1 // Iostreams base classes -*- C++ -*- 2 3 // Copyright (C) 1997, 1998, 1999, 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 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 _BASIC_IOS_H 37 #define _BASIC_IOS_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 _GLIBCXX_BEGIN_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 num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> > 80 __num_put_type; 81 typedef num_get<_CharT, istreambuf_iterator<_CharT, _Traits> > 82 __num_get_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_ctype; 94 // For ostream. 95 const __num_put_type* _M_num_put; 96 // For istream. 97 const __num_get_type* _M_num_get; 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 // Flip the internal state on for the proper state bits, then re 147 // throws the propagated exception if bit also set in 148 // exceptions(). 149 void 150 _M_setstate(iostate __state) 151 { 152 // 27.6.1.2.1 Common requirements. 153 // Turn this on without causing an ios::failure to be thrown. 154 _M_streambuf_state |= __state; 155 if (this->exceptions() & __state) 156 __throw_exception_again; 157 } 158 159 /** 160 * @brief Fast error checking. 161 * @return True if no error flags are set. 162 * 163 * A wrapper around rdstate. 164 */ 165 bool 166 good() const 167 { return this->rdstate() == 0; } 168 169 /** 170 * @brief Fast error checking. 171 * @return True if the eofbit is set. 172 * 173 * Note that other iostate flags may also be set. 174 */ 175 bool 176 eof() const 177 { return (this->rdstate() & eofbit) != 0; } 178 179 /** 180 * @brief Fast error checking. 181 * @return True if either the badbit or the failbit is set. 182 * 183 * Checking the badbit in fail() is historical practice. 184 * Note that other iostate flags may also be set. 185 */ 186 bool 187 fail() const 188 { return (this->rdstate() & (badbit | failbit)) != 0; } 189 190 /** 191 * @brief Fast error checking. 192 * @return True if the badbit is set. 193 * 194 * Note that other iostate flags may also be set. 195 */ 196 bool 197 bad() const 198 { return (this->rdstate() & badbit) != 0; } 199 200 /** 201 * @brief Throwing exceptions on errors. 202 * @return The current exceptions mask. 203 * 204 * This changes nothing in the stream. See the one-argument version 205 * of exceptions(iostate) for the meaning of the return value. 206 */ 207 iostate 208 exceptions() const 209 { return _M_exception; } 210 211 /** 212 * @brief Throwing exceptions on errors. 213 * @param except The new exceptions mask. 214 * 215 * By default, error flags are set silently. You can set an 216 * exceptions mask for each stream; if a bit in the mask becomes set 217 * in the error flags, then an exception of type 218 * std::ios_base::failure is thrown. 219 * 220 * If the error flage is already set when the exceptions mask is 221 * added, the exception is immediately thrown. Try running the 222 * following under GCC 3.1 or later: 223 * @code 224 * #include <iostream> 225 * #include <fstream> 226 * #include <exception> 227 * 228 * int main() 229 * { 230 * std::set_terminate (__gnu_cxx::__verbose_terminate_handler); 231 * 232 * std::ifstream f ("/etc/motd"); 233 * 234 * std::cerr << "Setting badbit\n"; 235 * f.setstate (std::ios_base::badbit); 236 * 237 * std::cerr << "Setting exception mask\n"; 238 * f.exceptions (std::ios_base::badbit); 239 * } 240 * @endcode 241 */ 242 void 243 exceptions(iostate __except) 244 { 245 _M_exception = __except; 246 this->clear(_M_streambuf_state); 247 } 248 249 // Constructor/destructor: 250 /** 251 * @brief Constructor performs initialization. 252 * 253 * The parameter is passed by derived streams. 254 */ 255 explicit 256 basic_ios(basic_streambuf<_CharT, _Traits>* __sb) 257 : ios_base(), _M_tie(0), _M_fill(), _M_fill_init(false), _M_streambuf(0), 258 _M_ctype(0), _M_num_put(0), _M_num_get(0) 259 { this->init(__sb); } 260 261 /** 262 * @brief Empty. 263 * 264 * The destructor does nothing. More specifically, it does not 265 * destroy the streambuf held by rdbuf(). 266 */ 267 virtual 268 ~basic_ios() { } 269 270 // Members: 271 /** 272 * @brief Fetches the current @e tied stream. 273 * @return A pointer to the tied stream, or NULL if the stream is 274 * not tied. 275 * 276 * A stream may be @e tied (or synchronized) to a second output 277 * stream. When this stream performs any I/O, the tied stream is 278 * first flushed. For example, @c std::cin is tied to @c std::cout. 279 */ 280 basic_ostream<_CharT, _Traits>* 281 tie() const 282 { return _M_tie; } 283 284 /** 285 * @brief Ties this stream to an output stream. 286 * @param tiestr The output stream. 287 * @return The previously tied output stream, or NULL if the stream 288 * was not tied. 289 * 290 * This sets up a new tie; see tie() for more. 291 */ 292 basic_ostream<_CharT, _Traits>* 293 tie(basic_ostream<_CharT, _Traits>* __tiestr) 294 { 295 basic_ostream<_CharT, _Traits>* __old = _M_tie; 296 _M_tie = __tiestr; 297 return __old; 298 } 299 300 /** 301 * @brief Accessing the underlying buffer. 