1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 11 #define _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 12 13 #include <__config> 14 #include <__functional/invoke.h> 15 #include <__functional/weak_result_type.h> 16 #include <__memory/addressof.h> 17 #include <__type_traits/enable_if.h> 18 #include <__type_traits/remove_cvref.h> 19 #include <__utility/declval.h> 20 #include <__utility/forward.h> 21 22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 23 # pragma GCC system_header 24 #endif 25 26 _LIBCPP_BEGIN_NAMESPACE_STD 27 28 template <class _Tp> 29 class _LIBCPP_TEMPLATE_VIS reference_wrapper : public __weak_result_type<_Tp> 30 { 31 public: 32 // types 33 typedef _Tp type; 34 private: 35 type* __f_; 36 37 static void __fun(_Tp&) _NOEXCEPT; 38 static void __fun(_Tp&&) = delete; 39 40 public: 41 template <class _Up, class = __enable_if_t<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(std::declval<_Up>())) > > 42 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 43 reference_wrapper(_Up&& __u) _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) { 44 type& __f = static_cast<_Up&&>(__u); 45 __f_ = _VSTD::addressof(__f); 46 } 47 48 // access 49 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 50 operator type&() const _NOEXCEPT {return *__f_;} 51 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 52 type& get() const _NOEXCEPT {return *__f_;} 53 54 // invoke 55 template <class... _ArgTypes> 56 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 57 typename __invoke_of<type&, _ArgTypes...>::type 58 operator() (_ArgTypes&&... __args) const 59 #if _LIBCPP_STD_VER >= 17 60 // Since is_nothrow_invocable requires C++17 LWG3764 is not backported 61 // to earlier versions. 62 noexcept(is_nothrow_invocable_v<_Tp&, _ArgTypes...>) 63 #endif 64 { 65 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...); 66 } 67 }; 68 69 #if _LIBCPP_STD_VER >= 17 70 template <class _Tp> 71 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>; 72 #endif 73 74 template <class _Tp> 75 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 76 reference_wrapper<_Tp> 77 ref(_Tp& __t) _NOEXCEPT 78 { 79 return reference_wrapper<_Tp>(__t); 80 } 81 82 template <class _Tp> 83 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 84 reference_wrapper<_Tp> 85 ref(reference_wrapper<_Tp> __t) _NOEXCEPT 86 { 87 return __t; 88 } 89 90 template <class _Tp> 91 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 92 reference_wrapper<const _Tp> 93 cref(const _Tp& __t) _NOEXCEPT 94 { 95 return reference_wrapper<const _Tp>(__t); 96 } 97 98 template <class _Tp> 99 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 100 reference_wrapper<const _Tp> 101 cref(reference_wrapper<_Tp> __t) _NOEXCEPT 102 { 103 return __t; 104 } 105 106 template <class _Tp> void ref(const _Tp&&) = delete; 107 template <class _Tp> void cref(const _Tp&&) = delete; 108 109 _LIBCPP_END_NAMESPACE_STD 110 111 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 112