libstdc++
fstream.tcc
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00001 // File based streams -*- C++ -*-
00002 
00003 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
00004 // 2007, 2008, 2009, 2010, 2011
00005 // Free Software Foundation, Inc.
00006 //
00007 // This file is part of the GNU ISO C++ Library.  This library is free
00008 // software; you can redistribute it and/or modify it under the
00009 // terms of the GNU General Public License as published by the
00010 // Free Software Foundation; either version 3, or (at your option)
00011 // any later version.
00012 
00013 // This library is distributed in the hope that it will be useful,
00014 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00015 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00016 // GNU General Public License for more details.
00017 
00018 // Under Section 7 of GPL version 3, you are granted additional
00019 // permissions described in the GCC Runtime Library Exception, version
00020 // 3.1, as published by the Free Software Foundation.
00021 
00022 // You should have received a copy of the GNU General Public License and
00023 // a copy of the GCC Runtime Library Exception along with this program;
00024 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00025 // <http://www.gnu.org/licenses/>.
00026 
00027 /** @file bits/fstream.tcc
00028  *  This is an internal header file, included by other library headers.
00029  *  Do not attempt to use it directly. @headername{fstream}
00030  */
00031 
00032 //
00033 // ISO C++ 14882: 27.8  File-based streams
00034 //
00035 
00036 #ifndef _FSTREAM_TCC
00037 #define _FSTREAM_TCC 1
00038 
00039 #pragma GCC system_header
00040 
00041 #include <bits/cxxabi_forced.h>
00042 
00043 namespace std _GLIBCXX_VISIBILITY(default)
00044 {
00045 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00046 
00047   template<typename _CharT, typename _Traits>
00048     void
00049     basic_filebuf<_CharT, _Traits>::
00050     _M_allocate_internal_buffer()
00051     {
00052       // Allocate internal buffer only if one doesn't already exist
00053       // (either allocated or provided by the user via setbuf).
00054       if (!_M_buf_allocated && !_M_buf)
00055     {
00056       _M_buf = new char_type[_M_buf_size];
00057       _M_buf_allocated = true;
00058     }
00059     }
00060 
00061   template<typename _CharT, typename _Traits>
00062     void
00063     basic_filebuf<_CharT, _Traits>::
00064     _M_destroy_internal_buffer() throw()
00065     {
00066       if (_M_buf_allocated)
00067     {
00068       delete [] _M_buf;
00069       _M_buf = 0;
00070       _M_buf_allocated = false;
00071     }
00072       delete [] _M_ext_buf;
00073       _M_ext_buf = 0;
00074       _M_ext_buf_size = 0;
00075       _M_ext_next = 0;
00076       _M_ext_end = 0;
00077     }
00078 
00079   template<typename _CharT, typename _Traits>
00080     basic_filebuf<_CharT, _Traits>::
00081     basic_filebuf() : __streambuf_type(), _M_lock(), _M_file(&_M_lock),
00082     _M_mode(ios_base::openmode(0)), _M_state_beg(), _M_state_cur(),
00083     _M_state_last(), _M_buf(0), _M_buf_size(BUFSIZ),
00084     _M_buf_allocated(false), _M_reading(false), _M_writing(false), _M_pback(), 
00085     _M_pback_cur_save(0), _M_pback_end_save(0), _M_pback_init(false),
00086     _M_codecvt(0), _M_ext_buf(0), _M_ext_buf_size(0), _M_ext_next(0),
00087     _M_ext_end(0)
00088     {
00089       if (has_facet<__codecvt_type>(this->_M_buf_locale))
00090     _M_codecvt = &use_facet<__codecvt_type>(this->_M_buf_locale);
00091     }
00092 
00093   template<typename _CharT, typename _Traits>
00094     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
00095     basic_filebuf<_CharT, _Traits>::
00096     open(const char* __s, ios_base::openmode __mode)
00097     {
00098       __filebuf_type *__ret = 0;
00099       if (!this->is_open())
00100     {
00101       _M_file.open(__s, __mode);
00102       if (this->is_open())
00103         {
00104           _M_allocate_internal_buffer();
00105           _M_mode = __mode;
00106 
00107           // Setup initial buffer to 'uncommitted' mode.
00108           _M_reading = false;
00109           _M_writing = false;
00110           _M_set_buffer(-1);
00111 
00112           // Reset to initial state.
