1// Stream iterators
2
3// Copyright (C) 2001-2021 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/stream_iterator.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{iterator}
28 */
29
30#ifndef _STREAM_ITERATOR_H
31#define _STREAM_ITERATOR_H 1
32
33#pragma GCC system_header
34
35#include <debug/debug.h>
36
37namespace std _GLIBCXX_VISIBILITY(default)
38{
39_GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 /**
42 * @addtogroup iterators
43 * @{
44 */
45
46 /// Provides input iterator semantics for streams.
47 template<typename _Tp, typename _CharT = char,
48 typename _Traits = char_traits<_CharT>, typename _Dist = ptrdiff_t>
49 class istream_iterator
50 : public iterator<input_iterator_tag, _Tp, _Dist, const _Tp*, const _Tp&>
51 {
52 public:
53 typedef _CharT char_type;
54 typedef _Traits traits_type;
55 typedef basic_istream<_CharT, _Traits> istream_type;
56
57 private:
58 istream_type* _M_stream;
59 _Tp _M_value;
60 // This bool becomes false at end-of-stream. It should be sufficient to
61 // check _M_stream != nullptr instead, but historically we did not set
62 // _M_stream to null when reaching the end, so we need to keep this flag.
63 bool _M_ok;
64
65 public:
66 /// Construct end of input stream iterator.
67 _GLIBCXX_CONSTEXPR istream_iterator()
68 : _M_stream(0), _M_value(), _M_ok(false) {}
69
70 /// Construct start of input stream iterator.
71 istream_iterator(istream_type& __s)
72 : _M_stream(std::__addressof(__s)), _M_ok(true)
73 { _M_read(); }
74
75 istream_iterator(const istream_iterator& __obj)
76 : _M_stream(__obj._M_stream), _M_value(__obj._M_value),
77 _M_ok(__obj._M_ok)
78 { }
79
80#if __cplusplus > 201703L && __cpp_lib_concepts
81 constexpr
82 istream_iterator(default_sentinel_t)
83 noexcept(is_nothrow_default_constructible_v<_Tp>)
84 : istream_iterator() { }
85#endif
86
87#if __cplusplus >= 201103L
88 istream_iterator& operator=(const istream_iterator&) = default;
89 ~istream_iterator() = default;
90#endif
91
92 const _Tp&
93 operator*() const
94 {
95 __glibcxx_requires_cond(_M_ok,
96 _M_message(__gnu_debug::__msg_deref_istream)
97 ._M_iterator(*this));
98 return _M_value;
99 }
100
101 const _Tp*
102 operator->() const { return std::__addressof((operator*())); }
103
104 istream_iterator&
105 operator++()
106 {
107 __glibcxx_requires_cond(_M_ok,
108 _M_message(__gnu_debug::__msg_inc_istream)
109 ._M_iterator(*this));
110 _M_read();
111 return *this;
112 }
113
114 istream_iterator
115 operator++(int)
116 {
117 __glibcxx_requires_cond(_M_ok,
118 _M_message(__gnu_debug::__msg_inc_istream)
119 ._M_iterator(*this));
120 istream_iterator __tmp = *this;
121 _M_read();
122 return __tmp;
123 }
124
125 private:
126 bool
127 _M_equal(const istream_iterator& __x) const
128 {
129 // Ideally this would just return _M_stream == __x._M_stream,
130 // but code compiled with old versions never sets _M_stream to null.
131 return (_M_ok == __x._M_ok) && (!_M_ok || _M_stream == __x._M_stream);
132 }
133
134 void
135 _M_read()
136 {
137 if (_M_stream && !(*_M_stream >> _M_value))
138 {
139 _M_stream = 0;
140 _M_ok = false;
141 }
142 }
143
144 /// Return true if the iterators refer to the same stream,
145 /// or are both at end-of-stream.
146 friend bool
147 operator==(const istream_iterator& __x, const istream_iterator& __y)
148 { return __x._M_equal(__y); }
149
150 /// Return true if the iterators refer to different streams,
151 /// or if one is at end-of-stream and the other is not.
152 friend bool
153 operator!=(const istream_iterator& __x, const istream_iterator& __y)
154 { return !__x._M_equal(__y); }
155
156#if __cplusplus > 201703L && __cpp_lib_concepts
157 friend bool
158 operator==(const istream_iterator& __i, default_sentinel_t)
159 { return !__i._M_stream; }
160#endif
161 };
162
163 /**
164 * @brief Provides output iterator semantics for streams.
165 *
166 * This class provides an iterator to write to an ostream. The type Tp is
167 * the only type written by this iterator and there must be an
168 * operator<<(Tp) defined.
169 *
170 * @tparam _Tp The type to write to the ostream.
171 * @tparam _CharT The ostream char_type.
172 * @tparam _Traits The ostream char_traits.
173 */
174 template<typename _Tp, typename _CharT = char,
175 typename _Traits = char_traits<_CharT> >
176 class ostream_iterator
177 : public iterator<output_iterator_tag, void, void, void, void>
178 {
179 public:
180 ///@{
181 /// Public typedef
182#if __cplusplus > 201703L
183 using difference_type = ptrdiff_t;
184#endif
185 typedef _CharT char_type;
186 typedef _Traits traits_type;
187 typedef basic_ostream<_CharT, _Traits> ostream_type;
188 ///@}
189
190 private:
191 ostream_type* _M_stream;
192 const _CharT* _M_string;
193
194 public:
195#if __cplusplus > 201703L
196 constexpr ostream_iterator() noexcept
197 : _M_stream(nullptr), _M_string(nullptr) { }
198#endif
199
200 /// Construct from an ostream.
201 ostream_iterator(ostream_type& __s)
202 : _M_stream(std::__addressof(__s)), _M_string(0) {}
203
204 /**
205 * Construct from an ostream.
206 *
207 * The delimiter string @a c is written to the stream after every Tp
208 * written to the stream. The delimiter is not copied, and thus must
209 * not be destroyed while this iterator is in use.
210 *
211 * @param __s Underlying ostream to write to.
212 * @param __c CharT delimiter string to insert.
213 */
214 ostream_iterator(ostream_type& __s, const _CharT* __c)
215 : _M_stream(std::__addressof(__s)), _M_string(__c) { }
216
217 /// Copy constructor.
218 ostream_iterator(const ostream_iterator& __obj)
219 : _M_stream(__obj._M_stream), _M_string(__obj._M_string) { }
220
221#if __cplusplus >= 201103L
222 ostream_iterator& operator=(const ostream_iterator&) = default;
223#endif
224
225 /// Writes @a value to underlying ostream using operator<<. If
226 /// constructed with delimiter string, writes delimiter to ostream.
227 ostream_iterator&
228 operator=(const _Tp& __value)
229 {
230 __glibcxx_requires_cond(_M_stream != 0,
231 _M_message(__gnu_debug::__msg_output_ostream)
232 ._M_iterator(*this));
233 *_M_stream << __value;
234 if (_M_string)
235 *_M_stream << _M_string;
236 return *this;
237 }
238
239 ostream_iterator&
240 operator*()
241 { return *this; }
242
243 ostream_iterator&
244 operator++()
245 { return *this; }
246
247 ostream_iterator&
248 operator++(int)
249 { return *this; }
250 };
251
252 /// @} group iterators
253
254_GLIBCXX_END_NAMESPACE_VERSION
255} // namespace
256
257#endif
258

source code of include/c++/11/bits/stream_iterator.h