Manpages

NAME

__gnu_cxx::stdio_filebuf< _CharT, _Traits > - Provides a layer of compatibility for C/POSIX.

SYNOPSIS

Inherits std::basic_filebuf< _CharT, std::char_traits< _CharT > >.

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 std::size_t size_t
typedef _Traits traits_type

Public Member Functions

stdio_filebuf ()
stdio_filebuf (int __fd, std::ios_base::openmode __mode, size_t __size=static_cast< size_t >(BUFSIZ))
stdio_filebuf (std::__c_file *__f, std::ios_base::openmode __mode, size_t __size=static_cast< size_t >(BUFSIZ))
stdio_filebuf (stdio_filebuf &&)=default
virtual ~stdio_filebuf ()
__filebuf_type * close ()
Closes the currently associated file.
int fd ()
std::__c_file * 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.
__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.
stdio_filebuf & operator= (stdio_filebuf &&)=default
locale pubimbue (const locale &__loc)
Entry point for imbue().
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.
basic_streambuf * pubsetbuf (char_type *__s, streamsize __n)
Entry points for derived buffer functions.
int pubsync ()
Calls virtual sync function.
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 &)
void swap (stdio_filebuf &__fb)

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 ()
char_type * eback () const
Access to the get area.
char_type * egptr () const
char_type * epptr () const
void gbump (int __n)
Moving the read position.
char_type * gptr () const
virtual void imbue (const locale &__loc __attribute__((__unused__)))
Changes translations.
virtual void imbue (const locale &__loc)
virtual int_type overflow (int_type __c __attribute__((__unused__))=traits_type::eof())
Consumes data from the buffer; writes to the controlled sequence.
virtual int_type overflow (int_type __c=_Traits::eof())
virtual int_type pbackfail (int_type __c __attribute__((__unused__))=traits_type::eof())
Tries to back up the input sequence.
virtual int_type pbackfail (int_type __c=_Traits::eof())
char_type * pbase () const
Access to the put area.
void pbump (int __n)
Moving the write position.
char_type * pptr () const
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 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 __pos, ios_base::openmode __mode=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 __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.

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.
char_type _M_pback
char_type * _M_pback_cur_save
char_type * _M_pback_end_save
bool _M_pback_init
bool _M_reading
__state_type _M_state_beg
__state_type _M_state_cur
__state_type _M_state_last
bool _M_writing

Detailed Description

template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
class __gnu_cxx::stdio_filebuf< _CharT, _Traits >" Provides a layer of compatibility for C/POSIX.

This GNU extension provides extensions for working with standard C FILE*’s and POSIX file descriptors. It must be instantiated by the user with the type of character used in the file stream, e.g., stdio_filebuf<char>.

Definition at line 50 of file stdio_filebuf.h.

Constructor & Destructor Documentation

template<typename _CharT , typename _Traits = std::char_traits<_CharT>> __gnu_cxx::stdio_filebuf< _CharT, _Traits >::stdio_filebuf () [inline]
deferred initialization

Definition at line 65 of file stdio_filebuf.h.

template<typename _CharT , typename _Traits > __gnu_cxx::stdio_filebuf< _CharT, _Traits >::stdio_filebuf (int __fd, std::ios_base::openmode __mode, size_t __size = static_cast<size_t>(BUFSIZ))
Parameters

__fd An open file descriptor.
__mode Same meaning as in a standard filebuf.
__size Optimal or preferred size of internal buffer, in chars.

This constructor associates a file stream buffer with an open POSIX file descriptor. The file descriptor will be automatically closed when the stdio_filebuf is closed/destroyed.

Definition at line 136 of file stdio_filebuf.h.

template<typename _CharT , typename _Traits > __gnu_cxx::stdio_filebuf< _CharT, _Traits >::stdio_filebuf (std::__c_file * __f, std::ios_base::openmode __mode, size_t __size = static_cast<size_t>(BUFSIZ))
Parameters

__f An open FILE*.
__mode Same meaning as in a standard filebuf.
__size Optimal or preferred size of internal buffer, in chars. Defaults to system’s BUFSIZ.