00113           _M_state_last = _M_state_cur = _M_state_beg;
00114 
00115           // 27.8.1.3,4
00116           if ((__mode & ios_base::ate)
00117           && this->seekoff(0, ios_base::end, __mode)
00118           == pos_type(off_type(-1)))
00119         this->close();
00120           else
00121         __ret = this;
00122         }
00123     }
00124       return __ret;
00125     }
00126 
00127   template<typename _CharT, typename _Traits>
00128     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
00129     basic_filebuf<_CharT, _Traits>::
00130     close()
00131     {
00132       if (!this->is_open())
00133     return 0;
00134 
00135       bool __testfail = false;
00136       {
00137     // NB: Do this here so that re-opened filebufs will be cool...
00138     struct __close_sentry
00139     {
00140       basic_filebuf *__fb;
00141       __close_sentry (basic_filebuf *__fbi): __fb(__fbi) { }
00142       ~__close_sentry ()
00143       {
00144         __fb->_M_mode = ios_base::openmode(0);
00145         __fb->_M_pback_init = false;
00146         __fb->_M_destroy_internal_buffer();
00147         __fb->_M_reading = false;
00148         __fb->_M_writing = false;
00149         __fb->_M_set_buffer(-1);
00150         __fb->_M_state_last = __fb->_M_state_cur = __fb->_M_state_beg;
00151       }
00152     } __cs (this);
00153 
00154     __try
00155       {
00156         if (!_M_terminate_output())
00157           __testfail = true;
00158       }
00159     __catch(__cxxabiv1::__forced_unwind&)
00160       {
00161         _M_file.close();
00162         __throw_exception_again;
00163       }
00164     __catch(...)
00165       { __testfail = true; }
00166       }
00167 
00168       if (!_M_file.close())
00169     __testfail = true;
00170 
00171       if (__testfail)
00172     return 0;
00173       else
00174     return this;
00175     }
00176 
00177   template<typename _CharT, typename _Traits>
00178     streamsize
00179     basic_filebuf<_CharT, _Traits>::
00180     showmanyc()
00181     {
00182       streamsize __ret = -1;
00183       const bool __testin = _M_mode & ios_base::in;
00184       if (__testin && this->is_open())
00185     {
00186       // For a stateful encoding (-1) the pending sequence might be just
00187       // shift and unshift prefixes with no actual character.
00188       __ret = this->egptr() - this->gptr();
00189 
00190 #if _GLIBCXX_HAVE_DOS_BASED_FILESYSTEM
00191       // About this workaround, see libstdc++/20806.
00192       const bool __testbinary = _M_mode & ios_base::binary;
00193       if (__check_facet(_M_codecvt).encoding() >= 0
00194           && __testbinary)
00195 #else
00196       if (__check_facet(_M_codecvt).encoding() >= 0)
00197 #endif
00198         __ret += _M_file.showmanyc() / _M_codecvt->max_length();
00199     }
00200       return __ret;
00201     }
00202 
00203   template<typename _CharT, typename _Traits>
00204     typename basic_filebuf<_CharT, _Traits>::int_type
00205     basic_filebuf<_CharT, _Traits>::
00206     underflow()
00207     {
00208       int_type __ret = traits_type::eof();
00209       const bool __testin = _M_mode & ios_base::in;
00210       if (__testin)
00211     {
00212       if (_M_writing)
00213         {
00214           if (overflow() == traits_type::eof())
00215         return __ret;
00216           _M_set_buffer(-1);
00217           _M_writing = false;
00218         }
00219       // Check for pback madness, and if so switch back to the
00220       // normal buffers and jet outta here before expensive
00221       // fileops happen...
00222       _M_destroy_pback();
00223 
00224       if (this->gptr() < this->egptr())
00225         return traits_type::to_int_type(*this->gptr());
00226 
00227       // Get and convert input sequence.
00228       const size_t __buflen = _M_buf_size > 1 ? _M_buf_size - 1 : 1;
00229 
00230       // Will be set to true if ::read() returns 0 indicating EOF.
00231       bool __got_eof = false;
00232       // Number of internal characters produced.
00233       streamsize __ilen = 0;
00234       codecvt_base::result __r = codecvt_base::ok;
00235       if (__check_facet(_M_codecvt).always_noconv())
00236         {
00237           __ilen = _M_file.xsgetn(reinterpret_cast<char*>(this->eback()),
00238                       __buflen);
00239           if (__ilen == 0)
00240         __got_eof = true;
00241         }
00242       else
00243         {
00244               // Worst-case number of external bytes.
00245           // XXX Not done encoding() == -1.
00246           const int __enc = _M_codecvt->encoding();
00247           streamsize __blen; // Minimum buffer size.
00248           streamsize __rlen; // Number of chars to read.
