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 <__algorithm/iterator_operations.h>
13#include <__algorithm/move.h>
14#include <__algorithm/move_backward.h>
15#include <__algorithm/swap_ranges.h>
16#include <__config>
17#include <__iterator/iterator_traits.h>
18#include <__utility/move.h>
19#include <__utility/pair.h>
20#include <type_traits>
21
22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23#  pragma GCC system_header
24#endif
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28template <class _AlgPolicy, class _ForwardIterator>
29_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
30__rotate_left(_ForwardIterator __first, _ForwardIterator __last)
31{
32    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
33    using _Ops = _IterOps<_AlgPolicy>;
34
35    value_type __tmp = _Ops::__iter_move(__first);
36    _ForwardIterator __lm1 = std::__move<_AlgPolicy>(
37        _Ops::next(__first), __last, __first).second;
38    *__lm1 = _VSTD::move(__tmp);
39    return __lm1;
40}
41
42template <class _AlgPolicy, class _BidirectionalIterator>
43_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator
44__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
45{
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 = _VSTD::move(__tmp);
53    return __fp1;
54}
55
56template <class _AlgPolicy, class _ForwardIterator>
57_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _ForwardIterator
58__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
59{
60    _ForwardIterator __i = __middle;
61    while (true)
62    {
63        _IterOps<_AlgPolicy>::iter_swap(__first, __i);
64        ++__first;
65        if (++__i == __last)
66            break;
67        if (__first == __middle)
68            __middle = __i;
69    }
70    _ForwardIterator __r = __first;
71    if (__first != __middle)
72    {
73        __i = __middle;
74        while (true)
75        {
76            _IterOps<_AlgPolicy>::iter_swap(__first, __i);
77            ++__first;
78            if (++__i == __last)
79            {
80                if (__first == __middle)
81                    break;
82                __i = __middle;
83            }
84            else if (__first == __middle)
85                __middle = __i;
86        }
87    }
88    return __r;
89}
90
91template<typename _Integral>
92inline _LIBCPP_INLINE_VISIBILITY
93_LIBCPP_CONSTEXPR_SINCE_CXX17 _Integral
94__algo_gcd(_Integral __x, _Integral __y)
95{
96    do
97    {
98        _Integral __t = __x % __y;
99        __x = __y;
100        __y = __t;
101    } while (__y);
102    return __x;
103}
104
105template <class _AlgPolicy, typename _RandomAccessIterator>
106_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _RandomAccessIterator
107__rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
108{
109    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
110    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
111    using _Ops = _IterOps<_AlgPolicy>;
112
113    const difference_type __m1 = __middle - __first;
114    const difference_type __m2 = _Ops::distance(__middle, __last);
115    if (__m1 == __m2)
116    {
117        std::__swap_ranges<_AlgPolicy>(__first, __middle, __middle, __last);
118        return __middle;
119    }
120    const difference_type __g = _VSTD::__algo_gcd(__m1, __m2);
121    for (_RandomAccessIterator __p = __first + __g; __p != __first;)
122    {
123        value_type __t(_Ops::__iter_move(--__p));
124        _RandomAccessIterator __p1 = __p;
125        _RandomAccessIterator __p2 = __p1 + __m1;
126        do
127        {
128            *__p1 = _Ops::__iter_move(__p2);
129            __p1 = __p2;
130            const difference_type __d = _Ops::distance(__p2, __last);
131            if (__m1 < __d)
132                __p2 += __m1;
133            else
134                __p2 = __first + (__m1 - __d);
135        } while (__p2 != __p);
136        *__p1 = _VSTD::move(__t);
137    }
138    return __first + __m2;
139}
140
141template <class _AlgPolicy, class _ForwardIterator>
142inline _LIBCPP_INLINE_VISIBILITY
143_LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
144__rotate_impl(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last,
145         _VSTD::forward_iterator_tag)
146{
147    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
148    if (is_trivially_move_assignable<value_type>::value)
149    {
150        if (_IterOps<_AlgPolicy>::next(__first) == __middle)
151            return std::__rotate_left<_AlgPolicy>(__first, __last);
152    }
153    return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
154}
155
156template <class _AlgPolicy, class _BidirectionalIterator>
157inline _LIBCPP_INLINE_VISIBILITY
158_LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator
159__rotate_impl(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
160         bidirectional_iterator_tag)
161{
162    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
163    if (is_trivially_move_assignable<value_type>::value)
164    {
165        if (_IterOps<_AlgPolicy>::next(__first) == __middle)
166            return std::__rotate_left<_AlgPolicy>(__first, __last);
167        if (_IterOps<_AlgPolicy>::next(__middle) == __last)
168            return std::__rotate_right<_AlgPolicy>(__first, __last);
169    }
170    return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
171}
172
173template <class _AlgPolicy, class _RandomAccessIterator>
174inline _LIBCPP_INLINE_VISIBILITY
175_LIBCPP_CONSTEXPR_SINCE_CXX14 _RandomAccessIterator
176__rotate_impl(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
177         random_access_iterator_tag)
178{
179    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
180    if (is_trivially_move_assignable<value_type>::value)
181    {
182        if (_IterOps<_AlgPolicy>::next(__first) == __middle)
183            return std::__rotate_left<_AlgPolicy>(__first, __last);
184        if (_IterOps<_AlgPolicy>::next(__middle) == __last)
185            return std::__rotate_right<_AlgPolicy>(__first, __last);
186        return std::__rotate_gcd<_AlgPolicy>(__first, __middle, __last);
187    }
188    return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
189}
190
191template <class _AlgPolicy, class _Iterator, class _Sentinel>
192_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
193pair<_Iterator, _Iterator>
194__rotate(_Iterator __first, _Iterator __middle, _Sentinel __last) {
195  using _Ret = pair<_Iterator, _Iterator>;
196  _Iterator __last_iter = _IterOps<_AlgPolicy>::next(__middle, __last);
197
198  if (__first == __middle)
199      return _Ret(__last_iter, __last_iter);
200  if (__middle == __last)
201      return _Ret(std::move(__first), std::move(__last_iter));
202
203  using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_Iterator>;
204  auto __result = std::__rotate_impl<_AlgPolicy>(
205      std::move(__first), std::move(__middle), __last_iter, _IterCategory());
206
207  return _Ret(std::move(__result), std::move(__last_iter));
208}
209
210template <class _ForwardIterator>
211inline _LIBCPP_INLINE_VISIBILITY
212_LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
213rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
214{
215  return std::__rotate<_ClassicAlgPolicy>(
216      std::move(__first), std::move(__middle), std::move(__last)).first;
217}
218
219_LIBCPP_END_NAMESPACE_STD
220
221#endif // _LIBCPP___ALGORITHM_ROTATE_H
222