source: Daodan/MSYS2/mingw32/include/c++/11.2.0/ostream@ 1186

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1// Output streams -*- C++ -*-
2
3// Copyright (C) 1997-2021 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 include/ostream
26 * This is a Standard C++ Library header.
27 */
28
29//
30// ISO C++ 14882: 27.6.2 Output streams
31//
32
33#ifndef _GLIBCXX_OSTREAM
34#define _GLIBCXX_OSTREAM 1
35
36#pragma GCC system_header
37
38#include <ios>
39#include <bits/ostream_insert.h>
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @brief Template class basic_ostream.
47 * @ingroup io
48 *
49 * @tparam _CharT Type of character stream.
50 * @tparam _Traits Traits for character type, defaults to
51 * char_traits<_CharT>.
52 *
53 * This is the base class for all output streams. It provides text
54 * formatting of all builtin types, and communicates with any class
55 * derived from basic_streambuf to do the actual output.
56 */
57 template<typename _CharT, typename _Traits>
58 class basic_ostream : virtual public basic_ios<_CharT, _Traits>
59 {
60 public:
61 // Types (inherited from basic_ios):
62 typedef _CharT char_type;
63 typedef typename _Traits::int_type int_type;
64 typedef typename _Traits::pos_type pos_type;
65 typedef typename _Traits::off_type off_type;
66 typedef _Traits traits_type;
67
68 // Non-standard Types:
69 typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
70 typedef basic_ios<_CharT, _Traits> __ios_type;
71 typedef basic_ostream<_CharT, _Traits> __ostream_type;
72 typedef num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> >
73 __num_put_type;
74 typedef ctype<_CharT> __ctype_type;
75
76 /**
77 * @brief Base constructor.
78 *
79 * This ctor is almost never called by the user directly, rather from
80 * derived classes' initialization lists, which pass a pointer to
81 * their own stream buffer.
82 */
83 explicit
84 basic_ostream(__streambuf_type* __sb)
85 { this->init(__sb); }
86
87 /**
88 * @brief Base destructor.
89 *
90 * This does very little apart from providing a virtual base dtor.
91 */
92 virtual
93 ~basic_ostream() { }
94
95 /// Safe prefix/suffix operations.
96 class sentry;
97 friend class sentry;
98
99 ///@{
100 /**
101 * @brief Interface for manipulators.
102 *
103 * Manipulators such as @c std::endl and @c std::hex use these
104 * functions in constructs like "std::cout << std::endl". For more
105 * information, see the iomanip header.
106 */
107 __ostream_type&
108 operator<<(__ostream_type& (*__pf)(__ostream_type&))
109 {
110 // _GLIBCXX_RESOLVE_LIB_DEFECTS
111 // DR 60. What is a formatted input function?
112 // The inserters for manipulators are *not* formatted output functions.
113 return __pf(*this);
114 }
115
116 __ostream_type&
117 operator<<(__ios_type& (*__pf)(__ios_type&))
118 {
119 // _GLIBCXX_RESOLVE_LIB_DEFECTS
120 // DR 60. What is a formatted input function?
121 // The inserters for manipulators are *not* formatted output functions.
122 __pf(*this);
123 return *this;
124 }
125
126 __ostream_type&
127 operator<<(ios_base& (*__pf) (ios_base&))
128 {
129 // _GLIBCXX_RESOLVE_LIB_DEFECTS
130 // DR 60. What is a formatted input function?
131 // The inserters for manipulators are *not* formatted output functions.
132 __pf(*this);
133 return *this;
134 }
135 ///@}
136
137 ///@{
138 /**
139 * @name Inserters
140 *
141 * All the @c operator<< functions (aka <em>formatted output
142 * functions</em>) have some common behavior. Each starts by
143 * constructing a temporary object of type std::basic_ostream::sentry.
144 * This can have several effects, concluding with the setting of a
145 * status flag; see the sentry documentation for more.
146 *
147 * If the sentry status is good, the function tries to generate
148 * whatever data is appropriate for the type of the argument.
149 *
150 * If an exception is thrown during insertion, ios_base::badbit
151 * will be turned on in the stream's error state without causing an
152 * ios_base::failure to be thrown. The original exception will then
153 * be rethrown.
154 */
155
156 ///@{
157 /**
158 * @brief Integer arithmetic inserters
159 * @param __n A variable of builtin integral type.
160 * @return @c *this if successful
161 *
162 * These functions use the stream's current locale (specifically, the
163 * @c num_get facet) to perform numeric formatting.
164 */
165 __ostream_type&
166 operator<<(long __n)
167 { return _M_insert(__n); }
168
169 __ostream_type&
170 operator<<(unsigned long __n)
171 { return _M_insert(__n); }
172
173 __ostream_type&
174 operator<<(bool __n)
175 { return _M_insert(__n); }
176
177 __ostream_type&
178 operator<<(short __n);
179
180 __ostream_type&
181 operator<<(unsigned short __n)
182 {
183 // _GLIBCXX_RESOLVE_LIB_DEFECTS
184 // 117. basic_ostream uses nonexistent num_put member functions.
185 return _M_insert(static_cast<unsigned long>(__n));
186 }
187
188 __ostream_type&
189 operator<<(int __n);
190
191 __ostream_type&
192 operator<<(unsigned int __n)
193 {
194 // _GLIBCXX_RESOLVE_LIB_DEFECTS
195 // 117. basic_ostream uses nonexistent num_put member functions.
196 return _M_insert(static_cast<unsigned long>(__n));
197 }
198
199#ifdef _GLIBCXX_USE_LONG_LONG
200 __ostream_type&
201 operator<<(long long __n)
202 { return _M_insert(__n); }
203
204 __ostream_type&
205 operator<<(unsigned long long __n)
206 { return _M_insert(__n); }
207#endif
208 ///@}
209
210 ///@{
211 /**
212 * @brief Floating point arithmetic inserters
213 * @param __f A variable of builtin floating point type.
214 * @return @c *this if successful
215 *
216 * These functions use the stream's current locale (specifically, the
217 * @c num_get facet) to perform numeric formatting.
218 */
219 __ostream_type&
220 operator<<(double __f)
221 { return _M_insert(__f); }
222
223 __ostream_type&
224 operator<<(float __f)
225 {
226 // _GLIBCXX_RESOLVE_LIB_DEFECTS
227 // 117. basic_ostream uses nonexistent num_put member functions.
228 return _M_insert(static_cast<double>(__f));
229 }
230
231 __ostream_type&
232 operator<<(long double __f)
233 { return _M_insert(__f); }
234 ///@}
235
236 /**
237 * @brief Pointer arithmetic inserters
238 * @param __p A variable of pointer type.
239 * @return @c *this if successful
240 *
241 * These functions use the stream's current locale (specifically, the
242 * @c num_get facet) to perform numeric formatting.
243 */
244 __ostream_type&
245 operator<<(const void* __p)
246 { return _M_insert(__p); }
247
248#if __cplusplus >= 201703L
249 __ostream_type&
250 operator<<(nullptr_t)
251 { return *this << "nullptr"; }
252#endif
253
254 /**
255 * @brief Extracting from another streambuf.
256 * @param __sb A pointer to a streambuf
257 *
258 * This function behaves like one of the basic arithmetic extractors,
259 * in that it also constructs a sentry object and has the same error
260 * handling behavior.
261 *
262 * If @p __sb is NULL, the stream will set failbit in its error state.
263 *
264 * Characters are extracted from @p __sb and inserted into @c *this
265 * until one of the following occurs:
266 *
267 * - the input stream reaches end-of-file,
268 * - insertion into the output sequence fails (in this case, the
269 * character that would have been inserted is not extracted), or
270 * - an exception occurs while getting a character from @p __sb, which
271 * sets failbit in the error state
272 *
273 * If the function inserts no characters, failbit is set.
274 */
275 __ostream_type&
276 operator<<(__streambuf_type* __sb);
277 ///@}
278
279 ///@{
280 /**
281 * @name Unformatted Output Functions
282 *
283 * All the unformatted output functions have some common behavior.
284 * Each starts by constructing a temporary object of type
285 * std::basic_ostream::sentry. This has several effects, concluding
286 * with the setting of a status flag; see the sentry documentation
287 * for more.
288 *
289 * If the sentry status is good, the function tries to generate
290 * whatever data is appropriate for the type of the argument.
291 *
292 * If an exception is thrown during insertion, ios_base::badbit
293 * will be turned on in the stream's error state. If badbit is on in
294 * the stream's exceptions mask, the exception will be rethrown
295 * without completing its actions.
296 */
297
298 /**
299 * @brief Simple insertion.
300 * @param __c The character to insert.
301 * @return *this
302 *
303 * Tries to insert @p __c.
304 *
305 * @note This function is not overloaded on signed char and
306 * unsigned char.
307 */
308 __ostream_type&
309 put(char_type __c);
310
311 /**
312 * @brief Core write functionality, without sentry.
313 * @param __s The array to insert.
314 * @param __n Maximum number of characters to insert.
315 */
316 void
317 _M_write(const char_type* __s, streamsize __n)
318 {
319 const streamsize __put = this->rdbuf()->sputn(__s, __n);
320 if (__put != __n)
321 this->setstate(ios_base::badbit);
322 }
323
324 /**
325 * @brief Character string insertion.
326 * @param __s The array to insert.
327 * @param __n Maximum number of characters to insert.
328 * @return *this
329 *
330 * Characters are copied from @p __s and inserted into the stream until
331 * one of the following happens:
332 *
333 * - @p __n characters are inserted
334 * - inserting into the output sequence fails (in this case, badbit
335 * will be set in the stream's error state)
336 *
337 * @note This function is not overloaded on signed char and
338 * unsigned char.
339 */
340 __ostream_type&
341 write(const char_type* __s, streamsize __n);
342 ///@}
343
344 /**
345 * @brief Synchronizing the stream buffer.
346 * @return *this
347 *
348 * If @c rdbuf() is a null pointer, changes nothing.
349 *
350 * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
351 * sets badbit.
352 */
353 __ostream_type&
354 flush();
355
356 /**
357 * @brief Getting the current write position.
358 * @return A file position object.
359 *
360 * If @c fail() is not false, returns @c pos_type(-1) to indicate
361 * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
362 */
363 pos_type
364 tellp();
365
366 /**
367 * @brief Changing the current write position.
368 * @param __pos A file position object.
369 * @return *this
370 *
371 * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
372 * that function fails, sets failbit.
373 */
374 __ostream_type&
375 seekp(pos_type);
376
377 /**
378 * @brief Changing the current write position.
379 * @param __off A file offset object.
380 * @param __dir The direction in which to seek.
381 * @return *this
382 *
383 * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
384 * If that function fails, sets failbit.
385 */
386 __ostream_type&
387 seekp(off_type, ios_base::seekdir);
388
389 protected:
390 basic_ostream()
391 { this->init(0); }
392
393#if __cplusplus >= 201103L
394 // Non-standard constructor that does not call init()
395 basic_ostream(basic_iostream<_CharT, _Traits>&) { }
396
397 basic_ostream(const basic_ostream&) = delete;
398
399 basic_ostream(basic_ostream&& __rhs)
400 : __ios_type()
401 { __ios_type::move(__rhs); }
402
403 // 27.7.3.3 Assign/swap
404
405 basic_ostream& operator=(const basic_ostream&) = delete;
406
407 basic_ostream&
408 operator=(basic_ostream&& __rhs)
409 {
410 swap(__rhs);
411 return *this;
412 }
413
414 void
415 swap(basic_ostream& __rhs)
416 { __ios_type::swap(__rhs); }
417#endif
418
419 template<typename _ValueT>
420 __ostream_type&
421 _M_insert(_ValueT __v);
422 };
423
424 /**
425 * @brief Performs setup work for output streams.
426 *
427 * Objects of this class are created before all of the standard
428 * inserters are run. It is responsible for <em>exception-safe prefix and
429 * suffix operations</em>.
430 */
431 template <typename _CharT, typename _Traits>
432 class basic_ostream<_CharT, _Traits>::sentry
433 {
434 // Data Members.
435 bool _M_ok;
436 basic_ostream<_CharT, _Traits>& _M_os;
437
438 public:
439 /**
440 * @brief The constructor performs preparatory work.
441 * @param __os The output stream to guard.
442 *
443 * If the stream state is good (@a __os.good() is true), then if the
444 * stream is tied to another output stream, @c is.tie()->flush()
445 * is called to synchronize the output sequences.
446 *
447 * If the stream state is still good, then the sentry state becomes
448 * true (@a okay).
449 */
450 explicit
451 sentry(basic_ostream<_CharT, _Traits>& __os);
452
453#pragma GCC diagnostic push
454#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
455 /**
456 * @brief Possibly flushes the stream.
457 *
458 * If @c ios_base::unitbuf is set in @c os.flags(), and
459 * @c std::uncaught_exception() is true, the sentry destructor calls
460 * @c flush() on the output stream.
461 */
462 ~sentry()
463 {
464 // XXX MT
465 if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
466 {
467 // Can't call flush directly or else will get into recursive lock.
468 if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
469 _M_os.setstate(ios_base::badbit);
470 }
471 }
472#pragma GCC diagnostic pop
473
474 /**
475 * @brief Quick status checking.
476 * @return The sentry state.
477 *
478 * For ease of use, sentries may be converted to booleans. The
479 * return value is that of the sentry state (true == okay).
480 */
481#if __cplusplus >= 201103L
482 explicit
483#endif
484 operator bool() const
485 { return _M_ok; }
486 };
487
488 ///@{
489 /**
490 * @brief Character inserters
491 * @param __out An output stream.
492 * @param __c A character.
493 * @return out
494 *
495 * Behaves like one of the formatted arithmetic inserters described in
496 * std::basic_ostream. After constructing a sentry object with good
497 * status, this function inserts a single character and any required
498 * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
499 * called.
500 *
501 * If @p __c is of type @c char and the character type of the stream is not
502 * @c char, the character is widened before insertion.
503 */
504 template<typename _CharT, typename _Traits>
505 inline basic_ostream<_CharT, _Traits>&
506 operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
507 { return __ostream_insert(__out, &__c, 1); }
508
509 template<typename _CharT, typename _Traits>
510 inline basic_ostream<_CharT, _Traits>&
511 operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
512 { return (__out << __out.widen(__c)); }
513
514 // Specialization
515 template<typename _Traits>
516 inline basic_ostream<char, _Traits>&
517 operator<<(basic_ostream<char, _Traits>& __out, char __c)
518 { return __ostream_insert(__out, &__c, 1); }
519
520 // Signed and unsigned
521 template<typename _Traits>
522 inline basic_ostream<char, _Traits>&
523 operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
524 { return (__out << static_cast<char>(__c)); }
525
526 template<typename _Traits>
527 inline basic_ostream<char, _Traits>&
528 operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
529 { return (__out << static_cast<char>(__c)); }
530
531#if __cplusplus > 201703L
532 // The following deleted overloads prevent formatting character values as
533 // numeric values.
534
535#ifdef _GLIBCXX_USE_WCHAR_T
536 template<typename _Traits>
537 basic_ostream<char, _Traits>&
538 operator<<(basic_ostream<char, _Traits>&, wchar_t) = delete;
539#endif // _GLIBCXX_USE_WCHAR_T
540
541#ifdef _GLIBCXX_USE_CHAR8_T
542 template<typename _Traits>
543 basic_ostream<char, _Traits>&
544 operator<<(basic_ostream<char, _Traits>&, char8_t) = delete;
545#endif
546
547 template<typename _Traits>
548 basic_ostream<char, _Traits>&
549 operator<<(basic_ostream<char, _Traits>&, char16_t) = delete;
550
551 template<typename _Traits>
552 basic_ostream<char, _Traits>&
553 operator<<(basic_ostream<char, _Traits>&, char32_t) = delete;
554
555#ifdef _GLIBCXX_USE_WCHAR_T
556#ifdef _GLIBCXX_USE_CHAR8_T
557 template<typename _Traits>
558 basic_ostream<wchar_t, _Traits>&
559 operator<<(basic_ostream<wchar_t, _Traits>&, char8_t) = delete;
560#endif // _GLIBCXX_USE_CHAR8_T
561
562 template<typename _Traits>
563 basic_ostream<wchar_t, _Traits>&
564 operator<<(basic_ostream<wchar_t, _Traits>&, char16_t) = delete;
565
566 template<typename _Traits>
567 basic_ostream<wchar_t, _Traits>&
568 operator<<(basic_ostream<wchar_t, _Traits>&, char32_t) = delete;
569#endif // _GLIBCXX_USE_WCHAR_T
570#endif // C++20
571 ///@}
572
573 ///@{
574 /**
575 * @brief String inserters
576 * @param __out An output stream.
577 * @param __s A character string.
578 * @return out
579 * @pre @p __s must be a non-NULL pointer
580 *
581 * Behaves like one of the formatted arithmetic inserters described in
582 * std::basic_ostream. After constructing a sentry object with good
583 * status, this function inserts @c traits::length(__s) characters starting
584 * at @p __s, widened if necessary, followed by any required padding (as
585 * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
586 */
587 template<typename _CharT, typename _Traits>
588 inline basic_ostream<_CharT, _Traits>&
589 operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
590 {
591 if (!__s)
592 __out.setstate(ios_base::badbit);
593 else
594 __ostream_insert(__out, __s,
595 static_cast<streamsize>(_Traits::length(__s)));
596 return __out;
597 }
598
599 template<typename _CharT, typename _Traits>
600 basic_ostream<_CharT, _Traits> &
601 operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
602
603 // Partial specializations
604 template<typename _Traits>
605 inline basic_ostream<char, _Traits>&
606 operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
607 {
608 if (!__s)
609 __out.setstate(ios_base::badbit);
610 else
611 __ostream_insert(__out, __s,
612 static_cast<streamsize>(_Traits::length(__s)));
613 return __out;
614 }
615
616 // Signed and unsigned
617 template<typename _Traits>
618 inline basic_ostream<char, _Traits>&
619 operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
620 { return (__out << reinterpret_cast<const char*>(__s)); }
621
622 template<typename _Traits>
623 inline basic_ostream<char, _Traits> &
624 operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
625 { return (__out << reinterpret_cast<const char*>(__s)); }
626
627#if __cplusplus > 201703L
628 // The following deleted overloads prevent formatting strings as
629 // pointer values.
630
631#ifdef _GLIBCXX_USE_WCHAR_T
632 template<typename _Traits>
633 basic_ostream<char, _Traits>&
634 operator<<(basic_ostream<char, _Traits>&, const wchar_t*) = delete;
635#endif // _GLIBCXX_USE_WCHAR_T
636
637#ifdef _GLIBCXX_USE_CHAR8_T
638 template<typename _Traits>
639 basic_ostream<char, _Traits>&
640 operator<<(basic_ostream<char, _Traits>&, const char8_t*) = delete;
641#endif // _GLIBCXX_USE_CHAR8_T
642
643 template<typename _Traits>
644 basic_ostream<char, _Traits>&
645 operator<<(basic_ostream<char, _Traits>&, const char16_t*) = delete;
646
647 template<typename _Traits>
648 basic_ostream<char, _Traits>&
649 operator<<(basic_ostream<char, _Traits>&, const char32_t*) = delete;
650
651#ifdef _GLIBCXX_USE_WCHAR_T
652#ifdef _GLIBCXX_USE_CHAR8_T
653 template<typename _Traits>
654 basic_ostream<wchar_t, _Traits>&
655 operator<<(basic_ostream<wchar_t, _Traits>&, const char8_t*) = delete;
656#endif
657
658 template<typename _Traits>
659 basic_ostream<wchar_t, _Traits>&
660 operator<<(basic_ostream<wchar_t, _Traits>&, const char16_t*) = delete;
661
662 template<typename _Traits>
663 basic_ostream<wchar_t, _Traits>&
664 operator<<(basic_ostream<wchar_t, _Traits>&, const char32_t*) = delete;
665#endif // _GLIBCXX_USE_WCHAR_T
666#endif // C++20
667 ///@}
668
669 // Standard basic_ostream manipulators
670
671 /**
672 * @brief Write a newline and flush the stream.
673 *
674 * This manipulator is often mistakenly used when a simple newline is
675 * desired, leading to poor buffering performance. See
676 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
677 * for more on this subject.
678 */
679 template<typename _CharT, typename _Traits>
680 inline basic_ostream<_CharT, _Traits>&
681 endl(basic_ostream<_CharT, _Traits>& __os)
682 { return flush(__os.put(__os.widen('\n'))); }
683
684 /**
685 * @brief Write a null character into the output sequence.
686 *
687 * <em>Null character</em> is @c CharT() by definition. For CharT
688 * of @c char, this correctly writes the ASCII @c NUL character
689 * string terminator.
