Add forceloading

builtin/builtin.lua

@@ -34,3 +34,4 @@ dofile(modpath.."/falling.lua")
 dofile(modpath.."/features.lua")
 dofile(modpath.."/voxelarea.lua")
 dofile(modpath.."/vector.lua")
+dofile(modpath.."/forceloading.lua")

builtin/forceloading.lua

+-- Prevent anyone else accessing those functions
+local forceload_block = minetest.forceload_block
+local forceload_free_block = minetest.forceload_free_block
+minetest.forceload_block = nil
+minetest.forceload_free_block = nil
+
+local blocks_forceloaded
+local total_forceloaded = 0
+
+local BLOCKSIZE = 16
+local function get_blockpos(pos)
+	return {
+		x = math.floor(pos.x/BLOCKSIZE),
+		y = math.floor(pos.y/BLOCKSIZE),
+		z = math.floor(pos.z/BLOCKSIZE)}
+end
+
+function minetest.forceload_block(pos)
+	local blockpos = get_blockpos(pos)
+	local hash = minetest.hash_node_position(blockpos)
+	if blocks_forceloaded[hash] ~= nil then
+		blocks_forceloaded[hash] = blocks_forceloaded[hash] + 1
+		return true
+	else
+		if total_forceloaded >= (minetest.setting_get("max_forceloaded_blocks") or 16) then
+			return false
+		end
+		total_forceloaded = total_forceloaded+1
+		blocks_forceloaded[hash] = 1
+		forceload_block(blockpos)
+		return true
+	end
+end
+
+function minetest.forceload_free_block(pos)
+	local blockpos = get_blockpos(pos)
+	local hash = minetest.hash_node_position(blockpos)
+	if blocks_forceloaded[hash] == nil then return end
+	if blocks_forceloaded[hash] > 1 then
+		blocks_forceloaded[hash] = blocks_forceloaded[hash] - 1
+	else
+		total_forceloaded = total_forceloaded-1
+		blocks_forceloaded[hash] = nil
+		forceload_free_block(blockpos)
+	end
+end
+
+-- Keep the forceloaded areas after restart
+local wpath = minetest.get_worldpath()
+local function read_file(filename)
+	local f = io.open(filename, "r")
+	if f==nil then return {} end
+	local t = f:read("*all")
+	f:close()
+	if t=="" or t==nil then return {} end
+	return minetest.deserialize(t)
+end
+
+local function write_file(filename, table)
+	local f = io.open(filename, "w")
+	f:write(minetest.serialize(table))
+	f:close()
+end
+
+blocks_forceloaded = read_file(wpath.."/force_loaded.txt")
+for _, __ in pairs(blocks_forceloaded) do
+	total_forceloaded = total_forceloaded + 1
+end
+
+minetest.after(5, function()
+	for hash, _ in pairs(blocks_forceloaded) do
+		local blockpos = minetest.get_position_from_hash(hash)
+		forceload_block(blockpos)
+	end
+end)
+
+minetest.register_on_shutdown(function()
+	write_file(wpath.."/force_loaded.txt", blocks_forceloaded)
+end)

builtin/misc.lua

@@ -64,6 +64,16 @@ function minetest.hash_node_position(pos)
 	return (pos.z+32768)*65536*65536 + (pos.y+32768)*65536 + pos.x+32768
 end
 
+function minetest.get_position_from_hash(hash)
+	local pos = {}
+	pos.x = (hash%65536) - 32768
+	hash = math.floor(hash/65536)
+	pos.y = (hash%65536) - 32768
+	hash = math.floor(hash/65536)
+	pos.z = (hash%65536) - 32768
+	return pos
+end
+
 function minetest.get_item_group(name, group)
 	if not minetest.registered_items[name] or not
 			minetest.registered_items[name].groups[group] then

doc/lua_api.txt

@@ -1590,6 +1590,15 @@ minetest.rotate_node(itemstack, placer, pointed_thing)
   the creative mode setting, and checks for "sneak" to set the invert_wall
   parameter.
 
