libstdc++
istream
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1 // Input streams -*- C++ -*-
2 
3 // Copyright (C) 1997-2024 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 //
26 // ISO C++ 14882: 27.6.1 Input streams
27 //
28 
29 /** @file include/istream
30  * This is a Standard C++ Library header.
31  */
32 
33 #ifndef _GLIBCXX_ISTREAM
34 #define _GLIBCXX_ISTREAM 1
35 
36 #pragma GCC system_header
37 
38 #include <bits/requires_hosted.h> // iostreams
39 
40 #include <ios>
41 #include <ostream>
42 
43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46 
47  /**
48  * @brief Template class basic_istream.
49  * @ingroup io
50  *
51  * @tparam _CharT Type of character stream.
52  * @tparam _Traits Traits for character type, defaults to
53  * char_traits<_CharT>.
54  *
55  * This is the base class for all input streams. It provides text
56  * formatting of all builtin types, and communicates with any class
57  * derived from basic_streambuf to do the actual input.
58  */
59  template<typename _CharT, typename _Traits>
60  class basic_istream : virtual public basic_ios<_CharT, _Traits>
61  {
62  public:
63  // Types (inherited from basic_ios (27.4.4)):
64  typedef _CharT char_type;
65  typedef typename _Traits::int_type int_type;
66  typedef typename _Traits::pos_type pos_type;
67  typedef typename _Traits::off_type off_type;
68  typedef _Traits traits_type;
69 
70  // Non-standard Types:
71  typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
72  typedef basic_ios<_CharT, _Traits> __ios_type;
73  typedef basic_istream<_CharT, _Traits> __istream_type;
74  typedef num_get<_CharT, istreambuf_iterator<_CharT, _Traits> >
75  __num_get_type;
76  typedef ctype<_CharT> __ctype_type;
77 
78  protected:
79  // Data Members:
80  /**
81  * The number of characters extracted in the previous unformatted
82  * function; see gcount().
83  */
84  streamsize _M_gcount;
85 
86  public:
87  /**
88  * @brief Base constructor.
89  *
90  * This ctor is almost never called by the user directly, rather from
91  * derived classes' initialization lists, which pass a pointer to
92  * their own stream buffer.
93  */
94  explicit
95  basic_istream(__streambuf_type* __sb)
96  : _M_gcount(streamsize(0))
97  { this->init(__sb); }
98 
99  /**
100  * @brief Base destructor.
101  *
102  * This does very little apart from providing a virtual base dtor.
103  */
104  virtual
105  ~basic_istream()
106  { _M_gcount = streamsize(0); }
107 
108  /// Safe prefix/suffix operations.
109  class sentry;
110  friend class sentry;
111 
112  ///@{
113  /**
114  * @brief Interface for manipulators.
115  *
116  * Manipulators such as @c std::ws and @c std::dec use these
117  * functions in constructs like
118  * <code>std::cin >> std::ws</code>.
119  * For more information, see the iomanip header.
120  */
121  __istream_type&
122  operator>>(__istream_type& (*__pf)(__istream_type&))
123  { return __pf(*this); }
124 
125  __istream_type&
126  operator>>(__ios_type& (*__pf)(__ios_type&))
127  {
128  __pf(*this);
129  return *this;
130  }
131 
132  __istream_type&
133  operator>>(ios_base& (*__pf)(ios_base&))
134  {
135  __pf(*this);
136  return *this;
137  }
138  ///@}
139 
140  ///@{
141  /**
142  * @name Extractors
143  *
144  * All the @c operator>> functions (aka <em>formatted input
145  * functions</em>) have some common behavior. Each starts by
146  * constructing a temporary object of type std::basic_istream::sentry
147  * with the second argument (noskipws) set to false. This has several
148  * effects, concluding with the setting of a status flag; see the
149  * sentry documentation for more.
150  *
151  * If the sentry status is good, the function tries to extract
152  * whatever data is appropriate for the type of the argument.
153  *
154  * If an exception is thrown during extraction, ios_base::badbit
155  * will be turned on in the stream's error state (without causing an
156  * ios_base::failure to be thrown) and the original exception will
157  * be rethrown if badbit is set in the exceptions mask.
158  */
159 
160  ///@{
161  /**
162  * @brief Integer arithmetic extractors
163  * @param __n A variable of builtin integral type.
164  * @return @c *this if successful
165  *
166  * These functions use the stream's current locale (specifically, the
167  * @c num_get facet) to parse the input data.
168  */
169  __istream_type&
170  operator>>(bool& __n)
171  { return _M_extract(__n); }
172 
173  __istream_type&
174  operator>>(short& __n);
175 
176  __istream_type&
177  operator>>(unsigned short& __n)
178  { return _M_extract(__n); }
179 
180  __istream_type&
181  operator>>(int& __n);
182 
183  __istream_type&
184  operator>>(unsigned int& __n)
185  { return _M_extract(__n); }
186 
187  __istream_type&
188  operator>>(long& __n)
189  { return _M_extract(__n); }
190 
191  __istream_type&
192  operator>>(unsigned long& __n)
193  { return _M_extract(__n); }
194 
195 #ifdef _GLIBCXX_USE_LONG_LONG
196  __istream_type&
197  operator>>(long long& __n)
198  { return _M_extract(__n); }
199 
200  __istream_type&
201  operator>>(unsigned long long& __n)
202  { return _M_extract(__n); }
203 #endif
204  ///@}
205 
206  ///@{
207  /**
208  * @brief Floating point arithmetic extractors
209  * @param __f A variable of builtin floating point type.
210  * @return @c *this if successful
211  *
212  * These functions use the stream's current locale (specifically, the
213  * @c num_get facet) to parse the input data.
214  */
215  __istream_type&
216  operator>>(float& __f)
217  { return _M_extract(__f); }
218 
219  __istream_type&
220  operator>>(double& __f)
221  { return _M_extract(__f); }
222 
223  __istream_type&
224  operator>>(long double& __f)
225  { return _M_extract(__f); }
226  ///@}
227 
228 #if defined(__STDCPP_FLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
229  __attribute__((__always_inline__))
230  __istream_type&
231  operator>>(_Float16& __f)
232  {
233  float __flt;
234  __istream_type& __ret = _M_extract(__flt);
235  ios_base::iostate __err = ios_base::goodbit;
236  if (__flt < -__FLT16_MAX__)
237  {
238  __f = -__FLT16_MAX__;
239  __err = ios_base::failbit;
240  }
241  else if (__flt > __FLT16_MAX__)
242  {
243  __f = __FLT16_MAX__;
244  __err = ios_base::failbit;
245  }
246  else
247  __f = static_cast<_Float16>(__flt);
248  if (__err)
249  this->setstate(__err);
250  return __ret;
251  }
252 #endif
253 
254 #if defined(__STDCPP_FLOAT32_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
255  __attribute__((__always_inline__))
256  __istream_type&
257  operator>>(_Float32& __f)
258  {
259  float __flt;
260  __istream_type& __ret = _M_extract(__flt);
261  __f = static_cast<_Float32> (__flt);
262  return __ret;
263  }
264 #endif
265 
266 #if defined(__STDCPP_FLOAT64_T__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64)
267  __attribute__((__always_inline__))
268  __istream_type&
269  operator>>(_Float64& __f)
270  {
271  double __dbl;
272  __istream_type& __ret = _M_extract(__dbl);
273  __f = static_cast<_Float64> (__dbl);
274  return __ret;
275  }
276 #endif
277 
278 #if defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_LDOUBLE_IS_IEEE_BINARY128)
279  __attribute__((__always_inline__))
280  __istream_type&
281  operator>>(_Float128& __f)
282  {
283  long double __ldbl;
284  __istream_type& __ret = _M_extract(__ldbl);
285  __f = static_cast<_Float128> (__ldbl);
286  return __ret;
287  }
288 #endif
289 
290 #if defined(__STDCPP_BFLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
291  __attribute__((__always_inline__))
292  __istream_type&
293  operator>>(__gnu_cxx::__bfloat16_t & __f)
294  {
295  float __flt;
296  __istream_type& __ret = _M_extract(__flt);
297  ios_base::iostate __err = ios_base::goodbit;
298  if (__flt < -__BFLT16_MAX__)
299  {
300  __f = -__BFLT16_MAX__;
301  __err = ios_base::failbit;
302  }
303  else if (__flt > __BFLT16_MAX__)
304  {
305  __f = __BFLT16_MAX__;
306  __err = ios_base::failbit;
307  }
308  else
309  __f = static_cast<__gnu_cxx::__bfloat16_t>(__flt);
310  if (__err)
311  this->setstate(__err);
312  return __ret;
313  }
314 #endif
315 
316  /**
317  * @brief Basic arithmetic extractors
318  * @param __p A variable of pointer type.
319  * @return @c *this if successful
320  *
321  * These functions use the stream's current locale (specifically, the
322  * @c num_get facet) to parse the input data.
323  */
324  __istream_type&
325  operator>>(void*& __p)
326  { return _M_extract(__p); }
327 
328  /**
329  * @brief Extracting into another streambuf.
330  * @param __sb A pointer to a streambuf
331  *
332  * This function behaves like one of the basic arithmetic extractors,
333  * in that it also constructs a sentry object and has the same error
334  * handling behavior.
335  *
336  * If @p __sb is NULL, the stream will set failbit in its error state.
337  *
338  * Characters are extracted from this stream and inserted into the
339  * @p __sb streambuf until one of the following occurs:
340  *
341  * - the input stream reaches end-of-file,
342  * - insertion into the output buffer fails (in this case, the
343  * character that would have been inserted is not extracted), or
344  * - an exception occurs (and in this case is caught)
345  *
346  * If the function inserts no characters, failbit is set.
347  */
348  __istream_type&
349  operator>>(__streambuf_type* __sb);
350  ///@}
351 
352  // [27.6.1.3] unformatted input
353  /**
354  * @brief Character counting
355  * @return The number of characters extracted by the previous
356  * unformatted input function dispatched for this stream.
357  */
358  streamsize
359  gcount() const
360  { return _M_gcount; }
361 
362  ///@{
363  /**
364  * @name Unformatted Input Functions
365  *
366  * All the unformatted input functions have some common behavior.
367  * Each starts by constructing a temporary object of type
368  * std::basic_istream::sentry with the second argument (noskipws)
369  * set to true. This has several effects, concluding with the
370  * setting of a status flag; see the sentry documentation for more.
371  *
372  * If the sentry status is good, the function tries to extract
373  * whatever data is appropriate for the type of the argument.
374  *
375  * The number of characters extracted is stored for later retrieval
376  * by gcount().
377  *
378  * If an exception is thrown during extraction, ios_base::badbit
379  * will be turned on in the stream's error state (without causing an
380  * ios_base::failure to be thrown) and the original exception will
381  * be rethrown if badbit is set in the exceptions mask.
382  */
383 
384  /**
385  * @brief Simple extraction.
386  * @return A character, or eof().
387  *
388  * Tries to extract a character. If none are available, sets failbit
389  * and returns traits::eof().
390  */
391  int_type
392  get();
393 
394  /**
395  * @brief Simple extraction.
396  * @param __c The character in which to store data.
397  * @return *this
398  *
399  * Tries to extract a character and store it in @a __c. If none are
400  * available, sets failbit and returns traits::eof().
401  *
402  * @note This function is not overloaded on signed char and
403  * unsigned char.
404  */
405  __istream_type&
406  get(char_type& __c);
407 
408  /**
409  * @brief Simple multiple-character extraction.
410  * @param __s Pointer to an array.
411  * @param __n Maximum number of characters to store in @a __s.
412  * @param __delim A "stop" character.
413  * @return *this
414  *
415  * Characters are extracted and stored into @a __s until one of the
416  * following happens:
417  *
418  * - @c __n-1 characters are stored
419  * - the input sequence reaches EOF
420  * - the next character equals @a __delim, in which case the character
421  * is not extracted
422  *
423  * If no characters are stored, failbit is set in the stream's error
424  * state.
425  *
426  * In any case, a null character is stored into the next location in
427  * the array.
428  *
429  * @note This function is not overloaded on signed char and
430  * unsigned char.
431  */
432  __istream_type&
433  get(char_type* __s, streamsize __n, char_type __delim);
434 
435  /**
436  * @brief Simple multiple-character extraction.
437  * @param __s Pointer to an array.
438  * @param __n Maximum number of characters to store in @a s.
439  * @return *this
440  *
441  * Returns @c get(__s,__n,widen(&apos;\\n&apos;)).
442  */
443  __istream_type&
444  get(char_type* __s, streamsize __n)
445  { return this->get(__s, __n, this->widen('\n')); }
446 
447  /**
448  * @brief Extraction into another streambuf.
449  * @param __sb A streambuf in which to store data.
450  * @param __delim A "stop" character.
451  * @return *this
452  *
453  * Characters are extracted and inserted into @a __sb until one of the
454  * following happens:
455  *
456  * - the input sequence reaches EOF
457  * - insertion into the output buffer fails (in this case, the
458  * character that would have been inserted is not extracted)
459  * - the next character equals @a __delim (in this case, the character
460  * is not extracted)
461  * - an exception occurs (and in this case is caught)
462  *
463  * If no characters are stored, failbit is set in the stream's error
464  * state.
