libcxx/include/__algorithm/find.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_FIND_H
  11 #define _LIBCPP___ALGORITHM_FIND_H
  12
  13 #include <__algorithm/find_segment_if.h>
  14 #include <__algorithm/min.h>
  15 #include <__algorithm/unwrap_iter.h>
  16 #include <__bit/countr.h>
  17 #include <__bit/invert_if.h>
  18 #include <__config>
  19 #include <__functional/identity.h>
  20 #include <__fwd/bit_reference.h>
  21 #include <__iterator/segmented_iterator.h>
  22 #include <__string/constexpr_c_functions.h>
  23 #include <__type_traits/enable_if.h>
  24 #include <__type_traits/invoke.h>
  25 #include <__type_traits/is_equality_comparable.h>
  26 #include <__type_traits/is_integral.h>
  27 #include <__type_traits/is_signed.h>
  28 #include <__utility/move.h>
  29 #include <limits>
  30
  31 #if _LIBCPP_HAS_WIDE_CHARACTERS
  32 #  include <cwchar>
  33 #endif
  34
  35 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  36 #  pragma GCC system_header
  37 #endif
  38
  39 _LIBCPP_PUSH_MACROS
  40 #include <__undef_macros>
  41
  42 _LIBCPP_BEGIN_NAMESPACE_STD
  43
  44 // generic implementation
  45 template <class _Iter, class _Sent, class _Tp, class _Proj>
  46 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter
  47 __find(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
  48   for (; __first != __last; ++__first)
  49     if (std::__invoke(__proj, *__first) == __value)
  50       break;
  51   return __first;
  52 }
  53
  54 // trivially equality comparable implementations
  55 template <class _Tp,
  56           class _Up,
  57           class _Proj,
  58           __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
  59                             sizeof(_Tp) == 1,
  60                         int> = 0>
  61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __find(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
  62   if (auto __ret = std::__constexpr_memchr(__first, __value, __last - __first))
  63     return __ret;
  64   return __last;
  65 }
  66
  67 #if _LIBCPP_HAS_WIDE_CHARACTERS
  68 template <class _Tp,
  69           class _Up,
  70           class _Proj,
  71           __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
  72                             sizeof(_Tp) == sizeof(wchar_t) && _LIBCPP_ALIGNOF(_Tp) >= _LIBCPP_ALIGNOF(wchar_t),
  73                         int> = 0>
  74 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __find(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
  75   if (auto __ret = std::__constexpr_wmemchr(__first, __value, __last - __first))
  76     return __ret;
  77   return __last;
  78 }
  79 #endif // _LIBCPP_HAS_WIDE_CHARACTERS
  80
  81 // TODO: This should also be possible to get right with different signedness
  82 // cast integral types to allow vectorization
  83 template <class _Tp,
  84           class _Up,
  85           class _Proj,
  86           __enable_if_t<__is_identity<_Proj>::value && !__libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
  87                             is_integral<_Tp>::value && is_integral<_Up>::value &&
  88                             is_signed<_Tp>::value == is_signed<_Up>::value,
  89                         int> = 0>
  90 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
  91 __find(_Tp* __first, _Tp* __last, const _Up& __value, _Proj& __proj) {
  92   if (__value < numeric_limits<_Tp>::min() || __value > numeric_limits<_Tp>::max())
  93     return __last;
  94   return std::__find(__first, __last, _Tp(__value), __proj);
  95 }
  96
  97 // __bit_iterator implementation
  98 template <bool _ToFind, class _Cp, bool _IsConst>
  99 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, _IsConst>
 100 __find_bool(__bit_iterator<_Cp, _IsConst> __first, typename __size_difference_type_traits<_Cp>::size_type __n) {
 101   using _It            = __bit_iterator<_Cp, _IsConst>;
 102   using __storage_type = typename _It::__storage_type;
 103
 104   const int __bits_per_word = _It::__bits_per_word;
 105   // do first partial word
 106   if (__first.__ctz_ != 0) {
 107     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
 108     __storage_type __dn    = std::min(__clz_f, __n);
 109     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
 110     __storage_type __b     = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
 111     if (__b)
 112       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
 113     if (__n == __dn)
 114       return __first + __n;
 115     __n -= __dn;
 116     ++__first.__seg_;
 117   }
 118   // do middle whole words
 119   for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word) {
 120     __storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_);
 121     if (__b)
 122       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
 123   }
 124   // do last partial word
 125   if (__n > 0) {
 126     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
 127     __storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
 128     if (__b)
 129       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
 130   }
 131   return _It(__first.__seg_, static_cast<unsigned>(__n));
 132 }
 133
 134 template <class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
 135 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cp, _IsConst>
 136 __find(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
 137   if (static_cast<bool>(__value))
 138     return std::__find_bool<true>(
 139         __first, static_cast<typename __size_difference_type_traits<_Cp>::size_type>(__last - __first));
 140   return std::__find_bool<false>(
 141       __first, static_cast<typename __size_difference_type_traits<_Cp>::size_type>(__last - __first));
 142 }
 143
 144 // segmented iterator implementation
 145
 146 template <class>
 147 struct __find_segment;
 148
 149 template <class _SegmentedIterator,
 150           class _Tp,
 151           class _Proj,
 152           __enable_if_t<__is_segmented_iterator<_SegmentedIterator>::value, int> = 0>
 153 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
 154 __find(_SegmentedIterator __first, _SegmentedIterator __last, const _Tp& __value, _Proj& __proj) {
 155   return std::__find_segment_if(std::move(__first), std::move(__last), __find_segment<_Tp>(__value), __proj);
 156 }
 157
 158 template <class _Tp>
 159 struct __find_segment {
 160   const _Tp& __value_;
 161
 162   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __find_segment(const _Tp& __value) : __value_(__value) {}
 163
 164   template <class _InputIterator, class _Proj>
 165   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _InputIterator
 166   operator()(_InputIterator __first, _InputIterator __last, _Proj& __proj) const {
 167     return std::__find(__first, __last, __value_, __proj);
 168   }
 169 };
 170
 171 // public API
 172 template <class _InputIterator, class _Tp>
 173 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
 174 find(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
 175   __identity __proj;
 176   return std::__rewrap_iter(
 177       __first, std::__find(std::__unwrap_iter(__first), std::__unwrap_iter(__last), __value, __proj));
 178 }
 179
 180 _LIBCPP_END_NAMESPACE_STD
 181
 182 _LIBCPP_POP_MACROS
 183
 184 #endif // _LIBCPP___ALGORITHM_FIND_H