libstdc++-v3/include/bits/fstream.tcc

   1 // File based streams -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 //
  32 // ISO C++ 14882: 27.8  File-based streams
  33 //
  34
  35 #ifndef _FSTREAM_TCC
  36 #define _FSTREAM_TCC 1
  37
  38 #pragma GCC system_header
  39
  40 namespace std
  41 {
  42   template<typename _CharT, typename _Traits>
  43     void
  44     basic_filebuf<_CharT, _Traits>::
  45     _M_allocate_internal_buffer()
  46     {
  47       // Allocate internal buffer only if one doesn't already exist
  48       // (either allocated or provided by the user via setbuf).
  49       if (!_M_buf_allocated && !this->_M_buf)
  50         {
  51           this->_M_buf = new char_type[this->_M_buf_size];
  52           _M_buf_allocated = true;
  53         }
  54     }
  55
  56   template<typename _CharT, typename _Traits>
  57     void
  58     basic_filebuf<_CharT, _Traits>::
  59     _M_destroy_internal_buffer() throw()
  60     {
  61       if (_M_buf_allocated)
  62         {
  63           delete [] this->_M_buf;
  64           this->_M_buf = NULL;
  65           _M_buf_allocated = false;
  66         }
  67       delete [] _M_ext_buf;
  68       _M_ext_buf = NULL;
  69       _M_ext_buf_size = 0;
  70       _M_ext_next = NULL;
  71       _M_ext_end = NULL;
  72     }
  73
  74   template<typename _CharT, typename _Traits>
  75     basic_filebuf<_CharT, _Traits>::
  76     basic_filebuf() : __streambuf_type(), _M_lock(), _M_file(&_M_lock),
  77     _M_mode(ios_base::openmode(0)), _M_state_beg(), _M_state_cur(),
  78     _M_state_last(), _M_buf(NULL), _M_buf_size(BUFSIZ),
  79     _M_buf_allocated(false), _M_reading(false), _M_writing(false), _M_pback(),
  80     _M_pback_cur_save(0), _M_pback_end_save(0), _M_pback_init(false),
  81     _M_codecvt(0), _M_ext_buf(0), _M_ext_buf_size(0), _M_ext_next(0),
  82     _M_ext_end(0)
  83     {
  84       if (has_facet<__codecvt_type>(this->_M_buf_locale))
  85         _M_codecvt = &use_facet<__codecvt_type>(this->_M_buf_locale);
  86     }
  87
  88   template<typename _CharT, typename _Traits>
  89     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
  90     basic_filebuf<_CharT, _Traits>::
  91     open(const char* __s, ios_base::openmode __mode)
  92     {
  93       __filebuf_type *__ret = NULL;
  94       if (!this->is_open())
  95         {
  96           _M_file.open(__s, __mode);
  97           if (this->is_open())
  98             {
  99               _M_allocate_internal_buffer();
 100               this->_M_mode = __mode;
 101
 102               // Setup initial buffer to 'uncommitted' mode.
 103               _M_reading = false;
 104               _M_writing = false;
 105               _M_set_buffer(-1);
 106
 107               // Reset to initial state.
 108               _M_state_last = _M_state_cur = _M_state_beg;
 109
 110               // 27.8.1.3,4
 111               if ((__mode & ios_base::ate)
 112                   && this->seekoff(0, ios_base::end, __mode)
 113                   == pos_type(off_type(-1)))
 114                 this->close();
 115               else
 116                 __ret = this;
 117             }
 118         }
 119       return __ret;
 120     }
 121
 122   template<typename _CharT, typename _Traits>
 123     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
 124     basic_filebuf<_CharT, _Traits>::
 125     close() throw()
 126     {
 127       __filebuf_type* __ret = NULL;
 128       if (this->is_open())
 129         {
 130           bool __testfail = false;
 131           try
 132             {
 133               if (!_M_terminate_output())
 134                 __testfail = true;
 135             }
 136           catch(...)
 137             { __testfail = true; }
 138
 139           // NB: Do this here so that re-opened filebufs will be cool...
