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1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H10#define _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H11 12#include <__config>13#include <__fwd/pair.h>14#include <__fwd/tuple.h>15#include <__type_traits/enable_if.h>16#include <__type_traits/is_same.h>17#include <__type_traits/remove_const.h>18#include <__type_traits/remove_const_ref.h>19#include <__utility/declval.h>20#include <__utility/forward.h>21#include <__utility/piecewise_construct.h>22#include <__utility/priority_tag.h>23 24#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)25# pragma GCC system_header26#endif27 28_LIBCPP_BEGIN_NAMESPACE_STD29 30template <class _KeyT, class _Ret, class _WithKey, class _WithoutKey, class... _Args>31_LIBCPP_HIDE_FROM_ABI _Ret32__try_key_extraction_impl(__priority_tag<0>, _WithKey, _WithoutKey __without_key, _Args&&... __args) {33 return __without_key(std::forward<_Args>(__args)...);34}35 36template <class _KeyT,37 class _Ret,38 class _WithKey,39 class _WithoutKey,40 class _Arg,41 __enable_if_t<is_same<_KeyT, __remove_const_ref_t<_Arg> >::value, int> = 0>42_LIBCPP_HIDE_FROM_ABI _Ret43__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, _Arg&& __arg) {44 return __with_key(__arg, std::forward<_Arg>(__arg));45}46 47template <class _KeyT,48 class _Ret,49 class _WithKey,50 class _WithoutKey,51 class _Arg,52 __enable_if_t<__is_pair_v<__remove_const_ref_t<_Arg> > &&53 is_same<__remove_const_t<typename __remove_const_ref_t<_Arg>::first_type>, _KeyT>::value,54 int> = 0>55_LIBCPP_HIDE_FROM_ABI _Ret56__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, _Arg&& __arg) {57 return __with_key(__arg.first, std::forward<_Arg>(__arg));58}59 60template <class _KeyT,61 class _Ret,62 class _WithKey,63 class _WithoutKey,64 class _Arg1,65 class _Arg2,66 __enable_if_t<is_same<_KeyT, __remove_const_ref_t<_Arg1> >::value, int> = 0>67_LIBCPP_HIDE_FROM_ABI _Ret68__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, _Arg1&& __arg1, _Arg2&& __arg2) {69 return __with_key(__arg1, std::forward<_Arg1>(__arg1), std::forward<_Arg2>(__arg2));70}71 72#ifndef _LIBCPP_CXX03_LANG73template <class _KeyT,74 class _Ret,75 class _WithKey,76 class _WithoutKey,77 class _PiecewiseConstruct,78 class _Tuple1,79 class _Tuple2,80 __enable_if_t<is_same<__remove_const_ref_t<_PiecewiseConstruct>, piecewise_construct_t>::value &&81 __is_tuple_v<_Tuple1> && tuple_size<_Tuple1>::value == 1 &&82 is_same<__remove_const_ref_t<typename tuple_element<0, _Tuple1>::type>, _KeyT>::value,83 int> = 0>84_LIBCPP_HIDE_FROM_ABI _Ret __try_key_extraction_impl(85 __priority_tag<1>,86 _WithKey __with_key,87 _WithoutKey,88 _PiecewiseConstruct&& __pc,89 _Tuple1&& __tuple1,90 _Tuple2&& __tuple2) {91 return __with_key(92 std::get<0>(__tuple1),93 std::forward<_PiecewiseConstruct>(__pc),94 std::forward<_Tuple1>(__tuple1),95 std::forward<_Tuple2>(__tuple2));96}97#endif // _LIBCPP_CXX03_LANG98 99// This function tries extracting the given _KeyT from _Args...100// If it succeeds to extract the key, it calls the `__with_key` function with the extracted key and all of the101// arguments. Otherwise it calls the `__without_key` function with all of the arguments.102//103// Both `__with_key` and `__without_key` must take all arguments by reference.104template <class _KeyT, class _WithKey, class _WithoutKey, class... _Args>105_LIBCPP_HIDE_FROM_ABI decltype(std::declval<_WithoutKey>()(std::declval<_Args>()...))106__try_key_extraction(_WithKey __with_key, _WithoutKey __without_key, _Args&&... __args) {107 using _Ret = decltype(__without_key(std::forward<_Args>(__args)...));108 return std::__try_key_extraction_impl<_KeyT, _Ret>(109 __priority_tag<1>(), __with_key, __without_key, std::forward<_Args>(__args)...);110}111 112_LIBCPP_END_NAMESPACE_STD113 114#endif // _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H115