You’d define a streambuf
subclass wrapping the vector
, and pass an instance of that to the istream constructor.
If the data does not change after construction, it is sufficient to set up the data pointers using streambuf::setg()
; the default implementation for the other members does the right thing:
template<typename CharT, typename TraitsT = std::char_traits<CharT> >
class vectorwrapbuf : public std::basic_streambuf<CharT, TraitsT> {
public:
vectorwrapbuf(std::vector<CharT> &vec) {
setg(vec.data(), vec.data(), vec.data() + vec.size());
}
};
std::vector<char> data;
// ...
vectorwrapbuf<char> databuf(data)
std::istream is(&databuf);
If you need anything more advanced than that, override the streambuf::underflow
method.