From 0528a1e49a82221e63039abc7f759a43f4d4ffc9 Mon Sep 17 00:00:00 2001
From: John Wiegley <johnw@newartisans.com>
Date: Fri, 4 May 2007 13:41:23 +0000
Subject: Added boost::optional support for using with Boost.Python.

---
 src/pyutils.h | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 65 insertions(+), 9 deletions(-)

(limited to 'src/pyutils.h')

diff --git a/src/pyutils.h b/src/pyutils.h
index 4ff33f8f..84a0db7e 100644
--- a/src/pyutils.h
+++ b/src/pyutils.h
@@ -1,22 +1,78 @@
 #ifndef _PY_UTILS_H
 #define _PY_UTILS_H
 
-template<class T, class TfromPy>
-struct ObjFromPy {
-  ObjFromPy() {
+template <typename T, typename TfromPy>
+struct object_from_python
+{
+  object_from_python() {
     boost::python::converter::registry::push_back
-	  (&TfromPy::convertible,
-	   &TfromPy::construct,
-	   boost::python::type_id<T>());
+      (&TfromPy::convertible, &TfromPy::construct,
+       boost::python::type_id<T>());
   }
 };
 
-template<class T, class TtoPy, class TfromPy>
-struct register_python_conversion {
+template <typename T, typename TtoPy, typename TfromPy>
+struct register_python_conversion
+{
   register_python_conversion() {
     boost::python::to_python_converter<T, TtoPy>();
-    ObjFromPy<T, TfromPy>();
+    object_from_python<T, TfromPy>();
   }
 };
 
+template <typename T>
+struct python_optional : public boost::noncopyable
+{
+  struct optional_to_python
+  {
+    static PyObject * convert(const boost::optional<T>& value)
+    {
+      return (value ? boost::python::to_python_value<T>()(*value) :
+	              boost::python::detail::none());
+    }
+  };
+   
+  struct optional_from_python
+  {
+    static void * convertible(PyObject * source)
+    {
+      using namespace boost::python::converter;
+
+      if (source == Py_None)
+	return source;
+
+      const registration& converters(registered<T>::converters);
+
+      if (implicit_rvalue_convertible_from_python(source, converters)) {
+	rvalue_from_python_stage1_data data =
+	  rvalue_from_python_stage1(source, converters);
+	return rvalue_from_python_stage2(source, data, converters);
+      }
+      return NULL;
+    }
+
+    static void construct(PyObject * source,
+			  boost::python::converter::rvalue_from_python_stage1_data * data)
+    {
+      using namespace boost::python::converter;
+
+      void * const storage = ((rvalue_from_python_storage<T> *) data)->storage.bytes;
+
+      if (data->convertible == source)	    // == None
+	new (storage) boost::optional<T>(); // A Boost uninitialized value
+      else
+	new (storage) boost::optional<T>(*static_cast<T *>(data->convertible));
+
+      data->convertible = storage;
+    }
+  };
+
+  explicit python_optional() {
+    register_python_conversion<boost::optional<T>,
+      optional_to_python, optional_from_python>();
+  }
+};
+
+//boost::python::register_ptr_to_python< boost::shared_ptr<Base> >();
+
 #endif // _PY_UTILS_H
-- 
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