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

   1 // File based streams -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
   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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  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 /** @file fstream.tcc
  32  *  This is an internal header file, included by other library headers.
  33  *  You should not attempt to use it directly.
  34  */
  35
  36 //
  37 // ISO C++ 14882: 27.8  File-based streams
  38 //
  39
  40 #ifndef _FSTREAM_TCC
  41 #define _FSTREAM_TCC 1
  42
  43 #pragma GCC system_header
  44
  45 _GLIBCXX_BEGIN_NAMESPACE(std)
  46
  47   template<typename _CharT, typename _Traits>
  48     void
  49     basic_filebuf<_CharT, _Traits>::
  50     _M_allocate_internal_buffer()
  51     {
  52       // Allocate internal buffer only if one doesn't already exist
  53       // (either allocated or provided by the user via setbuf).
  54       if (!_M_buf_allocated && !_M_buf)
  55         {
  56           _M_buf = new char_type[_M_buf_size];
  57           _M_buf_allocated = true;
  58         }
  59     }
  60
  61   template<typename _CharT, typename _Traits>
  62     void
  63     basic_filebuf<_CharT, _Traits>::
  64     _M_destroy_internal_buffer() throw()
  65     {
  66       if (_M_buf_allocated)
  67         {
  68           delete [] _M_buf;
  69           _M_buf = NULL;
  70           _M_buf_allocated = false;
  71         }
  72       delete [] _M_ext_buf;
  73       _M_ext_buf = NULL;
  74       _M_ext_buf_size = 0;
  75       _M_ext_next = NULL;
  76       _M_ext_end = NULL;
  77     }
  78
  79   template<typename _CharT, typename _Traits>
  80     basic_filebuf<_CharT, _Traits>::
  81     basic_filebuf() : __streambuf_type(), _M_lock(), _M_file(&_M_lock),
  82     _M_mode(ios_base::openmode(0)), _M_state_beg(), _M_state_cur(),
  83     _M_state_last(), _M_buf(NULL), _M_buf_size(BUFSIZ),
  84     _M_buf_allocated(false), _M_reading(false), _M_writing(false), _M_pback(),
  85     _M_pback_cur_save(0), _M_pback_end_save(0), _M_pback_init(false),
  86     _M_codecvt(0), _M_ext_buf(0), _M_ext_buf_size(0), _M_ext_next(0),
  87     _M_ext_end(0)
  88     {
  89       if (has_facet<__codecvt_type>(this->_M_buf_locale))
  90         _M_codecvt = &use_facet<__codecvt_type>(this->_M_buf_locale);
  91     }
  92
  93   template<typename _CharT, typename _Traits>
  94     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
  95     basic_filebuf<_CharT, _Traits>::
  96     open(const char* __s, ios_base::openmode __mode)
  97     {
  98       __filebuf_type *__ret = NULL;
  99       if (!this->is_open())
 100         {
 101           _M_file.open(__s, __mode);
 102           if (this->is_open())
 103             {
 104               _M_allocate_internal_buffer();
 105               _M_mode = __mode;
 106
 107               // Setup initial buffer to 'uncommitted' mode.
 108               _M_reading = false;
 109               _M_writing = false;
 110               _M_set_buffer(-1);
 111
 112               // Reset to initial state.
 113               _M_state_last = _M_state_cur = _M_state_beg;
 114
 115               // 27.8.1.3,4
 116               if ((__mode & ios_base::ate)
 117                   && this->seekoff(0, ios_base::end, __mode)
 118                   == pos_type(off_type(-1)))
 119                 this->close();
 120               else
 121                 __ret = this;
 122             }
 123         }
 124       return __ret;
 125     }
 126
 127   template<typename _CharT, typename _Traits>
 128     typename basic_filebuf<_CharT, _Traits>::__filebuf_type*
 129     basic_filebuf<_CharT, _Traits>::
 130     close() throw()
 131     {
 132       __filebuf_type* __ret = NULL;
 133       if (this->is_open())
 134         {
 135           bool __testfail = false;
 136           try
 137             {
 138               if (!_M_terminate_output())
 139                 __testfail = true;
 140             }
 141           catch(...)
