Index: updater.py
===================================================================
--- updater.py	(revision 10)
+++ updater.py	(working copy)
@@ -4,29 +4,33 @@
 import md5
 import wsgiref.handlers
 import url_lookup
+import re
 from google.appengine.api import urlfetch
 from google.appengine.ext import db
 from google.appengine.ext import webapp
 
-
 class Digest(db.Model):
   '''An entry in the SB list'''
   hash = db.StringProperty(required=True)
 
-
 class HandleUpdate(webapp.RequestHandler):
   '''Handles  /update request.'''
   def post(self):
-    data = self.request.get("data")
-    count = 0
-    for hash in data.split(','):
-      if Digest.gql("WHERE hash = :1", hash).get() is None:
-        digest = Digest(hash=hash)
-        digest.put()
-        count += 1
+    data = self.request.get('data')
+    add_count, del_count = 0, 0
 
-    logging.info("Added %d digests." % count)
+    for m in re.finditer('([+-])([a-zA-Z0-9]{32})', data):
+      op, hash = m.group(1), m.group(2)
+      digest = Digest.gql('WHERE hash = :1', hash).get()
+      if op == '+' and digest is None:
+        Digest(hash=hash).put()
+        add_count += 1
+      elif op == '-' and digest is not None:
+        digest.delete()
+        del_count += 1
 
+    logging.info('Added %d digests. Removed %d digests' % (add_count, del_count))
+
 def main():
   application = webapp.WSGIApplication(
       [('/update', HandleUpdate)],
@@ -34,5 +38,5 @@
   wsgiref.handlers.CGIHandler().run(application)
 
 
-if __name__ == "__main__":
+if __name__ == '__main__':
   main()