00001 // Stream buffer classes -*- C++ -*- 00002 00003 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 00004 // 2006, 2007, 2008, 2009 Free Software Foundation, Inc. 00005 // 00006 // This file is part of the GNU ISO C++ Library. This library is free 00007 // software; you can redistribute it and/or modify it under the 00008 // terms of the GNU General Public License as published by the 00009 // Free Software Foundation; either version 3, or (at your option) 00010 // any later version. 00011 00012 // This library is distributed in the hope that it will be useful, 00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00015 // GNU General Public License for more details. 00016 00017 // Under Section 7 of GPL version 3, you are granted additional 00018 // permissions described in the GCC Runtime Library Exception, version 00019 // 3.1, as published by the Free Software Foundation. 00020 00021 // You should have received a copy of the GNU General Public License and 00022 // a copy of the GCC Runtime Library Exception along with this program; 00023 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00024 // <http://www.gnu.org/licenses/>. 00025 00026 /** @file streambuf 00027 * This is a Standard C++ Library header. 00028 */ 00029 00030 // 00031 // ISO C++ 14882: 27.5 Stream buffers 00032 // 00033 00034 #ifndef _GLIBXX_STREAMBUF 00035 #define _GLIBXX_STREAMBUF 1 00036 00037 #pragma GCC system_header 00038 00039 #include <bits/c++config.h> 00040 #include <iosfwd> 00041 #include <bits/localefwd.h> 00042 #include <bits/ios_base.h> 00043 #include <bits/cpp_type_traits.h> 00044 #include <ext/type_traits.h> 00045 00046 _GLIBCXX_BEGIN_NAMESPACE(std) 00047 00048 template<typename _CharT, typename _Traits> 00049 streamsize 00050 __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*, 00051 basic_streambuf<_CharT, _Traits>*, bool&); 00052 00053 /** 00054 * @brief The actual work of input and output (interface). 00055 * 00056 * This is a base class. Derived stream buffers each control a 00057 * pair of character sequences: one for input, and one for output. 00058 * 00059 * Section [27.5.1] of the standard describes the requirements and 00060 * behavior of stream buffer classes. That section (three paragraphs) 00061 * is reproduced here, for simplicity and accuracy. 00062 * 00063 * -# Stream buffers can impose various constraints on the sequences 00064 * they control. Some constraints are: 00065 * - The controlled input sequence can be not readable. 00066 * - The controlled output sequence can be not writable. 00067 * - The controlled sequences can be associated with the contents of 00068 * other representations for character sequences, such as external 00069 * files. 00070 * - The controlled sequences can support operations @e directly to or 00071 * from associated sequences. 00072 * - The controlled sequences can impose limitations on how the 00073 * program can read characters from a sequence, write characters to 00074 * a sequence, put characters back into an input sequence, or alter 00075 * the stream position. 00076 * . 00077 * -# Each sequence is characterized by three pointers which, if non-null, 00078 * all point into the same @c charT array object. The array object 00079 * represents, at any moment, a (sub)sequence of characters from the 00080 * sequence. Operations performed on a sequence alter the values 00081 * stored in these pointers, perform reads and writes directly to or 00082 * from associated sequences, and alter "the stream position" and 00083 * conversion state as needed to maintain this subsequence relationship. 00084 * The three pointers are: 00085 * - the <em>beginning pointer</em>, or lowest element address in the 00086 * array (called @e xbeg here); 00087 * - the <em>next pointer</em>, or next element address that is a 00088 * current candidate for reading or writing (called @e xnext here); 00089 * - the <em>end pointer</em>, or first element address beyond the 00090 * end of the array (called @e xend here). 