1 // Input streams -*- C++ -*-
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4 // 2006, 2007, 2008, 2009, 2010, 2011
5 // Free Software Foundation, Inc.
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28 // ISO C++ 14882: 27.6.1 Input streams
31 /** @file include/istream
32 * This is a Standard C++ Library header.
35 #ifndef _GLIBCXX_ISTREAM
36 #define _GLIBCXX_ISTREAM 1
38 #pragma GCC system_header
43 namespace std _GLIBCXX_VISIBILITY(default)
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
47 // [27.6.1.1] Template class basic_istream
49 * @brief Controlling input.
52 * This is the base class for all input streams. It provides text
53 * formatting of all builtin types, and communicates with any class
54 * derived from basic_streambuf to do the actual input.
56 template<typename _CharT, typename _Traits>
57 class basic_istream : virtual public basic_ios<_CharT, _Traits>
60 // Types (inherited from basic_ios (27.4.4)):
61 typedef _CharT char_type;
62 typedef typename _Traits::int_type int_type;
63 typedef typename _Traits::pos_type pos_type;
64 typedef typename _Traits::off_type off_type;
65 typedef _Traits traits_type;
67 // Non-standard Types:
68 typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
69 typedef basic_ios<_CharT, _Traits> __ios_type;
70 typedef basic_istream<_CharT, _Traits> __istream_type;
71 typedef num_get<_CharT, istreambuf_iterator<_CharT, _Traits> >
73 typedef ctype<_CharT> __ctype_type;
78 * The number of characters extracted in the previous unformatted
79 * function; see gcount().
84 // [27.6.1.1.1] constructor/destructor
86 * @brief Base constructor.
88 * This ctor is almost never called by the user directly, rather from
89 * derived classes' initialization lists, which pass a pointer to
90 * their own stream buffer.
93 basic_istream(__streambuf_type* __sb)
94 : _M_gcount(streamsize(0))
98 * @brief Base destructor.
100 * This does very little apart from providing a virtual base dtor.
104 { _M_gcount = streamsize(0); }
106 // [27.6.1.1.2] prefix/suffix
110 // [27.6.1.2] formatted input
111 // [27.6.1.2.3] basic_istream::operator>>
114 * @brief Interface for manipulators.
116 * Manipulators such as @c std::ws and @c std::dec use these
117 * functions in constructs like
118 * <code>std::cin >> std::ws</code>.
119 * For more information, see the iomanip header.
122 operator>>(__istream_type& (*__pf)(__istream_type&))
123 { return __pf(*this); }
126 operator>>(__ios_type& (*__pf)(__ios_type&))
133 operator>>(ios_base& (*__pf)(ios_base&))
140 // [27.6.1.2.2] arithmetic extractors
142 * @name Arithmetic Extractors
144 * All the @c operator>> functions (aka <em>formatted input
145 * functions</em>) have some common behavior. Each starts by
146 * constructing a temporary object of type std::basic_istream::sentry
147 * with the second argument (noskipws) set to false. This has several
148 * effects, concluding with the setting of a status flag; see the
149 * sentry documentation for more.
151 * If the sentry status is good, the function tries to extract
152 * whatever data is appropriate for the type of the argument.
154 * If an exception is thrown during extraction, ios_base::badbit
155 * will be turned on in the stream's error state without causing an
156 * ios_base::failure to be thrown. The original exception will then
161 * @brief Basic arithmetic extractors
162 * @param A variable of builtin type.
163 * @return @c *this if successful
165 * These functions use the stream's current locale (specifically, the
166 * @c num_get facet) to parse the input data.
169 operator>>(bool& __n)
170 { return _M_extract(__n); }
173 operator>>(short& __n);
176 operator>>(unsigned short& __n)
177 { return _M_extract(__n); }
180 operator>>(int& __n);
183 operator>>(unsigned int& __n)
184 { return _M_extract(__n); }
187 operator>>(long& __n)
188 { return _M_extract(__n); }
191 operator>>(unsigned long& __n)
192 { return _M_extract(__n); }
194 #ifdef _GLIBCXX_USE_LONG_LONG
196 operator>>(long long& __n)
197 { return _M_extract(__n); }
200 operator>>(unsigned long long& __n)
201 { return _M_extract(__n); }
205 operator>>(float& __f)
206 { return _M_extract(__f); }
209 operator>>(double& __f)
210 { return _M_extract(__f); }
213 operator>>(long double& __f)
214 { return _M_extract(__f); }
217 operator>>(void*& __p)
218 { return _M_extract(__p); }
221 * @brief Extracting into another streambuf.
