ceph/src/boost/boost/parameter/aux_/unwrap_cv_reference.hpp

   1 // Copyright Daniel Wallin, David Abrahams 2005.
   2 // Copyright Cromwell D. Enage 2017.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_PARAMETER_AUX_UNWRAP_CV_REFERENCE_HPP
   8 #define BOOST_PARAMETER_AUX_UNWRAP_CV_REFERENCE_HPP
   9
  10 namespace boost {
  11
  12     template <typename T>
  13     class reference_wrapper;
  14 } // namespace boost
  15
  16 #include <boost/parameter/aux_/yesno.hpp>
  17
  18 namespace boost { namespace parameter { namespace aux {
  19
  20     //
  21     // reference_wrapper support -- if perfect forwarding is unsupported,
  22     // then when passing arguments positionally by non-const reference,
  23     // we ask users of named parameter interfaces to use ref(x) to wrap them.
  24     //
  25
  26     template <typename U>
  27     ::boost::parameter::aux::yes_tag
  28         is_cv_reference_wrapper_check(
  29             ::boost::reference_wrapper<U> const volatile*
  30         );
  31
  32     ::boost::parameter::aux::no_tag is_cv_reference_wrapper_check(...);
  33 }}} // namespace boost::parameter::aux
  34
  35 #include <boost/parameter/config.hpp>
  36
  37 #if !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
  38 #include <functional>
  39
  40 namespace boost { namespace parameter { namespace aux {
  41
  42     // Support for std::ref(x) -- Cromwell D. Enage
  43     template <typename U>
  44     ::boost::parameter::aux::yes_tag
  45         is_cv_reference_wrapper_check(
  46             ::std::reference_wrapper<U> const volatile*
  47         );
  48 }}} // namespace boost::parameter::aux
  49 #endif
  50
  51 #include <boost/parameter/aux_/preprocessor/nullptr.hpp>
  52
  53 #if defined(BOOST_PARAMETER_CAN_USE_MP11) && !( \
  54         BOOST_WORKAROUND(BOOST_MSVC, >= 1900) && \
  55         BOOST_WORKAROUND(BOOST_MSVC, < 1910) \
  56     )
  57 #include <boost/mp11/integral.hpp>
  58 #include <boost/mp11/utility.hpp>
  59 #include <type_traits>
  60 #else   // !defined(BOOST_PARAMETER_CAN_USE_MP11) || MSVC-14.0
  61 #include <boost/mpl/bool.hpp>
  62 #include <boost/type_traits/remove_reference.hpp>
  63 #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) && \
  64     !BOOST_WORKAROUND(BOOST_GCC, < 40000)
  65 #include <boost/mpl/eval_if.hpp>
  66 #endif
  67 #endif  // BOOST_PARAMETER_CAN_USE_MP11 && not MSVC-14.0
  68
  69 namespace boost { namespace parameter { namespace aux {
  70
  71 #if defined(BOOST_PARAMETER_CAN_USE_MP11) && !( \
  72         BOOST_WORKAROUND(BOOST_MSVC, >= 1900) && \
  73         BOOST_WORKAROUND(BOOST_MSVC, < 1910) \
  74     )
  75     // This metafunction returns mp11::mp_true if T is of type
  76     // reference_wrapper<U> cv.
  77     template <typename T>
  78     using is_cv_reference_wrapper = ::boost::mp11::mp_bool<
  79         sizeof(
  80             ::boost::parameter::aux::is_cv_reference_wrapper_check(
  81                 static_cast<
  82                     typename ::std::remove_reference<T>::type*
  83                 >(BOOST_PARAMETER_AUX_PP_NULLPTR)
  84             )
  85         ) == sizeof(::boost::parameter::aux::yes_tag)
  86     >;
  87
  88     // Needed for unwrap_cv_reference below. T might be const, so
  89     // mp_eval_if<> might fail because of deriving from T const on EDG.
  90     template <typename T>
  91     using unwrap_cv_reference_impl = typename ::std::remove_reference<T>::type;
  92
  93     // Produces the unwrapped type to hold a reference to in
  94     // tagged_argument<>.  Can't use boost::unwrap_reference<> here
  95     // because it doesn't handle the case where T = reference_wrapper<U> cv.
  96     template <typename T>
  97     using unwrap_cv_reference = ::boost::mp11::mp_eval_if<
  98         ::boost::parameter::aux::is_cv_reference_wrapper<T>
  99       , ::boost::parameter::aux::unwrap_cv_reference_impl<T>
 100       , ::std::remove_reference
 101       , T
 102     >;
 103 #else  // !defined(BOOST_PARAMETER_CAN_USE_MP11) || MSVC-14.0
 104     // This metafunction returns mpl::true_ if T is of type
 105     // reference_wrapper<U> cv.
 106     template <typename T>
 107     struct is_cv_reference_wrapper
 108     {
 109         BOOST_STATIC_CONSTANT(
 110             bool, value = (
 111                 sizeof(
 112                     ::boost::parameter::aux::is_cv_reference_wrapper_check(
 113                         static_cast<
 114                             typename ::boost::remove_reference<T>::type*
 115                         >(BOOST_PARAMETER_AUX_PP_NULLPTR)
 116                     )
 117                 ) == sizeof(::boost::parameter::aux::yes_tag)
 118             )
 119         );
 120
 121         typedef boost::mpl::bool_<
 122 #if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
 123             is_cv_reference_wrapper::
 124 #endif
 125         value> type;
 126     };
 127
 128 #if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) || \
 129     BOOST_WORKAROUND(BOOST_GCC, < 40000)
 130     template <
 131         typename T
 132       , typename = typename ::boost::parameter::aux
 133         ::is_cv_reference_wrapper<T>::type
 134     >
 135     struct unwrap_cv_reference : ::boost::remove_reference<T>
 136     {
 137     };
 138
 139     template <typename T>
 140     struct unwrap_cv_reference<T const,::boost::mpl::false_>
 141     {
 142         typedef T const type;
 143     };
 144
 145     template <typename T>
 146     struct unwrap_cv_reference<T,::boost::mpl::true_> : T
 147     {
 148     };
 149 #else   // no Borland or GCC 3- workarounds needed
 150     // Needed for unwrap_cv_reference below. T might be const, so
 151     // eval_if<> might fail because of deriving from T const on EDG.
 152     template <typename T>
 153     struct unwrap_cv_reference_impl : ::boost::remove_reference<T>::type
 154     {
 155     };
 156
 157     // Produces the unwrapped type to hold a reference to in
 158     // tagged_argument<>.  Can't use boost::unwrap_reference<> here
 159     // because it doesn't handle the case where T = reference_wrapper<U> cv.
 160     template <typename T>
 161     struct unwrap_cv_reference
 162       : ::boost::mpl::eval_if<
 163             ::boost::parameter::aux::is_cv_reference_wrapper<T>
 164           , ::boost::parameter::aux::unwrap_cv_reference_impl<T>
 165           , ::boost::remove_reference<T>
 166         >
 167     {
 168     };
 169 #endif  // Borland or GCC 3- workarounds needed
 170 #endif  // BOOST_PARAMETER_CAN_USE_MP11 && not MSVC-14.0
 171 }}} // namespace boost::parameter::aux
 172
 173 #endif  // include guard
 174