streambuf

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00001 // Stream buffer classes -*- C++ -*-
00002 
00003 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003
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.  You should @c #include this header
00037  *  in your programs, rather than any of the "st[dl]_*.h" implementation files.
00038  */
00039 
00040 #ifndef _CPP_STREAMBUF
00041 #define _CPP_STREAMBUF  1
00042 
00043 #pragma GCC system_header
00044 
00045 #include <bits/c++config.h>
00046 #include <iosfwd>
00047 #include <cstdio>   // For SEEK_SET, SEEK_CUR, SEEK_END
00048 #include <bits/localefwd.h>
00049 #include <bits/ios_base.h>
00050 
00051 namespace std
00052 {
00053   /**
00054    *  @if maint
00055    *  Does stuff.
00056    *  @endif
00057   */
00058   template<typename _CharT, typename _Traits>
00059     streamsize
00060     __copy_streambufs(basic_ios<_CharT, _Traits>& _ios,
00061               basic_streambuf<_CharT, _Traits>* __sbin,
00062               basic_streambuf<_CharT, _Traits>* __sbout);
00063   
00064   /**
00065    *  @brief  The actual work of input and output (interface).
00066    *
00067    *  This is a base class.  Derived stream buffers each control a
00068    *  pair of character sequences:  one for input, and one for output.
00069    *
00070    *  Section [27.5.1] of the standard describes the requirements and
00071    *  behavior of stream buffer classes.  That section (three paragraphs)
00072    *  is reproduced here, for simplicity and accuracy.
00073    *
00074    *  -# Stream buffers can impose various constraints on the sequences
00075    *     they control.  Some constraints are:
00076    *     - The controlled input sequence can be not readable.
00077    *     - The controlled output sequence can be not writable.
00078    *     - The controlled sequences can be associated with the contents of
00079    *       other representations for character sequences, such as external
00080    *       files.
00081    *     - The controlled sequences can support operations @e directly to or
00082    *       from associated sequences.
00083    *     - The controlled sequences can impose limitations on how the
00084    *       program can read characters from a sequence, write characters to
00085    *       a sequence, put characters back into an input sequence, or alter
00086    *       the stream position.
00087    *     .
00088    *  -# Each sequence is characterized by three pointers which, if non-null,
00089    *     all point into the same @c charT array object.  The array object
00090    *     represents, at any moment, a (sub)sequence of characters from the
00091    *     sequence.  Operations performed on a sequence alter the values
00092    *     stored in these pointers, perform reads and writes directly to or
00093    *     from associated sequences, and alter "the stream position" and
00094    *     conversion state as needed to maintain this subsequence relationship.
00095    *     The three pointers are:
00096    *     - the <em>beginning pointer</em>, or lowest element address in the
00097    *       array (called @e xbeg here);
00098    *     - the <em>next pointer</em>, or next element address that is a
00099    *       current candidate for reading or writing (called @e xnext here);
00100    *     - the <em>end pointer</em>, or first element address beyond the
00101    *       end of the array (called @e xend here).
00102    *     .
00103    *  -# The following semantic constraints shall always apply for any set
00104    *     of three pointers for a sequence, using the pointer names given
00105    *     immediately above:
00106    *     - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
00107    *       also be non-null pointers into the same @c charT array, as
00108    *       described above; otherwise, @e xbeg and @e xend shall also be null.
00109    *     - If @e xnext is not a null pointer and @e xnext < @e xend for an
00110    *       output sequence, then a <em>write position</em> is available.
00111    *       In this case, @e *xnext shall be assignable as the next element
00112    *       to write (to put, or to store a character value, into the sequence).
00113    *     - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
00114    *       input sequence, then a <em>putback position</em> is available.
00115    *       In this case, @e xnext[-1] shall have a defined value and is the
00116    *       next (preceding) element to store a character that is put back
00117    *       into the input sequence.
00118    *     - If @e xnext is not a null pointer and @e xnext< @e xend for an
00119    *       input sequence, then a <em>read position</em> is available.
00120    *       In this case, @e *xnext shall have a defined value and is the
00121    *       next element to read (to get, or to obtain a character value,
00122    *       from the sequence).
