libstdc++
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, 2009, 2010, 2011 Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /** @file include/streambuf
00027  *  This is a Standard C++ Library header.
00028  */
00029 
00030 //
00031 // ISO C++ 14882: 27.5  Stream buffers
00032 //
00033 
00034 #ifndef _GLIBXX_STREAMBUF
00035 #define _GLIBXX_STREAMBUF 1
00036 
00037 #pragma GCC system_header
00038 
00039 #include <bits/c++config.h>
00040 #include <iosfwd>
00041 #include <bits/localefwd.h>
00042 #include <bits/ios_base.h>
00043 #include <bits/cpp_type_traits.h>
00044 #include <ext/type_traits.h>
00045 
00046 namespace std _GLIBCXX_VISIBILITY(default)
00047 {
00048 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00049 
00050   template<typename _CharT, typename _Traits>
00051     streamsize
00052     __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
00053               basic_streambuf<_CharT, _Traits>*, bool&);
00054 
00055   /**
00056    *  @brief  The actual work of input and output (interface).
00057    *  @ingroup io
00058    *
00059    *  This is a base class.  Derived stream buffers each control a
00060    *  pair of character sequences:  one for input, and one for output.
00061    *
00062    *  Section [27.5.1] of the standard describes the requirements and
00063    *  behavior of stream buffer classes.  That section (three paragraphs)
00064    *  is reproduced here, for simplicity and accuracy.
00065    *
00066    *  -# Stream buffers can impose various constraints on the sequences
00067    *     they control.  Some constraints are:
00068    *     - The controlled input sequence can be not readable.
00069    *     - The controlled output sequence can be not writable.
00070    *     - The controlled sequences can be associated with the contents of
00071    *       other representations for character sequences, such as external
00072    *       files.
00073    *     - The controlled sequences can support operations @e directly to or
00074    *       from associated sequences.
00075    *     - The controlled sequences can impose limitations on how the
00076    *       program can read characters from a sequence, write characters to
00077    *       a sequence, put characters back into an input sequence, or alter
00078    *       the stream position.
00079    *     .
00080    *  -# Each sequence is characterized by three pointers which, if non-null,
00081    *     all point into the same @c charT array object.  The array object
00082    *     represents, at any moment, a (sub)sequence of characters from the
00083    *     sequence.  Operations performed on a sequence alter the values
00084    *     stored in these pointers, perform reads and writes directly to or
00085    *     from associated sequences, and alter <em>the stream position</em> and
00086    *     conversion state as needed to maintain this subsequence relationship.
00087    *     The three pointers are:
00088    *     - the <em>beginning pointer</em>, or lowest element address in the
00089    *       array (called @e xbeg here);
00090    *     - the <em>next pointer</em>, or next element address that is a
00091    *       current candidate for reading or writing (called @e xnext here);
00092    *     - the <em>end pointer</em>, or first element address beyond the
00093    *       end of the array (called @e xend here).
00094    *     .
00095    *  -# The following semantic constraints shall always apply for any set
00096    *     of three pointers for a sequence, using the pointer names given
00097    *     immediately above:
00098    *     - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
00099    *       also be non-null pointers into the same @c charT array, as
00100    *       described above; otherwise, @e xbeg and @e xend shall also be null.
00101    *     - If @e xnext is not a null pointer and @e xnext < @e xend for an
00102    *       output sequence, then a <em>write position</em> is available.
00103    *       In this case, @e *xnext shall be assignable as the next element
00104    *       to write (to put, or to store a character value, into the sequence).
00105    *     - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
00106    *       input sequence, then a <em>putback position</em> is available.
00107    *       In this case, @e xnext[-1] shall have a defined value and is the
00108    *       next (preceding) element to store a character that is put back
00109    *       into the input sequence.
00110    *     - If @e xnext is not a null pointer and @e xnext< @e xend for an
00111    *       input sequence, then a <em>read position</em> is available.
00112    *       In this case, @e *xnext shall have a defined value and is the
00113    *       next element to read (to get, or to obtain a character value,
00114    *       from the sequence).
00115   */
00116   template<typename _CharT, typename _Traits>
00117     class basic_streambuf 
00118     {
00119     public:
00120       //@{
00121       /**
00122        *  These are standard types.  They permit a standardized way of
00123        *  referring to names of (or names dependant on) the template
00124        *  parameters, which are specific to the implementation.
00125       */
00126       typedef _CharT                    char_type;
00127       typedef _Traits                   traits_type;
00128       typedef typename traits_type::int_type        int_type;
00129       typedef typename traits_type::pos_type        pos_type;
00130       typedef typename traits_type::off_type        off_type;
00131       //@}
00132 
00133       //@{
00134       /// This is a non-standard type.
00135       typedef basic_streambuf<char_type, traits_type>   __streambuf_type;
00136       //@}
00137       
00138       friend class basic_ios<char_type, traits_type>;
00139       friend class basic_istream<char_type, traits_type>;
00140       friend class basic_ostream<char_type, traits_type>;
00141       friend class istreambuf_iterator<char_type, traits_type>;
00142       friend class ostreambuf_iterator<char_type, traits_type>;
00143 
00144       friend streamsize
00145       __copy_streambufs_eof<>(__streambuf_type*, __streambuf_type*, bool&);
00146 
00147       template<bool _IsMove, typename _CharT2>
00148         friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 
00149                            _CharT2*>::__type
00150         __copy_move_a2(istreambuf_iterator<_CharT2>,
00151                istreambuf_iterator<_CharT2>, _CharT2*);
00152 
00153       template<typename _CharT2>
00154         friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
00155                   istreambuf_iterator<_CharT2> >::__type
00156         find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
00157          const _CharT2&);
00158 
00159       template<typename _CharT2, typename _Traits2>
00160         friend basic_istream<_CharT2, _Traits2>&
00161         operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
00162 
00163       template<typename _CharT2, typename _Traits2, typename _Alloc>
00164         friend basic_istream<_CharT2, _Traits2>&
00165         operator>>(basic_istream<_CharT2, _Traits2>&,
00166            basic_string<_CharT2, _Traits2, _Alloc>&);
00167 
00168       template<typename _CharT2, typename _Traits2, typename _Alloc>
00169         friend basic_istream<_CharT2, _Traits2>&
00170         getline(basic_istream<_CharT2, _Traits2>&,
00171         basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
00172 
00173     protected:
00174       //@{
00175       /**
00176        *  This is based on _IO_FILE, just reordered to be more consistent,
00177        *  and is intended to be the most minimal abstraction for an
00178        *  internal buffer.
00179        *  -  get == input == read
00180        *  -  put == output == write
00181       */
00182       char_type*        _M_in_beg;     // Start of get area. 
00183       char_type*        _M_in_cur;     // Current read area. 
00184       char_type*        _M_in_end;     // End of get area. 
00185       char_type*        _M_out_beg;    // Start of put area. 
00186       char_type*        _M_out_cur;    // Current put area. 
00187       char_type*        _M_out_end;    // End of put area.
00188 
00189       /// Current locale setting.
00190       locale            _M_buf_locale;  
00191 
00192   public:
00193       /// Destructor deallocates no buffer space.
00194       virtual 
00195       ~basic_streambuf() 
00196       { }
00197 
00198       // [27.5.2.2.1] locales
00199       /**
00200        *  @brief  Entry point for imbue().
00201        *  @param  __loc  The new locale.
00202        *  @return  The previous locale.
00203        *
00204        *  Calls the derived imbue(__loc).
00205       */
00206       locale 
00207       pubimbue(const locale& __loc)
00208       {
00209     locale __tmp(this->getloc());
00210     this->imbue(__loc);
00211     _M_buf_locale = __loc;
00212     return __tmp;
00213       }
00214 
00215       /**
00216        *  @brief  Locale access.
00217        *  @return  The current locale in effect.
00218        *
00219        *  If pubimbue(loc) has been called, then the most recent @c loc
00220        *  is returned.  Otherwise the global locale in effect at the time
00221        *  of construction is returned.
00222       */
00223       locale   
00224       getloc() const
00225       { return _M_buf_locale; } 
00226 
00227       // [27.5.2.2.2] buffer management and positioning
00228       //@{
00229       /**
00230        *  @brief  Entry points for derived buffer functions.
00231        *
00232        *  The public versions of @c pubfoo dispatch to the protected
00233        *  derived @c foo member functions, passing the arguments (if any)
00234        *  and returning the result unchanged.
