Provided by: libstdc++-13-doc_13.2.0-23ubuntu4_all bug

NAME

       std::basic_filebuf< _CharT, _Traits > - The actual work of input and output (for files).

SYNOPSIS

       #include <fstream>

       Inherits std::basic_streambuf< _CharT, _Traits >.

       Inherited by __gnu_cxx::stdio_filebuf< _CharT, _Traits >.

   Public Types
       typedef codecvt< char_type, char, __state_type > __codecvt_type
       typedef __basic_file< char > __file_type
       typedef basic_filebuf< char_type, traits_type > __filebuf_type
       typedef traits_type::state_type __state_type
       typedef basic_streambuf< char_type, traits_type > __streambuf_type
       typedef _CharT char_type
       typedef traits_type::int_type int_type
       typedef traits_type::off_type off_type
       typedef traits_type::pos_type pos_type
       typedef _Traits traits_type

   Public Member Functions
       basic_filebuf ()
           Does not open any files.
       basic_filebuf (basic_filebuf &&)
       basic_filebuf (const basic_filebuf &)=delete
       virtual ~basic_filebuf ()
           The destructor closes the file first.
       __filebuf_type * close ()
           Closes the currently associated file.
       locale getloc () const
           Locale access.
       streamsize in_avail ()
           Looking ahead into the stream.
       bool is_open () const  throw ()
           Returns true if the external file is open.
       template<typename _Path > _If_fs_path< _Path, __filebuf_type * > open (const _Path &__s,
           ios_base::openmode __mode)
           Opens an external file.
       __filebuf_type * open (const char *__s, ios_base::openmode __mode)
           Opens an external file.
       __filebuf_type * open (const std::string &__s, ios_base::openmode __mode)
           Opens an external file.
       basic_filebuf & operator= (basic_filebuf &&)
       basic_filebuf & operator= (const basic_filebuf &)=delete
       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.
       void swap (basic_filebuf &)

           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
       void __safe_gbump (streamsize __n)
       void __safe_pbump (streamsize __n)
       void _M_allocate_internal_buffer ()
       bool _M_convert_to_external (char_type *, streamsize)
       void _M_create_pback ()
       void _M_destroy_internal_buffer ()  throw ()
       void _M_destroy_pback ()  throw ()
       int _M_get_ext_pos (__state_type &__state)
       pos_type _M_seek (off_type __off, ios_base::seekdir __way, __state_type __state)
       void _M_set_buffer (streamsize __off)
       bool _M_terminate_output ()
       void gbump (int __n)
           Moving the read position.
       virtual void imbue (const locale &__loc)
           Changes translations.
       virtual int_type overflow (int_type __c=_Traits::eof())
           Consumes data from the buffer; writes to the controlled sequence.
       virtual int_type pbackfail (int_type __c=_Traits::eof())
           Tries to back up the input sequence.
       void pbump (int __n)
           Moving the write position.
       virtual pos_type seekoff (off_type __off, ios_base::seekdir __way, ios_base::openmode
           __mode=ios_base::in|ios_base::out)
           Alters the stream positions.
       virtual pos_type seekpos (pos_type __pos, ios_base::openmode
           __mode=ios_base::in|ios_base::out)
           Alters the stream positions.
       virtual __streambuf_type * setbuf (char_type *__s, streamsize __n)
           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
       char_type * _M_buf
           Pointer to the beginning of internal buffer.
       bool _M_buf_allocated
       locale _M_buf_locale
           Current locale setting.
       size_t _M_buf_size
       const __codecvt_type * _M_codecvt
       char * _M_ext_buf
       streamsize _M_ext_buf_size
       char * _M_ext_end
       const char * _M_ext_next
       __file_type _M_file
       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.
       __c_lock _M_lock
       ios_base::openmode _M_mode
           Place to stash in || out || in | out settings for current filebuf.
       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.
       bool _M_reading
       __state_type _M_state_beg
       __state_type _M_state_cur
       __state_type _M_state_last
       bool _M_writing

           char_type _M_pback
           char_type * _M_pback_cur_save
           char_type * _M_pback_end_save
           bool _M_pback_init

   Friends
       class ios_base

Detailed Description

   template<typename _CharT, typename _Traits>
       class std::basic_filebuf< _CharT, _Traits >"The actual work of input and output (for
       files).