00123   */
00124   template<typename _CharT, typename _Traits>
00125     class basic_streambuf 
00126     {
00127     public:
00128       //@{
00129       /**
00130        *  These are standard types.  They permit a standardized way of
00131        *  referring to names of (or names dependant on) the template
00132        *  parameters, which are specific to the implementation.
00133       */
00134       typedef _CharT                    char_type;
00135       typedef _Traits                   traits_type;
00136       typedef typename traits_type::int_type        int_type;
00137       typedef typename traits_type::pos_type        pos_type;
00138       typedef typename traits_type::off_type        off_type;
00139       //@}
00140 
00141       //@{
00142       /**
00143        *  @if maint
00144        *  These are non-standard types.
00145        *  @endif
00146       */
00147       typedef ctype<char_type>                  __ctype_type;
00148       typedef basic_streambuf<char_type, traits_type>   __streambuf_type;
00149       typedef typename traits_type::state_type      __state_type;
00150       //@}
00151       
00152       friend class basic_ios<char_type, traits_type>;
00153       friend class basic_istream<char_type, traits_type>;
00154       friend class basic_ostream<char_type, traits_type>;
00155       friend class istreambuf_iterator<char_type, traits_type>;
00156       friend class ostreambuf_iterator<char_type, traits_type>;
00157 
00158       friend streamsize
00159       __copy_streambufs<>(basic_ios<char_type, traits_type>& __ios,
00160               __streambuf_type* __sbin,__streambuf_type* __sbout);
00161       
00162     protected:
00163       /**
00164        *  @if maint
00165        *  Pointer to the beginning of internally-allocated space.  Filebuf
00166        *  manually allocates/deallocates this, whereas stringstreams attempt
00167        *  to use the built-in intelligence of the string class.  If you are
00168        *  managing memory, set this.  If not, leave it NULL.
00169        *  @endif
00170       */
00171       char_type*        _M_buf;     
00172 
00173       /**
00174        *  @if maint
00175        *  Actual size of allocated internal buffer, in bytes.
00176        *  @endif
00177       */
00178       size_t            _M_buf_size;
00179 
00180       /**
00181        *  @if maint
00182        *  Optimal or preferred size of internal buffer, in bytes.
00183        *  @endif
00184       */
00185       size_t            _M_buf_size_opt;
00186 
00187       /**
00188        *  @if maint
00189        *  True iff _M_in_* and _M_out_* buffers should always point to
00190        *  the same place.  True for fstreams, false for sstreams.
00191        *  @endif
00192       */
00193       bool          _M_buf_unified; 
00194 
00195       //@{
00196       /**
00197        *  @if maint
00198        *  This is based on _IO_FILE, just reordered to be more consistent,
00199        *  and is intended to be the most minimal abstraction for an
00200        *  internal buffer.
00201        *  -  get == input == read
00202        *  -  put == output == write
00203        *  @endif
00204       */
00205       char_type*        _M_in_beg;      // Start of get area. 
00206       char_type*        _M_in_cur;  // Current read area. 
00207       char_type*        _M_in_end;  // End of get area. 
00208       char_type*        _M_out_beg;     // Start of put area. 
00209       char_type*        _M_out_cur;     // Current put area. 
00210       char_type*        _M_out_end;     // End of put area. 
00211       //@}
00212 
00213       /**
00214        *  @if maint
00215        *  Place to stash in || out || in | out settings for current streambuf.
00216        *  @endif
00217       */
00218       ios_base::openmode    _M_mode;    
00219 
00220       /**
00221        *  @if maint
00222        *  Current locale setting.
00223        *  @endif
00224       */
00225       locale            _M_buf_locale;  
00226 
00227       /**
00228        *  @if maint
00229        *  True iff locale is initialized.
00230        *  @endif
00231       */
00232       bool          _M_buf_locale_init;
00233 
00234       //@{
00235       /**
00236        *  @if maint
00237        *  Necessary bits for putback buffer management. Only used in
00238        *  the basic_filebuf class, as necessary for the standard
00239        *  requirements. The only basic_streambuf member function that
00240        *  needs access to these data members is in_avail...
00241        *  
00242        *  @note pbacks of over one character are not currently supported.
