libcxx/include/__cxx03/__algorithm/rotate.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_ROTATE_H
  10 #define _LIBCPP___ALGORITHM_ROTATE_H
  11
  12 #include <__cxx03/__algorithm/iterator_operations.h>
  13 #include <__cxx03/__algorithm/move.h>
  14 #include <__cxx03/__algorithm/move_backward.h>
  15 #include <__cxx03/__algorithm/swap_ranges.h>
  16 #include <__cxx03/__config>
  17 #include <__cxx03/__iterator/iterator_traits.h>
  18 #include <__cxx03/__type_traits/is_trivially_assignable.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 _ForwardIterator>
  32 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
  33 __rotate_left(_ForwardIterator __first, _ForwardIterator __last) {
  34   typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
  35   using _Ops = _IterOps<_AlgPolicy>;
  36
  37   value_type __tmp       = _Ops::__iter_move(__first);
  38   _ForwardIterator __lm1 = std::__move<_AlgPolicy>(_Ops::next(__first), __last, __first).second;
  39   *__lm1                 = std::move(__tmp);
  40   return __lm1;
  41 }
  42
  43 template <class _AlgPolicy, class _BidirectionalIterator>
  44 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator
  45 __rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last) {
  46   typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
  47   using _Ops = _IterOps<_AlgPolicy>;
  48
  49   _BidirectionalIterator __lm1 = _Ops::prev(__last);
  50   value_type __tmp             = _Ops::__iter_move(__lm1);
  51   _BidirectionalIterator __fp1 = std::__move_backward<_AlgPolicy>(__first, __lm1, std::move(__last)).second;
  52   *__first                     = std::move(__tmp);
  53   return __fp1;
  54 }
  55
  56 template <class _AlgPolicy, class _ForwardIterator>
  57 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _ForwardIterator
  58 __rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
  59   _ForwardIterator __i = __middle;
  60   while (true) {
  61     _IterOps<_AlgPolicy>::iter_swap(__first, __i);
  62     ++__first;
  63     if (++__i == __last)
  64       break;
  65     if (__first == __middle)
  66       __middle = __i;
  67   }
  68   _ForwardIterator __r = __first;
  69   if (__first != __middle) {
  70     __i = __middle;
  71     while (true) {
  72       _IterOps<_AlgPolicy>::iter_swap(__first, __i);
  73       ++__first;
  74       if (++__i == __last) {
  75         if (__first == __middle)
  76           break;
  77         __i = __middle;
  78       } else if (__first == __middle)
  79         __middle = __i;
  80     }
  81   }
  82   return __r;
  83 }
  84
  85 template <typename _Integral>
  86 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Integral __algo_gcd(_Integral __x, _Integral __y) {
  87   do {
  88     _Integral __t = __x % __y;
  89     __x           = __y;
  90     __y           = __t;
  91   } while (__y);
  92   return __x;
  93 }
  94
  95 template <class _AlgPolicy, typename _RandomAccessIterator>
  96 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _RandomAccessIterator
  97 __rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last) {
  98   typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
  99   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
 100   using _Ops = _IterOps<_AlgPolicy>;
 101
 102   const difference_type __m1 = __middle - __first;
 103   const difference_type __m2 = _Ops::distance(__middle, __last);
 104   if (__m1 == __m2) {
 105     std::__swap_ranges<_AlgPolicy>(__first, __middle, __middle, __last);
 106     return __middle;
 107   }
 108   const difference_type __g = std::__algo_gcd(__m1, __m2);
 109   for (_RandomAccessIterator __p = __first + __g; __p != __first;) {
 110     value_type __t(_Ops::__iter_move(--__p));
 111     _RandomAccessIterator __p1 = __p;
 112     _RandomAccessIterator __p2 = __p1 + __m1;
 113     do {
 114       *__p1                     = _Ops::__iter_move(__p2);
 115       __p1                      = __p2;
 116       const difference_type __d = _Ops::distance(__p2, __last);
 117       if (__m1 < __d)
 118         __p2 += __m1;
 119       else
 120         __p2 = __first + (__m1 - __d);
 121     } while (__p2 != __p);
 122     *__p1 = std::move(__t);
 123   }
 124   return __first + __m2;
 125 }
 126
 127 template <class _AlgPolicy, class _ForwardIterator>
 128 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
 129 __rotate_impl(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, std::forward_iterator_tag) {
 130   typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
 131   if (is_trivially_move_assignable<value_type>::value) {
 132     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
 133       return std::__rotate_left<_AlgPolicy>(__first, __last);
 134   }
 135   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
 136 }
 137
 138 template <class _AlgPolicy, class _BidirectionalIterator>
 139 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator __rotate_impl(
 140     _BidirectionalIterator __first,
 141     _BidirectionalIterator __middle,
 142     _BidirectionalIterator __last,
 143     bidirectional_iterator_tag) {
 144   typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
 145   if (is_trivially_move_assignable<value_type>::value) {
 146     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
 147       return std::__rotate_left<_AlgPolicy>(__first, __last);
 148     if (_IterOps<_AlgPolicy>::next(__middle) == __last)
 149       return std::__rotate_right<_AlgPolicy>(__first, __last);
 150   }
 151   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
 152 }
 153
 154 template <class _AlgPolicy, class _RandomAccessIterator>
 155 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _RandomAccessIterator __rotate_impl(
 156     _RandomAccessIterator __first,
 157     _RandomAccessIterator __middle,
 158     _RandomAccessIterator __last,
 159     random_access_iterator_tag) {
 160   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
 161   if (is_trivially_move_assignable<value_type>::value) {
 162     if (_IterOps<_AlgPolicy>::next(__first) == __middle)
 163       return std::__rotate_left<_AlgPolicy>(__first, __last);
 164     if (_IterOps<_AlgPolicy>::next(__middle) == __last)
 165       return std::__rotate_right<_AlgPolicy>(__first, __last);
 166     return std::__rotate_gcd<_AlgPolicy>(__first, __middle, __last);
 167   }
 168   return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
 169 }
 170
 171 template <class _AlgPolicy, class _Iterator, class _Sentinel>
 172 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iterator, _Iterator>
 173 __rotate(_Iterator __first, _Iterator __middle, _Sentinel __last) {
 174   using _Ret            = pair<_Iterator, _Iterator>;
 175   _Iterator __last_iter = _IterOps<_AlgPolicy>::next(__middle, __last);
 176
 177   if (__first == __middle)
 178     return _Ret(__last_iter, __last_iter);
 179   if (__middle == __last)
 180     return _Ret(std::move(__first), std::move(__last_iter));
 181
 182   using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_Iterator>;
 183   auto __result = std::__rotate_impl<_AlgPolicy>(std::move(__first), std::move(__middle), __last_iter, _IterCategory());
 184
 185   return _Ret(std::move(__result), std::move(__last_iter));
 186 }
 187
 188 template <class _ForwardIterator>
 189 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 190 rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
 191   return std::__rotate<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last)).first;
 192 }
 193
 194 _LIBCPP_END_NAMESPACE_STD
 195
 196 _LIBCPP_POP_MACROS
 197
 198 #endif // _LIBCPP___ALGORITHM_ROTATE_H