iostreams/detail/wrap_unwrap.hpp

0001 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
0002 // (C) Copyright 2003-2007 Jonathan Turkanis
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
0005
0006 // See http://www.boost.org/libs/iostreams for documentation.
0007
0008 #ifndef BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED
0009 #define BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED
0010
0011 #if defined(_MSC_VER)
0012 # pragma once
0013 #endif
0014
0015 #include <boost/config.hpp>                             // SFINAE, MSVC.
0016 #include <boost/detail/workaround.hpp>
0017 #include <boost/iostreams/detail/enable_if_stream.hpp>
0018 #include <boost/iostreams/traits_fwd.hpp>               // is_std_io.
0019 #include <boost/mpl/bool.hpp>
0020 #include <boost/mpl/identity.hpp>
0021 #include <boost/mpl/eval_if.hpp>
0022 #include <boost/mpl/if.hpp>
0023 #include <boost/ref.hpp>
0024
0025 namespace boost { namespace iostreams { namespace detail {
0026
0027 //------------------Definition of wrap/unwrap traits--------------------------//
0028
0029 template<typename T>
0030 struct wrapped_type
0031     : mpl::if_<is_std_io<T>, reference_wrapper<T>, T>
0032     { };
0033
0034 template<typename T>
0035 struct unwrapped_type
0036     : unwrap_reference<T>
0037     { };
0038
0039 template<typename T>
0040 struct unwrap_ios
0041     : mpl::eval_if<
0042           is_std_io<T>,
0043           unwrap_reference<T>,
0044           mpl::identity<T>
0045       >
0046     { };
0047
0048 //------------------Definition of wrap----------------------------------------//
0049
0050 #ifndef BOOST_NO_SFINAE //----------------------------------------------------//
0051     template<typename T>
0052     inline T wrap(const T& t BOOST_IOSTREAMS_DISABLE_IF_STREAM(T))
0053     { return t; }
0054
0055     template<typename T>
0056     inline typename wrapped_type<T>::type
0057     wrap(T& t BOOST_IOSTREAMS_ENABLE_IF_STREAM(T)) { return boost::ref(t); }
0058 #else // #ifndef BOOST_NO_SFINAE //-------------------------------------------//
0059     template<typename T>
0060     inline typename wrapped_type<T>::type // BCC 5.x needs namespace qualification.
0061     wrap_impl(const T& t, mpl::true_) { return boost::ref(const_cast<T&>(t)); }
0062
0063     template<typename T>
0064     inline typename wrapped_type<T>::type // BCC 5.x needs namespace qualification.
0065     wrap_impl(T& t, mpl::true_) { return boost::ref(t); }
0066
0067     template<typename T>
0068     inline typename wrapped_type<T>::type
0069     wrap_impl(const T& t, mpl::false_) { return t; }
0070
0071     template<typename T>
0072     inline typename wrapped_type<T>::type
0073     wrap_impl(T& t, mpl::false_) { return t; }
0074
0075     template<typename T>
0076     inline typename wrapped_type<T>::type
0077     wrap(const T& t) { return wrap_impl(t, is_std_io<T>()); }
0078
0079     template<typename T>
0080     inline typename wrapped_type<T>::type
0081     wrap(T& t) { return wrap_impl(t, is_std_io<T>()); }
0082 #endif // #ifndef BOOST_NO_SFINAE //------------------------------------------//
0083
0084 //------------------Definition of unwrap--------------------------------------//
0085
0086 template<typename T>
0087 typename unwrapped_type<T>::type&
0088 unwrap(const reference_wrapper<T>& ref) { return ref.get(); }
0089
0090 template<typename T>
0091 typename unwrapped_type<T>::type& unwrap(T& t) { return t; }
0092
0093 template<typename T>
0094 const typename unwrapped_type<T>::type& unwrap(const T& t) { return t; }
0095
0096 } } } // End namespaces detail, iostreams, boost.
0097
0098 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_WRAP_UNWRAP_HPP_INCLUDED