October 2013 - cffi-devel - mailman3.common-lisp.net

Returning errno as a second value
by Felix Filozov 28 Jan '14

28 Jan '14

Hi all, In Allegro CL, the only safe way to get errno after a foreign function call is to configure the foreign function definition to return it as a second value. CFFI doesn't deal with errno. There has been some previous discussion ( http://lists.common-lisp.net/pipermail/cffi-devel/2009-January/003017.html) to return errno safely, but doesn't seem like it went anywhere. So any library that tries to get errno is potentially broken in Allegro CL. I'm seeing this in practice with lisp-zmq, for example. I'd like to introduce a new option to defcfun and foreign-funcall called :errno. It would look like this: (foreign-funcall ("strlen" :errno t) :string "foo" :int), or (defcfun (strlen "strlen" :errno t) :int (s :string)). Calling (strlen) would return two values, the return value of the foreign call, and errno. In some Lisps, the only way to get errno is to make an additional foreign call. Then perhaps that call could be made by CFFI and returns as the second value. I've created a pull request (https://github.com/cffi/cffi/pull/28) with a very rudimentary implementation for Allegro CL. Since CFFI delegates the handling of errno to the implementation, perhaps we could preserve the status quo and not get bugged down in grandiose plans of portability. Thoughts and suggestions are welcome. Thanks, Felix

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[cffi-devel] Help with recursive struct member
by Joeish W 01 Nov '13

01 Nov '13

here is the way CvMemStorage is defined typedef struct CvMemStorage { int signature; CvMemBlock* bottom; /* First allocated block. */ CvMemBlock* top; /* Current memory block - top of the stack. */ struct CvMemStorage* parent; /* We get new blocks from parent as needed. */ int block_size; /* Block size. */ int free_space; /* Remaining free space in current block. */ } CvMemStorage; bu i get unknown CFFI type: (:STRUCT CV-MEM-STORAGE). [Condition of type SIMPLE-ERROR] when i wrap like this....i know lisp is known for recursion how do i bypass this (defcstruct cv-mem-storage (signature :int) (bottom (:pointer (:struct cv-mem-block))) (top (:pointer (:struct cv-mem-block))) (parent (:pointer (:struct cv-mem-storage))) (block-size :int) (free-space :int))

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[cffi-devel] Need some one to show me how to write this defcstruct correctly
by Joeish W 31 Oct '13

31 Oct '13

it is the CvSeq struct from opencv and it is defined a wee bit different than the others here it is as defined #define CV_TREE_NODE_FIELDS(node_type) \ int flags; /* Miscellaneous flags. */ \ int header_size; /* Size of sequence header. */ \ struct node_type* h_prev; /* Previous sequence. */ \ struct node_type* h_next; /* Next sequence. */ \ struct node_type* v_prev; /* 2nd previous sequence. */ \ struct node_type* v_next /* 2nd next sequence. */ /* Read/Write sequence. Elements can be dynamically inserted to or deleted from the sequence. */ #define CV_SEQUENCE_FIELDS() \ CV_TREE_NODE_FIELDS(CvSeq); \ int total; /* Total number of elements. */ \ int elem_size; /* Size of sequence element in bytes. */ \ schar* block_max; /* Maximal bound of the last block. */ \ schar* ptr; /* Current write pointer. */ \ int delta_elems; /* Grow seq this many at a time. */ \ CvMemStorage* storage; /* Where the seq is stored. */ \ CvSeqBlock* free_blocks; /* Free blocks list. */ \ CvSeqBlock* first; /* Pointer to the first sequence block. */ typedef struct CvSeq { CV_SEQUENCE_FIELDS() } the CV_SEQUENCE_FIELDS() part of the typedef struct CvSeq threw me I dont really know what to do with can someone just show me how to write it so I can then wrap all other structs like this....I could show things i tried but t hat would take up so much space it would be exhausting to look at...below is the swig wrapped struct i'm working with but it hasn't been working right so if you can show me how to edit it i would be very grateful =) (defcstruct cv-seq (flags :int) (header-size :int) (h-prev :pointer) (h-next :pointer) (v-prev :pointer) (v-next :pointer) (total :int) (elem-size :int) (block-max :pointer) (ptr :pointer) (delta-elems :int) (storage :pointer) (free-blocks :pointer) (first :pointer)) note normally when i add members like this CvSeqBlock* first; i do it like this (first (:pointer (:struct cv-block))) the new cffi style so if you can show me the new way on this that would be perfect =)

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[cffi-devel] What foreign type would this be...I could use help writing a function definition for documentation
by Joeish W 29 Oct '13

