# HG changeset patch
# User Siddharth Agarwal <sid0@fb.com>
# Date 2014-10-04 01:45:56
# Node ID d9585dda63c37cc731b0664e492b083a8e720dde
# Parent  80f2b63dd83a1c22ae056a2522571c153e0bebb8

encoding.lower: use fast ASCII lower

This benefits, among other things, the case collision auditor.

On a Linux system with a large real-world repo where all filenames are ASCII,
hg perfcca:

before: wall 0.260157 comb 0.270000 user 0.230000 sys 0.040000 (best of 38)
after:  wall 0.164616 comb 0.160000 user 0.160000 sys 0.000000 (best of 54)

diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -270,8 +270,7 @@ asciilower = getattr(parsers, 'asciilowe
 def lower(s):
     "best-effort encoding-aware case-folding of local string s"
     try:
-        s.decode('ascii') # throw exception for non-ASCII character
-        return s.lower()
+        return asciilower(s)
     except UnicodeDecodeError:
         pass
     try: