[PATCH 1 of 2] revlog: extract 'checkhash' method

[Wojciech Lopata]

# HG changeset patch
# User Wojciech Lopata <lopek at fb.com>
# Date 1376935598 25200
#      Mon Aug 19 11:06:38 2013 -0700
# Node ID 59ee8426d8064e4efb4bf961fdb060769ae1b308
# Parent  d4a0055af149cdea20b3136b66cae8a24b2e2a98
revlog: extract 'checkhash' method

Extract method that decides whether nodeid is correct for paricular revision
text and parent nodes. Having this method extracted will allow revlog
subclasses to implement custom way of computing nodes. In particular this
change is necessary to implement manifest compression.

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -14,7 +14,7 @@
 # import stuff from node for others to import from revlog
 from node import bin, hex, nullid, nullrev
 from i18n import _
-import ancestor, mdiff, parsers, error, util
+import ancestor, mdiff, parsers, error, util, templatefilters
 import struct, zlib, errno
 
 _pack = struct.pack
@@ -943,10 +943,16 @@
 
     def _checkhash(self, text, node, rev):
         p1, p2 = self.parents(node)
+        self.checkhash(text, p1, p2, node, rev)
+        return text
+
+    def checkhash(self, text, p1, p2, node, rev=None):
         if node != hash(text, p1, p2):
-            raise RevlogError(_("integrity check failed on %s:%d")
-                              % (self.indexfile, rev))
-        return text
+            revornode = rev
+            if revornode is None:
+                revornode = templatefilters.short(hex(node))
+            raise RevlogError(_("integrity check failed on %s:%s")
+                % (self.indexfile, revornode))
 
     def checkinlinesize(self, tr, fp=None):
         if not self._inline or (self.start(-2) + self.length(-2)) < _maxinline:
@@ -1063,9 +1069,7 @@
             ifh.flush()
             basetext = self.revision(self.node(cachedelta[0]))
             btext[0] = mdiff.patch(basetext, cachedelta[1])
-            chk = hash(btext[0], p1, p2)
-            if chk != node:
-                raise RevlogError(_("consistency error in delta"))
+            self.checkhash(btext[0], p1, p2, node)
             return btext[0]
 
         def builddelta(rev):