FFI related questions

Hello and a happy new year!,

first of i would like to express a big thumbs up for the tremendous effort  
you
all have been doing the last months wrt the trunk image. Its really  
amazing :-)

I have some FFI on Windows related questions.
(fyi, i am using the trunk image on which i loaded the latest FFI code
 from SqueakSource, FFI-Kernel-ar.12.mcz and FFI-Pools-ar.1.mcz)

Is it possible, in general, to pass down to C "basic" Smalltalk objects,  
like Integers,
Floats etc. and have their value changed by the C routine? I am trying to  
do something
like:

   anInteger := 5.

that i want to send to C and simply change it by, say :

   apiChangeInteger: anInteger
   <cdecl: void 'change_integer' (long*) module:'MyDLL'>

   (which finally in C reads like: void set_integer(int* anInteger) {  
*anInteger = *anInteger + 5; } )

I have found the above scheme to not work as i would expect.

Interestingly, if i push down to C an array of basic values like:

   integers := {10. 20. 30} asIntegerArray

the C routine can change the values. For completeness, passing down arrays  
of values
works for FloatArrays like:

   singlePrecisionFloats := {10.5. 20.5. 30.5} asFloatArray
   (and then passed to a C routine having a float* argument)

but not for :

   doublePrecisionFloats := {10.5. 20.5. 30.5}
   (with the C routine having a double* argument)

Probably i am not using FFI as intended although i would expect to be able  
to do all this.
Can someone (Andreas?) please shed some light to all this?


Another thing that isn't clear to me is if its possible to have FFI create  
Smalltalk objects
in behalf of a requesting client. In Java's JNI for instance one can say:

   jni->NewFloatArray(length of the array);

If it can be done (i mean no VM restrictions) and you also think that it  
would be generally useful (i do),
i am willing to implement such "helper" routines.

Cheers
  - Vagelis

2010/1/5 vagy <[hidden email]>: The difference between FloatArray and Array of floats (or array of
arbitrary objects)
is in storage format. While first storing a number of native
floating-point values, edigible for C,
while second stores references to other objects (oop-s).

>
> Another thing that isn't clear to me is if its possible to have FFI create
> Smalltalk objects
> in behalf of a requesting client. In Java's JNI for instance one can say:
>
>  jni->NewFloatArray(length of the array);
>

in that case, i think, you'd better create a VM plugin, which having
an access to something similar to 'jni'
object, which in squeak is called 'interpreterProxy'.

Thinking about it, i came to interesting idea, that really, we could
pass a pointer to interpreterProxy
variable to FFI function, so, potentially, it could make use of VM API
functions to create objects, or access existing ones.
I don't know if that will be ever used, since writing a plugin looks
much more appropriate in that case.

> If it can be done (i mean no VM restrictions) and you also think that it
> would be generally useful (i do),
> i am willing to implement such "helper" routines.
>
> Cheers
>  - Vagelis


--
Best regards,
Igor Stasenko AKA sig.