sol2/sol/protected_function.hpp

// The MIT License (MIT) 

// Copyright (c) 2013-2017 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
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// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#ifndef SOL_PROTECTED_FUNCTION_HPP
#define SOL_PROTECTED_FUNCTION_HPP

#include "reference.hpp"
#include "stack.hpp"
#include "protected_function_result.hpp"
#include "unsafe_function.hpp"
#include <cstdint>
#include <algorithm>

namespace sol {
	namespace detail {
		inline const char (&default_handler_name())[11] {
			static const char name[11] = "sol.\xF0\x9F\x94\xA9";
			return name;
		}

		template <bool b, typename target_t = reference>
		struct protected_handler {
			typedef std::is_base_of<stack_reference, 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 (!is_stack::value && stackindex != 0) {
					lua_remove(target.lua_state(), stackindex);
				}
			}
		};

		template <typename base_t, typename T>
		basic_function<base_t> force_cast(T& p) {
			return p;
		}
	} // detail
	
	template <typename base_t, bool aligned = false, typename handler_t = reference>
	class basic_protected_function : public base_t {
	public:
		typedef std::is_base_of<stack_reference, handler_t> is_stack_handler;

		static handler_t get_default_handler(lua_State* L) {
			if (is_stack_handler::value || L == nullptr)
				return handler_t(L, lua_nil);
			lua_getglobal(L, detail::default_handler_name());
			auto pp = stack::pop_n(L, 1);
			return handler_t(L, -1);
		}

		template <typename T>
		static void set_default_handler(const T& ref) {
			if (ref.lua_state() == nullptr) {
				return;
			}
			if (!ref.valid()) {
				lua_pushnil(ref.lua_state());
				lua_setglobal(ref.lua_state(), detail::default_handler_name());
			} 
			else {
				ref.push();
				lua_setglobal(ref.lua_state(), detail::default_handler_name());
			}
		}

	private:
		template <bool b>
		call_status luacall(std::ptrdiff_t argcount, std::ptrdiff_t resultcount, detail::protected_handler<b, handler_t>& h) const {
			return static_cast<call_status>(lua_pcallk(lua_state(), static_cast<int>(argcount), static_cast<int>(resultcount), h.stackindex, 0, nullptr));
		}

		template<std::size_t... I, bool b, typename... Ret>
		auto invoke(types<Ret...>, std::index_sequence<I...>, std::ptrdiff_t n, detail::protected_handler<b, handler_t>& h) const {
			luacall(n, sizeof...(Ret), h);
			return stack::pop<std::tuple<Ret...>>(lua_state());
		}

		template<std::size_t I, bool b, typename Ret>
		Ret invoke(types<Ret>, std::index_sequence<I>, std::ptrdiff_t n, detail::protected_handler<b, handler_t>& h) const {
			luacall(n, 1, h);
			return stack::pop<Ret>(lua_state());
		}

		template <std::size_t I, bool b>
		void invoke(types<void>, std::index_sequence<I>, std::ptrdiff_t n, detail::protected_handler<b, handler_t>& h) const {
			luacall(n, 0, h);
		}

		template <bool b>
		protected_function_result invoke(types<>, std::index_sequence<>, std::ptrdiff_t n, detail::protected_handler<b, handler_t>& h) const {
			int stacksize = lua_gettop(lua_state());
			int poststacksize = stacksize;
			int firstreturn = 1;
			int returncount = 0;
			call_status code = call_status::ok;
#ifndef SOL_NO_EXCEPTIONS
			auto onexcept = [&](const char* error) {
				h.stackindex = 0;
				if (b) {
					h.target.push();
					stack::push(lua_state(), error);
					lua_call(lua_state(), 1, 1);
				}
				else {
					stack::push(lua_state(), error);
				}
			};
			try {
#endif // No Exceptions
				firstreturn = (std::max)(1, static_cast<int>(stacksize - n - static_cast<int>(h.valid())));
				code = luacall(n, LUA_MULTRET, h);
				poststacksize = lua_gettop(lua_state()) - static_cast<int>(h.valid());
				returncount = poststacksize - (firstreturn - 1);
#ifndef SOL_NO_EXCEPTIONS
			}
			// Handle C++ errors thrown from C++ functions bound inside of lua
			catch (const char* error) {
				onexcept(error);
				firstreturn = lua_gettop(lua_state());
				return protected_function_result(lua_state(), firstreturn, 0, 1, call_status::runtime);
			}
			catch (const std::exception& error) {
				onexcept(error.what());
				firstreturn = lua_gettop(lua_state());
				return protected_function_result(lua_state(), firstreturn, 0, 1, call_status::runtime);
			}
			catch (...) {
				onexcept("caught (...) unknown error during protected_function call");
				firstreturn = lua_gettop(lua_state());
				return protected_function_result(lua_state(), firstreturn, 0, 1, call_status::runtime);
			}
#endif // No Exceptions
			return protected_function_result(lua_state(), firstreturn, returncount, returncount, code);
		}

