libstdc++
move.h
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00001 // Move, forward and identity for C++0x + swap -*- C++ -*-
00002 
00003 // Copyright (C) 2007-2013 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file bits/move.h
00026  *  This is an internal header file, included by other library headers.
00027  *  Do not attempt to use it directly. @headername{utility}
00028  */
00029 
00030 #ifndef _MOVE_H
00031 #define _MOVE_H 1
00032 
00033 #include <bits/c++config.h>
00034 #include <bits/concept_check.h>
00035 
00036 namespace std _GLIBCXX_VISIBILITY(default)
00037 {
00038 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00039 
00040   // Used, in C++03 mode too, by allocators, etc.
00041   /**
00042    *  @brief Same as C++11 std::addressof
00043    *  @ingroup utilities
00044    */
00045   template<typename _Tp>
00046     inline _Tp*
00047     __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
00048     {
00049       return reinterpret_cast<_Tp*>
00050     (&const_cast<char&>(reinterpret_cast<const volatile char&>(__r)));
00051     }
00052 
00053 _GLIBCXX_END_NAMESPACE_VERSION
00054 } // namespace
00055 
00056 #if __cplusplus >= 201103L
00057 #include <type_traits> // Brings in std::declval too.
00058 
00059 namespace std _GLIBCXX_VISIBILITY(default)
00060 {
00061 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00062 
00063   /**
00064    *  @addtogroup utilities
00065    *  @{
00066    */
00067 
00068   /**
00069    *  @brief  Forward an lvalue.
00070    *  @return The parameter cast to the specified type.
00071    *
00072    *  This function is used to implement "perfect forwarding".
00073    */
00074   template<typename _Tp>
00075     constexpr _Tp&&
00076     forward(typename std::remove_reference<_Tp>::type& __t) noexcept
00077     { return static_cast<_Tp&&>(__t); }
00078 
00079   /**
00080    *  @brief  Forward an rvalue.
00081    *  @return The parameter cast to the specified type.
00082    *
00083    *  This function is used to implement "perfect forwarding".
00084    */
00085   template<typename _Tp>
00086     constexpr _Tp&&
00087     forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
00088     {
00089       static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
00090             " substituting _Tp is an lvalue reference type");
00091       return static_cast<_Tp&&>(__t);
00092     }
00093 
00094   /**
00095    *  @brief  Convert a value to an rvalue.
00096    *  @param  __t  A thing of arbitrary type.
00097    *  @return The parameter cast to an rvalue-reference to allow moving it.
00098   */
00099   template<typename _Tp>
00100     constexpr typename std::remove_reference<_Tp>::type&&
00101     move(_Tp&& __t) noexcept
00102     { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
00103 
00104 
00105   template<typename _Tp>
00106     struct __move_if_noexcept_cond
00107     : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
00108                     is_copy_constructible<_Tp>>::type { };
00109 
00110   /**
00111    *  @brief  Conditionally convert a value to an rvalue.
00112    *  @param  __x  A thing of arbitrary type.
00113    *  @return The parameter, possibly cast to an rvalue-reference.
00114    *
00115    *  Same as std::move unless the type's move constructor could throw and the
00116    *  type is copyable, in which case an lvalue-reference is returned instead.
00117    */
00118   template<typename _Tp>
00119     inline constexpr typename
00120     conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
00121     move_if_noexcept(_Tp& __x) noexcept
00122     { return std::move(__x); }
00123 
00124   // declval, from type_traits.
00125 
00126   /**
00127    *  @brief Returns the actual address of the object or function
00128    *         referenced by r, even in the presence of an overloaded
00129    *         operator&.
00130    *  @param  __r  Reference to an object or function.
00131    *  @return   The actual address.
00132   */
00133   template<typename _Tp>
00134     inline _Tp*
00135     addressof(_Tp& __r) noexcept
00136     { return std::__addressof(__r); }
00137 
00138   /// @} group utilities
00139 _GLIBCXX_END_NAMESPACE_VERSION
00140 } // namespace
00141 
00142 #define _GLIBCXX_MOVE(__val) std::move(__val)
00143 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
00144 #else
00145 #define _GLIBCXX_MOVE(__val) (__val)
00146 #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
00147 #endif
00148 
00149 namespace std _GLIBCXX_VISIBILITY(default)
00150 {
00151 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00152 
00153   /**
00154    *  @addtogroup utilities
00155    *  @{
00156    */
00157 
00158   /**
00159    *  @brief Swaps two values.
00160    *  @param  __a  A thing of arbitrary type.
00161    *  @param  __b  Another thing of arbitrary type.
00162    *  @return   Nothing.
00163   */
00164   template<typename _Tp>
00165     inline void
00166     swap(_Tp& __a, _Tp& __b)
00167 #if __cplusplus >= 201103L
00168     noexcept(__and_<is_nothrow_move_constructible<_Tp>,
00169                 is_nothrow_move_assignable<_Tp>>::value)
00170 #endif
00171     {
00172       // concept requirements
00173       __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
00174 
00175       _Tp __tmp = _GLIBCXX_MOVE(__a);
00176       __a = _GLIBCXX_MOVE(__b);
00177       __b = _GLIBCXX_MOVE(__tmp);
00178     }
00179 
00180   // _GLIBCXX_RESOLVE_LIB_DEFECTS
00181   // DR 809. std::swap should be overloaded for array types.
00182   /// Swap the contents of two arrays.
00183   template<typename _Tp, size_t _Nm>
00184     inline void
00185     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
00186 #if __cplusplus >= 201103L
00187     noexcept(noexcept(swap(*__a, *__b)))
00188 #endif
00189     {
00190       for (size_t __n = 0; __n < _Nm; ++__n)
00191     swap(__a[__n], __b[__n]);
00192     }
00193 
00194   /// @} group utilities
00195 _GLIBCXX_END_NAMESPACE_VERSION
00196 } // namespace
00197 
00198 #endif /* _MOVE_H */