 142             { __testfail = true; }
 143
 144           // NB: Do this here so that re-opened filebufs will be cool...
 145           _M_mode = ios_base::openmode(0);
 146           _M_pback_init = false;
 147           _M_destroy_internal_buffer();
 148           _M_reading = false;
 149           _M_writing = false;
 150           _M_set_buffer(-1);
 151           _M_state_last = _M_state_cur = _M_state_beg;
 152
 153           if (!_M_file.close())
 154             __testfail = true;
 155
 156           if (!__testfail)
 157             __ret = this;
 158         }
 159       return __ret;
 160     }
 161
 162   template<typename _CharT, typename _Traits>
 163     streamsize
 164     basic_filebuf<_CharT, _Traits>::
 165     showmanyc()
 166     {
 167       streamsize __ret = -1;
 168       const bool __testin = _M_mode & ios_base::in;
 169       if (__testin && this->is_open())
 170         {
 171           // For a stateful encoding (-1) the pending sequence might be just
 172           // shift and unshift prefixes with no actual character.
 173           __ret = this->egptr() - this->gptr();
 174
 175 #if _GLIBCXX_HAVE_DOS_BASED_FILESYSTEM
 176           // About this workaround, see libstdc++/20806.
 177           const bool __testbinary = _M_mode & ios_base::binary;
 178           if (__check_facet(_M_codecvt).encoding() >= 0
 179               && __testbinary)
 180 #else
 181           if (__check_facet(_M_codecvt).encoding() >= 0)
 182 #endif
 183             __ret += _M_file.showmanyc() / _M_codecvt->max_length();
 184         }
 185       return __ret;
 186     }
 187
 188   template<typename _CharT, typename _Traits>
 189     typename basic_filebuf<_CharT, _Traits>::int_type
 190     basic_filebuf<_CharT, _Traits>::
 191     underflow()
 192     {
 193       int_type __ret = traits_type::eof();
 194       const bool __testin = _M_mode & ios_base::in;
 195       if (__testin && !_M_writing)
 196         {
 197           // Check for pback madness, and if so swich back to the
 198           // normal buffers and jet outta here before expensive
 199           // fileops happen...
 200           _M_destroy_pback();
 201
 202           if (this->gptr() < this->egptr())
 203             return traits_type::to_int_type(*this->gptr());
 204
 205           // Get and convert input sequence.
 206           const size_t __buflen = _M_buf_size > 1 ? _M_buf_size - 1 : 1;
 207
 208           // Will be set to true if ::read() returns 0 indicating EOF.
 209           bool __got_eof = false;
 210           // Number of internal characters produced.
 211           streamsize __ilen = 0;
 212           codecvt_base::result __r = codecvt_base::ok;
 213           if (__check_facet(_M_codecvt).always_noconv())
 214             {
 215               __ilen = _M_file.xsgetn(reinterpret_cast<char*>(this->eback()),
 216                                       __buflen);
 217               if (__ilen == 0)
 218                 __got_eof = true;
 219             }
 220           else
 221             {
 222               // Worst-case number of external bytes.
 223               // XXX Not done encoding() == -1.
 224               const int __enc = _M_codecvt->encoding();
 225               streamsize __blen; // Minimum buffer size.
 226               streamsize __rlen; // Number of chars to read.
 227               if (__enc > 0)
 228                 __blen = __rlen = __buflen * __enc;
 229               else
 230                 {
 231                   __blen = __buflen + _M_codecvt->max_length() - 1;
 232                   __rlen = __buflen;
 233                 }
 234               const streamsize __remainder = _M_ext_end - _M_ext_next;
 235               __rlen = __rlen > __remainder ? __rlen - __remainder : 0;
 236
 237               // An imbue in 'read' mode implies first converting the external
 238               // chars already present.
 239               if (_M_reading && this->egptr() == this->eback() && __remainder)
 240                 __rlen = 0;
 241
 242               // Allocate buffer if necessary and move unconverted
 243               // bytes to front.
