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