ceph/src/boost/boost/python/return_arg.hpp

   1 // Copyright David Abrahams and Nikolay Mladenov 2003.
   2 // Distributed under the Boost Software License, Version 1.0. (See
   3 // accompanying file LICENSE_1_0.txt or copy at
   4 // http://www.boost.org/LICENSE_1_0.txt)
   5 #ifndef RETURN_ARG_DWA2003719_HPP
   6 # define RETURN_ARG_DWA2003719_HPP
   7 # include <boost/python/default_call_policies.hpp>
   8 # include <boost/python/detail/none.hpp>
   9 # include <boost/python/detail/value_arg.hpp>
  10
  11 #ifndef BOOST_PYTHON_NO_PY_SIGNATURES
  12 # include <boost/python/converter/pytype_function.hpp>
  13 #endif
  14
  15 # include <boost/python/detail/type_traits.hpp>
  16
  17 # include <boost/mpl/int.hpp>
  18 # include <boost/mpl/at.hpp>
  19
  20 # include <boost/static_assert.hpp>
  21 # include <boost/python/refcount.hpp>
  22
  23 # include <cstddef>
  24
  25 namespace boost { namespace python {
  26
  27 namespace detail
  28 {
  29   template <std::size_t>
  30   struct return_arg_pos_argument_must_be_positive
  31 # if defined(__GNUC__) || defined(__EDG__)
  32   {}
  33 # endif
  34   ;
  35
  36   struct return_none
  37   {
  38       template <class T> struct apply
  39       {
  40           struct type
  41           {
  42               static bool convertible()
  43               {
  44                   return true;
  45               }
  46
  47               PyObject *operator()( typename value_arg<T>::type ) const
  48               {
  49                   return none();
  50               }
  51 #ifndef BOOST_PYTHON_NO_PY_SIGNATURES
  52               PyTypeObject const *get_pytype() const { return converter::expected_pytype_for_arg<T>::get_pytype() ; }
  53 #endif
  54           };
  55       };
  56   };
  57 }
  58
  59 template <
  60     std::size_t arg_pos=1
  61   , class Base = default_call_policies
  62 >
  63 struct return_arg : Base
  64 {
  65  private:
  66     BOOST_STATIC_CONSTANT(bool, legal = arg_pos > 0);
  67
  68  public:
  69     typedef typename mpl::if_c<
  70         legal
  71         , detail::return_none
  72         , detail::return_arg_pos_argument_must_be_positive<arg_pos>
  73         // we could default to the base result_converter in case or
  74         // arg_pos==0 since return arg 0 means return result, but I
  75         // think it is better to issue an error instead, cause it can
  76         // lead to confusions
  77     >::type result_converter;
  78
  79     template <class ArgumentPackage>
  80     static PyObject* postcall(ArgumentPackage const& args, PyObject* result)
  81     {
  82         // In case of arg_pos == 0 we could simply return Base::postcall,
  83         // but this is redundant
  84         BOOST_STATIC_ASSERT(arg_pos > 0);
  85
  86         result = Base::postcall(args,result);
  87         if (!result)
  88             return 0;
  89         Py_DECREF(result);
  90         return incref( detail::get(mpl::int_<arg_pos-1>(),args) );
  91     }
  92
  93     template <class Sig>
  94     struct extract_return_type : mpl::at_c<Sig, arg_pos>
  95     {
  96     };
  97
  98 };
  99
 100 template <
 101     class Base = default_call_policies
 102     >
 103 struct return_self
 104   : return_arg<1,Base>
 105 {};
 106
 107 }} // namespace boost::python
 108
 109 #endif // RETURN_ARG_DWA2003719_HPP