00235       */
00236       __streambuf_type* 
00237       pubsetbuf(char_type* __s, streamsize __n) 
00238       { return this->setbuf(__s, __n); }
00239 
00240       /**
00241        *  @brief  Alters the stream position.
00242        *  @param  __off  Offset.
00243        *  @param  __way  Value for ios_base::seekdir.
00244        *  @param  __mode Value for ios_base::openmode.
00245        *
00246        *  Calls virtual seekoff function.
00247       */
00248       pos_type 
00249       pubseekoff(off_type __off, ios_base::seekdir __way, 
00250          ios_base::openmode __mode = ios_base::in | ios_base::out)
00251       { return this->seekoff(__off, __way, __mode); }
00252 
00253       /**
00254        *  @brief  Alters the stream position.
00255        *  @param  __sp  Position
00256        *  @param  __mode Value for ios_base::openmode.
00257        *
00258        *  Calls virtual seekpos function.
00259       */
00260       pos_type 
00261       pubseekpos(pos_type __sp,
00262          ios_base::openmode __mode = ios_base::in | ios_base::out)
00263       { return this->seekpos(__sp, __mode); }
00264 
00265       /**
00266        *  @brief  Calls virtual sync function.
00267       */
00268       int 
00269       pubsync() { return this->sync(); }
00270       //@}
00271 
00272       // [27.5.2.2.3] get area
00273       /**
00274        *  @brief  Looking ahead into the stream.
00275        *  @return  The number of characters available.
00276        *
00277        *  If a read position is available, returns the number of characters
00278        *  available for reading before the buffer must be refilled.
00279        *  Otherwise returns the derived @c showmanyc().
00280       */
00281       streamsize 
00282       in_avail() 
00283       { 
00284     const streamsize __ret = this->egptr() - this->gptr();
00285     return __ret ? __ret : this->showmanyc();
00286       }
00287 
00288       /**
00289        *  @brief  Getting the next character.
00290        *  @return  The next character, or eof.
00291        *
00292        *  Calls @c sbumpc(), and if that function returns
00293        *  @c traits::eof(), so does this function.  Otherwise, @c sgetc().
00294       */
00295       int_type 
00296       snextc()
00297       {
00298     int_type __ret = traits_type::eof();
00299     if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 
00300                                __ret), true))
00301       __ret = this->sgetc();
00302     return __ret;
00303       }
00304 
00305       /**
00306        *  @brief  Getting the next character.
00307        *  @return  The next character, or eof.
00308        *
00309        *  If the input read position is available, returns that character
00310        *  and increments the read pointer, otherwise calls and returns
00311        *  @c uflow().
00312       */
00313       int_type 
00314       sbumpc()
00315       {
00316     int_type __ret;
00317     if (__builtin_expect(this->gptr() < this->egptr(), true))
00318       {
00319         __ret = traits_type::to_int_type(*this->gptr());
00320         this->gbump(1);
00321       }
00322     else 
00323       __ret = this->uflow();
00324     return __ret;
00325       }
00326 
00327       /**
00328        *  @brief  Getting the next character.
00329        *  @return  The next character, or eof.
00330        *
00331        *  If the input read position is available, returns that character,
00332        *  otherwise calls and returns @c underflow().  Does not move the 
00333        *  read position after fetching the character.
00334       */
00335       int_type 
00336       sgetc()
00337       {
00338     int_type __ret;
00339     if (__builtin_expect(this->gptr() < this->egptr(), true))
00340       __ret = traits_type::to_int_type(*this->gptr());
00341     else 
00342       __ret = this->underflow();
00343     return __ret;
00344       }
00345 
00346       /**
00347        *  @brief  Entry point for xsgetn.
00348        *  @param  __s  A buffer area.
00349        *  @param  __n  A count.
00350        *
00351        *  Returns xsgetn(__s,__n).  The effect is to fill @a __s[0] through
00352        *  @a __s[__n-1] with characters from the input sequence, if possible.
00353       */
00354       streamsize 
00355       sgetn(char_type* __s, streamsize __n)
00356       { return this->xsgetn(__s, __n); }
00357 
00358       // [27.5.2.2.4] putback
00359       /**
00360        *  @brief  Pushing characters back into the input stream.
00361        *  @param  __c  The character to push back.
00362        *  @return  The previous character, if possible.
00363        *
00364        *  Similar to sungetc(), but @a __c is pushed onto the stream
00365        *  instead of <em>the previous character.</em> If successful,
00366        *  the next character fetched from the input stream will be @a
00367        *  __c.
00368       */
00369       int_type 
00370       sputbackc(char_type __c)
00371       {
00372     int_type __ret;
00373     const bool __testpos = this->eback() < this->gptr();
00374     if (__builtin_expect(!__testpos || 
00375                  !traits_type::eq(__c, this->gptr()[-1]), false))
00376       __ret = this->pbackfail(traits_type::to_int_type(__c));
00377     else 
00378       {
00379         this->gbump(-1);
00380         __ret = traits_type::to_int_type(*this->gptr());
00381       }
00382     return __ret;
00383       }
00384 
00385       /**
00386        *  @brief  Moving backwards in the input stream.
00387        *  @return  The previous character, if possible.
00388        *
00389        *  If a putback position is available, this function decrements
00390        *  the input pointer and returns that character.  Otherwise,
00391        *  calls and returns pbackfail().  The effect is to @a unget
00392        *  the last character @a gotten.
00393       */
00394       int_type 
00395       sungetc()
00396       {
00397     int_type __ret;
00398     if (__builtin_expect(this->eback() < this->gptr(), true))
00399       {
00400         this->gbump(-1);
00401         __ret = traits_type::to_int_type(*this->gptr());
00402       }
00403     else 
00404       __ret = this->pbackfail();
00405     return __ret;
00406       }
00407 
00408       // [27.5.2.2.5] put area
00409       /**
00410        *  @brief  Entry point for all single-character output functions.
00411        *  @param  __c  A character to output.
00412        *  @return  @a __c, if possible.
00413        *
00414        *  One of two public output functions.
00415        *
00416        *  If a write position is available for the output sequence (i.e.,
00417        *  the buffer is not full), stores @a __c in that position, increments
00418        *  the position, and returns @c traits::to_int_type(__c).  If a write
00419        *  position is not available, returns @c overflow(__c).
00420       */
00421       int_type 
00422       sputc(char_type __c)
00423       {
00424     int_type __ret;
00425     if (__builtin_expect(this->pptr() < this->epptr(), true))
00426       {
00427         *this->pptr() = __c;
00428         this->pbump(1);
00429         __ret = traits_type::to_int_type(__c);
00430       }
00431     else
00432       __ret = this->overflow(traits_type::to_int_type(__c));
00433     return __ret;
00434       }
00435 
00436       /**
00437        *  @brief  Entry point for all single-character output functions.
00438        *  @param  __s  A buffer read area.
00439        *  @param  __n  A count.
00440        *
00441        *  One of two public output functions.
00442        *
00443        *
00444        *  Returns xsputn(__s,__n).  The effect is to write @a __s[0] through
00445        *  @a __s[__n-1] to the output sequence, if possible.
00446       */
00447       streamsize 
00448       sputn(const char_type* __s, streamsize __n)
00449       { return this->xsputn(__s, __n); }
00450 
00451     protected:
00452       /**
00453        *  @brief  Base constructor.
00454        *
00455        *  Only called from derived constructors, and sets up all the
00456        *  buffer data to zero, including the pointers described in the
00457        *  basic_streambuf class description.  Note that, as a result,
00458        *  - the class starts with no read nor write positions available,
00459        *  - this is not an error
00460       */
00461       basic_streambuf()
00462       : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 
00463       _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
00464       _M_buf_locale(locale()) 
00465       { }
00466 
00467       // [27.5.2.3.1] get area access
00468       //@{
00469       /**
00470        *  @brief  Access to the get area.
00471        *
00472        *  These functions are only available to other protected functions,
00473        *  including derived classes.
00474        *
00475        *  - eback() returns the beginning pointer for the input sequence
00476        *  - gptr() returns the next pointer for the input sequence
00477        *  - egptr() returns the end pointer for the input sequence
00478       */
00479       char_type* 
00480       eback() const { return _M_in_beg; }
00481 
00482       char_type* 
00483       gptr()  const { return _M_in_cur;  }
00484 
00485       char_type* 
00486       egptr() const { return _M_in_end; }
00487       //@}
00488 
00489       /**
00490        *  @brief  Moving the read position.
00491        *  @param  __n  The delta by which to move.
00492        *
00493        *  This just advances the read position without returning any data.
00494       */
00495       void 
00496       gbump(int __n) { _M_in_cur += __n; }
00497 
00498       /**
00499        *  @brief  Setting the three read area pointers.
00500        *  @param  __gbeg  A pointer.
00501        *  @param  __gnext  A pointer.
00502        *  @param  __gend  A pointer.
00503        *  @post  @a __gbeg == @c eback(), @a __gnext == @c gptr(), and
00504        *         @a __gend == @c egptr()
00505       */
00506       void 
00507       setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
00508       {
00509     _M_in_beg = __gbeg;
00510     _M_in_cur = __gnext;
00511     _M_in_end = __gend;
00512       }
00513 
00514       // [27.5.2.3.2] put area access
00515       //@{
00516       /**
00517        *  @brief  Access to the put area.
00518        *
00519        *  These functions are only available to other protected functions,
00520        *  including derived classes.
00521        *
00522        *  - pbase() returns the beginning pointer for the output sequence
00523        *  - pptr() returns the next pointer for the output sequence
00524        *  - epptr() returns the end pointer for the output sequence
00525       */
00526       char_type* 
00527       pbase() const { return _M_out_beg; }
00528 
00529       char_type* 
00530       pptr() const { return _M_out_cur; }
00531 
00532       char_type* 
00533       epptr() const { return _M_out_end; }
00534       //@}
00535 
00536       /**
00537        *  @brief  Moving the write position.
00538        *  @param  __n  The delta by which to move.
00539        *
00540        *  This just advances the write position without returning any data.
00541       */
00542       void 
00543       pbump(int __n) { _M_out_cur += __n; }
00544 
00545       /**
00546        *  @brief  Setting the three write area pointers.
00547        *  @param  __pbeg  A pointer.
00548        *  @param  __pend  A pointer.
00549        *  @post  @a __pbeg == @c pbase(), @a __pbeg == @c pptr(), and
00550        *         @a __pend == @c epptr()
00551       */
00552       void 
00553       setp(char_type* __pbeg, char_type* __pend)
00554       { 
00555     _M_out_beg = _M_out_cur = __pbeg; 
00556     _M_out_end = __pend;
00557       }
00558 
00559       // [27.5.2.4] virtual functions
00560       // [27.5.2.4.1] locales
00561       /**
00562        *  @brief  Changes translations.
00563        *  @param  __loc  A new locale.
00564        *
00565        *  Translations done during I/O which depend on the current
00566        *  locale are changed by this call.  The standard adds,
00567        *  <em>Between invocations of this function a class derived
00568        *  from streambuf can safely cache results of calls to locale
00569        *  functions and to members of facets so obtained.</em>
00570        *
00571        *  @note  Base class version does nothing.
00572       */
00573       virtual void 
00574       imbue(const locale& __loc) 
00575       { }
00576 
00577       // [27.5.2.4.2] buffer management and positioning
00578       /**
00579        *  @brief  Manipulates the buffer.
00580        *
00581        *  Each derived class provides its own appropriate behavior.  See
00582        *  the next-to-last paragraph of 
00583        *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
00584        *  for more on this function.
00585        *
00586        *  @note  Base class version does nothing, returns @c this.
00587       */
00588       virtual basic_streambuf<char_type,_Traits>* 
00589       setbuf(char_type*, streamsize)
00590       { return this; }
00591       
00592       /**
00593        *  @brief  Alters the stream positions.
00594        *
00595        *  Each derived class provides its own appropriate behavior.
00596        *  @note  Base class version does nothing, returns a @c pos_type
00597        *         that represents an invalid stream position.
00598       */
00599       virtual pos_type 
00600       seekoff(off_type, ios_base::seekdir,
00601           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00602       { return pos_type(off_type(-1)); } 
00603 
00604       /**
00605        *  @brief  Alters the stream positions.
00606        *
00607        *  Each derived class provides its own appropriate behavior.
