Armed with a text editor

mmap_move_method(mmap_object *self, PyObject *args)
{
        unsigned long dest, src, count;
        CHECK_VALID(NULL);
        if (!PyArg_ParseTuple (args, "iii:move", &dest, &src, &count) ||
            !is_writeable(self)) {
                return NULL;
        } else {
                /* bounds check the values */
                if (/* end of source after end of data?? */
                        ((src+count) > self->size)
                        /* dest will fit? */
                        || (dest+count > self->size)) {
                        PyErr_SetString (PyExc_ValueError,
                                         "source or destination out of range");
                        return NULL;
                } else {
                        memmove (self->data+dest, self->data+src, count);
                        Py_INCREF (Py_None);
                        return Py_None;
                }
        }
}