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 | |
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 | ~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 | |