00608        *  @note  Base class version does nothing, returns a @c pos_type
00609        *         that represents an invalid stream position.
00610       */
00611       virtual pos_type 
00612       seekpos(pos_type, 
00613           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00614       { return pos_type(off_type(-1)); } 
00615 
00616       /**
00617        *  @brief  Synchronizes the buffer arrays with the controlled sequences.
00618        *  @return  -1 on failure.
00619        *
00620        *  Each derived class provides its own appropriate behavior,
00621        *  including the definition of @a failure.
00622        *  @note  Base class version does nothing, returns zero.
00623       */
00624       virtual int 
00625       sync() { return 0; }
00626 
00627       // [27.5.2.4.3] get area
00628       /**
00629        *  @brief  Investigating the data available.
00630        *  @return  An estimate of the number of characters available in the
00631        *           input sequence, or -1.
00632        *
00633        *  <em>If it returns a positive value, then successive calls to
00634        *  @c underflow() will not return @c traits::eof() until at
00635        *  least that number of characters have been supplied.  If @c
00636        *  showmanyc() returns -1, then calls to @c underflow() or @c
00637        *  uflow() will fail.</em> [27.5.2.4.3]/1
00638        *
00639        *  @note  Base class version does nothing, returns zero.
00640        *  @note  The standard adds that <em>the intention is not only that the
00641        *         calls [to underflow or uflow] will not return @c eof() but
00642        *         that they will return immediately.</em>
00643        *  @note  The standard adds that <em>the morphemes of @c showmanyc are
00644        *         @b es-how-many-see, not @b show-manic.</em>
00645       */
00646       virtual streamsize 
00647       showmanyc() { return 0; }
00648 
00649       /**
00650        *  @brief  Multiple character extraction.
00651        *  @param  __s  A buffer area.
00652        *  @param  __n  Maximum number of characters to assign.
00653        *  @return  The number of characters assigned.
00654        *
00655        *  Fills @a __s[0] through @a __s[__n-1] with characters from the input
00656        *  sequence, as if by @c sbumpc().  Stops when either @a __n characters
00657        *  have been copied, or when @c traits::eof() would be copied.
00658        *
00659        *  It is expected that derived classes provide a more efficient
00660        *  implementation by overriding this definition.
00661       */
00662       virtual streamsize 
00663       xsgetn(char_type* __s, streamsize __n);
00664 
00665       /**
00666        *  @brief  Fetches more data from the controlled sequence.
00667        *  @return  The first character from the <em>pending sequence</em>.
00668        *
00669        *  Informally, this function is called when the input buffer is
00670        *  exhausted (or does not exist, as buffering need not actually be
00671        *  done).  If a buffer exists, it is @a refilled.  In either case, the
00672        *  next available character is returned, or @c traits::eof() to
00673        *  indicate a null pending sequence.
00674        *
00675        *  For a formal definition of the pending sequence, see a good text
00676        *  such as Langer & Kreft, or [27.5.2.4.3]/7-14.
00677        *
00678        *  A functioning input streambuf can be created by overriding only
00679        *  this function (no buffer area will be used).  For an example, see
00680        *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.html
00681        *
00682        *  @note  Base class version does nothing, returns eof().
00683       */
00684       virtual int_type 
00685       underflow()
00686       { return traits_type::eof(); }
00687 
00688       /**
00689        *  @brief  Fetches more data from the controlled sequence.
00690        *  @return  The first character from the <em>pending sequence</em>.
00691        *
00692        *  Informally, this function does the same thing as @c underflow(),
00693        *  and in fact is required to call that function.  It also returns
00694        *  the new character, like @c underflow() does.  However, this
00695        *  function also moves the read position forward by one.
00696       */
00697       virtual int_type 
00698       uflow() 
00699       {
00700     int_type __ret = traits_type::eof();
00701     const bool __testeof = traits_type::eq_int_type(this->underflow(), 
00702                             __ret);
00703     if (!__testeof)
00704       {
00705         __ret = traits_type::to_int_type(*this->gptr());
00706         this->gbump(1);
00707       }
00708     return __ret;    
00709       }
00710 
00711       // [27.5.2.4.4] putback
00712       /**
00713        *  @brief  Tries to back up the input sequence.