29 Oct '13

the question is about CvArr* in OpenCV it is defined in the source like this /* CvArr* is used to pass arbitrary * array-like data structures * into functions where the particular * array type is recognized at runtime: */ typedef void CvArr; and documentation like this CvArr struct CvArr This is the “metatype” used only as a function parameter. It denotes that the function accepts arrays of multiple types, such as IplImage*, CvMat* or even CvSeq* sometimes. The particular array type is determined at runtime by analyzing the first 4 bytes of the header. In C++ interface the role of CvArr is played by InputArray and OutputArray. I'm writing my libraries documentation so i was wondering when i show my function definition as in c below CvMat* cvGetCol(const CvArr* arr, CvMat* submat, int col) How i would do it ? since CvMat is a struct i so far have this but is it the best it could be (get-cols (arr cv-arr) (:pointer (:struct submat)) (col :int)) but how would someone more skilled in cffi write the int part(col) and the CvArr part. In my library CvArr* is defined as this (defctype cv-arr :pointer)....I would appreciate any help on this

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[cffi-devel] How would i write the exact equivelant of a C New Operator
by Joeish W 29 Oct '13

29 Oct '13

Im converting this code here int board_n = board_w * board_h; CvPoint2D32f* corners = new CvPoint2D32f[ board_n ]; from this link http://dasl.mem.drexel.edu/~noahKuntz/openCVTut10.html and in the code is a new operator id like to convert but i could use guidance how. first of all i looked on google and there actually doesnt appear to be a C new operator only C++ which is a little weird because the code at the above link is full of only OpenCV C functions so either there is a C new operator or the author is using C and C++ together. I was going to do foreign-alloc but at thislink about the new operator for C++ it says "Allocatescountbytes from free store. Calls the function pointer returned by std::get_new_handler on failure and repeats allocation attempts until new handler does not return or becomes a null pointer, at which time throws std::bad_alloc." I dont really know what to make of that and that link is for C++...thus the reason for my question....any guidance is appreciated

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Fw: [cffi-devel] How would i use a function with a callback parameter
by Joeish W 28 Oct '13

28 Oct '13

On , Joeish W <joeish80829(a)yahoo.com> wrote: > >I got the callback working somewhat to illustrate here is my code so far below and again im attempting to convert the lowest function on this page: http://opencv-srf.blogspot.com/2011/11/track-bars.html > >(defcallback a :void ((contrast :int) (img cv-arr) (dest cv-arr)) > (format t "img-1: ~a~%~%" img) >(format t "dest-1: ~a~%~%" dest) >(format t "Trackbar level-1: ~a~%~%" contrast)) > > > >(defun create-trackbar-example (&optional (camera-index *camera-index*) (width *default-width*) > (height *default-height*)) > "Creates a trackbar and attaches it to the specified window. > Move the slider to adjust the brightess of the camera output" > (with-capture (capture (create-camera-capture camera-index)) > (let ((window-name "CREATE-TRACKBAR Example") > (contrast (foreign-alloc :int :initial-contents '(10))) > (dest (create-image (size width height) +ipl-depth-8u+ 3))) > (set-capture-property capture +cap-prop-frame-width+ width) > (set-capture-property capture +cap-prop-frame-height+ height) > (named-window window-name) > (move-window window-name 600 175) > (do* ((img (query-frame capture) (query-frame capture)) > (img (clone-image img)) > (scale 0) > (n 0)) > ((plusp (wait-key *millis-per-frame*)) nil) > (create-trackbar "Contrast" window-name contrast 21 (callback a)) > (format t "img-2: ~a~%~%" img) > (format t "dest-2: ~a~%~%" dest) > (format t "Trackbar level-2: ~a~%~%" (mem-ref contrast :int)) > (show-image window-name img)) > (release-image dest) > (destroy-window window-name)))) > > >im testing the callback function and it works, it is called when the trackbar is moved, i know this because the Trackbar level-2 format output from the callback function prints which it should and the output of the contrast variable in that format function also changes.....the contrast variable is changed in the create-trackbar-example function and the callback function picks up that variable with the (contrast :int) parameter... my new question is how do i get the callback function to pick up the img and dest variables from the create-trackbar-example function....when the code runs the output of the format t functions from the call back with the img and dest variables in them are different from the output of the format t functions from the create-trackbar-example with the img and dest in them which means the callback isnt picking those up but it is picking up the variable contrast...and oddly enough i dont have to mem-ref the contrast variable in the callback function....when i just evaluate the variable contrast it prints a number....I think the parameters of the callback are defined righ,t the img and dest are defined as cv-arr (a defctype :pointer) in my library >...any help is appreciated > >On Sunday, October 27, 2013 12:03 AM, "f9cef2aa(a)yandex.ru" <f9cef2aa(a)yandex.ru> wrote: > >>here is my attempt but i have no idea how to define a function as a pointer and ive tried alot of variations but is too long to post. The defun change contrast compiles btw...i tried using make-pointer to make the change-contrast function a pointer but make-pointer wants it to be a real...so cant use foreign-alloc i dont think because the function needs to be converted to a pointer first to use that...any guidance is appreciated >>> >>>(defun change-contrast (&optional contrast img dest) >>>(if (< contrast 10) (scale img dest (/ 1 (coerce (- 11 contrast) 'double-float))) >>> (if (>= contrast 10) (scale img dest (- contrast 9)))) >>> (show-image "MyImage" dest)) >>> >>>(defun display (filename) >>> "Open the image FILENAME and show it in a window." >>> (let* ((img (load-image filename 1)) >>> (img-size (get-size img)) >>> (dest (create-image img-size +ipl-depth-8u+ 3)) >>> (contrast (cffi:foreign-alloc :int :initial-contents '(10)) >>> (test "not sure what to do here"))) >>> (named-window "MyWindow" 1) >>> (create-trackbar "conrast" "MyWindow" contrast 21 test) >>> (princ (mem-ref contrast :int)) >>> (change-contrast (mem-ref contrast :int) img dest) >>> (loop while (not (= (wait-key 0) 27))) >>> (release-image img) >>> (release-image dest) >>> (destroy-window "MyWindow"))) >> >>Have you read defcallback documentation? If no, read it and try to use >>defcallback. If yes, what was your problem when using defcallback? >> >> >> >> >> >> >> >> > >

