Upload limits

Hi,

this time I would like to know something about "Upload limits" in WebDAV. 
I have once seen a Jahia configuration, where one can set the maximum file 
upload size for a single upload. 

Now we would need limits not just for a current upload, but we would like 
to set limits to the available disk space for a 

a) site
b) user
c) specific WebDAV directory

Is there already something we could use? Of course it would be cool, if we 
could set a default size limit for each site or each user, but could 
override the setting with a specific limit.

If there is nothing in place yet, is there at least a Slide-API, which 
returns the used space for a site, user or specific WebDAV directory?

Greetings,
Benjamin Papez