libcxx/include/__cxx03/__algorithm/search_n.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_SEARCH_N_H
  11 #define _LIBCPP___ALGORITHM_SEARCH_N_H
  12
  13 #include <__cxx03/__algorithm/comp.h>
  14 #include <__cxx03/__algorithm/iterator_operations.h>
  15 #include <__cxx03/__config>
  16 #include <__cxx03/__functional/identity.h>
  17 #include <__cxx03/__functional/invoke.h>
  18 #include <__cxx03/__iterator/advance.h>
  19 #include <__cxx03/__iterator/concepts.h>
  20 #include <__cxx03/__iterator/distance.h>
  21 #include <__cxx03/__iterator/iterator_traits.h>
  22 #include <__cxx03/__ranges/concepts.h>
  23 #include <__cxx03/__type_traits/is_callable.h>
  24 #include <__cxx03/__utility/convert_to_integral.h>
  25 #include <__cxx03/__utility/pair.h>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj>
  34 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter, _Iter> __search_n_forward_impl(
  35     _Iter __first, _Sent __last, _SizeT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
  36   if (__count <= 0)
  37     return std::make_pair(__first, __first);
  38   while (true) {
  39     // Find first element in sequence that matchs __value, with a mininum of loop checks
  40     while (true) {
  41       if (__first == __last) { // return __last if no element matches __value
  42         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
  43         return std::make_pair(__first, __first);
  44       }
  45       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
  46         break;
  47       ++__first;
  48     }
  49     // *__first matches __value, now match elements after here
  50     _Iter __m = __first;
  51     _SizeT __c(0);
  52     while (true) {
  53       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
  54         return std::make_pair(__first, ++__m);
  55       if (++__m == __last) { // Otherwise if source exhaused, pattern not found
  56         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
  57         return std::make_pair(__first, __first);
  58       }
  59
  60       // if there is a mismatch, restart with a new __first
  61       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value)) {
  62         __first = __m;
  63         ++__first;
  64         break;
  65       } // else there is a match, check next elements
  66     }
  67   }
  68 }
  69
  70 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj, class _DiffT>
  71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 std::pair<_Iter, _Iter> __search_n_random_access_impl(
  72     _Iter __first, _Sent __last, _SizeT __count, const _Type& __value, _Pred& __pred, _Proj& __proj, _DiffT __size1) {
  73   using difference_type = typename iterator_traits<_Iter>::difference_type;
  74   if (__count == 0)
  75     return std::make_pair(__first, __first);
  76   if (__size1 < static_cast<_DiffT>(__count)) {
  77     _IterOps<_AlgPolicy>::__advance_to(__first, __last);
  78     return std::make_pair(__first, __first);
  79   }
  80
  81   const auto __s = __first + __size1 - difference_type(__count - 1); // Start of pattern match can't go beyond here
  82   while (true) {
  83     // Find first element in sequence that matchs __value, with a mininum of loop checks
  84     while (true) {
  85       if (__first >= __s) { // return __last if no element matches __value
  86         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
  87         return std::make_pair(__first, __first);
  88       }
  89       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
  90         break;
  91       ++__first;
  92     }
  93     // *__first matches __value_, now match elements after here
  94     auto __m = __first;
  95     _SizeT __c(0);
  96     while (true) {
  97       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
  98         return std::make_pair(__first, __first + _DiffT(__count));
  99       ++__m; // no need to check range on __m because __s guarantees we have enough source
 100
 101       // if there is a mismatch, restart with a new __first
 102       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value)) {
 103         __first = __m;
 104         ++__first;
 105         break;
 106       } // else there is a match, check next elements
 107     }
 108   }
 109 }
 110
 111 template <class _Iter,
 112           class _Sent,
 113           class _DiffT,
 114           class _Type,
 115           class _Pred,
 116           class _Proj,
 117           __enable_if_t<__has_random_access_iterator_category<_Iter>::value, int> = 0>
 118 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter, _Iter>
 119 __search_n_impl(_Iter __first, _Sent __last, _DiffT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
 120   return std::__search_n_random_access_impl<_ClassicAlgPolicy>(
 121       __first, __last, __count, __value, __pred, __proj, __last - __first);
 122 }
 123
 124 template <class _Iter1,
 125           class _Sent1,
 126           class _DiffT,
 127           class _Type,
 128           class _Pred,
 129           class _Proj,
 130           __enable_if_t<__has_forward_iterator_category<_Iter1>::value &&
 131                             !__has_random_access_iterator_category<_Iter1>::value,
 132                         int> = 0>
 133 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter1, _Iter1>
 134 __search_n_impl(_Iter1 __first, _Sent1 __last, _DiffT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
 135   return std::__search_n_forward_impl<_ClassicAlgPolicy>(__first, __last, __count, __value, __pred, __proj);
 136 }
 137
 138 template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
 139 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator search_n(
 140     _ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value, _BinaryPredicate __pred) {
 141   static_assert(
 142       __is_callable<_BinaryPredicate, decltype(*__first), const _Tp&>::value, "BinaryPredicate has to be callable");
 143   auto __proj = __identity();
 144   return std::__search_n_impl(__first, __last, std::__convert_to_integral(__count), __value, __pred, __proj).first;
 145 }
 146
 147 template <class _ForwardIterator, class _Size, class _Tp>
 148 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 149 search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value) {
 150   return std::search_n(__first, __last, std::__convert_to_integral(__count), __value, __equal_to());
 151 }
 152
 153 _LIBCPP_END_NAMESPACE_STD
 154
 155 #endif // _LIBCPP___ALGORITHM_SEARCH_N_H