protected virtual member function
<streambuf> <iostream>
Get number of characters available
Virtual function (to be read s-how-many-c) called by other member functions to get an estimate on the number of characters available in the associated input sequence.
It is called by public member function basic_streambuf::in_avail when there are no read positions available at the get pointer (gptr ).
The return value provides information on the possible behavior of the protected member functions underflow and uflow :
| return value | description | expected behavior for underflow and uflow |
|---|
>0 | characters known to be available | Successive calls will succeed in retrieving characters until at least as many characters as the value returned have been extracted. |
0 | no information | Further calls may either retrieve more characters or return traits_type::eof() . |
-1 | sequence unavailable | Further calls will fail (either throwing or returning "immediately"). |
Its default behavior in basic_streambuf is to always return zero. basic_filebuf overrides this member function (see basic_filebuf::showmanyc ).
Return Value
Returns zero.
streamsize is a signed integral type.
Data races
Introduces no data races, but overriden versions in derived classes may.
Exception safety
No-throw guarantee: this default definition never throws exceptions.