libcxx/include/__cxx03/__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 <__cxx03/__algorithm/iterator_operations.h>
  14 #include <__cxx03/__algorithm/min.h>
  15 #include <__cxx03/__bit/invert_if.h>
  16 #include <__cxx03/__bit/popcount.h>
  17 #include <__cxx03/__config>
  18 #include <__cxx03/__functional/identity.h>
  19 #include <__cxx03/__functional/invoke.h>
  20 #include <__cxx03/__fwd/bit_reference.h>
  21 #include <__cxx03/__iterator/iterator_traits.h>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 _LIBCPP_PUSH_MACROS
  28 #include <__cxx03/__undef_macros>
  29
  30 _LIBCPP_BEGIN_NAMESPACE_STD
  31
  32 // generic implementation
  33 template <class _AlgPolicy, class _Iter, class _Sent, class _Tp, class _Proj>
  34 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename _IterOps<_AlgPolicy>::template __difference_type<_Iter>
  35 __count(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
  36   typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __r(0);
  37   for (; __first != __last; ++__first)
  38     if (std::__invoke(__proj, *__first) == __value)
  39       ++__r;
  40   return __r;
  41 }
  42
  43 // __bit_iterator implementation
  44 template <bool _ToCount, class _Cp, bool _IsConst>
  45 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __bit_iterator<_Cp, _IsConst>::difference_type
  46 __count_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n) {
  47   using _It             = __bit_iterator<_Cp, _IsConst>;
  48   using __storage_type  = typename _It::__storage_type;
  49   using difference_type = typename _It::difference_type;
  50
  51   const int __bits_per_word = _It::__bits_per_word;
  52   difference_type __r       = 0;
  53   // do first partial word
  54   if (__first.__ctz_ != 0) {
  55     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
  56     __storage_type __dn    = std::min(__clz_f, __n);
  57     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
  58     __r                    = std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
  59     __n -= __dn;
  60     ++__first.__seg_;
  61   }
  62   // do middle whole words
  63   for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
  64     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_));
  65   // do last partial word
  66   if (__n > 0) {
  67     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
  68     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
  69   }
  70   return __r;
  71 }
  72
  73 template <class, class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
  74 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<__bit_iterator<_Cp, _IsConst> >
  75 __count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
  76   if (__value)
  77     return std::__count_bool<true>(__first, static_cast<typename _Cp::size_type>(__last - __first));
  78   return std::__count_bool<false>(__first, static_cast<typename _Cp::size_type>(__last - __first));
  79 }
  80
  81 template <class _InputIterator, class _Tp>
  82 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<_InputIterator>
  83 count(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
  84   __identity __proj;
  85   return std::__count<_ClassicAlgPolicy>(__first, __last, __value, __proj);
  86 }
  87
  88 _LIBCPP_END_NAMESPACE_STD
  89
  90 _LIBCPP_POP_MACROS
  91
  92 #endif // _LIBCPP___ALGORITHM_COUNT_H