1// Stream buffer classes -*- 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/** @file include/streambuf
26 * This is a Standard C++ Library header.
27 */
28
29//
30// ISO C++ 14882: 27.5 Stream buffers
31//
32
33#ifndef _GLIBXX_STREAMBUF
34#define _GLIBXX_STREAMBUF 1
35
36#pragma GCC system_header
37
38#include <bits/requires_hosted.h> // iostreams
39
40#include <bits/c++config.h>
41#include <iosfwd>
42#include <bits/localefwd.h>
43#include <bits/ios_base.h>
44#include <bits/cpp_type_traits.h>
45#include <ext/type_traits.h>
46
47namespace std _GLIBCXX_VISIBILITY(default)
48{
49_GLIBCXX_BEGIN_NAMESPACE_VERSION
50
51#define _IsUnused __attribute__ ((__unused__))
52
53 template<typename _CharT, typename _Traits>
54 streamsize
55 __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
56 basic_streambuf<_CharT, _Traits>*, bool&);
57
58 /**
59 * @brief The actual work of input and output (interface).
60 * @ingroup io
61 *
62 * @tparam _CharT Type of character stream.
63 * @tparam _Traits Traits for character type, defaults to
64 * char_traits<_CharT>.
65 *
66 * This is a base class. Derived stream buffers each control a
67 * pair of character sequences: one for input, and one for output.
68 *
69 * Section [27.5.1] of the standard describes the requirements and
70 * behavior of stream buffer classes. That section (three paragraphs)
71 * is reproduced here, for simplicity and accuracy.
72 *
73 * -# Stream buffers can impose various constraints on the sequences
74 * they control. Some constraints are:
75 * - The controlled input sequence can be not readable.
76 * - The controlled output sequence can be not writable.
77 * - The controlled sequences can be associated with the contents of
78 * other representations for character sequences, such as external
79 * files.
80 * - The controlled sequences can support operations @e directly to or
81 * from associated sequences.
82 * - The controlled sequences can impose limitations on how the
83 * program can read characters from a sequence, write characters to
84 * a sequence, put characters back into an input sequence, or alter
85 * the stream position.
86 * .
87 * -# Each sequence is characterized by three pointers which, if non-null,
88 * all point into the same @c charT array object. The array object
89 * represents, at any moment, a (sub)sequence of characters from the
90 * sequence. Operations performed on a sequence alter the values
91 * stored in these pointers, perform reads and writes directly to or
92 * from associated sequences, and alter <em>the stream position</em> and
93 * conversion state as needed to maintain this subsequence relationship.
94 * The three pointers are:
95 * - the <em>beginning pointer</em>, or lowest element address in the
96 * array (called @e xbeg here);
97 * - the <em>next pointer</em>, or next element address that is a
98 * current candidate for reading or writing (called @e xnext here);
99 * - the <em>end pointer</em>, or first element address beyond the
100 * end of the array (called @e xend here).
101 * .
102 * -# The following semantic constraints shall always apply for any set
103 * of three pointers for a sequence, using the pointer names given
104 * immediately above:
105 * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
106 * also be non-null pointers into the same @c charT array, as
107 * described above; otherwise, @e xbeg and @e xend shall also be null.
108 * - If @e xnext is not a null pointer and @e xnext < @e xend for an
109 * output sequence, then a <em>write position</em> is available.
110 * In this case, @e *xnext shall be assignable as the next element
111 * to write (to put, or to store a character value, into the sequence).
112 * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
113 * input sequence, then a <em>putback position</em> is available.
114 * In this case, @e xnext[-1] shall have a defined value and is the
115 * next (preceding) element to store a character that is put back
116 * into the input sequence.
117 * - If @e xnext is not a null pointer and @e xnext< @e xend for an
118 * input sequence, then a <em>read position</em> is available.
119 * In this case, @e *xnext shall have a defined value and is the
120 * next element to read (to get, or to obtain a character value,
121 * from the sequence).
