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