libstdc++: syncstream Source File

libstdc++

syncstream
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1// <syncstream> -*- C++ -*-
2
3// Copyright (C) 2020-2026 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 include/syncstream
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_SYNCSTREAM
30#define _GLIBCXX_SYNCSTREAM 1
31
32#ifdef _GLIBCXX_SYSHDR
33#pragma GCC system_header
34#endif
35
36#include <bits/requires_hosted.h> // iostreams
37
38#include <bits/c++config.h>
39
40#define __glibcxx_want_syncbuf
41#include <bits/version.h>
42
43#ifdef __cpp_lib_syncbuf // C++ >= 20 && HOSTED && CXX11ABI
44#include <sstream>
45
46#include <bits/alloc_traits.h>
47#include <bits/allocator.h>
48#include <bits/std_mutex.h>
49
50namespace std _GLIBCXX_VISIBILITY(default)
51{
52_GLIBCXX_BEGIN_NAMESPACE_VERSION
53
54 template<typename _CharT, typename _Traits, typename _Alloc>
55 class basic_syncbuf : public __syncbuf_base<_CharT, _Traits>
56 {
57 public:
58 using char_type = _CharT;
59 using int_type = typename _Traits::int_type;
60 using pos_type = typename _Traits::pos_type;
61 using off_type = typename _Traits::off_type;
62 using traits_type = _Traits;
63 using allocator_type = _Alloc;
64 using streambuf_type = basic_streambuf<_CharT, _Traits>;
65
66 basic_syncbuf()
67 : basic_syncbuf(nullptr, allocator_type{})
68 { }
69
70 explicit
71 basic_syncbuf(streambuf_type* __obuf)
72 : basic_syncbuf(__obuf, allocator_type{})
73 { }
74
75 basic_syncbuf(streambuf_type* __obuf, const allocator_type& __alloc)
76 : __syncbuf_base<_CharT, _Traits>(__obuf)
77 , _M_impl(__alloc)
78 , _M_mtx(__obuf)
79 { }
80
81 basic_syncbuf(basic_syncbuf&& __other)
82 : __syncbuf_base<_CharT, _Traits>(__other._M_wrapped)
83 , _M_impl(std::move(__other._M_impl))
84 , _M_mtx(std::move(__other._M_mtx))
85 {
86 this->_M_emit_on_sync = __other._M_emit_on_sync;
87 this->_M_needs_sync = __other._M_needs_sync;
88 __other._M_wrapped = nullptr;
89 }
90
91 ~basic_syncbuf()
92 {
93 __try
94 {
95 emit();
96 }
97 __catch (...)
98 { }
99 }
100
101 basic_syncbuf&
102 operator=(basic_syncbuf&& __other)
103 {
104 emit();
105
106 _M_impl = std::move(__other._M_impl);
107 this->_M_emit_on_sync = __other._M_emit_on_sync;
108 this->_M_needs_sync = __other._M_needs_sync;
109 this->_M_wrapped = __other._M_wrapped;
110 __other._M_wrapped = nullptr;
111 _M_mtx = std::move(__other._M_mtx);
112
113 return *this;
114 }
115
116 void
117 swap(basic_syncbuf& __other)
118 {
119 using _ATr = allocator_traits<_Alloc>;
120 if constexpr (!_ATr::propagate_on_container_swap::value)
121 __glibcxx_assert(get_allocator() == __other.get_allocator());
122
123 std::swap(_M_impl, __other._M_impl);
124 std::swap(this->_M_emit_on_sync, __other._M_emit_on_sync);
125 std::swap(this->_M_needs_sync, __other._M_needs_sync);
126 std::swap(this->_M_wrapped, __other._M_wrapped);
127 std::swap(_M_mtx, __other._M_mtx);
128 }
129
130 bool
131 emit()
132 {
133 if (!this->_M_wrapped)
134 return false;
135
136 auto __s = std::move(_M_impl).str();
137
138 const lock_guard<__mutex> __l(_M_mtx);
139 if (auto __size = __s.size())
140 {
141 auto __n = this->_M_wrapped->sputn(__s.data(), __size);
142 if (__n != __size)
143 {
144 __s.erase(0, __n);
145 _M_impl.str(std::move(__s));
146 return false;
147 }
148 }
149
150 if (this->_M_needs_sync)
151 {
152 this->_M_needs_sync = false;
153 if (this->_M_wrapped->pubsync() != 0)
154 return false;
155 }
156 return true;
157 }
158
159 streambuf_type*
160 get_wrapped() const noexcept
161 { return this->_M_wrapped; }
162
163 allocator_type
164 get_allocator() const noexcept
165 { return _M_impl.get_allocator(); }
166
167 void
168 set_emit_on_sync(bool __b) noexcept
169 { this->_M_emit_on_sync = __b; }
170
171 protected:
172 int
173 sync() override
174 {
175 this->_M_needs_sync = true;
176 if (this->_M_emit_on_sync && !emit())
177 return -1;
178 return 0;
179 }
180
181 int_type
182 overflow(int_type __c) override
183 {
184 int_type __eof = traits_type::eof();
185 if (__builtin_expect(!traits_type::eq_int_type(__c, __eof), true))
186 return _M_impl.sputc(__c);
187 return __eof;
188 }
189
190 streamsize
191 xsputn(const char_type* __s, streamsize __n) override
192 { return _M_impl.sputn(__s, __n); }
193
194 private:
195 basic_stringbuf<char_type, traits_type, allocator_type> _M_impl;
196
197 struct __mutex
198 {
199#if _GLIBCXX_HAS_GTHREADS
200 mutex* _M_mtx = nullptr;
201
202 __mutex(void* __t) // __t is the underlying sbuf, as hash seed.
203 {
204 extern mutex& __syncbuf_get_mutex(void*); // in src/c++20/syncbuf.cc
205 if (__t) _M_mtx = &__syncbuf_get_mutex(__t);
206 }
207
208 void
209 swap(__mutex& __other) noexcept
210 { std::swap(_M_mtx, __other._M_mtx); }
211
212 void
213 lock()
214 {
215 _M_mtx->lock();
216 }
217
218 void
219 unlock()
220 {
221 _M_mtx->unlock();
222 }
223#else
224 __mutex(void*) { }
225 void swap(__mutex&&) noexcept { }
226 void lock() { }
227 void unlock() { }
228#endif
229 __mutex(__mutex&&) = default;
230 __mutex& operator=(__mutex&&) = default;
231 };
232 __mutex _M_mtx;
233 };
234
235 template <typename _CharT, typename _Traits, typename _Alloc>
236 class basic_osyncstream : public basic_ostream<_CharT, _Traits>
237 {
238 using __ostream_type = basic_ostream<_CharT, _Traits>;
239
240 public:
241 // Types:
242 using char_type = _CharT;
243 using traits_type = _Traits;
244 using allocator_type = _Alloc;
245 using int_type = typename traits_type::int_type;
246 using pos_type = typename traits_type::pos_type;
247 using off_type = typename traits_type::off_type;
248 using syncbuf_type = basic_syncbuf<_CharT, _Traits, _Alloc>;
249 using streambuf_type = typename syncbuf_type::streambuf_type;
250
251 private:
252 syncbuf_type _M_syncbuf;
253
254 public:
255 basic_osyncstream(streambuf_type* __buf, const allocator_type& __a)
256 : _M_syncbuf(__buf, __a)
257 { this->init(std::__addressof(_M_syncbuf)); }
258
259 explicit basic_osyncstream(streambuf_type* __buf)
260 : _M_syncbuf(__buf)
261 { this->init(std::__addressof(_M_syncbuf)); }
262
263 basic_osyncstream(basic_ostream<char_type, traits_type>& __os,
264 const allocator_type& __a)
265 : basic_osyncstream(__os.rdbuf(), __a)
266 { this->init(std::__addressof(_M_syncbuf)); }
267
268 explicit basic_osyncstream(basic_ostream<char_type, traits_type>& __os)
269 : basic_osyncstream(__os.rdbuf())
270 { this->init(std::__addressof(_M_syncbuf)); }
271
272 basic_osyncstream(basic_osyncstream&& __rhs) noexcept
273 : __ostream_type(std::move(__rhs)),
274 _M_syncbuf(std::move(__rhs._M_syncbuf))
275 { __ostream_type::set_rdbuf(std::__addressof(_M_syncbuf)); }
276
277 ~basic_osyncstream() = default;
278
279 basic_osyncstream& operator=(basic_osyncstream&&) = default;
280
281 syncbuf_type* rdbuf() const noexcept
282 { return const_cast<syncbuf_type*>(&_M_syncbuf); }
283
284 streambuf_type* get_wrapped() const noexcept
285 { return _M_syncbuf.get_wrapped(); }
286
287 void emit()
288 {
289 if (!_M_syncbuf.emit())
290 this->setstate(ios_base::failbit);
291 }
292 };
293
294 template <class _CharT, class _Traits, class _Allocator>
295 inline void
296 swap(basic_syncbuf<_CharT, _Traits, _Allocator>& __x,
297 basic_syncbuf<_CharT, _Traits, _Allocator>& __y) noexcept
298 { __x.swap(__y); }
299
300 using syncbuf = basic_syncbuf<char>;
301 using wsyncbuf = basic_syncbuf<wchar_t>;
302
303 using osyncstream = basic_osyncstream<char>;
304 using wosyncstream = basic_osyncstream<wchar_t>;
305_GLIBCXX_END_NAMESPACE_VERSION
306} // namespace std
307#endif // __cpp_lib_syncbuf
308
309#endif /* _GLIBCXX_SYNCSTREAM */
sstream
allocator.h
version.h
requires_hosted.h
std_mutex.h
c++config.h
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:138
std::__addressof
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition move.h:52
std::lock
void lock(_L1 &__l1, _L2 &__l2, _L3 &... __l3)
Generic lock.
Definition mutex:686
std
ISO C++ entities toplevel namespace is std.
std::streamsize
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition postypes.h:73
std::basic_ostream
Template class basic_ostream.
Definition ostream.h:67
std::ios_base::failbit
static const iostate failbit
Indicates that an input operation failed to read the expected characters, or that an output operation...
Definition ios_base.h:465
alloc_traits.h