1 // Output streams -*- C++ -*-
3 // Copyright (C) 1997-2021 Free Software Foundation, Inc.
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)
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.
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.
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/>.
25 /** @file include/ostream
26 * This is a Standard C++ Library header.
30 // ISO C++ 14882: 27.6.2 Output streams
33 #ifndef _GLIBCXX_OSTREAM
34 #define _GLIBCXX_OSTREAM 1
36 #pragma GCC system_header
39 #include <bits/ostream_insert.h>
41 namespace std _GLIBCXX_VISIBILITY(default)
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46 * @brief Template class basic_ostream.
49 * @tparam _CharT Type of character stream.
50 * @tparam _Traits Traits for character type, defaults to
51 * char_traits<_CharT>.
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.
57 template<typename _CharT, typename _Traits>
58 class basic_ostream : virtual public basic_ios<_CharT, _Traits>
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;
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> >
74 typedef ctype<_CharT> __ctype_type;
77 * @brief Base constructor.
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.
84 basic_ostream(__streambuf_type* __sb)
88 * @brief Base destructor.
90 * This does very little apart from providing a virtual base dtor.
95 /// Safe prefix/suffix operations.
101 * @brief Interface for manipulators.
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.
108 operator<<(__ostream_type& (*__pf)(__ostream_type&))
110 // _GLIBCXX_RESOLVE_LIB_DEFECTS
111 // DR 60. What is a formatted input function?
112 // The inserters for manipulators are *not* formatted output functions.
117 operator<<(__ios_type& (*__pf)(__ios_type&))
119 // _GLIBCXX_RESOLVE_LIB_DEFECTS
120 // DR 60. What is a formatted input function?
121 // The inserters for manipulators are *not* formatted output functions.
127 operator<<(ios_base& (*__pf) (ios_base&))
129 // _GLIBCXX_RESOLVE_LIB_DEFECTS
130 // DR 60. What is a formatted input function?
131 // The inserters for manipulators are *not* formatted output functions.
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.
147 * If the sentry status is good, the function tries to generate
148 * whatever data is appropriate for the type of the argument.
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
158 * @brief Integer arithmetic inserters
159 * @param __n A variable of builtin integral type.
160 * @return @c *this if successful
162 * These functions use the stream's current locale (specifically, the
163 * @c num_get facet) to perform numeric formatting.
167 { return _M_insert(__n); }
170 operator<<(unsigned long __n)
171 { return _M_insert(__n); }
175 { return _M_insert(__n); }
178 operator<<(short __n);
181 operator<<(unsigned short __n)
183 // _GLIBCXX_RESOLVE_LIB_DEFECTS
184 // 117. basic_ostream uses nonexistent num_put member functions.
185 return _M_insert(static_cast<unsigned long>(__n));
192 operator<<(unsigned int __n)
194 // _GLIBCXX_RESOLVE_LIB_DEFECTS
195 // 117. basic_ostream uses nonexistent num_put member functions.
196 return _M_insert(static_cast<unsigned long>(__n));
199 #ifdef _GLIBCXX_USE_LONG_LONG
201 operator<<(long long __n)
202 { return _M_insert(__n); }
205 operator<<(unsigned long long __n)
206 { return _M_insert(__n); }
212 * @brief Floating point arithmetic inserters
213 * @param __f A variable of builtin floating point type.
214 * @return @c *this if successful
216 * These functions use the stream's current locale (specifically, the
217 * @c num_get facet) to perform numeric formatting.
220 operator<<(double __f)
221 { return _M_insert(__f); }
224 operator<<(float __f)
226 // _GLIBCXX_RESOLVE_LIB_DEFECTS
227 // 117. basic_ostream uses nonexistent num_put member functions.
228 return _M_insert(static_cast<double>(__f));
232 operator<<(long double __f)
233 { return _M_insert(__f); }
237 * @brief Pointer arithmetic inserters
238 * @param __p A variable of pointer type.
239 * @return @c *this if successful
241 * These functions use the stream's current locale (specifically, the
242 * @c num_get facet) to perform numeric formatting.
245 operator<<(const void* __p)
246 { return _M_insert(__p); }
248 #if __cplusplus >= 201703L
250 operator<<(nullptr_t)
251 { return *this << "nullptr"; }
254 #if __cplusplus > 202002L
255 __attribute__((__always_inline__))
257 operator<<(const volatile void* __p)
258 { return _M_insert(const_cast<const void*>(__p)); }
262 * @brief Extracting from another streambuf.
263 * @param __sb A pointer to a streambuf
265 * This function behaves like one of the basic arithmetic extractors,
266 * in that it also constructs a sentry object and has the same error
269 * If @p __sb is NULL, the stream will set failbit in its error state.