465  */
466  __istream_type&
467  get(__streambuf_type& __sb, char_type __delim);
468 
469  /**
470  * @brief Extraction into another streambuf.
471  * @param __sb A streambuf in which to store data.
472  * @return *this
473  *
474  * Returns @c get(__sb,widen(&apos;\\n&apos;)).
475  */
476  __istream_type&
477  get(__streambuf_type& __sb)
478  { return this->get(__sb, this->widen('\n')); }
479 
480  /**
481  * @brief String extraction.
482  * @param __s A character array in which to store the data.
483  * @param __n Maximum number of characters to extract.
484  * @param __delim A "stop" character.
485  * @return *this
486  *
487  * Extracts and stores characters into @a __s until one of the
488  * following happens. Note that these criteria are required to be
489  * tested in the order listed here, to allow an input line to exactly
490  * fill the @a __s array without setting failbit.
491  *
492  * -# the input sequence reaches end-of-file, in which case eofbit
493  * is set in the stream error state
494  * -# the next character equals @c __delim, in which case the character
495  * is extracted (and therefore counted in @c gcount()) but not stored
496  * -# @c __n-1 characters are stored, in which case failbit is set
497  * in the stream error state
498  *
499  * If no characters are extracted, failbit is set. (An empty line of
500  * input should therefore not cause failbit to be set.)
501  *
502  * In any case, a null character is stored in the next location in
503  * the array.
504  */
505  __istream_type&
506  getline(char_type* __s, streamsize __n, char_type __delim);
507 
508  /**
509  * @brief String extraction.
510  * @param __s A character array in which to store the data.
511  * @param __n Maximum number of characters to extract.
512  * @return *this
513  *
514  * Returns @c getline(__s,__n,widen(&apos;\\n&apos;)).
515  */
516  __istream_type&
517  getline(char_type* __s, streamsize __n)
518  { return this->getline(__s, __n, this->widen('\n')); }
519 
520  /**
521  * @brief Discarding characters
522  * @param __n Number of characters to discard.
523  * @param __delim A "stop" character.
524  * @return *this
525  *
526  * Extracts characters and throws them away until one of the
527  * following happens:
528  * - if @a __n @c != @c std::numeric_limits<int>::max(), @a __n
529  * characters are extracted
530  * - the input sequence reaches end-of-file
531  * - the next character equals @a __delim (in this case, the character
532  * is extracted); note that this condition will never occur if
533  * @a __delim equals @c traits::eof().
534  *
535  * NB: Provide three overloads, instead of the single function
536  * (with defaults) mandated by the Standard: this leads to a
537  * better performing implementation, while still conforming to
538  * the Standard.
539  */
540  __istream_type&
541  ignore(streamsize __n, int_type __delim);
542 
543  __istream_type&
544  ignore(streamsize __n);
545 
546  __istream_type&
547  ignore();
548 
549  /**
550  * @brief Looking ahead in the stream
551  * @return The next character, or eof().
552  *
553  * If, after constructing the sentry object, @c good() is false,
554  * returns @c traits::eof(). Otherwise reads but does not extract
555  * the next input character.
556  */
557  int_type
558  peek();
559 
560  /**
561  * @brief Extraction without delimiters.
562  * @param __s A character array.
563  * @param __n Maximum number of characters to store.
564  * @return *this
565  *
566  * If the stream state is @c good(), extracts characters and stores
567  * them into @a __s until one of the following happens:
568  * - @a __n characters are stored
569  * - the input sequence reaches end-of-file, in which case the error
570  * state is set to @c failbit|eofbit.
571  *
572  * @note This function is not overloaded on signed char and
573  * unsigned char.
574  */
575  __istream_type&
576  read(char_type* __s, streamsize __n);
577 
578  /**
579  * @brief Extraction until the buffer is exhausted, but no more.
580  * @param __s A character array.
581  * @param __n Maximum number of characters to store.
582  * @return The number of characters extracted.
583  *
584  * Extracts characters and stores them into @a __s depending on the
585  * number of characters remaining in the streambuf's buffer,
586  * @c rdbuf()->in_avail(), called @c A here:
587  * - if @c A @c == @c -1, sets eofbit and extracts no characters
588  * - if @c A @c == @c 0, extracts no characters
589  * - if @c A @c > @c 0, extracts @c min(A,n)
590  *
591  * The goal is to empty the current buffer, and to not request any
592  * more from the external input sequence controlled by the streambuf.
593  */
594  streamsize
595  readsome(char_type* __s, streamsize __n);
596 
597  /**
598  * @brief Unextracting a single character.
