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_COPY_BACKWARD_H 10 #define _LIBCPP___ALGORITHM_COPY_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/iterator_traits.h> 17 #include <__iterator/segmented_iterator.h> 18 #include <__type_traits/common_type.h> 19 #include <__type_traits/enable_if.h> 20 #include <__type_traits/is_constructible.h> 21 #include <__utility/move.h> 22 #include <__utility/pair.h> 23 24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 25 # pragma GCC system_header 26 #endif 27 28 _LIBCPP_PUSH_MACROS 29 #include <__undef_macros> 30 31 _LIBCPP_BEGIN_NAMESPACE_STD 32 33 template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter> 34 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_InIter, _OutIter> 35 __copy_backward(_InIter __first, _Sent __last, _OutIter __result); 36 37 template <class _AlgPolicy> 38 struct __copy_backward_impl { 39 template <class _InIter, class _Sent, class _OutIter> 40 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 41 operator()(_InIter __first, _Sent __last, _OutIter __result) const { 42 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last); 43 auto __original_last_iter = __last_iter; 44 45 while (__first != __last_iter) { 46 *--__result = *--__last_iter; 47 } 48 49 return std::make_pair(std::move(__original_last_iter), std::move(__result)); 50 } 51 52 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0> 53 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 54 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 55 using _Traits = __segmented_iterator_traits<_InIter>; 56 auto __sfirst = _Traits::__segment(__first); 57 auto __slast = _Traits::__segment(__last); 58 if (__sfirst == __slast) { 59 auto __iters = 60 std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result)); 61 return std::make_pair(__last, __iters.second); 62 } 63 64 __result = 65 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result)) 66 .second; 67 --__slast; 68 while (__sfirst != __slast) { 69 __result = 70 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result)) 71 .second; 72 --__slast; 73 } 74 __result = std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result)) 75 .second; 76 return std::make_pair(__last, std::move(__result)); 77 } 78 79 template <class _InIter, 80 class _OutIter, 81 __enable_if_t<__has_random_access_iterator_category<_InIter>::value && 82 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value, 83 int> = 0> 84 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 85 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 86 using _Traits = __segmented_iterator_traits<_OutIter>; 87 auto __orig_last = __last; 88 auto __segment_iterator = _Traits::__segment(__result); 89 90 // When the range contains no elements, __result might not be a valid iterator 91 if (__first == __last) 92 return std::make_pair(__first, __result); 93 94 auto __local_last = _Traits::__local(__result); 95 while (true) { 96 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type; 97 98 auto __local_first = _Traits::__begin(__segment_iterator); 99 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first); 100 auto __iter = std::__copy_backward<_AlgPolicy>(__last - __size, __last, __local_last).second; 101 __last -= __size; 102 103 if (__first == __last) 104 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter))); 105 --__segment_iterator; 106 __local_last = _Traits::__end(__segment_iterator); 107 } 108 } 109 110 // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer. 111 template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0> 112 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*> 113 operator()(_In* __first, _In* __last, _Out* __result) const { 114 return std::__copy_backward_trivial_impl(__first, __last, __result); 115 } 116 }; 117 118 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2> 119 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2> 120 __copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) { 121 return std::__copy_move_unwrap_iters<__copy_backward_impl<_AlgPolicy> >( 122 std::move(__first), std::move(__last), std::move(__result)); 123 } 124 125 template <class _BidirectionalIterator1, class _BidirectionalIterator2> 126 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2 127 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) { 128 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value && 129 std::is_copy_constructible<_BidirectionalIterator1>::value, 130 "Iterators must be copy constructible."); 131 132 return std::__copy_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second; 133 } 134 135 _LIBCPP_END_NAMESPACE_STD 136 137 _LIBCPP_POP_MACROS 138 139 #endif // _LIBCPP___ALGORITHM_COPY_BACKWARD_H 140