libcxx/include/__algorithm/find_end.h

   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 <__algorithm/comp.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__algorithm/search.h>
  16 #include <__config>
  17 #include <__functional/identity.h>
  18 #include <__functional/invoke.h>
  19 #include <__iterator/advance.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__iterator/next.h>
  22 #include <__iterator/reverse_iterator.h>
  23 #include <__utility/pair.h>
  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 <
  32     class _AlgPolicy,
  33     class _Iter1,
  34     class _Sent1,
  35     class _Iter2,
  36     class _Sent2,
  37     class _Pred,
  38     class _Proj1,
  39     class _Proj2>
  40 _LIBCPP_HIDE_FROM_ABI inline _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter1, _Iter1> __find_end_impl(
  41     _Iter1 __first1,
  42     _Sent1 __last1,
  43     _Iter2 __first2,
  44     _Sent2 __last2,
  45     _Pred& __pred,
  46     _Proj1& __proj1,
  47     _Proj2& __proj2,
  48     forward_iterator_tag,
  49     forward_iterator_tag) {
  50   // modeled after search algorithm
  51   _Iter1 __match_first = _IterOps<_AlgPolicy>::next(__first1, __last1); // __last1 is the "default" answer
  52   _Iter1 __match_last = __match_first;
  53   if (__first2 == __last2)
  54     return pair<_Iter1, _Iter1>(__match_last, __match_last);
  55   while (true) {
  56     while (true) {
  57       if (__first1 == __last1) // if source exhausted return last correct answer (or __last1 if never found)
  58         return pair<_Iter1, _Iter1>(__match_first, __match_last);
  59       if (std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
  60         break;
  61       ++__first1;
  62     }
  63     // *__first1 matches *__first2, now match elements after here
  64     _Iter1 __m1 = __first1;
  65     _Iter2 __m2 = __first2;
  66     while (true) {
  67       if (++__m2 == __last2) { // Pattern exhaused, record answer and search for another one
  68         __match_first = __first1;
  69         __match_last = ++__m1;
  70         ++__first1;
  71         break;
  72       }
  73       if (++__m1 == __last1) // Source exhausted, return last answer
  74         return pair<_Iter1, _Iter1>(__match_first, __match_last);
  75        // mismatch, restart with a new __first
  76       if (!std::__invoke(__pred, std::__invoke(__proj1, *__m1), std::__invoke(__proj2, *__m2)))
  77       {
  78         ++__first1;
  79         break;
  80       } // else there is a match, check next elements
  81     }
  82   }
  83 }
  84
  85 template <
  86     class _IterOps,
  87     class _Pred,
  88     class _Iter1,
  89     class _Sent1,
  90     class _Iter2,
  91     class _Sent2,
  92     class _Proj1,
  93     class _Proj2>
  94 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter1 __find_end(
  95     _Iter1 __first1,
  96     _Sent1 __sent1,
  97     _Iter2 __first2,
  98     _Sent2 __sent2,
  99     _Pred& __pred,
 100     _Proj1& __proj1,
 101     _Proj2& __proj2,
 102     bidirectional_iterator_tag,
 103     bidirectional_iterator_tag) {
 104   auto __last1 = _IterOps::next(__first1, __sent1);
 105   auto __last2 = _IterOps::next(__first2, __sent2);
 106   // modeled after search algorithm (in reverse)
 107   if (__first2 == __last2)
 108     return __last1; // Everything matches an empty sequence
 109   _Iter1 __l1 = __last1;
 110   _Iter2 __l2 = __last2;
 111   --__l2;
 112   while (true) {
 113     // Find last element in sequence 1 that matchs *(__last2-1), with a mininum of loop checks
 114     while (true) {
 115       if (__first1 == __l1) // return __last1 if no element matches *__first2
 116         return __last1;
 117       if (std::__invoke(__pred, std::__invoke(__proj1, *--__l1), std::__invoke(__proj2, *__l2)))
 118         break;
 119     }
 120     // *__l1 matches *__l2, now match elements before here
 121     _Iter1 __m1 = __l1;
 122     _Iter2 __m2 = __l2;
 123     while (true) {
 124       if (__m2 == __first2) // If pattern exhausted, __m1 is the answer (works for 1 element pattern)
