1 // Stream buffer classes -*- C++ -*-
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4 // 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
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26 /** @file include/streambuf
27 * This is a Standard C++ Library header.
31 // ISO C++ 14882: 27.5 Stream buffers
34 #ifndef _GLIBXX_STREAMBUF
35 #define _GLIBXX_STREAMBUF 1
37 #pragma GCC system_header
39 #include <bits/c++config.h>
41 #include <bits/localefwd.h>
42 #include <bits/ios_base.h>
43 #include <bits/cpp_type_traits.h>
44 #include <ext/type_traits.h>
46 namespace std _GLIBCXX_VISIBILITY(default)
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
50 template<typename _CharT, typename _Traits>
52 __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
53 basic_streambuf<_CharT, _Traits>*, bool&);
56 * @brief The actual work of input and output (interface).
59 * This is a base class. Derived stream buffers each control a
60 * pair of character sequences: one for input, and one for output.
62 * Section [27.5.1] of the standard describes the requirements and
63 * behavior of stream buffer classes. That section (three paragraphs)
64 * is reproduced here, for simplicity and accuracy.
66 * -# Stream buffers can impose various constraints on the sequences
67 * they control. Some constraints are:
68 * - The controlled input sequence can be not readable.
69 * - The controlled output sequence can be not writable.
70 * - The controlled sequences can be associated with the contents of
71 * other representations for character sequences, such as external
73 * - The controlled sequences can support operations @e directly to or
74 * from associated sequences.
75 * - The controlled sequences can impose limitations on how the
76 * program can read characters from a sequence, write characters to
77 * a sequence, put characters back into an input sequence, or alter
78 * the stream position.
80 * -# Each sequence is characterized by three pointers which, if non-null,
81 * all point into the same @c charT array object. The array object
82 * represents, at any moment, a (sub)sequence of characters from the
83 * sequence. Operations performed on a sequence alter the values
84 * stored in these pointers, perform reads and writes directly to or
85 * from associated sequences, and alter <em>the stream position</em> and
86 * conversion state as needed to maintain this subsequence relationship.
87 * The three pointers are:
88 * - the <em>beginning pointer</em>, or lowest element address in the
89 * array (called @e xbeg here);
90 * - the <em>next pointer</em>, or next element address that is a
91 * current candidate for reading or writing (called @e xnext here);
92 * - the <em>end pointer</em>, or first element address beyond the
93 * end of the array (called @e xend here).
95 * -# The following semantic constraints shall always apply for any set
96 * of three pointers for a sequence, using the pointer names given
98 * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
99 * also be non-null pointers into the same @c charT array, as
100 * described above; otherwise, @e xbeg and @e xend shall also be null.
101 * - If @e xnext is not a null pointer and @e xnext < @e xend for an
102 * output sequence, then a <em>write position</em> is available.
103 * In this case, @e *xnext shall be assignable as the next element
104 * to write (to put, or to store a character value, into the sequence).
105 * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
106 * input sequence, then a <em>putback position</em> is available.
107 * In this case, @e xnext[-1] shall have a defined value and is the
108 * next (preceding) element to store a character that is put back
109 * into the input sequence.
110 * - If @e xnext is not a null pointer and @e xnext< @e xend for an
111 * input sequence, then a <em>read position</em> is available.
112 * In this case, @e *xnext shall have a defined value and is the
113 * next element to read (to get, or to obtain a character value,
114 * from the sequence).
116 template<typename _CharT, typename _Traits>
117 class basic_streambuf
122 * These are standard types. They permit a standardized way of
123 * referring to names of (or names dependant on) the template
124 * parameters, which are specific to the implementation.
126 typedef _CharT char_type;
127 typedef _Traits traits_type;
128 typedef typename traits_type::int_type int_type;
129 typedef typename traits_type::pos_type pos_type;
130 typedef typename traits_type::off_type off_type;
134 /// This is a non-standard type.
