Section [27.5.1] of the standard describes the requirements and behavior of stream buffer classes. That section (three paragraphs) is reproduced here, for simplicity and accuracy.
charT
array object. The array object represents, at any moment, a (sub)sequence of characters from the sequence. Operations performed on a sequence alter the values stored in these pointers, perform reads and writes directly to or from associated sequences, and alter "the stream position" and conversion state as needed to maintain this subsequence relationship. The three pointers are:charT
array, as described above; otherwise, xbeg and xend shall also be null.
Definition at line 124 of file streambuf.
typedef _CharT std::basic_streambuf< _CharT, _Traits >::char_type |
These are standard types. They permit a standardized way of referring to names of (or names dependant on) the template parameters, which are specific to the implementation.
Reimplemented in __gnu_cxx::stdio_filebuf< _CharT, _Traits >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
typedef traits_type::int_type std::basic_streambuf< _CharT, _Traits >::int_type |
These are standard types. They permit a standardized way of referring to names of (or names dependant on) the template parameters, which are specific to the implementation.
Reimplemented in __gnu_cxx::stdio_filebuf< _CharT, _Traits >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
typedef traits_type::off_type std::basic_streambuf< _CharT, _Traits >::off_type |
These are standard types. They permit a standardized way of referring to names of (or names dependant on) the template parameters, which are specific to the implementation.
Reimplemented in __gnu_cxx::stdio_filebuf< _CharT, _Traits >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
typedef traits_type::pos_type std::basic_streambuf< _CharT, _Traits >::pos_type |
These are standard types. They permit a standardized way of referring to names of (or names dependant on) the template parameters, which are specific to the implementation.
Reimplemented in __gnu_cxx::stdio_filebuf< _CharT, _Traits >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
typedef _Traits std::basic_streambuf< _CharT, _Traits >::traits_type |
These are standard types. They permit a standardized way of referring to names of (or names dependant on) the template parameters, which are specific to the implementation.
Reimplemented in __gnu_cxx::stdio_filebuf< _CharT, _Traits >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
virtual std::basic_streambuf< _CharT, _Traits >::~basic_streambuf | ( | ) | [inline, virtual] |
std::basic_streambuf< _CharT, _Traits >::basic_streambuf | ( | ) | [inline, protected] |
Base constructor.
Only called from derived constructors, and sets up all the buffer data to zero, including the pointers described in the basic_streambuf class description. Note that, as a result,
char_type* std::basic_streambuf< _CharT, _Traits >::eback | ( | ) | const [inline, protected] |
Access to the get area.
These functions are only available to other protected functions, including derived classes.
Definition at line 478 of file streambuf.
Referenced by std::basic_filebuf< _CharT, _Traits >::imbue(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::overflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_filebuf< _CharT, _Traits >::seekoff(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), std::basic_filebuf< _CharT, _Traits >::underflow(), and std::basic_filebuf< _CharT, _Traits >::xsgetn().
char_type* std::basic_streambuf< _CharT, _Traits >::egptr | ( | ) | const [inline, protected] |
Access to the get area.
These functions are only available to other protected functions, including derived classes.
Definition at line 484 of file streambuf.
Referenced by std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_filebuf< _CharT, _Traits >::seekoff(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::underflow(), std::basic_filebuf< _CharT, _Traits >::underflow(), and std::basic_filebuf< _CharT, _Traits >::xsgetn().
void std::basic_streambuf< _CharT, _Traits >::gbump | ( | int | __n | ) | [inline, protected] |
Moving the read position.
n | The delta by which to move. |
Definition at line 494 of file streambuf.
Referenced by std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), and std::basic_filebuf< _CharT, _Traits >::xsgetn().
locale std::basic_streambuf< _CharT, _Traits >::getloc | ( | ) | const [inline] |
char_type* std::basic_streambuf< _CharT, _Traits >::gptr | ( | ) | const [inline, protected] |
Access to the get area.
These functions are only available to other protected functions, including derived classes.
Definition at line 481 of file streambuf.