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[cffi-devel] How would i write the exact equivelant of a C New Operator
by Joeish W 28 Oct '13

28 Oct '13

Im converting this code here int board_n = board_w * board_h; CvPoint2D32f* corners = new CvPoint2D32f[ board_n ]; from this link http://dasl.mem.drexel.edu/~noahKuntz/openCVTut10.html and in the code is a new operator id like to convert but i could use guidance how. first of all i looked on google and there actually doesnt appear to be a C new operator only C++ which is a little weird because the code at the above link is full of only OpenCV C functions so either there is a C new operator or the author is using C and C++ together. I was going to do foreign-alloc but at thislink about the new operator for C++ it says "Allocatescountbytes from free store. Calls the function pointer returned by std::get_new_handler on failure and repeats allocation attempts until new handler does not return or becomes a null pointer, at which time throws std::bad_alloc." I dont really know what to make of that and that link is for C++...thus the reason for my question....any guidance is appreciated

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[cffi-devel] How would i use a function with a callback parameter
by Joeish W 27 Oct '13

27 Oct '13

the below function create-trackbar-example works except for the last parameter of create-trackbar, "test" ..the test parameter is supposed to be a function that gets called when the trackbar moves. cvCreateTrackbar, the function I'm wrapping, creates a gui slider on the Opencv output window it can either change the variable of a running program or call a function when the slider is moved more info on the last parameter of cvCreateTrackbar, called onChange, herehttp://docs.opencv.org/modules/highgui/doc/user_interface.html?highligh… In the documentation for cvCreateTrackbar it says: for onChange: "onChange – Pointer to the function to be called every time the slider changes position. This function should be prototyped as void Foo(int,void*); , where the first parameter is the trackbar position and the second parameter is the user data (see the next parameter). If the callback is the NULL pointer, no callbacks are called, but only value is updated." im trying to convert the second code on this page to lisp http://opencv-srf.blogspot.com/2011/11/track-bars.html ...Im pretty sure i have all functions wrapped correctly but in theory create-trackbar could be wrong the last parameter in my wrapper is a defctype of :pointer type called cv-trackbar-callback here is my attempt but i have no idea how to define a function as a pointer and ive tried alot of variations but is too long to post. The defun change contrast compiles btw...i tried using make-pointer to make the change-contrast function a pointer but make-pointer wants it to be a real...so cant use foreign-alloc i dont think because the function needs to be converted to a pointer first to use that...any guidance is appreciated (defun change-contrast (&optional contrast img dest) (if (< contrast 10) (scale img dest (/ 1 (coerce (- 11 contrast) 'double-float))) (if (>= contrast 10) (scale img dest (- contrast 9)))) (show-image "MyImage" dest)) (defun display (filename) "Open the image FILENAME and show it in a window." (let* ((img (load-image filename 1)) (img-size (get-size img)) (dest (create-image img-size +ipl-depth-8u+ 3)) (contrast (cffi:foreign-alloc :int :initial-contents '(10)) (test "not sure what to do here"))) (named-window "MyWindow" 1) (create-trackbar "conrast" "MyWindow" contrast 21 test) (princ (mem-ref contrast :int)) (change-contrast (mem-ref contrast :int) img dest) (loop while (not (= (wait-key 0) 27))) (release-image img) (release-image dest) (destroy-window "MyWindow")))

