changeset 39201:45e05d39d9ce

pycompat: wrap xrange for py2 to provide efficient __contains__ The C implementation of xrange in Python 2 provides a O(n) membership test, which is noticable on pull-based clones of large repositories. Avoid this by providing a wrapper class with O(1) membership test based on the edges of the range. Differential Revision: https://phab.mercurial-scm.org/D4313
author Joerg Sonnenberger <joerg@bec.de>
date Fri, 17 Aug 2018 00:51:46 +0200
parents d859b48730b8
children 27bbd62e9957
files mercurial/changelog.py mercurial/pycompat.py
diffstat 2 files changed, 22 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/changelog.py	Mon Aug 20 09:48:08 2018 -0700
+++ b/mercurial/changelog.py	Fri Aug 17 00:51:46 2018 +0200
@@ -556,8 +556,8 @@
         if revs is not None:
             if revs:
                 assert revs[-1] + 1 == rev
-                revs = pycompat.xrange(revs[0], rev + 1)
+                revs = pycompat.membershiprange(revs[0], rev + 1)
             else:
-                revs = pycompat.xrange(rev, rev + 1)
+                revs = pycompat.membershiprange(rev, rev + 1)
             transaction.changes['revs'] = revs
         return node
--- a/mercurial/pycompat.py	Mon Aug 20 09:48:08 2018 -0700
+++ b/mercurial/pycompat.py	Fri Aug 17 00:51:46 2018 +0200
@@ -278,6 +278,7 @@
     hasattr = _wrapattrfunc(builtins.hasattr)
     setattr = _wrapattrfunc(builtins.setattr)
     xrange = builtins.range
+    membershiprange = builtins.range
     unicode = str
 
     def open(name, mode='r', buffering=-1, encoding=None):
@@ -343,6 +344,25 @@
     strurl = identity
     bytesurl = identity
 
+    class membershiprange(object):
+        "Like xrange(a,b) but with constant-time membership test"
+        def __init__(self, a, b):
+            self._range = xrange(a, b)
+        def __getitem__(self, n):
+            return self._range[n]
+        def __hash__(self):
+            return hash(self._range)
+        def __iter__(self):
+            return iter(self._range)
+        def __len__(self):
+            return len(self._range)
+        def __reversed__(self):
+            return reversed(self._range)
+        def __contains__(self, n):
+            if not self._range:
+                return False
+            return n >= self._range[0] and n <= self._range[-1]
+
     # this can't be parsed on Python 3
     exec('def raisewithtb(exc, tb):\n'
          '    raise exc, None, tb\n')