sol2/include/sol/protected_handler.hpp

// sol3 

// The MIT License (MIT)

// Copyright (c) 2013-2020 Rapptz, ThePhD and contributors

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#ifndef SOL_PROTECTED_HANDLER_HPP
#define SOL_PROTECTED_HANDLER_HPP

#include <sol/reference.hpp>
#include <sol/stack.hpp>
#include <sol/protected_function_result.hpp>
#include <sol/unsafe_function.hpp>
#include <cstdint>

namespace sol {
	namespace detail {
		inline const char(&default_handler_name())[9]{
			static const char name[9] = "sol.\xF0\x9F\x94\xA9";
			return name;
		}

		template <bool b, typename target_t = reference>
		struct protected_handler {
			typedef is_stack_based<target_t> is_stack;
			const target_t& target;
			int stackindex;

			protected_handler(std::false_type, const target_t& target)
				: target(target), stackindex(0) {
				if (b) {
					stackindex = lua_gettop(target.lua_state()) + 1;
					target.push();
				}
			}

			protected_handler(std::true_type, const target_t& target)
				: target(target), stackindex(0) {
				if (b) {
					stackindex = target.stack_index();
				}
			}

			protected_handler(const target_t& target)
				: protected_handler(is_stack(), target) {
			}

			bool valid() const noexcept {
				return b;
			}

			~protected_handler() {
				if constexpr (!is_stack::value) {
					if (stackindex != 0) {
						lua_remove(target.lua_state(), stackindex);
					}
				}
			}
		};

		template <typename base_t, typename T>
		basic_function<base_t> force_cast(T& p) {
			return p;
		}

		template <typename Reference, bool is_main_ref = false>
		static Reference get_default_handler(lua_State* L) {
			if (is_stack_based<Reference>::value || L == nullptr)
				return Reference(L, lua_nil);
			L = is_main_ref ? main_thread(L, L) : L;
			lua_getglobal(L, default_handler_name());
			auto pp = stack::pop_n(L, 1);
			return Reference(L, -1);
		}

		template <typename T>
		static void set_default_handler(lua_State* L, const T& ref) {
			if (L == nullptr) {
				return;
			}
			if (!ref.valid()) {
#if SOL_IS_ON(SOL_SAFE_STACK_CHECK_I_)
				luaL_checkstack(L, 1, detail::not_enough_stack_space_generic);
#endif // make sure stack doesn't overflow
				lua_pushnil(L);
				lua_setglobal(L, default_handler_name());
			}
			else {
				ref.push(L);
				lua_setglobal(L, default_handler_name());
			}
		}
	} // namespace detail
} // namespace sol

#endif // SOL_PROTECTED_HANDLER_HPP