libcxx/include/__algorithm/count.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_COUNT_H
  11 #define _LIBCPP___ALGORITHM_COUNT_H
  12
  13 #include <__algorithm/iterator_operations.h>
  14 #include <__algorithm/min.h>
  15 #include <__bit/invert_if.h>
  16 #include <__bit/popcount.h>
  17 #include <__config>
  18 #include <__functional/identity.h>
  19 #include <__fwd/bit_reference.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__type_traits/enable_if.h>
  22 #include <__type_traits/invoke.h>
  23
  24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  25 #  pragma GCC system_header
  26 #endif
  27
  28 _LIBCPP_PUSH_MACROS
  29 #include <__undef_macros>
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 // generic implementation
  34 template <class _AlgPolicy, class _Iter, class _Sent, class _Tp, class _Proj>
  35 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename _IterOps<_AlgPolicy>::template __difference_type<_Iter>
  36 __count(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
  37   typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __r(0);
  38   for (; __first != __last; ++__first)
  39     if (std::__invoke(__proj, *__first) == __value)
  40       ++__r;
  41   return __r;
  42 }
  43
  44 // __bit_iterator implementation
  45 template <bool _ToCount, class _Cp, bool _IsConst>
  46 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __bit_iterator<_Cp, _IsConst>::difference_type
  47 __count_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n) {
  48   using _It             = __bit_iterator<_Cp, _IsConst>;
  49   using __storage_type  = typename _It::__storage_type;
  50   using difference_type = typename _It::difference_type;
  51
  52   const int __bits_per_word = _It::__bits_per_word;
  53   difference_type __r       = 0;
  54   // do first partial word
  55   if (__first.__ctz_ != 0) {
  56     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
  57     __storage_type __dn    = std::min(__clz_f, __n);
  58     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
  59     __r                    = std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
  60     __n -= __dn;
  61     ++__first.__seg_;
  62   }
  63   // do middle whole words
  64   for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
  65     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_));
  66   // do last partial word
  67   if (__n > 0) {
  68     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
  69     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
  70   }
  71   return __r;
  72 }
  73
  74 template <class, class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
  75 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<__bit_iterator<_Cp, _IsConst> >
  76 __count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
  77   if (__value)
  78     return std::__count_bool<true>(__first, static_cast<typename _Cp::size_type>(__last - __first));
  79   return std::__count_bool<false>(__first, static_cast<typename _Cp::size_type>(__last - __first));
  80 }
  81
  82 template <class _InputIterator, class _Tp>
  83 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<_InputIterator>
  84 count(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
  85   __identity __proj;
  86   return std::__count<_ClassicAlgPolicy>(__first, __last, __value, __proj);
  87 }
  88
  89 _LIBCPP_END_NAMESPACE_STD
  90
  91 _LIBCPP_POP_MACROS
  92
  93 #endif // _LIBCPP___ALGORITHM_COUNT_H