Pickling extension types

[Stefan Kuzminski]

Hi all,

I have an extension type written in C, but I cannot get it to pickle, any
insights would be greatly appreciated.

I see in the docs that I should define a __reduce__ method and that does get
called, but I don't know specifically the type of the 'callable object' that
should be the first thing in the tuple returned by __reduce__.

thx,
S
start listing..

#include "Python.h"

static PyObject *mv_new(PyTypeObject *type, PyObject *args, PyObject *kw);
static int mv_cmp(PyObject *self, PyObject *other);

/*



 * print MV



 */
static PyObject *mv_repr(MV *mv){
  PyObject *rtn;

  rtn = PyString_FromFormat("MV(%d)", mv->index);
  return rtn;

}

/*



 * get mv's index



 */
static PyObject *mv_idx(PyObject *self, PyObject *ags){
  MV *mv;

  mv = (MV*)self;
  return PyInt_FromLong( (long)mv->index );
}


/*



 * get mv's index as str



 */
static PyObject *mv_reduce(PyObject *self, PyObject *ags){
  MV *mv;

  mv = (MV*)self;
  return PyString_FromString( "foo" );

}

/*



 * get mv's index as str



 */
static PyObject *mv_reduce(PyObject *self, PyObject *ags){
  MV *mv;
  mv = (MV*)self;
  PyObject *return_tuple;

  // build the return tuple



  return_tuple = PyTuple_New(5);

  // THIS IS THE QUESTION, what to set as "callable object??"



  //  PyTuple_SetItem( return_tuple, 0, mv_new );




  PyTuple_SetItem( return_tuple, 1 PyTuple_New());

  return return_tuple;

}

static PyMethodDef mv_methods[] = {
  {"index", mv_idx, METH_VARARGS},
  {"__reduce__", mv_reduce, METH_VARARGS},
  {NULL,                NULL}           /* sentinel */
};

PyTypeObject PyMV_Type = {
        PyObject_HEAD_INIT(&PyType_Type)
        0,                      /* Number of items for varobject */
        "MV",           /* Name of this type */
        sizeof(MV),     /* Basic object size */
        0,                      /* Item size for varobject */
        (destructor)PyObject_Del, /* tp_dealloc */
        0,                      /* tp_print */
        0,                      /* tp_getattr */
        0,                      /* tp_setattr */
        mv_cmp,                 /* tp_compare */
        (reprfunc)mv_repr,      /* tp_repr */
        0,                      /* tp_as_number */
        0,      /* tp_as_sequence */
        0,                      /* tp_as_mapping */
        mv_idx,                 /* tp_hash */
        0,                      /* tp_call */
        0,                      /* tp_str */
        PyObject_GenericGetAttr,  /* tp_getattro */
        PyObject_GenericSetAttr,  /* tp_setattro */
        0,                      /* tp_as_buffer */
        Py_TPFLAGS_DEFAULT,     /* tp_flags */
        0,              /* tp_doc */
0,                      /* tp_traverse */
        0,                      /* tp_clear */
0,                      /* tp_richcompare */
        0,                      /* tp_weaklistoffset */
        0,              /* tp_iter */
        0,                      /* tp_iternext */
        mv_methods,             /* tp_methods */
        0,                      /* tp_members */
0,                      /* tp_getset */
        0,                      /* tp_base */
        0,                      /* tp_dict */
        0,                      /* tp_descr_get */
0,                      /* tp_descr_set */
0,                      /* tp_dictoffset */
        0,                      /* tp_init */
        0,                      /* tp_alloc */
        mv_new,         /* tp_new */
};

/*



 * cmp MV



 */
static int mv_cmp(PyObject *mv, PyObject *other){

  if( other->ob_type == &PyMV_Type ) {
    if( ((MV*)mv)->index == ((MV*)other)->index ) {
      return 0;
    } else {
      return -1;
    }
  }
  return -1;
}

/*



 * new MV



 */
static PyObject *mv_new(PyTypeObject *type, PyObject *args, PyObject *kw){
  MV *mv;
  int index;

  mv = PyObject_New(MV, &PyMV_Type);
  if (mv == NULL){
    return NULL;
  }
  // get the args



  if( !PyArg_ParseTuple( args,(char *)"i:MV", &index )){
      return NULL;
  }

  // store index



  mv->index = index;

  return (PyObject*)mv;
 }
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