streambuf

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00001 // Stream buffer classes -*- C++ -*-
00002 
00003 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
00004 // 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 along
00018 // with this library; see the file COPYING.  If not, write to the Free
00019 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
00020 // 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 //
00032 // ISO C++ 14882: 27.5  Stream buffers
00033 //
00034 
00035 /** @file streambuf
00036  *  This is a Standard C++ Library header.
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 
00049 namespace std
00050 {
00051   /**
00052    *  @if maint
00053    *  Does stuff.
00054    *  @endif
00055   */
00056   template<typename _CharT, typename _Traits>
00057     streamsize
00058     __copy_streambufs(basic_streambuf<_CharT, _Traits>* __sbin,
00059               basic_streambuf<_CharT, _Traits>* __sbout);
00060   
00061   /**
00062    *  @brief  The actual work of input and output (interface).
00063    *
00064    *  This is a base class.  Derived stream buffers each control a
00065    *  pair of character sequences:  one for input, and one for output.
00066    *
00067    *  Section [27.5.1] of the standard describes the requirements and
00068    *  behavior of stream buffer classes.  That section (three paragraphs)
00069    *  is reproduced here, for simplicity and accuracy.
00070    *
00071    *  -# Stream buffers can impose various constraints on the sequences
00072    *     they control.  Some constraints are:
00073    *     - The controlled input sequence can be not readable.
00074    *     - The controlled output sequence can be not writable.
00075    *     - The controlled sequences can be associated with the contents of
00076    *       other representations for character sequences, such as external
00077    *       files.
00078    *     - The controlled sequences can support operations @e directly to or
00079    *       from associated sequences.
00080    *     - The controlled sequences can impose limitations on how the
00081    *       program can read characters from a sequence, write characters to
00082    *       a sequence, put characters back into an input sequence, or alter
00083    *       the stream position.
00084    *     .
00085    *  -# Each sequence is characterized by three pointers which, if non-null,
00086    *     all point into the same @c charT array object.  The array object
00087    *     represents, at any moment, a (sub)sequence of characters from the
00088    *     sequence.  Operations performed on a sequence alter the values
00089    *     stored in these pointers, perform reads and writes directly to or
00090    *     from associated sequences, and alter "the stream position" and
00091    *     conversion state as needed to maintain this subsequence relationship.
00092    *     The three pointers are:
00093    *     - the <em>beginning pointer</em>, or lowest element address in the
00094    *       array (called @e xbeg here);
00095    *     - the <em>next pointer</em>, or next element address that is a
00096    *       current candidate for reading or writing (called @e xnext here);
00097    *     - the <em>end pointer</em>, or first element address beyond the
00098    *       end of the array (called @e xend here).
00099    *     .
00100    *  -# The following semantic constraints shall always apply for any set
00101    *     of three pointers for a sequence, using the pointer names given
00102    *     immediately above:
00103    *     - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
00104    *       also be non-null pointers into the same @c charT array, as
00105    *       described above; otherwise, @e xbeg and @e xend shall also be null.
00106    *     - If @e xnext is not a null pointer and @e xnext < @e xend for an
00107    *       output sequence, then a <em>write position</em> is available.
00108    *       In this case, @e *xnext shall be assignable as the next element
00109    *       to write (to put, or to store a character value, into the sequence).
00110    *     - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
00111    *       input sequence, then a <em>putback position</em> is available.
00112    *       In this case, @e xnext[-1] shall have a defined value and is the
00113    *       next (preceding) element to store a character that is put back
00114    *       into the input sequence.
00115    *     - If @e xnext is not a null pointer and @e xnext< @e xend for an
00116    *       input sequence, then a <em>read position</em> is available.
00117    *       In this case, @e *xnext shall have a defined value and is the
00118    *       next element to read (to get, or to obtain a character value,
00119    *       from the sequence).