00249           if (__enc > 0)
00250         __blen = __rlen = __buflen * __enc;
00251           else
00252         {
00253           __blen = __buflen + _M_codecvt->max_length() - 1;
00254           __rlen = __buflen;
00255         }
00256           const streamsize __remainder = _M_ext_end - _M_ext_next;
00257           __rlen = __rlen > __remainder ? __rlen - __remainder : 0;
00258 
00259           // An imbue in 'read' mode implies first converting the external
00260           // chars already present.
00261           if (_M_reading && this->egptr() == this->eback() && __remainder)
00262         __rlen = 0;
00263 
00264           // Allocate buffer if necessary and move unconverted
00265           // bytes to front.
00266           if (_M_ext_buf_size < __blen)
00267         {
00268           char* __buf = new char[__blen];
00269           if (__remainder)
00270             __builtin_memcpy(__buf, _M_ext_next, __remainder);
00271 
00272           delete [] _M_ext_buf;
00273           _M_ext_buf = __buf;
00274           _M_ext_buf_size = __blen;
00275         }
00276           else if (__remainder)
00277         __builtin_memmove(_M_ext_buf, _M_ext_next, __remainder);
00278 
00279           _M_ext_next = _M_ext_buf;
00280           _M_ext_end = _M_ext_buf + __remainder;
00281           _M_state_last = _M_state_cur;
00282 
00283           do
00284         {
00285           if (__rlen > 0)
00286             {
00287               // Sanity check!
00288               // This may fail if the return value of
00289               // codecvt::max_length() is bogus.
00290               if (_M_ext_end - _M_ext_buf + __rlen > _M_ext_buf_size)
00291             {
00292               __throw_ios_failure(__N("basic_filebuf::underflow "
00293                           "codecvt::max_length() "
00294                           "is not valid"));
00295             }
00296               streamsize __elen = _M_file.xsgetn(_M_ext_end, __rlen);
00297               if (__elen == 0)
00298             __got_eof = true;
00299               else if (__elen == -1)
00300             break;
00301               _M_ext_end += __elen;
00302             }
00303 
00304           char_type* __iend = this->eback();
00305           if (_M_ext_next < _M_ext_end)
00306             __r = _M_codecvt->in(_M_state_cur, _M_ext_next,
00307                      _M_ext_end, _M_ext_next,
00308                      this->eback(),
00309                      this->eback() + __buflen, __iend);
00310           if (__r == codecvt_base::noconv)
00311             {
00312               size_t __avail = _M_ext_end - _M_ext_buf;
00313               __ilen = std::min(__avail, __buflen);
00314               traits_type::copy(this->eback(),
00315                     reinterpret_cast<char_type*>
00316                     (_M_ext_buf), __ilen);
00317               _M_ext_next = _M_ext_buf + __ilen;
00318             }
00319           else
00320             __ilen = __iend - this->eback();
00321 
00322           // _M_codecvt->in may return error while __ilen > 0: this is
00323           // ok, and actually occurs in case of mixed encodings (e.g.,
00324           // XML files).
00325           if (__r == codecvt_base::error)
00326             break;
00327 
00328           __rlen = 1;
00329         }
00330           while (__ilen == 0 && !__got_eof);
00331         }
00332 
00333       if (__ilen > 0)
00334         {
00335           _M_set_buffer(__ilen);
00336           _M_reading = true;
00337           __ret = traits_type::to_int_type(*this->gptr());
00338         }
00339       else if (__got_eof)
00340         {
00341           // If the actual end of file is reached, set 'uncommitted'
00342           // mode, thus allowing an immediate write without an
00343           // intervening seek.
00344           _M_set_buffer(-1);
00345           _M_reading = false;
00346           // However, reaching it while looping on partial means that
00347           // the file has got an incomplete character.
00348           if (__r == codecvt_base::partial)
00349         __throw_ios_failure(__N("basic_filebuf::underflow "
00350                     "incomplete character in file"));
00351         }
00352       else if (__r == codecvt_base::error)
00353         __throw_ios_failure(__N("basic_filebuf::underflow "
00354                 "invalid byte sequence in file"));
00355       else
00356         __throw_ios_failure(__N("basic_filebuf::underflow "
00357                 "error reading the file"));
00358     }
00359       return __ret;
00360     }
00361 
00362   template<typename _CharT, typename _Traits>
00363     typename basic_filebuf<_CharT, _Traits>::int_type
00364     basic_filebuf<_CharT, _Traits>::
00365     pbackfail(int_type __i)
00366     {
00367       int_type __ret = traits_type::eof();
00368       const bool __testin = _M_mode & ios_base::in;
00369       if (__testin)
00370     {
00371       if (_M_writing)
00372         {
00373           if (overflow() == traits_type::eof())
00374         return __ret;
00375           _M_set_buffer(-1);
00376           _M_writing = false;
00377         }
00378       // Remember whether the pback buffer is active, otherwise below
00379       // we may try to store in it a second char (libstdc++/9761).