122 */
123 template<typename _CharT, typename _Traits>
124 class basic_streambuf
125 {
126 public:
127 ///@{
128 /**
129 * These are standard types. They permit a standardized way of
130 * referring to names of (or names dependent on) the template
131 * parameters, which are specific to the implementation.
132 */
133 typedef _CharT char_type;
134 typedef _Traits traits_type;
135 typedef typename traits_type::int_type int_type;
136 typedef typename traits_type::pos_type pos_type;
137 typedef typename traits_type::off_type off_type;
138 ///@}
139
140 ///@{
141 /// This is a non-standard type.
142 typedef basic_streambuf<char_type, traits_type> __streambuf_type;
143 ///@}
144
145 friend class basic_ios<char_type, traits_type>;
146 friend class basic_istream<char_type, traits_type>;
147 friend class basic_ostream<char_type, traits_type>;
148 friend class istreambuf_iterator<char_type, traits_type>;
149 friend class ostreambuf_iterator<char_type, traits_type>;
150
151 friend streamsize
152 __copy_streambufs_eof<>(basic_streambuf*, basic_streambuf*, bool&);
153
154 template<bool _IsMove, typename _CharT2>
155 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
156 _CharT2*>::__type
157 __copy_move_a2(istreambuf_iterator<_CharT2>,
158 istreambuf_iterator<_CharT2>, _CharT2*);
159
160 template<typename _CharT2>
161 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
162 istreambuf_iterator<_CharT2> >::__type
163 find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
164 const _CharT2&);
165
166 template<typename _CharT2, typename _Distance>
167 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
168 void>::__type
169 advance(istreambuf_iterator<_CharT2>&, _Distance);
170
171 friend void __istream_extract(istream&, char*, streamsize);
172
173 template<typename _CharT2, typename _Traits2, typename _Alloc>
174 friend basic_istream<_CharT2, _Traits2>&
175 operator>>(basic_istream<_CharT2, _Traits2>&,
176 basic_string<_CharT2, _Traits2, _Alloc>&);
177
178 template<typename _CharT2, typename _Traits2, typename _Alloc>
179 friend basic_istream<_CharT2, _Traits2>&
180 getline(basic_istream<_CharT2, _Traits2>&,
181 basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
182
183 protected:
184 /*
185 * This is based on _IO_FILE, just reordered to be more consistent,
186 * and is intended to be the most minimal abstraction for an
187 * internal buffer.
188 * - get == input == read
189 * - put == output == write
190 */
191 char_type* _M_in_beg; ///< Start of get area.
192 char_type* _M_in_cur; ///< Current read area.
193 char_type* _M_in_end; ///< End of get area.
194 char_type* _M_out_beg; ///< Start of put area.
195 char_type* _M_out_cur; ///< Current put area.
196 char_type* _M_out_end; ///< End of put area.
197
198 /// Current locale setting.
199 locale _M_buf_locale;
200
201 public:
202 /// Destructor deallocates no buffer space.
203 virtual
204 ~basic_streambuf()
205 { }
206
207 // [27.5.2.2.1] locales
208 /**
209 * @brief Entry point for imbue().
210 * @param __loc The new locale.
211 * @return The previous locale.
212 *
213 * Calls the derived imbue(__loc).
214 */
215 locale
216 pubimbue(const locale& __loc)
217 {
218 locale __tmp(this->getloc());
219 this->imbue(__loc);
220 _M_buf_locale = __loc;
221 return __tmp;
222 }
223
224 /**
225 * @brief Locale access.
226 * @return The current locale in effect.
227 *
228 * If pubimbue(loc) has been called, then the most recent @c loc
229 * is returned. Otherwise the global locale in effect at the time
230 * of construction is returned.
231 */
232 locale
233 getloc() const
234 { return _M_buf_locale; }
235
236 // [27.5.2.2.2] buffer management and positioning
237 ///@{
238 /**
239 * @brief Entry points for derived buffer functions.
240 *
241 * The public versions of @c pubfoo dispatch to the protected
242 * derived @c foo member functions, passing the arguments (if any)
243 * and returning the result unchanged.
244 */
245 basic_streambuf*
246 pubsetbuf(char_type* __s, streamsize __n)
247 { return this->setbuf(__s, __n); }
248
249 /**
250 * @brief Alters the stream position.
251 * @param __off Offset.
252 * @param __way Value for ios_base::seekdir.
253 * @param __mode Value for ios_base::openmode.
254 *
255 * Calls virtual seekoff function.
256 */
257 pos_type
258 pubseekoff(off_type __off, ios_base::seekdir __way,
259 ios_base::openmode __mode = ios_base::in | ios_base::out)
260 { return this->seekoff(__off, __way, __mode); }
261
262 /**
263 * @brief Alters the stream position.
264 * @param __sp Position
265 * @param __mode Value for ios_base::openmode.
266 *
267 * Calls virtual seekpos function.
268 */
269 pos_type
270 pubseekpos(pos_type __sp,
271 ios_base::openmode __mode = ios_base::in | ios_base::out)
272 { return this->seekpos(__sp, __mode); }
273
274 /**
275 * @brief Calls virtual sync function.
276 */
277 int
278 pubsync() { return this->sync(); }
279 ///@}
280
281 // [27.5.2.2.3] get area
282 /**
283 * @brief Looking ahead into the stream.
284 * @return The number of characters available.
285 *
286 * If a read position is available, returns the number of characters
287 * available for reading before the buffer must be refilled.
288 * Otherwise returns the derived @c showmanyc().
289 */
290 streamsize
291 in_avail()
292 {
293 const streamsize __ret = this->egptr() - this->gptr();
294 return __ret ? __ret : this->showmanyc();
295 }
296
297 /**
298 * @brief Getting the next character.
299 * @return The next character, or eof.
300 *
301 * Calls @c sbumpc(), and if that function returns
302 * @c traits::eof(), so does this function. Otherwise, @c sgetc().
303 */
304 int_type
305 snextc()
306 {
307 int_type __ret = traits_type::eof();
308 if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(),
309 __ret), true))
310 __ret = this->sgetc();
311 return __ret;
312 }
313
314 /**
315 * @brief Getting the next character.
316 * @return The next character, or eof.
317 *
318 * If the input read position is available, returns that character
319 * and increments the read pointer, otherwise calls and returns
320 * @c uflow().
321 */
322 int_type
323 sbumpc()
324 {
325 int_type __ret;
326 if (__builtin_expect(this->gptr() < this->egptr(), true))
327 {
328 __ret = traits_type::to_int_type(*this->gptr());
329 this->gbump(1);
330 }
331 else
332 __ret = this->uflow();
333 return __ret;
334 }
335
336 /**
337 * @brief Getting the next character.
338 * @return The next character, or eof.
339 *
340 * If the input read position is available, returns that character,
341 * otherwise calls and returns @c underflow(). Does not move the
342 * read position after fetching the character.
343 */
344 int_type
345 sgetc()
346 {
347 int_type __ret;
348 if (__builtin_expect(this->gptr() < this->egptr(), true))
349 __ret = traits_type::to_int_type(*this->gptr());
350 else
351 __ret = this->underflow();
352 return __ret;
353 }
354
355 /**
356 * @brief Entry point for xsgetn.
357 * @param __s A buffer area.
358 * @param __n A count.
359 *
360 * Returns xsgetn(__s,__n). The effect is to fill @a __s[0] through
361 * @a __s[__n-1] with characters from the input sequence, if possible.
362 */
363 streamsize
364 sgetn(char_type* __s, streamsize __n)
365 { return this->xsgetn(__s, __n); }
366
367 // [27.5.2.2.4] putback
368 /**
369 * @brief Pushing characters back into the input stream.
370 * @param __c The character to push back.
371 * @return The previous character, if possible.
