Hello and good day,
I am having trouble with calling a certain COM interface, (a closed-source
32-bit COM interface DLL of a Robot controller) from my Python application.
Because so far my entire application is made in Python, it would be a nice
bonus if I could call this interface directly from Python too. The win32com
library seemed perfect for this task.
One of the functions in this interface is the following:
BOOL _DataNumReg::SetValuesInt(
[in] LONG Index,
[in, out] LONG* Value,
[in] LONG Count
);
With the parameter Value being a pointer to the first element of a C-style
array.
My idea was to create a C array in Python using the ctypes library, and use the
ctypes.addressof() function to get the pointer to the array,
and then pass this pointer to the COM interface with win32com.
The issue, as you might've guessed is that win32com automatically creates a new
pointer to, what already is a pointer.
This was already mentioned earlier in 2013,
https://mail.python.org/pipermail/python-win32/2013-May/012821.html
In which is told that "passing the address of a Python integer object clearly
isn't correct - or to put it another way - what exact are you hoping to pass as
this parameter?",
while for my specific case, passing a Python integer IS correct, as it is
already a valid pointer.
Because the COM library is closed source I can't change it to expect a pointer
to a pointer, so as far as I can come up with, my only solutions left are:
A. Write a Win32 DLL wrapper that can call the COM interface.
B. Change the win32com library myself to stop creating pointers automatically,
or accept a Python list, copy it to a buffer, and send a pointer to that buffer.
C. Hope that you might have more advice or information I missed.
I already tried changing the .py wrapper generated by makepy.py to hopefully
make win32com think that the COM interface requires a VT_UI4/VT_I4 instead of
the generated VT_BYREF | VT_I4, but that didn't work, the behavior of win32com
creating a pointer to a pointer was still occurring. Nor did changing the [in,
out] (3) to [in] (1) in the .py wrapper help.
Can you give me any more advice/tricks on how to make the COM interface receive
a pointer to a C-array instead of a single value, preferably using win32com?
Any information is greatly appreciated.
Regards,
Simon van Bezooijen
_______________________________________________
python-win32 mailing list
python-win32@python.org
https://mail.python.org/mailman/listinfo/python-win32
