1 // Stream buffer classes -*- C++ -*- 2 3 // Copyright (C) 1997-2013 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 * 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 */ 831
