libstdc++-v3/include/bits/basic_ios.h

   1 // Iostreams base classes -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2001, 2002, 2003
   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 /** @file basic_ios.h
  32  *  This is an internal header file, included by other library headers.
  33  *  You should not attempt to use it directly.
  34  */
  35
  36 #ifndef _CPP_BITS_BASICIOS_H
  37 #define _CPP_BITS_BASICIOS_H 1
  38
  39 #pragma GCC system_header
  40
  41 #include <bits/streambuf_iterator.h>
  42 #include <bits/localefwd.h>
  43 #include <bits/locale_classes.h>
  44 #include <bits/locale_facets.h>
  45
  46 namespace std
  47 {
  48   // 27.4.5  Template class basic_ios
  49   /**
  50    *  @brief  Virtual base class for all stream classes.
  51    *
  52    *  Most of the member functions called dispatched on stream objects
  53    *  (e.g., @c std::cout.foo(bar);) are consolidated in this class.
  54   */
  55   template<typename _CharT, typename _Traits>
  56     class basic_ios : public ios_base
  57     {
  58     public:
  59       //@{
  60       /**
  61        *  These are standard types.  They permit a standardized way of
  62        *  referring to names of (or names dependant on) the template
  63        *  parameters, which are specific to the implementation.
  64       */
  65       typedef _CharT                                 char_type;
  66       typedef typename _Traits::int_type             int_type;
  67       typedef typename _Traits::pos_type             pos_type;
  68       typedef typename _Traits::off_type             off_type;
  69       typedef _Traits                                traits_type;
  70       //@}
  71
  72       //@{
  73       /**
  74        *  @if maint
  75        *  These are non-standard types.
  76        *  @endif
  77       */
  78       typedef ctype<_CharT>                          __ctype_type;
  79       typedef ostreambuf_iterator<_CharT, _Traits>   __ostreambuf_iter;
  80       typedef num_put<_CharT, __ostreambuf_iter>     __numput_type;
  81       typedef istreambuf_iterator<_CharT, _Traits>   __istreambuf_iter;
  82       typedef num_get<_CharT, __istreambuf_iter>     __numget_type;
  83       //@}
  84
  85       // Data members:
  86     protected:
  87       basic_ostream<_CharT, _Traits>*                _M_tie;
  88       mutable char_type                              _M_fill;
  89       mutable bool                                   _M_fill_init;
  90       basic_streambuf<_CharT, _Traits>*              _M_streambuf;
  91
  92       // Cached use_facet<ctype>, which is based on the current locale info.
  93       const __ctype_type*                            _M_fctype;
  94       // For ostream.
  95       const __numput_type*                           _M_fnumput;
  96       // For istream.
  97       const __numget_type*                           _M_fnumget;
  98
  99     public:
 100       //@{
 101       /**
 102        *  @brief  The quick-and-easy status check.
 103        *
 104        *  This allows you to write constructs such as
 105        *  "if (!a_stream) ..." and "while (a_stream) ..."
 106       */
 107       operator void*() const
 108       { return this->fail() ? 0 : const_cast<basic_ios*>(this); }
 109
 110       bool
 111       operator!() const
 112       { return this->fail(); }
 113       //@}
 114
 115       /**
 116        *  @brief  Returns the error state of the stream buffer.
 117        *  @return  A bit pattern (well, isn't everything?)
 118        *
 119        *  See std::ios_base::iostate for the possible bit values.  Most
 120        *  users will call one of the interpreting wrappers, e.g., good().
 121       */
 122       iostate
 123       rdstate() const
 124       { return _M_streambuf_state; }
 125
 126       /**
 127        *  @brief  [Re]sets the error state.
 128        *  @param  state  The new state flag(s) to set.
 129        *
 130        *  See std::ios_base::iostate for the possible bit values.  Most
 131        *  users will not need to pass an argument.
 132       */
 133       void
 134       clear(iostate __state = goodbit);
 135
 136       /**
 137        *  @brief  Sets additional flags in the error state.
 138        *  @param  state  The additional state flag(s) to set.
 139        *
 140        *  See std::ios_base::iostate for the possible bit values.
 141       */
 142       void
 143       setstate(iostate __state)
 144       { this->clear(this->rdstate() | __state); }
 145
 146       /**
 147        *  @brief  Fast error checking.
 148        *  @return  True if no error flags are set.
 149        *
 150        *  A wrapper around rdstate.
 151       */
 152       bool
 153       good() const
 154       { return this->rdstate() == 0; }
 155
 156       /**
 157        *  @brief  Fast error checking.
 158        *  @return  True if the eofbit is set.
 159        *
 160        *  Note that other iostate flags may also be set.
