libcxx/include/__algorithm/ranges_swap_ranges.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_RANGES_SWAP_RANGES_H
#define _LIBCPP___ALGORITHM_RANGES_SWAP_RANGES_H

#include <__algorithm/in_in_result.h>
#include <__algorithm/iterator_operations.h>
#include <__algorithm/min.h>
#include <__algorithm/swap_ranges.h>
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/iter_swap.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/dangling.h>
#include <__type_traits/is_same.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>

#if _LIBCPP_STD_VER >= 20

_LIBCPP_BEGIN_NAMESPACE_STD

namespace ranges {

template <class _I1, class _I2>
using swap_ranges_result = in_in_result<_I1, _I2>;

struct __swap_ranges {
  template <input_iterator _I1, sentinel_for<_I1> _S1, input_iterator _I2, sentinel_for<_I2> _S2>
    requires indirectly_swappable<_I1, _I2>
  _LIBCPP_HIDE_FROM_ABI constexpr swap_ranges_result<_I1, _I2>
  operator()(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2) const {
    if constexpr (sized_sentinel_for<_I1, _S1> && sized_sentinel_for<_I2, _S2> &&
                  (random_access_iterator<_I1> || random_access_iterator<_I2> ||
                   (is_same_v<_I1, _S1> && is_same_v<_I2, _S2>))) {
      auto __offset = std::min(__last1 - __first1, __last2 - __first2);

      auto __ret = [&] {
        if constexpr (random_access_iterator<_I1>)
          return std::__swap_ranges<_RangeAlgPolicy>(__first1, __first1 + __offset, std::move(__first2));
        else if constexpr (random_access_iterator<_I2>)
          return std::__swap_ranges<_RangeAlgPolicy>(__first2, __first2 + __offset, std::move(__first1));
        else if (__last2 - __first2 < __last1 - __first1) {
          auto __reversed =
              std::__swap_ranges<_RangeAlgPolicy>(std::move(__first2), std::move(__last2), std::move(__first1));
          return std::pair<_I1, _I2>(std::move(__reversed.second), std::move(__reversed.first));
        } else
          return std::__swap_ranges<_RangeAlgPolicy>(std::move(__first1), std::move(__last1), std::move(__first2));
      }();
      return {std::move(__ret.first), std::move(__ret.second)};
    } else {
      while (__first1 != __last1 && __first2 != __last2) {
        ranges::iter_swap(__first1, __first2);
        ++__first1;
        ++__first2;
      }

      return {std::move(__first1), std::move(__first2)};
    }
  }

  template <input_range _R1, input_range _R2>
    requires indirectly_swappable<iterator_t<_R1>, iterator_t<_R2>>
  _LIBCPP_HIDE_FROM_ABI constexpr swap_ranges_result<borrowed_iterator_t<_R1>, borrowed_iterator_t<_R2>>
  operator()(_R1&& __r1, _R2&& __r2) const {
    return operator()(ranges::begin(__r1), ranges::end(__r1), ranges::begin(__r2), ranges::end(__r2));
  }
};

inline namespace __cpo {
inline constexpr auto swap_ranges = __swap_ranges{};
} // namespace __cpo
} // namespace ranges

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_STD_VER >= 20

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_RANGES_SWAP_RANGES_H