libcxx/include/__cxx03/__algorithm/move_backward.h

   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 <__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 _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
  32 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
  33 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);
  34
  35 template <class _AlgPolicy>
  36 struct __move_backward_impl {
  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 = _IterOps<_AlgPolicy>::__iter_move(--__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::__move_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::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__local(__last), std::move(__result))
  64             .second;
  65     --__slast;
  66     while (__sfirst != __slast) {
  67       __result =
  68           std::__move_backward<_AlgPolicy>(_Traits::__begin(__slast), _Traits::__end(__slast), std::move(__result))
  69               .second;
  70       --__slast;
  71     }
  72     __result = std::__move_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     using _DiffT  = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;
  86
  87     // When the range contains no elements, __result might not be a valid iterator
  88     if (__first == __last)
  89       return std::make_pair(__first, __result);
  90
  91     auto __orig_last = __last;
  92
  93     auto __local_last       = _Traits::__local(__result);
  94     auto __segment_iterator = _Traits::__segment(__result);
  95     while (true) {
  96       auto __local_first = _Traits::__begin(__segment_iterator);
  97       auto __size        = std::min<_DiffT>(__local_last - __local_first, __last - __first);
  98       auto __iter        = std::__move_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
 104       __local_last = _Traits::__end(--__segment_iterator);
 105     }
 106   }
 107
 108   // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
 109   template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
 110   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
 111   operator()(_In* __first, _In* __last, _Out* __result) const {
 112     return std::__copy_backward_trivial_impl(__first, __last, __result);
 113   }
 114 };
 115
 116 template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
 117 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
 118 __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
 119   static_assert(std::is_copy_constructible<_BidirectionalIterator1>::value &&
 120                     std::is_copy_constructible<_BidirectionalIterator1>::value,
 121                 "Iterators must be copy constructible.");
 122
 123   return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
 124       std::move(__first), std::move(__last), std::move(__result));
 125 }
 126
 127 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
 128 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _BidirectionalIterator2
 129 move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last, _BidirectionalIterator2 __result) {
 130   return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result)).second;
 131 }
 132
 133 _LIBCPP_END_NAMESPACE_STD
 134
 135 _LIBCPP_POP_MACROS
 136
 137 #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H