c - 使用 cffi-libffi 按值传递结构？

Question

我的印象是 CFFI 不能按值传递结构，但 CFFI 文档说:

To pass or return a structure by value to a function, load the cffi-libffi system and specify the structure as (:struct structure-name). To pass or return the pointer, you can use either :pointer or (:pointer (:struct structure-name)).

我正在重新包装 cl-opencv 函数 get-size ，它是这个 opencv 函数的包装器:

CvSize cvGetSize(const CvArr* arr)

并且由于我不认为 CFFI 在 cl-opencv 的作者编写库时能够使用 cffi-libffi 系统按值传递结构体，因此他不得不使用以下所有代码来包装 cvGetSize :

 (defmacro make-structure-serializers (struct slot1 slot2)
  "Create a serialization and deserialization function for the
structure STRUCT with integer slots SLOT1 and SLOT2. These functions
will pack and unpack the structure into an INT64."
  (let ((pack-fn (intern (concatenate 'string (string struct) 
                       (string '->int64))))
    (slot1-fn (intern (concatenate 'string (string struct) "-" 
                        (string slot1))))
    (slot2-fn (intern (concatenate 'string (string struct) "-" 
                        (string slot2))))
    (unpack-fn (intern (concatenate 'string (string 'int64->) 
                    (string struct))))
    (make-fn (intern (concatenate 'string (string 'make-) 
                       (string struct)))))
     `(progn
        (defun ,pack-fn (s)
     (+ (,slot1-fn s) (ash (,slot2-fn s) 32)))
        (defun ,unpack-fn (n)
     (,make-fn ,slot1 (logand n #x00000000ffffffff)
            ,slot2 (ash n -32))))))


;; CvSize - Input = (defparameter a (make-size :width 640 :height 480)) Output = #S(SIZE :WIDTH 640 :HEIGHT 480) for 
;; following the two.
(defstruct size (width 0) (height 0))
(make-structure-serializers :size :width :height)

;; CvSize cvGetSize(const CvArr* arr)
(cffi:defcfun ("cvGetSize" %get-size) :int64
  (arr cv-array))

(defun get-size (arr)
  "Get the dimensions of the OpenCV array ARR. Return a size struct with the
dimensions."
  (let ((nsize (%get-size arr)))
     (int64->size nsize)))

鉴于上面引用的 CFFI 文档，我将如何通过这个 cvGetSize结构 CvSize按值(value)？

我打算更新 cl-opencv包，我想知道在 cl-opencv 包中的何处以及如何根据 CFFI 文档“加载 cffi-libffi 系统”，以及在哪里“将结构指定为 (:struct structure-name)”和“使用: ” pointer or (:pointer (:struct structure-name))""传递或返回指针。"

我可以使用上面的 cvGetSize 来详细说明如何做到这一点。包装器:

;; CvSize cvGetSize(const CvArr* arr)
(cffi:defcfun ("cvGetSize" %get-size) :int64
  (arr cv-array))

(defun get-size (arr)
  "Get the dimensions of the OpenCV array ARR. Return a size struct with the
dimensions."
  (let ((nsize (%get-size arr)))
     (int64->size nsize)))

编辑@Rörd

我很欣赏你的意见回应

无论哪种方式，我都会遇到相同的错误……但是出于测试目的，可以说我加载了 cffi-libffi
像这样进入我当前的 session (带输出)

CL-OPENCV> (asdf:oos 'asdf:load-op :cffi-libffi) 
#<ASDF:LOAD-OP NIL {10076CCF13}>
NIL

它加载所以我只运行 defcfun 和你提供的 defcstruct
像这样(带输出):

 CL-OPENCV> (cffi:defcstruct cv-size
           (width :int)
           (height :int))

  (:STRUCT CV-SIZE)
  CL-OPENCV> 
  (defcfun ("cvGetSize" %get-size) (:struct cv-size)
    (arr cv-array))
  ; in: DEFCFUN ("cvGetSize" %GET-SIZE)
  ;     ("cvGetSize" CL-OPENCV::%GET-SIZE)
  ; 
  ; caught ERROR:
  ;   illegal function call
  ; 
  ; compilation unit finished
  ;   caught 1 ERROR condition

  Execution of a form compiled with errors.
  Form:
    ("cvGetSize" %GET-SIZE)
  Compile-time error:
    illegal function call
     [Condition of type SB-INT:COMPILED-PROGRAM-ERROR]

  Restarts:
   0: [RETRY] Retry SLIME REPL evaluation request.
   1: [*ABORT] Return to SLIME's top level.
   2: [ABORT] Abort thread (#<THREAD "repl-thread" RUNNING {1007BA8063}>)

      Backtrace:
             0: ((LAMBDA ()))
                 [No Locals]
             1: (SB-INT:SIMPLE-EVAL-IN-LEXENV ("cvGetSize" %GET-SIZE) #<NULL-LEXENV>)
                 Locals:
                   SB-DEBUG::ARG-0 = ("cvGetSize" %GET-SIZE)
                   SB-DEBUG::ARG-1 = #<NULL-LEXENV>
             2: (SB-INT:SIMPLE-EVAL-IN-LEXENV (DEFCFUN ("cvGetSize" %GET-SIZE) (:STRUCT CV-SIZE) (ARR CV-ARRAY)) #<NULL-LEXENV>)
                 Locals:
                   SB-DEBUG::ARG-0 = (DEFCFUN ("cvGetSize" %GET-SIZE) (:STRUCT CV-SIZE) (ARR CV-ARRAY))
                   SB-DEBUG::ARG-1 = #<NULL-LEXENV>
             3: (EVAL (DEFCFUN ("cvGetSize" %GET-SIZE) (:STRUCT CV-SIZE) (ARR CV-ARRAY)))
                 Locals:

我知道 libffi 安装正确，因为加载了 gsll(使用 cffi-libffi)
我运行了 gsll 测试，它们都通过了这里显示的(带输出)

(ql:quickload "lisp-unit")
  (in-package :gsl)
  (lisp-unit:run-tests)
To load "lisp-unit":
  Load 1 ASDF system:
    lisp-unit
     Loading "lisp-unit"
..................................
Unit Test Summary
 | 4023 assertions total
 | 4022 passed
 | 1 failed
 | 0 execution errors
 | 0 missing tests

#<TEST-RESULTS-DB Total(4023) Passed(4022) Failed(1) Errors(0)>

它似乎没有用 (:struct cv-size) 调用 defcfun
作为问题，因为当我称之为

(defcfun ("cvGetSize" %get-size) cv-size
  (arr cv-array))

我得到同样的错误

Execution of a form compiled with errors.
Form:
  ("cvGetSize" %GET-SIZE)
Compile-time error:

我可以像这样运行我的 ipl-image 结构

CL-OPENCV> ;; ;(cffi:foreign-type-size '(:struct ipl-image)) = 144
(cffi:defcstruct ipl-image
(n-size :int)
(id :int)
(n-channels :int)
(alpha-channel :int)
(depth :int)
(color-model :pointer) 
(channel-seq :pointer) 
(data-order :int)
(origin :int)
(align :int)
(width :int)
(height :int)
(roi :pointer)
(mask-roi :pointer)
(image-id :pointer)
(tile-info :pointer)
(image-size :int)
(image-data :string)
(width-step :int)
(border-mode :pointer)
(border-const :pointer)
(image-data-origin :string))

   output>(:STRUCT IPL-IMAGE)

和我的 create-image 包装器现在加载了 cffi-libffi 和你的 (:struct ipl-image)
它运行良好，但......显示输出

;; IplImage* cvCreateImage(CvSize size, int depth, int channels)
(cffi:defcfun ("cvCreateImage" %create-image) (:struct ipl-image)
  (size :int64)
  (depth :int)
  (channels :int))

(defun create-image (size depth channels)
  "Create an image with dimensions given by SIZE, DEPTH bits per
channel, and CHANNELS number of channels."
 (let ((nsize (size->int64 size)))
    (%create-image nsize depth channels)))

创建图像

但是当我运行时

(defparameter img-size (make-size :width 640 :height 480))

(defparameter img (create-image img-size +ipl-depth-8u+ 1))

在 repl 创建一个图像没有任何 react repl 只是挂起...

