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# std::basic_filebuf

From cppreference.com
< cpp‎ | io

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 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.

Two specializations for common character types are also defined:

Defined in header `<streambuf>`
Type | Definition
`filebuf` | basic_filebuf<char>
`wfilebuf` | basic_filebuf<wchar_t>

### [edit] Member types

Member type | Definition
`char_type` | CharT[edit]
`traits_type` | Traits[edit]
`int_type` | Traits::int_type[edit]
`pos_type` | Traits::pos_type which is required to be std::fpos<Traits::state_type>
`off_type` | Traits::off_type[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]
(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 the std::swap algorithm (function template) [edit]

## Inherited from std::basic_streambuf

### Member types

Member type | Definition
`char_type` | CharT[edit]
`traits_type` | Traits[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`) [edit]
##### Locales
pubimbue | invokes imbue() (public member function of `std::basic_streambuf`) [edit]
getloc | obtains a copy of the associated locale (public member function of `std::basic_streambuf`) [edit]
##### Positioning
pubsetbuf | invokes setbuf() (public member function of `std::basic_streambuf`) [edit]
pubseekoff | invokes seekoff() (public member function of `std::basic_streambuf`) [edit]
pubseekpos | invokes seekpos() (public member function of `std::basic_streambuf`) [edit]
pubsync | invokes sync() (public member function of `std::basic_streambuf`) [edit]
##### Get area
in_avail | obtains the number of characters immediately available in the get area (public member function of `std::basic_streambuf`) [edit]
snextc | advances the input sequence, then reads one character without advancing again (public member function of `std::basic_streambuf`) [edit]
sbumpc | reads one character from the input sequence and advances the sequence (public member function of `std::basic_streambuf`) [edit]
stossc (deprecated) (until C++17) | advances the input sequence as if by calling sbumpc() and discarding the result (public member function) [edit]
sgetc | reads one character from the input sequence without advancing the sequence (public member function of `std::basic_streambuf`) [edit]
sgetn | invokes xsgetn() (public member function of `std::basic_streambuf`) [edit]
##### Put area
sputc | writes one character to the put area and advances the next pointer (public member function of `std::basic_streambuf`) [edit]
sputn | invokes xsputn() (public member function of `std::basic_streambuf`) [edit]
##### Putback
sputbackc | puts one character back in the input sequence (public member function of `std::basic_streambuf`) [edit]
sungetc | moves the next pointer in the input sequence back by one (public member function of `std::basic_streambuf`) [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] | changes the associated locale (virtual protected member function of `std::basic_streambuf`) [edit]
##### Positioning
setbuf [virtual] | replaces the buffer with user-defined array, if permitted (virtual protected member function of `std::basic_streambuf`) [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`) [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`) [edit]
sync [virtual] | synchronizes the buffers with the associated character sequence (virtual protected member function of `std::basic_streambuf`) [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`) [edit]
underflow [virtual] | reads characters from the associated input sequence to the get area (virtual protected member function of `std::basic_streambuf`) [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`) [edit]
xsgetn [virtual] | reads multiple characters from the input sequence (virtual protected member function of `std::basic_streambuf`) [edit]
eback gptr egptr | 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`) [edit]
overflow [virtual] | writes characters to the associated output sequence from the put area (virtual protected member function of `std::basic_streambuf`) [edit]
pbase pptr epptr | 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`) [edit]

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