Async environment for mods to do concurrent tasks (#11131)

builtin/game/async.lua

@@ -0,0 +1,22 @@
+
+core.async_jobs = {}
+
+function core.async_event_handler(jobid, retval)
+	local callback = core.async_jobs[jobid]
+	assert(type(callback) == "function")
+	callback(unpack(retval, 1, retval.n))
+	core.async_jobs[jobid] = nil
+end
+
+function core.handle_async(func, callback, ...)
+	assert(type(func) == "function" and type(callback) == "function",
+		"Invalid minetest.handle_async invocation")
+	local args = {n = select("#", ...), ...}
+	local mod_origin = core.get_last_run_mod()
+
+	local jobid = core.do_async_callback(func, args, mod_origin)
+	core.async_jobs[jobid] = callback
+
+	return true
+end
+

builtin/game/init.lua

@@ -34,5 +34,6 @@ dofile(gamepath .. "voxelarea.lua")
 dofile(gamepath .. "forceloading.lua")
 dofile(gamepath .. "statbars.lua")
 dofile(gamepath .. "knockback.lua")
+dofile(gamepath .. "async.lua")
 
 profiler = nil

builtin/game/misc.lua

@@ -235,3 +235,32 @@ end
 
 -- Used for callback handling with dynamic_add_media
 core.dynamic_media_callbacks = {}
+
+
+-- Transfer of certain globals into async environment
+-- see builtin/async/game.lua for the other side
+
+local function copy_filtering(t, seen)
+	if type(t) == "userdata" or type(t) == "function" then
+		return true -- don't use nil so presence can still be detected
+	elseif type(t) ~= "table" then
+		return t
+	end
+	local n = {}
+	seen = seen or {}
+	seen[t] = n
+	for k, v in pairs(t) do
+		local k_ = seen[k] or copy_filtering(k, seen)
+		local v_ = seen[v] or copy_filtering(v, seen)
+		n[k_] = v_
+	end
+	return n
+end
+
+function core.get_globals_to_transfer()
+	local all = {
+		registered_items = copy_filtering(core.registered_items),
+		registered_aliases = core.registered_aliases,
+	}
+	return core.serialize(all)
+end