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_COPY_BACKWARD_H
10 #define _LIBCPP___CXX03___ALGORITHM_COPY_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
31 template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
32 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> __copy_backward(_InIter __first, _Sent __last, _OutIter __result);
33
34 template <class _AlgPolicy>
35 struct __copy_backward_impl {
36 template <class _InIter, class _Sent, class _OutIter>
operator__copy_backward_impl37 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _Sent __last, _OutIter __result) const {
38 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
39 auto __original_last_iter = __last_iter;
40
41 while (__first != __last_iter) {
42 *--__result = *--__last_iter;
43 }
44
45 return std::make_pair(std::move(__original_last_iter), std::move(__result));
46 }
47
48 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
operator__copy_backward_impl49 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _InIter __last, _OutIter __result) const {
50 using _Traits = __segmented_iterator_traits<_InIter>;
51 auto __sfirst = _Traits::__segment(__first);
52 auto __slast = _Traits::__segment(__last);
53 if (__sfirst == __slast) {
54 auto __iters =
55 std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result));
56 return std::make_pair(__last, __iters.second);
57 }
58
59 __result =
60 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
61 .second;
62 --__slast;
63 while (__sfirst != __slast) {
64 __result =
65 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
66 .second;
67 --__slast;
68 }
69 __result = std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result))
70 .second;
71 return std::make_pair(__last, std::move(__result));
72 }
73
74 template <class _InIter,
75 class _OutIter,
76 __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
77 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
78 int> = 0>
operator__copy_backward_impl79 _LIBCPP_HIDE_FROM_ABI pair<_InIter, _OutIter> operator()(_InIter __first, _InIter __last, _OutIter __result) const {
80 using _Traits = __segmented_iterator_traits<_OutIter>;
81 auto __orig_last = __last;
82 auto __segment_iterator = _Traits::__segment(__result);
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 __local_last = _Traits::__local(__result);
89 while (true) {
90 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
91
92 auto __local_first = _Traits::__begin(__segment_iterator);
93 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first);
94 auto __iter = std::__copy_backward<_AlgPolicy>(__last - __size, __last, __local_last).second;
95 __last -= __size;
96
97 if (__first == __last)
98 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter)));
99 --__segment_iterator;
100 __local_last = _Traits::__end(__segment_iterator);
101 }
102 }
103
104 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
105 template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
operator__copy_backward_impl106 _LIBCPP_HIDE_FROM_ABI pair<_In*, _Out*> operator()(_In* __first, _In* __last, _Out* __result) const {
107 return std::__copy_backward_trivial_impl(__first, __last, __result);
108 }
109 };
110
111 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
112 _LIBCPP_HIDE_FROM_ABI pair<_BidirectionalIterator1, _BidirectionalIterator2>
__copy_backward(_BidirectionalIterator1 __first,_Sentinel __last,_BidirectionalIterator2 __result)113 __copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
114 return std::__copy_move_unwrap_iters<__copy_backward_impl<_AlgPolicy> >(
115 std::move(__first), std::move(__last), std::move(__result));
116 }
117
118 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
119 inline _LIBCPP_HIDE_FROM_ABI _BidirectionalIterator2
copy_backward(_BidirectionalIterator1 __first,_BidirectionalIterator1 __last,_BidirectionalIterator2 __result)120 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
121 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
122 std::is_copy_constructible<_BidirectionalIterator1>::value,
123 "Iterators must be copy constructible.");
124
125 return std::__copy_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
126 }
127
128 _LIBCPP_END_NAMESPACE_STD
129
130 _LIBCPP_POP_MACROS
131
132 #endif // _LIBCPP___CXX03___ALGORITHM_COPY_BACKWARD_H
133