libcxx/include/__algorithm/rotate.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_ROTATE_H
#define _LIBCPP___ALGORITHM_ROTATE_H

#include <__algorithm/copy.h>
#include <__algorithm/copy_backward.h>
#include <__algorithm/iterator_operations.h>
#include <__algorithm/min.h>
#include <__algorithm/move.h>
#include <__algorithm/move_backward.h>
#include <__algorithm/swap_ranges.h>
#include <__config>
#include <__fwd/bit_reference.h>
#include <__iterator/iterator_traits.h>
#include <__type_traits/is_trivially_assignable.h>
#include <__utility/move.h>
#include <__utility/pair.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _AlgPolicy, class _ForwardIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
__rotate_left(_ForwardIterator __first, _ForwardIterator __last) {
  typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
  using _Ops = _IterOps<_AlgPolicy>;

  value_type __tmp       = _Ops::__iter_move(__first);
  _ForwardIterator __lm1 = std::__move<_AlgPolicy>(_Ops::next(__first), __last, __first).__out_;
  *__lm1                 = std::move(__tmp);
  return __lm1;
}

template <class _AlgPolicy, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator
__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last) {
  typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
  using _Ops = _IterOps<_AlgPolicy>;

  _BidirectionalIterator __lm1 = _Ops::prev(__last);
  value_type __tmp             = _Ops::__iter_move(__lm1);
  _BidirectionalIterator __fp1 = std::__move_backward<_AlgPolicy>(__first, __lm1, std::move(__last)).__out_;
  *__first                     = std::move(__tmp);
  return __fp1;
}

template <class _AlgPolicy, class _ForwardIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _ForwardIterator
__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
  _ForwardIterator __i = __middle;
  while (true) {
    _IterOps<_AlgPolicy>::iter_swap(__first, __i);
    ++__first;
    if (++__i == __last)
      break;
    if (__first == __middle)
      __middle = __i;
  }
  _ForwardIterator __r = __first;
  if (__first != __middle) {
    __i = __middle;
    while (true) {
      _IterOps<_AlgPolicy>::iter_swap(__first, __i);
      ++__first;
      if (++__i == __last) {
        if (__first == __middle)
          break;
        __i = __middle;
      } else if (__first == __middle)
        __middle = __i;
    }
  }
  return __r;
}

template <class _AlgPolicy, class _Iter, class _Sent>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter
__rotate_random_access(_Iter __first, _Iter __middle, _Sent __sent) {
  auto __left  = _IterOps<_AlgPolicy>::distance(__first, __middle);
  auto __right = _IterOps<_AlgPolicy>::distance(__middle, __sent);
  auto __last  = __first + __right;

  auto __min_len = std::min(__left, __right);

  while (__min_len > 0) {
    if (__left <= __right) {
      do {
        std::__swap_ranges<_AlgPolicy>(__first, __first + __left, __first + __left);
        __first += __left;
        __right -= __left;
      } while (__left <= __right);
      __min_len = __right;
    } else {
      do {
        std::__swap_ranges<_AlgPolicy>(__first + (__left - __right), __first + __left, __first + __left);
        __left -= __right;
      } while (__left > __right);
      __min_len = __left;
    }
  }
  return __last;
}

template <class _AlgPolicy, class _ForwardIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
__rotate_impl(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, std::forward_iterator_tag) {
  typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
  if (is_trivially_move_assignable<value_type>::value) {
    if (_IterOps<_AlgPolicy>::next(__first) == __middle)
      return std::__rotate_left<_AlgPolicy>(__first, __last);
  }
  return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
}

template <class _AlgPolicy, class _BidirectionalIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _BidirectionalIterator __rotate_impl(
    _BidirectionalIterator __first,
    _BidirectionalIterator __middle,
    _BidirectionalIterator __last,
    bidirectional_iterator_tag) {
  typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
  if (is_trivially_move_assignable<value_type>::value) {
    if (_IterOps<_AlgPolicy>::next(__first) == __middle)
      return std::__rotate_left<_AlgPolicy>(__first, __last);
    if (_IterOps<_AlgPolicy>::next(__middle) == __last)
      return std::__rotate_right<_AlgPolicy>(__first, __last);
  }
  return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
}

template <class _AlgPolicy, class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _RandomAccessIterator __rotate_impl(
    _RandomAccessIterator __first,
    _RandomAccessIterator __middle,
    _RandomAccessIterator __last,
    random_access_iterator_tag) {
  typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
  if (is_trivially_move_assignable<value_type>::value) {
    if (_IterOps<_AlgPolicy>::next(__first) == __middle)
      return std::__rotate_left<_AlgPolicy>(__first, __last);
    if (_IterOps<_AlgPolicy>::next(__middle) == __last)
      return std::__rotate_right<_AlgPolicy>(__first, __last);
    return std::__rotate_random_access<_AlgPolicy>(__first, __middle, __last);
  }
  return std::__rotate_forward<_AlgPolicy>(__first, __middle, __last);
}

template <class _AlgPolicy, class _Iterator, class _Sentinel>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iterator, _Iterator>
__rotate(_Iterator __first, _Iterator __middle, _Sentinel __last) {
  using _Ret            = pair<_Iterator, _Iterator>;
  _Iterator __last_iter = _IterOps<_AlgPolicy>::next(__middle, __last);

  if (__first == __middle)
    return _Ret(__last_iter, __last_iter);
  if (__middle == __last)
    return _Ret(std::move(__first), std::move(__last_iter));

  using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_Iterator>;
  auto __result = std::__rotate_impl<_AlgPolicy>(std::move(__first), std::move(__middle), __last_iter, _IterCategory());

  return _Ret(std::move(__result), std::move(__last_iter));
}

template <class, class _Cp>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cp, false>, __bit_iterator<_Cp, false> >
__rotate(__bit_iterator<_Cp, false> __first, __bit_iterator<_Cp, false> __middle, __bit_iterator<_Cp, false> __last) {
  using _I1             = __bit_iterator<_Cp, false>;
  using difference_type = typename _I1::difference_type;
  difference_type __d1  = __middle - __first;
  difference_type __d2  = __last - __middle;
  _I1 __r               = __first + __d2;
  while (__d1 != 0 && __d2 != 0) {
    if (__d1 <= __d2) {
      if (__d1 <= __bit_array<_Cp>::capacity()) {
        __bit_array<_Cp> __b(__d1);
        std::copy(__first, __middle, __b.begin());
        std::copy(__b.begin(), __b.end(), std::copy(__middle, __last, __first));
        break;
      } else {
        __bit_iterator<_Cp, false> __mp = std::swap_ranges(__first, __middle, __middle);
        __first                         = __middle;
        __middle                        = __mp;
        __d2 -= __d1;
      }
    } else {
      if (__d2 <= __bit_array<_Cp>::capacity()) {
        __bit_array<_Cp> __b(__d2);
        std::copy(__middle, __last, __b.begin());
        std::copy_backward(__b.begin(), __b.end(), std::copy_backward(__first, __middle, __last));
        break;
      } else {
        __bit_iterator<_Cp, false> __mp = __first + __d2;
        std::swap_ranges(__first, __mp, __middle);
        __first = __mp;
        __d1 -= __d2;
      }
    }
  }
  return std::make_pair(__r, __last);
}

template <class _ForwardIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) {
  return std::__rotate<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last)).first;
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_ROTATE_H