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