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_PERFECT_FORWARD_H 11 #define _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H 12 13 #include <__config> 14 #include <__cstddef/size_t.h> 15 #include <__type_traits/enable_if.h> 16 #include <__type_traits/invoke.h> 17 #include <__type_traits/is_constructible.h> 18 #include <__utility/declval.h> 19 #include <__utility/forward.h> 20 #include <__utility/integer_sequence.h> 21 #include <__utility/move.h> 22 #include <tuple> 23 24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 25 # pragma GCC system_header 26 #endif 27 28 _LIBCPP_PUSH_MACROS 29 #include <__undef_macros> 30 31 _LIBCPP_BEGIN_NAMESPACE_STD 32 33 #if _LIBCPP_STD_VER >= 17 34 35 template <class _Op, class _Indices, class... _BoundArgs> 36 struct __perfect_forward_impl; 37 38 template <class _Op, size_t... _Idx, class... _BoundArgs> 39 struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _BoundArgs...> { 40 private: 41 tuple<_BoundArgs...> __bound_args_; 42 43 public: 44 template <class... _Args, class = enable_if_t< is_constructible_v<tuple<_BoundArgs...>, _Args&&...> >> 45 _LIBCPP_HIDE_FROM_ABI explicit constexpr __perfect_forward_impl(_Args&&... __bound_args) 46 : __bound_args_(std::forward<_Args>(__bound_args)...) {} 47 48 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl const&) = default; 49 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl&&) = default; 50 51 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default; 52 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl&&) = default; 53 54 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs&..., _Args...>>> 55 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) & noexcept( 56 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...))) 57 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) { 58 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...); 59 } 60 61 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs&..., _Args...>>> 62 auto operator()(_Args&&...) & = delete; 63 64 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const&..., _Args...>>> 65 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const& noexcept( 66 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...))) 67 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) { 68 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...); 69 } 70 71 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const&..., _Args...>>> 72 auto operator()(_Args&&...) const& = delete; 73 74 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs..., _Args...>>> 75 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) && noexcept( 76 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...))) 77 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) { 78 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...); 79 } 80 81 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs..., _Args...>>> 82 auto operator()(_Args&&...) && = delete; 83 84 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const..., _Args...>>> 85 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&& noexcept( 86 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...))) 87 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) { 88 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...); 89 } 90 91 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const..., _Args...>>> 92 auto operator()(_Args&&...) const&& = delete; 93 }; 94 95 // __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require]. 96 template <class _Op, class... _Args> 97 using __perfect_forward _LIBCPP_NODEBUG = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>; 98 99 #endif // _LIBCPP_STD_VER >= 17 100 101 _LIBCPP_END_NAMESPACE_STD 102 103 _LIBCPP_POP_MACROS 104 105 #endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H 106