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

   1 // Move, forward and identity for C++0x + swap -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009 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 #ifdef __GXX_EXPERIMENTAL_CXX0X__
  38 #include <type_traits>
  39
  40 _GLIBCXX_BEGIN_NAMESPACE(std)
  41
  42   /// identity
  43   template<typename _Tp>
  44     struct identity
  45     {
  46       typedef _Tp type;
  47     };
  48
  49   /// forward (as per N2835)
  50   /// Forward lvalues as rvalues.
  51   template<typename _Tp>
  52     inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
  53     forward(typename std::identity<_Tp>::type& __t)
  54     { return static_cast<_Tp&&>(__t); }
  55
  56   /// Forward rvalues as rvalues.
  57   template<typename _Tp>
  58     inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
  59     forward(typename std::identity<_Tp>::type&& __t)
  60     { return static_cast<_Tp&&>(__t); }
  61
  62   // Forward lvalues as lvalues.
  63   template<typename _Tp>
  64     inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
  65     forward(typename std::identity<_Tp>::type __t)
  66     { return __t; }
  67
  68   // Prevent forwarding rvalues as const lvalues.
  69   template<typename _Tp>
  70     inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
  71     forward(typename std::remove_reference<_Tp>::type&& __t) = delete;
  72
  73   /**
  74    *  @brief Move a value.
  75    *  @ingroup mutating_algorithms
  76    *  @param  __t  A thing of arbitrary type.
  77    *  @return Same, moved.
  78   */
  79   template<typename _Tp>
  80     inline typename std::remove_reference<_Tp>::type&&
  81     move(_Tp&& __t)
  82     { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
  83
  84 _GLIBCXX_END_NAMESPACE
  85
  86 #define _GLIBCXX_MOVE(_Tp) std::move(_Tp)
  87 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
  88 #else
  89 #define _GLIBCXX_MOVE(_Tp) (_Tp)
  90 #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
  91 #endif
  92
  93 _GLIBCXX_BEGIN_NAMESPACE(std)
  94
  95   /**
  96    *  @brief Swaps two values.
  97    *  @ingroup mutating_algorithms
  98    *  @param  __a  A thing of arbitrary type.
  99    *  @param  __b  Another thing of arbitrary type.
 100    *  @return   Nothing.
 101   */
 102   template<typename _Tp>
 103     inline void
 104     swap(_Tp& __a, _Tp& __b)
 105     {
 106       // concept requirements
 107       __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
 108
 109       _Tp __tmp = _GLIBCXX_MOVE(__a);
 110       __a = _GLIBCXX_MOVE(__b);
 111       __b = _GLIBCXX_MOVE(__tmp);
 112     }
 113
 114   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 115   // DR 809. std::swap should be overloaded for array types.
 116   template<typename _Tp, size_t _Nm>
 117     inline void
 118     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
 119     {
 120       for (size_t __n = 0; __n < _Nm; ++__n)
 121         swap(__a[__n], __b[__n]);
 122     }
 123
 124 _GLIBCXX_END_NAMESPACE
 125
 126 #endif /* _MOVE_H */