 244               if (_M_ext_buf_size < __blen)
 245                 {
 246                   char* __buf = new char[__blen];
 247                   if (__remainder)
 248                     std::memcpy(__buf, _M_ext_next, __remainder);
 249
 250                   delete [] _M_ext_buf;
 251                   _M_ext_buf = __buf;
 252                   _M_ext_buf_size = __blen;
 253                 }
 254               else if (__remainder)
 255                 std::memmove(_M_ext_buf, _M_ext_next, __remainder);
 256
 257               _M_ext_next = _M_ext_buf;
 258               _M_ext_end = _M_ext_buf + __remainder;
 259               _M_state_last = _M_state_cur;
 260
 261               do
 262                 {
 263                   if (__rlen > 0)
 264                     {
 265                       // Sanity check!
 266                       // This may fail if the return value of
 267                       // codecvt::max_length() is bogus.
 268                       if (_M_ext_end - _M_ext_buf + __rlen > _M_ext_buf_size)
 269                         {
 270                           __throw_ios_failure(__N("basic_filebuf::underflow "
 271                                               "codecvt::max_length() "
 272                                               "is not valid"));
 273                         }
 274                       streamsize __elen = _M_file.xsgetn(_M_ext_end, __rlen);
 275                       if (__elen == 0)
 276                         __got_eof = true;
 277                       else if (__elen == -1)
 278                         break;
 279                       _M_ext_end += __elen;
 280                     }
 281
 282                   char_type* __iend;
 283                   __r = _M_codecvt->in(_M_state_cur, _M_ext_next,
 284                                        _M_ext_end, _M_ext_next, this->eback(),
 285                                        this->eback() + __buflen, __iend);
 286                   if (__r == codecvt_base::noconv)
 287                     {
 288                       size_t __avail = _M_ext_end - _M_ext_buf;
 289                       __ilen = std::min(__avail, __buflen);
 290                       traits_type::copy(this->eback(),
 291                                         reinterpret_cast<char_type*>(_M_ext_buf), __ilen);
 292                       _M_ext_next = _M_ext_buf + __ilen;
 293                     }
 294                   else
 295                     __ilen = __iend - this->eback();
 296
 297                   // _M_codecvt->in may return error while __ilen > 0: this is
 298                   // ok, and actually occurs in case of mixed encodings (e.g.,
 299                   // XML files).
 300                   if (__r == codecvt_base::error)
 301                     break;
 302
 303                   __rlen = 1;
 304                 }
 305               while (__ilen == 0 && !__got_eof);
 306             }
 307
 308           if (__ilen > 0)
 309             {
 310               _M_set_buffer(__ilen);
 311               _M_reading = true;
 312               __ret = traits_type::to_int_type(*this->gptr());
 313             }
 314           else if (__got_eof)
 315             {
 316               // If the actual end of file is reached, set 'uncommitted'
 317               // mode, thus allowing an immediate write without an
 318               // intervening seek.
 319               _M_set_buffer(-1);
 320               _M_reading = false;
 321               // However, reaching it while looping on partial means that
 322               // the file has got an incomplete character.
 323               if (__r == codecvt_base::partial)
 324                 __throw_ios_failure(__N("basic_filebuf::underflow "
 325                                     "incomplete character in file"));
 326             }
 327           else if (__r == codecvt_base::error)
 328             __throw_ios_failure(__N("basic_filebuf::underflow "
 329                                 "invalid byte sequence in file"));
 330           else
 331             __throw_ios_failure(__N("basic_filebuf::underflow "
 332                                 "error reading the file"));
 333         }
 334       return __ret;
 335     }
 336
 337   template<typename _CharT, typename _Traits>
 338     typename basic_filebuf<_CharT, _Traits>::int_type
 339     basic_filebuf<_CharT, _Traits>::
 340     pbackfail(int_type __i)
 341     {
 342       int_type __ret = traits_type::eof();
 343       const bool __testin = _M_mode & ios_base::in;
 344       if (__testin && !_M_writing)
 345         {
 346           // Remember whether the pback buffer is active, otherwise below
 347           // we may try to store in it a second char (libstdc++/9761).