222 * @param sb A pointer to a streambuf
224 * This function behaves like one of the basic arithmetic extractors,
225 * in that it also constructs a sentry object and has the same error
228 * If @a sb is NULL, the stream will set failbit in its error state.
230 * Characters are extracted from this stream and inserted into the
231 * @a sb streambuf until one of the following occurs:
233 * - the input stream reaches end-of-file,
234 * - insertion into the output buffer fails (in this case, the
235 * character that would have been inserted is not extracted), or
236 * - an exception occurs (and in this case is caught)
238 * If the function inserts no characters, failbit is set.
241 operator>>(__streambuf_type* __sb);
244 // [27.6.1.3] unformatted input
246 * @brief Character counting
247 * @return The number of characters extracted by the previous
248 * unformatted input function dispatched for this stream.
252 { return _M_gcount; }
255 * @name Unformatted Input Functions
257 * All the unformatted input functions have some common behavior.
258 * Each starts by constructing a temporary object of type
259 * std::basic_istream::sentry with the second argument (noskipws)
260 * set to true. This has several effects, concluding with the
261 * setting of a status flag; see the sentry documentation for more.
263 * If the sentry status is good, the function tries to extract
264 * whatever data is appropriate for the type of the argument.
266 * The number of characters extracted is stored for later retrieval
269 * If an exception is thrown during extraction, ios_base::badbit
270 * will be turned on in the stream's error state without causing an
271 * ios_base::failure to be thrown. The original exception will then
276 * @brief Simple extraction.
277 * @return A character, or eof().
279 * Tries to extract a character. If none are available, sets failbit
280 * and returns traits::eof().
286 * @brief Simple extraction.
287 * @param c The character in which to store data.
290 * Tries to extract a character and store it in @a c. If none are
291 * available, sets failbit and returns traits::eof().
293 * @note This function is not overloaded on signed char and
300 * @brief Simple multiple-character extraction.
301 * @param s Pointer to an array.
302 * @param n Maximum number of characters to store in @a s.
303 * @param delim A "stop" character.
306 * Characters are extracted and stored into @a s until one of the
309 * - @c n-1 characters are stored
310 * - the input sequence reaches EOF
311 * - the next character equals @a delim, in which case the character
314 * If no characters are stored, failbit is set in the stream's error
317 * In any case, a null character is stored into the next location in
320 * @note This function is not overloaded on signed char and
324 get(char_type* __s, streamsize __n, char_type __delim);
327 * @brief Simple multiple-character extraction.
328 * @param s Pointer to an array.
329 * @param n Maximum number of characters to store in @a s.
332 * Returns @c get(s,n,widen('\\n')).
335 get(char_type* __s, streamsize __n)
336 { return this->get(__s, __n, this->widen('\n')); }
339 * @brief Extraction into another streambuf.
340 * @param sb A streambuf in which to store data.
341 * @param delim A "stop" character.
344 * Characters are extracted and inserted into @a sb until one of the
347 * - the input sequence reaches EOF
348 * - insertion into the output buffer fails (in this case, the
349 * character that would have been inserted is not extracted)
350 * - the next character equals @a delim (in this case, the character
352 * - an exception occurs (and in this case is caught)
354 * If no characters are stored, failbit is set in the stream's error
358 get(__streambuf_type& __sb, char_type __delim);
361 * @brief Extraction into another streambuf.
362 * @param sb A streambuf in which to store data.
365 * Returns @c get(sb,widen('\\n')).
368 get(__streambuf_type& __sb)
369 { return this->get(__sb, this->widen('\n')); }
372 * @brief String extraction.
373 * @param s A character array in which to store the data.
374 * @param n Maximum number of characters to extract.
375 * @param delim A "stop" character.
378 * Extracts and stores characters into @a s until one of the
379 * following happens. Note that these criteria are required to be
380 * tested in the order listed here, to allow an input line to exactly
381 * fill the @a s array without setting failbit.