599  * @param __c The character to push back into the input stream.
600  * @return *this
601  *
602  * If @c rdbuf() is not null, calls @c rdbuf()->sputbackc(c).
603  *
604  * If @c rdbuf() is null or if @c sputbackc() fails, sets badbit in
605  * the error state.
606  *
607  * @note This function first clears eofbit. Since no characters
608  * are extracted, the next call to @c gcount() will return 0,
609  * as required by DR 60.
610  */
611  __istream_type&
612  putback(char_type __c);
613 
614  /**
615  * @brief Unextracting the previous character.
616  * @return *this
617  *
618  * If @c rdbuf() is not null, calls @c rdbuf()->sungetc(c).
619  *
620  * If @c rdbuf() is null or if @c sungetc() fails, sets badbit in
621  * the error state.
622  *
623  * @note This function first clears eofbit. Since no characters
624  * are extracted, the next call to @c gcount() will return 0,
625  * as required by DR 60.
626  */
627  __istream_type&
628  unget();
629 
630  /**
631  * @brief Synchronizing the stream buffer.
632  * @return 0 on success, -1 on failure
633  *
634  * If @c rdbuf() is a null pointer, returns -1.
635  *
636  * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
637  * sets badbit and returns -1.
638  *
639  * Otherwise, returns 0.
640  *
641  * @note This function does not count the number of characters
642  * extracted, if any, and therefore does not affect the next
643  * call to @c gcount().
644  */
645  int
646  sync();
647 
648  /**
649  * @brief Getting the current read position.
650  * @return A file position object.
651  *
652  * If @c fail() is not false, returns @c pos_type(-1) to indicate
653  * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,in).
654  *
655  * @note This function does not count the number of characters
656  * extracted, if any, and therefore does not affect the next
657  * call to @c gcount(). At variance with putback, unget and
658  * seekg, eofbit is not cleared first.
659  */
660  pos_type
661  tellg();
662 
663  /**
664  * @brief Changing the current read position.
665  * @param __pos A file position object.
666  * @return *this
667  *
668  * If @c fail() is not true, calls @c rdbuf()->pubseekpos(__pos). If
669  * that function fails, sets failbit.
670  *
671  * @note This function first clears eofbit. It does not count the
672  * number of characters extracted, if any, and therefore does
673  * not affect the next call to @c gcount().
674  */
675  __istream_type&
676  seekg(pos_type);
677 
678  /**
679  * @brief Changing the current read position.
680  * @param __off A file offset object.
681  * @param __dir The direction in which to seek.
682  * @return *this
683  *
684  * If @c fail() is not true, calls @c rdbuf()->pubseekoff(__off,__dir).
685  * If that function fails, sets failbit.
686  *
687  * @note This function first clears eofbit. It does not count the
688  * number of characters extracted, if any, and therefore does
689  * not affect the next call to @c gcount().
690  */
691  __istream_type&
692  seekg(off_type, ios_base::seekdir);
693  ///@}
694 
695  protected:
696  basic_istream()
697  : _M_gcount(streamsize(0))
698  { this->init(0); }
699 
700 #if __cplusplus >= 201103L
701  basic_istream(const basic_istream&) = delete;
702 
703  basic_istream(basic_istream&& __rhs)
704  : __ios_type(), _M_gcount(__rhs._M_gcount)
705  {
706  __ios_type::move(__rhs);
707  __rhs._M_gcount = 0;
708  }
709 
710  // 27.7.3.3 Assign/swap
711 
712  basic_istream& operator=(const basic_istream&) = delete;
713 
714  basic_istream&
715  operator=(basic_istream&& __rhs)
716  {
717  swap(__rhs);
718  return *this;
719  }
720 
721  void
722  swap(basic_istream& __rhs)
723  {
724  __ios_type::swap(__rhs);
725  std::swap(_M_gcount, __rhs._M_gcount);
726  }
727 #endif
728 
729  template<typename _ValueT>
730  __istream_type&
731  _M_extract(_ValueT& __v);
732  };
733 
734  /// Explicit specialization declarations, defined in src/istream.cc.
735  template<>
736  basic_istream<char>&
737  basic_istream<char>::
738  getline(char_type* __s, streamsize __n, char_type __delim);
739 
740  template<>
741  basic_istream<char>&
742  basic_istream<char>::
743  ignore(streamsize __n);
744 
745  template<>
746  basic_istream<char>&
747  basic_istream<char>::
748  ignore(streamsize __n, int_type __delim);
749 
750 #ifdef _GLIBCXX_USE_WCHAR_T
751  template<>
752  basic_istream<wchar_t>&
753  basic_istream<wchar_t>::
754  getline(char_type* __s, streamsize __n, char_type __delim);
755 
756  template<>
757  basic_istream<wchar_t>&
758  basic_istream<wchar_t>::
759  ignore(streamsize __n);
760 
761  template<>
762  basic_istream<wchar_t>&
763  basic_istream<wchar_t>::
764  ignore(streamsize __n, int_type __delim);
765 #endif
766 
767  /**
768  * @brief Performs setup work for input streams.
769  *
770  * Objects of this class are created before all of the standard
771  * extractors are run. It is responsible for <em>exception-safe
772  * prefix and suffix operations,</em> although only prefix actions
773  * are currently required by the standard.
774  */
775  template<typename _CharT, typename _Traits>
776  class basic_istream<_CharT, _Traits>::sentry
777  {
778  // Data Members.
779  bool _M_ok;
780 
781  public:
782  /// Easy access to dependent types.
783  typedef _Traits traits_type;
784  typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
785  typedef basic_istream<_CharT, _Traits> __istream_type;
786  typedef typename __istream_type::__ctype_type __ctype_type;
787  typedef typename _Traits::int_type __int_type;
788 
789  /**
790  * @brief The constructor performs all the work.
791  * @param __is The input stream to guard.
792  * @param __noskipws Whether to consume whitespace or not.
793  *
794  * If the stream state is good (@a __is.good() is true), then the
795  * following actions are performed, otherwise the sentry state
796  * is false (<em>not okay</em>) and failbit is set in the
797  * stream state.
798  *
799  * The sentry's preparatory actions are:
800  *
801  * -# if the stream is tied to an output stream, @c is.tie()->flush()
802  * is called to synchronize the output sequence
803  * -# if @a __noskipws is false, and @c ios_base::skipws is set in
804  * @c is.flags(), the sentry extracts and discards whitespace
805  * characters from the stream. The currently imbued locale is
806  * used to determine whether each character is whitespace.
807  *
808  * If the stream state is still good, then the sentry state becomes
809  * true (@a okay).
810  */
811  explicit
812  sentry(basic_istream<_CharT, _Traits>& __is, bool __noskipws = false);
813 
814  /**
815  * @brief Quick status checking.
816  * @return The sentry state.
817  *
818  * For ease of use, sentries may be converted to booleans. The
819  * return value is that of the sentry state (true == okay).
820  */
821 #if __cplusplus >= 201103L
822  explicit
823 #endif
824  operator bool() const
825  { return _M_ok; }
826  };
827 
828  ///@{
829  /**
830  * @brief Character extractors
831  * @param __in An input stream.
832  * @param __c A character reference.
833  * @return in
834  *
835  * Behaves like one of the formatted arithmetic extractors described in
836  * std::basic_istream. After constructing a sentry object with good
837  * status, this function extracts a character (if one is available) and
838  * stores it in @a __c. Otherwise, sets failbit in the input stream.
839  */
840  template<typename _CharT, typename _Traits>
841  basic_istream<_CharT, _Traits>&
842  operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c);
843 
844  template<class _Traits>
845  inline basic_istream<char, _Traits>&
846  operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
847  { return (__in >> reinterpret_cast<char&>(__c)); }
848 
849  template<class _Traits>
850  inline basic_istream<char, _Traits>&
851  operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
852  { return (__in >> reinterpret_cast<char&>(__c)); }
853  ///@}
854 
855 
856  template<typename _CharT, typename _Traits>
857  void
858  __istream_extract(basic_istream<_CharT, _Traits>&, _CharT*, streamsize);
859 
860  void __istream_extract(istream&, char*, streamsize);
861 
862  ///@{
863  /**
864  * @brief Character string extractors
865  * @param __in An input stream.
866  * @param __s A character array (or a pointer to an array before C++20).
867  * @return __in
868  *
869  * Behaves like one of the formatted arithmetic extractors described in
870  * `std::basic_istream`. After constructing a sentry object with good
871  * status, this function extracts up to `n` characters and stores them
872  * into the array `__s`. `n` is defined as:
873  *
874  * - if `width()` is greater than zero, `n` is `min(width(), n)`
875  * - otherwise `n` is the number of elements of the array
876  * - (before C++20 the pointer is assumed to point to an array of
877  * the largest possible size for an array of `char_type`).
878  *
879  * Characters are extracted and stored until one of the following happens:
880  * - `n - 1` characters are stored
881  * - EOF is reached
882  * - the next character is whitespace according to the current locale
883  *
884  * `width(0)` is then called for the input stream.
885  *
886  * If no characters are extracted, sets failbit.
887  */
888 
889 #if __cplusplus <= 201703L
890  template<typename _CharT, typename _Traits>
891  __attribute__((__nonnull__(2), __access__(__write_only__, 2)))
892  inline basic_istream<_CharT, _Traits>&
893  operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
894  {
895 #ifdef __OPTIMIZE__
896  // Function inlining might make the buffer size known, allowing us to
897  // prevent overflow.
898  size_t __n = __builtin_object_size(__s, 0);
899  if (__n < sizeof(_CharT))
900  {
901  // There is not even space for the required null terminator.
902  __glibcxx_assert(__n >= sizeof(_CharT));
903  // No point calling __istream_extract, but still need to reset width.
904  __in.width(0);
905  __in.setstate(ios_base::failbit);
906  }
907  else if (__n != (size_t)-1)
908  {
909  __n /= sizeof(_CharT);
910  streamsize __w = __in.width();
911  std::__istream_extract(__in, __s, __n);
912  if (__in.good() && (__w <= 0 || __n < __w))
913  {
914  // Stopped extracting early to avoid overflowing the buffer,
915  // but might have stopped anyway (and set eofbit) if at EOF.
916  const typename _Traits::int_type __c = __in.rdbuf()->sgetc();
917  const bool __eof = _Traits::eq_int_type(__c, _Traits::eof());
918  if (__builtin_expect(__eof, true)) // Assume EOF, not overflow.
919  __in.setstate(ios_base::eofbit);
920  }
921  }
922  else
923 #endif // __OPTIMIZE
924  {
925  // Buffer size is unknown, have to assume it's huge.
926  streamsize __n = __gnu_cxx::__numeric_traits<streamsize>::__max;
927  __n /= sizeof(_CharT);
928  std::__istream_extract(__in, __s, __n);
929  }
930  return __in;
931  }
932 
933  template<class _Traits>
934  __attribute__((__nonnull__(2), __access__(__write_only__, 2)))
935  inline basic_istream<char, _Traits>&
936  operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
937  { return __in >> reinterpret_cast<char*>(__s); }
938 
939  template<class _Traits>
940  __attribute__((__nonnull__(2), __access__(__write_only__, 2)))
941  inline basic_istream<char, _Traits>&
942  operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
943  { return __in >> reinterpret_cast<char*>(__s); }
944 #else
945  // _GLIBCXX_RESOLVE_LIB_DEFECTS
946  // 2499. operator>>(istream&, char*) makes it hard to avoid buffer overflows
947  template<typename _CharT, typename _Traits, size_t _Num>
948  inline basic_istream<_CharT, _Traits>&
949  operator>>(basic_istream<_CharT, _Traits>& __in, _CharT (&__s)[_Num])
950  {
951  static_assert(_Num <= __gnu_cxx::__numeric_traits<streamsize>::__max);
952  std::__istream_extract(__in, __s, _Num);
953  return __in;
954  }
955 
956  template<class _Traits, size_t _Num>
957  inline basic_istream<char, _Traits>&
958  operator>>(basic_istream<char, _Traits>& __in, unsigned char (&__s)[_Num])
959  { return __in >> reinterpret_cast<char(&)[_Num]>(__s); }
960 
961  template<class _Traits, size_t _Num>
962  inline basic_istream<char, _Traits>&
963  operator>>(basic_istream<char, _Traits>& __in, signed char (&__s)[_Num])
964  { return __in >> reinterpret_cast<char(&)[_Num]>(__s); }
965 #endif
966  ///@}
967 
968  /**
969  * @brief Template class basic_iostream
970  * @ingroup io
971  *
972  * @tparam _CharT Type of character stream.
973  * @tparam _Traits Traits for character type, defaults to
974  * char_traits<_CharT>.
975  *
976  * This class multiply inherits from the input and output stream classes
977  * simply to provide a single interface.
978  */
979  template<typename _CharT, typename _Traits>
980  class basic_iostream
981  : public basic_istream<_CharT, _Traits>,
982  public basic_ostream<_CharT, _Traits>
983  {
984  public:
985  // _GLIBCXX_RESOLVE_LIB_DEFECTS
986  // 271. basic_iostream missing typedefs
987  // Types (inherited):
988  typedef _CharT char_type;
989  typedef typename _Traits::int_type int_type;
990  typedef typename _Traits::pos_type pos_type;
991  typedef typename _Traits::off_type off_type;
992  typedef _Traits traits_type;
993 
994  // Non-standard Types:
995  typedef basic_istream<_CharT, _Traits> __istream_type;
996  typedef basic_ostream<_CharT, _Traits> __ostream_type;
997 
998  /**
999  * @brief Constructor does nothing.
