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

 

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std::basic_filebuf

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basic_filebuf::basic_filebuf

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basic_filebuf::showmanyc

basic_filebuf::underflow

basic_filebuf::uflow

basic_filebuf::pbackfail

basic_filebuf::overflow

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basic_filebuf::imbue

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swap(std::basic_filebuf) (C++11)

 

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

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

See also

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)

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