l_base.h

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// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
 
#pragma once
 
#include "common/c_types.h"
#include "common/helper.h"
#include "config.h"
#include "debug.h"
#include "gamedef.h"
 
extern "C" {
#include <lua.h>
#include <lauxlib.h>
}
 
#if CHECK_CLIENT_BUILD()
class Client;
class GUIEngine;
#endif
class EmergeThread;
class ScriptApiBase;
class Server;
class Environment;
class SSCSMEnvironment;
class ServerInventoryManager;
 
class ModApiBase : protected LuaHelper {
public:
        static ScriptApiBase*   getScriptApiBase(lua_State *L);
        static Server*          getServer(lua_State *L);
        static ServerInventoryManager *getServerInventoryMgr(lua_State *L);
        #if CHECK_CLIENT_BUILD()
        static Client*          getClient(lua_State *L);
        static GUIEngine*       getGuiEngine(lua_State *L);
        static SSCSMEnvironment *getSSCSMEnv(lua_State *L);
        #endif // !SERVER
        static EmergeThread*    getEmergeThread(lua_State *L);
 
        static IGameDef*        getGameDef(lua_State *L);
 
        static Environment*     getEnv(lua_State *L);
 
        // When we are not loading the mod, this function returns "."
        static std::string      getCurrentModPath(lua_State *L);
 
        // Get an arbitrary subclass of ScriptApiBase
        // by using dynamic_cast<> on getScriptApiBase()
        template<typename T>
        static T* getScriptApi(lua_State *L) {
                ScriptApiBase *scriptIface = getScriptApiBase(L);
                T *scriptIfaceDowncast = dynamic_cast<T*>(scriptIface);
                if (!scriptIfaceDowncast) {
                        throw LuaError("Requested unavailable ScriptApi - core engine bug!");
                }
                return scriptIfaceDowncast;
        }
 
        static bool registerFunction(lua_State *L,
                        const char* name,
                        lua_CFunction func,
                        int top);
 
        template<typename T>
        static void registerClass(lua_State *L,
                        const luaL_Reg *methods,
                        const luaL_Reg *metamethods)
        {
                luaL_newmetatable(L, T::className);
                luaL_register(L, NULL, metamethods);
                int metatable = lua_gettop(L);
 
                lua_newtable(L);
                luaL_register(L, NULL, methods);
                int methodtable = lua_gettop(L);
 
                lua_pushvalue(L, methodtable);
                lua_setfield(L, metatable, "__index");
 
                lua_getfield(L, metatable, "__tostring");
                bool default_tostring = lua_isnil(L, -1);
                lua_pop(L, 1);
                if (default_tostring) {
                        lua_pushcfunction(L, ModApiBase::defaultToString<T>);
                        lua_setfield(L, metatable, "__tostring");
                }
 
                // Protect the real metatable.
                lua_pushvalue(L, methodtable);
                lua_setfield(L, metatable, "__metatable");
 
                // Pop methodtable and metatable.
                lua_pop(L, 2);
        }
 
        template<typename T>
        static inline T *checkObject(lua_State *L, int narg)
        {
                T *obj = *reinterpret_cast<T**>(luaL_checkudata(L, narg, T::className));
                if (!obj)
                        luaL_error(L, "Object of type %s has been deleted already", T::className);
                return obj;
        }
 
        /*
         * Lua does not actually guarantee that an object entirely disappears after `__gc` is called,
         * so to avoid potential use-after-free we have to unset the pointer upon deleting.
         * This helper takes the pointer (unsetting it), and returns the old pointer.
         */
        template<typename T>
        static inline T *takeObjectForGC(lua_State *L)
        {
                T **ud = reinterpret_cast<T **>(lua_touserdata(L, 1));
                T *o = *ud;
                *ud = nullptr;
                return o;
        }

        static int l_deprecated_function(lua_State *L, const char *good, const char *bad, lua_CFunction func);
 
private:
 
        template<typename T>
        static int defaultToString(lua_State *L)
        {
                auto *t = checkObject<T>(L, 1);
                lua_pushfstring(L, "%s: %p", T::className, t);
                return 1;
        }
};