00243        *  @endif
00244       */
00245       static const size_t       _S_pback_size = 1; 
00246       char_type         _M_pback[_S_pback_size]; 
00247       char_type*        _M_pback_cur_save;
00248       char_type*        _M_pback_end_save;
00249       bool          _M_pback_init; 
00250       //@}
00251 
00252       /**
00253        *  @if maint
00254        *  Yet unused.
00255        *  @endif
00256       */
00257       fpos<__state_type>    _M_pos;
00258 
00259       // Initializes pback buffers, and moves normal buffers to safety.
00260       // Assumptions:
00261       // _M_in_cur has already been moved back
00262       void
00263       _M_pback_create()
00264       {
00265     if (!_M_pback_init)
00266       {
00267         size_t __dist = _M_in_end - _M_in_cur;
00268         size_t __len = min(_S_pback_size, __dist);
00269         traits_type::copy(_M_pback, _M_in_cur, __len);
00270         _M_pback_cur_save = _M_in_cur;
00271         _M_pback_end_save = _M_in_end;
00272         this->setg(_M_pback, _M_pback, _M_pback + __len);
00273         _M_pback_init = true;
00274       }
00275       }
00276 
00277       // Deactivates pback buffer contents, and restores normal buffer.
00278       // Assumptions:
00279       // The pback buffer has only moved forward.
00280       void
00281       _M_pback_destroy() throw()
00282       {
00283     if (_M_pback_init)
00284       {
00285         // Length _M_in_cur moved in the pback buffer.
00286         size_t __off_cur = _M_in_cur - _M_pback;
00287         
00288         // For in | out buffers, the end can be pushed back...
00289         size_t __off_end = 0;
00290         size_t __pback_len = _M_in_end - _M_pback;
00291         size_t __save_len = _M_pback_end_save - _M_buf;
00292         if (__pback_len > __save_len)
00293           __off_end = __pback_len - __save_len;
00294 
00295         this->setg(_M_buf, _M_pback_cur_save + __off_cur, 
00296                _M_pback_end_save + __off_end);
00297         _M_pback_cur_save = NULL;
00298         _M_pback_end_save = NULL;
00299         _M_pback_init = false;
00300       }
00301       }
00302 
00303       // Correctly sets the _M_in_cur pointer, and bumps the
00304       // _M_out_cur pointer as well if necessary.
00305       void 
00306       _M_in_cur_move(off_type __n) // argument needs to be +-
00307       {
00308     bool __testout = _M_out_cur;
00309     _M_in_cur += __n;
00310     if (__testout && _M_buf_unified)
00311       _M_out_cur += __n;
00312       }
00313 
00314       // Correctly sets the _M_out_cur pointer, and bumps the
00315       // appropriate _M_*_end pointers as well. Necessary for the
00316       // un-tied stringbufs, in in|out mode.
00317       // Invariant:
00318       // __n + _M_out_[cur, end] <= _M_buf + _M_buf_size
00319       // Assuming all _M_*_[beg, cur, end] pointers are operating on
00320       // the same range:
00321       // _M_buf <= _M_*_ <= _M_buf + _M_buf_size
00322       void 
00323       _M_out_cur_move(off_type __n) // argument needs to be +-
00324       {
00325     bool __testin = _M_in_cur;
00326 
00327     _M_out_cur += __n;
00328     if (__testin && _M_buf_unified)
00329       _M_in_cur += __n;
00330     if (_M_out_cur > _M_out_end)
00331       {
00332         _M_out_end = _M_out_cur;
00333         // NB: in | out buffers drag the _M_in_end pointer along...
00334         if (__testin)
00335           _M_in_end += __n;
00336       }
00337       }
00338 
00339       // Return the size of the output buffer.  This depends on the
00340       // buffer in use: allocated buffers have a stored size in
00341       // _M_buf_size and setbuf() buffers don't.
00342       off_type
00343       _M_out_buf_size()
00344       {
00345     off_type __ret = 0;
00346     if (_M_out_cur)
00347       {
00348         // Using allocated buffer.
00349         if (_M_out_beg == _M_buf)
00350           __ret = _M_out_beg + _M_buf_size - _M_out_cur;
00351         // Using non-allocated buffer.
00352         else
00353           __ret = _M_out_end - _M_out_cur;
00354       }
00355     return __ret;
00356       }
00357 
00358   public:
00359       /// Destructor deallocates no buffer space.
00360       virtual 
00361       ~basic_streambuf() 
00362       {
00363     _M_buf_unified = false;
00364     _M_buf_size = 0;
00365     _M_buf_size_opt = 0;
00366     _M_mode = ios_base::openmode(0);
00367       }
00368 
00369       // [27.5.2.2.1] locales
00370       /**
00371        *  @brief  Entry point for imbue().
00372        *  @param  loc  The new locale.
00373        *  @return  The previous locale.
00374        *
00375        *  Calls the derived imbue(loc).
00376       */
00377       locale 
00378       pubimbue(const locale &__loc)
00379       {
00380     locale __tmp(this->getloc());
00381     this->imbue(__loc);
00382     _M_buf_locale = __loc;
00383     return __tmp;
00384       }
00385 
00386       /**
00387        *  @brief  Locale access.
00388        *  @return  The current locale in effect.
00389        *
00390        *  If pubimbue(loc) has been called, then the most recent @c loc
00391        *  is returned.  Otherwise the global locale in effect at the time
00392        *  of construction is returned.
00393       */
00394       locale   
00395       getloc() const
00396       { return _M_buf_locale; } 
00397 
00398       // [27.5.2.2.2] buffer management and positioning
00399       //@{
00400       /**
00401        *  @brief  Entry points for derived buffer functions.
00402        *
00403        *  The public versions of @c pubfoo dispatch to the protected
00404        *  derived @c foo member functions, passing the arguments (if any)
00405        *  and returning the result unchanged.
00406       */
00407       __streambuf_type* 
00408       pubsetbuf(char_type* __s, streamsize __n) 
00409       { return this->setbuf(__s, __n); }
00410 
00411       pos_type 
00412       pubseekoff(off_type __off, ios_base::seekdir __way, 
00413          ios_base::openmode __mode = ios_base::in | ios_base::out)
00414       { return this->seekoff(__off, __way, __mode); }
00415 
00416       pos_type 
00417       pubseekpos(pos_type __sp,
00418          ios_base::openmode __mode = ios_base::in | ios_base::out)
00419       { return this->seekpos(__sp, __mode); }
00420 
00421       int 
00422       pubsync() { return this->sync(); }
00423       //@}
00424 
00425       // [27.5.2.2.3] get area
00426       /**
00427        *  @brief  Looking ahead into the stream.
00428        *  @return  The number of characters available.
00429        *
00430        *  If a read position is available, returns the number of characters
00431        *  available for reading before the buffer must be refilled.
00432        *  Otherwise returns the derived @c showmanyc().
00433       */
00434       streamsize 
00435       in_avail() 
00436       { 
00437     streamsize __ret;
00438     if (_M_in_cur && _M_in_cur < _M_in_end)
00439       {
00440         if (_M_pback_init)
00441           {
00442         size_t __save_len =  _M_pback_end_save - _M_pback_cur_save;
00443         size_t __pback_len = _M_in_cur - _M_pback;
00444         __ret = __save_len - __pback_len;
00445           }
00446         else
00447           __ret = this->egptr() - this->gptr();
00448       }
00449     else
00450       __ret = this->showmanyc();
00451     return __ret;
00452       }
00453 
00454       /**
00455        *  @brief  Getting the next character.
00456        *  @return  The next character, or eof.
00457        *
00458        *  Calls @c sbumpc(), and if that function returns
00459        *  @c traits::eof(), so does this function.  Otherwise, @c sgetc().
00460       */
00461       int_type 
00462       snextc()
00463       {
00464     int_type __eof = traits_type::eof();
00465     return (traits_type::eq_int_type(this->sbumpc(), __eof) 
00466         ? __eof : this->sgetc());
00467       }
00468 
00469       /**
00470        *  @brief  Getting the next character.
00471        *  @return  The next character, or eof.
00472        *
00473        *  If the input read position is available, returns that character
00474        *  and increments the read pointer, otherwise calls and returns
00475        *  @c uflow().
00476       */
00477       int_type 
00478       sbumpc();
00479 
00480       /**
00481        *  @brief  Getting the next character.
00482        *  @return  The next character, or eof.
