1 // Stream iterators
2 
3 // Copyright (C) 2001-2020 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 
_GLIBCXX_VISIBILITY(default)37 namespace 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