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[cffi-devel] getting There is no applicable method for the generic function wrapping cvFont
by Joeish W 25 Oct '13

25 Oct '13

I wrapped this function how i normally do which is usually correct the function im wrapping is here...info at least and a small example of its usage is there also at the end of the postl ;; CvFont cvFontQt(const char* nameFont, int pointSize = -1, CvScalar color = cvScalarAll(0), int weight = CV_FONT_NORMAL, ;; int style = CV_STYLE_NORMAL, int spacing = 0) (cffi:defcfun ("cvFontQt" %font-qt) (:struct cv-font) (name-font :string) (point-size :int) (color (:struct cv-scalar)) (weight :int) (style :int) (spacing :int)) (defun font-qt (name-font &optional (point-size -1) (color (scalar-all 0)) (weight +font-normal+) (style +style-normal+) (spacing 0)) "Creates the font to draw a text on an image." (%font-qt name-font point-size color weight style spacing)) im getting this error message when i run each of these (with-foreign-object (font '(:struct cv-font)) (setf (mem-ref font `(:pointer (:struct cv-font))) (font-qt "Monospace"))) (defparameter font (foreign-alloc '(:struct cv-font) :initial-element (list (font-qt "")))) (font-qt "") There is no applicable method for the generic function #<STANDARD-GENERIC-FUNCTION TRANSLATE-INTO-FOREIGN-MEMORY (5)> when called with arguments ("" #<CFFI::FOREIGN-STRING-TYPE :UTF-8> #.(SB-SYS:INT-SAP #X7FFFE1467FF0)). [Condition of type SIMPLE-ERROR] it seems to be written right and I'm just running the function so i could use a little help on this . I never use any of cffi foreign-string functions for const char* just :string and they always run right

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Re: [cffi-devel] How do i cast variables
by Martin Simmons 25 Oct '13

25 Oct '13

[ please post back to the list, not private email ] It looks like you are confused about the difference in CFFI between a pointer to a struct and a pointer to a pointer to a struct. Unfortunately, CFFI pointers are untyped so you don't get errors by doing the wrong thing. To call cvFindContours as in the example, you need a pointer to a pointer to a struct (&contour in the C code). Whenever you want to translate C code that uses &variable, you need to allocate a pointer to hold the value and then dereference it after calling the function. E.g. something like this (untested): (cffi:with-foreign-object (contour-ptr (:pointer (:struct cv-seq))) ;; contour-ptr has foreign type (:pointer (:pointer (:struct cv-seq))) (cv-find-contours ... contour-ptr ...) (mem-ref contour-ptr '(:pointer (:struct cv-seq)))) __Martin >>>>> On Wed, 23 Oct 2013 17:04:07 -0700 (PDT), Joeish W said: > > well I'm trying to learn about Sequences in opencv. So this was practice at making the code at this link > > http://opencv-srf.blogspot.com/2011/09/object-detection-tracking-using-cont… > > under the > > Shape Detection & Tracking using Contours > heading . in that code there is this line CvSeq* contours; since i dont know how to initialize a struct pointer in lisp as it is done there ive been using CvSeq* contours = cvCreateSeq(0, sizeof(CvSeq),sizeof(CvPoint),storage); which also initializes a CvSeq* and works in that example. if you could advise me initializing structs I would be most grateful.....Basically I'm starting off by mastering the CvSeq parts of the code. > . > > > > On Wednesday, October 23, 2013 3:23 AM, Martin Simmons <martin(a)lispworks.com> wrote: > >>>>> On Tue, 22 Oct 2013 15:48:50 -0700 (PDT), Joeish W said: > > > >> > >> take this for instance > >> > >> CvPoint points[2]; > >> > >> > >> id like to be able to cast points[2] to the CvPoint struct more info here http://docs.opencv.org/modules/core/doc/old_basic_structures.html?highlight… > >> > >> > >> here is my struct which works for other things > >> > >> > >> > >> ;; (cffi:foreign-type-size '(:struct cv-point)) = 8 > >> (cffi:defcstruct cv-point > >> (x :int) > >> (y :int)) > >> > >> > >> put in a defparameter you cant just go > >> > >> (defparameter points (cffi:foreign-alloc :int :count 2)) > >> > >> (defparameter a ((:struct cv-point) points)) > >> > >> > >> you get an illegal function call error...any help is appreciated > > > >Your example is inconsistent -- in C, your points variable is an array of two > >CvPoints, but in Lisp it is an array of two ints. > > > >What are you really trying to do? > > > >I suggest you post the C code that you are trying to convert. The opencv doc > >for CvPoint doesn't use casting or arrays of ints. > > > >__Martin > > > > > > > > > > >

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