From 35612572861815d54b3764a8a88332b206bf6f5e Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Mon, 16 Jan 2023 14:59:33 +0200
Subject: [PATCH] BAN: Add basic Function for function pointers and member
 functions

---
 BAN/include/BAN/Function.h | 110 +++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 BAN/include/BAN/Function.h

diff --git a/BAN/include/BAN/Function.h b/BAN/include/BAN/Function.h
new file mode 100644
index 00000000..c171d42a
--- /dev/null
+++ b/BAN/include/BAN/Function.h
@@ -0,0 +1,110 @@
+#pragma once
+
+#include <BAN/Errors.h>
+
+namespace BAN
+{
+
+	template<typename>
+	class Function;
+	template<typename Ret, typename... Args>
+	class Function<Ret(Args...)>
+	{
+	public:
+		Function() {}
+		Function(Ret(*function)(Args...))
+		{
+			static_assert(sizeof(CallablePointer) <= m_size);
+			new (m_storage) CallablePointer(function);
+		}
+		template<typename Own>
+		Function(Ret(Own::*function)(Args...), Own* owner)
+		{
+			static_assert(sizeof(CallableMember<Own>) <= m_size);
+			new (m_storage) CallableMember<Own>(function, owner);
+		}
+		template<typename Own>
+		Function(Ret(Own::*function)(Args...) const, const Own* owner)
+		{
+			static_assert(sizeof(CallableMemberConst<Own>) <= m_size);
+			new (m_storage) CallableMemberConst<Own>(function, owner);
+		}
+
+		Ret operator()(const Args&... args)
+		{
+			ASSERT(HasFunction());
+			return ((CallableBase*)m_storage)->call(args...);
+		}
+
+		bool HasFunction() const
+		{
+			for (size_t i = 0; i < m_size; i++)
+				if (m_storage[i])
+					return true;
+			return false;
+		}
+		
+	private:
+		struct CallableBase
+		{
+			virtual ~CallableBase() {}
+			virtual Ret call(const Args&...) = 0;
+		};
+
+		struct CallablePointer : public CallableBase
+		{
+			CallablePointer(Ret(*function)(Args...))
+				: m_function(function)
+			{ }
+
+			virtual Ret call(const Args&... args) override
+			{
+				return m_function(args...);
+			}
+
+		private:
+			Ret(*m_function)(Args...) = nullptr;
+		};
+
+		template<typename Own>
+		struct CallableMember : public CallableBase
+		{
+			CallableMember(Ret(Own::*function)(Args...), Own* owner)
+				: m_owner(owner)
+				, m_function(function)
+			{ }
+
+			virtual Ret call(const Args&... args) override
+			{
+				return (m_owner->*m_function)(args...);
+			}
+
+		private:
+			Own* m_owner = nullptr;
+			Ret(Own::*m_function)(Args...) = nullptr;
+		};
+
+		template<typename Own>
+		struct CallableMemberConst : public CallableBase
+		{
+			CallableMemberConst(Ret(Own::*function)(Args...) const, const Own* owner)
+				: m_owner(owner)
+				, m_function(function)
+			{ }
+
+			virtual Ret call(const Args&... args) override
+			{
+				return (m_owner->*m_function)(args...);
+			}
+
+		private:
+			const Own* m_owner = nullptr;
+			Ret(Own::*m_function)(Args...) const = nullptr;
+		};
+
+	private:
+		static constexpr size_t m_size = sizeof(void*) * 4;
+		alignas(max_align_t) uint8_t m_storage[m_size] { 0 };
+	};
+
+}
\ No newline at end of file