xref: /llvm-project/libcxx/include/__algorithm/stable_sort.h (revision 438e2ccd4ad18d23fc800d0ad9f4f667a547f868) 
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_STABLE_SORT_H
10 #define _LIBCPP___ALGORITHM_STABLE_SORT_H
11 
12 #include <__algorithm/comp.h>
13 #include <__algorithm/comp_ref_type.h>
14 #include <__algorithm/inplace_merge.h>
15 #include <__algorithm/iterator_operations.h>
16 #include <__algorithm/radix_sort.h>
17 #include <__algorithm/sort.h>
18 #include <__config>
19 #include <__cstddef/ptrdiff_t.h>
20 #include <__debug_utils/strict_weak_ordering_check.h>
21 #include <__iterator/iterator_traits.h>
22 #include <__memory/construct_at.h>
23 #include <__memory/destruct_n.h>
24 #include <__memory/unique_ptr.h>
25 #include <__memory/unique_temporary_buffer.h>
26 #include <__type_traits/desugars_to.h>
27 #include <__type_traits/enable_if.h>
28 #include <__type_traits/is_integral.h>
29 #include <__type_traits/is_same.h>
30 #include <__type_traits/is_trivially_assignable.h>
31 #include <__type_traits/remove_cvref.h>
32 #include <__utility/move.h>
33 #include <__utility/pair.h>
34 
35 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
36 #  pragma GCC system_header
37 #endif
38 
39 _LIBCPP_PUSH_MACROS
40 #include <__undef_macros>
41 
42 _LIBCPP_BEGIN_NAMESPACE_STD
43 
44 template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
45 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __insertion_sort_move(
46     _BidirectionalIterator __first1,
47     _BidirectionalIterator __last1,
48     typename iterator_traits<_BidirectionalIterator>::value_type* __first2,
49     _Compare __comp) {
50   using _Ops = _IterOps<_AlgPolicy>;
51 
52   typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
53   if (__first1 != __last1) {
54     __destruct_n __d(0);
55     unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
56     value_type* __last2 = __first2;
57     std::__construct_at(__last2, _Ops::__iter_move(__first1));
58     __d.template __incr<value_type>();
59     for (++__last2; ++__first1 != __last1; ++__last2) {
60       value_type* __j2 = __last2;
61       value_type* __i2 = __j2;
62       if (__comp(*__first1, *--__i2)) {
63         std::__construct_at(__j2, std::move(*__i2));
64         __d.template __incr<value_type>();
65         for (--__j2; __i2 != __first2 && __comp(*__first1, *--__i2); --__j2)
66           *__j2 = std::move(*__i2);
67         *__j2 = _Ops::__iter_move(__first1);
68       } else {
69         std::__construct_at(__j2, _Ops::__iter_move(__first1));
70         __d.template __incr<value_type>();
71       }
72     }
73     __h.release();
74   }
75 }
76 
77 template <class _AlgPolicy, class _Compare, class _InputIterator1, class _InputIterator2>
78 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __merge_move_construct(
79     _InputIterator1 __first1,
80     _InputIterator1 __last1,
81     _InputIterator2 __first2,
82     _InputIterator2 __last2,
83     typename iterator_traits<_InputIterator1>::value_type* __result,
84     _Compare __comp) {
85   using _Ops = _IterOps<_AlgPolicy>;
86 
87   typedef typename iterator_traits<_InputIterator1>::value_type value_type;
88   __destruct_n __d(0);
89   unique_ptr<value_type, __destruct_n&> __h(__result, __d);
90   for (; true; ++__result) {
91     if (__first1 == __last1) {
92       for (; __first2 != __last2; ++__first2, (void)++__result, __d.template __incr<value_type>())
93         std::__construct_at(__result, _Ops::__iter_move(__first2));
94       __h.release();
95       return;
96     }
97     if (__first2 == __last2) {
98       for (; __first1 != __last1; ++__first1, (void)++__result, __d.template __incr<value_type>())
99         std::__construct_at(__result, _Ops::__iter_move(__first1));
100       __h.release();
101       return;
102     }
103     if (__comp(*__first2, *__first1)) {
104       std::__construct_at(__result, _Ops::__iter_move(__first2));
105       __d.template __incr<value_type>();
106       ++__first2;
107     } else {
108       std::__construct_at(__result, _Ops::__iter_move(__first1));
109       __d.template __incr<value_type>();
110       ++__first1;
111     }
112   }
113 }
114 
115 template <class _AlgPolicy, class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
116 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __merge_move_assign(
117     _InputIterator1 __first1,