但是当我使用 ipl-image 而不是 (:struct ipl-image) 运行创建图像包装器时

我可以运行:

 (defparameter img-size (make-size :width 640 :height 480))

 (defparameter img (create-image img-size +ipl-depth-8u+ 1))

很好然后运行它来访问结构值(带输出)

 (cffi:with-foreign-slots ((
  n-size
  id
  n-channels
  alpha-channel
  depth
  color-model
  channel-seq
  data-order
  origin
  align
  width
  height
  roi
  mask-roi
  image-id
  tile-info
  image-size
  image-data
  width-step
  border-mode
  border-const
  image-data-origin) img (:struct ipl-image))
            (cffi:mem-ref img :char )
            (format t "n-size ~a ~%" n-size)
            (format t "id ~a ~%" id)
            (format t "n-channels ~a ~%" n-channels)
            (format t "alpha-channel ~a ~%" alpha-channel)
            (format t "depth ~a ~%" depth)
            (format t "color-model ~a ~%" color-model)
            (format t "channel-seq ~a ~%" channel-seq)
            (format t "data-order ~a ~%" data-order)
            (format t "origin ~a ~%" origin)
            (format t "align ~a ~%" align)
            (format t "width ~a ~%" width)
            (format t "height ~a ~%" height)
            (format t "roi ~a ~%" roi)
            (format t "mask-roi ~a ~%" mask-roi)
            (format t "image-id ~a ~%" image-id)
            (format t "tile-info ~a ~%" tile-info)
            (format t "image-size ~a ~%" image-size)
            (format t "image-data ~a ~%" image-data)
            (format t "width-step ~a ~%" width-step)
            (format t "border-mode ~a ~%" border-mode)
            (format t "border-const ~a ~%" border-const)
            (format t "image-data-origin ~a ~%" image-data-origin))
  output>
  n-size 144 
  id 0 
  n-channels 1 
  alpha-channel 0 
  depth 8 
  color-model #.(SB-SYS:INT-SAP #X59415247) 
  channel-seq #.(SB-SYS:INT-SAP #X400000000) 
  data-order 640 
  origin 480 
  align 0 
  width 0 
  height 0 
  roi #.(SB-SYS:INT-SAP #X00000000) 
  mask-roi #.(SB-SYS:INT-SAP #X00000000) 
  image-id #.(SB-SYS:INT-SAP #X0004B000) 
  tile-info #.(SB-SYS:INT-SAP #X7FFFF7F04020) 
  image-size 640 
  image-data NIL 
  width-step 0 
  border-mode #.(SB-SYS:INT-SAP #X00000000) 
  border-const #.(SB-SYS:INT-SAP #X00000000) 
  image-data-origin  

但我没有得到一个按值(value)得到的结构体

 color-model #.(SB-SYS:INT-SAP #X59415247) 

当我用这个在 c 中计算出该值 img->colorModel 时

IplImage* img=cvCreateImage(cvSize(640,480), IPL_DEPTH_8U, 3);
cout << "colorModel = " << endl << " " << img->colorModel << endl << endl;

output> colorModel = 
 RGB

所以任何帮助将不胜感激

好的 1 编辑:

我再次尝试，它在这里工作是我的输出

  CL-OPENCV> (asdf:oos 'asdf:load-op :cffi-libffi)
  #<ASDF:LOAD-OP NIL {1006D7B1F3}>
  NIL
  CL-OPENCV> 
  ;; ;(cffi:foreign-type-size '(:struct cv-size)) = 8
  (cffi:defcstruct cv-size
      (width :int)
      (height :int))

  ;; CvSize cvGetSize(const CvArr* arr)
  (cffi:defcfun ("cvGetSize" %get-size) (:struct cv-size)
    (arr cv-array))

  STYLE-WARNING: redefining CL-OPENCV::%GET-SIZE in DEFUN
  %GET-SIZE
  CL-OPENCV> 

   (defparameter img-size (make-size :width 640 :height 480))