383 * -# the input sequence reaches end-of-file, in which case eofbit
384 * is set in the stream error state
385 * -# the next character equals @c delim, in which case the character
386 * is extracted (and therefore counted in @c gcount()) but not stored
387 * -# @c n-1 characters are stored, in which case failbit is set
388 * in the stream error state
390 * If no characters are extracted, failbit is set. (An empty line of
391 * input should therefore not cause failbit to be set.)
393 * In any case, a null character is stored in the next location in
397 getline(char_type* __s, streamsize __n, char_type __delim);
400 * @brief String extraction.
401 * @param s A character array in which to store the data.
402 * @param n Maximum number of characters to extract.
405 * Returns @c getline(s,n,widen('\\n')).
408 getline(char_type* __s, streamsize __n)
409 { return this->getline(__s, __n, this->widen('\n')); }
412 * @brief Discarding characters
413 * @param n Number of characters to discard.
414 * @param delim A "stop" character.
417 * Extracts characters and throws them away until one of the
419 * - if @a n @c != @c std::numeric_limits<int>::max(), @a n
420 * characters are extracted
421 * - the input sequence reaches end-of-file
422 * - the next character equals @a delim (in this case, the character
423 * is extracted); note that this condition will never occur if
424 * @a delim equals @c traits::eof().
426 * NB: Provide three overloads, instead of the single function
427 * (with defaults) mandated by the Standard: this leads to a
428 * better performing implementation, while still conforming to
435 ignore(streamsize __n);
438 ignore(streamsize __n, int_type __delim);
441 * @brief Looking ahead in the stream
442 * @return The next character, or eof().
444 * If, after constructing the sentry object, @c good() is false,
445 * returns @c traits::eof(). Otherwise reads but does not extract
446 * the next input character.
452 * @brief Extraction without delimiters.
453 * @param s A character array.
454 * @param n Maximum number of characters to store.
457 * If the stream state is @c good(), extracts characters and stores
458 * them into @a s until one of the following happens:
459 * - @a n characters are stored
460 * - the input sequence reaches end-of-file, in which case the error
461 * state is set to @c failbit|eofbit.
463 * @note This function is not overloaded on signed char and
467 read(char_type* __s, streamsize __n);
470 * @brief Extraction until the buffer is exhausted, but no more.
471 * @param s A character array.
472 * @param n Maximum number of characters to store.
473 * @return The number of characters extracted.
475 * Extracts characters and stores them into @a s depending on the
476 * number of characters remaining in the streambuf's buffer,
477 * @c rdbuf()->in_avail(), called @c A here:
478 * - if @c A @c == @c -1, sets eofbit and extracts no characters
479 * - if @c A @c == @c 0, extracts no characters
480 * - if @c A @c > @c 0, extracts @c min(A,n)
482 * The goal is to empty the current buffer, and to not request any
483 * more from the external input sequence controlled by the streambuf.
486 readsome(char_type* __s, streamsize __n);
489 * @brief Unextracting a single character.
490 * @param c The character to push back into the input stream.
493 * If @c rdbuf() is not null, calls @c rdbuf()->sputbackc(c).
495 * If @c rdbuf() is null or if @c sputbackc() fails, sets badbit in
498 * @note This function first clears eofbit. Since no characters
499 * are extracted, the next call to @c gcount() will return 0,
500 * as required by DR 60.
503 putback(char_type __c);
506 * @brief Unextracting the previous character.
509 * If @c rdbuf() is not null, calls @c rdbuf()->sungetc(c).
511 * If @c rdbuf() is null or if @c sungetc() fails, sets badbit in
514 * @note This function first clears eofbit. Since no characters
515 * are extracted, the next call to @c gcount() will return 0,
516 * as required by DR 60.
522 * @brief Synchronizing the stream buffer.
523 * @return 0 on success, -1 on failure
525 * If @c rdbuf() is a null pointer, returns -1.
527 * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
528 * sets badbit and returns -1.
530 * Otherwise, returns 0.
532 * @note This function does not count the number of characters
533 * extracted, if any, and therefore does not affect the next
534 * call to @c gcount().
540 * @brief Getting the current read position.
541 * @return A file position object.
543 * If @c fail() is not false, returns @c pos_type(-1) to indicate
544 * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,in).
546 * @note This function does not count the number of characters
547 * extracted, if any, and therefore does not affect the next
548 * call to @c gcount(). At variance with putback, unget and
549 * seekg, eofbit is not cleared first.
555 * @brief Changing the current read position.
556 * @param pos A file position object.
559 * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
560 * that function fails, sets failbit.
562 * @note This function first clears eofbit. It does not count the
563 * number of characters extracted, if any, and therefore does
564 * not affect the next call to @c gcount().
570 * @brief Changing the current read position.
571 * @param off A file offset object.
572 * @param dir The direction in which to seek.
575 * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
576 * If that function fails, sets failbit.
578 * @note This function first clears eofbit. It does not count the
579 * number of characters extracted, if any, and therefore does
580 * not affect the next call to @c gcount().
583 seekg(off_type, ios_base::seekdir);
588 : _M_gcount(streamsize(0))
591 template<typename _ValueT>
593 _M_extract(_ValueT& __v);
596 // Explicit specialization declarations, defined in src/istream.cc.
599 basic_istream<char>::
600 getline(char_type* __s, streamsize __n, char_type __delim);
604 basic_istream<char>::
605 ignore(streamsize __n);
609 basic_istream<char>::
610 ignore(streamsize __n, int_type __delim);
612 #ifdef _GLIBCXX_USE_WCHAR_T
614 basic_istream<wchar_t>&
615 basic_istream<wchar_t>::
616 getline(char_type* __s, streamsize __n, char_type __delim);
619 basic_istream<wchar_t>&
620 basic_istream<wchar_t>::
621 ignore(streamsize __n);
624 basic_istream<wchar_t>&
625 basic_istream<wchar_t>::
626 ignore(streamsize __n, int_type __delim);
630 * @brief Performs setup work for input streams.
632 * Objects of this class are created before all of the standard
633 * extractors are run. It is responsible for <em>exception-safe
634 * prefix and suffix operations,</em> although only prefix actions
635 * are currently required by the standard.
637 template<typename _CharT, typename _Traits>
638 class basic_istream<_CharT, _Traits>::sentry
644 /// Easy access to dependant types.
645 typedef _Traits traits_type;
646 typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
647 typedef basic_istream<_CharT, _Traits> __istream_type;
648 typedef typename __istream_type::__ctype_type __ctype_type;
649 typedef typename _Traits::int_type __int_type;
652 * @brief The constructor performs all the work.
653 * @param is The input stream to guard.
654 * @param noskipws Whether to consume whitespace or not.
656 * If the stream state is good (@a is.good() is true), then the
657 * following actions are performed, otherwise the sentry state
658 * is false (<em>not okay</em>) and failbit is set in the
661 * The sentry's preparatory actions are:
663 * -# if the stream is tied to an output stream, @c is.tie()->flush()
664 * is called to synchronize the output sequence
665 * -# if @a noskipws is false, and @c ios_base::skipws is set in
666 * @c is.flags(), the sentry extracts and discards whitespace
667 * characters from the stream. The currently imbued locale is
668 * used to determine whether each character is whitespace.
670 * If the stream state is still good, then the sentry state becomes
674 sentry(basic_istream<_CharT, _Traits>& __is, bool __noskipws = false);
677 * @brief Quick status checking.
678 * @return The sentry state.
680 * For ease of use, sentries may be converted to booleans. The
681 * return value is that of the sentry state (true == okay).
683 #ifdef __GXX_EXPERIMENTAL_CXX0X__
686 operator bool() const
690 // [27.6.1.2.3] character extraction templates
693 * @brief Character extractors
694 * @param in An input stream.
695 * @param c A character reference.
698 * Behaves like one of the formatted arithmetic extractors described in
699 * std::basic_istream. After constructing a sentry object with good
700 * status, this function extracts a character (if one is available) and
701 * stores it in @a c. Otherwise, sets failbit in the input stream.
703 template<typename _CharT, typename _Traits>
704 basic_istream<_CharT, _Traits>&
705 operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c);
707 template<class _Traits>
708 inline basic_istream<char, _Traits>&
709 operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
710 { return (__in >> reinterpret_cast<char&>(__c)); }
712 template<class _Traits>
713 inline basic_istream<char, _Traits>&
714 operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
715 { return (__in >> reinterpret_cast<char&>(__c)); }
720 * @brief Character string extractors
721 * @param in An input stream.
