There is a STL
streambuf* std::basic_ios::rdbuf (streambuf* sb);
Returns: the previous value of.
The buffer is owned by whoever originally installed the buffer into the stream object. A stream object comes with an internal buffer, and a default-constructed stream object uses it by default.
So, unless your code explicitly installed a non-default buffer, using the
rdbuf() method, the answer is that the buffer is valid as long as the stream object exists.
If you did not install the buffer, you should obviously not