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/min.h>
  14 #include <__algorithm/unwrap_iter.h>
  15 #include <__bit/countr.h>
  16 #include <__bit/invert_if.h>
  17 #include <__config>
  18 #include <__functional/identity.h>
  19 #include <__functional/invoke.h>
  20 #include <__fwd/bit_reference.h>
  21 #include <__string/constexpr_c_functions.h>
  22 #include <__type_traits/is_same.h>
  23
  24 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
  25 #  include <cwchar>
  26 #endif
  27
  28 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  29 #  pragma GCC system_header
  30 #endif
  31
  32 _LIBCPP_PUSH_MACROS
  33 #include <__undef_macros>
  34
  35 _LIBCPP_BEGIN_NAMESPACE_STD
  36
  37 // generic implementation
  38 template <class _Iter, class _Sent, class _Tp, class _Proj>
  39 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter
  40 __find_impl(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
  41   for (; __first != __last; ++__first)
  42     if (std::__invoke(__proj, *__first) == __value)
  43       break;
  44   return __first;
  45 }
  46
  47 // trivially equality comparable implementations
  48 template <class _Tp,
  49           class _Up,
  50           class _Proj,
  51           __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
  52                             sizeof(_Tp) == 1,
  53                         int> = 0>
  54 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
  55 __find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
  56   if (auto __ret = std::__constexpr_memchr(__first, __value, __last - __first))
  57     return __ret;
  58   return __last;
  59 }
  60
  61 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
  62 template <class _Tp,
  63           class _Up,
  64           class _Proj,
  65           __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
  66                             sizeof(_Tp) == sizeof(wchar_t) && _LIBCPP_ALIGNOF(_Tp) >= _LIBCPP_ALIGNOF(wchar_t),
  67                         int> = 0>
  68 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
  69 __find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
  70   if (auto __ret = std::__constexpr_wmemchr(__first, __value, __last - __first))
  71     return __ret;
  72   return __last;
  73 }
  74 #endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
  75
  76 // __bit_iterator implementation
  77 template <bool _ToFind, class _Cp, bool _IsConst>
  78 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, _IsConst>
  79 __find_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n) {
  80   using _It            = __bit_iterator<_Cp, _IsConst>;
  81   using __storage_type = typename _It::__storage_type;
  82
  83   const int __bits_per_word = _It::__bits_per_word;
  84   // do first partial word
  85   if (__first.__ctz_ != 0) {
  86     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
  87     __storage_type __dn    = std::min(__clz_f, __n);
  88     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
  89     __storage_type __b     = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
  90     if (__b)
  91       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
  92     if (__n == __dn)
  93       return __first + __n;
  94     __n -= __dn;
  95     ++__first.__seg_;
  96   }
  97   // do middle whole words
  98   for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word) {
  99     __storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_);
 100     if (__b)
 101       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
 102   }
 103   // do last partial word
 104   if (__n > 0) {
 105     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
 106     __storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
 107     if (__b)
 108       return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
 109   }
 110   return _It(__first.__seg_, static_cast<unsigned>(__n));
 111 }
 112
 113 template <class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
 114 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cp, _IsConst>
 115 __find_impl(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
 116   if (static_cast<bool>(__value))
 117     return std::__find_bool<true>(__first, static_cast<typename _Cp::size_type>(__last - __first));
 118   return std::__find_bool<false>(__first, static_cast<typename _Cp::size_type>(__last - __first));
 119 }
 120
 121 template <class _InputIterator, class _Tp>
 122 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
 123 find(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
 124   __identity __proj;
 125   return std::__rewrap_iter(
 126       __first, std::__find_impl(std::__unwrap_iter(__first), std::__unwrap_iter(__last), __value, __proj));
 127 }
 128
 129 _LIBCPP_END_NAMESPACE_STD
 130
 131 _LIBCPP_POP_MACROS
 132
 133 #endif // _LIBCPP___ALGORITHM_FIND_H