1 // Iostreams base classes -*- C++ -*-
3 // Copyright (C) 1997-2024 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
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25 /** @file bits/basic_ios.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{ios}
31 #define _BASIC_IOS_H 1
33 #pragma GCC system_header
35 #include <bits/localefwd.h>
36 #include <bits/locale_classes.h>
37 #include <bits/locale_facets.h>
38 #include <bits/streambuf_iterator.h>
39 #include <bits/move.h>
41 namespace std
_GLIBCXX_VISIBILITY(default)
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 template<typename _Facet
>
47 __check_facet(const _Facet
* __f
)
55 * @brief Template class basic_ios, virtual base class for all
59 * @tparam _CharT Type of character stream.
60 * @tparam _Traits Traits for character type, defaults to
61 * char_traits<_CharT>.
63 * Most of the member functions called dispatched on stream objects
64 * (e.g., @c std::cout.foo(bar);) are consolidated in this class.
66 template<typename _CharT
, typename _Traits
>
67 class basic_ios
: public ios_base
69 #if __cplusplus >= 202002L
70 static_assert(is_same_v
<_CharT
, typename
_Traits::char_type
>);
76 * These are standard types. They permit a standardized way of
77 * referring to names of (or names dependent on) the template
78 * parameters, which are specific to the implementation.
80 typedef _CharT char_type
;
81 typedef typename
_Traits::int_type int_type
;
82 typedef typename
_Traits::pos_type pos_type
;
83 typedef typename
_Traits::off_type off_type
;
84 typedef _Traits traits_type
;
89 * These are non-standard types.
91 typedef ctype
<_CharT
> __ctype_type
;
92 typedef num_put
<_CharT
, ostreambuf_iterator
<_CharT
, _Traits
> >
94 typedef num_get
<_CharT
, istreambuf_iterator
<_CharT
, _Traits
> >
100 basic_ostream
<_CharT
, _Traits
>* _M_tie
;
101 mutable char_type _M_fill
;
102 mutable bool _M_fill_init
;
103 basic_streambuf
<_CharT
, _Traits
>* _M_streambuf
;
105 // Cached use_facet<ctype>, which is based on the current locale info.
106 const __ctype_type
* _M_ctype
;
108 const __num_put_type
* _M_num_put
;
110 const __num_get_type
* _M_num_get
;
115 * @brief The quick-and-easy status check.
117 * This allows you to write constructs such as
118 * <code>if (!a_stream) ...</code> and <code>while (a_stream) ...</code>
120 #if __cplusplus >= 201103L
121 explicit operator bool() const
122 { return !this->fail(); }
124 operator void*() const
125 { return this->fail() ? 0 : const_cast<basic_ios
*>(this); }
130 { return this->fail(); }
134 * @brief Returns the error state of the stream buffer.
135 * @return A bit pattern (well, isn't everything?)
137 * See std::ios_base::iostate for the possible bit values. Most
138 * users will call one of the interpreting wrappers, e.g., good().
142 { return _M_streambuf_state
; }
145 * @brief [Re]sets the error state.
146 * @param __state The new state flag(s) to set.
148 * See std::ios_base::iostate for the possible bit values. Most
149 * users will not need to pass an argument.
152 clear(iostate __state
= goodbit
);
155 * @brief Sets additional flags in the error state.
156 * @param __state The additional state flag(s) to set.
158 * See std::ios_base::iostate for the possible bit values.
161 setstate(iostate __state
)
162 { this->clear(this->rdstate() | __state
); }
164 // Flips the internal state on for the proper state bits, then
165 // rethrows the propagated exception if bit also set in
166 // exceptions(). Must only be called within a catch handler.
168 _M_setstate(iostate __state
)
170 // 27.6.1.2.1 Common requirements.
171 // Turn this on without causing an ios::failure to be thrown.
172 _M_streambuf_state
|= __state
;
173 if (this->exceptions() & __state
)
174 __throw_exception_again
;
178 * @brief Fast error checking.
179 * @return True if no error flags are set.
181 * A wrapper around rdstate.
185 { return this->rdstate() == 0; }
188 * @brief Fast error checking.
189 * @return True if the eofbit is set.
191 * Note that other iostate flags may also be set.
