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