372 *
373 * Similar to sungetc(), but @a __c is pushed onto the stream
374 * instead of <em>the previous character.</em> If successful,
375 * the next character fetched from the input stream will be @a
376 * __c.
377 */
378 int_type
379 sputbackc(char_type __c)
380 {
381 int_type __ret;
382 const bool __testpos = this->eback() < this->gptr();
383 if (__builtin_expect(!__testpos ||
384 !traits_type::eq(__c, this->gptr()[-1]), false))
385 __ret = this->pbackfail(traits_type::to_int_type(__c));
386 else
387 {
388 this->gbump(-1);
389 __ret = traits_type::to_int_type(*this->gptr());
390 }
391 return __ret;
392 }
393
394 /**
395 * @brief Moving backwards in the input stream.
396 * @return The previous character, if possible.
397 *
398 * If a putback position is available, this function decrements
399 * the input pointer and returns that character. Otherwise,
400 * calls and returns pbackfail(). The effect is to @a unget
401 * the last character @a gotten.
402 */
403 int_type
404 sungetc()
405 {
406 int_type __ret;
407 if (__builtin_expect(this->eback() < this->gptr(), true))
408 {
409 this->gbump(-1);
410 __ret = traits_type::to_int_type(*this->gptr());
411 }
412 else
413 __ret = this->pbackfail();
414 return __ret;
415 }
416
417 // [27.5.2.2.5] put area
418 /**
419 * @brief Entry point for all single-character output functions.
420 * @param __c A character to output.
421 * @return @a __c, if possible.
422 *
423 * One of two public output functions.
424 *
425 * If a write position is available for the output sequence (i.e.,
426 * the buffer is not full), stores @a __c in that position, increments
427 * the position, and returns @c traits::to_int_type(__c). If a write
428 * position is not available, returns @c overflow(__c).
429 */
430 int_type
431 sputc(char_type __c)
432 {
433 int_type __ret;
434 if (__builtin_expect(this->pptr() < this->epptr(), true))
435 {
436 *this->pptr() = __c;
437 this->pbump(1);
438 __ret = traits_type::to_int_type(__c);
439 }
440 else
441 __ret = this->overflow(traits_type::to_int_type(__c));
442 return __ret;
443 }
444
445 /**
446 * @brief Entry point for all single-character output functions.
447 * @param __s A buffer read area.
448 * @param __n A count.
449 *
450 * One of two public output functions.
451 *
452 *
453 * Returns xsputn(__s,__n). The effect is to write @a __s[0] through
454 * @a __s[__n-1] to the output sequence, if possible.
455 */
456 streamsize
457 sputn(const char_type* __s, streamsize __n)
458 { return this->xsputn(__s, __n); }
459
460 protected:
461 /**
462 * @brief Base constructor.
463 *
464 * Only called from derived constructors, and sets up all the
465 * buffer data to zero, including the pointers described in the
466 * basic_streambuf class description. Note that, as a result,
467 * - the class starts with no read nor write positions available,
468 * - this is not an error
469 */
470 basic_streambuf()
471 : _M_in_beg(0), _M_in_cur(0), _M_in_end(0),
472 _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
473 _M_buf_locale(locale())
474 { }
475
476 // [27.5.2.3.1] get area access
477 ///@{
478 /**
479 * @brief Access to the get area.
480 *
481 * These functions are only available to other protected functions,
482 * including derived classes.
483 *
484 * - eback() returns the beginning pointer for the input sequence
485 * - gptr() returns the next pointer for the input sequence
486 * - egptr() returns the end pointer for the input sequence
487 */
488 char_type*
489 eback() const { return _M_in_beg; }
490
491 char_type*
492 gptr() const { return _M_in_cur; }
493
494 char_type*
495 egptr() const { return _M_in_end; }
496 ///@}
497
498 /**
499 * @brief Moving the read position.
500 * @param __n The delta by which to move.
501 *
502 * This just advances the read position without returning any data.
503 */
504 void
505 gbump(int __n) { _M_in_cur += __n; }
506
507 /**
508 * @brief Setting the three read area pointers.