00483        *
00484        *  If the input read position is available, returns that character,
00485        *  otherwise calls and returns @c underflow().  Does not move the 
00486        *  read position after fetching the character.
00487       */
00488       int_type 
00489       sgetc()
00490       {
00491     int_type __ret;
00492     if (_M_in_cur && _M_in_cur < _M_in_end)
00493       __ret = traits_type::to_int_type(*(this->gptr()));
00494     else 
00495       __ret = this->underflow();
00496     return __ret;
00497       }
00498 
00499       /**
00500        *  @brief  Entry point for xsgetn.
00501        *  @param  s  A buffer area.
00502        *  @param  n  A count.
00503        *
00504        *  Returns xsgetn(s,n).  The effect is to fill @a s[0] through
00505        *  @a s[n-1] with characters from the input sequence, if possible.
00506       */
00507       streamsize 
00508       sgetn(char_type* __s, streamsize __n)
00509       { return this->xsgetn(__s, __n); }
00510 
00511       // [27.5.2.2.4] putback
00512       /**
00513        *  @brief  Pushing characters back into the input stream.
00514        *  @param  c  The character to push back.
00515        *  @return  The previous character, if possible.
00516        *
00517        *  Similar to sungetc(), but @a c is pushed onto the stream instead
00518        *  of "the previous character".  If successful, the next character
00519        *  fetched from the input stream will be @a c.
00520       */
00521       int_type 
00522       sputbackc(char_type __c);
00523 
00524       /**
00525        *  @brief  Moving backwards in the input stream.
00526        *  @return  The previous character, if possible.
00527        *
00528        *  If a putback position is available, this function decrements the
00529        *  input pointer and returns that character.  Otherwise, calls and
00530        *  returns pbackfail().  The effect is to "unget" the last character
00531        *  "gotten".
00532       */
00533       int_type 
00534       sungetc();
00535 
00536       // [27.5.2.2.5] put area
00537       /**
00538        *  @brief  Entry point for all single-character output functions.
00539        *  @param  c  A character to output.
00540        *  @return  @a c, if possible.
00541        *
00542        *  One of two public output functions.
00543        *
00544        *  If a write position is available for the output sequence (i.e.,
00545        *  the buffer is not full), stores @a c in that position, increments
00546        *  the position, and returns @c traits::to_int_type(c).  If a write
00547        *  position is not available, returns @c overflow(c).
00548       */
00549       int_type 
00550       sputc(char_type __c);
00551 
00552       /**
00553        *  @brief  Entry point for all single-character output functions.
00554        *  @param  s  A buffer read area.
00555        *  @param  n  A count.
00556        *
00557        *  One of two public output functions.
00558        *
00559        *
00560        *  Returns xsputn(s,n).  The effect is to write @a s[0] through
00561        *  @a s[n-1] to the output sequence, if possible.
00562       */
00563       streamsize 
00564       sputn(const char_type* __s, streamsize __n)
00565       { return this->xsputn(__s, __n); }
00566 
00567     protected:
00568       /**
00569        *  @brief  Base constructor.
00570        *
00571        *  Only called from derived constructors, and sets up all the
00572        *  buffer data to zero, including the pointers described in the
00573        *  basic_streambuf class description.  Note that, as a result,
00574        *  - the class starts with no read nor write positions available,
00575        *  - this is not an error
00576       */
00577       basic_streambuf()
00578       : _M_buf(NULL), _M_buf_size(0), _M_buf_size_opt(BUFSIZ), 
00579       _M_buf_unified(false), _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 
00580       _M_out_beg(0), _M_out_cur(0), _M_out_end(0), 
00581       _M_mode(ios_base::openmode(0)), _M_buf_locale(locale()), 
00582       _M_pback_cur_save(0), _M_pback_end_save(0), 
00583       _M_pback_init(false)
00584       { }
00585 
00586       // [27.5.2.3.1] get area access
00587       //@{
00588       /**
00589        *  @brief  Access to the get area.
00590        *
00591        *  These functions are only available to other protected functions,
00592        *  including derived classes.