 140           this->_M_mode = ios_base::openmode(0);
 141           this->_M_pback_init = false;
 142           _M_destroy_internal_buffer();
 143           _M_reading = false;
 144           _M_writing = false;
 145           _M_set_buffer(-1);
 146           _M_state_last = _M_state_cur = _M_state_beg;
 147
 148           if (!_M_file.close())
 149             __testfail = true;
 150
 151           if (!__testfail)
 152             __ret = this;
 153         }
 154       return __ret;
 155     }
 156
 157   template<typename _CharT, typename _Traits>
 158     streamsize
 159     basic_filebuf<_CharT, _Traits>::
 160     showmanyc()
 161     {
 162       streamsize __ret = -1;
 163       const bool __testin = this->_M_mode & ios_base::in;
 164       if (__testin && this->is_open())
 165         {
 166           // For a stateful encoding (-1) the pending sequence might be just
 167           // shift and unshift prefixes with no actual character.
 168           __ret = this->egptr() - this->gptr();
 169           if (__check_facet(_M_codecvt).encoding() >= 0)
 170             __ret += _M_file.showmanyc() / _M_codecvt->max_length();
 171         }
 172       return __ret;
 173     }
 174
 175   template<typename _CharT, typename _Traits>
 176     typename basic_filebuf<_CharT, _Traits>::int_type
 177     basic_filebuf<_CharT, _Traits>::
 178     underflow()
 179     {
 180       int_type __ret = traits_type::eof();
 181       const bool __testin = this->_M_mode & ios_base::in;
 182       if (__testin && !_M_writing)
 183         {
 184           // Check for pback madness, and if so swich back to the
 185           // normal buffers and jet outta here before expensive
 186           // fileops happen...
 187           _M_destroy_pback();
 188
 189           if (this->gptr() < this->egptr())
 190             return traits_type::to_int_type(*this->gptr());
 191
 192           // Get and convert input sequence.
 193           const size_t __buflen = this->_M_buf_size > 1
 194                                   ? this->_M_buf_size - 1 : 1;
 195
 196           // Will be set to true if ::read() returns 0 indicating EOF.
 197           bool __got_eof = false;
 198           // Number of internal characters produced.
 199           streamsize __ilen = 0;
 200           codecvt_base::result __r = codecvt_base::ok;
 201           if (__check_facet(_M_codecvt).always_noconv())
 202             {
 203               __ilen = _M_file.xsgetn(reinterpret_cast<char*>(this->eback()),
 204                                       __buflen);
 205               if (__ilen == 0)
 206                 __got_eof = true;
 207             }
 208           else
 209             {
 210               // Worst-case number of external bytes.
 211               // XXX Not done encoding() == -1.
 212               const int __enc = _M_codecvt->encoding();
 213               streamsize __blen; // Minimum buffer size.
 214               streamsize __rlen; // Number of chars to read.
 215               if (__enc > 0)
 216                 __blen = __rlen = __buflen * __enc;
 217               else
 218                 {
 219                   __blen = __buflen + _M_codecvt->max_length() - 1;
 220                   __rlen = __buflen;
 221                 }
 222               const streamsize __remainder = _M_ext_end - _M_ext_next;
 223               __rlen = __rlen > __remainder ? __rlen - __remainder : 0;
 224
 225               // An imbue in 'read' mode implies first converting the external
 226               // chars already present.
 227               if (_M_reading && this->egptr() == this->eback() && __remainder)
 228                 __rlen = 0;
 229
 230               // Allocate buffer if necessary and move unconverted
 231               // bytes to front.
 232               if (_M_ext_buf_size < __blen)
 233                 {
 234                   char* __buf = new char[__blen];
 235                   if (__remainder)
 236                     std::memcpy(__buf, _M_ext_next, __remainder);
 237
 238                   delete [] _M_ext_buf;
 239                   _M_ext_buf = __buf;
 240                   _M_ext_buf_size = __blen;
 241                 }
 242               else if (__remainder)
 243                 std::memmove(_M_ext_buf, _M_ext_next, __remainder);
 244
 245               _M_ext_next = _M_ext_buf;
 246               _M_ext_end = _M_ext_buf + __remainder;
 247               _M_state_last = _M_state_cur;
 248
 249               do
 250                 {
 251                   if (__rlen > 0)
 252                     {
 253                       // Sanity check!