00380       const bool __testpb = _M_pback_init;
00381       const bool __testeof = traits_type::eq_int_type(__i, __ret);
00382       int_type __tmp;
00383       if (this->eback() < this->gptr())
00384         {
00385           this->gbump(-1);
00386           __tmp = traits_type::to_int_type(*this->gptr());
00387         }
00388       else if (this->seekoff(-1, ios_base::cur) != pos_type(off_type(-1)))
00389         {
00390           __tmp = this->underflow();
00391           if (traits_type::eq_int_type(__tmp, __ret))
00392         return __ret;
00393         }
00394       else
00395         {
00396           // At the beginning of the buffer, need to make a
00397           // putback position available.  But the seek may fail
00398           // (f.i., at the beginning of a file, see
00399           // libstdc++/9439) and in that case we return
00400           // traits_type::eof().
00401           return __ret;
00402         }
00403 
00404       // Try to put back __i into input sequence in one of three ways.
00405       // Order these tests done in is unspecified by the standard.
00406       if (!__testeof && traits_type::eq_int_type(__i, __tmp))
00407         __ret = __i;
00408       else if (__testeof)
00409         __ret = traits_type::not_eof(__i);
00410       else if (!__testpb)
00411         {
00412           _M_create_pback();
00413           _M_reading = true;
00414           *this->gptr() = traits_type::to_char_type(__i);
00415           __ret = __i;
00416         }
00417     }
00418       return __ret;
00419     }
00420 
00421   template<typename _CharT, typename _Traits>
00422     typename basic_filebuf<_CharT, _Traits>::int_type
00423     basic_filebuf<_CharT, _Traits>::
00424     overflow(int_type __c)
00425     {
00426       int_type __ret = traits_type::eof();
00427       const bool __testeof = traits_type::eq_int_type(__c, __ret);
00428       const bool __testout = _M_mode & ios_base::out;
00429       if (__testout)
00430     {
00431           if (_M_reading)
00432             {
00433               _M_destroy_pback();
00434               const int __gptr_off = _M_get_ext_pos(_M_state_last);
00435               if (_M_seek(__gptr_off, ios_base::cur, _M_state_last)
00436                   == pos_type(off_type(-1)))
00437                 return __ret;
00438             }
00439       if (this->pbase() < this->pptr())
00440         {
00441           // If appropriate, append the overflow char.
00442           if (!__testeof)
00443         {
00444           *this->pptr() = traits_type::to_char_type(__c);
00445           this->pbump(1);
00446         }
00447 
00448           // Convert pending sequence to external representation,
00449           // and output.
00450           if (_M_convert_to_external(this->pbase(),
00451                      this->pptr() - this->pbase()))
00452         {
00453           _M_set_buffer(0);
00454           __ret = traits_type::not_eof(__c);
00455         }
00456         }
00457       else if (_M_buf_size > 1)
00458         {
00459           // Overflow in 'uncommitted' mode: set _M_writing, set
00460           // the buffer to the initial 'write' mode, and put __c
00461           // into the buffer.
00462           _M_set_buffer(0);
00463           _M_writing = true;
00464           if (!__testeof)
00465         {
00466           *this->pptr() = traits_type::to_char_type(__c);
00467           this->pbump(1);
00468         }
00469           __ret = traits_type::not_eof(__c);
00470         }
00471       else
00472         {
00473           // Unbuffered.
00474           char_type __conv = traits_type::to_char_type(__c);
00475           if (__testeof || _M_convert_to_external(&__conv, 1))
00476         {
00477           _M_writing = true;
00478           __ret = traits_type::not_eof(__c);
00479         }
00480         }
00481     }
00482       return __ret;
00483     }
00484 
00485   template<typename _CharT, typename _Traits>
00486     bool
00487     basic_filebuf<_CharT, _Traits>::
00488     _M_convert_to_external(_CharT* __ibuf, streamsize __ilen)
00489     {
00490       // Sizes of external and pending output.
00491       streamsize __elen;
00492       streamsize __plen;
00493       if (__check_facet(_M_codecvt).always_noconv())
00494     {
00495       __elen = _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen);
00496       __plen = __ilen;
00497     }
00498       else
00499     {
00500       // Worst-case number of external bytes needed.
