Add minetest.register_lbm() to run code on block load only

builtin/game/register.lua

@@ -11,10 +11,11 @@ local register_alias_raw = core.register_alias_raw
 core.register_alias_raw = nil
 
 --
--- Item / entity / ABM registration functions
+-- Item / entity / ABM / LBM registration functions
 --
 
 core.registered_abms = {}
+core.registered_lbms = {}
 core.registered_entities = {}
 core.registered_items = {}
 core.registered_nodes = {}
@@ -79,6 +80,13 @@ function core.register_abm(spec)
 	spec.mod_origin = core.get_current_modname() or "??"
 end
 
+function core.register_lbm(spec)
+	-- Add to core.registered_lbms
+	check_modname_prefix(spec.name)
+	core.registered_lbms[#core.registered_lbms + 1] = spec
+	spec.mod_origin = core.get_current_modname() or "??"
+end
+
 function core.register_entity(name, prototype)
 	-- Check name
 	if name == nil then

doc/lua_api.txt

@@ -1793,6 +1793,7 @@ Call these functions only at load time!
 
 * `minetest.register_entity(name, prototype table)`
 * `minetest.register_abm(abm definition)`
+* `minetest.register_lbm(lbm definition)`
 * `minetest.register_node(name, node definition)`
 * `minetest.register_tool(name, item definition)`
 * `minetest.register_craftitem(name, item definition)`
@@ -3305,6 +3306,21 @@ Definition tables
         action = func(pos, node, active_object_count, active_object_count_wider),
     }
 
+### LBM (LoadingBlockModifier) definition (`register_lbm`)
+
+    {
+        name = "modname:replace_legacy_door",
+        nodenames = {"default:lava_source"},
+    --  ^ List of node names to trigger the LBM on.
+    --    Also non-registered nodes will work.
+    --    Groups (as of group:groupname) will work as well.
+        run_at_every_load = false,
+    --  ^ Whether to run the LBM's action every time a block gets loaded,
+    --    and not just for blocks that were saved last time before LBMs were
+    --    introduced to the world.
+        action = func(pos, node),
+    }
+
 ### Item definition (`register_node`, `register_craftitem`, `register_tool`)
 
     {

src/environment.cpp

@@ -48,6 +48,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #define PP(x) "("<<(x).X<<","<<(x).Y<<","<<(x).Z<<")"
 
+#define LBM_NAME_ALLOWED_CHARS "abcdefghijklmnopqrstuvwxyz0123456789_:"
+
 Environment::Environment():
 	m_time_of_day_speed(0),
 	m_time_of_day(9000),
@@ -270,6 +272,223 @@ ABMWithState::ABMWithState(ActiveBlockModifier *abm_):
 	timer = myrand_range(minval, maxval);
 }
 