00091 * . 00092 * -# The following semantic constraints shall always apply for any set 00093 * of three pointers for a sequence, using the pointer names given 00094 * immediately above: 00095 * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall 00096 * also be non-null pointers into the same @c charT array, as 00097 * described above; otherwise, @e xbeg and @e xend shall also be null. 00098 * - If @e xnext is not a null pointer and @e xnext < @e xend for an 00099 * output sequence, then a <em>write position</em> is available. 00100 * In this case, @e *xnext shall be assignable as the next element 00101 * to write (to put, or to store a character value, into the sequence). 00102 * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an 00103 * input sequence, then a <em>putback position</em> is available. 00104 * In this case, @e xnext[-1] shall have a defined value and is the 00105 * next (preceding) element to store a character that is put back 00106 * into the input sequence. 00107 * - If @e xnext is not a null pointer and @e xnext< @e xend for an 00108 * input sequence, then a <em>read position</em> is available. 00109 * In this case, @e *xnext shall have a defined value and is the 00110 * next element to read (to get, or to obtain a character value, 00111 * from the sequence). 00112 */ 00113 template<typename _CharT, typename _Traits> 00114 class basic_streambuf 00115 { 00116 public: 00117 //@{ 00118 /** 00119 * These are standard types. They permit a standardized way of 00120 * referring to names of (or names dependant on) the template 00121 * parameters, which are specific to the implementation. 00122 */ 00123 typedef _CharT char_type; 00124 typedef _Traits traits_type; 00125 typedef typename traits_type::int_type int_type; 00126 typedef typename traits_type::pos_type pos_type; 00127 typedef typename traits_type::off_type off_type; 00128 //@} 00129 00130 //@{ 00131 /// This is a non-standard type. 00132 typedef basic_streambuf<char_type, traits_type> __streambuf_type; 00133 //@} 00134 00135 friend class basic_ios<char_type, traits_type>; 00136 friend class basic_istream<char_type, traits_type>; 00137 friend class basic_ostream<char_type, traits_type>; 00138 friend class istreambuf_iterator<char_type, traits_type>; 00139 friend class ostreambuf_iterator<char_type, traits_type>; 00140 00141 friend streamsize 00142 __copy_streambufs_eof<>(__streambuf_type*, __streambuf_type*, bool&); 00143 00144 template<bool _IsMove, typename _CharT2> 00145 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 00146 _CharT2*>::__type 00147 __copy_move_a2(istreambuf_iterator<_CharT2>, 00148 istreambuf_iterator<_CharT2>, _CharT2*); 00149 00150 template<typename _CharT2> 00151 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 00152 istreambuf_iterator<_CharT2> >::__type 00153 find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>, 00154 const _CharT2&); 00155 00156 template<typename _CharT2, typename _Traits2> 00157 friend basic_istream<_CharT2, _Traits2>& 00158 operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*); 00159 00160 template<typename _CharT2, typename _Traits2, typename _Alloc> 00161 friend basic_istream<_CharT2, _Traits2>& 00162 operator>>(basic_istream<_CharT2, _Traits2>&, 00163 basic_string<_CharT2, _Traits2, _Alloc>&); 00164 00165 template<typename _CharT2, typename _Traits2, typename _Alloc> 00166 friend basic_istream<_CharT2, _Traits2>& 00167 getline(basic_istream<_CharT2, _Traits2>&, 00168 basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2); 00169 00170 protected: 00171 //@{ 00172 /** 00173 * This is based on _IO_FILE, just reordered to be more consistent, 00174 * and is intended to be the most minimal abstraction for an 00175 * internal buffer. 00176 * - get == input == read 00177 * - put == output == write 00178 */ 00179 char_type* _M_in_beg; // Start of get area. 00180 char_type* _M_in_cur; // Current read area. 00181 char_type* _M_in_end; // End of get area. 00182 char_type* _M_out_beg; // Start of put area. 00183 char_type* _M_out_cur; // Current put area. 00184 char_type* _M_out_end; // End of put area. 00185 00186 /// Current locale setting. 