std::basic_filebuf

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

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)

 

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)

 

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

std::basic_filebuf is a std::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 with std::basic_filebuf are the same as std::FILEs.

The functions underflow() and overflow() / sync() perform the actual I/O between the file and the get and put areas of the buffer. When CharT is not char, most implementations store multibyte characters in the file and a std::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>

Member types

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

Member functions

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

Non-member functions

std::swap(std::basic_filebuf) (C++11)

specializes the std::swap algorithm (function template)

Inherited from std::basic_streambuf

Member types

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

Member functions

(destructor) [virtual]	destructs the basic_streambuf object (virtual public member function of std::basic_streambuf<CharT,Traits>)
Locales
pubimbue	invokes imbue() (public member function of std::basic_streambuf<CharT,Traits>)
getloc	obtains a copy of the associated locale (public member function of std::basic_streambuf<CharT,Traits>)
Positioning
pubsetbuf	invokes setbuf() (public member function of std::basic_streambuf<CharT,Traits>)
pubseekoff	invokes seekoff() (public member function of std::basic_streambuf<CharT,Traits>)
pubseekpos	invokes seekpos() (public member function of std::basic_streambuf<CharT,Traits>)
pubsync	invokes sync() (public member function of std::basic_streambuf<CharT,Traits>)
Get area
in_avail	obtains the number of characters immediately available in the get area (public member function of std::basic_streambuf<CharT,Traits>)
snextc	advances the input sequence, then reads one character without advancing again (public member function of std::basic_streambuf<CharT,Traits>)
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>)
sgetc	reads one character from the input sequence without advancing the sequence (public member function of std::basic_streambuf<CharT,Traits>)
sgetn	invokes xsgetn() (public member function of std::basic_streambuf<CharT,Traits>)
Put area
sputc	writes one character to the put area and advances the next pointer (public member function of std::basic_streambuf<CharT,Traits>)
sputn	invokes xsputn() (public member function of std::basic_streambuf<CharT,Traits>)
Putback
sputbackc	puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>)
sungetc	moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>)

Protected member functions

(constructor)	constructs a basic_streambuf object (protected member function)
operator= (C++11)	replaces a basic_streambuf object (protected member function)
swap (C++11)	swaps two basic_streambuf objects (protected member function)
Locales
imbue [virtual]	changes the associated locale (virtual protected member function of std::basic_streambuf<CharT,Traits>)
Positioning
setbuf [virtual]	replaces the buffer with user-defined array, if permitted (virtual protected member function of std::basic_streambuf<CharT,Traits>)
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>)
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>)
sync [virtual]	synchronizes the buffers with the associated character sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>)
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>)
underflow [virtual]	reads characters from the associated input sequence to the get area (virtual protected member function of std::basic_streambuf<CharT,Traits>)
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>)
xsgetn [virtual]	reads multiple characters from the input sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>)
ebackgptregptr	returns a pointer to the beginning, current character and the end of the get area (protected member function)
gbump	advances the next pointer in the input sequence (protected member function)
setg	repositions the beginning, next, and end pointers of the input sequence (protected member function)
Put area
xsputn [virtual]	writes multiple characters to the output sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>)
overflow [virtual]	writes characters to the associated output sequence from the put area (virtual protected member function of std::basic_streambuf<CharT,Traits>)
pbasepptrepptr	returns a pointer to the beginning, current character and the end of the put area (protected member function)
pbump	advances the next pointer of the output sequence (protected member function)
setp	repositions the beginning, next, and end pointers of the output sequence (protected member function)
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>)

Notes

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

See also

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