Question

I’d like to write a simple ostream which wraps an argument ostream and changes the stream in some way before passing it on to the argument stream. The transformation is something simple like changing a letter or erasing a word

What would a simple class inheriting from ostream look like? What methods should I override?

Answer 1

std::ostream is not the best place to implement filtering. It doesn’t have the appropriate virtual functions to let you do this.

You probably want to write a class derived from std::streambuf containing a wrapped std::ostream (or a wrapped std::streambuf) and then create a std::ostream using this std::streambuf.

std::streambuf has a virtual function overflow which you can override and use to alter the bytes before passing them to the wrapped output class.