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_PARTITION_H
10 #define _LIBCPP___ALGORITHM_STABLE_PARTITION_H
11
12 #include <__algorithm/iterator_operations.h>
13 #include <__algorithm/rotate.h>
14 #include <__config>
15 #include <__iterator/advance.h>
16 #include <__iterator/distance.h>
17 #include <__iterator/iterator_traits.h>
18 #include <__memory/destruct_n.h>
19 #include <__memory/temporary_buffer.h>
20 #include <__memory/unique_ptr.h>
21 #include <__utility/move.h>
22 #include <__utility/pair.h>
23 #include <new>
24 #include <type_traits>
25
26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27 # pragma GCC system_header
28 #endif
29
30 _LIBCPP_BEGIN_NAMESPACE_STD
31
32 template <class _AlgPolicy, class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
33 _LIBCPP_HIDE_FROM_ABI _ForwardIterator
__stable_partition_impl(_ForwardIterator __first,_ForwardIterator __last,_Predicate __pred,_Distance __len,_Pair __p,forward_iterator_tag __fit)34 __stable_partition_impl(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
35 _Distance __len, _Pair __p, forward_iterator_tag __fit)
36 {
37 using _Ops = _IterOps<_AlgPolicy>;
38
39 // *__first is known to be false
40 // __len >= 1
41 if (__len == 1)
42 return __first;
43 if (__len == 2)
44 {
45 _ForwardIterator __m = __first;
46 if (__pred(*++__m))
47 {
48 _Ops::iter_swap(__first, __m);
49 return __m;
50 }
51 return __first;
52 }
53 if (__len <= __p.second)
54 { // The buffer is big enough to use
55 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
56 __destruct_n __d(0);
57 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
58 // Move the falses into the temporary buffer, and the trues to the front of the line
59 // Update __first to always point to the end of the trues
60 value_type* __t = __p.first;
61 ::new ((void*)__t) value_type(_Ops::__iter_move(__first));
62 __d.template __incr<value_type>();
63 ++__t;
64 _ForwardIterator __i = __first;
65 while (++__i != __last)
66 {
67 if (__pred(*__i))
68 {
69 *__first = _Ops::__iter_move(__i);
70 ++__first;
71 }
72 else
73 {
74 ::new ((void*)__t) value_type(_Ops::__iter_move(__i));
75 __d.template __incr<value_type>();
76 ++__t;
77 }
78 }
79 // All trues now at start of range, all falses in buffer
80 // Move falses back into range, but don't mess up __first which points to first false
81 __i = __first;
82 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
83 *__i = _Ops::__iter_move(__t2);
84 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
85 return __first;
86 }
87 // Else not enough buffer, do in place
88 // __len >= 3
89 _ForwardIterator __m = __first;
90 _Distance __len2 = __len / 2; // __len2 >= 2
91 _Ops::advance(__m, __len2);
92 // recurse on [__first, __m), *__first know to be false
93 // F?????????????????
94 // f m l
95 _ForwardIterator __first_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
96 __first, __m, __pred, __len2, __p, __fit);
97 // TTTFFFFF??????????
98 // f ff m l
99 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
100 _ForwardIterator __m1 = __m;
101 _ForwardIterator __second_false = __last;
102 _Distance __len_half = __len - __len2;
103 while (__pred(*__m1))
104 {
105 if (++__m1 == __last)
106 goto __second_half_done;
107 --__len_half;
108 }
109 // TTTFFFFFTTTF??????
