[Cffi-devel] Fw: readded broken link from last post

[Joeish W]

Thank you very much for all the help recently,   actually the Rect is a OpenCv C class here:
http://docs.opencv.org/trunk/modules/core/doc/basic_structures.html?highlight=rect#Rect_...does your advice on making a defcstruct for it stand..Remember, the same code works evaluating the same way at the REPL creating a vector<Rectt> like this:


Functions:

;; template < class T, class Alloc = allocator<T> > class vector
;; vector_##t * carray_to_std_vector##tn( t * a, size_t len )
(defcfun ("carray_to_std_vectorr" %c-arr-to-vector-rect) (:pointer vector-rect)
  (a :pointer)
  (len :unsigned-int))

;; template < class T, class Alloc = allocator<T> > class vector
;; t * std_vector##tn##_to_carray( vector_##t * v ) 
(defcfun ("std_vectorr_to_carray" %vector-rect-to-c-array) (:pointer rect) 
  (s (:pointer vector-rect)))



(%c-arr-to-vector-rect
         (foreign-alloc :pointer :initial-contents 
                (list (rect 1 2 3 4) 
                      (rect 5 6 7 8))) 2)


VECTOR-RECT-SIZE just gets the size of the vector


(dotimes (ic (%vector-rect-size faces))
(setf n (%vector-rect-to-c-array faces))
(format t "~a~%" (rect-x (mem-aref n :pointer ic))))
; 
; caught WARNING:
;   undefined variable: N
; 
; compilation unit finished
;   Undefined variable:
;     N
;   caught 1 WARNING condition
1 <-- both x values
5




On Saturday, April 26, 2014 4:41 AM, Willem Rein Oudshoorn <woudshoo at xs4all.nl> wrote:
 
Joeish W <joeish80829 at yahoo.com> writes:
>
>> Lisp code is here https://gist.github.com/W-Net-AI/11205892
>>  ...
>> LCV> (dotimes (ic (vector-rect-size faces)) 
>>             (setf n (%vector-rect-to-c-array faces))
>>             (rect-x (mem-aref n :pointer ic)))
>>
>> this is where it fails, rect-x, my Lisp wrapper for C wrapper for the
>> c++ Rect class member x in this statement isn't getting a Rect* so it
>> outputs error: Unhandled ;memory fault at #xC9000000D5.  The
>> %vector-rect-to-c-array function is a wrapper for the c function in
>> the posted c/c++ code. It works as expected on everything else but the
>> vector<Rect> output of detectMultiScale.
>
>This fails because `n` is a pointer the data of vector<Rect>.  
>So it points to an array of Rect structures, NOT an array of Rect*
>(pointers to Rect).
>
>What would work (but I am advising against this), is:
>
>(rect-x (inc-pointer n (* ic SIZE_OF_RECT)))
>
>Where SIZE_OF_RECT is the size of the Rect struct.
>
>What you should do is look into `defcstruct` to properly wrap the Rect
>struct and start from there.
>
>Wim Oudshoorn.
>
>
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