std::basic_streambuf<CharT,Traits>:: showmanyc

protected : virtual std:: streamsize showmanyc ( ) ;

Estimates the number of characters available for input in the associated character sequence. underflow() is guaranteed not to return Traits :: eof ( ) or throw an exception until at least that many characters are extracted.

Parameters

(none)

Return value

The number of characters that are certainly available in the associated character sequence, or - 1 if showmanyc can determine, without blocking, that no characters are available. If showmanyc returns - 1 , underflow() and uflow() will definitely return Traits :: eof or throw.

The base class version returns ​ 0 ​ , which has the meaning of "unsure if there are characters available in the associated sequence".

Notes

The name of this function stands for "stream: how many characters?", so it is pronounced "S how many C", rather than "show many C".

Example

This section is incomplete Reason: no example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 159	C++98	underflow() is guaranteed not to fail until at least showmanyc() characters are supplied	extended the guarantee to allow at least showmanyc() characters to be extracted

See also

in_avail	obtains the number of characters immediately available in the get area (public member function)
showmanyc [virtual]	optionally provides the number of characters available for input from the file (virtual protected member function of std::basic_filebuf<CharT,Traits> )