How to convert unicode string to unsigned char *

[Simon Posnjak]

On Mon, May 5, 2008 at 4:16 PM, Jean-Paul Calderone <exarkun at divmod.com> wrote:
>
> On Mon, 5 May 2008 16:05:08 +0200, Simon Posnjak <sposnjak at gmail.com> wrote:
>
> > On Mon, May 5, 2008 at 3:48 PM, Jean-Paul Calderone <exarkun at divmod.com>
> wrote:
> >
> > > On Mon, 5 May 2008 15:41:08 +0200, Simon Posnjak <sposnjak at gmail.com>
> wrote:
> > >
> > > > Hi!
> > > >
> > > > I have a C module for which I created a wrapper with swig. The
> function
> > > def is:
> > > >
> > > > C:
> > > >
> > > > int some_thing(unsigned char * the_str);
> > > >
> > > > eg:
> > > >
> > > > Python:
> > > >
> > > > some_module.some_thing (the_str)
> > > >
> > > > Now I would like to feed it with a UTF-8 formatted string:
> > > >
> > > > test = u'Make \u0633\u0644\u0627\u0645, not war.'
> > > >
> > >
> > >  `test´ is not a UTF-8 encoded string.  It's a unicode string.
> > >
> > >  To get a UTF-8 encoded string from a unicode string, use the `encode´
> > >  method:
> > >
> > >   some_module.some_thing(test.encode('utf-8'))
> > >
> >
> > Yes you are correct. It is unicode string. But still if I use encode I
> > get the same error:
> >
> > TypeError with message: in method 'some_thing', argument 1 of type
> > 'unsigned char *'
> >
> > So I am looking for a way to "cast" unicode string to unsigned char *.
> >
> >
>
>  You need to provide some more information about `some_module.some_thing´.
>  How is it implemented?  What Python type does it expect?  If it doesn't
>  take a unicode string and it doesn't take a byte string, I don't know
>  what kind of string it does take.

some_module.some_thing(the_string) function is a swig generated
function from a C lib. The C lib function expects unsigned char *.

The generated function is:

SWIGINTERN PyObject *_wrap_some_thing(PyObject *SWIGUNUSEDPARM(self),
PyObject *args) {
  PyObject *resultobj = 0;
  unsigned char *arg1 = (unsigned char *) 0 ;
  unsigned char result;
  void *argp1 = 0 ;
  int res1 = 0 ;
  PyObject * obj0 = 0 ;

  if (!PyArg_ParseTuple(args,(char
*)"O:cpot_printer_simple_printf",&obj0)) SWIG_fail;
  res1 = SWIG_ConvertPtr(obj0, &argp1,SWIGTYPE_p_unsigned_char, 0 |  0 );
  if (!SWIG_IsOK(res1)) {
    SWIG_exception_fail(SWIG_ArgError(res1), "in method '"
some_thing"" "', argument " "1"" of type '" "unsigned char *""'");
  }
  arg1 = (unsigned char *)(argp1);
  result = (unsigned char)some_thing(arg1);
  resultobj = SWIG_From_unsigned_SS_char((unsigned char)(result));
  return resultobj;
fail:
  return NULL;
}