std::basic_filebuf

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Input/output library

I/O manipulators
Print functions(C++23)
C-style I/O
Buffers
basic_streambuf
basic_filebuf
basic_stringbuf
basic_spanbuf (C++23)
strstreambuf (C++98/26*)
basic_syncbuf (C++20)
Streams
Abstractions
ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I/O
basic_ifstream
basic_ofstream
basic_fstream
String I/O
basic_istringstream
basic_ostringstream
basic_stringstream
Array I/O
basic_ispanstream (C++23)
basic_ospanstream (C++23)
basic_spanstream (C++23)
istrstream (C++98/26*)
ostrstream (C++98/26*)
strstream (C++98/26*)
Synchronized Output
basic_osyncstream (C++20)
Types
streamoff
streamsize
fpos
Error category interface
iostream_category (C++11)
io_errc (C++11)

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std::basic_filebuf

Public member functions
basic_filebuf::basic_filebuf
basic_filebuf::~basic_filebuf
basic_filebuf::operator= (C++11)
basic_filebuf::swap (C++11)
basic_filebuf::native_handle (C++26)
basic_filebuf::is_open
basic_filebuf::open
basic_filebuf::close
Protected member functions
basic_filebuf::showmanyc
basic_filebuf::underflow
basic_filebuf::uflow
basic_filebuf::pbackfail
basic_filebuf::overflow
basic_filebuf::setbuf
basic_filebuf::seekoff
basic_filebuf::seekpos
basic_filebuf::sync
basic_filebuf::imbue
Non-member functions
swap(std::basic_filebuf) (C++11)

[edit]

Defined in header`<fstream>`
template< class CharT, class Traits=std::char_traits<CharT> >class basic_filebuf:publicstd::basic_streambuf<CharT, Traits>

std::basic_filebuf is astd::basic_streambuf whose associated character sequence is a file. Both the input sequence and the output sequence are associated with the same file, and a joint file position is maintained for both operations. The restrictions on reading and writing a sequence withstd::basic_filebuf are the same asstd::FILEs.

The functionsunderflow() andoverflow() /sync() perform the actual I/O between the file and the get and put areas of the buffer. WhenCharT is notchar, most implementations store multibyte characters in the file and astd::codecvt facet is used to perform wide/multibyte character conversion.

Several typedefs for common character types are provided:

Defined in header`<fstream>`
Type	Definition
`std::filebuf`	std::basic_filebuf<char>
`std::wfilebuf`	std::basic_filebuf<wchar_t>

[edit]Member types

Type	Definition
`char_type`	`CharT`[edit]
`traits_type`	`Traits`; the program is ill-formed if`Traits::char_type` is not`CharT`.[edit]
`int_type`	`Traits::int_type`[edit]
`pos_type`	`Traits::pos_type` which is required to bestd::fpos<Traits::state_type>
`off_type`	`Traits::off_type`[edit]
`native_handle_type`(C++26)	implementation-defined type that isTriviallyCopyable and`semiregular`[edit]

[edit]Member functions

Public member functions
(constructor)	constructs a`basic_filebuf` object (public member function)[edit]
operator= (C++11)	assigns a`basic_filebuf` object (public member function)[edit]
swap (C++11)	swaps two`basic_filebuf` objects (public member function)[edit]
native_handle (C++26)	returns the underlying implementation-defined handle (public member function)[edit]
(destructor) [virtual]	destructs a`basic_filebuf` object and closes the file if it is open (virtual public member function)[edit]
is_open	checks if the associated file is open (public member function)[edit]
open	opens a file and configures it as the associated character sequence (public member function)[edit]
close	flushes the put area buffer and closes the associated file (public member function)[edit]
Protected member functions
showmanyc [virtual]	optionally provides the number of characters available for input from the file (virtual protected member function)[edit]
underflow [virtual]	reads from the associated file (virtual protected member function)[edit]
uflow [virtual]	reads from the associated file and advances the next pointer in the get area (virtual protected member function)[edit]
pbackfail [virtual]	backs out the input sequence to unget a character, not affecting the associated file (virtual protected member function)[edit]
overflow [virtual]	writes characters to the associated file from the put area (virtual protected member function)[edit]
setbuf [virtual]	provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function)[edit]
seekoff [virtual]	repositions the file position, using relative addressing (virtual protected member function)[edit]
seekpos [virtual]	repositions the file position, using absolute addressing (virtual protected member function)[edit]
sync [virtual]	writes characters to the associated file from the put area (virtual protected member function)[edit]
imbue [virtual]	changes the associated locale (virtual protected member function)[edit]

[edit]Non-member functions

std::swap(std::basic_filebuf)

(C++11)

specializes thestd::swap algorithm
(function template)[edit]

Inherited fromstd::basic_streambuf

Member types

Member type	Definition
`char_type`	`CharT`[edit]
`traits_type`	`Traits`; the program is ill-formed if`Traits::char_type` is not`CharT`.[edit]
`int_type`	`Traits::int_type`[edit]
`pos_type`	`Traits::pos_type`[edit]
`off_type`	`Traits::off_type`[edit]

Member functions

(destructor) [virtual]	destructs the`basic_streambuf` object (virtual public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Locales
pubimbue	changes the associated locale and invokesimbue() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
getloc	obtains a copy of the associated locale (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Positioning
pubsetbuf	invokessetbuf() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
pubseekoff	invokesseekoff() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
pubseekpos	invokesseekpos() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
pubsync	invokessync() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Get area
in_avail	obtains the number of characters immediately available in the get area (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
snextc	advances the input sequence, then reads one character without advancing again (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sbumpcstossc (removed in C++17)	reads one character from the input sequence and advances the sequence (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sgetc	reads one character from the input sequence without advancing the sequence (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sgetn	invokesxsgetn() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Put area
sputc	writes one character to the put area and advances the next pointer (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sputn	invokesxsputn() (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Putback
sputbackc	puts one character back in the input sequence (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sungetc	moves the next pointer in the input sequence back by one (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]

Protected member functions

(constructor)	constructs a`basic_streambuf` object (protected member function)[edit]
operator= (C++11)	replaces a`basic_streambuf` object (protected member function)[edit]
swap (C++11)	swaps two`basic_streambuf` objects (protected member function)[edit]
Locales
imbue [virtual]	reacts to a change of the associated locale (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Positioning
setbuf [virtual]	replaces the buffer with user-defined array, if permitted (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
seekoff [virtual]	repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
seekpos [virtual]	repositions the next pointer in the input sequence, output sequence, or both using absolute addressing (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sync [virtual]	synchronizes the buffers with the associated character sequence (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
Get area
showmanyc [virtual]	obtains the number of characters available for input in the associated input sequence, if known (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
underflow [virtual]	reads characters from the associated input sequence to the get area (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
uflow [virtual]	reads characters from the associated input sequence to the get area and advances the next pointer (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
xsgetn [virtual]	reads multiple characters from the input sequence (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
ebackgptregptr	returns a pointer to the beginning, current character and the end of the get area (protected member function)[edit]
gbump	advances the next pointer in the input sequence (protected member function)[edit]
setg	repositions the beginning, next, and end pointers of the input sequence (protected member function)[edit]
Put area
xsputn [virtual]	writes multiple characters to the output sequence (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
overflow [virtual]	writes characters to the associated output sequence from the put area (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
pbasepptrepptr	returns a pointer to the beginning, current character and the end of the put area (protected member function)[edit]
pbump	advances the next pointer of the output sequence (protected member function)[edit]
setp	repositions the beginning, next, and end pointers of the output sequence (protected member function)[edit]
Putback
pbackfail [virtual]	puts a character back into the input sequence, possibly modifying the input sequence (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]

[edit]Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_fstream_native_handle`	`202306L`	(C++26)	native handles support

[edit]See also

FILE	object type, capable of holding all information needed to control a C I/O stream (typedef)[edit]

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std::basic_filebuf

Contents

[edit]Member types

[edit]Member functions

Public member functions

Protected member functions

[edit]Non-member functions

Inherited fromstd::basic_streambuf

Member types

Member functions

Locales

Positioning

Get area

Put area

Putback

Protected member functions

Locales

Positioning

Get area

Put area

Putback

[edit]Notes

[edit]See also

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