+/*
+	LBMManager
+*/
+
+void LBMContentMapping::deleteContents()
+{
+	for (std::vector<LoadingBlockModifierDef *>::iterator it = lbm_list.begin();
+			it != lbm_list.end(); ++it) {
+		delete *it;
+	}
+}
+
+void LBMContentMapping::addLBM(LoadingBlockModifierDef *lbm_def, IGameDef *gamedef)
+{
+	// Add the lbm_def to the LBMContentMapping.
+	// Unknown names get added to the global NameIdMapping.
+	INodeDefManager *nodedef = gamedef->ndef();
+
+	lbm_list.push_back(lbm_def);
+
+	for (std::set<std::string>::const_iterator it = lbm_def->trigger_contents.begin();
+			it != lbm_def->trigger_contents.end(); ++it) {
+		std::set<content_t> c_ids;
+		bool found = nodedef->getIds(*it, c_ids);
+		if (!found) {
+			content_t c_id = gamedef->allocateUnknownNodeId(*it);
+			if (c_id == CONTENT_IGNORE) {
+				// Seems it can't be allocated.
+				warningstream << "Could not internalize node name \"" << *it
+					<< "\" while loading LBM \"" << lbm_def->name << "\"." << std::endl;
+				continue;
+			}
+			c_ids.insert(c_id);
+		}
+
+		for (std::set<content_t>::const_iterator iit =
+				c_ids.begin(); iit != c_ids.end(); ++iit) {
+			content_t c_id = *iit;
+			map[c_id].push_back(lbm_def);
+		}
+	}
+}
+
+const std::vector<LoadingBlockModifierDef *> *
+		LBMContentMapping::lookup(content_t c) const
+{
+	container_map::const_iterator it = map.find(c);
+	if (it == map.end())
+		return NULL;
+	// This first dereferences the iterator, returning
+	// a std::vector<LoadingBlockModifierDef *>
+	// reference, then we convert it to a pointer.
+	return &(it->second);
+}
+
+LBMManager::~LBMManager()
+{
+	for (std::map<std::string, LoadingBlockModifierDef *>::iterator it =
+			m_lbm_defs.begin(); it != m_lbm_defs.end(); ++it) {
+		delete it->second;
+	}
+	for (lbm_lookup_map::iterator it = m_lbm_lookup.begin();
+			it != m_lbm_lookup.end(); ++it) {
+		(it->second).deleteContents();
+	}
+}
+
+void LBMManager::addLBMDef(LoadingBlockModifierDef *lbm_def)
+{
+	// Precondition, in query mode the map isn't used anymore
+	FATAL_ERROR_IF(m_query_mode == true,
+		"attempted to modify LBMManager in query mode");
+
+	if (!string_allowed(lbm_def->name, LBM_NAME_ALLOWED_CHARS)) {
+		throw ModError("Error adding LBM \"" + lbm_def->name +
+			"\": Does not follow naming conventions: "
+			"Only chararacters [a-z0-9_:] are allowed.");
+	}
+
+	m_lbm_defs[lbm_def->name] = lbm_def;
+}
+
+void LBMManager::loadIntroductionTimes(const std::string &times,
+		IGameDef *gamedef, u32 now)
+{
+	m_query_mode = true;
+
+	// name -> time map.
+	// Storing it in a map first instead of
+	// handling the stuff directly in the loop
+	// removes all duplicate entries.
+	// TODO make this std::unordered_map
+	std::map<std::string, u32> introduction_times;
+
+	/*
+	The introduction times string consists of name~time entries,
+	with each entry terminated by a semicolon. The time is decimal.
+	 */
+
+	size_t idx = 0;
+	size_t idx_new;
+	while ((idx_new = times.find(";", idx)) != std::string::npos) {
+		std::string entry = times.substr(idx, idx_new - idx);
+		std::vector<std::string> components = str_split(entry, '~');
+		if (components.size() != 2)
+			throw SerializationError("Introduction times entry \""
+				+ entry + "\" requires exactly one '~'!");
+		const std::string &name = components[0];
+		u32 time = from_string<u32>(components[1]);
+		introduction_times[name] = time;
+		idx = idx_new + 1;
+	}
+
+	// Put stuff from introduction_times into m_lbm_lookup
+	for (std::map<std::string, u32>::const_iterator it = introduction_times.begin();
+			it != introduction_times.end(); ++it) {
+		const std::string &name = it->first;
+		u32 time = it->second;
+
+		std::map<std::string, LoadingBlockModifierDef *>::iterator def_it =
+			m_lbm_defs.find(name);
+		if (def_it == m_lbm_defs.end()) {
+			// This seems to be an LBM entry for
+			// an LBM we haven't loaded. Discard it.
+			continue;
+		}
+		LoadingBlockModifierDef *lbm_def = def_it->second;
+		if (lbm_def->run_at_every_load) {
+			// This seems to be an LBM entry for
+			// an LBM that runs at every load.
+			// Don't add it just yet.
+			continue;
+		}
+
+		m_lbm_lookup[time].addLBM(lbm_def, gamedef);
+
+		// Erase the entry so that we know later
+		// what elements didn't get put into m_lbm_lookup
+		m_lbm_defs.erase(name);
+	}
+
+	// Now also add the elements from m_lbm_defs to m_lbm_lookup
+	// that weren't added in the previous step.
+	// They are introduced first time to this world,
+	// or are run at every load (introducement time hardcoded to U32_MAX).
+
+	LBMContentMapping &lbms_we_introduce_now = m_lbm_lookup[now];
+	LBMContentMapping &lbms_running_always = m_lbm_lookup[U32_MAX];
+
+	for (std::map<std::string, LoadingBlockModifierDef *>::iterator it =
+			m_lbm_defs.begin(); it != m_lbm_defs.end(); ++it) {
+		if (it->second->run_at_every_load) {
+			lbms_running_always.addLBM(it->second, gamedef);
+		} else {
+			lbms_we_introduce_now.addLBM(it->second, gamedef);
+		}
+	}
+
+	// Clear the list, so that we don't delete remaining elements
+	// twice in the destructor
+	m_lbm_defs.clear();
+}
+
+std::string LBMManager::createIntroductionTimesString()
+{
+	// Precondition, we must be in query mode
+	FATAL_ERROR_IF(m_query_mode == false,
+		"attempted to query on non fully set up LBMManager");
+
+	std::ostringstream oss;
+	for (lbm_lookup_map::iterator it = m_lbm_lookup.begin();
+			it != m_lbm_lookup.end(); ++it) {
+		u32 time = it->first;
+		std::vector<LoadingBlockModifierDef *> &lbm_list = it->second.lbm_list;
+		for (std::vector<LoadingBlockModifierDef *>::iterator iit = lbm_list.begin();
+				iit != lbm_list.end(); ++iit) {
+			// Don't add if the LBM runs at every load,
+			// then introducement time is hardcoded
+			// and doesn't need to be stored
+			if ((*iit)->run_at_every_load)
+				continue;
+			oss << (*iit)->name << "~" << time << ";";
+		}
+	}
+	return oss.str();
+}
+
+void LBMManager::applyLBMs(ServerEnvironment *env, MapBlock *block, u32 stamp)
+{
+	// Precondition, we need m_lbm_lookup to be initialized
+	FATAL_ERROR_IF(m_query_mode == false,
+		"attempted to query on non fully set up LBMManager");
+	v3s16 pos_of_block = block->getPosRelative();
+	v3s16 pos;
+	MapNode n;
+	content_t c;
+	lbm_lookup_map::const_iterator it = getLBMsIntroducedAfter(stamp);
+	for (pos.X = 0; pos.X < MAP_BLOCKSIZE; pos.X++)
+	for (pos.Y = 0; pos.Y < MAP_BLOCKSIZE; pos.Y++)
+	for (pos.Z = 0; pos.Z < MAP_BLOCKSIZE; pos.Z++)
+	{
+		n = block->getNodeNoEx(pos);
+		c = n.getContent();
+		for (LBMManager::lbm_lookup_map::const_iterator iit = it;
+				iit != m_lbm_lookup.end(); ++iit) {
+			const std::vector<LoadingBlockModifierDef *> *lbm_list =
+				iit->second.lookup(c);
+			if (!lbm_list)
+				continue;
+			for (std::vector<LoadingBlockModifierDef *>::const_iterator iit =
+					lbm_list->begin(); iit != lbm_list->end(); ++iit) {
+				(*iit)->trigger(env, pos + pos_of_block, n);
+			}
+		}
+	}
+}
+
 /*
 	ActiveBlockList
 */
@@ -505,6 +724,9 @@ void ServerEnvironment::saveMeta()
 	args.setU64("game_time", m_game_time);
 	args.setU64("time_of_day", getTimeOfDay());
 	args.setU64("last_clear_objects_time", m_last_clear_objects_time);
+	args.setU64("lbm_introduction_times_version", 1);
+	args.set("lbm_introduction_times",
+		m_lbm_mgr.createIntroductionTimesString());
 	args.writeLines(ss);
 	ss<<"EnvArgsEnd\n";
 
