diff mercurial/utils/stringutil.py @ 40723:e6c9ef5e11a0

match: provide and use a quick way to escape a single byte

The previous function has a lot of overhead (including being a function). In
the `_globre` case, we always escape a single byte. So we provide a dictionary
dedicated to this use case. We directly use the dictionary to avoid a function
call, these are expensive in Python.

Again, this raise a very significant performance gain:

Before: ! wall 0.059793 comb 0.060000 user 0.060000 sys 0.000000 (median of 100)
After:  ! wall 0.020390 comb 0.020000 user 0.020000 sys 0.000000 (median of 146)

Total improvement for the full series:

Before: ! wall 0.153153 comb 0.150000 user 0.150000 sys 0.000000 (median of 66)
After:  ! wall 0.020390 comb 0.020000 user 0.020000 sys 0.000000 (median of 146)

--- a/mercurial/utils/stringutil.py	Mon Nov 19 16:50:21 2018 +0000
+++ b/mercurial/utils/stringutil.py	Mon Nov 19 18:54:44 2018 +0000
@@ -28,6 +28,7 @@
 # which was part of Python 3.7.
 _respecial = pycompat.bytestr(b'()[]{}?*+-|^$\\.&~# \t\n\r\v\f')
 _regexescapemap = {ord(i): (b'\\' + i).decode('latin1') for i in _respecial}
+regexbytesescapemap = {i: (b'\\' + i) for i in _respecial}
 
 def reescape(pat):
     """Drop-in replacement for re.escape."""