	public:
		using base_t::lua_state;

		handler_t error_handler;

		basic_protected_function() = default;
		template <typename T, meta::enable<
			meta::neg<std::is_same<meta::unqualified_t<T>, basic_protected_function>>, 
			meta::neg<std::is_base_of<proxy_base_tag, meta::unqualified_t<T>>>, 
			meta::neg<std::is_same<base_t, stack_reference>>, 
			std::is_base_of<base_t, meta::unqualified_t<T>>
		> = meta::enabler>
		basic_protected_function(T&& r) noexcept : base_t(std::forward<T>(r)) {
#ifdef SOL_CHECK_ARGUMENTS
			if (!is_function<meta::unqualified_t<T>>::value) {
				auto pp = stack::push_pop(*this);
				constructor_handler handler{};
				stack::check<basic_protected_function>(lua_state(), -1, handler);
			}
#endif // Safety
		}
		basic_protected_function(const basic_protected_function&) = default;
		basic_protected_function& operator=(const basic_protected_function&) = default;
		basic_protected_function(basic_protected_function&&) = default;
		basic_protected_function& operator=(basic_protected_function&&) = default;
		basic_protected_function(const basic_function<base_t>& b) : basic_protected_function(b, get_default_handler(b.lua_state())) {}
		basic_protected_function(basic_function<base_t>&& b) : basic_protected_function(std::move(b), get_default_handler(b.lua_state())) {}
		basic_protected_function(const basic_function<base_t>& b, handler_t eh) : base_t(b), error_handler(std::move(eh)) {}
		basic_protected_function(basic_function<base_t>&& b, handler_t eh) : base_t(std::move(b)), error_handler(std::move(eh)) {}
		basic_protected_function(const stack_reference& r) : basic_protected_function(r.lua_state(), r.stack_index(), get_default_handler(r.lua_state())) {}
		basic_protected_function(stack_reference&& r) : basic_protected_function(r.lua_state(), r.stack_index(), get_default_handler(r.lua_state())) {}
		basic_protected_function(const stack_reference& r, handler_t eh) : basic_protected_function(r.lua_state(), r.stack_index(), std::move(eh)) {}
		basic_protected_function(stack_reference&& r, handler_t eh) : basic_protected_function(r.lua_state(), r.stack_index(), std::move(eh)) {}

		template <typename Super>
		basic_protected_function(const proxy_base<Super>& p) : basic_protected_function(p, get_default_handler(p.lua_state())) {}
		template <typename Super>
		basic_protected_function(proxy_base<Super>&& p) : basic_protected_function(std::move(p), get_default_handler(p.lua_state())) {}
		template <typename Proxy, typename Handler, meta::enable<
			std::is_base_of<proxy_base_tag, meta::unqualified_t<Proxy>>,
			meta::neg<is_lua_index<meta::unqualified_t<Handler>>>
		> = meta::enabler>
		basic_protected_function(Proxy&& p, Handler&& eh) : basic_protected_function(detail::force_cast<base_t>(p), std::forward<Handler>(eh)) {}

		template <typename T, meta::enable<meta::neg<is_lua_index<meta::unqualified_t<T>>>> = meta::enabler>
		basic_protected_function(lua_State* L, T&& r) : basic_protected_function(L, std::forward<T>(r), get_default_handler(L)) {}
		template <typename T, meta::enable<meta::neg<is_lua_index<meta::unqualified_t<T>>>> = meta::enabler>
		basic_protected_function(lua_State* L, T&& r, handler_t eh) : basic_protected_function(L, sol::ref_index(r.registry_index()), std::move(eh)) {}