00593        *
00594        *  - eback() returns the beginning pointer for the input sequence
00595        *  - gptr() returns the next pointer for the input sequence
00596        *  - egptr() returns the end pointer for the input sequence
00597       */
00598       char_type* 
00599       eback() const { return _M_in_beg; }
00600 
00601       char_type* 
00602       gptr()  const { return _M_in_cur;  }
00603 
00604       char_type* 
00605       egptr() const { return _M_in_end; }
00606       //@}
00607 
00608       /**
00609        *  @brief  Moving the read position.
00610        *  @param  n  The delta by which to move.
00611        *
00612        *  This just advances the read position without returning any data.
00613       */
00614       void 
00615       gbump(int __n) { _M_in_cur += __n; }
00616 
00617       /**
00618        *  @brief  Setting the three read area pointers.
00619        *  @param  gbeg  A pointer.
00620        *  @param  gnext  A pointer.
00621        *  @param  gend  A pointer.
00622        *  @post  @a gbeg == @c eback(), @a gnext == @c gptr(), and
00623        *         @a gend == @c egptr()
00624       */
00625       void 
00626       setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
00627       {
00628     _M_in_beg = __gbeg;
00629     _M_in_cur = __gnext;
00630     _M_in_end = __gend;
00631     if (!(_M_mode & ios_base::in) && __gbeg && __gnext && __gend)
00632       _M_mode = _M_mode | ios_base::in;
00633       }
00634 
00635       // [27.5.2.3.2] put area access
00636       //@{
00637       /**
00638        *  @brief  Access to the put area.
00639        *
00640        *  These functions are only available to other protected functions,
00641        *  including derived classes.
00642        *
00643        *  - pbase() returns the beginning pointer for the output sequence
00644        *  - pptr() returns the next pointer for the output sequence
00645        *  - epptr() returns the end pointer for the output sequence
00646       */
00647       char_type* 
00648       pbase() const { return _M_out_beg; }
00649 
00650       char_type* 
00651       pptr() const { return _M_out_cur; }
00652 
00653       char_type* 
00654       epptr() const { return _M_out_end; }
00655       //@}
00656 
00657       /**
00658        *  @brief  Moving the write position.
00659        *  @param  n  The delta by which to move.
00660        *
00661        *  This just advances the write position without returning any data.
00662       */
00663       void 
00664       pbump(int __n) { _M_out_cur += __n; }
00665 
00666       /**
00667        *  @brief  Setting the three write area pointers.
00668        *  @param  pbeg  A pointer.
00669        *  @param  pend  A pointer.
00670        *  @post  @a pbeg == @c pbase(), @a pbeg == @c pptr(), and
00671        *         @a pend == @c epptr()
00672       */
00673       void 
00674       setp(char_type* __pbeg, char_type* __pend)
00675       { 
00676     _M_out_beg = _M_out_cur = __pbeg; 
00677     _M_out_end = __pend; 
00678     if (!(_M_mode & ios_base::out) && __pbeg && __pend)
00679       _M_mode = _M_mode | ios_base::out;
00680       }
00681 
00682       // [27.5.2.4] virtual functions
00683       // [27.5.2.4.1] locales
00684       /**
00685        *  @brief  Changes translations.
00686        *  @param  loc  A new locale.
00687        *
00688        *  Translations done during I/O which depend on the current locale
00689        *  are changed by this call.  The standard adds, "Between invocations
00690        *  of this function a class derived from streambuf can safely cache
00691        *  results of calls to locale functions and to members of facets
00692        *  so obtained."
00693        *
00694        *  @note  Base class version does nothing.
00695       */
00696       virtual void 
00697       imbue(const locale&) 
00698       { }
00699 
00700       // [27.5.2.4.2] buffer management and positioning
00701       /**
00702        *  @brief  Maniuplates the buffer.
00703        *
00704        *  Each derived class provides its own appropriate behavior.  See
00705        *  the next-to-last paragraph of 
00706        *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for
00707        *  more on this function.
00708        *
00709        *  @note  Base class version does nothing, returns @c this.
00710       */
00711       virtual basic_streambuf<char_type,_Traits>* 
00712       setbuf(char_type*, streamsize)
00713       { return this; }
00714       
00715       /**
00716        *  @brief  Alters the stream positions.
00717        *
00718        *  Each derived class provides its own appropriate behavior.