This constructor associates a file stream buffer with an open C FILE*. The FILE* will not be automatically closed when the stdio_filebuf is closed/destroyed.

Definition at line 152 of file stdio_filebuf.h.

template<typename _CharT , typename _Traits > __gnu_cxx::stdio_filebuf< _CharT, _Traits >::~stdio_filebuf [virtual]
Closes the external data stream if the file descriptor constructor was used.

Definition at line 132 of file stdio_filebuf.h.

Member Function Documentation

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

Definition at line 199 of file fstream.

void std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_destroy_pback [inline], [protected], [inherited]
Deactivates pback buffer contents, and restores normal buffer. Assumptions: The pback buffer has only moved forward.

Definition at line 216 of file fstream.

void std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_set_buffer (streamsize __off) [inline], [protected], [inherited]
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.

Definition at line 443 of file fstream.

basic_filebuf< _CharT, std::char_traits< _CharT > >::__filebuf_type * std::basic_filebuf< _CharT, std::char_traits< _CharT > >::close [inherited]
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 345 of file fstream.tcc.

char_type* std::basic_streambuf< _CharT, std::char_traits< _CharT > >::eback [inline], [protected], [inherited]
Access to the get area. These functions are only available to other protected functions, including derived classes.

Definition at line 489 of file streambuf.

template<typename _CharT , typename _Traits = std::char_traits<_CharT>> int __gnu_cxx::stdio_filebuf< _CharT, _Traits >::fd () [inline]
Returns

The underlying file descriptor.

Once associated with an external data stream, this function can be used to access the underlying POSIX file descriptor. Note that there is no way for the library to track what you do with the descriptor, so be careful.

Definition at line 118 of file stdio_filebuf.h.

template<typename _CharT , typename _Traits = std::char_traits<_CharT>> std::__c_file* __gnu_cxx::stdio_filebuf< _CharT, _Traits >::file () [inline]
Returns

The underlying FILE*.

This function can be used to access the underlying ’C’ file pointer. Note that there is no way for the library to track what you do with the file, so be careful.

Definition at line 128 of file stdio_filebuf.h.

void std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 505 of file streambuf.

locale std::basic_streambuf< _CharT, std::char_traits< _CharT > >::getloc [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 233 of file streambuf.

virtual void std::basic_streambuf< _CharT, std::char_traits< _CharT > >::imbue (const locale &__loc __attribute__(__unused__)) [inline], [protected], [virtual], [inherited]
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.

Definition at line 583 of file streambuf.

streamsize std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 291 of file streambuf.

bool std::basic_filebuf< _CharT, std::char_traits< _CharT > >::is_open [inline], [inherited]
Returns true if the external file is open.

Definition at line 260 of file fstream.

basic_filebuf< _CharT, std::char_traits< _CharT > >::__filebuf_type * std::basic_filebuf< _CharT, std::char_traits< _CharT > >::open (const char * __s, ios_base::openmode __mode) [inherited]
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 |
+---------------------------------------------------------+

Definition at line 305 of file fstream.tcc.

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

Parameters

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

Returns

this on success, NULL on failure

Definition at line 315 of file fstream.

virtual int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::overflow (int_type __c __attribute__(__unused__) = traits_type::eof()) [inline], [protected], [virtual], [inherited]
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().

Definition at line 775 of file streambuf.

virtual int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::pbackfail (int_type __c __attribute__(__unused__) = traits_type::eof()) [inline], [protected], [virtual], [inherited]
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().

Definition at line 731 of file streambuf.

char_type* std::basic_streambuf< _CharT, std::char_traits< _CharT > >::pbase [inline], [protected], [inherited]
Access to the put area. These functions are only available to other protected functions, including derived classes.

Definition at line 536 of file streambuf.

void std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 552 of file streambuf.

locale std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 216 of file streambuf.

pos_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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.

Definition at line 258 of file streambuf.

pos_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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.

Definition at line 270 of file streambuf.

basic_streambuf* std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 246 of file streambuf.

int std::basic_streambuf< _CharT, std::char_traits< _CharT > >::pubsync [inline], [inherited]
Calls virtual sync function.

