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/iterator_operations.h> 15 #include <__algorithm/min.h> 16 #include <__config> 17 #include <__fwd/bit_reference.h> 18 #include <__iterator/iterator_traits.h> 19 #include <__iterator/segmented_iterator.h> 20 #include <__type_traits/common_type.h> 21 #include <__type_traits/enable_if.h> 22 #include <__type_traits/is_constructible.h> 23 #include <__utility/move.h> 24 #include <__utility/pair.h> 25 26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 27 # pragma GCC system_header 28 #endif 29 30 _LIBCPP_PUSH_MACROS 31 #include <__undef_macros> 32 33 _LIBCPP_BEGIN_NAMESPACE_STD 34 35 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2> 36 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2> 37 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result); 38 39 template <class _AlgPolicy> 40 struct __move_backward_impl { 41 template <class _InIter, class _Sent, class _OutIter> 42 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 43 operator()(_InIter __first, _Sent __last, _OutIter __result) const { 44 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last); 45 auto __original_last_iter = __last_iter; 46 47 while (__first != __last_iter) { 48 *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last_iter); 49 } 50 51 return std::make_pair(std::move(__original_last_iter), std::move(__result)); 52 } 53 54 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0> 55 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 56 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 57 using _Traits = __segmented_iterator_traits<_InIter>; 58 auto __sfirst = _Traits::__segment(__first); 59 auto __slast = _Traits::__segment(__last); 60 if (__sfirst == __slast) { 61 auto __iters = 62 std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result)); 63 return std::make_pair(__last, __iters.second); 64 } 65 66 __result = 67 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result)) 68 .second; 69 --__slast; 70 while (__sfirst != __slast) { 71 __result = 72 std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result)) 73 .second; 74 --__slast; 75 } 76 __result = std::__move_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result)) 77 .second; 78 return std::make_pair(__last, std::move(__result)); 79 } 80 81 template <class _InIter, 82 class _OutIter, 83 __enable_if_t<__has_random_access_iterator_category<_InIter>::value && 84 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value, 85 int> = 0> 86 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 87 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 88 using _Traits = __segmented_iterator_traits<_OutIter>; 89 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type; 90 91 // When the range contains no elements, __result might not be a valid iterator 92 if (__first == __last) 93 return std::make_pair(__first, __result); 94 95 auto __orig_last = __last; 96 97 auto __local_last = _Traits::__local(__result); 98 auto __segment_iterator = _Traits::__segment(__result); 99 while (true) { 100 auto __local_first = _Traits::__begin(__segment_iterator); 101 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first); 102 auto __iter = std::__move_backward<_AlgPolicy>(__last - __size, __last, __local_last).second; 103 __last -= __size; 104 105 if (__first == __last) 106 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter))); 107 108 __local_last = _Traits::__end(--__segment_iterator); 109 } 110 } 111 112 template <class _Cp, bool _IsConst> 113 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cp, _IsConst>, __bit_iterator<_Cp, false> > 114 operator()(__bit_iterator<_Cp, _IsConst> __first, 115 __bit_iterator<_Cp, _IsConst> __last, 116 __bit_iterator<_Cp, false> __result) { 117 return std::__copy_backward<_ClassicAlgPolicy>(__first, __last, __result); 118 } 119 120 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer. 121 template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0> 122 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*> 123 operator()(_In* __first, _In* __last, _Out* __result) const { 124 return std::__copy_backward_trivial_impl(__first, __last, __result); 125 } 126 }; 127 128 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2> 129 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2> 130 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) { 131 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value && 132 std::is_copy_constructible<_BidirectionalIterator1>::value, 133 "Iterators must be copy constructible."); 134 135 return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >( 136 std::move(__first), std::move(__last), std::move(__result)); 137 } 138 139 template <class _BidirectionalIterator1, class _BidirectionalIterator2> 140 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2 141 move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) { 142 return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second; 143 } 144 145 _LIBCPP_END_NAMESPACE_STD 146 147 _LIBCPP_POP_MACROS 148 149 #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H 150