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