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istream.hpp
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1 // Range v3 library
3 //
4 // Copyright Eric Niebler 2013-present
5 //
6 // Use, modification and distribution is subject to the
7 // Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // Project home: https://github.com/ericniebler/range-v3
12 //
13 
14 #ifndef RANGES_V3_VIEW_ISTREAM_HPP
15 #define RANGES_V3_VIEW_ISTREAM_HPP
16 
17 #include <istream>
18 
19 #include <range/v3/range_fwd.hpp>
20 
23 #include <range/v3/utility/static_const.hpp>
24 #include <range/v3/view/facade.hpp>
25 
26 #include <range/v3/detail/prologue.hpp>
27 
28 namespace ranges
29 {
32  template<typename Val>
33  struct istream_view : view_facade<istream_view<Val>, unknown>
34  {
35  private:
36  friend range_access;
37  std::istream * sin_;
38  semiregular_box_t<Val> obj_;
39  struct cursor
40  {
41  private:
42  friend range_access;
43  using single_pass = std::true_type;
44  istream_view * rng_ = nullptr;
45 
46  public:
47  cursor() = default;
48  explicit cursor(istream_view * rng)
49  : rng_(rng)
50  {}
51  void next()
52  {
53  rng_->next();
54  }
55  Val & read() const noexcept
56  {
57  return rng_->cached();
58  }
59  bool equal(default_sentinel_t) const
60  {
61  return !rng_->sin_;
62  }
63  bool equal(cursor that) const
64  {
65  return !rng_->sin_ == !that.rng_->sin_;
66  }
67  };
68  void next()
69  {
70  if(!(*sin_ >> cached()))
71  sin_ = nullptr;
72  }
73  cursor begin_cursor()
74  {
75  return cursor{this};
76  }
77 
78  public:
79  istream_view() = default;
80  explicit istream_view(std::istream & sin)
81  : sin_(&sin)
82  , obj_{}
83  {
84  next(); // prime the pump
85  }
86  Val & cached() noexcept
87  {
88  return obj_;
89  }
90  };
91 
93  template<typename Val>
94  using istream_range RANGES_DEPRECATED(
95  "istream_range<T> has been renamed to istream_view<T>") = istream_view<Val>;
97 
99  namespace _istream_
100  {
102  template(typename Val)(
103  requires copy_constructible<Val> AND default_constructible<Val>)
104  inline istream_view<Val> istream(std::istream & sin)
105  {
106  return istream_view<Val>{sin};
107  }
109  } // namespace _istream_
110  using namespace _istream_;
112 
113  namespace cpp20
114  {
115  template<typename Val>
116  using basic_istream_view = ::ranges::istream_view<Val>;
117  } // namespace cpp20
119 } // namespace ranges
120 
121 #include <range/v3/detail/epilogue.hpp>
122 
123 #endif
Definition: default_sentinel.hpp:26
Definition: istream.hpp:34
A utility for constructing a view from a (derived) type that implements begin and end cursors.
Definition: facade.hpp:66