       Template Parameters
           _CharT Type of character stream.
           _Traits Traits for character type, defaults to char_traits<_CharT>.

       This class associates both its input and output sequence with an external disk file, and
       maintains a joint file position for both sequences. Many of its semantics are described in
       terms of similar behavior in the Standard C Library's FILE streams.

       Requirements on traits_type, specific to this class:

       • traits_type::pos_type must be fpos<traits_type::state_type>

       • traits_type::off_type must be streamoff

       • traits_type::state_type must be Assignable and DefaultConstructible,

       • traits_type::state_type() must be the initial state for codecvt.

Constructor & Destructor Documentation

   template<typename _CharT , typename _Traits > std::basic_filebuf< _CharT, _Traits
       >::basic_filebuf ()
       Does not open any files. The default constructor initializes the parent class using its
       own default ctor.

       References std::basic_streambuf< _CharT, _Traits >::_M_buf_locale.

   template<typename _CharT , typename _Traits > virtual std::basic_filebuf< _CharT, _Traits
       >::~basic_filebuf () [inline],  [virtual]
       The destructor closes the file first.

Member Function Documentation

   template<typename _CharT , typename _Traits > void std::basic_filebuf< _CharT, _Traits
       >::_M_create_pback () [inline],  [protected]
       Initializes pback buffers, and moves normal buffers to safety. Assumptions: _M_in_cur has
       already been moved back

   template<typename _CharT , typename _Traits > void std::basic_filebuf< _CharT, _Traits
       >::_M_destroy_pback () [inline],  [protected]
       Deactivates pback buffer contents, and restores normal buffer. Assumptions: The pback
       buffer has only moved forward.

   template<typename _CharT , typename _Traits > void std::basic_filebuf< _CharT, _Traits
       >::_M_set_buffer (streamsize __off) [inline],  [protected]
       This function sets the pointers of the internal buffer, both get and put areas. Typically:

       __off == egptr() - eback() upon underflow/uflow (read mode); __off == 0 upon overflow
       (write mode); __off == -1 upon open, setbuf, seekoff/pos (uncommitted mode).

       NB: epptr() - pbase() == _M_buf_size - 1, since _M_buf_size reflects the actual allocated
       memory and the last cell is reserved for the overflow char of a full put area.

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits >::__filebuf_type
       * std::basic_filebuf< _CharT, _Traits >::close ()
       Closes the currently associated file.

       Returns
           this on success, NULL on failure

       If no file is currently open, this function immediately fails.

       If a put buffer area exists, overflow(eof) is called to flush all the characters. The file
       is then closed.

       If any operations fail, this function also fails.

   template<typename _CharT , typename _Traits > char_type * std::basic_streambuf< _CharT,
       _Traits >::eback () const [inline],  [protected],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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 > void std::basic_filebuf< _CharT, _Traits
       >::imbue (const locale & __loc) [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::cur.

   template<typename _CharT , typename _Traits > streamsize std::basic_streambuf< _CharT, _Traits
       >::in_avail () [inline],  [inherited]
       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 > bool std::basic_filebuf< _CharT, _Traits
       >::is_open () const [inline]
       Returns true if the external file is open.

   template<typename _CharT , typename _Traits > template<typename _Path > _If_fs_path< _Path,
       __filebuf_type * > std::basic_filebuf< _CharT, _Traits >::open (const _Path & __s,
       ios_base::openmode __mode) [inline]
       Opens an external file.

       Parameters
           __s The name of the file, as a filesystem::path.
           __mode The open mode flags.

       Returns
           this on success, NULL on failure

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits >::__filebuf_type
       * std::basic_filebuf< _CharT, _Traits >::open (const char * __s, ios_base::openmode
       __mode)
       Opens an external file.

