retrieve top-level lua_State?

[Graham Wakefield <lists@...>]

Hi,

Just wondering if any lua guru can suggest a way I might retrieve the  
top-level lua_State pointer in a module's C function.

Given that a lua_State * can be spawned from another with  
coroutine.create() or lua_newthread(L), it's not always guaranteed  
that the lua_State * pointer you receive in module functions is always  
the same, but the top-level state would always be. Even the lua_State  
* received in the luaopen_xxx call might not be the top level (e.g.  
require() was called in a coroutine.)

The reason is that I need a unique index with which to call back into  
distinct Lua universes, in a situation where several such universes  
may coexist (but not interact) in the same application, and  
(distinctly) load the same module. I would prefer not to defer this  
responsibility to the application itself or require modifications to  
Lua itself, as it would reduce the portability of the module in  
question.

I hope the question is clear. Any ideas?

Thanks