509 * @param __gbeg A pointer.
510 * @param __gnext A pointer.
511 * @param __gend A pointer.
512 * @post @a __gbeg == @c eback(), @a __gnext == @c gptr(), and
513 * @a __gend == @c egptr()
514 */
515 void
516 setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
517 {
518 _M_in_beg = __gbeg;
519 _M_in_cur = __gnext;
520 _M_in_end = __gend;
521 }
522
523 // [27.5.2.3.2] put area access
524 ///@{
525 /**
526 * @brief Access to the put area.
527 *
528 * These functions are only available to other protected functions,
529 * including derived classes.
530 *
531 * - pbase() returns the beginning pointer for the output sequence
532 * - pptr() returns the next pointer for the output sequence
533 * - epptr() returns the end pointer for the output sequence
534 */
535 char_type*
536 pbase() const { return _M_out_beg; }
537
538 char_type*
539 pptr() const { return _M_out_cur; }
540
541 char_type*
542 epptr() const { return _M_out_end; }
543 ///@}
544
545 /**
546 * @brief Moving the write position.
547 * @param __n The delta by which to move.
548 *
549 * This just advances the write position without returning any data.
550 */
551 void
552 pbump(int __n) { _M_out_cur += __n; }
553
554 /**
555 * @brief Setting the three write area pointers.
556 * @param __pbeg A pointer.
557 * @param __pend A pointer.
558 * @post @a __pbeg == @c pbase(), @a __pbeg == @c pptr(), and
559 * @a __pend == @c epptr()
560 */
561 void
562 setp(char_type* __pbeg, char_type* __pend)
563 {
564 _M_out_beg = _M_out_cur = __pbeg;
565 _M_out_end = __pend;
566 }
567
568 // [27.5.2.4] virtual functions
569 // [27.5.2.4.1] locales
570 /**
571 * @brief Changes translations.
572 * @param __loc A new locale.
573 *
574 * Translations done during I/O which depend on the current
575 * locale are changed by this call. The standard adds,
576 * <em>Between invocations of this function a class derived
577 * from streambuf can safely cache results of calls to locale
578 * functions and to members of facets so obtained.</em>
579 *
580 * @note Base class version does nothing.
581 */
582 virtual void
583 imbue(const locale& __loc _IsUnused)
584 { }
585
586 // [27.5.2.4.2] buffer management and positioning
587 /**
588 * @brief Manipulates the buffer.
589 *
590 * Each derived class provides its own appropriate behavior. See
591 * the next-to-last paragraph of
592 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
593 * for more on this function.
594 *
595 * @note Base class version does nothing, returns @c this.
596 */
597 virtual basic_streambuf<char_type,_Traits>*
598 setbuf(char_type*, streamsize)
599 { return this; }
600
601 /**
602 * @brief Alters the stream positions.
603 *
604 * Each derived class provides its own appropriate behavior.
605 * @note Base class version does nothing, returns a @c pos_type
606 * that represents an invalid stream position.
607 */
608 virtual pos_type
609 seekoff(off_type, ios_base::seekdir,
610 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
611 { return pos_type(off_type(-1)); }
612
613 /**
614 * @brief Alters the stream positions.
615 *
616 * Each derived class provides its own appropriate behavior.
617 * @note Base class version does nothing, returns a @c pos_type
618 * that represents an invalid stream position.
619 */
620 virtual pos_type
621 seekpos(pos_type,
622 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
623 { return pos_type(off_type(-1)); }
624
625 /**
626 * @brief Synchronizes the buffer arrays with the controlled sequences.
627 * @return -1 on failure.
628 *
629 * Each derived class provides its own appropriate behavior,
630 * including the definition of @a failure.
631 * @note Base class version does nothing, returns zero.
632 */
633 virtual int
634 sync() { return 0; }
635
636 // [27.5.2.4.3] get area
637 /**
638 * @brief Investigating the data available.
639 * @return An estimate of the number of characters available in the
640 * input sequence, or -1.
