BAN: Add basic Optional

BAN/include/BAN/Optional.h

@@ -0,0 +1,119 @@
+#pragma once
+
+#include <BAN/Assert.h>
+#include <BAN/Move.h>
+
+#include <stdint.h>
+
+namespace BAN
+{
+
+	template<typename T>
+	class Optional
+	{
+	public:
+		Optional();
+		Optional(const T&);
+		Optional(T&&);
+		~Optional();
+
+		Optional& operator=(const Optional&);
+		Optional& operator=(Optional&&);
+
+		bool has_value() const;
+
+		T&& release_value();
+		const T& value() const;
+		T& value();
+
+		void clear();
+
+	private:
+		alignas(T) uint8_t m_storage[sizeof(T)];
+		bool m_has_value { false };
+	};
+
+	template<typename T>
+	Optional<T>::Optional()
+		: m_has_value(false)
+	{}
+
+	template<typename T>
+	Optional<T>::Optional(const T& value)
+		: m_has_value(true)
+	{
+		new (m_storage) T(value);	
+	}
+
+	template<typename T>
+	Optional<T>::Optional(T&& value)
+		: m_has_value(true)
+	{
+		new (m_storage) T(BAN::move(value));
+	}
+
+	template<typename T>
+	Optional<T>::~Optional()
+	{
+		clear();
+	}
+
+	template<typename T>
+	Optional<T>& Optional<T>::operator=(const Optional& other)
+	{
+		clear();
+		if (other.has_value())
+		{
+			m_has_value = true;
+			new (m_storage) T(other.value());
+		}
+	}
+
+	template<typename T>
+	Optional<T>& Optional<T>::operator=(Optional&& other)
+	{
+		clear();
+		if (other.has_value)
+		{
+			m_has_value = true;
+			new (m_storage) T(BAN::move(other.relase_value()));
+		}
+	}
+
+	template<typename T>
+	bool Optional<T>::has_value() const
+	{
+		return m_has_value;
+	}
+
+	template<typename T>
+	T&& Optional<T>::release_value()
+	{
+		ASSERT(has_value());
+		m_has_value = false;
+		return BAN::move((T&)m_storage);
+	}
+
+	template<typename T>
+	const T& Optional<T>::value() const
+	{
+		ASSERT(has_value());
+		return (const T&)m_storage;
+	}
+	
+	template<typename T>
+	T& Optional<T>::value()
+	{
+		ASSERT(has_value());
+		return (T&)m_storage;
+	}
+
+	template<typename T>
+	void Optional<T>::clear()
+	{
+		if (m_has_value)
+			value().~T();
+		m_has_value = false;
+	}
+
+}