__cxx03/__algorithm/count.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_COUNT_H
0011 #define _LIBCPP___CXX03___ALGORITHM_COUNT_H
0012
0013 #include <__cxx03/__algorithm/iterator_operations.h>
0014 #include <__cxx03/__algorithm/min.h>
0015 #include <__cxx03/__bit/invert_if.h>
0016 #include <__cxx03/__bit/popcount.h>
0017 #include <__cxx03/__config>
0018 #include <__cxx03/__functional/identity.h>
0019 #include <__cxx03/__functional/invoke.h>
0020 #include <__cxx03/__fwd/bit_reference.h>
0021 #include <__cxx03/__iterator/iterator_traits.h>
0022
0023 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0024 #  pragma GCC system_header
0025 #endif
0026
0027 _LIBCPP_PUSH_MACROS
0028 #include <__cxx03/__undef_macros>
0029
0030 _LIBCPP_BEGIN_NAMESPACE_STD
0031
0032 // generic implementation
0033 template <class _AlgPolicy, class _Iter, class _Sent, class _Tp, class _Proj>
0034 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename _IterOps<_AlgPolicy>::template __difference_type<_Iter>
0035 __count(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
0036   typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __r(0);
0037   for (; __first != __last; ++__first)
0038     if (std::__invoke(__proj, *__first) == __value)
0039       ++__r;
0040   return __r;
0041 }
0042
0043 // __bit_iterator implementation
0044 template <bool _ToCount, class _Cp, bool _IsConst>
0045 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __bit_iterator<_Cp, _IsConst>::difference_type
0046 __count_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n) {
0047   using _It             = __bit_iterator<_Cp, _IsConst>;
0048   using __storage_type  = typename _It::__storage_type;
0049   using difference_type = typename _It::difference_type;
0050
0051   const int __bits_per_word = _It::__bits_per_word;
0052   difference_type __r       = 0;
0053   // do first partial word
0054   if (__first.__ctz_ != 0) {
0055     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
0056     __storage_type __dn    = std::min(__clz_f, __n);
0057     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
0058     __r                    = std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
0059     __n -= __dn;
0060     ++__first.__seg_;
0061   }
0062   // do middle whole words
0063   for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
0064     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_));
0065   // do last partial word
0066   if (__n > 0) {
0067     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
0068     __r += std::__libcpp_popcount(std::__invert_if<!_ToCount>(*__first.__seg_) & __m);
0069   }
0070   return __r;
0071 }
0072
0073 template <class, class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
0074 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<__bit_iterator<_Cp, _IsConst> >
0075 __count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
0076   if (__value)
0077     return std::__count_bool<true>(__first, static_cast<typename _Cp::size_type>(__last - __first));
0078   return std::__count_bool<false>(__first, static_cast<typename _Cp::size_type>(__last - __first));
0079 }
0080
0081 template <class _InputIterator, class _Tp>
0082 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_diff_t<_InputIterator>
0083 count(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
0084   __identity __proj;
0085   return std::__count<_ClassicAlgPolicy>(__first, __last, __value, __proj);
0086 }
0087
0088 _LIBCPP_END_NAMESPACE_STD
0089
0090 _LIBCPP_POP_MACROS
0091
0092 #endif // _LIBCPP___CXX03___ALGORITHM_COUNT_H