  (defparameter img (create-image img-size +ipl-depth-8u+ 1))

  IMG
  CL-OPENCV> 

   (defparameter size (%get-size img))
  SIZE
  CL-OPENCV> size
  (HEIGHT 480 WIDTH 640)
  CL-OPENCV> 

不知道我第一次做错了什么但是......如果你能检查我的结果并验证我刚刚通过值传递了一个结构，我将永远感激

谢谢罗德

好的，如果您仍然有兴趣帮助我调试 Rord，请再次编辑

如果出现错误:

  The value (HEIGHT 480 WIDTH 640)
   is not of type
   SB-SYS:SYSTEM-AREA-POINTER.
   [Condition of type TYPE-ERROR]

这是导致它的历史记录(这是在我发布 prev.edit 之后直接发生的，所以我的 emacs 仍然加载了所有 prev.edits 代码):

   CL-OPENCV> (defun get-size (arr)
    "Get the dimensions of the OpenCV array ARR. Return a size struct with the
  dimensions."
    (cffi:with-foreign-slots ((width height) (%get-size arr) (:struct cv-size))
      (make-size :width width :height height)))
  STYLE-WARNING: redefining CL-OPENCV:GET-SIZE in DEFUN
  GET-SIZE
  CL-OPENCV> 

   (defparameter img-size (make-size :width 640 :height 480))

  (defparameter img (create-image img-size +ipl-depth-8u+ 1))

  IMG
  CL-OPENCV> 

   (defparameter size (get-size img))


  The value (HEIGHT 480 WIDTH 640)
   is not of type
   SB-SYS:SYSTEM-AREA-POINTER.
   [Condition of type TYPE-ERROR]

我明白了，因为:

(defparameter size (get-size img)) 

访问您的 defun ......我跟踪它，所以当我刚运行时 - 显示输出:

CL-OPENCV> 
;; ;(cffi:foreign-type-size '(:struct cv-size)) = 8
(cffi:defcstruct cv-size
        (width :int)
        (height :int))

;; CvSize cvGetSize(const CvArr* arr)
 (cffi:defcfun ("cvGetSize" %get-size) (:struct cv-size)
  (arr cv-array))

STYLE-WARNING: redefining CL-OPENCV::%GET-SIZE in DEFUN
%GET-SIZE
CL-OPENCV> (defparameter capture (create-camera-capture 0))
CAPTURE
CL-OPENCV> (defparameter frame (query-frame capture))
FRAME
CL-OPENCV> 

(defparameter size (%get-size frame))
SIZE
CL-OPENCV> size
(HEIGHT 480 WIDTH 640)
CL-OPENCV> (cffi:with-foreign-slots ((width height) size (:struct cv-size))
        (list width height ))

我得到错误:

The value (HEIGHT 480 WIDTH 640)
  is not of type
    SB-SYS:SYSTEM-AREA-POINTER.
     [Condition of type 

我认为这是因为您的 defcfun 的输出只是一个列表，而 with-foreign-slots 需要一个指针

我跑了这个:

(HEIGHT 480 WIDTH 640)
CL-OPENCV> (first size)
HEIGHT

验证，它只是一个列表

顺便说一句，我使用这些功能进行测试

(defparameter capture (create-camera-capture 0))

(defparameter frame (query-frame capture))

因为有更纯的输出...create-image 使用了我最初发布在此顶部的 get-size 的hackery？

我想使用 create-image 和 get-size w/o 所有的hackery，只使用结构来返回，这样我就可以停止使用 make-size 并使它更纯......所以任何建议都会成为金子……这是我想要创建图像的方式……我只需要让它接受来自您(罗德的)defcfun 的输出……我现在正在尝试将您的 defcfun 输出((高度) 480 WIDTH 640)) 指向一个指针......所以它只会在这个

;; IplImage* cvCreateImage(CvSize size, int depth, int channels)
(cffi:defcfun ("cvCreateImage" %create-image) ipl-image
  (size cv-size)
  (depth :int)
  (channels :int))

或者整个制作尺寸的东西将成为必需品......

