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 #include <boost/optional.hpp>
  13 #include <boost/python.hpp>
  14
  15
  16 namespace boost { namespace python {
  17
  18 template<typename T>
  19 struct optional_ : private boost::noncopyable {
  20         struct conversion :
  21                 public boost::python::converter::expected_from_python_type<T>
  22         {
  23                 static PyObject* convert(boost::optional<T> const& value)
  24                 {
  25                         using namespace boost::python;
  26                         return incref((value ? object(*value) : object()).ptr());
  27                 }
  28         };
  29
  30         static void* convertible(PyObject* obj) {
  31                 using namespace boost::python;
  32                 return obj == Py_None || extract<T>(obj).check() ? obj : NULL;
  33         }
  34
  35         static void constructor(
  36                 PyObject* obj,
  37                 boost::python::converter::rvalue_from_python_stage1_data* data
  38         ) {
  39                 using namespace boost::python;
  40                 void* const storage = reinterpret_cast<
  41                         converter::rvalue_from_python_storage<optional<T> >*
  42                 >(data)->storage.bytes;
  43                 if (obj == Py_None) {
  44                         new (storage) boost::optional<T>();
  45                 } else {
  46                         new (storage) boost::optional<T>(extract<T>(obj));
  47                 }
  48                 data->convertible = storage;
  49         }
  50
  51         explicit optional_() {
  52                 using namespace boost::python;
  53                 if (!extract<boost::optional<T> >(object()).check()) {
  54                         to_python_converter<boost::optional<T>, conversion, true>();
  55                         converter::registry::push_back(
  56                                 &convertible,
  57                                 &constructor,
  58                                 type_id<boost::optional<T> >(),
  59                                 &conversion::get_pytype
  60                         );
  61                 }
  62         }
  63 };
  64
  65 } } // namespace boost::python
  66