looking up c++ documentation inside of vim

I code c++, using vim.

Often times, I find myself wasting time (and brekaing flow) looking up trivial things like:

is std::string.substring does it take (start, length) or (start, end).

This often results in open browser; wait; search on google; first link useless, try second link; okay, done.

How do others do this in vim? Is there a nice *.tgz I can download of standard function documentation and somehow reference them inside of vim?

Thanks!