271 * Characters are extracted from @p __sb and inserted into @c *this
272 * until one of the following occurs:
274 * - the input stream reaches end-of-file,
275 * - insertion into the output sequence fails (in this case, the
276 * character that would have been inserted is not extracted), or
277 * - an exception occurs while getting a character from @p __sb, which
278 * sets failbit in the error state
280 * If the function inserts no characters, failbit is set.
283 operator<<(__streambuf_type* __sb);
288 * @name Unformatted Output Functions
290 * All the unformatted output functions have some common behavior.
291 * Each starts by constructing a temporary object of type
292 * std::basic_ostream::sentry. This has several effects, concluding
293 * with the setting of a status flag; see the sentry documentation
296 * If the sentry status is good, the function tries to generate
297 * whatever data is appropriate for the type of the argument.
299 * If an exception is thrown during insertion, ios_base::badbit
300 * will be turned on in the stream's error state. If badbit is on in
301 * the stream's exceptions mask, the exception will be rethrown
302 * without completing its actions.
306 * @brief Simple insertion.
307 * @param __c The character to insert.
310 * Tries to insert @p __c.
312 * @note This function is not overloaded on signed char and
319 * @brief Character string insertion.
320 * @param __s The array to insert.
321 * @param __n Maximum number of characters to insert.
324 * Characters are copied from @p __s and inserted into the stream until
325 * one of the following happens:
327 * - @p __n characters are inserted
328 * - inserting into the output sequence fails (in this case, badbit
329 * will be set in the stream's error state)
331 * @note This function is not overloaded on signed char and
335 write(const char_type* __s, streamsize __n);
339 * @brief Synchronizing the stream buffer.
342 * If @c rdbuf() is a null pointer, changes nothing.
344 * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
351 * @brief Getting the current write position.
352 * @return A file position object.
354 * If @c fail() is not false, returns @c pos_type(-1) to indicate
355 * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
361 * @brief Changing the current write position.
362 * @param __pos A file position object.
365 * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
366 * that function fails, sets failbit.
372 * @brief Changing the current write position.
373 * @param __off A file offset object.
374 * @param __dir The direction in which to seek.
377 * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
378 * If that function fails, sets failbit.
381 seekp(off_type, ios_base::seekdir);
387 #if __cplusplus >= 201103L
388 // Non-standard constructor that does not call init()
389 basic_ostream(basic_iostream<_CharT, _Traits>&) { }
391 basic_ostream(const basic_ostream&) = delete;
393 basic_ostream(basic_ostream&& __rhs)
395 { __ios_type::move(__rhs); }
397 // 27.7.3.3 Assign/swap
399 basic_ostream& operator=(const basic_ostream&) = delete;
402 operator=(basic_ostream&& __rhs)
409 swap(basic_ostream& __rhs)
410 { __ios_type::swap(__rhs); }
413 template<typename _ValueT>
415 _M_insert(_ValueT __v);
418 #if !_GLIBCXX_INLINE_VERSION
420 _M_write(const char_type* __s, streamsize __n)
421 { std::__ostream_insert(*this, __s, __n); }
426 * @brief Performs setup work for output streams.
428 * Objects of this class are created before all of the standard
429 * inserters are run. It is responsible for <em>exception-safe prefix and
430 * suffix operations</em>.
432 template <typename _CharT, typename _Traits>
433 class basic_ostream<_CharT, _Traits>::sentry
437 basic_ostream<_CharT, _Traits>& _M_os;
441 * @brief The constructor performs preparatory work.
442 * @param __os The output stream to guard.
444 * If the stream state is good (@a __os.good() is true), then if the
445 * stream is tied to another output stream, @c is.tie()->flush()
446 * is called to synchronize the output sequences.
448 * If the stream state is still good, then the sentry state becomes
452 sentry(basic_ostream<_CharT, _Traits>& __os);
454 #pragma GCC diagnostic push
455 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
457 * @brief Possibly flushes the stream.
459 * If @c ios_base::unitbuf is set in @c os.flags(), and
460 * @c std::uncaught_exception() is true, the sentry destructor calls
461 * @c flush() on the output stream.
466 if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
468 // Can't call flush directly or else will get into recursive lock.
469 if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
470 _M_os.setstate(ios_base::badbit);
473 #pragma GCC diagnostic pop
476 * @brief Quick status checking.
477 * @return The sentry state.
479 * For ease of use, sentries may be converted to booleans. The
480 * return value is that of the sentry state (true == okay).
482 #if __cplusplus >= 201103L
485 operator bool() const
491 * @brief Character inserters
492 * @param __out An output stream.
493 * @param __c A character.
496 * Behaves like one of the formatted arithmetic inserters described in
497 * std::basic_ostream. After constructing a sentry object with good
498 * status, this function inserts a single character and any required
499 * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
502 * If @p __c is of type @c char and the character type of the stream is not
503 * @c char, the character is widened before insertion.
505 template<typename _CharT, typename _Traits>
506 inline basic_ostream<_CharT, _Traits>&
507 operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
508 { return __ostream_insert(__out, &__c, 1); }
510 template<typename _CharT, typename _Traits>
511 inline basic_ostream<_CharT, _Traits>&
512 operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
513 { return (__out << __out.widen(__c)); }
516 template<typename _Traits>
517 inline basic_ostream<char, _Traits>&
518 operator<<(basic_ostream<char, _Traits>& __out, char __c)
519 { return __ostream_insert(__out, &__c, 1); }
521 // Signed and unsigned
522 template<typename _Traits>
523 inline basic_ostream<char, _Traits>&
524 operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
525 { return (__out << static_cast<char>(__c)); }
527 template<typename _Traits>
528 inline basic_ostream<char, _Traits>&
529 operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
530 { return (__out << static_cast<char>(__c)); }
532 #if __cplusplus > 201703L
533 // The following deleted overloads prevent formatting character values as
536 template<typename _Traits>
537 basic_ostream<char, _Traits>&
538 operator<<(basic_ostream<char, _Traits>&, wchar_t) = delete;
540 #ifdef _GLIBCXX_USE_CHAR8_T
541 template<typename _Traits>
542 basic_ostream<char, _Traits>&
543 operator<<(basic_ostream<char, _Traits>&, char8_t) = delete;
546 template<typename _Traits>
547 basic_ostream<char, _Traits>&
548 operator<<(basic_ostream<char, _Traits>&, char16_t) = delete;
550 template<typename _Traits>
551 basic_ostream<char, _Traits>&
552 operator<<(basic_ostream<char, _Traits>&, char32_t) = delete;
554 #ifdef _GLIBCXX_USE_WCHAR_T
555 #ifdef _GLIBCXX_USE_CHAR8_T
556 template<typename _Traits>
557 basic_ostream<wchar_t, _Traits>&
558 operator<<(basic_ostream<wchar_t, _Traits>&, char8_t) = delete;
559 #endif // _GLIBCXX_USE_CHAR8_T
561 template<typename _Traits>
562 basic_ostream<wchar_t, _Traits>&
563 operator<<(basic_ostream<wchar_t, _Traits>&, char16_t) = delete;
565 template<typename _Traits>
566 basic_ostream<wchar_t, _Traits>&
567 operator<<(basic_ostream<wchar_t, _Traits>&, char32_t) = delete;
568 #endif // _GLIBCXX_USE_WCHAR_T
574 * @brief String inserters
575 * @param __out An output stream.
576 * @param __s A character string.
578 * @pre @p __s must be a non-NULL pointer
580 * Behaves like one of the formatted arithmetic inserters described in
581 * std::basic_ostream. After constructing a sentry object with good
582 * status, this function inserts @c traits::length(__s) characters starting
583 * at @p __s, widened if necessary, followed by any required padding (as
584 * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
586 template<typename _CharT, typename _Traits>
587 inline basic_ostream<_CharT, _Traits>&
588 operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
591 __out.setstate(ios_base::badbit);
593 __ostream_insert(__out, __s,
594 static_cast<streamsize>(_Traits::length(__s)));
598 template<typename _CharT, typename _Traits>
599 basic_ostream<_CharT, _Traits> &
600 operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
602 // Partial specializations
603 template<typename _Traits>
604 inline basic_ostream<char, _Traits>&
605 operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
608 __out.setstate(ios_base::badbit);
610 __ostream_insert(__out, __s,
611 static_cast<streamsize>(_Traits::length(__s)));
615 // Signed and unsigned
616 template<typename _Traits>
617 inline basic_ostream<char, _Traits>&
618 operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
619 { return (__out << reinterpret_cast<const char*>(__s)); }
621 template<typename _Traits>
622 inline basic_ostream<char, _Traits> &
623 operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
624 { return (__out << reinterpret_cast<const char*>(__s)); }
626 #if __cplusplus > 201703L
627 // The following deleted overloads prevent formatting strings as
630 template<typename _Traits>
631 basic_ostream<char, _Traits>&
632 operator<<(basic_ostream<char, _Traits>&, const wchar_t*) = delete;
634 #ifdef _GLIBCXX_USE_CHAR8_T
635 template<typename _Traits>
636 basic_ostream<char, _Traits>&
637 operator<<(basic_ostream<char, _Traits>&, const char8_t*) = delete;
638 #endif // _GLIBCXX_USE_CHAR8_T
640 template<typename _Traits>
641 basic_ostream<char, _Traits>&
642 operator<<(basic_ostream<char, _Traits>&, const char16_t*) = delete;
644 template<typename _Traits>
645 basic_ostream<char, _Traits>&
646 operator<<(basic_ostream<char, _Traits>&, const char32_t*) = delete;
648 #ifdef _GLIBCXX_USE_WCHAR_T
649 #ifdef _GLIBCXX_USE_CHAR8_T
650 template<typename _Traits>
651 basic_ostream<wchar_t, _Traits>&
652 operator<<(basic_ostream<wchar_t, _Traits>&, const char8_t*) = delete;
655 template<typename _Traits>
656 basic_ostream<wchar_t, _Traits>&
657 operator<<(basic_ostream<wchar_t, _Traits>&, const char16_t*) = delete;
659 template<typename _Traits>
660 basic_ostream<wchar_t, _Traits>&
661 operator<<(basic_ostream<wchar_t, _Traits>&, const char32_t*) = delete;
662 #endif // _GLIBCXX_USE_WCHAR_T
666 // Standard basic_ostream manipulators
669 * @brief Write a newline and flush the stream.
