How to make an asynchronous HTTP call with callback in Lua?


I need to make asynchronous HTTP call to my server in order to receive XML response. After I get the response I will call a [previously specified] function if it is success or some other function if it's an error.

So what I thought about in the first place was coroutines. Unfortunately, after I make the http.get call I cannot yield, as it will wait for the whole thing to finish. I know I can use separate functions to read the response, however I have to wait at least for the first bytes of data in order for this function to be triggered which would allow me to yield. Anyway, for what I wan to do using coroutines doesn't look like the way to go.

Then I've tried calling a C function from lua, creating separate thread to get the XML and then call a function in Lua, however this doesn't work because of lua_state changing after a new thread is created. Before the thread is created I can see 3 parameters on the stack, and after creation of the new thread [I am passing lua_State as the argument] it has only one. Anyway, from what I understand lua_State will be closed once the original cfunction call is finished, so I won't be able to call back.

Since I'm just starting with lua and I'm even less familiar with lua to c bindings I can only hope I'm making some stupid mistakes and it will be easy to solve. For now however I'm stuck with no idea on how to progress further.

The story behind this issue: I'm porting my game from Cocos2D objective C framework to Cocos2d-X C++ framework. I want to use Lua bindings as I think I will fail to port it to C++. Anyway I want to do it in Lua. So I've got a scene where someone accesses a list of inventory they have in the game. If the response is immediate they will basically see a window opened with list of inventory. However, if it takes a tad bit longer to get the data [connection issues, sever overload... whatever] screen will fade out and some animation indicating data transfer will be shown on screen. At least this is how it works on the objc version of the game and I want the same thing.

Is there something I have missed during my research, is it possible to do it?

BTW I have seen Lua socket asynchronous calls and it doesn't help me because it still waits for the beginning of the transfer before it will start another one.

Something like Luvit ?

Luvit is an attempt to do something crazy by taking nodeJS's awesome architecture and dependencies and seeing how it fits in the Lua language.

This project is still under heavy development, but it's showing promise. In initial benchmarking with a hello world server, this is between 2 and 4 times faster than nodeJS.