Stephen Hines | c6ca60f | 2023-05-09 02:19:22 -0700 | [diff] [blame^] | 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-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |
| 10 | #define _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |
| 11 | |
| 12 | #include <__config> |
| 13 | #include <__fwd/pair.h> |
| 14 | #include <__type_traits/conditional.h> |
| 15 | #include <__type_traits/integral_constant.h> |
| 16 | #include <__type_traits/is_same.h> |
| 17 | #include <__type_traits/remove_const.h> |
| 18 | #include <__type_traits/remove_const_ref.h> |
| 19 | |
| 20 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 21 | # pragma GCC system_header |
| 22 | #endif |
| 23 | |
| 24 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 25 | |
| 26 | // These traits are used in __tree and __hash_table |
| 27 | struct __extract_key_fail_tag {}; |
| 28 | struct __extract_key_self_tag {}; |
| 29 | struct __extract_key_first_tag {}; |
| 30 | |
| 31 | template <class _ValTy, class _Key, class _RawValTy = __remove_const_ref_t<_ValTy> > |
| 32 | struct __can_extract_key |
| 33 | : __conditional_t<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag, __extract_key_fail_tag> {}; |
| 34 | |
| 35 | template <class _Pair, class _Key, class _First, class _Second> |
| 36 | struct __can_extract_key<_Pair, _Key, pair<_First, _Second> > |
| 37 | : __conditional_t<_IsSame<__remove_const_t<_First>, _Key>::value, __extract_key_first_tag, __extract_key_fail_tag> { |
| 38 | }; |
| 39 | |
| 40 | // __can_extract_map_key uses true_type/false_type instead of the tags. |
| 41 | // It returns true if _Key != _ContainerValueTy (the container is a map not a set) |
| 42 | // and _ValTy == _Key. |
| 43 | template <class _ValTy, class _Key, class _ContainerValueTy, |
| 44 | class _RawValTy = __remove_const_ref_t<_ValTy> > |
| 45 | struct __can_extract_map_key |
| 46 | : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {}; |
| 47 | |
| 48 | // This specialization returns __extract_key_fail_tag for non-map containers |
| 49 | // because _Key == _ContainerValueTy |
| 50 | template <class _ValTy, class _Key, class _RawValTy> |
| 51 | struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy> |
| 52 | : false_type {}; |
| 53 | |
| 54 | _LIBCPP_END_NAMESPACE_STD |
| 55 | |
| 56 | #endif // _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H |