 125         return __m1;
 126       if (__m1 == __first1) // Otherwise if source exhaused, pattern not found
 127         return __last1;
 128
 129       // if there is a mismatch, restart with a new __l1
 130       if (!std::__invoke(__pred, std::__invoke(__proj1, *--__m1), std::__invoke(__proj2, *--__m2)))
 131       {
 132         break;
 133       } // else there is a match, check next elements
 134     }
 135   }
 136 }
 137
 138 template <
 139     class _AlgPolicy,
 140     class _Pred,
 141     class _Iter1,
 142     class _Sent1,
 143     class _Iter2,
 144     class _Sent2,
 145     class _Proj1,
 146     class _Proj2>
 147 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter1 __find_end(
 148     _Iter1 __first1,
 149     _Sent1 __sent1,
 150     _Iter2 __first2,
 151     _Sent2 __sent2,
 152     _Pred& __pred,
 153     _Proj1& __proj1,
 154     _Proj2& __proj2,
 155     random_access_iterator_tag,
 156     random_access_iterator_tag) {
 157   typedef typename iterator_traits<_Iter1>::difference_type _D1;
 158   auto __last1 = _IterOps<_AlgPolicy>::next(__first1, __sent1);
 159   auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __sent2);
 160   // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
 161   auto __len2 = __last2 - __first2;
 162   if (__len2 == 0)
 163     return __last1;
 164   auto __len1 = __last1 - __first1;
 165   if (__len1 < __len2)
 166     return __last1;
 167   const _Iter1 __s = __first1 + _D1(__len2 - 1); // End of pattern match can't go before here
 168   _Iter1 __l1 = __last1;
 169   _Iter2 __l2 = __last2;
 170   --__l2;
 171   while (true) {
 172     while (true) {
 173       if (__s == __l1)
 174         return __last1;
 175       if (std::__invoke(__pred, std::__invoke(__proj1, *--__l1), std::__invoke(__proj2, *__l2)))
 176         break;
 177     }
 178     _Iter1 __m1 = __l1;
 179     _Iter2 __m2 = __l2;
 180     while (true) {
 181       if (__m2 == __first2)
 182         return __m1;
 183       // no need to check range on __m1 because __s guarantees we have enough source
 184       if (!std::__invoke(__pred, std::__invoke(__proj1, *--__m1), std::__invoke(*--__m2))) {
 185         break;
 186       }
 187     }
 188   }
 189 }
 190
 191 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
 192 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
 193 _ForwardIterator1 __find_end_classic(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 194                                      _ForwardIterator2 __first2, _ForwardIterator2 __last2,
 195                                      _BinaryPredicate& __pred) {
 196   auto __proj = __identity();
 197   return std::__find_end_impl<_ClassicAlgPolicy>(
 198              __first1,
 199              __last1,
 200              __first2,
 201              __last2,
 202              __pred,
 203              __proj,
 204              __proj,
 205              typename iterator_traits<_ForwardIterator1>::iterator_category(),
 206              typename iterator_traits<_ForwardIterator2>::iterator_category())
 207       .first;
 208 }
 209
 210 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
 211 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 212 _ForwardIterator1 find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 213                            _ForwardIterator2 __first2, _ForwardIterator2 __last2,
 214                            _BinaryPredicate __pred) {
 215   return std::__find_end_classic(__first1, __last1, __first2, __last2, __pred);
 216 }
 217
 218 template <class _ForwardIterator1, class _ForwardIterator2>
 219 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 220 _ForwardIterator1 find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 221                            _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
 222   return std::find_end(__first1, __last1, __first2, __last2, __equal_to());
 223 }
 224
 225 _LIBCPP_END_NAMESPACE_STD
 226
 227 #endif // _LIBCPP___ALGORITHM_FIND_END_OF_H