110 // f ff m m1 l
111 __second_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
112 __m1, __last, __pred, __len_half, __p, __fit);
113 __second_half_done:
114 // TTTFFFFFTTTTTFFFFF
115 // f ff m sf l
116 return std::__rotate<_AlgPolicy>(__first_false, __m, __second_false).first;
117 // TTTTTTTTFFFFFFFFFF
118 // |
119 }
120
121 template <class _AlgPolicy, class _Predicate, class _ForwardIterator>
122 _LIBCPP_HIDE_FROM_ABI _ForwardIterator
__stable_partition_impl(_ForwardIterator __first,_ForwardIterator __last,_Predicate __pred,forward_iterator_tag)123 __stable_partition_impl(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
124 forward_iterator_tag)
125 {
126 const unsigned __alloc_limit = 3; // might want to make this a function of trivial assignment
127 // Either prove all true and return __first or point to first false
128 while (true)
129 {
130 if (__first == __last)
131 return __first;
132 if (!__pred(*__first))
133 break;
134 ++__first;
135 }
136 // We now have a reduced range [__first, __last)
137 // *__first is known to be false
138 typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
139 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
140 difference_type __len = _IterOps<_AlgPolicy>::distance(__first, __last);
141 pair<value_type*, ptrdiff_t> __p(0, 0);
142 unique_ptr<value_type, __return_temporary_buffer> __h;
143 if (__len >= __alloc_limit)
144 {
145 // TODO: Remove the use of std::get_temporary_buffer
146 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
147 __p = _VSTD::get_temporary_buffer<value_type>(__len);
148 _LIBCPP_SUPPRESS_DEPRECATED_POP
149 __h.reset(__p.first);
150 }
151 return std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
152 std::move(__first), std::move(__last), __pred, __len, __p, forward_iterator_tag());
153 }
154
155 template <class _AlgPolicy, class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
156 _BidirectionalIterator
__stable_partition_impl(_BidirectionalIterator __first,_BidirectionalIterator __last,_Predicate __pred,_Distance __len,_Pair __p,bidirectional_iterator_tag __bit)157 __stable_partition_impl(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
158 _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
159 {
160 using _Ops = _IterOps<_AlgPolicy>;
161
162 // *__first is known to be false
163 // *__last is known to be true
164 // __len >= 2
165 if (__len == 2)
166 {
167 _Ops::iter_swap(__first, __last);
168 return __last;
169 }
170 if (__len == 3)
171 {
172 _BidirectionalIterator __m = __first;
173 if (__pred(*++__m))
174 {
175 _Ops::iter_swap(__first, __m);
176 _Ops::iter_swap(__m, __last);
177 return __last;
178 }
179 _Ops::iter_swap(__m, __last);
180 _Ops::iter_swap(__first, __m);
181 return __m;
182 }
183 if (__len <= __p.second)
184 { // The buffer is big enough to use
185 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
186 __destruct_n __d(0);
187 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
188 // Move the falses into the temporary buffer, and the trues to the front of the line
189 // Update __first to always point to the end of the trues
190 value_type* __t = __p.first;
191 ::new ((void*)__t) value_type(_Ops::__iter_move(__first));
192 __d.template __incr<value_type>();
193 ++__t;
194 _BidirectionalIterator __i = __first;
195 while (++__i != __last)
196 {
197 if (__pred(*__i))
198 {
199 *__first = _Ops::__iter_move(__i);
200 ++__first;
201 }
202 else
203 {
204 ::new ((void*)__t) value_type(_Ops::__iter_move(__i));
205 __d.template __incr<value_type>();
206 ++__t;
207 }
208 }
209 // move *__last, known to be true
210 *__first = _Ops::__iter_move(__i);
211 __i = ++__first;
212 // All trues now at start of range, all falses in buffer
213 // Move falses back into range, but don't mess up __first which points to first false
214 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
215 *__i = _Ops::__iter_move(__t2);
216 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
217 return __first;
218 }
219 // Else not enough buffer, do in place
220 // __len >= 4
221 _BidirectionalIterator __m = __first;
222 _Distance __len2 = __len / 2; // __len2 >= 2
223 _Ops::advance(__m, __len2);
