libstdc++
ostream
Go to the documentation of this file.
1 // Output streams -*- C++ -*-
2 
3 // Copyright (C) 1997-2015 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 
41 namespace 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  /**
249  * @brief Extracting from another streambuf.
250  * @param __sb A pointer to a streambuf
251  *
252  * This function behaves like one of the basic arithmetic extractors,
253  * in that it also constructs a sentry object and has the same error
254  * handling behavior.
255  *
256  * If @p __sb is NULL, the stream will set failbit in its error state.
257  *
258  * Characters are extracted from @p __sb and inserted into @c *this
259  * until one of the following occurs:
260  *
261  * - the input stream reaches end-of-file,
262  * - insertion into the output sequence fails (in this case, the
263  * character that would have been inserted is not extracted), or
264  * - an exception occurs while getting a character from @p __sb, which
265  * sets failbit in the error state
266  *
267  * If the function inserts no characters, failbit is set.
268  */
269  __ostream_type&
270  operator<<(__streambuf_type* __sb);
271  //@}
272 
273  //@{
274  /**
275  * @name Unformatted Output Functions
276  *
277  * All the unformatted output functions have some common behavior.
278  * Each starts by constructing a temporary object of type
279  * std::basic_ostream::sentry. This has several effects, concluding
280  * with the setting of a status flag; see the sentry documentation
281  * for more.
282  *
283  * If the sentry status is good, the function tries to generate
284  * whatever data is appropriate for the type of the argument.
285  *
286  * If an exception is thrown during insertion, ios_base::badbit
287  * will be turned on in the stream's error state. If badbit is on in
288  * the stream's exceptions mask, the exception will be rethrown
289  * without completing its actions.
290  */
291 
292  /**
293  * @brief Simple insertion.
294  * @param __c The character to insert.
295  * @return *this
296  *
297  * Tries to insert @p __c.
298  *
299  * @note This function is not overloaded on signed char and
300  * unsigned char.
301  */
302  __ostream_type&
303  put(char_type __c);
304 
305  /**
306  * @brief Core write functionality, without sentry.
307  * @param __s The array to insert.
308  * @param __n Maximum number of characters to insert.
309  */
310  void
311  _M_write(const char_type* __s, streamsize __n)
312  {
313  const streamsize __put = this->rdbuf()->sputn(__s, __n);
314  if (__put != __n)
315  this->setstate(ios_base::badbit);
316  }
317 
318  /**
319  * @brief Character string insertion.
320  * @param __s The array to insert.
321  * @param __n Maximum number of characters to insert.
322  * @return *this
323  *
324  * Characters are copied from @p __s and inserted into the stream until
325  * one of the following happens:
326  *
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)
330  *
331  * @note This function is not overloaded on signed char and
332  * unsigned char.
333  */
334  __ostream_type&
335  write(const char_type* __s, streamsize __n);
336  //@}
337 
338  /**
339  * @brief Synchronizing the stream buffer.
340  * @return *this
341  *
342  * If @c rdbuf() is a null pointer, changes nothing.
343  *
344  * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
345  * sets badbit.
346  */
347  __ostream_type&
348  flush();
349 
350  /**
351  * @brief Getting the current write position.
352  * @return A file position object.
353  *
354  * If @c fail() is not false, returns @c pos_type(-1) to indicate
355  * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
356  */
357  pos_type
358  tellp();
359 
360  /**
361  * @brief Changing the current write position.
362  * @param __pos A file position object.
363  * @return *this
364  *
365  * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
366  * that function fails, sets failbit.
367  */
368  __ostream_type&
369  seekp(pos_type);
370 
371  /**
372  * @brief Changing the current write position.
373  * @param __off A file offset object.
374  * @param __dir The direction in which to seek.
375  * @return *this
376  *
377  * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
378  * If that function fails, sets failbit.
379  */
380  __ostream_type&
381  seekp(off_type, ios_base::seekdir);
382 
383  protected:
384  basic_ostream()
385  { this->init(0); }
386 
387 #if __cplusplus >= 201103L
388  // Non-standard constructor that does not call init()
389  basic_ostream(basic_iostream<_CharT, _Traits>&) { }
390 
391  basic_ostream(const basic_ostream&) = delete;
392 
393  basic_ostream(basic_ostream&& __rhs)
394  : __ios_type()
395  { __ios_type::move(__rhs); }
396 
397  // 27.7.3.3 Assign/swap
398 
399  basic_ostream& operator=(const basic_ostream&) = delete;
400 
401  basic_ostream&
402  operator=(basic_ostream&& __rhs)
403  {
404  swap(__rhs);
405  return *this;
406  }
407 
408  void
409  swap(basic_ostream& __rhs)
410  { __ios_type::swap(__rhs); }
411 #endif
412 
413  template<typename _ValueT>
414  __ostream_type&
415  _M_insert(_ValueT __v);
416  };
417 
418  /**
419  * @brief Performs setup work for output streams.
420  *
421  * Objects of this class are created before all of the standard
422  * inserters are run. It is responsible for <em>exception-safe prefix and
423  * suffix operations</em>.
424  */
425  template <typename _CharT, typename _Traits>
426  class basic_ostream<_CharT, _Traits>::sentry
427  {
428  // Data Members.
429  bool _M_ok;
430  basic_ostream<_CharT, _Traits>& _M_os;
431 
432  public:
433  /**
434  * @brief The constructor performs preparatory work.
435  * @param __os The output stream to guard.
436  *
437  * If the stream state is good (@a __os.good() is true), then if the
438  * stream is tied to another output stream, @c is.tie()->flush()
439  * is called to synchronize the output sequences.
440  *
441  * If the stream state is still good, then the sentry state becomes
442  * true (@a okay).
443  */
444  explicit
445  sentry(basic_ostream<_CharT, _Traits>& __os);
446 
447  /**
448  * @brief Possibly flushes the stream.
449  *
450  * If @c ios_base::unitbuf is set in @c os.flags(), and
451  * @c std::uncaught_exception() is true, the sentry destructor calls
452  * @c flush() on the output stream.
453  */
454  ~sentry()
455  {
456  // XXX MT
457  if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
458  {
459  // Can't call flush directly or else will get into recursive lock.
460  if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
461  _M_os.setstate(ios_base::badbit);
462  }
463  }
464 
465  /**
466  * @brief Quick status checking.
467  * @return The sentry state.
468  *
469  * For ease of use, sentries may be converted to booleans. The
470  * return value is that of the sentry state (true == okay).
471  */
472 #if __cplusplus >= 201103L
473  explicit
474 #endif
475  operator bool() const
476  { return _M_ok; }
477  };
478 
479  //@{
480  /**
481  * @brief Character inserters
482  * @param __out An output stream.
483  * @param __c A character.
484  * @return out
485  *
486  * Behaves like one of the formatted arithmetic inserters described in
487  * std::basic_ostream. After constructing a sentry object with good
488  * status, this function inserts a single character and any required
489  * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
490  * called.
491  *
492  * If @p __c is of type @c char and the character type of the stream is not
493  * @c char, the character is widened before insertion.
494  */
495  template<typename _CharT, typename _Traits>
496  inline basic_ostream<_CharT, _Traits>&
497  operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
498  { return __ostream_insert(__out, &__c, 1); }
499 
500  template<typename _CharT, typename _Traits>
501  inline basic_ostream<_CharT, _Traits>&
502  operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
503  { return (__out << __out.widen(__c)); }
504 
505  // Specialization
506  template <class _Traits>
507  inline basic_ostream<char, _Traits>&
508  operator<<(basic_ostream<char, _Traits>& __out, char __c)
509  { return __ostream_insert(__out, &__c, 1); }
510 
511  // Signed and unsigned
512  template<class _Traits>
513  inline basic_ostream<char, _Traits>&
514  operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
515  { return (__out << static_cast<char>(__c)); }
516 
517  template<class _Traits>
518  inline basic_ostream<char, _Traits>&
519  operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
520  { return (__out << static_cast<char>(__c)); }
521  //@}
522 
523  //@{
524  /**
525  * @brief String inserters
526  * @param __out An output stream.
