std::basic_filebuf
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::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
<streambuf> | |
Type | Definition |
std::filebuf
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std::basic_filebuf<char> |
std::wfilebuf
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std::basic_filebuf<wchar_t> |
Contents |
[edit] Member types
Member type | Definition |
char_type
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CharT
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traits_type
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Traits ; the program is ill-formed if Traits::char_type is not CharT .
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int_type
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Traits::int_type
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pos_type
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Traits::pos_type which is required to be std::fpos<Traits::state_type>
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off_type
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Traits::off_type
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native_handle_type (C++26)
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implementation-defined type that is TriviallyCopyable and semiregular
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[edit] 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] |
destructs a basic_filebuf object and closes the file if it is open (virtual public member function) |
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) | |
Protected member functions | |
[virtual] |
optionally provides the number of characters available for input from the file (virtual protected member function) |
[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) |
[virtual] |
writes characters to the associated file from the put area (virtual protected member function) |
[virtual] |
provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function) |
[virtual] |
repositions the file position, using relative addressing (virtual protected member function) |
[virtual] |
repositions the file position, using absolute addressing (virtual protected member function) |
[virtual] |
writes characters to the associated file from the put area (virtual protected member function) |
[virtual] |
changes the associated locale (virtual protected member function) |
[edit] Non-member functions
specializes the std::swap algorithm (function template) |
Inherited from std::basic_streambuf
Member types
Member type | Definition |
char_type
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CharT
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traits_type
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Traits ; the program is ill-formed if Traits::char_type is not CharT .
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int_type
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Traits::int_type
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pos_type
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Traits::pos_type
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off_type
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Traits::off_type
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Member functions
[virtual] |
destructs the basic_streambuf object (virtual public member function of std::basic_streambuf<CharT,Traits> )
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Locales | |
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 | |
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> )
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invokes seekpos() (public member function of std::basic_streambuf<CharT,Traits> )
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invokes sync() (public member function of std::basic_streambuf<CharT,Traits> )
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Get area | |
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) |
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 | |
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 | |
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> )
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Positioning | |
[virtual] |
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] |
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> )
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[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> )
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[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) | |
advances the next pointer in the input sequence (protected member function) | |
repositions the beginning, next, and end pointers of the input sequence (protected member function) | |
Put area | |
[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) | |
repositions the beginning, next, and end pointers of the output sequence (protected member function) | |
Putback | |
[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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[edit] Notes
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_fstream_native_handle |
202306L | (C++26) | native handles support |
[edit] See also
object type, capable of holding all information needed to control a C I/O stream (typedef) |