libstdc++
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00001 // Stream buffer classes -*- C++ -*- 00002 00003 // Copyright (C) 1997-2019 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file include/streambuf 00026 * This is a Standard C++ Library header. 00027 */ 00028 00029 // 00030 // ISO C++ 14882: 27.5 Stream buffers 00031 // 00032 00033 #ifndef _GLIBXX_STREAMBUF 00034 #define _GLIBXX_STREAMBUF 1 00035 00036 #pragma GCC system_header 00037 00038 #include <bits/c++config.h> 00039 #include <iosfwd> 00040 #include <bits/localefwd.h> 00041 #include <bits/ios_base.h> 00042 #include <bits/cpp_type_traits.h> 00043 #include <ext/type_traits.h> 00044 00045 namespace std _GLIBCXX_VISIBILITY(default) 00046 { 00047 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00048 00049 #define _IsUnused __attribute__ ((__unused__)) 00050 00051 template<typename _CharT, typename _Traits> 00052 streamsize 00053 __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*, 00054 basic_streambuf<_CharT, _Traits>*, bool&); 00055 00056 /** 00057 * @brief The actual work of input and output (interface). 00058 * @ingroup io 00059 * 00060 * @tparam _CharT Type of character stream. 00061 * @tparam _Traits Traits for character type, defaults to 00062 * char_traits<_CharT>. 00063 * 00064 * This is a base class. Derived stream buffers each control a 00065 * pair of character sequences: one for input, and one for output. 00066 * 00067 * Section [27.5.1] of the standard describes the requirements and 00068 * behavior of stream buffer classes. That section (three paragraphs) 00069 * is reproduced here, for simplicity and accuracy. 00070 * 00071 * -# Stream buffers can impose various constraints on the sequences 00072 * they control. Some constraints are: 00073 * - The controlled input sequence can be not readable. 00074 * - The controlled output sequence can be not writable. 00075 * - The controlled sequences can be associated with the contents of 00076 * other representations for character sequences, such as external 00077 * files. 00078 * - The controlled sequences can support operations @e directly to or 00079 * from associated sequences. 00080 * - The controlled sequences can impose limitations on how the 00081 * program can read characters from a sequence, write characters to 00082 * a sequence, put characters back into an input sequence, or alter 00083 * the stream position. 00084 * . 00085 * -# Each sequence is characterized by three pointers which, if non-null, 00086 * all point into the same @c charT array object. The array object 00087 * represents, at any moment, a (sub)sequence of characters from the 00088 * sequence. Operations performed on a sequence alter the values 00089 * stored in these pointers, perform reads and writes directly to or 00090 * from associated sequences, and alter <em>the stream position</em> and 00091 * conversion state as needed to maintain this subsequence relationship. 00092 * The three pointers are: 00093 * - the <em>beginning pointer</em>, or lowest element address in the 00094 * array (called @e xbeg here); 00095 * - the <em>next pointer</em>, or next element address that is a 00096 * current candidate for reading or writing (called @e xnext here); 00097 * - the <em>end pointer</em>, or first element address beyond the 00098 * end of the array (called @e xend here). 00099 * . 00100 * -# The following semantic constraints shall always apply for any set 00101 * of three pointers for a sequence, using the pointer names given 00102 * immediately above: 00103 * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall 00104 * also be non-null pointers into the same @c charT array, as 00105 * described above; otherwise, @e xbeg and @e xend shall also be null. 00106 * - If @e xnext is not a null pointer and @e xnext < @e xend for an 00107 * output sequence, then a <em>write position</em> is available. 00108 * In this case, @e *xnext shall be assignable as the next element 00109 * to write (to put, or to store a character value, into the sequence). 00110 * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an 00111 * input sequence, then a <em>putback position</em> is available. 