Estimates the number of characters available for input in the associated character sequence. Template:rlpf is guaranteed not to return Traits::eof() until at least that many characters are extracted.
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, Template:rlpf and Template:rlpf will definitely return Traits::eof.
The base class version returns 0, which has the meaning of "unsure if there are characters available in the associated sequence".
|This section is incomplete|
Reason: no example