ceph/src/boost/libs/iostreams/include/boost/iostreams/detail/wrap_unwrap.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2003-2007 Jonathan Turkanis
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   5
   6 // See http://www.boost.org/libs/iostreams for documentation.
   7
   8 #ifndef BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED
   9 #define BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED
  10
  11 #if defined(_MSC_VER)
  12 # pragma once
  13 #endif
  14
  15 #include <boost/config.hpp>                             // SFINAE, MSVC.
  16 #include <boost/detail/workaround.hpp>
  17 #include <boost/iostreams/detail/enable_if_stream.hpp>
  18 #include <boost/iostreams/traits_fwd.hpp>               // is_std_io.
  19 #include <boost/mpl/bool.hpp>
  20 #include <boost/mpl/identity.hpp>
  21 #include <boost/mpl/eval_if.hpp>
  22 #include <boost/mpl/if.hpp>
  23 #include <boost/ref.hpp>
  24
  25 namespace boost { namespace iostreams { namespace detail {
  26
  27 //------------------Definition of wrap/unwrap traits--------------------------//
  28
  29 template<typename T>
  30 struct wrapped_type
  31     : mpl::if_<is_std_io<T>, reference_wrapper<T>, T>
  32     { };
  33
  34 template<typename T>
  35 struct unwrapped_type
  36     : unwrap_reference<T>
  37     { };
  38
  39 template<typename T>
  40 struct unwrap_ios
  41     : mpl::eval_if<
  42           is_std_io<T>,
  43           unwrap_reference<T>,
  44           mpl::identity<T>
  45       >
  46     { };
  47
  48 //------------------Definition of wrap----------------------------------------//
  49
  50 #ifndef BOOST_NO_SFINAE //----------------------------------------------------//
  51     template<typename T>
  52     inline T wrap(const T& t BOOST_IOSTREAMS_DISABLE_IF_STREAM(T))
  53     { return t; }
  54
  55     template<typename T>
  56     inline typename wrapped_type<T>::type
  57     wrap(T& t BOOST_IOSTREAMS_ENABLE_IF_STREAM(T)) { return boost::ref(t); }
  58 #else // #ifndef BOOST_NO_SFINAE //-------------------------------------------//
  59     template<typename T>
  60     inline typename wrapped_type<T>::type // BCC 5.x needs namespace qualification.
  61     wrap_impl(const T& t, mpl::true_) { return boost::ref(const_cast<T&>(t)); }
  62
  63     template<typename T>
  64     inline typename wrapped_type<T>::type // BCC 5.x needs namespace qualification.
  65     wrap_impl(T& t, mpl::true_) { return boost::ref(t); }
  66
  67     template<typename T>
  68     inline typename wrapped_type<T>::type
  69     wrap_impl(const T& t, mpl::false_) { return t; }
  70
  71     template<typename T>
  72     inline typename wrapped_type<T>::type
  73     wrap_impl(T& t, mpl::false_) { return t; }
  74
  75     template<typename T>
  76     inline typename wrapped_type<T>::type
  77     wrap(const T& t) { return wrap_impl(t, is_std_io<T>()); }
  78
  79     template<typename T>
  80     inline typename wrapped_type<T>::type
  81     wrap(T& t) { return wrap_impl(t, is_std_io<T>()); }
  82 #endif // #ifndef BOOST_NO_SFINAE //------------------------------------------//
  83
  84 //------------------Definition of unwrap--------------------------------------//
  85
  86 template<typename T>
  87 typename unwrapped_type<T>::type&
  88 unwrap(const reference_wrapper<T>& ref) { return ref.get(); }
  89
  90 template<typename T>
  91 typename unwrapped_type<T>::type& unwrap(T& t) { return t; }
  92
  93 template<typename T>
  94 const typename unwrapped_type<T>::type& unwrap(const T& t) { return t; }
  95
  96 } } } // End namespaces detail, iostreams, boost.
  97
  98 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED