[erlang-questions] inets - mod_esi accessing #mod.config_db

[Serge Aleynikov]

I am having trouble trying to figure out how to get the web server's 
document_root (or how to convert some RequestURI's document path to a 
filesystem path) inside a mod_esi's execution function.

Say, we have a function callable by a client through mod_esi:

get_image(SessionID, Env, Input) ->
     ImageFile = doc_root(filename:join(["/images", Input, ".gif"])),
     case read_image(ImageFile) of
     {ok, Image} ->
         mod_esi:deliver(SessionID, [
             "Content-type: image/gif\r\n\r\n",
         ]);
     {error, Reason} ->
         mod_esi:deliver(SessionID, [
             "status: ", integer_to_list(400), " Not Found\r\n\r\n"
         ])
     end.

doc_root(DocPath) ->
     ???

How do we implement the function doc_root?  It's quite easy if we have 
access to the #mod.config_db:
    mod_alias:path(Info#mod.data, Info#mod.config_db, DocPath)

However #mod{} record is not passed to the mod_esi's callback, so it's 
not possible to use mod_alias:path/3 as is.

Serge