Lib/python/pyclasses.swg

#ifdef __cplusplus

/*
  SwigPtr_PyObject is used as a replacement of PyObject *, where
  the INCREF/DECREF are applied as needed.

  You can use SwigPtr_PyObject in a container, such as
  
     std::vector<SwigPtr_PyObject>;

  or as a member variable:
  
     struct A {
       SwigPtr_PyObject _obj;
       A(PyObject *o) : _obj(o) {
       }
     };

   or as a input/output value 

     SwigPtr_PyObject func(SwigPtr_PyObject obj) {     
       SwigPtr_PyObject out = PyUnicode_FromFormat("hello %s", PyObject_AsString(obj));
       SWIG_Py_DECREF(out);
       return out;
     }

   just remember to pair the object creation with the proper DECREF,
   the same as with plain PyObject *ptr, since SwigPtr_PyObject always add
   one reference at construction.

   SwigPtr_PyObject is 'visible' at the wrapped side, so you can do:


      %template(pyvector) std::vector<swig::SwigPtr_PyObject>;

   and all the proper typemaps will be used.
   
*/

/*
  The director wrapper variable holding a director method argument is a
  SwigVar_PyObject, which DECREFs on scope exit.  The argument itself is a
  borrowed reference, so INCREF it to balance that DECREF, otherwise the
  reference count is decremented on each and every director upcall until the
  object is freed while still in use.

  The cast to PyObject * is required.  Without it, a SwigVar_PyObject argument
  is assigned via the implicitly declared copy assignment operator, which adds a
  reference of its own, and the object then leaks one reference per upcall.  The
  cast selects SwigVar_PyObject::operator=(PyObject *) instead, which does not
  adjust the count, leaving the SWIG_Py_XINCREF below as the one and only
  increment for every argument type handled here.

  This must be declared before the %apply directives below so that
  SwigPtr_PyObject and SwigVar_PyObject arguments are covered too.
*/
%typemap(directorin,noblock=1) PyObject *, PyObject *const& {
  $input = (PyObject *)$1;
  SWIG_Py_XINCREF($input);
}

namespace swig {
  %ignore SwigPtr_PyObject;
  struct SwigPtr_PyObject {};
  %apply PyObject * {SwigPtr_PyObject};
  %apply PyObject * const& {SwigPtr_PyObject const&};

  %typemap(typecheck,precedence=SWIG_TYPECHECK_SWIGOBJECT,noblock=1) SwigPtr_PyObject const& "$1 = ($input != 0);"


  /* For output */
  %typemap(out,noblock=1)  SwigPtr_PyObject {
    $result = (PyObject *)$1;
    SWIG_Py_INCREF($result);
  }
  
  %typemap(out,noblock=1)  SwigPtr_PyObject const & {
    $result = (PyObject *)*$1;
    SWIG_Py_INCREF($result);
  }
  
}

%{
namespace swig {
  class SwigPtr_PyObject {
  protected:
    PyObject *_obj;

  public:
    SwigPtr_PyObject() :_obj(0)
    {
    }

    SwigPtr_PyObject(const SwigPtr_PyObject& item) : _obj(item._obj)
    {
      SWIG_PYTHON_THREAD_BEGIN_BLOCK;
      SWIG_Py_XINCREF(_obj);
      SWIG_PYTHON_THREAD_END_BLOCK;
    }
    
    SwigPtr_PyObject(PyObject *obj, bool initial_ref = true) :_obj(obj)
    {
      if (initial_ref) {
        SWIG_PYTHON_THREAD_BEGIN_BLOCK;
        SWIG_Py_XINCREF(_obj);
        SWIG_PYTHON_THREAD_END_BLOCK;
      }
    }
    
    SwigPtr_PyObject & operator=(const SwigPtr_PyObject& item) 
    {
      SWIG_PYTHON_THREAD_BEGIN_BLOCK;
      SWIG_Py_XINCREF(item._obj);
      SWIG_Py_XDECREF(_obj);
      _obj = item._obj;
      SWIG_PYTHON_THREAD_END_BLOCK;
      return *this;      
    }
    
    ~SwigPtr_PyObject() 
    {
      SWIG_PYTHON_THREAD_BEGIN_BLOCK;
      SWIG_Py_XDECREF(_obj);
      SWIG_PYTHON_THREAD_END_BLOCK;
    }
    
    operator PyObject *() const
    {
      return _obj;
    }

    PyObject *operator->() const
    {
      return _obj;
    }
  };
}
%}

/*
  SwigVar_PyObject is used to manage 'in the scope' PyObject * variables,
  as in

  int func () {
    SwigVar_PyObject obj = PyUnicode_FromString("hello");
  }

  ie, 'obj' is created and destructed in the same scope from
  a python object that carries at least one reference value.
  
  SwigVar_PyObject just take care of applying the proper Py_DECREF.

  Hence, this class is purely internal and not visible at the wrapped side.
 */
namespace swig {
  %ignore SwigVar_PyObject;
  struct SwigVar_PyObject {};
  %apply PyObject * {SwigVar_PyObject};
  %apply PyObject * const& {SwigVar_PyObject const&};
}

%{
namespace swig {
  struct SwigVar_PyObject : SwigPtr_PyObject {
    SwigVar_PyObject(PyObject* obj = 0) : SwigPtr_PyObject(obj, false) { }
    
    SwigVar_PyObject & operator = (PyObject* obj)
    {
      SWIG_Py_XDECREF(_obj);
      _obj = obj;
      return *this;      
    }
  };
}
%}


#endif