@@ -555,6 +777,26 @@ void ServerEnvironment::loadMeta()
 		// If missing, do as if clearObjects was never called
 		m_last_clear_objects_time = 0;
 	}
+
+	std::string lbm_introduction_times = "";
+	try {
+		u64 ver = args.getU64("lbm_introduction_times_version");
+		if (ver == 1) {
+			lbm_introduction_times = args.get("lbm_introduction_times");
+		} else {
+			infostream << "ServerEnvironment::loadMeta(): Non-supported"
+				<< " introduction time version " << ver << std::endl;
+		}
+	} catch (SettingNotFoundException &e) {
+		// No problem, this is expected. Just continue with an empty string
+	}
+	m_lbm_mgr.loadIntroductionTimes(lbm_introduction_times, m_gamedef, m_game_time);
+
+}
+
+void ServerEnvironment::loadDefaultMeta()
+{
+	m_lbm_mgr.loadIntroductionTimes("", m_gamedef, m_game_time);
 }
 
 struct ActiveABM
@@ -770,6 +1012,9 @@ void ServerEnvironment::activateBlock(MapBlock *block, u32 additional_dtime)
 	// Activate stored objects
 	activateObjects(block, dtime_s);
 
+	/* Handle LoadingBlockModifiers */
+	m_lbm_mgr.applyLBMs(this, block, stamp);
+
 	// Run node timers
 	std::map<v3s16, NodeTimer> elapsed_timers =
 		block->m_node_timers.step((float)dtime_s);
@@ -795,6 +1040,11 @@ void ServerEnvironment::addActiveBlockModifier(ActiveBlockModifier *abm)
 	m_abms.push_back(ABMWithState(abm));
 }
 
+void ServerEnvironment::addLoadingBlockModifierDef(LoadingBlockModifierDef *lbm)
+{
+	m_lbm_mgr.addLBMDef(lbm);
+}
+
 bool ServerEnvironment::setNode(v3s16 p, const MapNode &n)
 {
 	INodeDefManager *ndef = m_gamedef->ndef();

src/environment.h

@@ -139,7 +139,7 @@ private:
 };
 
 /*
-	Active block modifier interface.
+	{Active, Loading} block modifier interface.
 
 	These are fed into ServerEnvironment at initialization time;
 	ServerEnvironment handles deleting them.
@@ -177,6 +177,77 @@ struct ABMWithState
 	ABMWithState(ActiveBlockModifier *abm_);
 };
 
+struct LoadingBlockModifierDef
+{
+	// Set of contents to trigger on
+	std::set<std::string> trigger_contents;
+	std::string name;
+	bool run_at_every_load;
+
+	virtual ~LoadingBlockModifierDef() {}
+	virtual void trigger(ServerEnvironment *env, v3s16 p, MapNode n){};
+};
+
+struct LBMContentMapping
+{
+	typedef std::map<content_t, std::vector<LoadingBlockModifierDef *> > container_map;
+	container_map map;
+
+	std::vector<LoadingBlockModifierDef *> lbm_list;
+
+	// Needs to be separate method (not inside destructor),
+	// because the LBMContentMapping may be copied and destructed
+	// many times during operation in the lbm_lookup_map.
+	void deleteContents();
+	void addLBM(LoadingBlockModifierDef *lbm_def, IGameDef *gamedef);
+	const std::vector<LoadingBlockModifierDef *> *lookup(content_t c) const;
+};
+
+class LBMManager
+{
+public:
+	LBMManager():
+		m_query_mode(false)
+	{}
+
+	~LBMManager();
+
+	// Don't call this after loadIntroductionTimes() ran.
+	void addLBMDef(LoadingBlockModifierDef *lbm_def);
+
+	void loadIntroductionTimes(const std::string &times,
+		IGameDef *gamedef, u32 now);
+
+	// Don't call this before loadIntroductionTimes() ran.
+	std::string createIntroductionTimesString();
+
+	// Don't call this before loadIntroductionTimes() ran.
+	void applyLBMs(ServerEnvironment *env, MapBlock *block, u32 stamp);
+
+	// Warning: do not make this std::unordered_map, order is relevant here
+	typedef std::map<u32, LBMContentMapping> lbm_lookup_map;
+
+private:
+	// Once we set this to true, we can only query,
+	// not modify
+	bool m_query_mode;
+
+	// For m_query_mode == false:
+	// The key of the map is the LBM def's name.
+	// TODO make this std::unordered_map
+	std::map<std::string, LoadingBlockModifierDef *> m_lbm_defs;
+
+	// For m_query_mode == true:
+	// The key of the map is the LBM def's first introduction time.
+	lbm_lookup_map m_lbm_lookup;
+
+	// Returns an iterator to the LBMs that were introduced
+	// after the given time. This is guaranteed to return
+	// valid values for everything
+	lbm_lookup_map::const_iterator getLBMsIntroducedAfter(u32 time)
+	{ return m_lbm_lookup.lower_bound(time); }
+};
+
 /*
 	List of active blocks, used by ServerEnvironment
 */
@@ -254,6 +325,9 @@ public:
 	*/
 	void saveMeta();
 	void loadMeta();
+	// to be called instead of loadMeta if
+	// env_meta.txt doesn't exist (e.g. new world)
+	void loadDefaultMeta();
 