00719        *  @note  Base class version does nothing, returns a @c pos_type
00720        *         that represents an invalid stream position.
00721       */
00722       virtual pos_type 
00723       seekoff(off_type, ios_base::seekdir,
00724           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00725       { return pos_type(off_type(-1)); } 
00726 
00727       /**
00728        *  @brief  Alters the stream positions.
00729        *
00730        *  Each derived class provides its own appropriate behavior.
00731        *  @note  Base class version does nothing, returns a @c pos_type
00732        *         that represents an invalid stream position.
00733       */
00734       virtual pos_type 
00735       seekpos(pos_type, 
00736           ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
00737       { return pos_type(off_type(-1)); } 
00738 
00739       /**
00740        *  @brief  Synchronizes the buffer arrays with the controlled sequences.
00741        *  @return  -1 on failure.
00742        *
00743        *  Each derived class provides its own appropriate behavior,
00744        *  including the definition of "failure".
00745        *  @note  Base class version does nothing, returns zero.
00746       */
00747       virtual int 
00748       sync() { return 0; }
00749 
00750       // [27.5.2.4.3] get area
00751       /**
00752        *  @brief  Investigating the data available.
00753        *  @return  An estimate of the number of characters available in the
00754        *           input sequence, or -1.
00755        *
00756        *  "If it returns a positive value, then successive calls to
00757        *  @c underflow() will not return @c traits::eof() until at least that
00758        *  number of characters have been supplied.  If @c showmanyc()
00759        *  returns -1, then calls to @c underflow() or @c uflow() will fail."
00760        *  [27.5.2.4.3]/1
00761        *
00762        *  @note  Base class version does nothing, returns zero.
00763        *  @note  The standard adds that "the intention is not only that the
00764        *         calls [to underflow or uflow] will not return @c eof() but
00765        *         that they will return "immediately".
00766        *  @note  The standard adds that "the morphemes of @c showmanyc are
00767        *         "es-how-many-see", not "show-manic".
00768       */
00769       virtual streamsize 
00770       showmanyc() { return 0; }
00771 
00772       /**
00773        *  @brief  Multiple character extraction.
00774        *  @param  s  A buffer area.
00775        *  @param  n  Maximum number of characters to assign.
00776        *  @return  The number of characters assigned.
00777        *
00778        *  Fills @a s[0] through @a s[n-1] with characters from the input
00779        *  sequence, as if by @c sbumpc().  Stops when either @a n characters
00780        *  have been copied, or when @c traits::eof() would be copied.
00781        *
00782        *  It is expected that derived classes provide a more efficient
00783        *  implementation by overriding this definition.
00784       */
00785       virtual streamsize 
00786       xsgetn(char_type* __s, streamsize __n);
00787 
00788       /**
00789        *  @brief  Fetches more data from the controlled sequence.
00790        *  @return  The first character from the <em>pending sequence</em>.
00791        *
00792        *  Informally, this function is called when the input buffer is
00793        *  exhausted (or does not exist, as buffering need not actually be
00794        *  done).  If a buffer exists, it is "refilled".  In either case, the
00795        *  next available character is returned, or @c traits::eof() to
00796        *  indicate a null pending sequence.
00797        *
00798        *  For a formal definiton of the pending sequence, see a good text
00799        *  such as Langer & Kreft, or [27.5.2.4.3]/7-14.
00800        *
00801        *  A functioning input streambuf can be created by overriding only
00802        *  this function (no buffer area will be used).  For an example, see
00803        *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6
00804        *
00805        *  @note  Base class version does nothing, returns eof().
00806       */
00807       virtual int_type 
00808       underflow()
00809       { return traits_type::eof(); }
00810 
00811       /**
00812        *  @brief  Fetches more data from the controlled sequence.
00813        *  @return  The first character from the <em>pending sequence</em>.
00814        *
00815        *  Informally, this function does the same thing as @c underflow(),
00816        *  and in fact is required to call that function.  It also returns
00817        *  the new character, like @c underflow() does.  However, this
00818        *  function also moves the read position forward by one.
