std::basic_filebuf - cppreference.com (original) (raw)
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:
| Type | Definition |
| std::filebuf | std::basic_filebuf<char> |
| std::wfilebuf | std::basic_filebuf<wchar_t> |
Contents
- 1 Member types
- 2 Member functions
- 3 Public member functions
- 4 Protected member functions
- 5 Non-member functions
- 6 Inherited from std::basic_streambuf
[edit] Member types
| Type | Definition |
|---|---|
| char_type | CharT[edit] |
| traits_type | Traits; the program is ill-formed if Traits::char_type is not CharT.[edit] |
| int_type | Traits::int_type[edit] |
| pos_type | Traits::pos_type which is required to be std::fposTraits::state\_type\ |
| off_type | Traits::off_type[edit] |
| native_handle_type(C++26) | implementation-defined type that is TriviallyCopyable and semiregular[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] |
| native_handle(C++26) | returns the underlying implementation-defined handle (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
Inherited from std::basic_streambuf
Member types
| Member type | Definition |
|---|---|
| char_type | CharT[edit] |
| traits_type | Traits; the program is ill-formed if Traits::char_type is not CharT.[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<CharT,Traits>) [edit] |
|---|---|
| Locales | |
| pubimbue | changes the associated locale and invokes imbue() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| getloc | obtains a copy of the associated locale (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| Positioning | |
| pubsetbuf | invokes setbuf() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| pubseekoff | invokes seekoff() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| pubseekpos | invokes seekpos() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| pubsync | invokes sync() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| Get area | |
| in_avail | obtains the number of characters immediately available in the get area (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| snextc | advances the input sequence, then reads one character without advancing again (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| 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>) [edit] |
| sgetc | reads one character from the input sequence without advancing the sequence (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| sgetn | invokes xsgetn() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| Put area | |
| sputc | writes one character to the put area and advances the next pointer (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| sputn | invokes xsputn() (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| Putback | |
| sputbackc | puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>) [edit] |
| sungetc | moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>) [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] | reacts to a change of the associated locale (virtual protected member function of std::basic_streambuf<CharT,Traits>) [edit] |
| Positioning | |
| setbuf[virtual] | replaces the buffer with user-defined array, if permitted (virtual protected member function of std::basic_streambuf<CharT,Traits>) [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<CharT,Traits>) [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<CharT,Traits>) [edit] |
| sync[virtual] | synchronizes the buffers with the associated character sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) [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<CharT,Traits>) [edit] |
| underflow[virtual] | reads characters from the associated input sequence to the get area (virtual protected member function of std::basic_streambuf<CharT,Traits>) [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<CharT,Traits>) [edit] |
| xsgetn[virtual] | reads multiple characters from the input sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) [edit] |
| ebackgptregptr | 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<CharT,Traits>) [edit] |
| overflow[virtual] | writes characters to the associated output sequence from the put area (virtual protected member function of std::basic_streambuf<CharT,Traits>) [edit] |
| pbasepptrepptr | 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<CharT,Traits>) [edit] |
[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) [edit] | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |