| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |
| #define _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |
| |
| #include <__config> |
| #include <__fwd/pair.h> |
| #include <__type_traits/conditional.h> |
| #include <__type_traits/integral_constant.h> |
| #include <__type_traits/is_same.h> |
| #include <__type_traits/remove_const.h> |
| #include <__type_traits/remove_const_ref.h> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| // These traits are used in __tree and __hash_table |
| struct __extract_key_fail_tag {}; |
| struct __extract_key_self_tag {}; |
| struct __extract_key_first_tag {}; |
| |
| template <class _ValTy, class _Key, class _RawValTy = __remove_const_ref_t<_ValTy> > |
| struct __can_extract_key |
| : __conditional_t<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag, __extract_key_fail_tag> {}; |
| |
| template <class _Pair, class _Key, class _First, class _Second> |
| struct __can_extract_key<_Pair, _Key, pair<_First, _Second> > |
| : __conditional_t<_IsSame<__remove_const_t<_First>, _Key>::value, __extract_key_first_tag, __extract_key_fail_tag> { |
| }; |
| |
| // __can_extract_map_key uses true_type/false_type instead of the tags. |
| // It returns true if _Key != _ContainerValueTy (the container is a map not a set) |
| // and _ValTy == _Key. |
| template <class _ValTy, class _Key, class _ContainerValueTy, class _RawValTy = __remove_const_ref_t<_ValTy> > |
| struct __can_extract_map_key : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {}; |
| |
| // This specialization returns __extract_key_fail_tag for non-map containers |
| // because _Key == _ContainerValueTy |
| template <class _ValTy, class _Key, class _RawValTy> |
| struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy> : false_type {}; |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |