source: NonGTP/Boost/boost/variant/detail/move.hpp @ 857

Revision 857, 4.2 KB checked in by igarcia, 19 years ago (diff)
RevLine 
[857]1//-----------------------------------------------------------------------------
2// boost variant/detail/move.hpp header file
3// See http://www.boost.org for updates, documentation, and revision history.
4//-----------------------------------------------------------------------------
5//
6//  Copyright (c) 2002-2003 Eric Friedman
7//  Copyright (c) 2002 by Andrei Alexandrescu
8//
9//  Use, modification and distribution are subject to the
10//  Boost Software License, Version 1.0. (See accompanying file
11//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
12//
13//  This file derivative of MoJO. Much thanks to Andrei for his initial work.
14//  See <http://www.cuj.com/experts/2102/alexandr.htm> for information on MOJO.
15//  Re-issued here under the Boost Software License, with permission of the original
16//  author (Andrei Alexandrescu).
17
18
19#ifndef BOOST_VARIANT_DETAIL_MOVE_HPP
20#define BOOST_VARIANT_DETAIL_MOVE_HPP
21
22#include <iterator> // for iterator_traits
23#include <new> // for placement new
24
25#include "boost/config.hpp"
26#include "boost/detail/workaround.hpp"
27#include "boost/mpl/if.hpp"
28#include "boost/type_traits/is_base_and_derived.hpp"
29
30namespace boost {
31namespace detail { namespace variant {
32
33//////////////////////////////////////////////////////////////////////////
34// forward declares
35//
36// NOTE: Incomplete until (if?) Boost.Move becomes part of Boost.
37//
38template <typename Deriving> class moveable;
39template <typename T>        class move_source;
40template <typename T>        class move_return;
41
42namespace detail {
43
44// (detail) moveable_tag
45//
46// Concrete type from which moveable<T> derives.
47//
48// TODO: Move into moveable_fwd.hpp and define has_move_constructor.
49//
50template <typename Deriving>
51struct moveable_tag
52{
53};
54
55} // namespace detail
56
57//////////////////////////////////////////////////////////////////////////
58// function template move
59//
60// Takes a T& and returns, if T derives moveable<T>, a move_source<T> for
61// the object; else, returns the T&.
62//
63
64namespace detail {
65
66// (detail) class template move_type
67//
68// Metafunction that, given moveable T, provides move_source<T>, else T&.
69//
70template <typename T>
71struct move_type
72{
73public: // metafunction result
74
75    typedef typename mpl::if_<
76          is_base_and_derived<detail::moveable_tag<T>, T>
77        , move_source<T>
78        , T&
79        >::type type;
80
81};
82
83} // namespace detail
84
85template <typename T>
86inline
87    typename detail::move_type<T>::type
88move(T& source)
89{
90    typedef typename detail::move_type<T>::type
91        move_t;
92
93    return move_t(source);
94}
95
96//////////////////////////////////////////////////////////////////////////
97// class template return_t
98//
99// Metafunction that, given moveable T, provides move_return<T>, else T.
100//
101template <typename T>
102struct return_t
103{
104public: // metafunction result
105
106    typedef typename mpl::if_<
107          is_base_and_derived<moveable<T>, T>
108        , move_return<T>
109        , T
110        >::type type;
111
112};
113
114//////////////////////////////////////////////////////////////////////////
115// function template move_swap
116//
117// Swaps using Koenig lookup but falls back to move-swap for primitive
118// types and on non-conforming compilers.
119//
120
121#if   defined(BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP)   \
122 ||   BOOST_WORKAROUND(__GNUC__, BOOST_TESTED_AT(2))
123
124// [Indicate that move_swap by overload is disabled...]
125#define BOOST_NO_MOVE_SWAP_BY_OVERLOAD
126
127// [...and provide straight swap-by-move implementation:]
128template <typename T>
129inline void move_swap(T& lhs, T& rhs)
130{
131    T tmp( boost::detail::variant::move(lhs) );
132    lhs = boost::detail::variant::move(rhs);
133    rhs = boost::detail::variant::move(tmp);
134}
135
136#else// !workaround
137
138namespace detail { namespace move_swap {
139
140template <typename T>
141inline void swap(T& lhs, T& rhs)
142{
143    T tmp( boost::detail::variant::move(lhs) );
144    lhs = boost::detail::variant::move(rhs);
145    rhs = boost::detail::variant::move(tmp);
146}
147
148}} // namespace detail::move_swap
149
150template <typename T>
151inline void move_swap(T& lhs, T& rhs)
152{
153    using detail::move_swap::swap;
154
155    swap(lhs, rhs);
156}
157
158#endif // workaround
159
160}} // namespace detail::variant
161} // namespace boost
162
163#endif // BOOST_VARIANT_DETAIL_MOVE_HPP
164
165
166
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