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_PARTITION_H
10#define _LIBCPP___ALGORITHM_PARTITION_H
11
12#include <__algorithm/iterator_operations.h>
13#include <__config>
14#include <__iterator/iterator_traits.h>
15#include <__utility/move.h>
16#include <__utility/pair.h>
17#include <type_traits>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20#  pragma GCC system_header
21#endif
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25template <class _Predicate, class _AlgPolicy, class _ForwardIterator, class _Sentinel>
26_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
27__partition_impl(_ForwardIterator __first, _Sentinel __last, _Predicate __pred, forward_iterator_tag)
28{
29    while (true)
30    {
31        if (__first == __last)
32            return std::make_pair(std::move(__first), std::move(__first));
33        if (!__pred(*__first))
34            break;
35        ++__first;
36    }
37
38    _ForwardIterator __p = __first;
39    while (++__p != __last)
40    {
41        if (__pred(*__p))
42        {
43            _IterOps<_AlgPolicy>::iter_swap(__first, __p);
44            ++__first;
45        }
46    }
47    return std::make_pair(std::move(__first), std::move(__p));
48}
49
50template <class _Predicate, class _AlgPolicy, class _BidirectionalIterator, class _Sentinel>
51_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, _BidirectionalIterator>
52__partition_impl(_BidirectionalIterator __first, _Sentinel __sentinel, _Predicate __pred,
53            bidirectional_iterator_tag)
54{
55    _BidirectionalIterator __original_last = _IterOps<_AlgPolicy>::next(__first, __sentinel);
56    _BidirectionalIterator __last = __original_last;
57
58    while (true)
59    {
60        while (true)
61        {
62            if (__first == __last)
63                return std::make_pair(std::move(__first), std::move(__original_last));
64            if (!__pred(*__first))
65                break;
66            ++__first;
67        }
68        do
69        {
70            if (__first == --__last)
71                return std::make_pair(std::move(__first), std::move(__original_last));
72        } while (!__pred(*__last));
73        _IterOps<_AlgPolicy>::iter_swap(__first, __last);
74        ++__first;
75    }
76}
77
78template <class _AlgPolicy, class _ForwardIterator, class _Sentinel, class _Predicate, class _IterCategory>
79inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
80pair<_ForwardIterator, _ForwardIterator> __partition(
81    _ForwardIterator __first, _Sentinel __last, _Predicate&& __pred, _IterCategory __iter_category) {
82  return std::__partition_impl<__remove_cvref_t<_Predicate>&, _AlgPolicy>(
83      std::move(__first), std::move(__last), __pred, __iter_category);
84}
85
86template <class _ForwardIterator, class _Predicate>
87inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
88_ForwardIterator
89partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
90{
91  using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
92  auto __result = std::__partition<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __pred, _IterCategory());
93  return __result.first;
94}
95
96_LIBCPP_END_NAMESPACE_STD
97
98#endif // _LIBCPP___ALGORITHM_PARTITION_H
99