302 * @return The current stream buffer. 303 * 304 * This does not change the state of the stream. 305 */ 306 basic_streambuf<_CharT, _Traits>* 307 rdbuf() const 308 { return _M_streambuf; } 309 310 /** 311 * @brief Changing the underlying buffer. 312 * @param sb The new stream buffer. 313 * @return The previous stream buffer. 314 * 315 * Associates a new buffer with the current stream, and clears the 316 * error state. 317 * 318 * Due to historical accidents which the LWG refuses to correct, the 319 * I/O library suffers from a design error: this function is hidden 320 * in derived classes by overrides of the zero-argument @c rdbuf(), 321 * which is non-virtual for hysterical raisins. As a result, you 322 * must use explicit qualifications to access this function via any 323 * derived class. For example: 324 * 325 * @code 326 * std::fstream foo; // or some other derived type 327 * std::streambuf* p = .....; 328 * 329 * foo.ios::rdbuf(p); // ios == basic_ios<char> 330 * @endcode 331 */ 332 basic_streambuf<_CharT, _Traits>* 333 rdbuf(basic_streambuf<_CharT, _Traits>* __sb); 334 335 /** 336 * @brief Copies fields of __rhs into this. 337 * @param __rhs The source values for the copies. 338 * @return Reference to this object. 339 * 340 * All fields of __rhs are copied into this object except that rdbuf() 341 * and rdstate() remain unchanged. All values in the pword and iword 342 * arrays are copied. Before copying, each callback is invoked with 343 * erase_event. After copying, each (new) callback is invoked with 344 * copyfmt_event. The final step is to copy exceptions(). 345 */ 346 basic_ios& 347 copyfmt(const basic_ios& __rhs); 348 349 /** 350 * @brief Retreives the "empty" character. 351 * @return The current fill character. 352 * 353 * It defaults to a space (' ') in the current locale. 354 */ 355 char_type 356 fill() const 357 { 358 if (!_M_fill_init) 359 { 360 _M_fill = this->widen(' '); 361 _M_fill_init = true; 362 } 363 return _M_fill; 364 } 365 366 /** 367 * @brief Sets a new "empty" character. 368 * @param ch The new character. 369 * @return The previous fill character. 370 * 371 * The fill character is used to fill out space when P+ characters 372 * have been requested (e.g., via setw), Q characters are actually 373 * used, and Q<P. It defaults to a space (' ') in the current locale. 374 */ 375 char_type 376 fill(char_type __ch) 377 { 378 char_type __old = this->fill(); 379 _M_fill = __ch; 380 return __old; 381 } 382 383 // Locales: 384 /** 385 * @brief Moves to a new locale. 386 * @param loc The new locale. 387 * @return The previous locale. 388 * 389 * Calls @c ios_base::imbue(loc), and if a stream buffer is associated 390 * with this stream, calls that buffer's @c pubimbue(loc). 391 * 392 * Additional l10n notes are at 393 * http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html 394 */ 395 locale 396 imbue(const locale& __loc); 397 398 /** 399 * @brief Squeezes characters. 400 * @param c The character to narrow. 401 * @param dfault The character to narrow. 402 * @return The narrowed character. 403 * 404 * Maps a character of @c char_type to a character of @c char, 405 * if possible. 406 * 407 * Returns the result of 408 * @code 409 * std::use_facet<ctype<char_type> >(getloc()).narrow(c,dfault) 410 * @endcode 411 * 412 * Additional l10n notes are at 413 * http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html 414 */ 415 char 416 narrow(char_type __c, char __dfault) const; 417 418 /** 419 * @brief Widens characters. 420 * @param c The character to widen. 421 * @return The widened character. 422 * 423 * Maps a character of @c char to a character of @c char_type. 424 * 425 * Returns the result of 426 * @code 427 * std::use_facet<ctype<char_type> >(getloc()).widen(c) 428 * @endcode 429 * 430 * Additional l10n notes are at 431 * http://gcc.gnu.org/onlinedocs/libstdc++/22_locale/howto.html 432 */ 433 char_type 434 widen(char __c) const; 435 436 protected: 437 // 27.4.5.1 basic_ios constructors 438 /** 439 * @brief Empty. 440 * 441 * The default constructor does nothing and is not normally 442 * accessible to users. 443 */ 444 basic_ios() 445 : ios_base(), _M_tie(0), _M_fill(char_type()), _M_fill_init(false), 446 _M_streambuf(0), _M_ctype(0), _M_num_put(0), _M_num_get(0) 447 { } 448 449 /** 450 * @brief All setup is performed here. 451 * 452 * This is called from the public constructor. It is not virtual and 453 * cannot be redefined. 454 */ 455 void 456 init(basic_streambuf<_CharT, _Traits>* __sb); 457 458 void 459 _M_cache_locale(const locale& __loc); 460 }; 461 462 _GLIBCXX_END_NAMESPACE 463 464 #ifndef _GLIBCXX_EXPORT_TEMPLATE 465 #include <bits/basic_ios.tcc> 466 #endif 467 468 #endif /* _BASIC_IOS_H */ 469