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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___ALGORITHM_MOVE_BACKWARD_H
10#define _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
11
12#include <__algorithm/copy_backward.h>
13#include <__algorithm/copy_move_common.h>
14#include <__algorithm/iterator_operations.h>
15#include <__algorithm/min.h>
16#include <__config>
17#include <__fwd/bit_reference.h>
18#include <__iterator/iterator_traits.h>
19#include <__iterator/segmented_iterator.h>
20#include <__type_traits/common_type.h>
21#include <__type_traits/enable_if.h>
22#include <__type_traits/is_constructible.h>
23#include <__utility/move.h>
24#include <__utility/pair.h>
25
26#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27# pragma GCC system_header
28#endif
29
30_LIBCPP_PUSH_MACROS
31#include <__undef_macros>
32
33_LIBCPP_BEGIN_NAMESPACE_STD
34
35template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
36_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
37__move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);
38
39template <class _AlgPolicy>
40struct __move_backward_impl {
41 template <class _InIter, class _Sent, class _OutIter>
42 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
43 operator()(_InIter __first, _Sent __last, _OutIter __result) const {
44 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
45 auto __original_last_iter = __last_iter;
46
47 while (__first != __last_iter) {
48 *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last_iter);
49 }
50
51 return std::make_pair(std::move(__original_last_iter), std::move(__result));
52 }
53
54 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
55 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
56 operator()(_InIter __first, _InIter __last, _OutIter __result) const {
57 using _Traits = __segmented_iterator_traits<_InIter>;
58 auto __sfirst = _Traits::__segment(__first);
59 auto __slast = _Traits::__segment(__last);
60 if (__sfirst == __slast) {
61 auto __iters =
62 std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
63 return std::make_pair(__last, __iters.second);
64 }
65
66 __result =
67 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
68 .second;
69 --__slast;
70 while (__sfirst != __slast) {
71 __result =
72 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
73 .second;
74 --__slast;
75 }
76 __result = std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
77 .second;
78 return std::make_pair(__last, std::move(__result));
79 }
80
81 template <class _InIter,
82 class _OutIter,
83 __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
84 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
85 int> = 0>
86 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
87 operator()(_InIter __first, _InIter __last, _OutIter __result) const {
88 using _Traits = __segmented_iterator_traits<_OutIter>;
89 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
90
91 // When the range contains no elements, __result might not be a valid iterator
92 if (__first == __last)
93 return std::make_pair(__first, __result);
94
95 auto __orig_last = __last;
96
97 auto __local_last = _Traits::__local(__result);
98 auto __segment_iterator = _Traits::__segment(__result);
99 while (true) {
100 auto __local_first = _Traits::__begin(__segment_iterator);
101 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first);
102 auto __iter = std::__move_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
103 __last -= __size;
104
105 if (__first == __last)
106 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
107
108 __local_last = _Traits::__end(--__segment_iterator);
109 }
110 }
111
112 template <class _Cp, bool _IsConst>
113 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cp, _IsConst>, __bit_iterator<_Cp, false> >
114 operator()(__bit_iterator<_Cp, _IsConst> __first,
115 __bit_iterator<_Cp, _IsConst> __last,
116 __bit_iterator<_Cp, false> __result) {
117 return std::__copy_backward<_ClassicAlgPolicy>(__first, __last, __result);
118 }
119
120 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
121 template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
122 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
123 operator()(_In* __first, _In* __last, _Out* __result) const {
124 return std::__copy_backward_trivial_impl(__first, __last, __result);
125 }
126};
127
128template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
129_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
130__move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
131 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
132 std::is_copy_constructible<_BidirectionalIterator1>::value,
133 "Iterators must be copy constructible.");
134
135 return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
136 std::move(__first), std::move(__last), std::move(__result));
137}
138
139template <class _BidirectionalIterator1, class _BidirectionalIterator2>
140inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
141move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
142 return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
143}
144
145_LIBCPP_END_NAMESPACE_STD
146
147_LIBCPP_POP_MACROS
148
149#endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H