libstdc++-v3/include/std/istream

   1 // Input streams -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   4 // 2006, 2007, 2008, 2009, 2010, 2011, 2012
   5 // Free Software Foundation, Inc.
   6 //
   7 // This file is part of the GNU ISO C++ Library.  This library is free
   8 // software; you can redistribute it and/or modify it under the
   9 // terms of the GNU General Public License as published by the
  10 // Free Software Foundation; either version 3, or (at your option)
  11 // any later version.
  12
  13 // This library is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // Under Section 7 of GPL version 3, you are granted additional
  19 // permissions described in the GCC Runtime Library Exception, version
  20 // 3.1, as published by the Free Software Foundation.
  21
  22 // You should have received a copy of the GNU General Public License and
  23 // a copy of the GCC Runtime Library Exception along with this program;
  24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 // <http://www.gnu.org/licenses/>.
  26
  27 //
  28 // ISO C++ 14882: 27.6.1  Input streams
  29 //
  30
  31 /** @file include/istream
  32  *  This is a Standard C++ Library header.
  33  */
  34
  35 #ifndef _GLIBCXX_ISTREAM
  36 #define _GLIBCXX_ISTREAM 1
  37
  38 #pragma GCC system_header
  39
  40 #include <ios>
  41 #include <ostream>
  42
  43 namespace std _GLIBCXX_VISIBILITY(default)
  44 {
  45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  46
  47   /**
  48    *  @brief  Template class basic_istream.
  49    *  @ingroup io
  50    *
  51    *  @tparam _CharT  Type of character stream.
  52    *  @tparam _Traits  Traits for character type, defaults to
  53    *                   char_traits<_CharT>.
  54    *
  55    *  This is the base class for all input streams.  It provides text
  56    *  formatting of all builtin types, and communicates with any class
  57    *  derived from basic_streambuf to do the actual input.
  58   */
  59   template<typename _CharT, typename _Traits>
  60     class basic_istream : virtual public basic_ios<_CharT, _Traits>
  61     {
  62     public:
  63       // Types (inherited from basic_ios (27.4.4)):
  64       typedef _CharT                                    char_type;
  65       typedef typename _Traits::int_type                int_type;
  66       typedef typename _Traits::pos_type                pos_type;
  67       typedef typename _Traits::off_type                off_type;
  68       typedef _Traits                                   traits_type;
  69
  70       // Non-standard Types:
  71       typedef basic_streambuf<_CharT, _Traits>          __streambuf_type;
  72       typedef basic_ios<_CharT, _Traits>                __ios_type;
  73       typedef basic_istream<_CharT, _Traits>            __istream_type;
  74       typedef num_get<_CharT, istreambuf_iterator<_CharT, _Traits> >
  75                                                         __num_get_type;
  76       typedef ctype<_CharT>                             __ctype_type;
  77
  78     protected:
  79       // Data Members:
  80       /**
  81        *  The number of characters extracted in the previous unformatted
  82        *  function; see gcount().
  83       */
  84       streamsize                _M_gcount;
  85
  86     public:
  87       /**
  88        *  @brief  Base constructor.
  89        *
  90        *  This ctor is almost never called by the user directly, rather from
  91        *  derived classes' initialization lists, which pass a pointer to
  92        *  their own stream buffer.
  93       */
  94       explicit
  95       basic_istream(__streambuf_type* __sb)
  96       : _M_gcount(streamsize(0))
  97       { this->init(__sb); }
  98
  99       /**
 100        *  @brief  Base destructor.
 101        *
 102        *  This does very little apart from providing a virtual base dtor.
 103       */
 104       virtual
 105       ~basic_istream()
 106       { _M_gcount = streamsize(0); }
 107
 108       /// Safe prefix/suffix operations.
 109       class sentry;
 110       friend class sentry;
 111
 112       //@{
 113       /**
 114        *  @brief  Interface for manipulators.
 115        *
 116        *  Manipulators such as @c std::ws and @c std::dec use these
 117        *  functions in constructs like
 118        *  <code>std::cin >> std::ws</code>.
 119        *  For more information, see the iomanip header.
 120       */
 121       __istream_type&
 122       operator>>(__istream_type& (*__pf)(__istream_type&))
 123       { return __pf(*this); }
 124
 125       __istream_type&
 126       operator>>(__ios_type& (*__pf)(__ios_type&))
 127       {
 128         __pf(*this);
 129         return *this;
 130       }
 131
 132       __istream_type&
 133       operator>>(ios_base& (*__pf)(ios_base&))
 134       {
 135         __pf(*this);
 136         return *this;
 137       }
 138       //@}
 139
 140       //@{
 141       /**
 142        *  @name Extractors
 143        *
 144        *  All the @c operator>> functions (aka <em>formatted input
 145        *  functions</em>) have some common behavior.  Each starts by
 146        *  constructing a temporary object of type std::basic_istream::sentry
 147        *  with the second argument (noskipws) set to false.  This has several
 148        *  effects, concluding with the setting of a status flag; see the
 149        *  sentry documentation for more.
 150        *
 151        *  If the sentry status is good, the function tries to extract
 152        *  whatever data is appropriate for the type of the argument.
 153        *
 154        *  If an exception is thrown during extraction, ios_base::badbit
 155        *  will be turned on in the stream's error state without causing an
 156        *  ios_base::failure to be thrown.  The original exception will then
 157        *  be rethrown.
 158       */
 159
 160       //@{
 161       /**
 162        *  @brief  Integer arithmetic extractors
 163        *  @param  __n A variable of builtin integral type.
 164        *  @return  @c *this if successful
 165        *
 166        *  These functions use the stream's current locale (specifically, the
 167        *  @c num_get facet) to parse the input data.
 168       */
 169       __istream_type&
 170       operator>>(bool& __n)
 171       { return _M_extract(__n); }
 172
 173       __istream_type&
 174       operator>>(short& __n);
 175
 176       __istream_type&
 177       operator>>(unsigned short& __n)
 178       { return _M_extract(__n); }
 179
 180       __istream_type&
 181       operator>>(int& __n);
 182
 183       __istream_type&
 184       operator>>(unsigned int& __n)
 185       { return _M_extract(__n); }
 186
 187       __istream_type&
 188       operator>>(long& __n)
 189       { return _M_extract(__n); }
 190
 191       __istream_type&
 192       operator>>(unsigned long& __n)
 193       { return _M_extract(__n); }
 194
 195 #ifdef _GLIBCXX_USE_LONG_LONG
 196       __istream_type&
 197       operator>>(long long& __n)
 198       { return _M_extract(__n); }
 199
 200       __istream_type&
 201       operator>>(unsigned long long& __n)
 202       { return _M_extract(__n); }
 203 #endif
 204       //@}
 205
 206       //@{
 207       /**
 208        *  @brief  Floating point arithmetic extractors
 209        *  @param  __f A variable of builtin floating point type.
 210        *  @return  @c *this if successful
 211        *
 212        *  These functions use the stream's current locale (specifically, the
 213        *  @c num_get facet) to parse the input data.
 214       */
 215       __istream_type&
 216       operator>>(float& __f)
 217       { return _M_extract(__f); }
 218
 219       __istream_type&
 220       operator>>(double& __f)
 221       { return _M_extract(__f); }
 222
 223       __istream_type&
 224       operator>>(long double& __f)
 225       { return _M_extract(__f); }
 226       //@}
 227
 228       /**
 229        *  @brief  Basic arithmetic extractors
 230        *  @param  __p A variable of pointer type.
 231        *  @return  @c *this if successful
 232        *
 233        *  These functions use the stream's current locale (specifically, the
 234        *  @c num_get facet) to parse the input data.
 235       */
 236       __istream_type&
 237       operator>>(void*& __p)
 238       { return _M_extract(__p); }
 239
 240       /**
 241        *  @brief  Extracting into another streambuf.
 242        *  @param  __sb  A pointer to a streambuf
 243        *
 244        *  This function behaves like one of the basic arithmetic extractors,
 245        *  in that it also constructs a sentry object and has the same error
 246        *  handling behavior.
 247        *
 248        *  If @p __sb is NULL, the stream will set failbit in its error state.
 249        *
 250        *  Characters are extracted from this stream and inserted into the
 251        *  @p __sb streambuf until one of the following occurs:
 252        *
 253        *  - the input stream reaches end-of-file,
 254        *  - insertion into the output buffer fails (in this case, the
 255        *    character that would have been inserted is not extracted), or
 256        *  - an exception occurs (and in this case is caught)
 257        *
 258        *  If the function inserts no characters, failbit is set.
 259       */
 260       __istream_type&
 261       operator>>(__streambuf_type* __sb);
 262       //@}
 263
 264       // [27.6.1.3] unformatted input
 265       /**
 266        *  @brief  Character counting
 267        *  @return  The number of characters extracted by the previous
 268        *           unformatted input function dispatched for this stream.
 269       */
 270       streamsize
 271       gcount() const
 272       { return _M_gcount; }
 273
 274       //@{
 275       /**
 276        *  @name Unformatted Input Functions
 277        *
 278        *  All the unformatted input functions have some common behavior.
 279        *  Each starts by constructing a temporary object of type
 280        *  std::basic_istream::sentry with the second argument (noskipws)
 281        *  set to true.  This has several effects, concluding with the
 282        *  setting of a status flag; see the sentry documentation for more.
 283        *
 284        *  If the sentry status is good, the function tries to extract
 285        *  whatever data is appropriate for the type of the argument.
 286        *
 287        *  The number of characters extracted is stored for later retrieval
 288        *  by gcount().
 289        *
 290        *  If an exception is thrown during extraction, ios_base::badbit
 291        *  will be turned on in the stream's error state without causing an
 292        *  ios_base::failure to be thrown.  The original exception will then
 293        *  be rethrown.
 294       */
 295
 296       /**
 297        *  @brief  Simple extraction.
 298        *  @return  A character, or eof().
 299        *
 300        *  Tries to extract a character.  If none are available, sets failbit
 301        *  and returns traits::eof().
 302       */
 303       int_type
 304       get();
 305
 306       /**
 307        *  @brief  Simple extraction.
 308        *  @param  __c  The character in which to store data.
 309        *  @return  *this
 310        *
 311        *  Tries to extract a character and store it in @a __c.  If none are
 312        *  available, sets failbit and returns traits::eof().
 313        *
 314        *  @note  This function is not overloaded on signed char and
 315        *         unsigned char.
 316       */
 317       __istream_type&
 318       get(char_type& __c);
 319
 320       /**
 321        *  @brief  Simple multiple-character extraction.
 322        *  @param  __s  Pointer to an array.
 323        *  @param  __n  Maximum number of characters to store in @a __s.
 324        *  @param  __delim  A "stop" character.
 325        *  @return  *this
 326        *
 327        *  Characters are extracted and stored into @a __s until one of the
 328        *  following happens:
 329        *
 330        *  - @c __n-1 characters are stored
 331        *  - the input sequence reaches EOF
 332        *  - the next character equals @a __delim, in which case the character
 333        *    is not extracted
 334        *
 335        * If no characters are stored, failbit is set in the stream's error
 336        * state.
 337        *
 338        * In any case, a null character is stored into the next location in
 339        * the array.
 340        *
 341        *  @note  This function is not overloaded on signed char and
 342        *         unsigned char.
 343       */
 344       __istream_type&
 345       get(char_type* __s, streamsize __n, char_type __delim);
 346
 347       /**
 348        *  @brief  Simple multiple-character extraction.
 349        *  @param  __s  Pointer to an array.
 350        *  @param  __n  Maximum number of characters to store in @a s.
 351        *  @return  *this
 352        *
 353        *  Returns @c get(__s,__n,widen(&apos;\\n&apos;)).
 354       */
 355       __istream_type&
 356       get(char_type* __s, streamsize __n)
 357       { return this->get(__s, __n, this->widen('\n')); }
 358
 359       /**
 360        *  @brief  Extraction into another streambuf.
 361        *  @param  __sb  A streambuf in which to store data.
 362        *  @param  __delim  A "stop" character.
 363        *  @return  *this
 364        *
 365        *  Characters are extracted and inserted into @a __sb until one of the
 366        *  following happens:
 367        *
 368        *  - the input sequence reaches EOF
 369        *  - insertion into the output buffer fails (in this case, the
 370        *    character that would have been inserted is not extracted)
 371        *  - the next character equals @a __delim (in this case, the character
 372        *    is not extracted)
 373        *  - an exception occurs (and in this case is caught)
 374        *
 375        * If no characters are stored, failbit is set in the stream's error
 376        * state.
 377       */
 378       __istream_type&
 379       get(__streambuf_type& __sb, char_type __delim);
 380
 381       /**
 382        *  @brief  Extraction into another streambuf.
 383        *  @param  __sb  A streambuf in which to store data.
 384        *  @return  *this
 385        *
 386        *  Returns @c get(__sb,widen(&apos;\\n&apos;)).
 387       */
 388       __istream_type&
 389       get(__streambuf_type& __sb)
 390       { return this->get(__sb, this->widen('\n')); }
 391
 392       /**
 393        *  @brief  String extraction.
 394        *  @param  __s  A character array in which to store the data.
 395        *  @param  __n  Maximum number of characters to extract.
 396        *  @param  __delim  A "stop" character.
 397        *  @return  *this
 398        *
 399        *  Extracts and stores characters into @a __s until one of the
 400        *  following happens.  Note that these criteria are required to be
 401        *  tested in the order listed here, to allow an input line to exactly
 402        *  fill the @a __s array without setting failbit.
 403        *
 404        *  -# the input sequence reaches end-of-file, in which case eofbit
 405        *     is set in the stream error state
 406        *  -# the next character equals @c __delim, in which case the character
 407        *     is extracted (and therefore counted in @c gcount()) but not stored
 408        *  -# @c __n-1 characters are stored, in which case failbit is set
 409        *     in the stream error state
 410        *
 411        *  If no characters are extracted, failbit is set.  (An empty line of
 412        *  input should therefore not cause failbit to be set.)
 413        *
 414        *  In any case, a null character is stored in the next location in
 415        *  the array.
 416       */
 417       __istream_type&
 418       getline(char_type* __s, streamsize __n, char_type __delim);
 419
 420       /**
 421        *  @brief  String extraction.
 422        *  @param  __s  A character array in which to store the data.
 423        *  @param  __n  Maximum number of characters to extract.
 424        *  @return  *this
 425        *
 426        *  Returns @c getline(__s,__n,widen(&apos;\\n&apos;)).
 427       */
 428       __istream_type&
 429       getline(char_type* __s, streamsize __n)
 430       { return this->getline(__s, __n, this->widen('\n')); }
 431
 432       /**
 433        *  @brief  Discarding characters
 434        *  @param  __n  Number of characters to discard.
 435        *  @param  __delim  A "stop" character.
 436        *  @return  *this
 437        *
 438        *  Extracts characters and throws them away until one of the
 439        *  following happens:
 440        *  - if @a __n @c != @c std::numeric_limits<int>::max(), @a __n
 441        *    characters are extracted
 442        *  - the input sequence reaches end-of-file
 443        *  - the next character equals @a __delim (in this case, the character
 444        *    is extracted); note that this condition will never occur if
 445        *    @a __delim equals @c traits::eof().
 446        *
 447        *  NB: Provide three overloads, instead of the single function
 448        *  (with defaults) mandated by the Standard: this leads to a
 449        *  better performing implementation, while still conforming to
 450        *  the Standard.