00120   */
00121   template<typename _CharT, typename _Traits>
00122     class basic_streambuf 
00123     {
00124     public:
00125       //@{
00126       /**
00127        *  These are standard types.  They permit a standardized way of
00128        *  referring to names of (or names dependant on) the template
00129        *  parameters, which are specific to the implementation.
00130       */
00131       typedef _CharT                    char_type;
00132       typedef _Traits                   traits_type;
00133       typedef typename traits_type::int_type        int_type;
00134       typedef typename traits_type::pos_type        pos_type;
00135       typedef typename traits_type::off_type        off_type;
00136       //@}
00137 
00138       //@{
00139       /**
00140        *  @if maint
00141        *  This is a non-standard type.
00142        *  @endif
00143       */
00144       typedef basic_streambuf<char_type, traits_type>   __streambuf_type;
00145       //@}
00146       
00147       friend class basic_ios<char_type, traits_type>;
00148       friend class basic_istream<char_type, traits_type>;
00149       friend class basic_ostream<char_type, traits_type>;
00150       friend class istreambuf_iterator<char_type, traits_type>;
00151       friend class ostreambuf_iterator<char_type, traits_type>;
00152 
00153       friend streamsize
00154       __copy_streambufs<>(__streambuf_type* __sbin,
00155               __streambuf_type* __sbout);
00156 
00157       template<typename _CharT2, typename _Traits2, typename _Alloc>
00158         friend basic_istream<_CharT2, _Traits2>&
00159         getline(basic_istream<_CharT2, _Traits2>&,
00160         basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
00161 
00162     protected:
00163       //@{
00164       /**
00165        *  @if maint
00166        *  This is based on _IO_FILE, just reordered to be more consistent,
00167        *  and is intended to be the most minimal abstraction for an
00168        *  internal buffer.
00169        *  -  get == input == read
00170        *  -  put == output == write
00171        *  @endif
00172       */
00173       char_type*        _M_in_beg;     // Start of get area. 
00174       char_type*        _M_in_cur;     // Current read area. 
00175       char_type*        _M_in_end;     // End of get area. 
00176       char_type*        _M_out_beg;    // Start of put area. 
00177       char_type*        _M_out_cur;    // Current put area. 
00178       char_type*        _M_out_end;    // End of put area.
00179 
00180       /**
00181        *  @if maint
00182        *  Current locale setting.
00183        *  @endif
00184       */
00185       locale            _M_buf_locale;  
00186 
00187   public:
00188       /// Destructor deallocates no buffer space.
00189       virtual 
00190       ~basic_streambuf() 
00191       { }
00192 
00193       // [27.5.2.2.1] locales
00194       /**
00195        *  @brief  Entry point for imbue().
00196        *  @param  loc  The new locale.
00197        *  @return  The previous locale.
00198        *
00199        *  Calls the derived imbue(loc).
00200       */
00201       locale 
00202       pubimbue(const locale &__loc)
00203       {
00204     locale __tmp(this->getloc());
00205     this->imbue(__loc);
00206     _M_buf_locale = __loc;
00207     return __tmp;
00208       }
00209 
00210       /**
00211        *  @brief  Locale access.
00212        *  @return  The current locale in effect.
00213        *
00214        *  If pubimbue(loc) has been called, then the most recent @c loc
00215        *  is returned.  Otherwise the global locale in effect at the time
00216        *  of construction is returned.
00217       */
00218       locale   
00219       getloc() const
00220       { return _M_buf_locale; } 
00221 
00222       // [27.5.2.2.2] buffer management and positioning
00223       //@{
00224       /**
00225        *  @brief  Entry points for derived buffer functions.
00226        *
00227        *  The public versions of @c pubfoo dispatch to the protected
00228        *  derived @c foo member functions, passing the arguments (if any)
00229        *  and returning the result unchanged.
