Line data Source code
1 : // Stream buffer classes -*- C++ -*-
2 :
3 : // Copyright (C) 1997-2014 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 :
45 : namespace 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 0 : ~basic_streambuf()
198 0 : { }
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 0 : 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 0 : _M_buf_locale(locale())
467 0 : { }
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 0 : 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 0 : pbase() const { return _M_out_beg; }
530 :
531 : char_type*
532 0 : 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 : * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
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 : * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.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 : private:
800 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
801 : // Side effect of DR 50.
802 : basic_streambuf(const basic_streambuf& __sb)
803 : : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur),
804 : _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg),
805 : _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
806 : _M_buf_locale(__sb._M_buf_locale)
807 : { }
808 :
809 : basic_streambuf&
810 : operator=(const basic_streambuf&) { return *this; };
811 : };
812 :
813 : // Explicit specialization declarations, defined in src/streambuf.cc.
814 : template<>
815 : streamsize
816 : __copy_streambufs_eof(basic_streambuf<char>* __sbin,
817 : basic_streambuf<char>* __sbout, bool& __ineof);
818 : #ifdef _GLIBCXX_USE_WCHAR_T
819 : template<>
820 : streamsize
821 : __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
822 : basic_streambuf<wchar_t>* __sbout, bool& __ineof);
823 : #endif
824 :
825 : _GLIBCXX_END_NAMESPACE_VERSION
826 : } // namespace
827 :
828 : #include <bits/streambuf.tcc>
829 :
830 : #endif /* _GLIBCXX_STREAMBUF */
|
