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 <__type_traits/integral_constant.h>
45#include <cstddef>
46
47#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
48#  pragma GCC system_header
49#endif
50
51_LIBCPP_BEGIN_NAMESPACE_STD
52
53template <class _Iterator>
54struct __segmented_iterator_traits;
55/* exposition-only:
56{
57  using __segment_iterator = ...;
58  using __local_iterator   = ...;
59
60  static __segment_iterator __segment(_Iterator);
61  static __local_iterator __local(_Iterator);
62  static __local_iterator __begin(__segment_iterator);
63  static __local_iterator __end(__segment_iterator);
64  static _Iterator __compose(__segment_iterator, __local_iterator);
65};
66*/
67
68template <class _Tp, size_t = 0>
69struct __has_specialization : false_type {};
70
71template <class _Tp>
72struct __has_specialization<_Tp, sizeof(_Tp) * 0> : true_type {};
73
74template <class _Iterator>
75using __is_segmented_iterator = __has_specialization<__segmented_iterator_traits<_Iterator> >;
76
77_LIBCPP_END_NAMESPACE_STD
78
79#endif // _LIBCPP___SEGMENTED_ITERATOR_H
80