_ptr;
+		}
+
+		[[nodiscard]]
+		constexpr bool has_value() const noexcept {
+			return m_ptr;
+		}
+
+		explicit constexpr operator bool() const noexcept {
+			return m_ptr;
+		}
+
+		constexpr void reset() noexcept {
+			get()->~T();
+			m_ptr = nullptr;
+		}
+
+};
+
+}

deps/ox/src/ox/std/std.hpp

@@ -24,6 +24,7 @@
 #include "memops.hpp"
 #include "memory.hpp"
 #include "new.hpp"
+#include "optional.hpp"
 #include "random.hpp"
 #include "stacktrace.hpp"
 #include "stddef.hpp"