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_FIND_END_OF_H
11 #define _LIBCPP___ALGORITHM_FIND_END_OF_H
12 
13 #include <__config>
14 #include <__algorithm/comp.h>
15 #include <__iterator/iterator_traits.h>
16 #include <type_traits>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #pragma GCC system_header
20 #endif
21 
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24 
25 _LIBCPP_BEGIN_NAMESPACE_STD
26 
27 template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
28 _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1 __find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
29                                                            _ForwardIterator2 __first2, _ForwardIterator2 __last2,
30                                                            _BinaryPredicate __pred, forward_iterator_tag,
31                                                            forward_iterator_tag) {
32   // modeled after search algorithm
33   _ForwardIterator1 __r = __last1; // __last1 is the "default" answer
34   if (__first2 == __last2)
35     return __r;
36   while (true) {
37     while (true) {
38       if (__first1 == __last1) // if source exhausted return last correct answer
39         return __r;            //    (or __last1 if never found)
40       if (__pred(*__first1, *__first2))
41         break;
42       ++__first1;
43     }
44     // *__first1 matches *__first2, now match elements after here
45     _ForwardIterator1 __m1 = __first1;
46     _ForwardIterator2 __m2 = __first2;
47     while (true) {
48       if (++__m2 == __last2) { // Pattern exhaused, record answer and search for another one
49         __r = __first1;
50         ++__first1;
51         break;
52       }
53       if (++__m1 == __last1) // Source exhausted, return last answer
54         return __r;
55       if (!__pred(*__m1, *__m2)) // mismatch, restart with a new __first
56       {
57         ++__first1;
58         break;
59       } // else there is a match, check next elements
60     }
61   }
62 }
63 
64 template <class _BinaryPredicate, class _BidirectionalIterator1, class _BidirectionalIterator2>
65 _LIBCPP_CONSTEXPR_AFTER_CXX17 _BidirectionalIterator1 __find_end(
66     _BidirectionalIterator1 __first1, _BidirectionalIterator1 __last1, _BidirectionalIterator2 __first2,
67     _BidirectionalIterator2 __last2, _BinaryPredicate __pred, bidirectional_iterator_tag, bidirectional_iterator_tag) {
68   // modeled after search algorithm (in reverse)
69   if (__first2 == __last2)
70     return __last1; // Everything matches an empty sequence
71   _BidirectionalIterator1 __l1 = __last1;
72   _BidirectionalIterator2 __l2 = __last2;
73   --__l2;
74   while (true) {
75     // Find last element in sequence 1 that matchs *(__last2-1), with a mininum of loop checks
76     while (true) {
77       if (__first1 == __l1) // return __last1 if no element matches *__first2
78         return __last1;
79       if (__pred(*--__l1, *__l2))
80         break;
81     }
82     // *__l1 matches *__l2, now match elements before here
83     _BidirectionalIterator1 __m1 = __l1;
84     _BidirectionalIterator2 __m2 = __l2;
85     while (true) {
86       if (__m2 == __first2) // If pattern exhausted, __m1 is the answer (works for 1 element pattern)
87         return __m1;
88       if (__m1 == __first1) // Otherwise if source exhaused, pattern not found
89         return __last1;
90       if (!__pred(*--__m1, *--__m2)) // if there is a mismatch, restart with a new __l1
91       {
92         break;
93       } // else there is a match, check next elements
94     }
95   }
96 }
97 
98 template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
99 _LIBCPP_CONSTEXPR_AFTER_CXX11 _RandomAccessIterator1 __find_end(
100     _RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1, _RandomAccessIterator2 __first2,
101     _RandomAccessIterator2 __last2, _BinaryPredicate __pred, random_access_iterator_tag, random_access_iterator_tag) {
102   // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
103   typename iterator_traits<_RandomAccessIterator2>::difference_type __len2 = __last2 - __first2;
104   if (__len2 == 0)
105     return __last1;
106   typename iterator_traits<_RandomAccessIterator1>::difference_type __len1 = __last1 - __first1;
107   if (__len1 < __len2)
108     return __last1;
109   const _RandomAccessIterator1 __s = __first1 + (__len2 - 1); // End of pattern match can't go before here
110   _RandomAccessIterator1 __l1 = __last1;
111   _RandomAccessIterator2 __l2 = __last2;
112   --__l2;
113   while (true) {
114     while (true) {
115       if (__s == __l1)
116         return __last1;
117       if (__pred(*--__l1, *__l2))
118         break;
119     }
120     _RandomAccessIterator1 __m1 = __l1;
121     _RandomAccessIterator2 __m2 = __l2;
122     while (true) {
123       if (__m2 == __first2)
124         return __m1;
125       // no need to check range on __m1 because __s guarantees we have enough source
126       if (!__pred(*--__m1, *--__m2)) {
127         break;
128       }
129     }
130   }
131 }
132 
133 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
134 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
135 find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2,
136          _BinaryPredicate __pred) {
137   return _VSTD::__find_end<typename add_lvalue_reference<_BinaryPredicate>::type>(
138       __first1, __last1, __first2, __last2, __pred, typename iterator_traits<_ForwardIterator1>::iterator_category(),
139       typename iterator_traits<_ForwardIterator2>::iterator_category());
140 }
141 
142 template <class _ForwardIterator1, class _ForwardIterator2>
143 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
144 find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
145   typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
146   typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
147   return _VSTD::find_end(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
148 }
149 
150 _LIBCPP_END_NAMESPACE_STD
151 
152 _LIBCPP_POP_MACROS
153 
154 #endif // _LIBCPP___ALGORITHM_FIND_END_OF_H
155