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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-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef _LIBCPP___SEGMENTED_ITERATOR_H |
| 10 | #define _LIBCPP___SEGMENTED_ITERATOR_H |
| 11 | |
| 12 | // Segmented iterators are iterators over (not necessarily contiguous) sub-ranges. |
| 13 | // |
| 14 | // For example, std::deque stores its data into multiple blocks of contiguous memory, |
| 15 | // which are not stored contiguously themselves. The concept of segmented iterators |
| 16 | // allows algorithms to operate over these multi-level iterators natively, opening the |
| 17 | // door to various optimizations. See http://lafstern.org/matt/segmented.pdf for details. |
| 18 | // |
| 19 | // If __segmented_iterator_traits can be instantiated, the following functions and associated types must be provided: |
| 20 | // - Traits::__local_iterator |
| 21 | // The type of iterators used to iterate inside a segment. |
| 22 | // |
| 23 | // - Traits::__segment_iterator |
| 24 | // The type of iterators used to iterate over segments. |
| 25 | // Segment iterators can be forward iterators or bidirectional iterators, depending on the |
| 26 | // underlying data structure. |
| 27 | // |
| 28 | // - static __segment_iterator Traits::__segment(It __it) |
| 29 | // Returns an iterator to the segment that the provided iterator is in. |
| 30 | // |
| 31 | // - static __local_iterator Traits::__local(It __it) |
| 32 | // Returns the local iterator pointing to the element that the provided iterator points to. |
| 33 | // |
| 34 | // - static __local_iterator Traits::__begin(__segment_iterator __it) |
| 35 | // Returns the local iterator to the beginning of the segment that the provided iterator is pointing into. |
| 36 | // |
| 37 | // - static __local_iterator Traits::__end(__segment_iterator __it) |
| 38 | // Returns the one-past-the-end local iterator to the segment that the provided iterator is pointing into. |
| 39 | // |
| 40 | // - static It Traits::__compose(__segment_iterator, __local_iterator) |
| 41 | // Returns the iterator composed of the segment iterator and local iterator. |
| 42 | |
| 43 | #include <__config> |
| 44 | #include <__cstddef/size_t.h> |
| 45 | #include <__iterator/iterator_traits.h> |
| 46 | #include <__type_traits/integral_constant.h> |
| 47 | |
| 48 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 49 | # pragma GCC system_header |
| 50 | #endif |
| 51 | |
| 52 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 53 | |
| 54 | template <class _Iterator> |
| 55 | struct __segmented_iterator_traits; |
| 56 | /* exposition-only: |
| 57 | { |
| 58 | using __segment_iterator = ...; |
| 59 | using __local_iterator = ...; |
| 60 | |
| 61 | static __segment_iterator __segment(_Iterator); |
| 62 | static __local_iterator __local(_Iterator); |
| 63 | static __local_iterator __begin(__segment_iterator); |
| 64 | static __local_iterator __end(__segment_iterator); |
| 65 | static _Iterator __compose(__segment_iterator, __local_iterator); |
| 66 | }; |
| 67 | */ |
| 68 | |
| 69 | template <class _Tp, size_t = 0> |
| 70 | struct __has_specialization : false_type {}; |
| 71 | |
| 72 | template <class _Tp> |
| 73 | struct __has_specialization<_Tp, sizeof(_Tp) * 0> : true_type {}; |
| 74 | |
| 75 | template <class _Iterator> |
| 76 | using __is_segmented_iterator _LIBCPP_NODEBUG = __has_specialization<__segmented_iterator_traits<_Iterator> >; |
| 77 | |
| 78 | template <class _SegmentedIterator> |
| 79 | struct __has_random_access_local_iterator |
| 80 | : __has_random_access_iterator_category< |
| 81 | typename __segmented_iterator_traits< _SegmentedIterator >::__local_iterator > {}; |
| 82 | |
| 83 | _LIBCPP_END_NAMESPACE_STD |
| 84 | |
| 85 | #endif // _LIBCPP___SEGMENTED_ITERATOR_H |
| 86 |
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