195 lines
6.7 KiB
C++
195 lines
6.7 KiB
C++
//////////////////////////////////////////////////////////////////////////////
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//
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// (C) Copyright Ion Gaztanaga 2012-2012.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// See http://www.boost.org/libs/move for documentation.
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//
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//////////////////////////////////////////////////////////////////////////////
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//! \file
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#ifndef BOOST_MOVE_MOVE_UTILITY_HPP
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#define BOOST_MOVE_MOVE_UTILITY_HPP
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#include <boost/move/detail/config_begin.hpp>
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#include <boost/move/core.hpp>
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#include <boost/move/detail/meta_utils.hpp>
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#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_MOVE_DOXYGEN_INVOKED)
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namespace boost {
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template<class T>
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struct enable_move_utility_emulation
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{
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static const bool value = true;
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};
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//////////////////////////////////////////////////////////////////////////////
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//
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// move()
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//
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//////////////////////////////////////////////////////////////////////////////
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template <class T>
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inline typename ::boost::move_detail::enable_if_c
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< enable_move_utility_emulation<T>::value && !has_move_emulation_enabled<T>::value, T&>::type
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move(T& x)
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{
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return x;
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}
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template <class T>
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inline typename ::boost::move_detail::enable_if_c
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< enable_move_utility_emulation<T>::value && has_move_emulation_enabled<T>::value, rv<T>&>::type
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move(T& x)
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{
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return *static_cast<rv<T>* >(::boost::move_detail::addressof(x));
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}
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template <class T>
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inline typename ::boost::move_detail::enable_if_c
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< enable_move_utility_emulation<T>::value && has_move_emulation_enabled<T>::value, rv<T>&>::type
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move(rv<T>& x)
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{
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return x;
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}
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//////////////////////////////////////////////////////////////////////////////
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//
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// forward()
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//
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//////////////////////////////////////////////////////////////////////////////
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template <class T>
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inline typename ::boost::move_detail::enable_if_c
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< enable_move_utility_emulation<T>::value && ::boost::move_detail::is_rv<T>::value, T &>::type
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forward(const typename ::boost::move_detail::identity<T>::type &x)
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{
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return const_cast<T&>(x);
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}
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template <class T>
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inline typename ::boost::move_detail::enable_if_c
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< enable_move_utility_emulation<T>::value && !::boost::move_detail::is_rv<T>::value, const T &>::type
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forward(const typename ::boost::move_detail::identity<T>::type &x)
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{
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return x;
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}
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} //namespace boost
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#else //#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_MOVE_DOXYGEN_INVOKED)
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#if defined(BOOST_MOVE_USE_STANDARD_LIBRARY_MOVE)
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#include <utility>
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namespace boost{
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using ::std::move;
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using ::std::forward;
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} //namespace boost
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#else //!BOOST_MOVE_USE_STANDARD_LIBRARY_MOVE
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#include <boost/type_traits/remove_reference.hpp>
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namespace boost {
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//! This trait's internal boolean `value` is false in compilers with rvalue references
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//! and true in compilers without rvalue references.
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//!
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//! A user can specialize this trait for a type T to false to SFINAE out `move` and `forward`
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//! so that the user can define a different move emulation for that type in namespace boost
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//! (e.g. another Boost library for its types) and avoid any overload ambiguity.
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template<class T>
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struct enable_move_utility_emulation
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{
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static const bool value = false;
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};
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//////////////////////////////////////////////////////////////////////////////
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//
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// move
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//
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//////////////////////////////////////////////////////////////////////////////
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#if defined(BOOST_MOVE_DOXYGEN_INVOKED)
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//! This function provides a way to convert a reference into a rvalue reference
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//! in compilers with rvalue references. For other compilers converts T & into
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//! <i>::boost::rv<T> &</i> so that move emulation is activated.
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template <class T>
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rvalue_reference move (input_reference);
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#elif defined(BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES)
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//Old move approach, lvalues could bind to rvalue references
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template <class T>
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inline typename remove_reference<T>::type && move(T&& t)
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{ return t; }
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#else //BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES
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template <class T>
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inline typename remove_reference<T>::type && move(T&& t)
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{ return static_cast<typename remove_reference<T>::type &&>(t); }
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#endif //BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES
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//////////////////////////////////////////////////////////////////////////////
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//
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// forward
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//
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//////////////////////////////////////////////////////////////////////////////
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#if defined(BOOST_MOVE_DOXYGEN_INVOKED)
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//! This function provides limited form of forwarding that is usually enough for
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//! in-place construction and avoids the exponential overloading for
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//! achieve the limited forwarding in C++03.
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//!
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//! For compilers with rvalue references this function provides perfect forwarding.
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//!
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//! Otherwise:
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//! * If input_reference binds to const ::boost::rv<T> & then it output_reference is
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//! ::boost::rv<T> &
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//!
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//! * Else, output_reference is equal to input_reference.
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template <class T> output_reference forward(input_reference);
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#elif defined(BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES)
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//Old move approach, lvalues could bind to rvalue references
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template <class T>
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inline T&& forward (typename ::boost::move_detail::identity<T>::type&& t)
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{ return t; }
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#else //Old move
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//Implementation #5 from N2951, thanks to Howard Hinnant
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template <class T, class U>
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inline T&& forward(U&& t
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, typename ::boost::move_detail::enable_if_c<
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move_detail::is_lvalue_reference<T>::value ? move_detail::is_lvalue_reference<U>::value : true>::type * = 0/*
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, typename ::boost::move_detail::enable_if_c<
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move_detail::is_convertible
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<typename remove_reference<U>::type*, typename remove_reference<T>::type*>::value>::type * = 0*/)
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{ return static_cast<T&&>(t); }
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#endif //BOOST_MOVE_DOXYGEN_INVOKED
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} //namespace boost {
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#endif //#if defined(BOOST_MOVE_USE_STANDARD_LIBRARY_MOVE)
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#endif //BOOST_NO_CXX11_RVALUE_REFERENCES
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#include <boost/move/detail/config_end.hpp>
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#endif //#ifndef BOOST_MOVE_MOVE_UTILITY_HPP
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