How to use a C++ class, exported from a DLL

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Hi,
I have a logic to parse a file in c++. It is implemented as a class say logReader.
What I am trying to achieve is, export this class from a file and use that in Python.
so to create the Dll what i did is created 2 functions and exported that from the dll.

it looks something like this

#ifndef DLL_EXPORT_IMPORT
#define DLL_EXPORT_IMPORT extern "C" __declspec (dllexport)
#else
#define DLL_EXPORT_IMPORT extern "C" __declspec (dllimport)
#endif

typedef mudpLog*(*fpGetMudp)();
typedef void (*fpDeleteMudp)( LogReader*& pObj);

DLL_EXPORT_IMPORT LogReader* GetLogPtr();
DLL_EXPORT_IMPORT void DeleteLogReader( LogReader*& mudpObj);

and in the python end i am using something like this

from ctypes import *;
class Sample(object):
    def __init__(self, object):
        mudp_data = (c_ubyte*32008)();
        self._lib = CDLL(object);
        self._handle = self._lib.GetLogPtr;
=>        self._handle.restype = pointer();  ##Here i done knw what i should give
        self._handle.argtype = None;
=>        self._handle.restype = pointer(); ##Here i done knw what i should give
        print self._handle.Open( "E:\\log_20180406_141933_001.txt" );#

       # self._handle.ReadNext(_data); ## Invoke a function with the class object pointer


lib = Sample("mudp_library.dll");

Is there a provision to do this? I got so many articles mentioning about c functions. I am still researching and found some other articles like BOOST_PYTHON_MODULE & SWIG, Cython.

What will be the best to use and is there any other provision to do the same other than using any of these wrappers.

What I have tried:

Research over the internet and still continuing

Posted 1-Jun-18 9:57am

kuttiylajai

Updated 1-Jun-18 22:58pm

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2 solutions

Solution 1

I can't tell you exactly what Python needs but I have written many interfaces to use C++ classes in a script language using LoadLibrary calls. What I did was wrap all of the exported functions in this:

C++

extern "C"
{
// exported function implementation goes here
}

and each function had a "__declspec( dllexport )" tag in front of it. This has worked quite well for me. I used a macro for the export tag. Something like :

C++

#define DLLexport  __declspec(dllexport)

so the functions look like this :

C++

extern "C"
{
DLLexport int MyFunction( ... )
{
}
} // extern C

Posted 1-Jun-18 12:51pm

Rick York

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Richard MacCutchan · Accepted Answer · 2018-06-01T23:00:00

Solution 2

See 1. Extending Python with C or C++ — Python 2.7.15 documentation[^].

Posted 1-Jun-18 23:00pm

Richard MacCutchan