OpenEuphoria

2. Re: Calling Callback function

• Posted by Daniel Berstein <daber at PAIR.COM> Jan 29, 1999
• 689 views
• Last edited Jan 30, 1999

At 03:24 p.m. 29-01-99 +0000, you wrote:
>Hi,
>Does any one know how to call a euphoria function from a C++ DLL, using it's
>callback address?

I don't know C++, but in Delphi all you do is assign to a
procedure/function type the
address of the callback function:

In Euphoria:

atom cb
cb = call_back(routine_id(my_func))

Then you must pass the address of my_func (cb) to the DLL.

MyDLL = open_dll("MyDLL")
SomeProc = define_c_proc(MyDLL, "SomeProc", {C_POINTER})
c_proc(SomeProc, {cb})

On the DLL use something like:

//In C this should be a typedef
type
        TEuCallback: procedure([parameter list]; stdcall;

var
        EuCallback: TEuCallback;

//The address of (@) operator is used to assign the callback address
procedure SomeProc (cb: pointer);
begin
        @EuCallback := cb;
end;

And to call the callback routine "execute" the callback routine:

EuCallback([parameters]);

It's important you use stdcall as the calling convention (if it's not the
default
on your language, I belive C uses stdcall by default).


Regards,
        Daniel   Berstein
        daber at pair.com