如何在python3中使用ctypes void **指針

Question

我將通過它的DLL連接一個光譜儀，其中一個功能定義為

UINT UAI_SpectrometerOpen(unsigned int dev, void** handle, unsigned int VID,  unsigned int PID)

從文檔開始，dev是指定光譜儀句柄的索引是返回光譜儀句柄的指針VID是提供指定的VID PID是提供指定的PID dev，VID，PID是已知的，但我不知道如何設置句柄。 我當前的代碼是

import ctypes
otoDLL = ctypes.CDLL('UserApplication.dll')
spectrometerOpen = otoDLL.UAI_SpectrometerOpen
spectrometerOpen.argtypes = (ctypes.c_uint, ctypes.POINTER(c_void_p),
                         ctypes.c_uint, ctypes.c_uint)
spectrometerOpen.restypes = ctypes.c_uint
handle = ctypes.c_void_p
errorCode = spectrometerOpen(0, handle, 1592, 2732)

當我運行以上代碼時，出現錯誤

runfile('C:/Users/Steve/Documents/Python Scripts/otoDLL.py', wdir='C:/Users/Steve/Documents/Python Scripts')
Traceback (most recent call last):

  File "<ipython-input-1-73fe9922d732>", line 1, in <module>
    runfile('C:/Users/Steve/Documents/Python Scripts/otoDLL.py', wdir='C:/Users/Steve/Documents/Python Scripts')

  File "C:\Users\Steve\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 685, in runfile
    execfile(filename, namespace)

  File "C:\Users\Steve\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 85, in execfile
    exec(compile(open(filename, 'rb').read(), filename, 'exec'), namespace)

  File "C:/Users/Steve/Documents/Python Scripts/otoDLL.py", line 5, in <module>
    spectrometerOpen.argtypes = (ctypes.c_uint, ctypes.POINTER(c_void_p),

NameError: name 'c_void_p' is not defined

我對ctypes和C不熟悉，誰能幫助我解決此問題。 非常感謝。

Answer 1

根據您的錯誤輸出：

  File "C:/Users/Steve/Documents/Python Scripts/otoDLL.py", line 5, in <module>
    spectrometerOpen.argtypes = (ctypes.c_uint, ctypes.POINTER(c_void_p),

您忘記將ctypes放在c_void_p之前，因此：

spectrometerOpen.argtypes = (ctypes.c_uint, ctypes.POINTER(ctypes.c_void_p),
                         ctypes.c_uint, ctypes.c_uint)

根據您的函數簽名，handle參數是一個指向void*的指針，因此您需要像這樣傳遞它：

import ctypes
otoDLL = ctypes.CDLL('UserApplication.dll')
spectrometerOpen = otoDLL.UAI_SpectrometerOpen
spectrometerOpen.argtypes = (ctypes.c_uint, ctypes.POINTER(ctypes.c_void_p),
                         ctypes.c_uint, ctypes.c_uint)
spectrometerOpen.restypes = ctypes.c_uint

# declare HANDLE type, which is a void*
HANDLE = ctypes.c_void_p

# example: declare an instance of HANDLE, set to NULL (0)
my_handle = HANDLE(0)

#pass the handle by reference (works like passing a void**)
errorCode = spectrometerOpen(0, ctypes.byref(my_handle), 1592, 2732)

注意：這僅是一個示例，您應該查看spectrometerOpen函數的文檔，以查看其正真正等待handle參數的內容（可以為NULL，其確切類型是什么，等等）。