libstdc++: stream_iterator.h Source File

libstdc++

stream_iterator.h
Go to the documentation of this file.
1// Stream iterators
2
3// Copyright (C) 2001-2026 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#ifdef _GLIBCXX_SYSHDR
34#pragma GCC system_header
35#endif
36
37#include <bits/iosfwd.h>
38#include <bits/move.h>
39#include <bits/stl_iterator_base_types.h>
40#include <debug/debug.h>
41
42namespace std _GLIBCXX_VISIBILITY(default)
43{
44_GLIBCXX_BEGIN_NAMESPACE_VERSION
45
46 /**
47 * @addtogroup iterators
48 * @{
49 */
50
51// Ignore warnings about std::iterator.
52#pragma GCC diagnostic push
53#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
54
55 /// Provides input iterator semantics for streams.
56 template<typename _Tp, typename _CharT = char,
57 typename _Traits = char_traits<_CharT>, typename _Dist = ptrdiff_t>
58 class istream_iterator
59 : public iterator<input_iterator_tag, _Tp, _Dist, const _Tp*, const _Tp&>
60 {
61 public:
62 typedef _CharT char_type;
63 typedef _Traits traits_type;
64 typedef basic_istream<_CharT, _Traits> istream_type;
65
66 private:
67 istream_type* _M_stream;
68 _Tp _M_value;
69 // This bool becomes false at end-of-stream. It should be sufficient to
70 // check _M_stream != nullptr instead, but historically we did not set
71 // _M_stream to null when reaching the end, so we need to keep this flag.
72 bool _M_ok;
73
74 public:
75 /// Construct end of input stream iterator.
76 _GLIBCXX_CONSTEXPR istream_iterator()
77 _GLIBCXX_NOEXCEPT_IF(is_nothrow_default_constructible<_Tp>::value)
78 : _M_stream(0), _M_value(), _M_ok(false) {}
79
80 /// Construct start of input stream iterator.
81 istream_iterator(istream_type& __s)
82 : _M_stream(std::__addressof(__s)), _M_ok(true)
83 { _M_read(); }
84
85 _GLIBCXX_CONSTEXPR
86 istream_iterator(const istream_iterator& __obj)
87 _GLIBCXX_NOEXCEPT_IF(is_nothrow_copy_constructible<_Tp>::value)
88 : _M_stream(__obj._M_stream), _M_value(__obj._M_value),
89 _M_ok(__obj._M_ok)
90 { }
91
92#if __cplusplus > 201703L && __cpp_lib_concepts
93 constexpr
94 istream_iterator(default_sentinel_t)
95 noexcept(is_nothrow_default_constructible_v<_Tp>)
96 : istream_iterator() { }
97#endif
98
99#if __cplusplus >= 201103L
100 istream_iterator& operator=(const istream_iterator&) = default;
101 ~istream_iterator() = default;
102#endif
103
104 _GLIBCXX_NODISCARD
105 const _Tp&
106 operator*() const _GLIBCXX_NOEXCEPT
107 {
108 __glibcxx_requires_cond(_M_ok,
109 _M_message(__gnu_debug::__msg_deref_istream)
110 ._M_iterator(*this));
111 return _M_value;
112 }
113
114 _GLIBCXX_NODISCARD
115 const _Tp*
116 operator->() const _GLIBCXX_NOEXCEPT
117 { return std::__addressof((operator*())); }
118
119 istream_iterator&
120 operator++()
121 {
122 __glibcxx_requires_cond(_M_ok,
123 _M_message(__gnu_debug::__msg_inc_istream)
124 ._M_iterator(*this));
125 _M_read();
126 return *this;
127 }
128
129 istream_iterator
130 operator++(int)
131 {
132 __glibcxx_requires_cond(_M_ok,
133 _M_message(__gnu_debug::__msg_inc_istream)
134 ._M_iterator(*this));
135 istream_iterator __tmp = *this;
136 _M_read();
137 return __tmp;
138 }
139
140 private:
141 bool
142 _M_equal(const istream_iterator& __x) const _GLIBCXX_NOEXCEPT
143 {
144 // Ideally this would just return _M_stream == __x._M_stream,
145 // but code compiled with old versions never sets _M_stream to null.
146 return (_M_ok == __x._M_ok) && (!_M_ok || _M_stream == __x._M_stream);
147 }
148
149 void
150 _M_read()
151 {
152 if (_M_stream && !(*_M_stream >> _M_value))
153 {
154 _M_stream = 0;
155 _M_ok = false;
156 }
157 }
158
159 /// Return true if the iterators refer to the same stream,
160 /// or are both at end-of-stream.
161 _GLIBCXX_NODISCARD
162 friend bool
163 operator==(const istream_iterator& __x, const istream_iterator& __y)
164 _GLIBCXX_NOEXCEPT
165 { return __x._M_equal(__y); }
166
167#if __cpp_impl_three_way_comparison < 201907L
168 /// Return true if the iterators refer to different streams,
169 /// or if one is at end-of-stream and the other is not.
170 _GLIBCXX_NODISCARD
171 friend bool
172 operator!=(const istream_iterator& __x, const istream_iterator& __y)
173 _GLIBCXX_NOEXCEPT
174 { return !__x._M_equal(__y); }
175#endif
176
177#if __cplusplus > 201703L && __cpp_lib_concepts
178 [[nodiscard]]
179 friend bool
180 operator==(const istream_iterator& __i, default_sentinel_t) noexcept
181 { return !__i._M_stream; }
182#endif
183 };
184
185 /**
186 * @brief Provides output iterator semantics for streams.
187 *
188 * This class provides an iterator to write to an ostream. The type Tp is
189 * the only type written by this iterator and there must be an
190 * operator<<(Tp) defined.
