C++: Problems inheriting std::basic_streambuf

Question

I'd like to inherit std::basic_streambuf to implement a stream buffer based on a TCP connection. I don't understand exactly the role of the pointers eback, gptr, egptr, pbase, pptr, epptr. I was thinking of a stream buffer as an entity that simply lets u read characters from or write characters to a stream, and possibly to reposition the read/write pointers (not in my case). These pointers don't make sense for me, as I was thinking to implement a circular buffer for the input and output (so it's possible that, e.g., gend < gbeg). Do I really have to implement those pointers (eback, gptr, etc...), or I can just set them all to nullptr and everything will work fine? Or there is some function that would use them?

Answer 1

(First off, it's great to see the decision to make a TCP streambuf rather than a TCP stream.)

Angelika Langer & Klaus Kleft have very good stuff on this, besides the book, here is a whole section of tutorials.

However, streambufs often involve lots of boilerplate code, and, therefore, for an actual problem such as yours, I'd use boost::iostreams, in particular source (for a source tcp stream; obviously use target for the other way).

Note how this class has abstracted away the lower level ops you mentioned. You basically need to implement

std::streamsize read(char* s, std::streamsize n);

and it will take care of the rest for you (without much overhead).

As for your (reasonable sounding) idea to use a circular buffer, you might use boost::circular_buffer. Alternatively, see this question.