libstdc++
sstream
Go to the documentation of this file.
1 // String based streams -*- C++ -*-
2 
3 // Copyright (C) 1997-2017 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/sstream
26  * This is a Standard C++ Library header.
27  */
28 
29 //
30 // ISO C++ 14882: 27.7 String-based streams
31 //
32 
33 #ifndef _GLIBCXX_SSTREAM
34 #define _GLIBCXX_SSTREAM 1
35 
36 #pragma GCC system_header
37 
38 #include <istream>
39 #include <ostream>
40 
41 namespace std _GLIBCXX_VISIBILITY(default)
42 {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44 _GLIBCXX_BEGIN_NAMESPACE_CXX11
45 
46  // [27.7.1] template class basic_stringbuf
47  /**
48  * @brief The actual work of input and output (for std::string).
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  * @tparam _Alloc Allocator type, defaults to allocator<_CharT>.
55  *
56  * This class associates either or both of its input and output sequences
57  * with a sequence of characters, which can be initialized from, or made
58  * available as, a @c std::basic_string. (Paraphrased from [27.7.1]/1.)
59  *
60  * For this class, open modes (of type @c ios_base::openmode) have
61  * @c in set if the input sequence can be read, and @c out set if the
62  * output sequence can be written.
63  */
64  template<typename _CharT, typename _Traits, typename _Alloc>
65  class basic_stringbuf : public basic_streambuf<_CharT, _Traits>
66  {
67  struct __xfer_bufptrs;
68  public:
69  // Types:
70  typedef _CharT char_type;
71  typedef _Traits traits_type;
72  // _GLIBCXX_RESOLVE_LIB_DEFECTS
73  // 251. basic_stringbuf missing allocator_type
74  typedef _Alloc allocator_type;
75  typedef typename traits_type::int_type int_type;
76  typedef typename traits_type::pos_type pos_type;
77  typedef typename traits_type::off_type off_type;
78 
79  typedef basic_streambuf<char_type, traits_type> __streambuf_type;
80  typedef basic_string<char_type, _Traits, _Alloc> __string_type;
81  typedef typename __string_type::size_type __size_type;
82 
83  protected:
84  /// Place to stash in || out || in | out settings for current stringbuf.
85  ios_base::openmode _M_mode;
86 
87  // Data Members:
88  __string_type _M_string;
89 
90  public:
91  // Constructors:
92  /**
93  * @brief Starts with an empty string buffer.
94  * @param __mode Whether the buffer can read, or write, or both.
95  *
96  * The default constructor initializes the parent class using its
97  * own default ctor.
98  */
99  explicit
100  basic_stringbuf(ios_base::openmode __mode = ios_base::in | ios_base::out)
101  : __streambuf_type(), _M_mode(__mode), _M_string()
102  { }
103 
104  /**
105  * @brief Starts with an existing string buffer.
106  * @param __str A string to copy as a starting buffer.
107  * @param __mode Whether the buffer can read, or write, or both.
108  *
109  * This constructor initializes the parent class using its
110  * own default ctor.
111  */
112  explicit
113  basic_stringbuf(const __string_type& __str,
114  ios_base::openmode __mode = ios_base::in | ios_base::out)
115  : __streambuf_type(), _M_mode(), _M_string(__str.data(), __str.size())
116  { _M_stringbuf_init(__mode); }
117 
118 #if __cplusplus >= 201103L
119  basic_stringbuf(const basic_stringbuf&) = delete;
120 
121  basic_stringbuf(basic_stringbuf&& __rhs)
122  : basic_stringbuf(std::move(__rhs), __xfer_bufptrs(__rhs, this))
123  { __rhs._M_sync(const_cast<char_type*>(__rhs._M_string.data()), 0, 0); }
124 
125  // 27.8.2.2 Assign and swap:
126 
127  basic_stringbuf&
128  operator=(const basic_stringbuf&) = delete;
129 
130  basic_stringbuf&
131  operator=(basic_stringbuf&& __rhs)
132  {
133  __xfer_bufptrs __st{__rhs, this};
134  const __streambuf_type& __base = __rhs;
135  __streambuf_type::operator=(__base);
136  this->pubimbue(__rhs.getloc());
137  _M_mode = __rhs._M_mode;
138  _M_string = std::move(__rhs._M_string);
139  __rhs._M_sync(const_cast<char_type*>(__rhs._M_string.data()), 0, 0);
140  return *this;
141  }
142 
143  void
144  swap(basic_stringbuf& __rhs)
145  {
146  __xfer_bufptrs __l_st{*this, std::__addressof(__rhs)};
147  __xfer_bufptrs __r_st{__rhs, this};
148  __streambuf_type& __base = __rhs;
149  __streambuf_type::swap(__base);
150  __rhs.pubimbue(this->pubimbue(__rhs.getloc()));
151  std::swap(_M_mode, __rhs._M_mode);
152  std::swap(_M_string, __rhs._M_string);
153  }
154 #endif
155 
156  // Get and set:
157  /**
158  * @brief Copying out the string buffer.
