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_INPLACE_MERGE_H
10#define _LIBCPP___ALGORITHM_INPLACE_MERGE_H
11
12#include <__algorithm/comp.h>
13#include <__algorithm/comp_ref_type.h>
14#include <__algorithm/iterator_operations.h>
15#include <__algorithm/lower_bound.h>
16#include <__algorithm/min.h>
17#include <__algorithm/move.h>
18#include <__algorithm/rotate.h>
19#include <__algorithm/upper_bound.h>
20#include <__config>
21#include <__functional/identity.h>
22#include <__iterator/advance.h>
23#include <__iterator/distance.h>
24#include <__iterator/iterator_traits.h>
25#include <__iterator/reverse_iterator.h>
26#include <__memory/destruct_n.h>
27#include <__memory/temporary_buffer.h>
28#include <__memory/unique_ptr.h>
29#include <__utility/pair.h>
30#include <new>
31
32#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
33#  pragma GCC system_header
34#endif
35
36_LIBCPP_PUSH_MACROS
37#include <__undef_macros>
38
39_LIBCPP_BEGIN_NAMESPACE_STD
40
41template <class _Predicate>
42class __invert // invert the sense of a comparison
43{
44private:
45  _Predicate __p_;
46
47public:
48  _LIBCPP_HIDE_FROM_ABI __invert() {}
49
50  _LIBCPP_HIDE_FROM_ABI explicit __invert(_Predicate __p) : __p_(__p) {}
51
52  template <class _T1>
53  _LIBCPP_HIDE_FROM_ABI bool operator()(const _T1& __x) {
54    return !__p_(__x);
55  }
56
57  template <class _T1, class _T2>
58  _LIBCPP_HIDE_FROM_ABI bool operator()(const _T1& __x, const _T2& __y) {
59    return __p_(__y, __x);
60  }
61};
62
63template <class _AlgPolicy,
64          class _Compare,
65          class _InputIterator1,
66          class _Sent1,
67          class _InputIterator2,
68          class _Sent2,
69          class _OutputIterator>
70_LIBCPP_HIDE_FROM_ABI void __half_inplace_merge(
71    _InputIterator1 __first1,
72    _Sent1 __last1,
73    _InputIterator2 __first2,
74    _Sent2 __last2,
75    _OutputIterator __result,
76    _Compare&& __comp) {
77  for (; __first1 != __last1; ++__result) {
78    if (__first2 == __last2) {
79      std::__move<_AlgPolicy>(__first1, __last1, __result);
80      return;
81    }
82
83    if (__comp(*__first2, *__first1)) {
84      *__result = _IterOps<_AlgPolicy>::__iter_move(__first2);
85      ++__first2;
86    } else {
87      *__result = _IterOps<_AlgPolicy>::__iter_move(__first1);
88      ++__first1;
89    }
90  }
91  // __first2 through __last2 are already in the right spot.
92}
93
94template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
95_LIBCPP_HIDE_FROM_ABI void __buffered_inplace_merge(
96    _BidirectionalIterator __first,
97    _BidirectionalIterator __middle,
98    _BidirectionalIterator __last,
99    _Compare&& __comp,
100    typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
101    typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
102    typename iterator_traits<_BidirectionalIterator>::value_type* __buff) {
103  typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
104  __destruct_n __d(0);
105  unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
106  if (__len1 <= __len2) {
107    value_type* __p = __buff;
108    for (_BidirectionalIterator __i = __first; __i != __middle;
109         __d.template __incr<value_type>(), (void)++__i, (void)++__p)
110      ::new ((void*)__p) value_type(_IterOps<_AlgPolicy>::__iter_move(__i));
111    std::__half_inplace_merge<_AlgPolicy>(__buff, __p, __middle, __last, __first, __comp);
112  } else {
113    value_type* __p = __buff;
114    for (_BidirectionalIterator __i = __middle; __i != __last;
115         __d.template __incr<value_type>(), (void)++__i, (void)++__p)
116      ::new ((void*)__p) value_type(_IterOps<_AlgPolicy>::__iter_move(__i));
117    typedef __unconstrained_reverse_iterator<_BidirectionalIterator> _RBi;
118    typedef __unconstrained_reverse_iterator<value_type*> _Rv;
119    typedef __invert<_Compare> _Inverted;
120    std::__half_inplace_merge<_AlgPolicy>(
121        _Rv(__p), _Rv(__buff), _RBi(__middle), _RBi(__first), _RBi(__last), _Inverted(__comp));
122  }
123}
124
125template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
126void __inplace_merge(
127    _BidirectionalIterator __first,
128    _BidirectionalIterator __middle,
129    _BidirectionalIterator __last,
130    _Compare&& __comp,
131    typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
132    typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
133    typename iterator_traits<_BidirectionalIterator>::value_type* __buff,
134    ptrdiff_t __buff_size) {
135  using _Ops = _IterOps<_AlgPolicy>;
136
137  typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
138  while (true) {
139    // if __middle == __last, we're done
140    if (__len2 == 0)
141      return;
142    if (__len1 <= __buff_size || __len2 <= __buff_size)