		basic_protected_function(lua_State* L, int index = -1) : basic_protected_function(L, index, get_default_handler(L)) {}
		basic_protected_function(lua_State* L, int index, handler_t eh) : base_t(L, index), error_handler(std::move(eh)) {
#ifdef SOL_CHECK_ARGUMENTS
			constructor_handler handler{};
			stack::check<basic_protected_function>(L, index, handler);
#endif // Safety
		}
		basic_protected_function(lua_State* L, absolute_index index) : basic_protected_function(L, index, get_default_handler(L)) {}
		basic_protected_function(lua_State* L, absolute_index index, handler_t eh) : base_t(L, index), error_handler(std::move(eh)) {
#ifdef SOL_CHECK_ARGUMENTS
			constructor_handler handler{};
			stack::check<basic_protected_function>(L, index, handler);
#endif // Safety
		}
		basic_protected_function(lua_State* L, raw_index index) : basic_protected_function(L, index, get_default_handler(L)) {}
		basic_protected_function(lua_State* L, raw_index index, handler_t eh) : base_t(L, index), error_handler(std::move(eh)) {
#ifdef SOL_CHECK_ARGUMENTS
			constructor_handler handler{};
			stack::check<basic_protected_function>(L, index, handler);
#endif // Safety
		}
		basic_protected_function(lua_State* L, ref_index index) : basic_protected_function(L, index, get_default_handler(L)) {}
		basic_protected_function(lua_State* L, ref_index index, handler_t eh) : base_t(L, index), error_handler(std::move(eh)) {
#ifdef SOL_CHECK_ARGUMENTS
			auto pp = stack::push_pop(*this);
			constructor_handler handler{};
			stack::check<basic_protected_function>(L, -1, handler);
#endif // Safety
		}

		template<typename... Args>
		protected_function_result operator()(Args&&... args) const {
			return call<>(std::forward<Args>(args)...);
		}

		template<typename... Ret, typename... Args>
		decltype(auto) operator()(types<Ret...>, Args&&... args) const {
			return call<Ret...>(std::forward<Args>(args)...);
		}

		template<typename... Ret, typename... Args>
		decltype(auto) call(Args&&... args) const {
			if (!aligned) {
				// we do not expect the function to already be on the stack: push it
				if (error_handler.valid()) {
					detail::protected_handler<true, handler_t> h(error_handler);
					base_t::push();
					int pushcount = stack::multi_push_reference(lua_state(), std::forward<Args>(args)...);
					return invoke(types<Ret...>(), std::make_index_sequence<sizeof...(Ret)>(), pushcount, h);
				}
				else {
					detail::protected_handler<false, handler_t> h(error_handler);
					base_t::push();
					int pushcount = stack::multi_push_reference(lua_state(), std::forward<Args>(args)...);
					return invoke(types<Ret...>(), std::make_index_sequence<sizeof...(Ret)>(), pushcount, h);
				}
			}
			else {
				// the function is already on the stack at the right location
				if (error_handler.valid()) {
					// the handler will be pushed onto the stack manually,
					// since it's not already on the stack this means we need to push our own
					// function on the stack too and swap things to be in-place
					if (!is_stack_handler::value) {
						// so, we need to remove the function at the top and then dump the handler out ourselves
						base_t::push();
					}
					detail::protected_handler<true, handler_t> h(error_handler);
					if (!is_stack_handler::value) {
						lua_replace(lua_state(), -3);
						h.stackindex = lua_absindex(lua_state(), -2);
					}
					int pushcount = stack::multi_push_reference(lua_state(), std::forward<Args>(args)...);
					return invoke(types<Ret...>(), std::make_index_sequence<sizeof...(Ret)>(), pushcount, h);
				}
				else {
					detail::protected_handler<false, handler_t> h(error_handler);
					int pushcount = stack::multi_push_reference(lua_state(), std::forward<Args>(args)...);
					return invoke(types<Ret...>(), std::make_index_sequence<sizeof...(Ret)>(), pushcount, h);
				}
			}
		}
	};
} // sol

#endif // SOL_FUNCTION_HPP