00819       */
00820       virtual int_type 
00821       uflow() 
00822       {
00823     int_type __ret = traits_type::eof();
00824     bool __testeof = traits_type::eq_int_type(this->underflow(), __ret);
00825     bool __testpending = _M_in_cur && _M_in_cur < _M_in_end;
00826     if (!__testeof && __testpending)
00827       {
00828         __ret = traits_type::to_int_type(*_M_in_cur);
00829         ++_M_in_cur;
00830         if (_M_buf_unified && _M_mode & ios_base::out)
00831           ++_M_out_cur;
00832       }
00833     return __ret;    
00834       }
00835 
00836       // [27.5.2.4.4] putback
00837       /**
00838        *  @brief  Tries to back up the input sequence.
00839        *  @param  c  The character to be inserted back into the sequence.
00840        *  @return  eof() on failure, "some other value" on success
00841        *  @post  The constraints of @c gptr(), @c eback(), and @c pptr()
00842        *         are the same as for @c underflow().
00843        *
00844        *  @note  Base class version does nothing, returns eof().
00845       */
00846       virtual int_type 
00847       pbackfail(int_type /* __c */  = traits_type::eof())
00848       { return traits_type::eof(); }
00849 
00850       // Put area:
00851       /**
00852        *  @brief  Multiple character insertion.
00853        *  @param  s  A buffer area.
00854        *  @param  n  Maximum number of characters to write.
00855        *  @return  The number of characters written.
00856        *
00857        *  Writes @a s[0] through @a s[n-1] to the output sequence, as if
00858        *  by @c sputc().  Stops when either @a n characters have been
00859        *  copied, or when @c sputc() would return @c traits::eof().
00860        *
00861        *  It is expected that derived classes provide a more efficient
00862        *  implementation by overriding this definition.
00863       */
00864       virtual streamsize 
00865       xsputn(const char_type* __s, streamsize __n);
00866 
00867       /**
00868        *  @brief  Consumes data from the buffer; writes to the
00869        *          controlled sequence.
00870        *  @param  c  An additional character to consume.
00871        *  @return  eof() to indicate failure, something else (usually
00872        *           @a c, or not_eof())
00873        *
00874        *  Informally, this function is called when the output buffer is full
00875        *  (or does not exist, as buffering need not actually be done).  If a
00876        *  buffer exists, it is "consumed", with "some effect" on the
00877        *  controlled sequence.  (Typically, the buffer is written out to the
00878        *  sequence verbatim.)  In either case, the character @a c is also
00879        *  written out, if @a c is not @c eof().
00880        *
00881        *  For a formal definiton of this function, see a good text
00882        *  such as Langer & Kreft, or [27.5.2.4.5]/3-7.
00883        *
00884        *  A functioning output streambuf can be created by overriding only
00885        *  this function (no buffer area will be used).
00886        *
00887        *  @note  Base class version does nothing, returns eof().
00888       */
00889       virtual int_type 
00890       overflow(int_type /* __c */ = traits_type::eof())
00891       { return traits_type::eof(); }
00892 
00893 #ifdef _GLIBCPP_DEPRECATED
00894     // Annex D.6
00895     public:
00896       /**
00897        *  @brief  Tosses a character.
00898        *
00899        *  Advances the read pointer, ignoring the character that would have
00900        *  been read.
00901        *
00902        *  See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
00903        *
00904        *  @note  This function has been deprecated by the standard.  You
00905        *         must define @c _GLIBCPP_DEPRECATED to make this visible; see
00906        *         c++config.h.
00907       */
00908       void 
00909       stossc() 
00910       {
00911     if (_M_in_cur < _M_in_end) 
00912       ++_M_in_cur;
00913     else 
00914       this->uflow();
00915       }
00916 #endif
00917 
00918 #ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
00919     // Side effect of DR 50. 
00920     private:
00921       basic_streambuf(const __streambuf_type&) { }; 
00922 
00923       __streambuf_type& 
00924       operator=(const __streambuf_type&) { return *this; };
00925 #endif
00926     };
00927 } // namespace std
00928 
00929 #ifdef _GLIBCPP_NO_TEMPLATE_EXPORT
00930 # define export
00931 #endif
00932 #ifdef  _GLIBCPP_FULLY_COMPLIANT_HEADERS
00933 #include <bits/streambuf.tcc>
00934 #endif
00935 
00936 #endif  

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