如何在公共lisp/cffi中使用windows句柄调用本机c函数

本机c标头：

typedef HANDLE HCAMERA;
int Begin(HCAMERA* h);
int End(HCAMERA h);

句柄定义为：

typedef void *HANDLE;

本机c源代码我想要：

HCAMERA h;
int r = 0;
r = Begin(&h);
VERIFY(r);
r = End(h);
VERIFY(r);

我尝试了sbcl 1.3.1中的以下代码，但不起作用

(cffi:use-foreign-library "camera.dll")

(cffi:defcfun "Begin" :int
  (handle :pointer))

(cffi:defcfun "End" :int
  (handle :pointer))

(defparameter *camera* (cffi:foreign-alloc :pointer)) ; alloc handle

(cffi:with-foreign-object (handle :pointer)
  (setf (cffi:mem-ref handle :pointer) *camera*) ; handle address
  (Begin handle)
  (End *camera*))

---

顺便问一句：如何获取外物（相机）的地址？我做得对吗？

你可以得到如下地址：

(defun get-foreign-address (obj)
  (write-to-string (cffi:pointer-address obj) :base 16))

如果你有这个C文件

#include <stdio.h>

typedef void *HANDLE;
typedef HANDLE HCAMERA;

int Begin(HCAMERA* h);
int End(HCAMERA h);

int Begin(HCAMERA* h) {
    printf("Address from Begin: %p\n", h);
    return 0;
};
int End(HCAMERA h) {
    printf("Address from End: %p\n", (void*)&h);
    return 0;
};

---

可能的陷阱：如果我使用Emacs中的lisp代码，我看不到C中的stdout。我使用

sbcl--script file.lisp从命令行执行它。希望，这对您有所帮助。
我最终通过以下代码找到了答案：

(defparameter *camera-handle* (cffi:null-pointer))
(defun camera-open ()
  (unless (cffi:null-pointer-p *camera-handle*)
    (EndHVDevice (cffi:mem-ref *camera-handle* :pointer))
    (cffi:foreign-free *camera-handle*))
  (setf *camera-handle* (cffi:foreign-alloc :pointer))
  (BeginHVDevice *camera-handle*))

(defun camera-close ()
  (unless (cffi:null-pointer-p *camera-handle*)
    (EndHVDevice (cffi:mem-ref *camera-handle* :pointer))
    (cffi:foreign-free *camera-handle*)
    (setf *camera-handle* (cffi:null-pointer))))

(defparameter *camera-handle* (cffi:null-pointer))
(defun camera-open ()
  (unless (cffi:null-pointer-p *camera-handle*)
    (EndHVDevice (cffi:mem-ref *camera-handle* :pointer))
    (cffi:foreign-free *camera-handle*))
  (setf *camera-handle* (cffi:foreign-alloc :pointer))
  (BeginHVDevice *camera-handle*))

(defun camera-close ()
  (unless (cffi:null-pointer-p *camera-handle*)
    (EndHVDevice (cffi:mem-ref *camera-handle* :pointer))
    (cffi:foreign-free *camera-handle*)
    (setf *camera-handle* (cffi:null-pointer))))