What's the difference between istringstream, ostringstream and stringstream? / Why not use stringstream in every case?

Question

When would I use std::istringstream, std::ostringstream and std::stringstream and why shouldn\'t I just use std::stringstream

Answer 1

std::ostringstream::str() creates a copy of the stream's content, which doubles memory usage in some situations. You can use std::stringstream and its rdbuf() function instead to avoid this.

More details here: how to write ostringstream directly to cout