191 *
192 * @tparam _Tp The type to write to the ostream.
193 * @tparam _CharT The ostream char_type.
194 * @tparam _Traits The ostream char_traits.
195 */
196 template<typename _Tp, typename _CharT = char,
197 typename _Traits = char_traits<_CharT> >
198 class ostream_iterator
199 : public iterator<output_iterator_tag, void, void, void, void>
200 {
201 public:
202 ///@{
203 /// Public typedef
204#if __cplusplus > 201703L
205 using difference_type = ptrdiff_t;
206#endif
207 typedef _CharT char_type;
208 typedef _Traits traits_type;
209 typedef basic_ostream<_CharT, _Traits> ostream_type;
210 ///@}
211
212 private:
213 ostream_type* _M_stream;
214 const _CharT* _M_string;
215
216 public:
217 /// Construct from an ostream.
218 ostream_iterator(ostream_type& __s) _GLIBCXX_NOEXCEPT
219 : _M_stream(std::__addressof(__s)), _M_string(0) {}
220
221 /**
222 * Construct from an ostream.
223 *
224 * The delimiter string @a c is written to the stream after every Tp
225 * written to the stream. The delimiter is not copied, and thus must
226 * not be destroyed while this iterator is in use.
227 *
228 * @param __s Underlying ostream to write to.
229 * @param __c CharT delimiter string to insert.
230 */
231 ostream_iterator(ostream_type& __s, const _CharT* __c) _GLIBCXX_NOEXCEPT
232 : _M_stream(std::__addressof(__s)), _M_string(__c) { }
233
234 /// Copy constructor.
235 ostream_iterator(const ostream_iterator& __obj) _GLIBCXX_NOEXCEPT
236 : _M_stream(__obj._M_stream), _M_string(__obj._M_string) { }
237
238#if __cplusplus >= 201103L
239 ostream_iterator& operator=(const ostream_iterator&) = default;
240#endif
241
242 /// Writes @a value to underlying ostream using operator<<. If
243 /// constructed with delimiter string, writes delimiter to ostream.
244 ostream_iterator&
245 operator=(const _Tp& __value)
246 {
247 __glibcxx_requires_cond(_M_stream != 0,
248 _M_message(__gnu_debug::__msg_output_ostream)
249 ._M_iterator(*this));
250 *_M_stream << __value;
251 if (_M_string)
252 *_M_stream << _M_string;
253 return *this;
254 }
255
256 _GLIBCXX_NODISCARD
257 ostream_iterator&
258 operator*() _GLIBCXX_NOEXCEPT
259 { return *this; }
260
261 ostream_iterator&
262 operator++() _GLIBCXX_NOEXCEPT
263 { return *this; }
264
265 ostream_iterator&
266 operator++(int) _GLIBCXX_NOEXCEPT
267 { return *this; }
268 };
269#pragma GCC diagnostic pop
270
271 /// @} group iterators
272
273_GLIBCXX_END_NAMESPACE_VERSION
274} // namespace
275
276#endif
move.h
stl_iterator_base_types.h
debug.h
std::operator*
constexpr complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition complex:434
std::__addressof
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition move.h:52
std
ISO C++ entities toplevel namespace is std.
std::basic_istream
Template class basic_istream.
Definition istream:73
std::is_nothrow_default_constructible
is_nothrow_default_constructible
Definition type_traits:1352
std::is_nothrow_copy_constructible
is_nothrow_copy_constructible
Definition type_traits:1361
std::char_traits
Basis for explicit traits specializations.
Definition char_traits.h:329
std::basic_ostream
Template class basic_ostream.
Definition ostream.h:72
std::iterator
Common iterator class.
Definition stl_iterator_base_types.h:133
std::istream_iterator
Provides input iterator semantics for streams.
Definition stream_iterator.h:60
std::istream_iterator::istream_iterator
istream_iterator(istream_type &__s)
Construct start of input stream iterator.
Definition stream_iterator.h:81
std::istream_iterator::istream_iterator
constexpr istream_iterator() noexcept(/*conditional */)
Construct end of input stream iterator.
Definition stream_iterator.h:76
std::istream_iterator::operator==
friend bool operator==(const istream_iterator &__x, const istream_iterator &__y) noexcept
Return true if the iterators refer to the same stream, or are both at end-of-stream.
Definition stream_iterator.h:163
std::ostream_iterator
Provides output iterator semantics for streams.
Definition stream_iterator.h:200
std::ostream_iterator::char_type
_CharT char_type
Public typedef.
Definition stream_iterator.h:207
std::ostream_iterator::ostream_iterator
ostream_iterator(ostream_type &__s) noexcept
Construct from an ostream.
Definition stream_iterator.h:218
std::ostream_iterator::ostream_iterator
ostream_iterator(ostream_type &__s, const _CharT *__c) noexcept
Definition stream_iterator.h:231
std::ostream_iterator::traits_type
_Traits traits_type
Public typedef.
Definition stream_iterator.h:208
std::ostream_iterator::operator=
ostream_iterator & operator=(const _Tp &__value)
Writes value to underlying ostream using operator<<. If constructed with delimiter string,...
Definition stream_iterator.h:245
std::ostream_iterator::difference_type
ptrdiff_t difference_type
Public typedef.
Definition stream_iterator.h:205
std::ostream_iterator::ostream_type
basic_ostream< _CharT, _Traits > ostream_type
Public typedef.
Definition stream_iterator.h:209
std::ostream_iterator::ostream_iterator
ostream_iterator(const ostream_iterator &__obj) noexcept
Copy constructor.
Definition stream_iterator.h:235