| //===----------------------------------------------------------------------===// |
| // |
| // 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___SEGMENTED_ITERATOR_H |
| #define _LIBCPP___SEGMENTED_ITERATOR_H |
| |
| // Segmented iterators are iterators over (not necessarily contiguous) sub-ranges. |
| // |
| // For example, std::deque stores its data into multiple blocks of contiguous memory, |
| // which are not stored contiguously themselves. The concept of segmented iterators |
| // allows algorithms to operate over these multi-level iterators natively, opening the |
| // door to various optimizations. See http://lafstern.org/matt/segmented.pdf for details. |
| // |
| // If __segmented_iterator_traits can be instantiated, the following functions and associated types must be provided: |
| // - Traits::__local_iterator |
| // The type of iterators used to iterate inside a segment. |
| // |
| // - Traits::__segment_iterator |
| // The type of iterators used to iterate over segments. |
| // Segment iterators can be forward iterators or bidirectional iterators, depending on the |
| // underlying data structure. |
| // |
| // - static __segment_iterator Traits::__segment(It __it) |
| // Returns an iterator to the segment that the provided iterator is in. |
| // |
| // - static __local_iterator Traits::__local(It __it) |
| // Returns the local iterator pointing to the element that the provided iterator points to. |
| // |
| // - static __local_iterator Traits::__begin(__segment_iterator __it) |
| // Returns the local iterator to the beginning of the segment that the provided iterator is pointing into. |
| // |
| // - static __local_iterator Traits::__end(__segment_iterator __it) |
| // Returns the one-past-the-end local iterator to the segment that the provided iterator is pointing into. |
| // |
| // - static It Traits::__compose(__segment_iterator, __local_iterator) |
| // Returns the iterator composed of the segment iterator and local iterator. |
| |
| #include <__config> |
| #include <__type_traits/integral_constant.h> |
| #include <cstddef> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template <class _Iterator> |
| struct __segmented_iterator_traits; |
| /* exposition-only: |
| { |
| using __segment_iterator = ...; |
| using __local_iterator = ...; |
| |
| static __segment_iterator __segment(_Iterator); |
| static __local_iterator __local(_Iterator); |
| static __local_iterator __begin(__segment_iterator); |
| static __local_iterator __end(__segment_iterator); |
| static _Iterator __compose(__segment_iterator, __local_iterator); |
| }; |
| */ |
| |
| template <class _Tp, size_t = 0> |
| struct __has_specialization : false_type {}; |
| |
| template <class _Tp> |
| struct __has_specialization<_Tp, sizeof(_Tp) * 0> : true_type {}; |
| |
| template <class _Iterator> |
| using __is_segmented_iterator = __has_specialization<__segmented_iterator_traits<_Iterator> >; |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___SEGMENTED_ITERATOR_H |