__cxx03/__ranges/istream_view.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___RANGES_ISTREAM_VIEW_H
0011 #define _LIBCPP___CXX03___RANGES_ISTREAM_VIEW_H
0012
0013 #include <__cxx03/__concepts/constructible.h>
0014 #include <__cxx03/__concepts/derived_from.h>
0015 #include <__cxx03/__concepts/movable.h>
0016 #include <__cxx03/__config>
0017 #include <__cxx03/__fwd/istream.h>
0018 #include <__cxx03/__fwd/string.h>
0019 #include <__cxx03/__iterator/default_sentinel.h>
0020 #include <__cxx03/__iterator/iterator_traits.h>
0021 #include <__cxx03/__memory/addressof.h>
0022 #include <__cxx03/__ranges/view_interface.h>
0023 #include <__cxx03/__type_traits/remove_cvref.h>
0024 #include <__cxx03/__utility/forward.h>
0025 #include <__cxx03/cstddef>
0026
0027 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0028 #  pragma GCC system_header
0029 #endif
0030
0031 #if _LIBCPP_STD_VER >= 20
0032
0033 _LIBCPP_BEGIN_NAMESPACE_STD
0034
0035 namespace ranges {
0036
0037 template <class _Val, class _CharT, class _Traits>
0038 concept __stream_extractable = requires(basic_istream<_CharT, _Traits>& __is, _Val& __t) { __is >> __t; };
0039
0040 template <movable _Val, class _CharT, class _Traits = char_traits<_CharT>>
0041   requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
0042 class basic_istream_view : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> {
0043   class __iterator;
0044
0045 public:
0046   _LIBCPP_HIDE_FROM_ABI constexpr explicit basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
0047       : __stream_(std::addressof(__stream)) {}
0048
0049   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
0050     *__stream_ >> __value_;
0051     return __iterator{*this};
0052   }
0053
0054   _LIBCPP_HIDE_FROM_ABI constexpr default_sentinel_t end() const noexcept { return default_sentinel; }
0055
0056 private:
0057   basic_istream<_CharT, _Traits>* __stream_;
0058   _LIBCPP_NO_UNIQUE_ADDRESS _Val __value_ = _Val();
0059 };
0060
0061 template <movable _Val, class _CharT, class _Traits>
0062   requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
0063 class basic_istream_view<_Val, _CharT, _Traits>::__iterator {
0064 public:
0065   using iterator_concept = input_iterator_tag;
0066   using difference_type  = ptrdiff_t;
0067   using value_type       = _Val;
0068
0069   _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(basic_istream_view<_Val, _CharT, _Traits>& __parent) noexcept
0070       : __parent_(std::addressof(__parent)) {}
0071
0072   __iterator(const __iterator&)                  = delete;
0073   _LIBCPP_HIDE_FROM_ABI __iterator(__iterator&&) = default;
0074
0075   __iterator& operator=(const __iterator&)                  = delete;
0076   _LIBCPP_HIDE_FROM_ABI __iterator& operator=(__iterator&&) = default;
0077
0078   _LIBCPP_HIDE_FROM_ABI __iterator& operator++() {
0079     *__parent_->__stream_ >> __parent_->__value_;
0080     return *this;
0081   }
0082
0083   _LIBCPP_HIDE_FROM_ABI void operator++(int) { ++*this; }
0084
0085   _LIBCPP_HIDE_FROM_ABI _Val& operator*() const { return __parent_->__value_; }
0086
0087   _LIBCPP_HIDE_FROM_ABI friend bool operator==(const __iterator& __x, default_sentinel_t) {
0088     return !*__x.__get_parent_stream();
0089   }
0090
0091 private:
0092   basic_istream_view<_Val, _CharT, _Traits>* __parent_;
0093
0094   _LIBCPP_HIDE_FROM_ABI constexpr basic_istream<_CharT, _Traits>* __get_parent_stream() const {
0095     return __parent_->__stream_;
0096   }
0097 };
0098
0099 template <class _Val>
0100 using istream_view = basic_istream_view<_Val, char>;
0101
0102 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
0103 template <class _Val>
0104 using wistream_view = basic_istream_view<_Val, wchar_t>;
0105 #  endif
0106
0107 namespace views {
0108 namespace __istream {
0109
0110 // clang-format off
0111 template <class _Tp>
0112 struct __fn {
0113   template <class _Up, class _UnCVRef = remove_cvref_t<_Up>>
0114     requires derived_from<_UnCVRef, basic_istream<typename _UnCVRef::char_type,
0115                                                   typename _UnCVRef::traits_type>>
0116   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Up&& __u) const
0117     noexcept(noexcept(basic_istream_view<_Tp, typename _UnCVRef::char_type,
0118                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u))))
0119     -> decltype(      basic_istream_view<_Tp, typename _UnCVRef::char_type,
0120                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u)))
0121     {   return        basic_istream_view<_Tp, typename _UnCVRef::char_type,
0122                                               typename _UnCVRef::traits_type>(std::forward<_Up>(__u));
0123     }
0124 };
0125 // clang-format on
0126
0127 } // namespace __istream
0128
0129 inline namespace __cpo {
0130 template <class _Tp>
0131 inline constexpr auto istream = __istream::__fn<_Tp>{};
0132 } // namespace __cpo
0133 } // namespace views
0134
0135 } // namespace ranges
0136
0137 _LIBCPP_END_NAMESPACE_STD
0138
0139 #endif // _LIBCPP_STD_VER >= 20
0140
0141 #endif // _LIBCPP___CXX03___RANGES_ISTREAM_VIEW_H