135 typedef basic_streambuf<char_type, traits_type> __streambuf_type;
138 friend class basic_ios<char_type, traits_type>;
139 friend class basic_istream<char_type, traits_type>;
140 friend class basic_ostream<char_type, traits_type>;
141 friend class istreambuf_iterator<char_type, traits_type>;
142 friend class ostreambuf_iterator<char_type, traits_type>;
145 __copy_streambufs_eof<>(__streambuf_type*, __streambuf_type*, bool&);
147 template<bool _IsMove, typename _CharT2>
148 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
150 __copy_move_a2(istreambuf_iterator<_CharT2>,
151 istreambuf_iterator<_CharT2>, _CharT2*);
153 template<typename _CharT2>
154 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
155 istreambuf_iterator<_CharT2> >::__type
156 find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
159 template<typename _CharT2, typename _Traits2>
160 friend basic_istream<_CharT2, _Traits2>&
161 operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
163 template<typename _CharT2, typename _Traits2, typename _Alloc>
164 friend basic_istream<_CharT2, _Traits2>&
165 operator>>(basic_istream<_CharT2, _Traits2>&,
166 basic_string<_CharT2, _Traits2, _Alloc>&);
168 template<typename _CharT2, typename _Traits2, typename _Alloc>
169 friend basic_istream<_CharT2, _Traits2>&
170 getline(basic_istream<_CharT2, _Traits2>&,
171 basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
176 * This is based on _IO_FILE, just reordered to be more consistent,
177 * and is intended to be the most minimal abstraction for an
179 * - get == input == read
180 * - put == output == write
182 char_type* _M_in_beg; // Start of get area.
183 char_type* _M_in_cur; // Current read area.
184 char_type* _M_in_end; // End of get area.
185 char_type* _M_out_beg; // Start of put area.
186 char_type* _M_out_cur; // Current put area.
187 char_type* _M_out_end; // End of put area.
189 /// Current locale setting.
190 locale _M_buf_locale;
193 /// Destructor deallocates no buffer space.
198 // [27.5.2.2.1] locales
200 * @brief Entry point for imbue().
201 * @param loc The new locale.
202 * @return The previous locale.
204 * Calls the derived imbue(loc).
207 pubimbue(const locale &__loc)
209 locale __tmp(this->getloc());
211 _M_buf_locale = __loc;
216 * @brief Locale access.
217 * @return The current locale in effect.
219 * If pubimbue(loc) has been called, then the most recent @c loc
220 * is returned. Otherwise the global locale in effect at the time
221 * of construction is returned.
225 { return _M_buf_locale; }
227 // [27.5.2.2.2] buffer management and positioning
230 * @brief Entry points for derived buffer functions.
232 * The public versions of @c pubfoo dispatch to the protected
233 * derived @c foo member functions, passing the arguments (if any)
234 * and returning the result unchanged.
237 pubsetbuf(char_type* __s, streamsize __n)
238 { return this->setbuf(__s, __n); }
241 pubseekoff(off_type __off, ios_base::seekdir __way,
242 ios_base::openmode __mode = ios_base::in | ios_base::out)
243 { return this->seekoff(__off, __way, __mode); }
246 pubseekpos(pos_type __sp,
247 ios_base::openmode __mode = ios_base::in | ios_base::out)
248 { return this->seekpos(__sp, __mode); }
251 pubsync() { return this->sync(); }
254 // [27.5.2.2.3] get area
256 * @brief Looking ahead into the stream.
257 * @return The number of characters available.
259 * If a read position is available, returns the number of characters
260 * available for reading before the buffer must be refilled.
261 * Otherwise returns the derived @c showmanyc().
266 const streamsize __ret = this->egptr() - this->gptr();
267 return __ret ? __ret : this->showmanyc();
271 * @brief Getting the next character.
272 * @return The next character, or eof.
274 * Calls @c sbumpc(), and if that function returns
275 * @c traits::eof(), so does this function. Otherwise, @c sgetc().
280 int_type __ret = traits_type::eof();
281 if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(),
283 __ret = this->sgetc();
288 * @brief Getting the next character.
289 * @return The next character, or eof.
291 * If the input read position is available, returns that character
292 * and increments the read pointer, otherwise calls and returns
299 if (__builtin_expect(this->gptr() < this->egptr(), true))
301 __ret = traits_type::to_int_type(*this->gptr());
305 __ret = this->uflow();
310 * @brief Getting the next character.