00230       */
00231       __streambuf_type* 
00232       pubsetbuf(char_type* __s, streamsize __n) 
00233       { return this->setbuf(__s, __n); }
00234 
00235       pos_type 
00236       pubseekoff(off_type __off, ios_base::seekdir __way, 
00237          ios_base::openmode __mode = ios_base::in | ios_base::out)
00238       { return this->seekoff(__off, __way, __mode); }
00239 
00240       pos_type 
00241       pubseekpos(pos_type __sp,
00242          ios_base::openmode __mode = ios_base::in | ios_base::out)
00243       { return this->seekpos(__sp, __mode); }
00244 
00245       int 
00246       pubsync() { return this->sync(); }
00247       //@}
00248 
00249       // [27.5.2.2.3] get area
00250       /**
00251        *  @brief  Looking ahead into the stream.
00252        *  @return  The number of characters available.
00253        *
00254        *  If a read position is available, returns the number of characters
00255        *  available for reading before the buffer must be refilled.
00256        *  Otherwise returns the derived @c showmanyc().
00257       */
00258       streamsize 
00259       in_avail() 
00260       { 
00261     const streamsize __ret = this->egptr() - this->gptr();
00262     return __ret ? __ret : this->showmanyc();
00263       }
00264 
00265       /**
00266        *  @brief  Getting the next character.
00267        *  @return  The next character, or eof.
00268        *
00269        *  Calls @c sbumpc(), and if that function returns
00270        *  @c traits::eof(), so does this function.  Otherwise, @c sgetc().
00271       */
00272       int_type 
00273       snextc()
00274       {
00275     int_type __ret = traits_type::eof();
00276     if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 
00277                                __ret), true))
00278       __ret = this->sgetc();
00279     return __ret;
00280       }
00281 
00282       /**
00283        *  @brief  Getting the next character.
00284        *  @return  The next character, or eof.
00285        *
00286        *  If the input read position is available, returns that character
00287        *  and increments the read pointer, otherwise calls and returns
00288        *  @c uflow().
00289       */
00290       int_type 
00291       sbumpc()
00292       {
00293     int_type __ret;
00294     if (__builtin_expect(this->gptr() < this->egptr(), true))
00295       {
00296         __ret = traits_type::to_int_type(*this->gptr());
00297         this->gbump(1);
00298       }
00299     else 
00300       __ret = this->uflow();
00301     return __ret;
00302       }
00303 
00304       /**
00305        *  @brief  Getting the next character.
00306        *  @return  The next character, or eof.
00307        *
00308        *  If the input read position is available, returns that character,
00309        *  otherwise calls and returns @c underflow().  Does not move the 
00310        *  read position after fetching the character.
00311       */
00312       int_type 
00313       sgetc()
00314       {
00315     int_type __ret;
00316     if (__builtin_expect(this->gptr() < this->egptr(), true))
00317       __ret = traits_type::to_int_type(*this->gptr());
00318     else 
00319       __ret = this->underflow();
00320     return __ret;
00321       }
00322 
00323       /**
00324        *  @brief  Entry point for xsgetn.
00325        *  @param  s  A buffer area.
00326        *  @param  n  A count.
00327        *
00328        *  Returns xsgetn(s,n).  The effect is to fill @a s[0] through
00329        *  @a s[n-1] with characters from the input sequence, if possible.
00330       */
00331       streamsize 
00332       sgetn(char_type* __s, streamsize __n)
00333       { return this->xsgetn(__s, __n); }
00334 
00335       // [27.5.2.2.4] putback
00336       /**
00337        *  @brief  Pushing characters back into the input stream.
00338        *  @param  c  The character to push back.
00339        *  @return  The previous character, if possible.
00340        *
00341        *  Similar to sungetc(), but @a c is pushed onto the stream instead
00342        *  of "the previous character".  If successful, the next character
00343        *  fetched from the input stream will be @a c.
00344       */
00345       int_type 
00346       sputbackc(char_type __c)
00347       {
00348     int_type __ret;
00349     const bool __testpos = this->eback() < this->gptr();
00350     if (__builtin_expect(!__testpos || 
00351                  !traits_type::eq(__c, this->gptr()[-1]), false))
00352       __ret = this->pbackfail(traits_type::to_int_type(__c));
00353     else 
00354       {
00355         this->gbump(-1);
00356         __ret = traits_type::to_int_type(*this->gptr());
00357       }
00358     return __ret;
00359       }
00360 
00361       /**
00362        *  @brief  Moving backwards in the input stream.