00501       // XXX Not done encoding() == -1.
00502       streamsize __blen = __ilen * _M_codecvt->max_length();
00503       char* __buf = static_cast<char*>(__builtin_alloca(__blen));
00504 
00505       char* __bend;
00506       const char_type* __iend;
00507       codecvt_base::result __r;
00508       __r = _M_codecvt->out(_M_state_cur, __ibuf, __ibuf + __ilen,
00509                 __iend, __buf, __buf + __blen, __bend);
00510 
00511       if (__r == codecvt_base::ok || __r == codecvt_base::partial)
00512         __blen = __bend - __buf;
00513       else if (__r == codecvt_base::noconv)
00514         {
00515           // Same as the always_noconv case above.
00516           __buf = reinterpret_cast<char*>(__ibuf);
00517           __blen = __ilen;
00518         }
00519       else
00520         __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
00521                     "conversion error"));
00522   
00523       __elen = _M_file.xsputn(__buf, __blen);
00524       __plen = __blen;
00525 
00526       // Try once more for partial conversions.
00527       if (__r == codecvt_base::partial && __elen == __plen)
00528         {
00529           const char_type* __iresume = __iend;
00530           streamsize __rlen = this->pptr() - __iend;
00531           __r = _M_codecvt->out(_M_state_cur, __iresume,
00532                     __iresume + __rlen, __iend, __buf,
00533                     __buf + __blen, __bend);
00534           if (__r != codecvt_base::error)
00535         {
00536           __rlen = __bend - __buf;
00537           __elen = _M_file.xsputn(__buf, __rlen);
00538           __plen = __rlen;
00539         }
00540           else
00541         __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
00542                     "conversion error"));
00543         }
00544     }
00545       return __elen == __plen;
00546     }
00547 
00548   template<typename _CharT, typename _Traits>
00549     streamsize
00550     basic_filebuf<_CharT, _Traits>::
00551     xsgetn(_CharT* __s, streamsize __n)
00552     {
00553       // Clear out pback buffer before going on to the real deal...
00554       streamsize __ret = 0;
00555       if (_M_pback_init)
00556     {
00557       if (__n > 0 && this->gptr() == this->eback())
00558         {
00559           *__s++ = *this->gptr(); // emulate non-underflowing sbumpc
00560           this->gbump(1);
00561           __ret = 1;
00562           --__n;
00563         }
00564       _M_destroy_pback();
00565     }
00566       else if (_M_writing)
00567     {
00568       if (overflow() == traits_type::eof())
00569         return __ret;
00570       _M_set_buffer(-1);
00571       _M_writing = false;
00572     }
00573  
00574       // Optimization in the always_noconv() case, to be generalized in the
00575       // future: when __n > __buflen we read directly instead of using the
00576       // buffer repeatedly.
00577       const bool __testin = _M_mode & ios_base::in;
00578       const streamsize __buflen = _M_buf_size > 1 ? _M_buf_size - 1 : 1;
00579  
00580       if (__n > __buflen && __check_facet(_M_codecvt).always_noconv()
00581        && __testin)
00582      {
00583        // First, copy the chars already present in the buffer.
00584        const streamsize __avail = this->egptr() - this->gptr();
00585        if (__avail != 0)
00586          {
00587            traits_type::copy(__s, this->gptr(), __avail);
00588            __s += __avail;
00589            this->setg(this->eback(), this->gptr() + __avail,
00590               this->egptr());
00591            __ret += __avail;
00592            __n -= __avail;
00593          }
00594  
00595        // Need to loop in case of short reads (relatively common
00596        // with pipes).
00597        streamsize __len;
00598        for (;;)
00599          {
00600            __len = _M_file.xsgetn(reinterpret_cast<char*>(__s),
00601                       __n);
00602            if (__len == -1)
00603          __throw_ios_failure(__N("basic_filebuf::xsgetn "
00604                      "error reading the file"));
00605            if (__len == 0)
00606          break;
00607  
00608            __n -= __len;
00609            __ret += __len;
00610            if (__n == 0)
00611          break;
00612  
00613            __s += __len;
00614          }
00615  
00616        if (__n == 0)
00617          {
00618            _M_set_buffer(0);
00619            _M_reading = true;
00620          }
00621        else if (__len == 0)
00622          {
00623            // If end of file is reached, set 'uncommitted'
00624            // mode, thus allowing an immediate write without
00625            // an intervening seek.
