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_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_impl {
37 template <class _InIter, class _Sent, class _OutIter>
38 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
operator__move_backward_impl39 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>
operator__move_backward_impl52 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<__has_random_access_iterator_category<_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>
operator__move_backward_impl83 operator()(_InIter __first, _InIter __last, _OutIter __result) const {
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 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
109 template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
110 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
operator__move_backward_impl111 operator()(_In* __first, _In* __last, _Out* __result) const {
112 return std::__copy_backward_trivial_impl(__first, __last, __result);
113 }
114 };
115
116 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
117 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
__move_backward(_BidirectionalIterator1 __first,_Sentinel __last,_BidirectionalIterator2 __result)118 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
119 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
120 std::is_copy_constructible<_BidirectionalIterator1>::value,
121 "Iterators must be copy constructible.");
122
123 return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
124 std::move(__first), std::move(__last), std::move(__result));
125 }
126
127 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
128 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
move_backward(_BidirectionalIterator1 __first,_BidirectionalIterator1 __last,_BidirectionalIterator2 __result)129 move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
130 return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
131 }
132
133 _LIBCPP_END_NAMESPACE_STD
134
135 _LIBCPP_POP_MACROS
136
137 #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
138