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> // Brings in std::declval too. 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 /// declval, from type_traits. 85 86 _GLIBCXX_END_NAMESPACE 87 88 #define _GLIBCXX_MOVE(_Tp) std::move(_Tp) 89 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val) 90 #else 91 #define _GLIBCXX_MOVE(_Tp) (_Tp) 92 #define _GLIBCXX_FORWARD(_Tp, __val) (__val) 93 #endif 94 95 _GLIBCXX_BEGIN_NAMESPACE(std) 96 97 /** 98 * @brief Swaps two values. 99 * @ingroup mutating_algorithms 100 * @param __a A thing of arbitrary type. 101 * @param __b Another thing of arbitrary type. 102 * @return Nothing. 103 */ 104 template<typename _Tp> 105 inline void 106 swap(_Tp& __a, _Tp& __b) 107 { 108 // concept requirements 109 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>) 110 111 _Tp __tmp = _GLIBCXX_MOVE(__a); 112 __a = _GLIBCXX_MOVE(__b); 113 __b = _GLIBCXX_MOVE(__tmp); 114 } 115 116 // _GLIBCXX_RESOLVE_LIB_DEFECTS 117 // DR 809. std::swap should be overloaded for array types. 118 template<typename _Tp, size_t _Nm> 119 inline void 120 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) 121 { 122 for (size_t __n = 0; __n < _Nm; ++__n) 123 swap(__a[__n], __b[__n]); 124 } 125 126 _GLIBCXX_END_NAMESPACE 127 128 #endif /* _MOVE_H */ 129