ICAP vectoring points

Squid currently implements ICAP vectoring points for reqmod_precache
(ICAP server is between the client and the cache and intercepting
requests) and respmod_precache (ICAP server is between the server and
the cache and intercepting responses).

I have a requirement for a respmod_postcache vectoring point (ICAP
server is between the cache and the client and intercepts responses).
I've not done a lot of work on the Squid internals, so would anyone be
able to give me some pointers on what is involved in implementing this
and where to start looking? Am I correct in thinking that since this
hasn't been implemented yet, it is reasonably non-trivial?

Thanks.

-- 
  - Steve Hill
    Technical Director
    Opendium Limited     http://www.opendium.com
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