libcxx/include/__ranges/istream_view.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___RANGES_ISTREAM_VIEW_H
  11 #define _LIBCPP___RANGES_ISTREAM_VIEW_H
  12
  13 #include <__concepts/constructible.h>
  14 #include <__concepts/derived_from.h>
  15 #include <__concepts/movable.h>
  16 #include <__config>
  17 #include <__fwd/istream.h>
  18 #include <__fwd/string.h>
  19 #include <__iterator/default_sentinel.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__memory/addressof.h>
  22 #include <__ranges/view_interface.h>
  23 #include <__type_traits/remove_cvref.h>
  24 #include <__utility/forward.h>
  25 #include <cstddef>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 #if _LIBCPP_STD_VER >= 20
  32
  33 _LIBCPP_BEGIN_NAMESPACE_STD
  34
  35 namespace ranges {
  36
  37 template <class _Val, class _CharT, class _Traits>
  38 concept __stream_extractable = requires(basic_istream<_CharT, _Traits>& __is, _Val& __t) { __is >> __t; };
  39
  40 template <movable _Val, class _CharT, class _Traits = char_traits<_CharT>>
  41   requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
  42 class basic_istream_view : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> {
  43   class __iterator;
  44
  45 public:
  46   _LIBCPP_HIDE_FROM_ABI constexpr explicit basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
  47       : __stream_(std::addressof(__stream)) {}
  48
  49   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
  50     *__stream_ >> __value_;
  51     return __iterator{*this};
  52   }
  53
  54   _LIBCPP_HIDE_FROM_ABI constexpr default_sentinel_t end() const noexcept { return default_sentinel; }
  55
  56 private:
  57   basic_istream<_CharT, _Traits>* __stream_;
  58   _LIBCPP_NO_UNIQUE_ADDRESS _Val __value_ = _Val();
  59 };
  60
  61 template <movable _Val, class _CharT, class _Traits>
  62   requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
  63 class basic_istream_view<_Val, _CharT, _Traits>::__iterator {
  64 public:
  65   using iterator_concept = input_iterator_tag;
  66   using difference_type  = ptrdiff_t;
  67   using value_type       = _Val;
  68
  69   _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(basic_istream_view<_Val, _CharT, _Traits>& __parent) noexcept
  70       : __parent_(std::addressof(__parent)) {}
  71
  72   __iterator(const __iterator&)                  = delete;
  73   _LIBCPP_HIDE_FROM_ABI __iterator(__iterator&&) = default;
  74
  75   __iterator& operator=(const __iterator&)                  = delete;
  76   _LIBCPP_HIDE_FROM_ABI __iterator& operator=(__iterator&&) = default;
  77
  78   _LIBCPP_HIDE_FROM_ABI __iterator& operator++() {
  79     *__parent_->__stream_ >> __parent_->__value_;
  80     return *this;
  81   }
  82
  83   _LIBCPP_HIDE_FROM_ABI void operator++(int) { ++*this; }
  84
  85   _LIBCPP_HIDE_FROM_ABI _Val& operator*() const { return __parent_->__value_; }
  86
  87   _LIBCPP_HIDE_FROM_ABI friend bool operator==(const __iterator& __x, default_sentinel_t) {
  88     return !*__x.__get_parent_stream();
  89   }
  90
  91 private:
  92   basic_istream_view<_Val, _CharT, _Traits>* __parent_;
  93
  94   _LIBCPP_HIDE_FROM_ABI constexpr basic_istream<_CharT, _Traits>* __get_parent_stream() const {
  95     return __parent_->__stream_;
  96   }
  97 };
  98
  99 template <class _Val>
 100 using istream_view = basic_istream_view<_Val, char>;
 101
 102 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 103 template <class _Val>
 104 using wistream_view = basic_istream_view<_Val, wchar_t>;
 105 #  endif
 106
 107 namespace views {
 108 namespace __istream {
 109
 110 // clang-format off
 111 template <class _Tp>
 112 struct __fn {
 113   template <class _Up, class _UnCVRef = remove_cvref_t<_Up>>
 114     requires derived_from<_UnCVRef, basic_istream<typename _UnCVRef::char_type,
 115                                                   typename _UnCVRef::traits_type>>
 116   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Up&& __u) const
 117     noexcept(noexcept(basic_istream_view<_Tp, typename _UnCVRef::char_type,
 118                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u))))
 119     -> decltype(      basic_istream_view<_Tp, typename _UnCVRef::char_type,
 120                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u)))
 121     {   return        basic_istream_view<_Tp, typename _UnCVRef::char_type,
 122                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u));
 123     }
 124 };
 125 // clang-format on
 126
 127 } // namespace __istream
 128
 129 inline namespace __cpo {
 130 template <class _Tp>
 131 inline constexpr auto istream = __istream::__fn<_Tp>{};
 132 } // namespace __cpo
 133 } // namespace views
 134
 135 } // namespace ranges
 136
 137 _LIBCPP_END_NAMESPACE_STD
 138
 139 #endif // _LIBCPP_STD_VER >= 20
 140
 141 #endif // _LIBCPP___RANGES_ISTREAM_VIEW_H