python - 如何在python3中使用ctypes void **指针

Question

我想通过它的DLL连接光谱仪，其中一个函数定义为

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

来自文档，dev 是指定光谱仪的索引handle 返回光谱仪 handle 指针VID 是提供指定的VIDPID 是 提供指定的PIDdev、VID、PID已知，但我不知道如何设置句柄。我当前的代码如下

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)

当我运行上面的代码时，出现错误

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

我对ctypes和C不熟悉，谁能帮我解决这个问题。非常感谢。

Answer 1

根据您的错误输出:

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

您忘记将 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)

根据你的函数签名，句柄参数是一个指向void*的指针，因此你需要像这样传递它:

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:这只是一个示例，您应该检查 spectrometerOpen 函数的文档，以了解它到底在等待 handle 参数(可以是NULL，它到底是什么类型，等等)。