Having trouble using CTypes with a custom function

[tkondal at gmail.com]

Hi Chris.

I know that it is easy to fix the problem using C++.  However, I do not
want to code a wrapper DLL.  I was wondering if there was a workaround
with Python. Everything has to be done in Python as we do not have the
tools for C++ (and we are not planning on getting any).

Thanks.

Chris Mellon wrote:
> <please don't top post>
>
> On 4 Oct 2006 11:35:11 -0700, tkondal at gmail.com <tkondal at gmail.com> wrote:
> > Would you have any example of a wrapper for such data types?
> >
> > Thanks.
> >
> > Chris Mellon wrote:
> > > On 4 Oct 2006 11:18:16 -0700, tkondal at gmail.com <tkondal at gmail.com> wrote:
> > > > Hi all.
> > > >
> > > > I just started looking at Python's ctypes lib and I am having trouble
> > > > using it for a function.
> > > >
> > > > For starters, here's my Python code:
> > > >
> > > >
> > > > from ctypes import*;
> > > > myStringDLL= cdll.LoadLibrary("myStringDLL.dll");
> > > >
> > > > GetMyString = getattr(myStringDLL,
> > > > "?GetMyString@@YA_NAAV?$basic_string at DU?$char_traits at D@std@@V?$allocator at D@2@@std@@@Z")
> > > >
> > > > strString =  create_string_buffer('\000' * 256);
> > > > GetMyString.restype = c_int;
> > > > GetMyString.argtypes = [c_char_p];
> > > >
> > > > bResult = GetMyString (strSerialNumber);
> > > >
> > > > print (bResult);
> > > > print (strSerialNumber);
> > > >
> > > > #C++ Prototype of the function I want to call:
> > > > #bool GetMyString (string& stringParam) ;
> > > >
> > > >
> > > >
> > > >
> > > > I do not have access to the source code of this function so don't ask
> > > > me to try different things in C++.  This DLL is working fine.
> > > >
> > > > The problem that I have is that print (strSerialNumber) does not seem
> > > > to print the correct string.  What I get is some garbage value of
> > > > unprintable characters.  Am I using this the correct way?
> > > >
> > >
> > >
> > >
> > >
> > > This function is expecting a C++ std::string object, not a regular C
> > > style string. You'll need a wrapper function, and one which uses the
> > > same compiler and STL as the C++ source.
> > >
> > > > Thanks.
> > > >
> > > > --
> > > > http://mail.python.org/mailman/listinfo/python-list
> > > >
> >
>
> in this case it'd be very simple:
>
> bool WrapGetMyString(char * c) {
>   return GetMyString(c)
> }
>
>
> (Note: This isn't unicode safe).
>
> The C++ compiler will handle converting from the char * to the std::string.
>
>
>
> 
> 
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >