Question

I have the following setup:

• GDAL library with Python bindings (SWIG)
• Some glue code (Python)
• A C library, interfaced with ctypes

I want to pass the underlying dataset pointer/handle of the SWIG Dataset object to my C library. How can I retrieve this pointer?

I do not want to interface the C library with SWIG.

Answer 1

It was actually quite easy, and I hope that my solution is portable. Given, that my C function definition looks somewhat like this:

int myfunc(GDALDatasetH ds);

Then my ctypes definition is like this:

_lib = C.LibraryLoader(C.CDLL).LoadLibrary(lib_path)
_myfunc = _lib.myfunc
_myfunc.argtypes = [C.c_void_p]
_myfunc.restype = C.POINTER(C.c_char)

And I can call the C function with:

ds = gdal.Open(path)
...
_myfunc(C.c_void_p(long(ds.this)))