1000  *
1001  * Both of the parent classes are initialized with the same
1002  * streambuf pointer passed to this constructor.
1003  */
1004  explicit
1005  basic_iostream(basic_streambuf<_CharT, _Traits>* __sb)
1006  : __istream_type(__sb), __ostream_type(__sb) { }
1007 
1008  /**
1009  * @brief Destructor does nothing.
1010  */
1011  virtual
1012  ~basic_iostream() { }
1013 
1014  protected:
1015  basic_iostream()
1016  : __istream_type(), __ostream_type() { }
1017 
1018 #if __cplusplus >= 201103L
1019  basic_iostream(const basic_iostream&) = delete;
1020 
1021  basic_iostream(basic_iostream&& __rhs)
1022  : __istream_type(std::move(__rhs)), __ostream_type(*this)
1023  { }
1024 
1025  // 27.7.3.3 Assign/swap
1026 
1027  basic_iostream& operator=(const basic_iostream&) = delete;
1028 
1029  basic_iostream&
1030  operator=(basic_iostream&& __rhs)
1031  {
1032  swap(__rhs);
1033  return *this;
1034  }
1035 
1036  void
1037  swap(basic_iostream& __rhs)
1038  { __istream_type::swap(__rhs); }
1039 #endif
1040  };
1041 
1042  /**
1043  * @brief Quick and easy way to eat whitespace
1044  *
1045  * This manipulator extracts whitespace characters, stopping when the
1046  * next character is non-whitespace, or when the input sequence is empty.
1047  * If the sequence is empty, @c eofbit is set in the stream, but not
1048  * @c failbit.
1049  *
1050  * The current locale is used to distinguish whitespace characters.
1051  *
1052  * Example:
1053  * @code
1054  * MyClass mc;
1055  *
1056  * std::cin >> std::ws >> mc;
1057  * @endcode
1058  * will skip leading whitespace before calling operator>> on cin and your
1059  * object. Note that the same effect can be achieved by creating a
1060  * std::basic_istream::sentry inside your definition of operator>>.
1061  */
1062  template<typename _CharT, typename _Traits>
1063  basic_istream<_CharT, _Traits>&
1064  ws(basic_istream<_CharT, _Traits>& __is);
1065 
1066 #if __cplusplus >= 201103L
1067  // C++11 27.7.2.6 Rvalue stream extraction [istream.rvalue]
1068  // _GLIBCXX_RESOLVE_LIB_DEFECTS
1069  // 2328. Rvalue stream extraction should use perfect forwarding
1070  // 1203. More useful rvalue stream insertion
1071 
1072 #if __cpp_concepts >= 201907L && __glibcxx_type_trait_variable_templates
1073  template<typename _Is, typename _Tp>
1074  requires __derived_from_ios_base<_Is>
1075  && requires (_Is& __is, _Tp&& __t) { __is >> std::forward<_Tp>(__t); }
1076  using __rvalue_stream_extraction_t = _Is&&;
1077 #else
1078  template<typename _Is, typename _Tp,
1079  typename = _Require_derived_from_ios_base<_Is>,
1080  typename = decltype(std::declval<_Is&>() >> std::declval<_Tp>())>
1081  using __rvalue_stream_extraction_t = _Is&&;
1082 #endif
1083 
1084  /**
1085  * @brief Generic extractor for rvalue stream
1086  * @param __is An input stream.
1087  * @param __x A reference to the extraction target.
1088  * @return __is
1089  *
1090  * This is just a forwarding function to allow extraction from
1091  * rvalue streams since they won't bind to the extractor functions
1092  * that take an lvalue reference.
1093  */
1094  template<typename _Istream, typename _Tp>
1095  inline __rvalue_stream_extraction_t<_Istream, _Tp>
1096  operator>>(_Istream&& __is, _Tp&& __x)
1097  {
1098  __is >> std::forward<_Tp>(__x);
1099  return std::move(__is);
1100  }
1101 #endif // C++11
1102 
1103 _GLIBCXX_END_NAMESPACE_VERSION
1104 } // namespace
1105 
1106 #include <bits/istream.tcc>
1107 
1108 #endif /* _GLIBCXX_ISTREAM */