159  * @return A copy of one of the underlying sequences.
160  *
161  * <em>If the buffer is only created in input mode, the underlying
162  * character sequence is equal to the input sequence; otherwise, it
163  * is equal to the output sequence.</em> [27.7.1.2]/1
164  */
165  __string_type
166  str() const
167  {
168  __string_type __ret;
169  if (this->pptr())
170  {
171  // The current egptr() may not be the actual string end.
172  if (this->pptr() > this->egptr())
173  __ret = __string_type(this->pbase(), this->pptr());
174  else
175  __ret = __string_type(this->pbase(), this->egptr());
176  }
177  else
178  __ret = _M_string;
179  return __ret;
180  }
181 
182  /**
183  * @brief Setting a new buffer.
184  * @param __s The string to use as a new sequence.
185  *
186  * Deallocates any previous stored sequence, then copies @a s to
187  * use as a new one.
188  */
189  void
190  str(const __string_type& __s)
191  {
192  // Cannot use _M_string = __s, since v3 strings are COW
193  // (not always true now but assign() always works).
194  _M_string.assign(__s.data(), __s.size());
195  _M_stringbuf_init(_M_mode);
196  }
197 
198  protected:
199  // Common initialization code goes here.
200  void
201  _M_stringbuf_init(ios_base::openmode __mode)
202  {
203  _M_mode = __mode;
204  __size_type __len = 0;
205  if (_M_mode & (ios_base::ate | ios_base::app))
206  __len = _M_string.size();
207  _M_sync(const_cast<char_type*>(_M_string.data()), 0, __len);
208  }
209 
210  virtual streamsize
211  showmanyc()
212  {
213  streamsize __ret = -1;
214  if (_M_mode & ios_base::in)
215  {
216  _M_update_egptr();
217  __ret = this->egptr() - this->gptr();
218  }
219  return __ret;
220  }
221 
222  virtual int_type
223  underflow();
224 
225  virtual int_type
226  pbackfail(int_type __c = traits_type::eof());
227 
228  virtual int_type
229  overflow(int_type __c = traits_type::eof());
230 
231  /**
232  * @brief Manipulates the buffer.
233  * @param __s Pointer to a buffer area.
234  * @param __n Size of @a __s.
235  * @return @c this
236  *
237  * If no buffer has already been created, and both @a __s and @a __n are
238  * non-zero, then @c __s is used as a buffer; see
239  * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
240  * for more.
241  */
242  virtual __streambuf_type*
243  setbuf(char_type* __s, streamsize __n)
244  {
245  if (__s && __n >= 0)
246  {
247  // This is implementation-defined behavior, and assumes
248  // that an external char_type array of length __n exists
249  // and has been pre-allocated. If this is not the case,
250  // things will quickly blow up.
251 
252  // Step 1: Destroy the current internal array.
253  _M_string.clear();
254 
255  // Step 2: Use the external array.
