Re: [gobo-eiffel-develop] Callback from C to Eiffel

[Emmanuel S. [ES] <ma...@ei...>]

The easiest way for doing this kind of callback is to store the eiffel
routine address by doing:

c_set_address (p: POINTER) is
	external
		"C inline use <your.h>"
	alias
		"signal_callback = $p"
	end

where you do:

	c_set_address (your_eiffel_routine_callback)


To store the object needed for the call:

c_set_object (a: POINTER) is
	external
		"C inline use <your.h>"
	alias
		"signal_object = eif_protect($a);"
	end

where you do:

	c_set_object ($Current) -- Current or any other entity

Then the C code should simply look like:

	(signal_callback) (eif_adopt(signal_object), sig)

That way there is no need to worry about freezing objects.

Manu 

> -----Original Message-----
> From: gob...@li... 
> [mailto:gob...@li...] On 
> Behalf Of Berend de Boer
> Sent: Thursday, November 15, 2007 3:01 PM
> To: Gobo Developers Mailing List
> Subject: [gobo-eiffel-develop] Callback from C to Eiffel
> 
> Hi Eric,
> 
> Can I callback from C to Eiffel? Need this at a few places in 
> eposix, for example to support signals.
> 
> For example this the code used for ISE:
> 
>   EIF_TYPE_ID tid;
>   EIF_OBJECT temp;
>   if ( signal_switch != NULL ) {
>     temp = signal_switch;
>     signal_switch = NULL;
>     eif_unfreeze (frozen_signal_switch);
>     frozen_signal_switch = NULL;
>     eif_wean (temp);
>   }
>   if ( a_switch != NULL ) {
>     tid = eif_type_id ("STDC_SIGNAL_SWITCH");
>     signal_callback = eif_procedure ("switcher", tid);
>     if (signal_callback == 0)
>       { eif_panic ("switcher feature not found."); }
>     frozen_signal_switch = eif_freeze (a_switch);
>     signal_switch = eif_adopt (a_switch);
>   }
> 
> I.e. the callback pointer is "calculated" at set time and 
> stored in signal_switch. When a signal occurs, this call is made:
> 
>   (signal_callback) (frozen_signal_switch, sig);
> 
> 
> SmartEiffel has a different strategy. When a feature is 
> exported, SE simply generates a prototype for it in the cecil.h file:
> 
>   /* Available Eiffel routines via -cecil:
>   */
>   void stdc_exit_switch_at_exit(void* C);
>   void stdc_signal_switch_switcher(void* C,T2 a1);
> 
> And within C I can simply call stdc_signal_switch_switcher to 
> make the callback to Eiffel.
> 
> --
> Cheers,
> 
> Berend de Boer
>