我正在开发一个项目，我必须使用 python 为开发板构建一个 GUI，我也是新手。我得到了 DLL，它具有与开发板通信所需的功能。 我有 LabVIEW 等效函数原型，如下所示：
int32_t WriteFPGARegsC(int16_t *USBdev, int32_t *DUTSelect, int32_t *Array_RegsIn, int32_t *Array_RegsOut, int32_t *Array_RegEnable);
对于 Visual Basic，相同的原型也如下所示：
Public Declare Function WriteFPGARegsC Lib "USB_IO_for_VB6.dll" (ByRef USBdev As Short, ByVal DUTSelect As Integer, ByRef Array_RegsIn As Integer, ByRef Array_RegsOut As Integer, ByRef Array_RegEnable As Integer) As Integer
由于存在很多问题，我尝试使用 python 而不是 LabVIEW 来访问此函数。
传递给函数的最后三个参数需要是包含 255 个元素的数组的地址。
我不知道如何在Python中的函数中传递指针！
我编写了以下短代码来在 python 中访问此函数：
USBdev = [0]
DUTSelect = [0]
RegsIn = [0] * 255
RegsOut = [0] * 255
RegEnable = [0] * 255
from ctypes import*
mydll = cdll.LoadLibrary("USB_IO_for_VB6.dll")
retmydll = mydll.WriteFPGARegsC(USBdev, DUTSelect, RegsIn, RegsOut, RegEnable)
执行此代码后，我收到以下错误消息：
Traceback (most recent call last):
File "D:\Kushal\ATLASS\Source_code\Atlass.py", line 12, in <module>
retmydll = mydll.WriteFPGARegsC(id(USBdev), id(DUTSelect), id(RegsIn), id(RegsOut), id(RegEnable))
ValueError: Procedure called with not enough arguments (20 bytes missing) or wrong calling convention
任何帮助将不胜感激！ 非常感谢！
清单 [Python.Docs]：ctypes - Python 的外部函数库。
在一切之前，请检查[SO]：通过 ctypes 从 Python 调用的 C 函数返回不正确的值（@CristiFati 的答案），了解使用 CTypes（调用函数）时的常见陷阱。
无论如何，我准备了一个虚拟示例（不要介意容易出错），它只是为了说明机制。
dll00.c:
#if defined(_WIN32)
# define DLL00_EXPORT_API __declspec(dllexport)
#else
# define DLL00_EXPORT_API
#endif
#include <stdint.h>
#include <stdio.h>
#define DIM 10 // Must be the SAME (well, or lower) than the constant defined in the Python code
DLL00_EXPORT_API int32_t __stdcall WriteFPGARegsC(int16_t *USBdev, int32_t *DUTSelect, int32_t *ArrayRegsIn, int32_t *ArrayRegsOut, int32_t *ArrayRegEnable)
{
int32_t ret = 99;
printf("From C:\n\t*USBdev: %d\n\t*DUTSelect: %d\n\tArray_RegsIn[0]: %d\n\tArray_RegsOut[0]: %d\n\tArray_RegEnable[0]: %d\n\n\tReturning: %d\n",
*USBdev, *DUTSelect, ArrayRegsIn[0], ArrayRegsOut[0], ArrayRegEnable[0], ret);
for (int i = 0; i < DIM; i++) {
ArrayRegsOut[i] *= *DUTSelect;
}
return ret;
}
code00.py:
#!/usr/bin/env python
import ctypes as cts
import sys
DIM = 10 # Should be 255, but for demo purposes keep it smaller
UIntArr = cts.c_uint * DIM
UShortArr = cts.c_ushort * DIM
UIntPtr = cts.POINTER(cts.c_uint)
UShortPtr = cts.POINTER(cts.c_ushort)
def main(*argv):
dll = cts.WinDLL("./USB_IO_for_VB6.dll")
dll_func = dll.WriteFPGARegsC
dll_func.argtypes = (UShortPtr, UIntPtr, UIntPtr, UIntPtr, UIntPtr)
dll_func.restype = cts.c_uint
usb_dev = cts.c_ushort(25)
dut_select = cts.c_uint(2)
regs_in = UIntArr(*range(20, 20 + DIM))
regs_out = UIntArr(*range(30, 30 + DIM))
reg_enable = UIntArr(*range(40, 40 + DIM))
nth = 5
print("Output register array: {:s}".format(" ".join(["{:d}".format(item) for item in regs_out])))
print("\tIts {:d}th element: {:d}\n".format(nth, regs_out[nth]))
ret = dll_func(cts.byref(usb_dev), cts.byref(dut_select), regs_in, regs_out, reg_enable)
print("\nFunction returned: {:d}".format(ret))
print("Output register array: {:s}".format(" ".join(["{:d}".format(item) for item in regs_out])))
print("\tIts {:d}th element: {:d}\n".format(nth, regs_out[nth]))
if __name__ == "__main__":
print(
"Python {:s} {:03d}bit on {:s}\n".format(
" ".join(elem.strip() for elem in sys.version.split("\n")),
64 if sys.maxsize > 0x100000000 else 32,
sys.platform,
)
)
rc = main(*sys.argv[1:])
print("\nDone.\n")
sys.exit(rc)
输出：
(py35x64_test) e:\Work\Dev\StackOverflow\q051289410> "c:\Install\x86\Microsoft\Visual Studio Community\2015\vc\vcvarsall.bat" amd64 (py35x64_test) e:\Work\Dev\StackOverflow\q051289410> dir /b dll00.c code00.py (py35x64_test) e:\Work\Dev\StackOverflow\q051289410> cl /nologo dll00.c /link /DLL /OUT:USB_IO_for_VB6.dll dll00.c Creating library USB_IO_for_VB6.lib and object USB_IO_for_VB6.exp (py35x64_test) e:\Work\Dev\StackOverflow\q051289410> dir /b dll00.c dll00.obj code00.py USB_IO_for_VB6.dll USB_IO_for_VB6.exp USB_IO_for_VB6.lib (py35x64_test) e:\Work\Dev\StackOverflow\q051289410> "e:\Work\Dev\VEnvs\py35x64_test\Scripts\python.exe" ./code00.py Python 3.5.4 (v3.5.4:3f56838, Aug 8 2017, 02:17:05) [MSC v.1900 64 bit (AMD64)] 064BIT on win32 Output register array: 30 31 32 33 34 35 36 37 38 39 Its 5th element: 35 From C: *USBdev: 25 *DUTSelect: 2 Array_RegsIn[0]: 20 Array_RegsOut[0]: 30 Array_RegEnable[0]: 40 Returning: 99 Function returned: 99 Output register array: 60 62 64 66 68 70 72 74 76 78 Its 5th element: 70
修改答案尽可能贴近真实场景，也解决评论中的问题