256  _M_sync(__s, __n, 0);
257  }
258  return this;
259  }
260 
261  virtual pos_type
262  seekoff(off_type __off, ios_base::seekdir __way,
263  ios_base::openmode __mode = ios_base::in | ios_base::out);
264 
265  virtual pos_type
266  seekpos(pos_type __sp,
267  ios_base::openmode __mode = ios_base::in | ios_base::out);
268 
269  // Internal function for correctly updating the internal buffer
270  // for a particular _M_string, due to initialization or re-sizing
271  // of an existing _M_string.
272  void
273  _M_sync(char_type* __base, __size_type __i, __size_type __o);
274 
275  // Internal function for correctly updating egptr() to the actual
276  // string end.
277  void
278  _M_update_egptr()
279  {
280  const bool __testin = _M_mode & ios_base::in;
281  if (this->pptr() && this->pptr() > this->egptr())
282  {
283  if (__testin)
284  this->setg(this->eback(), this->gptr(), this->pptr());
285  else
286  this->setg(this->pptr(), this->pptr(), this->pptr());
287  }
288  }
289 
290  // Works around the issue with pbump, part of the protected
291  // interface of basic_streambuf, taking just an int.
292  void
293  _M_pbump(char_type* __pbeg, char_type* __pend, off_type __off);
294 
295  private:
296 #if __cplusplus >= 201103L
297 #if _GLIBCXX_USE_CXX11_ABI
298  // This type captures the state of the gptr / pptr pointers as offsets
299  // so they can be restored in another object after moving the string.
300  struct __xfer_bufptrs
301  {
302  __xfer_bufptrs(const basic_stringbuf& __from, basic_stringbuf* __to)
303  : _M_to{__to}, _M_goff{-1, -1, -1}, _M_poff{-1, -1, -1}
304  {
305  const _CharT* const __str = __from._M_string.data();
306  const _CharT* __end = nullptr;
307  if (__from.eback())
308  {
309  _M_goff[0] = __from.eback() - __str;
310  _M_goff[1] = __from.gptr() - __str;
311  _M_goff[2] = __from.egptr() - __str;
312  __end = __from.egptr();
313  }
314  if (__from.pbase())
315  {
316  _M_poff[0] = __from.pbase() - __str;
317  _M_poff[1] = __from.pptr() - __from.pbase();
318  _M_poff[2] = __from.epptr() - __str;
319  if (__from.pptr() > __end)
320  __end = __from.pptr();
321  }
322 
323  // Set _M_string length to the greater of the get and put areas.
324  if (__end)
325  {
326  // The const_cast avoids changing this constructor's signature,
327  // because it is exported from the dynamic library.
328  auto& __mut_from = const_cast<basic_stringbuf&>(__from);
329  __mut_from._M_string._M_length(__end - __str);
330  }
331  }
332 
333  ~__xfer_bufptrs()
334  {
335  char_type* __str = const_cast<char_type*>(_M_to->_M_string.data());
336  if (_M_goff[0] != -1)
337  _M_to->setg(__str+_M_goff[0], __str+_M_goff[1], __str+_M_goff[2]);
338  if (_M_poff[0] != -1)
339  _M_to->_M_pbump(__str+_M_poff[0], __str+_M_poff[2], _M_poff[1]);
340  }
341 
342  basic_stringbuf* _M_to;
343  off_type _M_goff[3];
344  off_type _M_poff[3];
345  };
346 #else
347  // This type does nothing when using Copy-On-Write strings.
348  struct __xfer_bufptrs
349  {
350  __xfer_bufptrs(const basic_stringbuf&, basic_stringbuf*) { }
351  };
352 #endif
353 
354  // The move constructor initializes an __xfer_bufptrs temporary then
355  // delegates to this constructor to performs moves during its lifetime.
356  basic_stringbuf(basic_stringbuf&& __rhs, __xfer_bufptrs&&)
357  : __streambuf_type(static_cast<const __streambuf_type&>(__rhs)),
358  _M_mode(__rhs._M_mode), _M_string(std::move(__rhs._M_string))
359  { }
360 #endif
361  };
362 
363 
364  // [27.7.2] Template class basic_istringstream
365  /**
366  * @brief Controlling input for std::string.
367  * @ingroup io
368  *
369  * @tparam _CharT Type of character stream.
370  * @tparam _Traits Traits for character type, defaults to
371  * char_traits<_CharT>.
372  * @tparam _Alloc Allocator type, defaults to allocator<_CharT>.
373  *
374  * This class supports reading from objects of type std::basic_string,
375  * using the inherited functions from std::basic_istream. To control
376  * the associated sequence, an instance of std::basic_stringbuf is used,
377  * which this page refers to as @c sb.
378  */
379  template<typename _CharT, typename _Traits, typename _Alloc>
380  class basic_istringstream : public basic_istream<_CharT, _Traits>
381  {
382  public:
383  // Types:
384  typedef _CharT char_type;
385  typedef _Traits traits_type;
386  // _GLIBCXX_RESOLVE_LIB_DEFECTS
387  // 251. basic_stringbuf missing allocator_type
388  typedef _Alloc allocator_type;
389  typedef typename traits_type::int_type int_type;
390  typedef typename traits_type::pos_type pos_type;
391  typedef typename traits_type::off_type off_type;
392 
393  // Non-standard types:
394  typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
395  typedef basic_stringbuf<_CharT, _Traits, _Alloc> __stringbuf_type;
396  typedef basic_istream<char_type, traits_type> __istream_type;
397 
398  private:
399  __stringbuf_type _M_stringbuf;
400 
401  public:
402  // Constructors:
403  /**
404  * @brief Default constructor starts with an empty string buffer.
405  * @param __mode Whether the buffer can read, or write, or both.
406  *
407  * @c ios_base::in is automatically included in @a __mode.
408  *
409  * Initializes @c sb using @c __mode|in, and passes @c &sb to the base
410  * class initializer. Does not allocate any buffer.
411  *
412  * That's a lie. We initialize the base class with NULL, because the
413  * string class does its own memory management.
414  */
415  explicit
416  basic_istringstream(ios_base::openmode __mode = ios_base::in)
417  : __istream_type(), _M_stringbuf(__mode | ios_base::in)
418  { this->init(&_M_stringbuf); }
419 
420  /**
421  * @brief Starts with an existing string buffer.
422  * @param __str A string to copy as a starting buffer.
423  * @param __mode Whether the buffer can read, or write, or both.
424  *
425  * @c ios_base::in is automatically included in @a mode.
426  *
427  * Initializes @c sb using @a str and @c mode|in, and passes @c &sb
428  * to the base class initializer.
429  *
430  * That's a lie. We initialize the base class with NULL, because the
431  * string class does its own memory management.
432  */
433  explicit
434  basic_istringstream(const __string_type& __str,
435  ios_base::openmode __mode = ios_base::in)
436  : __istream_type(), _M_stringbuf(__str, __mode | ios_base::in)
437  { this->init(&_M_stringbuf); }
438 
439  /**
440  * @brief The destructor does nothing.
441  *
442  * The buffer is deallocated by the stringbuf object, not the
443  * formatting stream.
444  */
445  ~basic_istringstream()
446  { }
447 
448 #if __cplusplus >= 201103L
449  basic_istringstream(const basic_istringstream&) = delete;
450 
451  basic_istringstream(basic_istringstream&& __rhs)
452  : __istream_type(std::move(__rhs)),
453  _M_stringbuf(std::move(__rhs._M_stringbuf))
454  { __istream_type::set_rdbuf(&_M_stringbuf); }
455 
456  // 27.8.3.2 Assign and swap:
457 
458  basic_istringstream&
459  operator=(const basic_istringstream&) = delete;
460 
461  basic_istringstream&
462  operator=(basic_istringstream&& __rhs)
463  {
464  __istream_type::operator=(std::move(__rhs));
465  _M_stringbuf = std::move(__rhs._M_stringbuf);
466  return *this;
467  }
468 
469  void
470  swap(basic_istringstream& __rhs)
471  {
472  __istream_type::swap(__rhs);
473  _M_stringbuf.swap(__rhs._M_stringbuf);
474  }
475 #endif
476 
477  // Members:
478  /**
479  * @brief Accessing the underlying buffer.
480  * @return The current basic_stringbuf buffer.
481  *
482  * This hides both signatures of std::basic_ios::rdbuf().
483  */
484  __stringbuf_type*
485  rdbuf() const
486  { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
487 
488  /**
489  * @brief Copying out the string buffer.
490  * @return @c rdbuf()->str()
491  */
492  __string_type
493  str() const
494  { return _M_stringbuf.str(); }
495 
496  /**
497  * @brief Setting a new buffer.
498  * @param __s The string to use as a new sequence.
499  *
500  * Calls @c rdbuf()->str(s).
501  */
502  void
503  str(const __string_type& __s)
504  { _M_stringbuf.str(__s); }
505  };
506 
507 
508  // [27.7.3] Template class basic_ostringstream
509  /**
510  * @brief Controlling output for std::string.
511  * @ingroup io
512  *
513  * @tparam _CharT Type of character stream.
514  * @tparam _Traits Traits for character type, defaults to
515  * char_traits<_CharT>.
516  * @tparam _Alloc Allocator type, defaults to allocator<_CharT>.
517  *
518  * This class supports writing to objects of type std::basic_string,
519  * using the inherited functions from std::basic_ostream. To control
520  * the associated sequence, an instance of std::basic_stringbuf is used,
521  * which this page refers to as @c sb.
522  */
523  template <typename _CharT, typename _Traits, typename _Alloc>
524  class basic_ostringstream : public basic_ostream<_CharT, _Traits>
525  {
526  public:
527  // Types:
528  typedef _CharT char_type;
529  typedef _Traits traits_type;
530  // _GLIBCXX_RESOLVE_LIB_DEFECTS
531  // 251. basic_stringbuf missing allocator_type
532  typedef _Alloc allocator_type;
533  typedef typename traits_type::int_type int_type;
534  typedef typename traits_type::pos_type pos_type;
535  typedef typename traits_type::off_type off_type;
536 
537  // Non-standard types:
538  typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
539  typedef basic_stringbuf<_CharT, _Traits, _Alloc> __stringbuf_type;
540  typedef basic_ostream<char_type, traits_type> __ostream_type;
541 
542  private:
543  __stringbuf_type _M_stringbuf;
544 
545  public:
546  // Constructors/destructor:
547  /**
548  * @brief Default constructor starts with an empty string buffer.
549  * @param __mode Whether the buffer can read, or write, or both.
550  *
551  * @c ios_base::out is automatically included in @a mode.
552  *
553  * Initializes @c sb using @c mode|out, and passes @c &sb to the base
554  * class initializer. Does not allocate any buffer.
555  *
556  * That's a lie. We initialize the base class with NULL, because the
557  * string class does its own memory management.
558  */
559  explicit
560  basic_ostringstream(ios_base::openmode __mode = ios_base::out)
561  : __ostream_type(), _M_stringbuf(__mode | ios_base::out)
562  { this->init(&_M_stringbuf); }
563 
564  /**
565  * @brief Starts with an existing string buffer.
566  * @param __str A string to copy as a starting buffer.
567  * @param __mode Whether the buffer can read, or write, or both.
568  *
569  * @c ios_base::out is automatically included in @a mode.
570  *
571  * Initializes @c sb using @a str and @c mode|out, and passes @c &sb
572  * to the base class initializer.
573  *
574  * That's a lie. We initialize the base class with NULL, because the
575  * string class does its own memory management.
576  */
577  explicit
578  basic_ostringstream(const __string_type& __str,
579  ios_base::openmode __mode = ios_base::out)
580  : __ostream_type(), _M_stringbuf(__str, __mode | ios_base::out)
581  { this->init(&_M_stringbuf); }
582 
583  /**
584  * @brief The destructor does nothing.
585  *
586  * The buffer is deallocated by the stringbuf object, not the
587  * formatting stream.
588  */
589  ~basic_ostringstream()
590  { }
591 
592 #if __cplusplus >= 201103L
593  basic_ostringstream(const basic_ostringstream&) = delete;
594 
595  basic_ostringstream(basic_ostringstream&& __rhs)
596  : __ostream_type(std::move(__rhs)),
597  _M_stringbuf(std::move(__rhs._M_stringbuf))
598  { __ostream_type::set_rdbuf(&_M_stringbuf); }
599 
600  // 27.8.3.2 Assign and swap:
601 
602  basic_ostringstream&
603  operator=(const basic_ostringstream&) = delete;
604 
605  basic_ostringstream&
606  operator=(basic_ostringstream&& __rhs)
607  {
608  __ostream_type::operator=(std::move(__rhs));
609  _M_stringbuf = std::move(__rhs._M_stringbuf);
610  return *this;
611  }
612 
613  void
614  swap(basic_ostringstream& __rhs)
615  {
616  __ostream_type::swap(__rhs);
617  _M_stringbuf.swap(__rhs._M_stringbuf);
618  }
619 #endif
620 
621  // Members:
622  /**
623  * @brief Accessing the underlying buffer.
624  * @return The current basic_stringbuf buffer.
625  *
626  * This hides both signatures of std::basic_ios::rdbuf().
627  */
628  __stringbuf_type*
629  rdbuf() const
630  { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
631 
632  /**
633  * @brief Copying out the string buffer.
634  * @return @c rdbuf()->str()
635  */
636  __string_type
637  str() const
638  { return _M_stringbuf.str(); }
639 
640  /**
641  * @brief Setting a new buffer.
642  * @param __s The string to use as a new sequence.
643  *
644  * Calls @c rdbuf()->str(s).
645  */
646  void
647  str(const __string_type& __s)
648  { _M_stringbuf.str(__s); }
649  };
650 
651 
652  // [27.7.4] Template class basic_stringstream
653  /**
654  * @brief Controlling input and output for std::string.
655  * @ingroup io
656  *
657  * @tparam _CharT Type of character stream.
658  * @tparam _Traits Traits for character type, defaults to
659  * char_traits<_CharT>.
660  * @tparam _Alloc Allocator type, defaults to allocator<_CharT>.
661  *
662  * This class supports reading from and writing to objects of type
663  * std::basic_string, using the inherited functions from
664  * std::basic_iostream. To control the associated sequence, an instance
665  * of std::basic_stringbuf is used, which this page refers to as @c sb.
666  */
667  template <typename _CharT, typename _Traits, typename _Alloc>
668  class basic_stringstream : public basic_iostream<_CharT, _Traits>
669  {
670  public:
671  // Types:
672  typedef _CharT char_type;
673  typedef _Traits traits_type;
674  // _GLIBCXX_RESOLVE_LIB_DEFECTS
675  // 251. basic_stringbuf missing allocator_type
676  typedef _Alloc allocator_type;
677  typedef typename traits_type::int_type int_type;
678  typedef typename traits_type::pos_type pos_type;
679  typedef typename traits_type::off_type off_type;
680 
681  // Non-standard Types:
682  typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
683  typedef basic_stringbuf<_CharT, _Traits, _Alloc> __stringbuf_type;
684  typedef basic_iostream<char_type, traits_type> __iostream_type;
685 
686  private:
687  __stringbuf_type _M_stringbuf;
688 
689  public:
690  // Constructors/destructors
691  /**
692  * @brief Default constructor starts with an empty string buffer.
693  * @param __m Whether the buffer can read, or write, or both.
694  *
695  * Initializes @c sb using the mode from @c __m, and passes @c
696  * &sb to the base class initializer. Does not allocate any
697  * buffer.
698  *
699  * That's a lie. We initialize the base class with NULL, because the
700  * string class does its own memory management.
701  */
702  explicit
703  basic_stringstream(ios_base::openmode __m = ios_base::out | ios_base::in)
704  : __iostream_type(), _M_stringbuf(__m)
705  { this->init(&_M_stringbuf); }
706 
707  /**
708  * @brief Starts with an existing string buffer.
709  * @param __str A string to copy as a starting buffer.
710  * @param __m Whether the buffer can read, or write, or both.
