streambuf

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00001 // Stream buffer classes -*- C++ -*-
00002 
00003 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
00004 // 2006, 2007, 2008 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 2, 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 // You should have received a copy of the GNU General Public License
00018 // along with this library; see the file COPYING.  If not, write to
00019 // the Free Software Foundation, 51 Franklin Street, Fifth Floor,
00020 // Boston, MA 02110-1301, USA.
00021 
00022 // As a special exception, you may use this file as part of a free software
00023 // library without restriction.  Specifically, if other files instantiate
00024 // templates or use macros or inline functions from this file, or you compile
00025 // this file and link it with other files to produce an executable, this
00026 // file does not by itself cause the resulting executable to be covered by
00027 // the GNU General Public License.  This exception does not however
00028 // invalidate any other reasons why the executable file might be covered by
00029 // the GNU General Public License.
00030 
00031 /** @file streambuf
00032  *  This is a Standard C++ Library header.
00033  */
00034 
00035 //
00036 // ISO C++ 14882: 27.5  Stream buffers
00037 //
00038 
00039 #ifndef _GLIBXX_STREAMBUF
00040 #define _GLIBXX_STREAMBUF 1
00041 
00042 #pragma GCC system_header
00043 
00044 #include <bits/c++config.h>
00045 #include <iosfwd>
00046 #include <bits/localefwd.h>
00047 #include <bits/ios_base.h>
00048 #include <bits/cpp_type_traits.h>
00049 #include <ext/type_traits.h>
00050 
00051 _GLIBCXX_BEGIN_NAMESPACE(std)
00052 
00053   template<typename _CharT, typename _Traits>
00054     streamsize
00055     __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
00056               basic_streambuf<_CharT, _Traits>*, bool&);
00057 
00058   /**
00059    *  @brief  The actual work of input and output (interface).
00060    *
00061    *  This is a base class.  Derived stream buffers each control a
00062    *  pair of character sequences:  one for input, and one for output.
00063    *
00064    *  Section [27.5.1] of the standard describes the requirements and
00065    *  behavior of stream buffer classes.  That section (three paragraphs)
00066    *  is reproduced here, for simplicity and accuracy.
00067    *
00068    *  -# Stream buffers can impose various constraints on the sequences
00069    *     they control.  Some constraints are:
00070    *     - The controlled input sequence can be not readable.
00071    *     - The controlled output sequence can be not writable.
00072    *     - The controlled sequences can be associated with the contents of
00073    *       other representations for character sequences, such as external
00074    *       files.
00075    *     - The controlled sequences can support operations @e directly to or
00076    *       from associated sequences.
00077    *     - The controlled sequences can impose limitations on how the
00078    *       program can read characters from a sequence, write characters to
00079    *       a sequence, put characters back into an input sequence, or alter
00080    *       the stream position.
00081    *     .
00082    *  -# Each sequence is characterized by three pointers which, if non-null,
00083    *     all point into the same @c charT array object.  The array object
00084    *     represents, at any moment, a (sub)sequence of characters from the
00085    *     sequence.  Operations performed on a sequence alter the values
00086    *     stored in these pointers, perform reads and writes directly to or
00087    *     from associated sequences, and alter "the stream position" and
00088    *     conversion state as needed to maintain this subsequence relationship.
00089    *     The three pointers are:
00090    *     - the <em>beginning pointer</em>, or lowest element address in the
00091    *       array (called @e xbeg here);
00092    *     - the <em>next pointer</em>, or next element address that is a
00093    *       current candidate for reading or writing (called @e xnext here);
00094    *     - the <em>end pointer</em>, or first element address beyond the
00095    *       end of the array (called @e xend here).
00096    *     .
00097    *  -# The following semantic constraints shall always apply for any set
00098    *     of three pointers for a sequence, using the pointer names given
00099    *     immediately above:
00100    *     - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
00101    *       also be non-null pointers into the same @c charT array, as
00102    *       described above; otherwise, @e xbeg and @e xend shall also be null.
00103    *     - If @e xnext is not a null pointer and @e xnext < @e xend for an
00104    *       output sequence, then a <em>write position</em> is available.
00105    *       In this case, @e *xnext shall be assignable as the next element
00106    *       to write (to put, or to store a character value, into the sequence).
00107    *     - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
00108    *       input sequence, then a <em>putback position</em> is available.
00109    *       In this case, @e xnext[-1] shall have a defined value and is the
00110    *       next (preceding) element to store a character that is put back
00111    *       into the input sequence.
00112    *     - If @e xnext is not a null pointer and @e xnext< @e xend for an
00113    *       input sequence, then a <em>read position</em> is available.
00114    *       In this case, @e *xnext shall have a defined value and is the
00115    *       next element to read (to get, or to obtain a character value,
00116    *       from the sequence).
00117   */
00118   template<typename _CharT, typename _Traits>
00119     class basic_streambuf 
00120     {
00121     public:
00122       //@{
00123       /**
00124        *  These are standard types.  They permit a standardized way of
00125        *  referring to names of (or names dependant on) the template
00126        *  parameters, which are specific to the implementation.
00127       */
00128       typedef _CharT                    char_type;
00129       typedef _Traits                   traits_type;
00130       typedef typename traits_type::int_type        int_type;
00131       typedef typename traits_type::pos_type        pos_type;
00132       typedef typename traits_type::off_type        off_type;
00133       //@}
00134 
00135       //@{
00136       /// This is a non-standard type.
00137       typedef basic_streambuf<char_type, traits_type>   __streambuf_type;
00138       //@}
00139       
00140       friend class basic_ios<char_type, traits_type>;
00141       friend class basic_istream<char_type, traits_type>;
00142       friend class basic_ostream<char_type, traits_type>;
00143       friend class istreambuf_iterator<char_type, traits_type>;
00144       friend class ostreambuf_iterator<char_type, traits_type>;
00145 
00146       friend streamsize
00147       __copy_streambufs_eof<>(__streambuf_type*, __streambuf_type*, bool&);
00148 
00149       template<bool _IsMove, typename _CharT2>
00150         friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 
00151                            _CharT2*>::__type
00152         __copy_move_a2(istreambuf_iterator<_CharT2>,
00153                istreambuf_iterator<_CharT2>, _CharT2*);
00154 
00155       template<typename _CharT2>
00156         friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
00157                   istreambuf_iterator<_CharT2> >::__type
00158         find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
00159          const _CharT2&);
00160 
00161       template<typename _CharT2, typename _Traits2>
00162         friend basic_istream<_CharT2, _Traits2>&
00163         operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
00164 
00165       template<typename _CharT2, typename _Traits2, typename _Alloc>
00166         friend basic_istream<_CharT2, _Traits2>&
00167         operator>>(basic_istream<_CharT2, _Traits2>&,
00168            basic_string<_CharT2, _Traits2, _Alloc>&);
00169 
00170       template<typename _CharT2, typename _Traits2, typename _Alloc>
00171         friend basic_istream<_CharT2, _Traits2>&
00172         getline(basic_istream<_CharT2, _Traits2>&,
00173         basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
00174 
00175     protected:
00176       //@{
00177       /**
00178        *  This is based on _IO_FILE, just reordered to be more consistent,
00179        *  and is intended to be the most minimal abstraction for an
00180        *  internal buffer.
00181        *  -  get == input == read
00182        *  -  put == output == write
00183       */
00184       char_type*        _M_in_beg;     // Start of get area. 
00185       char_type*        _M_in_cur;     // Current read area. 
00186       char_type*        _M_in_end;     // End of get area. 
00187       char_type*        _M_out_beg;    // Start of put area. 
00188       char_type*        _M_out_cur;    // Current put area. 
00189       char_type*        _M_out_end;    // End of put area.
00190 
00191       /// Current locale setting.
00192       locale            _M_buf_locale;  
00193 
00194   public:
00195       /// Destructor deallocates no buffer space.
00196       virtual 
00197       ~basic_streambuf() 
00198       { }
00199 
00200       // [27.5.2.2.1] locales
00201       /**
00202        *  @brief  Entry point for imbue().
00203        *  @param  loc  The new locale.
00204        *  @return  The previous locale.
00205        *
00206        *  Calls the derived imbue(loc).
00207       */
00208       locale 
00209       pubimbue(const locale &__loc)
00210       {
00211     locale __tmp(this->getloc());
00212     this->imbue(__loc);
00213     _M_buf_locale = __loc;
00214     return __tmp;
00215       }
00216 
00217       /**
00218        *  @brief  Locale access.
00219        *  @return  The current locale in effect.
00220        *
00221        *  If pubimbue(loc) has been called, then the most recent @c loc
00222        *  is returned.  Otherwise the global locale in effect at the time
00223        *  of construction is returned.
00224       */
00225       locale   
00226       getloc() const
00227       { return _M_buf_locale; } 
00228 
00229       // [27.5.2.2.2] buffer management and positioning
00230       //@{
00231       /**
00232        *  @brief  Entry points for derived buffer functions.
00233        *
00234        *  The public versions of @c pubfoo dispatch to the protected
00235        *  derived @c foo member functions, passing the arguments (if any)
00236        *  and returning the result unchanged.
00237       */
00238       __streambuf_type* 
00239       pubsetbuf(char_type* __s, streamsize __n) 
00240       { return this->setbuf(__s, __n); }
00241 
00242       pos_type 
00243       pubseekoff(off_type __off, ios_base::seekdir __way, 
00244          ios_base::openmode __mode = ios_base::in | ios_base::out)
00245       { return this->seekoff(__off, __way, __mode); }
00246 
00247       pos_type 
00248       pubseekpos(pos_type __sp,
00249          ios_base::openmode __mode = ios_base::in | ios_base::out)
00250       { return this->seekpos(__sp, __mode); }
00251 
00252       int 
00253       pubsync() { return this->sync(); }
00254       //@}
00255 
00256       // [27.5.2.2.3] get area
00257       /**
00258        *  @brief  Looking ahead into the stream.
00259        *  @return  The number of characters available.
00260        *
00261        *  If a read position is available, returns the number of characters
00262        *  available for reading before the buffer must be refilled.
00263        *  Otherwise returns the derived @c showmanyc().
00264       */
00265       streamsize 
00266       in_avail() 
00267       { 
00268     const streamsize __ret = this->egptr() - this->gptr();
00269     return __ret ? __ret : this->showmanyc();
00270       }
00271 
00272       /**
00273        *  @brief  Getting the next character.
00274        *  @return  The next character, or eof.
00275        *
00276        *  Calls @c sbumpc(), and if that function returns
00277        *  @c traits::eof(), so does this function.  Otherwise, @c sgetc().
00278       */
00279       int_type 
00280       snextc()
00281       {
00282     int_type __ret = traits_type::eof();
00283     if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 
00284                                __ret), true))
00285       __ret = this->sgetc();
00286     return __ret;
00287       }
00288 
00289       /**
00290        *  @brief  Getting the next character.
00291        *  @return  The next character, or eof.
00292        *
00293        *  If the input read position is available, returns that character
00294        *  and increments the read pointer, otherwise calls and returns
00295        *  @c uflow().
00296       */
00297       int_type 
00298       sbumpc()
00299       {
00300     int_type __ret;
00301     if (__builtin_expect(this->gptr() < this->egptr(), true))
00302       {
00303         __ret = traits_type::to_int_type(*this->gptr());
00304         this->gbump(1);
00305       }
00306     else 
00307       __ret = this->uflow();
00308     return __ret;
00309       }
00310 
00311       /**
00312        *  @brief  Getting the next character.
00313        *  @return  The next character, or eof.
00314        *
00315        *  If the input read position is available, returns that character,
00316        *  otherwise calls and returns @c underflow().  Does not move the 
00317        *  read position after fetching the character.
00318       */
00319       int_type 
00320       sgetc()
00321       {
00322     int_type __ret;
00323     if (__builtin_expect(this->gptr() < this->egptr(), true))
00324       __ret = traits_type::to_int_type(*this->gptr());
00325     else 
00326       __ret = this->underflow();
00327     return __ret;
00328       }
00329 
00330       /**
00331        *  @brief  Entry point for xsgetn.
00332        *  @param  s  A buffer area.
00333        *  @param  n  A count.
00334        *
00335        *  Returns xsgetn(s,n).  The effect is to fill @a s[0] through
00336        *  @a s[n-1] with characters from the input sequence, if possible.
00337       */
00338       streamsize 
00339       sgetn(char_type* __s, streamsize __n)
00340       { return this->xsgetn(__s, __n); }
00341 
00342       // [27.5.2.2.4] putback
00343       /**
00344        *  @brief  Pushing characters back into the input stream.
00345        *  @param  c  The character to push back.
00346        *  @return  The previous character, if possible.
00347        *
00348        *  Similar to sungetc(), but @a c is pushed onto the stream instead
00349        *  of "the previous character".  If successful, the next character
00350        *  fetched from the input stream will be @a c.
00351       */
00352       int_type 
00353       sputbackc(char_type __c)
00354       {
00355     int_type __ret;
00356     const bool __testpos = this->eback() < this->gptr();
00357     if (__builtin_expect(!__testpos || 
00358                  !traits_type::eq(__c, this->gptr()[-1]), false))
00359       __ret = this->pbackfail(traits_type::to_int_type(__c));
00360     else 
00361       {
00362         this->gbump(-1);
00363         __ret = traits_type::to_int_type(*this->gptr());
00364       }
00365     return __ret;
00366       }
00367 
00368       /**
00369        *  @brief  Moving backwards in the input stream.
00370        *  @return  The previous character, if possible.
00371        *
00372        *  If a putback position is available, this function decrements the
00373        *  input pointer and returns that character.  Otherwise, calls and
00374        *  returns pbackfail().  The effect is to "unget" the last character
00375        *  "gotten".
00376       */
00377       int_type 
00378       sungetc()
00379       {
00380     int_type __ret;
00381     if (__builtin_expect(this->eback() < this->gptr(), true))
00382       {
00383         this->gbump(-1);
00384         __ret = traits_type::to_int_type(*this->gptr());
00385       }
00386     else 
00387       __ret = this->pbackfail();
00388     return __ret;
00389       }
00390 
00391       // [27.5.2.2.5] put area
00392       /**
00393        *  @brief  Entry point for all single-character output functions.
00394        *  @param  c  A character to output.
00395        *  @return  @a c, if possible.
00396        *
00397        *  One of two public output functions.
00398        *
00399        *  If a write position is available for the output sequence (i.e.,
00400        *  the buffer is not full), stores @a c in that position, increments
00401        *  the position, and returns @c traits::to_int_type(c).  If a write
00402        *  position is not available, returns @c overflow(c).
00403       */
00404       int_type 
00405       sputc(char_type __c)
00406       {
00407     int_type __ret;
00408     if (__builtin_expect(this->pptr() < this->epptr(), true))
00409       {
00410         *this->pptr() = __c;
00411         this->pbump(1);
00412         __ret = traits_type::to_int_type(__c);
00413       }
00414     else
00415       __ret = this->overflow(traits_type::to_int_type(__c));
00416     return __ret;
00417       }
00418 
00419       /**
00420        *  @brief  Entry point for all single-character output functions.
00421        *  @param  s  A buffer read area.
00422        *  @param  n  A count.
00423        *
00424        *  One of two public output functions.
00425        *
00426        *
00427        *  Returns xsputn(s,n).  The effect is to write @a s[0] through
00428        *  @a s[n-1] to the output sequence, if possible.
00429       */
00430       streamsize 
00431       sputn(const char_type* __s, streamsize __n)
00432       { return this->xsputn(__s, __n); }
00433 
00434     protected:
00435       /**
00436        *  @brief  Base constructor.
00437        *
00438        *  Only called from derived constructors, and sets up all the
00439        *  buffer data to zero, including the pointers described in the
00440        *  basic_streambuf class description.  Note that, as a result,
00441        *  - the class starts with no read nor write positions available,
00442        *  - this is not an error
00443       */
00444       basic_streambuf()
00445       : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 
00446       _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
00447       _M_buf_locale(locale()) 
00448       { }
00449 
00450       // [27.5.2.3.1] get area access
00451       //@{
00452       /**
00453        *  @brief  Access to the get area.
00454        *
00455        *  These functions are only available to other protected functions,
00456        *  including derived classes.
00457        *
00458        *  - eback() returns the beginning pointer for the input sequence
00459        *  - gptr() returns the next pointer for the input sequence
00460        *  - egptr() returns the end pointer for the input sequence
00461       */
00462       char_type* 
00463       eback() const { return _M_in_beg; }
00464 
00465       char_type* 
00466       gptr()  const { return _M_in_cur;  }
00467 
00468       char_type* 
00469       egptr() const { return _M_in_end; }
00470       //@}
00471 
00472       /**
00473        *  @brief  Moving the read position.
00474        *  @param  n  The delta by which to move.
00475        *
00476        *  This just advances the read position without returning any data.
00477       */
00478       void 
00479       gbump(int __n) { _M_in_cur += __n; }
00480 
00481       /**
00482        *  @brief  Setting the three read area pointers.
00483        *  @param  gbeg  A pointer.
00484        *  @param  gnext  A pointer.
00485        *  @param  gend  A pointer.
00486        *  @post  @a gbeg == @c eback(), @a gnext == @c gptr(), and
00487        *         @a gend == @c egptr()
00488       */
00489       void 
00490       setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
00491       {
00492     _M_in_beg = __gbeg;
00493     _M_in_cur = __gnext;
00494     _M_in_end = __gend;
00495       }
00496 
00497       // [27.5.2.3.2] put area access
00498       //@{
00499       /**
00500        *  @brief  Access to the put area.
00501        *
00502        *  These functions are only available to other protected functions,
00503        *  including derived classes.
00504        *
00505        *  - pbase() returns the beginning pointer for the output sequence
00506        *  - pptr() returns the next pointer for the output sequence
00507        *  - epptr() returns the end pointer for the output sequence
00508       */
00509       char_type* 
00510       pbase() const { return _M_out_beg; }
00511 
00512       char_type* 
00513       pptr() const { return _M_out_cur; }
00514 
00515       char_type* 
00516       epptr() const { return _M_out_end; }
00517       //@}
00518 
00519       /**
00520        *  @brief  Moving the write position.
00521        *  @param  n  The delta by which to move.
00522        *
00523        *  This just advances the write position without returning any data.
00524       */
00525       void 
00526       pbump(int __n) { _M_out_cur += __n; }
00527 
00528       /**
00529        *  @brief  Setting the three write area pointers.
00530        *  @param  pbeg  A pointer.
00531        *  @param  pend  A pointer.
00532        *  @post  @a pbeg == @c pbase(), @a pbeg == @c pptr(), and
00533        *         @a pend == @c epptr()
00534       */
00535       void 
00536       setp(char_type* __pbeg, char_type* __pend)
00537       { 
00538     _M_out_beg = _M_out_cur = __pbeg; 
00539     _M_out_end = __pend;
00540       }
00541 
00542       // [27.5.2.4] virtual functions
00543       // [27.5.2.4.1] locales
00544       /**
00545        *  @brief  Changes translations.
00546        *  @param  loc  A new locale.
00547        *
00548        *  Translations done during I/O which depend on the current locale
00549        *  are changed by this call.  The standard adds, "Between invocations
00550        *  of this function a class derived from streambuf can safely cache
00551        *  results of calls to locale functions and to members of facets
00552        *  so obtained."
00553        *
00554        *  @note  Base class version does nothing.
00555       */
00556       virtual void 
00557       imbue(const locale&) 
00558       { }
00559 
00560       // [27.5.2.4.2] buffer management and positioning
00561       /**
00562        *  @brief  Manipulates the buffer.
00563        *
00564        *  Each derived class provides its own appropriate behavior.  See
00565        *  the next-to-last paragraph of 
00566        *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
00567        *  for more on this function.
00568        *
00569        *  @note  Base class version does nothing, returns @c this.
00570       */
00571       virtual basic_streambuf<char_type,_Traits>* 
00572       setbuf(char_type*, streamsize)
00573       { return this; }
00574       
00575       /**
00576        *  @brief  Alters the stream positions.
00577        *
00578        *  Each derived class provides its own appropriate behavior.
00579        *  @note  Base class version does nothing, returns a @c pos_type
00580        *         that represents an invalid stream position.
00581       */
00582       virtual pos_type 
00583       seekoff(off_type, ios_base::seekdir,
00584           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00585       { return pos_type(off_type(-1)); } 
00586 
00587       /**
00588        *  @brief  Alters the stream positions.
00589        *
00590        *  Each derived class provides its own appropriate behavior.
00591        *  @note  Base class version does nothing, returns a @c pos_type
00592        *         that represents an invalid stream position.
00593       */
00594       virtual pos_type 
00595       seekpos(pos_type, 
00596           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00597       { return pos_type(off_type(-1)); } 
00598 
00599       /**
00600        *  @brief  Synchronizes the buffer arrays with the controlled sequences.
00601        *  @return  -1 on failure.
00602        *
00603        *  Each derived class provides its own appropriate behavior,
00604        *  including the definition of "failure".
00605        *  @note  Base class version does nothing, returns zero.
00606       */
00607       virtual int 
00608       sync() { return 0; }
00609 
00610       // [27.5.2.4.3] get area
00611       /**
00612        *  @brief  Investigating the data available.
00613        *  @return  An estimate of the number of characters available in the
00614        *           input sequence, or -1.
00615        *
00616        *  "If it returns a positive value, then successive calls to
00617        *  @c underflow() will not return @c traits::eof() until at least that
00618        *  number of characters have been supplied.  If @c showmanyc()
00619        *  returns -1, then calls to @c underflow() or @c uflow() will fail."
00620        *  [27.5.2.4.3]/1
00621        *
00622        *  @note  Base class version does nothing, returns zero.
00623        *  @note  The standard adds that "the intention is not only that the
00624        *         calls [to underflow or uflow] will not return @c eof() but
00625        *         that they will return "immediately".
00626        *  @note  The standard adds that "the morphemes of @c showmanyc are
00627        *         "es-how-many-see", not "show-manic".
00628       */
00629       virtual streamsize 
00630       showmanyc() { return 0; }
00631 
00632       /**
00633        *  @brief  Multiple character extraction.
00634        *  @param  s  A buffer area.
00635        *  @param  n  Maximum number of characters to assign.
00636        *  @return  The number of characters assigned.
00637        *
00638        *  Fills @a s[0] through @a s[n-1] with characters from the input
00639        *  sequence, as if by @c sbumpc().  Stops when either @a n characters
00640        *  have been copied, or when @c traits::eof() would be copied.
00641        *
00642        *  It is expected that derived classes provide a more efficient
00643        *  implementation by overriding this definition.
00644       */
00645       virtual streamsize 
00646       xsgetn(char_type* __s, streamsize __n);
00647 
00648       /**
00649        *  @brief  Fetches more data from the controlled sequence.
00650        *  @return  The first character from the <em>pending sequence</em>.
00651        *
00652        *  Informally, this function is called when the input buffer is
00653        *  exhausted (or does not exist, as buffering need not actually be
00654        *  done).  If a buffer exists, it is "refilled".  In either case, the
00655        *  next available character is returned, or @c traits::eof() to
00656        *  indicate a null pending sequence.
00657        *
00658        *  For a formal definition of the pending sequence, see a good text
00659        *  such as Langer & Kreft, or [27.5.2.4.3]/7-14.
00660        *
00661        *  A functioning input streambuf can be created by overriding only
00662        *  this function (no buffer area will be used).  For an example, see
00663        *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.html
00664        *
00665        *  @note  Base class version does nothing, returns eof().
00666       */
00667       virtual int_type 
00668       underflow()
00669       { return traits_type::eof(); }
00670 
00671       /**
00672        *  @brief  Fetches more data from the controlled sequence.
00673        *  @return  The first character from the <em>pending sequence</em>.
00674        *
00675        *  Informally, this function does the same thing as @c underflow(),
00676        *  and in fact is required to call that function.  It also returns
00677        *  the new character, like @c underflow() does.  However, this
00678        *  function also moves the read position forward by one.
00679       */
00680       virtual int_type 
00681       uflow() 
00682       {
00683     int_type __ret = traits_type::eof();
00684     const bool __testeof = traits_type::eq_int_type(this->underflow(), 
00685                             __ret);
00686     if (!__testeof)
00687       {
00688         __ret = traits_type::to_int_type(*this->gptr());
00689         this->gbump(1);
00690       }
00691     return __ret;    
00692       }
00693 
00694       // [27.5.2.4.4] putback
00695       /**
00696        *  @brief  Tries to back up the input sequence.