 254                       // This may fail if the return value of
 255                       // codecvt::max_length() is bogus.
 256                       if (_M_ext_end - _M_ext_buf + __rlen > _M_ext_buf_size)
 257                         {
 258                           __throw_ios_failure(__N("basic_filebuf::underflow "
 259                                               "codecvt::max_length() "
 260                                               "is not valid"));
 261                         }
 262                       streamsize __elen = _M_file.xsgetn(_M_ext_end, __rlen);
 263                       if (__elen == 0)
 264                         __got_eof = true;
 265                       else if (__elen == -1)
 266                         break;
 267                       _M_ext_end += __elen;
 268                     }
 269
 270                   char_type* __iend;
 271                   __r = _M_codecvt->in(_M_state_cur, _M_ext_next,
 272                                        _M_ext_end, _M_ext_next, this->eback(),
 273                                        this->eback() + __buflen, __iend);
 274                   if (__r == codecvt_base::noconv)
 275                     {
 276                       size_t __avail = _M_ext_end - _M_ext_buf;
 277                       __ilen = std::min(__avail, __buflen);
 278                       traits_type::copy(this->eback(),
 279                                         reinterpret_cast<char_type*>(_M_ext_buf), __ilen);
 280                       _M_ext_next = _M_ext_buf + __ilen;
 281                     }
 282                   else
 283                     __ilen = __iend - this->eback();
 284
 285                   // _M_codecvt->in may return error while __ilen > 0: this is
 286                   // ok, and actually occurs in case of mixed encodings (e.g.,
 287                   // XML files).
 288                   if (__r == codecvt_base::error)
 289                     break;
 290
 291                   __rlen = 1;
 292                 }
 293               while (__ilen == 0 && !__got_eof);
 294             }
 295
 296           if (__ilen > 0)
 297             {
 298               _M_set_buffer(__ilen);
 299               _M_reading = true;
 300               __ret = traits_type::to_int_type(*this->gptr());
 301             }
 302           else if (__got_eof)
 303             {
 304               // If the actual end of file is reached, set 'uncommitted'
 305               // mode, thus allowing an immediate write without an
 306               // intervening seek.
 307               _M_set_buffer(-1);
 308               _M_reading = false;
 309               // However, reaching it while looping on partial means that
 310               // the file has got an incomplete character.
 311               if (__r == codecvt_base::partial)
 312                 __throw_ios_failure(__N("basic_filebuf::underflow "
 313                                     "incomplete character in file"));
 314             }
 315           else if (__r == codecvt_base::error)
 316             __throw_ios_failure(__N("basic_filebuf::underflow "
 317                                 "invalid byte sequence in file"));
 318           else
 319             __throw_ios_failure(__N("basic_filebuf::underflow "
 320                                 "error reading the file"));
 321         }
 322       return __ret;
 323     }
 324
 325   template<typename _CharT, typename _Traits>
 326     typename basic_filebuf<_CharT, _Traits>::int_type
 327     basic_filebuf<_CharT, _Traits>::
 328     pbackfail(int_type __i)
 329     {
 330       int_type __ret = traits_type::eof();
 331       const bool __testin = this->_M_mode & ios_base::in;
 332       if (__testin && !_M_writing)
 333         {
 334           // Remember whether the pback buffer is active, otherwise below
 335           // we may try to store in it a second char (libstdc++/9761).
 336           const bool __testpb = this->_M_pback_init;
 337           const bool __testeof = traits_type::eq_int_type(__i, __ret);
 338           int_type __tmp;
 339           if (this->eback() < this->gptr())
 340             {
 341               this->gbump(-1);
 342               __tmp = traits_type::to_int_type(*this->gptr());
 343             }
 344           else if (this->seekoff(-1, ios_base::cur) != pos_type(off_type(-1)))
 345             {
 346               __tmp = this->underflow();
 347               if (traits_type::eq_int_type(__tmp, __ret))
 348                 return __ret;
 349             }
 350           else
 351             {
 352               // At the beginning of the buffer, need to make a
 353               // putback position available.  But the seek may fail
 354               // (f.i., at the beginning of a file, see
 355               // libstdc++/9439) and in that case we return
 356               // traits_type::eof().
 357               return __ret;
 358             }
 359
 360           // Try to put back __i into input sequence in one of three ways.
 361           // Order these tests done in is unspecified by the standard.
 362           if (!__testeof && traits_type::eq_int_type(__i, __tmp))
 363             __ret = __i;
 364           else if (__testeof)
 365             __ret = traits_type::not_eof(__i);
 366           else if (!__testpb)
 367             {
 368               _M_create_pback();
 369               _M_reading = true;
 370               *this->gptr() = traits_type::to_char_type(__i);
 371               __ret = __i;
 372             }
 373         }
 374       return __ret;
 375     }
 376
 377   template<typename _CharT, typename _Traits>
 378     typename basic_filebuf<_CharT, _Traits>::int_type
 379     basic_filebuf<_CharT, _Traits>::
 380     overflow(int_type __c)
 381     {
 382       int_type __ret = traits_type::eof();
 383       const bool __testeof = traits_type::eq_int_type(__c, __ret);
 384       const bool __testout = this->_M_mode & ios_base::out;
 385       if (__testout && !_M_reading)
 386         {
 387           if (this->pbase() < this->pptr())
 388             {
 389               // If appropriate, append the overflow char.
 390               if (!__testeof)
 391                 {
 392                   *this->pptr() = traits_type::to_char_type(__c);
 393                   this->pbump(1);
 394                 }
 395
 396               // Convert pending sequence to external representation,
 397               // and output.
 398               if (_M_convert_to_external(this->pbase(),
 399                                          this->pptr() - this->pbase())
 400                   && (!__testeof || !_M_file.sync()))
 401                 {
 402                   _M_set_buffer(0);
 403                   __ret = traits_type::not_eof(__c);
 404                 }
 405             }
 406           else if (this->_M_buf_size > 1)
 407             {
 408               // Overflow in 'uncommitted' mode: set _M_writing, set
 409               // the buffer to the initial 'write' mode, and put __c
 410               // into the buffer.
 411               _M_set_buffer(0);
 412               _M_writing = true;
 413               if (!__testeof)
 414                 {
 415                   *this->pptr() = traits_type::to_char_type(__c);
 416                   this->pbump(1);
 417                 }
 418               __ret = traits_type::not_eof(__c);
 419             }
 420           else
 421             {
 422               // Unbuffered.
 423               char_type __conv = traits_type::to_char_type(__c);
 424               if (__testeof || _M_convert_to_external(&__conv, 1))
 425                 {
 426                   _M_writing = true;
 427                   __ret = traits_type::not_eof(__c);
 428                 }
 429             }
 430         }
 431       return __ret;
 432     }
 433
 434   template<typename _CharT, typename _Traits>
 435     bool
 436     basic_filebuf<_CharT, _Traits>::
 437     _M_convert_to_external(_CharT* __ibuf, streamsize __ilen)
 438     {
 439       // Sizes of external and pending output.
 440       streamsize __elen;
 441       streamsize __plen;
 442       if (__check_facet(_M_codecvt).always_noconv())
 443         {
 444           __elen = _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen);
 445           __plen = __ilen;
 446         }
 447       else
 448         {
 449           // Worst-case number of external bytes needed.
 450           // XXX Not done encoding() == -1.
