_basic_auth

# File lib/webrick/httpauth.rb, line 57
    def _basic_auth(req, res, realm, req_field, res_field, err_type,
                    block) # :nodoc:
      user = pass = nil
      if /^Basic\s+(.*)/ =~ req[req_field]
        userpass = $1
        user, pass = userpass.unpack("m*")[0].split(":", 2)
      end
      if block.call(user, pass)
        req.user = user
        return
      end
      res[res_field] = "Basic realm=\"#{realm}\""
      raise err_type
    end