690 */
691 template<typename _CharT, typename _Traits>
692 inline basic_ostream<_CharT, _Traits>&
693 ends(basic_ostream<_CharT, _Traits>& __os)
694 { return __os.put(_CharT()); }
695
696 /**
697 * @brief Flushes the output stream.
698 *
699 * This manipulator simply calls the stream's @c flush() member function.
700 */
701 template<typename _CharT, typename _Traits>
702 inline basic_ostream<_CharT, _Traits>&
703 flush(basic_ostream<_CharT, _Traits>& __os)
704 { return __os.flush(); }
705
706#if __cplusplus >= 201103L
707 // C++11 27.7.3.9 Rvalue stream insertion [ostream.rvalue]
708 // _GLIBCXX_RESOLVE_LIB_DEFECTS
709 // 1203. More useful rvalue stream insertion
710
711#if __cpp_lib_concepts
712 // Use concepts if possible because they're cheaper to evaluate.
713 template<typename _Tp>
714 concept __derived_from_ios_base = is_class_v<_Tp>
715 && (!is_same_v<_Tp, ios_base>)
716 && requires (_Tp* __t, ios_base* __b) { __b = __t; };
717
718 template<typename _Os, typename _Tp>
719 requires __derived_from_ios_base<_Os>
720 && requires (_Os& __os, const _Tp& __t) { __os << __t; }
721 using __rvalue_stream_insertion_t = _Os&&;
722#else
723 template<typename _Tp>
724 using _Require_derived_from_ios_base
725 = _Require<is_class<_Tp>, __not_<is_same<_Tp, ios_base>>,
726 is_convertible<typename add_pointer<_Tp>::type, ios_base*>>;
727
728 template<typename _Os, typename _Tp,
729 typename = _Require_derived_from_ios_base<_Os>,
730 typename
731 = decltype(std::declval<_Os&>() << std::declval<const _Tp&>())>
732 using __rvalue_stream_insertion_t = _Os&&;
733#endif
734
735 /**
736 * @brief Generic inserter for rvalue stream
737 * @param __os An input stream.
738 * @param __x A reference to the object being inserted.
739 * @return __os
740 *
741 * This is just a forwarding function to allow insertion to
742 * rvalue streams since they won't bind to the inserter functions
743 * that take an lvalue reference.
744 */
745 template<typename _Ostream, typename _Tp>
746 inline __rvalue_stream_insertion_t<_Ostream, _Tp>
747 operator<<(_Ostream&& __os, const _Tp& __x)
748 {
749 __os << __x;
750 return std::move(__os);
751 }
752
753#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
754 template<typename _CharT, typename _Traits>
755 class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
756 {
757 public:
758 static bool*
759 _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
760 {
761#if __cpp_rtti
762 if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
763 return &__p->_M_emit_on_sync;
764#endif
765 return nullptr;
766 }
767
768 protected:
769 __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
770 : _M_wrapped(__w)
771 { }
772
773 basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
774 bool _M_emit_on_sync = false;
775 bool _M_needs_sync = false;
776 };
777
778 template<typename _CharT, typename _Traits>
779 inline basic_ostream<_CharT, _Traits>&
780 emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
781 {
782 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
783 *__flag = true;
784 return __os;
785 }
786
787 template<typename _CharT, typename _Traits>
788 inline basic_ostream<_CharT, _Traits>&
789 noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
790 {
791 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
792 *__flag = false;
793 return __os;
794 }
795
796 template<typename _CharT, typename _Traits>
797 inline basic_ostream<_CharT, _Traits>&
798 flush_emit(basic_ostream<_CharT, _Traits>& __os)
799 {
800 struct _Restore
801 {
802 ~_Restore() { *_M_flag = _M_prev; }
803
804 bool _M_prev = false;
805 bool* _M_flag = &_M_prev;
806 } __restore;
807
808 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
809 {
810 __restore._M_prev = *__flag;
811 __restore._M_flag = __flag;
812 *__flag = true;
813 }
814
815 __os.flush();
816 return __os;
817 }
818
819#endif // C++20
820
821#endif // C++11
822
823_GLIBCXX_END_NAMESPACE_VERSION
824} // namespace std
825
826#include <bits/ostream.tcc>
827
828#endif /* _GLIBCXX_OSTREAM */
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