 451           streamsize __blen = __ilen * _M_codecvt->max_length();
 452           char* __buf = static_cast<char*>(__builtin_alloca(__blen));
 453
 454           char* __bend;
 455           const char_type* __iend;
 456           codecvt_base::result __r;
 457           __r = _M_codecvt->out(_M_state_cur, __ibuf, __ibuf + __ilen,
 458                                 __iend, __buf, __buf + __blen, __bend);
 459
 460           if (__r == codecvt_base::ok || __r == codecvt_base::partial)
 461             __blen = __bend - __buf;
 462           else if (__r == codecvt_base::noconv)
 463             {
 464               // Same as the always_noconv case above.
 465               __buf = reinterpret_cast<char*>(__ibuf);
 466               __blen = __ilen;
 467             }
 468           else
 469             __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
 470                                     "conversion error"));
 471
 472           __elen = _M_file.xsputn(__buf, __blen);
 473           __plen = __blen;
 474
 475           // Try once more for partial conversions.
 476           if (__r == codecvt_base::partial && __elen == __plen)
 477             {
 478               const char_type* __iresume = __iend;
 479               streamsize __rlen = this->pptr() - __iend;
 480               __r = _M_codecvt->out(_M_state_cur, __iresume,
 481                                     __iresume + __rlen, __iend, __buf,
 482                                     __buf + __blen, __bend);
 483               if (__r != codecvt_base::error)
 484                 {
 485                   __rlen = __bend - __buf;
 486                   __elen = _M_file.xsputn(__buf, __rlen);
 487                   __plen = __rlen;
 488                 }
 489               else
 490                 __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
 491                                         "conversion error"));
 492             }
 493         }
 494       return __elen == __plen;
 495     }
 496
 497    template<typename _CharT, typename _Traits>
 498      streamsize
 499      basic_filebuf<_CharT, _Traits>::
 500      xsgetn(_CharT* __s, streamsize __n)
 501      {
 502        // Clear out pback buffer before going on to the real deal...
 503        streamsize __ret = 0;
 504        if (this->_M_pback_init)
 505          {
 506            if (__n > 0 && this->gptr() == this->eback())
 507              {
 508                *__s++ = *this->gptr();
 509                this->gbump(1);
 510                __ret = 1;
 511                --__n;
 512              }
 513            _M_destroy_pback();
 514          }
 515
 516        // Optimization in the always_noconv() case, to be generalized in the
 517        // future: when __n > __buflen we read directly instead of using the
 518        // buffer repeatedly.
 519        const bool __testin = this->_M_mode & ios_base::in;
 520        const streamsize __buflen = this->_M_buf_size > 1 ? this->_M_buf_size - 1
 521                                                          : 1;
 522        if (__n > __buflen && __check_facet(_M_codecvt).always_noconv()
 523            && __testin && !_M_writing)
 524          {
 525            // First, copy the chars already present in the buffer.
 526            const streamsize __avail = this->egptr() - this->gptr();
 527            if (__avail == 1)
 528              *__s = *this->gptr();
 529            else if (__avail > 1)
 530              traits_type::move(__s, this->gptr(), __avail);
 531            __s += __avail;
 532            this->gbump(__avail);
 533            __ret += __avail;
 534            __n -= __avail;
 535
 536            const streamsize __len = _M_file.xsgetn(reinterpret_cast<char*>(__s),
 537                                                    __n);
 538            if (__len == -1)
 539              __throw_ios_failure(__N("basic_filebuf::xsgetn "
 540                                      "error reading the file"));
 541            __ret += __len;
 542            if (__len == __n)
 543              {
 544                _M_set_buffer(0);
 545                _M_reading = true;
 546              }
 547            else if (__len == 0)
 548              {
 549                // If end of file is reached, set 'uncommitted'
 550                // mode, thus allowing an immediate write without
 551                // an intervening seek.
 552                _M_set_buffer(-1);
 553                _M_reading = false;
 554              }
 555          }
 556        else
 557          __ret += __streambuf_type::xsgetn(__s, __n);
 558
 559        return __ret;
 560      }
 561
 562    template<typename _CharT, typename _Traits>
 563      streamsize
 564      basic_filebuf<_CharT, _Traits>::
 565      xsputn(const _CharT* __s, streamsize __n)
 566      {
 567        // Optimization in the always_noconv() case, to be generalized in the
 568        // future: when __n is sufficiently large we write directly instead of
 569        // using the buffer.
