# HG changeset patch
# User Matt Mackall <mpm@selenic.com>
# Date 1421015877 21600
# Node ID e880036719e389e75d6ad1ebd9d78ef841cb8071
# Parent  2763edaba85721ba665014a23296a251af38c801
readmarkers: fast-path single successors and parents

This gives about a 5% performance bump.

diff -r 2763edaba857 -r e880036719e3 mercurial/obsolete.py
--- a/mercurial/obsolete.py	Sun Jan 11 15:35:09 2015 -0600
+++ b/mercurial/obsolete.py	Sun Jan 11 16:37:57 2015 -0600
@@ -308,25 +308,39 @@
 
         if flags & sha2flag:
             # read 0 or more successors
-            o2 = o1 + sha2size * numsuc
-            sucs = unpack(sha2fmt * numsuc, data[o1:o2])
+            if numsuc == 1:
+                o2 = o1 + sha2size
+                sucs = (data[o1:o2],)
+            else:
+                o2 = o1 + sha2size * numsuc
+                sucs = unpack(sha2fmt * numsuc, data[o1:o2])
 
             # read parents
             if numpar == noneflag:
                 o3 = o2
                 parents = None
+            elif numpar == 1:
+                o3 = o2 + sha2size
+                parents = (data[o2:o3],)
             else:
                 o3 = o2 + sha2size * numpar
                 parents = unpack(sha2fmt * numpar, data[o2:o3])
         else:
             # read 0 or more successors
-            o2 = o1 + sha1size * numsuc
-            sucs = unpack(sha1fmt * numsuc, data[o1:o2])
+            if numsuc == 1:
+                o2 = o1 + sha1size
+                sucs = (data[o1:o2],)
+            else:
+                o2 = o1 + sha1size * numsuc
+                sucs = unpack(sha1fmt * numsuc, data[o1:o2])
 
             # read parents
             if numpar == noneflag:
                 o3 = o2
                 parents = None
+            elif numpar == 1:
+                o3 = o2 + sha1size
+                parents = (data[o2:o3],)
             else:
                 o3 = o2 + sha1size * numpar
                 parents = unpack(sha1fmt * numpar, data[o2:o3])