accepting cStringIO in an extension

[garyjefferson123 at yahoo.com]

I want to accept a cStringIO object in a function in a python extension
module.  How do I do this?

e.g.,

static PyObject *myfunc(PyObject *self, PyObject *args)
{
    PyObject *cstringio;
    if (!PyArg_ParseTuple(args, "O:cStringIO", &cstringio)) {
            PyErr_SetString(PyExc_ValueError,
                    "value must be a cstringio");
            return NULL;
    }
    /* how to get at the data buffer or call read() on cstringio? */

}

I understand that I probably want PyEval_CallObject(), but I don't know
how to get at the read() method of cstringio.

Thanks,
Gary