cffi-devel June 2020

cffi-devel@common-lisp.net

3 participants
3 discussions

Passing a pointer to a cstruct
by basho1600＠pm.me 30 Jun '20

30 Jun '20

I am using SBCL and trying to pass a pointer to a c-struct to a CFFI routine. The difficulty I am having is in formulating the function call correctly. I have tried 'define-alien-routine' but was getting nowhere. So now I am using cffi:foreign-funcall directly. Here is the call: (cffi:foreign-funcall "v4lconvert_convert" :POINTER convert-info :POINTER *camera-format* :POINTER *display-format* :POINTER raw-image :INT *local-length* :POINTER pixdata :INT pixbuf-size :INT) It is the pointers to the two '-format' items that are causing the trouble I think. Both of them were defined using defcstruct. But the error message I get is complaining about the expansion of the foreign-funcall macro and makes no sense at all to me. Can somebody help me interpret this? ; (CFFI:FOREIGN-FUNCALL "v4lconvert_convert" ; :POINTER ENCOMM.GUI::CONVERT-INFO ; :POINTER ENCOMM.GUI::*CAMERA-FORMAT* :POINTER ; ENCOMM.GUI::*DISPLAY-FORMAT* :POINTER ; ENCOMM.GUI::RAW-IMAGE :INT ENCOMM.GUI::*LOCAL-LENGTH* ; ...) ; --> LET LET LET LET LET LET LET CFFI-SYS:%FOREIGN-FUNCALL ; --> CFFI-SYS::%%FOREIGN-FUNCALL ALIEN-FUNCALL ; --> SB-ALIEN-INTERNALS:INVOKE-WITH-SAVED-FP-AND-PC LAMBDA FUNCTION ; --> SB-ALIEN-INTERNALS:NATURALIZE LET LET LET LET LET LET LET ; --> SB-ALIEN-INTERNALS:MAYBE-WITH-PINNED-OBJECTS PROGN SB-C:%ALIEN-FUNCALL ; ==> ; (SB-ALIEN-INTERNALS:DEPORT #:G77 ; '#<SB-ALIEN::ALIEN-SYSTEM-AREA-POINTER-TYPE SB-SYS:SYSTEM-AREA-POINTER>) ; ; caught WARNING: ; Derived type of #:G77 is ; (VALUES (ALIEN (* T)) &OPTIONAL), ; conflicting with its asserted type ; SB-SYS:SYSTEM-AREA-POINTER. ; See also: ; The SBCL Manual, Node "Handling of Types"

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Re: How can we convert C 0x00000001u (unsigned int in C) to Common Lisp ?
by Luís Oliveira 28 Jun '20

28 Jun '20

The various C integer types map to Lisp integers, so if you want to define the 0x00000010u constant you can use the Lisp value 16. (You can use Lisp's hexadecimal syntax, of course: #x10.) You may find the cl-sdl2 project <https://github.com/lispgames/cl-sdl2> interesting. You can use it and/or read its source to learn how to access SDL2 using CFFI. Cheers, Luís On Sat, 27 Jun 2020 at 13:40, oleg harput <olegharput(a)gmail.com> wrote: > > i am trying to reach C SDL2 using CFFI, in C SDL2 there many functions like int "SDL_Init(Uint32 flags)" > its return value is integer but its are arguments are defined like (in source code) > #define SDL_INIT_TIMER 0x00000001u > #define SDL_INIT_AUDIO 0x00000010u > #define SDL_INIT_VIDEO 0x00000020u /**< SDL_INIT_VIDEO implies SDL_INIT_EVENTS */ > #define SDL_INIT_JOYSTICK 0x00000200u /**< SDL_INIT_JOYSTICK implies SDL_INIT_EVENTS */ > #define SDL_INIT_HAPTIC 0x00001000u > #define SDL_INIT_GAMECONTROLLER 0x00002000u /**< SDL_INIT_GAMECONTROLLER implies SDL_INIT_JOYSTICK */ > #define SDL_INIT_EVENTS 0x00004000u > #define SDL_INIT_SENSOR 0x00008000u > when calling "SDL_Init" using CFFI in CL i did not know how to call arguments like SDL_INIT_TIMER,SDL_INIT_AUDIO,SDL_INIT_VIDEO,... so i tried instead of calling them, i tried to insert their corresping values (they are hexidecimal unsigned integers in C) like > (cffi:foreign-funcall "SDL_Init" > :uint32 32;;for #define SDL_INIT_VIDEO 0x00000020u > :int) > but i am not sure that was a valid transformation or not(32 in CL corresponds to 0x00000020u in C or not) > A better option is to call SDL_INIT_TIMER,SDL_INIT_AUDIO,... directly from cffi but i don not know how because they seemed undefined. > Do you know how to call SDL_INIT_TIMER, SDL_INIT_AUDIO ... using CFFI? > And can you tell me the transformation rules (if there are any) the numbers from C to CL using CFFI? > > пт, 26 июн. 2020 г. в 23:58, Luís Oliveira <luismbo(a)gmail.com>: >> >> On Fri, 26 Jun 2020 at 20:52, oleg harput <olegharput(a)gmail.com> wrote: >> > How can we convert C 0x00000001u (unsigned int in C) to Common Lisp using CFFI? >> > >> > Can we type directly 1?(Is this a valid translation to CL?) >> >> In what context? >> >> -- >> Luís Oliveira >> http://kerno.org/~luis/ -- Luís Oliveira http://kerno.org/~luis/

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How can we convert C 0x00000001u (unsigned int in C) to Common Lisp ?
by oleg harput 26 Jun '20

26 Jun '20

How can we convert C 0x00000001u (unsigned int in C) to Common Lisp using CFFI? Can we type directly 1?(Is this a valid translation to CL?)

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cffi-devel June 2020