Initialising caml values from C

Initialising caml values from C

[Jonathan Roewen]

Hi,

I'm building an ocaml-native program (actually an OS). Anyways, I
initialise the ocaml runtime from C, but the problem I have is that I
want a couple of caml values to be initialised by calling into C-land.

Something like: (lfb is a linear frame buffer)

external get_lfb: unit -> (int32, Bigarray.int32_elt,
Bigarray.c_layout) Bigarray.Array2.t = "get_lfb"

(* the part that doesn't seem to work *)

(* create a cairo instance for drawing into the LFB *)
let cairo = Cairo.create ()
(* gets the LFB, makes it into a cairo image, then sets it as surface
   for cairo to draw into *)
let _ = Cairo.set_target_image cairo (of_bigarr_32 true (get_lfb ()))

If I instead call some initialiser functions to set up the cairo
instances, it seems to be okay... but it'd make life a lot easier if
the above would work correctly. It'd especially help with other parts
of the code that use the above (and other functions/values).

Jon

Re: [Caml-list] Initialising caml values from C

[Olivier Andrieu]

 Jonathan Roewen [Tue, 19 Apr 2005]:
 > I'm building an ocaml-native program (actually an OS). Anyways, I
 > initialise the ocaml runtime from C, but the problem I have is that I
 > want a couple of caml values to be initialised by calling into C-land.
 > 
 > Something like: (lfb is a linear frame buffer)
 > 
 > external get_lfb: unit -> (int32, Bigarray.int32_elt,
 > Bigarray.c_layout) Bigarray.Array2.t = "get_lfb"
 > 
 > (* the part that doesn't seem to work *)
 > 
 > (* create a cairo instance for drawing into the LFB *)
 > let cairo = Cairo.create ()
 > (* gets the LFB, makes it into a cairo image, then sets it as surface
 >    for cairo to draw into *)
 > let _ = Cairo.set_target_image cairo (of_bigarr_32 true (get_lfb
 > ()))
 > 
 > If I instead call some initialiser functions to set up the cairo
 > instances, it seems to be okay... but it'd make life a lot easier
 > if the above would work correctly. It'd especially help with other
 > parts of the code that use the above (and other functions/values).
 
I don't quite understand your problem.

Is it that the code (with Cairo) isn't working ? (and if yes,
what exactly isn't working ?)

Or you want help on how to write the get_lfb function ?

-- 
   Olivier

Re: [Caml-list] Initialising caml values from C

[Jonathan Roewen]

> I don't quite understand your problem.
> 
> Is it that the code (with Cairo) isn't working ? (and if yes,
> what exactly isn't working ?)

Yes, cairo doesn't draw anything if I try initialise the values that way.

The problem is initialising the global values. They don't seem to work
if initialising them requires calling an external function.

like:
let height = get_lfb_height () (* where that is an external function *)

Basically, I want to avoid creating global refs, especially to more
complex structures.