# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 2016-02-28 06:25:14
# Node ID 1778770e198244405bdb5f435e9b4186ccbc6adc
# Parent  f5ae291dfedf8627efd1782dba3e724eee1b5f09

changelog: lazy decode description (API)

Currently, changelog reading decodes read values. This is wasteful
because a lot of times consumers aren't interested in some of these
values.

This patch changes description decoding to occur in changectx as
needed.

revsets reading changelog entries appear to speed up slightly:

revset #7: author(lmoscovicz)
   plain
0) 0.906329
1) 0.872653

revset #8: author(mpm)
   plain
0) 0.903478
1) 0.878037

revset #9: author(lmoscovicz) or author(mpm)
   plain
0) 1.817855
1) 1.778680

revset #10: author(mpm) or author(lmoscovicz)
   plain
0) 1.837052
1) 1.764568

diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -334,12 +334,20 @@ class changelog(revlog.revlog):
         (.*)            : comment (free text, ideally utf-8)
 
         changelog v0 doesn't use extra
+
+        Returns a 6-tuple consisting of the following:
+          - manifest node (binary)
+          - user (encoding.localstr)
+          - (time, timezone) 2-tuple of a float and int offset
+          - list of files modified by the cset
+          - commit message / description (binary)
+          - dict of extra entries
         """
         text = self.revision(node)
         if not text:
             return nullid, "", (0, 0), [], "", _defaultextra
         last = text.index("\n\n")
-        desc = encoding.tolocal(text[last + 2:])
+        desc = text[last + 2:]
         l = text[:last].split('\n')
         manifest = bin(l[0])
         user = encoding.tolocal(l[1])
diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -554,7 +554,7 @@ class changectx(basectx):
     def files(self):
         return self._changeset[3]
     def description(self):
-        return self._changeset[4]
+        return encoding.tolocal(self._changeset[4])
     def branch(self):
         return encoding.tolocal(self._changeset[5].get("branch"))
     def closesbranch(self):