libstdc++-v3/include/bits/move.h

   1 // Move, forward and identity for C++0x + swap -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file move.h
  26  *  This is an internal header file, included by other library headers.
  27  *  You should not attempt to use it directly.
  28  */
  29
  30 #ifndef _MOVE_H
  31 #define _MOVE_H 1
  32
  33 #include <bits/c++config.h>
  34 #include <cstddef>
  35 #include <bits/concept_check.h>
  36
  37 _GLIBCXX_BEGIN_NAMESPACE(std)
  38
  39   // Used, in C++03 mode too, by allocators, etc.
  40   template<typename _Tp>
  41     inline _Tp*
  42     __addressof(_Tp& __r)
  43     {
  44       return reinterpret_cast<_Tp*>
  45         (&const_cast<char&>(reinterpret_cast<const volatile char&>(__r)));
  46     }
  47
  48 _GLIBCXX_END_NAMESPACE
  49
  50 #ifdef __GXX_EXPERIMENTAL_CXX0X__
  51 #include <type_traits> // Brings in std::declval too.
  52
  53 _GLIBCXX_BEGIN_NAMESPACE(std)
  54
  55   /// identity
  56   template<typename _Tp>
  57     struct identity
  58     {
  59       typedef _Tp type;
  60     };
  61
  62   /// forward (as per N2835)
  63   /// Forward lvalues as rvalues.
  64   template<typename _Tp>
  65     inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
  66     forward(typename std::identity<_Tp>::type& __t)
  67     { return static_cast<_Tp&&>(__t); }
  68
  69   /// Forward rvalues as rvalues.
  70   template<typename _Tp>
  71     inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
  72     forward(typename std::identity<_Tp>::type&& __t)
  73     { return static_cast<_Tp&&>(__t); }
  74
  75   // Forward lvalues as lvalues.
  76   template<typename _Tp>
  77     inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
  78     forward(typename std::identity<_Tp>::type __t)
  79     { return __t; }
  80
  81   // Prevent forwarding rvalues as const lvalues.
  82   template<typename _Tp>
  83     inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
  84     forward(typename std::remove_reference<_Tp>::type&& __t) = delete;
  85
  86   /**
  87    *  @brief Move a value.
  88    *  @ingroup mutating_algorithms
  89    *  @param  __t  A thing of arbitrary type.
  90    *  @return Same, moved.
  91   */
  92   template<typename _Tp>
  93     inline typename std::remove_reference<_Tp>::type&&
  94     move(_Tp&& __t)
  95     { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
  96
  97   /// declval, defined in <type_traits>.
  98
  99   /**
 100    *  @brief Returns the actual address of the object or function
 101    *         referenced by r, even in the presence of an overloaded
 102    *         operator&.
 103    *  @param  __r  Reference to an object or function.
 104    *  @return   The actual address.
 105   */
 106   template<typename _Tp>
 107     inline _Tp*
 108     addressof(_Tp& __r)
 109     { return std::__addressof(__r); }
 110
 111 _GLIBCXX_END_NAMESPACE
 112
 113 #define _GLIBCXX_MOVE(_Tp) std::move(_Tp)
 114 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
 115 #else
 116 #define _GLIBCXX_MOVE(_Tp) (_Tp)
 117 #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
 118 #endif
 119
 120 _GLIBCXX_BEGIN_NAMESPACE(std)
 121
 122   /**
 123    *  @brief Swaps two values.
 124    *  @ingroup mutating_algorithms
 125    *  @param  __a  A thing of arbitrary type.
 126    *  @param  __b  Another thing of arbitrary type.
 127    *  @return   Nothing.
 128   */
 129   template<typename _Tp>
 130     inline void
 131     swap(_Tp& __a, _Tp& __b)
 132     {
 133       // concept requirements
 134       __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
 135
 136       _Tp __tmp = _GLIBCXX_MOVE(__a);
 137       __a = _GLIBCXX_MOVE(__b);
 138       __b = _GLIBCXX_MOVE(__tmp);
 139     }
 140
 141   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 142   // DR 809. std::swap should be overloaded for array types.
 143   template<typename _Tp, size_t _Nm>
 144     inline void
 145     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
 146     {
 147       for (size_t __n = 0; __n < _Nm; ++__n)
 148         swap(__a[__n], __b[__n]);
 149     }
 150
 151 _GLIBCXX_END_NAMESPACE
 152
 153 #endif /* _MOVE_H */