Python 3调用具有自定义数据类型的外部DLL

Question

我正在尝试调用一个外部DLL，该DLL在C.中具有以下头定义

typedef long            EPC_INT32;
typedef void*           EPC_ADDR32;
typedef struct {EPC_CHAR a [16];} EPC_Str16;
typedef struct
{
EPC_INT32 UseUSB;
EPC_INT32 BoardNumber;
EPC_INT32 FIFOSamples;
EPC_INT32 MaxProbes;
EPC_Str16 DeviceNumber;
EPC_Str16 SerialNumber;
EPC_INT32 ExternalScaling;
EPC_ADDR32 DacScaling;
EPC_ADDR32 AdcScaling;
} LIH_OptionsType;
typedef LIH_OptionsType* LIH_OptionsPtr;
EPC_INT32 EPC_Calling LIH_InitializeInterface(
EPC_Str256Ptr ErrorMessage,
EPC_INT32 Amplifier, 
EPC_INT32 ADBoard,
LIH_OptionsPtr OptionsPtr,
EPC_INT32 OptionsSize ) EPC_Import;

Python代码：

import ctypes
import sys
class LIH_Options(ctypes.Structure):
_fields_ = [("UseUSB",          ctypes.c_int32) ,
("BoardNumber",     ctypes.c_int32),
("FIFOSamples",     ctypes.c_int32),
("MaxProbes",       ctypes.c_int32),
("DeviceNumber",    ctypes.c_wchar_p),
("SerialNumber",    ctypes.c_wchar_p),
("ExternalScaling", ctypes.c_int32),
("DataScaling",     ctypes.c_void_p),
("AdcScaling",      ctypes.c_void_p)]
OptionsSize = sys.getsizeof(LIH_Options)
my_LIH_Options = LIH_Options(0,0,1024,0,'','',0, 0,0)  #create an instance
EPC = ctypes.WinDLL('EpcDLL.dll')

EPC.LIH_InitializeInterface.argtypes = [ctypes.c_char_p,
ctypes.c_int32, ctypes.c_int32,
ctypes.POINTER(LIH_Options),
ctypes.c_int32]
szErrMssg  = ctypes.create_string_buffer(256)
status = EPC.LIH_InitializeInterface(szErrMssg, 0, 3, my_LIH_Options, OptionsSize)

这将返回一个Tracback错误：status=EPC.LIH_InitializeInterface(szErrMssg，0，int(LIH.Board(，my_LIH_Options，OptionsSize(S错误：异常：写入0xFFFFFFFF 时发生访问冲突

如果呼叫被取代

status = EPC.LIH_InitializeInterface(szErrMssg, 0, 3, None, OptionsSize)

它可以使用LIH_Options的默认值。因此，问题在于传递数据类型LIH_Options。

Answer 1

数组类型和结构大小不正确。这应该工作，但未经测试，因为我没有你的DLL。None通常用于NULL指针，但0也应该起作用。对char数组使用字节字符串(b''(。

import ctypes
# define the types for easier match to original C structure.
EPC_INT32 = ctypes.c_int32;
EPC_ADDR32 = ctypes.c_void_p; # Only 32-bit on a 32-bit OS.
EPC_CHAR = ctypes.c_char;     # Assumption...not defined in question
EPC_Str16 = EPC_CHAR * 16;    # Correct type of char[16] array
class LIH_Options(ctypes.Structure):
_fields_ = [("UseUSB",          EPC_INT32),
("BoardNumber",     EPC_INT32),
("FIFOSamples",     EPC_INT32),
("MaxProbes",       EPC_INT32),
("DeviceNumber",    EPC_Str16),
("SerialNumber",    EPC_Str16),
("ExternalScaling", EPC_INT32),
("DataScaling",     EPC_ADDR32),
("AdcScaling",      EPC_ADDR32)]
OptionsSize = ctypes.sizeof(LIH_Options)  # sys.getsizeof returns size of Python object, not C
my_LIH_Options = LIH_Options(0,0,1024,0,b'',b'',0,None,None)  #create an instance
EPC = ctypes.WinDLL('EpcDLL.dll')
EPC.LIH_InitializeInterface.argtypes = [ctypes.c_char_p,
EPC_INT32, EPC_INT32,
ctypes.POINTER(LIH_Options),
EPC_INT32]
szErrMssg  = ctypes.create_string_buffer(256)
status = EPC.LIH_InitializeInterface(szErrMssg, 0, 3, my_LIH_Options, OptionsSize)