671 * This manipulator is often mistakenly used when a simple newline is
672 * desired, leading to poor buffering performance. See
673 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
674 * for more on this subject.
676 template<typename _CharT, typename _Traits>
677 inline basic_ostream<_CharT, _Traits>&
678 endl(basic_ostream<_CharT, _Traits>& __os)
679 { return flush(__os.put(__os.widen('\n'))); }
682 * @brief Write a null character into the output sequence.
684 * <em>Null character</em> is @c CharT() by definition. For CharT
685 * of @c char, this correctly writes the ASCII @c NUL character
688 template<typename _CharT, typename _Traits>
689 inline basic_ostream<_CharT, _Traits>&
690 ends(basic_ostream<_CharT, _Traits>& __os)
691 { return __os.put(_CharT()); }
694 * @brief Flushes the output stream.
696 * This manipulator simply calls the stream's @c flush() member function.
698 template<typename _CharT, typename _Traits>
699 inline basic_ostream<_CharT, _Traits>&
700 flush(basic_ostream<_CharT, _Traits>& __os)
701 { return __os.flush(); }
703 #if __cplusplus >= 201103L
704 // C++11 27.7.3.9 Rvalue stream insertion [ostream.rvalue]
705 // _GLIBCXX_RESOLVE_LIB_DEFECTS
706 // 1203. More useful rvalue stream insertion
708 #if __cpp_lib_concepts
709 // Use concepts if possible because they're cheaper to evaluate.
710 template<typename _Tp>
711 concept __derived_from_ios_base = is_class_v<_Tp>
712 && (!is_same_v<_Tp, ios_base>)
713 && requires (_Tp* __t, ios_base* __b) { __b = __t; };
715 template<typename _Os, typename _Tp>
716 requires __derived_from_ios_base<_Os>
717 && requires (_Os& __os, const _Tp& __t) { __os << __t; }
718 using __rvalue_stream_insertion_t = _Os&&;
720 template<typename _Tp>
721 using _Require_derived_from_ios_base
722 = _Require<is_class<_Tp>, __not_<is_same<_Tp, ios_base>>,
723 is_convertible<typename add_pointer<_Tp>::type, ios_base*>>;
725 template<typename _Os, typename _Tp,
726 typename = _Require_derived_from_ios_base<_Os>,
728 = decltype(std::declval<_Os&>() << std::declval<const _Tp&>())>
729 using __rvalue_stream_insertion_t = _Os&&;
733 * @brief Generic inserter for rvalue stream
734 * @param __os An input stream.
735 * @param __x A reference to the object being inserted.
738 * This is just a forwarding function to allow insertion to
739 * rvalue streams since they won't bind to the inserter functions
740 * that take an lvalue reference.
742 template<typename _Ostream, typename _Tp>
743 inline __rvalue_stream_insertion_t<_Ostream, _Tp>
744 operator<<(_Ostream&& __os, const _Tp& __x)
747 return std::move(__os);
750 #if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
751 template<typename _CharT, typename _Traits>
752 class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
756 _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
759 if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
760 return &__p->_M_emit_on_sync;
766 __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
770 basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
771 bool _M_emit_on_sync = false;
772 bool _M_needs_sync = false;
775 template<typename _CharT, typename _Traits>
776 inline basic_ostream<_CharT, _Traits>&
777 emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
779 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
784 template<typename _CharT, typename _Traits>
785 inline basic_ostream<_CharT, _Traits>&
786 noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
788 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
793 template<typename _CharT, typename _Traits>
794 inline basic_ostream<_CharT, _Traits>&
795 flush_emit(basic_ostream<_CharT, _Traits>& __os)
799 ~_Restore() { *_M_flag = _M_prev; }
801 bool _M_prev = false;
802 bool* _M_flag = &_M_prev;
805 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
807 __restore._M_prev = *__flag;
808 __restore._M_flag = __flag;
820 _GLIBCXX_END_NAMESPACE_VERSION
823 #include <bits/ostream.tcc>
825 #endif /* _GLIBCXX_OSTREAM */