init

Telegram/lib_base/base/unique_any.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+#include <any>
+
+namespace base {
+namespace details {
+
+template <typename Value>
+struct moveable_as_copyable_wrap {
+	moveable_as_copyable_wrap(Value &&other)
+	: value(std::move(other)) {
+	}
+	moveable_as_copyable_wrap &operator=(Value &&other) {
+		value = std::move(other);
+		return *this;
+	}
+	moveable_as_copyable_wrap(moveable_as_copyable_wrap &&other)
+	: value(std::move(other.value)) {
+	}
+	moveable_as_copyable_wrap(
+			const moveable_as_copyable_wrap &other) {
+		Unexpected("Attempt to copy-construct a move-only type.");
+	}
+	moveable_as_copyable_wrap &operator=(
+			moveable_as_copyable_wrap &&other) {
+		value = std::move(other.value);
+		return *this;
+	}
+	moveable_as_copyable_wrap &operator=(
+			const moveable_as_copyable_wrap &other) {
+		Unexpected("Attempt to copy-assign a move-only type.");
+	}
+
+	Value value;
+
+};
+
+template <
+	typename Value,
+	typename = std::enable_if_t<
+		std::is_move_constructible_v<std::decay_t<Value>>
+		&& !std::is_lvalue_reference_v<Value>>>
+auto wrap_moveable_as_copyable(Value &&value) {
+	return moveable_as_copyable_wrap<Value>(std::move(value));
+}
+
+} // namespace details
+
+class unique_any;
+
+template <typename Value>
+Value *any_cast(unique_any *value) noexcept;
+
+template <typename Value>
+const Value *any_cast(const unique_any *value) noexcept;
+
+class unique_any final {
+public:
+	// Construction and destruction [any.cons]
+	constexpr unique_any() noexcept {
+	}
+
+	unique_any(const unique_any &other) = delete;
+	unique_any &operator=(const unique_any &other) = delete;
+
+	unique_any(unique_any &&other) noexcept
+	: _impl(std::move(other._impl)) {
+	}
+
+	unique_any &operator=(unique_any &&other) noexcept {
+		_impl = std::move(other._impl);
+		return *this;
+	}
+
+	template <
+		typename Value,
+		typename = std::enable_if_t<
+			!std::is_same_v<std::decay_t<Value>, unique_any>>>
+	unique_any(Value &&other)
+	: unique_any(
+		std::forward<Value>(other),
+		std::is_copy_constructible<std::decay_t<Value>>()) {
+	}
+
+	template <
+		typename Value,
+		typename = std::enable_if_t<
+			!std::is_same_v<std::decay_t<Value>, unique_any>>>
+	unique_any &operator=(Value &&other) {
+		if constexpr (std::is_copy_constructible_v<std::decay_t<Value>>) {
+			_impl = std::forward<Value>(other);
+		} else if constexpr (std::is_move_constructible_v<std::decay_t<Value>>
+			&& !std::is_lvalue_reference_v<Value>) {
+			_impl = details::wrap_moveable_as_copyable(std::move(other));
+		} else {
+			static_assert(
+				false_t(Value{}),
+				"Bad value for base::unique_any.");
+		}
+		return *this;
+	}
+
+	template <
+		typename Value,
+		typename ...Args,
+		typename = std::enable_if_t<
+			std::is_constructible_v<std::decay_t<Value>, Args...>
+			&& std::is_copy_constructible_v<decay_t<Value>>>>
+	std::decay_t<Value> &emplace(Args &&...args) {
+		return _impl.emplace<Value>(std::forward<Args>(args)...);
+	}
+
+	void reset() noexcept {
+		_impl.reset();
+	}
+
+	void swap(unique_any &other) noexcept {
+		_impl.swap(other._impl);
+	}
+
+	bool has_value() const noexcept {
+		return _impl.has_value();
+	}
+
+	// Should check if it is a moveable_only wrap first.
+	//const std::type_info &type() const noexcept {
+	//	return _impl.type();
+	//}
+
+private:
+	template <
+		typename Value,
+		typename = std::enable_if_t<
+			!std::is_same_v<std::decay_t<Value>, unique_any>
+			&& std::is_copy_constructible_v<std::decay_t<Value>>>>
+	unique_any(Value &&other, std::true_type)
+	: _impl(std::forward<Value>(other)) {
+	}
+
+	template <
+		typename Value,
+		typename = std::enable_if_t<
+			!std::is_same_v<std::decay_t<Value>, unique_any>
+			&& !std::is_copy_constructible_v<std::decay_t<Value>>
+			&& std::is_move_constructible_v<std::decay_t<Value>>
+			&& !std::is_lvalue_reference_v<Value>>>
+	unique_any(Value &&other, std::false_type)
+	: _impl(details::wrap_moveable_as_copyable(std::move(other))) {
+	}
+
+	template <
+		typename Value,
+		typename ...Args>
+	friend unique_any make_any(Args &&...args);
+
+	template <typename Value>
+	friend const Value *any_cast(const unique_any *value) noexcept;
+
+	template <typename Value>
+	friend Value *any_cast(unique_any *value) noexcept;
+
+	std::any _impl;
+
+};
+
+inline void swap(unique_any &a, unique_any &b) noexcept {
+	a.swap(b);
+}
+
+template <
+	typename Value,
+	typename ...Args>
+inline auto make_any(Args &&...args)
+-> std::enable_if_t<
+		std::is_copy_constructible_v<std::decay_t<Value>>,
+		unique_any> {
+	return std::make_any<Value>(std::forward<Args>(args)...);
+}
+
+template <
+	typename Value,
+	typename ...Args>
+inline auto make_any(Args &&...args)
+-> std::enable_if_t<
+		!std::is_copy_constructible_v<std::decay_t<Value>>
+		&& std::is_move_constructible_v<std::decay_t<Value>>,
+		unique_any> {
+	return Value(std::forward<Args>(args)...);
+}
+
+template <typename Value>
+inline Value *any_cast(unique_any *value) noexcept {
+	if constexpr (std::is_copy_constructible_v<Value>) {
+		return std::any_cast<Value>(&value->_impl);
+	} else if constexpr (std::is_move_constructible_v<Value>) {
+		auto wrap = std::any_cast<
+			details::moveable_as_copyable_wrap<Value>
+		>(&value->_impl);
+		return wrap ? &wrap->value : nullptr;
+	} else {
+		static_assert(
+			false_t(Value{}),
+			"Bad type for base::any_cast.");
+	}
+}
+
+template <typename Value>
+inline const Value *any_cast(const unique_any *value) noexcept {
+	if constexpr (std::is_copy_constructible_v<Value>) {
+		return std::any_cast<Value>(&value->_impl);
+	} else if constexpr (std::is_move_constructible_v<Value>) {
+		auto wrap = std::any_cast<
+			details::moveable_as_copyable_wrap<Value>
+		>(&value->_impl);
+		return wrap ? &wrap->value : nullptr;
+	} else {
+		static_assert(
+			false_t(Value{}),
+			"Bad type for base::any_cast.");
+	}
+}
+
+} // namespace base