224 // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
225 // F????????????????T
226 // f m l
227 _BidirectionalIterator __m1 = __m;
228 _BidirectionalIterator __first_false = __first;
229 _Distance __len_half = __len2;
230 while (!__pred(*--__m1))
231 {
232 if (__m1 == __first)
233 goto __first_half_done;
234 --__len_half;
235 }
236 // F???TFFF?????????T
237 // f m1 m l
238 __first_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
239 __first, __m1, __pred, __len_half, __p, __bit);
240 __first_half_done:
241 // TTTFFFFF?????????T
242 // f ff m l
243 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
244 __m1 = __m;
245 _BidirectionalIterator __second_false = __last;
246 ++__second_false;
247 __len_half = __len - __len2;
248 while (__pred(*__m1))
249 {
250 if (++__m1 == __last)
251 goto __second_half_done;
252 --__len_half;
253 }
254 // TTTFFFFFTTTF?????T
255 // f ff m m1 l
256 __second_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
257 __m1, __last, __pred, __len_half, __p, __bit);
258 __second_half_done:
259 // TTTFFFFFTTTTTFFFFF
260 // f ff m sf l
261 return std::__rotate<_AlgPolicy>(__first_false, __m, __second_false).first;
262 // TTTTTTTTFFFFFFFFFF
263 // |
264 }
265
266 template <class _AlgPolicy, class _Predicate, class _BidirectionalIterator>
267 _LIBCPP_HIDE_FROM_ABI _BidirectionalIterator
__stable_partition_impl(_BidirectionalIterator __first,_BidirectionalIterator __last,_Predicate __pred,bidirectional_iterator_tag)268 __stable_partition_impl(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
269 bidirectional_iterator_tag)
270 {
271 typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
272 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
273 const difference_type __alloc_limit = 4; // might want to make this a function of trivial assignment
274 // Either prove all true and return __first or point to first false
275 while (true)
276 {
277 if (__first == __last)
278 return __first;
279 if (!__pred(*__first))
280 break;
281 ++__first;
282 }
283 // __first points to first false, everything prior to __first is already set.
284 // Either prove [__first, __last) is all false and return __first, or point __last to last true
285 do
286 {
287 if (__first == --__last)
288 return __first;
289 } while (!__pred(*__last));
290 // We now have a reduced range [__first, __last]
291 // *__first is known to be false
292 // *__last is known to be true
293 // __len >= 2
294 difference_type __len = _IterOps<_AlgPolicy>::distance(__first, __last) + 1;
295 pair<value_type*, ptrdiff_t> __p(0, 0);
296 unique_ptr<value_type, __return_temporary_buffer> __h;
297 if (__len >= __alloc_limit)
298 {
299 // TODO: Remove the use of std::get_temporary_buffer
300 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
301 __p = _VSTD::get_temporary_buffer<value_type>(__len);
302 _LIBCPP_SUPPRESS_DEPRECATED_POP
303 __h.reset(__p.first);
304 }
305 return std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
306 std::move(__first), std::move(__last), __pred, __len, __p, bidirectional_iterator_tag());
307 }
308
309 template <class _AlgPolicy, class _Predicate, class _ForwardIterator, class _IterCategory>
310 _LIBCPP_HIDE_FROM_ABI
__stable_partition(_ForwardIterator __first,_ForwardIterator __last,_Predicate && __pred,_IterCategory __iter_category)311 _ForwardIterator __stable_partition(
312 _ForwardIterator __first, _ForwardIterator __last, _Predicate&& __pred, _IterCategory __iter_category) {
313 return std::__stable_partition_impl<_AlgPolicy, __remove_cvref_t<_Predicate>&>(
314 std::move(__first), std::move(__last), __pred, __iter_category);
315 }
316
317 template <class _ForwardIterator, class _Predicate>
318 inline _LIBCPP_INLINE_VISIBILITY
319 _ForwardIterator
stable_partition(_ForwardIterator __first,_ForwardIterator __last,_Predicate __pred)320 stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
321 {
322 using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
323 return std::__stable_partition<_ClassicAlgPolicy, _Predicate&>(
324 std::move(__first), std::move(__last), __pred, _IterCategory());
325 }
326
327 _LIBCPP_END_NAMESPACE_STD
328
329 #endif // _LIBCPP___ALGORITHM_STABLE_PARTITION_H
330