也仅供引用，我更改了您添加的 defun

(defun get-size (arr)
  "Get the dimensions of the OpenCV array ARR. Return a size struct with the
dimensions."
  (setf arr (%get-size arr))
  (make-size :width (cadddr arr) :height (cadr arr)))

现在它可以工作了......如果我搞砸了一些东西并且你的defun会更好，它仍然是古玩

编辑!!!!我想通了!!!!!

here is the repl output :

; SLIME 2012-05-25
CL-OPENCV> ;; CvSize cvGetSize(const CvArr* arr)
(cffi:defcfun ("cvGetSize" get-size) (:pointer (:struct cv-size))
  (arr cv-array))
STYLE-WARNING: redefining CL-OPENCV:GET-SIZE in DEFUN
GET-SIZE
CL-OPENCV> ;; IplImage* cvCreateImage(CvSize size, int depth, int channels)
(cffi:defcfun ("cvCreateImage" create-image) (:pointer (:struct ipl-image))
   (size (:pointer (:struct ipl-image)))
  (depth :int)
  (channels :int))


STYLE-WARNING: redefining CL-OPENCV:CREATE-IMAGE in DEFUN
CREATE-IMAGE
CL-OPENCV> (defun detect-red-objects (&optional (camera-index 0))
   "Uses IN-RANGE-SCALAR to detect red objects"
  (with-capture (capture (create-camera-capture camera-index))
    (let ((window-name-1 "Video")
          (window-name-2 "Ball"))
           (named-window window-name-1)
           (named-window window-name-2)
           (move-window window-name-1 290 225)
           (move-window window-name-2 940 225)
      (do* ((frame (query-frame capture) (query-frame capture))
             (img (clone-image frame))
              (frame (clone-image img))
              (img-size (get-size frame))          
              (img-hsv (create-image img-size +ipl-depth-8u+ 3))
              (img-hsv-size (get-size img-hsv))
            (img-thresh (create-image img-hsv-size +ipl-depth-8u+ 1))
             (scalar-1 (make-cv-scalar 170.0 160.0 60.0))
             (scalar-2 (make-cv-scalar 180.0 256.0 256.0)))
         ((plusp (wait-key *millis-per-frame*)) nil)
             (smooth frame frame +gaussian+ 3 3)
             (cvt-color frame img-hsv +bgr2hsv+)
             (in-range-s img-hsv scalar-1 scalar-2 img-thresh)
             (smooth img-thresh img-thresh +gaussian+ 3 3)
             (show-image window-name-1 frame)
             (show-image window-name-2 img-thresh))
          (destroy-all-windows))))
DETECT-RED-OBJECTS

(the function detect-red-objects runs btw!...

编辑!!!!我明白了!!!!!...部分....II - 更好!

I messed up the struct on create-image the first time but it still ran...weird...but it runs when put the create-image struct back to cv-size....so no prob there...here is revised repl output


; SLIME 2012-05-25
CL-OPENCV> ;; CvSize cvGetSize(const CvArr* arr)
(cffi:defcfun ("cvGetSize" get-size) (:pointer (:struct cv-size))
  (arr cv-array))
STYLE-WARNING: redefining CL-OPENCV:GET-SIZE in DEFUN
GET-SIZE
CL-OPENCV> ;; IplImage* cvCreateImage(CvSize size, int depth, int channels)
(cffi:defcfun ("cvCreateImage" create-image) (:pointer (:struct ipl-image))
  (size (:pointer (:struct cv-size)))
  (depth :int)
  (channels :int))