 348           const bool __testpb = _M_pback_init;
 349           const bool __testeof = traits_type::eq_int_type(__i, __ret);
 350           int_type __tmp;
 351           if (this->eback() < this->gptr())
 352             {
 353               this->gbump(-1);
 354               __tmp = traits_type::to_int_type(*this->gptr());
 355             }
 356           else if (this->seekoff(-1, ios_base::cur) != pos_type(off_type(-1)))
 357             {
 358               __tmp = this->underflow();
 359               if (traits_type::eq_int_type(__tmp, __ret))
 360                 return __ret;
 361             }
 362           else
 363             {
 364               // At the beginning of the buffer, need to make a
 365               // putback position available.  But the seek may fail
 366               // (f.i., at the beginning of a file, see
 367               // libstdc++/9439) and in that case we return
 368               // traits_type::eof().
 369               return __ret;
 370             }
 371
 372           // Try to put back __i into input sequence in one of three ways.
 373           // Order these tests done in is unspecified by the standard.
 374           if (!__testeof && traits_type::eq_int_type(__i, __tmp))
 375             __ret = __i;
 376           else if (__testeof)
 377             __ret = traits_type::not_eof(__i);
 378           else if (!__testpb)
 379             {
 380               _M_create_pback();
 381               _M_reading = true;
 382               *this->gptr() = traits_type::to_char_type(__i);
 383               __ret = __i;
 384             }
 385         }
 386       return __ret;
 387     }
 388
 389   template<typename _CharT, typename _Traits>
 390     typename basic_filebuf<_CharT, _Traits>::int_type
 391     basic_filebuf<_CharT, _Traits>::
 392     overflow(int_type __c)
 393     {
 394       int_type __ret = traits_type::eof();
 395       const bool __testeof = traits_type::eq_int_type(__c, __ret);
 396       const bool __testout = _M_mode & ios_base::out;
 397       if (__testout && !_M_reading)
 398         {
 399           if (this->pbase() < this->pptr())
 400             {
 401               // If appropriate, append the overflow char.
 402               if (!__testeof)
 403                 {
 404                   *this->pptr() = traits_type::to_char_type(__c);
 405                   this->pbump(1);
 406                 }
 407
 408               // Convert pending sequence to external representation,
 409               // and output.
 410               if (_M_convert_to_external(this->pbase(),
 411                                          this->pptr() - this->pbase()))
 412                 {
 413                   _M_set_buffer(0);
 414                   __ret = traits_type::not_eof(__c);
 415                 }
 416             }
 417           else if (_M_buf_size > 1)
 418             {
 419               // Overflow in 'uncommitted' mode: set _M_writing, set
 420               // the buffer to the initial 'write' mode, and put __c
 421               // into the buffer.
 422               _M_set_buffer(0);
 423               _M_writing = true;
 424               if (!__testeof)
 425                 {
 426                   *this->pptr() = traits_type::to_char_type(__c);
 427                   this->pbump(1);
 428                 }
 429               __ret = traits_type::not_eof(__c);
 430             }
 431           else
 432             {
 433               // Unbuffered.
 434               char_type __conv = traits_type::to_char_type(__c);
 435               if (__testeof || _M_convert_to_external(&__conv, 1))
 436                 {
 437                   _M_writing = true;
 438                   __ret = traits_type::not_eof(__c);
 439                 }
 440             }
 441         }
 442       return __ret;
 443     }
 444
 445   template<typename _CharT, typename _Traits>
 446     bool
 447     basic_filebuf<_CharT, _Traits>::
 448     _M_convert_to_external(_CharT* __ibuf, streamsize __ilen)
 449     {
 450       // Sizes of external and pending output.
 451       streamsize __elen;
 452       streamsize __plen;
 453       if (__check_facet(_M_codecvt).always_noconv())
 454         {
 455           __elen = _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen);
 456           __plen = __ilen;
 457         }
 458       else
 459         {
 460           // Worst-case number of external bytes needed.
 461           // XXX Not done encoding() == -1.