311 * @return The next character, or eof.
313 * If the input read position is available, returns that character,
314 * otherwise calls and returns @c underflow(). Does not move the
315 * read position after fetching the character.
321 if (__builtin_expect(this->gptr() < this->egptr(), true))
322 __ret = traits_type::to_int_type(*this->gptr());
324 __ret = this->underflow();
329 * @brief Entry point for xsgetn.
330 * @param s A buffer area.
333 * Returns xsgetn(s,n). The effect is to fill @a s[0] through
334 * @a s[n-1] with characters from the input sequence, if possible.
337 sgetn(char_type* __s, streamsize __n)
338 { return this->xsgetn(__s, __n); }
340 // [27.5.2.2.4] putback
342 * @brief Pushing characters back into the input stream.
343 * @param c The character to push back.
344 * @return The previous character, if possible.
346 * Similar to sungetc(), but @a c is pushed onto the stream
347 * instead of <em>the previous character.</em> If successful,
348 * the next character fetched from the input stream will be @a
352 sputbackc(char_type __c)
355 const bool __testpos = this->eback() < this->gptr();
356 if (__builtin_expect(!__testpos ||
357 !traits_type::eq(__c, this->gptr()[-1]), false))
358 __ret = this->pbackfail(traits_type::to_int_type(__c));
362 __ret = traits_type::to_int_type(*this->gptr());
368 * @brief Moving backwards in the input stream.
369 * @return The previous character, if possible.
371 * If a putback position is available, this function decrements
372 * the input pointer and returns that character. Otherwise,
373 * calls and returns pbackfail(). The effect is to @a unget
374 * the last character @a gotten.
380 if (__builtin_expect(this->eback() < this->gptr(), true))
383 __ret = traits_type::to_int_type(*this->gptr());
386 __ret = this->pbackfail();
390 // [27.5.2.2.5] put area
392 * @brief Entry point for all single-character output functions.
393 * @param c A character to output.
394 * @return @a c, if possible.
396 * One of two public output functions.
398 * If a write position is available for the output sequence (i.e.,
399 * the buffer is not full), stores @a c in that position, increments
400 * the position, and returns @c traits::to_int_type(c). If a write
401 * position is not available, returns @c overflow(c).
407 if (__builtin_expect(this->pptr() < this->epptr(), true))
411 __ret = traits_type::to_int_type(__c);
414 __ret = this->overflow(traits_type::to_int_type(__c));
419 * @brief Entry point for all single-character output functions.
420 * @param s A buffer read area.
423 * One of two public output functions.
426 * Returns xsputn(s,n). The effect is to write @a s[0] through
427 * @a s[n-1] to the output sequence, if possible.
430 sputn(const char_type* __s, streamsize __n)
431 { return this->xsputn(__s, __n); }
435 * @brief Base constructor.
437 * Only called from derived constructors, and sets up all the
438 * buffer data to zero, including the pointers described in the
439 * basic_streambuf class description. Note that, as a result,
440 * - the class starts with no read nor write positions available,
441 * - this is not an error
444 : _M_in_beg(0), _M_in_cur(0), _M_in_end(0),
445 _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
446 _M_buf_locale(locale())
449 // [27.5.2.3.1] get area access
452 * @brief Access to the get area.
454 * These functions are only available to other protected functions,
455 * including derived classes.
457 * - eback() returns the beginning pointer for the input sequence
458 * - gptr() returns the next pointer for the input sequence
459 * - egptr() returns the end pointer for the input sequence
462 eback() const { return _M_in_beg; }
465 gptr() const { return _M_in_cur; }
468 egptr() const { return _M_in_end; }
472 * @brief Moving the read position.
473 * @param n The delta by which to move.
475 * This just advances the read position without returning any data.
478 gbump(int __n) { _M_in_cur += __n; }
481 * @brief Setting the three read area pointers.
482 * @param gbeg A pointer.
483 * @param gnext A pointer.
484 * @param gend A pointer.
485 * @post @a gbeg == @c eback(), @a gnext == @c gptr(), and
486 * @a gend == @c egptr()
489 setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
496 // [27.5.2.3.2] put area access
499 * @brief Access to the put area.
501 * These functions are only available to other protected functions,
502 * including derived classes.
504 * - pbase() returns the beginning pointer for the output sequence
505 * - pptr() returns the next pointer for the output sequence
506 * - epptr() returns the end pointer for the output sequence
509 pbase() const { return _M_out_beg; }
512 pptr() const { return _M_out_cur; }
515 epptr() const { return _M_out_end; }
519 * @brief Moving the write position.
520 * @param n The delta by which to move.
522 * This just advances the write position without returning any data.
525 pbump(int __n) { _M_out_cur += __n; }
528 * @brief Setting the three write area pointers.
529 * @param pbeg A pointer.
530 * @param pend A pointer.
531 * @post @a pbeg == @c pbase(), @a pbeg == @c pptr(), and
532 * @a pend == @c epptr()
535 setp(char_type* __pbeg, char_type* __pend)
537 _M_out_beg = _M_out_cur = __pbeg;
541 // [27.5.2.4] virtual functions
542 // [27.5.2.4.1] locales
544 * @brief Changes translations.
545 * @param loc A new locale.
547 * Translations done during I/O which depend on the current
548 * locale are changed by this call. The standard adds,
549 * <em>Between invocations of this function a class derived
550 * from streambuf can safely cache results of calls to locale
551 * functions and to members of facets so obtained.</em>
553 * @note Base class version does nothing.
559 // [27.5.2.4.2] buffer management and positioning
561 * @brief Manipulates the buffer.
563 * Each derived class provides its own appropriate behavior. See
564 * the next-to-last paragraph of
565 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
566 * for more on this function.
568 * @note Base class version does nothing, returns @c this.
570 virtual basic_streambuf<char_type,_Traits>*
571 setbuf(char_type*, streamsize)
575 * @brief Alters the stream positions.
577 * Each derived class provides its own appropriate behavior.
578 * @note Base class version does nothing, returns a @c pos_type
579 * that represents an invalid stream position.
582 seekoff(off_type, ios_base::seekdir,
583 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
584 { return pos_type(off_type(-1)); }
587 * @brief Alters the stream positions.
589 * Each derived class provides its own appropriate behavior.
590 * @note Base class version does nothing, returns a @c pos_type
591 * that represents an invalid stream position.
595 ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
596 { return pos_type(off_type(-1)); }
599 * @brief Synchronizes the buffer arrays with the controlled sequences.
600 * @return -1 on failure.
602 * Each derived class provides its own appropriate behavior,
603 * including the definition of @a failure.
604 * @note Base class version does nothing, returns zero.
609 // [27.5.2.4.3] get area
611 * @brief Investigating the data available.
612 * @return An estimate of the number of characters available in the
613 * input sequence, or -1.
615 * <em>If it returns a positive value, then successive calls to
616 * @c underflow() will not return @c traits::eof() until at
617 * least that number of characters have been supplied. If @c
618 * showmanyc() returns -1, then calls to @c underflow() or @c
619 * uflow() will fail.</em> [27.5.2.4.3]/1
621 * @note Base class version does nothing, returns zero.
622 * @note The standard adds that <em>the intention is not only that the
623 * calls [to underflow or uflow] will not return @c eof() but
624 * that they will return immediately.</em>
625 * @note The standard adds that <em>the morphemes of @c showmanyc are
626 * @b es-how-many-see, not @b show-manic.</em>
629 showmanyc() { return 0; }
632 * @brief Multiple character extraction.
633 * @param s A buffer area.
634 * @param n Maximum number of characters to assign.
635 * @return The number of characters assigned.
637 * Fills @a s[0] through @a s[n-1] with characters from the input
638 * sequence, as if by @c sbumpc(). Stops when either @a n characters
639 * have been copied, or when @c traits::eof() would be copied.
641 * It is expected that derived classes provide a more efficient
642 * implementation by overriding this definition.
645 xsgetn(char_type* __s, streamsize __n);
648 * @brief Fetches more data from the controlled sequence.
649 * @return The first character from the <em>pending sequence</em>.
651 * Informally, this function is called when the input buffer is
652 * exhausted (or does not exist, as buffering need not actually be
653 * done). If a buffer exists, it is @a refilled. In either case, the
654 * next available character is returned, or @c traits::eof() to
655 * indicate a null pending sequence.
657 * For a formal definition of the pending sequence, see a good text
658 * such as Langer & Kreft, or [27.5.2.4.3]/7-14.
660 * A functioning input streambuf can be created by overriding only
661 * this function (no buffer area will be used). For an example, see
662 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25.html
664 * @note Base class version does nothing, returns eof().
668 { return traits_type::eof(); }
671 * @brief Fetches more data from the controlled sequence.
672 * @return The first character from the <em>pending sequence</em>.
674 * Informally, this function does the same thing as @c underflow(),
675 * and in fact is required to call that function. It also returns
676 * the new character, like @c underflow() does. However, this
677 * function also moves the read position forward by one.
682 int_type __ret = traits_type::eof();
683 const bool __testeof = traits_type::eq_int_type(this->underflow(),
687 __ret = traits_type::to_int_type(*this->gptr());
693 // [27.5.2.4.4] putback
695 * @brief Tries to back up the input sequence.
696 * @param c The character to be inserted back into the sequence.
697 * @return eof() on failure, <em>some other value</em> on success
698 * @post The constraints of @c gptr(), @c eback(), and @c pptr()
699 * are the same as for @c underflow().
701 * @note Base class version does nothing, returns eof().
704 pbackfail(int_type /* __c */ = traits_type::eof())
705 { return traits_type::eof(); }
709 * @brief Multiple character insertion.
710 * @param s A buffer area.
711 * @param n Maximum number of characters to write.
712 * @return The number of characters written.
714 * Writes @a s[0] through @a s[n-1] to the output sequence, as if
715 * by @c sputc(). Stops when either @a n characters have been
716 * copied, or when @c sputc() would return @c traits::eof().
718 * It is expected that derived classes provide a more efficient
719 * implementation by overriding this definition.
722 xsputn(const char_type* __s, streamsize __n);
725 * @brief Consumes data from the buffer; writes to the
726 * controlled sequence.
727 * @param c An additional character to consume.
728 * @return eof() to indicate failure, something else (usually
729 * @a c, or not_eof())
731 * Informally, this function is called when the output buffer
732 * is full (or does not exist, as buffering need not actually
733 * be done). If a buffer exists, it is @a consumed, with
734 * <em>some effect</em> on the controlled sequence.
735 * (Typically, the buffer is written out to the sequence
736 * verbatim.) In either case, the character @a c is also
737 * written out, if @a c is not @c eof().
739 * For a formal definition of this function, see a good text
740 * such as Langer & Kreft, or [27.5.2.4.5]/3-7.
742 * A functioning output streambuf can be created by overriding only
743 * this function (no buffer area will be used).
745 * @note Base class version does nothing, returns eof().
748 overflow(int_type /* __c */ = traits_type::eof())
749 { return traits_type::eof(); }
751 #if _GLIBCXX_USE_DEPRECATED
755 * @brief Tosses a character.
757 * Advances the read pointer, ignoring the character that would have
760 * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
765 if (this->gptr() < this->egptr())
773 // _GLIBCXX_RESOLVE_LIB_DEFECTS
774 // Side effect of DR 50.
775 basic_streambuf(const __streambuf_type& __sb)
776 : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur),
777 _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg),
778 _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
779 _M_buf_locale(__sb._M_buf_locale)
783 operator=(const __streambuf_type&) { return *this; };
786 // Explicit specialization declarations, defined in src/streambuf.cc.
789 __copy_streambufs_eof(basic_streambuf<char>* __sbin,
790 basic_streambuf<char>* __sbout, bool& __ineof);
791 #ifdef _GLIBCXX_USE_WCHAR_T
794 __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
795 basic_streambuf<wchar_t>* __sbout, bool& __ineof);
798 _GLIBCXX_END_NAMESPACE_VERSION
801 #include <bits/streambuf.tcc>
803 #endif /* _GLIBCXX_STREAMBUF */