641 *
642 * <em>If it returns a positive value, then successive calls to
643 * @c underflow() will not return @c traits::eof() until at
644 * least that number of characters have been supplied. If @c
645 * showmanyc() returns -1, then calls to @c underflow() or @c
646 * uflow() will fail.</em> [27.5.2.4.3]/1
647 *
648 * @note Base class version does nothing, returns zero.
649 * @note The standard adds that <em>the intention is not only that the
650 * calls [to underflow or uflow] will not return @c eof() but
651 * that they will return immediately.</em>
652 * @note The standard adds that <em>the morphemes of @c showmanyc are
653 * @b es-how-many-see, not @b show-manic.</em>
654 */
655 virtual streamsize
656 showmanyc() { return 0; }
657
658 /**
659 * @brief Multiple character extraction.
660 * @param __s A buffer area.
661 * @param __n Maximum number of characters to assign.
662 * @return The number of characters assigned.
663 *
664 * Fills @a __s[0] through @a __s[__n-1] with characters from the input
665 * sequence, as if by @c sbumpc(). Stops when either @a __n characters
666 * have been copied, or when @c traits::eof() would be copied.
667 *
668 * It is expected that derived classes provide a more efficient
669 * implementation by overriding this definition.
670 */
671 virtual streamsize
672 xsgetn(char_type* __s, streamsize __n);
673
674 /**
675 * @brief Fetches more data from the controlled sequence.
676 * @return The first character from the <em>pending sequence</em>.
677 *
678 * Informally, this function is called when the input buffer is
679 * exhausted (or does not exist, as buffering need not actually be
680 * done). If a buffer exists, it is @a refilled. In either case, the
681 * next available character is returned, or @c traits::eof() to
682 * indicate a null pending sequence.
683 *
684 * For a formal definition of the pending sequence, see a good text
685 * such as Langer & Kreft, or [27.5.2.4.3]/7-14.
686 *
687 * A functioning input streambuf can be created by overriding only
688 * this function (no buffer area will be used). For an example, see
689 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html
690 *
691 * @note Base class version does nothing, returns eof().
692 */
693 virtual int_type
694 underflow()
695 { return traits_type::eof(); }
696
697 /**
698 * @brief Fetches more data from the controlled sequence.
699 * @return The first character from the <em>pending sequence</em>.
700 *
701 * Informally, this function does the same thing as @c underflow(),
702 * and in fact is required to call that function. It also returns
703 * the new character, like @c underflow() does. However, this
704 * function also moves the read position forward by one.
705 */
706 virtual int_type
707 uflow()
708 {
709 int_type __ret = traits_type::eof();
710 const bool __testeof = traits_type::eq_int_type(this->underflow(),
711 __ret);
712 if (!__testeof)
713 {
714 __ret = traits_type::to_int_type(*this->gptr());
715 this->gbump(1);
716 }
717 return __ret;
718 }
719
720 // [27.5.2.4.4] putback
721 /**
722 * @brief Tries to back up the input sequence.
723 * @param __c The character to be inserted back into the sequence.
724 * @return eof() on failure, <em>some other value</em> on success
725 * @post The constraints of @c gptr(), @c eback(), and @c pptr()
726 * are the same as for @c underflow().
727 *
728 * @note Base class version does nothing, returns eof().
729 */
730 virtual int_type
731 pbackfail(int_type __c _IsUnused = traits_type::eof())
732 { return traits_type::eof(); }
733
734 // Put area:
735 /**
736 * @brief Multiple character insertion.
737 * @param __s A buffer area.
738 * @param __n Maximum number of characters to write.
739 * @return The number of characters written.
740 *
741 * Writes @a __s[0] through @a __s[__n-1] to the output sequence, as if
742 * by @c sputc(). Stops when either @a n characters have been
743 * copied, or when @c sputc() would return @c traits::eof().
744 *
745 * It is expected that derived classes provide a more efficient
746 * implementation by overriding this definition.
