ceph/src/boost/boost/type_index/runtime_cast/boost_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_BOOST_SHARED_PTR_CAST_HPP
  10 #define BOOST_TYPE_INDEX_RUNTIME_CAST_BOOST_SHARED_PTR_CAST_HPP
  11
  12 /// \file boost_shared_ptr_cast.hpp
  13 /// \brief Contains the overload of boost::typeindex::runtime_pointer_cast for
  14 /// boost::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
  19 #ifdef BOOST_HAS_PRAGMA_ONCE
  20 # pragma once
  21 #endif
  22
  23 namespace boost {
  24     template<class T> class shared_ptr;
  25 }
  26
  27 namespace boost { namespace typeindex {
  28
  29 /// \brief Creates a new instance of std::shared_ptr whose stored pointer is obtained from u's
  30 /// stored pointer using a runtime_cast.
  31 ///
  32 /// The new shared_ptr will share ownership with u, except that it is empty if the runtime_cast
  33 /// performed by runtime_pointer_cast returns a null pointer.
  34 /// \tparam T The desired target type to return a pointer of.
  35 /// \tparam U A complete class type of the source instance pointed to from u.
  36 /// \return If there exists a valid conversion from U* to T*, returns a boost::shared_ptr<T>
  37 /// that points to an address suitably offset from u.
  38 /// If no such conversion exists, returns boost::shared_ptr<T>();
  39 template<typename T, typename U>
  40 boost::shared_ptr<T> runtime_pointer_cast(boost::shared_ptr<U> const& u) {
  41     T* value = detail::runtime_cast_impl<T>(u.get(), boost::is_base_and_derived<T, U>());
  42     if(value)
  43         return boost::shared_ptr<T>(u, value);
  44     return boost::shared_ptr<T>();
  45 }
  46
  47 }} // namespace boost::typeindex
  48
  49 #endif // BOOST_TYPE_INDEX_RUNTIME_CAST_BOOST_SHARED_PTR_CAST_HPP