00363        *  @return  The previous character, if possible.
00364        *
00365        *  If a putback position is available, this function decrements the
00366        *  input pointer and returns that character.  Otherwise, calls and
00367        *  returns pbackfail().  The effect is to "unget" the last character
00368        *  "gotten".
00369       */
00370       int_type 
00371       sungetc()
00372       {
00373     int_type __ret;
00374     if (__builtin_expect(this->eback() < this->gptr(), true))
00375       {
00376         this->gbump(-1);
00377         __ret = traits_type::to_int_type(*this->gptr());
00378       }
00379     else 
00380       __ret = this->pbackfail();
00381     return __ret;
00382       }
00383 
00384       // [27.5.2.2.5] put area
00385       /**
00386        *  @brief  Entry point for all single-character output functions.
00387        *  @param  c  A character to output.
00388        *  @return  @a c, if possible.
00389        *
00390        *  One of two public output functions.
00391        *
00392        *  If a write position is available for the output sequence (i.e.,
00393        *  the buffer is not full), stores @a c in that position, increments
00394        *  the position, and returns @c traits::to_int_type(c).  If a write
00395        *  position is not available, returns @c overflow(c).
00396       */
00397       int_type 
00398       sputc(char_type __c)
00399       {
00400     int_type __ret;
00401     if (__builtin_expect(this->pptr() < this->epptr(), true))
00402       {
00403         *this->pptr() = __c;
00404         this->pbump(1);
00405         __ret = traits_type::to_int_type(__c);
00406       }
00407     else
00408       __ret = this->overflow(traits_type::to_int_type(__c));
00409     return __ret;
00410       }
00411 
00412       /**
00413        *  @brief  Entry point for all single-character output functions.
00414        *  @param  s  A buffer read area.
00415        *  @param  n  A count.
00416        *
00417        *  One of two public output functions.
00418        *
00419        *
00420        *  Returns xsputn(s,n).  The effect is to write @a s[0] through
00421        *  @a s[n-1] to the output sequence, if possible.
00422       */
00423       streamsize 
00424       sputn(const char_type* __s, streamsize __n)
00425       { return this->xsputn(__s, __n); }
00426 
00427     protected:
00428       /**
00429        *  @brief  Base constructor.
00430        *
00431        *  Only called from derived constructors, and sets up all the
00432        *  buffer data to zero, including the pointers described in the
00433        *  basic_streambuf class description.  Note that, as a result,
00434        *  - the class starts with no read nor write positions available,
00435        *  - this is not an error
00436       */
00437       basic_streambuf()
00438       : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 
00439       _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
00440       _M_buf_locale(locale()) 
00441       { }
00442 
00443       // [27.5.2.3.1] get area access
00444       //@{
00445       /**
00446        *  @brief  Access to the get area.
00447        *
00448        *  These functions are only available to other protected functions,
00449        *  including derived classes.
00450        *
00451        *  - eback() returns the beginning pointer for the input sequence
00452        *  - gptr() returns the next pointer for the input sequence
00453        *  - egptr() returns the end pointer for the input sequence
00454       */
00455       char_type* 
00456       eback() const { return _M_in_beg; }
00457 
00458       char_type* 
00459       gptr()  const { return _M_in_cur;  }
00460 
00461       char_type* 
00462       egptr() const { return _M_in_end; }
00463       //@}
00464 
00465       /**
00466        *  @brief  Moving the read position.
00467        *  @param  n  The delta by which to move.
00468        *
00469        *  This just advances the read position without returning any data.
00470       */
00471       void 
00472       gbump(int __n) { _M_in_cur += __n; }
00473 
00474       /**
00475        *  @brief  Setting the three read area pointers.
00476        *  @param  gbeg  A pointer.
00477        *  @param  gnext  A pointer.
00478        *  @param  gend  A pointer.
00479        *  @post  @a gbeg == @c eback(), @a gnext == @c gptr(), and
00480        *         @a gend == @c egptr()
00481       */
00482       void 
00483       setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
00484       {
00485     _M_in_beg = __gbeg;
00486     _M_in_cur = __gnext;
00487     _M_in_end = __gend;
00488       }
00489 
00490       // [27.5.2.3.2] put area access
00491       //@{
00492       /**
00493        *  @brief  Access to the put area.
00494        *
00495        *  These functions are only available to other protected functions,
00496        *  including derived classes.
00497        *
00498        *  - pbase() returns the beginning pointer for the output sequence
00499        *  - pptr() returns the next pointer for the output sequence
00500        *  - epptr() returns the end pointer for the output sequence
00501       */
00502       char_type* 
00503       pbase() const { return _M_out_beg; }
00504 
00505       char_type* 
00506       pptr() const { return _M_out_cur; }
00507 
00508       char_type* 
00509       epptr() const { return _M_out_end; }
00510       //@}
00511 
00512       /**
00513        *  @brief  Moving the write position.
00514        *  @param  n  The delta by which to move.
00515        *
00516        *  This just advances the write position without returning any data.
00517       */
00518       void 
00519       pbump(int __n) { _M_out_cur += __n; }
00520 
00521       /**
00522        *  @brief  Setting the three write area pointers.
00523        *  @param  pbeg  A pointer.
00524        *  @param  pend  A pointer.
00525        *  @post  @a pbeg == @c pbase(), @a pbeg == @c pptr(), and
00526        *         @a pend == @c epptr()
00527       */
00528       void 
00529       setp(char_type* __pbeg, char_type* __pend)
00530       { 
00531     _M_out_beg = _M_out_cur = __pbeg; 
00532     _M_out_end = __pend;
00533       }
00534 
00535       // [27.5.2.4] virtual functions
00536       // [27.5.2.4.1] locales
00537       /**
00538        *  @brief  Changes translations.
00539        *  @param  loc  A new locale.
00540        *
00541        *  Translations done during I/O which depend on the current locale
00542        *  are changed by this call.  The standard adds, "Between invocations
00543        *  of this function a class derived from streambuf can safely cache
00544        *  results of calls to locale functions and to members of facets
00545        *  so obtained."
00546        *
00547        *  @note  Base class version does nothing.
00548       */
00549       virtual void 
00550       imbue(const locale&) 
00551       { }
00552 
00553       // [27.5.2.4.2] buffer management and positioning
00554       /**
00555        *  @brief  Maniuplates the buffer.
00556        *
00557        *  Each derived class provides its own appropriate behavior.  See
00558        *  the next-to-last paragraph of 
00559        *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for
00560        *  more on this function.
00561        *
00562        *  @note  Base class version does nothing, returns @c this.
00563       */
00564       virtual basic_streambuf<char_type,_Traits>* 
00565       setbuf(char_type*, streamsize)
00566       { return this; }
00567       
00568       /**
00569        *  @brief  Alters the stream positions.
00570        *
00571        *  Each derived class provides its own appropriate behavior.
00572        *  @note  Base class version does nothing, returns a @c pos_type
00573        *         that represents an invalid stream position.
00574       */
00575       virtual pos_type 
00576       seekoff(off_type, ios_base::seekdir,
00577           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00578       { return pos_type(off_type(-1)); } 
00579 
00580       /**
00581        *  @brief  Alters the stream positions.
00582        *
00583        *  Each derived class provides its own appropriate behavior.
00584        *  @note  Base class version does nothing, returns a @c pos_type
00585        *         that represents an invalid stream position.
00586       */
00587       virtual pos_type 
00588       seekpos(pos_type, 
00589           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00590       { return pos_type(off_type(-1)); } 
00591 
00592       /**
00593        *  @brief  Synchronizes the buffer arrays with the controlled sequences.
00594        *  @return  -1 on failure.
