basic_filebuf::overflow

basic_filebuf::overflow

virtual int_type overflow(int_type c = T::eof());

If c != T::eof(), the protected virtual member function endeavors to insert the element T::to_char_type(c) into the output buffer. It can do so in various ways:

• If a write position is available, it can store the element into the write position and increment the next pointer for the output buffer.
• It can make a write position available by allocating new or additional storage for the output buffer.
• It can convert any pending output in the output buffer, followed by c, by using the file conversion facetfac to call fac.out as needed. Each element x of type char thus produced is written to the associated stream designated by the file pointerfp as if by successive calls of the form fputc``(x, fp). If any conversion or write fails, the function does not succeed.

If the function cannot succeed, it returns T::eof(). Otherwise, it returns T::not_eof(c).