00626            _M_set_buffer(-1);
00627            _M_reading = false;
00628          }
00629      }
00630       else
00631      __ret += __streambuf_type::xsgetn(__s, __n);
00632  
00633       return __ret;
00634     }
00635 
00636   template<typename _CharT, typename _Traits>
00637     streamsize
00638     basic_filebuf<_CharT, _Traits>::
00639     xsputn(const _CharT* __s, streamsize __n)
00640     {
00641       streamsize __ret = 0;
00642       // Optimization in the always_noconv() case, to be generalized in the
00643       // future: when __n is sufficiently large we write directly instead of
00644       // using the buffer.
00645       const bool __testout = _M_mode & ios_base::out;
00646       if (__check_facet(_M_codecvt).always_noconv()
00647        && __testout && !_M_reading)
00648     {
00649       // Measurement would reveal the best choice.
00650       const streamsize __chunk = 1ul << 10;
00651       streamsize __bufavail = this->epptr() - this->pptr();
00652 
00653       // Don't mistake 'uncommitted' mode buffered with unbuffered.
00654       if (!_M_writing && _M_buf_size > 1)
00655         __bufavail = _M_buf_size - 1;
00656 
00657       const streamsize __limit = std::min(__chunk, __bufavail);
00658       if (__n >= __limit)
00659         {
00660           const streamsize __buffill = this->pptr() - this->pbase();
00661           const char* __buf = reinterpret_cast<const char*>(this->pbase());
00662           __ret = _M_file.xsputn_2(__buf, __buffill,
00663                        reinterpret_cast<const char*>(__s),
00664                        __n);
00665           if (__ret == __buffill + __n)
00666         {
00667           _M_set_buffer(0);
00668           _M_writing = true;
00669         }
00670           if (__ret > __buffill)
00671         __ret -= __buffill;
00672           else
00673         __ret = 0;
00674         }
00675       else
00676         __ret = __streambuf_type::xsputn(__s, __n);
00677     }
00678        else
00679      __ret = __streambuf_type::xsputn(__s, __n);
00680        return __ret;
00681     }
00682 
00683   template<typename _CharT, typename _Traits>
00684     typename basic_filebuf<_CharT, _Traits>::__streambuf_type*
00685     basic_filebuf<_CharT, _Traits>::
00686     setbuf(char_type* __s, streamsize __n)
00687     {
00688       if (!this->is_open())
00689     {
00690       if (__s == 0 && __n == 0)
00691         _M_buf_size = 1;
00692       else if (__s && __n > 0)
00693         {
00694           // This is implementation-defined behavior, and assumes that
00695           // an external char_type array of length __n exists and has
00696           // been pre-allocated. If this is not the case, things will
00697           // quickly blow up. When __n > 1, __n - 1 positions will be
00698           // used for the get area, __n - 1 for the put area and 1
00699           // position to host the overflow char of a full put area.
00700           // When __n == 1, 1 position will be used for the get area
00701           // and 0 for the put area, as in the unbuffered case above.
00702           _M_buf = __s;
00703           _M_buf_size = __n;
00704         }
00705     }
00706       return this;
00707     }
00708 
00709 
00710   // According to 27.8.1.4 p11 - 13, seekoff should ignore the last
00711   // argument (of type openmode).
00712   template<typename _CharT, typename _Traits>
00713     typename basic_filebuf<_CharT, _Traits>::pos_type
00714     basic_filebuf<_CharT, _Traits>::
00715     seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmode)
00716     {
00717       int __width = 0;
00718       if (_M_codecvt)
00719     __width = _M_codecvt->encoding();
00720       if (__width < 0)
00721     __width = 0;
00722 
00723       pos_type __ret = pos_type(off_type(-1));
00724       const bool __testfail = __off != 0 && __width <= 0;
00725       if (this->is_open() && !__testfail)
00726     {
00727       // tellg and tellp queries do not affect any state, unless
00728       // ! always_noconv and the put sequence is not empty.
00729       // In that case, determining the position requires converting the
00730       // put sequence. That doesn't use ext_buf, so requires a flush.
00731       bool __no_movement = __way == ios_base::cur && __off == 0
00732         && (!_M_writing || _M_codecvt->always_noconv());
00733 
00734       // Ditch any pback buffers to avoid confusion.
00735       if (!__no_movement)
00736         _M_destroy_pback();
00737 
00738       // Correct state at destination. Note that this is the correct
00739       // state for the current position during output, because
00740       // codecvt::unshift() returns the state to the initial state.
00741       // This is also the correct state at the end of the file because
00742       // an unshift sequence should have been written at the end.
00743       __state_type __state = _M_state_beg;
00744       off_type __computed_off = __off * __width;
00745       if (_M_reading && __way == ios_base::cur)
00746         {
00747           __state = _M_state_last;
00748           __computed_off += _M_get_ext_pos(__state);
00749         }
00750       if (!__no_movement)
00751         __ret = _M_seek(__computed_off, __way, __state);
00752       else
00753         {
00754           if (_M_writing)
00755         __computed_off = this->pptr() - this->pbase();
00756           
00757           off_type __file_off = _M_file.seekoff(0, ios_base::cur);
00758           if (__file_off != off_type(-1))
00759         {
00760           __ret = __file_off + __computed_off;
00761           __ret.state(__state);
00762         }
00763         }
00764     }
00765       return __ret;
00766     }
00767 
00768   // _GLIBCXX_RESOLVE_LIB_DEFECTS
00769   // 171. Strange seekpos() semantics due to joint position
00770   // According to the resolution of DR 171, seekpos should ignore the last
00771   // argument (of type openmode).
00772   template<typename _CharT, typename _Traits>
00773     typename basic_filebuf<_CharT, _Traits>::pos_type
00774     basic_filebuf<_CharT, _Traits>::
00775     seekpos(pos_type __pos, ios_base::openmode)
00776     {
00777       pos_type __ret =  pos_type(off_type(-1));
00778       if (this->is_open())
00779     {
00780       // Ditch any pback buffers to avoid confusion.
00781       _M_destroy_pback();
00782       __ret = _M_seek(off_type(__pos), ios_base::beg, __pos.state());
00783     }
00784       return __ret;
00785     }
00786 
00787   template<typename _CharT, typename _Traits>
00788     typename basic_filebuf<_CharT, _Traits>::pos_type
00789     basic_filebuf<_CharT, _Traits>::
00790     _M_seek(off_type __off, ios_base::seekdir __way, __state_type __state)
00791     {
00792       pos_type __ret = pos_type(off_type(-1));
00793       if (_M_terminate_output())
00794     {
00795       off_type __file_off = _M_file.seekoff(__off, __way);
00796       if (__file_off != off_type(-1))
00797         {
00798           _M_reading = false;
00799           _M_writing = false;
00800           _M_ext_next = _M_ext_end = _M_ext_buf;
00801           _M_set_buffer(-1);
00802           _M_state_cur = __state;
00803           __ret = __file_off;
00804           __ret.state(_M_state_cur);
00805         }
00806     }
00807       return __ret;
00808     }
00809 
00810   // Returns the distance from the end of the ext buffer to the point
00811   // corresponding to gptr(). This is a negative value. Updates __state
00812   // from eback() correspondence to gptr().
00813   template<typename _CharT, typename _Traits>
00814     int basic_filebuf<_CharT, _Traits>::
00815     _M_get_ext_pos(__state_type& __state)
00816     {
00817       if (_M_codecvt->always_noconv())
00818         return this->gptr() - this->egptr();
00819       else
00820         {
00821           // Calculate offset from _M_ext_buf that corresponds to
00822           // gptr(). Precondition: __state == _M_state_last, which
00823           // corresponds to eback().
00824           const int __gptr_off =
00825             _M_codecvt->length(__state, _M_ext_buf, _M_ext_next,
00826                                this->gptr() - this->eback());
00827           return _M_ext_buf + __gptr_off - _M_ext_end;
00828         }
00829     }
00830     
00831   template<typename _CharT, typename _Traits>
00832     bool
00833     basic_filebuf<_CharT, _Traits>::
00834     _M_terminate_output()
00835     {
00836       // Part one: update the output sequence.
00837       bool __testvalid = true;
00838       if (this->pbase() < this->pptr())
00839     {
00840       const int_type __tmp = this->overflow();
00841       if (traits_type::eq_int_type(__tmp, traits_type::eof()))
00842         __testvalid = false;
00843     }
00844 
00845       // Part two: output unshift sequence.
00846       if (_M_writing && !__check_facet(_M_codecvt).always_noconv()
00847       && __testvalid)
00848     {
00849       // Note: this value is arbitrary, since there is no way to
00850       // get the length of the unshift sequence from codecvt,
00851       // without calling unshift.