 161       */
 162       bool
 163       eof() const
 164       { return (this->rdstate() & eofbit) != 0; }
 165
 166       /**
 167        *  @brief  Fast error checking.
 168        *  @return  True if either the badbit or the failbit is set.
 169        *
 170        *  Checking the badbit in fail() is historical practice.
 171        *  Note that other iostate flags may also be set.
 172       */
 173       bool
 174       fail() const
 175       { return (this->rdstate() & (badbit | failbit)) != 0; }
 176
 177       /**
 178        *  @brief  Fast error checking.
 179        *  @return  True if the badbit is set.
 180        *
 181        *  Note that other iostate flags may also be set.
 182       */
 183       bool
 184       bad() const
 185       { return (this->rdstate() & badbit) != 0; }
 186
 187       /**
 188        *  @brief  Throwing exceptions on errors.
 189        *  @return  The current exceptions mask.
 190        *
 191        *  This changes nothing in the stream.  See the one-argument version
 192        *  of exceptions(iostate) for the meaning of the return value.
 193       */
 194       iostate
 195       exceptions() const
 196       { return _M_exception; }
 197
 198       /**
 199        *  @brief  Throwing exceptions on errors.
 200        *  @param  except  The new exceptions mask.
 201        *
 202        *  By default, error flags are set silently.  You can set an
 203        *  exceptions mask for each stream; if a bit in the mask becomes set
 204        *  in the error flags, then an exception of type
 205        *  std::ios_base::failure is thrown.
 206        *
 207        *  If the error flage is already set when the exceptions mask is
 208        *  added, the exception is immediately thrown.  Try running the
 209        *  following under GCC 3.1 or later:
 210        *  @code
 211        *  #include <iostream>
 212        *  #include <fstream>
 213        *  #include <exception>
 214        *
 215        *  int main()
 216        *  {
 217        *      std::set_terminate (__gnu_cxx::__verbose_terminate_handler);
 218        *
 219        *      std::ifstream f ("/etc/motd");
 220        *
 221        *      std::cerr << "Setting badbit\n";
 222        *      f.setstate (std::ios_base::badbit);
 223        *
 224        *      std::cerr << "Setting exception mask\n";
 225        *      f.exceptions (std::ios_base::badbit);
 226        *  }
 227        *  @endcode
 228       */
 229       void
 230       exceptions(iostate __except)
 231       {
 232         _M_exception = __except;
 233         this->clear(_M_streambuf_state);
 234       }
 235
 236       // Constructor/destructor:
 237       /**
 238        *  @brief  Constructor performs initialization.
 239        *
 240        *  The parameter is passed by derived streams.
 241       */
 242       explicit
 243       basic_ios(basic_streambuf<_CharT, _Traits>* __sb)
 244       : ios_base(), _M_fctype(0), _M_fnumput(0), _M_fnumget(0)
 245       { this->init(__sb); }
 246
 247       /**
 248        *  @brief  Empty.
 249        *
 250        *  The destructor does nothing.  More specifically, it does not
 251        *  destroy the streambuf held by rdbuf().
 252       */
 253       virtual
 254       ~basic_ios() { }
 255
 256       // Members:
 257       /**
 258        *  @brief  Fetches the current @e tied stream.
 259        *  @return  A pointer to the tied stream, or NULL if the stream is
 260        *           not tied.
 261        *
 262        *  A stream may be @e tied (or synchronized) to a second output
 263        *  stream.  When this stream performs any I/O, the tied stream is
 264        *  first flushed.  For example, @c std::cin is tied to @c std::cout.
 265       */
 266       basic_ostream<_CharT, _Traits>*
 267       tie() const
 268       { return _M_tie; }
 269
 270       /**
 271        *  @brief  Ties this stream to an output stream.
 272        *  @param  tiestr  The output stream.
 273        *  @return  The previously tied output stream, or NULL if the stream
 274        *           was not tied.
 275        *
 276        *  This sets up a new tie; see tie() for more.
 277       */
 278       basic_ostream<_CharT, _Traits>*
 279       tie(basic_ostream<_CharT, _Traits>* __tiestr)
 280       {
 281         basic_ostream<_CharT, _Traits>* __old = _M_tie;
 282         _M_tie = __tiestr;
 283         return __old;
 284       }
 285
 286       /**
 287        *  @brief  Accessing the underlying buffer.
 288        *  @return  The current stream buffer.
 289        *
 290        *  This does not change the state of the stream.
 291       */
 292       basic_streambuf<_CharT, _Traits>*
 293       rdbuf() const
 294       { return _M_streambuf; }
 295
 296       /**
 297        *  @brief  Changing the underlying buffer.
 298        *  @param  sb  The new stream buffer.
 299        *  @return  The previous stream buffer.
 300        *
 301        *  Associates a new buffer with the current stream, and clears the
 302        *  error state.
 303        *
 304        *  Due to historical accidents which the LWG refuses to correct, the
 305        *  I/O library suffers from a design error:  this function is hidden
 306        *  in derived classes by overrides of the zero-argument @c rdbuf(),
 307        *  which is non-virtual for hysterical raisins.  As a result, you
 308        *  must use explicit qualifications to access this function via any
 309        *  derived class.  For example:
 310        *
 311        *  @code
 312        *  std::fstream     foo;         // or some other derived type
 313        *  std::streambuf*  p = .....;
 314        *
 315        *  foo.ios::rdbuf(p);            // ios == basic_ios<char>
 316        *  @endcode
 317       */
 318       basic_streambuf<_CharT, _Traits>*
 319       rdbuf(basic_streambuf<_CharT, _Traits>* __sb);
 320
 321       /**
 322        *  @doctodo
 323       */
 324       basic_ios&
 325       copyfmt(const basic_ios& __rhs);
 326
 327       /**
 328        *  @brief  Retreives the "empty" character.
 329        *  @return  The current fill character.
 330        *
 331        *  It defaults to a space (' ') in the current locale.
 332       */
 333       char_type
 334       fill() const
 335       {
 336         if (!_M_fill_init)
 337           {
 338             _M_fill = this->widen(' ');
 339             _M_fill_init = true;
 340           }
 341         return _M_fill;
 342       }
 343
 344       /**
 345        *  @brief  Sets a new "empty" character.
 346        *  @param  ch  The new character.
 347        *  @return  The previous fill character.
 348        *
 349        *  The fill character is used to fill out space when P+ characters
 350        *  have been requested (e.g., via setw), Q characters are actually
 351        *  used, and Q<P.  It defaults to a space (' ') in the current locale.
 352       */
 353       char_type
 354       fill(char_type __ch)
 355       {
 356         char_type __old = this->fill();
 357         _M_fill = __ch;
 358         return __old;
 359       }
 360
 361       // Locales:
 362       /**
 363        *  @brief  Moves to a new locale.
 364        *  @param  loc  The new locale.
 365        *  @return  The previous locale.
 366        *
 367        *  Calls @c ios_base::imbue(loc), and if a stream buffer is associated
 368        *  with this stream, calls that buffer's @c pubimbue(loc).
 369        *
 370        *  Additional l10n notes are at
 371        *  http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html
 372       */
 373       locale
 374       imbue(const locale& __loc);
 375
 376       /**
 377        *  @brief  Squeezes characters.
 378        *  @param  c  The character to narrow.
 379        *  @param  dfault  The character to narrow.
 380        *  @return  The narrowed character.
 381        *
 382        *  Maps a character of @c char_type to a character of @c char,
 383        *  if possible.
 384        *
 385        *  Returns the result of
 386        *  @code
 387        *    std::use_facet< ctype<char_type> >(getloc()).narrow(c,dfault)
 388        *  @endcode
 389        *
 390        *  Additional l10n notes are at
 391        *  http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html
 392       */
 393       char
 394       narrow(char_type __c, char __dfault) const;
 395
 396       /**
 397        *  @brief  Widens characters.
 398        *  @param  c  The character to widen.
 399        *  @return  The widened character.
 400        *
 401        *  Maps a character of @c char to a character of @c char_type.
 402        *
 403        *  Returns the result of
 404        *  @code
 405        *    std::use_facet< ctype<char_type> >(getloc()).widen(c)
 406        *  @endcode
 407        *
 408        *  Additional l10n notes are at
 409        *  http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html
 410       */
 411       char_type
 412       widen(char __c) const;
 413
 414     protected:
 415       // 27.4.5.1  basic_ios constructors
 416       /**
 417        *  @brief  Empty.
 418        *
 419        *  The default constructor does nothing and is not normally
 420        *  accessible to users.
 421       */
 422       basic_ios() : ios_base()
 423       { }
 424
 425       /**
 426        *  @brief  All setup is performed here.
 427        *
 428        *  This is called from the public constructor.  It is not virtual and
 429        *  cannot be redefined.
 430       */
 431       void
 432       init(basic_streambuf<_CharT, _Traits>* __sb);
 433
 434       bool
 435       _M_check_facet(const locale::facet* __f) const
 436       {
 437         if (!__f)
 438           __throw_bad_cast();
 439         return true;
 440       }
 441
 442       void
 443       _M_cache_locale(const locale& __loc);
 444     };
 445 } // namespace std
 446
 447 #ifdef _GLIBCPP_NO_TEMPLATE_EXPORT
 448 # define export
 449 #include <bits/basic_ios.tcc>
 450 #endif
 451
 452 #endif /* _CPP_BITS_BASICIOS_H */