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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___CXX03___ALGORITHM_MOVE_BACKWARD_H
10#define _LIBCPP___CXX03___ALGORITHM_MOVE_BACKWARD_H
11
12#include <__cxx03/__algorithm/copy_move_common.h>
13#include <__cxx03/__algorithm/iterator_operations.h>
14#include <__cxx03/__algorithm/min.h>
15#include <__cxx03/__config>
16#include <__cxx03/__iterator/segmented_iterator.h>
17#include <__cxx03/__type_traits/common_type.h>
18#include <__cxx03/__type_traits/is_constructible.h>
19#include <__cxx03/__utility/move.h>
20#include <__cxx03/__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 <__cxx03/__undef_macros>
28
29_LIBCPP_BEGIN_NAMESPACE_STD
30
31template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
32_LIBCPP_HIDE_FROM_ABI pair<_BidirectionalIterator1, _BidirectionalIterator2>
33__move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);
34
35template <class _AlgPolicy>
36struct __move_backward_impl {
37 template <class _InIter, class _Sent, class _OutIter>
38 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _Sent __last, _OutIter __result) const {
39 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
40 auto __original_last_iter = __last_iter;
41
42 while (__first != __last_iter) {
43 *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last_iter);
44 }
45
46 return std::make_pair(std::move(__original_last_iter), std::move(__result));
47 }
48
49 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
50 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _InIter __last, _OutIter __result) const {
51 using _Traits = __segmented_iterator_traits<_InIter>;
52 auto __sfirst = _Traits::__segment(__first);
53 auto __slast = _Traits::__segment(__last);
54 if (__sfirst == __slast) {
55 auto __iters =
56 std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
57 return std::make_pair(__last, __iters.second);
58 }
59
60 __result =
61 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
62 .second;
63 --__slast;
64 while (__sfirst != __slast) {
65 __result =
66 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
67 .second;
68 --__slast;
69 }
70 __result = std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
71 .second;
72 return std::make_pair(__last, std::move(__result));
73 }
74
75 template <class _InIter,
76 class _OutIter,
77 __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
78 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
79 int> = 0>
80 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _InIter __last, _OutIter __result) const {
81 using _Traits = __segmented_iterator_traits<_OutIter>;
82 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
83
84 // When the range contains no elements, __result might not be a valid iterator
85 if (__first == __last)
86 return std::make_pair(__first, __result);
87
88 auto __orig_last = __last;
89
90 auto __local_last = _Traits::__local(__result);
91 auto __segment_iterator = _Traits::__segment(__result);
92 while (true) {
93 auto __local_first = _Traits::__begin(__segment_iterator);
94 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first);
95 auto __iter = std::__move_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
96 __last -= __size;
97
98 if (__first == __last)
99 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
100
101 __local_last = _Traits::__end(--__segment_iterator);
102 }
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 pair<_In*, _Out*> operator()(_In* __first, _In* __last, _Out* __result) const {
108 return std::__copy_backward_trivial_impl(__first, __last, __result);
109 }
110};
111
112template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
113_LIBCPP_HIDE_FROM_ABI pair<_BidirectionalIterator1, _BidirectionalIterator2>
114__move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
115 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
116 std::is_copy_constructible<_BidirectionalIterator1>::value,
117 "Iterators must be copy constructible.");
118
119 return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
120 std::move(__first), std::move(__last), std::move(__result));
121}
122
123template <class _BidirectionalIterator1, class _BidirectionalIterator2>
124inline _LIBCPP_HIDE_FROM_ABI _BidirectionalIterator2
125move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
126 return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
127}
128
129_LIBCPP_END_NAMESPACE_STD
130
131_LIBCPP_POP_MACROS
132
133#endif // _LIBCPP___CXX03___ALGORITHM_MOVE_BACKWARD_H
134

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source code of libcxx/include/__cxx03/__algorithm/move_backward.h