[Boost-users] I search information about directory_iterator

I have: #include namespace fs=boost::filesystem; for (auto& de : fs::directory_iterator("D:\\prog\\alg\\Diff")) { fs::path p = de.path(); auto ext = fs::extension(p); } directory_iterator is object or non-objective method? How can I write something similar, but database iterator. I want get information from mySQL. The simplest way is add everything returning by select to vector of vector of string. But I prefer database iterator. How it write? How is in general directory_iterator as a iterator model?