00112 * In this case, @e xnext[-1] shall have a defined value and is the 00113 * next (preceding) element to store a character that is put back 00114 * into the input sequence. 00115 * - If @e xnext is not a null pointer and @e xnext< @e xend for an 00116 * input sequence, then a <em>read position</em> is available. 00117 * In this case, @e *xnext shall have a defined value and is the 00118 * next element to read (to get, or to obtain a character value, 00119 * from the sequence). 00120 */ 00121 template<typename _CharT, typename _Traits> 00122 class basic_streambuf 00123 { 00124 public: 00125 //@{ 00126 /** 00127 * These are standard types. They permit a standardized way of 00128 * referring to names of (or names dependent on) the template 00129 * parameters, which are specific to the implementation. 00130 */ 00131 typedef _CharT char_type; 00132 typedef _Traits traits_type; 00133 typedef typename traits_type::int_type int_type; 00134 typedef typename traits_type::pos_type pos_type; 00135 typedef typename traits_type::off_type off_type; 00136 //@} 00137 00138 //@{ 00139 /// This is a non-standard type. 00140 typedef basic_streambuf<char_type, traits_type> __streambuf_type; 00141 //@} 00142 00143 friend class basic_ios<char_type, traits_type>; 00144 friend class basic_istream<char_type, traits_type>; 00145 friend class basic_ostream<char_type, traits_type>; 00146 friend class istreambuf_iterator<char_type, traits_type>; 00147 friend class ostreambuf_iterator<char_type, traits_type>; 00148 00149 friend streamsize 00150 __copy_streambufs_eof<>(basic_streambuf*, basic_streambuf*, bool&); 00151 00152 template<bool _IsMove, typename _CharT2> 00153 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 00154 _CharT2*>::__type 00155 __copy_move_a2(istreambuf_iterator<_CharT2>, 00156 istreambuf_iterator<_CharT2>, _CharT2*); 00157 00158 template<typename _CharT2> 00159 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 00160 istreambuf_iterator<_CharT2> >::__type 00161 find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>, 00162 const _CharT2&); 00163 00164 template<typename _CharT2, typename _Distance> 00165 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 00166 void>::__type 00167 advance(istreambuf_iterator<_CharT2>&, _Distance); 00168 00169 template<typename _CharT2, typename _Traits2> 00170 friend basic_istream<_CharT2, _Traits2>& 00171 operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*); 00172 00173 template<typename _CharT2, typename _Traits2, typename _Alloc> 00174 friend basic_istream<_CharT2, _Traits2>& 00175 operator>>(basic_istream<_CharT2, _Traits2>&, 00176 basic_string<_CharT2, _Traits2, _Alloc>&); 00177 00178 template<typename _CharT2, typename _Traits2, typename _Alloc> 00179 friend basic_istream<_CharT2, _Traits2>& 00180 getline(basic_istream<_CharT2, _Traits2>&, 00181 basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2); 00182 00183 protected: 00184 /* 00185 * This is based on _IO_FILE, just reordered to be more consistent, 00186 * and is intended to be the most minimal abstraction for an 00187 * internal buffer. 00188 * - get == input == read 00189 * - put == output == write 00190 */ 00191 char_type* _M_in_beg; ///< Start of get area. 00192 char_type* _M_in_cur; ///< Current read area. 00193 char_type* _M_in_end; ///< End of get area. 00194 char_type* _M_out_beg; ///< Start of put area. 00195 char_type* _M_out_cur; ///< Current put area. 00196 char_type* _M_out_end; ///< End of put area. 00197 00198 /// Current locale setting. 00199 locale _M_buf_locale; 00200 00201 public: 00202 /// Destructor deallocates no buffer space. 00203 virtual 00204 ~basic_streambuf() 00205 { } 00206 00207 // [27.5.2.2.1] locales 00208 /** 00209 * @brief Entry point for imbue(). 00210 * @param __loc The new locale. 00211 * @return The previous locale. 00212 * 00213 * Calls the derived imbue(__loc). 00214 */ 00215 locale 00216 pubimbue(const locale& __loc) 00217 { 00218 locale __tmp(this->getloc()); 00219 this->imbue(__loc); 00220 _M_buf_locale = __loc; 00221 return __tmp; 00222 } 00223 00224 /** 00225 * @brief Locale access. 00226 * @return The current locale in effect. 00227 * 00228 * If pubimbue(loc) has been called, then the most recent @c loc 00229 * is returned. Otherwise the global locale in effect at the time 00230 * of construction is returned. 00231 */ 00232 locale 00233 getloc() const 00234 { return _M_buf_locale; } 00235 00236 // [27.5.2.2.2] buffer management and positioning 00237 //@{ 00238 /** 00239 * @brief Entry points for derived buffer functions. 00240 * 00241 * The public versions of @c pubfoo dispatch to the protected 00242 * derived @c foo member functions, passing the arguments (if any) 00243 * and returning the result unchanged. 00244 */ 00245 basic_streambuf* 00246 pubsetbuf(char_type* __s, streamsize __n) 00247 { return this->setbuf(__s, __n); } 00248 00249 /** 00250 * @brief Alters the stream position. 00251 * @param __off Offset. 00252 * @param __way Value for ios_base::seekdir. 00253 * @param __mode Value for ios_base::openmode. 00254 * 00255 * Calls virtual seekoff function. 00256 */ 00257 pos_type 00258 pubseekoff(off_type __off, ios_base::seekdir __way, 00259 ios_base::openmode __mode = ios_base::in | ios_base::out) 00260 { return this->seekoff(__off, __way, __mode); } 00261 00262 /** 00263 * @brief Alters the stream position. 00264 * @param __sp Position 00265 * @param __mode Value for ios_base::openmode. 00266 * 00267 * Calls virtual seekpos function. 00268 */ 00269 pos_type 00270 pubseekpos(pos_type __sp, 00271 ios_base::openmode __mode = ios_base::in | ios_base::out) 00272 { return this->seekpos(__sp, __mode); } 00273 00274 /** 00275 * @brief Calls virtual sync function. 00276 */ 00277 int 00278 pubsync() { return this->sync(); } 00279 //@} 00280 00281 // [27.5.2.2.3] get area 00282 /** 00283 * @brief Looking ahead into the stream. 00284 * @return The number of characters available. 00285 * 00286 * If a read position is available, returns the number of characters 00287 * available for reading before the buffer must be refilled. 00288 * Otherwise returns the derived @c showmanyc(). 00289 */ 00290 streamsize 00291 in_avail() 00292 { 00293 const streamsize __ret = this->egptr() - this->gptr(); 00294 return __ret ? __ret : this->showmanyc(); 00295 } 00296 00297 /** 00298 * @brief Getting the next character. 00299 * @return The next character, or eof. 00300 * 00301 * Calls @c sbumpc(), and if that function returns 00302 * @c traits::eof(), so does this function. Otherwise, @c sgetc(). 00303 */ 00304 int_type 00305 snextc() 00306 { 00307 int_type __ret = traits_type::eof(); 00308 if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 00309 __ret), true)) 00310 __ret = this->sgetc(); 00311 return __ret; 00312 } 00313 00314 /** 00315 * @brief Getting the next character. 00316 * @return The next character, or eof. 00317 * 00318 * If the input read position is available, returns that character 00319 * and increments the read pointer, otherwise calls and returns 00320 * @c uflow(). 00321 */ 00322 int_type 00323 sbumpc() 00324 { 00325 int_type __ret; 00326 if (__builtin_expect(this->gptr() < this->egptr(), true)) 00327 { 00328 __ret = traits_type::to_int_type(*this->gptr()); 00329 this->gbump(1); 00330 } 00331 else 00332 __ret = this->uflow(); 00333 return __ret; 00334 } 00335 00336 /** 00337 * @brief Getting the next character. 00338 * @return The next character, or eof. 00339 * 00340 * If the input read position is available, returns that character, 00341 * otherwise calls and returns @c underflow(). Does not move the 00342 * read position after fetching the character. 00343 */ 00344 int_type 00345 sgetc() 00346 { 00347 int_type __ret; 00348 if (__builtin_expect(this->gptr() < this->egptr(), true)) 00349 __ret = traits_type::to_int_type(*this->gptr()); 00350 else 00351 __ret = this->underflow(); 00352 return __ret; 00353 } 00354 00355 /** 00356 * @brief Entry point for xsgetn. 00357 * @param __s A buffer area. 00358 * @param __n A count. 00359 * 00360 * Returns xsgetn(__s,__n). The effect is to fill @a __s[0] through 00361 * @a __s[__n-1] with characters from the input sequence, if possible. 00362 */ 00363 streamsize 00364 sgetn(char_type* __s, streamsize __n) 00365 { return this->xsgetn(__s, __n); } 00366 00367 // [27.5.2.2.4] putback 00368 /** 00369 * @brief Pushing characters back into the input stream. 00370 * @param __c The character to push back. 00371 * @return The previous character, if possible. 00372 * 00373 * Similar to sungetc(), but @a __c is pushed onto the stream 00374 * instead of <em>the previous character.</em> If successful, 00375 * the next character fetched from the input stream will be @a 00376 * __c. 00377 */ 00378 int_type 00379 sputbackc(char_type __c) 00380 { 00381 int_type __ret; 00382 const bool __testpos = this->eback() < this->gptr(); 00383 if (__builtin_expect(!__testpos || 00384 !traits_type::eq(__c, this->gptr()[-1]), false)) 00385 __ret = this->pbackfail(traits_type::to_int_type(__c)); 00386 else 00387 { 00388 this->gbump(-1); 00389 __ret = traits_type::to_int_type(*this->gptr()); 00390 } 00391 return __ret; 00392 } 00393 00394 /** 00395 * @brief Moving backwards in the input stream. 00396 * @return The previous character, if possible. 00397 * 00398 * If a putback position is available, this function decrements 00399 * the input pointer and returns that character. Otherwise, 00400 * calls and returns pbackfail(). The effect is to @a unget 00401 * the last character @a gotten. 00402 */ 00403 int_type 00404 sungetc() 00405 { 00406 int_type __ret; 00407 if (__builtin_expect(this->eback() < this->gptr(), true)) 00408 { 00409 this->gbump(-1); 00410 __ret = traits_type::to_int_type(*this->gptr()); 00411 } 00412 else 00413 __ret = this->pbackfail(); 00414 return __ret; 00415 } 00416 00417 // [27.5.2.2.5] put area 00418 /** 00419 * @brief Entry point for all single-character output functions. 00420 * @param __c A character to output. 00421 * @return @a __c, if possible. 00422 * 00423 * One of two public output functions. 00424 * 00425 * If a write position is available for the output sequence (i.e., 00426 * the buffer is not full), stores @a __c in that position, increments 00427 * the position, and returns @c traits::to_int_type(__c). If a write 00428 * position is not available, returns @c overflow(__c). 00429 */ 00430 int_type 00431 sputc(char_type __c) 00432 { 00433 int_type __ret; 00434 if (__builtin_expect(this->pptr() < this->epptr(), true)) 00435 { 00436 *this->pptr() = __c; 00437 this->pbump(1); 00438 __ret = traits_type::to_int_type(__c); 00439 } 00440 else 00441 __ret = this->overflow(traits_type::to_int_type(__c)); 00442 return __ret; 00443 } 00444 00445 /** 00446 * @brief Entry point for all single-character output functions. 00447 * @param __s A buffer read area. 00448 * @param __n A count. 00449 * 00450 * One of two public output functions. 00451 * 00452 * 00453 * Returns xsputn(__s,__n). The effect is to write @a __s[0] through 00454 * @a __s[__n-1] to the output sequence, if possible. 00455 */ 00456 streamsize 00457 sputn(const char_type* __s, streamsize __n) 00458 { return this->xsputn(__s, __n); } 00459 00460 protected: 00461 /** 00462 * @brief Base constructor. 00463 * 00464 * Only called from derived constructors, and sets up all the 00465 * buffer data to zero, including the pointers described in the 00466 * basic_streambuf class description. Note that, as a result, 00467 * - the class starts with no read nor write positions available, 00468 * - this is not an error 00469 */ 00470 basic_streambuf() 00471 : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 00472 _M_out_beg(0), _M_out_cur(0), _M_out_end(0), 00473 _M_buf_locale(locale()) 00474 { } 00475 00476 // [27.5.2.3.1] get area access 00477 //@{ 00478 /** 00479 * @brief Access to the get area. 00480 * 00481 * These functions are only available to other protected functions, 00482 * including derived classes. 00483 * 00484 * - eback() returns the beginning pointer for the input sequence 00485 * - gptr() returns the next pointer for the input sequence 00486 * - egptr() returns the end pointer for the input sequence 00487 */ 00488 char_type* 00489 eback() const { return _M_in_beg; } 00490 00491 char_type* 00492 gptr() const { return _M_in_cur; } 00493 00494 char_type* 00495 egptr() const { return _M_in_end; } 00496 //@} 00497 00498 /** 00499 * @brief Moving the read position. 00500 * @param __n The delta by which to move. 00501 * 00502 * This just advances the read position without returning any data. 00503 */ 00504 void 00505 gbump(int __n) { _M_in_cur += __n; } 00506 00507 /** 00508 * @brief Setting the three read area pointers. 00509 * @param __gbeg A pointer. 00510 * @param __gnext A pointer. 00511 * @param __gend A pointer. 00512 * @post @a __gbeg == @c eback(), @a __gnext == @c gptr(), and 00513 * @a __gend == @c egptr() 00514 */ 00515 void 00516 setg(char_type* __gbeg, char_type* __gnext, char_type* __gend) 00517 { 00518 _M_in_beg = __gbeg; 00519 _M_in_cur = __gnext; 00520 _M_in_end = __gend; 00521 } 00522 00523 // [27.5.2.3.2] put area access 00524 //@{ 00525 /** 00526 * @brief Access to the put area. 00527 * 00528 * These functions are only available to other protected functions, 00529 * including derived classes. 00530 * 00531 * - pbase() returns the beginning pointer for the output sequence 00532 * - pptr() returns the next pointer for the output sequence 00533 * - epptr() returns the end pointer for the output sequence 00534 */ 00535 char_type* 00536 pbase() const { return _M_out_beg; } 00537 00538 char_type* 00539 pptr() const { return _M_out_cur; } 00540 00541 char_type* 00542 epptr() const { return _M_out_end; } 00543 //@} 00544 00545 /** 00546 * @brief Moving the write position. 00547 * @param __n The delta by which to move. 00548 * 00549 * This just advances the write position without returning any data. 00550 */ 00551 void 00552 pbump(int __n) { _M_out_cur += __n; } 00553 00554 /** 00555 * @brief Setting the three write area pointers. 00556 * @param __pbeg A pointer. 00557 * @param __pend A pointer. 00558 * @post @a __pbeg == @c pbase(), @a __pbeg == @c pptr(), and 00559 * @a __pend == @c epptr() 00560 */ 00561 void 00562 setp(char_type* __pbeg, char_type* __pend) 00563 { 00564 _M_out_beg = _M_out_cur = __pbeg; 00565 _M_out_end = __pend; 00566 } 00567 00568 // [27.5.2.4] virtual functions 00569 // [27.5.2.4.1] locales 00570 /** 00571 * @brief Changes translations. 00572 * @param __loc A new locale. 00573 * 00574 * Translations done during I/O which depend on the current 00575 * locale are changed by this call. The standard adds, 00576 * <em>Between invocations of this function a class derived 00577 * from streambuf can safely cache results of calls to locale 00578 * functions and to members of facets so obtained.</em> 00579 * 00580 * @note Base class version does nothing. 00581 */ 00582 virtual void 00583 imbue(const locale& __loc _IsUnused) 00584 { } 00585 00586 // [27.5.2.4.2] buffer management and positioning 00587 /** 00588 * @brief Manipulates the buffer. 00589 * 00590 * Each derived class provides its own appropriate behavior. See 00591 * the next-to-last paragraph of 00592 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering 00593 * for more on this function. 00594 * 00595 * @note Base class version does nothing, returns @c this. 00596 */ 00597 virtual basic_streambuf<char_type,_Traits>* 00598 setbuf(char_type*, streamsize) 00599 { return this; } 00600 00601 /** 00602 * @brief Alters the stream positions. 00603 * 00604 * Each derived class provides its own appropriate behavior. 00605 * @note Base class version does nothing, returns a @c pos_type 00606 * that represents an invalid stream position. 00607 */ 00608 virtual pos_type 00609 seekoff(off_type, ios_base::seekdir, 00610 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) 00611 { return pos_type(off_type(-1)); } 00612 00613 /** 00614 * @brief Alters the stream positions. 00615 * 00616 * Each derived class provides its own appropriate behavior. 00617 * @note Base class version does nothing, returns a @c pos_type 00618 * that represents an invalid stream position. 00619 */ 00620 virtual pos_type 00621 seekpos(pos_type, 00622 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) 00623 { return pos_type(off_type(-1)); } 00624 00625 /** 00626 * @brief Synchronizes the buffer arrays with the controlled sequences. 00627 * @return -1 on failure. 00628 * 00629 * Each derived class provides its own appropriate behavior, 00630 * including the definition of @a failure. 00631 * @note Base class version does nothing, returns zero. 00632 */ 00633 virtual int 00634 sync() { return 0; } 00635 00636 // [27.5.2.4.3] get area 00637 /** 00638 * @brief Investigating the data available. 00639 * @return An estimate of the number of characters available in the 00640 * input sequence, or -1. 00641 * 00642 * <em>If it returns a positive value, then successive calls to 00643 * @c underflow() will not return @c traits::eof() until at 00644 * least that number of characters have been supplied. If @c 00645 * showmanyc() returns -1, then calls to @c underflow() or @c 00646 * uflow() will fail.</em> [27.5.2.4.3]/1 00647 * 00648 * @note Base class version does nothing, returns zero. 00649 * @note The standard adds that <em>the intention is not only that the 00650 * calls [to underflow or uflow] will not return @c eof() but 00651 * that they will return immediately.</em> 00652 * @note The standard adds that <em>the morphemes of @c showmanyc are 00653 * @b es-how-many-see, not @b show-manic.</em> 00654 */ 00655 virtual streamsize 00656 showmanyc() { return 0; } 00657 00658 /** 00659 * @brief Multiple character extraction. 00660 * @param __s A buffer area. 00661 * @param __n Maximum number of characters to assign. 00662 * @return The number of characters assigned. 00663 * 00664 * Fills @a __s[0] through @a __s[__n-1] with characters from the input 00665 * sequence, as if by @c sbumpc(). Stops when either @a __n characters 00666 * have been copied, or when @c traits::eof() would be copied. 00667 * 00668 * It is expected that derived classes provide a more efficient 00669 * implementation by overriding this definition. 00670 */ 00671 virtual streamsize 00672 xsgetn(char_type* __s, streamsize __n); 00673 00674 /** 00675 * @brief Fetches more data from the controlled sequence. 00676 * @return The first character from the <em>pending sequence</em>. 00677 * 00678 * Informally, this function is called when the input buffer is 00679 * exhausted (or does not exist, as buffering need not actually be 00680 * done). If a buffer exists, it is @a refilled. In either case, the 00681 * next available character is returned, or @c traits::eof() to 00682 * indicate a null pending sequence. 00683 * 00684 * For a formal definition of the pending sequence, see a good text 00685 * such as Langer & Kreft, or [27.5.2.4.3]/7-14. 00686 * 00687 * A functioning input streambuf can be created by overriding only 00688 * this function (no buffer area will be used). For an example, see 00689 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html 00690 * 00691 * @note Base class version does nothing, returns eof(). 00692 */ 00693 virtual int_type 00694 underflow() 00695 { return traits_type::eof(); } 00696 00697 /** 00698 * @brief Fetches more data from the controlled sequence. 00699 * @return The first character from the <em>pending sequence</em>. 00700 * 00701 * Informally, this function does the same thing as @c underflow(), 00702 * and in fact is required to call that function. It also returns 00703 * the new character, like @c underflow() does. However, this 00704 * function also moves the read position forward by one. 00705 */ 00706 virtual int_type 00707 uflow() 00708 { 00709 int_type __ret = traits_type::eof(); 00710 const bool __testeof = traits_type::eq_int_type(this->underflow(), 00711 __ret); 00712 if (!__testeof) 00713 { 00714 __ret = traits_type::to_int_type(*this->gptr()); 00715 this->gbump(1); 00716 } 00717 return __ret; 00718 } 00719 00720 // [27.5.2.4.4] putback 00721 /** 00722 * @brief Tries to back up the input sequence. 00723 * @param __c The character to be inserted back into the sequence. 00724 * @return eof() on failure, <em>some other value</em> on success 00725 * @post The constraints of @c gptr(), @c eback(), and @c pptr() 00726 * are the same as for @c underflow(). 00727 * 00728 * @note Base class version does nothing, returns eof(). 00729 */ 00730 virtual int_type 00731 pbackfail(int_type __c _IsUnused = traits_type::eof()) 00732 { return traits_type::eof(); } 00733 00734 // Put area: 00735 /** 00736 * @brief Multiple character insertion. 00737 * @param __s A buffer area. 00738 * @param __n Maximum number of characters to write. 00739 * @return The number of characters written. 00740 * 00741 * Writes @a __s[0] through @a __s[__n-1] to the output sequence, as if 00742 * by @c sputc(). Stops when either @a n characters have been 00743 * copied, or when @c sputc() would return @c traits::eof(). 00744 * 00745 * It is expected that derived classes provide a more efficient 00746 * implementation by overriding this definition. 00747 */ 00748 virtual streamsize 00749 xsputn(const char_type* __s, streamsize __n); 00750 00751 /** 00752 * @brief Consumes data from the buffer; writes to the 00753 * controlled sequence. 00754 * @param __c An additional character to consume. 00755 * @return eof() to indicate failure, something else (usually 00756 * @a __c, or not_eof()) 00757 * 00758 * Informally, this function is called when the output buffer 00759 * is full (or does not exist, as buffering need not actually 00760 * be done). If a buffer exists, it is @a consumed, with 00761 * <em>some effect</em> on the controlled sequence. 00762 * (Typically, the buffer is written out to the sequence 00763 * verbatim.) In either case, the character @a c is also 00764 * written out, if @a __c is not @c eof(). 00765 * 00766 * For a formal definition of this function, see a good text 00767 * such as Langer & Kreft, or [27.5.2.4.5]/3-7. 00768 * 00769 * A functioning output streambuf can be created by overriding only 00770 * this function (no buffer area will be used). 00771 * 00772 * @note Base class version does nothing, returns eof(). 00773 */ 00774 virtual int_type 00775 overflow(int_type __c _IsUnused = traits_type::eof()) 00776 { return traits_type::eof(); } 00777 00778 #if _GLIBCXX_USE_DEPRECATED && __cplusplus <= 201402L 00779 // Annex D.6 (removed in C++17) 00780 public: 00781 /** 00782 * @brief Tosses a character. 00783 * 00784 * Advances the read pointer, ignoring the character that would have 00785 * been read. 00786 * 00787 * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html 00788 */ 00789 #if __cplusplus >= 201103L 00790 [[__deprecated__("stossc is deprecated, use sbumpc instead")]] 00791 #endif 00792 void 00793 stossc() 00794 { 00795 if (this->gptr() < this->egptr()) 00796 this->gbump(1); 00797 else 00798 this->uflow(); 00799 } 00800 #endif 00801 00802 // Also used by specializations for char and wchar_t in src. 00803 void 00804 __safe_gbump(streamsize __n) { _M_in_cur += __n; } 00805 00806 void 00807 __safe_pbump(streamsize __n) { _M_out_cur += __n; } 00808 00809 #if __cplusplus < 201103L 00810 private: 00811 #else 00812 protected: 00813 #endif 00814 basic_streambuf(const basic_streambuf&); 00815 00816 basic_streambuf& 00817 operator=(const basic_streambuf&); 00818 00819 #if __cplusplus >= 201103L 00820 void 00821 swap(basic_streambuf& __sb) 00822 { 00823 std::swap(_M_in_beg, __sb._M_in_beg); 00824 std::swap(_M_in_cur, __sb._M_in_cur); 00825 std::swap(_M_in_end, __sb._M_in_end); 00826 std::swap(_M_out_beg, __sb._M_out_beg); 00827 std::swap(_M_out_cur, __sb._M_out_cur); 00828 std::swap(_M_out_end, __sb._M_out_end); 00829 std::swap(_M_buf_locale, __sb._M_buf_locale); 00830 } 00831 #endif 00832 }; 00833 00834 #if __cplusplus >= 201103L 00835 template<typename _CharT, typename _Traits> 00836 std::basic_streambuf<_CharT, _Traits>:: 00837 basic_streambuf(const basic_streambuf&) = default; 00838 00839 template<typename _CharT, typename _Traits> 00840 std::basic_streambuf<_CharT, _Traits>& 00841 std::basic_streambuf<_CharT, _Traits>:: 00842 operator=(const basic_streambuf&) = default; 00843 #endif 00844 00845 // Explicit specialization declarations, defined in src/streambuf.cc. 00846 template<> 00847 streamsize 00848 __copy_streambufs_eof(basic_streambuf<char>* __sbin, 00849 basic_streambuf<char>* __sbout, bool& __ineof); 00850 #ifdef _GLIBCXX_USE_WCHAR_T 00851 template<> 00852 streamsize 00853 __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin, 00854 basic_streambuf<wchar_t>* __sbout, bool& __ineof); 00855 #endif 00856 00857 #undef _IsUnused 00858 00859 _GLIBCXX_END_NAMESPACE_VERSION 00860 } // namespace 00861 00862 #include <bits/streambuf.tcc> 00863 00864 #endif /* _GLIBCXX_STREAMBUF */