You might want to take a look at the elisp-only completion I wrote for nevermore. Address harvesting is pretty fast and anyway is asynchronous. https://github.com/tjim/nevermore/blob/42febedb45da6158e26503359f864f772d332de0/nm.el#L561
Subject: Re: [PATCH v1 0/3] Address completion entirely in elisp.
Date: Sat, 06 Sep 2014 01:36:14 +0000 (GMT)
To: David Edmondson
From: Trevor Jim
You might want to take a look at the elisp-only completion I wrote for nevermore. Address harvesting is pretty fast and anyway is asynchronous. https://github.com/tjim/nevermore/blob/42febedb45da6158e26503359f864f772d332de0/nm.el#L561