167 lines
4.1 KiB
C++
167 lines
4.1 KiB
C++
//-----------------------------------------------------------------------------
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// boost variant/detail/move.hpp header file
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// See http://www.boost.org for updates, documentation, and revision history.
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//-----------------------------------------------------------------------------
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//
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// Copyright (c) 2002-2003 Eric Friedman
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// Copyright (c) 2002 by Andrei Alexandrescu
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//
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// This file derivative of MoJO. Much thanks to Andrei for his initial work.
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// See <http://www.cuj.com/experts/2102/alexandr.htm> for information on MOJO.
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// Re-issued here under the Boost Software License, with permission of the original
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// author (Andrei Alexandrescu).
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#ifndef BOOST_VARIANT_DETAIL_MOVE_HPP
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#define BOOST_VARIANT_DETAIL_MOVE_HPP
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#include <iterator> // for iterator_traits
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#include <new> // for placement new
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#include "boost/config.hpp"
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#include "boost/detail/workaround.hpp"
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#include "boost/mpl/if.hpp"
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#include "boost/type_traits/is_base_and_derived.hpp"
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namespace boost {
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namespace detail { namespace variant {
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//////////////////////////////////////////////////////////////////////////
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// forward declares
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//
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// NOTE: Incomplete until (if?) Boost.Move becomes part of Boost.
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//
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template <typename Deriving> class moveable;
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template <typename T> class move_source;
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template <typename T> class move_return;
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namespace detail {
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// (detail) moveable_tag
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//
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// Concrete type from which moveable<T> derives.
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//
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// TODO: Move into moveable_fwd.hpp and define has_move_constructor.
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//
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template <typename Deriving>
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struct moveable_tag
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{
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};
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} // namespace detail
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//////////////////////////////////////////////////////////////////////////
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// function template move
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//
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// Takes a T& and returns, if T derives moveable<T>, a move_source<T> for
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// the object; else, returns the T&.
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//
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namespace detail {
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// (detail) class template move_type
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//
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// Metafunction that, given moveable T, provides move_source<T>, else T&.
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//
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template <typename T>
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struct move_type
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{
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public: // metafunction result
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typedef typename mpl::if_<
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is_base_and_derived<detail::moveable_tag<T>, T>
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, move_source<T>
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, T&
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>::type type;
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};
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} // namespace detail
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template <typename T>
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inline
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typename detail::move_type<T>::type
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move(T& source)
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{
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typedef typename detail::move_type<T>::type
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move_t;
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return move_t(source);
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}
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//////////////////////////////////////////////////////////////////////////
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// class template return_t
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//
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// Metafunction that, given moveable T, provides move_return<T>, else T.
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//
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template <typename T>
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struct return_t
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{
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public: // metafunction result
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typedef typename mpl::if_<
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is_base_and_derived<moveable<T>, T>
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, move_return<T>
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, T
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>::type type;
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};
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//////////////////////////////////////////////////////////////////////////
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// function template move_swap
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//
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// Swaps using Koenig lookup but falls back to move-swap for primitive
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// types and on non-conforming compilers.
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//
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#if defined(BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP) \
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|| BOOST_WORKAROUND(__GNUC__, BOOST_TESTED_AT(2))
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// [Indicate that move_swap by overload is disabled...]
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#define BOOST_NO_MOVE_SWAP_BY_OVERLOAD
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// [...and provide straight swap-by-move implementation:]
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template <typename T>
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inline void move_swap(T& lhs, T& rhs)
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{
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T tmp( boost::detail::variant::move(lhs) );
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lhs = boost::detail::variant::move(rhs);
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rhs = boost::detail::variant::move(tmp);
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}
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#else// !workaround
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namespace detail { namespace move_swap {
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template <typename T>
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inline void swap(T& lhs, T& rhs)
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{
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T tmp( boost::detail::variant::move(lhs) );
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lhs = boost::detail::variant::move(rhs);
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rhs = boost::detail::variant::move(tmp);
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}
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}} // namespace detail::move_swap
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template <typename T>
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inline void move_swap(T& lhs, T& rhs)
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{
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using detail::move_swap::swap;
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swap(lhs, rhs);
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}
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#endif // workaround
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}} // namespace detail::variant
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} // namespace boost
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#endif // BOOST_VARIANT_DETAIL_MOVE_HPP
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