std::basic_filebuf< CharT, Traits > Class Template Reference

The actual work of input and output (for files). More...

Inheritance diagram for std::basic_filebuf< CharT, Traits >:

[legend]Collaboration diagram for std::basic_filebuf< CharT, Traits >:

[legend]List of all members.

Public Types
typedef CharT	char_type
Public Member Functions
	basic_filebuf ()
	Does not open any files.
virtual	~basic_filebuf ()
	The destructor closes the file first.
bool	is_open () const throw ()
	Returns true if the external file is open.
__filebuf_type *	open (const char *s, ios_base::openmode __mode)
	Opens an external file.
__filebuf_type *	close () throw ()
	Closes the currently associated file.
locale	pubimbue (const locale &__loc)
	Entry point for imbue().
locale	getloc () const
	Locale access.
streambuf_type *	pubsetbuf (char_type *s, streamsize n)
	Entry points for derived buffer functions.
streamsize	in_avail ()
	Looking ahead into the stream.
int_type	snextc ()
	Getting the next character.
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	sputbackc (char_type c)
	Pushing characters back into the input stream.
int_type	sungetc ()
	Moving backwards in 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.
Protected Member Functions
virtual streamsize	showmanyc ()
	Investigating the data available.
virtual int_type	underflow ()
	Fetches more data from the controlled sequence.
virtual int_type	pbackfail (int_type c=Traits::eof())
	Tries to back up the input sequence.
virtual int_type	overflow (int_type c=Traits::eof())
	Consumes data from the buffer; writes to the controlled sequence.
virtual streambuf_type *	setbuf (char_type *s, streamsize n)
	Manipulates the buffer.
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 position, ios_base::openmode __mode=ios_base::in|ios_base::out)
	Alters the stream positions.
virtual int	sync ()
	Synchronizes the buffer arrays with the controlled sequences.
virtual void	imbue (const locale &__loc)
	Changes translations.
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.
void	gbump (int n)
	Moving the read position.
void	setg (char_type *__gbeg, char_type *__gnext, char_type *__gend)
	Setting the three read area pointers.
char_type *	pbase () const
	Access to the put area.
void	pbump (int n)
	Moving the write position.
void	setp (char_type *__pbeg, char_type *__pend)
	Setting the three write area pointers.
virtual int_type	uflow ()
	Fetches more data from the controlled sequence.

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Detailed Description

template<typename CharT, typename Traits>
class std::basic_filebuf< CharT, Traits >

The actual work of input and output (for files).

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 sematics are described in terms of similar behavior in the Standard C Library's FILE streams.

Definition at line 69 of file fstream.

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Member Typedef Documentation

template<typename CharT, typename Traits> typedef CharT std::basic_filebuf< 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 from std::basic_streambuf< CharT, Traits >. Reimplemented in __gnu_cxx::stdio_filebuf< CharT, Traits >. Definition at line 73 of file fstream.

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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. Definition at line 76 of file fstream.tcc.

template<typename CharT, typename Traits> virtual std::basic_filebuf< CharT, Traits >::~basic_filebuf (   )  [inline, virtual]

The destructor closes the file first. Definition at line 277 of file fstream.

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Member Function Documentation

template<typename CharT, typename Traits> basic_filebuf< CharT, Traits >::__filebuf_type * std::basic_filebuf< CharT, Traits >::close (   )  throw ()

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. Definition at line 125 of file fstream.tcc. Referenced by std::basic_filebuf< CharT, Traits >::open(), and std::basic_filebuf< CharT, enc_char_traits< CharT > >::~basic_filebuf().

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 Definition at line 452 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_streambuf< CharT, enc_char_traits< CharT > >::sputbackc(), and std::basic_filebuf< CharT, Traits >::underflow().

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. Definition at line 468 of file streambuf. Referenced by std::basic_stringbuf< CharT, Traits, Alloc >::pbackfail(), std::basic_filebuf< CharT, Traits >::pbackfail(), std::basic_streambuf< CharT, enc_char_traits< CharT > >::sbumpc(), std::basic_stringbuf< CharT, Traits, Alloc >::seekoff(), std::basic_stringbuf< CharT, Traits, Alloc >::seekpos(), std::basic_streambuf< CharT, enc_char_traits< CharT > >::sputbackc(), std::basic_streambuf< CharT, enc_char_traits< CharT > >::sungetc(), std::basic_streambuf< CharT, enc_char_traits< CharT > >::uflow(), and std::basic_streambuf< CharT, Traits >::xsgetn().

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. Definition at line 215 of file streambuf.

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 >. Definition at line 807 of file fstream.tcc. References std::ios_base::cur, std::basic_streambuf< CharT, Traits >::eback(), and std::basic_filebuf< CharT, Traits >::seekoff().

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(). Definition at line 255 of file streambuf.

template<typename CharT, typename Traits> bool std::basic_filebuf< CharT, Traits >::is_open (   )  const throw () [inline]

Returns true if the external file is open. Definition at line 285 of file fstream.

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 gives the relation between openmode combinations and the equivalent fopen() flags, but the table has not been copied yet.] Definition at line 91 of file fstream.tcc. References std::ios_base::ate, std::basic_filebuf< CharT, Traits >::close(), and std::ios_base::end.

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 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). Note: Base class version does nothing, returns eof(). Reimplemented from std::basic_streambuf< CharT, Traits >. Definition at line 380 of file fstream.tcc. References std::ios_base::out, std::basic_streambuf< CharT, Traits >::pbase(), and std::basic_streambuf< CharT, Traits >::pbump(). Referenced by std::basic_filebuf< CharT, Traits >::sync().

template<typename CharT, typename Traits> basic_filebuf< CharT, Traits >::int_type std::basic_filebuf< CharT, Traits >::pbackfail (  int_type  __i = 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 >. Definition at line 328 of file fstream.tcc. References std::ios_base::cur, std::basic_streambuf< CharT, Traits >::gbump(), std::ios_base::in, and std::basic_filebuf< CharT, Traits >::underflow().

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 Definition at line 499 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(), and std::basic_stringbuf< CharT, Traits, Alloc >::seekpos().

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. Definition at line 515 of file streambuf. Referenced by std::basic_filebuf< CharT, Traits >::overflow(), std::basic_stringbuf< CharT, Traits, Alloc >::seekoff(), std::basic_stringbuf< CharT, Traits, Alloc >::seekpos(), std::basic_streambuf< CharT, enc_char_traits< CharT > >::sputc(), and std::basic_streambuf< CharT, Traits >::xsputn().

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). Definition at line 198 of file streambuf.

template<typename CharT, typename Traits> streambuf_type* 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. Definition at line 228 of file streambuf.

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(). Definition at line 287 of file streambuf. Referenced by std::operator>>().

template<typename CharT, typename Traits> basic_filebuf< CharT, Traits >::pos_type std::basic_filebuf< CharT, Traits >::seekoff (  off_type  __off, ios_base::seekdir  __way, ios_base::openmode  __mode = 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 >. Definition at line 641 of file fstream.tcc. References std::ios_base::cur, and std::basic_streambuf< CharT, Traits >::eback(). Referenced by std::basic_filebuf< CharT, Traits >::imbue().

template<typename CharT, typename Traits> basic_filebuf< CharT, Traits >::pos_type std::basic_filebuf< CharT, Traits >::seekpos (  pos_type  position, ios_base::openmode  __mode = 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 >. Definition at line 694 of file fstream.tcc. 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 http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for more. Reimplemented from std::basic_streambuf< CharT, Traits >. Definition at line 614 of file fstream.tcc.

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() Definition at line 479 of file streambuf.

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() Definition at line 525 of file streambuf.

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. Definition at line 309 of file streambuf. Referenced by std::basic_streambuf< CharT, enc_char_traits< CharT > >::snextc().

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. Definition at line 328 of file streambuf.

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 >. Definition at line 160 of file fstream.tcc. References 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(). Definition at line 269 of file streambuf.

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. Definition at line 342 of file streambuf. Referenced by std::operator>>().

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). Definition at line 394 of file streambuf. Referenced by std::basic_stringbuf< CharT, Traits, Alloc >::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. Definition at line 420 of file streambuf.

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". Definition at line 367 of file streambuf.

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 >. Definition at line 790 of file fstream.tcc. References std::basic_filebuf< CharT, Traits >::overflow().

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. Definition at line 670 of file streambuf. Referenced by std::basic_streambuf< CharT, enc_char_traits< CharT > >::sbumpc(), and std::basic_streambuf< CharT, Traits >::xsgetn().

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 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 Note: Base class version does nothing, returns eof(). Reimplemented from std::basic_streambuf< CharT, Traits >. Definition at line 178 of file fstream.tcc. References std::basic_streambuf< CharT, Traits >::eback(), std::ios_base::in, and std::min(). Referenced by std::basic_filebuf< CharT, Traits >::pbackfail().

template<typename CharT, typename Traits> virtual 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 >.

template<typename CharT, typename Traits> virtual 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 >.

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The documentation for this class was generated from the following files:

• fstream
• fstream.tcc

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