 451       */
 452       __istream_type&
 453       ignore(streamsize __n, int_type __delim);
 454
 455       __istream_type&
 456       ignore(streamsize __n);
 457
 458       __istream_type&
 459       ignore();
 460
 461       /**
 462        *  @brief  Looking ahead in the stream
 463        *  @return  The next character, or eof().
 464        *
 465        *  If, after constructing the sentry object, @c good() is false,
 466        *  returns @c traits::eof().  Otherwise reads but does not extract
 467        *  the next input character.
 468       */
 469       int_type
 470       peek();
 471
 472       /**
 473        *  @brief  Extraction without delimiters.
 474        *  @param  __s  A character array.
 475        *  @param  __n  Maximum number of characters to store.
 476        *  @return  *this
 477        *
 478        *  If the stream state is @c good(), extracts characters and stores
 479        *  them into @a __s until one of the following happens:
 480        *  - @a __n characters are stored
 481        *  - the input sequence reaches end-of-file, in which case the error
 482        *    state is set to @c failbit|eofbit.
 483        *
 484        *  @note  This function is not overloaded on signed char and
 485        *         unsigned char.
 486       */
 487       __istream_type&
 488       read(char_type* __s, streamsize __n);
 489
 490       /**
 491        *  @brief  Extraction until the buffer is exhausted, but no more.
 492        *  @param  __s  A character array.
 493        *  @param  __n  Maximum number of characters to store.
 494        *  @return  The number of characters extracted.
 495        *
 496        *  Extracts characters and stores them into @a __s depending on the
 497        *  number of characters remaining in the streambuf's buffer,
 498        *  @c rdbuf()->in_avail(), called @c A here:
 499        *  - if @c A @c == @c -1, sets eofbit and extracts no characters
 500        *  - if @c A @c == @c 0, extracts no characters
 501        *  - if @c A @c > @c 0, extracts @c min(A,n)
 502        *
 503        *  The goal is to empty the current buffer, and to not request any
 504        *  more from the external input sequence controlled by the streambuf.
 505       */
 506       streamsize
 507       readsome(char_type* __s, streamsize __n);
 508
 509       /**
 510        *  @brief  Unextracting a single character.
 511        *  @param  __c  The character to push back into the input stream.
 512        *  @return  *this
 513        *
 514        *  If @c rdbuf() is not null, calls @c rdbuf()->sputbackc(c).
 515        *
 516        *  If @c rdbuf() is null or if @c sputbackc() fails, sets badbit in
 517        *  the error state.
 518        *
 519        *  @note  This function first clears eofbit.  Since no characters
 520        *         are extracted, the next call to @c gcount() will return 0,
 521        *         as required by DR 60.
 522       */
 523       __istream_type&
 524       putback(char_type __c);
 525
 526       /**
 527        *  @brief  Unextracting the previous character.
 528        *  @return  *this
 529        *
 530        *  If @c rdbuf() is not null, calls @c rdbuf()->sungetc(c).
 531        *
 532        *  If @c rdbuf() is null or if @c sungetc() fails, sets badbit in
 533        *  the error state.
 534        *
 535        *  @note  This function first clears eofbit.  Since no characters
 536        *         are extracted, the next call to @c gcount() will return 0,
 537        *         as required by DR 60.
 538       */
 539       __istream_type&
 540       unget();
 541
 542       /**
 543        *  @brief  Synchronizing the stream buffer.
 544        *  @return  0 on success, -1 on failure
 545        *
 546        *  If @c rdbuf() is a null pointer, returns -1.
 547        *
 548        *  Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
 549        *  sets badbit and returns -1.
 550        *
 551        *  Otherwise, returns 0.
 552        *
 553        *  @note  This function does not count the number of characters
 554        *         extracted, if any, and therefore does not affect the next
 555        *         call to @c gcount().
 556       */
 557       int
 558       sync();
 559
 560       /**
 561        *  @brief  Getting the current read position.
 562        *  @return  A file position object.
 563        *
 564        *  If @c fail() is not false, returns @c pos_type(-1) to indicate
 565        *  failure.  Otherwise returns @c rdbuf()->pubseekoff(0,cur,in).
 566        *
 567        *  @note  This function does not count the number of characters
 568        *         extracted, if any, and therefore does not affect the next
 569        *         call to @c gcount().  At variance with putback, unget and
 570        *         seekg, eofbit is not cleared first.
 571       */
 572       pos_type
 573       tellg();
 574
 575       /**
 576        *  @brief  Changing the current read position.
 577        *  @param  __pos  A file position object.
 578        *  @return  *this
 579        *
 580        *  If @c fail() is not true, calls @c rdbuf()->pubseekpos(__pos).  If
 581        *  that function fails, sets failbit.
 582        *
 583        *  @note  This function first clears eofbit.  It does not count the
 584        *         number of characters extracted, if any, and therefore does
 585        *         not affect the next call to @c gcount().
 586       */
 587       __istream_type&
 588       seekg(pos_type);
 589
 590       /**
 591        *  @brief  Changing the current read position.
 592        *  @param  __off  A file offset object.
 593        *  @param  __dir  The direction in which to seek.
 594        *  @return  *this
 595        *
 596        *  If @c fail() is not true, calls @c rdbuf()->pubseekoff(__off,__dir).
 597        *  If that function fails, sets failbit.
 598        *
 599        *  @note  This function first clears eofbit.  It does not count the
 600        *         number of characters extracted, if any, and therefore does
 601        *         not affect the next call to @c gcount().
 602       */
 603       __istream_type&
 604       seekg(off_type, ios_base::seekdir);
 605       //@}
 606
 607     protected:
 608       basic_istream()
 609       : _M_gcount(streamsize(0))
 610       { this->init(0); }
 611
 612       template<typename _ValueT>
 613         __istream_type&
 614         _M_extract(_ValueT& __v);
 615     };
 616
 617   /// Explicit specialization declarations, defined in src/istream.cc.
 618   template<>
 619     basic_istream<char>&
 620     basic_istream<char>::
 621     getline(char_type* __s, streamsize __n, char_type __delim);
 622
 623   template<>
 624     basic_istream<char>&
 625     basic_istream<char>::
 626     ignore(streamsize __n);
 627
 628   template<>
 629     basic_istream<char>&
 630     basic_istream<char>::
 631     ignore(streamsize __n, int_type __delim);
 632
 633 #ifdef _GLIBCXX_USE_WCHAR_T
 634   template<>
 635     basic_istream<wchar_t>&
 636     basic_istream<wchar_t>::
 637     getline(char_type* __s, streamsize __n, char_type __delim);
 638
 639   template<>
 640     basic_istream<wchar_t>&
 641     basic_istream<wchar_t>::
 642     ignore(streamsize __n);
 643
 644   template<>
 645     basic_istream<wchar_t>&
 646     basic_istream<wchar_t>::
 647     ignore(streamsize __n, int_type __delim);
 648 #endif
 649
 650   /**
 651    *  @brief  Performs setup work for input streams.
 652    *
 653    *  Objects of this class are created before all of the standard
 654    *  extractors are run.  It is responsible for <em>exception-safe
 655    *  prefix and suffix operations,</em> although only prefix actions
 656    *  are currently required by the standard.
 657   */
 658   template<typename _CharT, typename _Traits>
 659     class basic_istream<_CharT, _Traits>::sentry
 660     {
 661       // Data Members.
 662       bool _M_ok;
 663
 664     public:
 665       /// Easy access to dependant types.
 666       typedef _Traits                                   traits_type;
 667       typedef basic_streambuf<_CharT, _Traits>          __streambuf_type;
 668       typedef basic_istream<_CharT, _Traits>            __istream_type;
 669       typedef typename __istream_type::__ctype_type     __ctype_type;
 670       typedef typename _Traits::int_type                __int_type;
 671
 672       /**
 673        *  @brief  The constructor performs all the work.
 674        *  @param  __is  The input stream to guard.
 675        *  @param  __noskipws  Whether to consume whitespace or not.
 676        *
 677        *  If the stream state is good (@a __is.good() is true), then the
 678        *  following actions are performed, otherwise the sentry state
 679        *  is false (<em>not okay</em>) and failbit is set in the
 680        *  stream state.
 681        *
 682        *  The sentry's preparatory actions are:
 683        *
 684        *  -# if the stream is tied to an output stream, @c is.tie()->flush()
 685        *     is called to synchronize the output sequence
 686        *  -# if @a __noskipws is false, and @c ios_base::skipws is set in
 687        *     @c is.flags(), the sentry extracts and discards whitespace
 688        *     characters from the stream.  The currently imbued locale is
 689        *     used to determine whether each character is whitespace.
 690        *
 691        *  If the stream state is still good, then the sentry state becomes
 692        *  true (@a okay).
 693       */
 694       explicit
 695       sentry(basic_istream<_CharT, _Traits>& __is, bool __noskipws = false);
 696
 697       /**
 698        *  @brief  Quick status checking.
 699        *  @return  The sentry state.
 700        *
 701        *  For ease of use, sentries may be converted to booleans.  The
 702        *  return value is that of the sentry state (true == okay).
 703       */
 704 #if __cplusplus >= 201103L
 705       explicit
 706 #endif
 707       operator bool() const
 708       { return _M_ok; }
 709     };
 710
 711   //@{
 712   /**
 713    *  @brief  Character extractors
 714    *  @param  __in  An input stream.
 715    *  @param  __c  A character reference.
 716    *  @return  in
 717    *
 718    *  Behaves like one of the formatted arithmetic extractors described in
 719    *  std::basic_istream.  After constructing a sentry object with good
 720    *  status, this function extracts a character (if one is available) and
 721    *  stores it in @a __c.  Otherwise, sets failbit in the input stream.
 722   */
 723   template<typename _CharT, typename _Traits>
 724     basic_istream<_CharT, _Traits>&
 725     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c);
 726
 727   template<class _Traits>
 728     inline basic_istream<char, _Traits>&
 729     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
 730     { return (__in >> reinterpret_cast<char&>(__c)); }
 731
 732   template<class _Traits>
 733     inline basic_istream<char, _Traits>&
 734     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
 735     { return (__in >> reinterpret_cast<char&>(__c)); }
 736   //@}
 737
 738   //@{
 739   /**
 740    *  @brief  Character string extractors
 741    *  @param  __in  An input stream.
 742    *  @param  __s  A pointer to a character array.
 743    *  @return  __in
 744    *
 745    *  Behaves like one of the formatted arithmetic extractors described in
 746    *  std::basic_istream.  After constructing a sentry object with good
 747    *  status, this function extracts up to @c n characters and stores them
 748    *  into the array starting at @a __s.  @c n is defined as:
 749    *
 750    *  - if @c width() is greater than zero, @c n is width() otherwise
 751    *  - @c n is <em>the number of elements of the largest array of *
 752    *  - @c char_type that can store a terminating @c eos.</em>
 753    *  - [27.6.1.2.3]/6
 754    *
 755    *  Characters are extracted and stored until one of the following happens:
 756    *  - @c n-1 characters are stored
 757    *  - EOF is reached
 758    *  - the next character is whitespace according to the current locale
 759    *  - the next character is a null byte (i.e., @c charT() )
 760    *
 761    *  @c width(0) is then called for the input stream.
 762    *
 763    *  If no characters are extracted, sets failbit.
 764   */
 765   template<typename _CharT, typename _Traits>
 766     basic_istream<_CharT, _Traits>&
 767     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s);
 768
 769   // Explicit specialization declaration, defined in src/istream.cc.
