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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_move_common.h>
13 : #include <__algorithm/iterator_operations.h>
14 : #include <__algorithm/min.h>
15 : #include <__config>
16 : #include <__iterator/segmented_iterator.h>
17 : #include <__type_traits/common_type.h>
18 : #include <__type_traits/is_copy_constructible.h>
19 : #include <__utility/move.h>
20 : #include <__utility/pair.h>
21 :
22 : #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 : # pragma GCC system_header
24 : #endif
25 :
26 : _LIBCPP_PUSH_MACROS
27 : #include <__undef_macros>
28 :
29 : _LIBCPP_BEGIN_NAMESPACE_STD
30 :
31 : template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
32 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
33 : __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);
34 :
35 : template <class _AlgPolicy>
36 : struct __move_backward_loop {
37 : template <class _InIter, class _Sent, class _OutIter>
38 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
39 : operator()(_InIter __first, _Sent __last, _OutIter __result) const {
40 : auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
41 : auto __original_last_iter = __last_iter;
42 :
43 : while (__first != __last_iter) {
44 : *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last_iter);
45 : }
46 :
47 : return std::make_pair(std::move(__original_last_iter), std::move(__result));
48 : }
49 :
50 : template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
51 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
52 : operator()(_InIter __first, _InIter __last, _OutIter __result) const {
53 : using _Traits = __segmented_iterator_traits<_InIter>;
54 : auto __sfirst = _Traits::__segment(__first);
55 : auto __slast = _Traits::__segment(__last);
56 : if (__sfirst == __slast) {
57 : auto __iters =
58 : std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
59 : return std::make_pair(__last, __iters.second);
60 : }
61 :
62 : __result =
63 : std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
64 : .second;
65 : --__slast;
66 : while (__sfirst != __slast) {
67 : __result =
68 : std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
69 : .second;
70 : --__slast;
71 : }
72 : __result = std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
73 : .second;
74 : return std::make_pair(__last, std::move(__result));
75 : }
76 :
77 : template <class _InIter,
78 : class _OutIter,
79 : __enable_if_t<__is_cpp17_random_access_iterator<_InIter>::value &&
80 : !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
81 : int> = 0>
82 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
83 : operator()(_InIter __first, _InIter __last, _OutIter __result) {
84 : using _Traits = __segmented_iterator_traits<_OutIter>;
85 : using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
86 :
87 : // When the range contains no elements, __result might not be a valid iterator
88 : if (__first == __last)
89 : return std::make_pair(__first, __result);
90 :
91 : auto __orig_last = __last;
92 :
93 : auto __local_last = _Traits::__local(__result);
94 : auto __segment_iterator = _Traits::__segment(__result);
95 : while (true) {
96 : auto __local_first = _Traits::__begin(__segment_iterator);
97 : auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first);
98 : auto __iter = std::__move_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
99 : __last -= __size;
100 :
101 : if (__first == __last)
102 : return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
103 :
104 : __local_last = _Traits::__end(--__segment_iterator);
105 : }
106 : }
107 : };
108 :
109 : struct __move_backward_trivial {
110 : // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
111 : template <class _In, class _Out,
112 : __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
113 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
114 0 : operator()(_In* __first, _In* __last, _Out* __result) const {
115 0 : return std::__copy_backward_trivial_impl(__first, __last, __result);
116 : }
117 : };
118 :
119 : template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
120 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
121 0 : __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
122 : static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
123 : std::is_copy_constructible<_BidirectionalIterator1>::value, "Iterators must be copy constructible.");
124 :
125 0 : return std::__dispatch_copy_or_move<_AlgPolicy, __move_backward_loop<_AlgPolicy>, __move_backward_trivial>(
126 0 : std::move(__first), std::move(__last), std::move(__result));
127 : }
128 :
129 : template <class _BidirectionalIterator1, class _BidirectionalIterator2>
130 : inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
131 0 : move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
132 0 : return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
133 : }
134 :
135 : _LIBCPP_END_NAMESPACE_STD
136 :
137 : _LIBCPP_POP_MACROS
138 :
139 : #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
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