 	/*
 		External ActiveObject interface
@@ -312,11 +386,12 @@ public:
 	void activateBlock(MapBlock *block, u32 additional_dtime=0);
 
 	/*
-		ActiveBlockModifiers
+		{Active,Loading}BlockModifiers
 		-------------------------------------------
 	*/
 
 	void addActiveBlockModifier(ActiveBlockModifier *abm);
+	void addLoadingBlockModifierDef(LoadingBlockModifierDef *lbm);
 
 	/*
 		Other stuff
@@ -427,6 +502,7 @@ private:
 	u32 m_last_clear_objects_time;
 	// Active block modifiers
 	std::vector<ABMWithState> m_abms;
+	LBMManager m_lbm_mgr;
 	// An interval for generally sending object positions and stuff
 	float m_recommended_send_interval;
 	// Estimate for general maximum lag as determined by server.

src/nodedef.cpp

@@ -419,7 +419,7 @@ public:
 	inline virtual const ContentFeatures& get(const MapNode &n) const;
 	virtual bool getId(const std::string &name, content_t &result) const;
 	virtual content_t getId(const std::string &name) const;
-	virtual void getIds(const std::string &name, std::set<content_t> &result) const;
+	virtual bool getIds(const std::string &name, std::set<content_t> &result) const;
 	virtual const ContentFeatures& get(const std::string &name) const;
 	content_t allocateId();
 	virtual content_t set(const std::string &name, const ContentFeatures &def);
@@ -603,22 +603,23 @@ content_t CNodeDefManager::getId(const std::string &name) const
 }
 
 
-void CNodeDefManager::getIds(const std::string &name,
+bool CNodeDefManager::getIds(const std::string &name,
 		std::set<content_t> &result) const
 {
 	//TimeTaker t("getIds", NULL, PRECISION_MICRO);
 	if (name.substr(0,6) != "group:") {
 		content_t id = CONTENT_IGNORE;
-		if(getId(name, id))
+		bool exists = getId(name, id);
+		if (exists)
 			result.insert(id);
-		return;
+		return exists;
 	}
 	std::string group = name.substr(6);
 
 	std::map<std::string, GroupItems>::const_iterator
 		i = m_group_to_items.find(group);
 	if (i == m_group_to_items.end())
-		return;
+		return true;
 
 	const GroupItems &items = i->second;
 	for (GroupItems::const_iterator j = items.begin();
@@ -627,6 +628,7 @@ void CNodeDefManager::getIds(const std::string &name,
 			result.insert((*j).first);
 	}
 	//printf("getIds: %dus\n", t.stop());
+	return true;
 }
 
 

src/nodedef.h

@@ -303,7 +303,8 @@ public:
 	virtual bool getId(const std::string &name, content_t &result) const=0;
 	virtual content_t getId(const std::string &name) const=0;
 	// Allows "group:name" in addition to regular node names
-	virtual void getIds(const std::string &name, std::set<content_t> &result)
+	// returns false if node name not found, true otherwise
+	virtual bool getIds(const std::string &name, std::set<content_t> &result)
 			const=0;
 	virtual const ContentFeatures &get(const std::string &name) const=0;
 