+minetest.forceload_block(pos)
+^ forceloads the position pos.
+^ returns true if area could be forceloaded
+
+minetest.forceload_free_block(pos)
+^ stops forceloading the position pos.
+
+Please note that forceloaded areas are saved when the server restarts.
+
 Global objects:
 minetest.env - EnvRef of the server environment and world.
 ^ Any function in the minetest namespace can be called using the syntax

minetest.conf.example

@@ -301,6 +301,8 @@
 # This is a trade-off between sqlite transaction overhead and
 # memory consumption (4096=100MB, as a rule of thumb)
 #max_clearobjects_extra_loaded_blocks = 4096
+# Maximum number of forceloaded blocks
+#max_forceloaded_blocks = 16
 # Interval of sending time of day to clients
 #time_send_interval = 5
 # Length of day/night cycle. 72=20min, 360=4min, 1=24hour, 0=day/night/whatever stays unchanged

src/environment.cpp

@@ -258,7 +258,7 @@ void ActiveBlockList::update(std::list<v3s16> &active_positions,
 	/*
 		Create the new list
 	*/
-	std::set<v3s16> newlist;
+	std::set<v3s16> newlist = m_forceloaded_list;
 	for(std::list<v3s16>::iterator i = active_positions.begin();
 			i != active_positions.end(); ++i)
 	{

src/environment.h

@@ -170,6 +170,7 @@ class ActiveBlockList
 	}
 
 	std::set<v3s16> m_list;
+	std::set<v3s16> m_forceloaded_list;
 
 private:
 };
@@ -305,6 +306,8 @@ class ServerEnvironment : public Environment
 	// is weather active in this environment?
 	bool m_use_weather;
 	
+	std::set<v3s16>* getForceloadedBlocks() { return &m_active_blocks.m_forceloaded_list; };
+	
 private:
 
 	/*

src/script/lua_api/l_env.cpp

@@ -798,6 +798,27 @@ int ModApiEnvMod::l_get_humidity(lua_State *L)
 	return 1;
 }
 
+// minetest.forceload_block(blockpos)
+// blockpos = {x=num, y=num, z=num}
+int ModApiEnvMod::l_forceload_block(lua_State *L)
+{
+	GET_ENV_PTR;
+
+	v3s16 blockpos = read_v3s16(L, 1);
+	env->getForceloadedBlocks()->insert(blockpos);
+	return 0;
+}
+
+// minetest.forceload_free_block(blockpos)
+// blockpos = {x=num, y=num, z=num}
+int ModApiEnvMod::l_forceload_free_block(lua_State *L)
+{
+	GET_ENV_PTR;
+
+	v3s16 blockpos = read_v3s16(L, 1);
+	env->getForceloadedBlocks()->erase(blockpos);
+	return 0;
+}
 
 void ModApiEnvMod::Initialize(lua_State *L, int top)
 {
@@ -836,4 +857,6 @@ void ModApiEnvMod::Initialize(lua_State *L, int top)
 	API_FCT(transforming_liquid_add);
 	API_FCT(get_heat);
 	API_FCT(get_humidity);
+	API_FCT(forceload_block);
+	API_FCT(forceload_free_block);
 }

src/script/lua_api/l_env.h

@@ -151,6 +151,14 @@ class ModApiEnvMod : public ModApiBase {
 	static int l_get_heat(lua_State *L);
 	static int l_get_humidity(lua_State *L);
 	
+	// minetest.forceload_block(blockpos)
+	// forceloads a block
+	static int l_forceload_block(lua_State *L);
+	
+	// minetest.forceload_free_block(blockpos)
+	// stops forceloading a position
+	static int l_forceload_free_block(lua_State *L);
+	
 public:
 	static void Initialize(lua_State *L, int top);
 };