 462           streamsize __blen = __ilen * _M_codecvt->max_length();
 463           char* __buf = static_cast<char*>(__builtin_alloca(__blen));
 464
 465           char* __bend;
 466           const char_type* __iend;
 467           codecvt_base::result __r;
 468           __r = _M_codecvt->out(_M_state_cur, __ibuf, __ibuf + __ilen,
 469                                 __iend, __buf, __buf + __blen, __bend);
 470
 471           if (__r == codecvt_base::ok || __r == codecvt_base::partial)
 472             __blen = __bend - __buf;
 473           else if (__r == codecvt_base::noconv)
 474             {
 475               // Same as the always_noconv case above.
 476               __buf = reinterpret_cast<char*>(__ibuf);
 477               __blen = __ilen;
 478             }
 479           else
 480             __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
 481                                     "conversion error"));
 482
 483           __elen = _M_file.xsputn(__buf, __blen);
 484           __plen = __blen;
 485
 486           // Try once more for partial conversions.
 487           if (__r == codecvt_base::partial && __elen == __plen)
 488             {
 489               const char_type* __iresume = __iend;
 490               streamsize __rlen = this->pptr() - __iend;
 491               __r = _M_codecvt->out(_M_state_cur, __iresume,
 492                                     __iresume + __rlen, __iend, __buf,
 493                                     __buf + __blen, __bend);
 494               if (__r != codecvt_base::error)
 495                 {
 496                   __rlen = __bend - __buf;
 497                   __elen = _M_file.xsputn(__buf, __rlen);
 498                   __plen = __rlen;
 499                 }
 500               else
 501                 __throw_ios_failure(__N("basic_filebuf::_M_convert_to_external "
 502                                         "conversion error"));
 503             }
 504         }
 505       return __elen == __plen;
 506     }
 507
 508    template<typename _CharT, typename _Traits>
 509      streamsize
 510      basic_filebuf<_CharT, _Traits>::
 511      xsgetn(_CharT* __s, streamsize __n)
 512      {
 513        // Clear out pback buffer before going on to the real deal...
 514        streamsize __ret = 0;
 515        if (_M_pback_init)
 516          {
 517            if (__n > 0 && this->gptr() == this->eback())
 518              {
 519                *__s++ = *this->gptr();
 520                this->gbump(1);
 521                __ret = 1;
 522                --__n;
 523              }
 524            _M_destroy_pback();
 525          }
 526
 527        // Optimization in the always_noconv() case, to be generalized in the
 528        // future: when __n > __buflen we read directly instead of using the
 529        // buffer repeatedly.
 530        const bool __testin = _M_mode & ios_base::in;
 531        const streamsize __buflen = _M_buf_size > 1 ? _M_buf_size - 1 : 1;
 532
 533        if (__n > __buflen && __check_facet(_M_codecvt).always_noconv()
 534            && __testin && !_M_writing)
 535          {
 536            // First, copy the chars already present in the buffer.
 537            const streamsize __avail = this->egptr() - this->gptr();
 538            if (__avail != 0)
 539              {
 540                if (__avail == 1)
 541                  *__s = *this->gptr();
 542                else
 543                  traits_type::copy(__s, this->gptr(), __avail);
 544                __s += __avail;
 545                this->gbump(__avail);
 546                __ret += __avail;
 547                __n -= __avail;
 548              }
 549
 550            // Need to loop in case of short reads (relatively common
 551            // with pipes).
 552            streamsize __len;
 553            for (;;)
 554              {
 555                __len = _M_file.xsgetn(reinterpret_cast<char*>(__s),
 556                                       __n);
 557                if (__len == -1)
 558                  __throw_ios_failure(__N("basic_filebuf::xsgetn "
 559                                          "error reading the file"));
 560                if (__len == 0)
 561                  break;
 562
 563                __n -= __len;
 564                __ret += __len;
 565                if (__n == 0)
 566                  break;
 567
 568                __s += __len;
 569              }
 570
 571            if (__n == 0)
 572              {
 573                _M_set_buffer(0);
 574                _M_reading = true;
 575              }
 576            else if (__len == 0)
 577              {
 578                // If end of file is reached, set 'uncommitted'
 579                // mode, thus allowing an immediate write without
 580                // an intervening seek.
 581                _M_set_buffer(-1);
 582                _M_reading = false;
 583              }
 584          }
 585        else
 586          __ret += __streambuf_type::xsgetn(__s, __n);
 587
 588        return __ret;
 589      }
 590
 591    template<typename _CharT, typename _Traits>
 592      streamsize
 593      basic_filebuf<_CharT, _Traits>::
 594      xsputn(const _CharT* __s, streamsize __n)
 595      {
 596        // Optimization in the always_noconv() case, to be generalized in the
 597        // future: when __n is sufficiently large we write directly instead of
 598        // using the buffer.
 599        streamsize __ret = 0;
 600        const bool __testout = _M_mode & ios_base::out;
 601        if (__check_facet(_M_codecvt).always_noconv()
 602            && __testout && !_M_reading)
 603         {
 604           // Measurement would reveal the best choice.
 605           const streamsize __chunk = 1ul << 10;
 606           streamsize __bufavail = this->epptr() - this->pptr();
 607
 608           // Don't mistake 'uncommitted' mode buffered with unbuffered.
 609           if (!_M_writing && _M_buf_size > 1)
 610             __bufavail = _M_buf_size - 1;
 611
 612           const streamsize __limit = std::min(__chunk, __bufavail);
 613           if (__n >= __limit)
 614             {
 615               const streamsize __buffill = this->pptr() - this->pbase();
 616               const char* __buf = reinterpret_cast<const char*>(this->pbase());
 617               __ret = _M_file.xsputn_2(__buf, __buffill,
 618                                        reinterpret_cast<const char*>(__s),
 619                                        __n);
 620               if (__ret == __buffill + __n)
 621                 {
 622                   _M_set_buffer(0);
 623                   _M_writing = true;
 624                 }
 625               if (__ret > __buffill)
 626                 __ret -= __buffill;
 627               else
 628                 __ret = 0;
 629             }
 630           else
 631             __ret = __streambuf_type::xsputn(__s, __n);
 632         }
 633        else
 634          __ret = __streambuf_type::xsputn(__s, __n);
 635        return __ret;
 636     }
 637
 638   template<typename _CharT, typename _Traits>
 639     typename basic_filebuf<_CharT, _Traits>::__streambuf_type*
 640     basic_filebuf<_CharT, _Traits>::
 641     setbuf(char_type* __s, streamsize __n)
 642     {
 643       if (!this->is_open())
 644         if (__s == 0 && __n == 0)
 645           _M_buf_size = 1;
 646         else if (__s && __n > 0)
 647           {
 648             // This is implementation-defined behavior, and assumes that
 649             // an external char_type array of length __n exists and has
 650             // been pre-allocated. If this is not the case, things will
 651             // quickly blow up. When __n > 1, __n - 1 positions will be
 652             // used for the get area, __n - 1 for the put area and 1
 653             // position to host the overflow char of a full put area.
 654             // When __n == 1, 1 position will be used for the get area
 655             // and 0 for the put area, as in the unbuffered case above.
 656             _M_buf = __s;
 657             _M_buf_size = __n;
 658           }
 659       return this;
 660     }
 661
 662
 663   // According to 27.8.1.4 p11 - 13, seekoff should ignore the last
 664   // argument (of type openmode).
 665   template<typename _CharT, typename _Traits>
 666     typename basic_filebuf<_CharT, _Traits>::pos_type
 667     basic_filebuf<_CharT, _Traits>::
 668     seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmode)
 669     {
 670       int __width = 0;
 671       if (_M_codecvt)
 672         __width = _M_codecvt->encoding();
 673       if (__width < 0)
 674         __width = 0;
 675
 676       pos_type __ret =  pos_type(off_type(-1));
 677       const bool __testfail = __off != 0 && __width <= 0;
 678       if (this->is_open() && !__testfail)
 679         {
 680           // Ditch any pback buffers to avoid confusion.
 681           _M_destroy_pback();
 682
 683           // Correct state at destination. Note that this is the correct
 684           // state for the current position during output, because
 685           // codecvt::unshift() returns the state to the initial state.
 686           // This is also the correct state at the end of the file because
 687           // an unshift sequence should have been written at the end.
