std::basic_streambuf<CharT,Traits>::showmanyc - cppreference.com (original) (raw)
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.
[edit] Parameters
(none)
[edit] 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".
[edit] 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".
[edit] Example
[edit] 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 untilat least showmanyc() characters are supplied | extended the guarantee to allow at leastshowmanyc() characters to be extracted |
[edit] See also
| | obtains the number of characters immediately available in the get area (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | optionally provides the number of characters available for input from the file (virtual protected member function of std::basic_filebuf<CharT,Traits>) [edit] |