ceph/src/boost/libs/type_index/include/boost/type_index/runtime_cast/reference_cast.hpp

   1 //
   2 // Copyright (c) Chris Glover, 2016.
   3 //
   4 //
   5 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   6 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8
   9 #ifndef BOOST_TYPE_INDEX_RUNTIME_CAST_REFERENCE_CAST_HPP
  10 #define BOOST_TYPE_INDEX_RUNTIME_CAST_REFERENCE_CAST_HPP
  11
  12 /// \file reference_cast.hpp
  13 /// \brief Contains the overload of boost::typeindex::runtime_cast for
  14 /// reference types.
  15
  16 #include <boost/core/addressof.hpp>
  17 #include <boost/type_index/runtime_cast/detail/runtime_cast_impl.hpp>
  18 #include <boost/throw_exception.hpp>
  19 #include <boost/type_traits/add_reference.hpp>
  20 #include <boost/type_traits/remove_reference.hpp>
  21 #include <boost/type_traits/is_base_and_derived.hpp>
  22
  23 #ifdef BOOST_HAS_PRAGMA_ONCE
  24 # pragma once
  25 #endif
  26
  27 namespace boost { namespace typeindex {
  28
  29 /// \brief Indicates that runtime_cast was unable to perform the desired cast operation
  30 /// because the source instance was not also an instance of the target type.
  31 struct bad_runtime_cast : std::exception
  32 {};
  33
  34 /// \brief Safely converts references to classes up, down, and sideways along the inheritance hierarchy.
  35 /// \tparam T The desired target type. Like dynamic_cast, must be a pointer to complete class type.
  36 /// \tparam U A complete class type of the source instance, u.
  37 /// \return If there exists a valid conversion from U& to T, returns a T that references an address
  38 /// suitably offset from u. If no such conversion exists, throws boost::typeindex::bad_runtime_cast.
  39 template<typename T, typename U>
  40 typename boost::add_reference<T>::type runtime_cast(U& u) {
  41     typedef typename boost::remove_reference<T>::type impl_type;
  42     impl_type* value = detail::runtime_cast_impl<impl_type>(
  43         boost::addressof(u), boost::is_base_and_derived<T, U>());
  44     if(!value)
  45         BOOST_THROW_EXCEPTION(bad_runtime_cast());
  46     return *value;
  47 }
  48
  49 /// \brief Safely converts references to classes up, down, and sideways along the inheritance hierarchy.
  50 /// \tparam T The desired target type. Like dynamic_cast, must be a pointer to complete class type.
  51 /// \tparam U A complete class type of the source instance, u.
  52 /// \return If there exists a valid conversion from U const& to T const, returns a T const that references an address
  53 /// suitably offset from u. If no such conversion exists, throws boost::typeindex::bad_runtime_cast.
  54 template<typename T, typename U>
  55 typename boost::add_reference<const T>::type runtime_cast(U const& u) {
  56     typedef typename boost::remove_reference<T>::type impl_type;
  57     impl_type* value = detail::runtime_cast_impl<impl_type>(
  58         boost::addressof(u), boost::is_base_and_derived<T, U>());
  59     if(!value)
  60         BOOST_THROW_EXCEPTION(bad_runtime_cast());
  61     return *value;
  62 }
  63
  64 }} // namespace boost::typeindex
  65
  66 #endif // BOOST_TYPE_INDEX_RUNTIME_CAST_REFERENCE_CAST_HPP