 770   template<>
 771     basic_istream<char>&
 772     operator>>(basic_istream<char>& __in, char* __s);
 773
 774   template<class _Traits>
 775     inline basic_istream<char, _Traits>&
 776     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
 777     { return (__in >> reinterpret_cast<char*>(__s)); }
 778
 779   template<class _Traits>
 780     inline basic_istream<char, _Traits>&
 781     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
 782     { return (__in >> reinterpret_cast<char*>(__s)); }
 783   //@}
 784
 785   /**
 786    *  @brief  Template class basic_iostream
 787    *  @ingroup io
 788    *
 789    *  @tparam _CharT  Type of character stream.
 790    *  @tparam _Traits  Traits for character type, defaults to
 791    *                   char_traits<_CharT>.
 792    *
 793    *  This class multiply inherits from the input and output stream classes
 794    *  simply to provide a single interface.
 795   */
 796   template<typename _CharT, typename _Traits>
 797     class basic_iostream
 798     : public basic_istream<_CharT, _Traits>,
 799       public basic_ostream<_CharT, _Traits>
 800     {
 801     public:
 802       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 803       // 271. basic_iostream missing typedefs
 804       // Types (inherited):
 805       typedef _CharT                                    char_type;
 806       typedef typename _Traits::int_type                int_type;
 807       typedef typename _Traits::pos_type                pos_type;
 808       typedef typename _Traits::off_type                off_type;
 809       typedef _Traits                                   traits_type;
 810
 811       // Non-standard Types:
 812       typedef basic_istream<_CharT, _Traits>            __istream_type;
 813       typedef basic_ostream<_CharT, _Traits>            __ostream_type;
 814
 815       /**
 816        *  @brief  Constructor does nothing.
 817        *
 818        *  Both of the parent classes are initialized with the same
 819        *  streambuf pointer passed to this constructor.
 820       */
 821       explicit
 822       basic_iostream(basic_streambuf<_CharT, _Traits>* __sb)
 823       : __istream_type(__sb), __ostream_type(__sb) { }
 824
 825       /**
 826        *  @brief  Destructor does nothing.
 827       */
 828       virtual
 829       ~basic_iostream() { }
 830
 831     protected:
 832       basic_iostream()
 833       : __istream_type(), __ostream_type() { }
 834     };
 835
 836   /**
 837    *  @brief  Quick and easy way to eat whitespace
 838    *
 839    *  This manipulator extracts whitespace characters, stopping when the
 840    *  next character is non-whitespace, or when the input sequence is empty.
 841    *  If the sequence is empty, @c eofbit is set in the stream, but not
 842    *  @c failbit.
 843    *
 844    *  The current locale is used to distinguish whitespace characters.
 845    *
 846    *  Example:
 847    *  @code
 848    *     MyClass   mc;
 849    *
 850    *     std::cin >> std::ws >> mc;
 851    *  @endcode
 852    *  will skip leading whitespace before calling operator>> on cin and your
 853    *  object.  Note that the same effect can be achieved by creating a
 854    *  std::basic_istream::sentry inside your definition of operator>>.
 855   */
 856   template<typename _CharT, typename _Traits>
 857     basic_istream<_CharT, _Traits>&
 858     ws(basic_istream<_CharT, _Traits>& __is);
 859
 860 #if __cplusplus >= 201103L
 861   // [27.7.1.6] Rvalue stream extraction
 862   /**
 863    *  @brief  Generic extractor for rvalue stream
 864    *  @param  __is  An input stream.
 865    *  @param  __x  A reference to the extraction target.
 866    *  @return  is
 867    *
 868    *  This is just a forwarding function to allow extraction from
 869    *  rvalue streams since they won't bind to the extractor functions
 870    *  that take an lvalue reference.
 871   */
 872   template<typename _CharT, typename _Traits, typename _Tp>
 873     inline basic_istream<_CharT, _Traits>&
 874     operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
 875     { return (__is >> __x); }
 876 #endif // C++11
 877
 878 _GLIBCXX_END_NAMESPACE_VERSION
 879 } // namespace
 880
 881 #include <bits/istream.tcc>
 882
 883 #endif  /* _GLIBCXX_ISTREAM */