| blob | 535088068e01c16939bb2b2c2d917bb1ace3af8e |
1 // Stream buffer classes -*- C++ -*-
3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
4 // 2006, 2007, 2008, 2009, 2010, 2011, 2013 Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
26 /** @file include/streambuf
27 * This is a Standard C++ Library header.
28 */
30 //
31 // ISO C++ 14882: 27.5 Stream buffers
32 //
34 #ifndef _GLIBXX_STREAMBUF
35 #define _GLIBXX_STREAMBUF 1
37 #pragma GCC system_header
39 #include <bits/c++config.h>
40 #include <iosfwd>
41 #include <bits/localefwd.h>
42 #include <bits/ios_base.h>
43 #include <bits/cpp_type_traits.h>
44 #include <ext/type_traits.h>
46 namespace std _GLIBCXX_VISIBILITY(default)
47 {
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
50 template<typename _CharT, typename _Traits>
51 streamsize
52 __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
53 basic_streambuf<_CharT, _Traits>*, bool&);
55 /**
56 * @brief The actual work of input and output (interface).
57 * @ingroup io
58 *
59 * This is a base class. Derived stream buffers each control a
60 * pair of character sequences: one for input, and one for output.
61 *
62 * Section [27.5.1] of the standard describes the requirements and
63 * behavior of stream buffer classes. That section (three paragraphs)
64 * is reproduced here, for simplicity and accuracy.
65 *
66 * -# Stream buffers can impose various constraints on the sequences
67 * they control. Some constraints are:
68 * - The controlled input sequence can be not readable.
69 * - The controlled output sequence can be not writable.
70 * - The controlled sequences can be associated with the contents of
71 * other representations for character sequences, such as external
72 * files.
73 * - The controlled sequences can support operations @e directly to or
74 * from associated sequences.
75 * - The controlled sequences can impose limitations on how the
76 * program can read characters from a sequence, write characters to
77 * a sequence, put characters back into an input sequence, or alter
78 * the stream position.
79 * .
80 * -# Each sequence is characterized by three pointers which, if non-null,
81 * all point into the same @c charT array object. The array object
82 * represents, at any moment, a (sub)sequence of characters from the
83 * sequence. Operations performed on a sequence alter the values
84 * stored in these pointers, perform reads and writes directly to or
85 * from associated sequences, and alter <em>the stream position</em> and
86 * conversion state as needed to maintain this subsequence relationship.
87 * The three pointers are:
88 * - the <em>beginning pointer</em>, or lowest element address in the
89 * array (called @e xbeg here);
90 * - the <em>next pointer</em>, or next element address that is a
91 * current candidate for reading or writing (called @e xnext here);
92 * - the <em>end pointer</em>, or first element address beyond the
93 * end of the array (called @e xend here).
94 * .
95 * -# The following semantic constraints shall always apply for any set
96 * of three pointers for a sequence, using the pointer names given
97 * immediately above:
98 * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
99 * also be non-null pointers into the same @c charT array, as
100 * described above; otherwise, @e xbeg and @e xend shall also be null.
101 * - If @e xnext is not a null pointer and @e xnext < @e xend for an
102 * output sequence, then a <em>write position</em> is available.
103 * In this case, @e *xnext shall be assignable as the next element
104 * to write (to put, or to store a character value, into the sequence).
105 * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
106 * input sequence, then a <em>putback position</em> is available.
107 * In this case, @e xnext[-1] shall have a defined value and is the
108 * next (preceding) element to store a character that is put back
109 * into the input sequence.
110 * - If @e xnext is not a null pointer and @e xnext< @e xend for an
111 * input sequence, then a <em>read position</em> is available.
112 * In this case, @e *xnext shall have a defined value and is the
113 * next element to read (to get, or to obtain a character value,
114 * from the sequence).
115 */
116 template<typename _CharT, typename _Traits>
117 class basic_streambuf
118 {
119 public:
120 //@{
121 /**
122 * These are standard types. They permit a standardized way of
123 * referring to names of (or names dependant on) the template
124 * parameters, which are specific to the implementation.
125 */
126 typedef _CharT char_type;
127 typedef _Traits traits_type;
128 typedef typename traits_type::int_type int_type;
129 typedef typename traits_type::pos_type pos_type;
130 typedef typename traits_type::off_type off_type;
131 //@}
133 //@{
134 /// This is a non-standard type.