@@ -327,7 +328,7 @@ public:
 	// If not found, returns CONTENT_IGNORE
 	virtual content_t getId(const std::string &name) const=0;
 	// Allows "group:name" in addition to regular node names
-	virtual void getIds(const std::string &name, std::set<content_t> &result)
+	virtual bool getIds(const std::string &name, std::set<content_t> &result)
 		const=0;
 	// If not found, returns the features of CONTENT_UNKNOWN
 	virtual const ContentFeatures &get(const std::string &name) const=0;

src/script/cpp_api/s_base.h

@@ -83,6 +83,7 @@ public:
 
 protected:
 	friend class LuaABM;
+	friend class LuaLBM;
 	friend class InvRef;
 	friend class ObjectRef;
 	friend class NodeMetaRef;

src/script/cpp_api/s_env.cpp

@@ -86,13 +86,12 @@ void ScriptApiEnv::initializeEnvironment(ServerEnvironment *env)
 	setEnv(env);
 
 	/*
-		Add ActiveBlockModifiers to environment
+		Add {Loading,Active}BlockModifiers to environment
 	*/
 
 	// Get core.registered_abms
 	lua_getglobal(L, "core");
 	lua_getfield(L, -1, "registered_abms");
-	luaL_checktype(L, -1, LUA_TTABLE);
 	int registered_abms = lua_gettop(L);
 
 	if(lua_istable(L, registered_abms)){
@@ -154,6 +153,58 @@ void ScriptApiEnv::initializeEnvironment(ServerEnvironment *env)
 			// removes value, keeps key for next iteration
 			lua_pop(L, 1);
 		}
+	} else {
+		lua_pop(L, 1);
+		throw LuaError("core.registered_abms was not a lua table, as expected.");
+	}
+	lua_pop(L, 1);
+
+	// Get core.registered_lbms
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "registered_lbms");
+	int registered_lbms = lua_gettop(L);
+
+	if (!lua_istable(L, registered_lbms)) {
+		lua_pop(L, 1);
+		throw LuaError("core.registered_lbms was not a lua table, as expected.");
+	}
+
+	lua_pushnil(L);
+	while (lua_next(L, registered_lbms)) {
+		// key at index -2 and value at index -1
+		int id = lua_tonumber(L, -2);
+		int current_lbm = lua_gettop(L);
+
+		std::set<std::string> trigger_contents;
+		lua_getfield(L, current_lbm, "nodenames");
+		if (lua_istable(L, -1)) {
+			int table = lua_gettop(L);
+			lua_pushnil(L);
+			while (lua_next(L, table)) {
+				// key at index -2 and value at index -1
+				luaL_checktype(L, -1, LUA_TSTRING);
+				trigger_contents.insert(lua_tostring(L, -1));
+				// removes value, keeps key for next iteration
+				lua_pop(L, 1);
+			}
+		} else if (lua_isstring(L, -1)) {
+			trigger_contents.insert(lua_tostring(L, -1));
+		}
+		lua_pop(L, 1);
+
+		std::string name;
+		getstringfield(L, current_lbm, "name", name);
+
+		bool run_at_every_load = getboolfield_default(L, current_lbm,
+			"run_at_every_load", false);
+
+		LuaLBM *lbm = new LuaLBM(L, id, trigger_contents, name,
+			run_at_every_load);
+
+		env->addLoadingBlockModifierDef(lbm);
+
+		// removes value, keeps key for next iteration
+		lua_pop(L, 1);
 	}
 	lua_pop(L, 1);
 }

src/script/lua_api/l_env.cpp

@@ -90,6 +90,46 @@ void LuaABM::trigger(ServerEnvironment *env, v3s16 p, MapNode n,
 	lua_pop(L, 1); // Pop error handler
 }
 