00595        *
00596        *  Each derived class provides its own appropriate behavior,
00597        *  including the definition of "failure".
00598        *  @note  Base class version does nothing, returns zero.
00599       */
00600       virtual int 
00601       sync() { return 0; }
00602 
00603       // [27.5.2.4.3] get area
00604       /**
00605        *  @brief  Investigating the data available.
00606        *  @return  An estimate of the number of characters available in the
00607        *           input sequence, or -1.
00608        *
00609        *  "If it returns a positive value, then successive calls to
00610        *  @c underflow() will not return @c traits::eof() until at least that
00611        *  number of characters have been supplied.  If @c showmanyc()
00612        *  returns -1, then calls to @c underflow() or @c uflow() will fail."
00613        *  [27.5.2.4.3]/1
00614        *
00615        *  @note  Base class version does nothing, returns zero.
00616        *  @note  The standard adds that "the intention is not only that the
00617        *         calls [to underflow or uflow] will not return @c eof() but
00618        *         that they will return "immediately".
00619        *  @note  The standard adds that "the morphemes of @c showmanyc are
00620        *         "es-how-many-see", not "show-manic".
00621       */
00622       virtual streamsize 
00623       showmanyc() { return 0; }
00624 
00625       /**
00626        *  @brief  Multiple character extraction.
00627        *  @param  s  A buffer area.
00628        *  @param  n  Maximum number of characters to assign.
00629        *  @return  The number of characters assigned.
00630        *
00631        *  Fills @a s[0] through @a s[n-1] with characters from the input
00632        *  sequence, as if by @c sbumpc().  Stops when either @a n characters
00633        *  have been copied, or when @c traits::eof() would be copied.
00634        *
00635        *  It is expected that derived classes provide a more efficient
00636        *  implementation by overriding this definition.
00637       */
00638       virtual streamsize 
00639       xsgetn(char_type* __s, streamsize __n);
00640 
00641       /**
00642        *  @brief  Fetches more data from the controlled sequence.
00643        *  @return  The first character from the <em>pending sequence</em>.
00644        *
00645        *  Informally, this function is called when the input buffer is
00646        *  exhausted (or does not exist, as buffering need not actually be
00647        *  done).  If a buffer exists, it is "refilled".  In either case, the
00648        *  next available character is returned, or @c traits::eof() to
00649        *  indicate a null pending sequence.
00650        *
00651        *  For a formal definiton of the pending sequence, see a good text
00652        *  such as Langer & Kreft, or [27.5.2.4.3]/7-14.
00653        *
00654        *  A functioning input streambuf can be created by overriding only
00655        *  this function (no buffer area will be used).  For an example, see
00656        *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6
00657        *
00658        *  @note  Base class version does nothing, returns eof().
00659       */
00660       virtual int_type 
00661       underflow()
00662       { return traits_type::eof(); }
00663 
00664       /**
00665        *  @brief  Fetches more data from the controlled sequence.
00666        *  @return  The first character from the <em>pending sequence</em>.
00667        *
00668        *  Informally, this function does the same thing as @c underflow(),
00669        *  and in fact is required to call that function.  It also returns
00670        *  the new character, like @c underflow() does.  However, this
00671        *  function also moves the read position forward by one.
00672       */
00673       virtual int_type 
00674       uflow() 
00675       {
00676     int_type __ret = traits_type::eof();
00677     const bool __testeof = traits_type::eq_int_type(this->underflow(), 
00678                             __ret);
00679     if (!__testeof)
00680       {
00681         __ret = traits_type::to_int_type(*this->gptr());
00682         this->gbump(1);
00683       }
00684     return __ret;    
00685       }
00686 
00687       // [27.5.2.4.4] putback
00688       /**
00689        *  @brief  Tries to back up the input sequence.
00690        *  @param  c  The character to be inserted back into the sequence.
00691        *  @return  eof() on failure, "some other value" on success
00692        *  @post  The constraints of @c gptr(), @c eback(), and @c pptr()
00693        *         are the same as for @c underflow().
