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

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)

Parameters

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.

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

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

Parameters

Return value

Notes

Example

See also