143      return std::__buffered_inplace_merge<_AlgPolicy>(__first, __middle, __last, __comp, __len1, __len2, __buff);
144    // shrink [__first, __middle) as much as possible (with no moves), returning if it shrinks to 0
145    for (; true; ++__first, (void)--__len1) {
146      if (__len1 == 0)
147        return;
148      if (__comp(*__middle, *__first))
149        break;
150    }
151    // __first < __middle < __last
152    // *__first > *__middle
153    // partition [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last) such that
154    //     all elements in:
155    //         [__first, __m1)  <= [__middle, __m2)
156    //         [__middle, __m2) <  [__m1, __middle)
157    //         [__m1, __middle) <= [__m2, __last)
158    //     and __m1 or __m2 is in the middle of its range
159    _BidirectionalIterator __m1; // "median" of [__first, __middle)
160    _BidirectionalIterator __m2; // "median" of [__middle, __last)
161    difference_type __len11;     // distance(__first, __m1)
162    difference_type __len21;     // distance(__middle, __m2)
163    // binary search smaller range
164    if (__len1 < __len2) { // __len >= 1, __len2 >= 2
165      __len21 = __len2 / 2;
166      __m2    = __middle;
167      _Ops::advance(__m2, __len21);
168      __m1    = std::__upper_bound<_AlgPolicy>(__first, __middle, *__m2, __comp, std::__identity());
169      __len11 = _Ops::distance(__first, __m1);
170    } else {
171      if (__len1 == 1) { // __len1 >= __len2 && __len2 > 0, therefore __len2 == 1
172                         // It is known *__first > *__middle
173        _Ops::iter_swap(__first, __middle);
174        return;
175      }
176      // __len1 >= 2, __len2 >= 1
177      __len11 = __len1 / 2;
178      __m1    = __first;
179      _Ops::advance(__m1, __len11);
180      __m2    = std::lower_bound(__middle, __last, *__m1, __comp);
181      __len21 = _Ops::distance(__middle, __m2);
182    }
183    difference_type __len12 = __len1 - __len11; // distance(__m1, __middle)
184    difference_type __len22 = __len2 - __len21; // distance(__m2, __last)
185    // [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last)
186    // swap middle two partitions
187    __middle = std::__rotate<_AlgPolicy>(__m1, __middle, __m2).first;
188    // __len12 and __len21 now have swapped meanings
189    // merge smaller range with recursive call and larger with tail recursion elimination
190    if (__len11 + __len21 < __len12 + __len22) {
191      std::__inplace_merge<_AlgPolicy>(__first, __m1, __middle, __comp, __len11, __len21, __buff, __buff_size);
192      __first  = __middle;
193      __middle = __m2;
194      __len1   = __len12;
195      __len2   = __len22;
196    } else {
197      std::__inplace_merge<_AlgPolicy>(__middle, __m2, __last, __comp, __len12, __len22, __buff, __buff_size);
198      __last   = __middle;
199      __middle = __m1;
200      __len1   = __len11;
201      __len2   = __len21;
202    }
203  }
204}
205
206template <class _AlgPolicy, class _BidirectionalIterator, class _Compare>
207_LIBCPP_HIDE_FROM_ABI void __inplace_merge(
208    _BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last, _Compare&& __comp) {
209  typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
210  typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
211  difference_type __len1     = _IterOps<_AlgPolicy>::distance(__first, __middle);
212  difference_type __len2     = _IterOps<_AlgPolicy>::distance(__middle, __last);
213  difference_type __buf_size = std::min(__len1, __len2);
214  // TODO: Remove the use of std::get_temporary_buffer
215  _LIBCPP_SUPPRESS_DEPRECATED_PUSH
216  pair<value_type*, ptrdiff_t> __buf = std::get_temporary_buffer<value_type>(__buf_size);
217  _LIBCPP_SUPPRESS_DEPRECATED_POP
218  unique_ptr<value_type, __return_temporary_buffer> __h(__buf.first);
219  return std::__inplace_merge<_AlgPolicy>(
220      std::move(__first), std::move(__middle), std::move(__last), __comp, __len1, __len2, __buf.first, __buf.second);
221}
222
223template <class _BidirectionalIterator, class _Compare>
224inline _LIBCPP_HIDE_FROM_ABI void inplace_merge(
225    _BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last, _Compare __comp) {
226  std::__inplace_merge<_ClassicAlgPolicy>(
227      std::move(__first), std::move(__middle), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp));
228}
229
230template <class _BidirectionalIterator>
231inline _LIBCPP_HIDE_FROM_ABI void
232inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last) {
233  std::inplace_merge(std::move(__first), std::move(__middle), std::move(__last), __less<>());
234}
235
236_LIBCPP_END_NAMESPACE_STD
237
238_LIBCPP_POP_MACROS
239
240#endif // _LIBCPP___ALGORITHM_INPLACE_MERGE_H
241