00187 locale _M_buf_locale; 00188 00189 public: 00190 /// Destructor deallocates no buffer space. 00191 virtual 00192 ~basic_streambuf() 00193 { } 00194 00195 // [27.5.2.2.1] locales 00196 /** 00197 * @brief Entry point for imbue(). 00198 * @param loc The new locale. 00199 * @return The previous locale. 00200 * 00201 * Calls the derived imbue(loc). 00202 */ 00203 locale 00204 pubimbue(const locale &__loc) 00205 { 00206 locale __tmp(this->getloc()); 00207 this->imbue(__loc); 00208 _M_buf_locale = __loc; 00209 return __tmp; 00210 } 00211 00212 /** 00213 * @brief Locale access. 00214 * @return The current locale in effect. 00215 * 00216 * If pubimbue(loc) has been called, then the most recent @c loc 00217 * is returned. Otherwise the global locale in effect at the time 00218 * of construction is returned. 00219 */ 00220 locale 00221 getloc() const 00222 { return _M_buf_locale; } 00223 00224 // [27.5.2.2.2] buffer management and positioning 00225 //@{ 00226 /** 00227 * @brief Entry points for derived buffer functions. 00228 * 00229 * The public versions of @c pubfoo dispatch to the protected 00230 * derived @c foo member functions, passing the arguments (if any) 00231 * and returning the result unchanged. 00232 */ 00233 __streambuf_type* 00234 pubsetbuf(char_type* __s, streamsize __n) 00235 { return this->setbuf(__s, __n); } 00236 00237 pos_type 00238 pubseekoff(off_type __off, ios_base::seekdir __way, 00239 ios_base::openmode __mode = ios_base::in | ios_base::out) 00240 { return this->seekoff(__off, __way, __mode); } 00241 00242 pos_type 00243 pubseekpos(pos_type __sp, 00244 ios_base::openmode __mode = ios_base::in | ios_base::out) 00245 { return this->seekpos(__sp, __mode); } 00246 00247 int 00248 pubsync() { return this->sync(); } 00249 //@} 00250 00251 // [27.5.2.2.3] get area 00252 /** 00253 * @brief Looking ahead into the stream. 00254 * @return The number of characters available. 00255 * 00256 * If a read position is available, returns the number of characters 00257 * available for reading before the buffer must be refilled. 00258 * Otherwise returns the derived @c showmanyc(). 00259 */ 00260 streamsize 00261 in_avail() 00262 { 00263 const streamsize __ret = this->egptr() - this->gptr(); 00264 return __ret ? __ret : this->showmanyc(); 00265 } 00266 00267 /** 00268 * @brief Getting the next character. 00269 * @return The next character, or eof. 00270 * 00271 * Calls @c sbumpc(), and if that function returns 00272 * @c traits::eof(), so does this function. Otherwise, @c sgetc(). 00273 */ 00274 int_type 00275 snextc() 00276 { 00277 int_type __ret = traits_type::eof(); 00278 if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 00279 __ret), true)) 00280 __ret = this->sgetc(); 00281 return __ret; 00282 } 00283 00284 /** 00285 * @brief Getting the next character. 00286 * @return The next character, or eof. 00287 * 00288 * If the input read position is available, returns that character 00289 * and increments the read pointer, otherwise calls and returns 00290 * @c uflow(). 00291 */ 00292 int_type 00293 sbumpc() 00294 { 00295 int_type __ret; 00296 if (__builtin_expect(this->gptr() < this->egptr(), true)) 00297 { 00298 __ret = traits_type::to_int_type(*this->gptr()); 00299 this->gbump(1); 00300 } 00301 else 00302 __ret = this->uflow(); 00303 return __ret; 00304 } 00305 00306 /** 00307 * @brief Getting the next character. 00308 * @return The next character, or eof. 00309 * 00310 * If the input read position is available, returns that character, 00311 * otherwise calls and returns @c underflow(). Does not move the 00312 * read position after fetching the character. 00313 */ 00314 int_type 00315 sgetc() 00316 { 00317 int_type __ret; 00318 if (__builtin_expect(this->gptr() < this->egptr(), true)) 00319 __ret = traits_type::to_int_type(*this->gptr()); 00320 else 00321 __ret = this->underflow(); 00322 return __ret; 00323 } 00324 00325 /** 00326 * @brief Entry point for xsgetn. 00327 * @param s A buffer area. 00328 * @param n A count. 00329 * 00330 * Returns xsgetn(s,n). The effect is to fill @a s[0] through 00331 * @a s[n-1] with characters from the input sequence, if possible. 00332 */ 00333 streamsize 00334 sgetn(char_type* __s, streamsize __n) 00335 { return this->xsgetn(__s, __n); } 00336 00337 // [27.5.2.2.4] putback 00338 /** 00339 * @brief Pushing characters back into the input stream. 00340 * @param c The character to push back. 00341 * @return The previous character, if possible. 00342 * 00343 * Similar to sungetc(), but @a c is pushed onto the stream instead 00344 * of "the previous character". If successful, the next character 00345 * fetched from the input stream will be @a c. 00346 */ 00347 int_type 00348 sputbackc(char_type __c) 00349 { 00350 int_type __ret; 00351 const bool __testpos = this->eback() < this->gptr(); 00352 if (__builtin_expect(!__testpos || 00353 !traits_type::eq(__c, this->gptr()[-1]), false)) 00354 __ret = this->pbackfail(traits_type::to_int_type(__c)); 00355 else 00356 { 00357 this->gbump(-1); 00358 __ret = traits_type::to_int_type(*this->gptr()); 00359 } 00360 return __ret; 00361 } 00362 00363 /** 00364 * @brief Moving backwards in the input stream. 00365 * @return The previous character, if possible. 00366 * 00367 * If a putback position is available, this function decrements the 00368 * input pointer and returns that character. Otherwise, calls and 00369 * returns pbackfail(). The effect is to "unget" the last character 00370 * "gotten". 00371 */ 00372 int_type 00373 sungetc() 00374 { 00375 int_type __ret; 00376 if (__builtin_expect(this->eback() < this->gptr(), true)) 00377 { 00378 this->gbump(-1); 00379 __ret = traits_type::to_int_type(*this->gptr()); 00380 } 00381 else 00382 __ret = this->pbackfail(); 00383 return __ret; 00384 } 00385 00386 // [27.5.2.2.5] put area 00387 /** 00388 * @brief Entry point for all single-character output functions. 00389 * @param c A character to output. 00390 * @return @a c, if possible. 00391 * 00392 * One of two public output functions. 00393 * 00394 * If a write position is available for the output sequence (i.e., 00395 * the buffer is not full), stores @a c in that position, increments 00396 * the position, and returns @c traits::to_int_type(c). If a write 00397 * position is not available, returns @c overflow(c). 00398 */ 00399 int_type 00400 sputc(char_type __c) 00401 { 00402 int_type __ret; 00403 if (__builtin_expect(this->pptr() < this->epptr(), true)) 00404 { 00405 *this->pptr() = __c; 00406 this->pbump(1); 00407 __ret = traits_type::to_int_type(__c); 00408 } 00409 else 00410 __ret = this->overflow(traits_type::to_int_type(__c)); 00411 return __ret; 00412 } 00413 00414 /** 00415 * @brief Entry point for all single-character output functions. 00416 * @param s A buffer read area. 00417 * @param n A count. 00418 * 00419 * One of two public output functions. 00420 * 00421 * 00422 * Returns xsputn(s,n). The effect is to write @a s[0] through 00423 * @a s[n-1] to the output sequence, if possible. 00424 */ 00425 streamsize 00426 sputn(const char_type* __s, streamsize __n) 00427 { return this->xsputn(__s, __n); } 00428 00429 protected: 00430 /** 00431 * @brief Base constructor. 00432 * 00433 * Only called from derived constructors, and sets up all the 00434 * buffer data to zero, including the pointers described in the 00435 * basic_streambuf class description. Note that, as a result, 00436 * - the class starts with no read nor write positions available, 00437 * - this is not an error 00438 */ 00439 basic_streambuf() 00440 : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 00441 _M_out_beg(0), _M_out_cur(0), _M_out_end(0), 00442 _M_buf_locale(locale()) 00443 { } 00444 00445 // [27.5.2.3.1] get area access 00446 //@{ 00447 /** 00448 * @brief Access to the get area. 00449 * 00450 * These functions are only available to other protected functions, 00451 * including derived classes. 