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/segmented_iterator.h> 17 #include <__type_traits/common_type.h> 18 #include <__type_traits/is_copy_constructible.h> 19 #include <__utility/move.h> 20 #include <__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 <__undef_macros> 28 29 _LIBCPP_BEGIN_NAMESPACE_STD 30 31 template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter> 32 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_InIter, _OutIter> 33 __copy_backward(_InIter __first, _Sent __last, _OutIter __result); 34 35 template <class _AlgPolicy> 36 struct __copy_backward_loop { 37 template <class _InIter, class _Sent, class _OutIter> 38 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 39 operator()(_InIter __first, _Sent __last, _OutIter __result) const { 40 auto __last_iter = _IterOps<_AlgPolicy>::next(__first, __last); 41 auto __original_last_iter = __last_iter; 42 43 while (__first != __last_iter) { 44 *--__result = *--__last_iter; 45 } 46 47 return std::make_pair(std::move(__original_last_iter), std::move(__result)); 48 } 49 50 template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0> 51 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 52 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 53 using _Traits = __segmented_iterator_traits<_InIter>; 54 auto __sfirst = _Traits::__segment(__first); 55 auto __slast = _Traits::__segment(__last); 56 if (__sfirst == __slast) { 57 auto __iters = 58 std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__local(__last), std::move(__result)); 59 return std::make_pair(__last, __iters.second); 60 } 61 62 __result = 63 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result)) 64 .second; 65 --__slast; 66 while (__sfirst != __slast) { 67 __result = 68 std::__copy_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result)) 69 .second; 70 --__slast; 71 } 72 __result = std::__copy_backward<_AlgPolicy>(_Traits::__local(__first), _Traits::__end(__slast), std::move(__result)) 73 .second; 74 return std::make_pair(__last, std::move(__result)); 75 } 76 77 template <class _InIter, 78 class _OutIter, 79 __enable_if_t<__has_random_access_iterator_category<_InIter>::value && 80 !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value, 81 int> = 0> 82 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> 83 operator()(_InIter __first, _InIter __last, _OutIter __result) const { 84 using _Traits = __segmented_iterator_traits<_OutIter>; 85 auto __orig_last = __last; 86 auto __segment_iterator = _Traits::__segment(__result); 87 88 // When the range contains no elements, __result might not be a valid iterator 89 if (__first == __last) 90 return std::make_pair(__first, __result); 91 92 auto __local_last = _Traits::__local(__result); 93 while (true) { 94 using _DiffT = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type; 95 96 auto __local_first = _Traits::__begin(__segment_iterator); 97 auto __size = std::min<_DiffT>(__local_last - __local_first, __last - __first); 98 auto __iter = std::__copy_backward<_AlgPolicy>(__last - __size, __last, __local_last).second; 99 __last -= __size; 100 101 if (__first == __last) 102 return std::make_pair(std::move(__orig_last), _Traits::__compose(__segment_iterator, std::move(__iter))); 103 --__segment_iterator; 104 __local_last = _Traits::__end(__segment_iterator); 105 } 106 } 107 }; 108 109 struct __copy_backward_trivial { 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, 112 __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0> 113 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*> 114 operator()(_In* __first, _In* __last, _Out* __result) const { 115 return std::__copy_backward_trivial_impl(__first, __last, __result); 116 } 117 }; 118 119 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2> 120 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2> 121 __copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) { 122 return std::__dispatch_copy_or_move<_AlgPolicy, __copy_backward_loop<_AlgPolicy>, __copy_backward_trivial>( 123 std::move(__first), std::move(__last), std::move(__result)); 124 } 125 126 template <class _BidirectionalIterator1, class _BidirectionalIterator2> 127 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 128 _BidirectionalIterator2 129 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, 130 _BidirectionalIterator2 __result) 131 { 132 static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value && 133 std::is_copy_constructible<_BidirectionalIterator1>::value, "Iterators must be copy constructible."); 134 135 return std::__copy_backward<_ClassicAlgPolicy>( 136 std::move(__first), std::move(__last), std::move(__result)).second; 137 } 138 139 _LIBCPP_END_NAMESPACE_STD 140 141 _LIBCPP_POP_MACROS 142 143 #endif // _LIBCPP___ALGORITHM_COPY_BACKWARD_H 144