 570        streamsize __ret = 0;
 571        const bool __testout = this->_M_mode & ios_base::out;
 572        if (__check_facet(_M_codecvt).always_noconv()
 573            && __testout && !_M_reading)
 574         {
 575           // Measurement would reveal the best choice.
 576           const streamsize __chunk = 1ul << 10;
 577           streamsize __bufavail = this->epptr() - this->pptr();
 578
 579           // Don't mistake 'uncommitted' mode buffered with unbuffered.
 580           if (!_M_writing && this->_M_buf_size > 1)
 581             __bufavail = this->_M_buf_size - 1;
 582
 583           const streamsize __limit = std::min(__chunk, __bufavail);
 584           if (__n >= __limit)
 585             {
 586               const streamsize __buffill = this->pptr() - this->pbase();
 587               const char* __buf = reinterpret_cast<const char*>(this->pbase());
 588               __ret = _M_file.xsputn_2(__buf, __buffill,
 589                                        reinterpret_cast<const char*>(__s),
 590                                        __n);
 591               if (__ret == __buffill + __n)
 592                 {
 593                   _M_set_buffer(0);
 594                   _M_writing = true;
 595                 }
 596               if (__ret > __buffill)
 597                 __ret -= __buffill;
 598               else
 599                 __ret = 0;
 600             }
 601           else
 602             __ret = __streambuf_type::xsputn(__s, __n);
 603         }
 604        else
 605          __ret = __streambuf_type::xsputn(__s, __n);
 606        return __ret;
 607     }
 608
 609   template<typename _CharT, typename _Traits>
 610     typename basic_filebuf<_CharT, _Traits>::__streambuf_type*
 611     basic_filebuf<_CharT, _Traits>::
 612     setbuf(char_type* __s, streamsize __n)
 613     {
 614       if (!this->is_open())
 615         if (__s == 0 && __n == 0)
 616           this->_M_buf_size = 1;
 617         else if (__s && __n > 0)
 618           {
 619             // This is implementation-defined behavior, and assumes that
 620             // an external char_type array of length __n exists and has
 621             // been pre-allocated. If this is not the case, things will
 622             // quickly blow up. When __n > 1, __n - 1 positions will be
 623             // used for the get area, __n - 1 for the put area and 1
 624             // position to host the overflow char of a full put area.
 625             // When __n == 1, 1 position will be used for the get area
 626             // and 0 for the put area, as in the unbuffered case above.
 627             this->_M_buf = __s;
 628             this->_M_buf_size = __n;
 629           }
 630       return this;
 631     }
 632
 633
 634   // According to 27.8.1.4 p11 - 13, seekoff should ignore the last
 635   // argument (of type openmode).
 636   template<typename _CharT, typename _Traits>
 637     typename basic_filebuf<_CharT, _Traits>::pos_type
 638     basic_filebuf<_CharT, _Traits>::
 639     seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmode)
 640     {
 641       int __width = 0;
 642       if (_M_codecvt)
 643         __width = _M_codecvt->encoding();
 644       if (__width < 0)
 645         __width = 0;
 646
 647       pos_type __ret =  pos_type(off_type(-1));
 648       const bool __testfail = __off != 0 && __width <= 0;
 649       if (this->is_open() && !__testfail)
 650         {
 651           // Ditch any pback buffers to avoid confusion.
 652           _M_destroy_pback();
 653
 654           // Correct state at destination. Note that this is the correct
 655           // state for the current position during output, because
 656           // codecvt::unshift() returns the state to the initial state.
 657           // This is also the correct state at the end of the file because
 658           // an unshift sequence should have been written at the end.
 659           __state_type __state = _M_state_beg;
 660           off_type __computed_off = __off * __width;
 661           if (_M_reading && __way == ios_base::cur)
 662             {
 663               if (_M_codecvt->always_noconv())
 664                 __computed_off += this->gptr() - this->egptr();
 665               else
 666                 {
 667                   // Calculate offset from _M_ext_buf that corresponds
 668                   // to gptr(). Note: uses _M_state_last, which
 669                   // corresponds to eback().
 670                   const int __gptr_off =
 671                     _M_codecvt->length(_M_state_last, _M_ext_buf, _M_ext_next,
 672                                        this->gptr() - this->eback());
 673                   __computed_off += _M_ext_buf + __gptr_off - _M_ext_end;
 674
 675                   // _M_state_last is modified by codecvt::length() so
 676                   // it now corresponds to gptr().
 677                   __state = _M_state_last;
 678                 }
 679             }
 680           __ret = _M_seek(__computed_off, __way, __state);
 681         }
 682       return __ret;
 683     }
 684
 685   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 686   // 171. Strange seekpos() semantics due to joint position
 687   // According to the resolution of DR 171, seekpos should ignore the last
 688   // argument (of type openmode).
 689   template<typename _CharT, typename _Traits>
 690     typename basic_filebuf<_CharT, _Traits>::pos_type
 691     basic_filebuf<_CharT, _Traits>::
 692     seekpos(pos_type __pos, ios_base::openmode)
 693     {
 694       pos_type __ret =  pos_type(off_type(-1));
 695       if (this->is_open())
 696         {
 697           // Ditch any pback buffers to avoid confusion.
 698           _M_destroy_pback();
 699           __ret = _M_seek(off_type(__pos), ios_base::beg, __pos.state());
 700         }
 701       return __ret;
 702     }
 703
 704   template<typename _CharT, typename _Traits>
 705     typename basic_filebuf<_CharT, _Traits>::pos_type
 706     basic_filebuf<_CharT, _Traits>::
 707     _M_seek(off_type __off, ios_base::seekdir __way, __state_type __state)
 708     {
 709       pos_type __ret = pos_type(off_type(-1));
 710       if (_M_terminate_output())
 711         {
 712           // Returns pos_type(off_type(-1)) in case of failure.
 713           __ret = pos_type(_M_file.seekoff(__off, __way));
 714           _M_reading = false;
 715           _M_writing = false;
 716           _M_ext_next = _M_ext_end = _M_ext_buf;
 717           _M_set_buffer(-1);
 718           _M_state_cur = __state;
 719           __ret.state(_M_state_cur);
 720         }
 721       return __ret;
 722     }
 723
 724   template<typename _CharT, typename _Traits>
 725     bool
 726     basic_filebuf<_CharT, _Traits>::
 727     _M_terminate_output()
 728     {
 729       // Part one: update the output sequence.
 730       bool __testvalid = true;
 731       if (this->pbase() < this->pptr())
 732         {
 733           const int_type __tmp = this->overflow();
 734           if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 735             __testvalid = false;
 736         }
 737
 738       // Part two: output unshift sequence.
 739       if (_M_writing && !__check_facet(_M_codecvt).always_noconv()
 740           && __testvalid)
 741         {
 742           // Note: this value is arbitrary, since there is no way to
 743           // get the length of the unshift sequence from codecvt,
 744           // without calling unshift.
 745           const size_t __blen = 128;
 746           char __buf[__blen];
 747           codecvt_base::result __r;
 748           streamsize __ilen = 0;
 749
 750           do
 751             {
 752               char* __next;
 753               __r = _M_codecvt->unshift(_M_state_cur, __buf,
 754                                         __buf + __blen, __next);
 755               if (__r == codecvt_base::error)
 756                 __testvalid = false;
 757               else if (__r == codecvt_base::ok ||
 758                        __r == codecvt_base::partial)
 759                 {
 760                   __ilen = __next - __buf;
 761                   if (__ilen > 0)
 762                     {
 763                       const streamsize __elen = _M_file.xsputn(__buf, __ilen);
 764                       if (__elen != __ilen)
 765                         __testvalid = false;
 766                     }
 767                 }
 768             }
 769           while (__r == codecvt_base::partial && __ilen > 0 && __testvalid);
 770
 771           if (__testvalid)
 772             {
 773               // This second call to overflow() is required by the standard,
 774               // but it's not clear why it's needed, since the output buffer
 775               // should be empty by this point (it should have been emptied
 776               // in the first call to overflow()).