00452 * 00453 * - eback() returns the beginning pointer for the input sequence 00454 * - gptr() returns the next pointer for the input sequence 00455 * - egptr() returns the end pointer for the input sequence 00456 */ 00457 char_type* 00458 eback() const { return _M_in_beg; } 00459 00460 char_type* 00461 gptr() const { return _M_in_cur; } 00462 00463 char_type* 00464 egptr() const { return _M_in_end; } 00465 //@} 00466 00467 /** 00468 * @brief Moving the read position. 00469 * @param n The delta by which to move. 00470 * 00471 * This just advances the read position without returning any data. 00472 */ 00473 void 00474 gbump(int __n) { _M_in_cur += __n; } 00475 00476 /** 00477 * @brief Setting the three read area pointers. 00478 * @param gbeg A pointer. 00479 * @param gnext A pointer. 00480 * @param gend A pointer. 00481 * @post @a gbeg == @c eback(), @a gnext == @c gptr(), and 00482 * @a gend == @c egptr() 00483 */ 00484 void 00485 setg(char_type* __gbeg, char_type* __gnext, char_type* __gend) 00486 { 00487 _M_in_beg = __gbeg; 00488 _M_in_cur = __gnext; 00489 _M_in_end = __gend; 00490 } 00491 00492 // [27.5.2.3.2] put area access 00493 //@{ 00494 /** 00495 * @brief Access to the put area. 00496 * 00497 * These functions are only available to other protected functions, 00498 * including derived classes. 00499 * 00500 * - pbase() returns the beginning pointer for the output sequence 00501 * - pptr() returns the next pointer for the output sequence 00502 * - epptr() returns the end pointer for the output sequence 00503 */ 00504 char_type* 00505 pbase() const { return _M_out_beg; } 00506 00507 char_type* 00508 pptr() const { return _M_out_cur; } 00509 00510 char_type* 00511 epptr() const { return _M_out_end; } 00512 //@} 00513 00514 /** 00515 * @brief Moving the write position. 00516 * @param n The delta by which to move. 00517 * 00518 * This just advances the write position without returning any data. 00519 */ 00520 void 00521 pbump(int __n) { _M_out_cur += __n; } 00522 00523 /** 00524 * @brief Setting the three write area pointers. 00525 * @param pbeg A pointer. 00526 * @param pend A pointer. 00527 * @post @a pbeg == @c pbase(), @a pbeg == @c pptr(), and 00528 * @a pend == @c epptr() 00529 */ 00530 void 00531 setp(char_type* __pbeg, char_type* __pend) 00532 { 00533 _M_out_beg = _M_out_cur = __pbeg; 00534 _M_out_end = __pend; 00535 } 00536 00537 // [27.5.2.4] virtual functions 00538 // [27.5.2.4.1] locales 00539 /** 00540 * @brief Changes translations. 00541 * @param loc A new locale. 00542 * 00543 * Translations done during I/O which depend on the current locale 00544 * are changed by this call. The standard adds, "Between invocations 00545 * of this function a class derived from streambuf can safely cache 00546 * results of calls to locale functions and to members of facets 00547 * so obtained." 00548 * 00549 * @note Base class version does nothing. 00550 */ 00551 virtual void 00552 imbue(const locale&) 00553 { } 00554 00555 // [27.5.2.4.2] buffer management and positioning 00556 /** 00557 * @brief Manipulates the buffer. 00558 * 00559 * Each derived class provides its own appropriate behavior. See 00560 * the next-to-last paragraph of 00561 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html 00562 * for more on this function. 00563 * 00564 * @note Base class version does nothing, returns @c this. 00565 */ 00566 virtual basic_streambuf<char_type,_Traits>* 00567 setbuf(char_type*, streamsize) 00568 { return this; } 00569 00570 /** 00571 * @brief Alters the stream positions. 00572 * 00573 * Each derived class provides its own appropriate behavior. 00574 * @note Base class version does nothing, returns a @c pos_type 00575 * that represents an invalid stream position. 00576 */ 00577 virtual pos_type 00578 seekoff(off_type, ios_base::seekdir, 00579 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) 00580 { return pos_type(off_type(-1)); } 00581 00582 /** 00583 * @brief Alters the stream positions. 