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/pair.h>
23 #include <type_traits>  // __convert_to_integral
24 
25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
26 #  pragma GCC system_header
27 #endif
28 
29 _LIBCPP_BEGIN_NAMESPACE_STD
30 
31 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj>
32 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
__search_n_forward_impl(_Iter __first,_Sent __last,_SizeT __count,const _Type & __value,_Pred & __pred,_Proj & __proj)33 pair<_Iter, _Iter> __search_n_forward_impl(_Iter __first, _Sent __last,
34                                            _SizeT __count,
35                                            const _Type& __value,
36                                            _Pred& __pred,
37                                            _Proj& __proj) {
38   if (__count <= 0)
39     return std::make_pair(__first, __first);
40   while (true) {
41     // Find first element in sequence that matchs __value, with a mininum of loop checks
42     while (true) {
43       if (__first == __last) { // return __last if no element matches __value
44         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
45         return std::make_pair(__first, __first);
46       }
47       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
48         break;
49       ++__first;
50     }
51     // *__first matches __value, now match elements after here
52     _Iter __m = __first;
53     _SizeT __c(0);
54     while (true) {
55       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
56         return std::make_pair(__first, ++__m);
57       if (++__m == __last) { // Otherwise if source exhaused, pattern not found
58         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
59         return std::make_pair(__first, __first);
60       }
61 
62       // if there is a mismatch, restart with a new __first
63       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value))
64       {
65         __first = __m;
66         ++__first;
67         break;
68       } // else there is a match, check next elements
69     }
70   }
71 }
72 
73 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj, class _DiffT>
74 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
__search_n_random_access_impl(_Iter __first,_Sent __last,_SizeT __count,const _Type & __value,_Pred & __pred,_Proj & __proj,_DiffT __size1)75 std::pair<_Iter, _Iter> __search_n_random_access_impl(_Iter __first, _Sent __last,
76                                                       _SizeT __count,
77                                                       const _Type& __value,
78                                                       _Pred& __pred,
79                                                       _Proj& __proj,
80                                                       _DiffT __size1) {
81   using difference_type = typename iterator_traits<_Iter>::difference_type;
82   if (__count == 0)
83     return std::make_pair(__first, __first);
84   if (__size1 < static_cast<_DiffT>(__count)) {
85     _IterOps<_AlgPolicy>::__advance_to(__first, __last);
86     return std::make_pair(__first, __first);
87   }
88 
89   const auto __s = __first + __size1 - difference_type(__count - 1); // Start of pattern match can't go beyond here
90   while (true) {
91     // Find first element in sequence that matchs __value, with a mininum of loop checks
92     while (true) {
93       if (__first >= __s) { // return __last if no element matches __value
94         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
95         return std::make_pair(__first, __first);
96       }
97       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
98         break;
99       ++__first;
100     }
101     // *__first matches __value_, now match elements after here
102     auto __m = __first;
103     _SizeT __c(0);
104     while (true) {
105       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
106         return std::make_pair(__first, __first + _DiffT(__count));
107       ++__m; // no need to check range on __m because __s guarantees we have enough source
108 
109       // if there is a mismatch, restart with a new __first
110       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value))
111       {
112         __first = __m;
113         ++__first;
114         break;
115       } // else there is a match, check next elements
116     }
117   }
118 }
119 
120 template <class _Iter, class _Sent,
121           class _DiffT,
122           class _Type,
123           class _Pred,
124           class _Proj>
125 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
126 pair<_Iter, _Iter> __search_n_impl(_Iter __first, _Sent __last,
127                                    _DiffT __count,
128                                    const _Type& __value,
129                                    _Pred& __pred,
130                                    _Proj& __proj,
131                                    __enable_if_t<__is_cpp17_random_access_iterator<_Iter>::value>* = nullptr) {
132   return std::__search_n_random_access_impl<_ClassicAlgPolicy>(__first, __last,
133                                                                __count,
134                                                                __value,
135                                                                __pred,
136                                                                __proj,
137                                                                __last - __first);
138 }
139 
140 template <class _Iter1, class _Sent1,
141           class _DiffT,
142           class _Type,
143           class _Pred,
144           class _Proj>
145 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
146 pair<_Iter1, _Iter1> __search_n_impl(_Iter1 __first, _Sent1 __last,
147                                      _DiffT __count,
148                                      const _Type& __value,
149                                      _Pred& __pred,
150                                      _Proj& __proj,
151                                      __enable_if_t<__is_cpp17_forward_iterator<_Iter1>::value
152                                                && !__is_cpp17_random_access_iterator<_Iter1>::value>* = nullptr) {
153   return std::__search_n_forward_impl<_ClassicAlgPolicy>(__first, __last,
154                                                          __count,
155                                                          __value,
156                                                          __pred,
157                                                          __proj);
158 }
159 
160 template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
161 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
search_n(_ForwardIterator __first,_ForwardIterator __last,_Size __count,const _Tp & __value,_BinaryPredicate __pred)162 _ForwardIterator search_n(_ForwardIterator __first, _ForwardIterator __last,
163                           _Size __count,
164                           const _Tp& __value,
165                           _BinaryPredicate __pred) {
166   static_assert(__is_callable<_BinaryPredicate, decltype(*__first), const _Tp&>::value,
167                 "BinaryPredicate has to be callable");
168   auto __proj = __identity();
169   return std::__search_n_impl(__first, __last, std::__convert_to_integral(__count), __value, __pred, __proj).first;
170 }
171 
172 template <class _ForwardIterator, class _Size, class _Tp>
173 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
search_n(_ForwardIterator __first,_ForwardIterator __last,_Size __count,const _Tp & __value)174 _ForwardIterator search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value) {
175   typedef typename iterator_traits<_ForwardIterator>::value_type __v;
176   return std::search_n(__first, __last, std::__convert_to_integral(__count), __value, __equal_to<__v, _Tp>());
177 }
178 
179 _LIBCPP_END_NAMESPACE_STD
180 
181 #endif // _LIBCPP___ALGORITHM_SEARCH_N_H
182