527  * @param __s A character string.
528  * @return out
529  * @pre @p __s must be a non-NULL pointer
530  *
531  * Behaves like one of the formatted arithmetic inserters described in
532  * std::basic_ostream. After constructing a sentry object with good
533  * status, this function inserts @c traits::length(__s) characters starting
534  * at @p __s, widened if necessary, followed by any required padding (as
535  * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
536  */
537  template<typename _CharT, typename _Traits>
538  inline basic_ostream<_CharT, _Traits>&
539  operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
540  {
541  if (!__s)
542  __out.setstate(ios_base::badbit);
543  else
544  __ostream_insert(__out, __s,
545  static_cast<streamsize>(_Traits::length(__s)));
546  return __out;
547  }
548 
549  template<typename _CharT, typename _Traits>
550  basic_ostream<_CharT, _Traits> &
551  operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
552 
553  // Partial specializations
554  template<class _Traits>
555  inline basic_ostream<char, _Traits>&
556  operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
557  {
558  if (!__s)
559  __out.setstate(ios_base::badbit);
560  else
561  __ostream_insert(__out, __s,
562  static_cast<streamsize>(_Traits::length(__s)));
563  return __out;
564  }
565 
566  // Signed and unsigned
567  template<class _Traits>
568  inline basic_ostream<char, _Traits>&
569  operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
570  { return (__out << reinterpret_cast<const char*>(__s)); }
571 
572  template<class _Traits>
573  inline basic_ostream<char, _Traits> &
574  operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
575  { return (__out << reinterpret_cast<const char*>(__s)); }
576  //@}
577 
578  // Standard basic_ostream manipulators
579 
580  /**
581  * @brief Write a newline and flush the stream.
582  *
583  * This manipulator is often mistakenly used when a simple newline is
584  * desired, leading to poor buffering performance. See
585  * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
586  * for more on this subject.
587  */
588  template<typename _CharT, typename _Traits>
589  inline basic_ostream<_CharT, _Traits>&
590  endl(basic_ostream<_CharT, _Traits>& __os)
591  { return flush(__os.put(__os.widen('\n'))); }
592 
593  /**
594  * @brief Write a null character into the output sequence.
595  *
596  * <em>Null character</em> is @c CharT() by definition. For CharT
597  * of @c char, this correctly writes the ASCII @c NUL character
598  * string terminator.
599  */
600  template<typename _CharT, typename _Traits>
601  inline basic_ostream<_CharT, _Traits>&
602  ends(basic_ostream<_CharT, _Traits>& __os)
603  { return __os.put(_CharT()); }
604 
605  /**
606  * @brief Flushes the output stream.
607  *
608  * This manipulator simply calls the stream's @c flush() member function.
609  */
610  template<typename _CharT, typename _Traits>
611  inline basic_ostream<_CharT, _Traits>&
612  flush(basic_ostream<_CharT, _Traits>& __os)
613  { return __os.flush(); }
614 
615 #if __cplusplus >= 201103L
616  /**
617  * @brief Generic inserter for rvalue stream
618  * @param __os An input stream.
619  * @param __x A reference to the object being inserted.
620  * @return os
621  *
622  * This is just a forwarding function to allow insertion to
623  * rvalue streams since they won't bind to the inserter functions
624  * that take an lvalue reference.
625  */
626  template<typename _CharT, typename _Traits, typename _Tp>
627  inline basic_ostream<_CharT, _Traits>&
628  operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
629  {
630  __os << __x;
631  return __os;
632  }
633 #endif // C++11
634 
635 _GLIBCXX_END_NAMESPACE_VERSION
636 } // namespace std
637 
638 #include <bits/ostream.tcc>
639 
640 #endif /* _GLIBCXX_OSTREAM */