00694        *
00695        *  @note  Base class version does nothing, returns eof().
00696       */
00697       virtual int_type 
00698       pbackfail(int_type /* __c */  = traits_type::eof())
00699       { return traits_type::eof(); }
00700 
00701       // Put area:
00702       /**
00703        *  @brief  Multiple character insertion.
00704        *  @param  s  A buffer area.
00705        *  @param  n  Maximum number of characters to write.
00706        *  @return  The number of characters written.
00707        *
00708        *  Writes @a s[0] through @a s[n-1] to the output sequence, as if
00709        *  by @c sputc().  Stops when either @a n characters have been
00710        *  copied, or when @c sputc() would return @c traits::eof().
00711        *
00712        *  It is expected that derived classes provide a more efficient
00713        *  implementation by overriding this definition.
00714       */
00715       virtual streamsize 
00716       xsputn(const char_type* __s, streamsize __n);
00717 
00718       /**
00719        *  @brief  Consumes data from the buffer; writes to the
00720        *          controlled sequence.
00721        *  @param  c  An additional character to consume.
00722        *  @return  eof() to indicate failure, something else (usually
00723        *           @a c, or not_eof())
00724        *
00725        *  Informally, this function is called when the output buffer is full
00726        *  (or does not exist, as buffering need not actually be done).  If a
00727        *  buffer exists, it is "consumed", with "some effect" on the
00728        *  controlled sequence.  (Typically, the buffer is written out to the
00729        *  sequence verbatim.)  In either case, the character @a c is also
00730        *  written out, if @a c is not @c eof().
00731        *
00732        *  For a formal definiton of this function, see a good text
00733        *  such as Langer & Kreft, or [27.5.2.4.5]/3-7.
00734        *
00735        *  A functioning output streambuf can be created by overriding only
00736        *  this function (no buffer area will be used).
00737        *
00738        *  @note  Base class version does nothing, returns eof().
00739       */
00740       virtual int_type 
00741       overflow(int_type /* __c */ = traits_type::eof())
00742       { return traits_type::eof(); }
00743 
00744 #ifdef _GLIBCXX_DEPRECATED
00745     // Annex D.6
00746     public:
00747       /**
00748        *  @brief  Tosses a character.
00749        *
00750        *  Advances the read pointer, ignoring the character that would have
00751        *  been read.
00752        *
00753        *  See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
00754        *
00755        *  @note  This function has been deprecated by the standard.  You
00756        *         must define @c _GLIBCXX_DEPRECATED to make this visible; see
00757        *         c++config.h.
00758       */
00759       void 
00760       stossc() 
00761       {
00762     if (this->gptr() < this->egptr()) 
00763       this->gbump(1);
00764     else 
00765       this->uflow();
00766       }
00767 #endif
00768 
00769     private:
00770       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00771       // Side effect of DR 50. 
00772       basic_streambuf(const __streambuf_type& __sb)
00773       : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur), 
00774       _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg), 
00775       _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
00776       _M_buf_locale(__sb._M_buf_locale) 
00777       { }
00778 
00779       __streambuf_type& 
00780       operator=(const __streambuf_type&) { return *this; };
00781     };
00782 
00783   // Explicit specialization declarations, defined in src/streambuf.cc.
00784   template<>
00785     streamsize
00786     __copy_streambufs(basic_streambuf<char>* __sbin,
00787               basic_streambuf<char>* __sbout);
00788 #ifdef _GLIBCXX_USE_WCHAR_T
00789   template<>
00790     streamsize
00791     __copy_streambufs(basic_streambuf<wchar_t>* __sbin,
00792               basic_streambuf<wchar_t>* __sbout);
00793 #endif
00794 } // namespace std
00795 
00796 #ifndef _GLIBCXX_EXPORT_TEMPLATE
00797 # include <bits/streambuf.tcc>
00798 #endif
00799 
00800 #endif /* _GLIBCXX_STREAMBUF */

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