[PATCH 2 of 4] imported patch newdef

[Pradeepkumar Gayam]

# HG changeset patch
# User Pradeepkumar Gayam <in3xes at gmail.com>
# Date 1277183801 -19800
# Node ID 3c0cf3b7fd9ece7f7d31c6119eb83eea5807f89d
# Parent  466d7fb61dca5cb1e54e4e38fb941fba1a5d0909
imported patch newdef

diff -r 466d7fb61dca -r 3c0cf3b7fd9e mercurial/revlog.py
--- a/mercurial/revlog.py	Tue Jun 22 10:46:41 2010 +0530
+++ b/mercurial/revlog.py	Tue Jun 22 10:46:41 2010 +0530
@@ -997,9 +997,17 @@
     def _chunkclear(self):
         self._chunkcache = (0, '')
 
+    def deltaparent(self, rev):
+        if self.base(rev) == rev:
+            return nullrev
+        elif self.flags(rev) & REVLOG_PARENTDELTA_FLAGS:
+            return self.parentrevs(rev)[0]
+        else:
+            return rev-1
+
     def revdiff(self, rev1, rev2):
         """return or calculate a delta between two revisions"""
-        if rev1 + 1 == rev2 and self.base(rev1) == self.base(rev2):
+        if rev1 != nullrev and self.deltaparent(rev2) == rev1:
             return self._chunk(rev2)
 
         return mdiff.textdiff(self.revision(self.node(rev1)),
@@ -1007,6 +1015,14 @@
 
     def flags(self, rev):
         return gettype(self.index[rev][0])
+
+    def deltachain(self, rev):
+        chain = []
+        while self.base(rev) != rev:
+            chain.append(rev)
+            rev = self.deltaparent(rev)
+        chain.reverse()
+        return rev, chain
     
     def revision(self, node):
         """return an uncompressed revision of a given node"""
@@ -1018,7 +1034,7 @@
         # look up what we need to read
         text = None
         rev = self.rev(node)
-        base = self.base(rev)
+        base, chain = self.deltachain(rev)
 
         # check rev flags
         if self.flags(rev) & ~1:
@@ -1026,16 +1042,21 @@
                               (self.flags(rev)))
 
         # do we have useful data cached?
-        if self._cache and self._cache[1] >= base and self._cache[1] < rev:
-            base = self._cache[1]
-            text = self._cache[2]
+        if self._cache:
+            try:
+                intersect = chain.index(self._cache[1])
+            except ValueError:
+                pass
+            else:
+                base, chain = chain[intersect], chain[intersect + 1:]
+                text = self._cache[2]
 
         self._loadindex(base, rev + 1)
         self._chunkraw(base, rev)
         if text is None:
             text = self._chunk(base)
 
-        bins = [self._chunk(r) for r in xrange(base + 1, rev + 1)]
+        bins = [self._chunk(r) for r in chain]
         text = mdiff.patches(text, bins)
         p1, p2 = self.parents(node)
         if node != hash(text, p1, p2):