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