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