std::basic_filebuf
| Defined in header <fstream>
|
||
| template< class CharT, |
||
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 | |
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) |
Non-member functions
| 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>) |
Locales | |
| changes the associated locale and invokes imbue() (public member function of std::basic_streambuf<CharT,Traits>) | |
| obtains a copy of the associated locale (public member function of std::basic_streambuf<CharT,Traits>) | |
Positioning | |
| invokes setbuf() (public member function of std::basic_streambuf<CharT,Traits>) | |
| 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 | |
| obtains the number of characters immediately available in the get area (public member function of std::basic_streambuf<CharT,Traits>) | |
| advances the input sequence, then reads one character without advancing again (public member function of std::basic_streambuf<CharT,Traits>) | |
| (removed in C++17) |
reads one character from the input sequence and advances the sequence (public member function of std::basic_streambuf<CharT,Traits>) |
| reads one character from the input sequence without advancing the sequence (public member function of std::basic_streambuf<CharT,Traits>) | |
| invokes xsgetn() (public member function of std::basic_streambuf<CharT,Traits>) | |
Put area | |
| writes one character to the put area and advances the next pointer (public member function of std::basic_streambuf<CharT,Traits>) | |
| invokes xsputn() (public member function of std::basic_streambuf<CharT,Traits>) | |
Putback | |
| puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>) | |
| moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>) | |
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] |
reacts to a change of the associated locale (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
Positioning | |
| [virtual] |
replaces the buffer with user-defined array, if permitted (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
| [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>) |
| [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>) |
| [virtual] |
synchronizes the buffers with the associated character sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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>) |
| [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>) |
| 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>) |
| [virtual] |
writes characters to the associated output sequence from the put area (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
| 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>) |
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) |