711  *
712  * Initializes @c sb using @a __str and @c __m, and passes @c &sb
713  * to the base class initializer.
714  *
715  * That's a lie. We initialize the base class with NULL, because the
716  * string class does its own memory management.
717  */
718  explicit
719  basic_stringstream(const __string_type& __str,
720  ios_base::openmode __m = ios_base::out | ios_base::in)
721  : __iostream_type(), _M_stringbuf(__str, __m)
722  { this->init(&_M_stringbuf); }
723 
724  /**
725  * @brief The destructor does nothing.
726  *
727  * The buffer is deallocated by the stringbuf object, not the
728  * formatting stream.
729  */
730  ~basic_stringstream()
731  { }
732 
733 #if __cplusplus >= 201103L
734  basic_stringstream(const basic_stringstream&) = delete;
735 
736  basic_stringstream(basic_stringstream&& __rhs)
737  : __iostream_type(std::move(__rhs)),
738  _M_stringbuf(std::move(__rhs._M_stringbuf))
739  { __iostream_type::set_rdbuf(&_M_stringbuf); }
740 
741  // 27.8.3.2 Assign and swap:
742 
743  basic_stringstream&
744  operator=(const basic_stringstream&) = delete;
745 
746  basic_stringstream&
747  operator=(basic_stringstream&& __rhs)
748  {
749  __iostream_type::operator=(std::move(__rhs));
750  _M_stringbuf = std::move(__rhs._M_stringbuf);
751  return *this;
752  }
753 
754  void
755  swap(basic_stringstream& __rhs)
756  {
757  __iostream_type::swap(__rhs);
758  _M_stringbuf.swap(__rhs._M_stringbuf);
759  }
760 #endif
761 
762  // Members:
763  /**
764  * @brief Accessing the underlying buffer.
765  * @return The current basic_stringbuf buffer.
766  *
767  * This hides both signatures of std::basic_ios::rdbuf().
768  */
769  __stringbuf_type*
770  rdbuf() const
771  { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
772 
773  /**
774  * @brief Copying out the string buffer.
775  * @return @c rdbuf()->str()
776  */
777  __string_type
778  str() const
779  { return _M_stringbuf.str(); }
780 
781  /**
782  * @brief Setting a new buffer.
783  * @param __s The string to use as a new sequence.
784  *
785  * Calls @c rdbuf()->str(s).
786  */
787  void
788  str(const __string_type& __s)
789  { _M_stringbuf.str(__s); }
790  };
791 
792 #if __cplusplus >= 201103L
793  /// Swap specialization for stringbufs.
794  template <class _CharT, class _Traits, class _Allocator>
795  inline void
796  swap(basic_stringbuf<_CharT, _Traits, _Allocator>& __x,
797  basic_stringbuf<_CharT, _Traits, _Allocator>& __y)
798  { __x.swap(__y); }
799 
800  /// Swap specialization for istringstreams.
801  template <class _CharT, class _Traits, class _Allocator>
802  inline void
803  swap(basic_istringstream<_CharT, _Traits, _Allocator>& __x,
804  basic_istringstream<_CharT, _Traits, _Allocator>& __y)
805  { __x.swap(__y); }
806 
807  /// Swap specialization for ostringstreams.
808  template <class _CharT, class _Traits, class _Allocator>
809  inline void
810  swap(basic_ostringstream<_CharT, _Traits, _Allocator>& __x,
811  basic_ostringstream<_CharT, _Traits, _Allocator>& __y)
812  { __x.swap(__y); }
813 
814  /// Swap specialization for stringstreams.
815  template <class _CharT, class _Traits, class _Allocator>
816  inline void
817  swap(basic_stringstream<_CharT, _Traits, _Allocator>& __x,
818  basic_stringstream<_CharT, _Traits, _Allocator>& __y)
819  { __x.swap(__y); }
820 #endif
821 
822 _GLIBCXX_END_NAMESPACE_CXX11
823 _GLIBCXX_END_NAMESPACE_VERSION
824 } // namespace
825 
826 #include <bits/sstream.tcc>
827 
828 #endif /* _GLIBCXX_SSTREAM */