 688           __state_type __state = _M_state_beg;
 689           off_type __computed_off = __off * __width;
 690           if (_M_reading && __way == ios_base::cur)
 691             {
 692               if (_M_codecvt->always_noconv())
 693                 __computed_off += this->gptr() - this->egptr();
 694               else
 695                 {
 696                   // Calculate offset from _M_ext_buf that corresponds
 697                   // to gptr(). Note: uses _M_state_last, which
 698                   // corresponds to eback().
 699                   const int __gptr_off =
 700                     _M_codecvt->length(_M_state_last, _M_ext_buf, _M_ext_next,
 701                                        this->gptr() - this->eback());
 702                   __computed_off += _M_ext_buf + __gptr_off - _M_ext_end;
 703
 704                   // _M_state_last is modified by codecvt::length() so
 705                   // it now corresponds to gptr().
 706                   __state = _M_state_last;
 707                 }
 708             }
 709           __ret = _M_seek(__computed_off, __way, __state);
 710         }
 711       return __ret;
 712     }
 713
 714   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 715   // 171. Strange seekpos() semantics due to joint position
 716   // According to the resolution of DR 171, seekpos should ignore the last
 717   // argument (of type openmode).
 718   template<typename _CharT, typename _Traits>
 719     typename basic_filebuf<_CharT, _Traits>::pos_type
 720     basic_filebuf<_CharT, _Traits>::
 721     seekpos(pos_type __pos, ios_base::openmode)
 722     {
 723       pos_type __ret =  pos_type(off_type(-1));
 724       if (this->is_open())
 725         {
 726           // Ditch any pback buffers to avoid confusion.
 727           _M_destroy_pback();
 728           __ret = _M_seek(off_type(__pos), ios_base::beg, __pos.state());
 729         }
 730       return __ret;
 731     }
 732
 733   template<typename _CharT, typename _Traits>
 734     typename basic_filebuf<_CharT, _Traits>::pos_type
 735     basic_filebuf<_CharT, _Traits>::
 736     _M_seek(off_type __off, ios_base::seekdir __way, __state_type __state)
 737     {
 738       pos_type __ret = pos_type(off_type(-1));
 739       if (_M_terminate_output())
 740         {
 741           // Returns pos_type(off_type(-1)) in case of failure.
 742           __ret = pos_type(_M_file.seekoff(__off, __way));
 743           _M_reading = false;
 744           _M_writing = false;
 745           _M_ext_next = _M_ext_end = _M_ext_buf;
 746           _M_set_buffer(-1);
 747           _M_state_cur = __state;
 748           __ret.state(_M_state_cur);
 749         }
 750       return __ret;
 751     }
 752
 753   template<typename _CharT, typename _Traits>
 754     bool
 755     basic_filebuf<_CharT, _Traits>::
 756     _M_terminate_output()
 757     {
 758       // Part one: update the output sequence.
 759       bool __testvalid = true;
 760       if (this->pbase() < this->pptr())
 761         {
 762           const int_type __tmp = this->overflow();
 763           if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 764             __testvalid = false;
 765         }
 766
 767       // Part two: output unshift sequence.
 768       if (_M_writing && !__check_facet(_M_codecvt).always_noconv()
 769           && __testvalid)
 770         {
 771           // Note: this value is arbitrary, since there is no way to
 772           // get the length of the unshift sequence from codecvt,
 773           // without calling unshift.
 774           const size_t __blen = 128;
 775           char __buf[__blen];
 776           codecvt_base::result __r;
 777           streamsize __ilen = 0;
 778
 779           do
 780             {
 781               char* __next;
 782               __r = _M_codecvt->unshift(_M_state_cur, __buf,
 783                                         __buf + __blen, __next);
 784               if (__r == codecvt_base::error)
 785                 __testvalid = false;
 786               else if (__r == codecvt_base::ok ||
 787                        __r == codecvt_base::partial)
 788                 {
 789                   __ilen = __next - __buf;
 790                   if (__ilen > 0)
 791                     {
 792                       const streamsize __elen = _M_file.xsputn(__buf, __ilen);
 793                       if (__elen != __ilen)
 794                         __testvalid = false;
 795                     }
 796                 }
 797             }
 798           while (__r == codecvt_base::partial && __ilen > 0 && __testvalid);
 799
 800           if (__testvalid)
 801             {
 802               // This second call to overflow() is required by the standard,
 803               // but it's not clear why it's needed, since the output buffer
 804               // should be empty by this point (it should have been emptied
 805               // in the first call to overflow()).
