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 public: 31 // types 32 typedef _Tp type; 33 34 private: 35 type* __f_; 36 37 static void __fun(_Tp&) _NOEXCEPT; 38 static void __fun(_Tp&&) = delete; 39 40 public: 41 template < 42 class _Up, 43 class = __enable_if_t<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(std::declval<_Up>())) > > 44 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper(_Up&& __u) 45 _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) { 46 type& __f = static_cast<_Up&&>(__u); 47 __f_ = std::addressof(__f); 48 } 49 50 // access 51 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 operator type&() const _NOEXCEPT { return *__f_; } 52 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 type& get() const _NOEXCEPT { return *__f_; } 53 54 // invoke 55 template <class... _ArgTypes> 56 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __invoke_of<type&, _ArgTypes...>::type 57 operator()(_ArgTypes&&... __args) const 58 #if _LIBCPP_STD_VER >= 17 59 // Since is_nothrow_invocable requires C++17 LWG3764 is not backported 60 // to earlier versions. 61 noexcept(is_nothrow_invocable_v<_Tp&, _ArgTypes...>) 62 #endif 63 { 64 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...); 65 } 66 }; 67 68 #if _LIBCPP_STD_VER >= 17 69 template <class _Tp> 70 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>; 71 #endif 72 73 template <class _Tp> 74 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> ref(_Tp& __t) _NOEXCEPT { 75 return reference_wrapper<_Tp>(__t); 76 } 77 78 template <class _Tp> 79 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> 80 ref(reference_wrapper<_Tp> __t) _NOEXCEPT { 81 return __t; 82 } 83 84 template <class _Tp> 85 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> cref(const _Tp& __t) _NOEXCEPT { 86 return reference_wrapper<const _Tp>(__t); 87 } 88 89 template <class _Tp> 90 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> 91 cref(reference_wrapper<_Tp> __t) _NOEXCEPT { 92 return __t; 93 } 94 95 template <class _Tp> 96 void ref(const _Tp&&) = delete; 97 template <class _Tp> 98 void cref(const _Tp&&) = delete; 99 100 _LIBCPP_END_NAMESPACE_STD 101 102 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 103