std:: basic_filebuf
From cppreference.com
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Defined in header
<fstream>
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template
<
class
CharT,
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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::FILE
s.
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:
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Defined in header
<fstream>
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| 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
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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 |
|
constructs a
basic_filebuf
object
(public member function) |
|
|
(C++11)
|
assigns a
basic_filebuf
object
(public member function) |
|
(C++11)
|
swaps two
basic_filebuf
objects
(public member function) |
|
(C++26)
|
returns the underlying implementation-defined handle
(public member function) |
|
[virtual]
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destructs a
basic_filebuf
object and closes the file if it is open
(virtual public member function) |
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checks if the associated file is open
(public member function) |
|
|
opens a file and configures it as the associated character sequence
(public member function) |
|
|
flushes the put area buffer and closes the associated file
(public member function) |
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Protected member functions |
|
|
[virtual]
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optionally provides the number of characters available for input from the file
(virtual protected member function) |
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[virtual]
|
reads from the associated file
(virtual protected member function) |
|
[virtual]
|
reads from the associated file and advances the next pointer in the get area
(virtual protected member function) |
|
[virtual]
|
backs out the input sequence to unget a character, not affecting the associated file
(virtual protected member function) |
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[virtual]
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writes characters to the associated file from the put area
(virtual protected member function) |
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[virtual]
|
provides user-supplied buffer or turns this filebuf unbuffered
(virtual protected member function) |
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[virtual]
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repositions the file position, using relative addressing
(virtual protected member function) |
|
[virtual]
|
repositions the file position, using absolute addressing
(virtual protected member function) |
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[virtual]
|
writes characters to the associated file from the put area
(virtual protected member function) |
|
[virtual]
|
changes the associated locale
(virtual protected member function) |
Non-member functions
|
(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
|
[virtual]
|
destructs the
basic_streambuf
object
(virtual public member function of
std::basic_streambuf<CharT,Traits>
)
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Locales |
|
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invokes
imbue
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
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obtains a copy of the associated locale
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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Positioning |
|
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invokes
setbuf
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
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invokes
seekoff
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
|
invokes
seekpos
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
|
invokes
sync
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
Get area |
|
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obtains the number of characters immediately available in the get area
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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advances the input sequence, then reads one character without advancing again
(public member function of
std::basic_streambuf<CharT,Traits>
)
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(removed in C++17)
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reads one character from the input sequence and advances the sequence
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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reads one character from the input sequence without advancing the sequence
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
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invokes
xsgetn
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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Put area |
|
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writes one character to the put area and advances the next pointer
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
|
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invokes
xsputn
(
)
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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Putback |
|
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puts one character back in the input sequence
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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moves the next pointer in the input sequence back by one
(public member function of
std::basic_streambuf<CharT,Traits>
)
|
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Protected member functions
constructs a
basic_streambuf
object
(protected member function) |
|
|
(C++11)
|
replaces a
basic_streambuf
object
(protected member function) |
|
(C++11)
|
swaps two
basic_streambuf
objects
(protected member function) |
Locales |
|
|
[virtual]
|
changes the associated locale
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
Positioning |
|
|
[virtual]
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replaces the buffer with user-defined array, if permitted
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
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[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>
)
|
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[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>
)
|
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[virtual]
|
synchronizes the buffers with the associated character sequence
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
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Get area |
|
|
[virtual]
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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>
)
|
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[virtual]
|
reads characters from the associated input sequence to the get area
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
|
[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>
)
|
|
[virtual]
|
reads multiple characters from the input sequence
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
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returns a pointer to the beginning, current character and the end of the get area
(protected member function) |
|
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advances the next pointer in the input sequence
(protected member function) |
|
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repositions the beginning, next, and end pointers of the input sequence
(protected member function) |
|
Put area |
|
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[virtual]
|
writes multiple characters to the output sequence
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
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[virtual]
|
writes characters to the associated output sequence from the put area
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
|
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returns a pointer to the beginning, current character and the end of the put area
(protected member function) |
|
|
advances the next pointer of the output sequence
(protected member function) |
|
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repositions the beginning, next, and end pointers of the output sequence
(protected member function) |
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Putback |
|
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[virtual]
|
puts a character back into the input sequence, possibly modifying the input sequence
(virtual protected member function of
std::basic_streambuf<CharT,Traits>
)
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Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_fstream_native_handle
|
202306L | (C++26) | native handles support |
See also
|
object type, capable of holding all information needed to control a C I/O stream
(typedef) |