class ActionDispatch::Request

def request_parameters_list
  # We don't use Rack's parse result, but we must call it so Rack
  # can populate the rack.request.* keys we need.
  rack_post = rack_request.POST
  if form_pairs = get_header("rack.request.form_pairs")
    # Multipart
    form_pairs
  elsif form_vars = get_header("rack.request.form_vars")
    # URL-encoded
    ActionDispatch::QueryParser.each_pair(form_vars)
  elsif rack_post && !rack_post.empty?
    # It was multipart, but Rack did not preserve a pair list
    # (probably too old). Flat parameter list is not available.
    nil
  else
    # No request body, or not a format Rack knows
    []
  end
end