hash_for_*_url documentation

Is there any documentation for hash_for_*_url arguments?

What does this function do?

It returns a hash that makes up the pieces of the url necessary for url_for and the one expires_page that wants a hash.

The arguments are whatever you'd pass to "url_for"... that is...

<%=h news_post_path(:id => 1).inspect %>
<%=h hash_for_news_post_path(:id => 1).inspect %>

"/news/1"
{:category=>"News", :use_route=>:news_post, :only_path=>true, :controller=>"articles", :action=>"post", :id=>1}