       Parameters
           __s The name of the file.
           __mode The open mode flags.

       Returns
           this on success, NULL on failure

       If a file is already open, this function immediately fails. Otherwise it tries to open the
       file named __s using the flags given in __mode.

       Table 92, adapted here, gives the relation between openmode combinations and the
       equivalent fopen() flags. (NB: lines app, in|out|app, in|app, binary|app,
       binary|in|out|app, and binary|in|app per DR 596)

       +---------------------------------------------------------+
       | ios_base Flag combination            stdio equivalent   |
       |binary  in  out  trunc  app                              |
       +---------------------------------------------------------+
       |             +                        w                  |
       |             +           +            a                  |
       |                         +            a                  |
       |             +     +                  w                  |
       |         +                            r                  |
       |         +   +                        r+                 |
       |         +   +     +                  w+                 |
       |         +   +           +            a+                 |
       |         +               +            a+                 |
       +---------------------------------------------------------+
       |   +         +                        wb                 |
       |   +         +           +            ab                 |
       |   +                     +            ab                 |
       |   +         +     +                  wb                 |
       |   +     +                            rb                 |
       |   +     +   +                        r+b                |
       |   +     +   +     +                  w+b                |
       |   +     +   +           +            a+b                |
       |   +     +               +            a+b                |
       +---------------------------------------------------------+

       References std::ios_base::ate, and std::ios_base::end.

   template<typename _CharT , typename _Traits > __filebuf_type * std::basic_filebuf< _CharT,
       _Traits >::open (const std::string & __s, ios_base::openmode __mode) [inline]
       Opens an external file.

       Parameters
           __s The name of the file.
           __mode The open mode flags.

       Returns
           this on success, NULL on failure

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits >::int_type
       std::basic_filebuf< _CharT, _Traits >::overflow (int_type __c = _Traits::eof())
       [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::app, std::ios_base::cur, and std::ios_base::out.

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits >::int_type
       std::basic_filebuf< _CharT, _Traits >::pbackfail (int_type __c = _Traits::eof())
       [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::cur, and std::ios_base::in.

   template<typename _CharT , typename _Traits > char_type * std::basic_streambuf< _CharT,
       _Traits >::pbase () const [inline],  [protected],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       Calls virtual sync function.

   template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
       >::sbumpc () [inline],  [inherited]
       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 > basic_filebuf< _CharT, _Traits >::pos_type
       std::basic_filebuf< _CharT, _Traits >::seekoff (off_type, ios_base::seekdir,
       ios_base::openmode = ios_base::in | ios_base::out) [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::cur.

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits >::pos_type
       std::basic_filebuf< _CharT, _Traits >::seekpos (pos_type, ios_base::openmode =
       ios_base::in | ios_base::out) [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::beg.

   template<typename _CharT , typename _Traits > basic_filebuf< _CharT, _Traits
       >::__streambuf_type * std::basic_filebuf< _CharT, _Traits >::setbuf (char_type * __s,
       streamsize __n) [protected],  [virtual]
       Manipulates the buffer.

       Parameters
           __s Pointer to a buffer area.
           __n Size of __s.

       Returns
           this

       If no file has been opened, and both __s and __n are zero, then the stream becomes
       unbuffered. Otherwise, __s is used as a buffer; see
       https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering for
       more.

       Reimplemented from std::basic_streambuf< _CharT, _Traits >.

   template<typename _CharT , typename _Traits > void std::basic_streambuf< _CharT, _Traits
       >::setg (char_type * __gbeg, char_type * __gnext, char_type * __gend) [inline],
       [protected],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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 > streamsize std::basic_filebuf< _CharT, _Traits
       >::showmanyc () [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::binary, and std::ios_base::in.

   template<typename _CharT , typename _Traits > int_type std::basic_streambuf< _CharT, _Traits
       >::snextc () [inline],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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],  [inherited]
       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 > int std::basic_filebuf< _CharT, _Traits >::sync
       () [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 from std::basic_streambuf< _CharT, _Traits >.

   template<typename _CharT , typename _Traits > virtual int_type std::basic_streambuf< _CharT,
       _Traits >::uflow () [inline],  [protected],  [virtual],  [inherited]
       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 > basic_filebuf< _CharT, _Traits >::int_type
       std::basic_filebuf< _CharT, _Traits >::underflow () [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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::in.

   template<typename _CharT , typename _Traits > streamsize std::basic_filebuf< _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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::in.

   template<typename _CharT , typename _Traits > streamsize std::basic_filebuf< _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 from std::basic_streambuf< _CharT, _Traits >.

       References std::ios_base::app, and std::ios_base::out.

Member Data Documentation

   template<typename _CharT , typename _Traits > char_type* std::basic_filebuf< _CharT, _Traits
       >::_M_buf [protected]
       Pointer to the beginning of internal buffer.

   template<typename _CharT , typename _Traits > locale std::basic_streambuf< _CharT, _Traits
       >::_M_buf_locale [protected],  [inherited]
       Current locale setting.

       Referenced by std::basic_filebuf< _CharT, _Traits >::basic_filebuf().

   template<typename _CharT , typename _Traits > size_t std::basic_filebuf< _CharT, _Traits
       >::_M_buf_size [protected]
       Actual size of internal buffer. This number is equal to the size of the put area + 1
       position, reserved for the overflow char of a full area.

   template<typename _CharT , typename _Traits > char* std::basic_filebuf< _CharT, _Traits
       >::_M_ext_buf [protected]
       Buffer for external characters. Used for input when codecvt::always_noconv() == false.
       When valid, this corresponds to eback().

   template<typename _CharT , typename _Traits > streamsize std::basic_filebuf< _CharT, _Traits
       >::_M_ext_buf_size [protected]
       Size of buffer held by _M_ext_buf.

   template<typename _CharT , typename _Traits > const char* std::basic_filebuf< _CharT, _Traits
       >::_M_ext_next [protected]
       Pointers into the buffer held by _M_ext_buf that delimit a subsequence of bytes that have
       been read but not yet converted. When valid, _M_ext_next corresponds to egptr().

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_in_beg [protected],  [inherited]
       Start of get area.

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_in_cur [protected],  [inherited]
       Current read area.

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_in_end [protected],  [inherited]
       End of get area.

   template<typename _CharT , typename _Traits > ios_base::openmode std::basic_filebuf< _CharT,
       _Traits >::_M_mode [protected]
       Place to stash in || out || in | out settings for current filebuf.

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_out_beg [protected],  [inherited]
       Start of put area.

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_out_cur [protected],  [inherited]
       Current put area.

   template<typename _CharT , typename _Traits > char_type* std::basic_streambuf< _CharT, _Traits
       >::_M_out_end [protected],  [inherited]
       End of put area.

   template<typename _CharT , typename _Traits > char_type std::basic_filebuf< _CharT, _Traits
       >::_M_pback [protected]
       Necessary bits for putback buffer management.

       Note
           pbacks of over one character are not currently supported.

   template<typename _CharT , typename _Traits > char_type* std::basic_filebuf< _CharT, _Traits
       >::_M_pback_cur_save [protected]
       Necessary bits for putback buffer management.

       Note
           pbacks of over one character are not currently supported.

   template<typename _CharT , typename _Traits > char_type* std::basic_filebuf< _CharT, _Traits
       >::_M_pback_end_save [protected]
       Necessary bits for putback buffer management.

       Note
           pbacks of over one character are not currently supported.

   template<typename _CharT , typename _Traits > bool std::basic_filebuf< _CharT, _Traits
       >::_M_pback_init [protected]
       Necessary bits for putback buffer management.

       Note
           pbacks of over one character are not currently supported.

   template<typename _CharT , typename _Traits > bool std::basic_filebuf< _CharT, _Traits
       >::_M_reading [protected]
       _M_reading == false && _M_writing == false for uncommitted mode; _M_reading == true for
       read mode; _M_writing == true for write mode;

       NB: _M_reading == true && _M_writing == true is unused.

Author

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