Definition at line 278 of file streambuf.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 323 of file streambuf.

basic_filebuf< _CharT, std::char_traits< _CharT > >::pos_type std::basic_filebuf< _CharT, std::char_traits< _CharT > >::seekoff (off_type __off, ios_base::seekdir __way, ios_base::openmode __mode = ios_base::in | ios_base::out) [protected], [virtual], [inherited]
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.

Definition at line 400 of file fstream.tcc.

virtual pos_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::seekoff (off_type, ios_base::seekdir, ios_base::openmode = ios_base::in | ios_base::out) [inline], [protected], [virtual], [inherited]
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.

Definition at line 609 of file streambuf.

basic_filebuf< _CharT, std::char_traits< _CharT > >::pos_type std::basic_filebuf< _CharT, std::char_traits< _CharT > >::seekpos (pos_type __pos, ios_base::openmode __mode = ios_base::in | ios_base::out) [protected], [virtual], [inherited]
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.

Definition at line 404 of file fstream.tcc.

virtual pos_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::seekpos (pos_type, ios_base::openmode = ios_base::in | ios_base::out) [inline], [protected], [virtual], [inherited]
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 __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >.

Definition at line 621 of file streambuf.

basic_filebuf< _CharT, std::char_traits< _CharT > >::__streambuf_type * std::basic_filebuf< _CharT, std::char_traits< _CharT > >::setbuf (char_type * __s, streamsize __n) [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 397 of file fstream.tcc.

void std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 516 of file streambuf.

void std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 562 of file streambuf.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 345 of file streambuf.

streamsize std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 364 of file streambuf.

streamsize std::basic_filebuf< _CharT, std::char_traits< _CharT > >::showmanyc [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 356 of file fstream.tcc.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 305 of file streambuf.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 379 of file streambuf.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 431 of file streambuf.

streamsize std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 457 of file streambuf.

int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 404 of file streambuf.

int std::basic_filebuf< _CharT, std::char_traits< _CharT > >::sync (void) [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 415 of file fstream.tcc.

virtual int_type std::basic_streambuf< _CharT, std::char_traits< _CharT > >::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 >.

Definition at line 707 of file streambuf.

basic_filebuf< _CharT, std::char_traits< _CharT > >::int_type std::basic_filebuf< _CharT, std::char_traits< _CharT > >::underflow [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 364 of file fstream.tcc.

streamsize std::basic_filebuf< _CharT, std::char_traits< _CharT > >::xsgetn (char_type * __s, streamsize __n) [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 421 of file fstream.tcc.

streamsize std::basic_filebuf< _CharT, std::char_traits< _CharT > >::xsputn (const char_type * __s, streamsize __n) [protected], [virtual], [inherited]
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, std::char_traits< _CharT > >.

Definition at line 424 of file fstream.tcc.

Member Data Documentation

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

Definition at line 136 of file fstream.

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

Definition at line 199 of file streambuf.

size_t std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_buf_size [protected], [inherited]
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.

Definition at line 143 of file fstream.

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

Definition at line 178 of file fstream.

streamsize std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_ext_buf_size [protected], [inherited]
Size of buffer held by _M_ext_buf.

Definition at line 183 of file fstream.

const char* std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_ext_next [protected], [inherited]
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().

Definition at line 190 of file fstream.

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

Definition at line 191 of file streambuf.

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

Definition at line 192 of file streambuf.

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

Definition at line 193 of file streambuf.

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

Definition at line 121 of file fstream.

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

Definition at line 194 of file streambuf.

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

Definition at line 195 of file streambuf.

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

Definition at line 196 of file streambuf.

char_type std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_pback [protected], [inherited]
Necessary bits for putback buffer management.

Note

pbacks of over one character are not currently supported.

Definition at line 164 of file fstream.

bool std::basic_filebuf< _CharT, std::char_traits< _CharT > >::_M_reading [protected], [inherited]
_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.

Definition at line 155 of file fstream.

Author

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