Question

我必须在CTypes中使用DLL中的2个函数。这些函数以void*为参数。但无论我尝试什么，我都无法使它发挥作用。我收到一个错误，告诉我使用了错误的类型。我查了很多帖子并阅读了文档，但我无法弄清楚。任何帮助，将不胜感激。我在Windows上使用Python 2.7。

我的C函数是：

void WriteRam(unsigned address, unsigned length, void* buffer)
void ReadRam(unsigned address, unsigned length, void* buffer)

在Python中，我正在尝试将列表传递给函数，如下所示：

audioVolume = 32767
for i in range(buffSize):
    txBuff.append(int(audioVolume * math.sin(i)) )
WriteRam(0, 64, txBuff)

我的Python函数是：

WriteRam = DPxDll['DPxWriteRam']
def DPxWriteRam(address=None, length=None, buffer=None):
    #test = ctypes.c_void_p.from_buffer(buffer) # not working
    #p_buffer = ctypes.cast(buffer, ctypes.c_void_p) # not working
    p_buffer = ctypes.cast(ctypes.py_object(buffer), ctypes.c_void_p) # not working
    #p_buffer = ctypes.c_void_p() # not working
    WriteRam.argtypes = [ctypes.c_uint, ctypes.c_uint, ctypes.c_void_p] 
    WriteRam(address, length, ctypes.byref(p_buffer))

Answer 1

假设txBuff是一个整数列表，那么你需要将它们打包成一个数组。以下代码应该可以工作，但我无法测试它......

def DPxWriteRam(address, int_list):
    int_size = ctypes.sizeof(ctypes.c_int)
    item_count = len(int_list)
    total_size = int_size * item_count
    packed_data = (ctypes.c_int * item_count)(*int_list)
    WriteRam(ctypes.c_uint(address), ctypes.c_uint(total_size), packed_data)

DPxWriteRam(whatever, [0, 1, 2, 3])

...虽然如果WriteRam几乎只是做memcpy()，那么你可以使用它......

import ctypes
libc = ctypes.CDLL('msvcrt.dll')

def DPxWriteRam(address, int_list):
    int_size = ctypes.sizeof(ctypes.c_int)
    item_count = len(int_list)
    total_size = int_size * item_count
    packed_data = (ctypes.c_int * item_count)(*int_list)
    libc.memcpy(address, packed_data, total_size)

...我可以测试......

>>> l = range(4)
>>> p = libc.malloc(1000)
>>> DPxWriteRam(p, l)
>>> s = ' ' * 16
>>> libc.memcpy(s, p, 16)
>>> print repr(s)
'\x00\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00'

Python - Ctypes：如何传递Void *作为参数

1 个答案: