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_H
11 #define _LIBCPP___ALGORITHM_SEARCH_H
12 
13 #include <__algorithm/comp.h>
14 #include <__config>
15 #include <__iterator/iterator_traits.h>
16 #include <type_traits>
17 #include <utility>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #pragma GCC system_header
21 #endif
22 
23 _LIBCPP_PUSH_MACROS
24 #include <__undef_macros>
25 
26 _LIBCPP_BEGIN_NAMESPACE_STD
27 
28 template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
29 pair<_ForwardIterator1, _ForwardIterator1>
30     _LIBCPP_CONSTEXPR_AFTER_CXX11 __search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
31                                            _ForwardIterator2 __first2, _ForwardIterator2 __last2,
32                                            _BinaryPredicate __pred, forward_iterator_tag, forward_iterator_tag) {
33   if (__first2 == __last2)
34     return _VSTD::make_pair(__first1, __first1); // Everything matches an empty sequence
35   while (true) {
36     // Find first element in sequence 1 that matchs *__first2, with a mininum of loop checks
37     while (true) {
38       if (__first1 == __last1) // return __last1 if no element matches *__first2
39         return _VSTD::make_pair(__last1, __last1);
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) // If pattern exhausted, __first1 is the answer (works for 1 element pattern)
49         return _VSTD::make_pair(__first1, __m1);
50       if (++__m1 == __last1) // Otherwise if source exhaused, pattern not found
51         return _VSTD::make_pair(__last1, __last1);
52       if (!__pred(*__m1, *__m2)) // if there is a mismatch, restart with a new __first1
53       {
54         ++__first1;
55         break;
56       } // else there is a match, check next elements
57     }
58   }
59 }
60 
61 template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
62 _LIBCPP_CONSTEXPR_AFTER_CXX11 pair<_RandomAccessIterator1, _RandomAccessIterator1>
63 __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1, _RandomAccessIterator2 __first2,
64          _RandomAccessIterator2 __last2, _BinaryPredicate __pred, random_access_iterator_tag,
65          random_access_iterator_tag) {
66   typedef typename iterator_traits<_RandomAccessIterator1>::difference_type _D1;
67   typedef typename iterator_traits<_RandomAccessIterator2>::difference_type _D2;
68   // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
69   const _D2 __len2 = __last2 - __first2;
70   if (__len2 == 0)
71     return _VSTD::make_pair(__first1, __first1);
72   const _D1 __len1 = __last1 - __first1;
73   if (__len1 < __len2)
74     return _VSTD::make_pair(__last1, __last1);
75   const _RandomAccessIterator1 __s = __last1 - (__len2 - 1); // Start of pattern match can't go beyond here
76 
77   while (true) {
78     while (true) {
79       if (__first1 == __s)
80         return _VSTD::make_pair(__last1, __last1);
81       if (__pred(*__first1, *__first2))
82         break;
83       ++__first1;
84     }
85 
86     _RandomAccessIterator1 __m1 = __first1;
87     _RandomAccessIterator2 __m2 = __first2;
88     while (true) {
89       if (++__m2 == __last2)
90         return _VSTD::make_pair(__first1, __first1 + __len2);
91       ++__m1; // no need to check range on __m1 because __s guarantees we have enough source
92       if (!__pred(*__m1, *__m2)) {
93         ++__first1;
94         break;
95       }
96     }
97   }
98 }
99 
100 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
101 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
102 search(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2,
103        _BinaryPredicate __pred) {
104   return _VSTD::__search<typename add_lvalue_reference<_BinaryPredicate>::type>(
105              __first1, __last1, __first2, __last2, __pred,
106              typename iterator_traits<_ForwardIterator1>::iterator_category(),
107              typename iterator_traits<_ForwardIterator2>::iterator_category()).first;
108 }
109 
110 template <class _ForwardIterator1, class _ForwardIterator2>
111 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
112 search(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
113   typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
114   typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
115   return _VSTD::search(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
116 }
117 
118 #if _LIBCPP_STD_VER > 14
119 template <class _ForwardIterator, class _Searcher>
120 _LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
121 search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher& __s) {
122   return __s(__f, __l).first;
123 }
124 
125 #endif
126 
127 _LIBCPP_END_NAMESPACE_STD
128 
129 _LIBCPP_POP_MACROS
130 
131 #endif // _LIBCPP___ALGORITHM_SEARCH_H
132