722 * @param s A pointer to a character array.
725 * Behaves like one of the formatted arithmetic extractors described in
726 * std::basic_istream. After constructing a sentry object with good
727 * status, this function extracts up to @c n characters and stores them
728 * into the array starting at @a s. @c n is defined as:
730 * - if @c width() is greater than zero, @c n is width() otherwise
731 * - @c n is <em>the number of elements of the largest array of *
732 * - @c char_type that can store a terminating @c eos.</em>
735 * Characters are extracted and stored until one of the following happens:
736 * - @c n-1 characters are stored
738 * - the next character is whitespace according to the current locale
739 * - the next character is a null byte (i.e., @c charT() )
741 * @c width(0) is then called for the input stream.
743 * If no characters are extracted, sets failbit.
745 template<typename _CharT, typename _Traits>
746 basic_istream<_CharT, _Traits>&
747 operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s);
749 // Explicit specialization declaration, defined in src/istream.cc.
752 operator>>(basic_istream<char>& __in, char* __s);
754 template<class _Traits>
755 inline basic_istream<char, _Traits>&
756 operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
757 { return (__in >> reinterpret_cast<char*>(__s)); }
759 template<class _Traits>
760 inline basic_istream<char, _Traits>&
761 operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
762 { return (__in >> reinterpret_cast<char*>(__s)); }
765 // 27.6.1.5 Template class basic_iostream
767 * @brief Merging istream and ostream capabilities.
770 * This class multiply inherits from the input and output stream classes
771 * simply to provide a single interface.
773 template<typename _CharT, typename _Traits>
775 : public basic_istream<_CharT, _Traits>,
776 public basic_ostream<_CharT, _Traits>
779 // _GLIBCXX_RESOLVE_LIB_DEFECTS
780 // 271. basic_iostream missing typedefs
781 // Types (inherited):
782 typedef _CharT char_type;
783 typedef typename _Traits::int_type int_type;
784 typedef typename _Traits::pos_type pos_type;
785 typedef typename _Traits::off_type off_type;
786 typedef _Traits traits_type;
788 // Non-standard Types:
789 typedef basic_istream<_CharT, _Traits> __istream_type;
790 typedef basic_ostream<_CharT, _Traits> __ostream_type;
793 * @brief Constructor does nothing.
795 * Both of the parent classes are initialized with the same
796 * streambuf pointer passed to this constructor.
799 basic_iostream(basic_streambuf<_CharT, _Traits>* __sb)
800 : __istream_type(__sb), __ostream_type(__sb) { }
803 * @brief Destructor does nothing.
806 ~basic_iostream() { }
810 : __istream_type(), __ostream_type() { }
813 // [27.6.1.4] standard basic_istream manipulators
815 * @brief Quick and easy way to eat whitespace
817 * This manipulator extracts whitespace characters, stopping when the
818 * next character is non-whitespace, or when the input sequence is empty.
819 * If the sequence is empty, @c eofbit is set in the stream, but not
822 * The current locale is used to distinguish whitespace characters.
828 * std::cin >> std::ws >> mc;
830 * will skip leading whitespace before calling operator>> on cin and your
831 * object. Note that the same effect can be achieved by creating a
832 * std::basic_istream::sentry inside your definition of operator>>.
834 template<typename _CharT, typename _Traits>
835 basic_istream<_CharT, _Traits>&
836 ws(basic_istream<_CharT, _Traits>& __is);
838 #ifdef __GXX_EXPERIMENTAL_CXX0X__
839 // [27.7.1.6] Rvalue stream extraction
841 * @brief Generic extractor for rvalue stream
842 * @param is An input stream.
843 * @param x A reference to the extraction target.
846 * This is just a forwarding function to allow extraction from
847 * rvalue streams since they won't bind to the extractor functions
848 * that take an lvalue reference.
850 template<typename _CharT, typename _Traits, typename _Tp>
851 inline basic_istream<_CharT, _Traits>&
852 operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
853 { return (__is >> __x); }
854 #endif // __GXX_EXPERIMENTAL_CXX0X__
856 _GLIBCXX_END_NAMESPACE_VERSION
859 #include <bits/istream.tcc>
861 #endif /* _GLIBCXX_ISTREAM */