135 typedef basic_streambuf<char_type, traits_type> __streambuf_type;
136 //@}
138 friend class basic_ios<char_type, traits_type>;
139 friend class basic_istream<char_type, traits_type>;
140 friend class basic_ostream<char_type, traits_type>;
141 friend class istreambuf_iterator<char_type, traits_type>;
142 friend class ostreambuf_iterator<char_type, traits_type>;
144 friend streamsize
145 __copy_streambufs_eof<>(__streambuf_type*, __streambuf_type*, bool&);
147 template<bool _IsMove, typename _CharT2>
148 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
149 _CharT2*>::__type
150 __copy_move_a2(istreambuf_iterator<_CharT2>,
151 istreambuf_iterator<_CharT2>, _CharT2*);
153 template<typename _CharT2>
154 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
155 istreambuf_iterator<_CharT2> >::__type
156 find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
157 const _CharT2&);
159 template<typename _CharT2, typename _Traits2>
160 friend basic_istream<_CharT2, _Traits2>&
161 operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
163 template<typename _CharT2, typename _Traits2, typename _Alloc>
164 friend basic_istream<_CharT2, _Traits2>&
165 operator>>(basic_istream<_CharT2, _Traits2>&,
166 basic_string<_CharT2, _Traits2, _Alloc>&);
168 template<typename _CharT2, typename _Traits2, typename _Alloc>
169 friend basic_istream<_CharT2, _Traits2>&
170 getline(basic_istream<_CharT2, _Traits2>&,
171 basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
173 protected:
174 /*
175 * This is based on _IO_FILE, just reordered to be more consistent,
176 * and is intended to be the most minimal abstraction for an
177 * internal buffer.
178 * - get == input == read
179 * - put == output == write
180 */
181 char_type* _M_in_beg; ///< Start of get area.
182 char_type* _M_in_cur; ///< Current read area.
183 char_type* _M_in_end; ///< End of get area.
184 char_type* _M_out_beg; ///< Start of put area.
185 char_type* _M_out_cur; ///< Current put area.
186 char_type* _M_out_end; ///< End of put area.
188 /// Current locale setting.
189 locale _M_buf_locale;
191 public:
192 /// Destructor deallocates no buffer space.
193 virtual
194 ~basic_streambuf()
195 { }
197 // [27.5.2.2.1] locales
198 /**
199 * @brief Entry point for imbue().
200 * @param __loc The new locale.
201 * @return The previous locale.
202 *
203 * Calls the derived imbue(__loc).
204 */
205 locale
206 pubimbue(const locale& __loc)
207 {
208 locale __tmp(this->getloc());
209 this->imbue(__loc);
210 _M_buf_locale = __loc;
211 return __tmp;
212 }
214 /**
215 * @brief Locale access.
216 * @return The current locale in effect.
217 *
218 * If pubimbue(loc) has been called, then the most recent @c loc
219 * is returned. Otherwise the global locale in effect at the time
220 * of construction is returned.
221 */
222 locale
223 getloc() const
224 { return _M_buf_locale; }
226 // [27.5.2.2.2] buffer management and positioning
227 //@{
228 /**
229 * @brief Entry points for derived buffer functions.
230 *
231 * The public versions of @c pubfoo dispatch to the protected
232 * derived @c foo member functions, passing the arguments (if any)
233 * and returning the result unchanged.
234 */
235 __streambuf_type*
236 pubsetbuf(char_type* __s, streamsize __n)
237 { return this->setbuf(__s, __n); }
239 /**
240 * @brief Alters the stream position.
241 * @param __off Offset.
242 * @param __way Value for ios_base::seekdir.
243 * @param __mode Value for ios_base::openmode.
244 *
245 * Calls virtual seekoff function.
246 */
247 pos_type
248 pubseekoff(off_type __off, ios_base::seekdir __way,
249 ios_base::openmode __mode = ios_base::in | ios_base::out)
250 { return this->seekoff(__off, __way, __mode); }
252 /**
253 * @brief Alters the stream position.
254 * @param __sp Position
255 * @param __mode Value for ios_base::openmode.
256 *
257 * Calls virtual seekpos function.
258 */
259 pos_type
260 pubseekpos(pos_type __sp,
261 ios_base::openmode __mode = ios_base::in | ios_base::out)
262 { return this->seekpos(__sp, __mode); }
264 /**
265 * @brief Calls virtual sync function.
266 */
267 int
268 pubsync() { return this->sync(); }
269 //@}
271 // [27.5.2.2.3] get area
272 /**
273 * @brief Looking ahead into the stream.
274 * @return The number of characters available.
275 *
276 * If a read position is available, returns the number of characters
277 * available for reading before the buffer must be refilled.
278 * Otherwise returns the derived @c showmanyc().
279 */
280 streamsize
281 in_avail()
282 {
283 const streamsize __ret = this->egptr() - this->gptr();
284 return __ret ? __ret : this->showmanyc();
285 }
287 /**
288 * @brief Getting the next character.
289 * @return The next character, or eof.
290 *
291 * Calls @c sbumpc(), and if that function returns
292 * @c traits::eof(), so does this function. Otherwise, @c sgetc().
293 */
294 int_type
295 snextc()
296 {
297 int_type __ret = traits_type::eof();
298 if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(),
299 __ret), true))
300 __ret = this->sgetc();
301 return __ret;
302 }
304 /**
305 * @brief Getting the next character.
306 * @return The next character, or eof.
307 *
308 * If the input read position is available, returns that character
309 * and increments the read pointer, otherwise calls and returns
310 * @c uflow().
311 */
312 int_type
313 sbumpc()
314 {
315 int_type __ret;
316 if (__builtin_expect(this->gptr() < this->egptr(), true))
317 {
318 __ret = traits_type::to_int_type(*this->gptr());
319 this->gbump(1);
320 }
321 else
322 __ret = this->uflow();
323 return __ret;
324 }
326 /**
327 * @brief Getting the next character.
328 * @return The next character, or eof.
329 *
330 * If the input read position is available, returns that character,
331 * otherwise calls and returns @c underflow(). Does not move the
332 * read position after fetching the character.
333 */
334 int_type
335 sgetc()
336 {
337 int_type __ret;
338 if (__builtin_expect(this->gptr() < this->egptr(), true))
339 __ret = traits_type::to_int_type(*this->gptr());
340 else
341 __ret = this->underflow();
342 return __ret;
343 }
345 /**
346 * @brief Entry point for xsgetn.
347 * @param __s A buffer area.
348 * @param __n A count.
349 *
350 * Returns xsgetn(__s,__n). The effect is to fill @a __s[0] through
351 * @a __s[__n-1] with characters from the input sequence, if possible.
352 */
353 streamsize
354 sgetn(char_type* __s, streamsize __n)
355 { return this->xsgetn(__s, __n); }
357 // [27.5.2.2.4] putback
358 /**
359 * @brief Pushing characters back into the input stream.
360 * @param __c The character to push back.
361 * @return The previous character, if possible.
362 *
363 * Similar to sungetc(), but @a __c is pushed onto the stream
364 * instead of <em>the previous character.</em> If successful,
365 * the next character fetched from the input stream will be @a
366 * __c.
367 */
368 int_type
369 sputbackc(char_type __c)
370 {
371 int_type __ret;
372 const bool __testpos = this->eback() < this->gptr();
373 if (__builtin_expect(!__testpos ||
374 !traits_type::eq(__c, this->gptr()[-1]), false))
375 __ret = this->pbackfail(traits_type::to_int_type(__c));
376 else
377 {
378 this->gbump(-1);
379 __ret = traits_type::to_int_type(*this->gptr());
380 }
381 return __ret;
382 }
384 /**
385 * @brief Moving backwards in the input stream.
386 * @return The previous character, if possible.
387 *
388 * If a putback position is available, this function decrements
389 * the input pointer and returns that character. Otherwise,
390 * calls and returns pbackfail(). The effect is to @a unget
391 * the last character @a gotten.
392 */
393 int_type
394 sungetc()
395 {
396 int_type __ret;
397 if (__builtin_expect(this->eback() < this->gptr(), true))
398 {
399 this->gbump(-1);
400 __ret = traits_type::to_int_type(*this->gptr());
401 }
402 else
403 __ret = this->pbackfail();
404 return __ret;
405 }
407 // [27.5.2.2.5] put area
408 /**
409 * @brief Entry point for all single-character output functions.
410 * @param __c A character to output.
411 * @return @a __c, if possible.
412 *
413 * One of two public output functions.
414 *
415 * If a write position is available for the output sequence (i.e.,
416 * the buffer is not full), stores @a __c in that position, increments
417 * the position, and returns @c traits::to_int_type(__c). If a write
418 * position is not available, returns @c overflow(__c).
419 */
420 int_type
421 sputc(char_type __c)
422 {
423 int_type __ret;
424 if (__builtin_expect(this->pptr() < this->epptr(), true))
425 {
426 *this->pptr() = __c;
427 this->pbump(1);
428 __ret = traits_type::to_int_type(__c);
429 }
430 else
431 __ret = this->overflow(traits_type::to_int_type(__c));
432 return __ret;
433 }
435 /**
436 * @brief Entry point for all single-character output functions.
437 * @param __s A buffer read area.
438 * @param __n A count.
439 *
440 * One of two public output functions.
441 *
442 *
443 * Returns xsputn(__s,__n). The effect is to write @a __s[0] through
444 * @a __s[__n-1] to the output sequence, if possible.
445 */
446 streamsize
447 sputn(const char_type* __s, streamsize __n)
448 { return this->xsputn(__s, __n); }
450 protected:
451 /**
452 * @brief Base constructor.
453 *
454 * Only called from derived constructors, and sets up all the
455 * buffer data to zero, including the pointers described in the
456 * basic_streambuf class description. Note that, as a result,
457 * - the class starts with no read nor write positions available,
458 * - this is not an error
459 */
460 basic_streambuf()
461 : _M_in_beg(0), _M_in_cur(0), _M_in_end(0),
462 _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
463 _M_buf_locale(locale())
464 { }
466 // [27.5.2.3.1] get area access
467 //@{
468 /**
469 * @brief Access to the get area.
470 *
471 * These functions are only available to other protected functions,
472 * including derived classes.
473 *
474 * - eback() returns the beginning pointer for the input sequence
475 * - gptr() returns the next pointer for the input sequence
476 * - egptr() returns the end pointer for the input sequence
477 */
478 char_type*
479 eback() const { return _M_in_beg; }
481 char_type*
482 gptr() const { return _M_in_cur; }
484 char_type*
485 egptr() const { return _M_in_end; }
486 //@}
488 /**
489 * @brief Moving the read position.
490 * @param __n The delta by which to move.
491 *
492 * This just advances the read position without returning any data.
493 */
494 void
495 gbump(int __n) { _M_in_cur += __n; }
497 /**
498 * @brief Setting the three read area pointers.
499 * @param __gbeg A pointer.
500 * @param __gnext A pointer.
501 * @param __gend A pointer.
502 * @post @a __gbeg == @c eback(), @a __gnext == @c gptr(), and
503 * @a __gend == @c egptr()
504 */
505 void
506 setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
507 {
508 _M_in_beg = __gbeg;
509 _M_in_cur = __gnext;
510 _M_in_end = __gend;
511 }
513 // [27.5.2.3.2] put area access
514 //@{
515 /**
516 * @brief Access to the put area.
517 *
518 * These functions are only available to other protected functions,
519 * including derived classes.
520 *
521 * - pbase() returns the beginning pointer for the output sequence
522 * - pptr() returns the next pointer for the output sequence
523 * - epptr() returns the end pointer for the output sequence
524 */
525 char_type*
526 pbase() const { return _M_out_beg; }
528 char_type*
529 pptr() const { return _M_out_cur; }
531 char_type*
532 epptr() const { return _M_out_end; }
533 //@}
535 /**
536 * @brief Moving the write position.
537 * @param __n The delta by which to move.
538 *
539 * This just advances the write position without returning any data.
540 */
541 void
542 pbump(int __n) { _M_out_cur += __n; }
544 /**
545 * @brief Setting the three write area pointers.
546 * @param __pbeg A pointer.
547 * @param __pend A pointer.
548 * @post @a __pbeg == @c pbase(), @a __pbeg == @c pptr(), and
549 * @a __pend == @c epptr()
550 */
551 void
552 setp(char_type* __pbeg, char_type* __pend)
553 {
554 _M_out_beg = _M_out_cur = __pbeg;
555 _M_out_end = __pend;
556 }
558 // [27.5.2.4] virtual functions
559 // [27.5.2.4.1] locales
560 /**
561 * @brief Changes translations.
562 * @param __loc A new locale.
563 *
564 * Translations done during I/O which depend on the current
565 * locale are changed by this call. The standard adds,
566 * <em>Between invocations of this function a class derived
567 * from streambuf can safely cache results of calls to locale
568 * functions and to members of facets so obtained.</em>
569 *
570 * @note Base class version does nothing.
571 */
572 virtual void
573 imbue(const locale& __loc)
574 { }
576 // [27.5.2.4.2] buffer management and positioning
577 /**
578 * @brief Manipulates the buffer.
579 *
580 * Each derived class provides its own appropriate behavior. See
581 * the next-to-last paragraph of
582 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
583 * for more on this function.
584 *
585 * @note Base class version does nothing, returns @c this.
586 */
587 virtual basic_streambuf<char_type,_Traits>*
588 setbuf(char_type*, streamsize)
589 { return this; }
591 /**
592 * @brief Alters the stream positions.
593 *
594 * Each derived class provides its own appropriate behavior.
595 * @note Base class version does nothing, returns a @c pos_type
596 * that represents an invalid stream position.
597 */
598 virtual pos_type
599 seekoff(off_type, ios_base::seekdir,
600 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
601 { return pos_type(off_type(-1)); }
603 /**
604 * @brief Alters the stream positions.
605 *
606 * Each derived class provides its own appropriate behavior.
607 * @note Base class version does nothing, returns a @c pos_type
608 * that represents an invalid stream position.
609 */
610 virtual pos_type
611 seekpos(pos_type,
612 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
613 { return pos_type(off_type(-1)); }
615 /**
616 * @brief Synchronizes the buffer arrays with the controlled sequences.
617 * @return -1 on failure.
618 *
619 * Each derived class provides its own appropriate behavior,
620 * including the definition of @a failure.
621 * @note Base class version does nothing, returns zero.
622 */
623 virtual int
624 sync() { return 0; }
626 // [27.5.2.4.3] get area
627 /**
628 * @brief Investigating the data available.
629 * @return An estimate of the number of characters available in the
630 * input sequence, or -1.
631 *
632 * <em>If it returns a positive value, then successive calls to
633 * @c underflow() will not return @c traits::eof() until at
634 * least that number of characters have been supplied. If @c
635 * showmanyc() returns -1, then calls to @c underflow() or @c
636 * uflow() will fail.</em> [27.5.2.4.3]/1
637 *
638 * @note Base class version does nothing, returns zero.
639 * @note The standard adds that <em>the intention is not only that the
640 * calls [to underflow or uflow] will not return @c eof() but
641 * that they will return immediately.</em>
642 * @note The standard adds that <em>the morphemes of @c showmanyc are
643 * @b es-how-many-see, not @b show-manic.</em>
644 */
645 virtual streamsize
646 showmanyc() { return 0; }
648 /**
649 * @brief Multiple character extraction.
650 * @param __s A buffer area.
651 * @param __n Maximum number of characters to assign.
652 * @return The number of characters assigned.
653 *
654 * Fills @a __s[0] through @a __s[__n-1] with characters from the input
655 * sequence, as if by @c sbumpc(). Stops when either @a __n characters
656 * have been copied, or when @c traits::eof() would be copied.
657 *
658 * It is expected that derived classes provide a more efficient
659 * implementation by overriding this definition.
660 */
661 virtual streamsize
662 xsgetn(char_type* __s, streamsize __n);
664 /**
665 * @brief Fetches more data from the controlled sequence.
666 * @return The first character from the <em>pending sequence</em>.
667 *
668 * Informally, this function is called when the input buffer is
669 * exhausted (or does not exist, as buffering need not actually be
670 * done). If a buffer exists, it is @a refilled. In either case, the
671 * next available character is returned, or @c traits::eof() to
672 * indicate a null pending sequence.
673 *
674 * For a formal definition of the pending sequence, see a good text
675 * such as Langer & Kreft, or [27.5.2.4.3]/7-14.
676 *
677 * A functioning input streambuf can be created by overriding only
678 * this function (no buffer area will be used). For an example, see
679 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.html
680 *
681 * @note Base class version does nothing, returns eof().
682 */
683 virtual int_type
684 underflow()
685 { return traits_type::eof(); }
687 /**
688 * @brief Fetches more data from the controlled sequence.
689 * @return The first character from the <em>pending sequence</em>.
690 *
691 * Informally, this function does the same thing as @c underflow(),
692 * and in fact is required to call that function. It also returns
693 * the new character, like @c underflow() does. However, this
694 * function also moves the read position forward by one.
695 */
696 virtual int_type
697 uflow()
698 {
699 int_type __ret = traits_type::eof();
700 const bool __testeof = traits_type::eq_int_type(this->underflow(),
701 __ret);
702 if (!__testeof)
703 {
704 __ret = traits_type::to_int_type(*this->gptr());
705 this->gbump(1);
706 }
707 return __ret;
708 }
710 // [27.5.2.4.4] putback
711 /**
712 * @brief Tries to back up the input sequence.
713 * @param __c The character to be inserted back into the sequence.
714 * @return eof() on failure, <em>some other value</em> on success
715 * @post The constraints of @c gptr(), @c eback(), and @c pptr()
716 * are the same as for @c underflow().
717 *
718 * @note Base class version does nothing, returns eof().
719 */
720 virtual int_type
721 pbackfail(int_type __c = traits_type::eof())
722 { return traits_type::eof(); }
724 // Put area:
725 /**
726 * @brief Multiple character insertion.
727 * @param __s A buffer area.
728 * @param __n Maximum number of characters to write.
729 * @return The number of characters written.
730 *
731 * Writes @a __s[0] through @a __s[__n-1] to the output sequence, as if
732 * by @c sputc(). Stops when either @a n characters have been
733 * copied, or when @c sputc() would return @c traits::eof().
734 *
735 * It is expected that derived classes provide a more efficient
736 * implementation by overriding this definition.
737 */
738 virtual streamsize
739 xsputn(const char_type* __s, streamsize __n);
741 /**
742 * @brief Consumes data from the buffer; writes to the
743 * controlled sequence.
744 * @param __c An additional character to consume.
745 * @return eof() to indicate failure, something else (usually
746 * @a __c, or not_eof())
747 *
748 * Informally, this function is called when the output buffer
749 * is full (or does not exist, as buffering need not actually
750 * be done). If a buffer exists, it is @a consumed, with
751 * <em>some effect</em> on the controlled sequence.
752 * (Typically, the buffer is written out to the sequence
753 * verbatim.) In either case, the character @a c is also
754 * written out, if @a __c is not @c eof().
755 *
756 * For a formal definition of this function, see a good text
757 * such as Langer & Kreft, or [27.5.2.4.5]/3-7.
758 *
759 * A functioning output streambuf can be created by overriding only
760 * this function (no buffer area will be used).
761 *
762 * @note Base class version does nothing, returns eof().
763 */
764 virtual int_type
765 overflow(int_type __c = traits_type::eof())
766 { return traits_type::eof(); }
768 #if _GLIBCXX_USE_DEPRECATED
769 // Annex D.6
770 public:
771 /**
772 * @brief Tosses a character.
773 *
774 * Advances the read pointer, ignoring the character that would have
775 * been read.
776 *
777 * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
778 */
779 void
780 stossc()
781 {
782 if (this->gptr() < this->egptr())
783 this->gbump(1);
784 else
785 this->uflow();
786 }
787 #endif
789 // Also used by specializations for char and wchar_t in src.
790 void
791 __safe_gbump(streamsize __n) { _M_in_cur += __n; }
793 void
794 __safe_pbump(streamsize __n) { _M_out_cur += __n; }
796 private:
797 // _GLIBCXX_RESOLVE_LIB_DEFECTS
798 // Side effect of DR 50.
799 basic_streambuf(const __streambuf_type& __sb)
800 : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur),
801 _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg),
802 _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
803 _M_buf_locale(__sb._M_buf_locale)
804 { }
806 __streambuf_type&
807 operator=(const __streambuf_type&) { return *this; };
808 };
810 // Explicit specialization declarations, defined in src/streambuf.cc.
811 template<>
812 streamsize
813 __copy_streambufs_eof(basic_streambuf<char>* __sbin,
814 basic_streambuf<char>* __sbout, bool& __ineof);
815 #ifdef _GLIBCXX_USE_WCHAR_T
816 template<>
817 streamsize
818 __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
819 basic_streambuf<wchar_t>* __sbout, bool& __ineof);
820 #endif
822 _GLIBCXX_END_NAMESPACE_VERSION
823 } // namespace
825 #include <bits/streambuf.tcc>
827 #endif /* _GLIBCXX_STREAMBUF */