 777               const int_type __tmp = this->overflow();
 778               if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 779                 __testvalid = false;
 780             }
 781         }
 782       return __testvalid;
 783     }
 784
 785   template<typename _CharT, typename _Traits>
 786     int
 787     basic_filebuf<_CharT, _Traits>::
 788     sync()
 789     {
 790       // Make sure that the internal buffer resyncs its idea of
 791       // the file position with the external file.
 792       // NB: _M_file.sync() will be called within.
 793       int __ret = 0;
 794       if (this->pbase() < this->pptr())
 795         {
 796           const int_type __tmp = this->overflow();
 797           if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 798             __ret = -1;
 799         }
 800       return __ret;
 801     }
 802
 803   template<typename _CharT, typename _Traits>
 804     void
 805     basic_filebuf<_CharT, _Traits>::
 806     imbue(const locale& __loc)
 807     {
 808       bool __testvalid = true;
 809
 810       const __codecvt_type* _M_codecvt_tmp = 0;
 811       if (__builtin_expect(has_facet<__codecvt_type>(__loc), true))
 812         _M_codecvt_tmp = &use_facet<__codecvt_type>(__loc);
 813
 814       if (this->is_open())
 815         {
 816           // encoding() == -1 is ok only at the beginning.
 817           if ((_M_reading || _M_writing)
 818               && __check_facet(_M_codecvt).encoding() == -1)
 819             __testvalid = false;
 820           else
 821             {
 822               if (_M_reading)
 823                 {
 824                   if (__check_facet(_M_codecvt).always_noconv())
 825                     {
 826                       if (_M_codecvt_tmp
 827                           && !__check_facet(_M_codecvt_tmp).always_noconv())
 828                         __testvalid = this->seekoff(0, ios_base::cur, this->_M_mode)
 829                                       != pos_type(off_type(-1));
 830                     }
 831                   else
 832                     {
 833                       // External position corresponding to gptr().
 834                       _M_ext_next = _M_ext_buf
 835                         + _M_codecvt->length(_M_state_last, _M_ext_buf, _M_ext_next,
 836                                              this->gptr() - this->eback());
 837                       const streamsize __remainder = _M_ext_end - _M_ext_next;
 838                       if (__remainder)
 839                         std::memmove(_M_ext_buf, _M_ext_next, __remainder);
 840
 841                       _M_ext_next = _M_ext_buf;
 842                       _M_ext_end = _M_ext_buf + __remainder;
 843                       _M_set_buffer(-1);
 844                       _M_state_last = _M_state_cur = _M_state_beg;
 845                     }
 846                 }
 847               else if (_M_writing && (__testvalid = _M_terminate_output()))
 848                 _M_set_buffer(-1);
 849             }
 850         }
 851
 852       if (__testvalid)
 853         _M_codecvt = _M_codecvt_tmp;
 854       else
 855         _M_codecvt = 0;
 856     }
 857
 858   // Inhibit implicit instantiations for required instantiations,
 859   // which are defined via explicit instantiations elsewhere.
 860   // NB:  This syntax is a GNU extension.
 861 #if _GLIBCXX_EXTERN_TEMPLATE
 862   extern template class basic_filebuf<char>;
 863   extern template class basic_ifstream<char>;
 864   extern template class basic_ofstream<char>;
 865   extern template class basic_fstream<char>;
 866
 867 #ifdef _GLIBCXX_USE_WCHAR_T
 868   extern template class basic_filebuf<wchar_t>;
 869   extern template class basic_ifstream<wchar_t>;
 870   extern template class basic_ofstream<wchar_t>;
 871   extern template class basic_fstream<wchar_t>;
 872 #endif
 873 #endif
 874 } // namespace std
 875
 876 #endif