[PATCH] revlog: allow custom nodeids in subclasses

[Wojciech Lopata]

# HG changeset patch
# User Wojciech Lopata <lopek at fb.com>
# Date 1376497815 25200
#      Wed Aug 14 09:30:15 2013 -0700
# Node ID 1e1e57b10f2a1927781408b8c01ab84dc84e8d3f
# Parent  df54cc67b91bea97c4fc299241a67aeecf099d00
revlog: allow custom nodeids in subclasses

Modify revlog class to allow its subclasses to use custom method of computing
nodeids. In particular this change is necesary to implement manifest
compression.

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
old mode 100644
new mode 100755
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -943,11 +943,15 @@
 
     def _checkhash(self, text, node, rev):
         p1, p2 = self.parents(node)
-        if node != hash(text, p1, p2):
+        if not self._ishashcorrect(text, p1, p2, node):
             raise RevlogError(_("integrity check failed on %s:%d")
                               % (self.indexfile, rev))
         return text
 
+    def _ishashcorrect(self, text, p1, p2, node):
+        # subclass will override this method if it uses custom hashing strategy
+        return node == hash(text, p1, p2)
+
     def checkinlinesize(self, tr, fp=None):
         if not self._inline or (self.start(-2) + self.length(-2)) < _maxinline:
             return
@@ -987,7 +991,8 @@
         tr.replace(self.indexfile, trindex * self._io.size)
         self._chunkclear()
 
-    def addrevision(self, text, transaction, link, p1, p2, cachedelta=None):
+    def addrevision(self, text, transaction, link, p1, p2, cachedelta=None,
+                    node=None):
         """add a revision to the log
 
         text - the revision data to add
@@ -995,11 +1000,14 @@
         link - the linkrev data to add
         p1, p2 - the parent nodeids of the revision
         cachedelta - an optional precomputed delta
+        node - nodeid of revision; typically node is not specified, and it is
+            computed by default as hash(text, p1, p2), however subclasses might
+            use different hashing method (they need to override _ishashcorrect)
         """
         if link == nullrev:
             raise RevlogError(_("attempted to add linkrev -1 to %s")
                               % self.indexfile)
-        node = hash(text, p1, p2)
+        node = node or hash(text, p1, p2)
         if node in self.nodemap:
             return node
 
@@ -1063,8 +1071,7 @@
             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:
+            if not self._ishashcorrect(btext[0], p1, p2, node):
                 raise RevlogError(_("consistency error in delta"))
             return btext[0]