helper.h

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// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2018 nerzhul, Loic Blot <loic.blot@unix-experience.fr>
 
#pragma once
 
#include <string_view>
#include <type_traits>
 
extern "C" {
#include <lua.h>
}
 
class LuaHelper
{
public:

        static bool geti(lua_State *L, int table, int i)
        {
                lua_rawgeti(L, table, i + 1);
                if (lua_isnil(L, -1)) {
                        lua_pop(L, 1);
                        return false;
                }
                return true;
        }

        template <typename F>
        static void for_ipairs(lua_State *L, int table, const F &f)
        {
                if (table < 0)
                        table = lua_gettop(L) + table + 1;
                static_assert(std::is_same_v<std::invoke_result_t<F>, void>);
                for (int i = 0; geti(L, table, i); ++i, lua_pop(L, 1))
                        f();
        }
 
 
protected:
        template <typename T>
        static T readParam(lua_State *L, int index);

        template <typename T>
        static inline T readParam(lua_State *L, int index, const T &default_value)
        {
                return lua_isnoneornil(L, index) ? default_value : readParam<T>(L, index);
        }
};
 
// (only declared for documentation purposes:)

template <>
std::string_view LuaHelper::readParam(lua_State *L, int index);