 806               const int_type __tmp = this->overflow();
 807               if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 808                 __testvalid = false;
 809             }
 810         }
 811       return __testvalid;
 812     }
 813
 814   template<typename _CharT, typename _Traits>
 815     int
 816     basic_filebuf<_CharT, _Traits>::
 817     sync()
 818     {
 819       // Make sure that the internal buffer resyncs its idea of
 820       // the file position with the external file.
 821       int __ret = 0;
 822       if (this->pbase() < this->pptr())
 823         {
 824           const int_type __tmp = this->overflow();
 825           if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 826             __ret = -1;
 827         }
 828       return __ret;
 829     }
 830
 831   template<typename _CharT, typename _Traits>
 832     void
 833     basic_filebuf<_CharT, _Traits>::
 834     imbue(const locale& __loc)
 835     {
 836       bool __testvalid = true;
 837
 838       const __codecvt_type* _M_codecvt_tmp = 0;
 839       if (__builtin_expect(has_facet<__codecvt_type>(__loc), true))
 840         _M_codecvt_tmp = &use_facet<__codecvt_type>(__loc);
 841
 842       if (this->is_open())
 843         {
 844           // encoding() == -1 is ok only at the beginning.
 845           if ((_M_reading || _M_writing)
 846               && __check_facet(_M_codecvt).encoding() == -1)
 847             __testvalid = false;
 848           else
 849             {
 850               if (_M_reading)
 851                 {
 852                   if (__check_facet(_M_codecvt).always_noconv())
 853                     {
 854                       if (_M_codecvt_tmp
 855                           && !__check_facet(_M_codecvt_tmp).always_noconv())
 856                         __testvalid = this->seekoff(0, ios_base::cur, _M_mode)
 857                                       != pos_type(off_type(-1));
 858                     }
 859                   else
 860                     {
 861                       // External position corresponding to gptr().
 862                       _M_ext_next = _M_ext_buf
 863                         + _M_codecvt->length(_M_state_last, _M_ext_buf, _M_ext_next,
 864                                              this->gptr() - this->eback());
 865                       const streamsize __remainder = _M_ext_end - _M_ext_next;
 866                       if (__remainder)
 867                         std::memmove(_M_ext_buf, _M_ext_next, __remainder);
 868
 869                       _M_ext_next = _M_ext_buf;
 870                       _M_ext_end = _M_ext_buf + __remainder;
 871                       _M_set_buffer(-1);
 872                       _M_state_last = _M_state_cur = _M_state_beg;
 873                     }
 874                 }
 875               else if (_M_writing && (__testvalid = _M_terminate_output()))
 876                 _M_set_buffer(-1);
 877             }
 878         }
 879
 880       if (__testvalid)
 881         _M_codecvt = _M_codecvt_tmp;
 882       else
 883         _M_codecvt = 0;
 884     }
 885
 886   // Inhibit implicit instantiations for required instantiations,
 887   // which are defined via explicit instantiations elsewhere.
 888   // NB:  This syntax is a GNU extension.
 889 #if _GLIBCXX_EXTERN_TEMPLATE
 890   extern template class basic_filebuf<char>;
 891   extern template class basic_ifstream<char>;
 892   extern template class basic_ofstream<char>;
 893   extern template class basic_fstream<char>;
 894
 895 #ifdef _GLIBCXX_USE_WCHAR_T
 896   extern template class basic_filebuf<wchar_t>;
 897   extern template class basic_ifstream<wchar_t>;
 898   extern template class basic_ofstream<wchar_t>;
 899   extern template class basic_fstream<wchar_t>;
 900 #endif
 901 #endif
 902
 903 _GLIBCXX_END_NAMESPACE
 904
 905 #endif