195 { return (this->rdstate() & eofbit
) != 0; }
198 * @brief Fast error checking.
199 * @return True if either the badbit or the failbit is set.
201 * Checking the badbit in fail() is historical practice.
202 * Note that other iostate flags may also be set.
206 { return (this->rdstate() & (badbit
| failbit
)) != 0; }
209 * @brief Fast error checking.
210 * @return True if the badbit is set.
212 * Note that other iostate flags may also be set.
216 { return (this->rdstate() & badbit
) != 0; }
219 * @brief Throwing exceptions on errors.
220 * @return The current exceptions mask.
222 * This changes nothing in the stream. See the one-argument version
223 * of exceptions(iostate) for the meaning of the return value.
227 { return _M_exception
; }
230 * @brief Throwing exceptions on errors.
231 * @param __except The new exceptions mask.
233 * By default, error flags are set silently. You can set an
234 * exceptions mask for each stream; if a bit in the mask becomes set
235 * in the error flags, then an exception of type
236 * std::ios_base::failure is thrown.
238 * If the error flag is already set when the exceptions mask is
239 * added, the exception is immediately thrown. Try running the
240 * following under GCC 3.1 or later:
242 * #include <iostream>
244 * #include <exception>
248 * std::set_terminate (__gnu_cxx::__verbose_terminate_handler);
250 * std::ifstream f ("/etc/motd");
252 * std::cerr << "Setting badbit\n";
253 * f.setstate (std::ios_base::badbit);
255 * std::cerr << "Setting exception mask\n";
256 * f.exceptions (std::ios_base::badbit);
261 exceptions(iostate __except
)
263 _M_exception
= __except
;
264 this->clear(_M_streambuf_state
);
267 // Constructor/destructor:
269 * @brief Constructor performs initialization.
271 * The parameter is passed by derived streams.
274 basic_ios(basic_streambuf
<_CharT
, _Traits
>* __sb
)
275 : ios_base(), _M_tie(0), _M_fill(), _M_fill_init(false), _M_streambuf(0),
276 _M_ctype(0), _M_num_put(0), _M_num_get(0)
277 { this->init(__sb
); }
282 * The destructor does nothing. More specifically, it does not
283 * destroy the streambuf held by rdbuf().
290 * @brief Fetches the current @e tied stream.
291 * @return A pointer to the tied stream, or NULL if the stream is
294 * A stream may be @e tied (or synchronized) to a second output
295 * stream. When this stream performs any I/O, the tied stream is
296 * first flushed. For example, @c std::cin is tied to @c std::cout.
298 basic_ostream
<_CharT
, _Traits
>*
303 * @brief Ties this stream to an output stream.
304 * @param __tiestr The output stream.
305 * @return The previously tied output stream, or NULL if the stream
308 * This sets up a new tie; see tie() for more.
310 basic_ostream
<_CharT
, _Traits
>*
311 tie(basic_ostream
<_CharT
, _Traits
>* __tiestr
)
313 basic_ostream
<_CharT
, _Traits
>* __old
= _M_tie
;
319 * @brief Accessing the underlying buffer.
320 * @return The current stream buffer.
322 * This does not change the state of the stream.
324 basic_streambuf
<_CharT
, _Traits
>*
326 { return _M_streambuf
; }
329 * @brief Changing the underlying buffer.
330 * @param __sb The new stream buffer.
331 * @return The previous stream buffer.
333 * Associates a new buffer with the current stream, and clears the
336 * Due to historical accidents which the LWG refuses to correct, the
337 * I/O library suffers from a design error: this function is hidden
338 * in derived classes by overrides of the zero-argument @c rdbuf(),
339 * which is non-virtual for hysterical raisins. As a result, you
340 * must use explicit qualifications to access this function via any
341 * derived class. For example:
344 * std::fstream foo; // or some other derived type
345 * std::streambuf* p = .....;
347 * foo.ios::rdbuf(p); // ios == basic_ios<char>
350 basic_streambuf
<_CharT
, _Traits
>*
351 rdbuf(basic_streambuf
<_CharT
, _Traits
>* __sb
);
354 * @brief Copies fields of __rhs into this.
355 * @param __rhs The source values for the copies.
356 * @return Reference to this object.
358 * All fields of __rhs are copied into this object except that rdbuf()
359 * and rdstate() remain unchanged. All values in the pword and iword
360 * arrays are copied. Before copying, each callback is invoked with
361 * erase_event. After copying, each (new) callback is invoked with
362 * copyfmt_event. The final step is to copy exceptions().
365 copyfmt(const basic_ios
& __rhs
);
368 * @brief Retrieves the @a empty character.
369 * @return The current fill character.
371 * It defaults to a space (' ') in the current locale.
376 if (__builtin_expect(!_M_fill_init
, false))
377 return this->widen(' ');
382 * @brief Sets a new @a empty character.
383 * @param __ch The new character.
384 * @return The previous fill character.
386 * The fill character is used to fill out space when P+ characters
387 * have been requested (e.g., via setw), Q characters are actually
388 * used, and Q<P. It defaults to a space (' ') in the current locale.
393 char_type __old
= _M_fill
;
401 * @brief Moves to a new locale.
402 * @param __loc The new locale.
403 * @return The previous locale.
405 * Calls @c ios_base::imbue(loc), and if a stream buffer is associated
406 * with this stream, calls that buffer's @c pubimbue(loc).
408 * Additional l10n notes are at
409 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/localization.html
412 imbue(const locale
& __loc
);
415 * @brief Squeezes characters.
416 * @param __c The character to narrow.
417 * @param __dfault The character to narrow.
418 * @return The narrowed character.
420 * Maps a character of @c char_type to a character of @c char,
423 * Returns the result of
425 * std::use_facet<ctype<char_type> >(getloc()).narrow(c,dfault)
428 * Additional l10n notes are at
429 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/localization.html
432 narrow(char_type __c
, char __dfault
) const
433 { return __check_facet(_M_ctype
).narrow(__c
, __dfault
); }
436 * @brief Widens characters.
437 * @param __c The character to widen.
438 * @return The widened character.
440 * Maps a character of @c char to a character of @c char_type.
442 * Returns the result of
444 * std::use_facet<ctype<char_type> >(getloc()).widen(c)
447 * Additional l10n notes are at
448 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/localization.html
451 widen(char __c
) const
452 { return __check_facet(_M_ctype
).widen(__c
); }
455 // 27.4.5.1 basic_ios constructors
459 * The default constructor does nothing and is not normally
460 * accessible to users.
463 : ios_base(), _M_tie(0), _M_fill(char_type()), _M_fill_init(false),
464 _M_streambuf(0), _M_ctype(0), _M_num_put(0), _M_num_get(0)
468 * @brief All setup is performed here.
470 * This is called from the public constructor. It is not virtual and
471 * cannot be redefined.
474 init(basic_streambuf
<_CharT
, _Traits
>* __sb
);
476 #if __cplusplus >= 201103L
477 basic_ios(const basic_ios
&) = delete;
478 basic_ios
& operator=(const basic_ios
&) = delete;
481 move(basic_ios
& __rhs
)
483 ios_base::_M_move(__rhs
);
484 _M_cache_locale(_M_ios_locale
);
485 this->tie(__rhs
.tie(nullptr));
486 _M_fill
= __rhs
._M_fill
;
487 _M_fill_init
= __rhs
._M_fill_init
;
488 _M_streambuf
= nullptr;
492 move(basic_ios
&& __rhs
)
493 { this->move(__rhs
); }
496 swap(basic_ios
& __rhs
) noexcept
498 ios_base::_M_swap(__rhs
);
499 _M_cache_locale(_M_ios_locale
);
500 __rhs
._M_cache_locale(__rhs
._M_ios_locale
);
501 std::swap(_M_tie
, __rhs
._M_tie
);
502 std::swap(_M_fill
, __rhs
._M_fill
);
503 std::swap(_M_fill_init
, __rhs
._M_fill_init
);
507 set_rdbuf(basic_streambuf
<_CharT
, _Traits
>* __sb
)
508 { _M_streambuf
= __sb
; }
512 _M_cache_locale(const locale
& __loc
);
515 _GLIBCXX_END_NAMESPACE_VERSION
518 #include <bits/basic_ios.tcc>
520 #endif /* _BASIC_IOS_H */