Creating swig wrapper for C++ (pointers) to python

Question

I a very new to swig and I am trying to create a swig wrapper in order to use a few C++ files in python. I have the following C++ class.

The following is a snippet o

Answer 1

If I've understood this correctly the problem you're facing isn't that they're pointers, it's that they're potentially unbounded arrays.

You can warp an unbounded C array using carrays.i and the "%array_class" macro, e.g.:

%module packet
%include "stdint.i"

%{
    #include "packet.h"
%}

%include "carrays.i"
%array_class(uint8_t, buffer);

%include "packet.h"

Would then allow you to in Python write something like:

a = packet.buffer(10000000) 
p = packet.CPacketBuffer(a.cast(), 10000000)

Note that you'll need to ensure the life of the buffer is sufficient - if the Python object gets released without the C++ code being aware you'll end up with undefined behaviour.

You can convert uint8_t* pointers (unbounded arrays) to buffer instances in Python using the frompointer methods that the %array_class macro also creates, e.g.:

r = packet.GetBuffer()
buf = packet.buffer_frompointer(r)

You can add additional Python code to automate/hide most of the conversion between buffers if desired, or use MemoryViews to integrate tighter with Python on the C API side.

In general though since this is C++ I'd suggest using std::vector for this - it's much nicer to use on the Python side than the unbounded arrays and the cost is minimal for the safety and simplicity it gives you.