118     _InputIterator1 __last1,
119     _InputIterator2 __first2,
120     _InputIterator2 __last2,
121     _OutputIterator __result,
122     _Compare __comp) {
123   using _Ops = _IterOps<_AlgPolicy>;
124 
125   for (; __first1 != __last1; ++__result) {
126     if (__first2 == __last2) {
127       for (; __first1 != __last1; ++__first1, (void)++__result)
128         *__result = _Ops::__iter_move(__first1);
129       return;
130     }
131     if (__comp(*__first2, *__first1)) {
132       *__result = _Ops::__iter_move(__first2);
133       ++__first2;
134     } else {
135       *__result = _Ops::__iter_move(__first1);
136       ++__first1;
137     }
138   }
139   for (; __first2 != __last2; ++__first2, (void)++__result)
140     *__result = _Ops::__iter_move(__first2);
141 }
142 
143 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
144 _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
145     _RandomAccessIterator __first,
146     _RandomAccessIterator __last,
147     _Compare __comp,
148     typename iterator_traits<_RandomAccessIterator>::difference_type __len,
149     typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
150     ptrdiff_t __buff_size);
151 
152 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
153 _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort_move(
154     _RandomAccessIterator __first1,
155     _RandomAccessIterator __last1,
156     _Compare __comp,
157     typename iterator_traits<_RandomAccessIterator>::difference_type __len,
158     typename iterator_traits<_RandomAccessIterator>::value_type* __first2) {
159   using _Ops = _IterOps<_AlgPolicy>;
160 
161   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
162   switch (__len) {
163   case 0:
164     return;
165   case 1:
166     std::__construct_at(__first2, _Ops::__iter_move(__first1));
167     return;
168   case 2:
169     __destruct_n __d(0);
170     unique_ptr<value_type, __destruct_n&> __h2(__first2, __d);
171     if (__comp(*--__last1, *__first1)) {
172       std::__construct_at(__first2, _Ops::__iter_move(__last1));
173       __d.template __incr<value_type>();
174       ++__first2;
175       std::__construct_at(__first2, _Ops::__iter_move(__first1));
176     } else {
177       std::__construct_at(__first2, _Ops::__iter_move(__first1));
178       __d.template __incr<value_type>();
179       ++__first2;
180       std::__construct_at(__first2, _Ops::__iter_move(__last1));
181     }
182     __h2.release();
183     return;
184   }
185   if (__len <= 8) {
186     std::__insertion_sort_move<_AlgPolicy, _Compare>(__first1, __last1, __first2, __comp);
187     return;
188   }
189   typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
190   _RandomAccessIterator __m                                             = __first1 + __l2;
191   std::__stable_sort<_AlgPolicy, _Compare>(__first1, __m, __comp, __l2, __first2, __l2);
192   std::__stable_sort<_AlgPolicy, _Compare>(__m, __last1, __comp, __len - __l2, __first2 + __l2, __len - __l2);
193   std::__merge_move_construct<_AlgPolicy, _Compare>(__first1, __m, __m, __last1, __first2, __comp);
194 }
195 
196 template <class _Tp>
197 struct __stable_sort_switch {
198   static const unsigned value = 128 * is_trivially_copy_assignable<_Tp>::value;
199 };
200 
201 #if _LIBCPP_STD_VER >= 17
202 template <class _Tp>
203 _LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_min_bound() {
204   static_assert(is_integral<_Tp>::value);
205   if constexpr (sizeof(_Tp) == 1) {
206     return 1 << 8;
207   }
208 
209   return 1 << 10;
210 }
211 
212 template <class _Tp>
213 _LIBCPP_HIDE_FROM_ABI constexpr unsigned __radix_sort_max_bound() {
214   static_assert(is_integral<_Tp>::value);
215   if constexpr (sizeof(_Tp) >= 8) {
216     return 1 << 15;
217   }
218 
219   return 1 << 16;
220 }
221 #endif // _LIBCPP_STD_VER >= 17
222 
223 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
224 _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
225     _RandomAccessIterator __first,
226     _RandomAccessIterator __last,
227     _Compare __comp,
228     typename iterator_traits<_RandomAccessIterator>::difference_type __len,
229     typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
230     ptrdiff_t __buff_size) {
231   typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
232   typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
