Fix modstore/favourites hang by adding asynchronous lua job support

builtin/async_event.lua

@@ -0,0 +1,59 @@
+local tbl = engine or minetest
+
+tbl.async_jobs = {}
+
+if engine ~= nil then
+	function tbl.async_event_handler(jobid, serialized_retval)
+		local retval = nil
+		if serialized_retval ~= "ERROR" then
+			retval= marshal.decode(serialized_retval)
+		else
+			tbl.log("error","Error fetching async result")
+		end
+
+		assert(type(tbl.async_jobs[jobid]) == "function")
+		tbl.async_jobs[jobid](retval)
+		tbl.async_jobs[jobid] = nil
+	end
+else
+
+	minetest.register_globalstep(
+		function(dtime)
+			local list = tbl.get_finished_jobs()
+
+			for i=1,#list,1 do
+				local retval = marshal.decode(list[i].retval)
+
+				assert(type(tbl.async_jobs[jobid]) == "function")
+				tbl.async_jobs[list[i].jobid](retval)
+				tbl.async_jobs[list[i].jobid] = nil
+			end
+		end)
+end
+
+function tbl.handle_async(fct, parameters, callback)
+
+	--serialize fct
+	local serialized_fct = marshal.encode(fct)
+
+	assert(marshal.decode(serialized_fct) ~= nil)
+
+	--serialize parameters
+	local serialized_params = marshal.encode(parameters)
+
+	if serialized_fct == nil or
+		serialized_params == nil or
+		serialized_fct:len() == 0 or
+		serialized_params:len() == 0 then
+		return false
+	end
+
+	local jobid = tbl.do_async_callback(	serialized_fct,
+											serialized_fct:len(),
+											serialized_params,
+											serialized_params:len())
+
+	tbl.async_jobs[jobid] = callback
+
+	return true
+end