class Sinatra::Base

def static!

a matching file is found, returns nil otherwise.
Attempt to serve static files from public directory. Throws :halt when 
def static!
  return if (public_dir = settings.public_folder).nil?
  public_dir = File.expand_path(public_dir)
  path = File.expand_path(public_dir + unescape(request.path_info))
  return unless path.start_with?(public_dir) and File.file?(path)
  env['sinatra.static_file'] = path
  cache_control(*settings.static_cache_control) if settings.static_cache_control?
  send_file path, :disposition => nil
end