747 */
748 virtual streamsize
749 xsputn(const char_type* __s, streamsize __n);
750
751 /**
752 * @brief Consumes data from the buffer; writes to the
753 * controlled sequence.
754 * @param __c An additional character to consume.
755 * @return eof() to indicate failure, something else (usually
756 * @a __c, or not_eof())
757 *
758 * Informally, this function is called when the output buffer
759 * is full (or does not exist, as buffering need not actually
760 * be done). If a buffer exists, it is @a consumed, with
761 * <em>some effect</em> on the controlled sequence.
762 * (Typically, the buffer is written out to the sequence
763 * verbatim.) In either case, the character @a c is also
764 * written out, if @a __c is not @c eof().
765 *
766 * For a formal definition of this function, see a good text
767 * such as Langer & Kreft, or [27.5.2.4.5]/3-7.
768 *
769 * A functioning output streambuf can be created by overriding only
770 * this function (no buffer area will be used).
771 *
772 * @note Base class version does nothing, returns eof().
773 */
774 virtual int_type
775 overflow(int_type __c _IsUnused = traits_type::eof())
776 { return traits_type::eof(); }
777
778#if _GLIBCXX_USE_DEPRECATED && __cplusplus <= 201402L
779 // Annex D.6 (removed in C++17)
780 public:
781 /**
782 * @brief Tosses a character.
783 *
784 * Advances the read pointer, ignoring the character that would have
785 * been read.
786 *
787 * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
788 */
789 _GLIBCXX_DEPRECATED_SUGGEST("std::basic_streambuf::sbumpc")
790 void
791 stossc()
792 {
793 if (this->gptr() < this->egptr())
794 this->gbump(1);
795 else
796 this->uflow();
797 }
798#endif
799
800 // Also used by specializations for char and wchar_t in src.
801 void
802 __safe_gbump(streamsize __n) { _M_in_cur += __n; }
803
804 void
805 __safe_pbump(streamsize __n) { _M_out_cur += __n; }
806
807#if __cplusplus < 201103L
808 private:
809#else
810 protected:
811#endif
812 basic_streambuf(const basic_streambuf&);
813
814 basic_streambuf&
815 operator=(const basic_streambuf&);
816
817#if __cplusplus >= 201103L
818 void
819 swap(basic_streambuf& __sb)
820 {
821 std::swap(_M_in_beg, __sb._M_in_beg);
822 std::swap(_M_in_cur, __sb._M_in_cur);
823 std::swap(_M_in_end, __sb._M_in_end);
824 std::swap(_M_out_beg, __sb._M_out_beg);
825 std::swap(_M_out_cur, __sb._M_out_cur);
826 std::swap(_M_out_end, __sb._M_out_end);
827 std::swap(_M_buf_locale, __sb._M_buf_locale);
828 }
829#endif
830 };
831
832#if __cplusplus >= 201103L
833 template<typename _CharT, typename _Traits>
834 std::basic_streambuf<_CharT, _Traits>::
835 basic_streambuf(const basic_streambuf&) = default;
836
837 template<typename _CharT, typename _Traits>
838 std::basic_streambuf<_CharT, _Traits>&
839 std::basic_streambuf<_CharT, _Traits>::
840 operator=(const basic_streambuf&) = default;
841#endif
842
843 // Explicit specialization declarations, defined in src/streambuf.cc.
844 template<>
845 streamsize
846 __copy_streambufs_eof(basic_streambuf<char>* __sbin,
847 basic_streambuf<char>* __sbout, bool& __ineof);
848#ifdef _GLIBCXX_USE_WCHAR_T
849 template<>
850 streamsize
851 __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
852 basic_streambuf<wchar_t>* __sbout, bool& __ineof);
853#endif
854
855#undef _IsUnused
856
857_GLIBCXX_END_NAMESPACE_VERSION
858} // namespace
859
860#include <bits/streambuf.tcc>
861
862#endif /* _GLIBCXX_STREAMBUF */
863