00852       const size_t __blen = 128;
00853       char __buf[__blen];
00854       codecvt_base::result __r;
00855       streamsize __ilen = 0;
00856 
00857       do
00858         {
00859           char* __next;
00860           __r = _M_codecvt->unshift(_M_state_cur, __buf,
00861                     __buf + __blen, __next);
00862           if (__r == codecvt_base::error)
00863         __testvalid = false;
00864           else if (__r == codecvt_base::ok ||
00865                __r == codecvt_base::partial)
00866         {
00867           __ilen = __next - __buf;
00868           if (__ilen > 0)
00869             {
00870               const streamsize __elen = _M_file.xsputn(__buf, __ilen);
00871               if (__elen != __ilen)
00872             __testvalid = false;
00873             }
00874         }
00875         }
00876       while (__r == codecvt_base::partial && __ilen > 0 && __testvalid);
00877 
00878       if (__testvalid)
00879         {
00880           // This second call to overflow() is required by the standard,
00881           // but it's not clear why it's needed, since the output buffer
00882           // should be empty by this point (it should have been emptied
00883           // in the first call to overflow()).
00884           const int_type __tmp = this->overflow();
00885           if (traits_type::eq_int_type(__tmp, traits_type::eof()))
00886         __testvalid = false;
00887         }
00888     }
00889       return __testvalid;
00890     }
00891 
00892   template<typename _CharT, typename _Traits>
00893     int
00894     basic_filebuf<_CharT, _Traits>::
00895     sync()
00896     {
00897       // Make sure that the internal buffer resyncs its idea of
00898       // the file position with the external file.
00899       int __ret = 0;
00900       if (this->pbase() < this->pptr())
00901     {
00902       const int_type __tmp = this->overflow();
00903       if (traits_type::eq_int_type(__tmp, traits_type::eof()))
00904         __ret = -1;
00905     }
00906       return __ret;
00907     }
00908 
00909   template<typename _CharT, typename _Traits>
00910     void
00911     basic_filebuf<_CharT, _Traits>::
00912     imbue(const locale& __loc)
00913     {
00914       bool __testvalid = true;
00915 
00916       const __codecvt_type* _M_codecvt_tmp = 0;
00917       if (__builtin_expect(has_facet<__codecvt_type>(__loc), true))
00918     _M_codecvt_tmp = &use_facet<__codecvt_type>(__loc);
00919 
00920       if (this->is_open())
00921     {
00922       // encoding() == -1 is ok only at the beginning.
00923       if ((_M_reading || _M_writing)
00924           && __check_facet(_M_codecvt).encoding() == -1)
00925         __testvalid = false;
00926       else
00927         {
00928           if (_M_reading)
00929         {
00930           if (__check_facet(_M_codecvt).always_noconv())
00931             {
00932               if (_M_codecvt_tmp
00933               && !__check_facet(_M_codecvt_tmp).always_noconv())
00934             __testvalid = this->seekoff(0, ios_base::cur, _M_mode)
00935                           != pos_type(off_type(-1));
00936             }
00937           else
00938             {
00939               // External position corresponding to gptr().
00940               _M_ext_next = _M_ext_buf
00941             + _M_codecvt->length(_M_state_last, _M_ext_buf,
00942                          _M_ext_next,
00943                          this->gptr() - this->eback());
00944               const streamsize __remainder = _M_ext_end - _M_ext_next;
00945               if (__remainder)
00946             __builtin_memmove(_M_ext_buf, _M_ext_next, __remainder);
00947 
00948               _M_ext_next = _M_ext_buf;
00949               _M_ext_end = _M_ext_buf + __remainder;
00950               _M_set_buffer(-1);
00951               _M_state_last = _M_state_cur = _M_state_beg;
00952             }
00953         }
00954           else if (_M_writing && (__testvalid = _M_terminate_output()))
00955         _M_set_buffer(-1);
00956         }
00957     }
00958 
00959       if (__testvalid)
00960     _M_codecvt = _M_codecvt_tmp;
00961       else
00962     _M_codecvt = 0;
00963     }
00964 
00965   // Inhibit implicit instantiations for required instantiations,
00966   // which are defined via explicit instantiations elsewhere.
00967 #if _GLIBCXX_EXTERN_TEMPLATE
00968   extern template class basic_filebuf<char>;
00969   extern template class basic_ifstream<char>;
00970   extern template class basic_ofstream<char>;
00971   extern template class basic_fstream<char>;
00972 
00973 #ifdef _GLIBCXX_USE_WCHAR_T
00974   extern template class basic_filebuf<wchar_t>;
00975   extern template class basic_ifstream<wchar_t>;
00976   extern template class basic_ofstream<wchar_t>;
00977   extern template class basic_fstream<wchar_t>;
00978 #endif
00979 #endif
00980 
00981 _GLIBCXX_END_NAMESPACE_VERSION
00982 } // namespace std
00983 
00984 #endif