00714        *  @param  __c  The character to be inserted back into the sequence.
00715        *  @return  eof() on failure, <em>some other value</em> on success
00716        *  @post  The constraints of @c gptr(), @c eback(), and @c pptr()
00717        *         are the same as for @c underflow().
00718        *
00719        *  @note  Base class version does nothing, returns eof().
00720       */
00721       virtual int_type 
00722       pbackfail(int_type __c  = traits_type::eof())
00723       { return traits_type::eof(); }
00724 
00725       // Put area:
00726       /**
00727        *  @brief  Multiple character insertion.
00728        *  @param  __s  A buffer area.
00729        *  @param  __n  Maximum number of characters to write.
00730        *  @return  The number of characters written.
00731        *
00732        *  Writes @a __s[0] through @a __s[__n-1] to the output sequence, as if
00733        *  by @c sputc().  Stops when either @a n characters have been
00734        *  copied, or when @c sputc() would return @c traits::eof().
00735        *
00736        *  It is expected that derived classes provide a more efficient
00737        *  implementation by overriding this definition.
00738       */
00739       virtual streamsize 
00740       xsputn(const char_type* __s, streamsize __n);
00741 
00742       /**
00743        *  @brief  Consumes data from the buffer; writes to the
00744        *          controlled sequence.
00745        *  @param  __c  An additional character to consume.
00746        *  @return  eof() to indicate failure, something else (usually
00747        *           @a __c, or not_eof())
00748        *
00749        *  Informally, this function is called when the output buffer
00750        *  is full (or does not exist, as buffering need not actually
00751        *  be done).  If a buffer exists, it is @a consumed, with
00752        *  <em>some effect</em> on the controlled sequence.
00753        *  (Typically, the buffer is written out to the sequence
00754        *  verbatim.)  In either case, the character @a c is also
00755        *  written out, if @a __c is not @c eof().
00756        *
00757        *  For a formal definition of this function, see a good text
00758        *  such as Langer & Kreft, or [27.5.2.4.5]/3-7.
00759        *
00760        *  A functioning output streambuf can be created by overriding only
00761        *  this function (no buffer area will be used).
00762        *
00763        *  @note  Base class version does nothing, returns eof().
00764       */
00765       virtual int_type 
00766       overflow(int_type __c  = traits_type::eof())
00767       { return traits_type::eof(); }
00768 
00769 #if _GLIBCXX_USE_DEPRECATED
00770     // Annex D.6
00771     public:
00772       /**
00773        *  @brief  Tosses a character.
00774        *
00775        *  Advances the read pointer, ignoring the character that would have
00776        *  been read.
00777        *
00778        *  See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
00779        */
00780       void 
00781       stossc() 
00782       {
00783     if (this->gptr() < this->egptr()) 
00784       this->gbump(1);
00785     else 
00786       this->uflow();
00787       }
00788 #endif
00789 
00790       // Also used by specializations for char and wchar_t in src.
00791       void 
00792       __safe_gbump(streamsize __n) { _M_in_cur += __n; }
00793 
00794       void
00795       __safe_pbump(streamsize __n) { _M_out_cur += __n; }
00796 
00797     private:
00798       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00799       // Side effect of DR 50. 
00800       basic_streambuf(const __streambuf_type& __sb)
00801       : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur), 
00802       _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg), 
00803       _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
00804       _M_buf_locale(__sb._M_buf_locale) 
00805       { }
00806 
00807       __streambuf_type& 
00808       operator=(const __streambuf_type&) { return *this; };
00809     };
00810 
00811   // Explicit specialization declarations, defined in src/streambuf.cc.
00812   template<>
00813     streamsize
00814     __copy_streambufs_eof(basic_streambuf<char>* __sbin,
00815               basic_streambuf<char>* __sbout, bool& __ineof);
00816 #ifdef _GLIBCXX_USE_WCHAR_T
00817   template<>
00818     streamsize
00819     __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
00820               basic_streambuf<wchar_t>* __sbout, bool& __ineof);
00821 #endif
00822 
00823 _GLIBCXX_END_NAMESPACE_VERSION
00824 } // namespace
00825 
00826 #include <bits/streambuf.tcc>
00827 
00828 #endif /* _GLIBCXX_STREAMBUF */