ceph/src/boost/libs/type_index/include/boost/type_index/runtime_cast/std_shared_ptr_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_STD_SHARED_PTR_CAST_HPP
  10 #define BOOST_TYPE_INDEX_RUNTIME_CAST_STD_SHARED_PTR_CAST_HPP
  11
  12 /// \file std_shared_ptr_cast.hpp
  13 /// \brief Contains the overload of boost::typeindex::runtime_pointer_cast for
  14 /// std::shared_ptr types.
  15
  16 #include <boost/type_index/runtime_cast/detail/runtime_cast_impl.hpp>
  17 #include <boost/type_traits/is_base_and_derived.hpp>
  18 #include <memory>
  19
  20 #ifdef BOOST_HAS_PRAGMA_ONCE
  21 # pragma once
  22 #endif
  23
  24 namespace boost { namespace typeindex {
  25
  26 /// \brief Creates a new instance of std::shared_ptr whose stored pointer is obtained from u's
  27 /// stored pointer using a runtime_cast.
  28 ///
  29 /// The new shared_ptr will share ownership with u, except that it is empty if the runtime_cast
  30 /// performed by runtime_pointer_cast returns a null pointer.
  31 /// \tparam T The desired target type to return a pointer of.
  32 /// \tparam U A complete class type of the source instance pointed to from u.
  33 /// \return If there exists a valid conversion from U* to T*, returns a std::shared_ptr<T>
  34 /// that points to an address suitably offset from u.
  35 /// If no such conversion exists, returns std::shared_ptr<T>();
  36 template<typename T, typename U>
  37 std::shared_ptr<T> runtime_pointer_cast(std::shared_ptr<U> const& u) {
  38     T* value = detail::runtime_cast_impl<T>(u.get(), boost::is_base_and_derived<T, U>());
  39     if(value)
  40         return std::shared_ptr<T>(u, value);
  41     return std::shared_ptr<T>();
  42 }
  43
  44 }} // namespace boost::typeindex
  45
  46 #endif // BOOST_TYPE_INDEX_RUNTIME_CAST_STD_SHARED_PTR_CAST_HPP