00584 * 00585 * Each derived class provides its own appropriate behavior. 00586 * @note Base class version does nothing, returns a @c pos_type 00587 * that represents an invalid stream position. 00588 */ 00589 virtual pos_type 00590 seekpos(pos_type, 00591 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) 00592 { return pos_type(off_type(-1)); } 00593 00594 /** 00595 * @brief Synchronizes the buffer arrays with the controlled sequences. 00596 * @return -1 on failure. 00597 * 00598 * Each derived class provides its own appropriate behavior, 00599 * including the definition of "failure". 00600 * @note Base class version does nothing, returns zero. 00601 */ 00602 virtual int 00603 sync() { return 0; } 00604 00605 // [27.5.2.4.3] get area 00606 /** 00607 * @brief Investigating the data available. 00608 * @return An estimate of the number of characters available in the 00609 * input sequence, or -1. 00610 * 00611 * "If it returns a positive value, then successive calls to 00612 * @c underflow() will not return @c traits::eof() until at least that 00613 * number of characters have been supplied. If @c showmanyc() 00614 * returns -1, then calls to @c underflow() or @c uflow() will fail." 00615 * [27.5.2.4.3]/1 00616 * 00617 * @note Base class version does nothing, returns zero. 00618 * @note The standard adds that "the intention is not only that the 00619 * calls [to underflow or uflow] will not return @c eof() but 00620 * that they will return "immediately". 00621 * @note The standard adds that "the morphemes of @c showmanyc are 00622 * "es-how-many-see", not "show-manic". 00623 */ 00624 virtual streamsize 00625 showmanyc() { return 0; } 00626 00627 /** 00628 * @brief Multiple character extraction. 00629 * @param s A buffer area. 00630 * @param n Maximum number of characters to assign. 00631 * @return The number of characters assigned. 00632 * 00633 * Fills @a s[0] through @a s[n-1] with characters from the input 00634 * sequence, as if by @c sbumpc(). Stops when either @a n characters 00635 * have been copied, or when @c traits::eof() would be copied. 00636 * 00637 * It is expected that derived classes provide a more efficient 00638 * implementation by overriding this definition. 00639 */ 00640 virtual streamsize 00641 xsgetn(char_type* __s, streamsize __n); 00642 00643 /** 00644 * @brief Fetches more data from the controlled sequence. 00645 * @return The first character from the <em>pending sequence</em>. 00646 * 00647 * Informally, this function is called when the input buffer is 00648 * exhausted (or does not exist, as buffering need not actually be 00649 * done). If a buffer exists, it is "refilled". In either case, the 00650 * next available character is returned, or @c traits::eof() to 00651 * indicate a null pending sequence. 00652 * 00653 * For a formal definition of the pending sequence, see a good text 00654 * such as Langer & Kreft, or [27.5.2.4.3]/7-14. 00655 * 00656 * A functioning input streambuf can be created by overriding only 00657 * this function (no buffer area will be used). For an example, see 00658 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.html 00659 * 00660 * @note Base class version does nothing, returns eof(). 00661 */ 00662 virtual int_type 00663 underflow() 00664 { return traits_type::eof(); } 00665 00666 /** 00667 * @brief Fetches more data from the controlled sequence. 00668 * @return The first character from the <em>pending sequence</em>. 00669 * 00670 * Informally, this function does the same thing as @c underflow(), 00671 * and in fact is required to call that function. It also returns 00672 * the new character, like @c underflow() does. However, this 00673 * function also moves the read position forward by one. 00674 */ 00675 virtual int_type 00676 uflow() 00677 { 00678 int_type __ret = traits_type::eof(); 00679 const bool __testeof = traits_type::eq_int_type(this->underflow(), 00680 __ret); 00681 if (!