std::basic_filebuf<CharT,Traits>::overflow
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< cpp | io | 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)
conststd::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 |
[edit]Parameters
| ch | - | the character to store in the put area |
[edit]Return value
Traits::not_eof(ch) to indicate success or Traits::eof() to indicate failure.
[edit]Notes
If a_codecvt.always_noconv() returns true, the call to a_codecvt.out() may be skipped.
[edit]Example
| This section is incomplete Reason: no example |
[edit]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) |
