__cxx03/__algorithm/search_n.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03___ALGORITHM_SEARCH_N_H
0011 #define _LIBCPP___CXX03___ALGORITHM_SEARCH_N_H
0012
0013 #include <__cxx03/__algorithm/comp.h>
0014 #include <__cxx03/__algorithm/iterator_operations.h>
0015 #include <__cxx03/__config>
0016 #include <__cxx03/__functional/identity.h>
0017 #include <__cxx03/__functional/invoke.h>
0018 #include <__cxx03/__iterator/advance.h>
0019 #include <__cxx03/__iterator/concepts.h>
0020 #include <__cxx03/__iterator/distance.h>
0021 #include <__cxx03/__iterator/iterator_traits.h>
0022 #include <__cxx03/__ranges/concepts.h>
0023 #include <__cxx03/__type_traits/is_callable.h>
0024 #include <__cxx03/__utility/convert_to_integral.h>
0025 #include <__cxx03/__utility/pair.h>
0026
0027 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0028 #  pragma GCC system_header
0029 #endif
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj>
0034 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter, _Iter> __search_n_forward_impl(
0035     _Iter __first, _Sent __last, _SizeT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
0036   if (__count <= 0)
0037     return std::make_pair(__first, __first);
0038   while (true) {
0039     // Find first element in sequence that matchs __value, with a mininum of loop checks
0040     while (true) {
0041       if (__first == __last) { // return __last if no element matches __value
0042         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
0043         return std::make_pair(__first, __first);
0044       }
0045       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
0046         break;
0047       ++__first;
0048     }
0049     // *__first matches __value, now match elements after here
0050     _Iter __m = __first;
0051     _SizeT __c(0);
0052     while (true) {
0053       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
0054         return std::make_pair(__first, ++__m);
0055       if (++__m == __last) { // Otherwise if source exhaused, pattern not found
0056         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
0057         return std::make_pair(__first, __first);
0058       }
0059
0060       // if there is a mismatch, restart with a new __first
0061       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value)) {
0062         __first = __m;
0063         ++__first;
0064         break;
0065       } // else there is a match, check next elements
0066     }
0067   }
0068 }
0069
0070 template <class _AlgPolicy, class _Pred, class _Iter, class _Sent, class _SizeT, class _Type, class _Proj, class _DiffT>
0071 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 std::pair<_Iter, _Iter> __search_n_random_access_impl(
0072     _Iter __first, _Sent __last, _SizeT __count, const _Type& __value, _Pred& __pred, _Proj& __proj, _DiffT __size1) {
0073   using difference_type = typename iterator_traits<_Iter>::difference_type;
0074   if (__count == 0)
0075     return std::make_pair(__first, __first);
0076   if (__size1 < static_cast<_DiffT>(__count)) {
0077     _IterOps<_AlgPolicy>::__advance_to(__first, __last);
0078     return std::make_pair(__first, __first);
0079   }
0080
0081   const auto __s = __first + __size1 - difference_type(__count - 1); // Start of pattern match can't go beyond here
0082   while (true) {
0083     // Find first element in sequence that matchs __value, with a mininum of loop checks
0084     while (true) {
0085       if (__first >= __s) { // return __last if no element matches __value
0086         _IterOps<_AlgPolicy>::__advance_to(__first, __last);
0087         return std::make_pair(__first, __first);
0088       }
0089       if (std::__invoke(__pred, std::__invoke(__proj, *__first), __value))
0090         break;
0091       ++__first;
0092     }
0093     // *__first matches __value_, now match elements after here
0094     auto __m = __first;
0095     _SizeT __c(0);
0096     while (true) {
0097       if (++__c == __count) // If pattern exhausted, __first is the answer (works for 1 element pattern)
0098         return std::make_pair(__first, __first + _DiffT(__count));
0099       ++__m; // no need to check range on __m because __s guarantees we have enough source
0100
0101       // if there is a mismatch, restart with a new __first
0102       if (!std::__invoke(__pred, std::__invoke(__proj, *__m), __value)) {
0103         __first = __m;
0104         ++__first;
0105         break;
0106       } // else there is a match, check next elements
0107     }
0108   }
0109 }
0110
0111 template <class _Iter,
0112           class _Sent,
0113           class _DiffT,
0114           class _Type,
0115           class _Pred,
0116           class _Proj,
0117           __enable_if_t<__has_random_access_iterator_category<_Iter>::value, int> = 0>
0118 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter, _Iter>
0119 __search_n_impl(_Iter __first, _Sent __last, _DiffT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
0120   return std::__search_n_random_access_impl<_ClassicAlgPolicy>(
0121       __first, __last, __count, __value, __pred, __proj, __last - __first);
0122 }
0123
0124 template <class _Iter1,
0125           class _Sent1,
0126           class _DiffT,
0127           class _Type,
0128           class _Pred,
0129           class _Proj,
0130           __enable_if_t<__has_forward_iterator_category<_Iter1>::value &&
0131                             !__has_random_access_iterator_category<_Iter1>::value,
0132                         int> = 0>
0133 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter1, _Iter1>
0134 __search_n_impl(_Iter1 __first, _Sent1 __last, _DiffT __count, const _Type& __value, _Pred& __pred, _Proj& __proj) {
0135   return std::__search_n_forward_impl<_ClassicAlgPolicy>(__first, __last, __count, __value, __pred, __proj);
0136 }
0137
0138 template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
0139 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator search_n(
0140     _ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value, _BinaryPredicate __pred) {
0141   static_assert(
0142       __is_callable<_BinaryPredicate, decltype(*__first), const _Tp&>::value, "BinaryPredicate has to be callable");
0143   auto __proj = __identity();
0144   return std::__search_n_impl(__first, __last, std::__convert_to_integral(__count), __value, __pred, __proj).first;
0145 }
0146
0147 template <class _ForwardIterator, class _Size, class _Tp>
0148 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
0149 search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value) {
0150   return std::search_n(__first, __last, std::__convert_to_integral(__count), __value, __equal_to());
0151 }
0152
0153 _LIBCPP_END_NAMESPACE_STD
0154
0155 #endif // _LIBCPP___CXX03___ALGORITHM_SEARCH_N_H