__testeof) 00682 { 00683 __ret = traits_type::to_int_type(*this->gptr()); 00684 this->gbump(1); 00685 } 00686 return __ret; 00687 } 00688 00689 // [27.5.2.4.4] putback 00690 /** 00691 * @brief Tries to back up the input sequence. 00692 * @param c The character to be inserted back into the sequence. 00693 * @return eof() on failure, "some other value" on success 00694 * @post The constraints of @c gptr(), @c eback(), and @c pptr() 00695 * are the same as for @c underflow(). 00696 * 00697 * @note Base class version does nothing, returns eof(). 00698 */ 00699 virtual int_type 00700 pbackfail(int_type /* __c */ = traits_type::eof()) 00701 { return traits_type::eof(); } 00702 00703 // Put area: 00704 /** 00705 * @brief Multiple character insertion. 00706 * @param s A buffer area. 00707 * @param n Maximum number of characters to write. 00708 * @return The number of characters written. 00709 * 00710 * Writes @a s[0] through @a s[n-1] to the output sequence, as if 00711 * by @c sputc(). Stops when either @a n characters have been 00712 * copied, or when @c sputc() would return @c traits::eof(). 00713 * 00714 * It is expected that derived classes provide a more efficient 00715 * implementation by overriding this definition. 00716 */ 00717 virtual streamsize 00718 xsputn(const char_type* __s, streamsize __n); 00719 00720 /** 00721 * @brief Consumes data from the buffer; writes to the 00722 * controlled sequence. 00723 * @param c An additional character to consume. 00724 * @return eof() to indicate failure, something else (usually 00725 * @a c, or not_eof()) 00726 * 00727 * Informally, this function is called when the output buffer is full 00728 * (or does not exist, as buffering need not actually be done). If a 00729 * buffer exists, it is "consumed", with "some effect" on the 00730 * controlled sequence. (Typically, the buffer is written out to the 00731 * sequence verbatim.) In either case, the character @a c is also 00732 * written out, if @a c is not @c eof(). 00733 * 00734 * For a formal definition of this function, see a good text 00735 * such as Langer & Kreft, or [27.5.2.4.5]/3-7. 00736 * 00737 * A functioning output streambuf can be created by overriding only 00738 * this function (no buffer area will be used). 00739 * 00740 * @note Base class version does nothing, returns eof(). 00741 */ 00742 virtual int_type 00743 overflow(int_type /* __c */ = traits_type::eof()) 00744 { return traits_type::eof(); } 00745 00746 #if _GLIBCXX_DEPRECATED 00747 // Annex D.6 00748 public: 00749 /** 00750 * @brief Tosses a character. 00751 * 00752 * Advances the read pointer, ignoring the character that would have 00753 * been read. 00754 * 00755 * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html 00756 */ 00757 void 00758 stossc() 00759 { 00760 if (this->gptr() < this->egptr()) 00761 this->gbump(1); 00762 else 00763 this->uflow(); 00764 } 00765 #endif 00766 00767 private: 00768 // _GLIBCXX_RESOLVE_LIB_DEFECTS 00769 // Side effect of DR 50. 00770 basic_streambuf(const __streambuf_type& __sb) 00771 : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur), 00772 _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg), 00773 _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur), 00774 _M_buf_locale(__sb._M_buf_locale) 00775 { } 00776 00777 __streambuf_type& 00778 operator=(const __streambuf_type&) { return *this; }; 00779 }; 00780 00781 // Explicit specialization declarations, defined in src/streambuf.cc. 00782 template<> 00783 streamsize 00784 __copy_streambufs_eof(basic_streambuf<char>* __sbin, 00785 basic_streambuf<char>* __sbout, bool& __ineof); 00786 #ifdef _GLIBCXX_USE_WCHAR_T 00787 template<> 00788 streamsize 00789 __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin, 00790 basic_streambuf<wchar_t>* __sbout, bool& __ineof); 00791 #endif 00792 00793 _GLIBCXX_END_NAMESPACE 00794 00795 #ifndef _GLIBCXX_EXPORT_TEMPLATE 00796 # include <bits/streambuf.tcc> 00797 #endif 00798 00799 #endif /* _GLIBCXX_STREAMBUF */