+void LuaLBM::trigger(ServerEnvironment *env, v3s16 p, MapNode n)
+{
+	GameScripting *scriptIface = env->getScriptIface();
+	scriptIface->realityCheck();
+
+	lua_State *L = scriptIface->getStack();
+	sanity_check(lua_checkstack(L, 20));
+	StackUnroller stack_unroller(L);
+
+	int error_handler = PUSH_ERROR_HANDLER(L);
+
+	// Get registered_lbms
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "registered_lbms");
+	luaL_checktype(L, -1, LUA_TTABLE);
+	lua_remove(L, -2); // Remove core
+
+	// Get registered_lbms[m_id]
+	lua_pushnumber(L, m_id);
+	lua_gettable(L, -2);
+	FATAL_ERROR_IF(lua_isnil(L, -1), "Entry with given id not found in registered_lbms table");
+	lua_remove(L, -2); // Remove registered_lbms
+
+	scriptIface->setOriginFromTable(-1);
+
+	// Call action
+	luaL_checktype(L, -1, LUA_TTABLE);
+	lua_getfield(L, -1, "action");
+	luaL_checktype(L, -1, LUA_TFUNCTION);
+	lua_remove(L, -2); // Remove registered_lbms[m_id]
+	push_v3s16(L, p);
+	pushnode(L, n, env->getGameDef()->ndef());
+
+	int result = lua_pcall(L, 2, 0, error_handler);
+	if (result)
+		scriptIface->scriptError(result, "LuaLBM::trigger");
+
+	lua_pop(L, 1); // Pop error handler
+}
+
 void LuaEmergeAreaCallback(v3s16 blockpos, EmergeAction action, void *param)
 {
 	ScriptCallbackState *state = (ScriptCallbackState *)param;

src/script/lua_api/l_env.h

@@ -220,6 +220,24 @@ public:
 			u32 active_object_count, u32 active_object_count_wider);
 };
 
+class LuaLBM : public LoadingBlockModifierDef
+{
+private:
+	int m_id;
+public:
+	LuaLBM(lua_State *L, int id,
+			const std::set<std::string> &trigger_contents,
+			const std::string &name,
+			bool run_at_every_load):
+		m_id(id)
+	{
+		this->run_at_every_load = run_at_every_load;
+		this->trigger_contents = trigger_contents;
+		this->name = name;
+	}
+	virtual void trigger(ServerEnvironment *env, v3s16 p, MapNode n);
+};
+
 struct ScriptCallbackState {
 	GameScripting *script;
 	int callback_ref;

src/server.cpp

@@ -344,10 +344,11 @@ Server::Server(
 	servermap->addEventReceiver(this);
 
 	// If file exists, load environment metadata
-	if(fs::PathExists(m_path_world + DIR_DELIM "env_meta.txt"))
-	{
-		infostream<<"Server: Loading environment metadata"<<std::endl;
+	if (fs::PathExists(m_path_world + DIR_DELIM "env_meta.txt")) {
+		infostream << "Server: Loading environment metadata" << std::endl;
 		m_env->loadMeta();
+	} else {
+		m_env->loadDefaultMeta();
 	}
 
 	// Add some test ActiveBlockModifiers to environment

src/util/string.h

@@ -299,15 +299,6 @@ inline s32 mystoi(const std::string &str, s32 min, s32 max)
 }
 
 
-/// Returns a 64-bit value represented by the string \p str (decimal).
-inline s64 stoi64(const std::string &str)
-{
-	std::stringstream tmp(str);
-	s64 t;
-	tmp >> t;
-	return t;
-}
-
 // MSVC2010 includes it's own versions of these
 //#if !defined(_MSC_VER) || _MSC_VER < 1600
 
@@ -346,9 +337,22 @@ inline float mystof(const std::string &str)
 #define stoi mystoi
 #define stof mystof
 
+/// Returns a value represented by the string \p val.
+template <typename T>
+inline T from_string(const std::string &str)
+{
+	std::stringstream tmp(str);
+	T t;
+	tmp >> t;
+	return t;
+}
+
+/// Returns a 64-bit signed value represented by the string \p str (decimal).
+inline s64 stoi64(const std::string &str) { return from_string<s64>(str); }
+
 // TODO: Replace with C++11 std::to_string.
 
-/// Returns A string representing the value \p val.
+/// Returns a string representing the value \p val.
 template <typename T>
 inline std::string to_string(T val)
 {