src/python-optional.h

   1 /*********************************
   2 ** Tsunagari Tile Engine        **
   3 ** python-optional.h            **
   4 ** Copyright 2011-2012 OmegaSDG **
   5 *********************************/
   6
   7 /*
   8  * Based on
   9  * http://stackoverflow.com/questions/6274822/boost-python-no-to-python-converter-found-for-stdstring
  10  */
  11
  12 #ifndef PYTHON_OPTIONAL_H
  13 #define PYTHON_OPTIONAL_H
  14
  15 #include <boost/optional.hpp>
  16 #include <boost/python.hpp>
  17
  18
  19 namespace boost { namespace python {
  20
  21 template<typename T>
  22 struct optional_ : private boost::noncopyable {
  23         struct conversion :
  24                 public boost::python::converter::expected_from_python_type<T>
  25         {
  26                 static PyObject* convert(boost::optional<T> const& value)
  27                 {
  28                         using namespace boost::python;
  29                         return incref((value ? object(*value) : object()).ptr());
  30                 }
  31         };
  32
  33         static void* convertible(PyObject* obj) {
  34                 using namespace boost::python;
  35                 return obj == Py_None || extract<T>(obj).check() ? obj : NULL;
  36         }
  37
  38         static void constructor(
  39                 PyObject* obj,
  40                 boost::python::converter::rvalue_from_python_stage1_data* data
  41         ) {
  42                 using namespace boost::python;
  43                 void* const storage = reinterpret_cast<
  44                         converter::rvalue_from_python_storage<optional<T> >*
  45                 >(data)->storage.bytes;
  46                 if (obj == Py_None) {
  47                         new (storage) boost::optional<T>();
  48                 } else {
  49                         new (storage) boost::optional<T>(extract<T>(obj));
  50                 }
  51                 data->convertible = storage;
  52         }
  53
  54         explicit optional_() {
  55                 using namespace boost::python;
  56                 if (!extract<boost::optional<T> >(object()).check()) {
  57                         to_python_converter<boost::optional<T>, conversion, true>();
  58                         converter::registry::push_back(
  59                                 &convertible,
  60                                 &constructor,
  61                                 type_id<boost::optional<T> >(),
  62                                 &conversion::get_pytype
  63                         );
  64                 }
  65         }
  66 };
  67
  68 } } // namespace boost::python
  69
  70 #endif