Referenced by std::basic_filebuf< _CharT, _Traits >::pbackfail(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_filebuf< _CharT, _Traits >::showmanyc(), and std::basic_filebuf< _CharT, _Traits >::xsgetn().
virtual void std::basic_streambuf< _CharT, _Traits >::imbue | ( | const locale & | ) | [inline, protected, virtual] |
Changes translations.
loc | A new locale. |
Reimplemented in std::basic_filebuf< _CharT, _Traits >.
streamsize std::basic_streambuf< _CharT, _Traits >::in_avail | ( | ) | [inline] |
Looking ahead into the stream.
showmanyc()
.
virtual int_type std::basic_streambuf< _CharT, _Traits >::overflow | ( | int_type | = traits_type::eof() |
) | [inline, protected, virtual] |
Consumes data from the buffer; writes to the controlled sequence.
c | An additional character to consume. |
eof()
.For a formal definiton of this function, see a good text such as Langer & Kreft, or [27.5.2.4.5]/3-7.
A functioning output streambuf can be created by overriding only this function (no buffer area will be used).
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
Definition at line 763 of file streambuf.
Referenced by std::basic_streambuf< _CharT, _Traits >::xsputn().
virtual int_type std::basic_streambuf< _CharT, _Traits >::pbackfail | ( | int_type | = traits_type::eof() |
) | [inline, protected, virtual] |
Tries to back up the input sequence.
c | The character to be inserted back into the sequence. |
gptr()
, eback()
, and pptr()
are the same as for underflow()
.Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
char_type* std::basic_streambuf< _CharT, _Traits >::pbase | ( | ) | const [inline, protected] |
Access to the put area.
These functions are only available to other protected functions, including derived classes.
Definition at line 525 of file streambuf.
Referenced by std::basic_stringbuf< _CharT, _Traits, _Alloc >::overflow(), std::basic_filebuf< _CharT, _Traits >::overflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), and std::basic_filebuf< _CharT, _Traits >::xsputn().
void std::basic_streambuf< _CharT, _Traits >::pbump | ( | int | __n | ) | [inline, protected] |
Moving the write position.
n | The delta by which to move. |
Definition at line 541 of file streambuf.
Referenced by std::basic_stringbuf< _CharT, _Traits, _Alloc >::_M_sync(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::overflow(), std::basic_filebuf< _CharT, _Traits >::overflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), and std::basic_streambuf< _CharT, _Traits >::xsputn().
locale std::basic_streambuf< _CharT, _Traits >::pubimbue | ( | const locale & | __loc | ) | [inline] |
pos_type std::basic_streambuf< _CharT, _Traits >::pubseekoff | ( | off_type | __off, | |
ios_base::seekdir | __way, | |||
ios_base::openmode | __mode = ios_base::in | ios_base::out | |||
) | [inline] |
pos_type std::basic_streambuf< _CharT, _Traits >::pubseekpos | ( | pos_type | __sp, | |
ios_base::openmode | __mode = ios_base::in | ios_base::out | |||
) | [inline] |
__streambuf_type* std::basic_streambuf< _CharT, _Traits >::pubsetbuf | ( | char_type * | __s, | |
streamsize | __n | |||
) | [inline] |
int std::basic_streambuf< _CharT, _Traits >::pubsync | ( | ) | [inline] |
Locale access.
loc
is returned. Otherwise the global locale in effect at the time of construction is returned.
Definition at line 268 of file streambuf.
Referenced by std::basic_istream< _CharT, _Traits >::sync().
int_type std::basic_streambuf< _CharT, _Traits >::sbumpc | ( | ) | [inline] |
Getting the next character.
uflow()
.
Definition at line 313 of file streambuf.
Referenced by std::basic_istream< _CharT, _Traits >::getline(), std::basic_istream< _CharT, _Traits >::ignore(), std::istreambuf_iterator< _CharT, _Traits >::operator++(), and std::operator>>().
virtual pos_type std::basic_streambuf< _CharT, _Traits >::seekoff | ( | off_type | , | |
ios_base::seekdir | , | |||
ios_base::openmode | = ios_base::in | ios_base::out | |||
) | [inline, protected, virtual] |
Alters the stream positions.
Each derived class provides its own appropriate behavior.
pos_type
that represents an invalid stream position. Reimplemented in std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
virtual pos_type std::basic_streambuf< _CharT, _Traits >::seekpos | ( | pos_type | , | |
ios_base::openmode | = ios_base::in | ios_base::out | |||
) | [inline, protected, virtual] |
Alters the stream positions.
Each derived class provides its own appropriate behavior.
pos_type
that represents an invalid stream position. Reimplemented in std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
virtual basic_streambuf<char_type,_Traits>* std::basic_streambuf< _CharT, _Traits >::setbuf | ( | char_type * | , | |
streamsize | ||||
) | [inline, protected, virtual] |
Maniuplates the buffer.
Each derived class provides its own appropriate behavior. See the next-to-last paragraph of http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for more on this function.
this
. Reimplemented in std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
void std::basic_streambuf< _CharT, _Traits >::setg | ( | char_type * | __gbeg, | |
char_type * | __gnext, | |||
char_type * | __gend | |||
) | [inline, protected] |
void std::basic_streambuf< _CharT, _Traits >::setp | ( | char_type * | __pbeg, | |
char_type * | __pend | |||
) | [inline, protected] |
int_type std::basic_streambuf< _CharT, _Traits >::sgetc | ( | ) | [inline] |
Getting the next character.
underflow()
. Does not move the read position after fetching the character.
Definition at line 335 of file streambuf.
Referenced by std::__copy_streambufs_eof(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::getline(), std::basic_istream< _CharT, _Traits >::ignore(), and std::basic_istream< _CharT, _Traits >::sentry::sentry().
streamsize std::basic_streambuf< _CharT, _Traits >::sgetn | ( | char_type * | __s, | |
streamsize | __n | |||
) | [inline] |
virtual streamsize std::basic_streambuf< _CharT, _Traits >::showmanyc | ( | ) | [inline, protected, virtual] |
Investigating the data available.
underflow()
will not return traits::eof()
until at least that number of characters have been supplied. If showmanyc()
returns -1, then calls to underflow()
or uflow()
will fail." [27.5.2.4.3]/1
The standard adds that "the intention is not only that the calls [to underflow or uflow] will not return eof()
but that they will return "immediately".
The standard adds that "the morphemes of showmanyc
are "es-how-many-see", not "show-manic".
Reimplemented in std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
int_type std::basic_streambuf< _CharT, _Traits >::snextc | ( | ) | [inline] |
Getting the next character.
sbumpc()
, and if that function returns traits::eof()
, so does this function. Otherwise, sgetc()
.
Definition at line 295 of file streambuf.
Referenced by std::__copy_streambufs_eof(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::getline(), std::basic_istream< _CharT, _Traits >::ignore(), and std::basic_istream< _CharT, _Traits >::sentry::sentry().
int_type std::basic_streambuf< _CharT, _Traits >::sputbackc | ( | char_type | __c | ) | [inline] |
Pushing characters back into the input stream.
c | The character to push back. |
Definition at line 368 of file streambuf.
Referenced by std::operator>>(), and std::basic_istream< _CharT, _Traits >::putback().
int_type std::basic_streambuf< _CharT, _Traits >::sputc | ( | char_type | __c | ) | [inline] |
Entry point for all single-character output functions.
c | A character to output. |
If a write position is available for the output sequence (i.e., the buffer is not full), stores c in that position, increments the position, and returns traits::to_int_type(c)
. If a write position is not available, returns overflow(c)
.
Definition at line 420 of file streambuf.
Referenced by std::__copy_streambufs_eof(), std::basic_istream< _CharT, _Traits >::get(), and std::ostreambuf_iterator< _CharT, _Traits >::operator=().
streamsize std::basic_streambuf< _CharT, _Traits >::sputn | ( | const char_type * | __s, | |
streamsize | __n | |||
) | [inline] |
void std::basic_streambuf< _CharT, _Traits >::stossc | ( | ) | [inline] |
Tosses a character.
Advances the read pointer, ignoring the character that would have been read.
See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
_GLIBCXX_DEPRECATED
to make this visible; see c++config.h. int_type std::basic_streambuf< _CharT, _Traits >::sungetc | ( | ) | [inline] |
Moving backwards in the input stream.
Definition at line 393 of file streambuf.
Referenced by std::basic_istream< _CharT, _Traits >::unget().
virtual int std::basic_streambuf< _CharT, _Traits >::sync | ( | ) | [inline, protected, virtual] |
Synchronizes the buffer arrays with the controlled sequences.
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, and std::basic_filebuf< _CharT, _Traits >.
virtual int_type std::basic_streambuf< _CharT, _Traits >::uflow | ( | ) | [inline, protected, virtual] |
Fetches more data from the controlled sequence.
underflow()
, and in fact is required to call that function. It also returns the new character, like underflow()
does. However, this function also moves the read position forward by one.
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >.
virtual int_type std::basic_streambuf< _CharT, _Traits >::underflow | ( | ) | [inline, protected, virtual] |
Fetches more data from the controlled sequence.
traits::eof()
to indicate a null pending sequence.For a formal definiton of the pending sequence, see a good text such as Langer & Kreft, or [27.5.2.4.3]/7-14.
A functioning input streambuf can be created by overriding only this function (no buffer area will be used). For an example, see http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
streamsize std::basic_streambuf< _CharT, _Traits >::xsgetn | ( | char_type * | __s, | |
streamsize | __n | |||
) | [protected, virtual] |
Multiple character extraction.
s | A buffer area. | |
n | Maximum number of characters to assign. |
sbumpc()
. Stops when either n characters have been copied, or when traits::eof()
would be copied.It is expected that derived classes provide a more efficient implementation by overriding this definition.
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, and std::basic_filebuf< _CharT, _Traits >.
Definition at line 50 of file streambuf.tcc.
References std::copy(), and std::min().
Referenced by std::basic_filebuf< _CharT, _Traits >::xsgetn().
streamsize std::basic_streambuf< _CharT, _Traits >::xsputn | ( | const char_type * | __s, | |
streamsize | __n | |||
) | [protected, virtual] |
Multiple character insertion.
s | A buffer area. | |
n | Maximum number of characters to write. |
sputc()
. Stops when either n characters have been copied, or when sputc()
would return traits::eof()
.It is expected that derived classes provide a more efficient implementation by overriding this definition.
Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, and std::basic_filebuf< _CharT, _Traits >.
Definition at line 84 of file streambuf.tcc.
References std::copy(), std::basic_streambuf< _CharT, _Traits >::epptr(), std::min(), std::basic_streambuf< _CharT, _Traits >::overflow(), std::basic_streambuf< _CharT, _Traits >::pbump(), and std::basic_streambuf< _CharT, _Traits >::pptr().
Referenced by std::basic_filebuf< _CharT, _Traits >::xsputn().
locale std::basic_streambuf< _CharT, _Traits >::_M_buf_locale [protected] |
Locale access.
loc
is returned. Otherwise the global locale in effect at the time of construction is returned.
Definition at line 207 of file streambuf.
Referenced by std::basic_filebuf< _CharT, _Traits >::basic_filebuf().
char_type* std::basic_streambuf< _CharT, _Traits >::_M_in_beg [protected] |
char_type* std::basic_streambuf< _CharT, _Traits >::_M_in_cur [protected] |
char_type* std::basic_streambuf< _CharT, _Traits >::_M_in_end [protected] |
char_type* std::basic_streambuf< _CharT, _Traits >::_M_out_beg [protected] |
char_type* std::basic_streambuf< _CharT, _Traits >::_M_out_cur [protected] |
char_type* std::basic_streambuf< _CharT, _Traits >::_M_out_end [protected] |