STYLE-WARNING: redefining CL-OPENCV:CREATE-IMAGE in DEFUN
CREATE-IMAGE
CL-OPENCV> (defun detect-red-objects (&optional (camera-index 0))
   "Uses IN-RANGE-SCALAR to detect red objects"
  (with-capture (capture (create-camera-capture camera-index))
    (let ((window-name-1 "Video")
          (window-name-2 "Ball"))
           (named-window window-name-1)
           (named-window window-name-2)
           (move-window window-name-1 290 225)
           (move-window window-name-2 940 225)
      (do* ((frame (query-frame capture) (query-frame capture))
             (img (clone-image frame))
              (frame (clone-image img))
              (img-size (get-size frame))           
              (img-hsv (create-image img-size +ipl-depth-8u+ 3))
              (img-hsv-size (get-size img-hsv))
            (img-thresh (create-image img-hsv-size +ipl-depth-8u+ 1))
             (scalar-1 (make-cv-scalar 170.0 160.0 60.0))
             (scalar-2 (make-cv-scalar 180.0 256.0 256.0)))
         ((plusp (wait-key *millis-per-frame*)) nil)
             (smooth frame frame +gaussian+ 3 3)
             (cvt-color frame img-hsv +bgr2hsv+)
             (in-range-s img-hsv scalar-1 scalar-2 img-thresh)
             (smooth img-thresh img-thresh +gaussian+ 3 3)
             (show-image window-name-1 frame)
             (show-image window-name-2 img-thresh)) 
          (destroy-all-windows))))
DETECT-RED-OBJECTS

@利亚姆编辑

好的，我试过你的从外国翻译的方法，它确实有效
我在 structs.lisp 文件中定义了这些

(cffi:defcstruct (cv-size :class cv-size-type)
  (width :int)
  (height :int))

(defmethod cffi:translate-from-foreign (p (type cv-size-type))
  (let ((plist (call-next-method)))
    (make-size :width (getf plist 'width)
               :height (getf plist 'height))))

和 get-size 和 create-image 是这样定义的

;; CvSize cvGetSize(const CvArr* arr)
 (cffi:defcfun ("cvGetSize" get-size) (:struct cv-size)
   (arr cv-arr))

 ;; IplImage* cvCreateImage(CvSize size, int depth, int channels)
 (cffi:defcfun ("cvCreateImage" %create-image) ipl-image
   (size :int64)
   (depth :int)
   (channels :int))

 (defun create-image (size depth channels)
   "Create an image with dimensions given by SIZE, DEPTH bits per
 channel, and CHANNELS number of channels."
   (let ((nsize (size->int64 size)))
     (%create-image nsize depth channels)))

这里是 size->int64 的定义

  (DEFUN SIZE->INT64 (S) (+ (SIZE-WIDTH S) (ASH (SIZE-HEIGHT S) 32)))

但我喜欢翻译外国定义方法的想法

所以我想知道你是否可以向我展示如何从方法中制作下面的翻译成外国版本这真的会让我的图书馆唱歌......我的目标是为 opencv 制作一个完整的 cffi 包装器和 gsll 一样好是 gsl 所以这真的有助于更快地发生....再次感谢您对这一切的帮助

(defmethod cffi:translate-from-foreign (p (type cv-size-type))
  (let ((plist (call-next-method)))
    (make-size :width (getf plist 'width)
               :height (getf plist 'height))))

Answer 1

要“加载 cffi-libffi 系统”，您需要在库的 .asd 中将其指定为依赖项。文件。 (注意:cffi-libffi 需要在您的系统上安装 C 库 libffi。)

才能使用(:struct structure-name) , 你需要先用 cffi:defcstruct 定义结构体，像这样(我在这里假设 cffi:defcstruct 、 cffi:defcfun 和 cffi:with-foreign-slots 是在当前包中导入的):

(defcstruct cv-size
  (width :int)
  (height :int))

然后您可以使用 (:struct cv-size)在 defcfun像这样:

(defcfun ("cvGetSize" %get-size) (:struct cv-size)
  (arr cv-array))

编辑 : 固定 get-size对于传值结构。

最后定义 get-size像这样:

(defun get-size (arr)
  "Get the dimensions of the OpenCV array ARR. Return a size struct with the
dimensions."
  (let ((%size (%get-size arr)))
    (make-size :width (getf %size 'width)
               :height (getf %size 'height))))

编辑 2 :

如果我正确理解 Liam 的回答，这就是如何写 translate-from-foreign方法，以便它直接创建结构，而无需创建中间 plist:

(defmethod cffi:translate-from-foreign (p (type cv-size-type))
  (with-foreign-slots ((width height) p (:struct cv-size))
    (make-size :width width :height height)))