1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___ALGORITHM_SEARCH_N_H
11 #define _LIBCPP___ALGORITHM_SEARCH_N_H
12 
13 #include <__algorithm/comp.h>
14 #include <__algorithm/iterator_operations.h>
15 #include <__config>
16 #include <__functional/identity.h>
17 #include <__iterator/advance.h>
18 #include <__iterator/concepts.h>
19 #include <__iterator/distance.h>
20 #include <__iterator/iterator_traits.h>
21 #include <__ranges/concepts.h>
22 #include <__utility/convert_to_integral.h>
23 #include <__utility/pair.h>
24 #include <type_traits>  // __convert_to_integral
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 _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj>
33 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
__search_n_forward_impl(_Iter __first,_Sent __last,_SizeT __count,const _Type & __value,_Pred & __pred,_Proj & __proj)34 pair<_Iter, _Iter> __search_n_forward_impl(_Iter __first, _Sent __last,
35                                            _SizeT __count,
36                                            const _Type& __value,
37                                            _Pred& __pred,
38                                            _Proj& __proj) {
39   if (__count <= 0)
40     return std::make_pair(__first, __first);
41   while (true) {
42     // Find first element in sequence that matchs __value, with a mininum of loop checks
43     while (true) {
44       if (__first == __last) { // return __last if no element matches __value
45         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
46         return std::make_pair(__first, __first);
47       }
48       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
49         break;
50       ++__first;
51     }
52     // *__first matches __value, now match elements after here
53     _Iter __m = __first;
54     _SizeT __c(0);
55     while (true) {
56       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
57         return std::make_pair(__first, ++__m);
58       if (++__m == __last) { // Otherwise if source exhaused, pattern not found
59         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
60         return std::make_pair(__first, __first);
61       }
62 
63       // if there is a mismatch, restart with a new __first
64       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value))
65       {
66         __first = __m;
67         ++__first;
68         break;
69       } // else there is a match, check next elements
70     }
71   }
72 }
73 
74 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj, class _DiffT>
75 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
__search_n_random_access_impl(_Iter __first,_Sent __last,_SizeT __count,const _Type & __value,_Pred & __pred,_Proj & __proj,_DiffT __size1)76 std::pair<_Iter, _Iter> __search_n_random_access_impl(_Iter __first, _Sent __last,
77                                                       _SizeT __count,
78                                                       const _Type& __value,
79                                                       _Pred& __pred,
80                                                       _Proj& __proj,
81                                                       _DiffT __size1) {
82   using difference_type = typename iterator_traits<_Iter>::difference_type;
83   if (__count == 0)
84     return std::make_pair(__first, __first);
85   if (__size1 < static_cast<_DiffT>(__count)) {
86     _IterOps<_AlgPolicy>::__advance_to(__first, __last);
87     return std::make_pair(__first, __first);
88   }
89 
90   const auto __s = __first + __size1 - difference_type(__count - 1); // Start of pattern match can't go beyond here
91   while (true) {
92     // Find first element in sequence that matchs __value, with a mininum of loop checks
93     while (true) {
94       if (__first >= __s) { // return __last if no element matches __value
95         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
96         return std::make_pair(__first, __first);
97       }
98       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
99         break;
100       ++__first;
101     }
102     // *__first matches __value_, now match elements after here
103     auto __m = __first;
104     _SizeT __c(0);
105     while (true) {
106       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
107         return std::make_pair(__first, __first + _DiffT(__count));
108       ++__m; // no need to check range on __m because __s guarantees we have enough source
109 
110       // if there is a mismatch, restart with a new __first
111       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value))
112       {
113         __first = __m;
114         ++__first;
115         break;
116       } // else there is a match, check next elements
117     }
118   }
119 }
120 
121 template <class _Iter, class _Sent,
122           class _DiffT,
123           class _Type,
124           class _Pred,
125           class _Proj>
126 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
127 pair<_Iter, _Iter> __search_n_impl(_Iter __first, _Sent __last,
128                                    _DiffT __count,
129                                    const _Type& __value,
130                                    _Pred& __pred,
131                                    _Proj& __proj,
132                                    __enable_if_t<__is_cpp17_random_access_iterator<_Iter>::value>* = nullptr) {
133   return std::__search_n_random_access_impl<_ClassicAlgPolicy>(__first, __last,
134                                                                __count,
135                                                                __value,
136                                                                __pred,
137                                                                __proj,
138                                                                __last - __first);
139 }
140 
141 template <class _Iter1, class _Sent1,
142           class _DiffT,
143           class _Type,
144           class _Pred,
145           class _Proj>
146 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
147 pair<_Iter1, _Iter1> __search_n_impl(_Iter1 __first, _Sent1 __last,
148                                      _DiffT __count,
149                                      const _Type& __value,
150                                      _Pred& __pred,
151                                      _Proj& __proj,
152                                      __enable_if_t<__is_cpp17_forward_iterator<_Iter1>::value
153                                                && !__is_cpp17_random_access_iterator<_Iter1>::value>* = nullptr) {
154   return std::__search_n_forward_impl<_ClassicAlgPolicy>(__first, __last,
155                                                          __count,
156                                                          __value,
157                                                          __pred,
158                                                          __proj);
159 }
160 
161 template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
162 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
search_n(_ForwardIterator __first,_ForwardIterator __last,_Size __count,const _Tp & __value,_BinaryPredicate __pred)163 _ForwardIterator search_n(_ForwardIterator __first, _ForwardIterator __last,
164                           _Size __count,
165                           const _Tp& __value,
166                           _BinaryPredicate __pred) {
167   static_assert(__is_callable<_BinaryPredicate, decltype(*__first), const _Tp&>::value,
168                 "BinaryPredicate has to be callable");
169   auto __proj = __identity();
170   return std::__search_n_impl(__first, __last, std::__convert_to_integral(__count), __value, __pred, __proj).first;
171 }
172 
173 template <class _ForwardIterator, class _Size, class _Tp>
174 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
search_n(_ForwardIterator __first,_ForwardIterator __last,_Size __count,const _Tp & __value)175 _ForwardIterator search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value) {
176   return std::search_n(__first, __last, std::__convert_to_integral(__count), __value, __equal_to());
177 }
178 
179 _LIBCPP_END_NAMESPACE_STD
180 
181 #endif // _LIBCPP___ALGORITHM_SEARCH_N_H
182