iterator_traits.h (2410B)
1 // Copyright 2025 The Abseil Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // ----------------------------------------------------------------------------- 16 // File: internal/iterator_traits.h 17 // ----------------------------------------------------------------------------- 18 // 19 // Helpers for querying traits of iterators, for implementing containers, etc. 20 21 #ifndef ABSL_BASE_INTERNAL_ITERATOR_TRAITS_H_ 22 #define ABSL_BASE_INTERNAL_ITERATOR_TRAITS_H_ 23 24 #include <iterator> 25 #include <type_traits> 26 27 #include "absl/base/config.h" 28 #include "absl/meta/type_traits.h" 29 30 namespace absl { 31 ABSL_NAMESPACE_BEGIN 32 namespace base_internal { 33 34 template <typename Iterator, typename = void> 35 struct IteratorCategory {}; 36 37 template <typename Iterator> 38 struct IteratorCategory< 39 Iterator, 40 absl::void_t<typename std::iterator_traits<Iterator>::iterator_category>> { 41 using type = typename std::iterator_traits<Iterator>::iterator_category; 42 }; 43 44 template <typename Iterator, typename = void> 45 struct IteratorConceptImpl : IteratorCategory<Iterator> {}; 46 47 template <typename Iterator> 48 struct IteratorConceptImpl< 49 Iterator, 50 absl::void_t<typename std::iterator_traits<Iterator>::iterator_concept>> { 51 using type = typename std::iterator_traits<Iterator>::iterator_concept; 52 }; 53 54 // The newer `std::iterator_traits<Iterator>::iterator_concept` if available, 55 // else `std::iterator_traits<Iterator>::iterator_category`. 56 template <typename Iterator> 57 using IteratorConcept = typename IteratorConceptImpl<Iterator>::type; 58 59 template <typename IteratorTag, typename Iterator> 60 using IsAtLeastIterator = 61 std::is_convertible<IteratorConcept<Iterator>, IteratorTag>; 62 63 template <typename Iterator> 64 using IsAtLeastForwardIterator = 65 IsAtLeastIterator<std::forward_iterator_tag, Iterator>; 66 67 } // namespace base_internal 68 ABSL_NAMESPACE_END 69 } // namespace absl 70 71 #endif // ABSL_BASE_INTERNAL_ITERATOR_TRAITS_H_