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 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...); 60 } 61 }; 62 63 #if _LIBCPP_STD_VER > 14 64 template <class _Tp> 65 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>; 66 #endif 67 68 template <class _Tp> 69 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 70 reference_wrapper<_Tp> 71 ref(_Tp& __t) _NOEXCEPT 72 { 73 return reference_wrapper<_Tp>(__t); 74 } 75 76 template <class _Tp> 77 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 78 reference_wrapper<_Tp> 79 ref(reference_wrapper<_Tp> __t) _NOEXCEPT 80 { 81 return __t; 82 } 83 84 template <class _Tp> 85 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 86 reference_wrapper<const _Tp> 87 cref(const _Tp& __t) _NOEXCEPT 88 { 89 return reference_wrapper<const _Tp>(__t); 90 } 91 92 template <class _Tp> 93 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 94 reference_wrapper<const _Tp> 95 cref(reference_wrapper<_Tp> __t) _NOEXCEPT 96 { 97 return __t; 98 } 99 100 template <class _Tp> void ref(const _Tp&&) = delete; 101 template <class _Tp> void cref(const _Tp&&) = delete; 102 103 _LIBCPP_END_NAMESPACE_STD 104 105 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 106