--- a/hgext3rd/evolve/obscache.py	Fri May 12 18:52:59 2017 +0200
+++ b/hgext3rd/evolve/obscache.py	Fri May 12 18:56:42 2017 +0200
@@ -88,24 +88,6 @@
 
 emptykey = (node.nullrev, node.nullid, 0, 0, node.nullid)
 
-def _checkkey(changelog, obsstore, key):
-    """internal function"""
-    if key is None:
-        return None
-
-    ### Is the cache valid ?
-    keytiprev, keytipnode, keyobslength, keyobssize, keyobskey = key
-    # check for changelog strip
-    tiprev = len(changelog) - 1
-    if (tiprev < keytiprev
-            or changelog.node(keytiprev) != keytipnode):
-        return None
-    # check for obsstore strip
-    obssize, obskey = obsstore.cachekey(index=keyobssize)
-    if obskey != keyobskey:
-        return None
-    return tiprev, obssize, obskey
-
 # XXX copied as is from Mercurial 4.2 and added the "offset" parameters
 @util.nogc
 def _readmarkers(data, offset=None):
@@ -197,10 +179,29 @@
         self._cachekey = emptykey if reset else None
         self._data = bytearray()
 
+    def _checkkey(self, changelog, obsstore):
+        """internal function"""
+        key = self._cachekey
+        if key is None:
+            return None
+
+        ### Is the cache valid ?
+        keytiprev, keytipnode, keyobslength, keyobssize, keyobskey = key
+        # check for changelog strip
+        tiprev = len(changelog) - 1
+        if (tiprev < keytiprev
+                or changelog.node(keytiprev) != keytipnode):
+            return None
+        # check for obsstore strip
+        obssize, obskey = obsstore.cachekey(index=keyobssize)
+        if obskey != keyobskey:
+            return None
+        return tiprev, obssize, obskey
+
     def uptodate(self, repo):
         if self._cachekey is None:
             self.load(repo)
-        status = _checkkey(repo.changelog, repo.obsstore, self._cachekey)
+        status = self._checkkey(repo.changelog, repo.obsstore)
         return (status is not None
                 and status[0] == self._cachekey[0] # tiprev
                 and status[1] == self._cachekey[3]) # obssize
@@ -225,7 +226,7 @@
 
         reset = False
 
-        status = _checkkey(cl, obsstore, key)
+        status = self._checkkey(cl, obsstore)
         if status is None:
             reset = True
             key = emptykey