00697        *  @param  c  The character to be inserted back into the sequence.
00698        *  @return  eof() on failure, "some other value" on success
00699        *  @post  The constraints of @c gptr(), @c eback(), and @c pptr()
00700        *         are the same as for @c underflow().
00701        *
00702        *  @note  Base class version does nothing, returns eof().
00703       */
00704       virtual int_type 
00705       pbackfail(int_type /* __c */  = traits_type::eof())
00706       { return traits_type::eof(); }
00707 
00708       // Put area:
00709       /**
00710        *  @brief  Multiple character insertion.
00711        *  @param  s  A buffer area.
00712        *  @param  n  Maximum number of characters to write.
00713        *  @return  The number of characters written.
00714        *
00715        *  Writes @a s[0] through @a s[n-1] to the output sequence, as if
00716        *  by @c sputc().  Stops when either @a n characters have been
00717        *  copied, or when @c sputc() would return @c traits::eof().
00718        *
00719        *  It is expected that derived classes provide a more efficient
00720        *  implementation by overriding this definition.
00721       */
00722       virtual streamsize 
00723       xsputn(const char_type* __s, streamsize __n);
00724 
00725       /**
00726        *  @brief  Consumes data from the buffer; writes to the
00727        *          controlled sequence.
00728        *  @param  c  An additional character to consume.
00729        *  @return  eof() to indicate failure, something else (usually
00730        *           @a c, or not_eof())
00731        *
00732        *  Informally, this function is called when the output buffer is full
00733        *  (or does not exist, as buffering need not actually be done).  If a
00734        *  buffer exists, it is "consumed", with "some effect" on the
00735        *  controlled sequence.  (Typically, the buffer is written out to the
00736        *  sequence verbatim.)  In either case, the character @a c is also
00737        *  written out, if @a c is not @c eof().
00738        *
00739        *  For a formal definition of this function, see a good text
00740        *  such as Langer & Kreft, or [27.5.2.4.5]/3-7.
00741        *
00742        *  A functioning output streambuf can be created by overriding only
00743        *  this function (no buffer area will be used).
00744        *
00745        *  @note  Base class version does nothing, returns eof().
00746       */
00747       virtual int_type 
00748       overflow(int_type /* __c */ = traits_type::eof())
00749       { return traits_type::eof(); }
00750 
00751 #if _GLIBCXX_DEPRECATED
00752     // Annex D.6
00753     public:
00754       /**
00755        *  @brief  Tosses a character.
00756        *
00757        *  Advances the read pointer, ignoring the character that would have
00758        *  been read.
00759        *
00760        *  See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
00761        */
00762       void 
00763       stossc() 
00764       {
00765     if (this->gptr() < this->egptr()) 
00766       this->gbump(1);
00767     else 
00768       this->uflow();
00769       }
00770 #endif
00771 
00772     private:
00773       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00774       // Side effect of DR 50. 
00775       basic_streambuf(const __streambuf_type& __sb)
00776       : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur), 
00777       _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg), 
00778       _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
00779       _M_buf_locale(__sb._M_buf_locale) 
00780       { }
00781 
00782       __streambuf_type& 
00783       operator=(const __streambuf_type&) { return *this; };
00784     };
00785 
00786   // Explicit specialization declarations, defined in src/streambuf.cc.
00787   template<>
00788     streamsize
00789     __copy_streambufs_eof(basic_streambuf<char>* __sbin,
00790               basic_streambuf<char>* __sbout, bool& __ineof);
00791 #ifdef _GLIBCXX_USE_WCHAR_T
00792   template<>
00793     streamsize
00794     __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
00795               basic_streambuf<wchar_t>* __sbout, bool& __ineof);
00796 #endif
00797 
00798 _GLIBCXX_END_NAMESPACE
00799 
00800 #ifndef _GLIBCXX_EXPORT_TEMPLATE
00801 # include <bits/streambuf.tcc>
00802 #endif
00803 
00804 #endif /* _GLIBCXX_STREAMBUF */

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