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std::basic_filebuf<CharT,Traits>:: overflow

From cppreference.net
C++
Input/output library
std::basic_filebuf
protected :
virtual int_type overflow ( int_type ch = Traits :: eof ( ) ) ;

Writes some data from the put area to the associated character sequence (to the file).

Behaves like the base class version std::basic_streambuf::overflow() , except that the behavior of “consuming characters” is defined as follows:

1) First, uses std::codecvt::out of the imbued locale to convert the characters into external (possibly multibyte) representation, stored in a temporary buffer, as follows: ( XSIZE is some unspecified buffer size) 
const std::codecvt<CharT, char, typename Traits::state_type>& a_codecvt =
    std::use_facet<std::codecvt<CharT, char, typename Traits::state_type>>(getloc());
typename Traits::state_type state;
CharT* end;
char xbuf[XSIZE];
char* xbuf_end;
std::codecvt_base::result r =
    a_codecvt.out(state, pbase(), pptr(), end, xbuf, xbuf + XSIZE, xbuf_end);
2) Then writes all fully-converted characters from the buffer into the file. Formally, performs the following steps based on the value of r :
r Operation
std:: codecvt_base :: ok Output characters in [ xbuf , xbuf_end ) to the file, and fail if output fails. At this point if pbase ( ) ! = pptr ( ) and pbase ( ) == end are both true (which means xbuf is not large enough for even one external character), then increase XSIZE and repeat from the beginning.
std:: codecvt_base :: partial Output the converted external characters in [ xbuf , xbuf_end ) to the file, and repeat using the remaining unconverted internal characters in [ end , pptr ( ) ) . If output fails, fail (without repeating).
std:: codecvt_base :: noconv Output characters in [ pbase ( ) , pptr ( ) ) to the file.
std:: codecvt_base :: error Fail.
If the associated file is not open ( is_open() returns false ), output will always fail.
3) Establishes an observable checkpoint .
(since C++26)

Contents

Parameters

ch - the character to store in the put area

Return value

Traits :: not_eof ( ch ) to indicate success or Traits :: eof ( ) to indicate failure.

Notes

If a_codecvt. always_noconv ( ) returns true , the call to a_codecvt. out ( ) may be skipped.

Example

This section is incomplete
Reason: no example

See also

[virtual]
writes characters to the associated output sequence from the put area
(virtual protected member function of std::basic_streambuf<CharT,Traits> )
[virtual]
reads from the associated file
(virtual protected member function)