Provided by: libstdc++-13-doc_13.2.0-23ubuntu4_all 
NAME
std::basic_streambuf< _CharT, _Traits > - The actual work of input and output (interface).
SYNOPSIS
#include <streambuf>
Inherited by std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >,
std::basic_filebuf< _CharT, std::char_traits< _CharT > >, std::basic_filebuf< char_type,
traits_type >, __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf<
_CharT, _Traits >, std::basic_stringbuf< _CharT, _Traits, _Alloc >, and
std::wbuffer_convert< _Codecvt, _Elem, _Tr >.
Public Types
typedef _CharT char_type
typedef _Traits traits_type
typedef traits_type::int_type int_type
typedef traits_type::pos_type pos_type
typedef traits_type::off_type off_type
typedef basic_streambuf< char_type, traits_type > __streambuf_type
This is a non-standard type.
Public Member Functions
virtual ~basic_streambuf ()
Destructor deallocates no buffer space.
locale getloc () const
Locale access.
streamsize in_avail ()
Looking ahead into the stream.
locale pubimbue (const locale &__loc)
Entry point for imbue().
int_type sbumpc ()
Getting the next character.
int_type sgetc ()
Getting the next character.
streamsize sgetn (char_type *__s, streamsize __n)
Entry point for xsgetn.
int_type snextc ()
Getting the next character.
int_type sputbackc (char_type __c)
Pushing characters back into the input stream.
int_type sputc (char_type __c)
Entry point for all single-character output functions.
streamsize sputn (const char_type *__s, streamsize __n)
Entry point for all single-character output functions.
int_type sungetc ()
Moving backwards in the input stream.
basic_streambuf * pubsetbuf (char_type *__s, streamsize __n)
Entry points for derived buffer functions.
pos_type pubseekoff (off_type __off, ios_base::seekdir __way, ios_base::openmode
__mode=ios_base::in|ios_base::out)
Alters the stream position.
pos_type pubseekpos (pos_type __sp, ios_base::openmode
__mode=ios_base::in|ios_base::out)
Alters the stream position.
int pubsync ()
Calls virtual sync function.
Protected Member Functions
basic_streambuf ()
Base constructor.
basic_streambuf (const basic_streambuf &)
void __safe_gbump (streamsize __n)
void __safe_pbump (streamsize __n)
void gbump (int __n)
Moving the read position.
virtual void imbue (const locale &__loc)
Changes translations.
basic_streambuf & operator= (const basic_streambuf &)
virtual int_type overflow (int_type __c=traits_type::eof())
Consumes data from the buffer; writes to the controlled sequence.
virtual int_type pbackfail (int_type __c=traits_type::eof())
Tries to back up the input sequence.
void pbump (int __n)
Moving the write position.
virtual pos_type seekoff (off_type, ios_base::seekdir,
ios_base::openmode=ios_base::in|ios_base::out)
Alters the stream positions.
virtual pos_type seekpos (pos_type, ios_base::openmode=ios_base::in|ios_base::out)
Alters the stream positions.
virtual basic_streambuf< char_type, _Traits > * setbuf (char_type *, streamsize)
Manipulates the buffer.
void setg (char_type *__gbeg, char_type *__gnext, char_type *__gend)
Setting the three read area pointers.
void setp (char_type *__pbeg, char_type *__pend)
Setting the three write area pointers.
virtual streamsize showmanyc ()
Investigating the data available.
void swap (basic_streambuf &__sb)
virtual int sync ()
Synchronizes the buffer arrays with the controlled sequences.
virtual int_type uflow ()
Fetches more data from the controlled sequence.
virtual int_type underflow ()
Fetches more data from the controlled sequence.
virtual streamsize xsgetn (char_type *__s, streamsize __n)
Multiple character extraction.
virtual streamsize xsputn (const char_type *__s, streamsize __n)
Multiple character insertion.
char_type * eback () const
Access to the get area.
char_type * gptr () const
Access to the get area.
char_type * egptr () const
Access to the get area.
char_type * pbase () const
Access to the put area.
char_type * pptr () const
Access to the put area.
char_type * epptr () const
Access to the put area.
Protected Attributes
locale _M_buf_locale
Current locale setting.
char_type * _M_in_beg
Start of get area.
char_type * _M_in_cur
Current read area.
char_type * _M_in_end
End of get area.
char_type * _M_out_beg
Start of put area.
char_type * _M_out_cur
Current put area.
char_type * _M_out_end
End of put area.
Friends
template<bool _IsMove, typename _CharT2 > __gnu_cxx::__enable_if< __is_char< _CharT2
>::__value, _CharT2 * >::__type __copy_move_a2 (istreambuf_iterator< _CharT2 >,
istreambuf_iterator< _CharT2 >, _CharT2 *)
streamsize __copy_streambufs_eof (basic_streambuf *, basic_streambuf *, bool &)
void __istream_extract (istream &, char *, streamsize)
template<typename _CharT2 , typename _Distance > __gnu_cxx::__enable_if< __is_char<
_CharT2 >::__value, void >::__type advance (istreambuf_iterator< _CharT2 > &,
_Distance)
class basic_ios< char_type, traits_type >
class basic_istream< char_type, traits_type >
class basic_ostream< char_type, traits_type >
template<typename _CharT2 > __gnu_cxx::__enable_if< __is_char< _CharT2 >::__value,
istreambuf_iterator< _CharT2 > >::__type find (istreambuf_iterator< _CharT2 >,
istreambuf_iterator< _CharT2 >, const _CharT2 &)
template<typename _CharT2 , typename _Traits2 , typename _Alloc > basic_istream< _CharT2,
_Traits2 > & getline (basic_istream< _CharT2, _Traits2 > &, basic_string< _CharT2,
_Traits2, _Alloc > &, _CharT2)
class istreambuf_iterator< char_type, traits_type >
template<typename _CharT2 , typename _Traits2 , typename _Alloc > basic_istream< _CharT2,
_Traits2 > & operator>> (basic_istream< _CharT2, _Traits2 > &, basic_string< _CharT2,
_Traits2, _Alloc > &)
class ostreambuf_iterator< char_type, traits_type >
Detailed Description
template<typename _CharT, typename _Traits>
class std::basic_streambuf< _CharT, _Traits >"The actual work of input and output
(interface).
Template Parameters
_CharT Type of character stream.
_Traits Traits for character type, defaults to char_traits<_CharT>.
This is a base class. Derived stream buffers each control a pair of character sequences:
one for input, and one for output.
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.
1. Stream buffers can impose various constraints on the sequences they control. Some
constraints are:
• The controlled input sequence can be not readable.
• The controlled output sequence can be not writable.
• The controlled sequences can be associated with the contents of other representations
for character sequences, such as external files.
• The controlled sequences can support operations directly to or from associated
sequences.
• The controlled sequences can impose limitations on how the program can read characters
from a sequence, write characters to a sequence, put characters back into an input
sequence, or alter the stream position.
2. Each sequence is characterized by three pointers which, if non-null, all point into
the same 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:
• the beginning pointer, or lowest element address in the array (called xbeg here);
• the next pointer, or next element address that is a current candidate for reading or
writing (called xnext here);
• the end pointer, or first element address beyond the end of the array (called xend
here).
3. The following semantic constraints shall always apply for any set of three pointers
for a sequence, using the pointer names given immediately above:
• If xnext is not a null pointer, then xbeg and xend shall also be non-null pointers
into the same charT array, as described above; otherwise, xbeg and xend shall also be
null.
• If xnext is not a null pointer and xnext < xend for an output sequence, then a write
position is available. In this case, *xnext shall be assignable as the next element to
write (to put, or to store a character value, into the sequence).
• If xnext is not a null pointer and xbeg < xnext for an input sequence, then a putback
position is available. In this case, xnext[-1] shall have a defined value and is the
next (preceding) element to store a character that is put back into the input
sequence.
• If xnext is not a null pointer and xnext< xend for an input sequence, then a read
position is available. In this case, *xnext shall have a defined value and is the next
element to read (to get, or to obtain a character value, from the sequence).
Member Typedef Documentation
template<typename _CharT , typename _Traits > typedef basic_streambuf<char_type, traits_type>
std::basic_streambuf< _CharT, _Traits >::__streambuf_type
This is a non-standard type.
template<typename _CharT , typename _Traits > 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 dependent on) the template parameters, which are specific to the implementation.
template<typename _CharT , typename _Traits > 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 dependent on) the template parameters, which are specific to the implementation.
template<typename _CharT , typename _Traits > 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 dependent on) the template parameters, which are specific to the implementation.
template<typename _CharT , typename _Traits > 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 dependent on) the template parameters, which are specific to the implementation.
template<typename _CharT , typename _Traits > 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 dependent on) the template parameters, which are specific to the implementation.
Constructor & Destructor Documentation
template<typename _CharT , typename _Traits > virtual std::basic_streambuf< _CharT, _Traits
>::~basic_streambuf () [inline], [virtual]
Destructor deallocates no buffer space.
template<typename _CharT , typename _Traits > 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,
• the class starts with no read nor write positions available,
• this is not an error
Member Function Documentation
template<typename _CharT , typename _Traits > 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.
• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence
template<typename _CharT , typename _Traits > 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.
• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence
Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::underflow().
template<typename _CharT , typename _Traits > char_type * std::basic_streambuf< _CharT,
_Traits >::epptr () const [inline], [protected]
Access to the put area. These functions are only available to other protected functions,
including derived classes.
• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence
template<typename _CharT , typename _Traits > void std::basic_streambuf< _CharT, _Traits
>::gbump (int __n) [inline], [protected]
Moving the read position.
Parameters
__n The delta by which to move.
This just advances the read position without returning any data.
template<typename _CharT , typename _Traits > locale std::basic_streambuf< _CharT, _Traits
>::getloc () const [inline]
Locale access.
Returns
The current locale in effect.
If pubimbue(loc) has been called, then the most recent loc is returned. Otherwise the
global locale in effect at the time of construction is returned.
template<typename _CharT , typename _Traits > 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.
• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence
Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::underflow().
template<typename _CharT , typename _Traits > virtual void std::basic_streambuf< _CharT,
_Traits >::imbue (const locale & __loc) [inline], [protected], [virtual]
Changes translations.
Parameters
__loc A new locale.
Translations done during I/O which depend on the current locale are changed by this call.
The standard adds, Between invocations of this function a class derived from streambuf can
safely cache results of calls to locale functions and to members of facets so obtained.
Note
Base class version does nothing.
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, and std::basic_filebuf< char_type, traits_type >.
template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
>::in_avail () [inline]
Looking ahead into the stream.
Returns
The number of characters available.
If a read position is available, returns the number of characters available for reading
before the buffer must be refilled. Otherwise returns the derived showmanyc().
template<typename _CharT , typename _Traits > virtual int_type std::basic_streambuf< _CharT,
_Traits >::overflow (int_type __c = traits_type::eof()) [inline], [protected], [virtual]
Consumes data from the buffer; writes to the controlled sequence.
Parameters
__c An additional character to consume.
Returns
eof() to indicate failure, something else (usually __c, or not_eof())
Informally, this function is called when the output buffer is full (or does not exist, as
buffering need not actually be done). If a buffer exists, it is consumed, with some effect
on the controlled sequence. (Typically, the buffer is written out to the sequence
verbatim.) In either case, the character c is also written out, if __c is not eof().
For a formal definition 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).
Note
Base class version does nothing, returns eof().
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, __gnu_cxx::stdio_sync_filebuf< _CharT,
_Traits >, std::basic_stringbuf< _CharT, _Traits, _Alloc >, and std::wbuffer_convert<
_Codecvt, _Elem, _Tr >.
template<typename _CharT , typename _Traits > virtual int_type std::basic_streambuf< _CharT,
_Traits >::pbackfail (int_type __c = traits_type::eof()) [inline], [protected],
[virtual]
Tries to back up the input sequence.
Parameters
__c The character to be inserted back into the sequence.
Returns
eof() on failure, some other value on success
Postcondition
The constraints of gptr(), eback(), and pptr() are the same as for underflow().
Note
Base class version does nothing, returns eof().
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, __gnu_cxx::stdio_sync_filebuf< _CharT,
_Traits >, and std::basic_stringbuf< _CharT, _Traits, _Alloc >.
template<typename _CharT , typename _Traits > 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.
• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence
template<typename _CharT , typename _Traits > void std::basic_streambuf< _CharT, _Traits
>::pbump (int __n) [inline], [protected]
Moving the write position.
Parameters
__n The delta by which to move.
This just advances the write position without returning any data.
template<typename _CharT , typename _Traits > char_type * std::basic_streambuf< _CharT,
_Traits >::pptr () const [inline], [protected]
Access to the put area. These functions are only available to other protected functions,
including derived classes.
• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence
template<typename _CharT , typename _Traits > locale std::basic_streambuf< _CharT, _Traits
>::pubimbue (const locale & __loc) [inline]
Entry point for imbue().
Parameters
__loc The new locale.
Returns
The previous locale.
Calls the derived imbue(__loc).
template<typename _CharT , typename _Traits > 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]
Alters the stream position.
Parameters
__off Offset.
__way Value for ios_base::seekdir.
__mode Value for ios_base::openmode.
Calls virtual seekoff function.
template<typename _CharT , typename _Traits > pos_type std::basic_streambuf< _CharT, _Traits
>::pubseekpos (pos_type __sp, ios_base::openmode __mode = ios_base::in | ios_base::out)
[inline]
Alters the stream position.
Parameters
__sp Position
__mode Value for ios_base::openmode.
Calls virtual seekpos function.
template<typename _CharT , typename _Traits > basic_streambuf * std::basic_streambuf< _CharT,
_Traits >::pubsetbuf (char_type * __s, streamsize __n) [inline]
Entry points for derived buffer functions. The public versions of pubfoo dispatch to the
protected derived foo member functions, passing the arguments (if any) and returning the
result unchanged.
template<typename _CharT , typename _Traits > int std::basic_streambuf< _CharT, _Traits
>::pubsync () [inline]
Calls virtual sync function.
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::sbumpc () [inline]
Getting the next character.
Returns
The next character, or eof.
If the input read position is available, returns that character and increments the read
pointer, otherwise calls and returns uflow().
template<typename _CharT , typename _Traits > 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.
Note
Base class version does nothing, returns a pos_type that represents an invalid stream
position.
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, and std::basic_stringbuf< _CharT,
_Traits, _Alloc >.
template<typename _CharT , typename _Traits > 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.
Note
Base class version does nothing, returns a pos_type that represents an invalid stream
position.
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, and std::basic_stringbuf< _CharT,
_Traits, _Alloc >.
template<typename _CharT , typename _Traits > virtual basic_streambuf< char_type, _Traits > *
std::basic_streambuf< _CharT, _Traits >::setbuf (char_type *, streamsize) [inline],
[protected], [virtual]
Manipulates the buffer. Each derived class provides its own appropriate behavior. See the
next-to-last paragraph of
https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering for
more on this function.
Note
Base class version does nothing, returns this.
Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, and std::basic_stringbuf< _CharT,
_Traits, _Alloc >.
template<typename _CharT , typename _Traits > void std::basic_streambuf< _CharT, _Traits
>::setg (char_type * __gbeg, char_type * __gnext, char_type * __gend) [inline],
[protected]
Setting the three read area pointers.
Parameters
__gbeg A pointer.
__gnext A pointer.
__gend A pointer.
Postcondition
__gbeg == eback(), __gnext == gptr(), and __gend == egptr()
Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::wbuffer_convert().
template<typename _CharT , typename _Traits > void std::basic_streambuf< _CharT, _Traits
>::setp (char_type * __pbeg, char_type * __pend) [inline], [protected]
Setting the three write area pointers.
Parameters
__pbeg A pointer.
__pend A pointer.
Postcondition
__pbeg == pbase(), __pbeg == pptr(), and __pend == epptr()
Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::wbuffer_convert().
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::sgetc () [inline]
Getting the next character.
Returns
The next character, or eof.
If the input read position is available, returns that character, otherwise calls and
returns underflow(). Does not move the read position after fetching the character.
template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
>::sgetn (char_type * __s, streamsize __n) [inline]
Entry point for xsgetn.
Parameters
__s A buffer area.
__n A count.
Returns xsgetn(__s,__n). The effect is to fill __s[0] through __s[__n-1] with characters
from the input sequence, if possible.
template<typename _CharT , typename _Traits > virtual streamsize std::basic_streambuf< _CharT,
_Traits >::showmanyc () [inline], [protected], [virtual]
Investigating the data available.
Returns
An estimate of the number of characters available in the input sequence, or -1.
If it returns a positive value, then successive calls to 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
Note
Base class version does nothing, returns zero.
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 >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, std::basic_filebuf< char_type, traits_type >, and std::basic_stringbuf< _CharT,
_Traits, _Alloc >.
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::snextc () [inline]
Getting the next character.
Returns
The next character, or eof.
Calls sbumpc(), and if that function returns traits::eof(), so does this function.
Otherwise, sgetc().
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::sputbackc (char_type __c) [inline]
Pushing characters back into the input stream.
Parameters
__c The character to push back.
Returns
The previous character, if possible.
Similar to sungetc(), but __c is pushed onto the stream instead of the previous character.
If successful, the next character fetched from the input stream will be __c.
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::sputc (char_type __c) [inline]
Entry point for all single-character output functions.
Parameters
__c A character to output.
Returns
__c, if possible.
One of two public output functions.
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).
Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::overflow().
template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
>::sputn (const char_type * __s, streamsize __n) [inline]
Entry point for all single-character output functions.
Parameters
__s A buffer read area.
__n A count.
One of two public output functions.
Returns xsputn(__s,__n). The effect is to write __s[0] through __s[__n-1] to the output
sequence, if possible.
template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
>::sungetc () [inline]
Moving backwards in the input stream.
Returns
The previous character, if possible.
If a putback position is available, this function decrements the input pointer and returns
that character. Otherwise, calls and returns pbackfail(). The effect is to unget the last
character gotten.
template<typename _CharT , typename _Traits > virtual int std::basic_streambuf< _CharT,
_Traits >::sync () [inline], [protected], [virtual]
Synchronizes the buffer arrays with the controlled sequences.
Returns
-1 on failure.
Each derived class provides its own appropriate behavior, including the definition of
failure.
Note
Base class version does nothing, returns zero.
Reimplemented in std::wbuffer_convert< _Codecvt, _Elem, _Tr >,
__gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >,
std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT,
std::char_traits< _CharT > >, and std::basic_filebuf< char_type, traits_type >.
template<typename _CharT , typename _Traits > virtual int_type std::basic_streambuf< _CharT,
_Traits >::uflow () [inline], [protected], [virtual]
Fetches more data from the controlled sequence.
Returns
The first character from the pending sequence.
Informally, this function does the same thing as 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 >.
template<typename _CharT , typename _Traits > virtual int_type std::basic_streambuf< _CharT,
_Traits >::underflow () [inline], [protected], [virtual]
Fetches more data from the controlled sequence.
Returns
The first character from the pending sequence.
Informally, this function is called when the input buffer is exhausted (or does not exist,
as buffering need not actually be done). If a buffer exists, it is refilled. In either
case, the next available character is returned, or traits::eof() to indicate a null
pending sequence.
For a formal definition 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
https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html
Note
Base class version does nothing, returns eof().
Reimplemented in std::wbuffer_convert< _Codecvt, _Elem, _Tr >,
__gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >,
std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT,
std::char_traits< _CharT > >, std::basic_filebuf< char_type, traits_type >, and
std::basic_stringbuf< _CharT, _Traits, _Alloc >.
template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
>::xsgetn (char_type * __s, streamsize __n) [protected], [virtual]
Multiple character extraction.
Parameters
__s A buffer area.
__n Maximum number of characters to assign.
Returns
The number of characters assigned.
Fills __s[0] through __s[__n-1] with characters from the input sequence, as if by
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 std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, and std::basic_filebuf< char_type, traits_type >.
References std::min().
template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
>::xsputn (const char_type * __s, streamsize __n) [protected], [virtual]
Multiple character insertion.
Parameters
__s A buffer area.
__n Maximum number of characters to write.
Returns
The number of characters written.
Writes __s[0] through __s[__n-1] to the output sequence, as if by 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 std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT,
encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT >
>, and std::basic_filebuf< char_type, traits_type >.
References std::min().
Member Data Documentation
template<typename _CharT , typename _Traits > locale std::basic_streambuf< _CharT, _Traits
>::_M_buf_locale [protected]
Current locale setting.
Referenced by std::basic_filebuf< _CharT, _Traits >::basic_filebuf().
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_in_beg [protected]
Start of get area.
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_in_cur [protected]
Current read area.
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_in_end [protected]
End of get area.
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_out_beg [protected]
Start of put area.
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_out_cur [protected]
Current put area.
template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
>::_M_out_end [protected]
End of put area.
Author
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