233   switch (__len) {
234   case 0:
235   case 1:
236     return;
237   case 2:
238     if (__comp(*--__last, *__first))
239       _IterOps<_AlgPolicy>::iter_swap(__first, __last);
240     return;
241   }
242   if (__len <= static_cast<difference_type>(__stable_sort_switch<value_type>::value)) {
243     std::__insertion_sort<_AlgPolicy, _Compare>(__first, __last, __comp);
244     return;
245   }
246 
247 #if _LIBCPP_STD_VER >= 17
248   constexpr auto __default_comp =
249       __desugars_to_v<__totally_ordered_less_tag, __remove_cvref_t<_Compare>, value_type, value_type >;
250   constexpr auto __integral_value =
251       is_integral_v<value_type > && is_same_v< value_type&, __iter_reference<_RandomAccessIterator>>;
252   constexpr auto __allowed_radix_sort = __default_comp && __integral_value;
253   if constexpr (__allowed_radix_sort) {
254     if (__len <= __buff_size && __len >= static_cast<difference_type>(__radix_sort_min_bound<value_type>()) &&
255         __len <= static_cast<difference_type>(__radix_sort_max_bound<value_type>())) {
256       std::__radix_sort(__first, __last, __buff);
257       return;
258     }
259   }
260 #endif // _LIBCPP_STD_VER >= 17
261 
262   typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
263   _RandomAccessIterator __m                                             = __first + __l2;
264   if (__len <= __buff_size) {
265     __destruct_n __d(0);
266     unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
267     std::__stable_sort_move<_AlgPolicy, _Compare>(__first, __m, __comp, __l2, __buff);
268     __d.__set(__l2, (value_type*)nullptr);
269     std::__stable_sort_move<_AlgPolicy, _Compare>(__m, __last, __comp, __len - __l2, __buff + __l2);
270     __d.__set(__len, (value_type*)nullptr);
271     std::__merge_move_assign<_AlgPolicy, _Compare>(
272         __buff, __buff + __l2, __buff + __l2, __buff + __len, __first, __comp);
273     //         std::__merge<_Compare>(move_iterator<value_type*>(__buff),
274     //                                  move_iterator<value_type*>(__buff + __l2),
275     //                                  move_iterator<_RandomAccessIterator>(__buff + __l2),
276     //                                  move_iterator<_RandomAccessIterator>(__buff + __len),
277     //                                  __first, __comp);
278     return;
279   }
280   std::__stable_sort<_AlgPolicy, _Compare>(__first, __m, __comp, __l2, __buff, __buff_size);
281   std::__stable_sort<_AlgPolicy, _Compare>(__m, __last, __comp, __len - __l2, __buff, __buff_size);
282   std::__inplace_merge<_AlgPolicy>(__first, __m, __last, __comp, __l2, __len - __l2, __buff, __buff_size);
283 }
284 
285 template <class _AlgPolicy, class _RandomAccessIterator, class _Compare>
286 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
287 __stable_sort_impl(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare& __comp) {
288   using value_type      = typename iterator_traits<_RandomAccessIterator>::value_type;
289   using difference_type = typename iterator_traits<_RandomAccessIterator>::difference_type;
290 
291   difference_type __len = __last - __first;
292   __unique_temporary_buffer<value_type> __unique_buf;
293   pair<value_type*, ptrdiff_t> __buf(0, 0);
294   if (__len > static_cast<difference_type>(__stable_sort_switch<value_type>::value)) {
295     __unique_buf = std::__allocate_unique_temporary_buffer<value_type>(__len);
296     __buf.first  = __unique_buf.get();
297     __buf.second = __unique_buf.get_deleter().__count_;
298   }
299 
300   std::__stable_sort<_AlgPolicy, __comp_ref_type<_Compare> >(__first, __last, __comp, __len, __buf.first, __buf.second);
301   std::__check_strict_weak_ordering_sorted(__first, __last, __comp);
302 }
303 
304 template <class _RandomAccessIterator, class _Compare>
305 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
306 stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
307   std::__stable_sort_impl<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __comp);
308 }
309 
310 template <class _RandomAccessIterator>
311 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
312 stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
313   std::stable_sort(__first, __last, __less<>());
314 }
315 
316 _LIBCPP_END_NAMESPACE_STD
317 _LIBCPP_POP_MACROS
318 
319 #endif // _LIBCPP___ALGORITHM_STABLE_SORT_H
320